A lens refractive index testing device and testing method

Abstract

This invention relates to the field of lens testing technology, and more particularly to a lens refractive index testing device and method. The device includes a frame with a top plate and a bottom plate opposite to the top plate; a positioning component disposed on the bottom plate for placing the lens under test; and a calibration light source module disposed on the top plate, vertically opposite to the positioning component. This invention uses broadband low-coherence light, red light, and blue light coupled to the same optical axis via an optical path converging component to test the lens. This effectively reduces the impact of environmental vibration, temperature changes, and mechanical errors on the test results. Furthermore, the high spatial resolution of the broadband low-coherence light is used to distinguish interference peaks on the upper and lower surfaces of the lens for measuring lens thickness. During the same testing process, the refractive index parameters of the lens under test at different light source wavelengths are calculated, and the dispersion coefficient of the lens material is obtained based on the refractive index parameters, thereby improving lens testing efficiency.

Description

Technical Field

[0001] This invention relates to the field of lens testing technology, and in particular to a lens refractive index testing device and testing method. Background Technology

[0002] Refractive index is one of the important indicators for evaluating the performance of optical lenses. By measuring the refractive index of optical lenses, the imaging quality of the lenses can be ensured. Traditional methods for measuring the refractive index of lenses include contact measuring instruments and non-contact methods such as the minimum deviation angle method.

[0003] The Abbe refractometer is used to measure the curvature of the upper and lower surfaces of a lens, its center thickness, and its optical power. The refractive index at the test wavelength is then calculated using the optical power formula. However, this method is not suitable for measuring aspherical lenses.

[0004] However, using the minimum deviation angle method requires processing the material to be tested into a bipolar mirror with two precision polished surfaces for light refraction. At the same time, it is necessary to accurately measure the angle of the bipolar mirror. The bipolar mirror is difficult to manufacture and takes a long time, making it difficult to meet the needs of rapid and efficient detection of the refractive index of the lens. Summary of the Invention

[0005] The purpose of this invention is to provide a lens refractive index detection device and detection method to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A lens refractive index detection device, comprising:

[0008] frame;

[0009] A positioning component, mounted on the frame, is used to support the lens being tested;

[0010] A detection light source assembly, mounted on the frame, is used to emit detection light;

[0011] The first beam splitter is used to split the detection light into a reference light and a measurement light. The measurement light is reflected by the lens under test to form the measurement reflected light.

[0012] Interference detection component, used to detect the interference signal formed by the reflected light and the reference light;

[0013] The drive mechanism is mounted on the frame;

[0014] A reflection measurement assembly includes a reflector and a measurement component. The reflector is located on the optical axis path of a reference light for reflecting the reference light, and the reflector is driven to move along the optical axis path of the reference light to change the optical path of the reference light.

[0015] The measuring component is used to measure the displacement of the reflector along the optical axis to determine the corresponding movement distance of the reflector when the interference signal appears.

[0016] Preferably, the detection light source assembly includes a first light source module, a second light source module, and a third light source module, wherein the first light source module, the second light source module, and the third light source module are respectively used to emit detection light of different wavelengths.

[0017] Preferably, the second light source module and the third light source module are further provided with a light source shaping module;

[0018] The light source shaping module includes an aperture, a rear lens, and a front lens, which are coaxially arranged from top to bottom in the vertical direction.

[0019] Preferably, the frame is further equipped with an optical path converging assembly, which includes a first bipolar mirror, a second bipolar mirror, a third bipolar mirror, and a focusing lens;

[0020] The first bidirectional color mirror is positioned vertically relative to the first light source module;

[0021] The second bidirectional color mirror is positioned vertically relative to the second light source module;

[0022] The third bidirectional color mirror is positioned vertically relative to the third light source module;

[0023] The first bipolar mirror, the second bipolar mirror, the third bipolar mirror, and the focusing lens are located on the same height plane of the frame. The focusing lens is used to couple the detection light of different wavelengths provided by the first light source module, the second light source module, and the third light source module to the same optical axis.

[0024] Preferably, the first beam splitter includes a fourth bipolar mirror and a fifth bipolar mirror, wherein the fourth bipolar mirror is disposed opposite to the focusing lens and is used to split the detection light into a reference light and a measurement light;

[0025] The fifth bipolar mirror is located on the propagation path of the reference light and is positioned opposite to the reflection measurement component to guide the propagation of the reference light.

[0026] Preferably, a second beam splitter is also installed on the rack. The second beam splitter includes a sixth bicolor mirror and a seventh bicolor mirror, which are used to guide interference signals corresponding to different wavelengths to the interference detection component, respectively.

[0027] Preferably, the interference detection component includes a first photoelectric detection module, a second photoelectric detection module, and a third photoelectric detection module, which are used to detect interference signals corresponding to different wavelengths, respectively.

[0028] Preferably, the drive module includes a stepper motor;

[0029] The measuring component includes a grating ruler guide rail and a grating ruler slider. The grating ruler slider is slidably connected to the grating ruler guide rail. The grating ruler guide rail is connected to the frame and is on the same horizontal plane as the optical axis of the reference light.

[0030] The stepper motor drives the slider of the grating ruler to move along the guide rail of the grating ruler;

[0031] The reflector is fixedly mounted on the slider of the grating ruler.

[0032] Preferably, it also includes a calibration light source module, which is mounted on the frame and is arranged vertically opposite to the positioning component to assist the positioning component in calibrating the placement position of the lens under test.

[0033] A method for measuring the refractive index of a lens includes the following steps:

[0034] S1. Obtain the first interference signal and the first motion distance corresponding to different wavelengths of detection light;

[0035] The first interference signal is the interference signal generated by the measurement light and the reference light when the lens under test is not placed;

[0036] The first movement distance is the mirror displacement parameter corresponding to the first interference signal.

[0037] S2. Obtain the second interference signal and the second motion distance corresponding to the lens under test;

[0038] The second interference signal is the interference signal generated by measuring the reflected light and the reference light after the lens under test is placed;

[0039] The second motion distance is the mirror displacement parameter corresponding to the second interference signal.

[0040] S3. Determine the interface position parameters of the lens under test based on the second motion distance corresponding to the broadband low coherence light, and calculate the thickness parameters of the lens under test based on the interface position parameters.

[0041] The interface position parameters include the first interface position parameters corresponding to the upper surface of the lens under test and the second interface position parameters corresponding to the lower surface of the lens under test.

[0042] The thickness parameter is the physical distance between the upper and lower surfaces of the lens being measured.

[0043] S4. Calculate the corresponding refractive index parameters based on the first motion distance, second motion distance, and thickness parameters corresponding to different wavelengths of detection light;

[0044] The refractive index parameters include a first refractive index parameter corresponding to broadband low-coherence light, a second refractive index parameter corresponding to red light, and a third refractive index parameter corresponding to blue light.

[0045] S5. Calculate the dispersion coefficient of the lens under test based on the first refractive index parameter, the second refractive index parameter, and the third refractive index parameter.

[0046] This invention employs broadband low-coherence light, red light, and blue light coupled to the same optical axis via an optical path converging component to detect the lens under test. This effectively reduces the impact of environmental vibration, temperature changes, and mechanical errors on the detection results. Furthermore, the high spatial resolution of the broadband low-coherence light is utilized to distinguish the interference peaks on the upper and lower surfaces of the lens for measuring lens thickness. In the same detection process, the refractive index parameters of the lens under test under different light source wavelengths are calculated, and the dispersion coefficient of the lens material is obtained based on the refractive index parameters, thereby improving the lens detection efficiency. Attached Figure Description

[0047] Figure 1 This is a front view structural diagram of the present invention;

[0048] Figure 2 This is a partially enlarged schematic diagram of the positioning component structure of the present invention;

[0049] Figure 3 This is a schematic diagram of the Hartmann grating structure of the present invention;

[0050] Figure 4 This is a partially enlarged schematic diagram of the structure of the second light source module of the present invention;

[0051] Figure 5 This is a partially enlarged schematic diagram of the third light source module structure of the present invention;

[0052] Figure 6 This is a partially enlarged schematic diagram of the reflection measurement component structure of the present invention;

[0053] Figure 7 This is a front view schematic diagram of the beam propagation path structure during the detection stage of the present invention;

[0054] Figure 8 This is a schematic flowchart of the lens refractive index detection method of the present invention.

[0055] In the picture:

[0056] 100. Frame; 110. Top plate; 120. Bottom plate; 130. Side plate;

[0057] 200. Positioning component; 210. Hartmann grating; 220. Image sensor; 211. Reflection point; 212. Transmitting point;

[0058] 300. Detection light source assembly; 310. First light source module; 320. Second light source module; 330. Third light source module;

[0059] 400. Optical path converging assembly; 410. First bipolar mirror; 420. Second bipolar mirror; 430. Third bipolar mirror; 440. Focusing lens;

[0060] 500. First beam splitter; 510. Fourth bipolar mirror; 520. Fifth bipolar mirror;

[0061] 600. Reflection measurement assembly; 610. Stepper motor; 620. Grating ruler slider; 630. Reflector; 640. Grating ruler guide rail;

[0062] 700. Second beam splitter; 710. Sixth bipolar mirror; 720. Seventh bipolar mirror;

[0063] 800. Interference detection component; 810. First photoelectric detection module; 820. Second photoelectric detection module; 830. Third photoelectric detection module.

[0064] 900. Light source shaping module; 910. Aperture; 920. Rear lens; 930. Front lens;

[0065] 1000. Calibrate the light source module. Detailed Implementation

[0066] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0067] In the description of this invention, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0068] like Figure 1 - Figure 7 As shown, a lens refractive index detection device includes:

[0069] The frame 100 has a top plate 110 at the top and a bottom plate 120 at the bottom opposite to the top plate 110. A side plate 130 is connected between the top plate 110 and the bottom plate 120.

[0070] The positioning component 200 is mounted on the base plate 120 of the frame 100 and is used to place the lens to be tested.

[0071] The detection light source assembly 300 is used to provide multiple detection lights of different wavelengths;

[0072] The first beam splitter 500 is used to split the detection light into two beams of reference light and measurement light with different optical axis directions;

[0073] A drive mechanism is mounted on the frame 100 and drives the reflection measurement component 600. The reflection measurement component 600 is located on the optical axis path of the reference light. The drive mechanism drives the reflection measurement component 600 to move along the optical axis path of the reference light to change the optical path of the reference light. The reflection measurement component 600 is used to reflect the reference light and measures the displacement of the reflection measurement component 600 along the optical axis direction of the reference light to obtain the optical path information corresponding to the interference signal.

[0074] The reflection measurement assembly 600 includes a reflector 630 and a measurement assembly. The reflector 630 is located on the optical axis path of the reference light and is used for total internal reflection of the reference light. Under the drive of the drive mechanism, the reflector 630 moves relative to the frame 100 along the optical axis path of the reference light to change the optical path of the reference light so that the reference light and different measurement reflected light satisfy the interference conditions and form corresponding interference signals.

[0075] The measurement component is used to measure the displacement of the reflector 630 along the optical axis to determine the movement distance of the reflector 630 when the interference signal appears.

[0076] The positioning component 200 is located in the direction of the optical axis of the measuring light and is used to place the lens to be measured;

[0077] Interference detection component 800 is used to detect the interference signal generated when the optical path difference between the measurement reflected light and the reference light reflected by the lens under test satisfies the interference condition.

[0078] In an embodiment, such as Figure 1 As shown, the detection light source assembly 300 includes a first light source module 310, a second light source module 320, and a third light source module 330.

[0079] The first light source module 310, the second light source module 320, and the third light source module 330 are equidistantly mounted on the top plate 110;

[0080] The first light source module 310 is used to provide detection light of the first wavelength, specifically broadband low-coherence light with a wavelength above 800nm ​​and a spectral bandwidth of more than 20nm.

[0081] Specifically, broadband low-coherence light has a short coherence length. Therefore, a significant interference signal will only be generated when the optical path difference between the reference light and the measurement reflected light enters its coherence length range. This allows the reference light to generate corresponding interference signals with the measurement reflected light formed by the reflections from the upper and lower surfaces of the lens under test at different optical path positions. Furthermore, broadband low-coherence light has a wide spectral bandwidth, which gives its interference peaks high spatial resolution, thereby reducing the impact of stray interference on the detection results.

[0082] The second light source module 320 is used to provide detection light of a second wavelength, which is red light with a wavelength in the range of 645-675nm;

[0083] The third light source module 330 is used to provide detection light of a third wavelength, which is blue light with a wavelength in the range of 455-485nm;

[0084] Among them, red and blue light have longer coherence lengths. Therefore, the measurement reflected light reflected from the upper and lower surfaces of the lens will simultaneously satisfy the interference condition with the corresponding reference light, and the resulting interference signals will be superimposed.

[0085] Since light of different wavelengths travels at different speeds in the same lens under test, the corresponding refractive index parameters differ. By obtaining the position of the interference signal corresponding to the detection light of different wavelengths, and the displacement distance of the mirror 630 corresponding to the interference signal, the refractive index data of the lens under test at different wavelengths can be calculated. By adopting a multi-wavelength synchronous detection method, the identification error caused by the single wavelength in the traditional single-wavelength measurement process can be avoided, thereby improving the accuracy of lens refractive index detection.

[0086] Furthermore, the dispersion coefficient of the tested lens material can be calculated based on the refractive index data corresponding to different wavelengths.

[0087] In an embodiment, such as Figure 4 , Figure 5 As shown, the second light source module 320 and the third light source module 330 are also equipped with light source shaping modules 900;

[0088] The light source shaping module 900 includes an aperture 910, a rear lens 920, and a front lens 930. The aperture 910, rear lens 920, and front lens 930 are coaxially arranged from top to bottom in the vertical direction. The aperture 910 is used to limit the light-transmitting aperture of the light beam. By limiting the light-transmitting aperture, the divergence angle of the light beam can be reduced, ensuring that the light beam entering the rear lens 920 has a specific size and divergence angle, and avoiding interference with detection due to the decrease in the stability of the interference signal caused by stray light at the edges.

[0089] The rear lens 920 and the front lens 930 together form a collimation and shaping structure. The rear lens 920 is used to initially collimate the beam passing through the aperture 910 so that it is directed to the front lens 930 in an approximately parallel state. The front lens 930 further optimizes the beam, corrects the beam wavefront and adjusts the spot size, so that the output beam meets the requirements of parallelism and spot size for subsequent interferometric detection.

[0090] In an embodiment, such as Figure 1 As shown, the rack 100 is also equipped with an optical path converging assembly 400 for coupling detection light of different wavelengths to the same optical axis. The optical path converging assembly includes a first bipolar mirror 410, a second bipolar mirror 420, a third bipolar mirror 430 and a focusing lens 440 mounted on the side plate 130, and the first bipolar mirror 410, the second bipolar mirror 420, the third bipolar mirror 430 and the focusing lens 440 are at the same horizontal height of the rack 100.

[0091] Furthermore, the first bidirectional color mirror 410 is arranged vertically relative to the first light source module 310. The first bidirectional color mirror 410 has a total internal reflection mirror surface, which is used to reflect the broadband low coherence light emitted by the first light source module 310 to change its propagation direction, so that the broadband low coherence light propagates towards the focusing lens 440 in the horizontal direction.

[0092] The second bipolar mirror 420 is set vertically relative to the second light source module 320. The second bipolar mirror 420 has high transmittance in the band above 750nm and high reflectance in the band below 700nm, so that broadband low coherence light can be completely transmitted, and red light propagates horizontally toward the focusing lens 440.

[0093] The third bipolar mirror 430 is set vertically relative to the third light source module 330. The third bipolar mirror 430 has high transmittance in the band greater than 530nm, allowing broadband low coherence light and red light to pass through completely. It has high reflectivity in the band less than 500nm, which is used to reflect blue light, so that the blue light propagates horizontally toward the focusing lens 440.

[0094] Furthermore, the focusing lens 440 is used to couple the broadband low-coherence light, red light and blue light provided by the first light source module 310, the second light source module 320 and the third light source module 330 to the same optical axis, so that the detection light of different wavelengths can propagate along the same detection optical path, ensuring that there is a consistent optical path reference during the detection of different wavelengths, avoiding the systematic errors that exist in multi-optical path detection, and improving the accuracy of refractive index measurement.

[0095] The dispersion coefficient can be further calculated based on the refractive index parameters corresponding to different wavelengths. The dispersion coefficient can be used to further identify the type of lens material and evaluate the chromatic aberration performance of the tested lens.

[0096] Secondly, the first bipolar mirror 410, the second bipolar mirror 420, the third bipolar mirror 430 and the focusing lens 440 are used to combine the light in stages to avoid crosstalk between beams of different wavelengths.

[0097] In an embodiment, such as Figure 1 As shown, the first beam splitter 500 includes a fourth bipolar mirror 510 and a fifth bipolar mirror 520. Both the fourth bipolar mirror 510 and the fifth bipolar mirror 520 are located on the central axis of the positioning component 200 in the vertical direction, and the fourth bipolar mirror 510 and the fifth bipolar mirror 520 are symmetrically arranged in the horizontal direction. The fourth bipolar mirror 510 has high transmittance in the 520-550nm and 360-400nm wavelength bands, and the fifth bipolar mirror 520 has 50% reflectance and 50% transmittance in the 300nm-1000nm wavelength band, so that green light can pass through for initialization reference.

[0098] Among them, such as Figure 1 As shown, the fourth bipolar mirror 510 and the focusing lens 440 are on the same horizontal plane and are arranged opposite to each other, and are used to reflect the detection light coupled by the focusing lens 440 to the fifth bipolar mirror 520.

[0099] The fifth bipolar mirror 520 is used to split the incident detection light to form a reference light and a measurement light. The reference light propagates along the reference optical path, and the reflection measurement component 600 is located on the optical path of the reference light. The measurement light propagates toward the positioning component 200 and is reflected by the lens under test to form the measurement reflected light. The reference light interferes with the measurement reflected light after being reflected by the mirror 630, provided that the preset optical path condition (optical path difference is less than the coherence length) is met.

[0100] In an embodiment, such as Figure 1 As shown, a second beam splitter 700 is also installed on the rack 100. The second beam splitter 700 includes a sixth bipolar mirror 710 and a seventh bipolar mirror 720. The sixth bipolar mirror 710 and the seventh bipolar mirror 720 are in the same vertical direction, and the sixth bipolar mirror 710 and the fifth bipolar mirror 520 are in the same horizontal plane.

[0101] Specifically, the sixth dichroic mirror 710 has high transmittance in the 400–500 nm band and high reflectance in the 650–900 nm band, and the seventh dichroic mirror 720 has high reflectance in the 400–690 nm band and high transmittance in the 720–900 nm band, and is used to guide the interference signals corresponding to different wavelengths to the interference detection component 800 respectively.

[0102] In an embodiment, such as Figure 1As shown, the interference detection assembly 800 includes a first photoelectric detection module 810, a second photoelectric detection module 820, and a third photoelectric detection module 830. The first photoelectric detection module 810 is disposed on the top plate 110, and the first photoelectric detection module 810, the sixth bipolar mirror 710, and the seventh bipolar mirror 720 are in the same vertical direction. The second photoelectric detection module 820 and the third photoelectric detection module 830 are both disposed at the end of the side plate 130 of the frame 100 away from the drive mechanism. The second photoelectric detection module 820 and the seventh bipolar mirror 720 are disposed opposite each other in the horizontal direction, and the third photoelectric detection module 830 and the sixth bipolar mirror 710 are disposed opposite each other in the horizontal direction.

[0103] The first photoelectric detection module 810 is an ultra-amplitude photodiode used to detect interference signals of light with wavelengths above 800nm;

[0104] The second photoelectric detection module 820 is a red photodiode used to detect interference signals in the 645-675nm wavelength band;

[0105] The third photoelectric detection module 830 is a blue photodiode used to detect interference signals in the 455-485nm wavelength band.

[0106] In an embodiment, such as Figure 6 As shown, the drive module includes a stepper motor 610;

[0107] The measuring assembly includes a grating ruler guide rail 640 and a grating ruler slider 620. The grating ruler slider 620 is slidably connected to the grating ruler guide rail 640. The grating ruler guide rail 640 is connected to the frame 100 and is on the same horizontal plane as the optical axis of the reference light.

[0108] The stepper motor 610 drives the grating ruler slider 620 to move along the grating ruler guide rail 640 through a lead screw transmission structure;

[0109] The reflector 630 is fixedly mounted on the grating ruler slider 620. The reflector 630 is fixedly set on the side of the grating ruler slider 620 near the fifth bipolar mirror 520. A displacement detection unit is provided in the grating ruler guide rail 640. When the grating ruler slider 620 moves along the grating ruler guide rail 640, the displacement detection unit detects the movement position of the grating ruler slider 620 relative to the grating ruler guide rail 640 in real time and outputs the corresponding position data.

[0110] Since the reflector 630 is fixedly mounted on the grating ruler slider 620, the reflector 630 and the grating ruler slider 620 move synchronously. The position data of the grating ruler slider 620 corresponds to the position data of the reflector 630 along the optical axis of the reference light. When the interference detection component 800 detects the interference signal, it synchronously reads the position data output by the grating ruler guide rail 640 and associates the position data with the corresponding interference signal to obtain the displacement distance information of the reflector 630 corresponding to each interference signal.

[0111] Since the reference light returns along its original path after being reflected by the mirror 630, there is a fixed correspondence between the change in the position of the mirror 630 and the change in the optical path of the reference light. Based on the displacement distance of the mirror 630 corresponding to each interference signal, when the mirror 630 moves a distance Δx along the optical axis of the reference light, the change in the optical path of the reference light is 2Δx.

[0112] The fifth bipolar mirror 520 splits the measurement light into a reference light and a measurement light. The mirror 630 reflects the reference light, causing the reflected reference light and the measurement reflected light reflected by the mirror of the measured lens to re-combine at the position of the fifth bipolar mirror 520. The driving mechanism drives the mirror 630 to move along the optical axis of the reference light to continuously change the optical path length of the reference light, so that the optical path difference between the reference light of the same wavelength and the measurement reflected light of the corresponding wavelength gradually changes. When the optical path difference between the two enters the coherence length range of the corresponding detection light, an interference signal is generated.

[0113] In this embodiment, a calibration light source module 1000 is also included. The calibration light source module 1000 is mounted on the frame 100. The calibration light source module 1000 is used to provide reference light and is arranged opposite to the positioning component 200 in the vertical direction, so that the reference light beam can enter the positioning component 200 in a direction perpendicular to the surface of the lens under test, and is used to assist the positioning component 200 in calibrating the placement position of the lens under test.

[0114] Specifically, such as Figure 2 , Figure 3As shown, the positioning component 200 includes a base, an image sensor 220 is provided at the bottom of the base, and a Hartmann grating 210 is installed at the top of the base. The image sensor 220 and the Hartmann grating 210 are coaxially arranged. The Hartmann grating 210 includes a substrate and light-transmitting points 212 and reflecting points 211 disposed on the substrate. The reflecting points 211 are located at the center of the substrate. The light-transmitting points 212 are light-transmitting through-hole structures. There are several light-transmitting points 212, which are equidistantly distributed around the central reflecting point 211 in an array to divide the incident light into multiple sub-beams. After the reference light passes through the Hartmann grating 210, it forms a regularly arranged array of sub-beams, which are received by the image sensor 220 to form a corresponding light spot array image. Therefore, when the lens under test is offset, tilted, or its position changes, the position of the light spot array received by the image sensor 220 will also change accordingly. By analyzing the center position, arrangement, and offset direction of the light spot array, the position status of the lens under test can be detected and calibrated.

[0115] When the lens under test is not placed, the image sensor 220 pre-acquires a standard light spot array under no-load conditions as an initialization reference.

[0116] After the lens under test is placed, the image sensor 220 acquires the actual light spot array again and calculates the offset between the actual light spot array and the initial reference through the image processing algorithm to determine the center position deviation of the lens under test. This guides the operator to adjust the position of the lens under test so that it coincides with the optical axis center of the system, avoiding the impact of the installation deviation of the lens under test on the accuracy of subsequent interferometric measurements. It is suitable for the positioning and detection of aspherical lenses, spherical lenses, cylindrical lenses and irregular lenses.

[0117] The reference light is green light with a wavelength in the range of 520-530nm;

[0118] like Figure 8 As shown, a method for detecting the refractive index of a lens, applied to a lens refractive index detection device, includes the following steps:

[0119] S1. Obtain the first interference signal and the first motion distance corresponding to different wavelengths of detection light;

[0120] The first interference signal is the interference signal generated by the measuring light and the reference light when the lens under test is not placed;

[0121] The first motion distance is the displacement parameter of the reflector 630 corresponding to the first interference signal.

[0122] Furthermore, the detection light of different wavelengths includes broadband low-coherence light, red light, and blue light;

[0123] Specifically, the first light source module 310, the second light source module 320, and the third light source module 330 are activated, allowing broadband low-coherence light, red light, and blue light to enter the optical path converging component 400, respectively. After optical path coupling through the first bipolar mirror 410, the second bipolar mirror 420, the third bipolar mirror 430, and the focusing lens 440, a coaxial detection light is formed. The detection light propagates along the optical axis and is refracted through the fourth bipolar mirror 510 to the fifth bipolar mirror 520. After being split by the fifth bipolar mirror 520, a reference light and a measurement light are formed. The measurement light propagates along the measurement optical path to the positioning component 200 and is then controlled by Hart. The reflection point 211 of the Mann grating 210 reflects back along its own optical path. The reference light propagates along the reference optical path to the reflector 630 and is reflected by the reflector 630 and returns along its own optical path. During this process, the control drive mechanism drives the reflector 630 to move along the optical axis of the reference light to continuously change the optical path of each wavelength of the reference light. This allows the interference detection component 800 to detect the corresponding first interference signal generated when different wavelength beams interfere in real time. When the empty interference peak of the corresponding wavelength is detected, the measurement component synchronously reads the current position data of the reflector 630 and records the first movement distance of the reflector 630.

[0124] The first motion distance corresponding to the reflector 630 includes:

[0125] When unloaded, the blue light interferes with the reflection beam reflected by the reflection point 211 of the Hartmann grating 210, and the corresponding mirror 630 displacement Y1 is generated.

[0126] When unloaded, the red light interferes with the reflected beam reflected by the reflection point 211 of the Hartmann grating 210, and the corresponding mirror 630 displacement Y2 is generated.

[0127] When unloaded, the displacement YM of the mirror 630 corresponds to the interference of the broadband low-coherence light with the reflected beam at the reflection point 211 of the Hartmann grating 210.

[0128] S2. Obtain the second interference signal and the second motion distance corresponding to the lens under test;

[0129] The second interference signal is the interference signal generated by the interference between the reference light and the measured reflected light after the lens under test is placed.

[0130] The second motion distance is the displacement parameter of the reflector 630 corresponding to the second interference signal.

[0131] Specifically, when the lens under test is not placed, the calibration light source module 1000 is activated to emit reference light. The reference light passes through the Hartmann grating 210 and forms a regularly arranged array of light spots. The image sensor 220 collects the corresponding array of light spots as the first light spot image and uses the first light spot image as the initial reference.

[0132] The lens under test is placed on the positioning component 200, and the calibration light source module 1000 is activated to emit reference light. The reference light passes through the lens under test and the Hartmann grating 210 to form a regularly arranged array of light spots. The image sensor 220 acquires the array of light spots after the lens under test is placed as the second light spot image, and calculates the center offset, array offset direction and arrangement change between the second light spot image and the first light spot image. Based on the calculation results, position adjustment information is generated to guide the operator to adjust the position of the lens so that the center of the lens coincides with the center of the optical axis.

[0133] After the lens under test is positioned, the first light source module 310, the second light source module 320, and the third light source module 330 are activated, allowing broadband low-coherence light, red light, and blue light to enter the optical path converging component 400, respectively. After optical path coupling via the first bipolar mirror 410, the second bipolar mirror 420, the third bipolar mirror 430, and the focusing lens 440, a coaxial detection light is formed. The detection light propagates along the optical axis and is refracted by the fourth bipolar mirror 510 to the fifth bipolar mirror 520. After being split by the fifth bipolar mirror 520, a reference light and a measurement light are formed, enabling the reference light to be focused and measured. The reference light propagates along the reference light path to the reflector 630, and the measurement light propagates along the measurement light path to the lens under test, and is reflected by the lens under test along the original light path to form the measurement reflected light. The stepper motor 610 drives the reflector 630 to move along the optical axis of the reference light, reflecting the reference light, so that the reference light and the measurement reflected light of the same wavelength are combined at the position of the fifth bipolar mirror 520, and interference occurs when the interference condition is met. The interference detection component 800 detects the corresponding second interference signal generated during the interference in real time and records the second movement distance of the reflector 630.

[0134] Because broadband low-coherence light has a short coherence length, a significant interference peak is only generated when the optical path difference between the reference light and the corresponding measured reflected light enters its coherence length range. That is, when the reference light and the measured reflected light reflected from the upper surface of the lens under test satisfy the interference condition, the first broadband interference peak is generated; when the reference light continues to change its optical path and satisfies the interference condition with the measured reflected light reflected from the lower surface of the lens, the second broadband interference peak is generated.

[0135] For red and blue light, since their coherence length is greater than the thickness of the lens, the interference signals formed by reflections from different interfaces of the lens are superimposed, and the system obtains the overall interference position of the corresponding wavelength.

[0136] Whenever an effective interference peak is detected, the measurement component synchronously reads the current position of the reflector 630 and associates the displacement distance of the reflector 630 with the corresponding interference signal.

[0137] Specifically, the second motion distance corresponding to the reflector 630 includes:

[0138] The displacement YM1 of the mirror 630 corresponding to the interference of the broadband low-coherence light after passing through the lens under test with the beam reflected by the reflection point 211 of the Hartmann grating 210;

[0139] The displacement YM2 of the mirror 630 corresponding to the interference between the broadband low-coherence light passing through the lens under test and the beam reflected from the lower surface of the Hartmann grating 210;

[0140] The displacement YM3 of the reflector corresponding to the interference between the broadband low-coherence light and the beam reflected from the upper surface of the lens under test;

[0141] The blue light interferes with the beam reflected by the lens under test, corresponding to a mirror displacement of 630° YX1.

[0142] The interference between the red light and the beam reflected by the lens under test corresponds to a mirror displacement of 630° YX2.

[0143] S3. Determine the interface position parameters of the lens under test based on the second motion distance corresponding to the broadband low coherence light, and calculate the thickness parameters of the lens under test based on the interface position parameters.

[0144] The interface position parameters include the first interface position parameters corresponding to the upper surface of the lens under test and the second interface position parameters corresponding to the lower surface of the lens under test.

[0145] The thickness parameter includes the physical distance between the upper and lower surfaces of the lens being measured;

[0146] The optical path length information corresponding to the propagation of the measurement light inside the lens can be determined based on the optical path difference between the two interface positions corresponding to the broadband low coherence light. Since there is a fixed correspondence between the displacement of the mirror 630 and the optical path change of the reference light, the lens thickness t can be calculated based on the absolute value of the difference in the displacement of the mirror 630.

[0147] The formula for calculating the thickness t at the physical center of a lens is:

[0148] t=|(YM2-YM3)-(YM1-YM)|.

[0149] S4. Calculate the corresponding refractive index parameters based on the first motion distance, second motion distance, and thickness parameters corresponding to different wavelengths of detection light;

[0150] The refractive index parameters include the first refractive index parameter corresponding to broadband low-coherence light, the second refractive index parameter corresponding to red light, and the third refractive index parameter corresponding to blue light.

[0151] Specifically, the displacement distance parameters YX1 of the blue light interference position mirror 630, YX2 of the red light interference position mirror 630, and Y1 and Y2 of the unloaded interference position mirrors 630 corresponding to blue and red light are extracted respectively. By comparing the difference in displacement distance between the tested lens under test and the unloaded state, the additional optical path length introduced by the corresponding wavelength beam propagating inside the lens is determined. Since the optical path length and the lens thickness satisfy the refractive index correspondence, the refractive index parameters of the lens under different wavelengths can be calculated in reverse.

[0152] Specifically, the formula for the refractive index of blue light is:

[0153] n 蓝 =1+(YX1-Y1) / t;

[0154] The formula for the refractive index of red light is:

[0155] n 红 =1+(YX2-Y2) / t;

[0156] The formula for the refractive index of broadband low-coherence light is:

[0157] n 宽 =1+(YM1-YM) / t.

[0158] S5. Calculate the dispersion coefficient of the lens under test based on the first refractive index parameter, the second refractive index parameter, and the third refractive index parameter.

[0159] Specifically, the nblue, nred, and nwidth values ​​calculated in step S6 are read, and the dispersion coefficient of the lens material is calculated based on the refractive index parameters corresponding to different wavelengths.

[0160] Specifically, the dispersion coefficient Vd of the lens material is calculated based on the difference in refractive index corresponding to different wavelengths.

[0161] The formula for calculating the dispersion coefficient Vd is as follows:

[0162] Vd=(n 红 -1) / (n 蓝 -n 宽 ).

[0163] Using the above method, lens positioning and lens thickness detection can be completed simultaneously in the same detection process, and the refractive index parameters of different wavelengths of the tested lens and the dispersion coefficient of the material can be calculated, thereby improving the lens detection efficiency. Furthermore, since different wavelength detection lights share the same detection optical path, the impact of environmental vibration, temperature changes and mechanical errors on the detection results can be effectively reduced.

[0164] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A lens refractive index detection device, characterized in that, include: Rack (100); A positioning component (200) is mounted on the frame (100) and is used to carry the lens under test; A detection light source assembly (300) is mounted on the frame (100) and is used to emit detection light; The first beam splitter (500) is used to split the detection light into a reference light and a measurement light, and the measurement light is reflected by the lens under test to form the measurement reflected light. Interference detection component (800) is used to detect the interference signal between the reflected light and the reference light; A drive mechanism is mounted on the frame (100). The reflection measurement assembly (600) includes a reflector (630) and a measurement assembly. The reflector (630) is located on the optical axis path of the reference light for reflecting the reference light, and the reflector (630) is driven to move along the optical axis path of the reference light to change the optical path of the reference light. The measuring component is used to measure the displacement of the reflector (630) along the optical axis to determine the movement distance of the reflector (630) when the interference signal appears.

2. The lens refractive index detection device according to claim 1, characterized in that, The detection light source assembly (300) includes a first light source module (310), a second light source module (320), and a third light source module (330), which are used to emit detection light of different wavelengths.

3. The lens refractive index detection device according to claim 2, characterized in that, The second light source module (320) and the third light source module (330) are also provided with light source shaping modules (900); The light source shaping module (900) includes an aperture (910), a rear lens (920), and a front lens (930), which are coaxially arranged from top to bottom in the vertical direction.

4. The lens refractive index detection device according to claim 3, characterized in that, The frame (100) is also equipped with an optical path converging assembly (400), which includes a first bipolar mirror (410), a second bipolar mirror (420), a third bipolar mirror (430), and a focusing lens (440). The first bidirectional color mirror (410) is positioned vertically relative to the first light source module (310); The second bidirectional color mirror (420) is positioned vertically relative to the second light source module (320); The third bidirectional color mirror (430) is positioned vertically relative to the third light source module (330); The first bipolar mirror (410), the second bipolar mirror (420), the third bipolar mirror (430) and the focusing lens (440) are located on the same height plane of the frame (100). The focusing lens (440) is used to couple the detection light of different wavelengths provided by the first light source module (310), the second light source module (320) and the third light source module (330) to the same optical axis.

5. The lens refractive index detection device according to claim 4, characterized in that, The first beam splitter (500) includes a fourth bipolar mirror (510) and a fifth bipolar mirror (520). The fourth bipolar mirror (510) is disposed opposite to the focusing lens (440) and is used to split the detection light into a reference light and a measurement light. The fifth bipolar mirror (520) is located on the propagation path of the reference light and is positioned opposite to the reflection measurement component (600) to guide the propagation of the reference light.

6. The lens refractive index detection device according to claim 5, characterized in that, The frame (100) is also equipped with a second beam splitter (700), which includes a sixth bipolar mirror (710) and a seventh bipolar mirror (720). The sixth bipolar mirror (710) and the seventh bipolar mirror (720) are used to guide interference signals corresponding to different wavelengths to the interference detection component (800).

7. The lens refractive index detection device according to claim 6, characterized in that, The interference detection component (800) includes a first photoelectric detection module (810), a second photoelectric detection module (820), and a third photoelectric detection module (830), which are used to detect interference signals corresponding to different wavelengths.

8. The lens refractive index detection device according to claim 1, characterized in that, The drive module includes a stepper motor (610). The measuring component includes a grating ruler guide rail (640) and a grating ruler slider (620). The grating ruler slider (620) is slidably connected to the grating ruler guide rail (640). The grating ruler guide rail (640) is connected to the frame (100) and is on the same horizontal plane as the optical axis of the reference light. The stepper motor (610) drives the grating ruler slider (620) to move along the grating ruler guide rail (640); The reflector (630) is fixedly mounted on the grating ruler slider (620).

9. The lens refractive index detection device according to claim 1, characterized in that, It also includes a calibration light source module (1000), which is mounted on the frame (100) and is arranged opposite to the positioning component (200) in the vertical direction, and is used to assist the positioning component (200) in calibrating the placement position of the lens under test.

10. A method for detecting the refractive index of a lens, characterized in that, The detection using the lens refractive index detection device according to any one of claims 1 to 9 includes the following steps: S1. Obtain the first interference signal and the first motion distance corresponding to different wavelengths of detection light; The first interference signal is the interference signal generated by the measurement light and the reference light when the lens under test is not placed; The first movement distance is the displacement parameter of the reflector (630) corresponding to the first interference signal. S2. Obtain the second interference signal and the second motion distance corresponding to the lens under test; The second interference signal is the interference signal generated by measuring the reflected light and the reference light after the lens under test is placed; The second motion distance is the displacement parameter of the reflector (630) corresponding to the second interference signal. S3. Determine the interface position parameters of the lens under test based on the second motion distance corresponding to the broadband low coherence light, and calculate the thickness parameters of the lens under test based on the interface position parameters. The interface position parameters include the first interface position parameters corresponding to the upper surface of the lens under test and the second interface position parameters corresponding to the lower surface of the lens under test. The thickness parameter is the physical distance between the upper and lower surfaces of the lens being measured. S4. Calculate the corresponding refractive index parameters based on the first motion distance, second motion distance, and thickness parameters corresponding to different wavelengths of detection light; The refractive index parameters include a first refractive index parameter corresponding to broadband low-coherence light, a second refractive index parameter corresponding to red light, and a third refractive index parameter corresponding to blue light. S5. Calculate the dispersion coefficient of the lens under test based on the first refractive index parameter, the second refractive index parameter, and the third refractive index parameter.

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