Pixel alignment method of double-space light modulation system and double-space light modulation system

Abstract

The invention discloses a pixel alignment method of a double-space light modulation system and the double-space light modulation system, and the method comprises the steps: encoding the phase information of a light spot original image and the phase information extracted by a virtual lens in a checkerboard form through a phase control technology to generate a reconstructed phase image, and enabling a phase space light modulator to load the reconstructed phase image, the modulated light beam is reflected by a digital micro-mirror device and then is projected on a screen to generate a plurality of light spots, so that rough alignment of the double-space light modulator is realized based on the light spots; furthermore, the digital micro-mirror device constructs double slits to obtain double-slit interference fringes on the projection screen, then the phase space light modulator loads a phase diagram with a phase value of pi at a specified position, and one slit loads an initial phase with a phase value of pi by adjusting the position of the digital micro-mirror device, so that the interference fringes are moved, and the interference fringes are obtained. Therefore, the high-precision pixel alignment is realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of laser projection display, and in particular relates to a pixel alignment method of a dual spatial light modulation system and a dual spatial light modulation system. Background Art

[0002] A dual spatial light modulation system refers to the simultaneous use of two spatial light modulators in an optical system to achieve more complex and flexible light field control. In many laser applications, a dual spatial light modulator cascade is often used to improve the modulation effect, such as increasing the contrast in laser displays, achieving high-precision control of the light field, and simultaneously modulating the amplitude and phase of the light field. If the two spatial light modulators are not pixel-aligned in the laser light path during application, deviations in light field control will occur. Especially in the field of laser imaging, such deviations will cause distortion of the projected image, such as blurring in the bright and dark intersection areas of complex images. Summary of the Invention

[0003] The present invention proposes a pixel alignment method for a dual spatial light modulation system, which uses the double-slit interference principle to achieve pixel alignment of a phase-type spatial light modulator and an amplitude-type spatial light modulator.

[0004] The present invention is achieved by adopting the following technical solutions: A pixel alignment method for a dual spatial light modulation system is proposed. The dual spatial light modulation system includes: A phase spatial light modulator, used to phase modulate the light emitted by the laser light source; A digital micromirror device, used to reflect the phase-modulated light source and project it onto a projection screen; The method comprises: S1: Based on phase control, the light beam modulated by the phase spatial light modulator is reflected by the digital micromirror device and then projected onto the screen to generate multiple light spots; S2: Pixel alignment is performed based on the light spot distribution in the projected image; S3: Use a digital micromirror device to construct a double slit and obtain double slit interference fringes on the projection screen, and load a phase pattern with a phase value of π at a specified position of the phase spatial light modulator; S4: Implement secondary pixel alignment based on the changes in interference fringes on the projection screen.

[0005] In some embodiments of the present invention, step S1 specifically includes: Use the phase recovery algorithm to obtain the phase information of the original image; Extracting phase information of a virtual lens with a set focal length; The phase information of the original image and the phase information extracted by the virtual lens are encoded in a checkerboard format to obtain a reconstructed phase map; wherein the pixel alignment accuracy is limited by the number of pixels occupied by a grid in the checkerboard; The phase spatial light modulator is loaded with the reconstructed phase image, and the micromirrors of the digital micromirror device are kept fully open, so that only the light spots generated by the virtual lens are projected on the screen.

[0006] In some embodiments of the present invention, when the reconstructed phase image is obtained by encoding in a checkerboard form, the method further includes: Fill the white area of ​​the checkerboard with the phase information of the original image; Filling the black areas of the checkerboard with phase information of the virtual lens; and In the reconstructed phase image, the phases of the vertical centerline position and the horizontal centerline position are retained without superimposing the phase information of the virtual lens.

[0007] In some embodiments of the present invention, S4 specifically includes: Adjust the position of the DMD until the interference fringes on the projection screen appear misaligned.

[0008] In some embodiments of the present invention, the method further comprises: The accuracy of the secondary pixel alignment is limited by the number of pixels in the region width with a phase value of π.

[0009] In some embodiments of the present invention, the method further comprises: The length of the region where the phase value is set to π is less than the double-slit length.

[0010] In some embodiments of the present invention, step S3 includes: Horizontal pixel alignment: A vertical double slit is constructed using a digital micromirror device to obtain vertical double slit interference fringes on the projection screen, and a phase pattern with a phase value of π is loaded at a specified vertical position on the phase spatial light modulator; Vertical pixel alignment: A horizontal double slit is constructed using a digital micromirror device to obtain horizontal double slit interference fringes on the projection screen, and a phase pattern with a phase value of π is loaded at a specified horizontal position on the phase spatial light modulator; Tilt correction: Use a digital micromirror device to construct a diagonal double slit to obtain diagonal double slit interference fringes on the projection screen, and load a phase diagram with a phase value of π at a specified diagonal position on the phase spatial light modulator.

[0011] A dual spatial light modulation system is proposed, comprising: A phase spatial light modulator, used to phase modulate the light emitted by the laser light source; A digital micromirror device, used to reflect the phase-modulated light source and project it onto a projection screen; A primary pixel alignment unit is used to generate multiple light spots on the screen after the light beam modulated by the phase spatial light modulator is reflected by the digital micromirror device based on phase control; and to achieve primary pixel alignment according to the distribution of light spots in the projected image; The secondary pixel alignment unit is used to construct a double slit using a digital micromirror device to obtain double slit interference fringes on the projection screen, load a phase diagram with a phase value of π at a specified position of the phase spatial light modulator, and realize secondary pixel alignment according to the changes of the interference fringes on the projection screen.

[0012] In some embodiments of the present invention, the system further comprises: The digital micromirror device adjustment device is used to adjust the position of the digital micromirror device in the primary pixel alignment so that the spot distribution meets the alignment standard; and to adjust the position of the digital micromirror device in the secondary pixel alignment so that the interference fringes on the projection screen are misaligned.

[0013] In some embodiments of the present invention, the secondary pixel alignment unit includes: The horizontal pixel alignment subunit is used to construct a vertical double slit using a digital micromirror device to obtain vertical double slit interference fringes on the projection screen, and to load a phase pattern with a phase value of π at a specified position in the vertical direction of the phase spatial light modulator; The vertical pixel alignment subunit is used to construct a horizontal double slit using a digital micromirror device to obtain horizontal double slit interference fringes on the projection screen, and to load a phase pattern with a phase value of π at a specified horizontal position of the phase spatial light modulator; The tilt correction subunit is used to construct a diagonal double slit using a digital micromirror device to obtain diagonal double slit interference fringes on the projection screen, and load a phase diagram with a phase value of π at a specified diagonal upward position of the phase spatial light modulator.

[0014] In the pixel alignment method for a dual spatial light modulation system proposed by the present invention, the phase information of the original image and the phase information extracted by the virtual lens are encoded in a checkerboard format using phase control technology to generate a reconstructed phase map. This reconstructed phase map is then loaded onto a phase spatial light modulator, causing the modulated light beam to reflect through a digital micromirror device (DMD) and then produce multiple light spots on the projection screen. Because the phase information of the original image generates four first-order diffraction images, half of the light is shifted to the surrounding area of ​​the projected image, avoiding crosstalk caused by the projection light spots. Based on the light spots, rough alignment of the dual spatial light modulators can be achieved, with the alignment accuracy determined by the number of pixels occupied by the checkerboard grid. Furthermore, the DMD constructs a double slit to generate double-slit interference fringes on the projection screen. A phase map with a phase value of π is then loaded onto a specified position of the phase spatial light modulator. By adjusting the position of the DMD, one of the slits is loaded with an initial phase of π, thereby shifting the interference fringes and causing fringe misalignment. This achieves high-precision pixel alignment, with the alignment accuracy determined by the number of pixels in the region with the phase value of π.

[0015] The dual spatial light modulation system proposed in this invention can achieve high-precision pixel alignment of the dual spatial light modulators by observing the changes in the interference fringes. It is simple to operate and convenient to experiment with, and does not require the aid of high-precision auxiliary devices. The pixel matching accuracy is less than 2 pixels. This provides a method reference for using two spatial light modulators to achieve high dynamic range, precise control of the light field, and the construction of optical paths for complex amplitude modulation, thereby improving imaging quality.

[0016] Other features and advantages of the present invention will become more apparent after detailed description of the embodiments of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0018] Figure 1 Schematic diagram of the optical path of the cascaded PLM and DMD to implement the HDR laser projection display system in an embodiment of the present invention; Figure 2 Schematic diagram of the relative position relationship between a phase-type spatial light modulator and an amplitude-type spatial light modulator in a dual spatial light modulation system composed of a phase-type spatial light modulator and an amplitude-type spatial light modulator in an embodiment of the present invention; Figure 3 Flowchart of the phase control method in step S1 of an embodiment of the present invention; Figure 4 The projection image after the reconstructed phase image is loaded into the PLM in the embodiment of the present invention; Figure 5 The light spot distribution on the projection screen when the PLM chip and the DMD chip are not aligned once per pixel in the embodiment of the present invention; Figure 6 The light spot distribution on the projection screen after the PLM chip and the DMD chip are aligned once per pixel in the embodiment of the present invention; Figure 7 Schematic diagram of achieving secondary pixel alignment based on the double-slit interference principle in an embodiment of the present invention; Figure 8 Schematic diagram of the phase diagram of PLM loading in horizontal pixel alignment in an embodiment of the present invention; Figure 9 Schematic diagram of the amplitude of DMD loading in horizontal pixel alignment according to an embodiment of the present invention; Figure 10 The relative position states of the PLM and DMD and the interference fringes in the horizontal pixel alignment (implementing secondary pixel alignment) in an embodiment of the present invention; Figure 11 The relative positions of the PLM and DMD and the interference fringes in horizontal pixel alignment in an embodiment of the present invention (secondary pixel alignment is not implemented); Figure 12 Schematic diagram of the phase diagram of PLM loading in vertical pixel alignment according to an embodiment of the present invention; Figure 13 Schematic diagram of the amplitude of DMD loading in vertical pixel alignment according to an embodiment of the present invention; Figure 14 The relative position states of the PLM and DMD and the interference fringes in the vertical pixel alignment (implementing secondary pixel alignment) in an embodiment of the present invention; Figure 15 The relative positions of the PLM and DMD and the interference fringes in vertical pixel alignment in an embodiment of the present invention (secondary pixel alignment is not implemented); Figure 16 Schematic diagram of the phase diagram of PLM loading in the embodiment of the present invention without tilt correction; Figure 17 Schematic diagram of amplitude of DMD loading without tilt correction in an embodiment of the present invention; Figure 18 The relative position states of the PLM and DMD and the interference fringes in the embodiment of the present invention without tilt correction (implementing secondary pixel alignment); Figure 19 In the embodiment of the present invention, there is no relative position state of the PLM and DMD and interference fringes in the tilt correction (secondary pixel alignment is not achieved); Figure 20 FIG. 4 is a schematic diagram of the pixel alignment method of the dual spatial light modulation system proposed in the present invention. DETAILED DESCRIPTION

[0019] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0020] In the embodiment of the present invention, an HDR (high dynamic range) laser display system implemented by cascading a phase spatial light modulator (PLM) and a digital micromirror device (DMD) is used as an example to illustrate a pixel alignment method.

[0021] The optical path of the dual spatial light modulation system is as follows: Figure 1 As shown in the figure, the laser light source is collimated and expanded to form parallel light, and then phase modulated by PLM to achieve redistribution of the light field, and then the light field is secondary modulated by the DMD laser projection display system to achieve HDR.

[0022] The PLM chip and DMD chip need to be aligned in the vertical, horizontal and tilt directions. The relative position diagram is as follows Figure 2 When the PLM chip and DMD chip are not aligned in the laser light path, the projected image will be blurred, which greatly affects the imaging quality.

[0023] To solve the problem of projected image distortion caused by the misalignment of two spatial light modulators in the laser optical path, the present invention constructs a double slit through a DMD chip, allows the PLM to modulate the light field to cause interference between the double slits, and then completes the pixel alignment of the dual spatial light modulators based on the changes in the interference fringes.

[0024] Experimental preparation: Use a six-axis gimbal to fix the DMD module (DMD chip and TIR prism) to meet the requirements of the DMD module's horizontal, vertical, rotation and tilt adjustment, and the accuracy can reach 3μm. In this way, you only need to adjust the position of the DMD module without changing the position of the PLM, making the experimental operation more convenient. Then follow the steps below to implement pixel alignment, such as Figure 20 As shown: S1: Based on phase control, the light beam modulated by the phase spatial light modulator is reflected by the digital micromirror device to generate multiple light spots on the projection screen.

[0025] In order to achieve rough alignment between the PLM chip and the DMD chip and provide conditions for more efficient and precise matching, the present invention uses phase control technology to allow the PLM modulated light beam to form multiple light spots on the projection screen after being reflected by the DMD chip, and then achieves the first alignment based on the light spot distribution, such as Figure 3 As shown, specifically including: 1. Use the phase recovery algorithm to obtain the phase information of the original spot image.

[0026] This embodiment uses the GS (Gerchberg-Saxton) phase retrieval algorithm to obtain phase information for an original light spot image of m*n pixels with a bright center. First, an initial random phase is set, and the light field distribution on the image plane is obtained through a Fourier transform. After comparison with the target light field, the complex amplitude at the incident plane is obtained through an inverse Fourier transform, and the phase is then extracted for the next iteration. When the light field on the image plane meets the design requirements, the phase of the incident plane is extracted to obtain the phase information of the original light spot image.

[0027] In the following embodiment, m=640 and m=800 are used as examples for description.

[0028] 2. Extract the phase information of a virtual lens with a size of l*l pixels and a focal length equal to the set focal length.

[0029] In the following description, l=32 is taken as an example in this embodiment.

[0030] 3. The phase information of the original spot image obtained by the GS algorithm and the phase information extracted by the virtual lens are encoded in a checkerboard form to obtain a reconstructed phase map.

[0031] Specifically, such as Figure 3 As shown, each grid in the checkerboard is set to 32*32 pixels, and a period of 64*64 pixels is used. The white area in the checkerboard is filled with the phase information of the original light spot image, and the black area is filled with the phase information of the virtual lens. In this way, a reconstructed phase image of a set size is obtained. The purpose of this is to avoid light spot crosstalk that affects the judgment of pixel alignment.

[0032] In the embodiment of the present invention, Figure 3 The position marked by the red dotted line in the reconstructed phase image is the calibration stripe, that is, the phase of the vertical centerline position and the horizontal centerline position is retained without superimposing the phase of the virtual lens. Instead, the phase value is kept at 0. The purpose of this is to divide the phase area into four phase areas so that the relative position of the spot can be better distinguished when observing the spot distribution later.

[0033] 4. Let the PLM chip load the reconstructed phase image and keep the DMD micromirror in the "ON" state.

[0034] Since the phase information of the original spot image in the reconstructed phase image will generate four first-order diffraction images, half of the light is moved to the outer area of ​​the projected image, such as Figure 4 The light spots in the red box are selected, so that there are only light spots on the projection screen that are spaced and staggered from each other and generated by the virtual lens.

[0035] S2: A pixel alignment is performed based on the light spot distribution in the projected image.

[0036] like Figure 5 and Figure 6 As shown in the figure, according to the spot distribution in the projected image and the relative position of the calibration stripes, the position of the DMD module is adjusted using a six-axis gimbal, which can achieve pixel matching with an accuracy within 32*32 pixels and complete the first rough alignment.

[0037] S3: Use a digital micromirror device to construct a double slit and obtain double slit interference fringes on the projection screen, and load a phase diagram with a phase value of π at the specified position of the phase spatial light modulator.

[0038] After completing the rough matching of the PLM chip and the DMD chip, the present invention then realizes the precise alignment of the PLM chip and the DMD chip based on the double-slit interference principle. Figure 7 As shown, the DMD chip constructs a double slit, and the interference effect of the double slit can be obtained by observing the projection screen. Then, a phase difference is loaded at the corresponding position of the PLM chip, which will cause an initial optical path difference between the two slits in the DMD chip, thereby causing the double-slit interference fringes on the projection screen to change. Pixel alignment can be achieved based on the change in the interference fringes on the projection screen.

[0039] In the embodiment of the present invention, the pixel size of the PLM chip is 10.8 um, and the pixel size of the DMD chip is 5.4 um. Therefore, in this embodiment, one pixel of the PLM matches four pixels of the DMD.

[0040] Specifically include: 1. PLM loads the phase diagram with the phase value of π at the specified position, and the other phase values ​​in the phase diagram are 0.

[0041] like Figure 8 、 Figure 12 and Figure 16 As shown, in the phase image loaded by PLM, the area with a phase value of π is located at a specified position (taking the middle position as an example), with a width of two pixels, and the length of the area with a phase value of π (taking 400 pixels as an example) is shorter than the length of the double slit (800 pixels); the phase value at other positions of the phase image is 0.

[0042] 2. The DMD chip has a double slit structure.

[0043] Let the DMD chip load double stripes with a width of 4 pixels, such as Figure 9 (vertical double slits, used to achieve horizontal pixel alignment), Figure 13 (horizontal double slits, used to achieve vertical pixel alignment) and Figure 17As shown in Figure 1 (slanted double slits, used to achieve pixel alignment in the oblique direction), the line spacing between the double stripes is 100 pixels, and one of the stripes is located in the center.

[0044] Guidance based on the following formula: (1) (2) is the height of adjacent micromirrors of the PLM chip The phase difference caused by is the period of the interference fringes, is the movement of the interference fringes. It can be seen that when a slit on the DMD is loaded with an initial phase of π, according to formulas 1 and 2, the initial phase of the upper half of the slit changes from 0 to π, which causes the interference fringes to move half a cycle, resulting in the following Figure 10 、 14 , 18 stripe misalignment phenomenon.

[0045] In this embodiment, the PLM loads a phase diagram with a phase value of π at the middle position, and the stripes at the middle position are used as the alignment standard. When the slit at the middle position of the DMD is loaded with an initial phase with a phase value of π, it indicates that the two spatial light modulators have achieved pixel alignment. At this time, the interference stripes produce a misalignment phenomenon, such as Figure 10 、 14 As shown in Figure 18. If pixel alignment is not achieved, the slit in the middle of the DMD structure cannot load the initial phase with a phase value of π, and the interference fringes will not be misaligned, for example Figure 11 、 15 and 19.

[0046] Of course, in actual applications, the alignment standard is not limited to the middle position. Based on the above idea, any specified position can be achieved.

[0047] S4: Implement secondary pixel alignment based on the changes in interference fringes on the projection screen.

[0048] Based on the idea of ​​step S3, if the interference fringes do not appear to be misaligned, the position of the DMD module is changed by adjusting the six-axis gimbal, and the changes in the interference fringes are observed until the interference fringes appear to be misaligned.

[0049] In this embodiment, the slit has a width of two pixels. Therefore, when pixel alignment is implemented, the pixel matching accuracy is within 2 pixels.

[0050] like Figures 8 to 11As shown, the PLM loads a phase image with a phase value of π in the vertical middle position. The length of the area with the phase value of π is 400 pixels. The DMD constructs a double slit with a vertical length of 800 pixels, one of which is located in the vertical middle position. By adjusting the position of the DMD and observing the interference fringes on the projection screen, the pixels of the PLM chip and the DMD chip can be aligned in the horizontal direction.

[0051] like Figures 12 to 15 As shown, the PLM loads a phase diagram with a phase value of π in the horizontal middle position. The length of the area with the phase value of π is 400 pixels. The DMD constructs a double slit with a horizontal length of 800 pixels, one of which is located in the horizontal middle position. By adjusting the position of the DMD and observing the interference fringes on the projection screen, the pixels of the PLM chip and the DMD chip can be aligned in the vertical direction.

[0052] like Figures 16 to 19 As shown, the PLM loads a phase diagram with a phase value of π at the diagonal position, and the length of the area with the phase value of π is half the length of the diagonal. The DMD constructs a double slit in the diagonal direction, where one slit is located in the diagonal direction and has a length equal to the diagonal length. By adjusting the position of the DMD and observing the interference fringes on the projection screen, the tilt correction of the PLM chip and the DMD chip can be achieved.

[0053] In the above embodiment of the present invention, if no obvious interference fringes appear in the projected image when the DMD is loaded with double slits, the width and spacing of the two bright fringes may be changed.

[0054] In the above embodiment, the length of the area where the phase value of PLM is loaded is half the length of the double slit. The purpose of this is to set the initial phase of only one side of a DMD stripe to π, resulting in a misalignment between the two parts of the stripe, which facilitates the judgment of whether they are aligned.

[0055] Based on the above-mentioned pixel alignment method, the present invention further proposes a dual spatial light modulation system, comprising: A phase spatial light modulator is used to perform phase modulation on the light emitted by a laser light source.

[0056] A digital micromirror device is used to reflect a phase-modulated light source and project it onto a projection screen.

[0057] The primary pixel alignment unit is used to control the phase of the light beam modulated by the phase spatial light modulator and then project it onto the screen to generate multiple light spots after being reflected by the digital micromirror device; and to achieve primary pixel alignment according to the distribution of light spots in the projected image.

[0058] The secondary pixel alignment unit is used to construct a double slit using a digital micromirror device to obtain double slit interference fringes on the projection screen, load a phase diagram with a phase value of π at a specified position of the phase spatial light modulator, and realize secondary pixel alignment according to the changes of the interference fringes on the projection screen.

[0059] The digital micromirror device adjustment device is used to adjust the position of the digital micromirror device in the secondary pixel alignment so that the interference fringes on the projection screen are misaligned.

[0060] In some embodiments of the present invention, the secondary pixel alignment unit includes: The horizontal pixel alignment subunit is used to construct a vertical double slit using a digital micromirror device to obtain vertical double slit interference fringes on the projection screen, and load a phase diagram with a phase value of π at a specified position in the vertical direction of the phase spatial light modulator.

[0061] The vertical pixel alignment subunit is used to construct a horizontal double slit using a digital micromirror device to obtain horizontal double slit interference fringes on the projection screen, and load a phase diagram with a phase value of π at a specified horizontal position of the phase spatial light modulator.

[0062] The tilt correction subunit is used to construct a diagonal double slit using a digital micromirror device to obtain diagonal double slit interference fringes on the projection screen, and load a phase diagram with a phase value of π at a specified diagonal upward position of the phase spatial light modulator.

[0063] The advantage of this system is that high-precision pixel alignment of dual spatial light modulators can be achieved by observing changes in interference fringes. It is simple to operate and convenient to experiment with, and does not require the aid of high-precision auxiliary devices. The pixel matching accuracy is less than 2 pixels, providing a method reference for using two spatial light modulators to achieve high dynamic range, precise control of the light field, and the construction of optical paths for complex amplitude modulation, thereby improving imaging quality.

[0064] There are many implementation methods of the present invention, and all technical solutions formed by equivalent transformation or equivalent transformation fall within the protection scope of the present invention.

[0065] It should be pointed out that the above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by ordinary technicians in this technical field within the essential scope of the present invention should also fall within the scope of protection of the present invention.

Claims

1. A pixel alignment method for a dual spatial light modulation system, the dual spatial light modulation system comprising: A phase spatial light modulator, used to phase modulate the light emitted by the laser light source; A digital micromirror device, used to reflect the phase-modulated light source and project it onto a projection screen; Characterized in that the method comprises: S1: Based on phase control, the light beam modulated by the phase spatial light modulator is reflected by the digital micromirror device and then projected onto the screen to generate multiple light spots; S2: Pixel alignment is performed based on the light spot distribution in the projected image; S3: Use a digital micromirror device to construct a double slit and obtain double slit interference fringes on the projection screen, and load a phase pattern with a phase value of π at a specified position of the phase spatial light modulator; S4: Implement secondary pixel alignment based on the changes in interference fringes on the projection screen.

2. The pixel alignment method of the dual spatial light modulation system according to claim 1, characterized in that: Step S1 specifically includes: The phase information of the original spot image is obtained using the phase recovery algorithm; Extracting phase information of a virtual lens with a set focal length; The phase information of the original spot image and the phase information extracted by the virtual lens are encoded in a checkerboard format to obtain a reconstructed phase map. The pixel alignment accuracy is limited by the number of pixels occupied by a grid in the checkerboard. The phase spatial light modulator is loaded with the reconstructed phase image, and the micromirrors of the digital micromirror device are kept fully open, so that only the light spots generated by the virtual lens are projected on the screen.

3. The pixel alignment method of the dual spatial light modulation system according to claim 2, characterized in that: When the reconstructed phase image is obtained by encoding in a checkerboard form, the method further includes: Fill the white area of ​​the checkerboard with the phase information of the original spot image; Filling the black areas of the checkerboard with phase information of the virtual lens; and In the reconstructed phase image, the phases of the vertical centerline position and the horizontal centerline position are retained without superimposing the phase information of the virtual lens.

4. The pixel alignment method of the dual spatial light modulation system according to claim 1, wherein: S4 specifically includes: Adjust the position of the DMD until the interference fringes on the projection screen appear misaligned.

5. The pixel alignment method of the dual spatial light modulation system according to claim 1, wherein: The method further comprises: The accuracy of the secondary pixel alignment is limited by the number of pixels in the region width with a phase value of π.

6. The pixel alignment method of the dual spatial light modulation system according to claim 1, wherein: The method further comprises: The length of the region where the phase value is set to π is less than the double-slit length.

7. The pixel alignment method of the dual spatial light modulation system according to claim 1, wherein: Step S3 includes: Horizontal pixel alignment: A vertical double slit is constructed using a digital micromirror device to obtain vertical double slit interference fringes on the projection screen, and a phase pattern with a phase value of π is loaded at a specified position in the vertical direction of the phase spatial light modulator; Vertical pixel alignment: A horizontal double slit is constructed using a digital micromirror device to obtain horizontal double slit interference fringes on the projection screen, and a phase pattern with a phase value of π is loaded at a specified horizontal position of the phase spatial light modulator; Tilt correction: Use a digital micromirror device to construct a diagonal double slit to obtain diagonal double slit interference fringes on the projection screen, and load a phase diagram with a phase value of π at a specified diagonal upward position of the phase spatial light modulator.

8. Dual spatial light modulation system, including: A phase spatial light modulator, used to phase modulate the light emitted by the laser light source; A digital micromirror device, used to reflect the phase-modulated light source and project it onto a projection screen; It is characterized by further comprising: A primary pixel alignment unit is used to generate multiple light spots on the screen after the light beam modulated by the phase spatial light modulator is reflected by the digital micromirror device based on phase control; and to achieve primary pixel alignment according to the distribution of light spots in the projected image; The secondary pixel alignment unit is used to construct a double slit using a digital micromirror device to obtain double slit interference fringes on the projection screen, load a phase diagram with a phase value of π at a specified position of the phase spatial light modulator, and realize secondary pixel alignment according to the changes of the interference fringes on the projection screen.

9. The dual spatial light modulation system according to claim 8, wherein: The system further comprises: The digital micromirror device adjustment device is used to adjust the position of the digital micromirror device in the primary pixel alignment so that the spot distribution meets the alignment standard; and to adjust the position of the digital micromirror device in the secondary pixel alignment so that the interference fringes on the projection screen are misaligned.

10. The dual spatial light modulation system according to claim 8, wherein: The secondary pixel alignment unit includes: The horizontal pixel alignment subunit is used to construct a vertical double slit using a digital micromirror device to obtain vertical double slit interference fringes on the projection screen, and to load a phase pattern with a phase value of π at a specified position in the vertical direction of the phase spatial light modulator; The vertical pixel alignment subunit is used to construct a horizontal double slit using a digital micromirror device to obtain horizontal double slit interference fringes on the projection screen, and to load a phase pattern with a phase value of π at a specified horizontal position of the phase spatial light modulator; The tilt correction subunit is used to construct a diagonal double slit using a digital micromirror device to obtain diagonal double slit interference fringes on the projection screen, and load a phase diagram with a phase value of π at a specified diagonal upward position of the phase spatial light modulator.

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