JP2010197118A - Distance measuring device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem that when a distance is measured by receiving a plurality of beams of scattered light from a target, calculation processing becomes complicated due to an increase of the number of counters. <P>SOLUTION: A comparator 1 generates a starting pulse from a transmission light pulse accompanied by laser light, and a comparator 2 outputs each of received light pulses from N-pieces of targets as binarized N-bit data. A distance measuring circuit 5 measures the time between stop pulses among the start pulse and the N-bit data which becomes "1" in the earliest time, and outputs it as a standard time. A delay line 6 outputs only M-pieces of delayed pulses corresponding to distance resolution capability, and the delayed pulses are the stop pulses delayed at a desired delay step to the target. A latch circuit 7 outputs the N-bit data as the delayed data by being latched with the stop pulses and the delayed pulses. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention irradiates the target whose distance is to be measured with a pulsed laser beam and receives the scattered light from the target, so that the distance to the target can be determined from the time difference between the laser beam transmission time and the light reception time. More particularly, the present invention relates to a multi-channel distance measurement device that detects a plurality of scattered lights from a target.

  Conventional example 1 of this type is provided with four systems each for the time until light emitted from four semiconductor laser elements (LD elements) toward a measurement object in a predetermined order is received by the same number of light receiving elements. It is counted by the counter unit (Patent Document 1). The period of the clock for performing the counting usually depends on the distance resolution to the measurement object, and becomes a short period when high resolution is required. Therefore, according to this conventional method, counters that operate with a high-speed clock are required for the number of light receiving systems, and the scale and power consumption of the apparatus increase.

  Conventional example 2 has a plurality of light receiving systems in which scattered light from the same target is optically branched as a countermeasure when the detector performs dark counting (malfunction) by thermal electrons other than the incidence of photons, The same number of counter circuits that count the time from the transmission of the laser light to the light reception in the light receiving system are provided to eliminate count values with little correlation (Patent Document 2). In the case of this method, there are the same problems as described above, and the calculation unit individually calculates distance values based on the counting results of a plurality of distance measuring circuits, and the processing becomes complicated.

JP-A-7-198850 JP-A-9-101368

  The problem to be solved is that when a plurality of scattered lights from the target are received and the distance is measured, the number of counters increases and the arithmetic processing becomes complicated.

  The present invention is provided with a counter circuit for only light reception pulses from one target, and based on the reference time calculated by the counter circuit, the light reception pulses from a plurality of targets are converted into time-series digital data with respect to the reference time. The main feature is to perform matrix expansion and computation.

  The distance measuring device of the present invention calculates the reference time with one counter circuit, and the light reception timing from all the targets is obtained as a relative time with respect to the reference time, so that the number of counter circuits can be reduced. There is.

  Further, since the received light pulses from all targets are converted into time-series digital data with respect to the reference time and calculated by matrix development, there is an advantage that the calculation function can be simplified.

FIG. 1 is a block diagram of an embodiment of the apparatus of the present invention. FIG. 2 is a diagram illustrating the waveforms of the input / output signals of the stop comparator. FIG. 3 is a diagram illustrating input / output signals of the latch circuit.

  FIG. 1 is a block diagram of an embodiment of the apparatus of the present invention. 1, this distance measuring device includes a start comparator 1, a stop comparator 2, an OR circuit 3, a flip-flop circuit 4, a distance measuring circuit 5, a delay line 6, a latch circuit 7, a laser unit 8, a light receiving unit 9, and a calculation unit. 10 is comprised. The laser unit 8 irradiates a plurality of targets (not shown) whose distances are to be measured with pulsed laser light, and the light receiving unit 9 receives scattered light from the N targets. The distance to the target can be measured from the time difference between the light transmission time and the light reception time. Here, the target may be N objects or may have N parts or uneven surfaces of one object.

  The start comparator 1 receives a light transmission pulse associated with the laser light from the laser unit 8 and outputs only a voltage level equal to or higher than a threshold value Vref1 and outputs a start pulse. The stop comparator 2 receives the light reception pulses output from the N light detectors 9-1 to 9-N constituting the light receiving unit 9, and only the voltage level equal to or higher than the threshold value Vref2 is validated to receive the N light reception pulses. Output. This light reception pulse is expressed as N-bit data D1 to DN if the validity corresponds to “1” and the invalidity corresponds to “0”.

  The OR circuit 3 detects the earliest pulse among the N received light pulses, that is, the pulse that becomes “1” first among the N-bit data D1 to DN, and the flip-flop circuit 4 detects the pulse from this pulse. Generate a stop pulse. Ranging circuit 5HA measures the time between the start pulse and stop pulse, and outputs this as the reference time.

  The delay line 6 outputs delay pulses DL1 to DLM obtained by delaying the stop pulse in M ways by the delay step time T. The delay step time T is determined in consideration of a desired distance resolution with respect to the target, that is, a variation in distance value from the distance reference value to each target assumed. The latch circuit 7 includes (M + 1) latches 7-1 to 7- (M + 1), the latch 7-1 is a stop pulse, and the latches 7-2 to 7- (M + 1) are delay pulses DL1 to DL1. N-bit data D1 to DN are sequentially latched at the delay step time T using DLM as a latch clock, and the data (delay 0 data to delay (M + 1) data) is stored.

  The arithmetic unit 10 inputs the reference time that is the output of the distance measuring circuit 5, and then the delay 0 data to the delay M data stored in the latches 7-1 to 7-(M + 1) of the latch circuit 7. Are sequentially read out and expanded into a matrix, the time difference between the stop pulse and the reflected light input from the target is obtained, and the actual distance to the target is calculated based on the distance reference value based on the reference time.

  FIG. 2 illustrates the waveforms of the input / output signals of the stop comparator 2. Here, N = 16, and the light receiving pulse 9 is shown as an example (2 in FIG. 2) where the light receiving pulse 9-1 and the 16-bit data D1 are large as an example where the level of the light receiving pulse is small (1 in FIG. 2). -16 and 16-bit data D16. As described above, since the received light pulse is binarized into “1” and “0” by the threshold Vref2, the number of “1” is small when the input level is small, and “1” when the input level is large. The number increases.

  FIG. 3 is a matrix display where the input / output signal of the latch circuit 7 is M = 10 when the received light pulses 9-1 and 9-16 are input to the stop comparator 2 as shown in FIG. . In this table, the vertical axis represents 16-bit data D1 to D16 which are inputs to the latch circuit 7, and the horizontal axis represents delay 0 data to delay 10 data. That is, the horizontal axis indicates at which point the 16-bit data D1 to D16 is stored in which latch 7-1 to 7- (M + 1) of the latch circuit 7. From the left side of FIG. 3, 16-bit data 1000 to 00 are latches 7-1 to 7-3 as delay 0 data to delay 2 data, and 16-bit data 0000 to 00 are latches 7-4 and 16-bit data as delay 3 data. 0000 to 01 are stored in latches 7-5 to 7-9 as delay 4 data to delay 8 data, and 16-bit data 0000 to 00 are stored in latches 7-10 to 7-11 as delay 9 data to delay 1 data 10.

  Now, the operation of the apparatus of the present invention will be described on the assumption that the received light pulses 9-1 and 9-16 as shown in FIG. The start comparator 1 outputs a start pulse when the voltage level of the light transmission pulse accompanying the laser light becomes equal to or higher than the threshold value Vref1. Next, the received light pulse 9-1 is first input to the stop comparator 2, and when the voltage level becomes equal to or higher than the threshold value Vref2, the 16-bit data D1 becomes “1” during that time. The same applies to the 16-bit data D16 input with a delay from the received light pulse 9-1. In this example, it is assumed that there are no received light pulses 9-2 to 9-15, and the 16-bit data D2 to D15 always maintain “0”.

  The 16-bit data D1 to D16 are input to the flip-flop circuit 4 via the OR circuit 3, and the flip-flop circuit 4 outputs a stop pulse at the rising edge of the 16-bit data D1, as shown in FIG. The distance measuring circuit 5 inputs a start pulse and a stop pulse, measures the time from the start pulse input to the first stop pulse input, and outputs this to the arithmetic unit 10 as a reference time. If the number of clocks from the start pulse input to the first stop pulse input is 80 and the clock frequency is 100 MHz, the reference time is 800 ns. In this case, the distance resolution by the distance measuring circuit 5 is 1.5 m by dividing the value obtained by multiplying the clock period by the speed of light by 2.

  The latch 7-1 of the latch circuit 7 latches the 16-bit data D1 to D16 at the time when the stop pulse is input as digital 16-bit data and outputs it to the arithmetic unit 10 as delay 0 data. Now, assuming that the delay step time T = 1 ns, the stop pulse input to the delay line 6 is delayed by 1 ns from the delay of 1 ns to the time MT = 10 ns, and is delayed by 1 ns as delay pulses DL1 to DL10, which are latch circuits Are output to the latches 7-1 to 7-11. In this case, the distance resolution due to the difference in stop pulse generation time is 15 cm by dividing the value obtained by multiplying the delay step time T by the speed of light by 2.

  As a result, the latch circuit 7 sequentially latches the 16-bit data D1 to D16 as digital 16-bit data in 1 ns steps by the delay pulses DL1 to DL10, and outputs them to the arithmetic unit 10 as delay 1 data to delay 10 data. For example, the latch 7-11 outputs 16-bit data D1 to D16 after 10 ns from the stop pulse output to the computing unit 10 as delay 10 data.

  The computing unit 10 expands the reference time and the delay 0 data to the delay 10 data input as described above in a matrix as shown in FIG. 3, and calculates the actual distance to the target. When attention is paid to the 16-bit data D1, since “1” is latched from the delay 0 data to the delay 2 data, the center position is the delay 1 data, that is, (reference time + 1 ns). Therefore, the target distance corresponding to the received light pulse 9-1 is 120.15 m by multiplying this time by the speed of light and dividing by 2.

  Similarly, paying attention to the 16-bit data D16, since “1” is latched from the delay 4 data to the delay 8 data, the center position is the delay 6 data, that is, (reference time + 6 ns). Accordingly, the target distance corresponding to the received light pulses 9-16 is 120.90 m by multiplying this time by the speed of light and dividing by 2.

  As described above, the circuit according to the present invention can simultaneously acquire the round-trip time to 16 targets and can determine the distance of 16 targets by one measurement.

DESCRIPTION OF SYMBOLS 1 Start comparator 2 Stop comparator 3 OR circuit 4 Flip-flop circuit 5 Ranging circuit 6 Delay line 7 Latch circuit 8 Laser part 9 Light receiving part 10 Calculation part

Claims (4)

  The reflected light from the N targets is received by each light receiving system, and the distance information to the shortest target is obtained by measuring the time until the earliest light receiving timing, and at the same time, the light receiving timing is The reflected pulse train from the target is sequentially digitized and held while having a delay time at a constant interval after the first data holding time, and the distance to the N targets is calculated from the reference value and the reflected pulse train. Distance measuring device. In a distance measuring device that measures the distance to N targets from the time difference between the time of laser light transmission and the time of light reception,
A start comparator for generating a start pulse from a light transmission pulse accompanying the laser beam;
A stop comparator that binarizes each light-receiving pulse from the N targets according to a voltage level and outputs the received light as N-bit data in time series;
A distance measuring circuit that measures a time between the start pulse and a pulse (stop pulse) that becomes “1” earliest in the N-bit data and outputs it as a reference time;
A delay line for outputting a delay pulse obtained by delaying the stop pulse at a delay step time interval determined according to a desired distance resolution for the target by a number M corresponding to the distance resolution;
A latch circuit that latches the N-bit data with the stop pulse and the delay pulses and outputs the delayed data as delay data;
A distance measuring apparatus that calculates a distance to the target based on the reference time and the delay data.   In the calculation, an arithmetic unit sequentially reads the reference time and the delay data, expands them into a matrix, obtains a time difference between the stop pulse and the reflected light input from the target, and a distance reference value based on the reference time. The distance measuring device according to claim 2, wherein a distance to the target is calculated based on   4. The distance measuring device according to claim 2, wherein the delay data for obtaining the time difference is a time closest to a peak value of the light reception pulse.

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