On-line multi-directional linear illumination device for cold-rolled steel and its use

Abstract

This invention discloses a multi-directional linear lighting device for online inspection of cold-rolled steel and its application, comprising an upper surface lighting body, a lower surface lighting body, and a connecting structure. The upper and lower surface lighting bodies have identical structures, each including several lighting units fixed by array connectors. Each lighting unit includes a housing composed of a heat sink, a shell, and a light outlet, and within the shell are an LED array, a focusing device, a transverse grating, a homogenizing device, and a longitudinal grating. The LED array consists of several RGB LED beads arranged in a line. The focusing device is used to converge the light generated by the LED array. The transverse grating is used to eliminate stray light within the lighting unit. The homogenizing device is used to homogenize the light passing through the transverse grating. The longitudinal grating is used to shape the light source into longitudinally intersecting light perpendicular to the direction of object movement. Using this invention, suitable lighting can be flexibly adjusted according to the width and surface reflectivity of the cold-rolled steel strip product.

Description

Technical Field

[0001] This invention belongs to the field of optical inspection devices, and in particular relates to a multi-directional linear illumination device for online inspection of cold-rolled steel and its application. Background Technology

[0002] In the industrial production of cold-rolled steel, raw materials undergo multiple processing steps to form the final product. However, damage to the product often occurs during these processes due to handling operations or inter-stage transportation. Therefore, defect detection in industrial products is crucial for improving product yield and reducing industrial costs. In industrial production, long strip products such as cold-rolled steel often operate at high speeds on assembly lines, posing a significant challenge to inspection speed. Currently, machine vision inspection methods, such as high-speed linear scan camera scanning, are commonly used in industrial production lines to replace manual inspection, saving substantial human resources.

[0003] In machine vision inspection technology, illumination is a crucial component. Its primary goal is to project light onto the object under test in an appropriate manner, highlighting the contrast of the measured features. Good lighting design can improve the overall system resolution, simplify software computation, and reduce the overall system workload. Inappropriate lighting, on the other hand, can cause numerous problems. For example, speckles and overexposure can obscure important information; shadows can lead to false detections of edges; and reduced signal-to-noise ratio and uneven lighting can make it difficult to select image processing thresholds. Different lighting methods must be employed for each different object to highlight its features, sometimes requiring a combination of several methods. The optimal lighting method and light source selection often require extensive experimentation to find.

[0004] In high-speed linear scan camera inspection technology, linear illumination devices are generally arranged perpendicular to the object's direction of movement (lateral direction), failing to simultaneously illuminate the direction parallel to the object's movement (vertical direction). This results in longitudinal scratch information not being prominent and thus not being effectively detected by the high-speed linear scan camera. Secondly, illuminating objects of different widths often requires changing linear illumination devices with different illumination ranges. If the illumination range is insufficient to cover the object's width, the object's edges may not be detected; conversely, if the illumination range exceeds the object's width, reflections and scattering from surrounding objects can lead to unsatisfactory results. Furthermore, different long strip products, such as cold-rolled steel, have varying surface reflectivity. Some product surfaces respond better to bright-field illumination, while others respond better to dark-field illumination. Therefore, the design of the inspection system often needs to consider both bright-field and dark-field illumination. Additionally, to improve production efficiency and yield, long strip products such as cold-rolled steel require simultaneous inspection of both upper and lower surfaces. The corresponding illumination device also needs to illuminate both surfaces simultaneously, while existing linear illumination devices can only illuminate one surface of the object.

[0005] Among existing linear lighting devices, patent CN103090254A achieves coaxial lighting, but only has one lighting direction perpendicular to the light outlet, and cannot adjust the lighting range for objects of different widths; patent CN103884650A achieves multi-angle linear lighting, but requires multiple lighting devices to be set, and cannot be flexibly adjusted and changed in conjunction with the imaging system; patent CN114815459A can only achieve horizontal lighting and cannot effectively illuminate vertical scratches.

[0006] Therefore, in order to achieve better detection results, a linear illumination device for both upper and lower surfaces is needed to integrate longitudinal illumination, transverse bright field illumination, and dark field illumination to adapt to the production of long strip products such as cold-rolled steel with different widths in industry. Summary of the Invention

[0007] This invention provides a multi-directional linear lighting device for online inspection of cold-rolled steel and its application, which can realize longitudinal lighting, transverse bright field lighting and dark field lighting, and can be flexibly adjusted according to the width and surface reflection characteristics of cold-rolled steel strip products of equal length to provide suitable lighting.

[0008] A multi-directional linear lighting device for online inspection of cold-rolled steel includes an upper surface lighting body and a lower surface lighting body that are adjustable and fixed by a connecting structure;

[0009] The upper surface lighting body and the lower surface lighting body have the same structure, both including several lighting units fixed by array connectors;

[0010] Each lighting unit includes an outer shell consisting of a heat sink, a housing, and a light outlet, and an LED array, a focusing device, a transverse grating, a homogenizing device, and a longitudinal grating arranged sequentially within the housing along the direction from the heat sink to the light outlet.

[0011] The LED array consists of several RGB LED beads arranged in a line, each RGB LED bead emitting light independently; the focusing device is used to converge the light generated by the LED array; the horizontal grating is used to eliminate stray light in the lighting unit and reduce the divergence angle of the light source; the homogenizing device is used to homogenize the light passing through the horizontal grating; the vertical grating is used to control the lighting direction, shaping the light source into a vertically intersecting light perpendicular to the direction of object movement.

[0012] Furthermore, the longitudinal grating has several square through holes, each with a side length of d; near the center of the longitudinal grating, the distance between adjacent through holes is d; near both ends of the longitudinal grating, the distance between adjacent through holes is a, where a = 3d;

[0013] Each through hole has an electric switch and a light guide structure on its inner and outer sides, respectively. Each light guide structure is arranged at an angle, with the angle pointing towards the front or rear end of the longitudinal grating.

[0014] In the longitudinal grating, the distance between two adjacent back-to-back light guide structures is d, and the distance between two adjacent opposite light guide structures is composed of the side lengths of two through holes and the interval between adjacent through holes. That is, the distance between two adjacent opposite light guide structures is a = 3d, and the distance between two adjacent light guide structures in the same tilt direction is a + d.

[0015] In the longitudinal grating, light guide structures with different tilt directions are alternately arranged near the middle position; four light guide structures facing the rear end are continuously arranged near the front end of the longitudinal grating, with a total interval length of L; four light guide structures facing the front end are continuously arranged near the rear end of the longitudinal grating, with a total interval length of L; where L=3(a+d).

[0016] The electric switch is used to control the light guide structure switch. With the cooperation of the electric switch, two light guide structures spaced 4a+3d apart form a pair of cross lighting, with the lighting direction perpendicular to the movement direction of the cold-rolled steel, i.e., the longitudinal direction. Several pairs of longitudinal cross lighting are adjacent to each other and spliced ​​together to form a large-scale longitudinal lighting.

[0017] The connecting structure includes a connecting rod and two seat slots sleeved on the connecting rod. The connecting rod is provided with a lifting scale, and the seat slots are fixed at a designated position on the connecting rod by a locking structure.

[0018] The array connector includes a locking extension structure with a rotating angle disc. The locking extension structure is arc-shaped and fixes several lighting units to the seat groove by a knob.

[0019] The relative distance between the upper and lower surface lighting bodies can be changed by adjusting the positions of the two seat slots on the connecting rod, and the lighting angle between the upper and lower surface lighting bodies can be changed by adjusting the knob.

[0020] Furthermore, no lighting units are provided on the central axis of the upper surface lighting body and the lower surface lighting body, and the lighting units in other directions are arranged with different light emission angles; the overall arrangement direction of each lighting unit is parallel to the movement direction of the cold-rolled steel, and they emit light independently without being related to each other.

[0021] The present invention also provides three applications for detection using the lighting device of the present invention.

[0022] A method for detecting longitudinal scratches on the surface of cold-rolled steel includes the following steps:

[0023] Step 1: Pass the long strip of cold-rolled steel through the middle of the upper surface lighting body and the lower surface lighting body, and adjust the angle between the upper surface lighting body and the lower surface lighting body and the cold (2) according to the requirements;

[0024] Step 2: Turn on the corresponding RGB LEDs on the LED array according to the position of the cold-rolled steel strip, and turn on the corresponding number of RGB LEDs according to the width of the cold-rolled steel strip.

[0025] Step 3: Turn on the electric switch of the through hole on the vertical grating, and turn on the electric switch of the corresponding through hole and light guide structure according to the lit RGB LED, and turn off the electric switch of the corresponding through hole and light guide structure of the unlit RGB LED.

[0026] Step 4: Based on the surface characteristics of cold-rolled steel, switch the LED array light to one of four colors: red, green, blue, and white, and select the one with the best lighting effect for testing;

[0027] Step 5: The longitudinal scratches on the surface of the cold-rolled steel strip are illuminated on both sides by longitudinal cross light in the vertical direction, which makes it easier for the high-speed linear array camera to detect the longitudinal scratches on the surface.

[0028] A method for detecting surface defects in cold-rolled steel includes the following steps:

[0029] Step 1: Pass the long strip of cold-rolled steel through the middle of the upper surface lighting body and the lower surface lighting body, and adjust the distance between the upper surface lighting body, the lower surface lighting body and the surface of the cold-rolled steel as needed; at the same time, adjust the angle between the upper surface lighting body and the lower surface lighting body.

[0030] Step 2: Turn on the corresponding RGB LEDs on the LED array according to the position of the cold-rolled steel strip, and turn on the corresponding number of RGB LEDs according to the width of the cold-rolled steel strip.

[0031] Step 3: Turn on the electric switch of the through hole on the vertical grating (9), and turn on the electric switch of the corresponding through hole and light guide structure according to the lit RGB LED, and turn off the electric switch of the corresponding through hole and light guide structure of the unlit RGB LED.

[0032] Step 4: Based on the surface characteristics of cold-rolled steel, switch the LED array light to one of four colors: red, green, blue, and white, and select the one with the best lighting effect for testing;

[0033] Step 5: Arrange the two high-speed line scan cameras perpendicular to the upper and lower surfaces of the cold-rolled steel, respectively, and align them with the central axes of the upper and lower surface lighting bodies, respectively.

[0034] Step 6: The high-speed linear array camera receives the reflected and scattered light from the cold-rolled steel as it moves, captures information about the upper and lower surfaces, and further identifies defects.

[0035] A method for detecting the surface of cold-rolled steel under bright and dark illumination includes the following steps:

[0036] Step 1: Pass the long strip of cold-rolled steel through the middle of the upper surface lighting body and the lower surface lighting body. Adjust the distance between the upper surface lighting body, the lower surface lighting body, and the surface of the cold-rolled steel as needed. At the same time, adjust the angle between the upper surface lighting body and the lower surface lighting body, and record the reading of the rotation angle disk on the array connector as a.

[0037] Step 2: Turn on the corresponding RGB LEDs on the LED array according to the position of the cold-rolled steel strip, and turn on the corresponding number of RGB LEDs according to the width of the cold-rolled steel strip.

[0038] Step 3: Turn on the electric switch of the through hole on the vertical grating, and turn on the electric switch of the corresponding through hole and light guide structure according to the lit RGB LED, and turn off the electric switch of the corresponding through hole and light guide structure of the unlit RGB LED.

[0039] Step 4: Based on the surface characteristics of cold-rolled steel, switch the LED array light to one of four colors: red, green, blue, and white, and select the one with the best lighting effect for testing;

[0040] Step 5: Arrange the two high-speed line scan cameras obliquely, determine the angle θ between the shooting direction of the high-speed line scan cameras and the surface of the cold-rolled steel, and obtain the corresponding structural parameters of the lighting device based on the calculations below:

[0041] β=θ+a

[0042] Where β is the angle corresponding to the lighting unit when the lighting device provides bright field illumination, and α is the deviation angle between the central axis of the lighting body and the normal of the surface of the detected object. When the upper surface lighting body or the lower surface lighting body rotates away from the line scan camera, α is a positive value, and when the upper surface lighting body or the lower surface lighting body rotates towards the line scan camera, α is a negative value.

[0043] Step 6: Activate the lighting device according to the actual detection requirements. When the bright field is illuminated, activate the lighting unit within the corresponding angle β in the lighting device. At this time, the surface information of the detected object, including the longitudinal surface information, is directly reflected into the target surface of the line array camera.

[0044] Step 7: When the dark field is illuminated, the illumination unit other than the corresponding angle β in the illumination device is activated. At this time, the surface information of the detected object, including the longitudinal surface information, is scattered and enters the target surface of the linear array camera.

[0045] Step 8: When the bright field and dark field are illuminated simultaneously, all illumination units of the illumination device are activated. At this time, the surface information of the detected object, including the longitudinal surface information, is received by the target surface of the line scan camera.

[0046] Compared with the prior art, the present invention has the following beneficial effects:

[0047] This invention can simultaneously illuminate both the upper and lower surfaces of an object, and achieve multi-directional linear illumination at multiple angles (longitudinal and transverse) relative to the object's direction of movement. During detection, four colors of light—red, green, blue, and white—can be selected for illumination based on the object's surface characteristics. Furthermore, partial illumination can be applied according to the width of the object's surface, enhancing surface information and reducing false negatives. It overcomes the limitation of traditional linear illumination, which is limited to transverse illumination, enabling the detection of longitudinal scratches. In addition, this invention allows for flexible adjustment of rotation and illumination distance based on the detection system layout, and can also be configured with bright field, dark field, or a combination of both, providing hardware enhancements for the final imaging results. Attached Figure Description

[0048] Figure 1 This is a schematic diagram of the overall structure of a multi-directional linear lighting device for online detection of cold-rolled steel according to the present invention;

[0049] Figure 2 This is a schematic diagram of the lighting unit in this invention;

[0050] Figure 3 This is a schematic diagram of the longitudinal grating in this invention;

[0051] Figure 4 This is a schematic diagram of the longitudinal lighting of the present invention;

[0052] Figure 5 This is a schematic diagram of the lighting unit array in this invention;

[0053] Figure 6 This is a schematic diagram of the structure of the lighting body in this invention;

[0054] Figure 7 This is a schematic diagram of longitudinal scratch detection of cold-rolled steel using a multi-directional linear lighting device in Example 1;

[0055] Figure 8 This is a schematic diagram of the use of a multi-directional linear lighting device to inspect the upper and lower surfaces of cold-rolled steel in Example 2;

[0056] Figure 9 This is a schematic diagram of the bright and dark field illumination detection of the surface of cold-rolled steel using a multi-directional linear illumination device in Example 3. Detailed Implementation

[0057] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be noted that the embodiments described below are intended to facilitate the understanding of the present invention and do not constitute any limitation thereof.

[0058] like Figure 1 As shown, a multi-directional linear lighting device for online inspection of cold-rolled steel includes an upper surface lighting body 1, a lower surface lighting body 2, and a connecting structure 3. The upper surface lighting body 1 and the lower surface lighting body 2 have the same structure, both consisting of an array of lighting units and an array connector 111, wherein the array of lighting units consists of several lighting units.

[0059] like Figure 2 As shown, each lighting unit consists of a housing 4, an LED array 5, a focusing device 6, a horizontal grating 7, a homogenizing device 8, and a vertical grating 9. The housing 4 comprises a heat sink 411, a shell, and a light outlet 412. The heat sink 411 covers the upper surface of the shell. The shell encapsulates the LED array 5, the focusing device 6, the horizontal grating 7, the homogenizing device 8, and the vertical grating 9. The light outlet 412 restricts the output light source to prevent light divergence. The LED array 5 consists of several RGB LED beads arranged in a line. Each RGB LED bead emits light independently and can be controlled to emit red, green, blue, and white light. The focusing device 6 is a linear device made of an optically transmissive material that can converge the divergent light generated by the LED array 5. The horizontal grating 7 further eliminates stray light within the lighting unit and reduces the divergence angle of the light source. The homogenizing device 8 homogenizes the light passing through the horizontal grating 7, and the vertical grating 9 finally controls the lighting direction, shaping the light source into a longitudinally intersecting beam perpendicular to the direction of object movement.

[0060] like Figure 3 As shown, the longitudinal grating 9 has several square through holes and light guide structures 912. Each through hole corresponds one-to-one with a light guide structure 912, and each through hole has an electric switch 911. The side length of each through hole is d; the distance between adjacent through holes near the middle of the longitudinal grating 9 is d; the distance between adjacent through holes near the ends of the longitudinal grating 9 is a, where a = 3d. Each light guide structure 912 is arranged at an angle, with the angle pointing towards the front or rear end of the longitudinal grating 9.

[0061] The distance between two adjacent back-to-back light guide structures 912 is d. The distance between two adjacent opposite light guide structures 192 is composed of the side lengths of two through holes and the interval between adjacent through holes. That is, the distance between two adjacent opposite light guide structures 192 is a = 3d. The distance between two adjacent light guide structures 912 with the same tilt direction is a + d.

[0062] In the longitudinal grating 9, light guide structures 192 with different tilt directions are alternately arranged near the middle position; four light guide structures 192 facing the rear end are continuously arranged near the front end of the longitudinal grating 9, with a total interval length of L; four light guide structures 192 facing the front end are continuously arranged near the rear end of the longitudinal grating 9, with a total interval length of L; where L=3(a+d).

[0063] The LED array 5 can be partially lit. When the LED array 5 is partially lit, the electric switch 911 on the vertical grating 9 corresponding to the unlit part is in the closed state, and the electric switch 911 corresponding to the lit part is in the open state, and the light source is output by the corresponding light guide structure 912.

[0064] like Figure 4 As shown, with the cooperation of the electric switch 911, two light guide structures 912 spaced L+a=4a+3d apart form a pair of intersecting lights, with the lighting direction perpendicular to the direction of the object's movement, i.e., the longitudinal direction. Several pairs of longitudinally intersecting lights are adjacent to each other and can be further spliced ​​together to form a longitudinal lighting with a larger illumination range.

[0065] like Figure 5 As shown, the upper surface lighting unit 1 and the lower surface lighting unit 2 are composed of several lighting units spliced ​​together parallel to the direction of the object's movement, and each unit emits light independently without any connection to the others. There are no lighting units on the central axis, and the lighting units in other directions are arranged with different light emission angles. For example... Figure 6 As shown, the array connector 111 consists of a rotating angle disk, a locking extension structure, and a knob. The various lighting units are arranged and fixed into an upper surface lighting body 1 or a lower surface lighting body 2 through the array connector 111.

[0066] like Figure 1 As shown, the upper surface lighting body 1 and the lower surface lighting body 2 are assembled with the seat groove 311 of the connecting structure 3 via the locking extension structure in the array connector 111. The connecting structure 3 has a locking structure and a lifting scale. By adjusting the up and down position of the seat groove 311, the relative distance between the upper surface lighting body 1 and the lower surface lighting body 2 can be changed. On the seat groove 311, in conjunction with rotating the knob of the array connector 111, the upper surface lighting body 1 or the lower surface lighting body 2 can be rotated relative to the connecting structure 3 to change the lighting angle.

[0067] The following three examples illustrate three applications of the lighting device of the present invention for detection.

[0068] Example 1

[0069] like Figure 7 As shown, a method for detecting longitudinal scratches on the surface of cold-rolled steel can be used to detect longitudinal scratches on the surface of long strip products of different widths, such as industrial cold-rolled steel, and includes the following steps:

[0070] Step 1: Pass the long strip of cold-rolled steel through the middle of the upper surface lighting body 1 and the lower surface lighting body 2, and then adjust the connecting structure 3 to raise and lower the lighting device so that the edge of the detected object is parallel to the zero mark on the lifting structure of the connecting structure; and adjust the distance between the upper surface lighting body 1, the lower surface lighting body 2 and the surface of the detected object as needed, and lock them through the locking structure of the connecting structure 3.

[0071] Step 2: Based on the layout of the detection system, rotate the upper surface lighting body 1 and the lower surface lighting body 2 through the connecting structure 3, and fix the angle through the knob of the array connector 111.

[0072] Step 3: Turn on the corresponding RGB LEDs on LED array 5 according to the position of the cold-rolled steel strip, and turn on the corresponding number of RGB LEDs according to the width of the cold-rolled steel strip.

[0073] Step 4: Turn on the electric switch of the through hole on the vertical grating 9, and turn on the electric switch of the corresponding through hole and light guide structure according to the lit RGB LED, and turn off the electric switch of the corresponding through hole and light guide structure of the unlit RGB LED.

[0074] Step 5: Based on the surface characteristics of the cold-rolled steel, switch the LED array 5 lights to one of the four colors: red, green, blue, and white, and select the one with the best lighting effect for testing.

[0075] At this time, the longitudinal scratches on the surface of the cold-rolled steel strip are illuminated on both sides in the vertical direction, so that the high-speed linear array camera can detect more comprehensive surface information.

[0076] Example 2

[0077] like Figure 8 As shown, a method for detecting surface defects in cold-rolled steel can be used to inspect the upper and lower surfaces of industrial cold-rolled steel strips of equal length, and includes the following steps:

[0078] Step 1: Pass the long strip of cold-rolled steel through the middle of the upper surface lighting body 1 and the lower surface lighting body 2, and then adjust the connecting structure 3 to raise and lower the lighting device so that the edge of the detected object is parallel to the zero mark on the lifting structure of the connecting structure; and adjust the distance between the upper surface lighting body 1, the lower surface lighting body 2 and the surface of the detected object as needed, and lock them through the locking structure of the connecting structure 3.

[0079] Step 2: Turn on the corresponding RGB LEDs on LED array 5 according to the position of the cold-rolled steel strip, and turn on the corresponding number of RGB LEDs according to the width of the cold-rolled steel strip.

[0080] Step 3: Turn on the electric switch of the through hole on the vertical grating 9, and turn on the electric switch of the corresponding through hole and light guide structure according to the lit RGB LED, and turn off the electric switch of the corresponding through hole and light guide structure of the unlit RGB LED.

[0081] Step 4: Based on the surface characteristics of cold-rolled steel, switch the LED array 5 to one of the four colors: red, green, blue, and white, and select the one with the best lighting effect for detection.

[0082] Step 5: Two high-speed line scan cameras are set perpendicular to the upper and lower surfaces of the cold-rolled steel, respectively, and aligned with the central axes of the upper surface lighting body 1 and the lower surface lighting body 2.

[0083] Step 6: The high-speed linear array camera receives the reflected and scattered light from the cold-rolled steel as it moves, and captures information about the upper and lower surfaces.

[0084] Example 3

[0085] like Figure 9 As shown, a method for detecting the surface of cold-rolled steel under bright and dark illumination includes the following steps:

[0086] Step 1: Based on the layout of the detection system, rotate the upper surface lighting body 1 and the lower surface lighting body 2 through the connecting structure 3, and lock the lighting device through the locking structure of the connecting structure 3. Then, rotate the angle dial to check the reading α according to the angle.

[0087] Step 2: Turn on the corresponding RGB LEDs on LED array 5 according to the position of the cold-rolled steel strip, and turn on the corresponding number of RGB LEDs according to the width of the cold-rolled steel strip.

[0088] Step 3: Turn on the electric switch of the through hole on the vertical grating 9, and turn on the electric switch of the corresponding through hole and light guide structure according to the lit RGB LED, and turn off the electric switch of the corresponding through hole and light guide structure of the unlit RGB LED.

[0089] Step 4: Based on the surface characteristics of cold-rolled steel, switch the LED array 5 to one of the four colors: red, green, blue, and white, and select the one with the best lighting effect for detection.

[0090] Step 5: Determine the angle θ between the high-speed linear scan camera's shooting direction and the surface of the product being inspected based on the layout of the detection system, and calculate the corresponding structural parameters of the lighting device based on the following calculations:

[0091] β=θ+a

[0092] Where β is the angle corresponding to the lighting unit when the lighting device provides bright field illumination, and α is the deviation angle between the central axis of the lighting body and the normal of the surface of the detected object. When the upper surface lighting body 1 or the lower surface lighting body 2 rotates away from the line scan camera, α is a positive value, and when the upper surface lighting body 1 or the lower surface lighting body 2 rotates towards the line scan camera, α is a negative value.

[0093] Step 6: Activate the lighting device according to the actual detection requirements. When the bright field is illuminated, the β illumination unit of the lighting device is activated. At this time, the surface information of the object being detected, including the longitudinal surface information, is directly reflected onto the target surface of the line array camera.

[0094] Step 7: When the dark field is illuminated, the illumination unit other than the β illumination unit is activated. At this time, the surface information of the detected object, including the longitudinal surface information, is scattered and enters the target surface of the linear array camera.

[0095] Step 8: When the bright field and dark field are illuminated simultaneously, all illumination units of the illumination device are activated. At this time, the surface information of the object, including the longitudinal surface information, is received by the target surface of the line scan camera.

[0096] The embodiments described above provide a detailed explanation of the technical solutions and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, additions, and equivalent substitutions made within the scope of the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A multi-directional linear lighting device for online inspection of cold-rolled steel, characterized in that, It includes an upper surface lighting body (1) and a lower surface lighting body (2) that are adjustable and fixed by a connecting structure (3); The upper surface lighting body (1) and the lower surface lighting body (2) have the same structure, both including several lighting units fixed by array connectors (111); Each lighting unit includes a housing (4) consisting of a heat sink (411), a housing and a light outlet (412), and an LED array (5), a focusing device (6), a transverse grating (7), a homogenizing device (8) and a longitudinal grating (9) arranged sequentially in the housing along the direction from the heat sink (411) to the light outlet (412). The LED array (5) consists of several RGB LED beads arranged in a line, each RGB LED bead emitting light independently; the focusing device (6) is used to converge the light generated by the LED array (5); the horizontal grating (7) is used to eliminate stray light in the lighting unit and reduce the divergence angle of the light source; the homogenizing device (8) is used to homogenize the light passing through the horizontal grating (7); the vertical grating (9) is used to control the lighting direction and shape the light source into a vertically intersecting light perpendicular to the direction of object movement; The longitudinal grating (9) has several square through holes, each with a side length of d. The distance between adjacent through holes near the middle of the longitudinal grating (9) is d. The distance between adjacent through holes near both ends of the longitudinal grating (9) is a, where a = 3d. Each through hole has an electric switch (911) and a light guide structure (912) on its inner and outer sides respectively. Each light guide structure (912) is arranged at an angle, with the angle facing the front or rear end of the longitudinal grating (9).

2. The multi-directional linear lighting device for online inspection of cold-rolled steel according to claim 1, characterized in that, In the longitudinal grating (9), the distance between two adjacent back-to-back light guide structures (912) is d, and the distance between two adjacent opposite light guide structures (912) is composed of the side length of two through holes and the interval between adjacent through holes. That is, the distance between two adjacent opposite light guide structures (912) is a=3d, and the distance between two adjacent light guide structures (912) in the same tilt direction is a+d.

3. The multi-directional linear lighting device for online detection of cold-rolled steel according to claim 2, characterized in that, In the longitudinal grating (9), light guide structures (912) with different tilt directions are alternately arranged near the middle position; four light guide structures (912) facing the rear end are continuously arranged near the front end of the longitudinal grating (9), with a total interval length of L; four light guide structures (912) facing the front end are continuously arranged near the rear end of the longitudinal grating (9), with a total interval length of L; where L=3(a+d).

4. The multi-directional linear lighting device for online detection of cold-rolled steel according to claim 3, characterized in that, The electric switch (911) is used to control the switch of the light guide structure (912). With the cooperation of the electric switch (911), two light guide structures (912) spaced 4a+3d apart form a pair of cross lighting. The lighting direction is perpendicular to the movement direction of the cold-rolled steel, i.e., the longitudinal direction. Several pairs of longitudinal cross lighting are adjacent to each other and spliced ​​together to form a large range of longitudinal lighting.

5. The multi-directional linear lighting device for online inspection of cold-rolled steel according to claim 1, characterized in that, The connecting structure (3) includes a connecting rod and two seat grooves (311) sleeved on the connecting rod. The connecting rod is provided with a lifting scale, and the seat grooves (311) are fixed at a designated position on the connecting rod by a locking structure. The array connector (111) includes a locking extension structure with a rotating angle disk. The locking extension structure is arc-shaped and fixes several lighting units to the seat groove (311) by a knob. The relative distance between the upper surface lighting body (1) and the lower surface lighting body (2) can be changed by adjusting the position of the two seat slots (311) on the connecting rod, and the lighting angle of the upper surface lighting body (1) and the lower surface lighting body (2) can be changed by adjusting the knob.

6. The multi-directional linear lighting device for online inspection of cold-rolled steel according to claim 1, characterized in that, No lighting units are provided on the central axis of the upper surface lighting body (1) and the lower surface lighting body (2), and the lighting units in other directions are arranged with different light emission angles; the overall arrangement direction of each lighting unit is parallel to the movement direction of the cold-rolled steel, and they emit light independently without being related to each other.

7. A method for detecting longitudinal scratches on the surface of cold-rolled steel, characterized in that, The illumination is provided by the multi-directional linear lighting device for online detection of cold-rolled steel according to any one of claims 1 to 6, specifically including the following steps: Step 1: Pass the long strip of cold-rolled steel through the middle of the upper surface lighting body (1) and the lower surface lighting body (2), and adjust the distance between the upper surface lighting body (1), the lower surface lighting body (2) and the surface of the cold-rolled steel according to the requirements; at the same time, adjust the angle between the upper surface lighting body (1) and the lower surface lighting body (2); Step 2: Turn on the corresponding RGB LEDs on the LED array (5) according to the position of the cold-rolled steel strip, and turn on the corresponding number of RGB LEDs according to the width of the cold-rolled steel strip. Step 3: Turn on the electric switch of the through hole on the vertical grating (9), and turn on the electric switch of the corresponding through hole and light guide structure according to the lit RGB LED, and turn off the electric switch of the corresponding through hole and light guide structure of the unlit RGB LED. Step 4: Based on the surface characteristics of cold-rolled steel, switch the light of the LED array (5) to one of the four colors: red, green, blue and white, and select the one with the best lighting effect for detection; Step 5: The longitudinal scratches on the surface of the cold-rolled steel strip are illuminated on both sides by longitudinal cross light in the vertical direction, which makes it easier for the high-speed linear array camera to detect the longitudinal scratches on the surface.

8. A method for detecting surface defects in cold-rolled steel, characterized in that, The illumination is provided by the multi-directional linear lighting device for online detection of cold-rolled steel according to any one of claims 1 to 6, specifically including the following steps: Step 1: Pass the long strip of cold-rolled steel through the middle of the upper surface lighting body (1) and the lower surface lighting body (2), and adjust the distance between the upper surface lighting body (1), the lower surface lighting body (2) and the surface of the cold-rolled steel according to the requirements; at the same time, adjust the angle between the upper surface lighting body (1) and the lower surface lighting body (2); Step 2: Turn on the corresponding RGB LEDs on the LED array (5) according to the position of the cold-rolled steel strip, and turn on the corresponding number of RGB LEDs according to the width of the cold-rolled steel strip. Step 3: Turn on the electric switch of the through hole on the vertical grating (9), and turn on the electric switch of the corresponding through hole and light guide structure according to the lit RGB LED, and turn off the electric switch of the corresponding through hole and light guide structure of the unlit RGB LED. Step 4: Based on the surface characteristics of cold-rolled steel, switch the light of the LED array (5) to one of the four colors: red, green, blue and white, and select the one with the best lighting effect for detection; Step 5: Arrange the two high-speed line array cameras perpendicular to the upper and lower surfaces of the cold-rolled steel, respectively, and align them with the central axes of the upper surface lighting body (1) and the lower surface lighting body (2), respectively. Step 6: The high-speed linear array camera receives the reflected and scattered light from the cold-rolled steel as it moves, captures information about the upper and lower surfaces, and further identifies defects.

9. A method for detecting the surface of cold-rolled steel under bright and dark illumination, using the multi-directional linear illumination device for online detection of cold-rolled steel as described in any one of claims 1 to 6, specifically comprising the following steps: Step 1: Pass the long strip of cold-rolled steel through the middle of the upper surface lighting body (1) and the lower surface lighting body (2). Adjust the distance between the upper surface lighting body (1), the lower surface lighting body (2), and the surface of the cold-rolled steel as needed. At the same time, adjust the angle between the upper surface lighting body (1) and the lower surface lighting body (2), and record the reading on the rotation angle dial on the array connector (111). ; Step 2: Turn on the corresponding RGB LEDs on the LED array (5) according to the position of the cold-rolled steel strip, and turn on the corresponding number of RGB LEDs according to the width of the cold-rolled steel strip. Step 3: Turn on the electric switch of the through hole on the vertical grating (9), and turn on the electric switch of the corresponding through hole and light guide structure according to the lit RGB LED, and turn off the electric switch of the corresponding through hole and light guide structure of the unlit RGB LED. Step 4: Based on the surface characteristics of cold-rolled steel, switch the light of the LED array (5) to one of the four colors: red, green, blue and white, and select the one with the best lighting effect for detection; Step 5: Arrange the two high-speed line scan cameras obliquely, determine the angle θ between the shooting direction of the high-speed line scan cameras and the surface of the cold-rolled steel, and obtain the corresponding structural parameters of the lighting device based on the calculations below: in, β is the angle corresponding to the lighting unit when the lighting device illuminates the bright field, and α is the deviation angle between the central axis of the lighting body and the normal of the surface of the detected object. When the upper surface lighting body (1) or the lower surface lighting body (2) rotates away from the line scan camera, α is a positive value. When the upper surface lighting body (1) or the lower surface lighting body (2) rotates towards the line scan camera, α is a negative value. Step 6: Activate the lighting device according to the actual detection requirements. When the bright field is illuminated, activate the lighting unit within the corresponding angle β in the lighting device. At this time, the surface information of the detected object, including the longitudinal surface information, is directly reflected into the target surface of the line array camera. Step 7: When the dark field is illuminated, the illumination unit other than the corresponding angle β in the illumination device is activated. At this time, the surface information of the detected object, including the longitudinal surface information, is scattered and enters the target surface of the linear array camera. Step 8: When the bright field and dark field are illuminated simultaneously, all illumination units of the illumination device are activated. At this time, the surface information of the detected object, including the longitudinal surface information, is received by the target surface of the line scan camera.

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