JPH02271280A - Optical body detecting apparatus - Google Patents

Abstract

PURPOSE:To make it possible to perform detection accurately at a required detecting distance without the effects of color, the shape and the like of a body to be detected by arranging a plurality of light emitting elements or photodetectors so that the distance to one photodetector or light emitting element is different. CONSTITUTION:The output signal from an oscillator 3 and its inverted signal (the output of an inverter 4) become the signals for both A and B channels, and light emitting elements 1A and 1B are driven. When the emitted light rays from both light emitting elements 1A and 1B are projected on a body to be detected, the reflected light rays are inputted into a photodetector 2. The received light signals are amplified in an amplifier 7. The signals are divided into the signals for both A and B channels with analog switches 8A and 8B. Both signals are converted into DCs through smoothing circuits 9A and 9B. Thereafter, the signals are inputted into a voltage comparator 11. At this time, the signal SA undergoes level adjustment with a variable resistor 10 and S'A is obtained. When S'A>=SB is obtained, the output of the comparator is inverted, and the detected signal of the body is outputted from an output circuit 12.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical object detection device that emits light in a predetermined direction and determines the presence or absence of an object or the degree of approach from the reflection thereof.

[Conventional technology]

For example, as shown in FIG. 5, if light is emitted from the light emitting element 51 toward the detected object S and the reflected light is received by the light receiving element 52, the degree of approach can be determined based on the level of the received light. It is used as an obstacle detection sensor in automobiles, etc.

[Problem to be solved by the invention]

However, if discrimination is made based solely on the level of reflected light, if the reflection efficiency or shape of the object S changes or the light emitting/receiving surface becomes dirty, this will directly affect the amount of light received and the detection distance will decrease. changes.

An object of the present invention is to provide an optical object detection device that can accurately detect an object up to a required point without being affected by the color or shape of the object to be detected or dirt on the light emitting/receiving surface. .

[Means to solve the problem]

The present invention includes a plurality of light receiving elements or one light receiving element that emits light emitted in a detection direction, one or more light receiving elements that receive reflected light from an object to be detected, and a light emitting current required for the light emitting element. a light emitting drive unit that supplies light, and a discrimination/processing unit that performs discrimination, comparison, etc. on light reception signals to determine whether an object is detected between required detection paths, and includes a plurality of light emitting elements or light receiving elements. The device is characterized by being arranged at different distances from the light receiving element or light emitting element 111.

〔Example〕

Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

FIGS. 1 and 2 show one embodiment of the present invention.
A and 1B are light emitting elements (for example, LEDs), and 2 is a light receiving element. As shown in FIG. 2, the light-emitting elements 1A and IB are on a line that is perpendicular to a straight line connecting the light-receiving probe 2 with an interval d and the light-receiving point P of the object to be detected, and that passes through the light-receiving element 2, as shown in FIG.
The light-receiving element 2 has a different distance (the light-emitting element 1A has a different distance)
The light emitting element 1B is placed at a position a, and the light emitting element 1B is placed at a position a distance away from the light emitting element 1B.

3 is an oscillator, 4 is an inverter for inverting the output of the oscillator 3, 5A and 5B are one-shot multivibrators, and 6A and 6B are amplifiers. After the oscillator 3, a one-shot multivibrator 5A and an A channel of an amplifier 6A, an inverter 4, and a one-shot multivibrator 5A are installed.
A B channel of a multivibrator 5B and an amplifier 6B are provided, and the A channel signal (output of the oscillator 3) drives the light emitting element 1A, and the B channel signal (inverted signal of the output of the oscillator 3, that is, the output of the inverter 4) drives the light emitting element 1A. The light emitting elements 1B are respectively driven. The one-shot multi-by-breaks 5A and 15B are added for the purpose of removing extraneous light, thereby reducing the duty ratio.

7 is an amplifier for amplifying the light reception signal of the light receiving cable 2; 8A;
and 8B is the one-shot multivibrator 5A
9A and 9B are smoothing circuits, and 10 is a level adjustment (detection distance) provided on the output side of the smoothing circuit 9A of one channel (for example, A channel). 11 is the A channel light reception signal after level adjustment (signal at the output end of the variable resistor 10) S',
and B channel light reception signal (output signal of smoothing circuit 9B)
A voltage comparator 12 compares the voltage with S8, 12 is the comparison result (S'
≧88, the output of the comparator 11 is inverted).

Next, the effect will be explained.

First, the principle of operation will be explained based on FIG.

The radiation intensity of the light-receiving point P in front of the light-receiving element 2 (in the X direction) is ■, and the distance between the light-receiving element 2 and the light-receiving point P is d.
Then, the radiation point E of point P. is expressed by the following equation. However, to simplify the explanation, the light emitting element 1A is assumed to be at the same position as the light receiving element 2 (a=0).

Furthermore, assuming that the point P is a perfectly diffusing surface with a reflectance ρ, the radiance of each element will be different. As can be seen from these equations, the light emitting element 1A and the light emitting element 1B have different luminance characteristics with respect to distance. Also, 'eA/LO
By using R as a sieve, the distance can be determined regardless of the reciprocal rate ρ of the object to be detected.

Figure 3 shows that for a specific distance ado, L is 1 and eA'
It is a characteristic diagram of equations (3) and (4) when eB.

An example of a configuration based on the above principle of operation is shown in FIG.
, 1B are driven. When the emitted light beams from both optical elements IA and 1B illuminate an object to be detected, reflection occurs and the reflected light enters the light receiving element 2. The received light signal is amplified by an amplifier 7,
Analog switches 8A and 8B separate the signals into A and 8 channel signals. Both signals are exchanged into direct current by smoothing circuits 9A and 9B, and then input to voltage comparator 11. At this time, the level of the signal SA is adjusted by the variable resistor 10 and becomes the signal S'. When S'5≧S, the output of the comparator 11 is inverted and an object detection signal is output from the output circuit 12.

In the above embodiment, the light emitting elements 1A and 1B are arranged on the left and right sides of the light receiving cable 2, but they may be arranged in the front and back direction. Also, the fourth
As shown in the figure, a plurality of light receiving elements 2A and 2B, for example two light receiving elements 2A and 2B, may be arranged with respect to one light emitting element 1 at different distances from the light emitting element 1. Furthermore, the distance can be calculated in detail by computing the signals @S and S using a microcomputer or the like.

〔Effect of the invention〕

As described above, according to the present invention, since the ratio of reflected light is calculated using a plurality of light emitting elements or light receiving elements, it is not affected by the color and shape of the object to be detected, dirt on the light emitting and light receiving surfaces, etc. Accurate detection can be performed at the required detection distance without any trouble. In addition, since it is composed of a small number of light emitting elements and light receiving elements and a simple circuit, it can be manufactured compactly and at low cost.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the optical object detection device according to the present invention, FIG. 2 is an explanatory diagram showing the arrangement relationship between the light emitting element and the light receiving element of the same embodiment, and FIG. 3 is the same embodiment. distance d
and brightness. FIG. 4 is an explanatory diagram showing another example of the arrangement relationship between a light emitting element and a light receiving element, and FIG. 5 is a basic explanatory diagram when detecting an object using light. 1.1A and 1B... Light emitting element, 2.2A and 2B... Light receiving element, 3... Oscillator, 4... Inverter, 5A and 5B... One shot multivibrator, 6A, 6B and 7...Amplifier, 8A and 8B...Analog switch, 9A and 9B...
...Smoothing circuit, 10...Variable resistor for level adjustment, 11...Voltage comparator, 12...Output circuit. Patent applicant: Stanley Electric Co., Ltd. Representative: Teruo Akimoto, 1.1]
1 person Figure 1 Figure 2

Claims (1)

[Claims] A plurality of light emitting elements or one light emitting element that emits light emitted in a detection direction, one or more light receiving elements that receive reflected light from an object to be detected, and a light emitting drive that supplies a required light emitting current to the light emitting element. and a discrimination/processing section that discriminates the light reception signal, performs comparison calculations, etc. to determine whether or not an object is detected at a required detection distance. An optical object detection device characterized in that the light emitting elements are arranged at different distances from each other.