TWI496091B - Thin film detecting method and detecting device - Google Patents

Description

Film detecting method and detecting device

The invention relates to a detection method, in particular to a film detection method.

Referring to FIG. 1, a phase retarder film 900 attached to a display panel (not shown) is mainly used for generating 3D images. The phase retardation film 900 includes a plurality of first phase display regions 910 and a plurality of second phase display regions 920. The first phase display regions 910 and the second phase display regions 920 are parallel and staggered. In practice, since the phase retardation film 900 is subjected to the expansion and contraction of the polymer film itself, the width Dpixel of the first phase display region 910 and the second phase display region 920 is changed, and the pixel on the panel cannot be accurately matched. , which in turn affects the 3D effect of the image.

However, a common detection method today is to measure the total length Dtotal of the phase retardation film 900, and then calculate the number of the first phase display region 910 and the second phase display region 920 of the phase retardation film 900, and finally the total length of the phase retardation film. By dividing Dtotal by the number of total phase display areas, the average width Dpixel (average) of each phase display area can be obtained. And whether the Dpixel (average) is within a predetermined range, thereby predicting the performance of the phase retardation film 900 on the panel, but the detection method does not know the Dpixel data of each phase display region in the phase retardation film 900, and thus cannot The 3D effect of each phase display area on the phase retardation film 900 on the display panel is accurately estimated.

Accordingly, it is an object of the present invention to provide a film detecting method which can more accurately detect the uniformity of a film to be tested.

Therefore, the film detecting method of the present invention detects a film to be tested attached to a display panel, and the film detecting method comprises the following steps:

(A) reading a reference position associated with the film to be tested;

(B) taking a majority of the detected images at intervals of the pixel arrangement direction of the panel to be tested;

(C) calculating a distance difference between a calibration position corresponding to the reference position and the reference position in the detected images, and correspondingly generating a plurality of offset values;

(D) outputting the offset values to determine the uniformity of the film to be tested by the offset values. In detail, step (D) is to output the offset values generated by all processing units in a graphical manner.

In addition, the film to be tested includes a plurality of first phase display regions and second phase display regions that are parallel and staggered, and the reference position is located at a boundary between one of the first phase display regions and the adjacent second phase display region. position. Further, the reference position is located at an ideal center position of each of the detected images, and the calibration position is a boundary position between the first phase display area and the second phase display area located in the middle of each of the detected images.

Further, another object of the present invention is to provide a detecting device which can perform the above-described film detecting method.

The detecting device of the present invention is configured to detect a film to be tested attached to a display panel, and includes a storage unit, an image capturing unit, a processing unit coupled to the storage unit and the image capturing unit, and a coupling unit The output unit of the processing unit. The storage unit stores a reference position related to the film to be tested; the camera unit is configured to capture a plurality of detection images at intervals corresponding to the pixel arrangement direction of the display panel of the film to be tested; the processing unit reads the reference position from the storage unit, and Calculating a distance difference between a calibration position and a reference position corresponding to the reference position in the detected images to generate a plurality of offset values; the output unit is configured to output the offset values by using the offset values Determine the uniformity of the film to be tested.

The output unit outputs the offset values generated by all the processing units in a graphical manner, or outputs the offset values to a detecting circuit, and the detecting circuit respectively compares the offset values with a standard deviation value. A comparison is made to detect the film to be tested.

However, the film detecting method of the present invention may also comprise the following steps:

(A) reading a reference image related to the film to be tested;

(B) taking a majority of the detected images at intervals of the pixel arrangement direction of the panel to be tested;

(C) subtracting the detected images from the reference image to generate a plurality of difference images;

(D) generating an offset corresponding to the uniformity of the film to be tested according to the difference image; and

(E) outputting the offset to determine the uniformity of the film to be tested by the offset.

In this detection method, step (D) may include the following sub-steps:

(D-1) calculating a grayscale value of the difference image is higher than a preset value, and if the grayscale value of the difference image is higher than a preset value, the difference image is regarded as an all white image. If the grayscale value of the difference image is lower than the preset value, the difference image is regarded as a full black screen;

(D-2) dividing the number of all-white pictures in the calculated difference image by the resolution of the detected images to obtain a ratio of grayscale values in the detected images to be higher than a preset value;

(D-3) According to the ratio of the grayscale value in the detected image being higher than the preset value, an offset corresponding to the ratio is generated.

And step (A) is to take a reference image on the film to be tested, or read the reference image from a storage unit.

Further, another object of the present invention is to provide a detecting device which can perform the above-described film detecting method.

The detecting device of the present invention detects a film to be tested attached to a display panel, and includes a camera unit, a storage unit, a processing unit coupled to the storage unit and the camera unit, and a coupling unit The output unit of the processing unit.

The camera unit is configured to capture a plurality of detection images at intervals of a pixel arrangement direction of the display panel corresponding to the display panel; the storage unit stores the image captured by the camera unit; and the processing unit reads a reference image related to the film to be tested. And subtracting the detected images from the reference image to generate a plurality of difference images, and generating an offset corresponding to the uniformity of the film to be tested according to the difference images; the output unit outputs the offset The amount is determined by determining the uniformity of the film to be tested by the offset.

Further, the detecting device further includes a counting unit coupled to the processing unit, and the processing unit controls the counting unit to count when the grayscale value of the difference image is higher than a preset value, and the counting unit counts The number of all white images in the difference image is divided by the resolution of the detected images to obtain a ratio of grayscale values in the detected images that are higher than a preset value, and an offset is generated according to the ratio.

In addition, the reference image may be captured by the film to be tested of the camera unit and stored in the storage unit, and the processing unit may read the reference image from the storage unit, or the reference image may be pre-stored in the storage unit, and the processing unit is from the storage unit. Read the reference image in .

The effect of the invention is that the performance of the film to be tested can be graphically attached to the display panel, and the film to be tested can be detected more accurately.

The above and other technical contents, features and advantages of the present invention will be apparent from the following detailed description of the accompanying drawings.

Referring to FIG. 2 to FIG. 4, a first embodiment of a method for detecting a film according to the present invention is applied to a detecting device 100 for a film to be tested 200 attached to a display panel (not shown). In the present embodiment, the detecting device 100 is an Automated Optical Inspection (AOI), and the film to be tested 200 is a phase retardation film, which includes a plurality of first phase displays that are parallel and staggered. The area 210 and the second phase display area 220.

The detecting device 100 includes a storage unit 10, an imaging unit 20, a processing unit 30, and an output unit 40. The storage unit 10 is a memory for storing a reference position P _ref related to the film to be tested 200. The imaging unit 20 can be an imaging element such as a charge coupled device (CCD) or a complementary CMOS sensor for capturing an image of the film to be tested 200. The processing unit 30 is coupled to the storage unit 10 and the imaging unit 20 for processing the image captured by the camera unit 20 and generating a corresponding offset value. The output unit 40 is coupled to the processing unit 30 for outputting the offset values.

Referring to FIG. 2, FIG. 3 and FIG. 5, the detailed process of the film detecting method of the first embodiment is as follows:

In step S11, the processing unit 30 reads from the storage unit 10 a reference position P _ref related to the film to be tested 200 and positioned at a boundary position between one of the first phase display regions 210 and the second phase display region 220 adjacent thereto. In this embodiment, the reference position P _ref is located at an ideal center position of the image captured by the image capturing unit 20 , but is not limited thereto.

In step S12, the imaging unit 20 captures the plurality of detection images 50 at intervals corresponding to the pixel arrangement direction of the display panel of the film to be tested 200. Referring to FIG. 6 , the image capturing unit 20 of the embodiment captures a detection image 50 every 40 pixel distances, and each of the detection images 50 includes at least two first phase display regions 210 and at least The second phase display area 220 is alternately arranged with the two first phase display areas 210. For convenience of description, only four detection images 50 are shown in FIG. 6, and are respectively labeled 51 to 54, but the distance is 撷, The number of images taken and the number of the first phase display area 210 and the second phase display area 220 included in each detected image are not limited to the embodiment.

In step S13, the processing unit 30 calculates a distance difference between the center position of the detected images 51 to 54 (ie, the boundary position between the first phase display area 210 and the second phase display area 220 in the middle) and the reference position P _ref , and correspondingly generates Most offset values. Taking FIG. 6 as an example, the distance between the center positions of the four detection images 51 to 54 and the reference position P _ref is D1 to D4. In particular, since the reference position P _ref of the embodiment is set in the middle of each image, and ideally, the width of each of the first phase display area 210 and the second phase display area 220 is a display panel. The width of one of the pixels, therefore, in the case where the positioning accuracy of the image capturing unit 20 is sufficient, a calibration position (ie, a center position) corresponding to the reference position P _ref in each of the detected images 51 to 54 is supposed to be the reference position P _{The refs are} completely overlapped. If there is a deviation between the two, it means that the first phase display area 210 or the second phase display area 220 may not be a pixel width due to process error or self-expansion characteristics, so The offset value can detect the actual offset width of the first phase display area 210 or the second phase display area 220. Of course, the calibration position for determining the width of the first phase display area 210 or the second phase display area 220 may also be set at a different position, for example, the first phase display area 210 located at the rightmost of the detected images 51-54 The boundary position of the two-phase display area 220 or the boundary position between the leftmost first phase display area 210 and the second phase display area 220 is not limited to the intermediate position.

In step S14, the output unit 40 outputs the offset values. In the present embodiment, the output unit 40 draws the offset values generated by all the processing units 30 into a characteristic graph output, as shown in FIG. The horizontal axis of FIG. 7 is the number of pitches of the phase display region, and the vertical axis is the actual offset value (μm) corresponding to the phase display region. FIG. 7 can show the distribution of the offset value characteristic of the entire film to be tested 200. The change is judged by the uniformity of the film 200 to be tested.

Referring to FIG. 5 to FIG. 7 , in the embodiment, the image capturing unit 20 extracts the detection image 50 from the one side (such as the left side) of the film to be tested 200 to the other side (such as the right side). The detected image 50 of the second capture may have an offset value corresponding to the width error of each of the first phase display area 210 and the second phase display area 220 of the interval, and therefore, the detection of the left side of the film to be tested 200 is adjacent. The deviation value corresponding to the image 50 may be lower than the deviation value corresponding to the detection image 50 on the right side of the film to be tested 200. Of course, the reference position P _ref can also be located at the boundary position between the first phase display area 210 and the second phase display area 220 in the middle of the film to be tested 200. The camera unit 20 can be centered on the boundary position, and the left and right sides respectively The detection image 50 is captured on opposite sides of the film to be tested 200. Thus, the deviation of the detection image 50 adjacent to the film 200 to be tested is lower than the detection image 50 on the opposite side of the film 200 to be tested. Corresponding to the generated deviation value, the characteristic curve outputted by the output unit 40 is as shown in FIG. 8 and is not limited to this embodiment.

In practical applications, the detecting device 100 of the embodiment can be used in conjunction with a testing machine (not shown). As shown in FIG. 9, the whole film is conveyed and cut through the testing machine to form different specifications. The detecting film 200 of the display panel, the detecting device 100 uses the above-mentioned detecting method to respectively take a plurality of detection images for the opposite sides (such as the T point position) of each of the films to be tested 200, and separately generate the generated images. A plurality of offset values are plotted as two characteristic graphs for the tester to detect the uniformity of the film to be tested 200 by the two characteristic graphs. If the offset values are less than a standard curve L1 corresponding to the specification of the display panel, as shown in FIG. 10, it is regarded as passing the test, and the test machine transports the film to be tested 200 to the good product area; The offset value is partially larger than the standard curve L1. As shown by the broken line in FIG. 11, it is regarded as the detection failure, and the test machine transports the film to be tested 200 to the repair or scrap area. In this way, the film 200 to be tested can be detected more accurately and more quickly to achieve the effect of the present invention.

In particular, in order to achieve fully automated detection, the output unit 40 can also output all offset values to a detection circuit (not shown, which can be built in or external to the processing unit 30), which is used to The offset values are respectively compared with a standard deviation of a pair of standard curve L1 (as shown in FIG. 10 and FIG. 11 and its value is 150). If all the offset values are smaller than the standard deviation, the detection is passed. If at least one offset value is greater than the standard deviation, it means that the detection fails, and then the test machine cooperates with the detection circuit to deliver the film to be tested 200 to the corresponding area, which will save the manpower of the test. Reduce test costs. In addition, the position at which the detecting device 100 captures images is not limited to the opposite sides of the film 200 to be tested, and may be opposite sides and intermediate positions of the film 200 to be tested, or any number of positions to detect each of the images more accurately. The film to be tested 200.

12 and FIG. 13 are a second embodiment of the method for detecting a film according to the present invention. In the embodiment, the detecting method is applied to a detecting device 100. The detecting device 100 includes a storage unit 10 and an image capturing unit 20, A processing unit 30, an output unit 40 and a counting unit 60. The storage unit 10 is a memory for storing images captured by the camera unit 20. The imaging unit 20 can be an imaging element such as a charge coupled device (CCD) or a complementary CMOS sensor for capturing an image of the film 200 to be tested. The processing unit 30 is coupled to the storage unit 10 and the imaging unit 20 for processing the image captured by the camera unit 20 and generating a corresponding offset value. The output unit 40 is coupled to the processing unit 30 for outputting the offset. The counting unit 60 is coupled to the processing unit 30, and its function is explained in the following paragraph.

Referring to FIG. 12 to FIG. 14, the detailed process of the film detecting method of the second embodiment is as follows:

In step S21, the camera unit 20 captures a reference image Image(ref) on the film to be tested 200 and stores it in the storage unit 10 for reading by the processing unit 30.

In step S22, the imaging unit 20 captures a plurality of detected images Image(N) at intervals of the pixel arrangement direction of the display panel 200 corresponding to the display panel, where N is a positive integer. The image capturing unit 20 of the embodiment also captures one detected image every 40 pixel distances, and the image range of each detected image is the same.

In step S23, the processing unit 30 subtracts the detected image Image(N) from the reference image Image(ref) stored in the storage unit 10 to generate a plurality of difference images Image_delta, as shown in FIG. 15 to FIG. .

Referring to FIG. 15 to FIG. 17, if the width of each of the first phase display area 210 and the second phase display area 220 in the image Image (N) is detected and each of the first phase display areas 210 and the reference image Image (ref) The width of the two-phase display area 220 is the same, and after subtracting the two, the difference image Image_delta will become a full black picture, as shown in FIG. 15, if there is a deviation between the two, the first phase display area 210 or the second is indicated. The phase display area 220 may have a width that is not a pixel width due to a process error, and a white stripe image may appear in the difference image Image_delta, as shown in FIG. 16, if the first phase of the detected image Image(N) is displayed. The area 210 and the second phase display area 220 are completely interlaced with the first phase display area 210 and the second phase display area 220 in the reference image Image (ref), that is, the deviation is up to one pixel distance, and the difference image Image_delta is completely white. The picture is shown in Figure 17. As can be seen from FIG. 15 to FIG. 17, the actual width of the first phase display region 210 or the second phase display region 220 in the detected image Image(N) can be determined by the ratio of the white stripe image in the difference image Image_delta.

Therefore, referring to FIG. 12 and FIG. 13, in step S24, the processing unit 30 generates a pair of offsets of the uniformity of the film 200 to be tested according to the difference image Image_delta. In detail, referring to FIG. 18, step S24 includes the following sub-steps:

Step S241, the processing unit 30 determines whether the gray level of the difference image Image_delta is higher than a preset value, and if yes, executing step S242, the processing unit 30 regards the difference image Image_delta as an all white screen, and controls the counting unit. 60 is counted, and then step S244 is performed; if no, step S243 is executed, and the processing unit 30 regards the difference image Image_delta as a full black screen, and then executes step S244.

In step S244, the processing unit 30 divides the number of all white pictures in the difference image counted by the counting unit 60 by the resolution (such as 640*480) of the detected image Image(N) to obtain the detected image Image ( N) is the ratio of the all white screen.

In step S245, the processing unit 30 generates an offset corresponding to the ratio according to the ratio of the detected image Image(N) to the all white screen. In this embodiment, the processing unit 30 generates a corresponding offset according to the comparison table of the full white screen ratio and the offset amount as shown in FIG. 19, and the horizontal axis thereof is the ratio of the all white screen, as shown in FIG. The vertical axis is the offset (μm), and the processing unit 30 transmits the curve in FIG. 19 to know how many offsets the number of detected images Image(N) of the all-white image is, and the offset is The detected images Image(N) are the ratio of the full white screen multiplied by the interval at which the images are captured.

After the offset is generated in step S245, step S25 is performed.

In step S25, the output unit 40 outputs the offset to determine the uniformity of the film to be tested 200 according to the offset.

It is to be noted that the film detecting method of the second embodiment is different from the first embodiment in that the film detecting method of the present embodiment takes an image as a reference image before the film 200 to be tested. And storing in the storage unit 10, and then taking a plurality of detection images Image(N) from the pixel arrangement direction of the display panel of the film to be tested, and using the reference image as a reference, and all the detection images. Compared with Image(N), the corresponding offset generated can also reflect the uniformity of the film to be tested 200.

In addition, referring to FIG. 12, FIG. 13, and FIG. 15, the reference image Image(ref) of the present embodiment may also be stored in the storage unit 10 in advance as in the first embodiment, and in step S21, the processing unit 30 may be from the storage unit. The reference image Image (ref) is read in 10 and compared with the detected image Image(N), and is not limited to this embodiment.

In summary, the film detecting method of the present invention compares the calibration position in the plurality of detection images 50 with a reference position to generate a plurality of offset values of the uniformity of the film 200 to be tested, or The plurality of detection images Image(N) are compared with a reference image Image(ref) to generate an offset that can reflect the uniformity of the film to be tested 200. Thus, the difference detection method can pattern the film to be tested 200. The performance attached to the display panel allows the film 200 to be tested to be more accurately detected, so that the object of the present invention can be achieved.

The above is only the preferred embodiment of the present invention, and the scope of the invention is not limited thereto, that is, the simple equivalent changes and modifications made by the scope of the invention and the description of the invention are All remain within the scope of the invention patent.

S11~S14. . . step

S21~S25. . . step

S241~S245. . . step

100. . . Testing device

200. . . Film to be tested

210. . . First phase display area

220. . . Second phase display area

10. . . Storage unit

20. . . Camera unit

30. . . Processing unit

40. . . Output unit

50. . . Detection image

51~54. . . Detection image

60. . . Counting unit

900. . . Phase retardation film

910. . . First phase display area

920. . . Second phase display area

Dpixel. . . Display area width

Dpixel (average). . . Average width of the display area

D1~D4. . . Distance difference

Figure 1 is an illustration;

Figure 2 is a flow chart for explaining the film detecting method of the first embodiment;

Figure 3 is a circuit block diagram showing the detecting device of the first embodiment;

4 is a schematic view showing a film to be tested according to the present invention, comprising a plurality of first phase display regions and second phase display regions arranged in parallel and staggered;

5 is a diagram illustrating that the image capturing unit captures a plurality of detected images at intervals in a pixel arrangement direction of the corresponding display panel of the film to be tested;

FIG. 6 is a view showing four detection images captured by the image capturing unit;

7 is a characteristic diagram illustrating the uniformity of a film to be tested, wherein the image pickup unit generates an offset value by extracting a detection image from a side of one side of the film to be tested to the other side thereof;

FIG. 8 is a characteristic diagram illustrating the uniformity of the film to be tested, wherein the image capturing unit generates an offset value by extracting a detection image from the middle of the film to be tested to the opposite sides;

Figure 9 is a schematic view showing the use of the detecting device of the present invention in conjunction with a testing machine;

FIG. 10 is a characteristic diagram corresponding to the film to be tested for detecting passing; FIG.

Figure 11 is a graph showing the characteristic curve corresponding to the film to be tested that has failed to pass;

Figure 12 is a flow chart for explaining the film detecting method of the second embodiment;

Figure 13 is a circuit block diagram showing the detecting device of the second embodiment;

FIG. 14 is a view showing that the image capturing unit captures a plurality of detection images at intervals in a pixel arrangement direction of the corresponding display panel of the film to be tested;

15 is a schematic diagram showing that the detected image completely overlaps with the reference image, and the difference image is a full black image;

FIG. 16 is a schematic diagram showing a deviation between a detected image and a reference image, and a white stripe image is displayed on the difference image;

17 is a schematic diagram illustrating a deviation of a detected image from a reference image by a pixel distance, so that the difference image is an all-white image;

FIG. 18 is a flow chart illustrating the processing unit according to the second embodiment generating an offset according to the difference image; and

Fig. 19 is a table for explaining the ratio of the full white screen and the offset.

S11~S14. . . step

Claims (16)

A film detecting method for detecting a film to be tested attached to a display panel, the film detecting method comprising the steps of: (A) reading a reference position related to the film to be tested; (B) The film to be tested is obtained by taking a majority of the detected images at intervals corresponding to the pixel arrangement direction of the display panel; (C) calculating a distance difference between a calibration position corresponding to the reference position and the reference position in the detected images, and correspondingly generating a majority And (D) outputting the offset values, wherein the film to be tested comprises a plurality of first phase display regions and second phase display regions arranged in parallel and staggered, wherein the reference position is located therein A boundary position of a first phase display area and its adjacent second phase display area. The film detecting method according to claim 1, wherein the step (D) is to output the offset value generated by all the processing units in a graphical manner. The film detecting method according to claim 1, wherein the reference position is positioned at a desired center position of each of the detected images. The film detecting method according to claim 3, wherein the calibration position is a boundary position between the first phase display region and the second phase display region located in the middle of each of the detected images. A film detecting method for detecting a film to be tested attached to a display panel, the film detecting method comprising the following steps: (A) reading a reference image associated with the film to be tested; (B) extracting a plurality of detection images at intervals corresponding to a pixel arrangement direction of the display panel; (C) respectively separating the detection images Subtracting from the reference image to generate a plurality of difference images; (D) generating a pair of offsets corresponding to the uniformity of the film to be tested according to the difference images; and (E) outputting the offset, Wherein, the step (D) comprises the following sub-steps: (D-1) calculating a grayscale value of the difference image is higher than a preset value; (D-2) calculating the calculated difference image The number of white screens is divided by the resolution of the detected images to obtain a ratio of grayscale values in the detected images that are higher than the preset values; and (D-3) the grayscale values in the detected images. A ratio higher than the preset value produces an offset corresponding to the ratio. The method for detecting a film according to claim 5, wherein the step (A) is to take the reference image on the film to be tested. The film detecting method according to claim 5, wherein the reference image is stored in advance in the storage unit, and the step (A) reads the reference image from a storage unit. The method for detecting a film according to claim 5, wherein if the grayscale value of the difference image is higher than the preset value, the difference image is regarded as an all white image, if the difference image is The grayscale value is lower than the preset value. Then, the difference image is regarded as a full black picture. A detecting device for detecting a film to be tested attached to a display panel, the detecting device comprising: a storage unit for storing a reference position related to the film to be tested; and an image capturing unit for The film to be tested is spaced apart from the pixel arrangement direction of the display panel to capture a plurality of detection images; a processing unit is coupled to the storage unit and the image capturing unit, and the processing unit reads the reference position from the storage unit. And calculating a distance difference between a calibration position corresponding to the reference position and the reference position in the detection image to generate a plurality of offset values; and an output unit coupled to the processing unit for outputting the offsets a value, wherein the film to be tested includes a plurality of first phase display regions and a second phase display region that are parallel and staggered, the reference position being located in a first phase display region and a second phase display adjacent thereto The intersection of the areas. The detecting device according to claim 9, wherein the output unit outputs the offset values generated by all the processing units in a graphical manner. The detecting device according to claim 9, wherein the output unit outputs the offset values to a detecting circuit, and the detecting circuit compares the offset values with a standard deviation value to detect the Film to be tested. The detecting device according to claim 9, wherein the reference position is located at a desired center position of each of the detected images. The detecting device according to claim 12, wherein the calibration position is a boundary position between the first phase display region and the second phase display region located in the middle of each of the detected images. A detecting device for detecting a film to be tested attached to a display panel, the detecting device comprising: an image capturing unit for spacing the pixels of the film to be tested corresponding to the direction of the pixel arrangement of the display panel a plurality of sheets of image detection; a storage unit for storing images captured by the camera unit; a processing unit coupled to the storage unit and the camera unit, the processing unit reading a reference image associated with the film to be tested, And subtracting the detected images from the reference image to generate a plurality of difference images, and generating a pair of offsets corresponding to the uniformity of the film to be tested according to the difference images; Connected to the processing unit, the processing unit determines that the grayscale value of the difference image is higher than a preset value, controls the counting unit to count, and displays the difference image counted by the counting unit in an all white screen. The number is divided by the resolution of the detected images to obtain a ratio of grayscale values in the detected images that are higher than the preset value, and the offset is generated according to the ratio; and an output unit, Connected to the processing unit, for outputting the offset. According to the detecting device of claim 14, wherein the reference The image is taken from the film to be tested by the camera unit and stored in the storage unit, and the processing unit reads the reference image from the storage unit. The detecting device according to claim 14, wherein the reference image is stored in advance in the storage unit, and the processing unit reads the reference image from the storage unit.