JP3759812B2 - Compact wide-angle resonant optical scanner - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a resonance type scanner using a torsion bar among light beam scanners that scan a light beam by applying a light beam such as a laser beam to the mirror surface and rotating and oscillating the mirror surface.
[0002]
[Prior art]
In a conventional resonance type scanner, a movable body base, a mirror, a driving permanent magnet, and the like are fixed on a torsion bar as a structure of a resonator for reciprocating rotational vibration of a mirror surface. Yes. When the torsion bar has a large diameter and can be self-supporting, it is common to fix both ends near the free end of the torsion bar, and fix the movable body at the center when the diameter is small. In any case, a rod-like or linear spring material obtained by punching a piano wire or a spring material with a press is used as it is as a torsion bar.
[0003]
[Problems to be solved by the invention]
In the above-described conventional resonance scanner, the natural frequency is determined by the moment of inertia of the entire movable body and various characteristics of the torsion bar. In order to obtain a semi-permanent life, the amplitude is also limited to a certain angle or less by the value of the torsional allowable stress determined by the length and outer diameter of the torsion bar.
[0004]
Briefly, when a piano wire is used as a torsion bar, if the length is constant, the twisting angle within the allowable stress, that is, the amplitude can be increased as the linearity becomes narrower. However, when the moment of inertia of the entire movable body including the drive unit and the mirror unit is constant, the natural frequency decreases as the wire diameter decreases. In order to obtain a constant amplitude at a higher predetermined frequency, the length of the torsion bar must be increased so that the torsional stress at the required amplitude falls within the allowable stress value at the same time as increasing the wire diameter. I must. Increasing the length of the torsion bar with the same wire diameter also decreases the natural frequency so that the wire diameter of the torsion bar increases as described above, and the torsional stress with a predetermined amplitude falls within the allowable value. In addition, the length of the torsion bar must be increased so that all conditions such as vibration frequency, amplitude, and life are satisfied. Since the external dimensions of the scanner are determined as a result of the above, if the external dimensions of the scanner are determined in advance for incorporation into other equipment, the mirror dimensions, vibration frequency, amplitude, life, etc. required for the performance of the equipment There were many cases where the requirements could not be met.
[0005]
In order to increase the natural vibration frequency, the moment of inertia of the movable part can be reduced, and there is a practical limit to miniaturization of the mirror, and the resonance scanner with a large amplitude can be downsized at a predetermined frequency. Was impossible with the conventional method.
[0006]
The present invention has been made in view of the above-mentioned reasons, and an object thereof is to provide a small-sized and large-amplitude resonant scanner.
[0007]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the first aspect uses a coil spring in place of a bar material obtained by punching out a piano wire or a leaf spring conventionally used as a torsion bar.
In order to solve the above problem, a small wide-angle resonant optical scanner according to claim 1 according to the present invention is provided.
A driving coil 7 with an iron core 6, a base frame 5 for supporting the driving coil 7, the movable body base 4 for holding the permanent magnet 3 and the mirror 2 corresponding to the iron core 6 Hisashi Naka portion, the movable body base 4 comprising a pair of movable bodies Besuneji 4A was kicked set on both ends of, and 4B, 2 pieces of coil springs 1A, and 1B, the pair of frame fixing screw 8A fits on the end of each coil spring, and 8B, the A resonant optical scanner,
One end of each coil spring is screwed and fixed to the movable body base screws 4A and 4B, respectively.
The other end of each coil spring is inserted and fixed to the fixing screws 8A and 8B, respectively.
The coil springs 1A and 1B are fixed to the base frame 5 with the fixing screws 8A and 8B.
Furthermore, the small wide-angle resonant optical scanner according to claim 2 according to the present invention is the small wide-angle resonant optical scanner according to claim 1,
The resonance frequency is adjusted by changing the degree of insertion of the coil springs 1A, 1B and the fixing screws 8A, 8B.
[0008]
As a result, if the target frequency is about 500 Hz or less, the frequency, amplitude can be reduced without disturbing the demand for miniaturization by changing the linearity, winding diameter, and number of turns of the spring material forming the coil spring. It is easy to satisfy various conditions such as allowable stress.
[0009]
When using a coil spring as a torsion bar, one of the problems with the stabilization of the rotational vibration shaft is to insert a screw that fits the end of the coil spring without using a hook as a method for fixing the coil spring. The problem was solved by fixing the screw to the base frame and by extending the coil spring in the axial direction and applying an appropriate tension.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the invention will be described based on an example with reference to the drawings.
FIG. 1 is a side view showing an embodiment. In the figure, a mirror 2 and a permanent magnet 3 are arranged at the center of a movable body base 4 having screw portions at both ends so that the S pole is the front and the other is an N pole. It is fixed. The direction of the magnetic pole may be reversed. A coil spring 1 is screwed and fixed to the screw portions at both ends of the movable body base 4. A screw 8 is similarly screwed into the other end of the coil spring 1, and is fixed to the base frame 5 at the other end of the screw 8.
[0011]
At this time, the vibration shaft can be stabilized by applying tension to the coil spring 1. Further, by changing the insertion degree of the screw at the fixed end of the coil spring 1, the effective length of the coil spring 1 that acts in the same manner as the torsion bar can be changed, and the resonance frequency can be adjusted.
FIG. 3 is a longitudinal sectional view showing details of a fixing method of the movable part and the coil spring.
As shown in FIG. 1, the drive coil 7 is fixed to the base frame 5 together with the iron core 6. A permanent magnet 3 and a mirror 2 corresponding to the iron core 6 are held at the center of the movable body base 4. A pair of movable body base screws 4 </ b> A and 4 </ b> B are provided at both ends of the movable body base 4. One coil spring 1A is coupled to one fixing screw 8A and one movable body base screw 4A at both ends thereof. The other coil spring 1B is coupled to the other fixing screw 8B and the other movable body base screw 4B at both ends thereof.
[0012]
When a current is passed through the drive coil, an attractive force is applied to one of the magnetic poles and a repulsive force is applied to the other magnetic pole, with the torsion bar as an axis, on the permanent magnet fixed to the movable body base. Therefore, when an alternating current having the same frequency as the natural frequency is applied to the drive coil, the movable body causes a resonance phenomenon and reciprocates around the axis.
[0013]
【The invention's effect】
As described above, according to the present invention, the following effects can be obtained by using a coil spring as a torsion bar as compared with a conventional small resonance scanner. For convenience of comparison, the resonance frequency is 500 Hz, which is compared with the conventional type. (See Japanese Patent Application No. 8-28384)
The conventional one has a limit of about ± 10 degrees when expecting a life of 10 11 times or more as a mechanical deflection angle, but according to the present invention, a large amplitude of ± 45 degrees was obtained. In addition, the size is changed from the conventional 15 mm × 20 mm × 13 mm to 10 mm × 12 mm × 22 mm, and the volume ratio can be reduced by 50%.
[Brief description of the drawings]
FIG. 1 is a side view showing an embodiment.
FIG. 2 is a plan view showing an embodiment of the present invention.
FIG. 3 is a longitudinal sectional view showing details of a method for fixing a movable part and a coil spring.
FIG. 4 is a side view showing a conventional example.
[Explanation of symbols]
1 (1A, 1B) Coil spring 2 Mirror 3 Permanent magnet 4 Movable base 4A, 4B Movable base screw 5 Base frame 6 Iron core 7 Drive coil 8 (8A, 8B) Screw (fixing screw)
9 Piano wire

Claims (2)

A driving coil having a core, a base frame for supporting the driving coil, the movable body base for holding the permanent magnet and mirror corresponding to the core to the medium-central portion, a pair of which is eclipsed set to both ends of the movable body based A resonance type optical scanner including a movable body base screw, two coil springs, and a pair of frame fixing screws adapted to ends of the coil springs,
One end of each coil spring is screwed and fixed to the movable body base screw, respectively.
Insert and fix the other end of each coil spring to the fixing screw, respectively.
A compact wide-angle resonant optical scanner configured by fixing the coil spring to the base frame with the fixing screw . 2. The compact wide-angle resonant optical scanner according to claim 1 , wherein the resonance frequency is adjusted by changing the insertion degree of the coil spring and the fixing screw .

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