JP5537473B2 - Optical line sensor device and method for identifying valuable paper - Google Patents

Description

  The present invention relates to an optical line sensor device, and more particularly to a discrimination optical line sensor device for the purpose of differentiating securities, banknotes, credit cards, etc. (referred to as valuable paper or medium).

  With recent remarkable improvements in printing and copying technologies, counterfeiting of banknotes, securities, credit cards, etc. has become increasingly sophisticated, and the social order is maintained by accurately identifying and eliminating these counterfeits. Because it is important. In particular, in a device that handles banknotes such as ATMs and banknote processors, there is a strong demand for a higher-speed and higher-performance discrimination system for authenticity determination purposes.

As a method for discriminating these bills and securities, pattern identification using an optical line sensor device has been used for some time.
The optical line sensor device includes a reduction optical line sensor device combining a reduction lens, a mirror, and a CCD, and a contact type optical line sensor device using an equal magnification optical system such as a selfoc lens, and the reduction optical system is a system. The unit price is low, the resolution can be easily adjusted, and the focal depth is deep. However, there are disadvantages that the volume of the sensor is large and that there are many troubles due to dust and foreign matter. Therefore, a contact type optical line sensor device that is easy to maintain has been widely used recently.

On the other hand, for the purpose of preventing counterfeiting, ink, fibers, threads, and the like that emit fluorescence when irradiated with ultraviolet light have been embedded in predetermined portions of the valuable paper as marks for determining authenticity.
Therefore, in devices that handle valuable paper such as ATMs and banknote processors, it has been desired to install an optical line sensor device using ultraviolet light as a light source for a discrimination sensor used in the device. There is an expectation that the authenticity judgment ability will be further improved by irradiating the object with ultraviolet light and making fluorescent substances contained in the ink, paper, and constituent materials of the printed matter fluoresce and detecting the weak output and wavelength. Because.

This ultraviolet optical line sensor device emits ultraviolet light from the mounted ultraviolet light source and irradiates the target medium, so that fluorescent components such as ink contained in the target medium are excited by the ultraviolet light and visible. In addition, fluorescence of infrared light is emitted, and light detection signals are collected at the light receiving unit to form image data, and authenticity determination is performed based on this.
Cold cathode tubes, halogen lamps, ultraviolet LED light sources, etc. can be used as the light source of the ultraviolet optical line sensor device, but recently, gallium nitride LEDs with less visible light components and improved luminance are preferred. Has been.

A line CCD element, a sensor IC with a built-in sensor part, an amorphous silicon element, or the like is used as the line sensor that constitutes the light receiving part of the ultraviolet optical line sensor device.
Patent Document 2 below discloses a fluorescent sensor including an optical filter that transmits only an ultraviolet component (for example, about 300 to 400 nm) of light emitted from an ultraviolet light source.
Patent Document 3 below discloses a fluorescence sensor in which an ultraviolet light cut filter that removes an ultraviolet component of light reflected from the surface of valuable paper is disposed in a light receiving element.

Japanese Patent Laid-Open No. 2002-230618 JP 2004-265208 A JP 2004-265104 A

In a line sensor using an ultraviolet LED light source, the fluorescence output emitted by ultraviolet light irradiation from ink such as numbers and patterns printed on valuable paper is extremely weak, and in the combination of the light source and the light receiving unit In some cases, sufficient detection sensitivity as a sensor cannot be secured.
For example, when the valuable paper surface is irradiated with ultraviolet light, the fluorescent material contained in the paper base material itself of the valuable paper surface may emit blue (400 to 450 nm) visible fluorescent light. Due to this blue light, there is a phenomenon in which red and green fluorescence emitted from patterns such as numbers printed on valuable paper is buried.

  That is, when the relationship between the ultraviolet light wavelength of the ultraviolet light LED light source and the fluorescence characteristics of the ink such as numbers and patterns printed on valuable paper is examined in detail, the ultraviolet light component close to visible light is more valuable than the fluorescence of the ink. The paper substrate itself of the securities becomes a factor of fluorescence. The fluorescence from the paper substrate itself hinders the target ink detection ability. Therefore, to increase the detection sensitivity, it is effective to select the peak wavelength of the ultraviolet LED light source and to cut the long wavelength ultraviolet light component among the fluorescent components.

When attention is paid to the light emission side, the light emitted from the ultraviolet LED light source may include a weak long wavelength component of ultraviolet light or a short wavelength component of visible light. There is a phenomenon in which the output covers red and green fluorescence emitted from ink such as numbers and patterns printed on valuable paper.
Furthermore, in order to ensure the long-term reliability of the ultraviolet LED light source, as shown in FIG. 8, a low-cost aluminum oxide / ceramic sintered body 52 with little ultraviolet light deterioration is adopted as the mounting case of the LED element 54. In addition, an ultraviolet LED light source mounting product 50 that can withstand long-term operation with high reliability has been developed.

In FIG. 8, “53” indicates an encapsulating resin. FIG. 9 is a perspective view showing a state in which the ultraviolet LED light source mounted product 50 is mounted on the substrate 51.
Actually, however, faint fluorescence (indicated by broken-line arrows in FIG. 8) near the wavelength of 690 nm was confirmed from the ultraviolet LED light source mounted product 50 employing this aluminum oxide / ceramic sintered body 52 when irradiated with ultraviolet light. As a result of investigating the cause of the light emission, the light emitted from the LED element 54 is emitted from the region directly irradiated, and from the light emission wavelength, chromium (which forms a ruby component), which is an impurity of aluminum oxide, may be the cause. is assumed. It has been found that the fluorescence around 690 nm is emitted from the ultraviolet LED light source.

Some of the phenomena described above reduce the contrast of the fluorescence output of the component part in which the fluorescent material on the valuable paper is incorporated, and hinder the detection ability as a sensor.
Therefore, the conventional technology described above has insufficient performance as a wavelength filter applied to ultraviolet light irradiated from an ultraviolet light source and a wavelength filter applied to visible light incident on a light receiving element.

  Accordingly, the present invention provides an optical line sensor device capable of ensuring a precise authenticity judgment function of valuable paper surface and a valuable paper surface discrimination method in an optical line sensor device that detects a fluorescent component such as valuable paper surface using an ultraviolet light source. The purpose is to do.

  The present inventor examined the fluorescence output of the valuable paper surface by the light receiving sensor, and the fluorescence spectrum from the fluorescent material contained in the base material itself of the valuable paper surface is concentrated in the vicinity of the wavelength of 400 to 450 nm. Further, it has been found that the detection sensitivity is further improved by shielding the light output of 410 nm or less, preferably 420 nm or less, more preferably 450 nm or less, from the fluorescence output of valuable paper. Moreover, by cutting not only the visible light component of wavelength 400nm to 700nm of the ultraviolet light source but also the ultraviolet light component of wavelength 385nm or more, the fluorescence amount of the paper base material can be reduced, and the fluorescent substance with respect to the fluorescence amount of the paper base material It has been found that the amount of fluorescence can be increased as a ratio.

  Therefore, an optical line sensor device according to the present invention is an ultraviolet LED light source that irradiates ultraviolet light in an optical line sensor device that irradiates ultraviolet light onto the medium and detects fluorescence of a fluorescent material embedded in the medium. A sensor unit in which the ultraviolet LED light source having one filter mounted on the emission side, and a light receiving element that receives reflected light that is irradiated from the ultraviolet LED light source to the medium and reflected from the medium at a predetermined angle are arranged. A second filter is mounted on the optical path between the medium and the sensor unit, the first filter has a characteristic of cutting ultraviolet light and visible light having a wavelength of 385 nm or more, and the second filter The filter has a characteristic of cutting visible light and ultraviolet light having a wavelength of 410 nm or less.

  With this configuration, by attaching the first filter to the ultraviolet LED light source, the ultraviolet light component having a wavelength of 385 nm or more and the visible light component emitted from the ultraviolet LED light source are blocked, and these light components are It is possible to prevent the light from directly entering the light receiving unit or reflecting the medium into the light receiving unit. In addition, a second filter can be attached to the incident side of the sensor unit to prevent visible light and ultraviolet light having a wavelength of 410 m or less, which are emitted from the ultraviolet LED light source and reflected from the medium, from entering the light receiving unit. According to the present invention, it is possible to enhance the ability of detecting an original fluorescent substance when the medium is irradiated with ultraviolet light as an optical line sensor and to improve the ability of the optical line sensor device.

  According to another aspect of the present invention, the ultraviolet LED light source includes an LED element that irradiates light containing an ultraviolet light component, and a mounting housing that mounts the LED element. The filter has a property of blocking light near a wavelength of 690 nm, and at least a part of the mounting housing is formed of an aluminum oxide sintered body that emits fluorescence near 690 nm when irradiated with ultraviolet light. And the light of around 690 nm is blocked by the first filter.

  With this configuration, even if light emission having a wavelength of around 690 nm is present from the light source casing when irradiated with the ultraviolet LED light source, the light emission at around 690 nm can be blocked by the first filter. Therefore, it is possible to prevent this light component from directly entering the light receiving part, or reflecting the medium and entering the light receiving part, and the original fluorescent substance when the medium is irradiated with ultraviolet light as an optical line sensor. The detection capability can be further enhanced.

  The valuable paper surface discrimination method of the present invention is a method according to the invention that is substantially the same as the optical line sensor device of the present invention.

It is sectional drawing which shows the optical line sensor apparatus which detects the image of medium S, such as securities and a banknote. FIG. 6 is a cross-sectional view showing a state in which an ultraviolet light cut film 30a is attached to an end of the rod lens array 23 on the sensor light receiving unit 24 side as a modification of FIG. 2 is a perspective view showing a structure of a UV light source 22 in which a visible light cut filter layer 28 is formed so as to cover an upper surface of a mounting substrate 20 and a light emitting element 29. FIG. It is a graph which shows an example of the light transmission characteristic of the film | membrane (1st filter) which cuts a part of visible light and ultraviolet light. It is a graph which shows an example of the light transmission characteristic of the film | membrane (2nd filter) which cuts the wavelength of a part of ultraviolet light and visible light. It is the graph which measured and contrasted the spectral characteristic of the reflected light from the paper base | substrate part of valuable paper, and the reflected light from a flag part, when the cutoff wavelength of a 2nd filter was 410 nm. It is the graph which measured and contrasted the spectral characteristic of the reflected light from the paper base material part of valuable paper, and the reflected light from a flag part, when the cutoff wavelength of a 2nd filter was 450 nm. It is sectional drawing which shows the structure of the ultraviolet-light LED light source mounting product 50 which mounted the LED element 54 in the mounting housing | casing which employ | adopted the aluminum oxide ceramic sintered body 52. FIG. It is a perspective view which shows the state which mounted the ultraviolet light LED light source mounting product 50 of FIG. 8 on the board | substrate.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a cross-sectional view showing an optical line sensor device that detects an image of securities, bills, and the like (hereinafter referred to as “medium S”). The optical line sensor device has detection units 12 and 13 arranged to face the banknote transport path 11 for transporting the medium S linearly in the x direction. The banknote conveyance path 11 conveys the medium S straightly in a posture along the conveyance direction x. Each detection unit 12 and 13 is the same shape, and is arrange | positioned symmetrically. Hereinafter, the structure of the upper detection unit 12 will be mainly described.

  The detection unit 12 has a dimension in the length direction (y direction perpendicular to the paper surface in FIG. 1) compared to a dimension in the thickness direction (z direction in FIG. 1) and a dimension in the width direction (x direction in FIG. 1). It is quite long and has an elongated shape. The detection unit 12 includes an elongated box-shaped casing 16 provided with an opening in the lower direction, an elongated plate-shaped translucent cover 17 attached to the casing 16 so as to close the opening, and a casing. The unit body is housed in the body 16.

  The material of the housing 16 is preferably a substance such as a metal or a resin that is durable against ultraviolet light irradiation and does not emit fluorescence even when irradiated with ultraviolet light. For example, if it is a metal, it is iron, stainless steel, aluminum, copper, brass or the like. If it is a metal itself, it does not emit fluorescence, but it may fluoresce depending on the rust preventive material coated on the surface, and it is desirable to actually use ultraviolet light to confirm the presence or absence of fluorescence. As the resin, general-purpose resins such as polycarbonate, polyacetal, nylon, ABS, saturated and unsaturated polyester can be used. Similarly, the resin may emit fluorescence from added fillers, stabilizers, pigments, UV absorbers, etc., and it is preferable to adopt after confirming the presence or absence of fluorescence.

  The translucent cover 17 is made of a transparent material such as glass that transmits ultraviolet light and visible light, and is chamfered 36 that is inclined at both end portions in the width (x) direction so that the thickness decreases toward the front end side. Is given. This chamfering 36 is for preventing the medium S from becoming an obstacle to be caught when passing through the detection unit. In addition, as the translucent cover 17, you may use the integrally molded resin molded product which does not emit the fluorescence which minimized the level | step difference of the junction part with a transparent material.

  The inside of the unit body is partitioned by two elongated walls 18a and 18b extending in the length (y) direction. These two partition walls 18a and 18b and both outer walls of the housing 16 divide three elongated rooms U, V, and W arranged in the width (x) direction. The room U located at the most downstream side in the x direction accommodates the transmissive light source 21, and the central room V accommodates the light emitting element 29 that is an ultraviolet LED light source, and an emission opening for emitting ultraviolet light emitted from the light emitting element 29 is formed. ing. The room W in the uppermost stream in the x direction accommodates the rod lens array 23 and is formed with an incident opening through which the reflected light from the medium S is incident. Furthermore, a room T in which the sensor light receiving unit 24 is installed is partitioned in the back of the room W in which the rod lens array 23 is installed, that is, on the opposite side to the light transmitting cover 17. This sensor light-receiving part 24 has an elongated shape like the translucent cover 17 and is mounted in the casing 16 with its length (y) direction coincided with the length (y) direction of the unit body. ing. The sensor light receiving unit 24 has the image detection direction (−z direction) directed toward the translucent cover 17.

A sensor light receiving unit 24 is installed in a room T in the back of the room W. The sensor light receiving unit 24 takes in the light emitted from the rod lens array 23 through an opening provided on the boundary surface between the room W and the room T.
For example, the sensor light receiving unit 24 includes a sensor IC chip in which an image detection sensor configured by a photodiode, a phototransistor, and the like and a driver unit are integrated, and is mounted on a substrate. The driver unit is a circuit part that generates and supplies a bias current for driving the light receiving element. The signal processing unit 33 is a circuit portion that reads and processes the light detection signal of the light receiving element. Although the kind of light receiving element is not limited, for example, a silicon PN diode or a PIN diode is used.

  In the room W in the unit main body, a rod lens array 23 having a shape elongated in the length (y) direction is arranged facing the sensor light receiving unit 24. The rod lens array 23 is a lens element for forming a fluorescent image of the medium S on the photosensitive surface of the sensor light receiving unit 24 as an equal-magnification erect image. The rod lens array 23 is attached to the housing 16 in a state where positions of the unit main body in the width (x) direction and the length (y) direction are entirely superimposed on the sensor light receiving unit 24.

  The rod lens array 23 has a detection area of an image to be observed (the other focal point of the rod lens array 23 when the sensor light receiving unit 24 is one focal point of the rod lens array 23; referred to as an observation line). The detection area is set outside by a predetermined distance from the outer surface (this detection area is indicated by R1 in FIG. 1), and a straight line extending from the detection area R1 and passing through the central axis (optical axis) of the rod lens array 23 is the z-axis. It becomes parallel and reaches the photosensitive surface of the sensor light receiving unit 24. The detection area R1 also extends in the length (y) direction in the same manner as the unit body.

Furthermore, in the room T, the ultraviolet light that has passed through the rod lens array 23 is placed at a certain distance from the photosensitive surface on the sensor light receiving unit side so as to close the opening provided in the boundary wall between the room W and the room T. However, a UV cut layer 30 (second filter) for preventing the light from entering the sensor light receiving unit 24 is disposed.
The UV cut layer 30 is not particularly limited, and any material / structure can be used as long as it sharply blocks the target wavelength range of the present invention. For example, an ultraviolet light absorbing film in which an organic ultraviolet light absorber is mixed or coated on a transparent film, and a thin film of metal oxide or dielectric material having different transmittance and refractive index such as titanium oxide and silicon oxide is deposited on the glass surface in multiple layers. The interference wave filter (bandpass filter) obtained by the above is preferable.

In the case where an interference wave filter is used for the UV cut layer 30, when the target transmission region cannot be adjusted only by the interference wave filter, a thin film of a metal or its oxide, nitride, or fluoride is further used thereon. It is possible to ensure desired wavelength characteristics by stacking films.
Thin film materials used for interference wave filters include silicon oxide, magnesium oxide, zinc oxide, aluminum oxide, titanium oxide, tantalum pentoxide, zirconium oxide, yttrium oxide, hafnium oxide and other metal oxides, magnesium fluoride, fluoride Fluorides such as lanthanum and nitrides such as silicon nitride are used, and desired bandpass filter characteristics can be ensured by adjusting the transmittance, refractive index, and film thickness of each. Needless to say, there is no particular limitation on the use of a band-pass filter that has been conventionally produced for ordinary optical-related industries as long as it satisfies the required performance.

  The optical characteristics of the band-pass filter used in the present invention must be such that the desired wavelength range is efficiently transmitted, and that other wavelengths are sharply cut. A preferable wavelength characteristic, which cuts ultraviolet light and has a characteristic of cutting a short wavelength side of a visible light region (400 nm to 700 nm) having a wavelength of 410 nm or less, preferably a wavelength of 420 nm, and more preferably a wavelength of 450 nm or less. .

Further, it is preferable that the slope to be cut is steeper. For example, it is desirable for stabilizing the detection sensitivity that the difference (wavelength width) between the wavelength at which the light transmittance is reduced to 50% and the wavelength at which the light transmittance is reduced to 10% is in the range of 100 nm or less, particularly preferably 50 nm or less.
The UV cut layer 30 may be configured independently, but may be directly vapor deposited on an optical member such as a lens or a protective glass plate. Similarly, an ultraviolet light blocking paint that is an organic material may be applied to an optical member such as a lens or a glass plate.

  In the above-described example, the UV cut layer 30 is installed so as to close the opening provided in the boundary wall between the room W and the room T, but is not limited to this structure. For example, the UV cut layer may be attached so as to cover the photosensitive surface of the sensor light receiving unit 24. Alternatively, there is a method in which an ultraviolet light cut film is attached to an end portion or an intermediate portion of the rod lens array 23. FIG. 2 is a cross-sectional view showing a state in which an ultraviolet light cut film 30a is attached to the end of the rod lens array 23 on the sensor light receiving unit 24 side as a modification of FIG.

In short, it is only necessary to prevent the ultraviolet light passing through the rod lens array 23 from entering the sensor light receiving unit 24.
Further, as described above, the sensor light receiving unit 24 is partitioned by the outer wall of the housing 16 and the partition wall 18b, so that stray light other than the light passing through the rod lens array 23 is not incident on the sensor light receiving unit 24.

In the room T, an elongated sensor substrate 25 having a length substantially equal to or longer than that of the sensor light receiving unit 24 is installed, and the sensor light receiving unit 24 includes a predetermined electrode terminal (not shown). They are connected to the sensor substrate 25 by wire bonding or the like.
With the above configuration, the sensor light receiving unit 24 can form an erect image of an image existing in the detection area R <b> 1 set outside the translucent cover 17 via the rod lens array 23.

In the center room V in the next unit main body, an elongated ultraviolet LED light source 22 capable of irradiating ultraviolet light obliquely toward the detection area R1 is provided. The ultraviolet LED light source 22 is attached to the housing 16 in a state parallel to the sensor light receiving unit 24 and the rod lens array 23 along the length (y) direction of the unit main body.
The ultraviolet LED light source 22 includes a light emitting element 29 made of a semiconductor element that emits ultraviolet light, a visible light cut filter layer 28 (first filter) that is disposed so as to cover the light emitting element 29 and transmits ultraviolet light. have. Furthermore, in order to guide the light from the ultraviolet LED light source 22 obliquely, a light guide resin 27 made of a transparent material such as elongated glass is provided. The light emitting element 29 is an LED element capable of emitting ultraviolet light having a wavelength of 300 nm or more, and includes predetermined electrode terminals (not shown), which are arranged on the back side of the casing 16 by wire bonding or the like. The light source substrate 26 is connected. The ultraviolet light emitted from the light emitting element 29 has a shorter wavelength and a stronger emission intensity, so that a larger fluorescence output can be obtained. In the gallium nitride system, an ultraviolet LED having a peak at a wavelength of 350 nm to 380 nm is practical and preferable.

  The structure of the ultraviolet LED light source 22 is shown in a perspective view in FIG. The ultraviolet LED light source 22 has light emitting elements 29 mounted on the mounting substrate 20 extending in the length (y) direction of the unit main body at predetermined intervals, and covers the upper surface of the mounting substrate 20 and the light emitting elements 29 so as to cut visible light. A filter layer 28 is formed. The material and structure of the visible light cut filter layer 28 is, for example, a multilayer interference wave filter obtained by multilayer deposition of metal oxide or dielectric thin films on the glass surface.

The optical characteristic of the multilayer interference wave filter of the visible light cut filter layer 28 is a characteristic that cuts visible light and cuts the wavelength region on the long wavelength side of 385 nm or more in the ultraviolet region (up to 400 nm). It is preferable to have.
Further, when the ultraviolet LED light source 22 employs the mounting substrate 20 that emits fluorescence having a wavelength of around 690 nm when irradiated with ultraviolet light, such as an aluminum oxide / ceramic sintered body, the fluorescence at around 690 nm is converted into the ultraviolet light LED light source. Therefore, it is necessary to prevent leakage from the irradiation. Therefore, it is preferable that the multilayer interference wave filter is designed so that the optical characteristic thereof has a characteristic of reliably blocking light having a wavelength of around 690 nm. Specifically, the film thickness and refractive index of each film constituting the multilayer interference wave filter are preferably designed so that the transmittance has a low value near the wavelength of 690 nm.

  In addition, the installation method of the visible light cut filter layer 28 is arbitrary, and the upper surface of the mounting substrate 20 and the light emitting element 29 may be coated by coating or vapor deposition. Alternatively, a film-like or plate-like visible light cut filter layer 28 may be prepared and attached on the mounting substrate 20 and the light emitting element 29 or attached at a certain distance from the light emitting element 29. Further, the visible light cut filter layer 28 may be disposed as a film on the light emitting surface of the light guide resin 27. Further, when the light guide resin 27 is molded, a substance that transmits ultraviolet light and cuts visible light may be added to the light guide resin 27.

  Further, as shown in FIG. 1, the partition wall of the central room V is provided with a reflector 31 for guiding the ultraviolet light emitted from the ultraviolet LED light source 22 obliquely. Like the unit main body, the reflector 31 also has an elongated shape in the length (y) direction, and has a parallel groove along the length (y) direction, and the ultraviolet LED light source 22 is accommodated in the groove. Yes. One side of the groove that accommodates the ultraviolet LED light source 22 (side adjacent to the room U) is formed in the yz plane, but the other side (side adjacent to the room W) has a thickness (- It spreads while inclining as it goes away in the z) direction. That is, it is formed in a shape such that the opening cross-sectional area increases as the distance from the ultraviolet LED light source 22 increases. This is a contrivance to prevent the emitted light amount from changing as much as possible even when the light emitted from the ultraviolet LED is irradiated by the object with a uniform light amount and the object moves up and down in the optical axis direction. The material of the reflecting plate 31 is preferably a substance such as a metal or a resin that is durable to ultraviolet light irradiation and does not emit fluorescence even when irradiated with ultraviolet light, as in the case 16.

At the bottom (upper end in the z direction) of the partition walls 18a and 18b of the room V, the bottom wall portion 32 is arranged without a gap, and the above-described light source substrate 26 is installed on the back side. The bottom wall portion 32 is preferably formed integrally with the partition walls 18a and 18b.
As described above, the left and right sides of the ultraviolet LED light source 22 are partitioned by the partition walls 18 a and 18 b with the reflector 31, and the bottom wall portion 32 is provided behind the partition walls 18 a and 18 b, so Light is prevented from entering the housing 16 as stray light as much as possible.

With this configuration, the sensor light receiving unit 24 of the upper detection unit 12 shown in FIG. 1 can detect the reflected image that is irradiated from the upper UV LED light source 22 shown in FIG. 1 and reflected by the detection area R1.
A transmission light source 21 for irradiating the medium S with visible light and / or infrared light is installed in a room U next to the room V (on the left side of the drawing). The transmissive light source 21 includes a plurality of light emitting elements (not shown). Each light-emitting element can emit light having a wavelength of 800 nm or more, and three light-emitting elements that can emit light in a desired wavelength region of visible light corresponding to three primary colors such as red, green, blue (RGB) or cyan, magenta, and yellow. And an infrared light emitting element. Each light emitting element includes predetermined electrode terminals (not shown), which are connected to the light source substrate 26 by wire bonding or the like.

Each light emitting element can irradiate light of different wavelength regions, and therefore, by selecting an electrode terminal for applying a voltage to each element, the light emitting element can be switched simultaneously or temporally to emit light. It has become.
The lower detection unit 13 in FIG. 1 is opposed to the upper detection unit 12 in a posture in which the detection unit 13 is inverted 180 degrees around an axis along the length (y) direction with the banknote transport path 11 in between. That is, the detection unit 13 is provided with an opening in the upward direction of the elongated box-shaped housing 16, and the translucent cover 17 is attached to the housing 16 so as to close the opening. The detection unit 13 and the detection unit 12 face each other with the main surfaces of the translucent covers 17 and 17 parallel to the banknote transport path 11 with a gap of 1.5 to 3 mm.

  The element arrangement in the casing 16 of the detection unit 13 includes a transmissive light source 21, an ultraviolet LED light source 22, a rod lens array 23, and a sensor light receiving unit 24 having the same configuration as described above. The transmissive light source 21 is disposed relative to the sensor light receiving unit 24 of the detection unit 12, and the light emitted from the transmissive light source 21 and transmitted through the medium S passes through the rod lens array 23 to the sensor light receiving unit 24. Incident.

With this configuration, the sensor light receiving unit 24 of the upper detection unit 12 shown in FIG. 1 can detect a transmission image in the detection area R1 of the lower detection unit 13 shown in FIG. 1, and the lower detection shown in FIG. The sensor light receiving unit 24 of the unit 13 can detect a transmission image in the detection area R1 of the detection unit 12 on the upper side in FIG.
Further, the sensor light receiving unit 15 of the lower detection unit 13 in FIG. 1 can detect the reflected image of the detection area R <b> 2 irradiated from the ultraviolet LED light source 22.

  The ultraviolet LED light source 22 of the upper detection unit 12 and the transmission light source 21 of the lower detection unit 13 are temporally switched so that the transmitted image and the reflected image do not enter the sensor light receiving unit 24 at the same time. The light emission is controlled by. Similarly, the ultraviolet LED light source 22 of the lower detection unit 13 and the transmissive light source 21 of the upper detection unit 12 are also controlled so that light does not coexist.

  With the above configuration, a transmission image or a reflection image of an object irradiated through the transparent cover 17 on the surface of the housing is formed as an equal-magnification erect image on the surface of the sensor light receiving unit 24 via the rod lens array 23. The

  0.3mm thick borosilicate glass with an interference wave filter film that cuts the visible light region with a multilayer film of silicon oxide and tantalum oxide on the package surface of the reflow type ultraviolet LED element manufactured by Nichia Corporation The plate was bonded with a transparent silicone resin. FIG. 4 shows the light transmission characteristics of the visible cut multilayer film (first filter). As shown in the figure, this multilayer film cuts visible light having a wavelength of 400 nm to 700 nm and ultraviolet light having a wavelength of 385 nm or more. The cut-off wavelength is determined at a wavelength at which the transmittance is reduced to approximately 50%.

  The cut-off wavelength of the filter can be changed arbitrarily by adjusting the film thickness, refractive index, etc. of the multilayer film. In this example, the visible cut multilayer film is designed to cut light near the wavelength of 690 nm. (See FIG. 4). Due to the characteristic of cutting light at a wavelength of about 690 nm, the ultraviolet LED light source 22 employs a mounting substrate 20 that emits fluorescence at a wavelength of about 690 nm when irradiated with ultraviolet light, such as an aluminum oxide / ceramic sintered body. In this case, the fluorescence around 690 nm can be prevented from being leaked from the ultraviolet LED light source 22 and irradiated.

Sixteen visible light cut ultraviolet LED elements were arranged on a printed board on a straight line.
A bar-shaped transparent light guide made of a cycloolefin resin that satisfactorily transmits the ultraviolet light of the LED is mounted on the upper part, and the local light emission of the LED chip is reduced to obtain an ultraviolet light source.
This ultraviolet light source is incorporated into the unit so that the medium S can be irradiated obliquely, and the reflected light of the medium S is passed through a Selfoc lens manufactured by Nippon Sheet Glass Co., Ltd. The output waveform was detected by the sensor light receiving unit used.

  To block the ultraviolet light input to the sensor light receiving part, either apply a multilayered deposition film of silicon oxide and titanium oxide on the surface of the SELFOC lens, or UV cut film (second filter) between the SELFOC lens and the sensor light receiving part. We coped by putting on. FIG. 5 is a graph showing light transmission characteristics when a multi-layer deposited film of silicon oxide and titanium oxide is applied to the surface of the SELFOC lens. As shown in the figure, this multilayer deposited film cuts ultraviolet light and visible light having a wavelength of 420 nm or less. The cut-off wavelength is determined based on the wavelength value at which the transmittance is reduced to approximately 50%.

As is well known, the cutoff wavelength of the filter can be arbitrarily changed by adjusting the film thickness, refractive index, etc. of the multilayer deposited film or film. For example, it is possible to have a characteristic of cutting visible light having a wavelength of 450 nm or less.
The ultraviolet LED was turned on with a pulse of 45 mA per element and a lighting time of 200 μs. The reading condition of the sensor was an accumulation time of 500 μsec per line, and examination was performed while changing various transmission wavelength ranges of the visible light cut filter attached to the ultraviolet light LED and the ultraviolet light cut used in the sensor unit.

  Using 50 euro banknotes, the output ratio (contrast) between the base part (ground part) and the flag part (usually blue) that emits green fluorescence, and the part of numeral 50 that emits yellow-green light on the base part and the back side The output ratio (contrast) with (usually brown) was measured.

No visible light cut filter or UV cut filter is mounted in Comparative Example 1, only UV cut filter is mounted in Comparative Examples 2-4, and both the visible light cut filter and UV cut filter are mounted in Examples 1-7. is there.
According to the table, in Comparative Example 1, the output ratio of the flag portion emitting green fluorescence is 0.74, and the output ratio of the numerical portion emitting yellow-green light is 0.88, both of which are buried in the background. Yes.

In Examples 1 to 7, the output ratio of the flag part that emits green fluorescence is 1.42 or more, and the output ratio of the numerical part that emits yellow-green light is 1.24 or more, both of which are easy to identify without being buried in the background. It has become.
Since Comparative Examples 2 to 4 are equipped with UV cut filters, they have larger numbers than Comparative Example 1, but no visible light cut filters are attached, so the numbers are lower than those of Examples 1 to 7. It has become.

  In Examples 1 to 3, the visible light cut filter has a cutoff wavelength of 400 nm, whereas in Examples 4 to 7, the visible light cut filter has a cutoff wavelength of 385 nm. For this reason, although the output ratio of the flag part in which green fluorescence is emitted is reversed in some of the third and fourth embodiments, the fifth to seventh embodiments have a larger value than the first to second embodiments. (It seems that the reverse is due to the cutoff wavelength of the UV cut filter). As for the output ratio of the numerical site | part which light-emits yellow-green, Example 4-7 has a larger value than Examples 1-3. Therefore, it can be said that a higher output ratio can be obtained by setting the cut-off wavelength of the visible light cut filter to 385 nm, which is part of the ultraviolet region, rather than setting it to 400 nm. Therefore, according to this example, by setting the cut-off wavelength of the visible light cut filter to 385 nm which is part of the ultraviolet region rather than setting to 400 nm, the wavelength of visible light is irradiated when ultraviolet light is irradiated on valuable paper. When light in the long wavelength region of the ultraviolet light connected to the short wavelength region of the range is included in the ultraviolet light, the paper substrate itself on the valuable paper surface reacts sensitively and emits strong fluorescence over the visible light wavelength range. For this reason, it has been proved that the problem that “red and green fluorescence emitted from patterns such as numbers printed on valuable paper is buried” is solved.

  Regarding the UV cut filter, for Examples 1 to 3, the output ratio of the flag portion where green fluorescence is emitted as the cutoff wavelength increases to 400 nm in Example 1, 410 nm in Example 2, and 420 nm in Example 3. In addition, the output ratio of the numerical part emitting yellowish green is increased. Also in Examples 4 to 7, the cutoff wavelength is 400 nm in Example 4, 410 nm in Example 5, 420 nm in Example 6, 450 nm in Example 7, and the output of the flag portion where green fluorescence is emitted. Both the ratio and the output ratio of the numerical part emitting yellowish green are increasing. Therefore, according to the present embodiment, when the cut-off wavelength of the UV cut filter is set to 410 nm that enters the visible light region rather than to 400 nm, “the fluorescence emitted from the valuable paper surface irradiated with ultraviolet light is the wavelength of visible light. It may include long-wavelength ultraviolet light that leads to the short-wavelength region of the range, and red or green fluorescence emitted from patterns such as numbers printed on valuable paper. It has been proved that it can solve the problem of

It is more effective to set the cutoff wavelength of the UV cut filter to 420 nm longer than 410 nm, and it is more effective to set it to 450 nm longer than 420 nm.
6 and 7 are graphs in which the spectral characteristics of the reflected light from the paper base portion of the valuable paper and the reflected light from the flag portion are measured and compared when the cutoff wavelength of the UV cut filter is changed. . In FIG. 6, since the cutoff wavelength of the UV cut filter is 410 nm, a considerable amount of reflected light from the paper substrate portion is output in the region of 410 nm to 450 nm surrounded by a broken line. Reflected light from the flag part is also output in the same area, but the reflected light from the paper base part is more quantitative, so the reflected light from the flag part is used as a molecule and reflected from the paper base part. The output ratio with light as the denominator is relatively lowered. On the other hand, in FIG. 7, the cutoff wavelength is 450 nm. For this reason, both the reflected light from the portion of the paper base material in the region of 410 nm to 450 nm and the reflected light from the flag part are cut. In particular, as a result of a large amount of reflected light from the paper base material being cut, a higher value than the case of FIG. 6 can be obtained as the output ratio. From this measurement, it was proved that it is more effective to set the cutoff wavelength of the UV cut filter to 450 nm longer than 410 nm.

  From the results of the above examples, a large characteristic difference was confirmed in the detection sensitivity of the fluorescent component on the valuable paper surface, and by using the configuration of the present invention as an ultraviolet light line sensor, it is possible to distinguish the valuable paper surface with higher accuracy. It became clear.

12, 13 Detection unit 24 Sensor light receiving unit 22 Ultraviolet light LED light source 28 Visible light cut filter layer (first filter)
30 UV cut filter (second filter)
33 Signal processor S Media such as securities and banknotes

Claims (7)

In the optical line sensor device that detects the fluorescence of the fluorescent material embedded in the medium by irradiating the medium with ultraviolet light,
An ultraviolet LED light source for irradiating ultraviolet light, wherein the ultraviolet LED light source has a first filter mounted on the emission side;
A sensor unit in which a light receiving element that receives reflected light that is irradiated onto the medium from the ultraviolet LED light source and reflected at a predetermined angle from the medium is arranged, and
A second filter is mounted on the optical path between the medium and the sensor unit;
The first filter has a characteristic of cutting ultraviolet light and visible light having a wavelength of 385 nm or more, and the second filter has a characteristic of cutting visible light and ultraviolet light having a wavelength of 410 nm or less. Optical line sensor device.   The optical line sensor device according to claim 1, wherein the second filter has a characteristic of cutting visible light and ultraviolet light having a wavelength of 420 nm or less.   The optical line sensor device according to claim 1, wherein the second filter has a characteristic of cutting visible light and ultraviolet light having a wavelength of 450 nm or less. The ultraviolet LED light source includes an LED element that irradiates light containing an ultraviolet light component, and a mounting housing that mounts the LED element.
The first filter has a characteristic of blocking light around a wavelength of 690 nm,
The at least one part of the said mounting housing | casing is formed with the aluminum oxide sintered compact which receives the irradiation of an ultraviolet light, and emits the fluorescence of 690 nm vicinity, The any one of Claims 1-3. Optical line sensor device.   The optical line sensor device according to any one of claims 1 to 4, wherein the ultraviolet LED light source is a gallium nitride LED.   The signal processing part which discriminate | determines the fluorescence color information of a medium based on the optical signal which reflects a medium and permeate | transmits said 2nd filter and was detected by the said sensor part is provided. 2. An optical line sensor device according to item 1. A method of identifying valuable paper by irradiating a medium with ultraviolet light and detecting fluorescence of a fluorescent substance embedded in the valuable paper,
From ultraviolet LED light source that irradiates ultraviolet light, irradiate valuable paper with ultraviolet light through the first filter,
The reflected light reflected at a predetermined angle from the medium is received by the sensor unit in which the light receiving elements are arranged through the second filter,
The first filter has a characteristic of cutting ultraviolet light and visible light having a wavelength of 385 nm or more, and the second filter has a characteristic of cutting visible light and ultraviolet light having a wavelength of 410 nm or less. Discrimination method for valuable paper.

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