JP3432422B2 - Object detection device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] 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 a countermeasure against contamination attached to a cover covering an optical system. 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, it is a common practice to irradiate a beam from a light emitting unit, collect the reflected light of the beam from an object with a lens, and guide it 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 light emitting part and the light receiving part of the beam are contained in a case. [0003] Such an object detection device is applied to a vehicle,
A device for determining whether an occupant is sitting in a seat is disclosed in
-206514. [0004] In the apparatus and the like disclosed in the above publication, if dirt adheres to the case, the light transmittance of the case decreases. Since the irradiation light and the reflected light each pass through the case, the light amount of the light beam detected by the light receiving unit decreases by the square of the decrease in the transmittance. For example, the light transmittance is 1 /
When it becomes 2, the detected light amount becomes 1/4. Further, the image may be blurred due to scattering of light due to dirt. There is a problem that the detection accuracy is reduced due to the decrease in the detected light amount and the blur of the image. SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and has as its object to provide an object detecting device capable of keeping a case surface clean. In order to achieve the above-mentioned object, an object detection apparatus according to the present invention comprises a light-emitting section for emitting a beam, a light-receiving section for receiving reflected light of the beam, and at least a light-receiving section for receiving the reflected light of the beam. A case that covers the light-emitting unit and the light-receiving unit; and a catalyst layer containing a photocatalytic material is formed on at least a portion of the outer surface of the case where the beam and the reflected light are transmitted. The photocatalyst decomposes the adhered dirt and keeps the outer surface of the case, particularly the part where the beam and its reflected light are transmitted, clean. [0007] The photocatalytic material can be titanium oxide. Since titanium oxide has high hydrophilicity, water adhering to the outer surface of the case does not form water droplets but forms a film. Therefore,
Light scattering due to water droplets does not occur, and the occurrence of image blur and the like can be suppressed. Further, an ultraviolet light source can be provided in the case. The photocatalyst functions by the irradiation of ultraviolet rays, and can exert a purifying action even at night when sunlight cannot be expected. The ultraviolet light source is
When the value is equal to or less than a predetermined value, ultraviolet light can be irradiated. Further, a transparent conductive layer and a power supply unit for supplying power to the transparent conductive layer may be provided on at least a portion of the inner surface of the case where the beam and the reflected light are transmitted. When an electric current is supplied from the power supply unit to the transparent conductive layer, the electric current is generated and the dew condensation on the outer surface of the case can be prevented. An embodiment of the present invention (hereinafter, referred to as an embodiment) 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 detection 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, which is a light emitting unit, is configured by an LED that emits near-infrared light 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 filter material that absorbs visible light and transmits near infrared rays and ultraviolet rays.
By using such a filter material, visible light is cut off, and the contents of the sensor become invisible to an occupant, thereby improving design. Further, by cutting the visible light, the influence of disturbance light (such as sunlight) can be reduced. This case 22
A Fresnel lens 24 and a prism 26 are formed at a position on the lower surface facing each light source 14. Less than,
This surface will be described as an optical surface 28. On the surface of the optical surface 28 inside the case 22,
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 viewed 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 changes its direction after passing through the Fresnel lens 24 and the prism 26, 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. A catalyst layer 32 containing a photocatalytic material is formed on the outer surface of the case 22. In the present embodiment, the catalyst layer 32 is a layer of titanium oxide. When the catalyst layer 32 is irradiated with sunlight or ultraviolet rays, active oxygen is generated from oxygen or water in the air by the energy of the ultraviolet rays. Due to the oxidizing power of the active oxygen, dirt such as cigarettes and grease on the hands adhered to the outer surface of the case is decomposed and cleaned. As a result, it is possible to reduce a reduction in the amount of transmitted light due to dirt and an occurrence of erroneous determination due to blurring of an image. Therefore, the accuracy of the detection device is improved. The catalyst layer 32 needs to be provided on the outer surface of the case on the path of the beam and the path of the reflected light received by the light receiving unit 16. The catalyst layer 32 does not actually have a thickness as shown in the figure, but is formed as a very thin layer. Further, since the titanium oxide layer has a high hardness,
It also contributes to protecting the outer surface of the case. Scratches on the outer surface of the case scatter the beam and its reflected light, thereby reducing the amount of received light, which can be suppressed by the titanium oxide layer. From this surface, it is sufficient if the titanium oxide layer is provided on the outer surface of the case on the path of the beam and the reflected light, but it is preferable that the layer is formed on the entire case from the design surface. Furthermore, titanium oxide has high hydrophilicity,
Water droplets can be prevented from being formed on the outer surface of the case. Water droplets scatter light, which is one of the causes of erroneous determination. However, if this can be prevented, the accuracy of the detection device is improved. Further, an ultraviolet light source 34 is provided on the substrate 12. As described above, since the case 22 is a material that transmits the near-infrared region and the ultraviolet region, the ultraviolet rays reach the outer surface of the case. With this ultraviolet light, a cleaning action by the photocatalytic effect can be expected even at night when no external ultraviolet light is received. UV light source 3
No. 4 preferably irradiates ultraviolet rays only at night when sunlight cannot be expected. The nighttime determination can be made based on the entire light amount of the light receiving unit 16. That is, the light receiving unit 1
When the light amount of No. 6 becomes equal to or less than a predetermined threshold value, it can be determined that it is nighttime. Further, on the inner surface of the case 22, a transparent conductive layer 36 is provided. This layer may be formed by attaching a film, or may be formed by sputtering the case 22. Power is supplied to the transparent conductive layer 36 from a power source (not shown), and Joule heat is generated by a flowing current. This heat prevents water droplets from forming on the outer surface of the case. The prevention of the adhesion of water droplets can suppress the decrease in the amount of light due to the scattering of light by the water droplets themselves, and can also prevent the water droplets from adsorbing dust in the air and remaining on the case surface after drying. The transparent conductive layer 36 does not actually have a thickness as shown in the figure, but is formed as a very thin layer. In this embodiment, the Fresnel lens 2
Although the optical system such as the optical system 4 and the prism 26 are provided integrally with the case 22, it is also possible to adopt a configuration in which an optical system having the same function as these optical systems is arranged in the case as a light emitting unit together with the light source. . 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. When applied to a vehicle, the ultraviolet light source 3
Regarding the night lighting of No. 4, the following configuration can be adopted. Some vehicles currently on the market adopt a conlight system that automatically controls the turning on and off of headlights and the like according to the surrounding brightness. In this system, the brightness around the vehicle is measured by a conlite scanner provided near a windshield in the vehicle interior. Nighttime can be determined based on the output of the conlite scanner. In addition, nighttime can be determined when the headlight switch operated by the driver is on.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view showing 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. [Description of Signs] 10 object detection device, 12 substrate, 14 light source, 16
Light receiving part, 22 case, 32 catalyst layer, 34 ultraviolet light source, 36 transparent conductive layer.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-6-206514 (JP, A) JP-A-9-229767 (JP, A) JP-A-9-145482 (JP, A) 79445 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) G01V 8/10

Claims (1)

(57) 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, wherein the object emits the beam A light-emitting unit, a light-receiving unit that receives the reflected light of the beam, and a case that covers at least the light-emitting unit and the light-receiving unit; and a portion of the external surface of the case where at least the beam and the reflected light are transmitted. In the, a catalyst layer containing a photocatalytic material is formed, further has an ultraviolet light source in the case, the ultraviolet light source, when the light amount of the light receiving portion is less than a predetermined value, is to irradiate ultraviolet light, Object detection device.