JP3560640B2 - Digital copier - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to a digital copying apparatus capable of outputting read image data in black and colors other than black.
[0002]
[Prior art]
As one of the conventional digital copying apparatuses, a digital copying apparatus having a two-color copy mode capable of outputting read image data in two colors of black and colors other than black has been provided. In general, such a digital copying apparatus is configured to process RGB reading signals in parallel, and the background removing apparatus that corrects the density of the background of a document to remove the background also supports the three colors of RGB. It is prepared for you.
[0003]
However, when the background removal devices are arranged corresponding to the three colors of RGB and the background removal is performed for each color by the three background removal devices, the operation of the background removal device varies. When the color mode copy is performed, there is a disadvantage that the gray balance is lost and the color detection does not work well.
[0004]
For this reason, in order to perform color detection with high accuracy, a high-precision AE mechanism is mounted as disclosed in Japanese Patent Application Laid-Open No. Hei 4-21266, "Digital Scanner Sensitivity Adjustment Device", to change the copy image density. There has been provided an apparatus that prevents occurrence of color and can perform color detection with high accuracy.
[0005]
[Problems to be solved by the invention]
However, according to the above-mentioned conventional technology, since it is necessary to mount a high-precision AE mechanism, there are problems that the number of components constituting the device increases and that the cost increases.
[0006]
The present invention has been made in view of the above, and an object of the present invention is to enable color detection to be performed normally without increasing the number of parts constituting an apparatus and increasing the cost.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides an image reading means for optically reading an original image and image data read by the image reading means, and corrects the density of the background of the original to remove the background. Background removal means, image output means for outputting image data input via the background removal means in black and colors other than black, and designation for designating whether the original is copied in a single color or in multiple colors Means for controlling the execution and prohibition of the operation of the background removing means, and when a single-color copy is designated via the designation means, The background removal unit is operated to execute the background removal, and when multi-color copying is designated, the background removal is prohibited by the control unit so that the gray balance of the output data is maintained. It is intended.
[0008]
Further, according to the present invention, when the specifying means is an operation panel of a digital copying apparatus, the multicolor copying is a two-color copy mode, and the control means specifies the two-color copy mode from the operation panel, The operation of the background removing means is prohibited.
[0009]
Also, the present invention provides an A / D converter in which the background removing means receives an RGB analog input signal, compares the analog input signal with a reference voltage and determines a digital data output, and A Vref determination circuit for determining the reference voltage from the voltage value obtained by the peak hold means for holding the maximum voltage value.
[0010]
[Action]
The digital copying apparatus of the present invention operates the background removing means to execute the background removal when the copying in single color is designated, and executes the operation of the background removing means when the copying in the multicolor is designated. Inhibiting the background removal and avoiding the gray balance collapse at the time of multicolor copying.
[0011]
When the two-color copy mode is designated from the operation panel, the operation of the background removing unit is prohibited. In the background removing means, the Vref determining circuit determines a reference voltage from the voltage value obtained by the peak hold means, and the A / D converter compares the analog input signal with the reference voltage to determine digital data output.
[0012]
【Example】
Hereinafter, an embodiment of the digital copying apparatus of the present invention will be described.
(1) Schematic configuration and operation of the digital copying apparatus of this embodiment (2) Overall configuration of image processing unit (3) Configuration and operation of video processing circuit (4) Configuration and operation of image processing circuit (5) Two-color copy The operation of the mode will be described in detail with reference to the drawings.
[0013]
(1) Schematic Configuration and Operation of Digital Copying Apparatus of the Present Embodiment FIG. 1 shows a schematic configuration diagram of a digital copying apparatus of the present embodiment. This digital copying apparatus is roughly divided into a scanner unit 101 and a plotter unit 111. The necessary copy conditions are set by an operation panel 201, which will be described later. When the copy start key on the button 201 is pressed, the scanner unit 101 starts reading a document image on the contact glass 102.
[0014]
That is, by moving the traveling body 105 integrated with the first mirror 103, the light source 104, and the like to the left in the drawing, the lower surface (image surface) of the original placed on the contact glass 102 is optically scanned (scanning). ). Thereby, the reflected light image from the document surface is sequentially guided to the lens 108 via the first mirror 103, the second mirror 106, and the third mirror 107, and is formed on the light receiving surface of the CCD color image sensor 109. Note that the image data read by the CCD color image sensor 109 is output to an image processing unit 200 described later, and subjected to image processing.
[0015]
On the other hand, the plotter unit 111 receives the image data processed by the image processing unit 200 and forms an image on transfer paper. That is, at the same time as rotating the photosensitive drum 112 in the direction of the arrow in the figure, the remaining toner and the uneven potential attached to the photosensitive drum 112 do not reach the charging charger 113 and the developing devices 114 and 115. The surface of the photosensitive drum 112 after passing through the neutralizing lamp 116 by driving the neutralizing lamp (QL) 116, the neutralizing lamp before transfer (PTL) 117, the transfer charger 118, the separation charger 119, the eraser 120, and the cleaning unit 121. The potential is set to approximately zero.
[0016]
Thereafter, the surface of the photosensitive drum 112 is uniformly charged by the charging charger 113, and a laser beam is emitted from a semiconductor laser 144a described later according to the black image data. The laser light emitted from the semiconductor laser 144a is condensed by a cylinder lens (not shown) and is incident on a polygon mirror (laser light generator) 122 that rotates and scans, and the reflected light is reflected by an optical system (lens) 123 and a mirror 124. And irradiates the surface of the photosensitive drum 112 via the, to form an electrostatic latent image.
[0017]
Next, the latent image formed on the photosensitive drum 112 is removed by an eraser 120 from a non-image portion (unnecessary portion protruding from an image forming area), and black toner is adhered by a black developing device 115 to form a visible image. Become At this time, the density of the image can be adjusted by changing the developing bias potential.
[0018]
Next, an electrostatic latent image is formed again on the surface of the photosensitive drum 112 by the light emission of the LED array 140 according to the color image data, and a color toner is adhered by the color developing unit 114 to make the image visible.
[0019]
The formation of the electrostatic latent image of the color image with respect to the black image is adjusted using a predetermined memory (not shown) because the image position on the transfer paper does not match unless the image is delayed by a predetermined time. . This time is obtained by dividing the distance from the exposure position on the photosensitive drum 112 by the semiconductor laser to the exposure position by the LED array 140 by the rotation speed of the surface of the photosensitive drum.
[0020]
On the other hand, by turning on a paper feed clutch which can selectively take out the drive of a main motor (not shown), one of the call rollers 125, 126a, 126b and 126c is driven and set to a preselected paper feed stage (described later). Is fed to the stopped registration roller pair 127.
[0021]
A registration sensor 128 is provided in front of the registration roller pair 127. The registration sensor 128 is, for example, a reflection type photo sensor, and is turned on when the leading end of the transfer paper arrives at a position facing the registration sensor 128. After a lapse of a predetermined time since the registration sensor 128 is turned on, the paper feeding clutch is returned to the off state, and the transfer paper being conveyed is stopped.
[0022]
The OFF timing of the paper feed clutch is set longer than the time during which the transfer paper is transported between the registration sensor 128 and the registration roller pair 127. Therefore, the leading end of the transfer paper is applied to the pair of registration rollers 127, and the transfer paper is deflected on the leading end side to stand by in a state where skew or the like is prevented. Thereafter, a registration clutch (not shown) is turned on at a timing corresponding to the leading edge of the black image on the photosensitive drum 112, and the registration roller pair 127 is driven to rotate. Transported again toward.
[0023]
When the transfer paper arrives at the transfer section, the toner image on the photosensitive drum 112 is transferred onto the transfer paper by the action of the transfer charger 118, and subsequently the paper surface is operated by the action of the separation charger 119 which is integrally held with the transfer charger 118. After lowering the above charging potential to reduce the adhesion between the transfer paper and the photosensitive drum 112, the transfer paper is separated from the surface of the photosensitive body by a separation claw (not shown).
[0024]
Next, the transfer paper is sent to a fixing unit by a transport belt 130 stretched by two rollers, and the toner image is thermally fixed by the fixing roller 131. Then, if a one-sided mode is selected as a copy mode, a switching claw is used. The paper is discharged to the external paper discharge tray 133 through the upper side of 132 and is sent to the lower re-feeding conveyance path by switching of the switching claw 132 if the duplex mode is selected.
[0025]
The residual toner on the photosensitive drum 112 after the image transfer is removed by a cleaning brush 121a and a cleaning blade 121b constituting the cleaning unit 121 and collected in a toner collection tank 121c. The entire surface is exposed by a discharge lamp 116.
[0026]
In this copying apparatus, "red toner" and "blue toner" can be used as color toners, and the operator can use the color developing device 114 for the toner of the required color by removing and replacing the toner appropriately. .
[0027]
In addition, this copying apparatus is detachably provided with three paper cassettes 134 to 136 each containing transfer paper of a different size as ordinary paper cassettes that can collectively store only transfer paper of a specific size. Also provided is a manual feed table (manual feed tray) 137 on which transfer paper not stored in any of the paper feed cassettes, that is, transfer paper of an unspecified size can be set.
[0028]
When copying using transfer paper stored in any of the paper feed cassettes 134 to 136, the user selects the cassette size using the size selection key on the operation panel 201 and then presses the copy start key. As a result, the transfer paper is fed from the paper feed cassette.
[0029]
Reference numerals 138a to 138c denote size detection sensors for detecting the size of each sheet stored in each of the paper feed cassettes 134 to 136. For example, five photo interrupters are used.
[0030]
(2) Overall Configuration of Image Processing Unit FIG. 2 is a block diagram showing a schematic configuration of the image processing unit 200 of the present embodiment. The image processing unit 200 controls a video processing circuit 141 that inputs and converts A / D analog signals of RGB read by the CCD color image sensor 109, an image processing circuit 142 that performs image processing, and a plotter unit 111. A video writing processing circuit 143, an LD control unit 144 for controlling the semiconductor laser 144a, an LED control unit 145 for controlling the LED array 140, a CPU 146 for controlling the entire device, and a control program are stored. ROM 147 and a RAM 148 temporarily used by the control program. In the figure, reference numeral 151 denotes an address data bus, 152 denotes a system bus, and 201 denotes an operation panel for the user to set various modes to input numerical values.
[0031]
As shown in the figure, the video processing circuit 141, the image processing circuit 142, and the video writing processing circuit 143 share an address bus and a data bus with the CPU 146, and communication is performed through the shared bus. The CPU 146 also controls the motors of the scanner unit 101 and the plotter unit 111. It also controls various clutches and solenoids.
[0032]
(3) Configuration and Operation of Video Processing Circuit Next, a specific configuration and operation of the video processing circuit 141 will be described. FIG. 3 shows a part of the circuit configuration of the video processing circuit 141. The CCD color image sensor 109 outputs the read RGB analog signals by dividing them into odd pixels and even pixels. This analog signal is pre-amplified by the amplifiers 301 and 302 and then converted into a DC level signal by the zero clamp circuits 303 and 304.
[0033]
After that, the odd number pixel and the odd number pixel are combined into one channel by the multiplexer 305, the light amount is corrected by an AGC (auto gain amplifier) 306, and input to the A / D converter 307.
[0034]
The A / D converter 307 is configured to compare the Vref input from the Vref determination circuit 308 with the input _VIN and output digital data Dw. Therefore, if the Vref determination circuit 308 changes Vref, the A / D conversion characteristics change. In the figure, reference numeral 309 denotes a gain determining circuit for determining the gain DAGC of the _AGC 306, and reference numerals 310 and 311 denote ROM and RAM.
[0035]
Next, the configuration of the Vref determination circuit 308 will be described with reference to FIG. The Vref determination circuit 308 generates Vref using the analog signal V. In the figure, the peak hold circuit 401 detects Vb = Va, max = R4 / (R3 + R4) * Vmax in order to obtain the maximum value of Va = R4 / (R3 + R4) * V.
[0036]
Eventually, Vref outputs R4 / (R3 + R4) * (R5 + R6) / R6 * Vmax = A * Vmax or Vc, whichever is larger. Therefore, Tr2 is turned ON, so that A * Vmax is generally selected.
[0037]
The background removal operates by using the Vref determined in this way as a reference voltage of the A / D converter 307. The analog signal of the read image is A / D-converted by an A / D converter 307 and output as 8-bit digital data RDT0-7, GDT0-7, BDT0-7 synchronized with a predetermined reference clock.
[0038]
Although not shown, the video processing circuit 141 has a shading correction circuit, performs black offset correction, shading correction, and pixel position correction on each image data, and performs 8-bit digital data RDT0 synchronized with a reference clock. , GDT0-7, and BDT0-7. Here, the black offset correction is a correction for subtracting the black level of the dark current of the CCD color image sensor 109 from the image data. Shading correction refers to reading a white board with a uniform density before the start of document scanning, in order to eliminate unevenness in the light amount of the light source in the main scanning direction and unevenness due to the sensitivity difference between the pixels of the CCD color image sensor 109. Is stored for each pixel, and the correction is performed by dividing the image data being read by the original document by the stored white plate data for each pixel. Further, the pixel position correction is to correct the pixel position shift in the sub-scanning direction when the CCD color image sensor 109 has three lines.
[0039]
(4) Configuration and Operation of Image Processing Circuit FIG. 5 is a block diagram showing a schematic configuration of the image processing circuit 142. In the image processing circuit 142, first, the color separation circuit 501 performs color separation of black data and red data from the RGB signals. Here, when separating red, R-G is calculated, and when it is larger than a predetermined value, red data is generated.
[0040]
The 8-bit black data BLK0 to BLK7 output from the color separation circuit 501 and the 1-bit red data are subjected to MTF correction or binarization processing by the MTF correction circuit 502 or the binarization circuit 503, and then transformed. Electric magnification in the main scanning direction is performed by the doubler circuit 504, γ correction is performed by the γ correction circuit 505, and finally image quality processing such as dither and error diffusion is performed by the image quality processing circuit 506. The MTF correction is to correct the deterioration of the optical frequency characteristic or the like by using a two-dimensional spatial filter.
[0041]
The black data BLKDT0 to BLKDT7 and REDDT thus subjected to various corrections are sent to the video writing processing circuit 143.
[0042]
On the other hand, the video writing processing circuit 143 converts the speed to the writing speed of the plotter unit 111. The LD control unit 144 controls the pulse width and amount of current applied to the semiconductor laser 144a in accordance with the 8-bit 256-gradation image data, controls the light emission amount of the semiconductor laser 144a, and outputs a black signal. Controls image density.
[0043]
The LED control unit 145 is a control unit for writing a red (or blue) image, and controls the light emission of the LED array 140. The LED array 140 is composed of 2400 LEDs arranged in the longitudinal direction and a selfoc lens that collects light. The LED array 140 forms a small writing system with lower resolution and lower gradation than the laser writing system. can do. Thus, in this embodiment, writing of red (or blue) is performed.
[0044]
(5) Operation in Two-Color Copy Mode In the digital copying apparatus of the present embodiment, a black-and-white copy mode in which the density of an original is printed in black and white and a red (or blue) portion of the original are set to red (or (Blue) color output mode.
[0045]
In the character original mode at the time of the normal black-and-white copy mode, it is desirable that only the characters are output clearly without displaying the background. Therefore, the background removal mode ON (AEMODE signal = H) is sent from the CPU 146 to the video processing circuit 141 as a default. Is set. At this time, the image processing circuit 142 is set by the CPU 146 to a black and white character mode (the color separation circuit 501 does not perform color separation and does not output a color signal, and the filter is for the character mode). In this state, a copying operation is performed by the digital copying apparatus.
[0046]
In the above operation, the color separation circuit 501 mixes the RGB read signals at a certain ratio to form 8-bit black data. Therefore, the RGB output data may be slightly changed due to variations in the background removal circuit of each of the RGB channels. Loss of balance does not matter.
[0047]
On the other hand, in the character original mode in the two-color copy mode, the CPU 146 sets the background removal mode OFF (AEMODE signal = L) to the video processing circuit 141 by default. This is because if the background removal mode is turned on, the output data of RGB is slightly out of balance due to the variation of the background removal circuit of each of the RGB channels, the read image is colored, and the malfunction of the color separation circuit 501 may increase. Because there is. In the image processing circuit 142, the setting of the two-color character mode (the color separation is performed by the color separation circuit 501, and the filter is for the character mode) is performed by the CPU 146.
[0048]
In the present embodiment, by selecting the two-color copy mode from the operation panel 201, the background removal circuit is automatically turned off, so that the color separation failure (ie, the color detection failure) due to the variation of the RGB background removal circuit. ) Can be avoided.
[0049]
As described above, in this embodiment, color detection can be performed normally without providing a special mechanism. In other words, color detection can be performed normally without increasing the number of parts constituting the apparatus and increasing the cost.
[0050]
【The invention's effect】
As described above, the digital copying apparatus of the present invention operates the background removing means to execute the background removal when the copying in a single color is designated, and executes the removal in the multicolor when the copying is designated. The operation of the background removal means is prohibited so that the background removal is not performed, and the gray balance is not destroyed when copying in multiple colors. Therefore, the number of parts constituting the apparatus and the cost are increased. , Color detection can be performed normally.
[0051]
If the two-color copy mode is designated from the operation panel, the operation of the background removal unit is prohibited, so that color separation failure (ie, color detection failure) due to variations in the RGB background removal circuit can be avoided.
[0052]
In addition, the background removal means receives an RGB analog input signal, compares the analog input signal with a reference voltage and determines a digital data output, and holds a maximum voltage value of the analog input signal. Since there is provided a Vref determining circuit for determining a reference voltage from a voltage value obtained by the peak hold means, an effect is obtained that if the Vref determining circuit changes Vref, the A / D conversion characteristic changes.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a digital copying apparatus according to an embodiment.
FIG. 2 is a block diagram illustrating a schematic configuration of an image processing unit according to the embodiment.
FIG. 3 is an explanatory diagram illustrating a part of a circuit configuration of a video processing circuit.
FIG. 4 is an explanatory diagram illustrating a configuration of a Vref determination circuit.
FIG. 5 is a block diagram illustrating a schematic configuration of the image processing circuit of FIG. 2;
[Explanation of symbols]
200 Image processing unit 141 Video processing circuit 142 Image processing circuit 143 Video writing processing circuit 144 LD control unit 144a Semiconductor laser 145 LED control unit 140 LED array 201 Operation panel 501 Color separation circuit

Claims (3)

Image reading means for optically reading a document image; inputting image data read by the image reading means; correcting the density of the background of the document to remove the background; Image output means for outputting the input image data in black and colors other than black, designating means for specifying whether the original is copied in a single color or in multiple colors, and executing the operations of the background removing means. Control means for controlling the copying or prohibition,
When copying in a single color is designated via the designation means, the background removal means is operated to execute the background removal. When copying in multiple colors is designated, the background removal is performed by the control means. The digital copying apparatus is characterized in that the gray balance of output data is prevented from being lost by prohibiting the image data. The designation means is an operation panel of a digital copying machine, and the multi-color copying is in a two-color copy mode;
2. The digital copying apparatus according to claim 1, wherein the control unit prohibits the operation of the background removal unit when the two-color copy mode is designated from an operation panel. The background removing means receives an RGB analog input signal, and compares the analog input signal with a reference voltage to determine a digital data output, and holds a maximum voltage value of the analog input signal. 2. The digital copying apparatus according to claim 1, further comprising a Vref determination circuit that determines the reference voltage from a voltage value obtained by a peak hold unit.

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