Photocopying – Projection printing and copying cameras – Multicolor picture
Reexamination Certificate
1998-10-01
2001-09-18
Adams, Russell (Department: 2851)
Photocopying
Projection printing and copying cameras
Multicolor picture
C349S077000
Reexamination Certificate
active
06292251
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
This invention relates to systems that input digital image files of varying size and resolution, process images with workstation software, rasterize images for the purpose of exposing photo-sensitive media, and produce photographic quality prints or film as the output product.
BACKGROUND OF THE INVENTION
The methods of the present invention were motivated by the detailed metaphors of the prophet, Ezekiel, when he revealed in the
Bible
the architecture and illumination of God's future temple.
Digital photographic printing systems can be identified as belonging to one of three general classifications—dot stream printing, line at a time printing, and area printing.
Dot stream printing is most typified by laser printers which project one dot of the image at a time. A movable mirror advances the dots across the X direction of the media and micro-stepping the media advances the dots down the Y direction of the media. Color printing requires a red laser, green laser, and blue laser to be optically positioned with perfect alignment. Lasers can produce small dot sizes with high resolution. However, the serial nature of printing every dot sequentially requires long exposure times, especially where ultra high resolution images contain over a hundred million dots. Also the extensive and frequent mechanical and optical alignments of laser printing makes laser systems expensive to purchase and maintain.
Line at a time printing electronically advances the mastering dots across the media with such speed that the entire line is considered to be printed simultaneously when compared to mechanical scanning. Special CRTs print one line of the image at a time. One line represents the X direction of the media and micro-stepping the media or the CRT advances the lines down the Y direction of the media. The resolution of line-type CRTs require multiple use in ultra high resolution printing. Because of mechanical limitations, multiple CRTs impose geometric alignment problems that complicate the raster image processing. Although CRTs print each line very fast, overall printing time is significantly slowed by the serial nature of sequencing thousands of lines mechanically and the general lack of intensity from CRTs.
Area printing is the simultaneous exposure of the entire area of an image in one optical projection. Traditional photographic film is classified as “area printing.” For digital area printing, full screen CRTs, LCDs, and Digital Mirror Devices (DMDs) can print the entire X and Y directions of the image in one relatively short exposure time. Most area printing devices that use CRTs and LCDs use fiber optic face plates for connecting the emitted image to the media.
Area printing represents the fastest photographic printing technique, however full screen CRTs, LCDs, and DMDs lack significant resolution to print ultra high resolution images in a single area exposure. Additionally, CRTs lack high intensity and LCDs lack high contrast. Multiple DMDs have been utilized to multiply the resolution of an image by a factor of 2. The DMD geometry yields good contrast, but because of mechanical restrictions, ultra high resolution has not been achieved. When multiple DMDs have been used, these devices are non-moving and project simultaneous motion images.
Digital images come in a wide range of sizes and aspect ratios. However, photographic media has strict size standards by comparison. Resizing decisions must be made about each image. Normally the best image quality is maintained when no resizing is done. However, if a small image is to be printed at large magnifications then pixelization may become objectionable. Increasing the number of pixels will also increase the size of the image and require less magnification.
Raster Image Processing or RIPing is a procedure that is very output device specific. Raster requires light and this procedure produces a specific bitmap for driving the electronics that generates the light for each pixel. In most digital printing systems the image file format must be converted into one very large stream of instructions. For a “dot stream printing” system, up to 30 minutes of computer time for each image may be needed. To save time but not expense, this procedure is usually off loaded to a dedicated workstation or file server. Service bureaus have emerged for batch processing many RIP files going to a specific digital printer.
When increasing the size of an image it is very important that it be “resampled” to the larger size. Resampling is creating new pixels by interpolating selected neighboring pixels. One exhaustive interpolating algorithm is bicubic. The best interpolation for new pixels will also take the longest processing time. To maintain maximum image quality, the ratio of the old size to the new size is a very important consideration during resampling. Different resampling algorithms are dictated by different sizing ratios.
A need has thus arisen for an improved digital image printing system.
SUMMARY OF THE INVENTION
Every classification of digital image printing has advantages and limitations. The present invention establishes a new enhanced classification called “moving-matrix area printing” that uniquely combines the reliability and short exposure time enjoyed by area printing with the ultra high resolution desired from scanned printing. The present method of moving-matrix area printing reconstructs a digital image from multiple area exposures where the image pixel detail required for full resolution is synchronously mapped with the printing container pixel geometry required for full contrast. The entire X and Y dimensions of the image are printed during each exposure using a light valve which functions as a spatial area light modulator.
The most geometrically suitable technology for a moving-matrix design is the Thin Film Transistor LCD module. However, the highest resolution LCD module available provides only a “skeleton” for the photo quality that is ultimately produced to reconstruct ultra high resolution images. The results of printing one image with a LCD module is like viewing the image through a window screen matrix. The screen is so coarse that little more than 4% of the image is printed on the media, making a single matrix exposure look extremely low contrast. Low contrast is normally considered a major drawback to LCDs and the reason why LCDs are rejected for high definition printing. Low contrast geometry is an important attribute of the present invention and the moving-matrix design. Micro-stepping the LCD module as a moving-matrix and synchronously printing
24
“unique views” of the image reconstructs 100% of the image on photo-sensitive media.
Because of the mechanical design of CRTs and DMDs, these devices are not geometrically efficient with the moving-matrix design. However, that does not preclude their eventual use or the use of any spatial light modulator as a moving-matrix imaging device compatible with the present invention for the purpose of reconstructing ultra high resolution images by multiple sub-image area exposures.
The LCD module is the most geometrically efficient spatial light modulator or light valve for the geometric derivations used to multiply the resolution in the moving-matrix design. A LCD module for use with the present invention is the SHARP Electronics LQ10PX01. This LCD module geometry provides an excellent fit for the moving-matrix area printing method. Other LCD modules of slightly differing geometry only require computational adjustments for positioning and their use is not excluded from the present invention.
The LCD module is constructed with a repeating pattern of red, green, and blue filtered windows or pels. One set of RGB pels equals one pixel. There is also significant dead space surrounding each pel. Dead space is normally unrastered spatial modulation and accounts for the low contrast of LCD modules. In the moving-matrix design of the present invention, the “dead space” actually represents the additional “sub-image space” required to reconstruct high resolution images.
Holley J. David
Holley Steven E.
Adams Russell
Electronic Systems Engineering Co.
Kim Peter B.
Locke Liddell & Sapp LLP
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