ADD-ON IMAGING MODULE FOR OFF-AXIS RECORDING OF POLARIZATION CODED WAVES

Abstract

The invention relates to an add-on imaging module for the off-axis recording of polarization coded waves, that might be connected to any polarization adapted interferometric system, and which incorporates the first polarization sensitive beam splitter, the first optical system of the module and the detector, wherein the first optical system of the module includes the first imaging system and the linear polarizer.

Claims

1-15. (canceled)

16. An imaging module for the off-axis recording of the polarization coded waves wherein it incorporates gradually from the light source the first polarization sensitive beam splitter adapted to splitting polarization coded waves wherein each of the polarization coded waves propagates in a different direction, the first optical system of the module and the detector, wherein the first optical system of the module includes gradually from the light source the second imaging system, the linear polarizer adapted to projecting the electric field oscillations of the polarization coded waves into the same direction and the first imaging system adapted to project the polarization coded waves onto the detector.

17. The imaging module according to the claim 16 wherein the first polarization sensitive beam splitter is realized as a geometric-phase grating.

18. The imaging module according to the claim 16 wherein the first imaging system contains at least one imaging element with the positive optical power.

19. The imaging module according to the claim 16 wherein the second imaging system contains at least one imaging element with the positive optical power.

20. The imaging module according to the claim 16 wherein the first optical system of the module further contains the quarter-wave plate, which is placed between the first polarization sensitive beam splitter and the linear polarizer.

21. The imaging module according to the claim 16 wherein it incorporates the second optical system of the module, whilst the second optical system of the module is placed in front of the first polarization sensitive beam splitter, and it further contains the second polarization sensitive beam splitter, which is placed between the first polarization sensitive beam splitter and the first imaging system.

22. The imaging module according to the claim 21 wherein it further contains the quarter-wave plate, whilst the quarter wave plate is placed between the second polarization sensitive beam splitter and the linear polarizer.

23. The imaging module according to claim 16 wherein it further contains the quarter-wave plate, which is place between the polarization adapted optical system and the first polarization sensitive beam splitter.

24. A method for the off-axis recording of the polarization coded waves by the imaging module according to any of the preceding claims wherein two polarization coded waves are divided into two directions in the image plane by passage through the first polarization sensitive beam splitter, wherein each of the polarization coded waves propagates in a different direction, two polarization coded waves enter the first optical system of the module, in which the electric field oscillations of the waves are projected into the same direction by the linear polarizer, two linearly polarized waves with the same direction of the electric field oscillations are projected by the first imaging system on the detector, two polarized waves with the same direction of the electric field oscillations interfere at the detector, where the off-axis hologram with the spatial carrier frequency independent of the wavelength is created.

25. The method for the off-axis recording of the polarization coded waves by the imaging module according to the claim 24 wherein the propagation direction of both polarization coded waves is influenced by the imaging system after division of the waves by the first polarization sensitive beam splitter, the second imaging system is designed and positioned with respect to the first polarization sensitive beam splitter in such a way so as to create its image in infinity, two polarization coded waves pass through the linear polarizer that projects their electric field oscillations into the same direction, two linearly polarized waves with the same direction of the electric field oscillations are projected by the first imaging system on the detector, two linearly polarized waves with the same direction of the electric field oscillations interfere at the detector, where the off-axis hologram with the spatial carrier frequency independent of the wavelength is created.

26. The method for the off-axis recording of the polarization coded waves by the imaging module according to the claim 24 wherein two polarization coded waves pass, before impinging on the linear polarizer, through the quarter-wave plate that converts the orthogonal circular polarizations of the waves to the orthogonal linear polarization states, two polarization coded waves pass through the linear polarizer that projects the electric field oscillations of the waves into the same direction, while affecting the amplitude of the waves in dependence on the angular orientation of the linear polarizer.

27. The method for the off-axis recording of the polarization coded waves by the imaging module according to the claim 24 wherein two polarization coded waves are transformed from the image plane to the plane of the polarization sensitive beam splitter by the second optical system of the module, two polarization coded waves are divided into two propagation directions by passing through the polarization sensitive beam splitter, wherein each of the polarization coded waves propagates in a different direction, the propagation direction of both polarization coded waves is further affected by the second polarization sensitive beam splitter, wherein the new propagation direction coincides with the propagation direction of both waves in front of the first polarization sensitive beam splitter, two polarization coded waves enter the first optical system of the module, in which the electric field oscillations of the waves are projected into the same direction by the linear polarizer, two polarized waves with the same direction of the electric field oscillations interfere at the detector, where the off-axis hologram with the spatial carrier frequency independent of the wavelength is created.

28. The method for the off-axis recording of the polarization coded waves by the imaging module according to the claim 27 wherein two polarization coded waves pass, before impinging on the linear polarizer, through the quarter-wave plate that converts the orthogonal circular polarizations of the waves to the orthogonal linear polarization states, two polarization coded waves pass through the linear polarizer that projects the electric field oscillations of the waves into the same direction, while affecting the amplitude of the waves in dependence on the angular orientation of the linear polarizer.

29. The method for the off-axis recording of the polarization coded waves by the imaging module according to the claim 24 wherein the polarization coded waves, possessing the orthogonal linear polarizations at the output of the polarization adapted optical system, pass through the input quarter-wave plate that converts the orthogonal linear polarizations of the waves to the orthogonal circular polarization states.

Description

LIST OF EXEMPLARY EMBODIMENTS OF THE INVENTION

[0031] FIG. 1 illustrates an optical system providing the polarization coded waves and the scheme of the connected add-on imaging module for the recording of the off-axis holograms working with the first polarization sensitive beam splitter, the detector and the first optical system of the module, which is composed of the linear polarizer and the first optical sub-system.

[0032] FIG. 2 illustrates the scheme of the add-on imaging module for the off-axis recording of the polarization coded waves working with the first polarization sensitive beam splitter, the detector and the first optical system of the module, which is composed of the linear polarizer and the first and the second optical sub-system.

[0033] FIG. 3 illustrates the scheme of the add-on imaging module for the off-axis recording of the polarization coded waves working with the first polarization sensitive beam splitter, the detector and the first optical system of the module, which is composed of the quarter-wave plate, the linear polarizer and the first and the second optical sub-system.

[0034] FIG. 4 illustrates an optical system providing the polarization coded waves and the scheme of the connected add-on imaging module for the recording of the off-axis holograms working with the second optical system of the module, the first and the second polarization sensitive beam splitter, the detector and the first optical system of the module, which is composed of the linear polarizer and the first optical sub-system.

[0035] FIG. 5 illustrates the scheme of the add-on imaging module for the off-axis recording of the polarization coded waves working with the second optical system of the module, the first and the second polarization sensitive beam splitter, the detector and the first optical system of the module, which is composed of the linear polarizer and the first optical sub-system.

[0036] FIG. 6 illustrates the scheme of the add-on imaging module for the off-axis recording of the polarization coded waves working with the second optical system of the module, the first and the second polarization sensitive beam splitter, the detector and the first optical system of the module, which is composed of the quarter-wave plate, the linear polarizer and the first optical sub-system.

[0037] FIG. 7 illustrates an optical system providing the polarization coded waves and the scheme of the connected add-on imaging module for recording of the off-axis holograms working with the quarter-wave plate transforming the orthogonal linear polarizations of the signal and reference waves coming from the optical system to the orthogonal circular polarizations.

EXAMPLES OF PREFERRED EMBODIMENTS

[0038] FIG. 1 shows the scheme of the add-on imaging module 3 for the off-axis recording of the polarization coded waves. The add-on imaging module 3 is connected to a polarization adapted system 2 working with the polychromatic, spatially incoherent light source 1. The polarization adapted system 2 divides light emitted by the source 1 into the signal path 2.1 and the reference path 2.2. The measured sample is placed in the object plane of the signal path, while in the object plane of the reference path, the reference sample is placed. The reference sample might be for example a plane mirror, a microscope slide or any other element providing known modulation of the transmitted or reflected wave. Both the signal and reference paths are designed to create images of their object planes at the image plane of the polarization adapted system 2.3. Optical components of the signal and reference path are chosen to provide the same optical path length, i.e. the light needs the same time for passing the signal and reference paths.

[0039] The polarization adapted system 2 is further assumed to provide the polarization coded waves that travel through the paths 2.1 and 2.2. These waves are determined by the Jones vectors J.sub.i, i=1, 2, satisfying the orthogonality condition J.sub.1.sup..Math.J.sub.2=0, where J.sub.i, i=1, 2, is the Hermitian conjugate vector.

[0040] The add-on imaging module 3 is connected at the output of the polarization adapted system 2. The add-on imaging module 3 is composed of the first polarization sensitive beam splitter 4, the first optical system 5 of the module and the detector 6. The first optical system 5 of the module is composed of the first optical sub-system 5.1 and the linear polarizer 9. When connecting the add-on imaging module 3 to the polarization adapted system 2, the image plane 2.3 is set to coincide with the plane of the polarization sensitive beam splitter 4. The first polarization sensitive beam splitter 4 provides the directional separation of the individual light beams originating from the signal path 2.1 and the reference path 2.2 in such a way that the axes of the beams are inclined by the angle 2. The angle 2 is given by the grating equation sin()=/d, where is the wavelength and d denotes the spatial period of the grating.

[0041] The first optical system 5 of the module is composed of the first optical sub-system 5.1. The imaging system 5.1 is designed in such a way that the plane 2.3, i.e. the plane of the polarization sensitive beam splitter 4, is imaged with the lateral magnification m to the image plane of the module 3, which coincides with the detector 6. The first optical system 5 of the module further contains the linear polarizer 9 that projects the electric field oscillations of the waves coming from the signal path 2.1 and the reference path 2.2 into the same direction before the waves hit the detector 6.

[0042] The polarization coded light beams, axes of which form the angle 2 behind the polarization sensitive beam splitter 4, recombine with the mutual angular inclination 2 in the plane of the detector 6. This angular inclination is determined by sin()=/(m.Math.d). The interference of the beams creates the off-axis hologram that is recorded at the detector 6 and its spatial carrier frequency is independent of the wavelength, .sub.N=2/(m.Math.d). The spatial carrier frequency is given by the optical parameters of the module 3. These parameters must be optimized to create the spatial carrier frequency allowing separation of the true holographic image from the non-diffracted light, when the holographic records are processed by the methods of Fourier optics.

[0043] In the preferred embodiment, the signal path 2.1 and the reference path 2.2 share any number of optical components and work in the common-path configuration. The polarization sensitive beam splitter might be represented by the geometric-phase grating that operates on the Pancharatnam-Berry phase and creates the angular separation 2 between the axes of the beams with the left-hand and right-hand circular polarization, while achieving the efficiency higher than 90%. The linear polarizer 9 might be any polarization component that transforms general polarization state to linear polarization (for example polarization circular to linear). The first optical sub-system 5.1 might be composed of any number of optical components such as lenses, lens systems or objectives that satisfy the above defined conditions for recording of the off-axis hologram with the optimal spatial carrier frequency.

[0044] FIG. 2 shows the scheme of the imaging module 3. In this embodiment, the imaging module 3 gradually consists of the first polarization sensitive beam splitter 4, the second optical sub-system 5.2, the linear polarizer 9, the first optical sub-system 5.1 and the detector 6. The optical components of the first optical sub-system 5.1 and the second optical sub-system 5.2 are selected to create parallel rays between both optical systems and transfer the image from the image plane 2.3 to the plane coinciding with the detector 6. Between the first optical sub-system 5.1 and the second optical sub-system 5.2 the linear polarizer 9 is inserted that ensures projection of the electric field oscillations of the polarization coded waves into the same direction. The mutual position of the linear polarizer 9 and the first optical sub-system 5.1 may vary in different embodiments.

[0045] FIG. 3 shows the scheme of the imaging module 3. In this embodiment, the imaging module 3 gradually consists of the first polarization sensitive beam splitter 4, the second optical sub-system 5.2, the quarter-wave plate 10, the linear polarizer 9, the first optical sub-system 5.1 and the detector 6. The optical components of the first optical sub-system 5.1 and the second optical sub-system 5.2 are selected to create parallel rays between both optical systems and transfer image from the image plane 2.3 to the plane coinciding with the detector 6. Between the second optical sub-system 5.2 and the linear polarizer 9 the quarter-wave plate 10 is inserted, ensuring transformation of the orthogonal circular polarization states of the polarization coded waves to their orthogonal linear polarizations. The linear polarizer 9 projects the electric field oscillations of the polarization coded waves into the same direction. The mutual position of the linear polarizer 9, the first optical sub-system 5.1 and the second optical sub-system 5.2 may vary in different embodiments. The combination of the quarter-wave plate 10 and the linear polarizer 9 allows controlling the amplitude of the transmitted waves and optimizing the contrast of the interference patterns.

[0046] FIG. 4 shows the scheme of the imaging module 3 for the off-axis recording of the polarization coded waves. The imaging module 3 is connected to the polarization adapted optical system 2, which is further connected to the polychromatic and spatially incoherent light source 1. The light emitted by the source 1 enters the polarization adapted system 2, where it is divided into the signal path 2.1 and the reference path 2.2. Both the signal and the reference imaging paths are designed to image their object planes to the same image plane 2.3. The optical components of the signal and reference path are selected to provide the same optical path length, i.e. the light needs the same time for passing the signal and reference path.

[0047] The polarization adapted system 2 is further assumed to provide the polarization coded waves that travel through the paths 2.1 and 2.2. These waves are determined by the Jones vectors J.sub.i, i=1, 2, satisfying the orthogonality condition J.sub.1.sup..Math.J.sub.2=0, where J.sub.1.sup. is the Hermitian conjugate vector.

[0048] The add-on imaging module 3 is connected at the output of the polarization adapted system 2. The add-on imaging module 3 gradually consists of the second optical system 7 of the module, the first polarization sensitive beam splitter 4, the second polarization sensitive beam splitter 8, the first optical system 5 of the module and the detector 6. The second optical system 7 of the module is placed between the image plane 2.3 and the first polarization sensitive beam splitter 4 and might be composed of any optical components. The optical components of the second optical system 7 of the module are selected in such a way that the image from the image plane 2.3 is transferred to infinity and the parallel rays hit the first polarization sensitive beam splitter 4.

[0049] The first polarization sensitive beam splitter 4 is advantageously realized as a geometric-phase grating that introduces the angular separation 2 between the orthogonally polarized light beams coming from the signal path 2.1 and the reference path 2.2. The angle 2 is given by the grating equation sin =/d, where is the wavelength and d denotes the grating period. The second polarization sensitive beam splitter 8 is advantageously realized as a geometric-phase grating that creates the opposite angular inclination of the polarization coded waves compared to that introduced by the first polarization sensitive beam splitter 4, and compensates its diffractive dispersion. In this way, the orthogonally polarized beams are laterally shifted according to their wavelength behind the polarization sensitive beam splitter 8, while the propagation directions of the beams remain the same as those prior to entering the first polarization sensitive beam splitter 4.

[0050] The first optical system 5 of the module might be composed of any optical components ensuring that the image of the plane 2.3 is created at the image plane of the imaging module 3 coinciding with the detector 6. The first optical system 5 of the module is composed of the first optical sub-system 5.1 and the linear polarizer 9. The linear polarizer 9 projects the electric field oscillations of the polarization coded waves coming from the signal path 2.1 and the reference path 2.2 into the same direction, before the waves hit the detector 6.

[0051] The polarization coded collimated light beams, axes of which form the angle 2 behind the polarizing sensitive beam splitter 4, recombine with the mutual angular inclination 2 in the plane of the detector 6. In the paraxial approximation, the angle is given by =L.Math./(f.Math.d), where L is the distance between the first polarization sensitive beam splitter 4 and the second polarization sensitive beam splitter 8 and f denotes the focal length of the first optical sub-system 5.1. The interference of the beams creates the off-axis hologram that is recorded at the detector 6 and its spatial carrier frequency .sub.N=2L/(f.Math.d) is independent of the wavelength. The spatial carrier frequency is given by the optical parameters of the imaging module 3. These parameters must be optimized to create spatial carrier frequency allowing separation of the true holographic image from the non-diffracted light, when the holographic records are processed by the methods of Fourier optics.

[0052] In the preferred embodiment, the signal path 2.1 and the reference path 2.2 share any number of optical components and work in the common-path configuration. The first polarization sensitive beam splitter 4 and the second polarization sensitive beam splitter 8 might be realized as geometric-phase gratings working on the Pancharatnam-Berry phase. The first polarization sensitive beam splitter 4 deflects incident collimated wave with the left-hand circular polarization by the angle while changing its polarization state to the right-hand circular polarization. The incident wave with the right-hand circular polarization is deflected by the angle while its polarization state is changed to the left-hand circular polarization. Hence, the propagation directions of the beams with the orthogonal circular polarizations are inclined by the angle 2 when the beams leave the first polarization sensitive beam splitter 4. The second polarization sensitive beam splitter 8, realized as a geometric-phase grating, works similarly to the polarization sensitive beam splitter 4 and introduces the directional inclination of the collimated beams according to the handedness of their circular polarization. Consequently, the beam incident on the first polarization sensitive beam splitter 4 with the left-hand polarization maintains both the polarization state and the propagation direction when it leaves the second polarization sensitive beam splitter 8. The same situation occurs in the case of the beam incident on the first polarization sensitive beam splitter 4 with the right-hand circular polarization. The second polarization sensitive beam splitter 8 compensates the diffractive dispersion of the first polarization sensitive beam splitter 4; hence the orthogonally polarized beams are laterally shifted according to their wavelength behind the polarization sensitive beam splitter 8, while the propagation directions of the beams remain the same as those prior to entering the first polarization sensitive beam splitter 4. The individual imaging systems of the module might be composed of any number of optical components such as lenses, lens systems or objectives that satisfy the above defined conditions for recording of the off-axis hologram with the optimal spatial carrier frequency.

[0053] FIG. 5 shows the scheme of the imaging module 3. In this embodiment, the imaging module 3 is composed of the second optical system 7 of the module, the first polarization sensitive beam splitter 4, the second polarization sensitive beam splitter 8, the linear polarizer 9, the first optical sub-system 5.1 and the detector 6. The first polarization sensitive beam splitter 4 introduces the angular separation 2 between the orthogonally polarized light beams coming from the signal path 2.1 and the reference path 2.2. The angle is given by the grating equation sin =/d. The second polarization sensitive beam splitter 8 creates the opposite angular inclination of the polarization coded waves compared to that introduced by the first polarization sensitive beam splitter 4, and compensates its diffractive dispersion. In this way, the orthogonally polarized beams are laterally shifted according to their wavelength behind the polarization sensitive beam splitter 8, while the propagation directions of the beams remain the same as those prior to entering the first polarization sensitive beam splitter 4. The linear polarizer 9 projects the electric field oscillation of the polarization coded waves into the same direction.

[0054] FIG. 6 shows the scheme of the imaging module 3. In this embodiment, the imaging module 3 gradually consists of the second optical system 7 of the module, the first polarization sensitive beam splitter 4, the second polarization sensitive beam splitter 8, the quarter-wave plate 10, the linear polarizer 9, the first optical sub-system 5.1 and the detector 6. The optical components of the second optical system 7 of the module are selected in such a way that the image from the image plane 2.3 is transferred to infinity and the parallel rays hit the first polarization sensitive beam splitter 4.

[0055] The first polarization sensitive beam splitter 4 introduces the angular separation 2 between the orthogonally polarized light waves coming from the signal path 2.1 and the reference path 2.2. The angle 2 is given by the grating equation sin =/d. The second polarization sensitive beam splitter 8 creates the opposite angular inclination of the polarization coded waves compared to that introduced by the first polarization sensitive beam splitter 4, and compensates its diffractive dispersion. In this way, the orthogonally polarized beams are laterally shifted according to their wavelength behind the polarization sensitive beam splitter 8, while the propagation directions of the beams remain the same as those prior to entering the first polarization sensitive beam splitter 4.

[0056] Between the second polarization sensitive beam splitter 8 and the linear polarizer 9 the quarter-wave plate 10 is inserted that converts the light waves coded in the orthogonal circular polarizations to the waves with the orthogonal linear polarizations. The linear polarizer 9 projects the electric field oscillations of the polarization coded waves into the same direction. The combination of the quarter-wave plate 10 and the linear polarizer 9 allows controlling the amplitude of the transmitted waves and optimizing the contrast of the interference patterns.

[0057] FIG. 7 shows the scheme of the imaging module 3 for the off-axis recording of the polarization coded waves. The imaging module 3 is connected to the polarization adapted optical system 2, which is further connected to the polychromatic and spatially incoherent light source 1. The light emitted from the source 1 enters the polarization adapted system 2, where it is divided into the signal path 2.1 and the reference path 2.2. Both the signal and reference imaging paths are designed to image their object planes to the same image plane 2.3. The optical components of the signal and reference path are selected to provide the same optical path length, i.e. the light needs the same time for passing the signal and reference path.

[0058] The polarization adapted system 2 is further assumed to provide the polarization coded waves that travel through the paths 2.1 and 2.2. These waves are determined by the Jones vectors J.sub.i, i=1, 2, satisfying the orthogonality condition J.sub.1.sup..Math.J.sub.2=0, where J.sub.1.sup. is the Hermitian conjugate vector.

[0059] Provided that the light waves are coded into the orthogonal linear polarizations at the output of the polarization adapted system 2, the input quarter-wave plate 11 is used to transform the orthogonal linear polarizations of the waves into the orthogonal circular polarization states. If the polarization adapted system provides waves with the orthogonal circular polarization, the quarter-wave plate 11 is omitted and the light waves enter the imaging module 3.

[0060] The imaging module 3 might be connected to any polarization adapted optical system 2 providing the signal and reference waves that are orthogonally polarized in the basis of the circular or linear polarization states.

LIST OF REFERENCE SIGNS

[0061] 1 . . . light source [0062] 2 . . . polarization adapted interferometric system [0063] 2.1 . . . imaging signal path [0064] 2.2 . . . imaging reference path [0065] 2.3 . . . image plane [0066] 3 . . . imaging module [0067] 4 . . . first polarization sensitive beam splitter [0068] 5 . . . first optical system of the module [0069] 5.1 . . . first optical sub-system [0070] 5.2 . . . second optical sub-system [0071] 6 . . . detector [0072] 7 . . . second optical system of the module [0073] 8 . . . second polarization sensitive beam splitter [0074] 9 . . . linear polarizer [0075] 10 . . . quarter-wave plate [0076] 11 . . . input quarter-wave plate