Off-axis tracking focusing device based on structured light

Abstract

The utility model provides a kind of off-axis tracking focusing device based on structured light, device includes: area array camera, first telecentric lens, first reflector is arranged vertically from top to bottom order, forms one side light path;LED light source, condenser, structure template, second telecentric lens, second reflector is arranged vertically from top to bottom order, forms other side light path;The position symmetry arrangement of one side light path and other side light path relative to detection head, the detection head includes imaging lens.The utility model solves the requirement of higher detection accuracy, is not affected by process, and uneven position will not appear focusing deviation.

Description

Technical Field

[0001] This invention belongs to the field of optical detection technology, specifically relating to an off-axis tracking and focusing device based on structured light. Background Technology

[0002] As the resolution of LCD, OLED, and Micro LED screens gradually increases, the requirements for the accuracy of their testing equipment also rise. However, with this increased accuracy, the depth of field of the testing head decreases. When the testing platform cannot ensure that the flatness of the product remains within the depth of field of the testing head throughout the testing process, the testing head needs to have tracking and focusing capabilities. To improve testing efficiency, testing heads typically use line scan lenses, requiring off-axis tracking and focusing devices.

[0003] like Figure 1 As shown, existing off-axis tracking focusing devices use laser triangulation to detect the height change of the product relative to the detection head, which is then fed back to the controller to control the detection head to make corresponding movements. However, the drawback of this existing technology is that its accuracy cannot meet the requirements of higher detection accuracy, it is easily affected by process interference, and uneven positions will cause focusing shift. Utility Model Content

[0004] The objective of this utility model is achieved through the following technical solution.

[0005] Specifically, this utility model provides an off-axis tracking focusing device based on structured light, comprising: The area array camera, the first telecentric lens, and the first reflector are arranged vertically from top to bottom to form one side of the optical path; the LED light source, the condenser lens, the structural template, the second telecentric lens, and the second reflector are arranged vertically from top to bottom to form the other side of the optical path. The optical paths on one side and the optical paths on the other side are arranged symmetrically with respect to the position of the detection head, and the detection head includes an imaging lens.

[0006] Furthermore, the detection head also includes a TDI camera.

[0007] Furthermore, the light emitted by the LED light source passes sequentially through a condenser lens, a structural template, a second telecentric lens, and a second reflector before shining onto the glass surface to be tested. After being reflected by the glass surface, the light then passes sequentially through a first reflector and a first telecentric lens before being projected onto a surface array camera. The surface array camera then images the structural template.

[0008] Furthermore, the magnification of the two telecentric lenses is 2x.

[0009] Furthermore, the structural template is made by engraving a certain regular pair of opaque lines on the glass.

[0010] Furthermore, the aforementioned pattern is a coding cycle.

[0011] Furthermore, the device further includes an FPGA-based high frame rate real-time autofocus system connected to the area scan camera, the system comprising: FPGA chip and MCU chip; the FPGA chip analyzes and calculates the image, calculates the offset and sends it to the MCU chip, the MCU controls the Z-axis motor to adjust the height of the detection head and the off-axis tracking focusing device; The FPGA chip, MCU chip, and CMOS chip of the area scan camera are located on the same PCB board.

[0012] The advantages of this invention are: it solves the requirement for higher detection accuracy, is not affected by the manufacturing process, and will not cause focusing shift in uneven positions. Attached Figure Description

[0013] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings: Figure 1 A schematic diagram of an existing off-axis tracking focusing device is shown.

[0014] Figure 2 A schematic diagram of an off-axis tracking focusing device based on structured light according to an embodiment of the present invention is shown.

[0015] Figure 3 A schematic diagram of the control principle of an off-axis tracking focusing device based on structured light according to an embodiment of the present invention is shown. Detailed Implementation

[0016] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0017] The key point of this utility model is to use structured light imaging to solve the effects of process and unevenness, and to use the structured light imaging offset when the object distance changes to measure the offset of the structured light, so as to improve the accuracy. The point to be protected is the off-axis tracking focusing device based on structured light.

[0018] like Figure 2As shown, the off-axis tracking and focusing device based on structured light of this utility model includes: an area array camera, a first telecentric lens, a first reflecting mirror (located on the left), an LED light source, a condenser lens, a structural template, a second telecentric lens, a second reflecting mirror (located on the right), and a detection head (including...). Figure 2 The detection head consists of an imaging lens and a TDI camera. The area array camera, first telecentric lens, and first reflector are arranged vertically from top to bottom, forming the left optical path; the LED light source, condenser lens, structural template, second telecentric lens, and second reflector are arranged vertically from top to bottom, forming the right optical path. The central detection head includes an imaging lens and a TDI camera. The left and right optical paths are symmetrically arranged relative to the detection head, ensuring that the light emitted from the LED light source passes sequentially through the condenser lens, structural template, second telecentric lens, and second reflector before illuminating the surface of the glass under test. After reflection from the glass surface, the light enters the left optical path, then passes sequentially through the first reflector and first telecentric lens before reaching the area array camera. The area array camera then obtains an image of the structural template.

[0019] The light source in this invention can be more than just LED; other types of light sources can also be considered. The magnification of the two telecentric lenses is approximately 2x. If the magnification is too high, the working distance will be insufficient; if the magnification is too low, the resolution will be insufficient.

[0020] The structural template in this utility model is generally made by engraving a certain regularity of opaque line pairs on the glass. For example, in a specific implementation case, three types of line pairs, 20um, 40um, and 80um, are etched onto the glass in a coded manner, such as 111 (20um line pair x1, 40um line pair x1, 80um line pair x1), 211, 311, 411, 121, 221, etc.

[0021] like Figure 2 As shown, this invention employs an off-axis structured light imaging design. The structured light source assembly (light source + structure) on the right illuminates the object surface through an illumination lens and a reflector, while the structured light image on the object surface is imaged onto an area array camera through a reflector and an imaging lens on the left. When the relative height between the object surface and the structure (the device of this invention, the entire structured light off-axis tracking and focusing device) changes, the structured light image will shift.

[0022] like Figure 3 As shown, this utility model employs machine vision and control design. After the area scan camera captures the image, it is connected to a high frame rate real-time automatic focusing system based on FPGA. The FPGA chip analyzes and calculates the image, informing the MCU chip of the offset. The MCU then controls the Z-axis motor to adjust the height of the detection head and the off-axis structured light imaging device. The FPGA, MCU, and CMOS chip are all on the same PCB board. Furthermore, the FPGA can directly control the Z-axis motor, eliminating the need for the MCU. The CMOS chip is... Figure 2The image sensor of the internal camera is located there. The Z-axis motor is situated within... Figure 2 On the back, drive Figure 2 The entire device moves up and down. A single Z-axis motor can simultaneously adjust the height of the imaging lens inside the detection head and the height of the structured light imaging device, specifically referring to the entire off-axis structured light focusing device.

[0023] The following details the implementation scheme of the high frame rate real-time autofocus system based on FPGA of this invention.

[0024] (1) Core Principles This system is based on active vision triangulation and absolute coded grating technology. It projects a grating pattern with a unique spacing code onto the surface of the object being measured. It utilizes the linear translation effect of the image on the imaging surface when the image is out of focus. The FPGA acquires the image in real time and uses sub-pixel edge positioning technology to decode the absolute position information of the grating. By comparing the current absolute position with the reference position calibrated when the image is in sharp focus, the system directly calculates the defocus amount and direction without cumulative error and converts it into a high-precision pulse signal to drive the servo motor (i.e., the Z-axis motor) to complete the lens position correction. This creates a high-speed, high-precision optical closed-loop focusing control system.

[0025] (2) System workflow 1. Projection: The coded grating is projected onto the surface of the object to be measured.

[0026] 2. Acquisition: A black and white high-speed camera acquires grating images of the deformed light.

[0027] 3. Processing: The FPGA performs real-time image processing (vertical integration, edge detection) and decodes the phase information of the current grating.

[0028] 4. Calculation: Compare the decoding result with the reference code of the sharp focus position (Make0) to calculate the defocus distance and direction.

[0029] 5. Control: The defocus amount is converted into control commands for the Panasonic servo motor, which drives the lens to move, forming a closed-loop control.

[0030] (3) System architecture and component selection Main control FPGA Xilinx Artix-7 series (XC7A100T) It boasts abundant logic resources, supports high-speed I / O, and has a large amount of built-in Block RAM for image caching. Crucially, it supports the Vivado simulation toolchain for easy verification. Image sensor Global shutter monochrome CMOS camera Resolution: Supports 1280x1024, with resolution cropped to 1280x16 via ROI (Region of Interest) to achieve a frame rate of ≥1K fps. Interface: MIPI. Executive agency MINAS A6 Series Servo Motors and Drivers High responsiveness and high precision. Supports pulse / direction control modes for easy direct FPGA control. Optical components LED + coded grating sheet, industrial lens This forms a triangulation ranging optical path. Debugging interface Gigabit Ethernet on FPGA development board Used to send image data streams to a PC for visual verification. (4) Key parameters Camera horizontal resolution 1280 pixels Image resolution changed from 1280*1024@240fps to 1280*16@2500fps Pixel size 4 μm Single pixel corresponding to object size 4 μm The basic scale for decoding: A 1-pixel movement in the image corresponds to a 4μm physical movement of the raster. Optical system YZ ratio 4 : 1 Object defocus ΔZ = 1μm → raster image offset ΔY = 4μm. This is the cornerstone of accuracy and range calculation. Camera depth of field (Z-axis) ±200μm The Z-axis range that the system needs to focus on. The grating needs to cover the Y-axis offset. ±800μm ΔY = ΔZ * 4 = ±200μm * 4 = ±800μm. Camera field of view (FOV) 5120μm 1280 pixels * 4 μm / pixel = 5120 μm. Minimum total width of grating 6720μm FOV + The above description is merely a preferred embodiment of this utility model, but the protection scope of this utility model is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this utility model should be included within the protection scope of this utility model. Therefore, the protection scope of this utility model should be determined by the scope of the claims.

Claims

1. An off-axis tracking focusing device based on structured light, characterized in that, include: The area array camera, the first telecentric lens, and the first reflecting mirror are arranged vertically from top to bottom to form an optical path on one side. The LED light source, condenser lens, structural template, second telecentric lens, and second reflector are arranged vertically from top to bottom to form the light path on the other side. The optical paths on one side and the optical paths on the other side are arranged symmetrically with respect to the position of the detection head, and the detection head includes an imaging lens.

2. The off-axis tracking focusing device based on structured light according to claim 1, characterized in that, The detection head further includes a TDI camera.

3. An off-axis tracking focusing device based on structured light according to claim 1 or 2, characterized in that, The light emitted by the LED light source passes sequentially through a condenser lens, a structural template, a second telecentric lens, and a second reflector before shining onto the glass surface to be tested. After being reflected by the glass surface, the light then passes sequentially through a first reflector and a first telecentric lens before being projected onto a surface array camera. The surface array camera then images the structural template.

4. An off-axis tracking focusing device based on structured light according to claim 1 or 2, characterized in that, The magnification of the two telecentric lenses is 2x.

5. An off-axis tracking focusing device based on structured light according to claim 1 or 2, characterized in that, The structural template is made by engraving a certain regularity of opaque lines on the glass.

6. The off-axis tracking focusing device based on structured light according to claim 5, characterized in that, The pattern described is a coding cycle.

7. An off-axis tracking focusing device based on structured light according to claim 1 or 2, characterized in that, The device further includes an FPGA-based high frame rate real-time autofocus system connected to the area scan camera, the system comprising: FPGA chip, MCU chip; the FPGA chip, MCU chip and CMOS chip of area scan camera are located on the same PCB board.

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