Meter reading device, meter reading program, and meter reading method

Abstract

The present invention comprises: an image acquisition unit (1) that acquires a captured image; an indication needle detection unit (4) that detects the indicated position indicated by an indication needle on a captured image by comparing the captured image acquired by the image acquisition unit (1) with a reference image which shows the indication needle and which serves as a reference for detecting, on a meter, the indicated position indicated by the indication needle, and that creates an indication needle detection result based on the comparison result of the reference image and the captured image captured when the indicated position is detected; and a reference image updating unit (7) that, during comparison of the captured image and the reference image, re-creates a reference image on the basis of the indication needle detection result created by the indication needle detection unit (4), and that performs a reference image update by using an update reference image which is the re-created reference image.

Description

Meter reading device, meter reading program, and meter reading method

[0001] The present disclosure relates to a meter reading device, a meter reading program, and a meter reading method.

[0002] There is a technology for automatically reading the indicated value, which is the numerical value indicated by the meter pointer, from an image of the meter captured, instead of a human visually checking the meter. For example, Patent Document 1 discloses a technology for reading the pointer of an analog meter, in which a scanned image of the meter dial and a scanned image of the pointer based on pre-stored information indicating the shape of the pointer are created from an image of the meter dial, and a comparison is made between the scanned image of the dial and the scanned image of the pointer to calculate a likelihood distribution indicating the likelihood that the pointer is captured in the scanned image of the dial, and the numerical value indicated by the meter pointer is identified based on the distribution of the calculated likelihood in a direction perpendicular to the scale. More specifically, the information indicating the shape of the pointer includes information on the outline of the pointer and the needle color. The scanned image of the pointer is created by drawing a background image that is sufficiently larger than the length and width of the pointer stored in advance in the color of the scale dial stored in advance, drawing the outline of the pointer corresponding to the length and width based on the outline information in the center of this background image, and drawing the inside of the outline in the needle color stored in advance, and then scanning the image of the pointer created in a direction perpendicular to the scale of the captured image.

[0003] Japanese Patent Application Laid-Open No. 2020-038188

[0004] In the prior art, the scanned image of the pointer used to identify the position of the meter pointer is created from pre-stored information indicating the shape of the pointer, including information on the outline of the pointer and the needle color. Therefore, if the environmental conditions under which the meter is imaged, such as lighting, change and a difference occurs between the appearance of the pointer in the image of the meter dial and the appearance of the pointer based on the pre-stored information indicating the pointer shape, there is a problem that the accuracy of reading the meter reading may decrease.

[0005] The present disclosure has been made to solve the above-mentioned problems, and aims to provide a meter reading device that can prevent a decrease in reading accuracy even when the environmental conditions under which the meter is photographed change.

[0006] The meter reading device of the present disclosure is a meter reading device that calculates an indicated value, which is a numerical value indicated by an indicator needle, from the indicated position of the indicator needle on an image detected based on an image in which at least the dial of the meter is imaged, and is equipped with an image acquisition unit that acquires the image, an indicator needle detection unit that detects the indicated position of the indicator needle on the image by comparing the image acquired by the image acquisition unit with a reference image showing the indicator needle, which serves as a standard for detecting the indicated position of the indicator needle on the meter, and creates an indicator needle detection result based on the comparison result between the image acquired when the indicated position is detected and the reference image, and a reference image update unit that recreates the reference image based on the indicator needle detection result created by the indicator needle detection unit when comparing the image with the reference image, and updates the reference image with the recreated reference image, which is an update reference image.

[0007] According to the meter reading device of the present invention, even if the environmental conditions under which the meter is photographed change, it is possible to prevent a decrease in reading accuracy.

[0008] 11A and 11B are diagrams illustrating an example of the configuration of a meter reading device according to embodiment 1 and a meter reading system including the meter reading device. FIG. 11A is a diagram illustrating an example of the configuration of a main part of a reference image updating unit in the meter reading device according to embodiment 1. FIG. 11B is a diagram illustrating an example of a meter image according to embodiment 1. FIG. 11C is a diagram illustrating an example of setting information input by a user according to embodiment 1. FIG. 11D is a diagram illustrating an example of a polar coordinate system meter image according to embodiment 1. FIG. 11E is a diagram illustrating an example of template scanning in template matching performed by a needle detection unit according to embodiment 1. FIG. 11F is a diagram illustrating an example of a needle imaging area cut out on a polar coordinate system meter image by an initial reference image creation unit according to embodiment 1. FIG. 11F is a flowchart illustrating the operation of an "initial setting process" of the meter reading device according to embodiment 1. FIG. 11B is a flowchart illustrating the operation of a "reading process" of the meter reading device according to embodiment 1.

[0009] In order to explain the present disclosure in more detail, embodiments of the present disclosure will be described below with reference to the accompanying drawings.

[0010] Embodiment 1. A meter reading device according to embodiment 1 calculates a numerical value (hereinafter referred to as an "indicated value") indicated by a pointer of a meter to be read from the position of the pointer on the captured image detected based on an image of at least the dial of the meter. In this way, the meter reading device reads the indicated value of the meter's pointer. Hereinafter, the meter's pointer will also be simply referred to as an "indicator needle." In embodiment 1, the meter is assumed to be an analog meter that reads the scale on the dial with a pointer (i.e., pointer). Examples of the meter include a power meter for measuring power consumption, a temperature meter for measuring temperature, or a pressure meter for measuring air or liquid pressure, which are installed in factories. Note that this is merely an example, and the meter may be a general analog meter whose dial can be imaged at least from a fixed angle. In the following embodiment 1, the meter is assumed to be a rotary analog meter that indicates a numerical value by the movement of a rotating pointer.

[0011] 1 is a diagram showing an example of the configuration of a meter reading device 100 according to the first embodiment and a meter reading system 1000 including the meter reading device 100. As shown in FIG. 1, the meter reading system 1000 includes an imaging device 300, the meter reading device 100, and an external device 200.

[0012] The imaging device 300 is provided so as to be able to capture an image of at least the dial of a meter (not shown) and captures an image of the meter. The position and angle of view of the imaging device 300 relative to the meter are fixed, and the imaging device 300 captures an image of the meter at a predetermined angle. In the first embodiment, as an example, the imaging device 300 captures an image of the meter from the front of the meter.

[0013] The meter reading device 100 is provided, for example, in a meter. The meter reading device 100 acquires an image of the meter captured by the imaging device 300, detects the position of the indicator needle on the acquired image based on the acquired image, and calculates an indicated value from the detected indicated position of the indicator needle. Specifically, the meter reading device 100 acquires information on the meter scale and indicator needle set by the user from the external device 200, and calculates an indicated value from the detected indicated position of the indicator needle using the acquired information. The meter reading device 100 outputs the calculated indicated value to the external device 200, thereby presenting the indicated value to the user. Details of the meter reading device 100 will be described later.

[0014] The external device 200 is, for example, a PC (Personal Computer) or a mobile terminal. The PC or mobile terminal is assumed to be a PC or mobile terminal used by a user. The external device 200 receives various information from a user. The user inputs various information by operating, for example, an input device (not shown) such as a mouse or a keyboard provided in the external device 200, or a touch panel display device (not shown) provided in the external device 200. Details of the input of various information by the user will be described later. When the external device 200 receives information related to the meter scale and indicator needle, it outputs the received information to the meter reading device 100. The external device 200 also outputs various information. For example, the external device 200 displays the indicated value read by the meter reading device 100 on a display device. The user checks the indicated value displayed on the display device.

[0015] An example configuration of the meter reading device 100 will be described. As shown in Fig. 1, the meter reading device 100 includes an image acquisition unit 1, an interface unit 2, a polar coordinate conversion unit 3, a pointer detection unit 4, an indication value calculation unit 5, a reading result storage unit 6, a reference image update unit 7, and a reference image storage unit 8. Fig. 2 is a diagram showing an example configuration of the main parts of the reference image update unit 7 in the meter reading device 100 according to the first embodiment. As shown in Fig. 2, the reference image update unit 7 includes an initial reference image creation unit 71, an update execution determination unit 72, an update candidate image creation unit 73, an update image determination unit 74, and an erroneous update detection unit 75.

[0016] In the first embodiment, the meter reading device 100 performs an "initial setting process" to create an initial reference image D7 and a "reading process" to read the indicated value of the indicator needle. In the "initial setting process," the image acquisition unit 1, the interface unit 2, the polar coordinate conversion unit 3, and the initial reference image creation unit 71 function. In the "reading process," the image acquisition unit 1, the interface unit 2, the polar coordinate conversion unit 3, the indicator needle detection unit 4, the indicated value calculation unit 5, the update execution determination unit 72, the update candidate image creation unit 73, the update image determination unit 74, and the erroneous update detection unit 75 function. Details of the "initial setting process" and the "reading process" will be described later.

[0017] The image acquisition unit 1 acquires the captured image captured by the imaging device 300. In the following first embodiment, the captured image captured by the imaging device 300 is also referred to as a "meter image D1."

[0018] 3 is a diagram showing an example of a meter image D1 in Embodiment 1. For convenience, only the scale of the meter captured in the meter image D1 is shown in FIG. 3. The origin O, axis (X, Y), point P (x, y), line segment L, and angle θ in FIG. 3 will be described later.

[0019] The image acquisition unit 1 outputs the meter image D1 acquired from the imaging device 300 to the interface unit 2 and the polar coordinate conversion unit 3 .

[0020] The interface unit 2 connects the meter reading device 100 and the external device 200, enabling the user to perform various controls on the meter reading system 1000 and present information to the user. Specifically, the interface unit 2 acquires information related to the meter scale and pointer that is set by the user via the external device 200. In the first embodiment, the information related to the meter scale and pointer is referred to as "setting information D2." The setting information D2 includes the position on the meter image D1 of the rotation axis of the pointer that is the target of reading by the meter reading device 100 (hereinafter referred to as the "rotation axis position"), the position on the meter image D1 of the tip of the pointer (hereinafter referred to as the "tip position"), the width of the pointer on the meter image D1 (hereinafter referred to as the "needle width"), the position of the meter scale on the meter image D1 (hereinafter referred to as the "scale position"), the maximum value that the pointer can indicate, and the minimum value that the pointer can indicate. In the setting information D2, the position of the axis of rotation of the indicator needle, the position of the tip of the indicator needle, and the position of the meter scale are expressed by coordinates on the meter image D1. Also, in the setting information D2, the needle width is expressed, for example, by the number of pixels on the meter image D1.

[0021] Here, a method for the user to input setting information D2 from external device 200 will be described. The user inputs setting information D2 to interface unit 2 via external device 200. Fig. 4 is a diagram showing an example of setting information D2 input by the user in the first embodiment.

[0022] For example, a user looks at a meter image D1 displayed on a display device provided in the external device 200 and inputs, on the meter image D1, the rotation axis position of the indicator needle to be read, the tip position of the indicator needle, the needle width of the indicator needle, the scale position of the meter, and the maximum and minimum indicated values, thereby inputting the setting information D2. The user, for example, operates an input device or the like of the external device 200 to input an instruction to display an input screen for the setting information D2. Here, the input screen for the setting information D2 is, for example, a screen displaying the meter image D1, as shown in FIG. 4. The interface unit 2 receives an instruction from the user via the external device 200 to display the input screen for the setting information D2, and upon receiving the instruction, causes the display device to display the input screen for the setting information D2.

[0023] For example, the user operates the mouse provided in the external device 200 and clicks on the position of the axis of rotation of the indicator needle (indicated by "A" in FIG. 4) on the screen displaying the meter image D1 to specify the position of the axis of rotation of the indicator needle. In this way, the user inputs the position of the axis of rotation of the indicator needle. Similarly, the user inputs the position of the tip of the indicator needle by clicking on the position of the tip of the indicator needle (indicated by "B" in FIG. 4) and the scale position (indicated by "D" in FIG. 4) on the screen.

[0024] The user also inputs the needle width (indicated by "C" in FIG. 4) and the maximum and minimum indicated values ​​(indicated by "E" in FIG. 4). For example, the interface unit 2 displays input fields (not shown) for the needle width, maximum indicated value, and minimum indicated value along with the meter image D1 on the input screen for the setting information D2. The user operates a keyboard, for example, to input the needle width and the maximum and minimum indicated values ​​into the input fields displayed on the input screen. Note that the maximum and minimum indicated values ​​indicated by "E" in FIG. 4 are illustrative examples of the input maximum and minimum indicated values. As for the meter scale position, the user only needs to specify the scale corresponding to at least the maximum and minimum indicated values, as described above. If the maximum and minimum indicated values ​​and their positions on the meter image D1 are known, the external device 200 can interpolate the values ​​and positions therebetween.

[0025] In the first embodiment, as described above, the input of the setting information D2 by the user from the external device 200 is referred to as "initial setting."

[0026] When the external device 200 receives the setting information D2 input by the user, it outputs the setting information D2 to the interface unit 2. The interface unit 2 acquires the setting information D2 from the external device 200. The interface unit 2 outputs the acquired setting information D2 to the polar coordinate conversion unit 3, the indication value calculation unit 5, and the reference image update unit 7.

[0027] The interface unit 2 also outputs user-presented information D9 to the external device 200. Here, the user-presented information D9 includes screen information for displaying an input screen for the setting information D2, as described with reference to FIG. 4 , which the user refers to when inputting the setting information D2, and screen information for displaying a screen showing the meter reading results read by the meter reading device 100. The interface unit 2 creates screen information for displaying the input screen for the setting information D2, for example, based on the meter image D1 output from the image acquisition unit 1, and causes the display device of the external device 200 to display the input screen. The interface unit 2 also creates screen information for displaying a screen showing the meter reading results, for example, based on information output from the indication value calculation unit 5, and causes the display device of the external device 200 to display the screen showing the reading results. Details of the indication value calculation unit 5 and the information output from the indication value calculation unit 5 will be described later.

[0028] The polar coordinate conversion unit 3 converts the meter image D1 into polar coordinates using the captured image acquired by the image acquisition unit 1, i.e., the meter image D1, and the setting information D2 acquired by the interface unit 2. More specifically, the polar coordinate conversion unit 3 performs polar coordinate conversion on the coordinate information included in the meter image D1 and the setting information D2. The center of the polar coordinate conversion is the position of the rotation axis of the indicator needle. The radius of the polar coordinate conversion is a value obtained by adding a fixed value to the length of the indicator needle (hereinafter referred to as the "indicator needle length") calculated from the rotation axis position and tip position of the meter indicator needle and extending the length. In the first embodiment, the meter image D1 converted into polar coordinates is referred to as a "polar coordinate system meter image," and the coordinate information of the meter image D1 converted into polar coordinates is referred to as "polar coordinate system coordinate information."

[0029] Here, Fig. 5 is a diagram showing an example of a polar coordinate system meter image in Embodiment 1. The polar coordinate system meter image shown in Fig. 5 is obtained by polar coordinate conversion of the meter image D1 shown in Figs. 3 and 4, for example.

[0030] The polar coordinate conversion unit 3 calculates the angle θ between the reference axis X and the length L of the extended pointer OP obtained by adding a fixed value to the pointer length, based on the coordinate values ​​of a pixel on the meter image D1 (for example, P(x, y) in FIG. 3) as viewed from a reference axis (X, Y) with the rotation axis position of the pointer as the origin O, and converts the meter image D1 into a polar coordinate system meter image by converting the coordinates into the L-θ polar coordinate system. In the polar coordinate system meter image shown in FIG. 5, the horizontal axis is θ and the vertical axis is L.

[0031] The polar coordinate conversion unit 3 outputs the polar coordinate system meter image and the polar coordinate system coordinate information together as polar coordinate system data D3 to the pointer detection unit 4 and the reference image update unit 7.

[0032] The needle detection unit 4 detects the position of the needle in the polar coordinate system meter image from the polar coordinate system data D3 output from the polar coordinate conversion unit 3 and the reference image D7 stored in the reference image storage unit 8. In the first embodiment, the needle detection unit 4 detects the position of the needle in the polar coordinate system meter image, in other words, the position of the needle, which is the tip position of the needle, in other words, the indicated position of the needle. The indicated position of the needle in the polar coordinate system meter image is represented by coordinates on the polar coordinate system meter image.

[0033] Here, the reference image D7 will be described. In the first embodiment, the reference image D7 is an image showing an indicator needle, which serves as a reference for calculating the position of the indicator needle on the meter. Fig. 6 is a diagram showing an example of the reference image D7 in the first embodiment. The method for creating the reference image D7 will be described later in the description of the reference image update unit 7.

[0034] The reference image D7 stored in the reference image storage unit 8 is assigned information on the creation date and time of the reference image D7 and a use flag. In the first embodiment, the use flag is a flag for identifying the reference image D7 to be used for meter reading, in other words, the reference image D7 to be used by the needle detection unit 4 to detect the indicated position of the needle, and is indicated, for example, by "0: unused" or "1: in use." A plurality of reference images D7 can be stored in the reference image storage unit 8. In the first embodiment, the use flag is used to identify the reference image D7 to be used for meter reading from the plurality of reference images D7. Note that this is merely an example; it is sufficient that it is possible to identify which reference image D7 is currently being used for meter reading from the plurality of reference images D7 stored in the reference image storage unit 8. In the first embodiment, the needle detection unit 4 acquires the reference image D7 to which the use flag "1: in use" is assigned from the reference image storage unit 8.

[0035] The indicator needle detection unit 4 detects the indicated position of the indicator needle by calculating the similarity (hereinafter referred to as "reference similarity") between the polar coordinate system meter image and the reference image D7 at each coordinate in the direction of the declination axis of the polar coordinate system meter image (i.e., the horizontal axis in the polar coordinate system meter image of FIG. 5).

[0036] For example, the needle detection unit 4 calculates the reference similarity by template matching using a known template matching method with the reference image D7 as a template. That is, the needle detection unit 4 performs template matching on the polar coordinate system meter image with the reference image D7 as a template. FIG. 7 is a diagram for explaining an example of template scanning in template matching performed by the needle detection unit 4 in the first embodiment. Note that in FIG. 7, the polar coordinate system meter image is assumed to be the polar coordinate system meter image shown in FIG. 5. In scanning the template, the needle detection unit 4 aligns the bottom side of the reference image D7 with the rotation axis side of the polar coordinate system meter image, i.e., with the bottom side of the image in the polar coordinate system meter image, and scans the reference image D7, which is the template, in the direction of the deflection axis on the polar coordinate system meter image.

[0037] The needle detection unit 4 obtains the difference in pixel values ​​between the reference image D7 and an area on the polar coordinate system meter image that corresponds to the reference image D7, in other words, that is matched with the reference image D7 (hereinafter referred to as the "matching area"), and calculates the reference similarity so that the smaller the pixel value difference, the higher the reference similarity. Note that the needle detection unit 4 may, for example, calculate the difference in pixel value for each pixel between the reference image D7 and the matching area, and use the sum of the calculated pixel value differences for each pixel as the pixel value difference between the reference image D7 and the matching area. The needle detection unit 4 then detects, as the indicated position of the needle, a point in the matching area that has the highest reference similarity and that corresponds to the tip position of the needle on the reference image D7.

[0038] In this case, the needle detection unit 4 may assign a higher weight to the reference similarity closer to the tip of the needle. That is, when comparing the polar coordinate system meter image with the reference image D7 by template matching, the needle detection unit 4 may perform the comparison by assigning a higher weight to areas corresponding to the tip of the needle. It is assumed that the area corresponding to the needle of the reference image D7 in the matching area on the polar coordinate system meter image becomes smaller as it approaches the tip of the needle. Also, for example, if the meter has multiple needles, the multiple needles may overlap on the side closer to the rotation axis of the needle, thereby blocking the needle to be read. For these reasons, it can be said that the tip side of the needle is more important in detecting the needle. When comparing the polar coordinate system meter image with the reference image D7 by template matching, the needle detection unit 4 performs the comparison by assigning a higher weight to areas corresponding to the tip of the needle, thereby allowing the comparison to take into account areas that are more important in detecting the needle. As a result, the needle detection unit 4 can more accurately detect the indicated position of the needle.

[0039] When the needle detection unit 4 compares the reference image D7 with the polar coordinate system meter image, it generates information (hereinafter referred to as "needle detection information") that associates three items: the coordinates of the needle's indicated position, the maximum value of the reference similarity, and an image obtained by cutting out the matching area where the reference similarity is maximum. In the first embodiment, the image obtained by cutting out the matching area where the reference similarity is maximum is referred to as a "detection position image." The needle detection unit 4 outputs the generated needle detection information to the indicated value calculation unit 5 as the needle detection result D4.

[0040] The indication value calculation unit 5 calculates an indication value D5, which is a numerical value indicated by the indicator, from the setting information D2 output from the interface unit 2 and the indicator detection result D4 output from the indicator detection unit 4. The indication value calculation unit 5 may obtain the setting information D2 via the polar coordinate conversion unit 3 and the indicator detection unit 4.

[0041] Here, a specific example will be given to explain how the indicated value calculation unit 5 calculates the indicated value D5. The indicated value calculation unit 5 calculates the relative position of the coordinates of the indicated position of the indicator needle included in the indicator needle detection result D4 with respect to the scale position of the meter, and then calculates the indicated value D5 by linear interpolation based on the maximum and minimum values ​​of the meter. As a specific example, assume that the scale position indicating the minimum value of the meter is XMIN=100, the scale position indicating the maximum value of the meter is XMAX=200, the minimum value of the meter is VMIN=20, the maximum value of the meter is VMAX=80, and the coordinate X of the indicated position of the indicator needle is 175. At this time, the indication value calculation unit 5 calculates the indication value V indicated by the coordinates of the indication position of the indicator needle as follows: V = (X - XMIN) / (XMAX - XMIN) * (VMAX - VMIN) + VMIN = (175 - 100) / (200 - 100) * (80 - 20) + 20 = 75 / 100 * 60 + 20 = 65.

[0042] After calculating the indication value D5, the indication value calculation unit 5 combines the indicator needle detection result D4 output from the indicator needle detection unit 4 with the calculated indication value D5, and stores information in which the indicator needle detection result D4 and the indication value D5 are associated as a reading result D6 in the reading result storage unit 6. At this time, the indication value calculation unit 5 adds, for example, the time when the indication value D5 was calculated to the reading result D6, and stores the reading result in the reading result storage unit 6. The indication value calculation unit 5 also outputs the indicator needle detection result D4 output from the indicator needle detection unit 4 and the calculated indication value D5 to the interface unit 2.

[0043] When the indicator needle detection result D4 and the indicator value D5 are output from the indication value calculation unit 5, the interface unit 2 creates screen information as user presentation information D9 for displaying a screen showing the meter reading result D6 read by the meter reading device 100 based on the output indicator needle detection result D4 and the indicator value D5, and outputs the created user presentation information D9 to the external device 200. For example, the interface unit 2 creates screen information for displaying a screen showing the indicator value D5. Furthermore, for example, the interface unit 2 may create screen information for displaying a screen showing the indicator value D5 and the reference similarity based on which the indicator value D5 was calculated. For example, by checking the screen displayed on the display device of the external device 200 based on the screen information created by the interface unit 2, the user can understand the indicator value D5 and the degree to which the indicator value D5 was calculated based on the similarity of the indicator value D5 with the reference image D7, in other words, the accuracy of the indicator value D5.

[0044] The reading result storage unit 6 stores the reading result D6. The reading result storage unit 6 does not store only the latest reading result D6 output from the indication value calculation unit 5, but also stores the past several reading results D6. In other words, the reading result storage unit 6 is a database that can refer to past data (more specifically, past reading results D6). The number of past reading results D6 that the reading result storage unit 6 stores is determined in advance as appropriate by a user or the like. Note that, as shown in FIG. 1 , the reading result storage unit 6 is provided in the meter reading device 100, but this is merely an example. For example, the reading result storage unit 6 may be provided in a location outside the meter reading device 100 that can be referenced by the meter reading device 100.

[0045] The reference image update unit 7 initially creates the reference image D7 and updates the reference image D7. As shown in Fig. 2 , in the first embodiment, the reference image update unit 7 includes an initial reference image creation unit 71, an update execution determination unit 72, an update candidate image creation unit 73, an update image determination unit 74, and an erroneous update detection unit 75.

[0046] When initial settings are performed, the initial reference image creation unit 71 cuts out an area on the polar coordinate system meter image where the pointer is captured (hereinafter referred to as the "pointer needle capture area") based on the setting information D2 output from the interface unit 2 and the polar coordinate system data D3 output from the polar coordinate conversion unit 3, and creates an initial reference image D7 from the cut-out pointer capture area. The initial reference image creation unit 71 uses the cut-out pointer capture area as the initial reference image D7. Note that in the first embodiment, the "initial reference image D7" refers to the reference image D7 used to read the meter when the meter reading device 100 starts a meter reading operation for the first time, i.e., the initial value of the reference image D7. More specifically, the reference image D7 used to read the meter is the reference image D7 to which the usage flag "In Use: 1" is assigned. This reference image D7 is updated as necessary during the second or subsequent meter reading operation by the meter reading device 100. The update image determination unit 74 updates the reference image D7. The update image determination unit 74 will be described in detail later.

[0047] In the first embodiment, the above-mentioned needle image capturing area is a rectangular area on the polar coordinate system meter image. The initial reference image creating unit 71 obtains the position and size of the needle image capturing area from the tip position and needle width of the needle.

[0048] FIG. 8 is a diagram illustrating an example of a needle image capture area cut out by the initial reference image creation unit 71 on the polar coordinate system meter image in the first embodiment. In FIG. 8, the needle image capture area is a rectangular area indicated by a dotted line. For convenience, FIG. 8 illustrates only the peripheral area of ​​the needle image capture area on the polar coordinate system meter image. As shown in FIG. 8, the initial reference image creation unit 71 creates a rectangular area on the polar coordinate system meter image, with the tip position of the needle as its center, lines extending from the center in the positive and negative directions of the declination axis (i.e., the horizontal axis) at a distance equal to the needle width plus a preset fixed value as its horizontal sides, and a line segment parallel to a vertical line from the tip position of the needle to a point on the bottom of the polar coordinate system meter image as its vertical side, as the initial reference image D7. Information on the needle tip position and needle width is included in the setting information D2. In the first embodiment, "parallel" does not necessarily mean strictly parallel, but also includes approximately parallel.

[0049] The initial reference image D7 shown in FIG. 8 is merely an example. For example, the initial reference image creation unit 71 may set the vertical length of the polar coordinate system meter image in the reference image D7 to the length of a vertical line in the polar coordinate system meter image from the tip of the pointer to a point on a line parallel to the horizontal axis of the polar coordinate system meter image that passes through the base of the pointer. In other words, the initial reference image creation unit 71 may use a rectangular region with shorter vertical sides than the initial reference image D7 shown in FIG. 8 as the initial reference image D7. For example, if there is a pattern around the rotation axis, it is better to create the reference image D7 by avoiding the area containing the pattern. This is to reduce the influence of the pattern when the needle detection unit 4 compares the polar coordinate system meter image with the reference image D7. Another method for reducing the influence of the pattern is to adjust the weight used by the needle detection unit 4 when calculating the reference similarity. Although the reference image D7 is a rectangular region here, this is merely an example. The reference image D7 can be a region of any shape.

[0050] After creating the initial reference image D7, the initial reference image creation unit 71 stores the created initial reference image D7 in the reference image storage unit 8. At this time, the initial reference image creation unit 71 assigns a usage flag of "1: in use" and information on the creation date and time to the initial reference image D7, and stores the image in the reference image storage unit 8.

[0051] The update execution determination unit 72 acquires the latest read result D6 from the read results D6 stored in the read result storage unit 6 and determines whether to update the reference image D7 based on the acquired latest read result D6. More specifically, the update execution determination unit 72 determines whether to update the reference image D7 based on whether the reference similarity included in the needle detection result D4 in the read result D6 is equal to or less than a preset threshold (hereinafter referred to as the "reference similarity determination threshold"). The reference similarity determination threshold is set in advance by a user or the like and stored in a buffer or the like of the update execution determination unit 72. The update execution determination unit 72 determines to update the reference image D7 when the reference similarity included in the needle detection result D4 is equal to or less than the reference similarity determination threshold. In the latest read result D6, the reference similarity included in the needle detection result D4 is the reference similarity obtained when the needle detection unit 4 most recently compared the reference image D7 with the polar coordinate system meter image. If the update execution determination unit 72 determines that update processing of the reference image D7 should be performed, it outputs information indicating that it has determined that update processing of the reference image D7 should be performed (hereinafter referred to as an ``update execution instruction'') to the update candidate image creation unit 73.

[0052] In the first embodiment, the reference image D7 update process refers to a process of recreating the reference image D7 and updating the reference image D7 with the re-created reference image D7. Here, the reference image D7 updated in the reference image D7 update process is the reference image D7 currently being used by the needle detection unit 4 for comparison with the polar coordinate system meter image. More specifically, the reference image D7 updated in the reference image D7 update process is the reference image D7 to which a usage flag "1: in use" is assigned. In the first embodiment, the reference image D7 recreated to update the reference image D7 currently being used by the needle detection unit 4 for comparison with the polar coordinate system meter image is also referred to as an "update reference image." The creation of the update reference image and the update of the reference image D7 are performed by an update candidate image creation unit 73 and an update image determination unit 74, respectively. The update candidate image creation unit 73 and the update image determination unit 74 will be described in detail below.

[0053] When an update execution instruction is output from the update execution determination unit 72, the update candidate image creation unit 73 acquires the most recent several read results D6 from the read results D6 stored in the read result storage unit 6, and creates a plurality of images (hereinafter referred to as "update candidate images") that are candidates for the update reference image based on the most recent several acquired read results D6. More specifically, the update candidate image creation unit 73 creates a plurality of update candidate images based on the detection position images included in the indicator needle detection result D4 in the most recent several acquired read results D6.

[0054] A description will be given of an example of creating a plurality of update candidate images by the update candidate image creating unit 73. For example, the update candidate image creating unit 73 creates a plurality of detection position images acquired from the read result storage unit 6 as a plurality of update candidate images.

[0055] The above-described creation method is merely an example, and the update candidate image creation unit 73 may create the update candidate image using other methods. For example, the update candidate image creation unit 73 may create images (hereinafter referred to as "processed detection position images") by applying image processing to each of the multiple detection position images acquired from the read result storage unit 6, and use the detection position images acquired from the read result storage unit 6 and the processed detection position images as update candidate images. The image processing performed by the update candidate image creation unit 73 on the detection position images may include, for example, brightness modification, contrast modification, edge enhancement, or noise addition. The update candidate image creation unit 73 may apply any one of these image processing methods, or may apply a combination of multiple image processing methods. Note that the brightness modification, contrast modification, edge enhancement, and noise addition image processing are well-known image processing methods, and therefore detailed description thereof will be omitted. By adding the processed detection position image to the update candidate image, the update candidate image creation unit 73 can prepare an update candidate image for an update reference image that enables the reference image D7 to be updated to accommodate a wider range of environmental changes when updating the reference image D7.

[0056] In addition, if only the most recent reading result D6 is stored in the reading result memory unit 6, the update candidate image creation unit 73 acquires the reading result D6 of that one reading and creates an update candidate image from the acquired reading result D6.

[0057] The update candidate image creating unit 73 outputs the created update candidate image to the update image determining unit 74 .

[0058] The update image determination unit 74 determines which of the update candidate images to use to update the reference image D7, and updates the reference image D7. More specifically, the update image determination unit 74 determines an update reference image from among the plurality of update candidate images created by the update candidate image creation unit 73, and updates the reference image D7 with the determined update reference image.

[0059] An example of a method for determining an update reference image by the update image determination unit 74 will be described. The update image determination unit 74 determines an update reference image by, for example, calculating the similarity (hereinafter referred to as "candidate similarity") between the polar coordinate system meter image and the update candidate image in the deflection axis direction of the polar coordinate system meter image for each update candidate image. The update image determination unit 74 calculates the candidate similarity by template matching using the update candidate image as a template using a known template matching method. The specific method by which the update image determination unit 74 calculates the candidate similarity by template matching using the update candidate image as a template is similar to the specific method by which the indicator needle detection unit 4 calculates the reference similarity by template matching using the reference image D7 as a template, as described above, and therefore will not be described in detail. The update image determination unit 74 calculates the candidate similarity for each of the multiple update candidate images. The polar coordinate system meter image is included in the polar coordinate system data D3 output from the polar coordinate conversion unit 3. Note that in FIG. 2, the arrow from the polar coordinate conversion unit 3 to the update image determination unit 74 is omitted. The polar coordinate conversion unit 3 may obtain the polar coordinate system data D3 from the polar coordinate conversion unit 3 via the initial reference image creation unit 71, or may obtain the polar coordinate system data D3 directly from the polar coordinate conversion unit 3.

[0060] After calculating the candidate similarity for all of the multiple update candidate images, the update image determination unit 74 determines the update candidate image, among the multiple update candidate images, whose pointer is most likely to be the update candidate image as the update reference image. More specifically, the update image determination unit 74 compares the multiple update candidate images with the polar coordinate system meter image to detect areas in the polar coordinate system meter image that are similar to the update candidate image (hereinafter referred to as "candidate similar areas"), and calculates the candidate similarity between the update candidate image and the detected candidate similar area. The update image determination unit 74 then determines the update candidate image with the highest candidate similarity as the update reference image. A high candidate similarity means that the pointer on the update candidate image is closer to the pointer on the latest polar coordinate system meter image. In other words, the pointer on the update candidate image with a high candidate similarity can be said to be a pointer captured under environmental conditions similar to the pointer on the meter image D1 captured under the current environmental conditions.

[0061] Once the update image determination unit 74 determines the update reference image, it updates the reference image D7 with the determined update reference image. Specifically, the update image determination unit 74 sets the use flag of the reference image D7 stored in the reference image storage unit 8 to "0: unused" for the reference image D7 to which the use flag "1: in use" has been assigned. The update image determination unit 74 then assigns the use flag "1: in use" to the determined update reference image, and stores the update reference image with the assigned use flag in the reference image storage unit 8. This updates the reference image D7. Thereafter, the indicator needle detection unit 4 uses the reference image D7 updated by the update image determination unit 74 for comparison with the polar coordinate system meter image.

[0062] An erroneous update detection unit 75 detects an erroneous update of a reference image D7 stored in a reference image storage unit 8, where the reference image D7 has been updated with an incorrect reference image D7, and when an erroneous update is detected, returns the reference image D7 to the reference image D7 before the update.

[0063] The erroneous update detection unit 75 acquires the read result D6 from the read result storage unit 6 and detects erroneous updating of the reference image D7 by analyzing the pointer detection results D4 included in the read result D6 in chronological order. For example, the erroneous update detection unit 75 acquires, from the read result storage unit 6, the pointer detection results D4 stored after the timing at which the reference image D7 was previously updated. For example, when the update image determination unit 74 updates the reference image D7 with an update reference image, it notifies the erroneous update detection unit 75 that the reference image D7 has been updated. The erroneous update detection unit 75 may acquire the pointer detection results D4 stored in the read result storage unit 6 on or after the date and time at which it received the notification from the update image determination unit 74 that the reference image D7 has been updated. Note that the read result D6 stored in the read result storage unit 6 is accompanied by the time at which the indication value D5 was calculated. The erroneous update detection unit 75 may use the time stamp attached to the read result D6 to determine the pointer detection result D4 stored in the read result storage unit 6 after the date and time when the erroneous update detection unit 75 received a notification from the update image determination unit 74 that the reference image D7 has been updated. In FIG. 2 , the arrow from the update image determination unit 74 to the erroneous update detection unit 75 is omitted.

[0064] When the erroneous update detection unit 75 acquires the read result D6, it detects outliers in the time-series distribution of the reference similarity in the pointer detection result D4 included in the acquired read result D6. The erroneous update detection unit 75 then detects erroneous updating of the reference image D7 by determining whether the outliers of the reference similarity are increasing. For example, if the increase in the outliers of the reference similarity is equal to or greater than a predetermined threshold (hereinafter referred to as the "outlier determination threshold"), the erroneous update detection unit 75 determines that erroneous updating of the reference image D7 has occurred, i.e., that the update of the reference image D7 by the update image determination unit 74 using the update reference image was performed using an incorrect update reference image. If the increase in the outliers of the reference similarity is less than the outlier determination threshold, the erroneous update detection unit 75 determines that erroneous updating of the reference image D7 has not occurred, i.e., that the update of the reference image D7 by the update image determination unit 74 using the update reference image was performed using a correct update reference image.

[0065] When the erroneous update detection unit 75 detects an erroneous update of the reference image D7, it restores the reference image D7 stored in the reference image storage unit 8 and used by the needle detection unit 4 to detect the position of the needle to the reference image D7 before the update. Specifically, the erroneous update detection unit 75 sets the use flag of the reference image D7 (assuming it is the used reference image) to "0: unused" if the use flag "1: in use" is assigned to it, and sets the use flag assigned to the reference image D7 immediately before the used reference image to "1: in use." This restores the reference image D7 used by the needle detection unit 4 to detect the position of the needle to the reference image D7 before the update. Thereafter, the needle detection unit 4 uses the restored reference image D7 before the update for comparison with the polar coordinate system meter image. The erroneous update detection unit 75 may identify the immediately previous reference image D7 from the creation date and time information assigned to the reference image D7. In the reference image storage unit 8, the reference image D7 is provided with information about the date and time when the reference image D7 was created.

[0066] The reference image storage unit 8 stores the reference image D7. In the first embodiment, the reference image storage unit 8 does not store only the most recent reference image D7, but also stores several reference images D7 from the past. That is, the reference image storage unit 8 is a database from which past reference images D7 can be referenced. The number of past reference images D7 that the reference image storage unit 8 stores is determined in advance as appropriate by a user or the like. The reference image storage unit 8 stores the reference image D7 together with information on the date and time when the reference image D7 was created. Note that, in FIG. 1 , the reference image storage unit 8 is provided in the meter reading device 100, but this is merely an example. For example, the reference image storage unit 8 may be provided in a location outside the meter reading device 100 that can be referenced by the meter reading device 100.

[0067] The operation of the meter reading device 100 according to the first embodiment will be described separately for the "initial setting process" and the "reading process."

[0068] First, the operation of the meter reading device 100 in the "initial setting process" will be described. Fig. 9 is a flowchart for explaining the operation of the meter reading device 100 in the "initial setting process" according to the first embodiment. As described above, the image acquisition unit 1, the interface unit 2, the polar coordinate conversion unit 3, and the initial reference image creation unit 71 of the reference image update unit 7 function in the "initial setting process." For example, when the power is turned on for the first time after the meter reading device 100 is shipped, the meter reading device 100 performs the operation of the "initial setting process" as shown in the flowchart in Fig. 9 once.

[0069] The image acquisition unit 1 acquires the meter image D1 captured by the imaging device 300 (step ST11). The image acquisition unit 1 outputs the meter image D1 acquired from the imaging device 300 to the interface unit 2 and the polar coordinate conversion unit 3.

[0070] The interface unit 2 acquires the setting information D2 set by the user from the external device 200 (step ST12). Specifically, the interface unit 2 outputs to the external device 200 user presentation information D9, which is screen information for displaying an input screen for the setting information D2 that the user refers to when inputting the setting information D2, and presents the input screen to the user. The interface unit 2 acquires the setting information D2 input by the user from the input screen by operating the external device 200, via the external device 200. The interface unit 2 outputs the acquired setting information D2 to the polar coordinate conversion unit 3, the indication value calculation unit 5, and the reference image update unit 7.

[0071] The polar coordinate conversion unit 3 converts the meter image D1 into polar coordinates (step ST13) using the meter image D1 acquired by the image acquisition unit 1 in step ST11 and the setting information D2 acquired by the interface unit 2 in step ST12. The polar coordinate conversion unit 3 outputs polar coordinate system data D3 to the indicator needle detection unit 4 and the reference image update unit 7.

[0072] The initial reference image creating unit 71 of the reference image updating unit 7 cuts out an indicator needle imaged area where the indicator needle is imaged on the polar coordinate system meter image based on the setting information D2 output from the interface unit 2 in step ST12 and the polar coordinate system data D3 output from the polar coordinate conversion unit 3 in step ST13, and creates an initial reference image D7 from the cut-out indicator needle imaged area (step ST14). After creating the initial reference image D7, the initial reference image creating unit 71 stores the created initial reference image D7 in the reference image storage unit 8.

[0073] Next, the operation of the meter reading device 100 in the "reading process" will be described. The "reading process" is executed on the premise that the "initial setting process" has been completed. As described above, in the "reading process," the image acquisition unit 1, interface unit 2, polar coordinate conversion unit 3, pointer detection unit 4, indicated value calculation unit 5, update execution determination unit 72 of the reference image update unit 7, update candidate image creation unit 73, update image determination unit 74, and erroneous update detection unit 75 function.

[0074] FIG. 10 is a flowchart for explaining the operation of the "reading process" of the meter reading device 100 according to the first embodiment. For example, when the meter reading device 100 receives an instruction to start the operation from a control unit (not shown) of the meter reading device 100, the meter reading device 100 performs the operation of the "reading process" as shown in the flowchart of FIG. 10. For example, when the meter reading device 100 is powered on or when the control unit receives an instruction to start reading from a user via the external device 200, the control unit refers to the reference image storage unit 8 and confirms that a reference image D7 having a usage flag set to "1: in use" is stored. When the control unit confirms that the reference image D7 is stored, the control unit outputs an operation start instruction to the image acquisition unit 1, the interface unit 2, the polar coordinate conversion unit 3, the indicator needle detection unit 4, the indication value calculation unit 5, and the reference image update unit 7. The image acquisition unit 1, interface unit 2, polar coordinate conversion unit 3, needle detection unit 4, indicated value calculation unit 5, and reference image update unit 7 start their operations when an operation start instruction is output from the control unit. Furthermore, when the control unit receives, for example, an instruction from a user to end meter reading via the external device 200, it outputs an operation end instruction to the image acquisition unit 1, interface unit 2, polar coordinate conversion unit 3, needle detection unit 4, indicated value calculation unit 5, and reference image update unit 7. When the operation end instruction is output from the control unit, the image acquisition unit 1, interface unit 2, polar coordinate conversion unit 3, needle detection unit 4, indicated value calculation unit 5, and reference image update unit 7 end their operations. When the operation start instruction is output from the control unit, the image acquisition unit 1, interface unit 2, polar coordinate conversion unit 3, needle detection unit 4, indicated value calculation unit 5, and reference image update unit 7 repeatedly perform the operations in the "reading process" shown in the flowchart of FIG. 10 until an operation end instruction is output. The meter reading device 100 may terminate the operation of the "reading process" as shown in the flowchart of Figure 10 not only when it receives an instruction from the user via the external device 200 to terminate meter reading, but also when a predetermined time has elapsed or a predetermined date and time has arrived, in accordance with conditions specific to the meter reading system 1000.

[0075] The image acquisition unit 1 acquires the meter image D1 captured by the imaging device 300 (step ST21). The image acquisition unit 1 outputs the meter image D1 acquired from the imaging device 300 to the interface unit 2 and the polar coordinate conversion unit 3.

[0076] The polar coordinate conversion unit 3 converts the meter image D1 into polar coordinates using the meter image D1 acquired by the image acquisition unit 1 in step ST21 and the setting information D2 (step ST22). The setting information D2 is the setting information D2 acquired by the interface unit 2 in the "initial setting process" (see step ST12 in FIG. 9). The polar coordinate conversion unit 3 stores the setting information D2 acquired from the interface unit 2 in a buffer or the like of the polar coordinate conversion unit 3. The polar coordinate conversion unit 3 outputs polar coordinate system data D3 to the indicator needle detection unit 4 and the reference image update unit 7.

[0077] The pointer detection unit 4 detects the position of the pointer in the polar coordinate system meter image from the polar coordinate system data D3 output from the polar coordinate conversion unit 3 in step ST22 and the reference image D7 stored in the reference image storage unit 8 (step ST23). The pointer detection unit 4 outputs the pointer detection result D4 to the indicated value calculation unit 5.

[0078] The indication value calculation unit 5 calculates an indication value D5, which is a numerical value indicated by the indicator, from the setting information D2 and the indicator detection result D4 output from the indicator detection unit 4 (step ST24). After calculating the indication value D5, the indication value calculation unit 5 stores a reading result D6 in the reading result storage unit 6. At this time, the indication value calculation unit 5 adds, for example, the time when the indication value D5 was calculated to the reading result D6, and stores it in the reading result storage unit 6. The indication value calculation unit 5 also outputs the indicator detection result D4 output from the indicator detection unit 4 and the calculated indication value D5 to the interface unit 2.

[0079] When the indicator needle detection result D4 and the indicator value D5 are output from the indication value calculation unit 5 in step ST24, the interface unit 2 creates screen information as user-presented information D9 for displaying a screen showing the meter reading result D6 read by the meter reading device 100 based on the output indicator needle detection result D4 and indication value D5, and outputs the created user-presented information D9 to the external device 200 (step ST25).

[0080] The update execution determination unit 72 of the reference image update unit 7 obtains the latest reading result D6 from the reading result D6 stored in the reading result memory unit 6, and determines whether or not to perform the update process of the reference image D7 based on the obtained latest reading result D6 (step ST26).

[0081] If the update execution determination unit 72 determines in step ST26 that the update process of the reference image D7 is to be executed (if "YES" in step ST26), that is, if the update execution determination unit 72 outputs an instruction to execute update, the update candidate image creation unit 73 acquires the most recent several read results D6 from the read results D6 stored in the read result storage unit 6, and creates a plurality of update candidate images based on the acquired most recent several read results D6 (step ST27). The update candidate image creation unit 73 outputs the created update candidate images to the update image determination unit 74.

[0082] The update image determination unit 74 determines which of the update candidate images to use to update the reference image D7, and updates the reference image D7. More specifically, the update image determination unit 74 determines an update reference image from among the plurality of update candidate images created by the update candidate image creation unit 73 in step ST27, and updates the reference image D7 with the determined update reference image (step ST28).

[0083] In step ST26, if the update execution determination unit 72 determines not to perform the update process for the reference image D7 (in the case of "NO" in step ST26), or if the update image determination unit 74 updates the reference image D7 in step ST28, the operation of the meter reading device 100 proceeds to the processing of step ST29.

[0084] The erroneous update detection unit 75 determines whether or not an erroneous update of the reference image D7 stored in the reference image storage unit 8 with an incorrect reference image D7 has been detected (step ST29). Specifically, the erroneous update detection unit 75 acquires, from the reading result storage unit 6, the needle detection results D4 stored after the timing at which the reference image D7 was previously updated, and detects outliers in the time-series distribution of the reference similarity in the needle detection results D4 included in the acquired reading result D6. The erroneous update detection unit 75 then detects an erroneous update of the reference image D7 by determining whether or not the outliers of the reference similarity are increasing.

[0085] If an erroneous update is detected in step ST29 (if "YES" in step ST29), specifically, if the increase in the outlier value of the reference similarity is equal to or greater than the outlier determination threshold, the erroneous update detection unit 75 determines that an erroneous update of the reference image D7 has occurred, in other words, that the update of the reference image D7 by the update image determination unit 74 using an erroneous update reference image was performed using an erroneous update reference image. The erroneous update detection unit 75 restores the reference image D7 stored in the reference image storage unit 8 and used by the pointer detection unit 4 to detect the pointer position to the reference image D7 before the update (step ST30). Then, the operation of the meter reading device 100 ends the processing shown in the flowchart of FIG. 10.

[0086] On the other hand, if no erroneous update is detected in step ST29 (NO in step ST29), specifically, if the increase in the outlier value of the reference similarity is less than the outlier determination threshold, the erroneous update detection unit 75 determines that there is no erroneous update of the reference image D7, in other words, that the update of the reference image D7 by the update image determination unit 74 with the correct update reference image. Then, the operation of the meter reading device 100 ends the processing shown in the flowchart of FIG. 10.

[0087] Through the above-described operations, the meter reading device 100 according to the first embodiment stores past reading results D6 and automatically updates the needle detection standard (i.e., the reference image D7) based on the past reading results D6. Therefore, the meter reading device 100 can reduce the possibility of reading failure even when continuous environmental changes occur during meter reading. Continuous environmental changes include gradual changes in brightness due to the influence of external light or gradual shadows on the meter, which gradually affect the meter image D1. In situations where such environmental changes occur, the conventional methods of the prior art described above do not change the needle detection standard from the initial setting. This gradually reduces the accuracy of needle detection as the environment changes, and ultimately may make the needle undetectable. In contrast, the meter reading device 100 according to the first embodiment automatically updates the reference image D7 so that it is the reference image D7 that most closely resembles the area of ​​the needle captured in the latest meter image D1, thereby enabling meter reading that is robust to continuous environmental changes.

[0088] Furthermore, the meter reading device 100 according to the first embodiment is capable of applying various types of image processing when creating candidates for the reference image D7 (update candidate images), which allows the meter reading device 100 to adapt to a wider range of environmental changes.

[0089] Furthermore, when performing template matching using the reference image D7 to detect the indicator needle, the meter reading device 100 according to the first embodiment assigns more weight to the tip of the indicator needle. This takes advantage of the structure of an analog meter, in which the tip of the indicator needle indicates the value, and allows the meter reading device 100 to detect the indicator needle with greater accuracy than when a normal template matching method is used.

[0090] Furthermore, if the reference image D7 is updated with an incorrect reference image D7 when it is automatically updated, there is a problem that it becomes impossible to detect the indicator needle thereafter. To address this problem, the meter reading device 100 stores the reading results D6, analyzes the distribution of similarities (reference similarities) over time, and detects outliers to detect erroneous updates of the reference image D7. If an erroneous update of the reference image D7 is detected, the reference image D7 can be restored to its pre-update state. This allows the meter reading device 100 to reduce the possibility of updating the reference image D7 with an incorrect reference image D7 (update reference image).

[0091] <Modification> In the first embodiment described above, the meter reading device 100 acquires the meter image D1 captured by the imaging device 300 from the imaging device 300. However, this is merely an example. For example, the meter reading device 100 may acquire the meter image D1 from a storage device such as a hard disk drive that stores a meter image D1 captured in advance. In this case, in the meter reading system 1000, the meter reading device 100 is connected to the storage device instead of the imaging device 300.

[0092] In the first embodiment described above, the needle detection unit 4 in the meter reading device 100 calculates the reference similarity by template matching using the reference image D7 as a template. However, this is merely an example. The needle detection unit 4 may calculate the reference similarity by any method as long as the method allows the likelihood of needle detection in the meter image D1 to be obtained in the form of a similarity to the reference image D7. For example, instead of template matching, the meter reading device 100 may detect the needle using a convolutional neural network (CNN) trained on the reference image D7. More specifically, in the meter reading device 100, the needle detection unit 4 may compare the polar coordinate system meter image with the reference image D7 using, for example, a trained model (hereinafter referred to as a "machine learning model"). The machine learning model receives the polar coordinate system meter image and the reference image D7 as inputs and outputs information indicating the position of the needle on the polar coordinate system meter image. The machine learning model is created in advance and stored in a location that can be referenced by the meter reading device 100. The needle detection unit 4 inputs the polar coordinate system meter image and the reference image D7 into the machine learning model to obtain information indicating the position of the needle on the polar coordinate system meter image, thereby detecting the position of the needle on the polar coordinate system meter image. In this case, the meter reading device 100 is configured to include a learning processing unit so that learning is performed each time the reference image D7 is updated in the meter reading device 100.

[0093] Furthermore, in the above-described first embodiment, the update candidate image creation unit 73 in the meter reading device 100 references the most recent several read results D6 and creates an update candidate image based on the detection position image included in the needle detection result D4 in each read result D6. However, this is merely an example. For example, the update candidate image creation unit 73 may acquire, from the read result storage unit 6, read results D6 from a fixed time interval in the past, rather than the most recent several read results D6. For example, the update candidate image creation unit 73 may acquire read results D6 from up to five minutes ago every 10 seconds, and create an update candidate image based on the detection position image included in the needle detection result D4 in each of the past read results D6 every 10 seconds. There is a possibility that the detection position image in the most recent several read results D6 has changed little. The update candidate image creating unit 73 can create update candidate images of various patterns with changes by creating update candidate images based on past read results D6 at regular time intervals, more specifically, based on detection position images included in the pointer detection results D4 in the past read results D6 at regular time intervals. As a result, the update image determining unit 74 can determine an update reference image from update candidate images of various patterns with changes when updating the reference image D7.

[0094] In the first embodiment, the meter reading device 100 is configured to include the polar coordinate conversion unit 3, but this is merely an example. The polar coordinate conversion unit 3 is not an essential component of the meter reading device 100. In a configuration without the polar coordinate conversion unit 3, the needle detection unit 4 in the meter reading device 100 compares the captured image (meter image D1) acquired by the image acquisition unit 1 with the reference image D7 to detect the indication position on the captured image (meter image D1) of the needle, and creates a needle detection result D4 based on the comparison result between the captured image (meter image D1) and the reference image D7 when the indication position is detected. The reference image update unit 7 recreates the reference image D7 (update reference image) based on the needle detection result D4 created by the needle detection unit 4 when comparing the captured image (meter image D1) with the reference image D7, and updates the reference image D7 with the recreated update reference image. In addition, the initial reference image creation unit 71 of the reference image update unit 7 cuts out the needle imaging area in which the needle is imaged on the captured image (meter image D1) based on the captured image (meter image D1) acquired by the image acquisition unit 1 and the setting information D2, and creates a reference image D7 from the cut-out needle imaging area.

[0095] In this case, the image acquisition unit 1 outputs the captured image (meter image D1) to the interface unit 2, the needle detection unit 4, and the reference image update unit 7. Furthermore, in the operation of the meter reading device 100 shown in the flowchart of FIG. 9, the processing of step ST13 is omitted. Furthermore, in the operation of the meter reading device 100 shown in the flowchart of FIG. 10, the processing of step ST22 is omitted. However, when comparing the captured image (meter image D1) with the reference image D7 created from the captured image (meter image D1), consideration must be given to rotation, etc. The meter reading device 100 includes a polar coordinate conversion unit 3, which simplifies the comparison by comparing the captured image (meter image D1) with the reference image D7 on a polar coordinate system meter image. For example, in the case of comparing a polar coordinate system meter image with the reference image D7 by template matching, the meter reading device 100 simply scans the reference image D7, which is a template, in the direction of the deflection axis on the polar coordinate system meter image, thereby simplifying the comparison.

[0096] Furthermore, in the above-described first embodiment, the meter reading device 100 includes the initial reference image creation unit 71, but this is merely an example. The initial reference image creation unit 71 is not an essential component of the meter reading device 100. In a configuration that does not include the initial reference image creation unit 71, for example, an administrator or the like creates an initial reference image D7 at the time of shipping the meter reading device 100 and stores it in the reference image storage unit 8. In this case, the meter reading device 100 can be configured not to perform the "initial setting process." The operation of the meter reading device 100 shown in the flowchart of FIG. 9 is unnecessary. In this case, a process in which the interface unit 2 acquires setting information D2 is added between the process of step ST21 and the process of step ST22 in the operation of the meter reading device 100 shown in the flowchart of FIG. 10.

[0097] Furthermore, in the first embodiment described above, the erroneous update detection unit 75 may detect erroneous updating of the reference image D7 at a predetermined timing, and if erroneous updating is detected, perform processing to restore the reference image D7 to the reference image D7 before updating. In this case, for example, a step for determining whether the erroneous update detection unit 75 is ready to detect erroneous updating of the reference image D7 may be added to the operation of the meter reading device 100 shown in the flowchart of FIG. 10 before the processing of step ST29. If the erroneous update detection unit 75 determines that the timing to detect erroneous updating of the reference image D7 has arrived, the operation of the meter reading device 100 proceeds to the processing of step ST29.

[0098] In the first embodiment, the meter is a rotary analog meter, but this is merely an example. For example, the meter may be an analog meter having an indicator needle that moves up and down or left and right.

[0099] In the first embodiment, the meter reading device 100 is provided in a meter, but this is merely an example. For example, the meter reading device 100 may be provided in a device external to the meter reading device 100, such as a server. In the meter reading device 100, for example, some of the image acquisition unit 1, interface unit 2, polar coordinate conversion unit 3, needle detection unit 4, indicated value calculation unit 5, and reference image update unit 7 may be provided in the meter, and the rest may be provided in the server, so that the meter and the server form a system.

[0100] 11A and 11B are diagrams illustrating an example of the hardware configuration of a meter reading device 100 according to the first embodiment. In the first embodiment, the functions of the image acquisition unit 1, the interface unit 2, the polar coordinate conversion unit 3, the needle detection unit 4, the indicated value calculation unit 5, the reference image update unit 7, and a control unit (not shown) are realized by a processing circuit 101. That is, the meter reading device 100 includes the processing circuit 101 for storing past reading results D6 and controlling automatic updating of the needle detection standard (i.e., the reference image D7) based on the results. The processing circuit 101 may be dedicated hardware as shown in FIG. 11A, or a processor 104 that executes a program stored in memory as shown in FIG. 11B.

[0101] When processing circuitry 101 is dedicated hardware, processing circuitry 101 may be, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), or a combination thereof.

[0102] When the processing circuit is the processor 104, the functions of the image acquisition unit 1, the interface unit 2, the polar coordinate conversion unit 3, the pointer detection unit 4, the indicated value calculation unit 5, the reference image update unit 7, and a control unit (not shown) are realized by software, firmware, or a combination of software and firmware. The software or firmware is written as a program and stored in the memory 105. The processor 104 reads and executes the program stored in the memory 105 to execute the functions of the image acquisition unit 1, the interface unit 2, the polar coordinate conversion unit 3, the pointer detection unit 4, the indicated value calculation unit 5, the reference image update unit 7, and a control unit (not shown). In other words, the meter reading device 100 includes the memory 105 for storing a program that, when executed by the processor 104, results in the execution of steps ST11 to ST14 in FIG. 9 and steps ST21 to ST30 in FIG. 10 described above. Furthermore, it can be said that the program stored in memory 105 causes the computer to execute the processing procedures or methods of the image acquisition unit 1, interface unit 2, polar coordinate conversion unit 3, pointer detection unit 4, indication value calculation unit 5, reference image update unit 7, and a control unit not shown. Here, the memory 105 may be, for example, a non-volatile or volatile semiconductor memory such as a RAM, a ROM (Read Only Memory), a flash memory, an EPROM (Erasable Programmable Read Only Memory), or an EEPROM (registered trademark; hereinafter omitted) (Electrically Erasable Programmable Read-Only Memory), a magnetic disk, a flexible disk, an optical disk, a compact disk, a mini disk, or a DVD (Digital Versatile Disc).

[0103] The functions of the image acquisition unit 1, interface unit 2, polar coordinate conversion unit 3, pointer detection unit 4, indication value calculation unit 5, reference image update unit 7, and a control unit (not shown) may be partially implemented by dedicated hardware and partially implemented by software or firmware. For example, the functions of the image acquisition unit 1 and interface unit 2 may be implemented by a processing circuit 101 as dedicated hardware, while the functions of the polar coordinate conversion unit 3, pointer detection unit 4, indication value calculation unit 5, reference image update unit 7, and a control unit (not shown) may be implemented by a processor 104 reading and executing programs stored in a memory 105. The reading result storage unit 6 and reference image update unit 7 are configured by the memory 105 or a hard disk drive, etc. The meter reading device 100 also includes an input interface unit 102 and an output interface unit 103 that communicate with devices such as an external device 200 or an imaging device 300 via wired or wireless communication.

[0104] As described above, the meter reading device 100 according to the first embodiment is configured to include an image acquisition unit 1 that acquires a captured image (meter image D1), a needle detection unit 4 that detects the position of the needle on the captured image (meter image D1) by comparing the captured image (meter image D1) acquired by the image acquisition unit 1 with a reference image D7 showing the needle, which serves as a reference for detecting the position of the needle on the meter, and creates a needle detection result D4 based on the comparison result between the captured image (meter image D1) and the reference image D7 when the position is detected, and a reference image update unit 7 that recreates the reference image D7 based on the needle detection result D4 created by the needle detection unit 4 when comparing the captured image (meter image D1) with the reference image D7, and updates the reference image D7 with the recreated reference image D7, which is an update reference image. Therefore, the meter reading device 100 can prevent a decrease in reading accuracy even when the environmental conditions under which the meter is photographed change. In other words, the meter reading device 100 can reduce the possibility of reading failure even when continuous environmental changes occur during meter reading. The meter reading device 100 automatically updates the reference image D7 so that the reference image D7 has the highest similarity to the area in which the indicator needle is captured in the latest meter image D1, thereby enabling meter reading that is robust against continuous environmental changes.

[0105] Furthermore, in the meter reading device 100 according to the first embodiment, the reference image update unit 7 includes an update candidate image creation unit 73 that creates a plurality of update candidate images to be candidates for the update reference image based on the detection position image, and an update image determination unit 74 that determines, as the update reference image, an update candidate image in which the indicator needle is likely to be the update reference image from among the plurality of update candidate images created by the update candidate image creation unit 73. When updating the reference image D7, the meter reading device 100 creates a plurality of update candidate images and determines the update reference image from among them, thereby enabling the update of the reference image D7 to respond to a wide range of environmental changes.

[0106] Specifically, the update candidate image creation unit 73 sets a plurality of detection position images included in the pointer detection result D4 as a plurality of update candidate images, thereby enabling the meter reading device 100 to update the reference image D7 in response to a wide range of environmental changes.

[0107] The update candidate image creation unit 73 also creates processed detection position images by performing image processing on the detection position images included in the pointer detection result D4, and sets the detection position images and the processed detection position images as update candidate images, which allows the meter reading device 100 to update the reference image D7 in response to a wider range of environmental changes.

[0108] Furthermore, in the meter reading device 100 according to the first embodiment, when comparing the polar coordinate system meter image with the reference image D7, the needle detection unit 4 performs the comparison by weighting the area closer to the tip of the needle. This allows the meter reading device 100 to detect the needle with greater accuracy. Note that the same effect can be achieved when the meter reading device 100 performs the comparison by weighting the area closer to the tip of the needle when comparing the captured image (meter image D1) with the reference image D7.

[0109] Furthermore, in the meter reading device 100 according to the first embodiment, the reference image update unit 7 is configured to include an erroneous update detection unit 75 that detects erroneous updating of the reference image D7 by analyzing the pointer detection result D4 in chronological order and, if an erroneous update is detected, returns the reference image D7 to the reference image D7 before the update. This enables the meter reading device 100 to reduce the possibility that the reference image D7 will be updated with an erroneous reference image D7 (update reference image).

[0110] Furthermore, in the meter reading device 100 according to the first embodiment, the reference image updating unit 7 is configured to include an initial reference image creating unit 71 that cuts out an indicator needle imaged area in the captured image (meter image D1) where the indicator needle is imaged based on the captured image (meter image D1) acquired by the image acquiring unit 1 and setting information D2 related to the meter scale and indicator needle, and creates a reference image D7 from the cut-out indicator needle imaged area. The indicator needle detection unit 4 detects the indication position on the captured image (meter image D1) of the indicator needle by comparing the captured image (meter image D1) acquired by the image acquiring unit 1 with the reference image D7 created by the initial reference image creating unit 71. The meter reading device 100 can set the initial reference image D7 to a reference image D7 that corresponds to the environmental conditions of the meter.

[0111] Furthermore, the meter reading device 100 according to the first embodiment includes a polar coordinate conversion unit 3 that converts the captured image (meter image D1) into polar coordinates using the captured image (meter image D1) acquired by the image acquisition unit 1 and setting information D2 related to the meter scale and indicator needle. The indicator needle detection unit 4 is configured to detect the position of the indicator needle on the polar coordinate system meter image and generate an indicator needle detection result D4 by comparing the polar coordinate system meter image, which is the captured image (meter image D1) after polar coordinate conversion by the polar coordinate conversion unit 3, with a reference image D7. The reference image update unit 7 recreates the reference image D7 based on the indicator needle detection result D4 created by the indicator needle detection unit 4 when comparing the polar coordinate system meter image with the reference image D7, and updates the reference image D7 with the recreated update reference image. The meter reading device 100 simplifies the comparison by comparing the captured image (meter image D1) with the reference image D7 on the polar coordinate system meter image.

[0112] In addition, in the present disclosure, any of the components of the embodiments may be modified or omitted.

[0113] The meter reading device according to the present disclosure can prevent a decrease in reading accuracy even when the environmental conditions under which the meter is photographed change.

[0114] Various aspects of the present disclosure are summarized below as appendices.

[0115] (Supplementary Note 1) A meter reading device that calculates an indicated value, which is a numerical value indicated by an indicator needle, from the indicated position of the indicator needle on a captured image detected based on an image of at least a dial of a meter, comprising: an image acquisition unit that acquires the captured image; a needle detection unit that detects the indicated position of the indicator needle on the captured image by comparing the captured image acquired by the image acquisition unit with a reference image of the indicator needle, which serves as a reference for detecting the indicated position of the indicator needle on the meter, and creates an indicator needle detection result based on a comparison result between the captured image when the indicated position is detected and the reference image; and a reference image update unit that recreates the reference image based on the indicator needle detection result created by the indicator needle detection unit when comparing the captured image with the reference image, and updates the reference image with an update reference image that is the recreated reference image. (Supplementary Note 2) The meter reading device according to Supplementary Note 1, further comprising: an indicated value calculation unit that calculates the indicated value based on the indicator needle detection result created by the indicator needle detection unit and setting information related to the meter scale and the indicator needle. (Supplementary Note 3) The meter reading device according to Supplementary Note 1 or Supplementary Note 2, wherein the needle detection result includes a detection position image obtained by cutting out an area determined to be similar to the reference image in the captured image, and the reference image update unit comprises: an update candidate image creation unit that creates a plurality of update candidate images to be candidates for the update reference image based on the detection position image, and an update image determination unit that determines, as the update reference image, an update candidate image in which the indicator needle on the update candidate image is likely to be, from the plurality of update candidate images created by the update candidate image creation unit. (Supplementary Note 4) The meter reading device according to Supplementary Note 3, wherein the update candidate image determination unit compares, for the plurality of update candidate images, the update candidate images with the captured image to detect candidate similar areas in the captured image that are similar to the update candidate image, calculates candidate similarities between the update candidate images and the detected candidate similar areas, and determines the update candidate image with the highest calculated candidate similarity as the update reference image.(Supplementary Note 5) The meter reading device according to Supplementary Note 3 or Supplementary Note 4, wherein the update candidate image creation unit sets the detection position image as the update candidate image. (Supplementary Note 6) The meter reading device according to Supplementary Note 3 or Supplementary Note 4, wherein the update candidate image creation unit creates a processed detection position image by applying image processing to the detection position image, and sets the detection position image and the processed detection position image as the update candidate image. (Supplementary Note 7) The meter reading device according to Supplementary Note 6, wherein the image processing includes changing brightness, changing contrast, edge emphasis, or adding noise. (Supplementary Note 8) The meter reading device according to any one of Supplementary Notes 1 to 7, wherein the indicator needle detection unit, when comparing the captured image with the reference image, performs the comparison by weighting an area corresponding to the tip side of the indicator needle more heavily. (Supplementary Note 9) The meter reading device according to any one of Supplementary Notes 1 to 8, wherein the reference image update unit detects erroneous updating of the reference image by analyzing the needle detection results in time series, and includes an erroneous update detection unit that returns the reference image to the reference image before updating if the erroneous updating is detected. (Supplementary Note 10) The meter reading device according to Supplementary Note 9, wherein the needle detection results include a detection position image obtained by cutting out an area determined to be similar to the reference image in the captured image, and a reference similarity between the detection position image and the reference image, and the erroneous update detection unit detects the erroneous updating of the reference image by determining whether an outlier of the reference similarity has increased after the reference image has been updated, based on the needle detection results in time series. (Supplementary Note 11) The meter reading device according to any one of Supplementary Notes 1 to 10, characterized in that the reference image update unit includes an initial reference image creation unit that cuts out an indicator needle image area in which the indicator needle is imaged on the captured image based on the captured image acquired by the image acquisition unit and setting information related to the meter scale and the indicator needle, and creates the reference image from the cut-out indicator needle image area, and the indicator needle detection unit detects the indication position of the indicator needle on the captured image by comparing the captured image acquired by the image acquisition unit with the reference image created by the initial reference image creation unit.(Supplementary Note 12) The meter reading device according to any one of Supplementary Notes 1 to 11, wherein the needle detection unit compares the captured image with the reference image by template matching using the reference image as a template, and detects the indication position of the needle on the captured image from coordinates of an area on the captured image that has a high similarity to the reference image. (Supplementary Note 13) The meter reading device according to any one of Supplementary Notes 1 to 11, wherein the needle detection unit compares the captured image with the reference image using a machine learning model that receives the captured image and the reference image as inputs and outputs information indicating the indication position on the captured image, and detects the indication position on the captured image by inputting the captured image and the reference image to the machine learning model to obtain information indicating the indication position on the captured image. (Supplementary Note 14) The meter reading device according to any one of Supplementary Notes 1 to 13, further comprising: a polar coordinate conversion unit that converts the captured image acquired by the image acquisition unit into polar coordinates using setting information related to the meter scale and the pointer; the pointer detection unit detects the indication position of the pointer on the polar coordinate system meter image by comparing the reference image with a polar coordinate system meter image, which is the captured image after the polar coordinate conversion by the polar coordinate conversion unit; and creates the pointer detection result; and the reference image update unit recreates the reference image based on the pointer detection result created by the pointer detection unit when comparing the polar coordinate system meter image with the reference image, and updates the reference image with the update reference image, which is the recreated reference image.(Supplementary Note 15) A meter reading program that calculates an indicated value, which is a numerical value indicated by an indicator needle, from the indicated position of the indicator needle on an image that is detected based on an image in which at least the dial of a meter is imaged, causing a computer to function as: an image acquisition unit that acquires the image; a needle detection unit that detects the indicated position of the indicator needle on the image by comparing the image acquired by the image acquisition unit with a reference image showing the indicator needle, which serves as a reference for detecting the indicated position of the indicator needle on the meter, and creates an indicator needle detection result based on a comparison result between the image acquired by the indicator needle detection unit when the indicated position is detected and the reference image; and a reference image update unit that recreates the reference image based on the indicator needle detection result created by the indicator needle detection unit when comparing the image with the reference image, and updates the reference image with an update reference image, which is the recreated reference image. (Supplementary Note 16) A meter reading method for calculating an indicated value, which is a numerical value indicated by an indicator needle, from the indicated position of the indicator needle on an image detected based on an image in which at least a dial of a meter is imaged, the meter reading method comprising: a step in which an image acquisition unit acquires the image; a step in which a needle detection unit detects the indicated position of the indicator needle on the image by comparing the image acquired by the image acquisition unit with a reference image showing the indicator needle, which serves as a reference for detecting the indicated position of the indicator needle on the meter, and creates an indicator needle detection result based on a comparison result between the image acquired by the image acquisition unit and the reference image when the indicated position is detected; and a step in which a reference image update unit recreates the reference image based on the indicator needle detection result created by the indicator needle detection unit when comparing the image acquired with the reference image, and updates the reference image with an update reference image, which is the recreated reference image.

[0116] 100 Meter reading device, 1 Image acquisition unit, 2 Interface unit, 3 Polar coordinate conversion unit, 4 Pointer detection unit, 5 Indication value calculation unit, 6 Reading result storage unit, 7 Reference image update unit, 71 Initial reference image creation unit, 72 Update execution determination unit, 73 Update candidate image creation unit, 74 Update image determination unit, 75 Error update detection unit, 8 Reference image storage unit, 200 External device, 300 Imaging device, 1000 Meter reading system, 101 Processing circuit, 102 Input interface device, 103 Output interface device, 104 Processor, 105 Memory.

Claims

1. A meter reading device that calculates an indication value, which is a numerical value indicated by a needle, from the indicated position of the needle on an image detected based on an image in which at least the scale of a meter is captured, comprising: an image acquisition unit that acquires the captured image; a needle detection unit that detects the indicated position of the needle on the captured image by comparing the captured image acquired by the image acquisition unit with a reference image of the needle that serves as a standard for detecting the indicated position of the needle on the meter, and creates a needle detection result based on a comparison result between the captured image when the indicated position is detected and the reference image; and a reference image update unit that recreates the reference image based on the needle detection result created by the needle detection unit when comparing the captured image with the reference image, and updates the reference image with an update reference image, which is the recreated reference image.

2. A meter reading device as claimed in claim 1, further comprising an indication value calculation section which calculates the indication value based on the indication needle detection result generated by the indication needle detection section and setting information relating to the meter scale and the indication needle.

3. A meter reading device as described in claim 1 or claim 2, characterized in that the needle detection result includes a detection position image in which an area determined to be similar to the reference image in the captured image is cut out, and the reference image update unit comprises an update candidate image creation unit that creates a plurality of update candidate images that are candidates for the update reference image based on the detection position image, and an update image determination unit that determines, from the plurality of update candidate images created by the update candidate image creation unit, the update candidate image on which the indicator needle is most likely to be located as the update reference image.

4. The meter reading device according to claim 3, characterized in that the update image determination unit compares a plurality of update candidate images with the captured image to detect candidate similar areas in the captured image that are similar to the update candidate images, calculates a candidate similarity between the update candidate images and the detected candidate similarity areas, and determines the update candidate image having the highest calculated candidate similarity as the update reference image.

5. The meter reading device according to claim 3, wherein said update candidate image creation section sets said detection position image as said update candidate image.

6. The meter reading device according to claim 3, characterized in that the update candidate image creation unit creates a processed detection position image by applying image processing to the detection position image, and sets the detection position image and the processed detection position image as the update candidate image.

7. The meter reading device according to claim 6, wherein the image processing includes brightness modification, contrast modification, edge enhancement, or noise addition.

8. The meter reading device according to claim 1, characterized in that, when comparing the captured image with the reference image, the pointer detection unit performs the comparison by weighting the area corresponding to the tip side of the pointer more heavily.

9. The meter reading device according to claim 1, characterized in that the reference image update unit detects erroneous updating of the reference image by analyzing the pointer detection results in chronological order, and further comprises an erroneous update detection unit which returns the reference image to the reference image before the update when the erroneous update is detected.

10. The meter reading device of claim 9, characterized in that the needle detection result includes a detection position image obtained by cutting out an area in the captured image that is determined to be similar to the reference image, and a reference similarity between the detection position image and the reference image, and the erroneous update detection unit detects the erroneous update of the reference image by determining whether or not an outlier of the reference similarity has increased after the reference image is updated based on the needle detection result in time series.

11. The meter reading device of claim 1, characterized in that the reference image update unit includes an initial reference image creation unit that cuts out a needle imaging area in which the needle is imaged on the captured image based on the captured image acquired by the image acquisition unit and setting information related to the meter scale and the needle, and creates the reference image from the cut-out needle imaging area, and the needle detection unit detects the indication position on the captured image of the needle by comparing the captured image acquired by the image acquisition unit with the reference image created by the initial reference image creation unit.

12. The meter reading device of claim 1, characterized in that the pointer detection unit compares the captured image with the reference image by template matching using the reference image as a template, and detects the indication position of the pointer on the captured image from the coordinates of an area on the captured image that has a high similarity to the reference image.

13. The meter reading device of claim 1, characterized in that the pointer detection unit compares the captured image with the reference image using a machine learning model that receives the captured image and the reference image as input and outputs information indicating the indication position on the captured image, and detects the indication position on the captured image by inputting the captured image and the reference image into the machine learning model to obtain information indicating the indication position on the captured image.

14. A meter reading device as described in claim 1, further comprising a polar coordinate conversion unit which converts the captured image acquired by the image acquisition unit into polar coordinates using the captured image and setting information related to the meter scale and the pointer, wherein the pointer detection unit detects the indication position of the pointer on the polar coordinate system meter image by comparing the captured image after polar coordinate conversion by the polar coordinate conversion unit with the reference image and creates the pointer detection result, and the reference image update unit recreates the reference image based on the pointer detection result created by the pointer detection unit when comparing the polar coordinate system meter image with the reference image, and updates the reference image with the update reference image which is the recreated reference image.

15. A meter reading program that calculates an indication value, which is a numerical value indicated by an indicator needle, from the indication position of the indicator needle on an image detected based on an image in which at least the scale of a meter is captured, causing a computer to function as: an image acquisition unit that acquires the captured image; a needle detection unit that detects the indication position of the indicator needle on the captured image by comparing the captured image acquired by the image acquisition unit with a reference image of the indicator needle that serves as a standard for detecting the indication position of the indicator needle on the meter, and creates a needle detection result based on a comparison result between the captured image and the reference image when the indication position is detected; and a reference image update unit that recreates the reference image based on the needle detection result created by the needle detection unit when comparing the captured image with the reference image, and updates the reference image with the recreated reference image, which is an update reference image.

16. A meter reading method for calculating an indicated value, which is a numerical value indicated by an indicator needle, from the indicated position of the indicator needle on an image detected based on an image in which at least the dial of a meter is captured, comprising the steps of: an image capture unit captures the captured image; a needle detection unit detects the indicated position of the indicator needle on the captured image by comparing the captured image captured by the image capture unit with a reference image of the indicator needle, which serves as a reference for detecting the indicated position of the indicator needle on the meter, and creates a needle detection result based on a comparison result between the captured image and the reference image when the indicated position is detected; and a reference image update unit recreates the reference image based on the needle detection result created by the needle detection unit when comparing the captured image with the reference image, and updates the reference image with the recreated reference image, which is an update reference image.

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