Optical element transmittance and reflectance tester and measurement method, and calibration method thereof

Abstract

The application discloses an optical element transmission and reflection rate tester and a measuring method and a calibration method thereof. The tester comprises a laser, a light splitting sheet, a sample holder, a reference sensor and a detection sensor. The light splitting sheet splits the laser into detection light and reference light. The reference sensor detects the light intensity of the reference light. The sample holder drives the optical element to rotate horizontally so that the detection light is incident on the optical element at different incident angles. The rotation shaft of the sample holder is on the reflection surface of the optical element and vertically intersects with the detection light. The optical element reflects and transmits the detection light to form reflected light and transmitted light. The detection sensor can rotate around the rotation shaft of the sample holder to the front of the propagation direction of the reflected light to measure the light intensity of the reflected light or to the front of the propagation direction of the transmitted light to measure the light intensity of the transmitted light. The optical path between the detection sensor and the light splitting sheet is equal to the optical path between the reference sensor and the light splitting sheet. The application can effectively eliminate the fluctuation of the light source and support high-precision multi-angle scanning.

Description

Technical Field

[0001] This invention relates to the field of optical measurement technology, specifically to an optical element transmittance and reflectance tester and measurement method, and its calibration method. Background Technology

[0002] Transmittance and reflectance are key indicators for evaluating the core optical performance of optical components, directly determining the actual application effect of optical devices and the quality of products leaving the factory. Therefore, stringent requirements are placed on the accuracy, efficiency, automation level and multi-angle adaptability of their measurement process.

[0003] Currently, the mainstream transmittance and reflectance measurement equipment in the industry is the spectrophotometer. The basic accuracy of this type of equipment is typically 0.1% to 1%, and it cannot achieve automatic scanning of the incident angle or continuous multi-angle measurement, making it difficult to meet the high-efficiency testing requirements of batch optical components. Furthermore, in the existing measurement process, external interference factors such as random fluctuations in light source power, dark noise from photoelectric sensors, and dynamic changes in ambient temperature directly superimpose on the measurement signal, causing signal distortion and significantly reducing measurement accuracy. Some existing technologies also only allow manual adjustment of the test angle, failing to achieve automated adjustment; this cumbersome manual operation reduces the instrument's measurement accuracy.

[0004] While some existing automatic transmission and reflection meters have achieved basic automatic data acquisition, they still have many technical shortcomings and cannot meet the comprehensive needs of actual testing. For example, the optical path calibration and debugging error is large. Although some existing technologies can perform multi-angle transmission and reflection tests, they do not perform precise optical path calibration for the angles, making it difficult to guarantee the accuracy of the incident angle. Summary of the Invention

[0005] To address the problems in the background art, this invention proposes an optical element transmittance and reflectance tester and measurement method that can effectively eliminate light source fluctuations and support high-precision multi-angle scanning, and also provides a corresponding calibration method for the optical element transmittance and reflectance tester.

[0006] The present invention adopts the following technical solution: An optical element transmittance and reflectance tester includes: a laser, a beam splitter, a sample holder, a reference photoelectric sensor, and a probe photoelectric sensor. The laser emits laser light into the beam splitter, which splits the laser light into a probe beam and a reference beam. The reference photoelectric sensor is located in front of the propagation direction of the reference beam and is used to detect the intensity of the reference beam. The sample holder is located in front of the propagation direction of the probe beam. The optical element is mounted on the sample holder, which can drive the optical element to rotate horizontally so that the probe beam can be incident on the reflective surface of the optical element at different incident angles. The rotation axis of the sample holder is on the reflective surface of the optical element and intersects perpendicularly with the probe beam. The optical element reflects and transmits the probe beam to form reflected and transmitted light. The probe photoelectric sensor can rotate relative to the sample holder about the rotation axis of the sample holder until it is located in front of the propagation direction of the reflected beam to measure the intensity of the reflected beam, or in front of the propagation direction of the transmitted beam to measure the intensity of the transmitted beam. The optical path between the probe photoelectric sensor and the beam splitter is equal to the optical path between the reference photoelectric sensor and the beam splitter.

[0007] As a further improvement to the above technical solution: The sample holder is mounted on an upper rotating stage, and the upper rotating stage and the detection photoelectric sensor are mounted on a lower rotating stage. The rotation axes of the upper and lower rotating stages are arranged coaxially. When the upper rotating stage rotates horizontally, it drives the sample holder to rotate horizontally around its rotation axis. When the lower rotating stage rotates horizontally, it drives the sample holder and the detection photoelectric sensor to rotate horizontally around its rotation axis.

[0008] The sample holder is mounted on the upper rotating stage via a first angle adjustment mechanism. The first angle adjustment mechanism is used to adjust the pitch angle of the sample holder so that the rotation axis of the sample holder is perpendicular to the probe light.

[0009] A three-dimensional translation stage is provided between the first angle adjustment mechanism and the upper rotary stage. The three-dimensional translation stage is used to adjust the position of the sample holder relative to the upper rotary stage so that the rotation axis of the upper rotary stage is on the reflective surface of the optical element.

[0010] An adjustable aperture is provided on the lower rotating stage. The adjustable aperture is located between the sample holder and the detection photoelectric sensor. The adjustable aperture can rotate with the lower rotating stage within 0-180° to allow transmitted light, or vertically incident calibration light and its reflected light to pass through.

[0011] The beam splitter is mounted on a second angle adjustment mechanism, which is used to adjust the pitch angle of the beam splitter so that the probe light intersects perpendicularly with the rotation axis of the sample holder.

[0012] A first reflector is provided between the beam splitter and the laser. The first reflector is used to reflect the laser emitted by the laser to the beam splitter. The first reflector is mounted on a third angle adjustment mechanism. The third angle adjustment mechanism is used to adjust the pitch angle of the first reflector so that the laser emitted by the laser is reflected vertically to the beam splitter.

[0013] A first camera is located on the side of the beam splitter facing away from the sample holder. The first camera is used to collect the reflected light spot of the probe light incident on the calibration mirror at 0° when the calibration mirror is placed on the sample holder. A second camera is located in front of the propagation direction of the reflected light of the probe light incident on the calibration mirror at 45°. The second camera is used to collect the reflected light spot of the probe light incident on the calibration mirror at 45°.

[0014] The spectrometer, sample holder, reference photoelectric sensor, detection photoelectric sensor, first reflector, first camera, and second camera are all located in a single enclosure. The laser is located outside the enclosure. Inside the enclosure, there is also an optical fiber collimator electrically connected to the laser. The laser emitted by the laser is collimated by the optical fiber collimator and then incident on the first reflector at a 45° angle.

[0015] A half-wave plate is provided between the fiber collimator and the first reflector. The half-wave plate is fixed in the chassis by a one-dimensional displacement platform. The one-dimensional displacement platform is used to control the movement of the half-wave plate to realize the switching of the laser between the S polarization state and the P polarization state.

[0016] A plano-convex lens and an electronically controlled shutter are sequentially arranged between the first reflecting mirror and the beam splitter. The first reflecting mirror, plano-convex lens, electronically controlled shutter, and beam splitter are all installed in a cage-like system. The plano-convex lens is used to shape the laser, and the electronically controlled shutter controls the on / off state of the laser output.

[0017] The chassis also contains a second reflector, which is positioned in front of the direction of reference light propagation and is used to reflect the reference light perpendicularly to the reference photoelectric sensor.

[0018] As a general inventive concept, the present invention also provides a method for measuring the transmittance and reflectance of an optical element using the aforementioned testing instrument, comprising: mounting the optical element onto a sample holder, turning on the laser, recording the light intensity U1′ of the reference light detected by the reference photoelectric sensor, rotating the sample holder to drive the optical element to rotate horizontally so that the probe light can be incident on the reflective surface of the optical element at different incident angles, rotating the probe photoelectric sensor relative to the sample holder about the rotation axis of the sample holder until it is in front of the direction of propagation of the transmitted light, recording the light intensity U2′ of the transmitted light measured by the probe photoelectric sensor, and then rotating the probe photoelectric sensor relative to the sample holder about the rotation axis of the sample holder until it is in front of the direction of propagation of the reflected light, recording the light intensity U2″ of the reflected light measured by the probe photoelectric sensor. The transmittance T of the optical element is calculated by the following formula: T = (U2′ / U1′) / ((k2η2) / (k1η1)); The reflectivity R of the optical element is calculated by the following formula: R = (U2″ / U1′ / ((k2η2) / (k1η1)); Where η1 is the photoelectric conversion efficiency of the reference photoelectric sensor, η2 is the photoelectric conversion efficiency of the probe photoelectric sensor, and k2 / k1 is the intensity ratio of the probe light to the reference light.

[0019] As a general inventive concept, the present invention also provides a calibration method for the above-mentioned optical element transmittance and reflectance tester, comprising the following steps: S1: Disassemble the detection photoelectric sensor and perform the following factory calibration: S1.1: An adjustable aperture is added. The adjustable aperture can rotate with the sample holder within 0-180° and can rotate horizontally relative to the sample holder. When the aperture of the adjustable aperture is adjusted to the minimum, the laser is turned on and the pitch angle of the beam splitter is adjusted so that the probe light passes through the aperture of the adjustable aperture located at the 0 position and the 180 position. S1.2: Install a calibration mirror on the sample holder, and set up a first camera on the side of the beam splitter facing away from the sample holder. The first camera is located at 180°. Adjust the pitch angle of the sample holder until the first camera collects the reflected light spot of the probe light incident on the calibration mirror at 0° and marks it as the 0° spot. S1.3: A second camera is placed in front of the direction of propagation of the reflected light of the probe light incident on the calibration mirror at a 45° angle. The sample holder is rotated so that the probe light is incident on the calibration mirror at different incident angles. The adjustable aperture is rotated horizontally relative to the sample holder until it is in front of the direction of propagation of the reflected light of the calibration mirror. The three-dimensional position of the sample holder is adjusted so that the reflected light of the calibration mirror can pass through the aperture of the adjustable aperture. The second camera collects the reflected light spot of the probe light incident on the calibration mirror at a 45° angle and marks it as the 45° spot.

[0020] As a further improvement to the above technical solution: Also includes: S2: Install the photoelectric sensor, mount the optical element to be tested on the sample holder, and perform the following pre-test calibration: S2.1: Rotate the sample holder so that the probe light is incident on the optical element to be tested at 0°, turn on the first camera, and finely adjust the pitch angle of the sample holder so that the light spot presented by the first camera coincides with the 0° light spot; S2.2: Rotate the sample holder so that the probe light is incident on the optical element to be tested at a 45° angle. Turn on the second camera and fine-tune the three-dimensional position of the sample holder so that the light spot presented by the second camera coincides with the 45° light spot.

[0021] Compared with the prior art, the advantages of the present invention are as follows: The optical element transmittance and reflectance tester of this invention is based on the dual-path differential method. It uses a beam splitter to divide the laser source into a probe beam and a reference beam. The probe beam and reference beam have equal optical path lengths, ensuring that the spot sizes of the two beams illuminating the detector are consistent. This avoids the slight power deviation caused by the photodetector detecting light of different spot sizes. The beam splitting ratio (A) can be obtained by detecting the light intensities of the two beams. This ratio not only includes the beam splitting characteristics of the beam splitter but also integrates the difference in photoelectric conversion efficiency between the reference photoelectric sensor and the probe photoelectric sensor, making it an inherent characteristic parameter of the device. During transmittance and reflectance measurement, the light intensities of the reference beam, transmitted beam, and reflected beam are measured separately. Combined calculations are performed on the reference beam and transmitted beam, and on the reference beam and reflected beam, respectively, to obtain the transmittance and reflectance. The transmittance is only related to the aforementioned beam splitting ratio and transmittance / reference intensity ratio, and the reflectance is only related to the aforementioned beam splitting ratio and reflectance / reference intensity ratio. Therefore, laser power fluctuations are completely eliminated in the ratio calculation, effectively solving the interference of light source power fluctuations and noise interference on measurement accuracy, and fundamentally eliminating the influence of light source power fluctuations. Furthermore, by rotating the sample holder, the optical elements can be rotated horizontally, thereby controlling the incident angle of the probe light and achieving fully automatic multi-angle scanning, significantly improving efficiency and accuracy. Moreover, the photoelectric sensor is configured to rotate relative to the sample holder around its rotation axis. This rotation allows for the measurement of both transmitted and reflected light intensity. Since reflection and transmission share the same detector, errors caused by differences in photoelectric conversion efficiency between different sensors are eliminated, improving testing accuracy. Furthermore, this rotation method also enables precise calibration of the optical path, achieving a transmittance and reflectance measurement accuracy of 0.02%. Attached Figure Description

[0022] To facilitate understanding of the invention, it will be described in more detail with reference to the specific embodiments shown in the accompanying drawings. These drawings depict only typical embodiments of the invention and should not be considered as limiting the scope of protection of the invention.

[0023] Figure 1 This is a schematic diagram of the optical element transmittance and reflectance tester according to an embodiment of the present invention.

[0024] Figure 2 This is a schematic diagram of the internal structure of the optical element transmittance and reflectance tester according to an embodiment of the present invention.

[0025] Figure 3 This is a schematic diagram of the sample holder mounted on a rotary table in an embodiment of the present invention.

[0026] Figure 4 This is a reference measurement principle diagram for an embodiment of the present invention when no sample is installed.

[0027] Figure 5This is a schematic diagram illustrating the principle of measuring transmittance and reflectance of samples in an embodiment of the present invention.

[0028] Figure 6 This is a schematic diagram illustrating the principle of using three sensors to measure transmittance and reflectance in an embodiment of the present invention.

[0029] Figure 7 Schematic diagrams illustrating two scenarios where significant installation errors occur when placing different samples into the sample holder.

[0030] Figure 8 This is a schematic diagram of incident light calibration according to an embodiment of the present invention.

[0031] Figure 9 This is a schematic diagram of the 0° incident light path calibration according to an embodiment of the present invention.

[0032] Figure 10 This is a schematic diagram showing the position of the reflected light spot recorded by the software at 0° / 45° incident angle.

[0033] Figure 11 This is a schematic diagram illustrating the calibration of the reflective surface position of the calibration mirror according to an embodiment of the present invention.

[0034] Figure 12 This is a schematic diagram of the 45° incident light path calibration according to an embodiment of the present invention. Detailed Implementation

[0035] The embodiments of the present invention are described below with reference to the accompanying drawings to enable those skilled in the art to better understand and implement the present invention. However, the listed embodiments are not intended to limit the present invention. In the absence of conflict, the following embodiments and the technical features in the embodiments can be combined with each other, wherein the same components are indicated by the same reference numerals.

[0036] like Figure 1 and Figure 2As shown, this embodiment provides an optical element transmittance and reflectance tester, including: a laser 1, a beam splitter 7, a sample holder 8, a reference photoelectric sensor 15, and a detection photoelectric sensor 10. The laser 1 emits laser light into the beam splitter 7, which splits the laser light into a detection beam and a reference beam. The reference photoelectric sensor 15 is located in front of the propagation direction of the reference beam and is used to detect the intensity of the reference beam. The sample holder 8 is located in front of the propagation direction of the detection beam. The optical element is mounted on the sample holder 8, which can drive the optical element to rotate horizontally so that the detection beam can be incident at different angles. The light is incident on the reflective surface of the optical element. The rotation axis of the sample holder 8 is on the reflective surface of the optical element and intersects perpendicularly with the probe light. The optical element reflects and transmits the probe light to form reflected light and transmitted light. The detection photoelectric sensor 10 can rotate relative to the sample holder 8 around the rotation axis of the sample holder 8 until it is in front of the direction of propagation of the reflected light to measure the intensity of the reflected light, or in front of the direction of propagation of the transmitted light to measure the intensity of the transmitted light. The optical path between the detection photoelectric sensor 10 and the beam splitter 7 is equal to the optical path between the reference photoelectric sensor 15 and the beam splitter 7.

[0037] like Figure 3 As shown, the sample holder 8 is mounted on an upper rotating stage 22, and the upper rotating stage 22 and the detection photoelectric sensor 10 are mounted on a lower rotating stage 23. The rotation axes of the upper rotating stage 22 and the lower rotating stage 23 are arranged coaxially. When the upper rotating stage 22 rotates horizontally, it drives the sample holder 8 to rotate horizontally around its rotation axis. When the lower rotating stage 23 rotates horizontally, it drives the sample holder 8 and the detection photoelectric sensor 10 to rotate horizontally around its rotation axis.

[0038] In this embodiment, the sample holder 8 is mounted on the upper rotary table 22 via a first angle adjustment mechanism 26. The first angle adjustment mechanism 26 is used to adjust the pitch angle of the sample holder 8 so that the rotation axis of the sample holder 8 is perpendicular to the probe light.

[0039] In this embodiment, a three-dimensional translation stage 21 is provided between the first angle adjustment mechanism 26 and the upper rotating stage 22. The three-dimensional translation stage 21 is used to adjust the position of the sample holder 8 relative to the upper rotating stage 22 so that the rotation axis of the upper rotating stage 22 is on the reflective surface of the optical element.

[0040] In this embodiment, an adjustable aperture 9 is provided on the lower rotating stage 23. The adjustable aperture 9 is located between the sample holder 8 and the detection photoelectric sensor 10. The adjustable aperture 9 can rotate with the lower rotating stage 23 within 0-180° to allow transmitted light, or vertically incident calibration light and its reflected light to pass through.

[0041] In this embodiment, the beam splitter 7 is mounted on a second angle adjustment mechanism, which is used to adjust the pitch angle of the beam splitter 7 so that the probe light intersects perpendicularly with the rotation axis of the sample holder 8.

[0042] In this embodiment, a first reflector 4 is provided between the beam splitter 7 and the laser 1. The first reflector 4 is used to reflect the laser emitted by the laser 1 to the beam splitter 7. The first reflector 4 is mounted on a third angle adjustment mechanism, which is used to adjust the pitch angle of the first reflector 4 so that the laser emitted by the laser 1 is reflected vertically to the beam splitter 7.

[0043] In this embodiment, a first camera 11 is provided on the side of the beam splitter 7 facing away from the sample holder 8. The first camera 11 is used to collect the reflected light spot of the probe light incident on the calibration mirror at 0° when the calibration mirror is placed on the sample holder 8. A second camera 12 is provided in front of the propagation direction of the reflected light of the probe light incident on the calibration mirror at 45°. The second camera 12 is used to collect the reflected light spot of the probe light incident on the calibration mirror at 45°.

[0044] In this embodiment, the beam splitter 7, sample holder 8, reference photoelectric sensor 15, detection photoelectric sensor 10, first reflector 4, first camera 11 and second camera 12 are all located in a chassis, the laser 1 is located outside the chassis, and the chassis is also equipped with an optical fiber collimator electrically connected to the laser 1. The laser emitted by the laser 1 is collimated by the optical fiber collimator and then incident on the first reflector 4 at 45°.

[0045] In this embodiment, a half-wave plate 3 is provided between the fiber collimator and the first reflector 4. The half-wave plate 3 is fixed in the chassis by a one-dimensional displacement platform 19. The one-dimensional displacement platform 19 is used to control the movement of the half-wave plate 3 to realize the switching of the laser between the S polarization state and the P polarization state.

[0046] In this embodiment, a plano-convex lens 5 and an electronically controlled shutter 6 are sequentially arranged between the first reflector 4 and the beam splitter 7. The first reflector 4, the plano-convex lens 5, the electronically controlled shutter 6 and the beam splitter 7 are all installed in a cage system. The plano-convex lens 5 is used to shape the laser, and the electronically controlled shutter 6 controls the on / off state of the laser output.

[0047] In this embodiment, a second reflector 14 is also provided inside the chassis. The second reflector 14 is located in front of the direction of reference light propagation and is used to reflect the reference light vertically to the reference photoelectric sensor 15.

[0048] The following is a further explanation of the functions and parameters of the core components of this testing instrument: Laser Module: Laser 1 uses a helium-neon laser with an output wavelength of 632.8nm. It features high power stability and is located outside the chassis to prevent the laser's temperature from affecting the photoelectric sensor. The laser provides stable incident laser power for measurements. The laser is installed within the temperature control module 18, allowing for preheating to help it reach temperature equilibrium more quickly. Once stable, the temperature control module is shut off to allow the laser to reach natural temperature equilibrium. For other applications, other lasers can be used, such as gas lasers of different wavelengths or semiconductor lasers with temperature and power control. The laser is coupled via a fiber optic coupler; fiber optic output facilitates device connection, but spatial light output can also be used.

[0049] Polarization switching module: It consists of a half-wave plate 3 and an electric one-dimensional displacement platform 19. The electric one-dimensional displacement platform 19 controls the entry / exit of the half-wave plate 3 to realize fast, accurate and automatic switching between S polarization state and P polarization state. The beam shaping and splitting module consists of a reflector 4, a plano-convex lens 5, an electronically controlled shutter 6, and a beam splitter 7. The reflector 4 and beam splitter 7 can adjust the position and angle of the incident light. The plano-convex lens 5 shapes the laser beam, ensuring collimation and beam uniformity, and the beam size can be adjusted according to measurement requirements. The cage-like system allows for easy addition of different lenses to the optical path. The electronically controlled shutter 6, installed at the end of the cage-like system, controls the laser input and output. The shutter 6 is only opened when measurement is required, preventing prolonged laser exposure to the sensor and avoiding sensor overheating that could cause conversion coefficient drift. Even if the same sample is placed back into the sample holder, installation errors will inevitably exist.

[0050] Sample holder and motorized rotation module: Sample holder 8 is used to mount samples. Sample holder 8 is modified from a two-dimensional angle adjustment frame, which can be adjusted in two dimensions to ensure that the sample is perpendicular to the incident light when the incident light is 0°, that is, the rotation axis of sample holder 8 is perpendicular to the detection light. Rotary stage 13 includes an upper motorized turntable (upper turntable 22) and a lower motorized turntable (lower turntable 23). The upper turntable 22 and the lower turntable 23 are coaxially mounted. The three-dimensional translation stage 21 is used to adjust the position of the sample holder to ensure that the reflective surface of the sample is on the rotation axis of the motorized turntable. The lower turntable 23 is used to adjust the angle of the detection photoelectric sensor 10, and its rotation will also drive the upper turntable 22 to rotate. The upper turntable 22 is used to adjust the angle of the sample relative to the incident light, that is, the incident angle. Sensor fixing arm 24 is used to mount the detection photoelectric sensor 10. Limit switch baffle 25 is used to trigger the limit switch to ensure that the lower motorized turntable rotates within the range of 0° to 180° to avoid collision with other components of the equipment.

[0051] Signal detection module: Reference photoelectric sensor 15 and detection photoelectric sensor 10 respectively collect optical signals from the reference optical path and the detection optical path, and convert the optical signals into electrical signals and transmit them to computer 16; Adjustable aperture 9 is used to filter stray light, such as scattered light and secondary reflection light from optical devices, to ensure the purity of the detection signal; The visual calibration module consists of a first camera 11 and a second camera 12. Both the first camera 11 and the second camera 12 are industrial cameras, which are used to calibrate the position of the light spot at 0° and 45° reflection, respectively. The light spot images captured by the cameras are displayed in real time on the computer software interface to ensure that the light spot is in the same position at 0° and 45° reflection, thus providing visual assistance for optical path calibration. Data processing module: Based on computer 16, equipped with dedicated measurement software, it realizes functions such as signal acquisition, data calculation, result display, and file saving, and integrates parameter setting, optical path calibration, and automatic measurement of the entire process.

[0052] The method for measuring the transmittance and reflectance of an optical element using the testing instrument of this embodiment includes the following steps: The optical element is mounted on a sample holder 8; the laser 1 is turned on; the intensity U1′ of the reference light detected by the reference photoelectric sensor is recorded; the sample holder 8 is rotated to cause the optical element to rotate horizontally, so that the detection light can be incident on the reflective surface of the optical element at different incident angles; the detection photoelectric sensor 10 is rotated relative to the sample holder 8 around the rotation axis of the sample holder 8 until it is in front of the direction of transmission light propagation; the intensity U2′ of the transmitted light measured by the detection photoelectric sensor 10 is recorded; the detection photoelectric sensor 10 is then rotated relative to the sample holder 8 around the rotation axis of the sample holder 8 until it is in front of the direction of reflection light propagation; the intensity U2″ of the reflected light measured by the detection photoelectric sensor 10 is recorded. The transmittance T of the optical element is calculated by the following formula: T = (U2′ / U1′) / ((k2η2) / (k1η1)); The reflectivity R of an optical element is calculated using the following formula: R = (U2″ / U1′ / ((k2η2) / (k1η1)); Where η1 is the photoelectric conversion efficiency of the reference photoelectric sensor 15, η2 is the photoelectric conversion efficiency of the detection photoelectric sensor 10, and k2 / k1 is the intensity ratio of the detection light and the reference light.

[0053] The measurement process and principle of the electronic element transmittance and reflectance tester in this embodiment are further explained below: Step 1: Reference measurement: Measure without a sample to determine the spectrophotometric ratio.

[0054] like Figure 4As shown, the laser source is split into a reference beam and a probe beam by a beam splitter. The reference beam enters photodetector one (i.e., the reference photodetector) to obtain a reference signal; the probe beam enters photodetector two (i.e., the probe photodetector) to obtain a probe signal. The probe beam and the reference beam have equal optical path lengths, ensuring that the spot size of the two beams illuminating the detector is consistent, thus avoiding slight power deviations caused by the photodetector detecting light of different spot sizes.

[0055] Let the incident light intensity be I. After the light is split by the beam splitter, the light intensities of the reference light path and the detector light path are k1I and k2I, respectively. The photoelectric conversion efficiencies of photoelectric sensor one and photoelectric sensor two are η1 and η2, respectively. Then the signals measured by the two sensors are: Reference signal: U1 = k1η1I, Detection signal: U2 = k2η2I, Define the splitting ratio A = U2 / U1, then A = (k2η2) / ( k1η1).

[0056] Note: The spectrophotometer ratio A in this invention not only incorporates the spectrophotometric characteristics of the spectrometer but also integrates the difference in photoelectric conversion efficiency between photoelectric sensor one and photoelectric sensor two, making it an inherent characteristic parameter of the device. The spectrophotometer ratio A fluctuates with ambient temperature; therefore, the device needs to be preheated, and testing should begin after the temperature stabilizes. Furthermore, a reference measurement is performed to obtain the spectrophotometer ratio A before each test.

[0057] Step 2: Sample Measurement: After placing the sample, perform measurements and calculate the transmittance or reflectance.

[0058] like Figure 5 As shown, after the sample is placed in the sample, the detection light is divided into transmitted light and reflected light. The second photoelectric sensor can directly measure the transmitted light signal. The second photoelectric sensor is mounted on a turntable and can be rotated 90° clockwise to detect the reflected signal.

[0059] Transmittance Measurement: The sample to be tested is placed in the instrument. At this time, the laser intensity changes to I′ due to power fluctuations. Let the actual transmittance of the sample be T. The instrument collects the reference sensor signal U1′ and the sample sensor signal U2′. Then: U1′= k1η1I′, U2′= Tk2η2I′, Define the ratio BT = U2′ / U1′, then BT = (Tk2η2I′) / (k1η1I′) =T・A, and finally derive T = BT / A.

[0060] As can be seen from the above formula, the laser power fluctuation is completely eliminated in the ratio calculation, effectively solving the interference of light source power fluctuation on measurement accuracy.

[0061] Reflectance measurement: The photoelectric sensor is rotated 90° for measurement. The calculation method is the same as for transmittance measurement. Let the reflectance be R. The instrument collects the reference sensor signal U1′ and the sample sensor signal U2″, then: U1′= k1η1I′, U2″= Rk2η2I′, Define the ratio BR = U2″ / U1′, then BR = (Rk2η2I′) / (k1η1I′) = R・A, and finally derive R = BR / A.

[0062] As the above calculations show, laser power fluctuations are completely eliminated in the calculation, effectively solving the interference of light source power fluctuations and noise on measurement accuracy. Reflection and transmission share the same detector, eliminating errors caused by differences in photoelectric conversion efficiency between different sensors and improving test accuracy. If three sensors are used for testing, such as... Figure 6 As shown, reflectivity testing is performed using an additional photoelectric sensor (type 3). The differences in photoelectric conversion efficiency between different sensors significantly affect the accuracy of reflectivity measurement. Furthermore, photoelectric conversion efficiency is affected by ambient temperature, therefore, a reference measurement calibration must be performed before each test. However, photoelectric sensor type 3 cannot be calibrated at any time, leading to substantial errors.

[0063] The calibration method for the optical element transmittance and reflectance tester in this embodiment includes the following steps: S1: Disassemble the detection photoelectric sensor 10 and perform the following factory calibration: S1.1: An adjustable aperture 9 is added. The adjustable aperture 9 can rotate with the sample holder 8 within the range of 0-180°. The adjustable aperture 9 can also rotate horizontally relative to the sample holder 8. When the aperture of the adjustable aperture 9 is adjusted to the minimum, the laser 1 is turned on, and the pitch angle of the beam splitter 7 is adjusted so that the probe light passes through the aperture of the adjustable aperture 9 located at the 0 position and the 180 position. S1.2: Install a calibration mirror on the sample holder 8, and set a first camera 11 on the side of the beam splitter 7 facing away from the sample holder 8. The first camera 11 is located at 180°. Adjust the pitch angle of the sample holder 8 until the first camera 11 collects the reflected light spot of the probe light incident on the calibration mirror at 0° and marks it as the 0° spot. S1.3: A second camera 12 is placed in front of the direction of propagation of the reflected light of the probe light incident on the calibration mirror at a 45° angle. The sample holder 8 is rotated so that the probe light is incident on the calibration mirror at different incident angles. The adjustable aperture 9 is rotated horizontally relative to the sample holder 8 until the adjustable aperture 9 is in front of the direction of propagation of the reflected light of the calibration mirror. The three-dimensional position of the sample holder 8 is adjusted so that the reflected light of the calibration mirror can pass through the aperture of the adjustable aperture 9. The second camera 12 collects the reflected light spot of the probe light incident on the calibration mirror at a 45° angle and marks it as the 45° spot.

[0064] S2: Install the photoelectric sensor 10, install the optical element to be tested on the sample holder 8, and perform the following pre-test calibration: S2.1: Rotate the sample holder 8 so that the probe light is incident on the optical element to be tested at 0°, turn on the first camera 11, and finely adjust the pitch angle of the sample holder 8 so that the light spot presented by the first camera 11 coincides with the 0° light spot; S2.2: Rotate the sample holder 8 so that the probe light is incident on the optical element to be tested at a 45° angle, turn on the second camera 12, and fine-tune the three-dimensional position of the sample holder 8 so that the light spot presented by the second camera 12 coincides with the 45° light spot.

[0065] The optical path calibration and standardization method of the optical element transmittance and reflectance tester in this embodiment will be further described below: like Figure 7 As shown, different samples placed in the sample holder will exhibit significant installation errors. Even re-clamping the same sample will result in installation errors. These installation errors will lead to differences in the sample tilt angle and the position of the reflecting surface, resulting in inaccurate incident angle of the laser relative to the sample and deviations in the angle of reflected light. Any deviation may affect the measurement accuracy of optical power. This invention utilizes an electric turntable and dual-camera vision-assisted calibration to achieve precise calibration and standardization of the incident angle of the incident light relative to the sample. The specific steps are as follows: 1. Factory calibration: Before calibration, remove the photodetector 10. The calibration steps are as follows: a. Incident light calibration: Calibration objective: The incident light needs to be on the same plane as the rotation axis of the rotary stage 13 in order to ensure that the position of the incident light illuminating the sample surface remains unchanged after the electric rotary stage rotates.

[0066] Calibration method: Adjust the aperture of the adjustable stop 9 to its minimum. Mount the beam splitter 7 and the first reflecting mirror 4 on the two-dimensional angle adjustment frame. The height and angle of the incident light can be adjusted by adjusting the angles of the beam splitter 7 and the first reflecting mirror 4. Figure 8As shown, when the lower rotary stage 23 is rotated to 0° and 180° respectively, if the incident light passes through the aperture of the aperture 9, the incident light will inevitably pass through the rotation axis of the rotary stage; by adjusting the angle of the beam splitter 7 and the first reflecting mirror 4, the incident light meets this requirement, and the calibration step is completed.

[0067] b. Calibration and marking of the 0° incident optical path: Calibration objective: Both the upper and lower rotating stages of rotary stage 13 are rotated to 0°. However, due to installation errors, it cannot be guaranteed that the light is incident on the sample at 0°. After adjustment, it is ensured that the incident light is incident on the calibration mirror at 0°, and the position of the reflected light spot is recorded with an industrial camera for future testing and calibration.

[0068] Calibration method: A silver-plated reflector is used as the calibration reflector and placed in the sample holder. Both the upper and lower rotating stages of the rotating stage 13 are rotated to 0°. Since the laser light will return along its original path when incident at 0°, the angle of the calibration reflector is changed by adjusting the sample holder 8. Figure 9 As shown, when the incident light and the reflected light completely overlap, the laser is determined to be incident at 0°. At this point, the first camera 11 is activated, and a white light spot can be seen on the computer screen, as shown... Figure 10 As shown, the gray spot is the center marker of the white spot calculated by the software, denoted as the marker point. Subsequent tests will consider the incident light to be incident at 0° if the reflected light coincides with the gray spot.

[0069] c. Calibrate the position of the reflecting surface of the mirror: Calibration objective: The axis of the upper and lower electric rotary table 13 must be on the reflection point of the calibration mirror so that the reflection point on the surface of the calibration mirror will not change during rotation.

[0070] Calibration method: Using the adjustable aperture 9, adjust the aperture to its minimum. After placing the silver-plated calibration mirror into the sample holder, rotate the electric stage angle. By adjusting the three-dimensional translation stage 21, ensure that the reflected light from the mirror always passes through the aperture. This proves that the reflection point of the light is on the axis of rotation. If it is not on the axis of rotation, the reflected light will deviate from the aperture. Figure 11 As shown, several angles can be selected during actual calibration, such as 0°, 30°, 60°, and 90° (for example, when adjusting to 60°, the lower rotary table 23 rotates 60°, and the upper rotary table 22 follows suit and rotates 60°. Therefore, the upper rotary table 22 needs to rotate 30° to ensure an incident angle of 30°).

[0071] d. 45° incident light path marking: Calibration objective: To mark the spot of reflected light when incident at 45°, and record the spot position with an industrial camera for future testing and calibration.

[0072] Calibration method: such as Figure 12As shown, the upper rotating stage 22 rotates 45°, at which point the calibration reflector rotates 45°, and the incident light is incident on the calibration reflector at a 45° angle. At this time, the second camera 12 is turned on, and a white spot of reflected light from the 45° incident light can be seen on the computer (e.g., ...). Figure 10 As shown in the image, the software records the location of the light spot as a gray circular spot.

[0073] After calibration using the calibration mirror, the software records the position of the gray circular spot. As long as the system optical path remains unchanged, there is no need for recalibration.

[0074] 2. Calibration before testing: There will be installation errors after each test sample is placed. The sample needs to be calibrated first to ensure that the sample is perpendicular to the incident light at 0° and that the reflective surface of the sample is on the axis of the electric turntable.

[0075] a. 0° Calibration: Calibration purpose: To calibrate before each test, with the sample perpendicular to the incident light at 0°.

[0076] Calibration method: Test optical path and Figure 9 Similarly, place the test sample in the machine and rotate the electric turntable to 0°. Theoretically, the laser has a 0° incident angle relative to the sample at this point. However, due to installation errors, the angle may deviate. Turn on the first camera 11 to see the laser spot image. Adjust the two-dimensional turntable to fine-tune the sample angle so that the red circle on the image coincides with the recorded gray circle. At this point, the sample surface is perpendicular to the incident light, and the incident light has a 0° incident angle relative to the sample, thus completing the 0° incident angle optical path calibration.

[0077] b. 45° calibration: Calibration purpose: Before each test, calibration is performed so that the reflection point of the laser on the sample after the sample is rotated coincides with the axis of the turntable.

[0078] Calibration method: Test optical path and Figure 12 Similarly, the upper motorized turntable is rotated 45°. At this point, the laser is at a 45° incident angle relative to the sample. Because of sample installation errors, the position of the reflecting surface will be deviated. The second camera 12 is turned on to acquire the laser spot image of the reflected light path. By adjusting the three-dimensional displacement platform 21, the horizontal position of the spot is finely adjusted so that the red circle on the image coincides with the recorded gray circle. This indicates that the sample reflection point coincides with the axis of the motorized turntable.

[0079] The instrument preheating requirements are as follows: To eliminate the impact of temperature drift on measurement accuracy, the instrument needs to be preheated before formal measurement to allow the laser and sensor to reach temperature equilibrium. Alternatively, the preheating time can be shortened by heating the laser 1 using a temperature controller 18. After preheating, transmittance measurement without a sample can be performed, with a transmittance of 1. If the stability can be below 0.02%, high-precision results can be obtained for formal measurement at this point. Using a semiconductor laser or fiber laser with temperature and power control can achieve faster preheating, but the cost is higher. This invention uses a fiber optic interface, allowing the laser to be replaced as needed.

[0080] The advantages of this invention are summarized as follows: 1) Dual-path fitting calibration eliminates interference from light source power fluctuations in principle.

[0081] 2) Electric turntable and dual-camera vision calibration ensure accurate incident angle.

[0082] 3) Fully automatic multi-angle scanning, no manual adjustment required, greatly improving efficiency and accuracy.

[0083] 4) The fiber optic interface allows for interchangeable lasers, enabling multi-wavelength measurements.

[0084] 5) The accuracy of transmittance and reflectance measurement can reach 0.02%.

[0085] The embodiments described above are merely preferred embodiments of the present invention. The terms "in one embodiment," "in another embodiment," "in yet another embodiment," or "in still another embodiment" used in this specification all refer to one or more of the same or different embodiments according to this disclosure. Ordinary variations and substitutions made by those skilled in the art within the scope of the present invention should be included within the protection scope of the present invention.

Claims

1. An optical element transmittance and reflectance tester, characterized in that, include: The system comprises a laser (1), a beam splitter (7), a sample holder (8), a reference photoelectric sensor (15), and a detection photoelectric sensor (10). The laser (1) emits laser light into the beam splitter (7), which splits the laser light into a probe light and a reference light. The reference photoelectric sensor (15) is located in front of the direction of reference light propagation and is used to detect the intensity of the reference light. The sample holder (8) is located in front of the direction of probe light propagation. Optical elements are mounted on the sample holder (8), which can drive the optical elements to rotate horizontally so that the probe light can be incident on the reflection of the optical elements at different incident angles. On the reflective surface, the rotation axis of the sample holder (8) is on the reflective surface of the optical element and intersects perpendicularly with the probe light. The optical element reflects and transmits the probe light to form reflected light and transmitted light. The detection photoelectric sensor (10) can rotate relative to the sample holder (8) around the rotation axis of the sample holder (8) until it is in front of the direction of reflection of the light propagation to measure the intensity of the reflected light, or in front of the direction of transmission of the light propagation to measure the intensity of the transmitted light. The optical path between the detection photoelectric sensor (10) and the beam splitter (7) is equal to the optical path between the reference photoelectric sensor (15) and the beam splitter (7).

2. The optical element transmittance and reflectance tester according to claim 1, characterized in that, The sample holder (8) is mounted on an upper rotating stage (22), and the upper rotating stage (22) and the detection photoelectric sensor (10) are mounted on a lower rotating stage (23). The rotation axes of the upper rotating stage (22) and the lower rotating stage (23) are arranged coaxially. When the upper rotating stage (22) rotates horizontally, it drives the sample holder (8) to rotate horizontally around its rotation axis. When the lower rotating stage (23) rotates horizontally, it drives the sample holder (8) and the detection photoelectric sensor (10) to rotate horizontally around its rotation axis.

3. The optical element transmittance and reflectance tester according to claim 2, characterized in that, The sample holder (8) is mounted on the upper rotary table (22) via a first angle adjustment mechanism (26). The first angle adjustment mechanism (26) is used to adjust the pitch angle of the sample holder (8) so that the rotation axis of the sample holder (8) intersects the probe light perpendicularly.

4. The optical element transmittance and reflectance tester according to claim 3, characterized in that, A three-dimensional translation stage (21) is provided between the first angle adjustment mechanism (26) and the upper rotary stage (22). The three-dimensional translation stage (21) is used to adjust the position of the sample holder (8) relative to the upper rotary stage (22) so that the rotation axis of the upper rotary stage (22) is on the reflective surface of the optical element.

5. The optical element transmittance and reflectance tester according to claim 4, characterized in that, An adjustable aperture (9) is provided on the lower rotating stage (23). The adjustable aperture (9) is located between the sample holder (8) and the detection photoelectric sensor (10). The adjustable aperture (9) can rotate with the lower rotating stage (23) within 0-180° to allow transmitted light, or vertically incident calibration light and its reflected light to pass through.

6. The optical element transmittance and reflectance tester according to claim 5, characterized in that, The beam splitter (7) is mounted on a second angle adjustment mechanism, which is used to adjust the pitch angle of the beam splitter (7) so that the probe light intersects perpendicularly with the rotation axis of the sample holder (8).

7. The optical element transmittance and reflectance tester according to claim 6, characterized in that, A first camera (11) is provided on the side of the beam splitter (7) facing away from the sample holder (8). The first camera (11) is used to collect the reflected light spot of the probe light incident on the calibration mirror at 0° when the calibration mirror is placed on the sample holder (8). A second camera (12) is provided in front of the propagation direction of the reflected light of the probe light incident on the calibration mirror at 45°. The second camera (12) is used to collect the reflected light spot of the probe light incident on the calibration mirror at 45°.

8. A method for measuring the transmittance and reflectance of an optical element using the testing instrument as described in any one of claims 1-7, comprising: The optical element is mounted on the sample holder (8), the laser (1) is turned on, and the intensity U1′ of the reference light detected by the reference photoelectric sensor (15) is recorded. The sample holder (8) is rotated to drive the optical element to rotate horizontally so that the detection light can be incident on the reflective surface of the optical element at different incident angles. The detection photoelectric sensor (10) is rotated relative to the sample holder (8) around the rotation axis of the sample holder (8) until it is in front of the direction of transmission light propagation. The intensity U2′ of the transmitted light measured by the detection photoelectric sensor (10) is recorded. Then the detection photoelectric sensor (10) is rotated relative to the sample holder (8) around the rotation axis of the sample holder (8) until it is in front of the direction of reflection light propagation. The intensity U2″ of the reflected light measured by the detection photoelectric sensor (10) is recorded. The transmittance T of the optical element is calculated by the following formula: T=( U2′ / U1′) / ( (k2η2) / ( k1η1)); The reflectivity R of the optical element is calculated by the following formula: R=( U2″ / U1′ / ((k2η2) / ( k1η1)); Wherein, η1 is the photoelectric conversion efficiency of the reference photoelectric sensor (15), η2 is the photoelectric conversion efficiency of the probe photoelectric sensor (10), and k2 / k1 is the light intensity ratio of the probe light and the reference light.

9. A calibration method for an optical element transmittance and reflectance tester as described in any one of claims 1-7, comprising the following steps: S1: Disassemble the detection photoelectric sensor (10) and perform the following factory calibration: S1.1: An adjustable aperture (9) is added. The adjustable aperture (9) can rotate with the sample holder (8) within 0-180°. The adjustable aperture (9) can rotate horizontally relative to the sample holder (8). The aperture of the adjustable aperture (9) is adjusted to the minimum. The laser (1) is turned on, and the pitch angle of the beam splitter (7) is adjusted so that the probe light passes through the aperture of the adjustable aperture (9) located at the 0 position and the 180 position. S1.2: Install a calibration mirror on the sample holder (8), and set a first camera (11) on the side of the beam splitter (7) facing away from the sample holder (8). The first camera (11) is located at 180°. Adjust the pitch angle of the sample holder (8) until the first camera (11) collects the reflected light spot of the probe light incident on the calibration mirror at 0° and marks it as the 0° spot. S1.3: A second camera (12) is set in front of the direction of propagation of the reflected light of the probe light incident on the calibration mirror at 45°. The sample holder (8) is rotated so that the probe light is incident on the calibration mirror at different incident angles. The adjustable aperture (9) is rotated horizontally relative to the sample holder (8) until the adjustable aperture (9) is in front of the direction of propagation of the reflected light of the calibration mirror. The three-dimensional position of the sample holder (8) is adjusted so that the reflected light of the calibration mirror can pass through the aperture hole of the adjustable aperture (9). The second camera (12) collects the reflected light spot of the probe light incident on the calibration mirror at 45° and marks it as the 45° spot.

10. The calibration method for the optical element transmittance and reflectance tester according to claim 9, characterized in that, Also includes: S2: Install the detection photoelectric sensor (10), install the optical element to be tested on the sample holder (8), and perform the following pre-test calibration: S2.1: Rotate the sample holder (8) so that the probe light is incident on the optical element to be tested at 0°, turn on the first camera (11), and finely adjust the pitch angle of the sample holder (8) so that the light spot presented by the first camera (11) coincides with the 0° light spot; S2.2: Rotate the sample holder (8) so that the probe light is incident on the optical element to be tested at 45°, turn on the second camera (12), and fine-tune the three-dimensional position of the sample holder (8) so that the light spot presented by the second camera (12) coincides with the 45° light spot.

Images