JP2019203735A - Distance measuring device and distance measuring method - Google Patents

Abstract

To prevent the accuracy of distance measurement from being adversely affected by positionally or temporally differing brightness in a space where measurement points exist.SOLUTION: A distance measuring device 100-1 measures the distance to a measurement point P by triangulation using the position of the measurement point P as a parameter. The distance measuring device 100-1 comprises a light emitting unit 2 for irradiating the measurement point P with a light beam L, an imaging unit 3 for receiving the reflected light RL of the light beam L with which the measurement point P is irradiated and generating a first signal S1 that indicates the brightness of the reflected light RL and receiving background light and generating a second signal S2 that indicates the brightness of background, and a computation unit 13 for computing the position of the measurement point P on the basis of a difference between the first signal S1 and the second signal S2.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a triangulation type ranging technique.

  In a garbage incineration facility, deposits on which dust or the like generated by garbage incineration adheres to piping connected to a garbage incinerator, and the deposits gradually grow. When the deposit grows, the flow of gas (for example, high-temperature air) through the pipe is deteriorated, and at the worst, the pipe is clogged. For this reason, it is necessary to monitor the thickness of the deposit adhering to the inner wall of the pipe.

  By repeatedly measuring the distance to the deposit, the thickness of the deposit can be monitored. One of the techniques for measuring this distance is a triangulation type distance measurement technique using a light beam. However, when the triangulation type distance measurement technique is used, the presence of a scatterer (for example, dust) that floats in the pipe and scatters light reduces the distance measurement accuracy.

  As a technique for solving this, for example, Patent Document 1 discloses light irradiation means for irradiating light toward a measurement object existing in a space including a scatterer, and reflected light reflected by the measurement object. Light receiving means for receiving light, and based on the received light intensity information of the reflected light obtained by the light receiving means, the measurement distance of the measurement object existing in the space including the scatterer by triangulation method Disclosed is a method for measuring a distance of an object to be measured in a scatterer characterized by performing calculation.

  The measurement object of Patent Document 1 is, for example, the above deposit.

JP 2017-219440 A

  The brightness in the piping differs in position and time. For example, a flame is generated when dust floating in a pipe burns. Thereby, the brightness differs depending on the position in the pipe even at the same time, and the brightness is different if the time is different at the same position in the pipe. The present inventor has found that ranging accuracy is adversely affected if the brightness in the pipe is different in position and time during the ranging period. Although the description has been given by taking the deposit in which the measurement point adheres to the inside of the pipe as an example, if the brightness differs in position and time in the space where the measurement point exists, the distance measurement accuracy is adversely affected.

  An object of the present invention is to provide a distance measuring device and a distance measuring method that can prevent adversely affecting distance measuring accuracy even if brightness varies in position and time in a space where measurement points exist. .

  A distance measuring apparatus according to one aspect of the present invention is a distance measuring apparatus that measures the distance to the measurement point by a triangulation method using the position of the measurement point as a parameter, and irradiates the measurement point with a light beam. A light emitting unit, and a first signal indicating the brightness of the reflected light by receiving the reflected light of the light beam applied to the measurement point, and a second signal indicating the brightness of the background by receiving the background light. An imaging unit to be generated; and an arithmetic unit that calculates a position of the measurement point based on a difference between the first signal and the second signal.

  The brightness of the space where the measurement point exists is reflected in the brightness of the background (the background can also be referred to as the background of the measurement point or the background of reflected light). The calculation unit measures the distance from the distance measuring device to the measurement point based on the difference between the first signal indicating the brightness of the reflected light and the second signal indicating the brightness of the background. Thereby, the brightness of the background of the space where the measurement point exists can be canceled. Therefore, according to the distance measuring device according to one aspect of the present invention, it is possible to prevent the distance measurement accuracy from being adversely affected even if the brightness varies in position and time in the space where the measurement point exists.

  In the above-described configuration, the light emitting unit further includes a control unit configured to make the measurement point not irradiated with a light beam, and the calculation unit generates the background light received by the imaging unit under the state. Then, the signal indicating the brightness at the same position as the reflected light image is regarded as the second signal, and the position of the measurement point is calculated.

  Since the brightness of the space where the measurement point exists differs depending on the position in the space, it is preferable that the position of the reflected light image (the position of the measurement point) and the position of the background are the same. According to this configuration, the position of the reflected light image and the position of the background can be made the same.

  In the above configuration, the calculation unit is generated by receiving the background light in the imaging unit in a state where the light emitting unit irradiates the measurement point with a light beam, and brightness at a position different from the image of the reflected light. Is calculated as the second signal.

  Since the brightness of the space where the measurement point exists fluctuates in time series, it is preferable to measure the brightness of the reflected light and the brightness of the background at the same time. According to this configuration, these brightnesses can be measured simultaneously.

  In the above configuration, the range finder further includes a housing that houses the light emitting unit, the imaging unit, and the calculation unit, and includes a window that transmits the light beam and the reflected light that are applied to the measurement point. The distance to the measurement point is measured in an environment where there is a scatterer that floats in the space between the window and the measurement point and scatters the light beam applied to the measurement point.

  This environment is, for example, an environment in a pipe that communicates with a gas incinerator. The distance measuring device according to one embodiment of the present invention can be applied to the measurement of the distance to the deposit (measurement point) attached to the pipe in this environment.

  In the above-described configuration, the image forming unit further includes an image generation unit that generates a correction image based on a plurality of images arranged in time series captured by the imaging unit in a state where the light emitting unit irradiates the measurement point with a light beam, The calculation unit calculates a position of the measurement point by regarding a signal indicating the image of the reflected light, which is copied in the corrected image, as the first signal.

  In an environment where there is a scatterer that floats in the space between the distance measuring device and the measurement point and scatters the light beam that irradiates the measurement point, the image of the reflected light (hereinafter referred to as the reflected light image) It appears in a line on the captured image. The reflected light image shows the path of the light beam irradiated to the measurement point by the light emitting unit in two dimensions. As it goes from one end of the reflected light image to the other end, the position of the light beam on the path becomes farther from the distance measuring device, and the other end becomes a measurement point. The calculation unit calculates the distance using the position of the pixel indicating the other end of the reflected light image as the position of the measurement point.

  Due to the size of the scatterer floating in the space between the distance measuring device and the measurement point, the reflected light image may be lost, and the reflected light image may appear as a discontinuous line (the line may be in the middle) Separated by). In such a case, since the other end of the reflected light image cannot be specified, the measurement point cannot be specified.

  Therefore, the image generation unit generates a correction image using a plurality of images arranged in time series captured by the imaging unit in a state where the light emitting unit irradiates the measurement point with the light beam. Thereby, even if the reflected light image is copied in a discontinuous line shape in each of the plurality of images, the reflected light image is copied in one line shape in the corrected image.

  There are a first method and a second method as a method of generating a corrected image. The first method will be described. The image generation unit indicates a value indicated by the pixel from values (values may be luminance or pixel value) indicated by pixels located in the same order in a plurality of images arranged in time series captured by the imaging unit. A value that is larger than the average value of the values and satisfies the requirement of not more than the maximum value indicated by the pixel is selected. The image generation unit sets the selected value to the value of the pixel located in that order of the corrected image, and generates a corrected image. The value to be selected will be specifically described by taking the maximum value as an example. In this case, when the maximum value in the value of the first pixel is α1 in a plurality of images arranged in time series, the value of the first pixel is α1 in the corrected image, and the maximum value in the value of the second pixel Is α2, the value of the second pixel in the corrected image is α2. The values of the remaining pixels of the corrected image are determined in the same manner.

  In the reflected light image copied in the corrected image generated by the first method, the brightness of the background of the space where the measurement point exists is not canceled. Therefore, the calculation unit calculates the position of the measurement point by regarding the signal indicating the reflected light image copied in the corrected image as the first signal.

  The second method will be described. The image generation unit generates a plurality of difference images indicating differences from the background image for each of the plurality of images arranged in time series captured by the imaging unit. The difference image is an image in which the fluctuation of the brightness of the background of the space where the measurement point exists is cancelled.

  The image generation unit is greater than an average value of the values indicated by the pixels from among the values indicated by the pixels located in the same order in the plurality of difference images (the value may be a luminance or a pixel value), and Then, a value that satisfies the requirements below the maximum value indicated by the pixel is selected. The image generation unit sets the selected value to the value of the pixel located in that order of the corrected image, and generates a corrected image.

  In the reflected light image copied in the corrected image generated by the second method, the brightness of the background of the space where the measurement point exists is canceled. Therefore, the calculation unit calculates the position of the measurement point by regarding the signal indicating the reflected light image captured in the corrected image as the difference between the first signal and the second signal.

  A distance measuring method according to another aspect of the present invention is a distance measuring method for measuring a distance to the measurement point by a triangulation method using the position of the measurement point as a parameter, and a light emitting unit is provided at the measurement point. An irradiation step of irradiating the light beam, and the imaging unit receives the reflected light of the light beam irradiated to the measurement point and receives the first signal indicating the brightness of the reflected light and the background light to receive the background. A generating step for generating a second signal indicating the brightness of the light source, and a calculating step for calculating the position of the measurement point based on a difference between the first signal and the second signal. .

  The distance measuring method according to another aspect of the present invention defines the distance measuring device according to one aspect of the present invention from the viewpoint of the method, and has the same effects as the distance measuring device according to one aspect of the present invention. .

  According to the present invention, it is possible to prevent the ranging accuracy from being adversely affected even if the brightness differs in position and time in a space where measurement points exist.

It is a block diagram which shows the structure of the distance measuring device which concerns on embodiment. It is a schematic diagram which shows the relationship between the distance measuring device which concerns on embodiment, and piping in which this distance measuring device is arrange | positioned. It is a schematic diagram which shows the example of the relationship between the image which the imaging part imaged in the state which the light emission part is not irradiating the measurement point, and a brightness | luminance group. It is a schematic diagram which shows the example of the relationship between the image and brightness graph which the imaging part imaged in the state in which the light emission part is irradiating the measurement point with light. It is a graph which shows the luminance graph which shows the difference of a 1st signal and a 2nd signal. It is a flowchart explaining operation | movement of the distance measuring device which concerns on embodiment. It is a schematic diagram of an example of the image applied to a modification. 10 is a flowchart for explaining the operation of Modification 1; It is a schematic diagram which shows the example of the relationship between the image and luminance graph in which the discontinuous line-shaped reflected light image was copied. It is a graph which shows the luminance graph which shows the difference of a 1st signal and a 2nd signal. It is a block diagram which shows the structure of the ranging apparatus which concerns on the modification 2. FIG. 11 is an explanatory diagram for explaining generation of a corrected image using the first method in Modification 2. FIG. 12 is an explanatory diagram for explaining generation of a corrected image using a second method in Modification 2. It is a graph which shows the luminance graph of the reflected light image copied on each of n difference images, and the luminance graph of the reflected light image copied on the correction image.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In each figure, the structure which attached | subjected the same code | symbol shows that it is the same structure, The description is abbreviate | omitted about the content which has already demonstrated the structure. In the present specification, when referring generically, it is indicated by a reference symbol without a suffix (for example, image Im), and when referring to an individual configuration, it is indicated by a reference symbol with a suffix (for example, image Im-1). ).

  FIG. 1 is a block diagram illustrating a configuration of a distance measuring device 100-1 according to the embodiment. FIG. 2 is a schematic diagram illustrating a relationship between the distance measuring device 100-1 according to the embodiment and the pipe 6 in which the distance measuring device 100-1 is disposed. FIG. 2 shows a part of the pipe 6, and the pipe 6 communicates with a garbage incinerator (not shown). High-temperature air warmed by exhaust heat from garbage incineration passes through the pipe 6. Dust and the like generated by incineration of dust are floating in the pipe 6, and deposits 7 on which dust and the like are deposited adhere to the inner wall of the pipe 6.

  With reference to FIGS. 1 and 2, the distance measuring device 100-1 includes a main body 1, a light emitting unit 2, an imaging unit 3, and a housing 4. The main body 1, the light emitting unit 2, and the imaging unit 3 are disposed inside the housing 4. A glass window 41 is formed on the front surface of the housing 4. A port 61 through which the inside of the pipe 6 can be observed is formed in the pipe 6. The distance measuring device 100-1 is attached to the port 61 with the glass window 41 facing the opening of the port 61. Since the inside of the pipe 6 is high temperature, the inside of the housing 4 is cooled by an air cooling method in order to prevent the light emitting unit 2, the imaging unit 3, and the main body unit 1 from being damaged by the high temperature.

  The measurement point P is a point at which the distance is measured by the distance measuring device 100-1 and is at a position facing the port 61. If there is no deposit 7 at this position, the inner wall (for example, point Q) of the pipe 6 becomes the measurement point P. If the deposit 7 adheres to the inner wall of the pipe 6, the deposit 7 becomes the measurement point P. . As the deposit 7 grows and the thickness of the deposit 7 increases, the distance between the distance measuring device 100-1 and the deposit 7 decreases.

  The light emitting unit 2 irradiates the measurement point P with the light beam L. The light emitting unit 2 is realized by, for example, a laser diode or a light emitting diode. The light emitting unit 2 preferably has a high output (for example, 100 mW or more) and an output adjustment function. The wavelength of the light beam L emitted from the light emitting unit 2 is preferably longer than the particle diameter of dust or the like floating in the pipe 6.

  The optical axis 21 of the light emitting unit 2 is set in an oblique direction with respect to the measurement point P. The light beam L emitted from the light emitting unit 2 passes through the glass window 41 and is irradiated to the measurement point P from an oblique direction. When the measurement point P is irradiated with the light beam L from the light emitting unit 2, the light beam L is reflected at the measurement point P to generate reflected light RL. The imaging unit 3 is arranged in the traveling direction of the reflected light RL. The optical axis 31 of the imaging unit 3 is set in a direction perpendicular to the measurement point P. The optical axis 21 of the light emitting unit 2 may be set in a direction perpendicular to the measurement point P, and the optical axis 31 of the imaging unit 3 may be set in an oblique direction with respect to the measurement point P. The imaging unit 3 is realized by, for example, a digital camera or a line sensor.

  The imaging unit 3 receives the reflected light RL through the glass window 41, thereby generating a first signal S1 indicating the brightness of the reflected light RL. The first signal S1 may be a signal indicating a luminance value or a signal indicating a pixel value (for example, 256 gradations in the case of 8 bits). The imaging unit 3 transmits the first signal S1 to the main body unit 1.

  In addition to the function of generating the first signal S1, the imaging unit 3 generates the second signal S2 indicating the brightness of the background (the background of the measurement point P and the background of the reflected light RL) by receiving the background light. It has the function to do. The second signal S2 may be a signal indicating a luminance value or a signal indicating a pixel value. The imaging unit 3 transmits the second signal S2 to the main body unit 1.

  The light emitting unit 2 and the imaging unit 3 must have a relationship in which the imaging unit 3 has sensitivity to the light beam L irradiated by the light emitting unit 2 to the measurement point P. For example, when the imaging unit 3 is a visible light camera, the light beam L emitted from the light emitting unit 2 must be visible light. For example, when the imaging unit 3 is an infrared camera, the light beam L emitted from the light emitting unit 2 must be infrared light.

  The dust or the like floating in the pipe 6 becomes a scatterer (light scatterer) that scatters the light beam L that the light emitting unit 2 irradiates the measurement point P. For this reason, the inside of the pipe 6 is an environment in which a scatterer that floats in the space between the glass window 41 and the measurement point P and scatters the light beam L irradiated to the measurement point P exists. Moreover, the inside of the pipe 6 is an environment in which the brightness differs in position and time during the distance measurement period due to a flame generated by burning floating dust or the like.

  The main body unit 1 is a computer device that includes a control processing unit 11, a communication unit 12, and a calculation unit 13 as functional blocks. The control processing unit 11 and the calculation unit 13 are hardware processors. Specifically, these are hardware such as a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), and an HDD (Hard Disk Drive), and the functions for executing the functions of the above functional blocks. Realized by programs and data. What has been described above also applies to the image generation unit 14 (FIG. 11) described later.

  The control processing unit 11 is a device for controlling each unit (the communication unit 12 and the calculation unit 13) of the main body unit 1 according to the function of each unit.

  The communication unit 12 is a communication circuit for performing communication according to the control of the control processing unit 11. The communication unit 12 communicates with a computer device 51 disposed in the central control room 5 of the garbage disposal facility. The communication unit 12 is realized by a communication interface circuit. The garbage disposal facility includes an incinerator (not shown), a pipe 6 connected to the incinerator, and a central control room 5, and for example, treats household garbage.

  The calculator 13 calculates the position of the measurement point P based on the difference between the first signal S1 and the second signal S2. The calculation unit 13 calculates the distance to the measurement point P by the triangulation method (triangular distance measurement method) using the position of the measurement point P as one of the parameters. The control processing unit 11 causes the communication unit 12 to transmit distance information indicating the distance calculated by the calculation unit 13 with the computer device 51 as a destination. The computer device 51 displays the distance indicated by the received distance information on the display of the computer device 51.

  Hereinafter, the description of the embodiment will be continued on the assumption that the light emitting unit 2 is a laser diode that emits visible light and the imaging unit 3 is a visible light camera.

  FIG. 3 is a schematic diagram illustrating an example of a relationship between the image Im-1 captured by the imaging unit 3 and the luminance graph G-1 in a state where the light emitting unit 2 does not irradiate the measurement point P with the light beam L. FIG. 4 is a schematic diagram illustrating an example of a relationship between the image Im-2 captured by the imaging unit 3 and the luminance graph G-2 in a state where the light emitting unit 2 irradiates the measurement point P with the light beam L.

  With reference to FIGS. 2, 3 and 4, the x-axis is displayed at the center of the image Im. The x axis will be described. The optical axis 21 of the light emitting unit 2 indicates the path of the light beam L emitted from the light emitting unit 2 toward the measurement point P. The optical axis 21 of the light emitting unit 2 is an axis that defines a three-dimensional space. The x-axis is an axis obtained by converting the optical axis 21 of the light emitting unit 2 from three dimensions to two dimensions.

  A line superimposed on the x-axis of the image Im-2 indicates an image of the reflected light RL (hereinafter referred to as a reflected light image im) copied to the image Im-2. As described above, the reflected light RL is light generated when the light emitting unit 2 irradiates the measurement point P with the light beam L. If there is no dust or the like in the pipe 6, the reflected light image im is a single point image. If there is dust or the like in the pipe 6, the reflected light image im becomes a line-shaped image. This is because the light beam L emitted from the light emitting unit 2 toward the measurement point P is also reflected by dust or the like floating in the path of the light beam L, and the reflected light is received by the imaging unit 3. Because.

  The position on the path of the light beam L becomes farther from the distance measuring device 100-1 as it goes from the left end to the right end (from one end to the other end) of the reflected light image im. The right end (the other end) of the reflected light image im is the measurement point P. As the thickness of the deposit 7 increases, the right end (the other end) of the reflected light image im moves to the left on the x-axis. The calculation unit 13 uses the position x0 of the pixel indicating the right end (the other end) of the reflected light image im among the pixels constituting the image Im-2 captured by the imaging unit 3 as the position of the measurement point P. The distance to is calculated.

  The luminance graph G is a graph showing the luminance on the x-axis of the image Im. The graph line g-1 indicates the luminance of the pixel on the x axis in a state where the light emitting unit 2 does not irradiate the measurement point P with the light beam L. A graph line g-2 indicates the luminance of the pixel on the x axis in a state where the light emitting unit 2 irradiates the measurement point P with the light beam L. A graph line g-2 indicates the luminance of the reflected light RL (reflected light image im), and is generated using the first signal S1. A graph line g-1 indicates the luminance of the background of the reflected light RL, and is generated using the second signal S2. A pixel value may be used instead of the luminance.

  As indicated by the graph line g-1, the luminance is not uniform even in a state where the light emitting unit 2 does not irradiate the measurement point P with the light beam L, and varies depending on the position on the x-axis. This is because the brightness in the pipe 6 varies depending on the position in the pipe 6. For this reason, the luminance of the reflected light RL and the luminance of the background may be close to each other. In this case, it becomes difficult to specify the right end (the other end) of the reflected light image im from the graph line g-2.

  The inventor specifies the right end (the other end) of the reflected light image im according to the difference between the graph line g-2 and the graph line g-1 (difference between the first signal S1 and the second signal S2). I found out that I can do it. FIG. 5 is a luminance graph G-3 showing a difference between the graph line g-2 and the graph line g-1 (difference between the first signal S1 and the second signal S2). A graph line g-3 is a difference between the graph line g-2 and the graph line g-1. Thereby, since the brightness of the background in the pipe 6 is canceled, the right end (the other end) of the reflected light image im, that is, the measurement point P can be specified.

  The operation of the distance measuring device 100-1 according to the embodiment will be described. FIG. 6 is a flowchart for explaining this. With reference to FIG. 1, FIG. 2, and FIG. 6, the control processing unit 11 controls the light emitting unit 2 to emit the light beam L (step S1). The light beam L is reflected at the measurement point P to generate reflected light RL.

  The imaging unit 3 captures an image of the reflected light RL (Step S2). That is, the imaging unit 3 captures an image in a state where the light beam L from the light emitting unit 2 is irradiated on the measurement point P. This image includes the reflected light image im (first signal S1), and is, for example, an image Im-2 shown in FIG. Hereinafter, this image is referred to as a reflected light image. The imaging unit 3 transmits the reflected light image to the main body unit 1. The control processing unit 11 stores the transmitted reflected light image (step S3).

  The control processing unit 11 (control unit) controls the light emitting unit 2 to stop emitting the light beam L (step S4). As a result, the light emitting unit 2 is not irradiated with the light P at the measurement point P. Note that a shutter may be provided between the light emitting unit 2 and the glass window 41, and the control processing unit 11 may continue control to emit the light beam L to the light emitting unit 2 and perform control to close the shutter.

  The imaging unit 3 captures an image (background light image) in a state where the light beam L from the light emitting unit 2 is not applied to the measurement point P (step S5). This image includes the background (second signal S2) of the reflected light RL, and is, for example, an image Im-1 shown in FIG. Hereinafter, this image is referred to as a background light image. The imaging unit 3 transmits a background light image to the main body unit 1. The control processing unit 11 stores the transmitted background light image (step S6).

  The calculation unit 13 extracts the reflected light image im (first signal S1) from the reflected light image stored in the control processing unit 11. The computing unit 13 extracts an image (second signal S2) at the same position as the reflected light image im from the background light image stored in the control processing unit 11 (step S7). The calculator 13 calculates the difference between the first signal S1 and the second signal S2, and uses this difference to calculate the position of the measurement point P (step S8). As described above, the calculation unit 13 is generated by receiving the background light in the imaging unit 3 in a state where the light emitting unit 2 does not irradiate the measurement point P with the light beam L, and is at the same position as the reflected light image im. The signal indicating brightness is regarded as the second signal S2, and the position of the measurement point P is calculated. The calculation unit 13 calculates the distance to the measurement point P using the calculated position of the measurement point P as one of the parameters (step S9).

  The main effects of the embodiment will be described. Referring to FIGS. 1 and 2, the brightness in the pipe 6 is the brightness of the background (the background can also be referred to as the background of the measurement point P or the background of the reflected light RL). Reflected. The calculation unit 13 calculates the distance from the distance measuring device 100-1 to the measurement point P based on the difference between the first signal S1 indicating the brightness of the reflected light RL and the second signal S2 indicating the brightness of the background. taking measurement. Thereby, the brightness of the background in the pipe 6 can be canceled. Therefore, according to the embodiment, it is possible to prevent the distance measurement accuracy from being adversely affected even if the brightness varies in position and time in the pipe 6.

  Since the brightness in the pipe 6 varies depending on the position in the pipe 6, it is preferable that the position of the reflected light image im (position of the measurement point P) and the background position are the same. As shown in FIGS. 3 and 4, in the embodiment, the position of the reflected light image im is the same as the position of the background.

  A modification of the embodiment will be described. As described with reference to FIG. 6, the embodiment extracts the first signal S1 from the reflected light image and extracts the second signal S2 from the background light image (step S7). On the other hand, in the first modification, the first signal S1 and the second signal S2 are extracted from the reflected light image. The functional block diagram of the distance measuring apparatus according to Modification 1 is the same as FIG.

  FIG. 7 is a schematic diagram of an example of an image Im-3 applied to the first modification. Image Im-3 is a reflected light image, and there is a reflected light image im on the x-axis. In the image Im-3, the region r at a position different from the reflected light image im is the background.

  The calculation unit 13 sets the region r at the same position as the reflected light image im in the image Im-3. The region r is preferably in the vicinity of the reflected light image im. This is because the brightness in the pipe 6 is similar when the distance is short. In the region r, the calculation unit 13 calculates an average value of the luminance of the pixels at the same position of the x coordinate (for example, the average value of the luminance of the pixel at the position of x1, the average of the luminance of the pixel at the position of x2) Value), which is the second signal S2. As described above, the calculation unit 13 is a signal that is generated by receiving the background light in the imaging unit 3 in a state where the light emitting unit 2 irradiates the measurement point P, and indicates the brightness at a position different from the reflected light image im. Is regarded as the second signal S2.

  The operation of the first modification will be described. FIG. 8 is a flowchart for explaining the operation of the first modification. Steps S1 to S3 are the same as steps S1 to S3 in FIG. With reference to FIG. 1, FIG. 7, and FIG. 8, the calculation unit 13 reads the reflected light image (for example, the image Im-3) stored in the control processing unit 11 in step S3, and the first signal S1 from the reflected light image. The second signal S2 is extracted (step S11). The processing of step S8 and step S9 after step S11 is the same as the processing of step S8 and step S9 shown in FIG.

  Since the brightness of the space where the measurement point P exists varies in time series, it is preferable to measure the brightness of the reflected light RL and the brightness of the background at the same time. According to the modification 1, these brightnesses can be measured simultaneously.

  Modification 2 will be described. The reflected light images im shown in FIGS. 4 and 7 are one line-shaped image. However, the reflected light image im may be a discontinuous line image instead of a single line image. For example, if there is relatively large dust in the path of the light beam L shown in FIG. 2, the reflected light image im becomes a discontinuous line image due to the dust.

  FIG. 9 is a schematic diagram illustrating an example of a relationship between an image Im-4 on which a discontinuous line-shaped reflected light image im is captured and a luminance graph G-4. The reflected light image im is divided into two and is discontinuous. Although the reflected light image im has been described as an example of being divided into two, it may be divided into a larger number.

  The graph line g-4 indicates the luminance of the reflected light RL (reflected light image im), similar to the graph line g-2 shown in FIG. 4, and is generated using the first signal S1. The luminance of the graph line g-4 is greatly reduced at the location where the reflected light image im is divided. A graph line g-5 indicates the luminance of the region r (background) described in the first modification.

  FIG. 10 is a luminance graph G-5 showing a difference between the graph line g-4 and the graph line g-5 (difference between the first signal S1 and the second signal S2). A graph line g-6 is a difference between the graph line g-4 and the graph line g-5. In the case of the graph line g-6, there are a plurality of places where the luminance is greatly reduced. For this reason, it becomes difficult to specify the right end position (position of the measurement point P) of the reflected light image im. Modification 2 can solve this.

  FIG. 11 is a block diagram illustrating a configuration of a distance measuring apparatus 100-2 according to the second modification. 11 is different from FIG. 1 in that an image generation unit 14 is added to the main body unit 1. The image generation unit 14 generates a corrected image. There are a first method and a second method for generating a corrected image.

  The first method will be described. FIG. 12 is an explanatory diagram illustrating generation of the corrected image Im-2 (c) using the first method in the second modification. The imaging unit 3 continuously has n images (image Im-2 (1), image Im-2 (2),..., With the light emitting unit 2 irradiating the measurement point P with the light beam L. , Image Im-2 (n)). n is 2 or more (plural). Thereby, n images arranged in time series are obtained.

  The images Im-2 (1) to Im-2 (n) correspond to the image Im-2 illustrated in FIG. 4 and the reflected light image im is captured. However, the reflected light image im has a discontinuous line shape like the reflected light image im shown in FIG.

  In the image Im-2 (1) to the image Im-2 (n), the image generation unit 14 is larger than the average value of the values indicated by the pixels from the values indicated by the pixels located in the same order, and A value that satisfies a requirement that is equal to or less than the maximum value indicated by the pixel is selected. The image generation unit 14 sets the selected value to the value of the pixel located in the order of the corrected image Im-2 (c), and generates the corrected image Im-2 (c). The value to be selected will be specifically described by taking the maximum value as an example. The image generation unit 14 determines the maximum value indicated by the first pixel in the images Im-2 (1) to Im-2 (n), and uses this value for the corrected image Im-2 (c). The value of the first pixel is assumed. The image generation unit 14 determines the maximum value indicated by the second pixel in the images Im-2 (1) to Im-2 (n), and uses this value for the corrected image Im-2 (c). The value of the second pixel is assumed. The image generation unit 14 performs the same process for the third and subsequent pixels.

  Any value that can achieve the purpose of the reflected light image im appearing in one line in the corrected image Im-2 (c) is not limited to the maximum value and can be selected from values larger than the average value (for example, the second value). May be selected, or the third largest value may be selected). The reason why the value is larger than the average value is that if the value is equal to or less than the average value, it is considered that the effect of correcting the reflected light image im into one line cannot be obtained. This is also true for the second method.

  In the reflected light image im copied to the corrected image Im-2 (c) generated by the first method, the brightness of the background of the space where the measurement point P exists is not canceled out. The calculating part 13 makes the signal which shows the reflected light image im copied to correction | amendment image Im-2 (c) 1st signal S1. The distance measuring device 100-2 extracts the second signal S2 from the background light image after performing the processing of steps S4 to S6 in FIG. The calculator 13 calculates the position of the measurement point P based on the difference between the first signal S1 and the second signal S2.

  The second method will be described. FIG. 13 is an explanatory diagram illustrating generation of the corrected image Im-2 (c) using the second method in the second modification. The images Im-2 (1) to Im-2 (n) are the same as the images Im-2 (1) to Im-2 (n) shown in FIG. The image Im-1 is the same as the image Im-1 shown in FIG.

  The image generation unit 14 generates n (plural) difference images indicating differences from the image Im-1 (background image) for each of the images Im-2 (1) to Im-2 (n).

  In the n difference images, the image generation unit 14 has a requirement that is larger than the average value of the values indicated by the pixels and not more than the maximum value of the values indicated by the pixels, among the values indicated by the pixels positioned in the same order. Select a value that satisfies. The image generation unit 14 sets the selected value to the value of the pixel located in the order of the corrected image Im-2 (c), and generates the corrected image Im-2 (c). The value to be selected will be specifically described by taking the maximum value as an example. The image generation unit 14 determines the maximum value indicated by the first pixel in the n difference images, and sets this value as the value of the first pixel of the corrected image Im-2 (c). The image generation unit 14 determines the maximum value indicated by the second pixel in the n difference images, and sets this value as the value of the second pixel of the corrected image Im-2 (c). The image generation unit 14 performs the same process for the third and subsequent pixels.

  FIG. 14 is a graph showing the luminance graph of the reflected light image im copied to each of the n difference images and the luminance graph of the reflected light image im copied to the corrected image Im-2 (c). is there. A graph line g-7 indicates the luminance of the reflected light image im shown in the difference image between the image Im-2 (1) and the image Im-1 shown in FIG. A graph line g-8 indicates the luminance of the reflected light image im that is captured in the difference image between the image Im-2 (2) and the image Im-1. A graph line g-9 indicates the luminance of the reflected light image im that is captured in the difference image between the image Im-2 (n) and the image Im-1. A graph line g-10 indicates the luminance of the reflected light image im captured in the corrected image Im-2 (c). From these graph lines, it can be seen that the brightness of the background of the space where the measurement point P exists is canceled out.

  In the reflected light image im copied to the corrected image Im-2 (c) generated by the second method, the brightness of the background of the space where the measurement point P exists is canceled out. Therefore, the calculating part 13 makes the signal which shows the reflected light image im copied to correction image Im-2 (c) the difference of 1st signal S1 and 2nd signal S2. The calculator 13 calculates the position of the measurement point P based on this difference.

DESCRIPTION OF SYMBOLS 1 Main-body part 2 Light emission part 21 Optical axis 3 Image pick-up part 31 Optical axis 4 Case 41 Glass window part 6 Piping 61 Port 7 Deposits 100-1, 100-2 Ranging device G-1 to G-5 Luminance graph g- 1 to g-10 Graph line Im-1 to Im-4 Image Im-2 (c) Corrected image im Reflected light image L Light beam P Measurement point Q Point r on inner wall Region RL Reflected light S1 First signal S2 Second Signal x0 Position of measurement point P

Claims (7)

A distance measuring device that measures the distance to the measurement point by a triangulation method using the position of the measurement point as a parameter,
A light emitting unit for irradiating the measurement point with a light beam;
An imaging unit that receives the reflected light of the light beam applied to the measurement point and generates a first signal indicating the brightness of the reflected light and a second signal indicating the background brightness by receiving the background light. When,
A distance measuring device comprising: a calculation unit that calculates a position of the measurement point based on a difference between the first signal and the second signal. A control unit for making the light emitting unit not irradiate the measurement point with a light beam;
In the state, the calculation unit receives the background light by the imaging unit and generates a signal indicating brightness at the same position as the reflected light image as the second signal. The distance measuring device according to claim 1, wherein the position is calculated.   In the state where the light emitting unit irradiates the measurement point with the light beam, the arithmetic unit receives the background light generated by the imaging unit and generates a signal indicating the brightness at a position different from the reflected light image. The distance measuring device according to claim 1, wherein the distance measuring device calculates the position of the measurement point on the basis of the second signal. A housing that houses the light emitting unit, the imaging unit, and the computing unit, and that has a window that transmits the light beam irradiated to the measurement point and the reflected light;
The distance measuring device floats in a space between the window portion and the measurement point, and the distance to the measurement point in an environment where a scatterer that scatters a light beam irradiated to the measurement point exists. The distance measuring device according to any one of claims 1 to 3, wherein In a state where the light emitting unit irradiates the measurement point with a light beam, a value indicated by the pixel is selected from among values indicated by pixels located in the same order in a plurality of images arranged in time series captured by the imaging unit. Select a value that is larger than the average value and satisfies the requirements of the maximum value indicated by the pixel, and set the selected value to the value of the pixel located in the order of the corrected image to generate the corrected image An image generation unit
5. The distance measuring device according to claim 4, wherein the calculation unit calculates a position of the measurement point by regarding a signal indicating the image of the reflected light, which is copied in the corrected image, as the first signal. In the state where the light emitting unit irradiates the measurement point with a light beam, for each of a plurality of images arranged in time series captured by the imaging unit, a plurality of difference images indicating a difference from the background image are generated, In the plurality of difference images, a value that is larger than the average value of the values indicated by the pixels and satisfies a requirement equal to or less than the maximum value of the values indicated by the pixels is selected from the values indicated by the pixels positioned in the same order. An image generation unit configured to generate the corrected image by setting the selected value to a value of a pixel located in the order of the corrected image;
The calculation unit calculates a position of the measurement point by regarding a signal indicating the image of the reflected light, which is reflected in the corrected image, as a difference between the first signal and the second signal. The distance measuring device described in 1. A distance measurement method for measuring the distance to the measurement point by a triangulation method using the position of the measurement point as a parameter,
A light emitting unit that irradiates the measurement point with a light beam; and
The imaging unit receives a reflected light of the light beam applied to the measurement point and receives a first signal indicating the brightness of the reflected light, and a second signal indicating the brightness of the background by receiving background light. A generation step to generate;
A distance measuring method comprising: a calculation step in which a calculation unit calculates a position of the measurement point based on a difference between the first signal and the second signal.

Images