JPH07248374A - Distance measuring device - Google Patents

Abstract

PURPOSE:To provide a distance measuring device by which stains sticking to transmitting-receiving optical systems can be detected and high distance measuring accuracy can be maintained without increasing part items. CONSTITUTION:A reference object 10 is arranged in front of transmitting- receiving optical systems 2 and 3, and a light pulse from a light source 1 is reflected, and a reference signal is outputted by a light receiving means 4. The size of the reference signal is measured by a measuring means 17, and stains on front surfaces of the transmitting receiving systems 2 and 3 are detected according to the size. Output time of the reference signal is measured by a timer means 13, and a distance operation means 16 corrects going and returning time by the output time of the reference signal, and performs operation on a distance.

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, an automobile that measures the distance to the object to be measured by emitting a light pulse to the object to be measured and measuring the round-trip time of the light until the reflected light from the object to be measured is received. The present invention relates to a distance measuring device mounted on a moving body.

[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 Such a distance measuring device generally emits light from a light source to an object to be measured, receives light reflected by the object to be measured, and measures the distance to the object to be measured.

In this type of distance measuring device, if dirt or the like adheres to the portions of the cover glass that are on the optical paths of both the light projected onto the object to be measured and the light reflected and returned from the object to be measured, the optical measurement is performed optically. Such abnormalities may occur, give an error in the measured value, or decrease the maximum measurement distance. In addition, when measuring the transit time of light waves, a high time resolution of several nanoseconds or less is generally required, so the delay time of the electric circuits in the transmission drive system, reception processing system, and distance calculation system due to ambient temperature fluctuations, etc. Changes in the distance greatly affect the measurement accuracy of the rangefinder, and the error in the measured values due to environmental changes was not negligible.

Conventionally, in order to solve the problem of the error of the measured value due to the dirt of the optical system, for example, Japanese Patent Publication No. 3-301.
The technique disclosed in Japanese Patent No. 16 is known. The structure is shown in FIG. The light source 1 is a laser that emits projection light of an optical pulse for distance measurement, and the light-sending lens 2 is an optical system that collects the projection light and projects it on an object to be measured (not shown). The light-receiving lens 3 is an optical system that collects the reflected light that has been reflected and returned from the measurement target (not shown) after projection and makes it incident on the light-receiving element 4. The cover glass 5 is provided on the surface of the light-transmitting lens 2 and the light-receiving lens 3 facing toward the object to be measured,
The light source 1, the light-transmitting lens 2, the light-receiving lens 3, the light-receiving element 4, and other members are protected from the outside, and the projection light and the reflected light are transmitted through the cover glass 5. The reference light receiving element 6 measures the level of scattered light generated when dirt is attached to the cover glass 5 and detects dirt on the cover glass 5.

Further, in order to solve the problem of measurement value error due to environmental changes, for example, the technique shown in FIG. 5 is used. The light from the light source 1 is projected through the light transmitting lens 2, and the light reflected from the measurement object (not shown) enters the light receiving lens 3 and is received by the light receiving element 4. Part of the light emitted from the light source 1 is partially split into a reference optical path by the beam splitter 7, and is received by the reference light receiving element 6 to output a reference signal. Then, by subtracting the time obtained by passing through the reference optical path from the time obtained from the measurement object, the delay time change can be offset, and the distance to the target object can be obtained more accurately. .

[0006]

However, the technique shown in FIG. 4 requires the reference light receiving element. The arrangement position of the light source and the light receiving element is largely restricted, and the part irradiated with the light from the light source stays within a limited range, and the dirt is detected by the part through which the projection light of the cover glass is transmitted and through the reflected light. It is not possible for the whole part, and there is a problem that the dirt adhesion position of the cover glass where the light incident on the reference light receiving element is reflected and the position where the projected light and the reflected light are transmitted do not necessarily match. It was

Further, the technique shown in FIG. 5 requires a beam splitter and a reference light receiving element, and there is a problem in that the manufacturing cost increases as the number of parts increases.

In view of the above problems, the present invention can detect whether dirt is attached to any of the cover glass or the like where projection light is transmitted or where reflected light is transmitted, and does not increase the number of parts. An object of the present invention is to provide a distance measuring device that maintains high distance measuring accuracy.

[0009]

According to a first aspect of the present invention, there is provided a light source for generating an optical pulse in response to a lighting timing signal, a light transmitting lens for transmitting the optical pulse to an object, and the object. A light receiving lens for receiving the light pulse reflected by an object, a light receiving means for photoelectrically converting the light pulse to output a reception signal, and a time measuring means for measuring the output time of the lighting timing signal and the output time of the reception signal And a distance calculating device for calculating a distance to the object from a round-trip time of the light pulse to the object measured by the time measuring means, wherein light is transmitted from the light transmitting lens. A reference object arranged at a position where the optical path of the optical pulse and the optical path of the optical pulse received by the light receiving lens are superposed, and the light receiving means for receiving the optical pulse reflected by the reference object Measuring means for measuring the magnitude of the reference signal to be output, and dirt detecting means for detecting dirt on the front surface of the light transmitting lens or the light receiving lens based on the magnitude of the reference signal measured by the measuring means. It is equipped with.

The time measuring means measures the output time of the reference signal, and the distance calculating means calculates the distance to the object from the round-trip time corrected based on the output time of the reference signal. desirable.

According to a third aspect of the present invention, a light source for generating an optical pulse in response to a lighting timing signal, a light transmitting lens for transmitting the optical pulse to an object, and the light reflected by the object. A light-receiving lens for receiving a pulse, a cover glass for covering the front surfaces of the light-transmitting lens and the light-receiving lens,
Light receiving means for photoelectrically converting the light pulse to output a reception signal, time measuring means for measuring the output time of the lighting timing signal and the output time of the reception signal, and the light pulse of the light pulse measured by the time measuring means. In a distance measuring device comprising a distance calculating means for calculating a distance to the object from a round trip time to the object, an optical path of an optical pulse transmitted from the light transmitting lens outside the cover glass. A reference object arranged at a position where the optical path of the light pulse received by the light receiving lens is superposed, and the magnitude of the reference signal output by the light receiving means upon receiving the light pulse reflected by the reference object is measured. Contamination for detecting contamination of the cover glass on the front surface of the light-transmitting lens or the light-receiving lens based on the measuring means and the magnitude of the reference signal measured by the measuring means. Those having a detecting means.

The time measuring means measures the output time of the reference signal, and the distance calculating means calculates the distance to the object from the round-trip time corrected based on the output time of the reference signal. desirable.

[0013]

The light pulse from the light source travels back and forth to the object, and the distance is calculated by the distance calculation means from the round-trip time. At that time, a part of the light pulse sent from the light source through the light sending lens is reflected by the reference object, and a part of the reflected light pulse passes through the light receiving lens and outputs the reference signal by the light receiving means.
The size of the reference signal is measured by the measuring means, and the dirt detecting means detects dirt on the front surface of the light-transmitting lens or the light-receiving lens or on the front surface of the cover glass when there is a cover glass based on the size of the reference signal. On the other hand, the output time of the reference signal is measured by the time measuring means, and the distance calculating means calculates the distance to the object by correcting the round-trip time based on the output time of the reference signal.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to FIG. The light source 1 is a semiconductor laser that generates a light pulse signal for distance measurement, and the light transmitting lens 2 is an optical system that projects the light pulse signal onto the measurement target 8. The light receiving lens 3 is an optical system that collects the light pulse signal that is reflected from the measurement target 8 after the light pulse signal is projected and returns the light pulse signal to be incident on the light receiving element 4. The light-transmitting lens 2 and the light-receiving lens 3 are exposed directly to the front surface of the apparatus to be stained. The light receiving element 4 is a photodiode, and the electric signal amplifier 9 is a circuit for converting the electric signal photoelectrically converted by the light receiving element 4 into a current voltage and amplifying the amplified electric signal to output a reception signal.

The reference object 10 is arranged in the optical path of the optical pulse signal projected from the light transmitting lens 2. At that position, the light pulse signal projected on the reference object 10 is reflected, and a part of it is received by the light receiving lens 3 to receive the light receiving element 4.
It is a position that can be incident on.

The trigger generating section 11 is a circuit for outputting a pulse generating trigger to the pulse generating circuit 12 and the time measuring section 13. The pulse generating circuit 12 is a circuit for generating an optical pulse signal by the pulse generating trigger and driving the light source 1. is there. The time measuring unit 13 calculates the time difference between the output time of the pulse generation trigger and the output time of the reception signal output from the electric signal amplifier 9.
It is a circuit that counts the number of clocks output from the reference clock 15. The distance calculation unit 16 is a circuit that calculates the distance to the measurement target object 8 from the time difference measured.

The signal level measuring unit 17 is a circuit for measuring the magnitude of the received signal, and the dirt detection signal output unit 18 compares the measured signal level with a preset threshold value,
This circuit outputs a dirt detection signal when it is smaller than the threshold value.

Next, the operation will be described. When the pulse generation trigger is generated from the trigger generation unit 11, the light source 1 driven by the pulse generation circuit 12 generates an optical pulse signal. The light pulse signal projected from the light transmitting lens 2 is reflected by the measuring object 8 and part of it is reflected by the reference object 10. The optical pulse signal reflected by the measuring object 8 and the reference object 10 returns and enters the light receiving lens 3 and then enters the light receiving element 4. The electric signal output from the light receiving element 4 is current-voltage converted and amplified by the electric signal amplifier 9, and a reception signal is output. The received signal by the optical pulse signal reflected by the reference object 10 becomes a reference signal.

The received signal is input to the time measuring section 13, and the time measuring section 13 corrects the time difference between the output time of the pulse generation trigger output from the trigger generating section 11 and the output time of the received signal by the output time of the reference signal. Then, counting is performed by counting the number of clocks output from the reference clock 15. That is, as shown in FIG. 2, the pulse generation trigger output time T
The time difference between the output time T3 of the reference signal and the output time of the reception signal T2, not the time difference between 1 and the output time of the reception signal T2, is measured as the round trip time of the optical pulse signal. The distance calculator 16 calculates the distance to the measurement target object 8 from the time difference measured, and the calculated distance value is displayed (not shown).
Is displayed in.

On the other hand, the received signal is also input to the signal level measuring unit 17, and when the signal level of the reference signal is smaller than a preset threshold value, the signal level measuring unit 17 outputs the stain detection signal to the stain detection signal output unit 18. Output to. Since the reference signal is output immediately after the output of the optical pulse signal, the reference signal can be easily distinguished from the received signal output by the optical pulse signal reflected from the measurement object 8 and detected.

If the front surface of the light-transmitting lens 2 is dirty, the level of the optical pulse signal projected from the light-transmitting lens 2 is lowered, so that the level of the optical pulse signal reflected by the light pulse signal is lowered. Therefore, the signal level measuring unit 17
The signal level input to is reduced. When the front surface of the light receiving lens 3 is dirty, the level of the light pulse signal incident on the light receiving lens 3 is lowered even if the level of the light pulse signal projected from the light transmitting lens 2 is the same, and therefore the signal level is The signal level input to the measuring unit 17 decreases. When the signal level input to the signal level measuring unit 17 is lowered, it means that dirt is attached to the front surface of either or both lenses.

When this embodiment is mounted on an automobile, parts such as a grill on the front of the automobile can be used as the reference object as it is.

As described above, according to the present embodiment, it is possible to cancel the influence of the change in the delay time of the electric circuit due to the environmental temperature change without providing an optical system and a light receiving element dedicated for reference, and to the object. It is possible to measure the distance more accurately. Further, by measuring the decrease in the reception level, it is possible to detect the contamination of the transmission optical system or the reception optical system, notify the measurer of the state where normal measurement cannot be performed, and prompt the cleaning of the optical system.

Next, another embodiment will be described with reference to FIG. In this embodiment, the cover glass 5 is provided on the front part of the light-sending lens 2 and the light-receiving lens 3 facing the measurement object 8, and the light source 1, the light-sending lens 2, the light-receiving lens 3, and the light-receiving element 4 are provided.
Only the point that the other members are protected from the outside is different from the above-described one embodiment. Therefore, the description is omitted. In this embodiment, dirt on the cover glass 5 is detected instead of dirt on the lens. Therefore, as compared with the example of FIG. 1, in the example of FIG. 1, when the dirt is removed, the optical axis of the lens is easily displaced, and when the lens is replaced, it is necessary to adjust the optical axis. It is easy to use and easy to replace because it does not require optical axis adjustment.

[0025]

According to the present invention, even if dirt is attached to any of the light transmitting lens, the light receiving lens, or the portion of the cover glass where the projected light is transmitted and the portion where the reflected light is transmitted, it can be detected and the number of parts is increased. It is possible to configure a distance measuring device that maintains high distance measuring accuracy without inviting.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment according to the present invention.

FIG. 2 is a diagram showing a relationship between a signal and time according to an embodiment of the present invention.

FIG. 3 is a block diagram of another embodiment according to the present invention.

FIG. 4 is a block diagram of a conventional example.

FIG. 5 is a block diagram of a conventional example.

[Explanation of symbols]

 1 ... Light source 2 ... Light transmitting lens 3 ... Light receiving lens 4 ... Light receiving element 5 ... Cover glass 6 ... Reference light receiving element 7 ... Beam Splitter 8 ... Measurement target 9 ... Electrical signal amplifier 10 ... Reference object 11 ... Trigger generator 12 ... Pulse generator 13 ... Time measurement unit 15 ...・ ・ ・ Reference clock 16 ・ ・ ・ ・ Distance calculation unit 17 ・ ・ ・ Signal level measurement unit 18 ・ ・ ・ ・ Dirt detection signal output unit

Claims (4)

[Claims] 1. A light source for generating a light pulse in response to a lighting timing signal, a light transmitting lens for transmitting the light pulse to an object, and a light receiving lens for receiving the light pulse reflected by the object. , A light receiving means for photoelectrically converting the light pulse to output a reception signal, a time measuring means for measuring an output time of the lighting timing signal and an output time of the reception signal, and a light pulse of the light pulse measured by the time measuring means. In a distance measuring device comprising a distance calculating means for calculating a distance to the object from the round-trip time to the object,
A reference object arranged at a position where the optical path of the light pulse sent from the light sending lens and the optical path of the light pulse received by the light receiving lens are superposed, and the light pulse reflected by the reference object is received. Measuring means for measuring the magnitude of the reference signal output by the light receiving means, and a stain for detecting dirt on the front surface of the light transmitting lens or the light receiving lens based on the magnitude of the reference signal measured by the measuring means. A distance measuring device comprising a detecting means. 2. The time measuring means measures the output time of the reference signal, and the distance calculating means calculates from the round-trip time to the object of the optical pulse corrected using the output time of the reference signal. The distance measuring device according to claim 1, wherein a distance to the object is calculated. 3. A light source for generating an optical pulse in response to a lighting timing signal, a light transmitting lens for transmitting the light pulse, a light receiving lens for receiving the light pulse reflected by the object, and the light transmitting lens. A cover glass that covers the front surface of the light lens and the light receiving lens, a light receiving unit that photoelectrically converts the light pulse to output a reception signal, and a time measuring unit that measures the output time of the lighting timing signal and the output time of the reception signal. In the distance measuring device, comprising: a distance calculating unit that calculates a distance to the object from the round-trip time of the light pulse to the object measured by the time measuring unit, outside the cover glass, and A reference object arranged at a position where an optical path of an optical pulse sent from the light sending lens and an optical path of an optical pulse received by the light receiving lens are superposed, and the reference object Measuring the magnitude of the reference signal output by the light receiving means upon receiving the light pulse reflected by the light receiving means, and detecting the dirt on the cover glass based on the magnitude of the reference signal measured by the weighing means. A distance measuring device, comprising: 4. The time measuring means measures the output time of the reference signal, and the distance calculating means calculates the distance to the object from the round-trip time corrected based on the output time of the reference signal. The distance measuring device according to claim 3, wherein