JP2020094877A - Optical evaluation device, optical evaluation method, test object conveyance method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique for detecting various defects with higher accuracy with a smaller device. An optical evaluation device is an illuminating unit having a transmitting portion through which light is transmitted and a non-transmitting portion having a light transmittance lower than that of the transmitting portion, and a light source is a portion other than the transmitting portion in the illuminating unit. It has a lighting unit provided in. Further, the optical evaluation device includes an imaging unit that photographs an object illuminated by a light source through a transmission unit, and a control unit that emits at least a part of a plurality of light sources in the illumination unit. The relative positional relationship between the light source and the lighting unit can be changed. [Selection diagram] Fig. 1

Description

The present invention relates to a technique for optically evaluating a test object.

There are various types of defects existing on a workpiece as a test object, such as scratches, unevenness, and unevenness of surface roughness. A visual inspector who visually determines these various types of defects determines whether or not each defect type is a defect based on the result of visual observation in the arrangement in which the defect is most visible. That is, since the optimum illumination direction and image pickup direction for each defect type are different for each defect type, in order to detect various defect types, improvement of the directional freedom of illumination and image pickup becomes a problem. As a solution to the problem, a configuration capable of partially emitting light from a hemispherical (dome) illumination and a coaxial incident illumination can be adopted (Patent Document 1).

JP, 2007-003543, A

However, in the configuration described in Patent Document 1, it is necessary to secure a long distance in the imaging optical axis direction because of the half mirror that realizes the hemispherical illumination and the coaxial epi-illumination, and the entire apparatus becomes large. There are challenges. Further, since the image pickup is performed through the half mirror, it is necessary that the image pickup visual field range is entirely included in the half mirror, and there is a problem that the degree of freedom of the image pickup direction becomes low. The present invention provides a technique for detecting various defects with higher accuracy in a smaller device.

One embodiment of the present invention is an illumination unit having a transmissive portion that transmits light and a non-transmissive portion having a light transmittance lower than that of the transmissive portion, wherein the light source is other than the transmissive portion in the illuminating portion. A lighting unit provided at a location, a shooting unit that shoots an object illuminated by the light source through the transmission unit, and control for causing at least a part of a plurality of light sources in the lighting unit to emit light. And a relative position relationship between the object to be inspected and the illumination unit is changeable.

According to the configuration of the present invention, various defects can be detected with higher accuracy in a smaller device.

The figure which shows the structural example of an optical evaluation apparatus. FIG. 3 is a diagram showing a configuration example of a lighting unit 101. Sectional drawing of the illuminating part 101. The flowchart of the process which optically evaluates the surface of the workpiece 11. The figure which shows the cross-sectional image of line-shaped bright-dark noise. The figure which shows the structural example of an optical evaluation apparatus. The figure which shows the structural example of the illuminating part 110. Sectional drawing of the illuminating part 110. The flowchart of the process which optically evaluates the surface of the workpiece|work 12.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In addition, the embodiment described below shows an example of a case where the present invention is specifically implemented, and is one of the specific examples of the configurations described in the claims.

[First Embodiment]
First, a configuration example of the optical evaluation device according to the present embodiment will be described with reference to FIG. The optical evaluation apparatus 1 optically evaluates the surface of a work 11 (inspection object) having gloss. The work 11 is, for example, a metal part or a resin part whose surface is polished, which is used for industrial products. On the surface of the work 11, defects related to the shape (scratches, irregularities, etc.) (hereinafter referred to as shape defects), defects related to scattering (unevenness of surface roughness, etc.) (hereinafter referred to as scattering defects), reflection Various defects due to surface properties such as defect related to the rate may occur. The optical evaluation apparatus 1 detects these defects by acquiring an image of the surface of the work 11 and evaluating a composite image generated from the image, and based on the result of the detection, for example, the work 11 is a non-defective product. Or it is a defective product. There are various methods for determining whether the product is a good product or a defective product. For example, if the difference between the surface texture measured from the image and the surface shape preset as the surface texture of the non-defective product is smaller than the threshold value, it is determined as the non-defective product, and if the difference is larger than the threshold value. Is determined to be a defective product.

Further, the optical evaluation apparatus 1 may include a transfer device (not shown) that transfers the work 11 to a specified position (for example, a conveyor, a robot, a slider, a manual stage, or the like). The transfer device can change the transfer destination of the work 11 according to the determination result of the non-defective product/defective product with respect to the work 11. For example, when the determination result for the work 11 is “non-defective”, the work 11 is sent to the next step. In the subsequent steps, the work 11 is combined with various other parts, for example, and finally completed as a product. On the other hand, when the determination result for the work 11 is “defective product”, the work 11 is sent to a process for recycling. In the step, the work 11 is subjected to a treatment for removing surface defects (for example, a treatment for polishing the surface). After this process is completed, the optical evaluation device 1 re-evaluates the non-defective product/defective product.

Further, the optical evaluation device 1 may include an illumination unit 101 that illuminates the work 11, and a camera 102 that is an imaging unit that captures the work 11 from above the illumination unit 101 through the illumination unit 101. The camera 102 can use an image sensor in which pixels are two-dimensionally arranged, such as a CCD image sensor or a CMOS image sensor. By using such an area sensor camera, an image of a wider area can be collectively acquired as compared with a line sensor camera, so that it is possible to evaluate the surface of a wide range of the work surface at high speed. The camera 102 may use a subject-side telecentric optical system.

Here, a configuration example of the illumination unit 101 according to the present embodiment is shown in FIG. As shown in FIG. 2, the illumination unit 101 includes a plurality of line-shaped transmissive portions 1011 that at least partially transmit light, and a plurality of line-shaped non-transmissive portions 1012 having a light transmittance smaller than that of at least the transmissive portion 1011. And have members arranged alternately in a prescribed direction at a constant period P. This "specified direction" is the X direction in FIG. In this member, the transmissive portion 1011 may be an opening or a space, and the non-transmissive portion 1012 may be a light-shielding mask, each of which is longer than the X direction in the Y direction and is arranged at intervals of P along the X direction. .. Further, the member including the transmissive portion 1011 and the non-transmissive portion 1012 is held by the frame portion 1013. That is, in the illumination unit 101 of FIG. 2, the transmissive portions 1011 and the non-transmissive portions 1012 are alternately arranged in a direction (X direction) orthogonal to the line direction (Y direction) at a constant period P (line pattern. ) Member.

A cross-sectional view of the illumination unit 101 is shown in FIG. The illumination unit 101 may further include LEDs 1014a to 1014h that are light sources. Each of the LEDs 1014a to 1014h has a plurality of LED elements and a diffusion plate, and functions as a linear light emitting member. Each of the LEDs 1014a to 1014h is provided in the corresponding non-transmissive portion 1012 of the plurality of non-transmissive portions 1012 (arranged in the Y direction), and light toward the work 11 (-Z direction in FIG. 3). Irradiate. In the example of FIG. 3, for example, the LED 1014a is provided on the non-transmissive portion 1012 at the left end in the X direction.

The illumination unit 101 irradiates the work 11 with striped pattern light. A part of the light reflected or scattered by the work 11 is blocked by the non-transmissive part 1012 of the illuminating part 101, and a part of the light is transmitted through the transmissive part 1011 of the illuminating part 101. Part of the light transmitted through the transmissive portion 1011 of the illumination unit 101 reaches the camera 102, and the camera 102 captures the reached light, so that the workpiece 11 can be captured via the illumination unit 101.

In the present embodiment, the light source is the LEDs 1014a to 1014h, which are linear light emitting members including a plurality of LED elements and a diffusion plate, but the configuration of the illumination unit 101 is not limited to such a configuration. For example, the illumination unit 101 may be realized by a striped pattern printed on a film with a material having a property of scattering light.

As shown in FIG. 1, the illumination unit 101 is held by a movable mechanism 103 that is a drive unit of the illumination unit 101. The movable mechanism 103 moves the illumination unit 101 in a direction (X direction) orthogonal to the line direction (Y direction) of the transmissive unit 1011 and the non-transmissive unit 1012. In the present embodiment, the movable mechanism 103 moves the illumination unit 101 in the X direction to change the relative positional relationship between the workpiece 11 and the illumination unit 101, but the same purpose can be achieved. If so, another method may be adopted. For example, by moving the work 11 with respect to the illumination unit 101, the relative positional relationship between the illumination unit 101 and the work 11 may be changed. Further, it is possible to move only the transmissive part 1011 and the non-transmissive part 1012 without moving the entire illuminating part 101.

The movable mechanism 103 is connected to the control unit 104. The control unit 104 is mounted, for example, as a substrate having a processor such as a CPU and a memory, and the processor executes processing using a computer program and data stored in the memory, whereby the illumination unit 101, the camera 102, and the movable mechanism. 103 is controlled synchronously. The control unit 104 controls the illumination unit 101, the camera 102, and the movable mechanism 103 to cause the illumination unit 101 to emit light, cause the movable mechanism 103 to move the illumination unit 101, and cause the camera 102 to capture a plurality of images. it can. The configuration is not limited to this as long as the same purpose can be achieved. For example, after manually moving the movable mechanism 103 to move the illumination unit 101, the illumination unit 101 and the camera 102 may be controlled by a manual trigger to cause the camera 102 to capture a plurality of images of the work 11. ..

The optical evaluation device 1 may further include a PC (personal computer) 105 as an image processing unit and a display 106 as a display unit. The PC 105 according to this embodiment evaluates the surface of the work 11 based on the plurality of images obtained by the camera 102 (optically evaluates the work 11). Here, a hardware configuration example of the PC 105 will be described.

The CPU 191 executes processing using computer programs and data stored in the RAM 192 and ROM 193. As a result, the CPU 191 controls the operation of the entire PC 105, and also executes or controls each process described as being performed by the PC 105.

The RAM 192 has an area for storing computer programs and data loaded from the ROM 193 and the external storage device 195, and data received from the outside (such as the control unit 104) via the I/F (interface) 196. Further, the RAM 192 has a work area used when the CPU 191 executes various processes. In this way, the RAM 192 can provide various areas as needed. The ROM 193 stores information that does not require rewriting, such as the setting data of the PC 105 and the boot program.

The operation unit 194 includes a user interface such as a keyboard, a mouse, and a touch panel, and can be operated by a user to input various instructions to the CPU 191.

The external storage device 195 is a large capacity information storage device represented by a hard disk drive device. The external storage device 195 stores an OS (operating system) and computer programs and data for causing the CPU 191 to execute or control each process described as being performed by the PC 105. The data stored in the external storage device 195 also includes data used as known data by the PC 105. The computer programs and data stored in the external storage device 195 are appropriately loaded into the RAM 192 under the control of the CPU 191, and are processed by the CPU 191.

The I/F 196 is for connecting an external device to the PC 105, and the I/F 196 is connected to the control unit 104, the display 106, and the like. For example, an image captured by the camera 102 is input to the PC 105 via the control unit 104 and the I/F 196 and stored in the RAM 192 or the external storage device 195.

The CPU 191, RAM 192, ROM 193, operation unit 194, external storage device 195, and I/F 196 are all connected to the bus 197. The device applicable to the image processing unit is not limited to the PC 105, and may be, for example, a device dedicated to image processing (base or the like). Further, although the control unit 104 and the PC 105 are separate devices in FIG. 1, the control unit 104 and the PC 105 may be integrated.

Next, the process of optically evaluating the surface of the work 11 performed using the optical evaluation apparatus 1 according to this embodiment will be described with reference to the flowchart of FIG. In step S11, the light amounts of the LEDs 1014a to 1014h are adjusted. The light amount adjustment of the LEDs 1014a to 1014h is performed based on the gradation value distribution of the image captured by the camera 102 of the work 11 via the illumination unit 101. First, the target of the gradation value range is set within the range in which the gradation value at the peak position of the gradation value distribution does not reach the saturated state. Next, the light amounts of the LEDs 1014a to 1014h are adjusted so that the respective peak positions of the gradation value distribution fall within the set target. The control of the light amount may be performed by the control unit 104 or the PC 105.

Next, in order to acquire a plurality of images required to create a composite image, the processing of steps S12 to S15 (shooting loop 1) is performed a plurality of times (here, N times: N is an integer of 3 or more). By repeating the shooting loop 1 N times, N images can be acquired.

In step S13, the control unit 104 controls the movable mechanism 103 to move the illuminating unit 101 from the reference position in the X direction by ΔX _i (1≦i≦N), so that the illuminating unit 101 and the work 11 are separated from each other. Change the relative positional relationship of. The control unit 104 controls the movable mechanism 103 to stop the movement of the illumination unit 101 after the movement of the illumination unit 101 is completed.

In step S14, the control unit 104 causes the LEDs 1014a to 1014h in the illumination unit 101 to simultaneously emit light, and then causes the camera 102 to take an image. The camera 102 captures the light, which is transmitted from the work 11 illuminated by the illumination unit 101 (a part of the light reflected or scattered by the work 11) through the transmission unit 1011 and reaches the camera 102. Hereinafter, the image obtained by the i-th shooting is referred to as I _i . In the following, the brightness value at the pixel position (x, y) in the image I _i is expressed as I _i (x, y). The above-mentioned reference position is not limited to a specific position, and for example, ΔX ₁ =0 and the position of the first shooting may be used as the reference position. The image captured by the camera 102 is sent to the PC 105 via the control unit 104 and stored in the RAM 192 or the external storage device 195.

In step S16, the CPU 191 executes the following process. In other words, when the relative position (position in the X direction) between the illumination unit 101 and the work 11 changes by ΔX _i , the N pieces of information are used by using the information regarding the intensity change of the frequency component whose phase is shifted by 4πΔX _i /P radian. Generate a composite or processed image from the image. This frequency component is a frequency component corresponding to, for example, a striped pattern having a period P/2, which is generated on the image.

An example of a composite image is an amplitude image of frequency components whose phase shifts by 4πΔX _i /P radians. When the relative position in the X direction between the illumination unit 101 and the work 11 is shifted in steps of P/N (equal spacing) width, ΔX _i (i=1, 2,... N) is expressed by the following equation. To be done.

This expression includes the case where ΔX ₁ =0. When the image (I ₁ ) captured first is an image captured at a position changed from the reference position, ΔX _i is represented by the following formula.

At this time, the amplitude image A(x, y) can be calculated by the following formula.

This is a processed image including information about the surface of the test object, which is obtained by processing N images (N≧3). Further, it is a processed image generated using information regarding the intensity change of the frequency component (for example, the frequency component corresponding to the striped pattern of the period P/2) whose phase shifts by 4πΔX _i /P radian.

When the illumination unit 101 is moved, the brightness of the intensity changes at one point on the pixel of the camera 102. With respect to the work 11 having gloss, an amplitude corresponding to the difference between the light and dark is generated in a portion where the surface has normal gloss. On the other hand, in a portion having a defect such as a scratch or a minute unevenness, the difference in brightness is small, and the amplitude value is also small. Therefore, the shape image and the scattering defect can be visualized in the amplitude image.

Another example of the composite image is a phase image of frequency components whose phase shifts by 4πΔX _i /P radian. The phase image θ(x, y) can be calculated by the following formula.

Here, since the phase is calculated with a value of −π to π, if the phase changes more than that, discontinuity of the phase occurs in the phase image. For this reason, phase connection (phase unwrap) is necessary if necessary.

Although various algorithms have been proposed for phase unwrapping, an error may occur when the image noise is large. As a method for avoiding the phase connection, a phase difference corresponding to the phase differentiation may be calculated. The phase differences Δθ _x (x, y) and Δθ _y (x, y) can be calculated by the following formulas.

An example of a further composite image is the average image. The average image I _ave (x, y) can be calculated by the following formula.

At the start of step S16, for each of the N relative positions in the X direction with respect to the work 11, the light from the work 11 irradiated by the illumination unit 101 at the relative position is transmitted through the transmission unit 1011 to the camera 102. An image of the incoming light is obtained. That is, N images are obtained. Then, when the process of step S16 is completed, a composite image of these N images is obtained.

In the above-mentioned phase image, the inclination of the surface of the work 11 can be evaluated as the surface texture of the work 11. Therefore, in the phase image, it is possible to obtain information on a shape defect caused by a gradual shape change such as a depression on the surface of the work 11, and it is also possible to visualize it. Further, in the average image, the distribution of reflectance can be evaluated as the surface texture of the work 11. Therefore, in the average image, it is possible to obtain information on defects such as color loss, stains, and absorptive foreign matter that have a difference in reflectance from a normal portion, and it is possible to visualize defects related to reflectance.

However, depending on the type of defect, the visible illumination direction may be limited due to the influence of its reflection characteristic, and the defect may not be detected in the above-described combined image. In this case, it is necessary to further perform visualization with illumination suitable for each defect. In particular, scattering defects are judged by visually inspecting them with dark-field illumination, whereas in the above-mentioned composite image, there is no image equivalent to dark-field illumination, and the defect is judged. As a result, there is a problem that there is a discrepancy with the visual inspector.

Therefore, in step S17 and subsequent steps, a process for generating a synthetic image for detecting a scattering defect that is difficult to detect with the above-described synthetic image is performed. In step S17, the control unit 104 adjusts the light amount of each of the LEDs 1014a to 1014h. The light amount adjustment index is such that the light amount adjustment is performed so that the gradation value of the defect portion to be detected is sufficiently higher than the peripheral gradation values in the dark field area on the image. In this case, the bright field region in the image obtained by photographing the work 11 by the camera 102 via the illumination unit 101 may be saturated. The bright field area is an area in which light from the LEDs 1014a to 1014h specularly reflects the work 11 and the specularly reflected light reaches the camera 102 via the illumination unit 101. The dark field area is an area outside the bright field area where the light specularly reflected from the work 11 does not reach.

Then, in order to acquire a plurality of images necessary to create a composite image composed of a dark field image, the processing of steps S18 to S20 (shooting loop 2) is performed a plurality of times (for each of the LEDs 1014a to 1014h). By performing the imaging loop 2 for each of the LEDs 1014a to 1014h, an image corresponding to each of the LEDs 1014a to 1014h can be acquired.

In step S<b>19, the control unit 104 causes the LEDs (light emitting target LEDs) to be emitted this time among the LEDs 1014 a to 1014 h in the illuminating unit 101 to emit light (LEDs other than the light emitting target LEDs do not emit light), and the camera 102 of the work 11 is used. Let's take a picture. In the present embodiment, in the first imaging loop 2, the LED 1014a among the LEDs 1014a to 1014h is caused to emit light as an emission target LED (LEDs other than the emission target LED are not allowed to emit light), and the camera 102 captures an image of the work 11. .. In the second shooting loop 2, the LED 1014b among the LEDs 1014a to 1014h is caused to emit light (LEDs other than the light emitting target LED are not made to emit light), and the camera 102 is caused to shoot the work 11. The camera 102 captures the light, which is transmitted from the work 11 illuminated by the illumination unit 101 (a part of the light reflected or scattered by the work 11) through the transmission unit 1011 and reaches the camera 102.

In this way, each of the LEDs 1014a to 1014h is sequentially made to emit light to perform photographing. As a result, a photographed image of the work 11 when the LED 1014a emits light, a photographed image of the work 11 when the LED 1014b emits light, and the like, the photographed images of the work 11 corresponding to the LEDs 1014a to 1014h are acquired. be able to.

Hereinafter, LED1014w (w = a, b , c, d, e, f, g, h) the image of the workpiece 11 captured by the camera 102 when the light is emitted is denoted as _{I w.} In the following, the brightness value at the pixel position (x, y) in the image I _w will be referred to as I _w (x, y).

The photographed image has the above-mentioned bright field region and the other dark field region. Taking the image I _a as an example, if _a scattering defect exists in the dark field region of the image I _a , the light from the LED 1014 a is scattered, and the light goes in a direction different from the specular reflection, and the light is captured by the camera 102. This makes it possible to take a bright image of the defect portion with respect to the surroundings. In this way, the light from the scattering defect can be visualized in the dark field region.

In the present embodiment, each of the LEDs 1014a to 1014h is individually caused to emit light to photograph the work 11. However, for example, the non-adjacent LEDs (for example, the LED 1014a, the LED 1014d, and the LED 1014g) may be made to emit light simultaneously so that the work 11 is imaged so that the dark field region can be acquired. With such a configuration, the number of times the work 11 is imaged is reduced, and the time required for image capture and image processing can be shortened as compared with the present embodiment.

Note that there is a further problem with the processing in step S19 described above. The problem is that a part of the light from the emitted LED is reflected and scattered by the work 11 and the illumination unit 101, reaches the illumination unit 101 again, and is further reflected and scattered to illuminate the work 11. Is to do. Therefore, the image of the illumination unit 101 is photographed as linear bright and dark noise on the image photographed by the camera 102. For example, when the LED 1014a is caused to emit light, a part of the light is reflected and scattered by the work 11 and the illumination unit 101 and reaches the LEDs 1014b to 1014h. Since the light reaching the LEDs 1014b to 1014h illuminates the work 11 again, the images of the LEDs 1014b to 1014h are reflected in the image, which causes light and dark noise. The countermeasure will be described in detail with reference to FIGS. 1, 2, 3, and 5.

FIG. 5 shows a cross-sectional image of the line-shaped bright and dark noise. In FIG. 5, the horizontal axis is the X coordinate of the camera 102, which is equivalent to the X coordinate on the work 11 in FIG. 1, and the vertical axis shows the sectional image in which the gradation values of the image obtained by the camera 102 are plotted. It is a thing. As shown in FIG. 5, the light-dark noise appears as a periodic (spatial period L) change in gradation value. The spatial period L of the light-dark noise is determined by the numerical aperture (NA) of the optical system of the camera 102, the duty of the transmissive part of the illumination part 101 including the transmissive part and the non-transmissive part, the focus position of the optical system of the camera 102, and the like. .. The spatial period L of the light-dark noise can be obtained by measurement in advance or theoretically calculated from the design value of the device.

As a countermeasure against the above-mentioned line-shaped bright-dark noise, when the image is taken by the camera 102, the movable mechanism 103 described above causes a direction (X direction in FIG. 2) orthogonal to the lines of the transmissive portion 1011 and the non-transmissive portion 1012. The illumination unit 101 is moved at a constant speed. The control unit 104 establishes a relationship represented by the following equation regarding the constant velocity V [m/s] of the illumination unit 101, the spatial period L [m] of the light and dark noise, and the exposure time T [s] of the camera 102. To set.

That is, when the work 11 is illuminated by a part of the LEDs, the presence of the member including the transmissive portion 1011 and the non-transmissive portion 1012 is the distance at which the relative position changes within the exposure time required for the camera 102 to capture an image. Is set to an integral multiple of the cycle of the light and dark pattern generated in the image. It is desirable to be an integral multiple, but if the error is 5% or less (more preferably 3% or less), it may deviate from an integer multiple.

According to such a measuring method, the light-dark noise generated by the illumination unit 101 can be averaged for m periods, and the light-dark noise can be reduced by the averaging effect. In this embodiment, the movable mechanism 103 is used to move the illumination unit 101 at a constant speed. However, the same effect can be obtained by changing the positions of the camera 102 and the work 11 at a constant speed without moving the members. Be done.

Further, in the present embodiment, the configuration is such that the illumination unit 101 is moved at a constant speed within the exposure time of the camera 102, but it is also possible to perform a step movement in which the spatial period L of light-dark noise is divided into a plurality. In this case, the same effect can be obtained by acquiring a plurality of captured images for each step movement and averaging these images. Further, although the illumination unit 101 is moved by the movable mechanism 103, the relative position between the illumination unit 101 and the work 11 may be changed by moving the work 11 with respect to the illumination unit 101. In this case, the averaging of the plurality of captured images can be performed by performing the averaging after performing the image processing so that the positions of the works 11 on the images are the same. Image processing such as image averaging is performed by the CPU 191 of the PC 105.

Returning to FIG. 4, next, in step S21, the CPU 191 (generation unit) converts the images I _a , I _b , I _c , I _d , I _e , I _f , I _g , and I _h into a dark-field image. Generate a corresponding composite image.

First, NaN (Not a Number), which means invalid data, is set to the pixels in the bright-field region in the images I _a , I _b , I _c , I _d , I _e , _If , I _g , and I _h . .. Image I _a (x, y), I _b (x, y), I _c (x, y), I _d (x, y), I _e (x, y), I _f (x, y), I _{Of g} (x, y) and I _h , the maximum brightness value of the brightness values of the pixels for which NaN is not set is the brightness value of the pixel position (x, y) in the composite image.

The bright field area and the dark field area may be divided based on the gradation value obtained from the image, or may be divided into areas that are predicted in advance by optical simulation or the like. Further, when it is not desired to visualize the shape defect in the dark field image, invalid data may be set to the pixels in the area near the bright field area. The reason is that the shape defect is detected only in the vicinity of the bright field region, with respect to the normal part other than the defect, the defect part can be detected with a high gradation value, while the scattering defect is detected over the entire dark field region. This is because there is a difference that a defective portion can be detected with a high gradation value with respect to a normal portion other than a defect.

In step S22, the CPU 191 detects a defect on the surface of the work 11 based on the composite image generated in step S16 and the composite image generated in step S21.

In the present embodiment, after performing the process of setting invalid data in the bright field area, the dark field image is created by taking the maximum value for each pixel, but for each pixel (maximum value-minimum value), The calculation result such as the standard deviation may be used. Further, in order to reduce the step of setting invalid data in the bright field area, the minimum value for each pixel may be used.

The optical evaluation device 1 according to the present embodiment generates a composite image including information about the surface of the work 11, detects a defect from the composite image, and performs a quality determination inspection of the work 11, for example. However, the application of the device such as the optical evaluation device 1 is not limited to the detection of defects on the surface of the work 11, and for example, using the information of the phase image including the information of the inclination of the surface of the work 11, the shape of the work surface is used. It may be used for measurement. Here, in step S22, each composite image may be displayed on the display 106, may be transmitted to an external device via the I/F 196, or may be stored in the external storage device 195. good.

In the present embodiment, various synthetic image generation methods such as an amplitude image, a phase image, and an average image according to the type of the result are described, but all synthetic images may be generated, or some synthetic images may be generated. May be generated. Further, a composite image (for example, a composite image suitable for detecting and visualizing the designated defect) corresponding to the “type of defect to be detected” designated by the user operating the operation unit 194 may be generated. ..

In this way, in order to visualize defects, a composite image composed of a phase shift method using pattern illumination and a dark field image using partial emission of pattern illumination results in different optically evaluable surface properties, It is possible to detect a variety of visualized defects. In particular, in defect detection using a composite image consisting of dark field images, defects can be detected from images that are equivalent to visual inspection during dark field illumination, which is mainly used by inspectors. Defects can be detected with high accuracy.

As described above, according to the present embodiment, in a device that uses transmissive pattern illumination, has a high degree of freedom in the arrangement of the imaging system and various lights, and is capable of downsizing the device, it is possible to further improve the accuracy and variety of defects. Can be detected.

[Second Embodiment]
The difference from the first embodiment will be described below, and the same as the first embodiment unless otherwise mentioned below. First, a configuration example of the optical evaluation device according to the present embodiment will be described with reference to FIG. The optical evaluation device 2 of FIG. 6 optically evaluates the surface of the work 12 (inspection object) having scattering properties. On the surface of the work 12, various defects due to shape defects, scattering defects and surface properties may occur. The optical evaluation device 2 detects these defects by acquiring an image of the surface of the work 12 and evaluating a composite image generated from the image, and based on the result of the detection, for example, the work 12 is a non-defective product. Or it is a defective product.

The difference between the optical evaluation apparatus 1 and the optical evaluation apparatus 2 is the illumination unit 101 in FIG. 1 and the illumination unit 110 in FIG. Here, a method of capturing an image using the illumination unit 110 will be described with reference to FIGS. 6, 7, and 8.

FIG. 7 shows a configuration example of the illumination unit 110. As shown in FIG. 7, the illumination unit 110 has a dot pattern. The illumination unit 110 includes a transmissive unit 1101 that at least partially transmits light, and a plurality of dot-shaped non-transmissive units 1102 having a light transmissivity smaller than at least the transmissive unit 1101. The plurality of dots (non-transmissive portions 1102) are arranged at regular intervals. A member including the transmissive portion 1101 and the non-transmissive portion 1102 is held by the frame 1103. Further, LEDs 1104Y1 to 1104Y7, which are light sources, are arranged side by side in the Y direction on the left and right of the frame 1103, and LEDs 1104X1 to 1104X7 are arranged side by side in the X direction above and below the frame 1103. The LEDs that are turned on at the same time are designated by the same reference numerals. Further, the LED used in this embodiment is preferably an LED having high directivity. The effect of using the LED with high directivity is that the illumination azimuth range with respect to the work 12 can be reduced, and further, by arranging a large number of LEDs with high directivity, various illumination azimuths can be realized. .. Further, in the present embodiment, a method of using the illumination unit 110 having a dot pattern for illuminating the work 12 having a scattering property will be described, but the illumination unit 101 having a line pattern may be used, and the same. The effect of is obtained.

A cross-sectional view of the illumination unit 110 is shown in FIG. The lighting unit 110 may further include a light guide plate 1105. The light guide plate 1105 is, for example, a flat plate of acrylic or glass. The non-transmissive portion 1102 can be realized, for example, by printing a dot pattern on a film using a material having a property of scattering light. In such a case, the film portion that is not printed with the material that scatters light becomes the transmissive portion 1101. The film on which the dot pattern is printed is attached to the light guide plate 1105 in close contact with it. Note that a dot-shaped pattern may be printed directly on the light guide plate 1105 using a material having a property of scattering light. That is, the light guide plate may have a portion where the dot pattern printed using a material having a property of scattering light is arranged as a non-transmissive portion and a portion other than the portion as a transmissive portion.

Light with high directivity emitted from the LED 1104Y1 which is one of the LEDs provided around the light guide plate 1105 travels while being totally reflected inside the light guide plate 1105. Since a material having a property of scattering light is used for the non-transmissive portion 1102, a part of the incident light is scattered toward the work 12. At this time, since the LED having high directivity is used, the light reaches only the non-transmissive portion 1102 around the left and right LEDs 1104Y1 connected by a straight line. Therefore, the illumination direction and the range of the work 12 can be limited. On the other hand, since the light is hardly scattered in the transmission part 1101, almost no light is emitted from the transmission part 1101 toward the work 12. Therefore, the illumination unit 110 projects the dot-shaped pattern light on the work 12. Part of the light scattered by the work 12 is blocked by the non-transmissive part 1102 of the illumination unit 110, and part of the light scattered by the work 12 is transmitted through the transmissive part 1101 of the illumination unit 110. By photographing the transmitted light with the camera 102, the camera 102 can photograph the work 12 via the illumination unit 110.

As shown in FIG. 6, the illumination unit 110 is held by the movable mechanism 103. The movable mechanism 103 moves the illumination unit 110 within a two-dimensional plane (XY plane) perpendicular to the optical axis of the camera 102. In the present embodiment, the movable unit 103 moves the illumination unit 110. However, by moving the work 12 with respect to the illumination unit 110, the relative positional relationship between the illumination unit 110 and the work 12 is changed. Is also good. Further, it is possible to use a known transmissive display or the like and move only the transmissive part 1101 and the non-transmissive part 1102 without moving the entire illuminating part 110.

The control unit 104 synchronously controls the illumination unit 110, the camera 102, and the movable mechanism 103. The control unit 104 controls the illumination unit 110, the camera 102, and the movable mechanism 103 to cause the illumination unit 110 to emit light, cause the movable mechanism 103 to move the illumination unit 110, and cause the camera 102 to capture a plurality of images. it can. The PC 105 according to this embodiment evaluates the surface of the work 12 (optically evaluates the work 12) based on the information on the plurality of images obtained by the camera 102.

The image taken by the above-mentioned method has a further problem like the first embodiment. The problem is that the illumination unit 110 becomes a two-dimensional light source (light source arranged in a two-dimensional shape), and dot-shaped bright and dark noise is captured on the image captured by the camera 102. As a countermeasure to this, the illumination unit 110 is moved in the XY plane to take an image, and the taken images are averaged to average the dot-like bright and dark noises.

Next, a process of optically evaluating the surface of the work 12 performed using the optical evaluation device 2 according to the present embodiment will be described with reference to the flowchart of FIG. 9. The illumination loop of steps S101 to S110 is performed for each of the cases where the variable ii is X1, X2, X3,..., X7, Y1, Y2, Y3,.

The Y drive group of steps S102 to S108 is a drive loop for taking an image necessary for averaging the light-dark noise in the Y direction, and for each variable jj of 1, 2, 3,..., N. To do.

The X drive group of steps S104 to S107 is an X drive loop for taking an image necessary for averaging the light-dark noise in the X direction, and when the variable kk is 1, 2, 3,..., N, respectively. Do about.

In step S103, the control unit 104 controls the movable mechanism 103 to move the illumination unit 110 by ΔYjj from the reference position in the Y direction, thereby changing the relative positional relationship between the illumination unit 110 and the work 12. Let

In step S105, the control unit 104 controls the movable mechanism 103 to move the lighting unit 110 from the reference position in the X direction by ΔXkk, thereby changing the relative positional relationship between the lighting unit 110 and the work 12. Let

In step S106, the control unit 104 acquires the image I _jj,kk by causing the LED 1104ii to emit light and then causing the camera 102 to perform shooting. This image is sent to the PC 105 via the control unit 104 and stored in the RAM 192 or the external storage device 195.

By performing the X drive group of steps S104 to S107 for each of the cases where the variable kk is 1, 2, 3,..., N, and the sum of the drive amounts in the X direction is an integral multiple of the dot-shaped bright and dark noise, An image is taken in which dot-like bright and dark noise can be averaged in the X direction. In order to obtain the maximum averaging effect, it is desirable that the driving amounts in the X and Y directions are constant.

In step S109, the CPU 191 obtains an average value of I _1,1 (x, y) to I _N,N (x, y), and sets the average value to “the composite image I _ii obtained when the LED 1104ii emits light”. Is the luminance value at the pixel position (x, y).

In step S111, the CPU 191 generates a composite image from the images I _X1 , I _X2 , I _X3 ,..., I _X7 , I _Y1 , I _Y2 , I _Y3 ,..., I _Y7 . The method of generating the composite image is not limited to a specific generation method, but for example, shading correction is performed on each image, and the image after shading correction is combined using the minimum value, the maximum value, and the average value for each pixel. The image is generated as described above.

In the minimum image, which is a composite image using the above-mentioned minimum value, and the maximum image, which is a composite image using the maximum value, it is possible to obtain and visualize information on a defect whose gradation value changes depending on the illumination direction such as a flaw. You can also Furthermore, in an average image that is a composite image using the average value, the distribution of reflectance can be evaluated as the surface texture. Therefore, in the average image, it is possible to obtain information on defects such as color loss, stains, and absorptive foreign matter that have a difference in reflectance from a normal portion, and it is possible to visualize defects related to reflectance. As described above, since the defects are visualized, various visualized defects can be detected by the combined image including the images using the partial light emission of the pattern illumination.

In step S122, the CPU 191 detects a defect on the surface of the work 12 based on the composite image generated in step S109 and the composite image generated in step S111.

As described above, according to the present embodiment, in a device that uses transmissive pattern illumination and has a high degree of freedom in the arrangement of the imaging system and various illuminations, and is capable of downsizing the device, it is possible to further increase the accuracy and variety of defects. Can be detected.

The set of the illumination unit 101 and the camera 102 in the first embodiment and the set of the illumination unit 110 and the camera 102 in the second embodiment are merely examples of the image capturing apparatus having the following configurations.

That is, the imaging device is an illumination unit having a transmissive portion through which light is transmitted and a non-transmissive portion having a light transmittance lower than that of the transmissive portion, and the light source is located at a location other than the transmissive portion in the illumination portion. The lighting unit is provided. Further, the imaging device includes an imaging unit that images an object illuminated by the light source via the transmission unit, and a control unit that causes at least a part of the plurality of light sources in the illumination unit to emit light. The relative positional relationship between the test object and the illumination unit can be changed. The usage of such an image capturing device is not limited to the above example, and thus the configuration of the device (system) having such an image capturing device is not limited to the above example. For example, in each of the above-described embodiments, a composite image is generated from a plurality of images for the purpose of detecting defects, but for other purposes, it is not essential to generate a composite image, and in some cases Individual captured images may be used for that purpose.

The above optical evaluation method is only an example of the following optical evaluation method. That is, the optical evaluation method is provided in a position different from the transmissive part included in the illumination part including the transmissive part through which light is transmitted and the non-transmissive part having a light transmittance lower than that of the transmissive part. The method has an illumination step of illuminating an object with a plurality of light sources. Furthermore, the optical evaluation method includes a photographing step of photographing the test object illuminated by a plurality of light sources through the transmission section, and a control step of causing at least a part of the plurality of light sources to emit light in the photographing step. , Is provided. Further, in the optical evaluation method, the relative positional relationship between the test object and the illumination unit can be changed.

In addition, the above-described method of conveying an object is merely an example of the following method of conveying an object. That is, the method of transporting an object is provided at a position different from the transmissive portion, which is included in the illuminating portion having the transmissive portion that transmits light and the non-transmissive portion that has a lower light transmittance than the transmissive portion. An illumination step of illuminating an object to be inspected using the plurality of light sources provided. Further, the method of transporting an object includes a photographing step of photographing the object illuminated by a plurality of light sources through the transmitting section, and a control of causing at least a part of the plurality of light sources to emit light in the photographing step. And steps. Furthermore, the method of transporting the test object includes a transport step of switching the transport destination of the test object based on the image captured in the image capturing step.

Note that the description in each of the above embodiments is an example, and various modifications and changes are possible. For example, various processes can be considered for the process for generating one image from a plurality of images such as the amplitude image, the phase image, and the average image (the image generating process according to the content to be evaluated for the test object). However, the generation method is not limited to the above. Further, the numbers (number of LEDs, number of transmissive portions or non-transmissive portions, number of images to be photographed, etc.) appearing in the above description are used as examples for specifically explaining the number. It is not intended to be limited to.

Further, some or all of the embodiments described above may be appropriately combined and used. Further, some or all of the embodiments described above may be selectively used.

(Other embodiments)
The present invention supplies a program that implements one or more functions of the above-described embodiments to a system or apparatus via a network or a storage medium, and one or more processors in a computer of the system or apparatus read and execute the program. It can also be realized by the processing. It can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

1: Optical evaluation device 101: Illumination unit 102: Camera 103: Moving mechanism 104: Control unit 105: PC 106: Display

Claims (12)

An illuminating unit having a transmissive part through which light passes and a non-transmissive part having a light transmittance lower than that of the transmissive part, wherein the light source is provided at a position other than the transmissive part in the illuminating part. The lighting unit,
An imaging unit that images the object illuminated by the light source through the transmission unit,
A control unit for causing at least a part of the plurality of light sources in the illumination unit to emit light;
Equipped with
An optical evaluation apparatus, wherein a relative positional relationship between the object to be inspected and the illumination unit can be changed. The optical evaluation device according to claim 1, wherein the image capturing unit captures an image of the object from above the illumination unit via the transmitting unit. The illumination unit has a member in which the linear transmissive portion and the linear non-transmissive portion are alternately arranged,
The optical evaluation device according to claim 1 or 2, wherein the light source is provided in the non-transmissive portion and irradiates the test object with light. The illumination unit has a light guide plate having a portion where a dot-shaped pattern printed using a material having a property of scattering light is arranged as a non-transmissive portion, and having a portion other than the portion as a transmissive portion. ,
The light source emits light from the periphery of the light guide plate toward the light guide plate,
The light from the light source travels while being totally reflected inside the light guide plate, and a part of the light is scattered in the non-transmissive portion and irradiated toward the object to be inspected. Alternatively, the optical evaluation device described in 2. Furthermore,
The optical evaluation device according to claim 1, further comprising a drive unit that changes a relative positional relationship between the object to be inspected and the illumination unit. Further, a part of the plurality of light sources in the illumination section is caused to emit light by the control section, and the relative positional relationship between the object to be inspected and the illumination section is changed by the drive section, and the imaging section takes an image. The optical evaluation device according to claim 5, further comprising a generation unit that generates a composite image from a plurality of images. The generation unit causes the control unit to individually emit light from each of a plurality of light sources in the illumination unit to change the relative positional relationship between the object to be inspected and the illumination unit by the drive unit, and the imaging unit. The optical evaluation device according to claim 6, wherein a composite image is generated from a plurality of images captured by. The generation unit causes the control unit to cause light sources that are not adjacent to each other among the plurality of light sources in the illumination unit to emit light, and changes the relative positional relationship between the object to be inspected and the illumination unit by the drive unit to perform the imaging. The optical evaluation device according to claim 6, wherein a composite image is generated from a plurality of images captured by the unit. 9. The generating unit generates a composite image based on at least one of a maximum brightness value and a minimum brightness value for each pixel position in the plurality of images. The optical evaluation device described. The generation unit performs shading correction on each of the plurality of images, and generates a composite image using the minimum value, the maximum value, and the average value of each pixel of the image after the shading correction. The optical evaluation device according to claim 6. Using a plurality of light sources provided at a position different from the transmissive part, which is included in an illumination part having a transmissive part through which light is transmitted and a non-transmissive part having a light transmittance lower than that of the transmissive part, An illumination step of illuminating the object to be inspected,
An imaging step of imaging the subject illuminated by the plurality of light sources via the transmission section,
In the photographing step, a control step of causing at least a part of the plurality of light sources to emit light,
Equipped with
An optical evaluation method, wherein a relative positional relationship between the object to be inspected and the illumination unit can be changed. Using a plurality of light sources provided at a position different from the transmissive part, which is included in an illumination part having a transmissive part through which light is transmitted and a non-transmissive part having a light transmittance lower than that of the transmissive part, An illumination step of illuminating the object to be inspected,
An imaging step of imaging the subject illuminated by the plurality of light sources via the transmission section,
In the photographing step, a control step of causing at least a part of the plurality of light sources to emit light,
A transportation step for switching the transportation destination of the inspection object based on the image captured in the imaging step.

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