Patent Publication Number: US-8973730-B2

Title: Bank notes handling apparatus

Description:
FIELD OF THE INVENTION 
     The present invention relates to a paper sheet identification apparatus (or bank notes handling apparatus) which identifies the authenticity of a bill, a gift certificate, a coupon ticket, and so on (hereafter, these are collectively referred to as a paper sheet). 
     BACKGROUND ART 
     In general, a bill processing apparatus, which handles a bill as one of the embodiments of the paper sheet, is incorporated into a service device such as a game medium rental machine installed in a game hall, a vending machine or a ticket-vending machine installed in a public space, or the like which identifies the authenticity of the bill inserted from a bill insertion slot by a user and provides various types of products and services in accordance with a value of the bill having been judged as authentic. 
     The above-mentioned authenticity of the bill is judged, for example, by an authenticity judging device comprising a light emitting part irradiating the bill moving in a bill traveling route with light and a light receiving sensor receiving transmitted light and reflected light of the light irradiated by the light emitting part, and an authenticity judgment process is conducted by comparing received light data transmitted from the light receiving sensor with legitimate data as disclosed in Patent Reference 1. 
     Meanwhile, it is known that the above-mentioned light receiving sensor of the authenticity judging device has a device property to deteriorate with the lapse of time. As such deterioration is caused with the lapse of time, an output value is lowered such that received light data of the bill may represent dim light. Therefore, so-called black calibration (black balance) to correct a reference value of the output for the lowest brightness is performed every predetermined period of time. For example, it is typically performed that an output from the light receiving sensor is read in a state where no light is irradiated from the light receiving part when the bill processing apparatus is turned on and the received light data having been read in this way is set as the reference value for the lowest brightness.
     [Patent Reference 1] Japanese unexamined patent application publication No. 2001-279487   

     DISCLOSURE OF THE INVENTION 
     Problem to be Solved by the Invention 
     However, it is possible for the above-mentioned light receiving sensor to have the device property which may vary depending on an environmental change, for example, a temperature change inside the device or a temperature change of the environment around the device, in addition to the deterioration with the lapse of time. In concrete terms, when the internal temperature rises during the operation of the apparatus, it is possible that an output value of the light receiving sensor may be lowered. Because of such change in the device property, the device may not hold a true read level such that it is possible that even a legitimate bill may be identified as a fake bill. 
     In the present invention, a paper sheet processing apparatus may be provided with which an authenticity judgment process of the paper sheet may be performed accurately even if the environmental change occurs. 
     Means to Solve the Problem 
     In the present invention, a paper sheet processing apparatus includes: an insertion slot into which a paper sheet is inserted; a sensor which detects insertion of the paper sheet from the insertion slot; a traveling route in which the paper sheet inserted from the insertion slot is conveyed; a light emitting part which irradiates the traveling route with light; a light receiving part which receives light from the traveling route; a black calibration part which sets a reference value for the lowest brightness of light with respect to light received by the light receiving part in a state where emission by the light emitting part is made ineffective; and an authenticity judgment processing part which judges an authenticity by comparing a plurality of pixel data obtained by converting the light received by the light receiving part into data per unit pixel having a predetermined size and including color information having brightness as the light emitting part irradiates the paper sheet traveling in the traveling route with the light with reference pixel data with respect to a legitimate paper sheet based on the reference value set by the black calibration part, wherein the black calibration part can set the reference value before the authenticity judgment processing part judges the authenticity after the sensor detects the insertion of the paper sheet every time when the paper sheet is inserted. 
     Further features of the present invention, its nature, and various advantages will be more apparent from the accompanying drawings and the following description of the preferred embodiment. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view showing an entire structure to illustrate a configuration of a bill processing apparatus of this embodiment. 
         FIG. 2  is a perspective view showing the bill processing apparatus in a state that an open/close member is opened for a main body frame of an apparatus main body. 
         FIG. 3  is a right side view schematically showing a traveling route of a bill to be inserted from an insertion slot. 
         FIG. 4  is a right side view showing a schematic configuration of a power transmission mechanism for driving a presser plate arranged in a bill housing part. 
         FIG. 5  is a left side view showing a schematic configuration of a driving source and a driving force transmission mechanism to drive a bill conveyance mechanism. 
         FIG. 6  is a block diagram showing a configuration of control means which controls driving members of a bill conveyance mechanism, bill reading means, and the like. 
         FIG. 7  shows a flowchart (part one) illustrating processing operations for processing a bill in a bill processing apparatus of this embodiment. 
         FIG. 8  shows a flowchart (part two) illustrating processing operations for processing the bill in the bill processing apparatus of this embodiment. 
         FIG. 9  shows a flowchart (part three) illustrating processing operations for processing the bill in the bill processing apparatus of this embodiment. 
         FIG. 10  shows a flowchart illustrating processing operations of a traveling route opening process. 
         FIG. 11  shows a flowchart illustrating processing operations of a skew correction operating process. 
         FIG. 12  shows a flowchart illustrating processing operations of a traveling route closing process. 
         FIG. 13  shows a flowchart illustrating a multi-feed judgment process. 
         FIG. 14  shows an image diagram of an image based on image data of a bill when a black calibration is appropriately made. 
         FIG. 15  shows an image diagram of an image based on image data of a bill when a black calibration is made inappropriately. 
         FIG. 16  is a schematic diagram showing a bill in a state that a leading end of the bill is folded. 
         FIG. 17  is a schematic diagram showing two bills in a state that the two bills are overlapped. 
         FIG. 18  is a perspective view showing a bill processing apparatus in a state that an open/close member is opened for a main body frame of an apparatus main body according to another embodiment. 
         FIG. 19  is a diagram illustrating performance of a blackout curtain member. 
     
    
    
     DESCRIPTION OF NOTATIONS 
     
         
           1  bill processing apparatus 
           2  apparatus main body 
           3  bill traveling route 
           5  bill insertion slot 
           6  bill conveyance mechanism 
           8  bill reading means 
           10  skew correction mechanism 
           80   a  first light emitting part 
           81  light receiving/emitting unit 
           81   a  light receiving part 
           81   b  second light emitting part 
           200  control means 
       
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     Hereinafter, an embodiment of the present invention will be described with reference to the drawings. 
       FIGS. 1 to 5  are diagrams showing a configuration of a bill processing apparatus according to this embodiment.  FIG. 1  is a perspective view showing a general configuration thereof;  FIG. 2  is a perspective view showing the bill processing apparatus in a state that an open/close member is opened for a main body frame of an apparatus main body;  FIG. 3  is a right side view showing schematically a traveling route for a bill inserted from an insertion slot;  FIG. 4  is a right side view showing schematically a power transmission mechanism for driving a presser plate installed in a bill housing part; and  FIG. 5  is a left side view showing a schematic configuration of a driving source and a driving force transmission mechanism to drive a bill conveyance mechanism. 
     A bill processing apparatus  1  of this embodiment is so configured that it can be incorporated into, for example, various types of gaming machines such as a slot machine and the like, and the bill processing apparatus  1  includes an apparatus main body  2  and a housing part (stacker or cashbox)  100  which is provided to the apparatus main body  2  and is capable of stacking and housing a great number of bills. Here, the housing part  100  may be mountable to and demountable from the apparatus main body  2 , and it is possible, for example, to remove it from the apparatus main body  2  by pulling a handle  101  provided on a front face thereof in a state that a lock mechanism (not shown) is unlocked. 
     As shown in  FIG. 2 , the apparatus main body  2  has a main frame body  2 A and an open/close member  2 B being configured to be opened and closed for the main body frame  2 A by rotating around an axis positioned at one end thereof as a rotating center. Then, as shown in  FIG. 3 , the main body frame  2 A and the open/close member  2 B are configured to form a space (bill traveling route  3 ) through which a bill is conveyed such that both face each other across the space when the open/close member  2 B is closed for the main body frame  2 A, and to form a bill insertion slot  5  such that front exposed faces of both are aligned and that the bill traveling route  3  exits at the bill insertion slot  5 . In addition, the bill insertion slot  5  is a slit-like opening from which a short side of a bill can be inserted into the inside of the apparatus main body  2 . 
     Also, in the apparatus main body  2 , a bill conveyance mechanism  6  that conveys a bill along the bill traveling route  3 ; an insertion detecting sensor  7  that detects the bill inserted into the bill insertion slot  5 ; bill reading means  8  that is installed on a downstream side of the insertion detecting sensor  7  and reads out information on the bill in a traveling sate; a skew correction mechanism  10  that accurately positions and conveys the bill with respect to the bill reading means  8 ; a movable piece passage detecting sensor  12  that detects that the bill passes through a pair of movable pieces constituting the skew correction mechanism; and a discharge detecting sensor  18  that detects that the bill is discharged into a bill housing part  100  are provided. 
     Hereafter, the respective components mentioned above will be described in detail. The bill traveling route  3  extends from the bill insertion slot  5  toward the inside, and comprises a first traveling route  3 A and a second traveling route  3 B extending from the first traveling route  3 A toward the downstream side and being inclined downwardly at a predetermined angle to the first traveling route  3 A. The second traveling route  3 B is bent in a vertical direction on the downstream side and a discharge slot  3   a  from which the bill is discharged into the bill housing part  100  is formed at an end portion on the downstream side such that the bill discharged from the discharge slot  3   a  is fed into a feed port (receiving port)  103  of the bill housing part  100  in the vertical direction. 
     The bill conveyance mechanism  6  is a mechanism capable of conveying the bill inserted from the bill insertion slot  5  along the insertion direction, and of conveying back the bill in an insertion state toward the bill insertion slot  5 . The bill conveyance mechanism  6  comprises a motor  13  (refer to  FIG. 5 ) serving as a driving source installed in the apparatus main body  2 ; and conveyor roller pairs ( 14 A and  14 B), ( 15 A and  15 B), ( 16 A and  16 B), and ( 17 A and  17 B) which are installed with predetermined intervals along the bill traveling direction in the bill traveling route  3 , and are driven to rotate by the motor  13 . 
     The conveyor roller pairs are installed so as to be partially exposed on the bill traveling route  3 , and all the pairs are constituted of driving rollers of the conveyor rollers  14 B,  15 B,  16 B, and  17 B installed on the underside of the bill traveling route  3  and driven by the motor  13 ; and pinch-rollers of the conveyor rollers  14 A,  15 A,  16 A, and  17 A installed on the upperside and driven by the these driving rollers. In addition, the conveyor roller pair ( 14 A and  14 B) to first nip and hold therebetween the bill inserted from the bill insertion slot  5 , and to convey the bill toward the back side, as shown in  FIG. 2 , is installed in one portion of the center position of the bill traveling route  3 , and a couple of the conveyor roller pairs ( 15 A and  15 B), ( 16 A and  16 B), or ( 17 A and  17 B) being disposed in this order in a longitudinal direction toward a downstream side thereof are respectively installed in a couple of portions with a predetermined interval in the lateral direction of the bill traveling route  3 . 
     Further, the conveyor roller pair ( 14 A and  14 B) disposed in the vicinity of the bill insertion slot  5  is usually in a state that the upper conveyor roller  14 A is spaced from the lower conveyor roller  14 B, and the upper conveyor roller  14 A is driven to move toward the lower conveyor roller  14 B to nip and hold the inserted bill therebetween when insertion of the bill is detected by the insertion detecting sensor  7 . 
     Thus, the upper conveyor roller  14 A is controllably driven to be pressed against or spaced from the lower conveyor roller  14 B by a motor  70  (refer to  FIG. 6 ) for an up-and-down movement of the roller as a driving source. In this case, when a process (skew correction process) for positioning the bill with respect to the bill reading means  8  by eliminating inclination of the inserted bill is executed by the skew correction mechanism  10 , the upper conveyor roller  14 A is spaced from the lower conveyor roller  14 B so as to release the load on the bill, and when the skew correction process is completed, the upper conveyor roller  14 A is driven to move toward the lower conveyor roller  14 B again to hold (or nip) the bill therebetween. Here, the driving source may be constituted of a solenoid or the like instead of a motor. 
     Further, the skew correction mechanism  10  comprises a pair of right and left movable pieces  10 A (only one side is shown) such that the pair of right and left movable pieces  10 A are moved to get closer with each other by driving a motor  40  for a skew driving mechanism, whereby the skew correction process is performed for the bill. 
     The conveyor rollers  14 B,  15 B,  16 B, and  17 B installed on the underside of the bill traveling route  3  are, as shown in  FIG. 5 , driven to rotate via the motor  13  and pulleys  14 C,  15 C,  16 C, and  17 C installed at the ends of the driving shafts of the respective conveyor rollers. That is, a driving pulley  13 A is installed on the output shaft of the motor  13 , and a driving belt  13 B is wrapped around between the pulleys  14 C,  15 C,  16 C, and  17 C installed at the ends of the driving shafts of the respective conveyor rollers and the driving pulley  13 A. In addition, tension pulleys are engaged in places with the driving belt  13 B, which prevents the driving belt  13 B from loosening. 
     In accordance with the configuration described above, when the motor  13  is driven to normally rotate, the conveyor rollers  14 B,  15 B,  16 B, and  17 B are driven to normally rotate in synchronization therewith to convey the bill toward the insertion direction. When the motor  13  is driven to reversely rotate, the conveyor rollers  14 B,  15 B,  16 B, and  17 B are driven to reversely rotate in synchronization therewith to convey back the bill toward the bill insertion slot  5  side. 
     The insertion detecting sensor  7  is to generate a detection signal when a bill inserted into the bill insertion slot  5  is detected. And when the detection signal is generated, the motor  13  is driven in a normal direction and the bill is conveyed in the insertion direction. The insertion detecting sensor  7  of this embodiment is installed between the pair of conveyor rollers ( 14 A and  14 B) and the skew correction mechanism  10  and comprises, for example, an optical sensor such as a regressive reflection type photo sensor. However, the insertion detecting sensor  7  may comprise a mechanical sensor other than the optical sensor. 
     Further, the movable piece passage detecting sensor  12  is to generate a detection signal when it is detected that a leading end of the bill passes through a pair of right and left movable pieces  10 A constituting the skew correction mechanism  10 , and when the detection signal is generated, the driving by the motor  13  is stopped such that the skew correction is made. The movable piece passage detecting sensor  12  of this embodiment is disposed on the upstream side from the bill reading means  8  and also comprises an optical sensor or a mechanical sensor in the same way as mentioned before with respect to the insertion detecting sensor. 
     Further, the discharge detecting sensor  18  is to detect a trailing end of the bill passing through such that it is detected that the bill is discharged into the bill housing part  100 . The discharge detecting sensor  18  is disposed just in front of the receiving port  103  of the bill housing part  100  on the downstream side of the second traveling route  3 B. When the detection signal is transmitted from the discharge detecting sensor  18 , the driving by the motor  13  is stopped and the conveyance processing of the bill is terminated. The discharge detecting sensor  18  also comprises an optical sensor or a mechanical sensor in the same way as the aforementioned insertion detecting sensor. 
     The bill reading means  8  reads bill information on the bill conveyed in a state that the skew is eliminated by the skew correction mechanism  10 , and determines the validity (authenticity). In this embodiment, the bill reading means  8 , which is installed in the above-mentioned first traveling route  3 A, comprises a line sensor which irradiates the bill being conveyed from top and bottom sides thereof with light such that a transmitted light and a reflected light thereof are detected by a light receiving part so as to perform reading. 
     Here, the configuration of above-mentioned reading means  8  will be described in detail with reference to  FIGS. 2 and 3 . 
     The abovementioned bill reading means  8  has a light emitting unit  80  which is installed on the side of the open/close member  2 B and provided with a first light emitting part  80   a  capable of irradiating the upper side of the bill to be conveyed with the infrared light and the red light, and a light receiving/emitting unit  81  which is installed on the side of the main body frame  2 A. 
     The light receiving/emitting unit  81  has a light receiving part  81   a  which is provided with a light receiving sensor facing the first light emitting part  80   a  across the bill (bill traveling route) and second light receiving parts  81   b  which are installed adjacently on the both sides of the light receiving part  81   a  along the bill traveling direction and are capable of irradiating the object with the infrared light and the red light. 
     The first light emitting part  80   a  disposed to face the light receiving part  81   a  works as a light source for the transmissive light. This first light emitting part  80   a  is, as shown in  FIG. 2 , comprised of a rectangular bar-like body made of synthetic resin which emits the light guided through a light guiding body  80   c  provided inside from an LED element  80   b  fixed to one end of the bar-like body. The first light emitting part having such a configuration is linearly installed in parallel with the light receiving part  81   a  (light receiving sensor) so as to be capable of entirely and equally irradiating the entire range in the width direction of the traveling route of the bill to be conveyed although the configuration is simple. 
     The light receiving part  81   a  of the light receiving/emitting unit  81  is formed in a thin-walled plate shape having a band shape extending in a lateral direction of the bill traveling route  3  and having a width to an extent that the sensitivity of the light receiving sensor (not shown) provided in the light receiving part  81   a  is not affected. In addition, the light receiving sensor is configured as a so-called line sensor in which a plurality of CCDs (Charge Coupled Devices) are provided linearly in the center in the thickness direction of the light receiving part  81   a , and a GRIN lens array  81   c  is disposed linearly above these CCDs so as to collect the transmitted light and the reflected light. 
     The second light emitting part  81   b  of the light receiving/emitting unit  81  works as a light source for the reflection light. This second light emitting part  81   b  is, in a similar manner as the first emitting part  80   a , comprised of a rectangular bar-like body made of synthetic resin which emits the light guided through a light guiding body  81   e  provided inside from an LED element  81   d  fixed to one end of the bar-like body. The second light emitting part  81   b  is also configured to be linearly installed in parallel with the light receiving part  81   a  (line sensor). 
     The second light emitting parts  81   b  are capable of irradiating the bill with the light at an elevation angle of 45 degrees, for example, and are so installed that the light receiving part  81   a  may receive the reflected light from the bill. In this case, the lights irradiated to the bill by the second light emitting parts  81   b  are to be made incident at 45 degrees onto the light receiving part  81   a , but the incident angle is not limited to 45 degrees such that the arrangement may be re-arranged as appropriate as long as the lights are irradiated evenly without shading to the surface of the bill. Therefore, the arrangement of the second light emitting parts  81   b  and the light receiving part  81   a  may be appropriately changed in design in accordance with the structure of the bill processing apparatus. 
     Further, the second light emitting parts  81   b  are disposed on the both sides of the light receiving part  81   a  so as to be disposed across the light receiving part  81   a  and irradiate the bill with the respective lights at respective incident angles of 45 degrees. This is because, in the case where the surface of the bill has scratches or folded wrinkles, and in the case where the light is irradiated only from one side to an uneven surface generated by these scratches or folded wrinkles, it is unavoidable to make some portions shaded to cause shadow in the uneven surface. Therefore, the shadows made in the uneven surface may be prevented by irradiating the lights from the both sides, whereby the image data to be acquired can have a higher degree of precision than that acquired by the single side irradiation. Here, the second light emitting part  81   b  may be configured to be installed only on one side, and the configuration, the arrangement, and the like of the light emitting unit  80  and the light receiving/emitting unit  81  as described above are not limited to those described in this embodiment, and may be modified as appropriate. 
     An authenticity judgment process is conducted by comparing image data obtained by reflected light (irradiated light by the second light emitting part  81   b ) and transmitted light (irradiated light by the first light emitting part  80   a ) from the bill which are acquired by the above-mentioned light receiving part  81   a  with the image data of the legitimate bill. In this case, since the legitimate bill has some area from which different image data are acquired depending on the wavelengths of the lights (for example, visible light or infrared light) irradiated to the area, in the authenticity judgment process in this embodiment, a plurality of light sources, in consideration of this view point, irradiate different lights of different wavelengths (in this embodiment, a red light and an infrared light are irradiated) to the bill and a transmitted light therethrough and a reflected light thereon are detected such that the authenticity identification accuracy may be improved. That is, since the red light and the infrared light have different wavelengths, transmitted-light data and reflected-light data from a plurality of lights of different wavelengths may be utilized for the bill authenticity judgment whereby the judgment may use the nature that the transmittance of the transmitted light transmitted through the specific area and the reflectance of the reflected light reflected on the specific area in the legitimate bill are different from those of the counterfeit bill. Therefore, in the above-mentioned light emitting part (first light emitting part  80   a  and second light emitting part  81   b ), an attempt is made to further improve the bill authenticity identification accuracy by employing light sources where a plurality of wavelengths are available. 
     Here, since it is possible to acquire various kinds of received-light data (transmitted-light data and reflected-light data) depending on the wavelengths of the irradiated lights to the bill and the irradiated areas of the bill, although a concrete bill authenticity identification method will not be written in detail, the image appears greatly different depending on the lights in a watermark area of the bill, for example, if an image on the area is viewed with the lights of different wavelengths. Therefore, it can be considered that the bill to become an identification object is identified as the legitimate bill or the counterfeit bill by setting this portion as the specified area, acquiring transmitted-light data and reflected-light data from the specified area, and comparing such data with legitimate data from the same specified area of the legitimate bill having been stored in advance in storage means such as ROM. At this time, provided that specified areas are predetermined according to the kinds of the bills, and that predetermined weighting may be applied to the transmitted-light data and the reflected-light data from this specified area, the authenticity identification accuracy may be improved. 
     In addition, the above-mentioned light emitting part (first light emitting part  80   a  and second light emitting part  81   b ) is controlled to light with a predetermined interval and transmitted light and reflected light are detected by the light receiving part (line sensor)  81   a  when the bill passes. The light receiving part (line sensor)  81   a  can acquire contrasting density data (a plurality of pixel data per a predetermined size as a unit which include brightness data) in accordance with the brightness and it is also possible to generate two-dimensional image from such pixel data. 
     In this case, the image data acquired by the line sensor is converted into data containing color information having brightness for each pixel by a converter which will be described later. In addition, the color information of each pixel having brightness to be converted by the converter corresponds to a contrasting density value, i.e., a density value (luminance value), and a numerical value from 0 to 255 (0: black to 255: white) is allocated to each pixel, for example, as information of one byte according to its density value. 
     Therefore, in the authenticity judgment process, the predetermined area of the bill may be extracted; the pixel information (density values) contained in the area and the pixel information in the same area of the legitimate bill may be used so as to be substituted into an appropriate correlating equation; and then a coefficient of correlation may be obtained by carrying out an operation thereof, whereby the authenticity identification may be judged by the coefficient. Or, in addition to the above description, analog waveforms, for example, may be generated from the transmitted-light data and the reflected-light data, and the respective shapes of those waveforms may be compared with each other, whereby the authenticity identification may be judged by such comparison. Moreover, a process in which the length of the printed area of the bill is detected and the authenticity thereof is identified by utilizing the length information may be provided. 
     Further, the black calibration is conducted to correct the reference value of the output for the lowest brightness in the above-mentioned light receiving part (line sensor)  81   a  before the conveyed bill is read out. This black calibration is, as described later, to be conducted before it is started that the bill is actually read out after the bill having been inserted from the bill insertion slot  5  is detected by the insertion detecting sensor  7  at every time when the bill is inserted. 
     The black calibration is performed by the black calibration part (black calibration operation circuit) connected to the light receiving part  81   a , and it is executed by acquiring an output from the light receiving part  81   a  in as state that the light emission from the light emitting part (first light emitting part  80   a  and second light emitting part  81   b ) is made ineffective, for example, when the light emitting part is controlled to be off, before the reading process of the inserted bill is conducted. In concrete terms, a detection signal from the light receiving part  81   a  (detection signal detected in the state that light emission by the light emitting part is made to be ineffective) is converted into pixel information, which is set as the reference brightness (reference value) and stored. The reference value of brightness having been set by the black calibration part is made to be the reference value for the lowest brightness when bill information from the light emitting part  81   a  is actually detected and converted into pixel information, and the output value from the light emitting part  81   a  is corrected to be in an appropriate level. The light receiving part may be configured to be shielded, as a means for making the emission from the light emitting part to be ineffective, such that the light receiving part  81   a  would not receive the light from the light emitting part even if any one of the light emitting parts is turned on. 
     As described above, the black calibration is performed by the light receiving part  81   a  in a condition that the light emitting part would emit any light such that the reference value for the lowest brightness is set with respect to the brightness of the light received by the light receiving part  81   a  at every time of reading the bill. That is, even if an output value from the light receiving part varies according to the environment change and the like of the inside of the device and the device property of the light receiving part  81   a , it is possible to conduct the above-mentioned authenticity judgment process based on the correct brightness with respect to the information obtained by reading out the bill since the output value is corrected as the reference value of the brightness is corrected (black correction) with the black calibration at the above-mentioned black calibration part. 
     The actual authenticity judgment process is performed by obtaining the reference pixel data of the legitimate bill having been stored in advance in an ROM or the like, and the reflected light data of the reflected light and the transmitted light data of the light transmitted from the conveyed bill, a surface printing area of which the light emitting part (first light emitting part  80   a  and second light emitting part  81   b ) irradiates with light of a predetermined wavelength, and comparing these data with the pixel data having the appropriate brightness which has been corrected with the black calibration. 
     Here, a multi-feed judging part is provided in this embodiment, and the multi-feed judging part determines whether bills are conveyed in a double feed condition or not and whether the leading end portion is folded or not by comparing a density value for each pixel in the leading end portion of the bill having been read out by the line sensor with a density value for each reference pixel corresponding to the thus-read portion, in consideration that the line sensor can read out the entire width of the bill and the two-dimensional image can be acquired as the bill is conveyed. 
     Even if an environmental change or the like takes place as described above so that the brightness of the light received data of the bill having been read changes, it is possible to lower the probability for a multi-feed judging part to judge a bill in an appropriate condition erroneously as bills in a double feed condition by providing such multi-feed judging part since the above-described black calibration is implemented every time when the bill is inserted. 
     The bill housing part  100  which sequentially stacks and houses bills having been identified as being legitimate by the above-mentioned bill reading means  8  will be explained. 
     As shown in  FIGS. 3 to 5 , the main body frame  100 A constituting the bill housing part  100  is formed into a substantially rectangular parallelepiped (or cuboid) shape, and one end of bias means (e.g., bias spring)  106  is attached to an interior side of a front wall  102   a  thereof, and a placing plate  105  on which bills to be fed via the above-described receiving port  103  are sequentially stacked is provided to the other end thereof. Therefore, the placing plate  105  is in a state that it is pressed toward the presser plate  115 , which will be described later, by the bias means  106 . 
     In the main body frame  100 A, a press standby part  108  that keeps a dropping bill as it falls is provided so as to continuously communicate with the receiving port  103 . A pair of regulatory members  110  are disposed on both sides of the press standby part  108 , respectively, the regulatory members  110  extending in a vertical direction. An opening is formed between the pair of regulatory members  110  such that the presser plate  115  passes through the opening as bills are successively stacked onto the placing plate  105 . 
     Further, the presser plate  115  that presses toward the placing plate  105  a bill falling into the press standby part  108  from the receiving port  103  is installed in the main body frame  100 A. The presser plate  115  is formed in such a size that it may be capable of reciprocating through an opening formed between the pair of regulatory members  110 , and gets into the opening so as to be driven to reciprocate between a position where the bills are pressed against the placing plate  105  (a pressing position) and another position where the press standby part  108  is opened (an initial position). In this case, the bill passes through the opening as being flexibly bent in a pressing operation of the presser plate  115  and is then placed on the placing plate  105 . 
     The presser plate  115  is driven to reciprocate as described above via a presser plate driving mechanism  120  installed in the main body frame  100 A. The presser plate driving mechanism  120  comprises a pair of link members  115   a  and  115   b  having respective ends thereof supported pivotally by the presser plate  115  so as to allow the presser plate  115  to reciprocate in an arrow A direction in  FIGS. 3 and 4 , and these link members  115   a  and  115   b  are connected in a shape of letter “X”, and the other ends opposite to the respective ends are supported pivotally by a movable member  122  installed movably in a vertical direction (an arrow B direction). A rack is formed in the movable member  122 , and a pinion constituting the presser plate driving mechanism  120  is geared (engaged) with the rack. 
     As shown in  FIG. 4 , a housing part side gear train  124  constituting the presser plate driving mechanism  120  is connected to the pinion. For this case, as shown in  FIG. 4 , in this embodiment, a driving source (a motor  20 ) and a main body side gear train  21  sequentially engaged with the motor  20  are installed in the above-described apparatus main body  2 , and when the bill housing part  100  is mounted to the apparatus main body  2 , the main body side gear train  21  is to be connected to the housing part side gear train  124 . That is, the housing part side gear train  124  comprises a gear  124 B installed on the same axis of the pinion and gears  124 C,  124 D to be engaged sequentially with the gear  124 B, and when the bill housing part  100  is mounted to and demounted from the apparatus main body  2 , the gear  124 D is configured to be engaged with and disengaged from a final gear  21 A of the main body side train  21 . 
     As a result therefrom, the presser plate  115  is driven to reciprocate in the arrow A direction as the motor  20  installed in the apparatus main body  2  is driven to rotate so as to drive the main body side train  21  and in turn the presser plate driving mechanism  120  (the housing part side gear train  124 , the rack installed onto the movable member  122 , and the link members  115   a ,  115   b , etc.). 
     Conveyor members  150  which are capable of touching the bill conveyed-in from the receiving port  103  are installed in the main body frame  100 A. The conveyor members  150  take their own role to contact the bill conveyed-in so as to stably guide the bill to an appropriate position in the press standby part  108  (position where the bill can be stably pressed without causing the bill to be moved to the right or left side when the bill is pressed by the presser plate  115 ). In this embodiment, the conveyor members are constituted of belt-like members (hereafter called belts  150 ) installed so as to face the press standby part  108 . 
     In this case, the belts  150  are installed so as to extend along the conveying-in direction with respect to the bill, and are wrapped around the pair of pulleys  150 A and  150 B supported rotatably on both ends in the conveying-in direction. Further, the belts  150  contact a conveyor roller  150 C extending in an axis direction which is supported rotatably in the region of the receiving port  103 , and the belts  150  and the conveyor roller  150 C nip and hold the bill conveyed-in the receiving port  103  therebetween to guide the bill directly to the press standby part  108 . Moreover, in this embodiment, the pair of belts  150  are provided on the right and left sides, respectively, across the above-described presser plate  115  in order to be capable of contacting the surface on left and right sides of the bill. Here, the belts  150  may be prevented from loosening by not only being wrapped around the pulleys  150 A and  150 B at the both ends, but also causing tension pulleys to push the belts  150  at the intermediate positions, respectively. 
     The pair of belts  150  are configured to be driven by the motor  13  that drives the above-described plurality of conveyor rollers installed in the apparatus main body  2 . In detail, as shown in  FIG. 5 , the above-described driving belt  13 B driven by the motor  13  is wrapped around a pulley  13 D for the driving force transmission, and a gear train  153  installed at the end of the spindle of the pulley  150 A supported rotatably on the receiving port  103  side is engaged with a gear train  13 E for the power transmission sequentially installed onto the pulley  13 D. That is, when the bill housing part  100  is mounted to the apparatus main body  2 , an input gear of the gear train  153  is configured to be engaged with a final gear of the gear train  13 E, and the pair of belts  150  are configured to be driven to rotate in a synchronized manner with the above-described conveyor rollers  14 B,  15 B  16 B, and  17 B for conveying the bill by driving the motor  13  to rotate. 
     As described above, when the bill is inserted into the inside via the bill insertion slot  5 , the bill is moved inside the bill traveling route  3  by the bill conveyance mechanism  6 . The bill traveling route  3  is extended from the bill insertion slot  5  toward the back side, as shown in  FIG. 3 , and comprises a first traveling route  3 A and a second traveling route  3 B which is extended from the first traveling route  3 A toward downstream side and is inclined at a predetermined angle to the first traveling routes  3 A. 
     Further, a pull-out preventing member (shutter member)  170  that prevents the bill from being conveyed toward the bill insertion slot  5  is installed in the second traveling route  3 B. The pull-out preventing member  170  is biased to rotate in the arrow direction of  FIG. 3  (a direction in which the second traveling route  3 B is closed) via a spindle  170   a , and when the bill moves toward the side of the bill housing part  100 , the pull-out preventing member  170  is rotated so as to open the second traveling route against the biasing force, and when the bill once passes through the second traveling route, the pull-out preventing member  170  is rotated in the arrow direction to close the second traveling route  3 B. That is, when the rear end of the bill passes through the pull-out preventing member  170 , the second traveling route  3 B is closed by the pull-out preventing member  170 , not to allow the bill to be drawn out. 
     In addition, such pull-out preventing members may be installed at a plurality of places along the traveling route on the downstream side of the bill reading means  8 . Further, their installing positions may be on the side downstream from the position at which the bill is stopped at the time of carrying out the bill authenticity judgment process (an escrow position; a position on the downstream side by approximately 13 mm from the bill reading means  8  in this embodiment). 
     Next, control means  200  that controls the driving of the bill conveyance mechanism  6 , the bill reading means  8  and the like as mentioned above will be described with reference to a block diagram of  FIG. 6 . 
     The control means  200  as shown in a block diagram of  FIG. 6  comprises a control board  210  which controls the operations of the above-described respective drive units, and a CPU (Central Processing Unit)  220  controlling driving of each drive unit and constituting the bill identification means, a ROM (Read Only Memory)  222 , a RAM (Random Access Memory)  224 , and an authenticity judging part  230  are implemented on the control board  210 . 
     In the ROM  222 , permanent data such as various types of programs such as a multi-feed judging program for judging a double feed or a folded feed at a leading end portion of the bill; an authenticity judgment program by the authenticity judging part  230 , operation programs for the respective drive units such as the motor  13  for the bill conveyance mechanism, the motor  20  for the presser plate, the motor  40  for the skew correction mechanism, and the roller up-and-down motor  70  for lifting up and down rollers; and the like are stored. 
     The CPU  220  operates according to the programs stored in the ROM  222 , and carries out input and output of the signals with respect to the respective drive units described above via an I/O port  240 , so as to perform the entire operational control of the bill processing apparatus. That is, the motor  13  for the bill conveyance mechanism, the motor  20  for the presser plate, the motor  40  for the skew correction mechanism, and the roller up-and-down motor  70  are connected to the CPU  220  via the I/O port  240 , and the operations of these drive units are controlled by control signals transmitted from the CPU  220  in accordance with the operation programs stored in the ROM  222 . Further, the CPU  220  is so configured that detection signals from the insertion detecting sensor  7 , the movable piece passage detecting sensor  12 , and the base part detecting sensor  18  are input into the CPU  220  via the I/O port  240 , and the driving of the respective drive units is controlled based on these detection signals. 
     Moreover, the CPU  220  is so configured that a detection signal based on the transmitted light and the reflected light of the light which is irradiated to the bill as the identification object is input into the CPU  220  via the I/O port  240  from the light receiving part  81   a  in the bill reading means  8  as described. The first light emitting part  80   a  and the second light emitting parts  81   b  in the bill reading means  8  are controlled through a light emission control circuit  260  by a control signal from the CPU  220  in accordance with the operation programs stored in the abovementioned ROM  222  such that the lighting interval and the turning-off are controlled. 
     Further, a detection signal which is transmitted from the light receiving part  81   a  in the above-mentioned bill reading means  8  in a condition that the emission from the light emitting part (first light emitting part  80   a  and second light emitting part  81   b ) is made to be ineffective as the black calibration, which will be described later, is performed is input into the CPU  220  via the I/O port  240 , and, that is, the detection signal is to be input as the light is received from the traveling route in a condition that no emission of the light emitting part is made for the sake of convenience. 
     The RAM  224  temporarily stores data and programs used for the CPU  220  to operate, and also acquires and temporarily stores the received light data (image data constituted of a plurality of pixels) of the bill serving as the identification object. 
     The above-mentioned authenticity judging part  230  has a function to judge whether the conveyed bill is legitimate or not, and whether the conveyed bill is in a condition that the leading end thereof is folded or whether the conveyed bill is in a double feed condition. The authenticity judgment processing part  230  comprises: a converter  231  which converts the received light data of the identification object stored in the RAM  224  into pixel information containing color information having brightness (density value) for each pixel, an image data processing part  232  which acquires image data based on the pixel information converted by the converter  231 , and a black calibration part  233  which conducts a black calibration before starting to read the bill, which has been inserted from the bill insertion slot  5 . 
     At the black calibration part  233 , the black calibration is implemented by acquiring a detection signal from the light receiving part  81   a  in a state that the light emission from the light emitting part (first light emitting part  80   a  and second light emitting part  81   b ) is made to be ineffective, for example, while the light emitting part is controlled to be turned off by a light emission control circuit  260 . Thus, the reference value for the lowest brightness is set with respect to the brightness of the light received by the light receiving part  81   a  at every time of the bill reading processing. 
     Further, the bill determination processing part  230  comprises: a reference data storage part  234  in which the reference data of the legitimate bill (pixel data of the legitimate bill) is stored, and a comparison judgment part  235  which compares the image data (pixel data) of the bill having been corrected in the image data processing part  232  with the reference data (reference pixel data) stored in the reference data storage part  234 , and carries out the determination process to determine whether the bill being conveyed is legitimate or not. 
     In this case, the reference data storage part  234  stores image data about the legitimate bill to be used, when the above-mentioned authenticity judgment process is carried out, and, in addition thereto, various kinds of reference data for respective kinds of bills to be utilized in the authenticity judgment, for example, reference values and the like of the printing length of the legitimate bill. Here, data which can be the reference data is stored in the dedicated reference data storage part  234 . However, the data may be stored in the above-mentioned ROM  222 . 
     Moreover, the comparison judgment part  235  comprises a multi-feed judging part  236  which compares a density value per a pixel in the leading end portion of the bill having been read by the light emitting part  81   a  with a density value (density value stored in the reference data storage part  234 ) per a pixel as a unit corresponding to each portion having been read, and determines whether the bill is conveyed in a folded condition at the bill leading portion or not and whether bills are conveyed in a double feed conditions or not. 
     The actual authenticity judgment process in the above-mentioned authenticity judgment processing part  230  is performed by irradiating a printing area on the surface of the bill being conveyed with light of a predetermined wavelength from the light emitting part (first light emitting part  80   a  and second light emitting part  81   b ), converting the reflected light data of the light reflected and the transmitted light data of the light transmitted from the bill into a plurality of pixel data having the brightness data per a predetermined size as the unit in the converter  231 , and comparing such data with the reference pixel data of the legitimate bill stored in advance with the reference data storage part  234 . In this case, with respect to individual brightness in a plurality of pixel data converted by the converter  231 , it is possible to lower the probability to judge erroneously the legitimate bill as the fake one when the comparison judgment is implemented since the correction is made on the basis of reference value having been set to the appropriate brightness by the black calibration part  233 . 
     That is, with respect to image data (a plurality of pixel data including brightness information) acquired by the image data processing part  232 , a reference value of the brightness is corrected (black calibration) by the black calibration part  233  before a reading process of the image data is performed, and the image data based on the reference value subject to the black calibration is used for the authenticity judgment process. Therefore, even if the acquired image data of the bill come to represent darker as the output from the light receiving part  81   a  serving as a light receiving sensor becomes weaker because of some factors such as an environmental temperature rise, for example, during the operation of the device, it is possible to conduct the authenticity judgment process appropriately since the reference value of the brightness of the light receiving part is corrected in accordance with such factors. 
     Next, the bill processing operation in the bill processing apparatus  1  executed by the control means  200  will be described according to the flowcharts of  FIGS. 7 to 13 . 
     When an operator inserts a bill into the bill insertion slot  5 , the conveyor roller pair ( 14 A and  1413 ) installed in the vicinity of the bill insertion slot is in a state that the rollers are spaced from each other in an initial stage (refer to ST 18  and ST 58  to be described later). Further, with respect to the presser plate  115 , the pair of link members  115   a  and  115   b  driving the presser plate  115  are located at the press standby part  108 , and the presser plate  115  is positioned in the standby position such that the bill cannot be conveyed-in the press standby part  108  from the receiving port  103  by the pair of link members  115   a  and  115   b . That is, in this state, the presser plate  115  is brought into the opening formed between the pair of regulatory members  110  such that the condition is so made as to prevent the bills stored in the bill housing part from being drawn out through the opening. 
     Moreover, the pair of movable pieces  10 A constituting the skew correction mechanism  10  located on the downstream side of the conveyor roller pair ( 14 A,  14 B) are in a state that the pair of movable pieces  10 A are moved to leave the minimum open width therebetween (for example, an interval between the pair of movable pieces  10 A is 52 mm; refer to ST 17  and ST 59  to be described later) so as to prevent the bill from being drawn out in the initial stage. 
     In the initial state of the above-described pair of conveyor rollers ( 14 A and  14 B), it is possible for the operator to easily insert even a bill having wrinkles into the paper sheet insertion slot  5 . Then, when an insertion of the bill is detected by the insertion detecting sensor  7  (ST 01 ), a black calibration process is conducted (ST 02 ) as a detection signal from the light receiving part  81   a  is acquired in a condition that the emission of the light emitting parts  80   a ,  81   b  is made to be ineffective. Here, as to the timing to implement the black calibration process, it may be implemented before the bill reading process is conducted by a line sensor as described later. 
     The driving motor  20  of the presser plate  115  as described above is driven to rotate reversely by a predetermine amount (ST 03 ) to move the presser plate  115  to the initial position. That is, the presser plate  115  is in a state that the presser plate  115  is moved and remains in the opening formed between the pair of regulatory members  110  such that it is so arranged that the bill cannot pass through the opening until the insertion of another bill is detected by the insertion detecting sensor  7 . 
     When the presser plate  115  is moved from the standby position to the initial position, the press standby part  108  becomes in an open state (refer to  FIG. 4 ) such that the apparatus is in a state that the bill can be conveyed into the bill housing part  100 . That is, by driving the motor  20  to rotate reversely for a predetermined amount, the presser plate  115  is moved from the standby position to the initial position via the main body side gear train  21  and the presser plate driving mechanism  120  (the housing part side gear train  124 , the rack formed on the movable member  122 , and the link members  115   a ,  115   b ). 
     Further, the above-described roller up-and-down motor  70  is driven to move the upper conveyor roller  14 A so as to make a contact with the lower conveyor roller  14 B. In accordance therewith, the inserted bill is nipped and held therebetween by the pair of conveyor rollers ( 14 A and  14 B) (ST 04 ). 
     Next, a traveling route opening process is conducted (ST 05 ). The opening process is conducted by driving the pair of movable pieces  10 A to move in separating directions so as to become apart with each other as the motor  40  for the skew correction mechanism is driven to rotate reversely as shown in the flow chart of  FIG. 10  (ST 100 ). At this time, when it is detected that the pair of movable pieces  10 A have moved to the predetermined positions (the maximum open width positions) by the movable piece detecting sensor (ST 101 ), the driving operation to rotate the motor  40  reversely is stopped (ST 102 ). This traveling route opening process makes the skew correction mechanism in such a condition as to allow the paper sheet to enter between the pair of movable pieces  10 A. Here, in the previous step of ST 05 , the bill traveling route  3  is in a closed state by a traveling route closing process (ST 17 , ST 59 ) to be described later. Thus, the bill traveling route  3  is closed in this way before an insertion of the bill so as to prevent an element such as a line sensor from being broken by, for example, inserting a plate-like member from the bill insertion slot for illicit purposes or the like. 
     Next, the bill conveyor motor  13  is driven to rotate normally (ST 06 ). The bill is conveyed into the inside of the apparatus by the conveyor roller pair ( 14 A and  14 B), and when the movable piece passage detecting sensor  12  installed on the downstream side from the skew correction mechanism  10  detects the leading end of the bill, the bill conveyor motor  13  is stopped (ST 07  and ST 08 ). At this time, the bill is located between the pair of movable pieces  10 A constituting the skew correction mechanism  10 . 
     Subsequently, the above-described roller up-and-down motor  70  is driven to allow the conveyor roller pair ( 14 A and  14 B) holding the bill therebetween to become apart from each other (ST 09 ). At this time, the bill is in a state that no load is applied. 
     Then, a skew correction operating process is executed as the bill remains in this state (ST 10 ). The skew correction operating process is conducted by driving the motor  40  for the skew correction mechanism to rotate normally to drive the pair of movable pieces  10 A to get closer with each other. That is, in this skew correction operating process, as shown in the flowchart of  FIG. 11 , the motor  40  described above is driven to rotate normally to move the pair of movable pieces  10 A in respective directions such that the pair of movable pieces  10 A get closer with each other (ST 110 ). The movement of the movable pieces is continued until the distance therebetween becomes the minimum width (for example; width of 62 mm) of the bill registered in the reference data storage part in the control means. And the skew is corrected by the movable pieces  10 A touching both sides of the bill such that the bill may be positioned at the accurate center position. 
     When the skew correction operating process as described above is completed, a traveling route opening process is subsequently executed (ST 11 ). This process is conducted by moving the pair of movable pieces  10 A in separating directions as the above-described motor  40  for the skew correction mechanism is driven to rotate reversely (refer to ST 100  to ST 102  of  FIG. 10 ). 
     Next, the above-described roller up-and-down motor  70  is driven to move the upper conveyor roller  14 A to contact the lower conveyor roller  14 B, and the bill is nipped and held between the pair of conveyor rollers ( 14 A and  14 B) (ST 12 ). Thereafter, the bill conveyor motor  13  is driven to rotate normally to convey the bill into the inside of the apparatus, and when the bill passes through the bill reading means  8 , a reading process of the bill is executed (ST 13  and ST 14 ). 
     Along with the beginning of the bill reading process, a multi-feed judgment process of the bill is executed by the multi-feed judging part  236  (ST 14 ). The multi-feed judgment process, as shown in the flow chart of  FIG. 13 , is to judge whether the bill is first read for a predetermined distance (ST 150 ), and when the reading process for the predetermined distance is completed, the total density value of the pixel by the transmissive light is calculated (ST 151 ). Here, the calculated density value is corrected with respect to the brightness based on the reference value set in the above-mentioned black calibration process (ST 02 ). 
     Then, the authenticity judgment processing part  230  of the control means  200  compares the total density value of the pixel data acquired in the leading end area of the bill with the density value of the reference data in the same area stored in the reference data storage part  234 , and conducts a determining process whether the bill is conveyed in a double feed condition (whether the leading end portion is folded or not) based on a predetermined threshold (ST 152 ). 
     When an output value from the light receiving part  81   a  is lowered because of some factors such as an environmental temperature change or the like during implementation of the determining process, it is typically possible to judge erroneously that the bill is conveyed in a double feed condition because the brightness of the image is lowered although the bill is inserted in an appropriate condition. However, it is possible to implement an accurate multi-feed judgment since the output value from the light receiving part  81   a  is corrected to an appropriate level through the above-mentioned black calibration process. 
     When it is determined that the bill is conveyed in a multi-feed condition in this ST 152  processing, the CPU  220  drives the bill conveyor motor  13  to rotate reversely so as to discharge the bill immediately from the bill insertion slot  5  (ST 152 : No, ST 53  to ST 55 ). That is, when it is determined that the bill is conveyed in the multi-feed condition in the process of ST 152  before the completion of the bill reading process, the bill is immediately conveyed back without carrying out the subsequent bill reading process so as to be discharged from the bill insertion slot  5 , and the series of processes for the bill is completed (ST 53  to ST 60 ). 
     Then, in the case where it is determined that the bill is not conveyed in the multi-feed condition in the above-mentioned determining process (ST 152 ), the bill reading process is continued as it is conveyed (ST 16 ). 
     Then, when the bill being conveyed passes through the bill reading means  8 , and the trailing end of the bill is detected by the movable piece passage detecting sensor  12  (ST 16 ), a process for closing the bill traveling route  3  is executed (ST 17 ). In this process, first, as shown in the flowchart of  FIG. 12 , after the trailing end of the bill is detected by the movable piece detecting sensor  12 , the above-described motor  40  is driven to normally rotate to move the pair of movable pieces  10 A in the directions that they get closer to each other (ST 130 ). Next, when it is detected by the movable piece detecting sensor that the movable pieces  10 A move to the predetermined positions (minimum open width positions: for example, width of 52 mm) (ST 131 ), the driving operation of the normal rotation of the motor  40  is stopped (ST 132 ). 
     With this traveling route closing process, the pair of movable pieces  10 A are moved to the positions of the minimum open width (width of 52 mm) narrower than the width of any bill allowed to be inserted, thereby effectively preventing the bill from being drawn out. That is, by executing such a bill traveling route closing process, an opening distance between the movable pieces  10 A is made shorter than the width of the inserted bill, thereby enabling the effective prevention of an action of drawing-out the bill in the direction toward the insertion slot by the operator for illicit purposes. 
     In succession to the traveling route closing process described above (ST 17 ), a conveyor roller pair spacing process in which the driving source  70  is driven to allow the conveyor roller pair ( 14 A and  14 B) coming to hold the paper sheet therebetween to be spaced from one another is executed (ST 18 ). By executing the conveyor roller pair spacing process, even if the operator additionally inserts (double insertion) another bill by mistake, the bill is not subject to a feeding operation by the conveyor roller pair ( 14 A and  14 B) and hits front ends of the pair of movable pieces  10 A in a closed state according to ST 17  such that it is possible to reliably prevent the operation of bill double-insertion. 
     Along with the bill traveling route closing process as mentioned above, when the bill reading means  8  reads the data up to the trailing end of the bill, the bill conveyor motor  13  is driven for a predetermined amount and stops the bill in a predetermined position (an escrow position; a position where the bill is conveyed toward the downstream by 13 mm from the center position of the bill reading means  8 ), and at this time, an authenticity judgment process of the bill is executed in the comparison judgment part  234  by referring to the reference data stored in the reference data storage part  233  in the authenticity judgment processing part  230  of the above-mentioned control means  200  (ST 19  to ST 22 ). 
     In the bill authenticity judgment process at ST 21  as described above, when the bill is judged as a legitimate bill (ST 23 ; Yes), the motor  13  for the bill conveyance is rotated normally (ST 24 ). While the bill is conveyed, the bill conveyor motor  13  is driven to rotate normally until the trailing end of the bill is detected by the discharge detecting sensor  18  (ST 25 ), and after the trailing end of the bill is detected by the discharge detecting sensor  18 , the bill conveyor motor  13  is driven to rotate normally for a predetermined amount (ST 26  and ST 27 ). 
     The process for driving the bill conveyor motor  13  to rotate normally in ST 26  and ST 27  corresponds to a driving amount for which the bill is conveyed in the receiving port  103  of the bill housing part  100  from the discharge slot  3   a  on the downstream side of the bill traveling route  3  of the apparatus main body  2  so that the pair of belts  150  contact the surface on both sides of the conveyed-in bill to guide the bill stably to the press standby part  108 . That is, by further driving the bill conveyor motor  13  to rotate normally for a predetermined amount after the trailing end of the bill is detected by the discharge detecting sensor  18 , the pair of belts  150  contact the bill conveyed-in and are driven in the bill feeding direction so as to guide the bill in a stable state to the press standby part  108 . 
     Then, after the above-described bill conveyor motor  13  is stopped, the process for driving the presser plate  115  is executed (ST 28 ) such that the bill is placed on the placing plate  105 . And, after the pressing process is completed, the presser plate  115  is again moved to the standby position and stopped to the position. 
     Further, in the above-mentioned process of ST 23 , when the bill is judged as a non-legitimate bill, a traveling route opening process is executed (ST 51 , refer to ST 100  to ST 102  of  FIG. 10 ). After that, the bill conveyor motor  13  is driven to rotate reversely and the conveyor roller pair ( 14 A,  14 B) are brought into a contact with each other such that the bill waiting at the escrow position is conveyed toward the bill insertion slot  5  (ST 52  and ST 53 ). 
     Further, with the configuration of this embodiment, even when it is judged that the read bill is not the legitimate bill, the bill is not immediately discharged out of the apparatus, but a reading process is repeated for a predetermined number of times (three times) as shown in the following steps. 
     That is, when the bill is conveyed toward the bill insertion slot  5  in ST 53  as described above, and the insertion detecting sensor  7  detects the trailing end of the bill to be returned toward the bill insertion slot  5 , the driving to reversely rotate the bill conveyor motor  13  is stopped (ST 54 , ST 55 ). At this time, when it is not determined that the bill is conveyed in a multi-feed condition in the above-mentioned bill multi-feed judging process (ST 56 , No), it is judged whether or not the bill authenticity judgment process has been carried out for three times (ST 57 ), and when the bill authenticity judgment process has not been carried out for three times (ST 57 , No), the above-mentioned processes in the step of ST 06  and subsequent steps thereof are performed (This re-try process is repeated twice). Further, when the bill authenticity judgment process has been carried out for three times (ST 57 , Yes), the bill authenticity judgment process is no longer carried out, and a discharge process thereof is performed. 
     This discharge process is executed by driving the roller up-and-down motor  70  to allow the conveyor roller pair ( 14 A and  14 B) holding the bill therebetween in the ST 52  to become apart from each other (ST 58 ). And, after that, the traveling route closing process is executed (refer to ST 59 , and ST 130  to ST 132  in  FIG. 12 ) and the driving motor  20  for the presser plate  115  is driven to rotate normally for a predetermined amount (ST 60 ) such that the presser plate  115  positioned in the initial position is driven to move to the standby position, and then a series of processes is completed. 
     In addition, as described above, a discharge process for the bill having been determined to be conveyed in the multi-feed condition is executed such that the bill is discharged immediately from the bill insertion slot  5  (ST 53  to ST 55 ) by reversely rotating the bill conveyor motor  13  during reading motion, and then the discharge process is performed without carrying out the bill reading processes for three times in total in ST 57  (ST 56 ; Yes), and then the series of processes are to be completed (ST 58  to ST 60 ). 
       FIGS. 14 and 15  are image diagrams illustrating an image M of a bill to be read with the bill reading processing apparatus  1  of the embodiment as described above. In practice, the range that the bill processing apparatus  1  reads is limited to a portion necessary for an authenticity identification of the bill or other objectives. Here, however, the image M to be obtained is schematically shown if the even whole bill is read.  FIG. 14  shows the image M (schematic view) of the bill based on image data in the case where the black calibration is appropriately implemented in the embodiment as described above. On the other hand,  FIG. 15  shows the image M (schematic view) of the bill based on image data in the case where the black calibration is not appropriately implemented. As being apparent from these figures, when the black calibration is insufficient, the contrast of the image data deteriorates. That is, in the case where a temperature is increased because the frequency of use is increased from when an environmental temperature of the bill processing apparatus  1  is low, or in the case where an environment facility such as an air conditioner or the like is not sufficiently effective such that the temperature is increased, the black calibration only in the initial stage is not sufficient such that the contrast may be lowered as shown in  FIG. 15 . 
       FIG. 16  shows schematically a case where the leading end of the bill M is bent to cause an overlapped portion. The leading end M 1  of the bill M is bent along a bent line M 3  so that an overlapped portion M 2  is caused, and a main body M 4  and a trailing end M 5  follow sequentially. Therefore, intensity of the transmitted light through the overlapped portion M 2  is lowered to be approximately one half as compared to a normal or non-overlapped bill. Accordingly, density values in this portion become large (dark) as compared to an ordinary portion. Thus, through the multi-feed determination process, it can be determined that bill conveyance in a double feed condition is caused. In this way, an abnormal state of the bill can be detected in an early stage by such an overlapped portion caused in the leading end portion such that a prompt processing can be performed. Since such a bent paper sheet may lead to an erroneous authenticity judgment as well as a paper jam, it is preferable to eject the bent paper sheet in an early stage. Moreover,  FIG. 17  shows schematically a case where two bills M and MM overlap with each other. The bill M overlaps with the bill MM in an area M 6  and the intensity of the transmitted light therethrough is reduced to about one half. Accordingly, density values in this portion become large (dark) as compared to a normal portion. Thus, it can be determined through the multi-feed determining process that the conveyance in the double feed is caused. It is preferable to implement the multi-feed multi-feed judging process ST 15  of  FIG. 8  while the bill M is being conveyed in order to improve the processing rate. It is possible to implement the judgment during conveyance of the bill since the judgment criterion is rather simple as compared to the case of the authenticity judgment. 
       FIG. 18  is a perspective view showing a state that an open/close member is opened for a main body frame of an apparatus main body. The apparatus main body  2  is basically identical to that shown in  FIG. 2 . This embodiment differs from the latter in that blackout curtain members  82  are disposed in front of and in back of the bill reading means along the traveling direction, the bill reading means including a light emitting unit  80  having a first light emitting part  80   a  and a light receiving/emitting unit  81  disposed on the main frame  2 A side. As shown in  FIG. 19 , this blackout curtain member  82  includes a blackout curtain member main body  82   a  and a blackout curtain  82   b . The blackout curtain members  82  are disposed at front and back positions in the traveling direction, and the blackout curtain  82   b  serves to shield the light leaking from a gap in the traveling direction in the black calibration processing ST 02 . When the black calibration processing ST 02  is completed, the blackout curtain  82   b  is wound into the blackout curtain member main body  82   a , and is controlled so as not to prevent the conveyance operation of the bill. The blackout curtain member main body  82   a  comprises a blackout curtain winding drive device capable of receiving a control signal from CPU  220 . 
     In accordance with the paper sheet processing apparatus with the concrete configuration as described above, since the black calibration is implemented at every time before a bill is inserted so that an authenticity judgment processing is carried out, even if the environmental change such as a temperature change and the like during the operation of the apparatus is caused such that the properties of the light receiving sensor are changed, it is possible to perform an accurate authenticity judgment processing. 
     Moreover, the apparatus may includes a multi-feed judging part which judges whether the paper sheet having been inserted into the insertion slot is in an overlapped condition or not based on a comparison result of brightness of the converted plural pixel data and a predestined brightness after setting of the reference value is executed. 
     In accordance with the paper sheet processing apparatus with the concrete configuration as described above, judgment whether or not a paper sheet or paper sheets are conveyed in a multi-feed condition (including a state where a plurality of paper sheets are inserted and overlapped, and a state where the bill is bent to cause an overlapped portion) can be implemented by the multi-feed judging part. In this case, even if the environmental change is caused so that the brightness of the light received data of the paper sheet having been read is changed, since the above-mentioned black calibration is implemented therebefore, it is possible to lower the probability that the paper sheet in an appropriate insertion condition may be erroneously judged as being in the multi-feed condition. 
     Moreover, the paper sheet processing apparatus comprises: an insertion slot into which a paper sheet is inserted; a sensor which detects insertion of the paper sheet with respect to the insertion slot; a traveling route along which the paper sheet inserted into the insertion slot is conveyed; a light emitting part which irradiates the traveling route with light; a light receiving part which receives light from the traveling route; a conveyance mechanism which conveys the paper sheet along the traveling route so that transmitted light and/or reflected light from the paper sheet which the light emitting part irradiates with light is received by the light receiving part; a storage part in which data can be stored; and a processor for controlling the above-mentioned components, wherein the processor is operative to receive, from the sensor, a detection signal indicating that it is detected that the paper sheet has been inserted into the insertion slot; to make the light emitting part to be ineffective; to allow the light receiving part having received light from the traveling route to transmit a light received signal therefrom in a state where the light emitting part is made to be ineffective; to set a reference value for the lowest brightness based on the light received signal; to allow the storage section to store the reference value thus set; to allow the conveyance mechanism to convey the paper sheet along the traveling route; to allow the light emitting part to irradiate the traveling paper sheet with light; to convert light received by the light receiving part into a plurality of pixel data of a predetermined size as a unit including color information having brightness; to store the pixel data thus obtained into the storage part; to compare, based on a reference value having been set by the black calibration part, the plurality of pixel data thus stored with reference pixel data of a legitimate paper sheet; to allow the storage part to record a comparison result thus obtained, thereby making it possible to judge the authenticity of the paper sheet. 
     Here, the above-described conveyance mechanism may include, e.g., conveyor rollers or conveyor roller pairs ( 14 A,  14 B), ( 15 A,  15 B), ( 16 A,  16 B) and ( 17 A,  17 B). Moreover, such a conveyance mechanism may include a motor  13  serving as a driving source and the like and/or pulley or belt and the like as drive force transmission means for allowing such components to interlock with each other. In addition, the above-described storage part may include a reference data storage part  234 , or a so-called memory except therefor. Then, the above-described processor may include the CPU  220 . Further, the processor may include other processors. Further, making the light emitting part to be ineffective may include controlling and turning off the above-described light emitting part (e.g., first light emitting part  80   a  and second light emitting part  81   b ), preventing the emitted light from reaching the above-mentioned light receiving part, or the like. In addition, e.g., the detection signal from the light receiving part  81   a  may be converted into pixel information so as to set such pixel information as reference brightness (reference value) and store the same. In accordance with the configuration as described above, the black calibration can be made at every time when the paper sheet is inserted. Thus, it is possible to obtain more accurate measured values with each correction for each time. 
     Moreover, in the above-described paper sheet processing apparatus, the processor can judge whether the bill having been inserted into the insertion slot is in an overlapped condition or not based on a comparison result of the predetermined brightness and the brightness of the plurality of pixel data having stored after setting of the reference value is executed. 
     Moreover, in the paper sheet processing method utilizing the paper sheet apparatus as described above, the method comprises: receiving, from the sensor, a detection signal indicating that the paper sheet has been inserted into the insertion slot; making the light emitting part to be ineffective based on the detection signal thus received; allowing the light receiving part having been received light from the traveling route to transmit a light receive signal therefrom in the state where the light emitting part is made to be ineffective; setting a reference value of the lowest brightness based on the light received signal; allowing the storage part to record the reference value thus set; allowing the light emitting part to irradiate the traveling paper sheet with light while the paper sheet is conveyed along the traveling route by the conveyance mechanism; converting light received by the light receiving part into a plurality of pixel data of a predetermined size as a unit including color information having brightness; and storing such pixel data thus obtained in the storage part. Further, the stored plural pixel data and reference pixel data of the legitimate paper sheet may be compared with each other based on the reference value having been set by the black calibration part. 
     Moreover, the conveyance mechanism may be controlled to discharge the paper sheet when the processor judges that the paper sheet is in an overlapped condition by determining whether the paper sheet having been inserted into the insertion slot is in as state that the paper sheet is in an overlapped condition or not based on a comparison result between the predetermined brightness and the brightness of the plurality of pixel data having been stored after setting of the reference value is executed. 
     In accordance with the paper sheet processing apparatus with the concrete configuration as described above, since the black calibration is executed with respect to the brightness of the light detected by light receiving part  81   a  which receives detection light from the bill at every time before the bill is inserted so that the authenticity judgment processing is performed, even if an environmental change such as a temperature change or the like, for example, happens during the operation of the apparatus such that the property of the light receiving part  81   a  is changed, it is possible to perform an accurate authenticity judgment processing. 
     In addition, a multi-feed judging part is provided in this embodiment, and the multi-feed judging part determines whether bills are conveyed in a double feed condition or not and whether the leading end portion is folded or not by comparing a density value for each pixel in the leading end portion of the bill having been read out by the line sensor with a density value for each reference pixel corresponding to the thus-read portion, in consideration that the line sensor can read out the entire width of the bill and the two-dimensional image can be acquired as the bill is conveyed. 
     By providing such a multi-feed judging part, even if the environmental change and the like occurs as described above such that the brightness of the light received data of the bill having been read is lowered, it is possible to lower the probability to judge erroneously the bill in an appropriate insertion condition as in a double feed condition since the above-mentioned black calibration is performed at every time when the bill is inserted. 
     As described above, the paper sheet processing apparatus may be provided with which the authenticity judgment process of the paper sheet may be performed accurately even if the environmental change occurs. 
     As mentioned above, the embodiment of the present invention is described. However, the present invention is not limited to the above-described embodiments, and various modifications of the present invention can be implemented. 
     The present invention is characterized in that the black calibration processing of the light receiving part constituting the bill reading means is performed at every time when the bill is inserted and the reading process is executed, and the other configuration is not limited to the above-described embodiments, but various modifications may be made to. For example, a configuration, arrangement, and the like of the bill reading mean  8  may be modified as appropriate. Further, the timing at which the black calibration is performed may also be changed as an occasion demands. 
     The present invention can be applied not only to the bill processing apparatus, but also to a device which provides various kinds of products and services when the paper sheet such as a service ticket and a coupon ticket, for example, is inserted. In particular, in accordance with the configuration of the present invention, in the paper sheet processing apparatus in which the authenticity judgment processing of a service ticket on which a bar code is printed or the like is executed, it is possible to prevent the judgment accuracy of the authenticity from lowering.