CN214375860U

CN214375860U - Separation system of spatial light modulator zero-order light

Info

Publication number: CN214375860U
Application number: CN202120223569.XU
Authority: CN
Inventors: 胡巍; 邝文辉; 寿倩; 陆大全; 刘明瀚
Original assignee: South China Normal University
Current assignee: South China Normal University
Priority date: 2021-01-26
Filing date: 2021-01-26
Publication date: 2021-10-08
Anticipated expiration: 2031-01-26

Abstract

The utility model discloses a piece-rate system of spatial light modulator zero order light, include: the spatial light modulator comprises a wave plate, a first convex lens, a second convex lens, a spatial light modulator and a third convex lens; the spatial light modulator is positioned on a second focal plane of the third convex lens, and the spatial light modulator and the 4f system are not coaxial; the incident laser sequentially passes through the wave plate, the first convex lens and the second convex lens, is subjected to phase modulation by the spatial light modulator, is reflected and passes through the third convex lens. The embodiment of the utility model provides a form the 4f system through wave plate, first convex lens and second convex lens, incident laser forms the light beam of collimation after through the 4f system, forms non-coaxial zero order light focus and reappears like the focus after the adjustment of collimated light beam through spatial light modulator, reduces the interference of zero order light to it is simple to improve imaging quality and experimental apparatus. The embodiment of the utility model provides a but wide application in space light field regulation and control field.

Description

Separation system of spatial light modulator zero-order light

Technical Field

The utility model relates to a space light field regulation and control field especially relates to a piece-rate system of spatial light modulator zero order light.

Background

The holographic projection display technology is widely applied to the field of 3D stereoscopic display, and is characterized in that a kinoform of a target image is generated by encoding through a computer, then the kinoform is loaded on a spatial light modulator, and imaging is performed by utilizing laser diffraction. The diffraction imaging of the spatial light modulator can completely record and reconstruct the wave front of a three-dimensional object, and provides all depth information required by a human visual system, which is incomparable with other projection display modes. However, due to the inherent pixel structure and limited fill factor of the spatial light modulator, the device structure thereof may form dead and active regions, and zero-order interference caused by the reflection of the laser light by the dead region part of the spatial light modulator cannot be avoided; when the coded kinoform is loaded on the spatial light modulator, the coded kinoform is loaded on a living area part of the spatial light modulator, and a dead area part has no light modulation function, so that the zero-order light is separated from a reproduced image, and the imaging quality can be improved.

At present, there is a method of separating zero-order light generated by a spatial light modulator from a reproduced image, and then eliminating the zero-order light by filtering; however, the zero-order light focus and the reproduced image focus are still at the collinear position, and the zero-order light focus is close to the reproduced image focus, so that the elimination of the zero-order light not only affects the imaging quality of the reproduced image, but also loses the energy of the re-phenomenon.

SUMMERY OF THE UTILITY MODEL

In view of this, an object of the embodiments of the present invention is to provide a separation system for zero-order light of a spatial light modulator, which can achieve non-coaxial separation of a zero-order light focus and a reproduced image focus, reduce interference of the zero-order light, improve imaging quality, and simplify an experimental apparatus.

The embodiment of the utility model provides a separation system of spatial light modulator zero order light, include: the spatial light modulator comprises a wave plate, a first convex lens, a second convex lens, a spatial light modulator and a third convex lens; the wave plate, the first convex lens and the second convex lens form a 4f system, the spatial light modulator is located at a second focal plane of the third convex lens, and the spatial light modulator is not coaxial with the 4f system; and the incident laser sequentially passes through the wave plate, the first convex lens and the second convex lens, is subjected to phase modulation by the spatial light modulator, is reflected and passes through the third convex lens.

Optionally, the wave plate is a half wave plate.

Optionally, the spatial light modulator is a liquid crystal spatial light modulator.

Optionally, an angle between an axis of the spatial light modulator and an axis of the 4f system is within a preset range.

Optionally, a focal length of the first convex lens is smaller than or equal to a focal length of the second convex lens.

Optionally, the focal length of the first convex lens is 100mm, and the focal length of the second convex lens is 600 mm.

Optionally, a focal length of the third convex lens is located between a focal length of the first convex lens and a focal length of the second convex lens.

Optionally, the focal length of the third convex lens is 500 mm.

Implement the embodiment of the utility model provides a include following beneficial effect: the embodiment of the utility model provides a form the 4f system through wave plate, first convex lens and second convex lens, incident laser forms the light beam of collimation after through the 4f system, forms non-coaxial zero order light focus and reappears like the focus after the adjustment of collimated light beam through spatial light modulator, reduces the interference of zero order light to it is simple to improve imaging quality and experimental apparatus.

Drawings

Fig. 1 is a schematic structural diagram of a separation system of zero-order light of a spatial light modulator according to an embodiment of the present invention.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.

As shown in fig. 1, the present invention provides a system for separating zero-order light of a spatial light modulator, including: a wave plate P, a first convex lens F1, a second convex lens F2, a spatial light modulator SLM and a third convex lens F3; wherein the wave plate P, the first convex lens F1 and the second convex lens F2 form a 4F system, the spatial light modulator SLM is located at the second focal plane of the third convex lens F3, and the spatial light modulator SLM is not coaxial with the 4F system; incident laser emitted by the laser L sequentially passes through the wave plate P, the first convex lens F1 and the second convex lens F2, is reflected after being subjected to phase modulation by the spatial light modulator SLM and passes through the third convex lens F3, the focus point of zero-order light is on the focal plane P1 of the third convex lens F3, and the focus point of the phenomenon is on the plane P2.

Specifically, a basic mode Gaussian beam output by a laser L passes through a wave plate P to generate horizontal polarized light, then passes through a 4F system consisting of a first convex lens F1 and a second convex lens F2 which are arranged in parallel to generate a collimated Gaussian beam, a spatial light modulator SLM is arranged at any position of the Gaussian beam and a front focal plane of a third convex lens F3, a modulation phase is loaded on the spatial light modulator SLM, the collimated Gaussian beam is reflected after being modulated by the phase of the spatial light modulator SLM, and the reflected beam is divided into two parts of non-coaxial zero-order light and a second phenomenon after passing through the third convex lens F3; wherein the zero order light is focused on the back focal plane of the third convex lens F3, and the reproduced image is focused on the focal plane delta Z away from the third convex lens F3.

It should be noted that the phase loaded by the spatial light modulator SLM is composed of two parts, one part is the phase of the original re-phenomenon, and the other part is the phase of the offset divergent spherical wave to be superimposed. Let the phase of the random recurrence be

Will shift the phase of the diverging spherical wave

And (3) superposing the phase distribution of the kinoform, wherein the superposed phase is as follows:

where k is 2 pi/λ, λ is an incident wavelength, r is a radius of a divergent spherical wave, a is an offset amount in the x direction, b is an offset amount in the y direction, a is a range of 5.5mm or less, b is a range of 5.5mm or less, and the offset amount is a focal point with respect to the third convex lens F3.

As will be understood by those skilled in the art, the calculation formula of Δ Z can be expressed as:

where r denotes the loaded spherical wave radius, z denotes the distance of the spatial light modulator SLM from the third convex lens F3, F₃The focal length of the third convex lens F3 is shown.

The working principle of the system is as follows: due to the pixel structure of the spatial light modulator SLM, the dead zone part of the SLM can not modulate incident light, so that zero-order light is formed; and the live portion is capable of modulating the incident beam to produce a reconstructed image. The loaded kinoform only acts on the living area part, and has no influence on zero-order light generated by the dead area; when the offset divergent spherical wave factor is not superimposed on the kinoform, the reproduced image and the focal plane of the zero-order light are both at the F3 focal plane; when the offset spherical wave factor is superposed on the kinoform, the superposed offset spherical wave factor also only acts on the living zone, and has no influence on zero-order light generated by the dead zone, and the offset spherical wave factor acts on the reproduced image to enable the focal plane of the reproduced image to be at the P2 plane, so that the introduction of the offset enables the focal point of the zero-order light to be not coaxial with the focal point of the reproduced image.

Optionally, the wave plate is a half wave plate.

Optionally, the spatial light modulator is a liquid crystal spatial light modulator. The liquid crystal on silicon has the advantages of high integration level, high resolution, large aperture opening ratio, small size, fast response and the like, and is widely applied to holographic optical systems.

Optionally, an angle between an axis of the spatial light modulator and an axis of the 4f system is within a preset range. Wherein the predetermined range of the included angle is related to the property of the spatial light modulator.

Optionally, the focal length of the third convex lens is 500 mm.

Implement the embodiment of the utility model provides a include following beneficial effect: the utility model discloses a wave plate, first convex lens and second convex lens form 4f system, and incident laser forms the light beam of collimation after through 4f system, forms non-coaxial zero order light focus and reappears like the focus after the adjustment of collimated light beam through spatial light modulator, reduces the interference of zero order light to it is simple to improve imaging quality and experimental apparatus.

The above system will be described with reference to a specific embodiment, where the laser is a he — ne laser, the wavelength is 532nm, the spatial light modulator is a liquid crystal spatial light modulator, the wave plate is a half wave plate, the focal length of the first lens is 100mm, the focal length of the second lens is 600mm, the focal length of the third lens is 500mm, and the distance between the spatial light modulator and F2 is 300mm and is on the focal plane of F3. Respectively loading a first kinoform and a second kinoform on a spatial light modulator, wherein the first kinoform is notSuperposing a kinoform of the divergent spherical wave factors; the second kinoform is a kinoform superposed with the divergent spherical wave, wherein the spherical wave radius of the superposed divergent spherical wave is 3000mm, the offset in the x direction is 5mm, the offset in the y direction is 0mm, and the phase of the loaded divergent spherical wave is calculated according to the formula (2)

Laser emitted by the helium-neon laser forms an image after passing through the system; the first kinoform without the overlapped divergent spherical wave factor forms an image at a focal plane P1 of the third lens, and zero-order light and a re-focusing point of the re-focusing phenomenon are at the same position and cannot be separated; the second kinoform superposed with the divergence spherical wave factor forms an image on a plane P2, a rectangular light spot is formed on the plane P2, and a light spot is arranged in the rectangular light spot, wherein the light spot is a focus point of the re-phenomenon, the rectangular light spot is a diffraction light spot of zero-order light on the plane P2, at the moment, the focus point of the zero-order light generated by the reflection of the spatial light modulator is still on the focal plane P1 of the third lens, and the focus point of the re-phenomenon is on the plane P2. Therefore, when the kinoform superimposes and shifts the divergent spherical wave factor in the spatial light modulator, the zero-order light and the focal plane of the reproduced image are well shifted and the focal point is not coaxial.

While the preferred embodiments of the present invention have been described, the present invention is not limited to the embodiments, and those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of the present invention, and such equivalent modifications or substitutions are intended to be included within the scope of the present invention as defined by the appended claims.

Claims

1. A system for separating zero order light from a spatial light modulator, comprising: the spatial light modulator comprises a wave plate, a first convex lens, a second convex lens, a spatial light modulator and a third convex lens; the wave plate, the first convex lens and the second convex lens form a 4f system, the spatial light modulator is located at a second focal plane of the third convex lens, and the spatial light modulator is not coaxial with the 4f system; and the incident laser sequentially passes through the wave plate, the first convex lens and the second convex lens, is subjected to phase modulation by the spatial light modulator, is reflected and passes through the third convex lens.

2. The system of claim 1, wherein the waveplate is a half waveplate.

3. The system for separating zero order light of a spatial light modulator according to claim 1, wherein said spatial light modulator is a liquid crystal spatial light modulator.

4. The system for separating zero order light of a spatial light modulator according to claim 1, wherein an angle between an axis of the spatial light modulator and an axis of the 4f system is within a preset range.

5. The system of claim 1, wherein the focal length of the first convex lens is less than or equal to the focal length of the second convex lens.

6. The system of claim 5, wherein the first convex lens has a focal length of 100mm and the second convex lens has a focal length of 600 mm.

7. The system of claim 5, wherein the focal length of the third convex lens is between the focal length of the first convex lens and the focal length of the second convex lens.

8. The system for separating zero order light of a spatial light modulator according to claim 7, wherein the focal length of the third convex lens is 500 mm.