JP2839810B2 - High density image forming method in LED printer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-density image forming method for an LED printer which enables formation of a high-density image by using a low-resolution print engine, and more particularly, to a method corresponding to Ndpi along a main scanning direction. 2Nd while effectively controlling the lighting of the LED element rows arranged on the line at intervals
LE capable of forming a high density image (latent image) of pi on a photoreceptor
The present invention relates to a high-density image forming method in a D printer.

[0002]

2. Description of the Related Art Conventionally, LED element groups arranged on a line in the main scanning direction are time-divisionally controlled to turn on the LED element rows corresponding to image information in units of n bits or in units of one main scanning line. An LED printer that forms an electrostatic latent image corresponding to the exposed image by forming the exposed image on the generatrix of the photosensitive drum is known, and this type of device is low in cost and compact. For example, 300 dpi printers having a low-density pitch interval have often been used for the reason described above. In recent years, however, the pitch interval has been increased to achieve higher image quality and higher resolution, and a printer of, for example, 600 dpi has been studied. Have been.

[0003]

However, unlike a laser printer, an LED printer has a pitch density (more specifically, a pitch density in the main scanning direction) of LE.
It depends on the arrangement interval of the LED elements on the D chip. Such an electrophotographic LED printer generally forms an image by reversal development. In order to briefly explain such a reversal developing method, first, a photosensitive member is uniformly charged in advance. Such charging is also performed by an independent charging device such as a charging roller or corona discharge.
In an image forming apparatus in which an ED unit is inserted in a photosensitive drum (JP-A-58-153957, etc.), in order to simplify the apparatus, an independent charger is not provided and the photosensitive drum and the developing sleeve are not provided. A toner rubbing area is provided on the developing sleeve, and a charge is injected into the photoconductive layer of the drum through the rubbing area using a developing bias applied to the developing sleeve side to perform charging.

[0004] Next, by controlling the lighting of an array-shaped LED unit in which LED chips are arranged in a row in accordance with image information, for example, when a beam dot is irradiated on a photosensitive member,
As shown in FIG. 8, on the photoconductor side, the charging potential distribution is reduced to a substantially normal distribution shape, and when the charge removal above the threshold value Vi, in other words, the latent image forming potential level, is performed, the photoconductor is charged to the charge removing section. The toner adheres to the upper portion, and a dot image is formed. For example, in a 300 dpi LED printer, by setting the light emission intensity of each LED element to be equal to or higher than the threshold value Ei, 300 dpi in the main scanning direction is set.
i can be printed, and in the sub-scanning direction, the lighting of the LED element is controlled every time printing corresponding to 300 dpi of the photoconductor.

Therefore, in order to form a printer of 600 dpi, it is necessary to set the arrangement interval of the LED elements for forming the exposure image to 1/2 of 300 dpi. Is about 0.8 mm, and it is not only difficult during manufacturing to further increase the density to 0.4 mm, but also to custom-manufacture a new 600 dpi LED chip. The cost is extremely high and is not practical. Therefore, the existing 300 dpi LED is processed while appropriately processing the 600 dpi high density image information transmitted from the host side.
It is preferable that a high-density image of 600 dpi can be formed using a printer.

For this reason, in a laser printer using an engine set to Ndpi, by setting a laser drive pulse time shorter than the time required for the laser to scan 1 / N inch, a technique for realizing high-density dots in the main scanning direction is realized. Has been proposed by the present applicant (JP-A-4-336).
859) However, as described above, in the LED printer, the pitch density depends on the arrangement interval of the LED elements, and thus it is impossible to increase the density in the main scanning direction only by the above-described hardware-based electric control. is there.

In view of the drawbacks of the prior art, the present invention provides a high-density image forming method for an LED printer capable of forming a 600-dpi high-density latent image using the existing print engine incorporating, for example, a 300 dpi LED chip array. To provide.

[0008]

SUMMARY OF THE INVENTION The present invention provides a method for controlling the number of LED elements arranged on a line at an interval corresponding to an image density N (positive integer) dpi along the main scanning direction while effectively controlling lighting of 2N dpi. High-density image forming method in an LED printer capable of forming a high-density image on a photoreceptor 1) m by the LED element row for each scan line
Is a positive integer , 2m times in the sub-scanning direction (for example, 2 × 8
Times) to generate the illuminable divisional exposure lines, the divided exposure
Neighbors in the line group forming one m times of the line
Dots can be formed in the sub-scanning direction by turning on lines
Point configured to capacity, i.e., more specifically, the illuminable configured Then Tomo LED element arrays 2m times every one scanning line
In addition, one dot is formed by the lighting light of one m-divided line.
Points to allow formation, 2) to exceed a multiple of the latent image forming a threshold on the photosensitive member by the lighting, the point which had been controlling the emission intensity of the LED elements previously, in one lighting if words Kaere is The point where the light emission intensity is controlled so as to exceed the threshold value by starting the lighting a plurality of times without exceeding the threshold value. 3) The interval corresponding to the image density Ndpi in the main scanning direction.
Superimposed or independent of the lighting light of the line groups adjacent to each other
In point is the dot formation, 4) while the lighting timing of the LED element on the dividing line and controlled as appropriate on the basis of the high density image information 2Ndpi transmitted from the host side, the high-density image 2Ndpi on the photoreceptor It is characterized by being formed into.

That is, the control will be described separately in the main scanning direction and the sub-scanning direction.
i, the formation of a latent image at a position corresponding to the specified density (a position corresponding to the conventional 300 dpi, in other words, a position corresponding to the even dot of 600 dpi), and a half of the specified density
At a position shifted from the interval , in other words, at a position corresponding to an odd-numbered dot of 600 dpi, the latent image generation method is changed and Ndpi is changed.
The latent image formation at the position corresponding to the specified density is controlled by (ma ( positive plural)) times or more in the sub-scanning direction at an arbitrary position on the divided exposure line, preferably in the sub-scanning direction. Try to generate an image. Meanwhile the determined density latent image formation position shifted half interval relative to the superimposed illumination count between adjacent prescribed density (m-a (positive s))
A dot latent image to be controlled to be turned on or off more times is generated. This allows 2N in the main scanning direction.
High-density latent images can be formed at intervals corresponding to dpi.

In this case, generally, a is (1/2) m
It is preferable to set before and after, but not limited to this. For example, at a position corresponding to the current specified density, ((m
−a) / 2) and b are positive integers, and ｛((ma) /
2) The dot latent image corresponds to 2Ndpi in the main scanning direction by performing lighting control of {((ma) / 2) -b} times at a position corresponding to the specified density of the next or preceding place + b times. The latent image is formed while being shifted to one side from the interval, thereby enabling smoothing with high density.

On the other hand, in order to increase the density in the sub-scanning direction, since the divided exposure lines are 2 m lines, a high-density image of 600 dpi can be easily formed basically by forming dots every m lines. According to the present invention, in particular, in correspondence with the main scanning direction, (ma ( positive plural)) times or more in the sub-scanning direction, preferably by continuous lighting , at intervals corresponding to 2 Ndpi in the sub-scanning direction. A high-density latent image is formed.

[0012]

In the case of an LED head array, a light image output from an LED element is formed on a photoreceptor using an imaging lens (such as a selfoc lens). Is approximately a normal distribution corresponding to the light intensity. Then, the charge level on the photoconductor is substantially in a normal distribution corresponding to the energy distribution,
For example, if the data transfer speed is set to 16 times that at 300 dpi and the divided exposure lines are set to 16 lines (2 m) in correspondence with this, for example, 4 lines (8 lines each in the upper and lower lines) are used. ma) By performing continuous lighting, specifically, as shown in FIG. 1A, the light emission intensity (energy) in each line is set to a threshold value or less, and
The emission intensity is set such that the combined energy Ge by superimposing the lines is greater than the threshold value Ei by continuously lighting the lines. As a result, the high-density control in the sub-scanning direction is performed by controlling the continuous lighting in the sub-scanning direction four times at an arbitrary dot position of 600 dpi corresponding to the arrangement position of the LED elements (a position corresponding to 300 dpi) at any position on the divided exposure line. By doing so, a dot latent image exceeding the threshold value Ei can be generated.

On the other hand, the formation of a latent image at a position shifted from the specified density by a half interval (an odd dot position at 600 dpi)
The number of times of superimposed lighting between adjacent specified densities (even number positions) is four or more, in other words, as shown in FIG. 1 and No. No. 2 is turned on, for example, two times at the specified density position. The combined energy at the density position of 1.5 becomes the energy for four times, and can exceed the threshold value Ei, so that 600 dpi in the main scanning direction.
High-density latent images can be formed at intervals corresponding to In this case N
o. 1 and No. The lighting of 2 is not limited to two times and is N
o. No. 3 three times at the specified density position. No. 2 is turned on once at the specified density position. 1.5 slightly from the density position of No. 1.5. A latent image can be formed at a position shifted to one side, thereby enabling smoothing as well as high density. When black dots are continuously generated at a position shifted from the specified density by a half interval , as shown in FIG. For example, four times with No. 1, No. 2 is turned on, for example, twice at the specified density position of No. 1 and N
o. The composite energy at the density position of 1.5 can exceed the threshold value Ei. 2 can form a white dot equal to or smaller than the threshold value Ei.

On the other hand, in order to increase the density in the sub-scanning direction, dots are basically formed every 8 lines because there are 16 divided exposure lines.
It becomes impossible to increase the density in the main scanning direction. Therefore, of the eight lines, as shown in FIG .
And so as to form a dense latent image at intervals of response.

[0015]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of the present invention; However, unless otherwise specified, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention, but are merely illustrative examples. Not just. First, the basic concept of the present invention will be specifically described. First, in the case where bitmap data of 600 dpi shown in the upper part of FIG. 2 is obtained from the host, the coordinates 1b, 2b,
3b is an even dot position of 600 dpi ( specified density 300
Coordinates 1a, 2a, and 3a (positions corresponding to dpi) are coordinates at positions shifted by an interval of 1/2 from the specified density (odd dot positions of 600 dpi). A, B and C are 300d
A1, A2, B in coordinates in the sub-scanning direction corresponding to pi
1, B2, C1, and C2 are coordinates in the sub-scanning direction corresponding to 600 dpi.

In the bitmap data,
The main scanning coordinate 2b on the sub-scanning coordinate A1 is a white dot, 3b
Is a black dot and if a black dot is hit on 3a, 2b is
By turning on the LED elements only for the divided lines (not exceeding the threshold value) and lighting the 5-division line LED elements for 3b (exceeding the threshold value Ei), a combined energy exceeding the threshold value Ei for 3a can be obtained. Also, on the sub-scanning coordinates A2,
The main scanning coordinates 1b, 2b, 3b are all black dots and 2
When a black dot is to be formed on a and 3a, the 5-division line LED element is lit on 1b and 3b, and the 8-division line LED element is lit on 2b (all exceed the threshold value), thereby setting the threshold on 2a and 3a. Exceeding combined energy is obtained.

Further, when the main scanning coordinates 2b on the sub-scanning coordinates B1 and B2 are black dots, 3b is a white dot, and 3a is a black dot, the LED element is turned on by 5 divided lines in 2b (threshold value). By turning on (not exceeding the threshold) the two-segment line LED element at 3b, a combined energy exceeding the threshold at 3a can be obtained. Further, when the main scanning coordinates 2b and 3b on the sub-scanning coordinate C1 are white dots and black dots are hit on 3a, the LED elements are turned on only on three divided lines on 2b and 3b (the threshold value is not exceeded). A combined energy exceeding the threshold value is obtained at 3a.

FIGS. 3 to 5 show an embodiment of the present invention showing the control section of the LED printer. The structure of the embodiment will be described in detail according to the operation. For example, as shown in FIG.
00 dpi video data is 1 from the main controller
When serially transmitted to the 6-bit input shift register 1, the register 1 converts the data into 16-bit units.
In other words, every time 16-bit data is stored in the shift register 1, it is written in parallel to the input buffer 4A of the SRAM 4 via the selector 2, selector 3, and 16-bit data bus 9 (FIG. 3) . In addition, SRAM
4 includes one input buffer 4A (5120 bits × 4 lines) to which data of 4 main scanning lines of 600 dpi can be input, and 300 dpi main scanning line data (2560 bits × 16 lines) corresponding to 16 divided lines. There are two storable processing / output buffers 4B and 4C.

After storing the bit map data of 3 lines or 4 lines necessary for the processing described later in the input buffer 4A, the latch 4A in the 9-bit matrix generator 5 in the sub-scanning direction in units of 3 bytes is stored in the buffer 4A. The data is transferred to the shift register 5A (FIG. 4) , and the generator 5 compares the 9-bit data with the template data in the templator 6 in the 3 * 3 bit window 5B, and turns on the 8-dot division line to the center dot of the window 5B. 8-bit data for determining the timing / number of times is generated, and the 8-hit data is stored in a coordinate converter (video data generator) 7.

The window 5B generates 8-bit data corresponding to an 8-divided line of the central dot corresponding to a prescribed density of 300 dpi while shifting the window 5B by 2 bits in the main scanning direction in order to correspond to 300 dpi. The coordinate converter performs 16 words (1) while rearranging (coordinate conversion) in the sub-scanning direction in units of 8 bits of the data.
After storing (6 × 8) data, the data is output to the output buffer 4C of the SRAM 4 via the 16-bit data bus.

As is clear from the timing charts of FIGS. 5 and 6, during the processing, the data corresponding to the preceding main scanning line data stored in the output buffer 4B in the previous cycle is transferred to the 16-bit data bus. 16 through 9
16-bit output shift registers 8A, 8 in bit units
The data is sequentially transferred to B, 8C, and 8D , and serially transmitted to the head circuit at a transfer speed of 16 times 300 dpi (8 times 600 dpi, in other words, 2 read cycles). Thereafter, the above operation is repeated every time the 16-bit data of 600 dpi is stored in the input shift register 1 sequentially, and after the data of one scan line (2560 bits × 16 lines) is stored in the output buffer 4C, the output buffer The above operation is repeated by switching the WRITE / READ cycle of 4B and 4C. That is, based on the timing chart, data input of 600 dpi to the input buffer 4A1, the data is processed and 300
pi processing data is generated and stored in the output buffer 4B or 4C in 16-bit units (for one divided line of 16 dots)
And the output buffer 4C or 4
The operation of selectively transferring the data of each divided line in parallel in units of 16 bits of the output shift register from B is performed in parallel.

In FIG. 3, reference numeral 10 denotes a timing controller, which is a video timing generator 11 for generating strobe and other various control signals for the engine system, and which is stored in the templator 6 corresponding to the light emission intensity of the LED element and the like. A control register 12 for selecting whether to use the template data, a clock generator 13 for generating a data transfer clock and the like, a cycle controller 14 for setting a switching cycle of the buffer, and the like are built in. It is controlled based on the synchronization signal Vsync. An address counter 15 designates a write or read address position in each of the buffers 4A, 4B and 4C in the SRAM 4 via a selector 16 and an address bus 17. The buffer switching cycle is switched based on the out enable OE and the write enable WE from the cycle controller 14.

FIG. 7 (A) shows the configuration of the LED head circuit, the output shift register 8 from the controller side of FIG. 3
Each shift register 21 corresponding serially from A to 8D
The 16-bit data transferred to A to 21D is (B)
As shown in FIG.
Are shifted and latched by the 16 × 4 bit latch circuit 22, and the common driver circuit 23 is driven based on the latch data of the latch circuit 22 to control the driving of each LED element 30a of the corresponding LED chip 30A. The shift register 21 (A to D) includes the latch circuit.
After 22 data transfer, and subsequently it continues to store the divided line data in the main scanning direction of the next order serially with latching the data into the latch circuit 22 side based on the latch signal every store the 16-bit data blocks Designation circuit 24
The connection of the common driver circuit 23 is switched to the next LED chip 30B based on the switching signal from the
The driving of each LED element 30a of the D chip 30B is controlled, and the same operation is continuously performed 40 times to output data for one divided line. Furthermore, the LED chips 1A to
By performing 1M drive control (40 × 16) times, 16
The LED element lighting control of one divided scanning line is controlled. The counter and the decoder control the lighting time and timing of the common driver circuit 23.

[0024]

As described above, according to the present invention, the existing low-density Ndpi engine can be used as it is to achieve high-density 2
Ndpi and a high-resolution latent image can be formed. Further, according to the present invention, since the densification is achieved separately in the main scanning direction and the sub-scanning direction, smoothing processing and gradation processing can be easily performed, and the practical value thereof is extremely large. . And so on.

[Brief description of the drawings]

FIG. 1 is a basic configuration diagram of the present invention showing the light emission energy of an LED element and a state of forming a latent image.

FIG. 2 is a graph showing a relationship between 600 dpi bitmap data and the number of light emission times of an LED element according to the embodiment of the present invention.

FIG. 3 is an overall circuit diagram of a controller according to an embodiment of the present invention.

FIG. 4 is a block explanatory diagram 1 showing the data flow and operation of FIG. 3;

FIG. 5 is a second block diagram showing the data flow and operation of FIG. 3;

FIG. 6 is a timing chart of FIG. 3;

FIG. 7 is an LED head circuit diagram used in the present embodiment.

FIG. 8 shows the emission energy of a conventional LED element and the state of formation of a latent image.

[Explanation of symbols]

 Ei, Vi Threshold 1 Input shift register 2, 3 Selector 4 SRAM 4A Input buffer 4B, 4C Output buffer 5 Matrix generator 5A Latch & shift register 5B Window 7 Coordinate converter 9 16-bit data bus 30A LED chip 30a LED element

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tadaharu Kusumi 2--14-9 Tamagawadai, Setagaya-ku, Tokyo Kyocera Corporation Tokyo Yoga Office (56) References JP-A-4-336859 (JP, A) JP-A-2-13979 (JP, A) JP-A-1-146748 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B41J 2/44 B41J 2/45 B41J 2/455 H04N 1/036

Claims (3)

(57) [Claims] 1. An image density N (positive uniformity) along a main scanning direction.
Number) LEDs arranged on the line at intervals corresponding to dpi
In a high-density image forming method for an LED printer capable of forming a high-density image of 2 Ndpi on a photosensitive member while effectively controlling the lighting of an element row , the LED element row provides 2 m (m) in a sub-scanning direction for each scanning line. : A positive integer) to generate a divided exposure line that can be turned on times, and to form one of the divided exposure lines m times
Side run by lighting adjacent lines in the in group
In the main scanning direction, adjacent dots are formed at intervals corresponding to the image density Ndpi.
The lighting light of the line groups is superimposed or
Is DOO formed, the only to exceed the latent image forming a threshold on the photosensitive member by a plurality of lighting divisional exposure line, previously controlling the emission intensity of the LED elements, based on the high density image information 2Ndpi A high-density image of 2 Ndpi on a photoreceptor while appropriately controlling the number of times the LED elements are turned on in the divided exposure line. 2. In high-density control in the main scanning direction, Nd
forming a latent image at a position corresponding to the specified image density of pi at an arbitrary position on the divided exposure line (ma (positive plural))
A dot latent image is generated by controlling lighting in the sub-scanning direction one or more times, and corresponds to 1 / (2N) dpi with respect to the specified image density .
Forming a latent image at a position shifted by an interval so that the number of times of superimposed lighting between adjacent specified image densities is (ma ( positive plural)) times or more, 2. The high-density image forming method according to claim 1, wherein high-density latent images can be formed at intervals corresponding to 2 Ndpi in the main scanning direction. 3. The density in the sub-scanning direction is increased in the sub-scanning direction by turning on ( ma ( positive plural)) times or more in an arbitrary position on the divided exposure line in the sub-scanning direction. 2. The high-density image forming method according to claim 1, wherein a high-density latent image can be formed at an interval corresponding to 2 Ndpi.