JP4037776B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus, and more particularly, to a color MFP (multifunction peripheral) and a monochrome MFP (multifunction peripheral) having a color scanning function.
[0002]
[Prior art]
In recent years, many devices called multifunction peripherals (MFPs) that integrate functions such as copying, facsimile, and printers into one unit have been used.
[0003]
The color MFP has a function capable of performing scanning, copying, printing, and the like in color.
[0004]
In a conventional color MFP, when copying a monochrome original (achromatic color), it is common to read the original with a color scanner and transfer this image information to a printer unit to form an image. When the color MFP is provided with a monochrome copy mode or a monochrome copy mode, the monochrome image information is extracted from the color image information read by the color scanner, and the printer is operated in the monochrome print mode. It is common to get
[0005]
As a configuration of the color MFP, a scanner unit incorporating a color sensor and a four-rotation color printer unit (described later) are generally installed.
[0006]
A monochrome MFP having a color scanning function has a function capable of performing scanning in color while copying and printing are performed in monochrome.
[0007]
In a monochrome MFP having a color scan function, when copying a monochrome document, as in the case of the color MFP, the document is read by a color scanner, monochrome image information is extracted from the read color image information, and the printer is Generally, a monochrome image is obtained by operating in a print mode.
[0008]
As a configuration of a monochrome MFP having a color scan function, a scanner unit incorporating a color sensor and a monochrome printer are generally installed.
[0009]
A CCD sensor used in these MFPs, that is, a CCD sensor as a color sensor incorporated in a scanner for reading a color image, has sensitivity only at a specific light wavelength, for example, R, G, B Generally, it is composed of three lines (R: red, G: green, B: blue, hereinafter abbreviated as R, G, B) (see, for example, Patent Document 1).
[0010]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 6-113073
[0011]
[Problems to be solved by the invention]
However, in the case where a document read by color scanning is copied as a monochrome document by a conventional method, there has been pointed out a problem that the image quality is lowered and the apparatus cost is high.
[0012]
When monochrome image information is obtained by the sensor described in Patent Document 1, the monochrome image information is synthesized from R, G, and B color information read separately. For this reason, if there is chromatic aberration in the lens characteristics or speed irregularities (jitter) occur in the drive system at the time of reading, the image captured by the R, G, B sensor will be displaced, so it is originally monochrome (achromatic) In particular, the edge portion of the image is captured as a colored image, or is captured as a larger image than an actual image in which color misregistration (chromatic aberration) occurs. Therefore, the monochrome image obtained based on such information is different from the original image, and the image quality is deteriorated.
[0013]
FIG. 20 illustrates this phenomenon. For example, when an original image (achromatic color) without a density gradient is read by an RGB three-line sensor and there is chromatic aberration or drive jitter, the image read by each RGB sensor is in the main scanning and sub-scanning directions. The image will be shifted. When such image information is output by the printer unit, the shape of the output image is distorted as shown in the figure, and a density gradient is generated at the edge portion. Therefore, the image quality output from the printer is degraded (image quality problem).
[0014]
Further, a dedicated conversion circuit (image processing unit) for converting R, G, B color image information into a monochrome image and a memory associated therewith are necessary, which is a factor of high cost (cost problem). .
[0015]
Further, the RGB three-line sensor built in the scanner section is usually provided with a color filter for allowing only light in a specific wavelength band to pass, and the sensitivity is higher than that of a sensor without a filter. Is low. For this reason, there has been a problem that the monochrome copy speed is lower than that of a monochrome-only device. In order to improve the speed, it is necessary to improve the sensitivity by increasing the size of the sensor, or to install a large light source, which increases the size of the apparatus (reading speed problem, increasing the size of the scanner section). problem).
[0016]
The present invention has been devised to solve the above-described problems, and can improve monochrome copy (single color copy) image quality, reduce apparatus cost, and reduce size in a color MFP and a monochrome MFP having a color scan function. An image forming apparatus is provided.
[0017]
[Means for Solving the Problems]
In order to achieve the above object, an image forming apparatus according to a first aspect of the present invention includes a first copy mode for copying a copy original with a plurality of colors corresponding to the color of the copy original, and a copy original. An image forming apparatus having a second copying mode for copying in a single color, which is a means for reading a document to be copied and outputting the image information, and includes an optical filter that transmits light of different wavelength bands. A first light receiving element array composed of a plurality of light receiving element arrays and means for reading a document to be copied and outputting image information thereof. The second light receiving element array including a single light receiving element array has a different wavelength band. First conversion means for converting read image information into signals for copying in a plurality of colors, and second conversion means for converting information read by a single light receiving element array into signals for copying in achromatic colors When, Third conversion means for converting information read by a single light receiving element array into a signal for copying in a single chromatic color, and when copying in the first copying mode, the first light receiving element array The image information to be output is converted into a signal for copying using the first conversion means, and the image information output from the second light receiving element array is copied to the second light when copying in the second copy mode. Is converted to a signal for copying using the converting means, and the image information output from the second light receiving element array is copied using the third converting means when copying in the third copying mode. Control means for controlling the first and second light receiving element arrays and the first, second, and third conversion means so as to convert the signal to Is provided.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0019]
FIG. 1 is a diagram showing an internal structure of the image forming apparatus according to the first embodiment of the present invention.
[0020]
The image forming apparatus includes an automatic document feeder (hereinafter abbreviated as ADF) 199, a scanner unit 2 as an image reading unit, a process unit 4 for forming an output image, a paper feeding unit 6, a control panel (panel) (not shown), and the like. It is composed of
[0021]
The scanner unit 2 irradiates a document supplied by the ADF or a document set on a document table with light from a light source, and reflects light from the document to a sensor (light receiving element) via an optical member such as a mirror or a lens. Then, photoelectric conversion is performed and the image data is output to the process unit 4, an external device (not shown), or a network.
[0022]
Next, the operation of the scanner unit 2 will be described.
[0023]
A document to be read by the scanner unit 2 is conveyed on the document table glass 110 at a constant speed by the ADF 199 or placed on the document table glass 110 downward. The original is irradiated by the light source 112, and the reflected light from the original is imaged on a four-line CCD 117 as a photoelectric conversion element via mirrors 113, 114, 115 and a lens 116.
[0024]
When reading a document placed on the platen glass 110, a first carriage 1A composed of a light source 112 and a mirror 113 and a second carriage 1B composed of mirrors 114 and 115 are not shown. By moving from left to right, the document is scanned by the light emitted from the light source 112 (sub-scanning direction). Here, the moving speed of the first carriage 1A is twice the moving speed of the second carriage 1B, and the optical path length from the original to the 4-line CCD 117 is always constant. When the document is conveyed by the ADF 199, the light emitted from the light source 112 does not move, and scanning is performed by moving the document.
[0025]
2 is an external view of the 4-line CCD sensor 117, and FIG. 2 (2) is an enlarged view of the light receiving portion 117a.
[0026]
The light receiving unit of the 4-line CCD sensor 117 includes a line sensor K in which no optical filter is arranged, that is, a second light receiving element array, a line sensor R in which an optical filter for giving sensitivity to red is arranged, and sensitivity in green. Four line sensors, a line sensor G in which an optical filter for providing the optical filter and a line sensor B in which an optical filter for providing a blue color sensitivity is provided, are arranged side by side. Line sensor R, line sensor G, and line sensor B are the first light receiving element array. In each line sensor, for example, photodiodes as light receiving elements are arranged in an effective pixel area for 7500 pixels at a pitch of 4.7 μm. Then, an image is read by the image reading unit using the first light receiving element array and the second light receiving element array.
[0027]
As described above, since the four line CCD sensor 117 has four line sensors arranged side by side, an image read by each line is shifted in the sub-scanning direction (vertical direction in (2) of FIG. 2). When reading a color image, it is common to store the image information read by a line memory and correct this deviation. However, the carriage movement speed in the sub-scanning direction and the document movement speed are uneven (jitter). If there is, there is not always complete correction.
[0028]
Next, features of the 4-line CCD sensor 117 will be described.
[0029]
3 shows the spectral sensitivity characteristics of the line sensor K constituting the 4-line CCD sensor 117, FIG. 4 shows the spectral sensitivity characteristics of the line sensors R, G, and B, and FIG. 5 shows the spectral distribution of the xenon lamp of the light source 112. FIG.
[0030]
As shown in FIG. 5, the light emitted from the xenon lamp of the light source 112 includes a wavelength of about 400 nm to 730 nm. Consider a case where such light from the light source 112 is reflected by a white original and is irradiated onto a 4-line CCD sensor.
[0031]
As shown in FIGS. 3 and 4, the line sensors R, G, and B are sensitive only to wavelengths in a specific region, whereas the line sensor K is sensitive to a portion from less than 400 nm to more than 1000 nm. Then, it is clear that the signal output from the line sensor K is larger than that of other line sensors. That is, the line sensor K has higher sensitivity than other line sensors.
[0032]
FIG. 6 is a schematic configuration diagram of the 4-line CCD sensor 117.
[0033]
Since the configuration of the line sensor K and the configuration of the line sensors R, G, and B are partially different, first, the configuration of the line sensors R, G, and B will be described.
[0034]
When the line sensors R, G, and B are irradiated with light, the light receiving elements constituting the respective line sensors generate charges according to the irradiation light amount and the irradiation time for each pixel. When the SH signal is input to each shift gate, the charge corresponding to each pixel is supplied to the analog shift register via the shift gate. The analog shift register serially outputs charges (image information) corresponding to the pixels from each line sensor in synchronization with the transfer clocks CLK1 and CLK2.
[0035]
Here, CLK1 and CLK2 form differential signals having opposite phases to each other in order to move charges at high speed.
[0036]
The signal output of the line sensor will be described in further detail using FIG.
[0037]
The line sensor is provided with a light shield pixel portion, a dummy pixel, and an idle feed portion in which the light receiving element is shielded with aluminum or the like so that light does not enter the preceding stage of 7500 effective pixels.
[0038]
Therefore, in order to transfer all the signal outputs of the line sensor to the outside, a transfer clock number exceeding 7500 pixels is required. Here, assuming that the total of the light shield pixel portion, the idle feed portion, and the dummy pixel portion is 500 pixels, a transfer clock for 8000 pixels is required, and this time is a large factor that determines the light accumulation time (tINT) of one line. It has become.
[0039]
That is, the light receiving element in the line sensor generates a charge according to the reflected light from the document during the light accumulation time (tINT) for one line, and the charge is converted into an analog register when the SH signal is input. The operation of outputting a signal to the outside in synchronization with the transfer clock is continuously repeated during the next optical storage time (tINT).
[0040]
Next, the line sensor K will be described. The basic operation is the same as that of the line sensors R, G, and B. As can be seen from FIG. 6, there are two sets of shift gates and analog shift registers.
[0041]
When the line sensor K is irradiated with light, the light receiving elements constituting the line sensor K generate charges according to the irradiation light amount and the irradiation time for each pixel. When the SH signal is input to the shift gate K_ODD and the shift gate K_EVEN, the charges corresponding to the odd pixels are supplied to the analog shift register K_ODD and the charges corresponding to the even pixels are supplied to the analog register K_EVEN via the respective shift gates. . Each analog shift register serially outputs charges (image information) corresponding to the odd and even pixels in synchronization with the transfer clocks CLK1 and CLK2.
[0042]
The signal output in the case of the line sensor K will be further described with reference to FIG.
[0043]
As with the line sensors R, G, and B, the line sensor K also includes light shield pixel portions, dummy pixels, and idle feed portions in which the light receiving element is shielded with aluminum or the like so that light does not enter the preceding stage of 7500 effective pixels. Is provided. The total of the light shield pixel portion, the idle feed portion, and the dummy pixel portion is also 500 pixels.
[0044]
In the case of the line sensor K, as described above, since the charge transfer is divided into the odd pixel and the even pixel, the transfer necessary for serially outputting the charge (image information) for 8000 pixels. The clock may be 4000 pixels. Therefore, the cycle of the SH signal input to the shift gate can be shortened, and the light accumulation time (tINT) for one line can be shortened. As described above, since the line sensor K has high sensitivity, no problem occurs even if the light accumulation time (tINT) of one line is shortened.
[0045]
FIG. 8 shows a case where the SH signal cycle (tINT-K) in the case of the K line sensor is set to ½ of the SH signal cycle (tINT) of the RGB line sensor described above. Also, the effective pixel area is 3750 pixels, and signals corresponding to the odd and even pixels are output separately from the analog shift registers.
[0046]
As described above, regarding the 4-line CCD sensor 117, it has been described that when the line sensor K is used, a reading speed twice as high as that when the line sensors R, G, and B are used can be realized.
[0047]
If the sensitivity of the line sensor K is sufficient, the speed can be further increased. This configuration is shown in FIG. FIG. 9 shows that a quadruple reading speed can be realized by dividing the output of the line sensor K into an odd number and an even number and further dividing the output into the output from the first half and the output from the second half.
[0048]
Next, the operation of the color printer unit will be described with reference to FIG.
[0049]
The process unit 4 outputs an image based on image data read from a document by the scanner unit 2 or image data input from an external device (not shown) on a sheet P (transfer medium). The paper supply unit 6 supplies the paper P to the process unit 4.
[0050]
The process unit 4 and the paper feed unit 6 are housed in the housing 3. A duplex unit 8 and a manual feed unit 9 are detachably attached to the right side of the housing 3. The duplex unit 8 inverts the paper P on which an image is formed on one side by the process unit 4 and supplies it again to the process unit 4. The manual feed unit 9 supplies the paper P to the process unit 4 by manual feed.
[0051]
Next, the structure of the process unit 4 will be described.
[0052]
The process unit 4 has a photosensitive drum 11 (image carrier) extending in the front-rear direction (paper surface direction) of the apparatus, and around the photosensitive member 11, a charging device 12, an exposure device 13, and a black developing device. A developing device 14 (second developing device), a revolver 15 (developing unit), an intermediate transfer belt 16 (intermediate transfer member), and a drum cleaner 17 (cleaning device). Direction).
[0053]
The charging device 12 charges the outer peripheral surface 11a (hereinafter referred to as the drum surface 11a) of the photosensitive drum 11 to a predetermined potential. The exposure device 13 is disposed near the lower end of the process unit 4 and exposes the drum surface 11a charged to a predetermined potential with a laser beam that scans, thereby forming an electrostatic latent image of each color on the drum surface 11a.
[0054]
The black developing device 14 is disposed between the photosensitive drum 11 and the exposure device 13, that is, opposed to the photosensitive drum 11 from below. The black developing unit 14 develops the black electrostatic latent image formed on the drum surface 11a by the exposure device 13, and forms a black developer image on the drum surface 11a. The black developing unit 14 is movably provided so that the developing roller is separated from and in contact with the drum surface 11a. When a black image is formed, the developing roller moves so as to be in contact with the drum surface 11a. When forming a color image, it is kept away from the drum surface 11a. The black developer 14 is supplied with a developer from the toner cartridge 14a.
[0055]
The revolver 15 is rotatably provided adjacent to the left side of the photosensitive drum 11 in the drawing. The revolver 15 includes a yellow developing device 15Y (first developing device), a magenta developing device 15M (second developing device), and a cyan developing device 15C (third developing device). Each developing device is detachably accommodated in the revolver 15 along the rotation direction of the revolver 15. Each developing device includes toner cartridges 15y, 15m, and 15c that store developers of respective colors.
[0056]
When forming an image, the revolver 15 is rotated in the clockwise direction, and a desired developing device is selectively disposed opposite to the photosensitive drum surface 11a.
[0057]
As described above, the developing unit incorporated in the process unit 4 includes only the black developing unit 14 independently, and includes the other three units of the yellow developing unit 15Y, the magenta developing unit 15M, and the cyan developing unit 15C. The developing device is disposed in the revolver 15.
[0058]
As is clear from this structure, when a yellow, magenta, and cyan image is formed, an operation such as rotating the revolver 15 is required, whereas when a black image is formed, It is only necessary to bring the black developing device 14 close to the drum surface 11a. Therefore, the time until image formation becomes possible has a structure in which black is shorter than other colors.
[0059]
The intermediate transfer belt 16 is disposed at a position in contact with the photosensitive drum 11 from above. The intermediate transfer belt 16 is stretched over a drive roller 16a, a pre-transfer roller 16b, a transfer counter roller 16c, and a tension roller 16d each having a rotation shaft extending in the front-rear direction (paper surface direction).
[0060]
Inside the intermediate transfer belt 16, there is provided a primary transfer roller 21 for pressing the intermediate transfer belt 16 against the drum surface 11a with a predetermined pressure and transferring the developer image formed on the drum surface 11a to the intermediate transfer belt. It has been.
[0061]
Around the intermediate transfer belt 16, a belt cleaner 22 for cleaning the belt and a secondary transfer roller 24 for transferring the developer image on the belt to the paper P are provided so as to be detachable from the belt surface. It has been.
[0062]
The paper feed unit 6 has two paper feed cassettes 26 and 28. A pick-up roller 31 for taking out the uppermost sheet P accommodated in the cassette is provided at the upper right end of each cassette 26, 28 in the drawing. A feed roller 32 and a separation roller 33 are disposed in contact with each other at positions adjacent to the downstream side in the sheet take-out direction by the pickup roller 31.
[0063]
At a position adjacent to the right side of the sheet feeding cassettes 26 and 28 in the drawing, a sheet conveyance path 26 is provided to the secondary transfer point where the intermediate transfer belt 16 and the secondary transfer roller 24 are in contact with each other. On the sheet conveyance path 26, a plurality of conveyance roller pairs 34 that sandwich and rotate the sheet P, an aligning sensor 35 that detects the arrival of the sheet P, and the secondary transfer point are fed at a predetermined timing. An aligning roller pair 36 is arranged in order.
[0064]
A fixing device 38 for fixing the developer transferred onto the paper P by heating and pressurizing is provided on the paper conveyance path 26 extending upward through the secondary transfer point. The fixing device 38 includes a heating roller 38b with a built-in heater and a pressure roller 38a that is pressed against the heating roller 38b.
[0065]
Next, operations when the image output unit outputs a monochrome image and operations when a color image is output will be described.
[0066]
The operation when outputting a monochrome image is as follows.
[0067]
First, the revolver is rotated to a home position where none of the developing units 15Y, 15M, 15C is opposed to the drum surface 11a. Then, the black developing device 14 is moved upward and is opposed to the drum surface 11a.
[0068]
The belt cleaner 22 is rotated clockwise around the shaft 22a to contact the intermediate transfer belt 16, and the secondary transfer roller 24 is moved to the left in the drawing and is brought into contact with the intermediate transfer belt 16.
[0069]
The exposure device 13 scans laser light on the drum surface 11a based on the image data for black, and an electrostatic latent image for black is formed on the drum surface 11a. Subsequently, a black developer is supplied to the electrostatic latent image on the drum surface 11a via the black developing device 14, and a black developer image is formed on the drum surface 11a.
[0070]
The black developer image on the drum surface 11 a formed in this way is moved by the rotation of the photosensitive drum 11 and reaches the primary transfer point in contact with the intermediate transfer belt 16. At the primary transfer point, a bias having a polarity opposite to the potential of the black developer image is applied via the primary transfer roller, and the black developer image on the drum surface 11 a is transferred onto the intermediate transfer belt 16.
[0071]
On the drum surface 11a that has passed the primary transfer point, the black developer remaining without being transferred by the drum cleaner 17 is removed, and at the same time, the residual charge is discharged. The drum surface 11a is uniformly charged by the charging device 12 to form the next black electrostatic latent image.
[0072]
When black image formation is continuously performed, a series of processes, that is, exposure → development → transfer to the intermediate transfer belt 16 is executed as in the previous operation, and the next black developer image is transferred to the intermediate transfer. Transferred onto the belt 16.
[0073]
The black developer image transferred onto the intermediate transfer belt is moved by the rotation of the intermediate transfer belt 16 and passed through the secondary transfer point between the secondary transfer roller 24 and the black developer image.
[0074]
At this time, the paper P taken out from the cassettes 26 and 28 by the pickup roller 31 is transported upward in the longitudinal transport path 26 by the transport roller pair 34, and once aligned by the aligning roller 36, at a predetermined timing. It is sent to the secondary transfer area.
[0075]
A bias opposite to the potential of the black developer image is applied via the secondary transfer roller 24, and the black developer on the intermediate transfer belt 16 is transferred onto the paper P. After the developer is transferred to the paper P, the black cleaner remaining on the intermediate transfer belt 16 is removed by the belt cleaner 22.
[0076]
Thereafter, the paper P to which the black developer has been transferred is passed through the fixing device 38 and heated and pressurized, and the developer images of the respective colors are fixed on the paper P, thereby forming a black image. Thus, the paper P on which the black image is formed is discharged to the paper discharge tray 44 via the discharge roller 42 provided on the downstream side of the fixing device 38.
[0077]
As described above, in the black image formation, it is not necessary to move a revolver, a belt cleaner, a secondary transfer roller, or the like, and an image can be continuously formed.
[0078]
Next, an operation when outputting a color image will be described.
[0079]
First, the black developing device 14 is moved downward and separated from the drum surface 11a. The revolver 15 is rotated clockwise so that the yellow developing device 15Y faces the drum surface 11a. The belt cleaner 22 is rotated counterclockwise about the shaft 22a to be separated from the intermediate transfer belt 16, and the secondary transfer roller 24 is moved in a direction away from the paper transport path 26 (right direction in the figure) to perform intermediate transfer. Separated from the belt 16.
[0080]
The exposure device 13 scans the drum surface 11a with laser light based on the yellow image data, and an electrostatic latent image for yellow is formed on the drum surface 11a. Subsequently, a yellow developer is supplied to the electrostatic latent image on the drum surface 11a via the yellow developing device 15Y, and a yellow developer image is formed on the drum surface 11a.
[0081]
The yellow developer image on the drum surface 11 a formed in this way is moved by the rotation of the photosensitive drum 11 and reaches the primary transfer point in contact with the intermediate transfer belt 16. At the primary transfer point, a bias having a polarity opposite to the potential of the yellow developer image is applied via the primary transfer roller 21, and the yellow developer image on the drum surface 11 a is transferred onto the intermediate transfer belt 16.
[0082]
On the drum surface 11a that has passed the primary transfer point, the yellow developer remaining without being transferred by the drum cleaner 17 is removed, and at the same time, the residual charge is discharged. The drum surface 11a is uniformly charged by the charging device 12 to form an electrostatic latent image for the next magenta, the revolver 15 rotates, and the magenta developer 15M is opposed to the drum surface 11a. In this state, as in the case of the previous yellow, a series of processes, that is, exposure → development → transfer to the intermediate transfer belt 16 is executed, and the magenta developer image is superimposed on the yellow developer image on the intermediate transfer belt 16. Is transcribed. After the magenta developer image is transferred in this manner, the cyan developer image is similarly transferred in an overlapping manner.
[0083]
Then, the revolver is rotated to the home position where none of the developing units 15Y, 15M, 15C is opposed to the drum surface 11a, and instead, the black developing unit 14 is raised and is opposed to the drum surface 11a. In this state, the same process as described above is executed, and the black developer image is transferred onto the intermediate transfer belt 16 so as to overlap the yellow developer image, the magenta developer image, and the cyan developer image.
[0084]
Here, the black developing device 14 is used because, when K (black) is expressed by YMC superposition, accurate color superposition is necessary. The reason is that using only K rather than using three colors of YMC saves toner.
[0085]
When the developer images of all colors are superimposed on the intermediate transfer belt in this way, the secondary transfer roller 24 is moved in the left direction in the figure to contact the intermediate transfer belt 16, and the belt cleaner 22 is also connected to the intermediate transfer belt. 16 is contacted. In this state, the developer images of all the colors superimposed on the intermediate transfer belt are moved by the rotation of the intermediate transfer belt 16 and passed through the secondary transfer point with the secondary transfer roller 24.
[0086]
At this time, the paper P taken out from the cassettes 26 and 28 by the pickup roller 31 is transported upward in the longitudinal transport path 26 by the transport roller pair 34, and once aligned by the aligning roller 36, at a predetermined timing. It is sent to the secondary transfer area.
[0087]
A bias opposite to the potential of the developer image of each color is applied via the secondary transfer roller 24, and the developer of each color on the intermediate transfer belt 16 is transferred onto the paper P. After the developer is transferred to the paper P, the belt cleaner 22 removes the developer remaining on the intermediate transfer belt 16.
[0088]
The paper P onto which the developer of each color has been transferred together is then passed through the fixing device 38 and heated and pressurized, and the developer image of each color is fixed on the paper P to form a color image. Thus, the paper P on which the color image is formed is discharged to the paper discharge tray 44 via the discharge roller 42 provided on the downstream side of the fixing device 38.
[0089]
As described above, when forming a color image, it is necessary to superimpose developer images of yellow, magenta, cyan, and black, and exposure, development, and transfer process to the intermediate transfer belt 16 are required four times. On the other hand, in the case of forming a black monochrome image, since exposure → development → transfer to the intermediate transfer belt 16 is performed once, it can be shortened to ¼ time, and high-speed and high-quality monochrome copy. Is possible.
[0090]
Even in the case of forming a mono-color image, the transfer process to the exposure-development-intermediate transfer belt 16 is executed for one or two of the color image forming operations described above based on the image data for black. Therefore, high-speed, high-quality monocolor copying is possible.
[0091]
Next, as a modification of monocolor image formation, a two-color superimposed monocolor image formation operation will be described.
[0092]
In this modification, a monocolor image is formed using two colors based on the image data for black.
[0093]
For example, when an image is formed by overlapping two colors of yellow and magenta, the output image becomes red. The operation of the printer unit when forming a red output image is the same as the color image forming operation described above until the image is transferred onto the intermediate transfer belt 16 in the order of yellow and magenta. However, after that, cyan and black images are not formed, and yellow and magenta images are transferred onto the paper P from the intermediate transfer belt 16.
[0094]
Similarly, in the other two-color monochromatic image forming operation, the unnecessary color image forming operation is omitted. For example, when a green image is formed, yellow and cyan images are formed. When a blue image is formed, only magenta and cyan images are formed.
[0095]
Next, the present invention will be described in the case where the configuration of the printer unit is an MFP different from the printer unit described above.
[0096]
FIG. 10 is a diagram showing the internal structure of the image forming apparatus according to the second embodiment of the present invention. The present embodiment is different from the first embodiment in that each color image forming unit of the printer unit is arranged in a quadruple tandem type.
[0097]
In FIG. 10, an image forming apparatus 201 includes an optical unit 202, an image forming unit necessary for forming each color image, a transfer belt 207, a suction roller 208, transfer belt rollers 209 and 210, and a transfer belt cleaner. 211, aligning rollers 212 and 213, a paper feed roller 214, a paper feed cassette 215 that accommodates and supplies paper P, and a fixing device 216.
[0098]
For each color, the image forming unit includes developing units 3Y, 3M, 3C, and 3K, photosensitive drums 4Y, 4M, 4C, and 4K, charging chargers 5Y, 5M, 5C, and 5K, and cleaners 6Y, 6M, 6C, and 6K. And transfer rollers 18Y, 18M, 18C, and 18K.
[0099]
Next, an operation for forming a color image using this apparatus will be described.
[0100]
The photosensitive drums 4Y, 4M, 4C, 4K and the transfer belt 207 are rotationally driven at a predetermined outer peripheral speed by a drive motor (not shown). The charging chargers 5Y, 5M, 5C, and 5K provided to face the surfaces of the photosensitive drums 4Y, 4M, 4C, and 4K have a predetermined potential applied to the surfaces of the photosensitive drums 4Y, 4M, 4C, and 4K, respectively. To charge.
[0101]
The four light beams output from the optical unit 202 are imaged as scanning light, which is a spot having a necessary resolution, at exposure positions on the photosensitive drums 4Y, 4M, 4C, 4K, which are exposed members, Scan exposure. As a result, electrostatic latent images corresponding to the image signals are formed on the respective photosensitive drums 4Y, 4M, 4C, and 4K.
[0102]
The electrostatic latent images formed on the photosensitive drums 4Y, 4M, 4C, and 4K are developed with toner as a developer supplied from the developing units 3Y, 3M, 3C, and 3K to form toner images. The For example, the electrostatic latent image formed on the photosensitive drum 4Y is developed as a yellow toner image by the developing device 3Y. Similarly, the electrostatic latent image on the photosensitive drum 4M is converted into a magenta toner image by the developing device 3M, and the electrostatic latent image on the photosensitive drum 4C is converted into a cyan toner image by the developing device 3C. The electrostatic latent image is developed into a black toner image by the developing device 3K.
[0103]
On the other hand, the paper P accommodated in the paper feed cassette 215 is conveyed to the aligning rollers 212 and 213 by the rotation of the paper feed roller 214 and is aligned (position adjusted), and then by the rotation of the aligning rollers 212 and 213. It is conveyed to the suction roller 208 and the transfer belt roller 209. A predetermined potential difference is provided between the suction roller 208 and the transfer belt roller 209, and the sheet P is sucked onto the transfer belt 207 by the rotation of the rollers 208 and 209 and the transfer belt roller 210. It is conveyed downstream in the state.
[0104]
The toner images of the respective colors on the photosensitive drums 4Y, 4M, 4C, and 4K developed by the developing units 3Y, 3M, 3C, and 3K are portions where the transfer belt 207 and the transfer rollers 18Y, 18M, 18C, and 18K are in contact with each other. It is transferred to the paper P.
[0105]
Next, the paper P is heated and pressurized by passing through the fixing device 216, and the toner image on the paper P is melted and securely fixed to the paper P. At this time, the photosensitive drums 4Y, 4M, 4C, and 4K that have been transferred to the paper P are returned to the initial state after the residual toner on the surface is removed by the cleaners 6Y, 6M, 6C, and 6K. Is ready for image formation. In addition, the transfer belt 207 that has finished transporting the paper is free of unnecessary toner adhering to the belt when passing through the transfer belt cleaner 211, so that the next paper can be transported.
[0106]
By repeating the above process, the color image forming operation is continuously performed.
[0107]
Next, a detailed configuration of the optical unit 202 and a light beam path during color image formation will be described.
[0108]
The optical unit 202 includes, for example, four semiconductor lasers (not shown), and light beams from the respective semiconductor lasers are reflected by the surface of the polygon mirror 221 rotated by the polygon motor 220 to be covered. The light beam scans the surfaces of the photosensitive drums 4Y, 4M, 4C, and 4K as exposure surfaces.
[0109]
Here, there is a possibility that beam light that may reach the photosensitive drum 4Y reaches BM-Y, and beam light that may reach the photosensitive drum 4M reaches BM-M and the photosensitive drum 4C. If the beam light is BM-C and the beam light that may reach the photosensitive drum 4K is BM-K, each beam light scanned by the polygon mirror 221 passes through the lenses LN1, LN2, and LN3, respectively. To do.
[0110]
About 50% of the beam light BM-Y that may reach the photosensitive drum 4Y passes through the lenses LN1, LN2, and LN3, and then is reflected by the half mirror HM-Y to become the beam light BM-Y1. Thereafter, the light is reflected by the mirror MR-Y1 and the mirror MR-Y2, and reaches the photosensitive drum 4Y. On the other hand, the light beam BM-Y2 that has passed through the half mirror HM-Y is shielded by the light shielding member (shutter) SHT-Y1, and does not reach any drum.
[0111]
Further, the beam light BM-M that may reach the photosensitive drum 4M passes through the lenses LN1, LN2, and LN3, and then is reflected by about 50% by the half mirror HM-M, and the beam light BM-M1. Become. Thereafter, the light is reflected by the mirror MR-M1 and the mirror MR-M2, and reaches the photosensitive drum 4M. On the other hand, the light beam BM-M2 that has passed through the half mirror HM-M is shielded by the light shielding member (shutter) SHT-M1 and does not reach any drum.
[0112]
Further, the beam light BM-C that may reach the photosensitive drum 4C passes through the lenses LN1, LN2, and LN3, and then is reflected by about 50% by the half mirror HM-C. Become. Thereafter, the light is reflected by the mirror MR-C1 and the mirror MR-C2, and reaches the photosensitive drum 4C. On the other hand, the light beam BM-C2 that has passed through the half mirror HM-C is shielded by the light shielding member (shutter) SHT-C1 and does not reach any drum.
[0113]
The beam light BM-K that reaches the photosensitive drum 4K passes through the lenses LN1, LN2, and LN3, and then is reflected by the mirror MR-K and reaches the photosensitive drum 4K.
[0114]
In this way, the light beams from the four semiconductor lasers (not shown) are reflected by the surface of the polygon mirror 221 that is rotationally driven by the polygon motor 220, and then pass through the respective paths and on the respective photosensitive drums. As a result, the color beam can be formed.
[0115]
Next, with reference to FIG. 11, description will be given of an operation and a beam path in the optical system when a monochrome (black) image is formed at high speed using a copying machine having the same configuration.
[0116]
The photosensitive drum 4K, the transfer belt 207, and the fixing device 216 are rotationally driven by a drive motor (not shown) at a speed four times that when the above-described color image is formed. On the other hand, the photosensitive drums 4Y, 4M, and 4C that are not used are not driven to rotate, and the developing rollers in the developing units 3Y, 3M, and 3C do not rotate.
[0117]
The four light beams output from the optical unit 202, unlike color image formation, are imaged as scanning light, which is a spot having the necessary resolution at the exposure location on the photosensitive drum 4K. Scan exposure is performed. That is, the photosensitive drum 4K is simultaneously scanned and exposed by the four light beams to form an electrostatic latent image corresponding to the image signal. Note that the light beam path in the optical unit 202 in this case will be described later.
[0118]
The electrostatic latent image formed on the photosensitive drum 4K is developed with toner (developer) from the developing device 3K to become a K toner image. In the monochrome mode, the transfer belt 207, the suction roller 208, the transfer belt roller 209, and the transfer rollers 18Y, 18M, and 18C are moved downward by a drive motor (not shown) so as not to contact the photosensitive drums 4Y, 4M, and 4C. Therefore, the transfer belt 207 contacts only with the photosensitive drum 4K.
[0119]
The toner image on the photosensitive drum 4K developed by the developing device 3K is transferred onto the paper P at a position where the transfer belt 207 and the transfer roller 18K are in contact with each other.
[0120]
Next, as the paper P passes through the fixing device 216, the paper P is heated and pressurized, and the toner image on the paper P is melted and securely fixed on the paper P.
[0121]
By repeating the operations in the above processes, the monochrome image forming operation is continuously performed at a speed four times that of the color image forming operation.
[0122]
Next, the light beam path in the optical unit when forming a monochrome (black) image will be described. As shown in FIG. 11, the difference from the color image formation is the positions of the light shielding members SHT-Y1, SHT-Y2, SHT-M1, SHT-M2, SHT-C1, and SHT-C2.
[0123]
For example, in the case of the beam light BM-Y1, the beam light BM-Y1 that has reached the photosensitive drum 4Y at the time of color image formation is shielded by the light shielding member SHT-Y2 and does not reach the photosensitive drum 4Y. On the other hand, the beam light BM-Y2 that has passed through the half mirror HM-Y is reflected by the mirror MR-Y3 and reaches the photosensitive drum 4K. The same applies to the light beams BM-M and BM-C, which do not reach the photosensitive drums 4M and 4C, but reach the photosensitive drum 4K. The light beam BM-K that has reached the photosensitive drum 4K at the time of color image formation reaches the photosensitive drum 4K without any particular change.
[0124]
As described above, in the monochrome image forming mode, the light paths to the photosensitive drums 4Y, 4M, and 4C are blocked by the light shielding members SH-Y2, SHT-M2, and SH-C2, and conversely, the light shielding members SHT-Y1, The optical path to the photosensitive drum 4K is secured by the displacement of SHT-M1 and SHT-C1. The light shielding members SHT-Y1, SHT-M1, SHT-C1, SHT-Y2, SHT-M2, and SHT-C2 are opened and closed by a driving unit (not shown).
[0125]
In this way, when the monochrome mode is designated, the light beams from the four semiconductor lasers (not shown) are reflected by the surface of the polygon mirror 221 rotated by the polygon motor 220 and then pass through the respective optical paths. All of the four light beams pass through and become light beams for scanning on the photosensitive drum 4K, and a monochrome image can be formed at a speed four times that in the case of color.
[0126]
The reason for using only the photosensitive drum 4K and not using the photosensitive drums 4Y, 4M, and 4C at the time of monochrome image formation is that the rotation of these photosensitive drums is stopped and separated from the transfer belt. This is to prevent deterioration of characteristics due to wear on the surface of the photosensitive drum.
[0127]
FIG. 12 is a diagram showing the internal structure of the image forming apparatus according to the third embodiment of the present invention. This figure shows the structure of a monochrome MFP having a color scan function.
[0128]
When executing the copying operation, monochrome image information read by the scanner unit 2 is output from the printing unit after being subjected to predetermined image processing. When operating as a scanner, RGB color image data output by the scanner unit is output as color scanner information to a network (not shown).
[0129]
Next, the operation of the image forming apparatus according to the present embodiment will be described.
[0130]
(1) of FIG. 13 is a diagram showing a control panel of the color MFP shown in FIGS.
[0131]
The buttons arranged on the left side are buttons for designating the operation of the color MFP.
[0132]
When the auto color button is pressed, the color MFP automatically determines whether the document is color or monochrome, and enters a mode for executing a copy operation in a mode suitable for the result. That is, in this mode, a color copy is executed for a color original, and a monochrome copy is executed for a monochrome original.
[0133]
When the full color button is pressed, the color MFP enters a mode for executing color copying.
[0134]
When the black button is pressed, the color MFP enters a mode for executing monochrome copying.
[0135]
When the mono color button is pressed, the color MFP enters a mode for executing mono color copying. The color can be specified on the touch panel of the display unit.
[0136]
The copy / scanner button is a button for selecting whether the color MFP operates as a scanner or a copier. The default is a copier.
[0137]
The display unit is a touch panel that can display the status of the color MFP and at the same time specify detailed operation. For example, it is possible to specify copy magnification and density, select paper, and select a color for mono color copying.
[0138]
Buttons 0 to 9 (numeric keys) are used to input the number of copies. The C button is a clear button and is used for clearing the number input.
[0139]
The reset button is used to return all the conditions set on the control panel to the initial (default) conditions.
[0140]
The stop button is used when the copying operation or the like is stopped halfway.
[0141]
The start button is used when starting a copying operation or a scanning operation.
[0142]
FIG. 13B is a diagram showing a control panel of the monochrome MFP shown in FIG.
[0143]
The buttons arranged on the left side are buttons for designating the operation of the monochrome MFP.
[0144]
When the copy button is pressed, the monochrome MFP enters a mode for operating monochrome copying.
[0145]
When the FAX button is pressed, the monochrome MFP enters a mode for performing a FAX operation.
[0146]
When the scanner button is pressed, the monochrome MFP enters a mode for performing a scanner operation. In the case of the monochrome MFP of the present invention, the scanner enters the color image reading mode (RGB sensor is effective).
[0147]
The other display units and buttons are basically the same as those of the color MFP described above, and a description thereof will be omitted.
[0148]
FIG. 14A is a block diagram showing a system configuration of a conventional color MFP.
[0149]
When auto color copy operation is specified on the control panel (the auto color button is pressed), the control unit performs predetermined operation settings for the scanner, and is sent from the scanner to the image processing unit. An instruction is issued to determine whether the document is color or monochrome from the RGB image information.
[0150]
From the document discrimination result of the image processing unit, when the document is color, YMCK (yellow, magenta, yellow) that can output the RGB image information sent from the scanner to the image processing unit with a color printer. (Cyan, Black) signal is instructed to be converted, and a color print mode for printing in four colors is set for the color printer.
[0151]
On the other hand, if the document discrimination result of the image processing unit is monochrome, the RGB image information sent from the scanner to the image processing unit can be output in monochrome only by the color printer. An instruction to convert to a signal (luminance information) is issued, and a monochrome print mode for printing with one black color is set for the color printer.
[0152]
When a color copy operation is designated on the control panel (a full color button is pressed), the control unit performs predetermined operation settings for the scanner, and the image processing unit receives RGB image information sent from the scanner. An instruction is given to convert the signal into a YMCK (yellow, magenta, cyan, black) signal that can be output by a color printer. For a color printer, a color print mode for printing in four colors is set.
[0153]
When the monochrome copy operation is designated on the control panel (the black button is pressed), the control unit performs a predetermined operation setting for the scanner, and is sent from the scanner to the image processing unit. An instruction is issued to convert the RGB image information into a K (black) signal (luminance information) that can be output in monochrome only by a color printer. For the color printer, a monochrome print mode for printing with one black color is set.
[0154]
FIG. 14B is a block diagram showing the system configuration of the color MFP of the present invention.
[0155]
The operation of this system will be described with reference to the flowchart of FIG.
[0156]
When the start button is pressed, the copy operation is started (step 1).
[0157]
At this time, if auto color copy operation is specified on the control panel (the auto color button is pressed), or if none of the mode setting buttons are pressed, the auto color copy is specified Judge. If another mode designation button has been pressed, it is determined that auto color copy has not been designated (step 2).
[0158]
When the auto color copy mode is designated, the control unit sets the scanner reading mode so that the image can be read by the RGB line sensor with respect to the scanner, that is, read by the first image reading means (step 3), and color scanning is performed. The operation is executed (step 4). Then, as a result of executing the color scan, it is determined whether or not the document is a color document (step 5).
[0159]
If the result of Step 2 is a color original, the RGB image information sent from the scanner to the image processing unit can be output in color by the color printer, that is, output by the first image forming means. An instruction is issued to select image processing that can be converted into YMCK (yellow, magenta, cyan, black) signals (step 17). For the color printer, a color print mode for printing in four colors is set (step 18). Then, the color copy operation is executed (step 19), and the series of operations is terminated (step 20).
[0160]
If the result of the determination in Step 2 is a monochrome document, the control unit sets the scanner reading mode so that the scanner can read the image at high speed only by the K line sensor, that is, the second image reading means. Set (step 10). The image processing unit is instructed to select a process capable of printing monochrome image information (K data: luminance information) sent from the scanner with one black color of the printer unit (step 11). A monochrome print mode in which a black image can be printed at high speed, that is, can be printed by the second image forming unit is set for the printer unit (step 12). Then, the monochrome copy operation is executed (step 19), and the series of operations is terminated (step 20).
[0161]
When the auto color copy mode is not designated, the control unit determines whether the monochrome copy mode is designated (step 6).
[0162]
When the monochrome copy mode is designated here (step 6), the control unit sets the scanner reading mode so that the image can be read at high speed only by the K line sensor (step 10). The image processing unit is supported to select a process capable of printing monochrome image information (K data: luminance information) sent from the scanner with one black color of the printer unit (step 11). A monochrome print mode capable of printing a black image at high speed is set for the printer unit (step 12). Then, the monochrome copy operation is executed (step 19), and the series of operations is terminated (step 20).
[0163]
If the monochrome copy mode is not designated in Step 6, the control unit determines whether the mono color copy mode is designated (Step 7).
[0164]
If the mono-color copy mode is designated here (step 7), the control unit sets the scanner reading mode so that the image can be read at high speed with only the K line sensor (step 13). For the image processing unit, monochrome image information (K data: luminance information) sent from the scanner is printed in one or two colors of YMC of the printer unit, so the same processing as the processing for black Support is given to select (step 14). For the printer unit, a mono-color print mode is set in which the image data sent from the image processing unit can be printed in a single color at high speed (step 15). Then, the mono-color copy operation is executed (step 19), and the series of operations is finished (step 20).
[0165]
If the mono color copy mode is not designated in Step 7, the control unit determines whether the color copy mode is designated (Step 8).
[0166]
When the color copy mode is designated here (step 8), the control unit sets the scanner reading mode so that the image can be read by the RGB line sensor to the scanner, that is, read by the first image reading means. (Step 16). The image processing unit is instructed to select image processing that can convert RGB image information sent from the scanner into YMCK (yellow, magenta, cyan, black) signals that can be output in color by a color printer ( step 17). For the color printer, a color print mode for printing in four colors is set (step 18). Then, the color copy operation is executed (step 19), and the series of operations is terminated (step 20).
[0167]
If the color copy mode is not designated in Step 8, since the copy mode has not been finalized even though the copy operation has started, it is processed as an error (Step 9).
[0168]
With the configuration and control flow described above, the color MFP according to the embodiment of the present invention can operate under optimum conditions for each operation mode.
[0169]
FIG. 16A is a block diagram showing a conventional configuration of a monochrome MFP capable of color scanning. As shown in the figure, the sensor of the scanner unit is composed of three lines of RGB.
[0170]
When copying is instructed by the control panel, the RGB color information read by the scanner unit is converted into K (monochrome) data (luminance information) by the image processing unit and sent to the monochrome printer unit. The monochrome printer unit prints out the K data (luminance information).
[0171]
Similarly, when FAX is specified on the control panel, the FAX modem outputs K data (luminance information) output from the image processing unit to the public line according to a predetermined format.
[0172]
When a scanner is designated on the control panel, RGB color information read by the scanner unit is converted into predetermined RGB data by the image processing unit and sent to the network interface. The network interface outputs this RGB data on a network (LAN) according to a predetermined format.
[0173]
Comparing the speeds required for the copying operation, FAX operation, and scanner operation (output to the network), the speed is most required for the copying operation, and generally high speed is not required for FAX or network scanning. For example, even a high-speed FAX has a transmission capability of about 10 sheets per minute. This is because there is a bottleneck in the communication line, and even if the scanner is speeded up, the system does not speed up. On the other hand, in the case of a copying operation, 20 or 30 sheets are common in one minute, and 80 or more machines are not uncommon.
[0174]
Therefore, when the copying function and the FAX or network scanning function are realized by using the same scanner (reading device), an overspec scanner is inevitably mounted for the FAX or network scanning function. In addition, when the print engine is monochrome, monochrome information (luminance information) is required for speed, but the conventional technology obtains monochrome information (luminance information) from the color sensor. There was an unreasonable demand.
[0175]
(2) of FIG. 16 is a block diagram showing a monochrome MFP system configuration of the present invention.
[0176]
This system operation will be described with reference to the flowchart of FIG.
[0177]
The operation starts when the start button is pressed. At this time, if the copy operation has been specified on the control panel (the copy specification button has been pressed), or if no mode setting button has been pressed, the control unit has specified the copy operation. (Step 30). If another mode designation button has been pressed, it is determined that the copy operation has not been designated (step 31).
[0178]
When the copy mode is designated, the control unit sets the scanner reading mode so that an image can be read at high speed with the K line sensor (step 35). The image processing unit is instructed to select image processing that can convert K image information (luminance information) sent from the scanner into K data (luminance information) that can be output by a (monochrome) printer ( step36). Then, the copy operation is executed (step 37), and the series of operations is terminated (step 44). By this operation, monochrome copying can be executed at high speed and with high image quality.
[0179]
If the copy operation is not specified in Step 31, the control unit determines whether the FAX operation mode is specified (Step 32).
[0180]
When the FAX operation mode is designated in Step 32, the control unit sets the scanner reading mode so that the image can be read by the K line sensor with respect to the scanner (step 38). The image processing unit is instructed to select image processing that can convert K image information (luminance information) sent from the scanner into a signal that can be output to the public line (step 39). Then, a predetermined setting is made for the FAX modem, a FAX operation (monochrome scan) is executed (step 40), and a series of operations is terminated (step 44).
[0181]
If the FAX operation is not designated in Step 32, the control unit determines whether the scanner operation mode is designated (Step 33).
[0182]
If the scanner operation is designated in Step 33, the control unit sets the scanner reading mode so that the image can be read by the RGB line sensor to the scanner (step 41). The image processing unit is instructed to select image processing that can convert RGB color image information sent from the scanner into a signal that can be output to the network (step 42). Then, a predetermined setting is applied to the network interface, the color scan operation is executed (step 43), and the series of operations is terminated (step 44).
[0183]
If the scanner operation is not designated in Step 33, the operation mode is not yet determined even though the operation is started, so that it is processed as an error (Step 34).
[0184]
With the configuration and control flow described above, the monochrome MFP according to the embodiment of the present invention can operate under optimum conditions for each operation mode.
[0185]
Next, the operation for continuously copying different types of originals using the four-rotation type color printer shown in FIG. 1 will be described.
[0186]
FIG. 18 is a timing chart showing operations of the scanner and the printer. Here, in order to simplify the description, the time required for the scanner to read a color image using RGB lines and the time required for the printer to form an image of one color are 2: 1. It is a ratio. The time required for the scanner to read a monochrome image using the K line and the time required for the printer to form a one-color image are set to a ratio of 1: 1.
[0187]
First, the color copy operation will be described with reference to (1) of FIG.
[0188]
First, the scanner reads the first original with the RGB sensor. In the chart, the first image reading information is represented as RGB1. The image processing unit converts the RGB1 signal into a YMCK signal used for printing. In the chart, the first YMCK signal converted by the image processing unit is represented as Y1, M1, C1, and K1, respectively.
[0189]
Since the printer cannot stop operating halfway, the printer starts printing the first Y1 signal after a while has passed since the scanner started operating. This is the timing when the scanner can finish reading the image when printing is completed.
[0190]
The first RGB1 signal read by the scanner or the M1, C1, and K1 signals converted by the image processing unit are stored in the memory, and the printer prints the M1, C1, and K1 signals after the Y1 signal is printed. Used when doing. By storing the image information in the memory in this way, the reading operation by the scanner can be performed once for one document.
[0191]
As is apparent from the timing chart, the printer needs to perform four cycles of Y, M, C, and K for forming a color image, and the printing operation for one color is 2 of the color image reading operation of the scanner. Even at twice the speed, there is a time margin before the next document must be read.
[0192]
In the case of this embodiment, in order to efficiently copy a color image, the scanner should start reading the second color image at the latest when the printer starts printing the K1 signal. The printer starts printing the Y2 signal based on the second RGB2 signal.
[0193]
By repeating this series of operations, continuous color copying of different types of documents is performed.
[0194]
Next, a conventional monochrome copy operation will be described with reference to FIG. Conventionally, as described above, RGB signals read by a scanner are converted into K signals (luminance information) by image processing. Accordingly, a series of copy operations is as follows.
[0195]
First, the scanner reads the first original with the RGB sensor. In the timing chart, this first image reading information is represented as RGB1. The image processing unit converts the RGB1 signal into a K signal (luminance information) used for monochrome printing. In the timing chart, the first K signal (luminance information) converted by the image processing unit is represented as K1. As in the case of the color copy operation, the printer cannot be stopped halfway, so the printer starts printing the first K1 signal after a while has passed since the scanner was operated. This is the timing at which the scanner can finish reading the image as soon as the printer finishes printing the K1 signal.
[0196]
As is apparent from the timing chart, the printer forms a monochrome image only in the one-cycle operation of K. In this case, there is a margin for the printer operation. That is, even if the printer finishes printing the first K1 signal and is ready to print out the second K2 signal, the scanner operation is half the speed of the printer operation. Information is not available, and continuous printing is not possible. Therefore, as apparent from the timing chart, the printing operation is interrupted.
[0197]
This means that not only the printer unit's potential printing speed can be utilized, but also the number of sheets printed out during that time will decrease even if the printer operates for the same time. In other words, useless operation time that does not contribute to printout occurs, and this causes the adverse effect of shortening the life of the machine and the life of the consumables such as the photosensitive drum.
[0198]
Next, a monochrome copy operation according to the present invention will be described with reference to (3) of FIG.
[0199]
As described above, the time required for the scanner to read a monochrome image using the K line and the time required for the printer to form a one-color image are 1: 1. As is clear from the time chart, if the balance between the scanner operation speed and the printer operation speed is good, useless time does not occur.
[0200]
That is, almost simultaneously with when the scanner starts reading the image information K1 of the first monochrome document on the K line, the printer starts the printing operation of the K1 signal, and almost when the scanner unit has finished reading the first image K1. At the same time, the printer unit finishes printing K1. Then, almost simultaneously with the start of reading the second image K2 on the K line by the scanner unit, the printer unit also starts printing K2. As described above, since the scan operation and the print operation proceed in synchronism with no dead time, the monochrome copy can be executed efficiently.
[0201]
Next, the operation for continuously copying different types of originals using the quadruple tandem color printer shown in FIGS.
[0202]
FIG. 19 is a timing chart showing operations of the scanner and the printer. In order to simplify the description, the time required for the scanner to read a color image using RGB lines and the time required for the printer to form a one-color image are 1: 1. It is a ratio.
[0203]
First, the color copy operation will be described with reference to (1) of FIG.
[0204]
First, the scanner reads the first original with the RGB sensor. In the timing chart, this first image reading information is represented as RGB1. The image processing unit converts the RGB1 signal into a YMCK signal used for printing. In the timing chart, the first YMCK signal converted by the image processing unit is represented as Y1, M1, C1, and K1, respectively.
[0205]
The printer unit starts outputting Y1 output from the image processing unit almost simultaneously with the start of the reading operation by the scanner unit. The outputs of M1, C1, and K1 are executed in parallel at a delay by the distance between the photosensitive drums of Y, M, C, and K.
[0206]
When the scanner unit starts reading the second original, the image processing unit starts to convert it into Y2, M2, C2, and K2, and the printer unit starts printing each signal.
[0207]
As is apparent from the timing chart, the scanner unit and the printer unit operate in synchronism, and no time is wasted.
[0208]
Next, the monochrome copy operation of the conventional configuration will be described with reference to (2) of FIG.
[0209]
As described above, when the printer unit outputs a monochrome image, the speed is four times as high. Accordingly, the time required for image formation is ¼.
[0210]
On the other hand, in the conventional configuration, since the scanner unit reads an original in RGB even for a monochrome image, there is no change in the time for capturing the image. Therefore, as shown in the timing chart, the printer unit starts outputting the monochrome image K1 after a while after the scanner unit starts the first document reading operation. As is apparent from the timing relationship, when the second copy is executed, the scanner unit starts reading the second original, and after a while the printer unit operates to output a black image. To do. When an image is output in this manner, only about 1/4 of the black image output capability of the printer unit can be used.
[0211]
Next, a monochrome copy operation according to the embodiment of the present invention will be described with reference to (3) of FIG.
[0212]
In the case of the configuration of the present invention, when copying a black image, the scanner unit can read the image at a speed four times that of color reading by using the K line shown in FIG. As shown in the timing chart, the time K1 required for capturing the monochrome image is ¼ of the time RGB1 required for capturing the previous color image. Accordingly, the printer unit can start operation almost at the same time when the scanner starts reading an image. Similarly, when copying the second sheet, the printer unit can form an image almost simultaneously with the start of reading of the image by the scanner unit. When an image is output in this way, the black image output capability of the printer unit can be fully utilized, and the performance can be increased four times.
[0213]
As described above, the embodiment according to the present invention is a one-line sensor without a color filter for reading a monochrome image in addition to a sensor for reading a color image (a three-line sensor having RGB color filters). Is incorporated in the color image reader.
[0214]
When performing monochrome copying, an image is read by a one-line sensor without a color filter, and a monochrome image is formed based on this image information. Since a one-line sensor without a color filter reads an image with one line, the image can be read sharply without color shift, and the read image quality is improved. In addition, since there is no filter, an image can be read at a higher speed and with higher sensitivity than a sensor with a color filter, so there is no need to increase the size of the scanner unit or mount a large light source.
[0215]
Further, since a conversion circuit for converting R, G, B signals into monochrome signals is not necessary, an inexpensive circuit configuration can be achieved.
[0216]
When copying monochrome images with a color MFP, high-speed, high-quality monochrome copying is possible by scanning images sharply at high speed with a single-line sensor without a color filter, and operating the printer at high speed in monochrome image formation mode. It has become. In addition, since the monochrome image reading operation of the scanner is fast even during monochrome continuous copying of different types of originals, there is no wasted time for print output, and the life of the apparatus and the life of consumables such as the photosensitive drum are not shortened.
[0217]
In the present embodiment, the optical filter is not disposed on the line sensor K of the 4-line CCD, but the present invention is not limited to this configuration, and a transparent optical filter member may be provided.
[0218]
In this embodiment, the printer unit is configured using an electrophotographic system. However, the printer unit is not limited to this mode, and may be configured using an inkjet method, a thermal printer, a known printing unit, or the like.
[0219]
【The invention's effect】
As described above, according to the present invention, it is possible to improve the quality of a monochrome copy image in a color MFP and a monochrome MFP having a color scan function.
[Brief description of the drawings]
FIG. 1 is a diagram showing an internal structure of an image forming apparatus according to a first embodiment of the present invention.
FIG. 2 is a diagram showing a 4-line CCD sensor.
FIG. 3 is a diagram showing spectral sensitivity characteristics of a line sensor K constituting a 4-line CCD sensor.
FIG. 4 is a diagram showing spectral sensitivity characteristics of line sensors R, G, and B.
FIG. 5 is a diagram showing a spectral distribution of a xenon lamp as a light source.
FIG. 6 is a diagram showing a schematic configuration of a 4-line CCD sensor.
FIG. 7 is a diagram illustrating signal output of a line sensor.
FIG. 8 is a diagram for explaining the signal output of the line sensor K;
FIG. 9 is a view for explaining signal output of the line sensor K;
FIG. 10 is a diagram showing an internal structure of an image forming apparatus according to a second embodiment of the present invention.
FIG. 11 is a diagram showing an internal structure of an image forming apparatus according to a second embodiment of the present invention.
FIG. 12 is a diagram showing an internal structure of an image forming apparatus according to a third embodiment of the present invention.
FIG. 13 is a diagram showing a control panel of a color MFP.
FIG. 14 is a block diagram showing a system configuration of a conventional color MFP.
FIG. 15 is a flowchart showing the operation of the color MFP system.
FIG. 16 is a block diagram showing a conventional configuration of a monochrome MFP capable of color scanning.
FIG. 17 is a flowchart showing the operation of the monochrome MFP system.
FIG. 18 is a timing chart illustrating operations of the scanner and the printer.
FIG. 19 is a timing chart showing operations of the scanner and the printer.
FIG. 20 is a diagram for explaining a phenomenon of image quality deterioration.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 2 ... Scanner part, 4 ... Process unit, 119 ... ADF, 117 ... CCD, 117a ... Light receiving part, 11 ... Photosensitive drum, 13 ... Exposure device, 14 ... Black developing device, 15 ... Revolver, 16 ... Intermediate transfer belt, DESCRIPTION OF SYMBOLS 201 ... Image forming apparatus 202 ... Optical unit 207 ... Transfer belt, 3Y ... Developing device, 3M ... Developing device, 3C ... Developing device, 3K ... Developing device, 4Y ... Photosensitive drum, 4M ... Photosensitive drum, 4C ... Photosensitive drum, 4K ... photosensitive drum.

Claims (2)

An image forming apparatus having a first copy mode for copying a copy original with a plurality of colors corresponding to the colors of the copy original and a second copy mode for copying the copy original with a single color,
Means for reading a document to be copied and outputting image information thereof; a first light receiving element array comprising a plurality of light receiving element arrays each provided with an optical filter that transmits light of different wavelength bands;
Means for reading a document to be copied and outputting image information thereof; a second light receiving element array comprising a single light receiving element array;
First conversion means for converting image information read in different wavelength bands into a signal for copying in a plurality of colors;
Second conversion means for converting information read by a single light receiving element array into a signal for copying in achromatic color;
Third conversion means for converting information read by a single light receiving element array into a signal for copying in a single chromatic color;
When copying in the first copying mode, the image information output from the first light receiving element array is converted into a signal for copying using the first converting means, and copying is performed in the second copying mode. In this case, the image information output from the second light receiving element array is converted into a signal for copying using the second conversion means, and the second light receiving is used in copying in the third copying mode. The first and second light receiving element arrays and the first, second and third converting means are controlled so as to convert image information output from the element array into a signal for copying using the third converting means. Control means;
An image forming apparatus comprising: The control means determines from the image information output from the first light receiving element array whether the document to be copied is a color document expressed in a plurality of colors or a single color document expressed in a single color. The image forming apparatus according to claim 1, wherein the first copy mode is selected and the second copy mode is selected in the case of an achromatic original.

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