Incremental printing of symbolic information – Light or beam marking apparatus or processes – Scan of light
Reexamination Certificate
1999-06-03
2001-05-15
Le, N. (Department: 2861)
Incremental printing of symbolic information
Light or beam marking apparatus or processes
Scan of light
C347S241000, C385S124000, C385S123000
Reexamination Certificate
active
06233001
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an image recording apparatus, and particularly to an image recording apparatus in which an optical fiber is used in a recording laser head to thereby improve the utility efficiency of energy when images, characters, etc. are recorded on a recording medium.
FIGS.
6
(
a
) and
6
(
b
) show a fundamental structure of an optical fiber. An optical fiber usually has a layer
2
called a clad portion and formed around a core portion (light transmitting portion)
1
which is circular in section. Optical fibers are roughly classified into two types, that is, a step-index type and a graded-index type. The step-index type optical fiber is designed so that the refractive index is stepwise changed in the interface between the core portion and the clad portion of the optical fiber. The refractive index of the core portion is made constant to be n
1
, while the refractive index of the clad portion is made constant to be n
2
(n
1
>n
2
). On the other hand, the graded-index type optical fiber is designed so that the refractive index of the core portion is changed gradually from the center portion toward the outer circumference. Specifically, the refractive index of the core portion takes a maximum at the center portion, which it decreases as the portion goes toward the interface with the clad portion.
FIG.
7
(
a
) shows the refractive index of the core portion and that of the clad portion in the step-index type optical fiber, and FIG.
8
(
a
) shows the refractive index of the core portion and that of the clad portion in the graded-index type optical fiber. In addition, FIG.
7
(
b
) and FIG.
8
(
b
) show intensity profiles of light emitted from the step-index type optical fiber and the graded-index type optical fiber, respectively, when the optical fiber is connected to a laser light source through a lens or the like. In the FIGS.
7
(
b
) and
8
(
b
), dashed lines indicate the refractive index of the respective core portions.
FIGS.
9
(
a
) and
9
(
b
) three-dimensionally show the intensity profiles of light emitted from the step-index type and graded-index type optical fibers respectively. That is, FIG.
9
(
a
) shows a top-hat shaped profile of laser light emitted from the step-index type optical fiber. FIG.
9
(
b
) shows a substantially Gaussian profile of laser light emitted from the graded-index type optical fiber.
In each of the laser light emission profiles of the top-hat shape and the substantially Gaussian shape shown in FIGS.
9
(
a
) and
9
(
b
), there is a problem that the energy of laser light cannot be utilized effectively. That is, though the energy could be utilized most effectively in a laser printer if the dot shape could be made square as much as possible, there is a problem that though recording can be attained only in the vicinity of the central portion of the light emission profile, it cannot be performed in the circumferential portion, because the dot shape is not completely square, as shown in FIG.
7
(
b
), FIG.
8
(
b
), and FIGS.
9
(
a
) and
9
(
b
) showing the dot shape in three dimensions, and the insufficiency of light intensity.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to solve the above problem in the related art by providing an image recording apparatus in which a laser light source and an optical fiber are used for a recording laser head so that the availability of energy can be improved when images, characters, etc. are recorded in a recording medium.
In order to achieve the above object, there is provided an image recording apparatus for recording an image on an image recording medium, comprising: a laser head for exposing the recording medium to laser light to record the image thereon; a laser light source for emitting the laser light; and an optical fiber connected between the laser light source and the laser head for guiding the laser light emitted from the laser light source to the laser head, the optical fiber having a core portion formed into a substantially rectangular shape in section, wherein a refractive index of the core portion along a first sectional axis is substantially constant and a refractive index along a second sectional axis perpendicular to the first sectional axis is gradually changed.
In the apparatus, an intensity profile of the emitted laser light from the laser light source along a first sectional axis is constant, an intensity profile along a second sectional axis perpendicular to the first sectional axis is substantially Gaussian shape, and the first and second sectional axes of the emitted laser light are made substantially coincident with the first and second sectional axes of the core portion, respectively.
In the apparatus, the second sectional axes of the emitted laser light and the core portion is substantially parallel with a main scanning direction of the recording medium.
REFERENCES:
patent: 5566267 (1996-10-01), Neuberger
patent: 5887009 (1999-03-01), Mandella et al.
patent: 6010787 (2000-01-01), Yamaguchi et al.
Fuji Photo Film Co. , Ltd.
Le N.
Pham Hai C.
Sughrue Mion Zinn Macpeak & Seas, PLLC
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