JPS59160128A - Deflecting method of laser beam - Google Patents

Abstract

PURPOSE:To obtain a deflected beam having uniform intensity at a deflection angle over a wide range by providing a filter circuit which can correct the intensity of the acoustic wave propagating in an acousttooptic element according to the frequency thereof within a driving circuit for the acoustooptic element. CONSTITUTION:The output frequency of a voltage controlling oscillator 1 is determined by the DC voltage value applied on an input terminal 6 for a control voltage in a laser beam deflector and the oscillated output thereof is applied through a filter 2 and a power amplifier 3 to an acoustooptic element 4. The electric power applied on the element 4 is corrected with the frequency thereof by the filter circuit 2 having a suitable characteristic to negate the fluctuation in the deflecting efficiency of a laser beam 8 in the acoustic frequency range to be used by the change in the intensity of the acoustic wave. The beam 7 is thus deflected with the uniform intensity. The frequency characteristic of the circuit 2 is required to be adjusted by the deflecting efficiency characteristic of the element 4 and is made variable from the outside.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an improvement in a laser beam deflection method, and more particularly to a laser beam deflection method suitable for high-speed precision processing equipment or display devices using lasers.

[Background technology]

What is the deflection efficiency of a laser beam by an acousto-optic element depending on the laser beam incidence angle and the inside of the element? It depends on the intensity and frequency of the propagating acoustic wave beam. When driving an acousto-optic element in the frequency range near where the Bragg condition is satisfied to control the deflection angle of the laser beam, conventional methods drive with a constant acoustic wave intensity, so the deflection efficiency changes as the deflection angle changes. This has the disadvantage that a deflected beam of uniform intensity cannot be obtained.

[Purpose of the invention]

An object of the present invention is to solve the above-mentioned problems and provide a high-speed laser beam deflection method that can obtain a deflected beam of uniform intensity over a wide range of deflection angles.

[Summary of the invention]

In order to achieve all of the above objectives, the present invention focuses on the change in laser beam deflection efficiency due to acoustic wave intensity, and installs an Oki wave circuit with appropriate characteristics in the acousto-optic element drive circuit to control the power applied to the acousto-optic element. It is possible to make corrections depending on the frequency. By appropriately selecting the characteristics of the Toba circuit,
Variations in deflection efficiency within the acoustic frequency range of use can be canceled out by changes in the total acoustic wave intensity.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIGS. 1, 2, 3, and 4. FIG. 1 shows a laser beam deflector to which the present invention is applied. In the figure, the lid is a voltage controlled oscillator (VCO), 2 is a door turntable, 3 is a power amplifier, 4 is an acousto-optic element, 5 is an aperture, 6 is a control voltage input terminal,
7 is an incident laser beam, 8 is a deflected laser beam,
9 is a laser beam that is not deflected and travels straight. In this laser beam deflector, the output frequency of the voltage ftjlJ (411) is determined by the DC voltage value applied to the control voltage terminal 6.
is applied to the four acousto-optic elements through a power amplifier.

Since the deflection angle of the acousto-optic element is determined by the applied frequency, the deflection angle of the laser beam can be controlled by the voltage applied to the laser beam deflection i-c'.

Now, the gain characteristics of the Oki transducer (2) can be determined by the characteristics of the acousto-optic element (4). Is Figure 2 an acousto-optic device that uses anisotropic Bragg diffraction? This is the deflection efficiency characteristic when driven with constant power. In the figure, the input high frequency C to the element
As the force increases, the relationship between input frequency and deflection efficiency becomes curve 10.
From this characteristic, which changes as →11 →12, the relationship between the input frequency to the element and the power that gives the highest deflection efficiency at that frequency can be determined as shown in FIG. When the input power to the element is given as shown in Figure 3, the deflection efficiency is obtained as the envelope of the curve group in Figure 2 as shown in Figure 4, and is much more uniform than when the input power is constant. It is possible to obtain excellent deflection efficiency characteristics. Therefore, in this device, the frequency characteristics of the door transceiver 2 are determined so that the power applied to the element has a value as shown in FIG. Specifically, the above-mentioned p-wave device 2 is a band-pass F-wave device consisting of a low-pass wave circuit and a high-pass p-wave circuit, and the corner frequency of the low-pass wave circuit and the high-pass wave circuit is The necessary frequency characteristics are obtained by adjusting.

Note that the characteristics of the Oki wave device required differ depending on the deflection efficiency characteristics of the high-acoustic optical element, and it is not limited to the bandpass p-wave device. However, none of these departs from the scope of the present invention.
As explained above for I/10, the frequency characteristics of the multi-unit circuit need to be adjusted according to the deflection efficiency characteristics of the acousto-optic element.
It is desirable to make it variable from the outside.

According to this embodiment, it is possible to obtain a deflected beam whose intensity is uniform and strong regardless of the deflection angle, and the characteristics of the laser beam deflector can be significantly improved.

〔Effect of the invention〕

According to the present invention, it is possible to deflect a laser beam with uniform intensity. When applied to laser beam processing of reticles and the like for semiconductor device manufacturing, highly accurate processing becomes possible. When scanning with a laser beam focused by a metal thin film stopper lens used for a reticle, the relationship between the laser beam intensity and the line width processed by the beam is as shown in FIG. As shown in the figure, does the change in laser beam intensity change the processing line width? This results in a decrease in machining accuracy. That is, if the intensity of the laser beam deflected according to the present invention becomes uniform, the processing accuracy will be improved compared to the conventional method. Furthermore, when applied to a two-dimensional display device using a laser, a good image can be obtained because the brightness of the entire screen becomes uniform due to the uniformity of the deflection efficiency. Furthermore, the usable deflection angle range is wider than when the power applied to the element is completely constant. As a result, the number of resolvable points increases, and the resolution over the entire deflection range improves in proportion.

[Brief explanation of the drawing]

Figure 1 is a block diagram showing the schematic configuration of the laser beam deflection method according to the present invention, Figure 2 is a curve diagram showing the deflection efficiency characteristics with respect to input frequency when the acousto-optic element is driven with constant power, and Figure 3 is A curve diagram showing the relationship between input frequency and input power that maximizes deflection efficiency. Figure 4 is a curve diagram showing the relationship between input power and input power that maximizes deflection efficiency. Is the input power corrected based on Figure 3? What are the deflection efficiency characteristics when it is carried out? FIG. 5 is a curve diagram showing the relationship between laser beam intensity and processing line width in laser beam processing of metal thin films. DESCRIPTION OF SYMBOLS 1... Voltage controlled oscillator, 2... F wave generator, 3... Power amplifier, 4... Acousto-optic element, and... Aperture.
6... Control voltage input terminal, 7... Incident laser beam, 8... Deflected laser beam, 9... Laser beam traveling straight without being deflected, 10.11 and 12...
・Deflection efficiency row when an acousto-optic element is driven with constant power Figure 1 Stone 2 Figure 4 Figure ■ 5 Figure L -1'8°

Claims (1)

[Claims] 1. In a laser beam deflection system consisting of an acousto-optic element and an acousto-optic element drive circuit, p-wave circuit? Shinkyo Laser beam deflection method 2, characterized in that it is provided in the acousto-optic element drive circuit, in the laser beam deflection method according to claim 1, the characteristics of the p-wave circuit in the acousto-optic element drive circuit are A laser beam deflection system that is externally adjustable and closed.