JPH06100459B2 - Distance measuring device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a distance measuring device for measuring displacement of an object from a reference plane.

[Conventional technology]

Conventionally, the displacement of the object from the reference plane has been mechanically measured. However, in the case of mechanical measurement, there are problems that it takes time for setting and measurement, and that the object is damaged because it is in direct contact with the object. The 4th was proposed here
It is the distance measuring device shown in the figure. In FIG. 4, 1 is a processing laser beam, 2 is a processing lens that focuses the processing laser beam 1, 3 is a processing head, 4 is a light source that emits a beam as measurement laser light, and 5 is a light source 4 , A light projecting lens for converging the emitted beam, a light receiving lens 6 for picking up a radiation beam image on the surface of the object W1, and a position detecting element 7 for generating an electric signal according to the image forming position of the radiation beam image.
PSD (Positive Ion Sensitive Detector), 8 and 9 are I / V converters that also convert the displacement detection currents 1a and 1b output from PSD7 into displacement detection voltages Va and Vb as displacement detection signals and also serve as preamplifiers. Is a V / I converter that inputs a laser drive voltage and outputs a laser drive current Id, 10a is a chopper, 11, 12
Is an amplifier that amplifies the displacement detection voltage Va, Vb, 13 and 14 are amplifiers
A band-pass filter that band-pass filters the outputs of 8, 9 is an A / D converter that converts the displacement detection voltages Va and Vb as analog signals into digital signals, and 16 is a laser drive signal that is a digital signal as an analog signal. D / A converter for converting to the laser drive voltage Vd of, 17 is the setting of the light emission timing of the light source 4,
An arithmetic processor for calculating the displacement ΔH of the object W1 and the like, SI is a switch for switching between Va and Vb.

The operation of the apparatus thus configured will be described. First, the operation of the optical system will be described with reference to FIG. The beam emitted from the light source 4 is turned into a light spot of an appropriate size by the light projecting lens 5 and is applied to the surface of the object W1. The light receiving lens 6 images this light spot and forms an image of the light spot on the light receiving surface of the PSD 7. The PSD 7 generates an electric signal according to the image forming position of the light spot image. That is, PS
The image forming position P of the light spot image is obtained as P = (Ia-Ib) / (Ia + Ib) according to the values of the currents Ia and Ib generated in the two electrodes of D7. In the above equation, since the PSD7 output produces an output in proportion to the position and intensity of the light spot image, the term (Ia + Ib) corresponding to the change in intensity of the light spot image is introduced and only the position of the light spot is introduced. You get an output proportional to.

Next, the operation of the electric system will be described with reference to FIG. FIG. 3 (a) shows the blinking of the light source 4, and FIG.
(C) shows the waveforms of the displacement detection voltages Va and Vb.

First, the operation when the surface of the object W1 is on the reference plane will be described. The light input to the light receiving lens 6 is applied to the PSD 7 as spot light. When the surface of the object W1 is on the reference plane and the center of gravity of this light is set to be the center P1 of the PSD7, the displacement detection currents Ia, Ib become equal to each other, and the displacement detection voltages Va, Vb also It will also be equal to each other. The displacement detection voltages Va and Vb are processed by the amplifiers 11 and 12 and the bandpass filters 13 and 14, and then time-divided by the analog switch S1 and converted into a digital signal by the A / D converter 15 and then processed by the arithmetic processor 17. Is entered. High-speed processor 17
Calculates the displacement ΔH from the displacement detection voltages Va and Vb converted into digital signals. In this case, since Va = Vb, the displacement ΔH = 0.

Next, the operation when the surface of the object is displaced downward by ΔH will be described. In this case, the light scattered on the surface of the object W1 passes through the light receiving lens 6 and then is separated from the center P1 of the PSD7 by X.
It is incident on P2 in the form of a spot. Displacement detection currents Ia and Ib are output by this incident light.
Are different from each other. Since ΔH and X have a proportional relationship, ΔH can be calculated and output by calculating X. In accordance with this output signal, a driving means (not shown) is operated to lower the processing head 3 to make the displacement of ΔH zero. In this way, the distance between the processing head 3 and the surface of the object W1 is always kept constant.

[Problems to be Solved by the Invention] In a device that operates in this way, there is background light in addition to the measurement laser light emitted from the light source 4 as incident light on the PSD 7, which causes an error in displacement measurement. There is.
Further, there is a problem that the output signals of the bandpass filters 13 and 14 are attenuated and oscillated due to the spike-shaped background light, and similarly an error is generated.

The present invention has been made in view of such a point, and an object of the present invention is to provide a distance measuring device in which an error due to background light is reduced in displacement measurement.

[Means for solving problems]

In order to achieve such an object, the present invention, in the distance measuring device, stops the detection of the displacement detection signal when the background light becomes equal to or higher than a predetermined first level, and a fixed time sufficient for the background light to be attenuated. The stop operation is released later.

[Action]

In the present invention, the displacement detection signal is detected at a timing that is not affected by the background light.

〔Example〕

FIG. 1 shows an embodiment in which a distance measuring device according to the present invention is applied to a laser processing machine. In FIG. 1, 18 is a comparator that outputs a signal when the background light level exceeds a predetermined first level, and 19 is a timer that starts time measurement by the signal output from the comparator 18 and outputs a constant time control signal. , 20, 21 are analog switches for closing the gates by a control signal, and the comparator 18, the timer 19, and the analog switches 20, 21 constitute stop means. In FIG. 1, the same or corresponding parts as those in FIG. 3 are designated by the same reference numerals.

The operation of the apparatus thus configured will be described with reference to FIGS. 1 and 3. Background light emitted from the surface of the object W1 by the irradiation of the processing laser beam 1 is incident on the PSD7, and a background light signal that is gradually attenuated from a large amplitude as shown in FIG. When output, this background light signal is input to the comparator 18. This background light signal includes the displacement detection voltages Va and Vb, but the displacement detection voltages Va and Vb are not shown in FIG. 3D because they are so large that they can be ignored. The comparator 18 outputs the first level TH1 when the background light signal indicates the third (d).
When the above is reached, the timer drive signal is output. The timer 19 starts time measurement by the rise of the timer drive signal, and stops the measurement when the set time T is reached. During the time T from the start to the stop of the time measurement, the timer 19 outputs the gate closing signal shown in FIG. 3 (e), and the analog switches 20 and 21 are closed. In this case, the set time T is set to a time when the background light is sufficiently attenuated. When the background light is generated in this way, the gates of the analog switches 20 and 21 are closed to stop the detection of the displacement detection signal, whereby the displacement measurement error of the object W1 due to the background light can be prevented. Further, by making the time T during which the timer 19 outputs the gate closing signal variable, various backgrounds can be dealt with.

Next, another embodiment is shown in FIG. In FIG. 2, reference numeral 22 is a comparator that outputs a gate closing signal from when the background light signal becomes equal to or higher than a predetermined first level to when it becomes equal to or lower than a predetermined second level lower than the first level. In FIG. 2, the same or corresponding parts as those in FIG. 1 are designated by the same reference numerals. The comparator 22 outputs the second light from when the background light signal becomes equal to or higher than the first level TH1 shown in FIG. 3 (d).
The gate closing signal is output during the time Tw until the level becomes TH2. This gate closing signal causes the analog switch 20,2
Set 1 to the gate closed state. When the background light is generated in this way, the gates of the analog switches 20 and 21 are closed to stop the detection of the displacement detection signal, so that the displacement measurement error of the object due to the background light can be prevented.

〔The invention's effect〕

As described above, according to the present invention, the detection of the displacement detection signal is stopped when the background light becomes equal to or higher than the predetermined first level, and the stop operation is canceled after a fixed time sufficient for the background light to be attenuated. Therefore, the displacement detection signal is detected at a timing that is not affected by the background light, and there is an effect that it is possible to prevent the output of the displacement measurement result whose accuracy is lowered by the background light.

[Brief description of drawings]

FIG. 1 is a block system diagram showing an embodiment in which a distance measuring device according to the present invention is applied to a laser processing machine, FIG. 2 is a block system diagram showing another embodiment, and FIG. 3 is a waveform diagram thereof. FIG. 4 is a block system diagram showing the case of application to a conventional distance measuring device and a laser processing machine. 1 ... Processing laser light, 2 ... Processing lens, 3 ... Processing head, 4 ... Light source, 5 ... Emitter lens, 6 ... Receiving lens, 7 ... PSD, 8, 9 ... I / V converter, 10 …… V / I converter, 10a …… Chopper, 11,12 …… Amplifier, 13,14 …… Band leaker, 15 …… A / D converter, 16 …… D / A converter, 17 ……
Arithmetic processor, 18 …… Comparator, 19 …… Timer,
20,21 …… Analog switch, S1 …… Analog switch

Front page continuation (72) Inventor Hidehiko Nakao 8-23 Asahi-cho, Nagasaki-shi, Nagasaki Taiyo Building Ryoden Engineering Co., Ltd. Nagasaki Plant (72) Inventor ▲ Kazuo Takashima 8-1, Tsukaguchi-honmachi, Amagasaki-shi, Hyogo No. 1 Sanritsu Electric Co., Ltd., Applied Equipment Research Laboratory (56) References JP-A-59-137805 (JP, A)

Claims (1)

[Claims] 1. A distance measuring device for calculating a displacement of a target from a reference plane by irradiating the target with a spot of a measuring laser beam and determining a barycentric position of returning scattered light on a position detecting element. A stop means for stopping the detection of the displacement detection signal when the background light reaches a predetermined first level or higher, and for canceling the stop operation after a fixed time sufficient for the background light to be attenuated. Distance measuring device.