JPS6040984A - Approaching matter detecting apparatus - Google Patents

Abstract

PURPOSE:To reduce the change of a detecting distance, by bringing the angle formed by the optical axis of one of a light emitting element and a light receiving element and the center line crossing the center point of a line connecting both elements at right angles to a specific range when the angle formed by the aforementioned center line and the optical axis of the other element is set to -theta. CONSTITUTION:When the center line crossing the center point of a straight line connecting a light emitting element T and a light receiving element R at right angles is set to CT, an approaching matter detecting apparatus is constituted so that the angle -theta formed by the optical axis O' of the light emitting element T and the center line CT comes to the incident angle to matter. In this case, the angle (light receiving angle) formed by the optical axis O' and the center line CT is set to a range of theta-20 deg.-theta-10 deg. or theta+10 deg.-theta+20 deg.. By this constitution, an error generated by the characteristics (shape, color and material quality) of the approaching objective matter from the aspect of a detecting distance can be made small as possible.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a nearby object detection device that optically detects objects at a short distance.

Conventionally, a method of optically detecting a nearby object that enters the blind spot from the driver's seat in the driving direction of a car uses a detection device DET with a light emitting element T and a light receiving element R separated vertically by about 10 to 20 cm, as shown in Fig. 1. There is a device installed on the outside wall of the vehicle to monitor the area directly in front of or behind the vehicle.

In this case, the horizontal half-value angle θH between the light-emitting element T and the light-receiving element R is wide as shown in FIG. 2(a), and the vertical half-value angle θ
V is generally set as narrow as (bl).

The feature of the detection device DET shown in Fig. 1 is that it has a symmetrical structure so that the optical axis 0 of element R and the optical axis ○' of element T intersect at the same angle with respect to the straight line connecting elements R and 7. It is a point. In this way, the reflected light from the object in the intersection area ARI (hatched area) where the directivity of the pixel elements R and T overlap can be received with higher sensitivity than the reflected light from objects in other areas. Objects (obstacles) within the area AR+ set within a range of 40 to 60 cm from DET can be easily determined.

However, if the target object is shiny like metal, the specular reflection component will be strong, so even outside the set area ARI, as shown at point P in Figure 1, a grill located on the front side of the device DET will receive strong reflected light. However, there is a problem in that the object detection area is actually expanded beyond the setting area AR+. In other words, in a proximity warning device using such a detection device, it is sufficient to issue a warning against an object that may collide with the object.

By the way, as shown in FIG. 3, reflection 11. It can be seen that there are differences in the reflection characteristics; for example, white cloth and cardboard have mostly diffuse components, whereas metals such as aluminum plates have strong specular reflection components. The characteristics in the figure are that the incident angle of the light irradiating the object is 110 degrees, and the incident light intensity is 4.
The reflected light intensity in the case of 08 dBm is shown with the light reception angle plotted on the horizontal axis. The intensity of reflected light from an object with a strong specular reflection component, such as an aluminum plate, is highest when the light-receiving element is placed at +10 degrees symmetrically with the light-emitting element. Light receiving element +10'
The reflected light intensity weakens whether it is moved further to the negative side or to the positive side. On the other hand, the intensity of reflected light from objects with strong scattering components, such as white cloth or cardboard, is approximately constant regardless of the position of the light receiving element.

In this case, if we pay attention to the diffused light component, we can see that there is a range in which there is not much difference in the intensity of light reflected by objects. As in this example, when the angle of incidence from the light emitting element to the object is -10°, the optical axis of the light receiving element is set between -10° and 0° with respect to the object.
"Or the range beyond 20° to 30°. Generally speaking, if the incident angle is 10, a peak of regular reflection from an aluminum plate, etc. will appear at 100°, but the range from β-20" to θ-10° Alternatively, in the range of θ+10° to θ+20°, the light receiving characteristics are similar to those shown in FIG. 3.

The present invention focuses on this point and attempts to construct a nearby object detection device in which the detection distance changes little with respect to changes in the object by receiving diffused light.

The present invention provides a reflection-type close object detection device that optically detects an object existing in a region where the directional characteristics of a pixel element intersect by intersecting the optical axes of the light emitting element and the light receiving element. When the angle formed by the optical axis of one element is 1 θ with respect to the center line perpendicular to the midpoint of the line connecting 10' or in the range of θ+10° to θ+20°, which will be described in detail below with reference to the illustrated embodiment.

FIG. 4 is an explanatory diagram showing one embodiment of the present invention, and the symbols of each part are the same as in FIG. 1. When CT is the center line perpendicular to the midpoint of the straight line connecting the light emitting element 1' and the light receiving element R, the angle -θ between the optical axis O' of the light emitting element T and the center line C is the angle of incidence on the object. becomes. In the example of FIG. 1, at this time the light receiving element R
The angle (acceptance angle) between the optical axis 0 and the center 1C,'+ line CT is set to +θ.
It is set in the range of 0° to θ-10° or θ+10° to θ+20°. AR2 is 2 in the object detection setting area at this time.
Chiru.

Figure 5 shows a specific example in which the detection device DET is attached to the rear bumper BNP of a car, where A is the boundary line where the emission intensity becomes zero, B is the boundary line corresponding to the half width G of the emission intensity, and C is the boundary line where the light receiving sensitivity becomes zero.

FIG. 6 is a detailed view of this, where I(60) to I(40) are the intensities incident on the object at distances of 60 CI11 to 40 cm, respectively. FIG. 7 (al-1h direction characteristic of light receiving element R, fbl is a simplified directional characteristic of light emitting element T, respectively.

If the target object is sufficiently large, the detection voltage of the light receiving element R that has received the reflected light from the object at a distance of @ffi (m) (vol.
t) is expressed as. Here, F is the total energy of effective light incident on the object, and corresponds to the area of the shaded part in FIG. In other words, if l = 0.5 m and F = Fo, then 12-Q,
(In i m, F = 0.IFo, and j2 = O
.

At 4m, F=5Fo. Therefore, if the detection voltage of the object at β-0.5 m is 0, J = 0.4 from the +11 formula.
At m, V = 7.8 Vo, and at 12-0.6 m, V = 0.08 Vo.

From this, it can be seen that even for the same object, the distance is from 0.4 m to 0.6 m.
It can be seen that as the value changes to m, the detected voltage changes approximately 100 times. If you look at it from a different perspective, the distance% ] It 0.4
Even if the distance is determined from the detected voltage for different objects with a 100 times difference in detection voltage at any point between m and 0.6 m, the result will be the distance RO, 4 m to 0.
．． This means that the detection range is within 6 m, which helps reduce the difference in detection distance due to the characteristics of the object.

Note that the arrangement relationship between the light emitting element T and the light receiving element R may be reversed. Furthermore, as the directional characteristics of each element are narrowed down, the degree to which surrounding influences can be avoided increases.

As described above, according to the present invention, errors in detection distance caused by the characteristics (shape, color, material) of a nearby target object can be minimized.

[Brief explanation of drawings]

Figure 1 shows an explanation of a conventional nearby object detection device.
The figure shows the orientation of the light receiving and light emitting elements. Figure 3 is an explanatory diagram of the principle of the present invention, Figure 4 is an explanatory diagram showing an embodiment of the present invention, Figure 5 is an explanatory diagram of a specific example thereof, Figure 6 is a detailed diagram of the main part, FIG. 7 is a directional characteristic diagram of the light receiving and light emitting elements. In the figure, T is the light emitting element, 0' is its optical axis, it light receiving element,
0 is the optical axis, AR2 is the intersection area of the directional characteristics, and CT is the center line. Applicant Fujitsu Ten Ltd. Representative Patent Attorney Minoru Aoyagi Figure 1 Figure 2 Figure 3 Figure 4 □Kai-like angle Figure 5 Figure 7 (al Figure 6 ■

Claims (1)

[Claims] In a reflection type close object detection device that optically detects an object existing in the intersection area of the directional characteristics of the pixel element by intersecting the optical axes of the light emitting element and the light receiving element, a line connecting the light emitting element and the light receiving element is used. When the angle between the optical axis of one element and the center line perpendicular to the midpoint is -θ, the angle between the optical axis of the other element and the center line is approximately θ~20°~θ−10° or θ+
A nearby object detection device that is set in the range of 10° to θ+20°.