JPH05240639A - Distance measuring instrument - Google Patents

Abstract

PURPOSE:To measure the distance to a reflecting object ahead without relying on the sense of sight by measuring the direction angles of reflected light from the object to two light receiving elements and calculating the distance to the object from the two direction angles and reference distance between the light receiving elements. CONSTITUTION:Light emitted from a light emitting element 1 irradiates the front after the irradiating extent of the light is widened through a projection lens 2. Reflected light rays from an object 3 to be irradiated respectively form images on light receiving elements 6 and 7 after passing through image forming lens systems 4 and 5. When the angles of the reflected light rays are measured, L=b.costheta2+c.costheta1 is obtained, where angle B=theta1, angle C=theta2, side BC=L, side AC=b, and side AB=c. In case L is 10cm and the (b) and (c) are several meters, the (b) and (c) become nearly equal to each other and can be regarded as the distance R to the object, since b>>L and c>>L. Therefore, the distance R can be calculated from R=L/(costheta1+costheta2).

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 which irradiates a target with light and measures the distance from the direction of reflected light to the target.

[0002]

2. Description of the Related Art One of the most popular conventional distance measuring devices is a camera autofocus function. FIG. 4 shows the measurement principle. This is the so-called triangulation method. That is, in order to obtain the distance from one point B to A of the right triangle, the angle of the apex angle A can be obtained, and it can be calculated from the known base line length BC using the formula AB = BC / tanA.

In an actual 35 mm lens shutter camera, as shown in FIG. 5, a beam of infrared light is emitted from one point B at an angle θ 1 toward a subject and the reflected light from the subject is received at the other point C. Then, if the incident angle θ2 at that time is measured, the distance to the subject can be obtained. The measurement of θ 2 is a mechanism in which an image of a subject is formed by an imaging lens and the position where infrared light strikes the image plane is detected.

In this configuration, it goes without saying that θ1 = 90
At the time of °, it is most simplified. For the subject,
Since the photographer looks through the viewfinder and selects it, the distance can be known by measuring only θ2.

[0005]

However, as an application of such a distance measuring device other than a camera, there is an object of detecting an obstacle in front of or detecting a specific object in front without visually detecting. In this case, it is contrary to the purpose to determine the object to be measured by looking through the finder.
That is, in order to achieve such an object, the distance measuring device holder or the vehicle equipped with the measuring device discovers the target object or obstacle without noticing it and informs of the measured distance and its existence. Or, you must resort to other means, such as issuing a safety alert.

In order to solve such a problem, the present invention applies triangulation to detect reflected light from an obstacle in front or a specific object in advance, and enables distance measurement without vision. It provides a method.

[0007]

According to the distance measuring method of the present invention, light is emitted forward from a light source, and reflected light from a certain object in front of the light source is captured by two light receiving elements, so that the light is emitted from the object. The direction angle of the reflected light to the light receiving element is measured, and the distance to the front reflecting object is calculated from these two direction angles and the reference distance between the light receiving elements. When configuring this in an actual device, The device uses at least one of the following elements.

1) The light source is infrared light.

2) The light source is a laser.

3) The light source has an optical scanning function.

4) The light source has a plurality of light emitting points.

5) The emitted light is parallel or emitted light.

6) The light source has a projection lens system.

7) The light receiving element is divided into two and is movable in the left and right directions.

8) The light receiving element is multi-divided.

9) The light receiving element is a 3-terminal position sensor.

10) The light receiving element has an image forming lens system or an image intensifying lens system in front of it.

11) The measuring device includes at least a light transmitting unit, a light receiving unit, a light source driving circuit, a light receiving amplifier circuit, and a signal arithmetic circuit.

[0019]

1 is a principle diagram of measurement showing the principle of the distance measuring method according to the present invention. The light emitted from the light emitting element 1 has its irradiation area expanded by the light projecting lens 2 and illuminates the front. Alternatively, the front is illuminated as parallel light having a certain area. The wavelength of light is infrared, so that it is not visible to human eyes,
In addition, a high light projecting property is desirable for obstacle detection and the like. However, it is not limited to this. In short, it is only necessary to select one that can be easily distinguished from the ambient light according to the application purpose. Further, when the amount of light reflected from a reflecting object is small, for example, when an object having a small reflectance itself or a reflection from a distant object is detected, it is desirable to use a laser as a light source. If that is not the case, a light emitting diode would be sufficient. Further, in order to widen the detection area, it is effective to use a light source having a plurality of (three in FIG. 1) light emitting points close to each other as shown in the figure, and irradiate the front side simultaneously or in order. The projecting lens system can also be simplified.

Now, the object to be irradiated 3 which has received the irradiation light in this way, that is, it is a specific object at one time, and
Sometimes it is an obstacle, but the light reflected from it is
The light receiving element 6 passes through the imaging lens systems 4 and 5, respectively.
Image on 7. Various methods can be considered for the imaging lens system in order to facilitate the angle detection. However, whether the angle detection range is several degrees or several tens degrees, or the required angular resolution is 0.1 degrees or 0 degrees. An image intensifying system may be incorporated and the configuration thereof may be changed according to whether or not it is 0.01 degree. Several methods can be considered for the light-receiving elements 6 and 7. Figure 2 (a)
Is a method of mechanically driving the two-divided photodiode. Usually, the imaged spot hits one of the diodes, so that the diode output is large. The photodiode is moved to a position where the outputs of the two diodes are balanced, that is, a position where the spot is divided by the dividing line, and the movement amount is converted into an angle. In FIG. 2B, instead of moving the photodiode, the strip is divided into multiple strips. That is, since the diode hitting the spot has the largest output, the position is converted into an angle. FIG. 2C uses a 3-terminal position sensor. This is because the ratio of the photocurrent between the terminals xy and the photocurrent between yz changes depending on the position of the spot, and the angle is determined from this current ratio. This method has a feature that the spot position can be continuously obtained. Although the light receiving element is a photodiode in the above description, a CCD, MOS
It goes without saying that other light receiving elements such as die type sensors and Photomul can be used.

Now, from the measurement control in this way,
If the reflected light angle can be detected, the distance may be calculated by the following method. In FIG. 1, assuming that angle B = θ1, angle C = θ2, side BC = L, side AC = b, side AB = c, from the first cosine theorem, L = b cos θ2 + a cos θ1 where L is 10 cm or less, a , B are several meters, a >> L and b >> L, so that a and b are almost equal, and the distance R to the object to be obtained can be set. Therefore, the distance R can be calculated with R = L / (cos θ1 + cos θ2). The distance L between the light receiving elements used in the above equation is a base length and is an important reference for distance measurement. Further, the distance R between the light source and the object can be obtained from the above-mentioned two-sided narrow side from the first cosine theorem and the sine theorem, but it was confirmed that the above approximation formula gives a very good approximation.

FIG. 3 is a block diagram of the entire structure of the distance measuring device. As described above, the light sending unit 8 is composed of a light source using a light emitting element and a light projecting lens system, and a light scanning system (mechanical or electronic) may be added. The drive circuit 9 is appropriately constituted by a stable current driver of the light source, a pulse driver, a switching circuit, or the like. Also,
When the condition for distance measurement is set, the light source is driven when necessary through the timing generation circuit 10 from the control system.

The light receiving system starts from the above-mentioned image forming lens and the light receiving unit 11 formed by the light receiving element. This includes optical measures against ambient light. The output of the light receiving element is shaped by passing through an amplifier 12 and a filter attached thereto, and an output is proportional to the angle amount in the angle detection system 13. At this time, in order to facilitate the next calculation, it is desirable to AD-convert the output. Based on the measured angle data, the distance calculation unit 14 calculates the cosine R
The necessary data is extracted from the OM table, and the result is substituted into the above formula to calculate the distance. 13 and 14 are collectively called an arithmetic unit. Although the basic function of distance measurement has been achieved as described above, when this is to be displayed, data is transferred from the output of the arithmetic unit to the display device 15 for digital display or analog display such as a meter. Further, the present distance measuring device can be used for imaging by narrowing the light and scanning so as to lick the front object. Therefore, it is conceivable to display on the CRT after performing image processing. In another application, when the safety is managed from the distance data, the measurement result is judged through the safety / danger judging circuit 16 (possibly software), and then the alarm generator 17 is judged. Controls on and off.

[0024]

As described above, in the distance measuring method according to the present invention, the owner of the measuring instrument, the vehicle equipped with the measuring instrument, or the like discovers the target object or the obstacle without noticing, and It has a function of notifying the distance and presence, issuing an alarm for safety, and further performing imaging. Specifically, helicopter forward obstacle detection during low-altitude flight, inter-vehicle distance measurement while driving, automatic driving, forward obstacle detection, robot visual function,
In-line process control for setting parts and gaps,
It can lead to endless applications such as identification of three-dimensional objects.

[Brief description of drawings]

FIG. 1 is an explanatory view of the principle of the distance measuring method of the present invention.

FIG. 2 is an explanatory diagram of a light receiving element.

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

FIG. 4 is a principle diagram of a conventional triangulation method.

FIG. 5 is a principle diagram of camera autofocus.

[Explanation of symbols]

 1 light source 2 light projecting lens 3 object 4, 5 light receiving lens 6, 7 light receiving element 8 light emitting unit 9 drive circuit 10 timing generation 11 light receiving unit 12 amplifier 13 angle detection 14 distance calculation 15 display device 16 judgment 17 alarm

Claims (12)

[Claims] 1. A directional angle of reflected light from an object to a light receiving element is measured by emitting light from a light source forward and capturing reflected light from an object in front of the light by two light receiving elements. A distance measuring device, wherein the distance from the measuring device to the front reflecting object is calculated from the two directional angles and the reference distance between the light receiving elements. 2. The distance measuring device according to claim 1, wherein the light source is infrared light. 3. The distance measuring device according to claim 1, wherein the light source is a laser. 4. The light source has a light scanning function.
The distance measuring device described in. 5. The light source has a plurality of light emitting points,
The distance measuring device according to 2, 3, or 4. 6. The distance measuring device according to claim 1, wherein the emitted light is parallel or emitted light. 7. The light source has a projection lens system.
The distance measuring device described in. 8. The distance measuring device according to claim 1, wherein the light receiving element is divided into two and is movable in the left and right directions. 9. The distance measuring device according to claim 1, wherein the light receiving element is multi-divided. 10. The distance measuring device according to claim 1, wherein the light receiving element is a three-terminal position sensor. 11. The light receiving element has an image forming lens system or an image intensifying lens system in front of the light receiving element.
9. The distance measuring device according to 9. 12. A distance measuring device, wherein the measuring device includes at least a light transmitting unit, a light receiving unit, a light source driving circuit, a light receiving amplifier circuit, and a signal arithmetic circuit.