JP2005338241A - Rocking body, image forming apparatus using the same and method of reducing speckle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suggest a compact and simple method as a means to move a phase plate and a diffusion element with which a light transmissive member is rocked as a substitute to rotation with the power of a motor. <P>SOLUTION: Transmissive light which is made incident on a light transmissive plane is moved in parallel to an optical axis by driving a movable part with respect to a supporting substrate by driving the movable part. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  In an image forming apparatus formed by two-dimensionally scanning and projecting coherent light such as a laser beam on a screen, the present invention suppresses the deterioration of the image quality of the formed image due to the speckle pattern observed on the screen. The present invention relates to an optical element that is disposed in an optical path from a screen to a screen to disturb the phase of a laser and reduce speckles on an image surface.

  The great attraction of forming an image with a laser is that the color gamut is expanded and the color saturation is very high. However, interference problems arise when using lasers. Since the laser is coherent light having a continuous relationship between phases, the phase pattern produces a special interference pattern called speckle. An image having speckles does not look clear. This is because the interference patterns cancel each other out and produce a blurred image with a lot of noise (interference noise). In particular, in order to display a color image, when three lasers of R (red), G (green), and B (blue) are used together, a desired image is lost due to noise.

  Patent Document 1 discloses a conventional example in which a diffusion element that rotates to cancel speckles is used. Patent Document 2 describes an image display apparatus using a diffusion element such as ground glass and provided with an apparatus for reducing speckles by rotating the element. This speckle reduction means uses a diffusing element placed between the light source and the screen to generate speckle already on the exceptional element, rotate the diffusing element at high speed, and move the speckle on the screen at high speed for observation. The speckles were reduced by averaging the eyes of the person. Further, Patent Document 3 shows an embodiment in which a mask having a plurality of patterns of wavelengths longer than that in an irregular arrangement in which the phase is shifted instead of ground glass is swung.

  Patent Document 4 describes a conventional example having means including a laser light source and a moving diffuser located in the laser beam between the spatial light modulators. Patent Document 5 discloses a conventional example in which speckle noise is reduced by rotating a pair of fly-eye lenses around an optical axis arranged in a telecentric relationship.

Summarizing these conventional methods for reducing speckle,
(1) Compounding polarized light to remove speckles (2) Combining polarized light using diffracted light (3) Rotating phase plate and rotating polarized light to remove (4) Screen itself Can be classified as those that vibrate.

Further, in (3), a method of rotating with a phase plate as a wedge is proposed as an embodiment.
JP-A-5-185924 Japanese Patent Laid-Open No. 6-208089 JP 2001-97663 A Japanese Patent Laid-Open No. 2002-240224 JP-A-9-220372

  The present invention proposes a small and simple method of oscillating a light transmitting member instead of rotating with a motor as power as a means for moving a phase plate or a diffusing element, which has been proposed conventionally. .

  Therefore, the present invention includes a support substrate, a movable portion that is supported by the support substrate in an elastic support portion so as to be able to torsionally vibrate about a torsion axis, and a light transmission portion formed in the movable portion, and the movable portion. By driving the oscillating member, an oscillating body is provided that is driven relative to the support substrate and moves the transmitted light incident on the light transmission surface parallel to the optical axis.

  By using a simple and small oscillating body, an image forming apparatus formed by scanning a laser beam two-dimensionally can suppress deterioration in image quality due to a speckle pattern observed on a screen.

  An oscillating body according to the present invention includes a support substrate, a movable portion that is supported by the support substrate in an elastic support portion so as to be able to torsionally vibrate about a torsion axis, and a light transmission portion formed in the movable portion, It is an oscillating body that is driven relative to the support substrate by driving the movable part and moves transmitted light incident on the light transmitting surface in parallel with the optical axis.

  In order to disturb the laser beam phase conditions and reduce speckles, the movable body composed of a light transmission member configured in a parallel plane is swung with respect to the incident optical axis of the laser beam, and the light transmission member is tilted. The laser beam emission axis displacement vibration determined by the thickness and the refractive index is generated to oscillate the light beam left and right in synchronization with the movement of the oscillator.

  FIG. 1a relates to an embodiment illustrating the principle of the present invention. 101 is an incident laser beam, and 102 is a cross-sectional view of the movable portion inclined with respect to the optical axis. Assuming that the inclination θ of the optical axis and the movable part, the refractive index n of the movable part that is a light transmitting member, and the refraction angle δ, the deviation L of the optical axis accompanying the oscillation is L = T · SINδ · COSθ from the law of refraction. = T · ASIN (COSθ / n). Reference numeral 101 'denotes a laser beam transmitted through the light transmitting member. An inorganic member, an organic member, or a composite of an organic member and an inorganic member is used as the light transmitting member.

  FIG. 1 b shows an embodiment in which the movable part 103 is composed of a light scattering transparent member. Reference numeral 100 denotes a swing center.

Figure 1c because increasing the transmission efficiency of light, a microlens 104 formed on both surfaces of the movable portion, the sum of the focal length f ₁ and f ₂ in the respective movable portion selected to be equal to the thickness of the movable portion This is an example.

  FIG. 2 is a diagram illustrating an optical arrangement of an image forming apparatus using the oscillator described in the first embodiment.

  The oscillator is disposed in the optical path from the light source to the screen. 201a, 201b, and 201c are R (red), G (green), and B (blue) laser light sources modulated by image signals, 101 is a laser beam, 202 is a collimator lens, and makes the laser beam substantially parallel. Be placed. Reference numeral 200 denotes an oscillating body, and 203 denotes a color combining prism, which combines three laser beams of R (red), G (green), and B (blue) into one.

  Reference numeral 204 denotes a condenser lens. A horizontal scanning mirror 204 and a vertical scanning mirror 205 scan the laser beam two-dimensionally and form an image in synchronization with the modulation of the laser light source. Reference numeral 206 denotes a two-dimensional scanning optical system that corrects image distortion and curvature distortion and constitutes a projection optical system together with a condenser lens. Reference numeral 207 denotes a screen for displaying an image. Note that when the spread of the laser beam from the light source can be ignored, the collimator lens is not necessary. Further, oscillators may be arranged at three locations on the light source side of the color synthesis prism. The movable part swings at a high speed, and the laser beam is reciprocated in parallel with the incident optical axis to reduce speckle.

  FIG. 3a shows an embodiment using magnetic force as an external force.

  A frame 301 in which the oscillating body 300 is formed of a light transmitting member, a shaft 302 and a movable portion 303 are integrally formed. The frame and the movable part are coupled by a shaft, and can be freely twisted.

  Reference numeral 304 denotes a fixed core magnet which generates a uniform magnetic field perpendicular to the axis. The coil 305 of the magnetic force generating part placed in a uniform magnetic field is joined to the movable part, and constitutes an electromagnetic actuator that swings by Lorentz force. By adding the alternating magnetic force so as to coincide with the natural vibration determined by the moment of inertia of the movable part and the torsional rigidity of the shaft, the movable part causes a resonance state and can be driven with a small amount of electric power. A yoke 310 has a hole in the light transmission portion.

  FIG. 3b shows another embodiment using magnetic force as an external force.

  Reference numeral 306 denotes a magnetic force generating portion of a fixed core, and a bar magnet 307 joined to the movable core is joined to the shaft 302 of the swinging portion at a right angle to form an electromagnetic actuator. Reference numeral 308 denotes a support substrate that supports the oscillator, and 309 denotes a hole through which the laser beam is transmitted. The bar magnet 307 is disposed at a position that does not interfere with the optical path of the laser beam. An alternating magnetic force is generated from the coil, and the oscillator swings.

  FIG. 4a shows an embodiment using an electrostatic force as an external force.

  A frame 401 in which the rocking body 400 is formed of a light transmitting member, a shaft 402 and a movable portion 403 are integrally formed. The frame and the movable part are coupled by a shaft, and can be freely twisted.

  Two electrodes 405a and 405b of the electric field generator are arranged symmetrically about the axis in the recess of the support substrate 404. One electrode 406 is disposed on the movable portion so as to be substantially close to the recessed electrode of the support substrate. The electrode 406 is grounded and is determined to be either + or − at the beginning of driving. Reference numeral 407 denotes a hole through which the laser beam is transmitted. An electrostatic actuator in which ± electric fields are alternately applied by two electric field generators arranged in the recesses of the support substrate is formed. Even if the hole of the support substrate is not particularly provided, the window may be formed of a light transmitting member, or the support substrate itself may be formed of a light transmitting member. If the electrodes themselves are also light transmissive, there is no need to avoid the optical axis.

  FIG. 4 b shows another embodiment using an electrostatic force as an external force.

  Two electrodes 408a and 408b of the electric field generator are arranged symmetrically with respect to the movable part 403. One electrode 409 is disposed on the support substrate so as to be substantially opposed to the electrode of the movable portion. It forms an electrostatic actuator in which ± electric fields are alternately applied by the two electric field generating parts of the movable part. This is an embodiment in which a light transmitting window is attached to a hole through which a laser beam is transmitted. In addition, if the electrode is transparent, it is not particularly necessary to place it away from the laser beam.

  FIG. 5 shows an embodiment in which a mechanical force accompanying the deformation of a substance is used as an external force.

  A frame body 501 in which the oscillating body 500 is formed of a light transmitting member, a shaft 502 and a movable portion 503 are integrally formed. The frame and the movable part are coupled by a shaft, and can be freely twisted.

  Piezoelectric deformation elements 504a and 504b are joined to both surfaces of the shaft portion. The piezo-deformation element is an electrode and is of a type that extends at right angles to the applied voltage direction. Furthermore, in order to use this for the torsional motion, it was joined at an angle of 45 ° with respect to the shaft 505 and in a direction in which the elongations of 504a and 504b are orthogonal. In this embodiment, the piezoelectric deformation element is used as the mechanical force, but mechanical deformation such as thermal expansion may be used.

  FIG. 6 shows an embodiment using an acoustic vibration force as an external force.

  A frame body 601 in which the rocking body 600 is formed of a light transmitting member, a shaft 602, and a movable portion 603 are integrally formed. The frame and the movable part are coupled by a shaft, and can be freely twisted.

  The acoustic speakers 604a and 604b are arranged symmetrically with respect to the axis in the vicinity of the movable part, and the 20 kHz sound whose phase is shifted (for example, 180 °) from the two speakers is transmitted to the movable part via the air to cause resonance vibration. . Reference numeral 605 denotes a support substrate that supports the oscillator and the acoustic speaker.

  In Examples 1 to 6, an example in which a frame, a shaft, and a movable part are integrally formed as an oscillating body constituted by a light transmitting member is shown. However, it is not always necessary to configure it integrally. For example, the oscillating portion, the shaft portion, and the frame body may be made separately and assembled. Further, a light transmission window may be provided without using a light transmission member.

  Further, not only the light diffusing element but also a phase plate, a mask containing a pattern, and a polarizing plate may be used as the optical element. Even if the light transmission part is not a parallel plate, it may have a wedge-shaped cross section, for example. Further, as a driving force, other physical force, for example, vortex vibration caused by a fluid may be used.

a is a diagram illustrating the principle of the present invention, b is an example in which the movable part is formed of a light scattering transmitting member, and c is an example in which a microlens is formed on the movable part. 1 is a diagram illustrating an optical arrangement of an image forming apparatus using a rocking body. a is an embodiment using magnetic force as an external force, and b is another embodiment using magnetic force as an external force. a is an embodiment using an electrostatic force as an external force, and b is another embodiment using an electrostatic force as an external force. An embodiment using mechanical force accompanying deformation of a substance as an external force. An embodiment using an acoustic vibration force as an external force.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Laser beam 102 Movable part 103 Movable part 100 Oscillation center 104 Microlens 201a, 201b, 201c Laser light source 202 Collimator lens 200 Oscillator 203 Color synthesis prism 204 Condensing lens, horizontal scanning mirror 205 Vertical scanning mirror 206 Two-dimensional scanning optical Series 207 screen
DESCRIPTION OF SYMBOLS 300 Oscillator 301 Frame 302 Shaft 303 Movable part 304 Magnet 305 Coil 307 Coil 307 Bar magnet 308 Support substrate 309 Hole 400 Oscillator 401 Frame body 402 Shaft 403 Movable part 404 Support substrate 405a, 405b Electrode 406 Electrode 407b 408a, 408 Electrode 409 Electrode 500 Oscillator 501 Frame 502 Shaft 503 Movable part 504a, 504b Piezo deformation element 505 Shaft 600 Oscillator 601 Frame 602 Shaft 603 Movable part 604a, 604b Acoustic speaker 605 Oscillator

Claims (17)

A movable part that is supported by the support board in a torsional vibration manner around a torsion axis by an elastic support part;
A light transmission part formed on the movable part,
By driving the movable part,
Driven relative to the support substrate,
An oscillating body that moves transmitted light incident on the light transmitting surface parallel to the optical axis.   The oscillating body according to claim 1, wherein the support substrate, the torsion shaft, and the movable portion are formed of an integral light transmitting member.   The oscillating body according to claim 1, wherein the movable part formed of the light transmitting member is a parallel plate.   The oscillating body according to any one of claims 1 to 3, wherein the movable portion formed of the light transmitting member is a light scattering member.   The oscillator according to any one of claims 1 to 4, wherein both surfaces of the movable portion made of the light transmitting member are made of microlenses. When the focal length of the movable member of the microlens and f _1, f _2, oscillator of claim 5, f 1 ₊ f ₂ is equal to or equal to the thickness of the movable portion.   The rocking body according to any one of claims 1 to 6, wherein both surfaces of the movable part formed of the light transmitting member and the light transmitting member are provided with an antireflection coating. The oscillator according to any one of claims 1 to 7, wherein the driving means is an electromagnetic actuator including a magnetic field generation unit for driving the movable unit and a movable core joined to the movable unit. The oscillating body according to any one of claims 1 to 7, wherein the driving means is an electromagnetic actuator including a fixed core for driving the movable part and a magnetic field generating part joined to the movable part. The oscillator according to any one of claims 1 to 7, wherein the driving means is an electrostatic actuator including an electric field generating unit for driving the movable unit and a fixed electrode joined to the movable unit. . The oscillating body according to claim 1, wherein the driving means is an electrostatic actuator including a fixed electrode for driving the movable part and an electric field generating part joined to the movable part. .   The oscillator according to any one of claims 8 to 11, wherein the driving means is disposed at a position where the optical paths of incident light and transmitted light are not obstructed.   The oscillator according to any one of claims 8 to 11, wherein a material of the driving means is a transmission member that does not obstruct an optical path of incident light and transmitted light. The oscillator according to any one of claims 1 to 12, wherein the frequency of the torsional vibration of the movable part is a vibration having a resonance frequency determined by the torsional rigidity of the shaft and the moment of inertia of the movable part. The driving force of the driving means is
The oscillator according to any one of claims 1 to 12, wherein the oscillator is an alternating force synchronized with a resonance frequency determined by a torsional rigidity of a shaft and an inertia moment of a movable part.   A laser light source, an optical deflector for deflecting light from the laser light source, and an oscillator according to any one of claims 1 to 15 disposed in the middle of an optical path from the laser light source to the optical deflector, An image forming apparatus comprising:   17. The speckle reduction method for an image forming apparatus according to claim 16, wherein the oscillating body is arranged in the middle of an optical path from the laser light source to the optical deflector to reduce speckles on the projected image surface. A speckle reduction method for an image forming apparatus.

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