A focal length detection device and method for long focal length optical system alignment process

Abstract

This invention discloses a focal length detection device and method for the assembly and adjustment process of a long focal length optical system, solving the problem of low detection accuracy and repeatability of existing technologies for large-aperture long focal length optical systems. The focal length detection device specifically includes a plane mirror disposed at the output end of the optical system under test, an interferometer lens and interferometer body disposed at the incident end of the optical system under test and mounted on a one-dimensional translation stage, as well as a length measuring mechanism and a diameter measuring mechanism. The interferometer body is used to emit a measurement beam to the incident end of the optical system under test. The aperture of the plane mirror is larger than the effective light transmission aperture D of the optical system under test. The one-dimensional translation stage is used to control the interferometer lens and the interferometer body to translate along the optical axis of the measurement beam. This invention establishes the relationship between the actual displacement before and after the dynamic interferometer and the wavefront power component of the system when the interferometer is used to detect the optical system under test, and calculates the focal length of the optical system using the least squares fitting method.

Description

Technical Field

[0001] This invention relates to a focal length detection device and method, specifically to a focal length detection device and method for the assembly and adjustment process of a long focal length optical system. Background Technology

[0002] Large-aperture, long-focal-length optical systems are widely used in Earth observation, astronomical research, and other fields, and their inspection and assembly are among the cutting-edge technologies. These long-focal-length optical systems have significant commercial value in various applications such as long-distance space imaging and laser weapon focusing. As the aperture of long-focal-length optical systems increases, the requirements for their optical inspection and assembly also rise.

[0003] Focal length, as a crucial physical quantity in optical systems, requires precise measurement, which is a key aspect of system development. Currently, commonly used methods for measuring the focal length of long-focal-length optical systems include methods combining theodolites and glass plates, as well as precise angle measurement methods.

[0004] The basic steps of the glass plate method involve mounting a glass plate on the focal plane of an optical system, illuminating it with a light source, and measuring the angles between the lines on the glass plate using a theodolite to calculate the focal length of the optical system. However, in practice, the glass plate method requires a high-precision theodolite to aim at the image point on the focal plane of the optical system. Due to the large focal length of the optical system, the extremely small image point size, and the influence of airflow and human eye resolution, significant errors can easily occur during observation. Therefore, this method has low accuracy and repeatability in focal length detection, making it difficult to meet the requirements of image quality inspection and assembly in modern optical systems.

[0005] Precision angle measurement typically requires placing the optical system on a turntable for rotation and using a large-aperture collimator to provide an image of the target at infinity, which places high demands on the hardware.

[0006] Therefore, there is an urgent need for a high-precision, convenient, and low-cost detection method and device to achieve accurate detection of the focal length of large-aperture, long-focal-length optical systems during assembly and adjustment. Summary of the Invention

[0007] To address the technical problems of low detection accuracy and repeatability or high detection cost of existing technologies for large-aperture long-focal-length optical systems, this invention provides a focal length detection device and method for the assembly and adjustment process of long-focal-length optical systems.

[0008] The inventive concept of this invention is:

[0009] This invention establishes the relationship between the actual displacement before and after the dynamic interferometer and the wavefront power (defocus) component of the system when the interferometer is used to test the optical system under test, and uses the least squares fitting method to calculate the focal length of the optical system.

[0010] To achieve the above objectives and complete the above inventive concept, the present invention adopts the following technical solution:

[0011] A focal length detection device for the assembly and adjustment process of a long focal length optical system is characterized by comprising: a plane mirror disposed at the output end of the optical system under test, an interferometer lens and an interferometer body disposed at the input end of the optical system under test and mounted on a one-dimensional translation stage, as well as a length measuring mechanism and a diameter measuring mechanism.

[0012] The interferometer body is used to emit a measurement beam to the incident end of the optical system under test and to measure the defocused wavefront PV value or power value Δw of the optical system under test.

[0013] The interferometer lens is used to converge the measurement beam into the optical system under test, and then the optical system under test converts it into parallel light.

[0014] The aperture of the plane mirror is larger than the effective light-transmitting aperture D of the optical system under test. It is used to reflect the parallel light emitted from the optical system under test back to the optical system under test, and then enter the interferometer body through the interferometer lens.

[0015] The one-dimensional translation stage is used to control the interferometer lens and the interferometer body to translate along the optical axis of the measurement beam.

[0016] The length measuring mechanism is used to monitor the displacement Δz of the one-dimensional translation stage;

[0017] The diameter measuring mechanism is used to measure the effective aperture D of the optical system under test.

[0018] Furthermore, the F-number of the interferometer lens is smaller than the F-number of the optical system under test.

[0019] Furthermore, the interferometer body is a dynamic interferometer.

[0020] Furthermore, the length measuring mechanism is a length measuring interferometer.

[0021] Furthermore, the diameter measuring mechanism is a coordinate measuring machine.

[0022] A method for detecting the focal length during the assembly and adjustment process of a long focal length optical system, characterized by the following steps:

[0023] Step 1: Construct the focal length detection device as described above for the assembly and adjustment process of the long focal length optical system;

[0024] Step 2: Start the interferometer body to emit a measurement beam towards the incident end of the optical system under test, and measure the defocused wavefront PV value or power value Δw of the optical system under test;

[0025] Step 3: Drive the interferometer lens and the interferometer body to move along the optical axis of the measurement beam using a one-dimensional translation stage, so that the defocused wavefront PV value or power value Δw measured by the interferometer body meets the preset requirements, and record the position of the interferometer body at this time as the step zero position.

[0026] Step 4: Drive the interferometer lens and the interferometer body to move back and forth multiple times along the optical axis of the measurement beam starting from the zero step position using a one-dimensional translation stage, and monitor the displacement Δz of the one-dimensional translation stage through the length measuring mechanism, while recording the defocused wavefront PV value or power value Δw corresponding to each displacement of the interferometer body.

[0027] Step 5: Calculate the focal length of the optical system under test corresponding to each displacement.

[0028] Step 6: Fit the calculated multiple focal length values ​​f to obtain the actual focal length value of the optical system under test, thus completing the focal length detection.

[0029] Furthermore, step 4 specifically involves:

[0030] The interferometer lens and the interferometer body are driven by a one-dimensional translation stage to move back and forth multiple times along the optical axis of the measurement beam starting from the zero step position. The displacement Δz of the one-dimensional translation stage is monitored by the length measuring mechanism. At the same time, after each displacement, the PV value or power value of the defocused wavefront is measured multiple times by the interferometer body and the average value is taken to obtain Δw.

[0031] Furthermore, in step 4:

[0032] When moving the interferometer lens and the interferometer body, it is necessary to monitor that the interference rings obtained by the interferometer body are always in the center of the image.

[0033] Furthermore, step 6 specifically includes:

[0034] The calculated focal length values ​​f are fitted using the least squares method to obtain the actual focal length value of the optical system under test, thus completing the focal length detection.

[0035] Furthermore, in step 5:

[0036] The effective aperture D of the optical system under test is measured by a coordinate measuring machine.

[0037] The beneficial effects of this invention are:

[0038] 1. The present invention provides a focal length detection device and method for the assembly and adjustment process of a long focal length optical system. Compared with the glass plate detection method, the present invention uses the defocus wavefront PV value or power value recorded by the interferometer to fit the displacement recorded by the length measuring mechanism to obtain the actual focal length of the optical system under test. This greatly reduces the detection error caused by human eye observation and the image point position drift caused by airflow disturbance, improves detection efficiency and detection accuracy, and has high repeatability.

[0039] 2. The present invention provides a focal length detection device and method for the assembly and adjustment process of a long focal length optical system, which can realize the quantitative measurement of the focal length of the long focal length optical system. Combined with the calculation and processing of the measurement data, the focal length offset of the long focal length optical system can be quantitatively given, providing precise guidance for system assembly, adjustment and detection.

[0040] 3. The present invention provides a focal length detection device for the assembly and adjustment process of a long focal length optical system. It has a simple structure and a short detection time, and can effectively solve the problem of high-precision and rapid quantitative measurement of focal length of long focal length optical systems under the usage posture. Attached Figure Description

[0041] Figure 1 This is a schematic diagram of an embodiment of a focal length detection device for the assembly and adjustment process of a long focal length optical system according to the present invention.

[0042] Icon labels:

[0043] 1-Plane mirror, 2-Optical system under test, 3-Focal plane, 4-Interferometer lens, 5-Interferometer body, 6-One-dimensional translation stage, 7-Length measuring mechanism. Detailed Implementation

[0044] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. 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.

[0045] This embodiment provides a focal length detection device for the assembly and adjustment process of a long focal length optical system, such as... Figure 1As shown, the testing device includes a plane mirror 1 disposed at the exit end of the optical system under test 2, an interferometer lens 4 and an interferometer body 5 disposed at the incident end of the optical system under test 2 and mounted on a one-dimensional translation stage 6, as well as a length measuring mechanism 7 and a diameter measuring mechanism. The interferometer body 5 is used to emit a measurement beam to the incident end of the optical system under test 2 and measure the defocused wavefront PV value or power value Δw of the optical system under test 2. The interferometer lens 4 is used to converge the measurement beam to the focal plane 3, and the optical system under test 2 then converts the converged beam into parallel light. The aperture of the plane mirror 1 is larger than the effective light transmission aperture D of the optical system under test 2, and is used to reflect the parallel light emitted from the optical system under test 2 back to the optical system under test 2, which then converges again to the focal plane 3 and enters the interferometer body 5 through the interferometer lens 4. The attitudes of the plane mirror 1 and the interferometer body 5 are adjusted to test the field of view position of interest of the optical system under test 2. In this embodiment, the interferometer body 5 is a dynamic interferometer; the F-number of the interferometer lens 4 is smaller than the F-number of the optical system under test 2. A one-dimensional translation stage 6 is used to control the translation of the interferometer lens 4 and the interferometer body 5 along the optical axis of the measurement beam; a length measuring mechanism 7 is used to monitor the displacement Δz of the one-dimensional translation stage 6; in this embodiment, the length measuring mechanism 7 is a length measuring interferometer. A diameter measuring mechanism is used to measure the effective aperture D of the optical system 2 under test. In this embodiment, the diameter measuring mechanism is a coordinate measuring machine.

[0046] The specific measurement steps are as follows:

[0047] Step 1: Construct the focal length detection device described above for the assembly and adjustment process of the long focal length optical system;

[0048] 1.1 Select an interferometer lens 4 with an F-number smaller than that of the optical system 2 under test and install it on the interferometer body 5, placing it at the focal plane 3 position;

[0049] 1.2 A one-dimensional translation stage 6, which moves along the optical axis, is fixed below the interferometer body 5;

[0050] 1.3. A length measuring interferometer is placed in the direction of motion of the one-dimensional translation stage 6 to monitor the displacement of the interferometer body 5;

[0051] 1.4 Place a plane mirror 1 at the light outlet of the optical system 2 under test (the aperture of the plane mirror 1 should be larger than the effective light transmission aperture D of the optical system 2 under test).

[0052] Step 2: Start the interferometer body 5 to emit a measurement beam to the incident end of the optical system under test 2, and measure the defocused wavefront PV value or power value Δw of the optical system under test 2.

[0053] Step 3: Drive the interferometer lens 4 and the interferometer body 5 to move along the optical axis of the measurement beam by the one-dimensional translation stage 6, so that the defocused wavefront PV value or power value Δw measured by the interferometer body 5 meets the preset requirements, and record the position of the interferometer body 5 at this time as the step zero position.

[0054] Step 4: Drive the interferometer lens 4 and the interferometer body 5 to move back and forth multiple times along the optical axis of the measurement beam starting from the zero step position using the one-dimensional translation stage 6. Monitor the displacement Δz of the one-dimensional translation stage 6 through the length measuring mechanism 7. Simultaneously, after each displacement, measure the defocused wavefront PV value or power value multiple times through the interferometer body 5 and take the average value to obtain Δw. When moving the interferometer lens 4 and the interferometer body 5, it is necessary to monitor that the interference ring obtained by the interferometer body 5 is always in the center of the image.

[0055] Step 5: Calculate the focal length of the optical system under test corresponding to each displacement. The effective aperture D of the optical system under test 2 is measured by a coordinate measuring machine, which can be measured before step 1.

[0056] Step 6: Fit the calculated focal length values ​​f using the least squares method to obtain the actual focal length value of the optical system 2 under test, thus completing the focal length detection.

[0057] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions within the technical scope disclosed in the present invention should be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A focal length detection method for a long focal length optical system alignment process, characterized in that, Includes the following steps: Step 1: Construct a focal length detection device for the assembly and adjustment process of a long focal length optical system. The focal length detection device includes a plane mirror (1) set at the exit end of the optical system under test (2), an interferometer lens (4) and an interferometer body (5) set at the incident end of the optical system under test (2) and mounted on a one-dimensional translation stage (6), as well as a length measuring mechanism (7) and a diameter measuring mechanism; the aperture of the plane mirror (1) is larger than the effective light transmission aperture D of the optical system under test (2); Step 2: Start the interferometer body (5) to emit a measurement beam to the incident end of the optical system under test (2), and measure the defocus wavefront PV value or power value of the optical system under test (2). ; Step 3: Drive the interferometer lens (4) and the interferometer body (5) along the optical axis of the measurement beam using a one-dimensional translation stage (6), so that the defocused wavefront PV value or power value measured by the interferometer body (5) is obtained. The preset requirements are met, and the position of the interferometer body (5) at this time is recorded as the step zero position; Step 4: Drive the interferometer lens (4) and the interferometer body (5) to move back and forth multiple times along the optical axis of the measurement beam starting from the zero step position using a one-dimensional translation stage (6). Monitor the displacement of the one-dimensional translation stage (6) through the length measuring mechanism (7), and record the defocus wavefront PV value or power value corresponding to each displacement of the interferometer body (5). ; Step 5, calculate the focal length value of the optical system (2) to be tested corresponding to each displacement amount ; Step 6: Fit the calculated multiple focal length values ​​f to obtain the actual focal length value of the optical system under test (2) and complete the focal length detection.

2. The focal length detection method for long focal length optical system alignment process according to claim 1, characterized in that, Step 4 specifically involves: The interferometer lens (4) and the interferometer body (5) are driven by a one-dimensional translation stage (6) to move back and forth multiple times along the optical axis of the measurement beam starting from the zero step position, and the displacement of the one-dimensional translation stage (6) is monitored by the length measuring mechanism (7). Meanwhile, after each displacement, the PV value or power value of the defocused wavefront is measured multiple times by the interferometer body (5) and the average value is obtained. .

3. The focal length detection method for long focal length optical system alignment process according to claim 2, characterized in that, In step 4: When moving the interferometer lens (4) and the interferometer body (5), it is necessary to monitor that the interference ring obtained by the interferometer body (5) is always in the center of the image.

4. The focal length detection method for long focal length optical system alignment process according to claim 3, characterized in that, Step 6 specifically involves: By fitting multiple calculated focal length values ​​f using the least squares method, the actual focal length value of the optical system under test (2) is obtained, and the focal length detection is completed.

5. The focal length detection method for long focal length optical system alignment process according to claim 4, characterized in that, In step 5: The effective aperture D of the optical system under test (2) was measured by a coordinate measuring machine.

6. The focal length detection method for long focal length optical system alignment process according to claim 5, wherein, In step 1: The F-number of the interferometer lens (4) is less than the F-number of the optical system under test (2).

7. The focal length detection method for long focal length optical system alignment process according to claim 6, wherein, In step 1: The interferometer body (5) is a dynamic interferometer.

8. The focal length detection method for long focal length optical system alignment process according to claim 7, characterized in that, In step 1: The length measuring mechanism (7) is a length measuring interferometer.

9. The focal length detection method for long focal length optical system alignment process according to claim 8, wherein, In step 1: The diameter measuring mechanism is a three-coordinate measuring machine.

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