Projection image display apparatus

• US 20020005829A1
• Filed: 07/03/2001
• Published: 01/17/2002
• Est. Priority Date: 07/07/2000
• Status: Active Grant

• Current Assignee: Canon Ayutthaya Limited (Canon Inc.)
• Original Assignee: Canon Ayutthaya Limited (Canon Inc.)
• Inventors: Ouchi, Akihiro
• Granted Patent: US 6,753,829 B2
• Time in Patent Office: Days
• US Class Current: 345/88
• CPC Class Codes: G09G 2310/0235 Field-sequential colour display
• CPC Class Codes: H04N 9/3114 by using a sequential colour filter producing one colour at a time

Abstract

To change image quality in accordance with the image to be displayed, a color filter plate 3 is driven to sequentially split the white light incident on an A portion into red, blue, and green light beams to irradiate a liquid crystal panel (not shown), thus displaying a full-color image by a so-called field sequential scheme. In this case, if a sector region 4BG of an auxiliary filter plate 4 is kept always matched to the A portion (FIG. 2A), the quality of a full-color image is defined by the color filter plate 3, resulting in an increase in luminance. In contrast to this, when a red filter section 3R and auxiliary red filter section 4R are synchronously driven to be simultaneously irradiated with white light, the quality of a full-color image is defined by both the color filter plate 3 and the auxiliary red filter section 4R. As a consequence, an image with excellent color reproducibility is obtained. The image quality can be changed by selectively driving/non-driving the auxiliary filter plate 4 in accordance with the image to be displayed.

Claims

1. A projection image display apparatus which comprises an image display element for sequentially displaying gradation images, and an illumination device for sequentially irradiating said image display element with light beams of different colors, and allows a full-color image to be recognized by synchronizing display of the images with light emission,

wherein said illumination device includes a white light source for emitting white light toward said image display element, first filter means rotatably supported between said image display element and said white light source, first filter driving means for driving to rotate said first filter means, second filter means supported movably along said first filter means, and second filter driving means for driving or non-driving said second filter means in accordance with an image to be displayed,

said first filter means is divided into at least first to third filter sections with different transmission light wavelength regions, and driven to be rotated by said first filter driving means to sequentially insert said filter sections in an optical path of the white light, and

said second filter means is set to a transmission light wavelength region overlapping said first filter section, and is driven by said second filter driving means such that, when said first filter section is inserted in the optical path of the white light, said second filter means is also inserted in the optical path, and, when said first filter section is removed from the optical path of the white light, said second filter means is also removed from the optical path.

2. An apparatus according to claim 1, wherein

said second filter means is set to a transmission light wavelength region narrower than said first filter section, and

when said first filter section is inserted in the optical path of the white light, said second filter means is also inserted in the optical path to narrow the transmission light wavelength region.

3. An apparatus according to claim 1, wherein

said first filter section comprises a red filter section for transmitting red light, and

said second and third filter sections comprise a blue filter section for transmitting blue light or a green filter section for transmitting green light.

4. An apparatus according to claim 3, wherein

said blue filter section transmits blue light in a wavelength region of not more than about 500 nm, said green filter section transmits green light in a wavelength region of about 500 nm to 570 nm, and said red filter section transmits red light in a wavelength region of not less than about 570 nm.

5. An apparatus according to claim 1, wherein said second filter driving means drives to rotate said second filter means.

6. An apparatus according to claim 1, wherein

said second filter driving means reciprocally drives said second filter means.

7. An apparatus according to claim 1, further comprising a color correction circuit for correcting a signal to said image display element when said second filter means is not driven.

8. An apparatus according to claim 7, wherein

said color correction circuit comprises addition means inserted in a third color video signal line extending to said image display element, a color correction signal line connected to said addition means, a switch which is inserted in said color correction signal line and ON/OFF-controlled by control means, and attenuator means, inserted in said correction signal line, for attenuating a first color video signal in a predetermined ratio, and

when said second filter means is not driven, said switch is turned on by the control means to cause said attenuator means to attenuate the first color video signal and cause said addition means to add the first color video signal to a third color video signal.

9. An apparatus according to claim 7, wherein

said color correction circuit comprises addition means inserted in a third color video signal line extending to said image display element, a color correction signal line connected to said addition means, a switch which is inserted in said color correction signal line and ON/OFF-controlled by control means, subtraction means, inserted in said color correction signal line, for generating a difference signal between the first color video signal and the third color video signal, and attenuator means, inserted in said color correction signal line, for attenuating the difference signal in a predetermined ratio, and

when said second filter means is not driven, said switch is turned on by the control means to cause said subtraction means to generate a difference signal between the first color video signal and the third color video signal and cause said addition means to add the difference signal to the third color video signal.