Abstract:
In a color reading apparatus for successively reading respective red, green, and blue colors in each line while a document is continuously conveyed to a plurality of line sensor units arranged in a zigzag manner, the line sensor units are arranged with a distance equal to or shorter than a unit of line to prevent a color shift. When read data of the plurality of line sensor units in a conveying direction are to be combined, image data shifted by the number of lines corresponding to distances between the line sensor units in the conveying direction are set as first combination candidates. A color code and a line code are added to each of the data. Image data having the same color code and the same line code are combined. According to the image reading apparatus structured as described above, it is possible to obtain data capable of reproducing read data for each color on the same line without errors.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to an image reading apparatus with respect to a combination of read data between a plurality of image reading sensor units. In particular, the present invention relates to an image reading apparatus in which a plurality of image reading sensor units are arranged in a zigzag manner. 
         [0003]    2. Related Background Art 
         [0004]    With respect to conventional technologies, a conventional technology for correcting the amount of shift in a direction orthogonal to an arrangement direction of sensor arrays arranged in a zigzag manner is disclosed in JP 62-258553 A. According to this technology, storing means having a data storage region corresponding to each of the sensor arrays is used and read data is stored in a storage region designated by an address determined based on the amount of shift. Circular addressing is used for memory saving. 
         [0005]    However, in the conventional technology, the correction is performed in a unit of line for each of the sensor arrays arranged in the zigzag manner, and hence no adjustment is performed based on a distance equal to or shorter than a distance between lines. In a case of a color reading apparatus for successively reading respective red, green, and blue colors in each line while a document is continuously conveyed, only the adjustment performed merely in a unit of line as in the conventional technology may cause a color shift. In other words, when the continuously conveyed document is to be subjected to color reading, the red, green, and blue colors are read for each line in order. Therefore, a read timing is shifted among the red, green, and blue colors. In addition, data is read at different timings among the respective sensor arrays. Thus, even when the adjustment is performed for each line, a read color may be different from a corresponding color of the document, and hence the accurate color of the document cannot be reproduced. 
       SUMMARY OF THE INVENTION 
       [0006]    According to the present invention, there is provided an image reading apparatus in which a plurality of image reading units for reading a document continuously conveyed are arranged in a zigzag manner, the image reading units read reflection light for each color on the document by photoelectric conversion elements arranged in line while light sources having a plurality of colors are successively turned on and off, to obtain digital data, and the digital data associated with the respective image reading units are combined to generate one-line image data, the digital data each including color data indicating one of the colors of the light sources used to obtain the digital data and read period data indicating one of capture periods of the digital data, the image reading apparatus characterized by including: first image detecting means for detecting, from the digital data obtained by reading by the image reading units, the digital data having the color data indicating a predetermined color and the read period data indicating a predetermined capture period; a memory including a plurality of addresses and corresponding storage regions, for storing, for each of the addresses, the digital data which is digital data determined based on a result obtained by detection by the first image detecting means, has the same color data and the same read period data, and is obtained by reading by each of the image reading units; and image control means for combining the digital data associated with the respective image reading units which are stored in the storage regions corresponding to the addresses from the memory, to generate the one-line image data. 
         [0007]    Further, the image reading apparatus may be characterized in that the first image detecting means performs detection at read timings of the image reading units and adjusts a write timing of the digital data into the memory to a timing based on a read timing when the digital data having the predetermined color data and the predetermined read period data is detected. 
         [0008]    Further, the image reading apparatus may be characterized in that, after the digital data is written into the memory at the write timing, the digital data obtained by reading by the image reading units are stored in the memory in synchronization with the read timings of the image reading units. 
         [0009]    Further, the image reading apparatus may be characterized in that an offset value is determined in advance based on a read line width of the image reading apparatus relative to an interval in a conveying direction between the image reading units arranged in the zigzag manner, and an address for starting storage of the digital data into the memory is determined based on the offset value. 
         [0010]    Further, the image reading apparatus may be characterized in that the offset value is determined based on an interval between a reference image reading unit which is one of the image reading units arranged in the zigzag manner and another one of the image reading units. 
         [0011]    Further, the image reading apparatus may be characterized in that: the color data has at least three values corresponding to three colors of red, green, and blue; and the read period data has at least four values larger than the number of colors recognized by the color data and is set to a value such that the digital data obtained by reading does not overlap with data of preceding and succeeding read lines. 
         [0012]    According to the image reading apparatus, the image data obtained by reading the colors on the same line can be read without errors. Therefore, the image data faithfully reproducing the read document can be obtained. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  is an arrangement view showing an image reading unit; 
           [0014]      FIG. 2  is a schematic view showing an image reading apparatus; 
           [0015]      FIG. 3  is a block diagram showing an electrical structure of a read portion according to the present invention; 
           [0016]      FIG. 4  is a read timing chart for respective CISs; 
           [0017]      FIG. 5  is a structural diagram showing data output from each of the CISs; and 
           [0018]      FIG. 6  is a schematic explanatory diagram showing data correction after primary correction. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0019]      FIG. 1  is an arrangement diagram showing image reading units. A contact image sensor unit is used as each of the image reading units. Hereinafter, the contact image sensor unit is referred to as a CIS. Five CISs, that is, a CIS-A  1 , a CIS-B  2 , a CIS-C  3 , a CIS-D  4 , and a CIS-E  5  are arranged in a zigzag manner to read a document  6  conveyed in a direction indicated by an arrow. Red, green, and blue LEDs are arranged in each of the CISs. The LEDs are used as light sources. Approximately 5,000 photoelectric conversion elements are arranged in line. Light reflected on the document  6  is subjected to photoelectric conversion to read the document, and then converted into digital data. The respective CISs are arranged so as to overlap with each other in a conveying direction of the document  6 , thereby performing overlap reading. 
         [0020]    Because the CISs are arranged in the zigzag manner, intervals are provided between the sensor units arranged in the conveying direction of the document. Line differences indicating the number of lines corresponding to the intervals in a case where each line of reading is set as a unit area line difference L 1 , a line difference L 2 , a line difference L 3 , and a line difference L 4 . Data of the line differences are stored as line difference data in a memory. When the image data captured by the respective sensor units are to be combined, the line difference data are readout from the memory, and then adjacent data originally constituting one line are combined based on the line difference data. The image data located in positions in which the line difference data corresponding to a distance difference between the image reading units becomes 0 are combined to each other. 
         [0021]      FIG. 2  is a schematic view showing an image reading apparatus. A read portion  8  in which the five CISs are arranged in the zigzag manner is provided under a glass  9  in a case  7 . A document base cover  13  is provided above the case  7  to block light from the outside. The document  6  taken into the apparatus is held by a first conveying roller pair  10  and a second conveying roller pair  11 , conveyed at a constant speed, and delivered to a document outlet  12 . The document  6  is read through the glass  9  by the read portion  8 . In the image reading apparatus, the document  6  is conveyed at a constant speed and read by the document read portion  8  to generate image data. 
         [0022]      FIG. 3  is a block diagram showing an electrical structure of the read portion according to the present invention. Digital data of the document read by the respective CISs, that is, the CIS-A  1 , the CIS-B  2 , the CIS-C  3 , the CIS-D  4 , and the CIS-E  5  are output to a sensor control circuit  14 . Color type data indicating read data obtained by turning on which color LED and a value (line number) obtained by circulating a value of 1 to 4 in order for each read line are added as a header to the digital data of the read document. The document is periodically read, and hence the line number is used as data indicating a read period. 
         [0023]    A first line detection circuit  15  is a circuit for detecting data having a header predetermined with respect to data obtained by reading for each line and each color. An offset value memory  16  is a memory for storing line difference data corresponding to an interval between adjacent CISs of the CISs arranged in the zigzag manner. 
         [0024]    A sensor control circuit  14  controls the respective CISs, processes data which are read and digitized by the CISs, and writes the data into an image memory  17 . The image memory  17  includes a sensor-A memory  18  for storing an image for the CIS-A  1 , a sensor-B memory  19  for storing an image for the CIS-B  2 , a sensor-C memory  20  for storing an image for the CIS-C  3 , a sensor-E memory  21  for storing an image for the CIS-D 4 , and a sensor-E memory  22  for storing an image for the CIS-E  5 . 
         [0025]    An address of the image memory  17  is an address  0  to an address n. In a data area designated by addresses, one-line image data read by each of the CISs is stored in a CIS memory for the corresponding CIS. An address control circuit  30  is a circuit for performing management and control so as to prevent an overlapped writing and overlapped reading to and from the image memory  17 . 
         [0026]    The sensor control circuit  14  starts data writing from an address of the image memory  17  which corresponds to each of the CISs based on a value stored in the offset value memory. For example, when line difference data from a reference point in the CIS-A  1  is 500 lines, the value of the offset value memory is 500, and hence data is written for each line from an address corresponding to a 500th line counted from the address  0 . For example, in  FIG. 3 , an address k- 1  is an address corresponding to the 500th line, and hence data is written from this address. Even in the case of each of the other CISs, data captured for each line from a position corresponding to line difference data from the reference is written. Writing of image data on each line starts from an address  1  in the CIS-B  2 , from the address k- 1  in the CIS-C  3 , from the address  1  in the CIS-D  4 , and from an address k in the CIS-E  5 . 
         [0027]    The first line detection circuit  15  determines, of read image data, first data to be stored in a first address for data writing. 
         [0028]    The first line detection circuit  15  reads colors of data from the CISs and circulated line numbers, compares predetermined header values to each other to find matched data. This is to detect data for starting writing to the image memory  17 . The data for starting the writing to the memory  17  and a timing thereof are determined based on the data detected by the circuit. The read image data is written for each line from a region designated by the predetermined address of the memory at the determined timing. The image memory  17  is used while an address thereof is circulated. 
         [0029]    An address of the image memory  17  is designated for each line. Consecutive other addresses are assigned for respective colors. For example, an address i is assigned to one-line data for red, a next address i+1 is assigned to one-line data for green, and a next address i+2 is assigned to one-line data for blue. Memory regions corresponding to three addresses are used for color to store one-line data. 
         [0030]    A CIS which performs final reading in the conveying direction, of the CISs arranged in the zigzag manner is a CIS corresponding to a maximum value of the offset value memory. When the writing of the image data corresponding to the CIS starts, one-line image data is completed. For example, data stored in a region corresponding to an address m of the image memory  17  is one-line data. One-line data obtained by reading by each of the CISs is stored in a region corresponding to the address m of each of the sensor-A memory  18 , the sensor-B memory  19 , the sensor-C memory  20 , the sensor-D memory  21 , and the sensor-E memory  22 . When the address m is designated, data corresponding to the originally same line, which is obtained by reading by the respective CISs, can be designated. 
         [0031]    Next, an overlap portion of the data in the arrangement direction of the CISs is processed. With respect to which part of the overlap portion is to be used, an overlap range is stored in advance in a combination position information memory  26 . A combination processing circuit  25  first reads, into a one-line-combination pre-processing buffer  27 , the one-line data read from the image memory  17 . Data portions to be used, of the data from the CISs are designated based on the data of the combination position information memory  26 , and hence overlap portion image data  29  which are unused portions are removed and resultant data portions are written into an one-line image data buffer  28 . 
         [0032]    When the data from all the CISs are combined, one-line image data is obtained. The combination processing circuit  25  successively writes the completed image data for each line into another memory to obtain read image data of the document by combination. The entire image data is transmitted for use to another apparatus such as a printing apparatus or an information processing apparatus. The image data can be transmitted to a recording medium and stored therein. Examples of the image reading apparatus include an image scanner, a copying machine, and a facsimile machine. 
         [0033]    Next, a read timing of each of the CISs is described.  FIG. 4  is a read timing chart of the respective CISs. Read timings of the respective CISs are shown. The respective CISs successively read respective colors of red, green, and blue on a line.  FIG. 4  shows signals, each of which indicates the start of reading of each of the CISs for each line. The rising of each of the signals is detected to turn on LEDs of respective colors of red, green, and blue in order, thereby reading the document for each of the colors. This figure shows only the signals indicating the start of reading for red. The same signals are used for green and blue. The signals for each of three colors are risen at equal intervals. A signal for one of the colors is risen between the risings of signals for the others thereof. Reading for the respective colors is started in response to the respective signals. Read start signals for green and blue are omitted here. A signal rising interval is determined in advance such that three-color reading is completed before the next rising of the read start signal for red. The read timings of the respective CISs are non-synchronous. 
         [0034]    The rising of each of the signals as indicated by a broken line  31  in  FIG. 4  is a timing for reading the originally same line. The respective CISs are arranged in the zigzag manner, and hence the timings are shifted correspondingly to the arrangement. For example, a time T 1  of the CIS-A, a time T 4  of the CIS-B, a time T 2  of the CIS-C, a time T 5  of the CIS-D, and a time T 3  of the CIS-E are read times of the respective CISs which are required to obtain the originally same line. The read interval is an equal interval, and hence it can be also said that the time difference exhibits the line difference among the arranged CISs. The amount of shift between the predetermined reference point and the originally same line to be obtained by the respective CISs, that is, the line difference data is stored in advance in the offset value memory  16 . 
         [0035]    Primary correction is performed based on the line difference data. Of data, read data to be originally adjacent are determined. Note that it is likely to cause an error of 1 line in maximum because of a unit of line interval. Therefore, it is necessary to more finely combine read data in accordance with the read timings among the respective CISs. 
         [0036]      FIG. 5  shows a structure of read data output from each of the CISs. This is data obtained by adding, to one-line image data  27  which is digital data read by the CIS, color type data  25  indicating read data obtained by turning on which color LED used as the light source and line data  26  indicating nth data, as header data. 
         [0037]    Three bits are used for the color type data. For example, “ 110 ” is used for red, “ 101 ” is used for green, and “ 011 ” is used for blue. A read color is indicated by a bit whose value is 0. Two bits are used for line data. Four lines are indicated by four values of “00”, “01”, “10”, and “11” and circulated for use. Three-color data are used for each line. Therefore, when data corresponding to four lines are used, whether data is data corresponding an adjacent line for the same color or data corresponding to the same line can be determined. When next processing is performed during this, the preceding and succeeding lines are not confused. 
         [0038]      FIG. 6  is a schematic explanatory diagram showing data correction after the primary correction. This shows read timings of the CISs for each line, and the color type data and the line data which are added to the read line data. Even in the following description, only a signal for red (R) is used as the read start signal. This also shows timings when image data from the respective CISs are written into the image memory  17 . 
         [0039]    Assume that reference CIS is the CIS-A  1 . When reading for a line starts, the first line detection circuit  15  operates. Then, data from the CIS-A  1  is read and detection continues until predetermined color type data is the red color indicated by “ 110 ” and data which is the line data “ 10 ” is read. After the detection, the first line detection circuit  15  writes, into corresponding predetermined addresses of the image memory  17 , read data from all the CISs on a line in which the color type data is the red color indicated by “ 110 ” and the line data is “ 00 ” after the next. Even in a case of image data on subsequent lines, the writing is performed with successive addresses in response to timings based on the read timings. For example, the writing is performed in synchronization with the read timings. 
         [0040]    In the case of the CIS-A, from the rising of data capture-A, data for each line from the address k- 1  of the sensor-A memory is written for each next rising of the image read interval from the rising of T 6  in the CIS-A as shown in  FIG. 6 . Similarly, image data are written into the image memory  17  from predetermined addresses at predetermined timings from T 7  in the CIS-B, from T 8  in the CIS-D, from T 9  in the CIS-E, and from T 10  in the CIS-C. The lines to be originally combined are stored in the same address region. With respect to other read data for green and blue, data writing is performed in response to the read timings as in the case of red. 
         [0041]    That is, when the reading of the document starts, the first line detection circuit  15  monitors the color type data and the line data which are added to the image data from the reference CIS. When predetermined line data of predetermined color type data is detected, the color type data and the line data which are added to the image data are monitored on read data for each line, of the respective image data from all the CISs. In this case, whether or not line data after the next of the predetermined line data of the predetermined color type data is detected is monitored. When the data is detected, the image data for each line are successively stored in a region of the image memory  17  which corresponds to the CIS which detects the data, from the address determined based on the line difference data stored in the offset value memory  16 . After that, the read image data are stored at predetermined timings. For example, read data are stored in the memory in synchronization with the image read timings. 
         [0042]    The image data of the same line are stored in the same address region. The reason why the line data after the next of the predetermined line data of the predetermined color type data is detected is as follows. Although correction in a unit of line is performed as correction between lines, a capture period for each color is not corrected. Therefore, when a processing time is included, it is likely to cause a delay corresponding to three periods in maximum, and hence writing is started from data delayed by two periods. Thus, the writing may be performed from predetermined line data after two lines. 
         [0043]    In other words, timings for reading on the originally same line by the CISs are varied among the respective CISs. Therefore, an error is corrected based on the write timings to the memory  17 , and hence the read data of the originally same line is accurately reproduced. 
         [0044]    Although the image data of the same line are stored in the same address region, the present invention is not limited thereto. For example, in order to extract image data of a desired line from separately stored image data, the image data captured by the respective CISs on the originally same line are marked in advance with identification codes to provide a correspondence relationship among data on the originally same line. A method of providing an identification code for each line and a method of adding an storage address of next data to be combined are also expected. Therefore, in order to obtain desired one-line image data, the one-line image data can be obtained based on a designated address.