JPH0276755A - Resolution conversion recording system - Google Patents

Abstract

PURPOSE:To minimize the load of hardware and record image data without any deformed black pixels by providing a variable modulation device which varies a laser beam modulation time per pixel for every recording line in a subscan direction. CONSTITUTION:If a selector controlled signal SLD is entered into a selector 26, laser beam is modulated, in a subscan direction, by the temporal width of a single pixel period for the first scan, 6/8 pixel period for the second scan and 5/8 pixel period for the third and fourth scans. Consequently, the distribution of optical intensity on a photosensitive surface is such as shown by (a), if the variation time remains unchanged. That is, the optical intensity in the boundary section with pixels PX becomes excessive, and 'black deformation' phenomenon occurs. However, if the variation time is allowed to change, the optical intensity (b) of a multi-recorded section 8 on the photosensitive surface becomes gradually lower with no 'black deformation', each time the frequency of recording is updated.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a resolution conversion recording method for an image recording device such as a laser printer that modulates a laser beam with an image signal to record an image. It is something.

(Prior Art) Conventionally, a laser beam is modulated by an image signal, and a photosensitive drum is scanned by the modulated laser beam to form a latent image on the surface of the photosensitive drum, and this latent image is developed with toner, etc. A laser printer is known that is configured to transfer and record onto recording paper after development with a dye.

Laser printers are often used as recording devices in computer systems, etc., but they are also widely used as recording units in facsimile machines, taking advantage of their ability to record high-resolution, clear images. It has become to.

By the way, in a facsimile machine that uses a laser printer as its recording unit, the recordable resolution is 1/n (n≧1
There are many cases where an image signal of f11 degrees is received and recorded on recording paper. In such a case, the rotational speed of the polygon mirror (rotating polygon mirror that scans the laser beam in the main scanning direction) and the recording paper transport motor of the laser link itself is fixed, so for example, the resolution in the main scanning direction may be 1/2.
2. If the image signal has a resolution of 1/4 in the sub-scanning direction, multiplex recording is performed twice per pixel in the main scanning direction and four times in the sub-scanning direction to correspond to the received image signal. configured to record images.

(Problems to be Solved by the Invention) However, when multiplex recording is performed n times per pixel, a problem arises in that the sharpness decreases due to "collapse" of black pixels. This "collapse" of black pixels can be improved by checking the phase relationship between the image signals of adjacent recording lines in the sub-scanning direction and correcting the image signals on the lines to be multiplexed by interpolation processing before recording. can. However, this method is undesirable because it requires a line memory for temporarily recording image signals of adjacent recording lines, and the interpolation processing algorithm is complicated, resulting in a heavy burden on the hardware.

SUMMARY OF THE INVENTION An object of the present invention is to provide a resolution conversion recording method that reduces the burden on hardware and can record images without "blurring" of black pixels.

[Structure of Defense] (Means for Solving the Problems) The present invention is constructed by providing a modulation variable means for varying the laser beam modulation time per pixel for each recording line in the mJ scanning direction.

(Function) The laser light modulation time per pixel is varied for each recording line in the sub-scanning direction. For example, when multiplexing the same recording line four times, the first line uses the normal modulation time, and the second line
- In the fourth line, the laser beam is modulated with a shorter modulation time than usual. As a result, considering the photosensitive surface of the photoreceptor, 1
The exposure time per pixel will change for each recording line. Therefore, by sequentially shortening (or lengthening) the exposure time, "collapse" of black pixels is eliminated.

(Embodiment) FIG. 1 is a block diagram showing the main configuration of a recording section of a facsimile apparatus to which the present invention is applied, including an image signal memory 1 that stores image signals to be recorded in page units, and this image signal memory 1. a laser modulator 2 that modulates the laser beam with both signals read from the image signal memory 1; a controller 3 that controls the read/write operation of the image signal to the image signal memory 1 and the modulation operation in the laser modulator 2 via the control bus 4; The scanner 6 deflects the generated laser beam 5 in the main scanning direction and scans the surface of a photoreceptor (not shown).

FIG. 2 is a circuit diagram showing the detailed configuration of the laser modulator 2, in which the bit-parallel image signal IDP read out from the image signal memory 1 is sent to the register 20 for parallel/serial conversion.
After being set by the pixel period modulation check signal GK, the image signal IDS in units of one pixel is output from the shift out terminal (SO) by being sequentially shifted to the upper bit side.
is converted and output. This pixel-by-pixel image signal LD
S is input to the AND gate 21 and is also input to the first stage 7 of the cascade-connected D-type flip 70 tubes 22 and 23.
It is input to the data input (D) of the lip-flop 22.

As shown in FIG. 3(b), the D-type flip 70 tubes 22 and 23 receive a modulated clock signal CK8 having a period eight times that of the clock signal CK (FIG. 3a) at the clock input terminal (CK), and The set output (Q) of the 7 flip-flop 22 at the first stage is input to the data input terminal (D) of the 70 flip flop 23 at the next stage. Therefore, from the set output (Q) of the first stage flip-flop 22, the image signal IDS is 1/
The signal ID5 (1/8) delayed by 8 pixel periods is output from the set output (Q) of the next-stage flip-flop 23, and the signal ID5 is obtained by delaying the image signal IDS by 2/8 pixel periods.
(2/8) will be output respectively.

On the other hand, the clock signal CK8 is also input to the output terminal (CK) of the octal counter 24, and the octal counter 24 is configured to take out a carry signal CR of 8/8 pixel period.

This carry signal CR is inverted by the inverter 25, and the clear terminal (CLR
) is entered. Therefore, flip 70 knob 22.
23 is cleared in one pixel period.

On the other hand, the set output (Q) of flip-flops 22 and 23
Both signals ID5 (1/8) and ID output from
s (2/8) is input to a three-manpower selector 26, and one of them is selected by a select control signal SLD given from the control section 3 and input to the AND gate 21.

Assuming that the above configuration is of a type that performs laser exposure when recording black pixels, the laser beam 5 during normal recording will be applied to the "black" portion as shown in FIG. 3(C). has the same time width as one pixel period. However, for example, for an image signal that performs multiple recording twice in the main scanning direction and four times in the sub-scanning direction, as shown in Figure 3 (
As shown in d), the time width of the laser beam 5 is varied so as to be shorter than one pixel period. That is, the image signal IQ(S) output from the register 20 is output from the flip-flop 22.
．． The image signal IDS (1/8), 10 is delayed by 1/8 pixel period by 23 and whose rising edge is shifted by 1/8.2/8 pixel with respect to the rising timing of the clock signal CK.
(2/8).

On the other hand, the octal counter 24 starts counting 1/8 pixel earlier than the rising timing of the clock signal GK, and generates the carry signal CR at a timing 1/8 pixel earlier than the rising timing of the next pixel.

Therefore, in the case of performing multiplex recording four times in the sub-scanning direction, the first time the image signal IDS, the second time the image signal IDS (1/8) delayed by 1/8 pixel, the third time the image signal IDS (1/8), The fourth time is 178 pixels extended image signal ID5 (2/8)
The control section 3 outputs a select control signal SLD such that the selector 26 selectively outputs the following.

Then, for example, in the third and fourth times, the selector 26
selects and outputs the image signal ID5 (2/8) delayed by 2/8 pixels. At this time, the flip-flops 22 and 23 receive 1/8 of the next pixel by the carry signal CR of the octal counter 24.
Cleared one pixel period in advance. Therefore, selector 26
The image signal IDS (2/8) output from
/8 pixel period. Therefore, this image signal ID5 (2/
8) is input to the AND gate 21, the AND gate 21 outputs an image signal 1080 with a 5/8 pixel period as shown in FIG. 3 (d>), and the laser beam is modulated by this image signal. As a result, the photosensitive surface is 5/8 of the normal size.
It will be exposed for an exposure time of .

Therefore, when the selector control signal SLD as described above is input to the selector 26, the first
The laser beam is modulated with a time width of 1 pixel period in the first time, 6/8 pixel period in the second time, and 5/8 pixel period in the third and fourth times.

Therefore, when the modulation time is not varied in this way, the light amount distribution on the photosensitive surface is as shown in FIG. 4(a), and the pixel P
The amount of light at the boundary of x becomes too large, resulting in “blackout”
A current meeting occurs. However, when the modulation time is made variable as in the embodiment, the light intensity of the multiplex recording portion 8 on the photosensitive surface becomes smaller sequentially as the number of recordings is updated, as shown in FIG. 4(b). There will be no "black spots".

In the embodiment, the modulation time can be shortened by 3/8 pixel period at most, but if it is necessary to shorten it further, a D-type flip-flop may be added. Also,
The variable width of the modulation time is in units of 1/8 pixel period, but this can be done by increasing or decreasing the frequency of the clock signal CK8.
Needless to say, it can be changed in any variable range.

Further, in the embodiment, the case where the present invention is applied to a facsimile machine has been described, but it goes without saying that the present invention can also be applied to a case where a laser printer is used alone.

〔Effect of the invention〕

As explained above, in the present invention, when recording an image with a resolution of 1/n of the recordable resolution, the exposure time per pixel is varied for each line in the sub-scanning direction, making it easy to With this hardware configuration, it is possible to record images without crushed shadows.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the main part showing one embodiment of the present invention;
FIG. 2 is a circuit diagram showing the detailed 1li8 configuration of the laser modulation section,
FIG. 3 is a timing chart for explaining the laser modulation operation, and FIG. 4 is an explanatory diagram showing the light amount distribution on the photosensitive surface. 1... Image signal memory, 2... Laser modulation section, 3...
・Control unit, 5... Laser light, 6... Scanner, 20
...Register, 21...And gate, 22.23
...D type flip-flop, 24...octal counter, 26...selector. Figure 1 Figure 2

Claims (1)

[Claims] The system is configured to record an image by modulating a laser beam according to an image signal, and for an image signal having a resolution of 1/n of the recording resolution of the image in the sub-scanning direction. An image recording device that performs multiple recording n times in the sub-scanning direction for the same pixel, characterized by comprising a modulation time variable means for varying the laser beam modulation time per pixel for each recording line in the sub-scanning direction. Resolution conversion recording method.