JP5324181B2 - Solar cell inspection device, solar cell inspection method, program, solar cell inspection system - Google Patents

Description

  The present invention relates to a solar cell inspection device, a solar cell inspection method, a program, and a solar cell inspection system, and more particularly to identification of a defect in a solar cell.

A solar cell that converts sunlight energy into electric power is generally composed of a semiconductor such as silicon. Such a solar cell is known to emit light when energized. Patent Document 1 discloses a technique for determining whether a solar cell is good or bad based on the overall light amount of the solar cell during energization. ing.
WO / 2006/059615

  By the way, in the solar battery cell, a dark region (dark area) in which light emission during energization is relatively weak may exist as a defect. Such a dark region exists in various lightnesses, from a lightness that is clearly low to a lightness that is slightly lower than the surroundings.

  However, when such a dark region is to be detected by a normal binarization process, the grain boundary of the crystal of the solar battery cell is also detected, and it is difficult to determine the dark region to be detected as a defect.

  The present invention has been made in view of the above circumstances, and provides a solar cell inspection device, a solar cell inspection method, a program, and a solar cell inspection system capable of determining a dark region to be detected as a defect. The main purpose.

  In order to solve the above problems, an inspection apparatus for a solar cell according to the present invention includes an image acquisition unit that acquires a cell image representing one or a plurality of solar cells in an energized state, and a linear shape whose brightness is lower than the surroundings. A pixel group having a predetermined area or more, in which a pixel group is specified in the cell image and crack position information generating means for generating crack position information of the solar battery cell, and pixels having a lightness of a predetermined value or less are gathered is the cell. Based on the positional relationship between the dark region and the crack, the dark region is caused by the crack based on the dark region position information generating means that is specified in the image and generates the position information of the dark region of the solar battery cell Dark region determining means for determining whether the region is a dark region.

  Further, the solar cell inspection method of the present invention acquires a cell image representing one or more solar cells in an energized state, and identifies a linear pixel group having a lower brightness than the surroundings in the cell image. And generating a positional information of the crack of the solar battery cell, specifying a pixel group having a predetermined area or more in which pixels having a lightness of a predetermined brightness or less are gathered in the cell image, and the position of the dark area of the solar battery cell Information is generated, and based on the positional relationship between the dark region and the crack, it is determined whether the dark region is a dark region caused by the crack.

  Further, the program of the present invention specifies an image acquisition means for acquiring a cell image representing one or a plurality of solar cells in an energized state, and identifies a linear pixel group having a lightness lower than that of the surrounding area in the cell image. A position information generating means for generating position information of the cracks of the solar battery cell, a pixel group having a predetermined area or more, in which pixels having a predetermined brightness or less are gathered, is specified in the cell image; Dark region position information generating means for generating dark region position information, and determining whether or not the dark region is a dark region caused by the crack based on a positional relationship between the dark region and the crack The computer is made to function as a dark region determination means to be performed. The computer is, for example, a personal computer. The program may be stored in a computer-readable information storage medium such as a CD-ROM.

  Furthermore, the solar cell inspection system of the present invention images one or more solar cells in an energized state, generates an image unit that represents the solar cells, and acquires the cell images. An acquisition means, a linear pixel group having a lightness lower than that of the surroundings are specified in the cell image, and a crack position information generation means for generating position information of the crack of the solar battery cell, A dark region position information generating unit that identifies a group of pixels having a predetermined area or more in the cell image and generates position information of a dark region of the solar battery cell, and a positional relationship between the dark region and the crack And a dark region determining means for determining whether or not the dark region is a dark region caused by the crack.

  The present inventors have found that a dark region to be detected as a defect is caused by a crack. Therefore, by performing the determination based on the positional relationship between the dark area and the crack, it is possible to improve the detection accuracy of the dark area caused by the crack.

  In the aspect of the invention, the crack position information generation unit may identify a boundary portion of a change in brightness in the cell image and generate position information of the crack of the solar battery cell. Moreover, a primary differential filter or a secondary differential filter can be used for specifying such a boundary portion. According to this, it becomes easy to specify the crack near the outer edge of the dark region.

  In the aspect of the invention, the dark region determination unit performs the determination based on the length of the crack along the outer edge of the dark region. According to this, it is possible to further improve the detection accuracy of dark regions caused by cracks.

  In the aspect of the invention, the dark region determination unit performs the determination based on the length of the crack existing in the dark region. According to this, it is possible to further improve the detection accuracy of dark regions caused by cracks.

  In these aspects, the dark region determination means may perform the determination based on a ratio between the length of the outer edge of the dark region and the length of the crack.

  Further, according to one aspect of the present invention, a quality determination unit that determines the quality of the solar battery cell based on the number of dark regions caused by the crack is further provided. According to this, the quality of a photovoltaic cell can be determined.

  Further, according to one aspect of the present invention, there is further provided display control means for identifying and displaying a dark region caused by the crack. According to this, the user can grasp the dark area resulting from the crack.

  Embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram illustrating a configuration example of a solar cell inspection system 1 according to an embodiment of the present invention. In this solar cell inspection system 1, an energization unit 3, a positioning unit 4, an imaging unit 5, an operation unit 8, and a display unit 9 are connected to a control unit 10 (solar cell inspection device) that controls the entire system. Yes.

  The energization unit 3 energizes the solar cell panel as the inspection target in response to a command from the control unit 10. This energization part 3 applies a voltage to the terminal of a solar cell panel by a probe (not shown), and supplies a forward current to each solar cell included in the solar cell panel.

  The imaging unit 5 is configured by a CCD camera or the like, and images a solar cell panel that is energized in response to a command from the control unit 10. The positioning unit 4 moves and positions the imaging unit 5 to a predetermined imaging position in response to a command from the control unit 10.

  Specifically, the imaging unit 5 is moved by the positioning unit 4 and sequentially images each solar battery cell included in the solar battery panel. Moreover, the data of the cell image showing a photovoltaic cell obtained by this are sequentially input into the control part 10.

  In addition, such a solar cell panel is imaged in a dark room. Further, since the EL (electroluminescence) light of the solar battery cell is weak, a camera with relatively high sensitivity is suitable as the imaging unit 5.

  Here, the solar cell panel as an inspection object will be described. FIG. 2A is a schematic diagram showing the solar cell panel 2. FIG. 2B is a schematic diagram showing the solar battery cell 21 included in the solar battery panel 2.

  As shown in FIG. 2A, in the solar cell panel 2, rectangular thin plate-like solar cells 21 made of a semiconductor such as silicon are two-dimensionally arranged, and these solar cells 21 are connected by lead wires 23. They are connected in series. These solar cells 21 are arranged inside a laminate 25 whose light-receiving surface side is a glass plate. The laminated body 25 has a laminated structure in which a filler, solar cells 21, a filler, and a back member are laminated in this order on a glass plate. In addition, the arrangement | sequence and number of sheets of the photovoltaic cell 21 are not restricted to the aspect of the figure. The solar cell panel 2 may be a thin film solar cell panel.

  As shown in FIG. 2B, the light receiving surface 27 of the solar battery cell 21 is formed with a pair of bus bars 28 and a number of fingers 29 for collecting power as electrodes for taking out the power to the outside. Yes. When the direction along the long side of the solar battery cell 21 is the longitudinal direction and the direction along the short side is the short direction, the bus bar 28 is configured in a strip shape extending in the short direction, and is located apart in the longitudinal direction. . The lead wires 23 are connected to the bus bars 28. Further, the fingers 29 are configured in a thin line shape extending in the longitudinal direction, and are arranged in parallel in the lateral direction. In addition, arrangement | positioning of the bus-bar 28 and the finger 29 is not restricted to the aspect of the figure.

  Returning to the description of FIG. 1, the control unit 10 is configured as a computer including a CPU (Central Processing Unit) and a RAM as a work area thereof. The control unit 10 includes a storage unit that stores programs and data necessary for the operation of the CPU. The operation unit 8 includes a keyboard, a mouse, and the like, and sends operation inputs based on user operations to the control unit 10. The display unit 9 is composed of a liquid crystal display or the like, and displays an image corresponding to a display command from the control unit 10.

  FIG. 3 is a block diagram illustrating a functional configuration example of the control unit 10. FIG. 4 is a flowchart showing a solar cell inspection method realized by the control unit 10. When the CPU executes a program stored in the storage unit, the control unit 10 causes the energization control unit 11, the position control unit 12, the image acquisition unit 13, the crack position information generation unit 14, the dark region position information generation unit 15, A dark region determination unit 16, a quality determination unit 17, and a display control unit 19 are functionally provided.

  The energization control unit 11 controls the energization unit 3 to execute energization to the solar battery cells 21 included in the solar battery panel 2. Thereby, each photovoltaic cell 21 emits EL light. Here, data of energization conditions such as a voltage value, a current value, and an energization time are stored in the storage unit of the control unit 10.

  The position control unit 12 controls the positioning unit 4 and executes position control of the imaging unit 5. Specifically, the position control unit 12 sequentially moves the imaging unit 5 to each imaging position where each solar cell 21 can be imaged. Such an imaging position is determined by the size and number of solar cells 21, the arrangement interval, and the like, and is stored as data in the storage unit of the control unit 10.

  The image acquisition unit 13 acquires cell image data representing the solar cells 21 in an energized state from the imaging unit 5 (S1). In addition, the image acquisition unit 13 performs preprocessing of the acquired cell image (S2).

  As the cell image preprocessing, for example, scaling processing for standardizing the brightness of the EL light of the solar battery cell 21, cell area extraction processing for extracting the solar battery cell 21 area, and the bus bar 28 portion of the solar battery cell 21 are excluded. There are a bus bar exclusion process, a shading process for correcting a brightness difference caused by the lens of the imaging unit 5, and the like.

  Then, the image acquisition unit 13 outputs the cell image data that has undergone the lower processing to the crack position information generation unit 14 and the dark region position information generation unit 15.

  FIG. 5 is a diagram illustrating an example of the cell image 30. In the cell image 30, the defective part of the solar battery cell 21 appears as a dark part with relatively low brightness. Such defective portions include cracks 32a to 32c and dark regions 34a and 34b.

  The cracks 32 a to 32 c appear in the cell image 30 as a linear pixel group with low brightness. These cracks 32a to 32c have a large difference in brightness from the portion where light emission is good. Such cracks 32 a to 32 c are generated by heat when soldering the lead wire 23 to the bus bar 28, load or impact during processing or transportation.

  The dark regions 34a and 34b appear in the cell image 30 as a pixel group having a certain area or more and low brightness. Such dark regions 34a and 34b are generated when the current supply is blocked by the cracks 32a and 32b. That is, the dark areas 34a and 34b are caused by the cracks 32a and 32b. Therefore, the cracks 32a and 32b often overlap at least part of the outer edges of the dark regions 34a and 34b.

  In addition, the brightness of the dark areas 34a and 34b is not uniform, and there are a dark area 34a having a slightly lower brightness than the surrounding area and a dark area 34b having a clearly lower brightness. Note that in the dark region 34b where the lightness is clearly low, even if a crack 32b occurs on the outer edge of the dark region 34b, it may be difficult to distinguish between the two because of the same lightness.

  In addition, a crystal grain boundary 36 of the solar battery cell 21 may appear in the cell image 30. Such a crystal grain boundary 36 is not a defect of the solar battery cell 21 but appears in the cell image 30 as a pixel group having a slightly lower brightness than the surroundings. In many cases, such crystal grain boundaries 36 have a relatively small shape.

  Returning to the description of FIGS. 3 and 4, the crack position information generation unit 14 identifies the positions of the cracks 32 a to 32 c in the cell image 30, and generates crack position information indicating the positions of the cracks 32 a to 32 c (S <b> 3). ). The crack position information generated in this way is output to the dark region determination unit 16, the quality determination unit 17, and the display control unit 19.

  Specifically, the crack position information generation unit 14 identifies the positions of the cracks 32 a to 32 c by extracting the boundary portion of the change in brightness in the cell image 30. Such extraction of the boundary portion can be realized by using a Laplacian filter (secondary differential filter). In addition, it is not restricted to this, You may make it use a primary differential filter.

  FIG. 6 is an explanatory diagram of generation of crack position information. When the Laplacian filter is applied to the cell image 30 shown in FIG. 5, the boundary portions 42a to 42c and 46 of the brightness change are extracted as shown in FIG. Of these, the boundary portions 42 a to 42 c correspond to the cracks 32 a to 32 c, respectively, and the boundary portion 46 corresponds to the crystal grain boundary 36.

  The crack position information generation unit 14 specifies the positions of the cracks 32a to 32c by selecting the boundary parts 42a to 42c extending linearly from the boundary parts 42a to 42c and 46 thus extracted. Such selection can be performed, for example, by determining the aspect ratio (ratio between the length in the longitudinal direction and the length in the width direction) of the minimum rectangle surrounding the pixel group constituting each of the boundary portions 42a to 42c, 46. is there. By performing such selection, it is possible to prevent the relatively small substantially circular boundary portion 46 corresponding to the crystal grain boundary 36 from being identified as a crack.

  Further, in the present embodiment, since the boundary portion of the brightness change is extracted by the Laplacian filter, as shown in FIG. 5 above, the dark region 34b having a clearly low brightness and the crack 32b that forms the outer edge thereof are formed. Even if the brightness is comparable, the position of the crack 32b can be specified.

  The crack position information indicating the positions of the cracks 32a to 32c specified in this way includes, for example, coordinate information of the cracks 32a to 32c. Specifically, each crack 32a to 32c is defined as a combination of straight lines, and coordinate information of the start point and end point of each straight line is included in the crack position information.

  Returning to the description of FIG. 3 and FIG. 4, the dark region position information generation unit 15 performs a binarization process on the cell image 30 and specifies a dark pixel group having a predetermined area or more, whereby the dark region 34a, Dark region position information representing a position such as 34b is generated (S4). The dark area position information generated in this way is output to the dark area determination unit 16.

  Here, the threshold value of the brightness of the binarization process is set to such an extent that each pixel in the dark region 34a (see FIG. 5) whose brightness is slightly lower than the surroundings is determined as a dark pixel.

  FIG. 7 is an explanatory diagram of generation of dark region position information. When the binarization process using the threshold value is performed on the cell image 30 shown in FIG. 5, as shown in FIG. 7, in addition to the dark regions 34 a and 34 b caused by the cracks 32 a to 32 c, crystal grains A dark region 56 corresponding to the boundary 36 may also be extracted.

  In addition to this, binarization is also performed due to factors such as the fact that the brightness of the outer peripheral portion of the solar battery cell 21 is slightly lower than the brightness of the central part and the brightness of the individual solar battery cells 21 varies. An unintended dark region may be extracted in the process.

  Therefore, the dark region position information includes information on the positions of the dark regions 34a and 34b caused by the cracks 32a to 32c as well as unintended dark regions such as the dark region 56 corresponding to the crystal grain boundaries 36. May contain information representing the location.

  The dark area position information includes coordinate information of the dark areas 34a and 34b. The dark area position information also includes coordinate information of the outer edges of the dark areas 34a, 34b and the like. Specifically, the outer edge of each dark region 34a, 34b, etc. is defined as a combination of straight lines, and the coordinate information of the start point and end point of each straight line is included in the dark region position information. The dark region position information may include information on the areas of the dark regions 34a and 34b.

  Returning to the description of FIG. 3 and FIG. 4, the dark area determination unit 16 generates a crack from the dark areas 34 a, 34 b, 56 extracted in S 4 based on the input crack position information and dark area position information. Dark regions 34a and 34b resulting from 32a to 32c are determined (S5). Then, the dark region determination unit 16 corrects the dark region position information according to the determination result, and outputs it to the quality determination unit 17 and the display control unit 19.

  FIG. 8 is an explanatory diagram of determination of a dark region. In the figure, the relationship between the position of the crack 32a represented by the crack position information and the position of the dark area 34a represented by the dark area position information is shown in an enlarged manner. As shown in the figure, a part of the crack 32a is located along the outer edge portion in the dark region 34a. For this reason, the dark region determination unit 16 performs determination based on the length of the crack 32a existing in the dark region 34a. Specifically, if the length of the crack 32a existing in the dark region 34a is equal to or greater than a predetermined ratio (for example, 30% or more) with respect to the length of the outer edge of the dark region 34a, the dark region 34a is cracked. It is determined that it is caused by 32a.

  Depending on the threshold value of the binarization processing of the dark area position information generation unit 15, the crack 32a may be located outside the dark area 34a. In this case, a predetermined value is applied from the outer edge of the dark area 34a. The determination may be made based on whether or not there is a crack 32a along the range.

  The quality determination unit 17 uses the number of cracks 32a to 32c specified in the cell image 30 and the number of dark regions 34a and 34b caused by the cracks 32a and 32b to indicate the solar battery cell represented in the cell image 30. The quality of 21 is determined and classification is performed (S6). Information on the quality class is output to the display control unit 19. Here, for the determination of quality, a simple sum of the numbers of cracks 32a to 32c and dark regions 34a and 34b may be used, or a weighted sum corresponding to these types may be used, or the magnitudes thereof may be used. A weighted sum corresponding to the size may be used. In addition, when the cell image 30 represents the several photovoltaic cell 21, quality is determined about each photovoltaic cell 21. FIG.

  The display control unit 19 generates a display image for identifying and displaying the cracks 32a to 32c specified in the cell image 30 and the dark regions 34a and 34b caused by the cracks 32a and 32b (S7). Is displayed on the display unit 9 (S8). FIG. 9 is a diagram illustrating an example of the display image 60. The display control unit 19 combines the crack identification images 62a to 62c and the dark region identification images 64a and 64b corresponding to the cracks 32a to 32c and the dark regions 34a and 34b of the cell image 30, respectively, for display. An image 60 is generated.

  Thus, by synthesizing the dark region identification images 64a and 64b at the positions of the dark regions 34a and 34b caused by the cracks 32a and 32b, the dark regions 34a and 34b caused by the cracks 32a and 32b become crystal grain boundaries. It is identified and displayed as 36 etc.

  Further, the display control unit 19 may identify and display the quality class of each solar cell 21 based on the information from the quality determination unit 17.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made by those skilled in the art.

  For example, the crack position information generation unit 14 specifies the positions of the cracks 32a to 32c using a Laplacian filter. However, the present invention is not limited to this mode. For example, a linear pixel whose brightness is lower than that of the surroundings in the cell image 30. You may make it extract a group and specify this as the crack 32a-32c.

  In this case, as shown in FIG. 5, it is difficult to specify the crack 32b when the dark region 34b having a clearly low brightness and the crack 32b forming the outer edge thereof have the same brightness, If the dark region position information generation unit 15 separately extracts a dark region 34b with clearly low brightness, the crack 32b may not be specified. That is, the dark region position information generation unit 15 performs binarization with a lightness threshold that does not extract the crystal grain boundary 36 because the dark region 34b having a clearly low lightness is extracted separately from the binarization process described above. Processing is performed, and the dark region 34b extracted by this processing may be handled as a dark region to be detected as a defect regardless of the presence or absence of the crack 32b.

  Further, for example, the determination by the dark region determination unit 16 is not limited to the above-described mode. For example, when the crack 32z and the dark region 34z are detected in a positional relationship as illustrated in FIG. If it is on the extension line of a part of the outer edge, the dark region 34z may be determined to be caused by the crack 32z.

It is a block diagram showing the example of a structure of the inspection system of the solar cell which concerns on one Embodiment of this invention. It is a schematic diagram showing a solar cell panel. It is a schematic diagram showing a photovoltaic cell. It is a block diagram showing the functional structural example of the inspection apparatus of the solar cell which concerns on one Embodiment of this invention. It is a flowchart showing the inspection method of the solar cell which concerns on one Embodiment of this invention. It is a figure showing the example of a cell image. It is explanatory drawing of the production | generation of crack position information. It is explanatory drawing of the production | generation of dark area position information. It is explanatory drawing of determination of a dark area. It is a figure showing the example of the image for a display. It is explanatory drawing of the modification of the determination of a dark area.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Solar cell inspection system, 2 Solar cell panel, 3 Current supply part, 4 Positioning part, 5 Imaging part, 8 Operation part, 9 Display part, 10 Solar cell inspection apparatus (control part), 11 Current supply control part, 12 Position Control unit, 13 Image acquisition unit, 14 Crack position information generation unit, 15 Dark region position information generation unit, 16 Dark region determination unit, 17 Quality determination unit, 19 Display control unit, 21 Solar cell, 23 Lead wire, 25 Stack Body, 27 light receiving surface, 28 bus bar, 29 finger, 30 cell image, 32a-32c crack, 34a, 34b dark region, 36 crystal grain boundary, 42a-42c, 46 boundary portion, 56 dark region, 60 display image, 62a-62c Crack identification image, 64a, 64b Dark area identification image.

Claims (12)

Image acquisition means for acquiring a cell image representing one or a plurality of polycrystalline solar cells in an energized state;
A linear pixel group having a lightness lower than that of the surroundings is specified in the cell image, and crack position information generating means for generating position information of the crack of the solar battery cell;
Dark region position information generating means for specifying a pixel group having a predetermined area or more in a cell image by binarization processing, and generating position information of the dark region of the solar battery cell. When,
Dark region determination means for determining whether or not the dark region is a dark region caused by the crack, based on a positional relationship between the dark region and the crack;
A solar cell inspection apparatus comprising: The crack position information generating means identifies a boundary part of a change in brightness in the cell image, and generates position information of the crack of the solar battery cell.
The solar cell inspection apparatus according to claim 1. The crack position information generating means identifies the boundary portion by a first-order differential filter;
The solar cell inspection apparatus according to claim 2. The crack position information generating means specifies the boundary portion by a second-order differential filter;
The solar cell inspection apparatus according to claim 2. The dark area determination means performs the determination based on the length of the crack along the outer edge of the dark area.
The solar cell inspection apparatus according to claim 1. The dark area determination means performs the determination based on the length of the crack existing in the dark area.
The solar cell inspection apparatus according to claim 1. The dark region determining means performs the determination based on a ratio between the length of the outer edge of the dark region and the length of the crack.
The solar cell inspection apparatus according to claim 5 or 6. Further comprising quality judging means for judging the quality of the solar battery cell based on the number of dark regions caused by the cracks
The solar cell inspection apparatus according to claim 1. It further comprises display control means for identifying and displaying a dark area caused by the crack,
The solar cell inspection apparatus according to claim 1. Obtaining a cell image representing one or more polycrystalline solar cells in an energized state;
A linear pixel group having a lightness lower than that of the surroundings is specified in the cell image, and position information on the crack of the solar battery cell is generated.
A pixel group having an area of a predetermined area or more in which pixels having a predetermined brightness or less are gathered is specified in the cell image by binarization processing , and position information of a dark region of the solar battery cell is generated,
Based on the positional relationship between the dark region and the crack, it is determined whether or not the dark region is a dark region caused by the crack.
Solar cell inspection method. An image acquisition means for acquiring a cell image representing one or a plurality of polycrystalline solar cells in an energized state;
Crack position information generating means for specifying a linear pixel group having a lightness lower than that of the surrounding area in the cell image and generating position information of the crack of the solar battery cell,
Dark region position information generating means for specifying a pixel group having a predetermined area or more in a cell image by binarization processing, and generating position information of the dark region of the solar battery cell. ,as well as,
Dark region determination means for determining whether or not the dark region is a dark region caused by the crack, based on a positional relationship between the dark region and the crack;
A program characterized by causing a computer to function. An imaging unit that images one or more polycrystalline solar cells in an energized state and generates a cell image representing the solar cells;
Image acquisition means for acquiring the cell image;
A linear pixel group having a lightness lower than that of the surroundings is specified in the cell image, and crack position information generating means for generating position information of the crack of the solar battery cell;
Dark region position information generating means for specifying a pixel group having a predetermined area or more in a cell image by binarization processing, and generating position information of the dark region of the solar battery cell. When,
Dark region determination means for determining whether or not the dark region is a dark region caused by the crack, based on a positional relationship between the dark region and the crack;
A solar cell inspection system comprising:

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