JP2006091471A - Light emitting apparatus and display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately reduce speckle noise with a very simple structure. <P>SOLUTION: A projector apparatus comprises: a laser light source 11 which emits coherent laser light; an illumination lens 12 which converts laser light emitted form the laser light source 11 into sheet-shaped laser light; a GLV 13 which varies the optical characteristic for every pixel by being irradiated with the sheet-shaped laser light converted with the illumination lens 12; a projection lens 14 which includes an optical filter to pass the laser light deflected with the GLV 13; and a scanning mirror 15 which scans and projects the laser light passing through the projection lens 14 on a screen 20. The projector apparatus also comprises a 1/2 wavelength phase difference plate 16 corresponding to the wavelength of laser light emitted from the laser light source 11, a motor 17 which drives the 1/2 wavelength phase difference plate 16 and a driving part 18 on the optical path on which the laser light emitted from the laser light source 11 passes. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a light emitting device that emits coherent light, and a display device that is configured using the light emitting device and displays various images on a display screen.

  In recent years, so-called overhead projectors and slide projectors have been widely used as display devices for presenting materials to audiences at meetings and the like. In general households, video projectors and movie film projectors using liquid crystals are becoming popular. Such various projector apparatuses are generally configured by combining a predetermined light source and an element capable of changing optical characteristics for each pixel.

  Furthermore, in recent years, a narrow band three primary color light source is used as a light source, and a so-called grating light valve (GLV) composed of a plurality of fine ribbon-like diffraction gratings is used as an element, and red, green and blue colors are used. A projector device that spatially modulates each light beam has also been developed. Projectors using such GLVs are attracting attention as being capable of realizing a high resolution and a wide color reproduction region.

  By the way, in a projector apparatus such as a projector apparatus using such a GLV, a laser that emits coherent light is often used as a light source, and as a result, a speckle pattern is projected on a screen that projects an image. It is a problem that appears. A speckle pattern is a speckled pattern with high contrast that occurs on a screen when coherent light is irradiated onto the screen or the like. Such a speckle pattern is a complex interference pattern that occurs when light scattered at each point on the screen interferes with each other in an irregular phase relationship, and is recognized as noise (speckle noise) by the human eye. Will be. Therefore, in an apparatus that projects an image on a screen, such as a projector apparatus, image quality deterioration is caused by the occurrence of speckle noise. Therefore, it is required to reduce it.

  As a technique for trying to reduce such speckle noise, for example, techniques described in Patent Documents 1 to 3 and the like have been proposed.

JP 2002-90881 A JP 2003-98476 A JP 2002-62582 A

  Specifically, Patent Document 1 discloses a light source, an image display device that can modulate light from the light source, a lens system that projects light from the image display device onto a screen, and an image display device to a screen. And an optical component that generates an optical path difference distribution that does not affect the image displayed on the screen, and a drive unit that moves the optical component so that the optical path difference distribution varies with time. A projector apparatus is disclosed. More specifically, in this projector apparatus, special processing is performed as an optical component so that an optical path difference distribution of about λ / 2 is generated when the outgoing light passes through an optical surface crossing the optical path. Is used.

  Further, Patent Document 2 discloses a laser light source for emitting a light beam, a beam expander for expanding the light beam, a spatial light modulator, and an enlargement for uniformly illuminating the spatial light modulator. Beam shaping optics for shaping a laser beam comprising a fly eye integrator having an array of small lenses, a moving diffuser located in the laser beam between the laser light source and the spatial light modulator, A display device is disclosed. More specifically, in this display device, a holographic diffuser, a randomized microlens array, or the like is used as the moving diffuser.

  Further, Patent Document 3 discloses an image display device that displays an image with light emitted from a light source and modulated by a spatial modulator. In particular, this image display device includes a polarization distribution conversion unit that converts a spatial polarization distribution of light emitted from a light source so that polarization directions of light incident on adjacent pixels of the spatial modulator are orthogonal to each other. It is provided. More specifically, in this image display device, a microlens array and a birefringent optical crystal are used as polarization distribution conversion means.

  By the way, in the conventional techniques including Patent Document 1 to Patent Document 3 described above, it is necessary to use a special one as an optical component provided in the optical system in order to reduce speckle noise, and the versatility is poor. However, since it is difficult to manufacture, there is a problem in that the cost increases. Further, in the technique described in Patent Document 1 described above, since an optical component processed into a concavo-convex shape so as to generate an optical path difference distribution of about λ / 2 is used, it is unnecessary at the boundary of the concavo-convex. There is no denying the possibility of reflection, and it is difficult to avoid degradation of image quality.

  The present invention has been made in view of such circumstances, and is configured using a light emitting device capable of reliably reducing speckle noise while having an extremely simple configuration, and the light emitting device. An object of the present invention is to provide a display device capable of avoiding image quality deterioration due to speckle noise at low cost.

  A light emitting device according to the present invention that achieves the above-described object is provided on a light source that emits coherent light and an optical path through which the light emitted from the light source passes, and has a wavelength of the light emitted from the light source. It comprises a corresponding wave plate and driving means for driving the wave plate so as to change the polarization of the light emitted from the light source.

  Such a light emitting device according to the present invention can change the polarization of light transmitted through the wave plate with time by driving the wave plate so as to change the polarization of light emitted from the light source. it can. Therefore, the light emitting device according to the present invention can shift and smooth a noise peak caused by scattering of the emitted light and interfering with time, so that speckle noise is visible to human eyes. It becomes difficult to be done.

  Here, as the wavelength plate, a ½ wavelength phase difference plate that changes the polarization direction of the light emitted from the light source can be used. In this case, it is desirable that the driving means rotate the half-wave retardation plate in a plane perpendicular to the optical axis of the light emitted from the light source in the half-wave retardation plate. As described above, in the light emitting device according to the present invention, by rotating the half-wave retardation plate, the driving of the half-wave retardation plate is easily controlled, and the half-wave retardation is thereby controlled. The time-dependent change in the polarization of light transmitted through the plate can be accelerated.

  In the light emitting device according to the present invention, the driving means includes a motor having a hollow rotor that is rotationally driven at a predetermined speed, and the half-wave retardation plate is attached to a hollow portion of the motor. Thus, the half-wave retardation plate can be driven with a very simple configuration.

  Note that the optical axis center of the light incident on the ½ wavelength phase difference plate is deviated from the rotation center of the ½ wavelength phase difference plate in order to increase the change with time in the polarization direction. desirable.

  Further, as the wavelength plate, besides the half wavelength retardation plate, a quarter wavelength retardation plate that switches between linearly polarized light and elliptically polarized light or circularly polarized light may be used. The same effect as when using can be obtained.

  In addition, a display device according to the present invention that achieves the above-described object is a display device that displays various images by projecting images on a predetermined screen, and includes a light source that emits coherent light and an optical device for each pixel. An optical element that changes various characteristics, a wave plate that is provided on an optical path through which light emitted from the light source passes, and that corresponds to the wavelength of the light emitted from the light source, and driving means that drives the wave plate It is characterized by having.

  Such a display device according to the present invention can change the polarization of light transmitted through the wavelength plate over time by driving the wavelength plate so as to change the polarization of light emitted from the light source. . Therefore, the display device according to the present invention is capable of shifting and smoothing the noise peak caused by the emitted light scattered at each point on the screen and interfering with each other, and is thus projected onto the screen. It is difficult for viewers of images to see speckle noise due to the eye integration effect, and high quality images can be displayed.

  Here, it is preferable that the driving unit drives the wavelength plate at a speed faster than a frame rate in order to suppress interference of light corresponding to an image displayed on the screen.

  The light source may be a plurality of light sources that respectively emit different colored lights. In this case, a plurality of the wave plates are provided corresponding to the wavelengths of the light emitted from each of the plurality of light sources.

  As the optical element, it is preferable to use a grating light valve composed of a plurality of ribbon-like diffraction gratings. In this case, the display device according to the present invention is diffracted by the optical member that converts the light emitted from the light source into flat light and irradiates the grating light valve, and the grating light valve. An optical filter that allows light to pass therethrough and a scanning mirror that scans the light that has passed through the optical filter and projects the light onto the screen.

  In the display device according to the present invention using such a grating light valve, since the light flux increases after the scanning mirror, the wavelength plate passes through the wave plate on the optical path through which the light emitted from the light source passes. It is efficient to provide it before the scanning mirror.

  In the present invention, the speckle noise can be surely reduced while driving the wave plate and the polarization direction of the laser light is changed over time. High image quality can be displayed.

  Hereinafter, specific embodiments to which the present invention is applied will be described in detail with reference to the drawings.

  This embodiment is a projector device as a display device that projects various images by projecting images on a predetermined screen. In particular, this projector apparatus includes a light source that emits coherent light, and can reduce so-called speckle noise by providing a wavelength plate on the optical path.

  Hereinafter, as a light source, a laser light source that emits red, green, and blue narrow-band three primary colors is used, and an element that spatially modulates each color beam emitted from these laser light sources is used as a plurality of fine light sources. A projector apparatus using a so-called grating light valve (hereinafter referred to as GLV) made of a ribbon-like diffraction grating will be described.

  As shown in FIG. 1, the projector device includes a laser light source 11 that emits a coherent single-wavelength laser beam, and an optical member that converts the laser beam emitted from the laser light source 11 into a sheet-like laser beam. Illumination lens 12 as an optical element, a GLV 13 as an optical element that changes optical characteristics for each pixel by irradiation with a sheet-like laser beam converted by the illumination lens 12, and a laser diffracted by the GLV 13 A projection lens 14 incorporating an optical filter that allows light to pass through, and a scanning mirror 15 that scans the laser light that has passed through the projection lens 14 and projects it onto a screen 20 are provided. In addition, the projector device includes a half-wave retardation plate 16 corresponding to the wavelength of the laser light emitted from the laser light source 11 on the optical path through which the laser light emitted from the laser light source 11 passes, and the 1 / A motor 17 as driving means for driving the two-wavelength phase difference plate 16 and a driving unit 18 for supplying driving power of the motor 17 are provided. In the drawing, an optical system for an arbitrary monochromatic light among red light, green light, and blue light is shown, and the projector apparatus includes such an optical system for each color.

  The laser light source 11 emits laser light L1 of any color among red light, green light, and blue light. For example, the laser light source 11 can use a semiconductor laser as the laser beam L1 that emits red laser light, and can use a semiconductor-excited solid laser as the laser beam L1 that emits green light or blue light. Can do. The laser light L 1 emitted from the laser light source 11 is incident on the half-wave retardation plate 16.

  The ½ wavelength phase difference plate 16 can be provided at any position on the optical path through which the laser light emitted from the laser light source L1 passes, as long as it is a stage preceding the scanning mirror 15. Specifically, the half-wave retardation plate 16 scans between the laser light source 11 and the illumination lens 12, between the illumination lens 12 and the GLV 13, between the GLV 13 and the projection lens 14, or scanned with the projection lens 14. It can be provided between the mirror 15. Here, the description will be made assuming that the laser light source 11 and the illumination lens 12 are provided. The half-wave retardation plate 16 can be a widely used general-purpose product. As shown in FIG. 2, the half-wave retardation plate 16 is formed in an arbitrary shape such as a circle, and the rotor is hollow. By being attached to the hollow portion of the motor 17, the laser light emitted from the laser light source 11 is inserted into the optical path through which it passes. The half-wave retardation plate 16 is laser light emitted from the laser light source 11 as indicated by an arrow a in FIG. 1 by a motor 17 that is rotationally driven at a predetermined speed based on electric power from the drive unit 18. Is rotated in a plane perpendicular to the optical axis. As a result, the polarization direction of the laser light L3 transmitted through the half-wave retardation plate 16 changes with time according to the rotation. At this time, it is desirable that the rotation speed of the ½ wavelength phase difference plate 16 is faster than the frame rate in order to suppress the interference of the laser beam corresponding to the image displayed on the screen 20. The optical axis center of the laser beam L1 incident on the half-wave retardation plate 16 is deviated from the rotation center of the half-wave retardation plate 16 in order to increase the change with time in the polarization direction. It is desirable. The laser beam L3 that has passed through the half-wave retardation plate 16 is incident on the illumination lens 12.

  The illumination lens 12 converts the laser light L3 emitted from the laser light source 11 and transmitted through the half-wave retardation plate 16 into a sheet-like laser light L2. The sheet-like laser light L2 converted by the illumination lens 12 is applied to the GLV 13.

  The GLV 13 is an optical element that functions as a diffraction grating that is irradiated with the sheet-like laser light L2 converted by the illumination lens 12 and diffracts the laser light L2. Specifically, the GLV 13 is configured by arranging a plurality of rows of ribbons 31 made of fine mirror-like electrodes along the lower electrode 32 as shown in FIG. Here, in the GLV 13, the ribbon 31 is configured by alternately arranging a fixed ribbon and a movable ribbon that is attracted to the lower electrode 32 by applying a voltage. In such a GLV 13, as shown in FIG. 3 (b), a voltage is applied to the ribbon 31, the movable ribbon is recessed by a quarter length of the wavelength of the incident laser beam L2, and irregularities are formed from a flat mirror surface. Change to a mirror surface. As a result, the laser beam L2 irradiated to the GLV 13 is simply reflected by a flat mirror surface when no voltage is applied to the ribbon 31, but is uneven when a voltage is applied to the ribbon 31. Is diffracted by a mirror surface exhibiting Such a GLV 13 uses, for example, six ribbons as diffraction elements for one pixel, and is configured by arranging ribbons at least for the pixels in the vertical direction of the image projected on the screen 20, and functions as a diffraction grating for each pixel. It is possible to control whether or not to make it. The laser beam L4 reflected or diffracted by the GLV 13 is incident on the projection lens 14.

  For example, as shown in FIG. 4, the projection lens 14 includes an optical filter 14 a in which a hole is formed so as to pass only ± first-order diffracted light out of the laser light L4 reflected or diffracted by the GLV 13, and the optical filter. Condensing lens 14b which condenses laser beam L5 as the ± 1st order diffracted light which passed 14a. The figure shows an optical system for one pixel. That is, the projection lens 14 is configured to pass only the light of the pixel that has been switched to the diffraction grating in the GLV 13. The laser beam L5 collected by the projection lens 14 is irradiated to the scanning mirror 15.

  The scanning mirror 15 is composed of, for example, a galvanometer mirror, and is configured to be able to scan in the horizontal direction by rotating in a direction indicated by an arrow b in FIG. 1 at a rotational speed corresponding to the frame rate by a driving mechanism (not shown). The Such a scanning mirror 15 scans the laser beam L5 as the ± first-order diffracted light that has passed through the projection lens 14 in the horizontal direction. That is, since the laser light L5 as the ± first-order diffracted light that has passed through the projection lens 14 corresponds to a one-dimensional image made up of pixels in the vertical direction of the image projected on the screen 20, the scanning mirror 15 has the laser A two-dimensional image is projected onto the screen 20 by scanning the light L5 in the horizontal direction. For example, when the scanning mirror 15 projects a full HD (High Definition) / progressive image of 1920 pixels (horizontal) × 1080 pixels (vertical) on the screen 20, the laser beam corresponding to a one-dimensional image of 1080 pixels. With respect to L5, the progressive video is projected onto the screen 20 by performing horizontal scanning corresponding to 1920 pixels 60 times per second.

  Now, in the projector device composed of such an optical system, the speckle pattern causing speckle noise is such that coherent laser light projected on the screen 20 is scattered at each point on the screen 20. Caused by interference with each other in an irregular phase relationship. Therefore, in order to reduce the occurrence of the speckle pattern, it is only necessary to suppress interference generated on the screen 20.

  Therefore, in the projector apparatus, as described above, the ½ wavelength phase difference plate 16 is placed at an arbitrary position in the optical path through which the laser light emitted from the laser light source L1 passes, as long as it is the front stage of the scanning mirror 15. By providing and rotating this, the polarization direction of the laser light L3 transmitted through the half-wave retardation plate 16 is changed with time. Specifically, when the linearly polarized laser beam L1 is incident on the ½ wavelength phase difference plate 16, the laser beam L3 transmitted through the ½ wavelength phase difference plate 16 maintains the linear polarization. The polarization direction changes according to the rotation of the half-wave retardation plate 16 as it is. In addition, when the circularly polarized laser beam L1 is incident on the ½ wavelength phase difference plate 16, the laser beam L3 transmitted through the ½ wavelength phase difference plate 16 is transmitted to the ½ wavelength phase difference plate. When 16 rotates, it becomes circularly polarized light in the reverse direction.

  Thereby, in the projector apparatus, the noise peak caused by the interference at each point on the screen 20 can be shifted in time and smoothed. Therefore, in the projector apparatus, it becomes difficult for a viewer of the image projected on the screen 20 to visually recognize speckle noise due to the eye integration effect, and a high-quality image can be displayed.

  As described above, in the projector apparatus shown as the embodiment of the present invention, the half-wave retardation plate 16 is rotated, and the polarization direction of the laser light is changed with time, thereby having a very simple configuration. However, speckle noise can be reliably reduced, and high-quality images can be displayed at low cost.

  The present invention is not limited to the embodiment described above. For example, in the above-described embodiment, the laser light source 11 is used as the light source. However, the present invention is not limited as long as it emits coherent light such as an LED (Light Emitting Diode). Can also be applied.

  In the above-described embodiment, the half-wave retardation plate has been described as being rotated. However, the present invention performs driving to change the polarization of light, for example, to vibrate the wavelength plate. Any form of drive can be applied as long as it is present.

  Further, in the above-described embodiment, the description has been made on the assumption that a half-wave retardation plate is used. However, the present invention is a quarter-wave retardation plate that switches between linearly polarized light and elliptically polarized light or circularly polarized light. A retardation plate may be used, and any wavelength plate that changes the polarization of light can be used.

  Furthermore, in the above-described embodiment, the description has been given on the assumption that the narrow band three primary color lights of red light, green light and blue light are used. However, not only red light, green light and blue light but also various colors such as cyan, magenta and yellow are used. The present invention can be applied even when different colored lights are used.

  Moreover, although the projector apparatus using GLV was demonstrated in embodiment mentioned above, if this invention is an apparatus provided with the light-projection apparatus which uses coherent light as a light source like a laser printer or a laser pointer, for example. Anything can be applied.

  Thus, it goes without saying that the present invention can be modified as appropriate without departing from the spirit of the present invention.

It is a figure explaining the structure of the projector apparatus shown as embodiment of this invention. It is a front view explaining the structure of the 1/2 wavelength phase difference plate attached to the hollow part of the motor in the projector apparatus. It is a figure explaining schematic structure of GLV in the projector device. It is a figure explaining the schematic structure of GLV in the projector apparatus, Comprising: It is a figure explaining a mode that the voltage was applied to the ribbon. It is a figure explaining schematic structure of the projection lens in the projector device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Laser light source, 12 Illumination lens, 13 GLV, 14 Projection lens, 14a Optical filter, 14b Condensing lens, 15 Scanning mirror, 16 1/2 wavelength phase difference plate, 17 Motor, 18 Drive part, 20 Screen, 31 Ribbon, 32 Lower electrode

Claims (16)

A light source that emits coherent light;
A wave plate provided on an optical path through which the light emitted from the light source passes, and corresponding to the wavelength of the light emitted from the light source;
A light emitting device comprising: driving means for driving the wave plate so as to change the polarization of the light emitted from the light source.   The light emitting device according to claim 1, wherein the wave plate is a half-wave retardation plate that changes a polarization direction of light emitted from the light source.   The said drive means rotates the said 1/2 wavelength phase difference plate in the surface perpendicular | vertical to the optical axis of the light radiate | emitted from the said light source in the said 1/2 wavelength phase difference plate. The light emission apparatus of description. The drive means includes a motor having a hollow rotor that is rotationally driven at a predetermined speed,
The light emitting device according to claim 3, wherein the half-wave retardation plate is attached to a hollow portion of the motor.   4. The light emitting device according to claim 3, wherein an optical axis center of light incident on the half-wave retardation plate is deviated from a rotation center of the half-wave retardation plate.   2. The light emitting device according to claim 1, wherein the wave plate is a quarter-wave retardation plate that switches between linearly polarized light and elliptically polarized light or circularly polarized light. A display device that displays various images by projecting images on a predetermined screen,
A light source that emits coherent light;
An optical element that changes optical characteristics for each pixel;
A wave plate provided on an optical path through which the light emitted from the light source passes, and corresponding to the wavelength of the light emitted from the light source;
A display device comprising: drive means for driving the wave plate.   The display device according to claim 7, wherein the wavelength plate is a half-wave retardation plate that changes a polarization direction of light emitted from the light source.   The said drive means rotates the said 1/2 wavelength phase difference plate within the surface perpendicular | vertical to the optical axis of the light radiate | emitted from the said light source in the said 1/2 wavelength phase difference plate. The display device described. The drive means includes a motor having a hollow rotor that is rotationally driven at a predetermined speed,
The display device according to claim 9, wherein the half-wave retardation plate is attached to a hollow portion of the motor.   The display device according to claim 9, wherein an optical axis center of light incident on the half-wave retardation plate is deviated from a rotation center of the half-wave retardation plate.   The display device according to claim 7, wherein the driving unit drives the wave plate at a speed faster than a frame rate. The light sources are a plurality of light sources that respectively emit different colored lights,
The display device according to claim 7, wherein a plurality of the wave plates are provided corresponding to wavelengths of light emitted from each of the plurality of light sources.   The display device according to claim 7, wherein the wavelength plate is a ¼ wavelength phase difference plate that switches between linearly polarized light and elliptically polarized light or circularly polarized light. The optical element is a grating light valve composed of a plurality of ribbon-like diffraction gratings,
The display device
An optical member that converts the light emitted from the light source into flat light and irradiates the grating light valve;
An optical filter that passes light diffracted by the grating light valve;
The display device according to claim 7, further comprising a scanning mirror that scans the light that has passed through the optical filter and projects the light onto the screen. The display device according to claim 15, wherein the wavelength plate is provided in front of the scanning mirror on an optical path through which light emitted from the light source passes.