JPS6138774Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a laser processing machine equipped with an automatic focusing function.

In recent years, lasers have come to be applied in various fields of machining, but especially in micro-machining and high-precision machining, the focal length of the condensing lens used becomes short, so it is difficult to control focusing. Technology is becoming a big issue. For example, the depth of focus of the condensing lens used to process 1 to 5 μm width using a YAG laser is only 1 to 2 μm. It is becoming increasingly difficult to keep up with manual focusing methods. Therefore, there is a need for a laser processing machine equipped with automatic focusing means to always correctly focus the laser beam onto the workpiece.

Conventionally, automatic focusing types include, for example:
A He-Ne laser is installed separately in a YAG laser processing machine for use in positioning and automatic focusing, etc., but in this case, two laser devices are required and the optical system is complicated. be. As yet another example, the reflection of laser light from a YAG laser for processing on the surface to be processed is utilized. However, in this case, since the surface to be processed is undergoing laser processing and its state is changing, it is difficult to perform accurate focusing.

The present invention was developed in view of the above circumstances, and to put it simply, the laser beam emitted from a laser device originally installed for the purpose of processing is divided into two, and one is used for conventional processing. The other laser beam is focused on the processing position on the workpiece as a laser beam, and the other is focused on another position on the same focal plane as the processing position for detection for automatic focusing, and the reflection of the laser beam for detection is used. The present invention provides a laser processing machine that automatically focuses the laser beam for processing.

According to the laser processing machine of the present invention, only one laser device is required, and since it is possible to use the reflected light from the surface of the workpiece immediately before laser processing for automatic focusing, there is no need for interference from processing phenomena. This allows for accurate focusing without any problems.

The details of the present invention will be explained below with reference to the drawings. However, the present invention is not limited thereby.

FIG. 1 is a diagram showing the principle of an embodiment of the present invention.

1 is a laser oscillator, and 2 is a collimator. It is assumed that the laser beam 3 emitted from the collimator 2 becomes parallel light. 4 is a beam splitter, and the laser beam 3 is split by the beam splitter 4 into two laser beams, namely a processing beam 3a and a detection beam 3b.

Reference numeral 5 denotes a condensing lens, which condenses the processing beam 3a at a predetermined position near the surface of the workpiece 6.

9 is its focal point.

On the other hand, the detection beam 3b has its energy attenuated by a laser power control means 10 such as an ND filter, passes through an optical system consisting of total reflection mirrors 11 and 12, and a beam splitter 13, and becomes an attenuated detection beam 3c. . Attenuated detection beam 3c
After passing through the beam splitter 4, it enters the condenser lens 5, but the total reflection mirror 11,
12 and a beam splitter 13 are installed, the light is focused by the condenser lens 5 onto a point 4 near the focal point 9. The focal point 9 and the focal point 14 are
Since the beams 3a and 3c are parallel lights, they exist on the same plane at the focal length position of the condenser lens 5. Therefore, it is possible to use the focusing point 9 for laser processing and the focusing point 14 for automatic focusing.

7 and 8 are workpiece holding stages, 7 is driven in the optical axis direction of the beam 3a, and 8 is driven in a direction perpendicular to the optical axis.

The attenuated detection beam 3c is reflected by the surface of the workpiece 6 near the condensing point 14 and enters the condensing lens 5 again. If the surface of the workpiece 6 is at the position of the condensing point 14, the condensing lens 5
The reflected light 3d emitted from the light becomes parallel light.

15 is an imaging lens. If the reflected light 3d is parallel light, it will form an image at the focal point of the lens, but if the surface of the workpiece 6 is slightly shifted back and forth from the focal point 14, the reflected light 3d will not become parallel light. , the image is formed at a position slightly shifted back and forth from the focal point of the lens. However, since a beam splitter 16 is installed between these imaging positions and the imaging lens 15 to split the imaging light into two, images are formed at two locations 17 and 18. Imaging lens 1
5 and beam splitter 16 constitute an imaging optical system.

Reference numerals 19 and 20 indicate light intensity detection elements, which are installed at a constant distance before and after the imaging position, respectively. 21 and 22 are pinholes installed just in front of the light intensity detection element. As mentioned above, since the imaging position changes depending on the position of the surface of the workpiece 6,
The amount of light passing through the pinholes 21 and 22 and entering the light intensity detection elements 19 and 20 also changes, and as a result, the outputs of the light intensity detection elements 19 and 20 also change. Second
The figure shows the position of the surface of the workpiece 6 and the light intensity detection element 1.
This shows the relationship between the outputs of 9 and 20, and 25
is the output of the light intensity detection element 19, and 26 is the output of the light intensity detection element 20.

A differential amplifier 23 outputs the difference between the outputs 25 and 26. FIG. 3 shows the relationship between the position of the surface of the workpiece 6 and the output 27 of the differential amplifier 23.

24 is a movement control section for stages 7 and 8.
The stage 7 is driven back and forth based on the output 27 from the differential amplifier 23 in an attempt to keep the output 27 at zero. Therefore, the surface to be processed is always maintained at the focal position of the condenser lens 5.

Next, the operation will be explained.

FIG. 4 is a schematic diagram of beam processing. A condensing point 9 and a condensing point 14 are formed by the condensing lens 5, but the condensing point 14 cannot be subjected to laser processing because the energy is small. The stage 8 is moving to the left in the figure, and the laser processing is progressing from the left to the right of the workpiece 6. Assuming that there are undulations on the surface of the workpiece 6, as the workpiece 6 moves, the condensing point 14 moves away from the workpiece 6, which causes the outputs of the light intensity detection elements 19 and 20 to change. Change. Since the outputs of the light intensity detection elements 19 and 20 are fed back to the stage 7 via the differential amplifier 23 and the movement control section 24,
The workpiece 6 constantly traces the focal plane of the condenser lens 5.

A prerequisite for this invention is that the detection beam is reflected by the surface of the workpiece, but most workpieces targeted for laser processing have a moderate reflectance, so in practice No problem. In addition, since the focal direction can be corrected while detecting the state of a point just in front of the processing point, it is possible to follow very sharp surface steps etc. well.

As understood from the above explanation, the present invention is
a beam splitting means for splitting the laser beam into a processing beam and a detection beam; a condensing lens for focusing the processing beam on a predetermined position; a power control means for reducing the energy of the detection beam; an optical system that causes the beam to enter a condensing lens from a direction slightly different from that of the processing beam and converges the beam at a position slightly different from the predetermined position;
A workpiece holding stage that holds the workpiece near the predetermined position and movable relative to the optical axis direction of the processing beam and in a direction perpendicular to the optical axis, and condenses the reflected light of the detection beam incident on the workpiece. and an imaging optical system that divides the workpiece into two and forms two images, a position slightly in front of one of the two images when the workpiece is at the predetermined position, and a position slightly in front of the other position. and a differential amplifier that outputs the difference between the outputs of the two light intensity detection elements, and a differential amplifier that outputs the difference between the outputs of the two light intensity detection elements, and the processing target according to the output of the differential amplifier. The present invention provides an automatic focusing laser processing machine equipped with a movement control means for controlling the relative movement of the object holding stage, which enables accurate automatic focusing, thereby achieving more precise laser processing. becomes possible.
In addition, the light source only requires one laser oscillator for processing, and the optical system uses a parallel beam section, so the structure is simple. Therefore, it has the advantage that it can be implemented with just a few modifications to a conventional laser processing machine.

The device of the present invention can be applied to various types of processing such as laser trimming, scribing, cutting, and drilling.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration explanatory diagram of an embodiment of the automatic focusing laser processing machine of the present invention, FIG. 2 is an output characteristic diagram of the light intensity detection element in the apparatus shown in FIG. 1, and FIG.
This figure is an output characteristic diagram of the differential amplifier in the apparatus shown in FIG. 1, and FIG. 4 is a perspective view of a main part for explaining the operation of the apparatus shown in FIG. 1. 3... Laser beam, 3a... Processing beam, 3
b...Detection beam, 3c...Attenuated detection beam, 3d...Reflected light, 3e...Reflected light of processing beam, 4...Split mirror, 5...Condensing lens, 6...Workpiece , 7, 8... Workpiece holding stage, 9... Focusing point of processing beam, 10... Laser power control means, 11, 12... Total reflection mirror, 13... Beam splitter, 14... Detection Beam condensing point, 15...imaging lens, 16...beam splitter, 17, 18...imaging position of reflected light of detection beam, 19,20...light intensity detection element, 21, 22... Pinhole, 23...Differential amplifier, 24...Movement control unit, 30...Auto-focus laser processing machine.

Claims (1)

[Scope of utility model registration request] a beam splitting means for splitting the laser beam into a processing beam and a detection beam; a condensing lens for focusing the processing beam on a predetermined position; a power control means for reducing the energy of the detection beam; an optical system that causes the beam to enter the condenser lens from a direction slightly different from that of the processing beam and converges the beam at a position slightly different from the predetermined position; A workpiece holding stage that holds the workpiece so as to be movable relative to the optical axis in a direction perpendicular to the optical axis.
An imaging optical system that divides the image into two images, one slightly in front of one of the two images when the workpiece is at the predetermined position, and one slightly behind the other. 2 each arranged in the position
a differential amplifier that outputs the difference between the outputs of the two light intensity detection elements, and a movement control that controls the relative movement of the workpiece holding stage according to the output of the differential amplifier. An automatic focusing laser processing machine comprising means for automatically maintaining the position of a workpiece at a focusing position of a processing beam.