JP3731024B2 - Writing device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a writing device having a light emitter array such as a light emitting diode array, which is used in a digital copying machine, a printer, a facsimile, and the like, and particularly when a light emitter array such as an LED array is used. The present invention relates to a writing apparatus that prevents vertical whiteout of an image that occurs because the interval is too wide.
[0002]
[Prior art]
2. Description of the Related Art In recent years, electrophotographic printers, digital copiers, and the like that have a writing device using a light emitter array composed of a light emitting diode (hereinafter referred to as LED) array have appeared in order to reduce the size of the device. In this electrophotographic printer, digital copier, etc., a drum-like photoreceptor, a belt-like photoreceptor, etc. are rotated by a main motor and uniformly charged by a charging means, and then an LED array is used in a writing device. The electrostatic latent image is formed by the exposure by the above, and an electrostatic latent image is formed. The electrostatic latent image is developed by the developing unit to become a toner image, and is transferred to a transfer material such as paper by the transfer unit. As shown in FIGS. 17 and 18, the LED array 1 includes a light emitter chip 3 composed of a plurality of, for example, 64 LED chips arranged in a row in accordance with the resolution. Are arranged in a row, for example, 78.
[0003]
Here, as a conventional technique related to the present application, Japanese Patent Laid-Open No. 4-326854 and Japanese Patent Laid-Open No. 4-326855 disclose that an image with a small dot interval has a small dot diameter and is not crushed. A binary image forming apparatus is described in which an image with a wide interval is obtained by increasing the dot diameter to obtain a good halftone image reproducibility as a thick and clear image.
[0004]
Specifically, Japanese Patent Laid-Open No. 4-326854 refers to binarized pixel data and a plurality of binarized peripheral pixel data on the same line as the binarized pixel data. In a binary image forming apparatus for expressing a halftone image by variably adjusting an actual print dot size for the target pixel data according to a state, from the binary target pixel data to a print pit of the binary peripheral pixel data And a dot size variable control means for variably controlling the actual print size of one dot of the binarized pixel data based on the distance information detected by the detection means. A characteristic binary image forming apparatus is described.
[0005]
Japanese Patent Laid-Open No. 4-326855 refers to binarized pixel data of interest and a plurality of binarized peripheral pixel data on the same line as the binarized pixel data of interest, and the pixel of interest depends on the state of the pixel data. In a binary image forming apparatus for expressing a halftone image by variably adjusting an actual print dot size for data, from a print pit of the binarized pixel data and binarized peripheral pixel data from a non-print pit or a non-print pit Conversion point detection means for detecting a change point to the print pit, change point counting means for counting the number of change points detected by the detection means, and the binary value based on the number of change points counted by the count means There is described a binary image forming apparatus characterized by comprising dot size variable control means for variably controlling the actual print size of one dot of target pixel data.
[0006]
Japanese Patent Application Laid-Open No. 5-176131 discloses a scanning type image recording apparatus that can prevent a black data shift of a pixel of interest and make it close to a theoretical dot diameter of one pixel. Specifically, this scanning type image recording apparatus includes an analog image signal generation unit that generates an analog image signal, an analog / digital conversion unit that converts the analog image signal into a digital image signal, and a digital image signal based on a predetermined reference. A binarization processing unit that binarizes at a level to obtain a binarized image signal, a reference level generation unit that generates the reference level, a pixel data memory unit that holds data of the binarized image signal, A laser ON / OFF signal generator for turning on / off the laser, a laser signal modulator for modulating the laser ON / OFF signal with a binary image signal of the pixel data memory unit, and the pixel data memory unit. In order to adjust the target pixel density, a laser power switching signal generator for generating a signal for switching the laser power of surrounding pixels, and the modulation signal and the laser of the laser signal modulator A laser power generating unit for emitting a laser by a power switching signal, is scanned with a laser beam to the photosensitive member, and a scanning type image recording apparatus characterized by comprising a laser scanning unit for exposing the photosensitive member.
[0007]
[Problems to be solved by the invention]
In the above-described printer and digital copying machine, when outputting a halftone image such as a photograph, there are cases where portions of the output image are slightly blanked out. This is because in the LED array 1 in which a plurality of LED chips 3 are arranged as shown in FIG. 17, a plurality of LED elements 2 are accurately arranged in accordance with the resolution on each LED chip 3. On the other hand, since the interval between the LED chips 3 has a slight error, the interval b between the LED chips 3 is wider than usual and wider than the interval a between the LED elements 2 as shown in FIG. This is because, in that case, the intervals between the LED chips 3 appear to be white on the output image.
[0008]
This phenomenon is particularly noticeable when a halftone image is output. In other words, this phenomenon is caused by the fact that when a high density image is output, the diameter of the light beam from each LED element 2 to the photosensitive member increases as shown in FIG. Because it tends to overlap, it is inconspicuous. However, when outputting a low density image, the diameter of the light beam from each LED element 2 to the photosensitive member becomes small as shown in FIG. White spots due to will be noticeable.
[0009]
Therefore, the present invention prevents image blanking by increasing the image data of the corresponding pixels between the LED chips 3 by a predetermined amount or converting the image data to a density that does not make white spots noticeable. When the correction is made, the correction is made even when the image data corresponding to the LED chips 3 is white, and conversely, a thin vertical line is formed on the white background, resulting in an uncomfortable image. Further, although the density is sufficient and white spots do not occur, unnecessary correction is applied.
[0010]
The present invention has been made in view of the above circumstances, detects the state of a pixel to be corrected and its surrounding pixels, and applies correction only in the case of a halftone where white spots are particularly problematic, thereby preventing white spots. Accordingly, it is an object of the present invention to provide a writing device capable of obtaining an image without a sense of incongruity, and the object of each claim is shown below.
[0011]
According to the first, second, and third aspects of the present invention, in the writing device using the light emitter array such as the LED array, the white spot generated due to the slightly wide space between the light emitter chips is located or a predetermined region including the position. It is an object to obtain an image without a sense of incongruity by determining the image state of the image and correcting the image data corresponding to the position according to the result to prevent the image data from increasing.
[0012]
According to the fourth aspect of the present invention, the correction is made even when the correction is unnecessary by correcting the image data only when the image data of the portion corresponding to the joint between the light emitting chips or the image data of the predetermined area including the portion is halftone. The purpose of this method is to prevent the vertical streaking that occurs in the image and to obtain an image that does not feel strange.
[0013]
According to the fifth aspect of the present invention, as the image data correction method, the image data value is easily corrected by increasing a predetermined amount to prevent white spots generated due to the slightly wide space between the light emitting chips, and an image without a sense of incongruity is obtained. For the purpose.
[0014]
The invention according to claim 6 can be easily corrected by changing the value of the image data uniformly to a predetermined value as a method of correcting the image data, and completely prevents white spots generated due to the slightly wide space between the light emitting chips, The purpose is to obtain an image without a sense of incongruity.
[0015]
[Means for Solving the Problems]
To achieve the above objective, Writing device according to the present invention Is composed of a plurality of light emitting chips arranged with a plurality of light emitting elements, and a light emitter array that irradiates light to the photoconductor and writes an image on the photoconductor one line at a time. Light emitter array control means for performing drive control of each light emitting element by image data, and data correction means for correcting image data corresponding to a specific position of the light emitter array among image data input to the light emitter array control means And a data determination unit that determines a state of image data corresponding to a specific position of the light emitter array or a predetermined area including the specific position, and the image is corrected by the data correction unit according to a determination result of the data determination unit. The correction of data is characterized in that white spots generated due to the slightly wide space between the light emitting chips are located at the position or a predetermined area including the position. Determining an image state can be prevented by increasing the amount by correcting the image data corresponding to the position according to the result.
[0016]
More details Claim 1 The invention according to Said In the writing apparatus, the data determination unit determines whether the image data corresponding to a specific position of the light emitter array or the image data corresponding to a predetermined area including the specific position is a halftone of a predetermined density range. The white spot that occurs because the gap between the light emitting chips is slightly wide is determined, the image state of the position or a predetermined area including the position is determined, and the position is determined according to the result. This can be prevented by correcting the corresponding image data to increase the amount of light.
[0017]
Claim 2 The writing device according to claim 1, wherein the specific position of the light emitter array is a joint portion between the plurality of light emitter chips, According to a third aspect of the present invention, in the writing device according to the second aspect, the data correction unit is configured to output image data corresponding to a joint position between the light emitting chips according to a determination result of the data determination unit. It is characterized by correcting White spots that occur because the gap between the light emitting chips is slightly wide, The joint between the phosphor chips Determine the image state of the position or a predetermined area including that position, and depending on the result The joint between the phosphor chips This can be prevented by correcting the image data corresponding to the position to increase the amount of light.
[0018]
The invention according to claim 4 is claimed in claim 3 In the writing device described above, the data correction means is , The data judging means Joint between the light emitting chips Position or Seam When the predetermined area including the position of the light emitter array is determined to be a halftone, the light emitter array of the image data input to the light emitter array control means Joint between light emitter chips The correction is made so that the amount of image data corresponding to the position of the light source increases, and the image data is obtained only when the image data of the portion corresponding to the joint between the light emitting chips or the predetermined area including the halftone is halftone. By correcting, it is possible to prevent vertical streaks caused by correction even when correction is unnecessary.
[0019]
The invention according to claim 5 is claimed in claim 4 In the writing apparatus according to the description, the correction method in the data correction unit is that of the light emitter array in the image data input to the light emitter array control unit. Joint between light emitter chips The image data value corresponding to the position is increased by a predetermined amount so that the light quantity of the light emitting element is increased. As a method for correcting the image data, the value of the image data is increased by a predetermined amount. Therefore, it is possible to easily correct, and to prevent white spots generated due to the slightly wide space between the light emitting chips.
[0020]
The invention according to claim 6 is the claim 4 In the writing apparatus according to the description, the correction method in the data correction unit is that of the light emitter array in the image data input to the light emitter array control unit. Joint between light emitter chips The value of the image data corresponding to the position of the light is corrected so as to increase the light quantity of the light emitting element by changing the value to a predetermined value. As a method for correcting the image data, the value of the image data is uniformly set. By changing to a predetermined value, correction can be easily made, and white spots that occur because the gap between the light emitting chips is slightly wide can be completely prevented.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0022]
FIG. 2 is a perspective view showing an embodiment of an electrophotographic image forming apparatus to which the present invention is applied. This embodiment is an embodiment of a digital copying machine to which the invention according to claims 1 to 6 is applied. A document table 11 and a pressure plate 12 (or an automatic document feeder (ADF)) are provided on the digital copying machine 10. And the operation part 13 is provided. The document is placed on the document table 11, and is pressed down by the pressure plate 12 (or the ADF transport belt) to be in close contact with the document table 11. The operation unit 13 sets a mode for reading a document, sets a copy magnification, displays for an operator, and the like.
[0023]
Further, the digital copying machine 10 is provided with a plurality of paper feeding units 14 to 18 on the lower side and a paper discharging unit 19 on the left side. Inside the digital copying machine 10, there are an original reading means including an imaging optical system, a paper feeding and conveying system, a drum-like photosensitive member as a photosensitive member, a charging unit, a developing unit, a transferring unit, a fixing unit, a paper discharging system, A well-known mechanism for performing an electrophotographic process, such as a cleaning device and a static eliminator, and a control device are incorporated.
[0024]
The document reading means illuminates the document on the document table 11 with a light source and forms an image of the reflected light on a line sensor composed of a CCD as an imaging device via the imaging optical system. The document on the document table 11 is scanned by a part of movement to read the document image at 400 dpi, for example, and an analog image signal from the line sensor is converted into digital image data by the A / D conversion unit and output.
[0025]
As will be described later, the digital image data is subjected to various corrections and sent to a writing device. The writing device uses a light emitter array 1 composed of an LED array having the structure shown in FIGS. It is a thing. This writing device drives each LED element 2 of the LED array 1 by image data as will be described later, and transmits a light beam from each LED element 2 arranged in a line in the main scanning direction of the LED array 1 to a drum-shaped photoconductor. To irradiate.
[0026]
The drum-shaped photoconductor is rotated in the sub-scanning direction by the rotation driving unit and is uniformly charged by the charging means, and then exposed by the light beam from each LED element 2 of the LED array 1 so that the image is line by line. An electrostatic latent image is formed by writing. The electrostatic latent image on the drum-shaped photoconductor is developed by a developing unit to become a toner image, and transfer paper as a transfer material is fed from the paper feeding unit designated by the operation unit 13 among the paper feeding units 14 to 18. Paper is fed by a paper feed system.
[0027]
In the transfer paper, the toner image on the drum-shaped photosensitive member is transferred by the transfer unit, the toner image is fixed by the fixing unit, and is discharged to the paper discharge unit 19 by the paper discharge system. The drum-shaped photoreceptor is prepared for the next electrophotographic process by removing the residual toner by the cleaning device after the toner image is transferred and removing the residual charge by the static eliminator. The control device controls the document reading unit and other units in accordance with instructions from the operation unit 13.
[0028]
FIG. 1 is a diagram showing an image data processing portion of the digital copying machine 10. The reading processing unit 20 performs various corrections such as shading correction on the image data read by the line sensor at 400 dpi and A / D converted by the A / D conversion unit, and the corrected image data D is processed by one pixel. Every 6 bits (64 gradations: 0/63 to 63/63), the data is output to the write data correction unit 21 having data determination means and data correction means.
[0029]
The write data correction unit 21 performs halftone adjustment of the image data corresponding to the position of the seam between the light emitting chips 3 made up of the LED chips of the LED array 1 and the surrounding image data in the image data D from the read processing unit 20. In this case, the value of the image data corresponding to the position of the joint is increased by a predetermined amount or converted to a constant value so that the light quantity of the LED element 2 is increased, and the corrected image data is written. To the unit 22. The write processing unit 22 performs drive control of each LED element 2 of the LED array 1 based on the corrected image data input from the write data correction unit 21 and writes an image on the drum-shaped photoconductor at 400 dpi. .
[0030]
The control unit 23 is connected to the operation unit 13, and controls the reading processing unit 20, the write data correction unit 21, and the writing processing unit 22 based on the original reading mode set by the operation unit 13. Here, the write data correction unit 21 and the write processing unit 22 are included in the writing device.
[0031]
FIG. 3 shows a configuration of the write data correction unit 21. The write data correction unit 21 detects halftones as data determination means that detects and determines whether the image data to be corrected and the surrounding image data are halftones. An area detection unit 60 and a data correction unit 61 as data correction means for actually correcting image data according to the detection result of the halftone area detection unit 60 are configured. Details of each part will be described below.
[0032]
FIG. 4 is a diagram showing a configuration example of the halftone area detection unit 60 in the write data correction unit 21 shown in FIG. FIG. 5 is a diagram showing the operation timing of the halftone area detection unit 60. Hereinafter, the operation of the halftone area detection unit 60 will be described with reference to FIGS.
[0033]
4 and 5, the halftone area detection unit 60 includes comparators 71 and 72, AND gates 73 and 78, and flip-flops 74 to 77, 79 and 80. The comparators 71 and 72 determine the magnitude relationship between the upper limit / lower limit threshold set by the control unit 23 and the image data, and the relationship between the image data and the upper limit / lower limit threshold is as follows.
Upper limit threshold> Image data> Lower limit threshold
At this time, the outputs of the comparators 71 and 72 are both set to the high level. Here, the upper limit threshold is a level at which white spots do not occur if the image density is higher than this, and the lower limit threshold is a black stripe where the correction is applied when the density is lower than this. As a level that will stand out as. Since the outputs of the comparators 71 and 72 are ANDed by an AND gate 73, the output of the AND gate 73 is at a high level when the relationship between the image data and the upper limit / lower limit threshold is as described above. It becomes.
[0034]
The output of the AND gate 73 is latched by the flip-flops 74 to 77, and the output of the AND gate 73 and each of the flip-flops 74 to 77 is taken by the AND gate 78, and this output is used as a halftone area signal. That is, here, the definition of halftone is determined as a halftone when the pixel of interest and the two pixels before and after the pixel are in a predetermined density range in the main scanning direction. The flip-flops 79 and 80 match the phase with the halftone area signal by latching the image data.
[0035]
6 is a diagram showing the configuration of the first embodiment of the data correction unit 61 in the write data correction unit 21 shown in FIG. 3, and FIG. 7 is a diagram showing the operation timing of the data correction unit 61. . Hereinafter, the operation of the data correction unit 61 will be described with reference to FIGS.
[0036]
6 and 7, the image data D from the read processing unit 20 that has passed through the halftone area detection unit 60 is input to a selector 24 as a selection unit and an adder 25 as an addition unit. The image data D is corrected by adding a predetermined correction value set by the control unit 23, for example, 10 to the image data D from the reading processing unit 20.
[0037]
The corrected image data C from the adder 25 is input to the selector 24. When the selector 24 detects that the image at the joint between the LED chips 3 is halftone by the halftone area detection unit 60, Corresponding to the position of the joint, the corrected image data C from the adder 25 is selected and output, and the image from the reading processing unit 20 corresponds to a position other than the joint position between the LED chips 3. Data D is selected and output.
[0038]
The position of the joint between the LED chips 3 is detected by a light-emitting chip joint detecting means comprising a counter 26 and a decoder 27. As described above, each LED chip 3 is provided with 64 LED elements 2. Therefore, image data corresponding to the position of the joint between the LED chips 3 appears every 64 pixels.
[0039]
Therefore, when the image data valid signal LGATE from the control unit 23 becomes high level, the counter 26 starts counting in synchronization with the reference clock CLK. During the period when the image data valid signal LGATE is high level, Counting is performed in synchronization with the reference clock CLK. Here, the image data is valid during a period when the image data valid signal LGATE is at a high level.
[0040]
Since the counter 26 is a 6-bit counter, the output signal e of the counter 26 changes from 0 to 63. The output signal e of the counter 26 is input to the decoder 27 together with the image data valid signal LGATE from the control unit 23 and the decode switching signal. The decoder 27 is high when the output signal e of the counter 26 is 0 or 63 in accordance with the decode switching signal during the period when the image data valid signal is high, and is low at other times. Output signal f is output.
[0041]
Note that the decoder 27 becomes high level only when the output signal e of the counter 26 is 63 according to the decode switching signal while the image data valid signal LGATE is high level, and low level at other times. An output signal f ′ may be output. In any case, the output signal f or f ′ of the decoder 27 is input to the AND gate 29.
[0042]
In the AND gate 29, the AND of the halftone area signal detected by the halftone area detection unit 60 and the output signal f or f ′ (the joint signal between the LED chips 3) of the decoder 27 is taken, and both signals are high. At the level, that is, when the joint between the LED chips 3 is halftone, the output signal i becomes high level.
[0043]
The selector 24 selects and outputs the image data D from the reading processing unit 20 when the output signal i of the AND gate 29 is at a low level, and when the output signal i of the AND gate 29 is at a high level, that is, an LED chip. When the joint between the three is halftone, the corrected image data c from the adder 25 is selected and output. The image data g from the selector 24 is latched by the flip-flop 28 with the reference clock CLK, and then input to the write processing unit 22 as image data h.
[0044]
FIG. 8 is a diagram showing the configuration of the second embodiment of the data correction unit 61 in the write data correction unit 21 shown in FIG. 3, and FIG. 9 is a diagram showing the operation timing of the data correction unit 61. . The first embodiment shown in FIGS. 6 and 7 and the second embodiment shown in FIGS. That is, in the first embodiment, the light amount of the LED element 2 is increased by adding a predetermined amount (10 in the example) to the image data D to prevent white spots. In this case, the image at the position of the seam is used. When the data density is about 20, even if 10 is added, the degree of white spots is reduced because it is about 30. However, some white spots may occur in some cases. Further, when the density of the image data is about 39, correction is made more than necessary.
[0045]
However, in the second embodiment, image data is converted to a predetermined value that eliminates white spots, thereby completely preventing white spots. That is, the input of the correction value of the selector 24 is directly set by the control unit 23, and in this case, the level 40 is set so that white spots do not occur. The rest of the configuration is the same as in the first embodiment, and the selector 24 outputs and corrects the correction value (level 40) from the control unit 23 when the joint between the LED chips 3 is a halftone, and other than that At that time, the image data D from the reading processor 20 is output. 7 and 9, the numbers of the image data indicate signal levels.
[0046]
Next, the writing processing unit 22 in the image data processing part shown in FIG. 1 will be described. As shown in FIG. 10, the write processing unit 22 includes an LED control unit 5 serving as a light emitter array control unit and an LED array 1. The LED control unit 5 converts the image data from the write data correction unit 21 in accordance with the data input format of the LED array 1, corrects the light amount of the LED array 1, and generates a control signal. The LED array 1 emits light based on the image data converted by the LED control unit 5, exposes the drum-shaped photoconductor, and writes an image on the drum-shaped photoconductor, thereby forming an electrostatic latent image on the drum-shaped photoconductor. Form.
[0047]
Next, the LED control unit 5 will be described. As shown in FIG. 11, the LED control unit 5 includes a control signal generation unit 30 and an image data conversion unit 31, and the image data conversion unit 31 includes line memories 32 to 35 and a data selection unit 36. FIG. 12 shows the operation timing of the LED control unit 5, and the operation of the LED control unit 5 will be described below with reference to FIG.
[0048]
The image data input from the write data correction unit 21 has the first half of each line stored in the line memories 32 and 34 while the write enable signal WE from the control signal generation unit 30 to the line memories 32 and 34 is at a high level. The second half of each line is written into the line memories 33 and 35 while the write enable signal WE from the control signal generator 30 to the line memories 33 and 35 is at a high level.
[0049]
The line memories 32 and 33 and the line memories 34 and 35 perform a toggle operation, and the write enable signal WE from the control signal generator 30 to the line memories 32 and 33 becomes high level, and image data is stored in the line memories 32 and 33. In the writing period, image data is read from the line memories 34 and 35 while the read enable signal RE from the control signal generator 30 to the line memories 34 and 35 is at a high level, and conversely from the control signal generator 30. The write enable signal WE from the control signal generator 30 to the line memories 34 and 35 is high during a period in which the read enable signal RE to the line memories 32 and 33 becomes high level and image data is read from the line memories 32 and 33. Image data is written in the line memories 34 and 35 while the level is reached.
[0050]
For example, as shown in FIG. 12, the first half and the second half of the image data of the nth line are written to the line memories 34 and 35 in the period in which the image data is written in the line memories 32 and 33, respectively. The first half and the second half of the image data are read out, and the first half and the second half of the (n + 1) th line of image data are read in the line memories 32 and 35 in the period in which the image data is written in the line memories 34 and 35, respectively. The first half portion and the second half portion of the image data of the nth line written in the previous cycle in 33 are read from the line memories 32 and 33, respectively.
[0051]
The data selection unit 36 switches and outputs each image data from the line memories 32 to 35 in response to a selection switching signal from the control signal generation unit 30, so that the image data of each line is converted into the first half part and the second half part in each cycle. Are output together. At this time, the image data read from the line memories 32 to 35 is divided into a first half portion and a second half portion for each line. Therefore, if the image data is only read from the line memory within one cycle, the image data is read from the line memory for one pixel. The period of the read clock for reading out each one can be reduced to a maximum of ½ period. However, since a period for causing the LED array 1 to emit light is also required within one period, one period is reduced to 60 to 70%. Image data is read from the line memories 32 to 35 during the period.
[0052]
The control signal generation unit 30 generates a write enable signal WE, a read enable signal RE, a write clock, and a read clock to be supplied to the line memories 32 to 35, and generates a selection switching signal to be supplied to the data selection unit 36. When the selection switching signal is at a high level, the image data from the line memories 32 and 33 is valid, and when the selection switching signal is at a low level, the image data from the line memories 34 and 35 is valid. The control signal generator 30 also generates control signals such as an image transfer clock TCK, a transfer end signal SET, and a light emission enable signal EN supplied to the LED array 1.
[0053]
Next, the LED array 1 will be described. FIG. 13 is a diagram showing a circuit configuration of the LED array 1. The LED array 1 receives 4992 (64 × 78) LED elements 2 that actually emit light, image data converted by the LED control unit 5, and control signals generated by the LED control unit 5. The image data from the input I / F unit 37 is transferred to the input interface (I / F) unit 37 to be sent to, the light amount control units 38 and 39 for controlling the light emission amount of each LED element 2 according to the image data value. Shift registers 40 and 41. There are two light quantity controllers 38 and 39 and two shift registers 40 and 41 corresponding to image data in which one line is divided into a first half part and a second half part, respectively.
[0054]
FIG. 14 shows the operation timing of the LED array 1, and the operation of the LED array 1 will be described below with reference to FIG. While the read enable signal RE is at the high level, the first half part and the second half part of the image data for each line are input from the LED control unit 5 to the shift registers 40 and 41 via the input I / F unit 37, respectively. The first half and the second half of the image data for the line are transferred to the shift registers 40 and 41 in synchronization with the transfer clock TCK input from the LED control unit 5 to the shift registers 40 and 41 via the input I / F unit 37, respectively. Is done.
[0055]
When all the image data for one line is transferred, one line in the shift registers 40 and 41 is transferred by the transfer end signal input from the LED control unit 5 to the light quantity control units 38 and 39 via the input I / F unit 37. The first half portion and the second half portion of the minute image data are latched by the light amount control units 38 and 39, respectively. The light emission effective signal EN input from the LED control unit 5 to the light amount control units 38 and 39 via the input I / F unit 37 has a width corresponding to 63 clocks of the light emission clock LCLK (= TCK × 10). It is.
[0056]
As shown in FIG. 15, the light amount control units 38 and 39 generate 64 signals having a width corresponding to 0 to 63 clocks of the light emission clock LCLK from the light emission effective signal EN. Then, the light quantity control units 38 and 39 select, as the light emission signal, a signal having a pulse width corresponding to the data value of the image data in which the high level period is latched earlier among the 64 signals.
[0057]
That is, when the data value of the image data is 1, the light quantity control units 38 and 39 select a signal that is high for a period corresponding to one clock of the light emission clock LCLK, and the data value of the image data is 2. A signal that is at a high level only during a period corresponding to two clocks of the light emission clock LCLK is selected, and a signal that is at a high level only during a period corresponding to three clocks of the light emission clock LCLK is selected when the data value of the image data is 3. In the same manner, a signal that is at a high level only during a period corresponding to the data value of the image data is selected, and when the data value of the image data is 0, a signal that is always at a low level is selected.
[0058]
The light amount control units 38 and 39 emit a signal that becomes a high level only for a period corresponding to each data value (data value for each pixel signal of the image data) of the image data for one line latched in the above manner. And the LED elements 2 of the LED array 1 corresponding to the image data for one line are turned on only during the high level period of the light emission signal. As described above, the light amount control units 38 and 39 change the light amount of the LED element 2 by changing the lighting time of the LED element 2 according to the data value of the image data, thereby realizing multi-value image writing.
[0059]
FIG. 16A shows writing dots when a low density image is output without correcting image data (correcting image data corresponding to the position of the joint portion of each LED chip 3) as in a conventional writing device. In FIG. 4, white spots appear between the LED chips 3 on the written image. FIG. 16B is a writing dot when the image data is corrected (image data corresponding to the position of the joint portion of each LED chip 3) is output by the writing apparatus of this embodiment to output a low density image. 4, the white spots at the intervals of the LED chips 3 on the written image are eliminated.
[0060]
In the above embodiment, the data value of the image data is increased by a predetermined amount so as to increase the light amount of the LED element 2 by correcting the image data of the adjacent portions of each LED chip 3 by the write data correction unit 21, so that the halftone image White streaks (white spots) that occur when the image is reproduced can be avoided, and the image quality can be improved.
[0061]
【The invention's effect】
As explained above, Writing device according to the present invention According to the present invention, a light emitter array configured by arranging a plurality of light emitter chips in which a plurality of light emitting elements are arranged, irradiating light on the photoconductor, and writing an image on the photoconductor one line at a time, and the light emitter Light emitter array control means for performing drive control of each light emitting element of the array by image data, and data for correcting image data corresponding to a specific position of the light emitter array among image data input to the light emitter array control means A correction unit; and a data determination unit that determines a state of the image data corresponding to a specific position of the light emitter array or a predetermined region including the specific position, and the data correction unit according to a determination result of the data determination unit Because the image data is corrected by, it detects the white spots that occur because the gap between the light emitting chips is slightly wide, and detects whether the position and the surrounding image are halftone Te, when a halftone reduces white spots by increasing the amount by correcting the image data corresponding to the position, or it is possible to prevent, it is possible to obtain an image without uncomfortable feeling.
[0062]
More details Claim 1 According to the invention according to Said In the writing apparatus, the data determination unit determines whether the image data corresponding to a specific position of the light emitter array or the image data corresponding to a predetermined area including the specific position is a halftone of a predetermined density range. Therefore, it is detected whether the position and the surrounding image are halftones by detecting the white spots that occur because the gap between the light emitting chips is slightly wide, and if it is halftone, the image data corresponding to the position By correcting the above and increasing the amount of light, white spots can be reduced or prevented, and an image with no sense of incongruity can be obtained.
[0063]
Claim 2, 3 According to the invention of claim 1, in the writing apparatus according to claim 1, the specific position of the light emitter array is a joint portion between the plurality of light emitter chips. And the data correction unit corrects image data corresponding to a joint position between the light emitting chips according to a determination result of the data determination unit. Therefore, it is detected whether white spots generated due to a slightly wide space between the light-emitting chip chips are detected at the position and the surrounding image, and in the case of the halftone, image data corresponding to the position is obtained. By correcting and increasing the amount of light, white spots can be reduced or prevented, and an image with no sense of incongruity can be obtained.
[0064]
According to the invention of claim 4, the claim 3 In the writing device described above, the data correction means is , The data judging means Joint between the light emitting chips Position or Seam When the predetermined area including the position of the light emitter array is determined to be a halftone, the light emitter array of the image data input to the light emitter array control means Joint between light emitter chips Since the image data corresponding to the position of the image data is corrected so that the amount of light is increased, the correction is performed by correcting the image data only when the image data of the portion corresponding to the joint between the light emitting chips or the predetermined area including the image data is halftone. Since it is possible to prevent correction even when unnecessary, it is possible to prevent vertical streaks caused by correction even when correction is unnecessary, and an image without a sense of incongruity can be obtained.
[0065]
According to the invention of claim 5, the claim 4 In the writing apparatus according to the description, the correction method in the data correction unit is that of the light emitter array in the image data input to the light emitter array control unit. Joint between light emitter chips Since the light amount of the light emitting element is corrected by increasing the value of the image data corresponding to the position by a predetermined amount, it is easily corrected by increasing the value of the image data by a predetermined amount as a method of correcting the image data, Since white spots that occur because the gap between the light emitting chips is slightly wide can be prevented, an image without a sense of incongruity can be obtained.
[0066]
According to the invention of claim 6, the claim 4 In the writing apparatus according to the description, the correction method in the data correction unit is that of the light emitter array in the image data input to the light emitter array control unit. Joint between light emitter chips By changing the value of the image data corresponding to the position to a predetermined value to correct the light quantity of the light emitting element, the image data value is corrected to a predetermined value that does not cause white spots as a method of correcting the image data. It is easily corrected by converting to a value, and white spots that occur because the gap between the light emitting chips is slightly wide can be completely prevented, so that an image without a sense of incongruity can be obtained.
[Brief description of the drawings]
FIG. 1 is a block diagram of an image data processing unit of an electrophotographic image forming apparatus showing an embodiment of the present invention.
FIG. 2 is a perspective view of an electrophotographic image forming apparatus showing an embodiment of the present invention.
FIG. 3 is a block diagram illustrating an example of a write data correction unit in the image data processing unit illustrated in FIG. 1;
4 is a block diagram showing an example of a halftone area detection unit in the write data correction unit shown in FIG. 3; FIG.
FIG. 5 is a timing chart showing an example of operation timing of the halftone area detection unit shown in FIG. 4;
6 is a block diagram showing a configuration of a first example of a data correction unit in the write data correction unit shown in FIG. 3; FIG.
7 is a timing chart illustrating an example of operation timing of the data correction unit illustrated in FIG. 6;
8 is a block diagram showing a configuration of a second example of the data correction unit in the write data correction unit shown in FIG. 3; FIG.
FIG. 9 is a timing chart illustrating an example of operation timing of the data correction unit illustrated in FIG. 8;
10 is a block diagram showing an example of a writing processing unit in the image data processing unit shown in FIG. 1. FIG.
11 is a block diagram showing an embodiment of an LED control unit in the write processing unit shown in FIG.
12 is a timing chart showing an example of operation timing of the LED control unit shown in FIG. 11. FIG.
13 is a block diagram showing a circuit configuration example of an LED array in the write processing unit shown in FIG.
14 is a timing chart showing an example of operation timing of the LED array shown in FIG.
15 is a timing chart showing an example of operation timing of the LED array shown in FIG.
FIG. 16 is a diagram showing writing dots by a conventional writing device and writing dots by a writing device according to an embodiment of the present invention.
FIG. 17 is a plan view showing a schematic configuration example of an LED array.
18 is an enlarged plan view showing a part of the LED array shown in FIG. 17; FIG.
FIG. 19 is a diagram illustrating an example of writing dots by a conventional writing apparatus.
[Explanation of symbols]
1: LED array (light emitter array)
2: LED element (light emitting element)
3: LED chip (light emitter chip)
5: LED control unit (light emitter array control means)
13: Operation unit
21: Write data correction unit
22: Write processing unit
23: Control unit
24: Selector
25: Adder
26: Counter
27: Decoder
29: Andgate
30: Control signal generator
31: Image data converter
32-35: Line memory
36: Data selection part
37: Input I / F part
38, 39: Light quantity control unit
40, 41: Shift register
60: Halftone area detection unit (data determination means)
61: Data correction unit (data correction means)
71, 72: Comparator
73, 78: Andgate
74-77, 79, 80: flip-flop

Claims (7)

A light emitter array write the image on the photoconductor a light emitter chip having an array of a plurality of light-emitting elements is configured by arranging a plurality by irradiating light to the photosensitive member, the respective light emitting elements of the light emitter array Light emitter array control means for performing drive control with image data, data correction means for correcting image data corresponding to a specific position of the light emitter array among image data input to the light emitter array control means, and the light emission A data determination unit that determines a state of image data corresponding to a specific position of the body array or a predetermined region including the specific position, and the data correction unit corrects the image data according to a determination result of the data determination unit; In the writing device to perform :
The data determining means determines whether image data corresponding to a specific position of the light emitter array or image data corresponding to a predetermined area including the specific position is a halftone of a predetermined density range. A writing device. 2. The writing apparatus according to claim 1, wherein the specific position of the light emitter array is a joint portion between the plurality of light emitter chips . 3. The writing apparatus according to claim 2 , wherein the data correction unit corrects image data corresponding to a joint position between the light emitting chips according to a determination result of the data determination unit. . In the writing apparatus according to claim 3, wherein said data correction means, when said data determination means determines the predetermined area including the location of the position or joint at the joint between the light emitter chip to be intermediate tone, the light emitting A writing apparatus for correcting the light quantity of the image data corresponding to the position of the joint between the light emitting chips of the light emitting array in the image data input to the body array control means. In the writing device according to claim 4, the correction method in the data correction means, the image data corresponding to the position of the joint between the light emitter chips of said light emitter array of the image data to be input to the light emitter array controller The writing apparatus is characterized in that the light amount of the light emitting element is increased by increasing the value of the predetermined amount by a predetermined amount. In the writing device according to claim 4, the correction method in the data correction means, the image data corresponding to the position of the joint between the light emitter chips of said light emitter array of the image data to be input to the light emitter array controller The writing apparatus is characterized in that the light quantity of the light-emitting element is corrected by changing the value of the value to a predetermined value. An image forming apparatus having a writing device for writing an image by irradiating light to a photoreceptor, wherein the writing device according to any one of claims 1 to 6 is provided as the writing device. apparatus.

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