JP3705639B2 - Color image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a color image forming apparatus such as a digital color copying machine and a color facsimile, and more particularly to operation control and image signal processing technology.
[0002]
[Prior art]
Conventionally, in digital color copiers, color facsimiles, etc., the input color signal is used to determine the chromatic and achromatic areas of the input image, and based on the result, whether the entire input image is an achromatic document or a chromatic document Then, various processing contents are switched according to the determination result. There is an automatic document feeder (hereinafter referred to as ADF) for continuously copying a plurality of documents.
[0003]
For example, in a certain type of color copying machine, a scanner for inputting an image by optical scanning is provided as an input means, and only one set of an image reproducing unit is provided, and a full-color image is obtained by repeating the copying process a plurality of times. It is like that. That is, the copy process for each of the four basic colors of cyan (C), magenta (M), yellow (Y), and black (Bk) (or only three of C, M, and Y) is sequentially executed. Then, these colors are transferred on one transfer sheet in a superimposed manner. When executing the single color mode (single color mode), one image is copied in one copy process.
[0004]
Therefore, in this type of copying machine, since the time required for the copying operation varies greatly between the full color mode and the single color mode, the operator needs to pay attention to the switching of the color mode. Switching operation must be performed.
[0005]
In order to eliminate this troublesome mode switching, in the technique disclosed in Japanese Patent Laid-Open No. 63-107274, whether or not an original is a specific color (or an original composed only of a specific color). And switching between the sequence operation of only a specific color or the sequence operation of full color. Here, a color copying machine equipped with a chromatic / achromatic automatic switching function with a specific color black has already been released.
[0006]
By the way, the operation determines whether the original is chromatic or achromatic by pre-scanning, and then determines and controls whether to operate in full-color mode or monochrome mode (pre-scan method), and the first operation. There are two types of methods: pre-scanless method, in which the image color is black and it is determined at the time of black image formation and the control for determining whether to continue the operation for the subsequent image formation color or to perform the transfer paper discharge as it is is there.
[0007]
[Problems to be solved by the invention]
However, in the former case, the first copy time is increased due to pre-scanning, and work efficiency is deteriorated.
[0008]
In the latter case, the picture part when the mode at the time of image formation is the photographic mode or the image is separated (determining whether it is a line drawing part or a picture part within a fine area of the image or in units of pixels and switching various processes). In general, the amount of under color removal (UCR) is limited to improve the reproducibility of the depth of the full-color image part, so the black density may be reduced or the image may not be imaged when determining black and white. There is a problem that it comes out. That is, in the pre-scanless state, black development is performed while reading a document. At that time, black processing is performed in full color, and the density is lowered.
[0009]
The present invention has been made in view of such a background, and presupposes the adoption of an automatic chromatic / achromatic original determination method (ACS; Auto Color Select) based on a pre-scanless method that does not increase the first copy time. An object of the present invention is to provide a color image forming apparatus capable of preventing the density of black from being lowered or a portion not being imaged from appearing at the time of black and white determination.
[0010]
[Means for Solving the Problems]
  The color image forming apparatus according to claim 1 is an image reading unit that reads an original image, an input unit that inputs a multicolor image signal generated by the image reading unit, and the multicolor input image is a chromatic color original. Discriminating means for discriminating whether the document is an achromatic manuscript,Output by colorSelecting means for selecting whether to output the image in one color or only one color, an output means for realizing and outputting an image in the output mode selected by the selecting means, and an automatic document feeder, In a color image forming apparatus comprising:
  Detecting means for detecting the size of the document by feeding the document from the automatic document feeder;
  Automatic document feederfromWhen feeding the document, move the image reading unit to the position where you can read the document in advance, scan the document being fed,About the range determined based on the document size and magnification detected by the detection means,Control means for determining whether the multicolor input image is a chromatic original or an achromatic original and executing either single color processing or full color processing according to the determination result is provided.
[0011]
The color image forming apparatus according to claim 2 is the color image forming apparatus according to claim 1, wherein the control unit sends a timing signal and main scanning of the leading and trailing edges of the document from the automatic document feeder to the image reading unit. The sub-scan size is notified, and control is performed to determine the region and timing for determining whether the multicolor input image is a chromatic color original or an achromatic original according to the notified data, transfer sheet size, scaling ratio, and mode. It is characterized by that.
[0012]
A color image forming apparatus according to a third aspect of the present invention is the color image forming apparatus according to the first aspect, wherein the control means controls the leading edge and trailing edge timings of the document from the automatic document feeder to the image reading means when the spread document is divided. In addition, the first and second originals are notified of the main scanning and sub-scanning sizes, and the multicolor input image is a chromatic original or an achromatic original depending on the notified data, transfer paper size, and scaling ratio. Determining the region and timing for determining whether or not the first and second discriminating results are stored, and at the time of copying each original, control is performed to embody and output an image according to the discriminating results. And
[0013]
A color image forming apparatus according to a fourth aspect of the present invention is the color image forming apparatus according to the first aspect, wherein when the two single-sided originals are aggregated, the control means feeds the first original from the automatic original feeder to the image reading means. Timing signal indicating the leading edge and trailing edge of the second document, the size of main scanning and sub scanning, and multi-color input based on the image range data, transfer paper size and scaling ratio for the two sheets A color image forming apparatus that performs control for determining an area and timing for determining whether an image is a chromatic original or an achromatic original.
[0014]
The color image forming apparatus according to claim 5 is the color image forming apparatus according to claim 1, wherein the control unit is configured to transfer the original document from the automatic document feeder to the image reading unit at the time of duplex document division and duplex document duplex copy. The size of scanning and sub-scanning is notified, the image reading unit is moved by the sub-scanning of the document during the document reversing operation, the document is reversed, and the document is returned to the stop position of the image reading unit. A color image that notifies edge timing and performs control to determine whether a multicolor input image is a chromatic original or an achromatic original according to the notified data, transfer paper size, and scaling ratio. Forming equipment.
[0015]
The color image forming apparatus according to claim 6 is the color image forming apparatus according to claim 1, wherein the control unit determines whether the multicolor input image is a chromatic original or an achromatic original, A color image forming apparatus, wherein an image reading unit is returned to a normal position to perform a copying operation.
[0016]
As described above, when using the ADF, in each mode, it is determined whether the original is chromatic or achromatic while feeding the ADF original. In other cases, the copying operation in the full color mode can solve the problem that the density of black at the time of black and white determination is lowered or a portion where no image is formed appears.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a block diagram of a one-drum digital color copying machine.
The copying machine includes a laser printer 100, an ADF 200, an operation board 300, and an image scanner 400.
[0018]
First, the laser printer 100 will be described.
Image reproduction is performed on the photosensitive drum 1. Around the photosensitive drum 1, a charging charger 5, a writing unit 3, a developing unit 4, a transfer drum 2, a cleaning unit 6, and the like are provided.
[0019]
First, the surface of the photosensitive drum 1 is uniformly charged to a high potential by a corona current generated by the charging charger 5. When this surface is irradiated with laser light emitted from the writing unit 3, the charging potential changes according to the intensity of the light. That is, a potential distribution according to the presence or absence of irradiation of laser light emitted from the laser diode is formed on the photosensitive drum 1.
[0020]
Laser light emitted from a laser diode (not shown) of the writing unit 3 is irradiated onto the surface of the photosensitive drum 1 through the polygon mirror 3b, the lens 3c, the mirror 3d, and the lens 3e. The polygon mirror 3b is driven to rotate at a constant speed by a motor 3a.
[0021]
The control device applies a binary signal (recorded / not recorded) corresponding to the image to be recorded to the laser diode so that each pixel position is synchronized with the rotational position of the polygon mirror 3b. In other words, at each scanning position of the image, the laser beam is on / off controlled according to the density of the pixel (recorded / not recorded).
[0022]
Therefore, the potential distribution formed on the photosensitive drum 1 constitutes an electrostatic latent image corresponding to the density of the original image. This electrostatic latent image is visualized by the toner of the developing unit 4 disposed downstream of the writing unit 3. In this example, the developing unit 4 includes four sets of developing devices 4M, 4C, 4Y, and 4Bk, and each developing device has toners of different colors, M, C, Y, and Bk. Is retained.
[0023]
In the case of this printer, since any one of the four developing devices is selectively energized, the electrostatic latent image is visualized with M, C, Y, or Bk toner.
[0024]
On the other hand, the transfer paper held in the cassette 11 is fed out by the paper feed roller 12, sent to the surface of the transfer drum 2 through the registration roller 13, and overlapped with the surface of the transfer drum 2 as the transfer drum 2 rotates. Move. Then, the toner image formed on the photosensitive drum 1 is transferred to the surface of the transfer paper by the urging of the transfer charger 7 in the state of being close to the surface of the photosensitive drum 1.
[0025]
In the single color mode, the transfer paper on which the transfer of the toner image has been completed is separated from the transfer drum 2 by the action of the separation charger 8 and the separation claw, fixed by the fixing device 9 and discharged to the paper discharge tray 10. Is done. In the case of the full color mode, it is necessary to superimpose four colors Bk, M, C, and Y on one transfer sheet.
[0026]
In that case, a Bk toner image is first formed on the photosensitive drum 1 and transferred to the transfer paper, and then the M-color toner image is formed on the photosensitive drum 1 without separating the transfer paper from the transfer drum 2. A toner image is formed, and the toner image is transferred again to the transfer paper. Further, for the C and Y colors, toner images are formed on the photosensitive drum 1 and transferred onto a transfer sheet. That is, by repeating the toner image formation and transfer process four times, one color image is formed on the transfer paper. When the transfer of all the toner images is completed, the transfer paper is separated from the transfer drum 2, fixed on the toner image by the fixing device 9, and then discharged to the paper discharge tray 10.
[0027]
The ADF 200 is disposed above the image scanner 400. A large number of documents can be held on the document table 210 in a stacked state. When the paper feeding operation is performed, the calling roller 212 comes into contact with the upper surface of the uppermost original and rotates to feed out the original in contact. A separation roller 213 for avoiding double feeding is provided. The document fed to a predetermined position is further conveyed on the contact glass 401 of the image scanner 400 by driving the pull-out roller 217 and the conveyance belt 216, and advances to a predetermined reading position, that is, the leading edge of the document is contact glass 401. Stops when the left end position is reached. When the reading is completed, the conveying belt 216 is driven again, so that the document on the contact glass 401 is discharged, and the next document is sent to the reading position.
[0028]
An optical sensor 211 is provided in front of the calling roller 212 for detecting whether or not there is a document on the document table 210. An optical sensor 214 for detecting the leading edge and size of the document is provided between the separation roller 213 and the pull-out roller 217. The optical sensor 214 is composed of a plurality of sensors arranged at positions different from each other in the main scanning direction (direction perpendicular to the paper surface), and the original size in the main scanning direction, that is, the original is determined by a combination of detection states of these sensors. The width can be detected.
[0029]
The drive motor (not shown) is provided with a pulse generator that outputs a pulse corresponding to the amount of rotation. The control device of the ADF 200 allows the number of pulses of the pulse generator and the document to pass through the optical sensor 214. The document size in the sub-scanning direction, that is, the length of the document and the amount of movement of the document can be detected, and signals indicating the document size and the leading edge and the trailing edge of the document can be generated.
[0030]
The calling roller 212 and the separation roller 213 are driven by a paper feed motor, and the pull-out roller 217 and the transport belt 216 are driven by a transport motor. The optical sensor 215 disposed downstream of the pull-out roller 217 is a registration sensor.
[0031]
The image scanner 400 mechanically drives an image reading unit disposed below the contact glass 401 in the left-right direction in the drawing, and performs sub-scanning. Light emitted from the illumination lamp 402 is reflected on the surface of the document placed on the contact glass 401 according to the density of the document image. This reflected light, that is, the detected light image, passes through a number of mirrors and lenses and enters the dichroic prism 410. The dichroic prism 410 separates incident light into three colors of R, G, and B according to the wavelength. The three separated lights are incident on different one-dimensional CCD image sensors. Therefore, each of the R, G, and B color components of one line in the main scanning direction on the original image can be detected simultaneously by the three one-dimensional image sensors provided in the image scanner 400. A two-dimensional image of the document can be read by sub-scanning of the image reading unit.
[0032]
FIG. 2 is a system block diagram of a digital color copying machine according to an embodiment of the present invention.
The overall control of the apparatus is controlled by a system controller 20 constituted by a microcomputer or the like. The synchronization control circuit 31 generates a clock pulse serving as a reference for control timing, inputs various signals in order to synchronize signals between the control units, and outputs various signals. In this example, the main scanning synchronization signal that is the basis of the scanning timing appears in synchronization with the scanning position of the polygon mirror of the laser printer 100.
[0033]
The image scanner 400 A / D converts the read R, G, and B color image signals, and outputs each as 8-bit color image information. This image information is output to the laser printer 100 after undergoing various processes in the image processing unit.
[0034]
The image processing unit includes a γ correction unit 21, a complementary color generation unit 22, a UCR unit 23, selectors 24 and 25, a gradation processing unit 26, a chromatic / achromatic determination unit 27, an image separation unit 28, and a delay memory 29. Each unit of the external I / F 30 is provided.
[0035]
The complementary color generation unit 22 converts each information of R, G, and B into information of each color of C, M, and Y using a masking equation or the like. The UCR unit 23 calculates Bk from the minimum values of C, M, and Y, and removes the black component from the input Y, M, and C signals. The UCR unit 23 outputs different black amounts in the character mode and the photo mode. The UCR unit 23 will be described in more detail later.
[0036]
The output of the γ correction unit 21 is sent to the chromatic / achromatic determination unit 27 and the image separation unit 28 simultaneously with the color correction unit (complementary color generation unit 22). The chromatic / achromatic determination unit 27 determines whether the input image is chromatic or achromatic for each pixel or each micro area block. In addition, the image separation unit 28 determines whether it is a line drawing or a pattern portion for each pixel or each micro area block. The determination signal is sent to the UCR unit 23 and the gradation processing unit 26, and is used for selection of a black amount, selection of a dither pattern, and the like.
[0037]
The selector 24 selectively outputs any one of Y, M, C, and Bk input in response to an instruction from the system controller 20 and applies it to the gradation processing unit 26. The gradation processing unit 26 performs dither processing on the input 8-bit density information. The dithered image information is applied to the laser printer 100.
[0038]
3A and 3B are explanatory diagrams of UCR in the full color mode.
A UCR in a normal full color mode will be described with reference to FIG. In the character mode or separation mode, when the image separation signal is a character, C, M, and Y are calculated from R, G, and B by nonlinear matrix calculation, and the minimum value of C, M, and Y is set to Bk. Further, Bk is subtracted from C, M, Y, and C ′, M ′, Y ′ are newly output as C, M, Y signals.
[0039]
Here, if the chromatic / achromatic determination signal for each pixel or each micro area block is determined to be achromatic, the C, M, and Y signals may be set to zero. When the image separation signal in the photo mode or the image separation mode is a picture, the minimum value of C, M, and Y itself is not set to Bk, but about 70% to 90% of the minimum value is set to Bk.
[0040]
This ratio may not be constant with respect to all the minimum values, and may be a method (skeleton black method) in which the ratio is increased as the data increases as it is almost 0% when the data is small. In any case, the reason why the black amount is not set to 100% is that black components are mixed over the entire recorded image, so that it is difficult to match the gradation of C, M, and Y, and a full color image is obtained. This is because there is a problem that the depth of the image is lost.
[0041]
However, even if it is 100%, it is also true that image quality deterioration can be suppressed as much as possible by controlling parameters of gradation processing and the like after that, compared to the case of about 80%. The Bk calculated in this way is subtracted from C, M, and Y to obtain new C, M, and Y as in the case of characters.
Here, in order to simplify the UCR circuit, Bk may be calculated at the same time when C, M, and Y are obtained from R, G, and B, and the UCR may be simply subtracted.
[0042]
In the case of single color modes such as Bk, C, M, Y, R, G, and B, a signal including all color components is calculated in advance from the R, G, and B signals by color correction (for example, R : G: B is set to 3: 6: 1) The UCR outputs this signal itself.
[0043]
In the system controller 20, the selection of single color is Bk, C, M, Y
In the case of, one of the image forming units is selected and controlled. In addition, this operation is repeated when a color necessary for two or more image formations such as R, G, and B has been selected. Needless to say, when a color that can be selected as a single color cannot be realized with the same values as the values of Bk, C, M, and Y, a value corresponding thereto is calculated by color correction. In the case of the single color mode, the signal is calculated regardless of the mode and the image separation result.
[0044]
FIG. 4 is a block diagram of the chromatic / achromatic determination unit 27.
The operation of chromatic / achromatic determination will be described based on this figure.
The R, G, and B 8-bit data for each pixel output from the image scanner 400 is detected by the difference detection unit 41 after the tone balance for each color is aligned by the γ correction unit 21 of the image processing unit. The maximum value calculation unit 42 calculates the maximum difference (d [i, j] = ΔRGB) of R, G, and B. Next, the number of pixels in which d [i, j] is smaller than the threshold value TH1 determined in units of 4 lines × 4 pixels is counted using the TH comparison unit 43 and the counter / TH comparison IC 44. When this number is larger than the threshold value TH2 in 16 pixels, this block is determined as a chromatic block (SG2 = H).
[0045]
Both of the two counters 45 and 46 for counting the chromatic block frequency and continuity are counted up by the determination signal for each block. The continuity counter 46 is reset when the block determination result becomes L. When one of the two counters 45 and 46 reaches a preset value, this document is determined to be chromatic. The chromatic / achromatic determination is performed only during Bk image formation, or the determination result is valid only during Bk image formation.
[0046]
If chromaticity determination is not made during Bk image formation, the system controller 20 performs control so that the sheet is transferred and discharged as it is. The image obtained here is exactly the same as in the single color monochrome mode.
In addition, the chromatic / achromatic determination unit 27 includes a line counter 47, a comparator 48, and a register 49 as shown in the figure.
[0047]
FIG. 5 is a block diagram of a color correction / UCR switching unit using a chromatic / achromatic determination signal.
First, the color is set to Bk single mode color correction and UCR. Here, a scanning operation for Bk image formation is performed, and at the same time, chromatic / achromatic determination is started. The case where chromatic determination is given will be described.
[0048]
When the chromatic determination is issued, the chromatic determination signal is immediately sent to the color correction unit (masking circuit; complementary color generation unit 22) and the UCR unit 23 via the selector 50, and the color correction unit and the UCR unit 23 are used for full color. Can be switched. When scanning for BK image formation is completed, C, M, and Y image formation is performed with the next full color processing. The determination result during the Bk image formation is sent to the system controller 20 by the end of the Bk image formation, and the image scanner 400, the printer 100, and the like are controlled to take a full color operation.
[0049]
The full color UCR used here is as high as possible, preferably 100%. If a low UCR ratio is used, after UCR on the image processed for Bk single mode with sufficient density that was used until chromatic judgment was obtained during C, M, Y image formation. This is because C, M, and Y are loaded and the density becomes high.
[0050]
Alternatively, the following method may be used. The address at which chromatic determination is given during Bk image formation is stored, and thereafter, Bk image formation is performed using a UCR ratio of less than 100%. Thereafter, for C, M, and Y, conversion is performed with 100% UCR up to the stored address, and conversion is performed with a normal UCR ratio after this address.
[0051]
In this case, in order to maintain the entire gradation, the gradation processing parameters may be switched in conjunction with the switching of the UCR. The switching at the time of C, M, and Y may be performed by outputting a switching signal from the chromatic / achromatic determining unit 27 or by sending an address to the system controller 20 and outputting the switching signal therefrom.
[0052]
In the chromatic / achromatic determination, it is apparent that there is a delay of at least 3 lines and 3 pixels. Therefore, a delay memory 29 for delaying data is arranged between the γ correction unit 21 and the color conversion unit (complementary color generation unit 22), or between the color conversion unit and the UCR unit 23, so as to delay three lines or more pixels. . In order to facilitate synchronization, the delay amount may be determined for each line.
Also, when repeating (that is, when copying a plurality of images with the same document instead of one-to-one copying), only the first sheet is operated as described above, and the second and subsequent sheets are the first sheet. The image is formed according to the mode determined by the determination result.
[0053]
Now, the case of reading from the image scanner 400 and outputting directly to the printer 100 has been described. However, when using only a printer having an external interface before the color conversion unit, or after converting to BK, C, M, Y, The present invention is also effective in reducing the processing speed when outputting to the external unit again.
[0054]
Next, the sequence in each ADF mode will be described with reference to FIG. In the operation corresponding to the first and second aspects of the invention, when the copy button is pressed after the document is set on the ADF 200, the carriage 403 of the image scanner 400 is separated from the home position sensor 404 and slightly to the right of the scale 405. Move to the position, turn on the lamp, and enter the image reading state.
[0055]
On the other hand, the ADF 200 notifies the size of the main scan during document feeding. Also, the image scanner 400 determines the ACS range based on the mode sent from the system controller 20. For example, if the transfer paper A4 is 100% and the ADF 200 notifies the A4 size, the ACS range is A4.
[0056]
Next, when a signal indicating the leading edge of the document sent from the ADF 200 is sent, the chromatic / achromatic discrimination is started. After the A4 size is finished, the discrimination is finished, and the carriage 403 is returned to the position of the home position sensor 404. The determination result is notified to the system controller 20, and single color processing or full color processing is performed depending on the result. The above procedure is summarized as follows.
[0057]
(1) The user sets an original on the ADF 200 and presses the copy button after mode confirmation (the original is A4, 100%, transfer paper A4, no aggregation / division, etc.).
(2) The ADF 200 moves the carriage 403 slightly to the right of the scale 405 at the same time as the document feeding starts, with the lamp lit.
(3) The ADF 200 notifies the document main scanning and sub-scanning sizes. The determination range is determined by this and the mode.
(4) The ADF 200 sends a document leading edge passing signal to the image scanner 400 when the document reaches the position of the carriage 403. Thereby, the discrimination is started.
(5) After completion of the determination, the image scanner 400 immediately returns the carriage 403 to the home position.
(6) After passing through the document, the ADF 200 notifies the image scanner 400 of a signal indicating the trailing edge of the document. This completes the determination, notifies the system controller 20 of the determination result, and starts a single color or full color sequence depending on the result.
[0058]
Similarly, at the time of split-page original division described in the invention of claim 3, for example, when the original is A3 and the transfer sheet A4 is 100%, the determination is made for each A4 size of the original of A3. That is, the determination is made only by the range of the document to be read.
[0059]
Similarly, when two single-sided originals are collected according to the invention of claim 4, it is determined whether the size of the two originals is chromatic or achromatic. That is, when two A4 originals are 100% on the transfer paper A3, the determination is made for the two A4 originals. At this time, since there is a gap between the first and second sheets, it is determined by signals indicating the leading and trailing edges of the document.
[0060]
At the time of double-sided original division and double-sided original double-sided copying according to the fifth aspect of the invention, the document is once reversed by the reversing unit 218 (FIG. 6) of the ADF 200 and then returned to the position of the scale 405. Then, after moving the carriage 403 and reversing the document, when returning the document, the document is read to determine whether it is chromatic or achromatic. That is, since the document size is known before the reversing operation, the carriage 403 is moved by that size, and the discrimination circuit is operated when the reversed document passes.
[0061]
【The invention's effect】
According to the first to sixth aspects of the invention, in the automatic chromatic / achromatic determination by the pre-scanless method, when the ADF is used, the original is being fed before the start of copying according to all modes using the ADF. Since chromatic or achromatic is discriminated, there is no delay until the first copy like the pre-scan method, and the image quality deteriorates in the black and white mode, which is a disadvantage of the conventional pre-scanless method. Can also be avoided.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a one-drum digital color copying machine.
FIG. 2 is a system block diagram of a digital color copying machine according to an embodiment of the present invention.
FIG. 3 is an explanatory diagram of UCR in a full color mode.
FIG. 4 is a block diagram of a chromatic / achromatic determination unit.
FIG. 5 is a block diagram of a color correction and UCR switching unit using a chromatic / achromatic determination signal.
FIG. 6 is an explanatory diagram showing the position of the carriage of the image scanner when the ADF mode is executed.
[Explanation of symbols]
20 System controller (control means)
100 printer
200 ADF
300 Operation unit
400 image scanner
403 Carriage

Claims (6)

Image reading means for reading an original image, input means for inputting a multicolor image signal generated by the image reading means, and determination means for determining whether the multicolor input image is a chromatic original or an achromatic original Selection means for selecting whether the output is divided and output for each color or only one color, and output means for realizing and outputting an image in the output mode selected by the selection means; In a color image forming apparatus provided with an automatic document feeder,
Detecting means for detecting the size of the document by feeding the document from the automatic document feeder;
When a document is fed from the automatic document feeder, the image reading unit is moved to a position where the document can be read in advance, the document being fed is read, and the range determined based on the document size and magnification detected by the detection unit, A color image characterized by comprising a control means for determining whether a multicolor input image is a chromatic original or an achromatic original and executing either single color processing or full color processing according to the determination result Forming equipment.   2. The color image forming apparatus according to claim 1, wherein the control unit notifies the image reading unit of the timing signal and the main scanning and sub scanning sizes of the document from the automatic document feeder to the notified data. And a color image forming apparatus for performing control for determining a region and timing for determining whether a multicolor input image is a chromatic original or an achromatic original depending on a transfer paper size, a scaling factor, and a mode.   2. The color image forming apparatus according to claim 1, wherein the control means sets the timing of the leading and trailing edges of the original and the size of the main scanning and the sub scanning from the automatic document feeder to the image reading means when the two-page spread original is divided. The second document is notified, and the region and timing for determining whether the multicolor input image is a chromatic document or an achromatic document are determined according to the notified data, transfer paper size, and scaling ratio. A color image forming apparatus characterized by storing the discrimination results of the first and second sheets, and performing control for embodying and outputting an image according to the discrimination results when copying each original.   2. The color image forming apparatus according to claim 1, wherein when the two single-sided originals are aggregated, the control means feeds the leading edge and the trailing edge of the first document from the automatic document feeder to the image reading means, and the leading edge of the second document. The timing signal indicating the trailing edge and the size of the main scanning and sub-scanning are notified, and the multicolor input image is a chromatic original or an achromatic original depending on the image range data for two sheets, the transfer paper size, and the scaling ratio. A color image forming apparatus which performs control for determining an area for determining whether or not there is a timing.   2. The color image forming apparatus according to claim 1, wherein the control unit notifies the image scanning unit of the main scanning and sub-scanning sizes from the automatic document feeder during duplex document division and duplex document duplex copying, and document inversion. During the operation, the image reading unit is moved by sub-scanning of the document, and after the document is reversed, the timing of the leading and trailing edges of the document is notified when the document is returned to the stop position of the image reading unit, and the notified data, A color image forming apparatus that performs control to determine whether a multicolor input image is a chromatic color original or an achromatic original according to a transfer paper size and a scaling ratio.   2. The color image forming apparatus according to claim 1, wherein the control unit determines whether the multicolor input image is a chromatic original or an achromatic original, and then returns the image reading unit to a normal position to perform a copying operation. A color image forming apparatus.

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