CN116698361A - Phase calibration system and method for pure phase reflection type liquid crystal spatial light modulator - Google Patents
Phase calibration system and method for pure phase reflection type liquid crystal spatial light modulator Download PDFInfo
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- CN116698361A CN116698361A CN202210181046.2A CN202210181046A CN116698361A CN 116698361 A CN116698361 A CN 116698361A CN 202210181046 A CN202210181046 A CN 202210181046A CN 116698361 A CN116698361 A CN 116698361A
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- 239000004973 liquid crystal related substance Substances 0.000 title claims abstract description 58
- 238000000034 method Methods 0.000 title claims abstract description 17
- 230000003287 optical effect Effects 0.000 claims abstract description 33
- 238000001914 filtration Methods 0.000 claims abstract description 16
- 238000010587 phase diagram Methods 0.000 claims description 6
- 239000004065 semiconductor Substances 0.000 claims description 2
- 239000007787 solid Substances 0.000 claims 1
- 238000001259 photo etching Methods 0.000 abstract description 8
- 238000002474 experimental method Methods 0.000 abstract 1
- 230000001276 controlling effect Effects 0.000 description 3
- 238000010586 diagram Methods 0.000 description 3
- 230000009977 dual effect Effects 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 238000000206 photolithography Methods 0.000 description 2
- 230000003044 adaptive effect Effects 0.000 description 1
- 230000001427 coherent effect Effects 0.000 description 1
- 239000000428 dust Substances 0.000 description 1
- 238000003384 imaging method Methods 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012634 optical imaging Methods 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 238000007493 shaping process Methods 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
- G01M11/00—Testing of optical apparatus; Testing structures by optical methods not otherwise provided for
- G01M11/02—Testing optical properties
- G01M11/0242—Testing optical properties by measuring geometrical properties or aberrations
- G01M11/0271—Testing optical properties by measuring geometrical properties or aberrations by using interferometric methods
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A90/00—Technologies having an indirect contribution to adaptation to climate change
- Y02A90/10—Information and communication technologies [ICT] supporting adaptation to climate change, e.g. for weather forecasting or climate simulation
Abstract
The application discloses a system and a method for generating stable interference fringes by utilizing a pure phase reflection type liquid crystal spatial light modulator, wherein the system comprises the following steps: the device comprises a light source module, a laser collimation filtering beam expanding module, a pure phase reflection type liquid crystal Spatial Light Modulator (SLM) control module and a CCD image acquisition module. The system can generate stable double-hole light spots by loading the gray gradient kinoform on the SLM, replaces the mode of generating the double-hole light spots by using a photoetching mask plate in the traditional physical optical interference experiment, can achieve a final result without using other devices, and is simple and convenient to operate. In addition, compared with the traditional interference systems such as Tasmann-Green, mach-Zehnder and the like, the output interference fringes cannot shake, the calculation of the later fringe movement amount is not affected, and the method has the characteristics of stable operation, flexible control and accurate calculation.
Description
Technical Field
The application belongs to the field of optical imaging, and particularly relates to the field of ghost imaging, in particular to a phase calibration system and method of a pure phase reflection type liquid crystal spatial light modulator.
Background
A liquid crystal spatial light modulator (Liquid Crystal Spatial Light Modulator, abbreviated as LC-SLM) is widely used in the fields of optical holographic projection, laser beam shaping, adaptive optics, coherent wavefront modulation, and the like as an optical diffraction element capable of one-dimensionally or two-dimensionally controlling the intensity, phase, frequency, and the like of an optical wave.
Because the birefringence effect of the liquid crystal spatial light modulator on the light with different wavelengths is different, namely the phase modulation effect on the light with different wavelengths is different, the liquid crystal spatial light modulator needs to be tested and phase calibrated before being used.
At present, the method adopted for the phase calibration of the liquid crystal spatial light modulator is mainly a double-slit interference method, a Mach-Zehnder interference method and a Taman-Green interference method. The double-slit interference light path is more stable relative to the Mach-Zehnder interference light path and the Taman-Green interference light path, and interference fringe shaking is not obvious. In the double-slit interference light path, the traditional mode is to generate double-hole light spots by using a photoetching mask plate, so that the structure is relatively complex and inconvenient to operate by means of other devices, the cost is high, and in addition, the photoetching mask plate can have the problems of inaccurate processing, unsmooth processing and the like, so that the calibration error is relatively large.
Disclosure of Invention
The application aims to solve the problems of the prior art, and provides a phase calibration system and a phase calibration method which are specially used for phase calibration of a pure phase reflection type liquid crystal spatial light modulator, can avoid calibration error problems caused by inaccurate and unsmooth processing brought by using a photoetching mask plate through a relatively simple optical structure, and can obtain interference fringes and obtain a phase-gray curve.
The technical solution for realizing the purpose of the application is as follows: the system comprises a light source module, a laser collimation filtering beam expanding module, a pure phase reflection type liquid crystal spatial light modulator SLM control module and an image acquisition module which are sequentially arranged along an optical axis;
the light source module is used for providing stable single longitudinal mode continuous laser output;
the laser collimation filtering beam expanding module is used for generating uniform light spots which can cover the SLM liquid crystal screen and filter scattered light;
the pure phase reflection type liquid crystal Spatial Light Modulator (SLM) control module is used for controlling loading of an SLM electric signal and performing kinoform projection to generate a double-hole light spot;
the image acquisition module is used for acquiring interference fringe images of the double-hole light spots.
Further, the light source module comprises a single-mode laser and an adjustable optical attenuation sheet which are sequentially arranged along an optical axis, and the thickness of a film on the surface of the adjustable optical attenuation sheet is adjustable, so that the single-mode laser can emit stable continuous laser.
Further, the laser collimation filtering beam expanding module comprises a microscope objective, a pinhole and a lens which are sequentially arranged along an optical axis; the pinhole is located at both the back focal plane of the microscope objective and the front focal plane of the lens.
Further, the pure phase reflection type liquid crystal spatial light modulator SLM control module comprises a half wave plate, a pure phase liquid crystal spatial light modulator SLM, an upper computer and a polaroid; the emergent light of the laser collimation filtering beam expansion module is incident to the pure phase liquid crystal Spatial Light Modulator (SLM) after passing through the half wave plate, and then is incident to the polaroid after being reflected by the pure phase liquid crystal Spatial Light Modulator (SLM); the half wave plate and the polaroid are regulated to make the pure phase liquid crystal spatial light modulator SLM reach the maximum modulation degree, and then the corresponding double-hole light spots are generated by loading the corresponding phase diagram of each gray value on the pure phase liquid crystal spatial light modulator SLM through an upper computer.
Further, the image acquisition module comprises a focusing lens, a CCD camera and an upper computer; the double-hole light spots are converged and interfered by a focusing lens, then an interference fringe image is acquired by a CCD camera, and the interference fringe image is transmitted to the upper computer; changing the gray value of one of the light spots, and measuring the fringe movement amount according to the interference fringe image to obtain a final calibration result.
The calibration method based on the phase calibration system of the pure phase reflection type liquid crystal spatial light modulator comprises the following steps:
step 1, a phase calibration system of a pure phase reflection type liquid crystal spatial light modulator is built;
step 2, adjusting the adjustable optical attenuation sheet and selecting the required optical power;
step 3, adjusting the position of the microscope objective to enable the light spots converged by the microscope objective to be opposite to the pinholes, and filtering to obtain uniform laser light spots;
step 4, loading a phase diagram capable of generating double-hole light spots on a pure phase liquid crystal Spatial Light Modulator (SLM);
step 5, converging the two light spots through a lens to generate interference, and then acquiring interference fringe images by a CCD camera and uploading the interference fringe images to an upper computer;
step 6, changing the gray value of one of the light spots to obtain and record the fringe movement amount corresponding to each gray value;
and 7, performing data processing and calculation to obtain phases corresponding to the gray values through the upper computer, drawing a curve, and completing calibration.
Compared with the prior art, the application has the remarkable advantages that:
1) The application provides a mode of loading corresponding kinoforms on the SLM to generate double-hole light spots, which has simple structure and easy operation compared with the traditional mode of generating double-hole light spots by using a photoetching mask.
2) The use of the photoetching mask plate is reduced, and the cost is lower.
3) Compared with the light spots generated by using a photoetching mask, the light spots generated by adopting the SLM are round and smooth in edges, the interference fringes are uniform in brightness, and the final measurement result is more accurate.
4) Compared with the traditional interference systems such as Thaman-Green, mach-Zehnder and the like, the output interference fringes cannot shake, the calculation of the later fringe movement amount is not affected, and the method has the characteristics of stable operation, flexible control and accurate calculation.
The application is described in further detail below with reference to the accompanying drawings.
Drawings
Fig. 1 is a schematic diagram of a phase calibration optical path system of a pure phase reflective liquid crystal spatial light modulator.
FIG. 2 is a pictorial illustration of the loading on the SLM when the target light field is distributed as a dual aperture spot.
FIG. 3 is a schematic diagram of a target light field as a dual aperture spot.
Fig. 4 is a schematic diagram of a dual-hole structure with gradation, in which the gradation of the right hole is gradually changed from left to right from top to bottom.
Detailed Description
The present application will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present application more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the application.
In one embodiment, referring to fig. 1, a phase calibration system of a pure phase reflective liquid crystal spatial light modulator is provided, where the system includes a light source module 1, a laser collimation filtering beam expanding module 2, a pure phase reflective liquid crystal spatial light modulator SLM control module 3 and an image acquisition module 4 sequentially arranged along an optical axis;
the light source module 1 is used for providing stable single longitudinal mode continuous laser output;
the laser collimation filtering beam expanding module 2 is used for generating uniform light spots which can cover an SLM liquid crystal screen and filter scattered light;
the pure phase reflection type liquid crystal Spatial Light Modulator (SLM) control module is used for controlling loading of an SLM electric signal and performing kinoform projection to generate a double-hole light spot;
the image acquisition module 4 is used for acquiring interference fringe images of the double-hole light spots.
Further, in one embodiment, the light source module 1 includes a single-mode laser 5 and an adjustable optical attenuation sheet 6 sequentially disposed along an optical axis, where the thickness of a film on the surface of the adjustable optical attenuation sheet 6 is adjustable, so that the single-mode laser 5 emits stable continuous laser light.
Here, the optical power attenuation is performed using the variable optical attenuation sheet 6, and the film thickness of the surface of the variable optical attenuation sheet is adjustable, so that the reflectance of the surface is also continuously adjustable.
Here, in one embodiment, the single-mode laser 5 is a green semiconductor pump solid-state laser, and has an emission wavelength of 532nm and a power of 400mW.
Further, in one embodiment, the laser collimation filtering beam expanding module 2 comprises a microscope objective 7, a pinhole 8 and a lens 9 which are sequentially arranged along an optical axis; the pinhole 8 is located at both the back focal plane of the microscope objective 7 and the front focal plane of the lens 9.
In one embodiment, the objective lens is preferably a microscope objective lens 7 with 40 times magnification, and a 25 μm pinhole 8 and a lens 9 are used together to filter scattered light caused by dust or impurities in the air or on optical components, so as to obtain a light spot with uniform light intensity distribution and a diameter of 7 mm.
Further, in one embodiment, the control module 3 of the pure phase reflective liquid crystal spatial light modulator SLM includes a half-wave plate 10, a pure phase liquid crystal spatial light modulator SLM11, an upper computer 13 and a polarizer 14; the outgoing light of the laser collimation filtering beam expansion module 2 enters a pure phase liquid crystal spatial light modulator SLM11 after passing through a half wave plate 10, and then enters a polaroid 14 after being reflected by the pure phase liquid crystal spatial light modulator SLM 11; the half wave plate 10 and the polaroid 14 are adjusted to enable the pure phase liquid crystal spatial light modulator SLM11 to reach the maximum modulation degree, and then a corresponding double-hole light spot is generated by loading a corresponding phase diagram of each gray value on the pure phase liquid crystal spatial light modulator SLM11 through the upper computer 13.
Preferably here, in one of the embodiments, the pure phase liquid crystal spatial light modulator SLM11 is of the LETO type product of HOLOEYE company, germany, with an angle of incidence of no more than ±5°.
Further, in one embodiment, the image acquisition module 4 includes a focusing lens 15, a CCD camera 16, and a host computer 13; the double-hole light spots are converged by a focusing lens 15 and interfere, then a CCD camera 16 collects interference fringe images, and the interference fringe images are transmitted to the upper computer 13; changing the gray value of one of the light spots, and measuring the fringe movement amount according to the interference fringe image to obtain a final calibration result.
In one embodiment, a method for calibrating the phase of a pure phase reflective liquid crystal spatial light modulator is provided, which comprises the following steps:
step 1, a phase calibration system of a pure phase reflection type liquid crystal spatial light modulator is built;
step 2, adjusting the adjustable optical attenuation sheet, and selecting the required optical power (the optical power which does not damage the surface of an optical component and the camera does not overexposure);
step 3, adjusting the position of the microscope objective to enable the light spots converged by the microscope objective to be opposite to the pinholes, and filtering to obtain uniform laser light spots;
step 4, loading a phase diagram which can generate double-hole light spots and is shown in figure 3 and is shown in figure 2 on a pure phase liquid crystal spatial light modulator SLM;
step 5, converging the two light spots through a lens to generate interference, and then acquiring interference fringe images by a CCD camera and uploading the interference fringe images to an upper computer;
step 6, changing the gray value of one of the light spots as shown in fig. 4, obtaining the fringe movement amount corresponding to each gray value and recording;
here, step 6 may be replaced by loading a gray scale map of gradation of one hole pattern in the prepared double holes onto the SLM to obtain and record the fringe movement amount corresponding to each gradation value;
and 7, performing data processing and calculation to obtain phases corresponding to the gray values through the upper computer, drawing a curve, and completing calibration.
In summary, the application proposes a method for loading corresponding kinoforms on the SLM to generate double-hole light spots, which has simple structure and easy operation, reduces the use of the photolithography mask and has lower cost compared with the traditional method for generating double-hole light spots by using the photolithography mask. Compared with the light spots generated by using a photoetching mask, the light spots generated by adopting the SLM are round and smooth in edges, the interference fringes are uniform in brightness, and the final measurement result is more accurate.
The foregoing has outlined and described the basic principles, features, and advantages of the present application. It will be understood by those skilled in the art that the present application is not limited to the embodiments described above, and that the above embodiments and descriptions are merely illustrative of the principles of the present application, and various changes and modifications may be made without departing from the spirit and scope of the application, which is defined in the appended claims.
Claims (8)
1. The phase calibration system of the pure phase reflection type liquid crystal spatial light modulator is characterized by comprising a light source module (1), a laser collimation filtering beam expanding module (2), a pure phase reflection type liquid crystal spatial light modulator SLM control module (3) and an image acquisition module (4) which are sequentially arranged along an optical axis;
the light source module (1) is used for providing stable single longitudinal mode continuous laser output;
the laser collimation filtering beam expanding module (2) is used for generating uniform light spots which can cover an SLM liquid crystal screen and filter scattered light;
the pure phase reflection type liquid crystal Spatial Light Modulator (SLM) control module is used for controlling loading of an SLM electric signal and performing kinoform projection to generate a double-hole light spot;
the image acquisition module (4) is used for acquiring interference fringe images of the double-hole light spots.
2. The phase calibration system of the pure phase reflection type liquid crystal spatial light modulator according to claim 1, wherein the light source module (1) comprises a single-mode laser (5) and an adjustable optical attenuation sheet (6) which are sequentially arranged along an optical axis, and the thickness of a film on the surface of the adjustable optical attenuation sheet (6) is adjustable, so that the single-mode laser (5) can emit stable continuous laser.
3. The phase calibration system of a pure phase reflective liquid crystal spatial light modulator according to claim 2, wherein the single mode laser (5) is a green semiconductor pumped solid state laser.
4. The phase calibration system of a pure phase reflective liquid crystal spatial light modulator according to claim 1, wherein the laser collimation filtering beam expansion module (2) comprises a microscope objective (7), a pinhole (8) and a lens (9) which are sequentially arranged along an optical axis; the pinhole (8) is located at both the back focal plane of the microscope objective (7) and the front focal plane of the lens (9).
5. The phase calibration system of the pure phase reflection type liquid crystal spatial light modulator according to claim 1, wherein the pure phase reflection type liquid crystal spatial light modulator SLM control module (3) comprises a half wave plate (10), a pure phase liquid crystal spatial light modulator SLM (11), an upper computer (13) and a polaroid (14); the emergent light of the laser collimation filtering beam expansion module (2) enters a pure phase liquid crystal Spatial Light Modulator (SLM) (11) after passing through a half wave plate (10), and enters a polaroid (14) after being reflected by the pure phase liquid crystal Spatial Light Modulator (SLM) (11); the half wave plate (10) and the polaroid (14) are adjusted to enable the pure phase liquid crystal Spatial Light Modulator (SLM) (11) to reach the maximum modulation degree, and then a corresponding double-hole light spot is generated by loading a corresponding phase diagram of each gray value on the pure phase liquid crystal Spatial Light Modulator (SLM) (11) through an upper computer (13).
6. The phase calibration system of a pure phase reflective liquid crystal spatial light modulator according to claim 5, characterized in that the pure phase liquid crystal spatial light modulator SLM (11) is of the LETO type product of HOLOEYE company, germany, with an angle of incidence of not more than ±5°.
7. The phase calibration system of a pure phase reflective liquid crystal spatial light modulator according to claim 1, wherein the image acquisition module (4) comprises a focusing lens (15), a CCD camera (16) and a host computer (13); the double-hole light spots are converged by a focusing lens (15) and interfere, then a CCD camera (16) collects interference fringe images, and the interference fringe images are transmitted to the upper computer (13); changing the gray value of one of the light spots, and measuring the fringe movement amount according to the interference fringe image to obtain a final calibration result.
8. Calibration method based on the phase calibration system of the pure phase reflective liquid crystal spatial light modulator according to any one of claims 1 to 7, characterized in that the method comprises the following steps:
step 1, a phase calibration system of a pure phase reflection type liquid crystal spatial light modulator is built;
step 2, adjusting the adjustable optical attenuation sheet and selecting the required optical power;
step 3, adjusting the position of the microscope objective to enable the light spots converged by the microscope objective to be opposite to the pinholes, and filtering to obtain uniform laser light spots;
step 4, loading a phase diagram capable of generating double-hole light spots on a pure phase liquid crystal Spatial Light Modulator (SLM);
step 5, converging the two light spots through a lens to generate interference, and then acquiring interference fringe images by a CCD camera and uploading the interference fringe images to an upper computer;
step 6, changing the gray value of one of the light spots to obtain and record the fringe movement amount corresponding to each gray value;
and 7, performing data processing and calculation to obtain phases corresponding to the gray values through the upper computer, drawing a curve, and completing calibration.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202210181046.2A CN116698361A (en) | 2022-02-25 | 2022-02-25 | Phase calibration system and method for pure phase reflection type liquid crystal spatial light modulator |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202210181046.2A CN116698361A (en) | 2022-02-25 | 2022-02-25 | Phase calibration system and method for pure phase reflection type liquid crystal spatial light modulator |
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