JP2019068388A - Line light source and light line sensor unit including the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a line light source capable of reproducing the color gamut of sRGB more faithfully and an optical line sensor unit provided with the line light source. A line light source 10 includes a white LED light source 3W and a plurality of monochromatic LED light sources (at least two monochromatic LED light sources 3R, 3G, and 3B of each RGB color). The white LED light source 3W generates white light by fluorescing a phosphor. The plurality of monochromatic LED light sources generate monochromatic light of at least two colors of red, green and blue. The line light source 10 illuminates paper leaves by simultaneously lighting a white LED light source 3W and a plurality of monochromatic LED light sources (at least two monochromatic LED light sources 3R, 3G, and 3B of each RGB color). [Selection diagram] Fig. 3

Description

  The present invention relates to a line light source used as an illumination light source of an optical line sensor unit that reads, for example, paper sheets such as banknotes and securities, and an optical line sensor unit provided with the same.

  Some light line sensor units that read paper sheets can acquire a color image of a paper sheet using a single color LED light source of each color of RGB or a white LED light source. As a white LED light source, what combined ultraviolet LED and fluorescent substance, what combined visible light LED, such as purple or blue, and fluorescent substance, etc. are known (for example, refer to the following patent documents 1).

  In the case of using a single color LED light source of each color of RGB, conventionally, a color image is obtained by sequentially turning on each single color LED light source. In recent years where speeding up of the reading speed of paper sheets is required, the single color LED light sources are simultaneously turned on, and a color filter is provided on the light receiving unit side, so that reading can be performed at three times the conventional speed. Has been proposed. Also in the configuration using a white LED light source, it is possible to speed up the reading speed of sheets.

JP, 2014-53882, A

  However, the above-described conventional methods have problems in terms of color reproduction. Specifically, in general electronic devices such as displays and printers, the international standard of the RGB color space defined by the International Electrotechnical Commission (IEC) called sRGB is adopted. By performing the color adjustment in accordance with sRGB, it is possible to reduce the difference in color between input and output. Also in the light line sensor unit, it is preferable to adopt sRGB, but there is a problem that there is no light source which can faithfully reproduce the color gamut of sRGB.

  FIG. 14 is a diagram showing an emission spectrum when the single color LED light sources of RGB colors are individually turned on. Thus, the peak wavelength of the emission spectrum corresponding to R (red) is about 650 nm, the peak wavelength of the emission spectrum corresponding to G (green) is about 520 nm, and the peak wavelength of the emission spectrum corresponding to B (blue) is about 460 nm.

  FIG. 15 is a view showing an emission spectrum when simultaneously emitting single color LED light sources of RGB colors. As described above, when the single color LED light sources of RGB are simultaneously turned on, three peaks having peak wavelengths of about 650 nm, about 520 nm, and about 460 nm appear as in the case of individually turning on each single color LED light source. .

  In the sRGB color gamut, the dominant wavelength of the emission spectrum corresponding to G (green) is about 550 nm. Therefore, as described above, the difference with the peak wavelength (about 520 nm) of the emission spectrum corresponding to G (green) when simultaneously turning on the RGB single color LED light sources is large, and the sRGB color gamut is faithfully reproduced. I can not do it.

  FIG. 16 is an xy chromaticity diagram showing the color gamut when simultaneously turning on a single color LED light source of each color of RGB in comparison with the color gamut of sRGB. The color gamut of sRGB is indicated by a solid line, and the color gamut when simultaneously turning on a single color LED light source of each color of RGB is indicated by a dashed dotted line.

  As described above, the color gamut when simultaneously emitting single color LED light sources of RGB colors is largely different from the color gamut of sRGB. Therefore, it is conceivable to approach the color gamut of sRGB by adjusting the spectral intensity of each color of RGB, but there is a limit to that, and it is difficult to approach the color gamut of sRGB.

  FIG. 17 is a diagram showing an emission spectrum when the white LED light source is turned on. Thus, when the white LED light source is turned on, a sharp emission spectrum having a peak wavelength of about 460 nm and a broad emission spectrum having a peak wavelength of about 550 nm appear.

  The peak wavelength (about 550 nm) of the broad emission spectrum is a preferable wavelength from the viewpoint of reproducing the color gamut of sRGB, but the color gamut of sRGB can not be faithfully reproduced. Although it is possible to adjust the intensity of each peak as shown by a broken line in FIG. 17 by changing the amount of phosphor in the white LED light source, it is still difficult to match the color gamut of sRGB.

  The present invention has been made in view of the above-described circumstances, and an object thereof is to provide a line light source capable of reproducing the color gamut of sRGB more faithfully, and an optical line sensor unit including the same.

  The line light source according to the present invention is a line light source used as an illumination light source of a light line sensor unit that reads a sheet, and includes a white LED light source and a plurality of single color LED light sources. The white LED light source generates white light by causing the phosphor to fluoresce. The plurality of monochromatic LED light sources generate monochromatic light of at least two colors having a peak wavelength different from a peak wavelength of an emission spectrum in a blue emission region of the white LED light source among red, green and blue. The line light source illuminates the paper sheet by simultaneously turning on the white LED light source and the plurality of single color LED light sources.

  According to such a configuration, the difference between the color gamut of sRGB and the color gamut of sRGB can be reduced by illuminating the paper sheet by simultaneously turning on the white LED light source and the plurality of single-color LED light sources. Therefore, the color gamut of sRGB can be reproduced more faithfully by appropriately setting the intensity of white light generated from the white LED light source and the intensity of each monochromatic light generated from the plurality of monochromatic LED light sources.

The intensity of white light generated from the white LED light source is preferably greater than the intensity of each monochromatic light generated from the plurality of monochromatic LED light sources.
Here, with the intensity, it is assumed that the light receiving sensor has a flat spectral sensitivity characteristic in the visible range, and the visible range when the spectral sensitivity spectrum of the light receiving sensor is multiplied by the emission spectrum of the LED light source The integral value in

  According to such a configuration, the intensity of white light generated from the white LED light source and the intensity of each single color light generated from the plurality of single color LED light sources can be set more appropriately. It can be reproduced more faithfully.

  The plurality of single color LED light sources may generate four colors of single color light of red, green, blue and purple.

  According to such a configuration, it is possible to further reduce the difference from the color gamut of sRGB by illuminating the paper by simultaneously turning on the monochromatic light of purple in addition to red, green and blue. , SRGB color gamut can be reproduced more faithfully.

  It is preferable that the emission spectrum of the white light generated from the white LED light source has a broader emission spectrum than the emission spectrum of each monochromatic light generated from the plurality of monochromatic LED light sources.

  According to such a configuration, the white LED light source that generates white light having a broad emission spectrum is simultaneously turned on with a plurality of single-color LED light sources, thereby further reducing the difference from the color gamut of sRGB. As a result, the color gamut of sRGB can be reproduced more faithfully.

  Each of the time for the output of the white LED light source to rise from 10% to 90% and the time for fall from 90% to 10% is preferably 2 μsec or less.

  According to such a configuration, by using a highly responsive white LED light source, it is possible to read paper sheets at high speed.

  The phosphor is preferably a YAG phosphor.

  According to such a configuration, by simultaneously turning on a white LED light source using a highly responsive YAG phosphor together with a plurality of single-color LED light sources, it is possible to read paper sheets at higher speed.

  The line light source may further include a light guide, a light diffusion pattern, and an ultraviolet light source. The light guide has an elongated shape, and an emission surface is formed along the longitudinal direction. The light diffusion pattern is provided along the longitudinal direction of the light guide, and diffuses light incident on the inside of the light guide and emits the light from the emission surface. The ultraviolet light source faces one end face in the longitudinal direction of the light guide, and makes ultraviolet light enter the inside of the light guide from the one end face. In this case, it is preferable that the white LED light source and the plurality of single-color LED light sources face the other end face in the longitudinal direction of the light guide, and light be incident on the inside of the light guide from the other end face .

  Alternatively, the line light source may further include a light guide, a plurality of ultraviolet light sources, and an infrared light source. The light guide has an elongated shape, and an emission surface is formed along the longitudinal direction. The plurality of ultraviolet light sources are provided side by side along the longitudinal direction of the light guide, and allow ultraviolet light to enter the inside of the light guide. The infrared light source faces one end face in the longitudinal direction of the light guide, and causes infrared light to enter the inside of the light guide from the one end face. In this case, it is preferable that the white LED light source and the plurality of single-color LED light sources face the other end face in the longitudinal direction of the light guide, and light be incident on the inside of the light guide from the other end face .

  An optical line sensor unit according to the present invention includes the line light source, a lens array, and a light receiving unit. The lens array guides light emitted from the line light source and reflected or transmitted by the sheet. The light receiving unit receives the light converged by the lens array and converts the light into an electrical signal.

  According to the present invention, the difference between the color gamut of sRGB and the color gamut of sRGB can be reduced by illuminating the paper sheet by simultaneously turning on the white LED light source and the single-color LED light sources. It can be faithfully reproduced.

It is sectional drawing which shows roughly the structure of the optical line sensor unit in embodiment of this invention. FIG. 7 is a cross-sectional view schematically illustrating an additional configuration of the light line sensor unit. It is a perspective view of a line light source. It is an exploded perspective view showing each component 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 arrangement | sequence of the light receiving element in a light-receiving part, and each color filter. It is the figure which showed the emission spectrum at the time of making the white LED light source and the monochromatic LED light source of RGB each light simultaneously light. It is xy chromaticity diagram which compared and showed the color gamut when simultaneously lighting a white LED light source and the monochromatic LED light source of RGB each color with the color gamut of sRGB. It is the figure which showed the emission spectrum at the time of making the white LED light source and the monochrome LED light source of each color of RGBV light simultaneously. It is xy chromaticity diagram which compared and showed the color gamut when simultaneously illuminating a white LED light source and a monochromatic LED light source of RGBV each color with the color gamut of sRGB. It is the figure which showed the emission spectrum at the time of making the white LED light source and the monochromatic LED light source of RG each color light simultaneously. It is xy chromaticity diagram which compared and showed the color gamut when simultaneously lighting a white LED light source and the monochromatic LED light source of RG each color with the color gamut of sRGB. It is the figure which showed the emission spectrum when the single color LED light source of RGB each color is individually lighted. It is the figure which showed the emission spectrum at the time of making the monochromatic LED light source of RGB each color light simultaneously. It is xy chromaticity diagram which compared and showed the color gamut when making the monochromatic LED light source of RGB each color simultaneously light with the color gamut of sRGB. It is the figure which showed the emission spectrum when making a white LED light source light.

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

The light line sensor unit includes a housing 16, a line light source 10 for illuminating a sheet, and a lens for guiding light emitted from the line light source 10 toward the focal plane 20 and reflected by the sheet. An array 11 and a light receiving unit 12 mounted on a substrate 13 and receiving transmitted light guided by the lens array 11 are provided. 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, 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 the sheet on the focal plane 20. The types of light emitted are visible light, white light and ultraviolet light, and infrared light may also be emitted.
This ultraviolet light has a peak wavelength of 300 nm to 400 nm, and the infrared light has a peak wavelength of up to 1500 nm.
Of these lights, at least ultraviolet light is emitted so as not to overlap with other lights in time (ie, switched in time). Infrared light may be emitted so as to overlap temporally with visible light, or may be emitted so as not to overlap temporally.

The light emitted from the line light source 10 is transmitted through the protective glass 14 and condensed on the focal plane 20. The protective glass 14 is not necessarily required and may be omitted, but the line light source 10 or the lens array may be used because of scattering or damage of in-use (in-use) dust (dust such as paper powder generated when transporting paper sheets) It is desirable to install in order to protect 11
The material of the protective glass 14 may be any material that transmits the 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 one that transmits ultraviolet light, such as white sheet glass and borosilicate glass.

  A substrate 5 for fixing a first light source unit 4 and a second light source unit 3 (see FIG. 4 and FIG. 5) installed at both ends of the line light source 10 is installed opposite to the bottom surface of the line light source 10 ing. The 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 first light source unit 4 and the second light source unit 3 are inserted into the holes formed in various places of the substrate 5 and the first light source unit 4 is joined to the wiring pattern by solder or the like on the back surface of the substrate. And the second light source unit 3 can be mounted and fixed on the substrate 5 and from the predetermined drive power source (not shown) to the first light source unit 4 and the second light source unit 3 through the wiring pattern on the back surface of the substrate. Power can be supplied to drive and control the light emission.

The lens array 11 is an optical element for forming an image of light reflected by a sheet on the light receiving unit 12, and a rod lens array such as SELFOC lens array (registered trademark: manufactured by Nippon Sheet Glass Co., Ltd.) can be used. In the embodiment of the present invention, the magnification of the lens array 11 is set to 1 (upright).
Preferably, an ultraviolet light blocking filter 15 is provided at an arbitrary position from the focal plane 20 to the light receiving unit 12 so as to block ultraviolet light by reflecting or absorbing the ultraviolet light so that ultraviolet light does not enter the light receiving unit 12. In the embodiment of the present invention, the ultraviolet light blocking filter 15 is attached to the surface of the lens array 11 to have a function of blocking ultraviolet light. As used herein, “blocking light” refers to reflecting or absorbing light but not transmitting it.

  The ultraviolet light blocking filter 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 absorbing agent is mixed or coated in a transparent film, or a thin film of metal oxide or dielectric such as titanium oxide or silicon oxide having different transmittance or refractive index is deposited on the glass surface. The interference filter (band pass filter) etc. which are obtained by

In addition, although the ultraviolet light blocking filter 15 is attached to the exit surface of the lens array 11, it may be attached to the incident surface or the middle part of the lens array 11, and it may be used by vapor deposition or coating directly on the inner surface of the protective glass 14. Good. In short, it is only necessary to prevent the ultraviolet light reflected by the sheet from entering the light receiving unit 12.
The light receiving unit 12 is mounted on the substrate 13 and is configured to include 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 limited, and photodiodes or phototransistors 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. Furthermore, a so-called multichip linear image sensor in which a plurality of integrated circuits (ICs) in which a photodiode, a phototransistor, a drive circuit and an amplification circuit are integrated are arranged can be used as the light receiving unit 12. In addition, an electric circuit such as a driver circuit or an amplifier circuit, a connector for extracting a signal to the outside, or the like can be mounted on the substrate 13 as necessary. Furthermore, 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 digital signals.

  The light line sensor unit described above is a reflection type light line sensor unit that receives the light emitted from the line light source 10 toward the paper sheet and reflected by the paper sheet, but as shown in FIG. A transmission type in which the line light source 10 is placed at a position opposite to the light receiving unit 12 with respect to the focal plane 20, and the light emitted from the line light source 10 toward the paper and received through the paper is received. It may be an optical line sensor unit. In this case, the position of the line light source 10 is only on the lower side of the focal plane 20, which is different from the arrangement of FIG. Further, both of the reflection type light line sensor unit and the transmission type light line sensor unit may be included.

<Line light source>
FIG. 3 is a perspective view schematically showing the appearance of the line light source 10 in the light 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 addition, illustration of the cover member 2 is abbreviate | omitted in FIG.
The line light source 10 is provided in the vicinity of the other end face in the longitudinal direction L, the transparent light guide 1 extending along the longitudinal direction L, the second light source part 3 provided in the vicinity of one end face in the longitudinal direction L Between the bottom side 1a and the left and right sides 1b, and the cover member 2 for holding the side faces (bottom side 1a and left and right sides 1b and 1c) of the light guide 1 Light which is formed on the light diffusion pattern forming surface 1g formed on the light source 1 and which is incident on the end faces 1e and 1f of the light guide 1 from the second light source unit 3 and the first light source unit 4 and travels in the light guide 1 It has a light diffusion pattern P to be diffused and refracted and to be emitted from the light emitting side 1 d of the light guide 1. Furthermore, preferably, the second optical filter 6 and the first optical filter 7 formed on the end faces 1 e and 1 f of the light guide 1 are provided.

The light guide 1 may be formed of a highly light transmitting resin such as an acrylic resin or an optical glass, but in the embodiment of the present invention, the first light source unit 4 for emitting ultraviolet light is used. The material of the light guide 1 is preferably a fluorine-based resin or a cycloolefin-based resin having relatively little attenuation to ultraviolet light.
The light guide 1 has an elongated columnar shape, and the cross section orthogonal to the longitudinal direction L has substantially the same shape and the same dimension at any cut in the longitudinal direction L. Further, the ratio of the proportion of the light guide 1, that is, the length of the light guide 1 in the longitudinal direction L, and the height H of the cross section orthogonal to the longitudinal direction L is larger than 10, preferably larger 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 surface of the light guide 1 is 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 (FIG. 4) It corresponds 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 curved shape of an outwardly smooth smooth surface in order to give a condensing effect of the lens. However, the light emitting side surface 1 d may not necessarily be formed in a convex shape, and may have a planar shape. In this case, it is preferable to dispose a lens for condensing the light emitted from the light guide 1 so as to face the light emitting side surface 1d.

The light diffusion pattern P on the light diffusion pattern formation surface 1g extends in a straight line along the longitudinal direction L of the light guide 1 while maintaining a constant width. The dimension along the longitudinal direction L of the light diffusion pattern P 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 composed of 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 in cross section.

  The light diffusion pattern P refracts and diffuses the light propagating from the end faces 1 e and 1 f of the light guide 1 in the longitudinal direction L and is substantially uniform along the longitudinal direction L. It can be illuminated from the light emitting side 1 d with brightness. Thereby, the light irradiated to the paper sheet can be made substantially constant in the entire longitudinal direction L of the light guide 1, and the illuminance unevenness can be eliminated.

The V shape of the groove of the light diffusion pattern P is an example, and may be arbitrarily changed, for example, into a U shape instead of the V shape as long as the uneven illuminance is not remarkable. The width of the light diffusion pattern P does not have to be maintained constant either, 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 be appropriately changed.
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 1a and the left and right sides 1b and 1c of the light guide 1 can be covered. It has a bottom surface 2a opposed to the pattern forming surface 1g, a right side surface 2b opposed to the right side surface 1b of the light guide 1, and a left side surface 2c opposed to the left side surface of the light guide 1. Each of these three side surfaces is a plane, and the three inner surfaces form a recess having a substantially U-shaped cross section, so that the light guide 1 can be inserted into the recess. In the 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 It adheres to the left side 1 c of the light 1. Therefore, 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 applies a white resin molded product with high reflectance, or the white resin, in order to reflect light leaked from the side surface other than the light emission side surface of the light guide 1 into the light guide 1 again. It may be a molded article of the resin. Alternatively, the cover member 2 may be formed of a metal such as stainless steel or aluminum.

  The second light source unit 3 includes a white LED light source 3W that generates white light (W), a single color LED light source 3R that generates single color light of red (R), and a single color LED that generates single color light of green (G) A light source 3G, a monochromatic LED light source 3B that generates monochromatic light of blue (B), and a monochromatic LED light source 3V that generates monochromatic light of purple (V). However, the second light source unit 3 may include an infrared light source that generates infrared light. The white LED light source 3W is a light source that generates white light by causing the fluorescent substance to fluoresce, for example, a white LED light source that generates white light by causing the fluorescent substance to fluoresce with a blue or purple LED A white LED light source or the like is used which causes the body to fluoresce to generate white light. The phosphor is mixed in a coating or sealant on the LED element, and by adding the light emission of the phosphor to the light from the LED, it becomes a white LED light source having an output in the entire visible light range.

  It is preferable that the white LED light source 3W has high responsiveness, for example, the response time for the output (relative light emission intensity) to rise to 10% to 90%, and the response time to fall to 90% to 10%, It is 2 μsec or less, particularly preferably 0.5 μsec or less. It is preferable to adopt a specific phosphor, since the white LED light source that generates white light by causing the phosphor to fluoresce is inhibited in response due to the use of the phosphor. For example, the LED element (not shown) of the white LED light source 3W is purple or blue, and has a structure in which a phosphor is covered on the element. By using a yellow-emitting YAG phosphor (YAG: Ce (cerium-doped yttrium oxide, sintered aluminum garnet)) as the phosphor, it is possible to obtain a white LED light source 3W having a high response speed.

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

  The second light source unit 3 and the first light source unit 4 are provided with terminals 31 to be mounted on the substrate 5, and the terminals 31 are inserted into the substrate 5 and joined by soldering or the like. Each is electrically connected to a driving power supply (not shown). The driving power supply selects the second light source unit 3 and the first light source unit by selecting an electrode terminal for applying a voltage to the second light source unit 3 and an electrode terminal for applying a voltage to the first light source unit 4. It has a circuit configuration that can switch 4 and emit light simultaneously or temporally. In addition, it is possible to select an arbitrary LED among the plurality of LEDs built in the second light source unit 3 and simultaneously or temporally switch and emit light.

  With the above configuration, white light and monochromatic light of plural colors can be incident on the light guide 1 from the end face 1e where the second light source unit 3 is installed in a compact configuration, and the first light source unit 4 Ultraviolet light can be incident on the light guide 1 from the end face 1 f to be 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 1 d of the light guide 1.

  Preferably, visible light of 420 nm or more is transmitted to the end face 1 e on which the second light source unit 3 of the light guide 1 is installed, and second light is blocked by reflecting or absorbing ultraviolet light of less than 400 nm. A filter 6 is provided. In addition, the first optical filter 7 transmits ultraviolet light of less than 400 nm to the end face 1 f on which the first light source unit 4 of the light guide 1 is disposed, and reflects or absorbs visible light of 420 nm or more. Is provided.

The second optical filter 6 and the first optical filter 7 are not particularly limited, and any material and structure may 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 (band pass filter) obtained by multi-deposition of thin films of metal oxides or dielectrics different in transmittance and refractive index on a glass surface is preferable.
As an interference filter to be reflected, for example, silicon oxide and tantalum pentoxide are adopted, and the desired band pass filter characteristics are secured by adjusting the transmittance, refractive index, and film thickness of each and performing multilayer deposition. can get. As a matter of course, there is no particular limitation in adoption as long as it is a band pass filter conventionally produced for ordinary optical related industries and satisfying 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 region can not be adjusted only by the interference filter, metal or its oxide, nitride, It is possible to secure desired wavelength characteristics by stacking films using fluoride thin films.
If the second optical filter 6 is an optical filter that absorbs ultraviolet light, it may be an ultraviolet light absorbing film in which an organic ultraviolet light absorbing agent is mixed or coated in a transparent film. Also, by using, for example, silicon oxide and titanium oxide in the interference filter, and adjusting the transmittance, refractive index, and film thickness of each layer to perform multilayer deposition, the ultraviolet light is blocked by both reflection and absorption functions. Desired wavelength characteristics may be secured.

If the first optical filter 7 is an optical filter that absorbs visible light, a substance that transmits ultraviolet light and cuts visible light may be added to the film.
In addition, the installation method to the light guide 1 of 2nd optical filter 6 and 1st optical filter 7 is arbitrary, and you may coat | cover the end surface 1e, 1f of the light guide 1 by application | coating or vapor deposition. In addition, a film-like or plate-like second optical filter 6 and a first optical filter 7 are prepared and brought into close contact with the end faces 1e and 1f of the light guide 1, or at a fixed distance from the end faces 1e and 1f. You may attach it.
Further, the second optical filter 6 and the first optical filter 7 may be provided not on the end faces 1 e and 1 f of the light guide 1 but on the second light source unit 3 and the first light source unit 4 is there. In this case, the light sources 3 and 4 may be coated with the optical filters 6 and 7 by coating or vapor deposition, or film-like or plate-like optical filters 6 and 7 are prepared. You may attach it. Alternatively, the second optical filter 6 may be configured by transmitting visible light and adding a substance that blocks ultraviolet light to the sealant of the second light source unit 3. Similarly, the first optical filter 7 may be configured by transmitting ultraviolet light and adding a substance that blocks visible light to the sealant of the first light source unit 4.

  If the first optical filter 7 is an optical filter that transmits ultraviolet light and reflects or absorbs visible light, the following advantages can be obtained. It is assumed that the first light source unit 4 adopts a mounting substrate such as an aluminum oxide ceramic sintered body that emits fluorescence near a wavelength of 690 nm when it is irradiated with ultraviolet light. When ultraviolet light is emitted from the first light source unit 4, the irradiation light impinges on the mounting substrate of the first light source unit 4 and secondary fluorescence of around 690 nm enters the light guide 1. Need to prevent. Therefore, by designing the first optical filter 7 so as to reflect or absorb visible light, secondary fluorescence is prevented from entering the light guide 1. Unnecessary emission of fluorescence from the light emission side 1 d can be prevented, and the contrast of ultraviolet fluorescence of paper sheets can be improved. In addition, what ultraviolet light fluoresces can prevent secondary irradiation similarly, also when the sealing resin fluoresces not only in aluminum oxide ceramic sintered compact.

  If the second optical filter 6 is an optical filter that transmits visible light and reflects or absorbs ultraviolet light, the following advantages can be obtained. It is assumed that the second light source unit 3 employs a mounting substrate such as an aluminum oxide ceramic sintered body that emits fluorescence near a wavelength of 690 nm when it is irradiated with ultraviolet light. When the ultraviolet light emitted from the first light source unit 4 passes through the end face 1 e of the light guide 1 and strikes the second light source unit 3, the fluorescence around 690 nm is secondarily irradiated from the second light source unit 3 Since it enters into the light guide 1, it is necessary to prevent this. Therefore, if the second optical filter 6 is designed to reflect or absorb ultraviolet light so that the ultraviolet light does not go out from the end face 1 e of the light guide 1, the second optical filter 6 hits the second light source unit 3. I have not. Therefore, unnecessary emission of fluorescence from the light emission side 1 d of the light guide 1 can be prevented. As a result, the contrast of the ultraviolet fluorescence of the paper can be improved.

  In the embodiment of the present invention, the second optical filter 6 transmits visible light and reflects ultraviolet light, which is preferable, and has the following advantages. Since the light amount of the ultraviolet light which 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 1 d of the light guide 1 The effect is obtained that the amount of emitted ultraviolet light from the light source is increased. In this case, since the second optical filter 6 transmits visible light emitted from the second light source unit 3, it does not prevent visible light from the second light source unit 3 from entering the light guide 1. .

  If the first optical filter 7 is an optical filter that transmits ultraviolet light and reflects visible light, the light is emitted from the second light source unit 3, is incident on the light guide 1, and is reflected by the first optical filter 7. Since the amount of visible light returned to the light guide 1 increases, as a result, the effect of increasing the amount of visible light emitted from the light emission side 1 d of the light guide 1 can be obtained. Further, since the first optical filter 7 transmits the ultraviolet light emitted from the first light source unit 4, the emission of the ultraviolet light from the light emission side 1 d of the light guide 1 is also possible.

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. As a result, fluorescence is generated from the sheet, and the fluorescent light emission is detected by the light receiving unit 12, whereby the sheet can be identified using ultraviolet light.
White light emitted from the white LED light source of the second light source unit 3 and monochromatic light of a plurality of colors emitted from the monochromatic LED light sources 3R, 3G, 3B and 3V are light guides through the second optical filter 6 1, and diffuse and refracted by the light diffusion pattern forming surface 1g, and the sheet (medium) on the focal plane 20 from the light emitting side surface 1d is irradiated. Thereby, identification of paper sheets using visible light can be performed.

<Light receiving unit>
FIG. 6 is a schematic view showing the element arrangement of the light receiving unit 12. The light receiving unit 12 is an array of sensor IC chips in which the signal processing unit 21 and the driver 22 are integrated with a plurality of light receiving elements (each formed of a photodiode, a phototransistor, etc.) linearly arranged in the y direction. And each light receiving element is covered with a color filter and mounted on a substrate. The driver 22 is a circuit portion that creates and supplies a bias current for driving the light receiving element, and the signal processing unit 21 is a circuit portion that reads and processes the light detection signal of the light receiving element. The type of light receiving element is not limited, and for example, a silicon PN diode or a PIN diode is used.

  By exposing the light receiving elements arranged in a line while the sheet is moving in the x direction (sub scanning direction), a predetermined width along the y direction (main scanning direction) is provided on the surface of the sheet. An observation line can be set. An exposure time (referred to as an optical reading time) for reading line information of paper sheets 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 the paper sheet in the x direction is 1500 to 2000 mm / sec in ATM or a bill processing machine, etc., and 0.5 to 1.0 msec is used as the optical reading time. 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 formed per pixel of the light receiving unit 12 (pixel means a spatial unit for reading and processing image data). It is arranged side by side. In FIG. 6, among the four light receiving elements, the first light receiving element is covered with the red (R) color filter, the second light receiving element is covered with the green (G) color filter, and the third light receiving element is Is covered with a blue (B) color filter. The fourth light receiving element is covered with a transparent filter (W) or not covered with each color filter. The color filters (R, G, B) are usually opaque to ultraviolet light of 300 to 400 nm and transparent to infrared light having a wavelength of 800 nm or more.
Thus, the visible light color filters (R, G, B) are provided in the light receiving unit 12 in association with the respective pixels, and the light transmitted through the color filters is incident on the respective light receiving elements. However, the color filters are not limited to three colors for each pixel.
Although only one element is covered with the color filter of the same color in FIG. 6, two or more light receiving elements may be covered with the color filter of the same color.

  Transparent (W) filters are "transparent" filters without any color. Alternatively, it may be a light transmission spectrum obtained by superposing the light transmission spectra of all the color filters. For example, it may be a light transmission spectrum having an outline obtained by superposing the light transmission spectrum of the R filter, the light transmission spectrum of the G filter, and the light transmission spectrum of the B filter. When the transmission band is connected to form an envelope, it may have the same light transmittance as the envelope. The material of the optical filter forming such a "transparent filter" is selected from transparent acrylic resins, cycloolefin resins, silicone resins, and fluorine resins as organic materials, and silicon nitride and silicon oxide as inorganic materials. It is chosen from among.

Each of these color filter materials is also transparent to ultraviolet light of 300 to 400 nm.
In addition, in the 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 has a plurality of light receiving elements and color filters covering the respective colors mounted on one pixel, each light alone in a desired wavelength region is not switched without switching the wavelength of the light source. By simultaneously turning on a plurality of light emitting elements that can be irradiated, it becomes possible to output color information of paper sheets at one time on one observation line.

  The light detection signal of the light receiving unit 12 having such a configuration is a signal obtained by simultaneously obtaining the light detection signal of each light receiving element, 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 transmitted through each of the R, G, and B color filters of the light receiving unit 12 and transmits the transparent (W) filter. Alternatively, based on the signal intensity not transmitted through each color filter, the total amount of light entering the pixel is calculated. As a result, it is possible to obtain image data based on the correct light amount of each color signal, with the total light amount as the denominator (reference).

However, the element arrangement of the light receiving unit 12 is not limited to the above embodiment. For example, as shown in FIG. 7A, the light receiving elements of the light receiving unit 12 are not necessarily arranged in a single row such as RGBWRGBW... Even if they are arranged in two or more rows Good. FIG. 7 (b) shows that the light receiving elements are arranged in 2 × 2 per pixel, and a transparent (W) filter or each color filter is formed at one corner of one of the two rows (for example, the lower row). An example in which a second light receiving element without light is arranged is shown. In FIG. 7C, the light receiving elements are arranged in four rows per pixel, and one of the four rows (for example, the lowermost row) is a transparent (W) filter or no color filter. An example is shown in which the second light receiving elements of are arranged. Even in these cases, each light receiving element which records the light signal detected through the transparent (W) filter or by the light receiving element without each color filter in one pixel and transmits each color filter (R, G, B) Signal strength can be detected.
Alternatively, an array such as RGBGRGBG may be provided by providing a green (G) color filter instead of the transparent (W) filter.

  In the present embodiment, as described below, the color gamut of sRGB can be reproduced in obtained color image data by illuminating a sheet by simultaneously turning on a white LED light source and a plurality of single color LED light sources. it can.

<Simultaneous lighting of white LED light source and single color LED light source of each color of RGB>
FIG. 8 is a diagram showing an emission spectrum when the white LED light source 3W and the single color LED light sources 3R, 3G, 3B of RGB colors are simultaneously lighted.

  The emission spectrum when only single color LED light sources 3R, 3G, 3B of RGB colors are simultaneously lit is a sharp emission spectrum (a wavelength range is narrow) corresponding to each wavelength of R, G, B as shown in FIG. Emission spectrum). On the other hand, the emission spectrum of the white light generated from the white LED light source 3W is broader than the emission spectrum of each monochromatic light generated from the monochromatic LED light sources 3R, 3G, 3B of RGB, as shown in FIG. It has an emission spectrum.

  By simultaneous lighting of such a white LED light source 3W and single color LED light sources 3R, 3G, 3B of RGB colors, as shown in FIG. 8, a light emission whose sharp emission spectrum appears in a part of a broad emission spectrum A spectrum is obtained. The intensity of white light generated from the white LED light source 3W is larger than the intensity of monochromatic light of each of the RGB colors generated from the plurality of monochromatic LED light sources 3R, 3G, 3B.

  FIG. 9 is an xy chromaticity diagram showing the color gamut when the white LED light source 3W and the RGB single color LED light sources 3R, 3G, 3B are simultaneously lighted in comparison with the color gamut of sRGB. The color gamut of sRGB is shown by a solid line, and the color gamut when the white LED light source 3W and the RGB single color LED light sources 3R, 3G, 3B are simultaneously lighted is shown by a two-dot chain line. As described above, the color gamut when simultaneously lighting the white LED light source 3W and the RGB single color LED light sources 3R, 3G, 3B of RGB colors (three colors) is close to the color gamut of sRGB.

  In the case where the white LED light source 3W and the RGB single color LED light sources 3R, 3G, 3B are simultaneously lighted, the single color LED light source 3V for generating purple single color light may be omitted. Alternatively, instead of the monochromatic LED light source 3V, the monochromatic LED light source 3B may be omitted, and the monochromatic LED light source 3V may be lit.

<Simultaneous lighting of white LED light source and single color LED light source of each color RGBV>
FIG. 10 is a diagram showing an emission spectrum when the white LED light source 3W and the RGBV single color LED light sources 3R, 3G, 3B and 3V are simultaneously lighted.

  Even when the white LED light source 3W and the RGBV single color LED light sources 3R, 3G, 3B, 3V are simultaneously lit, as shown in FIG. 10, an emission spectrum in which a sharp emission spectrum appears in part of a broad emission spectrum Is obtained. The intensity of white light generated from the white LED light source 3W is larger than the intensity of monochromatic light of each color RGBV generated from the plurality of monochromatic LED light sources 3R, 3G, 3B, and 3V.

  FIG. 11 is an xy chromaticity diagram showing the color gamut when the white LED light source 3W and the single color LED light sources 3R, 3G, 3B and 3V of RGBV are simultaneously lighted in comparison with the color gamut of sRGB. The color gamut of sRGB is indicated by a solid line, and the color gamut when simultaneous lighting of the white LED light source 3W and the monochromatic LED light sources 3R, 3G, 3B, and 3V of each color RGBV is indicated by a broken line. As described above, the color gamut when simultaneously lighting the white LED light source 3W and the RGBV (single color) LED light sources 3R, 3G, 3B, and 3V of RGBV (four colors) becomes closer to the color gamut of sRGB.

<Simultaneous lighting of white LED light source and single color LED light source of each RG>
FIG. 12 is a diagram showing an emission spectrum when the white LED light source 3W and the monochromatic LED light sources 3R and 3G of each color RG are simultaneously lighted.

  Even when the white LED light source 3W and the single color LED light sources 3R and 3G of each color RG are simultaneously lit, as shown in FIG. 12, an emission spectrum in which a sharp emission spectrum appears in part of a broad emission spectrum is obtained. The intensity of white light generated from the white LED light source 3W is larger than the intensity of monochromatic light of each of the RG colors generated from the plurality of monochromatic LED light sources 3R and 3G.

  FIG. 13 is an xy chromaticity diagram showing the color gamut when the white LED light source 3W and the single color LED light sources 3R and 3G of each color RG are simultaneously lighted in comparison with the color gamut of sRGB. The color gamut of sRGB is shown by a solid line, and the color gamut when the white LED light source 3W and the monochromatic LED light sources 3R and 3G of each color RG are simultaneously lighted is shown by a dotted line. As described above, the color gamut when the white LED light source 3W and the single color LED light sources 3R and 3G of each color (two colors) of RG are simultaneously lighted is closer to the color gamut of sRGB as compared with FIG.

  In the case where the white LED light source 3W and the single color LED light sources 3R and 3G for each color of RG are simultaneously lighted, the single color LED light sources 3B and 3V for generating single colors of blue and purple may be omitted. In addition, the two-color single-color LED light sources 3R and 3B for the two-color RB and the two-color single-color LED light sources 3G and 3B for the GB may simultaneously be lighted with the white-color LED light source 3W. In this case, the single-color LED light source 3G that generates single-color green light or the single-color LED light source 3R that generates single-color light of red may be omitted.

<Function effect>
In the present embodiment, the color gamut of sRGB is achieved by illuminating the paper sheets by simultaneously turning on the white LED light source 3W and a plurality of single color LED light sources (at least two of single color LED light sources 3R, 3G, 3B of RGB colors). And the difference between Therefore, the intensity of the white light generated from the white LED light source 3W and the intensities of the respective monochromatic lights generated from the plurality of single color LED light sources (at least two of the single color LED light sources 3R, 3G and 3B of RGB) are appropriately set. If so, the color gamut of sRGB can be reproduced more faithfully.

In particular, since the intensity of the white light generated from the white LED light source 3W is larger than the intensities of the respective monochromatic lights generated from the plurality of single color LED light sources (at least two of the single color LED light sources 3R, 3G, and 3B of RGB) The color gamut of sRGB can be reproduced more faithfully.
In this case, when the white LED light source 3W and a plurality of single color LED light sources (at least two of single color LED light sources 3R, 3G, 3B of RGB colors) are simultaneously used, the peak wavelength of each single color light is blue of the white LED light source 3W It is more desirable to be different from the peak wavelength of the emission spectrum in the wavelength region. In particular, if there is a peak wavelength of the emission spectrum of the single color LED light source 3B on the short wavelength side of the peak wavelength of the emission spectrum of the white LED light source 3W in the blue wavelength range, the four color light source effect can be obtained with the three color light source More preferred.

  Further, as shown in FIGS. 10 and 11, in the case where a plurality of single color LED light sources 3R, 3G, 3B and 3V generate single color lights of four colors of red, green, blue and purple, the color gamut of sRGB Therefore, the color gamut of sRGB can be reproduced more faithfully.

  Furthermore, the emission spectrum of the white light generated from the white LED light source 3W is broader than the emission spectrum of each monochromatic light generated from the plurality of monochromatic LED light sources (at least two of RGB single color LED light sources 3R, 3G, 3B) By having such an emission spectrum, the difference from the color gamut of sRGB can be further reduced, so that the color gamut of sRGB can be reproduced more faithfully.

  In addition, since the time for the output of the white LED light source 3W to rise from 10% to 90% and the time for the output to fall from 90% to 10% are each 2 μsec or less, the white LED with high responsiveness Paper sheets can be read at high speed using the light source 3W.

  In particular, since the white LED light source 3W uses a highly responsive YAG phosphor as a phosphor, it is possible to read paper sheets at a higher speed.

<Modification>
The line light source 10 is not limited to a configuration in which light is made to enter 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. The light may be directly irradiated to the focal plane 20 from the bottom side 1a through the light emitting side 1d (a so-called direct type). In this case, a plurality of ultraviolet light sources may be arrayed along the longitudinal direction of the light guide, and ultraviolet light may be incident on the inside of the light guide. In addition, the infrared light source may face one end face in the longitudinal direction of the light guide, and the infrared light may be incident to the inside of the light guide from the one end face. Furthermore, a white LED light source and a plurality of single color LED light sources (at least two of single color LED light sources 3R, 3G, 3B of RGB colors) face the other end face in the longitudinal direction of the light guide Light may be incident on the inside of the light.

DESCRIPTION OF SYMBOLS 1 light guide 3 2nd light source part 3W white LED light source 3R, 3G, 3B, 3V monochrome LED light source 4 1st light source part 10 line light source 11 lens array 12 light receiving part P light diffusion pattern

Claims (10)

A line light source used as an illumination light source of an optical line sensor unit for reading a sheet, the line light source comprising:
A white LED light source that generates white light by causing the phosphor to fluoresce;
A plurality of single color LED light sources for generating single color light of at least two of red, green and blue;
A line light source characterized by illuminating the paper sheets by simultaneously turning on the white LED light source and the plurality of single color LED light sources.   The line light source according to claim 1, wherein the intensity of white light generated from the white LED light source is larger than the intensity of each monochromatic light generated from the plurality of monochromatic LED light sources.   The line light source according to claim 1 or 2, wherein the plurality of single color LED light sources generate single color lights of four colors of red, green, blue and purple.   The emission spectrum of white light generated from the white LED light source has a broader emission spectrum than the emission spectrum of each monochromatic light generated from the plurality of monochromatic LED light sources. Line light source according to one item.   The time for the output of the white LED light source to rise from 10% to 90% and the time for the output to fall from 90% to 10% are each 2 μsec or less. Line light source according to any one of the preceding claims.   The line light source according to any one of claims 1 to 5, wherein the phosphor is a YAG phosphor. A light guide having an elongated shape and having an exit surface formed along the longitudinal direction;
A light diffusion pattern which is provided along the longitudinal direction of the light guide, diffuses the light incident on the inside of the light guide, and emits the light from the light exit surface;
An ultraviolet light source facing one end face in the longitudinal direction of the light guide and causing ultraviolet light to enter the inside of the light guide from the one end face;
The white LED light source and the single-color LED light sources are opposed to the other end face in the longitudinal direction of the light guide, and light is made to enter the inside of the light guide from the other end face. The line light source as described in any one of claim | item 1 -6. A light guide having an elongated shape and having an exit surface formed along the longitudinal direction;
A plurality of ultraviolet light sources provided side by side along the longitudinal direction of the light guide and causing ultraviolet light to enter the inside of the light guide;
An infrared light source which is opposed to one end face in the longitudinal direction of the light guide and allows infrared light to enter the inside of the light guide from the one end face,
The white LED light source and the single-color LED light sources are opposed to the other end face in the longitudinal direction of the light guide, and light is made to enter the inside of the light guide from the other end face. The line light source as described in any one of claim | item 1 -6.   The peak wavelength of the emission spectrum of the monochromatic LED light source generating the monochromatic light of blue among the plurality of monochromatic LED light sources generating the monochromatic light of at least two colors is the peak of the emission spectrum in the blue wavelength region of the white LED light source The line light source according to any one of claims 1 to 8, wherein the wavelength is shorter than the wavelength. The line light source according to any one of claims 1 to 9.
A lens array for guiding light emitted from the line light source and reflected or transmitted by the paper sheet;
An optical line sensor unit comprising: a light receiving unit which receives light converged by the lens array and converts the light into an electric signal.

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