JP2016070874A - Laser range finding device, program and correction method of laser range finding device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser range finding device that can reduce an influence of noise even when increasing a measurement range.SOLUTION: A laser range finding device 1 comprises: a table 102 in which a gain value with respect to a plurality of light reception elements is stored for each rotation angle of a scan mirror 15 so as to satisfy a prescribed condition; a reading unit that reads the gain value of each light reception element corresponding to the rotation angle of the san mirror 15 with reference to the table 102; and a correction unit that corrects a signal of the light reception element on the basis of the read gain value.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a laser distance measuring apparatus, a program, and a correction method for the laser distance measuring apparatus.

  2. Description of the Related Art Conventionally, a scanning laser radar that enlarges a monitoring visual field is known (for example, see Patent Document 1).

JP 2004-157044 A

  However, when the light receiving lens is widened and the measurement range is expanded, the noise increases, but the prior art cannot sufficiently reduce the influence of noise.

  An object of one aspect is to provide a laser distance measuring device or the like that can reduce the influence of noise even when the measurement range is increased.

  The laser distance measuring device disclosed in the present application refers to a table that stores gain values for a plurality of light receiving elements for each rotation angle of the scanning mirror so as to satisfy a predetermined condition, and the rotation angle of the scanning mirror with reference to the table. A reading unit that reads out the gain value of each light receiving element in response, and a correction unit that corrects a signal output from the light receiving element based on the read gain value.

  In one aspect, the influence of noise can be reduced even if the measurement range is increased.

It is explanatory drawing which shows the hardware group of a laser ranging apparatus. It is a circuit diagram which shows the principal part of a detection circuit. It is explanatory drawing which shows the record layout of a table. It is a flowchart which shows the procedure of the production | generation process of a table. It is a flowchart which shows the procedure of a measurement process. 6 is a block diagram illustrating a hardware group of a laser distance measuring device according to Embodiment 2. FIG. It is a flowchart which shows the production | generation process procedure of a table. It is a flowchart which shows the production | generation process procedure of a table. It is explanatory drawing which shows the outline | summary of a measurement system. FIG. 10 is a block diagram illustrating a hardware group of a laser distance measuring device according to a third embodiment. It is explanatory drawing which shows the record layout of a selection table. It is a flowchart which shows the selection process procedure of a table. It is a functional block diagram which shows operation | movement of the laser ranging apparatus of the form mentioned above. FIG. 10 is a block diagram illustrating a hardware group of a laser distance measuring device according to a fourth embodiment.

Embodiment 1
Hereinafter, embodiments will be described with reference to the drawings. FIG. 1 is an explanatory diagram showing a hardware group of the laser distance measuring device 1. The laser distance measuring device 1 includes a laser light source 13 that emits laser light, a laser drive circuit 12 that drives the laser light source 13, a scanning mirror 15 that scans the laser light, and a scanning mirror controller 14 that drives and controls the scanning mirror 15. Including. Further, the laser distance measuring device 1 has a light receiving element array 18 on which an optical image in a scanning region of a laser beam by the scanning mirror 15 is formed via an optical filter 16 and an imaging lens 17. In the light receiving element array 18, a large number of light receiving elements are arranged in a matrix. In addition, the laser distance measuring device 1 includes a detection circuit 19, a measurement circuit 101, a table 102, and a CPU (Central Processing Unit) 11.

  The CPU 11 serving as a control unit is connected to each hardware unit via a bus. The CPU 11 controls each part of the hardware according to a control program 15P stored in a RAM (Random Access Memory) 103. The RAM 103 is, for example, SRAM (Static RAM), DRAM (Dynamic RAM), flash memory, or the like. The RAM 103 temporarily stores various data generated when the CPU 11 executes various programs.

  The laser driving circuit 12 is driven by an operation start command output from the CPU 11 and periodically outputs a light transmission pulse to the laser light source 13. The laser light source 13 emits laser light to the scanning mirror 15 every time a light transmission pulse is input. As the scanning mirror 15, for example, a MEMS (Micro Electro Mechanical System) mirror manufactured by applying semiconductor micromachine technology is used. The scanning mirror 15 is not limited to a semiconductor mirror but may be a polygon mirror or a galvano mirror.

  The scanning mirror controller 14 is driven by an operation start command output from the CPU 11 and drives the scanning mirror 15 to swing. Further, the scanning mirror controller 14 sends the scanning position information of the scanning mirror 15 to the CPU 11 based on the drive current value supplied to the scanning mirror 15.

  The detection circuit 19 amplifies the signal output from the light receiving element array 18 for correction based on the gain stored in the table 102. The detection circuit 19 outputs the amplified signal to the measurement circuit 101. The measurement circuit 101 calculates the distance to the object based on the time from when the light transmission pulse generation information is output from the laser driving circuit 12 until the light reflected from the object (not shown) is received by the light receiving element array 18. .

  FIG. 2 is a circuit diagram showing a main part of the detection circuit 19. Each light receiving element of the light receiving element array 18 is indicated by D1, D2,... DN (represented by the light receiving element D in some cases). A resistor R and an amplifier circuit K are connected to the light receiving element D in series. Resistances connected to each light receiving element D are indicated by R1, R2,... RN (represented by resistance R in some cases). The gain values of the amplifier circuit K connected to each light receiving element D are represented by K1, K2,... KN.

  Here, when the signal components of each light receiving element D are a1, a2,... AN and the noise components are b1, b2,... BN, the signal-to-noise ratio (SNR) is expressed by the following equation 1. Can do. The noise component can be calculated by the root mean square of resistance thermal noise present in the circuit of the laser distance measuring device 1, shot noise caused by dark current, and shot noise caused by photocurrent.

  FIG. 3 is an explanatory diagram showing a record layout of the table 102. The table 102 stores gain values K1, K2,... KN corresponding to the light receiving elements D1, D2,... DN in association with the horizontal angle and the vertical angle that are the rotation angles of the scanning mirror 15. Yes. As each gain value corresponding to the horizontal angle and the vertical angle, a value at which the signal-to-noise ratio is maximized is stored. The CPU 11 irradiates a specific object and calculates the gain value with reference to Equation 1 so that the signal-to-noise ratio becomes the maximum value in each angle combination.

  FIG. 4 is a flowchart showing a procedure for generating the table 102. The CPU 11 performs initial setting of the horizontal angle and the vertical angle of the scanning mirror 15 (step S41). The CPU 11 reads the gain value combination from the RAM 103 (step S42). CPU11 irradiates a laser beam and acquires the signal component and noise component of each light receiving element D (step S43). The CPU 11 calculates a signal-to-noise ratio based on the signal component, noise component, and gain value of each light receiving element D (step S44). The CPU 11 determines whether or not processing corresponding to all combinations of gain values has been completed (step S45).

  If the CPU 11 determines that the process for all combinations of gain values has not been completed (NO in step S45), the process returns to step S42. The CPU 11 reads other combinations of gain values and repeats the above processing. As a result, signal-to-noise ratios for various combinations of gain values are calculated.

  If the CPU 11 determines that the process for all combinations of gain values has been completed (YES in step S45), the process proceeds to step S46. The CPU 11 extracts a gain value combination for each light receiving element D having the maximum signal-to-noise ratio from the signal-to-noise ratio calculated in step S44 (step S46). The CPU 11 stores gain value combinations in the table 102 in association with the horizontal angle and the vertical angle (step S47).

  The CPU 11 determines whether or not the processing for all combinations of horizontal angles and vertical angles has been completed (step S48). If the CPU 11 determines that the process has not ended (NO in step S48), the process proceeds to step S49. The CPU 11 sets a new horizontal angle and vertical angle that have not been processed yet (step S49). CPU11 returns a process to step S42. By repeating the above processing, the signal-to-noise ratio having the maximum value is calculated for various combinations of horizontal angle and vertical angle. If the CPU 11 determines that the processes for all combinations have been completed (YES in step S48), the series of processes is terminated.

  FIG. 5 is a flowchart showing the procedure of the measurement process. The CPU 11 sets the horizontal angle and the vertical angle of the scanning mirror 15 (step S51). The CPU 11 reads the gain values corresponding to the horizontal angle and the vertical angle from the table 102 calculated by the processing of FIG. 4, and sets the gain value in the gain circuit of the detection circuit 19 (step S52). CPU11 outputs the command which emits a laser beam to the laser drive circuit 12 (step S53).

  The CPU 11 detects reflected light from the light receiving element array 18 (step S54). The detection circuit 19 corrects the detection signal by multiplying the signal component of each light receiving element D by the set gain value (step S55). The detection circuit 19 outputs the corrected detection signal to the measurement circuit 101. The measurement circuit 101 calculates the distance based on the laser light emission time and the reflected light detection time (step S56). The measurement circuit 101 outputs the calculated distance to the CPU 11.

  CPU11 judges whether the process mentioned above was complete | finished about all the horizontal angles and vertical angles (step S57). If the CPU 11 determines that the above process has not been completed (NO in step S57), the process returns to step S51. The CPU 11 performs the same processing for the new horizontal angle and vertical angle. Thereby, the distance at each horizontal angle and vertical angle is calculated. If the CPU 11 determines that the processing for all horizontal angles and vertical angles has been completed (YES in step S57), the series of processing ends. Thereby, even when the capture angle is increased, the influence of noise can be reduced. In addition, since the table with the maximum signal-to-noise ratio is generated, distance measurement with higher accuracy is possible.

Embodiment 2
FIG. 6 is a block diagram showing a hardware group of the laser distance measuring apparatus 1 according to the second embodiment. As shown in FIG. 6, an object 2 such as Kent paper is placed on the entire surface of the laser distance measuring device 1, and laser irradiation is performed in a state where noise such as ambient light is as low as possible, and a gain value is calculated. good. In the first embodiment, the gain combination that maximizes the signal-to-noise ratio is calculated. However, as described below, a gain combination equal to or greater than the threshold value stored in advance in the RAM 103 may be employed.

  7 and 8 are flowcharts showing the procedure for generating the table 102. FIG. CPU11 reads a threshold value from RAM103 (step S70). The CPU 11 performs initial setting of the horizontal angle and the vertical angle of the scanning mirror 15 (step S71). The CPU 11 reads the gain value combination from the RAM 103 (step S72). CPU11 irradiates a laser beam and acquires the signal component and noise component of each light receiving element D (step S73). The CPU 11 calculates a signal-to-noise ratio based on the signal component, noise component, and gain value of each light receiving element D (step S74).

  The CPU 11 determines whether or not the calculated signal-to-noise ratio is greater than or equal to a threshold value (step S75). If the CPU 11 determines that the value is equal to or greater than the threshold (YES in step S75), the process proceeds to step S77. CPU11 extracts the combination of the gain value more than a threshold value (step S77). After that, the CPU 11 shifts the processing to step S79. If the CPU 11 determines that the signal-to-noise ratio is not equal to or greater than the threshold value (NO in step S75), the process proceeds to step S76. The CPU 11 determines whether or not the processing corresponding to all gain value combinations has been completed (step S76).

  If the CPU 11 determines that the process for all combinations of gain values has not been completed (NO in step S76), the process returns to step S72. The CPU 11 reads other combinations of gain values and repeats the above processing. As a result, signal-to-noise ratios for various combinations of gain values are calculated.

  If the CPU 11 determines that the process for all combinations of gain values has been completed (YES in step S76), the process proceeds to step S78. The CPU 11 extracts a gain value combination for each light receiving element D having the maximum signal-to-noise ratio from the signal-to-noise ratio calculated in step S74 (step S78). CPU11 transfers a process to step S79 after the process of step S78 and S77. The CPU 11 stores a combination of gain values in the table 102 in association with the horizontal angle and the vertical angle (step S79).

  The CPU 11 determines whether or not the processing for all combinations of horizontal angles and vertical angles has been completed (step S80). If the CPU 11 determines that the process has not ended (NO in step S80), the process proceeds to step S81. The CPU 11 sets a new horizontal angle and vertical angle that have not been processed yet (step S81). CPU11 returns a process to step S72.

  By repeating the above processing, a signal-to-noise ratio having a threshold value or a maximum value or a maximum value for various combinations of horizontal and vertical angles is calculated. If the CPU 11 determines that the processes for all combinations have been completed (YES in step S80), the series of processes is terminated. Thereby, an appropriate table can be generated at the time of shipment. In addition, it is possible to increase the processing speed by employing a combination of gain values exceeding a predetermined threshold.

  The second embodiment is as described above, and the other parts are the same as those of the first embodiment. Therefore, the corresponding parts are denoted by the same reference numerals, and detailed description thereof is omitted.

Embodiment 3
The third embodiment relates to a form using a plurality of types of tables. FIG. 9 is an explanatory diagram showing an outline of the measurement system. A device for acquiring environment information around the laser distance measuring device 1 is connected to the laser distance measuring device 1 by wire or wirelessly. The device is a vehicle speed sensor 3, a brightness sensor 4, a sensor such as a temperature sensor or an acceleration sensor (not shown), and a GPS (Global Positioning System). In the present embodiment, description will be made assuming that the devices are the vehicle speed sensor 3 and the brightness sensor 4. The description will be made assuming that the laser distance measuring device 1, the vehicle speed sensor 3, and the brightness sensor 4 are installed in the automobile. In addition to being attached to a moving body other than an automobile (for example, a robot, a train, a ship, a smartphone, etc.), it may be installed on a fixed object such as a surveillance camera.

  The vehicle speed sensor 3 outputs the vehicle speed of the automobile to the laser distance measuring device 1. The brightness sensor 4 outputs brightness information as brightness to the laser distance measuring device 1. FIG. 10 is a block diagram showing a hardware group of the laser distance measuring apparatus 1 according to the third embodiment. A selection table 104 is further provided.

  FIG. 11 is an explanatory diagram showing a record layout of the selection table 104. The selection table 104 stores first to fourth tables to be used from a plurality of types of tables 102 in association with vehicle speed and lightness. For example, when the vehicle speed is high (for example, 50 km / h or more) and the lightness is low (for example, 8 bits and the lightness is 120 or less. The higher the value, the brighter the light). A second table is selected. Although the embodiment shows an example of four classifications, it may be further subdivided and more tables 102 may be prepared.

  With the processing method described in FIG. 4 or FIG. 7 and FIG. 8, the CPU 11 is in a state where the vehicle speed output from the vehicle speed sensor 3 is “low” and the brightness output from the brightness sensor 4 is “low”. A first table is generated. With the processing method described in FIG. 4 or FIG. 7 and FIG. 8, the CPU 11 is in a state where the vehicle speed output from the vehicle speed sensor 3 is “high” and the brightness output from the brightness sensor 4 is “low”. A second table is generated.

  With the processing method described in FIG. 4 or 7 and 8, the CPU 11 is in a state where the vehicle speed output from the vehicle speed sensor 3 is “low” and the brightness output from the brightness sensor 4 is “high”. A third table is generated. With the processing method described in FIG. 4 or FIG. 7 and FIG. 8, the CPU 11 is in a state where the vehicle speed output from the vehicle speed sensor 3 is “high” and the brightness output from the brightness sensor 4 is “high”. A fourth table is generated. The CPU 11 stores the generated first to fourth tables in the table 102.

  FIG. 12 is a flowchart showing a table selection processing procedure. The CPU 11 determines whether or not a ranging instruction has been accepted (step S121). Specifically, the CPU 11 determines whether or not an input of a distance measurement instruction has been received from an unillustrated ECU (Engine Control Unit). If the CPU 11 has not received a distance measurement instruction (NO in step S121), the CPU 11 stands by until an instruction is received. CPU11 makes a process transfer to step S122, when a ranging instruction is received (it is YES at step S121). CPU11 acquires speed from speed sensor 3 (Step S122). CPU11 acquires the brightness from the brightness sensor 4 (step S123). The CPU 11 refers to the selection table 104 and calls the corresponding table 102 based on the acquired brightness and speed (step S124).

  The CPU 11 sets the horizontal angle and the vertical angle of the scanning mirror 15 (step S125). The CPU 11 reads the gain value corresponding to the horizontal angle and the vertical angle from the table 102 read out in step S124, and sets the gain value in the gain circuit of the detection circuit 19 (step S126). CPU11 outputs the command which emits a laser beam to the laser drive circuit 12 (step S127).

  The CPU 11 detects reflected light from the light receiving element array 18 (step S128). The detection circuit 19 corrects the detection signal by multiplying the signal component of each light receiving element D by the set gain value (step S129). The detection circuit 19 outputs the corrected detection signal to the measurement circuit 101. The measurement circuit 101 calculates the distance based on the laser light emission time and the reflected light detection time (step S1210). The measurement circuit 101 outputs the calculated distance to the CPU 11.

  CPU11 judges whether the process mentioned above was complete | finished about all the horizontal angles and vertical angles (step S1211). If the CPU 11 determines that the above process has not been completed (NO in step S1211), the process returns to step S125. The CPU 11 performs the same processing for the new horizontal angle and vertical angle. Thereby, the distance at each horizontal angle and vertical angle is calculated. If the CPU 11 determines that the processing for all horizontal angles and vertical angles has been completed (YES in step S1211), the series of processing ends. Thereby, according to the use environment of the laser distance measuring device 1, it becomes possible to utilize a suitable table and to improve a system | strain.

  The third embodiment is as described above, and the others are the same as in the first and second embodiments. Therefore, the corresponding parts are denoted by the same reference numerals, and detailed description thereof is omitted.

Embodiment 4
FIG. 13 is a functional block diagram showing the operation of the laser distance measuring apparatus 1 of the above-described form. When the CPU 11 executes the control program 15P, the computer 1 operates as follows. The reading unit 131 reads the gain value of each light receiving element D according to the rotation angle of the scanning mirror 15 with reference to the table 102. The correction unit 132 corrects the signal output from the light receiving element D based on the read gain value. The acquisition unit 133 acquires environmental information. The calling unit 134 calls the table 102 according to the acquired environment information.

  FIG. 14 is a block diagram illustrating a hardware group of the laser distance measuring apparatus 1 according to the fourth embodiment. A program for operating the laser distance measuring apparatus 1 can be a CD-ROM, a DVD (Digital Versatile Disc) disk, a memory card, or a USB (Universal Serial Bus) memory in the reading unit 10A such as a disk drive or a card drive. The portable recording medium 1A may be read and stored in the RAM 103. Further, a semiconductor memory 1B such as a flash memory storing the program may be mounted in the laser distance measuring device 1. Further, the program can be downloaded from another server computer (not shown) connected via a communication network such as the Internet. The contents will be described below.

  The laser distance measuring device 1 shown in FIG. 14 reads a program for executing the above-described various software processes from the portable recording medium 1A or the semiconductor memory 1B, or from another computer (not shown) via a communication network. to download. The program is installed as the control program 15P, loaded into the RAM 103, and executed. Thereby, it functions as the laser distance measuring device 1 described above.

  The fourth embodiment is as described above, and the others are the same as those of the first to third embodiments. Therefore, the corresponding parts are denoted by the same reference numerals and detailed description thereof is omitted.

  The following additional notes are further disclosed with respect to the embodiments including the first to third embodiments.

(Appendix 1)
A table storing gain values for a plurality of light receiving elements for each rotation angle of the scanning mirror so as to satisfy a predetermined condition;
A reading unit that reads the gain value of each light receiving element according to the rotation angle of the scanning mirror with reference to the table;
A laser distance measuring device comprising: a correction unit that corrects a signal output from a light receiving element based on a read gain value.

(Appendix 2)
The table stores, for each light receiving element, a gain value that maximizes the signal-to-noise ratio calculated based on the signal of each light receiving element that receives the laser light reflected by the scanning mirror at a predetermined angle. The laser distance measuring device according to 1.

(Appendix 3)
The table stores, for each light receiving element, a gain value at which the signal-to-noise ratio calculated based on the signal of each light receiving element that receives the laser light reflected by the scanning mirror at a predetermined angle is equal to or greater than a threshold value. The laser distance measuring device according to appendix 1.

(Appendix 4)
A plurality of the tables are provided in association with the environment information,
An acquisition unit for acquiring environmental information;
The laser range finder according to any one of appendices 1 to 3, further comprising: a calling unit that calls a table corresponding to the environmental information acquired by the acquiring unit.

(Appendix 5)
A plurality of the tables are provided in association with brightness,
The laser distance measuring device according to any one of appendices 1 to 3, further comprising: a calling unit that calls a table corresponding to the brightness acquired by the sensor that acquires the brightness.

(Appendix 6)
Laser distance measuring device
Refer to a table storing gain values for a plurality of light receiving elements for each rotation angle of the scanning mirror so as to satisfy a predetermined condition, and read out the gain values of the respective light receiving elements according to the rotation angles of the scanning mirror,
A program that executes processing to correct the signal output from the light receiving element based on the read gain value.

(Appendix 7)
Refer to a table storing gain values for a plurality of light receiving elements for each rotation angle of the scanning mirror so as to satisfy a predetermined condition, and read out the gain values of the respective light receiving elements according to the rotation angles of the scanning mirror,
A correction method for a laser distance measuring device that corrects a signal output from a light receiving element based on a read gain value.

DESCRIPTION OF SYMBOLS 1 Laser ranging device 1A Portable recording medium 1B Semiconductor memory 10A Reading part 2 Object 3 Vehicle speed sensor 4 Brightness sensor 11 CPU
DESCRIPTION OF SYMBOLS 12 Laser drive circuit 13 Laser light source 14 Scanning mirror controller 15 Scanning mirror 15P Control program 16 Optical filter 17 Imaging lens 18 Light receiving element array 19 Detection circuit 131 Reading part 132 Correction part 133 Acquisition part 134 Calling part D Light receiving element

Claims (4)

A table storing gain values for a plurality of light receiving elements for each rotation angle of the scanning mirror so as to satisfy a predetermined condition;
A reading unit that reads the gain value of each light receiving element according to the rotation angle of the scanning mirror with reference to the table;
A laser distance measuring device comprising: a correction unit that corrects a signal output from a light receiving element based on a read gain value. The table stores, for each light receiving element, a gain value that maximizes a signal-to-noise ratio calculated based on a signal of each light receiving element that receives the laser light reflected by the scanning mirror at a predetermined angle. Item 2. The laser distance measuring device according to Item 1. Laser distance measuring device
Refer to a table storing gain values for a plurality of light receiving elements for each rotation angle of the scanning mirror so as to satisfy a predetermined condition, and read out the gain values of the respective light receiving elements according to the rotation angles of the scanning mirror,
A program that executes processing to correct the signal output from the light receiving element based on the read gain value. Refer to a table storing gain values for a plurality of light receiving elements for each rotation angle of the scanning mirror so as to satisfy a predetermined condition, and read out the gain values of the respective light receiving elements according to the rotation angles of the scanning mirror,
A correction method for a laser distance measuring device that corrects a signal output from a light receiving element based on a read gain value.

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