JPS61105416A - Range measuring device for laser beam machine - Google Patents

Abstract

PURPOSE:To detect the displacement of the reference surface of an object with high accuracy by detecting the displacement a specific time later from the emission of laser beam for machining when by irradiating the object with laser beam for measurement and making scattered beam incident on a position detecting element. CONSTITUTION:The laser beam 1 for machining is emitted to the object 1, which is machined. Further, a machining head 3 is provided with a measurement laser beam emission source 4 and a machining point on the surface W1 of the object is irradiated with the laser beam. A reflected beam from the point is made incident on the position detecting element 7 to obtain displacement detection currents Ia and Ib. Then, these currents are converted by I/V converters 8 and 9 into displacement detection voltages Va and Vb. At this time, a displacement detection is detected the specific time later after the laser beam for work is emitted. Therefore, the displacement detection signal of timing at which there is an influence upon a background beam signal is removed the specific time after the work laser beam is emitted, so the displacement of the reference surface of the object is detected with high accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a distance measuring device for measuring the displacement of an object from a reference plane in laser processing.

[Conventional technology]

Conventionally, the displacement of an object from a reference plane has been measured mechanically. However, in the case of mechanical measurement, there are problems such as time required for setting and measurement, and direct contact with the object, which may damage the object. Therefore, the distance meter 11 device shown in FIG. 3 was proposed. In Fig. 3, 2 is a processing laser beam, 2 is a processing lens that focuses the processing laser beam 1, 3 is a processing head, and 4 is a half-power unit laser that emits a beam as a measurement laser beam. A light source, 5 is a projection lens that focuses the beam emitted from the light source 4, and 6 is a lens that captures the radiation beam image of the surface of the object W1.
7 is a light receiving lens, and 7 is a PSD (7) as a position detection element that generates an electric signal according to the imaging position of the radiation beam image.
Position 5enSitive Dete
ct.

r), 8.9 is the displacement detection current 1 output from PSD7
Displacement detection voltages Va, V with a, [b as displacement detection signals
10 is a V/I converter that inputs the laser drive voltage and outputs the laser drive current [d; 11.12 is the displacement detection voltage Va.
, an amplifier that amplifies Vb, 13.14 is the amplifier 11.1
15 is an A/D converter that converts the displacement detection voltages Va and Vb as analog signals into digital signals; 16 is an A/D converter that converts the laser drive signal as a digital signal into a laser as an analog signal; A D/A converter converts into a driving voltage Vd, 17 is a high-speed arithmetic processor that sets the emission timing of the half-quad laser 2, calculates the displacement ΔH of the object surface, etc., and Sl is a displacement detection voltage Va as a parallel signal. , a parallel signal that converts Vb into a serial signal.
It is a serial conversion switch.

The operation of the device configured in this way will be explained. First, the operation of the optical system will be explained using FIG. The beam emitted from the light source 4 becomes a light spot of an appropriate size by the projection lens 5 and is irradiated onto the surface of the object W1. The light receiving lens 6 images this light spot, and the PSD 7
An image of a light spot is formed on the light receiving surface. The PSD 7 generates an electric signal depending on the imaging position of the optical spot image. That is, the current 1a generated in the two electrodes of the PSD 7.

Based on the IbO value, the imaging position P of the optical spot image is P= (I
a-1b)/(Ia+Ib). Since the output of the PSD 7 is proportional to the position and intensity of the light spot image, the above equation introduces the term (Ia + Ib), which corresponds to the change in the intensity of the light spot image, and calculates only the position of the light spot. We are getting an output proportional to .

Next, the operation of the electrical system will be explained using FIG. 2. Figure 2 (al indicates blinking of the measurement laser beam output from the light source 4, Figure 2 (bl, (C1 is the displacement detection current 1a)
, Ib and the waveforms of 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 irradiated onto the PSD 7 in the form of a spot of light.

If the center of gravity of this light is set to be the center P1 of the PSD 7 when the surface of the object Wl is on the reference plane,
The displacement detection currents Ia and Ib are equal to each other, and the displacement detection voltages Va and Vb are also equal to each other. The displacement detection voltage is Va and Vb are the amplifiers 11 and 12 and the bandpass filter 1.
3. After processing in 14, parallel/serial conversion switch Sl
The signal is converted into a serial signal by the A/D converter 15, converted into a digital signal by the A/D converter 15, and input to the high-speed arithmetic processor 17. The high-speed calculation processor 17 calculates the displacement ΔH based on the displacement detection voltages Va and Vb converted into digital signals, and in this case, since Va=Vb, the displacement ΔH=0.

Next, the operation when the surface of the object W1 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 enters the PSD 7 at a point P2 which is X away from the center P1 in the form of a spot. Displacement detection currents Ia and Ib are outputted by this incident light, but the displacement detection currents 1a and Ib have different values. Δ
Since H and X are in a proportional relationship, by calculating X, ΔH can be calculated and output. In response to this output signal, a drive means (not shown) is operated to lower the machining head 3 and make the displacement ΔH zero. In this way, the distance between the processing head 3 and the surface of the object W1 is always kept constant.

[Problem that the invention seeks to solve]

In a device that operates in this manner, in addition to the light emitted from the light source 4 as the incident light to the PSD 7, the object W based on the irradiation of the processing laser beam 1 used for processing the object W1 is used.
There is a problem that there is background light from t, which causes errors in displacement measurement. Further, there is a problem in that the bandpass filter 13.14 vibrates due to the background light produced by the processing laser beam 1, which impairs the function of the bandpass filter 13.14.

The present invention has been made in view of these points, and its purpose is to provide a distance measuring device for a laser processing machine that does not cause errors in displacement measurement due to background light caused by processing laser light. be.

[Means for solving problems]

In order to achieve such an object, the present invention is a distance measuring device that detects a displacement detection signal after a certain period of time from the emission of a processing laser beam.

[Effect]

In the present invention, the measurement laser beam is detected at a timing that is not affected by background light caused by the processing laser beam used to process the object.

〔Example〕

FIG. 1 shows an embodiment of a distance measuring device according to the present invention. In FIG. 1, reference numeral 18.19 denotes an analog switch 20 whose gate opens at a timing that is not affected by the background light of the processing laser beam l used for processing the object W1.
is the analog switch 18.1 after a certain period of time T after inputting the timing pulse Pa for emitting the processing laser beam 1.
This is a gate pulse generator that outputs a gate pulse pb for driving 9 to open. This time T is the next timing pulse P
The value is set so that the gate pulse Pb is generated immediately before the pulse a is generated. In FIG. 1, the same or equivalent parts as in FIG. 3 are given the same reference numerals.

The operation of the apparatus configured as described above will be explained using FIG. 1 and FIG. 2. As shown in FIG. 2 Tdl, the timing pulse Pa is output at a constant cycle, and thereby the processing laser beam 1 is periodically emitted as shown in FIG. 2 +e). When the surface of the object W1 is impulsively irradiated with the processing laser beam 1, a background light signal that gradually attenuates from a large amplitude as shown in FIG.
is output from. Note that this background light signal is the displacement detection voltage Va.

However, since the displacement detection voltages Va and Vb are so large that they can be ignored, they are not shown in FIG.

Displacement detection voltage Va output from I/V converter 8.9,
The Vb and background light signals are input to analog switches 18.19. The gate pulse pb that drives the analog switches 18 and 19 open is as shown in FIG.
The processing laser beam 1 is output at the timing when the background light signal disappears after a time T from the emission of the processing laser beam 1. Due to this, the light source 4
The measurement laser beam output from the sensor is detected at a timing that is not affected by the background light signal, and displacement measurement errors due to the background light signal can be prevented.

〔Effect of the invention〕

As explained above, the present invention makes it possible to prevent the influence of the background light caused by the processing laser light by detecting the displacement detection signal after a certain period of time from the generation of the processing laser light. This has the effect of preventing an increase in the displacement error of the object and improving the accuracy of displacement measurement.

[Brief explanation of the drawing]

FIG. 1 is a block system diagram showing an embodiment of a distance measuring device for a laser processing machine according to the present invention, and FIG. 2 is a waveform diagram thereof.
FIG. 3 is a block system diagram showing a conventional distance measuring device for a laser processing machine. 1... Laser light for processing, 2... Lens for processing, 3... Processing head, 4... Light source, 5...
Emitter lens, 6...Receiver lens, 7...PSD
18,9...I/V converter, 10...V/I converter, 11.12...Amplifier, 13.14...
Bandpass filter, 15... A/D converter, 16. ...
D/A converter, 17... High-speed arithmetic processor, 18
．． 19... Analog switch, 20... Gate pulse generator, Sl... Parallel/serial conversion switch. Procedural amendment (voluntary) 20 Name of the invention Distance measuring device for rapping machine 3, Relationship to the case of the person making the amendment Patent applicant address 2-3 Ku-no-uchiki-chome, Chiyoda-ku, Tokyo Name (ω1) Mitsubishi Denki Co., Ltd. Representative: Yuhito Kata Department 4, Agent address: 2-3 Marunouchiki-chome, Chiyoda-ku, Tokyo (1) The scope of claims in the specification is amended as shown in the attached sheet. (2) “~V/I converter,” on page 2, line 17 of the specification.
” is followed by “10a is choppa.” (3) "High-speed calculation" on page 3, line 6 of the specification is corrected to "calculation." (4) "rsl is a conversion switch" in lines 7 to 9 of page 3 of the specification is corrected to "Sl is a changeover switch for Va and Vb." (5) Delete "displacement detection currents Ia, Ib and" from lines 8 to 9 of page 4 of the specification. (6) "Parallel/serial conversion switch" on page 4, line 20 of the specification is corrected to "analog switch." (7) "Converted into a serial signal" in the 20th line of page 4 to the 1st line of page 5 of the specification is corrected to "time-divided". (8) "High-speed arithmetic processor" in the second and third lines of page 5 of the specification is corrected to "arithmetic processor." (9) After "It is possible to..." on page 5, line 15 of the specification, add "Alternatively, the relationship between X and ΔH is determined in advance by actual measurement, and ΔH is determined from X." αω Delete “from the object Wl” on page 6, line 4 of the specification. (11) "The function is impaired by r13.14 in lines 7 and 8 of page 6 of the specification" is corrected to "dampened oscillation occurs in the output signals of r13 and 14, which similarly causes an error." (12) "No error occurs" on page 6, line 12 of the specification is amended to "reduces error." (13) "Detect a displacement detection signal" on page 6, line 17 of the specification is corrected to "output a distance measurement signal." (14) "Measurement laser light is detected" in the second line of page 7 of the specification is corrected to "a distance measurement value is detected." (15) r18 on page 7, lines 5 to 14 of the specification,
19 is set to ~. '' r18 is a processing laser oscillator, 19 is a gate pulse generation circuit, and 20 is a gate circuit that gates the distance measurement value output. ” he corrected. (16) [[] from page 7, line 19 to page 8, line 1 of the specification
The timing pulse is periodically corrected to ``rPa is output at a timing that coincides with the output of the processing laser, and only during the period when Pa is on''. (17) “(f
)” is corrected to r (e)J. (18) On page 8 of the specification, lines 9 to 11, "input is input to analog switch 18.19. Analog switch 18.19 is driven open" is replaced with "after distance calculation processing, etc. enter the circuit 20. Drive the gate circuit 20 open.'' (19) Correct r (g) J on page 8, line 12 of the specification to r (f) J. (20) “Time T from launch” on page 8, line 13 of the specification
"After" means "Time T after the start of launch T = T I+
T t later.'' (21) "The measurement laser beam output from the light source 4" on page 8, line 14 to line 15 of the specification is corrected to "the output of the distance calculation result is". (22) "Detect a displacement detection signal" on page 8, line 20 of the specification is corrected to "output a distance measurement signal." (23) Add "10a . . . chopper" after "~V/I converter," on page 9, line 14 of the specification. (24) "High-speed arithmetic processor" on page 9, line 17 of the specification is corrected to "arithmetic processor."゛(25
) “18°19” on page 9, lines 17 to 20 of the specification
~Parallel/serial conversion switch. " to "18... Laser oscillator for processing, 19... Gate pulse generation circuit, 2
0...Gate circuit, SL...Analog switch. ” he corrected. (26) Figures 1, 2, and 3 of the drawings will be corrected as shown in the attached sheet. ``When the object is irradiated with a processing laser beam.

Claims (1)

[Claims] When a target object is irradiated with a processing laser beam, the spot of the measurement laser beam is irradiated onto the object, and the center of gravity of the returning scattered light is determined on the position detection element to determine the position from the reference plane of the object. What is claimed is: 1. A distance measuring device for a laser processing machine, which detects a displacement detection signal at a timing after a predetermined period of time after emission of the processing laser beam.