Image processor

Abstract: An image processor having a circuit for holding data on features of registered specific images, a circuit for determining a similarity between features of an input image and the held features of each of the specific images, and a circuit for updating the held content of the holding circuit from the outside through a line. The image processor also has a judgment circuit for determining the degree of similarity between an input image and each of the specific images according to tint distributions of these images, and a circuit for registering data on the tint distribution of each specific image.

Description: BACKGROUND OF THE INVENTION Field of the Invention This invention relates to an apparatus having a function of detecting a specific original. Related Background Art Recently, with the development of copying machines capable of forming a multi-color copy having high image qualities, a risk of forgery of specific originals which should not be copied has arisen. Various types of image processors for use in copying machines have therefore been proposed which have a function of judging whether a specific original exists by previously storing data on features on the specific original and comparing the data with the features of an input image. Documents EP-A-0 342 060 and EP-A-0 382 549 disclose similar image processors. However, it is impossible for the conventional image processors to function suitably with respect to originals which should not be copied other than the registered specific originals, because the data on the features of the specific originals is fixedly stored in the processor. A technique of registering patterns of specific originals by converting input image data into binary data is disclosed in U.S. Patent Application Serial No. 426,044, but the performance of it is insufficient since only binary data can be registered. The same problem is encountered in the case of single printer units having a discrimination function other than the above-described copying machines or apparatuses having a function of discriminating security papers or the like. As one of the techniques for preventing an act of forging bank notes, securities, a technique of previously registering data on specific originals in an RGB color space and judging whether a color distribution of input image data coincides with one of the color distributions of the specific original data to discriminate the corresponding one of the specific originals has been proposed by the applicant of the present invention, as disclosed in European Applications EP-A-0 463 804, EP-A-0 488 797 and EP-A-0 488 796. More specifically, in accordance with this technique, distributions of red (R), green (G) and blue (B) signals of the data on an input original image in an RGB three-dimensional coordinate space corresponding distributions of a specific original in the three-dimensional coordinate space are compared, and, if the proportion of the matching part is greater than a certain value, it is determined that the original input to be copied contains the specific original. In this process, it is necessary to previously register tint distributions in the RGB color space of each of specific originals to be discriminated. However, there are various specific originals which should not be copied and the number and the kinds of such originals vary greatly with respect to countries, regions, occupations and the like in which the copying machine is used. Accordingly, it is impossible to register all the data on such originals in practice, and it is desirable that the copying machine can be operated in a simple manner to change the registered content or to newly register data according to the environment in which the machine is used. SUMMARY OF THE INVENTION An object of the present invention is to provide an image processor capable of registering data on a specific original to be discriminated. To achieve this object, according to the present invention, there is provided an image processor as set out in claim 1. Fig. 1 is a diagram of an example of a color copying machine embodying the present invention; Fig. 2 is an overall block diagram of a color image processor in accordance with an embodiment of the present invention; Fig. 3 is a diagram of color space matching judgement circuit 1109; Fig. 4 is a diagram of the content of EE-PROM 1204; Fig. 5 is a block diagram of smoothing circuits 1210 to 1217; Fig. 6 is a diagram of the operation of the smoothing circuits; Fig. 7 is a diagram of color space judgement circuits 1220 to 1227; Fig. 8 is a circuit block diagram of judgement signal generation circuit 1110; Fig. 9 is a flow chart of the processing in accordance with the embodiment; Fig. 10 is a diagram of detection of the position at which a specific original is detected. Copying machines will be described as embodiments of the present invention, but, needless to say, the present invention is not limited to them and can be applied to any other kind of apparatus. Fig. 1 schematically illustrates a copying machine in accordance with an embodiment of the present invention. In Fig. 1, a block 201 represents an image scanner unit which reads an original and performs digital signal processing. A block 202 represents a printer unit which prints, on a paper sheet, a full-color output image corresponding to an original image read by the image scanner 201. In the image scanner .201, an original .204 is placed on an original table glass (hereinafter referred to as a platen) 203 while being pressed by a specular pressing plate 200. The original 204 on the platen 203 is irradiated with a lamp 205, and reflection light from the original travels via mirrors 206, 297, and 208 to form an image on a three-line sensor (hereinafter referred to as a CCD) 210 through a lens 209. Full-color information having a red (R) component, a green (G) component and a blue (B) component is thereby obtained and is sent to a signal processing section 211. The lamp 1205 and the mirror 20-6 are mechanically moved at a speed v in a direction perpendicular to the direction of electrical scanning of the line sensor (a main scanning direction) and the mirrors 207 and 208 are also mechanically moved at a speed 1/2 v in the same direction to scan the surface of the original (in a sub scanning direction). In the signal processing section 211, the read image signal is electrically processed to be decomposed into a magenta (M) component, a cyan (C) component, a yellow (Y) component, and a black (Bk) component to be sent to the printer unit 202. In one cycle of original scanning of the image scanner 201, one of the components M, C, Y, and Bk is sent to the printer unit .202. One print of the reproduced image is completed by four cycles of original scanning. Each image signal M, C, Y or Bk sent from the image scanner unit 201 is sent to a laser driver 212. The laser driver 212 drives a semiconductor laser device 213 by modulating a driving signal. A surface of a sensitive drum 217 is scanned with laser light from the laser device led by a polygon mirror 214, an f- lens 215 and a mirror 216. A rotary development device 218 has a magenta development section 219, a cyan development section 220, a yellow development section 221 and a black development section 222. These development sections are alternately brought into contact with the sensitive drum 217 to develop, with a toner, an electrostatic latent image formed on the sensitive drum 217. A paper sheet supplied from a paper cassette 224 or 225 is wrapped around a transfer drum 223, and the image developed on the sensitive drum 217 is transferred to the paper sheet. After four colors M, C, Y and Bk have been successively transferred in this manner, the print sheet is passed through a fixation unit 226 and is discharged after the completion of fixation of the toner. The image signal processing section 211 in accordance with this embodiment will be described below. Fig. 2 is a signal processing block diagram of the color image processor in accordance with this embodiment. In Fig. 2, a block 1101 represents a CCD color sensor which reads an unillustrated color original with respect to lines and outputs read data to an analog amplifier 1102. A block 1103 represents an A/D converter which samples and holds an analog output from the amplifier 1102 and converts it into digital data. A block 1104 represents a shading correction circuit which serves to correct a luminance gradient of the image signal depending upon the reading position and sensitivity non-uniformity of the CCD. A block 1105 represents a logarithmic conversion circuit for converting the RGB signal into an YMCK signal for a printer output by a well-known color correction processing. Blocks 1106 and 1107 represent a black component extraction circuit and a masking/UCR (under color removal) circuit, respectively. A block 1108 represents a circuit for generating signals HS, CLK and VS which are read sync signals. All of these sync signals are supplied to all the circuit blocks. The signal HS is a main scanning period signal, the signal CLK is a pixel reading fundamental clock signal, and the signal VS is a period signal representing a sub scanning direction effective area. A block 1109 represents a color space matching circuit for calculating the degree of similarity between read image data and specific originals in a color space in a real time manner. A block 1110 represents a judgment signal generation circuit which outputs "1" if it is judged that one of the specific originals exists as a result of the matching in the color spacing matching circuit 1110, or "0" if it is judged that none of the specific originals exists. For example, a judgment signal output from the judgment signal generation circuit 1110 is input to the masking/UCR circuit 1107 to change a masking coefficient from an ordinary value so that the color reproducibility is deteriorated, that is, the quality of the result of a forging work is reduced. A block 1111 represents a frame memory for storing one frame of an input original image, and a block 1112 represents a CPU which accesses data in the frame memory 1111, and which also writes data in the circuits 1109 and 1110. Details of the memory 1111 and the CPU 1112 will be described later. Fig. 3 is a block diagram of the color space matching circuit 1109. Upper-5-bit data R1201 of an 8-bit red (R) signal is supplied from the shading correction circuit 1104. Also, upper-5-bit data G1202 and B1203 of green (B) and blue (B) signals are supplied. A block 1204 represents an EE-PROM (programmable/erasable memory) in which information on tints of a plurality of specific originals is stored. The above-mentioned R, G and B signals are input to addresses A 0 to A 14 of the EE-PROM 1204, and judgment signals each indicating the result of judgment as to whether the R, G and B signals coincide with the tint of each of the specific originals are output as data D 0 to D 7 . Information on the tints of the specific originals is stored in the ROM 1204. From the ROM 204, "1" is output as one of D 0 to D 7 if the input R, G and B signals coincide with the tint of the corresponding one of the specific originals, or "0" is output in the case of non-coincidence. Fig. 4 is a diagram of the relationship between the data on the plurality of originals stored in the ROM 1204 and the bit positions in the ROM 1204. In accordance with this relationship, items of information (each consisting 0 or 1) on the judgment with respect to the tints of the 8 kinds of specific originals (specific originals A to H) are output in parallel as D 0 to D 7 . Blocks 1210 to 1217 represent circuits for performing smoothing calculations of color judgment signals X 0 to X 7 . as shown in Figs. 5 and and 6. Fig. 5 is a block diagram of the arrangement of each of the smoothing circuits 1210 to 1217. Fig. 6 is a diagram of the relationship between an input Xn and an output value Yn obtained by smoothing. If input Xn continuously exhibits values "1", the value of Yn is increased. If Xn becomes "0", the value of Yn is gradually reduced. By this operation, if the input R, G and B signals continuously match the tint of the specific original, Xn continuously exhibits values "1" and Yn increases until it exceeds a predetermined threshold value. Each of outputs C 0 to C 7 from the smoothing circuits is obtained by changing Yn in a binary encoding manner based on the predetermined threshold value. Thus, "1" is output as each of C 0 to C 7 only in a case where pixels having the same tint as the corresponding specific original are sequential. The judgment accuracy is thereby improved. Color space judgment circuits 1220 to 1227 are circuits which calculate the degree of similarity between the specific original data and the input color signal in the RGB color space in a real time manner, and which output similarity determination signals MK 0 to MK 7 . Fig. 7 is a block diagram of each of the color space judgment circuits 1200 to 1227. Data Dn from a SRAM 1230 and a signal Cn from the smoothing circuit are OR-calculated in a circuit 1303, and the calculation result is written as Dn in the SRAM 1230 again. On the other hand, Dn, Cn and data Xn from the ROM 1204 are AND-calculated in a circuit 1302, and "1" is output from the circuit 1302 only when each of Xn and Cn is "1" and when Dn is changed from 0 to 1. When the output from the circuit 1302 is "1", a counter 1304 counts up the output. The counter 1304 is cleared at a rise of sub scanning period signal VS. A circuit 1305 serves to hold the maximum of the output value from the counter 1304. The maximum value of the counter output, which is output from the circuit 1305, is compared with a predetermined constant δn by a comparator 1307. If the maximum value is greater than δn, the comparator 1307 outputs "1" as MKn. If the maximum value is not greater than δn, the comparator 1307 outputs "0" as MKn. The value of δn is set as the value of S % in the volume occupied by the tint of the specific original in the color space. That is, if the number of "1" in the ROM 1204 shown in Fig. 4 is Vorg, δn = Vorg × S/100. The value of S is set so that, assuming that the specific original is placed on the original table, the judgment signal MKn is "1" when about a half of the specific original is read. Consequently, in this processing, each of the color space similarity judgment signal MK 0 to MK 7 becomes "1", when the input image data exhibits substantially the same shape as the specific original in the RGB three-dimensional color space. Fig. 8 is a block diagram of the judgment signal generation circuit 1110. If it is determined by this circuit that at least one of the plurality of specific originals registered in the ROM 1204 coincides with the input image data in the color space, the judgment signal f becomes "1" in a real time manner to effect a feedback to the masking/UCR circuit. The tint distribution data (in EE-PROM 1204 shown in Fig. 4 ) and the judgment threshold values (δn at 1306 in Fig. 7 , α at 1506 in Fig. 5 ) necessary for the above-described processing in the specific original judgment circuit are determined by the CPU 1112 with reference to the image data in the frame memory 1111. An example of this process will be described below with reference to Fig. 9. Fig. 9 is a flow chart of a process of registering a specific original. In step 1801, one of the eight specific original judgment circuits shown in Fig. 3 is selected to set parameters for it. The selected number is set as N (0 to 7). In step 1802, tint information corresponding to the Nth judgment circuit in the content of the EE-PROM 1204 shown in Fig. 4 is deleted. In step 1803, the specific original to be registered is placed on the original plate of the image reader and is read by scanning, and the read data is stored as an RGB image data in the frame memory 1111. At this time, the input data may be stored by being thinned out, for example, every other 16 pixels, because the storage of all the data on the original image requires a very large frame memory capacity. In step 1804, the position at which the specific original exists in the image stored in the memory 1111. This is because the position on the original plate at which the original (e.g., a bank note, negotiable paper or the like) is placed is not previously determined, and because it is therefore uncertain which area in the frame memory contains significant data. Fig. 10 illustrates such a situation. A region 1901 corresponds to all the data in the frame memory, and a region 1901 represents the necessary portion corresponding to the specific original. If the background portion in the image of the data 1901 is dark, the position at which the specific original exists can be ascertained, for example, by detecting pixels having signal levels higher than a certain threshold value and by obtaining the minimum value (1903) and the maximum value (1904) in the longitudinal direction and the minimum value (1905) and the maximum value (1906) in the lateral direction of the pixels. In step 1805, RGB data corresponding to one pixel in the region obtained in the preceding step, where the specific original exists, is read out of the memory 1111. In step 1806, tint information with addresses corresponding to the RGB values read in step 1805 is written in the EE-PROM 1204. ("1" is written at addresses corresponding to the RGB values in the Nth column in Fig. 4.) In step 1807, processing of steps 1805 and 1806 is repeated with respect to all the pixels in the data region 1902 shown in Fig. 10. When this processing is completed, the tint distribution of the specific original to be registered is registered in the EE-PROM. In step 1808, the judgment threshold values α and δn for the Nth judgment circuit are set to the upper limit of the range in which they can be set (255 in this case). In step 1809, the original image read in step 1803 is placed on the original plate again and is read again to operate the Nth judgment circuit. At this time, if the judgment threshold values set in step 1808 are suitable, it is necessary that the existence of the registered original is detected and that "1" is output as the Nth judgment output MKn. In step 1810, if MKn = 1 is output in step 1809, it is determined that the set threshold values are suitable, and the registration process is terminated (step 1811). If MKn = 0, the threshold values are not suitable, the values of α and δn are therefore decremented by predetermined values, and the judgment step 1809 is performed again with respect to the same original (step 1812). This processing is repeated until MKn = 1, thereby setting all the desired judgment parameters with respect to the specific original. An example of the application of the present invention to a color copying machine has been described above. However, the arrangement may alternatively be such that original images are read to an external computer, the same processing is performed by this computer, and parameters thereby generated are written in an EE-PROM which is incorporated in the image processor. In the above-described embodiment, tint distribution information and judgment threshold values are used as judgment parameters. Needless to say, the present invention can be applied to a system for setting either one of these two categories of data or other judgment parameters. According to the embodiments of the present invention, as described above, parameters of specific original judgment circuits can be easily set with respect to specific originals selected as desired. It is thereby possible to identify various kinds of specific originals. Moreover, the embodiments also ensure that judgment parameters can be selected so as to reflect variations of the judgment accuracy of color image processor units due to variations in device characteristics between the processors, thereby achieving constantly stable judgment. In accordance with the embodiments, as described above, data on specific originals to be discriminated can be registered. The present invention is not limited to the above-described embodiments, and various modifications and changes of the invention and application of the invention to various apparatuses can be made without departing from the scope set forth in the appended claims.

Claims: An image processing method for forming, in a memory, a judgement standard to be used for judging whether an input object is a specific object, comprising the steps of: inputting (1803) colour image data by an input means (1101); extracting (1805) colour component data corresponding to the specific object from the input colour image data; and forming (1806, 1807) a colour distribution of the specific object in a selected part of said memory, as the judgement standard, based on the extracted colour component data. A method according to claim 1, further comprising storing a plurality of colour distributions corresponding to a plurality of specific objects. A method according to claim 1 or 2, wherein said input means is an image reading means for scanning an original and generating colour image data. A method according to any preceding claim, further comprising the step of storing (1803) the colour image data input by said input means, into a frame memory (111). A method according to any preceding claim, wherein said colour component data is expressed by red, green and blue. A method according to any preceding claim, further comprising the step of confirming (1809) the colour distribution of the specific object formed in said memory.

Inventors: FUNADA MASAHIRO, OHTA EIJI, OHTA KEN-ICHI, TAKARAGI YOICHI, UDAGAWA YUTAKA, FUNADA, MASAHIRO, OHTA, EIJI, OHTA, KEN-ICHI, TAKARAGI, YOICHI, UDAGAWA, YUTAKA, FUNADA, MASAHIRO, C/O CANON KABUSHIKI KAISHA, Ohta, Eiji, c/o Canon Kabushiki Kaisha, Ohta, Ken-Ichi, c/o Canon Kabushiki Kaisha, TAKARAGI, YOICHI, C/O CANON KABUSHIKI KAISHA, Udagawa, Yutaka, c/o Canon Kabushiki Kaisha
Applicants: CANON KK, CANON KABUSHIKI KAISHA
Application year: 1992
Main classification: H04N1
IPC codes: H04N1