Surface shape analysis system and light irradiator for surface shape analysis system

Abstract

In a surface shape analysis system that analyzes the surface shape of a workpiece in a single image using the illuminance difference stereo method, the solid angle of illumination of each analysis light at each point on the surface of the workpiece is made equal, and the size is made more compact. [Solution] A surface shape analysis system comprising: a light irradiator comprising a plurality of light sources that emit analytical light having different wavelength components or polarization directions; an optical system that guides each analytical light emitted from the plurality of light sources to the irradiated surface of a workpiece; an imaging device that separates and acquires each analytical light reflected from the irradiated surface; and an analysis unit that analyzes the image obtained for each analytical light by the imaging device to analyze the shape of the irradiated surface, wherein the optical system is configured to have different declination angles for each analytical light emitted from the plurality of light sources, and for each of the plurality of light sources, the solid angle of illumination at each point on the irradiated surface is equal.

Description

[Technical Field]

[0001] The present invention relates to a surface shape analysis system for analyzing the surface shape of a workpiece using the illuminance difference stereo method, and a light irradiator for the surface shape analysis system. [Background technology]

[0002] One method for analyzing the surface shape (three-dimensional information) of a workpiece is the illuminance difference stereo method (also known as the photometric stereo method). This method involves sequentially shining analysis light onto the workpiece from multiple directions (at least three directions) and calculating the normal vector of the workpiece surface from the differences in shadows, thereby analyzing the surface shape of the workpiece.

[0003] In this type of general illuminance difference stereo method, images are sequentially captured while switching the light illuminator that illuminates the workpiece with analytical light. Therefore, when applied to a moving workpiece, there is a problem in that slight positional shifts occur in each captured image, making it impossible to accurately analyze the surface shape.

[0004] In recent years, there have been methods that use multiple light irradiators that emit analytical light with a fixed polarization direction or wavelength component (color), allowing for simultaneous irradiation of a workpiece with analytical light of different polarization directions or wavelength components from multiple directions in a single image, thereby enabling analysis of the surface shape of a moving workpiece (for example, Patent Document 1). [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2022-100524 [Overview of the project] [Problems that the invention aims to solve]

[0006] Incidentally, in the analysis method using the illuminance difference stereo method with multiple light irradiators as described above, the solid angle of illumination of each light irradiator on the irradiated surface of the workpiece is adjusted by adjusting the installation position and tilt of the multiple light irradiators prepared for different wavelength components or polarization directions. However, there is a problem that the solid angle of illumination of the analysis light at each point on the irradiated surface of the workpiece will differ for each light irradiator. In addition, there is the problem that the size of the apparatus becomes large because multiple light irradiators are used.

[0007] This invention has been made in view of the above problems, and its main objective is to provide a surface shape analysis system that analyzes the surface shape of a workpiece in a single image using the illuminance difference stereo method, in which the solid angle of illumination of each analysis light at each point on the surface of the workpiece can be made equal, and the size can be made compact. [Means for solving the problem]

[0008] In other words, the surface shape analysis system of the present invention comprises a light irradiator equipped with a plurality of light sources that emit analysis light having different wavelength components or polarization directions from each other, and an optical system that guides each analysis light emitted from the plurality of light sources to the irradiated surface of a workpiece, an imaging device that separates and acquires each analysis light reflected from the irradiated surface, and an analysis unit that analyzes the image obtained for each analysis light by the imaging device to analyze the shape of the irradiated surface, wherein the optical system is configured such that the declination angle differs for each analysis light emitted from the plurality of light sources, and the solid angle of illumination at each point on the irradiated surface is equal for each of the plurality of light sources.

[0009] With this configuration, the optical system is set up so that the declination angle differs for each analysis light emitted from multiple light sources. This allows for the acquisition of multiple images with different shading in a single shot, enabling analysis of the workpiece surface shape using the illuminance difference stereo method. Furthermore, since the optical system is configured so that the solid angle of illumination is equal at each point on the irradiated surface for each of the multiple light sources, inspection can be performed under the same conditions at any point on the irradiated surface. Additionally, because the solid angle of illumination is equal at each point on the irradiated surface, unevenness in irradiance at each point on the workpiece surface can be reduced, allowing for more accurate analysis of the surface shape. Furthermore, since it incorporates multiple light sources and optical systems that produce such different shadows as a single light irradiator, there is no need to arrange multiple light irradiators side by side, allowing the entire device to be made more compact.

[0010] One embodiment of the surface shape analysis system is one in which the light irradiator irradiates the surface to be irradiated with line-shaped analysis light along a predetermined direction, and at each point on the surface to be irradiated, the solid angle of irradiation from the plurality of light sources on a plane parallel to the predetermined direction including the optical axis of the optical system is axially symmetric with respect to the optical axis of the optical system, and the declination angle of each of the plurality of light sources is axially symmetric with respect to the optical axis of the optical system. With this configuration, the asymmetry of the solid angle of illumination resulting from multiple light sources at each point on the illuminated surface can be eliminated. This eliminates the asymmetry of shading generated by each analysis light, allowing for more accurate analysis of the workpiece surface shape.

[0011] It is preferable that the plurality of light sources are arranged parallel to the predetermined direction and on a plane that includes the optical axis of the optical system. This method makes it suitable for use in a surface shape analysis system that analyzes workpieces being transported using line sensors.

[0012] The light irradiator comprises a housing that accommodates the plurality of light sources and the optical system, and it is preferable that the length of the effective irradiation range on the irradiated surface in the predetermined direction is greater than half the length of the housing. In this way, when the light irradiators are arranged in the line direction and in multiple stages in the transport direction, the effective irradiation areas of adjacent objects in the line direction can be overlapped, making it possible to analyze the surface shape of wide workpieces.

[0013] Preferably, the optical system includes a lens whose radius of curvature is rotationally symmetric with respect to the optical axis of the optical system, and the plurality of light sources are arranged such that their distances from the lens along the direction of the optical axis are different from each other. In this way, even without using multiple lenses, it is possible to reduce the declination angle for each analytical light emitted from the multiple light sources and the unevenness of the solid angle of illumination at each point on the illuminated surface, which are caused by the effects of field curvature and chromatic aberration.

[0014] It is preferable that the multiple light sources are arranged so that their central axes (optical axes) are inclined relative to one another. This method improves the efficiency of light utilization from light sources placed outside the optical axis of the optical system, and also reduces unevenness in irradiance along the line.

[0015] It is preferable that the aforementioned plurality of light sources have a light distribution narrower than that which follows Lambert's cosine law (Lambertian light distribution). In the case of Lambertian beam pattern, the light source needs to be tilted significantly to uniformly illuminate the effective illumination area. However, by using a light source with a narrower beam pattern than Lambertian, the tilt angle of the light source can be reduced, simplifying the structure.

[0016] In addition, the light irradiator for the surface shape analysis system of the present invention irradiates a workpiece with a plurality of analysis lights, separates and acquires each of the analysis lights reflected from the irradiated surface of the workpiece by an imaging device, and analyzes the imaging images obtained for each analysis light by the imaging device to analyze the shape of the irradiated surface. It is for a surface shape analysis system, and includes a plurality of light sources that emit analysis lights having different wavelength components or polarization directions, and an optical system that guides each of the analysis lights emitted from the plurality of light sources to the irradiated surface of the workpiece. The optical system is configured such that the declination angle is made different for each of the analysis lights emitted from the plurality of light sources, and for each of the plurality of light sources, the irradiation solid angle at each point on the irradiated surface is equal. By doing so, the same operational effects as those of the light irradiator of the present invention described above can be achieved.

Effects of the Invention

[0017] According to the present invention configured as described above, in a surface shape analysis system that analyzes the surface shape of a workpiece by one-time shooting using the illuminance difference stereo method, the irradiation solid angle of each analysis light at each point on the surface of the workpiece can be made equal, and the size can be made compact.

Brief Description of the Drawings

[0018] [Figure 1] Schematic view of the configuration of the surface shape analysis system according to an embodiment of the present invention viewed from the line direction. [Figure 2] Schematic view of the configuration of the surface shape analysis system according to the same embodiment viewed from the conveyance direction. [Figure 3] Schematic view for explaining the declination angle and the irradiation solid angle. [Figure 4] Schematic view for explaining the arrangement of the light sources of the light irradiator according to the same embodiment. [Figure 5] Schematic view for explaining the light distribution of the light sources of the light irradiator according to the same embodiment. [Figure 6] Schematic view showing the configuration of the surface shape analysis system according to another embodiment.

Modes for Carrying Out the Invention

[0019] A surface shape analysis system 100 according to one embodiment of the present invention will be described below with reference to the drawings.

[0020] The surface shape analysis system 100 of this embodiment is used to photograph a workpiece W being transported in a factory or the like and analyze its three-dimensional shape. Specifically, this surface shape analysis system 100 analyzes the three-dimensional shape of the workpiece W by calculating the normal vector of the workpiece W's surface using the illuminance difference stereo method (also called the photometric stereo method), which utilizes shading information obtained by irradiating the surface of the workpiece W from multiple different directions (hereinafter referred to as analysis light). Examples of workpieces W to be analyzed include, but are not limited to, ceramic products such as insulators and knives, ceramic substrates, glass epoxy substrates, solder, paper, and even those with fine irregularities formed on their surface, such as those with a matte finish.

[0021] Specifically, as shown in Figures 1 and 2, this surface shape analysis system 100 includes a light irradiator 1 that emits a line-shaped analysis light toward the irradiated surface Ws of a workpiece W being transported at a constant speed in one direction (referred to as the transport direction), an imaging device 2 which is a line sensor camera that acquires the analysis light reflected from the irradiated surface Ws of the workpiece W, and an analysis unit 3 that analyzes the captured image acquired by the imaging device 2 to analyze the surface shape of the workpiece W.

[0022] In this embodiment of the surface shape analysis system 100, the light irradiator 1 is equipped with a plurality of light sources 11 that emit linear analysis light with different wavelength components, and the imaging device 2 is configured to acquire each analysis light reflected from the irradiated surface Ws of the workpiece W separately. This surface shape analysis system 100 is a so-called one-shot method, configured to analyze the surface shape of the workpiece W by simultaneously irradiating the workpiece W with analysis light from the plurality of light sources 11.

[0023] The following describes each part.

[0024] The light irradiator 1 is arranged such that the longitudinal direction (also called the line direction) of the analytical light irradiated onto the irradiated surface Ws of the workpiece W is perpendicular to the transport direction of the workpiece W. Specifically, this light irradiator 1 comprises a plurality (in this case, three) of light sources 11 that emit analytical light with different wavelength components, an optical system 12 positioned in front of the light emission direction of the light sources 11 and guiding each analytical light emitted from the plurality of light sources 11 to the irradiated surface Ws of the workpiece W, and a rectangular parallelepiped housing 13 that houses the plurality of light sources 11 and the optical system 12. In this embodiment, the light irradiator 1 comprises three light sources 11, which are light-emitting diodes that emit red light, green light, and blue light as analytical light, respectively. These three light sources 11 are arranged parallel to the line direction and on a plane containing the optical axis C1 of the optical system 12, and simultaneously irradiate the workpiece W with analytical light from different directions.

[0025] Furthermore, in this embodiment, the light irradiator 1 is configured such that, in the line direction, the length of the effective irradiation range of the analytical light on the irradiated surface Ws of the workpiece W is greater than half the length of the housing 13. The effective irradiation range of the analytical light is the range in which the irradiation ranges of each of the multiple light sources 11 all overlap.

[0026] The imaging device 2 comprises an imaging optical system (not shown) such as a lens, a line sensor 21 that receives the analysis light that has passed through the imaging optical system and converts it into image data, and a housing that houses these components. The imaging device 2 is arranged such that the longitudinal direction of the line sensor 21 is perpendicular to the transport direction of the workpiece W, and its linear imaging area (i.e., the field of view of the imaging device 2) is arranged to overlap with the irradiation area of ​​the analysis light from the light irradiator 1 on the irradiated surface Ws of the workpiece W.

[0027] The line sensor 21 is a color sensor capable of acquiring light of different wavelength components separately. It is configured to simultaneously receive each analysis light reflected from the workpiece W after being irradiated by multiple light sources 11 provided by the light irradiator 1, and to output image data for each analysis light (each wavelength component, each color). More specifically, the line sensor 21 images the effective irradiation range on the irradiated surface Ws of the workpiece W at predetermined short time intervals and outputs the obtained line-shaped images to the analysis unit 3. The analysis unit 3 stitches together the acquired line-shaped images to generate one area image for each analysis light.

[0028] The analysis unit 3 is a general-purpose or dedicated computer equipped with a CPU, memory, display, etc. This analysis unit 3 analyzes the surface shape of the workpiece W by analyzing the captured image (in this case, an area image) obtained by the imaging device 2 for each analysis light reflected from the workpiece W using a predetermined algorithm. Specifically, the analysis unit 3 compares multiple (in this case, three) captured images to analyze the differences in brightness of each pixel, and uses the position of each light source 11 and the brightness information of each pixel to calculate the normal vector (surface orientation) of the surface of the workpiece W. Then, it reconstructs the three-dimensional shape of the workpiece W from the calculated normal vector.

[0029] However, in the surface shape analysis system 100 of this embodiment, the optical system 12 provided in the light irradiator 1 is a so-called Köhler optical system, configured such that the declination angle differs for each analysis light emitted from the plurality of light sources 11, and the solid angle of illumination (collimation half-angle) at each point on the irradiated surface Ws of the workpiece W is equal for each of the plurality of light sources 11. Here, the declination angle is the angle between the light ray emitted from the center of the light source 11 and reaching the irradiated surface Ws of the workpiece W, as shown in Figure 3, and the normal to the irradiated surface Ws of the workpiece W.

[0030] Specifically, this optical system 12 is composed of a single lens (aspherical lens) 12L whose radius of curvature is rotationally symmetric with respect to its optical axis. That is, the analysis light emitted from each light source 11 is irradiated onto the workpiece W through the lens 12L of the common optical system 12. The lens 12L has a shape that is cut into a rectangular shape extending in the line direction when viewed from the direction of its optical axis.

[0031] Also, as shown in FIG. 4, in the light irradiator 1 of the present embodiment, the plurality of light sources 11 are installed such that the distances from the lens 12L along the optical axis direction of the optical system 12 are different from each other so as to correct chromatic aberration and field curvature in the optical system 12.

[0032] Furthermore, as shown in FIG. 4, in the light irradiator 1 of the present embodiment, the plurality of light sources 11 are installed such that their central axes C2 are inclined with respect to each other so that the irradiance distribution on the effective irradiation surface of the irradiated surface Ws of the workpiece W becomes uniform.

[0033] Also, in the light irradiator 1 of the present embodiment, all of the plurality of light sources 11 have a light distribution I(θ) that is narrower than the light distribution (Lambert light distribution: cosθ) that is rotationally symmetric with respect to the central axis C2 and follows Lambert's cosine law. Specifically, for example, as shown in FIG. 5, if the focal length of the lens 12L is 200 mm, the effective irradiation range is 120 mm, and the declination angles θ d is 20°, θ LED is 35°, then the brightness ratio between the upper and lower parts of the effective irradiation range is the brightness ratio (upper / lower): [(L1 / L2) 2 x I (θ2) x (cosθ2) 2 x (cosθ 22 )] / [I (θ1) x (cosθ1) 2 x (cosθ 11 )], and the light distribution I (θ) of each light source 11 is made to have the relationship of I (θ) =(cosθ) 3.4 .

[0034] In this embodiment of the surface shape analysis system 100, the optical system 12 is configured to have different declination angles for each analysis light emitted from the multiple light sources 11. This allows for the acquisition of multiple images with different shadows in a single shot, enabling analysis of the surface shape of the workpiece W using the illuminance difference stereo method. Furthermore, the optical system 12 is configured such that the solid angle of illumination at each point on the irradiated surface Ws is equal for each of the multiple light sources 11. This reduces unevenness in irradiance at each point on the surface of the workpiece W, allowing for more accurate analysis of the surface shape. Moreover, since multiple light sources 11 that produce different shadows and the optical system 12 are provided as a single light irradiator 1, there is no need to arrange multiple light irradiators 1 side by side, making the entire device more compact.

[0035] Furthermore, since the system is composed of a single lens 12L whose radius of curvature is rotationally symmetric with respect to its own optical axis, and the multiple light sources 11 are arranged so that their distances from the lens 12L along the optical axis axis are different from each other, and their own optical axes are tilted relative to each other, it is possible to reduce the number of lenses 12L and thus lower manufacturing costs while correcting chromatic aberration and field curvature, and also to make the irradiance distribution uniform.

[0036] However, the present invention is not limited to the embodiments described above. For example, in the surface shape analysis system 100 of the above embodiment, the light irradiator 1 is a line light irradiator 1 that irradiates the surface of the workpiece W with line-shaped analysis light, and the imaging device 2 is a line sensor camera, but it is not limited to this. In the surface shape analysis system 100 of other embodiments, the light irradiator 1 irradiates planar analysis light, and the imaging device 2 may be an area sensor camera.

[0037] Furthermore, although the above embodiment included three light sources 11, the light irradiator 1 is not limited to this. In other embodiments, the light irradiator 1 may include four or more light sources 11 arranged in a linear direction.

[0038] Furthermore, in the above embodiment, the multiple light sources 11 emitted analytical light with different wavelength components from each other, but this is not limited to this. In other embodiments, the multiple light sources 11 may emit analytical light with different polarization directions when viewed from the imaging axis direction of the imaging device 2. In this case, the imaging device 2 may be a polarization camera capable of acquiring light with multiple different polarization directions separately from each other. Also, the light distribution of the multiple light sources 11 was rotationally symmetric, but this is not limited to this. Another optical system may be provided on the optical system 12 side of the multiple light sources 11 to make the light distribution of the multiple light sources 11 rotationally symmetric.

[0039] Furthermore, while the surface shape analysis system 100 of the above embodiment irradiates the workpiece W with analysis light from a single light irradiator 1, it is not limited to this. In other embodiments of the surface shape analysis system 100, two light irradiators 1 may be combined and arranged facing each other to form a set of light irradiators 1X, and multiple sets of such combined light irradiators 1X may be arranged in a row. For example, as shown in Figure 6, multiple sets of light irradiators 1X may be arranged in a row along the line direction and in multiple rows along the transport direction. The effective irradiation ranges of each light irradiator 1X may be arranged in the front row and back row along the transport direction to overlap with each other in the line direction. In this way, the surface shape of a wide workpiece W can be analyzed.

[0040] Furthermore, it goes without saying that the present invention is not limited to the embodiments described above, and various modifications are possible without departing from its spirit. [Explanation of Symbols]

[0041] 100 ···Surface shape analysis system 1...Light irradiator 11...Light source 12...Optical system 12L ··Lens 13 ··· cabinet 2. Imaging device 21 ···Line Sensor 3...Analysis section W ···Work Ws ···Irradiated surface C1···Optical axis of the optical system C2 ··· Central Axis

Claims

1. A light irradiator comprising: a plurality of light sources that emit analytical light with different wavelength components or polarization directions; and an optical system that guides each analytical light emitted from the plurality of light sources to the irradiated surface of the workpiece; An imaging device that separates and acquires each analytical light reflected from the irradiated surface, The imaging device includes an analysis unit that analyzes the captured image obtained for each analysis light to analyze the shape of the irradiated surface, A surface shape analysis system in which the optical system is configured such that the declination angle differs for each analysis light emitted from the plurality of light sources, and the solid angle of illumination at each point on the irradiated surface is equal for each of the plurality of light sources.

2. The surface shape analysis system according to claim 1, wherein the light irradiator irradiates the surface to be irradiated with a line-shaped analytical light along a predetermined direction, and at each point on the surface to be irradiated, the solid angle of irradiation from the plurality of light sources on a plane parallel to the predetermined direction including the optical axis of the optical system is axially symmetric with respect to the optical axis of the optical system, and the declination angle of each of the plurality of light sources is axially symmetric with respect to the optical axis of the optical system.

3. The surface shape analysis system according to claim 1, wherein the plurality of light sources are parallel to the predetermined direction and arranged along the line direction on a plane including the optical axis of the optical system.

4. The surface shape analysis system according to claim 3, wherein the light irradiator comprises a housing that houses the plurality of light sources and the optical system, and in the predetermined direction, the length of the effective irradiation range on the irradiated surface is greater than half the length of the housing.

5. The optical system is configured to include a single lens whose radius of curvature is rotationally symmetric with respect to the optical axis of the optical system, The surface shape analysis system according to claim 1, wherein the plurality of light sources are arranged such that their distances from the lens along the direction of the optical axis are different from each other.

6. The surface shape analysis system according to claim 1, wherein the plurality of light sources are arranged such that their central axes are inclined relative to one another.

7. The surface shape analysis system according to claim 6, wherein the plurality of light sources have a light distribution narrower than that which conforms to Lambert's cosine law.

8. A light irradiator for a surface shape analysis system that irradiates a workpiece with multiple analytical lights, separates and acquires each analytical light reflected from the irradiated surface of the workpiece using an imaging device, and analyzes the image obtained for each analytical light using the imaging device to analyze the shape of the irradiated surface, Multiple light sources that emit analytical light with different wavelength components or polarization directions, The system includes an optical system that guides each analytical light emitted from the plurality of light sources to the irradiated surface of the workpiece, The optical system is configured such that the declination angle differs for each analytical light emitted from the plurality of light sources, and the solid angle of illumination at each point on the irradiated surface is equal for each of the plurality of light sources.

Images