Optical: systems and elements – Single channel simultaneously to or from plural channels – By surface composed of lenticular elements
Reexamination Certificate
2000-01-18
2001-12-04
Epps, Georgia (Department: 2873)
Optical: systems and elements
Single channel simultaneously to or from plural channels
By surface composed of lenticular elements
C359S452000, C359S454000, C359S641000
Reexamination Certificate
active
06327091
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to the technical field of collimating plates for collimating diffused light and backlight systems utilizing them. More particularly, the invention relates to a collimating plate that can produce adequately convergent collimated light and which hence is particularly suitable for use as a backlight for liquid-crystal displays, and a backlight system utilizing it.
The use of liquid-crystal displays (LCDs) as a display for word processors and computers is rapidly increasing today. The use of LCDs as a monitor in ultrasonic, CT and MRI diagnostic apparatus is under review. Conventionally, these medical diagnostic apparatus have primarily used CRTs (cathode-ray tubes) as a monitor.
LCDs have many advantages such as ease in size reduction, small thickness and lightweightness. On the other hand, they have poor viewing angle characteristics (narrow viewing angle) in that as the viewing direction or angle changes, the contrast ratio of an image decreases sharply and the gradation also reverses to have the image look differently. As a result, depending on the position of the viewer, the image cannot be viewed correctly.
In medical applications as described above, diagnosis with monitors is based on the difference in image density, so not only is it required to produce an image of high contrast ratio but at the same time, incorrect recognition of an image can cause wrong diagnosis or inconsistency in the results of diagnoses. Under these circumstances, it is required that high-contrast image be displayed over a wide range of viewing angles. Another problem peculiar to medical monitors is that image is usually displayed in monochrome (black and white colors) and, hence, suffers considerable drop in contrast as the viewing angle varies.
LCDs adapted for viewing over a wide range of angles include those operating in an IPS (in-plane switching) mode and a MVA (multi-domain vertical alignment) mode. However, even these LCDs do not have a sufficiently wide range of viewing angles to satisfy the requirement of monochromatic images, especially ones that are used in medical applications.
A LCD is known that can produce image of good contrast ratio over a wide range of viewing angles. It is backlighted with collimated light (which travels straight) and the light passing through the liquid-crystal panel is diffused with a diffusing plate.
In order to realize a wide-angle LCD, the diffused light issuing from the backlight source has to be condensed sufficiently to produce adequately collimated light. In particular, in order to realize a LCD that has a sufficiently wide range of viewing angles to be useful in medical applications, it is preferred to use collimated light the intensity of which drops by 50% at angles of no more than ±15 degrees.
Collimated light is usually produced by making diffused light convergent with a condensing sheet. The collimated light produced from conventional condensing sheets is reduced in intensity by 50% at angles of about ±20 degrees and it has been difficult to produce collimated light that practically serves to backlight LCDs for medical use.
SUMMARY OF THE INVENTION
The present invention has been accomplished under these circumstances and has as an object providing a collimating plate that has a sufficiently good condensing capability to produce collimated light the intensity of which drops by 50% at angles of no more than ±15 degrees and which, when used as a collimator with backlight for liquid-crystal displays, provides a good contrast ratio over a wide range of viewing angles to realize a liquid-crystal display that can advantageously be used as a monitor for medical diagnostic apparatus. Another object of the invention is to provide a backlight system utilizing the collimating plate.
In order to attain these objects, according to a first aspect of the invention, there is provided a collimating plate comprising:
a transparent support;
a multiple of light transmitting spheres fixed to the support in partial contact therewith; and
a light blocking area that blocks passage of light through areas other than light transmitting areas composed of areas of contact between the transparent support and the light transmitting spheres and nearby areas.
Preferably, the light transmitting areas have an open area ratio of 3-10% to a surface of the transparent support.
The light blocking area is preferably one of a light diffusing device, a light absorbing device and a light reflecting device. Further, the light diffusing device is preferably a binder that fixes the light transmitting spheres to the transparent support and in which a substance having a refractive index of at least 1.3 is dispersed. Furthermore, the light diffusing device has preferably a reflectance of at least 80% at a thickness one half average diameter of the light transmitting spheres.
According to a second aspect of the invention, there is also provided a backlight system comprising:
a collimating plate comprising a transparent support, a multiple of light transmitting spheres fixed to the support in partial contact therewith and a light blocking area that blocks passage of light through areas other than light transmitting areas composed of areas of contact between the transparent support and the light transmitting spheres and nearby areas; and
a housing that is optically closed by the collimating plate and that includes an inner surface having reflecting properties. It should be noted that the housing has light sources inside.
The inner surface of the housing has preferably a reflectance of at least 80%.
REFERENCES:
patent: 5429909 (1995-07-01), Kaszczuk et al.
patent: 5563738 (1996-10-01), Vance
patent: 5751388 (1998-05-01), Larson
patent: 5781344 (1998-07-01), Vance
patent: 5839812 (1998-11-01), Ge et al.
patent: 6163351 (2000-12-01), Nakayama
patent: 6172814 (2001-01-01), Watanabe et al.
patent: 6254245 (2001-07-01), Uehara
patent: 2 083 726 A (1982-03-01), None
patent: 9-104174 (1997-04-01), None
patent: 9-104173 (1997-04-01), None
patent: 10-226174 (1998-08-01), None
patent: 5-333202 (1993-12-01), None
patent: 6-67003 (1994-03-01), None
patent: 7-5306 (1995-01-01), None
patent: 7-174909 (1995-07-01), None
patent: 6-230230 (1994-08-01), None
patent: 3-87827 (1991-04-01), None
patent: 4-211252 (1992-08-01), None
Epps Georgia
Fuji Photo Film Co. , Ltd.
Seyrafi Saeed
Sughrue Mion Zinn Macpeak & Seas, PLLC
LandOfFree
Collimating plate and backlight system does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Collimating plate and backlight system, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Collimating plate and backlight system will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2590325