A coaxial line scanning light source main optical axis calibration method

Abstract

The application discloses a coaxial line scanning light source main optical axis calibration method, and the line scanning optical detection structure comprises a line array camera, an optical lens, a coaxial line scanning light source and an electric linear displacement table; the line array camera, the optical lens and the stepped sample are adjusted to be coaxial, and the stepped sample is located on the front focal plane of the optical lens; the coaxial line scanning light source is fixed on the electric linear displacement table, and the position of the coaxial line scanning light source is changed by moving the electric linear displacement table to perform imaging; the artifact width of the obtained picture in imaging is quantified, and the sine value of the light source divergence angle is further obtained; the place where the sine value is the smallest is found, that is, the place where the light source divergence angle is the smallest, and the place is the main axis of the coaxial line scanning light source. The application can be used for improving the detection precision of the line scanning optical detection system, effectively improving the image quality, improving the image resolution and avoiding the generation of artifacts.

Description

TECHNICAL FIELD

[0001] The application relates to a coaxial line scanning light source main optical axis calibration method. BACKGROUND

[0002] With the development of manufacturing industry, the control of product yield becomes extremely important. In the industrial detection process, surface detection technology constitutes an important link. Surface detection technology mainly extracts and detects three-dimensional surface information of various parts, and then finds defects. In the field of industrial detection, line scanning optical detection has gradually become a new optical detection technology widely used in the field of non-contact optical measurement of machine vision, and has good detection efficiency.

[0003] The line scanning optical detection system mainly comprises a light source, a line scanning lens and a line array camera. The light source can have multiple choices, such as a coaxial line scanning light source, a line light source and a ring light. The coaxial line scanning light source, as a highly integrated light source, can save a lot of space for the whole system, realize large-size high-precision detection requirements, and make the light source become an important part of the line scanning optical detection system.

[0004] With the improvement of detection requirements such as detection range, detection accuracy and detection rate in industrial detection, the assembly requirements of the line scanning optical detection system for hardware become extremely important. Small assembly deviations may cause the light emitted by the light source to be unable to be received by the line array camera, thereby causing imaging failure. During use, the coaxial line scanning light source must be kept coaxial with the lens, the camera and the sample, that is, the main optical axis of the light source is kept coaxial with the camera and the sample, otherwise the divergence angle of the light source will have a great influence on the detection of the sample. Under the prior art, it is difficult to ensure the coaxiality of the system through the naked eye to calibrate the coaxiality of the light source, the sample and the camera, which leads to the decline of imaging clarity and the decline of detection effect. SUMMARY

[0005] The application needs to solve the problem that the main optical axis of the existing line scanning coaxial light source deviates from the axis center due to assembly deviation or design deviation during assembly. A line scanning optical detection structure and a coaxial line scanning light source main optical axis calibration method are provided. The method can be used to improve the detection accuracy of the line scanning optical detection system, effectively improve the image quality, improve the image resolution and avoid the generation of artifacts.

[0006] The application can be implemented by the following technical solutions:

[0007] A line scanning optical detection structure, comprising a line array camera, an optical lens, a coaxial line scanning light source and an electric linear displacement table, the line array camera, the optical lens and the step-shaped sample are adjusted to be coaxial and the step-shaped sample is on the front focal plane of the optical lens; the coaxial line scanning light source is fixed on the electric linear displacement table and the position of the coaxial line scanning light source is changed by moving the electric linear displacement table for imaging; the width of the artifact of the obtained image is quantified, and the sine value of the divergence angle of the light source is further obtained; the place where the sine value is the smallest is found, that is, the place where the divergence angle of the light source is the smallest, and the main axis of the coaxial line scanning light source is at this place.

[0008] The application provides a main optical axis calibration method of a coaxial line scanning light source.

[0009] (1) a high-reflectivity sample in a step-shaped distribution is used, the center of the sample is the highest step, the height decreases along the two sides, the width of a single step is 0.4 mm, and the height difference between the steps is 2 mm;

[0010] (2) the line array camera, the optical lens and the step-shaped sample are adjusted to be coaxial, so that the center of the chip of the line array camera is right opposite to the center of the highest step in the middle of the step-shaped sample;

[0011] (3) the height of the line array camera and the optical lens is adjusted, so that the distance from the lens to the center of the step-shaped sample is equal to the focal length of the lens;

[0012] (4) ring light is used for illumination, and it is verified whether the sample is at the focal point position of the lens; if the imaging is clear, the next step is performed;

[0013] (5) the coaxial line scanning light source is fixed on the electric linear displacement table with a single-step advancing value of 3 um, and the coaxial line scanning light source is adjusted to an appropriate height and a position close to the axis where the camera, the lens and the sample are located;

[0014] (6) the coaxial line scanning light source is turned on to illuminate and scan the step-shaped sample to form an image;

[0015] (7) the imaging effect is observed, and the width of the generated artifact is recorded, and the divergence angle of the light source is further calculated;

[0016] (8) the electric linear displacement table is moved according to the bisection method, the position of the coaxial line scanning light source is adjusted, steps (6) and (7) are repeated, and then the position where the divergence angle is the smallest, that is, the position where the artifact is the smallest or no artifact is generated, is determined, and the main optical axis of the coaxial line scanning light source is at this position;

[0017] (9) the position of the coaxial line scanning light source at this time is calibrated, and the relative position between the coaxial line scanning light source and the lens is calibrated.

[0018] Compared with the prior art, the application has the following beneficial effects:

[0019] The present invention provides a method for calibrating the main optical axis of a coaxial line scanning light source. After fixing the positions of a linear array camera, a lens and a stepped sample, when it is necessary to calibrate the main optical axis position of the coaxial line scanning light source, the position of the coaxial line scanning light source is further adjusted by setting the position of an electric linear translation stage. Images formed at different positions are used as calibration standards. According to the artifacts of the image, the position with the smallest divergence angle of the light source is further calculated and found, which is the position of the main optical axis of the coaxial line scanning light source. The present invention effectively improves the calibration accuracy of the coaxial line scanning light source, avoids mechanical design errors caused by the inconsistency between the actual main optical axis position and the theoretical main optical axis position during mechanical design, optimizes the detection accuracy of the line scanning optical detection system, and improves the imaging quality and detection effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Schematic diagram of the line scanning optical detection structure of the present invention DETAILED DESCRIPTION

[0021] The following describes the embodiments of the present invention through specific embodiments. Those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification.

[0022] like Figure 1 As shown, a line scanning optical detection structure of the present invention includes a linear array camera 1, an optical lens 2, a coaxial line scanning light source 3, an electric linear displacement stage 4, a stepped sample 5, and a host computer 6; these devices are arranged in sequence as host computer 6, linear array camera 1, optical lens 2, coaxial line scanning light source 3, electric linear displacement stage 4, and stepped sample 5; among them, the black arrow under the electric displacement stage 4 is a schematic diagram of the light path from the coaxial line scanning light source 3 to the stepped sample 5, the black arrow on the left side of the coaxial line scanning light source 3 is the scanning direction of the entire system, and the black arrow above the coaxial line scanning light source 3 is a schematic diagram of the light path reflected back by the stepped sample 5.

[0023] The device is further described below with reference to examples.

[0024] The light emitted by the coaxial line scanning light source 3 is irradiated on the stepped sample 5. The light reflected by the stepped sample 5 enters the optical lens 2 and is finally imaged in the line array camera 1 through scanning. The obtained image is processed by the host computer 6, and the divergence angle of the light source is further calculated. The position of the coaxial line scanning light source 3 is changed by moving the electric linear translation stage 4, and imaging is performed at different positions. The position where the divergence angle of the light source is the smallest is found using the dichotomy method. This position is the position where the main optical axis of the coaxial line scanning light source is located.

[0025] A method for calibrating the main optical axis of a coaxial line scanning light source of the present invention comprises the following steps:

[0026] (1) using high reflectivity sample in a ladder distribution, the highest ladder in the center, the height of each ladder is 0.4mm, and the height difference between ladders is 2mm;

[0027] (2) adjusting the line array camera, optical lens and ladder sample to be coaxial, so that the center of the line array camera chip is right opposite to the center of the highest ladder in the ladder sample;

[0028] (3) adjusting the height of the line array camera and optical lens, so that the distance from the lens to the center of the ladder sample is equal to the focal length of the lens;

[0029] (4) using ring light illumination to verify whether the sample is at the focal point of the lens, and if the imaging is clear, the next step is carried out;

[0030] (5) fixing the coaxial line scanning light source on the motorized linear displacement stage with a single step value of 3um, and adjusting the coaxial line scanning light source to an appropriate height and close to the position of the axis of the camera, lens and sample;

[0031] (6) turning on the coaxial line scanning light source to illuminate and scan the ladder sample;

[0032] (7) observing the imaging effect and recording the width of the generated artifacts, and further calculating the divergence angle of the light source;

[0033] (8) moving the motorized linear displacement stage according to the bisection method, adjusting the position of the coaxial line scanning light source, repeating steps (6) and (7), and further determining the position with the smallest divergence angle, i.e. the position with the smallest or no artifacts, which is the main optical axis of the coaxial line scanning light source;

[0034] (9) calibrating the position of the coaxial line scanning light source at this time, and calibrating the relative position between the coaxial line scanning light source and the lens.

[0035] Based on this method, the main optical axis position of the coaxial line scanning light source can be effectively found, which further provides help for subsequent mechanical design or experimental test, avoids the mechanical design deviation caused by the deviation between the theoretical design main optical axis and the actual main optical axis of the coaxial line scanning light source, avoids the problem of generating large artifacts in the imaging process, and improves the imaging effect and detection efficiency.

[0036] The above only describes the preferred embodiments of the present application and is not intended to limit the present application, and any modifications, equivalent replacements and improvements made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method of aligning a main optical axis of a coaxial line light source, characterized by, The method comprises the following steps: (1) using a high reflectivity sample with a ladder-shaped distribution, the highest step is in the center, the height decreases along the two sides, the width of a single step is 0.4 mm, and the height difference between steps is 2 mm; (2) adjusting the line array camera, optical lens and ladder-shaped sample to be coaxial, so that the center of the line array camera chip is right opposite to the center of the highest step in the middle of the ladder-shaped sample; (3) adjusting the height of the line array camera and optical lens, so that the distance from the lens to the center of the ladder-shaped sample is equal to the focal length of the lens; (4) using ring light illumination, verifying whether the sample is at the focal point position of the lens, if the imaging is clear, the next step is performed; (5) fixing the coaxial line scanning light source on the motorized linear displacement stage with a single step advancing value of 3 um, and adjusting the coaxial line scanning light source to an appropriate height and close to the position of the axis where the camera, lens and sample are located; (6) turning on the coaxial line scanning light source to illuminate and scan the imaging of the ladder-shaped sample; (7) observing the imaging effect, recording the width of the generated artifacts, and further calculating the divergence angle of the light source; (8) moving the motorized linear displacement stage according to the bisection method, adjusting the position of the coaxial line scanning light source, repeating steps (6) and (7), and further determining the position with the minimum divergence angle, i.e. the position with the minimum artifacts or without artifacts, which is the main optical axis of the coaxial line scanning light source; (9) calibrating the position of the coaxial line scanning light source at this time, and calibrating the relative position between the coaxial line scanning light source and the lens.

Images