JPH07229965A - Distance measuring apparatus - Google Patents

Abstract

PURPOSE:To obtain a fast and highly accurate distance measuring apparatus which makes possible the preventing of erroneous measurement of a distance by interference by including a trigger interval altering means, a median selection means and the like. CONSTITUTION:In a measuring gate circuit 9, a fixed time of a measuring gate is formed with the receiving of a trigger signal of a trigger generation circuit 1 and a digital reception signal of a comparator 8 passes within the gate while it is cut outside the gate. A time measuring circuit 10 also starts the measuring of time when receiving a trigger of a circuit 1. The signal passing through the measuring gate is inputted into the circuit 10 to complete the measurement of time and a time measurement data obtained is outputted. An arithmetic processing circuit 11 stores a plurality of time measurement data by trigger signals varied in generation interval and selects a median by rearranging the data in the larger order to compute a distance based on the median of the time measurement data. When the number of erroneous distance measurement data is held under a half of the total number by this system of obtaining the median, it becomes possible to obtain a correct distance measured value free from the number and values of the erroneous distance measurement data.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distance measuring device. More specifically, a distance measurement that measures the distance to the distance measurement target by emitting a light pulse to the distance measurement target and measuring the round trip time of the light until the reflected light from the distance measurement target is received. It relates to the device.

[0002]

2. Description of the Related Art In recent years, there has been an increasing demand in various fields to obtain distance information by mounting a distance measuring device on a moving object for the purpose of improving safety and automation. For example, a distance measuring device is mounted on a robot, an automobile, or a train to prevent collision of these moving objects, or a distance measuring device is mounted on a carrier vehicle used in a factory to control the stop position of the carrier vehicle. It is used to As such a distance measuring device, a device that emits an optical pulse from a laser light source to a measurement target, receives an optical pulse reflected by the measurement target, and measures the distance to the distance measurement target is widely used. Since it can measure the distance in a short time, it is often used especially as a sensor for preventing collision of a moving body or the like.

The relationship between the distance L to the object to be measured and the round-trip time T of the light pulse is expressed by the following equation (1). T = (2L) / C Formula (1) where C is the speed of light. FIG. 3 is a block diagram of a configuration of a conventional example. At the same time as the light pulse is emitted from the light source 3 by the trigger signal output from the trigger generation circuit 20 at a constant cycle, the time measurement circuit 1
0 starts the measurement. The light pulse is emitted to the outside through a light transmitting optical system (not shown). The reflected light pulse from the measurement target enters a light receiving optical system (not shown) and enters the light receiver 6
The signal is photoelectrically converted by and the received signal is output. The received signal is amplified by the amplifier circuit 7, converted into a digital signal by the comparator 8, and input to the time measuring circuit 10 as a stop signal to complete the measurement. The distance is obtained from the measured round-trip time and the above-mentioned relational expression.

When such a distance measuring device is mounted on a moving body, interference may occur between the distance measuring device mounted on another moving body and the device. As a specific example, in a situation where two moving bodies equipped with a distance measuring device face each other or are parallel to each other toward the same measurement target, the light emitted from one distance measuring device is used. The pulse will also be input to the other distance measuring device.
As a result, there is a problem that erroneous distance measurement occurs depending on the timing of measurement.

A technique for solving this problem is disclosed in, for example, Japanese Patent Application Laid-Open No. 61-149879. This technique is a method of reducing the probability of interference by randomizing the light pulse emission period and shifting the measurement timing. Even if there is erroneous distance measurement data due to interference, the error is not generated in the distance measurement value by excluding it from the average value of a plurality of data.

[0006]

However, Japanese Unexamined Patent Application Publication No. Sho 6
In the technique disclosed in JP-A-1-149879, when the magnitude of error in erroneous distance measurement data is large or the number of errors is large, the average value deviates greatly from the true value, and a highly accurate distance measurement value is obtained. There was a problem that I could not get it.

In view of such a situation, an object of the present invention is to provide a high-speed and highly accurate distance measuring device which prevents erroneous distance measurement due to interference of other devices.

[0008]

A distance measuring device according to the present invention includes a trigger signal output means for outputting a trigger signal for emitting an optical pulse from a light source, and an optical pulse emitted by receiving the trigger signal for emission to a measurement target. A light transmitting means, a light receiving means for receiving reflected light from the measurement object and outputting a reception signal, a time measuring means for measuring a time from the trigger signal being output to the reception signal being output, In a distance measuring device comprising a calculating means for calculating the distance from the time value measured by the time measuring means to the measurement target, the trigger interval changing means for changing the interval of the trigger signal, and the interval by the trigger interval changing means. The method further comprises a median value selecting means for selecting a median value from the plurality of time values measured by the optical pulses emitted by the changed plurality of trigger signals. Stage, performs a calculation based on the median value.

[0009]

In the distance measuring device of the present invention, the light emitting interval of the light source is changed, the median value (median) is selected from the plurality of measured time values, and the distance to the object to be measured is calculated based on the median value. Is done.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. In FIG. 1 showing the configuration of the present embodiment, a variable trigger generating circuit 1 is a circuit which outputs a trigger signal at different intervals,
The pulse drive circuit 2 is a drive circuit that receives a trigger signal and supplies a pulse current to the light source 3, and the light source 3 is supplied with the pulse current and generates an optical pulse. The light transmitting system 4 is an optical system that emits a light pulse to the outside, and the light receiving system 5 is an optical system that collects and receives a part of the light pulse reflected by the measurement target. The light receiver 6 is a photoelectric conversion element that photoelectrically converts the light collected by the light receiving system 5 and outputs a reception signal. The amplifier circuit 7 is a circuit that amplifies the received signal and outputs the amplified signal.
Is a circuit that receives a received signal, converts it into a digital received signal, and outputs it.

The measurement gate circuit 9 is a variable trigger generation circuit 1.
It is a circuit that receives a trigger signal from the control gate to form a measurement gate for a certain period of time, and passes the digital reception signal from the comparator 8 in the measurement gate. Time measurement circuit 10
From the reception of the trigger signal from the variable trigger generation circuit 1,
This is a circuit that measures the time until the digital reception signal from the measurement gate is received. The arithmetic and measurement circuit 11 stores a plurality of time measurement data measured at different trigger signal generation intervals, rearranges these data in ascending order or in ascending order, and selects the median value. It is a circuit that calculates the distance based on.

Next, the operation will be described. When the trigger signal is output from the variable trigger generation circuit 1, the light source 3 is turned on via the pulse drive circuit 2 and an optical pulse is generated. The light pulse is photoelectrically converted by the light receiver 6 as reflected light from the measurement object via the light transmitting system 4 and the light receiving system 5. The received signal is amplified by the amplifier circuit 7, converted into a digital received signal by the comparator 8 and output.

On the other hand, the measurement gate circuit 9 receives a trigger signal to form a measurement gate for a fixed time, and the digital reception signal from the comparator 8 passes through the measurement gate if it is inside the measurement gate, and is outside the measurement gate. If there is, you will be blocked by this. The time measurement circuit 10 receives the trigger signal from the variable trigger generation circuit 1 and starts time measurement at the same time as reception, and the digital received signal that has passed through the measurement gate is input to the time measurement circuit 10 and becomes a stop signal. Then, the time measurement is completed and the obtained time measurement data is output.

The arithmetic processing circuit 11 stores a plurality of time measurement data by trigger signals having different generation intervals, sorts these data in ascending order or in ascending order and selects a median value. Calculate the distance based on.

The case where the measurement timing interferes with another measurement distance device (hereinafter referred to as another device) will be described with reference to the time chart shown in FIG. A series of n light pulses is a series of randomly generated trigger signals S1 → S2.
→ S3 ... → Sn causes the light source to emit light at random light emission intervals, T1 → T2 → T3 ... → Tn. The length t of the measurement gate is a length at which the reflected light from the maximum measurement distance determined by the specifications of this device can be detected. t is smaller than any of the random light emission intervals from the light source. The reception signal S1 ′ → S2 ′ → S3 ′ ... → Sn ′ is generated after the time td has elapsed from the output of the trigger signal, and the time td
The distance is calculated based on Since a series of n optical pulses are emitted for an extremely short time, the change in the distance between the device and the measurement object is extremely small, and the time from when the trigger signal is output until when the reception signal is output Time can be regarded as constant.

Here, if another measuring distance device (hereinafter referred to as another device) interferes, the trigger signal S2 is temporarily sent from this device.
When the optical pulse Q1 output from another device is incident and a reception signal is generated by the time when the corresponding reception signal S2 'is generated after the output of the output signal, the measurement signal passes through the measurement gate and an interference state occurs. At that point, the time measurement circuit 10 finishes the measurement and outputs the time measurement data to the arithmetic processing circuit 11. At this time, the time measurement data is erroneous distance data. However, since the light emitting period is random in this device, the probability of subsequent interference is t / T or less. Here, T is an average light emission interval.

The arithmetic processing circuit 11 stores n pieces of time measurement data measured by the above method, and rearranges them in ascending or descending order regardless of whether these data are erroneous distance values or not, A value is selected and the distance is calculated based on the median of the time measurement data. The simple rearrangement of the numerical values and the selection of the median value can be easily performed in the arithmetic processing circuit 11.

In order to obtain accurate data at high speed in the measurement of a moving body, it is desirable to emit a series of a large number of light pulses in a short time, which requires T to be as short as possible. This also increases the probability of incorrect distance measurement. In the conventional distance measuring device, since the method of averaging a plurality of data is used, the average value itself deviates from the true value as the probability of erroneous distance measurement increases, and it is correct even if data outside the average value is excluded. The problem was that no distance measurement value could be obtained. However, since this device uses the method of taking the median value of multiple data, if the number of erroneous distance measurement data is less than half, it is possible to obtain the correct distance measurement value regardless of the number or value of erroneous distance measurement data. However, it is possible to easily realize that the erroneous distance measurement data is less than half by setting t and T.

Although the light emitting interval of the light source is randomly changed in this embodiment, it is also possible to prevent the erroneous distance measurement by adopting another suitable changing method.

[0020]

According to the present invention, the light emitting interval of the light source is changed, and the median value of a plurality of measured data is selected to calculate the measurement distance, so that erroneous distance measurement due to interference of other devices is prevented. A high-speed and highly accurate distance measuring device can be obtained.

[Brief description of drawings]

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

FIG. 2 is a time chart showing the timing of one embodiment of the present invention.

FIG. 3 is a block diagram showing a configuration of a conventional example.

[Explanation of symbols]

 1 ... ・ Variable trigger generating circuit 2 ・ ・ ・ ・ ・ ・ Pulse driving circuit 3 ・ ・ ・ ・ Light source 4 ・ ・ ・ ・ Light transmitting system 5 ・ ・ ・ ・ Light receiving system 6 ・ ・ ・Amplification circuit 8 ... Comparator 9 ... Measurement gate circuit 10 ... Time measurement circuit 11 ... Arithmetic processing circuit

Front Page Continuation (72) Inventor Shin Nagase 2-8-4 Kitayuki Nishi-ku, Yokohama-shi, Kanagawa Prefecture Nikon System Co., Ltd.

Claims (1)

[Claims] 1. A trigger signal output means for outputting a trigger signal for emitting a light pulse from a light source, a light sending means for emitting the light pulse emitted in response to the trigger signal to a measurement target, and reflection from the measurement target. A light receiving unit that receives light and outputs a reception signal, a time measuring unit that measures the time from the trigger signal is output until the reception signal is output, and the measurement target is based on the time value measured by the time measuring unit. In a distance measuring device having a calculating means for calculating the distance to, a trigger interval changing means for changing the interval of the trigger signal and a plurality of trigger signals whose intervals are changed by the trigger interval changing means are emitted. It comprises a median value selecting means for selecting a median value from the plurality of time values measured by the light pulse, and the arithmetic means performs an arithmetic operation based on the median value. Distance measurement apparatus according to symptoms.