APPARATUS AND METHOD FOR COMPUTING HOLOGRAM DATA

Abstract

The invention relates to a preprocessing circuit for at least one hologram computation circuit that comprises an input interface device for receiving data of a scene to be displayed, a processing device for defined processing of the received data and for converting the data into a system-independent format with incorporation of specific parameters required for displaying the scene, and an output interface device for outputting and transmitting the converted data to at least one hologram computation circuit. An apparatus for computing a hologram for displaying a scene by means of a holographic display apparatus is also disclosed. The apparatus comprises at least one spatial light modulation device and a preprocessing circuit as described, and at least one hologram computation circuit for computing a hologram and for encoding the hologram for the at least one spatial light modulation device.

Claims

1. A preprocessing circuit for at least one hologram computation circuit, comprising: an input interface device for receiving data of a scene to be displayed, a processing device for defined processing of the received data and for converting the data into a system-independent format with incorporation of specific parameters required for displaying the scene, and an output interface device for outputting and transmitting the converted data to at least one hologram computation circuit.

2. The preprocessing circuit as claimed in claim 1, wherein the preprocessing circuit is implemented as a field-programmable gate array (FPGA) or as an application-specific integrated circuit (ASIC).

3. The preprocessing circuit as claimed in claim 1, wherein the data, parameters, and programs supplied to the preprocessing circuit are provided in an encrypted format.

4. The preprocessing circuit as claimed in claim 1, wherein the processing device is designed to correct imaging errors in the display of the scene.

5. The preprocessing circuit as claimed in claim 1, wherein the processing device is designed to correct imaging errors or to correct effects having a negative effect on a scene to be displayed of an optical system provided in a holographic display apparatus.

6. The preprocessing circuit as claimed in claim 1, wherein the processing device is designed in such a way that upon use of eye tracking data in conjunction with foveated rendering, the resolution, the degree of detail, and/or the holographic quality of the scene to be displayed is adaptable on the basis of a viewing direction of an eye of an observer in defined areas of a field of view of the observer.

7. The preprocessing circuit as claimed in claim 6, wherein, by means of the processing device, the data of the scene are processed in such a way that the resolution, the degree of detail, and/or the holographic quality of the scene is reduced in its edge area.

8. The preprocessing device as claimed in claim 1, wherein the processing unit is designed to control controllable components of at least one spatial light modulation device or a holographic display apparatus.

9. The preprocessing circuit as claimed in claim 1, wherein a combination of a permanent logic having paths switchable at the run time or paths switchable once at the run time and at least one processor is used in the processing device.

10. The preprocessing circuit as claimed in claim 1, wherein a timing controller is provided for generating control signals and/or synchronization signals.

11. The preprocessing circuit as claimed claim 2, wherein the processing device is designed to carry out analyses of the data of the scene to be displayed, in order to execute a hologram normalization.

12. The preprocessing circuit as claimed in claim 1, characterized by a scalability of the preprocessing circuit for various variables of the at least one spatial light modulation device and/or hologram resolutions and/or scene resolutions and/or parameters of the at least one spatial light modulation device by a variable activation of the computation paths.

13. An apparatus for computing a hologram for displaying a scene by means of a holographic display apparatus, which comprises at least one spatial light modulation device, comprising: a preprocessing circuit as claimed in claim 1, and at least one hologram computation circuit for computing a hologram and for encoding the hologram for the at least one spatial light modulation device.

14. The device as claimed in claim 13, wherein the at least one hologram computation circuit is implemented as a field-programmable gate array (FPGA) or as an application-specific integrated circuit (ASIC).

15. The device as claimed in claim 13, wherein the at least one hologram computation circuit comprises: an input interface device for receiving data processed by the preprocessing circuit, a hologram computation device for computing and encoding the hologram, and an output interface device for transmitting the data of the computed hologram to the at least one spatial light modulation device.

16. The device as claimed in claim 13, wherein the at least one hologram computation circuit is designed as part of the at least one spatial light modulation device or is implemented directly on a substrate of the at least one spatial light modulation device.

17. The device as claimed in claim 13, wherein at least two hologram computation circuits are provided, which are connected in series and/or are connected in parallel to one another.

18. The device as claimed in claim 13, wherein a supply of data of the scene processed by the preprocessing circuit in a system-independent format to the at least one hologram computation circuit is provided.

19. The device as claimed in claim 18, wherein the at least one hologram computation circuit is designed in such a way that the data of the scene supplied in a system-independent format are directly usable and the hologram is computable.

20. The device as claimed in claim 13, wherein an external data interface device is provided for the encrypted supply of data and programs to the preprocessing circuit.

21. The device as claimed in claim 20, wherein the encrypted data and programs supplied to the preprocessing circuit are stored in encrypted form on a nonvolatile memory.

22. The device as claimed in claim 13, wherein a mutual authentication is implemented between the preprocessing circuit and the at least one hologram computation circuit.

23. The device as claimed in claim 13, characterized by a scalability of the preprocessing circuit and/or the at least one hologram computation circuit for various variables of the at least one spatial light modulation device and/or hologram resolutions and/or scene resolutions and/or parameters of the at least one spatial light modulation device by a variable activation of computation paths.

24. The device as claimed in claim 13, wherein the at least one hologram computation circuit is provided for various embodiments or designs of the at least one spatial light modulation device.

25. A holographic display apparatus comprising: a preprocessing circuit as claimed in claim 1, at least one hologram computation circuit for computing a hologram, and at least one spatial light modulation device, for which the computed hologram is encoded.

26. The holographic display apparatus as claimed in claim 25, wherein at least one source driver is provided, using which data of the hologram computed using the at least one hologram computation circuit are transmittable to the at least one spatial light modulation device.

27. The holographic display apparatus as claimed in claim 25, wherein an illumination device, which comprises at least one light source, and an optical system are provided, by means of which a scene is reconstructable in conjunction with the at least one spatial light modulation device.

28. A pipeline for real-time computation of holograms, which comprises a preprocessing circuit for preprocessing data of a scene and for directly activating components of at least one spatial light modulation device and at least one hologram computation circuit for computing holograms, where the preprocessing circuit and the at least one hologram computation circuit are each implemented on the basis of a field-programmable gate array (FPGA) and/or an application-specific integrated circuit (ASIC).

29. The pipeline as claimed in claim 28, wherein the preprocessing circuit and the at least one hologram computation circuit are configurable at the run time.

30. The pipeline as claimed in claim 28, wherein the preprocessing circuit comprises a receiving interface device for receiving data for describing a scene to be displayed, a processing device for preprocessing the data of the scene to be displayed, and an output interface device for outputting and transmitting the preprocessed data to the at least one hologram computation circuit.

31. The pipeline as claimed in claim 28, wherein the at least one hologram computation circuit comprises an input interface device for receiving data preprocessed by the preprocessing circuit, a hologram computation device for computing and encoding a hologram, and an output interface device for transmitting the data of the computed hologram to at least one spatial light modulation device.

32. The pipeline as claimed in claim 28, wherein the preprocessing circuit and the at least one hologram computation circuit are separate circuits, which are connected to one another in such a way that the at least one hologram computation circuit is activatable by means of the preprocessing circuit, but the preprocessing circuit and the at least one hologram computation circuit are not assigned to a specific spatial light modulation device and/or holographic display apparatus.

33. The pipeline as claimed in claim 28, characterized by a scalability of the preprocessing circuit and/or the hologram computation circuit for various variables of the at least one spatial light modulation device and/or hologram resolutions and/or scene resolutions and/or parameters of the at least one spatial light modulation device by a variable activation of the computation paths.

34. A method for computing a hologram for displaying a scene by means of a holographic display apparatus, which comprises at least one spatial light modulation device, where the computation of the hologram is carried out by means of a preprocessing circuit and at least one hologram computation circuit.

35. The method as claimed in claim 34, wherein the preprocessing circuit processes data, which are only required once in the preprocessing to compute the hologram, and the at least one hologram computation circuit computes the hologram provided for encoding for the at least one spatial light modulation device from the data provided by the preprocessing circuit and outputs it to the at least one spatial light modulation device.

36. The method as claimed in claim 34, wherein an input interface device of the preprocessing circuit receives data of a scene to be displayed in encrypted format, decrypts them, and transmits them to a preprocessing device of the preprocessing circuit.

37. The method as claimed in claim 36, wherein by means of the preprocessing device, the transmitted data are preprocessed in accordance with the scene to be displayed and the preprocessed data are converted in consideration of specific parameters of the at least one spatial light modulation device into a system-independent format.

38. The method as claimed in claim 36, wherein aberrations of the scene to be displayed are corrected by the preprocessing device, by which data corrected for aberrations are generated.

39. The method as claimed in claim 36, wherein visual defects of an eye of an observer of the scene to be displayed are corrected by means of the preprocessing device by virtual shifting, rotation, and/or distortion of the scene.

40. The method as claimed in claim 36, wherein the resolution, the degree of detail, and/or the holographic quality of the scene to be displayed is adapted in consideration of a viewing direction of an eye of the observer by the preprocessing device in such a way that the displayed scene is computed in its edge area having a reduced resolution, a reduced degree of detail, and/or a reduced holographic quality by a hologram computation device of the at least one hologram computation circuit.

41. The method as claimed in claim 34, wherein occlusion data of the scene to be displayed are transmitted to the preprocessing circuit, where the preprocessing circuit extracts the required information for generating object points of the scene from the transmitted occlusion data.

42. The method as claimed in claim 36, wherein the data generated using the preprocessing device are converted into a system-independent format in consideration of specific parameters of the at least one spatial light modulation device and transmitted via an output interface device of the preprocessing circuit to the at least one hologram computation circuit for computing a hologram of the scene to be displayed.

43. The method as claimed in claim 34, wherein controllable components of a holographic display apparatus are activated to display the scene by means of the preprocessing circuit, where the control of the components takes place synchronously to the output of the computed hologram on the at least one spatial light modulation device.

44. The method as claimed claim 34, wherein in the specific parameters of the at least one spatial light modulation device, data, and programs for preprocessing of the scene to be displayed are stored in encrypted form on a nonvolatile memory, where these data are transmitted in encrypted form to the preprocessing circuit.

45. The method as claimed in claim 34, wherein the at least one spatial light modulation device and at least one source driver for driving the at least one spatial light modulation device are clocked and controlled via a timing controller of the preprocessing circuit.

46. The method as claimed in claim 34, wherein at least one analysis of the data of the scene to be displayed for a hologram normalization is carried out within the preprocessing circuit.

47. The method as claimed in claim 46, wherein to ascertain hologram normalization parameters for the hologram normalization, an analysis of the data transmitted to the input interface device is carried out by: analyzing a distribution of object points of the scene with respect to their depth and their lateral distribution in an observation area analyzing a brightness distribution of the object points in combination with the respective depth of the object points in the observation area, and ascertaining a total number of the object points.

48. The method as claimed in claim 47, wherein by analyzing the change of the scene to be displayed from frame to frame, hologram normalization parameters are estimated by an analysis module in the preprocessing circuit and transmitted to a coding module in the at least one hologram computation circuit, which applies these estimated hologram normalization parameters to the computed passing hologram data for normalization.

49. The method as claimed in claim 48, wherein by means of the passing computed data for hologram encoding, correct values of the hologram normalization parameters are ascertained by the encoding module and transmitted back to the analysis module in the preprocessing circuit.

50. The method as claimed in claim 48, wherein the estimated hologram normalization parameters and the correct values of the hologram normalization parameters are compared to one another at the end of each frame.

51. The method as claimed in claim 34, wherein in each case an object point of the scene to be displayed is encoded in a subhologram, where to describe phase values of pixels of the subhologram of an object point, the following parameters are determined by the preprocessing circuit and transferred to the at least one hologram computation circuit for computing the phase of the subhologram of the object point of the scene: a focal length or refractive power, which varies as a function of a depth of the object point in the observation area, and a phase offset of the object point.

52. The method as claimed in claim 51, wherein the focal length for the description of the phase values of the pixels of the subhologram of an object point is defined as the normed focal length F=f/p or its reciprocal value, where f is the focal length of the object point and p is a constant, which is preferably defined on the pixel pitch of the at least one spatial light modulation device.

53. The method as claimed in claim 51, wherein the focal length for the description of the phase values of the pixels of the subhologram of an object point is defined in system-independent form as a wavelength-normed focal length F′=fλ/p{circumflex over ( )}2 or its reciprocal value, where f is the focal length of the object point, λ is the wavelength of the light, and p is a constant which is preferably defined on the pixel pitch of the at least one spatial light modulation device.

54. The method as claimed in claim 51, wherein the phase value of pixels of the subhologram of the object point of the scene having equal distance from the center of the subhologram is computed using a circuit part of the at least one hologram computation circuit permanently assigned to this distance.

Description

[0173] There are now various possibilities for advantageously designing the teaching of the present invention and/or combining the described exemplary embodiments or designs with one another. For this purpose, reference is made, on the one hand, to the claims dependent on the other independent claims and, on the other hand, to the following explanation of the preferred exemplary embodiments of the invention on the basis of the drawings, in which generally preferred designs of the teaching are also explained. The invention is explained in principle here on the basis of the described exemplary embodiments, but is not to be restricted thereto.

[0174] In the figures:

[0175] FIG. 1: shows a graphic representation of an apparatus for computing a hologram according to the prior art;

[0176] FIG. 2: shows a graphic representation of an apparatus or pipeline according to the invention for computing a hologram;

[0177] FIG. 3: shows a graphic representation of a method according to the invention for normalizing hologram data;

[0178] FIG. 4: shows a graphic representation of a method according to the invention for converting the data into a system-independent format; and

[0179] FIG. 5 shows in principle a holographic display apparatus according to the invention for reconstructing a preferably three-dimensional scene.

[0180] FIG. 2 shows a graphic representation of an apparatus according to the invention for computing a hologram. This apparatus in FIG. 2 simultaneously also represents a pipeline for real-time computation of holograms. The apparatus or pipeline according to the invention comprises a preprocessing circuit 60 and at least one hologram computation circuit 70. In the exemplary embodiment shown according to FIG. 2, multiple hologram computation circuits 40, a total of four in number here, are provided, where the number of the hologram computation circuits 70 can be dependent on the dimensions of a spatial light modulation device 80, referred to hereinafter as SLM, in which a hologram is encoded, which will be discussed in detail hereinafter. In principle, only one hologram computation circuit 70 can also be provided. The preprocessing circuit 60 and the hologram computation circuit 70 are each implemented as independent or separate circuits. They can therefore be viewed, produced, and sold as independent circuits. The preprocessing circuit 60 and the hologram computation circuit 70 can both be permanently connected to one another, however, for example wired, and in this way form an apparatus for computing a hologram according to FIG. 2. Both circuits 60 and 70 can each be implemented or embodied as a field-programmable gate array (FPGA) or as an application-specific integrated circuit (ASIC). In the present exemplary embodiment, the circuits 60 and 70 are each implemented as an ASIC.

[0181] The preprocessing circuit 60 is connected via a simple user-defined or customer-specific interface S to the hologram computation circuits 70. To generate and compute a hologram, which is then transferred to the SLM 80 and encoded for it, the preprocessing device 60 comprises an input interface device 61, a processing device 62, and an output interface device 63. The input interface device 61 receives data 64 of object points of a scene to be computed and encoded in a hologram, where a three-dimensional scene is presumed here. However, it is also possible to display a two-dimensional scene. The input interface device 61 can have for this purpose a standardized interface, for example, one or more DisplayPort or HDMI interfaces, one or more network interfaces, or also any other interface having the required bandwidth. The data 64 of the three-dimensional scene can be provided for this purpose in various formats. They can be designed, for example, as a three-dimensional point cloud, as a three-dimensional volume, or also as a compilation of scanned images or two-dimensional (2D) matrices of one or more views from one or more planes in an observation area, i.e., images in color representation and depth, possibly in multiple planes for implementing transparency or volume in holograms. Any other formats are also possible. The resolution of the data 64 is flexible, where a provided SLM, for which the computed hologram is then to be encoded, possibly implements a specific maximum resolution for the reproduction and reconstruction of the three-dimensional scene, however.

[0182] The data 64 which the preprocessing circuit 60 uses and programs which are executed on the preprocessing circuit 60 are supplied in an encrypted form via an external data interface to the preprocessing circuit 60. These data 64 and programs are moreover stored encrypted on an external, nonvolatile memory 65. The preprocessing circuit 60 uses a combination made up of permanent logic having paths switchable at the run time or once and at least one embedded processor having at least one processor core, where multiple processors or processor cores can also be used, on which one or more program(s) and modules run to carry out all required tasks for the pre-computation of holograms. An embodiment without the use of programs or processors is also possible, however.

[0183] Moreover, the input interface device 61 decrypts and processes the received data 64 of the three-dimensional scene according to the requirements of the processing device 62 and passes them on as data 64-1 to the processing device 62. The processing device 62 then processes these data 64-1 according to defined requirements for a hologram to be computed. This means that the processing device 62 carries out various preprocessing actions of the data 64-1 transmitted thereto. These can include, for example, the correction of aberrations in the three-dimensional scene to be displayed. The processing device 62 can also be defined so that effects having a negative effect on a three-dimensional scene to be displayed of an optical system provided in a holographic display apparatus can be corrected by this device. For example, a color correction and/or a position correction of the object points of the three-dimensional scene to be displayed can be performed by means of the processing device 62, in that the data 64-1 are preprocessed in such a way that this correction then takes place in the display of the scene. It is also possible to design the preprocessing actions of the data 64-1 so that different corrections are carried out for each wavelength (color) of the light, using which the SLM 80 is then illuminated for reconstruction of the three-dimensional scene, in order, if necessary, to compensate for wavelength-dependent effects in the optical system of the holographic display apparatus differently. Moreover, the processing device 62 can also perform preprocessing actions for a defined correction of visual defects of at least one eye of an observer of the scene to be displayed. Such a subsequent correction of ocular visual defects can be carried out here in such a way that the object points of the three-dimensional scene are individually shifted, rotated, and/or distorted in each dimension or direction.

[0184] Using eye tracking data, i.e., for tracking the eyes of an observer in real time, for example to find out in which direction the viewer is presently looking or which part of the three-dimensional scene the observer aims or looks at at this moment, so-called foveated rendering can also be implemented, in that the resolution of the three-dimensional scene to be displayed is adapted on the basis of the present or predicted viewing direction of an eye of the observer. For this purpose, the resolution, the degree of detail, and/or the holographic quality of the scene can advantageously be reduced in the edge area of the fovea of the eye, by which the power consumption for computing the scene in the hologram computation circuit is significantly reduced. In defined areas of the field of view of the observer, the resolution, the degree of detail, and/or the holographic quality of the three-dimensional scene can thus be adapted accordingly. It is advantageous here to reduce the resolution, the degree of detail, and/or the holographic quality in the edge area of the three-dimensional scene. The viewing direction of the eye of the observer is computed for this purpose. Due to delays in the circuits 60 and 70 between the start of the computation and subsequent display of the hologram on the SLM 80, it is necessary to predict or estimate the viewing direction movement of the eye of the observer in the future in accordance with the delay time.

[0185] The preprocessing circuit 60 moreover also assumes the control of further components of the SLM 80, where the control generally takes place synchronously to the output of the holograms on the SLM 80. The processing device 62 of the preprocessing circuit 60 can also assume or carry out further functions. These can include, for example, a conversion of two-dimensional (2D) scene data into three-dimensional (3D) scene data, i.e., a so-called 2D/3D conversion, a generation of depth data from multiple views of a three-dimensional scene, or also a generation of additional three-dimensional data for filling shadows due to the holographic parallax (so-called occlusion data). Occlusion data can be generated in particular with the aid of point cloud-like three-dimensional scene data or if multiple image planes with/without transparency are provided. The occlusion data of the scene are transmitted in this case to the preprocessing circuit 60. The preprocessing circuit 60 then extracts the required information from these data in order to be able to generate the object points of the scene from the transmitted occlusion data.

[0186] After the processing device 62 has accordingly preprocessed or processed the data 64-1, these now preprocessed and optionally corrected data 64-2 of the three-dimensional scene are subsequently converted into a generalized format processable for the following hologram computation circuits 70 or into a system-independent format. Specific parameters of the SLM 80 are also incorporated in the conversion of the data 64-2 for this purpose. These parameters are, for example, items of information on the wavelengths used of the light incident on the SLM 80, the scanning of the SLM 80, resolutions of the SLM 80, on distances, for example distances between an eye of an observer and the SLM 80, correction tables and correction parameters, in order to carry out specific corrections, for example, of distortions or wavelength-dependent aberrations, items of interface information, interface configurations, and interface parameters.

[0187] The converted data 64-2 are transmitted to the output interface device 63, which transmits these preprocessed data 64-2 for computing a hologram to the individual separate hologram computation circuits 70 at a low bandwidth.

[0188] As is apparent in FIG. 2, four hologram computation circuits 70 are used here, which follow the separate preprocessing circuit 60. Like the preprocessing circuit 60, the hologram computation circuits 70 are also each designed as independent or separate circuits and preferably implemented here as ASIC. An implementation of the hologram computation circuits 70 as FPGA is also possible and could be more cost-effective depending on the number of the hologram computation circuits used or the number of the apparatuses to be produced (piece counts). As already mentioned, it can be advantageous to use not only one hologram computation circuit 70 in the number, but a defined number of multiple hologram computation circuits 70. The number of hologram computation circuits 70 advantageously to be used results from the required computing power which is necessary for the hologram, and the required bandwidth in the transmission of the hologram to the SLM 80. The computing power and the bandwidth generally also scale with the size or dimensions of the SLM 80. This means that the larger the SLM 80 is in its dimensions, the more advantageous it is to use a larger number of hologram computation circuits 70. The provision of multiple hologram computation circuits 70 moreover has the advantage of more uniform dissipation of the resulting waste heat via multiple small spots (hotspots) instead of one large spot in the case of only one hologram computation circuit 70 in the computation of a hologram. In FIG. 2, each two hologram computation circuits 70 are connected in parallel to one another, where the respective two hologram computation circuits 70 are connected in series to one another or form a series circuit. Of course, other possibilities for arranging the hologram computation circuits in relation to one another and to the SLM are also possible. In this way, each two hologram computation circuits 70 are arranged on two opposite sides of the SLM 80, so that two separate lines or transfer lines S are connected from the preprocessing circuit 60 to the respective hologram computation circuit 70 provided first in the series. The second hologram computation circuit 70 provided in the series is connected here via a corresponding line to the first hologram computation circuit 70, as is apparent from FIG. 2. The proximity of the hologram computation circuits 70 to the edge of the SLM 80 or to source drivers 81 of the spatial light modulation device enables short data lines, which significantly reduces the power consumption at the very high data rates.

[0189] The hologram computation circuits 70 can thus be located close to the connections of the SLM 80. It is also possible to integrate the hologram computation circuits into the SLM 80 as part thereof. In this case they can be provided in the vicinity of source drivers. Present developments could also give the impetus that such hologram computation circuits or circuits could be applied directly to a substrate of the SLM (chip on glass).

[0190] The interface to the SLM 80 is designed flexibly here and enables an adjustment of the data rate, the number of transfer lines, and the protocol to be used. For this purpose, in the production of the SLM 80 in conjunction with the hologram computation circuit(s) 70, the corresponding data paths can be permanently activated or configured on the hologram computation circuit 70. This can take place, on the one hand, at the run time upon the initialization of the hologram computation circuit 70 or can be permanently set via configuration bridges (antifuses).

[0191] An aspect particularly to be highlighted in combination with the generalized implementation of the hologram computation is the scalability. Such a hologram computation circuit 70 can be used multiple times within the apparatus or pipeline according to FIG. 2 and thus also multiple times in a holographic display apparatus for displaying three-dimensional scenes or objects. If certain requirements, for example, with respect to the aspect ratio of at least similar pixel pitch, are met, the same hologram computation circuit can also be used in various products of an apparatus according to FIG. 2 or a holographic display apparatus. This would be advantageous in particular with respect to the production costs of an ASIC or FPGA, because these can be enormous. Therefore, if the same type of ASIC or FPGA can be used multiple times in an apparatus, this would save a costly development and production of a hologram computation circuit according to the invention per product or apparatus. Smaller ASICs or FPGAs in their dimensions in comparison to an ASIC or FPGA large in its dimensions additionally have the significant advantage that a higher yield can be achieved in the production. The development and tests are therefore additionally less complex.

[0192] To reduce the power consumption and the piece count costs with respect to the hologram computation circuits, smaller process structures can be sought. This is worthwhile above all if high piece counts of hologram computation circuits are also planned, which is assisted by the generalization and the provision of multiple hologram computation circuits.

[0193] In principle, the provision of an independent hologram computation circuit and an independent or separate preprocessing circuit which is separate from the direct hologram computation advantageously enables marketing of the hologram computation circuit design and of the preprocessing circuit design. This in turn enables, for example, a producer of an SLM or a holographic display apparatus to adapt to their own processes and interfaces, and to use production methods which are their own or are suitable for them.

[0194] By means of the hologram computation circuits 70, after the transmission of the preprocessed data 64-2 of the three-dimensional scene by the preprocessing circuit 60, data for a required hologram of a scene, which is formed from computed and superimposed subholograms of object points of the scene, are now computed. The first hologram computation circuit 70 connected in series in each case according to FIG. 2 only extracts the required data in each case for the computation of a part of the hologram from the transmitted data for computing the hologram and transfers the remaining data to the second hologram computation circuit 70 provided in the series, which uses these data to also compute a part of the overall hologram or hologram. The data stream is conducted unchanged through the hologram computation circuits 70, where each hologram computation circuit 70 only extracts the data for computing the hologram which it requires. For this purpose, the hologram computation circuit 70 according to the enlarged illustration in FIG. 2 has an input interface device 71, a hologram computation device 72, and an output interface device 73. The input interface device 71 receives the data 64-2 of the three-dimensional scene, which are preprocessed by the preprocessing circuit 60 and are provided in a system-independent format, and transmits them to the hologram computation device 72 to compute a hologram. In the hologram computation device 72, the computation of the hologram, the accumulation of the individual subholograms of object points of the three-dimensional scene to form the overall hologram of the scene, and the encoding of the hologram take place here, as shown in FIG. 2. The computed hologram of the three-dimensional scene or the computed data of the hologram to be encoded are then transferred to the output interface device, which then outputs these data to source drivers 81. The source drivers 81 in turn transfer the data of the encoded hologram to the SLM 80, in which the computed and encoded hologram of the required three-dimensional scene is then inscribed.

[0195] For this purpose, a timing controller 66 (TCON) can be implemented in the preprocessing circuit 60. This timing controller 66 is used here to generate control signals, synchronization signals, and/or clock signals, so that the SLM 80 and the source driver 71 can be directly clocked and controlled. Furthermore, the timing controller 66 can also activate general components and circuits in order to drive the SLM 80 and transfer the data into the pixels or pixel cells of the SLM 80. The hologram computation circuits 70 are synchronized in accordance with this control of the SLM 80 for the smooth operation of the SLM 70.

[0196] Furthermore, the preprocessing circuit 60 assumes the overall control of the SLM 80 and components of a holographic display apparatus, which the SLM 80 has, i.e., all electronic or controllable components, for example, at least one light source of an illumination device or a device for deflecting light. A control of active optical elements for modulation and manipulation of incident light waves in the SLM 80 or the holographic display apparatus with the goal of synchronous and efficient operation and interaction is also possible by means of the preprocessing circuit 60.

[0197] The preprocessing circuit 60 only carries out special tasks, in which many functions with respect to calibration of the SLM 80, corrections of the hologram, and adaptation/upgrading of the three-dimensional scene are implemented. This is because at least one preprocessing circuit 60 for activating the at least one hologram computation circuit 70 is required per SLM product or holographic display apparatus. By way of various measures, such as protected non-externally readable data areas (EEPROMs), which are externally writable, but are only internally readable, in the preprocessing circuit 60, encryption technologies, for example, TSL or SSL, can be used in order to implement a mutual authentication of hologram computation circuit 70 and preprocessing circuit 60 for the purpose of an authenticity check between these two circuits 60 and 70 and to encrypt transfer channels. For this purpose, private keys can be stored in the protected area of the preprocessing circuit 60, which are required for decrypting the terminal parameters and programs on the external (or internal) nonvolatile memory 65. The preprocessing circuit 60 and the hologram computation circuit(s) 70 can mutually authenticate one another in this way, to each prove their authenticity. If this authentication were to fail, for example, the respective circuit, preprocessing circuit 60 and/or hologram computation circuit 70, could be put into a special invalid mode. This could have the effect that, for example, a corresponding item of information is overlaid in the SLM 80, the operation of the SLM or a holographic display apparatus is stopped, or the displayed three-dimensional scene is also displayed at a significantly reduced quality. However, these are only a few examples, where other possibilities of an invalid mode are also possible, of course.

[0198] FIG. 3 shows a sequence of a method for normalizing holograms. According to the prior art, buffering of a hologram is necessary to perform a normalization of the complex-valued data of the three-dimensional scene in the context of the encoding step, in order to enable the display of the data on pixels of the SLM having limited resolution. For this purpose, the complete data set, i.e., the complete hologram in full value resolution is required in order to determine the hologram normalization parameters before the normalization can be executed on discrete values. For this purpose, the hologram can be buffered in an external memory or stored in the circuit itself. However, these methods are costly and have a high power consumption.

[0199] To avoid these disadvantages, the buffer memory is avoided in the method according to the invention, so that the complexity and the power consumption of the hologram computation circuit 70 can be reduced by orders of magnitude. The method according to the invention for normalizing a hologram according to FIG. 3 is thus carried out without buffering of the complete data set or the complete hologram.

[0200] A hologram normalization within the meaning of the application can be viewed as the simplest method, for example, the definition of a maximum absolute value of all complex numbers in the hologram, i.e., for example, a maximum magnitude/amplitude. Other normalization methods or combinations thereof are also possible, for example, a normalization based on histograms.

[0201] To implement the hologram normalization in the last step in the hologram computation, the encoding, the preprocessing circuit 60 carries out special analyses, i.e., at least one analysis, on the basis of the data of the three-dimensional scene in order to enable an approximately correct hologram normalization, without the hologram computation circuit 70 requiring a buffer memory or an external memory. However, an absolutely exact normalization of the hologram data is not required, since a small deviation would only result in a barely perceptible variation in the displayed brightness of the hologram. The method for normalizing a hologram is based on an analysis of the incoming data stream. The following described features of the three-dimensional scene are observed in this analysis. The distribution of the object points of the three-dimensional scene is analyzed or assessed with respect to their depth and their lateral distribution in the observation area. Furthermore, the brightness distribution of the object points is analyzed or assessed in combination with the respective depth of the object points in the observation area. In addition, the total number of the object points of the three-dimensional scene is ascertained in order to determine the degree of filling of the scene in the observation area. These items of information can each be analyzed and studied by statistical methods. The analyzed items of information can be stored, for example, in histograms in order to be able to read the relevant parameters for normalizing a hologram efficiently. Of course, it is possible to analyze further statistical data of the three-dimensional scene.

[0202] Due to the analysis of the change of the three-dimensional scene from frame to frame, the change of the hologram normalization parameters to be expected can be estimated. These estimated hologram normalization parameters by the preprocessing circuit 60 are transmitted to an encoding module in the hologram computation circuit 70, which applies the estimated parameters for normalization to the passing hologram data. In this method according to FIG. 3, the computed hologram is therefore not buffered in the hologram computation circuit 70 or an external memory, but rather further processed directly in passage. At the same time, the encoding module ascertains the actual correct value of the hologram normalization parameters on the basis of the passing data of the hologram and returns this value at the end of the present frame to an analysis module 91 in the preprocessing circuit 60. This analysis module 91 uses this correct measured value of the past frame for error assessment and dynamic adaptation, so-called fine tuning, of the hologram normalization parameters in order to improve the renewed estimation for the next frame.

[0203] In this way, an estimation of the new normalization parameters for the hologram for the present frame can be carried out by an analysis of the change of the present three-dimensional scene and use of the known correct hologram normalization parameters of the last frame.

[0204] In general, the following relationships or rules can be defined for the estimation of the normalization parameters for a hologram. These include, for example: [0205] If the three-dimensional scene or sequence of scenes becomes lighter or darker on average in its light intensity during its display from frame to frame, the maximum magnitude is to be increased or reduced, since on average the magnitudes in the hologram increase or decrease. [0206] Additionally, however, the brightness dynamic of the scene is also to be taken into consideration. In order that, for example, a scene which is dark in its light intensity can accordingly also be reproduced dark, the maximum magnitude in the hologram is accordingly to be defined high, i.e., the ratio of scene brightness to maximum brightness is also to be taken into consideration in the selection of the maximum magnitude and is approximately to be the ratio of maximum magnitude of the hologram to set maximum magnitude. [0207] In contrast, if the three-dimensional scene becomes deeper, i.e., more extended, or more compressed, which means that the object points change their distance to the observer, the maximum magnitude of the hologram is accordingly to be increased or reduced.

[0208] These rules or also algorithms for the estimation of the normalization parameters for a hologram only form examples, however, where arbitrary variants and combinations are possible. These can be defined in dependence on the type and the properties of an SLM used.

[0209] Methods of machine learning or artificial intelligence (AI) instead of permanently defined rules can also be applied. For this purpose, in the scope of a training step for various three-dimensional reference scenes, the behavior to be expected can be specified and therefore trained, so that in the phase of the application of the AI with new unknown three-dimensional scenes, good estimated values are ascertained by the AI for the normalization of the hologram. In this embodiment, the estimation of the normalization parameters is executed on the basis of the trained AI model, without having drawn up specific rules.

[0210] After application of the estimated hologram normalization parameters, at the end of the present frame, i.e., after a completed passage of the presently computed hologram, with the aid of the ascertained actual hologram normalization parameters, a comparison is carried out between these two parameters of how good the estimation was. Possible brightness deviations resulting therefrom in the reproduction of the three-dimensional scene to be displayed can still be compensated for by slight variation of the exposure time of the SLM by the at least one light source of an illumination device, since the data have only been written up to this point in the SLM, but the exposure of the hologram in the SLM is only performed thereafter. For the case of an absolutely incorrect estimation of the hologram normalization parameters, for example, the light source, for example a laser, can temporarily not even be put into operation or can be switched off in order to avoid incorrect displays of the three-dimensional scene. Such an incorrect frame can be skipped in this way, so that this frame becomes like a black screen to an observer. Since exact hologram normalization parameters are now known due to the computation of the hologram normalization parameters, the following estimations of the hologram normalization parameters in the illustrated cycle according to FIG. 3 are again nearly correct. Such cases of incorrect displays usually only occur in the event of very abrupt scene changes in the received three-dimensional scenes. Due to the high frame rate of SLMs, omitting a frame, i.e., a black frame, would hardly be perceived by an observer of the displayed three-dimensional scene. A black frame is at least significantly less noticeable or disturbing to an observer than an incorrectly normalized hologram, which can act like a flash.

[0211] A more detailed sequence of the method for normalizing a hologram will be described hereinafter on the basis of FIG. 3. The preprocessing circuit 60, which carries out the main part of the normalization of a hologram, comprises the analysis module 91, using which the normalization of a hologram is carried out. For a normalization of a hologram, present data of a three-dimensional scene to be displayed are provided for a first frame, as can be seen in the top left area of the analysis module 91. The data required for the determination of normalization parameters for the normalization of the hologram associated with this scene are extracted from these data. In this case, the data stream coming into the analysis module 91 is analyzed with respect to the above-mentioned features of the three-dimensional scene, i.e., for example, by determining the object points of the scene with respect to their depth, brightness, color, and their lateral distribution in the observation area, etc. The above-mentioned features of the scene to be analyzed are also to apply here, of course, and are also to be specified without these being mentioned in detail here once again. These extracted features of the three-dimensional scene or the extracted data are thereupon stored in histograms or a memory, so that the relevant parameters of the data can be read or extracted easily and efficiently. Moreover, these data for a following frame are stored in a further memory, so that these data as data of a last or prior frame can also be incorporated in the determination of the hologram normalization parameters for a scene of a following frame. The extracted stored features are now used for an estimation of the normalization parameters for the hologram of the three-dimensional scene. After the estimation of the hologram normalization parameters, present estimated hologram normalization parameters are then provided, which are transferred to an encoding module 92 in one or more hologram computation circuits 70, as shown in FIG. 3. The encoding module 92 then applies these estimated hologram normalization parameters for normalization to the passing hologram data, which are therefore not stored at any location. This means that the hologram is thus not buffered, but rather further processed directly as it passes. Moreover, the encoding module 92 ascertains, during the passage of the hologram, the actual correct value of the hologram normalization parameters on the basis of the passing data. At the end of the frame, this correct value of the hologram normalization parameters is transmitted back to the analysis module 91 of the preprocessing circuit 60 again. After the application of the estimated hologram normalization parameters to the passing hologram, the estimated hologram normalization parameters and the computed correct values of the hologram normalization parameters are compared to one another in the analysis module 91 and it is ascertained how good the estimation of the hologram normalization parameters has been. The deviations resulting therefrom, for example, brightness deviations in the reproduction of the three-dimensional scene, can then be compensated for or remedied via fine tuning, for example, by variation of the exposure time of the SLM by a light source of an illumination device. This is possible since the data of the normalized hologram have already been transferred and inscribed in the SLM, but an exposure for reconstruction of the three-dimensional scene has not yet taken place. The light source could also not be switched on at all to illuminate the SLM, if the deviation should be sufficiently large that the three-dimensional scene is incorrectly reconstructed or displayed.

[0212] After the transmission of the correct normalization parameters for the hologram of the three-dimensional scene to the analysis module 91, these hologram normalization parameters of the preceding frame of a three-dimensional scene are also incorporated in the estimation of the hologram normalization parameters for the next or following frame. The extracted data or features of the three-dimensional scene to be displayed in the next frame are also incorporated in this estimation for the next frame, which are again stored in the histogram or memory, and the data or features of the prior three-dimensional scene. The estimated hologram normalization parameters are transmitted to the encoding module 92 again and applied to the passing hologram data. At the same time, the encoding module 92 ascertains the correct value of the hologram normalization parameters, so that then both values, i.e., the estimated and correctly computed values, are compared to one another and if necessary the deviations are attenuated or eliminated via fine tuning. Due to the analysis of the change of the present three-dimensional scene to be displayed and the use of the correct hologram normalization parameters of the last frame of the scene, in this way an estimation of the new hologram normalization parameters is carried out for the present frame.

[0213] For following frames or three-dimensional scenes to be displayed, the procedure as described is used to perform a normalization of a hologram.

[0214] As can be seen in the hologram computation circuit 70 in FIG. 3, the hologram computation takes place therein, by which a hologram is generated or created. This hologram is transferred to the encoding module 92, in which the hologram normalization parameters are applied to the passing hologram. In this way, an encoded, normalized hologram is generated which is inscribed in the SLM 80.

[0215] A method is shown in FIG. 4, using which the data of the three-dimensional scene to be displayed which are processed or generated in the preprocessing circuit can be converted into a system-independent format or a dimensionless format.

[0216] As known, for example, from US 2016/0132021 A1, object points of a three-dimensional scene to be reconstructed are encoded by means of a holographic display apparatus in subholograms on an SLM. In order to generate the individual subholograms of the object points, for each pixel of the SLM in which the subhologram is encoded, the phase and the amplitude are computed, using which the light used to display the three-dimensional scene is modulated by the SLM. The phase results in this case in particular from parameters such as the distance or the spacing of an object point to be displayed from the SLM, the wavelength and the spacing of the pixels (pixel pitch). Following the computation of the polar coordinates amplitude and phase, a computing step is carried out, namely the transformation of the phase and the amplitude into the Cartesian space having real and imaginary values. This enables the accumulation or the superposition of the computed subhologram with other subholograms in the overall hologram.

[0217] The further foundations for hologram computation with subholograms are not to be described further here. These are known, for example, from US 2016/0132021 A1.

[0218] A reduced object point description is used for the conversion of the preprocessed data in the preprocessing circuit into a system-independent format. For this purpose, a phase profile of a subhologram of an object point is computed as follows, if necessary even in approximated form.

[0219] After data of individual object points of the three-dimensional scene to be displayed are provided with their distances z to the SLM in the preprocessing circuit, according to FIG. 4, the focal length f of a subhologram is computed in accordance with the distance of its object point to be displayed in the scene:

[00007]$f=\frac{\mathrm{dz}}{d-z},$

[0220] wherein z is the distance of the object point to the SLM with positive values in the display of the object point between the SLM and an observer of the scene, and d is the distance of the observer to the SLM. The distance of the object point to the SLM is thus also incorporated in the computation of the focal length f, as shown in FIG. 4.

[0221] The phase of each pixel of the subhologram is then computed using:

[00008]$\Phi \left(r_{\mathrm{xy}}\right)=\frac{2\pi }{\lambda }f\left(1-\sqrt{1+{\left(\frac{r_{\mathrm{xy}}}{f}\right)}^2}\right)+{\Phi }_0,$

[0222] wherein λ is the wavelength of the light used, r.sub.xy is the radius of the respective complex subhologram pixel from the center of the subhologram, and ϕ.sub.0 is the phase offset of the object point.

[0223] It can be established in this case that the actual distance of an observer to the SLM and to the object point is irrelevant for the phase profile of the subhologram of an object point if the focal length is known. The nonlinearities over the depth range of the observation area, in which the three-dimensional scene can be displayed, like the knowledge that, viewed from the observer of the scene, well behind the SLM, the influence of object point shifts on the phase profile in the subhologram is very minor in the depth, while the influence of object point shifts on the phase profile in the subhologram in front of the SLM is large in contrast, also become irrelevant.

[0224] If these variables are now normed, wherein here, for example, the horizontal pixel pitch p.sub.x, abbreviated as p here, or also another value can preferably be used here, the phase of the pixel is calculated using the normed radius R.sub.xy, the normed focal length F, and the normed wavelength L:

[00009]$F=\frac{f}{p}$$L=\frac{\lambda }{p}$$R_{\mathrm{XY}}=\frac{r_{\mathrm{xy}}}{p}$

[0225] using the following formula:

[00010]$\Phi \left(R_{\mathrm{xy}}\right)=2\pi \frac{L}{F}\left(1-\sqrt{1+\frac{R_{\mathrm{xy}}^2}{F^2}}\right)+{\Phi }_0.$

[0226] The normed radius R.sub.xy is a dimensionless value, which is always positive, and varies over the area of the subhologram. It measures the spacing of a pixel on the subhologram from the center of the subhologram. Its value can be permanently assigned to a group of discrete subhologram pixels with the same or a similar radius within the subhologram generation. The value R.sub.XY can also be incorporated as a permanent variable in corresponding implementations of the at least one hologram computation circuit, by which a reduction of the complexity of the at least one hologram computation circuit is enabled and the reusability is increased with varied individual parameters, such as exact wavelength used or exact pixel pitch.

[0227] In this way, only three parameters still remain, which describe the phase profile of the subhologram of an object point of the three-dimensional scene independently of the properties of an SLM used. These three parameters are: [0228] the normed focal length F, the value of which is dimensionless but is signed. This means that the sign is dependent on whether the object point, viewed from the observer, is generated in front of or behind the SLM, for example a convex or concave lens function is written in the subhologram. Moreover, the value of the normed focal length F varies depending on the depth plane of the object point in the observation area. However, the singularity F=0 is avoided. [0229] The normed wavelength L, which is also dimensionless but is always positive. The value of the normed wavelength L only varies in the event of variation or change of the exposure of the SLM, however, and [0230] the phase offset ϕ.sub.0 of the object point.

[0231] It is advantageous to approximate the computation formula indicated above for the phase, in order to reduce the complexity of the computation of the phase. The Taylor series development with termination after the first element results in:

[00011]$\Phi \left(R_{\mathrm{xy}}\right)=2\pi \frac{L}{F}\left(1-\sqrt{1+\frac{R_{\mathrm{xy}}^2}{F^2}}\right)+{\Phi }_0$$\Phi \left(R_{\mathrm{xy}}\right)\approx -2\pi \frac{R_{\mathrm{xy}}^2}{2\mathrm{FL}}+{\Phi }_0$

[0232] A wavelength-normed focal length F′ can now be introduced, with:

[00012]$.Math.F^{\prime }=\mathrm{FL}=\frac{f\lambda }{p^2}$

[0233] The wavelength-normed focal length F′ is thus, like the normed focal length F, a signed dimensionless variable. According to FIG. 4, it can now be computed for each subhologram of the individual object points of the three-dimensional scene. As is apparent in FIG. 4, the wavelength λ of the light used, i.e., the color in which the three-dimensional scene is to be displayed, and the pixel pitch of the SLM are also incorporated in the computation for this purpose.

[0234] These parameters, i.e., the wavelength A used to display the three-dimensional scene, the pixel pitch of the SLM, and also the distance d of the observer to the SLM are then no longer required in the hologram coding by means of the at least one hologram computation circuit.

[0235] The wavelength-normed focal length F′ now permits, for the case of the use of the approximated computation of the phase and with the incorporation of the phase offset ϕ.sub.0, the complete description of the phase profile of the subhologram of an object point.

[0236] These data in the form of a reduced object point description are now provided as a system-independent format in the preprocessing circuit and are transmitted or transferred to the at least one hologram computation circuit to compute the hologram. By means of the at least one hologram computation circuit, the phase of the subhologram of an object point or a hologram is now computed using the formula:

ϕ(R.sub.XY)=−πR.sub.XY.sup.2/F′+ϕ.sub.0.

[0237] The wavelength-normed focal length F′ is therefore the only parameter which influences the relative phase distribution within the subhologram. This fact permits a strong simplification of the circuit parts or computation devices within the at least one hologram computation circuit, since only a division by the wavelength-normed focal length and the addition using the phase offset are used for a radius. If a normed radius R.sub.xy is permanently assigned to a circuit part or computation device within the at least one hologram computation circuit, the factor R.sub.xy.sup.2 can also be defined in the circuit creation, which can mean a strong simplification of the at least one hologram computation circuit.

[0238] At the same time, the wavelength-normed focal length F′ increases a possible reusability of the hologram computation circuit in various holographic display apparatuses upon a variation of parameters, for example, the wavelength used, the distances of the scene and the SLM to the observer, or the aspect ratios of the pixels in the SLM. At the same time, the wavelength-normed focal length F′ increases the efficiency of the transfer, since the advantages of the focal length-scaled description apply.

[0239] The wavelength-normed focal length F′ thus represents a maximum system-independent description of the phase profile of a subhologram of an object point of the three-dimensional scene with simultaneous optimization options in the hologram computation circuit. The phase value of the pixels of the subhologram can now be computed with the aid of many similarly designed circuit parts of the at least one hologram computation circuit, where the circuit parts are each assigned a normed radius R.sub.xy or normed distance of the pixels from the center of the subhologram and their radius or distance can be defined efficiently as a constant. These individual circuit parts now only still contain the division of a constant using the wavelength-normed focal length F′ and the addition using the phase offset ϕ.sub.0.

[0240] An implementation of the at least one hologram computation circuit, which only uses the above-mentioned reduced parameters in the form of a system-independent format at its input interface device, above all the wavelength-normed focal length F′, thus consists of an electronic circuit which can be implemented independently of the specific parameters for an SLM and is thus usable for various types of SLMs having various wavelengths, various distance ranges between the scene, the observer, and the SLM, and different pixel pitch. In this way, it is possible that the hologram computation circuit can be used for various SLMs and various holographic display apparatuses.

[0241] The use of the actual pixel pitch as a norming parameter p in the transfer of the normed focal length is not absolutely necessary. If this value is not used, the advantage still results of more efficient transfer between the preprocessing circuit and hologram computation circuit. In contrast, if the actual pixel pitch is used as a norming parameter or this is corrected in the at least one hologram computation circuit before the subhologram encoding to the actual pixel pitch, the above-described assignment of circuit parts of the at least one hologram computation circuit to the normed radius R.sub.xy can take place permanently, and the at least one hologram computation circuit would support multiple holographic display apparatuses in spite of this permanent assignment.

[0242] The specific parameters of the SLM therefore only have to be transmitted to the preprocessing circuit, which converts the data of the object points of the three-dimensional scene into the described reduced independent object point description or into the system-independent format and transfers them to the at least one hologram computation circuit.

[0243] The use of the wavelength-normed focal length F′ or also the normed focal length F at the interface between the preprocessing circuit and the at least one hologram computation circuit permits more efficient digital data transfer than in the case of the location description of the object point, since the nonlinearities disappear over the depth range of the scene due to this description.

[0244] Of course, the values or data of F and F′ can also be transferred in mathematically derived form, for example, by multiplication with constants and/or transfer of the reciprocal value, i.e., a refractive power instead of a focal length, and in various digital formats to the at least one hologram computation circuit.

[0245] A holographic display apparatus 100 for reconstructing or displaying a three-dimensional scene is shown in principle in a top view in FIG. 5.

[0246] The holographic display apparatus 100 comprises an illumination device, which has a light source 101 for emitting essentially coherent light, an optical system 102, which has at least one optical element, and an SLM 103 as a light-modulating optical element. A hologram is encoded in the SLM 103, which has pixels for light modulation, by means of an apparatus 104. By illuminating the SLM 103 using the essentially coherent light, the light is modulated by the hologram using the information of the three-dimensional scene to be displayed, so that a three-dimensional scene is reconstructed.

[0247] Furthermore, the holographic display apparatus 100 comprises the apparatus 104, which comprises a preprocessing circuit 105 and at least one hologram computation circuit 106, as described above and shown in FIGS. 2 to 4. The preprocessing circuit 105 and the at least one hologram computation circuit 106 are designed as independent or separate circuits and thus form the apparatus 104 as a combination. However, they can also be designed as separate independent circuits, which do not form an apparatus together. These circuits 105 and 106 thus have an array of functions and are configured to compute and encode a computer-generated hologram of a three-dimensional scene and to provide corresponding control signals for the at least one light source 101, the SLM 103, and, in a variant in which it can be regulated, for the optical system 102, as described with respect to FIGS. 2 to 4. For this purpose, the apparatus 104 is connected to these components via communication links 107.

[0248] The holographic display apparatus 100 moreover comprises an observer plane 108. However, this observer plane 108 is not a physically existing permanent plane. Rather, it is virtual and its distance to the SLM 103 can vary with the distance which an eye 109 of an observer has to the SLM 103. A visibility region or observer window 110 is defined in this observer plane 108, which is also virtual. The observer can observe a generated reconstructed three-dimensional scene 111 in the observer region, which can extend between the observer plane 108 and the SLM 103 and additionally beyond, if his eye 109 is at the location of the observer window 110 and he looks through it.

[0249] The three-dimensional scene 111 can be reconstructed here between the observer plane 108 and the SLM 103, for which the hologram is encoded. The three-dimensional scene can also be displayed and visible behind the SLM 103 viewed from the observer plane 108, however. It is also possible that a three-dimensional scene extends over the entire area, thus between the observer plane 108 and the SLM 103 and also behind the SLM 103.

[0250] The apparatus 104 is now designed or configured to carry out a method according to the invention as described above, using which the encoding of the SLM 103 using the computer-generated hologram is carried out by processing data only required once during the preprocessing for computing the hologram of the three-dimensional scene to be displayed by means of a preprocessing circuit and the actual computation of the hologram by means of the data provided by the preprocessing circuit is carried out by at least one hologram computation circuit. According to FIG. 4, the preprocessing circuit 105 provides the preprocessed data in a system-independent format to the at least one hologram computation circuit 106, as disclosed by the method of FIG. 4. Moreover, a normalization of the hologram is carried out by means of the preprocessing circuit 105, as described with respect to FIG. 3.

[0251] The invention is not to be restricted to the exemplary embodiments shown here.

[0252] Combinations of the exemplary embodiments, if possible, are also to be covered. Finally, it is very particularly to be noted that the above-described exemplary embodiments only serve to describe the claimed teaching, but the latter is not to be restricted to the exemplary embodiments.