The present invention relates to an optical scanner, and particularly to the optical scanner by which the light is 2-dimensionally scanned.
Presently, the optical scanner by which the ray such as the laser light is deflected and scanned, is used for an optical device such as a bar-code reader, laser printer, display. Conventionally, as the optical scanner such as this, there is a polygonal mirror in which a polygonal column mirror is rotated by a motor, and a galvano-mirror in which a plane mirror is rotation-oscillated by an electromagnetic actuator. However, in a mechanical structure which is driven by the motor or electromagnetic actuator, because the shape of the structural parts is large or cost is high, there is a problem that the downsizing of the device for which the optical scanner is used, is hindered, or results in high cost. Further, when the ray is 2-dimensionally scanned, generally, a device in which the polygonal mirror and the galvano-mirror are combined is used, however, in order to conduct the accurate 2-dimensional scanning, it is necessary that the respective scanning directions are accurately positioned so that the scanning directions by respective mirrors are orthogonal with each other, and there is also a problem that the optical adjustment is very complicated.
Therefore, in order to realize the downsizing, low cost, and the increase of the productivity, by using a micro-machining technology by which silicon or glass for which the semiconductor manufacturing technology is applied, is micro-machined, various micro optical scanners in which the structural parts such as the mirror or an elastic beam are integrally formed on the semiconductor substrate are successively developed.
For example, two frames of an inner frame for supporting the mirror through the first double holding beam, and an outer frame for supporting the inner frame through the second double holding beam are provided, the first and the second double holding beams are orthogonal with each other, and the bending-ness of the second double holding beam and the resonance frequency of the oscillation of the first double holding beam, are made close. Then, the magnetic distortion film is formed on the second double holding beam, and the engineering of the optical scanner (refer to Japanese Patent Unexamined Publication: Tokkai No. 2003-207737) by which, when the distortion and the bending oscillation are generated, the mirror is rotated by using the first and second double holding beams as 2 axes, and 2-dimensionally optical scanning is conducted, further, in almost the same structure] as the optical scanner disclosed in Patent Document 1, 2 frames and 2 double holding beams are provided, and by a plurality of piezoelectric elements arranged in the inner frame and the outer frame, when the rotation torque is respectively independently, acted on the inner frame and the mirror, the engineering of the optical scanner (refer to Tokkai-No. 2005-148459) which rotate the mirror when the first and the second double holding beams are made 2 axes, is disclosed.
However, the optical scanner disclosed in Patent document 1, the distortion and bending oscillation are simultaneously conducted on the second double holding beam by the actuator.
That is, because distortion and bending can not be independently conducted, it is considered to be difficult that the horizontal and vertical deflection are independently controlled. Further, because the resonance frequencies of the distortion oscillation of the first double holding beam and the bending oscillation of the second double holding beam are set so that they are almost same value, when the horizontal and the vertical deflection frequencies are largely different, that is, when the resonance frequencies of the distortion and the bending oscillation are largely different, it is considered to be difficult that the first double holding beam and the second double holding beam are resonated at respectively necessary deflection frequency. Further, the optical scanner disclosed in Patent Document 2, because, as for the horizontal deflection and the vertical deflection, a plurality of piezoelectric element are respectively independently provided, there is a possibility that it results in the complexity of the device, and high cost.