Optical: systems and elements – Optical modulator – Light wave temporal modulation
Reexamination Certificate
1998-09-25
2002-08-27
Dang, Hung Xuan (Department: 2873)
Optical: systems and elements
Optical modulator
Light wave temporal modulation
C359S270000, C359S274000
Reexamination Certificate
active
06441942
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to an information display device, and more particularly to an electrochromic device for inscribing and projecting or displaying images.
2. Description of the State of the Art
The use of overhead projection units or “projectors” and/or chalkboards are just two of the many devices available for conveying information visually to large audiences. Projectors are often used to project information appearing on transparent slides, foils, or “transparencies” onto a screen or wall. In using conventional overhead projection units, the transparency to be written on or containing the information to be projected is simply placed on the stage and is typically projected as a dark image on a light background. However, if the transparency does not lie flat on the stage of the overhead projector, the resultant enlargement of the information being projected may be distorted or may not be in focus. Furthermore, the transparency may be slippery, so when the projector is positioned in a manner with the stage slanted, the transparency may have to be held manually to prevent it from slipping in relation to the stage. Care also must be taken in the manner in which transparencies are handled, because ink from the markers that are typically used for writing on transparencies tend to smear easily.
To address the disadvantages that are common to transparencies, flat display panels are commonly used to display computer generated and other video information. Flat display panels are frequently used in direct-view applications, such as with laptop-style personal computers and are also used in projection display applications, such as overhead projection display panels that operate with conventional overhead projector light sources.
Projection display panels usually have liquid crystal displays and are typically coupled to personal computers that provide the graphic information to be projected for viewing. Despite the generally portable configurations of many projection display panels and laptop-style personal computers, they are quite expensive, and they can sometimes be inconvenient for individuals to transport and operate alone. Furthermore, liquid crystal displays suffer from the disadvantages of being operational in only a limited temperature range, and they have substantially no memory.
The disadvantages associated with chalkboards are primarily two-fold. First, lighting is essential for both presenters and viewers. Therefore, if a slide presentation is being made with the lights off to enhance viewing of the slide images, it is necessary to turn the lights back on before a chalkboard is used. Second, chalk is an irritant for some people, so those individuals who are prone to allergic reactions from chalk are not able to come into contact with chalk or chalk dust without suffering some negative physical effects. While “grease boards” are now common alternatives to chalkboards, they also require sufficient lighting to enable a viewer to see and read any information written on the board.
There have been some apparatus and methods developed for storing and reproducing images using electrochromic devices, since electrochronic materials afford the significant advantages of memory and reduced power consumption over other types of displays, such as liquid crystals. Such electrochromic devices employ an electrochromic material, which is responsive to the application of an electrical current of a given polarity to induce the material to undergo a change from a first persistent state that is transparent or bleached, in which the material is essentially non-absorptive of electromagnetic radiation, to a second persistent state in which the material absorbs electromagnetic radiation and darkens to a colored state, typically blue. For example, U.S. Pat. No. 4,500,174 to Conner discloses an electrochromic imaging apparatus utilizing electrochromic iridium oxide and a thin film solid ionic conductor. The Tsukada patent U.S. Pat. No. 3,986,771 discloses a light imaging and reproducing device for storage and reproduction of original images comprising an information storage medium including a member having a photoconductive substance and an electrochromic substance wherein, the member is supported electrodes. The Tsukada device further includes illuminating means and a power source. The Otake et. al. patent, U.S. Pat. No. 4,019,809, discloses a display device that includes a layer of photoconductive material and a layer of electrochromic material between electrodes, which is usefull as an image converter for the spectrum from X-rays to infra-red and as a memory device. Conner, Tsukada, and Otake all teach the use of photoconductors with an electrochromic materials. However, both Otake and Tsukada only teach image conversion and storage of such images. Neither of these Otake and Tsukada devices project the image or are capable of real-time writing. Similarly, Conner does not teach how an image may be projected or have real-time writing capabilities, but, instead, teaches imaging a static image that is seen in reflection and not as a projection.
SUMMARY OF THE INVENTION
Accordingly, it is a general object of this invention to provide an electrochromic device for projecting or displaying images in real-time.
A more specific object of the present invention is to provide an electrochromic image display device which is capable of being back-lighted and transmitting selective portions of such back lighting through a panel to produce images inscribed on a front surface of the panel in real time.
Another specific object of the present invention is to provide an electrochromic device for projecting or displaying images wherein the image clarity remains stable over time.
Additional objects, advantages and novel features of this invention shall be set forth in part in the description that follows, and in part will become apparent to those skilled in the art upon examination of the following specification or may be learned by the practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities, combinations, and methods particularly pointed out in the appended claims.
To achieve the foregoing and other objects and in accordance with the purposes of the present invention, as embodied and broadly described therein, the apparatus of this invention may comprise a photoconductive device arranged in tandem with an electrochromic opacity device, a light source positioned behind the electrochromic opacity device, an inscribing light positioned movably in front of the photoconductive device, and a light filter positioned between the light source and the electrochromic opacity device. The method of the invention includes inscribing and projecting an image with the apparatus by directing an inscribing light beam on the photoconductive device and, if desired, moving the inscribing beam in relation to the photoconductive device to inscribe and project a desired image.
REFERENCES:
patent: 3986771 (1976-10-01), Tsukada
patent: 4019809 (1977-04-01), Otake et al.
patent: 4053209 (1977-10-01), Hara et al.
patent: 4150876 (1979-04-01), Yevick
patent: 4324622 (1982-04-01), Deb
patent: 4500174 (1985-02-01), Conner
patent: 4596722 (1986-06-01), Warszawski
patent: 5069535 (1991-12-01), Baucke et al.
patent: 5220445 (1993-06-01), Takenaka et al.
patent: 5377037 (1994-12-01), Branz et al.
patent: 5500491 (1996-03-01), Watanabe
patent: 5541762 (1996-07-01), Levy
patent: 5604626 (1997-02-01), Teowee et al.
patent: 5784129 (1998-07-01), Konuma et al.
Benson David K.
Branz Howard M.
Dang Hung Xuan
Midwest Research Institute
Tra Tuyen
White Paul J.
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