A coaxial light source with switchable light source divergence angle

Abstract

This invention discloses a coaxial light source with switchable light divergence angle, comprising a first housing, a second housing, an LED light-emitting component, a focusing rod, an adjustable aperture, a diffuser plate, a total internal reflection plane mirror, a biconvex lens, a semi-reflective prism, a light outlet, and an anti-reflective glass. The divergent light emitted by the LED is converged by the focusing rod, homogenized by the diffuser plate, and then its diameter is adjusted by the adjustable aperture. After reflection by the total internal reflection plane mirror and collimation by the biconvex lens, the light is reflected by the semi-reflective prism and emitted from the light outlet to illuminate the object being measured. The light reflected from the object is transmitted through the semi-reflective prism and the anti-reflective glass and received by an external camera. The effective aperture of the adjustable aperture is located near the front focal plane of the biconvex lens; changing the aperture aperture switches the divergence angle of the emitted light, adapting to the detection of different materials and surface conditions. This light source has a compact structure, requires no replacement of the light source, and is highly adaptable.

Description

Technical Field

[0001] This invention relates to the field of machine vision inspection technology, and in particular to a coaxial light source with switchable light source divergence angle. Background Technology

[0002] In machine vision inspection, LED light sources are the most widely used light source, capable of meeting a variety of different project requirements. Currently, most brands have relatively fixed LED light source types, typically using conventional light sources such as ring lights, strip lights, coaxial lights, and surface lights for lighting tests.

[0003] Coaxial light sources achieve coaxiality between the light source and the camera through a semi-transparent, semi-reflective beam-splitting structure. This effectively highlights surface irregularities and overcomes interference caused by surface reflections, making them widely used for surface defect detection and dimensional measurement of highly reflective objects such as metals, glass, and chips. However, the divergence angle of the emitted light from traditional coaxial light sources is usually fixed. Different divergence angles are often required for coaxial light sources with different materials and surface conditions. For example, for planar mirror-like objects such as glass and silicon wafers, a telecentric coaxial light source with a smaller divergence angle is needed to highlight minute surface defects; while for planar frosted metals, a traditional coaxial light source with a larger divergence angle is needed to uniformly illuminate the surface texture and highlight severe defects.

[0004] In existing technologies, users typically need to configure different types of coaxial light sources for different application scenarios. This not only increases the cost of light source procurement and equipment installation space, but also requires frequent replacement of light sources when switching inspection tasks, affecting inspection efficiency. Furthermore, for the inspection of appearance defects on curved products, especially scratches, dents, and pressure marks, the curvature of curved products varies significantly. Since the divergence angle of light emitted from ordinary coaxial light sources is fixed, the brightness is uneven after illuminating the curved product surface, resulting in insufficient contrast between defects and the background. This leads to decreased image quality and increases the complexity of subsequent algorithm detection. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a coaxial light source with switchable light source divergence angle to solve the problems mentioned in the background art.

[0006] A coaxial light source with switchable light source divergence angle, comprising:

[0007] A first housing, with an LED light-emitting component installed at the rear opening of the first housing;

[0008] A focusing rod is disposed inside the first housing and located in front of the LED light-emitting component;

[0009] The second housing is connected to the front of the first housing, and a connection port is provided on the lower rear side of the second housing, which communicates with the first housing;

[0010] Adjustable aperture, installed at the connector;

[0011] A diffuser plate is positioned behind the adjustable aperture and in front of the focusing rod;

[0012] A total internal reflection plane mirror is disposed inside the lower side of the second housing, in front of the adjustable aperture. The total internal reflection plane mirror is set at 45° with the horizontal plane and is used to reflect the light from the adjustable aperture upward.

[0013] A biconvex lens is disposed inside the second housing and located above the total internal reflection plane mirror. The optical axis of the biconvex lens is perpendicular to the central axis of the adjustable aperture and is used to collimate the light rays reflected by the total internal reflection plane mirror.

[0014] A semi-reflective prism is disposed inside the second housing and above the biconvex lens. The beam-splitting surface of the semi-reflective prism is set at 45° with the horizontal plane and is used to reflect the light from the biconvex lens to the front.

[0015] The light outlet is located on the upper front side of the second housing and is used to face the object being measured.

[0016] Anti-reflective glass is located on the upper rear end of the second housing, behind the semi-reflective prism, and is used to allow the external camera to receive light.

[0017] Along the optical path, the optical distance between the adjustable aperture and the biconvex lens is equal to the focal length of the biconvex lens.

[0018] Preferably, a light-absorbing cloth is installed at the top of the interior of the second housing, and the light-absorbing cloth is located above the semi-reflective and semi-transparent prism.

[0019] Preferably, a heat sink and a cooling fan are sequentially installed at the rear of the LED light-emitting component.

[0020] Preferably, the light-concentrating rod is an integral light-transmitting body, the light-concentrating rod has a light-incident surface and a light-exiting surface, the light-incident surface faces the LED light-emitting component, and the light-exiting surface faces the diffuser plate.

[0021] Preferably, the total reflection plane mirror and the semi-reflective prism have the same tilt direction.

[0022] Preferably, the biconvex lens is a symmetrical biconvex lens.

[0023] Preferably, the adjustable aperture is an electronically controlled adjustable aperture.

[0024] This invention provides a method for controlling the divergence angle of a coaxial light source with switchable divergence angle, applied to the aforementioned coaxial light source with switchable divergence angle. The method includes the following steps: S1, Assembly and Positioning: The object to be measured is placed in front of the light outlet of the coaxial light source, and the external camera lens is aligned with the anti-reflection glass to complete the imaging optical path alignment; S2, Light Emission: The LED light-emitting component is turned on, and the light emitted by the LED light-emitting component is focused onto the diffuser plate by a focusing rod; S3, Adjusting the Size of the Light-Emitting Area: The adjustable aperture is adjusted according to the surface type of the object to be measured. The adjustable aperture controls the size of the light-emitting area of ​​the diffuser plate; the effective aperture surface of the adjustable aperture is located at the front focal plane of the biconvex lens after reflection by the total internal reflection plane mirror. By changing the size of the light-emitting area, the diameter of the beam incident on the biconvex lens is changed; S4. Light Path Reversal and Illumination Emission: The light emitted from the light-emitting area of ​​the diffuser plate is reflected by the total internal reflection plane mirror and then enters the biconvex lens to form a beam with a corresponding divergence angle; the beam enters the semi-reflective prism, half of the light transmitted by the semi-reflective prism is absorbed by the light-absorbing cloth, and the light reflected by the semi-reflective prism is emitted through the light outlet to illuminate the object under test; S5. Image Acquisition: The light reflected back from the object under test passes through the semi-reflective prism and the anti-reflective glass and is captured by the camera lens to complete image acquisition.

[0025] In the aforementioned divergence angle control method, in step S3, when the object being measured is a planar mirror object such as glass or silicon wafer, the adjustable aperture is reduced to decrease the light emission area of ​​the diffuser plate, and the biconvex lens outputs a small divergence angle beam to highlight the minute surface defects of the object being measured.

[0026] This invention provides a machine vision-based workpiece defect detection process, employing a method for controlling the divergence angle of a coaxial light source with switchable divergence angles. The process includes the following steps: T1, identifying the surface properties of the workpiece to be inspected, distinguishing between mirror-finished and frosted metal workpieces; T2, adjusting the adjustable aperture according to the workpiece surface properties to control the size of the diffuser plate's luminous area, thus configuring the coaxial light source's emission divergence angle; T3, activating the LED luminous component, illuminating the workpiece with the coaxial light source, and capturing an image of the workpiece surface using a camera; T4, identifying dents, scratches, cracks, or foreign object defects on the workpiece surface based on the acquired image; T5, changing the workpiece to a different surface type, readjusting the adjustable aperture to change the size of the diffuser plate's luminous area, switching the light source divergence angle, and repeating steps T2 and T4 to complete continuous defect detection of workpieces made of different materials.

[0027] The beneficial effects of this invention are:

[0028] 1. This invention, by setting an adjustable aperture and a biconvex lens, and placing the effective aperture surface of the adjustable aperture near the front focal plane of the biconvex lens, allows the divergence angle of the emitted light to be changed by adjusting the aperture size of the adjustable aperture. This enables the invention to adapt to objects of different materials and surface conditions on the same coaxial light source without the need to change the light source, thus significantly improving the adaptability of the test and the efficiency of the work.

[0029] 2. This invention achieves two 90° turns in the optical path through a total reflection plane mirror and a semi-reflective prism, allowing the overall optical path to be folded and arranged in a limited space, resulting in a compact structure and saving equipment installation space; at the same time, the semi-reflective prism achieves coaxiality between the illumination optical path and the imaging optical path, ensuring coaxial detection effect.

[0030] 3. This invention uses a focusing rod to converge the divergent light emitted by the LED light-emitting component, and works with a diffuser plate to improve the uniformity of light output. This effectively improves the light energy utilization and illumination uniformity, enhances the contrast between defects and the background, and reduces the complexity of subsequent algorithm detection. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the overall invention;

[0032] Figure 2 This is a top view of the entire invention;

[0033] Figure 3 For the present invention Figure 2 A schematic diagram of the AA cross-section.

[0034] In the diagram: 1-First housing, 2-LED light-emitting component, 3-focusing rod, 4-light outlet, 5-Second housing, 6-adjustable aperture, 7-diffuser plate, 8-total reflection plane mirror, 9-biconvex lens, 10-semi-reflective prism, 11-anti-reflective glass, 12-light-absorbing cloth, 13-heat dissipation fins, 14-heat dissipation fan. Detailed Implementation

[0035] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings. In the description of the present invention, it should be noted that the terms "upper," "lower," "left," "right," "front," and "rear," etc., indicate the orientation or positional relationship based on the accompanying drawings. Figure 1 The orientations or positional relationships shown are for the purpose of facilitating and simplifying the description of the present invention, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as limiting the present invention.

[0036] Please see Figures 1 to 3The present invention provides a coaxial light source with switchable light source divergence angle, including a first housing 1, a second housing 5, an LED light-emitting component 2, a light-concentrating rod 3, an adjustable aperture 6, a diffuser plate 7, a total reflection plane mirror 8, a biconvex lens 9, a semi-reflective prism 10, a light outlet 4, an anti-reflective glass 11, a light-absorbing cloth 12, a heat dissipation fin 13, and a heat dissipation fan 14.

[0037] An LED light-emitting component 2 is installed at the rear opening of the first housing 1. The LED light-emitting component 2 includes a lamp board and multiple LED beads. The lamp board is fixed at the rear opening of the first housing 1, and the multiple LED beads are arranged in a linear array on the lamp board. The LED beads can be surface-mount LED beads, and their wavelength, divergence angle, illuminance, and other parameters can be selected according to actual detection requirements. A heat sink fin 13 and a cooling fan 14 are sequentially installed at the rear of the LED light-emitting component 2. The heat sink fin 13 is thermally coupled to the lamp board of the LED light-emitting component 2 to conduct the heat generated by the LED beads to the heat sink fin 13, and the cooling fan 14 provides forced air cooling to ensure stable operation of the light source for a long time.

[0038] A focusing rod 3 is disposed within the first housing 1, located in front of the LED light-emitting component 2. The focusing rod 3 is a one-piece transparent body made of PMMA material. It has an incident surface and an exiting surface; the incident surface faces the LED light-emitting component 2, and the exiting surface faces the diffuser plate 7. The incident surface is an arc-shaped surface facing the LED light-emitting component 2, and the exiting surface is an arc-shaped surface facing the diffuser plate 7. After the divergent light emitted from the LED light-emitting component 2 enters the focusing rod 3, it is refracted by the incident and exiting surfaces, resulting in convergence of the emitted light and a significant increase in light concentration.

[0039] The second housing 5 is connected to the front of the first housing 1. A connection port is provided on the lower rear side of the second housing 5, communicating with the first housing 1. An adjustable aperture 6 is installed at the connection port, located on the light-emitting side of the focusing rod 3. A diffuser plate 7 is disposed behind the adjustable aperture 6 and in front of the focusing rod 3, i.e., the diffuser plate 7 is located between the focusing rod 3 and the adjustable aperture 6. The diffuser plate 7 is used to homogenize the light converged by the focusing rod 3, making the light entering the adjustable aperture 6 more uniform.

[0040] A total internal reflection plane mirror 8 is disposed inside the lower side of the second housing 5, in front of the adjustable aperture 6. The total internal reflection plane mirror 8 is set at 45° to the horizontal plane and is used to reflect horizontal light rays from the adjustable aperture 6 into vertical light rays. A biconvex lens 9 is disposed inside the second housing 5, above the total internal reflection plane mirror 8. The optical axis of the biconvex lens 9 is perpendicular to the central axis of the adjustable aperture 6; that is, the biconvex lens 9 is set vertically, and the adjustable aperture 6 is set horizontally. The biconvex lens 9 is used to collimate the vertical light rays reflected by the total internal reflection plane mirror 8.

[0041] In this embodiment, the optical distance between the adjustable aperture 6 and the biconvex lens 9 along the optical path is equal to the focal length of the biconvex lens 9. That is, the effective aperture surface of the adjustable aperture 6, after reflection by the total internal reflection plane mirror 8, is located at the front focal plane of the biconvex lens 9. Thus, when the aperture size of the adjustable aperture 6 is adjusted, the diameter of the light beam exiting the adjustable aperture 6 and incident on the biconvex lens 9 changes, and the divergence angle of the emitted light after collimation by the biconvex lens 9 also changes accordingly, thereby achieving the switching of the light source divergence angle.

[0042] A semi-reflective prism 10 is disposed within the second housing 5, above the biconvex lens 9. The beam-splitting surface of the semi-reflective prism 10 is set at 45° to the horizontal plane, used to reflect vertical light rays from the biconvex lens 9 into horizontal light rays, which then propagate forward. The tilt direction of the semi-reflective prism 10 is the same as that of the total internal reflection plane mirror 8, both at 45° to the horizontal plane. A semi-reflective coating is deposited on the beam-splitting surface of the semi-reflective prism 10, used to reflect the illumination light from the biconvex lens 9 towards the light outlet 4, while simultaneously transmitting reflected light from the surface of the object being measured.

[0043] The light exit port 4 is located on the upper front side of the second housing 5, facing the object being measured. Illumination light reflected by the semi-reflective prism 10 is emitted from the light exit port 4 and illuminates the surface of the object being measured. The light exit port 4 can be configured as an elongated opening or a circular opening, depending on the actual detection requirements and camera type.

[0044] Anti-reflective glass 11 is disposed on the upper rear end of the second housing 5, behind the semi-reflective prism 10. Anti-reflective glass 11 is used to reduce light reflection loss and allow the external camera to receive light. The light reflected from the surface of the object being measured enters the second housing 5 through the light outlet 4, passes through the semi-reflective prism 10, and then passes through the anti-reflective glass 11 to reach the external camera, thus achieving imaging.

[0045] A light-absorbing cloth 12 is installed at the top of the interior of the second housing 5, and the light-absorbing cloth 12 is located above the semi-reflective prism 10. The light-absorbing cloth 12 is used to absorb stray light transmitted above the semi-reflective prism 10, reduce internal reflection interference, and improve imaging contrast.

[0046] The working process is as follows: The object to be measured is placed in front of the light outlet 4. The LED light-emitting component 2 is turned on, and the LED beads emit light. The diverging light emitted by the LED light-emitting component 2 first enters the focusing rod 3, and after being converged by the focusing rod 3, it is directed towards the diffuser plate 7. The diffuser plate 7 homogenizes the converged light, allowing the light to pass evenly through the adjustable aperture 6. The adjustable aperture 6 limits the beam diameter, and the light, after passing through the adjustable aperture 6, is directed towards the total internal reflection plane mirror 8. The total internal reflection plane mirror 8 reflects the horizontal light into vertical light, which enters the biconvex lens 9. Since the effective aperture surface of the adjustable aperture 6 is located near the front focal plane of the biconvex lens 9, the biconvex lens 9 collimates the incident light into approximately parallel light. The collimated light is directed towards the semi-reflective prism 10, and after being reflected by the beam-splitting surface of the semi-reflective prism 10, it exits from the light outlet 4 and illuminates the surface of the object to be measured.

[0047] The light reflected from the surface of the object being measured enters the second housing 5 again through the light outlet 4, passes through the semi-reflective prism 10, and then is received by the external camera after passing through the anti-reflective glass 11, thus completing image acquisition.

[0048] When it is necessary to adjust the divergence angle of the emitted light, the aperture size of the adjustable aperture 6 is adjusted. When the aperture of the adjustable aperture 6 decreases, the diameter of the beam entering the biconvex lens 9 decreases, and the emitted light, after being collimated by the biconvex lens 9, becomes more concentrated, resulting in a smaller divergence angle. This is suitable for detecting minute defects on mirrored or highly reflective surfaces. When the aperture of the adjustable aperture 6 increases, the diameter of the beam entering the biconvex lens 9 increases, and the divergence angle of the emitted light increases. This is suitable for detecting frosted surfaces or in scenarios where uniform illumination of textures is required. The adjustable aperture 6 can be an electrically controlled adjustable aperture, allowing for automatic adjustment via an external controller, further improving detection efficiency.

[0049] Because this light source incorporates a focusing rod 3 and a diffuser plate 7, the emitted light has high brightness and uniformity, effectively enhancing the contrast between surface defects and the background, improving image quality, and reducing the complexity of subsequent algorithm detection. Simultaneously, through two optical path reversals via a total internal reflection plane mirror 8 and a semi-reflective prism 10, the overall structure of the light source is compact, saving installation space.

[0050] This invention provides a method for controlling the divergence angle of a coaxial light source with switchable divergence angle, applied to the aforementioned coaxial light source with switchable divergence angle. The method includes the following steps: S1, Assembly and Positioning: The object to be measured is placed in front of the light outlet of the coaxial light source, and the external camera lens is aligned with the anti-reflection glass to complete the imaging optical path alignment; S2, Light Emission: The LED light-emitting component is turned on, and the light emitted by the LED light-emitting component is focused onto the diffuser plate by a focusing rod; S3, Adjusting the Size of the Light-Emitting Area: The adjustable aperture is adjusted according to the surface type of the object to be measured. The adjustable aperture controls the size of the light-emitting area of ​​the diffuser plate; the effective aperture surface of the adjustable aperture is located at the front focal plane of the biconvex lens after reflection by the total internal reflection plane mirror. By changing the size of the light-emitting area, the diameter of the beam incident on the biconvex lens is changed; S4. Light Path Reversal and Illumination Emission: The light emitted from the light-emitting area of ​​the diffuser plate is reflected by the total internal reflection plane mirror and then enters the biconvex lens to form a beam with a corresponding divergence angle; the beam enters the semi-reflective prism, half of the light transmitted by the semi-reflective prism is absorbed by the light-absorbing cloth, and the light reflected by the semi-reflective prism is emitted through the light outlet to illuminate the object under test; S5. Image Acquisition: The light reflected back from the object under test passes through the semi-reflective prism and the anti-reflective glass and is captured by the camera lens to complete image acquisition.

[0051] In the aforementioned divergence angle control method, in step S3, when the object being measured is a planar mirror object such as glass or silicon wafer, the adjustable aperture is reduced to decrease the light emission area of ​​the diffuser plate, and the biconvex lens outputs a small divergence angle beam to highlight the minute surface defects of the object being measured.

[0052] This invention provides a machine vision-based workpiece defect detection process, employing a method for controlling the divergence angle of a coaxial light source with switchable divergence angles. The process includes the following steps: T1, identifying the surface properties of the workpiece to be inspected, distinguishing between mirror-finished and frosted metal workpieces; T2, adjusting the adjustable aperture according to the workpiece surface properties to control the size of the diffuser plate's luminous area, thus configuring the coaxial light source's emission divergence angle; T3, activating the LED luminous component, illuminating the workpiece with the coaxial light source, and capturing an image of the workpiece surface using a camera; T4, identifying dents, scratches, cracks, or foreign object defects on the workpiece surface based on the acquired image; T5, changing the workpiece to a different surface type, readjusting the adjustable aperture to change the size of the diffuser plate's luminous area, switching the light source divergence angle, and repeating steps T2 and T4 to complete continuous defect detection of workpieces made of different materials.

[0053] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A coaxial light source with switchable light source divergence angle, characterized in that, include: The first housing (1) has an LED light-emitting component (2) installed in the rear opening of the first housing (1). A focusing rod (3) is set inside the first housing (1) and located in front of the LED light-emitting component (2); The second housing (5) is connected to the front of the first housing (1). The lower rear side of the second housing (5) is provided with a connection port, which is connected to the first housing (1). Adjustable aperture (6), installed at the connector; A diffuser plate (7) is positioned behind the adjustable aperture (6) and in front of the focusing rod (3); A total reflection plane mirror (8) is set inside the lower side of the second housing (5) and in front of the adjustable aperture (6). The total reflection plane mirror (8) is set at 45° with the horizontal plane and is used to reflect the light from the adjustable aperture (6) upward. A biconvex lens (9) is disposed inside the second housing (5) and located above the total internal reflection plane mirror (8). The optical axis of the biconvex lens (9) is perpendicular to the central axis of the adjustable aperture (6) and is used to collimate the light reflected by the total internal reflection plane mirror (8). A semi-reflective prism (10) is disposed inside the second housing (5) and located above the biconvex lens (9). The beam-splitting surface of the semi-reflective prism (10) is set at 45° with the horizontal plane and is used to reflect the light from the biconvex lens (9) to the front. The light outlet (4) is located on the upper front side of the second housing (5) and is used to face the object being measured. Anti-reflective glass (11) is located on the upper rear end of the second housing (5), behind the semi-reflective prism (10), and is used to allow the external camera to receive light. Along the optical path, the optical distance between the adjustable aperture (6) and the biconvex lens (9) is equal to the focal length of the biconvex lens (9).

2. The coaxial light source with switchable light source divergence angle according to claim 1, characterized in that, The second housing (5) has a light-absorbing cloth (12) installed at the top inside, and the light-absorbing cloth (12) is located above the semi-reflective prism (10).

3. A coaxial light source with switchable light source divergence angle according to claim 1, characterized in that, The LED light-emitting component (2) is equipped with heat dissipation fins (13) and a cooling fan (14) in sequence at the rear.

4. A coaxial light source with switchable light source divergence angle according to claim 1, characterized in that, The light-concentrating rod (3) is an integral light-transmitting body. The light-concentrating rod (3) has a light-incident surface and a light-exit surface. The light-incident surface faces the LED light-emitting component (2), and the light-exit surface faces the diffuser plate (7).

5. A coaxial light source with switchable light source divergence angle according to claim 1, characterized in that, The total reflection plane mirror (8) and the semi-reflective prism (10) are tilted in the same direction.

6. A coaxial light source with switchable light source divergence angle according to claim 1, characterized in that, The biconvex lens (9) is a symmetrical biconvex lens.

7. A coaxial light source with switchable light source divergence angle according to claim 1, characterized in that, The adjustable aperture (6) is an electronically controlled adjustable aperture.

8. A method for controlling the divergence angle of a coaxial light source with switchable divergence angle, applied to the coaxial light source with switchable divergence angle as described in any one of claims 17, characterized in that, Includes the following steps: S1. Assembly and positioning: Place the object to be measured in front of the light outlet (4) of the coaxial light source, and align the external camera lens with the anti-reflection glass (11) to complete the imaging optical path docking; S2. Light emission from the light source: Turn on the LED light-emitting component (2), and the light emitted by the LED light-emitting component is focused onto the diffuser plate (7) by the condenser rod (3); S3. Adjusting the size of the light-emitting area: Adjust the adjustable aperture (6) according to the surface type of the object to be measured. The adjustable aperture (6) controls the size of the light-emitting area of ​​the diffuser plate (7); the effective aperture surface of the adjustable aperture (6) is located at the front focal plane of the biconvex lens (9) after being reflected by the total internal reflection plane mirror (8). By changing the size of the light-emitting area, the diameter of the beam incident on the biconvex lens (9) is changed; S4. Light path reversal and illumination emission: The light emitted from the light-emitting area of ​​the diffuser plate (7) is reflected by the total reflection plane mirror (8) and then enters the biconvex lens (9) to form a beam of light with a corresponding divergence angle; the beam enters the semi-reflective prism (10), half of the light transmitted by the semi-reflective prism (10) is absorbed by the light-absorbing cloth (12), and the light reflected by the semi-reflective prism (10) is emitted through the light outlet (4) to illuminate the object under test; S5. Image acquisition: The light reflected back from the object under test passes through the semi-reflective prism (10) and the anti-reflective glass (11) and is captured by the camera lens to complete the image acquisition.

9. The divergence angle control method according to claim 8, characterized in that, In step S3, when the object being measured is a flat mirror object such as glass or silicon wafer, the adjustable aperture (6) is reduced to shrink the light emission area of ​​the diffuser plate (7), and the biconvex lens (9) outputs a beam with a small divergence angle to highlight the minute surface defects of the object being measured.

10. A machine vision-based workpiece defect detection process, employing the divergence angle control method of a coaxial light source with switchable divergence angle as described in any one of claims 89, characterized in that... The process includes the following steps: T1. Identify the surface properties of the workpiece to be tested and distinguish whether the workpiece is a mirror-like workpiece or a frosted metal workpiece; T2. Adjust the adjustable aperture (6) according to the surface properties of the workpiece, control the size of the light-emitting area of ​​the diffuser plate (7), and complete the configuration of the coaxial light source emission divergence angle; T3. Start the LED light-emitting component (2), illuminate the workpiece under test with the coaxial light source, and the camera collects the workpiece surface image; T4. Identify the dents, scratches, cracks, or foreign object defects on the workpiece surface based on the collected image; T5. Change the workpiece under test with different surface types, readjust the adjustable aperture (6) to change the size of the light-emitting area of ​​the diffuser plate (7), switch the light source divergence angle, and repeat steps T2 and T4 to complete the continuous defect detection of workpieces of different materials.

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