Patent Publication Number: US-7715612-B2

Title: Discriminating apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2004-250463, filed Aug. 30, 2004, the entire contents of which are incorporated herein by reference. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a discriminating apparatus for discriminating whether printed matter is an original or a reproduction, particularly, to a discriminating apparatus for discriminating a reproduction obtained by using a base material differing from an original in the color of the base material of the printed matter. 
   2. Description of the Related Art 
   In recent years, a color scanner or a color printer that is connected to a digital color copying machine or a computer has been widely propagated so as to make it possible to easily obtain a reproduction of printed matter. Also, the performance of these copying machine, color scanner and color printer has been prominently improved so as to make it difficult to discriminate between an original and a reproduction of printed matter. Under the circumstances, research is being conducted in an attempt to develop a discriminating apparatus for discriminating between an original and a reproduction of printed matter. 
   The conventional discriminating apparatus for discriminating between an original and a reproduction of printed matter utilizes in general the difference in the printing system between the two. To be more specific, the original of printed matter, e.g., authentic securities certificate, is printed in general by a relief press. On the other hand, a reproduction obtained by a copying machine or a printer is printed by dots of cyan (C), yellow (Y), magenta (M), black (K), etc. Generally, an authentic securities certificate has a high density region in which the substrate surface (non-printing region) and a printed surface (printing region) are arranged at a high density. If that high density region on the authentic securities certificate is irradiated with a light beam, a brightness pattern having large amplitude conforming to the printing pattern is generated in the light beam passing through or reflected from the particular high density region. However, if the corresponding region on a reproduction of the securities certificate is irradiated with the light beam, the amplitude of the brightness pattern of the light beam passing through or reflected from the particular high density region is diminished. Such being the situation, in the conventional discriminating apparatus as disclosed in, for example, Japanese Patent Disclosure (Kokai) No. 2003-323656, the brightness pattern is obtained by a detector in a prescribed resolution, and the discrimination between the authentic securities certificate and a reproduction is performed on the basis of the brightness pattern thus obtained. 
   However, in order to irradiate the substrate surface and the printing surface with light beams for obtaining the brightness pattern contained in the transmitted light beam or the reflected light beam on the surface, it is necessary for a printing pattern providing a key to the detection to be present. To be more specific, if the reading line of the brightness pattern deviates even slightly, the read brightness pattern is rendered quite different from the brightness pattern contained in the transmitted light beam or the reflected light beam. 
   Also, in another conventional discriminating apparatus as disclosed in Japanese Patent Disclosure No. 2003-323656 referred to above, it is necessary to suppress the fluttering or wrinkling of the printed matter to a level lower than the depth of the focal point at which sufficient resolution can be obtained in the portion where a printing pattern providing a key to the detection is present. It follows that high accuracy is required in the transfer device of the discriminating apparatus, so as to make it difficult to discriminate the printed matter at high speed. This difficulty does not provide a critical defect in the discriminating apparatus mounted to an apparatus not requiring the processing at high speed such as an ATM because the serviceability ratio of the discriminating apparatus section is low, though the processing rate of, for example, the ATM is lowered. However, it is difficult to use such a discriminating apparatus in a machine required to handle a large amount of printed matter for performing the discrimination between the original and a reproduction. 
   It should also be noted in conjunction with the conventional discriminating apparatus that, if fluttering or wrinkling is generated in the printed matter in a magnitude larger than the depth of the focal point, the erroneous discrimination is increased. 
   BRIEF SUMMARY OF THE INVENTION 
   An object of the present invention is to provide a discriminating apparatus that permits discrimination between the original and a reproduction of printed matter at high speed and also permits suppressing the possibility of erroneous discrimination. 
   According to a first aspect of the present invention, there is provided an apparatus for discriminating a printed matter having a surface area, comprising: 
   a transfer device configured to transfer the printed matter; 
   a light source configured to project a light beam to the surface area to scan the surface area with the light beam, the surface area corresponding to one of a substrate region of an original and a printed region similar the substrate region; 
   a detector configured to detect the intensity of the light beam reflected from the surface area to generate an output signal including the output component reflected from one of the substrate region and the similar region; and 
   a discriminating unit configured to discriminate whether the printed matter is the original or not based on the amplitude of the output component. 
   Further, according to a second aspect of the present invention, there is provided an apparatus for discriminating a printed matter having a surface area, comprising: 
   a light source configured to project a light beam to a surface area of a printed matter, the surface area corresponding to one of a substrate region of an original and a printed region similar to the substrate region; 
   a detector configured to detect an intensity of the light beam reflected from the surface area to generate an output signal; 
   a moving mechanism configured to relatively move the detector and the printed matter to scan the surface area with the detector; and 
   a discriminating unit configured to discriminate whether the printed matter is the original or not based on the amplitude of the output signal component. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
       FIG. 1  is a block diagram schematically showing the construction of the discriminating apparatus according to a first embodiment of the present invention; 
       FIG. 2  schematically shows in a magnified fashion the printed matter that is subjected to the discrimination by the discriminating apparatus shown in  FIG. 1 ; 
       FIG. 3  schematically shows in a magnified fashion the optical system included in the discriminating apparatus shown in  FIG. 1 ; 
       FIGS. 4A and 4B  are a graph and a table, respectively, showing the MTF characteristics curve in the stigmatic lens having an NA value of 0.03 and the MTF characteristics data. 
       FIG. 5  is a flow chart exemplifying the process of obtaining a reproduction of printed matter  100 , which is to be subjected to the discrimination by the discriminating apparatus shown in  FIG. 1 , from the original; 
       FIGS. 6A and 6B  are plan views schematically showing the images obtained from a reproduction and from the original of printed matter  100  that is to be subjected to the discrimination by the discriminating apparatus shown in  FIG. 1 , the obtained images differing from each other; 
       FIGS. 7A and 7B  are a table and a graph, respectively, wherein  FIG. 7B  is a graph showing the output levels of the photodetector relative to the scanning distance, which were experimentally obtained by the discriminating apparatus shown in  FIG. 1 , and  FIG. 7A  is a table showing the measured data; 
       FIG. 8  is a flow chart showing the process of discriminating the printed matter by the discriminating apparatus shown in  FIG. 1 ; 
       FIG. 9  is a graph showing the sensitivity relative to the spatial frequency in the color of the human eye; 
       FIGS. 10A ,  10 B and  10 C are graph each showing the relationship between the reflectance and the wavelength of the light beam irradiating the inks of the general reddish purple, bluish green and yellow colors; 
       FIGS. 11A and 11B  are block diagrams schematically showing the construction of a discriminating apparatus according to a modification of the first embodiment of the present invention; and 
       FIG. 12  is a block diagram schematically showing the construction of a discriminating apparatus according to another modification of the first embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   A discriminating apparatus according to an embodiment of the present invention will now be described with reference to the accompanying drawings. 
   First Embodiment 
     FIG. 1  is a block diagram schematically showing the construction of a discriminating apparatus according to a first embodiment of the present invention. 
   The discriminating apparatus shown in  FIG. 1  comprises a transfer device  200  for transferring printed matter  100 , a lamp unit  300  for illuminating the printed matter  100 , a photodetector  400  for detecting the light beam reflected from the printed matter  100 , and a discriminating unit  500  for performing the discrimination as to whether the printed matter is the original or a reproduction in accordance with the detection signal generated from the photodetector  400 . It is also possible for the discriminating apparatus to include, if necessary, a selecting device  600  for selecting the printed matter  100  transferred by the transfer device  200  in accordance with the discrimination signal generated from the discriminating unit  500 . 
   The transfer device  200  includes a transfer belt  210  and a driving means  215 . The driving means  215  is mounted in a rotatable manner such that the driving means  215  can be rotated by a power source such as a motor. The transfer belt  210  is mounted to the driving means  215  in a manner to surround the driving means  215  like a crawler. The transfer belt  210  is designed to transfer the printed matter  100 , i.e. the workpiece, in a transfer direction  220 . 
   The printed matter  100  represents printed matter that impairs the social function if reproduced, e.g., securities certificate such as a paper currency, a stock certificate, or a merchandise bond. Unlike ordinary printed matter, the printed matter  100  is obtained by printing the print contents  150  on a substrate  110  of a specified color, e.g., a pale reddish purple substrate  110 . The print contents  150  are printed by a specified printing method, e.g., by employing a relief press. Further, the substrate  110  is formed of a sheet having a sufficient mechanical strength, e.g., a relatively thick paper sheet or a polyvinyl chloride sheet. 
   The lamp unit  300  includes a light source  310  and a lens  315 . The light source  310  is mounted for projecting a light beam  320  onto the printed matter  100  transferred by the transfer device  200 . It is necessary to set appropriately the angle between the surface of the printed matter  100  and the light beam  320 . To be more specific, in order to maintain high reflectance and to avoid the interference between the light beam  320  and the photodetector  400 , it is desirable for the angle between the surface of the printed matter  100  and the light beam  320  to be set at 45±10°. 
   It is desirable for the light beam  320  emitted from the light source  310  to be green. To be more specific, it is desirable for the light beam  320  noted above to have a wavelength of 520 to 535 nm. It is particularly desirable for the light source  310  to be formed of a light emitting linear diode (LED) or a laser diode because the amount of the light beam having an undesired extra wavelength, which is contained in the light beam emitted from these diodes, is very small, and the power consumption of these diodes is small. The lens  315  is mounted for converging the light beam emitted from the light source  310  onto a predetermined illuminating region  330 . 
     FIG. 2  shows the printed matter  100  under the state of being irradiated with the light beam emitted from the light source  310 . The illuminating region  330  on the substrate  110  of the printed matter  100  is irradiated with the light beam emitted from the light source  310  and converged by the lens  315 . Among the light beam irradiating the illuminating region  330 , the light beam reflected from within a spot  420  is detected by the photodetector  400 . In order to permit the photodetector  400  to detect the reflected portion of the light beam emitted from the light source  310  in spite of the fluttering or wrinkling of the printed matter  100 , it is desirable for the illuminating region  330  to have an appropriate area, i.e., a diameter of about 1.0±0.2 mm. 
   The photodetector  400  includes a sensor  410 , a lens  430 , and a pin hole  440 . The photodetector  400  is mounted for measuring the intensity of the reflected portion of the light beam  320  emitted from the light source  310  for irradiating the printed matter  100 . The photodetector  400  is mounted at a position at which the reflected portion of the light beam  320  emitted from the light source  310  for irradiating the printed matter  100  is incident on the photodetector  400 . The reflected light beam incident on the photodetector  400  is converged by the lens  430  and, then, is incident on a light beam receiving section  415  (see  FIG. 3 ) of the sensor  410 . Further, the sensor  410  serves to convert the intensity of the light beam incident on the light beam receiving section  415  into an electric signal (output signal). 
   The pin hole  440  is formed between the lens  430  and the sensor  410 . As shown in  FIG. 3 , a spot  420  and the pin hole  440  collectively form a conjugate (image forming) relations with respect to the lens  430 . To be more specific, a lens system including the lens  430  is constructed to permit the image-formed pin hole and the light source to have conjugate relations. The light beam passing through the pin hole  440  is incident on the light beam receiving section  415 . Also, a diaphragm  435  is arranged to be positioned between the lens  430  and the printed matter  100 . It is possible to control the amount of the reflected light incident on the light beam receiving section  415  by controlling the open area of the diaphragm  435 . 
   The lens  430  will now be described in detail. It is desirable for the numeral aperture NA of the lens  430  to be about 0.03. Also, the lens  430  has a diffraction limit performance such that the aberration of the lens  430  is sufficiently small, compared with the wavelength of the light beam, and the resolution of the discriminating apparatus is determined only by the wavelength of the light beam and the numerical aperture of the lens  430 . 
     FIG. 4A  is a graph showing the MTF characteristics, covering the case of using astigmatic lens having a numerical aperture NA of 0.03. In the graph of  FIG. 4A , MTF (contrast repeatability) is plotted on the ordinate, and the spatial frequency (lines/mm) is plotted on the abscissa. In the case of an ideal lens having a circular opening (stigmatic lens), the number of resolutions is MTF 9%. Also, in the case of a practical lens in which aberration remains unremoved to some extent, the number of resolutions is MTF 10 to 20%, as described in “Construction and Application of Optical System” compiled by Compiling Dept. of Optronics Inc. and published by Optronics Inc. It follows that, if a stigmatic lens having a numerical aperture (NA) of 0.03 is used in the case where it is possible for ±0.5 mm of deviation in the focal point to take place, the spatial frequency is 74 lines/mm and it is necessary for the spot  420  to have a diameter of at least 6.75 μm. 
   Incidentally, where the resolution of a reproduction of the printed matter  100  is coarser than 8 lines/mm, it can be visually confirmed easily by the naked eye whether the printed matter  100  is the original or a reproduction. It follows that it is unnecessary for the diameter of the spot  420  to be larger than 125 μm. 
   The relationship among the transfer device  200 , the lamp unit  300 , and the photodetector  400  will now be described. As described previously, the transfer device  200  is arranged to transfer the printed matter  100  in the transfer direction  220 . The transfer direction  220  is set to permit the lamp unit  300  to illuminate the surface (non-print section) of the substrate  110  of the printed matter  100  and to permit the photodetector  400  to scan the light beam reflected from the surface of the substrate  110 . The transfer direction  220  is also set to permit the print contents  150  of the printed matter  100  to be substantially in parallel to the printed surface (print surface). 
   Incidentally, the expression “substantially parallel” noted above implies that, when the photodetector  400  scans the light beam reflected from the surface of the substrate  110 , the print contents  150  is parallel to the printed surface to some extent such that at least a part of the printed matter  100  is movable within the depth of the focal point, i.e., movable within a range of ±0.5 mm in this embodiment. It should be noted that, within a range of ±0.5 mm of the depth of the focal point, it is possible to secure a sufficient resolution even in the event of occurrence of the maximum deviation of the focal point of ±0.5 mm. 
   The discriminating unit  500  is connected to the photodetector  400  via the output signal transmitting path  450 . It is possible for the discriminating unit  500  to be formed of an information processing apparatus such as a microcomputer or a sequencer comprising, for example, an arithmetic device or a memory means. The intensity of the light beam converted into an electric signal by the photodetector  400  is sampled (detected) by the discriminating unit  500  at a predetermined pitch. For example, where the transfer device  200  is set to transfer the printed matter  100  at a transfer rate of 1 m/sec, the sampling is performed at a pitch of 100,000 times (10 μm)/sec. Where the sampling pitch is set at 10 μm/sec, the capacity of the sampling data sampled by the discriminating unit  500  is about 100 kB/sec. Even in view of the process capacity of the microcomputer or the sequencer available nowadays, the data rate noted above sufficiently permits the discriminating unit  500  to perform its discriminating operation. 
   The discriminating unit  500  performs its discriminating function as to whether the printed matter  100  is the original or a reproduction based on the data on the intensity of the light beam sampled by the discriminating unit  500 . The result of the discriminating operation performed by the discriminating unit  500  is generated to the outside via the output path  510  of the result of the discrimination. 
   The selecting device  600  is connected to the output path  510  of the result of the discrimination. The selecting device  600  many be arranged as desired or may be omitted. For example, it is possible for the selecting device housed in an ATM or an automatic vending machine to be omitted. Also, it is desirable for the selecting device  600  to be mounted in the case where the discriminating apparatus is used in, for example, a bank as a currency discriminating apparatus. 
   Based on the result of the discrimination, which is generated through the output path  510  of the result of discrimination, the selecting device  600  classifies the printed matter  100  into originals and reproductions and discharges separately originals and the reproductions thus classified. Where the printed matter  100  has been found to be originals, the selecting device  600  discharges originals thus found to the ordinary discharge port of the discriminating apparatus. On the other hand, where the printed matter  100  has been found to be a reproduction, the selecting device  600  discharges the reproduction to the discharge port of the discriminating apparatus, which is arranged exclusively for the reproduction. In this case, it is possible to display the number of discharged originals and the number of discharged reproductions on a display screen by using a counter (not shown). 
   The discriminating operation using the discriminating apparatus according to the embodiment of the present invention will now be described in detail. In the first step, differences between the original and a reproduction of the printed matter  100  will now be described. 
   In the case of preparing a reproduction, the original is prepared first in general (step S 10  shown in  FIG. 5 ). In the original of the printed matter  100 , the print contents  150  is printed by a relief-printing on, for example, a pale reddish purple substrate  110 . On the other hand, in the preparation of a reproduction, the original of the printed matter  100  forming a sample is once converted into electronic data by using an imaging device such as a color scanner, as shown in  FIG. 5  (step S 12 ). Then, noise is removed from the electronic data thus converted by using an information processing device such as a CPU, which is mounted in a personal computer or a copying machine. Also, the data is processed so as to correct the color (step S 14 ). Further, the processed electronic data is printed on a paper sheet used for manufacturing a reproduction by using a printer such as an ink jet printer or a laser printer (step S 16 ). As a result, manufactured is a reproduction having a pattern and characters equal to those of the original printed thereon (step S 18 ). 
     FIGS. 6A and 6B  schematically show, respectively, the original  170  of the printed matter  100  prepared in advance and a reproduction  180  of the printed matter  100  manufactured by the process described above. As shown in  FIG. 6A , the substrate  110 , if observed in a magnified fashion, of the original  170  is formed of a plain foundation  175 . On the other hand, if that portion of the reproduction  180  which corresponds to the substrate  110  of the original  170  is observed in a magnified fashion, it is seen that dots  190  of a reddish purple ink (M for CYMK) are printed on a white paper sheet  185  at an interval conforming with the brightness of the pale reddish purple substrate, as apparent from  FIG. 6B . 
   The difference noted above between the reproduction  180  and the original  170  is brought about because the printer is designed on the basis that the printing is performed by using a paper sheet having a high degree of whiteness in order to increase the color reproducibility of the printer. It follows that if it is intended to reproduce the original  170  having a pale reddish purple color tint, the dots  190  as shown in  FIG. 6B  are also printed in that region of the original which corresponds to the substrate  110 . 
   Also, where the dots  190  are not printed, the original  170  and the reproduction  180  differ from each other in the color of that portion of the original  170  which corresponds to the substrate  110 , with the result that the discrimination between the original  170  and the reproduction  180  can be performed easily even with the naked eye. It should also be noted that, where the reproduction  180  is printed by using a pale reddish purple substrate  110  as in the printing of the original, the original  170  and the reproduction  180  differ from each other in the color of the print contents  150  so as to make it possible to discriminate easily between the original  170  and the reproduction  180  even with the naked eye. 
   Further, the ink particles used in a printer available nowadays are about 2 pL in the case of, for example, the ink jet printer, and the dots  190  printed on the substrate  110  have a diameter of about 16 μm. It follows that it is possible to perform the discrimination as to whether the printed matter  100  is the original or a reproduction by allowing the photodetector  400  to detect the dot  190  in the form of the intensity of the light beam and to convert the presence or absence of the dot  190  into the amplitude of the electric signal and by allowing the discriminating unit  500  to compare the amplitude of the electric signal with the amplitude of the light beam that is to be sampled in the original  170 . 
   The comparison in the amplitude of the electric signal, which is performed by the discriminating unit  500 , will now be described. Specifically, the discriminating unit  500  obtains the value forming a comparable index from the amplitude of the electric signal in a position corresponding to the substrate surface  110  of the original  170 . The index value noted above is obtained from among the data on the intensities of the sampled light beams. Then, the index is compared with a prescribed threshold value so as to determine whether or not the printed matter  100  is the original or a reproduction. For obtaining the threshold value, the data on the intensity of the light beam is obtained from a plurality of originals, and the threshold value is determined on the basis of the data thus obtained in view of the margin. 
   The index is provided by, for example, the difference between the maximum value and the minimum value obtained from the data on the intensities of the sampled light beams, the contrast value, the arithmetic average roughness, the maximum height, the 10 points average roughness or the square average roughness, or a combination of a plurality of these indexes. In this embodiment, the contrast value is taken up as an example. It should be noted that the arithmetic average roughness, the maximum height, the 10 points average roughness or the square average roughness are described in detail in JIS B 0601 and, thus, description thereof is omitted herein. 
   The contrast value is the value obtained by formula (1) given below:
 
(Amax−Amin)/(Amax+Amin)  (1)
 
   where Amax denotes the maximum value of the intensity of the sampled light beam, and Amin denotes the minimum value of the intensity of the sampled light beam. 
   It is necessary to suppress the influences given by fluttering and wrinkling of the printed matter  100  to the data on the intensity of the light beam as much as possible. Such being the situation, in sampling the data on the intensities of the light beams, the discriminating unit  500  selects a part of the data on the intensities of the light beams sampled at the portion where the printed matter  100  has been moved within a range of the focal point depth ±0.5 mm. For example, where the printed matter  100  was moved by 12 cm so as to bring about the fluttering of 2 mm as a whole and there was a deviation within a range of ±0.5 mm in the movement of the printed matter  100  by 3 cm after the movement by 12 cm, optional consecutive data, e.g., 7 data, are selected from the data on the intensities of the sampled light beams when the printed matter  100  was moved by 3 cm. Then, the contrast value is obtained from the selected optional data by using formula (1) given above. 
     FIGS. 7A and 7B  are a table and a graph, respectively, showing the experimental data, covering the case where the original and a reproduction of the printed matter are irradiated with the light beam emitted from the lamp unit  300  included in the discriminating apparatus shown in  FIG. 1 , followed by converting the intensities of the reflected light beams into electric signals by the photodetector  400  and subsequently sampling the electric signals thus obtained in the discriminating unit  500 . In the graph of  FIG. 7B , the output signal generated from the photodetector  410  and sampled by the discriminating unit  500  is plotted on the ordinate, and the distance moved by the printed matter  100  during the sampling operation, i.e., the scanning distance required for the photodetector  400  to scan the light beam reflected from the surface of the substrate  110 , is plotted on the abscissa. Also, in  FIG. 7B , graph I denotes the detected signals of the light beams reflected from the printed matter constituting the original, and graph II denotes the detected signals of the light beams reflected from the printed matter forming a reproduction. The contrast values obtained from the experimental data are given in the table of  FIG. 7A . As apparent from the table, the contrast value for the reproduction is about 10 times as large as that for the original. Such being the situation, it is considered reasonable to judge that the contrast value larger than 0.1 denotes a reproduction and that the contrast value not larger than 0.1 denotes the original. 
   As apparent from the description given above, in the discrimination of the printed matter utilizing the discriminating apparatus shown in  FIG. 1 , the discrimination as to whether the printed matter is the original or a reproduction is performed in accordance with the procedure shown in  FIG. 8 . 
   In starting the discriminating operation in step S 20  shown in  FIG. 8 , prepared is printed matter corresponding to the original as a comparative sample as shown in step S 22 . Then, the region in which appears the substrate color alone of the prepared original is determined as the scanning region as shown in step S 24 . For example, if there is a non-printed region in the edge of the original printed matter, the non-printed region is selected as a region that is to be scanned. The original printed matter is arranged on the transfer belt of the discriminating apparatus shown in  FIG. 1  so as to be positioned such that a prescribed region of the original printed matter is scanned by the light beam. Then, the discriminating apparatus shown in  FIG. 1  is operated so as to permit the prescribed region of the original printed matter to be scanned by the light beam as shown in step S 26 . The light beam reflected from the printed matter is detected by the photodetector  400  so as to obtain the data as shown in graph I of  FIG. 6B . A comparative index is prepared from the data thus obtained as shown in step S 28 . As described previously, the index includes the contrast value, the arithmetic average roughness, the maximum height, the 10 points average roughness, or the square average roughness or an index is prepared by combining a plurality of these indexes and is stored in a memory. 
   In the next step, prepared is printed matter that is to be discriminated. As shown in step S 30 , the printed matter to be discriminated is arranged on the transfer belt  210  of the discriminating apparatus so as to be positioned such that the printed matter to be discriminated is scanned by the light beam as in the original printed matter. Then, as shown in step S 32 , the printed matter to be discriminated is transferred by the transfer belt so as to be scanned by the light beam, and the reflected light beam is detected by the photodetector  400 . It follows that the data denoted by graph I or graph II in  FIG. 7B  are generated from the photodetector  400 . The detected data is processed as shown in step S 34  so as to obtain an index similar to that of the original printed matter. The index to be discriminated is compared with the comparative index of the original printed matter as shown in step S 36  so as to determine whether or not the printed matter to be discriminated is the original or a reproduction, as shown in step S 38 . Then, it is confirmed whether or not all the printed matters to be discriminated have been discriminated as shown in step S 40 . If there is printed matter that has not been discriminated, the operation is brought back to step S 32 . On the other hand, if it has been confirmed in step S 40  that the discrimination of all the printed matters has been completed, the discriminating operation is finished as shown in step S 42 . 
   As described above, the discriminating apparatus of the present invention makes it possible to perform discrimination at a high speed as to whether the printed matter  100  is the original or a reproduction. Since the printed matter need not be positioned accurately, the discrimination can be performed at a high speed in the present invention. To be more specific, it is unnecessary in the present invention to perform the positioning to irradiate the aimed printing pattern with the light beam for obtaining the brightness of the amplitude conforming with the printing pattern printed in advance on the printed matter  100 , and it suffices for the region corresponding to the substrate color of the original to be scanned. Such being the situation, a high speed processing can be achieved in the present invention. In general, the blank portion having a large area of the printed matter  100 , i.e., the surface of the substrate  110 , is irradiated with the light beam in the present invention so as to make it unnecessary to perform the positioning at a high accuracy. A blank portion having a width of about 5 mm is formed on the general printed matter  100  such as paper currency. It follows that the allowable error in the positioning of the printed matter  100  is about ±2 mm and, thus, an accurate discrimination can be performed by performing the positioning in a simple and easy method. 
   It should also be noted that, when discrimination is performed as to whether the printed matter is the original or a reproduction, the possibility of the erroneous discrimination is very low. Where the substrate surface and the printing surface are irradiated with the light beam for obtaining a brightness pattern conforming with the printing pattern, it is possible for an erroneous discrimination to be made if fluttering or wrinkling greater than the focal point depth of the photodetector  400  is included in the aimed printing pattern portion. However, the discriminating apparatus according to the embodiment of the present invention selects the data on the intensity of the light beam in the portion where the fluttering or wrinkling is included within the range of the focal point depth of the photodetector  400 . It follows that the possibility of erroneous discrimination is very low in the discriminating apparatus according to the embodiment of the present invention. 
   Incidentally, it is possible for the discriminating apparatus according to the embodiment of the present invention to comprise further a color sensor. If a color sensor is further included in the discriminating apparatus, it is possible to detect the color of the printed matter  100 , i.e., the color of the substrate  100  or the print contents  150 , so as to perform the discrimination as to whether the printed matter is the original or a reproduction by further using the detected color data. 
   Second Embodiment 
   A discriminating apparatus according to a second embodiment of the present invention will now be described with reference to  FIGS. 9 to 12 . In the following description, the same reference numerals are used to denote the portions equivalent to those in the first embodiment of the present invention described previously in conjunction with  FIGS. 1 to 8  to avoid overlapping description. 
     FIG. 9  is a graph showing the sensitivity relative to the color of the human eye. In the graph of  FIG. 9 , the relative sensitivity (dB) of the human eye is plotted on the ordinate, and the spatial frequency (lines/mm) is plotted on the abscissa. Also,  FIGS. 10A ,  10 B and  10 C are graphs each showing the relationship between the wavelength and the reflectance of the irradiating light beam in respect of the inks of the general colors of reddish purple (magenta), bluish green (cyan), and yellow, respectively. In each of these graphs, the reflectance (%) is plotted on the ordinate, and the wavelength (nm) is plotted on the abscissa. 
   The printed matter  100  is obtained by printing the print contents  150  on a pale yellow substrate  110 . The light beam  320  emitted from the light source  310  is colored blue. To be more specific, the wavelength of the light beam  320  noted above falls within a range of 400 to 500 nm. It is possible to use a blue LED or a blue laser diode as the light source  310 . The discriminating apparatus according to the second embodiment of the present invention will now be described in detail. 
   As shown in  FIG. 9 , the yellow pattern cannot be recognized by the human eye even if the density of the pattern is low, i.e., one tenth times as high as that of the black pattern and one third times as high as that of the reddish purple pattern. It follows that two kinds of yellow ink differing from each other in brightness is unlikely to be used as an ink in the ordinary printer, though it is possible to use in the ordinary printer two kinds of reddish purple and bluish green inks differing from each other in concentration. Such being the situation, a thick yellow ink alone is used in the printer by utilizing the low resolution of the human eye relative to the yellow color, and a pale yellow is represented by performing printing under the state that the interval between the thick yellow dots is increased. 
   Also, as shown in  FIGS. 10A ,  10 B and  10 C, the reflectance is very low in the case where a yellow ink is irradiated with a blue light beam having a wavelength not longer than 500 nm. On the other hand, the reflectance is very high when the yellow ink is irradiated with a light beam having a wavelength not shorter than 500 nm. In other words, in the case of the irradiation with a light beam having a wavelength not longer than 500 nm, the reflectance on the substrate surface is left unchanged, though the reflectance is very low in the portion printed with thick yellow dots. Incidentally, where a yellow ink is irradiated with a light beam having a wavelength shorter than 400 nm, it is possible for the reflectance to differ depending on the kind of the ink because the light beam of the wavelength noted above cannot be recognized by the human eye. Under the circumstances, the resolution of the yellow color performed by the photodetector  400  is improved if the wavelength of the light beam emitted from the light source  310  falls within a range of 400 to 500 nm. 
   The discriminating apparatus according to the second embodiment of the present invention described above makes it possible to perform the discrimination as to whether the printed matter  100  is the original or a reproduction at a high speed like the discriminating apparatus according to the first embodiment of the present invention described previously. Also, in performing the discrimination as to whether or not the printed matter is the original or a reproduction, the possibility of erroneous discrimination is very low. 
   Further, since the resolution of the yellow color performed by the photodetector  400  is improved, compared with the discriminating apparatus according to the first embodiment of the present invention, the possibility of an erroneous discrimination can be further lowered. It should also be noted that, since a pale yellow is achieved in the printed matter obtained by the printing with a printer by performing the printing under the state that the distance between the adjacent thick yellow dots is increased, the photodetector  400  exhibits sufficient allowance in the resolution of the yellow color so as to further lower the possibility of the erroneous discrimination. 
   Incidentally, in the embodiment described above, the light source  310  is formed of a green LED, a blue LED, a green laser diode or a blue laser diode. However, it is also possible to use as the light source  310  a lamp unit  311  for emitting a white light beam such as a halogen lamp unit in combination with an optical filter  316  capable of selectively transmitting the green light beam alone having a wavelength of 520 to 535 nm or the blue light beam alone having a wavelength of 400 to 500 nm, which are included in the white light beam emitted from the halogen lamp unit, as shown in  FIG. 11A . 
   Also, it is possible to use in place of the optical filter  316  a lamp unit light source  310  emitting a white light beam  320  and an optical filter  436  that is arranged between the printed matter  100  and the sensor  410  and permits selectively transmitting a green light beam alone having a wavelength of 520 nm to 535 nm or a blue light beam alone having a wavelength of 400 nm to 500 nm, which is included in the white light beam emitted from the lamp unit light source  310 . 
   Also, it is possible for the discriminating apparatus according to the second embodiment of the present invention to include further a color sensor like the discriminating apparatus according to the first embodiment of the present invention. It is also possible to combine a known discriminating method with the discriminating apparatus according to the second embodiment of the present invention. 
   Also, it is possible for the lamp unit  300  and the photodetector  400  to be mounted on a moving head  230  as shown in  FIG. 12 . In this case, the moving head  230  moves the lamp unit  300  and the photodetector  400  so as to permit the photodetector  400  to detect the light beam reflected from the surface of the substrate  110 . The moving direction in this stage is substantially parallel to the printing surface having the print contents  150  of the printed matter  100  printed thereon. In this case, it is unnecessary to set the transfer direction  220  in a manner to permit the photodetector  400  to detect and measure the light beam reflected from the surface of the substrate  110 . In other words, it suffices for the printed matter  100  and the photodetector  400  to be moved relative to each other so as to permit the printed matter  100  to be scanned by the photodetector  400 . 
   Further, the discriminating apparatus according to the first embodiment of the present invention is directed to the discrimination of the printed matter on a reddish purple substrate. Also, the discriminating apparatus according to the second embodiment of the present invention is directed to the discrimination of the printed matter on a yellow substrate. However, it is also possible to use in combination the constructions for discriminating the printed matter on substrates of other colors. Also, the discriminating apparatus according to the embodiments of the present invention is directed to an example of discriminating a reproduction having reddish purple or yellow dots printed thereon. However, a reproduction having dots, mesh lines or universal lines printed thereon can also be discriminated by using the similar construction. 
   As described above, the present invention provides a discriminating apparatus, which permits the discrimination at high speed as to whether the printed matter is the original or a reproduction, and which is low in the possibility of erroneous discrimination. 
   Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.