JP2002196428A - Method and apparatus for exposure recording - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily and efficiently obtain a high quality image while preventing the loss of light and the fluctuation of width of a beam spot on a recording medium. SOLUTION: A far-field pattern of a laser beam L emitted from a semiconductor laser 18 is refined by an aperture member, and then the aperture image is formed on a photosensitive material F. An exposure recording time for forming one pixel in the main scanning direction shown by the arrow X is controlled, and thereby the amount of light is adjusted, and the high quality image with uniformity is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of exposing an image by forming an image of a far field pattern of a light beam modulated in accordance with image information on a recording medium, and performing main scanning and sub scanning on the recording medium. The present invention relates to an exposure recording method and apparatus for recording.

[0002]

2. Description of the Related Art In the field of image recording, a laser recording apparatus which controls the driving of a laser optical system based on an image signal and exposes and records an image by area modulation on a recording medium is used. A recording medium such as a film on which an 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.

FIG. 1 shows a schematic configuration of such a laser recording apparatus. The laser beam L modulated according to the image signal and output from the light source 2 such as a laser diode is shaped by the aperture 4 and then formed into an image forming optical system 6.
Thus, the aperture image of the aperture 4 is formed on the photosensitive material F. In this case, the laser beam L forms a two-dimensional image by scanning the photosensitive material F in the main scanning direction in a direction perpendicular to the drawing and by sub-scanning in the arrow Y direction.

In the case of a laser beam L having a Gaussian intensity distribution as shown in FIG. 2, when the amount of light emitted from the light source 2 increases or decreases, as shown by the intensity distributions of the characteristics α and β, the spread range of the beam fluctuates. I do. In this case, for example, assuming that the coloring threshold value of the photosensitive material F is a value indicated by a dashed line,
In the characteristic α, the width of the beam spot on the photosensitive material F by the laser beam L passing through the opening 4 is regulated by the opening 4 to be a range a. On the other hand, in the characteristic β, the width of the beam spot on the photosensitive material F is
Is smaller than the width b. Therefore, in the case of the laser beam L having the light emission amount having the characteristic β, the beam spot shape cannot be shaped by the opening 4.

Further, as the light source 2, there is a so-called broad area light source having a wide intensity distribution in one scanning direction and a narrow intensity distribution in the other scanning direction. The far field pattern of the laser beam L output from the broad area light source has an intensity distribution as shown in FIG. In the case of this light source, when the amount of emitted light increases or decreases, the emission angle with respect to a wide direction of the intensity distribution increases or decreases. As a result, as shown in the intensity distribution of the characteristics γ and δ,
The spread range of the beam fluctuates. Therefore, in the characteristic γ,
The width of the beam spot on the photosensitive material F is regulated by the opening 4 and becomes a range c, and the characteristic δ becomes a range d regardless of the presence or absence of the opening 4.

FIG. 4 shows that a laser beam L having a different intensity distribution is output from the light source 2 as described above, and the photosensitive material F is exposed to the same exposure time t (width Δx in the main scanning direction (arrow X direction)) in the main scanning direction. FIG. 3 schematically illustrates pixel areas s1 to s5 of one pixel formed on the photosensitive material F when scanning is performed at a constant value. In this case, in the range of the light emission amounts a1 to a3, the width Δy in the sub-scanning direction (the direction of the arrow Y) is regulated by the opening 4, so that regardless of the light emission amounts a1 to a3,
Constant pixel areas s1 to s3 can be obtained.

On the other hand, a light emission amount a equal to or less than a predetermined amount
4 and a5, the opening 4 cannot regulate the width Δy in the sub-scanning direction (the direction of the arrow Y), and the pixel areas s4 and s5 fluctuate depending on the light emission amounts a4 and a5. . As a result, a desired density cannot be obtained in the area-modulated image.

Here, the intensity distribution of the laser beam L output from the light source 2 generally differs due to individual differences between the individual light sources 2. Therefore, in order to mainly absorb the individual difference, the beam spot is shaped so as to have a constant beam spot shape by using the aperture 4 having a fixed aperture width. , FIGS. 2 and 3
As shown in the characteristics β and δ, the width of the beam spot on the photosensitive material F may be reduced. In this case, a scanning line having a desired line width cannot be formed, which causes a deterioration in image quality. On the other hand, if the opening width of the opening 4 is set to be sufficiently small, there is no possibility of being affected by the fluctuation of the amount of emitted light. Will increase. Therefore, the light source 2 that can output the laser beam L with higher power is required, but there is a possibility that such a light source 2 cannot be obtained.

On the other hand, the sensitivity of the photosensitive material F generally varies depending on the type of the photosensitive material F, so it is necessary to individually adjust the sensitivity so as to obtain the optimum amount of received light for coloring. Also,
Since the color development range varies depending on the concentration of the developing solution after exposure, it is necessary to adjust the amount of received light in consideration of the influence. In this case, the amount of received light can be adjusted by controlling the amount of light emitted from the light source 2. However, when the amount of emitted light is adjusted, as described above, the beam spot width fluctuates, There is a problem that the laser beam L is greatly shaken and a light amount loss occurs.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems, and has no fluctuation in beam spot width or loss of light amount on a recording medium, and can easily produce high-quality images. An object of the present invention is to provide an exposure recording method and apparatus which can be obtained efficiently.

[0011]

An exposure recording method according to the present invention forms an image of a far-field pattern of a light beam modulated in accordance with image information on a recording medium, and scans the recording medium by main scanning and sub-scanning. In an exposure recording method for exposing and recording an image by scanning, an exposure amount is adjusted by controlling an exposure recording time for exposing one pixel in the main scanning direction of the light beam.

The exposure recording apparatus according to the present invention forms an image of a far field pattern of a light beam modulated according to image information on a recording medium, and performs main scanning and sub scanning on the recording medium. An exposure recording apparatus for exposing and recording an image, comprising an exposure recording time control means for controlling an exposure recording time for exposing one pixel in the main scanning direction of the light beam, and controlling an exposure amount by controlling the exposure recording time. It is characterized by performing.

In this case, a pixel having a desired shape is formed by controlling an exposure recording time for exposing one pixel to a recording medium, instead of adjusting a light emission amount of a light beam output from a light source. Can be. It should be noted that the exposure recording time is set by dividing it into a plurality of parts, the total recording time of one pixel is adjusted according to the desired amount of received light, and the period from the start of recording of one pixel to the completion of recording is controlled to be constant. By doing so, the pixel shape can be made constant.

[0014]

FIG. 5 and FIG. 6 show a laser recording apparatus 10 to which the exposure recording method and apparatus of the present invention are applied. The laser recording apparatus 10 records an area-modulated image by irradiating a plurality of laser beams L emitted from an exposure head 12 to a photosensitive material F (recording medium) mounted on a drum 14. It is. A two-dimensional image is formed on the photosensitive material F by moving the exposure head 12 in the sub-scanning direction (Y direction) with respect to the drum 14 rotating in the main scanning direction (X direction). Further, the area-modulated image means that a plurality of pixels are formed on the photosensitive material F by controlling on / off of a laser beam L according to image information, and a predetermined gradation is obtained according to an area occupied by the pixels. Image.

The exposure head 12 is composed of a plurality of light source units 16A to 16N arranged in the sub-scanning direction (the direction of arrow Y). Each of the light source units 16A to 16N includes a semiconductor laser 18 (light source) that outputs a laser beam L modulated according to image information, a collimator lens 20 that collimates the laser beam L, and a collimator lens 20.
Opening 24 located at the focal position of the laser beam L
, The width of which in the sub-scanning direction (the direction of arrow Y) is adjusted to form parallel light beams, cylindrical lenses 26 and 28, a half mirror 30 for detecting the amount of light received by the photosensitive material F of the laser beam L, and the laser beam L And an imaging lens 32 that condenses light on the photosensitive material F.

As the semiconductor laser 18, a broad area laser diode (BLD), which is a broad area light source in which the intensity distribution of the laser beam L is wide in the sub-scanning direction (arrow Y direction) and narrow in the main scanning direction (arrow X direction), is used. Can be used. In this case, the active layer of the semiconductor laser 18 is
It is set so as to be horizontal with the sub-scanning direction (arrow Y direction).

The collimator lens 20 includes the semiconductor laser 1
The far field pattern of the laser beam L output from 8 is imaged at the position of the opening 24. That is, as shown in FIG. 7, the semiconductor laser 18 is set so that the position of the focal distance f from the front principal point of the collimator lens 20 becomes the light emitting portion of the laser beam L, and the opening 24 is
The collimator lens 20 is set so as to be located at a focal distance f from the rear principal point position of the collimator lens 20.

The aperture 24 is provided with a laser beam L
Is restricted in the main scanning direction (arrow X direction) and the sub-scanning direction (arrow Y direction).

Above the half mirror 30, a photo sensor 36 is provided. The photo sensor 36 detects the light amount of each laser beam L guided by the half mirror 30. In addition, as a method of detecting the light amount of the laser beam L,
As shown in FIG. 6, the light source units 16 </ b> A to 16 </ b> N may detect the light amount and convert the detected value into the light amount on the drum 14. The detection may be performed directly on the drum 14.

FIG. 8 is a block diagram of a control circuit of the laser recording apparatus 10. The control circuit controls the entirety of the laser recording apparatus 10 (an exposure recording time control unit).
A drum rotation motor 42 that drives the drum 14 to rotate based on a control signal from the control unit 40, an encoder 44 that detects the rotation position of the drum 14, and an image memory that stores image information to be recorded on the photosensitive material F. 46, a light source driving unit 48 for driving the semiconductor laser 18 based on image information
And a setting unit 50 for setting the exposure recording time by the semiconductor laser 18 based on the amount of light detected by the photo sensor 36. The description of the moving means for moving the exposure head 12 in the sub-scanning direction (the direction of the arrow Y) is omitted.

The laser recording apparatus 10 according to the present embodiment is basically configured as described above. Next, the operation and effect thereof will be described.

First, a schematic operation of the laser recording apparatus 10 will be described.

5 to 8, the control unit 40 drives a drum rotation motor 42, thereby
Rotate in the main scanning direction (arrow X direction). The main scanning position, which is the rotation position of the drum 14, is detected by the encoder 44. The control unit 40 reads out image information from the image memory 46 based on the detected main scanning position and supplies the image information to the light source driving unit 48.

The light source driving section 48 drives the semiconductor laser 18 according to the image information read from the image memory 46. The laser beam L output from the semiconductor laser 18 modulated according to the image data is applied to a collimator lens 20.
After that, the far field pattern is imaged at the position of the opening 24. The far-field pattern shaped by the opening 24 is beam-shaped in the sub-scanning direction (the direction of the arrow Y) by the cylindrical lenses 26 and 28, and the aperture image of the opening 24 is formed by the imaging lens 32 on the photosensitive material F. Imaged on top.

In this case, the drum 14 on which the photosensitive material F is mounted is rotating in the main scanning direction (the direction of the arrow X), and N laser beams L output from each of the light source units 16A to 16N simultaneously cause N drums. A scanning line is formed. on the other hand,
The exposure head 12 moves in the sub-scanning direction (arrow Y direction), and a two-dimensional image is formed on the photosensitive material F by this movement.

By the way, since the individual semiconductor lasers 18 have individual differences, the emitted light amounts of the output laser beams L are not always the same. In this case, the recording width of one pixel in the sub-scanning direction (the direction of the arrow Y) corresponds to the aperture 24 arranged at the position where the far field pattern is imaged.
Can be made constant. Moreover, in a far-field pattern having a wide intensity distribution in the sub-scanning direction (arrow Y direction), such as the broad area light source used in the present embodiment, the light amount loss due to the opening 24 with respect to the entire intensity distribution is shown in FIG. Less than the laser light source having the Gaussian intensity distribution shown. However, the recording width of one pixel in the main scanning direction (the direction of the arrow X) varies depending on the amount of emitted light regardless of the width of the opening 24.

That is, the amount of light received on the photosensitive material F is
It is determined by the product of the intensity of the laser beam L and the exposure time. Therefore, assuming that the exposure time for forming one pixel is constant, the laser beam L scans the photosensitive material F in the main scanning direction (the direction of the arrow X). The shape of one pixel in the scanning direction (the direction of the arrow X) changes. It is not only inefficient but also very difficult to adjust this variation by controlling the amount of light emitted by the semiconductor laser 18, as described above.

On the other hand, in the present embodiment, the substantial light amount adjustment is performed by adjusting the exposure recording time of the laser beam L forming one pixel.

First, in the laser recording device 10, the photo sensor 36 detects the light amount of the laser beam L output from each semiconductor laser 18, and calculates the exposure recording time based on the light amount. In this case, the amount of light required for exposing the photosensitive material F is determined by the product of the intensity of the laser beam L and the exposure recording time. The shape of one pixel is determined by the shape of the opening 24.
In the sub-scanning direction (arrow Y direction) and the time from the start of exposure to the end of exposure in the main scanning direction (arrow X direction).

FIG. 9 shows the relationship between the amount of emitted light and the pixel area of one pixel formed when the intensity of the laser beam L output from each semiconductor laser 18 is constant. For example, main scanning direction (arrow X direction)
, The width in the main scanning direction (arrow X direction) is Δx, the width in the sub-scanning direction (arrow Y direction) is Δy, and the pixel area It is assumed that a pixel whose is c1 is formed.

In order to form a pixel having a pixel area (c2 + c3) on the photosensitive material F using the laser beam L having such an output characteristic, an exposure time t2 at which a light emission amount b2 can be obtained, a light emission time t2, The exposure time t3 at which the light quantity b3 can be obtained may be obtained, and the semiconductor laser 18 may be controlled so that the time from the start of exposure of one pixel to the end of exposure is constant at t1. In this case, for example, for the photosensitive material F, as shown in FIG. 10, a part of the pixel is formed by the laser beam L having the intensity distribution of the characteristic ε1 at the exposure time t2, and (t1-t2-t3) After some time,
At the exposure time t3, a part of the pixel is formed by the laser beam L having the intensity distribution of the characteristic ε2. These two
One pixel forms a pixel having a desired pixel area (c2 + c3). Since the width Δx of the formed pixels in the main scanning direction (the direction of the arrow X) is constant regardless of the amount of emitted light, pixels having substantially the same shape and different densities can be obtained.

Similarly, when a pixel having a pixel area of (c4 + c5) or (c6 + c7) is formed, the exposure time t4,
t5 or t6, t7 is obtained, and the semiconductor laser 18 is driven by dividing the exposure time into these exposure times, so that the laser beam L of the light emission amount (b4 + b5) or (b6 + b7) is obtained.
Can be formed.

As described above, instead of controlling the intensity of the laser beam L output from each of the semiconductor lasers 18, the exposure and recording time of the laser beam L by each of the semiconductor lasers 18 is controlled, whereby each of the photosensitive materials F The received light amount of the laser beam L can be constant. Therefore,
Even if there is an individual difference in the output characteristics of each semiconductor laser 18, the individual difference can be adjusted to form a uniform image.

FIG. 11 shows a case where the laser beam L is divided into four parts in the main scanning direction (the direction of the arrow X) and the exposure recording time of each laser beam L is controlled. In this case, one pixel is formed by the laser beam L having the intensity distribution composed of the four characteristics η1 to η4 shown in FIG.

In the above-described embodiment, each laser beam L is adjusted in order to adjust the individual difference between the plurality of semiconductor lasers 18.
Although the description has been given of the case where the light amount adjustment is performed, for example, the case where the light amount adjustment is performed so as to provide an appropriate light amount according to the sensitivity characteristics of the photosensitive material F, or the case where the development processing is performed on the photosensitive material F on which an image is recorded. It is needless to say that the present invention can be applied to the case where light quantity adjustment is performed to obtain an appropriate pixel size.

In the above-described embodiment, the semiconductor lasers 18 are arranged in the sub-scanning direction (arrow Y direction). However, the main scanning direction (arrow X direction) and the sub-scanning direction (arrow Y direction). By arranging the images two-dimensionally, the image can be configured to be exposed and recorded more efficiently.
In this case, the semiconductor lasers 18 arranged in the main scanning direction (arrow X direction) are arranged in the sub-scanning direction (arrow Y direction) so that the exposure positions of the semiconductor lasers 18 adjacent in the main scanning direction (arrow X direction) do not interfere. Must be arranged at predetermined intervals.

[0037]

As described above, according to the exposure recording method and apparatus of the present invention, when forming an image of a far field pattern of a light beam on a recording medium, one pixel is formed in the main scanning direction. By controlling the exposure recording time, a desired amount of light can be applied to the recording medium, and a desired image can be formed. Thus, an image having a desired density can be easily formed regardless of individual differences of light sources that output light beams, sensitivity of the recording medium, or conditions of post-processing such as development of the recording medium. . In addition, since the adjustment of the light amount is performed not by using the opening or the like but by controlling the exposure time, there is no light amount loss due to the adjustment, and image recording can be performed very efficiently.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a laser recording device.

FIG. 2 is an explanatory diagram of pixels formed when a recording medium is irradiated with a laser beam having a Gaussian intensity distribution through an opening.

FIG. 3 is an explanatory diagram of pixels formed when a recording medium is irradiated with a laser beam composed of a far field pattern output from a broad area laser through an opening.

FIG. 4 is an explanatory diagram showing a relationship between a light emission amount and a pixel area when the light emission intensity of a light source is adjusted.

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

FIG. 6 is a side view of the configuration of the laser recording apparatus according to the embodiment.

FIG. 7 is an explanatory diagram of an imaging position relationship of a far field pattern.

FIG. 8 is a block diagram illustrating a configuration of a control circuit in the laser recording apparatus according to the embodiment.

FIG. 9 is an explanatory diagram of the exposure recording method of the present embodiment.

FIG. 10 is an explanatory diagram of the intensity distribution of a laser beam when an image is exposed and recorded in the pattern shown in FIG. 9;

FIG. 11 is an explanatory diagram of another exposure recording method according to the embodiment.

12 is an explanatory diagram of the intensity distribution of a laser beam when an image is exposed and recorded in the pattern shown in FIG. 11;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Laser recording device 12 ... Exposure head 14 ... Drum 16A-16N ... Light source unit 18 ... Semiconductor laser 20 ... Collimator lens 24 ... Aperture 26,28 ... Cylindrical lens 32 ... Imaging lens 36 ... Photo sensor 40 ... Control part F ... photosensitive material L ... laser beam

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) G03F 7/20 505

Claims (6)

[Claims] An exposure recording method for forming an image of a far field pattern of a light beam modulated according to image information on a recording medium, and exposing and recording the image by main scanning and sub scanning of the recording medium. An exposure recording method for controlling an exposure amount by controlling an exposure recording time for exposing one pixel in the main scanning direction of the light beam. 2. The method according to claim 1, wherein the exposure recording time is divided into a plurality of portions, one pixel is exposed discretely in the main scanning direction, and a period from the start of exposure to the completion of exposure in each pixel. The exposure recording method, wherein the setting is made to be constant. 3. An exposure recording apparatus for forming an image of a far field pattern of a light beam modulated in accordance with image information on a recording medium, and exposing and recording the image by main-scanning and sub-scanning the recording medium. An exposure recording apparatus comprising: an exposure recording time control unit that controls an exposure recording time for exposing one pixel in the main scanning direction of the light beam, and adjusts an exposure amount by controlling the exposure recording time. . 4. The apparatus according to claim 3, wherein an opening for adjusting the width of the light beam in the sub-scanning direction is provided at an image forming position of the far field pattern. Exposure recording device. 5. The light source according to claim 3, wherein the light source that outputs the light beam is a broad area light source in which the intensity distribution of a near-field pattern in the sub-scanning direction is wider than in the main scanning direction. An exposure recording apparatus, comprising: 6. The apparatus according to claim 3, wherein a plurality of light sources for outputting the light beam are arranged in the sub-scanning direction, or at equal intervals in the sub-scanning direction. An exposure recording apparatus characterized in that pixels are two-dimensionally arranged so that pixels can be exposed and recorded by the method.