JPH01196345A - Image forming device - Google Patents

Abstract

PURPOSE:To enable formation of a high-quality intermediate tone image by driving each exposure means by using drive data of a pulse width corresponding to the weight of each bit of encoded data of image information. CONSTITUTION:Data corresponding to each exposure element in an image data storage part 31 and data in a corresponding image correction data storage part are corrected by an arithmetic and logic part 33, and the corrected data is stored in a data buffer 34. A counter 37 outputs a count completion pulse of a pulse width corresponding to the weight of encoded image data. A pulse width synthesizing circuit 35 generates a pulse width which corresponds to the weight of each bit of encoded data of image information, and generates a drive data pule by synthesizing each pulse width and the encoded data of each exposure element. The exposure element is driven by a string of drive data pulses.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image forming apparatus, and particularly to an image forming apparatus that controls the amount of exposure for each exposure element.

[Prior Art] Conventionally, there are image forming apparatuses that use a light emitting diode (hereinafter abbreviated as LED) or a liquid crystal shutter (hereinafter abbreviated as LC5) as an exposure element. For example, FIG. 4 shows the configuration of an image forming apparatus using LEDs, and FIG. 5 shows the driving section of the LEDs.

In FIG. 4, the photosensitive drum 1 rotates in the six directions of arrows, and light is formed on the photosensitive drum 1 by the charger 2 and the light from the LED array 5 focused by the SELFOC lens 4 in the LED head 3. A developing device 6 converts the latent image into a visible image. Further, the paper fed from the paper cassette 7 by the paper feed roller 8 is synchronized with the visible image on the photosensitive drum 1 by the registration roller 9, and the visible image on the photosensitive drum 1 is transferred by the transfer charger lO. The transferred image is scanned by the fixing device 11 and outputted to the stacker 12. 13 is a cleaner for cleaning the toner on the photosensitive drum 1;
is an erasing lamp for erasing the potential on the photosensitive drum 1.

FIG. 5 shows a drive circuit for LED elements arranged in an n-care array, in which the LED elements 21-1 to 21-n are
Transistors 23-1 to 23 through 2-1 to 22-n
-n. 24 is a latch circuit, 25 is a shift register, and image data (DATA) 2B is sent to the shift register 25 by a clock pulse (CLX) 27.
The parallel data from the shift register 25 is latched into the latch circuit 24 by the latch pulse 28, and the output signal from the latch circuit 24 is input to the bases of the transistors 23-1 to 23-n. , thus, the image data 26 causes the LED element 21 to
-1 to 21-n are driven.

30 is a power supply line, and 29 is a ground line.

[Problems to be Solved by the Invention] Using the image forming apparatus having the basic structure as described above, it is also possible to output a halftone image by finely turning on and off each pixel. Specifically, - at the same time as starting main scanning, the coded data of each pixel is compared with the number of times the exposure element is driven according to the pixel, and if the coded data is larger than the number of times of driving, the exposure element is driven. On the other hand, when the amount is low, the exposure is stopped.

As a result, a print pattern as shown in FIG. 6 is generated on the photosensitive drum.

The interval between encoder pulses is the time required for lifetime scanning, and the dot address is the number (position) of the exposure elements lined up in the main scanning direction. In the figure, exposure is performed 64 times for a lifetime scanning time.

However, this method has the drawback that since the encoder pulse is used as the reference, the black image is concentrated in the area corresponding to the timing when the pulse is output, and depending on the image formed, black streaks in the main scanning direction may be noticeable. was there.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and provide an image forming apparatus capable of producing high-quality halftone images.

[Means for Solving the Problems 1] The present invention comprises an exposure means in which a plurality of exposure elements are arranged in the main scanning direction, and a manual means for inputting coded data representing a corresponding gradation for each exposure element of the exposure means. , drive data output means for converting coded data from the input means into drive data having a pulse width corresponding to the weight of each bit constituting the coded data within one main scanning period; and means for driving and controlling the exposure means based on the drive data.

[Function] According to the present invention, a high-quality halftone image is formed by driving each exposure means using drive data with a pulse width that corresponds to the weight of each bit of coated data of image information. .

[Example] Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a block diagram of an image forming apparatus according to an embodiment of the present invention.

In FIG. 1, reference numeral 31 denotes an image data storage unit, which is comprised of a memory for storing image data, and stores image data sent from an image processing device, such as an image reader, connected to an image printing device. Image data consists of 6 bits per pixel. The data is (oooooo) 2
When , the pixel is white, that is, it is not printed, (11111
1) 2 indicates that the pixel is black, that is, to be printed.

Reference numeral 32 denotes an image correction data storage section (memory) in which correction data for each pixel data stored in the image data storage section 31 is stored. The correction data is, for example, image density data when an operator of an image forming apparatus wants to change the contrast of an image.

The calculation section 33 is connected to the exposure element (LE) in the image data storage section 31.
D) Perform correction calculations between the individual data and the data in the image correction data storage unit corresponding to the same exposure element, and store the results as 8-bit data in the data buffer 3.
Store in 4.

36 is an oscillator, 37 is a counter, and 38 is a frequency divider.

40 is an ED driving section including a latch, and drives the LED 21 via the resistor 22. 39 is a rotary encoder attached to the rotating shaft of the photosensitive drum 1;
Outputs a pulse indicating the rotation speed of the A pulse indicating this rotational speed is output every time the surface of the drum 1 moves by 25.4 mm/240 mm and 0.106 mm, and is used as a main scanning synchronization signal for the image.

The counter 37 outputs a count completion pulse having a pulse width corresponding to the weight of the image coded data. For example, in the case of 6-bit coded data, six types of pulse widths are sequentially output. The pulse width is twice that of the basic clock width,
It outputs 6 types: 4x, 8x, 16x, and up to 32x.

These six types of pulse signals are input to the pulse width synthesis circuit 35. The pulse width synthesis circuit 35 synthesizes each bit of the 6-bit encoded data of each exposure element from the data buffer 34 and the output pulse of the counter 37.

FIG. 2 shows an example of the connection between the counter 37 and the pulse width synthesis circuit 35. In FIG. 2, 47 is an AND circuit which gates the clock pulses for dividing the encoder pulse interval (one line printing interval) into 64. 49
- 54 are counters, and 49 counts up the clock pulse by 32, and the counter section 5
Apply the trigger to 0 and stop. Similarly, 50 counts up 16 counts, 51 counts up 8 counts, 52 counts up 4 counts, 53 counts up 2 counts, and 54 counts up 1 count.

The knob output resets the flip-flop (FF) 48.

Flip-flop 48 is set with encoder pulses. Therefore, clock pulses are input to each of the counters 49 to 54 for a time period corresponding to one line. In addition, each counter outputs its output only when counting is being performed.
TRUE" and inputs it to the AND circuits 51-1 to 51-n. 34 is the aforementioned data buffer; in this case, 1
Stores 6 bits x 2500 dots of information per line. The stored 6-bit data is stored in each AND circuit 5.
1-1 to 51-n. That is, if the data at dot address O is (101101)2, for example, the AND circuit 51-1 has "1", 51-
"O" is input to 2, "1" to 51-3, "l" to 51-4, "0" to 51-5, "1" to 51-6, and the AND circuit 51- 1.51-3.51-5.5
Gate 1-8 opens and counters 49, 51, 52.5
The signal No. 4 is input as is to the OR circuit 52-1.

FIG. 3 shows the state of the image on the photosensitive drum when the operation is performed as described above. The data at dot address O is (101
101)2. (000110)2, dot address 1
The data of (100100) 2 , (100000
) 2. The data of dot address 2 is (000000)
2. (111111)2, the data at dot address 3 is (111000)2. (101011)2.

In the above embodiment, pulses with six different pulse widths are arranged in descending order of pulse width, but the present invention is not limited to the order of pulse width.

For example, in the counter in Figure 2, 52.4
It may be set as 9, 53, 50.54.51.

Furthermore, as shown in Fig. 2, a counter that outputs pulses with six different count numbers was used, but when one counter was counted, the pulse count values were 1, 3, 8, 16, 3.
Six types of pulse widths may be generated by outputting a pulse when the value becomes 2.64 and sequentially setting and resetting flip-flops at the output timing of these pulses.

Furthermore, although AND circuit and OR circuit were used in Figure 2,
These are examples and are not limited thereto. Furthermore, although the present invention has been explained using an LED array,
It is clear that LCS may also be used.

As described above, a pulse width is generated according to the weight of each bit of coded data of image information, and a drive data pulse is generated by combining each pulse width with the coded data of each exposure element, and the drive data pulse is generated. By driving the exposure element with a data pulse train, it has become possible to obtain high-quality halftone images.

[Effects of the Invention] As described above, according to the present invention, it is possible to provide an image forming apparatus that can also form high-quality halftone images.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of an embodiment of the present invention; Fig. 2 is a detailed circuit diagram of the counter section and pulse width synthesis circuit; Fig. 3 is a diagram showing an example of a printing pattern according to the invention; Fig. 4 is a ED array. FIG. 5 is a block diagram of a drive circuit of the printer, and FIG. 6 is a diagram showing a conventional printing pattern. DESCRIPTION OF SYMBOLS 1... Photosensitive drum, 5... LED array, 33... Arithmetic unit, 34... Data storage unit, 35... Pulse width synthesis circuit. Procedural amendment April 13, 1986

Claims (1)

[Scope of Claims] Exposure means in which a plurality of exposure elements are arranged in the main scanning direction, input means for inputting coded data representing a corresponding gradation for each exposure element of the exposure means, and input means from the input means. drive data output means for converting the coded data into drive data having a pulse width corresponding to the weight of each bit constituting the coded data within one main scanning period; and drive data output from the drive data output means. An image forming apparatus comprising: means for driving and controlling the exposure means based on the exposure means.