Television – Stereoscopic – Stereoscopic display device
Reexamination Certificate
2000-09-13
2004-10-05
Lee, Young (Department: 2613)
Television
Stereoscopic
Stereoscopic display device
C345S008000
Reexamination Certificate
active
06801242
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
Not Applicable
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not Applicable
REFERENCE TO A MICROFICHE APPENDIX
Not Applicable
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention pertains generally to an apparatus and methods to reduce the perception of “flicker” by a viewer of three dimensional images on a broadcast television or similar visual display device. The invention can be implemented with a variety of electronic components and. optical transmission materials in the three dimensional viewing glasses. The invention has the primary benefits of: (a) operation with any of the national television broadcast standards in various countries around the world (such as NTSC or PAL); (b) low cost; (c) no viewer adjustment or control required for operation; and (d) compatibility with a variety of optical transmission materials as shutters in the three dimensional viewer glasses, including liquid crystal, ferro-magnetic and other similar materials;
2. Description of the Background Art
A wide variety of glasses for viewing three dimensional images have been developed, known and used since the beginning of three dimensional imaging. These special glasses are essentially all based upon the same principal: blocking the view of one eye while the other eye is shown an image that has been focused and converged on the subject of the optical image from approximately the same angle as that of the corresponding typical human eye looking at the same field of view, then quickly reversing the process so that the opposite eye is blocked from the field of view and the first eye is shown the same image recorded from approximately the same angle as that of the corresponding human eye. The average distance between human eyes is approximately 2.5 inches, and this is the distance that is normally used to separate the two recording devices that are used to create the separate stereo images of the subject matter that are shown to each eye in the above-sequence.
Prior to the relatively recent development of liquid crystal and ferromagnetic materials, the two primary methods of blocking the light (or view) into one eye, while the other eye is able to look the subject filed of view, were electro-mechanical shutters and polarized lenses. Electro-mechanical shutters for three dimensional glasses have largely been replaced due to cost, noise and vibration, and related ergonomic factors. Although polarized filters are still in wide use for three dimensional imaging and viewing, they are not generally applicable to the viewing of images from a standard broadcast television or similar video display system that cannot project polarized light.
The advent of liquid crystal and ferromagnetic materials that can vary from clear to black (little or no light transmission) under an applied dc voltage has revolutionized glasses for viewing three dimensional images. These materials are lighter, lower cost, require no moving parts, and generally give superior image quality. It should be noted that the amplitude and polarity of dc voltage applied to these materials differs from one to another and for the sake of clarity and simplicity in the following discussion the dc voltage (either positive or negative) required to turn one of these electronic materials into the “off” or “no light transmission” state will be referred to as the “high” voltage and the voltage required to turn such material to its opposite state will be referred to as the “low” voltage. It should also, be noted that when liquid crystal material is used, an opposite polarity and equal dc voltage must be applied so that the “colored” crystalline material does not accumulate on one side (i.e., against one electrode). Thus, in Applicant's Figures, as in actual operation, an opposite voltage is applied in the corresponding off period for the same electronic shutter.
To Applicant's knowledge, all of the currently available three dimensional viewing glasses produce a perception by the viewer of “flicker” when used with three dimensional images from interlaced video signals used on broadcast television and similar display systems. This flicker is a well known and documented phenomena in the three dimensional imaging industry. Flicker is generally perceived as a very short duration dark flash or blanking of the image in front of the eyes. It is caused by the refresh rate of interlaced video display systems, such as those employed in the various national broadcast television signals, being within the threshold of human perception. In the United States the television video refresh rate is 60 hz, while in Europe, The Peoples's Republic of China, and Japan for instance, the refresh rate is 50 hz. Three dimensional imaging on such broadcast television systems requires that one eye be essentially blocked from viewing the CRT display every other field. This enables the image of an object in the field of view to be shown to each eye from a slightly different angle (corresponding to the natural separation of human eyes), thereby producing a perception of depth in the subject video image. This blocking of one eye and then the other eye to obtain a perception of depth has the consequence of effectively dividing the effective refresh rate to one-half of the 60 or 50 hz interlaced field rate, that is, to 30 or 25 hz. Such a low effective refresh rate for three dimensional imaging on broadcast television (and similar display systems with a low refresh rate) causes the perception of flicker.
At faster refresh rates, such as those used on certain computer systems and in display systems designed for high definition viewing (such as military, scientific, or other “high end” applications) the human eye perceives little or no flicker from the turning on or off of the shutters in three dimensional viewing glasses. The average person sees little or no flicker once the refresh rate approaches 80 or more hz.
As a consequence of the flicker problem inherent in broadcast television due to the low refresh rates, three dimensional viewing on broadcast television has not gained a strong foothold amongst the viewing population. Numerous studies and attempts have been made to eliminate or reduce the flicker effect, including contrast filters, and other devices and methods. However, to applicant's knowledge, none of these efforts has been commercially successful.
Applicant's invention approaches the flicker problem in a novel and original manner that substantially reduces the perception of flicker in three dimensional images viewed on standard broadcast televisions and similar display systems. In addition, applicant's invention can be used with different types of shutter materials such as liquid crystal or ferromagnetic devices. However, as discussed below, Applicant's invention describes the use of a particular liquid crystal material as an electronic shutter that, under certain lighting and viewing conditions, further reduces the perception of flicker.
BRIEF SUMMARY OF THE INVENTION
The present invention consists of an apparatus and methods to reduce the perception of “flicker” by a viewer of three dimensional images on a broadcast television or similar visual display device. This apparatus and method controls the dc voltages applied to the electronic shutter such that for each eye, the amount of light transmission through the electronic shutter is in the range of a “window” defined by the “high” and “low” dc voltages applied to the shutter. The “low” dc voltage is set at a level that permits sufficient light for the viewer to perceive a three dimensional image during the “on” period, and the “high” dc is set to allow a certain amount of light to continue to pass through the electronic shutter so that the viewer does not see the image in front of the respective eye turn completely black or totally opaque. [Note, as discussed below, the actual voltages applied may be reversed if different liquid crystal or other transmission material is employed.]
In addition, the present invention
LandOfFree
Flicker reduction in three dimensional broadcast television... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Flicker reduction in three dimensional broadcast television..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Flicker reduction in three dimensional broadcast television... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3307476