JP2776127B2 - Distance measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distance measurement for irradiating a pulsed light toward an object, receiving a reflected pulsed light from the object, and measuring a required time from irradiation to light reception to obtain a distance to the object. It concerns the device.

[0002]

2. Description of the Related Art An optical radar apparatus disclosed in, for example, Japanese Patent Application Laid-Open No. 2-228579 is known as this type of conventional apparatus. FIG. 4 shows a configuration of a conventional distance measuring apparatus, in which 1 is a light transmitting section for driving a light emitting element such as a laser diode to emit pulse light, and 2 is a clock generator for generating a clock pulse for generating pulse light. A light receiving unit 3 converts the reflected pulse light from the object 7 irradiated with the pulse light into an electric signal, a sample pulse generator 4, a sample and hold circuit 5, a distance to the object 7 and the like are detected. It is a processing unit.

[0005] Next, the operation of the conventional apparatus having the above configuration will be described with reference to FIGS. FIG. 5 shows an operation waveform of the clock generator 2 within a clock pulse period, and FIG. 6 shows an operation waveform at a time interval for performing one distance measurement. FIG.
FIGS. 5A and 6A are clock pulses, FIGS. 5B and 6B are pulse light waveforms, FIGS. 5C and 6C are sample pulses, FIGS. 6D shows the output of the light receiving unit 3, and FIGS. 5E and 6E show the sample and hold circuit 5.
The output of

The clock generator 2 generates a clock pulse with a time interval T longer than the time corresponding to the maximum measurement distance as shown in FIG. The light transmitting unit 1 generates pulse light shown in FIG. 5B in synchronization with the clock pulse, and the pulse light is reflected by the object 7 and received by the light receiving unit 3. The light receiving unit 3 converts and amplifies the reflected pulse light into an electric signal by photoelectric conversion, and inputs an output signal shown in FIG.

On the other hand, the sample pulse generator 4 counts clock pulses from the clock generator 2, and counts one cycle of a clock pulse count value equal to or greater than a value M obtained by dividing a maximum measurement distance by a distance resolution (FIG. 6 (a)). The clock pulse count value n is calculated in a minute time ΔT corresponding to the distance resolution.
FIG. 5 in which the clock pulse is delayed by the time multiplied by
The sample pulse shown in (c) is generated.

The sample hold circuit 5 samples the pulse signal of the reflected light with the sample pulse, and holds the signal level until the next sample pulse as shown in FIG. The held signal is a signal obtained by frequency-converting the waveform of the high-frequency reflected pulse light into a low-frequency signal as shown in FIG.

The processing section 6 compares the low-frequency output signal of the sample-and-hold circuit 5 with a predetermined threshold value, as shown in FIG.
A and B signals are detected as shown in A and B, and the distance to the object 7 is obtained from the count value of the clock pulse of the sample pulse generator 4 by the equation (1). Distance = count value × ΔT × light speed / 2 (1) That is, the distance is １ ／ of the pulse light stroke obtained by multiplying the time from light emission to light reception obtained from the clock pulse count value by the light speed.

[0008]

In the above-mentioned conventional apparatus, in order to reproduce the waveform of the reflected pulse light as a low-frequency signal for one distance measurement, the distance from the closest distance to the time corresponding to the maximum measurement distance is measured. Since the light receiving signals are sampled sequentially, the pulse light needs to be generated M times. Further, since the intensity of the reflected pulse light from the target object 7 decreases in inverse proportion to the fourth power of the distance, the intensity of the pulse light is short, although the pulse width is short so that the pulse light can be detected with sufficient sensitivity even at the maximum measurement distance. A very strong one having a peak light output of about several tens of watts is used.

[0009] By the way, if the user continuously mistakenly looks directly at the pulse light at a close distance when handling such an apparatus, he or she will be repeatedly exposed to the strong pulse light, possibly causing retinal damage or the like. To measure the distance to the object 7, the processing unit 6 compares the low-frequency signal of the reflected pulse light with a predetermined threshold value, and calculates the expression (1) from the number of samples when the threshold value is exceeded. Can calculate the distance with
The low frequency signal waveform after distance detection is no longer needed. That is, the generation of the pulse light from the detection of the object 7 to the distance corresponding to the maximum measurement distance only increases the stress and power consumption of the light emitting element such as the laser diode.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and while maintaining the accuracy and performance of distance measurement, even if the pulsed light is directly viewed during handling, the eye may be damaged. It is an object of the present invention to provide a safe and highly reliable distance measuring device that can provide no stress and can reduce stress and power consumption of a light emitting element.

[0011]

A distance measuring apparatus according to the present invention detects presence / absence and distance of an object from an output of a sample hold circuit and a delay time of a sample pulse.
At the time of this detection, a processing unit for stopping generation of pulse light from the light transmitting unit is provided.

[0012]

When the reflected light from the object is detected, the processing unit in the present invention outputs a command to stop the generation of the pulsed light in the light transmitting unit at least until the start of the next sweep. As a result, generation of pulse light corresponding to the remaining sweep from the detection distance to the maximum measurement distance is suppressed.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a configuration according to this embodiment, wherein 1 is a light transmitting unit for driving a light emitting element such as a laser diode to generate pulsed light, and 2 is a clock for generating a clock pulse serving as a pulse light emission timing of the light transmitting unit 1. A generator 3 is a light receiving section, 4 is a sample pulse generator that counts the clock pulse, and generates a sample pulse delayed by the clock pulse by a time interval corresponding to the counted value. A sample and hold circuit 6 samples the output signal of the light receiving unit 3 with the generated sample pulse. The sample and hold circuit 6 compares the output signal of the sample and hold circuit 5 with a predetermined level, detects the object 7, calculates the distance, and sends a pulse to the light transmitting unit 1. The processing unit 7 for instructing the stop of light generation is a distance measurement target object.

Next, the operation of the above configuration will be described with reference to FIGS. FIG. 2 shows an operation waveform of the clock generator 2 within a clock pulse period, and FIG. 3 shows an operation waveform at a time interval for performing one distance measurement. FIG. 2 (a), FIG.
2 (a) is a clock pulse, FIGS. 2 (b) and 3 (b) are pulse light waveforms, FIGS. 2 (c) and 3 (c) are sample pulses, and FIGS. 2 (d) and 3 (d) are FIGS. 2E and 3E show output signals of the light receiving section 3 and FIGS.

The operation of irradiating the object 7 with pulsed light and obtaining the distance to the object 7 is the same as the conventional operation.
The operation after detecting is described. When the processing unit 6 compares the output signal of the sample hold circuit 5 with a predetermined threshold value and detects a signal level equal to or higher than the threshold value (FIG. 3 (e)).
A, B), the processing unit 6 receives the count value of the clock pulse of the sample pulse generator 4, obtains the distance to the object 7 according to the equation (1), and stops the light transmission unit 1 from emitting pulses thereafter. Output the command to be executed. In response to this command, the light transmitting unit 1 stops the pulse emission as shown by C in FIG. 3B even if a clock pulse is input from the clock generator 2.

The stop of the pulse emission of the light transmitting unit 1 is performed as shown in FIG.
As shown in (b), the sample pulse generator 4 continues counting the clock pulses from the clock generator 2 and, after reaching the count value corresponding to the maximum measurement distance, continues until the next distance measurement period starts. You. As a result, as shown in FIG. 3D, the light receiving signal waveform is not output from the light receiving section 3 during the pulse emission stop period, and the output signal of the sample and hold circuit 5 also returns to the no signal state as shown in FIG. . Thereafter, the clock pulse count value is initialized, and when the next measurement cycle starts, the processing unit 6 cancels the light transmission stop command output to the light transmission unit 1, and
The light transmitting unit 1 emits pulse light in synchronization with the clock pulse of the clock generator 2, and repeats the distance measuring operation.

Here, assuming that a person handling the apparatus or another person erroneously looks into the light transmitting unit 1 during the distance measurement and directly looks at the pulse light and is exposed to the radiation, conventionally, the person who was exposed to the pulse light continuously emits the pulse light. However, in this embodiment, the light receiving unit 3 receives the reflected pulse light from the A-bomb survivor, and the processing unit 6 detects it and immediately stops the pulse emission of the light transmitting unit 1. A-bomb survivors can significantly reduce the amount of pulsed light exposure.

For example, if the maximum measurement distance is 100 m, the distance resolution is 100 mm, and the measurement period is 0.1 s, the number of pulsed light beams generated in one distance measurement is 1,000.
Now, the pulse light exit (100 mm
Less than 10 s, the distance measurement is 1
Since it is performed 00 times, the number of times that the survivor is exposed to the pulse light is 100,000 times in the past. On the other hand, in this embodiment, since only one pulse is exposed for one measurement, a total of one pulse is exposed.
The exposure is 00 times, and the exposure dose is 1/1000 of the conventional dose, and it is an extremely safe distance measuring device.

As the distance between the distance measuring device and the A-bomb survivor increases, the degree of reduction in the number of exposures decreases, but the intensity of the pulsed light entering the pupil of the A-bomb survivor decreases in inverse proportion to the square of the distance. Exposure itself decreases. Therefore, this embodiment can ensure high security in all areas.

According to JIS C6802, the maximum allowable exposure (MP
Since E) must be reduced in proportion to the 1 / 4th power of the number of exposures N, the maximum allowable exposure amount in the embodiment is 5.
6 times larger. This means that assuming the same maximum allowable exposure amount as in the prior art, the output of the pulse light is 5.
Since the signal can be increased about six times, the S / N of the output signal of the light receiving unit 3 is improved by 5.6 times, and the distance measurement capability such as expansion of the maximum measurable distance can be greatly improved as compared with the related art. .

On the other hand, when the distance measuring device of this embodiment is used, if the chance of detecting the object 7 is on average within the distance measurement range from the front surface of the distance measuring device to the maximum measurement distance, the object 7 can be detected in the embodiment. Is detected, the generation of the pulse light is stopped, so that the total number of times of generation of the pulse light is の of that in the related art. As a result, the operating temperature of the light emitting element is reduced, and the stress applied to the light emitting element is reduced to half or less, so that the life of the element is extended more than twice and the reliability is greatly improved.

[0022]

As described above, according to the present invention, useless pulse light emission after detecting an object is suppressed, and the operator or the like directly looks at the pulse light on the front surface of the light transmitting unit. Also, since the processing unit detects the presence of the handler or the like and stops generating the pulse light thereafter, the exposure amount of the handler or the like can be reduced, and the safety can be increased without lowering the performance. . In addition, for the same exposure dose,
Since the maximum distance range that can be detected is increased , the performance can be dramatically improved. Further, since the total number of generations of the pulse light is reduced, the life of the light emitting element of the light transmitting unit is extended, and the reliability can be improved.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a device of the present invention.

FIG. 2 is an operation waveform diagram within a clock pulse period of the device of the present invention.

FIG. 3 is an operation waveform diagram of the device of the present invention at distance measurement time intervals.

FIG. 4 is a configuration diagram of a conventional device.

FIG. 5 is an operation waveform diagram in a clock pulse cycle of the conventional device.

FIG. 6 is an operation waveform diagram at a distance measurement interval of the conventional device.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 light transmitting unit 2 clock generator 3 light receiving unit 4 sample pulse generator 5 sample hold circuit 6 processing unit 7 object

Claims (1)

(57) [Claims] 1. A light transmitting unit for generating pulse light in synchronization with a clock pulse output from a clock generator, and a light receiving unit for receiving reflected pulse light from an object irradiated with the pulse light and converting the reflected pulse light into an electric signal. And a sample pulse that generates a sample pulse at a time delayed by a minute time interval corresponding to a predetermined distance from the generation timing of the pulse light in one sweep cycle with a plurality of pulse light generations as the sweep cycle A generator, a sample-and-hold circuit for sampling the output signal of the light-receiving unit by the sample pulse, and detecting the presence or absence of the object and the distance to the object from the output of the sample-and-hold circuit and the delay time of the sample pulse; A distance measuring unit comprising a processing unit for stopping generation of pulse light from the light transmitting unit when detecting presence / absence and a distance apparatus.