Typewriting machines – Typing by other than type-face or type-die
Reexamination Certificate
1999-11-23
2002-03-26
Hilten, John S. (Department: 2854)
Typewriting machines
Typing by other than type-face or type-die
C347S248000
Reexamination Certificate
active
06361227
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical writing printer head for printing onto sheets of photosensitive print paper, which are intermittently fed at a constant pitch (paper feeding pitch) in a paper feeding direction, by applying light energy to (exposing) the print paper when the sheets of paper are scanned in a scanning direction intersecting the paper feeding direction, and to a printer using such a printer head.
2. Description of the Related Art
The phrase “paper feeding pitch” as used herein indicates a sheet length of the print paper that is fed during a period starting from one exposure scanning operation to the subsequent exposure scanning operation while the sheets of print paper are intermittently fed in a paper feeding direction. The paper feeding pitch may be larger than a unit of length of the intermittent feed performed by a paper feeding means.
A conventional optical writing printer head of this type is provided with light source groups of three colors which are arranged in a scanning direction orthogonal to a paper feeding direction at a certain interval. The light source group of each color consists of a plurality of light sources practically having the same size which are arranged at the paper feeding pitch in the paper feeding direction. More specifically, in the conventional printer head of this type, a sub-region on a sheet of print paper is exposed to light from a first light source of one color. Then, light from a subsequent light source of the one color which is positioned at the downstream side of the paper feeding direction is further irradiated onto the sub-region while the sheet of paper is intermittently fed pitch by pitch. Thus, a print of a predetermined dot (a latent image formation) is performed. It should be noted that each light source is composed of a light source body formed of an LED (light emitting diode), and an aperture (diaphragm) formed before the light source body. The respective apertures of the light sources having substantially the same size are arranged at an equal interval along the paper feeding direction and the scanning direction, respectively.
However, in the conventional printer head of this type, as the pitch of the light sources coincides with a paper feeding pitch, the pitch of dots formed by the light sources coincides with the paper feeding pitch, so that the number of exposure controls for columns in the paper feeding direction becomes equal to or more than the number of rows in the paper feeding direction. If the print resolution (i.e., density of the dots to be printed on a sheet of print paper, or, in other words, the number of dots per unit of length in the paper feeding direction of the print paper) is high, the printing time will be hardly avoided from being long.
For example, if an exposure time per dot is 480 microseconds, the number of dots in the scanning direction is 320 dots per line, the inverse time in the scanning direction at the end of the scanning direction (the end of one row) is 0.05 seconds, and the number of dots (the number of rows) in the paper feeding direction is 144 dots, it will take the printing time of (480×320×10
−6
+0.05)×144 seconds, i.e., approximately 29.3 seconds.
SUMMARY OF THE INVENTION
The present invention has been devised in view of the foregoing drawbacks, and an object of the present invention is to provide a printer head capable of reducing the printing time in the proportion of the print resolution (dot density), and an optical writing printer using such a printer head.
This object is attained with an optical writing printer head for printing onto sheets of photosensitive print paper, which are intermittently fed at a constant paper feeding pitch in a paper feeding direction, by irradiating light onto the print paper when the paper is scanned in a scanning direction intersecting the paper feeding direction. The printer head according to the present invention is provided with a first light source group in the paper feeding direction, the first light source group including N light sources of one color which are arrayed along the paper feeding direction at the standard pitch of 1/N of the paper feeding pitch, where N is a natural number which is 2 or larger.
In the printer head according to the present invention, N light sources in the first light source group are arrayed at the standard pitch of 1/N of the paper feeding pitch along the paper feeding direction. Therefore, a simultaneous exposure (print such as a latent image formation) with N dots can be carried out using the N light sources for each pitch of the paper feed.
That is, according to the present invention, when the printer head has a print resolution identical with that of the conventional printer head, the pitch of the N light sources will coincide with the pitch of light sources in the conventional printer head. On the other hand, while the conventional printer has a pitch of the light sources in coincidence with the paper feeder pitch, the printer head of the present invention has a pitch of the N light sources corresponding to 1/N of the paper feeding pitch. Thus, the paper feeding pitch amounts to N times the paper feeding pitch in the conventional printer, so that the print speed amounts to substantially N times that of the conventional printer. In other words, with the same print resolution as that of the conventional one, a higher print speed will be attained, and the printing time will be reduced in proportion to the print resolution (dot density).
If a printer having a paper feeding pitch identical with the paper feeding pitch of the conventional printer, in the printer head of the present invention, the pitch of the N light sources equals to 1/N of the paper feeding pitch,a mounting to 1/N as compared with the pitch of the light sources in the conventional printer head which coincides with the paper feeding pitch. Therefore, the printer head of the present invention can practically print at the print resolution increased by a factor of N (dot pitch of 1/N) during the same printing time as that of the conventional one. That is, with the same printing time as that of the conventional one, a higher print resolution can be achieved, and the printing time will be reduced in proportion to the print resolution (dot density).
The phrase “standard pitch” as used herein means a minimum distance between the centers of the adjacent dots formed on the paper along the paper feeding direction (a dot pitch having the maximum resolution formed on the print paper). This coincides with a minimum distance between the centers of the adjacent light sources that form the adjacent light sources that form the adjacent dots. The “scanning direction” is typically orthogonal to the paper feeding direction, but it need not be orthogonal thereto in some cases so long as to intersect in direction. The number “N” is a natural number equal to 2 or 3, for example, but can also be 4 or more.
In terms of the N light sources, the “one color” means a color corresponding to a specific wavelength area such as red, blue or green. Note that it includes a color consisting of light in a plurality of wavelength areas, also including white color. Typically, the N light sources have the ability of emitting beams having substantially the same sectional shape, sectional area (size), angle of divergence, maximum intensity, etc., but at least any of these factors may be different in some cases.
Preferably, the first light source group includes an upstream side light source of the one color at an interval corresponding to the standard pitch positioned at the upstream side of the N light sources with respect to the paper feeding direction, and the upstream side light source has a length in the paper feeding direction equal to (N−1) times the standard pitch. The phrase “interval corresponding to the standard pitch” as used herein means an interval where the distance in the paper feeding direction between the center of the light source positioned at the most upstre
Adams & Wilks
Hilten John S.
Nolan, Jr. Charles H.
Seiko Instruments Inc.
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