JP2005250076A - Optical deflector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that the manufacturing cost of a device with a vibrator increases if a substrate provided with a driving means is separately prepared. <P>SOLUTION: The device with the vibrator of a nested structure which has a magnetic field generating means A at one needle and a magnetic field generating means B at another needle and in which the magnetic field generating means A and the magnetic field generating means B magnetically interact each other other to vibrate is provided. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an optical deflector using a vibrating body.

  Conventionally, a polygon mirror (rotating polyhedron) is known as an optical deflector used in a laser printer or the like. However, in order to achieve high-quality, high-quality printing and high-speed printing using a polygon mirror, the polygon mirror must be rotated at a higher speed. Currently, air bearings are used in polygon mirrors to maintain high-speed and stable rotation. However, problems such as inconvenience arise in order to obtain higher-speed rotation than before. In addition, increasing the size of the motor to prevent complications leads to an increase in the size of the device itself. On the other hand, an optical deflector that performs sinusoidal vibration can be manufactured by a semiconductor process, consumes less power, and can be made smaller than an optical deflector that uses a polygon mirror. In addition, a prototype of a micromirror using a silicon substrate has been reported recently, and an optical deflector made of a silicon single crystal theoretically has no metal fatigue and can be expected to be durable.

A conventional example of such a sine vibration type optical deflector is shown in FIGS. FIG. 7 is a perspective view of a conventional electrostatic drive type optical deflector. Supports are provided on the left and right sides of the vibrating body having a reflective surface. In this conventional example, the base substrate has a pair of left and right fixed electrodes, and the voltage applied between the opposing substrate on the vibrating body is switched by a switch. By switching the switch, the left and right sides of the vibrating body are alternately attracted to the fixed electrode and vibrated by electrostatic attraction. In the case of the electrostatic drive type, in order to increase the deflection angle (deflection angle) of the reflection mirror part, it is necessary to increase the gap interval between the reflection mirror part and the fixed electrode. Conversely, when the gap becomes large, a large voltage is required. It is disadvantageous in terms of low power consumption. FIG. 8 is a perspective view of a conventional electromagnetically driven optical deflector. Supports are provided on the left and right sides of the vibrating body having a reflective surface. In this conventional example, a pair of permanent magnets are arranged on the left and right sides of the base substrate. By energizing the drive coil around the reflective surface with drive power, the Lorentz force generated by the external magnetic field of the permanent magnet and the alternating current of the drive coil reciprocally sinely reciprocates around the pair of beams. is there. Compared to the electrostatic drive type, there is no restriction on the deflection angle, so the deflection angle can be increased. It is common to use an arcsin lens as a normal imaging optical system (imaging lens) in order to image the reflected and deflected light beam by performing these sinusoidal vibrations on the surface to be scanned and scan at a constant speed. . Patent Literature 1, Patent Literature 2, Patent Literature 3, and Patent Literature 4 have been proposed as optical scanning optical systems using an arcsin lens and an optical deflector that performs sinusoidal vibration.
Japanese Patent Laid-Open No. 9-230276 Japanese Patent Laid-Open No. 9-230277 JP-A-9-230278 JP-A-9-230279

  However, when the arcsin lens is used in an optical scanning optical system, problems as disclosed in Japanese Patent Application Laid-Open No. 2003-279879 occur. In other words, the arcsin lens has a characteristic that the Fno (F number) in the main scanning direction of the scanning end changes with respect to the scanning center. For this reason, the spot on the surface to be scanned between the scanning center and the scanning end. There is a problem that the diameter becomes non-uniform. Specifically, the spot diameter in the main scanning direction at the scanning end is larger than the spot diameter in the main scanning direction at the scanning center. This is a phenomenon that occurs because a beam whose angular velocity changes sinusoidally is scanned at a constant velocity on the surface to be scanned. Such a phenomenon becomes a problem when used in an image forming apparatus such as a laser printer or a digital copying machine. Specifically, the variation in spot diameter on the screen to be scanned induces deterioration in gradation reproducibility and fine line width in halftone images.

  Next, focusing on the structure of the conventional sinusoidal vibration type optical deflector, both the electrostatic drive type and the electromagnetic drive type have a base substrate and a vibrator provided with a reflecting surface, which are formed of different substrates. As described above, in order to increase the deflection angle, it is necessary to increase the gap between the base substrate and the substrate provided with the vibrator, which is disadvantageous for thinning.

The present invention has been made in view of the above problems of the prior art, and its purpose is as follows.
(1) Thinning is easy,
(2) Low cost
(3) Large deflection angle
(4) The optical scanning has a substantially constant acceleration,
It is to provide an optical deflector.

The optical deflector of the present invention that achieves such an object,
First, it has a support part, two movers provided in an internal and external positional relationship, and a plurality of torsion springs arranged on a straight line connecting the two movers and the support part in series. Nested vibrator,
One of the movable elements has magnetic field generating means A, the other movable element has magnetic field generating means B, and the magnetic field generating means A and the magnetic field generating means B vibrate due to magnetic interaction with each other. Body,
Second, there is provided an optical deflector characterized in that a light reflecting portion is provided on a part of the vibrating body to perform light deflection at the vibrating light reflecting portion,
Third, an image forming apparatus using the optical deflector.

  According to the present invention, since the optical deflector having a nested structure can be manufactured from a single substrate, the thickness can be easily reduced. Further, since the magnetic field generating means as a driving source is formed on each movable element, it is not necessary to prepare a separate substrate on which the driving means is provided, so that it can be manufactured at low cost. Further, since it is not necessary to prepare a separate substrate on which the driving means is provided, the rotational vibration obstacle of the mover and the rotation inhibition due to air resistance can be prevented, so that the deflection angle of the optical deflector can be increased. As a driving method, the angular velocity of the deflection scanning of the optical deflector becomes approximately equal angular velocity by driving the movable element at the frequency of the primary natural vibration mode and the frequency that is the same phase and three times the frequency. When the optical deflector of the present invention was introduced into the printer, printing could be performed satisfactorily.

  The above are the basic components and more specific aspects of the present invention, and the details and operations thereof will be described below by typical examples.

An optical deflector that achieves the above object is shown in FIG.
The first movable element 1 and the second movable element 2 provided in an internal and external positional relationship are connected in series. The first movable element 1 and the second movable element 2 are connected by a first spring part 3, and the second movable element 2 is connected by a frame 4 surrounding the second movable element and a second spring part 5. The first spring portion 3 and the second spring portion 5 are arranged on a straight line. A first gap 6 is provided around the first mover 1, and a second gap 7 is provided around the second mover 2. The first mover 1 and the second moveable When the child 2 vibrates, the movers do not contact each other. The first movable element 1 is provided with a magnetic field generating means A8, and the second movable element 2 is provided with a magnetic field generating means B9. The magnetic field generating means A8 and the magnetic field generating means B9 exhibit a magnetic interaction with each other. Therefore, the magnetic field generating means A8 and the magnetic field generating means B9 function as driving means. The first movable element 1 and the second movable element 2 vibrate around the spring portion by the magnetic interaction of the magnetism generating means provided in each movable element. By providing the first movable element 1 with a reflective surface (not shown), light incident on the reflective surface can be deflected. Here, the mover is driven at two frequencies, ie, the frequency of the primary natural vibration mode and the same phase as that of the first three times by the driving means proposed in US Pat. No. 4,859,846. Since the mover is simultaneously torsionally vibrated in the secondary natural vibration mode in addition to the primary natural vibration mode, the displacement angle of the deflection scanning of the light reflected by the mover 14 is determined by the two vibration modes. It is also possible to change to a substantially triangular wave instead of a sine wave. By doing so, the deflection scanning angular velocity has a wide area where the displacement angle is substantially equal to that of a sine wave, so the available area for the entire deflection scanning can be increased. become.

  The following specific embodiments can be suitably employed. First, glass, quartz, ceramic, resin, or metal can be used as the material of the substrate 10, but silicon that can be precisely processed by anisotropic etching and that has no metal fatigue in principle is preferable. In particular, since the natural frequency of the vibration system is sensitive to the spring constant, silicon is preferable for vibration as designed. A coil, a permanent magnet, or an electromagnet can be used for the magnetic field generating means A8 provided in the first movable element 1. A coil, a permanent magnet, or an electromagnet can also be used for the magnetic field generating means B9 provided in the second movable element 2. Thus, by forming the magnetic field generating means A8 and the magnetic field generating means B9 as driving means in the same substrate, a substrate provided with a mover and a substrate provided with a fixed electrode, a permanent magnet or the like as in the conventional example. Compared to an optical deflector having two substrates, the cost can be reduced because an optical deflector can be manufactured with a single substrate.

  Hereinafter, the optical deflector of the present invention will be described in detail with reference to the embodiments shown in the drawings of FIGS.

(First embodiment)
FIG. 2 is a perspective view for explaining the optical deflector according to the first embodiment of the present invention. The optical deflector of the present embodiment is a nested structure formed by anisotropic etching of a single crystal silicon wafer. As shown in FIG. 1, the first mover 1 and the first mover 1 are formed in an annular shape through a pair of first spring portions 3 and first gap portions 6 projecting from the central portions of both side surfaces. The second movable element 2 coupled to the first spring portion 3 at each central portion of the inner facing surface and the first spring portion 3 are aligned with the outer facing surface of the second mass portion, respectively. A pair of second spring portions 5 and a second mover 2 are formed in an annular shape around the first gap portion 7 and the second spring portion 5 is formed at each central portion of the inner facing surface. It is comprised from the flame | frame surrounding the 2nd needle | mover 2 couple | bonded. A permanent magnet is provided on the upper surface of the first movable portion, and a light reflecting portion (not shown) is formed on the back surface thereof. A drive coil is formed on the second movable part, and both ends of the drive coil are connected to a drive power source. As a result, the optical deflector of this embodiment is thin because the drive unit and the drive source of the magnetism generating means are formed on a single nested structure made of silicon. The first mover 1 and the second mover 2 are connected to each other by applying a constant voltage alternating current at a predetermined frequency determined by the vibration system of the first mover 1 and the second mover 2 from the drive power source. It rotates and vibrates about the spring part 3 and the second spring part 5 as axes. Since the magnetism generating means as a driving source is formed on one substrate, there is no obstacle to rotational vibration, so that large rotational vibration can be made and the deflection angle can be increased. At this time, light can be deflected with a constant amplitude by reflecting the light with the light reflecting portion provided on the back surface of the first vibrating body. When the light was incident on the light reflecting portion while driving the optical deflector of this example, the light deflection could be confirmed.

(Second embodiment)
FIG. 3 is a perspective view for explaining an optical deflector according to a second embodiment of the present invention. The optical deflector of the present embodiment is a nested structure formed by anisotropic etching of a single crystal silicon wafer as in the first embodiment. The difference from the first embodiment is the magnetic generation means provided in the first movable element 1 and the magnetic generation means provided in the second vibrating body. The magnetism generating means provided in the first mover 1 of this embodiment is a drive coil. The magnetism generating means provided in the second mover 2 is a permanent magnet. As shown in FIG. 2, the permanent magnet provided on the second mover 2 is a first pair of rectangular parallelepipeds parallel to the linear direction formed by the first spring portion 3 and the second spring portion 5. It arrange | positions so that the drive coil provided in the needle | mover 1 of this may be inserted | pinched. At this time, the N pole and the S pole are opposed to the magnetic pole on the surface where the two permanent magnets face each other. As in the first embodiment, when a constant voltage alternating current was applied from the drive power source to drive the optical deflector, light was incident on the light reflecting portion, and light deflection could be confirmed.

(Third embodiment)
FIG. 4 is a perspective view for explaining an optical deflector according to a third embodiment of the present invention. The optical deflector of the present embodiment is a nested structure formed by anisotropic etching of a single crystal silicon wafer as in the first embodiment. The difference from the first embodiment is the magnetic generation means provided in the first movable element 1 and the magnetic generation means provided in the second vibrating body. The magnetism generating means provided in the first mover 1 of this embodiment is a drive coil. The magnetism generating means provided in the second mover 2 is an electromagnetic coil. As shown in FIG. 4, the electromagnetic coil provided in the second movable element 2 is disposed so as to sandwich the drive coil provided in the first movable element 1. A current is applied so that the magnetic poles on the surfaces where the electromagnets face each other are opposite to each other. Similar to the first embodiment, when a constant voltage alternating current was applied from the driving power source to drive the optical deflector, light was incident on the light reflecting portion, and light deflection could be confirmed.

(Fourth embodiment)
The optical deflector 17 used in the first embodiment is used as a conventional optical scanner in the optical system of the semiconductor laser 15, the collimator lens 16, the imaging lens 18, and the photosensitive drum 19 in the laser beam printer of FIG. Used instead of the polygon mirror. As a driving method at that time, the movable element was driven at two frequencies of the frequency of the primary natural vibration mode and the same phase and three times the frequency. The first movable element 1 is torsionally vibrated simultaneously in the secondary natural vibration mode in addition to the primary natural vibration mode, and the displacement of the deflection scanning of the light reflected by the light reflecting portion of the first movable element 1 The angle is a superposition of these two vibration modes, and changes into a substantially triangular wave shape instead of a sine wave. As a result, the angular velocity of the deflection scan becomes substantially equal angular velocity, and printing can be performed satisfactorily.

(5th Example)
FIG. 5 is a perspective view for explaining an optical deflector according to a fifth embodiment of the present invention. The optical deflector of the present embodiment is a nested structure formed by anisotropic etching of a single crystal silicon wafer as in the first embodiment. A permanent magnet is provided on the upper surface of the first movable part, and a pair of permanent magnets is also provided on the frame surrounding the second movable element 2 so as to face each other. The magnetic poles of the opposing surfaces of the permanent magnet on the frame 4 surrounding the permanent magnet on the first movable part and the second movable element are opposite to each other. The second mover 2 is provided with a drive coil as a magnetic generation means. Both ends of the drive coil are connected to a drive power source. The first mover 1 and the second mover 2 are connected to each other by applying a constant voltage alternating current at a predetermined frequency determined by the vibration system of the first mover 1 and the second mover 2 from the drive power source. It rotates and vibrates about the spring part 3 and the second spring part 5 as axes. At this time, light can be deflected with a constant amplitude by reflecting the light with the light reflecting portion provided on the back surface of the first vibrating body. When the light was incident on the light reflecting portion while driving the optical deflector of this example, the light deflection could be confirmed.

It is a perspective view showing the optical deflector of this invention. It is a perspective view showing the optical deflector of 1st Example. It is a perspective view showing the optical deflector of 2nd Example. It is a perspective view showing the optical deflector of 3rd Example. It is a system figure at the time of applying the optical deflector of this invention of 4th Example to a laser printer. It is a perspective view showing the optical deflector of 5th Example. It is a perspective view showing the electromagnetic drive type optical deflector of a prior art example. It is a perspective view showing the electrostatic drive type optical deflector of a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 1st needle | mover 2 2nd needle | mover 3 1st spring part 4 Frame surrounding 2nd needle | mover 5 2nd spring part 6 1st space | gap part 7 1st space | gap part 8 Magnetic field generation means A
9 Magnetic field generation means B
DESCRIPTION OF SYMBOLS 10 Board | substrate 11 Permanent magnet 12 Drive coil 13 Drive power supply 14 Electromagnet 15 Semiconductor laser 16 Collimator lens 17 Optical deflector 18 Imaging lens 19 Photosensitive drum

Claims (3)

A nesting structure having a support portion, two movers provided in an internal and external positional relationship, and a plurality of torsion springs arranged on a straight line connecting the two movers and the support portion in series A vibrating body of
One of the movable elements has magnetic field generating means A, the other movable element has magnetic field generating means B, and the magnetic field generating means A and the magnetic field generating means B vibrate due to magnetic interaction with each other. body.   The light deflector according to claim 1, wherein a light reflecting portion is provided on a part of the vibrating body to perform light deflection at the vibrating light reflecting portion.   An image forming apparatus comprising the optical deflector according to claim 1.

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