JPH0580862B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a pixel recording pulse signal generation method,
The present invention relates to a method for generating a pixel recording pulse signal in a scanning recording type recording apparatus in which the density of a recorded image is expressed by the ratio of the recording area (coloring or coloring area) of each pixel constituting the image.

[Background of the invention]

In a scanning recording type recording apparatus, one method of changing the recording area of each pixel in order to express the density of an image is to modulate the pulse width of a pixel recording pulse signal using density data. Tokuko Showa 57-57679
The devices described in Japanese Patent Laid-Open No. 57-99866 are specific examples thereof.

By the way, in such a recording device, in order to record an image with high definition, it is necessary to increase the pixel density by making each pixel smaller. The dimension in the scanning direction of each pixel in scanning recording is determined by the scanning speed and the pixel recording pulse signal generation cycle, and in order to make the pixel smaller, the pixel recording pulse signal generation cycle must be shortened and the number of interruptions must be increased. However, when the number of times the pixel recording pulse signal is interrupted is increased, the image quality tends to deteriorate.

The reason for this will be specifically explained using an electrophotographic laser beam printer as an example.

In FIG. 2, a memory 1 stores density data of each pixel for one scanning line in an image signal from an image reading device, a computer, etc. (not shown). Then, according to a pixel clock signal PCLK1 given from a timing processing circuit 4, which will be described later, the data is sent to the latch 2 as pixel density data DA for each pixel according to the recording scanning position. When the pixel density is set from "0" (white) to "15" (black), the pixel density data DA becomes 4-bit data. In the pixel recording pulse signal generation circuit 9, the latch 2 holds (latches) the pixel density data DA in accordance with the pixel clock signal PCLK2 given from the timing processing circuit 4, and its holding time is equal to the period of recording and scanning one pixel area. equal. This held pixel density data DA is then given to the comparator 5. The counter 3 is a cyclic 4-bit binary counter that is controlled by the recording scanning signal LINE1 from the timing processing circuit 4 and clocked by the clock signal from the clock generator 10.
Count CLK1. Sixteen clock signals CLK1 are output during a recording scan period for one pixel area. Counter 3 counts up from “0” (white) to “15” (black), and the count contents are compared to the data DB.
The carry signal is applied to the comparator 5 as a pixel clock signal PCLK3, and the carry signal is applied to the timing processing circuit 4 as a pixel clock signal PCLK3. The timing processing circuit 4 generates the pixel clock signals PCLK1 and PCLK2 based on the pixel clock signal PCLK3, and also generates the detection signal from the laser beam detector 8.
LINE2 is used as a recording scan start synchronization signal for each scanning line.

Comparator 5 receives pixel density data DA and comparison data
The magnitude of DB is compared, and a binary pixel recording pulse signal S corresponding to "black" when DA>DB and "white" when DA≦DB is generated and given to the semiconductor laser circuit 6. The laser beam output from the semiconductor laser circuit 6 is deflected within a range of angle θ and scans and exposes the electrophotographic photosensitive drum 7 to form an electrostatic latent image, and the electrostatic latent image is developed with toner and then transferred onto recording paper. It is transferred and further fixed to become a recorded matter.

FIGS. 1A to 1C show timing charts of the pixel recording pulse signal generation operation and pixel recording of such a laser beam printer. a indicates a pixel number and pixel density data DA. b is the horizontal axis, t is the time axis, and the time required to record and scan one pixel is T. The vertical axis is the digital value corresponding to the pixel density, "0""white","15""black",
DA is pixel density data, and DB is comparison data.
In c, the horizontal axis x indicates the recording scanning position of the laser beam, and the shaded area is the recording area of each pixel.

In such a recording method, the laser beam output from the semiconductor laser circuit 6 has a spread in the scanning direction, so if this laser beam is intermittent with the pixel recording pulse signal S while scanning, each pixel recording surface is scanned. The exposure amount at both edges in the direction is an intermediate area between white and black, and the recording density in this area becomes unstable, causing a reduction in image quality. Therefore, if the pixels are made smaller and the number of intermittent laser beams is increased in an attempt to record a high-definition image, the area ratio of such unstable regions increases, resulting in a decrease in image quality.

This phenomenon occurs not only in laser beam printers, but also in thermal recording devices that control the recording energy applied to the recording medium intermittently while scanning, stylus electrostatic recording devices, and scanning exposure type electrophotography that uses liquid crystal light switches and emission diodes. This problem commonly occurs in scanning recording type recording devices such as printers.

[Purpose of the invention]

An object of the present invention is to reduce deterioration in image quality when recording high-definition images using this type of recording apparatus.

[Summary of the invention]

The present invention converts the density data of each pixel in an image signal into a pixel recording pulse signal having a time width proportional to the density for each pixel, and uses this pixel recording pulse signal to continuously control the generation of recording energy. In the method for generating a pixel recording pulse signal in a recording type recording device, the termination of the recording pulse signal of the preceding recording pixel in a pair of pixels adjacent in the recording scanning direction is made to coincide with the termination of the pixel, and the termination of the recording pulse signal of the pixel of the subsequent recording pixel is By aligning the starting edge of the recording pulse signal with the starting edge of the pixel and generating each,
The present invention is characterized in that recording energy is continuously generated between the pair of pixels, thereby reducing areas where recording density is unstable, thereby making it possible to reduce deterioration in image quality.

[Embodiments of the invention]

1d, e, f, and g are timing charts of the pixel recording pulse signal generation operation and pixel recording according to the present invention.

d is a pixel recording pulse signal generation operation by comparing the pixel density data DA and the comparison data DB, and the size of the comparison data DB increases in an odd pixel number area and decreases in an even pixel number area. For this purpose, pixel density data DA and comparison data are
The generation position of the pixel recording pulse signal S generated by comparing the magnitude of DB is such that in an odd pixel number area, the starting edge of the pixel recording pulse signal coincides with the starting edge of the pixel, and in an even pixel number area, the pixel recording pulse signal S coincides with the starting edge of the pixel. The end of the signal now coincides with the end of the pixel, and in the illustrated example, pixel numbers 2 and 3, and 4 and 5 are consecutive. Therefore, the recording pixels recorded based on this pixel recording pulse signal, as shown in e, have consecutive pixel numbers 2 and 3, 4 and 5, and there is no edge in the scanning direction between these pairs of pixels. The unstable region is reduced.

f is an example in which the size of the comparison data DB decreases in an odd pixel number area and increases in an even pixel number area, and the recorded pixels in this case are pixel numbers 1, 2, 3, and 4, as shown in g. are continuous.

Next, a pixel recording pulse signal generation circuit for performing such pixel recording will be explained. Figure 1d above
Generation of a pixel recording pulse signal by comparing the magnitudes of the pixel density data DA and the comparison data DB as shown in FIG. 2 can be performed by improving the circuit for generating the comparison data DB shown in FIG. Therefore,
Here, the circuit that generates this comparison data DB will be explained, and since the other circuits are the same as those of the conventional device, their explanation will be omitted. Note that the same reference numerals are used for the output terminals of each circuit and the signals generated at the terminals.

In FIG. 3, counter 13 is a hexadecimal counter that counts clock signal CLK1 input from clock generator 10 to clock terminal CLK.
The recording scanning signal LINE1 output from the timing processing circuit 4 is at a high level during recording scanning, and the counter 13 is connected to the clear terminal CLR.
The clock signal CLK1 is counted when this recording scanning signal LINE1 inputted to is at a high level, and is cleared to "0" when it is at a low level. The input terminal A of the data selector 14 inputs the count output signal Q ₁₃ of the counter 13 as it is, and the input terminal B inputs the inverted value of the count output signal Q ₁₃ of the counter 13. Therefore, the count output signal of the counter 13
When _Q13 is "0", input terminal A becomes "0" and input terminal B becomes "15". This data selector 14 selectively outputs the input signal of one of the input terminals A and B to the output terminal Y according to the signal level input to the selection control terminal Sel. An output signal _Q12 of an RS flip-flop (hereinafter referred to as FF) 12 is provided. The latch 15 outputs the signal input to the input terminal D as it is from the output terminal as an output signal Q ₁₅ (comparison data DB), and performs data latch according to the signal level of the pixel clock signal PCLK3 applied to the enable terminal En. Further, the carry signal outputted from the carry terminal Car of the counter 13 is inverted and becomes a pixel clock signal PCLK3, which is applied to the timing processing circuit 4, the clock terminal CLK of the FF 12, and the enable terminal En of the latch 15.

In the above circuit configuration, when the recording scanning signal LINE1 output from the timing processing circuit 4 becomes high level, the counter 13 clocks the clock generator 10.
The clock signal CLK1 given from the clock signal CLK1 is counted, and the value of the count output signal _Q13 is increased. Then, when the value of count output signal Q ₁₃ becomes “15”, the carry terminal Car
generates a carry signal. If the data selector 14 is set to select and output the signal of the input terminal A in the initial state, the comparison data DB, which is the output signal _Q15 of the latch 15, will be sequentially set from "0" to "15". increases to And the count value is “15”
When the carry signal Car is outputted, it is applied as the pixel clock signal PCLK3 to the enable terminal En of the latch 15, and the latch 15 latches "15". The pixel clock signal PCLK3 is
Since it is also applied to FF12, FF12 is inverted and the signal level of the output signal _Q12 changes, and this change in the signal level of the output signal _Q12 causes the data selector 14 to select the signal of the input terminal B and output it. Terminal Y
Output to. Therefore, the value of the output terminal Y of the data selector 14 changes from "15" to "0", but since "15" is latched in the latch 15, the comparison data DB is "15". This is pixel number 1
This is signal processing for pixels. When the next clock signal CLK1 is input, the value of the counter 13 becomes "0", and therefore the value of the output terminal Y of the data selector 14 becomes "15", and signal processing for the pixel number 2 is started. At the same time, the carry signal Car of the counter 13 disappears, so that the latch 15 outputs the signal at the input terminal D as it is.
Thereafter, the counter 13 counts the clock signal CLK1 and increases its value, but the data selector 14
outputs the value of the terminal B to which the inverted signal is input, so the comparison data DB, which is the output signal _Q15 of the latch 15, decreases sequentially. Then, when the value of the counter 13 becomes "15" (comparison data DB = 0), the carry signal Car is output, and the latch 1 is activated as described above.
5, FF 12 and data selector 14 are controlled.
At this time, the data selector 14 switches to select the signal at the input terminal A and output it to the output terminal Y.

By repeating this operation while the recording scanning signal LINE1 is at a high level, the comparative data
DB repeats increases and decreases as shown in FIG. 1d.

Such a comparison data generation circuit uses counter 1
This method has the advantage of enabling high-speed operation compared to the case of up-down.

If we compare the comparison data DB obtained in this way and the pixel density data DA in size, we can see in Figure 1 e.
It is possible to generate a pixel recording pulse signal S for performing pixel recording as shown in FIG.

Note that when the output signal Q ₁₂ of the FF 12 is initialized so that the data selector 14 selects and outputs the signal of the input terminal B in the initial state,
The comparison data DB changes as shown in Figure 1 f,
A pixel recording pulse signal S for performing pixel recording as shown in g in the figure is obtained.

Furthermore, the comparison data generation circuit shown in FIG. 3 further includes a counter 11 and a monostable multivibrator (hereinafter referred to as MM) 16. The timing processing circuit 4 outputs a print signal that goes high when the recording operation starts and goes low when it ends.
Generate PAGE. The counter 11 is a 2-bit binary counter in which the carry signal Car is set to high level when the count value reaches "3", and the print signal
Screen angle data when PAGE is low level
Load SD as initial value. When the carry signal Car of the counter 11 is at a low level, the FF 12 is preset, and as a result, the data selector 14 selects and outputs the signal of the input terminal A, so the initial value of the comparison data DB becomes "0" and the carry signal
When Car is at a high level, FF12 is cleared,
As a result, the data selector 14 selects and outputs the signal at the input terminal B, so the initial value of the comparison data DB becomes "15".

When recording for one scanning line is completed, the recording scanning signal
LINE1 becomes low level and counter 11 counts up. When the count value of the counter 11 changes from "0" to "1" or from "1" to "2", the carry signal Car remains at low level, so the recording scanning signal LINE1 changes to low level and MM16 changes. When triggered and a short pulse signal is generated at its output terminal Q ₁₆ , this pulse signal Q ₁₆
It is applied to the clear terminal CLR of FF12, and FF12 is cleared. The count value of counter 11 is “2” →
When it changes to "3", the carry signal Car becomes high level, so the pulse signal _Q16 generated from the MM16 is applied to the preset terminal PR of the FF12, and the FF12 is preset. Further, when the count value of the counter 11 is "3" and the carry signal Car is high level, the load terminal L of the counter 11 is at low level, so the next count value of the counter 11 is the screen angle data.
It becomes SD. Therefore, when the screen angle data SD is "3", FF12 is preset, and otherwise it is reset. This operation continues until recording is completed and the print signal PAGE becomes low level.

FIG. 4 is a timing chart of the pixel recording pulse signal S generation operation and pixel recording controlled by this circuit. h, i are screen angle data SD
is "3", h indicates the pixel recording pulse signal generation operation, and i is the pixel recording pattern resulting from the pixel recording pulse signal. The horizontal axis corresponds to the recording scanning direction, h is the time axis, and i is the scanning position, but here they are expressed by pixel numbers. The vertical axis corresponds to the feeding direction of the recording medium, h is the time axis, and i is the feed amount, but here they are displayed as scanning line numbers. Further, the count value of the counter 11 is also shown on the vertical axis. j and k are when the screen angle data SD is "2", l and m are when the screen angle data SD is "1", and n and p are when the screen angle data SD is "0".

When the screen angle data SD is "3", the count value of the counter 11 is always "3" as shown in FIG. FF12 is preset every time the signal LINE1 becomes low level, and therefore the initial value of the comparison data DB for each scanning line becomes "15", and the same pixel recording pulse signal generation operation shown in FIG. 1f is repeated. . The resulting pixel recording pattern of each scanning line based on the pixel recording pulse signal consists of successive pixels with pixel numbers 1 and 2, 3 and 4, as shown in FIG. 4i.

When the screen angle data SD is "2", the count value of the counter 11 changes as "2", "3", "2", "3", etc. in the order of the scanning line number as shown in Fig. 4j. The carry signal Car of the counter 11 repeats low level and high level, so the initial state of the FF 12 in each scanning line is cleared, preset, cleared, etc. in the order of the scanning line number. Therefore, the initial value of the comparison data DB for each scanning line is "0" for the odd scanning line number and "15" for the even scanning line number, and the same pixel recording pulse signal generation operation as in Fig. 1 d and f is performed alternately. repeated. As a result, as shown in FIG. 4k, in odd-numbered scanning lines, pixel number 2
, 3, 4, and 5 form a pair, and pixel recording is continuous, and in even-numbered scanning lines, pixel numbers 1 and 2, 3 and 4
Continuous pixel recording.

When the screen angle data SD is "1", the count value of the counter 11 is "1" as shown in FIG.
Repeat "2", "3", "1", "2", "3"...
Therefore, since the initial value of the comparison data DB for each scanning line repeats "0", "0", "15", etc. in the order of the scanning line number, the pixel recording pattern becomes as shown in FIG. 4m.

When the screen angle data SD is "0", the count value of the counter 11 is "0", "1", "2", "3", etc. repeatedly as shown in FIG.
Therefore, since the initial value of the comparison data DB repeats "0", "0", "0", "15", etc. in the order of the scanning line number,
The pixel recording pattern is as shown in FIG. 4p.

Comparing the pixel recording patterns i, k, m, and p in FIG. 4, it will be understood that the screen angle of the recording pattern differs depending on the value of the screen angle data SD. In a full-color laser beam printer using multiple recording, if the screen angles for each color are the same, moiré fringes will occur and the image quality will deteriorate.
Therefore, in the case of such color recording, a high-quality color image without moire fringes can be obtained by changing the value of the screen angle data SD for each color.

In the embodiment described above, pixel density data
Increase or decrease the number of bits of DA, comparison data DB, and screen angle data SD, change the waveform of comparison data DB, for example, change the shape to compensate for the T characteristic of the printer, and how to set the value of screen angle data SD. may be changed freely.

Of course, the present invention is applicable not only to laser beam printers but also to other scanning recording type recording apparatuses as described above.

〔Effect of the invention〕

As described above, the present invention continuously controls the generation of recording energy by converting the density data of each pixel in an image signal into a pixel recording pulse signal having a time width proportional to the density for each pixel. In a pair of pixels adjacent in the direction, the end of the recording pulse signal of the preceding recording pixel is made to coincide with the end of the pixel, and the starting end of the recording pulse signal of the subsequent recording pixel is made to coincide with the starting end of the pixel. Therefore, since recording energy is continuously generated between the pair of pixels, the factor of image quality deterioration caused by intermittent recording energy is reduced, and therefore the deterioration of image quality is reduced.

[Brief explanation of drawings]

1A to 1G are timing charts for explaining the operation, where a is the pixel number and pixel density data, b and c are the pixel recording pulse signal generation operation and pixel recording pattern in the conventional method, and d to g are the pixel recording pulses in the method of the present invention. 2 shows a block diagram of a conventional laser beam printer, FIG. 3 shows a comparison data generation circuit for implementing the present invention, and FIG. FIG. 3 is an explanatory diagram showing a pixel recording pulse signal generation operation and a pixel recording pattern. 4... Timing processing circuit, 5... Comparator, 6
... Semiconductor laser circuit, 13 ... Counter, 14
...Data selector, 15...Latch, DA...
Pixel density data, DB...comparison data.

Claims (1)

[Claims] 1. A scanning recording type that converts the density data of each pixel in an image signal into a pixel recording pulse signal having a time width proportional to the density for each pixel, and controls the generation of recording energy intermittently using this pixel recording pulse signal. In the method for generating a pixel recording pulse signal in a recording apparatus, the recording pulse signal of the preceding recording pixel in a pair of pixels adjacent in the recording scanning direction has its terminal end coincident with the terminal end of the pixel, and the recording pulse signal of the subsequent recording pixel is generated. A method for generating a pixel recording pulse signal, characterized in that each of is generated with a starting edge coincident with a starting edge of the pixel.