JP7316175B2 - rangefinder - Google Patents

Description

The present invention relates to a distance measuring device that uses laser light to measure the distance to an object.

A distance measuring device that uses light generates a distance to an object and other measurement values by detecting reflected light from an object irradiated with light, for example. As an example of this type of rangefinder, there is a laser rangefinder that determines the target distance by obtaining the time from the transmission of the pulsed laser beam to the reception of the reflected light (Patent Documents 1 and 2). Specifically, in the apparatus of Patent Document 1, an electric pulse signal obtained by converting a received pulsed laser beam into an electric signal is differentiated, and the peak value of the differentiated waveform is used to correct the distance based on a previously investigated function. 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 after the second time point corresponding to light reception, and the integration result from the second time point corresponding to light reception to the third time point The distance is determined from the difference from the integration result of .

However, the devices of Patent Documents 1 and 2 only obtain the target distance based on the time difference between the transmission of the pulsed laser beam and the reception of the reflected light. There is a problem that it is difficult to identify unmonitored objects such as reflections from.

JP-A-9-287914 JP 2013-3114 A

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned background art, and provides a distance measuring device capable of identifying and excluding non-monitored objects such as reflections from fog and dirty windows when measuring the distance of an object. for the purpose.

In order to achieve the above object, a distance measuring device according to the present invention is 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. and a light amount detection unit for detecting the amount of reflected light, and the light amount detection unit detects the amount of reflected light at a plurality of timings by switching a switch circuit.

According to the distance measuring device, the light intensity detection unit detects the light intensity of the reflected light at a plurality of timings by switching the switch circuit. For an object, intensity information of reflected light can be obtained as auxiliary data accompanying distance information. This allows operations such as identifying and excluding non-monitored objects, such as reflections from fog or dirt on windows.

According to a specific aspect of the present invention, in the rangefinder described above, the light intensity detection unit includes an integration circuit connected to a light receiving circuit for measuring reflected light, a plurality of peak hold circuits, and a plurality of peak hold circuits connected to the integration circuit. and a switch circuit for selecting a peak hold circuit to be selected from a plurality of peak hold circuits. With the integration circuit, the peak hold circuit, and the switch circuit, that is, with a single integration circuit, the amount of reflected light can be determined at a plurality of timings with matching accuracy.

According to another aspect of the present invention, the light intensity detector switches between a plurality of timings based on the output of a clock counter circuit started by a trigger signal. In this case, the detection result is stable and less likely to fluctuate due to disturbance.

According to still another aspect of the present invention, the light amount detector switches between a plurality of timings based on the output of an analog clock circuit started by a trigger signal. In this case, relatively reliable results can be obtained with a simple and inexpensive circuit configuration.

According to still another aspect of the present invention, the light amount detection section performs any one of rising detection, peak detection, falling detection, and resonance zero-cross detection with respect to the detection pulse output by the light receiving element for reflected light. to generate the trigger signal. By using the reception of the reflected light to generate the trigger signal, it is possible to use the distance detection result for the actual object to detect the distance and the amount of light for the next object behind it.

According to still another aspect of the present invention, the distance measuring device excludes targets that meet predetermined conditions from the detection results based on the distance to the target and the amount of light obtained from the reflected light. Here, the predetermined condition is, for example, whether or not the reflected light is of a low level that does not reach the reference light quantity assumed for the distance of interest. In this case, non-monitored objects, such as reflections from fog or dirty windows, can be identified and excluded from detection results.

(A) is a block diagram conceptually explaining the structure of the distance measuring device and its peripheral devices according to the first embodiment; FIG. 4 is a diagram illustrating corresponding distance zones; FIG. 2 is a block diagram illustrating a specific circuit configuration of a light amount measuring unit of the distance measuring device shown in FIG. 1(A); 3 is a diagram for explaining an analog clock circuit and the like among the device portions shown in FIG. 2; FIG. 3A to 3F are diagrams for explaining the operation of a part of the distance measuring device that uses the timing of light projection as a reference for the timing of detecting the amount of light; FIG. (A) to (J) are diagrams for explaining the operation of each part of the distance measuring device. It is a figure explaining the concrete circuit structure of the principal part concerning a change about the distance measuring device of 2nd Embodiment. (A) to (F) are diagrams for explaining the operation of a part of the distance measuring device that uses the light reception timing as a reference for the timing of light amount detection, and (G) is for explaining an example of a ghost signal in a received signal. It is a diagram. (A) is a diagram for explaining rising detection, (B) is a diagram for explaining peak detection, (C) is a diagram for explaining falling detection, and (D) is a diagram for explaining resonance zero crossing. It is a figure explaining detection. It is a figure explaining the concrete circuit structure of the principal part concerning a change about the distance measuring device of 3rd Embodiment. 10A to 10J are diagrams for explaining the operation of each part of the distance measuring device shown in FIG. 9; FIG.

[First embodiment]
An overview of a distance measuring device 100 according to the first embodiment of the present invention will be described with reference to FIG. The distance measuring device 100 is a scanning type distance detecting device, and includes a light projecting portion 10 that projects a laser beam L1, a light receiving portion 20 that receives a laser beam L2, and scans the laser beams L1 and L2 when projecting and receiving the laser beams L1 and L2. A two-dimensional scanning device 30, a timing detector 40 for detecting the irradiation or emission of the laser light L1, and a time for measuring the elapsed time from the irradiation or emission of the laser light L1 to the reception or incidence of the reflected light (laser light L2). It includes a measurement unit 51, a light amount measurement 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 light L1 when measuring time, that is, measuring distance, and operates as a distance image sensor. In the distance measuring device 100, the reflected light intensity (hereinafter referred to as light amount) of the target OB is acquired using the light amount measurement unit 160, and used as auxiliary data for distance measurement.

In the distance measuring device 100 , the light projecting section 10 , the light receiving section 20 , the two-dimensional scanning device 30 , the timing detecting section 40 , the time measuring section 51 , and the control section 70 constitute a distance measuring section 50 . In the distance measuring device 100 , the timing detection section 40 , the light amount measurement section 160 , and the control section 70 (particularly, the data processing section 72 and soundness determination section 73 ) constitute the light amount detection section 60 . In other words, the timing detection section 40 functions both as part of the distance measurement section 50 and as part of the light amount detection section 60 .

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

The distance measurement unit 50 measures the elapsed time from the emission or projection of the laser beam L1 to the incidence or reception of the reflected light (laser beam L2) to determine the distance. That is, the distance measuring unit 50 obtains the time difference between the timing of the laser beam L1 emitted from the light projecting unit 10 and the timing of the laser beam L2 entering the light receiving unit 20, and divides this half value by the propagation speed of the laser beam. Thus, the distance to the target OB is calculated.

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

The light-receiving unit 20 has a light-receiving element 21 into which the laser light L2, which is the return light reflected by the object OB existing in front of the distance measuring device 100, is incident, and a driving circuit 22 for operating the light-receiving element 21. , outputs a detection signal TS or a reception signal corresponding to the intensity of the laser light L2 at a timing corresponding to the incidence of the laser light 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 driving circuit 22 has a receiving amplifier for amplifying the detection signal TS from the light receiving element 21, and operates under the control of the control section 70 as necessary to adjust the detection gain.

The two-dimensional scanning device 30 has a scanner 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 part about two axes, the light reflected by the mirror scans a two-dimensional area. The scanner main body 31 performs an oscillating motion that enables two-dimensional scanning by means of a scanner drive circuit 32 that operates under the control of the controller 70 .

The laser beam L1 emitted from the light projecting unit 10 is two-dimensionally scanned within a scanning angle range of ±30°, for example, when reflected by the two-dimensional scanning device 30 . The laser light 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 light L2 reflected by the target OB and going backward is reflected again by the two-dimensional scanning device 30. and is incident on the light receiving section 20 . Note that the illumination laser light L1 and the return laser light L2 are split by a beam splitter (not shown) provided in association with 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 light projecting unit 10 . Specifically, the timing detection unit 40 detects the light projection timing as a light projection trigger signal LR obtained by detecting the laser light L1 with a light emission monitor (not shown) provided in the light projection unit 10 . Alternatively, the timing detection unit 40 may detect the projection timing of the laser beam L1 using the light projection trigger signal LR0 input to the light projection unit 10 . The timing detection unit 40 outputs a trigger signal TR as a timing start signal for measuring the amount of light to the light amount measurement unit 160 and outputs a timing start trigger SR to the time measurement unit 51 . In this embodiment, the trigger signal TR and the timing start trigger SR are the same.

The time measurement unit 51 measures the time from projection to reception based on the difference between the projection timing of the laser beam L1 and the timing of receiving the laser beam L2 based on the reception signal or the detection signal TS output from the light receiving unit 20 by the timing detection unit 40. The detection time, which is the time difference, is measured. The time measurement unit 51 includes a stop timing detection unit 51a that generates a time measurement stop trigger based on the detection signal TS from the light receiving unit 20 that has received the laser beam L2, and a time measurement start trigger SR from the timing detection unit 40 to measure time. It has a timekeeping circuit 51b that starts and stops timekeeping upon 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 timings of the laser beams L1 and L2. The time measuring unit 51 can perform a plurality of time measurements corresponding to a plurality of reflected lights generated by one light projection pulse with one circuit. That is, in a series of operations or events caused by the operation of the light projecting section 10, the time measuring section 51 can perform a plurality of time measurements required for distance conversion.

The light amount detection 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 a switching unit 60m in the light amount measurement unit 160, which will be 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 are the portions that set a plurality of timings for detecting the light amount of the reflected light received by the light receiving unit 20, that is, the integration period of the reflected light. is the part that sets the In the present embodiment, the trigger signal TR corresponding to the laser beam L1 obtained by the timing detector 40 is used as the light projection timing at the start of time measurement, and integration periods corresponding to a plurality of timings for detecting the amount of reflected light are calculated based on this. set. Although the details will be described later, when the light emission timing at the start of time measurement is used as a reference for the light amount detection timing, the light amount detection timing is set in a plurality of distance zones in the depth direction with respect to the area where the target OB may exist. are set accordingly. The distance zones are arranged in the same direction, for example, as shown in FIG. Zone Z3 is demarcated.

As shown in FIG. 2, the light intensity measurement unit 160 is connected to an analog clock circuit 61 that is started by a trigger signal TR from the timing detection unit 40 and a light receiving unit 20 that is a light receiving circuit for measuring reflected light. an integration circuit 62, a peak hold circuit group 63, a switch circuit 64 that selects a required peak hold circuit from the peak hold circuit group 63 and connects to the integration circuit 62, and a switch control section 65 that controls the operation of the switch circuit 64. , and an AD converter group 66 for AD-converting 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. Also, the analog clock circuit 61, the switch control section 65, and the switch circuit 64 constitute a switching section 60m. The switching unit 60m operates the switch circuit 64 and the like based on the output of the analog clock circuit 61, and switches between a plurality of timings or time zones corresponding to the divisions of the light amount measurement of the reflected light. As a result, the result of accumulating the detection signal TS from the light receiving section 20 in the desired time zone is held. The analog clock circuit 61 can provide relatively reliable results with a simple and inexpensive circuit configuration. In addition, by the integration circuit 62, the peak hold circuit group 63, and the switch circuit 64, that is, by the single integration circuit 62, the amount of reflected light can be determined at a plurality of timings with the same accuracy.

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

Returning to FIG. 2, the switch circuit 64 that operates based on the output of the analog clock circuit 61 or the switch control section 65 has a second 1 and second switches 64a, 64b are provided. The first and second switches 64a and 64b are composed of, for example, FETs, and input 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 should respond within several hundred ps to several ns.

In this embodiment, in the analog clock circuit 61, light projection timing information (specifically, switching from H to L of the digital output) by the trigger signal TR output from the timing detection unit 40 shown in FIG. The timing of detecting the amount of light is set based on In other words, the time from the start of timing based on the light projection timing information to the time when the voltage reaches predetermined thresholds (see threshold voltages Vref2 and Vref3 shown in FIG. 3) is defined as the predetermined time regarding the timing of light amount detection.

FIGS. 4(A) to 4(F) are timing charts for explaining an operation in which light projection timing is used as a reference for light amount detection timing. FIG. 4A shows laser light L1 emitted from the light projecting section 10 at the light projection timing. FIG. 4B shows the TIA output from the light receiving section 20. FIG. FIG. 4(C) shows the trigger signal TR for starting time measurement or the time measurement start signal output from the timing detection unit 40 . FIG. 4D shows integrated voltage values in the analog clock circuit 61. FIG. 4E shows the first switch control signal SW1 for the first switch 64a of the switch circuit 64. FIG. 4F shows the second switch control signal SW2 for the second switch 64b of the switch circuit 64. FIG. A 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 define the timing of light intensity 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 by the analog clock circuit 61 shown in FIG. As shown in 4(D), it corresponds to a first threshold TL1 for only the first stage assuming the integrated values of the time zones TZ1 and TZ2, and a second threshold TL2 assuming the integrated values up to the second stage. Further, as shown in FIGS. 4(E) and 4(F), the predetermined time related to the timing of light amount detection is the first delay time DT1 only for the first stage of the time zones TZ1 and TZ2, and the second stage. corresponds to the second delay time DT2 of . That is, the plurality of threshold values set for the timing of light intensity detection by the analog clock circuit 61 or the like shown in FIG. In a series of detection operations or events, each distance zone constituting a plurality of distance zones, specifically, corresponds to 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 a predetermined first threshold TL1 shown in FIG. 4(D). , and the first peak hold circuit 63a is separated from the integration circuit 62. After that, the switch control unit 65 turns off the second switch 64b of the switch circuit 64 when the voltage of the measurement signal Sa of the analog clock circuit 61 reaches a predetermined second threshold TL2 shown in FIG. The second peak hold circuit 63b is separated from the integration circuit 62.

In the analog clock circuit 61 shown in FIG. 3, the RC integration circuit 61a is activated while the trigger signal TR (see FIG. 4C) from the timing detection unit 40 shown in FIG. After charging at a constant rate, when the output (measurement signal Sa) of the RC integration circuit 61a of the analog clock circuit 61 reaches a certain threshold voltage Vref2, the output from the comparator CM2 operates the switch control unit 65 to operate the switch circuit 64. The first delay time DT1 shown in FIG. 4(E) is controlled by turning off the first switch 64a. 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, clock source, or the like. It should be noted that the delay time can be changed from the outside such as the CPU by using a digital potentiometer for the resistor R or by making the threshold voltage Vref2 of the comparator CM2 variable by a DA converter or the like. Similarly, for the second switch 64b of the switch circuit 64, when the output (measurement signal Sa) of the integration circuit 61a of the analog clock circuit 61 reaches a certain threshold voltage Vref3, the switch control unit 65 is operated by the output from the comparator CM3. Then, the second switch 64b is turned off, thereby controlling the second delay time DT2 shown in FIG. 4(F).

As described above, when the light emission timing is used as a reference for the light amount detection timing, the trigger signal TR is generated according to the emission timing of the laser light L1, as shown in FIG. 4(C). A stable trigger signal TR can be obtained by using the projection of the laser light L1 to generate the trigger signal TR. This makes it possible to set the absolute time from the light projection, and to facilitate the setting. For example, when observing through a window glass or when fog is generated, the first received signal or the first detection signal s1 returns immediately after the light is projected, so the reflected light from the window or fog can be reliably detected. can be acquired as the light intensity corresponding to them.

Returning to FIG. 2, the integration circuit 62 integrates the input voltage over time and outputs it. The integration circuit 62 integrates a plurality of detection signals (received signals or TIA signals) TS sequentially detected by the light receiving element 21 . In this embodiment, the light receiving element 21 sequentially outputs the first detection signal s1, the second detection signal s2, and the third detection signal s3. The integration output of the integration circuit 62 that receives the first to third detection signals s1 to s3 is converted to the first to the third detection signals s1 to s3 are sequentially output at predetermined timings through the peak hold circuit group 63 as voltages corresponding to the intensities of the third detection signals s1 to s3.

The peak hold circuit group 63 measures the amount of reflected light at a plurality of timings set with reference to the light projection timing. A 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 identical circuits, and measures the integrated output of the integrating circuit 62 through the switch circuit 64, that is, the amount of reflected light at a plurality of timings set by the switching section 60m. In this embodiment, the peak hold circuit group 63 is provided with three circuits of first to third peak hold circuits 63a to 63c. By selectively using each of 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 light receiving timings of the plurality of detection signals TS corresponding to the different reflected lights in the same direction correspond to the above-described light amount detection timings, and are assumed to be detected in each of the plurality of distance zones. is set as

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). A light intensity value obtained by integrating the output of the first detection signal s1 corresponding to light is held. The second peak hold circuit 63b outputs the first and second detection signals s1 and s2 corresponding to the first and second reflected lights connected to the integration circuit 62 up to the second stage of the time zone or distance zone. Holds the integrated light intensity value. The third peak hold circuit 63c is simply connected to the integration circuit 62 and holds light quantity values 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 input of each peak hold circuit 63a to 63c is switched by a combination of ON/OFF of the first and second switches 64a and 64b of the switch circuit 64. FIG.

An output signal PH from the peak hold circuit group 63 is input to the data processing section 72, soundness determination section 73, etc. of the control section 70 shown in FIG.

Returning to FIG. 1(A), the control unit 70 is, for example, a microprocessor including a CPU, a memory, etc., and operates according to a preinstalled program. The control unit 70 functionally includes an optical scanning control unit 71 , a data processing unit 72 , and a soundness determination unit 73 .

The optical scanning control unit 71 of the control unit 70 outputs a control signal to the driving circuit 12 of the light projecting unit 10 to control not only the emission timing of the laser light L1 but also the output of the laser light L1. Can be increased or decreased. The optical scanning control unit 71 can also increase or decrease the amplification factor for the detection signal TS of the laser light L2 by outputting a control signal to the drive circuit 22 of the light receiving unit 20 . Also, the optical scanning control section 71 controls the swing operation of the scanner body section 31 via the scanner driving 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 incidence of the laser beam L2 from the time difference between the light projection 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 section 72, and the data processing section 72 calculates the output values of the respective peak hold circuits 63a to 63c shown in FIG. Light amount values corresponding to the detection signals s1 to s3 are 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 values 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 regarding the distance to the target OB obtained by the data processing unit 72 . The soundness determination unit 73 excludes target OBs that meet predetermined conditions from the detection results based on the distance to the target OB and the amount of light obtained from each reflected light. Here, the predetermined condition is, for example, whether or not the reflected light is of a low level that does not reach the reference light quantity assumed for the distance of interest. This allows non-monitored objects, such as reflections from fog or dirty windows, to be identified and excluded from detection results.

More specifically, 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, the soundness determination unit 73 detects fog, dirt on the window, dust, water droplets, etc. etc., and the target OB is not determined to be an object. If the amount of light corresponding to the target OB is higher than a predetermined threshold, for example, if the range of the target OB is pinpoint, it may be determined that the target OB is not an object.

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

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

Next, as shown in FIG. 5B, when a plurality of reflected lights return from a single emission of the laser beam L1, the light receiving section 20 detects a plurality of reception signals or detection signals TS. In the illustrated example, the multiple detection signals TS are first to third detection signals s1 to s3.

As shown in FIGS. 5A and 5B, the time measurement unit 51 sets the peak time of the laser light L1 from the light projecting unit 10 as the light projection timing, and the peak time of the laser light L2 from the light receiving unit 20. Using hour 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 are detected. The time difference from the light receiving timing is detection time T3.

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

As shown in FIG. 5G, the integration circuit 62 sequentially integrates the first to third detection signals s1 to s3 and outputs the result.

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. During this period, the output of the integration 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 first threshold value TL1 corresponding to the lapse of the first delay time DT1, as shown in FIG. 5(E), the switch control unit 65 outputs a first switch control signal SW1 for turning off the first switch 64a. By turning off the first switch 64a, the first peak hold circuit 63a holds only the integration result of the first detection signal s1 out of the output 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 second threshold TL2 corresponding to the second delay time DT2, as shown in FIG. 5(F), The switch control section 65 outputs a second switch control signal SW2 that turns off the second switch 64b. By turning off the second switch 64b, in the second peak hold circuit 63b, the sum of the first and second detection signals s1 and s2 in the output of the integration circuit 62 is Holds the integration result. After that, the third peak hold circuit 63c holds the result of integration as the sum of the first to third detection signals s1 to s3 output from the integration circuit 62, as shown in FIG. 5(J).

As described above, a plurality of received signals or detection signals TS detected by the light receiving section 20 are sequentially integrated through the integrating circuit 62 and the peak hold circuit group 63, and the first to first signals corresponding to the respective peak hold circuits 63a to 63c are 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 light amount data, is sampled, for example, after a predetermined time from the light projection timing. During or after sampling, the integration output of the integration circuit 62 becomes zero, as shown in FIG. 5(G).

The light amount data output from the peak hold circuit group 63 is input to the data processing section 72, and the data processing section 72 converts the first detection signal by the first P/H output (P/H1) in the first peak hold circuit 63a. A light intensity value corresponding to s1 is calculated. Further, the data processing unit 72 subtracts the first P/H output (P/H1) of the first peak hold circuit 63a from the second P/H output (P/H2) of the second peak hold circuit 63b, thereby 2 Calculate the light intensity value corresponding to the detection signal s2. 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 to obtain the 3 A light amount value corresponding to the detection signal s3 is calculated. By increasing the number of peak hold circuit groups 63 in response to an increase in the number of received signals or detection signals TS to be received, it is possible to acquire the light intensity values of the reflected light for the increased number.

According to the distance measuring device described above, the light amount detection unit 60 detects the light amount of the reflected light at a plurality of timings by switching the switch circuit 64, so that a plurality of objects, OB, are detected at different distances in the same direction. In some cases, intensity information of reflected light can be acquired as auxiliary data accompanying distance information for the target OB, which is a plurality of such objects. This allows operations such as identifying and excluding non-monitored objects, such as reflections from fog or dirt on windows.

[Second embodiment]
A distance measuring device according to the second embodiment will be described below. The range finder of the second embodiment is a partial modification of the range finder of the first embodiment, and the items not particularly described are the same as those of the range finder of the first embodiment.

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

The timing detection unit 140 of this embodiment detects the timing of the laser light L2 incident on the light receiving unit 20 or the light reception timing in order to output the trigger signal TR or the timing start signal to the analog clock circuit 61 of the light amount measurement unit 160 . The timing detection section 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 section 20 that has received the laser beam L2. The signal processing circuit 140a is provided with a comparator (not shown), a differentiating circuit, and the like.

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

FIGS. 7A to 7F are diagrams for explaining the operation using the timing of light reception as a reference for the timing of detecting the amount of light. FIG. 7A shows the laser beam L1 emitted from the light projecting section 10 at light emission timing, and FIG. 7B shows the TIA output corresponding to the light reception timing outputted from the light receiving section 20. FIG. The waveforms shown in FIGS. 7A and 7B match those shown in FIGS. 4A and 4B. FIG. 7C shows the trigger signal TR for starting time measurement or the time measurement start signal output from the timing detection unit 140 . 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 of the switch circuit 64. FIG. 7F shows the second switch control signal SW2 for the second switch 64b of the switch circuit 64. FIG. When the timing of light reception is used as a reference for the timing of light amount detection, as shown in FIGS. Generated accordingly. The first and second switch control signals SW1 and SW2 shown in FIGS. 7(E) and 7(F) correspond to the first and second switch control signals SW1 and SW2 shown in FIGS. 4(A) and 4(B). There is a slight deviation from By using the reception of the reflected light to generate the trigger signal TR, the distance detection result for the target object OB, which is a real object, is used to detect the distance and the amount of light for the target object 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 versatility is enhanced.

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, the electrical influence of the light receiving unit 20 causes As shown, a ghost signal N may occur as a received signal at a position where the target OB should not exist. In such a case, by using a method in which the timing of light reception is used as a reference for the timing of detecting the amount of light, as in this embodiment, the amount of reflected light corresponding to the first detection signal s1, which is the first received signal, is equal to or greater than a certain value. In the case of , it can be determined that the reflected light is from the retroreflective object OB, and by performing processing to ignore the ghost signal N as the second received signal, more accurate distance measurement can be performed. can be done. As a result, accurate obstacle detection and the like can be performed. Examples of retroreflection include reflection from road signs and the like.

The timing detection unit 140 of the light amount detection unit 60 of the present embodiment performs (1) rising detection, (2) peak detection, and (3) falling detection with respect to the detection signal TS or the detection pulse output from the light receiving unit 20. and (4) performing at least one of resonant zero-crossing detection to generate a trigger signal TR. Note that the detection methods (1) to (4) can also be combined. Each detection method will be described below.

(1) Rising Detection or Rising Threshold Detection As shown in FIG. 8A, when the first detection signal s1 rises and reaches the threshold TL3, it is detected as light reception 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, there is a possibility that the timing will change, resulting in poor switch control accuracy.

(2) Peak Detection As shown in FIG. 8B, the peak P of the first detection signal s1 is detected as the light reception timing. In the case of peak detection, the same timing can be obtained regardless of the waveform amplitude, so the accuracy of switch control is improved. On the other hand, in the case of a signal with 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 reaches the threshold TL4 at the fall, it is detected as the light receiving timing. The advantages and disadvantages of falling threshold detection are the same as those of rising threshold detection.

(4) Resonance zero cross detection As shown in FIG. 8(D), a characteristic frequency component is extracted using a resonance circuit that resonates at 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 light receiving timing. In the case of resonance zero-cross detection, the timing can be detected with high sensitivity even with a signal having a small amplitude, and the accuracy of switch control can be improved. On the other hand, when a signal with a large amplitude is input, waveform distortion degrades timing accuracy, resulting in poor switch control accuracy.

[Third embodiment]
A distance measuring device according to the third embodiment will be described below. The range finder of the third embodiment is a partial modification of the range finder of the first embodiment, and the items not particularly described are the same as those of the range finder of the first embodiment.

A digital clock counter circuit 161 is provided in place of the analog clock circuit in the light amount measuring section 160 of the distance measuring device 100 shown in FIG. That is, the light amount measuring section 160 of the light amount detecting section 60 operates the switch circuit 64 or the like based on the output of the clock counter circuit 161 to switch between a plurality of timings. As a result, the detection result is stable and less likely to 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 a clock pulse counting operation upon input of light projection timing information by a trigger signal TR output from the timing detection unit 40, and after a predetermined time or a predetermined number of times corresponding to a predetermined number of pulses has elapsed, the counting operation is performed. to stop. The switch control unit 165 sequentially turns off the first and second switches 64a and 64b in two steps when the prescribed number of pulses is reached.

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

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

Next, as shown in FIG. 10B, when a plurality of reflected lights return from one emission of the laser beam L1, the light receiving section 20 detects a plurality of reception signals or detection signals TS. In the illustrated example, the multiple detection signals TS are 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 light L1 from the light projecting unit 10 as the light projecting timing, and the peak time of the laser light L2 from the light receiving unit 20. A detection time, which is the time difference between light projection and light reception, is measured using hour as the light reception timing.

As shown in FIG. 10C, the clock counter circuit 161 counts the trigger output from the timing detector 40 at the light projection timing detected by the timing detector 40, specifically at the peak of the laser beam L1. It receives the signal TR or the count start signal and starts counting.

As shown in FIG. 10G, the integration circuit 62 sequentially integrates and outputs the first to third detection signals s1 to s3.

As shown in FIGS. 10(E) and 10(F), the first and second switches 64a and 64b of the switch circuit 64 are both on, that is, a predetermined first delay time DT1 from the output of the trigger signal TR. During this period, the output of the integration 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. 10D, in the clock counter circuit 161, when the number of pulses corresponding to the lapse of the first delay time DT1 is reached, the switch control unit 165 switches to the first A first switch control signal SW1 for turning off the switch 64a is output. By turning off the first switch 64a, the first peak hold circuit 63a holds only the integration result of the first detection signal s1 out of the output of the integration circuit 62, as shown in FIG. 10(H). Next, as shown in FIG. 10(D), when the clock counter circuit 161 reaches the number of pulses corresponding to the second delay time DT2, the switch control unit 165 switches to , outputs a second switch control signal SW2 for turning off the second switch 64b. By turning off the second switch 64b, in the second peak hold circuit 63b, the sum of the first and second detection signals s1 and s2 in the output of the integration circuit 62 is Holds the integration result. Thereafter, the third peak hold circuit 63c holds the result of integration as the sum of the first to third detection signals s1 to s3 output from the integration circuit 62, as shown in FIG. 10(J).

As described above, a plurality of received signals or detection signals TS detected by the light receiving section 20 are sequentially integrated through the integrating circuit 62 and the peak hold circuit group 63, and the first to first signals corresponding to the respective peak hold circuits 63a to 63c are 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 light amount data, is sampled, for example, after a predetermined time from the light projection timing. During or after sampling, the integration output of the integration circuit 62 becomes zero, as shown in FIG. 10(G).

In addition, in this embodiment, as in the second embodiment, the timing of light reception may be used as a reference for the timing of detecting the amount of light.

The structures, shapes, sizes and arrangement relationships described in the above embodiments are merely schematic representations to the extent that the present invention can be understood and implemented. Therefore, the present invention is not limited to the described embodiments, but can be modified in various forms without departing from the scope of the technical concept indicated in the claims.

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

In the above-described embodiment, the timing reference for detecting the amount of light can be appropriately changed according to the application of the distance measuring device 100, and both the timing of light emission and the timing of light reception can be used as a reference. can also For example, in detecting the first detection signal s1, which is the first received signal, the 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). In the detection of the second detection signal s2, which is the received signal, the trigger signal TR is generated based on the light receiving operation of the light receiving section 20 to detect the light amount of the reflected light (laser light L2). In other words, in the case of the operation by the trigger signal TR using the light reception timing, it is necessary to start the measurement operation before that. In the detection of the reception signal, the light reception timing is used to generate the trigger signal TR. Note that the trigger signal TR can also be generated for each received signal. In the distance measuring apparatus 100, the timing of the return of the received signal always changes depending on the situation. The second detection signals s1 and s2 can be separated.

DESCRIPTION OF SYMBOLS 10... Light-emitting part 11... Light-emitting element 12... Drive circuit 20... Light-receiving part 21... Light-receiving element 22... Drive circuit 30... Two-dimensional scanning device 31... Scanner main-body part 32... Scanner drive circuit, 40 Timing detector 50 Distance measuring unit 51 Time measuring unit 60 Light intensity detector 61 Analog clock circuit 62 Integrating 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 determination unit 80 Case 100 Distance measuring device 160 Light amount measuring unit 161 Clock counter circuit 200 Host system L1, L2 Laser light OB Target TR Trigger signal TS, s1 to s3 Detection signal

Claims (4)

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;
A light amount detection unit that detects the amount of reflected light,
The light intensity detection unit detects the light intensity of the reflected light at a plurality of timings by switching the 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. a switch circuit;
A distance measuring device that excludes objects that meet predetermined conditions from detection results based on the distance to the object and the amount of light obtained from reflected light . 2. The distance measuring apparatus according to claim 1 , wherein said light amount detection section switches said switch circuit based on an output of a clock counter circuit started by a trigger signal for starting light amount measurement . 2. The distance measuring device according to claim 1 , wherein said light amount detection section switches said switch circuit based on an output of an analog clock circuit started by a trigger signal for starting light amount measurement . The light intensity detection unit performs any one of rising detection, peak detection, trailing edge detection, and resonance zero-crossing detection on the detection pulse output from the light receiving element for reflected light to detect the light intensity measurement start. 4. A ranging device according to any one of claims 2 and 3 , which generates a trigger signal.

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