Patent Publication Number: US-7224931-B2

Title: Image forming apparatus and image forming method

Description:
NOTICE OF COPYRIGHTS AND TRADE DRESS 
   A portion of the disclosure of this patent document contains material which is subject to copyright protection. This patent document may show and/or describe matter which is or may become trade dress of the owner. The copyright and trade dress owner has no objection to the facsimile reproduction by any one of the patent disclosure as it appears in the Patent and Trademark Office patent files or records, but otherwise reserves all copyright and trade dress rights whatsoever. 
   RELATED APPLICATION INFORMATION 
   This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2003-422834, filed on Dec. 19, 2003; the entire contents of which are incorporated herein by reference. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to an image forming apparatus such as a color copier, etc. equipped with a device to make the judgement as to whether input images are specific documents such as banknotes, securities, etc. and an image forming method. 
   2. Description of the Related Art 
   In a conventional color multi-functional image forming machine, when the copying is made, a document was placed and fixed on a document table and a document image was read by moving a scanner (hereinafter, this operation is described as a fixed document reading). Further, in a color multi-functional image forming machine, a means to detect a specific document and a means to smear away the whole surface of the image data when a specific document is detected by this detecting means in order to prohibit the copying of the specific document. 
   In recent years, with the speed-up of the color copying process, a system with an automatic document feeder (hereinafter, described as an ADF) installed to a color multi-functional image forming machine to read document images by a reading device while moving the document is increasing used. 
   In the Japanese Patent Application Publication No. 8-37595, a technology to make the judgement as to whether input images are specific documents such as banknotes, securities in a color copier using an ADF equipped with a specific image discriminator is disclosed. 
   However, a system equipped with an ADF to read images of documents, which are being moved, is susceptible to color shift by vibrations or other factors when compared with a conventional system to read fixed documents using a scanner that is moving. Accordingly, there is such a fear that a recognition rate of a specific document sensor retained by a color multi-functional image forming machine may drop depending upon kinds of specific documents such as banknotes, securities, etc. 
   On the other hand, a reading magnification (a reading speed) of a color multi-functional image forming machine equipped with such an ADF is normally adjusted for a simple body of scanner or a simple body of ADF at the time when an apparatus is assembled or installed so that the set copying magnification comes to agree with a copied image output from a printer. Definitely, when a document is read actually using an ADF and a scanner and the copied image is output by the printer, the magnifications of the scanner and the ADF are finely adjusted, respectively and the magnification of the copied image is adjusted properly. For example, when a magnification being set with a control panel is 100%, the scanner magnification is set to 99%, or the ADF magnification is set to 98% so that the image outputted by the printer may become 100%. 
   Furthermore, since the reading magnification read by the scanner or ADF was different as described above when the magnification inputted from the control panel is set as a specific document detection unit, there was a problem that a recognition rate further falls. 
   SUMMARY OF THE INVENTION 
   An object of the present invention is to provide an image forming apparatus and an image forming method capable of preventing a recognition rate by a specific document detection unit from falling even in a system to read document image while a document is moving. 
   According to the embodiments of the present invention, there is provided an image forming apparatus to read document image using an automatic document feeder and form an image based on the read image data comprising: copying magnification set-up means for setting copying magnifications; memory means for storing data showing reading magnification corresponding to the copying magnification set by the copying magnification set-up means when reading document images using the automatic document feeder; control means for controlling the document conveying speed of the automatic document feeder based on the data showing the reading magnification; specific document detection means for detecting whether an image data read from the document conveyed at a conveying speed controlled by the control means is an image data of a specific document; and image forming means for forming an unusable image or an unreadable image on a paper when the specific document detection means detects the image data of the specific document. 
   Further, according to the embodiments of the present invention, there is provided an image forming method to read a document image using an automatic document feeder and form an image based on the read image data comprising: storing data showing a reading magnification corresponding to a set copying magnification into a memory when a copying magnification is set; controlling a document conveying speed of the automatic document feeder based on the data showing the reading magnification stored in the memory; detecting as to whether the image data read from a document conveyed at the controlled conveying speed is a specific document; and forming an unusable image or an unreadable image on a paper when the image data of the specific document is detected. 

   
     DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a block diagram showing a schematic structure of a color multi-functional image forming machine equipped with a specific document detection unit in one embodiment of the image forming apparatus of the present invention; 
       FIG. 2  is a block diagram showing the detailed structure around the specific document detection unit; 
       FIG. 3  shows a first magnification conversion table; 
       FIG. 4  shows a second magnification conversion table; 
       FIG. 5  is a schematic cross sectional view showing a scanner which read an image of a document; 
       FIG. 6  is a schematic cross sectional view showing a scanner abd ADF which read an image of a document; 
       FIG. 7  is a flowchart for explaining the specific document detection operation; and 
       FIG. 8  is a graph showing the relationship of the specific document recognizing rate when differences are in setting magnification. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Preferred embodiments of the present invention will be described below in detail referring to the drawings. 
     FIG. 1  shows a color multi-functional image forming machine equipped with a specific document detection unit in an embodiment of the image forming apparatus of the present invention. That is, the color multi-functional image forming machine comprises a scanner  1 , a printer  2 , a control panel  3  and an automatic document feeder (ADF)  4 . 
   The scanner  1  comprises a CPU  10  to control the entire scanner, a CCD sensor  11  comprising plural line sensors for colors, an image processor  13  to perform the image processing, a specific document detection unit  15  to detect specific documents, a dictionary (specific image data), an EPROM  17  storing a control program, etc., a motor  19  for operating a scanner driver (not shown), and a motor driver  20  to drive the motor  19 . 
   The printer  2  is controlled by a CPU (not shown) and forms an image on a paper based on image data. 
   The control panel  3  has a ten-key, an LC display, etc. which are not shown, and a copying magnification, the number of output sheets, etc. are input by user. 
   The ADF  4  has an ADF driver including the motor  40  and the motor driver  41  and feeds a document placed on a document feed table and reads its image data while it is moving. 
     FIG. 2  shows the detailed construction around the specific document detection unit  15 . That is, red, green and blue image data read by the CCD sensor  11  are input into a pre-processing circuit  12 □ The pre-processing circuit  12  performs the pre-processing including amplification, A/D conversion, etc. of input image data (red, green and blue) and outputs the image data to the image processor  13 . 
   The image processor  13  makes the shading correction, in-line correction, etc. of the input image data (red, green and blue) and outputs the processed image data to the specific document detection unit  15  and a system unit  30 . 
   A dictionary (specific image data) for detecting specific documents read from the EPROM  17  by the CPU  10  is downloaded in advance in the specific document detection unit  15 . The specific document detection unit  15  makes the pattern matching of read image data with the dictionary (the specific image data) corresponding to a magnification and detects that are set whether the received image data is that of a specific document and outputs a detection signal to the CPU  10 . 
   Further, there is a SRAM  18  provided as a work memory jointly with the EPROM  17 . 
   The image processor  13  is connected to the specific document detection unit  15 , the EPROM  17  and the SRAM  18  with a read signal line  51 , a write signal line  52 , an address bus  53 , and a data bus  54 . 
   The CPU  10  and the ADF  4  are connected each other through the serial communication. 
   Also, the CPU  10  and the system unit  30  are connected each other through the serial communication. 
   The system unit  30  has a memory  31  and connected to the printer  2  and the control panel  3 , which sets a copying magnification shown in  FIG. 1 . A first magnification conversion table  32  (shown in  FIG. 3 ) storing ADF reading magnifications corresponding to copying magnifications set by user through the control panel  3  and used when a mode to read image while moving a document is selected and a second magnification conversion table  33  (shown in  FIG. 4 ) storing scanner reading magnifications corresponding to copying magnifications when a mode to read images by the scanner moving to a fixed document is selected by user are stored in the memory  31 . 
   The values stored in the first magnification conversion table  32  and the second magnification conversion table  33  are set up, respectively when the color multi-functional image forming machine was assembled/adjusted. 
     FIG. 5  shows the cross sectional view of the scanner  1  when reading a document image using the scanner  1 . 
   The scanner  1  includes a light source  60 , a reflector  61 , a document table  62 , a first mirror  63 , a second mirror  64 , a third mirror  65 , a lens  66 , and a CCD sensor  67 . 
   The light irradiated from the light source  60  and the light irradiated from the light source  60  and reflected on the reflector  61  are irradiated to a document D, and its reflecting light is focused on the CCD sensor  67  through the first mirror  63 , the second mirror  64 , the third mirror  65  and the lens  66 . 
   The document D is fixed by the document holding plate installed to the ADF  4 . The light source  60  is driven by an inverter that is not shown. The light source  60 , the inverter, the reflector  61  and the first mirror  63  are installed to the first carriage  69 . The second mirror  64  and the third mirror  65  are installed to the second carriage  69 . 
   A controller board  70  is arranged in the scanner. The CCD sensor  67  is installed on the controller board  70 . The controller board  70  drives the CCD sensor  67 , controls the scanner  1  and controls the communication with the system unit (not shown). 
   When reading an image of the document D that is fixed on the document table  62 , the first carriage  68  and the second carriage  69  are first moved to the position of the scanning original point by the rotation of the scanner driving motor (not shown). After the light source  60  is turned on, the first and second carriages  68  and  69  are moved to the lower position of the shading correcting plate (the white reference plate)  71  and read the shading correction plate  71 . Based on the result of reading the shading correction plate  71 , the shading correction is executed. 
   Then, the first carriage  68  is moved to the position below the document D and the image on the whole surface of the document D is read. The second carriage  69  moves at a speed that is half of the moving speed of the first carriage  68  and maintains the length of the optical path from the surface of the document D to the CCD sensor  66 . 
   The reflected light from the surface of the document D is converted into an analogue signal through the photoelectric transfer by the CCD sensor  66 . Further, this analogue signal is amplified in the controller board  70  and then, the A/D conversion and the shading correction are executed. The shading corrected analogue signal is converted into the digital signal. Based on the digital signal, the image process is made and the image processed signal is output to the outside of the scanner  1  as image data. The form of process to read an image on the whole surface of the document D by scanning the underside of the document D with the first carriage equipped with the light source  60 , the inverter, the reflector  61  and the first mirror  63  and the second carriage equipped with the second mirror  64  and the third mirror  65  is stipulated as the first scanning function  1   a  for the “Reading of Fixed Document Image” which will be described later. 
     FIG. 6  shows the cross sectional view of the scanner  1  when reading an image of the document D with the ADF  4 . 
   The light irradiated from the light source  60  and the light irradiated from the light source  60  and reflected on the reflector  61  are irradiated to the document D on the document table  62 , and its reflecting light is focused on the CCD sensor  67  by the lens  66  through the first mirror  63 , the second mirror  64 , and the third mirror  65 . 
   The document D that is set in the ADF  4  is conveyed by conveying rollers and a conveyor belt driven by a document conveying driving motor (not shown) provided in the ADF  4 , and passing on the contact glass  72  and discharged from the conveying unit. 
   When reading an image of the document D, the first carriage  68  and the second carriage  69  are first moved to the position of the scanning original point and after turning the light source  60  on, moved to the under side of the shading correction plate  71  and read the shading correction plate  71 . Based on the read result of the shading correction plate  71 , the shading correction is executed. 
   Next, the first carriage  68  is fixed under the contact glass  72  and the reflecting light from the surface of the conveyed document D is received by the CCD sensor  67 . This received light is converted into analogue signal through the photoelectric transfer. The analogue signal is further amplified in the controller board  70  and then, the A/D conversion and the shading correction are executed. The shading corrected analogue signal is converted into digital signal. Based on this digital signal, the image process, etc. are performed and the image processed signal is output to the outside of the scanner  1  as image data. The form of process to read an image on the whole surface of the document D conveyed by the ADF  4  with the first carriage  68  equipped with the light source  60 , the inverter, reflector  61  and the first mirror  63  fixed under the contact glass  72  and the second carriage equipped with the second mirror  64  and the third mirror  65  also fixed is stipulated as the second scanning function  1   b  for “Reading of Moving Document Image” which will be described later. 
   Next, the specific document detecting operation in the color multi-functional image forming machine in the structure as described above will be explained referring to the flowchart shown in  FIG. 7 . 
   First, when a copying magnification is set by user through the control panel (ST  1 ), the CPU  10  judges whether a document image is read while the document D is moving from the ADF  4 , that is the first scanning function  1   b  is performed, or the image is read from the document D placed on the document table  62  by the moving scanner, that is the second scanning function  1   a  is performed (ST 2 ). 
   When the image is read while the document D is moving, which the second scanning function  1   b  ( FIG. 6 ) is performed, the CPU refers to the first magnification conversion table  32  in the memory  31  of the system unit  30  (ST 3 ), converts the set magnification rate to the ADF read magnification rate (ST 4 ), and sets the ADF read magnification rate in the ADF driver (not shown) including the motor  40  and the motor driver  41  (ST 5 ). For example, when a document image is expanded to 104.9% when it was finally printed on a paper even when the copy magnification rate was set at 100% through the control panel  3 , the data set on Line No. 2 of the first magnification conversion table  32  is referred to. And then, the ADF reading magnification is set at 95.1% inversely. That is, the revolution speed of the motor  40  for driving the document conveying should be set at 5245 pps so that the document conveying speed becomes 220.29 mm/s. As a result, the document image is printed out at a 100% size finally as desired by user. Further, when finally printed on a paper, an image is contracted to a size of 95% although the copying magnification is set at 100% through the control panel  3 , the data set on Line No. 101 of the first magnification conversion table  32  is referred to, and the ADF reading magnification is set at 105% inversely. That is, the revolution speed of the motor  40  for driving the document conveying should be set at 4750 pps so that the document conveying speed becomes 199.5 mm/s. As a result, the document image is printed out in a size of 100% finally as desired by user. In the first magnification conversion table  32 , data are set in a step of 0.1% from No. 1 to No. 101 and magnifications can be adjusted at a high accuracy. 
   Further, the CPU  10  sets the magnifications that are set in the ADF driver also in the specific document detection unit  15  (ST 6 ). 
   Then, the specific document detection unit  15  performs the pattern matching to determine whether the read image data is read from a specific document using a dictionary (specific image data) of the set magnification and outputs a detection signal as a result of the pattern matching to the CPU  10  (ST 7 ). At this time, the CPU  10  controls the output of the applicable read image data by the printer  2  according to the detection signal. When the detection signal is the signal detecting a specific document, the CPU  10  prohibits the output of the applicable read image data. That is, an image corresponding to the read image data is not formed on a paper. In concreat terms, a white paper is output or a smeared away image is formed on a paper to be unreadable or unusable as an output. 
   Further, when an image data read by moving the scanner to the document D fixed on the document table  62  instead of the document D that is read while moving it in Step ST 2 , which the first scanning function  1   a  ( FIG. 5 ) is performed, the CPU  10  refers to the second magnification table  33  in the memory  31  of the system unit  30  (ST 8 ), converts the set magnification into the scanner reading magnification (ST 9 ) and sets the scanner read magnification in the scanner driver (not shown) including the motor  19  and the motor driver  20  (ST 10 ). For example, when an image is enlarged to a size of 105% when finally printed on a paper although the copy magnification was set at 100% through the control panel  3 , the data set on Line No. 1 of the second magnification conversion table  33  in  FIG. 4  is referred to. Therefore, the scanner reading magnification is set at 95%, inversely. That is, the revolution speed of the motor  19  to drive the scanner should be set at 6417.6 pps so that the scanner moving speed becomes 220.5 mm/s. As a result, the data is printed finally at a size of 100% as desired by user. Further, when the data is contracted to a size of 95% when finally printed although the copying magnification was set at 100% through the control panel  3 , the data set on Line No. 101 of the second magnification conversion table  33  shown in  FIG. 4  is referred to. Therefore, the scanner reading magnification is set at 105%, inversely. That is, the revolution speed of the scanner driving motor  19  should be set at 5806.4 pps so that the scanner moving speed becomes 199.5 mm/s. As a result, the data is printed at a size of 100% finally as desired by user. In the second magnification conversion table  33 , data is set on the table at a step of 0.1% from Line No. 1 to Line No. 101 and the magnifications can be adjusted at a high accuracy. 
   Further, in the first magnification conversion table  32  and the second magnification conversion table  33  shown in  FIG. 3  and  FIG. 4 , the magnifications of 100% only that are set through the control panel  3  are shown. Actually, however, data for setting ADF read magnification, document conveying speed, revolution speed of the motor for driving the document convey, scanner reading magnification, scanner moving speed and revolution speed of the scanner driving motor regarding contraction/enlargement magnifications such as 50%/200% are also stored as the magnification conversion tables. 
   Further, the CPU  10  sets the magnifications that are set in the scanner driver also for the specific document detection unit  15  (ST  10 ). 
   Then, the specific document detection unit  15  makes the pattern matching to determine whether the read image data is that of a specific document using the set magnification dictionary (specific image data) and outputs a detection signal as the result of the matching to the CPU  10  (ST 7 ). At this time, the CPU  10  controls the output of the applicable read image data by the printer  2  according to the detection signal. When the detection signal is for the detected specific document, the CPU  10  prohibits the output of the applicable read image data. That is, an image corresponding to the read image data is not formed on a paper. In concreat terms, a white paper is output or a smeared away image is formed on a paper to be unreadable or unusable as an output. 
     FIG. 8  shows the relation of a specific document recognition rate when there is a difference between the magnification to be set in the ADF driver or the scanner driver and the magnification to be set in the specific document detection unit  15 . 
   That is, the copying magnification that was set in the control panel  3  was so far set in the specific document detection unit  15  as it is and might differ from the magnification actually set in the ADF driver or the scanner driver. 
   As a result, in  FIG. 8 , for example, when a recognition rate is 100% when a magnification difference is 0% and a recognition rate drops to 70% when a magnification difference +1%. When such the magnification difference is generated, an image magnification of the read image data does not match with an image magnification of a dictionary used in the specific document detection unit  15  and the accurate pattern matching cannot be made. As a result, the recognition rate drops. 
   As explained above, according to the embodiment of the present invention, it is possible to prevent drop of the recognition rate by matching a magnification to be set in the specific document detection unit  15  with a magnification actually set in the ADF driver or the scanner driver by deciding a magnification that is set in the specific document detection unit  15  based on a magnification that is set in the control panel  3 . 
   The image forming apparatus of the present invention, it becomes possible to prevent drop of a recognition rate in the specific document detection by setting actual ADF reading magnification and scanner reading magnification in the specific document detection unit. 
   In the above explanation, an example of a color multi-functional image forming machine as an image forming apparatus equipped with both of a mode to read document image with a fixed scanner from a document moving using an automatic document feeder and a mode to read document images with a moving scanner from a fixed document was explained. However, this invention is not limited to the above and this invention can be realized with an image forming apparatus equipped with only a mode to read document image with a fixed scanner from a document moving by an automatic document feeder or with an image forming apparatus equipped with only a mode to read document image with a moving scanner from a fixed document. 
   The present invention is not restricted to the embodiments described above and various changes and modifications may be made at the stage of actual application without departing from the spirit and the scope thereof. Further, the embodiments may be combined as appropriate as could as possible and the combined effect can be obtained. Further, many inventions at various stages are contained in the above-mentioned embodiments and various inventions may be derived by variously combining disclosed structural requirements. For example, when the problems described above can be resolved and the effects described above can be obtained even when several structural requirements are deleted from whole structural requirement shown in the embodiments, the construction with these structural requirement deleted may be derived as another invention.