JPH062264U - Distance measuring device - Google Patents

Abstract

(57) [Summary] [Purpose] Even if the amount of received light changes, it enables high-speed and highly accurate distance measurement. [Structure] The first time measuring circuit 9 measures a rising time position at which the light receiving signal output from the light receiver 6 becomes a predetermined value or more, and the second time measuring circuit 10 measures the light receiving signal output from the light receiver 6. The fall time at which is less than or equal to a predetermined value is measured. The arithmetic processing circuit 11 calculates the distance based on the center position of the measured rise time position and fall time position.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a distance measuring device using light pulses.

[0002]

[Prior art]

 In recent years, there has been an increasing demand for distance sensors that can measure relatively long distances in real time for controlling automated guided vehicles and robots, or for preventing vehicle collisions. It is being advanced.

The measurement principle of the laser range finder uses the propagation time of the optical pulse, and measures the time until the optical pulse emitted from the light source is reflected by the measurement object and returns again. To find the distance. The relationship between the distance (L) and the propagation time (T) is represented by T = (2L) / C (C: speed of light), and is specifically measured by a system as shown in FIG.

In FIG. 3, first, in response to the trigger signal output from the trigger generation circuit 1, the pulse drive circuit 2 causes the laser light source 3 to emit an optical pulse, and at the same time, the time measurement circuit 12 measures the time. To start. The light pulse is emitted toward an object to be measured via a light transmitting system (not shown). The light pulse reflected by the measuring object is detected by the light receiver 6 via a light receiving system (not shown). The light receiving signal output from the light receiver 6 is amplified by the light receiving circuit 7 and then input to the comparator 8. The comparator 8 outputs a light reception timing signal when it is equal to or more than a predetermined threshold value. The time measuring circuit 12 ends the time measurement in response to the rising of the light receiving timing signal from the comparator 8. The distance L is obtained from the above relationship with the time T measured by the time measuring circuit 12.

[0005]

[Problems to be solved by the device]

 In the above-mentioned conventional laser distance measuring device, the time measuring circuit 12 receives the light receiving signal in response to the rising edge of the light receiving timing signal output from the comparator 8 when the output signal of the light receiving circuit 7 is equal to or higher than a predetermined threshold value. The time measurement is completed at the rising time position where is above the specified value.

However, in this method, as shown in FIG. 4, when the amount of received light, that is, the level of the received light signal changes, the rising time position becomes different like t1 and t2, and a distance measurement error occurs. There was a problem.

Conventionally, as a countermeasure against this, for example, as described in JP-B-51-8338, JP-B-51-8339 and JP-B-51-8340, the transmittance continuously variable inserted in the optical path. Although there is a method to perform measurement by adjusting the signal level to a constant level using a type optical filter, it is not suitable for real-time measurement because it requires adjustment time.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a distance measuring device capable of performing high-speed and highly accurate distance measurement even when the amount of received light changes. .

[0009]

[Means for Solving the Problems]

 The distance measuring device according to the present invention sends an optical pulse emitted from a light source to an object to be measured, receives a reflected pulse from the object to be measured by a light receiver, and measures the propagation time of the optical pulse. By measuring the distance to the object to be measured, the rise time position at which the received light signal output from the photodetector exceeds the specified value and the fall time at which the received light signal falls below the specified value. The time measuring means for measuring the position (for example, the first and second time measuring circuits 9 and 10 in the embodiment of FIG. 1) and the distance based on the measured center position of the rise time position and the fall time position. And an arithmetic processing unit (for example, the arithmetic processing circuit 11 of the embodiment of FIG. 1) for calculating

[0010]

[Action]

 In the distance measuring device of the present invention having the above configuration, the rising time position and the falling time position of the received light signal are measured, the center position of the received light signal is determined from these time positions, and the distance is calculated based on this center position. It is calculated.

[0011]

【Example】

 Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows an embodiment of a distance measuring device according to the present invention. First, in response to the trigger signal output from the trigger generation circuit 1, the pulse drive circuit 2 causes the laser light source 3 to emit an optical pulse, and at the same time, the first and second time measurement circuits 9 and 10 measure the time. To start. The light pulse is emitted toward the object to be measured via the light transmitting system 4.

The light pulse reflected by the measuring object is detected by the light receiver 6 via the light receiving system 5. The light receiving signal output from the light receiver 6 is amplified by the light receiving circuit 7 and then input to the comparator 8. The comparator 8 outputs a light receiving timing signal when the output signal of the light receiving circuit 7 is equal to or higher than a predetermined threshold value. The output of the comparator 8 is supplied to the first time measuring circuit 9 and the second time measuring circuit 10.

As shown in FIG. 2, the first time measurement circuit 9 finishes the measurement at the rise of the output of the comparator 8 and measures the time T1 to the rise time position at which the received light signal becomes a predetermined threshold value or more. taking measurement. As shown in FIG. 2, the second time measuring circuit 10 finishes the measurement at the fall of the output of the comparator 8 and measures the time T2 to the fall time position at which the received light signal becomes below a predetermined threshold value. The times T1 and T2 measured by the first and second time measuring circuits 9 and 10 are supplied to the arithmetic processing circuit 11. The arithmetic processing circuit 11 calculates the center position of the received light signal, that is, (T1 + T2) / 2, based on the times T1 and T2, and obtains the distance from this.

In the above embodiment, when the received light signal waveform is symmetrical, the obtained center position (T1 + T2) / 2 coincides with the peak position of the received light signal. Does not occur. In addition, the error is smaller than that of the conventional method even when the method is asymmetric.

In the above embodiment, the second time measuring circuit 10 measures the time T2 from the input of the trigger signal to the fall time position of the received light signal. A circuit for measuring the time interval between the rising time position and the falling time position may be provided, and the time interval thus measured may be measured by the first time measuring circuit 9 and added to the time T1. In essence, if the rise time position where the received light signal is above the specified value and the fall time position where the received light signal is below the specified value can be obtained, the center position of the received light signal can be obtained as in the above embodiment. Can be asked.

[0016]

[Effect of device]

 As described above, according to the present invention, the rising time position where the received light signal is above a predetermined value and the falling time position where the received light signal is below a predetermined value are measured, and the received light signal is measured from these time positions. Since the center position is calculated and the distance is calculated based on this center position, even if the amount of received light changes, high-speed and highly accurate distance measurement is possible.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of a distance measuring device of the present invention.

FIG. 2 is a view showing a method of measuring a light receiving signal position according to the present invention.

FIG. 3 is a block diagram showing a measurement system of a conventional laser distance measuring device.

FIG. 4 is a diagram showing a conventional method for measuring a received light signal position.

[Explanation of symbols]

 6 light receiver 7 light receiving circuit 8 comparator 9 first time measuring circuit 10 second time measuring circuit 11 arithmetic processing circuit

Claims (1)

[Scope of utility model registration request] 1. An optical pulse emitted from a light source is sent to an object to be measured, a reflected pulse from the object to be measured is received by a photodetector, and a propagation time of the optical pulse is measured. In a distance measuring device for measuring a distance to a measurement object, a rising time position at which a light reception signal output from the light receiver is a predetermined value or more and a falling time position at which the light reception signal is a predetermined value or less are measured. A distance measuring device comprising: time measuring means; and arithmetic processing means for calculating a distance based on a center position between the rising time position and the falling time position.