WO2018173210A1

WO2018173210A1 - Ultraviolet fluorescent color detection device and ultraviolet fluorescent color detection method

Info

Publication number: WO2018173210A1
Application number: PCT/JP2017/011802
Authority: WO
Inventors: 勉七尾
Original assignee: 株式会社ヴィーネックス
Priority date: 2017-03-23
Filing date: 2017-03-23
Publication date: 2018-09-27
Also published as: CN109155091A; JP6235765B1; CN109155091B; KR101825339B1; EP3474242A1; EP3474242A4; EP3474242B1; JPWO2018173210A1

Abstract

Provided are an ultraviolet fluorescent color detection device and an ultraviolet fluorescent color detection method capable of simply and accurately detecting the reading accuracy of a visible fluorescent color of a medium during irradiation with ultraviolet light. Ultraviolet rays are radiated to the medium from an ultraviolet light source (a first light source unit (4)). A white LED light source (a light source included in a second light source unit (3)) emits white light by causing fluorescence of a fluorescent substance. Light that has passed through at least one visible light color filter is incident on a plurality of light receiving elements provided in a light receiving unit. An output signal from each light receiving element obtained when the fluorescent light from the medium irradiated with the ultraviolet light from the ultraviolet light source is incident on the plurality of light receiving elements through the visible light color filter is corrected on the basis of output signals from the light receiving elements obtained when the light from a white reference material (200) irradiated with white light from the white LED light source is incident on the plurality of light receiving elements through the visible light color filter.

Description

Ultraviolet fluorescent color detection device and ultraviolet fluorescent color detection method

The present invention relates to an optical line sensor device, and more particularly to an optical line sensor device for identification purposes for the purpose of identifying securities or banknotes, and the fluorescent color emission of phosphors contained in securities or banknotes when irradiated with ultraviolet rays. The present invention relates to an ultraviolet fluorescent color detection device and an ultraviolet fluorescent color detection method that detect accurately.

With recent remarkable improvements in printing technology and copying technology, counterfeiting of banknotes, securities, etc. is becoming more and more sophisticated, and to accurately identify and eliminate these in order to maintain the national social order 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 (hereinafter abbreviated as “medium”), a contact optical line sensor device using an equal magnification optical system such as a SELFOC lens array (registered trademark: manufactured by Nippon Sheet Glass) has been widely used. ing.

With regard to the above optical line sensor device, there is a demand for a highly accurate discrimination method due to increasingly sophisticated counterfeiting of the medium. Visible light or infrared light is transmitted from the three directions of the front, back, and transmission of the target medium. Using a light source that emits light, an image for each of a plurality of wavelengths is captured to identify the medium.

For this reason, the light source unit of the optical line sensor device is equipped with a plurality of types of LEDs so that each wavelength can be emitted, and these LEDs are sequentially switched to emit light for each observation line. The light output unit superimposes the light output signals for the respective observation lines to form image data, and the medium is identified based on the image data.

Furthermore, along with the improvement of the performance of the ultraviolet LED, a means for identifying the fluorescent image by the ultraviolet excitation of the medium and the medium surface printing ink by mounting the ultraviolet LED in the reflection light source has been newly adopted.
The present invention relates to a sensor for distinguishing fluorescence of a medium by ultraviolet rays.

In the conventional method of identifying a medium using ultraviolet light, visible light or infrared light reflected on the surface of the medium that has been irradiated with ultraviolet light is received on an optical sensor while the ultraviolet light is shielded, and the output is output. Means for discriminating are taken. However, since this identification method detects the output in monotone, the image is very different from that when actually identifying fluorescence with the naked eye. Cannot be obtained with sufficient contrast.

In order to solve such problems, an attempt has been proposed including the present inventor to directly detect the fluorescent color of the medium by providing a visible light color filter film of at least one color on the pixel of the line sensor. It is coming. As a result, when the medium is irradiated with ultraviolet light, the fluorescent color of the medium can be directly detected, and further improvement in discrimination accuracy is expected.

However, it has been found that there are various problems in the above-mentioned means for detecting the reading accuracy of the color of the medium fluorescence at the time of ultraviolet irradiation with the same color balance as that with the naked eye.

That is, in the conventional discrimination sensor, visible light single color lights such as red, green, and blue can be sequentially turned on, and the tone balance of the output image of each medium can be corrected and synthesized into an appropriate color output image. In order to detect a fluorescent color by providing a color filter for each sensor pixel, there is a problem in that the output balance of each color filter cannot be corrected, and the density of the fluorescent color at the time of desired ultraviolet irradiation cannot be detected accurately.

JP 2006-39996 A JP 2001-229722 A

The present invention has been achieved by finding new means as a result of diligent efforts to solve the above problems.

By using an optical line sensor device characterized by providing a color filter on the sensor pixel, it is possible to detect the fluorescent color of the medium at the time of ultraviolet light irradiation, but to obtain an accurate color tone. In this case, there are the following problems.

For example, when the visible light source, for example, red, green, and blue LEDs are sequentially turned on and the ultraviolet light LED is turned on to detect the fluorescence of the medium as in the prior art, the output signal of each wavelength of the visible light LED is output. By adjusting and correcting the white balance, a visible light image that matches the actual situation can be obtained, but since the white balance of the color filter cannot be detected, another means is required for the color tone of the fluorescent color when irradiated with ultraviolet light. If not adopted, accurate information cannot be obtained. In addition, we examined the simultaneous lighting of red, green, and blue LEDs to correct the color filter density balance as a white light source. For each of the red, green, and blue LEDs, the temperature-output characteristics of each element, time It has been found that it is cumbersome to carry out correction of the change and further correction of the transmission characteristics of the color filter for a narrow wavelength range of LED emission.

The present invention has been made in view of the above circumstances, and provides an ultraviolet fluorescent color detection device and an ultraviolet fluorescent color detection method capable of easily and accurately detecting the reading accuracy of visible fluorescent color of a medium when irradiated with ultraviolet light. For the purpose.

The present inventor has made various studies to solve the above-described problems, uses a white light source that has an output in the entire visible light range, detects a white reference output for each color filter, and thereby performs sensitivity correction for each color filter. Thus, the fluorescent color of the medium when irradiated with ultraviolet light was tried to be taken out with good color balance, and it was found that the object could be achieved.

Further, in the above sensor, instead of using a visible light single wavelength LED such as RGB, which is a visible light source (since each RGB color LED has different temperature characteristics and changes over time, it is difficult to stabilize the color balance), By using a specific white LED covered with a phosphor for the LED, the light source reads out the white medium as a reference, and corrects the output for each color filter, so that the visible fluorescent color of the medium when irradiated with ultraviolet light is adjusted. It has been found that the reading accuracy can be detected easily and accurately.

An ultraviolet fluorescent color detection device according to the present invention is an ultraviolet fluorescent color detection device that irradiates a medium with ultraviolet light from an ultraviolet light source and detects a fluorescent color emission generated from the medium with a light receiving unit, and includes a white LED light source, A light receiving element and a correction processing unit are provided. The white LED light source generates white light by causing a fluorescent material to fluoresce. The plurality of light receiving elements are provided in the light receiving unit, and light which has passed through at least one or more visible light color filters is incident thereon. The correction processing unit receives light from a white reference object irradiated with white light from the white LED light source from each light receiving element obtained by entering the plurality of light receiving elements through the visible light color filter. Based on the output signal, the output signal from each light receiving element obtained by the fluorescence from the medium irradiated with the ultraviolet light from the ultraviolet light source entering the plurality of light receiving elements through the visible light color filter to correct.

According to such a configuration, white light is generated from the white LED light source by causing the phosphor to fluoresce, and the white reference object is irradiated with the white light so that the light from the white reference object is reflected by the visible light color filter. Through a plurality of light receiving elements. By using the output signals from the respective light receiving elements obtained at this time as reference pixel output values, it is possible to easily and accurately detect the reading accuracy of the visible fluorescent color of the medium when irradiated with ultraviolet light.

Specifically, when identifying a medium such as securities or banknotes, each medium is irradiated with ultraviolet light from an ultraviolet light source, and fluorescence from the medium is incident on a plurality of light receiving elements through a visible light color filter. An output signal from the light receiving element is obtained. By correcting the output signal using the reference pixel output value, the color balance of the fluorescent color at the time of ultraviolet light irradiation can be obtained, so that a high-quality image with a desired color balance is obtained. be able to.

The ultraviolet light source irradiates, for example, ultraviolet light having a wavelength of 400 nm or less, particularly preferably 300 to 400 nm. The ultraviolet light source is not particularly limited in composition and structure, but it is preferable that the luminous efficiency and output are large, and that there is no visible light subwavelength that becomes an obstacle. For example, it is preferable to use a semiconductor ultraviolet LED mainly composed of gallium nitride as an ultraviolet light source.

It is preferable that each of the time until the output of the white LED light source rises from 10% to 90% and the time until it falls from 90% to 10% are 2 μsec or less. In general, the LED for illumination normally uses a perovskite phosphor. As described in FIG. 9 as a comparative example, this phosphor has a slow response speed and has a rise time Tr2 and a fall time Tf2 of 1 ms. There are cases as described above, and it is necessary to evaluate the response speed in advance.

According to such a configuration, by using a white LED light source with high responsiveness, it is possible to obtain a higher quality image with a desired color balance when irradiated with ultraviolet light. That is, in order to identify the medium in a short time, it is necessary to read at high speed, and it is preferable to use a white LED light source with high responsiveness in order to switch many wavelengths in a short time.

For example, it is necessary to read the reflection and transmission of the front and back surfaces of the medium at a multi-wavelength with a reading time of 100 μsec or less per wavelength, preferably 50 μsec or less, and the output of the white LED light source is 10%. It is preferable that each of the time from the rise to 90% and the time from the 90% to 10% fall is 2 μsec or less, particularly 0.5 μsec or less.
For example, the LED element (not shown) is purple or blue and has a structure in which a phosphor is covered on the element. If YAG: Ce (cerium-doped yttrium oxide, aluminum garnet sintered body) that emits yellow light is used as the phosphor, a white LED light source with a high response speed can be obtained.

The plurality of light receiving elements may be arranged linearly along the main scanning direction. According to such a configuration, the visible fluorescent color of the medium when irradiated with ultraviolet light can be detected at high speed on one observation line.

An ultraviolet fluorescent color detection method according to the present invention is an ultraviolet fluorescent color detection method using an ultraviolet fluorescent color detection device that irradiates a medium with ultraviolet light from an ultraviolet light source and detects a fluorescent color emission generated from the medium at a light receiving unit. The ultraviolet fluorescent color detecting device includes a white LED light source that generates white light by causing a fluorescent material to fluoresce, and a plurality of light beams that are provided in the light receiving unit and that have passed through at least one or more visible light color filters. Light receiving element. In the ultraviolet fluorescent color detection method, each light receiving element obtained by allowing light from a white reference object irradiated with white light from the white LED light source to enter the plurality of light receiving elements through the visible light color filter Output from each light receiving element obtained by the fluorescence from the medium irradiated with the ultraviolet light from the ultraviolet light source entering the plurality of light receiving elements through the visible light color filter based on the output signal from Correct the signal.

According to the present invention, white light is generated from a white LED light source by fluorescing a phosphor, and an output signal from each light receiving element obtained by irradiating the white reference object with the white light is used as a reference pixel output value. By using it, the reading accuracy of the visible fluorescent color of the medium at the time of ultraviolet light irradiation can be detected easily and accurately.

It is sectional drawing which shows schematically the structure of the optical line sensor unit in embodiment of this invention. It is sectional drawing which shows schematically the additional structure of an optical line sensor unit. It is a perspective view of a line light source. It is a disassembled perspective view which shows each structural member of a line light source. It is a side view of a line light source. It is a schematic diagram which shows the element arrangement | sequence of a light-receiving part. It is a figure which shows the example of an array of the light receiving element in a light-receiving part, and each color filter. It is the schematic for demonstrating the aspect at the time of correct | amending by a correction process part. It is the figure which showed the Example and comparative example of the response speed of a white LED light source.

<Optical line sensor unit>
FIG. 1 is a schematic cross-sectional view showing a configuration of an optical line sensor unit according to an embodiment of the present invention.

The optical line sensor unit includes a housing 16, a line light source 10 for illuminating a paper sheet, and a lens for guiding light emitted from the line light source 10 toward the focal plane 20 and reflected by the paper sheet. An array 11 and a light receiving unit 12 that receives the transmitted light that is mounted on the substrate 13 and guided by the lens array 11 are provided. The paper sheets are conveyed in one direction x (sub-scanning direction) along the focal plane 20.
The casing 16, the line light source 10, the light receiving unit 12, and the lens array 11 extend in the y direction (main scanning direction), that is, in a direction perpendicular to the paper surface in FIG. 1, and FIG. ing.

The line light source 10 is a unit that emits light toward a paper sheet on the focal plane 20. The types of emitted light are visible light, white light, and ultraviolet light, and infrared light may be emitted.
The ultraviolet light has a wavelength peak of 300 nm to 400 nm, and the infrared light has a wavelength peak up to 1500 nm.
Among these lights, at least ultraviolet light is emitted so as not to overlap with other light in time (that is, while being temporally switched). Infrared light may be emitted over time with visible light or may be emitted without overlapping over time.

The light emitted from the line light source 10 passes through the protective glass 14 and is collected on the focal plane 20. The protective glass 14 is not always necessary and may be omitted. However, the line light source 10 and the lens array may be used because dust (dust such as paper dust generated when transporting paper sheets) is scattered or damaged during use (during use). It is desirable to install to protect 11.
The material of the protective glass 14 may be any material as long as it transmits light emitted from the line light source 10, and may be a transparent resin such as an acrylic resin or a cycloolefin resin. However, in the embodiment of the present invention, it is preferable to use a material that transmits ultraviolet light, such as white plate glass or borosilicate glass.

Opposite to the bottom surface of the line light source 10, a substrate 5 for fixing the second light source unit 3 and the first light source unit 4 (see FIGS. 4 and 5) installed at both ends of the line light source 10 is installed. ing. This substrate 5 is a thin insulating plate made of phenol, glass epoxy or the like, and a wiring pattern made of copper foil is formed on the back surface thereof. The terminals of the second light source unit 3 and the first light source unit 4 are inserted into holes formed in various places of the substrate 5 and joined to the wiring pattern with solder or the like on the back surface of the substrate 5 to thereby form the second light source unit 3. The first light source unit 4 can be mounted on and fixed to the substrate 5, and the second light source unit 3 and the first light source unit 4 can be fixed from a predetermined driving power source (not shown) through a wiring pattern on the back surface of the substrate. Electric power can be supplied to drive and control the light emission.

The lens array 11 is an optical element that forms an image of the light reflected by the paper sheet on the light receiving unit 12, and a rod lens array such as a SELFOC lens array (registered trademark: manufactured by Nippon Sheet Glass) can be used. In the embodiment of the present invention, the magnification of the lens array 11 is set to 1 (upright).
An ultraviolet light blocking filter as a “third optical filter” that blocks ultraviolet light by reflecting or absorbing ultraviolet light so that ultraviolet light does not enter the light receiving unit 12 at any position from the focal plane 20 to the light receiving unit 12. It is preferable to provide the film 15. In the embodiment of the present invention, an ultraviolet light blocking filter film 15 is attached to the surface of the lens array 11 to have a function of blocking ultraviolet light. As used herein, “blocking light” means reflecting or absorbing light and not transmitting it.

The ultraviolet light blocking filter film 15 is not particularly limited, and any material and structure can be used as long as ultraviolet light can be prevented from entering the light receiving unit 12. 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 filter (bandpass filter) obtained by (1) is preferable.

Although the ultraviolet light blocking filter film 15 is attached to the exit surface of the lens array 11, it may be attached to the entrance surface or intermediate portion of the lens array 11, and is used by directly depositing or coating on the inner surface of the protective glass 14. Also good. In short, it is only necessary to prevent the ultraviolet light reflected by the paper sheets from entering the light receiving unit 12.
The light receiving unit 12 is mounted on a substrate 13 and includes a light receiving element that receives reflected light and reads an image as an electrical output by photoelectric conversion. The material and structure of the light receiving element are not particularly defined, and a photodiode or a phototransistor using amorphous silicon, crystalline silicon, CdS, CdSe, or the like may be disposed. Moreover, a CCD (Charge Coupled Device) linear image sensor may be used. Further, as the light receiving unit 12, a so-called multichip linear image sensor in which a plurality of ICs (Integrated Circuits) in which a photodiode, a phototransistor, a drive circuit, and an amplifier circuit are integrated can be used. Further, if necessary, an electric circuit such as a drive circuit or an amplifier circuit or a connector for taking out a signal to the outside can be mounted on the substrate 13. Further, an A / D converter, various correction circuits, an image processing circuit, a line memory, an I / O control circuit, and the like can be simultaneously mounted on the substrate 13 and taken out as a digital signal.

The optical line sensor unit described above is a reflective optical line sensor unit that receives light emitted from the line light source 10 toward the paper sheet and reflected by the paper sheet, but as shown in FIG. The transmissive type light source 10 receives the light emitted from the line light source 10 toward the paper sheet and transmitted through the paper sheet, with the line light source 10 placed at a position opposite to the light receiving unit 12 with respect to the focal plane 20. It may be an optical line sensor unit. In this case, the position of the line light source 10 is located below the focal plane 20 only in the arrangement of FIG. 1, and the structure of the line light source 10 itself is not different from that described so far. Further, both a reflection type optical line sensor unit and a transmission type optical line sensor unit may be included.

<Line light source>
FIG. 3 is a perspective view schematically showing an appearance of the line light source 10 in the optical line sensor unit shown in FIG. FIG. 4 is an exploded perspective view of each component of the line light source 10, and FIG. 5 is a side view of the line light source 10. In FIG. 5, the cover member 2 is not shown.
The line light source 10 is provided near the transparent light guide 1 extending along the longitudinal direction L, the second light source unit 3 provided near one end face in the longitudinal direction L, and the other end face in the longitudinal direction L. Between the first light source unit 4 and the cover member 2 for holding the side surfaces (the bottom side surface 1a and the left and right side surfaces 1b and 1c) of the light guide 1, and the bottom side surface 1a and the left and right side surfaces 1b. Formed on the light diffusion pattern forming surface 1g formed on the first light source unit 3 and the first light source unit 4 and incident on the

end surfaces

1e and 1f of the light guide 1 and traveling through the light guide 1. It has a light diffusion pattern P that is diffused and refracted to be emitted from the light emission side surface 1 d of the light guide 1. In addition, preferably, it has a second optical filter 6 and a first optical filter 7 formed on the end faces 1e and 1f of the light guide 1, respectively.

The light guide 1 may be formed of a highly light-transmitting resin such as acrylic resin or optical glass, but in the embodiment of the present invention, the first light source unit 4 that emits ultraviolet light is used. As the material of the light guide 1, a fluorine-based resin or a cycloolefin-based resin that has relatively little attenuation with respect to ultraviolet light is preferable (see Patent Document 2).
The light guide 1 has an elongated columnar shape, and a cross section perpendicular to the longitudinal direction L has substantially the same shape and the same dimensions at any cut end in the longitudinal direction L. The ratio of the proportion of the light guide 1, that is, the length in the longitudinal direction L of the light guide 1 and the height H of the cross section perpendicular to the longitudinal direction L is greater than 10, preferably greater than 30. For example, if the length of the light guide 1 is 200 mm, the height H of the cross section orthogonal to the longitudinal direction L is about 5 mm.

The side surfaces of the light guide 1 are a light diffusion pattern forming surface 1g (corresponding to an oblique cut surface of the light guide 1 in FIG. 4), a bottom side surface 1a, left and right side surfaces 1b and 1c, and a light emitting side surface 1d (light guide in FIG. 4). (Corresponding to the upper surface of the body 1). The bottom side surface 1a and the left and right side surfaces 1b and 1c have a planar shape, and the light emitting side surface 1d is formed in a smooth convex curve outwardly so as to have a condensing effect of the lens. However, the light emission side surface 1d is not necessarily formed in a convex shape, and may be a planar shape. In this case, a lens for condensing the light emitted from the light guide 1 may be disposed so as to face the light emission side surface 1d.

The light diffusion pattern P on the light diffusion pattern forming surface 1g extends in a straight line along the longitudinal direction L of the light guide 1 while maintaining a certain width. The dimension of the light diffusion pattern P along the longitudinal direction L is formed to be longer than the reading length of the image sensor (that is, the width of the reading area of the light receiving unit 12).
The light diffusion pattern P is constituted by a plurality of V-shaped grooves engraved on the light diffusion pattern forming surface 1 g of the light guide 1. Each of the plurality of V-shaped grooves is formed to extend in a direction orthogonal to the longitudinal direction L of the light guide 1 and has the same length. The plurality of V-shaped grooves may have, for example, an isosceles triangle shape in cross section.

By this light diffusion pattern P, light that is incident from the end faces 1e and 1f of the light guide 1 and propagates in the light guide 1 in the longitudinal direction L is refracted and diffused, and is substantially uniform along the longitudinal direction L. It can irradiate from the light emission side surface 1d with brightness. Thereby, the light irradiated to paper sheets can be made substantially constant in the entire longitudinal direction L of the light guide 1, and unevenness in illuminance can be eliminated.

Note that the V-shape of the groove of the light diffusion pattern P is an example, and can be arbitrarily changed, for example, a U-shape instead of a V-shape, as long as the illuminance unevenness is not significant. The width of the light diffusion pattern P need not be maintained at a constant width, and the width may change along the longitudinal direction L of the light guide 1. The depth of the groove and the opening width of the groove can also be changed as appropriate.
The cover member 2 has an elongated shape along the longitudinal direction L of the light guide 1, and the light diffusion of the light guide 1 so that the bottom side surface 1a and the left and right side surfaces 1b and 1c of the light guide 1 can be covered. It has a bottom surface 2a facing the pattern forming surface 1g, a right side surface 2b facing the right side surface 1b of the light guide 1, and a left side surface 2c facing the left side surface of the light guide 1. These three side surfaces each form a flat surface, and a concave portion having a substantially U-shaped cross section is formed by these three inner surfaces, so that the light guide 1 can be inserted into the concave portion. In this covered state, the bottom surface 2a of the cover member 2 is in close contact with the bottom side surface 1a of the light guide 1, the right side surface 2b of the cover member 2 is in close contact with the right side surface 1b of the light guide 1, and the left side surface 2c is guided. The light body 1 is in close contact with the left side surface 1c. For this reason, the light guide 1 can be protected by the cover member 2.

The cover member 2 is not limited to a transparent cover, and may be translucent or opaque. For example, the cover member 2 is coated with a white resin molded product having a high reflectance or the white resin so that light leaking from the side surface other than the light emitting side surface of the light guide 1 is reflected again into the light guide 1. It may be a molded product of the prepared resin. Or you may form the cover member 2 with metal bodies, such as stainless steel and aluminum.

The second light source unit 3 includes a light source 3a that emits visible light or light having a wavelength ranging from visible to infrared, and a light source 3b that emits white light. The light source 3a has, for example, a plurality of LEDs (Light Emitting する Diode) that emit light of each wavelength of near infrared, red, green, and blue. The light source 3b is a white LED light source that generates white light by fluorescing the phosphor. For example, a white LED light source that generates white light by fluorescing the phosphor with a blue or purple LED, or a fluorescent light with an ultraviolet LED. A white LED light source that fluoresces the body to generate white light is used. The phosphor is mixed with a coating or sealing agent on the LED element, and becomes a white LED light source having an output in the entire visible light range by adding the light emission of the phosphor to the light from the LED.

The light source 3b as the white LED light source preferably has high responsiveness. As described in the embodiment in FIG. 9, for example, the response time (rise time Tr1) until the output (relative light emission intensity) rises from 10% to 90%. ), And the response time (fall time Tf1) until it falls from 90% to 10% is 2 μsec or less, particularly preferably 0.5 μsec or less. A white LED light source that fluoresces a fluorescent material to generate white light has a hindered response due to the use of the fluorescent material, and therefore it is preferable to employ a specific fluorescent material. For example, the LED element (not shown) of the light source 3b is purple or blue, and the phosphor is covered on the element. If YAG: Ce (cerium-doped yttrium oxide, aluminum garnet sintered body) that emits yellow light is used as the phosphor, a white LED light source with a high response speed can be obtained.

The first light source unit 4 is an ultraviolet light source that emits ultraviolet light to the light guide 1, and an ultraviolet LED light source of 300 nm to 400 nm or the like can be used. An ultraviolet light emitting diode having a peak emission wavelength in the range of 330 nm to 380 nm is preferably used.

In the second light source unit 3 and the first light source unit 4, a terminal 31 for mounting on the substrate 5 is formed. By inserting the terminal 31 into the substrate 5 and joining by soldering or the like, Each is electrically connected to a drive power supply (not shown). The drive power supply selects the electrode terminal that applies a voltage to the second light source unit 3 and the electrode terminal that applies a voltage to the first light source unit 4, so that the second light source unit 3 and the first light source unit are selected. 4 has a circuit configuration capable of emitting light by switching simultaneously or temporally. It is also possible to select any LED from among the plurality of LEDs built in the second light source unit 3 and to emit light by switching simultaneously or temporally.

With the above configuration, light in a wavelength range including visible light or visible light to infrared light is incident on the light guide 1 from the end face 1e where the second light source unit 3 (light source 3a) is installed in a compact configuration. The ultraviolet light can be incident on the light guide 1 from the end face 1f where the first light source unit 4 is installed. Thereby, the light emitted from the first light source unit 4 or the light emitted from the second light source unit 3 can be emitted from the light emitting side surface 1 d of the light guide 1. Further, white light can be incident on the light guide 1 by the light source 3b from the same end surface 1e on the side where the light source 3a is installed, and can be emitted from the light emission side surface 1d of the light guide 1.

Preferably, the end surface 1e on which the second light source unit 3 of the light guide 1 is installed transmits infrared light and visible light of 420 nm or more, and cuts off by reflecting or absorbing ultraviolet light of less than 400 nm. A second optical filter 6 is provided. In addition, the end face 1f of the light guide 1 on which the first light source unit 4 is installed transmits the ultraviolet light of less than 400 nm, and cuts off by reflecting or absorbing the infrared light and visible light of 420 nm or more. The optical filter 7 is provided.

The second optical filter 6 and the first optical filter 7 are not particularly limited, and any material and structure can be used as long as they block the target wavelength range. For example, in the case of an optical filter to be reflected, an interference filter (bandpass filter) obtained by multilayer deposition of metal oxide or dielectric thin films having different transmittances and refractive indexes on the glass surface is preferable.
As an interference filter to be reflected, for example, silicon oxide and tantalum pentoxide are adopted, and by adjusting the transmittance, refractive index, and film thickness of each layer, multilayer deposition is performed to secure desired bandpass filter characteristics. can get. Needless to say, there is no particular limitation on the use of the bandpass filter that has been conventionally produced for the normal optical related industry as long as it satisfies the required performance.

When an interference filter is used for the second optical filter 6 and the first optical filter 7, if the target transmission range cannot be adjusted only by the interference filter, a metal or oxide thereof, nitride, It is possible to ensure desired wavelength characteristics by stacking films using fluoride thin films.
If the second optical filter 6 is an optical filter that absorbs ultraviolet light, an ultraviolet light absorbing film obtained by mixing or coating an organic ultraviolet light absorbent in a transparent film may be used. In addition, the interference filter employs, for example, silicon oxide and titanium oxide, and adjusts the transmittance, refractive index, and film thickness of each layer to deposit multiple layers, thereby blocking ultraviolet light by both reflecting and absorbing functions. Desired wavelength characteristics may be secured.

If the first optical filter 7 is an optical filter that absorbs visible light and infrared light, a substance that transmits ultraviolet light and cuts visible light and infrared light may be added to the film.
In addition, the installation method to the light guide 1 of the 2nd optical filter 6 and the 1st optical filter 7 is arbitrary, and you may coat | cover the

end surfaces

1e and 1f of the light guide 1 by application | coating or vapor deposition. Also, a film-like or plate-like second optical filter 6 and a first optical filter 7 are prepared and are brought into close contact with the end faces 1e and 1f of the light guide 1 or at a certain distance from the end faces 1e and 1f. It may be attached.
Further, the second optical filter 6 and the first optical filter 7 may be provided on the second light source unit 3 and the first light source unit 4 instead of being provided on the end faces 1 e and 1 f of the light guide 1. is there. In this case, the light filters 3 and 4 may be coated with the optical filters 6 and 7 by coating or vapor deposition, or the film-like or plate-like optical filters 6 and 7 are prepared and are in close contact with the

light sources

3 and 4. It may be attached. Alternatively, by adding visible light or light in a wavelength range including visible light to infrared light to the sealant of the second light source unit 3 and adding a substance that blocks ultraviolet light, The optical filter 6 may be configured. Similarly, the first light source unit 4 may be sealed by adding a material that transmits ultraviolet light and blocks visible light or light in a wavelength range including visible light to infrared light. The optical filter 7 may be configured.

If the first optical filter 7 is an optical filter that transmits ultraviolet light and reflects or absorbs infrared light and visible light, the following advantages are obtained. Assume that the first light source unit 4 employs a mounting substrate that emits fluorescence having a wavelength of about 690 nm when irradiated with ultraviolet light, such as an aluminum oxide / ceramic sintered body. When ultraviolet light is irradiated from the first light source unit 4, the irradiation light hits the mounting substrate of the first light source unit 4, and fluorescence around 690 nm is secondarily irradiated and enters the light guide 1. There is a need to prevent. Therefore, the first optical filter 7 is designed so as to reflect or absorb infrared light and visible light so that the secondary irradiated fluorescence does not enter the light guide 1. Unnecessary fluorescence emission from the light emission side surface 1d of the light body 1 can be prevented, and the contrast of the ultraviolet fluorescence of the paper sheet can be improved. In addition, not only the aluminum oxide / ceramic sintered body that fluoresces ultraviolet light but also the case where the sealing resin fluoresces can prevent secondary irradiation.

If the second optical filter 6 is an optical filter that transmits infrared light and visible light and reflects or absorbs ultraviolet light, the following advantages are obtained. Assume that the second light source unit 3 employs a mounting substrate that emits fluorescence having a wavelength of about 690 nm when irradiated with ultraviolet light, such as an aluminum oxide / ceramic sintered body. When the ultraviolet light emitted from the first light source unit 4 passes through the end face 1e of the light guide 1 and hits the second light source unit 3, fluorescence near 690 nm is secondarily irradiated from the second light source unit 3. Since it enters the light guide 1, it is necessary to prevent this. Therefore, if the second optical filter 6 is designed so as to reflect or absorb ultraviolet light so that the ultraviolet light does not come out of the end face 1e of the light guide 1, it will hit the second light source unit 3. There is nothing. Therefore, unnecessary fluorescence emission from the light emission side surface 1d of the light guide 1 can be prevented. As a result, the contrast of the ultraviolet fluorescence of the paper sheet can be improved.

In the embodiment of the present invention, the second optical filter 6 is preferably an optical filter that transmits infrared light and visible light and reflects ultraviolet light, and has the following advantages. Since the amount of ultraviolet light that enters the light guide 1 from the first light source unit 4 and is reflected by the second optical filter 6 and returns to the light guide 1 increases, as a result, the light emission side surface 1d of the light guide 1 is increased. The effect that the emitted light quantity of the ultraviolet light from the light increases is obtained. In this case, since the second optical filter 6 transmits infrared light and visible light emitted from the second light source unit 3, the infrared light and visible light from the second light source unit 3 are guided by the light guide 1. There is no hindrance to entering.

Further, if the first optical filter 7 is an optical filter that transmits ultraviolet light and reflects visible light and infrared light, the first optical filter 7 is irradiated from the second light source unit 3 and is incident on the light guide 1 to be incident on the first optical filter. The amount of visible light and infrared light reflected by the filter 7 and returning to the light guide 1 increases, and as a result, the amount of visible light and infrared light emitted from the light exit side surface 1d of the light guide 1 increases. The effect is obtained. In addition, since the first optical filter 7 transmits the ultraviolet light emitted from the first light source unit 4, the ultraviolet light can be emitted from the light emitting side surface 1 d of the light guide 1.

The ultraviolet light emitted from the first light source unit 4 is incident on the light guide 1 through the first optical filter 7, diffused and refracted by the light diffusion pattern forming surface 1g, and focused from the light emitting side surface 1d. The sheet (medium) on the surface 20 is irradiated. Thereby, fluorescence is generated from the paper sheet, and the fluorescent color emission is detected by the light receiving unit 12, whereby the paper sheet using ultraviolet light can be identified.
Visible light emitted from the light source 3a of the second light source unit 3 or light in a wavelength range including visible light to infrared light is incident on the light guide 1 via the second optical filter 6 and diffuses light. The light is diffused and refracted by the pattern forming surface 1g, and is irradiated onto the paper sheet (medium) on the focal plane 20 from the light emitting side surface 1d. Thereby, the paper sheet can be identified using visible light or infrared light.

<Light receiver>
FIG. 6 is a schematic diagram showing an element arrangement of the light receiving unit 12. The light receiving unit 12 includes a plurality of light receiving elements (each composed of a photodiode, a phototransistor, etc.) arranged linearly in the y direction, and a sensor IC chip in which the signal processing unit 21 and the driver 22 are integrated. Each light receiving element is covered with a color filter and mounted on a substrate. The driver 22 is a circuit part that generates and supplies a bias current for driving the light receiving element, and the signal processing unit 21 is a circuit part that reads and processes a 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.

While the paper sheet moves in the x direction (sub-scanning direction), by exposing the light receiving elements arranged in a line, a predetermined width along the y direction (main scanning direction) is formed on the surface of the paper sheet. An observation line can be set. The exposure time for reading the line information of the paper sheet (referred to as optical reading time) can be arbitrarily set according to the intensity of the light source, the wavelength sensitivity of the sensor, and the like. For example, the moving speed of paper sheets in the x direction is 1500 to 2000 mm / sec in ATMs and banknote processors, and if the optical reading time is 0.5 to 1.0 ms, the x direction of the observation line The width is 0.75 to 2 mm.

In the embodiment of the present invention, as shown in FIG. 6, a plurality of, for example, four light receiving elements are linearly arranged per one pixel of the light receiving unit 12 (a pixel means a spatial unit for reading and processing image data). They are arranged side by side. In FIG. 6, among the four light receiving elements, the first light receiving element is covered with a red (R) color filter, the second light receiving element is covered with a green (G) color filter, and the third light receiving element is It is covered with a blue (B) color filter. The fourth light receiving element is covered with a transparent (W) filter or not covered with each color filter. The color filters (R, G, B) are usually opaque to 300 to 400 nm ultraviolet light and transparent to infrared light having a wavelength of 800 nm or more.
As described above, the light receiving unit 12 is provided with the visible light color filters (R, G, B) in association with the respective pixels, and light transmitted through the color filters is incident on the light receiving elements. However, the color filter is not limited to three colors for each pixel, and one or more color filters may be provided.
In FIG. 6, only one element is covered with the same color filter, but two or more light receiving elements may be covered with the same color filter.

The transparent (W) filter is a “transparent” filter without any coloring. For example, it is desirable to have a light transmittance obtained by adding the light transmittances of all the color filters. For example, it is desirable to have the same light transmittance as this envelope when an envelope is formed by connecting the light transmission band of the R filter, the light transmission band of the G filter, and the light transmission band of the B filter. The material of the film that forms such a “transparent filter” is selected from transparent acrylic resin, cycloolefin resin, silicone resin, and fluorine resin for organic materials, and silicon nitride film and silicon oxide for inorganic materials. Selected from among membranes.

Each of these color filter materials is transparent to ultraviolet light of 300 to 400 nm. These optical filter materials are transparent to infrared light having a wavelength of 800 nm or more.
In addition, in an organic material, since the transparent material containing the ultraviolet light absorber used for a liquid crystal use is not transparent with respect to ultraviolet light, it is not preferable to employ | adopt.
As described above, since the light receiving unit 12 is provided with a plurality of light receiving elements and color filters covering each color in one pixel, each of the light receiving units 12 independently emits light in a desired wavelength region without switching the wavelength of the light source. It is possible to simultaneously turn on a plurality of light emitting elements that can be irradiated and to output color information of paper sheets at one observation line.

The light detection signal of the light receiving unit 12 having such a configuration is a signal obtained by simultaneously acquiring the light detection signals of the respective light receiving elements, and these are input to the signal processing unit 21. The signal processing unit 21 determines the color information of the paper sheet based on the signal intensity of the light receiving element that has passed through the R, G, and B color filters of the light receiving unit 12, and transmits the transparent (W) filter. Alternatively, the total amount of light entering the pixel is calculated based on the signal intensity that does not pass through the color filters. Thereby, image data based on the accurate light amount of each color signal can be obtained with the total light amount as the denominator (reference).

A signal from the signal processing unit 21 is input to the control unit 100. The control unit 100 includes a CPU (Central Processing Unit), for example, and functions as the determination unit 101 and the correction processing unit 102 when the CPU executes a program.
The determination unit 101 determines authenticity, denomination, contamination, and the like by comparing the image data of the paper sheet read by the light receiving element with, for example, master data. The correction processing unit 102 generates corrected image data by correcting the signal input from the signal processing unit 21. The determination unit 101 performs determination based on the image data corrected by the correction processing unit 102.

However, the element arrangement of the light receiving unit 12 is not limited to the above-described form. For example, as shown in FIG. 7A, the light receiving elements of the light receiving unit 12 are not necessarily arranged in a row such as RGBWRGBW... Good. FIG. 7B is a diagram in which the light receiving elements are arranged 2 × 2 per pixel, and a transparent (W) filter or each color filter is provided at one corner of the two columns (for example, the lower column). An example in which a blank second light receiving element is arranged is shown. In FIG. 7C, the light receiving elements are arranged in four rows per pixel, and the transparent (W) filter or each color filter is not provided in the first row (for example, the lower row) among the four rows. An example in which the second light receiving elements are arranged is shown. Even in these cases, each light receiving element that records the optical signal detected through the transparent (W) filter or by the light receiving element without each color filter and transmits each color filter (R, G, B) within one pixel. Can be detected.
Further, instead of the transparent (W) filter, a green (G) color filter may be provided to arrange RGBGRGBG. As described above, the type and number of color filters provided in each pixel are arbitrary, and it is sufficient that at least one visible color filter is provided in each pixel.

<Correction process>
FIG. 8 is a schematic diagram for explaining an aspect when correction is performed by the correction processing unit 102. In the embodiment of the present invention, by performing correction using white light emitted from the light source 3b of the second light source unit 3, it is possible to achieve a color balance of the fluorescent color during ultraviolet light irradiation. ing.

Specifically, the white reference object 200 is conveyed in the x direction along the focal plane 20. The white reference object 200 is made of, for example, a white sheet having a high reflectance. When the white reference object 200 is transported, white light is emitted from the light source 3 b of the second light source unit 3, and the white light is emitted from the light emission side surface 1 d of the light guide 1 to be irradiated on the white reference object 200. The reflected light from the white reference object 200 irradiated with white light passes through the lens array 11 and enters the light receiving unit 12, and is received by a plurality of light receiving elements through the color filters of the light receiving unit 12. Thereby, the signal intensity of the output signal from each light receiving element is detected.
In this way, the value of the signal intensity corresponding to each RGB color in each pixel obtained from white light is divided by the smallest value in each pixel, whereby the ratio of the normalized output of each RGB color (Rn: Gn: Bn) is calculated for each pixel as a reference pixel output value.

Thereafter, the paper sheet (medium) is conveyed in the x direction along the focal plane 20. When the paper sheet is conveyed, ultraviolet light is emitted from the first light source unit 4, and the ultraviolet light is emitted from the light emitting side surface 1 d of the light guide 1 to be irradiated on the paper sheet. Fluorescence is generated from the paper sheet irradiated with ultraviolet light, and the fluorescence passes through the lens array 11 and enters the light receiving unit 12, and is received by a plurality of light receiving elements through each color filter of the light receiving unit 12. . Thereby, the signal strengths Rf, Gf, Bf of the output signals from the respective light receiving elements are detected.
In this way, the signal intensity values Rf, Gf, Bf corresponding to the RGB colors in each pixel obtained from the fluorescence are the ratios (Rn: Gn: Bn) of the normalized output of each RGB color calculated in advance in each pixel. Are respectively calculated to calculate corrected signal intensity values Rfc, Gfc, and Bfc for each pixel.

That is, the corrected signal intensity value Rfc corresponding to red (R) in each pixel is calculated by the following equation (1), and the corrected signal intensity value Gfc corresponding to green (G) in each pixel is The corrected signal intensity value Bfc corresponding to the blue color (B) in each pixel is calculated by the following equation (3).
Rfc = Rf / Rn (1)
Gfc = Gf / Gn (2)
Bfc = Bf / Bn (3)

<Effect>
In the embodiment of the present invention, the white LED light source (the light source 3b of the second light source unit 3) of the present invention, that is, the excitation light source is covered with a phosphor on purple and blue LEDs, and the light emission of the LED element and the phosphor By irradiating the white reference object 200 with white light obtained by synthesizing the fluorescence, light from the white reference object 200 enters the plurality of light receiving elements via the visible light color filter. By using the output signals from the respective light receiving elements obtained at this time as the reference pixel output values Rn, Gn, Bn, it is possible to easily and accurately detect the reading accuracy of the visible fluorescent color of the paper sheet when irradiated with ultraviolet light.

Specifically, when distinguishing paper sheets (medium) such as securities and banknotes, the ultraviolet light source (first light source unit 4) irradiates the paper sheets with ultraviolet light, and the fluorescence from the paper sheets is visible. By entering the light receiving elements through the optical color filter, output signals Rf, Gf, and Bf from the respective light receiving elements are obtained. The output signals Rf, Gf, Bf are corrected by the above formulas (1) to (3) using the reference pixel output values Rn, Gn, Bn. Thereby, since the color balance of the fluorescent color at the time of ultraviolet light irradiation can be taken, the quality image with the desired color balance can be obtained.

In particular, as in the above-described embodiment, by using a white LED light source (light source 3b of the second light source unit 3) that has a short rise time and a short fall time and high responsiveness, a desired color balance can be obtained during ultraviolet light irradiation. A higher quality image can be obtained. That is, in order to identify paper sheets in a short time, high-speed reading (for example, the reading speed of one line is 100 μsec or less) is required, and a large number of wavelengths are switched in a short time. It is preferable to use a high white LED light source.

Furthermore, in the embodiment of the present invention, in the light receiving unit 12, a plurality of light receiving elements are arranged linearly along the y direction (main scanning direction). Thereby, the visible fluorescent color of the paper sheet at the time of ultraviolet light irradiation can be detected at high speed on one observation line.

<Modification>
Although the embodiments of the present invention have been described above, the embodiments of the present invention are not limited to the above embodiments. For example, in the present invention, the light source 3a of the second light source unit 3 is a light source that emits visible light or light having a wavelength ranging from visible to infrared, but may be a light source that emits only visible light. The light source 3a of the second light source unit 3 may be omitted, and only the light source 3b as a white LED light source may be provided. Moreover, the formation surface of the light diffusion pattern P can be disposed on any surface other than the light emission side surface 1 d of the light guide 1. For example, a light diffusion pattern may be formed on the bottom side surface 1a, and this may be used as a surface on which the light diffusion pattern P is formed (in this case, it is not necessary to form a diagonal surface between the bottom side surface 1a and the left and right side surfaces 1b).

In the correction process, the second light source unit is not an output signal from each light receiving element obtained by the fluorescence from the paper sheet irradiated with ultraviolet light from the first light source unit 4 entering the light receiving unit 12. The output signal from each light receiving element obtained when the light from the paper sheet irradiated with the visible light from the light source 3a of 3 or the light having the wavelength ranging from visible to infrared is incident on the light receiving unit 12 is a reference pixel. Correction may be performed using the output values Rn, Gn, and Bn.

The line light source 10 is not limited to the configuration in which light is incident on the light guide 1 from one or both end faces in the longitudinal direction L, and the light is diffused and refracted by the light diffusion pattern P. A configuration in which light is directly irradiated onto the focal plane 20 from the bottom side surface 1a side through the light emission side surface 1d (so-called direct type) may be used. Thereby, even if it is a case where cheap LED with comparatively small output is used as a light source, a desired light quantity can be ensured by arranging in a direct type. In the case of such a direct type configuration, the light guide 1 can be omitted.

Further, the observation line is not limited to one line, and a plurality of observation lines extending along the y direction (main scanning direction) may be set side by side in the x direction (sub scanning direction). In this case, an average value of output signals in pixels in the same column in the x direction may be calculated, and correction processing may be performed using the average value.

DESCRIPTION OF SYMBOLS 1 Light guide 2 Cover member 3 2nd light source part 3a Light source 3b Light source (white LED light source)
4 First light source unit 6 Second optical filter 7 First optical filter 10 Line light source 11 Lens array 12 Light receiving unit 20 Focal plane 100 Control unit 101 Determination unit 102 Correction processing unit 200 White reference object

Claims

An ultraviolet fluorescent color detection device that irradiates a medium with ultraviolet light from an ultraviolet light source and detects a fluorescent color emission generated from the medium by a light receiving unit,
A white LED light source that generates white light by fluorescing the phosphor;
A plurality of light receiving elements that are provided in the light receiving unit and receive light that has passed through at least one visible color filter;
Based on an output signal from each light receiving element obtained when light from a white reference object irradiated with white light from the white LED light source enters the plurality of light receiving elements via the visible light color filter, A correction processing unit that corrects an output signal from each light receiving element obtained by the fluorescence from the medium irradiated with the ultraviolet light from the ultraviolet light source entering the plurality of light receiving elements through the visible light color filter; An ultraviolet fluorescent color detection device comprising:
The time until the output of the white LED light source rises from 10% to 90% and the time until the output falls from 90% to 10% are 2 μsec or less, respectively. UV fluorescent color detection device.
3. The ultraviolet fluorescent color detection apparatus according to claim 1, wherein the plurality of light receiving elements are arranged linearly along a main scanning direction.
An ultraviolet fluorescent color detection method using an ultraviolet fluorescent color detection device that irradiates a medium with ultraviolet light from an ultraviolet light source and detects a fluorescent color emission generated from the medium at a light receiving unit,
The ultraviolet fluorescent color detection device is:
A white LED light source that generates white light by fluorescing the phosphor;
A plurality of light receiving elements that are provided in the light receiving unit and receive light transmitted through at least one visible light color filter;
Based on an output signal from each light receiving element obtained when light from a white reference object irradiated with white light from the white LED light source enters the plurality of light receiving elements via the visible light color filter, Correcting the output signal from each light receiving element obtained by the fluorescence from the medium irradiated with ultraviolet light from the ultraviolet light source entering the plurality of light receiving elements via the visible light color filter, UV fluorescent color detection method.
The time until the output of the white LED light source rises from 10% to 90% and the time until the output falls from 90% to 10% are each 2 μsec or less. UV fluorescent color detection method.
6. The ultraviolet fluorescent color detection method according to claim 4, wherein the plurality of light receiving elements are arranged linearly along the main scanning direction.