JP3753792B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus such as a digital color copying machine, a digital color printer, and a digital color facsimile having a plurality of photosensitive members.
[0002]
[Prior art]
In the image forming apparatus, an electrostatic latent image is formed by writing image data of a plurality of different colors with scanning lines independently by a plurality of writing means on a plurality of photosensitive members rotated and driven by a driving mechanism. A digital color image forming apparatus such as a digital color copying machine that obtains a color image by developing these electrostatic latent images into different color visualized images by a plurality of developing means and superimposing them on a transfer material and transferring them. There is. In this digital color image forming apparatus, the writing means writes image data on the photosensitive member by scanning the photosensitive member through an optical component such as a writing lens with a scanning line made of a writing beam from a semiconductor laser or the like. An electrostatic latent image is formed.
[0003]
Further, in this digital color image forming apparatus, the position detection pattern for each color is written on the photosensitive member by the writing means, and the visible image of the position detection pattern for each color is transferred to a different position on the transfer material. Has been proposed in which a color sensor is measured with a photosensor through a slit member, and the shift of each color is corrected based on the measurement result.
[0004]
In the digital color image forming apparatus, the measuring means for measuring the positional deviation including the bending and the inclination of the scanning line of each writing means, and the image data in the sub-scanning direction or two-dimensionally according to the measurement result of the measuring means. And resampling means for correcting by interpolation, and correcting misalignment including bending and inclination of the scanning line with high accuracy and low cost without performing mechanical displacement, pixel clock sweep, etc. Things have been proposed. In this apparatus, the resampling means interpolates image data by interpolation using a sinc function, linear interpolation, interpolation by a spline function, or the like. The interpolation is performed so that the energy of the image data is equal.
[0005]
[Problems to be solved by the invention]
In the digital color image forming apparatus having the resampling means described above, image data including the photosensitive characteristics of the photoreceptor and the development γ characteristics of the developing means is formed after the image data is written. The line width of the image to be created is when the image data is resampled without any phase shift (corrected by interpolation) and when the image data is resampled by shifting the phase of the image data by 180 °. Are not the same, and there is a problem that unevenness in density and color of the image occurs. This is particularly noticeable when the line width of an image to be formed is a thin line width such as 1 to 2 dots.
[0006]
As an example of this problem, FIGS. 17 (a) and 17 (b) show the exposure state of the example when the developing bias of the developing means is changed for simplicity. This example is an example of creating a 2-dot image in the sub-scanning direction. FIG. 17A shows an exposure state when image data is not resampled, and FIG. The exposure state in the case of resampling by shifting the dot (180 ° in phase) is shown.
[0007]
When the developing bias of the developing means is high, the actual developing width of the image data is 1 in the cases of FIG. 17A and FIG. 17B.₁, L₂And almost l₁= L₂It becomes. However, when the development bias condition or the like is changed and the development bias of the developing means is low, the actual development width of the image data is as shown in FIG. 17A and FIG. 17B. L in case₁, L₂Thus, there is a problem that the actual development width of the image data becomes considerably thicker in the case of FIG. 17B than in the case of FIG.
This is due to the fact that the light spot formed by the scanning lines on the photosensitive member has a finite Gaussian width, and is considered to be influenced by the photosensitivity characteristics of the photosensitive member. .
[0008]
The present invention can make the development width after image data re-sampling constant to prevent image density unevenness and color unevenness, and makes the development width after image data re-sampling constant at any resampling phase. Image formation that can simplify the circuit, reduce costs, prevent uneven image density and color unevenness over time, and stabilize the line width of the image with high accuracy. An object is to provide an apparatus.
[0009]
[Means for Solving the Problems]
  In order to achieve the above object, the invention according to claim 1 includes a plurality of photoconductors, a plurality of writing units for forming an electrostatic latent image by writing image data to the plurality of photoconductors with scanning lines, respectively, A plurality of developing means for visualizing the electrostatic latent images on the plurality of photosensitive members; a measuring means for measuring the positional deviation of the scanning line; and the image data is resampled based on a measurement result of the measuring means. And a second correction unit that corrects the image data according to the phase of the resampling after the resampling. PreparationThe image data correction amount by the second correction means is set so that the line width of the image is constant without using the resampling.Therefore, the development width after resampling of image data can be made constant, and uneven density and color of the image can be prevented.Furthermore, the development width after resampling of image data can be made constant at any resampling phase.
[0010]
  The invention according to claim 2A plurality of photoconductors, a plurality of writing means for writing image data to the plurality of photoconductors by scanning lines to form an electrostatic latent image, and each electrostatic latent image on the plurality of photoconductors are visualized. A plurality of developing means, a measuring means for measuring the positional deviation of the scanning line, an interpolation parameter is calculated from the measurement result of the measuring means by an equation or a table, and the image data is resampled by the interpolation parameter. An image forming apparatus having a first correction unit that corrects a positional deviation of the scanning line, further comprising a variable unit that varies the equation or the table according to the phase of the resampling.Is,The circuit can be simplified and the cost can be reduced.
[0011]
  The invention according to claim 3A plurality of photoconductors, a plurality of writing means for writing image data to the plurality of photoconductors by scanning lines to form an electrostatic latent image, and each electrostatic latent image on the plurality of photoconductors are visualized. A plurality of developing means, a measuring means for measuring the positional deviation of the scanning line, an interpolation parameter is calculated from the measurement result of the measuring means by an equation or a table, and the image data is resampled by the interpolation parameter. In an image forming apparatus having a first correction unit that corrects a positional deviation of the scanning line, a line width measurement unit that measures a line width of a position detection pattern written on the photosensitive member by the writing unit, and sequentially Position detection created by writing the image data of the position detection pattern resampled by the first correction means while changing the phase to the photosensitive member by the writing means. The line width of the image regardless of the phase of the formula or table based on the measurement results the resampling of the line width measuring means for turn and means for determining to be constantIs,It is possible to prevent unevenness in image density and color over time.
[0012]
  The invention according to claim 42. The image forming apparatus according to claim 1, wherein a developing γ measuring unit that measures the development γ of the developing unit, and the image data correction amount by the second correcting unit is determined based on a measurement result of the developing γ measuring unit. With means toIs,The line width of the image can be stabilized with high accuracy.
[0013]
  The invention according to claim 53. The image forming apparatus according to claim 2, further comprising: a developing γ measuring unit that measures the developing γ of the developing unit; and a unit that determines the variable amount of the formula or the table based on the measurement result of the developing γ measuring unit. TheIs,The line width of the image can be stabilized with high accuracy.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
  Figure 2The present inventionOne embodiment is shown.
  This embodiment is an embodiment of a digital color image forming apparatus comprising a digital color copying machine having a plurality of photoconductors. A scanner unit 1 for reading a document image and a digital color image output from the scanner unit 1 An image processing unit 2 that electrically processes the signal and a printer unit 3 that forms an image on a transfer material made of transfer paper based on a digital color image signal from the image processing unit 2 are provided.
[0016]
In the scanner unit 1, a document placed on the document placement table 4 is illuminated by a light source 5 made of a fluorescent lamp, and the reflected light is reflected by a dichroic prism 10 through mirrors 6 to 8 and an imaging lens 9, for example. Imaging elements 11R, 11G, and 11B composed of CCDs for each wavelength (for each color) that are split into light of three types of wavelengths, red (hereinafter referred to as R), green (hereinafter referred to as G), and blue (hereinafter referred to as B). And the original is scanned by the movement of the fluorescent lamp 5 and the mirrors 6-8. The CCDs 11R, 11G, and 11B convert incident light of each color from the dichroic prism 10 into analog image signals of the respective colors, and the analog image signals of the respective colors are converted into digital image signals of the respective colors by an A / D converter (not shown). Input to the image processing unit 2.
[0017]
The image processing unit 2 performs predetermined processing on the digital image signals of each color from the scanner unit 1 and performs digital image signals of a plurality of recording colors, for example, black (hereinafter referred to as BK), yellow (hereinafter referred to as Y), magenta (Hereinafter referred to as “M”) and cyan (hereinafter referred to as “C”) are converted into digital image signals of respective recording colors, and are sent to writing means 12BK, 12Y, 12M, and 12C comprising a laser beam emitting device in the printer unit 3.
[0018]
In this embodiment, the full-color image is obtained by superimposing the four color images of BK, Y, M, and C, but the full-color image may be obtained by superimposing the three color images. In this case, the printer unit 3 can omit one set of the recording apparatuses 13BK, 13Y, 13M, and 13C that form the four colors of BK, Y, M, and C.
[0019]
In the printer unit 3, four sets of recording devices 13BK, 13Y, 13M, and 13C are arranged side by side. In the recording device 13C that forms a visible image of C, the photosensitive drum 14C as a photosensitive member is driven to rotate in the sub-scanning direction by a driving mechanism (not shown) and is uniformly charged by charging means 15C including a charging charger. Image data is written by the emission device 12C to form an electrostatic latent image.
[0020]
Here, the laser beam emitting device 12C drives the semiconductor laser by the semiconductor laser driving unit based on the C digital image signal from the image processing unit 2, and emits the laser beam whose intensity is modulated by the C digital image signal. The laser beam is repeatedly deflected in the main scanning direction by an optical deflector and irradiated to the photosensitive drum 14C as a scanning line, whereby a digital image signal of C is written on the photosensitive drum 14C to form an electrostatic latent image. The electrostatic latent image on the photosensitive drum 14C is developed by a developing device 16C as developing means with a one-component developer composed of C toner or a two-component developer composed of C toner and a carrier, and becomes a visible image of C.
[0021]
Similarly, in the other recording devices 13BK, 13Y, and 13M, the photosensitive drums 14BK, 14Y, and 14M as the photosensitive members are rotated in the sub-scanning direction by a driving mechanism (not shown) and are charged by a charging unit 15BK including a charging charger. , 15Y, and 15M, and the BK, Y, and M digital image signals are written by the laser beam emitting devices 12BK, 12Y, and 12M to form an electrostatic latent image.
[0022]
The laser beam emitting devices 12BK, 12Y, and 12M respectively drive the semiconductor lasers by the semiconductor laser driving units in accordance with the BK, Y, and M digital image signals from the image processing unit 2, and perform digital BK, Y, and M digital signals, respectively. A laser beam whose intensity is modulated by an image signal is emitted, these laser beams are repeatedly deflected in the main scanning direction by an optical deflector, and irradiated to the photosensitive drums 14BK, 14Y, and 14M as scanning lines. BK, Y, and M image data are written on the body drums 14BK, 14Y, and 14M, respectively, to form an electrostatic latent image. The electrostatic latent images on the photosensitive drums 14BK, 14Y, and 14M are converted into BK toner, Y toner, and M toner one-component developers or BK toner and carrier, Y by developing devices 16BK, 16Y, and 16M as developing means. Each toner is developed with a two-component developer of toner and carrier and M toner and carrier, respectively, and becomes a BK, Y, and M visible image.
[0023]
For example, a transfer material made of transfer paper is fed from one of two paper feed units 19 using two paper feed cassettes to a registration roller 20 by a paper feed roller 18, and the registration roller 20 takes the transfer paper in time. The transfer paper is sent to the transfer belt 21 and conveyed by the transfer belt 21. When the transfer paper on the transfer belt 21 passes through the nip portions of the transfer belt 21 and the photosensitive drums 14BK, 14C, 14M, and 14Y, the transfer chargers 17BK, 17C, 17M, and 17Y function as transfer means. A full-color image is formed by superimposing and transferring the visible images of the respective colors on the drums 14BK, 14C, 14M, and 14Y. The full-color image is fixed by the fixing device 22 and discharged to the outside by the discharge roller 23 as a color copy. Is done.
[0024]
The photosensitive drums 14BK, 14C, 14M, and 14Y are cleaned by the cleaning devices 24BK, 24C, 24M, and 24Y after the visible image transfer, respectively, to remove the residual toner. As shown in FIG. 3, the transfer belt 21 is stretched around a drive roller 25 and driven rollers 26 and 27, and is rotationally driven by the drive source via the drive roller 25 to convey the transfer paper from the registration roller 20. The cleaning device 28 cleans the transfer belt 21 after the transfer paper is conveyed.
[0025]
In addition, a reflection type photosensor comprising a plurality of sets of light emitting elements and a light receiving element 30, a slit member 31 and a plurality of condensing lenses 32 bend the scanning lines of the laser light emitting devices 12BK, 12C, 12M and 12Y. And a misalignment detection unit 33 (see FIG. 1) as a measuring means for measuring misalignment including tilt as needed.
[0026]
A plurality of slits of the slit member 31 are provided corresponding to a plurality of sets of light emitting elements 29 and light receiving elements 30 and arranged in the width direction (main scanning direction) of the transfer belt 21 or the width direction of the transfer belt 21 ( It is arranged two-dimensionally shifted in the main scanning direction) and the conveyance direction (sub-scanning direction), and is provided as a slit having a line width of a predetermined position detection pattern, for example, about the same as a line of about 0.1 mm.
[0027]
FIG. 1 shows the circuit configuration of this embodiment. The image processing unit 2 receives R, G, B digital image signals from the scanner unit 1, and receives R, G, B digital image signals from the external device 34 via the external controller 35. . In the image processing unit 2, the R, G, B digital image signals input from the scanner unit 1 or the R, G, B digital image signals input from the external device 34 via the external controller 35 are spatial. Moire removal processing or the like is performed by the filter 36, and the color conversion circuit (chromaticity coordinate conversion circuit) 37 converts the digital image signal of each recording color of Y, M, C, and BK. In some cases, Y, M, C, and BK digital image signals are directly sent to the image processing unit 2 from the outside.
[0028]
Each digital image signal of Y, M, C, and BK from the color conversion circuit 37 or the outside is subjected to a scaling process by a scaling unit 38, a creation unit 39 performs creation, and a tone correction unit 40 performs gradation. Correction is applied. The Y, M, C, and BK digital image signals from the gradation correction unit 40 are distances from the first photosensitive drum 14BK to the photosensitive drums 14BK, 14C, 14M, and 14Y by the inter-photosensitive memory 41. Are held and output for the time corresponding to each.
[0029]
On the other hand, the system control unit 42 as a control means outputs image data of position detection patterns of BK, C, M, and Y colors from the pattern creation unit 53 to the laser beam emitting devices 12BK, 12C, 12M, and 12Y at a predetermined timing. Let The laser beam emitting devices 12BK, 12C, 12M, and 12Y drive the semiconductor lasers at the semiconductor laser driving units based on the image data of the position detection patterns of the BK, C, M, and Y colors from the pattern creating unit 53, respectively. A laser beam whose intensity is modulated by the image data of the position detection pattern of each color of M, M, and Y is emitted, and these laser beams are repeatedly deflected by the optical deflector in the main scanning direction, respectively, and the photosensitive drums 14BK, 14C, 14M. , 14Y are irradiated as scanning lines, thereby writing position detection patterns for the colors BK, C, M, and Y on the photosensitive drums 14BK, 14C, 14M, and 14Y, thereby forming an electrostatic latent image of the position detection pattern for each color. To do.
[0030]
The electrostatic latent images of the position detection patterns on the photosensitive drums 14BK, 14C, 14M, and 14Y are developed by the developing devices 16BK, 16C, 16M, and 16Y, respectively, and the position detection patterns of the BK, C, M, and Y colors are detected. It becomes a visible image and is transferred by the transfer chargers 17BK, 17C, 17M, and 17Y so as not to directly overlap the transfer belt 21, and is not transferred to the transfer paper. The transfer belt 21 is irradiated with light beams from the respective illumination light sources 29 through the slits of the slit member 31, and the reflected light thereof is received by the respective light receiving elements 30 via the respective slits of the slit member 31 and the respective condensing lenses 32. A visible image of the position detection pattern of each of the colors BK, C, M, and Y on 21 is optically detected.
[0031]
The position deviation detection unit 33 calculates the output signal of each light receiving element 30 as needed to obtain the position deviation including the bending and inclination of the scanning lines of the laser beam emitting devices 12BK, 12C, 12M, and 12Y. The laser beam emitting devices 12BK, 12C, 12C, 12C, 12C, 12C, 12C, 12C, 12C, 12C, 12C, 12C, and 12C are detected by detecting the positional deviation of the position detection pattern of each color in the sub-scanning direction A positional deviation including bending and inclination of the scanning lines 12M and 12Y in the sub-scanning direction is detected, or light is received through a plurality of slits arranged two-dimensionally in the main scanning direction and the sub-scanning direction of the slit member 31. A laser beam is detected by detecting a two-dimensional positional shift in the main scanning direction and sub-scanning direction of the visible image of the position detection pattern of each color from the output signals of the plurality of light receiving elements 30. Morphism device 12BK, 12C, 12M, and detects the positional deviation including a two-dimensional curve and inclination of the main scanning direction and the sub scanning direction of 12Y of the scan line, and outputs the result as displacement data.
[0032]
The system control unit 42 approximates the positional deviation including the bending and inclination of the scanning lines of the laser beam emitting devices 12BK, 12C, 12M, and 12Y from the positional deviation data from the positional deviation detection unit 33 by an approximate expression in the main scanning direction. The amount of deviation of the scanning line corresponding to each arranged dot in the sub-scanning direction is calculated (or the scanning line corresponding to each dot arranged in the main scanning direction on the table by the position deviation data from the position deviation detecting unit 33. The amount of misalignment in the sub-scanning direction is calculated), and an interpolation parameter is created for each dot arranged in the main scanning direction or a plurality of dots arranged in the main scanning direction based on this misalignment amount. The data is stored in the interpolation memory of the correction device 43.
[0033]
The misregistration correction device 43 corrects the Y, M, C, and BK digital image signals that have passed through the inter-photosensitive memory 41 by interpolating in the sub-scanning direction or two-dimensionally using the interpolation parameters in the interpolation memory (re-alignment). The line width correction circuit 44 converts the Y, M, C, and BK digital image signals from the misregistration correction device 43 into the resampling phase based on the resampling phase information from the misregistration correction device 43. Accordingly, the correction is made and sent to the laser beam emitting devices 12BK, 12C, 12M, and 12Y of the printer unit 3. Here, resampling for correcting the image data in the sub-scanning direction or two-dimensionally in accordance with the measurement result of the displacement detection unit 33 is performed by the system control unit 42, the displacement correction device 43, and the image area determination unit 45. Configure the means.
[0034]
FIG. 4 shows a configuration for one color of the positional deviation correction device 43. The positional deviation correction device 43 has the same configuration for each color. The system control unit 42 performs weighting on pixels in the vicinity of the position where correction (resampling) of the image data misalignment is performed by an approximate expression (or table) according to the misalignment data from the misalignment detection unit 33. The weighting data is set as an interpolation parameter in the interpolation memory of the positional deviation correction device 43 in units of pixels or in units of a plurality of pixels.
[0035]
The misalignment correction device 43 includes a line memory 46 for a plurality of (m) lines as an interpolation memory for storing interpolation parameters, and a line memory for n lines for holding image data from the inter-photosensitive memory 41 for n lines. 47 and an interpolation data calculation circuit 48 as calculation means. Here, n is set to n ≧ m + (the amount of positional deviation including bending and inclination of the scanning line in the sub-scanning direction). The interpolation data calculation circuit 48 resamples the image data in the line memory 47 by linear interpolation, cubic function convolution, spline interpolation, or the like according to the interpolation parameters in the line memory 46, and corrects the data by the printer unit 3. To the laser beam emitting devices 12BK, 12C, 12M, and 12Y.
[0036]
Next, as a specific example of resampling image data, an example in which the number of pixels in the main scanning direction is 256 dots and the interpolation matrix size in the main scanning direction is 1 × 4 is used for the sake of simplification of explanation. The image data for two colors will be described. Here, as shown in FIG. 5, the scanning line of the laser beam emitting device for the first color is bent by +1 dot in the sub-scanning direction at the center (128th dot) in the main scanning direction, and the laser beam emitting device for the second color. It is assumed that the misalignment detection unit 33 detects that the scan line is bent by −1 dot in the sub-scanning direction at the center (128th dot) in the main scanning direction due to bending. The number of dots (256 dots) and the interpolation matrix size are for convenience of calculation, and are actually set to appropriate values.
[0037]
The positional deviation data from the positional deviation detection unit 33 is sent to the system control unit 42, and the system control unit 42 is arranged in the main scanning direction on the line to be resampled from the positional deviation data from the positional deviation detection unit 33. The amount of deviation of the scanning line corresponding to each dot in the sub-scanning direction is obtained by, for example, a linear approximation formula. In this case, the system control unit 42 uses the linear approximation formula, but performs resampling from the positional deviation data from the positional deviation detection unit 33 using a polynomial expression such as a quadratic expression or a cubic expression, a spline function, or the like. You may make it obtain | require the deviation | shift amount to the subscanning direction of the scanning line corresponding to each dot arranged in the main scanning direction on the power line.
[0038]
When calculating the shift amount in the sub-scanning direction of the scanning line corresponding to each dot arranged in the main scanning direction on the line to be resampled using the spline function, a curve can be freely set, It is also possible to cope with typical lens errors. When obtaining the shift amount in the sub-scanning direction of the scanning line corresponding to each dot arranged in the main scanning direction on the line to be resampled using the linear approximation formula, each scan of the first color and the second color The shift amount of the line in the sub-scanning direction is Y = ± X / 128 (0 to 0), where X is the dot position in the main scanning direction and Y is the scanning line shift amount in the sub-scanning direction. 127 dot range), Y = − {± (X−128) / 128} ± 1 (128 to 255 dot range).
[0039]
Next, the system control unit 42 calculates, for example, a sinc function as shown in FIG. 6 from the shift amount of the scanning line corresponding to each dot arranged in the main scanning direction on the line to be resampled in the sub scanning direction. The interpolation matrix is calculated as shown in FIG. That is, the system control unit 42 is adjacent in the sub-scanning direction from the resampling point based on the shift amount in the sub-scanning direction of the scanning line corresponding to each dot arranged in the main scanning direction on the line to be resampled. The calculation is such that the distance to ± 2 dots (depending on the size of the interpolation matrix) is obtained and the value of the sinc function corresponding to the distance (the position of π of the sinc function corresponds to 1 dot) is calculated. The calculation is performed sequentially for each dot in the scanning direction, and the calculation result is stored as an interpolation parameter in the interpolation memory of the misalignment correction device 43.
[0040]
FIG. 7 shows a specific example of the positional deviation correction device 43. The image data from the inter-photoreceptor memory 41 is a plurality of line memories 47 as the line memory 47.₀~ 47₆A plurality of lines are held at the same time. In this case, the line memory 47₀~ 47₆Is the line number counter 49₀~ 49₆The image data of the line number set in is held. Assume that the resampling point address of the image data is X in the main scanning direction address and the sub-scanning direction address is between the Y line and the Y + 1 line of the image data. Here, the line memory 47₀Is stored in the line memory 47.₁Is stored in the line memory 47.₂~ 47_FiveEach of the image data of the Yth to Y + 3rd lines is stored in the.
[0041]
Also, the interpolation line memory 46₀~ 46₆In, a weighting interpolation parameter for the image data of each line is written. The weighting of this interpolation parameter follows the sinc function as described above, and is set so that the weight corresponding to the line that is more than the distance from the line to be resampled to the adjacent ± 2 line is 0. ing.
[0042]
Line memory 47₀The interpolation parameter corresponding to the Xth value (image data at the main scanning direction address X) is the interpolation line memory 46.₀Are stored in the Xth position, and the corresponding both are read and integrated circuit 50₀Is accumulated. Similarly, the line memory 47₁~ 47_FiveX-th value and the corresponding interpolation line memory 46₁~ 46_FiveThe Xth interpolation parameter is read and the integration circuit 50₁~ 50_FiveIs accumulated respectively. In this case, the interpolation line memory 46₁~ 46_FiveOutputs the Xth interpolation parameter in synchronism with the column clock, and the line selector 51 is controlled by the system control unit 42 to control the line memory 47.₀~ 47_FiveThe Xth value of the integration circuit 50 is selected₀~ 50_FiveOutput to.
[0043]
At this time, the image data of the (Y + 4) th line from the inter-photoreceptor memory 41 is stored in the line memory 47.₆Is written at address X. Integration circuit 50₀~ 50₆Are added by the adding circuit 52 and sent to the laser beam emitting device of the printer unit 3 as resampled image data. Similarly, the (X + 1) th and subsequent image data are resampled. Therefore, the image data of the target pixel and a plurality of pixels in the vicinity thereof and the interpolation parameters corresponding to these are integrated and added, whereby the positional deviation of the image data is corrected.
[0044]
When the image data for one line is resampled to the image data of the final address in the main scanning direction, the resampling of the image data for the next one line is started. At this time, the line memory 47₁~ 47₆Is the line number counter 49₁~ 49₆The line numbers are shifted by the above, and the image data of the (Y-2) to (Y + 3) lines is stored, and the line memory 47₀Stores image data of (Y + 4) lines.
[0045]
In this way, image data for six lines in the vicinity of the resampling point is always read and the resampling of the image data is performed. At this time, if an overflow of the resampled image data occurs, the overflow is invalidated and the image data is set to the maximum value or the minimum value.
[0046]
FIG. 9 shows a case where the scanning line of the laser beam emitting device for the first color is bent by +1 dot in the sub-scanning direction at the center (128th dot) in the main scanning direction due to bending, as shown in FIG. FIG. 10 shows the image data after the positional deviation correction. FIG. 10 shows the positional deviation when the scanning line of the laser beam emitting device for the second color is bent by −1 dot in the sub-scanning direction at the center (128th dot) in the main scanning direction. The image data after the misalignment correction from the correction device 43 is shown. FIG. 8 shows the image data before the positional deviation correction by the positional deviation correction device 43.
[0047]
The composite image and the state of each dot when the two color images formed by the image data of these two colors are superimposed and combined are misaligned including the bending and inclination of the scanning line of the laser beam emitting device. In the case where there is not, the result is as shown in FIG. 12 and FIG. 15A, and in the case where there is a positional deviation including bending and inclination of the scanning line of the laser beam emitting device and the correction is not performed, FIG. 13 and FIG. FIG. 14 and FIG. 15 (c) show the case where there is a positional deviation including bending and inclination of the scanning line of the laser beam emitting device and correction is performed as described above. It becomes like this.
[0048]
The line width correction circuit 44 corrects each digital image signal of Y, M, C, and BK from the misalignment correction device 43 according to the resampling phase based on the resampling phase information from the misalignment correction device 43. However, for example, as shown in FIG. 16, the correction amount is a correction amount that linearly decreases the resampled image data in the range of −π to π in accordance with the resampling phase.
[0049]
As described above, FIGS. 17A and 17B show an example in which a 2-dot image is created in the sub-scanning direction, the exposure state when the image data is not resampled, and the image data by 1/2 dot (phase). And the exposure state when re-sampling is performed with a shift of 180 °. When the development bias is in a state of high development bias (2), the actual development width of the image data is L in the case of FIG. 17 (a) and FIG. 17 (b).₁, L₂Accordingly, the actual development width of the image data becomes considerably thicker in the case of FIG. 17B than in the case of FIG. Note that the image data has levels (255, 255) and (108, 255, 108) in the case of FIG. 17A and the case of FIG. 17B, respectively.
[0050]
Therefore, in this embodiment, each of the Y, M, C, and BK digital image signals from the misalignment correction device 43 is regenerated by the line width correction circuit 44 based on the resampling phase information from the misalignment correction device 43. Correction is performed as shown in FIG. 16 according to the sampling phase (the phase shift amount of each dot of the position shift correction device 43). When the dot phase shift amount is π (180 °), the image data is lowered by the level of −23 by the line width correction circuit 44, and the exposure distribution by the laser beam emitting device is shown in FIG. Thus, the actual development width of the image data is L in the case of FIG. 17 (a) and FIG. 17 (b).₁, L₂Become ‘L’₁= L₂The line width of the image is substantially the same when the image data is not resampled as shown in FIG. 17A and when the image data is resampled as shown in FIG.
[0051]
Note that the image data correction amount by the line width correction circuit 44 is set to an amount that linearly changes according to the resampling phase as shown in FIG. The table may be provided so as to be set according to the resampling phase according to the image forming conditions of each machine.
[0052]
As shown in FIG. 1, the image area determination unit 45 determines the type of image from the digital image signal from the scanner unit 1 or the external device 34, and the system control unit 42 determines the image from the determination result of the image area determination unit 45. For example, when an image area of an image type formed with only one black color is present, the image data resampling is notified to the misalignment correction device 43 in the image area of that image type and the through mode is in effect. Without passing through the image data. Accordingly, it is possible to prevent the MTF from being deteriorated due to resampling by not performing correction on an image portion that does not require positional deviation correction.
[0053]
In addition, the operation unit 53 can set, correct, and reset interpolation parameters with respect to the system control unit 42, and the system control unit 42 sets interpolation parameters from the operation unit 53 or performs measurement by the positional deviation detection unit 33. When an input signal for correcting or resetting the interpolation parameter obtained from the result is input, the interpolation parameter corresponding to the input signal is stored in the interpolation memory 46 of the misalignment correction device 43 or the interpolation memory. The interpolation parameter in 46 is corrected or reset according to the input signal from the operation unit 53.
[0054]
For example, the system control unit 42 bends and tilts the scanning lines of the laser beam emitting devices 12BK, 12C, 12M, and 12Y measured by the positional deviation detection unit 33 according to the coefficient of the approximate expression according to the input signal from the operation unit 53. Setting, correction, and reset of misalignment including Therefore, the user cancels the steady measurement error of the misalignment detection unit 33 by finely adjusting the interpolation parameter by the operation unit 53 while confirming the final image output from the printer unit 3, and more accurate misalignment. Correction can be performed.
[0055]
Further, the system control unit 42 detects the amount of misalignment including the bending and inclination of the scanning line immediately after measurement by the misalignment detection unit 33 and the misalignment including the bending and inclination of the scanning line immediately before measurement by the misalignment detection unit 33. When the difference exceeds the reference value, an abnormal signal is generated. For example, the positional deviation including the curve and the inclination of the scanning line is measured by the positional deviation detection unit 33 using the coefficient of the approximate expression. When the amount of fluctuation of the current measurement result with respect to the previous measurement result of the positional deviation detection unit 33 exceeds the reference value, an abnormality signal is generated and the positional deviation detection unit 33 performs remeasurement or the like. I do. As a result, it is possible to prevent the misregistration detection unit 33 from malfunctioning due to scratches or the like on the transfer belt 21.
[0056]
  Thus, this embodiment isThe present inventionIn this embodiment, the photosensitive drums 14BK, 14C, 14M, and 14Y as a plurality of photosensitive bodies and image data are written on the plurality of photosensitive bodies 14BK, 14C, 14M, and 14Y by scanning lines, respectively, and electrostatically. Laser light emitting devices 12BK, 12C, 12M, 12Y as a plurality of writing means for forming a latent image, and a plurality of electrostatic latent images on the plurality of photosensitive members 14BK, 14C, 14M, 14Y are visualized. Based on the measurement results of the developing means 16BK, 16C, 16M, and 16Y as developing means, the misregistration detecting unit 33 as measuring means for measuring misregistration including bending and inclination of the scanning line, and the measurement result of the measuring means 33 System control as a first correction unit that corrects misregistration including bending and inclination of the scanning line by re-sampling the image data 42 and a misregistration correction device 43, a digital color image forming apparatus comprising a digital color copying machine as a second correction means for correcting the image data in accordance with the phase of the resampling after the resampling. Since the width correction circuit 44 is provided, the development width after the re-sampling of the image data can be made constant, and uneven density and uneven color of the image can be prevented.
[0057]
  Claim1In one embodiment of the invention according tothe aboveEmbodiment(Hereinafter referred to as Embodiment 1)The line width correction circuit 44 corresponds to the resampling phase based on the resampling phase information from the misalignment correction device 43 based on the resampling phase information from the misalignment correction device 43. Thus, the image line width is corrected so as to be constant, and the image data correction amount is set so that the line width of the image is constant irrespective of the resampling phase. Therefore, the actual development width of the image data is the same L in the case of FIG. 17A and FIG.₁Thus, the line width of the image is exactly the same when the image data is not resampled as shown in FIG. 17A and when it is resampled as shown in FIG.
[0058]
  Thus, the claim1An embodiment of the invention according toEmbodiment 1 aboveSince the image data correction amount by the line width correction circuit 44 as the second correction means is set so that the line width of the image is constant without using resampling, the resampling phase is 180 °. In addition, the line width of the image data can be made constant at any resampling phase.
[0059]
  FIG. 18 claims21 shows an embodiment of the invention. In this embodiment, the aboveEmbodiment 1In FIG. 4, a positional deviation / line width detection unit 54 is used instead of the positional deviation detection unit 33, and a deviation correction circuit 55 is used instead of the positional deviation correction device 43 and the line width correction circuit 44. The misalignment / line width detection unit 54 constitutes a misregistration detection unit as a measuring unit for measuring misalignment including bending and inclination of the scanning lines of the laser beam emitting devices 12BK, 12C, 12M, and 12Y as needed, and Line width measuring means for measuring the line widths of the position detection patterns written on the photosensitive drums 14BK, 14C, 14M, and 14Y by the laser beam emitting devices 12BK, 12C, 12M, and 12Y is configured.
[0060]
The misregistration / line width detection unit 54 is similar to the misregistration detection unit 33 in that it includes a reflective photosensor, a slit member 31, and a plurality of condensing lenses, each of which includes an illumination light source 29 and a light receiving element 30 composed of a plurality of light emitting elements. 32, a plurality of slits of the slit member 31 are provided corresponding to the plurality of sets of light emitting elements 29 and light receiving elements 30, and are arranged in the width direction (main scanning direction) of the transfer belt 21, or The position detection pattern is arranged so as to be two-dimensionally shifted in the width direction (main scanning direction) and the conveyance direction (sub-scanning direction) and is provided as a slit having the same width as the line width of the position detection pattern, for example, about 0.1 mm.
[0061]
The system control unit 42 outputs the image data of the position detection patterns of the BK, C, M, and Y colors from the pattern creation unit 53 to the laser beam emitting devices 12BK, 12C, 12M, and 12Y at a predetermined timing as in the above embodiment. Let The laser beam emitting devices 12BK, 12C, 12M, and 12Y drive the semiconductor lasers at the semiconductor laser driving units based on the image data of the position detection patterns of the BK, C, M, and Y colors from the pattern creating unit 53, respectively. A laser beam whose intensity is modulated by the image data of the position detection pattern of each color of M, M, and Y is emitted, and these laser beams are repeatedly deflected by the optical deflector in the main scanning direction, respectively, and the photosensitive drums 14BK, 14C, 14M. , 14Y are irradiated as scanning lines, thereby writing position detection patterns for the colors BK, C, M, and Y on the photosensitive drums 14BK, 14C, 14M, and 14Y, thereby forming an electrostatic latent image of the position detection pattern for each color. To do.
[0062]
The electrostatic latent images of the position detection patterns on the photosensitive drums 14BK, 14C, 14M, and 14Y are developed by the developing devices 16BK, 16C, 16M, and 16Y, respectively, and the position detection patterns of the BK, C, M, and Y colors are obtained. It becomes a visible image and is transferred by the transfer chargers 17BK, 17C, 17M, and 17Y so as not to directly overlap the transfer belt 21, and is not transferred to the transfer paper. The transfer belt 21 is irradiated with light beams from the respective illumination light sources 29 through the slits of the slit member 31, and the reflected light thereof is received by the respective light receiving elements 30 via the respective slits of the slit member 31 and the respective condensing lenses 32. A visible image of the position detection pattern of each of the colors BK, C, M, and Y on 21 is optically detected.
[0063]
The position deviation / line width detection unit 54 calculates the output signal of each light receiving element 30 at any time to obtain the position deviation including the bending and inclination of the scanning lines of the laser beam emitting devices 12BK, 12C, 12M, and 12Y. The laser beam emitting device 12BK is detected by detecting the positional deviation of the position detection pattern of each color in the sub-scanning direction from the output signals of the plurality of light receiving elements 30 that receive light through the plurality of slits arranged in the main scanning direction of the member 31. , 12C, 12M, and 12Y, a plurality of slits that detect misalignment including bending and inclination in the sub-scanning direction, or two-dimensionally arranged in the main scanning direction and the sub-scanning direction of the slit member 31. Two-dimensional positional deviations in the main scanning direction and sub-scanning direction of the visible images of the position detection patterns of the respective colors are detected from the output signals of the plurality of light receiving elements 30 that receive light through The light emitting device 12BK, 12C, 12M, and detects the positional deviation including a two-dimensional curve and inclination of the main scanning direction and the sub scanning direction of 12Y of the scan line, and outputs the result as displacement data.
[0064]
Further, the positional deviation / line width detection unit 54 calculates the line width of the visible image of the position detection pattern of each color from the output signals of the plurality of light receiving elements 30 that receive light through the plurality of slits arranged in the main scanning direction of the slit member 31. taking measurement. For example, the misalignment / line width detection unit 54 detects and scans the position of the scanning line of the laser beam emitting device as the peak position of the amount of light transmitted through the slit member 31 (the output signal of the light receiving element 30) as shown in FIG. A positional deviation including the bending and inclination of the line is detected, the output signal of the light receiving element 30 is compared with a predetermined threshold level, the line width of the visible image of the position detection pattern is detected, and the system control is performed using the detection result as the line width data. To the unit 42.
[0065]
The system control unit 42, based on the positional deviation data from the positional deviation / line width detection unit 54, similarly to the above-described embodiment, includes positions including the bending and inclination of the scanning lines of the laser light emission devices 12BK, 12C, 12M, and 12Y. The deviation is approximated by an approximate expression, and the amount of deviation in the sub-scanning direction of the scanning line corresponding to each dot in the main scanning direction is calculated (or based on the position deviation data from the position deviation / line width detection unit 54 using a table). The amount of deviation of the scanning line corresponding to each dot in the main scanning direction in the sub-scanning direction is obtained), and a plurality of dots in the main scanning direction are obtained for each dot in the main scanning direction using the sinc function based on this amount of deviation. Create interpolation parameters for each. FIG. 20A shows an example in which the deviation of the interpolation parameter at this time is 180 °.
[0066]
The system control unit 42 further varies the approximate expression (or table) according to the resampling phase based on the created interpolation parameter based on the line width data from the positional deviation / line width detection unit 54, thereby generating an image. The data is corrected so that the line width of the image becomes constant according to the resampling phase (phase shift amount of each dot), and for example, the interpolation parameters as shown in FIG. 20A are shown in FIG. Such interpolation parameters are corrected and transferred to the interpolation memory 56 (see FIG. 21) of the deviation correction circuit 55. By correcting the interpolation parameter, the actual development width of the image data becomes as shown in FIG. 17C, and the line width of the image becomes constant. For this reason, the circuit can be simplified without providing the line width correction circuit 44.
[0067]
FIG. 21 shows a configuration for one color of the deviation correction circuit 55. The shift correction circuit 55 has the same configuration for each color. The system control unit 42 applies the correction (resampling) by the interpolation (resampling) of the positional deviation of the image data according to the approximate expression (or table) according to the positional deviation data from the positional deviation / line width detection unit 54. Weighting is performed, and the weighted data is set in the interpolation memory 56 of the shift correction circuit 55 in units of pixels or in units of a plurality of pixels as interpolation parameters.
[0068]
The misalignment correction circuit 55 receives a line memory 56 for a plurality of (m) lines as an interpolation memory for storing interpolation parameters, and image data for n lines from the inter-photoreceptor memory 41 and also interpolates from the line memory 56. And an interpolation data calculation circuit 57 as calculation means for inputting parameters. Here, n is set to n ≧ m + (the amount of positional deviation including bending and inclination of the scanning line in the sub-scanning direction).
[0069]
FIG. 22 shows the configuration of the interpolation data calculation circuit 57. In the interpolation data calculation circuit 57, image data for a plurality of lines from the inter-photoreceptor memory 41, for example, image data for five lines, is added via the line selector 58 to the integration circuit 59.₀~ 59_FourIs input. Assume that the resampling point address of the image data is X in the main scanning direction address and the sub-scanning direction address is between the Y line and the Y + 1 line of the image data. Here, it is assumed that the image data for five lines from the inter-photoreceptor memory 41 is the image data of lines 0 to 4.
[0070]
The interpolation line memory 56 is, for example, an interpolation line memory 56 for four lines.₀~ 56_ThreeThis interpolation line memory 56₀~ 56_ThreeThe system controller 42 writes weighting interpolation parameters for the image data of each line. The weighting of the interpolation parameter follows the sinc function as in the above embodiment, and the weight corresponding to a line that is more than the distance from the line to be resampled to the adjacent ± 2 line is 0. Is set.
[0071]
The clock counter 61 counts the column clock, and the interpolation line memory 56₀~ 56_ThreeAre designated by the count value of the clock counter 61. The line selector 58 is controlled by the system control unit 42. The interpolation parameter corresponding to the Xth image data of line 0 from the line selector 58 is the interpolation line memory 56.₀X corresponding to the integration circuit 59.₀Is accumulated. Similarly, the Xth image data of lines 1 to 3 from the line selector 58 and the corresponding interpolation line memory 56₁~ 56_ThreeX-th interpolation parameters of the respective integration circuits 59₁~ 59_ThreeIs accumulated. In this case, the interpolation line memory 56₀~ 56_ThreeThe address is specified by the column counter 61 and the Xth interpolation parameter is output, and the line selector 58 is controlled by the system control unit 42 to add the Xth image data of lines 0 to 3 to the integrating circuit 59.₀~ 59_ThreeOutput to.
[0072]
Integration circuit 59₀~ 59_ThreeAre added by the adding circuit 60 and sent to the laser beam emitting device of the printer unit 3. Similarly, the (X + 1) th and subsequent image data are resampled. Accordingly, the image data and the interpolation parameters of the target pixel and a plurality of pixels in the vicinity thereof are respectively added and added to correct the positional deviation of the image data.
[0073]
When the image data for one line is resampled up to the image data of the final address in the main scanning direction, the resampling of the image data for the next one line is started. Thus, the image data for four lines near the resampling point is always resampled. At this time, if an overflow of the resampled image data occurs, the overflow is invalidated and the image data is set to the maximum value or the minimum value.
[0074]
  Thus, the claim2In one embodiment of the present invention, photosensitive drums 14BK, 14C, 14M, and 14Y as a plurality of photosensitive bodies and image data are written on the plurality of photosensitive bodies 14BK, 14C, 14M, and 14Y by scanning lines, respectively, and A plurality of laser beam emitting devices 12BK, 12C, 12M, and 12Y as a plurality of writing means for forming an electrostatic latent image, and a plurality of electrostatic latent images on the plurality of photoconductors 14BK, 14C, 14M, and 14Y are visualized. Developing devices 16BK, 16C, 16M, and 16Y as developing means, a misregistration / line width detecting unit 54 as measuring means for measuring misregistration including bending and inclination of the scanning line, and measurement by the measuring means 54 An interpolation parameter is calculated from the result using an equation or a table, and the image data is resampled using the interpolation parameter, whereby the scan line curve is obtained. In a digital color image forming apparatus comprising a digital color copying machine having a system control unit 42 and a deviation correction circuit 55 as first correction means for correcting a positional deviation including a skew and an inclination, the above expression or table is resampled. Since the system control unit 42 is provided as variable means that can be varied according to the phase, the circuit can be simplified and the cost can be reduced.
[0075]
  By the way, aboveEmbodiment 1 and aboveClaim2,In the third embodiment, the sensitivity characteristics of the photoconductors 14BK, 14C, 14M, and 14Y, the development γ of the developing devices 16BK, 16C, 16M, and 16Y, and the like change with time, and are linked to this. As a result, the line width after re-sampling of the image data changes, and the color unevenness and density unevenness of the image occur over time. FIG. 23 shows how development γ changes over time. Therefore, the claim3In the embodiment of the invention according to the above-described embodiment, the line width after re-sampling of image data is periodically measured while changing the phase, and the image data correction amount (or interpolation parameter) is optimized based on the result. By doing so, the occurrence of uneven color and uneven density of the image over time is prevented.
[0076]
  Claim3In one embodiment of the invention according to FIG.Embodiment 1The system control unit 42 sequentially generates a plurality of interpolation parameters such that the resampling phase is sequentially shifted from 0 ° to 180 ° (the number of steps may be arbitrary, but the position detection pattern Is set in the interpolation memory of the misregistration correction device 43, and the image data of the position detection pattern is transferred from the pattern creation unit 53 to the tone correction unit 40 and between the photoconductors. A position detection pattern as shown in FIG. 25 is sequentially output by outputting it to the printer unit 3 via the memory 41, the positional deviation correction device 43, and the line width correction circuit 44.
[0077]
The position deviation / line width detection unit 54 bends and tilts the scanning lines of the laser beam emitting devices 12BK, 12C, 12M, and 12Y from the output signal of the light receiving element 30 with respect to the position detection pattern (position detection pattern on the transfer belt 21). Measure the position deviation and the line width of the position detection pattern.₁, L₂, L_ThreeMeasure as FIG. 26 is a graph of the line width measurement results. The system control unit 42 determines the image data correction amount based on the measurement result of the positional deviation / line width detection unit 54 as shown in FIG. 16, that is, the positional deviation data from the positional deviation / line width detection unit 54. And weighting the pixels in the vicinity of the position where resampling is performed, and interpolating the weighted data so that the line width of the image is constant according to the line width measurement result of the positional deviation / line width detection unit 54 The parameter is set in the interpolation memory of the positional deviation correction device 43 in units of pixels or in units of a plurality of pixels. For this reason, the line width of the image is stably output with high accuracy.
[0078]
  Claims3In another embodiment of the present invention, as shown in FIG.2In one embodiment of the present invention, the system control unit 42 sequentially generates a plurality of interpolation parameters such that the resampling phase is sequentially shifted from 0 ° to 180 ° (the number of steps is arbitrary). However, in consideration of the detection time of the position detection pattern, it is set in the interpolation memory of the deviation correction device 55 in about five steps (for example, three steps), and the tone correction is performed on the image data of the position detection pattern from the pattern creation unit 53. The position detection pattern as shown in FIG. 25 is sequentially output by outputting to the printer unit 3 via the unit 40, the inter-photoreceptor memory 41, and the deviation correction device 55.
[0079]
The position deviation / line width detection unit 54 detects the bending and inclination of the scanning lines of the laser beam emitting devices 12BK, 12C, 12M, and 12Y from the output signal of the light receiving element 30 with respect to the position detection pattern (position detection pattern on the transfer belt 21). The positional deviation including the line width of the position detection pattern is measured. Based on the positional deviation data from the positional deviation / line width detection unit 54, the system control unit 42 approximates the positional deviation including the bending and inclination of the scanning lines of the laser beam emitting devices 12BK, 12C, 12M, and 12Y by an approximate expression. Then, the amount of deviation of the scanning line corresponding to each dot in the main scanning direction in the sub-scanning direction is calculated (or, based on the position deviation data from the position deviation / line width detection unit 54, each dot in the main scanning direction is calculated using a table. The amount of deviation of the corresponding scanning line in the sub-scanning direction is obtained), and an interpolation parameter is created for each dot in the main scanning direction or for each of a plurality of dots in the main scanning direction using a sinc function based on this deviation amount. .
[0080]
The system control unit 42 further converts the created interpolation parameter based on the line width data from the positional deviation / line width detection unit 54 and the above approximate expression (or table) according to the resampling phase so that the line width of the image is constant. Thus, the image data is corrected according to the resampling phase (the phase shift amount of each dot) and transferred to the interpolation memory 56 of the shift correction circuit 55. For this reason, the line width of the image is stably output with high accuracy.
[0081]
  Thus, the claim3In the embodiment of the present invention, the photosensitive drums 14BK, 14C, 14M, and 14Y as a plurality of photosensitive bodies and the image data are written on the plurality of photosensitive bodies 14BK, 14C, 14M, and 14Y by scanning lines, respectively. Laser light emitting devices 12BK, 12C, 12M, 12Y as a plurality of writing means for forming a latent image, and a plurality of electrostatic latent images on the plurality of photosensitive members 14BK, 14C, 14M, 14Y are visualized. Development devices 16BK, 16C, 16M, and 16Y as developing means, a positional deviation / line width detector 54 as a measuring means for measuring positional deviation including bending and inclination of the scanning line, and measurement results of the measuring means 54 By calculating an interpolation parameter from the equation or table and re-sampling the image data with the interpolation parameter, the curvature of the scanning line is changed. In addition, in the image forming apparatus having the system control unit 42 as the first correction unit that corrects the positional deviation including the inclination and the positional deviation correction device 43 or the deviation correction circuit 55, the writing units 12BK, 12C, 12M, and 12Y A position shift / line width detector 54 as a line width measuring means for measuring the line width of the position detection pattern written on the photoreceptors 14BK, 14C, 14M, and 14Y, and the first correction by sequentially changing the phase. The line width with respect to the position detection pattern created by writing the image data of the position detection pattern resampled by the means 42, 43 or 55 to the photosensitive members 14BK, 14C, 14M, 14Y by the writing means 12BK, 12C, 12M, 12Y. The resampling of the formula or table based on the measurement result of the measuring means 54 Since the line width of the image regardless of the phase and a system control unit 42 as a means for determining to be constant, it is possible to prevent density unevenness and color unevenness with time in the image.
[0082]
  Claims4In each embodiment of the invention according to the above,Embodiment 1The above claims1In the embodiment according to the present invention, since the line width of the image changes even if the development γ of the developing devices 16BK, 16C, 16M, and 16Y changes, the developing devices 16BK, 16C, 16M, and 16Y each have Development γ measuring means for measuring the development γ of the developing devices 16BK, 16C, 16M, and 16Y by obtaining the fluctuation of the line width when the development γ fluctuates by experiment and storing it in the nonvolatile memory of the system control unit 42. The system control unit 42 changes the image data correction amount according to the content of the nonvolatile memory based on the measurement result of the development γ measuring means so that the line width of the image becomes constant. Even when the development γ fluctuates, the line width of the image can be stabilized with high accuracy.
[0083]
  Thus, the claim4An embodiment of the invention according toEmbodiment 1 aboveOrClaim 1In the image forming apparatus described above, a development γ measurement unit that measures the development γ of the development devices 16BK, 16C, 16M, and 16Y as the development unit, and the second correction unit based on a measurement result of the development γ measurement unit The system control unit 42 and the system control unit 42 as means for determining the image data correction amount by the line width correction circuit 44 are provided, so that the line width of the image can be stabilized with high accuracy.
[0084]
  Claim5An embodiment of the invention according to2In the embodiment of the invention, since the line width of the image changes even if the development γ of the development devices 16BK, 16C, 16M, and 16Y changes, the development γ of the development devices 16BK, 16C, 16M, and 16Y in advance. A development γ measuring means is provided for measuring the development γ of the developing devices 16BK, 16C, 16M, and 16Y by experimentally obtaining the fluctuation of the line width when the value fluctuates and storing it in the nonvolatile memory of the system control unit 42. The system control unit 42 changes the approximate expression (or table) according to the contents of the nonvolatile memory based on the measurement result of the development γ measuring means so that the line width of the image becomes constant, thereby adjusting the image data correction amount. The line width of the image can be stabilized with high accuracy even when the development γ fluctuates.
[0085]
  Thus, the claim5An embodiment of the invention according to claim2In the image forming apparatus described above, the developing γ measuring means for measuring the developing γ of the developing devices 16BK, 16C, 16M, and 16Y as the developing means, and the variable of the above formula or table based on the measurement result of the developing γ measuring means. Since the system control unit 42 is provided as means for determining the quantity, the line width of the image can be stabilized with high accuracy.
  The invention according to each claim is not limited to the above embodiment, and can be applied to an image forming apparatus such as a digital color printer other than the digital color copying machine and a digital color facsimile.
[0086]
【The invention's effect】
  As described above, according to the first aspect of the present invention, an electrostatic latent image is formed by writing a plurality of photoconductors and information of different colors on the plurality of photoconductors by using different color image data with scanning lines. A plurality of writing means to be formed; a plurality of developing means for visualizing the electrostatic latent images on the plurality of photoconductors into different colors; and a measuring means for measuring the positional deviation of the scanning lines. And an image forming apparatus including a first correction unit that corrects a positional deviation of the scanning line by re-sampling the image data based on a measurement result of the measurement unit. Second correction means for correcting according to the phase of the resampling is provided.The image data correction amount by the second correction means is set so that the line width of the image is constant without using the resampling.Therefore, the development width after resampling of image data can be made constant, and uneven density and color of the image can be prevented.The development width after resampling of image data can be made constant at any resampling phase.
[0087]
  According to the invention of claim 2,A plurality of photoconductors, a plurality of writing means for writing different color information by scanning lines on the plurality of photoconductors with different color image data to form an electrostatic latent image, and the plurality of photoconductors. A plurality of developing means for visualizing the electrostatic latent images into different colors, measuring means for measuring the positional deviation of the scanning line, and interpolation parameters from the measurement results of the measuring means using an equation or a table. And an image forming apparatus having a first correction unit that corrects a positional deviation of the scanning line by re-sampling the image data with the interpolation parameter. Since the variable means that varies according to the above is provided, the circuit can be simplified and the cost can be reduced.
[0088]
  According to the invention of claim 3,A plurality of photoconductors, a plurality of writing means for writing different color information by scanning lines on the plurality of photoconductors with different color image data to form an electrostatic latent image, and the plurality of photoconductors. A plurality of developing means for visualizing the electrostatic latent images into different colors, measuring means for measuring the positional deviation of the scanning line, and interpolation parameters from the measurement results of the measuring means using an equation or a table. In the image forming apparatus, the first correction unit that corrects the positional deviation of the scanning line by re-sampling the image data with the interpolation parameter and written on the photosensitive member by the writing unit Line width measuring means for measuring the line width of the position detection pattern, and image data of the position detection pattern resampled by the first correction means with the phase being changed sequentially Based on the measurement result of the line width measuring unit with respect to the position detection pattern created by writing on the photosensitive member by the only unit, the equation or the table is determined so that the line width of the image is constant regardless of the resampling phase. Therefore, it is possible to prevent uneven density and uneven color of the image over time.
[0089]
  According to the invention of claim 4,2. The image forming apparatus according to claim 1, wherein a developing γ measuring unit that measures the development γ of the developing unit, and the image data correction amount by the second correcting unit is determined based on a measurement result of the developing γ measuring unit. Therefore, the line width of the image can be stabilized with high accuracy.
[0090]
  According to the invention of claim 5,3. The image forming apparatus according to claim 2, further comprising: a developing γ measuring unit that measures the developing γ of the developing unit; and a unit that determines the variable amount of the formula or the table based on a measurement result of the developing γ measuring unit. Since it is provided, the line width of the image can be stabilized with high accuracy.
[Brief description of the drawings]
[Figure 1]The present inventionIt is a block diagram which shows the circuit structure of one Embodiment.
FIG. 2 is a cross-sectional view schematically showing the embodiment.
FIG. 3 is a cross-sectional view showing a part of the same embodiment.
FIG. 4 is a block diagram showing a configuration for one color of the misalignment correction apparatus in the embodiment.
FIG. 5 is a diagram illustrating an example when the scanning lines of the laser light emitting devices for the first color and the second color are shifted by +1 dot in the sub scanning direction at the center in the main scanning direction due to bending.
FIG. 6 is a characteristic curve diagram showing a sinc function.
FIG. 7 is a diagram showing a misalignment correction apparatus according to the embodiment.
FIG. 8 is a diagram showing image data before resampling by the misalignment correction apparatus of the embodiment.
FIG. 9 is a diagram showing image data after resampling when the scanning line of the laser beam emitting apparatus in the embodiment is shifted by +1 dot in the sub-scanning direction at the center in the main scanning direction due to bending.
FIG. 10 is a diagram showing image data after resampling in a case where the scanning line of the laser beam emitting apparatus in the embodiment is shifted by −1 dot in the sub scanning direction at the center in the main scanning direction due to bending.
FIG. 11 is a diagram showing an example of interpolation parameters of the same embodiment;
FIG. 12 is a diagram illustrating a combined image obtained by superimposing two-color images formed from two-color image data when there is no positional deviation including bending and inclination of a scanning line of a laser beam emitting device. It is.
FIG. 13 is a diagram illustrating correction of a misalignment including bending and inclination of a scanning line of a laser beam emitting device in a synthesized image obtained by superimposing and synthesizing two color images formed from two color image data. It is a figure shown about the case where it does not perform.
FIG. 14 shows a combined image obtained by superimposing two-color images formed from two-color image data, and there is a positional deviation including bending and inclination of the scanning line of the laser light emitting device. It is a figure shown about the case where sampling is performed in the said embodiment.
FIG. 15 is a diagram illustrating a state of each dot of a composite image when two color images formed from two color image data are superimposed and combined.
FIG. 16 is a diagram showing a relationship between a resampling phase and an image data correction amount in the embodiment.
FIG. 17 is a diagram illustrating each exposure state when a 2-dot image is created in the sub-scanning direction.
FIG. 18 claims2It is a block diagram which shows one Embodiment of the invention which concerns on.
FIG. 19 is a diagram for explaining a misalignment / line width detection unit according to the embodiment;
FIG. 20 is a diagram showing an example of interpolation parameters in the same embodiment.
FIG. 21 is a block diagram showing a configuration for one color of a shift correction circuit in the same embodiment;
FIG. 22 is a block diagram showing a configuration of an interpolation data calculation circuit in the deviation correction circuit.
FIG. 23 is a diagram showing how development γ changes over time.
FIG. 24 claims3It is a block diagram which shows one Embodiment of the invention which concerns on.
FIG. 25 is a diagram showing an example of a position detection pattern according to the embodiment.
FIG. 26 is a diagram illustrating a measurement result of a position / line width deviation detection unit according to the embodiment;
FIG. 27 claims3It is a block diagram which shows other embodiment of the invention which concerns on.
[Explanation of symbols]
  3 Printer section
  12BK, 12C, 12M, 12Y Laser beam emitting device
  14BK, 14C, 14M, 14Y Photosensitive drum 1
  16BK, 16C, 16M, 16Y Development device
  33 Misalignment detector
  42 System controller
  43 Misalignment correction device
  44 Line width correction circuit
  53 Pattern creation section
  54 Position shift / line width detector
  55 Deviation correction circuit

Claims (5)

A plurality of photoconductors, a plurality of writing means for writing image data to the plurality of photoconductors by scanning lines to form an electrostatic latent image, and each electrostatic latent image on the plurality of photoconductors are visualized. A plurality of developing means, a measuring means for measuring the positional deviation of the scanning line, and a first correction for correcting the positional deviation of the scanning line by re-sampling the image data based on a measurement result of the measuring means. The image forming apparatus includes a correction unit, and further includes a second correction unit that corrects the image data in accordance with the phase of the resampling after the resampling, and sets the image data correction amount by the second correction unit. An image forming apparatus, wherein the line width of an image is set to be constant regardless of the resampling . A plurality of photoconductors, a plurality of writing means for writing image data to the plurality of photoconductors by scanning lines to form an electrostatic latent image, and each electrostatic latent image on the plurality of photoconductors are visualized. A plurality of developing means, a measuring means for measuring the positional deviation of the scanning line, an interpolation parameter is calculated from the measurement result of the measuring means by an equation or a table, and the image data is resampled by the interpolation parameter. An image forming apparatus comprising: a first correcting unit that corrects a positional deviation of the scanning line; and a variable unit that varies the equation or the table according to the resampling phase. . A plurality of photoconductors, a plurality of writing means for writing image data to the plurality of photoconductors by scanning lines to form an electrostatic latent image, and each electrostatic latent image on the plurality of photoconductors are visualized. A plurality of developing means, a measuring means for measuring the positional deviation of the scanning line, an interpolation parameter is calculated from the measurement result of the measuring means by an equation or a table, and the image data is resampled by the interpolation parameter. In an image forming apparatus having a first correction unit that corrects a positional deviation of the scanning line, a line width measurement unit that measures a line width of a position detection pattern written on the photosensitive member by the writing unit, and sequentially Position detection created by writing the image data of the position detection pattern resampled by the first correction means while changing the phase to the photosensitive member by the writing means. Imaging, wherein a line width of the image regardless of the phase of the resampling of the formula or table based on the measurement result the line width measuring means and means for determining to be constant with respect to the turn apparatus. 2. The image forming apparatus according to claim 1, wherein a developing γ measuring unit that measures the development γ of the developing unit, and the image data correction amount by the second correcting unit is determined based on a measurement result of the developing γ measuring unit. an image forming apparatus comprising the means for. 3. The image forming apparatus according to claim 2, further comprising: a developing γ measuring unit that measures the developing γ of the developing unit; and a unit that determines the variable amount of the formula or the table based on the measurement result of the developing γ measuring unit. image type forming apparatus, characterized in that the.

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