Image processing apparatus

Abstract: An image forming apparatus having a function of detecting an image of a specific original document performs recording by detecting an image showing the specific original document such as paper money from inputted image data, generating a pattern denoting a manufacturer's serial number which is specific for the apparatus in a case where the image showing the specific original document has been detected and synthesizing the pattern with inputted image data.

Description: The invention relates to the field of image processing, as applied for example in digital colour copying apparatus, and in particular to the problem of forgery of documents. With recently-made development of color image forming apparatuses each having a device such as a CCD (solid-state imaging device) and digital color copying apparatuses such as laser beam printers or ink jet printers, reliable reproduction of multicolor original documents have been achieved while including elements of the color gradation. However, the aforesaid conventional example encounters a problem of a fear of forgery of paper sheets or documents such as money paper, the copying of which must be inhibited. Since each of the aforesaid apparatuses has no function designed while taking into consideration of the inhibition of copying of specific original documents such as paper money, a serious suffering can be foreseen if the specific original documents are copied. As a countermeasure taken against the forgery, a variety of systems for use in copying machines or the like for recognizing the specific original document have been suggested. Then, description will now be described about a system such as an electrophotographic color copying machine for forming an image according to a so-called frame sequential method. In a case where an image is formed according to the frame sequential method, an original document for, for example, one image plane is read. The read data is color-decomposed, and, first, a cyan (C) component for one image plane is copied onto copying paper. Then, the same original document is again read for one image plane and, as the ensuing component, a magenta (M) component is copied while being superposed on the same copying paper. Furthermore, the aforesaid operations are repeated in a sequential order of a yellow (Y) component and a black (BK) component. As a result, a full color image can be formed. Therefore, if the detection of the specific original document is performed during an operation of reading the original document for three image planes and an image such as a pattern which informs that the copied paper is a forged paper is printed at the time of performing the last printing operation in black, the forgery can be prevented. Such a copying machine is disclosed in EP-A-0382549. An object of the present invention is to provide an image processing apparatus capable of specifying an apparatus with which copying has been performed if a specific original document such as paper money is copied, so that the spread a suffering from copying of the specific original document can be prevented. In a first aspect of the present invention, there is provided an image forming apparatus as set out in claim 1. In a second aspect of the invention, there is provided an image processing apparatus as set out in claim 2. Another aspect of the invention comprises a method of operating an image forming apparatus as set out in claim 14. In a further aspect, the invention comprises a method of operating an image processing apparatus, as set out in claim 15. Additional features of the invention are set out in claims 3 to 13 and 16 to 23. The invention also comprises a digital colour copier incorporating an apparatus as claimed in any of claims 1 to 13. An embodiment of the present invention provides an image processing apparatus comprising: discriminating means for discriminating similarity between inputted image data and a specific image data which has been previously prepared; pattern generating means for generating a predetermined pattern signal representing information for identifying an apparatus; synthesizing means for synthesizing said predetermined pattern signal generated by said pattern generating means and said inputted image data in accordance with the similarity discriminated by said discriminating means; and output means for outputting the result of synthesizing performed by said synthesizing means. Other objectives and advantages besides those discussed above shall be apparent from the description made with reference to the accompanying drawings and claims. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic view which illustrates the shape of a digital color copying machine according to a first embodiment of the present invention; Fig. 2 is a cross sectional view which schematically illustrates the internal structure of the copying machine 10 shown in Fig. 1 when viewed from a side position; Fig. 3 is a view which illustrates the structure around a scanning carriage 58 according to the first embodiment; Fig. 4 is a block diagram which illustrates the structure of a control system in the copying machine 10 according to the first embodiment; Fig. 5 is a flow chart which illustrates an example of a routine for recording a manufacturer's serial number to be executed by a main CPU 100 according to the first embodiment; Fig. 6 is a view which illustrates an example of recording of the manufacturer's serial number according to the first embodiment; Fig. 7 is a view which illustrates an example of recording of the manufacturer's serial number according to the second embodiment; Fig. 8 is a flow chart which illustrates an example of a routine for recording a manufacturer's serial number to be executed by a main CPU 100' according to the second embodiment; Fig. 9 is a block diagram which illustrates the structure of a paper money detection.portion 120 shown in Fig. 4; Figs. 10, 11 and 12 are views which illustrate a binary-to-multivalue conversion method; Fig. 13 is a view which illustrates a multivalue conversion method in which image data is thinned; Fig.14 is a block diagram which illustrates the structure of an integrator; and Figs. 15 and 16 are views which illustrate an example of input/output of the integrator. DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will now be described with reference to the drawings. In the descriptions about the following embodiments, the specific original document is paper money, securities and confidential documents which are the subject of forgery. <First Embodiment> Fig. 1 illustrates the shape of a digital color copying machine 10 according to a first embodiment of the present invention. Referring to Fig. 1, the digital color copying machine (hereinafter called a "copying machine") 10 is composed of two major portions. That is, the first major portion is a color image scanner portion (hereinafter abbreviated to a "reader portion) 12 for reading the image of an original document positioned above the color image scanner portion 12 and outputting digital color image data for a plurality of color components each of which is composed of multivalue data. The reader portion 12 performs variable image processing operations such as a binarization of the digital color image data and includes a controller portion 14 having a processing function such as the interface function with external equipment. Th second major portion is a printer portion 20 disposed below the reader portion 12 to record a binary color digital image signal for each of Y (yellow), M (magenta), C (cyan) and BK (black) outputted from the control portion 14 of the reader portion 12 to the recording paper. The reader portion 12 further includes a mechanism disposed therein for the purpose of reading image information from an original document downwards placed on an original document holder (omitted from illustration) disposed below an original document retaining plate 16, the original document being formed variously in terms of the shape and the size, that is the original document is formed into a stereoscopic shape, a sheet shape or a large size sheet shape. The reader portion 12 has, an end portion of the top surface thereof, an operation portion 18 connected to the controller portion 14. The operation portion 18 has keys for inputting various information for use in the copying machine and information about the operation command, switches and a display portion for displaying menus and messages about the state of the operation. Furthermore, the controller portion 14 is constituted to instruct the operations of the reader portion 12 and the printer portion 20 according to information supplied via the operation portion 18. For example, if a complicated editorial operation is required, a digitizer or the like is mounted in place of the original document retaining plate 16 and is connected to the controller portion 14 for the purpose of enabling further advanced image processing operation to be performed. The printer portion 20 according to this embodiment is able to use a full-color ink jet printer having an ink bubble jet recording type recording head arranged as disclosed in Japanese Patent Laid-Open No. 54-59936, the ink jet printer as disclosed above being arranged to act according to the bubble jet recording method which is one of the ink bubble jet recording system. The bubble jet recording system uses a head of a type for discharging liquid droplets by utilizing film boiling taken place by heat energy. The aforesaid two major portions can be separated from each other and can be disposed away from each other while being connected to each other by a connection cable extended. The aforesaid major portions will now be described. Fig. 2 is a cross sectional view which schematically illustrates the internal structure of the copying machine 10 shown in Fig. 1 when viewed from a side position. (Reader Portion 12) First, the structure of the reader portion 12 of the copying machine 10 will now be described. The reader portion 12 has an exposure lamp 22, a lens 24 and an image sensor 26 (a CCD sensor according to this embodiment), which is capable of full-color reading a line image, to read the image of an original document placed on an original document retainer glass 28, a projected image formed by a projector or the image of a sheet-like original document fed by a sheet feeding mechanism 30. Then, image information thus read by the reader portion 12 is subjected to a variety of processes in the reader portion 12 and the controller portion 14. Then, information, which has been read and processed, is supplied to the printer portion 20 in which it is recorded to the recording paper. (Printer Portion 20) In the printer portion 20, the recording paper is selectively supplied in this way that small regular size (A4 to A3 size according to this embodiment) cut-sheets accommodated in a paper feeding cassette 32 or a roll paper 34 for recording information to large size (A2 to A1 size according to this embodiment) recording paper is selectively supplied. The paper feeding operation is commenced in response to a command to start printing supplied from the controller portion 14. Thus, the recording paper is conveyed to a position, at which first paper feeding rollers 44 are located, through the following passage. According to this embodiment, the recording paper can be supplied manually (supplied from an outside position of the apparatus) by sequentially supplying the same through a manual feeding portion 36 along a cover for the paper feeding portion. In a case where the recording paper is fed from the paper feeding cassette 32 loaded in the printer portion 20, a pickup roller 40 is brought into a position on the top surface of an end portion of the recording paper set in the paper feeding cassette 32, the pickup roller 40 being used to sequentially pick up the cut-sheets from the paper feeding cassette 32. Therefore, when the pickup roller 40 is rotated, the recording paper placed at the uppermost position in the paper feeding cassette 32 is picked up and is fed to cut paper feeding rollers 42. Then, the recording paper is conveyed to the first paper feeding rollers 44 by the cut-sheet feeding rollers 42. In a case of the roll paper 34, it is continuously fed by the action of roll paper feeding rollers 46 and is cut to have a regular length, the cut-sheet being then conveyed to the position at which the aforesaid first paper feeding rollers 44 are located. In a case where the recording paper is manually fed through the manual feeding port 36, the recording paper, which has been fed manually, is conveyed to the first paper feeding rollers 44 by manual feeding rollers 50. The pickup rollers 40, the cut-sheet feeding rollers 42, the roll paper feeding rollers 46, the first paper feeding rollers 44 and the manual feeding rollers 50 are driven by a paper feeding motor (a DC servo motor according to this embodiment and omitted from illustration) in such a manner that their rotations can be turned on/off by the actions of electromagnetic clutches respectively provided for the aforesaid rollers. The recording paper thus selected and fed through either of the aforesaid paper feeding passages is conveyed to the first paper feeding rollers 44. In order to prevent a skew of the recording paper, a paper loop of the recording paper is formed by a predetermined quantity and the first paper feeding rollers 44 are turned on to rotate Then, second paper feeding rollers 52 convey the recording paper. Furthermore, the recording paper is slackened to form a buffer between the first paper feeding rollers 44 and the second paper feeding rollers 52 by slackening the recording paper by a predetermined quantity in order to accurately feed the recording paper between paper feeding rollers 64 disposed above a recording head 56 and the second paper feeding rollers 52 disposed below the same. In order to detect the quantity of the buffer formed by the recording paper, a buffer quantity detection sensor 54 is disposed adjacent to the position at which the buffer is formed. Since the buffer of the recording paper is always formed during its conveyance, the load which acts on the paper feeding rollers 64 and the second paper feeding rollers 52 when large size recording paper is conveyed can be reduced, so that an accurate paper feeding operation can be performed. When printing is performed in the printer portion 20, in which the system for conveying the recording paper is formed, by using the recording head 56, a scanning carriage 58, on which the recording head 56 is mounted, is reciprocated by a scanning motor 62 on a carriage rail 60 in a direction perpendicularly to the surface of the accompanying drawing sheet and thereby scanning of the recording paper in the main scanning direction is performed. In the forward directional scanning operation, an image is printed onto the recording paper by the recording head 56, while a sub-scanning directional feeding operation, in which the recording paper is fed by a predetermined quantity by the paper feeding rollers 64, is performed in the returning scanning operation. The quantity of feeding in the sub-scanning direction is defined as a "constant quantity of movement" to be described later and is set to a length which corresponds to the width of the recording head 56 in the sub-scanning direction, that is a length which corresponds to the width of a suction hole (omitted from illustration) formed in a platen 74 at a position at which it confronts the recording head 56. The aforesaid suction hole acts to bring the recording paper into contact with the platen 74 in a hermetical manner. In the operation of controlling the recording paper performed by the scanning moor 62 at the time of the returning directional scanning operation, a predetermined quantity of the buffer is always maintained while detecting the quantity of the buffer by the buffer quantity detection sensor 54. The recording paper on which information has been printed is discharged onto a paper discharge tray 66. Thus, the aforesaid sequential printing operation is completed. (Structure of Scanning Carriage System) Fig. 3 illustrates the structure of a portion in the vicinity of the scanning carriage 58 according to the first embodiment. Referring to Fig. 3, reference numeral 68 represents a paper feeding motor serving as a driving power source for intermittently feeding the recording paper 35 in the sub-scanning direction. The quantity of the rotation of the paper feeding motor 68 can be changed to an arbitrary value so as to drive the second paper feeding rollers 52 via the paper feeding rollers and a clutch 70 for the second paper feeding rollers 52. The scanning motor 62 serves as the driving power source for reciprocating the scanning carriage 58 via a scanning belt 72 in the main scanning direction designated by arrows A and B. Since the paper feeding operation must be accurately controlled in this embodiment while establishing an arbitrary quantity of feeding, the paper feeding motor 68 and the scanning motor 62 are formed by pulse motors. In the structure according to this embodiment, a paper retaining member (omitted from illustration) is disposed at a position at which it confronts the lower end portion of the platen 74. The paper retaining member secures the recording paper 35 to the platen 74 during the scanning operation performed by the scanning carriage 58 in order to prevent the deviation of the recording paper 35 such as an undesirable movement. When the recording paper 35 reaches the second paper feeding rollers 52, the clutch 70 for the second paper feeding rollers 52 and the paper feeding motor 68 are respectively turned on. As a result, the leading portion of the recording paper 35 is conveyed on the platen 74 until it is held by the pair of the paper feeding rollers 64. The platen 74 has a paper detection sensor 76 disposed thereon. The recording paper 35 conveyed on the platen 74 is detected by the paper detection sensor 76. Information obtained by the paper detection sensor 76 is utilized to control the position and to prevent a jam and the like. When the leading portion of the recording paper 35 reaches the paper feeding roller 64, the clutch 70 for the second paper feeding rollers 52 and the paper feeding motor 68 are respectively turned off. As a result, the pressure of the space in the platen 74 is lowered to a negative level by the commencement of the action of the suction motor (omitted from illustration), so that a suction operation is commence . As a resut of this suction operation, the recording paper 35 is brought into contact with the surface of the platen in a hermetical manner. Simultaneously, the aforesaid paper retaining member secures the recording paper 35 to the platen 74. Prior to performing the operation of printing an image onto the recording paper 35, the scanning carriage 58 is moved to a position at which a home position sensor 78 is disposed, so that the forward scanning operation is performed in the direction designated by the arrow A. In this forward scanning operation, ink for cyan (C), that for magenta (M), that for yellow (Y) and that for black (BK) are respectively discharged from recording heads 56a, 56b, 56c and 56d from predetermined positions, so that an image is recorded (printed). When an operation of recording the image by a predetermined length in the main scanning direction has been completed, the direction of the rotation of the scanning motor 62 is reversed to move the scanning carriage 58 in the reverse direction, that is in the direction designated by the arrow B to commence the returning directional scanning operation. The scanning motor 62 is rotated reversely until the scanning carriage 58 returns to the position at which the home position sensor 78 is located. During the aforesaid returning directional scanning operation, the rotation of the paper feeding motor 68 is commenced to rotate the paper feeding rollers 64, so that the paper feeding operation by a length (the width of one recording head) recorded by the recording heads 56a, 56b, 56c and 56d in a sub-scanning direction designated by an arrow C is performed. According to this embodiment, the quantity of feeding the recording paper, that is the quantity of the movement in the sub-scanning direction is not limited to a constant quantity of the aforesaid movement of the width of one recording head but it may be set to the quantity of the one-way movement defined by the final line width. According to this embodiment, the recording head 56 is an ink jet nozzle unit formed by assembling 256 nozzles for each Y, M, C and BK. When the scanning carriage 58 is stopped at a home position defined by the home position sensor 78, an operation of recovering the recording head 56 is performed. The aforesaid recovery operation is performed to stabilize the recording operation by preventing irregular discharge at the time of the start take place due to change in the viscosity of ink left in the nozzles in the recording head 56. In this recovery operation, pressure is applied to each nozzle in the recording head 56 according to previously programmed conditions such as the time in which the recording paper is fed, the temperature in the apparatus and the time at which the discharge is commenced and the like to perform an idle discharge of ink from each nozzle. By repeating the aforesaid operations, a desired image can be recorded to the entire surface of the recording paper 35. (Structure of the System) Then, the operations of processing the image signal and controlling the same performed in the control system of the copying machine 10 according to this embodiment will now be described with reference to Fig. 4. Referring to Fig. 4, reference numeral 100 represents a main CPU which controls the overall operation of the apparatus and to which the following units are connected: a printer control CPU 102 for controlling the operation of the printer, a reader control CPU 104 for controlling the reading operation, a main image processing portion 106 for displaying an image, an operation portion 108 serving as an input portion used by an operator, a paper money detection portion 120 for detecting whether or not the image of paper money is present in the original document and a pattern generator 122 for generating an image signal denoting the manufacturer's serial number of this apparatus. The main CPU 100 is also connected to a ROM 100a which stores a program or the like according to its flow chart shown in Fig. 5 and a RAM 100b for use as a work area in which a variety of programs are executed. The printer control CPU 102 and the reader control CPU 104 respectively control the printer portion and the reader portion and are set as slaves with respect to the main CPU 100 serving as a master. The aforesaid main image processing portion 106 performs edge highlight smoothing, masking, black extraction and trimming operations and the like and binary-codes the image signal by making a comparison with the slice level. A synchronizing memory 110 is connected to the printer control CPU 102 and, via an image synthesizing portion 124, to the main image processing portion 106. The synchronizing memory 110 performs an operation of absorbing scattering of the input operation time and an operation of correcting the delays taken place due to the mechanical configuration of the aforesaid recording heads. The output of the synchronizing memory 110 is connected to the recording head 56. The printer control CPU 102 is connected to a printer portion drive system 114 for controlling the input operation to the printer portion. The reader control CPU 104 is connected to an input system image processing portion 116 for performing correction processes such as a shading correction, a color correction and a γ correction operations required for the reading system and a reader portion drive system 118 for controlling the input to the reader portion. Furthermore, the CCD line sensor 26 is connected to the input system image processing portion 116 which is connected to the main image processing portion 106. The paper money detection portion 120 is connected to the CCD line sensor 26 and the main CPU 100 so as to discriminate whether or not paper money or the like is included in the original document in response to a multivalue image signal for each color supplied from the CCD line sensor 26. If a fact that paper money is included in the original document is discriminated by the paper money detection portion 120, a routine of recording the manufacturer's serial number is commenced to start the pattern generator 122. The method of discrimination is later mentioned with respect to Fig. 9. The pattern generator 122 is connected to the main CPU 100 and the image synthesizing portion 124 to generate the manufacturer's serial number recorded on the ROM 100a in response to a command issued from the main CPU 100 so as to output it to the image synthesizing portion 124. The image synthesizing portion 124 is connected to the main image processing portion 106, the pattern generator 122 and the synchronizing memory 110 so as to synthesize the binary-coded image signal supplied from the main image processing portion 106 and a signal supplied from the pattern generator 122, the synthesized signal being then outputted to the synchronizing memory 110. The reader portion 12 is formed by the main CPU 100, the reader control CPU 104, the main image processing portion 106, the operation portion 108, the input system image processing portion 116, the paper money detection portion 120, the pattern generator 122, the reader portion drive system 118 and the CCD line sensor 26 serving as the image sensor. The printer portion 20 is formed by the printer control CPU 102, the synchronizing memory 110, the recording head 56 and the printer portion drive system 114. Then, the manufacturer's serial number recording routine commenced at the time of detecting paper money and executed by the main CPU 100 will now be described in detail with reference to a flow chart shown in Fig. 5. In a case where a discrimination is, by the paper money detection portion 120, made that an image of paper money or the like is included in the output signal outputted from the CCD 26 , the manufacturer's serial number recording routine is commenced and thereby the operation of the main CPU 100 proceeds to step 51 shown in Fig. 5. In step (hereinafter called "S") 51, a signal denoting the manufacturer's serial number for one scan is generated so as to be synthesized with the binary signal generated by the main image processing portion 106. In next step S52, a discrimination is made whether or not the copying operation has been completed. If the copying operation is being executed, the flow proceeds to S51. If the copying operation has been completed, the manufacturer's serial number recording routine is completed here. Fig. 6 illustrates an example of an operation of recording the manufacturer's serial number according to the first embodiment. Fig. 6 illustrates an example in which manufacturer's serial number "3851314" is recorded. It is premised that the length of the short side of paper money, which is the specific original document, is longer than any one of the marginal lengths J, K and L in the main scanning direction and the sub-scanning direction when the manufacturer's serial number is recorded. As a result, even if the image of paper money is formed on the recording paper, the manufacturer's serial number can be read from the image of the paper money formed. According to this embodiment, the manufacturer's serial number is printed and recorded with a yellow component because it cannot easily be recognized by human eyes. The color is not limited to this and it may, of course, be half tone color or may be formed by multi-color printing. According to this embodiment, a manufacturer's serial number signal denoting the manufacturer's serial number is generated in the pattern generator 122 in response to a signal detected by the paper money detection portion 120. Then, the manufacturer's serial number signal and the binary-coded image signal are synthesized by the image synthesizing portion 124, a synthesized image signal being used to form an image. As a result, the apparatus used to copy paper money can be detected from the image of the specific original document recorded on the recording paper, for example, the image of paper money. Consequently, the forgery of money paper can be prevented and it is expected that suffering of it can be prevented. <Second Embodiment> Then, a second embodiment of the present invention will now be described. According to the first embodiment, if the image denoting the specific original document such as paper money is detected, the pattern generator continues to generate the manufacturer's serial number signal until the copying operation is completed. However, the present invention is not limited to this. For example, a structure may be employed in which, if an image denoting a specific original document such as paper money is detected by the paper money detection portion, the pattern generator is commenced to synthesize the manufacturer's serial number with the binary-coded image signal and if nothing is detected, the pattern generator is stopped. An example of printed image in the aforesaid case is shown in Fig. 7. Referring to Fig. 7, reference numerals 150 and 151 represent paper money and 152 represents the recording paper. The paper money 150 and 151 are placed in the recording paper 152 as designated by a dashed line shown in Fig. 7. Symbol A denotes the length of the image in the sub-scanning direction formed by one scanning operation. Then, the routine for recording the manufacturer's serial number in a case shown in Fig. 7 will now be described. Fig. 8 is a flow chart which illustrates the routine for recording the manufacturer's serial number according to the second embodiment of the present invention. Since the structure of the second embodiment is the same as that shown in Fig. 1, its description is omitted here. In a case where the structure is shown at the time of describing the operation, dash is added to the reference numeral shown in Fig. 1. According to the first embodiment, in a case where a discrimination is, by the paper money detection portion 120′, made that the image of paper money or the like is included in the image signal outputted from the CCD 26′, the routine of recording the manufacturer's serial number is commenced and the flow of the operation performed by the main CPU 100′ proceeds to S81 shown in Fig. 8. In S81, waiting for predetermined time is performed in order to making the operations of the image processing portions 116′ and 106′ coincide with each other. In next S82, a pair of manufacturer's serial number image signals are generated so as to be synthesized with the binary signal. In next S83, whether or not the image of paper money or the like has been detected is confirmed. If the same has been detected, the flow proceeds to S81. If the same has not been detected, the routine of recording the manufacturer's serial number is completed. As described above, only in a case where the specific original document has been detected, the manufacturer's serial number can be added as the pattern. (Image Discriminating Portion) Fig. 9 is a block diagram which illustrates the structure of the paper money detection portion 120 shown in Fig. 4. First, binary-to-multivalue conversion performed in the paper money detection portion 120 will now be described with reference to Fig. 9 Referring to Fig. 9, reference numeral 801 represents a shift register for converting image signals for C, M, Y and BK supplied in the form of a serial signal into parallel signals in this way that a timing control portion (omitted from illustration) converts the serial binary image data for C, M, Y and BK into the parallel signals. Reference numeral 802 represents a binary-to-multivalue conversion portion for converting the binary image data, which has been converted into the parallel signal by the shift register 801, into the multivalue image data of 5 bits for each color. The reason why the width of the bit is determined to be 5 bits lies in that the load acting on the ensuing process in the circuit must be reduced and the specific original document must be detected reliably. Furthermore, the image data to be converted from the binary data into the multivalue data is selectively converted into the multivalue data in such a manner that one pixel for each four pixels is converted into the multivalue data. The reason for this also lies in the aforesaid requirements. Reference numeral 803 represents a matching lookup table (hereinafter called a "color tone matching LUT" hereinafter) which is a ROM for matching the color tones which are the characteristics of plural kinds of specific original documents. Reference numerals 804-1, 804-2,..., 804-8 represent color tone discriminating circuits respectively formed by similar hardware. As typically shown by the color tone discriminating circuit 804-1, each of the color tone discriminating circuit is formed by an integrator 805, a register 807 and a comparator 806 and is capable of discriminating whether or not the specific original document is present in the image data. Reference numeral 808 represents an OR circuit for outputting "1" as a result of a discrimination in a case where one-or more outputs from the color tone discriminating circuits 804-1 to 804-8 denote a fact that the specific original document is present. Since the contents of the register 807 are different for each discriminating circuit, comparisons with 8 types of the specific original documents can be performed simultaneously. (Binary-to-Multivalue Conversion Circuit) Figs. 10, 11 and 12 illustrate the binary-to-multivalue conversion method. The supplied binary image data is subjected to the area process as shown in Fig. 10 . That is, as shown in Fig.10 a matrix of 5 pixels x 5 pixels is used to obtain the sum of the cells in which image data is present for the purpose of obtaining the density level of a subject pixel 901. Each cell has a weight coefficient at this time and therefore a value multiplied by the weight coefficient becomes data about each cell. Assuming that the weight coefficient of each cell of the matrix is x i , y i (i, j = 1 to 5), density level e of the subject pixel can be obtained by the following Equation (1): where a is image data and is 1 or 0 because it is a binary image here Fig. 12 illustrates an example of the weight coefficient, wherein the highest density level is "61" in the decimal format and therefore all of the density levels can be expressed with the data width of 5 bits in the binary format. Then, a method of performing the multivalue-conversion while thinning the image data will now be described with reference to Fig. 13. When the image data is thinned before the multivalue conversion is performed, the subject pixel 1201 is converted into multivalue data, and the fifth image data is made to be the subject pixel which is converted into the multivalue data. The binary-to-multivalue conversion portion 802 has individual circuits for each color code C, M, Y and BK. The image data for C, M, Y and BK, which have been binary-to-multivalue converted by the aforesaid method are supplied to the color tone matching LUT 803 shown in Fig. 9. (Discriminating Circuit) The-color tone matching LUT 802 shown in Fig. 9 is formed by a ROM and performs the matching the color tone of the supplied image data and those of plural kinds of specific original documents (for example, paper money or securities which are the subject of the prevention of forgery), the color tone being the characteristics of an image. That is, the color tone matching LUT 803 stores color tone distribution previously examined about the 8 types of specific original documents and results of discriminations made whether or not the color tones of supplied image data coincide with the color tones of the aforesaid specific original document. As described above, the color tone matching LUT 803 has 20-bit address lines of A0 to A19 and, in units of 5 bits, receives image data for each C, M, Y and BK converted into the multivalue data by the binary-to-multivalue conversion portion 802. The color tone matching LUT 803 has 8-bit (D0 to D7) data output lines to discriminate 8 types of original documents since each bit corresponds one type of the specific original document. (Integrator) Fig. 14 is a block diagram which illustrates the structure of the integrator. Referring to Fig. 14, reference numerals 1301 and 1305 represent flip-flops for holding data at the timing of the first transition of a CLK signal. Reference numeral 1302 represents a multiplier which receives two input signals (A and B) of 8 bits and outputs an 8-bit signal (A x B/255) denoting the result of the multiplication. Reference numeral 1303 represents a multiplier which receives a 1-bit input signal (A) and an 8-bit input signal (B) and which outputs an 8-bit output signal (A x B) denoting the result. Reference numeral 1304 represents an adder which receives an 8-bit input signals (A and B) and which outputs an 8-bit signal (A + B). As a result of the aforesaid calculations, the integrator 805 receives a binary input signal x i and outputs an 8-bit output signal y i expressed by the following Equation (2): y i = (α/255) i-1 + β · x i-1 where α and β are predetermined constants which determine various characteristics of the integrator 805. Figs. 15 and 16 illustrate an example of input and output from the integrator. The integrator 805 receives x i as shown in Fig. 15 and outputs y i as shown in Fig. 16 That is, an input such a dots 1401 and 1402, the level of which is substantially "0" at its surrounding portion and the level of which is "1" or an input such as a dot 1403, the level of which is substantially "1" and the level of which is "0" are considered to be noise. When the aforesaid inputs are processed by the integrator 805, its output becomes as shown in Fig. 16. Accordingly, a threshold such as a level 1404 shown in Fig. 16 is provided for the register 807 shown in Fig. 16 so as to be used to binary-code the output yi from the integrator. As a result, the aforesaid noise can be eliminated. Although each of the aforesaid embodiments is described about an application to the ink-jet copying machine, the present invention is not limited to this and is therefore embodied in an electrophotographic system, a thermosensitive system and a photographic system. In particular, it may be applied to a so-called bubble jet type printer having a head of a type for discharging a liquid droplet by utilizing film boiling taken place by heat energy. Also the present invention is not limited to the color copying machine and it may be utilized in a monochrome digital copying machine for converting an image signal into a binary signal. Furthermore, the input is not limited to that made from the scanner as is done in the aforesaid copying machine. The present invention can be applied to a system for printing by processing an image supplied from external equipment via an I/F or a system in which an image supplied from a communication apparatus is processed so as to be printed. In addition, data to be generated by the pattern generator is not limited to the manufacturer's serial number, and any code such as the bar code may therefore by utilized if the apparatus can be specified according to the copied paper money. The data is not also limited to the code for identifying the apparatus, and therefore any code denoting the location of the apparatus, date, the name of an owner or user may be used. As for the color for use to record the identification code such as the manufacturer's serial number, any color can be employed to record it. Furthermore, the present invention is not limited to the paper money as the specific original document. It can therefore be applied to any document such as securities and variable document, the copy of which must be inhibited. In addition, the present invention can be applied to any postcard and document as well the document, the copy of which must be inhibited. The present invention may be applied to a system composed of a plurality of apparatuses or a system composed of one apparatus. The present invention may, of course, be applied to a case which is established by supplying a program to the system or an apparatus. Although in each of the aforesaid embodiments yellow is used as the added color, the present invention is not limited to this. For example, a quiet color such as yellow green or gray or a color having a high brightness such as purple or light green may be employed. Although in each of the aforementioned embodiments the image of the original document is inputted, the present invention is not limited to this. The original document may be that inputted by a still video camera or a video camera and the original document may be that processed according to the computer graphics. Although the invention has been described in its preferred form with a certain degree of particularly, it is understood that the present disclosure of the preferred form has been changed in the details of construction and the combination and arrangement of parts may be resorted to without departing from the scope of the invention as hereinafter claimed.

Claims: An image forming apparatus (10) comprising: input means (26) for receiving image data defining an input image; processing means (100; 106; 116) for processing the received image data so as to generate output image data; and printing means (20; 56) for using said output image data to print a visible image reproducing said input image; characterised in that: said output image data defines said visible image as a binary image; said image forming apparatus further comprises storage means (100a) storing identification information identifying said image forming apparatus, said identification information being stored so as to be non-rewritable by users; and said image forming apparatus is arranged to represent the identification information in the printed visible image in a form difficult to discriminate with normal naked human eyes. An image processing apparatus (100-110; 114-124) comprising: input means (116) for receiving image data defining an input image; and processing means (106; 116) for processing the received image data so as to generate output image data defining a visible image reproducing said input image; characterised in that: said output image data defines said visible image as a binary image; and said image processing apparatus further comprises: storage means (100a) storing identification information identifying said image processing apparatus, said identification information being stored so as to be non-rewritable by users; and synthesising means (124) arranged for synthesising identification data representing said identification information with said output image data so that a visible reproduction of said input image made using the synthesised output data will include a representation of said identification information in a form difficult to discriminate with normal naked human eyes. Apparatus according to claim 1, wherein said input image is a multi-colour image, and wherein: the printing means prints separate visible colour components so as to reproduce said multi-colour input image; and the identification information is represented in one or more of the printed visible colour components. Apparatus according to claim 2, wherein said input image is a multi-colour image and wherein said output image data comprises separate visible colour components. Apparatus according to claim 3 or 4, wherein said separate colour components comprise magenta, cyan, yellow and black images, and wherein said identification information is represented in the printed yellow colour component. Apparatus according to any preceding claim, further comprising: storage means (120) for storing reference data characteristic of at least one predetermined reference image; and comparison means (100; 120) for using the received image data and the stored reference data to determine whether the input image corresponds to the reference image; and wherein the identification information is represented in the printed visible image in dependence upon the determination. Apparatus according to claim 6, wherein the representation of the identification information appears only at locations (150; 151) in the printed visible image at which it is determined that the image corresponds to the reference image. Apparatus according to any preceding claim, wherein the image data defining said input image is multi-value image data, and wherein said apparatus further includes binary-coding means (106) for converting the multi-value image data to bi-level image data. Apparatus according to any preceding claim, wherein said identification information comprises a serial number of the apparatus. Apparatus according to any preceding claim, wherein the representation of the identification information occurs repeatedly in the printed visible image at a predetermined interval. Apparatus according to any preceding claim, wherein said input means comprises an image reader which includes a CCD sensor (26). Apparatus according to claim 1 or claim 3, wherein said printing means comprises a bubble jet type printer. Apparatus according to claim 12 when dependent upon claim 3, wherein said printing means records an image by using a plurality of nozzles for each colour component. A method of operating an image forming apparatus so as to form a reproduction image, comprising: receiving image data defining an input image; processing the received image data so as to generate output image data; and using said output image data to print a visible image reproducing said input image; characterised in that: said output image data defines said visible image as a binary image; and in that the method further comprises: storing identification information identifying said image forming apparatus, said identification information being stored so as to be non-rewritable by users; and representing the identification information in the printed visible image in a form difficult to discriminate with normal naked human eyes. A method of operating an image processing apparatus, comprising: receiving image data defining an input image; and processing the received image data so as to generate output image data defining a visible image reproducing said input image; characterised in that: said output image data defines said visible image as a binary image; and in that the method further comprises: storing identification information identifying said image processing apparatus, said identification information being stored so as to be non-rewritable by users; and synthesising identification data representing said identification information with said output image data so that a visible reproduction of said input image made using the synthesised output data will include a representation of said identification information in a form difficult to discriminate with normal naked human eyes. A method according to claim 14, wherein said input image is a multi-colour image, and wherein: separate visible colour components are printed so as to reproduce said multi-colour input image; and the identification information is represented in one or more of the printed visible colour components. A method according to claim 15, wherein said input image is a multi-colour image and wherein said output image data comprises separate visible colour components. A method according to claim 16 or 17, wherein said separate colour components comprise magenta, cyan, yellow and black images, and wherein said identification information is represented in the printed yellow colour component. A method according to any of claims 14 to 18, further comprising: storing reference data characteristic of at least one predetermined reference image; and using the received image data and the stored reference data to determine whether the input image corresponds to the reference image; and wherein the identification information is represented in the printed visible image in dependence upon the determination. A method according to claim 19, wherein the representation of the identification information appears only at locations in the printed visible image at which it is determined that the image corresponds to the reference image. A method according to any claims 14 to 20, wherein the image data defining said input image is multi-value image data, and wherein the method further includes the step of converting the multi-value image data to bi-level image data. A method according to any of claims 14 to 21, wherein said identification information comprises a serial number of the apparatus. A method according to any of claims 14 to 22, wherein the representation of the identification information occurs repeatedly in the printed visible image at a predetermined interval. A digital colour copying machine including an apparatus according to any of claims 1 to 13.

Inventors: KOMAKI YOSHIO, UDAGAWA YUTAKA, KOMAKI, YOSHIO, UDAGAWA, YUTAKA, Komaki, Yoshio, c/o Canon Kabushiki Kaisha, Udagawa, Yutaka, c/o Canon Kabushiki Kaisha
Applicants: CANON KK, CANON KABUSHIKI KAISHA
Application year: 1992
Main classification: G03G21
IPC codes: H04N1, G03G21, G06T7