Low-coherence interference lens thickness measuring system and method based on cube-corner prism scanning

Abstract

The invention relates to the technical field of optical lens parameter measurement, in particular to a low-coherence interference lens thickness measuring system and method based on cube-corner prism scanning, and the system comprises a beam splitter prism, a collimating lens, a to-be-measured lens, a plane mirror, a CCD camera and an upper computer. The system also comprises a low-phase interferometer and a cube-corner prism. The low-phase interferometer, the beam splitter prism and the cube-corner prism are sequentially connected through light paths to form a reference light path; according to the invention, the cube-corner prism is used for replacing a traditional double-wedge lens group and a plane reflecting mirror, so that the problems of complicated structure, cost reduction and complicated operation are solved, and the result that the center thickness of the lens can be obtained only through one-time clamping in a large-stroke, low-cost and non-contact manner is realized.

Description

Technical Field

[0001] This invention relates to the field of optical lens parameter measurement technology, specifically to a low-coherence interference lens thickness measurement system and method based on corner prism scanning. Background Technology

[0002] As high-end optical manufacturing continues to advance towards micron-level precision, ultra-thinness, and large-scale mass production, the center thickness of a lens has evolved from a traditional geometric dimension into a crucial parameter that determines the system's imaging quality, assembly tolerance, and long-term reliability.

[0003] Existing measurement methods have revealed significant shortcomings in balancing tolerance limits and the demands of large-scale applications. These include both contact and non-contact measurement methods. Among these, contact measurement methods carry a high risk of scratching the lens, leading to a greater adoption of high-precision non-contact measurement methods in practical applications.

[0004] Among existing non-contact measurement methods, traditional double-wedge mirror measurement has advantages in practical applications due to its accuracy of 0.1μm, low cost, and simple structure. However, traditional double-wedge mirror measurement also has drawbacks. Due to its double-wedge structure, it remains a complex structure that is difficult to maintain, install, and adjust, and is costly, making it unsuitable for practical applications.

[0005] Therefore, those skilled in the art urgently need to keep pace with technological advancements and further improve traditional double wedge mirror measurements to simplify the structure and reduce costs. Summary of the Invention

[0006] Therefore, the technical problem to be solved by the present invention is to overcome the defects existing in the prior art, thereby providing a low-coherence interference lens thickness measurement system and method based on corner prism scanning.

[0007] A low-coherence interferometric lens thickness measurement system based on corner bevel prism scanning includes: a beam splitter prism, a collimating mirror, a lens under test, a plane mirror, a CCD camera, and a host computer; it also includes: a low-phase interferometer and a corner bevel prism. The low-phase interferometer, beam splitter, and cornerstone prism are sequentially connected to form the reference optical path.

[0008] Preferably, it also includes: a first motor; The output end of the first motor is parallel to the optical path connecting the collimating mirror and the plane mirror. The lens under test is connected to the output end of the first motor so that the lens under test can rotate into or out between the collimating mirror and the plane mirror based on the control of the first motor. The first motor is connected to the host computer via signal.

[0009] Preferably, it also includes: a second motor and a horizontal guide rail; one end of the horizontal guide rail is connected to the output end of the second motor; The cornerstone prism is mounted on a horizontal guide rail via a cornerstone prism mounting base, and the cornerstone prism mounting base is slidably connected to the horizontal guide rail. The horizontal guide rail is parallel to the reference optical axis, and the vertex of the corner cube prism is on the reference optical axis of the reference optical path; The second motor is connected to the host computer via signal.

[0010] A method for thickness measurement of low-coherence interferometric lenses based on corner prism scanning is implemented using a low-coherence interferometric lens thickness measurement system based on corner prism scanning, and specifically includes the following steps: S1. Preparatory work: Assemble a device other than the lens to be measured in a low-coherence interference lens thickness measurement system based on corner prism scanning; S2. Drive the second motor to move the cornerstone prism on the horizontal guide rail. The host computer obtains the contrast of the interference fringes in real time by connecting to the CCD camera. S3. When the contrast of the interference fringes acquired in real time in step S2 reaches its maximum value, stop driving the second motor and record the position of the corner cube prism at this time. ; S4. Assemble the lens under test and the first motor, and drive the first motor until the optical axis of the lens under test coincides with the optical axis between the collimating mirror and the plane mirror; S5. Repeat steps S2 to S3 until the contrast of the interference fringes reaches its maximum value again. Stop driving the second motor and record the position of the corner cube prism at this time. ; S6. Based on the two positions of the cornerstone prism and The thickness of the lens under test is obtained by calculating the refractive index of the lens material.

[0011] Preferably, the formula for calculating the thickness of the lens to be measured is: ; ; In the formula, This represents the displacement difference of the cornerstone prism; Indicates the refractive index of the lens material under test; This indicates the thickness of the lens being measured.

[0012] The technical solution of this invention has the following advantages: This invention improves the double-wedge mirror measurement method by replacing the double-wedge mirror assembly and the plane mirror that works with it with a cornerstone prism. While maintaining the same principle, this simplifies the overall system structure. Furthermore, to improve the stability and ease of use of the moving parts, a motor is used to drive the corresponding components. Additionally, this invention uses a combination of a cornerstone prism and a horizontal slide rail to increase the detection stroke, avoiding the limitation on stroke imposed by the wedge angle in the wedge mirror measurement method. Attached Figure Description

[0013] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0014] Figure 1 This is a schematic diagram of the overall structure of a low-coherence interference lens thickness measurement system based on corner prism scanning according to the present invention; Figure 2 This is a schematic diagram illustrating the internal optical path of the cornerstone prism used in this invention. Figure 3 This is a schematic diagram of the movement trajectory of the lens under test.

[0015] Explanation of reference numerals in the attached figures: 1-Low-phase interferometer, 2-Host computer, 3-Beam splitter prism, 4-Pyramidal prism, 5-Collimating lens, 6-Lens to be tested, 7-First motor, 8-Plane mirror, 9-Pyramidal prism mounting base, 10-Horizontal guide rail, 11-Second motor, 12-CCD camera. Detailed Implementation

[0016] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0017] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for 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 the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0018] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0019] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0020] Example 1 First, it should be noted that, in existing technologies, the double-wedge mirror measurement method is an outstanding technical solution capable of achieving ultra-high precision and ultra-large-range measurements under ideal laboratory conditions in practical applications. However, its advantages also directly lead to its main disadvantages, such as high complexity, high cost, environmental sensitivity, and cumbersome operation.

[0021] Therefore, this embodiment discloses a scheme that replaces the double wedge mirror and the plane mirror with a corner pyramid prism 4. Compared with the traditional combination of double wedge mirrors and plane mirrors, both the fabrication process and the assembly complexity are significantly better than traditional double wedge mirror measurements. Figure 2 This is a schematic diagram of the internal optical path of the corner cube prism 4.

[0022] Specifically: This embodiment discloses a low-coherence interference lens thickness measurement system based on corner bevel prism scanning, including: a beam splitter prism 3, a collimating lens 5, a lens under test 6, a plane mirror 8, a CCD camera 12 and a host computer 2, and also includes: a low-phase interferometer 1 and a corner bevel prism 4. like Figure 1 As shown, the light emitted from the low-phase interferometer 1 is split into beams by the beam splitter 3; A beam is connected to the corner cube prism 4 to form a reference optical path; Another beam of light, together with collimating lens 5, lens under test 6, and plane mirror 8, forms the measurement optical path; Since the light rays from the measurement optical path return due to the action of the plane mirror 8, and similarly, the light rays from the reference optical path return due to the action of the cornerstone prism 4, the two returning beams interfere with each other. This embodiment employs a common optical path design, which increases system stability and reduces the system's sensitivity to environmental interference. Furthermore, in order to reduce the problem of cumbersome operation, this embodiment also includes a first motor 7, a second motor 11, and a horizontal guide rail 10; For the first motor 7: Among them, the output end of the first motor 7 is parallel to the optical path connecting the collimating mirror 5 and the plane mirror 8; like Figure 1 and 3 The lens under test 6 is connected to the output end of the first motor 7 so that the lens under test 6 can rotate into or out between the collimating mirror 5 and the plane mirror 8 under the control of the first motor 7. Based on this setting, this embodiment has a fast measurement speed and simple operation. The rotation of the first motor 7 drives the lens under test 6 to rotate into or out of the measurement optical path, avoiding repeated clamping during multiple measurements.

[0023] The first motor 7 is connected to the host computer 2 via signal transmission; It should be noted that, depending on actual needs, the first motor 7 can move parallel to the measuring optical axis to adjust the distance between the two sides of the lens 6 under test, the collimating mirror 5, and the plane mirror 8.

[0024] For the second motor 11 and the horizontal guide rail 10: One end of the horizontal guide rail 10 is connected to the output end of the second motor 11; The cornerstone prism 4 is mounted on the horizontal guide rail 10 via the cornerstone prism mounting base 9, and the cornerstone prism mounting base 9 is slidably connected to the horizontal guide rail 10. The horizontal guide rail 10 is parallel to the reference optical axis, and the vertex of the corner cube prism 4 is on the reference optical axis of the reference optical path; The second motor 11 is connected to the host computer 2 via signal.

[0025] Example 2 Based on Example 1, this example further discloses a non-contact method for measuring thickness, avoiding scratching the surface of the lens under test by the detection equipment during the detection process. Specifically, it is a method for measuring the thickness of low-coherence interference lenses based on corner prism scanning, implemented using the low-coherence interference lens thickness measurement system based on corner prism scanning from Example 1, and includes the following steps: S1. Preparatory work: Assemble a device other than the lens 6 to be measured in a low coherence interference lens thickness measurement system based on corner prism scanning; S2. Drive the second motor 11 to move the cornerstone prism 4 on the horizontal guide rail 10. The host computer 2 obtains the contrast of the interference fringes in real time by connecting with the CCD camera 12. S3. When the contrast of the interference fringes acquired in real time in step S2 reaches its maximum value, stop driving the second motor 11 and record the position of the corner cube prism 4 at this time. ; S4. Assemble the lens 6 to be tested and the first motor 7, and drive the first motor 7 until the optical axis of the lens 6 to be tested coincides with the optical axis between the collimating mirror 5 and the plane mirror 8; S5. Repeat steps S2 to S3 until the contrast of the interference fringes reaches its maximum value again, then stop driving the second motor 11 and record the position of the corner cube prism 4 at this time. ; S6. Based on the two positions of the cornerstone prism 4 and The thickness of lens 6 is obtained by calculating the refractive index of the material of lens 6 under test.

[0026] Preferably, the formula for calculating the thickness of the lens 6 to be tested is: ; ; In the formula, This represents the displacement difference of the cornerstone prism; Indicates the refractive index of the material of lens 6 under test; This indicates the thickness of lens 6 to be tested.

[0027] Compared with the traditional contact measurement method, this embodiment has higher measurement accuracy. The measurement method used in this embodiment calculates the center thickness based on the optical path difference introduced when the lens under test is placed in the detection optical path, and the measurement accuracy is better than that of traditional caliper measurement.

[0028] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A low-coherence interferometric lens thickness measurement system based on corner bevel prism scanning, comprising: The beam splitter (3), collimating lens (5), lens to be tested (6), plane mirror (8), CCD camera (12) and host computer (2) are characterized in that they also include: low phase interferometer (1) and corner prism (4). Among them, the low-phase interferometer (1), the beam splitter (3) and the corner cube prism (4) are connected in sequence to form a reference optical path.

2. The low-coherence interference lens thickness measurement system based on corner-pyramidal prism scanning according to claim 1, characterized in that, Also includes: First motor (7); Among them, the output end of the first motor (7) is parallel to the optical path connecting the collimating mirror (5) and the plane mirror (8); The lens under test (6) is connected to the output end of the first motor (7) so that the lens under test (6) can rotate into or out between the collimating mirror (5) and the plane mirror (8) based on the control of the first motor (7); The first motor (7) and the host computer (2) are connected by signals.

3. The low-coherence interference lens thickness measurement system based on corner bevel prism scanning according to claim 2, characterized in that, Also includes: Second motor (11), horizontal guide rail (10); one end of horizontal guide rail (10) is connected to the output end of second motor (11); The corner cube prism (4) is mounted on the horizontal guide rail (10) via the corner cube prism mounting base (9), and the corner cube prism mounting base (9) is slidably connected to the horizontal guide rail (10); The horizontal guide rail (10) is parallel to the reference optical axis, and the vertex of the corner bevel prism (4) is on the reference optical axis of the reference optical path; The second motor (11) is connected to the host computer (2) via signal connection.

4. A method for measuring the thickness of a low-coherence interference lens based on corner-pyramidal prism scanning, characterized in that, The application of the low-coherence interference lens thickness measurement system based on corner bevel prism scanning as described in claim 3 specifically includes the following steps: S1. Preparatory work: Assemble the device other than the lens to be measured (6) in a low coherence interference lens thickness measurement system based on corner prism scanning; S2. Drive the second motor (11) to move the corner cube prism (4) on the horizontal guide rail (10), and the host computer (2) obtains the contrast of the interference fringes in real time by connecting with the CCD camera (12); S3. When the contrast of the interference fringes acquired in real time in step S2 reaches its maximum value, stop driving the second motor (11) and record the position of the corner cube prism (4) at this time. ; S4. Assemble the lens (6) to be tested and the first motor (7), and drive the first motor (7) until the optical axis of the lens (6) to be tested coincides with the optical axis between the collimating mirror (5) and the plane mirror (8); S5. Repeat steps S2 to S3 until the contrast of the interference fringes reaches its maximum value again. Then stop driving the second motor (11) and record the position of the corner cube prism (4) at this time. ; S6. Based on the position of the cornerstone prism (4) twice. and The thickness of the lens (6) is obtained by calculating the refractive index of the material of the lens (6) under test.

5. The method for measuring the thickness of a low-coherence interference lens based on corner-pyramidal prism scanning according to claim 4, characterized in that, The formula for calculating the thickness of the lens (6) to be measured is: ； ； In the formula, This represents the displacement difference of the cornerstone prism; Indicates the refractive index of the material of the lens under test (6); This indicates the thickness of the lens (6) to be tested.

Images