Apparatus for image reading or processing

Abstract: There is disclosed an apparatus for image reading or processing, that can precisely identify the pattern of a particularly pattern, such as of banknotes or securities of which faithful copying is to be pro­ hibited. The apparatus is provided with a detecting unit for detecting the positional information of the original image, and a discriminating unit for extracting the pattern data of a certain part of the original image and discriminating whether the original image is the predetermined image, based on the similarly between the pattern data and a predetermined pattern.

Description: The present invention relates to a control device and method for use in image processing for discriminating whether an input image corresponds to a predetermined image. The technical development for hard copying, for example with copying machines, has been aimed at faithful reproduction of the original image. As a result, there is now available a high-quality copying machine which can provide a reproduced image excellent in colour reproduction and not distinguishable from the original image. Particularly the development of digital full-colour copying machine has improved the quality of copied images to a level not distinguishable from the original image by human eyes, and has enabled such copies to be made within a short time with a simple operation. However such image reproduction in a form very close to the original image will have significant social influence, as it may be abused for the forgery of banknotes or other valuable securities. Existing image processing apparatus, such as copying machines, are vulnerable to abuse for forgery. The present applicant has disclosed technologies for preventing the forgery of particular images in earlier European patent applications, now published as EP-A-0342060 and EP-A-0366399. EP-A-0342060 (published on 15/11/89) discloses techniques for altering the image forming process in case the original image to be copied is identified as a predetermined particular image, and for altering the process according to the level of similarity to the particular image. EP-A-0366399 (published on 02/05/90) discloses techniques for registering an image of which copying is to be prohibited by reading said image with a reader, and for renewing such registration. However such technologies still have room for improvement in the realization of the image processing apparatus capable of effectively preventing the forgery of particular images, particularly in the detection of particular images and in the image processing control in response to such detection. Concerning the detection of particular images, EP-A-0324060 proposes that identification of a banknote or the like can be performed either by pattern matching or by matching a colour spectrum of the original with that of a reference image. EP-A-0366399 proposes that original image data should be converted into ternary pattern data by reference to two threshold values, and compared with ternary reference data which has been converted similarly. The invention provides a control device for controlling an image processing device based on the image content of an input image signal so as to supply a control signal indicating whether the input image should be faithfully outputted, said control device comprising: input means for accepting an input signal representing a multi-coloured image; colour reference means for storing colour reference data defining with reference to plural colour components a specific region of colour space; extracting means for using the stored colour reference data to extract from the input signal pattern data representing a pattern present in colours within said specific region of colour space in the input image; comparing means for comparing said extracted pattern data with a predetermined reference pattern and for determining whether said pattern data matches said reference pattern; and means for generating a control signal when said comparing means determines that said extracted pattern data matches said reference pattern in order to prevent said image processing device from outputting the input image faithfully. The invention further provides a method of controlling the operation of an image processing apparatus so as to prevent the faithful output of a particular predetermined colour image or images, comprising the steps of: receiving an input signal representing a multi-coloured image; obtaining colour reference data defining with reference to plural colour components a specific region of colour space; extracting pattern data from the input signal using the stored colour reference data, said pattern data representing a pattern present in colours within said specific region of colour space in the input image; and comparing the extracted pattern data with a predetermined reference pattern and supplying a control signal to the apparatus being controlled when it is determined that said pattern data matches said reference pattern, the control signal indicating that faithful output of the image should be prevented. The colour or colour range selected for pattern extraction might correspond, for example, to the red of the "seal" on a Japanese banknote. Embodiments of the invention and other features will now be described, by way of example only, with reference to the accompanying drawings, in which: Fig. 1 is a view showing a banknote placed on an original support table; Fig. 2 is a schematic view of an apparatus constituting a first embodiment; Fig. 3 is a chart showing the relation between different modes and four scanning operations; Fig. 4 is a block diagram of an image scanner; Fig. 5 is a timing chart thereof; Fig. 6 is a block diagram of a window comparator shown in Fig. 4; Fig. 7 is a circuit diagram of a block processing unit shown in Fig. 4; Fig. 8 is a circuit diagram of a water-mark detection unit shown in Fig. 4; Fig. 9 is a circuit diagram of an address decoder shown in Fig. 4; Fig. 10 is a flow chart of the function of the apparatus; Fig. 11 is a view showing the principle of positional detection; Figs. 12, 13, 14A, 14B, 14C, 15A and 15B are views showing the principle of pattern matching; Fig. 16 is a block diagram of a further embodiment; Fig. 17 is a schematic view of said further embodiment; Fig. 18 is a block diagram of judgement means 3114; Fig. 19 is a block diagram of an address decoder 3115; Fig. 20 is a timing chart for counters 3401, 3402; Fig. 21 is a chart showing an example of output of the address decoder 4115; Fig. 22 is a view showing an example of input and output images; Fig. 23 is a block diagram of a selector 4110; Fig. 24 is a timing chart relating to a counter 4402; and Fig. 25 is a flow chart of the further embodiment. In the following embodiments there are shown applications of the present invention to a copying machine, but the present invention is not limited to such embodiments and is naturally applicable to various other apparatus. [1st embodiment] The first embodiment discloses a digital color copying machine for effecting color recording in plane-sequential manner, and the detection of predetermined image is conducted stepwise in sequential manner by plural scanning operations in relation to said plane-sequential recording. Fig. 2 is an external view of an apparatus constituting the first embodiment of the present invention. The apparatus shown in Fig. 2 is composed of an image scanner unit 201 for reading an original image and applying digital signal processing thereto, and a printer unit 202 for printing a full-color image corresponding to the original image read by the image scanner unit 201. An original document 204, supported between a mirror-faced pressing plate 200 and an original supporting glass plate (hereinafter called platen) 203 is illuminated by a lamp 205, and the reflected light is guided by mirrors 206, 207, 208 and is focused by a lens 209 onto a 3-line sensor (hereinafter called CCD) 210, which sends the full-color information in the form of red (R), green (G) and blue (B) components to a signal processing unit 211. The entire area of the original is scanned by mechanical movement of the lamp 205 and the mirror 206 with a speed v, and the mirrors 207, 208 with a speed v/2, in a direction perpendicular to the electrical scanning direction of the line sensor. The signal processing unit 211 electrically processes the signals obtained by said scanning operation to obtain components of magenta (M), cyan (C), yellow (Y) and black (Bk) which are sent to the printer unit 202. One of said components M, C, Y, Bk is supplied to the printer unit 202 at each original scanning operation in the image scanning unit 201, so that a printout is completed by four original scanning operations. The image signal of the component M, C, Y or Bk sent from the image scanner unit 201 is supplied to a laser driver 212, which in response modulates a semiconductor laser 213. The emitted laser beam scans a photosensitive drum 217, by means of a polygon mirror 214, an fϑ lens 215, and a mirror 216. A rotary developing unit 218 is composed of a magenta developing station 219, a cyan developing station 220, a yellow developing station 221 and a black developing station 222, which are in succession brought into contact with the photosensitive drum 217, thereby developing electrostatic latent images formed thereon with toner. A sheet fed from a sheet cassette 224 or 225 is wound on a transfer drum 223, and receives the transfer of the image developed on the photosensitive drum 217. After four color images of M, C, Y and Bk are transferred in succession, the sheet is discharged through a fixing unit 226. The present embodiment will be explained in detail with respect to the prevention of forgery of Japanese 10,000-Yen banknote (or bill), as an example of the predetermined image, but the present invention is naturally not limited to such embodiment, and is applicable to the prevention forgery of other predetermined images such as other banknotes, valuable securities, contract documents and so on. In the present embodiment, a copying operation is completed by four scanning operations as explained above, and the function of the image scanner unit 201 and the printer unit 202 in each scanning operation are shown in Fig. 3. In case of prevention of forgery of 10,000-Yen banknote, in the first scanning operation, the image scanner is in a mode 1 for detecting the approximate position of 10,000-Yen banknote, and the printer unit forms the magenta image. In the second scanning operation, the image scanner is in a mode 2 for detecting the exact position and angle of the banknote. In the third scanning operation, the image scanner is in a mode 3, for calculating the position of the red stamp mark of 10,000-Yen banknote from the position and angle detected in the second scanning operation, then extracts the data of said red stamp mark and discriminates whether it is actually the red stamp mark. At the same time the printer unit forms a yellow image. In the fourth scanning operation, the image scanner is in a mode 4, and effects the measure for prevention of forgery, if the forgery is identified to be intended in the third scanning operation. Fig. 5 is a timing chart showing the function of various parts of the image scanner of the present embodiment. A VSYNC signal, indicating the effective image section in the sub scanning direction, assumes a level "1" in the sections for effecting the image scanning operations for C, M, Y and Bk in succession. An effective image section signal VE in the main scanning direction assumes a level "1" where the image is rendered effective. A main scanning synchronization signal HSYNC regulates, in the section of level "1", the start position of the main scanning operation. A pixel synchronization (clock) signal CLK causes the transfer of the image data at the upshift from "0" to "1". A signal CLK16 regulates the timing of a 16 x 16 block processed signal to be explained later, at the upshift from "0" to "1". [Image scanner unit] Fig. 4 is a block diagram of the image scanner unit 201, in which CCD's 210-1, 210-2, 210-3 having spectral sensitivities respectively in red, green and blue colors generate signals digitized in 8 bits or levels from 0 to 255. Since said sensors 210-1, 210-2, 210-3 are mutually spaced as shown in Fig. 2 delay elements 401, 402 are provided for compensating the spatial aberration. Logarithmic converters 403, 404, 405 are composed of look-up table ROM's and convert luminance signals into density signals. A known masking and undercolor removal (UCR) circuit 406 generates, from input signals of three primary colors, output signals of Y, M, C, Bk with a predetermined number of bits (for example 8 bits), at each scanning operation. An OR gate 407 calculates the logic OR of the output of the circuit 406 and the value stored in a register 408. The register 408 normally has a value 00 H so that the output of the circuit 406 is transmitted to the printer unit, but, in case of a forgery preventing operation, a value FF H is set in the register 408 through a data bus from a CPU 417, thereby providing an image uniformly filled with toner. The CPU 417 controls the apparatus in various modes thereof. A window comparator 408' discriminates the input of a signal of a predetermined level designated by the CPU 417, thus detecting the background level in the modes 1 and 2, or the red stamp mark in the mode 3. A block process circuit 409 effects processing on every 16 x 16 block of the output signals of the window comparator 408′. A random access memory (RAM) 412 stores data switched by a selector 411, at addresses selected by a selector 413. A main scanning counter 419 is reset by the HSYNC signal, then effects a count-up operation in synchronization with the CLK signal, and generates 13-bit main scanning (X) addresses X12 - X0. A sub scanning address counter 420 is reset in the section "0" of the VSYNC signal, effects a count-up operation at the timing of the HSYNC signal, and generates 13-bit sub-scanning (Y) addresses Y12 - Y0. The CPU 417 effects data writing into and reading from the RAM 412 by controlling selectors 411, 413, 415, 416 and an address decoder 414, according to the operating mode. The CPU 417 is provided with a RAM/ROM 418. A watermark detection circuit 410 serves to detect the watermarked portion of the banknote. Fig. 6 is a block diagram of the window comparator 408′ shown in Fig. 4, wherein registers 601, 602, 603, 604, 605, 606 are connected to the data bus of the CPU 417 and store values designated by the CPU 417. Each of comparators 607, 608, 609, 610, 611, 612 releases an output signal "1" only when input singals A, B satisfy a condition A > B. An AND gate 613 releases an output signal "1" only when all the comparators provide output signals "1", and otherwise releases a signal "0". Thus, when the registers 601, 602, 603, 604, 605, 606 respectively stores R H , R L , G H , G L , B H , B L , the window comparator 408' releases an output signal "1" only when the input signals R, G, B satisfy all the relations. R L < R < R H : G L < G < G H : and B L < B < B H and an output signal "0" otherwise. Fig. 7 is a circuit diagram of the block process circuit 409 shown in Fig. 4. Serially connected fifteen D-flip-flops (DFF) 701 - 715 serve to delay the input signal in succession, in synchronization with the pixel clock signal CLK, and are cleared to "0" in the non-image section where VE = "0". There are also provided a 5-bit up-down counter 738, an OR gate 737 and an AND gate 740, which function as shown in the following table. Thus the output of the counter 738 is cleared to "0" in a period where the signal VSYNC or VE is "0"; retained when X t = X t-15 ; counted up when X t = 1 and X t-15 = 0; or counted down when X t = 0 and X t-15 = 1. In this manner there is obtained the total number "1" in sixteen data X t - X t-15 . Said output is further supplied to first-in first out (FIFO) memories 721 - 735 of one line each, whereby the data of 16 lines are simultaneously supplied to and added in an adder 741. Thus the total number SUM of "1" in a window of 16 x 16 pixels is obtained, ranging from 0 to 256. A digital comparator 742 compares the output SUM of the adder 741 with a reference value TW predetermined by the CPU 714 and releases the result "1" or "0". In this manner the noise elimination in a block of 16 x 16 pixels can be achieved by suitably selecting the reference value TW. Fig. 8 shows watermark detection circuit 410, which simultaneously processes 19 lines with 18 FIFO memories 819, ..., 820, ..., 821. Ten D-flip-flops are serially connected to each of said 19 lines, as indicated by 801, 802, 803, ..., 804; 805, 806, 807, ..., 808; ...; 809, 810, 811, ..., 812; ...; 813, 814, 815, ..., 816, and additional nine D-flip-flops, indicated by ..., 817, 818 are serially connected to the D-flip-flop 812. All these DFF's are driven by the clock signal CLK16. A signal "1" is released through AND gates 823, 824, 825 when the DFF's 804, 808, ..., 812, 816 (19 vertical blocks) and DFF's 809, 810, 811, 812, ..., 817, 818 (19 horizontal blocks) provide output signals "1", and the position in this state is latched and sent to the CPU 417. Fig. 9 is a block diagram of the address decoder 414. Registers 901 - 909 connected to the data bus of the CPU are respectively given desired values by said CPU. There are provided four circuit blocks 910 - 913, but the following explanation will be given on the block 910, since they are mutually identical in structure. Each of subtractors 914, 915 provides A - B based on inputs A, B. The most significant bit (MSB) of said output serves as a sign bit, which is "1" if A - B is negative. Each of comparators 916, 917 provides an output "1" if inputs A, B satisfy a relation A < B, but provides "0" if the MSB of the input A is "1", regardless of the input B. Thus, when the register 909 stores a value BXY, AND gates 918, 919, 920 of the block 910 provide outputs: X1 = X-address - RX1, Y1 = Y-address - RY1, E1 = 1, only if following conditions: are satisfied. Similarly, in the block 911, there are obtained outputs: X2 = X-address - RX2, Y2 = Y-address - RY2, E2 = 1, only if following conditions: Similarly, in the block 912, there are obtained outputs: X3 = X-address - RX3, Y3 = Y-address - RY3, E3 = 1, only if following conditions: are satisfied. Similarly, in the block 913, there are obtained outputs: X4 = X-address - RX4, Y4 = Y-address - RY4, E4 = 1, only if following conditions: are satisfied. When the values RX1, RY1, ..., RX4, RY4 are so selected that only one at maximum of the conditions (1), (2), (3) and (4) can be satisfied at the same time, OR gates 921, 922, 923, 924, 925 provide output signals in the following manner. The OR gate 921 releases one of X1, X2, X3 and X4. The OR gate 924 releases a signal "1" when any of said conditions is satisfied. The OR gate 925 releases one of Y1, Y2, Y3 and Y4. The OR gates 922, 923 provides outputs signals in the following manner: [Process flow] Fig. 3 shows four modes 1 - 4 of the image scanner unit and the outputs of the printer unit corresponding to four scanning operations in the present embodiment. Fig. 10 is a flow chart showing the control sequence of the CPU. In a step 1001, the CPU 417 sets the mode 1 for the first scanning operation. In said mode 1, the printer unit generates the magenta image, and the approximate position of the watermarked portion of the banknote is detected. For this purpose, the CPU 417 sets values for detecting the background of the banknote in the registers 601 - 606 of the window comparator 408′ shown in Fig. 6. In such state, a step 1002 starts the first scanning. Fig. 1 shows a 10,000-Yen banknote placed on the platen. In the first scanning in the mode 1, the window comparator provides output signals "1" in the hatched areas, namely in the watermarked area and the peripheral area. Since such signals continue in excess of a predetermined number of pixels in the vertical and horizontal directions in the watermarked area, the watermark detection circuit 410 latches an address corresponding to a position (Xc, Yc) and sends said address to the CPU 417. Thus the CPU 417 can know the approximate value of the center (Xc, Yc) of the banknote. Then a step 1003 sets the mode 2, in which the selectors 411, 413, 415, 416 are set at A, and the address decoder 414 is given following values: In the second scanning in a step 1004, by selecting T approximately equal to 128 mm in the RAM 412, there can be obtained a bit map in which the hatched areas alone are "1" in the broken-lined frame. Said dimension 128 mm is selected because the banknote can be contained in the broken-lined area regardless of the kind or position thereof. In a step 1005, the CPU 417 detects the exact position and angle of the banknote from said bit map. In this operation the CPU sets the selectors 411, 413 respectively at C, B for freely reading the data in the RAM 412. There is adopted a method of detecting four corners of the banknote, as shown in Fig. 11. More specifically, with the banknote position as shown in Fig.11, four corners are detected, based on facts that: and Although the details will not be explained, the conditions (5) and (6), if suitably employed, allow to detect the four corners regardless of the angle of the banknote. Also the angle ϑ in Fig. 1 can be obtained from an equation: ϑ = tan⁻¹ Y₁ - Y₀ X₁ - X₀ Also the position of the red stamp mark is determined from thus obtained position and angle. Since the banknote can be placed upward, downward, face up or face down, the red stamp mark appears one of the positions (X s1 , Y s1 ), (X s2 , Y s2) , (X s3 , Y s3 ) and (X s4 , Y s4 ) shown in Fig. 1. These positions can be determined by simple calculations from (X₀, Y₀) and ϑ. Then a step 1006 sets the mode 3 for the third scanning, in which the selectors 411, 413, 415 and 416 are respectively set at B, A, B and B. In the address decoder 414, there are set conditions; RX ₁ = X s1 , RY₁ = Y s1 , RX₂ = X s2 , RY₂ = Y s2 , RX₃ = X s3 , RY₃ = Y s3 , RX₄ = X s4 , RY₄ = Y s4 and BXY is selected at a number of pixels approximately corresponding to a size of 300 mm which sufficiently cover the red stamp mark shown in Fig. 1. Also the registers of the window comparator 408′ shown in Fig. 4 are given such values as to generate signal "1" only in the red color part of the red stamp mark. Then a step 1007 executes the third scanning, and the output of the window comparator 408′ is stored in the RAM 412, in four positions shown in Fig. 1, where the red stamp mark may appear. Subsequently a step 1008 extracts the red stamp mark by an algorithm to be explained later, and the mark is identified in a step 1009. In the absence of possibility of forgery, namely in the absence of the red stamp mark, a step 1010 executes the fourth scanning, and a step 1012 fixes the toners of four colors Y, M, C and Bk. On the other hand, if the step 1009 detects the red stamp mark, indicating the possibility of forgery, a step 1011 executes a measure for preventing the forgery. More specifically, a value FF H is set in the register, which normally stores 00 H , of the window comparator 408 shown in Fig. 4, whereby said signal FF H is sent to the printer unit, thus depositing the black toner over the entire surface and disabling the proper copying. In the foregoing description it is assumed that each scanning operation is conducted corresponding to the printing operation of the printer unit, but it is also possible to detect the position of the watermark at a pre-scanning operation if such pre-scanning is conducted. [Pattern matching] In the following there will be given a detailed explanation on the pattern matching conducted in the step 1008. Since a banknote has two red stamp marks respectively on top and bottom faces, two mark patterns are registered in advance for identifying a banknote. When the data of a predetermined area of the original image are stored in the RAM 412, the CPU 417 executes a pattern matching operation with reference to the content of said RAM 412, according to a flow chart shown in Fig. 12. Now the RAM 412 stores four sets of binary data, called areas 1 - 4, as candidates for the predetermined area. At first a sequence starting from a step 1102 is conducted on the data of the area 1; The step 1102 executes a window processing for noise elimination, in a similar manner as the 16 x 16 block process explained above. Fig. 13 shows an example of the binary image 1201 of the area 1, wherein each square represents a pixel which can be white, represented as blank, or black represented as hatched. This image is scanned with a window 1202 of 2 x 2 pixels, and a new black pixels is defined if the number of black pixels in said window is equal to or larger than 2. This scanning process provides a noise-eliminated pattern 1203 which is vertically and horizontally reduced to 1/2 in size. The window at the illustrated position, containing only one black pixel, is replaced by a white pixel in 1204. Then a step 1104 calculates the position of center of gravity of the pattern 1203, through the already known method, by projecting the pattern 1203 in the vertical and horizontal direction. Then the level of similarity is calculated by standard pattern matching. At first, in a step 1105, a standard pattern registered in advance as a dictionary is fetched from the ROM 418 to the CPU. Said standard pattern is the pattern of the red stamp mark of the banknote, but the simple comparison of the pattern in the step 1103 with said standard pattern does not necessarily provide satisfactory result, since the detected pattern may be rotated by the angle of the banknote on the platen. The above-explained situation is shown in Fig. 14. For this reason there may be stored, as the standard pattern, plural patterns obtained by rotating the pattern of the red stamp mark at a pitch of several degrees, and selected a suitable one from said plural patterns. For example there can be employed 24 patterns obtained by rotating the red stamp mark in a range of 0 - 360° at a pitch of 15°, and the calculation of similarity can be conducted with sufficient precision, by selecting one of said plural patterns according to the already detected angle ϑ of the banknote; namely a pattern of rotation angle of 0° for a range -8° ≦ ϑ < 8°, a pattern of rotation angle of 15° for a range 8° ≦ ϑ < 24°, a pattern of rotation angle of 30° for a range 24° ≦ ϑ < 40° and so on. Since the rotation angle ϑ of the banknote may be different from the rotation angle of the red stamp mark by 180°, it is necessary to select the standard pattern of 180° when that of 0° is selected. Likewise it is necessary to select the rotation angle 195° at selecting 15°, and the rotation angle 210° at selecting 30°. Thus the calculation of similarity is always conducted twice. Then a step 1106 calculates the similarity or correlation. This can be achieved in various methods, one of which will be explained in the following. The extracted pattern (a) is represented by B(i, j) while the selected standard pattern (b) of a certain rotation angle is represented by P(i, j), wherein said B(i, j) or P(i, j) assumes a value "1" for a black pixel or "0" for a white pixel. Using the center of gravity (i BC , j BC ) of the pattern B(i, j) and that (i PC , j PC ) of the pattern P(i, j), determined in the step 1104 shown in Fig. 12, the correlation of two patterns is deterimined by the following equation: wherein ⊕ means exclusive sum of P and B. Thus the equation (1) gives the Hamming distance of the patterns B(i, j) and P(i, j) when the centers of gravity thereof are matched. The similarity of both patterns is larger as COR increases. In the present embodiment, in order to improve the reliability of similarity and to minimize the mistaken recognition, the correlation is obtained by the following equation (2) modified from (1): wherein "." indicates logic product, and P(i-i PC , j-j PC ) indicates the discrimination of P, adding 2 to COR in case P and B are both black pixels but subtracting 1 from COR in case P = 0 and B = 1 thereby significantly improving the precision of recognition. After the calculation of the correlation or similarity COR, a step 1107 compares said COR with a predetermined threshold value Th. In case of COR > Th, indicating the presence of the red stamp mark, there is identified the presence of a banknote (step 1108), and the matching operation is terminated. In case of COR < Th, indicating the absence of the red stamp mark in the currently processed area, the value of n is increased by 1 if it is smaller than 4, and the pattern matching operation of the steps 1101 - 1109 is repeated for the next area. If the step 1109 identifies n = 4, indicating the absence of the red stamp mark in any of the ist to 4th areas, there is identified the absence of a banknote (step 1110) and the matching operation is terminated. Although the present embodiment has been explained in relation to the prevention of forgery of Japanese 10,000-Yen banknote, it has a wide field of application and is applicable for example to valuable securities, foreign banknotes or newly revised banknotes as long as then contain a relatively wide background and a characteristic pattern such as a red stamp mark or a particular design. It is also not limited to the copying machine of electrophotographic type, but is applicable to those of ink jet type, thermal imaging type etc. Furthermore it can be utilized as an additional function for an image scanner or a printer of stand-alone type. In the present embodiment, the size and position of the original placed on the platen are detected prior to the pattern matching with the pre-registered pattern. In case of an apparatus in which the original is fed continuously to the reader unit equipped with a line sensor, the present embodiment can be applied by reciprocating the original with respect to said reader unit so that the same original can be scanned plural times. The present embodiment enables to prevent the forgery of a banknote or the like, by detecting the position and angle of said banknote by the background part thereof, thereby identifying a characteristic pattern such as the red stamp mark, and effecting the pattern matching with said pattern. Thus the present embodiment can securely identify the predetermined image. Fig. 16 is a block diagram of a further embodiment of the image forming apparatus of the present invention. In image reading means 3101, red (R), green (G) and blue (B) images are respectively read by CCD's 3212, 3214, 3217, and the obtained analog signals are amplified by amplifiers 3106, 3107, 3108, and converted by A/D converters 3104, 3105, 3106 into digital signals of 4 bits for each or R, G, B. There are also shown an image memory 3114 for storing 4-bit data for R, G, B released from the image reading means 3101; image processing means 3102 composed of a color conversion unit 3109 and a selector 3110; image forming means 3103; judgement means 3112; an address decoder 3115; a 2-bit signal TC<1,0> consisting of an upper bit TC<1> and a lower bit TC<0> for designating signals Y, M, C, Bk; a judgement signal CHECK; and an address signal AD<10,0>. The function of the above-explained units is as follows. The image signals R, G, B read by the image reader means 3101 are sent to predetermined original judgement means 3112 and also stored in an image memory 3114. The read/write addresses of said memory 3114 are controlled by address data 3115, and the image signals read from the image memory 3114 are sent to signal processing means. In said signal processing means 3102, color conversion means 3109 calculates signals Y, M, C, Bk from the signals R, G, B, and one of said signals Y, M, C, Bk is sent, by a selector 3110, to image forming means 3103. On the other hand, the predetermined original judgement means 3112 discriminates whether the input image is the predetermined image according to an already known method, and sends a judgement signal, indicating the result of said discrimination, to the address decoder 3115. Said address decoder 3115 controls the read/write addresses of the image memory 3114 according to said judgement signal, and effects variation of image magnification, formation of an oblique image, formation of a mirror image etc. on at least one of the Y, M, C and Bk colors by varying the control of the address decoder 3115 at the signal reading from the image memory 3114. Since such image processing has to be applied to all the colors for obtaining a proper output image, so that the prevention of forgery of banknote or the like can be achieved. As an example, the signals R, G, B are stored in the image memory 3114 and read therefrom, with the address decoder 3115 being so controlled as to obtain a same-sized output, and converted by the color conversion means 3109 into signals Y, M which are sent in succession to the image forming means 3103. For the signals C and Bk, the address control at the reading of signals R, G, B from the image memory is modified, by the control of the address decoder 3115 according to the result of the judgement means 3112, so as to vary the magnification of the images C and Bk. Thus the image obtained by the image forming means 3103 based on the Y, M signals of same size and the C, Bk signals of modified magnfication is significantly different from and is easily distinguishable from the predetermined image of which copying is prohibited, and the prevention of forgery can be achieved in this manner. It is also possible to control the address decoder 3115 by a CPU in the image forming means 3103 so as to displace the image start position, thereby displacing the C, Bk images with respect to the Y, M images and enabling to distinguish the copied image from the original image. It is furthermore possible to control the address decoder 3115 by the CPU of the image forming means 3103 to generate random addresses for example in the reading of the C and Bk images, whereby the C and Bk images become totally different from the original images and the forgery of a banknote or the like can therefore be prevented. Fig. 17 is a schematic view of an image forming apparatus constituting an embodiment of the present invention. This image forming apparatus reads the three primary color components of red, green and blue of the original image in the form of electrical signals, calculating, from said signals, the signals of magenta, (M), cyan (C), yellow (Y) and black (Bk), and recording these signals in succession on a recording sheet. An original document 3201 to be read is placed, with the image bearing face downwards, on a platen glass plate 3202 and maintained in position by a pressing plate 3203. Said original 3201 is illuminated by an illuminating system 3203, and the reflected light is guided by mirrors 3204, 3205, 3206 and a lens 3207, and is split into three light beams by beam splitters 3208, 3209. The first light beam is guided through a mirror 3210 and a R-component passing filter 3211 and is focused on a R-CCD 3212. The second light beam is guided through a G-component passing filter 3213 and is focused on a G-CCD 3214. The third light beam is guided through a mirror 3215 and a B-component passing filter 3216, and is focused on a B-CCD 3217. The CCD's 3212, 3214, 3217, composed of line CCD's, are electrically scanned in the direction of array (called main scanning), and also mechanical scanning (sub scanning) is achieved by moving, by a motor 3218, the illuminating unit 3203 and the mirror 3204 with a speed v, and the mirrors 3205, 3206 with a speed v/2. The image signals from the CCD's 3212, 3214, 3217 are processed in an electrical processing unit 3219, and are used for driving a semiconductor laser 3220, of which light beam scans a photosensitive drum 3223 by means of a polygon mirror 3221 and a mirror 3222. The electrostatic latent image thus formed is developed by a developing unit 3226. On the other hand, a recording sheet fed from a sheet cassette 3224 is wound on a transfer drum 3225, and receives the transfer of thus developed image. The developing unit 3226 is composed of four developing stations respectively containing toners of four colors M, C, Y, Bk, which are switched for image development by lateral movement of the developing unit. The recording sheet wound on a transfer drum receives 4-color images in 4 turns, then is separated from said drum and is transported to a fixing unit 3227 for image fixation. In the following there will be explained a predetermined original judgement unit 3112, of which block diagram is shown in Fig. 18. The R, G, and B signals from image reader means are supplied to comparators 3401 - 3406 and an AND gate 3407 for judging a predetermined color. The AND gate 3407 shown in Fig. 18 provides a signal "1" only when: R L < R ≦ R U G L < G ≦ G U B L < B ≦ B U are satisfied, or otherwise a signal "0", and said signal is stored for each pixel in a RAM 3408. Thus said RAM 3408 separates the area of a predetermined color, such as of the red stamp mark in the banknote. The limit values R L , R U , G L , G U , B L and B U are so determined in advance as to define said predetermined color. The data stored in the RAM 3408 are compared with reference pattern information (hereinafter called template information) stored in a ROM 3410, and there is made a judgement whether these data mutually match. A pattern representative of the feature of the predetermined original is selected as said template information. Fig. 19 shows an example of the structure of the address decoder 3115. In Fig. 19 there are shown a counter 3401 for controlling the address of lines in the sub scanning direction; a counter 3402 for controlling the address of pixels in the main scanning direction; a horizontal synchronization signal HS and a vertical synchronization signal VS both supplied from the image forming means 3103 to the counter 3401; a counter control signal WRA* supplied from an unrepresented CPU; a judgement signal CHECK released from judgement means; a signal TC<1> composed of the upper bit of the color designation signal TC<1, 0> released from the image forming means 3103 for designating two out of four colors Y, M, C and Bk; and a pixel clock signal CLK. The counter 3402, for controlling the address of pixels in the main scanning direction, effects a counting operation in response to the clock signal CLK, and is reset by the synchronization signal HS. The initial value of said counter is 000 H in an up-counting operation, or 3FF H in a down-counting operation, and said up-counting or down-counting is selected according to the output of the AND gate 3403. The counter 3401, for controlling the line address in the sub scanning direction, effects an up-counting operation from an initial value 000 H to 3FF H , and is reset by the synchronization signal VS. The address of the image memory is composed of 20 bits, of which lower 10 bits are given by the output of the counter 3402, indicating the pixels in the main scanning line, while the upper 10 bits are given by the output of the counter 3401 indicating a line in the sub scanning direction. In the following there will be explained an example of image area having 1024 pixels (400 H ) in the main scanning direction, and 1024 lines (400 H ) in the sub scanning direction. Fig. 20 is a timing chart of principal synchronization signals. There are shown the pixel clock signal CLK; the main scanning synchronization signal HS for each line; and the sub scanning section signal VS for 1024 lines. Said signals HS and VS are generated by the image forming means 3103 and are synchronized with the clock signal CLK. Each of the R, G and B signals is for example given 4 bits, and the image memory stores said signals in the form of 12-bit data, of which upper 4 bits, middle 4 bits and lower 4 bits are respectively composed of said R, G and B signals. The address of the image memory is composed of 20 bits, of which lower 10 bits indicate pixels in a main scanning line, and upper 10 bits indicate the lines in the sub scanning direction. Now let us consider an input image shown in Fig. 22, as an example. The R, G and B signals obtained from said image are stored in the image memory, according to the address AD<19, 0> generated by the address decoder 3115. In this state the counter control signal WRA* sent from the unrepresented CPU to the address decoder 3115 assumes an L-level state to provide an L-level signal from the AND gate 3403, whereby the counters 3401, 3402 execute up-counting operation. In the image memory 3114, therefore, the R, G, B data 000 H are stored in the addresses 00000 H - 000FF H ; the data 444 H are stored in the addresses 00100 H - 001FF H ; the data 888 H are stored in the addresses 00200 H - 002FF H ; and the data FFF H are stored in the addresses 00300 H - 003FF H , whereby the data of the first line are stored at the addresses 00000 H - 003FF H . Since the image is uniform in the sub scanning direction as shown in Fig. 22, the data of 1024 lines are stored in the addresses 00000 H - FFFFF H of the image memory (cf. Fig. 21). In addition to the storage in the image memory, the R, G, B signals are supplied to the predetermined original judging means 3112 for discriminating whether the input image is the predetermined image of which copying is prohibited. If the input image is identified not as the predetermined image, the judgement signal CHECK sent from the judging means 3112 to the address decoder 3115 at the data reading from the image memory 3114 assumes an L-level state as shown in Fig. 24, thereby providing an L-level output from the AND gate 3403. Consequently the counters 3401, 3402 execute up-counting operation as in the data storage, whereby the R, G, B image data stored in the memory are supplied without change to color conversion means 3102, and the input image is reproduced by the image forming means 3103. On the other hand, if the input image is identified as the aforementioned predetermined image of which copying prohibited, the judgement signal CHECK assumes an H-level state at the data reading from the image memory, as shown in Fig. 24, and the counter control signal WRA of the address decoder 3115 also assumes an H-level state at the data reading from the memory 3114. The signals TC<1> and TC<0> for designating the signals Y, M, C, Bk sent to the image forming means 3103 are supplied to a selector 3110, and said signal TC<1> is also supplied to an AND gate 3403 of the address decoder. Thus, as shown in Fig. 23, the signal TC<1> is at the L-level state at the selection of the signal Y or M at the selector 3110, or the H-level state at the selection of the signal C or Bk. Consequently, when the selector 3110 selects the signal Y or M, the signal TC<1> supplied to the AND gate 3403 of the address decoder 3115 assumes the L-level state, thereby providing an L-level output from said AND gate 3403. Thus the counters 3401, 3402 execute up-counting operation to send normal Y or M image signal to the image forming means 3103. On the other hand, when the selector 3110 selects the signal C or Bk, the TC<1> signal assumes an H-level state, thereby obtaining an H-level output from the AND gate 3403. Consequently the counter 3402 executes a down-counting operation while the counter 3401 executes an up-counting operation, so that, at the reading of the R, G and B signals from the image memory, the address in the main scanning direction, indicated by the lower 10 bits of the address, varies inversely to that at the signal storage while the address in the sub scanning direction, indicated by the upper 10 bits, varies in the same manner as in the signal storage. Consequently the R, G and B signals in this state constitute a mirror image inverted in the main scanning direction, and the C or Bk signal corresponding to such mirror image is sent to the image forming means 3103. As a result the finally obtained image, formed by superposition of the normal Y and M images and the mirror C and Bk images, is significantly different from the original image, and the forgery can be prevented in this manner. The flow of the above-explained process is shown in Fig. 25. At first image reading is conducted (step S3001), and the address decoder is set at equal-size addressing (step S3002). The read data are stored in the image memory and are subjected to the judging of the predetermined image (S3003). If the input image is identified not as the predetermined image (S3004), the address decoder is so set as to effect the up-counting operation with the equal size (S3007), and the data reading from the image memory is conducted with the same size (S3008). On the other hand, if the input image is identified as the predetermined image (S3004), there is discriminated whether the conversion to the C or Bk signal is conducted next (S3005), and, if the next conversion is to the Y or M signal, the sequence proceeds to the step S3007. If the next conversion is to the C or Bk signal, the address decoder is set to effect a down-counting operation with same size (S3008), whereby a same-sized mirror image is obtained in the data reading (S3009). Thereafter the color conversion and image formation are conducted (S3010, S3011), and the sequence is repeated for four colors Y, M, C and Bk (S3012). In the foregoing explanation, the mirror image formation by address control is conducted on cyan and black colors, but it can be conducted on at least one color, for example only on cyan color, or on three colors including magenta. Also the process to be employed is not limited to such mirror image formation, but other processes such as enlargement, reduction or rotation applied to a particular recording color can provide similar effects. It is also possible to omit a particular recording colour from the recording operation. It is furthermore possible, upon detction of a predetermined image by detection of a magnetic pattern, to modify the process for at least a color, thereby obtaining an image easily distinguishable from the predetermined image. It is therefore rendered possible to prevent the forgery of the predetermined image. As explained in the foregoing, the present embodiment is designed to modify the process for a particular color, thereby enabling to distinguish the produced image clearly from the predetermined image and effectively preventing the forgery thereof. It is also possible to reduce the processing time and to simplify the circuit structure, since the image forming process is modified only in the predetermined color. As explained in the foregoing, the present embodiment is capable of preventing the forgery of banknote or the like, by modifying the image forming process for a predetermined color of the predetermined image, while maintaining the color reproducibility for ordinary images.

Claims: A control device (211; 3219) for controlling an image processing device based on the image content of an input image signal so as to supply a control signal (00 H , FF H ; CHECK) indicating whether a multi-coloured input image should be faithfully outputted, said control device comprising: input means for accepting an input signal representing the input image; colour reference means (601-606) for storing (601-606) colour reference data (R H , R L etc) defining with reference to plural colour components (R, G, B) a specific region of colour space; extracting means (607, 613) for using the stored colour reference data to extract from the input signal pattern data representing a pattern present in colours within said specific region of colour space in the input image; comparing means (412, 417, 418, 3408-3411) for comparing said extracted pattern data with a predetermined reference pattern and for determining whether said pattern data matches said reference pattern; and means (407, 408, 417, 3112) for generating a control signal (FF H ; CHECK H-Level) when said comparing means (412, 417, 418, 3408-3411) determines that said extracted pattern data matches said reference pattern in order to prevent said image processing device from outputting the input image faithfully. A control device according to claim 1 wherein said colour reference data (R H , R L , etc) can be stored so as to define a region of colour space having both upper and lower bounds in terms of said plural colour components (R,G,B). A control device according to claim 2 wherein said colour reference data comprises upper and lower threshold values (R H , R L ) for each of said plural colour components (R,G,B) and said extracting means includes means (607-612) for comparing the input signal with said thresholds for each said colour component, and logic means (613) for combining the results of said comparisons. A control device according to claim 1, 2 or 3 wherein said reference pattern corresponds to only a part of the input image and said comparing means (412, 417, 418, 3408-3411) is arranged to compare pattern data for that part of the image with said reference pattern. A control device according to any preceding claim wherein said input means is arranged to receive input signals from a plurality of scanning operations of an input image, and wherein said comparing means (412, 417, 418, 3408-3411) is arranged to compare the pattern data from the last scanning operation with said predetermined reference pattern. A control device according to claim 4 or 5, further comprising: means (417, 601-606, 408′, 410) responsive to input signals from a first scanning operation to obtain the approximate position of an input image with reference to a scanned area; means (417, 411-416) responsive to input signals from a second scanning operation to obtain the position and angle of the input image and to determine said part of the input image accordingly; and wherein the extracting means (408′, 417) and comparing means (412, 417, 418) are arranged to respond to data from a third scanning operation to determine whether said image pattern data in said part of the input image matches said reference pattern. A control device according to claim 6, wherein the colour reference means (408′, 417) is arranged to store colour reference data during the first and second scanning operations relating to a range or ranges of colour representing a background of said input image, for use in said position and angle determination. A control device according to any preceding claim, wherein said plural colour components comprise red, green and blue colour components. A control device according to any of claims 6 to 8, further comprising means (418) for storing data defining a plurality of reference patterns, and means (417) for selecting in dependence upon the obtained angle of the image one of said plurality of reference patterns to be compared by said comparing means with said image pattern data. A control device according to any preceding claim, wherein said reference pattern comprises a pattern in an area of a bank note. A device according to any preceding claim, further comprising image reading means (201, 210-1, 210-2, 210-3, 3101) for producing said input signals from a multi-colour original image. A device according to any preceding claim, further comprising image forming means (202, 3103) arranged to reproduce the image represented in the input signal faithfully or not, in accordance with said control signal. Image forming apparatus comprising: (a) a control device (211, 3219) according to any of claims 1 to 10; (b) scanning means (201, 3212, 3214, 3217, 3218, 3203, 3204) for scanning a multi-colour original image and supplying to the control device said input signal representing the scanned image; (c) image forming means (202, 3103) also connected to the scanning means and arranged to form an image in accordance with the control signal output by said control device, and arranged so that when the comparing means (412, 417, 418, 3408-3411) of said control device determines that said pattern data represents said reference pattern, the image forming means (202, 3103) is prevented from reproducing the original colour image faithfully. Apparatus according to claim 11, wherein said image forming means (202, 3103) includes control means responsive to said output signal for deactivating part of the image forming means (202, 3103) on receipt of said control signal. Apparatus according to claim 14, wherein the deactivated part of the image forming means (202) is: (a) a unit for illuminating an input image; (b) a driving unit for an input image reading optical system; (c) a driving unit for an input image reading sensor; (d) a charging unit for a photosensitive drum for use in an electrophotographic process; (e) a developing unit for use in an electrophotographic process; (f) an image transfer unit for use in an electrophotographic process; or (g) a feeding unit for feeding recording sheets. Apparatus according to claim 13, wherein said image forming means (202, 3103) includes operation control means for preventing faithful output of the input image by making changes in at least one colour component signal defining the image to be formed. Apparatus according to claim 16, wherein the change made by said operation control means is one of: (a) formation of a mirror image in a predetermined colour component; (b) rotation of the image in a predetermined colour component; (c) enlargement of the image in a predetermined colour component; (d) reduction of the image in a predetermined colour component; (e) changing the image recording start position; (f) generation of random addresses in the reading of at least two colour components so that the image in said at least two colour components becomes different from the input image; (g) change of the image data in part of the image to the same density; (h) change of the image data in a part of the image to zero; or (i) adding image data of a particular pattern to part of the image. A device or apparatus according to any preceding claim, wherein the extraction means includes means (741, 742) for forming a noise-eliminated pattern as said image pattern data, and wherein said comparing means (412, 417, 418) compares said noise-eliminated pattern with said reference pattern. A method of controlling the operation of an image processing apparatus so as to prevent the faithful output of a particular predetermined colour image or images, comprising the steps of: receiving an input signal representing a multicoloured image; obtaining colour reference data (R H , R L , etc) defining with reference to plural colour components (R, G, B) a specific region of colour space; extracting pattern data from the input signal using the stored colour reference data, said pattern data representing a pattern present in colours within said specific region of colour space in the input image; and comparing the extracted pattern data with a predetermined reference pattern and supplying a control signal to the apparatus being controlled when it is determined that said pattern data matches said reference pattern, the control signal indicating that faithful output of the image should be prevented. A method according to claim 19 wherein said colour reference data define a region of colour space having both upper and lower bounds in terms of said plural colour components. A method according to claim 20 wherein said colour reference data comprises upper and lower threshold values (R H , R L , etc) for each of said plural colour components (R, G, B) and said extracting step comprises comparing the input signal with said thresholds for each said colour component, and combining the results of said comparisons. A method according to any of claims 19 to 21 wherein the step of comparing pattern data with a reference pattern comprises comparing pattern data from only a part (1303) of the input image with said reference pattern. A method according to any of claims 19 to 22, wherein the receiving step comprises performing a plurality of optical scanning operations of an original input image, and the step of comparing pattern data with a reference pattern comprises comparing the image pattern data from the last scanning operation with said reference pattern. A method according to claim 22 or 23, wherein first, second and third scanning operations of the object image are carried out, and wherein: data from the first scanning operation (1002) is used to obtain the approximate position of an input image with reference to the scanned area; data from the second scanning operation (1004) is used to obtain the position and angle of the input image and to determine said part of the input image accordingly; and data from the third scanning operation (1007) is subjected to said comparison to determine whether the image pattern data in said part of the input image matches said reference pattern. A method according to claim 24, wherein during the first and second scans colour reference data is used relating to a range or ranges of colours representing a background of the input image in order to perform said position and angle determination. A method according to any of claims 19 to 25, wherein the reference pattern comprises a pattern in an area (1303) of a banknote. A method of image processing including the steps of: scanning a multi-colour original image to produce a signal representing said original image; performing the control method claimed in any of claims 19 to 26; and when it is determined that the image pattern data represents a reference pattern, altering the operation of a printer unit automatically to inhibit faithful output of the image.

Inventors: FUNADA MASAHIRO, KAWASE MICHIO, OHTA KENICHI, SUZUKI YOSHIYUKI, FUNADA, MASAHIRO, KAWASE, MICHIO, OHTA, KENICHI, SUZUKI, YOSHIYUKI
Applicants: CANON KK, CANON KABUSHIKI KAISHA
Application year: 1990
Main classification: G03G21
IPC codes: G03G15, G03G21, G07D7, H04N1, G06T1