Oblique lighting device for detecting concave-convex surface of elliptical or cylindrical object

Abstract

The utility model discloses an oblique lighting device for detecting the concave-convex surface of an elliptical or cylindrical object, which comprises a shell, a plurality of light source monomer components are uniformly arranged on a bottom plate in the shell along the X-axis direction, each light source monomer component comprises a plano-convex lens arranged along the Z-axis direction, a lamp strip is arranged on the left side of the plano-convex lens, and a light source is arranged on the right side of the plano-convex lens. The lamp strip comprises a plurality of lamp beads arranged in the Y-axis direction, an obliquely-arranged cover plate is arranged above the lamp beads, one end of the cover plate is connected with the top end of the plano-convex lens, the other end of the cover plate is connected with a bottom plate in the shell, and the cover plate comprises a light absorption down layer. A diffuse reflection layer opposite to the lamp beads is arranged on the inner end face of the light absorption down layer, and a polaroid and a light condensation rod which are arranged in the X-axis direction are sequentially arranged above the light source single body assembly. The light source is simple in structure, convenient to install, capable of stably emitting uniform and high-brightness oblique light and suitable for detecting dark field low-angle irradiation of concave-convex surfaces of elliptical or cylindrical objects.

Description

Technical Field

[0001] This utility model relates to the technical field of illumination for optical detection, and more specifically, to an oblique illumination device for detecting the surface irregularities of elliptical or cylindrical objects. Background Technology

[0002] Bright-field illumination is a common optical inspection method, typically using a forward-facing, linear light source. When inspecting an object's surface, light is uniformly incident on the surface from all directions, and the reflected light enters the inspection system. While simple and easy to use, bright-field illumination is susceptible to the smoothness and reflectivity of the object's surface, making it difficult to reveal subtle surface defects. For example, pits and bumps on the surface of elliptical or cylindrical objects have weak reflections and may be masked under bright-field illumination, resulting in low image contrast and inaccurate detection. Utility Model Content

[0003] In view of the above-mentioned technical problems in related technologies, this utility model provides an oblique lighting device for detecting the surface unevenness of elliptical or cylindrical objects, which can solve the above problems.

[0004] To achieve the above-mentioned technical objectives, the technical solution of this utility model is implemented as follows:

[0005] An oblique illumination device for detecting the surface irregularities of elliptical or cylindrical objects includes a housing. A plurality of light source unit assemblies are uniformly arranged along the X-axis on a base plate inside the housing. Each light source unit assembly includes a plano-convex lens arranged along the Z-axis, with a light-diffusing film at its planar end. A light strip is located on the left side of the plano-convex lens, comprising a plurality of LEDs arranged along the Y-axis. An obliquely arranged cover plate is positioned above the LEDs, with one end connected to the top of the plano-convex lens and the other end connected to the base plate inside the housing. The cover plate includes a light-absorbing velvet layer, with a diffuse reflection layer opposite to the LEDs on its inner end face. A polarizer and a focusing rod are sequentially arranged along the X-axis above each light source unit assembly.

[0006] Furthermore, the lamp bead is a surface-mount LED bead.

[0007] Furthermore, the root of the plano-convex lens is flush with the light-emitting surface of the lamp bead.

[0008] Furthermore, the LED is positioned at a distance of one focal length from the plano-convex lens.

[0009] Furthermore, the aperture of the plano-convex lens is 5 to 7 times the aperture of the light-emitting surface of the lamp bead.

[0010] Furthermore, the distance L between adjacent plano-convex lenses is greater than b / tanθ, where b is the aperture of the plano-convex lens and θ is the angle between the parallel beam emitted from the plano-convex lens and the principal optical axis of the plano-convex lens.

[0011] Furthermore, the distance between the LED bead and the diffuse reflection layer is not less than 5mm.

[0012] The beneficial effects of this utility model are: This application has a simple structure and is easy to install. It can stably emit uniform and bright oblique light, which is suitable for detecting the unevenness of the surface of elliptical or cylindrical objects under dark field low-angle irradiation. Attached Figure Description

[0013] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0014] The present invention will now be described in further detail with reference to the accompanying drawings.

[0015] Figure 1 This is a simplified structural diagram of an oblique lighting device for detecting the surface irregularities of an elliptical or cylindrical object, as described in an embodiment of this utility model.

[0016] Figure 2 yes Figure 1 A magnified view of the area on the left.

[0017] In the picture:

[0018] 1. Housing; 2. Light source unit assembly; 21. Plano-convex lens; 22. Lamp bead; 23. Light-absorbing velvet layer; 24. Diffuse reflection layer; 25. Light-diffusing film; 3. Polarizer; 4. Focusing rod. Detailed Implementation

[0019] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present utility model are within the protection scope of the present utility model.

[0020] like Figure 1-2As shown, this utility model discloses an oblique lighting device for detecting the surface irregularities of elliptical or cylindrical objects, comprising a housing 1. A plurality of light source unit components 2 are uniformly arranged along the X-axis on the bottom plate inside the housing 1. Each light source unit component 2 includes a plano-convex lens 21 arranged along the Z-axis. The plano-convex lens 21 has a light-diffusing film 25 at its flat end. A light strip is provided on the left side of the plano-convex lens 21. The light strip includes a plurality of LED beads 22 arranged along the Y-axis. An obliquely arranged cover plate is arranged above the LED beads 22. One end of the cover plate is connected to the top of the plano-convex lens 21, and the other end is connected to the bottom plate inside the housing 1. The cover plate includes a light-absorbing velvet layer 23. The inner end face of the light-absorbing velvet layer 23 has a diffuse reflection layer 24 opposite to the LED beads 22. A polarizer 3 and a focusing rod 4 arranged along the X-axis are sequentially arranged above the light source unit components 2.

[0021] Example:

[0022] The purpose of this lighting device design is to ensure that the final light path is obliquely parallel and to calibrate the beam generated by the LED beads. Based on the experience of non-imaging light path design, the aperture of the plano-convex lens is about 5 to 7 times the aperture of the LED bead's emitting surface. Since the selected LED bead 22 has an aperture of about 3mm, the aperture of the plano-convex lens 21 is about 15 to 21mm. In this application, the aperture of the plano-convex lens 21 is set to 20mm. In a specific practical application, the beam needs to be parallel to the X-axis at an angle of 30°. The root of the plano-convex lens 21 is flush with the emitting surface of the LED bead 22. Therefore, the horizontal distance C from the plano-convex lens 21 to the LED bead 22 is C = 10 / tan30°. According to the imaging law of convex lenses, to ensure that all rays emitted from the convex lens are parallel to the rays passing through the optical center, the LED bead needs to be placed at a position equal to one focal length of the convex lens, thus obtaining the focal length of the plano-convex lens 21.

[0023] Theoretically, the appropriate distance between adjacent plano-convex lenses 21 is L = 20 / tan30° ≈ 35mm. However, there is a diagonally positioned diffuse reflection layer 24 above each row of LED beads 22, which also reflects a portion of the light beam to the plano-convex lenses 21. The exit angle of this portion of light after passing through the plano-convex lenses 21 will be less than 30°. In order to minimize light obstruction, the distance between adjacent plano-convex lenses 21 needs to be increased. Experiments have shown that the distance between adjacent plano-convex lenses 21 can be 45mm. In addition, if the diffuse reflection layer 24 is too close to the LED beads 22, the high heat generated by the LED beads 22 during prolonged use will cause the diffuser plate to burn. Setting the distance between the LED beads 22 and the diffuse reflection layer 24 to 5mm (which is relatively safe) yields a theoretical angle of 48.4° between the cover plate and the plano-convex lens 21 according to the Pythagorean theorem. For ease of design, production, and installation, this angle is rounded to 50°.

[0024] Theoretically, only about 30% of the light from the LED 22 passes directly through the plano-convex lens 21. With fewer LEDs, the brightness is relatively low. Therefore, each light strip includes N LEDs 22 arranged along the Y-axis to increase the brightness of the light source. In a specific application, each light strip includes 4 surface-mount LEDs.

[0025] When the plano-convex lens 21 does not have a homogenizing film 25 on its flat side, the light from the LEDs passes directly through the lens and becomes uniform linear light with a flat-top distribution. Regardless of the spacing between the LEDs, there are obvious dark spots between any two beams. When the homogenizing film 25 is provided on the flat side of the plano-convex lens 21, the homogenizing film (1° x 30°) transforms a single light beam into a 30-degree diverging beam. This causes the LED light to become diverging after passing through the homogenizing film 25, and then, after passing through the plano-convex lens 21, the beam exhibits a Gaussian distribution. The overlapping edges of two Gaussian distributions create a uniform beam distribution, eliminating dark spots. Ultimately, the LED light, after passing through the homogenizing film 25 and the plano-convex lens 21, forms oblique light at a 30-degree angle along the light source direction.

[0026] In this application, the diffuse reflection layer 24 can reflect the light path of the lamp bead directly upwards onto the plano-convex lens on the right, increasing the brightness of the light, reducing light leakage from the lamp bead, and preventing the formation of highlights on the product surface, which would affect subsequent processing; the light-absorbing velvet layer 23 can further reduce light leakage from the lamp bead; and the polarizer can eliminate the highlights formed on the product surface by light leakage from the lamp bead.

[0027] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. An oblique illumination device for detecting the surface irregularities of an elliptical or cylindrical object, characterized in that, The device includes a housing (1), and a plurality of light source unit components (2) are uniformly arranged along the X-axis on the bottom plate inside the housing (1). The light source unit component (2) includes a plano-convex lens (21) arranged along the Z-axis. The plano-convex lens (21) has a light-diffusing film (25) on its flat end. A light strip is provided on the left side of the plano-convex lens (21). The light strip includes a plurality of lamp beads (22) arranged along the Y-axis. A cover plate is arranged obliquely above the lamp beads (22). One end of the cover plate is connected to the top of the plano-convex lens (21), and the other end is connected to the bottom plate inside the housing (1). The cover plate includes a light-absorbing velvet layer (23). The inner end face of the light-absorbing velvet layer (23) is provided with a diffuse reflection layer (24) opposite to the lamp beads (22). A polarizer (3) and a focusing rod (4) arranged along the X-axis are arranged sequentially above the light source unit component (2).

2. The oblique illumination device for detecting the surface irregularities of an elliptical or cylindrical object according to claim 1, characterized in that, The lamp bead (22) is a surface-mount LED lamp bead.

3. The oblique illumination device for detecting the surface irregularities of an elliptical or cylindrical object according to claim 2, characterized in that, The root of the plano-convex lens (21) is flush with the light-emitting surface of the lamp bead (22).

4. The oblique illumination device for detecting the surface irregularities of an elliptical or cylindrical object according to claim 3, characterized in that, The LED (22) is placed at a distance of one focal length from the plano-convex lens (21).

5. The oblique illumination device for detecting the surface irregularities of an elliptical or cylindrical object according to claim 1, characterized in that, The aperture of the plano-convex lens (21) is 5 to 7 times the aperture of the light-emitting surface of the lamp bead (22).

6. The oblique illumination device for detecting the surface irregularities of an elliptical or cylindrical object according to claim 1, characterized in that, The distance between adjacent plano-convex lenses (21) is L > b / tanθ, where b is the aperture of the plano-convex lens (21) and θ is the angle between the parallel beam emitted from the plano-convex lens (21) and the principal optical axis of the plano-convex lens (21).

7. The oblique illumination device for detecting the surface irregularities of an elliptical or cylindrical object according to claim 1, characterized in that, The distance between the lamp bead (22) and the diffuse reflection layer (24) is not less than 5 mm.

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