JP2021056115A - Distance measuring device - Google Patents

Abstract

To provide a distance measuring device that can recognize and exclude an object which is not a monitoring target such as reflections of fog or dirt on a window in a distance measurement of a target.SOLUTION: A distance measuring device 100 includes: a distance measuring unit 50 for emitting a laser beam L1, measuring a laser beam L2 as a reflected beam of the laser beam L1, and determining a distance from the lapsed time from when the laser beam L1 is emitted to when the reflected light is received; and a light amount detection unit 60 for detecting the amount of light of the reflected light. The light amount detection unit 60 detects the amount of light of the reflected light at plural timings by switching a switch circuit 64.SELECTED DRAWING: Figure 1

Description

The present invention relates to a distance measuring device that measures a distance to an object using a laser beam.

In a distance measuring device that uses light, for example, the distance to the target and other measured values are generated by detecting the reflected light from the object irradiated with the light. As an example of this type of ranging device, there is a laser ranging device that determines a target distance by obtaining the time from the transmission of pulsed laser light to the reception of reflected light (Patent Documents 1 and 2). Specifically, in the apparatus of Patent Document 1, the electric pulse signal obtained by converting the received pulse laser light into an electric signal is differentiated, the peak value of the differential waveform is used, and the distance is corrected based on a function investigated in advance. There is. Further, in the apparatus of Patent Document 2, the integration result from the first time point corresponding to light emission to the third time point corresponding to the light receiving time and the second time point corresponding to the light receiving time to the third time point mentioned above The distance is determined from the difference from the integration result of.

However, in the devices of Patent Documents 1 and 2, the target distance is only obtained based on the time difference between the transmission of the pulsed laser light and the reception of the reflected light, and for a plurality of objects in the same direction, for example, fog or dirt on the window. There is a problem that it is difficult to identify an object that is not monitored, such as reflection from the light.

Japanese Unexamined Patent Publication No. 9-287914 Japanese Unexamined Patent Publication No. 2013-3114

The present invention has been made in view of the above background technology, and provides a distance measuring device capable of identifying and excluding an object not to be monitored such as reflection from fog or window dirt in distance measurement of an object. The purpose is.

In order to achieve the above object, the distance measuring device according to the present invention is a distance measuring unit that irradiates laser light, measures the reflected light, and determines the distance from the elapsed time from the irradiation of the laser light to the reception of the reflected light. And a light amount detecting unit for detecting the amount of reflected light, and the light amount detecting unit detects the amount of reflected light at a plurality of timings by switching the switch circuit.

According to the above-mentioned ranging device, the light amount detection unit detects the amount of reflected light at a plurality of timings by switching the switch circuit, so that even when there are a plurality of objects at different distances in the same direction, the plurality of such objects For an object, the intensity information of the reflected light can be acquired as auxiliary data accompanying the distance information. This makes it possible to identify and exclude non-monitoring objects such as reflections from fog and window dirt.

According to a specific aspect of the present invention, in the distance measuring device, the light amount detection unit is connected to an integrating circuit connected to a light receiving circuit for measuring reflected light, a plurality of peak hold circuits, and an integrating circuit. It has a switch circuit for selecting a peak hold circuit from a plurality of peak hold circuits. The amount of reflected light can be determined by an integrator circuit, a peak hold circuit, and a switch circuit, that is, by a single integrator circuit, with matching accuracy at a plurality of timings.

According to another aspect of the present invention, the photodetector switches a plurality of timings based on the output of the clock counter circuit started by the trigger signal. In this case, the detection result is stable and does not easily fluctuate due to disturbance.

According to yet another aspect of the present invention, the photodetector switches between a plurality of timings based on the output of an analog clock circuit initiated by a trigger signal. In this case, a relatively reliable result can be obtained with a simple and inexpensive circuit configuration.

According to still another aspect of the present invention, the light amount detection unit is one of rise detection, peak detection, fall detection, and resonance zero cross detection for the detection pulse output by the light receiving element for reflected light. To generate a trigger signal. By using the received light of the reflected light to generate a trigger signal, it is possible to detect the distance and the amount of light of the next object behind the object by using the distance detection result of the actual object.

According to yet another aspect of the present invention, the ranging device excludes an object that meets a predetermined condition from the detection result based on the distance to the object obtained from the reflected light and the amount of light. Here, the predetermined condition is, for example, whether or not the reflected light is a low level reflected light that does not reach the assumed reference light amount with respect to the distance of interest. In this case, non-monitoring objects such as fog and reflections from window dirt can be identified and excluded from the detection results.

(A) is a block diagram conceptually explaining the structure of the distance measuring device of the first embodiment and its peripheral device, and (B) is a timing of detecting the amount of reflected light measured by the distance measuring device. It is a figure explaining the corresponding distance zone. It is a block diagram explaining the specific circuit structure about the light amount measuring part of the distance measuring device shown in FIG. 1A. It is a figure explaining the analog clock circuit and the like among the apparatus parts shown in FIG. FIGS. (A) to (F) are diagrams for explaining a part of the operation of the distance measuring device using the light projection timing as a reference for the light amount detection timing. (A) to (J) are diagrams for explaining the operation of each part of the distance measuring device. It is a figure explaining the specific circuit configuration of the main part which concerns on the change about the distance measuring apparatus of 2nd Embodiment. (A) to (F) are diagrams for explaining a part of the operation of the distance measuring device using the light receiving timing as a reference for the timing of light amount detection, and (G) explains an example of a ghost signal in the received signal. It is a figure. (A) is a diagram for explaining rise detection, (B) is a diagram for explaining peak detection, (C) is a diagram for explaining fall detection, and (D) is a resonance zero cross. It is a figure explaining the detection. It is a figure explaining the specific circuit configuration of the main part which concerns on the change about the distance measuring apparatus of 3rd Embodiment. (A) to (J) are diagrams for explaining the operation of each part of the distance measuring device shown in FIG.

[First Embodiment]
The outline of the distance measuring device 100 according to the first embodiment of the present invention will be described with reference to FIG. 1 (A). The distance measuring device 100 is a scanning type distance detecting device, and scans the light projecting unit 10 that projects the laser beam L1 and the light receiving unit 20 that receives the laser light L2, and the laser beams L1 and L2 at the time of projecting and receiving the light. The two-dimensional scanning device 30, the timing detection unit 40 that detects the irradiation or emission of the laser light L1, and the time for measuring the elapsed time from the irradiation or emission of the laser light L1 to the reception or incident of the reflected light (laser light L2). It includes a measuring unit 51, a light amount measuring unit 160 that measures the amount of reflected light (laser light L2), a control unit 70 that controls the operating state of each unit, and a case 80 that houses the entire unit. The distance measuring device 100 monitors the irradiation direction of the laser beam L1 at the time of time measurement, that is, distance measurement, and operates as a distance image sensor. In the distance measuring device 100, the light intensity measuring unit 160 is used to acquire the reflected light intensity (hereinafter referred to as light intensity) of the target OB and use it as auxiliary data for distance measurement.

Of the distance measuring device 100, the light emitting unit 10, the light receiving unit 20, the two-dimensional scanning device 30, the timing detecting unit 40, the time measuring unit 51, and the control unit 70 constitute the distance measuring unit 50. Further, among the distance measuring devices 100, the timing detection unit 40, the light amount measurement unit 160, and the control unit 70 (particularly, the data processing unit 72 and the soundness determination unit 73) constitute the light amount detection unit 60. That is, the timing detection unit 40 functions both as a part of the distance measurement unit 50 and as a part of the light amount detection unit 60.

The host system 200 can communicate with the control unit 70 and the like of the distance measuring device 100, and supplies electric power to the distance measuring device 100. The host system 200 monitors the operating state of the distance measuring device 100, and receives a distance value from the distance measuring unit 50. At this time, the host system 200 can also receive additional information including the soundness determination result from the distance measuring unit 50 for the reflected light excluded from the detection result.

The distance measuring unit 50 measures the elapsed time from the emission or projection of the laser beam L1 to the incident or reception of the reflected light (laser light L2) to determine the distance. That is, the distance measuring unit 50 obtains the time difference between the emission timing of the laser light L1 from the light emitting unit 10 and the incident timing of the laser light L2 on the light receiving unit 20, and divides this half value by the propagation speed of the laser light. By doing so, the distance to the target OB is calculated.

The light projecting unit 10 of the distance measuring unit 50 includes a light emitting element 11 that emits laser light L1 having a predetermined wavelength set in the infrared or other wavelength region, and a drive circuit 12 that operates the laser light L1. The laser beam L1 can be emitted at a desired timing. The drive circuit 12 operates under the control of the optical scanning control unit 71 of the control unit 70 to adjust the timing and intensity of the laser output.

The light receiving unit 20 includes a light receiving element 21 on which the laser beam L2, which is the return light reflected by the target OB, which is an object existing in front of the ranging device 100, is incident, and a drive circuit 22 for operating the light receiving element 21. , The detection signal TS or the received signal corresponding to the intensity of the laser beam L2 is output at the timing corresponding to the incident of the laser beam L2. Here, the detection signal TS or the reception signal is specifically a transimpedance signal (hereinafter, also referred to as a TIA signal) obtained by converting the current output of a sensor such as a photodiode into a voltage signal. The drive circuit 22 has a receiving amplifier that amplifies the detection signal TS by the light receiving element 21, and operates under the control of the control unit 70 as necessary to adjust the detection gain.

The two-dimensional scanning device 30 includes a scanner main body 31 and a scanner drive circuit 32. The scanner main body 31 is a two-dimensional scanning mirror, and by swinging the mirror provided in the movable portion around two axes, the light reflected by the mirror is scanned in the two-dimensional region. The scanner main body 31 performs a swing operation that enables two-dimensional scanning by a scanner drive circuit 32 that operates under the control of the control unit 70.

When the laser beam L1 emitted from the light projecting unit 10 is reflected by the two-dimensional scanning device 30, it is scanned two-dimensionally in a range of, for example, a scanning angle of ± 30 °. The laser beam L1 reflected by the two-dimensional scanning device 30 illuminates the target OB through the projection window 80a of the case 80, and the laser beam L2 reflected by the target OB and retrograde is reflected again by the two-dimensional scanning device 30. It is incident on the light receiving unit 20. The laser light L1 for illumination and the laser light L2 which is the return light are branched by a beam splitter (not shown) provided attached to the two-dimensional scanning device 30. The two-dimensional scanning device 30 measures the reflected light (laser light L2) from the corresponding direction while changing the irradiation direction of the laser light L1.

The timing detection unit 40 detects the emission or projection timing of the laser beam L1 emitted from the projection unit 10. Specifically, the timing detection unit 40 detects the projection timing as the projection trigger signal LR obtained by detecting the laser beam L1 by the light emission monitor (not shown) provided in the projection unit 10. Alternatively, the timing detection unit 40 may detect the projection timing of the laser beam L1 by using the projection trigger signal LR0 input to the projection unit 10. The timing detection unit 40 outputs a trigger signal TR which is a time measurement start signal of the light amount measurement to the light amount measurement unit 160, and outputs a time measurement start trigger SR to the time measurement unit 51. In the present embodiment, the trigger signal TR and the timekeeping start trigger SR are the same.

The time measuring unit 51 determines from the difference between the projection timing of the laser beam L1 by the timing detection unit 40 and the reception signal of the laser beam L2 by the reception signal output from the light receiving unit 20 or the detection signal TS, from the projection to the reception. Measure the detection time, which is the time difference. The time measurement unit 51 receives the timekeeping start trigger SR from the timing detection unit 40 and the stop timing detection unit 51a that generates a timekeeping stop trigger based on the detection signal TS from the light receiving unit 20 that has received the laser beam L2, and measures the time. It has a timekeeping circuit 51b that starts and ends the timekeeping by receiving a timekeeping stop trigger from the stop timing detection unit 51a, and an AD converter 51c that AD-converts the output of the timekeeping circuit 51b. Using the detection time obtained by the time measurement unit 51, the data processing unit 72 of the control unit 70, which will be described later, calculates the distance to the target OB based on the detection timing of the laser beams L1 and L2. The time measurement unit 51 can perform a plurality of time measurements corresponding to a plurality of reflected lights generated by one light projection pulse in one circuit. That is, in the case of a series of operations or events caused by the operation of the light projecting unit 10, the time measuring unit 51 can perform a plurality of time measurements necessary for distance conversion.

The light amount detecting unit 60 detects the light amount of the reflected light (laser light L2) at a plurality of timings by switching the detection signal TS from the light receiving unit 20 by the switching unit 60m in the light amount measuring unit 160 described later.

In the light amount detection unit 60, the timing detection unit 40 and the switching unit 60m of the light amount measurement unit 160 set a plurality of timings for detecting the light amount of the reflected light received by the light receiving unit 20, that is, the integrated period of the reflected light. It is the part to set. In the present embodiment, the trigger signal TR corresponding to the laser beam L1 obtained by the timing detection unit 40 is set as the light projection timing at the start of timekeeping, and based on this, the integration period corresponding to a plurality of timings for detecting the amount of reflected light is used. To set. The details will be described later, but when the light projection timing at the start of timekeeping is used as the reference for the light amount detection timing, the light amount detection timing is set to a plurality of distance zones in the depth direction with respect to the region where the target OB may exist. Correspondingly set. The distance zones are, for example, in the same direction, as shown in FIG. 1 (B), a first distance zone Z1 of 0 to 0.5 m, a second distance zone Z2 of 0.5 m to 3 m, and a third distance of 3 m or more. It is divided into zones Z3.

As shown in FIG. 2, the light amount measuring unit 160 is one connected to an analog clock circuit 61 started by a trigger signal TR from the timing detecting unit 40 and a light receiving unit 20 which is a light receiving circuit for measuring reflected light. An integrator circuit 62, a peak hold circuit group 63, a switch circuit 64 that selects a necessary peak hold circuit from the peak hold circuit group 63 and connects it to the integrator circuit 62, and a switch control unit 65 that controls the operation of the switch circuit 64. It has an AD converter group 66 that AD-converts the output of the peak hold circuit group 63. Here, the peak hold circuit group 63 includes three peak hold circuits 63a to 63c, and the AD converter group 66 includes three AD converters 66a. Further, the analog clock circuit 61, the switch control unit 65, and the switch circuit 64 form a switching unit 60 m. The switching unit 60m operates the switch circuit 64 or the like based on the output of the analog clock circuit 61, and switches a plurality of timings or time zones corresponding to the division of the light amount measurement of the reflected light. As a result, the result of the detection signal TS from the light receiving unit 20 being accumulated in the desired time zone is retained. The analog clock circuit 61 makes it possible to obtain relatively reliable results with a simple and inexpensive circuit configuration. Further, the amount of reflected light can be determined by matching the accuracy at a plurality of timings by the integrating circuit 62, the peak hold circuit group 63, and the switch circuit 64, that is, by the single integrating circuit 62.

Specifically, the analog clock circuit 61 of the light intensity measuring unit 160 measures the time by a circuit including the RC integrator circuit 61a and the comparators 61b and 61c as shown in FIG. 3, and the first and second switches at predetermined timings. The control signals SW1 and SW2 are generated. That is, the analog clock circuit 61 measures a predetermined time from the start of timekeeping, and outputs the first and second switch control signals SW1 and SW2 to the switch circuit 64. In the example shown in FIG. 3, the analog clock circuit 61 is a circuit that also functions as the switch control unit 65, but the switch control unit 65 can also be an independent circuit.

Returning to FIG. 2, the switch circuit 64, which operates based on the output of the analog clock circuit 61 or the switch control unit 65, has the first to switch the signal input to the first to third peak hold circuits 63a to 63c. The first and second switches 64a and 64b are provided. The first and second switches 64a and 64b are composed of, for example, FETs and the like, and input the first and second switch control signals SW1 and SW2 to their gate electrodes. It is desirable that the first and second switches 64a and 64b respond in a few hundred ps to a few ns.

In the present embodiment, in the analog clock circuit 61, the projection timing information by the trigger signal TR output from the timing detection unit 40 shown in FIG. 1 (A) (specifically, the digital output is switched from H to L). The timing of light intensity detection is set based on. That is, the time from the start of time counting based on the light projection timing information to the time when the voltage reaches a predetermined threshold value (see threshold voltages Vref2 and Vref3 shown in FIG. 3) is set as a predetermined time related to the timing of light amount detection.

4 (A) to 4 (F) are timing charts illustrating an operation in which the light projection timing is used as a reference for the light amount detection timing. FIG. 4A shows the laser beam L1 emitted from the light projecting unit 10 at the light projecting timing. FIG. 4B shows the TIA output output from the light receiving unit 20. FIG. 4C shows a timekeeping start trigger signal TR or a timekeeping start signal output from the timing detection unit 40. FIG. 4D shows the integrated voltage value in the analog clock circuit 61. FIG. 4E shows the first switch control signal SW1 for the first switch 64a in the switch circuit 64. FIG. 4F shows a second switch control signal SW2 for the second switch 64b in the switch circuit 64. The horizontal axis t shown in FIG. 4 (F) indicates a time axis common to FIGS. 4 (A) to 4 (F). The first to third time zones TZ1 to TZ3 shown at the bottom of FIG. 4 (F) correspond to the first to third distance zones Z1 to Z3 shown in FIG. 1 (B). In order to specify the timing of light amount detection (that is, the period for extracting the detection signals s1 and s2 from the TIA output shown in FIG. 4B), the predetermined threshold value set in the analog clock circuit 61 shown in FIG. 2 is shown in FIG. As shown in 4 (D), it corresponds to the first threshold value TL1 of only the first stage assuming the integrated value of the time zones TZ1 and TZ2, and the second threshold value TL2 assuming the integrated value up to the second stage. Further, as shown in FIGS. 4 (E) and 4 (F), the predetermined time regarding the timing of light amount detection is up to the first delay time DT1 and the second stage of only the first stage of the time zones TZ1 and TZ2. Corresponds to the second delay time DT2 of. That is, the plurality of threshold values set for the timing of light amount detection in the analog clock circuit 61 and the like shown in FIG. 2 or the time until the thresholds are reached are the amount of light related to the reflected light received by the light receiving unit 20 shown in FIG. 1 (A). In a series of detection operations or events, it corresponds to each distance zone constituting a plurality of distance zones, specifically, the first to third distance zones Z1 to Z3 shown in FIG. 1 (B). ..

The switch control unit 65 shown in FIG. 2 turns off the first switch 64a of the switch circuit 64 when the voltage of the measurement signal Sa of the analog clock circuit 61 reaches the predetermined first threshold value TL1 shown in FIG. 4 (D). Then, the first peak hold circuit 63a is separated from the integrating circuit 62. After that, when the voltage of the measurement signal Sa of the analog clock circuit 61 reaches the predetermined second threshold value TL2 shown in FIG. 4D, the switch control unit 65 turns off the second switch 64b of the switch circuit 64. The second peak hold circuit 63b is separated from the integrating circuit 62.

In the analog clock circuit 61 shown in FIG. 3, the RC integrating circuit 61a is inserted while the trigger signal TR (see FIG. 4C) from the timing detection unit 40 shown in FIG. 1A is L (that is, after the start of timing). When the output (measurement signal Sa) of the RC integration circuit 61a of the analog clock circuit 61 reaches a certain threshold voltage Vref2 after charging at a constant speed, the switch control unit 65 operates by the output from the comparator CM2 to operate the switch circuit 64. When the first switch 64a is turned off, the first delay time DT1 shown in FIG. 4 (E) is controlled. That is, the analog clock circuit 61 shown in FIG. 3 can control the delay time by adjusting the values of the resistor R and the capacitor C without using a high-speed digital IC, a clock source, or the like. The delay time can be changed from the outside such as a CPU by changing the portion of the resistor R to a digital potentiometer or changing the threshold voltage Vref2 of the comparator CM2 with a DA converter or the like. Similarly, for the second switch 64b of the switch circuit 64, the switch control unit 65 operates by the output from the comparator CM3 when the output (measurement signal Sa) of the integration circuit 61a of the analog clock circuit 61 reaches a certain threshold voltage Vref3. Then, the second switch 64b is turned off to control the second delay time DT2 shown in FIG. 4 (F).

As described above, when the light projection timing is used as the reference for the light amount detection timing, the trigger signal TR is generated according to the light projection timing of the laser beam L1 as shown in FIG. 4C. A stable trigger signal TR can be obtained by using the projection of the laser beam L1 to generate the trigger signal TR. Thereby, the absolute time from the flood can be set, and the setting can be facilitated. For example, when observing through a window glass or when fog is generated, the first received signal or the first detection signal s1 is returned immediately after the light is projected, so that the reflected light from the window or fog is surely returned. Can be obtained as the amount of light corresponding to them.

Returning to FIG. 2, the integrator circuit 62 integrates the input voltage with time and outputs it. In the integrating circuit 62, a plurality of detection signal (received signal or TIA signal) TS sequentially detected by the light receiving element 21 are integrated. In the present embodiment, the light receiving element 21 outputs the first detection signal s1, the second detection signal s2, and the third detection signal s3 in order. The integrated output of the integrating circuit 62 that has received the first to third detection signals s1 to s3 is obtained by appropriately turning on and off the first and second switches 64a and 64b of the switch circuit 64 by the operation of the switch control unit 65. -The voltage corresponding to the strength of the third detection signals s1 to s3 is sequentially output at a predetermined timing via the peak hold circuit group 63.

The peak hold circuit group 63 measures the amount of reflected light at a plurality of timings set with reference to the projection timing. The peak hold circuit group (P / H circuit group) 63 holds the peak value of the input signal by holding the integrated output of the integrating circuit 62. The peak hold circuit group 63 includes a plurality of the same circuits, and measures the integrated output of the integrating circuit 62, that is, the amount of reflected light at a plurality of timings set by the switching unit 60m via the switch circuit 64. In the present embodiment, the peak hold circuit group 63 is provided with three circuits, the first to third peak hold circuits 63a to 63c. By properly using the peak hold circuits 63a to 63c, it is possible to grasp the amount of light for each reflected light at different timings in substantially the same direction. It should be noted that the reception timing of the plurality of detection signals TS corresponding to different reflected lights in the same direction corresponds to the timing of the light amount detection described above, and it is assumed that the detection signals are detected in each distance zone of the plurality of distance zones. Is set.

The first peak hold circuit 63a is connected to the integrating circuit 62 only in the first stage of the time zones TZ1 to TZ3 shown in FIG. 4 (F) or the distance zones Z1 to Z3 shown in FIG. 1 (B), and the first reflection. The light quantity value obtained by integrating the output of the first detection signal s1 corresponding to the light is held. The second peak hold circuit 63b is connected to the integrating circuit 62 up to the second stage of the time zone or the distance zone, and outputs the first and second detection signals s1 and s2 corresponding to the first and second reflected light. Holds the integrated light intensity value. The third peak hold circuit 63c is simply connected to the integrating circuit 62 and holds the light quantity value obtained by integrating the outputs of the first to third detection signals s1 to s3 corresponding to all the reflected light. In the peak hold circuit group 63, the inputs of the peak hold circuits 63a to 63c are switched by the on / off combination of the first and second switches 64a and 64b of the switch circuit 64.

The output signal PH from the peak hold circuit group 63 is input to the data processing unit 72, the soundness determination unit 73, and the like of the control unit 70 shown in FIG. 1 (A) via the AD converter group 66.

Returning to FIG. 1A, the control unit 70 is a microprocessor including, for example, a CPU, a memory, and the like, and operates according to a program incorporated in advance. The control unit 70 includes an optical scanning control unit 71, a data processing unit 72, and a soundness determination unit 73 in terms of function.

The optical scanning control unit 71 of the control unit 70 not only controls the emission timing of the laser beam L1 but also outputs the laser beam L1 by outputting a control signal to the drive circuit 12 of the light projecting unit 10. You can adjust the increase / decrease. The optical scanning control unit 71 can also increase or decrease the amplification factor of the laser beam L2 with respect to the detection signal TS by outputting a control signal to the drive circuit 22 of the light receiving unit 20. Further, the optical scanning control unit 71 controls the swinging operation of the scanner main body 31 via the scanner drive circuit 32 of the two-dimensional scanning device 30.

The data processing unit 72 takes in information from the light projecting unit 10, the light amount measuring unit 160, the time measuring unit 51, and the like. Further, the data processing unit 72 calculates the distance to the target OB based on the detection timing of the emission of the laser beam L1 and the incident of the laser beam L2 from the time difference between the light emission and the light reception obtained by the time measurement unit 51. In addition, the data processing unit 72 can output information related to the determination to the soundness determination unit 73 and monitor the determination result.

The light amount data output from the peak hold circuit group 63 is input to the data processing unit 72, and the data processing unit 72 calculates the output values of the peak hold circuits 63a to 63c shown in FIG. The light amount value corresponding to the detection signals s1 to s3 is calculated. That is, the data processing unit 72 as the light amount detection unit 60 can grasp the light amount for each reflected light by calculating the light amount value obtained from the first to third peak hold circuits 63a to 63c.

The soundness determination unit 73 shown in FIG. 1 determines the usefulness of the distance information with respect to the distance to the target OB obtained by the data processing unit 72. The soundness determination unit 73 excludes the target OB corresponding to a predetermined condition from the detection result based on the distance to the target OB obtained from each reflected light and the amount of light. Here, the predetermined condition is, for example, whether or not the reflected light is a low level reflected light that does not reach the assumed reference light amount with respect to the distance of interest. This makes it possible to identify non-monitoring objects such as fog and reflections from window dirt and exclude them from the detection results.

More specifically, in the soundness determination unit 73, when the amount of light corresponding to the target OB is lower than a predetermined threshold value of the amount of light, which is a reference value determined for each distance zone, for example, fog, window dirt, dust, and water droplets. Etc., and it is determined that the target OB is not an object. If the amount of light corresponding to the target OB is higher than the predetermined threshold value, for example, if the range of the target OB is pinpoint, it may be determined that the target OB is not an object.

Hereinafter, the operation of each part of the distance measuring device 100 shown in FIG. 1 (A) will be described with reference to FIGS. 5 (A) to 5 (J). In the following operation description, reference to FIGS. 1 (A) and 2 showing each part of the distance measuring device 100 will be omitted. The horizontal axis shown in FIGS. 5 (A) to 5 (J) indicates time. FIG. 5A shows the laser beam L1 emitted from the light projecting unit 10 at the light projecting timing. FIG. 5B shows the TIA output output from the light receiving unit 20. FIG. 5C shows a timekeeping start trigger signal TR or a timekeeping start signal output from the timing detection unit 40. FIG. 5D shows the integrated voltage value in the analog clock circuit 61. FIG. 5 (E) shows the first switch control signal SW1 for the first switch 64a in the switch circuit 64. FIG. 5F shows the second switch control signal SW2 for the second switch 64b in the switch circuit 64. FIG. 5 (G) shows the integrated output of the integrating circuit 62. FIG. 5 (H) shows the first P / H output (P / H1) output by the first peak hold circuit 63a, and FIG. 5 (I) shows the second P / H output output by the second peak hold circuit 63b. (P / H2) is shown, and FIG. 5 (J) shows a third P / H output (P / H3) output by the third peak hold circuit 63c. In FIGS. 5 (A) to 5 (J), the first to third distance zones Z1 to Z3 shown in FIG. 1 (B) corresponding to the timing of light amount detection are the thirds shown in the lowermost stage of FIG. 5 (J). It corresponds to the 1st to 3rd time zones TZ1 to TZ3, respectively. In the illustrated example, the interval of the first time zone TZ1 and the interval of the second time zone TZ2 are substantially equal for convenience of explanation, but they can be changed as appropriate.

First, as shown in FIG. 5A, the drive circuit 12 of the light projecting unit 10 periodically generates a light projecting pulse under the control of the optical scanning control unit 71 of the control unit 70, and intermittently from the light emitting element 11. The laser beam L1 is emitted to the light. The light projection timing is, for example, the peak time of the laser light L1 from the light projecting unit 10, and is output to the timing detection unit 40 as a trigger signal TR.

Next, as shown in FIG. 5B, when a plurality of reflected lights are returned by one emission of the laser beam L1, a plurality of received signals or detection signal TSs are detected by the light receiving unit 20. In the illustrated example, the plurality of detection signals TS are the first to third detection signals s1 to s3.

As shown in FIGS. 5A and 5B, the time measuring unit 51 sets the peak time of the laser beam L1 from the light emitting unit 10 as the projection timing, and the peak of the laser light L2 from the light receiving unit 20. With time as the light reception timing, the detection time, which is the time difference between light projection and light reception, is measured. Specifically, the time difference between the light projection timing and the first light reception timing is the detection time T1, the time difference between the light projection timing and the second light reception timing is the detection time T2, and the light projection timing and the third light reception timing. The time difference from the light receiving timing is the detection time T3.

As shown in FIG. 5C, the analog clock circuit 61 has a trigger output from the timing detection unit 40 at the time of the projection timing detected by the timing detection unit 40, specifically, at the peak of the laser light L1. In response to the signal TR or the time measurement start signal, the time measurement is started.

As shown in FIG. 5 (G), in the integrating circuit 62, the first to third detection signals s1 to s3 are sequentially integrated and the result is output.

As shown in FIGS. 5 (E) and 5 (F), both the first and second switches 64a and 64b of the switch circuit 64 are in the on state, that is, a predetermined first delay time DT1 from the output of the trigger signal TR. The output of the integrating circuit 62 is input to all of the first to third peak hold circuits 63a to 63c, and the integration result of the first detection signal s1 is held. As shown in FIG. 5 (D), in the analog clock circuit 61, when the output value reaches the corresponding first threshold value TL1 after the first delay time DT1, as shown in FIG. 5 (E), the switch control unit. 65 outputs the first switch control signal SW1 that turns off the first switch 64a. When the first switch 64a is turned off, the first peak hold circuit 63a holds only the integration result of the first detection signal s1 out of the outputs of the integration circuit 62, as shown in FIG. 5 (H). Next, as shown in FIG. 5 (D), in the analog clock circuit 61, when the output value reaches the corresponding second threshold value TL2 after the second delay time DT2, as shown in FIG. 5 (F). The switch control unit 65 outputs a second switch control signal SW2 that turns off the second switch 64b. When the second switch 64b is turned off, in the second peak hold circuit 63b, as shown in FIG. 5 (I), the sum of the first and second detection signals s1 and s2 of the output of the integrator circuit 62 is used. The integration result is retained. After that, in the third peak hold circuit 63c, as shown in FIG. 5 (J), the integration result as the sum of the first to third detection signals s1 to s3 of the output of the integration circuit 62 is held.

As described above, the plurality of received signals or detection signal TSs detected by the light receiving unit 20 are sequentially integrated through the integrating circuit 62 and the peak hold circuit group 63, and the first to third received signals corresponding to the peak hold circuits 63a to 63c are sequentially integrated. The 3P / H outputs (P / H1 to P / H3) are converted by each AD converter 66a of the AD converter group 66 to obtain light amount data corresponding to each received signal. The peak value of the integration result, which is the light amount data, is sampled, for example, after a predetermined time of the projection timing. At the time of sampling or after that, as shown in FIG. 5 (G), the integrated output of the integrating circuit 62 becomes zero.

The light amount data output from the peak hold circuit group 63 is input to the data processing unit 72, and the data processing unit 72 receives the first detection signal by the first P / H output (P / H1) in the first peak hold circuit 63a. The light amount value corresponding to s1 is calculated. Further, the data processing unit 72 subtracts the first P / H output (P / H1) in the first peak hold circuit 63a from the second P / H output (P / H2) in the second peak hold circuit 63b. 2 The light amount value corresponding to the detection signal s2 is calculated. Further, the data processing unit 72 subtracts the second P / H output (P / H2) of the second peak hold circuit 63b from the third P / H output (P / H3) of the third peak hold circuit 63c. 3 The light amount value corresponding to the detection signal s3 is calculated. By increasing the number of the peak hold circuit group 63 in response to the increase in the number of received signals or detection signal TSs to be received, it is possible to acquire the light intensity value of the reflected light by the increased number.

According to the distance measuring device described above, the light amount detecting unit 60 detects the light amount of the reflected light at a plurality of timings by switching the switch circuit 64, so that the target OBs which are a plurality of objects at different distances in the same direction can be detected. Even in a certain case, the intensity information of the reflected light can be acquired as auxiliary data accompanying the distance information for the target OB which is such a plurality of objects. This makes it possible to identify and exclude non-monitoring objects such as reflections from fog and window dirt.

[Second Embodiment]
Hereinafter, the distance measuring device of the second embodiment will be described. The distance measuring device of the second embodiment is a partial modification of the distance measuring device of the first embodiment, and the matters not particularly described are the same as those of the distance measuring device of the first embodiment.

In the distance measuring device 100 shown in FIG. 6, the received signal or detection signal TS output from the light receiving unit 20 is output to the timing detection unit 140. In this case, the light receiving timing can be used as a reference for the light amount detection timing.

Since the timing detection unit 140 of the present embodiment outputs the trigger signal TR or the timekeeping start signal to the analog clock circuit 61 of the light amount measuring unit 160, it detects the incident or the light receiving timing of the laser beam L2 incident on the light receiving unit 20. The timing detection unit 140 has a signal processing circuit 140a that generates a trigger signal TR for the analog clock circuit 61 based on the detection signal TS from the light receiving unit 20 that has received the laser beam L2. The signal processing circuit 140a is provided with a comparator, a differentiating circuit, and the like (not shown).

Further, in the distance measurement unit 50 of the present embodiment, the time measurement unit 51 is configured to directly receive the timekeeping start trigger SR as the light projection timing from the light projection unit 10. In the present embodiment, the timekeeping start trigger SR corresponds to, for example, the projection trigger signal LR obtained by detecting the laser beam L1 by a light emission monitor (not shown) provided in the projection unit 10.

7 (A) to 7 (F) are diagrams for explaining an operation in which the light receiving timing is used as a reference for the light amount detection timing. FIG. 7 (A) shows the laser beam L1 emitted from the light emitting unit 10 at the light emitting timing, and FIG. 7 (B) shows the TIA output corresponding to the light receiving timing output from the light receiving unit 20. The waveforms shown in FIGS. 7 (A) and 7 (B) are consistent with those shown in FIGS. 4 (A) and 4 (B). FIG. 7C shows a timekeeping start trigger signal TR or a timekeeping start signal output from the timing detection unit 140. FIG. 7D shows the integrated voltage value in the analog clock circuit 61. FIG. 7E shows the first switch control signal SW1 for the first switch 64a in the switch circuit 64. FIG. 7F shows the second switch control signal SW2 for the second switch 64b in the switch circuit 64. When the light receiving timing is used as the reference for the light amount detection timing, as shown in FIGS. 7 (B) and 7 (C), the trigger signal TR is used for light detection of the light receiving element 21 for reflected light (laser light L2). Generated accordingly. The first and second switch control signals SW1 and SW2 shown in FIGS. 7 (E) and 7 (F) are the first and second switch control signals SW1 and SW2 shown in FIGS. 4 (A) and 4 (B). There is a slight deviation from the above. By using the received light of the reflected light to generate the trigger signal TR, the distance detection result for the target OB, which is a real object, is used to detect the distance and the amount of light for the target OB, which is the next object behind it. Detection becomes possible. As a result, the relative time from the first detection signal s1, which is the first received signal, is set, and the versatility is increased.

In addition, when the reflected light corresponding to the first detection signal s1 which is the first received signal is a strong reflected light such as retroreflection, it is shown in FIG. 7 (G) due to the electrical influence of the light receiving unit 20. As shown, a ghost signal N may be generated as a received signal at a position where the target OB should not originally exist. In such a case, by using the method of using the light receiving timing as the reference of the light amount detection timing as in the present embodiment, the reflected light amount corresponding to the first detected signal s1 which is the first received signal is equal to or more than a certain value. In this case, it can be determined that the light is reflected from the retroreflective target OB, and more accurate distance measurement can be performed by performing a process that ignores the ghost signal N as the second received signal. Can be done. As a result, accurate obstacle detection and the like can be performed. Examples of the retroreflection include reflections on road signs and the like.

Of the light amount detection units 60 of the present embodiment, the timing detection unit 140 detects (1) rising edge detection, (2) peak detection, and (3) falling edge detection with respect to the detection signal TS or detection pulse output by the light receiving unit 20. , And (4) at least one of resonance zero cross detection is performed to generate a trigger signal TR. The detection methods (1) to (4) can also be combined. Hereinafter, each detection method will be described.

(1) Rise detection or rise threshold detection As shown in FIG. 8A, when the first detection signal s1 rises and the threshold TL3 is reached, it is detected as the light receiving timing. In the case of rising threshold detection, the detection circuit is simple and the device can be manufactured at low cost. On the other hand, if the pulse width changes, the timing may change, and the accuracy of switch control deteriorates.

(2) Peak detection As shown in FIG. 8B, the peak P of the first detection signal s1 is detected as the light receiving timing. In the case of peak detection, the same timing can be acquired regardless of the waveform amplitude, so that the accuracy of switch control is improved. On the other hand, in the case of a signal having a small peak value, the accuracy of the peak deteriorates and the accuracy of switch control deteriorates.

(3) Fall detection or fall threshold detection As shown in FIG. 8C, when the first detection signal s1 falls and the threshold TL4 is reached, it is detected as the light receiving timing. The advantages and disadvantages of the falling threshold detection are the same as those of the rising threshold detection.

(4) Resonant Zero Cross Detection As shown in FIG. 8D, a characteristic frequency component is extracted using a resonance circuit that resonates with a specific frequency component included in the first detection signal s1, and the zero cross point of the extracted signal waveform z1. Z is detected as the light receiving timing. In the case of resonance zero cross detection, the timing can be detected with high sensitivity even for a signal having a small amplitude, and the accuracy of switch control can be improved. On the other hand, when a signal having a large amplitude is input, the timing accuracy deteriorates due to the waveform distortion, so that the accuracy of the switch control deteriorates.

[Third Embodiment]
Hereinafter, the distance measuring device of the third embodiment will be described. The distance measuring device of the third embodiment is a partial modification of the distance measuring device of the first embodiment, and the matters not particularly described are the same as those of the distance measuring device of the first embodiment.

In the light quantity measuring unit 160 of the distance measuring device 100 shown in FIG. 9, a digital clock counter circuit 161 is provided instead of the analog clock circuit. That is, the light amount detection unit 60 operates the switch circuit 64 and the like based on the output of the clock counter circuit 161 to switch a plurality of timings. As a result, the detection result is stable and does not easily fluctuate due to disturbance.

The clock counter circuit 161 counts a predetermined time by counting the number of clock pulses. The clock counter circuit 161 starts the clock pulse counting operation by inputting the projection timing information by the trigger signal TR output from the timing detection unit 40, and counts the clock pulse after a predetermined time or a predetermined number of times corresponding to a predetermined number of pulses. To stop. When the specified number of pulses is reached, the switch control unit 165 turns off the first and second switches 64a and 64b in two stages.

Hereinafter, the operation of each part of the distance measuring device 100 shown in FIG. 9 will be described with reference to FIGS. 10 (A) to 10 (J). FIG. 10A shows the laser beam L1 emitted from the light projecting unit 10 at the light projecting timing. FIG. 10B shows the TIA output output from the light receiving unit 20. FIG. 10C shows a count start trigger signal TR or a count start signal output from the timing detection unit 40. FIG. 10D shows a clock pulse in the clock counter circuit 161. FIG. 10E shows the first switch control signal SW1 for the first switch 64a in the switch circuit 64. FIG. 10F shows the second switch control signal SW2 for the second switch 64b in the switch circuit 64. FIG. 10 (G) shows the integrated output of the integrating circuit 62. FIG. 10 (H) shows the first P / H output (P / H1) output by the first peak hold circuit 63a, and FIG. 10 (I) shows the second P / H output output by the second peak hold circuit 63b. (P / H2) is shown, and FIG. 10 (J) shows a third P / H output (P / H3) output by the third peak hold circuit 63c.

First, as shown in FIG. 10A, the drive circuit 12 of the light projecting unit 10 periodically generates a light projecting pulse under the control of the optical scanning control unit 71 of the control unit 70, and intermittently from the light emitting element 11. The laser beam L1 is emitted to the light. The light projection timing is, for example, the peak time of the laser light L1 from the light projecting unit 10, and is output to the timing detection unit 40 as a trigger signal TR.

Next, as shown in FIG. 10B, when a plurality of reflected lights are returned by one emission of the laser beam L1, a plurality of received signals or detection signal TSs are detected by the light receiving unit 20. In the illustrated example, the plurality of detection signals TS are the first to third detection signals s1 to s3.

As shown in FIGS. 10A and 10B, the time measuring unit 51 sets the peak time of the laser beam L1 from the light emitting unit 10 as the projection timing, and the peak of the laser light L2 from the light receiving unit 20. With time as the light reception timing, the detection time, which is the time difference between light projection and light reception, is measured.

As shown in FIG. 10C, the clock counter circuit 161 has a trigger output from the timing detection unit 40 at the time of the projection timing detected by the timing detection unit 40, specifically, at the peak time of the laser light L1. The count is started by receiving the signal TR or the count start signal.

As shown in FIG. 10 (G), in the integrating circuit 62, the first to third detection signals s1 to s3 are sequentially integrated and output.

As shown in FIGS. 10 (E) and 10 (F), both the first and second switches 64a and 64b of the switch circuit 64 are in the on state, that is, a predetermined first delay time DT1 from the output of the trigger signal TR. The output of the integrating circuit 62 is input to all of the first to third peak hold circuits 63a to 63c, and the integration result of the first detection signal s1 is held. As shown in FIG. 10 (D), in the clock counter circuit 161, when the corresponding number of pulses is reached after the first delay time DT1, the switch control unit 165 is the first switch control unit 165 as shown in FIG. 10 (E). The first switch control signal SW1 that turns off the switch 64a is output. When the first switch 64a is turned off, the first peak hold circuit 63a holds only the integration result of the first detection signal s1 out of the outputs of the integration circuit 62, as shown in FIG. 10 (H). Next, as shown in FIG. 10 (D), in the clock counter circuit 161, when the corresponding number of pulses is reached after the second delay time DT2, as shown in FIG. 10 (F), the switch control unit 165 , The second switch control signal SW2 that turns off the second switch 64b is output. When the second switch 64b is turned off, in the second peak hold circuit 63b, as shown in FIG. 10 (I), the sum of the first and second detection signals s1 and s2 of the output of the integrator circuit 62 is used. The integration result is retained. After that, in the third peak hold circuit 63c, as shown in FIG. 10 (J), the integration result as the sum of the first to third detection signals s1 to s3 of the output of the integration circuit 62 is held.

As described above, the plurality of received signals or detection signal TSs detected by the light receiving unit 20 are sequentially integrated through the integrating circuit 62 and the peak hold circuit group 63, and the first to third received signals corresponding to the peak hold circuits 63a to 63c are sequentially integrated. The 3P / H outputs (P / H1 to P / H3) are converted by each AD converter 66a of the AD converter group 66 to obtain light amount data corresponding to each received signal. The peak value of the integration result, which is the light intensity data, is sampled, for example, after a predetermined time of the projection timing. At the time of sampling or after that, as shown in FIG. 10 (G), the integrated output of the integrating circuit 62 becomes zero.

In this embodiment, as in the second embodiment, the light receiving timing may be used as a reference for the light amount detection timing.

The structure, shape, size, and arrangement relationship described in the above embodiments are merely schematically shown to the extent that the present invention can be understood and implemented. Therefore, the present invention is not limited to the described embodiment, and can be changed to various forms as long as it does not deviate from the scope of the technical idea shown in the claims.

In the above embodiment, the configuration of the switch circuit can be appropriately changed so that the connection from the integrator circuit 62 to the peak hold circuit group 63 can be switched at a required timing.

In the above embodiment, the reference of the timing of light amount detection can be appropriately changed according to the application of the distance measuring device 100, and the case of using the light projection timing as a reference and the case of using the light receiving timing as a reference are used together. You can also. For example, in the detection of the first detection signal s1 which is the first received signal, a trigger signal TR is generated based on the light projecting operation of the light projecting unit 10 to detect the amount of reflected light (laser light L2), and the second time. In the detection of the second detection signal s2, which is the reception signal of the above, a trigger signal TR is generated based on the light receiving operation of the light receiving unit 20 to detect the amount of reflected light (laser light L2). That is, in the case of the operation by the trigger signal TR using the light receiving timing, it is necessary to start the measurement operation before that, and the flooding timing is used to generate the trigger signal TR in the first detection of the received signal, and the second time. In the detection of the received signal, the light receiving timing is used to generate the trigger signal TR. It is also possible to generate a trigger signal TR for each received signal. In the ranging device 100, the timing at which the received signal is returned always changes depending on the situation. Therefore, by generating the trigger signal TR for each received signal, the first and second received signals, which are the first and second received signals, are surely generated. The second detection signals s1 and s2 can be separated.

10 ... Light projecting unit, 11 ... Light emitting element, 12 ... Drive circuit, 20 ... Light receiving unit, 21 ... Light receiving element, 22 ... Drive circuit, 30 ... Two-dimensional scanning device, 31 ... Scanner body, 32 ... Scanner drive circuit, 40 ... Timing detection unit, 50 ... Distance measurement unit, 51 ... Time measurement unit, 60 ... Light intensity detection unit, 61 ... Analog clock circuit, 62 ... Integrator circuit, 63 ... Peak hold circuit group, 63a to 63c ... Peak hold circuit, 64 ... Switch circuit, 64a, 64b ... Switch, 65,165 ... Switch control unit, 66 ... AD converter group, 70 ... Control unit, 71 ... Optical scanning control unit, 72 ... Data processing unit, 73 ... Soundness judgment unit, 80 ... Case, 100 ... Distance measuring device, 160 ... Light quantity measuring unit, 161 ... Clock counter circuit, 200 ... Higher system, L1, L2 ... Laser light, OB ... Target, TR ... Trigger signal, TS, s1 to s3 ... Detection signal

Claims (6)

A distance measuring unit that irradiates a laser beam, measures the reflected light, and determines the distance from the elapsed time from the irradiation of the laser beam to the reception of the reflected light.
It is equipped with a light amount detection unit that detects the amount of reflected light.
The light amount detection unit is a distance measuring device that detects the amount of reflected light at a plurality of timings by switching a switch circuit. The light amount detection unit selects an integrating circuit connected to a light receiving circuit for measuring reflected light, a plurality of peak hold circuits, and a peak hold circuit connected to the integrating circuit from the plurality of peak hold circuits. The distance measuring device according to claim 1, further comprising a switch circuit. The distance measuring device according to any one of claims 1 and 2, wherein the light amount detecting unit switches the plurality of timings based on the output of a clock counter circuit started by a trigger signal. The distance measuring device according to any one of claims 1 and 2, wherein the light amount detecting unit switches the plurality of timings based on the output of an analog clock circuit started by a trigger signal. The light amount detection unit generates the trigger signal by performing any one of rise detection, peak detection, fall detection, and resonance zero cross detection with respect to the detection pulse output by the light receiving element for the reflected light. , The distance measuring device according to any one of claims 3 and 4. The distance measuring device according to any one of claims 1 to 5, wherein an object corresponding to a predetermined condition is excluded from the detection result based on the distance to the object obtained from the reflected light and the amount of light.

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