PIXEL TRANSFORM METHOD FOR JPEG/MPEG COMPRESSION OF DOUBLE PHASE-AMPLITUDE CODED HOLOGRAMS

Abstract

There is provided a pixel transform method for JPEG/MPEG compression of double phase-amplitude coded holograms. According to an embodiment, a hologram compression method transforms a hologram represented by a complex number into a hologram represented only by a phase, rearranges pixels of the transformed hologram, and compresses the rearranged hologram. Pixels of a DPAC hologram are rearranged before the DPAC hologram is compressed in a standardized image/video compression technique, so that a high frequency component is prevented from occurring when a hologram is compressed. Accordingly, hologram quality degradation occurring when a DPAC hologram is used in a standardized image/video compression technique can be prevented.

Claims

1. A hologram compression method comprising: a step of transforming a hologram represented by a complex number into a hologram represented only by a phase; a step of rearranging pixels of the transformed hologram; and a step of compressing the rearranged hologram.

2. The hologram compression method of claim 1, wherein the step of transforming comprises transforming the hologram represented by the complex number into a sum of two phase maps, dividing each phase map on a pixel basis, and arranging pixels in a checkerboard pattern not to neighbor one another.

3. The hologram compression method of claim 2, wherein the step of transforming comprises transforming the hologram by applying double phase-amplitude coding (DAPC).

4. The hologram compression method of claim 1, wherein the step of rearranging comprises rearranging pixels to reduce a high frequency component when the hologram is compressed.

5. The hologram compression method of claim 4, wherein the step of rearranging comprises rearranging pixels such that pixels divided on the same phase map neighbor one another.

6. The hologram compression method of claim 5, wherein the step of rearranging comprises dividing the hologram into a plurality of areas and rearranging pixels divided on the same phase map in the divided areas.

7. The hologram compression method of claim 6, wherein the step of rearranging comprises sorting and rearranging the pixels divided on the same phase map, based on arranged rows or columns.

8. The hologram compression method of claim 1, further comprising: a step of reconstructing the compressed hologram by decompressing; and a step of inversely rearranging pixels of the decompressed hologram.

9. The hologram compression method of claim 1, wherein the step of compressing comprises compressing the rearranged hologram according to JPEG standards or MPEG standards.

10. A hologram compression system comprising: a processor configured to transform a hologram represented by a complex number into a hologram represented only by a phase, to rearrange pixels of the transformed hologram, and to compress the rearranged hologram; and a storage unit configured to provide a necessary storage space to the processor.

11. A hologram reconstruction method comprising: a step of decompressing a hologram which is compressed by transforming a hologram represented by a complex number into a hologram represented only by a phase and then rearranging pixels; and a step of inversely rearranging pixels of the decompressed hologram.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] For a more complete understanding of the present disclosure and its advantages, reference is now made to the following description taken in conjunction with the accompanying drawings, in which like reference numerals represent like parts:

[0024] FIG. 1 is a view illustrating a DPAC algorithm to which an embodiment of the disclosure is applicable;

[0025] FIG. 2 is a view illustrating a DPAC algorithm to which an embodiment of the disclosure is applicable;

[0026] FIG. 3 is a view illustrating JPEG standard compression of a DPAC hologram;

[0027] FIG. 4 is a view illustrating JPEG standard compression of a DPAC hologram;

[0028] FIG. 5 is a view illustrating a hologram compression method applying DPAC pixel transform (DPT) and a hologram reconstruction method applying inverse DPT (IDPT) according to an embodiment of the disclosure;

[0029] FIG. 6 is a view illustrating a DPT process;

[0030] FIG. 7 is a view illustrating an IDPT process;

[0031] FIG. 8 is a view illustrating a result of an optical experiment regarding a hologram compression method according to an embodiment of the disclosure; and

[0032] FIG. 9 is a view illustrating a hologram compression/reconstruction system according to another embodiment of the disclosure.

DETAILED DESCRIPTION

[0033] Hereinafter, the disclosure will be described in more detail with reference to the accompanying drawings.

[0034] Embodiments of the disclosure provide a method for compressing by rearranging pixels of a double phase-amplitude coding (DPAC) hologram. The disclosure relates to a technology for rearranging pixels of a DPAC hologram to prevent a high frequency component from occurring during compression, prior to compressing the DPAC hologram in a standardized image/video compression technique.

[0035] FIG. 1 is a view illustrating a DPAC algorithm to which an embodiment of the disclosure is applicable, and FIG. 2 is a view illustrating a DPAC algorithm to which an embodiment of the disclosure is applicable. DPAC is an algorithm for transforming hologram information represented by a complex number into a hologram represented only by phase information. A DPAC hologram may be obtained by transforming a hologram represented by a complex number into a sum of two phase maps (.sub.1, .sub.2) through the equation shown in FIG. 1, and dividing the respective phase maps (.sub.1, .sub.2) on a pixel basis and arranging pixels in a checkerboard pattern not to neighbor each other as shown in FIG. 2.

[0036] FIG. 3 illustrates an example of directly applying JPEG standard compression to a DPAC hologram. As shown in FIG. 3, when JPEG compression is directly applied to a DPAC hologram, it appears that there is no big difference between the original hologram image and a compressed hologram image. However, referring to a result of reconstructing the compressed hologram to numerically show how the compressed hologram is viewed on a 3D space, it may be identified that color data is lost in the reconstructed compressed hologram as shown in FIG. 4.

[0037] FIG. 5 is a view illustrating a hologram compression method applying DPAC pixel transform (DPT) and a hologram reproduction method applying inverse DPT (IDPT).

[0038] In order to compress a hologram, DPT is performed prior to compressing a DPAC hologram as shown on the left side of FIG. 5. That is, DPT is performed on the DPAC hologram and then JPEG standard compression or MEPG standard compression is performed. DPT will be described in detail with reference to FIG. 6.

[0039] In order to reconstruct a compressed hologram, IDPT is performed after a DPAC hologram is decompressed as shown on the right side of FIG. 5. IDPT will be described in detail with reference to FIG. 7.

[0040] FIG. 6 is a view illustrating a DPT process. DPT is rearranging pixels to reduce a high frequency component when a DPAC hologram is compressed. Specifically, in DPT, pixels are rearranged such that pixels divided on the same phase map neighbor one another.

[0041] Specifically, pixels of a phase map .sub.1 and pixels of a phase map .sub.2 which are alternately arranged in a checkerboard pattern are rearranged as shown in the lower portion of FIG. 6, such that pixels of .sub.1 neighbor one another and pixels of .sub.2 neighbor one another.

[0042] In FIG. 6, pixels of the DPAC hologram are rearranged in four divided areas. That is, 1) pixels in the odd-numbered column among the pixels of .sub.1 are rearranged in an upper area of the left side of the DPAC hologram, 2) pixels in the odd-numbered column among the pixels of .sub.2 are rearranged in a lower area of the left side of the DPAC hologram, 3) pixels in the even-numbered column among the pixels of .sub.2 are rearranged in an upper area of the right side of the DPAC hologram, and 4) pixels in the even-numbered column among the pixels of .sub.1 are rearranged in a lower area of the right side of the DPAC hologram.

[0043] However, the above-described rearrangement method is merely an example and a change may be made thereto. For example, pixels may be divided into two divided areas, such that pixels of .sub.1 are rearranged in the left area and pixels of .sub.2 are rearranged in the right area, or pixels of .sub.1 are rearranged in the upper area and pixels of .sub.2 are rearranged in the lower area.

[0044] Furthermore, pixels may be divided into 8 divided areas or 16 divided areas. In this case, the technical ideal of the disclosure may be applied.

[0045] FIG. 7 is a view illustrating an IDPT process. As shown in FIG. 7, IDPT is a process of arranging pixels of .sub.1 and pixels of .sub.2 alternately in a checkerboard pattern by inversely rearranging pixels in the opposite way to the re-arrangement according to DPT in FIG. 6.

[0046] FIG. 8 illustrates a result of an optical experiment regarding a hologram compression method according to an embodiment of the disclosure. FIG. 8 illustrates a result of reconstructing an original hologram (1K resolution, 5.9 MB) for which JPEG compression has been directly performed, and a result of reconstructing a hologram that has been compressed after applying DPT according to an embodiment of the disclosure. It can be identified that color data which is lost when JPEG compression is directly applied to a hologram in a related-art method is preserved and compression performance is enhanced.

[0047] FIG. 9 is a view illustrating a configuration of a hologram compression/reconstruction system according to another embodiment of the disclosure. As shown in FIG. 9, the hologram compression/reconstruction system according to another embodiment may be implemented by a computing system including a communication unit 110, an output unit 120, a processor 130, an input unit 140, and a storage unit 150.

[0048] The communication unit 110 is a communication interface for connecting to an external network or an external device, and transmits and receives a hologram to be compressed or to be reconstructed. The output unit 120 is an output means for displaying a result of computing by the processor 130, and the input unit 140 is a user interface for receiving a user command and transmitting a user command to the processor 130.

[0049] The processor 130 compresses a hologram or reconstructs a compressed hologram according to the procedure shown in FIG. 5. The storage unit 150 provides a storage space necessary for functions and operations of the processor 130.

[0050] Up to now, a hologram compression method applying DPT and a hologram reconstruction method applying IDPT have been described in detail with reference to preferred embodiments.

[0051] In the above-described embodiments, pixels of a DPAC hologram are rearranged before the DPAC hologram is compressed in a standardized image/video compression technique, so that a high frequency component is prevented from occurring when a hologram is compressed.

[0052] Accordingly, a high frequency component of the DPAC hologram is transformed into a low frequency, so that loss of high frequency information occurring in related-art DCT-based compression can be avoided, and color quality degradation of the DPAC hologram occurring in a related-art compression process can be prevented.

[0053] The compression method and the reconstruction method described above may be applied to various commercial tools and platforms, and may be used in various applications such as streaming, and compression and reconstruction processes may be performed in real time.

[0054] The technical concept of the disclosure may be applied to a computer-readable recording medium which records a computer program for performing the functions of the apparatus and the method according to the present embodiments. In addition, the technical idea according to various embodiments of the disclosure may be implemented in the form of a computer readable code recorded on the computer-readable recording medium. The computer-readable recording medium may be any data storage device that can be read by a computer and can store data. For example, the computer-readable recording medium may be a read only memory (ROM), a random access memory (RAM), a CD-ROM, a magnetic tape, a floppy disk, an optical disk, a hard disk drive, or the like. A computer readable code or program that is stored in the computer readable recording medium may be transmitted via a network connected between computers.

[0055] In addition, while preferred embodiments of the present disclosure have been illustrated and described, the present disclosure is not limited to the above-described specific embodiments. Various changes can be made by a person skilled in the at without departing from the scope of the present disclosure claimed in claims, and also, changed embodiments should not be understood as being separate from the technical idea or prospect of the present disclosure.