Optical: systems and elements – Deflection using a moving element – By moving a reflective element
Patent
1991-10-25
1992-09-01
Ben, Loha
Optical: systems and elements
Deflection using a moving element
By moving a reflective element
359214, 359226, G02B 2610
Patent
active
051444704
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention broadly relates to a turning type scanner for a laser beam machine, in which a turning deflecting mirror deflects a laser beam for positioning the laser beam, particularly to improvements in a laser scanner driving apparatus employing a piezoelectric actuator as a driving power source for turning the mirror.
BACKGROUND ART
A conventional driving apparatus of a laser scanner is designed as shown in FIGS. 2 to 4, which comprises a mirror 1, a differential speed increaser 2 as a displacement amplifying means, a lever 4 fixed on a shaft 3, a laminate type piezoelectric actuator 5 and a reaction spring 6.
The inputted driving signals give rise to a rectilinear displacement of the piezoelectric actuator 5, as shown by arrow A. Such a displacement is transmitted by way of a pin 7 to one end portion of the lever 4, which turns against a reaction force of the reaction spring 6, counterclockwise in the drawings. Together with the lever 4, the shaft 3 turns, transmitting the rotational displacement to the differential amplifier 2, where the turning is amplified and then transmitted to an output shaft 10. Then the mirror rotates predetermined degrees .theta., deflecting a laser beam coming from a laser beam generator (not shown). For the differential speed increaser 2, a Harmonic Drive (a trade name) is usually used.
The free end portion of the piezoelectric actuator 5 abuts the pin 7, which engages with a notch 11 formed in the end portion of the lever 4, as shown in FIG. 4. The free end portion of the reaction spring 6 contacts the other end portion of the lever 4 through a piston 12. (Reference can be made to Japanese Laid-open Nos. 61-132919 and 61-134726.)
In the above driving apparatus, in which the pin 7 is stopped by the notch 11 formed in one end of the lever 4, when the lever 4 is rotated .DELTA..theta. by the piezoelectric actuator 5, the supporting point of the lever 4 shifts with respect to the line of action of the piezoelectric actuator 5. Accordingly, there occur both shearing force F.tau. to the piezoelectric actuator 5 and a relative movement between the pin 7 and the end surface of the piezoelectric actuator 5. Therefore, a force acting transversely onto the piezoelectric actuator 5 is generated, which may break the actuator 5. Also, the relative movement between the actuator 5 and the pin 7 causes loss due to a friction, affecting the precision in the positioning.
The present invention solves these problems by providing a laser scanner driving apparatus which: eliminates the force transverse to the line of action of the actuator during the operation of the actuator; eliminates the loss due to friction on the end surface of the actuator during the operation; therefore eliminates fear of breaking the actuator; and improves the positioning precision of a laser scanner driving apparatus.
SUMMARY OF THE INVENTION
A laser scanner driving apparatus according to the present invention, wherein a rectilinear displacement of a piezoelectric actuator rotates a lever against a reaction force of a reaction spring and then a displacement amplifier amplifies this rotational displacement to provide a large scanning angle, comprises rotatable contactors between the free end of the piezoelectric actuator and one contact portion of the lever, and between the reaction spring means and another contact portion of the lever.
When the actuator is displaced rectilinearly so that the lever is rotated, only rolling friction occurs between the free end of the actuator and the lever, and between the free end of the reaction spring means and the lever. Therefore, neither the actuator nor the reaction spring receives a force transverse to the line of action thereof, and thus the loss due to friction on the free end of the actuator can be substantially eliminated. As a result, the actuator will not break during its operation, and also the positioning precision of a laser scanner driving apparatus can be improved.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a partial cross sectional v
REFERENCES:
patent: 4090781 (1978-05-01), Godot et al.
patent: 4778233 (1988-10-01), Christenson et al.
patent: 4832425 (1989-05-01), Walther et al.
Ben Loha
Kabushiki Kaisha Komatsu Seisakusho
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