JPH0622090A - Exposure controller - Google Patents

Abstract

PURPOSE:To faithfully the black-and-white print of independent one dot to impressed image data by adjusting the light emitting intensity of a laser beam output means corresponding to whether the dots to issue laser beams are independent or continuous. CONSTITUTION:When image data read out of a buffer memory 22 are data to be printed, an intensity generation circuit 26 reads the peripheral pixel data as well. Then, it is judged whether the image data of these picture elements are coincident to a prescribed pattern impressed from a pattern generation circuit 24 or not. When this pattern is coincident, the picture element to be printed is independent one dot so that the intensity generation circuit 26 can output a signal for fully emitting an LD (laser diode) 30. When the pattern is not coincident, the picture element to be printed is not independent one dot so that the intensity generation circuit 26 can output a signal limiting the light emission of the LD 30 from the full light emission.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is capable of reliably printing both one independent black dot and one independent white dot on a surface when an image is formed using a laser beam. The present invention relates to an exposure control device.

[0002]

2. Description of the Related Art In recent years, printers using laser diodes have come to be used in order to meet the demand for higher definition image quality. An example of the image forming unit of this printer has a structure as shown in FIG. In the printer of the type shown in this figure, the thin film member 11 having a slightly longer circumference than the outer circumference of the developing roller 10 is attached to the outer circumference of the developing roller 10, and can meet the demand for high quality image quality. It was done like this.

The photosensitive drum 15 is adapted to rotate in the direction of the arrow in the figure, and the surface potential of the photosensitive drum 15 is uniformly charged to a predetermined potential by the charger 16.
After this charging is performed, at a position rotated by a predetermined amount, laser light is emitted based on the image data, whereby an electrostatic latent image is formed on the photosensitive drum 15. When the photosensitive drum 15 further rotates, the thin film member 1
The toner conveyed in 1 is adsorbed to the potential decreasing portion (the portion irradiated with the laser beam) of the photoconductor drum 15, so that the toner image is developed and visualized. When the visualized toner image reaches the transfer position, it is transferred to the recording paper 17 by the transfer device 16, and the transferred image is fixed on the recording paper 17 by the fixing device (not shown).

The emission state of the above laser light is controlled as shown in the flow chart of FIG. First, in a portion that controls the emission of laser light (not shown), image data for one pixel is read out, and it is determined whether the image data is a print pixel, that is, a pixel on which a toner image is to be formed. If the read pixel is a print pixel, the light emission duty ratio is set to 1 as shown in FIG. 13, and the laser light is set to emit light with a predetermined light amount for a time corresponding to one pixel width. On the other hand, if it is not a print pixel, the light emission duty ratio is set to 0 as shown in the figure so that the laser light is not emitted (S1 to S4). Next, based on the light emission duty ratio set in step S3 or S4, laser light is emitted to expose the photosensitive drum 15 (S5). When this exposure is completed, the process returns to step S1 to perform the same process as described above for the next pixel (S6), and the above process is sequentially performed for all the image data to form an image on the recording paper 17. To complete the printing.

[0005]

However, the conventional printer operating as described above exists independently because the emission or non-emission of the laser beam is simply controlled depending on the presence or absence of image data. There is a problem that it is difficult to faithfully print one dot of white or black.

For example, as shown in FIG. 14C, when only one dot in the image data of 6 dots is black data, the light amount of the laser is set so as to faithfully print this one dot as black. When controlled, even if 3 dots in the image data for 6 dots are data for which black should be printed continuously as shown in FIG. In the case where a large number of areas become black continuously and only one dot of the image data of 6 dots does not independently print black as shown in FIG. If so, all the dots will be printed as black.

The reason why such a printing state occurs is that it is clear from the light intensity distribution diagram of FIG. 14 that when a light beam approximated by a Gaussian distribution is scanned, non-printing is performed at the edge portion of the image. This is because the leaked light of the beam is slightly irradiated onto the pixel region. If the leaked light exceeds the threshold light amount shown in the figure, the pixel is printed in black. Therefore, FIG.
As shown in (B), a dot irradiated with a light amount exceeding the threshold light amount will be printed in black even if it is non-printed image data.

Such leaked light is shown in FIGS. 15 (A) and 15 (B).
The problem above should be solved by suppressing to a certain extent so that an independent 1-dot white can be reproduced, as shown in Fig. 5, but on the other hand, as shown in Fig. 6C, 1-dot independent black printing is possible. However, in the case of performing the above method, there is a conflicting problem that the amount of laser light does not exceed the threshold value and one dot black cannot be printed.

The present invention has been made in view of the above-mentioned problems of the prior art, and an independent 1-dot white print and an independent 1-dot black print are applied to a given image. An object of the present invention is to provide an exposure control device capable of faithfully performing data.

[0010]

The present invention for achieving the above object provides an image forming apparatus for forming an image on a record carrier by using a laser beam output from a laser beam output unit. Image data storage means for storing image data for storing the image data, detection means for reading out the image data from the image data storage means and detecting whether the dots for emitting laser light are independent, and detecting means for detecting the detection data. And a light emission control means for increasing the light emission intensity of the laser light output means.

In an image forming apparatus for forming an image on a record carrier by using a laser beam output from a laser beam output unit, an image data storage unit for storing image data for the image formation, and the image. A detection unit that reads out image data from the data storage unit and detects whether or not the dots for emitting laser light are continuous, and a light emission control unit that weakens the emission intensity of the laser light output unit according to the detection of the detection unit. It is characterized by having.

[0012]

The image data storage means stores the image data used for image formation. The detection means reads out the image data stored in the image data storage means and detects whether the dots for emitting laser light are independent. The light emission control means increases the light emission intensity when the dots to be emitted are independent.

Further, the detecting means reads out the image data stored in the image data storing means and detects whether or not the dots for emitting laser light are continuous. The light emission control means weakens the light emission intensity when the dots to be emitted are continuous.

Therefore, the laser light output means adjusts the light emission intensity according to whether the dots to emit the laser light are independent or continuous in the read image data, and one dot is independent. It becomes possible to print faithfully even with white and black print data.

[0015]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a block diagram showing a schematic configuration of an exposure control apparatus according to the present invention. In the figure, page memory 2
As shown in FIG. 2, 0 stores one page of image data to be recorded on the recording paper 17 as a record carrier, and constitutes image data storage means. Similarly, the buffer memory 22 as an image data storage means has a capacity for storing the image data stored in the page memory 20 for three lines, and the line to be printed and the lines before and after the line are to be printed. A total of 3 lines are updated and stored.

The pattern generation circuit 24 stores a predetermined pattern in a 3 × 3 matrix of pixels to be printed and its surrounding pixels. Data corresponding to the stored pattern is stored in the pattern generation circuit 24. Is output to the intensity generating circuit 26 in the subsequent stage connected to the. Here, the predetermined pattern is to detect an independent black or white dot, and a specific example thereof is as shown in FIG.

The intensity generation circuit 26 includes a buffer memory 22.
The image data of the pixel to be printed and the data of the pixels around the pixel are read from, and it is determined whether or not the read data matches a predetermined pattern given from the pattern generation circuit 24. Is output to the LD drive circuit 28 in the subsequent stage as a light emission intensity signal. The pattern generation circuit 24 and the intensity generation circuit 26 described above function as detection means. The LD drive circuit 28 functions as a detection means, image data to be printed is sequentially given from a buffer memory, and an LD (laser diode) as a laser light output means is based on this image data.
The light emission of 30 is controlled ON / OFF, and the light emission intensity (LD drive current) at that time is controlled based on the light emission intensity signal output from the intensity generation circuit 26.

The exposure control apparatus having such a configuration operates as follows based on the flow chart shown in FIG. It should be noted that this flowchart does not show the processing procedure of this apparatus, but shows the general operation of the apparatus.

The image data stored in the page memory 20 as shown in FIG.
Stored in 2. The intensity generation circuit 26 is the buffer memory 2
The image data of the pixel to be printed stored in 2 is read (S1), and it is determined whether the read image data is print data or non-print data (S2). When the read image data is non-printing data, that is, non-printing pixels, as shown in the timing chart of FIG. 5, a signal for setting the LD drive current I0 to 0, in other words, a signal for not causing the LD 30 to emit light. Is output as a light emission intensity signal (S3).

On the other hand, when the read image data is the data to be printed, that is, the print pixels, the pixel data around it is also read (S4), and the image data of these pixels is given from the pattern generation circuit 24. It is determined whether or not the pattern matches the pattern (S5).
If the patterns match, the pixel to be printed is an independent dot, and therefore the intensity generation circuit 26 is a signal that should be set to a predetermined LD drive current I2 that is set in advance to cause the LD 30 to emit full light. Is output as a light emission intensity signal (S6). If the patterns do not match, the pixel to be printed is not an independent dot, so the intensity generation circuit 26 limits the light emission of the LD 30 to the full light emission as shown in the timing chart of FIG. A signal to be set to the drive current I1 is output as a light emission intensity signal (S7). Next, LD
The drive circuit 28 causes the LD 30 to emit light based on the light emission intensity signal output from the intensity generation circuit 26.

That is, when the light emission intensity signal for setting the LD drive current to I0 is output, the input image data is in the LOW state as shown in the timing chart of FIG. It will not be done. When the light emission intensity signal for setting the LD drive current to I2 is output, the input image data is in the HI state as shown in FIG.
30 will be fully illuminated. Further, when the light emission intensity signal for setting the LD drive current to I1 is output, the light emission intensity of the LD30 is suppressed as compared with the full light emission as shown in the figure (S8). When the above process is completed, the same process is performed on the next pixel (S9).

Depending on whether or not the pixels to be printed are independent one dots, or not, L
By controlling the emission intensity of D30, it is possible to realize a print state faithful to data as shown in FIG. That is, when the data shown in FIG. 9A is input, the light emission of the LD 30 is performed with a light emission intensity lower than that at the time of full light emission. The light quantity is reduced below the threshold light quantity, and as a result, the print state becomes faithful to the data as shown in the figure. Also,
Even if there is independent 1-dot non-printing data in the data as shown in FIG. 6B, the emission intensity is limited in the same manner as described above. The amount of leaked light is less than the threshold amount of light, and the print state is faithful to the data. Further, when there is independent 1-dot print data as shown in FIG. 7C, the LD 30 emits full light, so that a light amount exceeding the threshold value is obtained at that dot. Even when 1-dot print data is given, a print state faithful to the data can be realized.

In the above embodiment, the predetermined pattern set in the pattern generation circuit 24 is not limited to the illustrated one, and a plurality of patterns are set. Good. For example, only one-dot data that exists completely independently as in the illustrated pattern is not considered to be independent, and even if there is data in the diagonal direction of the pixel to be printed, it is regarded as an independent pixel. You may set the pattern. Also,
The setting of the LD drive current for controlling the emission intensity is not limited to the example, and a plurality of LD drive currents may be set according to the type of record carrier used, or the LD drive current set according to the matching pattern. It is also conceivable that the mode changes.

FIG. 7 is a schematic block diagram of an exposure control apparatus showing another embodiment of the present invention. In this figure, the difference from the configuration of FIG. 1 showing the first embodiment is that a buffer memory 22, a pattern generating circuit 24 and an intensity generating circuit 2 are provided.
6 is that a delay circuit 32 and a comparison circuit 34 are provided between the page memory 20 and the LD drive circuit 28.

In this configuration, the delay circuit 32 has a function of delaying the image data read from the page memory 20 by one dot and outputting it. The comparison circuit 34 compares the image data of the pixel to be printed read from the page memory 20 with the previous image data D0 output from the delay circuit 32 and delayed by one dot from the image data D1 of the pixel to be printed. It has a function and also has a function of giving the LD drive circuit 28 an emission intensity signal (analog signal) according to the comparison result. Delay circuit 32 and comparison circuit 3
Both 4 are designed to directly read image data from the page memory 20 pixel by pixel in the order of data of each pixel. L
The D drive circuit 28 is configured to cause the LD 30 to emit light according to the light emission intensity signal output from the comparison circuit 34.

The apparatus thus configured operates as follows based on the flowchart shown in FIG. First, the comparison circuit 34 reads the previous pixel data delayed by one dot from the image data of the pixel to be printed, which is output from the delay circuit 32, and stores this as D0.
Further, the image data of the pixel to be printed, that is, the data of the current pixel is read out and stored as D1 (S1).
11, S12). The two read pixel data D0
And D1 are judged to be print pixels for each data (S13, S14). As a result, when the data of D1 is a non-printing pixel, it is not necessary to print, so the comparison circuit 34 outputs a light emission intensity signal for setting the LD drive current to I0 (S).
15). Further, as a result, when the data of D1 and D0 are both print pixels, in other words, when the print pixels are continuously arranged, the light emission intensity from the comparison circuit 34 to set the LD drive current to I2. A signal is output (S1
6). Further, as a result, the data of D1 is printed pixel D0.
If the data is a non-printing pixel, the pixel to be printed is an independent dot, so the comparison circuit 34 outputs a light emission intensity signal for setting the LD drive current to I1 (S17). .

Next, the LD drive circuit 28 causes the LD 30 to emit light based on the light emission intensity signal output from the comparison circuit 34. That is, when the light emission intensity signal for setting the LD drive current to I0 is output, the input image data is in the LOW state as shown in the timing chart of FIG. 9, and when it is LOW, the LD 30 does not emit light at all. It will be. Further, when the light emission intensity signal for setting the LD drive current to I2 is output, the input image data is in the HI state as shown in the figure, and in this case, the LD 30 is caused to emit full light. Furthermore, the LD drive current is set to I
When a light emission intensity signal to be set to 1 is output, the LD 30 is caused to emit light with a light emission intensity suppressed as compared with the full light emission of the LD 30 as shown in the figure (S18). When the above processing is completed, D1 is updated and stored as Do in order to replace the current pixel data with the previous pixel data (S19), and the same processing is performed for the next pixel (S20).

FIG. 10 is a diagram showing a comparison between the case where the exposure state of the LD 30 is controlled by the exposure control apparatus of the present invention and the conventional case. This is a calculation of the density distribution of an image based on the characteristics of the photoconductor and the developing device using the laser light having the following optical characteristics.

1 pixel width: 84 μm (300 DPI) 1 pixel scanning time: 0.3 μsec Laser emission intensity: 0 when I 0 Laser emission intensity: 0.4 mw when I 1 Laser emission intensity: 0.8 mw when I 2 Laser emission duty: 1 Still beam diameter (half-value width): Main scanning: 95 μm Sub-scanning: 110 μm (value considering scattering on the surface, inside and back surface of the photosensitive layer) In the conventional example, laser emission intensity: 0.4 mw and 0 .5m
w.

In this figure, the height of the mountain represents the density. In the conventional example, when the print pattern is a 1-dot white line, it is understood that the contrast of black and white is not so clear when the laser emission intensity is 0.5 mw. On the other hand, in the conventional example having a light emission intensity of 0.4 mw, it can be said that the contrast of black and white is clearer than that in the case of 0.5 mw, but conversely, the reproducibility of one independent black dot is lacking. It can be seen that it is difficult to improve the reproducibility of 1 dot white and 1 dot black at the same time in the conventional one, but in the present invention, the contrast is much higher than that in the conventional one. You can see that it is improving. Independent 1-dot black reproduction raises the emission intensity higher than before, and independent 1-dot white reproduction has the same emission intensity as that of the conventional one, so both sides obtain good contrast. ing. As described above, it is difficult to achieve both the 1-dot white print and the independent 1-dot black print in the related art, while the apparatus of the present invention achieves both.

[0031]

As described above, according to the present invention, the light emission intensity of the laser light output means is made different depending on whether the pixel to be printed is an independent one-dot black or not. Both independent 1-dot white printing and independent 1-dot black printing can be faithfully performed on given image data.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of an exposure control apparatus of the present invention.

FIG. 2 is a diagram showing an example of image data stored in a page memory in the configuration shown in FIG.

FIG. 3 is a diagram showing an example of a pattern output from a pattern generation circuit in the configuration shown in FIG.

FIG. 4 is a flowchart showing a process executed by the device shown in FIG.

5 is a timing chart showing the light emitting state of the LD executed according to the flowchart shown in FIG.

FIG. 6 is a diagram showing a print state realized by the flowchart shown in FIG.

FIG. 7 is a schematic block diagram showing another embodiment of the exposure control apparatus of the present invention.

8 is a flowchart showing a process executed by the device shown in FIG.

9 is a timing chart showing the light emitting state of the LD executed according to the flowchart shown in FIG.

FIG. 10 is a diagram for explaining the effect of the present invention.

FIG. 11 is a configuration diagram of a main part of a commonly used printer.

FIG. 12 is a flowchart showing the light emission intensity of a conventional LD.

FIG. 13 is a flowchart showing the light emission timing of the LD executed by the flowchart shown in FIG.

FIG. 14 is a diagram showing a conventional problem.

FIG. 15 is a diagram showing a conventional problem.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Developing roller 11 ... Thin film member 15 ... Photosensitive drum 17 ... Recording paper (recording carrier) 20 ... Page memory (image data storage means) 22 ... Memory buffer (image data storage means) 24 ... Pattern generation circuit (detection means) 26 ... Intensity generation circuit (detection means) 28 ... LD drive circuit (light emission control means) 30 ... LD (laser light output means) 32 ... Delay circuit (detection means) 34 ... Comparison circuit (detection means)

Claims (2)

[Claims] 1. An image forming apparatus for forming an image on a record carrier by using a laser beam output from a laser beam output unit, image data storage unit for storing image data for the image formation, and the image. Detection means for reading out image data from the data storage means and detecting whether or not the dots for emitting laser light are independent; and light emission control means for increasing the light emission intensity of the laser light output means according to the detection of the detection means. An exposure control apparatus comprising: 2. An image forming apparatus for forming an image on a record carrier by using a laser beam output from a laser beam output unit, an image data storage unit for storing image data for the image formation, and the image. A detection unit that reads out image data from the data storage unit and detects whether or not the dots that should emit laser light are continuous, and a light emission control unit that weakens the emission intensity of the laser light output unit according to the detection of the detection unit. An exposure control apparatus comprising: