Television – Camera – system and detail – With single image scanning device supplying plural color...
Reexamination Certificate
1999-11-03
2004-02-10
Garber, Wendy R. (Department: 2612)
Television
Camera, system and detail
With single image scanning device supplying plural color...
C348S272000, C348S268000
Reexamination Certificate
active
06690422
ABSTRACT:
FIELD OF THE INVENTION
This disclosure relates to the capture of color motion imagery, and specifically to the capture of color motion imagery by sequential frame samples of different color filtration, combined with a sensor having a color filter array overlaid on its imaging pixels.
BACKGROUND OF THE INVENTION
There are three basic approaches to capturing color motion imagery. The first uses three sensors, typically using red, green and blue filters, which simultaneously capture a scene's dynamic content. This technique is used with both tube pickup devices and with two dimensional sensor arrays, such as charge coupled devices (CCD) or composite metal-on-silicon (CMOS) devices, which are referred to as 3-CCD cameras.
The second approach uses a single two dimensional (2D) sensor having the color filtration applied separately to each pixel. Colors are arranged in spatially varying patterns that are designed to provide a high spatial bandwidth for luminance or green, and to minimize color aliasing artifacts. The result is that each color layer has incomplete samples per frame but special interpolation algorithms are used to reconstruct full dimensioned frames for each color layer. This approach is known as color filter array (CFA) camera capture.
The third approach is to use a single sensor with either no filtration, or uniform filtration across picture elements, and to combine this with a method to change the filtration over the whole sensor as a function of time. The idea is to temporally change the sensor filtration at rates faster than the temporal response of the eye, so that the sequential color lag, aka color breakup, is below visual threshold. It is most commonly referred to as field sequential color capture (FSC).
The primary disadvantage of the 3-CCD, or 3-tube, approach is the cost of three sensors. A second disadvantage is the problem of color mis-registration between the three sensors because of alignment in the optical path relative to the scene, which may impose tight manufacturing tolerances that increase manufacturing costs. Color mis-registration may cause luminance blur in textures with very small amounts of mis-registration, and may cause color bleeding, aka color fringing, at both achromatic and chromatic edges. If the registration is well aligned, this approach achieves the resolution of the sensors for all three color layers of a frame. Because of cost, however, this approach is only used for high-end studio video cameras, and digital still cameras designed for the professional and advanced hobbyist.
While the CFA approach is less expensive because of the use of a single sensor, it has many disadvantages. These include reduced spatial resolution, the necessity for an interpolation algorithm to reconstruct the three color frames for display, and the necessity for an anti-aliasing filter to prevent diagonal luminance high spatial frequencies from aliasing into lower frequency color patterns. Additionally, the color high spatial frequencies may alias into luminance or color patterns. Consequently, there is a trade-off between sharpness and color artifacts, which show up strongly in such common image content as highlight reflections in eyes, as well as the expected luminance high spatial frequencies such as in texture, e.g., hair, or geometric patterns. In current implementations, fairly complex interpolation algorithms that include pattern recognition are used in an attempt to maximize sharpness and minimize color spatial artifacts. Most cameras opt to avoid any chromatic aliasing because it is a new categorical distortion and favor the sharpness reduction, which is already present to some extent. In summary, CFA systems do not achieve the resolution of their sensor dimensions, either in luminance or in color.
The field sequential color technology is not presently a very active area, and much of the key work was done prior to the NTSC color standard, when field sequential color was a viable competitor for color television. Analog field sequential color video was difficult to accomplish at high frame rates. Its primary application was in telecine and other specialized applications. Recently, FSC activity increased because of full digitization of video systems. Digital video facilitates field sequential color capture to simultaneous color displays.
U.S. Pat. No. 2,738,377, to Weighton, granted Mar. 13, 1956 for Color Television, describes a color television system which uses a rotating color filter wheel, with equally spaced wedges in the order GRGBGRGB, with a single pickup tube, and a CRT to constitute a full color television system. The reference describes an eight-fold interlace, with the color wheel spinning fast enough to cause a different color filter for each interlace line. A sufficient number of lines are used to result in a captured image with 400 G lines and 200 R and B lines. The main difficulty with this approach is the extreme demand imposed on the system bandwidth due to the eightfold interlace. Another is that color field sequential display is required in this system, and because of eye movements, such displays are more susceptible to color breakup than color field sequential capture.
U.S. Pat. No. 3,604,839 to Kitsopoulos, granted Sep. 14, 1971 for Field-sequential color television apparatus employing color filter wheel and two camera tubes, describes a television system having a color filter wheel and two camera tubes, which is primarily aimed at telecine. The purpose of the two tubes is to allow for simultaneous capture of two different colors, thus allowing the exposure to lengthen, given the field rate constraints, and increase the signal to noise ratio.
U.S. Pat. No. 3,969,763 to Tan, granted Jul. 13, 1976, for Color television camera provided with a pickup device and color filter placed in front thereof, describes a color field sequential camera that uses a single pickup tube and a color filter wheel with many fine color strips. The purpose is to capture the color filtered sections of an image more spatially and temporally coincident. It approaches a color sequential interlace, and is primarily an analog hardware system addressing various delay and converter steps. The reference is notable because it discloses a system which uses liquid filters that are electronically controllable, rather than using a mechanical wheel. The system also captures in a YRB space, rather than the more common RGB.
U.S. Pat. No. 3,971,065 to Bayer, granted Jul. 20, 1976, for Color Imaging Array, describes the Bayer pattern color filter array.
U.S. Pat. No. 4,067,043, to Perry, granted Jan. 3, 1978 for Optical conversion method, describes the use of electro-optically controlling color filtration, in a field sequential mode, via the use of crossed polarizers.
U.S. Pat. No. 4,605,956 to Cok, granted Aug. 12, 1986, for Single-Chip Electronic Color Camera with Color-Dependent Birefringent Optical Spatial Filter and Red/Blue Signal Interpolating Circuit, describes an RGB CFA system, including birefringent optical prefilter and the interpolation algorithms for the subsampled R and B image layers.
U.S. Pat. No. 4,670,777 to Ishikawa et al., granted Jun. 2, 1987, for Colorfilter array having cyan, yellow, green, and magenta filter elements providing increased dynamic range for use with field integrating mode solid state imaging device, describes the use of subtractive color filters as well as an additive. The field integration refers to interlace fields, not color shutter fields.
U.S. Pat. No. 4,851,899 to Yoshida et al., granted Jul. 25, 1989, for Field-sequential color television camera, describes an RGB field sequential camera using a color wheel that causes the field order to be R1R2G1G2B1B2, etc. Because the first field of each color pair has a residual charge from the previous, different color, the system discards the first captured field in order to prevent color desaturation.
U.S. Pat. No. 4,967,264 to Parulski et al., granted Oct. 30, 1990, for Color sequential optical offset image sampling system, combines color field sequential concepts with sensor dith
Daly Scott J.
Feng Xiao-fan
Garber Wendy R.
Misleh Justin
Sharp Laboratories of America Inc.
Varitz, P.C. Robert D.
LandOfFree
Method and system for field sequential color image capture... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and system for field sequential color image capture..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and system for field sequential color image capture... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3342220