JP2014098754A - Laser display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser display device with a speckle noise removal mechanism having no movable parts.SOLUTION: A laser display device includes; a laser light source 11 which generates laser light; a speckle noise removal mechanism which removes speckle noise by converting the laser light generated by the laser light source 11 into diffused light with lower spatial coherence; a collimation lens 14 which collimates the diffused light; and image display means which displays desired images by selectively projecting the collimated light onto a screen. The speckle noise removal mechanism has a two-dimensional optical deflector 18 and a diffuser plate 13. The two-dimensional optical deflector 18 two-dimensionally sweeps and outputs the laser light generated by the laser light source 11 to different positions on the diffuser plate 13 which outputs the diffused light diffused to different degrees depending on the position of the diffuser plate 13, thereby converting the laser light into the diffused light with lower spatial coherence.

Description

  The present invention relates to a laser display device, and more particularly to a laser display device having a speckle noise removal mechanism.

  Laser displays have attracted attention in recent years because they have features such as low power consumption, excellent color reproducibility in principle, and the ability to reduce the size of projectors. On the other hand, in laser displays, since a laser is used as the light source, “speckle noise”, which is speckled image noise generated by interference of minute irregularities on the screen, is generated by coherent laser light, which significantly degrades image quality. It is known that there is a problem.

  As a configuration for removing the “speckle noise” and suppressing the deterioration of the image quality, a laser display device that removes speckle noise by combining an optical deflector and a diffusion plate as shown in FIG. 1 has been proposed. ing. In this laser display device, the laser light output from the laser light source 11 is diffused by the diffusion plate 13 and then directed to the two-dimensional spatial modulation element 15 by the lens 14. The two-dimensional spatial modulation element 15 selectively transmits only the light to be displayed on the display out of the received light and inputs it to the projection lens 16, and the light input to the projection lens 16 is projected onto the screen 17, thereby displaying the display. Display is performed.

  In the laser display using the two-dimensional spatial modulation element shown in FIG. 1, it is attempted to reduce speckle noise by vibrating the diffusion plate 13 by the vibrating means 12.

Kazuo Kuroda et al., “Commentary Laser Display”, Optronics, 2010

  Thus, in a laser display using a two-dimensional spatial modulation element, it has been attempted to reduce speckle noise by vibrating the diffusion plate as shown in FIG. 1, but since it has a movable part for vibrating, There was a problem that reliability was impaired and miniaturization was difficult.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a laser display device including a speckle noise removing mechanism having no movable part.

  In order to solve the above-described problems, an embodiment of the present invention includes a laser light source that outputs laser light, and speckle by using the laser light output from the laser light source as diffused light with reduced spatial coherence. A speckle noise removing mechanism for removing noise, a collimating lens for collimating the diffused light, and a display display means for displaying a desired image by selectively projecting the collimated light onto a screen. In the laser display device, the speckle noise removing mechanism includes a two-dimensional optical deflector and a diffuser plate, and the two-dimensional optical deflector scans the laser light output from the laser light source two-dimensionally. Laser output by outputting diffused light that is output to different positions on the diffuser and diffused to different extents depending on the position of the diffuser Which is a laser display apparatus characterized by a diffuse light spatial coherence decreased.

  According to the present invention, the light from the laser light source is two-dimensionally scanned in the diffusion plate by the two-dimensional optical deflector, thereby reducing the spatial coherence of the illumination light transmitted through the diffusion plate and reducing speckle noise. It becomes possible.

It is a figure which shows the conventional laser display apparatus. It is a figure which shows an example of the laser display apparatus of this invention. It is a figure which shows the structure of the two-dimensional optical deflector used with the laser display apparatus of this invention. It is a figure which shows another example of the laser display apparatus of this invention.

  Hereinafter, embodiments of the present invention will be described in detail.

  FIG. 2 shows a schematic configuration of the laser display device of the present invention. As shown in FIG. 2, the laser display device includes a laser light source 11, a two-dimensional light deflector 18, a diffusion plate 13, a collimator lens 14, a two-dimensional spatial modulation element 15, a projection lens 16, and a screen 17. And is configured.

  The laser light source 11 is composed of semiconductor lasers such as red, green, and blue, for example. Although any kind of laser can be used, a wavelength conversion laser may be used as the green laser.

  The two-dimensional optical deflector 18 causes the light output from the laser light source 11 to enter the diffusion plate 13 while scanning two-dimensionally. As the two-dimensional optical deflector 18, a deflecting element capable of two-dimensional deflection may be used, or as shown in FIG. 3, two one-dimensional optical deflecting elements may be combined.

FIG. 2 shows a two-dimensional optical deflection composed of K _{1 -y} Li _y Ta _{1 -x} Nb _x O ₃ (0 ≦ x ≦ 1, 0 ≦ y <1) optical deflection elements capable of wide-angle and high-speed optical scanning. Showed the vessel. Two K _1-y Li _y Ta _1-x Nb _x O ₃ (0 ≦ x ≦ 1, 0 ≦ y <1) metals formed by metal electrodes 22, 23, 26, 27 on the crystals 21, 25, respectively. A pair of electrodes is provided. By applying a voltage to the electrode pair 22, 23, 26, 27, the K _{1 -y} Li _y Ta _{1 -x} Nb _x O ₃ (0 ≦ x ≦ 1, 0 ≦ y <1) crystal 21 is in the y direction. The light deflection in the x direction is obtained with the crystal 25 of K _1-y Li _y Ta _1-x Nb _x O ₃ (0 ≦ x ≦ 1, 0 ≦ y <1). In order to cause wide-angle light deflection, it is necessary to enter polarized light parallel to the electric field applied to the crystal. Therefore, the polarization direction of the incident light is the y direction, and K _1-y Li _y Ta _1-x Nb After passing through the _x O ₃ (0 ≦ x ≦ 1, 0 ≦ y <1) crystal 21, the polarization direction is set to the x direction by the half-wave plate 24.

  The diffuser plate 13 diffuses the incident light to a different degree depending on the incident position. The diffused diffused light is set to be input to the collimating lens 14. A commercially available diffusion plate can be used as the diffusion plate 13, but a hologram is preferably used. If a hologram is used as the diffusing plate 13, even if the relative size and distance from the lens 14 are freely set, the light that deviates from the lens 14 can be eliminated. It becomes possible to suppress the target fluctuation. This is because the degree of diffusion can be controlled by setting the hologram pattern. When a hologram is not used as the diffusion plate 13, the diffusion plate 13 is set to input diffused light diffused by adjusting the relative size and distance from the collimating lens 14 to the collimating lens 14.

  The light input to the collimating lens 14 is collimated and input to the two-dimensional spatial modulation element 15. As the two-dimensional spatial modulation element 15, for example, HTPS (High Temperature Poly-Silicon) of transmissive liquid crystal can be used. The two-dimensional spatial modulation element 15 selectively transmits only the light to be displayed on the display among the input light and inputs the light to the projection lens 16. When light to be displayed on the display is input to the projection lens 16, it is projected on the display 17 so that a desired image is displayed on the display.

In the laser display device having the configuration shown in FIG. 2, the laser light that is two-dimensionally scanned by the two-dimensional optical deflector 18 is temporally different from the diffusion plate 13, so that the illumination light transmitted through the diffusion plate 13 is spatial coherence. Decreases. With this configuration, it is possible to suppress interference of minute irregularities on the screen and to reduce speckle noise. Specifically, when the area of the spot of the laser beam incident on the diffusion plate 13 is S1, and the area in the diffusion plate 13 that can be scanned by the optical deflector in one frame is S2, the speckle noise contrast. C is reduced to C = (S1 / S2) ^1/2 . Therefore, it can be seen that in order to reduce the speckle noise contrast, it is sufficient to increase the number of spots that can be scanned in one frame. That is, speckle noise can be more effectively reduced by using the two-dimensional optical deflector 18 capable of wide-angle and high-speed optical scanning.

  In the laser display device described above, the case where the transmissive liquid crystal HTPS is used as the two-dimensional spatial modulation element 15 has been described as an example. However, by changing the configuration as shown in FIG. It is also possible to use reflective liquid crystal on silicon (LCOS), which is a reflective spatial modulation element, or reflective micro electro mechanical systems (MEMS).

In order to illustrate the effect of the laser display device of the present invention, a laser display device having the same configuration as that of FIG. 2 was prepared. The laser light source was a semiconductor laser having a wavelength of 640 nm for red, a wavelength of 515 nm for green, and a wavelength of 450 nm for blue. As the two-dimensional optical deflector, two K _1-y Li _y Ta _1-x Nb _x O ₃ (0 ≦ x ≦ 1, 0 ≦ y <1) optical deflecting elements similar to those in FIG. 2 were used. A hologram is used as a diffusion plate to prevent light from coming off the collimating lens. The number of spot points in the diffusion plate was 100 × 100 points. As the two-dimensional spatial modulation element, transmissive liquid crystal HTPS (High Temperature Poly-Silicon) was used, and the frame rate was set to 60 fps.

The laser display device having the above configuration scans the first stage of K _{1 -y} Li _y Ta _1-x Nb _x O ₃ (0 ≦ x ≦ 1, 0 ≦ y <1) light deflection element 21 at 30 Hz. K _{1 -y} Li _y Ta _1-x Nb _x O ₃ (0 ≦ x ≦ 1, 0 ≦ y <1) of the stage is scanned at 3 kHz to perform raster scan, and 100 in one frame. Scanning of × 100 points was performed. As a result, the speckle noise contrast could be reduced to 1/100.

11 Laser light source 18 Two-dimensional optical deflector
13 Diffuser 14 Lens 15, 19 Two-dimensional spatial modulation element 16 Projection lens
17 screens
21, 25 K1-yLiyTa1-xNbxO3 (0≤x≤1, 0≤y <1) crystal 22, 23, 26, 27 Electrode 24 Half-wave plate

Claims (3)

A laser light source for outputting laser light;
A speckle noise removal mechanism that removes speckle noise by making the laser light output from the laser light source into diffused light with reduced spatial coherence;
A collimating lens for collimating the diffused light;
In a laser display device comprising display display means for displaying a desired image by selectively projecting the collimated light onto a screen,
The speckle noise removing mechanism includes a two-dimensional optical deflector and a diffuser plate, and the two-dimensional optical deflector scans the laser beam output from the laser light source two-dimensionally, so that different positions of the diffuser plate are obtained. The laser display device is characterized in that the laser light is converted into diffused light with reduced spatial coherence by outputting diffused light that is diffused to a different extent depending on the position of the diffuser plate. The two-dimensional optical deflector comprises two K _1-y Li _y Ta _1-x Nb _x O ₃ (0 ≦ x ≦ 1, 0 ≦ y <1) optical deflecting elements. The laser display device according to claim 1.   3. The laser display device according to claim 2, wherein the diffusion plate is a hologram, and the hologram has a pattern set so that diffused light is input to the collimating lens.

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