Incremental printing of symbolic information – Light or beam marking apparatus or processes – Scan of light
Reexamination Certificate
1998-09-29
2001-05-15
Le, N. (Department: 2861)
Incremental printing of symbolic information
Light or beam marking apparatus or processes
Scan of light
C347S120000
Reexamination Certificate
active
06232997
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a vacuum fluorescent color print head for printing paper. Generally, this type of fluorescent color print head includes a red luminous block having a plurality of luminous elements arranged in a main scanning direction and red color filters disposed at light emitting ends of the luminous elements, a green luminous block having a plurality of luminous elements arranged in the main scanning direction and green color filters disposed at light emitting ends of the luminous elements, and a blue luminous block having a plurality of luminous elements arranged in the main scanning direction and blue color filters disposed at light emitting ends of the luminous elements,
2. Description of the Related Art
A fluorescent color print head for use on a photographic printer for forming color images on a photosensitive medium includes three luminous blocks, i.e. an R (red) luminous block, a G (green) luminous block and a B (blue) luminous block as disclosed in U.S. Pat. No. 5,592,205 (corresponding to Japanese Patent Laying-Open Publication H5-92622), for example. Each luminous block has filamentary electrodes acting as cathodes for releasing thermions, control electrodes, and a plurality of strip-like anode electrodes covered by phosphorous objects of a predetermined size arranged at predetermined intervals, all sealed in a vacuum case. Color filters are disposed outside the vacuum case on the paths of light beams radiating from the phosphorous objects. Generally, the phosphorous objects are formed of ZnO:Zn phosphor. As shown in
FIG. 10
, the light beams radiating from these phosphorous objects have wavelengths in a wide band of the order of 430 nm to 760 nm. Thus, a color print head for emitting light beams in the three RGB primary colors is obtained by using red, green and blue filters as color filters for the respective luminous blocks. Theremion impingement upon the phosphorous objects, i.e. light emission from the phosphorous objects, is controlled by applying a voltage to the strip-like anode electrodes and applying control signals based on image data to the control electrodes.
The above color print head has been used mainly for forming latent images on the photoreceptor drum of an optical printer. It has been proposed in recent years to apply such print head to a digital exposing device, instead of a projection type optical exposing device, for exposing photographic printing paper (hereinafter referred to simply as printing paper). However, it is difficult to achieve color reproducibility comparable to the projection type optical exposing device which has attained technological maturity.
SUMMARY OF THE INVENTION
The object of this invention is to provide a color print head which realizes color reproducibility on printing paper comparable to a projection type optical exposing device.
The above object is fulfilled, according to this invention, by a vacuum fluorescent print head for photographic printing paper comprising color filters attached to light-emitting ends of luminous elements and having transmission characteristics matching sensitivity characteristics of the printing paper with respect to colors to be transmitted. With this construction, the transmission characteristics of the RGB filters are adjusted to sensitivity characteristics of the printing paper with respect to each of RGB colors. Thus, light beams radiating from the R luminous block and having passed through the R filters accurately act only on R-sensitive layer of the printing paper. Similarly, light beams radiating from the G or B luminous block and having passed through the G or B filters accurately act only on G- or B-sensitive layer of the printing paper. This construction realizes photographic prints with excellent color reproducibility without dull coloring, which has not been achieved with conventional constructions. Color filters used in conventional color print heads have transmission characteristics smoothly extending to the increased wavelength side. Leaked light beams in a band extending to the increased wavelength side cause coloring of non-target sensitive layers printing paper. The above solution according to this invention is based on this fact found by Inventors in this application. Thus, in this invention, the transmission characteristics of the RGB filters are adjusted to the sensitivity characteristics of the printing paper with respect to each of RGB colors. As a result, light beams having passed through the filters of a particular color are stripped of components that would cause coloring of layers on the printing paper sensitive to the colors other than this particular color, thereby to prevent color dulling.
In one embodiment of this invention for simply and effectively adjusting the transmission characteristic of the RGB filters to the sensitivity characteristics of the printing paper with respect to each of RGB colors, the transmission characteristics of the color filters with respect to a particular color have a narrower band than the sensitivity characteristics of the printing paper with respect to the particular color. As used herein, the term the characteristics having a narrow band refers to characteristics having no smooth extension at either side of a reference wavelength of the particular color such as R, G or B. Consequently, light beams having passed through the filters of a particular color are suppressed from adversely affecting layers on the printing paper sensitive to the colors other than this particular color.
In a preferred embodiment of this invention, each of the color filters is changeable to suit the sensitivity characteristics of the printing paper to be exposed. This assures a high degree of color reproducibility for different types of printing paper.
Other features and advantages of this invention will be apparent from the following description of the embodiments to be taken with reference to the drawings.
REFERENCES:
patent: 4050807 (1977-09-01), Barbieri
patent: 4685807 (1987-08-01), Picard
patent: 4942424 (1990-07-01), Terashita et al.
patent: 5475506 (1995-12-01), Kwon et al.
patent: 5592205 (1997-01-01), Shimizu et al.
patent: 5764183 (1998-06-01), Vergona
patent: 5767620 (1998-06-01), Onodaka
patent: 0713328 (1995-11-01), None
Morishima Hiromichi
Nakamura Shigetaka
Fulbright & Jaworski LLP
Le N.
Nguyen Lamson D.
Noritsu Koki Co., Ltd.
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