JPS63111413A - Optical distance measuring instrument - Google Patents

Abstract

PURPOSE:To accurately measure the distance to an object of measurement by combining plural lens systems which differ in focal length with image detecting means arranged at their image formation parts. CONSTITUTION:When the distance between a preceding vehicle and a following vehicle is, for example, long distance L1, light reflected by the rail lamp 10a of the preceding vehicle forms a sharp tail lamp image S1 at the position P1 of an image sensor 35 through the long-distance lens 32 of the following vehicle. In this case, an intermediate distance lens 33 and a short distance lens 34 are out of focus, so images S2 and S3 formed by those lenses are inferior in contrast. The image sensor 35 detects a photodetection image on the photodetection surface 35a from its lower end Pl to its upper end Pu and detects the position P1 of the sharp formed image S1 by using a high-pass filter. A distance measuring circuit determines the vehicle distance to the preceding vehicle on the basis of the position P1.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a distance measuring device, and particularly to an optical distance measuring device suitable for optically measuring the distance to a fixed object.

(Prior Art) Conventionally, there are distance measuring devices that measure the distance to a target using ultrasonic waves.

[Problem that the invention seeks to solve]

However, in such a configuration, since both an ultrasonic transmitter and an ultrasonic receiver are required, there is a problem that the size of this type of device becomes large. On the other hand, it is conceivable to use a laser to measure the distance to the target, but in such a case, this type of device becomes expensive.

Therefore, in order to deal with such problems, the present invention effectively utilizes the function of the image detection means and measures the distance to the target by combining the image detection means with a simple optical lens system. It is an object of the present invention to provide an optical distance measuring device as described above.

[Means for solving problems]

In order to solve this problem, the configuration of the present invention includes a first lens system and a second lens system that are arranged with their optical axes parallel to each other so as to face a fixed object in front, and the first lens system is arranged in front of the target. The second lens system has a predetermined focal length on the side, and based on this focal length, when receiving parallel light from the object to be fixed, images the object to be fixed behind it, and the second lens system has a predetermined focal length on the front side thereof. The lens has a predetermined focal length different from the focal length, and based on this focal length, when a parallel beam of light is received from the object to be fixed, the object to be fixed is imaged behind it, and the first and second lenses It has a light-receiving surface that is arranged at the rear and faces both of these lens systems, and the image formed by the first (or second) lens system is formed at one position (or another position) on the light-receiving surface. an image detection means that detects this and generates a first (or second) image detection signal, and a predetermined relationship between a predetermined measured distance to the fixed object and a position on the light receiving surface. and measurement distance determining means for determining the measurement distance according to the first (or second) image detection signal.

[Effect]

By configuring the present invention in this way, when the light from the object to be fixed enters the first lens system as a parallel ray, the object to be fixed is imaged at one position on the light receiving surface of the image detecting means. . Then, the image detection means generates a first image detection signal based on the image formed at one position on the light receiving surface, and the measurement distance determination means generates the first image detection signal based on the first image detection signal based on the predetermined relationship. Determine the measurement distance to the target.

Further, when the light from the object to be fixed enters the second lens system as parallel rays, the object to be fixed is imaged at another position on the light receiving surface of the image detecting means. Then,
The image detection means generates a second image detection signal based on the image formed at another position on the light receiving surface, and the measurement distance determination means generates the second image detection signal based on the predetermined relationship. Determine the measurement distance to a certain target.

〔effect〕

As understood from this effect, since the predetermined focal lengths of the first and second lens systems are different from each other, the first (or second
), when the object to be fixed is imaged behind the first (or second) lens system, the measurement distance from the first lens system to the object to be fixed and the first lens system are The measurement distances from the two lens systems to the fixed object are different from each other. Moreover, by making such a difference in measurement distance correspond to a difference in the light receiving position on the light receiving surface of the image detecting means, the difference in the light receiving position can be detected by the image detecting means, and the predetermined value can be adjusted according to the detection result. Based on the relationship, the measured distance is determined by the measured distance determining means. As a result, this kind of optical distance measuring device has the above-mentioned first image detecting means.
It can be provided at low cost with a simple optical configuration of combining the lens system and the second lens system.

〔Example〕

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.
The figure shows an example in which the optical distance measuring device according to the present invention is applied to a following vehicle 20 following a preceding vehicle 10.
This distance measuring device includes a device main body 30 and a signal processing section 40.
and a display 50. Device body 3
0 is disposed in the left front lower part of the following vehicle 20, and the device main body 30 is composed of a casing 31, convex lenses 32, 33, and 34, and an image sensor 35. The casing 31 is made of a light-shielding material and is formed into a rectangular parallelepiped shape.
The front wall 31a is fixed vertically to the inner end of the light guide path 21 formed at the lower left front portion of the following vehicle 20, and the light guide path 2
1 is provided in the left front lower part so as to be exposed to the front.

Three circular openings 31b, 31c, and 31d are bored in the front wall 31a of the casing 31 from the top to the bottom in FIG. 2, and each of these openings 31b
, 31c, 31d, each convex lens 32, 33.34 has its respective optical axis L1. L2 and L3 are fitted concentrically with each other parallel to each other. Each convex lens 32.33.3
4, the outer surfaces 32a, 33a, and 34a all have a predetermined radius of curvature Rb and a predetermined short focal length Fb, and the short focal length Fb of the outer surface 32a is on the optical axis L1. The short focal length Fb of the outer surface 33a is specified by the optical center 02 and focal point fb2 of the convex lens 33 on the optical axis L2, and the short focal length Fb of the outer surface 34a is specified by the optical center 01 and focal point fb1 of the convex lens 32. The distance %1IFb is specified by the optical center 03 of the convex lens 33 on the optical axis L3 and the focal point fb3.

On the other hand, the inner surfaces 32b, 3 of each convex lens 32, 33.
3b and 34b are different predetermined radii of curvature Ral,
Ra2. Ra3 and mutually different predetermined focal lengths Fai
, Fa2. Fa3, and Ral>Ra2>R
a3 and p'al>Fa2>Fa3. In such a case, the focal length Fal is the convex lens 32 on the optical axis L1.
is specified by the optical center 01 and focal point fal, and the focal length F
a2 is the optical center 02 of the convex lens 33 on the optical axis L2 and the focal point f
a2, and the focal length Fa3 is specified by the optical center o3 and focal point ra3 of the convex lens 34 on the optical axis L3. Moreover, each focal length F a 1 , F a
2 + F a 3 is the preceding vehicle 10 and the following vehicle 20
The predicted commuting distance between
It is designed to be able to clearly measure short distances in three stages.

The image sensor 35 is located behind each of the convex lenses 32, 33, and 34, and is fixed to the low wall 31e of the casing 31 in the vertical direction as shown in FIG. 35a is each focal point fbl, f
b2. Immediately after fb3, each optical axis Ll, L2 . It is orthogonal to L3. Therefore, in FIG. 2, the lower end and the upper end of the light receiving surface 35a are represented as Pl and Pu, respectively,
And when Px is a position on the light-receiving surface 35a that is upwardly separated by a height X from the lower end PR, the image sensor 35 is
An image formed by light at a position Px on the light receiving surface 35a is sequentially detected from the lower end PIl to the upper end Pu and is generated as an image detection signal.

In such a case, if the contrast of the image formed at the position Px on the light receiving surface 35a of the image sensor 35 is clear, the image detection signal will include a high frequency component due to the image formed. Furthermore, if the image formation has unclear contrast, such image formation will be included in the image detection signal as a low frequency component. However, the light receiving surface 35a of the image sensor 35 is formed by a plurality of pixel portions arranged in a band shape. Note that the image detection signal from the image sensor 35 is transmitted to the casing 31.
The lead wire l extends from the center of the bottom wall 31e through the rubber bushing 31f.

The signal processing unit 40 includes a bypass filter 41 connected to the image sensor 35 via a lead wire l, and a distance determining circuit 42 connected to the bypass filter 41.
5 through a lead wire β, and generates a high frequency component of the image detection signal as a filter signal representing the position fiPx. The distance determining circuit 42 is
Measurement distance from the front wall 31a of the casing 31 in the device body 30 to the target (hereinafter referred to as measurement distance)
and the position P on the light receiving surface 35a of the image sensor 35
A straight line q (see FIG. 4) representing the proportional relationship between the height of is determined and generated as a distance determination signal. As shown in FIG. 1, the display 50 is located on the instrument panel of the vehicle and displays the measured distance based on the distance determination signal from the distance determination circuit 42.

In this embodiment configured as described above, sunlight is reflected by the tail lamp 10a of the preceding vehicle 10 during the daytime when the following vehicle 20 is traveling following the preceding vehicle 10 as shown in FIG. The light guide path 21 of the following vehicle 20
It is assumed that the light enters the main body 30 of the apparatus through the. In such a case, if the inter-vehicle distance between the preceding vehicle 10 and the following vehicle 20 is long, the reflected sunlight from the tail lamp 10a of the preceding vehicle 10 will be directed to each convex lens 32, 33, 34 at its respective focal length Fa1. Fa2. It is incident as a parallel ray in relation to Fa3 (see Figure 2).

Therefore, the parallel light beam incident on the convex lens 32 is refracted by the convex lens 32 in relation to its short focal length Fb, passes through the focal point rb1, and reaches the light receiving surface 35 of the image sensor 35.
a and forms an image with clear contrast at the position PL (see FIG. 2) as a tail lamp image S1. However, the focal length Fa2 of each convex lens 33,34
+F a 3 is determined to be able to measure the width measurement distance and the dagger fixed distance, respectively, as described above, so that the parallel rays incident on the convex lens 33
The parallel rays are refracted in relation to the short focal length Fb, pass through the focal point fb2, and form an image in front of the light-receiving surface 35a of the image sensor 35, and the parallel rays incident on the convex lens 34 are refracted by the short focal length Fb. The image sensor 3 is refracted in relation to %1iFb and passes through the focal point fb3.
The image is formed in front of the light receiving surface 35a of No. 5. Therefore, the biconvex lens 33. which is formed on the light receiving surface 35a of the image sensor 35.
Both images formed by 34 have unclear contrast.

Next, the image sensor 35 sequentially detects the received light images from the lower end PR to the upper end Pu on the light receiving surface 35a, and sequentially generates the detection results at the position Px as an image detection signal. In such a case, the light receiving surface 35 of the image sensor 35
Since only the tail lamp image S1 at position P1 on a is included as a high frequency component in the image detection signal from the image sensor 35, the bypass filter 42 sequentially receives the image detection signals from the image sensor 35 and responds to the tail lamp image S1. A high frequency component is generated as a filter signal that specifies the position P1, and the distance measuring circuit 42
determines the inter-vehicle distance between the preceding vehicle 10 and the following vehicle 20 as a measurement capability MD-DI (see FIG. 4) in response to a filter signal from the bypass filter 41 based on the stored predetermined data, and generates a distance determination signal; The display 50 displays the measurement capability 1tlID1 based on the same distance determination signal. This allows the occupants of the following vehicle 20 to know that the inter-vehicle distance to the preceding vehicle 10 is a long distance.

Further, when the inter-vehicle distance between the preceding vehicle 10 and the following vehicle 20 is a medium distance, the parallel light beam from the tail lamp 10a that enters the convex lens 33 is refracted by the convex lens 33 in substantially the same manner as described above, and is focused at fb2. The light enters the light-receiving surface 35a of the image sensor 35 and forms a tail lamp image S2 at a position P2 (see FIG. 2) with clear contrast. However, the tail lamp 10a that enters the convex lens 32 in relation to its focal length Fal
The reflected sunlight is refracted by the convex lens 32 in relation to its short focal length Fb, passes through the focal point r b 1, and forms an image behind the light-receiving surface 35a of the image sensor 35, while being incident on the convex lens 34. The parallel light rays form an image in front of the light receiving surface 35a of the image sensor 35 in the same manner as described above. Therefore, images formed by the biconvex lenses 32 and 34 on the light receiving surface 35a of the image sensor 35 have unclear contrast.

Next, the image sensor 35 sequentially detects the light-receiving images on the light-receiving surface 35a and generates an image detection signal. In such a case, since only the tail lamp image S2 at position P2 on the light receiving surface 35a of the image sensor 35 is included as a high frequency component in the image detection signal from the image sensor 35, the bypass filter 42 sequentially receives the image detection signal from the image sensor 35. In response, a high frequency component corresponding to the tail lamp image S2 is generated as a filter signal for specifying the position P2, and the distance measuring circuit 42 uses the stored predetermined data to generate a high frequency component corresponding to the tail lamp image S2 as a filter signal from the bypass filter 41. The distance between the vehicle 20 and the vehicle 20 is determined as a measured distance D-D2 (see FIG. 4), and a distance determination signal is generated, and the display 50 displays the measured pressure %11D2 based on the distance determination signal. This allows the occupants of the following vehicle 20 to know that the inter-vehicle distance to the preceding vehicle 10 is a medium distance.

Further, when the distance between the preceding vehicle 10 and the following vehicle 20 is short, the parallel light beam from the tail lamp 10a that enters the convex lens 34 is refracted by the convex lens 34 in substantially the same manner as described above, and is focused at fb3. The light enters the light-receiving surface 35a of the image sensor 35 and forms a tail lamp image S3 at a position P3 (see FIG. 2) with clear contrast. However, the tail lamp 10 incident on the convex lens 32 in relation to its focal length Fal
The reflected sunlight from a is refracted by the convex lens 32 in substantially the same manner as described above, passes through the focal point fb1, and forms an image behind the light-receiving surface 35a of the image sensor 35. Reflected sunlight from the tail lamp 10a is refracted by the convex lens 33 in substantially the same manner as described above, and reaches the focal point fb2.
, and is imaged behind the light-receiving surface 35a of the image sensor 35. Therefore, images formed by the biconvex lenses 32 and 33 on the light receiving surface 35a of the image sensor 35 have unclear contrast.

Then, the image sensor 35 sequentially detects the received light images on the light receiving surface 35a in the same manner as described above, and generates an image detection signal. In such a case, only the tail lamp image S3 at position P3 on the light receiving surface 35a of the image sensor 35 is included as a high frequency component in the image detection signal from the image sensor 35, so the bypass filter 42 sequentially receives the image detection signal from the image sensor 35. In response, a high frequency component corresponding to the tail lamp image S3 is generated as a filter signal for specifying the position P3, and the distance measuring circuit 42 detects the preceding vehicle IO and the following vehicle according to the filter signal from the bypass filter 41 based on the stored predetermined data. The distance between the vehicle 20 and the vehicle 20 is determined as a measured pressure 1i11D=D3 (see FIG. 4), which is generated as a distance determination signal, and the display 50 displays the measured distance D3 based on the distance determination signal. This allows the occupants of the following vehicle 20 to know that the inter-vehicle distance to the preceding vehicle 10 is a short distance.

As understood from the above explanation, each convex lens 32.3
Focal length F a 1 + F a 2 of 3.34,
Since Fa3 are different from each other, the parallel light rays from the tail lamp 10a are incident on either of the convex lenses 32, 33, 34, so that the tail lamp 1 can be seen behind either of the convex lenses 32, 33, 34 with a clear contrast.
0a, each convex lens 32, 33 .
The measurable distance to the tail lamp 10a is different for every 34 units. Moreover, by making such a difference in measurement distance correspond to a difference in the light receiving position on the light receiving surface 35a of the image sensor 35, the difference in the light receiving position can be detected by the image sensor 35 in relation to the clear contrast. Based on this detection result (according to the output of the bypass filter 41), the distance determining circuit 42 determines the measurement distance from the predetermined data.As a result, this type of optical distance measuring device 34 can be provided at low cost with a simple optical configuration.

In the above description, the distance between vehicles during daytime driving is measured using sunlight reflected from the tail lamp 10a, but for example, when driving at night, the distance between vehicles can be measured using the light from the tail lamp 10a itself. It is.

Furthermore, in carrying out the present invention, in place of the convex lenses 32, 33, and 34 described in the previous embodiment, zoom lenses 36, 37° 38, as shown in FIG. 5, are used. It is also possible to achieve the same effects as in the above embodiment. In such a case, each zoom lens 36, 3 corresponding to the short focal length Fb of each convex lens 32, 33, 34,
The short focal length of 7.38 is Fbzl, Fbz2. Fbz3
Then, each zoom lens 3 from the tail lamp 10a
6. Parallel incident light rays to 37.38 to image sensor 35
Each of the short focal lengths Fbzl, Fbz2 . Set Fbz3 to be successively smaller. In addition, the focal pressure % of each convex lens 32, 33, 34
1tFal, Fa2. The focal lengths of the zoom lenses 36 and 37° 38 corresponding to Fa3 respectively have focal pressures MiFal.

)'a2. Define in the same way as Fa3.

In addition, in the above embodiment and its modified example, an example was described in which the number of convex lenses or zoom lenses was three, but the number is not limited to this, and the number of convex lenses or zoom lenses can be changed as necessary. It may also be carried out.

In addition, in the above-mentioned embodiments and variations thereof, an example was described in which the present invention was applied to measuring the distance between the front and rear of a vehicle. However, the present invention may be applied and implemented.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing an embodiment of the device of the present invention that is used in a following vehicle, Fig. 2 is an enlarged sectional view of the main body of the device in Fig. 1, and Fig. 3 is a signal processing section and display in Fig. 1. The block diagram of the device, Figure 4, shows the measurement ability Ii! A graph showing the relationship between iD and the height X above the light-receiving surface of the image sensor in FIG. 2, and FIG. 5 are enlarged sectional views of essential parts showing a modification of the embodiment. Explanation of symbols 10a...Tail lamp, 30...Device main body, 32
．． 33. 34... Convex lens, 35... Image sensor, 35a... Light receiving surface, 36, 37° 38... Zoom lens, 40... Signal processing unit, 41... Bypass filter, 42... ...Distance determination circuit.

Claims (1)

[Claims] A first lens system and a second lens system are arranged with their optical axes parallel to each other so as to face the object to be measured in front, and the first lens system has a predetermined focal length on the front side thereof. When a parallel beam of light is received from the object to be measured based on the focal length, the object to be measured is imaged behind it, and the second lens system has a predetermined focal length different from the focal length on the front side thereof. When a parallel beam of light is received from the object to be measured based on the focal length of the object, the object to be measured is imaged behind it;
and has a light-receiving surface disposed behind the first and second lenses and facing both lens systems, and the first (or second)
The image formed by the lens system is at one position on the light-receiving surface (or
Detect this when it occurs in the first (or second position)
), and the first (or second) An optical distance measuring device comprising: a measurement distance determining means for determining the measurement distance according to an image detection signal.