Incremental printing of symbolic information – Light or beam marking apparatus or processes – Scan of light
Reexamination Certificate
2001-11-14
2004-03-02
Pham, Hai (Department: 2861)
Incremental printing of symbolic information
Light or beam marking apparatus or processes
Scan of light
C347S248000
Reexamination Certificate
active
06700597
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to the technical field of an image recording method and an image recording apparatus, and more particularly, to an image recording technique using a group of light source elements of two-dimensional arrangement.
Mainly used in a digital image exposure system utilized in various types of printers is a so-called laser beam scan exposure (raster scan) for two-dimensionally exposing a recording medium with a laser beam modulated in accordance with an image to be recorded by deflecting the laser beam in a main scanning direction while relatively moving the recording medium and an optical system in an auxiliary scanning direction perpendicular to the main scanning direction.
In contrast, in recent years, various types of digital image exposure systems have been proposed, which use two-dimensional spatial light modulators (2DSLM) such as a liquid crystal display (hereinafter, referred to as “LCD”) and the micro mirror array (hereinafter, referred to as “MMA”) such as, for example, a digital micromirror device (trade mark hereinafter referred to as “DMD”) manufactured by Texas Instruments Inc.), which are utilized as display devices in displays, monitors and so on. In the exposure systems, a recording medium is basically exposed by forming an image displayed by the two-dimensional spatial light modulator on the recording medium.
In particular, the MMA is advantageous in exposure at high speed because the MMA has a modulation speed (response speed) faster than that of the LCD and moreover utilizes light more efficiently than the LCD.
Digital exposure systems using the spatial light modulator are disclosed in, for example, U.S. Pat. No. 5,049,901 B, EP 0992350 Al B, U.S. Pat. No. 5,132,723 B and JP 2000-19662 B.
The digital exposure systems disclosed in these publications each relate to an image recording apparatus in which an image is formed on a spatial light modulator such as the MMA in the form of an image signal and the image signal is imaged on a recording medium for recording. In the digital exposure systems, the image on the spatial light modulator is moved in synchronism with the movement or the recording medium, which is moved in a main scanning direction so that the image can remain stationary on the recording medium. This operation enables image recording of high resolution by obtaining a small recording light spot from an extended light source, which has difficulty in narrowing the area.
The principle of an image recording method using the conventional spatial light modulator will be described with reference to
FIGS. 12A
to
12
C. As shown in
FIG. 12A
, light impinges on a spatial light modulator
80
and is reflected by a mirror
80
a,
and the reflected light is imaged onto a recording medium
84
through an optical system such as a lens
82
, etc. It is assumed that the recording medium
84
moves at a constant speed as shown by the arrow shown in FIG.
12
A. In
FIG. 12A
, only the mirror
80
a
is activated and mirrors
80
b
and
80
c
are deactivated, and only the light reflected by the mirror
80
a
is imaged onto the recording medium
84
.
Next, when the recording medium
84
slightly moves as shown in
FIG. 12B
, the mirror
80
a
in the spatial light modulator
80
is deactivated and only the mirror
80
b
is activated instead in synchronism with the movement of the recording medium
84
, and the same point on the recording medium
84
as shown in
FIG. 12A
is exposed to the light reflected by the mirror
80
b.
Further, when the recording medium
84
moves as shown in
FIG. 12C
, only the mirror
80
c
in the spatial light modulator
80
is activated in synchronism with the movement of the recording medium
84
and images at the same position on the recording medium
84
.
As described above, in the illustrated example, the spatial light modulator
80
changes image signaling (moves image data) three times so that each of the mirrors
80
a,
80
b
and
80
c
exposes the recording medium
84
once, in total three times. As a result, the image is moved in synchronism with the movement of the recording medium
84
so as to remain stationary on the recording medium
84
in a main scan direction (a moving direction of the recording medium).
The (one-dimensional) movements of the mirrors concerning one pixel have been described in the above description. In reality, however, for instance, an image is recorded in the manner shown in
FIG. 13
with this conventional image recording method. A recording medium
92
is wound around the external surface of a rotating drum
90
, and image recording is performed by two-dimensionally exposing the recording medium
92
using an optical system that uses an image forming lens
96
and a two-dimensional spatial light modulator
94
(a group of two-dimensionally disposed light sources) irradiated with an illumination light flux. The rotating drum
90
rotates in the direction shown by the arrow T shown in FIG.
13
. Also, an image is two-dimensionally recorded by setting the direction shown by the arrow M shown in
FIG. 13
as the main scanning direction and setting the direction shown by the arrow S as the auxiliary scanning direction.
With the two-dimensional spatial light modulator
94
, an image to be recorded onto the recording medium
92
is divided into small segments and image recording is performed for each unit of one segment (hereinafter, referred to as the “frame”). Here, for ease of explanation, it is assumed that the two-dimensional spatial light modulator
94
includes 5×10 micromirrors. In this case, one frame is composed of 5×10 pixels. In
FIG. 13
, one frame of an image that is currently being recorded (exposed) is indicated by the reference symbol “G” and frames that have already been recorded are specified by the reference symbol “G
0
”. The rotating drum
90
continuously rotates at a constant speed in the direction of the arrow T, so that if the two-dimensional spatial light modulator
94
only exposes the frame G at the illustrated position, the recorded image of one frame G flows in accordance with the rotation of the rotating drum
90
.
In view of this problem, as shown in
FIGS. 14A
to
14
C, the image data on the two-dimensional spatial light modulator
94
is switched to have the recorded image of the frame G remain stationary on the recording medium
92
. In more detail, while data shown in
FIG. 14A
is being sent to the two-dimensional spatial light modulator
94
, the recording medium
92
moves downward in the drawing in accordance with the rotation of the rotating drum
90
. Therefore, as shown in
FIG. 14B
, image data is switched so that the image data on the two-dimensional spatial light modulator
94
is shifted downward by one pixel (downward by one line) in its entirety in synchronism with the movement of the recording medium
92
. When the recording medium
92
further moves downward by one pixel (by one line) in accordance with the rotation of the rotating drum
90
, the image data is further switched as shown in
FIG. 14C
so that the image data on the two-dimensional spatial light modulator
94
is shifted again downward by one line in its entirety.
By switching the image data on the two-dimensional spatial modulator
94
in synchronism with the rotation of the rotating drum
90
in this manner, the recorded image can remain stationary on the recording medium
92
and image flow is prevented.
Following this, when the rotating drum
90
has rotated once and image recording for one line is finished, the optical system including the two-dimensional spatial light modulator
94
or the like is moved in the auxiliary scanning direction S by one frame (by ten pixels in this example) while the rotating drum
90
is making the next rotation. Then, image recording in the main scanning direction M is performed for the next line in the same manner as above during the still next rotation of the drum
90
.
With the conventional image recording method described above, however, the image data of one frame held by the two-dimension
Fuji Photo Film Co. , Ltd.
Pham Hai
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