JPH0220680A - Focal position detecting device for laser device - Google Patents

Abstract

PURPOSE:To detect a focal position with respect to many kinds of objects to be irradiated whose reflection characteristics are different by providing a means for selecting that which has the maximum value from each output corresponding to plural detection use laser beams, and calculating the focal position. CONSTITUTION:A Z table 6 is set to an initial position, an optical image 10a by a first detection use laser beam 8a is formed on an XY plane 7 of a working surface 5, and its reflected light is detected by a photoelectric converting means 11. Subsequently, an optical image 10b by a second detection use laser beam 8b is formed, and its reflected is detected by the photoelectric converting means 11. Next, a larger one of outputs of the photoelectric converting means 11 corresponding to both the detection use laser beams 8a, 8b whose wavelengths are different from each other is selected by a laser beam selecting means 16, and its output is set to a binarizing circuit 12. From the data, a binarized image is derived, and a focal position is detected from a position of the working surface 5 on which its maximum width becomes minimum.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a device for detecting the focal position of a laser beam in a laser processing device or the like.

[Conventional technology]

FIG. 3 is a configuration diagram showing a focal position detection device of a conventional laser processing apparatus disclosed in, for example, Japanese Patent Laid-Open No. 159290/1982. In the figure, (1) is a processing laser beam;
(2) is half mirror 1 (3) is a condensing lens, (4) is half mirror 1 (5) is transmitted through half mirror (2), condensing lens (3), and reflected by half mirror (4). This is the processing surface onto which the processing laser beam (1) enters at a substantially right angle, and forms the upper surface of a Z table (6) that is movable in the direction of the incident axis (Z-axis) of the processing laser beam (1). (7) is the machined surface (5)
It is an XY plane formed in . (8) is coaxial and parfocal with the processing laser beam (1), reflected by a half mirror (2), transmitted through a condensing lens (3), and further reflected by a half mirror (4) to be applied to the processing surface. (5) is the detection laser beam irradiated, (9) is the detection laser generating means, 00 is X
The optical image Ql) of the detection laser beam (8) formed on the Y plane (7) is used as an optical image detection means to scan the XY plane (7), receive the optical image αO, and output it as an electrical signal. (6) is a binarization circuit that converts the output of the optical image αQ from the photoelectric conversion unit αυ into a binarized image, (to) is a maximum width detection unit that detects the maximum width of the binarized image The circuit α is a focal position detection circuit that detects the focal position of the detection laser beam (8) from the change in the maximum width of the binarized image when the Z table (6) is moved in the Z-axis direction. The value conversion circuit (6), the maximum width detection circuit (to), and the focus position detection circuit α constitute a focus position calculation means αυ.

Next, the operation will be explained. First, the Z table (6) is set at a predetermined initial position, and in this state, the processing surface (5
) on the XY plane (7) to obtain the optical image αQ. The photoelectric conversion means αυ is on the XY plane (
7) is scanned, and the binarization circuit (2) further converts it into a binarized image as the coordinate values of the optical image αQ for each scanning line.

The maximum width detection circuit (to) detects the maximum width at the initial position from the binarized image. The focus position detection circuit α→ is based on the relationship between the maximum width of the binarized image and the position of the Z table (6), which is found by sequentially moving the Z table (6) in the Z-axis direction. The minimum value of this maximum width is detected and the position of the processed surface (5) at that time is output as the focal position.

[Problem to be solved by the invention]

As described above, conventional focus position detection devices are designed to irradiate a detection laser beam onto the processing surface of the irradiated object and form an image, and then receive the reflected light of the light image to calculate the focus position. be. Therefore, depending on the type of object to be irradiated, the detection laser beam may not be reflected sufficiently, causing a problem in detecting the focal position. In particular, when processing thin films using laser light,
Due to the difficulty in controlling the thickness of the thin film that is the object to be irradiated, the film thickness varies depending on the sample, and its reflection characteristics vary accordingly.As a result, the ability to detect the focal position varies depending on the sample. There was a problem with being affected.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to obtain a focal position detection device for a laser device that exhibits stable performance even for various objects to be irradiated.

[Means and effects for solving the problem] In the focal position detection device for a laser device according to the present invention, the detection laser generation means generates a plurality of detection laser beams having mutually different wavelengths, and the laser beam selection means ( Therefore, the one with the maximum value is selected from the respective outputs corresponding to the respective detection laser beams, and the focal position is calculated from the maximum output.

In addition, the other devices are capable of changing the wavelength of the detection laser beam as a detection laser generating means, and the laser wavelength adjustment means is used to adjust the output of the optical image detection means to a predetermined value or more. The wavelength of the laser beam is adjusted, and the focal position is calculated from the adjusted output.

〔Example〕

FIG. 1 is a configuration diagram showing a focal position detection device of a laser processing apparatus in an embodiment of the present invention.

In the figure, (1), (3) to (7) αυ to (to) are the same as in the conventional case. (2) is a half mirror for making the detection laser beam (8) enter the condenser lens (3) from the same optical axis as the processing laser beam (1);
2b) consists of two half mirrors. (9a) is the first
A first laser generator emits a detection laser beam (8a) to a half mirror (2a), and (9b) a second detection laser beam having a different wavelength from the first detection laser beam (8a). (8b) to the half mirror (2b), and both laser generators (9a) and (9b) emit rain detection laser beams (8a) and (8b) to the processing laser beam (1).
) and are placed so that they are coaxial and parfocal. Both laser generators (9aX9b) constitute a detection laser generating means (9). αQ is each detection laser beam (8a)
This is a laser beam selection means for selecting the output having a larger value among the outputs of the photoelectric conversion means αη for (sb).

Next, the operation will be explained. First, as before, set the Z table (6) to the initial position and adjust the XY position of the machining surface (5).
A light image (10a) is formed by the first detection laser beam (8a) on the plane (7), and the reflected light is converted to the photoelectric conversion means q.
υ detects. Next, in the same manner, an optical image (10b) is formed by the second detection laser beam (8b) on the XY plane (7), and the photoelectric conversion means αυ detects the reflected light.

Here, the reflectance of the processed surface (5), that is, the surface of the object to be irradiated, is greatly influenced by the wavelength of the laser beam irradiated thereon. Therefore, rain detection laser beams (8a
) and (8b), a difference occurs between the outputs of the photoelectric conversion means αη, and the laser light selection means αQ selects whichever of these two forces is larger and sends the output to the binarization circuit @. The subsequent processing is the same as before. In other words, depending on the output data of the detection laser beam that increases the reflected light, 2
A valued image is obtained, and the focal position is detected from the position of the processing surface (5) where the maximum width thereof is the minimum.

Therefore, when the objects to be irradiated are different, in the conventional case, the wavelength of the detection laser beam was one type, and the detection of the focal position was difficult because the reflectance of the object to be irradiated was low for light of that wavelength. However, in the case shown in Figure 1, two types of laser beams with different wavelengths are used as detection laser beams, and the one with the largest amount of reflected light is selected for processing. By adopting this method, it becomes possible to detect more types of irradiated objects. In particular, it is useful for detecting the focal position in thin film processing where the reflection characteristics vary even within the same lot.

In the above embodiment, there are two types of detection laser beams, but by increasing the number of these types, it becomes possible to detect the focal position on a wider range of objects to be irradiated, and in this case, the laser beam selection means M selects the largest input data.

FIG. 2 shows the same detection device in another embodiment.

In the figure, (1) to αυ are the same as in the conventional case.

However, the detection laser generating means (9) uses a dye laser such as a liquid laser or a semiconductor laser as its light source.
The wavelength of the emitted detection laser beam (8) can be changed within a predetermined range. Further, aη is a laser wavelength adjusting means connected between the detection laser generating means (9) and the photoelectric conversion means αυ.

In this device as well, the detection laser beam (8)
is irradiated onto the XY plane (7) of the processing surface (5), and the reflected light of the optical image α0 is received by the photoelectric conversion means αυ that scans the XY plane (7). Here, if the magnitude of the output of the photoelectric conversion means αυ is at least a level that does not interfere with the subsequent processing in the focal position calculation means αe, the same processing is performed as is, but if it is less than the same level, the laser wavelength A signal is sent from the adjustment means α force to the detection laser generation means (9) to change its wavelength sequentially, and the wavelength of the detection laser light (8) at which the output of the photoelectric conversion means αη is equal to or higher than a predetermined level is selected. Based on the output, the following processing calculations are performed to detect the focal position.

Therefore, this device has the effect of being able to quickly detect the focal position of more types of irradiated objects with different reflection characteristics. Particularly effective.

In the embodiment shown in FIG. 2, the detection laser generating means (9
), a dye laser was used as the light source; however, it is not necessarily limited to this, and any laser with a variable wavelength may be used.

In addition, although the above embodiments have all been described as being applied to a laser processing device, the present invention can be similarly applied to laser devices other than laser processing, such as a laser measuring device.

Furthermore, in each of the above embodiments, the detection of the focal position is performed in two ways.
Although this is carried out by detecting the maximum width of the converted image, the present invention can also have similar effects when detecting the focal position by other methods, such as a method of calculating and detecting changes in the intensity of the reflected light of the detection laser beam. It is something that demonstrates the.

Furthermore, in each of the above embodiments, a method of moving the Z table (6) in the Z-axis direction was adopted as a method of changing the distance between the condenser lens (3) and the processing surface (5). (6) may be fixed and the condenser lens (3) may be moved in the direction of its optical axis.

〔Effect of the invention〕

As described above, in the invention of claim 1, the detection laser generating means generates a plurality of detection laser beams having mutually different wavelengths, and selects and processes the largest reflected light from the irradiated object. With this configuration, it becomes possible to detect the focal position of more types of objects to be irradiated with different reflection characteristics.

Further, in the invention of claim 2, since the wavelength-tunable detection laser generating means is provided and the wavelength of the detection laser light is adjusted so that the reflected light from the object to be irradiated is equal to or more than a predetermined value, the same can be said. This has the effect that the focal position can be detected in more types of objects having different reflection characteristics.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing a focal position detection device for a laser processing device in one embodiment of the present invention, FIG. 2 is a configuration diagram showing the same detection device in another embodiment, and FIG. 3 is a conventional same detection device. FIG. In the figure, (1) is a processing laser beam as a laser beam, (3) is a condenser lens, (5) is a processing surface as an irradiated object, (8) (82X8b) is a detection laser beam, (9 )
(9a) (9b) is a detection laser generating means, mouth 1
(10a) (10b) is a light image, (1υ is a photoelectric conversion means as a light image detection means, α is a focal position calculation means, (l
[19 is a laser beam selection means, αη is a laser wavelength adjustment means. Note that the same reference numerals in each figure indicate the same or corresponding parts. Agent: Masuo Oiwa, Patent Attorney Figure 1 Figure 2 @ 3: Senkou Shikyu F Near 7r: J Engineering 1 Figure 3

Claims (1)

[Claims] 1. A device for detecting the focal position of the laser beam of a laser device that focuses the laser beam on an object to be irradiated via a condensing lens, the focal position of which is the same as the optical axis of the laser beam. a detection laser generating means for emitting a detection laser beam from an optical axis to be focused on the object to be irradiated via the condenser lens; and an optical image formed by the detection laser beam on the object to be irradiated. a light image detection means for receiving the reflected light; and a focus position calculation means for calculating the focus position from a change in the output of the light image detection means when the distance between the object to be irradiated and the condensing lens is changed. The detection laser generating means generates a plurality of detection laser beams having mutually different wavelengths, and the value is determined from each output of the optical image detection means corresponding to each detection laser beam. A focal position detection device for a laser device, comprising: laser beam selection means for selecting the largest one and outputting it to the focal position calculation means. 2. A device for detecting the focal position of the laser beam of a laser device that focuses the laser beam on an object to be irradiated via a condensing lens, and which focuses the laser beam from the same optical axis as the optical axis of the laser beam. a detection laser generating means for emitting a detection laser beam to be focused on the irradiated object through a lens; and a detection laser generating means for receiving reflected light of a light image formed on the irradiation object by the detection laser beam. A device comprising a light image detection means and a focus position calculation means for calculating the focus position from a change in the output of the light image detection means when the distance between the irradiated object and the condensing lens is changed, The detection laser generating means is capable of changing the wavelength of the detection laser light, and includes a laser wavelength adjustment means for adjusting the wavelength of the detection laser light so that the output of the optical image detection means is equal to or higher than a predetermined value. A focal position detection device for a laser device, characterized in that: