JPH0463223A - Scanning method of laser beam - Google Patents

Abstract

PURPOSE:To execute high-speed scanning regardless of a scanning width by reflecting a laser beam by a rotary reflecting mirror, the reflecting mirror surface of which inclines with the plane orthogonal with a revolving shaft and synchronizing the irradiation timing of the above-mentioned laser beam with the rotation of the rotary reflecting mirror. CONSTITUTION:The reflected light advances along an optical axis L2 shifted by<theta from a reference optical axis L1 when the reflecting mirror surface of the rotary reflecting mirror 1 is intersected orthogonally with the revolving shaft when the laser beam is emitted while the rotary reflecting mirror 1 is held stopped. The position deviated by l from the point intersected with the above-mentioned reference optical axis L1 is irradiated with the spot of the laser beam on a material M to be irradiated. The reflected light draws the rotating locus of the generator in the circular conical shape having a vertical angle at <2theta when a motor 2 is rotated. The surface of the material M to be irradiated is so irradiated with this laser beam so as to draw the circular locus of a radius l centering at the point intersected with the reference optical axis. A condenser lens 5 is set in the position forming a focus just before the material M to be irradiated and covers the reflected light passing all of the optical axis L2 shifted by <theta from the reference optical axis L1.

Description

Detailed Description of the Invention A. Field of Industrial Application The present invention provides a laser beam that controls the scanning width of the irradiation beam according to the area to be irradiated with the laser beam when hardening or heat treatment is performed by irradiation with a laser beam. Concerning a scanning method.

0 Prior Art As a laser beam scanning method, a technique such as Hiro's conventional technique is known.

a. By vibrating the reflecting mirror 9 that reflects the laser beam from side to side, the irradiation spot P is scanned by reciprocating in a straight line with a constant width (FIG. 4a).

b. A polygon mirror 10 is used as a reflecting mirror to reflect the laser beam, and scanning is performed by giving an amplitude to the irradiation spot P by rotating the polygon mirror 10 (fourth
Figure b).

A beam focused in the shape of an irradiation spot P having a constant width is irradiated by means of an optical system such as the C1 cylindrical concave mirror 11 and the cylindrical lens 12 (Fig. 4 c, d).
.

C. Problems to be Solved by the Invention In the conventional scanning method described above, in technique a, the reflecting mirror must be vibrated from side to side, so increasing the scanning width makes high-speed scanning difficult; To do this, the scanning width must be reduced. Since the technique of Matasu restricts the scanning width with the masking 13, the scanning width cannot be changed freely.

Furthermore, the technology of C is based on the mode pattern of the focused beam (
The disadvantages are that uniform intensity cannot be obtained due to the intensity distribution) and that it is difficult to control the scanning width.

2. Means for Solving the Problems The present invention makes it possible to scan a focused beam at high speed and uniformly with a predetermined scanning width. A rotating reflector tilted with respect to a perpendicular plane reflects the light, and a condensing lens is arranged so that the reflected light illuminates the irradiated object as a spot while drawing a rotational trajectory. The purpose is to control the irradiation timing of the laser beam in synchronization with the rotation of the rotating reflecting mirror.

If the irradiation timing is set so that the laser beam is irradiated only on the necessary range on the rotational trajectory, the laser spot will be irradiated only on the circular trajectory, making it possible to scan the desired width. .

EXAMPLE A laser beam scanning method according to the present invention will be explained based on the drawings.

Reference numeral 1 denotes a rotating reflecting mirror that is disposed on the optical axis of a laser beam emitted from the horizontal direction, with its reflecting mirror surface oriented toward the emitting direction, with the reflecting mirror surface being inclined at approximately 45 degrees to the optical axis. This rotary reflecting mirror 1 is fixed to the tip of a rotating shaft of a motor 2, and is rotatable by the motor 2.The center line of the rotating shaft intersects with the optical axis of the laser beam on the reflecting mirror surface, and the reflecting mirror surface is It is inclined by Zθ with respect to a plane perpendicular to the rotation axis. The rotation of the motor 2 is controlled by a variable speed motor drive device 3, and
A rotation signal generator 4 is incorporated. A condensing lens 5 is arranged on the reflected light path of the laser beam, and an object M to be irradiated is set in front of the condensing lens 5.

In the scanning device formed in this way, when a laser beam is emitted with the rotating reflector l in a stopped state,
The reflected light has an optical axis L2 shifted by /θ with respect to the reference optical axis L1 when the reflective mirror surface of the rotating reflector is orthogonal to the rotation axis.
The laser beam is spot-irradiated onto the object M at a position offset by β from the point of intersection with the reference optical axis L1. When the motor 2 is rotated, the reflected light draws a rotation locus of the generatrix in a conical shape with an apex angle of Z2θ, and on the irradiated object M there is a radius β centered at the intersection with the reference optical axis. The light is irradiated in a circular trajectory (Figure 2).

The condensing lens 5 is set at a position where the reflected light is focused just in front of the irradiated object M, and is aligned with the reference optical axis L.
It is possible to cover all the reflected light passing through the optical axis L2 shifted by /θ with respect to +. If the scanning width is less than the width 2I2 of the circular locus, the scanning width can be set to a predetermined scanning width by controlling the laser beam to be irradiated only on the circular locus 6 corresponding to the scanning width.

For example, in order to start or stop the laser beam, a gate signal is sent from the gate signal generation circuit 7 to the laser transmission control device 8 in response to a signal from the rotation signal generator 4 incorporated in the motor 2 as shown in the third figure. If the laser oscillation control device 8 controls the irradiation timing by controlling the irradiation to be performed intermittently in synchronization with the rotation period of the rotating reflector l, the scanning width is determined by the oscillation timing of the laser beam. be done.

The radius of the circular locus drawn on the object to be irradiated is determined by the inclination angle of the rotating reflector, the distances between the rotating reflector and the condensing lens, and the distances between the condensing lens and the object. By adjusting the difference between the irradiation object and the focal length (defocus amount) and the scanning speed, it is possible to obtain the energy density according to the purpose.

In the above embodiment, the irradiation timing of the laser beam is controlled by intermittent control of laser oscillation, but it is also possible to control the irradiation timing of the laser beam by controlling the opening/closing operation of a mechanical shutter mechanism. You can also do it.

G. Effect According to the present invention, by employing a rotating reflecting mirror, scanning can be performed by rotating the reflecting mirror, so the object to be irradiated is irradiated with a beam of -like intensity, and high-speed scanning is possible regardless of the scanning width. becomes. Furthermore, the structure is simple and the laser beam irradiation timing can be easily controlled.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of an apparatus for performing the laser beam scanning method according to the present invention, FIG. 2 is an explanatory diagram showing the principle of scanning according to the present invention, and FIG. 3 is an explanatory diagram showing the timing of laser beam oscillation. Figure 4 a, b, c, d
is an explanatory diagram of a conventional example. 1. Rotating reflector, 2. Motor, 3. Motor variable speed drive device, 4. Rotating signal generator, 5. Condensing lens, 6
...Circular locus, 7.Geto signal generation circuit, 8.Laser transmission control device 9.Reflector, 10.Polygon mirror, 11.Cylindrical concave mirror, 12.Cylindrical lens, 13.Masking, L・・Optical axis, Ll ・・Reference optical axis, L2 ・・Optical axis (shifted by Zθ with respect to the reference optical axis)
, M... irradiated object, P... irradiated spot, Patent applicant Okuma Iron Works Co., Ltd. Figure 2 Figure 1 Figure 12-1 (C) Figure 4 (b) (d) Figure 3

Claims (1)

[Claims] The laser beam is reflected by a rotating mirror whose reflective mirror surface is inclined with respect to a plane perpendicular to the rotation axis, and a condenser lens is arranged so that the reflected light illuminates the irradiated object as a spot while drawing a rotational trajectory. and controlling the irradiation timing of the laser beam in synchronization with the rotation of a rotating reflector according to the required irradiation area.