JP2000284205A - Exposure recording device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exposure recording device which forms a high-precision image free of image unevenness in the vertical scanning direction of a recording medium with simple constitution. SOLUTION: A laser beam L outputted by a semiconductor laser LD has the polarization direction adjusted by a 1/2-wavelength plate 30 constituting a convergence optical system 16 and is separated by a polarizing optical element 32 into ordinary light Lo and extraordinary light Le, which are guided to a recording film F. In this case, the ordinary light Lo and extraordinary light Le which are separated and converged in the vertical scanning direction (shown by arrow Y) of the recording film F are put together to form a focus point having a nearly rectangular intensity distribution, thereby forming an image which is free of unevenness in the vertical scanning direction (shown by arrow Y).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure recording apparatus that scans a recording medium with light from a light source and records an image.

[0002]

2. Description of the Related Art In the field of image recording, a laser recording apparatus for controlling the drive of a laser optical system based on a digital signal subjected to image processing and exposing and recording an image by area modulation on a recording medium is used. The recording medium on which the image has been exposed and recorded is supplied to a developing machine as necessary, and is converted from a latent image to a visible image.

Here, as the laser light source, for example, a coherent light source such as a single transverse mode semiconductor laser or an optical fiber laser, or an incoherent light source such as an optical fiber coupled laser or an array semiconductor laser capable of obtaining a high output is used. Used. In particular, semiconductor lasers having advantages such as small size, light weight, high efficiency, and long life as compared with gas lasers have been receiving attention, and laser recording apparatuses incorporating such semiconductor lasers have been developed.

When a coherent light source is used, the intensity distribution of a focused spot of a laser beam formed on a recording medium has a Gaussian distribution.

In the case of an optical fiber coupled laser, since a laser beam is guided to the vicinity of a recording medium by an optical fiber, a circular condensed spot having a substantially uniform intensity distribution can be obtained. Here, in a laser recording apparatus, a two-dimensional image is usually formed by scanning a laser beam in the main scanning direction of a recording medium conveyed in a sub-scanning manner. The energy is integrated in the main scanning direction, thereby producing an intensity distribution having a shape close to a Gaussian distribution in the sub-scanning direction.

[0006]

When the integrated intensity of the laser beam on the recording medium has a Gaussian distribution in the sub-scanning direction as shown in FIG. 13, the intensity of the laser beam fluctuates. If the position of the laser beam converging point and the recording medium deviate from each other, the integrated intensity fluctuates as shown by the characteristic A or B, so that the coloring range determined by the coloring threshold of the recording medium is a or b. And it appears as uneven image density. This uneven density is
For example, in the case of an image having a linear edge along the main scanning direction, the position of the edge fluctuates in the sub-scanning direction. Further, even when the recording medium has uneven sensitivity or the developing machine has uneven developing, the color development threshold value varies, so that image unevenness similarly appears.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above-described problems, and has a simple configuration and is capable of forming a high-precision image capable of forming a highly accurate image without causing image unevenness in a sub-scanning direction of a recording medium. It is an object to provide a recording device.

[0008]

In the exposure recording apparatus according to the present invention, when the light output from the light source is condensed on the recording medium via the condensing optical system, the light is condensed by a plurality of converging point generating means. By dividing the recording medium into a plurality of focal points and generating a plurality of focal points close to the sub-scanning direction of the recording medium, a focal point having a substantially rectangular intensity distribution in the sub-scanning direction can be formed.

In this case, since the edges on both sides of the converging point on the recording medium become sharp, the light intensity fluctuation, the fluctuation of the coloring threshold of the recording medium, the displacement between the converging point and the recording medium, etc. In addition, a high-precision image without image unevenness in the sub-scanning direction can be recorded.

The plurality of focal point generating means for generating a plurality of focal points include a polarizing optical element for separating light into two lights having different polarization directions, and a polarizing optical element for separating light into ordinary light and extraordinary light. An element, a vertex whose vertex is set on the optical axis, and a prism that splits light symmetrically in the sub-scanning direction about the optical axis can be used.

In this case, the polarization optical element can be separated by disposing the polarization optical element at a position where the light becomes a substantially parallel light flux and emitting two lights having different polarization directions in different directions. Alternatively, the polarization optical element may be disposed at a portion where light diverges or converges, and two light beams having different polarization directions may be emitted from different positions in the sub-scanning direction to be separated.

When a polarizing optical element is used, a half-wave plate or a quarter-wave plate is provided between the light source and the polarizing optical element in order to equalize the distribution of the amounts of the two separated lights. It is desirable that these can be controlled to rotate around the optical axis. When a prism is used, a half-wave plate is provided on a surface for guiding one light in the sub-scanning direction so that the polarized light does not interfere, and the polarization directions are orthogonal to each other. Is desirable.

Further, if a plurality of light sources are provided, and the light from each light source is divided by a plurality of converging point generating means and simultaneously guided to the recording medium, high accuracy without image unevenness in the sub-scanning direction can be obtained. A simple image can be recorded at high speed.

[0014]

1 and 2 show a laser recording apparatus 10 to which an exposure recording apparatus according to the present invention is applied. The laser recording apparatus 10 records an area-modulated image by irradiating a recording film F (recording medium) mounted on a drum 14 with a laser beam L output from an exposure head 12. . In addition, the drum 14 rotates in the arrow X direction (main scanning direction) on the recording film F,
The two-dimensional image is formed by moving the exposure head 12 in the arrow Y direction (sub-scanning direction). The area-modulated image is an image in which a plurality of pixels are formed on the recording film F by controlling on / off of the laser beam L, and a predetermined gradation can be obtained depending on an area occupied by the pixels.

The exposure head 12 includes a semiconductor laser LD (light source) that outputs a laser beam L of substantially linearly polarized light,
A focusing optical system 16 for focusing the laser beam L on the recording film F; As the semiconductor laser LD, a single transverse mode semiconductor laser having an intensity distribution in which the central light intensity is high and the light intensity gradually decreases as the distance from the center is increased can be used. Other light sources may be used as long as they have such an intensity distribution.

The condensing optical system 16 includes a collimator lens 28, a half-wave plate 30, a polarizing optical element 32, cylindrical lenses 34, 36, 38, from the semiconductor laser LD side.
40 and a condenser lens 42 are arranged in order. The cylindrical lenses 34 and 38 are provided with a laser beam L
Are formed only in the sub-scanning direction (arrow Y direction), and the cylindrical lenses 36 and 40 are shaped optical elements that collect the laser beam L only in the main scanning direction (arrow X direction).

The half-wave plate 30 includes the collimator lens 2
8 adjusts the polarization direction of the laser beam L composed of substantially linearly polarized light collimated by the optical axis 8.
It is set in a direction along the incident surface of the wave plate 30, and is configured to be rotatable in the direction of the arrow θ shown in FIG.

The polarizing optical element 32 is composed of two uniaxial crystals 44 and 46 whose optical axes are orthogonal to each other, and applies a laser beam L in the sub-scanning direction of the recording film F (the direction of arrow Y).
Is separated into ordinary light Lo and extraordinary light Le (Ro
For example, as shown in FIG. 3, the optical axis of the uniaxial crystal 44 disposed on the incident side of the laser beam L is set parallel to the optical axis of the laser beam L, and Is set in a direction orthogonal to the sub-scanning direction (arrow Y direction).
In this case, the ordinary light Lo travels straight through the polarization optical element 32, and the extraordinary light Le is refracted by the polarization optical element 32 in the sub-scanning direction (arrow Y direction).

In the polarization optical element 32, the direction of the optical axis of the uniaxial crystal 44 is perpendicular to the optical axis of the laser beam L, and the direction of the optical axis of the uniaxial crystal 46 is perpendicular to the sub-scanning direction (the direction of arrow Y). (Wollaston prism).

The polarization optical element 32 need not necessarily separate the laser beam L into ordinary light Lo and extraordinary light Le, but may be any element that separates the laser beam L into two lights having different polarization directions.

The laser recording apparatus 10 of this embodiment is basically configured as described above. Next, the operation and effect of the apparatus will be described.

A laser beam L modulated according to image information and output from a semiconductor laser LD is converted into a parallel light beam by a collimator lens 28, and then a half-wave plate 30
Incident on. The substantially linearly polarized laser beam L incident on the half-wave plate 30 is supplied to the polarization optical element 32 with its polarization direction adjusted. In this case, for example, 1/2
Assuming that the polarization direction of the laser beam L with respect to the direction of the optical axis of the wave plate 30 is θ, the polarization direction of the laser beam L transmitted through the half-wave plate 30 is −θ. Therefore, 1/2
By controlling the rotation of the wave plate 30 around the optical axis, the laser beam L having an arbitrary polarization direction can be converted to the polarization optical element 3.
2 can be led.

When the laser beam L supplied to the polarization optical element 32 passes through the uniaxial crystals 44, 46, the ordinary light L
o and extraordinary light Le. In this case, in the uniaxial crystal 44, since the laser beam L travels along the optical axis, it is not separated into the ordinary light Lo and the extraordinary light Le.
In the uniaxial crystal 46, since the traveling direction of the laser beam L and the optical axis are orthogonal to each other, and the direction of the optical axis is set to a direction orthogonal to the sub-scanning direction (arrow Y direction),
The ordinary light Lo goes straight, but the extraordinary light Le is refracted by a predetermined angle in the sub-scanning direction (the direction of the arrow Y) and emitted. The refraction angle φ of the extraordinary light Le can be arbitrarily adjusted depending on the thickness or the material of the polarization optical element 32 in the optical axis direction.

Here, the intensity of the ordinary light Lo and the extraordinary light Le separated in the sub-scanning direction (the direction of the arrow Y) by the polarizing optical element 32 is equal to the intensity of the half-wave plate 30 disposed in the preceding stage.
Can be adjusted to the same intensity. That is,
By controlling the rotation of the half-wave plate 30 about the optical axis and adjusting the polarization direction of the laser beam L so as to be approximately 45 ° with respect to the optical axis direction of the uniaxial crystal 46, the ordinary light Lo can be controlled. The intensity and the intensity of the extraordinary light Le can be set to be the same.

Note that, instead of the half-wavelength plate 30, a quarter-wave plate is used.
Even when the laser beam L incident on the polarization optical element 32 is configured to be circularly polarized by controlling the rotation of the quarter-wave plate about the optical axis using a wavelength plate,
Similarly, the intensity of the ordinary light Lo and the intensity of the extraordinary light Le can be set to the same value. Further, the laser beam L supplied to the condensing optical system 16 is not limited to the linearly polarized light, but may be an elliptically polarized light or a circularly polarized light.

The ordinary light Lo and the extraordinary light Le which are separated in the sub-scanning direction (arrow Y direction) and whose intensity is adjusted are shaped only by the cylindrical lenses 34 and 38 in the sub-scanning direction (arrow Y direction). Lens 3
Only the main scanning direction (the direction of the arrow X) is shaped by 6 and 40, and the light is focused on the recording film F on the drum 14 via the focusing lens 42.

In this case, on the recording film F, as shown in FIG. 4, the integrated intensity Po due to the ordinary light Lo and the ordinary light Lo
Are integrated in the sub-scanning direction (the direction of arrow Y) with the integrated intensity Pe due to the extraordinary light Le condensed close to
e is obtained. The integrated intensity P indicates the integrated intensity when the laser beam L is not separated into the ordinary light Lo and the extraordinary light Le by the polarizing optical element 32.

As can be understood from the results, the obtained integrated intensity Poe has a substantially rectangular distribution in the sub-scanning direction (the direction of arrow Y), and the edges on both sides of the converging point are sharp. Therefore, even if the intensity of the laser beam L fluctuates, or the position of the converging point of the laser beam L and the recording film F deviate from each other in the optical axis direction, the fluctuation of the coloring range c is extremely small. Image unevenness with respect to (Y direction) does not appear.

FIG. 5 shows a laser recording apparatus 5 according to another embodiment.
Indicates 0. Note that the same components as those of the laser recording device 10 shown in FIGS. 1 and 2 are denoted by the same reference numerals, and detailed description thereof will be omitted.

The condensing optical system 52 constituting the laser recording apparatus 50 is different from the converging optical system 32 shown in FIGS. 1 and 2 in that the laser beam L between the cylindrical lenses 36 and 38 is used. Is formed by arranging a uniaxial crystal 54 at a portion where divergence occurs. In this case, the direction of the optical axis of the uniaxial crystal 54 is set so as to be between the optical axis direction of the laser beam L and the sub-scanning direction (the direction of the arrow Y). Note that the uniaxial crystal 54 may be provided at a portion between the condenser lens 42 and the recording film F where the laser beam L is focused.

The laser beam L whose polarization direction is adjusted by the half-wave plate 30 and diverged in the sub-scanning direction (the direction of arrow Y) by the cylindrical lens 34 is, as shown in FIG. As a result, the light is separated into ordinary light Lo and extraordinary light Le. In this case, since the refractive index of the uniaxial crystal 54 with respect to the ordinary light Lo is constant regardless of the direction of the optical axis, the laser beam L is emitted from the virtual light emitting point fo on the optical axis and guided to the cylindrical lens 38. On the other hand, the refractive index of the uniaxial crystal 54 with respect to the extraordinary light Le differs depending on the incident direction of the laser beam L and the direction of the optical axis, and the optical axis is in the optical axis direction of the laser beam L and the sub-scanning direction (the direction of arrow Y). Are emitted from the virtual light emitting point fe displaced by a predetermined amount in the sub-scanning direction (the direction of the arrow Y) from the optical axis of the laser beam L, and are guided to the cylindrical lens 38.

As a result, the ordinary light Lo and the extraordinary light Le are
Cylindrical lenses 38 and 40 and condenser lens 42
In the sub-scanning direction on the recording film F (arrow Y direction)
4 are focused at positions shifted by a predetermined distance from each other.
Is obtained.

FIG. 7 shows a laser recording apparatus 6 according to another embodiment.
Indicates 0. Note that the same components as those of the laser recording device 10 shown in FIGS. 1 and 2 are denoted by the same reference numerals, and detailed description thereof will be omitted.

The condensing optical system 62 constituting the laser recording apparatus 60 is different from the half-wave plate 30 and the polarizing optical element 32 constituting the condensing optical system 16 shown in FIGS. A prism 64 is provided between the lens and the condenser lens 42. In this case, as shown in FIG. 8, the prism 64 has emission surfaces 66a and 66b that are symmetrically inclined in the sub-scanning direction (the direction of the arrow Y) with respect to the optical axis of the laser beam L.

Laser beam L incident on prism 64
Are refracted at the emission surfaces 66a and 66b and guided to the recording film F as two sets of laser beams L1 and L2 shifted in the sub-scanning direction (the direction of the arrow Y), and similarly have the integrated intensity shown in FIG. An intensity distribution can be obtained. Note that the incident surface side of the prism 64 may be configured as an inclined surface. Also, the inclination direction of the exit surfaces 66a, 66b or the entrance surface may be symmetrical with respect to the optical axis,
For example, the prism 64 may be configured as a concave lens.

FIG. 9 shows a half-wave plate 6 on the side of the incidence surface of the prism 64 shown in FIG.
8 is provided. In this case, the half-wave plate 68
Is set at 45 ° with respect to the polarization direction of the laser beam L, which is substantially linearly polarized, so that the polarization direction of the laser beam L1 is set at 90 ° with respect to the polarization direction of the laser beam L2. it can. Accordingly, the laser beams L1 and L2 do not interfere with each other on the recording film F, and an intensity distribution having a rectangular shape in the sub-scanning direction (the direction of the arrow Y) can be obtained.

FIG. 10 shows a laser recording apparatus 70 according to another embodiment. Note that the same components as those of the laser recording device 60 shown in FIG. 5 are denoted by the same reference numerals, and detailed description thereof will be omitted.

The condensing optical system 72 of the laser recording device 70 is configured by disposing a uniaxial crystal 74 and a half-wave plate 76 in front of the uniaxial crystal 54. Uniaxial crystal 7
4 is set so that the direction of the optical axis is between the optical axis direction of the laser beam L and the sub-scanning direction (the direction of the arrow Y), similarly to the uniaxial crystal 54. The half-wave plate 76 is
Ordinary light Lo and extraordinary light L emitted from the uniaxial crystal 74
The direction of the optical axis is set so that the polarization direction of e is rotated by 45 °.

FIG. 11 is a diagram for explaining the functions of the uniaxial crystal 74, the half-wave plate 76 and the uniaxial crystal 54. The laser beam L whose polarization direction is adjusted by the half-wave plate 30 and diverged in the sub-scanning direction (the direction of arrow Y) by the cylindrical lens 34 is, like the embodiment of FIG. 5, a uniaxial crystal. The light is separated into ordinary light Lo and extraordinary light Le by 74. Then, these ordinary light L
The o and extraordinary light Le are guided to the uniaxial crystal 54 after the polarization direction is rotated by 45 ° by the half-wave plate 76. The uniaxial crystal 54 includes the ordinary light Lo and the extraordinary light Le.
To four extraordinary lights Loo, Leo and extraordinary light Lo
After separating into e and Lee, the recording film F is guided. In this case, the ordinary light Loo, Leo and the extraordinary light Loe, which are shifted in the sub-scanning direction (the direction of the arrow Y),
The four light condensing points of Lee are formed close to each other.

By forming the four converging points close to each other in this way, an intensity distribution closer to a rectangular shape is generated than in the case where two converging points are formed, and the sub-scanning direction (arrow Y direction) ), A highly accurate image can be formed.

FIG. 12 shows a laser recording apparatus 80 according to another embodiment. Note that the same components as those of the laser recording device 10 shown in FIG. 1 are denoted by the same reference numerals, and detailed description thereof will be omitted.

The laser recording device 80 is a laser recording device 1
Similarly to the case of 0, the recording film F mounted on the drum 14 is irradiated with a laser beam output from the exposure head 82 to record an area-modulated image. In this case, the exposure head 82 has a plurality of exposure units 84 a to 84 each outputting a plurality of divided laser beams.
e. Each of the exposure units 84a to 84e
Are configured similarly to the exposure head 12 of the laser recording apparatus 10.

The laser recording device 80 thus configured
In this case, the recording film F is irradiated with the laser beam derived from each of the exposure units 84a to 84e, and an image including a plurality of main scanning lines is formed at the same time. In this case, each of the main scanning lines is formed by a converging point which shows a substantially rectangular intensity distribution in the sub-scanning direction by combining a plurality of adjacent laser beams. Therefore, a high-precision image can be recorded at high speed without causing image unevenness in the sub-scanning direction.

[0044]

As described above, according to the exposure recording apparatus of the present invention, the intensity distribution of the laser beam on the recording medium becomes substantially rectangular in the sub-scanning direction, and the edges on both sides of the converging point are formed. Since the image is sharp, it is hardly affected by a change in the coloring threshold of the recording medium, a change in the intensity of the laser beam, and the like, and image unevenness in the sub-scanning direction is suitably suppressed. As described above, with an extremely simple configuration, it is possible to form an image without causing image unevenness in the sub-scanning direction of the recording medium.

Further, by arranging a plurality of light sources in the sub-scanning direction and simultaneously recording an image with a plurality of divided lights output from each light source, a high-precision image can be recorded at a high speed.

[Brief description of the drawings]

FIG. 1 is a perspective configuration diagram of a laser recording apparatus according to an embodiment.

FIG. 2 is a plan view of the laser recording apparatus shown in FIG. 1;

FIG. 3 is a diagram illustrating the operation of the polarization optical element shown in FIG.

FIG. 4 is an explanatory diagram of an intensity distribution of a laser beam at two focal points.

FIG. 5 is a plan view of a laser recording apparatus according to another embodiment.

6 is an operation explanatory view of the uniaxial crystal shown in FIG.

FIG. 7 is a plan view illustrating a configuration of a laser recording apparatus according to another embodiment.

8 is an operation explanatory view of the prism shown in FIG. 7;

9 is an explanatory diagram of a configuration in which a half-wave plate is provided in the prism shown in FIG. 7;

FIG. 10 is a plan view of a laser recording apparatus according to another embodiment.

FIG. 11 shows two uniaxial crystals and 図 shown in FIG.
FIG. 4 is an explanatory diagram of an operation of a wave plate.

FIG. 12 is a perspective configuration diagram of a laser recording device according to another embodiment.

FIG. 13 is an explanatory diagram of occurrence of image unevenness when a conventional Gaussian intensity distribution is used.

[Explanation of symbols]

10, 50, 60, 70, 80 ... laser recording device 12, 82 ... exposure head 14 ... drum 16, 52, 62, 72 ... condensing optical system 30, 76 ... 1
/ 2 wavelength plate 32 ... Polarizing optical element 54, 74 ... Uniaxial crystal 64 ... Prism F ... Recording film (recording medium) LD ... Semiconductor laser

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) H04N 1/113 H04N 1/04 104Z 1/06

Claims (9)

[Claims] An exposure recording apparatus that scans a recording medium with light from a light source and records an image, comprising: a condensing optical system that condenses light output from the light source and guides the light to the recording medium; By dividing into a plurality of portions and generating a plurality of light-condensing points on the recording medium by the light-condensing optical system close to the sub-scanning direction of the recording medium, a substantially rectangular shape is formed in the sub-scanning direction. An exposure recording apparatus, comprising: a plurality of focal point generating means for obtaining an intensity distribution; wherein the recording medium is main-scanned by the light having a substantially rectangular intensity distribution. 2. An apparatus according to claim 1, wherein said plurality of converging point generating means is a polarization optical element for separating said light into two lights having different polarization directions. 3. The exposure recording apparatus according to claim 2, wherein the polarizing optical element separates the light into ordinary light and extraordinary light. 4. The apparatus according to claim 2, wherein the polarization optical element is disposed at a position where the light becomes a substantially parallel light flux, and emits the two lights having different polarization directions at different angles. Exposure recording device. 5. The apparatus according to claim 2, wherein the polarization optical element is disposed at a portion where the light diverges or converges, and separates the two lights having different polarization directions with respect to the sub-scanning direction. An exposure recording apparatus that emits light from a position. 6. The apparatus according to claim 2, wherein a half of the light amount between said light source and said polarizing optical element is adjusted to adjust the distribution of the amount of light emitted from said polarizing optical element.
An exposure recording apparatus provided with a wave plate or a quarter wave plate. 7. The apparatus according to claim 1, wherein the plurality of converging point generating means has a vertex set on an optical axis of the light, and symmetrically moves the light about the optical axis in the sub-scanning direction. An exposure recording apparatus, which is a prism for splitting. 8. The apparatus according to claim 7, wherein the prism is provided with a half-wave plate on one surface in the sub-scanning direction that is symmetric about the optical axis. Exposure recording device. 9. The exposure recording apparatus according to claim 1, wherein a plurality of the light sources are arranged in the sub-scanning direction.