CN110779685A - Device and method for measuring focal length of long-focus optical system based on self-collimating plane mirror - Google Patents
Device and method for measuring focal length of long-focus optical system based on self-collimating plane mirror Download PDFInfo
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Abstract
The invention provides a device and a method for measuring a focal length of a long-focus optical system based on a self-aligning plane mirror. The device comprises a plane mirror arranged at the outlet of an optical system to be detected, a focal plane detection CCD arranged on the focal plane of the optical system to be detected, and an interferometer; the focus of the interferometer is positioned on the focal plane of the optical system to be detected, the focal plane detection CCD is arranged on a vertically arranged electric guide rail, and the plane mirror is arranged on the subdivision multi-tooth dividing table. The invention has strong universality, and different measuring systems do not need to replace any element or additionally increase elements.
Description
The technical field is as follows:
the invention relates to a device and a method for measuring a focal length of a long-focus optical system based on a self-aligning plane mirror, belonging to the technical field of optical equipment.
Background art:
in high resolution imaging applications or ground detection devices, long-focus and even ultra-long-focus optical systems are increasingly used, and generally, optical systems with a focal length of more than 10 meters are considered to be long-focus and even ultra-long-focus optical systems. The focus measurement accuracy is particularly important. The conventional precise angle measurement method uses a target plate and a theodolite to detect the focal length, and the measurement of a long focal length system has small incident angle and large relative measurement error of the theodolite due to the small target plate; the magnification method requires an optical system with a focal length of a considerable order, and has high detection cost and low universality. Therefore, the conventional focal length measuring method is difficult to be applied to the focal length measurement of the long-focal-length or ultra-long-focal-length optical system.
The invention content is as follows:
the present invention aims to provide a device and a method for measuring the focal length of a long-focus optical system based on a self-collimating plane mirror, which can generate parallel light required by detection through the plane mirror to complete the focal length measurement of the long-focus optical system.
The above purpose is realized by the following technical scheme:
the long-focus optical system focal length measuring device based on the self-collimating plane mirror comprises a plane mirror arranged at the outlet position of an optical system to be measured, a focal plane detection CCD arranged on the focal plane of the optical system to be measured, and an interferometer; the focus of the interferometer is positioned on the focal plane of the optical system to be detected, the focal plane detection CCD is arranged on a vertically arranged electric guide rail, and the plane mirror is arranged on the subdivision multi-tooth dividing table.
The long-focus optical system focus measuring device based on the autocollimation plane mirror is characterized in that the optical system to be measured comprises a primary mirror and a secondary mirror, and light beams are reflected by the primary mirror and the secondary mirror and then form images at a focal plane.
The device for measuring the focal length of the long-focus optical system based on the autocollimation plane mirror is characterized in that the main mirror adopts a concave reflecting mirror, and the secondary mirror adopts a concave reflecting mirror or a convex reflecting mirror.
The method for measuring the focal length of the long-focus optical system by using the focal length measuring device of the long-focus optical system based on the autocollimation plane mirror comprises the following steps:
(1) placing the interferometer so that the focal point of the interferometer is located at the focal plane of the optical system to be measured; placing a plane mirror on a subdivided multi-tooth dividing table and placing the plane mirror at a light outlet of an optical system to be tested;
(2) detecting the wave aberration of the optical system to be detected by using an interferometer and a plane mirror and adopting an auto-collimation interference detection method;
(3) arranging a focal plane detection CCD on an electric guide rail; then placing a focal plane detection CCD and an electric guide rail at the focal plane of the optical system to be detected;
(4) adjusting the angle of the multi-tooth dividing table to drive the plane mirror to rotate, receiving the image point returned from the focal plane by the CCD, adjusting the front and back positions of the CCD to minimize the image point, placing the CCD detection target surface on the focal plane of the optical system to be detected, and recording the centroid pixel coordinate a of the image point;
(5) continuously adjusting the angle of the multi-tooth dividing table to enable the multi-tooth dividing table to rotate by an angle theta, and returning to the parallel light beam to change the angle by 2 theta;
(6) the CCD is driven by the electric guide rail to translate, a new image point position is received, and the moving amount d1 of the electric guide rail and the pixel coordinate b of the centroid of the image point at the moment are recorded;
(7) the moving distance d = d1+ h (b-a) of the image point can be calculated according to the moving distance d1 of the electric guide rail, the coordinate change (b-a) of the center of mass of the image point detected by the CCD and the size h of the CCD pixel; the system focal length f is f = d/tan (2 θ);
(8) and (5) repeating the steps (5) to (7), and measuring the focal length of the system for multiple times and averaging to obtain the focal length of the system.
In the method for measuring the focal length of the long-focal-length optical system, the auto-collimation interference detection method in the step (2) is a detection method based on an interferometer and a plane mirror, and specifically comprises the following steps: spherical waves are emitted by the interferometer, converged on the focal plane of the optical system to be detected, reflected for multiple times by the optical system to be detected to become parallel light and emitted, reflected by the plane mirror to return along the original path, reflected for multiple times by the optical system to be detected to become spherical wave front, and received by the interferometer to perform system wave aberration detection.
In the method for measuring the focal length of the long-focal-length optical system, the measuring times in the step (8) are 3-10 times.
Has the advantages that:
1. according to the invention, high-precision parallel light is generated through the plane mirror, so that an optical system is prevented from being additionally used; the multi-tooth dividing table is used for improving the angle measurement precision of the parallel light; the CCD is used for adding the electric guide rail, so that the image point distance measurement precision is improved; the method is suitable for measuring the focal length of a long-focus system and even an ultra-long-focus system, has strong universality, and does not need to replace any element or additionally add elements when measuring different systems.
Description of the drawings:
fig. 1 is a front view of the present invention.
Fig. 2 is a top view of the present invention.
In the figure: 1-an optical system to be measured, 2-a plane mirror, 3-CCD, 4-an interferometer, 5-an electric guide rail, 6-a subdivided multi-tooth dividing table, 11-a main mirror and 12-a secondary mirror.
The specific implementation mode is as follows:
the invention relates to a focal length measuring device which consists of a plane mirror, a high-precision subdivision multi-tooth dividing table and a focal plane detection CCD. The plane mirror is arranged at a light outlet of the optical system to be detected and used for automatically and accurately reflecting the high-precision parallel light emitted by the optical system to be detected back to a focal plane of the system, and the focal plane detection CCD receives a focus returned from the collimation. The plane mirror is placed on a high-precision subdivision multi-tooth dividing table, the multi-tooth dividing table can rotate by an angle theta to drive the plane mirror to generate high-precision parallel light with a known angle 2 theta, the CCD drives the translation quantity of the image point of the receiving focal plane by an electric guide rail, and the image point moving distance d can be calculated according to the guide rail moving distance and the mass center coordinate of the image point received by the CCD. And calculating the system focal length f = d/tan (2 theta) according to the image point moving distance d and the parallel light angle change 2 theta.
Firstly, an interferometer and a plane mirror are utilized, and an auto-collimation interference detection method is adopted to detect the wave aberration of an optical system to be detected, so that the measured wavefront error is as small as possible, the quality of emergent parallel beams is improved, and the accuracy of the focal plane position is improved. The focal plane detection CCD and the electric guide rail are placed at the focal plane, the angle of the multi-tooth dividing table is adjusted to drive the angle change of the self-collimating plane mirror, the image point at the focal plane moves, and the moving image point is received by the focal plane detection CCD. And adjusting different angle quantities, respectively measuring corresponding image point movement quantities to calculate the system focal length, and averaging multiple times of measurement to obtain the final system focal length.
Specifically, the method comprises the following steps: as shown in fig. 1 to 2, the focal length measuring device of the long-focus optical system based on the autocollimation plane mirror of the present embodiment includes a plane mirror 2 disposed at an exit of an optical system to be measured 1, a focal plane detection CCD 3 disposed on a focal plane of the optical system to be measured, and an interferometer 4; the focus of the interferometer is positioned on the focal plane of the optical system to be detected, the focal plane detection CCD is arranged on a vertically arranged electric guide rail 5, and the plane mirror is arranged on a subdivision multi-tooth dividing table 6.
The optical system to be measured generally comprises a concave reflector called a primary mirror and a concave reflector or a convex reflector called a secondary mirror, and after light beams at infinite distance or limited distance are reflected by the primary mirror and the secondary mirror, the light beams are imaged at a focal plane.
The method for measuring the focal length of the long-focus optical system by using the focal length measuring device of the long-focus optical system based on the autocollimation plane mirror comprises the following steps:
(1) placing the interferometer so that the focal point of the interferometer is located at the focal plane of the optical system to be measured; placing a plane mirror on a subdivided multi-tooth dividing table and placing the plane mirror at a light outlet of an optical system to be tested;
(2) detecting the wave aberration of the optical system to be detected by using an interferometer and a plane mirror and adopting an auto-collimation interference detection method;
(3) arranging a focal plane detection CCD on an electric guide rail; then placing a focal plane detection CCD and an electric guide rail at the focal plane of the optical system to be detected;
(4) adjusting the angle of the multi-tooth dividing table to drive the plane mirror to rotate, receiving the image point returned from the focal plane by the CCD, adjusting the front and back positions of the CCD to minimize the image point, placing the CCD detection target surface on the focal plane of the optical system to be detected, and recording the centroid pixel coordinate a of the image point;
(5) continuously adjusting the angle of the multi-tooth dividing table to enable the multi-tooth dividing table to rotate by an angle theta, and returning to the parallel light beam to change the angle by 2 theta;
(6) the CCD is driven by the electric guide rail to translate, a new image point position is received, and the moving amount d1 of the electric guide rail and the pixel coordinate b of the centroid of the image point at the moment are recorded;
(7) the moving distance d = d1+ h (b-a) of the image point can be calculated according to the moving distance d1 of the electric guide rail, the coordinate change (b-a) of the center of mass of the image point detected by the CCD and the size h of the CCD pixel; the system focal length f is f = d/tan (2 θ);
(8) and (5) repeating the steps (5) to (7), and measuring the focal length of the system for multiple times and averaging to obtain the focal length of the system.
The method for measuring the focal length of the long-focus optical system is characterized in that the self-collimating interference detection method in the step (2) is a detection method based on an interferometer and a plane reflector, spherical waves are emitted by the interferometer, converged on a focal plane of a system to be detected, reflected for multiple times by the system to be detected to become parallel light and emitted, reflected by a plane mirror to return along an original path, reflected for multiple times by the system to be detected to become spherical wavefront, and received by the interferometer to perform system wave aberration detection.
In the method for measuring the focal length of the long-focal-length optical system, the measuring times in the step (8) are 3-10 times.
The technical means disclosed by the scheme of the invention are not limited to the technical means disclosed by the technical means, and also comprise the technical scheme formed by equivalent replacement of the technical features. The present invention is not limited to the details given herein, but is within the ordinary knowledge of those skilled in the art.
Claims (6)
1. The utility model provides a long focus optical system focus measuring device based on autocollimation level crossing, characterized by: the device comprises a plane mirror arranged at the outlet of an optical system to be detected, a focal plane detection CCD arranged on the focal plane of the optical system to be detected, and an interferometer; the focus of the interferometer is positioned on the focal plane of the optical system to be detected, the focal plane detection CCD is arranged on a vertically arranged electric guide rail, and the plane mirror is arranged on the subdivision multi-tooth dividing table.
2. The device for measuring the focal length of a long-focus optical system based on a self-collimating mirror as claimed in claim 1, wherein: the optical system to be measured comprises a primary mirror and a secondary mirror, and light beams are reflected by the primary mirror and the secondary mirror and then form an image at a focal plane.
3. The device for measuring the focal length of the long-focus optical system based on the autocollimator mirror as claimed in claim 2, wherein: the primary mirror adopts a concave reflector, and the secondary mirror adopts a concave reflector or a convex reflector.
4. A method for measuring the focal length of a long-focus optical system by using the focal length measuring device of the long-focus optical system based on the autocollimation plane mirror is characterized by comprising the following steps: the method comprises the following steps:
(1) placing the interferometer so that the focal point of the interferometer is located at the focal plane of the optical system to be measured; placing a plane mirror on a subdivided multi-tooth dividing table and placing the plane mirror at a light outlet of an optical system to be tested;
(2) detecting the wave aberration of the optical system to be detected by using an interferometer and a plane mirror and adopting an auto-collimation interference detection method;
(3) arranging a focal plane detection CCD on an electric guide rail; then placing a focal plane detection CCD and an electric guide rail at the focal plane of the optical system to be detected;
(4) adjusting the angle of the multi-tooth dividing table to drive the plane mirror to rotate, receiving the image point returned from the focal plane by the CCD, adjusting the front and back positions of the CCD to minimize the image point, placing the CCD detection target surface on the focal plane of the optical system to be detected, and recording the centroid pixel coordinate a of the image point;
(5) continuously adjusting the angle of the multi-tooth dividing table to enable the multi-tooth dividing table to rotate by an angle theta, and returning to the parallel light beam to change the angle by 2 theta;
(6) the CCD is driven by the electric guide rail to translate, a new image point position is received, and the moving amount d1 of the electric guide rail and the pixel coordinate b of the centroid of the image point at the moment are recorded;
(7) the moving distance d = d1+ h (b-a) of the image point can be calculated according to the moving distance d1 of the electric guide rail, the coordinate change (b-a) of the center of mass of the image point detected by the CCD and the size h of the CCD pixel; the system focal length f is f = d/tan (2 θ);
(8) and (5) repeating the steps (5) to (7), and measuring the focal length of the system for multiple times and averaging to obtain the focal length of the system.
5. The method of claim 4, wherein the step of measuring the focal length of the long-focus optical system comprises: the auto-collimation interference detection method in the step (2) is a detection method based on an interferometer and a plane mirror, and specifically comprises the following steps: spherical waves are emitted by the interferometer, converged on the focal plane of the optical system to be detected, reflected for multiple times by the optical system to be detected to become parallel light and emitted, reflected by the plane mirror to return along the original path, reflected for multiple times by the optical system to be detected to become spherical wave front, and received by the interferometer to perform system wave aberration detection.
6. The method of claim 4, wherein the step of measuring the focal length of the long-focus optical system comprises: the number of times of measurement in the step (8) is 3-10 times.
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| CN115166970A (en) * | 2022-07-27 | 2022-10-11 | 茂莱（南京）仪器有限公司 | Method for precisely adjusting wavefront of high-reflection system by using interferometer |
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