JPH1114753A - Object detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide size reduction in an object detector which irradiates a beam of light to a plurality of areas to be detected and detects presence of an object based on its reflected light. SOLUTION: A Fresnel lens 24 and a prism 26 are fitted at a position facing a light source 14 of a case 22. The beam of roughly parallel light is formed by the Fresnel lens 24, and the direction of the beam is determined by the prism 26. As a result, it is possible to determine the direction of the beam regardless of the arrangement of the light source and the lens. It is thus possible to form a plurality of Fresnel lens 24 on the same plane for size reduction in the device by reducing the restriction in the arrangement of lens or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an object detection device for detecting the presence or absence of an object in a target area, and more particularly to the structure of an optical system.

[0002]

2. Description of the Related Art There is known a sensor for detecting whether an object, such as a person or a vehicle, is present in a predetermined target area by light from the object. For example, a sensor of an automatic door provided at an entrance of a house such as a store corresponds to this.
In such a sensor, light from an object is generally collected by a lens and guided to a light receiving unit. When a plurality of target areas are set, a lens is provided for each target area, and when the distances of the target areas are different, the focal length of each lens is set according to this distance.

The above-mentioned plurality of lenses are often formed as Fresnel lenses on a substantially flat member in order to simplify the structure. In this case, the light path of the light from the object is obliquely incident on the lens in the target region that is largely deviated from the vertical direction of the flat plate, and the transmittance is reduced. Due to this decrease in transmittance, there is a problem that the sensitivity of the sensor decreases.

In order to solve this problem, Japanese Utility Model Application Laid-Open No.
In the device described in No. 110128, the condenser lenses provided respectively corresponding to the plurality of target regions are arranged so as to be substantially orthogonal to the optical path.

[0005]

However, according to the apparatus disclosed in the above-mentioned publication, the direction of the lens is changed for each target area, and the apparatus becomes larger than when the lens is formed on a simple flat plate. There's a problem.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and an object of the present invention is to provide an object detecting device which has a stable detection sensitivity in each of a plurality of target regions and has a simple configuration. And

[0007]

In order to achieve the above-mentioned object, an object detection apparatus according to the present invention detects presence or absence of an object in a target area based on reflected light of a beam applied to a predetermined target area. A light source, a lens that converts light from the light source into a substantially parallel light beam, a prism that directs the substantially parallel light beam to the target area, and receives reflected light of the beam. A light receiving unit,
The lens and the prism are formed on the front and back of the plate-like member.

According to this configuration, the direction of light is changed by the prism, so that restrictions on the lens arrangement are reduced.
In addition, since the lens and the prism are formed on the front and back of the plate-like member, a simple configuration can be achieved as compared with a case where these are separately provided.

Further, at least one of the light source, the lens and the prism can be provided for each target area. According to this configuration, the focus and direction of the beam can be set to optimal values for each target region, so that the detection accuracy can be kept high in any direction.

Further, the light source and the light receiving section can be arranged on the same substrate, and the plate-like member can be arranged substantially parallel to the substrate.

Further, the plate member on which the lens and the prism are formed can be formed as at least a part of a cover for covering the light source.

An object detection sensor according to another aspect of the present invention is an object detection sensor for detecting the presence or absence of an object in a target area based on light from a predetermined target area, wherein the light receiving unit receives the light. And a lens for condensing the light, and a prism for directing the light to a light receiving unit, wherein the lens and the prism can be formed on the front and back of a plate-like member. Also in this embodiment, as in the above-described embodiment, it is possible to provide one lens and one prism for each target area, and at least one of a cover that covers the light source with a plate member on which the lens and the prism are formed. It can also be formed as a part.

[0013]

Embodiments of the present invention (hereinafter, referred to as embodiments) will be described below with reference to the drawings. The present embodiment is an object detection device of a type that detects the presence or absence of an object based on reflected light of a beam emitted from a light source.

FIG. 1 is a sectional view showing a schematic configuration of an object detecting device 10 according to the present embodiment. A plurality of light sources 14 and one light receiving unit 16 are provided on the substrate 12. The light source 14 is configured by a near-infrared light emitting LED in the present embodiment. Further, the light receiving section 16 has a light receiving element array 18 in which a plurality of light receiving elements are arranged, and an imaging lens 20 for forming an image of the received light on the light receiving element array 18. In the present embodiment, an element (CCD or MOS type solid-state imaging element) having good sensitivity in the near infrared region is used as the light receiving element.

The substrate 12 is housed in a case 22. The case 22 is entirely formed of a so-called infrared filter material that absorbs visible light and transmits only near infrared rays (for example, Mitsubishi Rayon Co., Ltd. Acripet near infrared transmission filter PF-076). By using infrared filter material, visible light is cut,
The contents of the sensor become invisible to the occupant, increasing the design. Further, by cutting the visible light, the influence of disturbance light (such as sunlight) can be reduced. A Fresnel lens 2 is provided on the lower surface of the case 22 at a position facing each light source 14.
4 and a prism 26 are formed. Hereinafter, this surface will be described as an optical surface 28.

On the inner surface of the case 22 of the optical surface 28,
FIG. 2 shows a state in which the Fresnel lens 24 is formed and viewed from the arrow A shown in FIG. This Fresnel lens 2
Reference numeral 4 designates that the light emitted from the light source 14 is substantially parallel light, or acts so that the light is focused in a region where the presence or absence of an object is detected.

A prism 26 is formed on the outer surface of the case 22 of the optical surface 28, and FIG. 3 shows a state seen from the arrow B shown in FIG. The prism 26 is formed by arranging a plurality of small prisms, and appears as a stripe pattern similar to a Fresnel lens in FIG. The difference from the Fresnel lens is that the prism 26 only changes the path of the light and does not form a focal point, so that the stripes appear as parallel lines as shown.

The light emitted from the light source 14 passes through the Fresnel lens 24 and the prism 26, changes its direction, and proceeds to a predetermined target area for object detection. When the object 30 is on the optical path of this beam, the light reflected on the surface forms an image on the light receiving element array 18 at a position corresponding to the object. For example, when the object 30 is located at a position indicated by reference numeral 30a in FIG.
And at the position shown at 30b, it appears at point b. Further, if there is no object, no image appears on the light receiving element array 18. Based on the difference between the image forming positions on the light receiving element array 18 and the presence or absence of an image, a determination unit (not shown) determines whether an object is present in the detection target area.

In the above-described object detection device of the present embodiment, the Fresnel lens 24 and the prism 26 are formed on the cover 22, so that the configuration becomes simple and the size is reduced, and particularly, the size in the vertical direction in FIG. Can be. Further, since the Fresnel lens 24 is provided to face the front of the light source 14 and the irradiation direction of the beam is performed by the prism 26, the light incident on the Fresnel lens 24 is
It is substantially perpendicular to this, and the attenuation of the light amount by the lens can be suppressed.

FIG. 4 shows a case where the above-described object detection device 10 is used as a sensor for detecting the presence or absence of an occupant in the front seat of a vehicle. The object detection device 10 is arranged near the front end of the roof of the vehicle 50, and a plurality of beams having different directions are formed by the action of the Fresnel lens 24 and the prism 26 provided on the optical surface 28 described above. The beam on the optical path indicated by L1 in the figure is reflected by the occupant's thigh when the occupant is present in the seat, and is reflected by the seat cushion of the occupant otherwise. It is possible to determine whether or not there is an occupant in the seat based on the difference between the reflection positions. Further, when the child seat is mounted backward, the reflection position of the beam on the optical path L2 changes, so that it is possible to detect this.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a schematic configuration of an embodiment of the present invention.

FIG. 2 is a diagram illustrating a Fresnel lens formed in a case according to the present embodiment.

FIG. 3 is a diagram illustrating a prism formed on a case according to the embodiment.

4 is a diagram showing an example in which the embodiment shown in FIG. 1 is applied to a vehicle occupant detection device.

[Explanation of symbols]

10 object detection device, 12 substrate, 14 light source, 16
Light receiving section, 22 case, 24 Fresnel lens, 26
prism.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Shinya Oeda 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Mitsubishi Electric Corporation

Claims (5)

[Claims] An object detection device for detecting the presence or absence of an object in a target area based on reflected light of a beam applied to a predetermined target area, comprising: a light source; A lens for forming a beam, a prism for directing the substantially parallel light beam toward the target area, and a light receiving unit for receiving reflected light of the beam, wherein the lens and the prism are formed on the front and back of a plate-shaped member. There is an object detection device. 2. The object detection device according to claim 1, wherein the lens and the prism are provided at least one for each target area. 3. The object detection device according to claim 1, wherein the light source and the light receiving unit are disposed on a same substrate, and the plate member is disposed substantially parallel to the substrate. Object detection device. 4. The object detection device according to claim 1, wherein the plate member on which the lens and the prism are formed is at least a part of a cover that covers the light source. 5. An object detection sensor for detecting the presence or absence of an object in a target region based on light from a predetermined target region, wherein the light receiving unit receives the light; a lens for condensing the light; An object detection device, comprising: a prism for directing light to a light receiving unit, wherein the lens and the prism are formed on the front and back of a plate-like member.