1. Technical Field
The present invention relates to a video projector and, more particularly, to a video projector which is employed in the optical information field that utilizes a coherent light.
2. Background Art
A video projector which employs laser lights will be described as a prior art video projector (for example, Patent Document 1).
A block diagram of a conventional video projector will be shown in FIG. 11.
This video projector 100 has lasers 1, 2, and 3, as short-wavelength laser light sources, which emit three color laser lights P1, P2, and P3 of red, blue, and green, respectively. The video projector 100 further has mirrors 4a, 4b, 4c, 5a, 5b, and 5c, lens systems 6a and 6b, and a liquid crystal cell 7. Here, as red laser light source 1, a semiconductor laser is employed, as blue laser light source 2 and green laser light source 3, those which are obtained by the outputs of the semiconductor lasers being subjected to the wavelength conversion are employed. Further, a screen 10 employed in this video projector 100 is a screen of gain 1 that is usually used in a normal projector utilizing a mercury lamp, the size thereof is 90 inches.
Next, the operation will be described.
In the so-constructed video projector, the three-color (red, blue and green) laser lights P1 to P3 that are emitted from the short-wavelength laser light sources 1 to 3, respectively, are applied to the screen 10 through the liquid crystal cell 7.
More specifically, the red laser 1 exercises a continuous light emitting operation, and the laser light P1 emitted from the laser 1 is reflected by the mirrors 4a and 5a to change their destination. The laser light P1 reflected by the mirror 5a is projected by the lens system 6a onto the liquid crystal cell 7 and is modulated according to a video signal thereat. The laser light P1 modulated by the liquid crystal cell 7 is enlarged by the lens system 6b and is projected onto the screen 10. The laser lights P2 and P3 that are emitted from the blue laser 2 and the green laser 3 are respectively reflected by the mirrors 4b and 4c, and are further respectively reflected by the mirrors 5b and 5c so that their optical axes are aligned with that of the laser light P1 emitted from the red laser 1, and are projected by the lens system 6a onto the liquid crystal cell 7. The laser lights P2 and P3 projected onto the liquid crystal cell 7 are respectively modulated at the liquid crystal cell 7 according to a video signal, and the modulated laser lights P2 and P3 are enlarged by the lens system 6b to be projected onto the screen 10.
The modulation to the respective three-color laser lights P1 to P3 by the liquid crystal cell 7 is performed by time-sharing for each color.
A person can see the video projected on the screen 10, by observing light that is reflected or scattered by the screen 10 from the front face of the screen, i.e., from the side of projecting laser.
When this video projector 100 projects full white, the screen 10 has brightness of approximately 200 lux.
Patent Document 1: Pamphlet of International Publication No. 96/03875
However, the above-mentioned conventional video projector may occur a camera shake when a person intends to perform projection with holding the same in his or her hands. For example, usually, a person subtly jiggles-his or her hands at a frequency of several Hz. The influences on the projected images by this camera shake becomes hard to be avoided when the distance from the video projector to the screen becomes larger and the enlarging ratio becomes higher, and thereby on the projected video becomes difficult to be seen.
In addition, the conventional projector has a consumption power of 200 W or more, and the body of the projector becomes too hot to be held in one's hands due to heat generated by the light source.
The present invention is directed to solving the above-mentioned problems, and has for its object to provide a video projector which can avoid the projected video from being disturbed due to the camera shake when projecting a video with holding the same in one's hands.
USPTO Backgrounds
USPTO Backgrounds