JPS6095317A - Optical distance measuring device - Google Patents

Abstract

PURPOSE:To measure exactly a distance by differentiating and amplifying a photodetecting signal passing through a band pass filter to a reference voltage, and thereafter, feeding it back to an emitted light quantity controlling circuit of a projecting part having a projecting period modulating circuit. CONSTITUTION:A projecting period modulating circuit 18 is provided on an emitted light quantity controlling circuit 10 of a semiconductor laser diode 1, reflected light 4 by an object to be measured 3 of its projecting light 2 is photodetected by a photodetector 5, and a signal which passes through a photodetecting output voltage converting circuit 12 and a band pass filter 13 is divided into voltages (a), (b) proportional to a photodetecting position and a light quantity, respectively, by a photodetecting light quantity detecting circuit 14. Subsequently, the voltage (b) is rectified by a rectifying circuit 15, and thereafter, compared with an output of a reference voltage setting circuit 17 by a difference detecting and amplifying circuit 16, and its differential voltage is fed back to the circuit 10. In this way, said signal is separated from an external optical noise by the filter 13, the projecting quantity of the diode is controlled so that an output of the circuit 16 becomes constant, and an influence of a reflection factor of an object to be measured can be eliminated.

Description

[Detailed Description of the Invention] Industrial Application Field The present invention is directed to semiconductor light emitting devices (semiconductor laser diodes).
The present invention relates to an optical distance measuring device that uses a light source as a light source and measures the distance from the light source to an object in a non-contact manner.

Structure of the conventional example and its problems An optical distance measuring device using a semiconductor light emitting element as a light source, for example, a semiconductor laser diode 1 shown in FIG. In a device that receives light using a light-receiving element 5 and measures the distance d to an object to be measured, the light amount control of the semiconductor laser diode 1 is performed by attaching a photodiode 6 to the measurement surface of the semiconductor laser diode 1 and The light amount of the semiconductor laser diode 1 was controlled by controlling the output to be constant. 8 is a light projecting lens, 8 is a condensing lens, 9 is a distance detection circuit, and 1o is a semiconductor laser diode voltage control type light emission amount control circuit. However, in this case, the amount of received light changes due to differences in the surface reflectance of the object to be measured 3, and as a result, the object to be measured 3 is limited to objects with constant reflectance, and the amount of received light varies. It had the disadvantage of being slow in measuring moving objects. As a method to improve these drawbacks, a light receiving output voltage conversion circuit 1 as shown in FIG.
A light amount control method has been used in which the received light amount output of 1 is compared with a predetermined reference voltage, and the difference is fed back to the semiconductor laser diode voltage control type emitted light amount control circuit 10 to control the received light amount to be constant.

However, with this method, when measuring under ambient light, the light receiver cannot distinguish between the light projected by the emitter and the ambient light.
Therefore, it has a drawback that the light amount of the light projecting section cannot be controlled accurately.

OBJECTS OF THE INVENTION It is an object of the present invention to eliminate the above-mentioned drawbacks of the conventional methods, and to perform accurate distance measurement without being affected by the reflectance of an object to be measured, even in a measurement location where there is a lot of ambient light.

Structure of the Invention In order to achieve this object, the present invention includes a light projecting section that uses a semiconductor light emitting element as a light source, and a light projecting section that forms a constant angle with the optical axis of the light projecting section and projects the light projected from the light projecting section onto an object to be measured. and a distance detection circuit that processes the signal of the light receiving section and detects the distance, and the light projecting section includes a semiconductor light emitting element, a light emission amount control circuit, and a light projection period modulation circuit. The light receiving section is comprised of a light receiving element, a light receiving output voltage conversion circuit, a band pass filter, a received light amount detecting circuit, a rectifier circuit, a reference voltage setting circuit, a difference detection and amplification circuit, and the difference detection and amplification circuit. The amount of light received by the light receiving section is controlled to be constant by feeding back the output to the light emission amount control circuit. With this configuration, the semiconductor laser diode projection light modulated to a predetermined frequency by the light projection period modulation circuit is converted into a voltage in the light receiving section, and then filtered by a band pass filter (BPF) having the predetermined frequency as the center frequency. It is separated from the light and extracted. The received light signal separated from the disturbance light is converted into a received light amount signal by a received light amount detection circuit, then rectified, and the difference from the reference voltage is calculated. The difference from the reference voltage is amplified and then fed back to the light emission control circuit. The emitted light amount control circuit controls the emitted light amount based on the differential voltage.

By controlling the amount of light as described above, the amount of received light is always constant without being affected by the surface reflectance of the object to be measured or the disturbance light at the measurement location.

DESCRIPTION OF THE EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 3 and 4 of the drawings. 1.2r 3+ 41 51 71 819
+10id The same semiconductor laser diode, projected light, reflected light from the object to be measured 1, light receiving element, light projecting lens, condensing lens, distance detection circuit 1, and emitted light amount control circuit are the same as in the conventional +10id example. 12 is a received light output voltage conversion circuit, 13 is a band pass filter (BPF), 14 is a received light amount detection circuit, 15 is a rectifier circuit, 16 is a difference detection/amplification circuit, 17 is a reference voltage setting circuit, and 18 is a light emitting circuit. It is a period modulation circuit. The light source of the light projecting section is a semiconductor laser diode 1 with an output of 1 omW, and the light receiving element 5 is a one-dimensional Po5tion 5ensiti.
veDetector (PSD) was used. The modulation frequency of the light projection period modulation circuit 18 and the center frequency of BpH3 were set to 1 kHz. The 10 kHz 2 VC modulated projection light projected from the semiconductor laser diode 1 is converted into a parallel beam by the projection lens 7 and projected onto the object to be measured 3 . Reflected light 4 on the object to be measured s is received by a light receiving element (PSD) 5 that forms a predetermined angle α with the projected light 2 through a condenser lens 8 . The received light signal is converted into a voltage signal by a received light output voltage conversion circuit 12 using an operational amplifier, and then converted to a voltage signal by a BPF.
13, it is separated from the disturbance light noise. The received light signal separated from the disturbance light noise is output by the received light amount detection circuit 14 as a voltage a proportional to the light receiving position and a voltage S proportional to the received light amount. The voltage a proportional to the light receiving position is processed in the distance detection circuit 9 and output as distance data. Further, after the voltage proportional to the amount of received light is rectified by a rectifier circuit 16, it is compared with the output of a reference voltage setting circuit 17 by a difference detection and amplification circuit 16, and the comparison difference voltage is fed back to the light amount control circuit 10. With the above configuration, the amount of light projected by the semiconductor laser diode is controlled so that the output of the differential detection and amplification circuit 16 is always constant, and therefore the amount of received light is constant without being affected by the reflectance of the object to be measured.

When the optical distance measuring device of the present invention is used to measure distances using objects with different surface reflectances, the voltage proportional to the amount of received light is as shown in the characteristic curve l in Fig. 5. It is. The output voltage of the amount of received light when a similar object to be measured is measured using the conventional Type 9 distance measuring device is as shown in the characteristic curve m in FIG. In addition, 2 under 15W fluorescent lamps
When measuring the distance at 0 cfIL, it was impossible to measure with the conventional optical distance measuring device, but with the device of the present invention, it is possible to measure the distance at 100F#7 regardless of whether the fluorescent lamp is on or not.
Detection accuracy ±0.4 in the measurement range of 11-15omm
Detection was possible with mm.

Effects of the Invention As described above, the present invention provides an excellent effect of being able to measure distances with high accuracy without being affected by changes in the surface reflectance of the object to be measured or by external optical noise. It is.

[Brief explanation of the drawing]

1 and 2 are explanatory diagrams of a conventional optical distance measuring device, FIG. 3 is an explanatory diagram of an optical distance measuring device according to an embodiment of the present invention, and FIG. 4 is a circuit diagram of an open beam distance measuring device. FIG. 6 is a comparative characteristic diagram of the received light amount output voltage according to the present invention with a conventional example. 1... Semiconductor light emitting element (semiconductor laser diode), 2... Projected light, 3-... Measured object, 4... Reflected light, 5... ... Light receiving element, 7
...... Light projecting lens, 8... Condensing lens,
9...Distance detection circuit, 10...Emission light amount control circuit, 12...Light reception output voltage conversion circuit,
13...-band pass filter, 14...su...
Received light amount detection circuit, 15... Rectification circuit, 16.
...Difference detection. Amplification circuit, 17...Reference voltage setting circuit, 18.
...Light emission period modulation circuit. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2, ? Procedural amendment written on April 2, 1980, Patent Application No. 204069, filed in 1981. 2. Name of the invention: Optical distance measuring device 3. Correction Relationship with the case filed by the patentee Patent application Address 1006 Kadoma, Kadoma City, Osaka Name (
582) Matsushita Electric Industrial Co., Ltd. Representative Toshihiko Yamashita 4 Agent 571 Address 1006 Oaza Kadoma, Kadoma City, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd.

Claims (1)

[Claims] A semiconductor light emitting device is used as a light source. a light projecting section; a light receiving section that forms a certain angle with the optical axis of the light projecting section and receives reflected light from the object to be measured of the projection light of the light projecting section; and a distance detection section that processes signals from the light receiving section. The light emitting section includes a semiconductor light emitting element, a light emission amount control circuit, and a light emitting period modulation circuit, and the light receiving section includes a light receiving element, a light receiving output voltage conversion circuit, and a bandpass filter. It is composed of a received light amount detection circuit, a rectifier circuit, a reference voltage setting circuit, and a difference detection/amplification circuit, and the output of the difference detection/amplification circuit is fed back to the light emission amount control circuit to keep the amount of light received by the light receiving section constant. Controlled optical distance measuring device.