JPS61120006A - Signal detecting method of measuring head - Google Patents

Abstract

PURPOSE:To detect a signal with high precision irrelevantly to the intensity of incident light by detecting and storing the measurement output of a photodetecting element array by detecting means which differ in level, and selecting some bit string of a detection logical signal with the highest level. CONSTITUTION:The output of the photodetecting element array 11 corresponding to a scan is stored in memories 29-31 whose writing is controlled by FFs 26-28 through attenuators 18 and 19 of the detecting means which differ in level, sampling circuits 23-25, etc. Then when light incident on the array 1 is weak, three bits, their one center bit, etc., are stored in the memories 29 and 30 and when intense, five bits, three bits, and their one center bit are stored in the memories 29-31 respectively; and a switching control circuit 32 outputs some bit of the detection logical signal with the highest level and the bit string is outputted through the memory 30. Therefore, only center position information having the highest level is selected irrelevantly to variation in the intensity of the incident light which varies in the state of its reflected light and high- precision signal detection is performed by measuring the shape of a body optically.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a signal detection method of a diagonal measurement head for measuring the shape and position of a welding surface of a workpiece in a welding robot or the like.

(Prior art) The configuration of the control circuit of a conventional measurement head of this type is jlE/
As shown in the figure, the light receiving process consists of laser modulation, scanning by a swinging mirror, detection of the light receiving position by imaging the reflection of this laser beam on a light receiving element array, timing control of the above parts, and calculation processing by a processor. The target was detection methods.

To explain FIG. 7 in more detail, the operation is performed with the following configuration. Laser light modulation signal output f of oscillation circuit/
M is supplied to the laser 3 through the drive circuit, which modulates its intensity, and its output light beam travels at a constant angle on the surface to be measured (not shown), just like the oscillating movement of the oscillating mirror! It moves back and forth and scans.

The swinging mirror≠ is driven by the clock counter O and the mirror drive circuit 7, and the measurement period is between the detection sensors at the left and right ends,
output, determined by the measurement control logic IO.

The bright spot of the laser beam on the surface to be measured is imaged by the light receiving lens onto the light receiving element array //, and the scanning counter 12
, the output of the changeover switch /3 is turned on by the scanning of the changeover switch circuit /3, the output of the changeover switch /3 is turned off at the scanning timing of the light receiving element where the incident light is present, the amplifier /≠, the pass filter /1, and the rectification and smoothing circuit /6 demodulates. and becomes a DC level signal. This detection level is determined by a level determination holding circuit/7 using a sampling signal OL that is synchronized with switching of each light receiving element, and when light is being received, it is set to level "1".

are stored in a shift register or the like as logical signals, and are collected into appropriate processing units (for example, r bits) as detection signals Ds. Also, a beam movement direction instruction signal DI is sent from the clock counter 6, and a beam angle signal B is sent from the scan control counter.
Measurement range signals MA are communicated from the measurement control logic /Q to the respective processor processing systems.

The light-receiving element array // is composed of, for example, 6 light-receiving elements, and is scanned at a much higher speed than the swinging operation of the laser beam, so that during the switching output period of the elements, VC6≠
An output is generated only at the timing of the imaged element among the elements. The time relationship between the scanning of this light-receiving element array and the logic output is shown in diagram g1. Now, the input OL of the scanning counter 12, (/~) [FIG. 2(a)] changes the changeover switch circuit /3 to 1. - Switching sequentially like a mouth [Figure 2 (b)], during which the changeover switch outputs at the scanning timing of the element l receiving light [Figure 2 (d)]
)] a modulated wave is generated. Demodulate this and clock OL,
By sampling with [Fig. 2 (C)], the register receives a logic 1/1 signal [Fig. 2 (F)] in the first bit.
] is retained. At this time, the distance to the surface to be measured is determined from the laser beam angle and the position of the light receiving element i by a triangulation method.

(Problem to be Solved by the Invention) Here, the level of received light changes significantly depending on the reflectance of the surface to be measured. It is necessary to set the level. Furthermore, when receiving light from a highly reflective surface, the output level also increases (low-level output may also be generated from adjacent elements or other elements due to the influence of light reflection, etc.). When a signal is detected, the light receiving judgment range expands and many signals may be generated.Figure 2 (
The dotted line in dl shows this situation.Increasing the logical output like this requires centering the position on the average position of these light-receiving element outputs, which increases the processing content and at the same time slows down the calculation. This becomes a factor that reduces accuracy.

(Means for Solving the Problems) In order to eliminate the above-mentioned deterioration in calculation accuracy, the present invention provides multiple detection levels for large changes in the amount of incident light, and reduces the output that causes errors in light receiving position determination. The object of the present invention is to provide a signal detection method that can remove the light, determine the light receiving center position regardless of the strength of the incident light, and perform measurement with high accuracy. Hereinafter, it will be explained in detail with reference to the drawings of the embodiment.

(Structure of the Invention) The structure of the present invention provides a plurality of detection levels corresponding to the light receiving input level, sequentially accumulates the judgment output at each level during seven scans of the light receiving element array, and at the end of the scan. This is a signal detection method for a measurement head characterized in that a bit string having a detection logic signal at the highest level is selectively used for calculation processing.

<Embodiment> FIG. 3 is a block diagram showing an embodiment of the present invention, and FIG. 3 is a diagram explaining the detection/selection operation.

It has the same configuration and operation as in FIG. 1, including a light receiving element array l/, a changeover switch circuit/3, a scanning counter/2, and an amplifier/44Fi. A plurality of detection circuits having different detection levels are connected to the output of the amplifier l≠.

For the sake of explanation, FIG. 3 shows an example in which the detection level is changed to three levels, but the detection level may be increased further to improve accuracy. Here, the attenuators /r and /r each attenuate the signal by, for example, 20 dB, and the attenuators 20. u/l 2.2, and the outputs of the sampling and holding circuits 23.24t and 21 are sequentially 0.2.0. ≠O
It is configured to detect with a level difference of dB. This detection output is memo 1) 29.30. At the end of one scan of the light-receiving element, one pit of logic information with different detection levels is stored in each memory (the light-receiving element is 61A
41A bits) are stored at a time. The status of the logic 171 signal write to each memory is monitored by
6,27. λr is stored in the memory 33 after scanning is completed.
3/ is selected and transferred, giving a large amount of attenuation (due to the high-speed transfer period) and having an output memory. memory 3
The contents of 3 are sent to the processor processing system 3 in the first scan cycle.

Counter 34tFi Counter 79, 70, 3j, which indicates the address of the memory, Control 7, 7o, AND gate 36.3? .

The OR gate 31r is a gate that selects the clock of the counter 34t. The operations shown in FIG. 3 are controlled by scanning, transfer, and reset signals applied from another control section (not shown). During the scanning period, the output from the control flip-flop 3 puts the memory controller ~3/ into the write state and the memory 33 into the read state. f & switching judgment circuit 3 at the same time
2 is turned OFF and no transfer is performed. In this state, the counter J4C operates with the clock OL synchronized with the clock OL and sequentially writes the sampling results to the designated addresses. During the transfer period, control 7 lip-flops 3! is inverted, memories 22 to 31 are read, memory 33 is written,
The switching judgment circuit 3 becomes valid and transfers data from the memory selected from the memories 2 to 37 to the memory 33 in response to the high speed clock OLt inputted to the counter 3≠. These control parts may be controlled by a program.

Next, Figure ≠ will explain the contents of this memory and the state of transfer. In other words, when the scanning clock OL is used for the seven scanning sections shown in Figure (a), the changeover switch output a (fourth
'Figure (b)], detection level /, three light receiving elements i
/+ i, l +/ is sampled.

The light receiving element output sampled at detection level 2 is only i. This state is stored in the memory (memory contents/) and the memory 30 (memory contents), and the contents of the memo 930 are transferred in the transfer section after the end of scanning in ni, and only the / bit out of n pits is in the state of 111. shows. In addition, when the reflectance of the surface to be measured is high, as shown in the scanning section ■, the changeover switch output increases and at the same time the output from the adjacent element also increases, and the three memories j and j correspond to the detection level. , /bits are accumulated, and memory content 3 is selected and transferred during the transfer period.

In this way, the information transferred to the memory 33 is only the central bit position depending on the strength of the input light level. memory 3
3 is sent in a format valid for processing by the processor during the next scan period.

(Effects of the Invention) As explained above, according to the present invention, only the information of the center position with the highest level can be detected at multiple levels even for incident light where the state of reflected light changes significantly, such as from a welding head. This has the effect of reducing calculation processing and calculation errors due to the fact that many outputs can be selected by the means.

[Brief explanation of drawings]

Figure 1 is a block diagram of a conventional measurement head control circuit;
Figure 3 is a diagram explaining the relationship between detection timing and output.
The figure is a block configuration diagram of a signal detection circuit showing one embodiment of the present invention, and Figure 1 is a diagram explaining the signal level, detection output, and information selection in nine cases using the present invention. , ≠... Swinging mirror, //... Light receiving element array, /, 2... Scanning counter, 13... Changeover switch circuit, /Jr, /9... Attenuator, λ
0.28 2.2... Demodulation circuit, 23.21A, 21.
...Sampling holding circuit, 2, 30.3/...Detection information storage memory, 26. λ7, 21r...Light reception detection monitoring 71J tube 70 tube, 3.2...Memory switching judgment circuit, 33...Output information storage memory, 3...Processor processing system.

Claims (1)

[Claims] The reflected light of the laser beam that irradiates the surface to be measured and oscillates is imaged on a plurality of linearly arranged photodetector arrays, and the laser beam is modulated at a constant frequency to form a single received light beam. The light-receiving elements are switched at a frequency such that a plurality of modulated waves are present in the element, and all the light-receiving elements are scanned at a much higher speed than the swinging of the laser beam to detect the light-receiving element that is forming an image. The measurement head calculates the position on the surface to be measured and the distance from the measurement reference line from the irradiation beam angle and the position of the light-receiving element.The measurement head detects the received light modulation output and converts it into a logical signal to determine the position of the element receiving the light. This is performed using multiple detection means with different detection levels, and at the end of one scan of the light receiving element array, the light receiving element position is determined by selecting the result in which a detection logic signal exists at the highest level among the detection results at each detection level. A signal detection method for a measurement head, characterized in that: