JPS6088306A - Optical sensor - Google Patents

Abstract

PURPOSE:To perform a highly accurate and highly reliable sensing under an environment with a large disturbing noise by employing a received light signal as effective data subject to being below a specified value in the quantity of light received with a photoelectric sensor when a specified modulated light is projected to an object. CONSTITUTION:A modulated light above 10kHz is projected to a welding work 1 from a light source 10 through a projector controlling circuit 9 and mode to form a spot image 11 on a photoelectric sensor (PSD) 13 through a condenser 12. Light current signals X1 and X2 obtained from electrodes at both ends of the sensor 13 are inputted into an arithmetic circuit 17 via an amplification circuit 15 and a band pass filter 16 and a difference signal is divided by a sum signal to determine the image formation position, which is inputted into a signal processing circuit 18. On the other hand, the sum S of outputs X1' and X2' of the circuit 15 is obtained with an addition circuit 19 and is compared with the reference signal S0 from a reference setting circuit 20 with a comparator circuit 21. An image formation position signal detected for the time tS smaller than the value S0 is employed by the circuit 18. Thus, the sensing under the environment with a large disturbing noise can be done at a high accuracy and with a high reliability.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is applied to industrial robots 1. for automating manufacturing processes such as processing, assembly, and inspection. The present invention relates to optical sensors used in applications.

One of the problems with conventional optical sensors is that detection accuracy is reduced due to the influence of optical noise. For example, in the case of optical sensors for arc welding, it is difficult to detect weld lines and groove shapes due to arc light noise.

FIG. 1 shows a conventional example of weld line detection using an optical sensor. 1 is the welding workpiece, 2 is the groove center line (welding line)
, 3 is a light projector that emits a slit-shaped light, 4 is a control circuit that controls the projector 3, 6 is a projected light image projected onto the welding work 1, and 6 is a projecting light image 6 that is projected onto the welding workpiece 1. The ITv camera 7 for photographing binarizes the video signal of the ITV camera 6,
A preprocessing circuit 8 for extracting the projected light image 5 is an image processing circuit composed of a microcomputer or the like, and detects the position of the welding line 2 from the signal of the preprocessing circuit 7. In the case of automation of arc welding, detection of this weld line 2 is required to be performed in real time while welding is being performed. With conventional optical sensors (sensing devices) like this, in order to increase the S/Nf of the detection signal for arc light, it was necessary to move the detection position away from the arc and perform complex image processing. There are problems with optical sensors, such as the inability to use detected data due to thermal distortion after sensing, feedback control for robots, etc., and complex optical sensors themselves, which are large and extremely expensive. This was a major cause of hindering its application.

OBJECTS OF THE INVENTION The present invention aims to eliminate the above-mentioned drawbacks of the prior art, and particularly to enable optical sensing in an environment with large disturbance light noise such as arc light.

Structure of the Invention In order to achieve this object, the present invention provides an optical sensor that projects light onto an object and detects the projected light image with a photoelectric sensor to detect the position and shape of the object. A light emitter control circuit is provided to set the modulation frequency of light to 10 KHz or more, and a signal processing circuit is provided to use a light reception signal when the amount of light received by the photoelectric sensor is less than a predetermined value as valid data.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to FIGS. 2 to 6 of the drawings. 1 and 2 are the same acid liquid work and welding line as in the past, 9 is a floodlight control circuit that modulates and controls a light source such as a semiconductor laser to a frequency of 10 KHz or higher, and 1o is a light source such as a semiconductor laser and the spot light. This is a floodlight with an optical system that narrows down to a shape. By the way, solid line A in FIG. 3 is a characteristic curve showing the result of frequency analysis of arc light in arc welding. It was found from this that the arc light has many low frequency components of 10 KHz or higher. Therefore, if a light modulated at 10 KHz or higher, for example 60 KHz as shown by the dotted line B in Fig. 3, is used as the emitted light, the light emitted signal (Ia in Fig. 3) and the arc light noise (Ib in Fig. 3) The S/N (-1/Ib) is improved to that of dog IJ. This is the reason why the projected light is modulated to 10 Kl (z or more) in the present invention.

Next, the spot light image 11 projected onto the welding workpiece 1 is
When the sensor head 14 shown by the dashed line in FIG. Since it corresponds to the image position, by detecting this image formation position, the distance from the sensor head 14 to the spot light image 11 on the work surface can be determined. Furthermore, by scanning this sensor head 14 in a direction perpendicular to the welding line 2, a distance pattern from the sensor head 14 to the work surface is obtained, and it is easy to measure the welding line 2 and the groove shape from this. Also, as a photoelectric sensor, there is a photo semiconductor device sensor (PSD...).

Since x2) is weak, it is amplified by 1 in the amplification circuit 15 and converted into a voltage signal. This converted signal (X
1',
, the arc light component is cut, and only the modulated signal is extracted. This signal (X1″,
7, then take the sum and difference of stone ", X2', divide this difference by the sum, and find the imaging position (X) of the spot light image 11 on the PSD. 1. Incidentally, the same frequency component of the arc light as the projected light increases as the intensity of the arc light increases, so the S/N decreases by eight.

In order to prevent this, in this embodiment, as shown in FIG. 4, the amount of light received by the sensor S is set to a predetermined value S.

A signal detected in a period shorter than (1, 3) is adopted as a valid signal. As a circuit for this failure, for example, the second
As shown in the figure, in the adder circuit 19, the signal X1'lX2'
The sum S is taken, and this S is combined with the value S set by the reference value setting circuit 20. As shown in FIG.
It is also effective to use signals (X1LLJ, X2'LI) that are provided between the arc light noise and the low frequency components of the arc light noise are cut to some extent. The signal processing circuit 18 selects the signal of the arithmetic circuit 17 based on the signal of the comparison circuit 21, and based on this selected signal, the signal processing circuit 18 selects the signal of the welding workpiece 1t from the sensor head 14. It also performs processing to convert it into distance data.

Although an example in which a PSD is used as the photoelectric sensor 13 has been described, the present invention is not limited to this and can be applied to other optical sensors.

Similarly, the shape of the projected light is not limited to a spot shape.

Next, the embodiment shown in Fig. 2 is composed of a KHz semiconductor laser for arc welding weld line detection, a Collinault lens that narrows the laser beam to a spot of 0.5 cylinder ψ, and a light receiver that is a condensing laser combined with an interference filter. It consists of a lens and a PSD. The detection processing circuit is as shown in the block diagram in Figure 2.
Specifically, it is mainly composed of an operational amplifier, and in particular, an 8-bit microcomputer is used for the signal processing circuit 18.

Now, as welding work 1, ■ groove, gear lug width 1.0
m, the distance between the lower surface of the sensor head 14 and the surface of the welding workpiece 1 is fixed at 120M, a CO2 arc is lit at dm+q behind the light projection position, and the welding current and detectable distance d are calculated. We had a relationship. Here, the detectable distance d refers to the minimum arc-sensing distance within which the ffi distance between the welding workpiece 1 and the sensor head 14 determined by calculation processing varies within ±0.6 frames. The results are shown in FIG.

From this, it can be seen that the optical sensor of the present example (curve 1) has superior arc resistance compared to the case (P) in which sampling restriction control of sensor data is not performed at the modulation frequency I KHz.

Next, the sensor head 14 of this embodiment was scanned perpendicularly to the weld line 2 (using a pulse motor, and the gap was processed by another microcomputer to determine the center position of the groove and the gear width on the open side, and the arc light As a condition, d = 20
mn, in the case of welding current 20OA, each ±0.3+
We were able to obtain a detection accuracy of ++m.

Effects of the Invention As described above, according to the present invention, it is possible to detect the position and shape of an object without contact, and it is particularly effective for sensing in environments where the influence of ambient light noise is large, such as in arc welding. This has made it possible to sense the weld line and groove shape near the arc light with high precision, high reliability, compactness, and low cost, which has been difficult to achieve in the past, and it is possible to achieve extensive automation and robotization of arc welding. It has excellent effects that can be applied to the field of visual sensing under other optical noise environments.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of a conventional optical sensor for detecting welding lines, Fig. 2 is an explanatory diagram of an optical sensor in an embodiment of the present invention, Fig. 3 is a characteristic diagram showing the results of frequency analysis of arc light, and Fig. 4 The figure is an explanatory diagram of the data sampling period for the same optical sensor.
FIG. 6 is a circuit diagram showing an embodiment of the optical sensor, and FIG. 6 is a diagram showing arc light resistance characteristics of the optical sensor. 2. Welding line, 9. Floodlight control circuit, 10. Floodlight, 11. Spot light image, 12. Condensing lens, 13- - Winding sensor, 14...Sensor head, 15...Additional 1
] Circuit, 16... Bandpass filter, 17...
Arithmetic circuit, 1s circuit. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 4 Figure 3 11M179. (kH2J No. 45! I No. 5 / Zo No. 6 A

Claims (2)

[Claims] (1) In an optical sensor that projects light onto an object and detects the projected light image with a photoelectric sensor to detect the position and shape of the object, the modulation frequency of the projected light is set to 10 lo (z or more). 1. An optical sensor comprising: a light emitter control circuit for controlling the optical sensor; and a signal processing circuit for employing a light reception signal when the amount of light received by the photoelectric sensor is less than or equal to a predetermined value as valid data. (2) Claim No. 1 (1) in which a laser beam is used as the projected light and an optical semiconductor device sensor is used as the photoelectric sensor.
Optical sensor described in ).