JP2004289245A - Image read apparatus and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform image reading with high accuracy without influenced by the drive noise by employing a 4-line CCD sensor for controlling the lines in the same timing. <P>SOLUTION: The image read apparatus includes: a read section using the 4-line CCD sensor 9 having a line sensor 1K1 for an achromatic image and three line sensors 1R1, 1G1, 1B1 using the number of pixels different from that of the line sensor 1K1 for reading a chromatic image to read an original image; and a control section for generating control signals ψ1, ψ2, SH in the same timing and supplying the control signals to each line sensor to control a read operation of the read section, and can attain image reading with high accuracy without being influenced by drive noise because all lines are controlled in the same timing. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image reading apparatus having a CCD line sensor having a chromatic image reading line sensor and an achromatic image reading line sensor having different numbers of pixels, respectively, and an image forming apparatus using the same.
[0002]
[Prior art]
2. Description of the Related Art Recently, various image information devices using digital technology have become widespread, and high accuracy has been demanded for an image reading apparatus as one of them. In such an image reading apparatus, a three-line CCD sensor composed of three lines of RED, GREEN, and BLUE is generally employed. Since the three-line CCD sensor has a configuration in which three one-dimensional line sensors in which colored filters of RED, GREEN, and BLUE are arranged on the light receiving surface are arranged, all the line sensors simultaneously read the same portion of the document. I can't. Therefore, for the positional deviation in the document scanning direction, the image signals read by the respective line sensors are aligned using a memory circuit constituted by a line memory or the like.
[0003]
However, in such an image forming apparatus or an image reading apparatus, when a monochrome original composed of an achromatic color is read using the three-line CCD sensor, the line intervals of the three image information of RED, GREEN, and BLUE are similarly set. After the correction, black information is generated. Therefore, when the reading speed is not constant or when optical distortion or the like is present, the line interval is not constant, and as a result, the accuracy of the line interval correction processing is reduced.
[0004]
When the reading magnification is changed, for example, when the reading position of each line sensor on the original surface when reading at a reading magnification of 100% is four lines (when reading at a resolution of 600 dpi, the reading position on the original surface is shifted). (42.3 μm × 4 lines = 169.2 μm), assuming that the reading magnification is 141%, the reading speed is 1 / 1.41 times that at 100%, and the line interval is 1/4 of 4 lines. 5.64 lines, which is 41 times larger, complicates the correction.
[0005]
Also, in addition to the three-line CCD sensor for reading the color image, a line sensor for reading an achromatic image, in which a colored filter is not arranged on the light receiving surface, for reading an achromatic image is added to form a four-line configuration. CCD sensors have also been commercialized.
[0006]
When this 4-line CCD sensor is used, a chromatic color document is read by a 3-line CCD sensor having a color filter disposed on the light receiving surface, and an achromatic monochrome document is read by a CCD line sensor having no color filter disposed on the light receiving surface. Therefore, it is not necessary to generate black and white information from the three colors of RED, GREEN, and BLUE performed when reading a monochrome original using the above-described three-line CCD sensor. There is a merit that does not occur.
[0007]
As a related art related thereto, a four-line CCD sensor is used in some image forming apparatuses (for example, refer to Patent Literature 1, Patent Literature 2, and Patent Literature 3). In these image forming apparatuses, after each line sensor reads an image signal, the image signal is corrected and unified at an appropriate timing to be output as image information without color shift.
[0008]
[Patent Document 1]
JP-A-6-205159.
[0009]
[Patent Document 2]
JP-A-11-220569.
[0010]
[Patent Document 3]
JP-A-2000-69254.
[0011]
[Problems to be solved by the invention]
However, since the four-line CCD sensor in the above-described conventional apparatus includes three line sensors for reading color information and one line sensor for reading monochrome information, the driving of the former three line sensors is structurally difficult. There is a problem that noise affects the latter one line sensor.
[0012]
The present invention provides an image reading apparatus and an image forming apparatus capable of performing high-precision image reading unaffected by driving noise by controlling each line with a control signal at the same timing when using a 4-line CCD sensor. The purpose is to provide.
[0013]
[Means for Solving the Problems]
In order to solve the above problem, the present invention provides a CCD having at least a first line sensor having a first number of pixels and a second line sensor having a second number of pixels different from the first number of pixels. A reading unit that reads a document image using a line sensor, and a control signal at the same timing are generated and supplied to the first line sensor and the second line sensor, respectively, thereby controlling the reading operation of the reading unit. An image reading apparatus comprising:
[0014]
In the image reading apparatus according to the present invention, for example, in the case of a three-line sensor for reading a chromatic image and a four-line sensor including a line sensor for reading an achromatic image, even if the number of pixels differs between the two, each line sensor By using control signals supplied at the same timing, the operation timing of the chromatic image reading line sensor and that of the achromatic image line sensor become the same, so that high precision without mutual drive noise This makes it possible to read an image with ease.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an image reading apparatus according to an embodiment of the present invention and an image forming apparatus using the same will be described in detail with reference to the drawings.
[0016]
FIG. 1 is a sectional view showing an embodiment of an image reading apparatus according to the present invention, FIG. 2 is a block diagram showing this control system, and FIG. 3 is a 4-line CCD sensor included in the image reading apparatus according to the present invention. FIG. 4 is an explanatory diagram showing one embodiment of the pixels of the four-line CCD sensor, and FIG. 5 is a timing chart showing one embodiment of the drive timing of the CCD line sensor. FIG. 6 is a timing chart showing an embodiment of a drive timing of the CCD line sensor in pixel units, FIG. 7 is a timing chart showing an embodiment of a transfer clock of the CCD line sensor, and FIG. FIG. 9 is an explanatory diagram showing the reading resolution of the CCD line sensor, FIG. 9 is an explanatory diagram showing the reading resolution of the CCD line sensor, and FIG. It is a block diagram showing another embodiment of the support.
[0017]
<An example of the image reading apparatus according to the present invention>
The present invention controls the analog shift register of the four-line CCD sensor used in the image reading device by a control signal at a common timing, and in particular, the color image CCD sensor and the achromatic image CCD sensor mutually generate driving noise. This enables high-precision image reading without being affected. Hereinafter, an embodiment of an image reading apparatus according to the present invention will be described.
(Constitution)
First, an image reading apparatus according to the present invention will be described with reference to the drawings. A scanner 15 as an image reading apparatus according to the present invention includes a light source 1, a reflector 2 for correcting light distribution characteristics of the light source 1, and a first carriage 4 including a first mirror 3 in FIG. , A second carriage 7 composed of a second mirror 5 and a third mirror 6, a condenser lens 8, and a CCD sensor substrate 10 on which a CCD line sensor 9 is mounted. Further, a control board 11 for controlling the CCD sensor 9 and performing various processes, a white reference plate 12 serving as a white reference, a document glass 13 for placing the document O, and a document O are fixed so as not to float. It comprises a target document holding cover 14 and a scanner housing 15 for arranging these components described above.
[0018]
Here, the feature of the present invention relates to the CCD line sensor 9 and the control board 11. First, the schematic operation of the scanner will be described below with reference to FIG.
[0019]
The light emitted from the light source 1 passes through the original glass 13 and irradiates the original O. In addition, since the light distribution of the light emitted from the light source 1 is not uniform, and the illuminance on the document O has uneven light distribution, the reflected light from the reflector 2 is also irradiated on the document O, so that the document O The above light distribution can be made uniform.
[0020]
The reflected light from the document O is reflected by the first mirror 3, the second mirror 5, and the third mirror 6, passes through the condenser lens 8, and forms an image on the light receiving surface of the CCD line sensor 9. The CCD line sensor 9 is mounted on a CCD sensor board 10 and is controlled by a control signal input from a control board 11. Details of the control board 11 will be described later with reference to FIG.
[0021]
The document pressing cover presses the document O placed on the document glass 13 so that the reading surface of the document O comes into close contact with the document glass 13. The details of the configuration of the CCD line sensor 9 will be described later with reference to FIG. 3. The analog signal output from the CCD line sensor 9 uses high-frequency distortion due to variation in the conversion efficiency of each photoelectric conversion unit and the condensing lens 8. Since the low-frequency distortion including aberration caused by the reduction optical system is included, reference data is required for performing the normalization correction. In FIG. 1, the reference data is image data obtained when the white reference plate 12 is read.
[0022]
(Control system)
Next, a control system of the image reading apparatus according to the present invention will be described with reference to FIG. The control board 11 performs a process IC 11A that performs various processes, a various timing generation circuit 11B that generates various timings, processes analog signals from the CCD line sensor 9, and performs processes until the analog signals are converted into digital signals. It has various analog processing circuits 11C. Further, the digital signal output from the various analog processing circuits 11C includes shading correction for correcting the high-frequency and low-frequency distortions described above, and line-to-line correction processing for correcting line position deviation between a plurality of line sensors. An image processing circuit unit 11E for performing image correction and a line memory circuit 11D for delaying image data in line units when performing the above-described line-to-line correction processing are provided. Further, the processing IC 11A controls the CCD sensor control circuit 10A mounted on the CCD sensor substrate 10, controls the light emission of the light source 1, and moves the light source control circuit 16 and the above-described first and second carriages 4 and 7. This also controls the drive system control circuit 17 that controls the motor 18.
[0023]
The output of the image processing circuit 11E is connected to an interface 12 provided outside the control board 11, and supplies image information to an external image forming apparatus such as a multifunction copying machine or a PC (Personal Computer). I do.
[0024]
The CCD sensor substrate 10 includes a CCD line sensor 9, a CCD sensor control circuit 10 A for driving the CCD line sensor 9, and a CCD that receives the output of the CCD sensor control circuit 10 A and matches the driving conditions of the CCD line sensor 9. It is composed of a driver 10B.
[0025]
(CCD line sensor)
Further, the configuration and operation of the CCD line sensor 9 which is a feature of the present invention will be described below with reference to FIG. In FIG. 3, an RED photodiode array 1R1 in which a RED colored filter (not shown) is disposed on a light receiving surface converts the received light into an amount of electric charge according to the amount of light received by photoelectric conversion. To accumulate. The accumulated charge is transferred to the analog shift register 1R3 through the shift gate 1R2 by the control signal SH1 applied to the shift gate 1R2. The charges transferred to the analog shift register 1R3 are sequentially moved to the subsequent output amplifier 1R4 by the common control signals φ1 and φ2, and output to the outside from the output amplifier 1R4. The output signal at that time is referred to as OUTRD.
[0026]
Similarly, in a GREEN photodiode array 1G1 in which a GREEN color filter (not shown) is disposed on the light receiving surface, the GREEN photodiode array 1G1 converts the GREEN color filter into a charge amount according to the amount of light received by photoelectric conversion. To accumulate. The accumulated charge is transferred to the analog shift register 1G3 through the shift gate 1G2 by the control signal SH2 applied to the shift gate 1G2. The charges transferred to the analog shift register 1G3 are sequentially moved to the subsequent output amplifier 1G4 by the common control signals φ1 and φ2, and output to the outside from the output amplifier 1G4. The output signal at that time is defined as OUTGR.
[0027]
Similarly, also in the BLUE photodiode array 1B1 in which a BLUE color filter (not shown) is arranged on the light receiving surface, the BLUE photodiode array 1B1 converts this into a charge amount according to the amount of light received by photoelectric conversion, and charges each photodiode. To accumulate. The accumulated charges are transferred to the analog shift register 1B3 through the shift gate 1B2 by the control signal SH3 applied to the shift gate 1B2. The charges transferred to the analog shift register 1B3 are sequentially moved to the subsequent output amplifier 1B4 by the common control signals φ1 and φ2, and are output from the output amplifier 1B4 to the outside. The output signal at that time is referred to as OUTBL.
[0028]
Similarly, in the BLACK photodiode array 1K1 in which the colored filter is not arranged on the light receiving surface, the photoelectric conversion converts the received light into an amount of electric charge according to the amount of light received, and accumulates electric charge in each photodiode. The odd-numbered pixel charge of the accumulated charges is transferred to the analog shift register 1K3 through the shift gate 1K2 by the control signal SH4 applied to the shift gate 1K2, and the even-numbered pixel charge is applied to the control signal SH4 applied to the shift gate 1K5. Is transferred to the analog shift register 1K6 through the shift gate 1K5. The charges transferred to the analog shift register 1K3 are sequentially moved to the subsequent output amplifier 1K4 by the common control signals φ1 and φ2, and output to the outside from the output amplifier 1K4. The output signal at that time is referred to as OUTKO (BLACK ODD pixels). The charges transferred to the analog shift register 1K6 are sequentially moved to the output amplifier 1K7 in the subsequent stage by the common control signals φ1 and φ2, and are output from the output amplifier 1K7 to the outside. The output signal at that time is taken as OUTKE (EVEN pixel of BLACK).
[0029]
According to the present invention, the transfer clocks, which are the control signals φ1 and φ2 for transferring the electric charges as described above, are applied to all the analog shift registers at a common timing and controlled, so that drive noise is not generated. It is characterized by performing high-precision image reading. Next, the pixel area of each CCD line sensor, which is one of the conditions for realizing the present invention, will be described.
(Pixel area of CCD line sensor)
Next, the relationship between the area ratio of each pixel of the RED photodiode array 1R1, the GREEN photodiode 1G1, the BLUE photodiode 1B1, and the BLACK photodiode 1K1 according to the present invention will be described with reference to FIG. In FIG. 4A, the pixel size of the BLACK photodiode array 1K1 is m, the length in the pixel arrangement direction (hereinafter, referred to as the main scanning direction), which is the longitudinal direction of the device, is m, and the direction perpendicular to that direction (hereinafter, referred to as the main scanning direction). Assuming that the length is n, the pixel size of the RED photodiode array 1R1, the GREEN photodiode 1G1, and the BLUE photodiode array 1B1 is m × 2 in the main scanning direction and n × 2 in the sub-scanning direction. The length ratio of each pixel for monochrome reading and color reading is 1: 2. As a result, the number of pixels that can be arranged in the device at the same length is 2: 1 for monochrome reading and color reading.
[0030]
For example, if the length m of a pixel in the main scanning direction for reading an achromatic image is 4.7 μm and the number of pixels is 7500 pixels, the length of the BLACK photodiode 1K1 is 35.25 mm (4.7 μm × 7500 pixels); Assuming that the length m of the pixels for color reading in the main scanning direction is m × 2 = 9.4 μm and the number of pixels is 3750, the length of the RED photodiode array 1R1, the GREEN photodiode 1G1, and the BLUE photodiode 1B1 is 35.25 mm. (4.7 μm × 2 × 3750 pixels), even if the pixel size is different, by making the length of the photodiode array equal, the reading width of the original becomes equal.
[0031]
At this time, as shown in FIG. 3, the charge photoelectrically converted by the BLACK photodiode array 1K1 is separated into odd-numbered pixels and even-numbered pixels and output as OUTKO and OUTKE signals, respectively. The time required for ejection is 3,750 pixels, which is half of 7,500 pixels.
[0032]
(Operation timing)
Next, the operation timing of the four-line CCD sensor will be described with reference to FIG. As shown in FIG. 5, the sensor output signal includes, in addition to the effective pixel area of the photodiode array, a "idle feed portion" in which no signal output is provided even when the transfer clocks φ1 and φ2 are input in the previous stage, There is a “light shield part” that covers the light-receiving surface with aluminum or the like but does not enter light, a “dummy pixel part” located between the light shield part and the effective pixel area, and an effective pixel area and a transfer clock There is a “idle feed portion” where no signal is output even when φ1 and φ2 are input, and a “dummy pixel portion” located in the middle. The number of these pixels is also 2: 1 for monochrome and color. As a result, as shown in FIG. 5, the output timing of OUTKO / OUTKE which is the output at the time of monochrome reading and the output timing of OUTRD / GR / BL which is the output at the time of color reading can be matched.
[0033]
In the above description, the length ratio of pixels for monochrome reading and color reading is 1: 2, but FIG. 4B shows that the length ratio of pixels for monochrome reading and color reading is 1: 4. This is the example described. In this case, assuming that the number of pixels of the BLACK photodiode array 1K1 is 7,500, the number of pixels of the RED photodiode array 1R1, the GREEN photodiode 1G1, and the BLUE photodiode 1B1 needs to be 1875 pixels, which is 1/4 of 7,500 pixels. There is. The output signals OUTKO and OUTKE are further divided into two, and the output of the electric charge accumulated in the BLACK photodiode array 1K1 is output simultaneously by four systems, so that the output timing of the monochrome read signal and the color read signal can be adjusted. Can be matched.
[0034]
(Effects of CCD line sensor waveform and noise)
Further, in order to explain the advantage of applying the transfer clocks φ1 and φ2 in common to all the analog shift registers, the waveform of each pixel of a general CCD line sensor will be described with reference to FIG.
[0035]
The transfer clocks φ1 and φ2 are signals having a phase difference of 180 ° as shown in FIG. 6. When the potential of φ2 is at a high level, the potential of a floating capacitor (not shown) that stores charges in the output stage of the CCD line sensor is set to the reference potential. To return, a reset signal RS is applied. With this RS signal, the potential of the output signal becomes a reference DC output voltage (VOS). Thereafter, a clamp signal CP is applied for the purpose of stabilizing the DC signal component. Thereafter, the voltage of the OUT ** signal (**: RD / GR / BL / KO / KE) is generated at the falling portion of the transfer clock φ2, and thereafter, the signal is stabilized at the effective signal amplitude (VOUT). The time from when the voltage starts to be generated until the voltage is stabilized is the time until the charges sequentially transferred by the analog shift register are transferred to the floating capacitor and stabilized. Thereafter, a period until the RS signal is input again is a signal stable period.
[0036]
Since this output signal is a weak analog signal, there is a problem that the output signal is easily affected by other signals nearby. The reset noise caused by the RS signal and the induced noise caused by the transfer clocks φ1 and φ2 shown in FIG. 6 are well known.
[0037]
In the case of a 4-line CCD sensor in which a monochrome reading line sensor and a plurality of color reading line sensors are configured in the same chip, the output timing is adjusted by changing the monochrome reading frequency and the color reading frequency. Is also conceivable. However, in this method, as shown in FIG. 7, for example, the period of the transient characteristic (rising or falling portion) of the monochrome transfer clock φ2 affects OUTRD / GR / BL which is a color output as inductive noise, Conversely, the period of the transient characteristic of the color transfer clock φ2 affects the monochrome output OUTKO / KE as induced noise. Therefore, a stable period in which the effective signal amplitude shown in FIG. 6 is stable cannot be secured due to the induced noise, or a case where the effective signal does not have a stable period occurs. Therefore, as proposed by the present invention, a stable period can be created for the first time by applying the transfer clocks φ1 and φ2 at the same timing for monochrome reading and color reading.
[0038]
Further, by applying the transfer clocks φ1 and φ2 to all the analog shift registers at a common timing, the configuration of the various timing generation circuits 11B shown in FIG. 2 is simplified, and various analog processes receiving the outputs are performed. It goes without saying that the number of connection lines to the circuit 11C and the CCD sensor control circuit 10A can be reduced.
[0039]
As shown in FIG. 5, the shift pulse SH1 applied to the shift gate 1R2 for transferring the charge accumulated in the RED photodiode array 1R1 to the analog shift register 1R3, and the charge accumulated in the GREEN photodiode array 1G1 are used. A shift palace SH2 applied to the shift gate 1G2 for transferring to the analog shift register 1G3, a shift pulse SH3 applied to the shift gate 1B2 for transferring the charge accumulated in the BLUE photodiode array 1B1 to the analog shift register 1B3, The shift pulse SH4 applied to the shift gates 1K2 and 1K5 for transferring the charges accumulated in the BLACK photodiode array 1K1 to the analog shift registers 1K3 and 1K6 is shared. By applying at the time, it is possible to share the sub-scanning direction reading resolution monochrome reading and color reading.
[0040]
(Common use of shift pulse and resolution in the sub-scanning direction)
Next, the resolution in the sub-scanning direction will be described with reference to FIG. Assuming that the reading resolution of a monochrome document is 600 dpi, the reading range on the document surface per pixel is 42.3 μm × 42.3 μm (= 25.4 mm / 600 dpi) by the condenser lens 8. In order to read the original at the same resolution of 600 dpi, it is necessary to move the original reading position in the sub-scanning direction by 42.3 μm in a cycle of SH1 to SH4.
[0041]
The relationship between the pixel sizes of the BLACK photodiode array 1K1, the RED photodiode array 1R1, the GREEN photodiode array 1G1, and the BLUE photodiode array 1B1 shown in FIG. 4A is as shown in FIG. Is 84.6 μm × 84.6 μm (= 25.4 mm / 600 dpi × 2).
[0042]
In FIG. 8, for the sake of explanation, the central axis of the BLACK photodiode array (indicated by a dotted line) and the central axis of the other photodiode arrays are made coincident. However, they are actually arranged in the sub-scanning direction as shown in FIG. ing.
[0043]
Assuming that the image data at the time of reading a white original is 100 and the image data at the time of reading a black band shown in FIG. 8 is 0, as shown in the monochrome graph of (b) and the color graph of (c),
t = 1-2 Monochrome: 100.0, Color: 87.5
t = 2-3 Monochrome: 50.0, Color: 50.0
t = 3-4 Monochrome: 0.0, Color: 25.0
t = 4-5 Monochrome: 50.0, Color: 50.0
t = 5-6 Monochrome: 100.0, Color: 87.5
It becomes.
[0044]
Since the reading range on the document surface for color reading is equivalent to 300 dpi, a case where the resolution in the sub-scanning direction is read at 300 dpi with reference to FIG. 9 will be described. As shown in FIG. When acquired, as shown in the monochrome graph of (b) and the color graph of (c),
t = 1 to 3 Color: 62.5
t = 3-5 Color: 50.0
t = 5 Color: 93.75
It becomes.
[0045]
As described above, as shown in FIG. 8A, even when image information is obtained by line sensors having different pixel sizes, the resolution in the sub-scanning direction can be obtained by setting the cycle of the shift pulses SH1 to SH4 to be the same. It can be seen that can be improved.
[0046]
In the image reading apparatus according to the present invention, as shown in FIG. 10, as in the case where the transfer clocks φ1 and φ2 are applied at the common timing, the shift pulses SH1 to SH4 can be the shift pulse SH of the common signal. . Thus, the configuration of the various timing generation circuits 11B shown in FIG. 2 can be simplified, and the number of connection lines to the various analog processing circuits 11C and the CCD sensor control circuit 10A that receive the output can be reduced.
As described above, in the image reading apparatus according to the present invention, the read processing is performed by the common operation timing (φ1, φ2, SH) in the monochrome and color CCD line sensors having different numbers of pixels, so that the driving noise is reduced. A high-resolution reading process can be performed without being affected.
<Example of Image Forming Apparatus Using Image Reading Apparatus According to the Present Invention>
Hereinafter, an example of an image forming apparatus using the above-described image reading apparatus will be described in detail with reference to the drawings. FIG. 11 is a block diagram showing a control system of an embodiment of the image forming apparatus according to the present invention. FIG. 12 is a timing chart showing read and write operation timings of the embodiment of the image forming apparatus according to the present invention. FIG. 13 is a block diagram showing the timing generation circuit.
[0047]
(Configuration and operation)
As shown in FIG. 11, a multifunction copying apparatus C, which is an image forming apparatus using the image reading apparatus according to the present invention, includes a system control unit 20 for controlling the overall operation, and a user control unit connected to the system control unit 20. And a control panel 26 for receiving operation information, the image reading device 15 as the above-described image reading device, a recording medium 21 for storing input image information, and various types of color conversion processing, color correction, image reduction / enlargement, etc. An image processing unit 22 for performing image processing, a laser optical system 24 for generating laser light in accordance with given image information, and receiving the laser light to form an image on a drum serving as an image carrier; And an image forming unit 23 including an image forming unit 25 for fixing an image thereon.
Here, in the case where the image reading device 15 and the image forming unit 23 are operated in synchronization with each other, the period of the shift pulse SH is significantly related, and therefore, the image forming unit 23 will be described before the description.
[0048]
The image forming unit 23 emits / turns off the semiconductor laser according to the image information. When the semiconductor laser emits light, the surface potential of the photosensitive drum decreases, and the toner, which is a developing material, is applied to a portion where the potential decreases. Adhere to. The attached toner is transferred to a sheet to be printed, and then fixed by overheating by fixing. Therefore, a color is formed in a portion where the semiconductor laser emits light. These forming parts are constituted by four systems of BLACK in addition to YELLOW, MAGENTA and CYAN. When the semiconductor lasers of the three image forming units of YELLOW, MAGENTA, and CYAN emit light, the YELLOW toner, the MAGENTA toner, and the CYAN toner all overlap on the paper to be printed, and try to form black information. In general, a BLACK image forming unit is separately provided to reproduce black because it does not become information.
[0049]
Image information obtained by the CCD line sensor by the various image processing units 22 is converted into a light emission control signal of the semiconductor laser. The semiconductor laser control signal is converted by a laser control board (not shown) into a current signal for turning on or off the semiconductor laser connected to the laser control board, thereby controlling the semiconductor laser. Further, since a semiconductor laser has a characteristic that a current value changing from a spontaneous emission region to a laser oscillation region changes with temperature, an image is formed using a front beam which is a main output of the semiconductor laser, and a back output which is a sub output. By detecting the beam with the photodiode PD arranged in the semiconductor laser device, the light emission amount of the semiconductor laser is detected, and the difference between the light emission amount and the desired light emission amount is calculated to control the light emission amount of the semiconductor laser. APC (Auto Power Control) is common. Here, the desired light emission amount can be set by applying a certain voltage as a WRITE light emission level setting voltage to the laser control board.
[0050]
The light output from the semiconductor laser that has been subjected to the APC process is transmitted through the condenser lens 8, reflected by a polygon mirror that is a rotating polygon mirror, and becomes light that scans in a one-dimensional direction. The light reflected by the polygon mirror passes through the Fθ lens, is reflected by the first folding mirror, and irradiates a photosensitive drum for forming an image. A part of the light transmitted through the Fθ lens is reflected by a second turning mirror different from the first turning mirror, and is guided to the synchronization signal detection sensor. The output of the synchronizing signal detection sensor becomes the HSYNC signal of the periodic signal in the horizontal direction of printing.
[0051]
Each of the image forming units of YELLOW, MAGENTA, CYAN, and BLACK is controlled in synchronization with the HSYNC signal.
[0052]
a. During the full-color printing operation, the toner corresponding to the image information of YELLOW, the toner corresponding to the image information of MAGENTA, the toner corresponding to the image information of CYAN, and the toner corresponding to the image information of BLACK are respectively transferred onto the printed paper. Finally, a fixing process by overheating is performed and the sheet is discharged.
[0053]
b. At the time of monochrome printing operation, the belt for transporting the paper to be printed moves as shown in the figure, and only the BLACK-based image forming unit operates so as to contact the paper, so that only the toner corresponding to the BLACK image information is used. Is transferred to the sheet, and an image using only the monochrome toner is formed.
[0054]
Each of these printing operations is performed in synchronization with the HSYNC signal, during which the light output from the semiconductor laser scans the photosensitive drum once on one surface of the polygon mirror, and the paper to be printed is converted to the HSYNC signal. Conveyed synchronously.
[0055]
As in the case of reading, assuming that writing is performed at a resolution of 600 dpi in the sub-scanning direction and a copy magnification of 100%, the paper moves by 42.3 μm during one cycle of the HSYNC signal.
[0056]
As described above, when the resolution in the sub-scanning direction of the image reading device and the image forming unit 25 is the same, the document reading speed or the paper printing speed is 42.3 μm / 1 line. It is also possible to use an HSYNC signal, which is an output of a synchronization signal detection sensor inside, as a shift pulse SH of a CCD line sensor in an image reading device.
[0057]
In this case, the operations of the image reading device and the image forming unit are completely synchronized. FIG. 12 shows an example of the reading timing in such an image reading apparatus and the writing timing in the image forming unit.
[0058]
(Cooperation of operation between image reading device and image forming unit)
Further, in the image forming apparatus according to the present invention, an HSYNC signal which is a control signal of the image forming unit is used as an SH signal of the image reading apparatus.
[0059]
That is, as shown in FIG. 5, in the CCD line sensor, the charge accumulated in each photodiode array is transferred to the analog shift register by the shift pulse SH, so that the reading resolution in the sub-scanning direction is the same as the shift pulse SH cycle. It is determined by the moving speed of the first carriage 4 and the second carriage 7 for reading. The shift pulse SH falls and becomes an effective output signal shown after the idle feeding portion, the light shield portion, and the dummy pixel portion.
[0060]
Since which part of the effective output signal becomes the image information of the original is determined by the size of the original to be read, the effective image area in the horizontal direction (main scanning direction) is determined by the HDEN signal according to the original size.
[0061]
The image forming unit 25 causes the semiconductor laser to emit light at a timing such that the light output from the semiconductor laser irradiates the synchronization signal detection sensor. This control signal is the LDon signal in FIG. When the synchronization signal detection sensor detects the light output of the semiconductor laser and generates an HSYNC signal, the HSync signal controls the LDon signal to a level at which the LDon signal is turned off. When the photoconductor drum is irradiated with light energy, the surface potential of the photoconductor drum lowers and toner adheres to the photoconductor drum to form a latent image. Therefore, as described above, the photoconductor drum is turned off after the HSYNC signal is formed, so that unnecessary light output is obtained. Can be controlled so as not to be irradiated. As is clear from this timing, it is possible to use the HSYNC signal instead of the SH signal.
[0062]
FIG. 13 illustrates a CCD line sensor control signal generation unit 11B to which switching control between the SH signal and the HSYNC signal is added. MCLK is a master clock serving as a fundamental frequency of the circuit, and the circuit operates in synchronization with the MCLK. The MCLK is input to the main scanning counter, and based on the counter output, the HDEN signal indicating the image effective area in the scanning direction, shift pulses SH1 to SH4, and shift pulses SH1 to SH4 are applied to each shift gate of the CCD line sensor. During this period, the transfer clocks φ1 and φ2 need to be stopped, so that the CLK_EN signal for setting the stop period is generated. Further, transfer clocks φ1 and φ2 are generated by the CLK_EN signal and MCLK.
[0063]
As described above, the shift pulses SH1 to SH4 can use the HSYNC signal which is a synchronization signal from the laser optical system unit of the image forming unit 25 as described above. Therefore, the shift pulses SH1 to SH4 and the selection circuit for the HSYNC signal are used. A shift pulse to be input to the CCD line sensor is determined by a certain selector circuit.
[0064]
Therefore, in the present invention, all shift gates of the four-line CCD sensor are operated at a common timing. Therefore, when operating only a network scanner or an image reading device for filing purposes, the shift pulses SH1 to SH4 generated from MCLK are used. When the image reading apparatus is operated simultaneously with the image forming apparatus for copying, it is preferable to use an HSYNC signal as a synchronization signal as a shift pulse of the CCD line sensor. Thus, by using the HSYNC signal, which is a control signal of the image forming unit, it is possible to reliably synchronize the image forming unit and the image reading device, and perform image reading processing without driving noise in a stable operation. It is possible to provide an image reading apparatus capable of performing the image reading and an image forming apparatus using the same.
[0065]
As described above, according to the present invention, in an image reading apparatus having a plurality of line sensors having different numbers of pixels and combining output signals of the respective line sensors to form image information, the image signals are applied to the analog shift registers of all the line sensors. By using a common transfer clock, the control circuit can be simplified, and the circuit unit price can be reduced accordingly.
In addition, since the output timing of the effective signal of the CCD line sensor becomes the same, it is easy to grasp the influence of the induced noise due to the transfer clock generated in the effective signal portion for each pixel, and accordingly, the stable period of the effective signal portion is easily set. Can be secured.
Also, in an image reading apparatus that has a plurality of line sensors having different numbers of pixels and synthesizes output signals of the respective line sensors to form image information, control is performed by using a common shift pulse to be applied to all shift gates. The circuit can be simplified, and accordingly, the unit cost of the circuit can be reduced.
Further, the image forming apparatus and the image reading apparatus can be easily synchronized.
If the ratio of the number of pixels of the achromatic image reading line sensor to the number of pixels of the color line sensor is 2: 1 or 4: 1, the transfer clock and the shift pulse are shared as described above, The valid signal output timing from each line sensor can be the same timing.
[0066]
Those skilled in the art can realize the present invention from the various embodiments described above. However, it is easy for those skilled in the art to come up with various modifications of these embodiments, and the invention has an inventive capability. The present invention can be applied to various embodiments at least. Therefore, the present invention covers a wide range not inconsistent with the disclosed principle and novel features, and is not limited to the above-described embodiments.
[0067]
【The invention's effect】
As described in detail above, according to the present invention, in an image reading apparatus using a four-line CCD sensor or the like having different numbers of pixels, each line is controlled by a control signal at the same timing, so that, for example, an achromatic image reading line An image reading apparatus capable of performing high-accuracy reading processing without being affected by driving noise from the image reading apparatus, and an image forming apparatus using the same can be provided.
[Brief description of the drawings]
FIG. 1 is a sectional view showing an embodiment of an image reading apparatus according to the present invention.
FIG. 2 is a block diagram showing a control system of an embodiment of the image reading apparatus according to the present invention.
FIG. 3 is a configuration diagram showing one embodiment of a four-line CCD sensor included in the image reading apparatus according to the present invention.
FIG. 4 is an explanatory diagram showing one embodiment of a pixel of a four-line CCD sensor included in the image reading apparatus according to the present invention.
FIG. 5 is a timing chart showing one embodiment of a drive timing of a CCD line sensor of the image reading apparatus according to the present invention.
FIG. 6 is a timing chart showing an embodiment of a drive timing for each pixel of the CCD line sensor of the image reading apparatus according to the present invention.
FIG. 7 is a timing chart showing an embodiment of a transfer clock of a CCD line sensor of the image reading apparatus according to the present invention.
FIG. 8 is an explanatory diagram showing a reading resolution of a CCD line sensor of the image reading device according to the present invention.
FIG. 9 is an explanatory diagram showing a reading resolution of a CCD line sensor of the image reading device according to the present invention.
FIG. 10 is a configuration diagram showing another embodiment of a 4-line CCD sensor included in the image reading apparatus according to the present invention.
FIG. 11 is a block diagram showing a control system of an embodiment of the image forming apparatus according to the present invention.
FIG. 12 is a timing chart showing read and write operation timings of the image forming apparatus according to one embodiment of the present invention;
FIG. 13 is a block diagram showing a timing generation circuit included in an embodiment of the image forming apparatus according to the present invention.
DESCRIPTION OF SYMBOLS 1 ... light source, 2 ... reflector, 3 ... first mirror, 4 ... first carriage, 5 ... second mirror, 6 ... third mirror, 7 ... second carriage, 8 ... condensing lens, 9 ... CCD line sensor, 10 ... CCD sensor board, 11 ... Control board, 12 ... White reference board, 13 ... Document glass, 14 ... Document holding cover, 15 ... Housing, O ... Document, 10A ... CCD sensor control circuit, 10B ... CCD driver, 11A ... processing IC, 11B ... various timing generation circuits, 11C ... various analog processing circuits, 11D ... line memory circuit, 11E ... image processing circuit section, 16 ... light source control circuit, 17 ... drive system control circuit, 18 ... Motors, SH1 to SH4 ... Shift gate control signals.

Claims (7)

Reading an original image using a CCD line sensor having at least a first line sensor having a first number of pixels and a second line sensor having a second number of pixels different from the first number of pixels Means,
Control means for controlling the reading operation of the reading means by generating control signals at the same timing and supplying the control signals to the first line sensor and the second line sensor, respectively. Image reading device. The CCD line sensor of the reading unit includes a first analog shift register provided near the first line sensor and supplied with image information from the first line sensor, and a first analog shift register near the second line sensor. And a second analog shift register provided with image information from the second line sensor, and each of which operates by the control signal at the same timing. Image reading device. The control unit generates a control signal at the same timing based on a control signal supplied from an image forming apparatus connected to the image reading apparatus, and supplies the control signal to the first line sensor and the second line sensor. 2. The image reading apparatus according to claim 1, wherein the reading operation of the reading unit is controlled. In the first line sensor, a colored filter is not arranged on a light receiving surface, and in the second line sensor, a colored filter is arranged on a light receiving surface. 2. The image reading apparatus according to claim 1, wherein the first number of pixels is larger than the second number of pixels of the second line sensor. In the first line sensor, a colored filter is not arranged on a light receiving surface, and in the second line sensor, a colored filter is arranged on a light receiving surface. 2. The image reading apparatus according to claim 1, wherein a ratio between the first number of pixels and the second number of pixels of the second line sensor is n: 1 (n is an integer). Reading means for reading a document image using a CCD line sensor having at least a first line sensor having a first number of pixels and a second line sensor having a second number of pixels different from the first number of pixels When,
A control unit that generates a control signal at the same timing and supplies the control signal to the first line sensor and the second line sensor, thereby controlling a reading operation of the reading unit;
An image forming unit that forms an image on a recording medium based on the document image read by the reading unit under the control of the control unit;
An image forming apparatus comprising: The control unit is based on a control signal supplied from the image forming apparatus when an image is being formed, or based on a control signal generated in the image reading apparatus when a document image is being read. 7. The reading operation of the reading unit according to claim 6, wherein a control signal at the same timing is generated and supplied to the first line sensor and the second line sensor, respectively, thereby controlling a reading operation of the reading unit. Image forming device.

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