JPS61218978A - Distance-limited type optical sensor - Google Patents

Abstract

PURPOSE:To prolong the life of a light emitting element and to improve an S/N by integrating memory data plural times so as to make it into a detection signal of one time. CONSTITUTION:Light beams which is light-modulated by the frequency of an oscillating part 1 is emitted out of a light projecting part 3. Some of them enters a light receiving part 5 through an optical fiber 4, while remainders are reflected by a subject 6 and enter a light receiving part 11. The light receiving signals of respective parts are made into low frequency signals through amplifiers 7 and 12 and mixers 8 and 13, and given to an EX.OR gate 17 through filters 9 and 15 and waveform shaping circuits parts 10 and 16. The decision is made whether said signals are coincidence or not, and a pulse having a width corresponding to a distance up to the reflecting subject 6 is outputted from the gate 17. Then an output by taking an AND between said pulse and a clock pulse from a clock generating circuit 18 is counted 20, and the distance up to the subject 6 is calculated 21 on the basis of said counted value.

Description

[Detailed Description of the Invention] [Technical Field] The present invention measures the distance to a reflecting object using a phase difference,
This invention relates to a distance-limited optical sensor that uses light to limit the detection range.

[Background technology 1] In conventional distance-limited optical sensors that utilize light reflection, there have been some that increase the light output by passing a large current through the light emitting element in order to improve the S/N ratio, but the characteristics of the light emitting element Moreover, when a large current is applied, the deterioration occurs quickly unless the light emission time is shortened, and therefore there is a limit to the improvement of the SN ratio for detection within one light emission time.

[Objective of the Invention 1] The present invention has been provided in view of the above-mentioned points, and is aimed at improving the signal-to-noise ratio by integrating multiple signals on the light receiving side to form a single detection signal. A limited type optical sensor is provided.

[Disclosure of the invention 1 Embodiments of the present invention will be described below with reference to the drawings.

fIS1 diagram shows a block diagram of this optical sensor A, and the light emitting circuit includes an oscillating section 1 that oscillates a high frequency, a drive circuit 2 that amplifies the output of the oscillating section 1, and a light emitting circuit that is driven to emit light by the drive circuit 2. A structure consisting of a light projecting section 3 such as a diode
l! , has been. It should be noted that there is a plurality of light emitting parts 3,
It emits multiple light beams. The light receiving circuit is PIN
A pair of light receiving parts 5.11 such as diodes, and a light receiving part 5
, 11, and the local oscillator [14
mixers 8 and 13 that convert the quotient frequency signals of the amplifiers 7 and 12 into low frequencies at frequencies from 1 and 2; 16, an exclusive or date 17 that determines f1 whether the outputs of both waveform shaping sections 10 and 16 match, and an AND circuit that ANDs the output of the exclusive or date 17 and the clock pulse from the clock generation circuit 18. It is composed of a counter 20 that counts the output pulses of dates 19 and 7), and an arithmetic control section 21 consisting of a microcomputer that determines the set distance of the detection range and detects objects based on the output of the counter 20. . Further, the light projecting section 3 and the light receiving section 5 are optically coupled through an optical fiber 4, so that the light receiving section 5 immediately receives the light from the light projecting section 3.

The light driven by the drive circuit 2 and optically modulated at the frequency of the oscillator 1 is emitted by the light emitter 3, and a part of the light passes through the light 7 fiber 4 and immediately enters the light receiver 5, and the rest The light is reflected by the reflective object 6 and then received by the light receiving section 11. The signals received by the light receiving sections 5 and 11 are amplified by amplifiers 7 and 12, respectively, and then sent to the local oscillator 1 by mixers 8 and 13.
It is mixed with the signal of No. 4 and extracted as a low frequency signal. Furthermore, the waveform shaping section 1
0.16, the waveform is shaped and output as shown in FIGS. 2(a) and 2(b). The output from the waveform shaping section 16 is reflected by the reflective object 6, so it is output with a time delay, and has a certain phase difference from the output from the reflection shaping section 10. Then, the outputs of both waveform shaping units 10 and 16 are determined to be coincident or inconsistent in the exclusive or date 17, and as shown in FIG.
As shown in e), when the outputs do not match, an H level signal is output. This exclusive or date 1
As the output of 7, a pulse wave having a width corresponding to the distance of the reflective object 6 from the optical sensor A is output.

The width is ANDed with the clock of the clock generation circuit 18, and the counter 20 counts pulses as shown in FIG.
1 to know the distance to the reflective object 6. The light receiving circuit excluding the light receiving section 5.11 constitutes an object detection means.

By the way, in this case, the reflectance of the projectile is low,
When the object is far away, the signal component is small, so the output from the waveform shaping section 16 becomes unstable due to interaction with noise, making it difficult to obtain accurate distance information.To solve this problem, If a large current is passed through the light emitting element, the S/N ratio will be improved, but when a large current is passed, the light emitting time must be shortened from the viewpoint of the lifespan of the light emitting element.Therefore, in order to improve the S/N ratio, There will naturally be a limit to S.
In order to improve the N ratio, it is necessary to lengthen the measurement time, but for this purpose, instead of using one measurement as distance information to the object, as shown in FIG. The information output from the counter 20 is sequentially stored in the storage unit 22, and the n pieces of storage data stored in the storage unit 22 are integrated by the detection unit 23.
The total number of times is used as a distance signal to the object. By integrating the stored data for the nth time, the signal component is multiplied by 0, and the noise component is multiplied by Jl-, so by integrating one signal, the S/N ratio becomes /7 times, which makes it more accurate. Information can be obtained.

Therefore, even when a large current is passed through the light emitting element of the light projecting section 3, the light emitting time can be shortened, so that the life of the light emitting element can be extended.

Incidentally, FIG. 3 (&) shows the output waveform of the waveform shaping section 10,
FIG. 3(b) shows the output waveform of the waveform shaping section 16 when there is a sufficient amount of reflected light, and FIG. 3(e) shows the output waveform of the exclusive OR gate 17 when there is a sufficient amount of reflected light. , FIG. 3(d) shows the output waveform of the waveform shaping section 16 when the amount of reflected light is small, and FIG. 3(e) shows the output waveform of the waveform shaping section 16 when the amount of reflected light is small.

[Effects of the Invention] As described above, the present invention includes a light emitting section made of a light emitting element that emits a high frequency modulated optical signal, and a pair of light receiving sections, and one of the light receiving sections receives the optical signal. At the same time, the other light receiving section receives the reflected light of the optical signal from the detected object, and the distance to the detected object is detected in advance based on the phase difference between the received light signals output from both light receiving sections. In a distance-limited optical sensor that is provided with an object detection means for determining whether or not a detected object exists within a detection range of a set set distance, a distance-limited optical sensor is provided that uses light emitted from the light emitting element and reflected from the detected object. a storage unit that sequentially stores the signals;
Since it is equipped with a detection section that integrates the stored data stored in the storage section multiple times to produce a single detection signal, even when a large current is passed through the light emitting element on the light emitting side, Since it is possible to shorten the luminescence darkness, it is possible to extend the life of the light emitting element, and by integrating multiple signals, it is possible to improve the SN without putting a burden on the light emitting element.
This has the effect of improving the ratio.

[Brief explanation of drawings]

#s1 is a block diagram of an embodiment of the present invention, FIG. 2 is an operational waveform diagram of the same as above, vIJ3 is an operational waveform diagram of the same as above, and FIG. 4 is a main part block diagram of same as above. Reference numeral 3 indicates a light projecting section, 5 and 11 a light receiving section, 6 a reflecting object, 21 a calculation control section, 22 a storage section, and 23 a detection section. Agent: Patent Attorney Ishi 1) Voluntary author of the 7th Procedural Amendment) May 7, 1985

Claims (1)

[Claims] (1) Equipped with a light emitting section made of a light emitting element that emits a high frequency modulated optical signal and a pair of light receiving sections, one of the light receiving sections immediately receives the optical signal, and the other light receiving section receives the optical signal immediately. to receive the reflected light of the optical signal from the object to be detected,
Object detection means that detects the distance to the object to be detected based on the phase difference between the light reception signals output from both light receiving sections and determines whether or not the object to be detected exists within a detection range of a preset set distance. A distance-limited optical sensor comprising: a storage section that sequentially stores signals from light emitted from the light emitting element and reflected from the detected object; and a storage section that integrates the stored data stored in the storage section multiple times. What is claimed is: 1. A distance-limited optical sensor, characterized in that the distance-limited optical sensor is provided with a detection section that generates a single detection signal.