Crystal rotation-based birefringence and polarization splitting ratio measurement system and method

Abstract

The application discloses a birefringence and polarization beam splitting ratio measuring system and method based on crystal rotation, relates to the technical field of optical characteristic measurement, and comprises a birefringence measuring module, a polarization beam splitting ratio measuring module and a data processing module. The birefringence measuring module comprises a sodium lamp, a collimator tube, a crystal rotation stage, a first birefringent crystal, a first rotatable polarizer and a spectrometer telescope arranged along a first light path. The polarization beam splitting ratio measuring module comprises a laser, a second birefringent crystal and a second rotatable polarizer arranged along a second light path, and the output ends of the laser, the second birefringent crystal and the second rotatable polarizer are connected in parallel with a light screen with a scale and a photoelectric sensor. The data processing module is connected with an angle encoder, a double cursor scale and an oscilloscope respectively. The application can realize synchronous and accurate measurement of birefringence and polarization beam splitting ratio parameters, has the advantages of low measurement cost, improved data consistency, compact structure and convenient operation.

Description

Technical Field

[0001] This invention relates to the field of optical feature measurement, and more specifically to a birefringence and polarization beam splitting ratio measurement system and method based on crystal rotation. Background Technology

[0002] Birefringent crystals have significant applications in optics, and the accurate measurement of their optical properties is crucial for materials research and device development. Currently, the main methods for measuring birefringent crystals include conventional spectral analysis and intensity probing. While conventional spectral analysis can obtain average spectral data over a macroscopic region, it has significant limitations: firstly, it struggles to distinguish directional differences in materials; secondly, it cannot effectively acquire polarization information, resulting in low signal-to-noise ratios for transparent or weakly absorbing samples. Intensity probing, although capable of recording light intensity changes, suffers from several shortcomings in practical applications: it cannot accurately obtain key parameters such as optical path difference and refractive index changes, and the measurement process is easily affected by environmental interference.

[0003] Traditional measurement methods have significant drawbacks in terms of measurement accuracy, system stability, and ease of operation. Particularly in the simultaneous measurement of the two key parameters, birefringence and polarization beam splitting ratio, existing technologies often require separate measuring devices, which not only increases measurement costs but may also lead to inconsistent results. Furthermore, existing measurement systems are generally bulky and complex to operate, hindering their widespread application in laboratories and industrial settings.

[0004] To address the aforementioned issues, existing technologies urgently need improvement. Summary of the Invention

[0005] In view of this, the present invention provides a birefringence and polarization beam splitting ratio measurement system and method based on crystal rotation, which has the advantages of realizing simultaneous measurement of birefringence and polarization beam splitting ratio, reducing measurement cost, improving data consistency, compact structure and convenient operation.

[0006] In a first aspect, the present invention provides a birefringence and polarization beam splitting ratio measurement system based on crystal rotation, comprising: a birefringence measurement module, a polarization beam splitting ratio measurement module, and a data processing module;

[0007] The birefringence measurement module includes a sodium lamp, a collimator, a crystal rotating stage, a first birefringent crystal, a first rotatable polarizer, and a spectrometer telescope arranged sequentially along the first optical path.

[0008] The crystal rotating stage is equipped with a dual vernier scale and carries the first birefringent crystal, with the rotation angle fed back in real time via a built-in angle encoder. The spectrometer telescope is connected to the dual vernier scale and is used to dynamically capture the minimum deviation angle δ of the o-ray and e-ray.min1 δ min2 ;

[0009] The polarization beam splitting ratio measurement module includes a laser, a second birefringent crystal, and a second rotatable polarizer arranged sequentially along the second optical path.

[0010] The second rotatable polarizer has a screen and a photoelectric sensor arranged in parallel on its output optical path; the screen has a position scale for marking the coordinates of the o-ray spot. and the coordinates of the e-ray spot The photoelectric sensor is connected to an oscilloscope to output the peak-to-peak voltage of the o-ray / e-ray in real time. V o,pp , V e,pp ;

[0011] The data processing module is electrically connected to the angle encoder, the dual vernier scale, and the oscilloscope, respectively, and is used to determine the minimum deviation angle δ of the o-beam and e-beam. min1 δ min2 Calculate the refractive indices of the o-ray and e-ray respectively; and, based on the peak-to-peak voltages of the o-ray and e-ray... V o,pp , V e,pp Calculate the real-time polarization beam splitting ratio; and, for use with respect to the spot coordinates of the o-beam. and the coordinates of the e-ray spot Calculate the beam separation between the o-ray and e-ray.

[0012] In one optional implementation, the formula for calculating the refractive indices of the o-ray and e-ray is:

[0013] ;

[0014] ;

[0015] in, Let be the refractive index of the o-ray; Let be the refractive index of the e-ray; δ is the apex angle of a birefringent crystal. min1 The minimum deflection angle of the o-beam, δ min2 This is the minimum deflection angle of the e-beam.

[0016] In one optional implementation, the calculation steps for the polarization beam splitting ratio are as follows:

[0017] ;

[0018] in, The polarization beam splitting ratio; Peak-to-peak voltage of o-light Vo,pp The value corresponding to the maximum light intensity; Peak-to-peak voltage of e-beam V e,pp The value corresponding to the maximum light intensity.

[0019] In one optional implementation, the formula for calculating the beam separation amount is:

[0020] ;

[0021] in, This refers to the beam separation amount; These are the x-coordinates of the o-ray and e-ray spots, respectively; The coordinates of the light spots for the o-ray and e-ray are respectively.

[0022] In one alternative embodiment, the second birefringent crystal, the first rotatable polarizer, and the optical screen are on the same horizontal straight line.

[0023] Secondly, the present invention also provides a method for measuring birefringence and polarization beam splitting ratio based on crystal rotation, comprising:

[0024] S1. Based on the minimum deviation angle δ of the o-ray and e-ray. min1 δ min2 Calculate the refractive indices of the o-ray and e-ray respectively;

[0025] S2. Based on the peak-to-peak voltages of the o-ray and e-ray. V o,pp , V e,pp Calculate the real-time polarization beam splitting ratio, and based on the spot coordinates of the o-beam. and the coordinates of the e-ray spot Calculate the beam separation between the o-ray and e-ray.

[0026] In one optional implementation, S1 includes:

[0027] A beam of light is emitted by a sodium lamp, collimated by a collimating tube, and then incident on the first birefringent crystal on the crystal rotating stage.

[0028] Adjust the angle of the spectrometer telescope to make o-rays and e-rays appear in the field of view;

[0029] Adjust the angle of the first rotatable polarizer so that o-rays and e-rays can be distinguished in the field of view of the spectrometer telescope;

[0030] A rotating crystal stage is used to dynamically capture the minimum deviation angle δ of the o-ray and e-ray using a spectrometer telescope. min1 δ min2 Simultaneously record the readings of the dual vernier dials;

[0031] According to the minimum deviation angle δ min1 δ min2 The refractive index of the o-ray and the refractive index of the e-ray are calculated from the apex angle of the first birefringent crystal.

[0032] In one alternative implementation, S2 includes:

[0033] The laser is emitted by the laser, and after the laser is incident on the second birefringent crystal, it is modulated into linearly polarized light by the second rotatable polarizer;

[0034] Parallel execution at the output of the second rotatable polarizer: Marking the coordinates of the o-ray spot on a screen with a position scale. and the coordinates of the e-ray spot Furthermore, the peak-to-peak voltages of the o-ray and e-ray are collected in real time using photoelectric sensors. V o,pp , V e,pp The output is then displayed on an oscilloscope.

[0035] According to the peak-to-peak voltage V o,pp , V e,pp Calculate the real-time polarization beam splitting ratio;

[0036] According to the coordinates of the spot of the o-light and the coordinates of the e-ray spot Calculate the beam separation between the o-ray and e-ray.

[0037] In one alternative embodiment, the rotating crystal stage dynamically captures the minimum deviation angle δ of the o-ray and e-ray using a spectrometer telescope. min1 δ min2 ,include:

[0038] Locate the yellow spectral line refracted from the first birefringent crystal in the spectrometer telescope;

[0039] Rotate the crystal and the stage to make the yellow spectral line tend towards the direction of decreasing deflection angle; when the yellow spectral line begins to move in the opposite direction, take the current vernier readings on the left and right sides as the refraction angles of the left and right paths, respectively.

[0040] Remove the first birefringent crystal, rotate the spectrometer telescope to align with the collimator tube, and align the crosshairs with the slit. Use the current vernier readings on the left and right sides as the incident angles of the left and right paths, respectively.

[0041] Calculate the minimum deviation angle δ of the o-ray and e-ray. min1 δ min2 The calculation formula is as follows:

[0042] ;

[0043] in, , These are the refraction angles for the left path and the right path, respectively. These are the angles of incidence for the left path and the right path, respectively.

[0044] As can be seen from the above, the birefringence and polarization beam splitting ratio measurement system and method based on crystal rotation provided in this application achieve synchronous and accurate measurement of birefringence and polarization beam splitting ratio parameters by integrating a birefringence measurement module, a polarization beam splitting ratio measurement module and a data processing module. It has the advantages of reducing measurement costs, improving data consistency, compact structure and convenient operation. Attached Figure Description

[0045] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0046] Figure 1 This is a schematic diagram of a birefringence and polarization beam splitting ratio measurement system based on crystal rotation according to an embodiment of the present invention;

[0047] Figure 2 This is a schematic diagram of the birefringence measurement module according to an embodiment of the present invention;

[0048] Figure 3 This is a schematic diagram of the polarization beam splitting ratio measurement module according to an embodiment of the present invention. Detailed Implementation

[0049] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0050] In existing technologies, the optical properties of birefringent crystals are generally measured using spectral analysis and intensity probing methods. Spectral analysis struggles to capture material directional differences and loses polarization information, resulting in low signal-to-noise ratios for transparent or weakly absorbing samples. Intensity probing methods are sensitive to environmental interference and cannot accurately obtain optical path difference and refractive index changes. These shortcomings are particularly prominent in applications requiring dynamic detection of birefringence parameters, such as optical communication device calibration and laser polarization control, thus hindering the development efficiency of high-precision optical devices.

[0051] To address the aforementioned issues, the inability of traditional methods to simultaneously acquire polarization state changes and refractive index differences has become a key focus. Analysis revealed that while the minimum deviation angle principle of a spectrometer can accurately determine the refractive index, static measurements suffer from accumulated angular errors. Further research showed that dynamically rotating the crystal combined with dual vernier compensation can effectively reduce these errors. Simultaneously, the parallel setup of the photoelectric sensor and the screen can detect both light intensity changes and record spatial separation. Based on this, a proposed system integrates birefringence measurement and polarization beam splitting ratio detection into a collaborative system, achieving simultaneous calculation of multi-dimensional parameters through a data processing module.

[0052] Therefore, as Figures 1-3 As shown, this application proposes a birefringence and polarization beam splitting ratio measurement system based on crystal rotation, comprising a birefringence measurement module, a polarization beam splitting ratio measurement module, and a data processing module. The birefringence measurement module includes a sodium lamp, a collimator, a crystal rotation stage, a first birefringent crystal, a first rotatable polarizer, and a spectrometer telescope arranged sequentially along the first optical path. The crystal rotation stage is equipped with a dual vernier scale and carries the first birefringent crystal, with a built-in angle encoder providing real-time feedback of the rotation angle. The spectrometer telescope is connected to the dual vernier scale and is used to dynamically capture the minimum deviation angle δ of the o-ray and e-ray. min1 δ min2 The polarization beam splitting ratio measurement module includes a laser, a second birefringent crystal, and a second rotatable polarizer arranged sequentially along the second optical path; wherein, a screen and a photoelectric sensor are arranged in parallel along the output optical path of the second rotatable polarizer; the screen has a position scale for marking the coordinates of the o-ray spot. and the coordinates of the e-ray spot The photoelectric sensor is connected to an oscilloscope to output the peak-to-peak voltage of the o-ray / e-ray in real time. V o,pp , V e,pp The data processing module is electrically connected to the angle encoder, the dual vernier scale, and the oscilloscope, respectively, and is used to determine the minimum deviation angle δ of the o-ray and e-ray. min1 δ min2 Calculate the refractive indices of the o-ray and e-ray respectively; and, based on the peak-to-peak voltages of the o-ray and e-ray... V o,pp ,V e,pp Calculate the real-time polarization beam splitting ratio; and, for use with respect to the spot coordinates of the o-beam. and the coordinates of the e-ray spot Calculate the beam separation between the o-ray and e-ray.

[0053] The crystal rotating stage refers to a precision rotating platform equipped with dual vernier scales and an angle encoder. Specifically, it can be implemented using a stepper motor-driven rotary table combined with a photoelectric encoder, used to precisely control the crystal's rotation angle and provide real-time position data feedback. The spectrometer telescope is an optical observation device with dual vernier reading capabilities. Specifically, it can be implemented using an Abbe autocollimating telescope combined with a CCD image sensor, used to dynamically capture the process of minimum deviation angle changes. The parallel setup of the photoelectric sensor and the screen refers to combining a charge-coupled device (CCD) and a calibration grid plate in the same optical path. Specifically, it can be implemented using a silicon photodiode array combined with a precision-etched glass plate, used to simultaneously acquire light intensity signals and spatial coordinate data. The data processing module is a computing unit with multi-channel data acquisition capabilities. Specifically, it can be implemented using an embedded processor combined with an analog-to-digital converter circuit, used to fuse angle data, voltage signals, and coordinate information for joint calculations.

[0054] Specifically, the beam emitted by the sodium lamp is collimated by a collimator to form parallel light, which is then incident on the rotating crystal stage. As the stage rotates the first birefringent crystal, the spectrometer telescope records the minimum deviation angles of the o-ray and e-ray in real time using a dual vernier scale. A first rotatable polarizer filters out non-target polarized light, ensuring the spectrometer accurately distinguishes the two polarization states. In the polarization beam splitting ratio measurement, the laser beam is polarized by the second birefringent crystal. The second rotatable polarizer adjusts the incident polarization direction, and a photoelectric sensor detects the peak-to-peak voltages of the o-ray and e-ray. The screen records the spatial coordinate offset of the two beams. The data processing module synchronously receives the rotation angle from the angle encoder, the deviation angle data from the dual vernier scale, the voltage signal from the oscilloscope, and the screen coordinate data. It calculates the birefringence using the minimum deviation angle formula, calculates the polarization beam splitting ratio using the voltage ratio, and calculates the beam separation amount based on the coordinate difference.

[0055] Compared to existing technologies, traditional methods using a single detection mode result in incomplete parameter acquisition. This solution, however, achieves simultaneous detection of refractive index, polarization beam splitting ratio, and spatial offset through dual-optical-path collaborative measurement. Existing spectrometer measurements are static, single-read readings; this invention, through the dynamic coordination of a rotating crystal stage and a dual vernier system, improves angle measurement accuracy by an order of magnitude. In contrast to traditional photoelectric detection, which only acquires light intensity signals, this invention innovatively combines screen coordinate calibration, providing spatial dimension verification for polarization beam splitting.

[0056] Through the above technical solution, this invention effectively solves the problem of insufficient directional identification in birefringence measurement, and achieves multi-angle data acquisition through a rotating crystal stage. The problem of missing polarization information is overcome by the combined detection of a first rotatable polarizer and a photoelectric sensor, ensuring accurate differentiation between o-ray and e-ray. The measurement signal-to-noise ratio is significantly improved by dynamically capturing the minimum deviation angle using a spectrometer. At the same time, the parallel detection of screen coordinates and photoelectric signals provides a dual verification mechanism for the polarization beam splitting ratio, enhancing the reliability of the measurement results.

[0057] In one alternative implementation, the formulas for calculating the refractive indices of the o-ray and e-ray are as follows:

[0058] ;

[0059] ;

[0060] in, Let be the refractive index of the o-ray; Let be the refractive index of the e-ray; δ is the apex angle of a birefringent crystal. min1 The minimum deflection angle of the o-beam, δ min2 This is the minimum deflection angle of the e-beam.

[0061] The apex angle refers to the angle between two opposing crystal planes of a birefringent crystal. This angle can be calibrated using a spectrometer with a standard angle block. This parameter is pre-measured as an inherent property of the crystal and substituted into the formula. Minimum deviation angle δ min1 and δ min2 This refers to the minimum deflection angle of the light rays captured by the rotating crystal stage in the spectrometer, specifically the o-ray and e-ray. This parameter can be dynamically read through the dual vernier scale and the spectrometer telescope. This parameter eliminates the angle error in traditional static measurements through a real-time feedback mechanism.

[0062] Specifically, when the light beam emitted by the sodium lamp source is collimated into parallel light by the collimator and incident on the crystal, the o-ray and e-ray propagate along different paths due to birefringence. By rotating the crystal stage and simultaneously observing the direction of spectral line movement in the spectrometer telescope, the minimum deflection angle of the two polarized rays is dynamically determined. The apex angle is used as a known geometric parameter and dynamically captured δ min1 and δ min2 By substituting these values ​​into the formula, the refractive index can be directly calculated from the geometric relationship of the optical propagation path. This calculation process avoids the cumulative error caused by fixed angle measurements in traditional methods by combining the mathematical relationship between the crystal apex angle and the minimum deviation angle, thus accurately distinguishing the refractive index difference between the o-ray and e-ray.

[0063] Through the above technical solution, the present invention can accurately calculate the difference in refractive index between o-ray and e-ray in birefringent crystals, solving the problem of insufficient measurement accuracy caused by angular error and lack of directionality in traditional methods, and providing high-precision quantitative data support for the optical property analysis of birefringent crystals.

[0064] In one optional implementation, the calculation steps for the polarization beam splitting ratio are as follows:

[0065] ;

[0066] in, The polarization beam splitting ratio; Peak-to-peak voltage of o-light V o,pp The value corresponding to the maximum light intensity; Peak-to-peak voltage of e-beam V e,pp The value corresponding to the maximum light intensity.

[0067] Peak-to-peak voltage refers to the difference between the maximum and minimum values ​​of the voltage fluctuation range displayed on an oscilloscope for the electrical signal output by the photoelectric sensor. This can be achieved using a silicon photodiode as the photoelectric sensor, with a response time less than one-tenth of the polarizer rotation period to ensure dynamic sampling accuracy. The value at maximum light intensity refers to the voltage signal corresponding to the peak intensity of the o-light or e-light when the polarizer is rotated. This can be achieved by capturing the highest point of the voltage waveform using the oscilloscope's trigger mode. This method effectively eliminates the interference of ambient light noise on the measurement results.

[0068] Specifically, during the rotation of the second rotatable polarizer, the photoelectric sensor collects the changes in light intensity transmitted through the polarizer in real time and converts them into electrical signals, which are then transmitted to the oscilloscope. The oscilloscope processes the electrical signals into peak-to-peak voltage waveforms and records the voltage data when the intensity of the o-ray and e-ray reaches their respective maximum values. and Since light intensity and voltage signal have a linear relationship, selecting the voltage value corresponding to the maximum light intensity can eliminate measurement errors caused by optical path offset or light source fluctuations during polarizer angle adjustment. By calculating the ratio of the two, the polarization and beam splitting capability of the birefringent crystal for o-ray and e-ray is directly reflected, enabling continuous resolution of the beam splitting ratio during dynamic measurement.

[0069] Through the above technical solution, this invention achieves dynamic high-precision measurement of polarization beam splitting ratio, solving the problems of traditional methods being unable to track polarization state changes in real time and having poor anti-interference capabilities. By selecting the voltage value corresponding to the maximum light intensity for ratio calculation, light intensity fluctuations and environmental noise are effectively suppressed, ensuring that the beam splitting ratio calculation only reflects the differences in polarization characteristics of the crystal itself, thus providing a reliable quantitative basis for the performance evaluation of birefringent crystals.

[0070] In one optional implementation, the formula for calculating the beam separation amount is:

[0071] ;

[0072] in, This refers to the beam separation amount; These are the x-coordinates of the o-ray and e-ray spots, respectively; The coordinates of the light spots for the o-ray and e-ray are respectively.

[0073] The beam separation amount refers to the actual spatial separation distance between the o-beam and the e-beam. This can be achieved using a screen with a position scale. The screen surface has a two-dimensional coordinate system to mark the horizontal and vertical coordinates of the o-beam and e-beam spots. The formula for calculating the beam separation amount is based on the Euclidean distance principle, obtained by taking the square root of the sum of the squares of the differences between the horizontal and vertical coordinates of the two spots.

[0074] Specifically, the structure of the optical screen with a position scale uses a preset two-dimensional coordinate system to convert the positions of the o-ray and e-ray spots into specific coordinate data. For example, when the laser passes through the birefringent crystal, the o-ray and e-ray form two separate spots on the screen. The horizontal coordinates of these spots on the scale are then read. and ordinate Substituting these values ​​into the formula allows for the calculation of the actual spatial distance between the two objects. This formula eliminates the positive or negative influence of the coordinate difference through squaring and then restores the distance to a linear value by taking the square root, thus accurately reflecting the beam separation effect of the birefringent crystal.

[0075] Compared to existing technologies, traditional methods typically measure beam offset in only one direction, such as recording only the lateral or longitudinal coordinate difference, which fails to fully reflect the actual separation degree of the beam in a two-dimensional plane. This approach, by introducing a two-dimensional coordinate system and Euclidean distance calculation, can simultaneously capture both lateral and longitudinal separation components, thus more accurately quantifying the beam separation.

[0076] In one alternative implementation, the second birefringent crystal, the first rotatable polarizer, and the screen are on the same horizontal straight line.

[0077] The second birefringent crystal is a transparent optical element that decomposes the incident laser into o-rays and e-rays. It can be made of calcite or quartz crystal, and its optical axis forms a specific angle with the direction of incident light propagation. The second rotatable polarizer is a polarizing element that can rotate around the optical axis. It can be implemented using a polarizer holder with angle scales and is used to adjust the polarization direction of the emitted light. The screen is a planar receiving device with position scales. It can be implemented using a diffuse reflector plate with a coordinate grid on its surface and is used to record the positions of the o-ray and e-ray spots. The horizontally aligned linear structure of these three components constrains the direction of light propagation, preventing unexpected tilting or deflection of the beam during its spatial propagation.

[0078] Specifically, the second birefringent crystal decomposes the incident laser into o-ray and e-ray, and the two beams propagate along the transmission axis of the second rotatable polarizer. Since all three beams are on the same horizontal straight line, the o-ray and e-ray continue to propagate in their original direction to the screen after passing through the polarizer, ensuring that the measurement reference for the light spot coordinates is strictly aligned with the optical path axis. This design eliminates lateral displacement errors caused by optical path tilt, ensuring that the coordinate difference marked on the screen only reflects the beam separation caused by birefringence. Simultaneously, the horizontal straight-line layout provides a stable light intensity detection path for the photoelectric sensor, ensuring that the peak-to-peak voltage acquired by the oscilloscope is synchronized with the change in light spot position, avoiding signal delay caused by differences in optical path length.

[0079] Through the above technical solution, the present invention effectively eliminates the coordinate measurement error caused by the tilt of the optical path, ensures the time synchronization between the spot position and the photoelectric signal, and improves the dynamic measurement accuracy of the beam separation and polarization beam splitting ratio.

[0080] Furthermore, the present invention also provides a method for measuring birefringence and polarization beam splitting ratio based on crystal rotation, comprising:

[0081] Step S1: Based on the minimum deviation angle δ of the o-ray and e-ray min1 δ min2 Calculate the refractive indices of the o-ray and e-ray respectively;

[0082] Step S2: Based on the peak-to-peak voltages of the o-ray and e-ray. V o,pp , V e,pp Calculate the real-time polarization beam splitting ratio, and based on the spot coordinates of the o-beam. and the coordinates of the e-ray spot Calculate the beam separation between the o-ray and e-ray.

[0083] In one optional implementation, step S1 includes:

[0084] Step S11: A light beam is emitted through a sodium lamp, collimated by a collimating tube, and then incident on the first birefringent crystal on the crystal rotating stage;

[0085] Step S12: Adjust the angle of the spectrometer telescope so that o-rays and e-rays appear in the field of view;

[0086] Step S13: Adjust the angle of the first rotatable polarizer so that o-rays and e-rays can be distinguished in the field of view of the spectrometer telescope;

[0087] Step S14: Rotate the crystal rotating stage and dynamically capture the minimum deviation angle δ of the o-ray and e-ray using the spectrometer telescope. min1 δ min2 Simultaneously record the readings of the dual vernier dials;

[0088] Step S15: Based on the minimum deviation angle δ min1 δ min2 The refractive index of the o-ray and the refractive index of the e-ray are calculated from the apex angle of the first birefringent crystal.

[0089] The sodium lamp is a light source that emits monochromatic light, specifically a sodium D-line light source with a wavelength of 589.3 nanometers. Its function is to provide stable monochromatic incident light for birefringence measurement, avoiding measurement errors caused by polychromatic light. The collimator is an optical element that converts a diverging beam into a parallel beam, specifically implemented using a lens group or a mirror system. Its function is to ensure that the incident light enters the birefringent crystal in a collimated state, reducing the influence of beam divergence on angle measurement. The spectrometer telescope is a device used to observe and measure the angle of light refraction. It can be implemented using a telescope structure with eyepiece scale lines and an objective lens focusing mechanism. Its function is to capture the minimum deflection angle in real time by dynamically tracking changes in the optical path. The dual vernier dial refers to a device with two symmetrically distributed vernier reading devices, specifically implemented using a mechanical or photoelectric angle encoder. Its function is to eliminate eccentricity errors through symmetrical readings, improving the angle measurement accuracy to within 1 minute. Dynamic capture of minimum deflection angle refers to tracking the minimum value of light deflection by adjusting the crystal rotation angle in real time. Specifically, this can be achieved by using a servo motor to drive the stage and synchronously record angle data. Its function is to avoid errors caused by angle positioning deviation in static measurement through continuous monitoring.

[0090] Specifically, the monochromatic beam emitted by the sodium lamp is collimated by a collimator to form parallel light. When this light is incident on the first birefringent crystal, birefringence occurs, producing o-ray and e-ray. The angle of the spectrometer telescope is adjusted to simultaneously observe the refraction paths of both polarized lights, resulting in two separate spectral lines in the field of view. The angle of the first rotatable polarizer is adjusted to a specific direction, creating a contrast difference between the o-ray and e-ray in the field of view of the spectrometer telescope, thus clearly distinguishing the two polarization states. During the rotation of the crystal rotating stage, the relative angle between the birefringent crystal and the incident light changes. The spectrometer telescope monitors the changes in the deflection angles of the o-ray and e-ray in real time. When the deflection angle reaches its minimum value, the dual vernier scales simultaneously record the readings on both sides. The minimum deflection angle is calculated by comparing the difference between the angle of refraction and the angle of incidence. Finally, by combining the crystal's apex angle parameter with the refractive index formula, the refractive index values ​​of the o-ray and e-ray are obtained respectively.

[0091] Compared to existing technologies, traditional methods, which rely on fixed-angle measurements or single readings, cannot track the changing trend of the minimum deflection angle in real time, thus limiting measurement accuracy. Dynamic capture technology, by continuously rotating the crystal and simultaneously recording angle data, can accurately capture the minimum point of light deflection, avoiding systematic errors caused by angular positioning deviations. Furthermore, the application of dual vernier scales further eliminates eccentricity errors, improving angle measurement accuracy by an order of magnitude and solving the problem of difficulty in distinguishing directional differences in traditional spectral analysis.

[0092] Through the above technical solution, this invention achieves high-precision dynamic measurement of the minimum deviation angle of o-ray and e-ray in birefringent crystals, effectively distinguishing the directional differences between the two polarization states and completely preserving polarization information. The use of a collimated monochromatic light source and a symmetrical vernier reading device significantly reduces environmental interference and system errors, improving the signal-to-noise ratio. Finally, the refractive index is directly calculated through geometric optical relationships, avoiding the difficulty in quantifying optical path difference in traditional intensity detection methods, and providing a reliable experimental data foundation for the optical property analysis of birefringent crystals.

[0093] Through the above technical solution, the present invention solves the problem of the spatial separation of beams caused by the inability to accurately measure birefringent crystals in the prior art, and realizes high-precision measurement of the actual separation distance between o-beam and e-beam on a two-dimensional plane, providing a reliable spatial separation data basis for the optical characteristic analysis of birefringent crystals.

[0094] In one optional implementation, step S2 includes:

[0095] Step S21: A laser is emitted by a laser device. After the laser light is incident on the second birefringent crystal, it is modulated into linearly polarized light by the second rotatable polarizer.

[0096] Step S22, performed in parallel at the output end of the second rotatable polarizer: Mark the coordinates of the o-ray spot on the screen with the position scale. and the coordinates of the e-ray spot Furthermore, the peak-to-peak voltages of the o-ray and e-ray are collected in real time using photoelectric sensors. V o,pp , V e,pp The output is then displayed on an oscilloscope.

[0097] Step S23: Based on peak-to-peak voltage V o,pp , V e,pp Calculate the real-time polarization beam splitting ratio;

[0098] Step S24: Based on the coordinates of the o-ray spot and the coordinates of the e-ray spot Calculate the beam separation between the o-ray and e-ray.

[0099] The second rotatable polarizer refers to a polarization modulation device that can rotate around the optical axis. Specifically, it can be implemented using a polarizer holder driven by a stepper motor, used to adjust the polarization direction of the emitted light to match the detection reference of the photoelectric sensor. The screen with position scales refers to a projection plane with gridded coordinate markings on its surface, such as a transparent acrylic plate with millimeter-level scale lines printed on it. This is used to directly quantify the spatial separation effect caused by birefringence through differences in the position of the light spots. The photoelectric sensor is a detection unit that converts optical signals into electrical signals. For example, it uses a silicon photodiode in conjunction with a transimpedance amplifier circuit to capture the intensity changes of the o-ray and e-ray in real time and output peak-to-peak voltage signals. The beam separation amount refers to the spatial offset distance between the o-ray and e-ray, which can be calculated through coordinate differences. For example, the distance between the center points of the two light spots can be calculated using the Pythagorean theorem, used to characterize the beam separation capability of the birefringent crystal.

[0100] Specifically, the collimated beam output from the laser undergoes birefringence splitting after passing through the second birefringent crystal, forming two beams with orthogonal polarization directions: the o-beam and the e-beam. A second rotatable polarizer, adjusted by rotation, aligns the polarization directions of the two beams with the detection axis of the photoelectric sensor, ensuring effective extraction of the light intensity signal. At the optical output end, a position scale on the screen captures the projected positions of the two light spots, recording their coordinate data, while the photoelectric sensor simultaneously acquires the instantaneous light intensity of the two beams and converts it into peak-to-peak voltage signals. The data processing module calculates the polarization splitting ratio using the peak-to-peak voltage ratio, reflecting the energy distribution characteristics; simultaneously, it calculates the beam separation amount based on the coordinate difference, characterizing the degree of spatial offset. This parallel detection mechanism achieves simultaneous acquisition of the polarization splitting intensity and spatial parameters, avoiding the timing errors caused by step-by-step measurements in traditional methods.

[0101] Compared to existing technologies, traditional polarization beam splitting measurements typically rely on a combination of a beam splitter and a power meter, which can only obtain the light intensity ratio but cannot record the spatial separation, and requires multiple adjustments to the optical element positions. This invention, however, uses dual-mode detection—simultaneous acquisition of photoelectric signals and screen coordinate calibration—to simultaneously obtain both the beam splitting ratio and separation data in a single measurement, eliminating the operational complexity caused by repetitive equipment configuration. Furthermore, existing technologies for beam separation measurement often employ microscopic imaging or CCD scanning, which suffers from slow response times and complex data processing. This solution simplifies the spatial parameter acquisition process by directly reading the coordinates from a scaled screen.

[0102] Through the above technical solution, this invention achieves simultaneous execution of dynamic measurement of polarization beam splitting ratio and spatial positioning of beam separation, solving the problems of single-dimensional beam splitting characteristic characterization and asynchronous spatiotemporal data in traditional methods. The parallel data acquisition mechanism of photoelectric sensor and optical screen improves the real-time performance of measurement, while the direct reading method of coordinate scale enhances spatial resolution. In the detection of optical characteristics of birefringent crystals, this scheme can simultaneously output quantitative parameters of energy distribution and spatial offset, providing multi-dimensional data support for the performance evaluation of polarization devices.

[0103] In one alternative implementation, such as Figure 2 As shown, a rotating crystal rotating stage dynamically captures the minimum deviation angle δ of the o-ray and e-ray using a spectrometer telescope. min1 δ min2 include:

[0104] Step a: Locate the yellow spectral line refracted from the first birefringent crystal in the spectrometer telescope;

[0105] Step b: Rotate the crystal rotating stage to make the yellow spectral line tend towards the direction of decreasing deflection angle; when the yellow spectral line begins to move in the opposite direction, take the current vernier readings on the left and right sides as the refraction angles of the left path and the right path, respectively.

[0106] Step c: Remove the first birefringent crystal, rotate the spectrometer telescope to align with the collimator tube, and align the crosshairs with the slit. Use the current vernier readings on the left and right sides as the incident angles of the left and right paths, respectively.

[0107] Step d: Calculate the minimum deviation angle δ of the o-ray and e-ray. min1 δ min2 The calculation formula is as follows:

[0108] ;

[0109] in, , These are the refraction angles for the left path and the right path, respectively. These are the angles of incidence for the left path and the right path, respectively.

[0110] The yellow spectral lines refer to the characteristic spectral lines produced by a sodium lamp light source after passing through a birefringent crystal. Specifically, this can be achieved by emitting 589.3nm wavelength light from a sodium lamp and identifying it using a spectrometer telescope, used to locate the refraction paths of the o-ray and e-ray. The rotating crystal stage is a mechanical structure that can rotate around an axis and support the birefringent crystal. This can be achieved using a stepper motor driven by an integrated angle encoder, used to dynamically adjust the crystal angle to track the minimum deviation angle position. The dual vernier scale refers to an angle measuring device with symmetrical left and right vernier readings. This can be achieved using a spectrometer-compatible dual vernier system, eliminating the eccentricity error of a single vernier by synchronously recording readings from both sides. The incident angle and refraction angle are the angular parameters of light entering and leaving the crystal. This can be achieved by aligning the spectrometer telescope with the collimating tube slit and recording the vernier readings, used to construct the optical path geometry and calculate the minimum deviation angle.

[0111] Specifically, the spectrometer telescope captures the yellow spectral lines produced by a sodium lamp light source passing through a birefringent crystal. The rotation angle of the crystal stage is dynamically adjusted; when the direction of spectral line movement reverses, it indicates the minimum deviation angle critical point has been reached. At this point, the refraction angle readings of the left and right verniers are recorded simultaneously. Subsequently, the crystal is removed and realigned with the collimator slit, and the incident angle reading is recorded. The refraction angle and incident angle are calculated using the average of the left and right vernier readings, respectively, and then substituted into the formula to obtain the minimum deviation angle. This process effectively eliminates human judgment bias and instrument mechanical errors by dynamically tracking changes in the direction of spectral line movement and combining redundant data acquisition with dual verniers.

[0112] Compared to existing technologies, traditional methods rely on static angle measurements and single vernier readings, making them susceptible to operator visual errors and instrument assembly errors. This invention employs dynamic path tracking technology, determining the minimum deviation angle position by reversing the direction of spectral line movement. Combined with a dual-vernier symmetrical reading mechanism, this reduces angle measurement errors to within the instrument's inherent accuracy range. Furthermore, the separate measurement of the incident angle and the refraction angle avoids interference from crystal mounting errors in optical path calculations.

[0113] Through the above technical solution, this invention achieves accurate measurement of the minimum deflection angle of birefringent crystals, solving the measurement deviation problems caused by manual reading errors and angle drift. The combination of dynamic tracking and dual vernier redundancy verification ensures that the minimum deflection angle acquisition accuracy is limited only by the mechanical structure accuracy of the spectrometer, without relying on operator experience. The separate measurement method of incident angle and refraction angle further reduces the impact of crystal mounting position deviation on the calculation results, providing a reliable data foundation for high-precision calculation of birefringence.

[0114] Although embodiments of the invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the invention, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. A birefringence and polarization beam splitting ratio measurement system based on crystal rotation, characterized in that, include: Birefringence measurement module, polarization beam splitting ratio measurement module, and data processing module; The birefringence measurement module includes a sodium lamp, a collimator, a crystal rotating stage, a first birefringent crystal, a first rotatable polarizer, and a spectrometer telescope arranged sequentially along the first optical path. The crystal rotating stage is equipped with a dual vernier scale and carries the first birefringent crystal, with the rotation angle fed back in real time via a built-in angle encoder. The spectrometer telescope is connected to the dual vernier scale and is used to dynamically capture the minimum deviation angle of the o-ray and e-ray. ; The polarization beam splitting ratio measurement module includes a laser, a second birefringent crystal, and a second rotatable polarizer arranged sequentially along the second optical path. The second rotatable polarizer has a screen and a photoelectric sensor arranged in parallel on its output optical path; the screen has a position scale for marking the coordinates of the o-ray spot. and the coordinates of the e-ray spot The photoelectric sensor is connected to an oscilloscope to output the peak-to-peak voltage of the o-ray / e-ray in real time. ; The data processing module is electrically connected to the angle encoder, the dual vernier scale, and the oscilloscope, respectively, and is used to determine the minimum deviation angles of the o-ray and e-ray. Calculate the refractive indices of the o-ray and e-ray respectively; and, based on the peak-to-peak voltages of the o-ray and e-ray... Calculate the real-time polarization beam splitting ratio; and, for use with respect to the spot coordinates of the o-beam. and the coordinates of the e-ray spot Calculate the beam separation of o-ray and e-ray; The formula for calculating beam separation is: in, This refers to the beam separation amount; These are the x-coordinates of the o-ray and e-ray spots, respectively; The vertical coordinates of the o-ray and e-ray spots are respectively; The second birefringent crystal, the first rotatable polarizer, and the optical screen are on the same horizontal straight line.

2. The system according to claim 1, characterized in that, The formulas for calculating the refractive indices of the o-ray and e-ray are as follows: in, Let be the refractive index of the o-ray; Let be the refractive index of the e-ray; The apex angle of a birefringent crystal; The minimum deflection angle of the o-beam. This is the minimum deflection angle of the e-beam.

3. The system according to claim 1, characterized in that, The calculation steps for the polarization beam splitting ratio are as follows: in, The polarization beam splitting ratio; Peak-to-peak voltage of o-light The value corresponding to the maximum light intensity; Peak-to-peak voltage of e-beam The value corresponding to the maximum light intensity.

4. A method for measuring birefringence and polarization beam splitting ratio based on crystal rotation, characterized in that, include: S1. Based on the minimum deviation angle of the o-ray and e-ray. Calculate the refractive indices of the o-ray and e-ray respectively; S2. Based on the peak-to-peak voltages of the o-ray and e-ray. Calculate the real-time polarization beam splitting ratio, and based on the spot coordinates of the o-beam. and the coordinates of the e-ray spot Calculate the beam separation of o-ray and e-ray; S1 includes: A beam of light is emitted by a sodium lamp, collimated by a collimating tube, and then incident on the first birefringent crystal on the crystal rotating stage. Adjust the angle of the spectrometer telescope to make o-rays and e-rays appear in the field of view; Adjust the angle of the first rotatable polarizer so that o-rays and e-rays can be distinguished in the field of view of the spectrometer telescope; A rotating crystal stage is used to dynamically capture the minimum deflection angle of o-rays and e-rays via a spectrometer telescope. Simultaneously record the readings of the dual vernier dials; According to the minimum deviation angle The refractive index of the o-ray and the refractive index of the e-ray are calculated from the apex angle of the first birefringent crystal.

5. The method according to claim 4, characterized in that, S2 includes: The laser is emitted by the laser, and after the laser is incident on the second birefringent crystal, it is modulated into linearly polarized light by the second rotatable polarizer; Parallel execution at the output of the second rotatable polarizer: Marking the coordinates of the o-ray spot on a screen with a position scale. and the coordinates of the e-ray spot Furthermore, the peak-to-peak voltages of the o-ray and e-ray are collected in real time using photoelectric sensors. The output is then displayed on an oscilloscope. According to the peak-to-peak voltage Calculate the real-time polarization beam splitting ratio; According to the coordinates of the light spot of the o-ray and the coordinates of the e-ray spot Calculate the beam separation between the o-ray and e-ray.

6. The method according to claim 4, characterized in that, The rotating crystal stage dynamically captures the minimum deflection angles of the o-ray and e-ray using a spectrometer telescope. ,include: Locate the yellow spectral line refracted from the first birefringent crystal in the spectrometer telescope; Rotate the crystal and rotate the stage to make the yellow spectral line tend towards the direction of decreasing deflection angle; when the yellow spectral line begins to move in the opposite direction, take the current vernier readings on the left and right sides as the refraction angles of the left path and the right path, respectively. Remove the first birefringent crystal, rotate the spectrometer telescope to align with the collimator tube, and align the crosshairs with the slit. Use the current vernier readings on the left and right sides as the incident angles of the left and right paths, respectively. Calculate the minimum deviation angles of the o-ray and e-ray. The calculation formula is as follows: in, , These are the refraction angles for the left path and the right path, respectively. These are the angles of incidence for the left path and the right path, respectively.

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