JP3604961B2 - Image recording device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image forming apparatus such as a printer, a facsimile, a copier, and the like, and more particularly, to an image recording apparatus that forms a large-sized recording image by juxtaposing a plurality of image forming units (for example, an exposure device).
[0002]
[Prior art]
Image recording devices include a direct recording type that directly records an image on a recording medium such as paper and an indirect recording type that records an image on an intermediate recording medium and transfers it to a final recording medium. .
[0003]
A widely used indirect recording type system includes a laser printer using an electrophotographic process. In a laser printer using an electrophotographic process, a charged photoconductor is exposed according to recorded image information, an electrostatic latent image is formed, then visualized by a developing machine, and transferred to a recording medium such as paper to record an image. . In this method, a recorded image is formed in the form of an electrostatic latent image on a photosensitive member that is an intermediate recording member.
[0004]
As a means for forming image information on a photoconductor as an intermediate recording medium, a laser exposure apparatus operated by a polygon mirror or the like which rotates laser light is mainly used. Further, as other means for forming image information on the photoreceptor, an LED array exposure apparatus in which a large number of LEDs are arranged in an array, a liquid crystal shutter array exposure apparatus in which a liquid crystal shutter is arranged in an array to control exposure, and the like. It has been known.
[0005]
Examples of methods for directly recording an image on a recording medium such as paper include an ink jet recording method in which ink is ejected and recorded directly on paper in accordance with image information, a thermal recording method in which a heating element array is brought into direct contact with a thermal recording medium, and a thermal transfer method. A method such as a thermal transfer recording method in which an ink sheet is brought into contact with a recording medium and the ink is transferred to a recording pair by a heating element has been put to practical use.
[0006]
[Problems to be solved by the invention]
In order to obtain a large-sized recorded image by an image forming method using a laser exposure device, the scanning width of the laser must be widened. For this reason, it is necessary to increase the distance from the polygon mirror to the photosensitive member, which is a recording body, and the size of the exposure apparatus becomes very large. Further, when the scanning width is large, the clock of the image to be recorded must be increased because the scanning speed is increased. For these reasons, laser exposure apparatuses are not often used in large-format image recording apparatuses exceeding A3-A2.
[0007]
On the other hand, in an image forming method using an array head such as an LED array device or a liquid crystal shutter array, it is necessary to use an array head having a length corresponding to the recording width in order to obtain a large-sized recorded image. However, since an array head of an image printing apparatus requires a high definition of 300 to 600 dpi (dot per inch) or more, it is not easy to increase the length of an array head manufactured using a semiconductor process.
[0008]
Since the electrophotographic process is a page recording method, an array head corresponding to a recording width is required. On the other hand, in a recording method in which the recording head itself is moved and scanned in the main scanning direction, such as an ink jet recording method, a thermal recording method, and a thermal transfer recording method, an image recording apparatus for recording a large-sized image can be relatively easily constructed. However, the recording method for scanning the recording head has the disadvantage that the moving mechanism of the head becomes complicated and the recording time becomes longer as the size of the image becomes larger. In order to overcome this problem, it is effective to use a long array head corresponding to the recording width even in the method of scanning the recording head. However, it is difficult to manufacture a long array head.
[0009]
In order to obtain a long recording head with a recording head such as an LED array exposure device, it is necessary to manufacture an array recording head of a certain length using a semiconductor process and connect it with high precision. is there. The A3 size recording image width is required to be 300 mm and the A2 size image recording width is required to be 420 mm or more, and it is difficult to produce a long recording head only by a semiconductor process.
[0010]
Generally, an image recording apparatus requires a recording head element density of 300 to 600 dpi (dot per inch) or more, that is, 80 to 40 μm or less. It is difficult to connect a head having such a high definition recording density, resulting in a very expensive recording head. Further, since the pitch between the recording head elements easily changes at the connection position, there is a problem that the connection position is easily observed as an image unevenness in the recorded image.
[0011]
As a recording device capable of recording large-format images, a plurality of recording heads that irradiate a beam spot light onto a recording medium mounted on a cylindrical drum are driven side by side, and are simultaneously driven. There is a proposal of a method of detecting and correcting an error between heads (Japanese Patent Laid-Open No. 9-185196). However, in order to correct an error between heads by this method, a correction mechanism for mechanically adjusting the head position is required, and it is difficult to realize a correction mechanism that satisfies the above-described requirement for high definition.
[0012]
SUMMARY OF THE INVENTION It is an object of the present invention to provide a recording apparatus capable of recording a large format image with a relatively inexpensive configuration. In other words, large-format image recording can be realized simply and inexpensively without using a long recording head that is difficult to manufacture as described above or using a high-precision mechanical mechanism for correcting errors between a plurality of recording heads. A recording device is provided.
[0013]
[Means for Solving the Problems]
In order to achieve the above object, an image recording apparatus according to the present invention divides a recording image width into a plurality of areas, and arranges a plurality of image forming units for forming a recording image in each area. For example, in a laser printer using an electrophotographic process, a main scanning direction for performing laser scanning is divided into a plurality of sections, and laser scanning exposure apparatuses for exposing each area are arranged.
[0014]
Further, at least one or more relative position difference information among relative position information such as a start point position, an end point position, an enlargement ratio, and a rotation direction of an exposure recording area (an image sending area in the image forming unit) in each exposure device is used. An image information correcting means for changing at least one or more of the recording image information of each exposure recording area recorded by each exposure device so that the continuity of the recording image of the exposure recording area by each exposure device is compensated. .
[0015]
In order to solve the above-mentioned object, there is provided input means for inputting or changing relative position difference information between images at the time of recording by each exposure device (image information forming means) for changing the image information. Alternatively, there is provided image position information detecting means for detecting relative position difference information between images at the time of image recording by each exposure device (image information forming means).
[0016]
According to the above configuration, an image recording apparatus capable of recording a wide image can be provided because a plurality of image information transmitting units are arranged. Further, when a plurality of laser exposure apparatuses are located, a relatively small exposure apparatus can be used because the scanning width of one laser scanning exposure apparatus can be shortened. Further, since the scanning speed can be set relatively low, the number of revolutions of the polygon mirror (optical scanning mirror) can be reduced, so that a relatively low-cost exposure apparatus can be easily applied. In addition, even in the case of various methods using an array-shaped head, the use of a plurality of array-shaped heads having a relatively short length simplifies the manufacture and reduces the defect rate during head manufacturing, that is, the defect rate. Becomes possible.
[0017]
Further, in the image recording apparatus of the present invention, error information such as an image start point position, an end point position, an enlargement ratio, and a rotation direction on a recording medium in an image forming unit such as an exposure device or an array recording head is input or detected. Based on the error information, a change is made to the image information itself recorded by each recording image information transmitting unit so that continuity of the recording image position of each recording image information transmitting unit on an actual recording image is ensured. . For this reason, even when there is a shift in the image forming position due to a mechanical error or the like in the recording device of each recording image sending means, each recording image formed by each recording image sending means on the actually recorded image. Can be maintained relatively easily.
[0018]
For the reasons described above, it is possible to provide a recording apparatus capable of recording a large-sized image with a relatively inexpensive configuration. That is, it is possible to provide a recording apparatus capable of recording a large-sized image without using a large-sized laser scanning unit or a long recording head which is difficult to manufacture.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a configuration diagram showing an embodiment of the image recording apparatus of the present invention. (A) is a side sectional view of the image recording device, and (b) is a plan view of the image recording device of (a) viewed from above. A plurality of exposure devices 2a and 2b are juxtaposed. Further, there is provided a printing process control means 3 for obtaining image displacement information of a printing area from the displacement information of the exposure devices 2a and 2b and correcting the image information input to the exposure devices 2a and 2b.
[0020]
First, the printing mechanism and process of the image recording apparatus shown in FIG. 1 will be described. The image recording apparatus according to the present embodiment is a laser printer using an electrophotographic process. A charger 1, an exposing device 2, a developing device 5, a transfer device 11, a photoconductor cleaning 17, an erasing device 14 and the like are arranged around the photoconductor (drum) 13. A fixing unit 16 is disposed downstream of the image transfer position of the photoconductor 13.
[0021]
The photoconductor 13 is charged to a uniform charging potential by the charger 1, and is exposed according to image information by the exposure device 2, so that an electrostatic latent image is formed on the photoconductor 13. The electrostatic latent image formed on the photoconductor is developed and visualized by the developing device 5 with toner. The paper fed and transported by the pick roller 8 from the paper feed cassette 7 is transported to the transfer device 11 after the transport timing is adjusted by the registration mechanism 10, and the toner image formed on the photoreceptor 13 is formed. Is transcribed. After erasing the static electricity remaining on the surface of the photoreceptor 13 after the image transfer by the erasing device 14, the residual toner is cleaned by the cleaning device 17, and the charging by the charger 1 is performed again. The sheet after the toner transfer is conveyed to the fixing device 16 and after fixing the toner, is conveyed to the sheet discharge tray 15 to complete the printing operation.
[0022]
As shown in FIG. 1B, the exposure apparatus 2 of this embodiment has two exposure apparatuses 2a and 2b arranged side by side, and the right and left sides of the photoconductor 13 are respectively exposed using the two exposure apparatuses 2a and 2b. Exposure to form an electrostatic latent image. The printed image information 4 transmitted from a computer or the like is divided into the right side and the left side of the image, and is sent to the respective exposure devices 2a and 2b. Each of the exposure devices 2a and 2b exposes the right and left sides of the image based on the printed image information converted from the recorded image information 4.
[0023]
In order to perform high-quality image recording with this system, it is necessary to join the left and right electrostatic latent images formed by the exposure devices 2a and 2b with high precision. When the resolution of the exposure devices 2a, b is 600 dpi, one dot is about 42 μm, and it is necessary to join the images of the exposure devices 2a, b with an accuracy of several tens μm or less. However, it is difficult to arrange the two independent exposure apparatuses 2a and 2b while maintaining such high accuracy. Exposure devices 2a and 2b of this embodiment are used in a general laser printer, and are laser scanning exposure devices that expose the photoconductor 16 by scanning with polygon mirrors 19a and 19b (polygon mirrors) that rotate a laser. It is.
[0024]
As described above, in order to superimpose the images exposed by the two independent optical systems with high accuracy, the rotational speeds of the polygon mirrors 19a and 19b for scanning the laser must completely match. However, it is extremely difficult to completely match the rotational speeds of the polygon mirrors 19a and 19b rotating at a very high speed. Also, the fθ lenses 20a, b and various mirrors 22a, b in the four independent optical systems must be accurately arranged. When the speed of the rotating polygon mirrors 19a and 19b decreases, the width of the image when the same number of dots is recorded increases, and when the speed increases, the image shrinks. Due to a slight difference in the angle of the mirror, a lens accuracy error of the fθ lens, and the like, a difference occurs in the angle and speed in the laser scanning direction (main scanning direction) in the exposure devices 2a and 2b. Due to these factors, in the configuration of the present embodiment, it is necessary to keep the driving speed and the mounting position accuracy between the respective exposure apparatuses 2a and 2b high.
[0025]
However, it is difficult to reduce the superposition accuracy of the images exposed by the exposure devices 2a and 2b to several hundred μm or less only by the mechanical accuracy. Therefore, in order to ensure continuity of recorded images by a plurality of exposure devices, the image recording device of the present embodiment detects a superposition error of images by a mechanical mechanism, corrects the recorded image information 4 and performs bitmap correction. The developed printed image information is generated to absorb a joining (overlay) error at the time of printing on the photoconductor 13.
[0026]
First, the image recording apparatus of the present embodiment detects misregistration of the images formed by the exposure devices 2a and 2b from the specified values of the image starting point position, the image width, and the rotation angle in the main scanning direction and the sub-scanning direction. A CCD sensor 9 and a sensor control means 6 are provided as image detection means. The deviation of the printed image from the specified position of the exposure area of the exposure devices 2a and 2b is detected by the reference mark exposure / detection control means of the printing process control means 3 at the time of starting the apparatus and in the prescribed recording. The following procedure is performed for each sheet.
[0027]
FIG. 2 is an explanatory diagram of an image shift detection method according to the present embodiment. Outside the image exposure areas (real printing areas corresponding to recording media) 28 and 29 on the photoreceptor 13, four thin lines + are exposed by the exposure apparatus 2 a at four locations within the exposure areas 26 and 27 of the exposure apparatuses 2 a and b. The mark recordings 23a, b, c, and d are respectively exposed to the + mark recordings 24a, b, c, and d by the exposure device 2b, and the recording position marks 23 and 24 are exposed by the CCD 9 provided to face the drum 13. To detect. At this time, the exposure devices 2a and 2b are arranged so that the exposure areas 26 and 27 overlap each other at the boundary, and even if a shift occurs in both exposure areas, exposure to the actual print areas 28 and 29 is possible. It is to be. Actually, the exposure ranges 26 and 27 are set to a range in which printing on the actual print areas 28 and 29 can be reliably performed in consideration of a possible shift.
[0028]
A reference mark (“ず れ” or “|”) 25 may be provided in advance on the photoconductor 13 in order to detect an exposure position shift of the exposure devices 2a and 2b. The reference mark 25 is provided outside the actual printing areas 28 and 29, or a color that does not affect the photosensitive characteristics is used. The displacement of the exposure devices 2a and 2b can be measured from the displacement between the mark 25 recorded on the photoconductor 13 and the + marks 23 and 24 recorded by the exposure devices 2a and 2b.
[0029]
In order to detect the reference position marks 23, 24 and the reference mark 25 on the drum 13, divided small sensors 9a are provided at three places of the sensor arrangement A facing the marks. The integrated sensor 9b may be used, but arranging a plurality of small sensors reduces the cost. As another method, it is conceivable to move one small sensor within the measurement area, but the positioning accuracy at each measurement position is important.
[0030]
FIG. 3 is an explanatory view showing the principle of detecting an image shift, and is an enlarged view of a portion A shown in FIG. When there is no printing misalignment between the exposure devices 2a and 2b, the detected reference position marks 23 and 24 overlap and are located at the center of the reference mark 25. In the illustrated example, the exposure range 26 is shifted to the upper left, and the exposure range 27 is shifted to the lower right.
[0031]
In the present embodiment, the reference marks 23 and 24 exposed on the photoreceptor 13 and the reference mark 25 recorded in advance have different mark shapes, and the amount of deviation between the marks from the specified position is determined by the exposure apparatus 2a or 2b. A deviation from the specified exposure position is detected. As a result, it is possible to make a determination at an accurate position without mistaking a mark. Of course, it is also possible to perform marking so as to have the same shape at the same position when appropriate. In addition, by devising the shape and position of the reference mark by exposure and the reference mark on the photoconductor so that the reference mark at the center position of each exposure device is shifted by a specified amount when there is no image shift, Can be prevented from being mistaken at the time of detecting a reference mark recorded by the exposure apparatus.
[0032]
In the present embodiment, the reference position mark 25 is arranged on the photoconductor 13 and the shift amount of the printed image marks 23 and 24 by the exposure devices 2a and 2b is detected therefrom. It can be omitted. In this case, the amount of misalignment between the exposed and developed images of the exposure devices 2a and b is detected from the difference in the relative positions of the exposure and development patterns of the exposure devices 2a and b near the joint. However, the reference marks 23b and 24a of the joining position need to be detected by the same CCD sensor. Further, it is not possible to correct the absolute position with respect to the photoconductor or the recording paper. However, there is a margin in the positional accuracy required for the relative position of the image on the sheet with respect to the accuracy required for the bonding shift between the exposure devices, and thus does not pose a practical problem.
[0033]
If reference marks are not provided on the photoreceptor, it will be difficult to measure the relative position between the image areas. Therefore, it is required to more accurately determine the relative positional relationship between the reference marks provided at each corner in each image area. Is done. In order to accurately measure the relative positional relationship of the reference marks provided at each corner of each image area, it is necessary that the mounting accuracy and the positional relationship of each sensor 9a be accurately detected. For this purpose, it is preferable to dispose the sensor 9a on the same sensor base 9c as shown in the sensor position A in FIG. Further, when the reference mark at each corner of the image area is measured by the same sensor using the integrated sensor 9b as shown at the sensor position B, it is possible to measure the relative position with high accuracy.
[0034]
As the reference marks 23, 24, and 25, various patterns such as X, V, L, △, □, 字, and the like can be applied as long as the patterns can accurately measure the position in addition to + and −. In this embodiment, the positions and the number of the reference marks are arranged at the four corners of each actual exposure area, and the total number of the reference marks is four. In general, it is desirable to use several points sufficiently distant from the recording image area. However, an appropriate position and number can be set according to the item of the amount of displacement to be measured. In order to detect deviations from the specified values of the image starting point position, the image width, and the rotation angle in the main scanning and sub-scanning directions, it is necessary to detect the main scanning and sub-scanning coordinates at at least three points.
[0035]
The timing of detecting the deviation of the exposure / developed image from the specified position of each exposure apparatus is, in addition to the timing described above, when the surrounding environment changes more than the specified, after the maintenance work of the apparatus, and the position difference from the apparatus panel or the connected computer. There are methods to perform at various timings such as when an information detection command is input. Since the stability of the joining accuracy of the exposure image by each exposure device is affected by each of the main factors such as the accuracy and strength of the device, the detection timing is determined by experimenting with the stability of the joining accuracy of the printed image by each exposure device. It is desirable to decide after verification.
[0036]
If the printing position of the reference pattern is on the photoconductor outside the recording area of the sheet, it is possible to simultaneously perform the normal printing operation and the detection of the joining position of the printed image by each exposure device. With this, it is possible to control the detection of the bonding position of the printed image of each exposure apparatus for each printing, and it is possible to expect the highly accurate and stable exposure image bonding accuracy of each exposure apparatus. However, in general, the displacement of the image joining between the exposure apparatuses does not change greatly in the recording of several pages, so it is sufficient to measure the joining position at the prescribed timing.
[0037]
Next, the configuration and operation of the printing process control means 3 for correcting the printed image information based on the positional deviation amounts of four points in each exposure area detected by the CCD 9 will be described.
[0038]
FIG. 4 shows an embodiment of a printing process control means, in which a relative position difference detecting means 61 for calculating a relative position difference from a shift amount of an exposure position, and recording image information data sent from a computer or the like as printing image information. An image data correction conversion unit 62 for conversion is provided. It is preferable that each unit is arranged on the same control board together with the control unit for the whole printing process, in view of miniaturization of the apparatus and measures against noise.
[0039]
The relative position difference detection means 61 calculates a relative position difference (a shift amount) between the image starting point position, the image width, and the rotation angle in the main scanning direction and the sub-scanning direction based on the detected values of the shift amounts of the exposure position with respect to the reference position. ) Is calculated to make it possible to correct the three-dimensional distortion of the exposure area. The printing process control means 3 may be provided with a detection-time printing sequence control means (not shown), and may be provided with a sensor control means 6.
[0040]
The image data correction / conversion unit 62 divides the recorded image information 4 from a computer or the like into the actual print areas 28 and 29 based on the print area information 611, and the divided recorded images 622a and 622b. Image transformation / bitmap development means 623a / b for developing into printing bitmap information while correcting and converting in accordance with image position shift information 612a / b of the printing area, and storing bitmap data after conversion / expansion. Means 624a, 624b are provided. The corrected and converted bitmap information 612a, b is transferred to the exposure devices 2a, b via the printed image information output means 63. Note that the print area information 611 is a parameter that depends on the configuration of the recording apparatus, such as the number and arrangement of the exposure apparatuses, and is basically fixed information.
[0041]
In the printing process control means 3 of the present embodiment, the recorded image information 4 sent from a computer or the like is developed into a bitmap at a position corrected based on the image position deviation information calculated by the relative position difference detection means 61, and The bit map data corrected and converted as described above is output to each exposure apparatus. Accordingly, each exposure apparatus performs a normal exposure operation, so that the electrostatic latent images formed by the respective exposure apparatuses formed on the photoconductor can be joined with high accuracy.
[0042]
The image recording apparatus shown in FIG. 1 is configured such that the shift information (relative position difference from the reference position) of the exposure area used for the exposure position conversion operation is calculated based on the result detected by the CCD sensor 9. A method of inputting from a panel arranged in the image recording apparatus or a connected computer is also conceivable. In an image recording apparatus having a sufficient mechanical rigidity in which the displacement of each exposure apparatus at the time of exposure image joining hardly fluctuates, it is sufficient to manually input displacement information when the apparatus is completed or installed. In this case, the shift information detecting means 9 and the control means 6 of the present embodiment are not required, and a highly accurate continuity of the exposure image between the exposure apparatuses can be ensured with a simpler configuration.
[0043]
Next, relative position difference detecting means 61 Calculation of the relative position difference (shift amount) between the image viewpoint position, the image width, and the rotation angle in the main scanning direction and the sub-scanning direction, and the calculated shift information (the relative position difference from the reference position). A method for converting image information will be described with reference to FIGS.
[0044]
FIG. 5 is an explanatory diagram showing the relationship between the grid position and the exposure position of the reference image. The exposure position 31 for recording the character "A" is shown in black by using the exposure dot grid 30 as a reference at the time of exposure in the main scanning and sub-scanning directions. On the other hand, FIG. 6 shows a state in which the exposure dot grid 30, which is a reference at the time of exposure, is distorted due to various factors and mounting accuracy of the exposure apparatus.
[0045]
The rectangular frame 32 shown on the left side of FIG. 6 corresponds to the contour of the reference lattice without distortion, that is, the lattice contour 32 of FIG. The outer peripheral shape of the exposure dot lattice 30 shown on the right side extends △ X in the main scanning direction and contracts △ Y in the sub-scanning direction, and the main scanning direction is distorted by an angle θ. If the exposure dot grid 30 in FIG. 6 is exposed at the same position as in FIG. 5, the formed letter “A” will be distorted. Therefore, the exposure position on the dot lattice 30 in FIG. 6 is changed so that the “A” closest to the position corresponding to the character shape 33 of the reference “A” can be recorded. The grid position 31 of "A" painted black on the dot grid 30 in FIG. 6 indicates the changed exposure position.
[0046]
Next, an example of a method of changing the exposure position will be described. On the right side of FIG. 6, the undistorted grid outline 32 and the starting point (upper left corner) 36 of the distorted dot grid 30 are in the same position. In practice, the starting point 36 of the distorted exposure dot grid does not always coincide with the corner of the reference grid 32. Therefore, in order to calculate the exposure position overlapping with the reference image (A in FIG. 5), at least the main scanning dot pitch enlargement ratio XM (%), the sub-scanning dot pitch enlargement ratio YM (%), the rotational deviation in the main scanning direction, Six parameter values are required: the angle θX (degree), the rotational deviation angle θY (degree) in the sub-scanning direction, the starting point position deviation XS (mm) in the main scanning, and the starting point position deviation YS (mm) in the sub-scanning.
[0047]
By detecting these parameter values and using a general coordinate transformation method, the exposure grid position (FIG. 6) where the images overlap can be calculated. That is, assuming that the exposure position coordinates before the conversion are (X, Y), the coordinates (X ′, Y ′) after the image overlay correction conversion are given by the function of Expression 1.
[0048]
(Equation 1)
(X ′, Y ′) = F (XM, YM, θX, θY, XS, YS, (X, Y))
These six parameter values relating to the image shift information may not change or may have a certain relationship depending on the exposure method or the printing method. In such a case, it is not necessary to use a constant value or other information having a fixed relationship as the specified value regarding the image shift information. However, in order to perform image position correction with higher accuracy, it is necessary to correct expansion and contraction of a periodic image in the image, and a variable for describing the expansion and contraction may be required.
[0049]
FIG. 7 is a diagram for explaining the state of the junction point of the exposure images of the two exposure devices corrected based on Expression 1. In FIG. 5, the exposure device that exposes the left half of the image is in a state where the exposure dot grid 30 is not shifted from the reference grid outline 32 as shown in FIG. 5, and the exposure device that exposes the right half of the image is shown in FIG. 6 shows a case where the exposure dot grid 30 is shifted from the reference grid outer shape 32 as shown in FIG. fundamentally left Since the image formed by the exposure device has no shift in the exposure dot grid 30, no exposure position conversion is required. On the other hand, the exposure apparatus on the right side performs exposure position correction corresponding to the displacement of the exposure dot lattice 30. By performing such exposure conversion, the continuity of the image at the boundary position between the two exposure systems can be maintained.
[0050]
Next, a method of calculating each parameter value required to calculate the exposure position shift amount from Equation 1 will be described. The above six parameter values are obtained by the relative position difference detecting means 31 as follows. From the shift between the reference marks printed on the photoreceptor by each of the exposure devices shown in FIG. 2, the shift amount (relative position difference from the reference position) in the upper left, upper right, lower left, and lower right of the image can be detected. . That is, as shown in FIG. 3, the positions of the broken lines, which are the positions where the reference marks should be recorded by the respective exposure devices originally estimated from the reference marks on the photoreceptor, and the actual recording units of the printing units Assuming that the difference between the reference mark in the main scanning direction and the sub-scanning direction in (dX, dY) is (dX, dY) for each image from the upper left, upper right, lower left, and lower right mark positions of the image, _LF , (DX, dY) _RF , (DX, dY) _LR , (DX, dY) _RR 8 information is obtained.
[0051]
The starting point position shift amount XS (mm) of the main scanning start position position shift and the start point position shift amount YS (mm) of the sub-scanning are calculated from the coordinates of the upper left mark position by XS = dX _LF , YS = dY _LF Is given.
[0052]
The main scanning dot pitch enlargement ratio XM (%) and the sub-scanning dot pitch enlargement ratio YM (%) are represented by XW, the distance between the reference marks (the distance between the upper left reference mark and the upper right reference mark) of the transfer belt in the main scanning direction. Assuming that the distance between the reference marks of the transfer belt in the scanning direction (the distance between the upper left reference mark and the lower left reference mark) is YW, the deviation of the upper left main scanning and sub scanning directions and the deviation of the upper right main scanning direction and the lower left sub scanning direction are different. DX which is each detection value _RF , DX _LF , DY _LR , DY _LF And can be calculated by Equation 2.
[0053]
(Equation 2)
XM = 1 + (dX _RF -DX _LF ) / XW
YM = 1 + (dY _LR -DY _LF ) / YW
The rotational deviation angle θX (degree) in the main scanning direction and the rotational deviation angle θY (degree) in the sub-scanning direction are represented by XW, the distance between the reference marks (the distance between the upper left reference mark and the upper right reference mark) of the transfer belt in the main scanning direction. Assuming that the distance between the reference marks of the conveyance transfer belt in the scanning direction (the distance between the upper left reference mark and the lower left reference mark) is YW, dX which is the detection value of each of the upper left, upper right, lower left main scanning and sub scanning direction deviations. _LF , DY _LF , DX _RF , DY _RF , DX _LR , DY _LR And can be calculated by Equation 3.
[0054]
(Equation 3)
θX = ATN ((dY _RF -DY _LF ) / (XW + dX _RF -DX _LF ))
θY = ATN ((dX _LR -DX _RF ) / (YW + dY) _LR -DY _RF ))
Main scanning start point displacement XS (mm), sub-scanning start point displacement YS (mm), main scanning dot pitch enlargement ratio XM (%), sub-scanning dot pitch enlargement ratio YM (%), main scanning direction rotational deviation angle θX (degrees) and the rotational deviation angle θY (degrees) in the sub-scanning direction are the upper left, upper right, and lower left mark positional deviation amounts of the image (dX, dY). _LF , (DX, dY) _RF , (DX, dY) _LR Can be calculated from the three coordinates and the six information. In the present embodiment, furthermore, the lower right mark positional deviation amount (dX, dY) _RR Is used to reconfirm and fine-adjust the deviation amount calculation value.
[0055]
The distortion of the image area in which the image can be corrected based on the displacement amounts of the three points in the image is basically a case in which the rectangular drawing area 38 as shown in FIG. . As shown in FIG. 9, in a case where the rectangular drawing area 38 is deformed into a trapezoid 40, in order to correct the distortion of the image area, the shift amount including the lower right coordinate 44 of the fourth point is used. Need to detect. In general, the deformation as shown in FIG. 9 is unlikely to occur, and there are few cases in which it is necessary to detect a shift of four or more points.
[0056]
As described above, the starting point displacement XS (mm) of the main scanning, the starting point displacement YS (mm) of the sub-scanning, and the main scanning dot pitch enlargement rate XM calculated from the displacement of the coordinates of three or four points of each image. (%), The sub-scanning dot pitch enlargement ratio YM (%), the main scanning direction rotational shift angle θX (degrees), and the sub-scanning direction rotational shift angle θY (degrees), the exposure position coordinates before conversion ( X, Y) can be replaced by the coordinates (X ′, Y ′) after the image is subjected to the overlay correction conversion by the calculation of Expression 1.
[0057]
The image data converting means 32 of the present embodiment uses the above-mentioned six parameter values provided from the relative position difference detecting means 31 to set the exposure position coordinates (X, X, X) of the recorded image information 4 divided into the exposure devices 2a and 2b. Y) is converted into a corrected exposure coordinate position (X ′, Y ′), and a bitmap is developed using the X ′ and Y ′. As described above, by performing the operation of converting the exposure position of the image information input to each exposure device using the shift amount of the exposure image area of each exposure device, an image can be basically formed with an accuracy of 1 dot or less. It becomes possible to overlap. Furthermore, by using a laser scanning optical system with resolution enhancement technology, which is a commonly used technology to enhance the resolution in the scanning direction, the actual resolution can be increased several times, realizing even more accurate image superposition. Can be easily performed.
[0058]
As the image joining misalignment correction method of the multiple exposure apparatus of the present invention, the same method as that of the laser optical system described in the above embodiment can be applied to a method using various optical systems such as an LED and a liquid crystal shutter. . Further, the present invention can be applied to many direct recording methods such as an ink jet method, a thermal transfer method, and a thermal method. The same imprinting image misalignment correcting means can be used in these various exposure means and various printing methods, but a control method suitable for setting and detecting misalignment information and an image conversion method suitable for the exposure method and the printing method can be used. Is desirable.
[0059]
In an image forming apparatus using an electrophotographic process, an electrostatic latent image is formed on a photoreceptor. A method of directly detecting a shift amount from a reference position with an exposed electrostatic latent image on a body can be considered. This has the advantage that the deviation of the exposure pattern of the exposure apparatus from the reference position can be directly detected.
[0060]
The simplest and desirable method for correcting and converting image information according to the present invention is performed when image data is converted into bitmap data for exposure. A process that considers the shift information of the exposure position (information on the relative position difference from the reference exposure position) during the so-called raster development that converts the signal sent from the computer in a page description language such as PostScript into a bitmap for exposure. By adopting this method, this method can be implemented with little effect on printing speed and the like. In a GDI (Graphic Device Interface) system that performs a process of converting to a bitmap on a computer side, such as an operating system such as Windows of Microsoft Corporation in the United States, a computer that converts to a bitmap has an exposure device of each exposure apparatus. It is desirable to transmit the region information and the deviation information between the exposure regions of the respective exposure apparatuses, and perform the conversion processing of the present invention at the time of bitmap development by a computer.
[0061]
FIG. 10 is a schematic diagram showing how the correction processing conversion of the present invention is performed when a bitmap is developed by a computer. Upon receiving the print request 45 from the computer 48, the printer 49 transmits to the computer 48 the relative positional deviation information 46 of the exposure area together with the exposure area information of each exposure apparatus. The computer 48 uses the information 46 to perform exposure in each exposure apparatus. If you do Then, the printing bitmap information 47 which does not cause a joining shift in the image at the joining position of each exposure area is created and transferred to the printer 49. The printer 49 performs printing in accordance with the bitmap information 47. The exposure area information of each exposure apparatus transmitted to the computer 48 is generally fixed information, and may be transmitted separately from the relative positional deviation information 46.
[0062]
It is also possible to divide the printed image information transmitted after being bitmap-developed by a computer into each exposure area, and to re-convert the information into a bitmap in which the relative positional deviation of the exposure areas has been corrected. However, if the bitmap-converted image information is converted into a bitmap again, the error from the initial image information may increase. Therefore, when the bitmap conversion for each exposure apparatus is performed, the relative positional deviation correction conversion of each exposure area is performed at the same time, so that the exposure image connection correction can be performed with higher accuracy.
[0063]
The exposure apparatus shown in the above-described embodiments is developed into a bitmap when performing image recording, and thus performs displacement correction conversion of image data of each exposure apparatus during this development. At present, many image recording systems perform bitmap conversion, but the relative position shift correction conversion of the present invention can be applied to an image recording system that does not perform bitmap conversion, such as a plotter. For example, when image recording is performed using a combination of line drawings such as a plotter, the deviation between the start point position and the end point position of each drawing line including the connection position of the drawing lines located at the recording area boundary of each recording unit is corrected. In this case, the calculation method described in the above embodiment can be applied as it is.
[0064]
Next, some other embodiments in which the image joining misalignment correction method of the present invention is applied to a recording method different from the above-described embodiment using a plurality of exposure devices will be described. Since the method of the present invention corrects the original image information from the image position at the time of actual printing, a combination of exposure devices having different recording methods, such as a laser exposure device and an LED exposure device, and different resolutions are used. The present invention is also applicable to an image of an exposure device.
[0065]
FIG. 11 shows an image recording apparatus according to another embodiment. The laser exposure apparatus 2 of the present embodiment has a configuration in which one rotary polygon mirror 19 is used to scan the left and right regions with two laser light sources 18a and 18b from both sides. In the exposure apparatus 2, the scanning directions of the right beam 50b and the left beam 50a are reversed, and parallelism between the scanning beams is easily lost. However, by applying the image joining misalignment correction method of the multiple exposure apparatus described in the above embodiment, highly accurate joining of the left and right exposure regions can be easily realized.
[0066]
Since the exposure apparatus 2 of FIG. 11 uses one rotating polygon mirror 19, it is possible to provide a laser exposure apparatus that is lower in cost than a method that simply uses two exposure apparatuses. Further, since the scanning distance can be made shorter than that of a simple one-beam optical system, the optical path length can be shortened, the size of the exposure apparatus can be reduced, and the scanning clock of each exposure apparatus can be slowed. Can easily be realized. As described above, by using the image joining misalignment correction method of the present invention, the overlapping of the exposure regions of the multiple exposure apparatuses becomes easy, so that the design latitude for the exposure system is widened, and the cost and size can be reduced. But it is advantageous.
[0067]
12A and 12B are configuration diagrams of an ink jet printer to which the present invention is applied. FIG. 12A is a side sectional view, and FIG. 12B is a top view. The three ink jet heads 51a, 51b, and 51c are arranged in a zigzag pattern as shown in the drawing, so that the printing areas of the respective ink jet heads partially overlap. The recording paper fed and transported from the paper feed tray 7 by the pick roller 8 is transported by the registration mechanism 10 and then transported by the transport belt 52 directly below the inkjet heads 51a, 51b and 51c to print. Is performed.
[0068]
The printing for measuring the deviation of the reference mark of the printing area from the relative position of the image printing area of each printing head is performed on the transport belt 52. The CCD sensor 9 is disposed on the downstream side of the inkjet heads 51a, 51b, and 51c, facing the transport belt 52. In the present embodiment, the CCDs 9a, 9b, 9c, and 9d are divided into four at the boundaries and ends of the printing areas of the inkjet heads 51a, 51b, 51c. By applying the function of correcting the deviation amount of the measured value due to the positional relationship of each CCD (Equation 1) to the conversion of the print image information, it is possible to easily and more accurately join the print image areas of the print heads. Can be realized.
[0069]
The measurement of the deviation from the relative position of the image printing area of each printing head may be performed on the recording paper, but useless recording and paper discharging are performed every time the image area of each printing head is measured. . Further, the reference position pattern cannot be arranged on the recording paper, and must be used based on the end of the paper. For this reason, in the present embodiment, the recording is performed on the transport belt. However, in this case, a cleaning unit 53 for cleaning the ink image recorded on the transport belt is required.
[0070]
An intermediate transfer method using an intermediate transfer member instead of the transport belt of the present embodiment is also possible. The intermediate transfer method is a method in which each ink-jet image is not recorded directly on the paper as the final recording medium, but is synthesized on an intermediate transfer member, and then transferred collectively to the paper on the final recording medium. is there. In this case, it is possible to perform printing on the intermediate transfer member for measuring the reference mark of the printing area and the deviation of each printing head from the relative position of the image printing area. Unlike the photoreceptor, these transport belts and intermediate transfer members have relatively small changes in characteristics due to the reference marks, and therefore, it is relatively easy to arrange the reference marks in the recording image area within the image area.
[0071]
Similarly, it goes without saying that the present invention can be applied to various direct recording methods such as a thermal recording method and a thermal transfer recording method. In general, it is difficult to manufacture a long array head with high precision. However, by applying the present invention, a relatively short array printing head can be easily combined. A possible image recording apparatus can be provided at a low price.
[0072]
Further, in a laser printer using a tandem system, an exposure device is arranged for each printing unit. In this method, in order to reduce the size of the apparatus, it is necessary to reduce the arrangement interval between the printing units. When the present invention is used and the optical system for scanning one photoconductor is divided into a plurality of parts, the scanning width of one optical system is reduced, and the optical path length is shortened accordingly, so that an optical system with a small width can be used. . By applying the present invention to the optical system of each printing unit of a tandem laser printer and dividing it into a plurality of optical systems, it is possible to keep the width of the optical system small and reduce the arrangement interval between each printing unit. It will be easier. As described above, the present invention is an effective means for reducing the size of a tandem laser printer or the like.
[0073]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to the image recording apparatus of this invention, since the shift of the printing area by a several printing means is detected and the printing image information is corrected using the shift information, joining of an image is comparatively easy and high. There is an effect that can be realized with accuracy. Thus, an image forming apparatus using a plurality of printing units can be provided at low cost. That is, according to the present invention, since the images of the plurality of printing units can be joined with high accuracy, an image forming apparatus capable of recording a large-sized image can be provided easily and at low cost.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of an image recording apparatus using a laser exposure apparatus according to an embodiment of the present invention.
FIG. 2 is an explanatory view schematically showing a mechanism for detecting a displacement of an exposure area by two exposure apparatuses.
FIG. 3 is a partially enlarged view of FIG. 2;
FIG. 4 is a configuration diagram of a printing process control unit according to an embodiment of the image joining misalignment correction method of the present invention.
FIG. 5 is an explanatory diagram illustrating a relationship between a grid position and an exposure position of a reference image.
FIG. 6 is an explanatory diagram showing a conversion state of an exposure position under a lattice condition having distortion.
FIG. 7 is an explanatory diagram showing a joining state of exposure images in two exposure regions.
FIG. 8 is an explanatory diagram showing deformation of an image due to a displacement of an exposure device.
FIG. 9 is an explanatory diagram showing another deformation of an image due to a displacement of the exposure device.
FIG. 10 is an explanatory diagram of one embodiment in which image conversion is performed on the computer side.
FIG. 11 is a configuration diagram of an image recording apparatus that exposes two regions with one rotating polyhedron in an embodiment different from FIG. 1;
FIG. 12 is a configuration diagram of an image recording apparatus using a plurality of inkjet array heads in an embodiment different from FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Charger, 2 ... Exposure means, 3 ... Printing process control means, 4 ... Printed image information, 5 ... Development means, 6 ... Position detection control means, 7 ... Paper feed cassette, 8 ... Pick roller, 9 ... CCD sensor (image detection means), 10: registration means, 11: image transfer means, 13: photoconductor, 14: photoconductor erase means, 15: discharge tray, 16: fixing means, 17: photoconductor cleaning means, 18a , B: laser emitting means, 19a, b: rotating polygon mirror, 20a, b: fθ lens, 21a, b: beam timing detector, 22a, b: reflecting mirror, 23a, b, c, d: reference position mark ( Left exposure area), 24a, b, c, d: Reference position mark (right exposure area), 25: Reference mark (printing area reference mark), 26: Exposure area (left maximum exposure area), 27: Exposure possible Area (right maximum exposure area ), 28: image exposure area (left actual printing area), 29: image exposure area (right actual printing area), 30: reference dot grid, 32: grid outline, 33: character shape, 38: drawing area, 39: parallel Quadrilateral, 40: trapezoid, 45: print request, 46: relative displacement information, 47: bitmap information for printing, 48: computer, 49: printer, 50a, b: exposure beam, 51a, b, c: inkjet Head, 52: transport belt, 53: transport belt cleaning means, 61: relative position difference detecting means, 611: printing area information, 612a, b: image position shift information of printing area, 613a, b: bitmap information, 62: image data correction / conversion means, 621: image division means, 622a, b: divided recorded images, 623a, b: image deformation / bitmap development means, 624a, b ... Bitmap data storage means, 63 ... printed image information output means.

Claims (5)

In an image recording apparatus that forms a large recording image directly on a recording medium such as paper, or through an intermediate recording medium such as a photoconductor, a plurality of image information forming units are juxtaposed.
A real printing area for recording image information on the recording medium or the intermediate recording medium is divided into at least two at a boundary portion,
The image information forming unit, the registered seal shooting enables recording to the exposure area which is enlarged in the outer region, and with the overlapping regions in the exposure area and the boundary of the image information forming means adjacent said exposure area And
Image recording means for dividing the image information for forming the large-sized recorded image, in order to record from the plurality of juxtaposed image information forming means to each actual printing area,
The exposure area including the overlapping area, exposing the position marks of the three or four positions, the deviation amount between the pre said recording medium or said position mark and the reference position is recorded corresponding to the position mark on the photosensitive member A relative position difference detecting means for calculating a shift amount of the exposure area from the detected value of
An image recording apparatus comprising: an image information correcting unit that corrects the image information so that a record formed by each image information forming unit based on the shift amount of the exposing area matches the actual printing area. apparatus. 2. The apparatus according to claim 1, wherein the relative position difference detecting means calculates a relative position difference between an image starting point position, an image width, and a rotation angle in the main scanning direction and the sub-scanning direction from the detected value of the shift amount. Image recording device. 3. The image recording apparatus according to claim 1, wherein the image recording apparatus is an electrophotographic process for forming an image by a charging, exposing, and developing process on a photoconductor, and at least two of the image information forming units are an LED array and a liquid crystal array. An image recording apparatus, comprising an optical image information forming means comprising a combination of one or a plurality of methods such as a laser scanning device. 3. The image recording apparatus according to claim 1 or 2, wherein the image recording apparatus is an ink jet recording method for ejecting and recording ink on paper, a thermal recording method for recording by bringing a heating element array into contact with a thermal recording medium, and a thermal transfer ink sheet contacting a recording medium. A direct image recording apparatus for sending image information directly to a recording medium by one of a thermal transfer recording method of transferring ink to a recording pair by a heating element, wherein at least two or more of the image information forming units are arranged, An image recording apparatus, which is one of an inkjet head, a thermal head, a thermal transfer head, and the like, and is a direct recording head. 5. The image recording apparatus according to claim 1, wherein the change of the recording image information based on the shift amount of the exposing area is performed by the image recording apparatus when the computer issues a printing request. The detected relative position difference information between the recorded images in the image information forming means is returned, and by using the relative position difference information, the image information is transmitted to the relative position between the respective image information forming means by the computer which has transmitted the printing request. An image recording apparatus, which converts the information into a corrected information, transmits the converted information to each image information forming unit of the image recording apparatus, and performs image recording using the converted information.

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