Photocopying – Projection printing and copying cameras – Multicolor picture
Reexamination Certificate
2000-05-05
2004-12-07
Mathews, Alan A. (Department: 2851)
Photocopying
Projection printing and copying cameras
Multicolor picture
C355S035000, C358S001900, C358S302000
Reexamination Certificate
active
06829036
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to printing of digital images onto photographic paper, and more particularly to removable apparatus for producing photographs on photographic paper from digital images having a means for color correction.
BACKGROUND OF THE INVENTION
Color and black and white photography are a popular pastime for capturing memorable moments in time. One difficulty with photography, particularly color photography, is the production of photographs having a good image clarity, or sharpness, and having correct color. Conventional printers utilize a complex and expensive optical system and projector for producing images from negatives on photographic paper. After a negative has been developed, the procedure is typically to project light through the negative and focus the image onto the photographic paper. With respect to the printer itself and disregarding the photographic paper, the optical system and the lamp house are responsible for the quality of the image. The lamp house is also responsible for the color content of the resulting photograph. In color photographic printing, the process involves projecting light which has been filtered with the use of dichroic filters to correctly manage the spectrum of light so that the characteristics of the film negative and the characteristics of the photographic paper produce a desired positive print.
This difficulty of producing photographs having good image clarity and correct color is especially exaggerated when producing photographs from digital images. Digital images may be captured by conventional digital cameras or produced from non-digitized color photographs that are subsequently digitized by standard digital photoprocessing software. Unfortunately, photographs produced from digital images are limited in sharpness and clarity because of the digitized construction of the image itself or because of the means for exposing the image on photographic paper.
Adding to the complexity and difficulty of producing clear and color correct photographs is the commercial desire to mass produce photographs at high speeds. Depending on the type of projection device, conventional printers project digital images onto photographic paper using a line-by-line application similar to a raster technique. With this type of projection method, the line-by-line application must be synchronized with the movement of the paper web in the printer and must also account for any variance from horizontal based on the movement of the paper web. Misregistration is a common problem with this technique, and the multiple alignments required to counter misregistration is very difficult to accomplish if a desired image has high resolution. Additional operational software or algorithms are required when using this line-by-line application to offset the aforementioned variance.
Various types of projectors have been used to control the transmission of light onto the negative and to the photographic film in non-digital image photographic processing. The use of a cathode ray tube (CRT) as a means for projecting digital images for the printing of photographs is popular. With CRT projectors, two problems are presented. The first problem is the persistence of the phosphors on the face of the CRT which can cause image burn or smear. The second problem is the mismatch of the color in light that is emitted from the CRT. Current CRT projection systems are unsatisfactory because of color gamut and phosphor persistence which were not designed with photographic papers in mind. For example, conventional CRT projection systems provide a wavelength of red that is too short. Light emitted from a CRT has a much different color temperature than is desired to properly match the color response of the photographic paper. Attempting to correct this mismatch through the use of filtering the light from the CRT can produce color cross-over. This cross-over can result in printed images that do not have true color. One attempt at resolving the aforementioned problems is to incorporate a series of red, blue, and green filters with the CRT. The photographic paper is exposed multiple times with light passing through each of the filters in order to provide good resolution in the resulting photograph. Unfortunately, such procedure is slow and inefficient, particularly when used in mass photograph production.
The use of liquid crystal display (LCD) technology as a means for projecting digital images for the printing of photographs has recently gained some popularity. However, LCD projectors could require substantial optical manipulation and to accomplish the same. Further there is a limitation to the resolution and its effect on the light output. Currently, filter wheels having red-blue-green pass filters are used in combination with some LCD projectors in order to generate a colored image on photographic paper. Alternatively, three light/filter sources may be used in place of a filter wheel to provide red-blue-green light that is used to generate the colored image. Use of either the aforementioned filter wheel or the three light/filter sources requires three separate exposures thereby more consumption of time, adds to the complexity of the projection device and creates a potential source of system error in the production of color correct photographs from digital images. Additionally, such light source/filter combinations only allow for the generation of a colored image onto photographic paper that approximates the image as acquired by the system, for example by digital scanning. No color correction is provided for by these light source/filter combinations.
Depending on the lamp house that is used to produce a photographic image on the photographic paper, color correction may be necessary in order to produce a photograph with good color quality. A method for analyzing color photographs is disclosed by U.S. Pat. No. 4,676,628 (“the '628 patent”). As described in the '628 patent, the preparation of high quality prints from color negatives encounters the problem of variations in the spectral response characteristics based on particular printing paper lots and the effects of processing variables such as chemical strength, temperatures and processing times, and negative based materials. Accordingly, when a different printing paper is used for producing photographs, conventional printers must attempt to control the color content of the photographs or produce photographs having incorrect color.
What is therefore needed is a method and apparatus for creating a digital image on photographic paper and subsequent correction of color. Further needed is a digital image printer that is capable of rapidly producing digital images on photographic paper having good clarity and sharpness and correct color content. Further needed is a digital image printer having a modular controllable digital image projection device that is easily removed and easily coupled with conventional photograph printers and presents a complete image against the photographic paper without the use of a filter wheel of multiple light/filter source.
SUMMARY OF THE INVENTION
The present invention is a method and apparatus for creating a digital image on photographic paper and subsequent correction of color. The present invention provides a digital image printer that is capable of rapidly producing digital images on photographic paper having good clarity and sharpness and correct color content. Further, the present invention provides a digital image printer having a modular controllable digital image component that is easily removed and easily coupled with conventional photograph printers and presents a complete image against the photographic paper without the use of a filter wheel or multiple light/filter source.
The present invention utilizes the technology found in liquid crystal display (LCD) video projectors, digital light processing (DLP) video projectors, and direct drive image light amplifier (DILA) video projectors. This invention corrects the color content of the images to be printed. The prese
Dougherty, Clements Hofer, & Bernard
Mathews Alan A.
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