JP5950404B2 - Laser display device - Google Patents

Description

  The present invention relates to a laser display device, and more particularly to a laser display device with reduced speckle noise.

  The laser display is a display that uses three primary color lasers as a light source and displays an image by projecting it onto a screen while scanning the light source with scanning means such as a MEMS scanner. Since a laser is used as the light source, it has the advantages of low power consumption, excellent color reproducibility in principle, and a smaller projector than other projection displays. .

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

  However, since a laser is used as the light source, there is a problem that “speckle noise” that is speckled image noise generated by interference of minute unevenness of the screen is generated by the coherent laser light, and the image quality is significantly deteriorated. .

  When a conventional display device performs an optical scan, it only needs to two-dimensionally scan a point image projected on the screen and draw an image for one frame, so that speckle noise is unavoidable. there were.

  The present invention has been made in view of such problems, and an object thereof is to provide a laser display device in which speckle noise in a laser display is reduced.

In order to achieve the above object, according to the first aspect of the present invention, the light output from the laser light source is projected onto the screen while the two-dimensional light scanning projection optical system scans in the two-dimensional direction. In the laser display device that forms a display image by the above-described method, it is disposed on the optical path between the laser light source and the two-dimensional optical scanning projection optical system, and K _1-y Li _y Ta _1-x Nb _x O ₃ (0 ≦ x ≦ 1, 0 ≦ y <1) A speckle noise removal mechanism including an optical scanner is provided, and the two-dimensional optical scanning projection optical system is smaller than an eye resolution element that can be identified by eye resolution. An image is projected on the screen, and the speckle noise removing mechanism performs scanning so that the point image moves so as to fill the inside of the resolution element of the eye on the screen. is there.

As described above, according to the present invention, a MEMS type two-dimensional scanner or a K _1-y Li _y Ta _1-x Nb _x O ₃ (0 ≦ x ≦ 1, 0 ≦ y <1) two-dimensional scanner is used. In addition to two-dimensional scanning of point images smaller than the eye resolution, K _1-y Li _y Ta _1-x Nb _x O ₃ (0 ≦ x ≦ 1, 0 ≦ y) <1) By scanning the scanner, it is possible to remove speckle noise due to light interference in the resolution point of the eye and reduce speckle noise in the laser display.

It is a figure for demonstrating the structure of the laser display apparatus of this invention. It is a figure which shows the locus | trajectory of the scan spot (point image) of this invention. It is a figure for demonstrating operation | movement of the two-dimensional optical scanning projection optical system which has the function of the speckle noise removal mechanism of this invention.

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

  FIG. 1 shows the configuration of a basic laser display of the present invention. As shown in FIG. 1, the laser display of the present invention includes a laser light source 101, a speckle noise removing mechanism 102, and a two-dimensional light scanning projection optical system 103.

  The laser light source 101 can be configured using red, green, and blue semiconductor lasers. A wavelength conversion laser may be used as the green laser.

The speckle noise removal mechanism 102 is a means for removing speckle noise by scanning (optical scanning) the laser light output from the laser light source 101 and inputting it to the two-dimensional optical scanning projection optical system 103. For example, K _1-y Li _y Ta _1-x Nb _x O ₃ (0 ≦ x ≦ 1, 0 ≦ y <1) is configured using a one-dimensional optical scanner. K _1-y Li _y Ta _1-x Nb _x O ₃ (0 ≦ x ≦ 1, 0 ≦ y <1) Since the one-dimensional optical scanner can be controlled at high speed, the conventional speckle noise removing mechanism 102 is used. High-speed scanning can be realized compared to an optical scanner.

The two-dimensional optical scanning projection optical system 103 further scans (optically scans) the laser light input from the speckle noise removal mechanism 102 by raster scanning, and displays a point image set smaller than the resolution element of the eye. It is means for forming a display image by projecting onto the screen. Examples of the two-dimensional optical scanning projection optical system 103 include two one-dimensional MEMS scanners, one two-dimensional MEMS scanner, K _1-y Li _y Ta _1-x Nb _x O ₃ (0 ≦ x ≦ 1, 0 ≦ y <1) Either one of the two one-dimensional scanners can be used. The eye resolution element refers to the area that can be identified by the eye, and specifically the area on the screen that is the smallest size that can be identified by the human eye from the position that is assumed to be observed. Say. For example, the resolution element when a person with visual acuity 1 is 5 m away from the screen is about 1.5 mm.

  Here, the principle that speckles are removed by the speckle noise removing mechanism 102 will be described. FIG. 2 is a diagram illustrating a locus of a point image scanned by an optical system that is a combination of a speckle noise removal mechanism and a two-dimensional scanning projection optical system. In the laser display device of the present invention, as shown in FIG. 2, the point image 202 projected on the screen from the two-dimensional optical scanning projection optical system 103 is set smaller than the resolution element 201 of the eye. The point image 202 moves in the direction indicated by the locus 204 by being scanned by the two-dimensional optical scanning projection optical system 103 while moving as indicated by the locus 203 by being scanned by the speckle noise removing mechanism 102. To do. The optical scanning method such as the trajectory 204 is called raster scanning.

  By adding a light scan by the speckle noise removal mechanism 102 to the light scan by the two-dimensional scanning projection optical system 103, the inside of the eye resolution element is covered with the locus of the point image, and as a result the screen formed on the screen The whole will be covered up. As a result, even if the light scattered by the minute unevenness of the screen interferes with each other, the interference components are canceled and averaged, eliminating speckle noise and reducing speckle noise in the laser display. is there.

  Compared with the conventional case where a point image having the same size as the resolution element of the eye is optically scanned by the two-dimensional scanning projection optical system, the point image in the present invention is used. Spectra contrast is s / d, where s is the diameter of the eye and d is the diameter of the eye resolution element. The speckle contrast means that the smaller the value, the smaller the speckle noise.

  Table 1 below shows the number of resolution points and scanning frequency required for each optical scanner in the two-dimensional scanning projection optical system 103 and the speckle noise removal mechanism 102.

In Table 1, N _x and N _y indicate the number of resolution elements in the horizontal direction and the number of resolution elements in the vertical direction, respectively, and f _FR indicates the frame rate.

As shown in Table 1, in the present invention, the scanning frequency of the speckle noise removing mechanism 102 is very large, which is several MHz to several hundred MHz. Therefore, a K _1-y Li _y Ta _1-x Nb _x O ₃ (0 ≦ x ≦ 1, 0 ≦ y <1) one-dimensional optical scanner capable of realizing high-speed light deflection is used as the speckle noise removal mechanism 102. .

Next, in order to demonstrate the effect of the present invention, a laser display device according to the present invention was prepared. The configuration of the laser display is the same as in FIG. In this embodiment, the laser light source 101 is 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. The two-dimensional scanning optical system 103 is composed of one two-dimensional MEMS optical scanner. The speckle noise removal mechanism 102 is composed of a K _1-y Li _y Ta _1-x Nb _x O ₃ (0 ≦ x ≦ 1, 0 ≦ y <1) one-dimensional optical scanner.

  Laser display images were formed with 800 and 600 resolution elements in the horizontal and vertical directions, respectively, and the frame rate was 30 Hz. Each scanner realized the speckle contrast 1/5 with the number of resolution points and the scanning frequency shown in Table 2 below.

  As described above, according to the present invention, when a two-dimensional light scanning projection optical system projects a laser beam onto a screen as a point image while scanning in a two-dimensional direction at a predetermined period, two-dimensional light is projected. The speckle noise removal mechanism scans the laser beam in a one-dimensional direction with a period much shorter than the scanning period of the scanning projection optical system, so that the point image is filled in the resolution element of the eye on the screen. Therefore, the inside of the resolving element of the eye is covered with the locus of the point image. Therefore, the speckle noise removal mechanism can remove speckle noise due to light interference within the resolution point of the eye and reduce speckle noise in the laser display.

In the above description, the speckle noise removing mechanism 102 has been described as a scanning unit separate from the two-dimensional scanning optical system 103. However, the two-dimensional scanning optical system 103 is replaced with K _1-y Li _y Ta _1-x Nb _x. In the case of an O ₃ (0 ≦ x ≦ 1, 0 ≦ y <1) optical scanner, the speckle noise removing mechanism 102 and the two-dimensional scanning optical system 103 can be configured integrally. For example, if two _1- dimensional optical scanners are used as the two-dimensional scanning optical system 103, K _1-y Li _y Ta _1-x Nb _x O ₃ (0 ≦ x ≦ 1, 0 ≦ y <1) K _1-y Li _y Ta _1-x Nb _x O ₃ (0 ≦ x ≦ 1, 0 ≦ y <1) One of the one-dimensional optical scanners that scans in the vertical direction is a function of the speckle noise removal mechanism 102. Can be given.

FIG. 3 shows K _1-y Li _y Ta _1-x Nb _x O ₃ (0 ≦ x ≦ 1, 0 ≦ y <1) one-dimensional light that scans in the vertical direction and also has the function of the speckle noise removal mechanism 102. It is a figure for demonstrating the scanning by a scanner. The scan angle indicates the angle of light from the one-dimensional optical scanner with respect to the vertical direction of the screen to be projected, K _{1 -y} Li _y Ta _1-x Nb _x O ₃ (0 ≦ x ≦ 1, 0 ≦ y <1). Yes. As shown in FIG. 3, the _one- dimensional optical scanner of K _1-y Li _y Ta _1-x Nb _x O ₃ (0 ≦ x ≦ 1, 0 ≦ y <1) The two-dimensional scanning optical system 103 is scanned in the period 301.

DESCRIPTION OF SYMBOLS 101 Laser light source 102 Speckle noise removal mechanism 103 Two-dimensional optical scanning projection optical system 201 Eye resolution element 202 Point image 203 Speckle removal scan 204 Optical scanning locus by two-dimensional optical scanning projection optical system 301 Two-dimensional Period corresponding to the scanning frequency in the vertical direction of the scanning projection optical system 302 Period corresponding to the scanning frequency of the speckle removal system

Claims (2)

In a laser display device that forms a display image by projecting light output from a laser light source onto a screen while scanning in a two-dimensional direction by a two-dimensional light scanning projection optical system ,
The two-dimensional optical scanning projection optical system includes two one-dimensional scanners K _1-y Li _y Ta _1-x Nb _x O ₃ (0 ≦ x ≦ 1, 0 ≦ y <1). one of the one-dimensional scanner, as the eye resolution element is smaller than the point image that can be identified by the eyes of resolution projected on the screen, filling the pre-Symbol in eye resolution element on a screen A laser display device having a speckle removal function for performing scanning so that the point image moves.   2. The laser display device according to claim 1, wherein the laser light source is composed of red, green and blue laser light sources.

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