Incremental printing of symbolic information – Light or beam marking apparatus or processes – Scan of light
Reexamination Certificate
2001-05-03
2003-04-22
Pham, Hai (Department: 2861)
Incremental printing of symbolic information
Light or beam marking apparatus or processes
Scan of light
C347S244000
Reexamination Certificate
active
06552741
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an optical scanning device, an optical scanning method and a photographic processing device which perform an exposing operation by scanning a photoconductive material such as a printing sheet, etc., with laser beams modulated according to image data.
BACKGROUND OF THE INVENTION
Conventionally, for the printing of a photograph, an analog exposure is adopted wherein a light beam is projected onto a photographic film, and light having passed through the photographic film is projected onto a printing sheet, thereby printing the photograph. In recent years, a digital exposure is also adopted for the printing of a photograph, wherein based on digital image data obtained by reading an image on a photographic film by a scanner, etc., or digital image data taken by a digital camera, light beam in monochrome color of red, blue or green, is projected onto a printing sheet for each pixel, thereby printing the image.
For the foregoing digital exposure, various methods have been proposed, examples of which include: a structure wherein an exposing operation is performed by scanning a printing sheet with a laser beam modulated according to image data. The image printing device of the foregoing structure includes light sources for generating laser beams in blue, green and red, and a printing operation is performed in the following procedure. First, laser beams in respective colors are modulated according to digital image data as input. The laser beams as modulated are then deflected by a deflecting system such as a polygon mirror, etc., in a main scanning direction, and the resulting deflected light beams are projected onto a printing sheet via an optical system such as an f&thgr; lens. In the meantime, an exposing operation is performed by scanning with respect to the printing sheet being moved in a sub-scanning direction, thereby printing a two-dimensional color image onto the printing sheet.
As described, in the structure of projecting laser beams in respective colors onto the printing sheet, the laser beam in each color passes through a f&thgr;-lens. Here, a lens optical system such as the f&thgr;-lens is made of a material such as glass, etc., whose refractive index varies according to a wavelength of light transmitted therethrough. Therefore, when adopting the optical system of the foregoing structure, laser beams in respective colors incident on the optical system from the same direction are output therefrom in slightly different directions. The foregoing phenomenon that light beams in respective colors which are to be projected onto the same target position are displaced is known as “aberration in color”.
Therefore, as in the foregoing structure of projecting onto the printing sheet, laser beams in respective colors incident on the same f&thgr;-lens, problems arise due to the aberration in color in that the resulting print image becomes blur, or unwanted color appears in the print image. The foregoing problem of aberration in color can be suppressed to some extent by adopting the f&thgr;-lens of highly sophisticated performance; however, the use of such f&thgr;-lens results in an increase in an overall price of a device, besides, the problem of aberration in color cannot be eliminated completely.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an optical scanning device, an optical scanning method, and a photographic processing device which perform an exposing operation by scanning a photosensitive material such as a printing sheet, etc., with laser beams modulated according to image data without a problem of aberration in color caused by a shift in light beams in respective colors from the same target position.
In order to achieve the foregoing object, an optical scanning device which performs an exposing operation by scanning with respect to a photosensitive material being moved relatively is characterized by including:
a plurality of light sources for projecting light beams respectively having different wavelengths;
a plurality of light beam modulation means for modulating the light beams emitted from the light sources respectively according to image data;
timing control means for controlling a modulation timing for each of the plurality of light beam modulation means;
deflecting means for deflecting the light beams modulated by the plurality of light beam modulation means in a main scanning direction; and
optical means for converging light beams emitted from the deflecting means onto the photosensitive material,
wherein the timing control means controls a modulation timing for each of the plurality of light beam modulation means individually.
According to the foregoing arrangement, a plurality of light beams respectively having different wavelengths as emitted from the plurality of light sources are independently modulated by the plurality of light beam modulation means according to image data, and the resulting light beams are then deflected by the deflecting means in the main scanning direction, and is focused on the photosensitive material via the optical means, thereby performing an exposing operation by scanning. Further, by the timing control means, a modulation timing by the light beam modulation means is individually controlled for each of the plurality of light beam modulation means. Therefore, even in the case where the projected positions of the light beams in respective colors corresponding to the same pixel are shifted from the target position on the photosensitive material due to, for example, differences in refractive index by optical means among the light beams, the timing control means adjusts a modulation timing for each optical beam modulation means, and it is therefore possible to adjust the respective projection positions of the light beams in respective colors. As a result, a quality image which is free from a shift in color can be exposed on a photosensitive material.
In order to achieve the foregoing object, an optical scanning method for an optical scanning device which performs an exposing operation by scanning with respect to a photosensitive material being moved relatively, which includes i) a plurality of light sources for projecting light beams having different wavelengths respectively; ii) a plurality of light beam modulation means for modulating the light beams emitted from the light sources respectively according to image data; iii) deflecting means for deflecting the light beams modulated by the plurality of light beam modulation means respectively in a main scanning direction; and iv) optical means for converging a light beam emitted from the deflecting means onto the photosensitive material, is characterized in that the plurality of light beam modulation means modulate respective light beams at different modulation timings.
According to the optical scanning device adopted in the foregoing method, a plurality of light beams respectively having different wavelengths as emitted from the plurality of light sources are independently modulated by the plurality of light beam modulation means according to image data, and the resulting light beams are then deflected by the deflecting means in the main scanning direction, and is focused on the photosensitive material via the optical means, thereby performing an exposing operation by scanning. Further, the respective modulation timings for the light beam modulation means are controlled by the timing control means for each of the plurality of light beam modulation means individually. Therefore, even when areas irradiated with the light beams corresponding to the same pixel are displaced from the target position on the photosensitive material due to differences in refractive index among respective light beams in the optical means, the timing control means adjusts a modulation timing for each optical beam modulation means, and it is therefore possible to adjust a projection area of a light beam in each color. As a result, a quality image which is free from aberration in color can be exposed on the photosensitive material.
In ord
Hayashi Hirofumi
Hirooka Jun
Kayama Yasutaka
Nakahara Fumihiro
Nixon & Vanderhye P.C.
Noritsu Koki Co., Ltd.
Pham Hai
Presta Frank P.
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