Abstract:
An object of this invention is to provide a structure which meets a high-quality reading requirement and realize high-speed color reading when the reading section of a color image forming apparatus adopts a color contact image sensor using CCDs as reading elements. In order to achieve this object, the image sensor of a color image reading section uses a color contact image sensor in which a plurality of CCDs are aligned as reading elements in the main scanning direction. In this case, each CCD has one analog shift register for RGB time-division reading, and three R, G, and B reading apertures arranged parallel to each other at a pitch corresponding to the reading resolution. The pixel pitch in the main scanning direction is constant.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to an image sensor and an image reading apparatus having the same.  
         BACKGROUND OF THE INVENTION  
         [0002]    Recent development of so-called digital color copying machines which separate a color document into colors, electrically read the document, print the obtained color image data on a sheet, and thus copy the color image is outstanding. With the popularization of digital color copying systems, demands have arisen for higher printing qualities of color images. Particularly, a demand for printing black characters and thin black lines more black and shaper is strong. When a black document is separated into colors, yellow, magenta, cyan, and black color signals are generated as signals which reproduce black, and data is printed based on the obtained color signals. Black is reproduced by superposing the four colors, and thus even slight misregistration between the colors smears a thin black line. An originally black image cannot look black or blurs, greatly degrading the printing quality.  
           [0003]    To increase the printing quality, there is proposed a method of, e.g., extracting color information in an image signal or the feature of the special frequency such as a thin line or dot to detect the area of a black character, color character, or the like. Further, the image is separated into areas such as a halftone image area and dot image area, and the respective areas undergo corresponding processes. For example, if the area is a black character portion, the area is monochromated in black.  
           [0004]    To meet demands for cost reduction and reduction in power consumption of the light source, so-called contact image sensors (to be referred to as CISs hereinafter) are being utilized more and more. This CIS uses a light source such as an LED or xenon lamp, an equal-magnification imaging optical system such as a SELFOC lens, and a CCD or CMOS line sensor, in addition to an image scanner using a reduction optical system as a combination of CCDs and lenses.  
           [0005]    For example, when a document is read by a color copying machine at a reading rate of about 25 ipm (images/min), the reduction optical system using CCDs requires a document surface illuminance of about 30,000 lx. To the contrary, the examination results reveal that the use of the contact image sensor needs only a document surface illuminance of about 3,000 lx which is about {fraction (1/10)} that of the reduction optical system, and can offer the same S/N in reading at the same reading rate.  
           [0006]    As a color CIS which reads 600 dpi at the equal magnification, CISs as shown in FIGS. 10 and 11 are proposed. FIG. 10 shows an example of the sensor pixel array of the color CIS. One 42-μm pixel corresponding to 600 dpi is divided into three in the subscanning direction, and three R, G, and B reading lines are formed parallel to each other at a pixel pitch of ⅓.  
           [0007]    There is also proposed an in-line sensor in which one 42-μm pixel is divided into three in the main scanning direction and pixels are aligned in order of R. G, B, R, G, B . . . , as shown in FIG. 11.  
           [0008]    These two sensors, however, suffer the following problems.  
           [0009]    The area of the reading aperture is ⅓ the pixel per color, and the sensitivity is low. As a result, the light quantity of a light source must be directly increased, which poses a problem in increasing a speed of 30 sheets/min or more in a copying machine.  
           [0010]    The reading position shifts every ⅓ pixel in the subscanning direction or main scanning direction in accordance with R, G, and B color components, and correction processing for alignment must be executed. Assuming that a G component exists at the center, R and B components undergo alignment processing using linear interpolation. Since linear interpolation is smoothing processing, the MTFs of the R and B components become lower by about 30% than that of the G component.  
           [0011]    This leads to a blurred image, and the black character determination unit of the color copying machine tends to detect a thin black line as another color owing to the MTF difference between the R, G, and B components of the image. The color copying machine having the black character determination function cannot determine a black character at high precision, and the qualities of black characters and thin lines on a printed image are low.  
           [0012]    Especially in the copying machine, the image quality is most important in reading at the equal magnification of 100%, and then important in reading within the range of 70% to 140%. For this reason, the MTF difference between R, G, and B components is undesirable in reading at the equal magnification.  
           [0013]    In an existing color 3-line CCD for a reduction optical system, the interval between R, G, and B reading lines is an integer multiple of one pixel such as a pitch of four or two pixels. In reading at the equal magnification, read data of respective colors are stored in a line memory and read out with a shift corresponding to the line interval. Only this processing can realize reading position correction processing.  
           [0014]    A larger line interval, however, causes large color misregistration due to mechanical vibrations. Similar to the MTF difference, a thin black line is colored and leads to erroneous black color determination. Hence, the line interval is ideally one line. This also applies to a color CIS.  
           [0015]    A general color CCD for a reduction optical system has R, G, and B reading aperture lines formed parallel to the main scanning direction. The color CCD comprises two analog shift registers for charge transfer/reading in correspondence with each aperture line, i.e., a total of six analog shift registers. These analog shift registers do not pose any problem in the reduction optical system which uses only one color CCD.  
           [0016]    In the color CIS, however, 16 color CCD chips are aligned in the main scanning direction. The use of similar color CCDs results in 6×16=96 reading outputs. Wiring and an analog processor circuit for processing the outputs become bulky.  
           [0017]    In the pixel structure of the CIS, 468 pixels are arranged on one chip of a CCD reading element for each color. If 16 chips are aligned, 468×16=7,488 pixels are arranged in the main scanning direction. For example, to read an A4-size document in the longitudinal direction at 60 dpi, there is proposed a structure in which the pixel pitch between pixels on each chip in the main scanning direction is decreased at the end, instead of an equal pixel pitch.  
           [0018]    A change in pixel pitch does not generate any problem when the CIS having this structure reads a document such as a printing paper sheet having a document image with no periodicity. When a document image such as dotted printed matter with periodicity is read, a change in pitch at the end of the CCD reading element with respect to the spatial frequency of the document image generates moiré, and the density changes depending on the phase.  
           [0019]    The black character determination unit of a color copying machine adopts an image area separation technique to check whether an area in process is a dotted image or character area. Also in this case, the pixel pitch is desirably equal.  
         SUMMARY OF THE INVENTION  
         [0020]    The present invention has been made to overcome the conventional drawbacks, and has as its object to provide an optimum structure of a color CIS for a high-speed copying machine. More specifically, it is an object of the present invention to simultaneously rationally meet conditions: to realize high-speed reading while keeping a high S/N at high sensitivity, to enable reading without generating any MTF difference between R, G, and B colors, to minimize color misregistration caused by mechanical vibrations, to implement a color CIS with an appropriate circuit scale, and to accurately read a document having image periodicity.  
           [0021]    To achieve the above object, according to the present invention, an image sensor is characterized by comprising image pickup element arrays on a plurality of lines that output signals of different colors for the respective lines, and a charge transfer unit on one line for sequentially reading out the signals of different colors from said image pickup element arrays on the plurality of lines by time division.  
           [0022]    Other objects and advantages besides those discussed above shall be apparent to those skilled in the art from the description of a preferred embodiment of the invention which follows. In the description, reference is made to accompanying drawings, which form a part hereof, and which illustrate an example of the invention. Such example, however, is not exhaustive of the various embodiments of the invention, and therefore reference is made to the claims which follow the description for determining the scope of the invention. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0023]    [0023]FIG. 1 is a sectional view showing an image forming apparatus according to an embodiment of the present invention;  
         [0024]    [0024]FIG. 2 is a sectional view showing a CIS;  
         [0025]    [0025]FIG. 3 is a perspective view showing the structure of the CIS;  
         [0026]    [0026]FIG. 4 is an enlarged view showing the pixel structure of a color CIS according to the embodiment of the present invention;  
         [0027]    [0027]FIG. 5 is a timing chart for explaining an image signal reading timing from a CCD according to the embodiment of the present invention;  
         [0028]    [0028]FIG. 6 is a view macroscopically showing the color CIS;  
         [0029]    [0029]FIG. 7 is a view for explaining the joint between CCD chips according to the embodiment of the present invention;  
         [0030]    [0030]FIG. 8 is a view for explaining subscanning operation;  
         [0031]    [0031]FIG. 9 is a block diagram showing image processing according to the embodiment of the present invention;  
         [0032]    [0032]FIG. 10 is a view for explaining a color CIS in which one pixel is divided into three, R, G, and B colors in the subscanning direction; and  
         [0033]    [0033]FIG. 11 is a view for explaining another color CIS in which one pixel is divided into three, R, G, and B colors in the main scanning direction. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0034]    A preferred embodiment according to the present invention will be described in detail below with reference to the accompanying drawings.  
         [0035]    [0035]FIG. 1 is a sectional view showing the arrangement of an image forming apparatus according to the embodiment of the present invention. In FIG. 1, reference numeral  201  denotes an image scanner section which reads a document and performs digital signal processing; and  200 , a printer section which prints out on a sheet in full color an image corresponding to a document image read by the image scanner section  201 .  
         [0036]    A CIS module  202  incorporated in the image scanner section  201  will be explained. FIG. 2 is a sectional view of the CIS module  202 , and FIG. 3 is an exploded perspective view thereof.  
         [0037]    As shown in FIGS. 2 and 3, the CIS module  202  is constituted by attaching, to a mold  2026 , a cover glass  2021 , an illumination light source  2022  made up of an LED and light guide, an equal-magnification imaging lens  2023  formed from a SELFOC lens or the like, a color line sensor  2024 , and a board  2025  which holds the color line sensor  2024 .  
         [0038]    [0038]FIG. 4 is an enlarged view showing the microscopic portion of the color line sensor  2024  incorporated in the CIS module  202 . Each rectangle represents a photodiode serving as a reading pixel. The color line sensor  2024  is used for equal-magnification reading at 600 dpi, and the size of the aperture of one pixel is about 34×34 μm.  
         [0039]    Color filters of three, R, G, and B primary colors are formed on the photodiodes of the color line sensor  2024 .  
         [0040]    Reference numeral  2024 - 1  denotes a light-receiving element array (photosensor) prepared by aligning photodiodes which are covered with R filters and transmit a red wavelength component of visible light.  
         [0041]    Reference numerals  2024 - 2  and  2024 - 3  denote light-receiving element arrays prepared by aligning corresponding photodiodes which are covered with G and B filters and transmit green and blue wavelength components of visible light. The three R, G, and B line form reading lines, which generate charges corresponding to incident light quantities on the photodiodes during an accumulation time.  
         [0042]    Reference numeral  2024 - 4  denotes a CCD analog shift register serving as a charge transfer unit for transferring charges accumulated in the photodiodes  2024 - 1 ,  2024 - 2 , and  2024 - 3 ; and  2024 - 5 , an output amplifier for converting a charge signal into a voltage and outputting the voltage as a voltage output signal.  
         [0043]    The light-receiving element arrays  2024 - 1 ,  2024 - 2 , and  2024 - 3  having different optical characteristics on the three lines are arranged parallel to each other so as to read the same line of a document by the R, G, and B sensors. The CCD analog shift register  2024 - 4  is arranged adjacent and parallel to the B light-receiving element array  2024 - 3  outside the three light-receiving element arrays. The light-receiving element arrays  2024 - 1 ,  2024 - 2 , and  2024 - 3  and the CCD shift register  2024 - 4  have a monolithic structure on a single silicon chip.  
         [0044]    The photodiodes are arranged such that the pitch between pixels (distance between the centers of photodiodes) on each line in the main scanning direction is set to about 42 μm. Also, the photodiodes are arranged such that the interval between lines is set to about 42 μm.  
         [0045]    [0045]FIG. 5 is a timing chart for explaining the readout timing of an image signal from the color CIS.  
         [0046]    Charges of R, G, and B colors for one line that are accumulated in the photodiodes  2024 - 1 ,  2024 - 2 , and  2024 - 3  during one line period (e.g., 350 μs) are transferred at once to the CCD analog shift register  2024 - 4  serving as a charge transfer unit in response to a shift pulse φSH at the timing of the start of the next line.  
         [0047]    The charges which have been output to the CCD analog shift register  2024 - 4  and correspond to the respective pixels are sequentially transferred every pixel to the output amplifier  2024 - 5  in response to a charge transfer clock φM. The charges are converted into a voltage by the output amplifier  2024 - 5  and output as a voltage output signal. After the charge transfer unit  2024 - 4  transfers charges to the output amplifier  2024 - 5 , the charge transfer unit  2024 - 4  is reset by a reset pulse φRS.  
         [0048]    First, dummy signals d 1 , d 2 , . . . , d 6  are read out. Then, effective signals are read out for 468 pixels of each color in repetitive order of green, blue, and read: G 1 , B 1 , R 1 ; G 2 , B 2 , R 2 , . . . , G 468 , B 468 , and R 468 .  
         [0049]    Signals are read out at these timings because the CCD analog shift register on one line common to the three light-receiving element arrays transfers charges of three colors in this embodiment.  
         [0050]    [0050]FIG. 6 is a view macroscopically showing the color line sensor  2024 .  
         [0051]    Sixty sensor chips are aligned on a board  2024 - 6 . Signals are output from the respective sensor chips, and 16 ch signals are simultaneously read out in correspondence with the chips. The readout 16 ch signals are subjected to gain offset adjustment by an analog signal processing unit  101  (to be described later), and converted into digital signals by an internal A/D converter. Since each sensor chip outputs only 1 ch, the number of reading output channels can be decreased even with a plurality of sensor chips, compared to the prior art. Wiring and an analog processor circuit for processing output image signals can be simplified.  
         [0052]    [0052]FIG. 7 is an enlarged view showing joints between the 16 sensor chips. In FIG. 7, the charge transfer unit  2024 - 4  is not illustrated. In this embodiment, the pixel pitch (distance between the centers of photodiodes) between pixels at the ends of adjacent sensor chips is designed double a normal pitch (pixel pitch within a single sensor chip).  
         [0053]    In this arrangement, one pixel is omitted at the joint, but can be rationally interpolated by preceding and subsequent pixels. Even an image such as a dotted image with a periodic property can be accurately read without generating moiré or a density change.  
         [0054]    The operation of the overall apparatus will be explained. In the image scanner section  201  of FIG. 1, a document  204  set on a document glass (platen)  205  and pressed by a document press plate  203  is irradiated with light from the illumination light source  2022  incorporated in the CIS module  202  shown in FIG. 2. The light reflected by the document  204  forms an image on the color line sensor  2024  via the lens  2023  in FIG. 2.  
         [0055]    The color line sensor  2024  separates optical information of the document into red (R), green (G), and blue (B) color components to read the document in full color. The color line sensor  2024  outputs the R, G, and B color signals to a signal processor  207 .  
         [0056]    Each of the reading sensor lines of the respective color components in the color line sensor  2024  is formed from 7,500 pixels. The color line sensor  2024  can therefore read at a resolution of 600 dpi an A3-size document 297 mm in the widthwise direction, which is the maximum size among documents set on the document glass  205 .  
         [0057]    The CIS module  202  mechanically moves at a velocity V in a direction (subscanning direction) perpendicular to the electrical scanning direction (main scanning direction) of the reading sensor line, thereby scanning the entire surface of the document  204 .  
         [0058]    [0058]FIG. 8 is a top view showing the image reading apparatus of the embodiment for explaining an arrangement which performs subscanning operation.  
         [0059]    The color CIS  202  is stored in a resin carriage  410 . Slide members  419  and  420  are attached to the two ends of the color CIS  202 , and pressed against the platen glass by spring members (not shown) incorporated in the carriage  410 .  
         [0060]    The movement of the carriage  410  is restricted by a linear guide  418  so as to move in only the subscanning direction. A timing belt  411  is connected below the carriage  410 . As the timing belt  411  moves, the carriage  410  moves interlockingly.  
         [0061]    A stepping motor  413  transmits its power to the carriage  410  via the timing belt  411 , a timing belt  412 , and pulleys  414 ,  415 ,  416 , and  417  under the control of a CPU  131  (to be described later) serving as a control means. Then, the carriage  410  moves in the subscanning direction.  
         [0062]    Referring back to FIG. 1, a standard white plate  206  is white with an almost uniform reflecting characteristic to visible light. The standard white plate  206  corrects shading of R, G, and B data read by the color line sensor  2024 . Shading correction is performed for document reading data output from the R, G, and B sensors  2024 - 1 ,  2024 - 2 , and  2024 - 3  on the basis of data obtained by reading the standard white plate  206 .  
         [0063]    The image signal processor  207  electrically processes a read signal, separates it into magenta (M), cyan (C), yellow (Y), and black (Bk) components, and sends them to the printer section  200 . One of M, C, Y, and Bk components is transferred to the printer section  200  every document scanning (scan) of the image scanner section  201 . By a total of four document scanning operations, image data of one sheet is printed out.  
         [0064]    In the printer section  200 , M, C, Y, and Bk image signals from the image scanner section  201  are sent to a laser driver  212 . The laser driver  212  modulates and drives a semiconductor laser  213  in accordance with the image signals. A laser beam emitted by the semiconductor laser  213  scans a photosensitive drum  217  via a polygon mirror  214 , f-θ lens  215 , and mirror  216 .  
         [0065]    The developing device is made up of a magenta developing unit  219 , cyan developing unit  220 , yellow developing unit  221 , and black developing unit  222 . The four developing units alternately contact the photosensitive drum  217  to develop M, C, Y, and Bk electrostatic latent images formed on the photosensitive drum  217  with corresponding toners.  
         [0066]    A transfer drum  223  holds a sheet fed from a sheet cassette  224  or  225  around the transfer drum  223  itself, and a toner image developed on the photosensitive drum  217  is transferred to the sheet.  
         [0067]    After toner images of four, M, C, Y, and Bk colors are sequentially transferred, the sheet is discharged via a fixing unit  226 .  
         [0068]    The image signal processor  207  will be described.  
         [0069]    [0069]FIG. 9 is a block diagram showing the flow of an image signal in the image signal processor  207  of the image scanner section  201  according to the embodiment.  
         [0070]    The image signal processor  207  executes various processes using a register and memory under the control of the control means  131  implemented by a CPU.  
         [0071]    A clock generator  121  generates clocks for each pixel, and a main scanning address counter  122  counts clocks from the clock generator  121  to generate a pixel address output of one line. A decoder  123  decodes the main scanning address from the main scanning address counter  122 , and generates a line unit sensor driving signal such as a shift pulse or reset pulse, a signal VE representing an effective area in a 1-line reading signal output from the color image sensor, and a line sync signal HSYNC. The main scanning address counter  122  is cleared by a signal HSYNC, and starts counting the main scanning address of the next line.  
         [0072]    Image signals OS 1  to OS 16  output from the CIS module  202  are input to the analog signal processing unit  101 . The analog signal processing unit  101  analog-multiplexes the signals so as to assign OS 1  to OS 6  to ch 1 , OS 7  to OS 12  to ch 2 , and OS 13  to OS 16  to ch 3 . After gain adjustment and offset adjustment, the analog signal processing unit  101  converts the signals into an 8-bit digital image signal.  
         [0073]    The 8-bit digital image signal output from the analog signal processing unit  101  is separated into signals of R, G, and B color components by a rearrangement unit  102 . A shading correction unit  103  performs known shading correction using a reading signal of a standard white plate  211  for the signals of the respective colors.  
         [0074]    An inter-line correction unit  104  corrects spatial shifts between the shading-corrected color signals in the subscanning direction.  
         [0075]    In the CIS module  202  used in this embodiment, as shown in FIG. 4, the three light-receiving element arrays  2024 - 1 ,  2024 - 2 , and  2024 - 3  of the color image sensor  2024  are arranged parallel to each other at a predetermined distance (42 μm equal to the size of the aperture of one pixel in the subscanning direction). Since the R, G, and B lines shift from each other by one pixel in the subscanning direction, data at different positions are simultaneously read in the subscanning direction. The image data must be corrected to the same position, and thus a known so-called 3-line correction technique is adopted for correction.  
         [0076]    The 3-line correction is employed as an essential technique in the use of an existing color 3-line CCD. In general, an image signal (in this case, a B signal) of a previously read line is accumulated in a memory and combined with image signals (in this case, R and G signals) of subsequently read lines. The R and G color signals are delayed by lines in the subscanning direction with respect to the B signal so as to adjust the R and G color signals to the B signal, thereby correcting the spatial shift.  
         [0077]    In the color CIS used in the embodiment, the interval between the three, R, G, and B reading lines is one pixel pitch which is an integer multiple of the size of one pixel in the subscanning direction. This can simplify correction processing. As far as the interval is an integer multiple of the size of one pixel in the subscanning direction, the lines may be arranged at an interval of two or three times (two or three pixels).  
         [0078]    An output from the inter-line correction unit  104  is input to an input masking unit  106 . In order to transform the RGB signal reading color space read by the CIS module  202  into an NTSC standard color space, the input masking unit  106  executes the following matrix calculation:  
         [         R4           G4           B4         ]     =       [         a11       a12       a13           a21       a22       a23           a31       a32       a33         ]          [         R3           G3           B3         ]                             
 
         [0079]    Luminance signals R 4 , G 4 , and B 4  output from the input masking unit  106  are converted into density signals C 0 , M 0 , and Y 0  by a light quantity/density converter (LOG transformation unit)  107  formed from a lookup table ROM.  
         [0080]    A line delay memory  108  delays the image signals C 0 , M 0 , and Y 0  by lines until determination signals UCR, FILTER, SEN, and the like generated by a black character determination unit  113  (to be described later) from the signals R 4 , G 4 , and B 4 . As a result, the image signals C 1 , M 1 , and Y 1  and a black character determination signal for the same pixel are simultaneously input to a masking UCR circuit  109 .  
         [0081]    The masking UCR circuit  109  extracts a black signal (Bk) from the input three primary color signals Y 1 , M 1 , and C 1 . The masking UCR circuit  109  performs calculation of correcting color smear of a recording coloring material in a printer  212 . Then, the masking UCR circuit  109  sequentially outputs signals Y 2 , M 2 , C 2 , and Bk 2  with a predetermined bit width (8 bits) every reading operation.  
         [0082]    A main scanning scaling circuit  110  performs enlargement/reduction processing in the main scanning direction for an image signal and black character determination signal by known interpolation calculation.  
         [0083]    A spatial filter processing unit (output filter)  111  switches edge emphasis and smoothing processing on the basis of a 2-bit signal FILTER from a LUT  117 , and outputs the resultant signal to the printer  212 .  
         [0084]    The black character determination unit  113  will be explained. The basic operation is to determine whether an area of interest in a read image is a character/line image area or a dotted image area. If the area is determined to be a character/line image area, the UCR  109  increases the black amount to make black clear. The output filter  111  emphasizes the edge, and the printer  212  switches the number of printing lines to be output to a fine-image setting and prints a sharp, clear character/line image. If the area is determined to be a dotted area, the filter  111  executes filtering so as to blur dots, and the printer  212  switches the number of printing lines for higher tone level reproducibility.  
         [0085]    The black character determination unit  113  is disclosed in detail in Japanese Patent Laid-Open No. 7-203198 filed by the present applicant. A character thickness determination unit  114  determines the thickness of a character/line image portion in an image. An edge detection unit  115  obtains edge information of the character/line image, and a saturation determination unit  116  attains saturation information.  
         [0086]    Then, 4-bit determination signals ZONE and FCH from the character thickness determination unit  114 , a 3-bit determination signal EDGE from the edge detection unit  115 , and a 2-bit determination signal COL from the saturation determination unit  116  are input to the LUT (lookup table)  117 . In accordance with these 9-bit input signals, the LUT  117  outputs a 3-bit signal UCR for controlling the masking UCR unit  109 , a 2-bit signal FILTER for controlling the output filter  111 , and a 1-bit signal SEN for controlling the printer  212 .  
         [0087]    In this way, the masking UCR unit  109 , output filter unit  111 , and printer  212  are appropriately controlled in accordance with the determination results of the character thickness determination unit  114 , edge detection unit  115 , and saturation determination unit  116 . Proper image processing can be achieved in accordance with whether the current area is a black character, i.e., character/line image area or a dotted image area, and a clear printing result can be obtained.  
         [0088]    The above-described embodiment of the present invention has proposed an optimum structure of a color CIS for a high-speed copying machine. With the use of the proposed color CIS, high-speed reading can be realized with high sensitivity and high S/N. Further, reading with high reproducibility of a thin black character line can be performed without generating any MTF between R, G, and B colors.  
         [0089]    Since the pitch between lines is decreased, color misregistration by mechanical vibrations can be minimized. An image having periodicity can also be accurately read, and these improvements can be implemented with a proper circuit scale.  
         [0090]    The present invention can be applied to a system constituted by a plurality of devices or an apparatus formed from one device.  
         [0091]    As has been described above, this embodiment can realize high-speed reading at high sensitivity and high S/N by using a color contact image sensor.  
         [0092]    The present invention is not limited to the above embodiments and various changes and modifications can be made within the spirit and scope of the present invention. Therefore, to apprise the public of the scope of the present invention the following claims are made.