Television – Video display – Projection device
Reexamination Certificate
1998-06-30
2001-11-13
Eisenzopf, Reinhard J. (Department: 2614)
Television
Video display
Projection device
C348S756000, C348S757000, C348S776000, C348S779000, C348S780000, C348S761000, C353S031000, C359S285000, C359S305000
Reexamination Certificate
active
06317170
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a large area compact laser projection display using a hybrid video laser color mixer. In particular, the present invention for an apparatus projecting the information of a laser video image relates to a very small-sized and high-performance video image projection apparatus which uses a laser as a light source, modulates the light beam using an acousto-optic modulator or an electro-optic modulator according to the image signal and projects the modulated light beam to a screen using a light scanning system.
DESCRIPTION OF THE RELATED ART
The convenient phase of multimedia life in the 21st century may need a display screen of at least 60 inches or more. The prior typical means for displaying an image are flat plate elements such as cathode ray tubes (CRTs) of television receivers and liquid crystal devices (LCD). However, the larger the CRT or LCD is over a 40-inch screen, the more difficult manufacturing is and the resolution is decreased, so there are restrictions for commercialization. Therefore, the prior method of realizing a large area display has been to expand the image showed in a CRT or LCD and projecting it onto a screen. The method of projecting an image by expanding through the lens has a problem in that the image showed is only expanded, so the quality of the image projected to a screen is not clear. Additionally, the method has a problem in that the power of the light source is restricted because of the temperature characteristics of the means for displaying the image, so that the brightness is low.
Therefore, an apparatus for a laser projection display has been developed to solve these problems. Particularly, as the size of the laser display increases, the display improves. The advantages, when the laser is used for display, are as stated above. However, the difficult problems which now become urgent are manufacturing such displays in small sizes at low cost so that the laser display apparatus developed until now can be used for domestic use. U.S. Pat. No. 4,533,215, U.S. Pat. No. 4,720,747, U.S. Pat. No. 5,253,073 and U.S. Pat. No. 5,311,321 have disclosed fairly compact structures developed previously. However, these systems are under the restriction such that they have a large volume and high-price, that they are limited for domestic use.
FIG. 1
illustrates the structure of an exemplary prior art general laser display apparatus. Light source (
10
) may be a white-light laser or a gas laser for each of the red, green and blue wavelengths, as a laser light source. On the path of the light source (
10
), optical system (
20
) comprises high reflection mirror (
21
) changing the path of the laser beam generated by the light source, collimating lens (
22
) transforming the laser beam into parallel light beams and telescoping lens system (
23
,
24
) for adjusting the magnitude of the parallel light beams.
Light beam separating subsystem (
25
) separates the laser beam of white-light admitted from the telescoping lens system (
23
,
24
) of the optical system (
20
) into the monochromatic light beams of red, green and blue. Light beam separating subsystem (
25
) comprises two dichroic mirrors (
67
a
,
68
a
) and a high reflection mirror (
69
a
). The dichroic mirrors (
67
a
,
68
a
) separate the white-light into the light beams of red, green and blue, and the high reflection mirror (
69
a
) changes the light path of the monochromatic light beam. Here, the light beam separation optical system need not be used if a separate laser light source is used for each and of the red, green, and blue, light beams respectively.
The laser beam separated into the light beams of red, green and blue are focused on acousto-optic modulators (
61
,
62
,
63
) through focusing lenses (
64
a
,
65
a
,
66
a
) and modulated by an image signal. The video signal processing speed of the light modulator is related to the diameter of the laser beam penetrating the light modulator, and the smaller the diameter of the light beam is, the faster is the processing speed. The focusing lens plays a role in focusing of the laser beam to get a sufficient speed of processing of the light signal in the light modulator.
The collimating lens (
64
b
,
65
b
,
66
b
) is placed in the back-end of the light modulator (
61
,
62
,
63
) to restore the laser beam to a parallel light type before incidence on the focusing lenses (
64
a
,
65
a
,
66
a
).
Light beam combining sub-system (
65
) combines the monochromatic light beams modulated into one light beam. This is for effective light scanning. Light beam combining sub-system (
65
) comprises two dichroic mirrors (
67
b
,
68
b
) and a high reflection mirror (
69
b
). The dichroic mirrors (
67
b
,
68
b
) recombines the light beams of red, green and blue into white-light, and the high reflection mirror (
69
b
) changes the path of the monochromatic light beam.
The combined light beam is vertically scanned by galvanometer (
70
), horizontally scanned by polygonal mirror (
80
) and then forms an image on a screen (
90
). The galvanometer (
70
) vibrates up and down at the speed synchronized by a vertical synchronous signal and the polygonal mirror (
80
) rotates at a high-speed synchronized by a horizontal synchronous signal. Namely, the scanning path of the modulated light beam changes direction to the vertical by the galvanometer (
70
), the scanning path changes direction to the horizontal by the polygonal mirror (
80
) and the image is formed on the screen (
90
). Relay lens system (
31
,
32
) is placed between the galvanometer (
70
) and the polygonal mirror (
80
) and it concentrates the light beam so that the laser beam vertically scanned is made to enter the effective area of the surface of polygonal mirror (
80
), the surface of horizontal scanning. Relay lens system (
31
,
32
) comprises two lenses having the same focal length such that they are placed with an interval between them being the sum of their focal lengths. The f&thgr; lens system (
34
) may be placed in front of polygonal mirror (
80
), if necessary.
In the structure as described above, the size of the image is determined by the scanning angle and the scanning angle is determined by the horizontal scanning angle. The horizontal scanning angle is determined by the number of surfaces on the rotating polygonal mirror. In particular, the horizontal scanning angle (&thgr;) is determined by the value of 720° divided by the number of surfaces of the mirror.
For example, the horizontal scanning angle is fixed as 30° in case of a 24-side polygonal mirror. On the other hand, the galvanometer only vibrates up and down, so the vertical scanning angle may be adjusted arbitrarily. In the structure as described above, the vertical scanning angle of the galvanometer should be adjusted according to the horizontal scanning angle of the polygonal mirror so as to make an image with a ratio of 4:3 of a picture ratio to the image signal.
To implement a moving picture according to an NTSC image signal, the 525 horizontal lines should make 30 scans of the screen per second. By the calculation described above, the horizontal scanning speed is 15.75 kHz. For a 24-side polygonal mirror, it should rotate at a speed of 39,375 rpm to process that scanning speed.
As described above, for the prior laser image projection apparatus, the sizes of almost all systems developed to date have been more than 2 by 2 by 1.5 miters and the price is over one hundred million yen.
The cause of the large-sized and high-priced system like the above is, first of all, that the red R, green G, and blue B laser light sources must have a capacity of power that is, at least, several watts or more so as to achieve brightness with a sufficient magnitude on the screen size demanded. Only gas lasers meet the requirements for the laser light source to date. Therefore, the light source in itself is high-priced and large. The next cause of large-sized and high-priced systems is that the light modulator and the related optical system, light separation and combining optical system, the opti
Cha Seung Nam
Hwang Young Mo
Lee Jin Ho
Burns Doane Swecker & Mathis L.L.P.
Eisenzopf Reinhard J.
Samsung Electronics Co,. Ltd.
Yenke Brian P.
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