JP4458755B2 - Image reading apparatus and image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image reading apparatus using a 4-line CCD sensor that outputs a monochrome image signal and R (red), G (green), and B (blue) color image signals, and an image forming apparatus using the image reading apparatus.
[0002]
[Prior art]
In recent years, image reading apparatuses that read an image of an object have become widespread, and a wide variety of products have been sold. Among these, a color image reading apparatus using a color CCD has been reduced in price and speeded up in image reading, and is not limited to a single color image reading apparatus, but can be used for a color image forming apparatus (MFP = Multi Functional Peripheral). Widely used.
[0003]
The color CCD is mainly a 3-line CCD sensor that reads R, G, and B and outputs RGB signals. Further, a 4-line CCD sensor that outputs a BK (black) signal in addition to an RGB signal is also used. This 4-line CCD sensor is used in low-cost scanners for speeding up the reading of BK. As an image reading apparatus using a 3-line CCD sensor, there is, for example, Patent Document 1.
[0004]
[Patent Document 1]
JP 2002-112046 A
[0005]
[Problems to be solved by the invention]
The 4-line CCD sensor has a purpose of manufacturing / selling at a low price while suppressing the semiconductor cost, and the sensor length is reduced from 90 mm of the 3-line CCD sensor to 53.6 mm.
[0006]
Also, in the case of a 4-line CCD sensor, even if the sensor length is shortened, an image can be read with the same resolution as the 3-line CCD sensor. is doing.
[0007]
In the optical system of the image reading apparatus, the object to be read is illuminated, and image light from the illuminated object is converged by the reduction lens and is incident on the CCD sensor.
[0008]
If a 4-line CCD sensor is used in such an optical system, it is necessary to increase the reduction rate of image light by the reduction lens, compared to the case where a 3-line CCD sensor is used. If the reduction ratio is not increased, the distance between the reduction lens and the 4-line CCD sensor increases, leading to an increase in the size of the apparatus.
[0009]
When the reduction ratio of image light by the reduction lens is increased, the influence of optical chromatic aberration increases due to the difference in focal position for each RGB due to the convergence of the reduction lens. In order to reduce the influence of this chromatic aberration, for example, it is necessary to design a reduction lens in which a plurality of lenses are combined.
[0010]
However, the design of such a reduction lens is more difficult and an expensive reduction lens must be used. For this reason, there is a difficulty in realizing an inexpensive image reading apparatus using a 4-line CCD sensor.
[0011]
On the other hand, the 4-line CCD sensor includes a color / monochrome independent type that outputs monochrome image signals and color image signals independently, and a color / monochrome simultaneous output type that outputs monochrome image signals and color image signals simultaneously. Of these, the color / monochrome independent type does not require chromatic aberration correction for the monochrome image signal. In the color / monochrome simultaneous output type, when chromatic aberration correction is performed only on the color image signal, there is a problem that the influence of chromatic aberration due to the difference in the focal positions of BK and RGB by the reduction lens appears and image degradation occurs.
[0012]
Therefore, according to the present invention, the chromatic aberration correction is selectively performed on the monochrome image signal and the color image signal output from the 4-line CCD sensor, so that the cost can be reduced by using an inexpensive 4-line CCD sensor and a reduction lens. An object of the present invention is to provide an image reading apparatus and an image forming apparatus using the same.
[0013]
[Means for Solving the Problems]
The present invention receives a reduction lens that converges image light from an object to be read, and image light converged by the reduction lens, and outputs one or both of a monochrome image signal and an RGB color image signal 4. Output from line CCD sensor and 4-line CCD sensor Monochrome image signal and A sub-scanning position correction circuit that corrects a deviation in the reading position of the reading object in the sub-scanning direction when read by the 4-line CCD sensor with respect to the RGB color image signal, and four output signals from the sub-scanning position correction circuit. When the line CCD sensor array and the correction circuit for correcting the chromatic aberration given by the color component by the reduction lens and the monochrome image reading mode are selected, the monochrome image signal output from the 4-line CCD sensor is selected. The correction by the correction circuit for correcting the sub-scanning position correction circuit and the chromatic aberration is not performed. Output image signals to form an image for each color component with at least density correction, and a color image reading mode is selected. Monochrome image signal and RGB color image signal are output. Output from the 4-line CCD sensor and output from the correction circuit through the sub-scanning position correction circuit. Monochrome image signal and RGB color image signal When And an image processing circuit that outputs an output image signal for forming an image for each color component by performing at least color correction and density correction.
[0014]
The present invention also provides A reduction lens that converges image light from a reading object, and a 4-line CCD sensor that receives the image light converged by the reduction lens and outputs either one or both of a monochrome image signal and an RGB color image signal; Sub-scanning position correction for correcting the deviation of the reading position of the reading object in the sub-scanning direction when the monochrome image signal and RGB color image signal output from the 4-line CCD sensor are read by the 4-line CCD sensor When the circuit, the correction circuit for correcting the chromatic aberration given by the arrangement of the 4-line CCD sensor and the reduction lens according to the color component, and the monochrome image reading mode are selected, the output signal of the sub-scanning position correction circuit is 4 Sub-scanning position correction circuit and chromatic aberration correction for monochrome image signal output from line CCD sensor No correction is performed by a correction circuit that performs positive, and at least density correction is performed to output an output image signal for forming an image for each color component. Also, a color image reading mode is selected, and a monochrome image signal and RGB When the color image signal is output, at least color correction and density are performed on the monochrome image signal and the RGB color image signal output from the 4-line CCD sensor and output from the correction circuit through the sub-scanning position correction circuit. An image processing circuit that outputs an output image signal for forming an image for each color component by performing correction, and an image that forms an image based on image information acquired based on the output image signal output from the image processing circuit Forming part and An image forming apparatus.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings.
[0016]
FIG. 1 is a configuration diagram of an image forming apparatus using the image reading apparatus of the present invention. This image forming apparatus includes an automatic document feeder (hereinafter referred to as ADF) 1, a scanner section 2 as an image reading section, a process unit 3 for forming an output image, a paper feed unit 4, and a control panel (hereinafter referred to as a control panel). , Abbreviated as a control panel).
[0017]
The scanner unit 2 illuminates a reading object such as a document (reading object) supplied from the ADF 1 or a document set on a document table with light from a light source, and reflects light reflected from the document as an optical element such as a mirror or a lens. It is guided to a 4-line CCD sensor via a member, and photoelectrically converted to output image data to the process unit 3, an external device (not shown), or a network.
[0018]
In the scanner unit 2, a document to be read is moved on the document table glass 6 at a constant speed by the ADF 1, or placed downward on the document table glass 6. The original is illuminated by the light source 7, and reflected light from the original is imaged on the 4-line CCD sensor 12 via the mirrors 8 to 10 and the reduction lens 11.
[0019]
When reading a document placed on the platen glass 6, a first carriage 13 composed of a light source 7 and a mirror 8 and a second carriage 14 composed of each mirror 9, 10 are illustrated. Move from right to left on the drawing with a drive motor that does not. Thereby, the document is scanned by the illumination light from the light source 7 (sub-scanning direction).
[0020]
The moving speed of the first carriage 13 is twice the moving speed of the second carriage 14, and the optical path length from the original to the 4-line CCD sensor 12 is always constant. When the document is conveyed by the ADF 1, the light emitted from the light source 7 does not move, but is scanned by moving the document.
[0021]
FIG. 2 is an external view of the 4-line CCD sensor 12, and FIG. 3 is an enlarged view of the light receiving portion 12 a in the 4-line CCD sensor 12. The light receiving unit 12a in the 4-line CCD sensor 12 includes a line sensor BK in which no optical filter is disposed, a line sensor R in which an optical filter for imparting sensitivity to red is disposed, and an optical filter for imparting sensitivity to green. Four of the line sensor G that is arranged and the line sensor B that is arranged with an optical filter for imparting light sensitivity to blue are arranged side by side. In each of the line sensors K, R, G, and B, for example, photodiodes are arranged as light receiving elements for 7500 pixels at a pitch of 4.7 μm.
[0022]
As described above, since the four line CCD sensor 12 has the four line sensors BK, R, G, and B arranged side by side, the image read in each line is shifted in the sub-scanning direction. When reading a color image, it is common to store the image information read by a line memory or the like and correct this deviation. If there is unevenness (jitter) in the carriage moving speed and document moving speed in the sub-scanning direction, the correction cannot always be made completely.
[0023]
The characteristics of the 4-line CCD sensor 12 will be described. 4 is a diagram showing spectral sensitivity characteristics of the line sensor K constituting the 4-line CCD sensor 12, and FIG. 5 is a diagram showing spectral sensitivity characteristics of the line sensors R, G, B constituting the 4-line CCD sensor 12. As shown in FIG. FIG. 6 is a diagram showing the spectral distribution of the xenon stripe of the light source 7.
[0024]
As shown in FIG. 6, the light emitted from the xenon lip of the light source 7 has a wavelength (spectrum) from about 400 nm to 730 nm. Consider a case where the light from the light source 7 is reflected by a white original and enters the 4-line CCD sensor 12.
[0025]
As shown in FIGS. 4 and 5, each line sensor R, G, B has sensitivity only to the wavelength in the characteristic region, whereas the line sensor K has sensitivity from a wavelength region less than 400 nm to a wavelength region exceeding 1000 nm. Considering the decrease in the amount of light due to the RGB color optical filters, it is clear that the signal output from the line sensor BK is larger than those of the other line sensors R, G, B. That is, the line sensor K has higher sensitivity than the other line sensors R, G, and B.
[0026]
FIG. 7 is a schematic configuration diagram of the 4-line CCD sensor 12. The configuration of the line sensor BK and the configuration of each line sensor R, G, B are partially different.
[0027]
When each line sensor R, G, B is irradiated with light, the light receiving elements constituting the line sensors R, G, B respectively generate charges according to the irradiation light amount and the irradiation time for each pixel. When the SH signal is input to each shift gate, the charge corresponding to each pixel is supplied to the analog shift register via the shift gate. The analog shift register serially outputs charges (image information) corresponding to the pixels from the line sensors R, G, and B in synchronization with the transfer clocks CLK1 and CLK2.
[0028]
The signal output of each line sensor BK, R, G, B will be described with reference to FIG. Each of the line sensors BK, R, G, and B is provided with a light shield pixel portion, a dummy pixel, and an idle feed portion in which the light receiving element is shielded by an aluminum sheet or the like so that light does not enter the preceding stage of 7500 effective pixels. Yes.
[0029]
In order to transfer all the signal outputs of the line sensors BK, R, G, and B to the outside, the number of transfer clocks exceeding 7500 pixels is required. Here, if the total of the light shield pixel portion, the dummy pixel portion, and the idle feed portion is set to 500 pixels, a transfer clock for 8000 pixels is required, and this time determines the light accumulation time (tINT) for one line. It is a big factor.
[0030]
That is, the light receiving elements in each of the line sensors BK, R, G, and B generate charges according to the reflected light from the document during the light accumulation time (tINT) for one line, and the SH signal is input. Thus, the operation of transferring the charge to the analog shift register and outputting a signal to the outside in synchronization with the transfer clock is continuously repeated during the next optical accumulation time (tINT).
[0031]
Next, the line sensor BK will be described. The basic operation is the same as that of each of the line sensors R, G, and B, but is characterized by having two sets of shift gates and analog shift registers as can be seen from FIG. When the line sensor BK is irradiated with light, the light receiving elements constituting the line sensor BK generate charges according to the irradiation light amount and the irradiation time for each pixel. When the SH signal is input to the shift gate K_EVEN, the charge corresponding to the odd pixel is supplied to the analog shift register K_ODD and the charge corresponding to the odd pixel is supplied to the analog shift register K_EVEN via each shift gate. Each analog shift register serially outputs charges (image information) corresponding to the odd and even pixels in synchronization with the transfer clocks CLK1 and CLK2.
[0032]
The output signal of the line sensor BK will be described with reference to FIG. As with each of the line sensors R, G, and B, a light shield pixel portion, a dummy pixel, and a blank pixel in which the light receiving element is shielded with an aluminum sheet or the like so that light does not enter the preceding stage of the 7500 effective pixels in the line sensor BK. A feeding part is provided. The total of the light shield pixel portion, the dummy pixel, and the idle feed portion is also equivalent to 500 pixels.
[0033]
In the case of the line sensor BK, since the charge transfer is divided into the odd pixel and the even pixel as described above, the transfer clock necessary for serially outputting the charge (image information) for 8000 pixels is It may be 4000 pixels.
[0034]
Accordingly, the cycle of the SH signal input to the shift gate can be shortened, and the light accumulation time (tINT) for one line can be shortened. As described above, since the line sensor K has high sensitivity, there is no problem even if the light accumulation time (tINT) of one line is shortened. FIG. 10 shows that the period of the SH signal can be shortened by a dotted line, the effective pixel area is 3750 pixels, and signals corresponding to the odd and even pixels are separately output from the respective analog shift registers. .
[0035]
As described above, it has been described that when the line sensor BK is used for the 4-line CCD sensor 12, a reading speed twice as high as that when the line sensors R, G, and B are used can be realized. If the sensitivity of the line sensor K has a margin, the speed can be further increased. 11 and 12 show that the output of the line sensor BK is divided into an odd number and an even number, and further divided into an output from the first half and an output from the second half, so that a fourfold reading speed can be realized.
[0036]
Returning to FIG. 1, the configuration of the image forming apparatus will be described. The process unit 3 outputs an image based on image data read from an original by the scanner unit 2 or image data input from an external device (not shown) on a sheet (transfer medium) P. The paper supply unit 4 supplies the paper P to the process unit 3.
[0037]
The scanner unit 2, the process unit 3, and the paper feed unit 4 are housed in a housing 15. A duplex unit 16 and a manual feed unit 17 are detachably attached to the right side of the housing 15. The duplex unit 16 inverts the sheet P on which an image is formed on one side by the process unit 3 and supplies the sheet P to the process unit 3 again. The manual feed unit 17 supplies the paper P to the process unit 3 by manual feed.
[0038]
The process unit 3 includes a photosensitive drum (image carrier) 18 that extends in the front-rear direction (paper surface direction) of the apparatus. A charging device 19, an exposure device 20, a black developing device (second developing device) 21, a revolver (developing unit) 22, an intermediate transfer belt (intermediate) along the rotation direction of the photosensitive drum 18 (arrow direction in the drawing). A transfer member 23 and a drum cleaner (cleaning device) 24 are provided.
[0039]
The charging device 19 charges the outer peripheral surface (hereinafter referred to as drum surface) 18a of the photosensitive drum 18 to a predetermined potential.
[0040]
The exposure device 20 is disposed near the lower end of the process unit 3 and exposes the drum surface 18a charged to a predetermined potential with a laser beam that scans, thereby forming an electrostatic latent image of each color on the drum surface 18a.
[0041]
The black developing device 21 is disposed between the photosensitive drum 18 and the exposure device 20, that is, opposed to the photosensitive drum 18 from below. The black developing device 21 supplies black developer to the black electrostatic latent image formed on the drum surface 18a by the exposure device 20 and develops it, thereby forming the black developer on the drum surface 18a. The black developing device 21 is movably provided so that the developing roller is separated from and in contact with the drum surface 18a. When forming a black image, the developing roller moves so as to contact the drum surface 18a, and when forming an image of another color, the developing roller is moved away from the drum surface 18a. The black developer 21 is supplied with a developer from a toner cartridge 21a.
[0042]
The revolver 22 is rotatably provided adjacent to the left side of the photosensitive drum 18 in the drawing. The revolver 22 includes a yellow developing device (first developing device) 22Y, a magenta developing device (second developing device) 22M, and a cyan developing device (third developing device) 22C. These developing units 22Y, 22M, and 22C are detachably accommodated in the revolver 22 side by side in the rotation direction of the revolver 22.
[0043]
The developing units 22Y, 22M, and 22C include toner cartridges 22y, 22m, and 22c that store developers of the respective colors. When an image is formed, the revolver 22 is rotated in the clockwise direction, and desired developing devices 22Y, 22M, and 22C are selectively arranged to face the drum surface 18a of the photosensitive drum 18.
[0044]
As described above, only the black developing unit 21 is independently arranged in the developing unit built in the process unit 3, and the other yellow developing unit 22 Y, magenta developing unit 22 M, and cyan developing unit 22 C are arranged in the revolver 22. Has been.
[0045]
With such a structure, when a yellow, magenta, and cyan image is formed, an operation such as rotating the revolver 22 is necessary. On the other hand, when forming a black image, the drum surface is rotated. It is only necessary to bring the black developing device 21 close to 18a. Therefore, the time until image formation becomes possible has a structure in which black is shorter than other colors.
[0046]
The intermediate transfer belt 23 is disposed at a position in contact with the photosensitive drum 18 from above. The intermediate transfer belt 23 is suspended around a driving roller 23a, a pre-transfer roller 23b, a transfer counter roller 23c, and a tension roller 23d each having a rotation shaft extending in the front-rear direction (paper surface direction). Inside the intermediate transfer belt 23, there is a primary transfer roller 24 for pressing the intermediate transfer belt 23 against the drum surface 18a with a predetermined pressure and transferring the developer image formed on the drum surface 18a to the intermediate transfer belt 23. Is provided. Around the intermediate transfer belt 23, there are a belt cleaner 25 for cleaning the intermediate transfer belt 23 and a secondary transfer roller 26 for transferring the developer image on the intermediate transfer belt 23 to the paper P, respectively. It is provided so as to be able to be separated from the surface.
[0047]
The paper feed unit 4 has two paper feed cassettes 27 and 28. Pickup rollers 29 for taking out the uppermost sheet P accommodated in the cassettes are provided at the upper right end of the sheet feeding cassettes 27 and 28 in the drawing. A feed roller 30 and a separation roller 31 are arranged in contact with each other at positions adjacent to the downstream side in the sheet take-out direction by the pickup roller 29.
[0048]
At a position adjacent to the right side in the drawing of each of the paper feed cassettes 27 and 28, a paper transport path 32 is provided toward the secondary transfer point where the intermediate transfer belt 23 and the secondary transfer roller 26 are in contact. On this paper transport path 32, a plurality of transport roller pairs 33 that sandwich and rotate the paper P, an aligning sensor 34 that detects the arrival of the paper P, and the paper P at a secondary transfer point at a predetermined timing. An aligning roller pair 35 for feeding paper is provided in order.
[0049]
A fixing device 36 for fixing the developer transferred on the paper P by overheating and pressing is provided on the paper transport path 32 extending upward through the secondary transfer point. The fixing device 36 includes a superheater roller 36a having a built-in heater and a pressure roller 36b in which a pressure is positioned on the superheater roller 36a.
[0050]
The control panel 5 has a plurality of select switches for selecting a monochrome image reading mode, a color image reading mode, copying start, and the like.
[0051]
FIG. 13 shows an output image signal for image formation in the image forming apparatus shown in FIG. 1 by processing either one or both of the monochrome image signal and the RGB color image signal output from the 4-line CCD sensor 12. It is a schematic block diagram explaining an example of the image processing circuit 40 to produce | generate.
[0052]
The 4-line CCD sensor 12 is a type that outputs a monochrome image signal and a color image signal independently. Each line sensor BK, R, G, B of the 4-line CCD sensor 12 is connected to each amplifier 42a, 42b, 42c, 42d of the image signal processing unit 41, respectively. These amplifiers 42a, 42b, 42c, and 42d amplify the monochrome image signals or RGB color image signals output from the line sensors BK, R, G, and B, respectively, to a predetermined level under the control of the scanner CPU 43.
[0053]
Each A / D converter 44a, 44b, 44c, 44d is connected to each output terminal of each amplifier 42a, 42b, 42c, 42d. These A / D converters 44a, 44b, 44c and 44d are respectively monochrome image signals and RGB color image signals output from the line sensors BK, R, G and B amplified by the amplifiers 42a, 42b, 42c and 42d. Are converted into respective digital signals.
[0054]
The shading correction circuits 45a, 45b, 45c, and 45d are connected to the output terminals of the A / D converters 44a, 44b, 44c, and 44d, respectively. These shading correction circuits 45a, 45b, 45c, and 45d receive the digital signals output from the A / D converters 44a, 44b, 44c, and 44d in accordance with a threshold level set in advance based on the reflected light from the white reference plate. Correct the reference value for white level and black level.
[0055]
Among the shading correction circuits 45a, 45b, 45c, and 45d, the RGB shading correction circuits 45b, 45c, and 45d are connected to the sub-scanning position correction circuit 46. This sub-scanning position correction circuit 46 is in the sub-scanning direction (at the same time) when the output signals of the shading correction circuits 45b, 45c, 45d are read by the line sensors R, G, B under the control of the scanner CPU 57. The deviation of the reading position of the original is corrected and output to the correction circuit 47 in the next stage.
[0056]
This correction circuit 47 corrects chromatic aberration caused by the reduction lens 11, and the output signal of the sub-scanning position correction circuit 46 is controlled by the scanner CPU 43 by the arrangement of the line sensors R, G, B and the reduction lens 11. The influence of lateral chromatic aberration (lateral chromatic aberration) given according to the color component is corrected and sent to the image processing circuit 48 at the next stage.
[0057]
The correction circuit 47 is not limited to correcting the color image signals of the line sensors R and B based on the color image signal of the line sensor G, and any of the line sensors RGB in the image processing in the image processing circuit 48 in the subsequent stage. The reference color image signal may be changed to RG or B depending on whether it is important.
[0058]
The image processing circuit 48 is connected to the output terminal of the shading correction circuit 45 a corresponding to the line sensor BK and the output terminal of the correction circuit 47. That is, since the monochrome image signal output from the line sensor BK is a single output signal, the sub-scanning position correction and the chromatic aberration correction are not required unlike the color image signal.
[0059]
Therefore, the output terminal of the shading correction circuit 45 a corresponding to the line sensor BK is directly connected to the image processing circuit 48 without going through the sub-scanning position correction circuit 46 and the correction circuit 47.
[0060]
The image processing circuit 48 performs, for example, color correction (change of color balance) and density correction on the monochrome image signal from the line sensor BK and each color image signal from the correction circuit 47 under the control of the scanner CPU 43, Each image forming unit of the image forming apparatus 49 outputs an output image signal for forming an image for each color component. The output image signal output from the image processing circuit 48 is held in, for example, an image memory (RAM) or a buffer memory 52 under the control of the main CPU 51 of the main control board 50 of the image forming apparatus 49.
[0061]
Next, the operation of the apparatus configured as described above will be described.
[0062]
When copying the image information of the reading object, the object is positioned at a predetermined position on the platen glass 6.
[0063]
When the start of copying is instructed from the control panel 5, illumination light having a predetermined light intensity is emitted from the light source 7.
[0064]
The first and second carriages 13 and 14 move along the platen glass 6 at a predetermined speed according to the copying magnification, so that the image information of the object set on the platen glass 6 is received from the light source 7. Illuminated sequentially by illumination light. Thereby, reflected light including image information as light brightness and darkness is generated from the object. This reflected light is called image light.
[0065]
The image light is reflected toward the second carriage 14 by the mirror 8 fixed to the first carriage 13, is further reflected by the mirrors 9 and 10 of the second carriage 14, and enters the reduction lens 11. The image light incident on the reduction lens 11 forms an image on the light receiving portion 12 a of the 4-line CCD sensor 12.
[0066]
The image light imaged on the 4-line CCD sensor 12 is, for example, sequentially in four line sensors R, G, B, and BK corresponding to R, G, B, and BK images that are complementary colors of C, M, and Y, respectively. Photoelectrically converted and output at a predetermined timing.
[0067]
The monochrome image signal output from the BK line sensor of the 4-line CCD sensor 12 and the color image signal output from the R line sensor, the G line sensor, and the B line sensor are respectively the amplifiers 42a to 42a of the image signal processing unit 41. 42d and amplified to a predetermined level under the control of the scanner CPU 43.
[0068]
The outputs from the BK line sensor and the RGB line sensor amplified by the amplifiers 42a to 42d are converted into digital signals by the A / D converters 44a to 44d, respectively, and input to the shading correction circuits 45a to 45d. The white level and black level reference values are corrected according to the threshold level set based on the reflected light from the white reference plate.
[0069]
Here, when the monochrome image reading mode is selected on the control panel 5, only the output of the shading correction circuit 45 a corresponding to the BK line sensor is sent to the image processing circuit 48. This image processing circuit 48 performs density correction, for example, on the monochrome image signal from the line sensor BK under the control of the scanner CPU 43, so that each image forming unit of the image forming apparatus 49 forms an image for each color component. Output monochrome image signal.
[0070]
On the other hand, when the color image reading mode is selected on the control panel 5, the outputs of the shading correction circuits 45b to 45d corresponding to the RGB line sensors are sent to the sub-scanning position correction circuit 54 at the next stage.
[0071]
The RGB color image signal input to the sub-scanning position correction circuit 54 is controlled by the scanner CPU 43 to correct the deviation of the reading position of the document in the sub-scanning direction (at the same time) when read by the RGB line sensor. Then, it is sent to the correction circuit 47 in the next stage.
[0072]
The correction circuit 47 generally obtains a weighted average of adjacent pixels, for example. When there is a shift caused by chromatic aberration as shown in FIG. Deviation D _R For the i-th pixel R signal output: Ri
Rinew = (n + 1−D _R ) ・ Ri + n + (D _R -N) Ri + n + 1
However, n is n ≦ D _R <An integer that satisfies n + 1
Rinew is Ri after correction (1)
According to the above, the deviation D between BG around G is corrected. _B As for the i-th pixel B signal output: Bi
Binew = (n + 1−D _B ) ・ Bi + n + (D _B -N) Bi + n + 1
However, n is n ≦ D _B <An integer that satisfies n + 1
Binew is Bi after correction (2)
Thus, each deviation from G is corrected.
[0073]
In the above formulas (1) and (2), the positional deviation amount D _R , D _B More specifically, when there is a B image signal output that is shifted by a predetermined amount with respect to the output of the G image signal, the shift amount Bi of the B image that is shifted from the pixel at the i-th position of the G image. And the shift amount Bi-1 of the B image that is shifted with respect to the pixel at the i-1th position of the G image, the position of the ith pixel is i− with respect to the original position of the ith image. 1-D _B At the same time, i-1 + D with respect to the original position of the (i-1) th image _B Respectively. As a result, the correction coefficient parameter K _R , K _B , L _R , L _B Can be requested. These correction coefficient parameters K _R , K _B , L _R , L _B Thus, for example, the positional deviation between the R image signal and the B image signal with respect to the G image signal is corrected.
[0074]
The RGB color image signal input to the correction circuit 47 is controlled by the scanner CPU 43 to correct the influence of lateral chromatic aberration (lateral chromatic aberration) given according to the color component by the RGB line sensor array and the reduction lens 11. Are input to the image processing circuit 48 in the next stage.
[0075]
The image processing circuit 48 performs, for example, color correction and density correction on the RGB color image signal from the correction circuit 47 under the control of the scanner CPU 43, and each image forming unit of the image forming apparatus 49 performs an image for each color component. An output image signal for forming is output.
[0076]
The output image signal output from the image processing circuit 48 is held in, for example, an image memory (RAM) or a buffer memory 52 under the control of the main CPU 51 of the main control board 50 of the image forming apparatus 49.
[0077]
When the output image signal output from the image processing circuit 48 is held in the image memory (RAM) or the buffer memory 52 in this way, the image of the reading object is transferred to the paper P based on the image signal.
[0078]
Next, an operation for forming a monochrome image on the paper P will be described.
[0079]
In any of the developing units 22Y, 22M, and 22C, the revolver rotates to a position that does not face the drum surface 18a. Then, the black developing device 21 moves upward and faces the drum surface 18a.
[0080]
The belt cleaner 25 rotates clockwise about the shaft 25a to contact the intermediate transfer belt 23, and the secondary transfer roller 26 moves to the left in the drawing and is brought into contact with the intermediate transfer belt 23.
[0081]
The exposure apparatus 20 scans the laser beam on the drum surface 18a based on the monochrome image signal, and an electrostatic latent image of black BK is formed on the drum surface 18a. Subsequently, the black developer is supplied to the electrostatic latent image on the drum surface 18a via the black developing device 21, and the black developer is formed on the drum surface 18a.
[0082]
The black developer image on the drum surface 18 a formed in this way moves by the rotation of the photosensitive drum 18 and reaches the primary transfer point in contact with the intermediate transfer belt 23. At the primary transfer point, a bias having a polarity opposite to that of the black developer is applied via the primary transfer roller, and the black developer image on the drum surface 18 a is transferred onto the intermediate transfer belt 23.
[0083]
On the drum surface 18a that has passed the primary transfer point, the black developer remaining without being transferred by the drum cleaner 25 is removed, and at the same time, the residual charge is discharged. The drum surface 18a is uniformly charged by the charging device 19 in order to form the next black BK electrostatic latent image.
[0084]
When image formation of black BK is continuously performed, a series of processes, that is, exposure → development → transfer to the intermediate transfer belt 23 is executed as in the previous operation, and the next black developer image is transferred to the intermediate transfer belt. 23 is transferred.
[0085]
The electrostatic latent image of black BK transferred onto the intermediate transfer belt 23 is moved by the rotation of the intermediate transfer belt 23 and passes through the secondary transfer point between the secondary transfer roller 26 and the intermediate transfer belt 23.
[0086]
At this time, after the paper P taken out from the cassettes 27 and 28 is once aligned by the pickup roller 29, it is sent to the secondary transfer area at a predetermined timing.
[0087]
Then, a black developer image potential and a reverse bias are applied via the secondary transfer roller 26, and the black developer on the intermediate transfer belt 23 is transferred onto the paper P. After the black developer is transferred onto the paper P, the black developer remaining on the intermediate transfer belt 23 is removed by the drum cleaner 25.
[0088]
Thereafter, the paper P to which the black developer has been transferred passes through the fixing device 36 and is heated and pressurized, whereby the black developer image is fixed on the paper P and a black image is formed. The paper P on which the black image is thus formed is discharged to the discharge tray 61 via the discharge roller 60 provided on the downstream side of the fixing device 36.
[0089]
Next, an operation for transferring a color image onto the paper P will be described.
[0090]
The black developing device 21 moves downward and is separated from the drum surface 18a.
[0091]
The revolver rotates clockwise, and the yellow developing device 22Y faces the drum surface 18a. The belt cleaner 25 is rotated counterclockwise about the shaft 25a to be separated from the intermediate transfer belt 23, and the secondary transfer roller 26 is moved in the direction away from the paper transport path 32 (right direction in the figure) to be intermediate. Separated from the transfer belt 23.
[0092]
The exposure device 20 scans the drum surface 18a with laser light based on the yellow color image signal, and an electrostatic latent image for yellow is formed on the drum surface 18a. Subsequently, the yellow developer is supplied to the electrostatic latent image on the drum surface 18a via the yellow developer 22Y, and the yellow developer is formed on the drum surface 18a.
[0093]
The yellow developer image on the drum surface 18 a formed in this way moves by the rotation of the photosensitive drum 18 and reaches the primary transfer point in contact with the intermediate transfer belt 23. At the primary transfer point, a bias having a polarity opposite to the potential of the yellow developer is applied via the primary transfer roller, and the yellow developer image on the drum surface 18 a is transferred onto the intermediate transfer belt 23.
[0094]
On the drum surface 18a that has passed the primary transfer point, the yellow developer remaining without being transferred by the drum cleaner 25 is removed, and at the same time, the residual charge is discharged. Then, the drum surface 18a is uniformly charged by the charging device 19 to form the next magenta electrostatic latent image, the revolver 22 rotates, and the magenta developing device 22M faces the drum surface 18a.
[0095]
In this state, as in the case of the previous yellow, a series of processes, that is, exposure → development → transfer to the intermediate transfer belt 23 is executed, and the magenta developer image is superimposed on the yellow developer image on the intermediate transfer belt 23. Is transcribed. After the magenta developer image is transferred in this manner, it is similarly transferred to the cyan developer image.
[0096]
Then, the revolver rotates to a position where none of the developing units 22Y, 22M, 22C is opposed to the drum surface 18a. Then, the black developing device 21 moves upward and faces the drum surface 18a. In this state, a process similar to the above process is performed, and the black developer image is transferred onto the intermediate transfer belt 23 so as to overlap the yellow developer image, the magenta developer image, and the cyan developer image.
[0097]
When the developer images of all the colors are superimposed on the intermediate transfer belt 23 in this way, the secondary transfer roller 26 moves to the left in the drawing and comes into contact with the intermediate transfer belt 23, and the intermediate transfer belt 23 of the belt cleaner 25. To touch. In this state, the developer images of all the colors superimposed on the intermediate transfer belt 23 are moved by the rotation of the intermediate transfer belt 23 and pass through the secondary transfer point between the secondary transfer roller 26 and the intermediate transfer belt 23.
[0098]
At this time, the paper P taken out from the cassettes 27 and 28 by the pickup roller 29 is transported upward in the longitudinal transport path 32 by the transport roller pair 33, and once aligned by the aligning roller 35, at a predetermined timing. It is sent to the secondary transfer area.
[0099]
Then, a potential and a reverse bias of each color developer image are applied through the secondary transfer roller 26, and each color developer on the intermediate transfer belt 23 is transferred onto the paper P. After the developer is transferred to the paper P, the black developer remaining on the intermediate transfer belt 23 is removed by the drum cleaner 25.
[0100]
The paper P onto which the developer of each color has been transferred together is then heated and pressurized through the fixing device 36, and the developer image of each color is fixed on the paper P to form a color image. The paper P on which the color image is thus formed is discharged to the discharge tray 61 via the discharge roller 60 provided on the downstream side of the fixing device 36.
[0101]
As described above, in the first embodiment, when the 4-line CCD sensor 12 of a type that outputs a monochrome image signal and a color image signal independently is used, the monochrome image signal is output from the 4-line CCD sensor 12 during monochrome reading. Chromatic aberration correction caused by the reduction lens 11 is not performed on the monochrome image signal, but chromatic aberration correction is performed on the color image signal output from the 4-line CCD sensor 12 during color reading.
[0102]
Accordingly, chromatic aberration caused by the reduction lens 11 can be reliably performed only on the color image signal. For example, an inexpensive reduction lens 11 can be provided without using an expensive combination of a plurality of lenses for the reduction lens 11. Even if it is used, the chromatic aberration caused by the convergence of the inexpensive reduction lens 11 can be reliably corrected.
[0103]
Therefore, an inexpensive image reading apparatus can be realized using the 4-line CCD sensor 12 by combining the inexpensive reduction lens 11 and the inexpensive 4-line CCD sensor 12.
[0104]
Further, unnecessary chromatic aberration correction is not performed on the monochrome image signal at the time of monochrome reading, and chromatic aberration correction of chromatic aberration caused by the reduction lens 11 required at the time of color reading can be performed only on the color image signal. This makes it possible to speed up the reading time of an object to be read without performing chromatic aberration correction.
[0105]
Next, a second embodiment of the present invention will be described with reference to the drawings.
[0106]
In the second embodiment, a type in which a monochrome image signal and a color image signal are simultaneously output to the 4-line CCD sensor 12 is used, and the configuration of the image processing circuit 40 shown in FIG. It has been changed.
[0107]
FIG. 15 is a configuration diagram of the image processing circuit 70. The shading correction circuit 45a corresponding to the BK line sensor is connected to the sub-scanning position correction circuit 46.
[0108]
When the monochrome image reading mode is selected on the control panel 5, the scanner CPU 43 includes only the amplifier 42a, the A / D converter 44a, and the shading correction circuit 45a in order to process the monochrome image signal output from the BK line sensor. The output signal of the shading correction circuit 45a is passed through the sub-scanning position correction circuit 46 and the correction circuit 47 and sent to the image processing circuit 48.
[0109]
When the color image reading mode is selected on the control panel 5, the scanner CPU 43 performs processing on the color image signals output from the RGB line sensors, and the amplifiers 42b to 42d and the A / D converters 44b to 44b. d. Each shading correction circuit 45b-d is selected and operated, and each output signal of each shading correction circuit 45b-d is sent to the image processing circuit 48 through the sub-scanning position correction circuit 46 and the correction circuit 47.
[0110]
When the color image reading mode is selected on the control panel 5, the scanner CPU 43 selects the amplifiers 42a to 42d to process the monochrome image signal and the color image signal output from the BK and RGB line sensors. The A / D converters 44a to 44d and the shading correction circuits 45a to 45d are selected and operated, and the output signals of the shading correction circuits 45a to 45d are passed through the sub-scanning position correction circuit 46 and the correction circuit 47 for image processing. To circuit 48.
[0111]
Therefore, when the 4-line CCD sensor 12 of the type that outputs a monochrome image signal and a color image signal simultaneously is used, when the monochrome image reading mode is selected on the control panel 5, the correction circuit 47 converts the monochrome image signal into a monochrome image signal. On the other hand, it passes through without performing chromatic aberration correction, and outputs it as it is.
[0112]
When the color image reading mode is selected on the control panel 5, the correction circuit 47 performs chromatic aberration correction on the RGB color image signal.
[0113]
Further, when the monochrome image signal and the color image signal are simultaneously output from the 4-line CCD sensor 12, the correction circuit 47 performs chromatic aberration correction on both the monochrome image signal and the color image signal. That is, since the focal positions of BK, R, G, and B converged by the reduction lens 12 are different, chromatic aberration correction is necessary for the monochrome image signal and the RGB color image signal.
[0114]
The correction circuit 47 corrects the chromatic aberration of the monochrome image signal of each line sensor BK and the R and B color image signals based on the color image signal of the line sensor G. Alternatively, the correction circuit 47 may correct the chromatic aberration of the R, G, and B color image signals based on the monochrome image signal of the line sensor BK. The color image signal used as a reference may be changed to RG or B depending on which of the line sensors RGB is important in image processing in the image processing circuit 48 in the subsequent stage.
[0115]
The image processing circuit 48 performs, for example, color correction and density correction on the monochrome image signal or / and the RGB color image signal from the correction circuit 47 under the control of the scanner CPU 43, and each image forming unit of the image forming apparatus 49 An output image signal for forming an image for each color component is output.
[0116]
The output image signal output from the image processing circuit 48 is held in, for example, an image memory (RAM) or a buffer memory 52 under the control of the main CPU 51 of the main control board 50 of the image forming apparatus 49.
[0117]
When the output image signal output from the image processing circuit 48 is held in the image memory (RAM) or the buffer memory 52 in this way, the image of the reading object is transferred to the paper P based on the image signal.
[0118]
Since the operation of transferring the monochrome image or the color image to the paper P in the image forming apparatus 49 is the same as described above, the description thereof is omitted.
[0119]
As described above, in the second embodiment, when a 4-line CCD sensor 12 of a type that outputs a monochrome image signal and a color image signal at the same time is used, a through-pass is performed without correcting chromatic aberration for the monochrome image signal. Further, chromatic aberration correction is performed on the color image signal, and chromatic aberration correction is performed on both the monochrome image signal and the color image signal.
[0120]
Thus, it goes without saying that the same effects as those of the first embodiment are obtained, and the monochrome image reading mode, the color image reading mode, or the simultaneous output mode of the monochrome image signal and the color image signal in the control panel 5 is achieved. For this selection, a monochrome image signal and a color image signal to be corrected for chromatic aberration can be selected, and chromatic aberration can be corrected without using unnecessary time.
[0121]
In addition, this invention is not limited to the said 1st and 2nd embodiment, In the implementation stage, it can change variously in the range which does not deviate from the summary.
[0122]
Although the four-line CCD sensor 12 has been described with four line sensors BK, R, G, and B arranged, the present invention is not limited to this, and, for example, a sensor having two black line sensors BK is also applicable.
[0123]
Further, the image forming apparatus used in the first and second embodiments may use the image forming apparatus 80 having the configuration shown in FIG. The image forming apparatus 80 includes an optical unit 81, developing units 82Y, 82M, 82C, and 82K necessary for forming each color image, photosensitive drums 83Y, 83M, 83C, and 83K, and charging chargers 84Y, 84M, 84C, 84K, cleaners 85Y, 85M, 85C, 85K, transfer belt 86, suction roller 87, transfer belt rollers 88, 89, transfer belt cleaner 90, aligning rollers 91, 92, A sheet feeding roller 93, a sheet feeding cassette 94 that accommodates and supplies the sheet P, a fixing device 95, and transfer rollers 96Y, 96M, 96C, and 96K are configured.
[0124]
A color image forming operation will be described.
[0125]
Each of the photosensitive drums 83Y, 83M, 83C, 83K and the transfer belt 86 are rotationally driven at a predetermined outer peripheral speed by a drive motor (not shown). The charging chargers 84Y, 84M, 84C, and 84K provided so as to face the surfaces of the photosensitive drums 83Y, 83M, 83C, and 83K have the surface of the photosensitive drums 83Y, 83M, 83C, and 83K at a predetermined potential. Charge.
[0126]
The four lights output from the optical unit 81 are imaged as scanning light that is spot light having a necessary resolution at exposure positions on the photosensitive drums 83Y, 83M, 83C, and 83K, and are subjected to scanning exposure. As a result, electrostatic latent images corresponding to the image signals are formed on the photosensitive drums 83Y, 83M, 83C, and 83K.
[0127]
The electrostatic latent images formed on the photosensitive drums 83Y, 83M, 83C, and 83K are developed with toner as a developer supplied from the developing units 82Y, 82M, 82C, and 82K to form toner images. . For example, the electrostatic latent image formed on the photosensitive drum 83Y is developed as a yellow toner image by the developing device 82Y. Similarly, the electrostatic latent image formed on the photosensitive drum 83M is developed as a magenta toner image by the developing device 82M. The electrostatic latent image formed on the photosensitive drum 83C is developed as a cyan toner image by the developing unit 82C. The electrostatic latent image formed on the photosensitive drum 83K is developed as a black toner image by the developing device 82K.
[0128]
On the other hand, the paper P stored in the paper feed cassette 94 is conveyed to the aligning rollers 91 and 92 by the rotation of the paper feed roller 93 and is aligned (positioned), and then the rotation of the aligning rollers 91 and 92 is performed. Thus, the toner is conveyed to the suction roller 87 and the transfer belt roller 88.
[0129]
A predetermined potential difference is provided between the suction roller 87 and the transfer belt roller 88. The sheet P is conveyed downstream in a state where the sheet P is adsorbed on the transfer belt 86 by the rotation of the adsorption roller 87 and the transfer belt roller 88 and the transfer belt roller 89.
[0130]
The toner images of the respective colors on the photosensitive drums 83Y, 83M, 83C, and 83K developed by the developing units 82Y, 82M, 82C, and 82K are portions where the transfer belt 86 and the transfer rollers 96Y, 96M, 96C, and 96K are in contact with each other. Is transferred onto the paper P.
[0131]
Next, the paper P is heated and pressurized by passing through the fixing device 95. The toner image on the paper P is melted and securely fixed on the paper P. At this time, each of the photosensitive drums 83Y, 83M, 83C, and 83K that has been transferred to the paper P is returned to the initial state after the residual toner on the surface is removed by the cleaners 85Y, 85M, 85C, and 85K. A standby state for image formation is entered. In addition, the transfer belt 86 that has finished transporting the paper P is removed from unnecessary toner adhering to the belt 86 when passing through the transfer belt cleaner 90, and is ready for the next paper transport.
[0132]
By repeating the above process, a color image forming operation is continuously performed.
[0133]
Next, a detailed configuration of the optical unit 81 and an optical path during color image formation will be described.
[0134]
The optical unit 81 includes, for example, four semiconductor lasers (not shown). The light output from each semiconductor laser is reflected on the surface of the polygon mirror 101 rotated by the polygon motor 100 and becomes light that scans the surface of each photosensitive drum 83Y, 83M, 83C, 83K.
[0135]
Here, the light that may reach the photosensitive drum 83Y is BM-Y,
Assuming that light that may reach the photosensitive drum 83M is BM-M, light that may reach the photosensitive drum 83C is BM-C, and light that may reach the photosensitive drum 83K is BM-K, Each light scanned by the polygon motor 100 passes through the lenses LN1, LN2, and LN3, respectively.
[0136]
The light BM-Y that may reach the photosensitive drum 83Y passes through the lenses LN1, LN2, and LN3, and then is reflected by the half mirror HM-Y to be about 50% to become light BM-Y1. Thereafter, the light is reflected by the mirrors MR-Y1 and MR-Y2 and reaches the photosensitive drum 83Y. On the other hand, the light BM-Y2 that has passed through the half mirror HM-Y is blocked by the light blocking member (shutter) SHT-Y1, and does not reach any drum.
[0137]
Further, the light BM-M that may reach the photosensitive drum 83M passes through the lenses LN1, LN2, and LN3, and then is reflected by the half mirror HM-M to be light BM-M1. Thereafter, the light is reflected by the mirrors MR-M1 and MR-M2 and reaches the photosensitive drum 83M. On the other hand, the light BM-M2 that has passed through the half mirror HM-M is shielded by the light shielding member (shutter) SHT-M1 and does not reach any drum.
[0138]
The light BM-C that may reach the photosensitive drum 83C passes through the lenses LN1, LN2, and LN3, and then is reflected by the half mirror HM-C by about 50% to become the light BM-C1. Thereafter, the light is reflected by mirrors MR-C1 and MR-C2 and reaches the photosensitive drum 83C. On the other hand, the light BM-C2 that has passed through the half mirror HM-C is shielded by the light shielding member (shutter) SHT-C1 and does not reach any drum.
[0139]
The light BM-K that reaches the photosensitive drum 83K passes through the lenses LN1, LN2, and LN3, and then is reflected by the mirror MR-K and reaches the photosensitive drum 83K.
[0140]
In this way, the light from the four semiconductor lasers is reflected on the surface of the polygon mirror 101 that is rotationally driven by the polygon motor 100, and then passes through each path to become light that scans on each photosensitive drum. The image can be formed.
[0141]
Next, an operation for forming a monochrome image at high speed and an optical path in the optical system will be described.
[0142]
The photosensitive drum 83K, the transfer belt 86, and the fixing device 95 are rotationally driven by a driving motor (not shown) at a speed four times that at the time of forming the color image described above. The photosensitive drums 83Y, 83M, and 83C that are not used do not rotate the developing rollers in the developing units 82K, 82Y, 82M, and 82C that are not rotated.
[0143]
Unlike the color image formation, all four lights output from the optical unit 81 are imaged as scanning light that is a spot having a necessary resolution at an exposure location on the photosensitive drum 83K, and are subjected to scanning exposure. . That is, the photosensitive drum 83K is simultaneously scanned and exposed by four lights, and an electrostatic latent image corresponding to the image signal is formed. In this case, the optical path in the optical unit 81 will be described later. The electrostatic latent image formed on the photosensitive drum 83K is developed with toner from the developing device 82K to become a K toner image.
[0144]
In the monochrome mode, the transfer belt 86, the suction roller 87, the transfer belt roller 88, and the transfer rollers 96Y, 96M, and 96C are moved downward by a drive motor (not shown) so as not to contact the photosensitive drums 83Y, 83M, and 83C. ing. The transfer belt 86 is in contact with only the photosensitive drum 83K.
[0145]
The toner image on the photosensitive drum 83K developed by the developing device 82K is transferred onto the paper P at a location where the transfer belt 86 and the transfer roller 96K come into contact with each other.
[0146]
Next, the paper P passes over the fixing device 95 and is heated and pressurized. Thereby, the toner image on the paper P is melted and fixed on the paper P reliably.
[0147]
By repeating the operations in the above processes, the monochrome image forming operation is continuously performed at a speed four times that of the color image forming operation.
[0148]
Next, the optical path in the optical unit 81 when forming a monochrome image will be described.
[0149]
The difference from the color image formation is the position of each light shielding member SHT-Y1, SHT-Y2, SHT-M1, SHT-M2, SHT-C1, and SHT-C2. The light BM-Y1 that has reached the photosensitive drum 83Y during the color image formation is shielded by the light shielding member SHT-Y2 and does not reach the photosensitive drum 83Y.
[0150]
On the other hand, the light BM-M2 that has passed through the half mirror HM-M is reflected by the mirror MR-M3 and reaches the photosensitive drum 83Y. At the time of color image formation, the light BM-K that has reached the photosensitive drum 83Y reaches the photosensitive drum 83K without any particular change.
[0151]
As described above, in the monochrome image forming mode, the light paths to the photosensitive drums 83Y, 83M, and 83C are blocked by the light shielding members SHT-Y2, SHT-M2, and SHT-C2, and conversely, the light shielding members SHT-Y1. , SHT-M1 and SHT-C1 are displaced to secure an optical path to the photosensitive drum 83K. Each light shielding member SHT-Y1, SHT-Y2, SHT-M1, SHT-M2, SHT-C1, and SHT-C2 is opened and closed by a driving unit (not shown).
[0152]
When the monochrome mode is designated in this way, the laser beams from the four semiconductor lasers are reflected by the surface of the polygon mirror 101 rotated by the polygon motor 100, and then pass through the respective optical paths. All of the two lights become light that scans on the photosensitive drum 83K, and high-speed monochrome image formation becomes possible.
[0153]
【The invention's effect】
As described above in detail, according to the present invention, an inexpensive 4-line CCD sensor and a reduction lens can be obtained by selectively performing chromatic aberration correction on a monochrome image signal and a color image signal output from the 4-line CCD sensor. Use to reduce costs In addition, unnecessary chromatic aberration correction is not performed on a monochrome image signal at the time of monochrome reading, and chromatic aberration correction of chromatic aberration caused by a reduction lens required at the time of color reading can be performed only on the color image signal, which is useless. Chromatic aberration correction is not performed, and the reading time of the reading object can be increased. An image reading apparatus and an image forming apparatus using the image reading apparatus can be provided.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of an image forming apparatus using a first embodiment of an image reading apparatus according to the present invention.
FIG. 2 is an external view of a 4-line CCD sensor used in the apparatus.
FIG. 3 is an enlarged view of a light receiving unit in a 4-line CCD sensor used in the apparatus.
FIG. 4 is a view showing spectral sensitivity characteristics of a line sensor K constituting a 4-line CCD sensor used in the apparatus.
FIG. 5 is a view showing spectral sensitivity characteristics of line sensors R, G, and B constituting a 4-line CCD sensor used in the apparatus.
FIG. 6 is a diagram showing a spectral distribution of a xenon-type light source used in the apparatus.
FIG. 7 is a schematic configuration diagram of a 4-line CCD sensor used in the apparatus.
FIG. 8 is an explanatory diagram of signal output of each line sensor BK, R, G, B in the 4-line CCD sensor used in the apparatus.
FIG. 9 is an explanatory diagram of an output signal of the line sensor BK in the 4-line CCD sensor used in the apparatus.
FIG. 10 is a diagram for explaining realization of high-speed reading with a 4-line CCD sensor used in the apparatus.
FIG. 11 is a diagram for explaining realization of high-speed reading with a 4-line CCD sensor used in the apparatus.
FIG. 12 is a diagram for explaining realization of high-speed reading with a 4-line CCD sensor used in the apparatus.
FIG. 13 is a configuration diagram of an image processing circuit in an image forming apparatus used in the apparatus.
FIG. 14 is a diagram showing a shift caused by chromatic aberration.
FIG. 15 is a configuration diagram of an image processing circuit in the second embodiment of the image reading apparatus according to the present invention;
FIG. 16 is a configuration diagram of another image forming apparatus applied to the image reading apparatus according to the present invention.
[Explanation of symbols]
1: automatic document feeder (ADF), 2: scanner unit, 3: process unit, 4: paper feeding unit, 5: control panel, 6: original glass, 7: light source, 8-10: mirror, 11: reduction Lens: 12: 4-line CCD sensor, BK, R, G, B: line sensor, 13: first carriage, 14: second carriage, 15: housing, 18: photosensitive drum, 19: charging device, 20: Exposure device, 21: Black developer, 22: Revolver, 23: Intermediate transfer belt, 24: Drum cleaner, 22Y: Yellow developer, 22M: Magenta developer, 22C: Cyan developer, 22y, 22m, 22c: Toner cartridge, 23: intermediate transfer belt, 24: primary transfer roller, 25: belt cleaner, 26: secondary transfer roller, 27, 28: paper feed cassette, 29: 30: feed roller, 31: separation roller, 32: paper conveyance path, 33: conveyance roller pair, 34: aligning sensor, 35: aligning roller pair, 36: fixing device, 40: image processing circuit, 41: Image signal processing unit, 42a, 42b, 42c, 42d: each amplifier, 43: scanner CPU, 44a, 44b, 44c, 44d: A / D converter, 45a, 45b, 45c, 45d: shading correction circuit, 46: sub-scanning Position correction circuit, 47: correction circuit, 48: image processing circuit, 70: image processing circuit, 80: image forming apparatus, 81: optical unit, 82Y, 82M, 82C, 82K: developing unit, 83Y, 83M, 83C, 83K : Photosensitive drum, 84Y, 84M, 84C, 84K: Charging charger, 85Y, 85M, 85C, 85K: C 86, transfer belt, 87: suction roller, 88, 89: transfer belt roller, 90: transfer belt cleaner, 91, 92: aligning roller, 93: paper feed roller, 94: paper feed cassette, 95: fixing 96Y, 96M, 96C, 96K: transfer roller.

Claims (4)

A reduction lens that converges image light from the object to be read; and
A four-line CCD sensor that receives the image light converged by the reduction lens and outputs one or both of a monochrome image signal and an RGB color image signal;
A shift in the reading position of the reading object in the sub-scanning direction when the monochrome image signal and the RGB color image signal output from the 4-line CCD sensor are read by the 4-line CCD sensor is corrected. A sub-scanning position correction circuit;
A correction circuit that corrects the chromatic aberration given to the output signal of the sub-scanning position correction circuit according to the color component by the arrangement of the 4-line CCD sensor and the reduction lens;
When the monochrome image reading mode is selected, the monochrome image signal output from the 4-line CCD sensor is not corrected by the sub-scanning position correction circuit and the correction circuit for correcting the chromatic aberration, and at least An output image signal for forming an image for each color component after density correction is output, a color image reading mode is selected, and the monochrome image signal and the RGB color image signal are output . If, output from the four-line CCD sensor, subjected to at least color correction and density correction for said monochrome image signal and a color image signal of the RGB output from the correction circuit through the sub-scanning position correction circuit An image processing circuit for outputting an output image signal for forming an image for each color component;
An image reading apparatus comprising: The 4-line CCD sensor includes a BK line sensor that outputs the monochrome image signal and an RGB line sensor that outputs the RGB color image signal, and simultaneously outputs the monochrome image signal and the RGB color image signal. Output type,
The BK line sensor includes an amplifier that amplifies the monochrome image signal output from the BK line sensor, an A / D converter that converts the monochrome image signal amplified by the amplifier into a digital signal, and the A / D The sub-scanning position is input via the shading correction circuit that inputs the digital signal output from the converter and corrects the reference value of the white level and the black level in accordance with a threshold level set in advance based on the reflected light from the white reference plate. Connected to the correction circuit ,
The RGB line sensors respectively amplify the RGB color image signals output from the RGB line sensors, and convert the RGB color image signals amplified by the amplifiers into digital signals. Each A / D converter to be converted, and the RGB color image signal output from these A / D converters are input, and the white level and the black level according to the threshold level set in advance based on the reflected light from the white reference plate Connected to the sub-scanning position correction circuit via each shading correction circuit for correcting the reference value of
When the monochrome image reading mode is selected, the amplifier, the A / D converter, and the shading correction circuit are selectively operated, and the output of the shading correction circuit is passed through to the sub-scanning position correction circuit and the correction circuit. When the color image reading mode is selected, each amplifier, each A / D converter, each shading correction circuit is selected and each shading correction circuit When the output is sent to the image processing circuit through the sub-scanning position correction circuit and the correction circuit, and the 4-line CCD sensor outputs the monochrome image signal and the RGB color image signal simultaneously, the correction is performed. A monochrome image signal output from the 4-line CCD sensor by a circuit; Scanner CPU to correct the chromatic aberration for both signals of the RGB color image signal,
The image reading apparatus according to claim 1, characterized in that it comprises. A reduction lens that converges image light from the object to be read; and
A four-line CCD sensor that receives the image light converged by the reduction lens and outputs one or both of a monochrome image signal and an RGB color image signal;
A shift in the reading position of the reading object in the sub-scanning direction when the monochrome image signal and the RGB color image signal output from the 4-line CCD sensor are read by the 4-line CCD sensor is corrected. A sub-scanning position correction circuit;
A correction circuit that corrects the chromatic aberration given to the output signal of the sub-scanning position correction circuit according to the color component by the arrangement of the 4-line CCD sensor and the reduction lens;
When the monochrome image reading mode is selected, the monochrome image signal output from the 4-line CCD sensor is not corrected by the sub-scanning position correction circuit and the correction circuit for correcting the chromatic aberration, and at least When an output image signal for forming an image for each color component after density correction is output, or when a color image reading mode is selected and the monochrome image signal and the RGB color image signal are output The monochrome image signal and the RGB color image signal output from the 4-line CCD sensor and output from the correction circuit through the sub-scanning position correction circuit are subjected to at least color correction and density correction. An image processing circuit for outputting an output image signal for forming an image for each color component;
An image forming unit that forms an image based on image information acquired based on the output image signal output from the image processing circuit;
Images forming device you characterized by comprising a. The 4-line CCD sensor includes a BK line sensor that outputs the monochrome image signal and RGB line sensors that output the RGB color image signals. The monochrome image signal and the RGB color image signals are It is a type that outputs at the same time,
The BK line sensor includes an amplifier that amplifies the monochrome image signal output from the BK line sensor, an A / D converter that converts the monochrome image signal amplified by the amplifier into a digital signal, and the A / D The sub-scanning position is input via the shading correction circuit that inputs the digital signal output from the converter and corrects the reference value of the white level and the black level in accordance with a threshold level set in advance based on the reflected light from the white reference plate. Connected to the correction circuit,
The RGB line sensors respectively amplify the RGB color image signals output from the RGB line sensors, and convert the RGB color image signals amplified by the amplifiers into digital signals. Each A / D converter to be converted, and the RGB color image signal output from these A / D converters are input, and the white level and the black level according to the threshold level set in advance based on the reflected light from the white reference plate Connected to the sub-scanning position correction circuit via each shading correction circuit for correcting the reference value of
When the monochrome image reading mode is selected, the amplifier, the A / D converter, and the shading correction circuit are selectively operated, and the output of the shading correction circuit is passed through to the sub-scanning position correction circuit and the correction circuit. When the color image reading mode is selected, each amplifier, each A / D converter, each shading correction circuit is selected and each shading correction circuit When the output is sent to the image processing circuit through the sub-scanning position correction circuit and the correction circuit, and the 4-line CCD sensor outputs the monochrome image signal and the RGB color image signal simultaneously, the correction is performed. A monochrome image signal output from the 4-line CCD sensor by a circuit; Scanner CPU to correct the chromatic aberration for both signals of the RGB color image signal,
The image forming apparatus according to claim 3, characterized in that it comprises.

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