JPH0342191A - Control circuit for scanning driving apparatus - Google Patents

Abstract

PURPOSE:To restrain fine vibration of a scanner generating from difference between time constants in a piezoelectric actuator and scanner mechanism part by continuously varying output current limit from a power amplifier correspondingly to detected signal from a detecting part at a continuously variable current limit part and then inputting the varied output current to a piezoelectric actuator. CONSTITUTION:To a comparator 12 transmitting deviation signal in comparison with output signal from a command part 13 and feedback signal of movement of the piezoelectric actuator 4 in control circuit, a VRATE detector 20 for detecting variable speed of command voltage is arranged connecting parallel to a PID control part 14. Further, to downstream side of the power amplifier for amplifying output from the PID control part 14, the continuously variable current limit part 21 for continuously varying the output current limit of the power amplifier 15 correspondingly to the detected value from the Vrate detector 20, is arranged. By this method, both time constants in the piezoelctric actuator 4 and the scanner mechanism part can be eliminated and the fine vibration of the scanner generating from the difference between both time constants is restrained and the highly accurate beam scanning can be executed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a control circuit for a scanning drive device used in laser processing machines such as laser trimmers, laser summer power, and scratch repair, office automation equipment, and imaging equipment. be.

[Conventional technology]

4 and 5 show a laser scanner device, which includes a polarizing mirror 1, a differential amplifier 2 as a displacement amplification mechanism, a lever 3, a piezoelectric actuator 4, a reaction force spring 5, and a position sensor. 6, bracket 7, etc.

The piezoelectric actuator 4 is operated by the control circuit a, and generates a linear displacement (arrow A] j direction corresponding to the input drive (≦).The piezoelectric actuator 4 moves the pin 8 The lever 3 is in contact with the lever 3 through the lever 3.

The lever 3 is fixed to a shaft 9 and is rotatable around the lever 9, and an L-shaped bracket 7 is attached to the side surface of the lever 3. Further, the shaft 9 is connected to the differential speed increaser 2 . The polarizing mirror 1 is fixed to the output shaft 11 of the differential Toso speed machine 2. Further, the force of a reaction spring 5 acts on the lever 3 in the direction of arrow B through the piston 10, and the lever 3 receives a counterclockwise rotational force due to the displacement of the piezoelectric actuator 4, and the force of the reaction spring 5 acts on the lever 3 through the piston 10. 5
It is receiving a force that rotates it clockwise due to the reaction force of .

That is, the lever 3 converts the linear displacement ΔX of the piezoelectric actuator 4 into a rotational displacement Δθ. If the distance from the center of the shaft 9 to the center of the piezoelectric actuator 4 (the position of the pin 8) is L, the rotational displacement △θ is expressed by the following relational expression %. Measure the change ΔX in the distance to the bracket 7 attached to 3, and calculate this △
A signal Vs corresponding to X is input to the control circuit a as a feedback signal.

By the way, the control circuit a in the conventional laser scanner device is as shown in FIG.
The detection output Vs ("K+△X)" is input to the comparator 12.A command signal V0 for rotating the polarizing mirror 1 is input to the comparator 12 from the command section 13.
The comparator 12 takes these deviations ΔV (-Vo-Vs) and inputs it to the PID control section 14.

The PID control unit 14 inputs the input deviation signal ΔV to the power amplifier 15 as a drive signal for the piezoelectric actuator 4. 2ΔV of the signal amplified by the power amplifier 15 is input to the piezoelectric actuator 4, and the piezoelectric actuator 4 is subjected to linear displacement according to this input signal.

[Problem to be solved by the invention]

In the above-mentioned conventional control circuit, the output current limit of the power amplifier 15 is a fixed limit, and cannot correspond to the input frequency, so that it is not possible to suppress slight vibrations in the low frequency region.

That is, if the output current of the power amplifier 15 has a fixed limit, the relationship between the time constants of the piezoelectric actuator 4 and the scanner mechanism system is T, <<T. , which causes vibration. Here, T It is the time constant of the piezoelectric actuator 4, T. , is the time constant of the scanner mechanism system.

The present invention has been made in view of the above, and is a scanning drive capable of realizing more precise optical scanning by suppressing the slight vibrations of the scanner that occur due to the difference in time constant between the piezoelectric actuator and the scanner mechanism. Its purpose is to provide a control circuit for the device.

[Means to solve the problem]

In order to achieve the above objective 1.1, the control circuit in the scanning drive device according to the present invention includes a pressure 11i actuator that generates a linear displacement corresponding to an input drive signal, and a linear displacement of this piezoelectric actuator. a linear motion rotation conversion member that converts the rotational displacement into a rotational displacement; a displacement amplification mechanism that has a polarizing mirror coupled to the output shaft and that increases the rotational displacement of the linear motion rotation conversion member; and a drive signal that rotationally drives the polarization mirror. In a scanning drive device comprising a control circuit input to a piezoelectric actuator, the control circuit is connected to a comparator that compares an output signal from a command unit and a feedback signal of the operation of the piezoelectric actuator and outputs a deviation signal.
A VRATE detection section that detects the speed of change of the command voltage is connected in parallel with the PID control section, and a detection section from the VRATE detector is installed downstream of the power amplifier that outputs the output from the PID control section. The configuration includes a continuously variable current limit section that continuously varies the output current limit of the power amplifier in accordance with the value.

[For production]

When the PID controller outputs the deviation voltage to the power amplifier based on the deviation signal from the comparator, the change speed of the command voltage is detected by the VRATE detector, and the output current limit, which is the output signal from the power amplifier, is The continuously variable current limit section continuously varies the current in response to the detection signal from the V RATE detection section and inputs it to the piezoelectric actuator.

〔Example〕

An embodiment of the present invention will be described based on FIG.

In this embodiment, the same constituent members as those of the conventional example shown in FIGS.

V RATE is provided downstream of the comparator 12 to detect the speed of change Δ■/Δt of the command voltage Δ■ from the comparator 12.
A detection section 20 is provided in parallel with the PID control section 14. Further, on the downstream side of the power amplifier 15, a continuously variable current limit section 21 is provided that continuously varies the output current limit of the power amplifier 15 in accordance with the V RATH detected by the V RATE detection section 20. 22 is a high frequency generator connected between the PID control section 14 and the power amplifier 150.

The operation of the above configuration is shown in the flowchart of FIG.

That is, the command signal V is sent from the command unit 13. is output (step l). The comparator 12 receives the command signal V0 from the command section 13 and the feedback signal Vs from the position sensor 6.
The difference Δ■ is calculated (step 2). PIDilli
In the first part 14, 1△V is calculated as the deviation voltage to be applied to △V (step 3), and at the same time, the change speed of command voltage △V/△t is calculated in the V RATE detection unit 20 (step 3'). . Input 1△V to the deviation voltage calculated by the PID control unit 14 to the power amplifier 15 (step 4)
. Output voltage V from the power amplifier 14 based on the above deviation voltage by 1△V. .

(-K, ·K2ΔV) is output to the continuously variable current limiter 21 (step 5). The continuously variable current limiter 21 outputs the output voltage ■ from the power amplifier 14 .

1 is the detection signal V□ from the V RATE detection section 20
T,! , and a limit of 4 V RATI is set to I jlml, (-. Then, from this continuously variable current limiter 21, the time constant T1 of the piezoelectric actuator is set to 1/4V RATE displacement of the piezoelectric actuator. A signal △x (-1 ・K2 ・K3 △V) is output.

Due to the above action, the g9 constant T of the piezoelectric actuator 4.

and the time constant T10 of the scanner mechanism. are matched, and slight vibrations in the low frequency range are suppressed.

FIG. 3(A) shows the output signal ■ from the command unit 13.

This output signal V. On the other hand, the conventional scanner rotational output had slight vibrations in its waveform as shown in Figure 3 (B), but in the present invention, slight vibrations were generated as shown in Figure 3 (C). There wasn't.

According to this embodiment, a similar effect can be obtained even if a variable damping circuit is provided in the PID circuit and a limit of 1111 is added to VRATE.

〔Effect of the invention〕

According to the present invention, the piezoelectric actuator 4 and the scanner iso (
It is possible to eliminate the difference between the two time constants of the No. 1 part, thereby suppressing the slight vibration of the scanner that occurs due to the difference between the two constants, and realizing highly precise optical scanning. be able to.

[Brief explanation of drawings]

1 and 2 show an embodiment of the present invention, FIG. 1 is a schematic configuration diagram, FIG. 2 is a flowchart for explaining the operation of the embodiment, and FIG. 3 (A) 3B is a waveform diagram of the input command, FIG. 3B is a waveform diagram of the scanner rotational output in the conventional example, and FIG. 3C is a waveform diagram of the scanner rotational output in the present invention. FIGS. 4 and 5 are a longitudinal sectional view and a horizontal sectional view showing an example of a scanning drive device to which the present invention is applied, and FIG. 6 is a conventional control circuit diagram. 1 is a polarizing mirror, 2 is a differential speed increaser, 3 is a lever 4 is a piezoelectric actuator, 5 is a reaction force spring, 6 is a non-contact position sensor, 7 is a bracket, 9 is a shaft, 12 is a comparator, 13 is a command unit, 14 is a PID control unit, 15 is a power amplifier, 20
is a Vll, ATE detection section, and 21 is a continuously variable current limit section. Fig. 5 Fig. 3 (Al +B) (C1 Fig.

Claims (1)

[Claims] A piezoelectric actuator that generates a linear displacement corresponding to an input drive signal, a linear rotation conversion member that converts the linear displacement of the piezoelectric actuator into a rotational displacement, and a polarizing mirror coupled to the output shaft, In a scanning drive device comprising a displacement amplification mechanism that amplifies the rotational displacement of the rotation conversion member, and a control circuit that inputs a drive signal for rotationally driving the polarizing mirror to the piezoelectric actuator, the control circuit is configured to receive an output signal from a command unit. A comparator that compares the feedback signal of the operation of the piezoelectric actuator and outputs a deviation signal, and a V_R that detects the speed of change of the command voltage.
An _A_T_E detection section is connected in parallel with the PID control section, and an output current limit of the power amplifier is installed downstream of the power amplifier that amplifies the output from the PID control section in accordance with the detected value from the V_R_A_T_E detector. A control circuit for a scanning drive device, characterized in that a continuously variable current limiter is provided to continuously vary the current limiter.