Method and device for optical inspection of continuous strip-shaped stamped parts

Abstract

This invention discloses an optical inspection method for continuous strip-shaped stamped parts, including a trigger start-up step, in which a trigger sensor array preset at the entrance of the inspection area detects the marking hole positions of the part under test; a speed synchronization step, in which workpiece movement speed data is collected in real time and the image acquisition line frequency is dynamically adjusted; a segment end and cycle standby step, in which the inspection process is determined to end according to a preset threshold for the segment length of a single workpiece and a new round of inspection cycle is automatically started; an image acquisition and stitching step, in which optical images are acquired line by line under synchronous line frequency control through an optical image acquisition facility and stitched in real time to generate a complete two-dimensional inspection image; and a defect identification and closed-loop control step, in which visual algorithms are used to analyze and identify defect information in the stitched image in real time and feed it back to the production line control system. This invention solves the technical problem of real-time quality inspection of continuous strip-shaped stamped parts. This invention also discloses an optical inspection device for continuous strip-shaped stamped parts.

Description

Technical Field

[0001] This invention relates to the field of optical inspection, and in particular to an optical inspection method and apparatus for continuous strip-shaped stamped parts. Background Technology

[0002] Online quality inspection of continuously stamped strip parts has become a crucial aspect of quality control in modern production lines. Traditional manual inspection methods are inefficient and struggle to guarantee consistent accuracy; therefore, automated inspection technologies based on machine vision have been widely adopted.

[0003] However, existing visual inspection technologies still have many technical shortcomings when applied to the inspection of continuous strip stamped parts. For example, CN212340191U describes a line-scanning visual inspection system for large-format, high-precision surface inspection; and CN110681601A describes an online inspection and punching system for LED bracket strips. These inspection systems mostly use front-light illumination, which easily produces strong reflections on the surface of metal strips when inspecting them, severely affecting image quality and inspection accuracy. Furthermore, changes in ambient light in the production environment can seriously interfere with the measurement results of the inspection system, leading to a decrease in the stability and reliability of the inspection results.

[0004] Meanwhile, for ultra-long workpieces with individual dimensions reaching several meters, existing line scan camera inspection technology faces significant technical bottlenecks when conducting high-precision measurement operations. For example, CN117849046A, a device and method for detecting surface defects in stamped parts, struggles to achieve accurate inspection of complete workpieces. Therefore, for products that are continuously stamped but require segmented inspection, existing technologies lack effective trigger control and cyclic inspection strategies, making it impossible to accurately identify the boundaries of each workpiece and achieve precise segmented inspection. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide an optical inspection method for continuous strip stamping parts, which meets the requirements of high-precision and high-efficiency online inspection of continuous strip stamping parts.

[0006] To address the aforementioned technical problems, this invention provides an optical inspection method for continuous strip stamped parts, comprising a trigger start-up step, a speed synchronization step, a segmentation end and cycle standby step, an image acquisition and stitching step, and a defect identification and closed-loop control step.

[0007] In the triggering start-up step, the continuous strip stamping part to be tested moves at a uniform or non-uniform speed with the production line. When the trigger sensor array preset at the entrance of the detection area detects the preset mark hole position of the workpiece, it immediately sends a trigger signal to the control system to trigger the start of the detection process.

[0008] Preferably, in the speed synchronization step, the friction wheel encoder maintains stable contact with the surface of the continuous strip stamping part, collects the motion speed data of the workpiece in real time, and feeds the data back to the camera control system; the control system dynamically adjusts the acquisition line frequency of the line scan camera based on the speed data, so that the acquisition time of each line of the camera image is strictly matched with the displacement of the workpiece, so as to eliminate image stretching or blurring caused by high-speed motion.

[0009] Preferably, in the segment end and cycle standby steps, the control system accumulates the length rolled by the friction wheel encoder in real time. Based on the preset threshold for the segment length of a single workpiece, it determines that the detection process of a single segment has ended and the device enters standby mode. When the trigger sensor detects the next marker hole, a new round of detection cycle is automatically started. This design can adapt to the segment detection requirements of long workpieces, and the detection length of a single segment can support specifications at the level of several meters, ensuring the accuracy and process continuity of long segment detection.

[0010] Preferably, in the image acquisition and stitching step, the line scan camera, under the control of the synchronous line frequency, and in conjunction with the uniform transmission illumination provided by the strip light source, acquires the transmission optical images of the continuous strip stamping parts line by line, and generates a complete two-dimensional detection image through real-time stitching.

[0011] Preferably, in the defect identification and closed-loop control step, the visual algorithm performs real-time analysis on the stitched two-dimensional detection image, automatically identifies processing defects such as missed punches, multiple punches, cracks, deformations, and burrs, and outputs the location, type, and size information of the defects in real time; the detection results are synchronized to the production line control system to realize closed-loop quality control of the production process.

[0012] Preferably, the continuous strip stamped part has at least two different marking hole positions; different marking hole positions correspond to different preset thresholds for the segment length of a single workpiece.

[0013] This invention also provides an apparatus for an optical inspection method of continuous strip stamped parts, comprising: a production line body for carrying and driving the continuous strip stamped parts through an inspection area; a strip light source for illuminating the continuous strip stamped parts; a line scan camera for acquiring surface images of the continuous strip stamped parts line by line under the control of a trigger signal; a trigger sensor disposed at the front end of the inspection area for detecting the position of the marking holes on the continuous strip stamped parts to trigger the start of the image acquisition process; a friction wheel encoder in contact with the surface of the continuous strip stamped parts for acquiring the workpiece's motion speed and displacement data in real time; and a control module for receiving the trigger signal and encoder data, controlling the camera's line frequency synchronization, and completing image stitching and defect recognition algorithm calculations.

[0014] Preferably, the strip light source is positioned below the detection area; the line scan camera is positioned above the detection area.

[0015] Compared with the prior art, the beneficial technical effects of the present invention are as follows: 1. Transmissive high-contrast illumination: The strip light source is set below the detection area. During the detection process, the light source can pass directly through the perforated area of ​​the workpiece, presenting a bright state; while the unperforated metal substrate area blocks the light, presenting a dark state, thus forming an extremely high contrast between light and dark, effectively suppressing the interference of surface reflection of the metal plate and ambient stray light on the detection.

[0016] 2. High-speed line frequency and high-precision acquisition: The line scan camera is set above the detection area, and its lens is vertically aligned with the strip light source. It can directly view the transmitted light source through the punched hole of the workpiece. Therefore, only a very short exposure time is needed to complete the acquisition of a single frame of line image. This allows the camera line frequency to be set to a very high level, which significantly improves the detection resolution and measurement accuracy in the length direction of the workpiece.

[0017] 3. Motion speed synchronization control: This device is equipped with a friction wheel encoder, whose friction wheel maintains stable contact with the surface of the continuous strip stamping part to collect the motion speed and displacement data of the workpiece in real time; the data is fed back to the camera control system to dynamically adjust the acquisition line frequency of the line scan camera, thereby achieving precise synchronization between the image acquisition time and the workpiece motion displacement, effectively avoiding image stretching or blurring distortion under high-speed motion.

[0018] Furthermore, this invention uses multiple trigger sensor arrays to detect the workpiece marking hole position as the detection start signal and uses the workpiece running length data collected by the encoder as the basis for determining the end of segmented detection. It can realize continuous detection of continuous strip-shaped undivided workpieces. There is no hard limit on the length of a single part during the detection process, and it can adapt to the detection needs of ultra-long workpieces several meters long. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the apparatus for the optical inspection method of the continuous strip stamped parts of the present invention. Detailed Implementation

[0020] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can fully understand other advantages and technical effects of the present invention from the content disclosed in this specification. Example 1

[0021] An optical inspection method for continuous strip-shaped stamped parts includes the following steps: Triggering Start-up Procedure: A trigger sensor array is preset at the entrance of the detection area. When the trigger sensor array detects the preset marker hole position on the continuous strip stamping part to be tested, it sends a trigger signal in real time, triggering the start of the detection process. The trigger sensor array can accurately identify the marker hole position on the continuous strip stamping part, ensuring that the detection process starts at the correct time and avoiding false detections and missed detections.

[0022] Speed ​​synchronization step: Real-time acquisition of workpiece motion speed data. Through real-time statistical analysis of this speed data, the image acquisition line frequency is dynamically adjusted to ensure precise matching between the acquisition time of each image line and the workpiece displacement. This step uses a speed sensor or encoder to obtain the workpiece's real-time motion speed, calculates the workpiece's instantaneous displacement, and adjusts the image acquisition line frequency parameters accordingly to ensure that image acquisition remains synchronized with workpiece movement, eliminating image distortion or overlap caused by speed changes.

[0023] Segment End and Cyclic Standby Steps: The system continuously accumulates the movement length of the strip-shaped stamping parts. Based on a preset threshold for the segment length of a single workpiece, it determines the end of the inspection process for a single segment. When the accumulated length reaches the preset threshold, the system automatically ends the inspection process for the current segment and enters a cyclic standby state. A new inspection cycle automatically begins when the next marker hole is detected. This step ensures segmented inspection of continuous strip-shaped parts, avoids interference between different workpieces, and improves the accuracy and efficiency of the inspection.

[0024] Image acquisition and stitching steps: Under the control of synchronous line frequency and illumination provided by a preset light source, optical images of the continuous strip-shaped stamped parts are acquired line by line using an optical image acquisition device. The optical image acquisition device uses a line scan camera or area scan camera, scanning the workpiece surface line by line at a predetermined acquisition frequency under synchronous line frequency control. The preset light source provides uniform and stable illumination to ensure image quality. The acquired image data is transmitted to the image processing unit in real time, where an image stitching algorithm stitches the line-by-line acquired image data in real time to generate a complete two-dimensional inspection image. The workpiece's movement speed and acquisition sequence are considered during the stitching process to ensure the continuity and integrity of the stitched image.

[0025] Defect Identification and Closed-Loop Control Steps: The system uses visual algorithms to analyze the stitched 2D inspection images in real time, identifying various defects on the workpiece surface. The visual algorithms include sub-steps such as image preprocessing, feature extraction, defect classification, and discrimination. Based on preset defect discrimination criteria, the system automatically identifies defect types such as scratches, dents, stains, and dimensional deviations, generating detailed defect information reports. The identified defect information is synchronously transmitted to the production line control system, which automatically adjusts production parameters or implements corresponding quality control measures based on the defect information, achieving closed-loop quality control of the production process. This step ensures timely detection and handling of defects, improving product quality and production efficiency.

[0026] This optical inspection method achieves high-precision and high-efficiency inspection of continuous strip stamped parts by organically combining steps such as trigger start-up, speed synchronization, segmented looping, image stitching, and defect recognition, effectively improving the automation level of the production line and the product quality control capability.

[0027] Preferably, the continuous strip-shaped stamped part has at least two different marked hole positions; the different marked hole positions correspond to different preset threshold values ​​for the segment length of a single workpiece. This arrangement is suitable for continuous strip-shaped stamped parts with at least two different stamped parts. Example 2

[0028] like Figure 1 As shown, the present invention also discloses an apparatus for an optical inspection method for continuous strip stamped parts. The apparatus adopts the optical inspection method described in Embodiment 1 and can realize high-precision automated inspection of continuous strip stamped parts.

[0029] The device mainly includes core components such as the production line body, bar light source, trigger sensor, friction wheel encoder, and control module.

[0030] The production line serves as the foundational platform for the entire testing system, carrying and propelling the continuous strip of stamped parts through the testing area. Employing a conveyor belt or guide rail structure, the production line continuously transports the stamped parts to be tested at a stable speed, ensuring smooth movement within the testing area. Positioning and guiding mechanisms are designed on the line surface to prevent parts from shifting or vibrating during transport, guaranteeing testing accuracy.

[0031] A trigger sensor array is pre-positioned at the entrance of the detection area to detect the position of the marker holes on the continuous strip-shaped stamped parts, thus triggering the image acquisition process. The trigger sensors employ photoelectric or laser sensors, capable of accurately identifying the marker hole features on the parts. When the sensor detects a marker hole, it immediately sends a trigger signal to the control module, initiating the corresponding detection process and achieving precise control of the detection timing.

[0032] Friction wheel encoders are mounted on the drive wheels or guide wheels of the production line to collect real-time data on the workpiece's speed and displacement. The encoder converts mechanical motion into electrical signals through the rotation of the friction wheel, which is synchronized with the part's movement, accurately measuring the part's instantaneous speed and cumulative displacement. With high resolution and fast response, the encoder can track changes in the part's motion state in real time, providing accurate feedback data for speed synchronization control.

[0033] A strip light source is positioned below the inspection area to illuminate the continuous strip-shaped stamped parts from below. The light source employs a transmitted illumination mode, where light passes through or reflects upwards from below the parts, better highlighting their contour features and internal structural details. This downward-positioned light source configuration is particularly suitable for inspecting parts for issues such as holes, edge defects, and uneven material thickness. Variations in the intensity of the transmitted light clearly reveal the internal quality condition of the parts.

[0034] The line scan camera is positioned above the detection area, forming an opposing detection configuration with the strip light source below. The camera lens faces downwards, directly receiving transmitted or reflected light signals from the light source below. This top-mounted camera configuration offers advantages such as a wide field of view and ease of installation and maintenance, while avoiding shadow interference that may occur from side illumination. The opposing layout of the camera and light source ensures straight-line propagation of light, improving image clarity and contrast.

[0035] In this vertically opposed optical inspection configuration, when continuous strip-shaped stamped parts pass through the inspection area, the lower strip light source provides stable and uniform illumination. The light passes through or reflects onto the surface of the parts, while the upper linear scan camera receives the light signal and converts it into an electrical signal. This configuration effectively eliminates interference from ambient light, improving the stability and reliability of the inspection. Simultaneously, the vertically opposed layout minimizes the optical path between the light source and the camera, reducing light attenuation and scattering during propagation and ensuring consistent image quality.

[0036] Based on the real-time motion data provided by the friction wheel encoder, the control module precisely controls the acquisition frequency of the line scan camera, ensuring that image acquisition is synchronized with the movement of the part. After the trigger sensor detects the marked hole position, the control module starts the detection process. Under the synchronous line scan frequency control, the line scan camera acquires images of the part line by line, and stitches them together in real time to generate a complete two-dimensional detection image.

[0037] This device achieves more stable and reliable optical inspection results through the optimized configuration of a bottom-mounted bar light source and a top-mounted line scan camera, making it particularly suitable for inspection applications with high requirements for part transparency, hole structure, and edge quality.

[0038] The present invention has been described in detail above through specific embodiments and examples, but these are not intended to limit the invention. Many modifications and improvements can be made by those skilled in the art without departing from the principles of the invention, and these should also be considered within the scope of protection of the present invention.

Claims

1. An optical inspection method for continuous strip-shaped stamped parts, characterized in that, include: Trigger startup steps: Used to trigger the start of the detection process; Speed ​​synchronization step: used to match the image acquisition time with the workpiece displacement; Segmentation End and Loop Standby Steps: Used for segmented detection loop control; Image acquisition and stitching steps: used to stitch together complete two-dimensional detection images in real time; Defect identification and closed-loop control steps: used to identify and output defect information in real time and feed it back to the production line control system.

2. The optical inspection method for continuous strip-shaped stamped parts according to claim 1, characterized in that, The triggering condition for the triggering start-up step is that when the trigger sensor array preset at the entrance of the detection area detects the preset mark hole position of the continuous strip stamping part to be tested, a trigger signal is sent in real time to trigger the start of the detection process.

3. The optical inspection method for continuous strip-shaped stamped parts according to claim 1, characterized in that, The speed synchronization step is used to collect the motion speed data of the workpiece in real time, statistically analyze the data in real time, and dynamically adjust the acquisition line frequency of the image acquisition settings so that the acquisition time of each line of images matches the displacement of the workpiece.

4. The optical inspection method for continuous strip-shaped stamped parts according to claim 1, characterized in that, The segment end and cycle standby steps are used to accumulate the length of the strip stamping parts in real time. Based on the preset threshold for the length of a single workpiece segment, the detection process of a single segment is determined to be over. When the next marker hole is detected, a new round of detection cycle is automatically started.

5. The optical inspection method for continuous strip-shaped stamped parts according to claim 1, characterized in that... In the image acquisition and stitching step, optical images of continuous strip stamping parts are acquired line by line under the control of synchronous line frequency and with the illumination provided by a preset light source through optical image acquisition facilities, and then stitched in real time to generate a two-dimensional detection image.

6. The optical inspection method for continuous strip-shaped stamped parts according to claim 1, characterized in that, The defect identification and closed-loop control steps use visual algorithms to analyze the stitched two-dimensional detection images in real time, identify defect information, and synchronize it to the production line control system to achieve closed-loop quality control of the production process.

7. The optical inspection method for continuous strip-shaped stamped parts according to claim 2, characterized in that, The continuous strip stamped part has at least two different marking hole positions; different marking hole positions correspond to different preset single workpiece segment length thresholds. The segment end and cycle standby steps are used to accumulate the length of the strip stamping parts in real time, and determine the end of the detection process of a single segment based on the preset threshold of the segment length of a single workpiece. The detection cycle will automatically start when the next marker hole is detected.

8. An apparatus for optical inspection of continuous strip-shaped stamped parts, characterized in that, It uses the optical inspection method for continuous strip stamped parts as described in any one of claims 1-7, the apparatus comprising: The production line body is used to carry and drive continuous strip-shaped stamped parts through the inspection area; Strip light source, used for illuminating continuous strip-shaped stamped parts; Line scan camera: Used to acquire surface images of continuous strip-shaped stamped parts line by line under the control of a trigger signal; A trigger sensor is used to detect the position of the marking holes on the continuous strip-shaped stamped parts to trigger the start of the image acquisition process; Friction wheel encoders are used to acquire real-time data on the movement speed and displacement of workpieces. The control module is used to receive trigger signals and encoder data, control the camera's line frequency synchronization, and complete image stitching and defect recognition algorithm calculations.

9. The apparatus for optical inspection of continuous strip-shaped stamped parts according to claim 8, characterized in that, The linear array camera is positioned above the detection area, and the bar light source is positioned below the detection area.

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