JP4228829B2 - Distance measuring device - Google Patents

Description

  The present invention measures the distance to a distance measurement object by irradiating the distance measurement object with pulsed light and measuring the time from when the light is irradiated until the reflected light is received. The present invention relates to a type of distance measuring device.

  Distance measurement by measuring the distance to the distance measurement object by irradiating the distance measurement object with pulsed light and measuring the time from when the light is irradiated until the reflected light is received The apparatus is widely used for various purposes including a surveying apparatus. Examples conceivable as the configuration of such a distance measuring apparatus will be described with reference to FIGS. However, the circuit configuration itself shown in FIGS. 9 to 11 is not known or publicly used.

  This distance measuring device is mainly configured with a microprocessor unit (MPU) 21 as the center, and pulsed laser light is emitted from the semiconductor laser 23 via the drive circuit 22 in response to a command from the MPU 21. This light is converted into parallel light by the lens system 24 and irradiated toward the object to be measured. Reflected light from the object to be measured is converted into an electric signal by the photodetector 25 through the lens system 24, amplified by the amplifier 26, and then converted into a binary signal by the binarization circuit 27.

  The binarization circuit 27 outputs a signal of “1” when the output of the amplifier 26 exceeds the threshold given from the threshold setting circuit 33, and “0” when it does not exceed the threshold. This output is sampled and held by the sampling circuit 28. Sampling pulses are given to the sampling circuit 28 from the oscillator 29. This sampling pulse is also given to the counter circuit 30.

Now, let C be the speed of light, L be the distance to the object to be measured, and t be the time from when the laser beam is irradiated until the reflected light is received.
L = Ct / 2
Are in a relationship. Therefore, if a distance measurement is performed with a resolution of 1 m, the sampling pulse needs to be 150 MHz.

  The relationship among the sampling circuit 28, the oscillator 29, and the counter circuit 30 is shown in FIG. For example, when measuring a distance from 0 to 255 m, the counter circuit 30 is an 8-bit counter. The output of this counter enters the sampling circuit 28 and is decoded into 256 bits by the decoder 28a. That is, the decoder 28a has 256 outputs, and each time the counter circuit 30 is incremented, the terminal that outputs the signal “1” is shifted to the right by one. The output from the oscillator 29 and the output from the binarization circuit 27 are input to the AND gate group 28b together with the output of the decoder 28a.

  The register 28c of the sampling circuit 28 is reset by the output of the light emission detection circuit 31 in FIG. At the same time, the counter circuit 30 is also reset. At this timing, the output at the left end terminal of the decoder 28a becomes “1”, and the output at the left end of the AND gate group 28b opens at the timing when the output from the oscillator 29 becomes “1”. 27 outputs are input and stored in the leftmost bit of the register 28c.

  When the counter 30 is incremented by 1 due to the pulse from the oscillator 29, the output “1” of the decoder 28a moves to the right, and at the timing when the output from the oscillator 29 becomes “1”, the AND gate group 28b The second gate from the left end is opened, and the output of the binarization circuit 27 at that time is input and stored in the second bit from the left end of the register 28c.

  In this way, each time the counter 30 is incremented, the bit of the register 28c that stores the output of the binarization circuit 27 moves to the right. Therefore, at the timing when the value of the counter 30 reaches 255, the presence or absence of reflected light exceeding the threshold is stored in the register 28c in time series. After the counter 30 reaches 255, it does not return to 0 even if a pulse from the oscillator 20 is input unless it is reset.

  In this state, the MPU 21 reads the value of the sampling circuit 28, that is, the value of the register 28c, and integrates the accumulated value storage memory 32, which is a part of the memory, for each value of the register 28c. That is, the integrated value storage memory 32 is provided for each bit of the register 28c (that is, for each distance of a predetermined resolution).

  When this addition calculation is completed, the MPU 21 instructs the drive circuit 22 again to generate the next optical pulse. In this way, the operation of irradiating the object to be measured with the laser beam a predetermined number of times, receiving and processing the reflected light, and adding the result to the integrated value storage memory 32 is repeated. Then, at the stage where the predetermined number of measurements are completed, the MPU 21 reads the value of the integrated value storage memory 32 and stores it in the memory that gives the maximum value among the values of the memory provided corresponding to each bit of the register 28c. The corresponding distance is determined as the distance to the object to be measured, and is output and the measurement is terminated.

  Another example of the sampling circuit 28 is shown in FIG. In this example, the sampling circuit 28 includes a shift register 28d, an AND gate 28e, and a selector 28f. The selector 28 selects and outputs either the pulse from the MPU 21 or the pulse from the transmitter 29, and the pulse from the MPU 21 is selected in the initial state.

  Then, a signal for detecting laser emission is input from the light emission detection circuit 31, and the input of the selector 28 is switched to the AND gate 28 side. At the same time, the input gate of the counter 30 (in this case, attached to the counter 30 and not shown) is opened, and the pulse from the oscillator 29 is counted by the counter 30 and passes through the AND gate 28e and the selector 28f. A shift pulse is input to the shift register 28d. Note that the counter 30 is reset prior to the start of counting.

  The input of the shift register 28d is a binarized signal from the binarization circuit 27. The output of the binarization circuit 27 is taken into the shift register 28d and shifted every time one shift pulse is input.

  When the value of the counter 30 reaches a value corresponding to the maximum measurement distance, a clock input stop signal is output from the counter 30 (one input of the AND gate 28e becomes “0”). As a result, the AND gate 28 is closed and the pulse of the oscillator 29 is not input to the shift register 28d, so that the value of the shift register 28d is held as it is. The counter 30 is configured not to be further incremented when the value reaches a value corresponding to the maximum measurement distance.

  When a read request signal is received from the MPU 21 in this state, the selector 28f is switched to input a signal from the MPU oscillator. Therefore, the pulse from the MPU 21 becomes the shift pulse of the shift register 28d, and the contents of the shift register 28d are serially transferred to the MPU 21.

However, the conventional distance measuring apparatus as described above has the following problems.
The first is that the time from the start to the end of the measurement becomes longer. That is, as described above, every time one light irradiation is finished, the MPU 21 reads the contents of the sampling circuit 28 and adds them to the integrated value storage memory 32. Since the clock frequency of the MPU 21 is about 10 MHz, this calculation process takes time. Since the next light irradiation cannot be performed until this calculation process is completed, the measurement time is increased accordingly. If the MPU 21 that operates at a high clock frequency is used, the measurement time can be shortened, but there is a problem that the MPU becomes expensive.

  In the method as described above, the integrated value storage memory 32 is used, and noise is removed by determining the distance corresponding to the memory that gives the maximum value as the distance to the distance measuring object. However, even in this case, noise may not be sufficiently removed.

  Furthermore, since the intensity of the reflected light differs between when the object to be measured is far away and when it is close, it is necessary to change the threshold value accordingly. Conventionally, as a countermeasure, the threshold value is lowered with the passage of time from light irradiation, or the entire average value stored in the integrated storage memory is calculated by the MPU 21 shown in FIG. Therefore, the threshold value is changed by issuing a command to the threshold value setting circuit 33 so that the average value becomes a predetermined value. However, this method is not always satisfactory.

  The present invention has been made in view of such circumstances, and distance measurement that solves the above-described problems, enables measurement in a short time, and prevents measurement accuracy from being degraded by noise. It is an object to provide an apparatus.

A distance measuring device related to the present invention includes a light irradiation unit that irradiates a distance measuring object with pulsed light, and
A light receiving unit that receives reflected light from the distance measuring object and other objects, and determines that there is reflected light when the received light intensity exceeds a threshold; and
A counter unit having a plurality of counters provided corresponding to the division of time after irradiation with the light;
A distance measuring device having an arithmetic processing unit that reads the contents of the counter unit after a plurality of times of light irradiation, calculates the distance to the object to be measured by calculating the result,
When it is determined that there is the reflected light, the counter unit adds a predetermined number to the counter of the counter unit according to a time segment from when the light is irradiated until the reflected light is obtained. it is those, wherein the arithmetic processing unit, a distance measuring equipment, characterized in that it consists of an independent circuit.

The basic operation of the distance measuring device is the same as that of the prior art, but is different in that the counter unit that counts the number of times the reflected light is received is composed of a circuit independent of the arithmetic processing unit. Therefore, since the counter unit can be operated asynchronously at a speed independent of the arithmetic processing unit, the addition process can be accelerated and the measurement time can be shortened without increasing the speed of the entire arithmetic processing unit.

The distance measuring apparatus related to the present invention is the distance measuring apparatus described above , wherein the addition process for adding a predetermined number to the counter is a time segment from when the light is irradiated until the reflected light is received. there therefore also characterized by being performed in synchronization with the sampling pulse to determine.

In the distance measuring apparatus , the addition process for adding a predetermined number to the counter is performed in synchronization with the sampling pulse, so that the circuit configuration is simplified.

A distance measuring device related to the present invention includes a light irradiation unit that irradiates a distance measuring object with pulsed light, and
A light receiving unit that receives reflected light from the distance measuring object and other objects, and determines that there is reflected light when the received light intensity exceeds a threshold; and
A counter unit having a plurality of counters provided corresponding to the division of time after irradiation with the light;
A distance measuring device having an arithmetic processing unit that reads the contents of the counter unit after a plurality of times of light irradiation, calculates the distance to the object to be measured by calculating the result,
A continuity determination unit, and the continuity determination unit determines whether or not there is the reflected light with respect to a predetermined number of continuous light irradiations, and determines whether the reflected light is present after the light irradiation is performed. And a storage unit for storing the time according to the time division until a predetermined number of times is obtained, and a predetermined number is added to the counter of the counter unit corresponding to the time division determined to have been reflected light a predetermined number of times. a distance measuring equipment, characterized in that those.

In the distance measuring device , the continuity determination unit determines whether or not there is reflected light for a predetermined number of continuous light irradiations for each time interval from when the light irradiation is performed until the reflected light is obtained. A predetermined number is added to the counter of the corresponding counter unit for the time segment that has been determined and determined that there has been reflected light a predetermined number of times. Therefore, since the reflected light cannot be obtained continuously in the same time segment area, such as noise, it is not added to the counter, so that the noise can be more reliably removed.

A distance measuring device related to the present invention includes a light irradiation unit that irradiates a distance measuring object with pulsed light, and
A light receiving unit that receives reflected light from the distance measuring object and other objects, and determines that there is reflected light when the received light intensity exceeds a threshold; and
A counter unit having a plurality of counters provided corresponding to the division of time after irradiation with the light;
A distance measuring device having an arithmetic processing unit that reads the contents of the counter unit after a plurality of times of light irradiation, calculates the distance to the object to be measured by calculating the result,
A continuity determination unit, and the continuity determination unit obtains the reflected light after the irradiation of the light, indicating that the reflected light is present for a predetermined number of continuous light irradiations. a distance measuring equipment, characterized in that is to determine for each time segment to.

In the distance measuring device , the continuity determination unit determines whether or not there is reflected light for a predetermined number of continuous light irradiations for each time interval from when the light irradiation is performed until the reflected light is obtained. judge. Therefore, if there is such a time division (especially in the time division corresponding to a short distance), the light intensity is too strong and the laser emission intensity is reduced or the gain of the amplifier is lowered. Thus, the measurement state can be made appropriate.

A first means for solving the above-described problem includes a light irradiation unit that irradiates a distance measuring object with pulsed light, and
A light receiving unit that receives reflected light from the distance measuring object and other objects, and determines that there is reflected light when the received light intensity exceeds a threshold; and
A counter unit having a plurality of counters provided corresponding to the division of time after irradiation with the light;
A distance measuring device having an arithmetic processing unit that reads the contents of the counter unit after a plurality of times of light irradiation, calculates the distance to the object to be measured by calculating the result,
When it is determined that there is the reflected light, the counter unit adds a predetermined number to the counter of the counter unit according to a time segment from when the light is irradiated until the reflected light is obtained. Is,
And it has a continuity processing unit, and the continuity processing unit determines whether or not there is the reflected light with respect to one light irradiation, and determines whether the reflected light is emitted after the light irradiation is performed. A storage unit for storing each time interval until the above-mentioned is obtained, and evaluates the continuity of the determination that the reflected light is present within a predetermined time interval, and accordingly, the threshold value and the light irradiation the intensity of light irradiated from the parts, the a distance measuring apparatus characterized by having the indicated functions to adjust at least one of sensitivity of the light receiving portion (claim 1).

  In this means, for a single light irradiation, the continuity processing unit has a storage unit that stores data for each time interval from when the light irradiation is performed until the reflected light is obtained. In order to evaluate the continuity of the determination that there was reflected light in the time segment range, and adjust the threshold, the intensity of light emitted from the light irradiation unit, and the sensitivity of the light receiving unit accordingly. Instruct. “Instructing” means issuing a command to the circuit or arithmetic unit that adjusts the threshold value, the intensity of light emitted from the light irradiation unit, and the sensitivity of the light receiving unit. Thereby, even when measuring a long distance or when measuring a short distance, the signal level and the threshold level can be kept in appropriate ranges, and erroneous detection due to noise can be prevented.

  As described above, according to the present invention, it is possible to provide a distance measuring device that enables measurement in a short time and can prevent measurement accuracy from being lowered due to noise.

  Hereinafter, an example of an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a schematic configuration of a distance measuring apparatus according to the first embodiment of the present invention. This distance measuring device is mainly configured with a microprocessor unit (MPU) 1 as the center, and a pulsed laser beam is emitted from the semiconductor laser 3 through the drive circuit 2 in response to a command from the MPU 1. This light is converted into parallel light by the lens system 4 and irradiated toward the object to be measured. Reflected light from the distance measuring object is converted into an electric signal by the photodetector 5 through the lens system 4, amplified by the amplifier 6, and then converted into a binary signal by the binarization circuit 7.

  The binarization circuit 7 outputs a signal “1” when the output of the amplifier 6 exceeds the threshold given from the threshold setting circuit 13 and “0” when it does not exceed the threshold. This output is sampled by the sampling circuit 8 and integrated in the integrated value storage memory 9. Sampling pulses are given to the sampling circuit 8 from the oscillator 10. This sampling pulse is also given to the counter circuit 11.

  A relationship among the sampling circuit 8, the integrated value storage memory 9, the oscillator 10, and the counter circuit 11 is shown in FIG. For example, when the distance measurement from 0 to 255 m is performed, the counter circuit 11 is an 8-bit counter. The output of this counter enters the sampling circuit 8 and is decoded into 256 bits by the decoder 8a. That is, the decoder 8a has 256 outputs, and each time the counter circuit 11 is incremented, the terminal that outputs the signal "1" is shifted one by one to the right. The output from the oscillator 10 and the output from the binarization circuit 7 are input to the AND gate group 8b together with the output of the decoder 8a.

  The integrated value storage memory 9 is composed of 256 counter units, and one counter unit is composed of, for example, a 4-bit counter. Each counter unit corresponds to one AND gate of the AND gate group 8b, and is incremented by 1 when “1” is output from the corresponding AND gate.

  The integrated value storage memory 9 is reset by the output of the light emission detection circuit 14 in FIG. At the same time, the counter circuit 11 is also reset. At this timing, the output at the left end terminal of the decoder 8a becomes “1”, and the output at the left end of the AND gate group 8b is opened at the timing when the output from the oscillator 10 becomes “1”. 7 is input to the counter unit at the left end of the integrated value storage memory 9. If the output of the binarization circuit 7 is “1”, the counter unit at the left end is incremented by 1.

  When the counter circuit 11 is incremented by 1 due to the pulse from the oscillator 10, the output "1" of the decoder 8a moves to the right, and at the timing when the output from the oscillator 10 becomes "1", the AND gate group 8b The second gate from the left end is opened, and the output of the binarization circuit 7 at that time is input to the second counter unit from the left end of the integrated value storage memory 9. If the output of the binarization circuit 7 is “1”, the second counter unit from the left end is incremented by 1.

  In this way, each time the counter 11 is incremented, the counter unit of the integrated value storage memory 9 in which the output of the binarization circuit 7 is added and stored moves to the right. Therefore, at the timing when the value of the counter 10 reaches 255, the presence / absence of reflected light exceeding the threshold is accumulated in the accumulated value storage memory 9 in time series in the counter unit. After the counter 11 reaches 255, it does not return to 0 even if a pulse from the oscillator 10 is input unless it is reset.

  In this state, the MPU 1 immediately instructs the drive circuit 22 to generate the next optical pulse. In this manner, the operation of irradiating the object to be measured with a laser beam a predetermined number of times, receiving and processing the reflected light, and adding the result to the integrated value storage memory 9 is repeated. Then, at the stage where the predetermined number of measurements are completed, the MPU 1 reads the value of each counter unit in the integrated value storage memory 9, and determines the distance corresponding to the counter unit giving the maximum value as the distance to the distance measurement object. And output it to finish the measurement.

  As can be seen by comparing the operation of the circuit shown in FIG. 1 described above with the operation of the prior art circuit shown in FIG. 9, in the embodiment of the present invention shown in FIG. 1, the reflected light obtained for each light irradiation is obtained. 9 is performed in the integrated value storage memory 9 in synchronization with the sampling pulse of the oscillator 10, whereas in the conventional technique shown in FIG. Therefore, the embodiment of the present invention shown in FIG. 1 does not require time for the MPU 21 to perform integration, and accordingly, the light irradiation interval can be shortened accordingly, so that one measurement time can be obtained. Can be shortened.

  Outputs S1 to S256 of the AND gate group 8b of the sampling circuit 8 are also led to the data evaluation circuit 12. FIG. 3 shows an example of the data evaluation circuit. The data evaluation circuit includes a 256-bit register 12a and an AND gate 12b. The register 12a stores the values of the outputs S1 to S256 of the AND gate group 8b of the sampling circuit 8 immediately before being input to each bit.

  In this example, when all the values of 3 to 7 bits (corresponding to the distance 3 m to 7 m (short distance portion)) of the register 12a are “1”, that is, when there is reflected light from the distance between them, the AND gate The output of 12b is set to “1”. The MPU 1 in FIG. 1 reads this output before commanding the next light emission, and issues a command to the threshold setting circuit 13 to increase the threshold. Instead, the driver circuit 2 may be instructed to reduce the output of the semiconductor laser 3, or the amplifier 6 may be instructed to lower the gain. Two or more may be performed simultaneously.

  In this way, if the threshold value is initially reduced, the threshold value is increased sequentially, the threshold value is fixed when the output of the AND gate 12b first becomes “0”, and measurement is performed. Measurements can be made with a threshold. Similarly, even when the output of the semiconductor laser 3 or the gain of the amplifier 6 is controlled, measurement can be performed with an appropriate output and gain.

  If the measurement speed is not a problem, the circuit configuration as shown in FIGS. 9 and 10 shown in the description of the prior art is used, the MPU 21 itself has a data evaluation circuit function, and the value of the register 28c is read. Thus, it is possible to determine the degree of continuity of the bit that is “1” and thereby perform control such as raising or lowering the threshold value. As described above, if the MPU is provided with the function of the data evaluation circuit, it is possible to perform control with high flexibility by software processing. Of course, the same data evaluation as that of the MPU can be realized by the circuit if the circuit is not complicated.

  FIG. 4 shows an outline of the configuration of the distance measuring apparatus according to the second embodiment of the present invention. The embodiment shown in FIG. 4 differs from the embodiment shown in FIG. 1 only in the configuration of the integrated value storage memory 9 and the data evaluation circuit 12, and therefore, the other components that are the same as those in FIG. The same reference numerals as those in FIG.

  In the embodiment shown in FIG. 4, the output of the sampling circuit 8 is input to the integrated value storage memory 9 via the data evaluation circuit 12. Details of these circuits are shown in FIG.

  In FIG. 5, the operations of the oscillator 10, the counter 11, and the sampling circuit 8 are the same as those described in FIG. In FIG. 5, the data evaluation circuit 12 has two 256-bit registers 12d and 12e, which are reset at the start of measurement. The output of the AND gate group 8b of the sampling circuit is input to the register 12d of the data evaluation circuit 12. The contents of the register 12d are transferred to the register register 12e upon receiving the output of the light emission detection circuit 14, and the register 12d is reset. When the measurement is completed at one light emission timing, the current measurement result is stored in the register 12d, and the previous measurement result is stored in the register 12e.

  The corresponding bits of the registers 12d and 12e are respectively input to the AND gate group 12c, and the output of the bits for which both the registers 12d and 12e are “1” is output to the integrated value storage memory 9. The corresponding counter unit is incremented. In this manner, the operation of irradiating the object to be measured with a laser beam a predetermined number of times, receiving and processing the reflected light, and adding the result to the integrated value storage memory 9 is repeated. Then, at the stage where the predetermined number of measurements are completed, the MPU 1 reads the value of each counter unit in the integrated value storage memory 9, and determines the distance corresponding to the counter unit giving the maximum value as the distance to the distance measurement object. And output it to finish the measurement.

  The function of the data evaluation circuit 12 in FIG. 5 is to perform control so as to add to the integrated value storage memory 9 only for bits for which continuous output is obtained in two measurements. By performing such processing, noise that appears instantaneously can be removed.

  In FIG. 5, two registers are provided so that only two consecutive outputs are integrated. However, when three or more registers are provided, reflected light is detected three or more times continuously. May be detected only. Furthermore, when the measurement speed may be slow, it goes without saying that the functions of the data evaluation circuit 12 and the integrated value storage memory 9 may be performed by the MPU 1.

  Another example of the sampling circuit 8 and the integrated value storage memory 9 is shown in FIG. This example corresponds to the circuit shown in FIG. 11 as a conventional example. The output of the binarization circuit 7 is input to the shift register 8c. When a signal for detecting the light emission of the laser is input from the light emission detection circuit 14, the counter 11 is reset to start counting pulses from the oscillator 10, and the clock input stop signal as the output is turned off (" 1 "), the AND gate 8d is opened, and the pulse from the oscillator 10 is input to the shift register 8c as a shift pulse. Therefore, the output of the binarization circuit 7 is sequentially input to the shift register 8c.

  When the value of the counter 11 reaches a value corresponding to the maximum measurement distance, a clock input stop signal is output from the counter 11 (one input of the AND gate 8d becomes “0”). As a result, the AND gate 8 is closed and the pulse of the oscillator 10 is not input to the shift register 8c, so that the value of the shift register 8c is held as it is. The counter 30 is configured not to be further incremented when the value reaches a value corresponding to the maximum measurement distance.

  In this state, when the next light emission detection signal comes from the light emission detection circuit 14, the counter 11 is reset and the above operation is repeated again. At that time, the output overflowing from the latch circuit at the final stage of the shift register 8 c is input to the adder 9 d of the integrated value storage memory 9. On the other hand, the selector 8f selects the output of the oscillator 10, and accordingly, the pulse from the oscillator 10 is input to the address counter 8e. The address counter 8e selects the selector 9b and the gate of the selector 9c of the integrated value accumulation memory 9. That is, which bit is selected as input / output in the memory circuit 9a of the integrated value accumulation memory 9 is determined. The memory circuit 9a is an N-set memory from mem1 to memN, and the input / output corresponding to the count value of the address counter 8e is connected to the outside through the selector 9b and the selector 9c. Each of mem1 to memN is composed of a predetermined number of bits.

  When the address counter 8e is 1, the content of mem1 is input to the adder 9d through the selector 9c, added to the output of the shift register 8c, and the result is stored in mem1 again through the selector 9b. That is, when the output of the shift register 8c is “1”, the content of mem1 is incremented by 1. When the output of the shift register 8c is “0”, the previous value is held as it is.

  The above operation is repeated each time a pulse is received from the oscillator 10, and the output of the shift register 8c is sequentially added to mem1 to memN. In this way, every time one measurement is performed with the output from the light emission detection circuit 14, the presence or absence of reflected light corresponding to the measurement distance section is accumulated in the memory circuit 9a.

  When the distance measurement is performed a predetermined number of times in this way and the measurement is completed, a reading request is made from the MPU 1 and the input of the selector 8f is switched to the input from the MPU oscillator. As a result, the address counter advances, and the values of mem1 to memN in the memory circuit 9a corresponding to the counter value are sequentially read into the MPU1 through the selector 9c.

  FIG. 7 shows another example of the data evaluation circuit. This is coupled to the sampling circuit shown in FIG. 6 and detects a saturation of the reflected signal from a short distance, and a control signal for reducing the laser emission intensity or reducing the gain of the amplifier 6. Is a circuit that outputs. The output from the shift register 8c shown in FIG. 6 is input to the selector 12g as a bit serial signal. The pulses from the oscillator 10 are input to the shift register read counter 12h and added. The output of the shift register 8c is output to the gate corresponding to the count number of the shift register read counter 12h among the gates of the selector 12g.

  Since the pulse from the shift register 8c is synchronized with the pulse from the oscillator 10, the pulse from the shift register 8c is sequentially output to different AND gates 12k (for example, from the upper side to the lower side in the figure). It will be. A signal “1” is output from the other gates of the selector 12g not selected as the gate to the AND gate 12k.

  The output of the AND gate 12k is input to the corresponding latch circuit 12m, but the output itself of the latch circuit 12m is another input of the AND gate 12k. The latch circuit 12m is initially set to “1” at the start of measurement. Therefore, since the latch command input enters the latch circuit 12m for each pulse of the pulse oscillator 10, the value of the corresponding AND gate 12k at that time becomes a new input to the latch circuit 12m.

  Now, once the output from the shift register 8c corresponding to the predetermined distance becomes “0”, the output of the corresponding AND gate 12k becomes “0”, and therefore the latch circuit 12m also becomes “0”. Once the latch circuit 12m becomes “0”, the output is inputted to the AND gate 12k. Therefore, the output of the corresponding AND gate 12k is always “0”. Therefore, the output of the latch circuit 12m is next to the latch circuit. It does not become “1” until 12m is initially set.

  If such a circuit is provided for a signal corresponding to an output at a short distance, when a predetermined number of measurements are performed, the latch circuit 12m corresponding to the distance at which the signal was “1” in all the measurements. Only the output becomes 1, and the output of the latch circuit 12m corresponding to the distance where the signal becomes “0” even once is “0”.

  The output of each latch circuit 12m is input to the OR circuit 12n, and when the measurement is performed a predetermined number of times and there is a measurement distance in which the signal is “1”, the output of the OR circuit 12n is It becomes “1”, and a control signal for reducing the emission intensity of the laser or lowering the gain of the amplifier 6 is output.

  FIG. 8 shows another example of the data evaluation circuit. This is coupled to the sampling circuit shown in FIG. 6. When the light emission intensity of the laser beam is too strong or the gain of the amplifier is too high, the noise is affected and the distance is increased over a wide range. This is to prevent a measurement error from occurring as a result that a reflected signal is continuously obtained.

  The output of the shift register 8c shown in FIG. 6 is input to the shift register 12p, and the pulse from the pulse oscillator 10 is shifted as a shift command. The output of each latch circuit constituting the shift register 12p is input to the AND gate 12q, and the output of the AND gate 12q is used as a latch command for the latch circuit 12r. The signal input of the latch circuit 12r is always “1”. Therefore, once all the latch circuits of the shift register 12p become “1”, that is, when the shift register 12p is composed of M bits, reflected signals are obtained continuously over M distance intervals. When the state is detected, the output of the AND gate 12q becomes 1, and the latch circuit 12r becomes "1" and is held. When the latch circuit 12r is in the “1” state, control for lowering the laser emission intensity or lowering the gain of the amplifier is performed by the control output.

It is a figure which shows schematic structure of the distance measuring device which is the 1st Embodiment of this invention. It is a figure which shows the relationship between the sampling circuit in the distance measuring device shown in FIG. 1, an integrated value storage memory, an oscillator, and a counter circuit. It is an example of the data evaluation circuit in FIG. It is a figure which shows the outline | summary of a structure of the distance measuring device which is the 2nd Embodiment of this invention. FIG. 5 is a diagram illustrating a relationship among a sampling circuit, a data evaluation circuit, and an integrated value storage memory illustrated in FIG. 4. It is a figure which shows the other example of a sampling circuit. It is a figure which shows the other example of a data evaluation circuit. It is a figure which shows the other example of a data evaluation circuit. It is a figure which shows the example of a structure of the conventional distance measuring device. It is a figure which shows the relationship between the sampling circuit shown in FIG. 9, an oscillator, and a counter circuit. It is a figure which shows the other example of a sampling circuit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Microprocessor unit, 2 ... Drive circuit, 3 ... Semiconductor laser, 4 ... Lens system, 5 ... Photodetector, 6 ... Amplifier, 7 ... Binarization circuit, 8 ... Sampling circuit, 8a ... Decoder, 8b ... AND Gate group, 8c ... shift register, 8d ... AND gate, 8e ... address counter, 8f ... selector, 9 ... integrated value storage memory, 9a ... memory circuit, 9b ... selector, 9c ... selector, 9d ... adder, 10 ... oscillator 11 ... counter circuit, 12 ... data evaluation circuit, 12a ... register, 12b ... AND gate, 12c ... register, 12d ... register, 12e ... AND gate group, 12g ... selector, 12h ... shift register read counter, 12k ... AND gate , 12m ... latch circuit, 12n ... OR circuit, 12p ... shift register, 12q ... AND gate 12r ... latch circuit, 13 ... threshold setting circuit, 14 ... emission detection circuit

Claims (1)

A light irradiator for irradiating the object to be measured with pulsed light;
A light receiving unit that receives reflected light from the distance measuring object and other objects, and determines that there is reflected light when the received light intensity exceeds a threshold; and
A counter unit having a plurality of counters provided corresponding to the division of time after irradiation with the light;
A distance measuring device having an arithmetic processing unit that reads the contents of the counter unit after a plurality of times of light irradiation, calculates the distance to the object to be measured by calculating the result,
When it is determined that there is the reflected light, the counter unit adds a predetermined number to the counter of the counter unit according to a time segment from when the light is irradiated until the reflected light is obtained. Is,
And it has a continuity processing unit, and the continuity processing unit determines whether or not there is the reflected light with respect to one light irradiation, and determines whether the reflected light is emitted after the light irradiation is performed. A storage unit for storing each time interval until the above-mentioned is obtained, and evaluates the continuity of the determination that the reflected light is present within a predetermined time interval, and accordingly, the threshold value and the light irradiation A distance measuring device having a function of instructing to adjust at least one of the intensity of light emitted from the unit and the sensitivity of the light receiving unit.

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