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Timestamp: 2020-01-22 22:53:13
Document Index: 314174133

Matched Legal Cases: ['art.\n4', 'art.\n5', 'art 451', 'art 452', 'art 451', 'art 451', 'art 452', 'art 451']

DEFLECTOR, OPTICAL SCANNING UNIT, AND IMAGE FORMING APPARATUS - Nakajima, Tomohiro
United States Patent Application 20080024590
R<r, D>d, and D≧d·(r/R)̂2
Nakajima, Tomohiro (Tokyo, JP)
11/765166
G02B26/10; G02B26/08
Download PDF 20080024590 PDF help
20090303277 Image detection device of inkjet printing machine December, 2009 Cheng
1. A deflector, comprising: a vibrating mirror supported by a torsion beam provided as a rotational axis and reciprocally scanning a beam from a light emitting source; and a rotational part configured to give a rotational torque to the vibrating mirror for making oscillation; wherein the rotational part generates the rotational torque along one side separated from the rotational axis by length R in a direction perpendicular to the rotational axis; and the vibration mirror has relationships of
R<r, D>d, and D≧d·(r/R)̂2 where width in a direction perpendicular to the rotational axis of a mirror part that is a part of the vibrating mirror is 2r; width in a direction parallel with the rotational axis of the mirror part is d; and width of the separated one side causing generation of the rotational torque is D.
2. The deflector as claimed in claim 1, wherein the vibrating mirror includes a first substrate and a second substrate; the first substrate forms the mirror part; and the second substrate forms a vibrating plate part supported by the torsion beam.
3. The deflector as claimed in claim 2, wherein, in the vibrating mirror, a plurality of the mirror parts is arranged with the designated separated distance in a direction parallel with the rotational axis, and a common torsion beam is provided at the vibrating plate part.
4. The deflector as claimed in claim 2, wherein the vibrating plate part includes a reinforcing beam configured to reinforce the mirror part.
5. The deflector as claimed in claim 2, wherein the vibrating plate part includes a mass adjusting part configured to change a mass.
6. The deflector as claimed in claim 2, wherein the rotational part includes a surface coil and a permanent magnet; the surface coil is provided at the vibrating plate part; the permanent magnet forms a magnetic field in a direction perpendicular to the rotational axis; and an electric current flowing in the surface coil is controlled so that the vibrating mirror is oscillated.
7. The deflector as claimed in claim 1, wherein the rotational part includes a beam detection part configured to detect a beam scanned by the vibrating mirror; and an electric current flowing in the surface coil is controlled based on the result of detection so that the vibrating mirror is oscillated.
8. The deflector as claimed in claim 1, wherein the rotational part gives the rotational torque in a cycle different from a resonance vibration frequency of the vibrating mirror.
9. An optical scanning unit, comprising: a deflector including a vibrating mirror supported by a torsion beam provided as a rotational axis and reciprocally scanning a light beam from a light emitting source; and a rotational part configured to give a rotational torque to the vibrating mirror for making oscillation; wherein the rotational part generates the rotational torque along one side separated from the rotational axis by length R in a direction perpendicular to the rotational axis; the vibration mirror has relationships of
R<r, D>d, and D>d·(r/R)̂2 where width in a direction perpendicular to the rotational axis of a mirror part that is a part of the vibrating mirror is 2r; width in a direction parallel with the rotational axis of the mirror part is d; and width of the separated one side causing generation of the rotational torque is D; the light beam from the light source is deflected and a spot shape is formed by an image-formation optical system, so that a surface is scanned; and the light source is provided so that the light beam is deflected toward the rotational axis of the vibrating mirror.
10. An image forming apparatus wherein an electrostatic image is recorded on an image carrier by a light beam from a light source device modulated by an image signal and the electrostatic image is transformed by a toner so as to be transferred to a recording medium, the image forming apparatus comprising: an optical scanning unit having a deflector including a vibrating mirror supported by a torsion beam provided as a rotational axis and reciprocally scanning the light beam from the light source device; and a rotational part configured to give a rotational torque to the vibrating mirror for making oscillation; wherein the rotational part generates the rotational torque along one side separated from the rotational axis by length R in a direction perpendicular to the rotational axis; the vibration mirror has relationships of
R<r, D>d, and D≧d·(r/R)̂2 where width in a direction perpendicular to the rotational axis of a mirror part that is a part of the vibrating mirror is 2r; width in a direction parallel with the rotational axis of the mirror part is d; and width of the separated one side causing generation of the rotational torque is D; a light beam from a light source device is deflected and a spot shape is formed by an image-formation optical system, so that a surface is scanned; and the light source device is provided so that the light beam is deflected toward the rotational axis of the vibrating mirror.
The dimensions of the movable mirror are determined as 2r in width in a direction orthogonal to the rotational axis, d in width in a direction parallel to the rotational axis, and t in thickness. The dimensions of each twisting member are determined as h in length, and a in width. When the density of Si is ρ, and the material constant is G, the moment of inertia I=(4ρrdt/3)·r̂2, and the spring constant K=(G/2h)·{at(â2+t̂2)/12}. Thus, the resonance frequency f0 is:
f0=(½π)·√{square root over ( )}(K/I)=(½π)·√{square root over ( )}{Gat(â2+t̂2)/24LI}
θ=κ/I·f0̂2, where κ is a constant. (1)
On the other hand, the relationship between the torque T and the scan angle θ can be expressed by: θ=κ′·T/K where κ′ is a constant. . . . (2)
The vibrating mirror module includes a vibrating mirror board 440, a movable mirror 441, a torsion beam 442, a frame 447, a mounting board 448, a circuit board 445, a positioning part 451, an edge connecting part 452, a retaining claw 453, a connector 454, and wiring terminals 455.
The movable mirror 441 having a two-step structure is axially supported by the torsion beam 442. The vibrating mirror substrate 440 is prepared, as discussed below, by etching a single Si board to punch the outside shape out, and is mounted on the mounting board 448.
The supporting member 447 is formed of resin by molding, and is positioned in a predetermined location of the circuit board 449. The supporting unit 447 is integrally formed with the positing determining part 451 and the edge connecting unit 452.
The positing determining part 451 determines the position of the vibrating mirror board 440 so that the reflective surface of the movable mirror is parallel to the main scanning plane surface and tilted at a predetermined angle, or 60 degrees in this example, from the main scanning direction.
Thus, one side of the vibrating mirror board 440 is inserted into the edge connecting part 452 and fitted inside the retaining claw 453. The back of the vibrating mirror board 440 is supported with both side surfaces aligned along the position determining part 451, and the electric wiring is completed.
Furthermore, a control IC, a crystal oscillator and the like that drive the vibrating mirror are mounted on the circuit board 449, to which power is externally supplied via the connector 454.
FIG. 3 is a front view and a rear view of the vibrating mirror 440 of the embodiment of the present invention. More specifically, FIG. 2(a) shows a single-step mirror and FIG. 2(b) shows a two-step mirror. FIG. 4 is an exploded perspective view of the single-step mirror.
The vibrating mirror 440 includes the vibrating mirror 460 formed of the movable mirror 441, the torsion beam 442, the vibrating plate 443, a reinforcing beam 444, the frame 447, and others, the mounting board 448, the yoke 449, the permanent magnetic 450, and the wiring terminals 455.
The vibrating mirror 460 is formed of a first board 462 and a second board 461. The first board 462 is formed of the movable mirror 441 and the frame 447.
The second board 461 includes the torsion beam 442, the vibrating plate 443, the reinforcing beam 444, the frame 446, the coil pattern 463, the terminals 464, and a trimming patch 465.
First, the wafer is pierced from the top surface of the 140 μm thick second board 461 to the oxide film in portions other than the torsion beam 442, the vibrating board 443 on which a flat coil is formed, the reinforcing beam 444 which works as frameworks of the movable mirror 441, and the frame 446 by a dry process using plasma etching.
Next, the wafer is pierced from the top surface of the 60 μm thick first board 462 to the oxide film in portions other than the movable mirror 441 and the frame 447 by anisotropic-etching the 60 μm-thick board 462 by use of KOH, for example.
Furthermore, reflective surfaces are formed on the top surface of the first board 462, with a metal thin film such as an aluminum thin film. The trimming patch 465, the terminal 464 that is wired via the coil pattern 463 and the torsion beam 442 that is a copper thin film are formed on the top surface of the second board 461.
The vibration mirror 460 is mounted on the base 466 where a movable surface is exposed. Lorentz force is generated on the sides of the coil pattern 463 parallel to the rotational axis when the current flows between the terminals 464.
As a result, a torque T is generated, twisting the torsion member 442 to rotate the movable mirror 441. When the current is turned off, the movable mirror 441 is returned to the neutral position by a spring force of the torsion member 442.
Before being mounted on the mounting substrate 448, the vibrating mirror 460 is vibrated corresponding to the scanning frequency by an exciting device 503. A CO2 laser 504 is irradiated on the patch 465 from the rear side of the movable mirror 441 so that cutting is performed until the scan angle is immediately increased due to resonance.
D≧d·(r/R)̂2
θ=κ′·T/K where κ′ is a constant. (2)
While the first substrate 462 forming the movable mirror and the second substrate 461 forming the torsion beam are provided in this embodiment and are made of two pieces of Si substrate for selecting proper thickness in this embodiment, the present invention is not limited to this example. These may be made of a single substrate.
In addition, while the surface coil (coil pattern 463) is provided at the vibrating plate 463 and a pair of the permanent magnets 450 is connected to the yoke 449 in this embodiment, the present invention is not limited to this example. The permanent magnet may be provided at the vibrating plate 443 so that the permanent magnet 450 is not necessary and the surface coil may be provided at the frame 447 or 446 or the yoke 449.
Furthermore, while the surface coil is provided in this embodiment, the coil is not limited to be surface. This is applied to not only this embodiment but also other embodiments discussed below.
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