Multi-wavelength dual-beam calibration method and apparatus for liquid crystal variable phase delay devices

Abstract

This invention discloses a multi-wavelength dual-beam calibration method and apparatus for a liquid crystal variable phase retarder (LCVR). The apparatus includes a laser-driven white light source, an optical fiber, a cemented doublet collimating lens, an aperture, a filter wheel, a linear polarizer, the LCVR to be calibrated, a Savart plate, a cemented doublet composite image mirror, a detector, a rotation control mechanism, a temperature controller, and a liquid crystal controller. This invention enables calibration of the LCVR phase retardation at different temperatures and wavelengths, meeting the wavelength requirements of various astronomical polarization observations. By constructing a dual-beam optical path and calibration algorithm, it effectively eliminates the problem of large errors in calibration data caused by fluctuations in the intensity of the calibration light source, improving calibration stability and accuracy. Using a Savart plate to form orthogonal dual beams of polarization that are incident on the detector's focal plane at the same angle avoids image distortion between the two beams and image quality degradation as the beam splitting angle increases, while also reducing data processing difficulty.

Description

Technical Field

[0001] This invention belongs to the field of astronomical polarization detection technology, and specifically relates to a multi-wavelength dual-beam calibration method and apparatus for a liquid crystal variable phase delayer. Background Technology

[0002] In astronomical research, polarization measurements can obtain polarization information in the light from astronomical targets, which can then be used to study and analyze the physical properties and important characteristic parameters of the observed targets. Polarization detection plays an important role in research fields such as exoplanet detection and characterization, solar magnetic field measurement, circumstellar disk observation, and blazar monitoring.

[0003] Liquid Crystal Variable Retarder (LCVR), as an electrically controlled polarization element, differs from traditional crystal retarders primarily in that its phase delay is variable. By altering the driving voltage applied to the LCVR, its phase delay can be changed according to research needs, enabling precise polarization modulation for different wavelengths. Furthermore, LCVRs offer advantages such as no mechanical movement required during operation (static modulation), fast response speed (milliseconds), and low-voltage drive (0–25V). Since the phase delay generated by the electronic control of the LCVR is closely related to its device temperature, operating wavelength, and driving voltage, multi-wavelength calibration of the LCVR to obtain phase delay data corresponding to different driving voltages at different temperatures and wavelengths is crucial. This is an important prerequisite for subsequent multi-wavelength polarization modulation and polarization detection based on LCVR. For nighttime astronomical polarization detection, the LCVR temperature can be set between 15–20°C; for solar polarization detection, the LCVR temperature can be set between 42–45°C.

[0004] Chinese Patent Publication No. CN 108534993 A discloses a method and system for detecting the polarization characteristics of a liquid crystal variable phase retarder (LCVR). The method and system described in this invention are based on a Mueller matrix ellipsometer, requiring the Mueller matrix of the LCVR to be tested to be obtained first, followed by calculation of the phase retardation. This process is relatively complex. Furthermore, the LCVR lacks a temperature control device, and the retardation characteristics of the LCVR to be tested are affected by temperature changes.

[0005] Chinese Patent Publication No. CN 108303238 A discloses a spectral phase delay calibration system for a liquid crystal phase variable retarder (LCVR). This system employs a single-beam optical path design, and the calculated LCVR phase delay is related to the maximum light intensity during calibration detection. Therefore, the calibration results are easily affected by fluctuations in the intensity of the calibration light source. Furthermore, the system lacks an LCVR temperature control device, meaning the delay characteristics of the LCVR under test are affected by temperature changes. Summary of the Invention

[0006] To address the challenges of achieving high stability and automated calibration of the phase delay of LCVRs at different temperatures and wavelengths, this invention proposes a multi-wavelength dual-beam calibration method and apparatus for liquid crystal variable phase delay devices used in astronomical polarization detection.

[0007] To achieve the above objectives, the present invention provides a multi-wavelength dual-beam calibration method for a liquid crystal variable phase retarder, comprising the following steps:

[0008] Step 1: The laser-driven white light source is coupled through an optical fiber to form a broadband point light source. This point light source is located at the focal point of the double cemented collimating lens. After collimation, it forms parallel light. An aperture is used to limit the incident light aperture. Then, the ultraviolet light in the calibration light is filtered out by a pre-filter (to prevent the LCVR liquid crystal from being damaged by ultraviolet radiation).

[0009] Step 2: Narrowband filters of different wavelengths are installed on the filter wheel. By controlling the rotation of the filter wheel, one of the filters is placed in the optical path for calibration wavelength selection. The incident light passes through the filter.

[0010] Step 3: The incident light passes sequentially through a linear polarizer, the LCVR to be calibrated, and a Savart plate, generating two beams with orthogonal polarization states through the Savart plate. The azimuth angle of the transmission axis of the linear polarizer is set to θ, the azimuth angle of the fast axis of the LCVR to be calibrated is set to θ+45°, and the azimuth angles of the two transmission axes of the Savart plate are set to θ and θ+90° respectively, where θ can be any angle.

[0011] Step 4: The two beams are received by the detector focal plane after passing through the double-gel composite mirror. Received beam 1 is the polarized light corresponding to the azimuth angle of the Savart plate's transmission axis at θ, and received beam 2 is the polarized light corresponding to the azimuth angle of the Savart plate's transmission axis at θ+90°.

[0012] Furthermore, based on Mueller's calculations, the Stokes vector S corresponding to beam 1 and beam 2... out,1 and S out,2 Write them as follows:

[0013]

[0014] In the formula, M Savart This is the Mueller matrix of the Savart plate, where θ and θ+90° are its two transmission axis azimuths, M LCVR Here is the Mueller matrix of the LCVR to be calibrated, θ+45° is its fast axis azimuth angle, δ is its phase delay, and λ is the Mueller matrix of the LCVR to be calibrated. i T is the wavelength of the i-th filter. j It is the j-th temperature of LCVR, V kIt is the k-th drive voltage value of the LCVR, V k =kΔV, k = 0, 1, 2, ..., ΔV is the voltage step size, M Polarizer This is the Mueller matrix of the linear polarizer, θ is its transmission axis azimuth angle, and S in The Stokes vector of the incident unpolarized calibration light: S in =(I,Q,U,V) T =I0(1,0,0,0) T I represents the total intensity, Q and U represent the two linearly polarized components, V represents the circularly polarized component, T represents the transpose, and I0 is the incident light intensity.

[0015] Step 5: Set and keep the temperature of the LCVR to be calibrated constant, change the driving voltage applied to the LCVR to be calibrated, starting from 0V and gradually increasing it in a certain voltage step, and use the detector to synchronously record the intensity image of the dual beams at each voltage step point.

[0016] Furthermore, the detector only responds to intensity signals, and the intensities of the two beams measured by the detector are calculated as follows:

[0017]

[0018] In the formula, I1 and I2 are the light intensities of beam 1 and beam 2, respectively, I0 is the incident light intensity, δ is the phase retardation of LCVR, and λ i T is the wavelength of the i-th filter. j It is the j-th temperature of LCVR, V k It is the k-th drive voltage value of the LCVR, V k =kΔV, k = 0, 1, 2, ..., ΔV is the voltage step size.

[0019] Step 6: Calculate the phase delay of the LCVR to be calibrated at different driving voltages under the current temperature and calibration wavelength by combining the intensity data of the two beams;

[0020] Furthermore, through numerical calculation, the phase delay of the LCVR to be calibrated, calculated from the dual-beam intensity data received by the joint detector, is:

[0021]

[0022] In the formula, δ is the phase delay of the LCVR, and λ i T is the wavelength of the i-th filter. j It is the j-th temperature of LCVR, V k It is the k-th drive voltage value of the LCVR, V k=kΔV, k = 0, 1, 2, ..., ΔV is the voltage step size, and I1 and I2 are the light intensities of beam 1 and beam 2, respectively.

[0023] Step 7: Control the filter wheel to rotate to other filters in sequence, and repeat steps 5 to 6 to calibrate the phase delay of LCVR at different temperatures and wavelengths.

[0024] To achieve the above objectives, the present invention also provides a multi-wavelength dual-beam calibration device for a liquid crystal variable phase delay device, comprising the following parts: a laser-driven white light source, an optical fiber, a cemented doublet collimating lens, an aperture, a pre-filter, a filter wheel, a linear polarizer, an LCVR to be calibrated, a Savart plate, a cemented doublet composite image mirror, a detector, a rotation control mechanism, a temperature controller, and a liquid crystal controller. Wherein:

[0025] The calibration wavelength is selected using a filter wheel, the incident light is polarized using a linear polarizer, a Savart plate is used as a dual-beam analyzer, an intensity image of the dual beams is received using a detector, the temperature of the LCVR to be calibrated is set and kept constant using a temperature controller, and the driving voltage applied to the LCVR to be calibrated is changed using an LCD controller.

[0026] Furthermore, in the calibration device, the azimuth angle of the transmission axis of the linear polarizer is set to θ, the azimuth angle of the fast axis of the LCVR to be calibrated is set to θ+45°, and the azimuth angles of the two transmission axes of the Savart plate are set to θ and θ+90° respectively, where θ can be any angle.

[0027] The beneficial effects of this invention are as follows:

[0028] 1. The calibration method and apparatus proposed in this invention can calibrate the phase delay of LCVR at different temperatures and wavelengths. Furthermore, the number of filters installed on the filter wheel and the center wavelength can be increased, decreased, or replaced according to different research needs, meeting the requirements of various astronomical polarization observations for working wavelengths, and are flexible and convenient to use.

[0029] 2. The calibration method and apparatus proposed in this invention can effectively eliminate the problem of large errors in calibration data caused by fluctuations in the intensity of the calibration light source by constructing a dual-beam optical path and calibration algorithm, which is beneficial to improving calibration stability and calibration accuracy.

[0030] 3. The present invention uses a Savart plate to form a beam splitting angle of 0° between two polarized orthogonal double beams. This ensures that the two beams are incident on the focal plane of the detector at the same angle, avoiding the image distortion between the two beams and the degradation of image quality as the beam splitting angle increases when using a Wollaston prism (which typically has a beam splitting angle of 1° to 20°). It also reduces the difficulty of data processing.

[0031] 4. The calibration method and device proposed in this invention can achieve integrated control of the rotation control mechanism, temperature controller, LCD controller and detector through a self-developed LabVIEW electronic control program, so that the entire calibration process can be automated, reducing human interference and shortening the calibration time. Attached Figure Description

[0032] Figure 1 This is the flowchart of the multi-wavelength dual-beam calibration method for liquid crystal variable phase delay devices proposed in this invention.

[0033] Figure 2 This is a schematic diagram of the multi-wavelength dual-beam calibration device for the liquid crystal variable phase delay proposed in the embodiment;

[0034] Figure reference numerals: 1: Laser-driven white light source; 2: Optical fiber; 3: Double-cemented collimating lens; 4: Aperture; 5: Front filter; 6: Filter wheel; 7: Linear polarizer; 8: LCVR to be calibrated; 9: Savart plate; 10: Double-cemented composite imager; 11: Detector; 12: Stepper motor; 13: Temperature controller; 14: Liquid crystal controller. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0036] This invention is one of the results of the National Natural Science Foundation of China (Youth Fund Project) (Grant No. 11703058), the Strategic Priority Research Program on Space Science (Phase II) of the Chinese Academy of Sciences (Grant No. XDA15011100), and the Space Science Mission Concept Research Project (Grant No. XDA15072102).

[0037] The method described in this invention includes the design of a multi-wavelength dual-beam calibration method for liquid crystal variable phase delay (LCVR), and a calibration device. The calibration method and device proposed in this invention can calibrate the phase delay of LCVR at different temperatures and wavelengths, laying the foundation for subsequent research on multi-wavelength polarization modulation and polarization detection based on LCVR.

[0038] The multi-wavelength dual-beam calibration method for the liquid crystal variable phase delay device of the present invention is as follows: Figure 1 As shown, it includes the following steps:

[0039] Step 1: The laser-driven white light source is coupled through an optical fiber to form a broadband point light source. This point light source is located at the focal point of the double cemented collimating lens. After collimation, it forms parallel light. An aperture is used to limit the incident light aperture, and then the ultraviolet light in the calibration light is filtered out by a pre-filter.

[0040] Step 2: Narrowband filters of different wavelengths are installed on the filter wheel. By controlling the rotation control mechanism (preferably a stepper motor in this embodiment), the filter wheel can be rotated to place one of the filters in the optical path for calibration wavelength selection. The incident light passes through the filter.

[0041] Step 3: The incident light passes sequentially through a linear polarizer, the LCVR to be calibrated, and a Savart plate, generating two beams with orthogonal polarization states through the Savart plate. For ease of experimentation and data processing, in this embodiment, θ = 0° is preferred. Therefore, the azimuth angle of the transmission axis of the linear polarizer is set to 0°, the azimuth angle of the fast axis of the LCVR to be calibrated is set to 45°, and the azimuth angles of the two transmission axes of the Savart plate are set to 0° and 90°, respectively.

[0042] Step 4: The two beams are received by the focal plane of the detector after passing through the double-gel composite mirror. Received beam 1 is the polarized light corresponding to the azimuth angle of the Savart plate's transmission axis at 0°, and received beam 2 is the polarized light corresponding to the azimuth angle of the Savart plate's transmission axis at 90°.

[0043] Furthermore, based on Mueller's calculations, the Stokes vector S corresponding to beam 1 and beam 2... out,1 and S out,2 Write them as follows:

[0044]

[0045] In the formula, M Savart This is the Mueller matrix of the Savart plate, where 0° and 90° are its two transmission axis azimuths, M LCVR Here is the Mueller matrix of the LCVR to be calibrated, 45° is its fast axis azimuth angle, δ is its phase delay, and λ is the Mueller matrix of the LCVR to be calibrated. i T is the wavelength of the i-th filter. j It is the j-th temperature of LCVR, V k It is the k-th drive voltage value of the LCVR, V k =kΔV, k = 0, 1, 2, ..., ΔV is the voltage step size, M Polarizer This is the Mueller matrix of the linear polarizer, where 0° is the azimuth angle of its transmission axis, and S... in The Stokes vector of the incident unpolarized calibration light: S in =(I,Q,U,V) T =I0(1,0,0,0) TI represents the total intensity, Q and U represent the two linearly polarized components, V represents the circularly polarized component, T represents the transpose, and I0 is the incident light intensity.

[0046] Step 5: Use a temperature controller to set and keep the temperature of the LCVR to be calibrated constant, and use an LCD controller to change the driving voltage applied to the LCVR to be calibrated, starting from 0V and gradually increasing it in a certain voltage step. Use a detector to synchronously record the intensity image of the dual beams at each voltage step point.

[0047] Furthermore, the detector only responds to intensity signals, and the intensities of the two beams measured by the detector are calculated as follows:

[0048]

[0049] In the formula, I1 and I2 are the light intensities of beam 1 and beam 2, respectively, I0 is the incident light intensity, δ is the phase retardation of LCVR, and λ i T is the wavelength of the i-th filter. j It is the j-th temperature of LCVR, V k It is the k-th drive voltage value of the LCVR, V k =kΔV, k = 0, 1, 2, ..., ΔV is the voltage step size.

[0050] Step 6: Calculate the phase delay of the LCVR to be calibrated at different driving voltages under the current temperature and calibration wavelength by combining the intensity data of the two beams;

[0051] Furthermore, through numerical calculation, the phase delay of the LCVR to be calibrated, calculated from the dual-beam intensity data received by the joint detector, is:

[0052]

[0053] In the formula, δ is the phase delay of the LCVR, and λ i T is the wavelength of the i-th filter. j It is the j-th temperature of LCVR, V k It is the k-th drive voltage value of the LCVR, V k =kΔV, k = 0, 1, 2, ..., ΔV is the voltage step size, and I1 and I2 are the light intensities of beam 1 and beam 2, respectively.

[0054] Step 7: Control the filter wheel to rotate to other filters in sequence, and repeat steps 5 to 6 to calibrate the phase delay of LCVR at different temperatures and wavelengths.

[0055] In this embodiment, the specific structure of the calibration device is as follows: Figure 2As shown, the calibration device includes a laser-driven white light source 1, an optical fiber 2, a cemented doublet collimating lens 3, an aperture 4, a pre-filter 5, a filter wheel 6, a linear polarizer 7, an LCVR to be calibrated 8, a Savart plate 9, a cemented doublet image-combining mirror 10, a detector 11, a stepper motor 12, a liquid crystal controller 13, and a temperature controller 14. Specifically, the filter wheel is used to select the calibration wavelength, the linear polarizer is used to polarize the incident light, the Savart plate is used as a dual-beam analyzer, the detector is used to receive the intensity images of the two beams, the temperature controller is used to set and maintain the temperature of the LCVR to be calibrated, and the liquid crystal controller is used to change the driving voltage applied to the LCVR to be calibrated.

[0056] The laser-driven white light source 1 is a broadband light source with a working wavelength covering 170–2500 nm. After being coupled out through optical fiber 2, it forms a broadband point light source with an output power of 25 mW.

[0057] The doublet collimating lens 3 has a focal length range of f = 100–500 mm and is used to collimate a wide-band point light source into parallel light. The aperture of the stop 4 has a range of 10–20 mm.

[0058] The pre-filter 5 operates at a starting wavelength of 400nm, which can filter out ultraviolet light with wavelengths less than 400nm in the calibration light, thus protecting the LCVR 8 to be calibrated.

[0059] The number and center wavelength of the filters installed on the filter wheel 6 can be increased, decreased, or replaced according to different research needs. In this embodiment, eight filters are installed, with the center wavelengths of filters 1 to 8 being 450nm, 500nm, 550nm, 600nm, 650nm, 700nm, 750nm, and 800nm, respectively. The filter wheel 6 is first rotated to filter 1 by the stepper motor 12.

[0060] The transmission axis azimuth angle of the linear polarizer 7 is set to 0° (preferably 0° in this embodiment for ease of experimentation and data processing), and the extinction ratio is >10. 5 :1, to polarize the incident light.

[0061] LCVR 8 is the component to be calibrated, with the fast axis azimuth angle set to 45° (preferably 45° in this embodiment for ease of experimentation and data processing), and the phase delay adjustable range is 0nm to >λ.

[0062] The two transmission axes of the Savar plate 9 are set to 0° and 90° respectively (preferably 0° and 90° in this embodiment for ease of experimentation and data processing), and the extinction ratio is >10. 5 :1, to analyze the incident light and form a dual-beam optical path.

[0063] The focal length range of the dual-film composite imager 10 is f = 300–500 mm, which images the dual optical paths onto the focal plane of the detector 10. The left and right half-focal planes of the detector 11 receive the light intensity images in the horizontal polarization direction and the vertical polarization direction, respectively.

[0064] The temperature of the LCVR 8 is set and kept constant at 20°C using temperature controller 13, with a temperature control accuracy of ≤±0.1°C. The driving voltage applied to the LCVR 8 is precisely changed using LCD controller 14. The output voltage starts from 0V and gradually increases to 25V at voltage intervals of ΔV=10mV. Detector 10 synchronously records the intensity images of the dual beams at each voltage step point, thereby forming two sets of light intensity images, each set containing 2501 images.

[0065] Using the dual-beam intensity data set, the phase delay of the LCVR 8 to be calibrated at the current temperature and wavelength is obtained by jointly solving the formula (6) with different driving voltages.

[0066] Control the stepper motor 12 to rotate the filter wheel 6 to filter No. 2 to No. 8 in sequence. Repeat the above steps to complete the calibration of the phase delay of the LCVR 8 to be calibrated at different wavelengths.

[0067] This embodiment only illustrates the LCVR phase delay calibration process with a constant temperature of 20℃, a calibration wavelength of 450-800nm, and a driving voltage range of 0-25V. However, those skilled in the art will readily understand that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A multi-wavelength dual-beam calibration method for a liquid crystal variable phase retarder, characterized in that, Includes the following steps: Step 1: The laser-driven white light source is coupled through an optical fiber to form a broadband point light source. This point light source is located at the focal position of the double cemented collimating lens. After collimation, it forms parallel light. The aperture of the incident light is limited by the aperture stop. Step 2: Install narrowband filters of different wavelengths on the filter wheel, and place one of the filters in the optical path for calibration wavelength selection by controlling the rotation of the filter wheel. The incident light passes through the filter. Step 3: The incident light passes sequentially through a linear polarizer, the LCVR to be calibrated, and a Savart plate, and the Savart plate generates two beams with orthogonal polarization states; Step 4: The dual beams are received by the detector focal plane after passing through the double-gel composite mirror; Step 5: Set and keep the temperature of the LCVR to be calibrated constant, change the driving voltage applied to the LCVR to be calibrated, starting from 0V and gradually increasing it in predetermined voltage steps, and use the detector to synchronously record the intensity image of the dual beams at each voltage step point. Step 6: Calculate the phase delay of the LCVR to be calibrated at different driving voltages under the current temperature and calibration wavelength by combining the intensity data of the two beams; Step 7: Control the filter wheel to rotate sequentially to other filters, and repeat steps 5 to 6 to calibrate the phase delay of LCVR at different temperatures and wavelengths.

2. The multi-wavelength dual-beam calibration method for a liquid crystal variable phase retarder according to claim 1, characterized in that, In step 1, the light emitted through the aperture is filtered by a pre-filter to remove the ultraviolet light from the calibration light.

3. The multi-wavelength dual-beam calibration method for a liquid crystal variable phase delay device according to claim 1, characterized in that, In step 3, the azimuth angle of the transmission axis of the linear polarizer is set to θ, the azimuth angle of the fast axis of the LCVR to be calibrated is set to θ+45°, and the azimuth angles of the two transmission axes of the Savart plate are set to θ and θ+90° respectively, where θ is any angle; in step 4, one of the receiving beams is the polarized light corresponding to the azimuth angle of the transmission axis of the Savart plate when it is θ, and the other receiving beam is the polarized light corresponding to the azimuth angle of the transmission axis of the Savart plate when it is θ+90°.

4. The multi-wavelength dual-beam calibration method for a liquid crystal variable phase delay device according to claim 1, characterized in that, In step 4, the Stokes vector S corresponding to the two beams out,1 and S out,2 They are respectively: In the formula, M Savart This is the Mueller matrix of the Savart plate, where θ and θ+90° are its two transmission axis azimuths, M LCVR Here is the Mueller matrix of the LCVR to be calibrated, θ+45° is its fast axis azimuth angle, δ is its phase delay, and λ is the Mueller matrix of the LCVR to be calibrated. i T is the wavelength of the i-th filter. j It is the j-th temperature of LCVR, V k It is the k-th drive voltage value of the LCVR, V k =kΔV, k = 0, 1, 2, ..., ΔV is the voltage step size, M Polarizer This is the Mueller matrix of the linear polarizer, θ is its transmission axis azimuth angle, and S in The Stokes vector of the incident unpolarized calibration light: S in =(I,Q,U,V) T =I0(1,0,0,0) T I represents the total intensity, Q and U represent the two linearly polarized components, V represents the circularly polarized component, T represents the transpose, and I0 is the incident light intensity.

5. The multi-wavelength dual-beam calibration method for a liquid crystal variable phase delay device according to claim 1, characterized in that, In step 5, the detector only responds to the intensity signal, and the intensities of the two beams measured by the detector are calculated as follows: In the formula, I1 and I2 are the light intensities of beam 1 and beam 2, respectively, I0 is the incident light intensity, δ is the phase retardation of LCVR, and λ i T is the wavelength of the i-th filter. j It is the j-th temperature of LCVR, V k It is the k-th drive voltage value of the LCVR, V k =kΔV, k = 0, 1, 2, ..., ΔV is the voltage step size.

6. The multi-wavelength dual-beam calibration method for a liquid crystal variable phase delay device according to claim 1, characterized in that, In step 6, through numerical calculation, the phase delay of the LCVR to be calibrated is calculated from the dual-beam intensity data set received by the joint detector as follows: In the formula, δ is the phase delay of the LCVR, and λ i T is the wavelength of the i-th filter. j It is the j-th temperature of LCVR, V k It is the k-th drive voltage value of the LCVR, V k =kΔV, k = 0, 1, 2, ..., ΔV is the voltage step size, and I1 and I2 are the light intensities of beam 1 and beam 2, respectively.

7. A multi-wavelength dual-beam calibration apparatus for a liquid crystal variable phase retarder based on the method of any one of claims 1-6, characterized in that, The device includes a laser-driven white light source, an optical fiber, a cemented doublet collimating lens, an aperture, a filter wheel, a linear polarizer, an LCVR to be calibrated, a Savart plate, and a cemented doublet image-combining mirror, arranged sequentially along the optical path. The intensity images of the emitted dual beams are received by a detector connected to a computer. The device also includes a rotation control mechanism, a temperature controller, and a liquid crystal controller, all connected to the computer. The rotation control mechanism is used to select the calibration wavelength by controlling the rotation of the filter wheel. The linear polarizer is used to polarize the incident light. The Savart plate serves as a dual-beam analyzer. The temperature controller is used to set and maintain a constant temperature for the LCVR to be calibrated. The liquid crystal controller is used to change the driving voltage applied to the LCVR to be calibrated.

8. The multi-wavelength dual-beam calibration device for a liquid crystal variable phase delay unit according to claim 7, characterized in that, The azimuth angle of the transmission axis of the linear polarizer is set to θ, the azimuth angle of the fast axis of the LCVR to be calibrated is set to θ+45°, and the azimuth angles of the two transmission axes of the Savart plate are set to θ and θ+90° respectively, where θ is any angle.

9. The multi-wavelength dual-beam calibration device for a liquid crystal variable phase delay unit according to claim 7, characterized in that, A pre-filter for filtering out ultraviolet light in the calibration light is also provided between the aperture and the filter wheel.

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