Distance measuring device, distance measuring system, distance correction method, and distance measuring program

Abstract

To provide a distance measuring device, a distance measuring system, a distance correction method, and a distance measuring program that can correct a distance error occurring between pixels included in a light receiving sensor due to the influence of a different multipath for every pixel.SOLUTION: A distance measuring device comprises: an irradiation unit that irradiates an object to be measured with measuring light; a light receiving sensor that receives reflected light from the object to be measured, and detects an amount of exposure based on the reflected light; a storage unit that stores correction information indicating a correction formula set including a plurality of correction formulas associated respectively with a plurality of pixels and application ranges of the correction formulas; and a distance calculation unit that calculates a measured distance to the object to be measured on the basis of the amount of exposure. The distance calculation unit corrects the measured distance for every pixel on the basis of the correction information stored in the storage unit, by using a correction formula corresponding to an application distance range including the measured distance, of the plurality of correction formulas included in the correction formula set, and thereby executes distance correction calculation of calculating a post-correction measured distance for every pixel.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a distance measuring device, a distance measuring system, a distance correction method, and a distance measuring program. [Background technology]

[0002] Patent Document 1 discloses a method for correcting the measurement value of a distance measuring device (hereinafter referred to as "prior art"), which corrects distance errors caused by the multipath phenomenon. The multipath phenomenon occurs when the optical path length appears longer due to unwanted reflections from walls, floors, etc., when the device is used in an environment where highly reflective materials are used for the walls, floors, etc.

[0003] TOF (Time Of Flight) is a distance measuring device that measures distance by measuring the time it takes for infrared light emitted from a laser to reflect off an object and return to a light receiving element. Due to the principle of TOF, in environments that are strongly affected by multipath, there is a problem that distance errors occur because the distance measured by TOF is longer than the actual distance to the object.

[0004] In contrast, in the conventional technology, as a preparation step, a measurement sample is positioned so that the distance from the distance measuring device is a set value L1. In the conventional technology, the distance to the measurement sample is measured using the distance measuring device to obtain a measurement value L2. In the conventional technology, the set value L1 is changed and measurement values ​​L2 corresponding to multiple set values ​​L1 are obtained. In the conventional technology, a correction formula is created to convert the measurement value L2 to the set value L1 based on the relationship between the multiple obtained set values ​​L1 and the measurement value L2. In the conventional technology, as an actual measurement step, the distance to the object measured by the distance measuring device is corrected using the correction formula to calculate a correction value for the measured distance. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2021-117036 A Summary of the Invention [Problem to be solved by the invention]

[0006] When using a distance measuring device such as TOF in an environment strongly affected by multipath, the linearity of the distance measurement results is lost, and the result has the characteristic of having a curved (or mountain-shaped) inflection point and becoming like a broken line with two or more inclinations. Since this characteristic differs for each of the multiple pixels in the light receiving sensor, for example, if a floor surface is measured using a TOF sensor attached perpendicular to the floor surface, the flatness of the floor surface cannot be reproduced, and distance errors such as curvature or periodic undulations may occur.

[0007] This occurs because the degree of multipath influence differs for each pixel due to the lens characteristics, such as distortion aberration, used in the TOF sensor, the light quantity profile characteristics of the light source, the installation environment, etc. With conventional technology, it was not possible to correct distance errors that occur between pixels due to the influence of multipath, which differs for each pixel.

[0008] The present invention has been made to solve the above problems. That is, an object of the present invention is to provide a distance measuring device, a distance measuring system, a distance correction method, and a distance measuring program that are capable of correcting distance errors that occur between pixels due to the influence of multipath that differs for each pixel of a light receiving sensor. [Means for solving the problem]

[0009] In order to solve the above problem, the distance measuring device of the present invention comprises an irradiation unit that irradiates a measurement light onto a measurement object, a light receiving sensor having a plurality of pixels that receives reflected light from the measurement object and detects an exposure amount based on the reflected light, and a memory unit that stores correction information indicating a correction formula set including a plurality of correction formulas corresponding to each of the plurality of pixels and an application range of each correction formula or correction coefficients corresponding to each of the plurality of pixels, and a correction formula set for primary distance correction including a plurality of correction formulas and an application range of each correction formula, and a control device that calculates a measured distance to the measurement object for each pixel based on the exposure amount, and the control device is configured to perform a distance correction calculation to calculate a corrected measured distance for each pixel by correcting the measured distance for each pixel using the correction information stored in the memory unit.

[0010] The distance measuring system of the present invention is a distance measuring system having a distance measuring device and an external processing unit, wherein the distance measuring device comprises an irradiation unit that irradiates measurement light onto a measurement object, a light receiving sensor having a plurality of pixels that receives reflected light from the measurement object and detects an exposure amount based on the reflected light, and a control unit that calculates a measured distance to the measurement object for each pixel based on the exposure amount, and the external processing unit comprises a memory unit that stores correction information indicating a correction formula set including a plurality of correction formulas corresponding to each of the plurality of pixels and an application range of each correction formula, or correction coefficients corresponding to each of the plurality of pixels, as well as a correction formula set for primary distance correction including a plurality of correction formulas and an application range of each correction formula, and a distance calculation unit that performs a distance correction calculation that calculates a corrected measured distance for each pixel by correcting the measured distance for each pixel using the correction information stored in the memory unit.

[0011] The distance correction method of the present invention is a distance correction method applied to a distance measuring device that includes an irradiation unit that irradiates a measurement object with measurement light, a light receiving sensor having a plurality of pixels that receive reflected light from the measurement object and detects an exposure amount based on the reflected light, and a memory unit that stores correction information indicating a correction formula set including a plurality of correction formulas corresponding to each of the plurality of pixels and an application range of each correction formula or correction coefficients corresponding to each of the plurality of pixels, and a correction formula set for primary distance correction including a plurality of correction formulas and an application range of each correction formula, and a control device that calculates a measured distance to the measurement object for each pixel based on the exposure amount, wherein the control device performs a distance correction calculation to calculate a corrected measured distance for each pixel by correcting the measured distance for each pixel using the correction information stored in the memory unit.

[0012] The distance measuring program of the present invention causes the control device to execute the distance correction method. Effect of the Invention

[0013] According to the present invention, it is possible to correct distance errors occurring between pixels due to the influence of different multipaths for each pixel of a light receiving sensor. Note that the effects described here are not necessarily limited to those described herein, and may be any of the effects described in this disclosure. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a diagram showing an example of the configuration of a distance measuring device according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a diagram for explaining the principle of distance measurement by the distance measuring device. [Diagram 3] FIG. 3 is a graph showing the relationship between the actual distance and the measured distance. [Figure 4] FIG. 4 is a diagram for explaining the mechanism by which measurement errors occur due to the influence of multipath. [Figure 5A]FIG. 5A is a graph showing the relationship between an ideal actual distance and a measured distance, and the relationship between the actual distance and the measured distance when affected by multipath. [Figure 5B] FIG. 5B is a graph showing the relationship between the actual distance and the error in the measured distance. [Figure 6A] FIG. 6A is a graph showing an approximation model that approximates the relationship between the actual distance and the measurement error. [Figure 6B] FIG. 6B is a graph for explaining the correction formula for the measurement distance. [Figure 7] FIG. 7 is a diagram for explaining the evaluation of distance error (distribution). [Figure 8] FIG. 8 is a diagram for explaining the evaluation results. [Figure 9A] FIG. 9A is a diagram for explaining the evaluation results. [Figure 9B] FIG. 9B is a diagram for explaining the evaluation results. [Figure 10A] FIG. 10A is a diagram for explaining the evaluation results. [Figure 10B] FIG. 10B is a diagram for explaining the evaluation results. [Figure 10C] FIG. 10C is a diagram for explaining the evaluation results. [Figure 11A] FIG. 11A is a graph showing the relationship between the actual distance and the measurement error. [Figure 11B] FIG. 11B is a graph showing an approximation model that approximates the relationship between the actual distance and the measurement error. [Figure 12] FIG. 12 is a graph for explaining the correction formula for the measurement distance. [Figure 13] FIG. 13 is a diagram for explaining the correction table. [Figure 14] FIG. 14 is a flowchart showing a process flow executed by the distance calculation unit. [Figure 15] FIG. 15 is a graph for explaining the correction formula for the measurement distance for each installation environment. [Figure 16] FIG. 16 is a diagram for explaining the correction table. [Figure 17]FIG. 17 is a diagram showing an example of a GUI screen. [Figure 18] FIG. 18 is a flowchart showing a process flow of the correction equation setting process executed by the distance calculation unit. [Figure 19] FIG. 19 is a diagram for explaining the positions of pixels of a light receiving sensor included in a distance measuring device. [Figure 20] FIG. 20 is a diagram showing an approximation model showing the relationship between the measured distance of each pixel and the actual distance. [Figure 21] FIG. 21 is a diagram showing an example of the configuration of a distance measuring device according to the third embodiment. [Figure 22A] FIG. 22A is a diagram for explaining the correction coefficient map. [Figure 22B] FIG. 22B is a diagram for explaining the correction coefficient map. [Diagram 23] FIG. 23 is a diagram for explaining the correction table. [Figure 24] FIG. 24 is a flowchart showing a process flow executed by the distance calculation unit. [Figure 25A] FIG. 25A is a diagram for explaining the correction coefficient map. [Figure 25B] FIG. 25B is a diagram for explaining the correction coefficient map. [Figure 25C] FIG. 25C is a diagram for explaining the correction coefficient map. [Figure 26] FIG. 26 is a diagram for explaining an example of the configuration of a distance measuring device according to the fourth embodiment. [Figure 27] FIG. 27 is a flowchart showing a process flow executed by the distance calculation unit. [Figure 28] FIG. 28 is a diagram for explaining the correction table. [Figure 29] FIG. 29 is a flowchart showing a process flow executed by the distance calculation unit. [Diagram 30] FIG. 30 is a diagram for explaining a method for creating a correction coefficient map. [Diagram 31] FIG. 31 is a flowchart for explaining the correction coefficient generating process. [Diagram 32]FIG. 32 is a diagram for explaining a configuration example of a modified example of a distance measuring device. [Diagram 33] FIG. 33 is a diagram for explaining a configuration example of a modified example of a distance measuring device. [Diagram 34] FIG. 34 is a diagram for explaining a configuration example of a modified example of a distance measuring device. [Diagram 35] FIG. 35 is a diagram for explaining a configuration example of a modified example of a distance measuring device. [Diagram 36] FIG. 36 is a diagram showing an approximation model of the relationship between the actual distance and the measurement error. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Each embodiment of the present invention will be described below with reference to the drawings. In all the drawings of the embodiments, the same or corresponding parts may be given the same reference numerals. In the following description, when describing identification information, expressions such as "name" are used, but other identification information (e.g., identification number, etc.) may be substituted. In the following description, various information may be described using expressions such as "table," "record," "map," etc., but the various information may be expressed by data structures other than these. In the following description, processing may be described using a functional block as the subject, but the subject of the processing may be a CPU or a device instead of a functional block.

[0016] <<First embodiment>> Fig. 1 is a diagram showing an example of the configuration of a distance measuring device 100 according to a first embodiment of the present invention. As shown in Fig. 1, the distance measuring device 100 includes a laser diode 110, a light receiving sensor 120, a power source 130, and a control device 140. The distance measuring device 100 is connected to an external processing device 200 so as to be able to transmit and receive information to and from the external processing device 200. The laser diode 110 is a light source that functions as an irradiation unit that irradiates a measurement object OB1 with pulsed light having a wavelength in the infrared region as measurement light.

[0017] The light receiving sensor 120 includes an imaging element (e.g., a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor)) that converts received light into an electrical signal by photoelectric conversion and outputs the electrical signal. The imaging element includes a plurality of pixels (also called "pixels") arranged in a lattice pattern and a well-known readout circuit, etc. The light receiving sensor 120 generates and outputs an exposure signal indicating exposure and non-exposure operations. The light receiving sensor 120 receives light that is pulsed light emitted from the laser diode 110 and reflected by the measurement object OB1.

[0018] The power supply 130 supplies power to drive the distance measuring device 100 .

[0019] The control device 140 includes a light emission control unit 141, a distance calculation unit 142, and an image processing unit 143. The control device 140 can be configured by a computer including a processor such as a CPU and a storage device (storage medium) such as a memory. The CPU realizes the functions of the light emission control unit 141, the distance calculation unit 142, and the image processing unit 143 by reading and executing a program stored in the memory. Note that the control device 140 can also be configured in part or in whole by hardware. For example, the control device 140 may realize at least some of the functions of the light emission control unit 141, the distance calculation unit 142, and the image processing unit 143 using an FPGA (Field Programmable Gate Array) or the like.

[0020] Based on the exposure signal, the light emission control unit 141 controls the light emission time and the off time of the pulse light (rectangular pulse light) output by the laser diode 110. Note that the light emission control unit 141 may output a light emission signal for controlling the light emission time and the off time to the laser diode 110 and output an exposure signal indicating an exposure operation and a non-exposure operation to the light receiving sensor 120 to control the light emission time and the off time of the laser diode 110 and the exposure operation and the non-exposure operation of the light receiving sensor 120.

[0021] The light receiving sensor 120 detects the reflected light of the pulsed light reflected by the measurement object OB1. The light receiving sensor 120 exposes to the reflected light at the timing when the exposure signal indicates an exposure operation, and converts the exposure amount (amount of charge) at each pixel position of the light receiving sensor 120 into an electrical signal and outputs it (outputs it as light receiving data).

[0022] The distance calculation unit 142 calculates the distance to the measurement object OB1 for each pixel based on the electrical signal (exposure amount) from the light receiving sensor 120. The distance calculation unit 142 calculates the distance to the measurement object OB1 for each pixel, for example, according to a measurement principle described below. Note that this distance to the measurement object OB1 before correction is referred to as the "measurement distance."

[0023] The distance calculation unit 142 includes a correction table memory 144. The correction table memory 144 is configured, for example, by a non-volatile storage device (storage medium) from which data can be read and written. For convenience, the correction table memory 144 may also be referred to as a "storage unit." The correction table memory 144 stores correction information indicating a correction formula set including two correction formulas associated with each of a plurality of pixels (all pixels) included in the light receiving sensor 120 and the application range of each correction formula. Details of the correction information will be described later. The application range of a correction formula refers to the range of measurement distance to which the correction formula is applied.

[0024] Distance calculation unit 142 performs distance correction calculation 142a. Specifically, distance calculation unit 142 applies the measured distance for each pixel to a correction formula created (set) based on correction information stored in correction table memory 144, thereby correcting the measured distance for each pixel, thereby calculating the corrected distance for each pixel. Distance calculation unit 142 transmits the calculated corrected distance for each pixel to image processing unit 143 as distance data. Note that distance correction calculation 142a may be referred to as "distance correction calculation" for convenience. The corrected distance may be referred to as "corrected measured distance" for convenience.

[0025] The image processing unit 143 generates a distance image based on the distance data, and outputs the generated distance image to the external processing device 200. The image processing unit 143 may generate an infrared image (IR image) based on the received light data, and output the generated infrared image (IR image) to the external processing device 200.

[0026] The external processing device 200 is, for example, a computer such as a PC (Personal Computer). The external processing device 200 uses the distance image input from the image processing unit 143. For example, a display (not shown) is connected to the external processing device 200, and the external processing device 200 displays the input distance image on the display. The external processing device 200 may also use an infrared image (IR image) input from the image processing unit 143.

[0027] <Details of the problem to be solved by the present invention> In order to facilitate understanding of the present invention, the following detailed description will be given of the problem to be solved by the present invention.

[0028] The light emission control unit 141 of the control device 140 controls the light emission timing of the laser diode 110. The light receiving sensor 120 generates an exposure signal (exposure pulse) indicating exposure and non-exposure operations. The light emission pulse and exposure pulse have a pulse width T, and the exposure amount of the reflected light received during the pulse width T of the exposure pulse is converted into an electrical signal.

[0029] The light emission exposure period for measuring distance includes a first light emission exposure period (A0), a second light emission exposure period (A1), and a third light emission exposure period (A2).

[0030] In the first light emission exposure period (A0), the light emission pulse and the exposure pulse are synchronized. In the second light emission exposure period (A1), the exposure pulse is delayed in phase from the light emission pulse by a time T. In the third light emission exposure period (A2), the exposure pulse is delayed in phase from the light emission pulse by a predetermined time longer than T. In this case, the distance L to the measurement object OB1 can be calculated by the calculation formula (1) in FIG. 2 (in the calculation formula (1), c represents the speed of light. S0 represents the exposure amount in the first light emission exposure period (A0), S1 represents the exposure amount in the second light emission exposure period (A1), and S2 represents the exposure amount in the third light emission exposure period). In the third light emission exposure period (A2), the light emission pulse may be off.

[0031] If the installation environment of the distance measuring device 100 is ideal (ideal condition), distance calculation is performed using only the reflected light 312 of the pulsed light emitted from the laser diode 110, so that the reflected light changes continuously according to the change in the distance to the measurement object OB1.

[0032] Therefore, when the installation environment of the distance measuring device 100 is an ideal environment (ideal state), there is no error between the actual distance and the measured distance, as shown by the dotted line Ln1 in Figure 3, and linearity of the relationship between the actual distance and the measured distance (hereinafter also referred to as "linearity of the distance measurement result") is ensured.

[0033] However, according to the results of the inventor's verification, when the distance measuring device 100 is used in an environment strongly affected by multipath, the exposure amount used for distance calculation is affected by ambient reflected light, as shown in Fig. 4. This impairs the linearity of the distance measurement result, as shown by the solid line Ln2 in Fig. 5A. That is, as shown in Fig. 5A, the solid line Ln2 showing the relationship between the actual distance and the measured distance tends to be bow-shaped with an inflection point, while as shown in Fig. 5B, the solid line Ln3 showing the relationship between the actual distance and the error in the measured distance (measurement error) tends to be upwardly convex and mountain-shaped with an inflection point.

[0034] In contrast, the distance measuring device 100 creates "two correction formulas and an application range of each correction formula" for each measurement distance range that is divided in advance by inflection points, in order to correct measurement errors that occur when used in an environment where multipath occurs, and can correct measurement errors by applying the correction formulas to the measurement distance.

[0035] As described above, the solid line Ln4 showing the relationship between the measurement error (distance error) caused by the effect of multipath and the actual distance shown in Figure 6A is a curve like a convex mountain. Therefore, a simple approximation model of the distance error can be established as shown by the two straight lines with different slopes and intercepts shown by the dashed line Ln5.

[0036] FIG. 6B shows an XY coordinate system with the measured distance on the X-axis (horizontal axis) and the actual distance on the Y-axis (vertical axis). By fitting an approximation model of distance error to this, an approximate correction formula (solid line Ln7) for deriving the actual distance from the measured distance can be established. That is, the approximation model of distance error is represented by a dashed line Ln6 indicating the relationship between the measured distance having a distance error and the actual distance. From the dashed line Ln6, an approximate correction formula (two correction formulas (Ynear=anearX+offsetnear and Yfar=afarX+offsetfar) and the application range of each correction formula) showing the solid line Ln7 indicating the relationship between the measured distance and the actual distance can be established.

[0037] The distance measuring device 100 can correct the measured distance to the actual distance (to approach the actual distance) using this approximate correction formula (correction formula).

[0038] The two correction formulas need to be used at appropriate distance positions corresponding to the respective correction formulas. Therefore, the distance measuring device 100 appropriately uses the two correction formulas based on the measurement distance (=correction switching distance SwL) corresponding to the inflection point of the solid line Ln7.

[0039] Specifically, when the measured distance is greater than 0 and is within a distance range equal to or less than the correction switching distance SwL, the distance measuring device 100 corrects the measured distance using the correction equation Ynear=anearX+offsetnear. When the measured distance is greater than the correction switching distance SwL and is within a distance range equal to or less than the maximum measurement distance Lmax, the distance measuring device 100 corrects the measured distance using the correction equation Yfar=afarX+offsetfar. Note that Ynear and Yfar are corrected distances corresponding to the actual distance. Anear and afar, as well as offsetnear and offsetfar, indicate coefficients (fixed values) that are set in advance according to the environment in which the device is expected to be used. Anear and afar are different values. Offsetnear and offsetfar are different values.

[0040] The distance measuring device 100 corrects the measured distance using an appropriate correction formula according to the measured distance based on two correction formulas (Ynear=anearX+offsetnear and Yfar=afarX+offsetfar) and the application range of each correction formula. This allows the distance measuring device 100 to accurately measure the distance to the measurement object OB1 by reducing degradation of the linearity of the distance measurement result.

[0041] The above-mentioned correction method improves the linearity of the distance measurement result. However, there is a problem that the measurement distance error occurs between the pixels of the light receiving sensor 120, and the distance error is distributed within the detection range of the light receiving sensor 120 (each pixel of the sensor).

[0042] FIG. 7 shows an example of measuring a vertically flat floor surface FL1 from a distance measuring device 100 (hereinafter, sometimes referred to as a "TOF sensor") attached to a ceiling (not shown) above the floor surface FL1, and evaluating the distance error (distribution) between pixels of the light receiving sensor 120. The light receiving sensor 120 in FIG. 7 is shown to show the correspondence between the pixels of the light receiving sensor 120 of the distance measuring device 100 and the position of the floor surface FL1. In evaluating the distance error (distribution), the actual distance from the TOF sensor to the floor surface FL1 is calculated for each pixel, and the actual distance between pixels is compared with the measured distance of each pixel to evaluate the distance error (distribution). The actual distance Z between each pixel and the floor can be calculated by dividing the height h between the TOF sensor and the floor surface FL1 by cosθ. θ is the angle between the direction from the TOF sensor toward the position of the floor surface FL1 corresponding to each pixel and the vertical direction (the direction from the TOF sensor toward the position of the floor surface corresponding to the center pixel).

[0043] 8 to 10C are diagrams (graphs) for explaining the results of evaluating the linearity of the distance error between pixels (flatness of the floor surface). The flatness of the floor surface is sometimes referred to as the "flatness of the distance measurement results." The graphs of Figs. 8 to 10C show the distance error between the "measured distance of the corresponding pixel" between a-a' (or b-b') on the floor surface FL1 and the "actual distance Z from the TOF sensor to the floor surface FL1." As shown in the graph of Fig. 8, in an ideal state, there is no difference between the actual distance and the measured distance, and the flatness of the floor surface is reproduced. On the other hand, when used in environment 1 (environment 1 where the multi-bus phenomenon occurs) and environment 2 (environment 2 where the multi-bus phenomenon occurs), which is different from environment 1, the flatness of the floor surface cannot be reproduced, as shown in the graph of result example 1 for environment 1 in Fig. 9A and the graph of result example 2 for environment 2 in Fig. 9B, and distance errors may occur in which the line indicating the distance error is curved or has periodic undulations.

[0044] Also, when the installation height h of the TOF sensor from the floor surface FL1 is changed to h1 to h3 (h1 < h2 < h3), and the flatness of the floor surface (distance error per pixel) is similarly compared, as shown in the graphs of FIGS. 10A to 10C, it may occur that the flatness of the floor surface (distance error per pixel) changes according to the difference in the installation height h.

[0045] Such a phenomenon is considered to occur mainly due to complex factors such as distortion aberration by the lens of the TOF sensor and the light quantity profile of the light source, which cause a difference in the received light quantity of each pixel. For example, pixels with a strong incident light quantity are less affected by multipath, while pixels with a weak incident light quantity tend to be more affected by multipath. As a result, the degree of influence of multipath varies for each pixel, which appears as a distance error for each pixel.

[0046] On the other hand, for the purpose of correcting the measurement error that occurs when the distance measuring device 100 is used in an environment where multipath occurs, two correction formulas and the application range of each correction formula are created for each pixel for each measurement distance range pre-divided at the inflection point, and stored in the correction table memory 144.

[0047] As shown in FIG. 11A, the line showing the relationship between the measurement error (distance error) caused by the influence of multipath and the actual distance becomes a curve like a convex upward mountain shape as described above, and the shape of the curve is different for each pixel. Therefore, as shown in FIG. 11B, for the distance error of each pixel, a simple approximate model of the distance error can be established for each pixel by two straight lines with different slopes and intercepts.

[0048] FIG. 12 shows an XY coordinate system in which the measured distance for a certain pixel is the X-axis (horizontal axis) and the actual distance is the Y-axis (vertical axis). By fitting an approximation model of distance error to this, an approximate correction equation (solid line Ln7) that derives the actual distance from the measured distance can be established for a certain pixel. That is, the approximation model of the distance error for a certain pixel is represented by the dashed dotted line Ln6 that indicates the relationship between the measured distance having a distance error and the actual distance. From the dashed dotted line Ln6, an approximate correction equation (two correction equations (Ynear=anearX+offsetnear and Yfar=afarX+offsetfar) and the application range of each correction equation) that indicates the solid line Ln7 that indicates the relationship between the measured distance for a certain pixel and the actual distance can be established.

[0049] Therefore, for one pixel, an approximate correction equation (two correction equations (Ynear=anearX+offsetnear and Yfar=afarX+offsetfar) and the application range of each correction equation) showing the solid line Ln7 indicating the relationship between the measured distance and the actual distance is established. Similarly, similar approximate correction equations can be established for other pixels, so that an approximate correction equation showing the relationship between the measured distance and the actual distance can be established for each of the multiple pixels (all pixels) that the light receiving sensor 120 has.

[0050] The distance measuring device 100 corrects the measured distance for each pixel using an appropriate correction formula according to the measured distance based on two correction formulas (Ynear=anearX+offsetnear and Yfar=afarX+offsetfar) and the application range of each correction formula for each pixel. As a result, the distance measuring device 100 can improve the deterioration of the flatness of the distance error by reducing the deterioration of the linearity of the distance measurement result for each pixel and also reducing the distance error between pixels, and therefore can measure the distance to the measurement object OB1 with high accuracy.

[0051] <Outline of distance correction> The correction table memory 144 of the distance calculation unit 142 of the distance measuring device 100 stores a correction equation (Y=aX+b) in which Y is the corrected distance, X is the measured distance, and coefficients a and b are variables, and a correction table 1310. Note that the correction equation (Y=aX+b) and the correction table 1310 are information indicating a correction equation set including two correction equations associated with each of the multiple pixels (all pixels) included in the light receiving sensor 120 and the application range of each correction equation, and are "correction information."

[0052] Fig. 13 is a diagram for explaining the correction table 1310. In Fig. 13, examples of values ​​(numeric values) stored in the correction table 1310 are shown as combinations of alphabets and numbers (for example, "a-1near(1,1)", "offset-1near(1,1)", etc.) (the same applies to Figs. 16, 23, and 28).

[0053] The correction table 1310 includes an installation environment 1311, a pixel 1312, an AB correction 1313, a BC correction 1314, and an AB / BC correction switching distance 1315 as columns for storing information (values). The AB correction 1313 includes a tilt 1313a and an offset 1313b as sub-columns. The BC correction 1314 includes a tilt 1314a and an offset 1314b as sub-columns. In the correction table 1310, information corresponding to each column for creating (setting) two correction formulas for each pixel according to the installation environment and the application range of each correction formula is stored as information (records) in rows in association with each other. This information (records) in rows is information for setting two correction formulas and the application range of each correction formula for each pixel, and is referred to as "correction formula related information".

[0054] Specifically, the installation environment 1311 stores identification information for identifying the installation environment (the name of the installation environment). The pixel 1312 stores information indicating the position of the pixel (information for identifying the pixel). The slope 1313a stores a value applied to the coefficient a of the correction formula. The offset 1313b stores a value applied to the coefficient b of the correction formula. The slope 1314a stores a value applied to the coefficient a of the correction formula. The offset 1314b stores a value applied to the coefficient b of the correction formula. The AB / BC correction switching distance 1315 stores a correction switching distance.

[0055] The distance calculation unit 142 sets (specifies) the distance range between A and B and the distance range between B and C, which are measurement distance ranges that are the criteria for determining which correction formula (coefficient) to apply, based on the correction switching distance for each pixel. Specifically, for example, for a certain pixel (e.g., pixel (1,1)), the distance between A and B is greater than 0 and is less than the correction switching distance SwL-1 (1,1) For example, for a pixel (e.g., pixel (1,1)), the distance between B and C is set to the correction switching distance SwL-1 (1,1) It is set to a value larger than the maximum measurable measurement distance Lmax.

[0056] The distance calculation unit 142 specifies, for each pixel, a coefficient (slope and offset) to be applied to the correction equation having the coefficient as a variable, based on the measured distance, and the correction equation having the coefficient as a variable and the correction table 1310. The distance calculation unit 142 applies, for each pixel, the specified coefficient to the correction equation (Y=aX+b) having the coefficients a and b as variables, thereby setting, for each pixel, the correction equation used to correct the measured distance.

[0057] Specifically, when the measured distance of a certain pixel (e.g., pixel (1,1)) is within the distance range between AB, the distance calculation unit 142 applies the values ​​(a-1near(1,1), offset-1near(1,1)) stored in the slope 1313a and offset 1313b of the subcolumn of the AB correction 712 in the correction table 1310 to the coefficient variables of the correction formula. In this way, the distance calculation unit 142 sets the correction formula to be used for correcting the certain pixel (e.g., pixel (1,1)). The distance calculation unit 142 corrects the measured distance of the certain pixel (e.g., pixel (1,1)) using the correction formula, and calculates the measured distance of the certain pixel (e.g., pixel (1,1)) after correction.

[0058] When the measured distance of a pixel (e.g., pixel (1,1)) is within the distance range between B and C, the distance calculation unit 142 applies the values ​​(a-1far(1,1), offset-1far(1,1)) stored in the subcolumn slope 1314a and offset 1314b of the B and C correction 1314 in the correction table 1310 to the coefficient variables of the correction formula. In this way, the distance calculation unit 142 sets the correction formula to be used for correcting the pixel (e.g., pixel (1,1)). The distance calculation unit 142 corrects the measured distance of the pixel (e.g., pixel (1,1)) using the correction formula, and calculates the measured distance of the pixel (e.g., pixel (1,1)) after correction. The above-mentioned correction of the measured distance is performed for each of all pixels.

[0059] The correction equations and the correction table 1310 with coefficients as variables are created in advance based on an approximation model and stored in the correction table memory 144. The correction table 1310 is created based on, for example, an error between the actual distance to the target and the measured value when an operator measures the distance to the target using the distance measuring device 100 in an installation environment where the distance measuring device 100 is expected to be used.

[0060] <Specific operation> Fig. 14 is a flowchart showing a processing flow executed by the distance calculation unit 142. The distance calculation unit 142 executes the processing flow shown in Fig. 14 every time a predetermined time elapses, thereby outputting a corrected distance (distance data) for each pixel to the image processing unit 143.

[0061] The distance calculation unit 142 starts the process from step 1400 in FIG. 14, and repeats the processes from step 1405 to step 1415 until they have been performed on all pixels.

[0062] Step 1405: The distance calculation unit 142 calculates the measured distance for each pixel based on the electrical signal (exposure amount) from the light receiving sensor 120.

[0063] Step 1410: The distance calculation unit 142 sets (selects) a correction formula to be applied based on the measured distance. Specifically, when the measured distance of a pixel is between AB, the distance calculation unit 142 applies the values ​​of the slope 1313a and offset 1313b stored in the AB correction 1313 corresponding to the pixel to a correction formula with a coefficient as a variable, and sets the correction formula to be used for distance correction. When the measured distance of a pixel is between BC, the distance calculation unit 142 applies the values ​​of the slope 1314a and offset 1314b stored in the BC correction 1314 for the pixel to a correction formula with a coefficient as a variable, and sets the correction formula to be used for distance correction.

[0064] Step 1415: The distance calculation unit 142 corrects the measured distance for each pixel using the correction formula set in step 1410, thereby calculating the corrected distance for each pixel.

[0065] After performing the processes of steps 1405 to 1415 for all pixels, the distance calculation unit 142 proceeds to step 1420 and outputs the calculated corrected distance (distance data) for each pixel to the image processing unit 143. Thereafter, the distance calculation unit 142 proceeds to step 1495 and temporarily ends this processing flow.

[0066] <Effects> As described above, the distance measuring device 100 according to the first embodiment of the present invention can correct distance errors occurring between pixels due to the influence of multipath that differs for each pixel.

[0067] <<Second embodiment>> A distance measuring device 100 according to a second embodiment of the present invention will be described below. The distance measuring device 100 according to the second embodiment of the present invention differs from the distance measuring device 100 according to the first embodiment only in the following points.

[0068] In the distance measuring device 100 according to the first embodiment, the correction equation-related information for each of a plurality of pixels (all pixels) corresponding to one installation environment is stored in the correction table 1310 stored in the correction table memory 144. In contrast, in the distance measuring device 100 according to the second embodiment, the correction table 1610 is stored in the correction table memory 144 instead of the correction table 1310. The correction table 1610 stores the correction equation-related information for each of a plurality of pixels (all pixels) corresponding to each of a plurality of installation environments.

[0069] The distance measuring device 100 according to the second embodiment selects the "correction equation related information for each pixel" that is optimal for the installation environment from the correction table 1610 ("correction equation related information for each pixel" for each installation environment) stored in the correction table memory 144, and sets the "two correction equations and the application range of each correction equation" that is optimal for the installation environment for each pixel based on the selected "correction equation related information for each pixel" and a correction equation (Y=aX+b) with coefficients a and b as variables, and uses the set "two correction equations and the application range of each correction equation" to correct the measured distance for each pixel.

[0070] The following explanation will focus on these differences.

[0071] <Summary> The degree of measurement error, which is the difference between the actual distance and the measured distance, varies depending on the degree of multipath effect in the installation environment of the distance measuring device 100. For example, as shown in Fig. 15, the measurement errors in installation environment 1, installation environment 2, installation environment 3, and installation environment 4 are larger in installation environment 2 than in installation environment 1, larger in installation environment 3 than in installation environment 2, and larger in installation environment 4 than in installation environment 3. That is, the magnitude relationship of the measurement errors in these environments is installation environment 1<installation environment 2<installation environment 3<installation environment 4. Therefore, in order to calculate the measured distance with higher accuracy, it is preferable to use an appropriate correction formula according to the installation environment.

[0072] Therefore, in the distance measuring device 100 according to the second embodiment, information indicating "a correction formula set including two correction formulas for each pixel and an application range of each correction formula" corresponding to each of the multiple installation environments is stored in the correction table memory 144. The information indicating "a correction formula set including two correction formulas for each pixel and an application range of each correction formula" corresponding to each of the multiple installation environments is correction information indicating "two correction formulas used to correct the measured distance for each pixel and an application range of each correction formula" corresponding to each of the multiple installation environments, and includes "a correction formula (Y=aX+b) with coefficients as variables" and "correction table 1610".

[0073] Fig. 16 is a diagram showing an example of a correction table 1610. As shown in Fig. 16, the correction table 1610 is similar to the correction table 1310 of the first embodiment, except that "correction equation-related information for each pixel" is stored according to each of a plurality of installation environments.

[0074] In the environment where the distance measuring device 100 is installed, a correction formula setting process is executed, and "two correction formulas and the application range of each correction formula" that are optimal for the installation environment are set for each pixel. The correction formula setting process will be described in detail later.

[0075] After the "two correction equations and the application range of each correction equation" optimal for the installation environment is set for each pixel, the distance measuring device 100 sets an optimal correction equation for each pixel according to the measurement distance, and corrects the measurement distance for each pixel using the correction equation. In this way, the distance measuring device 100 can accurately measure the distance to the measurement object OB1 by reducing the degradation of the linearity of the distance measurement result for each pixel and reducing the degradation of the flatness of the distance measurement result caused by the distance error between pixels.

[0076] <Specific operation> 17 is a diagram showing an example of a GUI screen GM1 constituting a GUI (Graphical User Interface) used to execute a correction formula setting process. The GUI screen GM1 includes an input field 1211 for inputting the actual distance to the target, a calibration start button 1212, and a target designation image 1213.

[0077] The actual distance to the target is input in an input field 1211. The target is a measurement object used to set (select) the "two correction equations and the application range of each correction equation" that is optimal for the installation environment. The process of setting the "two correction equations and the application range of each correction equation" that is optimal for the installation environment is sometimes called "calibration."

[0078] The calibration start button 1212 is a button formed of an image for causing the distance measuring device 100 to start calibration.

[0079] The target designation image 1213 is an image for designating a measurement point of the measurement distance of a target in an image. This image may be a distance image or an IR image. For example, a user can designate a measurement point of the target by operating an input device to place a cursor on the target and execute a specific operation.

[0080] The GUI screen GM1 is displayed on a display device such as a display connected to the external processing device 200. A user operates the GUI (inputs information into the GUI screen GM1) via an input device such as a mouse or keyboard connected to the external processing device 200. The external processing device 200 transmits the information input into the GUI screen GM1 to the distance measuring device 100. The distance calculation unit 142 of the distance measuring device 100 acquires the information input into the GUI screen GM1 transmitted from the external processing device 200.

[0081] The user operates the GUI to specify the measurement point of the target and input the distance to the target. When the user operates the calibration start button 1212 with the measurement point of the target and the actual distance to the target inputted on the GUI screen GM1, the distance calculation unit 142 of the distance measuring device 100 starts the process of setting the correction formula.

[0082] Fig. 18 is a flowchart showing the process flow of setting a correction equation executed by the distance calculation unit 142. When the user operates the calibration start button 1212, the distance calculation unit 142 starts the process from step 1800 in Fig. 18, executes the processes from step 1805 to step 1825 described below in order, and then proceeds to step 1830.

[0083] Step 1805: The distance calculation unit 142 obtains the accurate distance to the measurement point of the target input by the user on the GUI screen GM1.

[0084] Step 1810: The distance calculation unit 142 starts measuring the distance to the measurement point of the target.

[0085] Step 1815 : The distance calculation unit 142 selects one of the installation environments in the correction table 1610 .

[0086] Step 1820: The distance calculation unit 142 acquires the correction equation-related information corresponding to the pixel of the measurement point of the target and the installation environment selected from the correction table 1610. The distance calculation unit 142 sets "two correction equations and the application range of each correction equation" for the pixel corresponding to the measurement point of the target corresponding to the installation environment, based on the correction equation (Y=aX+b) with coefficients as variables and the correction equation-related information. The distance calculation unit 142 measures the distance to the target (measurement point of the target) using an appropriate correction equation according to the measured distance. Note that if the measurement point of the target corresponds to multiple pixels, this distance may be calculated by measuring the average value of the distances of the multiple corresponding pixels.

[0087] Step 1825: The distance calculation unit 142 calculates the distance error, which is the difference between the measured distance and the accurate distance to the measurement point of the target (the actual distance entered in the input field 1211 of the GUI screen GM1), and stores (records) it in the correction table memory 144 as the distance error corresponding to the selected installation environment.

[0088] When the distance calculation unit 142 proceeds to step 1830, it determines whether or not the distance errors have been recorded for all the installation environments stored in the correction table 1610.

[0089] If distance errors have not been recorded for all installation environments stored in the correction table 1610, the distance calculation unit 142 judges "NO" in step 1830 and proceeds to step 1835, where it selects an unselected installation environment from the installation environments stored in the correction table 1610.

[0090] Thereafter, the distance calculation unit 142 returns to step 1820, and executes the processes of steps 1820 and 1825 in order again, and proceeds to step 1830.

[0091] When the processing of steps 1820 to 1835 is repeatedly executed and distance errors are recorded for all installation environments stored in the correction table 1610 in step 1830, the distance calculation unit 142 judges "YES" in step 1830 and sequentially executes the processing of steps 1840 and 1845 described below. After that, the distance calculation unit 142 proceeds to step 1895 and temporarily ends this processing flow.

[0092] Step 1840: The distance calculation unit 142 identifies the installation environment corresponding to the smallest distance error among the recorded distance errors to the target, and selects the "correction equation related information for each pixel" in the correction table 1610 corresponding to the identified installation environment.

[0093] Step 1845: The distance calculation unit 142 sets the selected "correction equation related information for each pixel" as the correction equation related information for each pixel to be used for correcting the measured distance for each pixel.

[0094] The distance calculation unit 142 sets the "correction equation related information for each pixel" corresponding to the installation environment as the correction equation related information to be used for correcting the measured distance, and then executes the processing flow of Figure 14 to output the corrected distance (distance data) for each pixel to the image processing unit 143.

[0095] <Effects> As described above, the distance measuring device 100 according to the second embodiment of the present invention corrects the measured distance for each pixel using "multiple correction equations and the application range of each correction equation" for each pixel that is optimal for the installation environment. This allows the distance measuring device 100 to more accurately correct distance errors for each pixel that occur due to the multipath phenomenon.

[0096] <<Third embodiment>> A distance measuring device 100 according to a third embodiment of the present invention will be described below. The distance measuring device 100 according to the third embodiment of the present invention differs from the distance measuring device 100 according to the first embodiment only in the following points.

[0097] Fig. 19 is a diagram for explaining the positions of pixels of the light receiving sensor 120 provided in the distance measuring device 100. Fig. 20 is an approximation model showing the relationship between the measured distance of each pixel and the actual distance. According to the approximation model shown in Fig. 20, the relationship between the distance error of the reference pixel A (Pixel A) and the distance error with other pixels can be expressed by the formula (2): distance error of each pixel (Pixel) = correction coefficient (correction magnification) of each pixel (Pixel) × distance error of the reference pixel A.

[0098] For example, when the correction coefficients (correction magnifications) of each pixel A (PixelA) to pixel E (PixelE) are the correction coefficients (correction magnifications) shown in Table 2000, the relationship between the distance error of pixel A and the distance error of reference pixel A can be expressed by the distance error of pixel A = 1 × the distance error of reference pixel A. The relationship between the distance error of pixel B and the distance error of reference pixel A can be expressed by the distance error of pixel B = β × the distance error of reference pixel A. The relationship between the distance error of pixel C and the distance error of reference pixel A can be expressed by the distance error of pixel C = γ × the distance error of reference pixel A. The relationship between the distance error of pixel D and the distance error of reference pixel A can be expressed by the distance error of pixel D = δ × the distance error of reference pixel A. The relationship between the distance error of pixel E and the distance error of reference pixel A can be expressed by the distance error of pixel E = ε × the distance error of reference pixel A.

[0099] In the distance measuring device 100 according to the third embodiment, the corrected distance is obtained by correcting the measured distances of the reference pixel A and other pixels using "two correction equations and the application range of each correction equation" according to the approximation model of the reference pixel A. This corrected distance may be referred to as the "primary error correction distance." For convenience, obtaining this corrected distance may be referred to as "primary distance correction." The "two correction equations and the application range of each correction equation" according to the approximation model of the reference pixel A may be referred to as the "correction equation set for primary distance correction."

[0100] The distance measuring device 100 obtains the distance error value of each pixel by calculating the difference between the first-order error correction distance and the measured distance for each pixel. As a result, a distance error value according to the approximation model of the reference pixel A is obtained for each pixel. As described above, the correct distance error value of each other pixel is the distance error value of the reference pixel A multiplied by a predetermined correction coefficient. It can be said that the correct distance error value of the reference pixel A is 1 time the distance error value of the reference pixel A. From this, the distance measuring device 100 obtains the correct distance error value of each pixel by multiplying the distance error value of each pixel by the correction coefficient set for each pixel. The distance measuring device 100 can obtain the corrected distance of each pixel (= measured distance - correct distance error value) by subtracting each correct distance error value from the measured distance for each pixel.

[0101] The following description will focus on these differences.

[0102] <Configuration> FIG. 21 shows a configuration example of the distance measuring device 100 according to the third embodiment. As shown in FIG. 21, in the distance measuring device 100 according to the third embodiment, the distance calculation unit 142 has a pixel correction coefficient memory 2100. The pixel correction coefficient memory 2100 stores a correction coefficient map shown in FIG. 22A. In the correction coefficient map, as shown in FIG. 22B, each pixel is associated with a correction coefficient value. Note that FIG. 22B is a diagram in which the correction coefficient map is made into a table to facilitate understanding of the correction coefficient map. The distance calculation unit 142 can acquire the correction coefficient of each pixel used to correct the measured distance of each pixel by referring to the correction coefficient map to acquire the correction coefficient associated with each pixel.

[0103] The correction table memory 144 stores a correction equation (Y=aX+b) with coefficients a and b as variables, and a correction table 2310 shown in Fig. 23. The correction table 2310 stores information related to the correction equation used when performing the primary distance correction.

[0104] In addition, information indicating the "correction coefficients associated with each of the multiple pixels" and the "set of correction equations for primary distance correction including multiple correction equations and the application range of each correction equation" may be referred to as "correction information."

[0105] Other than the above, the configuration is the same as that of the distance measuring device 100 shown in FIG.

[0106] <Specific operation> Fig. 24 is a flowchart showing a processing flow executed by the distance calculation unit 142. The distance calculation unit 142 executes the processing flow shown in Fig. 24 every time a predetermined time elapses, thereby outputting a corrected distance (distance data) for each pixel to the image processing unit 143.

[0107] The distance calculation unit 142 starts the process from step 2400 in FIG. 24, and after performing the processes from step 2405 to step 2430, proceeds to step 2495 and temporarily ends this processing flow.

[0108] Step 2405: The distance calculation unit 142 calculates the measured distance for each pixel for all pixels based on the electrical signal (exposure amount) from the light receiving sensor 120.

[0109] Step 2410: The distance calculation unit 142 temporarily obtains a corrected distance (first-order error-corrected distance) for all pixels using a common correction formula. That is, the distance calculation unit 142 uses the correction table 2310 to set (select) a correction formula (a correction formula corresponding to a measured distance) to be applied based on the measured distance, and calculates a first-order error-corrected distance for each pixel for all pixels by correcting the measured distance for each pixel using the set correction formula.

[0110] Step 2415: The distance calculation unit 142 calculates the difference (=measured distance value-first-order error correction distance) between the measured distance value of each pixel and the temporarily calculated corrected distance (first-order error correction distance) of each pixel for all pixels.

[0111] Step 2420: The distance calculation unit 142 multiplies the calculated difference between all pixels by the correction coefficient for each pixel to calculate a distance error value for each pixel (=difference between each pixel×correction coefficient for each pixel).

[0112] Step 2425: The distance calculation unit 142 calculates the corrected distance for each pixel (= measured distance value of each pixel - distance error value of each pixel) for all pixels by subtracting the distance error value of each pixel from the measured distance value of each pixel.

[0113] Step 2430: The distance calculation unit 142 outputs the calculated corrected distance (distance data) for each pixel to the image processing unit 143. After that, the distance calculation unit 142 proceeds to step 2495 and temporarily ends this processing flow.

[0114] <Effects> As described above, the distance measuring device 100 according to the third embodiment of the present invention can correct distance errors occurring between pixels due to the influence of multipaths that differ for each pixel, similar to the first embodiment. Furthermore, the distance measuring device 100 according to the third embodiment uses "correction equation-related information used for primary distance correction and correction coefficients for each pixel" which has a smaller data amount than the correction equation-related information for each pixel, instead of the correction equation-related information for each pixel, so that the amount of data required for distance error correction can be reduced.

[0115] <<Fourth embodiment>> A distance measuring device 100 according to a fourth embodiment of the present invention will be described below. The distance measuring device according to the fourth embodiment of the present invention differs from the distance measuring device 100 according to the third embodiment only in the following points.

[0116] The correction coefficient map depends on the received light intensity of each pixel, and is determined by the lens characteristics such as distortion aberration used in the distance measuring device 100, the light quantity profile characteristics of the light source, the installation environment, etc. For this reason, for example, the correction coefficient map differs when the distance measuring device 100 is installed facing directly downward (installation angle 90°) as shown in Fig. 25A and when the distance measuring device 100 is installed obliquely (installation angle 40°) as shown in Fig. 25B.

[0117] Therefore, in the distance measuring device 100 according to the fourth embodiment, a correction coefficient map for each installation angle of the distance measuring device 100 is stored in the Pixel correction coefficient memory 2100. In this example, a correction coefficient map Map1 corresponding to an installation angle of 90° shown in Fig. 25A and a correction coefficient map Map2 corresponding to an installation angle of 40° shown in Fig. 25B are stored. Note that Fig. 25C shows a diagram in which the correction coefficient map Map2 in Fig. 25B is tabulated to facilitate understanding of the correction coefficient map Map2.

[0118] 26, the distance measuring device 100 according to the fourth embodiment includes an angle sensor 2600. The distance measuring device 100 according to the fourth embodiment detects the mounting attitude (installation angle) of the distance measuring device 100 by the angle sensor 2600. The distance measuring device 100 sets an optimal correction coefficient map for the installation angle from the Pixel correction coefficient memory 2100, and uses the set correction coefficient map to correct the measured distance.

[0119] The following description will focus on these differences.

[0120] <Specific operation> Fig. 27 is a flowchart showing a processing flow executed by the distance calculation unit 142. Before performing distance measurement, the distance calculation unit 142 executes the processing flow shown in Fig. 27 to set an optimal correction coefficient map for the installation angle from the Pixel correction coefficient memory 2100.

[0121] The distance calculation unit 142 starts the process from step 2700 in FIG. 27, and executes the processes from step 2705 to step 2715 described below in order, and then proceeds to step 2795 to temporarily end this processing flow.

[0122] Step 2705 : The distance calculation unit 142 detects the mounting attitude (angle) of the distance measuring device 100 by the angle sensor 2600 .

[0123] Step 2710 : The distance calculation unit 142 refers to the Pixel correction coefficient memory 2100 and selects the correction coefficient map associated with the angle closest to the angle detected by the angle sensor 2600 .

[0124] Step 2715: The distance calculation unit 142 sets the selected correction coefficient map as the correction coefficient map to be used for correcting the measured distance.

[0125] When performing distance measurement after setting the correction coefficient map used to correct the measured distance, the distance calculation unit 142 executes the processing flow shown in Figure 24 described above every time a predetermined time elapses, thereby outputting the corrected distance (distance data) for each pixel to the image processing unit 143.

[0126] <Effects> As described above, the distance measuring device 100 according to the fourth embodiment of the present invention can correct the measured distance by using an appropriate correction coefficient map according to the installation angle. This allows the distance measuring device 100 to more accurately correct distance errors for each pixel that occur due to the multipath phenomenon.

[0127] <<Fifth embodiment>> A distance measuring device 100 according to a fifth embodiment of the present invention will be described below. The distance measuring device 100 according to the fifth embodiment differs from the distance measuring device 100 according to the fourth embodiment only in the following points.

[0128] In the distance measuring device 100 according to the fifth embodiment, a plurality of pieces of correction equation-related information for each installation environment to be used for the primary distance correction are stored in the correction table 2810 stored in the correction table memory 144. The distance measuring device 100 according to the fifth embodiment selects one piece of correction equation-related information that is optimal for the installation environment from the correction table 2810 (a plurality of pieces of correction equation-related information) stored in the correction table memory 144, and uses the selected correction equation-related information for the primary distance correction.

[0129] The following explanation will focus on these differences.

[0130] FIG. 28 is a diagram showing an example of the correction table 2810. As shown in FIG. 28, the correction table 2810 stores correction formula related information corresponding to each of a plurality of installation environments. The correction table 2810 includes an installation environment 2811, an AB correction 2812, a BC correction 2813, and an AB / BC correction switching distance 2814 as columns for storing information (values). The AB correction 2812 includes a slope 2812a and an offset 2812b as subcolumns. The BC correction 2813 includes a slope 2813a and an offset 2813b as subcolumns. In the correction table 2810, information corresponding to each column for creating (setting) a correction formula and an application range of the correction formula corresponding to the installation environment is stored as information (records) in rows in association with each other.

[0131] <<Specific operation>> The distance calculation unit 142 executes the process flow of Fig. 29 to set the correction equation related information optimal for the installation environment from the correction table 2810 of Fig. 28 as the correction equation related information used for correcting the measured distance (primary distance correction). Note that the distance measuring device 100 according to the fifth embodiment uses the GUI screen GM1 shown in Fig. 17.

[0132] Fig. 29 is a flowchart showing the process flow of the correction equation setting process executed by the distance calculation unit 142. When the user operates the calibration start button 1212 (see Fig. 17), the distance calculation unit 142 starts the process from step 2900 in Fig. 29, and executes the processes from step 2905 to step 2925 described below in order, and then proceeds to step 2930.

[0133] Step 2905: The distance calculation unit 142 obtains the accurate distance to the measurement point of the target input by the user on the GUI screen GM1.

[0134] Step 2910: The distance calculation unit 142 starts measuring the distance to the measurement point of the target.

[0135] Step 2915 : The distance calculation unit 142 selects one of the installation environments in the correction table 2810 .

[0136] Step 2920: The distance calculation unit 142 acquires the selected installation environment and the correction equation related information corresponding to the installation environment from the correction table 2810. The distance calculation unit 142 sets "two correction equations and the application range of each correction equation (i.e., a primary distance correction equation set)" corresponding to the installation environment based on the "correction equation (Y=aX+b) with coefficients as variables" and the correction equation related information. The distance calculation unit 142 measures the distance (primary error correction distance) to the target (measurement point of the target) using the correction equation appropriate for the measurement distance.

[0137] Step 2925: The distance calculation unit 142 calculates the distance error, which is the difference between the measured distance (first-order error corrected distance) and the accurate distance to the measurement point of the target (the actual distance entered in the input field 1211 of the GUI screen GM1), and stores (records) it in the correction table memory 144 as the distance error corresponding to the selected installation environment.

[0138] When the distance calculation unit 142 proceeds to step 2930, it determines whether or not the distance errors have been recorded for all the installation environments stored in the correction table 2810.

[0139] If distance errors have not been recorded for all installation environments stored in the correction table 2810, the distance calculation unit 142 judges "NO" in step 2930 and proceeds to step 2935, where it selects an unselected installation environment from the installation environments stored in the correction table 2810.

[0140] Thereafter, distance calculation unit 142 returns to step 2920, and executes the processes of steps 2920 and 2925 in order again, before proceeding to step 2930.

[0141] When the processing of steps 2920 to 2935 is repeatedly executed and distance errors are recorded for all installation environments stored in correction table 2810 in step 2930, distance calculation unit 142 judges "YES" in step 2930 and sequentially executes the processing of steps 2940 and 2945 described below. After that, distance calculation unit 142 proceeds to step 2995 and temporarily ends this processing flow.

[0142] Step 2940: The distance calculation unit 142 identifies the installation environment corresponding to the smallest distance error among the recorded distance errors to the target, and selects the correction equation related information of the correction table 2810 corresponding to the identified installation environment.

[0143] Step 2945: The distance calculation unit 142 sets the selected correction equation related information as correction equation related information to be used for the primary distance correction of the measured distance.

[0144] The distance calculation unit 142 executes the process flow of FIG. 27 to set the correction coefficient map according to the installation angle as the correction coefficient map to be used for correcting the measured distance.

[0145] The distance calculation unit 142 executes the processing flow of FIG. 24 to output the corrected distance (distance data) for each pixel to the image processing unit 143.

[0146] <Effects> As described above, the distance measuring device 100 according to the fifth embodiment of the present invention can correct the measured distance by using the appropriate correction equation related information according to the installation environment and the appropriate correction coefficient map according to the installation angle. This allows the distance measuring device 100 to more accurately correct the distance error for each pixel caused by the multipath phenomenon.

[0147] <<Sixth embodiment>> A distance measuring device 100 according to a sixth embodiment of the present invention will be described below. The distance measuring device 100 according to the sixth embodiment differs from the distance measuring device 100 according to the fourth embodiment only in the following points.

[0148] The distance measuring device 100 according to the fourth embodiment uses a plurality of correction coefficient maps adapted to the expected environment, which are recorded in advance in the distance measuring device 100. In contrast, the correction coefficient map is determined by the lens characteristics, such as distortion aberration, used in the distance measuring device 100, the light quantity profile characteristics of the light source, the installation environment, and the like.

[0149] Therefore, the distance measuring device 100 according to the sixth embodiment automatically generates a correction coefficient map according to the environment after being installed in the environment in which it will be used. After being installed in the environment in which it will be used, the distance measuring device 100 according to the sixth embodiment generates a correction coefficient map by calculating the ratio of each pixel to a reference pixel (for example, the center of the pixels of the light receiving sensor 120) from the amount of light received by each pixel, which is the basis for generating measured distance data, as a calibration operation upon installation. The distance measuring device 100 according to the sixth embodiment corrects the measured distance using the generated correction coefficient map.

[0150] The following description will focus on these differences.

[0151] <Summary> An outline of the automatic creation of a correction coefficient map of the distance measuring device 100 will be described. Note that in this example, the reference pixel is the center pixel (320, 240), but the position of the reference pixel is not limited to this.

[0152] When creating a correction coefficient map, the distance measuring device 100 measures the amount of light received at each pixel by measuring the flat floor surface after being attached facing directly downward. As a result, the distance measuring device 100 obtains a graph GR1 in which the amount of light received at each pixel is profiled, as shown in FIG. 30. Next, the distance measuring device 100 normalizes the amount of light received at the center pixel (320, 240) of the light receiving sensor 120 by setting it as a reference pixel for the correction coefficient and setting it to "1x". After that, the distance measuring device 100 calculates the ratio value of the normalized amount of light received at each pixel to the normalized amount of light received at the reference pixel (=normalized amount of light received at reference pixel / normalized amount of light received at pixel (x, y)), and sets this ratio value as the correction coefficient for each pixel, thereby creating the correction coefficient map shown by the graph GR2 in FIG. 30. In addition, the distance measuring device 100 may set the correction coefficient to a value obtained by multiplying the ratio of the normalized amount of light received by each pixel to the normalized amount of light received by the reference pixel (= normalized amount of light received by the reference pixel / normalized amount of light received at pixel (x, y)) by a reduction magnification.

[0153] <Specific operation> Fig. 31 is a flowchart showing a processing flow executed by the distance calculation unit 142. Before performing distance measurement, the distance calculation unit 142 executes the processing flow shown in Fig. 31 to automatically create a correction coefficient map that is optimal for the installation environment.

[0154] The distance calculation unit 142 starts the process from step 3100 and executes the processes from step 3105 to step 3120 described below, and then proceeds to step 3195 to temporarily end this processing flow.

[0155] Step 3105: The distance calculation unit 142 measures the amount of light received by each pixel by measuring the plane floor surface.

[0156] Step 3110: The distance calculation unit 142 normalizes the amount of received light with a correction magnification of 1, using the center pixel (320, 240) as the reference pixel.

[0157] Step 3115: The distance calculation unit 142 calculates the ratio of the normalized amount of light received by each pixel to the normalized amount of light received by the reference pixel (=normalized amount of light received by the reference pixel / normalized amount of light received at pixel (x, y)), and sets this ratio as the correction coefficient for each pixel. Note that the process of step 3115 is repeated until it is performed for all pixels.

[0158] Step 3120 : The distance calculation unit 142 records and stores the obtained correction coefficient map in the Pixel correction coefficient memory 2100 in the distance measuring device 100 .

[0159] When performing distance measurement after setting the correction coefficient map used to correct the measured distance, the distance calculation unit 142 executes the processing flow shown in Figure 24 described above every time a predetermined time elapses, thereby outputting the corrected distance (distance data) for each pixel to the image processing unit 143.

[0160] <Effects> As described above, the distance measuring device 100 according to the sixth embodiment of the present invention can automatically create an appropriate correction coefficient map according to the installation environment and correct the measured distance using the correction coefficient map. Note that the features of the distance measuring device 100 according to the sixth embodiment may be applied to the distance measuring device 100 according to the fifth embodiment.

[0161] <<Modifications>> The present invention is not limited to the above-described embodiments, and various modifications can be adopted within the scope of the present invention. Furthermore, the above-described embodiments can be combined with each other without departing from the scope of the present invention.

[0162] In the first and second embodiments, the distance correction calculation 142a performed by the distance calculation unit 142 may be performed by the external processing device 200. FIG. 32 is a diagram showing a configuration example of a distance measurement system including the distance measurement device 100 according to this modification. The external processing device 200 includes a distance calculation unit 3200. The distance calculation unit 3200 includes a correction table memory 144. The external processing device 200 receives the measured distance for each pixel before correction as distance data from the distance calculation unit 142. The distance calculation unit 3200 of the external processing device 200 performs the distance correction calculation 142a performed by the distance calculation unit 142 in the first and second embodiments. In this modification, as shown in FIG. 33, the process performed by the external processing device 200 may be performed by a cloud 3300 connected to the distance measurement device 100 via a network NW1 so as to be able to transmit and receive information. In this modification, the distance calculation unit 3200 may be configured by computer resources (such as a server and storage) of the cloud 3300, and the distance calculation unit 3200 on the cloud 3300 performs the distance correction calculation 142a executed by the distance calculation unit 142 in the first and second embodiments. Note that the external processing device 200 and the cloud 3300 may also be referred to as an "external processing unit" for convenience.

[0163] In the third to fifth embodiments, the distance correction calculation 142a performed by the distance calculation unit 142 may be performed by the external processing device 200. FIG. 34 is a diagram showing a configuration example of a distance device applied to this modification. The external processing device 200 includes a distance calculation unit 3400. The distance calculation unit 3400 includes a correction table memory 144. The external processing device 200 receives the measured distance for each pixel before correction as distance data from the distance calculation unit 142. The distance calculation unit 3400 of the external processing device 200 performs the distance correction calculation 142a performed by the distance calculation unit 142 in the third to fifth embodiments. In this modification, as shown in FIG. 35, the process performed by the external processing device 200 may be performed by a cloud 3300 connected to the distance measuring device 100 via a network NW1 so as to be able to transmit and receive information. In this modified example, the distance calculation unit 3400 may be configured by computer resources (servers, storage, etc.) of the cloud 3300, and the distance calculation unit 3400 on the cloud 3300 performs the distance correction calculation 142a performed by the distance calculation unit 142 in the third and fifth embodiments.

[0164] Depending on the installation environment, the relationship between the actual distance and the measurement error may have a shape as shown by line Ln21 in Fig. 36. In this case, a better correction effect can be obtained by establishing an approximation model (line Ln22) with three straight lines with different slopes and intercepts than by an approximation model with two straight lines with different slopes and intercepts. Therefore, three approximate correction formulas for the measured distance may be established from such an approximation model.

[0165] In this case, for example, a correction formula (Y=aX+b) with coefficients as variables, and information associating identification information indicating the installation environment, coefficient values ​​of the correction formula for each applicable range, and two correction switching distances (SwL1 and SwL2) as correction formula related information are stored in the correction table 1310. The distance calculation unit 142 sets the correction formula to be used for correction and the applicable range of the correction formula from the correction formula (Y=aX+b) and the correction formula related information. In each of the above embodiments, there may be four or more correction formulas (approximate correction formulas) for each applicable range.

[0166] In the above-described second embodiment, a set of correction-formula-related information for each pixel that is optimal for the installation environment is set by executing the processing flow shown in FIG. 18. However, the distance measuring device 100 may be provided with an operation unit (e.g., a touch panel) for selecting the installation environment, and the correction-formula-related information corresponding to the installation environment may be set based on the selection of the installation environment based on the user's operation of the operation unit.

[0167] In the above-described fifth embodiment, the processing flow shown in FIG. 29 is executed to set the correction equation-related information optimal for the installation environment. However, the distance measuring device 100 may be provided with an operation unit (e.g., a touch panel) for selecting the installation environment, and the correction equation-related information corresponding to the installation environment may be set based on the selection of the installation environment based on the user's operation of the operation unit.

[0168] In the fifth embodiment, there is one correction coefficient map as in the third embodiment, and the execution of the processing flow in FIG. 27 may be omitted.

[0169] The present invention can also have the following configuration.

[0170] [1] an irradiation unit that irradiates a measurement object with measurement light; a light receiving sensor having a plurality of pixels that receives reflected light from the measurement object and detects an exposure amount based on the reflected light; a control device including a memory unit that stores correction information indicating a correction formula set including a plurality of correction formulas corresponding to each of the plurality of pixels and an application range of each correction formula, or a correction coefficient corresponding to each of the plurality of pixels, and a correction formula set for primary distance correction including the plurality of correction formulas and an application range of each correction formula, and calculates a measurement distance to the measurement object for each of the pixels based on the exposure amount; A distance correction method applied to a distance measuring device comprising: By the control device, performing a distance correction calculation to calculate a corrected measured distance for each of the pixels by correcting the measured distance for each of the pixels using the correction information stored in the storage unit; Distance correction method.

[0171] [2] A distance measurement program that causes the control device to execute the distance correction method described in [1]. [Explanation of symbols]

[0172] 100... distance measuring device, 110... laser diode, 120... light receiving sensor, 130... power supply, 140... control device, 141... light emission control unit, 142... distance calculation unit, 143... image processing unit, 144... correction table memory, 200... external processing device

Claims

1. an irradiation unit that irradiates a measurement object with measurement light; a light receiving sensor having a plurality of pixels that receives reflected light from the measurement object and detects an exposure amount based on the reflected light; a control device including a memory unit that stores correction information indicating a correction formula set including a plurality of correction formulas corresponding to each of the plurality of pixels and an application range of each correction formula, or a correction coefficient corresponding to each of the plurality of pixels, and a correction formula set for primary distance correction including the plurality of correction formulas and an application range of each correction formula, and calculates a measurement distance to the measurement object for each of the pixels based on the exposure amount; Equipped with The control device includes: performing a distance correction calculation to calculate a corrected measured distance for each of the pixels by correcting the measured distance for each of the pixels using the correction information stored in the storage unit; It was configured as follows: Ranging device.

2. 2. The distance measuring device according to claim 1, the correction information indicates the correction equation set associated with each of the plurality of pixels; the control device executes the distance correction calculation by correcting the measured distance using, for each pixel, one of a plurality of correction equations included in the correction equation set corresponding to the pixel, the correction equation corresponding to the application range in which the measured distance is included, thereby calculating the corrected measured distance. It was configured as follows: Ranging device.

3. 3. The distance measuring device according to claim 2, the correction information indicates the correction formula sets associated with each of a plurality of the pixels, each of which corresponds to a plurality of installation environments; The control device includes: For each of the correction equation sets associated with each of the plurality of pixels corresponding to each of the plurality of installation environments, calculating the measured distance of the pixel corresponding to the predetermined measurement object, correcting the measured distance using one of the correction equations included in the correction equation set corresponding to the pixel corresponding to the predetermined measurement object, the correction equation corresponding to the application range in which the measured distance is included, thereby calculating the corrected measured distance, and performing a distance difference calculation to calculate a distance difference between an actual distance to the predetermined measurement object and the calculated corrected measured distance; setting the correction equation set associated with each of the plurality of pixels, including the correction equation used when obtaining the smallest distance difference among the calculated distance differences, as the correction equation set associated with each of the plurality of pixels used in the distance correction calculation; performing the distance correction calculation using the correction equation set associated with each of the set plurality of pixels; It was configured as follows: Ranging device.

4. 2. The distance measuring device according to claim 1, the correction information indicates the correction coefficients and the correction formula set for primary distance correction associated with each of a plurality of pixels, The control device includes: calculating a first-order error-corrected distance for each pixel by correcting the measured distance using a correction formula corresponding to the application range including the measured distance, among a plurality of correction formulas included in the correction formula set for first-order distance correction; Calculating a difference for each pixel by subtracting the first-order error corrected distance from the measured distance, calculating a distance error for each of the pixels by multiplying the difference by the correction coefficient; performing the distance correction calculation by calculating the corrected measured distance for each of the pixels by subtracting the distance error from the measured distance for each of the pixels; It was configured as follows: Ranging device.

5. 5. The distance measuring device according to claim 4, An angle sensor is provided for detecting an installation angle of the distance measuring device, the correction information indicates the correction coefficients associated with a plurality of pixels corresponding to a plurality of installation angles, The control device includes: determining the correction coefficients associated with each of the plurality of pixels to be used in the distance correction calculation based on the installation angle detected by the angle sensor, and executing the distance correction calculation using the determined correction coefficients associated with each of the plurality of pixels. It was configured as follows: Ranging device.

6. 5. The distance measuring device according to claim 4, the correction information indicates a set of correction formulas for primary distance correction corresponding to each of a plurality of installation environments, The control device includes: For each of the primary distance correction correction formula sets corresponding to each of the plurality of installation environments, calculating the measured distance of the pixel corresponding to the predetermined measurement object, correcting the measured distance using one of the correction formulas included in the correction formula sets for primary distance correction that corresponds to the application range in which the measured distance falls, thereby calculating the primary error-corrected distance, and performing a distance difference calculation to calculate a distance difference between an actual distance to the predetermined measurement object and the calculated primary error-corrected distance; setting the correction formula set for primary distance correction including the correction formula used when obtaining the smallest distance difference among the distance differences calculated for each of the plurality of correction formula sets for primary distance correction as the correction formula set for primary distance correction used in the distance correction calculation; Executing the distance correction calculation using the set correction formula set for primary distance correction. It was configured as follows: Ranging device.

7. 5. The distance measuring device according to claim 4, An angle sensor is provided for detecting an installation angle of the distance measuring device, the correction information indicates the correction coefficients associated with each of the plurality of pixels corresponding to each of a plurality of installation angles, and the correction formula sets for primary distance correction corresponding to each of a plurality of installation environments, The control device includes: determining a correction coefficient associated with each of the plurality of pixels to be used in the distance correction calculation based on the angle detected by the angle sensor, and using the determined correction coefficient associated with each of the plurality of pixels for the distance correction calculation; For each of the primary distance correction correction formula sets corresponding to each of the plurality of installation environments, calculating the measured distance of the pixel corresponding to the predetermined measurement object, correcting the measured distance using one of the correction formulas included in the correction formula sets for primary distance correction that corresponds to the application range in which the measured distance falls, thereby calculating the primary error-corrected distance, and performing a distance difference calculation to calculate a distance difference between an actual distance to the predetermined measurement object and the calculated primary error-corrected distance; setting the correction formula set for primary distance correction including the correction formula used when obtaining the smallest distance difference among the distance differences calculated for each of the plurality of correction formula sets for primary distance correction as the correction formula set for primary distance correction used in the distance correction calculation; The set correction formula set for primary distance correction is used for the distance correction calculation. It was configured as follows: Ranging device.

8. 5. The distance measuring device according to claim 4, The control device includes: measuring the amount of light received by each pixel by measuring the plane floor surface, and calculating the correction coefficient, which is a correction magnification of the distance error of the other pixels relative to the distance error of the reference pixel, based on the amount of light received by the reference pixel and the amount of light received by each pixel other than the reference pixel, thereby calculating the correction coefficient associated with each of the plurality of pixels, and storing the calculated correction coefficient in the storage unit; It was configured as follows: Ranging device.

9. 2. The distance measuring device according to claim 1, The plurality of correction equations are two correction equations each consisting of a linear function having a different slope and intercept. Ranging device.

10. A ranging system having a ranging device and an external processing unit, The distance measuring device is an irradiation unit that irradiates a measurement object with measurement light; a light receiving sensor having a plurality of pixels that receives reflected light from the measurement object and detects an exposure amount based on the reflected light; a control device that calculates a measurement distance to the measurement object for each pixel based on the exposure amount; Equipped with The external processing unit includes: a storage unit that stores correction information indicating a correction formula set including a plurality of correction formulas associated with each of the plurality of pixels and an application range of each correction formula, or a correction coefficient associated with each of the plurality of pixels, and a correction formula set for primary distance correction including the plurality of correction formulas and an application range of each correction formula; a distance calculation unit that executes a distance correction calculation to calculate a corrected measured distance for each of the pixels by correcting the measured distance for each of the pixels using the correction information stored in the storage unit; Equipped with Ranging system.

11. an irradiation unit that irradiates a measurement object with measurement light; a light receiving sensor having a plurality of pixels that receives reflected light from the measurement object and detects an exposure amount based on the reflected light; a control device including a memory unit that stores correction information indicating a correction formula set including a plurality of correction formulas corresponding to each of the plurality of pixels and an application range of each correction formula, or a correction coefficient corresponding to each of the plurality of pixels, and a correction formula set for primary distance correction including the plurality of correction formulas and an application range of each correction formula, and calculates a measurement distance to the measurement object for each of the pixels based on the exposure amount; A distance correction method applied to a distance measuring device comprising: By the control device, performing a distance correction calculation to calculate a corrected measured distance for each of the pixels by correcting the measured distance for each of the pixels using the correction information stored in the storage unit; Distance correction method.

12. A distance measuring program that causes the control device to execute the distance correction method according to claim 11.

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