JPH0939291A - Image recording apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To narrow the width of a fringe without extension of the blackening width. SOLUTION: The processing part 10 acts to shorten the ON-time width of a laser driving signal 18 for driving in an ON-OFF manner a laser generator device 1 such that the blackening width in the accumulative energy distribution of a laser beam becomes a predetermined width. Also, the processing part 10 serves to make the front peripheral part and rear peripheral part of the laser driving signal 18 during the period of ON-time larger than the level in the central part. In this way, rising and lowering of the accumulative energy distribution of the laser beam in the photosensitive material 8 become steep, and the skirts thereof becomes narrow. As a result, the width of the fringe can be made narrow without extending the blackening width.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image recording apparatus, and more specifically, it scans an exposure beam modulated according to image data in a main scanning direction of a photosensitive material and collects the photosensitive material and the exposure beam. The present invention relates to an apparatus for exposing and recording a predetermined two-dimensional image on a photosensitive material by relatively moving a spot and a sub-scanning direction orthogonal to the main scanning direction.

[0002]

BACKGROUND OF THE INVENTION As is well known, planar output scanners are
The laser beam is turned on / off (modulated) according to the pixel pattern of the image data, the modulated laser beam is scanned in the main scanning direction of the photosensitive material, and the photosensitive material is conveyed in the sub-scanning direction, so that a predetermined image is obtained. Is recorded on a light-sensitive material by exposure.

The power density of the laser beam spot formed on the photosensitive material by the above-mentioned flat type output scanner usually follows a Gaussian distribution, and what makes the photosensitive material black is
The portion where the stored energy exceeds a certain value, that is, the portion having a certain concentration or more on the light-sensitive material (FIG. 7A).
reference). On the other hand, whether or not the photosensitive material is blackened is not clearly separated by the density threshold value, and naturally the boundary area exists. This boundary area is generally called a fringe area and adversely affects image quality (for example, unevenness). Therefore, it is preferable that the fringe area is as narrow as possible.

[0004]

By the way, the width in the sub-scanning direction of the blackened region generated on the photosensitive material by the laser beam spot is determined by the power distribution of the laser beam spot.
The width of the cut edge is almost the same as the width of the cut edge when cut with the threshold value for blackening, but it becomes slightly complicated in the main scanning direction. This is because the image forming position of the laser beam spot on the photosensitive material constantly moves in the main scanning direction even when the same dot is exposed, so that the scanning speed of the laser beam spot and its drive waveform are This is because it is closely related to the blackening width in the main scanning direction. This will be described in more detail below.

Generally, the blackened area of a light-sensitive material has a shape of a distribution of accumulated energy applied on the light-sensitive material.
If it is a stationary laser beam spot, its distribution is
The Gaussian distribution is a distribution obtained by temporally integrating the driving waveform of the laser beam spot. At this time, since the imaging position of the laser beam spot does not change with time, the accumulated energy distribution becomes a Gaussian distribution similar to the accumulated energy distribution of the laser beam spot, and even if the drive pattern changes, In the blackened region, the magnitude of the blackening degree (accumulated energy amount) simply changes.

However, when the photosensitive material is actually exposed in the flat type output scanner, the laser beam spot is scanned in the main scanning direction as described above, and the image forming position changes with time. . The accumulated energy distribution generated on the photosensitive material in this case has a shape obtained by convolutionally integrating the Gaussian shape and the drive waveform of the laser beam power with respect to position and time.

FIG. 9 shows the energy distribution formed on the photosensitive material when recording dots while the laser beam spot moves in the main scanning direction. In FIG.
The laser irradiation time is T1 to T20. now,
Taking the case where the drive waveform of the laser beam power is an ideal rectangle as shown in FIG. 9A as an example, the accumulated energy distribution generated on the photosensitive material is the laser irradiated at each time T1 to T20. Beam spot energy distribution (Fig. 9
(See (b)) is synthesized (see FIG. 9C).

As shown in FIG. 8A, the Gaussian distribution due to the moving laser beam spot (that is, the accumulated energy distribution of the laser beam spot in the main scanning direction) rises and rises more than the Gaussian distribution due to the stationary laser beam spot. You can see that the fall is getting slower. That is, in the direction of exposure while scanning, the higher the scanning speed, the slower the rising and falling of the blackening accumulated energy, and as a result, the width of the fringe area is increased and This is the same as that the image forming performance is deteriorated. Furthermore, it is impossible in reality to make the drive waveform of the laser beam spot completely rectangular, and the drive waveform itself is generally blunt, and the width of the fringe region is further increased. work.

As is clear from FIG. 7A, the fringe region becomes narrower as the skirt of the accumulated energy distribution formed by the laser beam spot on the photosensitive material is narrower. Therefore, by increasing the drive pattern of the laser element from B1 to B2 in FIG. 7B, the gradient of the power density of the laser beam spot is made steep from A1 to A2 in FIG. It is possible to narrow the fringe area by. However, in such a method,
The blackening width becomes wider than originally expected, and the dots or halftone dots recorded on the photosensitive material become thick.

Therefore, an object of the present invention is to provide an image recording apparatus capable of narrowing the fringe width without widening the blackening width.

[0011]

The invention according to claim 1 is
The exposure beam modulated according to the image data is scanned in the main scanning direction of the photosensitive material, and the photosensitive material and the focused spot of the exposure beam are relatively moved in the sub-scanning direction orthogonal to the main scanning direction. A device for exposing and recording a two-dimensional image on a light-sensitive material, and a drive signal generating means for generating a drive signal for turning the light emitting device on and off based on image data, The on-time width of the drive signal is adjusted so that the blackened width of the accumulated energy distribution of the exposure beam on the photosensitive material becomes a predetermined width, which is provided in association with the drive signal generation means, and when the drive signal is on. Drive signal deforming means for increasing the front edge portion and the rear edge portion of the above in comparison with the level of the central portion.

[0012]

According to the present invention, the ON time width of the drive signal for driving the light emitting element ON / OFF is adjusted so that the blackening width of the accumulated energy distribution of the exposure beam on the photosensitive material becomes a predetermined width. I am trying to do it. Further, the leading edge portion and the trailing edge portion when the drive signal is turned on are made larger than the level of the central portion. by this,
The rising and falling edges of the accumulated energy distribution of the exposure beam on the photosensitive material become steep and the skirt thereof becomes narrow. Therefore, it is possible to reduce the fringe width without increasing the blackening width.

[0013]

FIG. 6 shows an example of energy distribution formed on a photosensitive material when recording dots while the laser beam spot moves in the main scanning direction in the image recording apparatus of the present invention. ing. Before describing a specific embodiment of the present invention, the principle of the present invention will be described with reference to FIG.

As described above, in the conventional flat type output scanner, the laser irradiation time is T1 to T20.
(See FIG. 9). On the other hand, in the present invention, FIG.
As shown in (a), the drive waveform of the laser power beam starts at time T2 and ends at time T19. That is, the time for which the photosensitive material is irradiated with the laser beam is T2 to T19. As described above, in the present invention, the irradiation time of the laser beam is shortened as compared with the conventional case. Moreover, in the present invention, the laser driving power of the leading edge portion and the trailing edge portion of the driving waveform of the laser power beam is made larger than the power of the intermediate portion.

As described above, the accumulated energy distribution generated on the photosensitive material by applying the driving waveform of the laser power beam deformed to a shape different from the conventional one to the laser emitting element is shown in FIG. 6 (c). It becomes like the curve α shown in. The accumulated energy distribution α shown in FIG. 6C is calculated at each time T2.
The energy distributions (see FIG. 6B) of the laser beam spots irradiated at T19 to T19 are combined.

As is apparent from FIG. 6 (c), the accumulated energy distribution α in the present invention has steep rising and falling edges as compared with the accumulated energy distribution β in the conventional planar output scanner. As a result, the fringe width F1 in the present invention is narrower than the fringe width F2 in the conventional flat output scanner.
In addition, the stored energy distribution α in the present invention has a narrower skirt than the stored energy distribution β in the conventional planar output scanner, so that the blackening width is almost the same as the conventional one. These things are optically
The equivalent effect of raising the condensing characteristic of the laser beam spot is brought about.

In the present invention, the amount by which the driving waveform of the laser power beam is shortened and the extent to which the power at both ends is made larger than the power at the central portion are not unique, and various types of devices and sensitive materials are used. It is determined by the conditions of.

FIG. 1 is a diagram showing the configuration of a flat output scanner according to an embodiment of the present invention. In FIG. 1, a laser beam 2 emitted from a laser oscillator 1 and modulated for image drawing is oscillated by a rotating mirror 3 and then focused on a photosensitive material exposure surface 5 through an F-θ lens 4. As a result, a beam spot 6 is formed on the photosensitive material exposure surface 5 which is moved and scanned at a constant speed. On the other hand, the transport roller 7 transports the roll sensitive material 8 downward in the drawing by rotating the transport sensitive material 8 while sandwiching the roll sensitive material 8 with another roller (not shown). By these two operations, a two-dimensional image is formed on the photosensitive material exposed surface 5.

The roller drive pulse motor 9 includes a processing unit 10
It is rotated at a high speed by the pulse drive motor signal 11 sent from. The rotation output of the roller driving pulse motor 9 is reduced to an appropriate number of rotations by the decelerator 15 and then transmitted to the conveyance roller 7 to rotate the conveyance roller 7. The rotating body mirror drive motor 12 rotates the rotating body mirror 3 in response to the rotating body mirror drive signal 13 sent from the processing unit 10. The start sensor 14 detects the timing before the beam spot 6 reaches the photosensitive material exposure surface 5, and determines the exposure start position in the main scanning direction. Further, the start sensor 14 is used to monitor and feed back the laser power each time the laser beam spot passes, and stabilize the laser power. The processing unit 10 generates a rotating body mirror drive signal 13 and a pulse motor drive signal 11. Further, the processing unit 10 generates a signal which is a feature of this embodiment, that is, a laser drive signal 18 for modulating and driving the laser oscillator 1.

FIG. 2 is a block diagram showing a more detailed structure of the processing unit 10 shown in FIG. In FIG. 2, the processing unit 10 includes a basic clock generation unit 20 and a laser drive unit 21.
And the rotary mirror drive unit 22 and the pulse motor drive unit 2
3 is provided.

The basic clock generation unit 20 generates various clock signals for controlling the entire system of the processing unit 10. The laser drive unit 2 is a particularly interesting clock signal.
1 to generate a high-speed basic clock 24 for processing. The pulse motor drive unit 23 creates a pulse motor drive signal 11 for driving the roller drive pulse motor 9. The rotating body mirror drive unit 22 generates a rotating body mirror drive signal 13 for driving the rotating body mirror drive motor 12 at a desired rotation speed. The laser drive unit 21 receives the image data 17 input from the outside, and in synchronization with this, generates a laser drive signal 18 having an appropriate laser power. The effect of narrowing the fringe width without widening the blackening width is achieved by converting the waveform of the laser drive signal 18 into a desired shape.

FIG. 3 is a block diagram showing a more detailed structure of the laser drive section 21 shown in FIG. In FIG.
The laser drive unit 21 includes a laser deformation drive signal generation unit 30.
A laser light amount setting unit 31, a laser light amount setting dial 32, and a laser drive signal generation unit 33.

The laser deformation drive signal generating section 30 takes in the image data 17 which is a digital signal, shortens the ON time of the image data 17 by a few clocks of the basic clock 24, and turns it ON and OFF ( That is, the laser deformation drive signal 34 having a signal waveform with higher power than others only at the leading edge portion and the trailing edge portion.
Create The laser light amount setting unit 31 uses the start signal 1
6 is taken in and the current laser power emitted from the laser oscillator 1 is monitored in real time, so that the laser power becomes the laser power set by the laser light amount setting dial 32.
A laser light amount value signal 35 is created. The laser drive signal creation unit 33 generates the final laser drive signal 18 by multiplying the laser deformation drive signal 34 and the laser light amount value signal 35.

FIG. 4 is a block diagram showing a more detailed structure of the laser deformation drive signal generating section 30 shown in FIG. FIG. 5 is a timing chart for explaining the operation of the laser deformation drive signal creation unit 30 shown in FIG. Hereinafter, the configuration and operation of the laser deformation drive signal generation unit 30, which is a characteristic component of the present embodiment, will be described with reference to FIGS. 4 and 5.

The shift register 40 stores the image data 17
Is delayed by several clocks of the basic clock 24 and then supplied as an output g to one input terminal of the AND gate 46.
The delay amount in the shift register 40 reduces the ON-time width of the laser drive signal 18, that is, the amount of the accumulated energy distribution of the laser beam spot on the photosensitive material.

The AND gate 46 is used for the shift register 40.
Output g from the above and the original image data 17 are calculated, and the digital signal a in which the image data 17 is shortened by the above delay is output. The output a of the AND gate 46 is
The level is converted by the operational amplifier 41. The output b of the operational amplifier 41 becomes a signal c whose rising and falling are slightly gentle due to the removal of high frequency components by the low pass filter 43. Further, the output b of the operational amplifier 41 is given to the delay element 42, and the low pass filter 43
It is delayed by the delay of the signal at. The subtractor 44 is
The output signal c of the low pass filter 43 is subtracted from the output signal d of the delay element 42. The adder 45 adds the output e of the subtractor 44 and the output d of the delay element 42 to obtain
The leading edge portion and the trailing edge portion output the drive signal f having larger power than the central portion. This drive signal f becomes the laser deformation drive signal 34 as it is. The adder 45 also has a limiter function in which the lower limit value is set to a predetermined level (for example, 0). As a result, the adder 45 causes the addition output f
Is prevented from undershooting below a predetermined level.

As described above, the laser deformation drive signal generating section 30 is made shorter than the on-time width of the original image data 17, and the power of the leading edge portion and the trailing edge portion is made larger than the power of the central portion. The laser deformation drive signal 34 is generated. As a result, as described with reference to FIG. 6, the accumulated energy distribution of the scan beam spot 6 on the photosensitive material 8 becomes sharper in rising and falling than the accumulated energy distribution in the conventional planar output scanner. As a result, the fringe width is narrower than that of the conventional flat output scanner. In addition, in the present embodiment, since the base of the accumulated energy distribution becomes narrow, the blackening width is almost the same as in the conventional case even if the rising and falling are steep.

In the above embodiment, the circuit as shown in FIG. 4 is used to modify the waveform of the laser drive signal. However, a circuit having another configuration (for example, a circuit for digitally processing all) is used. It is also possible to perform equivalent waveform transformation.

[0029]

According to the first aspect of the present invention, the ON time width of the drive signal for driving the light emitting element ON / OFF is set so that the blackened width of the accumulated energy distribution of the exposure beam on the photosensitive material becomes a predetermined width. In addition, the front edge and the rear edge when the drive signal is turned on are set to be larger than the central level, so that the fringe width should be narrowed without widening the blackening width. You can

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a planar output scanner according to an embodiment of the present invention.

2 is a block diagram showing a more detailed configuration of a processing unit 10 shown in FIG.

3 is a block diagram showing a more detailed configuration of a laser drive unit 21 shown in FIG.

FIG. 4 is a block diagram showing a more detailed configuration of a laser deformation drive signal creation unit 30 shown in FIG.

5 is a timing chart for explaining the operation of the laser deformation drive signal creation unit 30 shown in FIG.

FIG. 6 is a diagram showing an example of energy distribution formed on a photosensitive material when recording dots while the laser beam spot moves in the main scanning direction in the image recording apparatus of the present invention.

FIG. 7 is a diagram showing a stored energy distribution of a laser beam spot on a photosensitive material and a drive waveform thereof.

FIG. 8 is a diagram showing a relationship between a blackening energy distribution due to a stationary laser beam spot and a blackening energy distribution due to a moving laser beam spot.

FIG. 9 is a diagram showing an energy distribution formed on a photosensitive material when a dot is recorded while a laser beam spot moves in a main scanning direction in a conventional planar output scanner.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Laser oscillator 2 ... Laser beam 3 ... Rotating body mirror 4 ... f-theta lens 7 ... Conveying roller 8 ... Roll sensitive material 9 ... Roller drive pulse motor 10 ... Processing part 12 ... Rotating mirror motor 15 ... Decelerator 21 ... Laser Drive unit 30 ... Laser deformation drive signal generation unit

Claims (1)

[Claims] 1. An exposure beam modulated according to image data is scanned in a main scanning direction of a photosensitive material, and the photosensitive material and a focused spot of the exposure beam are relatively moved in a sub-scanning direction orthogonal to the main scanning direction. A device for exposing and recording a predetermined two-dimensional image on a light-sensitive material by causing the light emitting element to generate the exposure beam, and a drive signal for driving the light emitting element to turn on and off based on the image data. A drive signal generating means for generating the drive signal, and an on-time width of the drive signal provided in association with the drive signal generating means so that the blackening width of the accumulated energy distribution of the exposure beam on the photosensitive material becomes a predetermined width. And a drive signal deforming unit that adjusts the drive signal and makes the leading edge portion and the trailing edge portion larger when compared with the level of the central portion when the drive signal is turned on.