JP2972943B2 - Distance detection 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 detecting device, and more particularly to a distance detecting device which has a good response to a relatively large change in distance.

[0002]

2. Description of the Related Art Conventionally, Japanese Patent Laid-Open No.
The one described in JP-A-142488 is known.

That is, light is emitted from a light emitter forward in the traveling direction of a vehicle, the reflected light is received by a light receiver, and the distance is measured based on the time from transmission to reception of the light. When the distance measurement range is set to a relatively long distance (for example, about 100 m), the magnitude of the light receiving level decreases as the distance increases. As shown in FIG. 7, when the time when the light receiving level reaches a certain determination level is set as the light receiving time, the light receiving time depends on the level of the light receiving level. Near the middle of (T
2), near the peak portion (T3), and fluctuate to the peak portion (T4). Therefore, the amplification degree is increased with time in the amplification section,
Regardless of the distance, control the light reception level to an appropriate level,
The fluctuation of the light receiving time was suppressed. However, in such a distance detecting device, the closest distance (for example, 5 m or less)
In this case, the light receiving level was too high, the peak portion of the light receiving signal became saturated (P1), and a highly accurate distance measurement could not be performed. Therefore, in order to prevent the peak portion of the received light signal from becoming saturated, the change width of the received light level is limited by using a diaphragm mechanism or a variable attenuator, and the amount of received light is controlled to an appropriate level.

[0004]

However, in such a distance detecting device, when the amount of received light is controlled to an appropriate level using an aperture mechanism or a variable attenuator, a mechanical system such as a motor for driving the aperture mechanism is used. , The control speed was slow, and it was not suitable when high-speed response was required.

An object of the present invention is to solve the above-mentioned problem, and an object of the present invention is to provide a distance detecting device which has a good response to a relatively large change in distance from a long distance to a close distance.

[0006]

According to a first aspect of the present invention, there is provided a distance detecting apparatus for transmitting light to a target, and a light transmitting unit for separating reflected light from the target into at least two different light levels. A wave detector, a light receiving unit that receives the reflected light that has been demultiplexed, a time detecting unit that detects a time required for the light transmitted from the light receiving unit to reach the light receiving unit, Calculating means for calculating the distance to the target based on the output of
A selection unit for selecting any one of at least two calculation processes from the light receiving unit to the calculation means, wherein the selection unit is configured to perform a calculation based on the distance to the target calculated using each of the calculation processes. And selecting any one of the light receiving units.

According to a second aspect of the present invention, there is provided a distance detecting device for transmitting light to a target, and transmitting at least two light reflected from the target.
A splitter that splits light into two different light levels, a light receiving unit that receives the reflected light that has been split, and a time that detects the time required for the light transmitted from the light receiving unit to reach the light receiving unit. Detecting means, calculating means for calculating a distance to a target based on an output from the time detecting means, and selecting at least one of at least two calculating steps from the light receiving section to the calculating means. And a selection unit that selects any one of the light receiving units based on the distance to the target calculated by the calculation unit.

[0008]

[0009]

[0010]

[0011]

In the distance detecting apparatus of the present invention as described above, the reflected light from the target is split into at least two different light levels by the splitter, and each split light is The light is received by the light receiving unit. The time required for the light transmitted from the light transmitting unit to reach the light receiving unit is detected. The selecting unit selects one of at least two arithmetic processes from the light receiving unit to the arithmetic unit and detects a distance.

[0012]

As described above, according to the present invention, an accurate distance can be detected with good responsiveness to a relatively large change in distance from a long distance to a close distance.

[0013]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a block diagram of a first embodiment of the present invention.

The light transmitting unit 3 transmits light to a target (not shown) based on an output from the timing control unit 2 controlled by the computer 1. At the same time, each distance counter 4H, 4H
L starts counting pulses from the clock 5 that generates pulses of a fixed period (for example, 1 ns). The reflected light from the target is split by the splitter 6 into two different light levels (for example, light level ratio H: L = 10: 1). The higher light level H is reflected light for long distance (5 m or more), and the lower light level L is reflected light for close distance (within 5 m).
The reflected light on the higher light level H is reflected by a light attenuator (not shown) provided in the light receiving section 7H.
(5) where the light receiving level is highest in the distance measurement range of
An appropriate light receiving level is set so that the peak portion of the light receiving signal at the time of m) does not become saturated. The reflected light on the side L with the higher light level is an optical attenuator (not shown) provided in the light receiving section 7L.
Thus, the light receiving level is set to an appropriate light receiving level at which the peak portion of the light receiving signal at the distance where the light receiving level becomes the highest (closest distance) within the distance measurement range on the high light level side L does not become saturated. Each light is received by a light receiving element (not shown, for example, a photodiode) in each of the light receiving sections 7H and 7L. The output from each of the light receiving units 7H and 7L is
The appropriate level is always maintained by the STC circuit provided in H, 9L. Outputs from the amplifiers 9H and 9L are detected by the detectors 10H and 10L. Each distance counter 4H,
In 4L, the counting is stopped by the output from each of the detection units 10H and 10L. The computer 1 calculates the light transmitting unit 3 (each light receiving unit 7) from the counts of the distance counters 4H and 4L.
H, 7L) to the target, respectively, and select appropriate distance data. Next, the flow of control will be described with reference to the flowchart of FIG.

In step S1, a buffer timer (not shown, for example, 1 ms) is started so that the arithmetic processing time does not become longer than the light transmission cycle. In step S2, the light transmitting unit 3 transmits light to the target. In step S3, it is determined whether or not each of the light receiving units 7H and 7L has received reflected light.
If no light is received, in step S4, each of the distance counters 4H and 4L counts the pulses from the clock 5, and proceeds to step S3. If light is received, in step S5, each of the distance counters 4H and 4L
The counting of the pulses from is stopped, and the computer 1 calculates the distance from the outputs of the distance counters 4H and 4L. The required time T from the light transmitting unit 3 to the light receiving units 7H and 7L is obtained by T = N * t (N: count number, t: pulse cycle). Therefore, the light transmitting unit 3 (the light receiving units 7H and 7L)
The distance R from the target to the target is determined by R = T * C / 2 (C: speed of light).

In step S6, it is determined whether or not the distance RH when using the calculation process on the light receiving section 7H is within 5 m.
If the distance is less than 5 m, the light transmitting unit 3 (the light receiving unit
H, 7L) to the target is set as the distance RL when the calculation process on the light receiving unit 7L side is used, and the process proceeds to step S9. If it is 5 m or more, the light transmitting unit 3
The distance R from the (light receiving units 7H and 7L) to the target is set as the distance RH when the calculation process on the light receiving unit 7H side is used, and the process proceeds to step S9. In step S9, it is determined whether or not the time of the buffer timer has expired. When the time is up, in step S10, the buffer timer is reset,
In step S11, the distance counters 4H and 4L are reset, and the process returns to step S1. FIG. 3 is a block diagram of a second embodiment of the present invention.

The light transmitting unit 13 transmits light to a target (not shown) according to an output from the timing control unit 12 controlled by the computer 11. At the same time distance counter 14
Starts counting pulses from the clock 15 that generates pulses of a fixed period. The reflected light from the target is split by the splitter 16 into two different light levels. Each of the demultiplexed lights is set to an appropriate light level that does not become saturated by an optical attenuator (not shown) or the like.
The light is received by a 17L light receiving element (not shown). The output of either of the light receiving units 17H and 17L is always at an appropriate level by the STC circuit provided in the amplifying unit 19 via the switching unit 18 controlled by the computer 11.
The output from the amplifier 19 is detected by the detector 20. The distance counter 14 stops counting according to the output from the detection unit 20. The computer 11 has a distance counter 1
From the count number of 4, the light transmitting unit 13 (the light receiving units 17H, 17H)
The distance from L) to the target is calculated. Next, the flow of control will be described with reference to the flowchart of FIG.

In step S21, a buffer timer is started. In step S22, the light transmitting unit 13 transmits light to the target. At step S23, the light receiving sections 17H, 1
It is determined whether 7L has received the reflected light. If no light is received, the distance counter 14 counts pulses from the clock 15 at step S24, and
Move to 23. If light is received, step S25
Then, the distance counter 14 stops counting the pulses from the clock 15 and the computer 11 calculates the distance.

In step S26, it is determined whether the distance R is within 5 m. If it is within 5 m, the process moves to step S27. If it is 5 m or longer, the process proceeds to step S28.
In step S27, it is determined whether the switching unit 18 is on the L side. If it is on the L side, the process moves to step S29. In the case of the H side, in step S30, the switching unit 18 is set to the L side, and the process proceeds to step S29. In step S28, the switching unit 18
Is determined to be on the H side. In the case of H side, step S29
Move to In the case of the L side, in step S31, the switching unit 1
8 is set to the H side, and the routine goes to Step S29. In step S29, it is determined whether or not the time of the buffer timer has expired. When the time is up, the buffer timer is reset in step S32, the distance counter 14 is reset in step S33, and the process returns to step S21. FIG. 5 is a block diagram of a third embodiment of the present invention.

The light transmitter 23 transmits light to a target (not shown) in response to an output from the timing controller 22 controlled by the computer 21. At the same time distance counter 24
Starts counting pulses from the clock 25 that generates pulses of a fixed period. The reflected light from the target is split by the splitter 26 into two different light levels. Each of the demultiplexed lights is set to an appropriate light level that does not become saturated by an optical attenuator (not shown) or the like.
The light is received by a 27L light receiving element (not shown). The output of either of the light receiving units 27H and 27L is always at an appropriate level by the STC circuit provided in the amplifying unit 29 via the switching unit 28 controlled by the computer 21.
The output from the amplifier 29 is detected by the detector 30. The distance counter 24 stops counting according to the output from the detection unit 30. The computer 21 has a distance counter 2
4, the light transmitting unit 23 (the light receiving units 27H, 27
The distance from L) to the target is calculated. The detection unit 30
Are held at the peak value by the peak hold unit 31. The value is converted into digital data by the A / D conversion unit 32 and input to the computer 21 as light reception level data for controlling the switching unit 28. Next, the flow of control will be described with reference to the flowchart of FIG.

In step S41, a buffer timer is started. In step S42, the light transmitting unit 23 transmits light to the target. In step S43, the light receiving units 27H,
It is determined whether 7L has received the reflected light. If no light is received, in step S44, the distance counter 24 counts the pulses from the clock 25, and proceeds to step S44.
Move to 43. If light is received, step S45
Then, the distance counter 24 stops counting the pulses from the clock 25 and the computer 21 calculates the distance.

In step S46, it is determined whether the switching unit 28 is on the L side. If it is on the L side, the process moves to step S47. If it is on the H side, the process moves to step S48. In step S47, it is determined whether the light receiving level L is higher than a predetermined level L1. If it is larger, the process moves to step S49. If smaller, the switching unit 28 is set to the H side in step S50, and the process proceeds to step S49. Step S48
It is determined whether the light receiving level L is smaller than the predetermined level L2. If smaller, the process moves to step S49. If it is larger, in step S51, the switching unit 28 is set to the L side, and the flow shifts to step S49. In step S49, it is determined whether the time is up. When the time is up, the buffer timer is reset in step S52, and the distance counter 24 is reset in step S53. It moves to step S41. As described above, according to the present embodiment, it is possible to detect an accurate distance with good responsiveness to a relatively large change in distance from a long distance to a close distance.

In this embodiment, the selectors 18, 28
Is selected based on the distance or the light receiving level, but may be selected based on the required time (or the number of counts).

In this embodiment, the duplexers 6, 16, 2
Reference numeral 6 demultiplexes the light into two different light levels to perform control for long-distance and near-distance use. The same effect can be obtained even if the control is divided into three and the control for the short distance.

[Brief description of the drawings]

FIG. 1 is a block diagram of a first embodiment of the present invention.

FIG. 2 is a flowchart of the first embodiment.

FIG. 3 is a block diagram of a second embodiment of the present invention.

FIG. 4 is a flowchart of a second embodiment.

FIG. 5 is a block diagram of a third embodiment of the present invention.

FIG. 6 is a flowchart of the third embodiment.

FIG. 7 is a relationship between time and a light receiving level in a conventional example.

[Explanation of symbols]

 1, 11, 21 Computer 2, 12, 22 Timing control unit 3, 13, 23 Light transmitting unit 4H, 4L, 14, 24 Distance counter 6, 16, 26 Duplexer 7H, 7L, 17H 17L, 27H, 27L: Light receiving unit 18, 28: Switching unit 9H, 9L, 19, 29: Amplifying unit 31: Peak hold unit

Claims (2)

(57) [Claims] 1. A light transmitting unit for transmitting light to a target, a splitter for splitting reflected light from the target into at least two different light levels, and a light receiving unit for receiving the split reflected light Unit, time detecting means for detecting a time required for the light transmitted from the light receiving unit to reach the light receiving unit, and calculating a distance to the target based on an output from the time detecting means. Computing means, and at least two from the light receiving section to the computing means.
And a selection unit for selecting one of the two calculation processes, wherein the selection unit selects one of the light receiving units based on the distance to the target calculated using the calculation processes. A distance detecting device. 2. A light transmitting unit for transmitting light to a target, a splitter for splitting reflected light from the target into at least two different light levels, and a light receiving unit for receiving the split reflected light. Unit, time detecting means for detecting a time required for the light transmitted from the light receiving unit to reach the light receiving unit, and calculating a distance to the target based on an output from the time detecting means. Computing means, and at least two from the light receiving section to the computing means.
And a selecting unit for selecting any one of the two calculation processes. The selecting unit selects one of the light receiving units based on the distance to the target calculated by the calculating unit. Characteristic distance detection device.