CN113483995A - Detection system and method for refractive index distribution of self-focusing lens - Google Patents
Detection system and method for refractive index distribution of self-focusing lens Download PDFInfo
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- CN113483995A CN113483995A CN202110788884.1A CN202110788884A CN113483995A CN 113483995 A CN113483995 A CN 113483995A CN 202110788884 A CN202110788884 A CN 202110788884A CN 113483995 A CN113483995 A CN 113483995A
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- G01—MEASURING; TESTING
- G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
- G01M11/00—Testing of optical apparatus; Testing structures by optical methods not otherwise provided for
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- G01M11/0228—Testing optical properties by measuring refractive power
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Abstract
The invention relates to the technical field of optical measurement, and discloses a detection system and a detection method for refractive index distribution of a self-focusing lens, aiming at solving the problem of low refractive index detection precision caused by poor environment interference resistance of the existing detection method for refractive index distribution of the self-focusing lens. The Fizeau interferometer system has the advantages of strong anti-interference capability and small size.
Description
Technical Field
The invention relates to the technical field of optical measurement, in particular to a Fizeau interference principle-based detection method for refractive index distribution of a self-focusing lens.
Background
A self-focusing lens (GRIN lens, G-lens), also called gradient index lens, is a cylindrical optical lens with refractive index changing in gradient along the radial direction, and has focusing and imaging functions. The self-focusing lens realizes the periodic propagation of light rays in the lens by adjusting the radial gradient refractive index, and the light ray modulation period can be adjusted by changing the length of the self-focusing lens, so that an optical device with the same function as the lens is realized.
The self-focusing lens has end surface collimation, coupling and imaging characteristics, so that the self-focusing lens is widely applied to equipment such as a micro optical system, a medical optical instrument, an optical copying machine, a facsimile machine, a scanner and the like.
The performance of the optical device is inseparable from the law of the refractive index distribution of the optical device, so that the method for detecting the refractive index distribution of the self-focusing lens based on the Fizeau interference principle is always one of the problems of important research of the technicians in the field.
In prior art 1 (Zhoushengsheng, xu feng, yaoyusau, etc., a refractive index distribution testing device and an image acquisition device for a self-focusing lens, chinese utility model patent 201721734733.3) adopts mach-zehnder interference principle to realize high-precision and high-efficiency detection of refractive index distribution of the self-focusing lens, the method adopts a mach-zehnder interference system of optical path interference, and the system has general anti-environmental interference capability.
Compared with the prior art 1, the method improves the environmental interference resistance of the test system and the volume of the test system is small.
Disclosure of Invention
The technical problem solved by the invention is as follows: the refractive index detection method of the self-focusing lens in the prior art has poor environmental interference resistance, so that the refractive index detection precision is not high.
A self-focusing lens refractive index profile detection system, comprising: the device comprises a laser, a spatial filter, a collimating objective lens, a beam splitter, a self-focusing lens, a microscopic imaging system and an image processing system; the method is characterized in that: the microscopic imaging system comprises a microscope objective and a camera; laser generated by the laser is incident on the spatial filter to form a divergent beam; the collimating objective lens collimates the divergent light beams into collimated light beams; the collimated light beam penetrates through the beam splitter and then enters the self-focusing lens; the front surface of the self-focusing lens reflects collimated light to form a reference beam, the rear surface of the self-focusing lens reflects collimated light to form a test beam, interference fringes generated by the reference beam and the test beam are reflected by the beam splitter and then enter the microscopic imaging system, and a microscopic objective of the microscopic imaging system is used for amplifying the interference fringes and imaging the interference fringes on a camera; the image processing system processes interference fringes of the self-focusing lens collected by the camera and obtains the refractive index distribution of the self-focusing lens by analyzing the interference fringe information.
According to the technical scheme, the reference beam and the test beam share the optical path, the Fizeau interference optical path is adopted, the interference fringes of the front surface reflected light and the rear surface reflected light of the self-focusing lens are adopted to analyze the refractive index distribution of the self-focusing lens, the problem that optical elements are too many in the traditional detection method for the refractive index distribution of the self-focusing lens is avoided, and the environment interference resistance of the test system is improved to a certain extent. The Fizeau interferometer system adopts a common-path interference principle, the influence of the deviation of other optical elements in a light path on the optical path difference is almost the same, and the environmental interference can be well overcome; secondly, the method adopts the mutual interference of the reflected light of the front surface and the reflected light of the back surface of the self-focusing lens based on the Fizeau interference principle, and compared with the prior art, the method has the advantage that the number of optical elements of the test system is less.
Description of the drawings:
FIG. 1 is a schematic diagram of an optical path of a detection method for refractive index distribution of a self-focusing lens based on Fizeau interference principle;
wherein: the device comprises a 1-laser, a 2-spatial filter, a 3-collimating objective, a 4-beam splitter, a 5-self-focusing lens, a 6-microscope objective and a 7-camera.
Fig. 2 is a diagram of interference fringes taken at a wavelength of 632.8 nm.
Fig. 3 is a diagram of interference fringes taken at a wavelength of 1064 nm.
Fig. 4 is a graph of interference fringes taken at a wavelength of 1550 nm.
FIG. 5 is a graph of the refractive index profile of a self-focusing lens measured at a wavelength of 632.8 nm; fig. 5(a) shows the results of one measurement, and fig. 5(b) shows the results of measurement after changing the measurement conditions by manually moving the sample piece at intervals of 10 minutes.
FIG. 6 is a graph of the refractive index profile of a self-focusing lens measured at a wavelength of 1064 nm; fig. 6(a) shows the results of one measurement, and fig. 6(b) shows the results of measurement after changing the measurement conditions by manually moving the sample piece at intervals of 10 minutes.
FIG. 7 is a graph of a refractive index profile of a self-focusing lens measured at a wavelength of 1550 nm; fig. 7(a) shows the results of one measurement, and fig. 7(b) shows the results of measurement after changing the measurement conditions by manually moving the sample piece at intervals of 10 minutes.
Detailed Description
The invention provides a detection method for refractive index distribution of a self-focusing lens based on Fizeau interference principle, and in order to make the purpose, technical scheme and effect of the invention clearer and clearer, the invention is further described in detail below by referring to the attached drawings and taking examples. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Example one
A detection system for refractive index distribution of a self-focusing lens, as shown in fig. 1: the device comprises a laser 1, a spatial filter 2, a collimating objective 3, a beam splitter 4, a self-focusing lens 5, a microscopic imaging system and an image processing system; wherein, the microscopic imaging system comprises a microscope objective 6 and a camera 7; laser generated by the laser is incident on the spatial filter to form a divergent beam; the collimating objective lens collimates the divergent light beams into collimated light beams; the collimated light beam penetrates through the beam splitter and then enters the self-focusing lens; the front surface of the self-focusing lens reflects collimated light to form a reference beam, the rear surface of the self-focusing lens reflects collimated light to form a test beam, interference fringes generated by the reference beam and the test beam are reflected by the beam splitter and then enter the microscopic imaging system, and a microscopic objective of the microscopic imaging system is used for amplifying the interference fringes and imaging the interference fringes on a camera; the image processing system processes the interference fringes of the self-focusing lens collected by the camera 7, and obtains the refractive index distribution of the self-focusing lens by analyzing the interference fringe information.
Example two
A detection method of refractive index distribution of a self-focusing lens based on the detection system of refractive index distribution of a self-focusing lens; the method comprises the following steps:
placing a self-focusing lens to be detected behind the beam splitter, opening a laser to generate parallel light, filtering the light through a spatial filter, irradiating the light on the front and rear surfaces of the self-focusing lens after passing through the beam splitter, reflecting the light into two beams of light through the front and rear surfaces of the self-focusing lens to form an interference light path, reflecting the light to a microscopic imaging lens through the beam splitter, imaging interference fringes on a camera through the microscopic imaging lens, and resolving the interference fringes by an image processing system;
moving the imaging microscope system back and forth to enable the focal plane of the microscope objective to coincide with the surface of the self-focusing lens, namely forming a clear image on the self-focusing lens, and obtaining corresponding interference fringes through a camera;
and collecting an image by a back-end image processing system, and inputting the central refractive index of the central position of the self-focusing lens, the wavelength of the selected laser, the thickness of the self-focusing lens, the diameter of the end face and the central refractive index.
As shown in fig. 2, 3, and 4, the interference fringes are concentric rings, the outermost ring of the concentric rings of interference fringes forms a bright edge due to dense superposition of the fringes, the center of the concentric rings is the center of the ring fringe, the bright edge is a boundary, and the interference fringes surrounded by the boundary are an effective mask region; the steps of resolving the interference fringes are as follows: firstly, taking the center of the circular stripe as a starting point, and intercepting a one-dimensional gray array for an image in multiple directions within the range of an effective mask area; secondly, starting to search the peak-valley gray values of a plurality of one-dimensional gray arrays by using the starting point of the one-dimensional gray array; then, on the basis of determining the peak-valley positions of the plurality of one-dimensional gray array, carrying out recursive search on the subsequent peak-valley positions so as to determine all the fringe peak-valley positions of the one-dimensional gray array, and determining the integer level fringe level of each one-dimensional gray array peak-valley position by taking the starting point of the one-dimensional gray array as a zero-level fringe; and finally, determining the decimal fringe order between every two adjacent peak valleys according to the relative gray value, combining the integer fringe order and the decimal fringe order to obtain the fringe order distribution of the one-dimensional gray array, and finally calculating the optical path difference of the interference fringes through a formula so as to calculate the refractive index distribution of the self-focusing lens.
The specific formula of the refractive index distribution calculated from the fringe series distribution is as follows:
2·(n0-n)·d＝k·λ
wherein n is0The refractive index of the center of the self-focusing lens is shown, n is the refractive index to be solved, d is the thickness of the self-focusing lens, k is the fringe series distribution of the one-dimensional gray array, and lambda is the working wavelength of the laser. The refractive index profiles calculated from the fringes shown in fig. 2, 3, and 4 are shown in fig. 5, 6, and 7, in which (a) and (b) subgraphs of each graph correspond to two measurements after 10 minutes of interval and the sample is manually moved to change the measurement conditions.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the scope of the present invention, but rather as embodying the invention in a wide variety of equivalent variations and modifications within the scope of the appended claims.
Claims (3)
1. A self-focusing lens refractive index profile detection system, comprising: the device comprises a laser, a spatial filter, a collimating objective lens, a beam splitter, a self-focusing lens, a microscopic imaging system and an image processing system; the method is characterized in that: the microscopic imaging system comprises a microscope objective and a camera; laser generated by the laser is incident on the spatial filter to form a divergent beam; the collimating objective lens collimates the divergent light beams into collimated light beams; the collimated light beam penetrates through the beam splitter and then enters the self-focusing lens; the front surface of the self-focusing lens reflects collimated light to form a reference beam, the rear surface of the self-focusing lens reflects collimated light to form a test beam, interference fringes generated by the reference beam and the test beam are reflected by the beam splitter and then enter the microscopic imaging system, and a microscopic objective of the microscopic imaging system is used for amplifying the interference fringes and imaging the interference fringes on a camera; the image processing system processes interference fringes of the self-focusing lens collected by the camera and obtains the refractive index distribution of the self-focusing lens by analyzing the interference fringe information.
2. A detection method for refractive index distribution of a self-focusing lens is characterized in that: detecting using a self-focusing lens refractive index profile detection system of claim 1; placing a self-focusing lens to be detected behind the beam splitter, opening a laser to generate parallel light, filtering the light through a spatial filter, irradiating the light on the front and rear surfaces of the self-focusing lens after passing through the beam splitter, reflecting the light into two beams of light through the front and rear surfaces of the self-focusing lens to form an interference light path, reflecting the light to a microscopic imaging lens through the beam splitter, imaging interference fringes on a camera through the microscopic imaging lens, and resolving the interference fringes by an image processing system; moving the imaging microscope system back and forth to enable the focal plane of the microscope objective to coincide with the surface of the self-focusing lens, namely forming a clear image on the self-focusing lens, and obtaining corresponding interference fringes through a camera; and collecting an image by a back-end image processing system, and inputting the central refractive index of the self-focusing lens, the wavelength of the selected laser, the thickness of the self-focusing lens, the diameter of the end face and the central refractive index.
3. The method for detecting the refractive index distribution of a self-focusing lens according to claim 2, wherein: the interference fringes are concentric rings, the outermost ring of the concentric rings of the interference fringes forms a bright edge due to the dense superposition of the fringes, the circle center of the concentric rings is taken as the center of the fringes of the rings, the bright edge is taken as a boundary, and the interference fringes surrounded by the boundary are taken as an effective mask area; the steps of resolving the interference fringes are as follows: firstly, taking the center of the circular stripe as a starting point, and intercepting a one-dimensional gray array for an image in multiple directions within the range of an effective mask area; secondly, starting to search the peak-valley gray values of a plurality of one-dimensional gray arrays by using the starting point of the one-dimensional gray array; then, on the basis of determining the peak-valley positions of the plurality of one-dimensional gray array, carrying out recursive search on the subsequent peak-valley positions so as to determine all the fringe peak-valley positions of the one-dimensional gray array, and determining the integer level fringe level of each one-dimensional gray array peak-valley position by taking the starting point of the one-dimensional gray array as a zero-level fringe; and finally, determining the decimal fringe order between every two adjacent peak valleys according to the relative gray value, combining the integer fringe order and the decimal fringe order to obtain the fringe order distribution of the one-dimensional gray array, and finally calculating the optical path difference of the interference fringes through a formula so as to calculate the refractive index distribution of the self-focusing lens.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113639973A (en) * | 2021-10-15 | 2021-11-12 | 高视科技(苏州)有限公司 | Detection method and system for refractive index distribution of finished product of self-focusing lens |
| CN114383524A (en) * | 2021-12-27 | 2022-04-22 | 南京工业大学 | OpenCV-based Michelson interference image physical information extraction method |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113639973A (en) * | 2021-10-15 | 2021-11-12 | 高视科技(苏州)有限公司 | Detection method and system for refractive index distribution of finished product of self-focusing lens |
| CN113639973B (en) * | 2021-10-15 | 2022-02-08 | 高视科技(苏州)有限公司 | Detection method and system for refractive index distribution of finished product of self-focusing lens |
| CN114383524A (en) * | 2021-12-27 | 2022-04-22 | 南京工业大学 | OpenCV-based Michelson interference image physical information extraction method |
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