JPH06297175A - Gap sensor for laser beam machine - Google Patents

Abstract

PURPOSE:To make a distance measurement position and a work position on a surface to be worked almost matching and to continuously control the gap of a laser beam working head with high accuracy. CONSTITUTION:A gap sensor for a laser beam machine, which is used for measuring an interval between a surface to be worked and a working head, arranged adjacent to the working head 1 from which a laser beam L1 for working radiates to the surface to be worked, provided so that it is relatively attachable and detachable to a surface to be worked 6, is provided. A laser beam irradiating device 4 for measuring a distance, from which a laser beam L2 for measuring a distance irradiates with a prescribed angle near a position to be irradiated by a laser beam for working on the surface to be worked, and a light receiving device 5 receiving a reflected light of a laser beam for measuring a distance from the surface to be worked, are provided. The wave length of the laser beam for measuring a distance, is made different from that of the laser beam for working. The light receiving device is equipped with a transmission wave length select filter 7 having a characteristic selectively transmitting only a laser beam for measuring a distance. Consequently, a measurable range is enlarged, and accuracy is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser processing apparatus for forming fine irregularities or holes on the surface of a cylindrical rotating body used for, for example, continuous casting rolls, rolling rolls, etc. The present invention relates to a gap sensor for measuring a distance from a processing head.

[0002]

2. Description of the Related Art A technique for forming fine irregularities on a surface of a cylindrical body or forming fine holes with a laser beam has already been put into practical use (Japanese Patent Laid-Open No. 11285/1990 and Japanese Patent Laid-Open No. 11285/1985). 55-94790, etc.). Since the processing accuracy in such a laser processing apparatus depends on the accuracy of the focal length of the laser light, it is necessary to always keep the distance between the condenser lens and the surface to be processed within a predetermined range during the processing operation. is there.

As a method for keeping the distance between the condenser lens and the surface to be processed constant, for example, an eddy current type proximity sensor is provided at a position adjacent to the machining head having the condenser lens built therein, and the output of this proximity sensor is provided. It is known that the feedback control is performed based on the above to perform gap control with respect to the surface to be processed of the processing head.

[0004]

However, since it is virtually impossible to provide the gap sensor of the above-mentioned type at the same position as the machining head, the point at which the gap measurement is performed and the point at which the machining is actually performed. Between the sensor and the sensor, or because the sensitive part of the sensor does not face the surface to be measured due to the sensitivity characteristics of the gap sensor, the required signal cannot be obtained. The accuracy of the gap measurement between the machining head and the surface to be machined is reduced at the end of the roll in the axial direction where the area of the sensitive area of the sensor is insufficient, or on a curved surface with a relatively small curvature. However, there was an unavoidable need for a region in which the processing accuracy of (1) could not be obtained.

On the other hand, Japanese Patent Laid-Open No. 61-105416 discloses that
A method has been proposed in which a distance is measured by irradiating a target surface with a spot of distance measuring laser light and determining the center position of scattered light on a position detection element. However, this method cannot measure the distance under the influence of the laser light for processing and the light emitted from the processing surface. Therefore, in practice, the distance is measured between the pulses of the processing laser light. However, this makes it possible to measure the distance, but since the distance measurement positions on the surface to be processed are discrete, continuous shape changes cannot be detected, or the frequency of the laser pulse for processing is increased. The problem arises that you can't.

The present invention has been devised in order to eliminate such disadvantages of the prior art, and its main purpose is to make the distance measuring position and the processing position on the surface to be processed substantially equal,
An object of the present invention is to provide a gap sensor for a laser processing apparatus, which is improved so that the gap control of a laser processing head can be controlled continuously and with high accuracy.

[0007]

According to the present invention, such a purpose is to provide a processing laser which is provided so as to be able to come into contact with and separate from a surface to be processed, and irradiates the processing surface with a laser beam for processing. A gap sensor for a laser processing device, which is arranged adjacent to the head and measures the distance between the surface to be processed and the processing head, is provided with a predetermined angle near the irradiation position of the processing laser on the surface to be processed. With a distance measuring laser irradiation device for irradiating a distance measuring laser light and a light receiving device for sensing reflected light from the surface to be processed of the distance measuring laser light, the wavelength of the distance measuring laser light is Achieved by providing the light receiving device with a transmission wavelength selection filter having a characteristic different from the wavelength of the processing laser beam and having a characteristic of selectively transmitting only the distance measuring laser. It is.

[0008]

According to this structure, the processing laser beam and the distance measuring laser beam can be applied to substantially the same point, so that the deviation between the gap measuring position and the processing position can be substantially ignored. It can be of a degree. In addition to this, since the gap measurement can be performed using the light spot of the laser light, the area of the measurement surface can be small, and the measurable region is expanded.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of the present invention will be described in detail below with reference to specific embodiments shown in the accompanying drawings.

FIG. 1 shows a processing head 1 for a laser processing apparatus constructed according to the present invention. The laser irradiation nozzle 2 of the processing head 1 has a conical inner surface, and the condenser lens 3 is fixed inside the inner surface.

A distance measuring laser irradiator 4 is fixed to one side of the processing head 1, and a light receiver 5 for sensing the reflected light thereof is fixed to the other side.

A unit of the processing head 1 including this distance measuring device is mounted on a position adjusting table driven by a driving device (not shown) using a pulse motor, for example, and measures a predetermined set gap value and distance. By performing a comparison calculation with the signal, it is controlled so that the proper gap with respect to the surface 6 to be processed is kept constant.

For example, the processing laser beam L1 emitted from the YAG laser oscillator is emitted with an optical axis perpendicular to the surface 6 to be processed. Further, the measuring laser light L2 emitted from, for example, a semiconductor laser oscillator built in the distance measuring laser irradiator 4 is narrowed down by a light projecting lens and is irradiated onto the surface 6 to be processed at a predetermined angle α. Then, the reflected light from the surface 6 to be processed is condensed by the imaging lens built in the light receiver 5 and forms an image on the one-dimensional sensor. The position of the work surface 6 is determined from the position of the optical image on the one-dimensional sensor.

If the reflected component of the processing laser beam L1 is incident on the light receiver 5, the distance measurement is adversely affected. Therefore, the wavelengths of the processing laser beam L1 and the distance measurement laser beam L2 are different from each other. Together with laser light L for distance measurement
By providing the light receiving device 5 with the transmission wavelength selection filter 7 having the selection characteristic that the wavelength of 2 is transmitted but the wavelength of the processing laser beam L1 is not transmitted, the reflection component of the processing laser beam L1 does not affect the distance measurement. Is done.

The processing laser beam L1 and the distance measurement laser beam L2 are irradiated onto the surface 6 to be processed with a pulse beam having an appropriate frequency, and a phase difference is provided between the two. It is possible to prevent the reflected component of the light L1 from affecting the distance measurement.

[0016]

As described above, according to the present invention, the distance measuring position and the processing position on the surface to be processed can be made substantially equal, and the distance can be measured with a minute light spot.
The constant gap control of the laser processing head can be executed in real time. Therefore, it is possible to perform highly accurate laser processing over the entire area of the workpiece without requiring complicated correction control.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing a first embodiment of a laser processing head of the present invention.

[Explanation of symbols]

 1 Processing Head 2 Nozzle 3 Condenser Lens 4 Distance Measuring Laser Irradiator 5 Light Receiver 6 Worked Surface 7 Transmission Wavelength Selection Filter L1 Processing Laser Light L2 Measurement Laser Light

Claims (1)

[Claims] 1. A processing head, which is provided so as to be able to come into contact with and separate from a surface to be processed and which irradiates a laser beam for processing onto the surface to be processed, and is arranged between the surface to be processed and the processing head. A laser processing device gap sensor for measuring an interval, the distance measuring laser irradiation device irradiating a distance measuring laser beam at a predetermined angle in the vicinity of an irradiation position of the processing laser beam on the surface to be processed. And having a light receiving device for sensing the reflected light from the surface of the distance measurement laser light to be processed, the wavelength of the distance measurement laser light is different from the wavelength of the processing laser light, and the distance A gap sensor for a laser processing apparatus, wherein a transmission wavelength selection filter having a characteristic of selectively transmitting only a measurement laser beam is provided in the light receiving device.