JP2011169733A - Surface inspection method and device of the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface inspection method and surface inspection device capable of improving the accuracy for detecting a defect such as unevenness existing in a surface of an inspecting object without complicating the inspection process and the constitution of the inspection device. <P>SOLUTION: This surface inspection device includes a line lighting system 6 for emitting illumination light 7 to the surface 8 of the inspecting object 2, a CCD camera 14 for receiving regular reflection light 12 from the surface 8 of the inspecting object 2 of the illumination light 7, a light shielding section 18 that is arranged between the inspecting object 2 and CCD camera 14 and shields a part of the regular reflection light 12 entering the CCD camera 14, and an image processing section 25 for determining the existence of unevenness in the surface 8 of the inspecting object 2 based on the luminance information obtained from light 32 located in a periphery, of the regular reflection light 12 received by the CCD camera 14. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a surface inspection method and a surface inspection apparatus for inspecting defects such as irregularities having a very gentle inclination existing on the surface of an object having a smooth surface.

  A conventional surface inspection apparatus includes an optical system that forms a parallel light beam, and irradiates the parallel light beam formed by the optical system onto a substrate surface that is an object to be inspected. The reflected light was detected by a high-sensitivity CCD camera that can capture the unevenness of the substrate surface as a gray image. The analog video signal output from each element of the CCD camera is differentiated by a differentiation circuit, and the obtained differential video signal is digitized by an A / D conversion / frame memory, and the obtained digital video signal is converted into an image. Unevenness on the substrate surface has been detected by being processed by the processing processor. (For example, see Patent Document 1)

Japanese Patent No. 2923808 (pages 2 to 4, FIG. 1)

  In such a surface inspection apparatus, since the inclination of the unevenness existing on the substrate surface is very gentle, and the direction change of the regular reflection light due to the presence or absence of the unevenness is minute, In order to detect irregularities present on the substrate surface, it was necessary to use a highly sensitive CCD camera and differentiate a video signal output from the CCD camera by a differentiating circuit to emphasize the change in shading. Thus, in order to improve the accuracy of detecting irregularities present on the substrate surface, it is necessary to improve the performance of the light receiving element itself, to devise a method for signal processing of signals obtained from the light receiving element, There is a problem that the configuration of the inspection process and the inspection apparatus is complicated.

  The present invention has been made to solve the above-described problems, and has the accuracy of detecting defects such as irregularities present on the surface of the inspection object without complicating the configuration of the inspection process and the inspection apparatus. An object of the present invention is to provide a surface inspection method and a surface inspection apparatus that can be improved.

  The surface inspection method according to the present invention includes an irradiation step of irradiating illumination light onto the surface of the inspection object, and a part of the reflected light from the surface of the inspection object of the illumination light is shielded, and the reflected light that is not shielded A light receiving step for receiving light, and a determination step for determining the presence or absence of defects on the surface of the inspection object based on light information obtained from light located in the peripheral portion of the reflected light received in the light receiving step. Is.

  A surface inspection apparatus according to the present invention includes an illumination apparatus that irradiates illumination light onto the surface of an inspection object, a light receiving element that receives reflected light from the surface of the inspection object, and the inspection object and light reception. Based on light information obtained from light located at the periphery of the reflected light received by the light receiving element, and a light shielding part disposed between the element and shielding a part of the reflected light incident on the light receiving element And a determination unit that determines the presence or absence of defects on the surface of the inspection object.

  According to the surface inspection method according to the present invention, the irradiation step of irradiating the surface of the inspection object with illumination light, and a part of the reflected light from the surface of the inspection object of the illumination light is shielded and the reflection is not shielded. A light receiving step for receiving light, and a determination step for determining the presence or absence of defects on the surface of the inspection object based on optical information obtained from light located in the peripheral portion of the reflected light received in the light receiving step. By providing, the accuracy of detecting defects such as irregularities present on the surface of the inspection object can be improved without complicating the inspection process.

  Further, according to the surface inspection apparatus according to the present invention, the illumination apparatus that irradiates the surface of the inspection object with illumination light, the light receiving element that receives the reflected light from the surface of the inspection object, and the inspection object Between the light receiving element and the light receiving element. The light blocking part shields a part of the reflected light incident on the light receiving element, and the light information obtained from the light located in the peripheral part of the reflected light received by the light receiving element. And a determination unit for determining the presence or absence of defects on the surface of the inspection object based on the above, thereby detecting defects such as unevenness existing on the surface of the inspection object without complicating the configuration of the inspection apparatus. Accuracy can be improved.

It is a schematic block diagram which shows the surface inspection apparatus in Embodiment 1 of this invention. It is a figure which shows a mode that regular reflection light is irradiated to the light-receiving surface of the CCD camera in Embodiment 1 of this invention. It is a flowchart which shows the surface inspection method in Embodiment 1 of this invention. It is an optical path diagram showing the state of the light located in the center portion of the regular reflection light from the surface of the inspection object without a light shielding part, (a) when there is no unevenness on the surface of the inspection object, (B) is an optical path diagram showing a case where irregularities exist on the surface of the inspection object. It is an optical path figure which shows the mode of the light located in the center part among the regular reflection lights from the surface of the test object at the time of using the surface inspection apparatus provided with the light-shielding part in Embodiment 1 of this invention, (a ) Is an optical path diagram showing a case where unevenness is not present on the surface of the inspection object, and (b) is an optical path diagram showing a case where unevenness is present on the surface of the inspection object. It is an optical path figure which shows the mode of the light located in a peripheral part among the regular reflection lights from the surface of the test target object in Embodiment 1 of this invention, (a) is a case where an unevenness | corrugation does not exist in the surface of a test target object (B) is an optical path diagram which shows the case where an unevenness | corrugation exists in the surface of a test target object. It is a photograph which shows the result of having observed the light-receiving surface of the single crystal silicon photovoltaic cell in Embodiment 1 of this invention with the CCD camera, (a) is the smooth surface which does not have an unevenness | corrugation in the surface inspection apparatus provided with the light-shielding part. (B) is a surface inspection apparatus having a light shielding part, and a surface having a convex part is observed. (C) is a surface inspection apparatus having no light shielding part, and a surface having a convex part is observed. This is a picture of the case. It is a figure which shows the correspondence of the photograph which shows the result of having observed the light-receiving surface of the single crystal silicon photovoltaic cell in Embodiment 1 of this invention with the CCD camera, and the shape of the observed convex part, (a) shows an observation result. The photograph to show, (b) is a top view of a convex part, (c) is AA sectional drawing of (b). It is the photograph which shows the result of having observed the light-receiving surface of the single crystal silicon photovoltaic cell in Embodiment 1 of this invention with the CCD camera, and the state figure which shows the luminance change, (a) is a photograph which shows an observation result, ( FIG. 5B is a state diagram schematically showing a luminance change in the AA cross section of FIG. 5A, and FIG. 5C is a state diagram schematically showing a luminance change in the BB cross section of FIG. It is the photograph which shows the result of having observed the light-receiving surface of the single crystal silicon photovoltaic cell in Embodiment 1 of this invention with the CCD camera, and the state figure which shows the luminance change, (a) is a photograph which shows an observation result, ( b) is a state diagram schematically showing a change in luminance in the section AA in FIG.

Embodiment 1 FIG.
First, the surface inspection apparatus 1 in Embodiment 1 of this invention is demonstrated. FIG. 1 is a schematic configuration diagram showing a surface inspection apparatus 1 according to Embodiment 1 of the present invention.

  In FIG. 1, an inspection object 2 is placed on a moving stage 3 and fixed. Then, the line-shaped illumination light 7 emitted from the line illumination device 6 is irradiated onto the surface 8 of the inspection object 2. The regular reflection light 12 from the surface 8 of the inspection object 2 of the illumination light 7 is collected by the lens 13 and received by the CCD camera 14. A light shielding unit 18 is disposed between the lens 13 and the CCD camera 14, and a part of the regular reflection light 12 is shielded, and light of the regular reflection light 12 that is not shielded by the light shielding unit 18 is received by the CCD camera 14. It has become so. The CCD camera 14 and the moving stage 3 are connected to a control computer 19, and a display 20 is connected to the CCD camera 14.

  As the moving stage 3, for example, an XY stage having a driving motor and freely movable in a plane parallel to the surface on which the inspection object 2 is placed is used. The movement of the moving stage 3 is controlled by the control unit 24 of the control computer 19.

  The line illumination device 6 is, for example, an illumination device including a light guide having a slit-shaped opening, a bar-shaped light emitting diode, or the like, and is arranged so that its longitudinal direction extends in a direction perpendicular to the paper surface in FIG. Yes. The line-shaped illumination light 7 emitted from the line illumination device 6 is irradiated onto the surface 8 of the inspection object 2 at an incident angle θ. The illumination light 7 preferably has a uniform light intensity distribution with respect to the longitudinal direction. The incident angle θ is preferably about 20 to 30 °. Note that the illumination light 7 emitted from the line illumination device 6 is not parallel light and does not include an optical system that generates parallel light.

  The CCD camera 14 can capture a two-dimensional image and is arranged so as to receive the regular reflection light 12 from the surface 8 of the inspection object 2 of the illumination light 7. The CCD camera 14 has a shutter function and opens the shutter for a certain period of time by the image capture signal output from the control unit 24 of the control computer 19 to capture the specular reflection light 12. By using the shutter function, it is possible to perform imaging while moving the moving stage 3 without stopping the moving stage 3 every time imaging is performed. Then, the CCD camera 14 obtains the luminance information of the received regular reflection light 12, digitally converts it, and outputs it as an image signal to the display 20 and the image processor 25 of the control computer 19.

  For example, an iris diaphragm or a slit is used as the light shielding unit 18 and is arranged so as to shield part of the regular reflection light 12 from the surface 8 of the inspection object 2 of the illumination light 7. As a result, the light that has not been shielded by the light shielding unit 18 among the regularly reflected light 12 reaches the CCD camera 14. If the size of the opening of the light shielding portion 18 is reduced, the detection accuracy is improved, but if it is too small, the image is blurred due to the effect of light diffraction. In addition, when using a slit, it arrange | positions so that the longitudinal direction of the opening of a slit may turn into a paper surface perpendicular | vertical direction in FIG.

  Here, the light shielding portion 18 is disposed between the lens 13 and the CCD camera 14, but may be disposed between the inspection object 2 and the lens 13. Moreover, although the lens which condenses the illumination light 7 is not arrange | positioned between the line illumination apparatus 6 and the test object 2, you may arrange | position. Further, a mirror that bends the optical path of the illumination light 7 and the regular reflection light 12 may be appropriately disposed. By arranging the mirror and bending the optical path of the illumination light 7 and the regular reflection light 12, the line illumination device 6 and the CCD camera 14 do not necessarily have to be arranged in the direction of the incident angle θ and the reflection angle θ.

  In the following, as shown in FIG. 1, a description will be given of a case where the light shielding portion 18 has a rotationally symmetric or line-symmetric opening shape such as an iris diaphragm or a slit. The same effect can be obtained by using a light shielding plate that shields light.

  The control computer 19 includes a control unit 24, an image processing unit 25, and a storage unit 26.

  The control unit 24 controls the moving stage 3 and acquires position information of the moving stage 3. Then, information on the imaging position stored in the storage unit 26 in advance is read, and when the inspection object 2 comes to the set imaging position, an image capture signal is output to the CCD camera 14. Further, the position information of the moving stage 3 when the image capture signal is output to the CCD camera 14 is output to the storage unit 26.

  The image processing unit 25 receives the luminance information of the regular reflection light 12 received by the CCD camera 14 as an image signal, and detects a change in luminance by image processing. Then, the brightness change and the determination condition stored in the storage unit 26 are compared to determine the presence or absence of unevenness on the surface 8 of the inspection object 2. The determination result is stored in the storage unit 26 and also displayed on the display 20.

  When performing image processing, attention is paid to luminance information obtained from light located in the peripheral portion of the regular reflection light 12 received by the CCD camera 14. FIG. 2 is a diagram showing a state in which the regular reflection light 12 is irradiated onto the light receiving surface 30 of the CCD camera 14 according to Embodiment 1 of the present invention.

  As shown in FIG. 2, the light-receiving surface 30 of the CCD camera 14 is irradiated with the line-shaped regular reflection light 12. Of the regular reflection light 12 received by the light receiving surface 30, the image processing unit 25 does not use the light 31 located at the center portion but the light 32 located at the peripheral portion in the direction perpendicular to the longitudinal direction of the regular reflection light 12. Focus on the obtained luminance information. And the change in the longitudinal direction of the regular reflection light 12 of the luminance information obtained from the light 32 located in the peripheral part is detected by image processing, and compared with the determination condition stored in the storage unit 26, the inspection object 2 to determine whether there are irregularities on the surface 8.

  The storage unit 26 stores information on the imaging position at which the inspection object 2 is imaged and determination conditions used for determining the presence or absence of unevenness, and are read by the control unit 24 and the image processing unit 25, respectively. Further, the position information of the moving stage 3 when the control unit 24 outputs an image capture signal to the CCD camera 14 and the determination result in the image processing unit 25 are stored together, and the unevenness is the surface 8 of the inspection object 2. In FIG. 4, it is possible to know at which part the point is detected.

  The display 20 displays an image captured by the CCD camera 14 and a determination result in the image processing unit 25 so that an operator can check the state of the inspection. At this time, it is preferable to display where the irregularities are detected on the surface 8 of the inspection object 2.

  Examples of the inspection object 2 include a glass substrate and a semiconductor wafer. Here, a case where a single crystal silicon solar cell is used as the inspection object 2 will be described as an example. The single crystal silicon solar cell has a size of, for example, about 100 mm × 50 mm, and its light receiving surface is required to be very smooth. However, in the manufacturing process of the single crystal silicon solar cell, unevenness with a very gentle inclination may occur on the light receiving surface. The size of the unevenness is, for example, 1 μm or less with respect to a length of 5 to 10 mm, which has conventionally been difficult to detect.

  Next, a description will be given of a method for detecting the unevenness having a very gentle inclination as described above by using the surface inspection apparatus 1 according to the first embodiment of the present invention. FIG. 3 is a flowchart showing the surface inspection method according to Embodiment 1 of the present invention.

  First, the inspection object 2 is placed and fixed on the moving stage 3, and the inspection is started. Note that the imaging position for imaging the inspection object 2 and the determination condition for determining the presence or absence of unevenness are input and stored in the storage unit 26 in advance.

  Next, the irradiation process will be described. When the line illumination device 6 is turned on and the illumination light 7 is incident on the surface 8 of the inspection object 2 at the incident angle θ and the single crystal silicon solar cell is the inspection object 2, the light receiving surface is irradiated (S1). . Here, it is assumed that the line-shaped illumination light 7 has a uniform light intensity distribution in the longitudinal direction.

  Next, the moving process will be described. Controlled by the control unit 24 of the control computer 19, the moving stage 3 starts to move in a direction perpendicular to the longitudinal direction of the illumination light 7 (S2). At this time, since the line illumination device 6 remains fixed, the illumination light 7 is scanned on the surface 8 of the inspection object 2 as the moving stage 3 moves. The moving stage 3 is not stopped until the illumination light 7 has finished scanning the surface 8 of the inspection object 2.

  Next, the light receiving process will be described. The control unit 24 of the control computer 19 acquires the positional information of the moving stage 3 and grasps the positional relationship between the illumination light 7 and the inspection object 2. Then, the information of the imaging position input in advance to the storage unit 26 is read out, and compared with the position information of the moving stage 3, it is determined whether or not the inspection object 2 has arrived at the set imaging position (S3). ).

  When the inspection object 2 arrives at the imaging position, an image capture signal is output from the control unit 24 to the CCD camera 14 and the shutter of the CCD camera 14 is released. At this time, a part of the regular reflection light 12 from the surface 8 of the inspection object 2 of the illumination light 7 is shielded by the light shielding unit 18 (S4), and the CCD camera 14 captures the light that is not shielded in the regular reflection light 12. Light is received (S5).

  The CCD camera 14 obtains the luminance information of the received regular reflection light 12, digitally converts it, and then outputs it as an image signal to the display 20 and the image processor 25 of the control computer 19.

  The step S4 is not limited to being performed between S3 and S5, and may be performed between S1 and S2 or between S2 and S3.

  Next, the determination process will be described. The image processing unit 25 of the control computer 19 that has received the image signal from the CCD camera 14 pays attention to the luminance information obtained from the light 32 located in the peripheral portion of the regular reflection light 12 received by the CCD camera 14. That is, a change in the longitudinal direction of the regular reflection light 12 in the luminance information obtained from the light 32 located in the peripheral portion is detected by image processing. Then, the brightness change and the determination condition stored in the storage unit 26 are compared to determine the presence or absence of unevenness on the surface 8 of the inspection object 2 (S6). The determination result is stored in the storage unit 26 and displayed on the display 20.

  Here, the presence / absence of unevenness on the surface 8 of the inspection object 2 is determined by image processing. However, the operator may determine the image displayed on the display 20 by visual observation.

  Thereafter, it is determined whether or not the entire surface 8 of the inspection object 2 has been inspected (S7). If the entire surface inspection has not been completed, when the next imaging position is reached (S3), the following steps are repeated. When the entire inspection is completed, the inspection ends.

  In this case, the inspection is finished when the entire surface inspection is completed. However, even when the unevenness that has a fatal effect on the quality of the inspection object 2 is found even before the entire surface inspection is completed. May end the inspection halfway.

  Next, it will be described that the detection accuracy of the unevenness on the surface 8 of the inspection object 2 is improved by providing the light shielding part 18 and shielding a part of the regular reflection light 12.

  FIG. 4 is an optical path diagram showing the state of the light 31 located in the center portion of the regular reflection light 12 from the surface 8 of the inspection object 2 when the light shielding portion 18 is not provided, and (a) is the inspection object. (B) is an optical path diagram showing a case where the surface 8 of the inspection object 2 has an uneven surface. FIG. 5 shows the light 31 positioned at the center of the regular reflection light 12 from the surface 8 of the inspection object 2 when the surface inspection apparatus 1 having the light shielding unit 18 according to Embodiment 1 of the present invention is used. It is an optical path diagram which shows a mode, (a) is an optical path diagram which shows the case where an unevenness | corrugation exists in the surface 8 of the test object 2, and (b) is a case where an unevenness | corrugation exists in the surface 8 of the inspection object 2.

  4 and 5, the direction perpendicular to the paper surface coincides with the longitudinal direction of the line-shaped regular reflection light 12. Further, here, for the sake of explanation, a case is shown in which the illumination light 7 is irradiated so that the incident angle θ = 0 ° when it is assumed that the surface 8 of the inspection object 2 is not uneven. Further, the inclination of the unevenness is shown larger than the actual inclination.

  First, a case where the light shielding unit 18 is not provided will be described. When the surface 8 of the inspection object 2 is not uneven, as shown in FIG. 4A, when attention is focused on the light 31 located at the center of the regular reflected light 12, the direction in which the regular reflected light 12 is strongest. 36 a is in a direction perpendicular to the surface 8. The specularly reflected light 12 is collected by the lens 13 and the light range 37a reaching the light receiving surface 30 of the CCD camera 14 is a range surrounded by a solid line as shown in FIG.

  When the surface 8 of the inspection object 2 is uneven, the range 37a of light reaching the light receiving surface 30 of the CCD camera 14 is not changed, but the surface 8 is inclined by the unevenness as shown in FIG. Therefore, the direction 36b where the regular reflection light 12 is strongest is inclined. Thereby, the brightness | luminance of the light received with the CCD camera 14 becomes smaller than the case where an unevenness | corrugation does not exist.

  For this reason, a difference occurs in the brightness of light received by the CCD camera 14 depending on the presence or absence of unevenness, and the presence or absence of unevenness can be determined by detecting the difference in brightness. However, since the slope of the unevenness is very gentle, the direction change of the regular reflection light 12 becomes minute, and the difference in luminance becomes very small. In order to improve the detection accuracy of the unevenness, it is necessary to increase the difference in luminance of light reaching the light receiving surface 30 of the CCD camera 14 due to the presence or absence of the unevenness.

  Next, the case where the light shielding part 18 is provided and a part of the regular reflection light 12 is shielded will be described. When there is no unevenness on the surface 8 of the inspection object 2, as shown in FIG. 5A, when attention is paid to the light 31 located at the center of the regular reflected light 12, the direction in which the regular reflected light 12 is strongest. 36 a is in a direction perpendicular to the surface 8. The range 37b of light reaching the light receiving surface 30 of the CCD camera 14 is a range surrounded by a solid line as shown in FIG. 5A, and is narrower than the case where the light shielding portion 18 is not provided.

  When the surface 8 of the inspection object 2 has unevenness, as shown in FIG. 5B, the surface 8 is inclined by the unevenness, so the direction 36b where the specular reflection light 12 is strongest is inclined. In FIG. 5B, the direction 36b in which the specularly reflected light 12 is the strongest is within the light range 37b reaching the light receiving surface 30 of the CCD camera 14, but is positioned at the end of the light range 37b. Compared with the case where the unit 18 is not provided, the luminance of the light received by the CCD camera 14 becomes smaller.

  As described above, the difference in luminance of the regular reflection light 12 received by the CCD camera 14 caused by the presence or absence of unevenness becomes larger than that in the case where the light shielding portion 18 is not provided, and the unevenness detection accuracy is improved.

  Next, in the determination step, the image processing unit 25 of the control computer 19 pays attention to the luminance information obtained from the light 32 located in the peripheral portion of the regular reflection light 12 received by the CCD camera 14, thereby inspecting the inspection object. The improvement in the detection accuracy of the unevenness on the surface 8 of the object 2 will be described.

  FIG. 6 is an optical path diagram showing the state of the light 32 located in the peripheral portion of the regular reflection light 12 from the surface 8 of the inspection object 2 according to Embodiment 1 of the present invention, and (a) is the inspection object. (B) is an optical path diagram showing a case where the surface 8 of the inspection object 2 has an uneven surface.

  In FIG. 6, the direction perpendicular to the paper surface coincides with the longitudinal direction of the line-shaped regular reflection light 12. Further, here, for the sake of explanation, a case is shown in which the illumination light 7 is irradiated so that the incident angle θ = 0 ° when it is assumed that the surface 8 of the inspection object 2 is not uneven. Further, the inclination of the unevenness is shown larger than the actual inclination.

  When there is no unevenness on the surface 8 of the inspection object 2, as shown in FIG. 6A, when attention is paid to the light 32 located in the peripheral portion of the regular reflected light 12, the direction in which the regular reflected light 12 is the strongest. 36 a is in a direction perpendicular to the surface 8. Then, since the regular reflection light 12 is condensed by the lens 13 and part of the light is shielded by the light shielding portion 18, the light range 37c reaching the light receiving surface 30 of the CCD camera 14 is as shown in FIG. The range is surrounded by a solid line.

  When the surface 8 of the inspection object 2 has unevenness, the range 37c of light reaching the light receiving surface 30 of the CCD camera 14 does not change, but the surface 8 is inclined by the unevenness as shown in FIG. Therefore, the direction 36b where the regular reflection light 12 is strongest is inclined.

  At this time, the direction 36 b in which the specularly reflected light 12 is the strongest has deviated from the light range 37 c reaching the light receiving surface 30 of the CCD camera 4. Therefore, the brightness of the light received by the CCD camera 14 is significantly reduced when there is unevenness compared to when there is no unevenness. That is, when attention is paid to the light 32 located in the peripheral portion of the regular reflection light 12, the difference in the luminance of the light received by the CCD camera 14 caused by the presence or absence of irregularities is the light 31 located in the central portion of the regular reflection light 12. As compared with the case where attention is focused on, the detection accuracy of the unevenness is further improved.

  Next, the result of actually inspecting the light receiving surface of the single crystal silicon solar battery cell based on the surface inspection method using the surface inspection apparatus 1 described above will be described.

  FIG. 7 is a photograph showing the result of observing the light-receiving surface of the single crystal silicon solar battery cell according to Embodiment 1 of the present invention with the CCD camera 14, and (a) shows the surface inspection apparatus 1 provided with the light shielding portion 18. When a smooth surface having no unevenness is observed, (b) is a surface inspection device 1 provided with a light shielding part 18 and when a surface with a convex part is observed, (c) is a surface inspection without the light shielding part 18. It is a photograph at the time of observing the surface in which a convex part exists with an apparatus. FIG. 8 is a diagram showing a correspondence between a photograph showing the result of observing the light receiving surface of the single crystal silicon solar battery cell according to Embodiment 1 of the present invention with the CCD camera 14 and the shape of the observed convex portion. ) Is a photograph showing the observation result, (b) is a top view of the convex portion, and (c) is a cross-sectional view taken along line AA of (b). In the photographs of FIG. 7 and FIG. 8, the magnitude of the brightness is shown by shading, and the portion where the brightness is high is displayed in white and the portion where the brightness is low is displayed in black.

  First, a case where a smooth surface having no irregularities is observed with the surface inspection apparatus 1 provided with the light shielding unit 18 will be described. In this case, as shown in FIG. 7A, no change in luminance in the longitudinal direction of the regular reflection light 12 is observed.

  Next, the case where the convex part shown in FIG. 8 is observed with the surface inspection apparatus 1 provided with the light shielding part 18 will be described. In this case, as shown in FIG. 7B, the light 31 located in the central portion of the regular reflection light 12 does not show a large change in luminance in the longitudinal direction of the regular reflection light 12, but in the peripheral portion. A large change in luminance occurs in the positioned light 32. That is, a portion where the width of the portion with high luminance is narrower than the other is seen, and the convex portion exists here.

  A correspondence relationship between the photograph showing the observation result shown in FIG. 7B and the shape of the observed convex portion will be described. FIG. 7B and FIG. 8A are the same photographs. The convex portions observed in FIG. 8 (a) have a quadrangular pyramid shape as shown in FIGS. 8 (b) and 8 (c), and the top of the quadrangular pyramid is a portion with a high luminance in FIG. 8 (a). It corresponds to the place where the width is narrow. And the cross section of the part where the width | variety of the part with high brightness | luminance is narrow, ie, the AA cross section of Fig.8 (a) and (b), is FIG.8 (c), and an inclined surface exists by presence of a convex part. And it turns out that the brightness | luminance of the light 32 located in a peripheral part has become small.

  In addition, the size of the convex portion is 5 μm to 10 mm in length L, and the height H is 1 μm or less. In FIG. Shown at different scales.

  Next, the case where the convex part shown in FIG. 8 is observed with a surface inspection apparatus that does not include the light shielding part 18 will be described. In this case, as shown in FIG. 7C, no significant change in luminance occurs in either the light 31 located in the central portion or the light 32 located in the peripheral portion of the regular reflection light 12.

  In addition, although the case where the convex part was observed was demonstrated here, the same result is obtained even if a concave part is observed.

  From the above, by focusing on the luminance change of the light 32 located in the peripheral part, the detection accuracy of the unevenness can be improved, and it is possible to detect even unevenness whose slope is so gentle that it cannot be detected only by providing the light shielding part 18. I understand.

  Next, a description will be given of a method in which the image processing unit 25 detects a convex portion by image processing from the observation result shown in FIG. FIG. 9 is a photograph showing the result of observing the light-receiving surface of the single crystal silicon solar battery cell according to Embodiment 1 of the present invention with CCD camera 14, and a state diagram showing the luminance change. (B) is a state diagram schematically showing a luminance change in the AA cross section of (a), and (c) is a state diagram schematically showing a luminance change in the BB cross section of (a). 9B and 9C, the vertical axis indicates the brightness of the received regular reflection light 12, and the horizontal axis indicates the position in each cross section.

  FIG. 10 is a photograph showing a result of observing the light-receiving surface of the single crystal silicon solar battery cell according to Embodiment 1 of the present invention with the CCD camera 14 and a state diagram showing a change in luminance thereof. (A) is an observation result. (B) is a state diagram schematically showing a luminance change in the AA cross section of (a). In FIG. 10B, the vertical axis indicates the position in the cross section, and the horizontal axis indicates the luminance of the regular reflected light 12 received. 9 (a), 10 (a), and 7 (b) are the same photographs.

  A threshold value S1 is set in advance in the magnitude of luminance, and is stored in the storage unit 26. The image processing unit 25 checks the luminance change in the direction perpendicular to the longitudinal direction of the regular reflection light 12 as shown in FIGS. 9B and 9C and compares it with the luminance threshold value S1 read from the storage unit 26. The width W exceeding the luminance threshold value Sl is detected by image processing. Then, the width W exceeding the luminance threshold value Sl is detected in the longitudinal direction of the regular reflection light 12, and the change is examined.

  The threshold value Sw is set in advance for the width W exceeding the luminance threshold value Sl and stored in the storage unit 26. Then, the threshold value Sw of the width W read out to the image processing unit 25 is compared with the actually detected width W, and it is determined that there is unevenness at a position below the threshold value Sw. In FIG. 9, a threshold value Sw having a width W exceeding the luminance threshold value Sl is set so that W2 <Sw <W1.

  In FIG. 10A, when the longitudinal direction of the light 32 positioned in the peripheral portion of the specularly reflected light 12 received by the CCD camera 14, that is, the change in luminance in the AA cross section is examined, as shown in FIG. A change in luminance is obtained. In other words, the determination of the presence / absence of unevenness based on the threshold value Sw of the width W described above has changed from the state in which the luminance exceeds the threshold value Sl to the state below the threshold value Sl in FIG. This is the same as determining that there is unevenness at the location where the state has changed from the state to the state exceeding the threshold value Sl. The determination method based on the threshold Sw is just one example.

  Note that the determination conditions that are stored in the storage unit 26 in advance and used to determine the presence or absence of unevenness specifically refer to the threshold value Sl and the threshold value Sw described here.

  Here, the threshold value Sw is set to the width W exceeding the luminance threshold value Sl, but a threshold value is set to the change amount of the width W, and it is determined that there is unevenness when the width W becomes narrower than a certain amount. May be.

  In Embodiment 1 of the present invention, with the above-described configuration, it is possible to improve the accuracy of detecting irregularities on the surface 8 of the inspection object 2 simply by providing the light-shielding portion 18, and the specular reflection light. The detection accuracy can be further improved by detecting the luminance change of the light 32 located in the peripheral portion of the twelve. As a result, a normal CCD camera 14 is used instead of a high-sensitivity one, and parallel light is used as the illumination light 7 to be irradiated without performing signal processing such as differentiation of the signal obtained from the CCD camera 14. At least, sufficient detection accuracy can be obtained in order to detect unevenness with a very gentle inclination generated on the surface of the single crystal silicon solar battery cell. Accordingly, the performance of the light receiving element itself, signal processing such as differentiation of a signal obtained from the light receiving element, an optical system for generating parallel light, and the like are not required, and the configuration can be simplified. That is, there is an effect that the accuracy of detecting irregularities can be improved without complicating the configuration of the inspection process and the inspection apparatus. Further, since the device configuration can be simplified, the device cost can be suppressed.

  In addition, by irradiating the surface 8 of the inspection object 2 with the line-shaped illumination light 7 using the line illumination device 6, it is possible to inspect a wide range at a time, thereby reducing the time required for the inspection. Can do. Furthermore, by making the line-shaped illumination light 7 have a uniform light intensity distribution in the longitudinal direction, image processing for determining the presence or absence of unevenness is facilitated.

  In the determination step, the width W exceeding the threshold value Sl is detected by comparing the preset luminance threshold value Sl with the detected luminance value, and the width W is compared with the preset width threshold value Sw to compare the unevenness. Presence / absence can be determined. That is, since it is possible to determine the presence or absence of unevenness by simply setting the threshold value Sl and the threshold value Sw and comparing the detected luminance and width W with the respective threshold values, the determination process can be easily detected without making the determination process complicated. .

  Further, since the CCD camera 14 is not a high sensitivity but a normal one, the response of the CCD camera 14 is fast and the image is captured quickly. For this reason, since the exposure time can be shortened, it is possible to take an image using the shutter function of the CCD camera 14 without stopping the moving stage 3 during the inspection, and the time required for the inspection can be shortened.

  In the first embodiment of the present invention, the CCD camera 14 is not of high sensitivity because sufficient detection accuracy is obtained to detect unevenness with a gentle inclination generated on the surface of the single crystal silicon solar cell. A normal one is used, signal processing such as differentiation of the signal obtained from the CCD camera 14 is not performed, and parallel light is not used for the illumination light 7 to be irradiated. However, by using these together, detection accuracy is further improved. Needless to say.

  Although only the detection of unevenness with a gentle inclination has been described here, it is of course possible to detect unevenness with a larger inclination such as scratches and dust attached to the surface.

  In the first embodiment of the present invention, the regular reflection light 12 is received using the CCD camera 14 capable of capturing a two-dimensional image. However, the present invention is not limited to this, and a one-dimensional sensor may be used. When the one-dimensional sensor is used, the one-dimensional sensor is arranged so that the longitudinal direction of the one-dimensional sensor coincides with the longitudinal direction of the regular reflection light 12. Then, a two-dimensional image may be obtained by scanning in the direction perpendicular to the longitudinal direction of the regular reflection light 12 at the time of observation, or only the light 32 positioned at the peripheral portion of the regular reflection light 12 is received without scanning. You may do it.

  In the first embodiment of the present invention, in the determination step, the presence / absence of unevenness is determined based on two preset thresholds, that is, the threshold value Sl of the luminance and the threshold value Sw of the width W where the luminance exceeds the threshold value Sl. However, the present invention is not limited to this, and a change in the luminance in the longitudinal direction of the light 32 located in the peripheral portion of the regular reflection light 12 received by the CCD camera 14 is examined, and the threshold value Sl is set from a state where the luminance exceeds the threshold value Sl. Any other method may be used as long as it is determined that there is unevenness at a location where the state has changed to a state below the threshold value Sl or from the state below the threshold value Sl to the state above the threshold value Sl.

  Furthermore, in the first embodiment of the present invention, the line illumination device 6 is fixed, the moving stage 3 is moved, and the inspection object 2 is moved, so that the illumination light 7 is scanned on the surface 8 of the inspection object 2. did. However, conversely, the inspection object 2 may be fixed and the line illumination device 6 may be moved. In this case, when the field of view of the CCD camera 14 is not sufficiently wide, it is desirable to move the CCD camera 14 together with the line illumination device 6.

  In addition, in the first embodiment of the present invention, the line illumination device 6 is used to irradiate the surface 8 of the inspection object 2 with the line-shaped illumination light 7. However, the irradiated light does not need to be in a line shape, and spot light may be used.

  Moreover, in Embodiment 1 of this invention, the presence or absence of the unevenness | corrugation in the surface 8 of the test target object 2 was determined by the luminance information of the regular reflection light 12. However, the optical information used for determining the presence or absence of unevenness is not limited to luminance information, and may be other optical information related to light brightness such as light intensity and light flux.

DESCRIPTION OF SYMBOLS 1 Surface inspection apparatus 2 Inspection object 3 Moving stage 6 Line illumination apparatus 7 Illumination light 8 Surface of inspection object 12 Regular reflection light 14 CCD camera 18 Light-shielding part 25 Image processing part 32 Light located in peripheral part among regular reflection light

Claims (9)

An irradiation process for irradiating the surface of the inspection object with illumination light;
A light receiving step of shielding a part of the reflected light from the surface of the illumination light and receiving the reflected light that is not shielded;
Of the reflected light received in the light receiving step, a determination step of determining the presence or absence of defects on the surface based on optical information obtained from light located in the peripheral portion;
Surface inspection method with The illumination light is a linear illumination light having a uniform light intensity distribution in the longitudinal direction,
2. The surface inspection method according to claim 1, wherein the determination step determines whether or not there is a defect on the surface of the inspection object by detecting a change in optical information in the longitudinal direction of the reflected light. Light information is the brightness of light,
3. The surface inspection method according to claim 1, wherein the determination step determines that a defect is present at a location where the brightness falls below a predetermined threshold value. 4. A moving step of moving the irradiation position of the illumination light relative to the inspection object;
The light receiving step acquires relative positional information of the irradiation position of the illumination light with respect to the inspection object, and captures reflected light based on the positional information. The surface inspection method described in 1.   The surface inspection method according to any one of claims 1 to 4, wherein the inspection object is a solar battery cell. An illumination device for illuminating the surface of the inspection object with illumination light;
A light receiving element that receives reflected light from the surface of the illumination light;
A light-shielding portion that is disposed between the inspection object and the light-receiving element and shields a part of the reflected light incident on the light-receiving element;
Of the reflected light received by the light receiving element, a determination unit that determines the presence or absence of defects on the surface based on optical information obtained from light located in a peripheral portion;
Surface inspection device with The illumination device is a line illumination device that emits linear illumination light having a uniform light intensity distribution in the longitudinal direction,
The surface inspection apparatus according to claim 6, wherein the determination unit determines the presence or absence of a defect on the surface of the inspection object by detecting a change in optical information in the longitudinal direction of the reflected light. Light information is the brightness of light,
The surface inspection apparatus according to claim 6, wherein the determination unit determines that a defect is present at a location where the brightness falls below a predetermined threshold. A moving unit that moves the irradiation position of the illumination light relative to the inspection object,
The relative position information of the irradiation position of the illumination light with respect to the inspection object is acquired, and reflected light is taken into the light receiving element based on the position information. The surface inspection apparatus described.

Images