JP2004249549A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus in which a user can select any one of a high resolution mode capable of high resolution printing or a high speed mode capable of high speed printing not with high resolution (multilevel halftoning). <P>SOLUTION: Depending on a MODE signal indicative of a high resolution mode or a high speed mode, a timing signal generating section 42 in an LED head control circuit 3 generates a write period timing signal of high resolution mode or high speed mode for an LED head 28. In synchronism with the timing signal of each mode, a control signal output section 44 controls the LED head 28 not to perform area halftoning in high speed mode and to write data of N lines using continuous strobe signals only once although write strobe signal is required N times in high resolution mode thus realizing high speed processing. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image forming apparatus such as an LED printer.
[0002]
[Prior art]
With the spread of computers and the improvement of performance, the spread of printers and the improvement of performance have been remarkable, and there is a demand for printers to provide printed images with excellent print quality and high-speed processing. In order to respond to a demand for a print image having excellent print quality, one dot in the original image data input from the host device is configured to be reproduced by a plurality of pixels, and one dot in one dot is reproduced based on gradation information of one dot. A print image with excellent print quality is realized by expressing a gray scale by an area gray scale expression method in which the number of pixels for recording / non-recording is changed.
[0003]
For example, in a color LED printer, when printing is performed by a printer having an optical writing head in which a plurality of LEDs are arranged in the main scanning direction, the print head is moved in the sub-scanning direction by 1 / N of one dot width with respect to the original image data. In this manner, high-resolution (multi-gradation) printing is performed by controlling recording / non-recording of N (pixel) lines per dot width in one direction (for example, see Patent Document 1).
[0004]
[Patent Document 1]
JP-A-6-297766
[0005]
[Problems to be solved by the invention]
Considering only the print quality, it is naturally desirable to print at high resolution (multi-gradation), but on the other hand, high-resolution (multi-gradation) such as when printing text in monochrome. In some cases, it is not necessary to increase the printing speed. Therefore, there is a problem that both high-resolution printing and high-speed printing without gradation expression can be realized.
[0006]
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an image forming apparatus that can perform not only high-resolution multi-tone expression printing but also high-speed printing.
[0007]
[Means for Solving the Problems]
According to the present invention, in order to achieve the above object, a plurality of exposure elements are arranged in a main scanning direction, and one pixel is recorded on a recording medium by exposure of each of the plurality of exposure elements and a unit scanning operation of the recording medium. Image formation with a high-resolution mode for reproducing a one-dot image composed of N (N is an integer of 2 or more) pixels in the continuous sub-scanning direction by area gradation expression by a combination of recording / non-recording of the pixels The apparatus further includes a high-speed mode in which the area gradation is not performed in addition to the high-resolution mode in which the area gradation is performed. In the high-resolution mode in which the area gradation is performed, each pixel is synchronized with a write synchronization timing signal of one pixel. In the high-speed mode in which the area gradation is not performed, the exposure by the exposure element is intermittently controlled in synchronization with the write synchronization timing signal of N pixels. Characterized in that it comprises an exposure control means, for controlling the exposure by to the exposure device.
[0008]
According to such a configuration, when the high-resolution mode is selected, the area gradation processing is performed on the original image data, so that high-resolution printing with gradation expression is possible, and when the high-speed mode is selected, the high-resolution printing is performed. Recording is performed in synchronization with a high-speed mode timing signal that is faster than the mode timing signal, and high-speed printing is possible because area grayscale processing is not performed. As a result, the user can select the high resolution mode or the high speed mode according to the purpose of printing, so that the effect of improving usability is obtained.
[0009]
Further, in the present invention, a plurality of recording heads in which the plurality of exposure elements are arranged in the main scanning direction are provided in the sub scanning direction, and the plurality of recording heads are controlled in the high resolution mode for performing the area gradation. The color recording is performed.
This enables color printing as well as monochrome printing.
[0010]
Further, in the present invention, a plurality of recording heads in which the plurality of exposure elements are arranged in the main scanning direction are provided in the sub-scanning direction, and one of the plurality of recording heads is controlled in the high-speed mode in which the area gradation is not performed. Then, monochrome recording is performed.
This makes it possible to simplify the control of the recording head, so that monochrome printing can be performed at high speed.
[0011]
Still further, in the present invention, in the high-speed mode in which the area gradation is not performed, the exposure control means continuously performs exposure of N pixels in synchronization with a write synchronization timing signal of N pixels. .
By doing so, the exposure time can be shortened, and printing in the high-speed mode can be performed at high speed.
[0012]
In order to achieve the above object, according to the present invention, a plurality of exposure elements are arranged in a main scanning direction, and one pixel is recorded on a recording medium by exposure of each of the plurality of exposure elements and a unit scanning operation of the recording medium. A high-resolution mode that reproduces a one-dot image composed of N (N is an integer of 2 or more) pixels in the continuous sub-scanning direction by area gradation expression by a combination of recording / non-recording of the pixels; In an image forming apparatus having a high-speed mode for reproducing a one-dot image at a resolution, an interface control means for receiving print data and gradation designation information sent from a host device, and image data output by the interface control means Input means for inputting a pixel image, and generating record / non-record information of a pixel image from the image data based on the gradation designation information. Tone data converting means, timing signal generating means of a first cycle for generating N write synchronization timing signals during one dot line recording period in the high resolution mode, and said timing signal generating means during one dot line recording period in the high speed mode. A second cycle timing signal generating means for generating a write synchronization timing signal having a cycle shorter than the first cycle timing signal N times; and a write synchronization of the first cycle timing signal generating means in the high resolution mode. In synchronization with the timing signal, N pixel line data generated from the gradation data conversion means is output to the exposure element array, and in the high-speed mode, a write synchronization timing signal of the second timing signal generation means is output. In synchronization, the one-dot line data received by the receiving means is output to the exposure element array, and the exposure element array is output. Characterized by comprising the exposure element array drive control means for controlling the light emission driving.
[0013]
According to such a configuration, in the case of color printing in which printing is performed in the high-resolution mode, the original image data is subjected to area gradation processing, so that high-resolution printing with gradation expression can be performed. In the case of monochrome printing, recording is performed in synchronization with the write synchronization timing signal for the high-speed mode, which is faster than the write synchronization timing signal for the high-resolution mode, and high-speed printing is performed because the area gradation processing is not performed. Becomes possible. As a result, the high resolution mode or the high speed mode is selected according to the purpose of printing, so that the effect of improving usability is obtained.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a circuit configuration diagram of an image forming apparatus according to an embodiment of the present invention. The image forming apparatus used in the description of the present embodiment is a so-called tandem type color printer. 1, the color printer 1 includes an I / F (interface) controller 2, an LED head control circuit 3, and a printing mechanism 4.
[0015]
The I / F controller 2 receives, via the bus line 5A, image data and print data including gradation designation information transmitted from a PC (personal computer) 5 serving as a higher-level device, and receives each color of image (video) data. And outputs data for each color of yellow (Y), magenta (M), cyan (C), and black (K) to the LED head control circuit 3. That is, the I / F controller 2 includes a CPU 6, a ROM 7, a DMAC 8, a RAM 9, an image memory 10, and transfer circuits 11Y, 11M, 11C, and 11K. The overall control of the F controller 2 is performed.
[0016]
The image data sent from the PC 5 is temporarily stored in the RAM 9 and then separated into video data of Y, M, C, and K, and stored in the image memory 10 for each of the colors of Y, M, C, and K. It is memorized. That is, the image memory 10 has a storage area for storing one page of video data for each color of Y, M, C, and K. In response to a control signal of the CPU 6, one image in the main scanning direction of each page is provided. The video data for the lines is sequentially read and output to the yellow transfer circuit 11Y, the magenta transfer circuit 11M, the cyan transfer circuit 11C, and the black transfer circuit 11K for each color. The RAM 9 stores data transmitted from the PC 5 in addition to the image data, for example, data for distinguishing whether to print the image data in color or monochrome, and whether to print in a high-resolution mode described later or in a high-speed mode. It stores mode data and the like for discriminating whether to print, and also stores data and the like required by the CPU 6 in the process of executing the program. Further, the DMAC 8 controls the transmission of one line of video data from the image memory 10 to each of the transfer circuits 11Y, 11M, 11C and 11K without passing through the CPU 6.
[0017]
Each of the transfer circuits 11Y, 11M, 11C, and 11K that has received one line of video data outputs one line of video data VD to the LED head control circuit 3. At this time, the LED head control circuit 3 outputs a horizontal synchronizing signal (HSYN) 33 to each of the transfer circuits 11Y, 11M, 11C, and 11K according to the processing status of each image forming unit 13 of the printing mechanism 4 described later. The transfer circuits 11Y, 11M, 11C, and 11K transmit one line of video data VD to the LED head control circuit 3 together with the video signal synchronization clock (VCLK) 34 in synchronization with the horizontal synchronization signal (HSYN) 33. . As described above, mode data indicating whether printing is performed in the high-resolution mode or the high-speed mode is sent from the PC 5 and stored in the RAM 9, and the CPU 6 determines in which of the above-described modes the printing is performed. Is output to the LED head control circuit 3.
In another embodiment, the I / F controller 2 recognizes whether the print data input from the PC 5 is color print data or monochrome print data, and automatically switches the MODE signal to the high-resolution mode when the print data is color print data. In the case of monochrome print data, the MODE signal is switched to the high-speed mode.
[0018]
Next, the printing mechanism 4 includes a paper supply / transport mechanism 12, a plurality of image forming units 13, and a fixing device 14. The paper supply / conveyance mechanism 12 includes a paper supply cassette 16 in which the papers P are loaded and stored, and standby rollers 18 a and 18 b for temporarily transporting the papers P from the paper supply cassette 16 in the direction of the arrow 17 and then temporarily waiting the papers P. , Driven rollers 19 and 20 driven by a motor (not shown), and a transport belt 21 rotated by the driven rollers 19 and 20. That is, the sheet P carried out from the sheet cassette 16 in the direction of the arrow 17 is sent to the standby rollers 18a and 18b, and moves on the conveyor belt 21 at a timing coincident with a toner image formed on a photosensitive drum described later. I do. While the paper P moves on the transport belt 21, the toner of each color is transferred to the paper P on the transport belt 21 by the image forming units 22, 23, 24, and 25, and color transfer is performed on the paper P. Thereafter, a heat fixing process is performed by the fixing device 14, and the sheet P is carried out of the apparatus.
[0019]
The image forming units 22, 23, 24, and 25 of the image forming unit 13 transfer yellow (Y), magenta (M), cyan (C), and black (K), respectively, and transfer yellow (Y). , Magenta (M), cyan (C), and subtractive color mixing of the image forming units 22, 23, 24, and 25 for color printing. The black (K) image forming unit 25 is also used for monochrome printing. Each of the image forming units 22 to 25 has exactly the same configuration except for the (color of) the developer stored in the developing container. Here, among the four image forming units 22 to 25, the black (K) is used. The configuration will be described using the image forming unit 25 as an example.
[0020]
The photosensitive drum 26 has a peripheral surface made of, for example, an organic photoconductive material. In the vicinity of the peripheral surface of the photosensitive drum 26, a charger 27, an LED head 28, a developing roll 29b (a developing container 29a), and a transfer. The vessels 30 are sequentially arranged. The photoreceptor drum 26 rotates in the direction of the arrow 31, and first charges the peripheral surface of the photoreceptor drum 26 uniformly by applying a charge from the charger 27. Next, an electrostatic latent image is formed on the peripheral surface of the photosensitive drum 26 by optical writing based on the print information from the LED head 28, and a toner image is formed by a developing process using the developing roll 29b. At this time, the toner image formed on the peripheral surface of the photosensitive drum 26 is made of black (K) toner stored in the developing container 29a. The toner image formed on the peripheral surface of the photosensitive drum 26 in this way reaches the position of the transfer device 30 with the rotation of the photosensitive drum 26 in the direction of the arrow 31, and is transported on the transport belt 21 by the transfer device 30. Is transferred to the paper P to be printed.
[0021]
The LED head control circuit 3 outputs a control signal for printing the video data VD to the LED head 28 in synchronization with a clock signal (VCLK) 34 of the video signal sent from the I / F controller 2. A yellow (Y), magenta (M), cyan (C), and black (K) LED head control circuit 3 corresponding to each of the transfer circuits 11Y, 11M, 11C, and 11K described above. It is. Here, the black (K) LED head control circuit 3 will be described in detail below, but similar control circuits are provided for yellow (Y), magenta (M), and cyan (C). is there.
[0022]
A portion surrounded by a broken line in FIG. 2 is a circuit block diagram showing a detailed configuration of the above-described black (K) LED head control circuit 3. In the figure, the TW1 register 40 stores one cycle of time data TW1 of a reference timing signal (write synchronization timing signal for one pixel line) used in the high resolution mode, and the TW2 register 41 uses it in the high speed mode. The time data TW2 of one cycle of the reference timing signal shorter than TW1 is stored. The time data TW1 and TW2 are supplied to the timing signal generator 42.
[0023]
In the case of the high-resolution mode, the timing signal generator 42 reads the time data TW1 of the TW1 register 40 in response to the MODE signal indicating whether the mode is the high-resolution mode or the high-speed mode sent from the control signal output unit 44 described later. Φ1 is read, and in the case of the high-speed mode, the timing data Φ2 is generated by reading the time data TW2 of the TW2 register 41, and the I / F control signal output unit 43, the control signal output unit 44, the head control signal output unit 45, and Output to the photosensitive drum controller 60.
[0024]
The I / F control signal output unit 43 transmits a horizontal synchronizing signal (HSYN) 33 to the I / F controller 2 according to the MODE signal and the timing signal Φ1 in the high resolution mode or the timing signal Φ2 in the high speed mode.
[0025]
The control signal output unit 44 receives the MODE signal and the video signal synchronization clock (VCLK) 34 from the I / F controller 2, and outputs a timing signal generation unit 42, an I / F control signal output unit 43, and a head control signal output unit 45. Output a MODE signal. In addition, control of reception of video data VD for one line according to the timing signal Φ1 in the high resolution mode or the timing signal Φ2 in the high speed mode, and control as to whether or not to perform the area gradation by the area gradation data conversion unit 52, In addition, it controls output of a data signal synchronous clock (DCLK) to the LED head driver 28a and control of writing of the write data DATA.
[0026]
The control signal output unit 44 receives a CS1 signal for sequentially storing the video data VD sent from the I / F controller 2 in the four line buffers (LB1) 47 to the line buffer (LB4) 50. The video data of the line buffer (LB1) 47 to the line buffer (LB4) 50 is output to the divider 46 as means, and the video data of the line buffer (LB1) 47 to the line buffer (LB4) 50 is transmitted to the selector 53 via the area gradation data conversion unit 52 in the high resolution mode. In the high-speed mode, a CS2 signal, which is a control signal for directly supplying the selector 53, is output to the selector 51. Further, it outputs a CS3 signal, which is a control signal for converting the input line data into data of four lines, to the area gradation data conversion unit 52, and outputs the area gradation data conversion to the selector 53. A CS4 signal for selecting one of the data from the section 52 and the data from the selector 51 according to the mode. For a selector 59 to be described later, an output buffer (OLB1) 54 to an output buffer (OLB5) 58 to be described later are provided. A CS5 signal to be sequentially selected is output.
[0027]
As described above, in the case of the high resolution mode, the line data output from the selector 51 is converted into data for four lines by the area gradation data conversion unit 52 by controlling the CS3 signal, and is input to the selector 53 by controlling the CS4 signal. The data of the line buffer is sequentially stored in the five output buffers (OLB1) 54 to the output buffer (OLB5) 58. The output buffer data stored in the output buffer (OLB1) 54 to the output buffer (OLB5) 58 is selected by the selector 59 under the control of the CS5 signal and transmitted to the LED head driver 28a. From 45, a latch signal (LAT), which is a timing signal for holding the sent data in a buffer RAM (not shown) provided in the LED head driver 28a, and an LED to the LED head driver 28a. A strobe signal (STR) for controlling the light emission driving of is output. As a result, one line of data held in the buffer RAM in the LED head driver 28a is written to the LED head array 28b, thereby performing one line of exposure.
[0028]
The control of the operation speed of the photosensitive drum 26 for determining the process speed is performed by the photosensitive drum controller 60 in accordance with the timing signal Φ1 or Φ2 from the timing signal generator 42.
[0029]
Before describing the processing operation of the LED head control circuit 3, the area gradation in the high resolution mode will be described. As shown in FIG. 4A, in an image forming apparatus in which M exposure elements, for example, LEDs are arranged in a main scanning direction, and a recording medium or a print head moves in a sub-scanning direction, it is necessary to control gradation of an image. The following method is used. Here, an example in which a one-dot image is expressed by five gradations (however, white dots are included in the gradation) will be described with reference to FIG. In this case, the gradation value 0 is a white dot, and non-printing processing is performed on all pixels even when one dot is divided into four. On the other hand, a gradation value of 1 is 1/4 gradation, and a printing process is performed by supplying a strobe signal for instructing an exposure to the print head for one dot for one time. In the case of the gradation value 2, the strobe signal is supplied twice for one dot printing, and the printing process is performed. In the case of the gradation value 3 and the gradation value 4, The printing process is performed by supplying the strobe signal for the time for three times or the time for four times.
[0030]
Next, printing in the high-speed mode will be described. Even in the case where the print head capable of the above-described area gradation is used, in the high-speed mode in which the area gradation is not performed, two types of gradation values 0 and 4 shown in FIG. Only the gradation value is used. When the gradation value is 0, all four pixels are processed so as to be printed in white (non-printing). When the gradation value is 4, all four pixels are printed in black ( (Printing). That is, by performing the processing as described above, when the area gradation is performed in the high resolution mode, a high-accuracy color image including the gradation expression is reproduced as shown in FIG. When the key is not adjusted, a monochrome image without halftone is printed as shown in FIG. 5B.
[0031]
Next, the operation of the color printer 1 configured as described above will be described with reference to the time chart of FIG. 3A to 3G show time charts in the high-resolution mode, and H to I show time charts in the high-speed mode. First, in the high resolution mode, the processing is advanced by the timing signal Φ1 (A in FIG. 3) of the cycle TW1 generated by the timing signal generator 42.
[0032]
First, the line buffer (LB1) 47 and the line buffer (LB2) 48 are read from the video data VD of one line received from the I / F controller 2 through the divider 46 under the control of the CS1 signal in a TW1 × 4 reading time. , And sequentially stored in the line buffer (LB3) 49 and the line buffer (LB4) 50 (B in FIG. 3). After the line buffer (LB4) 50, the line buffer is switched so as to return to the line buffer (LB1) 47 again, and the previous line (n-1) and the current line (n) are always processed for area gradation processing. ) And the next line (n + 1). The stored data for three lines is selected by the selector 51 under the control of the CS2 signal, and the current line (n), the next line (n + 1), and the area gradation data conversion are sequentially performed from the previous line (n-1). Output to the unit 52.
[0033]
The area gradation data conversion unit 52 sequentially receives data of three lines under the control of the CS3 signal, performs conversion processing of the area gradation, and outputs the output data na of four lines corresponding to the current line (n). Output data n-b, output data nc, and output data nd are sequentially output. The output data na, output data nb, output data nc, and output data nd of the output four lines are output to the output buffer (OLB1) 54 via the selector 53 under the control of the CS4 signal. The data is sequentially stored in the buffer (OLB2) 55, the output buffer (OLB3) 56, the output buffer (OLB4) 57, and the output buffer (OLB5) 58 with the writing time of TW1 (C in FIG. 3). After the output buffer (OLB5) 58, the line buffer is switched so as to return to the output buffer (OLB1) 54 again and transmitted to the LED head driver 28a for transmission to the current line (n). The output data (na, nb, nc, nd) for the line is stored.
[0034]
Output data (na, nb, nc, nd) for four pixel lines after area gradation conversion corresponding to the current line (n) are sequentially output from the selector 59 by the control of the CS5 signal. While selecting, the data is transmitted to the LED head driver 28a in the write time of TW1 in synchronization with the latch signal (LAT) and the strobe signal (STR) transmitted by the head control signal output unit 45 and the data signal synchronous clock (DCLK). . In the LED head driver 28a, output data is sequentially held in the internal buffer RAM in synchronization with the latch signal (D in FIG. 3) (E in FIG. 3). As a result, four lines of output data (na, nb, nc, nd) are sequentially exposed by the LED head array 28b. That is, in the high resolution mode, the holding / exposure of the buffer RAM is intermittently repeated for four lines (G in FIG. 3).
[0035]
Next, the processing operation of the LED head control circuit 3 in the high-speed mode will be described. The process proceeds with a period TW2 (<TW1) timing signal Φ2 (H in FIG. 3) generated by the timing signal generation unit 42.
[0036]
First, the line buffer (LB1) 47 and the line buffer (LB2) 48 are read from the video data VD for one line received from the I / F controller 2 through the divider 46 under the control of the CS1 signal in a TW2 × 4 reading time. , And sequentially stored in the line buffer (LB3) 49 and the line buffer (LB4) 50 (I in FIG. 3). After the line buffer (LB4) 50, the data is stored while switching the line buffer so as to return to the line buffer (LB1) 47 again. The stored data for one line is selected by the selector 51 under the control of the CS2 signal and output to the selector 53.
[0037]
The output data of one line is output to the output buffer (OLB1) 54, the output buffer (OLB2) 55, the output buffer (OLB3) 56, the output buffer (OLB4) 57, the output buffer via the selector 53 under the control of the CS4 signal. (OLB5) 58 are sequentially stored with the write time of TW2 (J in FIG. 3). After the output buffer (OLB5) 58, one line of output data is stored for transmission to the LED head driver 28a while switching the line buffer to return to the output buffer (OLB1) 54 again.
[0038]
While sequentially selecting output data (n) for one dot line corresponding to the current line (n) by the selector 59 under the control of the CS5 signal, the latch signal (LAT) transmitted by the head control signal output unit 45 and the strobe signal In synchronization with the signal (STR) and the data signal synchronous clock (DCLK), the signal is transmitted to the LED head driver 28a only once during the writing time of TW2. At this time, the strobe signal (STR) is continuously output during the writing time of TW2 × 4 times. In the LED head driver 28a, output data is held in the internal buffer RAM in synchronization with the latch signal (K in FIG. 3) (L in FIG. 3). As a result, the output data (n, n, n, n) for four lines having the same value is exposed by the LED head array 28b in a shorter time than in the high resolution mode (N in FIG. 3).
[0039]
<Second embodiment>
Next, a second embodiment of the present invention will be described.
In the first embodiment, information for designating printing in the high-resolution mode or printing in the high-speed mode is input from the PC 5, and the I / F controller 2 switches the MODE signal according to the designation. However, in this example, there is no direct input of the high-resolution mode / high-speed mode designation information from the PC 5, and the I / F controller discriminates between color printing and monochrome printing, and automatically outputs the high-resolution MODE signal. The mode or the high-speed mode is switched.
[0040]
Specifically, as one method, the print data sent from the PC 5 includes a command for specifying color printing or a command for specifying monochrome printing. The command analyzer of the I / F controller recognizes this, and switches the MODE signal to the high-resolution mode or the high-speed mode.
[0041]
As another method, when image data sent from the PC 5 is stored in the RAM 9 and then separated into Y, M, C, and K data, if only monochrome data and K exist, In the case of color print data in which any of the data of Y, M, and C exists in the high-speed mode, the I / F controller switches the MODE signal to the high-resolution mode.
Further, as another method, it is determined whether or not the image data sent from the PC 5 includes information for specifying the gradation. If the image mode does not include the gradation designation information, the I / F controller switches the MODE signal to the high-speed mode.
The subsequent operation is the same as in the first embodiment.
[0042]
In the above embodiment, the LED head is used as the print head. However, the present invention is not limited to this, and a laser beam, a liquid crystal shutter, a thermal head, or the like may be used.
[0043]
Further, in the above embodiment, in the high-speed mode, the strobe signal (STR) is continuously output in the TW2 × 4 writing time to perform the exposure, but the output state of the strobe signal (STR) is changed. The exposure may be performed in the output state continuously during the writing time of TW2 × 3 times or TW2 × 2 times. This reduces exposure contrast, but saves photosensitizer.
[0044]
【The invention's effect】
As described above, in the present invention, the high-resolution (multi-gradation) mode and the high-speed mode are provided, and in the high-speed mode, the exposure head is controlled such that one exposure is an exposure for N consecutive lines. Therefore, recording can be performed at a higher speed than in the high-resolution mode in which exposure is performed for N lines in N exposures. If one of the high-resolution mode and the high-speed mode is selected depending on the purpose of use, the usability is improved. This has the effect.
[0045]
Further, in the second embodiment, even if the user does not designate the print mode of the high resolution mode or the high speed mode from the PC 5, the color printer determines the difference between the color print and the monochrome print by itself, and the appropriate method is used. Since the printing process is performed, there is no need for a user's judgment or operation, which is extremely convenient.
[Brief description of the drawings]
FIG. 1 is a circuit configuration diagram of an image forming apparatus according to an embodiment of the present invention.
FIG. 2 is a circuit configuration diagram of an LED head control circuit.
FIG. 3 is a time chart illustrating a processing operation of the LED head control circuit.
4A is a diagram showing a configuration of an LED head, FIG. 4B is a diagram showing print dots in a high resolution mode, and FIG. 4C is a diagram showing print dots in a high speed mode.
5A is a diagram illustrating a printing example when area gradation is performed, and FIG. 5B is a diagram illustrating a printing example when area gradation is not performed.
[Explanation of symbols]
1 color printer
2 I / F (interface) controller
3 LED head control circuit
4 Printing mechanism
5 PC (personal computer)
6 CPU
7 ROM
8 DMAC
9 RAM
10. Image memory
11Y, 11M, 11C, 11K transfer circuit
12 Paper supply / transport mechanism
13 Image forming unit
14 Fixing unit
16 Paper cassette
17 Arrow
18a, 18b standby roll
19, 20 Drive roll
21 Conveyor belt
22, 23, 24, 25 Image forming unit
26 Photoconductor drum
27 Charger
28 LED head
28a LED head driver
28b LED head array
29a, 29b Developing device
30 Transfer device
31, 32 arrow
33 horizontal synchronization signal (HSYN)
34 Video signal clock (VCLK)
40 TW1 register
41 TW2 register
42 Timing signal generator
43 I / F control signal output unit
44 Control signal output section
45 Head control signal output section
46 Divider
47 line buffer (LB1)
48 line buffer (LB2)
49 line buffer (LB3)
50 line buffer (LB4)
51 Selector
52 area gradation data converter
53 Selector
54 Output buffer (OLB1)
55 Output buffer (OLB2)
56 output buffer (OLB3)
57 Output buffer (OLB4)
58 Output buffer (OLB5)
59 Selector
60 Photoconductor drum controller

Claims (5)

A plurality of exposure elements are arranged in the main scanning direction. One pixel is recorded on the recording medium by exposure of each of the plurality of exposure elements and a unit scanning operation of the recording medium. An image forming apparatus having a high-resolution mode for reproducing a one-dot image composed of (integer of 2 or more) pixels by area gradation expression by a combination of recording / non-recording of the pixels;
In addition to the high-resolution mode in which the area gradation is performed, a high-speed mode in which the area gradation is not performed is provided. In the high-resolution mode in which the area gradation is performed, each pixel is intermittently synchronized with a write synchronization timing signal of one pixel. An exposure control means for controlling exposure by said exposure element, and continuously controlling exposure by said exposure element in synchronization with a write synchronization timing signal of N pixels in a high-speed mode in which said area gradation is not performed. Characteristic image forming apparatus. Further, a plurality of recording heads in which the plurality of exposure elements are arranged in the main scanning direction are provided in the sub-scanning direction. In the high resolution mode for performing the area gradation, the plurality of recording heads are controlled to perform color recording. The image forming apparatus according to claim 1, wherein: Further, a plurality of recording heads in which the plurality of exposure elements are arranged in the main scanning direction are provided in the sub-scanning direction. In the high-speed mode in which the area gradation is not performed, one of the plurality of recording heads is controlled to 2. The image forming apparatus according to claim 1, wherein recording is performed. 2. The exposure control unit according to claim 1, wherein the exposure control unit continuously performs exposure of N pixels in synchronization with a write synchronization timing signal of N pixels in the high-speed mode in which the area gradation is not performed. Image forming apparatus. A plurality of exposure elements are arranged in the main scanning direction. One pixel is recorded on the recording medium by exposure of each of the plurality of exposure elements and a unit scanning operation of the recording medium. A high-resolution mode that reproduces a one-dot image composed of two or more integer pixels by area gradation expression by a combination of recording / non-recording of the pixel; and a high-speed mode that reproduces a one-dot image at low resolution. Image forming apparatus,
Interface control means for receiving print data and gradation designation information sent from a higher-level device;
Input means for inputting image data output by the interface control means;
Gradation data conversion means for generating recording / non-recording information of a pixel image from the image data based on the gradation designation information;
Timing signal generating means of a first cycle for generating N write synchronization timing signals during one dot line recording period in the high resolution mode;
Timing signal generating means of a second cycle for generating a write synchronization timing signal of a cycle shorter than the timing signal of the first cycle N times during one dot line recording period in the high-speed mode;
In the high resolution mode, the N pixel line data generated from the gradation data conversion means is output to the exposure element array in synchronization with the write synchronization timing signal of the first cycle timing signal generation means, In the mode, the one-dot line data received by the receiving means is output to the exposure element array in synchronization with the write synchronization timing signal of the second timing signal generation means, and the light emission drive of the exposure element array is controlled. And an exposure element array drive control means.

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