Device for synchronously measuring refractive index and thickness of transparent material

Abstract

The utility model discloses a device for synchronously measuring the refractive index and the thickness of a transparent material, which is characterized in that a Michelson interferometer is improved on the basis of the Michelson interference principle, and three groups of interference fringes of different surfaces of the transparent material and a reflecting mirror are obtained by utilizing the reflecting mirror, an attenuation sheet with known refractive index and thickness and an optical screen after multiple light splitting design; and the surface appearance and the refractive index of the transparent material can be measured at the same time in combination with the stripe radius.

Description

Technical Field

[0001] This utility model belongs to the field of optical measurement technology and can be widely used in optical device manufacturing, materials science, criminal investigation, military and astronomical equipment and other fields. Specifically, it relates to a device for simultaneously measuring the refractive index and thickness of transparent materials. Background Technology

[0002] The geometric thickness and refractive index of optical materials are important parameters in materials engineering applications and scientific research. Various methods exist for measuring these parameters, but some methods can only measure one parameter at a time, such as thickness or refractive index. While many existing technologies can simultaneously measure geometric thickness and refractive index, each method has its advantages and disadvantages. Traditional methods (such as photometry and elliptic polarization methods) require separate measurements of the thickness and refractive index of transparent materials, resulting in low efficiency and large errors. Traditional Michelson interferometers can only indirectly calculate another parameter from known parameters (such as thickness or refractive index from optical path difference), failing to achieve simultaneous measurement. Furthermore, changes in the external environment (external forces, temperature, etc.) alter the refractive index (n) and thickness (l) of the material. Current technologies lack the ability to dynamically analyze the refractive index (n) and thickness (l) affected by external fields (such as stress and temperature), making it difficult to meet the needs of precision measurement.

[0003] Patent application CN101614526A discloses a method and apparatus for simultaneously measuring the geometric thickness and refractive index of transparent materials. After setting up the optical path, the coincident focal points on both sides are designated as standard points. After placing the material, the left and right optical paths are moved, and the principle of photodetector response maxima is used to ensure that the front and rear focal points hit the front and rear surfaces of the material respectively. The thickness of the material is obtained from the simple geometric movement of the left and right sides, and then the refractive index is calculated. However, this method uses manual movement of the confocal filter optical group to change the photodetector response value, requiring high precision in the operation of the moving stage and precise operation during manual movement. Patent application CN103983609A discloses a device and method for measuring the refractive index and thickness of transparent materials based on spectral interferometry. It abandons the reference arm of the Michelson interferometer and builds a single-optical-path system. Although simple to operate, it relies on a spectrometer and Fourier transform data processing, which affects the measurement accuracy.

[0004] With the development of optical device manufacturing and materials science, the requirements for the measurement accuracy of the thickness and refractive index of transparent materials are becoming increasingly stringent. Traditional methods cannot meet the needs of simultaneous and high-precision measurement, and there is an urgent need for a device and method that can simultaneously measure the thickness and refractive index and analyze its influence by external fields. Utility Model Content

[0005] Based on the above-mentioned technological status, this utility model improves the Michelson interferometer on the basis of the Michelson interferometer principle. After multiple beam splitting designs, it uses a mirror, an attenuator with known refractive index and thickness, and a screen to obtain three sets of interference fringes between different surfaces of the transparent material and the mirror. Combined with the fringe radius, it realizes the simultaneous measurement of the surface morphology and refractive index of the transparent material.

[0006] The technical solution adopted by this utility model is as follows: a device for simultaneously measuring the refractive index and thickness of transparent materials, including an optical path system and an image acquisition module;

[0007] The optical path system includes a light source, a beam splitter assembly, a reflector assembly, a screen assembly, and a test object clamping bracket. The beam splitter assembly includes beam splitter one, beam splitter two, beam splitter three, and a circular beam splitter. The reflector assembly includes reflector one, reflector two, reflector three, reflector four, reflector five, reflector six, and reflector seven. The screen assembly includes screen one and screen two for receiving interference fringes. The test object clamping bracket is used to hold transparent materials.

[0008] The light source, beam splitter three, and reflector two are arranged coaxially along a first axis. Reflector one is arranged on one side of beam splitter three, and reflector seven is arranged on one side of reflector two, with reflector one and reflector seven distributed on different sides of the first axis. Reflector three, beam splitter one, beam splitter two, and reflector six are arranged sequentially coaxially along a second axis, which is perpendicular to the first axis. The object-to-be-held bracket is arranged coaxially with the second axis between beam splitter one and beam splitter two. Reflector one and reflector three are coaxially along a third axis, and reflector seven and reflector six are coaxially along a fourth axis, both of which are parallel to the first axis. Reflector four, beam splitter one, and screen two are arranged sequentially coaxially along a fifth axis. Reflector five, circular beam splitter, beam splitter two, and screen one are arranged sequentially coaxially along a sixth axis.

[0009] The image acquisition module is set up for screen one and screen two, and is used to acquire interference fringes on the two screens.

[0010] Furthermore, the optical path system also includes a first attenuator and a second attenuator. The first attenuator is disposed between the first beam splitter and the object-under-test clamping bracket; the second attenuator is disposed between the fourth reflector and the first beam splitter. The placement of the two attenuators can optimize the contrast of interference fringes and suppress stray light.

[0011] Preferably, calibration plate one is provided on screen one and calibration plate two is provided on screen two, so as to help obtain the size data of interference fringes intuitively on the light screen.

[0012] The light source can be a laser; in the actual experiment, a 532nm laser was used. The image acquisition module uses a camera to acquire interference fringe images.

[0013] The device for simultaneously measuring the refractive index and thickness of transparent materials based on this invention includes the following steps in its specific measurement method:

[0014] Step 1: Place all components of the device on a horizontal table, turn on the light source, and check if the light source is working properly;

[0015] Step 2: Place the transparent material to be tested, such as K9 optical glass, sapphire, quartz, acrylic sheet, etc., into the sample clamping area of ​​the test object clamping bracket;

[0016] Step 3: Adjust the position of the transparent material to be tested so that the two light spots formed by the reflected light from its left surface and the reflected light from mirror four appear in the appropriate position on screen two, and the two light spots formed by the reflected light from its right surface and the reflected light from mirror five, as well as the two light spots formed by the light passing through the transparent material to be tested and the reflected light from the circular beam splitter, for a total of four light spots appear in the appropriate position on screen one.

[0017] Step 4: Adjust the adjustment knobs behind the four reflectors (the existing knobs that adjust the pitch and tilt angles of the reflectors) to change the pitch and tilt angles of the reflectors so that the two light spots formed by the light reflected from the left surface of the transparent material to be tested and the light reflected from the four reflectors form clear interference fringes M1 at appropriate positions on the screen.

[0018] Step 5: Adjust the adjustment knobs behind the five reflectors and the circular beam splitter so that the two light spots formed by the light reflected from the right surface of the transparent material under test and the light reflected from the five reflectors form a clear interference fringe M2 on the screen; and the two light spots formed by the light passing through the transparent material under test and the light reflected from the circular beam splitter form a clear interference fringe M3 at a suitable position on the right side of the screen.

[0019] Step 6: Place the camera on the one-dimensional slide rail in front of the two screens, so that it faces the interference fringes M1, M2, M3 and the two calibration plates, record the obtained interference image, upload the image to the computer program, and perform subsequent image processing and numerical calculation based on software such as Matlab.

[0020] Step 7: Measure the radius of the first ring of the interference fringes, including the radius r1 of the first ring of interference fringe M1, the radius r2 of the first ring of interference fringe M2, and the radius r3 of the first ring of interference fringe M3;

[0021] Step 8: Calculate the optical path difference based on the measured radius of the first ring;

[0022] The optical path difference of interference fringe M1 is:

[0023] The optical path difference of interference fringe M2 is:

[0024] The optical path difference of interference fringe M3 is:

[0025] In the formulas of this step: N represents the Nth bright ring of the equal-inclination interference fringe, λ is the wavelength of light, r1 is the radius of the first ring of interference fringe M1, r2 is the radius of the first ring of interference fringe M2, r3 is the radius of the first ring of interference fringe M3, L1 represents the total optical path from the light source forming interference fringe M1 to the screen, L2 represents the total optical path from the light source forming interference fringe M2 to the screen, and L3 represents the total optical path from the light source forming interference fringe M3 to the screen;

[0026] Step 9: Calculate the distance l from the left surface of the transparent material to the beam splitter by interfering with the light reflected from the fourth mirror. 10 ,

[0027] In the formula, l7 is the distance between the fourth reflecting mirror and the first beam splitter;

[0028] By utilizing the interference between the light reflected from the right surface of the transparent material under test and the light reflected by mirror five, the distance l from the right surface of the transparent material under test to beam splitter two can be obtained. 11 ,

[0029] In the formula, l'5 is the distance between mirror five and beam splitter two;

[0030] Step 10: Calculate the thickness l8 of the transparent material to be measured.

[0031] l8=l9-(l4+l 11 )-(l6+l 10 In the formula, l9 is the distance between mirror three and mirror six; l4 is the distance between beam splitter two and mirror six; l6 is the distance between mirror three and beam splitter one.

[0032] The refractive index n of the transparent material under test is calculated based on the interference between the light transmitted through the transparent material and the light reflected by the circular beam splitter, using the following formula:

[0033] l6+l 10 +nl8+l 11 -(l4+215)=Δl3 where l5 is the distance between the circular beam splitter and beam splitter II. Given the optical path difference, the refractive index n of the transparent material to be measured can be obtained.

[0034] The measurement method provided by this utility model has the following advantages:

[0035] 1. An improved Michelson interferometer was developed, combining two Michelson interferometers to simultaneously measure the refractive index n and thickness l in real time. The two interferometers compensate for each other, enabling precise measurement of n and l and dynamic analysis of them. This breaks through the limitations of traditional measurement methods and makes the measurement more accurate.

[0036] 2. Through optical path analysis, a new calculation formula for optical path difference based on the measurement of fringe radius was independently designed, thereby obtaining the material thickness and refractive index. This breaks through the traditional method of calculating optical path difference by counting fringe throughput, making the algorithm simpler and faster. Attached Figure Description

[0037] Figure 1 This is a design drawing of the optical path system of this utility model;

[0038] Figure 2 This is a schematic diagram illustrating the principle of the measurement method of this utility model;

[0039] Figure 3 This is a schematic diagram of the overall structure of the device of this utility model;

[0040] In the diagram: 1. Camera, 2. Laser, 3-1. Convex Lens 1, 3-2. Convex Lens 2, 4-1. Reflector 1, 4-2. Reflector 2, 4-3. Reflector 3, 4-4. Reflector 4, 4-5. Reflector 5, 4-6. Reflector 6, 4-7. Reflector 7, 5-1. Beam Spectrometer 1, 5-2. Beam Spectrometer 2, 5-3. Beam Spectrometer 3, 6. Attenuator, 7. Test Object Clamping Support, 8. Circular Beam Spectrometer, 9-1. Calibration Plate 1, 9-2. Calibration Plate 2. Detailed Implementation

[0041] See Figure 1 This is a design diagram of the optical path system of this utility model. All components are built on the measuring platform. The reflector three, beam splitter one, beam splitter two, and reflector six are placed coaxially in sequence. The object to be measured, i.e., the transparent material to be measured, is placed between beam splitter one and beam splitter two and adjusted to be coaxial with the aforementioned coaxial axis, forming the first coaxial axis. The laser emitted by the light source is split into two by beam splitter three. The first light is reflected by reflector one and enters reflector three, and then propagates along the first coaxial axis. The second light is reflected by reflector two to reflector seven, then by reflector seven to reflector six, then by reflector six to beam splitter two, and then also propagates along the coaxial axis.

[0042] A fourth reflector is placed on one side of a beam splitter, and a second screen is placed on the other side. The fourth reflector, the first beam splitter, and the second screen also form a coaxial axis for the propagation of light, which serves as the second coaxial axis and is perpendicular to the first coaxial axis. A fifth reflector and a circular beam splitter are placed on one side of a beam splitter, and a first screen is placed on the other side. The fifth reflector, the circular beam splitter, the second beam splitter, and the first screen form a coaxial axis for the propagation of light, which serves as the third coaxial axis and is also perpendicular to the first coaxial axis and parallel to the second coaxial axis.

[0043] Figure 2 This is a schematic diagram illustrating the principle of the measurement method of this utility model. The following is in conjunction with... Figure 1 and Figure 2 The optical path design concept and working principle of this utility model will be clearly explained first.

[0044] Specifically, multiple guide rails or grooves extending along the x and y axes can be set on the measuring platform. Each component is installed at its corresponding position along the guide rails or grooves, and its position is fixed and adjusted using short screws that can be loosely screwed onto the guide rails or grooves. See also Figure 1 The optical path distance between the light source and beam splitter three is set to l0. The optical path distance between the first beam splitter and mirror one is set to l2. The optical path distance between the second beam splitter and mirror two is set to l1. The optical path distance between mirror two and mirror seven is also set to l2. Both optical paths l2 are parallel to the first coaxial axis. The optical path distance between mirror seven and mirror six is ​​l3. Since mirror six and mirror three are coaxial, the optical path distance between mirror one and mirror three is (l1+l3). That is, optical paths l2 and (l1+l3) are perpendicular to the first coaxial axis. The optical path distance between mirror three and beam splitter one is set to l6. The optical path distance between beam splitter two and mirror six is ​​set to l4. The total optical path distance between mirror three and mirror six is ​​set to l9. The optical path distance between beam splitter one and screen two is set to l. 12 The optical path distance between beam splitter two and screen one is set to l. 13 Adjust the preset positions of each component along the guide rail or guide groove, and the optical path distances l0, l1, l2, l3, l4, l6, l9, l 12 l 13 All are known values ​​that can be adjusted.

[0045] See Figure 1 The illustration shows the design diagram of the optical path system of this utility model. Based on Figure 1 The measurement principle of this utility model is as follows:

[0046] By improving the Michelson interferometer and combining two Michelson interferometers, three sets of interference fringes were obtained, and then the material thickness l and refractive index n were calculated.

[0047] First set of interference fringes: The light reflected from the left surface of the material under test interferes with the light reflected back from the four mirrors, resulting in: l 10 ;

[0048] The second set of interference fringes: The light reflected from the right surface of the material under test interferes with the light reflected back from the fifth mirror, resulting in: l 11 ;

[0049] Depend on Figure 1 The geometric relationship in the figure easily yields the material thickness l8:

[0050] l8=l9-(l4+l 11 )-(l6+l 10 )

[0051] The third set of interference fringes: The light transmitted through the material under test interferes with the light reflected back from the circular beam splitter: the optical path difference Δl3 between the optical path of the transmitted material and its standard surface is obtained;

[0052] From its optical path difference, we can obtain:

[0053] l6+l 10 +nl8+l 11 -(l4+2l5)=Δl3

[0054] The refractive index n of the material under test is obtained.

[0055] See Figure 2 The diagram shows the equivalent optical path obtained by symmetry of the basic principle optical path, based on... Figure 2 The data processing principle of this invention is as follows: Based on the optical path of the Michelson interferometer, once the parameters of the device are fixed, the optical path difference between the two coherent beams is constant, and the radius of the interference fringe is related to k (standard plane). That is, this invention utilizes this correspondence to calculate the corresponding optical path difference by measuring the interference fringe radius, and finally calculates the material thickness l and refractive index n. Derivation:

[0056] Equal-inclination interference produced by the mirror and the light beam reflected from the upper surface of the material:

[0057] 2n0h cos i=kλ

[0058] Equal-inclination interference produced by the mirror and the beam reflected from the lower surface of the material:

[0059]

[0060] When the light ray is incident perpendicularly, i = 0, and the central order k is:

[0061]

[0062] The Nth bright ring of the equal-inclination interference fringes corresponds to iN :

[0063]

[0064] The optical path difference corresponds one-to-one with the radius of the bright ring:

[0065]

[0066] make

[0067] H = h1 + h2 + 2h′

[0068] Depend on Figure 2 Geometric relations yield:

[0069]

[0070] The optical path difference that produces standard ring interference fringe ④ is:

[0071] H1-H2=k1λ

[0072] again

[0073]

[0074] The optical path difference that produces interference fringe ⑤ is:

[0075] H′1-H′2=k2λ

[0076] make

[0077] k1=k2

[0078] get

[0079] H1-H2=H′1-H′2

[0080] Substituting the above equations, we get:

[0081]

[0082] That is, the distance Δ between the material surface and its standard plane (i.e., the optical path difference) and the interference fringe radius R2 have a quartic equation relationship.

[0083] Based on this design principle, the device for simultaneously measuring the refractive index and thickness of transparent materials according to this invention is as follows: Figure 3 As shown, it includes an optical path system and an image acquisition module;

[0084] The optical path system includes a light source, a beam splitter assembly, a reflector assembly, a screen assembly, and a test object clamping bracket. The beam splitter assembly includes beam splitter 1 (5-1), beam splitter 2 (5-2), beam splitter 3 (5-3), and a circular beam splitter 8. The reflector assembly includes reflector 1 (4-1), reflector 2 (4-2), reflector 3 (4-3), reflector 4 (4-4), reflector 5 (4-5), reflector 6 (4-6), and reflector 7 (4-7). The screen assembly includes screen 1 and screen 2 for receiving interference fringes.

[0085] The light source can be a laser 2, such as a 532nm laser. The laser 2, beam splitter 3 5-3, and reflector 2 4-2 are arranged coaxially along a first axis. Reflector 1 4-1 is arranged on one side of beam splitter 3 5-3, and reflector 7 4-7 is arranged on one side of reflector 2 4-2. Reflector 1 4-1 and reflector 7 4-7 are distributed on different sides of the first axis. Reflector 3 4-3, beam splitter 1 5-1, beam splitter 2 5-2, and reflector 6 4-6 are arranged sequentially coaxially along a second axis, and the second axis is perpendicular to the first axis. The object clamping bracket 7 is arranged coaxially with the second axis between beam splitter 1 5-1 and beam splitter 2 5-2. Reflector 1 4- Mirror 1 and mirror 3 (4-3) are coaxial along the third axis, and mirror 7 (4-7) and mirror 6 (4-6) are coaxial along the fourth axis. Both the third and fourth axes are parallel to the first axis, and correspondingly, both the third and fourth axes are perpendicular to the second axis. Mirror 4 (4-4), beam splitter 1 (5-1), and screen 2 are arranged sequentially with the fifth axis coaxial, i.e., beam splitter 1 (5-1) is located between mirror 4 (4-4) and screen 2, and the fifth axis is parallel to the first axis. Mirror 5 (4-5), circular beam splitter 8, beam splitter 2 (5-2), and screen 1 are arranged sequentially with the sixth axis coaxial, i.e., beam splitter 2 (5-2) is located between circular beam splitter 8 and screen 1, and the sixth axis is also parallel to the first axis.

[0086] The image acquisition module includes a camera 1, which is set to screen one and screen two and is used to acquire interference fringes on the two screens.

[0087] After collecting the interference fringes, the radius of the interference fringes is measured. The optical path difference can be calculated from this radius, and then the refractive index n and thickness l of the material can be calculated.

[0088] Furthermore, calibration plate 9-1 is set on screen one and calibration plate 9-2 is set on screen two, which can help to intuitively obtain the size data of interference fringes on the light screen.

[0089] In our experiments measuring a small number of samples, we observed speckle patterns and unsatisfactory interference fringe. Therefore, based on the principle of contrast, and assuming all beam splitters were 5:5, we calculated the energy. We then optimized the optical path by adding two attenuators, effectively overcoming the speckle phenomenon and obtaining a better interference pattern. See details... Figure 3 The transparent material to be tested is clamped on the test object clamping bracket 7, which provides a two-dimensional adjustment range. An attenuator 6 is set between the beam splitter 5-1 and the transparent material to be tested, and another attenuator (not shown in the figure) is set between the reflector 4-4 and the beam splitter 5-1. Adding two attenuators can optimize the contrast of interference fringes and suppress stray light.

[0090] Based on the device for simultaneously measuring the refractive index and thickness of transparent materials, the specific measurement method adopted by this utility model is as follows:

[0091] Step 1: Place all components of the device on a horizontal table, turn on laser 2, and check if laser 2 is working properly;

[0092] Step 2: Place the transparent material to be tested, such as K9 optical glass, sapphire, quartz, acrylic sheet, etc., into the sample clamping area of ​​the test object clamping bracket 7.

[0093] Step 3: Adjust the position of the transparent material to be tested so that the two light spots formed by the reflected light from its left surface and the reflected light from mirror 4-4 appear in the appropriate position on screen 2, and the two light spots formed by the reflected light from its right surface and the reflected light from mirror 4-5, as well as the two light spots formed by the light passing through the transparent material to be tested and the reflected light from the circular beam splitter 8, for a total of four light spots appear in the appropriate position on screen 1.

[0094] Step 4: Adjust the adjustment knob behind the reflector 4-4 (the existing reflector has a built-in knob for adjusting the pitch and tilt angle) to change the pitch and tilt angle of the reflector so that the two light spots formed by the light reflected from the left surface of the transparent material to be tested and the light reflected from the reflector 4-4 form a clear interference fringe M1 at a suitable position on the screen 2.

[0095] Step 5: Adjust the adjustment knobs behind the reflector 4-5 and the circular beam splitter 8 so that the two light spots formed by the light reflected from the right surface of the transparent material under test and the light reflected from the reflector 4-5 form a clear interference fringe M2 on the screen; and the two light spots formed by the light passing through the transparent material under test and the light reflected from the circular beam splitter 8 form a clear interference fringe M3 at an appropriate position on the right side of the screen.

[0096] Step 6: Place camera 1 on the one-dimensional slide rail in front of the two screens, so that it faces the interference fringes M1, M2, M3 and the two calibration plates, record the obtained interference image, upload the image to the computer program, and obtain the radius by fitting a circle to the interference fringes based on the source program provided by Matlab.

[0097] Step 7: Measure the radius of the first ring of the interference fringes, including the radius r1 of the first ring of interference fringe M1, the radius r2 of the first ring of interference fringe M2, and the radius r3 of the first ring of interference fringe M3;

[0098] Step 8: Substitute the measured radius of the first ring into the above formula (1) relating the ring radius and optical path difference to calculate the required optical path difference; the optical path difference of interference fringe M1 Where N represents the Nth bright ring of the equal-inclination interference fringe, and the first ring is chosen to have N=1, λ is the wavelength of light, and L1 represents the total optical path from the light source to the screen from which interference fringe M1 is formed. Interference fringe M1 is formed on the screen by the interference of the reflected light from the left surface of the object under test and the reflected light from mirror four. Therefore, see [reference needed]. Figure 1 The light from L1 passes sequentially through beam splitter three, mirror one, mirror three, beam splitter one, and mirror four. After being reflected by mirror four, it passes through beam splitter one and is then projected onto screen two. Combined with the attached... Figure 1 This can be expressed as L1 = l0 + l2 + l1 + l3 + l6 + 2l7 + l 12 It depends only on the placement distance between the optical components, which can be determined by actual measurement.

[0099] Optical path difference of interference fringe M2 In the formula, L2 represents the total optical path from the light source to the screen from which interference fringe M2 is formed. Interference fringe M2 is formed on the screen by the interference of the reflected light from the right surface of the object under test and the reflected light from mirror five. Similarly, combined with the attached... Figure 1 This can be expressed as L2 = l0 + l1 + l2 + l3 + l4 + 2l'5 + l 13 l'5 is the distance between mirror five and beam splitter two, which is also a predetermined value.

[0100] Optical path difference of interference fringe M3 In the formula, L3 represents the total optical path from the light source to the screen from which interference fringe M3 is formed. Interference fringe M3 is the interference fringe on the screen formed by the light transmitted through the object under test and the reflected light from the circular beam splitter. Similarly, combined with the attached... Figure 1 It can be represented as L3 = l0 + l1 + l2 + l3 + l4 + 2l5 + l 13 .

[0101] By utilizing the interference between the light reflected from the left surface of the transparent material under test and the light reflected by mirror 4-4, the distance l from the left surface of the transparent material under test to beam splitter 5-1 can be obtained. 10, l7 is the distance between mirror 4-4 and beam splitter 5-1;

[0102] By interfering with the light reflected from the right surface of the transparent material under test with the light reflected from mirror 4-5, the distance l from the right surface of the transparent material under test to beam splitter 5-2 can be obtained. 11 , l'5 is the distance between mirror 5-4-5 and beam splitter 2-5-2;

[0103] Furthermore, from Figure 1 The material thickness l8 can be easily obtained from the geometric relationship: l8 = l9 - (l4 + l) 11 )-(l6+l 10 Then, by utilizing the interference between the light transmitted through the transparent material to be tested and the light reflected by the circular beam splitter 8, the light is... Figure 1 The optical path length transmitted through the material and the distance Δl3 between it and its standard plane can be obtained. From the optical path difference, we can obtain: l6+l 10 +nl8+l 11 -(l4+2l5)=Δl3, and finally we can obtain the refractive index n of the transparent material to be tested.

[0104] To measure different sample thicknesses and refractive indices, simply replace the sample on the test fixture 7; the rest of the steps remain unchanged.

[0105] In the actual experiment, we used sapphire as the sample for measurement. The obtained interference fringe pattern was processed, and the radius values ​​of the first ring were obtained as follows: (In the table, R1 is the corresponding value obtained by the interference of the light transmitted through the sample and the reflected light from the circular beam splitter, R2 is the corresponding value obtained by the interference of the reflected light from the left surface of the sample and the reflected light from the fourth reflection of the mirror, and R3 is the corresponding value obtained by the interference of the reflected light from the right surface of the sample and the reflected light from the fifth reflection of the mirror).

[0106] Table 1. Measurement data of the radius of the first ring of interference fringes on sapphire samples.

[0107]

[0108] Substituting the measured average radius of the rings into the formula (1) relating the radius of the first ring of the interference fringes to the optical path difference, the calculated thickness and refractive index of the sapphire sample are as follows:

[0109] Table 2. Measurement data of sapphire sample thickness and refractive index.

[0110]

[0111] Based on the above data analysis, especially Table 1, the main error of the measurement method designed in this patent lies in the measurement of the radius of the interference fringe ring. Taking the average of multiple measurements will also introduce certain errors. In addition, when using a camera to capture interference images, the camera resolution will introduce uncertainty. Therefore, we used the Michelson white light interferometry principle for measurement as a comparative experiment. The results are shown in Table 3. The measurement method designed in this patent has a more accurate advantage over the traditional Michelson interferometry method in terms of the measurement accuracy of thickness and refractive index.

[0112] Table 3. Relative Errors of Sapphire Sample Measurement Results

[0113]

[0114] Although the specific embodiments of the present utility model have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present utility model. Those skilled in the art should understand that, based on the technical solution of the present utility model, various modifications or variations of equivalent structures or equivalent processes that can be made by those skilled in the art without creative effort, or directly or indirectly applied to other related technical fields, are still within the scope of protection of the present utility model.

Claims

1. A device for synchronously measuring the refractive index and thickness of a transparent material, characterized in that: it comprises an optical path system and an image acquisition module; the optical path system comprises a light source, a beam splitter assembly, a mirror assembly, a light screen assembly, and a sample clamping support, the beam splitter assembly comprises a beam splitter one, a beam splitter two, a beam splitter three, and a circular beam splitter, the mirror assembly comprises a mirror one, a mirror two, a mirror three, a mirror four, a mirror five, a mirror six, and a mirror seven, the light screen assembly comprises a screen one and a screen two for receiving interference fringes, and the sample clamping support is used to clamp the transparent material; the light source is coaxially arranged with the beam splitter three and the mirror two along a first axis, the mirror one is arranged on one side of the beam splitter three, the mirror seven is arranged on one side of the mirror two, and the mirror one and the mirror seven are distributed on different sides of the first axis; the mirror three, the beam splitter one, the beam splitter two, and the mirror six are coaxially arranged along a second axis in sequence, and the second axis is perpendicular to the first axis; the sample clamping support is coaxially arranged with the second axis between the beam splitter one and the beam splitter two; the mirror one and the mirror three are coaxial along a third axis, and the mirror seven and the mirror six are coaxial along a fourth axis, and the third axis and the fourth axis are parallel to the first axis; the mirror four, the beam splitter one, and the screen two are coaxial along a fifth axis in sequence; and the mirror five, the circular beam splitter, the beam splitter two, and the screen one are coaxial along a sixth axis in sequence. The image acquisition module is arranged corresponding to the screen one and the screen two, and is used to acquire the interference fringes on the two light screens. The optical path system further comprises a first attenuator and a second attenuator, the first attenuator is arranged between the beam splitter one and the sample clamping support, and the second attenuator is arranged between the mirror four and the beam splitter one. A calibration plate one is arranged on the screen one, and a calibration plate two is arranged on the screen two. The light source is a laser.

2. The apparatus for simultaneously measuring the refractive index and thickness of a transparent material according to claim 1, further characterized by: The image acquisition module uses a camera to acquire the interference fringe image.

3. The apparatus for simultaneously measuring the refractive index and thickness of a transparent material of claim 1, further characterized by: The transparent material is suitable for K9 optical glass, sapphire, quartz, or acrylic plate.

4. The apparatus for simultaneously measuring the refractive index and thickness of a transparent material of claim 1, further characterized by: A one-dimensional slide rail is further included, and the camera is arranged on the one-dimensional slide rail in front of the screen one and the screen two, and the position of the camera is adjusted by sliding.

5. The apparatus for simultaneously measuring the refractive index and thickness of a transparent material of claim 1, further characterized by:

2. The device according to claim 1, characterized in that: the light source is a laser.

6. The apparatus for simultaneously measuring the refractive index and thickness of a transparent material of claim 1, further characterized by:

3. The device according to claim 1, characterized in that: the image acquisition module uses a camera to acquire the interference fringe image.

7. The apparatus for simultaneously measuring the refractive index and thickness of a transparent material of claim 5, further characterized by:

4. The device according to claim 1, characterized in that: the transparent material is suitable for K9 optical glass, sapphire, quartz, or acrylic plate.

5. The device according to claim 1, characterized in that: a one-dimensional slide rail is further included, and the camera is arranged on the one-dimensional slide rail in front of the screen one and the screen two, and the position of the camera is adjusted by sliding.

Images