JP2002154238A - Image recording method and apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform good image recording preventing the distortion of a recording image into a parallelogrammatic shape even if main scanning and continuous sub-scanning are performed by a two-dimensionally arranged light source group. SOLUTION: In the image recording method for recording an image on a recording medium by performing the main scanning and sub-scanning of the recording medium by an optical system using the two-dimensionally arranged light source group, the modulation data of the two-dimensionally arranged light source group is shifted to the moving direction of the recording medium in synchronous relation to the movement of the recording medium and the optical system is moved in a sub-scanning direction at a constant speed and, corresponding to the image recording position in a main scanning direction, the modulation data is shafted in the direction reverse to the moving direction of the optical system and, with respect to the main scanning direction and the sub-scanning direction, the image is made relatively stationary with respect to the recording medium to suppress the distortion of the recording image into a parallelogrammatic shape.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention belongs to the technical field of an image recording method and apparatus, and more particularly, to an image recording technique using a two-dimensionally arranged light source group.

[0002]

2. Description of the Related Art In a digital image exposure system used in various printers and the like, a laser beam is deflected in a main scanning direction and a recording medium and an optical system are moved in a sub scanning direction orthogonal to the main scanning direction. By moving relatively,
The so-called laser beam scanning exposure (raster scan), in which a recording medium is two-dimensionally exposed with a laser beam modulated according to a recorded image, is mainly used.

On the other hand, in recent years, a two-dimensional space such as a liquid crystal display (hereinafter, referred to as an LCD) or a digital micromirror device (hereinafter, referred to as a DMD) has been used as a display means in a display or a monitor. Various digital image exposure systems using light modulation elements have been proposed. In this exposure system, the recording medium is basically exposed by forming an image displayed by the two-dimensional spatial light modulator on the recording medium. In particular, DMD is L
Since the modulation speed (response speed) is higher and the light use efficiency is higher than that of CD, it is advantageous for high-speed exposure.

A digital exposure system using such a spatial light modulator is disclosed in, for example, US Pat. No. 5,049,901, US Pat.
No. 5,132,723 or JP-A-2000-19662. All of the publications disclosed in these publications relate to an image recording apparatus that forms an image formed by an image signal on a spatial light modulation element such as a DMD on a recording medium and records the image. By moving the image on the spatial light modulator in accordance with the movement of the recording medium to be performed, the image on the recording medium is stopped, and thus, using a light source that is wide and difficult to reduce, A small recording beam is obtained to enable high-resolution image recording.

The principle of an image recording method using this conventional spatial light modulator will be described with reference to the drawings. As shown in FIG. 7, light from a light source (not shown) is reflected by a spatial light modulator 80, and recording light for carrying an image is converted to an image forming lens 82.
An image 86 is formed on the recording medium 84 via the. The recording medium 84 is moving at a constant speed as shown by the arrow A in the figure. Therefore, if one image 86 is continuously exposed, the image 86 flows as the recording medium 84 moves. Therefore, the image 86 is relatively stopped on the recording medium 84 as follows.

That is, as shown in FIG. 8A, G0, G1, G2, G3,.
, H0, H1, ..., I0, ..., J0, ...
, K0,..., And image recording is performed using the modulated data. G0,
The arrangement direction (column direction) of the pixels H0, I0, J0, and K0 coincides with the movement direction A of the recording medium 84, and G
It is assumed that the arrangement direction (row direction) of pixels 0, G1, G2, G3,... Is a direction perpendicular to the moving direction A of the recording medium 84. At this time, since the recording medium 84 is moving downward (in the direction of arrow A) in FIG. 8A, if the spatial light modulator 80 holds the modulated data as it is, Flows in the moving direction of the recording medium 84.

Therefore, when the recording medium 84 moves downward by one pixel, the spatial light modulator 80 as shown in FIG.
Above, the modulation data is shifted down by one line. That is, the modulation data G0, G1,.
.. Are shifted to the second row, and other modulation data are also shifted down by one row. And one more
In the row, the next modulated data F0, F1, F2, F3,.
・ Is sent. When the recording medium 84 is further moved down by one pixel, the modulated data is shifted down by one line on the spatial light modulator 80 as shown in FIG. E0, E1, E2,
... is introduced. As described above, by shifting the modulation data on the spatial light modulator in accordance with the movement of the recording medium, the image can be relatively stationary on the recording medium.

[0008]

However, in the above-described conventional image recording method, the scanning direction is one-dimensional.
An image is relatively stationary only with respect to the movement in the dimensional direction. If this method is to be applied as it is to a two-dimensional scan represented by, for example, an external cylindrical recording device, the following description will be given. Such a problem is that the recorded image is distorted into a parallelogram.

That is, as shown in FIG. 9, a recording medium 98 is wound around the outer surface of a rotating drum 96, and the light reflected by the spatial light modulator 90 is imaged on the recording medium 98 by an imaging lens 92. To record the image. The rotating drum 96 rotates in the direction of the arrow T, and the rotating direction of the rotating drum 98 is defined as the main scanning direction M, and the direction of the rotating shaft perpendicular to this is defined as the sub-scanning direction S. An optical system including the spatial light modulation element 90, the imaging lens 92, and the like is installed on the sub-scanning conveyance unit 94, and moves in the sub-scanning direction S.

While the modulation data is controlled as described above while the rotating drum 96 makes one rotation, the modulation data is shifted in the one-dimensional direction on the spatial light modulation element 90 while the image 99 in the first column is shifted.
Record a. At this time, the optical system does not move in the sub-scanning direction while recording the image 99a in the first column.
When the image recording of the first row is completed, the optical system is moved in the sub-scanning direction S during the next rotation of the rotating drum 96, and the image 99b of the second row is recorded by the next rotation of the rotating drum 96. In the so-called step-and-repeat recording method, the recording is performed once (for one row) while the rotating drum rotates twice.
The recording efficiency is very poor because only recording is possible.

Therefore, while the optical system is moved in the sub-scanning direction S at a constant speed by the sub-scanning conveyance means 94, image recording is continuously performed. At this time, if the modulation data is simply shifted one-dimensionally only in the main scanning direction M on the spatial light modulation element 90 as in the related art, the recorded image 99 is recorded on the recording medium 98 as shown in FIG. There is a problem that the shape is distorted into a parallelogram.

The present invention has been made in view of the above-mentioned conventional problems. For example, an optical system using a two-dimensionally arrayed light source group such as a spatial light modulator that reflects light from a light source is provided. When recording an image by scanning two-dimensionally, an image recording method and apparatus capable of performing good image recording without causing a recorded image to be distorted in a parallelogram shape even when performing continuous sub-scanning. The task is to provide.

[0013]

According to a first aspect of the present invention, there is provided an optical system using a two-dimensionally arranged light source group. A recording medium that moves relatively at a constant speed is main-scanned in the moving direction of the recording medium, and the optical system is moved relatively to the recording medium in a sub-scanning direction substantially orthogonal to the main scanning direction. An image recording method for recording an image on the recording medium by sub-scanning, wherein the modulation data of the two-dimensionally arranged light source group is synchronized with a movement of the recording medium, and the two-dimensional On the light source group arranged in the direction, the image is shifted in the moving direction of the recording medium, the image is relatively stopped with respect to the recording medium in the main scanning direction, and the optical system is moved at a constant speed in the sub-scanning direction. Move in the main scanning direction According to the image recording position, the modulated data is shifted in the direction opposite to the moving direction of the optical system on the two-dimensionally arranged light source group, and the image is also shifted in the sub-scanning direction. An image recording method is provided in which an image recorded on the recording medium is restrained from being distorted into a parallelogram by being relatively stationary with respect to the recording medium.

In the image recording method, it is preferable that a spatial light modulator that reflects an illumination light beam from the light source is used as the two-dimensionally arranged light source group.
It can also be realized by using a transmission type spatial light modulation element.

[0015] Similarly, in order to solve the above-mentioned problems,
A second aspect of the present invention is an optical system using a two-dimensionally arranged light source group, and the optical system moves relative to the optical system at a constant speed in a fixed direction, and the optical system performs the movement. A recording medium on which an image is recorded two-dimensionally while being main-scanned in the direction and sub-scanning in a direction substantially orthogonal to the main scanning direction, and modulation data control for controlling modulation data supplied to the light source group Means, and a sub-scanning drive means for moving the optical system at a constant speed in the sub-scanning direction relative to the recording medium, and in synchronization with the movement of the recording medium, the two-dimensionally On the arrayed light source group, the modulation data is shifted in the moving direction of the recording medium, and the image is relatively stationary with respect to the recording medium in the main scanning direction, and the image is recorded in the main scanning direction. Depending on the position, the modulation data Is shifted in the direction opposite to the moving direction of the optical system on the two-dimensionally arranged light source group, so that the image is relatively stationary with respect to the recording medium also in the sub-scanning direction. Accordingly, there is provided an image recording apparatus characterized in that an image recorded on the recording medium is prevented from being distorted into a parallelogram.

In the image recording apparatus, it is preferable that a spatial light modulator that reflects an illumination light beam from the light source is used as the two-dimensionally arranged light source group.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an image recording method and apparatus according to the present invention will be described in detail based on preferred embodiments shown in the accompanying drawings.

FIG. 1 is a block diagram showing a schematic configuration of an embodiment of an image recording apparatus for performing an image recording method according to the present invention. The image recording apparatus 10 in the illustrated example uses a so-called outer drum (external drum) as a two-dimensionally arranged light source group using a DMD (digital micromirror device) which is a two-dimensional spatial light modulator illuminated by an illumination light beam. ) Is a device for recording an image by two-dimensionally scanning and exposing a recording medium mounted on the recording medium.

In FIG. 1, an image recording apparatus 10 includes a rotating drum 14 on which a recording medium 12 is mounted on its outer surface,
6. DMD that reflects the illumination light beam emitted from light source 16
18, a sub-scanning driving means 20 for mounting these optical systems thereon and moving them in the sub-scanning direction,
And a main scanning position detecting unit 24 and a sub-scanning position detecting unit 26 for detecting a timing signal for controlling the modulation data. ing.

Rotary drum (hereinafter simply referred to as drum) 1
Reference numeral 4 denotes a cylinder around which the recording medium 12 is wound around the outer surface and which rotates around the axis at a constant speed in a direction indicated by an arrow T in the figure. As the recording medium 12, for example, an optical mode light-sensitive material, a heat mode light-sensitive material, and the like are exemplified. The recording medium 12 is not particularly limited, and may be a film or a plate, or a cylindrical medium having sensitivity to light or heat. As shown by the arrow in the drawing, a direction that coincides with the rotation direction of the drum 14 is defined as a main scanning direction M, and a direction that coincides with the axial direction of the drum 14 orthogonal to the direction is defined as a sub-scanning direction S.

An optical system for recording an image on the recording medium 12 includes:
The light source 16 is provided on the sub-scanning driving means 20, and includes a DMD 18 which is a two-dimensional spatial light modulator. As the light source 16, various light sources according to the spectral sensitivity of the target recording medium 12 can be used as long as the light source 16 can emit a sufficient amount of light. For example, if the recording medium is a plate making film or PS plate having sensitivity to visible light or ultraviolet light, an ultra-high pressure mercury lamp, a metal halide lamp, or the like may be used. For a heat mode film or PS plate having sensitivity to infrared light, an infrared broad area laser diode or the like may be used. In addition, LEDs, halogen lamps, xenon lamps, fiber lasers, solid-state lasers, and the like can be used according to the recording medium.

The DMD 18 is a two-dimensional spatial light modulator in which rectangular micromirrors that can rotate (oscillate) at a predetermined angle about a predetermined rotation axis are two-dimensionally arranged. Is rotated to turn on / off the exposure for each micromirror (= pixel) to modulate the light. Such a DMD 18 is formed on a silicon chip by a micro-machine technology applying a semiconductor device manufacturing process. The size of the DMD 18 is not particularly limited. For example, the pixel interval is 17 μm,
A DMD of 1024 pixels × 1280 pixels is exemplified. The spatial light modulator as a two-dimensionally arranged light source group used in the present invention includes a DMD as shown in the illustrated example.
The liquid crystal type, the PLZT type, the EO type, the AO type and the like are not limited to 18, and various types can be used. However, among them, DMD is most preferable in terms of modulation speed, light use efficiency, and the like.

The light emitted from the light source 16 and reflected by the DMD 18 forms an image on the recording medium 12 via a collimator lens and focusing lens (not shown). These optical systems are integrally formed, mounted on a sub-scanning drive unit (sub-scanning unit) 20, and continuously move at a constant speed in the sub-scanning direction S.

The DMD 18 is provided with modulation data control means 22 for switching the control pattern and supplying image data (modulation data) for each frame to the DMD 18. The modulation data control unit 22 generates modulation data from an input image signal, supplies the generated modulation data to the DMD 18, and controls the modulation data. In order to determine the timing for controlling the modulation data, the main scanning position detecting means 2
4 is provided on the drum 14. As the main scanning position detecting means 24, for example, a rotary encoder for detecting the rotational position of the drum 14 can be used. In order to detect the sub-scanning position, a sub-scanning position detecting means 2 is provided.
6 is provided in the sub-scanning drive unit 20.

Hereinafter, the operation of the image recording apparatus 10 of the present embodiment will be described with reference to the drawings. In the present embodiment, in order to record one image (the entire image recorded on one recording medium), the entire image is divided into small parts, and one small part is defined as one frame. It is assumed that not all of the DMD 18 is used to record a frame, but only a portion thereof.

FIG. 2 shows one row (a portion where an image is recorded by one rotation of the drum 14) of an image recording range of the recording medium 12.
0 shows how frames 30a to 30e are image-recorded. However, in this figure, the frames are displayed with a space between them for easy viewing, but actually, the frames are not necessarily empty. In the figure, the rotation direction of the drum 14, that is, the moving direction of the recording medium 12 is the direction indicated by the arrow T, the main scanning direction is M, and the sub-scanning direction is S. In the figure, the row 30 is obliquely tilted because the optical system is continuously moved in the sub-scanning direction, and thus the image is distorted as described above unless the modulation data is controlled in the sub-scanning direction. It indicates that.

In the present embodiment, the relative movement of the optical system and the recording medium 12 in the main scanning direction and the sub-scanning direction in order to prevent the image from being distorted in a parallelogram shape in the image recording using the outer drum method. The modulation data is shifted on the DMD 18 accordingly. For example, when recording the frame 30a in FIG. 2, it is assumed that modulated data is given to the DMD 18 and recorded as shown by hatching in FIG. When recording this frame 30a, the drum 14
Always rotates, and the recording medium 12 is moving in the direction of arrow T in FIG. Therefore, as shown in FIG. 8, in synchronization with the movement of the recording medium 12, the modulation data is shifted by the modulation data control means 22 in the direction opposite to the main scanning direction.

When the drum 14 rotates by one frame, the next frame 30b is supplied onto the DMD 18. At this time, the image flows in the sub-scanning direction,
In order to prevent the recorded image from being distorted into a parallelogram, according to the image recording position in the main scanning direction, as shown in FIG.
On the DMD 18, the modulation data (image data for recording the frame 30b) is shifted by the modulation data control means 22 in the direction opposite to the sub-scanning direction. At this time, the recording position in the main scanning direction is detected by the main scanning position detecting means 24,
The position in the sub-scanning direction is detected by the sub-scanning position detecting means 26. The modulation data is shifted in the direction opposite to the sub-scanning direction in accordance with the position in the main scanning direction. The relationship between this position and the shift amount will be described in detail later. That is, the rotational speed of the drum 14), the moving speed of the optical system in the sub-scanning direction, the size of the recording medium 12 (diameter of the drum 14), the recording pixel size, and the DMD1.
8 and the like.

Hereinafter, similarly, FIG.
As shown in FIG. 3C, the modulation data is shifted, the frame 30b shown in FIG. 2 is recorded, and as shown in FIG.
The frame 30d shown in FIG. 2 is recorded by shifting onto the MD 18, and the modulated data is shifted onto the DMD 18 as shown in FIG. In FIG. 2, the frames are displayed with a space between each frame. However, in actuality, recording is continuously performed without any gap, and a recorded image without distortion in a parallelogram shape is obtained.

FIG. 4 shows an example of a method of shifting modulated data. Another frame is a DMD18 as shown in FIG.
It is assumed that modulation data is supplied above. As the drum 14 rotates, the recording medium 12 moves downward in the figure (main scanning direction).
, And the modulation data is also synchronized with this in FIG.
Shift downward as in (b). To shift the modulation data down, new modulation data is introduced in the top row. Hereinafter, the modulation data is shifted in the main scanning direction (the opposite direction to the main scanning direction) until the recording medium 12 moves down by one frame, so that the image does not flow in the main scanning direction.

Then, the shift of the modulation data in the direction opposite to the main scanning direction is continued, and when the main scanning position detecting means 24 detects that the shift is just one frame, as shown in FIG. The modulation data is shifted leftward (in the direction opposite to the sub-scanning direction) in the figure (one pixel in the illustrated example). Now, FIG.
The frame next to (a) (for example, the top frame in one row in FIG. 2) is recorded. By performing image recording in this manner, as shown in FIG. 5, a recorded image having a substantially straight left end without being distorted into a parallelogram shape as shown by oblique lines on the recording medium 12 as shown in FIG. can get.

By the way, in the example described above, the amount of one shift of the modulation data in the sub-scanning direction is one pixel, but is not limited to one pixel. Of course, shifting only one pixel is preferable because the left end looks almost linear. As shown in FIG. 6, the shift amount is represented by L, the number of pixels in the main scanning direction in the image recording range of the recording medium 12,
Assuming that the size of one frame recorded by the DMD is M pixels in the main scanning direction and N pixels in the sub scanning direction, the following calculation is performed.

That is, when printing for one row is completed and the printing for the next row is started, it must be shifted by one frame in the sub-scanning direction. At this time, since L / M = n frames are recorded in one row in the main scanning direction, when shifting the modulation data for one frame in the sub-scanning direction, shifting is performed so that N / n = n0 pixels are shifted. It will be good. In the example described above, while the recording medium moves by one frame in the main scanning direction,
The modulation data is not shifted in the sub-scanning direction. However, depending on the relationship between the rotational speed of the drum and the moving speed in the sub-scanning direction, etc., even during the movement by one frame in the main scanning direction, the modulation data is not shifted in the sub-scanning direction. The modulation data may be shifted. If the shift is made as fine as possible, the control is more difficult, but the recorded image becomes smoother and more linear.

As described above, according to the present embodiment, the modulation data is shifted in the main scanning direction in synchronization with the movement of the recording medium, and also in the sub-scanning direction according to the recording position in the main scanning direction. Since the modulation data is shifted, it is possible to obtain a good recorded image without being distorted into a parallelogram. Further, since one pixel of the recorded image is formed by multiple exposure of a plurality of spatial light modulation elements, even if a part of the spatial light modulation element has a defect, it is hardly noticeable, It is also possible to eliminate the influence of defective pixels on the recorded image by making corrections such as changing the recording time with a portion having no defect.

Although the image recording method and apparatus of the present invention have been described in detail above, the present invention is not limited to the above examples, and various improvements and modifications can be made without departing from the scope of the present invention. Of course, you may.

[0036]

As described above, according to the present invention, the modulation data is shifted in the main scanning direction in synchronization with the movement of the recording medium, and according to the recording position in the main scanning direction,
Since the modulation data is shifted also in the sub-scanning direction, it is possible to obtain a good recorded image without being distorted into a parallelogram.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a schematic configuration of an embodiment of an image recording apparatus that performs an image recording method according to the present invention.

FIG. 2 is an explanatory diagram illustrating an image recording method according to the embodiment.

FIG. 3 (a), (b), (c), (d), (e)
FIGS. 4A and 4B are explanatory diagrams showing the manner in which modulated data is shifted in the present embodiment.

FIGS. 4 (a), (b), and (c) are explanatory diagrams showing a manner in which modulated data is shifted in the same embodiment.

FIG. 5 is an explanatory diagram illustrating an example of a recorded image in the present embodiment.

FIG. 6 is an explanatory diagram illustrating a method of calculating a shift amount of modulation data according to the present embodiment.

FIG. 7 is a schematic configuration diagram showing a conventional image recording apparatus.

FIGS. 8A, 8B and 8C are explanatory diagrams showing a method of shifting modulated data in a conventional image recording method.

FIG. 9 is a schematic configuration diagram illustrating an example of an outer cylindrical recording device (an outer drum type image recording device).

FIG. 10 is an explanatory diagram showing a problem in a conventional image recording method.

[Explanation of symbols]

 REFERENCE SIGNS LIST 10 image recording device 12 recording medium 14 rotating drum 16 light source 18 DMD (digital micromirror device) 20 sub-scanning drive unit 22 modulation data control unit 24 main scanning position detection unit 26 sub-scanning position detection unit

Claims (4)

[Claims] An optical system using a light source group arranged two-dimensionally scans a recording medium that moves relatively to the optical system in a fixed direction at a constant speed in a main scanning direction of the recording medium. An image recording method for recording an image on the recording medium by moving the optical system relative to the recording medium and performing sub-scanning in a sub-scanning direction substantially orthogonal to the main scanning direction. The modulation data of the two-dimensionally arranged light source group is shifted in the moving direction of the recording medium on the two-dimensionally arranged light source group in synchronization with the movement of the recording medium, and the main scanning is performed. With respect to the direction, while the image is relatively stationary with respect to the recording medium, the optical system is moved at a constant speed in the sub-scanning direction, and according to the image recording position in the main scanning direction, the modulation data is Two-dimensional array The light source group is shifted in the direction opposite to the moving direction of the optical system, and the image is recorded on the recording medium in the sub-scanning direction so that the image is relatively stationary with respect to the recording medium. An image recording method for suppressing distortion of an image to be formed into a parallelogram. 2. The light source group arranged two-dimensionally,
2. The image recording method according to claim 1, wherein a spatial light modulator that reflects or transmits an illumination light beam from a light source is used. 3. An optical system using a light source group arranged two-dimensionally, and relatively moving at a constant speed in a fixed direction with respect to the optical system, and main scanning in the moving direction by the optical system. And a recording medium that is sub-scanned in a direction substantially orthogonal to the main scanning direction to record a two-dimensional image, a modulation data control unit that controls modulation data supplied to the light source group, A sub-scanning driving means for moving the optical system at a constant speed in the sub-scanning direction relative to the recording medium; and the two-dimensionally arranged light sources in synchronization with the movement of the recording medium. On the group, the modulation data is shifted in the moving direction of the recording medium, and the image is relatively stationary with respect to the recording medium in the main scanning direction, and according to the image recording position in the main scanning direction. , The modulated data On the two-dimensionally arranged light source group, the optical system is shifted in the direction opposite to the moving direction, and also in the sub-scanning direction, the image is relatively stationary with respect to the recording medium. An image recording apparatus for suppressing an image recorded on the recording medium from being distorted into a parallelogram. 4. The light source group arranged two-dimensionally,
4. The image recording apparatus according to claim 3, wherein a spatial light modulator that reflects or transmits an illumination light beam from a light source is used.