JPS61105420A - Range measurement system - Google Patents

Abstract

PURPOSE:To select a normal detected value and detect the displacement of the reference surface of an object to be machined with high accuracy by projecting plural measurement laser spots near the point of laser projection on the object, and detecting projected beam and scattered beam correspondingly. CONSTITUTION:The object 4 to be machined is irradiated with beam from a laser 5 for machining. Further, laser beam from measurement use lasers 6(6a-6d) are projected on plural spots 8a-8d near the irradiation point of the object 4 and scattered beam is photodetected by a photodetector 12. Then, the displacement detection signal is inputted from the photodetector 12 to a computing element to detect the displacement of the reference surface of the object 4. At this time, the laser beam from the measurement lasers 6 are projected on the incidence spots 8a-8d successively and corresponding scattered beam is photodetected by the photodetector 12. Those projection and photodetection are detected electrically, and then the displacement is detected from an electric output directly when normal or after correction when abnormal. Therefore, the position of a beam spot having a defect is corrected, so the displacement of the object surface is detected accurately.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for measuring the opposing distance to a workpiece when performing processing such as welding or cutting by projecting a laser beam onto the workpiece. be.

[Conventional technology]

When processing by projecting a laser beam, it is necessary to measure the facing distance to the workpiece in order to maintain the facing distance to the workpiece according to the focal length of the lens that focuses the laser beam. A spot is projected onto the workpiece, the reflected light is imaged by an imaging lens, and the image formed by the imaging lens is projected onto a light receiving element that generates an electrical output according to the incident position of the light beam, and an electrical output is generated. The facing distance is calculated based on the following.

However, using only a single light spot will cause measurement errors if there are irregularities on the target surface of the workpiece, so multiple light spots are projected around the laser beam projection point and the reflected light is A method has been proposed in which the average facing distance of each spot is determined by simultaneously projecting the images onto a light-receiving element.

[Problem that the invention seeks to solve]

However, when using multiple light spots, if one of the light spots is projected onto a part cut by a laser beam or a part similarly drilled, there will be no reflection of the light spot. This will cause an error in distance measurement.

The present invention has the purpose of fundamentally solving such conventional problems, and is extremely effective in eliminating measurement errors even when one of a plurality of light spots does not produce reflected light. This provides a simple distance measurement method.

[Means for solving problems]

In order to achieve the above-mentioned object, the present invention is constructed by the following means.

That is, a plurality of light spots are sequentially and repeatedly projected onto the workpiece near the laser beam projection point at approximately symmetrical positions, and the reflected light from this projection is imaged by the same imaging lens, and the light beams are An image formed by an imaging lens is projected onto a light receiving element that produces an electrical output according to the incident position, and the electrical output of this light receiving element is detected in correspondence with the projection of a light spot. When the electrical output is normally generated, the position of the laser beam projection point is determined according to the electrical output for each projection of the light spot, and then the facing distance of this projection point position is determined, and the trap light receiving element for each projection of each spot is determined. When the electrical output is not produced normally, a correction calculation is performed to find the position of the laser beam projection point, and then the facing distance is determined.

[Effect]

Therefore, if the electrical output of the light receiving element corresponding to the sequential projection of the light spot does not occur normally, it is determined that the light spot at this time is in a non-reflecting state, and the electrical output does not occur normally. It is possible to freely correct the position of the light spot that is missing from the position of the light spot, and no error occurs in the measurement of the facing distance.

〔Example〕

Hereinafter, the present invention will be explained in detail with reference to figures showing examples.

Figure N2 is a cross-sectional view of the head that projects the laser beam. The laser beam 3, which is focused by the processing lens 2 provided inside the outer cylinder 1, is projected onto the workpiece 4 and processes this part. In addition, a laser beam 3 is provided in the outer wall on the west side of the inner cavity 5 of the outer cylinder 1.
Light sources 61 to 6d such as semiconductor laser oscillators that generate laser beams with different wavelengths are disposed. The light beams (K) are projected onto the vicinity of the laser beam 3 on the surface as optical spora (8a to 8d) at mutually symmetrical positions.

The optical spora) 8a to 8d are reflected on the surface of the workpiece 40, and enter the imaging lens 11 provided outside the outer tube 1 as reflected light, and the PSD (Positivity Spora) as a light receiving element.
on 8@n5itive Detector, ) 1
2 and is projected as an image from both ends of PSDI 20.
Current Z A l I depending on the incident position of the light ray due to imaging
B will be sent to each individual.

In particular, the imaging position RP on the PSDI 2 is determined by the facing distance t between the processing lens 2 and the workpiece 4, the horizontal distance between the original axis 9 of the laser beam 3 and the imaging lens 11, and the imaging lens 11 and the workpiece. determined according to the facing distance A with the workpiece 4],
When the current is I A + I B, it is given by the following equation.

[X: Distance between optical axis 13 and incident point, D: PSD12
(dimension from the end of the laser beam to the optical axis 13)]
(determined according to the angle θ between the optical axis 9 of lenses 8a to 8d and the optical axis 13 of the imaging lens 11), which is originally a constant value, and the difference between the facing distance FAA and the facing distance t, and the horizontal distance y Since these are also constant, the facing distance t is determined by the following formula according to the value of P based on these values.7. Z t=to-P...
(2) [K: Constant] However, the light sources 61 to 6d and the projection lenses 7m to 7d are arranged symmetrically in four directions centering on the laser beam 3 within the inner wall surface of the outer cylinder 1. emit light sequentially and repeatedly, and the corresponding output values representing P from the PSDI 2 are sequentially accumulated, and P is determined by averaging each output value.

That is, as the projection surface of the workpiece 4 is shown in FIG.
Since the light slots 8a to 8d are projected to mutually symmetrical positions with the laser beam 3 as the center, the projection point position of the laser beam 3 is determined based on the average position of the corresponding projection positions pa to Pd. It will be done.

Therefore, if the light spot 8d, for example, is projected onto the cutting section 21 from the state shown in FIG. 3(B) to the state shown in FIG. 3a, resulting in an error of
When the output of I2 is detected, it is possible to determine whether the reflected light is missing due to the optical spot 8d, and since the projection position of this is known, the corresponding correction value -jd is memorized and corrected for the average position 3d. By performing the correction based on the value, an accurate projection point position of the laser beam 3 can be determined, and based on this, the facing distance t can be accurately determined.

The fourth M processes the output of the PSD 12 and the light source 6
In the block diagram of the control unit that controls 1 to 6d, a processor such as a microprocessor (hereinafter referred to as CPU) 31
The main components are fixed memory (hereinafter referred to as ROM) 32, variable memory (hereinafter referred to as RAM) 33, and interface [
Hereinafter, it is assumed that I/F] 34 to 3T are arranged around the periphery and connected by a bus bar, and the CPU 31 executes instructions stored in the ROM 32 and performs control while accessing predetermined data to the RAM 33. It has become.

Further, switches 39a to 39d are inserted between the light sources 61 to 6d and the power supply section 38, respectively, and the switches 39a to 39d are connected to I/1'3.
4, each switch 39a to 39d
are turned on and off sequentially, and the light source 6 is turned on and off accordingly.
a to 6d individually emit and dim light, while PSD
The output currents i A l l m from 12 are each passed to a load resistor R whose terminal voltage is the amplifier 41A, 4
1B, each is amplified with the same gain, and I/
In response to the control signal from F3.5, it is applied to an analog-to-digital converter (hereinafter referred to as A/D) 43 via a selector 42 that performs a selection operation at a cycle faster than the light emission and dimming cycles of the light sources 6a to 6d. Here, after being converted into a digital signal, it is given to the I/F 36, and the signal St indicating the opposing distance t calculated based on this is sent out via the I/'F 37. ing.

FIG. 1 is a flowchart of the control situation by the CPO 31K, in which the light source 6a is set to a light emitting state by the switch "39aON" 101, and after determining "Is Φ output normal?" 102 via the I/F 36, this is Y (YES). If so, perform the “Pa operation” 103 at the 6m position using formula (1):
is stored in a predetermined address in the RAM 33, the light source 6a is dimmed by the switch "39a OFF" 105, and the light source 6a is dimmed by the switch "39b ON" 11 in the same manner.
1 to ``39dOFF'' 135 in sequence, and based on p and ~PdK in factor 33, perform ``projection point position calculation 11j,'' 141 of laser beam 3 based on the average of these, and then calculate the loss of reflected light. 1 error flag set whether or not occurred? "Checked by 142, this is N
If (No), the facing distance "' is calculated" (143) according to the formula (2) according to the result of step 141, and then Pl to Pd in the RAM 33 are cleared "145 and the signal via I/F 37". SZ sending'' 146 is performed, and steps 101 and subsequent steps are repeated.

Regarding the above, steps 102, 112, 122,
If 132 is N, "Pa error flag set" 151 to "Pd error 7 lag set" 154, respectively.
In order to perform this, the step 142 becomes Y in response to this, and the process moves to the judgment ``Number of errors equal to 2?'' 161, and if the number of missed reflected lights is up to two times, correction is possible. Therefore, the correction values corresponding to steps 151 to 154 are RO
“Correction calculation” 16 read from M32 and based on this
2 is performed on the result of step 141, and after ``Error 72 G Reset'' 163 is performed, the process moves to step 143.

Further, when step 161 is N, correction is impossible, and the process returns to step 101 after p@~p(1 clear ``171'' and ``error flag reset'' 172 in the RAM 33 are performed.

Therefore, even if any of the light spots 6&~6d coincides with the cut portion 21 or the hole and no reflected light is generated, if the number of missed reflected lights is less than or equal to the number of missed reflected lights that can be corrected, the correction is automatically made. Since the facing distance t can always be determined accurately, it is possible to drive the head according to the signal St and control the head in a direction in which the facing distance t is constant.

However, the number of light sources 6a to 6d may be 3 or more than 4, and accordingly step 161
The light sources 6a to 6d may be not only laser oscillators, but also light emitting elements such as lamps and light emitting diodes. In addition, an optical filter may be provided on the imaging lens 11 side to block the laser beam 3 and the emission wavelength due to heat generation at the processing point.

Also, instead of using the PSD, a 7-otodiode array or the like may be used, and the resistors R to A/D4 may be used accordingly.
The configuration shown in Fig. 1 can be selected arbitrarily, and the same applies if the circuit shown in Fig. Depending on the situation, various modifications can be made, such as replacing the steps, replacing them with other equivalent steps, or omitting unnecessary steps.

〔Effect of the invention〕

As is clear from the above explanation, according to the present invention, even if any of the light spots is missing reflected light, the correction will not cause any measurement error, and the facing distance will always be accurately measured. , a remarkable effect can be obtained in measuring the facing distance to the workpiece processed by the laser beam.

[Brief explanation of drawings]

The figures show an embodiment of the present invention, in which Fig. 1 is a flowchart of the control situation, Fig. 2 is a sectional view of the head, Fig. 3 is a plan view showing the projection situation of the laser beam and the light spot onto the workpiece, and Fig. FIG. 4 is a block diagram of the control section. 1φ@-e outer cylinder, 2...processing lens, 3...laser beam, 4...φ・workpiece, 6a-6d...
・Light source, 7a to 7d... Light projection lens, 8a to 8d.
...Light spot, 11-...Imaging lens, 12...
・・PSD (light receiving element), 21・e・・cutting part, 31
...CPU (Procera f), 32...-ROM
(fixed memory), 33...RAM (variable memory)
, 38...power supply section, 39a-39d...switch.

Claims (1)

[Claims] In a method of measuring the opposing distance to a workpiece to be machined by a laser beam by projecting a light spot, a plurality of light spots are sequentially projected at substantially symmetrical positions around the workpiece near the laser beam projection point. The reflected light from the projection is imaged by the same imaging lens, and the image formed by the imaging lens is projected onto a light receiving element that generates an electrical output according to the incident position of the light beam. The electrical output is detected in correspondence with the projection of the light spot, and when the electrical output is normally generated for each projection of the light spot, the electrical output of the laser beam projection point is detected in accordance with the electrical output for each projection. After determining the position, the facing distance of the projection point position is determined, and if the electrical output is not generated normally for each projection of each of the light spots, a correction calculation is performed to determine the position of the laser beam projection point. A distance measurement method characterized by determining the facing distance.