JP5653370B2 - Method for inspecting cracks in solar cells - Google Patents

Description

  The present invention relates to a method for inspecting a crack defect of a solar battery cell, particularly a single crystal cell.

  Conventionally, in a method for inspecting a crack defect of a solar battery cell, a binarization process is carried out by subtracting an image taken when light is irradiated from directly above the surface of the solar battery cell and an image when irradiated from an oblique direction. It was. For example, in the technique disclosed in Patent Document 1, the presence or absence of a crack is determined by the number of pixels (area value) obtained.

JP-A-3-218045

  On the surface of the solar cell, peeling of the grid line (hereinafter also referred to as grid line peeling) may occur. As for grid line peeling, as long as it is peeled by a certain amount or less, it may be determined not as a defective product but as a non-defective product.

  However, in the inspection method as described above, due to the binarization of the difference image, the grid line peeling may be extracted as a crack, and the solar cell that should be treated as a non-defective product is determined as a defective product. was there. When a solar cell to be treated as a non-defective product is determined to be a defective product, there is a problem that, for example, yield decreases and further inspection costs increase.

  This invention is made | formed in view of the above, Comprising: It aims at obtaining the inspection method of the photovoltaic cell which can detect a crack defect distinguished from grid line peeling.

  In order to solve the above-described problems and achieve the object, the present invention provides a step of performing edge enhancement processing on an input image in which solar cells are photographed, and an edge enhanced image subjected to edge enhancement processing. A step of performing binarization processing, a step of performing labeling on the binarized image that has been binarized, and a step of performing equivalent ellipse approximation on a blob obtained by labeling to obtain an equivalent ellipse And a step of determining that the blob portion is a crack defect when a principal axis angle, which is an angle formed between the major axis of the equivalent ellipse and a predetermined axis, is within a certain range. .

  According to the present invention, it is possible to detect a crack defect without including grid line peeling as much as possible, and it is possible to improve the yield and reduce the cost.

FIG. 1 is a flowchart showing a procedure of a solar cell inspection method according to an embodiment of the present invention. FIG. 2-1 is a diagram illustrating an example in which a crack defect is included in an input image obtained by photographing a solar battery cell. FIG. 2-2 is a diagram illustrating an example in which grid line peeling is included in an input image obtained by photographing solar cells. FIG. 3 is a diagram illustrating a blob obtained by labeling, and is a diagram for explaining the principal axis length and the principal axis angle of an equivalent ellipse. FIG. 4A is a diagram illustrating a detection example of a main axis angle of a crack defect, and is a diagram illustrating a relationship between the main axis angle and the main axis length. FIG. 4B is a diagram illustrating a detection example of the main axis angle of the grid line peeling, and is a diagram illustrating a relationship between the main axis angle and the main axis length.

  Below, the crack inspection method of the photovoltaic cell concerning embodiment of this invention is demonstrated in detail based on drawing. Note that the present invention is not limited to the embodiments.

Embodiment 1 FIG.
FIG. 1 is a flowchart showing a procedure of a solar cell inspection method according to an embodiment of the present invention. FIG. 2-1 is a diagram illustrating an example in which a crack defect is included in an input image obtained by photographing a solar battery cell. FIG. 2-2 is a diagram illustrating an example in which grid line peeling is included in an input image obtained by photographing solar cells.

  As shown in FIGS. 2A and 2B, the input image 1 obtained by photographing the solar battery cell may include a crack defect 3 or a grid line peeling 4. In the solar cell crack inspection method according to the present embodiment, the crack defect 3 and the grid line peeling 4 included in the input image 1 are distinguished and detected. Generally, there is a line called grid line 2 on the surface of the solar battery cell, and the grid line is peeled off when the grid line is peeled off.

  As shown in FIG. 1, in the crack inspection method for a solar battery cell according to the present embodiment, an image obtained by photographing the solar battery cell is input as an input image 1 (step S1). Next, edge enhancement processing is performed on the input image 1 (step S2). Next, binarization processing is performed on the edge-enhanced image that has been subjected to edge enhancement processing (step S3). Next, labeling is performed on the obtained binarized image (step S4), and a block of pixels (hereinafter referred to as a blob) is generated.

  FIG. 3 is a diagram illustrating a blob obtained by labeling, and is a diagram for explaining the principal axis length and the principal axis angle of an equivalent ellipse. For each blob 5 obtained by labeling, an equivalent ellipse approximation is performed to obtain an equivalent ellipse 6 (step S5). Depending on the input image 1, there may be a plurality of blobs 5.

  Next, the major axis of the equivalent ellipse 6 is the major axis 10, and the major axis length 7 that is the length of the major axis 10 and the major axis angle 8 that is the angle formed by the major axis 10 and the predetermined axis 11 are extracted as feature quantities of the blob 5. (Step S6). Here, when the spindle angle 8 is within a certain range (step S7, Yes), it is determined that the blob 5 portion is a crack defect (step S8).

  Furthermore, when the main shaft length 7 is equal to or longer than the predetermined length (step S9, Yes), it is determined that the solar cell is a defective product as being a crack defect 3 that is unacceptable on the product (step S10). . On the other hand, when the main shaft length 7 is smaller than the predetermined length (step S9, No), it is determined that the crack defect 3 is sufficiently small and acceptable, and the solar battery cell is determined to be a good product (step S11).

  In step S7, when the main shaft angle 8 is out of a certain range (step S7, No), it is determined that the blob 5 portion is grid line peeling (step S12). If the main shaft length 7 is equal to or longer than the predetermined length (step S13, Yes), it is determined that the solar cell is a defective product (step S10), and if the main shaft length 7 is smaller than the predetermined length (step S10). S13, No), it is determined that the solar battery cell is a non-defective product (step S11). Note that the predetermined length in step S9 and the predetermined length in step S13 are generally different lengths.

  In a solar battery cell, particularly a single crystal cell, the progress direction of the crack defect 3 tends to strongly depend on the crystal orientation. That is, since the main axis angle 8 of the crack defect 3 is likely to be within a certain range with respect to the predetermined axis 11, it can be determined whether or not the main axis angle 8 is the crack defect 3.

  FIG. 4A is a diagram illustrating a detection example of the main shaft angle 8 of the crack defect 3, and is a diagram illustrating a relationship between the main shaft angle 8 and the main shaft length 7. FIG. 4B is a diagram illustrating a detection example of the main shaft angle 8 of the grid line peeling 4 and is a diagram illustrating a relationship between the main shaft angle 8 and the main shaft length 7.

  4A and 4B, the principal axis angle 8 is plotted against various crack defects 3 and grid line peeling 4. In FIGS. 4A and 4B, the spindle angle 8 obtained by converting ± 90 degrees into an absolute value is plotted. As shown in FIGS. 4A and 4B, if the crack defect is 3, the main shaft angle 8 is likely to be within a certain range, and if the grid line peeling is 4, the main shaft angle 8 is likely to be out of the certain range. ing. For example, a certain range of the main shaft angle 8 determined as the crack defect 3 may be 30 to 60 degrees.

  The predetermined axis 11 may be set arbitrarily. In the present embodiment, the predetermined axis 11 is an axis substantially parallel to the grid line 2 without peeling. When a different axis is used as the predetermined axis 11, the range of the main shaft angle 8 for determining a crack defect may be changed accordingly.

  As described above, the method for inspecting a crack of a solar battery cell according to the present invention is useful for detecting a crack defect in distinction from grid line peeling.

1 Input Image 2 Grid Line 3 Crack Defect 4 Grid Line Peeling 5 Blob 6 Equivalent Ellipse 7 Spindle Length 8 Spindle Angle 10 Spindle 11 Predetermined Axis

Claims (4)

Performing an edge enhancement process on an input image in which solar cells are photographed;
Performing binarization processing on the edge enhanced image on which the edge enhancement processing has been performed;
Labeling the binarized image that has been binarized;
Performing an equivalent ellipse approximation on the blob obtained by the labeling to obtain an equivalent ellipse;
When the principal axis angle, which is the angle formed between the major axis of the equivalent ellipse and a predetermined axis, is within a certain range depending on the crystal direction of the solar battery cell , it is determined that the blob portion is a crack defect. A crack inspection method for a solar battery cell, comprising: a step.   The method further includes the step of determining that the solar battery cell is defective when a principal axis length, which is a length of a major axis of the equivalent ellipse determined to be the crack defect, is equal to or longer than a predetermined length. The method for inspecting cracks in a solar battery cell according to claim 1. The solar cell has grid lines,
The solar cell according to claim 1, further comprising a step of determining that the blob portion is stripped of a grid line when the principal axis angle of the equivalent ellipse is out of the certain range. Crack inspection method.   The method further includes the step of determining that the solar battery cell is defective when a principal axis length, which is a length of a major axis of the equivalent ellipse determined to be the grid line peeling, is equal to or longer than a predetermined length. The crack inspection method of the photovoltaic cell of Claim 3 characterized by these.