Abstract:
An image processing apparatus and an image forming apparatus can easily handle various kinds of documents including a special document and a normal document without problems of counterfeit by copy. The image processing apparatus and the image forming apparatus have a circuit for processing image data. A signal generating circuit generates a signal to prevent an image formation of a specified document. The signal generating circuit is detachably attached to the circuit for processing image data.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention generally relates to an image processing apparatus and an image forming apparatus having means for preventing an image formation of a special document such as a paper money, a security paper (policy form) or the like. 
   2. Description of the Related Art 
   With advanced development in an image processing technology and image forming technology, it has become capable of performing an image formation elaborately such that a copied paper money and a copied security paper printed by a color copy machine are not easily distinguishable from a real paper money and a real security paper. For this reason, a technique has been developed to discriminate a special document such as a paper money to prevent a copy of the special document, and a copy machine having a special document discriminating function has been developed by providing a function to discriminate a special document to a copy machine. 
   As such a copy machine, there is known by Japanese Laid-Open Patent Application No. 2001-292315 a copy machine, in which a paper money recognition control circuit recognizes, when a paper money as a special document is read by a scanner, image data of the read image as an image of a paper money; a notification is sent to a third party that a copy of a special document is being performed; a counter value for setting a time period from a power supply to a start of a starting process is increased; an error message is displayed on an LCD display part; and all processes are stopped. 
   Additionally, there is known by Japanese Laid-Open Open Patent Application No. 2001-144940 a copy machine as a copy machine having a special document discriminating function, in which a forgery determination processing module of a scanner driver compares image data generated by reading a document by a scanner with image data of a specific document so as to determine a level of coincidence; and a forgery prevention control module processes the image data generated by a scanner base on a result of the determination. 
   Further, there is known a copy machine by Japanese Laid-Open Patent Application No. 6-125459, which stores feature data of special documents of which copy is prevented in accordance with kinds of images of the special documents; extracts a feature image part from the input image data; compares the image data of the extracted image part with the stored feature data; prohibits a copy operation if a similarity as a result of the comparison corresponds to a predetermined first similarity; and providing a mark onto a recording paper if the similarity corresponds to a second similarity. 
   The invention disclosed in the above-mentioned Japanese Laid-Open Patent Application No. 2001-292315 prohibits a copy operation when an original document is determined as a special document. The invention disclosed in the above-mentioned Japanese Laid-Open Patent Application No. 2001-144940 processes copy image data when an original is determined as a special document. The invention disclosed in the above-mentioned Japanese Laid-Open Patent Application No. 6-125459 prohibits a copy operation or performs marking on a print paper in accordance with a degree of determination that an original document is a special document. 
   As mentioned above, the invention disclosed in each of the above-mentioned patent documents discriminates a special document, and, thereafter, takes measures for a forgery of the special document such as prohibiting a copy or processing a copy image based on a result of the discrimination. That is, although there is a difference in an accuracy of discrimination, each of the copy machines disclosed in the above-mentioned patent documents takes measures for a forgery of a special document on the assumption that the discriminating function of a special document is functioning normally. 
   However, since a copy machine having a special document discriminating function is capable of making a copy of a normal document without any restriction, if the special document discriminating function is made inactive, a special document may be copied in the same manner as a normal document. 
   Additionally, in recent years, a special document has not been limited to a conventional paper money or security paper, and has been expanded to many kinds of papers such as a gift certificate, a toll-road ticket, etc. However, the copy machines with a special document discriminating function disclosed in the above-mentioned patent documents are made in consideration of specific special documents, and are not oriented to a copy machine having a special document discriminating function, which is capable of acting according to various kinds of special documents. 
   Further, in recent years, users of copy machines tend to request preferably a copy machine having a cost advantage that has only necessary functions in accordance with circumstances of a copy machine of user&#39;s own use. However, since the copy machines having a special document discriminating function disclosed in the above-mentioned patent documents are always provided with the special document discriminating function as a general function, a function change cannot be made in response to the user&#39;, s needs. 
   SUMMARY OF THE INVENTION 
   It is a general object of the present invention to provide an improved and useful image processing apparatus and image forming apparatus in which the above-mentioned problems are eliminated. 
   A more specific object of the present invention is to provide an image processing apparatus and an image forming apparatus which can easily handle various kinds documents including a special document and a normal document. 
   Another aspect of the present invention is to provide an image processing apparatus and an image forming apparatus which can provide information regarding a state of a special document discriminating function. 
   A further object of the present invention is to provide an image processing apparatus and an image forming apparatus which can prevent a special document discriminating function from being inactivated. 
   In order to achieve the above-mentioned objects, there is provided according to the present invention An image processing apparatus comprising: a circuit for processing image data; and at least one signal generating circuit for generating a signal to prevent an image formation of a specified document, wherein the signal generating circuit is detachably attached to the circuit for processing image data. 
   In the image processing apparatus according to the present invention, a plurality of the signal generating circuits may be provided so that one of the signal generating circuits is selectable in accordance with the specified document. 
   In the image processing apparatus according to the present invention, the signal generating circuit may include a processor and a memory, and may be operated according to a process program that corresponds to the specified document and is stored in the memory. 
   The image processing apparatus according to the present invention may further comprise: means for detecting an operation of the signal generating circuit; and at least one of means for storing information regarding the state of the operation in accordance with a result of the detection, means for announcing the state of the operation in accordance with a result of the detection and means for stopping an image processing operation in accordance with a result of the detection. The means for detecting an operation of the signal generating circuit may include means for detecting an exchanging function to exchange specific information of the signal generating circuit. 
   Additionally, there is provided according to another aspect of the present invention an image forming apparatus comprising: image forming means for forming a visible image based on image data; and one of the image processing apparatuses mentioned above. 
   According to the present invention, the image processing apparatus or the image forming apparatus having the image processing apparatus can handle various kinds of documents including a normal document and a special document without problems of counterfeit by copy. Additionally, it is easy to know whether a discriminating function of a special document is valid or invalid. Further, an occurrence of an inactivated state where the special document discriminating function is inactivated or invalidated can be prevented. 
   Other objects, features and advantages of the present invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of a digital copy machine according to the present invention; 
       FIG. 2  is an illustrative side view of a scanner of the digital copy machine viewed from a front side of the digital copy machine according to an example of the present invention; 
       FIG. 3  is an illustration showing a relationship between an original document and control signals according to an example of the present invention; 
       FIG. 4  is an illustration of the original document indicating a main scanning direction and a sub-scanning direction according to an example of the present invention; 
       FIG. 5  is a time chart showing a relationship between an image data signal and main scanning and sub-scanning image range signals according to an example of the present invention; 
       FIG. 6  is a block diagram of major parts of the digital copy machine shown in  FIG. 1  according to an example of the present invention; 
       FIG. 7  is a block diagram for explaining an image processing mode in an image processing part shown in  FIG. 6  according to an example of the present invention; 
       FIG. 8  is a block diagram of a read-side image processing part to perform an image processing operation according to an example of the present invention; 
       FIG. 9  is a block diagram of the read-side image processing part having an image formation prohibiting circuit for prohibiting an image formation of a special document according to an example of the present invention; 
       FIG. 10  is a block diagram of a structure in which a pattern matching device having the pattern matching circuit and an output conversion circuit is provided separately from the read-side image processing part according to an example of the present invention; 
       FIG. 11  is a block diagram of a structure in which a pattern matching device having only a pattern matching circuit is provided separately from the read-side image processing part according to an example of the present invention; 
       FIG. 12A  is a block diagram showing an arrangement in which the pattern matching device is located between any adjacent two circuits according to an example of the present invention; 
       FIG. 12B  is a block diagram showing an arrangement in which the pattern matching device is located after a scanner and before the read-side image processing part according to an example of the present invention; 
       FIG. 12C  is a block diagram showing an arrangement in which the pattern matching device is located after the read-side image processing part and before an image accumulating part according to an example of the present invention; 
       FIG. 13  is a flowchart of a procedure of setting an operation of the pattern matching device according to an example of the present invention; 
       FIG. 14  is an illustration showing a concept of selection of a pattern matching device having a different feature pattern made by a main control part according to an example of the present invention; 
       FIG. 15  is a flowchart of a procedure of setting an operation to each of the pattern matching devices having different feature patterns according to an example of the present invention; 
       FIG. 16  is a block diagram of the read-side image processing part provided with a pattern matching device constituted by a digital signal processor according to an example of the present invention; 
       FIG. 17  is a block diagram of the pattern matching device constituted by a digital signal processor according to an example of the present invention; 
       FIG. 18  is a flowchart of a procedure of saving an operation history of the pattern matching device according to an example of the present invention; 
       FIG. 19  is a flowchart of a procedure of giving a warning that the pattern matching device is inactivated or invalidated according to an example of the present invention; 
       FIG. 20  is a flowchart of a procedure of giving a warning that the pattern matching device is inactivated or invalidated and also making the read-side image processing unusable according to an example of the present invention; 
       FIG. 21  is a block diagram of the read-side image processing part provided with a special pattern checking circuit according to an example of the present invention; and 
       FIG. 22  is a flowchart of a procedure of checking validity of the pattern matching device according to an example of the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   A description will now be given, with reference to the drawings, of a digital copy machine as an image forming apparatus according to the present invention. 
     FIG. 1  is a perspective view of a digital copy machine according to the present invention. In  FIG. 1 , the digital copy machine comprises a document table  1 , a document press  2 , an operation and display part  3  and a paper cassette  4 . Although not shown in  FIG. 1 , an optical reading unit (scanner) is installed under the document table  1 . An original document  5  is placed on the document table  1 . 
     FIG. 2  is an illustrative side view of the scanner of the digital copy machine viewed from a front side of the digital copy machine. In  FIG. 2 , the scanner  6  comprises a light source  7 , a scanning mirror  8 , an optical unit  9  having lenses and reflective mirrors, and an photoelectric transducer such as a charge coupled device (CCD)  10 . The scanner  6  reads the original document  5  placed on the document table  1  by moving in a sub-scanning direction (a left-to-right direction in the drawing) while scanning a light beam of the light source  7  in a main scanning direction (a front side to a back side of the drawing) on the original document  5  by being controlled by a control motor (not shown in the figure). 
     FIG. 3  is an illustration showing a relationship between an original document and control signals. In  FIG. 3 , a signal FGATE is a sub-scanning signal which represents an image range of the light source  7  and the scanning mirror  8  in the sub-scanning direction. A signal LSYNC is a main scanning synchronization signal which indicates a start point of a line in a reading direction of the charge coupled device  10 , that is, the main scanning direction. A signal LGATE is a main scanning signal representing and image range of an original-document reading surface in the main scanning direction. 
     FIG. 4  is an illustration of the original document indicating the main scanning direction and the sub-scanning direction. Ad shown in  FIG. 4 , scanning of line  1  is performed in the main scanning direction with a start point of the signal LSYNC as a reference, and scanning of line  2  is performed is performed in the main scanning direction by the light source  7  and the scanning mirror  8  moving in the sub-scanning direction. Thereafter, scanning is sequentially performed in the same manner along line  3 , line  4  and so on. 
     FIG. 5  is a time chart showing a relationship between image data signal and main scanning and sub-scanning image range signals. Triggered by the above-mentioned signal LSYNC, two-dimensional document image is converted into image data signal according to the signals FGATE and LGATE. The image data signal is processed by an image processing part of the digital copy machine mentioned later. 
     FIG. 6  is a block diagram of major parts of the digital copy machine shown in  FIG. 1 . As show in  FIG. 6 , the digital copy machine comprises a scanner  10 , an image processing part  20 , a main control part (Host-CPU)  30 , an image accumulating part  40  and a printer  50 . Image data generated by reading an original document by the scanner  10  and converted into an electric signal by the above mentioned photoelectric transducer (charge coupled device: CCD) is input to the image processing part  20  so as to be processed. The image accumulating part  40  has a semiconductor memory and a magnetic-disk type memory. The image accumulating part  40  temporarily acquires a memory area for image edition corresponding to one sheet of print paper, and receives the processed image data from the image processing part  20 . An amount of image information accumulated in the image accumulating part  40  is further increased by a compression and decompression function of the image control part  20 . Finally, print data is produced on a page unit basis, and is input to the printer  50 . The printer  50  is provided with image forming means of an electrophotography system so as to turn the image data signal of a page unit into a visible image and output by transferring the visible image onto a print paper. The main control part  30  controls an operation of each constitutional part in accordance with a predetermined program during the above-mentioned image forming operation. 
   A description will now be given of the processing of the image data signal in the image processing part  20  and a prohibition of an image formation of a special document.  FIG. 7  is a block diagram for explaining an image processing mode in the image processing part  20  shown in  FIG. 6 . As shown in  FIG. 7 , the image processing part  20  includes a read-side image processing part  21  and a write-side image processing part  22  so as to take a partial charge of the image processing. The image data signal received from the scanner  10  is processed by the read-side image processing part  21 , which mainly corrects an influence due to scanner characteristics, and, thereafter, temporarily accumulated in the image accumulating part  40 . The image data in the image accumulating part  40  is read by the write-side image processing part  22 , and write-side image processing, such as a gradation (image quality) process, a filtering process, a gradation conversion according to a gamma curve, etc., is applied to the read image data signal in accordance with an output data format. 
     FIG. 8  is a block diagram of the read-side image processing part  21  to perform an image processing operation. Referring to  FIG. 8 , the image data signal input from the scanner  10  is subjected to a black level correction by a black correction circuit  21   a , and is subjected to a correction of a light distribution of the light source  7  and a white reading level by a shading correction circuit  21   b . Then, a low-level background is deleted by following the background level of the read image data by a background elimination processing circuit  21   c , and the image data signal, which has been processed according to a brightness level, is converted into an image data signal based on an intensity level by a brightness-to-intensity conversion circuit  21   d . Thereafter, a read brightness characteristic of the scanner  6  is corrected by a scanner gamma conversion circuit  21   e , a low-level image is eliminated by a backside image eliminating circuit  21   f  so as to eliminate a low-intensity backside image of the original document, and, then, a resolution, which has been degraded by the scanner, is corrected by a scanner filter circuit  21   g . Thereafter, a mirroring is performed by a mirroring circuit  21   h  so as to match the main scanning direction if, for example, a sheet through feeding device is used for a reading system, and a leading end of the original document, which is placed on the document table or fed by a sheet through feeding device, is aligned with a leading end position of effective image data of the image data generated by the scanner (CCD)  10  by a registration adjusting circuit  21   i , and, finally, a selection of an output corresponding to a data format of an outputting unit is performed by an output selection circuit  21   j . 
   A description will now be given of a prohibition of an image formation of a special document.  FIG. 9  is a block diagram of the read-side image processing part  21  having an image formation prohibiting circuit for prohibiting an image formation of a special document. In  FIG. 9 , a structure of the black correction circuit  21   a through the output selection circuit  21   j  is the same as that shown in  FIG. 8 . In order to prevent an image formation of a special document from being performed, the read-side image processing part  21  shown in  FIG. 9  is provided with a pattern matching circuit  23   a  after the scanner gamma conversion circuit  21   e  and an image conversion circuit  23   b  after the output selection circuit  21   j . That is, the pattern matching circuit  23   a  and the image conversion circuit  23   b  are incorporated into the read-side image processing part  21  together with other circuits shown in  FIG. 8 . 
   The pattern matching circuit  23   a can be any pattern matching circuit generally used for preventing an image formation of a special document. For example, the pattern matching circuit  23   a  comprises: an image detection circuit that inputs the digitally processed image data and extracts a feature image portion (comparing portion); a memory such as a ROM for storing the feature data in accordance with a kind of an image of a special document beforehand; and comparison circuit that compares the comparing portion extracted by the image detection circuit with the feature date in the memory so as to acquire a similarity therebetween. According to the above-mentioned structure, when the digitally processed image data is input to the image detection circuit, the image detection circuit extracts the comparing portion. That is, the image detection circuit extracts feature data (for example, a sealed portion) of a special document such as a paper money, a security paper, etc., from the image data of the copy image data. After the feature data is extracted, the feature data stored in the memory beforehand is read, and the extracted feature data is compared with the read feature data, and the similarity is determined. The image conversion circuit  23   b  can also be an image conversion circuit generally used. For example, a circuit that converts digitally processed image data into other kinds of image data or converts a white portion or a black portion into a different color portion may be used. 
   In the structure of  FIG. 9 , an output of the scanner gamma conversion circuit  21   e  is branched and a part of the image data signal is input to the pattern matching circuit  23   a  so as to detect a special document. A result of the detection is supplied to the image conversion circuit  23   b  so as to convert the image data signal output from the output selection circuit  21   j . 
   First Embodiment 
   In the present embodiment, the pattern matching circuit is separated, as an independent device, from the read-side image processing part  21  so that the pattern matching circuit part is detachably attached to the read-side image processing part  21 . In this case, the pattern-matching device may have a pattern matching circuit and an output conversion circuit or have only the pattern matching circuit and the function of the output conversion circuit may be handed to existing other circuits. 
     FIG. 10  is a block diagram of a structure in which a pattern matching device having the pattern matching circuit and an output conversion circuit is provided separately from the read-side image processing part  21 . In  FIG. 10 , although the pattern matching device  23  comprises a pattern matching circuit  23   a , an output conversion circuit  23   b  and a ROM which stored feature patterns, the pattern matching device  23  may be configured and arranged to be detachably attached to the read-side image processing part  21 . 
     FIG. 11  is a block diagram of a structure in which a pattern matching device having only the pattern matching circuit is provided separately from the read-side image processing part  21 . In  FIG. 11 , the pattern matching device  23  has only the pattern matching circuit  23   a , and is configured and arranged to be detachably attached to the read-side image processing part  21 . In this case, the function of the output conversion circuit is handed to the output selection circuit  21   j . 
   Although it is mentioned that the pattern matching device  23  is located between the read-side image processing part  20  and the image accumulating part  40 , the pattern matching device  23  may be arranged as follows. 
   (1) Arranging at any position between the circuits of the read-side image processing circuit. 
   (2) Arranging after the scanner and before the read-side image processing part. 
   (3) Arranging after the read-side image processing part and before an image accumulating part. 
   The above-mentioned arrangements of the pattern matching device are shown in  FIG. 12A through 12C .  FIG. 12A  shows the arrangement in which the pattern matching device is located between any adjacent two circuits.  FIG. 12B  shows the arrangement in which the pattern matching device is located after the scanner and before the read-side image processing part.  FIG. 12C  shows the arrangement in which the pattern matching device is located after the read-side image processing part and before the image accumulating part. According to the above-mentioned variations in the arrangement of the pattern matching device, a degree of freedom in pattern detection is improved. 
   A description will be given of a control procedure of setting an operation of the pattern matching device. When the pattern matching device  23  is arranged at the locations in the circuit as mentioned above, the main control part  30  determines that the pattern matching device  23  is attached by detecting (a) contents of ports of the pattern matching device  23 , (b) contents of ports of the image processing part  20  containing the read-side image processing part  21  to which the pattern matching device  23  is connected, or (c) identification (ID) information regarding a board on which the pattern matching device  23  is mounted. Based on the judgment mentioned above, an operation setting of the pattern matching device  23  is performed. 
     FIG. 13  is a flowchart of a procedure of setting an operation of the pattern matching device  23 . In  FIG. 13 , when operation setting of the pattern matching device  23  is started, the main control part  30  determines, in step S 1 , whether or not the pattern matching device  23  is provided, that is, whether or not a special document processing system is attached. If it is determined that the pattern matching device  23  is attached, an operation of the pattern matching device is set in step S 2 , and, then, an operation of the read-side image processing part  21  is set in step S 3 . On the other hand, if it is determined, in step S 2 , that the pattern matching device  23  is not attached, the routine proceeds to step S 3  so as to set an operation of the read-side image processing part  21 . It should be noted that an operation of the pattern matching  23  is set first and thereafter an operation of the read-side image processing part  21  is set when the pattern matching device is attached in the above-mentioned procedure, the order of setting may be reversed. 
   Second Embodiment 
   In the present embodiment, an arbitrary pattern matching device is selectable from among a plurality of matching devices so that prevention of an image formation of different special documents can be achieved. As examples of different special documents, there are Japanese Yen bills, one thousand Yen bill, five-thousand Yen bill, ten-thousand Yen bill, etc. 
     FIG. 14  is an illustration showing a concept of selection of a pattern matching device having a different feature pattern made by the main control part. In  FIG. 14 , the pattern matching devices  23  are provided with the description patterns A, B and C corresponding to different special documents, respectively. The pattern matching devices  23  are provided, as mentioned above, at locations (a) between any adjacent circuits in the read-side image processing part, (b) after the scanner and before the read-side image processing part and (c) after the read-side image processing part and before the image accumulating part, respectively. 
   Thus, the main control part checks the locations of the pattern matching devices  23  by detecting the contents of ports of the pattern matching device  23  itself, the contents of the image processing part  20  containing the read-side image processing part  21  to which the pattern matching device  23  is connected or the identification (ID) information of a board on which the pattern matching device  23  is mounted. Then, appropriate operations are set to the checked pattern matching devices  23 , respectively. 
     FIG. 15  is a flowchart of a procedure of setting an operation to each of the pattern matching devices having different feature patterns. In  FIG. 15 , when operation setting of the pattern matching devices  23  is started, the main control part  30  determines, in step S 11 , whether or not one of the pattern matching devices  23  is provided, that is, whether or not a special document processing system is attached, by detecting the contents of ports of the pattern matching device  23  itself, the contents of the image processing part  20  containing the read-side image processing part  21  to which the pattern matching device  23  is connected and the identification (ID) information of a board on which the pattern matching device  23  is mounted. If one of the pattern matching devices  23  is attached, it is judged, in step S 12 , which of the pattern matching devices  23  is selected. Then, in steps S 13 , S 14  or S 15 , an operation is set to one of the pattern matching devices  23  which is judged to be selected. Then, in step S 16 , an operation is set to the read-side image processing part  21 . When it is determined, in step S 11 , that none of the pattern matching devices  23  is attached, the routine proceeds to step S 16  so as to set an operation to the read-side image processing part  21 . 
   Third Embodiment 
   In the present embodiment, the pattern matching device is constituted by a digital signal processor (DSP).  FIG. 16  is a block diagram of the read-side image processing part  21  provided with a pattern matching device constituted by DSP. In  FIG. 16 , the digital signal processor  26  is located before the read-side image processing part  21  and after the image accumulating part  40 .  FIG. 17  is a block diagram of the pattern matching device constituted by a digital signal processor. In  FIG. 17 , the digital signal process (DSP)  26  comprises a processor part  26   a  and a memory (RAM)  26   b . The processor part  26   a  performed an input of the digital image data signal, image data signal processing and an output of the image data signal. The memory  26   b  stores programs for controlling an operation of the processor  26   a  and also stores information regarding feature patterns. On the other hand, the main control part  30  of the digital copy machine has a memory (ROM)  30   a  which stores programs for controlling the DSP. The memory  30   a  also stores in a DSP program storing area the DSP control programs, information regarding various feature patterns and a download control program. 
   The main control part  30  changes an operation of the DSP  26  by selecting and downloading the DSP control program and information regarding one of the feature patterns in accordance with kinds of special documents. 
   According to the present embodiment, a hardware structure of the DSP  26  is fixed, and a prohibition of an image formation corresponding to a plurality of special documents can be achieved by merely changing the program in the fixed hardware structure. 
   Fourth Embodiment 
   In the present embodiment, if the pattern matching device is inactivated for some reasons such as, for example, a physical destruction or a functional destruction, the operation history is saved or a warning is given. A description will now be given below of the above-mentioned operations. 
   First, a description will be given of saving an operation history of the pattern matching device.  FIG. 18  is a flowchart of a procedure of saving an operation history of the pattern matching device. In  FIG. 18 , when an operation history saving operation of the pattern matching device  23  ( 26 ) is started, the main control part  30  determines, in step S 21 , whether or not the pattern matching device  23  ( 26 ) is provided, that is, whether or not the special document processing system is destructed. If it is determined that the pattern matching device  23  ( 26 ) is inactivated or invalidated, information representing the state where the pattern matching device  23  ( 26 ) is inactivated or invalidated is stored in the memory in step S 22 . Then, an operation is set to the read-side image processing part  21  in step S 23 . On the other hand, if it is determined, in step S 21 , that the pattern matching device  23  ( 26 ) is activated or validated, the routine proceeds to step S 23  where an operation is set to the read-side image processing part  21 . 
   It should be noted that the determination as to whether or not the pattern matching device  23  is activated or inactivated can be made by whether or not the main control part  30  can detect the contents of ports of the pattern matching device  23  itself, the contents of the image processing part  20  containing the read-side image processing part  21  to which the pattern matching device  23  is connected or the identification (ID) information of a board on which the pattern matching device  23  is mounted. 
   A description will now be given of a warning that the pattern matching device is inactivated or invalidated.  FIG. 19  is a flowchart of a procedure of giving a warning that the pattern matching device is inactivated or invalidated. In  FIG. 19 , when setting of an operation of the pattern matching device  23  ( 26 ) is started, the main control part  30  determines, in step S 31 , whether or not the pattern matching device  23  ( 26 ) is activated or validated without being destructed. If the pattern matching device  23  ( 26 ) is inactivated or invalidated, a notification is sent, in step S 32 , to an external part that the pattern matching device  23  ( 26 ) is inactivated or invalidated. Then, in step S 33 , an operation is set to the read-side image processing part  21 . On the other hand, if it is determined, in step S 31 , that the pattern matching device  23  ( 26 ) is actuated or validated, the routine proceeds to step S 33  where an operation is set to the read-side image processing part  21 . 
     FIG. 20  is a flowchart of a procedure of giving a warning that the pattern matching device is inactivated or invalidated and also making the read-side image processing unusable. In  FIG. 20 , when the operation is started, the main control part  30  determines, in step S 41 , whether or not the pattern matching device  23  ( 26 ) is activated or validated without being destructed. If the pattern matching device  23  ( 26 ) is inactivated or invalidated, the fact of the inactivation or invalidation is displayed as an alert or warning on a display of the operation part  3  in step S 42 . Then, in step S 43 , the read-side image processing part  21  is made unusable. On the other hand, if it is determined, in step S 41 , that the pattern matching device  23  ( 26 ) is activated or validated, the routine proceeds to step S 44  where an operation is set to the read-side image processing part  21 . 
   Further, a description will be given of the determination as to whether or not the pattern matching device is activated or validated. 
   Fifth Embodiment 
   In the present embodiment, a special pattern checking part exchanges feature patterns of special documents and a control part determines whether the pattern matching device is activated or validated. Accordingly, the digital copy machine comprises the special pattern checking part.  FIG. 21  is a block diagram of the read-side image processing part provided with a special pattern checking circuit. As shown in  FIG. 21 , the special pattern checking circuit  27  has information regarding special patterns for checking validity in a memory attached thereto so as to exchange the information regarding the special patterns with the pattern matching circuit  23   a  of the pattern matching device  23 . The main control part  30  determines whether or not the exchange is carried out normally so as to check validity of the pattern matching device. 
     FIG. 22  is a flowchart of a procedure of checking validity of the pattern matching device. In  FIG. 22 , when the operation is started, the main control part  30  initializes, in step S 51 , the read-side image processing part  21 . Then, the main control part reads the information regarding the special patterns for checking validity from the memory attached to the special pattern checking circuit  27 , and causes the pattern matching circuit  23   a  to send the information regarding the special patterns. The pattern matching circuit  23   a  returns, when normally operated, the information regarding the special patterns to the special pattern checking circuit  27 . The main control part  30  determines, in step S 53 , whether or not the exchange of the information is performed. If the exchange is performed (Yes of step S 53 ), the main control part  30  performs, in step S 55 , a normal process of preventing an image formation of a special document. On the other hand, if it is determined that the exchange is not performed (No of step S 53 ), the control part  30  performs, in step S 54 , an operation of a case where the special document processing is inactivated or invalidated, that is, an operation of giving a warning such as mentioned in the fourth embodiment. 
   The present invention is not limited to the specifically disclosed embodiments, and variations and modifications may be made without departing from the scope of the present invention. 
   The present application is based on Japanese priority application No. 2004-029854 filed Feb. 5, 2004, the entire contents of which are hereby incorporated herein by reference.