JPH06102343A - Detection method and device for state of body, and ranging method and device using the detection method - Google Patents

Abstract

PURPOSE:To focus return light to a fixed position in a ranging device for scanning irradiation light in multidirections to measure a distance from a plurality of targets. CONSTITUTION:Irradiation light is reflected by one surface of a rotating a polygon mirror 3 and focused by a focus lens 4 and then applied to a target, the range of which is to be found. Return light reflected by a target, the range of which is to be found, is reflected by another surface of the polygon mirror 3 and then focused to a light-intercepting element 2. The focal point of return light, which mas varied in the past, can be fixed to one point, so that the area of a light-intercepting element may be reduced. Thereby, the response of the light-intercepting element itself can be increased. At the same time, since light giving disturbance to the light-intercepting element is not received, sensitivity can be increased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting a state of an object, an apparatus therefor, and a distance measuring method and apparatus using the same, and more particularly, to optically detect the presence of an object, the state of the object, or the distance to the object. Regarding detection technology.

[0002]

2. Description of the Related Art As a conventional technique of this kind, a distance measuring technique known from, for example, Japanese Patent Laid-Open No. 61-259186, U.S. Pat. No. 4,632,543 or Japanese Patent Publication No. 51-7892 is well known. ing.

According to this distance-measuring technique, pulsed light or beam light emitted from a laser travels in front of the vehicle, and reflected light returned by hitting a vehicle or other object in front is received by a light-receiving element, and the received light is received. The distance between the vehicle and the preceding vehicle or other object is detected from the difference between the time and the emission time of the pulsed light.

The pulsed light emitted from the laser is provided with a plurality of lenses to allow the laser light to travel in different directions or to be reflected once by a mirror in order to detect a vehicle or other object in front in a wide range. There are used techniques such as so-called scanning, scanning, or sweeping, which is configured to cause the light to travel and to make laser light travel in different directions by changing the angle of the mirror.

[0005]

As described above, when the light emitted from the light source is scanned, the light receiving position of the light reflected and returned by the object is changed, and in some cases, the light is moved out of the light receiving element and cannot be received. There is.

An object of the present invention is to make it possible to receive the light which has returned to the object in a narrow range as much as possible even when the light emitted from the light source is scanned.

[0007]

The above object is achieved by reversely scanning the light returning upon hitting the object toward the light receiving element.

Specifically, predetermined light emitted from the light source is reflected on one surface of the rotary polygon mirror for scanning, and reflected light returned after hitting an object is reflected on another surface of the rotary polygon mirror. Reverse scanning was performed toward the light receiving means.

[0009]

In the present invention thus constructed, the light reflected by the object and returned is surely received by the light receiving means by the reverse scanning, so that the light receiving surface of the light receiving means can be made small, and the response due to the size increase of the light receiving means. It is possible to prevent a decrease in speed and a decrease in sensitivity of the light receiving system.

Therefore, if this idea is applied to an inter-vehicle distance measuring device such as an automobile or an obstacle detecting device, a small device capable of detecting an accurate inter-vehicle distance or a distance to an obstacle can be obtained.

Of course, the light emitted from the light source, such as a character reading device, an object surface unevenness detecting device, and an optical analysis system, is not limited to these and is applied to an object, and the light reflected by the object and returned is returned. Presence of the object based on the light receiving state,
It can be applied to any device that detects the status, position, etc.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an optical system layout of a distance measuring device according to the present invention. The polygon mirror 3 has a constant speed (for example, 1000
RPM). The light emitted from the light emitting element 1 is reflected on one surface of the polygon mirror, and the divergence angle is narrowed by the focusing lens 4 to travel toward the object to be measured.

In FIG. 1, the angle of the polygon mirror is set to the optical path 3
Showed the street. Although the light emitted from the light emitting element has a spread, only the central optical path is shown in the figure.

Here, assuming that the solid line represents the reference angle of the polygon mirror, the two-dot chain line represents-
Δθ, and the angle represented by the dotted line is + Δθ. At the same time, the light reflected by the polygon mirror is also shown by a two-dot chain line, a solid line, and a dotted line.

The mirror reflected light when the polygon mirror angle is −Δθ is shifted by −2Δθ, and the mirror reflected light when it is + Δθ is shifted by + 2Δθ. Each light is refracted by the focusing lens 4 and travels toward the object to be measured as shown by A, B and C in the figure.

The return light reflected by the object to be measured is A in FIG.
Like r, Br, and Cr, they return in parallel with the irradiation light, are focused by the condenser lens 5, are reflected by one surface of the polygon mirror 3, and are focused on the light receiving element 2. At this time, in the optical paths of Ar, Br, and Cr, the focusing positions on the mirror surface are different, but the mirror angle is also Δ.
Since it differs by θ, the focus position on the light receiving element does not change.

Actually, since there is a difference between the time when the light is emitted and the time when the light is received, the polygon mirror rotates during that time and shifts from the initial geometry, so an error will be described.
The rotation speed ω of the polygon mirror is 6000 deg / sec (100
0 RPM) and the distance L to the object is 500 m, the light emission-light reception time difference T is the speed of light C (= 2.998 * 10 ⁸ m / sec).
) Is used to represent the following equation.

[0018]

[Equation 1]

The deviation angle Δθp of the polygon mirror during this period is

[0020]

[Equation 2]

Substituting numerical values

[0022]

[Equation 3]

It is considered to be very small and smaller than the mounting error of the light receiving element itself, and the deviation angle Δθp of the polygon mirror due to the light emission-light receiving time difference T can be ignored and the light receiving position is considered to be constant.

With the above-described operation, even if the irradiation light is scanned, the light can be received at a fixed position, so that the area of the light receiving element can be reduced. Further, since the area of the light receiving element can be made small, it is not necessary to receive unnecessary light which becomes an element of disturbance, so that the sensitivity can be improved.

Next, the structure of the distance measuring device will be described with reference to the block diagram of FIG.

The distance measuring device 6 includes a light emitting element 1, a light receiving element 2, a polygon mirror 3, a focusing lens 4, a focusing lens 5, a motor 7, an amplifier 31, a threshold detector 32, a clock 33, an UP counter 34, a buffer 35, and a motor. It is composed of a control circuit 36, a microcomputer 39, a timing detector 38, and a driver 37.

Rotation or non-rotation of the motor control circuit 36 is determined by an ON or OFF drive signal. When the motor control circuit 36 is ON, the motor 7 is rotated at a constant speed. In order to control to a constant rotation, a rotation signal of n pulses per rotation is taken in from the motor and speed feedback control is performed to determine the supply current.

The microcomputer 39 turns on the drive signal, which is a motor rotation command, except when the system is abnormal. Further, the position of the polygon mirror is always grasped by inputting the pulse of the rotation signal.

The microcomputer 39 outputs a light emission command signal. The timing of the light emission command signal is shifted according to the scan angle with reference to the motor rotation signal.

The driver 37 comprises a power supply circuit for driving the light emitting element 1 and a switching circuit, and switches the light emitting element based on a light emission command signal.

The timing detection circuit 38 detects the current supplied to the light emitting element by the driver, determines the level, and outputs a light emission detection signal (start signal). The reason why the start signal is not used as the light emission command signal is that there is a time lag between the light emission command signal and the actual light emission timing, and there is an error in detecting the round-trip time of the irradiation light.

The light emitting element 1 emits light in accordance with a pulsed light emitting signal, and the direction of its output light is directed to the polygon mirror 3.

The light emitted from the light emitting element 1 is reflected by one surface of the polygon mirror 3, is focused by the focusing lens 4, and travels toward the distance measuring object 8 or 9. Distance measurement object 8 or 9
The light reflected at becomes the return light and is condensed by the condenser lens 5 and enters the light receiving element 2. The light receiving element 2 is an element that performs photoelectric conversion, and its output is amplified by the amplifier 31 and the threshold detector 32 determines the level of the amplified light receiving signal. The result of level judgment is used as a stop signal.

The UP counter 34 counts up the reference pulse of the clock 33, and start and stop are triggered by a start signal and a stop signal, respectively. That is, the time difference between light emission and light reception is counted by the pulse of the clock 33.

The counting result is a binary number in the temporary buffer 35.
Will be stored in. If the reset signal of the buffer 35 is shared with the stop signal, the counter value at the moment of receiving light is stored.

The microcomputer 39 periodically reads the count value temporarily stored in the buffer 35 and converts the count value.

When the count value is N when the clock frequency is F (Hz), the distance L (m) can be expressed by the following equation.

[0038]

[Equation 4]

Since C is a constant and F is a fixed value,

[0040]

[Equation 5]

[Mathematical formula-see original document]

[0042]

[Equation 6]

Only the multiplication of need be performed.

Next, the relationship between the signals will be described with reference to the timing chart shown in FIG.

When the motor rotation signal 41 rises at t1, the microcomputer delays T1 and outputs the light emission command signal 42 at t2. T1 is determined by the scan angle as follows. If the angle of deviation from the reference position of the polygon mirror at the moment of light emission is ± Δθp, it is expressed by the following equation.

[0046]

[Equation 7]

Here, T0 is a reference time, and it is set so that the light reflected from the polygon mirror advances exactly through the center of the focusing lens when light is emitted after t0 from t1.

The light emission signal 43 is not the same as the light emission command signal 42 due to the delay of the switching element. The light emission signal 43 is obtained by detecting the current supplied to the light emitting element 1 and converting it into a voltage, which is used as a light emission detection signal (start signal) 45 by comparison with the threshold value V1.

The amplified received light signal 44 is obtained by photoelectrically converting the collected return light, and compared with the threshold value V2 to form a received light detection signal (stop signal) 46.

The UP counter 34 counts the HI level time of the time difference signal 47, and the minimum time unit is determined by the frequency of the clock signal 48. The clock frequency may be increased to increase the resolution of the detection distance.

In terms of signal level, it is the time difference counting pulse 49 that is counted by the UP counter.

The right half of FIG. 4 shows a timing chart when the scan angle is changed. The difference with the left side is that T11> T1 because Δθp becomes large. The length of the time difference signal is T12> T2, whereas the distance measurement object 8 is detected at T2 as shown in FIG.
This is because the distance measurement target 9 is detected at T12.

When the irradiation light is scanned as described above, it is possible to detect the distances of a plurality of distance measurement objects.

Next, a system when the distance measuring device 6 is mounted on a vehicle will be described with reference to FIG.

The distance measuring device 6 can measure the distance to a plurality of other vehicles running around the host vehicle by scanning the irradiation light. By inputting the speed V of the host vehicle obtained by the vehicle speed sensor 59 to the distance measuring device, the relative speed Vc with the surrounding vehicles can be obtained.

For example, since it is possible to obtain the inter-vehicle distance Lv and the relative speed Vc with the vehicle ahead, the following system can be developed.

If the vehicle ahead suddenly decelerates, the relative speed Vc
Can be detected by, and the number of seconds after which the vehicle will collide when traveling with the same speed can be expressed by the following equation.

[0058]

[Equation 8]

Tc is a predicted collision time.

Therefore, the microcomputer 39 (Equation 8) of the distance measuring device
If the buzzer 51 is sounded when Tc is equal to or less than the specified value, the distance measuring device 6 can serve as a collision warning device.

Further, if the vehicle is advanced from the collision warning device and the brake is automatically applied instead of ringing the buzzer 51, it can be an active collision prevention device. In this case, the braking signal is sent from the microcomputer 39 of the distance measuring device 6 to the brake control device 57.
The brake actuators activate the brakes 58a to 58d of the vehicle.

Further, the throttle 55 is connected to the actuator 5
The constant speed control device 52 operated in 4 has been put into practical use,
It can also be applied to a system for keeping the inter-vehicle distance to a vehicle traveling ahead at a certain value or more. The microcomputer 39 of the distance measuring device 6 lowers the speed command when the inter-vehicle distance Lv with the preceding vehicle becomes shorter than a predetermined value. The constant speed control device 52 determines a position command for the throttle from the speed command and the vehicle speed signal. The throttle control device 53 controls the current supplied to the motor 54 based on the difference between the position signal measured by the throttle sensor 56 and the position command of the position of the throttle valve 55.

[0063]

According to the present invention, it is possible to collect the converging points in the light receiving portion, which have conventionally been scattered, for scanning the irradiation light for detection, so that it is not necessary to increase the area of the light receiving element. . As a result, the response speed of the light receiving element can be increased and the detection accuracy is improved. at the same time,
Since it became difficult to receive the disturbance light to the light receiving element, the detection sensitivity could be increased.

[Brief description of drawings]

FIG. 1 is a principle diagram of an optical system of a distance measuring device for an automobile according to an embodiment of the present invention.

FIG. 2 is a layout diagram of an optical system of a conventional distance measuring device.

FIG. 3 is a block diagram of a distance measuring device according to an embodiment of the present invention.

FIG. 4 is a timing chart of each signal of the distance measuring apparatus according to the present embodiment.

FIG. 5 is a diagram showing an application system of a vehicle ranging device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Light emitting element, 2 ... Light receiving element, 2 '... Larger light receiving element, 3 ... Polygon mirror, 4, 5 ... Focusing lens, 6 ... Distance measuring device, 7 ... Motor.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁵ Identification number Internal reference number FI Technical display location G01S 17/88 A 4240-5J G08B 7/00 A 4234-5G G08G 1/16 E 2105-3H

Claims (16)

[Claims] 1. When a predetermined light emitted from a light source is reflected on one surface of a rotating polygon mirror and the reflected light reflected by the mirror surface hits an object located in its path and is reflected back, the state of the reflected light is changed. In the method of detecting the presence of an object, the state of the object, or the distance to the object based on the above, the reflected light from the object is reflected by another surface of the rotating polygon mirror and received. How to detect the state of an object. 2. A method for detecting the state of an object according to claim 1, wherein the number of revolutions of the rotary polygon mirror is controlled to adjust the angle between the light from the light source and the mirror surface. 3. The rotary polygon mirror according to claim 1, wherein the number of revolutions of the rotary polygon mirror is constant, and the light emission timing of the light from the light source is controlled to adjust the angle between the light from the light source and the mirror surface. How to detect the state of an object. 4. The method for detecting the state of an object according to claim 1, wherein the light from the light source is pulsed laser light emitted at a predetermined cycle. 5. Existence of an object on the basis of the state of reflected light that is reflected and returned by irradiating the object with predetermined light emitted from a light source.
In a device for detecting the state of an object or the distance to the object, a light emitting means for emitting a pulse laser beam toward an object at a predetermined timing, a light receiving means for receiving the pulse laser beam reflected by the object, a motor Is rotated and driven by a surface for reflecting the pulsed laser light from the light emitting means toward the object, and another surface for reflecting light returning from the object and returning toward the light receiving means. An apparatus for detecting a state of an object, comprising: 6. A distance measuring device for optically measuring an inter-vehicle distance between an own vehicle and an object in front of the own vehicle, wherein pulse laser light emitted at a predetermined cycle is reflected on one surface of a polygon mirror to detect the distance from the front. Along with striking an object, the laser light reflected and returned there is reflected on another surface of the polygon mirror to be received by a light receiving element,
A distance measuring device which measures an inter-vehicle distance on the basis of a time difference from the generation time point of the pulsed laser light to the light reception time point. 7. A predetermined light emitted from a light source is scanned and applied to an object, the light reflected and returned is received by a light receiving means, and the existence of the object, the state of the object, or the object is determined based on the received light state. In the device for detecting the distance to the object etc., a device for detecting the state of the object is provided, which is provided with means for reversely scanning the light returning upon hitting the object toward the light receiving means. 8. A light emitting element and a light receiving element are provided, and when the light emitted toward the object to be measured is reflected and returned, the light receiving element is used to measure the time difference between light emission and light reception to obtain an object. In a distance measuring device for measuring a distance, a polygon mirror that is driven by a motor is provided, and light emitted from a light emitting element is reflected by one surface of the polygon mirror to illuminate an object, and return light is emitted on the other surface of the polygon mirror. A distance measuring device capable of scanning, which is reflected by the light and enters the light receiving element. 9. The distance measuring device according to claim 1, wherein the "one surface of the polygon mirror" and the "other surface" are surfaces symmetrical to a straight line connecting the rotation center of the polygon mirror and the object. apparatus. 10. The light emission timing from the light emitting element is based on a rotation signal of a polygon mirror rotation motor. Also, to change the scanning angle,
A distance measuring device which increases or decreases the time from the detection of a rotation signal of the motor to a constant rotation speed until the start of light emission. 11. A range finder according to claim 1, wherein a pulsed laser diode is used as the light emitting element and a photodiode is used as the light receiving element. 12. The distance measuring device according to claim 1, wherein the rotation detection pulse of the motor is n pulses per rotation when an n-sided polygon mirror is used. 13. A vehicle equipped with the distance measuring device according to claim 1,
An obstacle detection device for a vehicle, which detects an obstacle around the vehicle. 14. A vehicle equipped with the distance measuring device according to claim 1,
It is characterized by detecting an obstacle in front of the vehicle and issuing a warning to the driver's visual or auditory sense if it predicts from a distance from the obstacle and the speed of the vehicle that the vehicle will collide with the obstacle in front. Collision warning device for vehicles. 15. The distance measuring device according to claim 1 is mounted in an automobile,
A vehicle constant-speed traveling device that detects another vehicle in front of the vehicle and controls the angle of the throttle actuator so that the distance between the vehicle and the front vehicle does not fall below a predetermined value. 16. A vehicle equipped with the distance measuring device according to claim 1,
When detecting an obstacle in front of the vehicle and softly predicting that the vehicle will collide with the obstacle ahead based on the distance from the obstacle and the speed of the vehicle, the brake actuator is activated to prevent the vehicle from colliding with the obstacle. Collision prevention device for vehicles to prevent.