JPH06331732A - Optical distance sensor - Google Patents

Abstract

PURPOSE:To provide an optical distance sensor which can be manufactured at low cost using a light receiving element of irreducible minimum size and shape without requiring such a component as diaphragm. CONSTITUTION:When a light beam is projected from a light source 1 over a range equal to or wider than a predetermined region 10 and the range of the region 10 is projected to a receiving optical system 4, the image thereof has the shape and size matching those of the light receiving face of a light receiving element 5 arranged on the focal plane.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical distance sensor. More specifically, the present invention relates to an optical distance sensor that has a high radiation angle directivity and can be used as a vehicle-mounted distance sensor.

[0002]

2. Description of the Related Art Compared with a radio wave distance sensor, a sound wave distance sensor, etc., an optical distance sensor can easily set a light irradiation angle and give directivity. For example,
In the case of an on-vehicle distance sensor, when measuring the distance to an object such as a preceding vehicle, if the irradiation angle is too large, unnecessary objects such as surrounding walls will be detected, or if the irradiation angle is too narrow, the measurement object will be detected. You may overlook it. For this reason, the directivity of the irradiation angle is extremely important in the on-vehicle distance sensor and the like, and thus the optical distance sensor is widely used.

When the optical distance sensor is used as, for example, a vehicle-mounted distance sensor, the projection angle of the light flux is set to a predetermined value, and the object to be measured in a predetermined area, which is the area irradiated by the light, is set. It is set so that the reflected light flux from is received. This will be described with reference to FIG. The light emitted from the light source 1 is projected by the light projecting lens 2 at a predetermined light projecting angle, and is irradiated onto the measuring object 3 in a predetermined area, for example, the preceding vehicle. Then, the light reflected from the measuring object 3 is incident on the light receiving surface of the light receiving element 5 by the light receiving lens 4 and is photoelectrically converted.

At this time, light incident from a region other than a predetermined area, for example, incident light from the background such as sunlight is blocked by a diaphragm or a honeycomb filter provided in the light receiving optical system so as not to enter the light receiving element 5. Was becoming. Figure 4
Shown in. This figure shows the progress of light in one direction. The light emitted from the light source 1 is projected onto the predetermined area 10 via the light projecting lens 2. The light beam reflected by the measuring object 3 enters the light receiving lens 4 through the diaphragm 6 provided in front of the light receiving lens 4, and enters the light receiving surface of the light receiving element 5. Further, as shown in FIG. 5, the projected light beam cross section 7 at this time has the same size as the predetermined area. The received light beam cross section 8 which is the range of the light receiving surface of the light receiving element 5 is wider than the predetermined region, but the diaphragm 6 blocks all the light beams other than the predetermined region and receives only the reflected light beam from the predetermined region.

[0005]

However, when an LD is used as a light emitting element, it is difficult to freely set the shape and size of the light emitting surface due to problems such as heat dissipation. Therefore, it is simply combined with the projection optical system. It is often difficult to produce a light beam with a predetermined projection angle by just doing so, and devising of an optical system has been proposed, for example, Japanese Patent Laid-Open No. 61-283887.
It is disclosed in the publication. However, all of them have a problem that the number of parts increases and the structure becomes complicated. Further, there is a problem that the light receiving optical system requires a diaphragm or a honeycomb filter, and the light receiving element has a portion that is shielded by the diaphragm or the honeycomb filter and does not participate in light reception. There was a problem saying it was needed.

In view of the above problems, it is an object of the present invention to provide an optical distance sensor which does not require a component such as a diaphragm and can be manufactured at a low cost by using a light receiving element having a required minimum size and shape. And

[0007]

The present invention has a light source and a light projecting optical system, and a light projecting means for irradiating a light beam emitted from the light source to a predetermined region at a predetermined light projecting angle, and a light receiving optical system. And a light-receiving element, and light-receiving means for receiving and photoelectrically converting the reflected light flux reflected from the object to be measured in the predetermined region, and from the projection of the light flux by the light-projecting means to the light-receiving means. Measuring the time to receive the reflected light flux,
In the optical distance sensor that measures the distance to the measurement object, the predetermined projection angle is set so as to illuminate an area that is the same as or larger than the predetermined area, and the light receiving element is the focus of the light receiving optical system. A light-receiving surface arranged to coincide with a surface, and the light-receiving surface shape has a shape and a size in which the predetermined region is projected at a light-receiving surface position by the light-receiving optical system. .

It is preferable that the predetermined area has a rectangular cross section with respect to a plane perpendicular to the optical axis of the optical system, and the shape of the light receiving surface of the light receiving element is a rectangle similar to the rectangle. .

[0009]

With such a structure, the light beam projected from the light source irradiates the same area as or a range equal to or more than the predetermined area, but when the range of the predetermined area is projected by the light receiving optical system, the image thereof is formed. It matches the shape and size of the light receiving surface of the light receiving element arranged on the focal plane. When the predetermined area is set to a rectangle, the shape of the light receiving surface of the light receiving element may be a rectangle similar to that. In the case of a light receiving element such as a PIN photo diode or an APD (avalanche photo diode), there is no problem because the shape and size of the light emitting surface can be set relatively freely.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 2, the light source 1 is a light emitting element LD, and the emitted light is projected by the light projecting lens 2 at a light projecting angle θ. The light reflected by the measuring object 3 enters the light receiving lens 4 at an angle smaller than the light receiving angle φ and then enters the light receiving surface of the light receiving element 5 located on the focal plane of the light receiving lens 4. The light-receiving surface of the light-receiving element 5 is a rectangle composed of sides 5a, 5b, 5c, and 5d, as shown as a perspective dotted line in FIG.

Since the light beam projected from the light source 1 needs to illuminate the entire rectangular predetermined region 10, the projected light beam cross section 11 is the same as or larger than the predetermined region 10 as shown in FIG. There is.

The predetermined area 10 referred to here is a side 10a, a side 10b, a side 10c, which is drawn as a perspective dotted diagram in FIG.
It is a rectangle composed of the side 10d, and is the same as the projected cross section in the range of the light receiving angle φ on the plane orthogonal to the optical axis of the received light flux at the position of the measurement object 3. The light projected from the light source 1 and reflected by the light receiving element 5 is received by the light receiving element 5 within the projection section defined by the angle of the light receiving angle φ.

An image 13 obtained by projecting the predetermined area 10 is similar in shape to the predetermined area 10, and has sides 13a, 13b, 13c,
The side 13d is the side 10a, the side 10b, and the side 10 of the predetermined area 10.
c, corresponding to side 10d. That is, the predetermined area 10 is 6 °
If it is defined as × 3 °, the size of the image 13 becomes about 2 mm × about 1 mm when the focal length of the light receiving lens 4 is set to 20 mm. If the size of the light receiving surface of the light receiving element 5 is set to about 2 mm × about 1 mm based on this size / shape, all the reflected light from the measuring object 3 in the predetermined region 10 can be received.

On the other hand, light from areas other than the predetermined area 10 does not enter the light receiving surface of the light receiving element 5 even when entering the light receiving lens 4, and is not received by the light receiving element 5.

In the present embodiment, the light receiving angle φ is set to 3 ° in the vertical direction and 6 ° in the horizontal direction, but at other angles,
It goes without saying that it can be set so as to be a predetermined area having another shape.

Although the light emitting element LD is used as the light source in the present embodiment, it is needless to say that a single light source or a plurality of other light sources can be used, and the light receiving element can be a PIN photodiode, an APD or the like. Yes.

[0017]

As described above, according to the present invention, the light beam projected from the light source is applied to the same area as or a range equal to or more than the predetermined area, and a projection image in which the range of the predetermined area is formed by the light receiving optical system is formed. Since it matches the shape and size of the light receiving element placed on the focal plane of the system, unnecessary light that does not enter from outside the specified area is not received, so parts such as a diaphragm attached to the light receiving optical system are unnecessary. Becomes When the predetermined area is set to be a rectangle, the shape of the light receiving element is similar to that of the rectangle, so that the size is the minimum necessary, and the light receiving element can be manufactured at low cost.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of the principle of an optical distance measuring device.

FIG. 2 is a conceptual diagram showing a relationship between a predetermined area, a light receiving lens, and a light receiving surface of a light receiving element in one embodiment.

FIG. 3 is a diagram showing a projected light beam cross section and a received light beam cross section (predetermined region) in one embodiment.

FIG. 4 is a conceptual diagram showing a relationship between a predetermined area, a diaphragm, a light receiving lens, and a light receiving surface of a light receiving element in a conventional example.

FIG. 5 is a diagram showing a projected light beam cross section, an aperture of a diaphragm, and a received light beam cross section in a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Light source 2 ... Emitting lens 3 ... Measuring object 4 ... Light receiving lens 5 ... Light receiving element 7, 11 ... Projected light beam cross section 8, 12 ... Received light beam cross section 10 ... Predetermined area 13 ... Image obtained by projecting predetermined area by light receiving lens θ ... Projection angle φ ... Reception angle

Claims (2)

[Claims] 1. A light-projecting means having a light source and a light-projecting optical system for irradiating a predetermined region with a light beam emitted from the light source at a predetermined light-projecting angle, a light-receiving optical system and a light-receiving element, A time period from the projection of the light flux by the light projecting means to the reception of the reflected light flux by the light receiving means. In the optical distance sensor for measuring the distance to the measurement object, the predetermined projection angle is set so as to illuminate an area that is the same as or more than the predetermined area, and the light receiving element is the It has a light-receiving surface arranged to match the focal plane of the light-receiving optical system,
An optical distance sensor, wherein the shape of the light receiving surface matches the shape and size of a projected image of the predetermined area projected on the light receiving surface position by the light receiving optical system. 2. The predetermined region has a rectangular cross-sectional shape with respect to a plane perpendicular to the optical axis of the optical system, and the shape of the light-receiving surface of the light-receiving element is a rectangle similar to the rectangle. The optical distance sensor according to claim 1.