JP2013030100A - Image sensor unit, and paper sheet recognition device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image sensor unit capable of performing visible light reading and infrared light reading by using a photoelectric conversion module having sensitivity in a visible light region, and a paper sheet recognition device therewith.SOLUTION: The image sensor unit 1a and 1b of the paper sheet recognition device irradiates a bank note S with light, receives reflection light reflected by the bank note S, and reads an image of the bank note S. The image sensor unit includes a light source 2 that radiates the infrared light to the bank note S, a wavelength conversion layer 15 that converts the reflection light from the bank note S into visible light, and the photoelectric conversion module 141 that receives the reflection light converted by the wavelength conversion layer 15 and converts it into an electric signal. The wavelength conversion layer 15 is provided between the bank note S and the photoelectric conversion module 141.

Description

  The present invention relates to an image sensor unit and a paper sheet identification apparatus using the image sensor unit. In particular, the present invention relates to a paper sheet identification device that performs authenticity determination of a recording medium such as banknotes and securities.

  The banknotes are provided with regions where images obtained under visible light and infrared light are different for authenticity determination. For this reason, for example, Patent Document 1 or Patent Document 2 discloses a paper sheet identification apparatus in which an infrared image is read and an image sensor unit is incorporated.

Japanese Patent Laid-Open No. 06-203243 JP 2009-059214 A

  Incidentally, an image sensor unit of a general image reading apparatus has sensitivity in the visible light region but does not have sensitivity in the infrared region. For this reason, the image sensor unit of a general image reading apparatus cannot be applied to a paper sheet identification apparatus that reads an infrared image. Therefore, it is not possible to share parts between an image reading apparatus such as a general image scanner and a paper sheet identification apparatus that handles banknotes.

  In view of the above situation, the problem to be solved by the present invention is a paper on which reading of both the visible light region and the infrared region is performed by a photoelectric conversion module having sensitivity in the visible light region but not in the infrared region. An image sensor unit of a leaf identification device is provided.

  In order to solve the above problems, the present invention provides an image sensor unit that irradiates an object to be illuminated and reads the object to be illuminated, and includes a light source that irradiates infrared light, and a wavelength conversion layer that converts infrared light into visible light. And a photoelectric conversion module that receives light and converts it into an electrical signal, wherein the wavelength conversion layer is provided between the object to be illuminated and the photoelectric conversion module.

  ADVANTAGE OF THE INVENTION According to this invention, the infrared image of a to-be-illuminated body can be converted into a visible light image with a wavelength conversion layer, can be received with a photoelectric conversion module, and can be converted into an electrical signal. For this reason, the to-be-illuminated body which uses infrared rays can be implemented with the photoelectric conversion module which has a sensitivity in the area | region of visible light. Therefore, a photoelectric conversion module having no sensitivity in the infrared region as used in a general image scanner can be applied.

FIG. 1 is a schematic cross-sectional view of an image sensor unit. FIG. 2 is an exploded perspective view of the image sensor unit. FIG. 3 is a graph showing the sensitivity characteristics of the photoelectric conversion module provided in the image sensor unit and the characteristics of the wavelength conversion layer and the wavelength conversion member. FIG. 4 is a schematic cross-sectional view of an image sensor unit including a filter. FIG. 5 is an exploded perspective view of an image sensor unit including a filter. FIG. 6 is a schematic sectional view showing a modification of the image sensor unit. FIG. 7 is an exploded perspective view showing a modification of the image sensor unit. FIG. 8 is a schematic cross-sectional view showing a modification of the image sensor unit. FIG. 9 is a schematic cross-sectional view showing a modification of the image sensor unit. FIG. 10 is a schematic sectional view showing a modification of the image sensor unit. FIG. 11 is a diagram illustrating a configuration of the paper sheet identification apparatus.

  Embodiments of the present invention will be described below in detail with reference to the drawings. The image sensor unit 1a is used, for example, by being incorporated in a paper sheet identification device that handles banknotes S as paper sheets that are objects to be illuminated. And the image sensor unit 1a can read the surface of the banknote S using visible light. FIG. 1 is a schematic cross-sectional view of the image sensor unit 1a, and FIG. 2 is an exploded perspective view of the image sensor unit 1a. As shown in FIGS. 1 and 2, the image sensor unit 1 a includes a casing 11, a light emitting module 21 as a light source 2 and a light guide member 22, a rod lens array 17, a sensor substrate 14, a cover member 13, And a wavelength conversion layer 15.

  The casing 11 is a housing of the image sensor unit 1a and has, for example, a substantially rod-like configuration and is formed of a resin material. Inside the casing 11, an area that can accommodate the light guide member 22, an area that can accommodate the rod lens array 17, and an area that can accommodate the sensor substrate 14 are formed. Furthermore, an area in which the light emitting module 21 can be accommodated is formed at the end of the casing 11 in the longitudinal direction.

    The light emitting module 21 and the light guide member 22 as the light source 2 can irradiate the bill S with visible light and infrared light. As the light emitting module 21, a point light source including a light emitting element that emits visible light (for example, a red LED, a green LED, and a blue LED) and an element that emits infrared light (for example, an infrared LED) can be applied. In addition, the light emitting module 21 may not be a structure provided with the light emitting element of the color required for full color reading of the banknote S, for example, may be the structure provided with the light emitting element of only one color. The light guide member 22 is an optical member that linearizes visible light and infrared rays emitted from the light emitting module 21 and irradiates the bill S. The light guide member 22 is a transparent bar-shaped member having a predetermined cross-sectional shape, and is formed of, for example, an acrylic resin material, polycarbonate, or the like. An emission surface 221 and a reflection surface 222 are formed on the side surface of the light guide member 22. The exit surface 221 is a surface that emits light toward the banknote S. The reflective surface 222 is a surface having a surface property that easily reflects and diffuses light. A pattern (not shown) made of a light-reflective paint is formed on the reflecting surface 222 by, for example, silk printing. The exit surface 221 and the reflection surface 222 are both band-shaped surfaces extending in the longitudinal direction of the light guide member 22 and are formed at positions facing each other.

  The rod lens array 17 is an optical member as an imaging element for imaging visible light and infrared light reflected by the banknote S on a light receiving unit (not shown) on the surface of a photoelectric conversion module 141 (described later) provided on the sensor substrate 14. is there. The rod lens array 17 includes an incident surface 171 on which visible light and infrared light from the banknote S are incident, and an emission surface 172 that emits visible light and infrared light on the photoelectric conversion module 141. The rod lens array 17 has, for example, a configuration in which a plurality of erecting equal-magnification imaging elements are linearly arranged. A conventionally known rod lens array can be applied to the rod lens array 17.

  The sensor substrate 14 is a substrate on which a photoelectric conversion module 141 that receives visible light and converts it into an electrical signal is mounted. The photoelectric conversion module 141 includes a plurality of photoelectric conversion elements having sensitivity in the visible light region, and includes a configuration in which the plurality of photoelectric conversion elements are linearly arranged. Note that the photoelectric conversion element applied to the photoelectric conversion module 141 may not have sensitivity in the infrared region. Therefore, a photoelectric conversion module used in an image reading apparatus such as a general image scanner can be applied to the photoelectric conversion module 141.

  The cover member 13 is a member provided so as to cover the light guide member 22 and the rod lens array 17. The cover member 13 has a function of protecting the light guide member 22 and the rod lens array 17 and a function of keeping the sheet-shaped banknote S in contact with the plane. The cover member 13 is a flat member, and for example, a glass plate or a transparent resin plate can be applied.

  The wavelength conversion layer 15 converts infrared rays into visible light. For example, an up-conversion (frequency up-conversion) fluorescent material that emits visible light when excited by infrared rays can be applied to the wavelength conversion layer 15. In particular, a fluorescent material that is excited by infrared rays in the wavelength region of 1000 to 1500 nm and emits visible light in the wavelength region of 500 to 750 nm is suitable. As a fluorescent material having such characteristics, for example, fluoride microcrystals can be applied. The wavelength conversion layer 15 is provided on the visible light and infrared light path L between the bill S and the photoelectric conversion module 141 (in other words, between the cover member 13 in contact with the bill S and the photoelectric conversion module 141). . 1 and 2 show a configuration in which the wavelength conversion layer 15 is formed on the surface of the photoelectric conversion module 141. As a method of forming the wavelength conversion layer 15, for example, a method of applying a paint containing a fluorescent material to the surface of the photoelectric conversion module 141 and forming a film of a fluorescent agent as the wavelength conversion layer 15 can be applied. In addition, the structure (= member as the wavelength conversion layer 15) which consists of a material containing a fluorescent agent may be arrange | positioned on the surface of the photoelectric conversion module 141. For example, glass containing a fluorescent material can be applied to the member as the wavelength conversion layer 15. Thus, the wavelength conversion layer 15 may be configured to be provided integrally on the surface of the photoelectric conversion module 141 or may be configured to be provided as a separate member.

  Next, the assembly structure of the image sensor unit 1a will be described. The light guide member 22 and the rod lens array 17 are disposed substantially parallel to each other. The light emitting module 21 is arranged so that visible light and infrared light can be irradiated to the longitudinal end surface of the light guide member 22. For this reason, visible light and infrared rays emitted from the light emitting module 21 are incident on the inside from the end face of the light guide member 22. Visible light and infrared rays that have entered the light guide member 22 are reflected and diffused by the reflection surface 222 and emitted from the emission surface 221 toward the bill S. Since the emission surface 221 of the light guide member 22 is formed in a strip shape extending in the longitudinal direction, visible light and infrared rays emitted from the light emitting module 21 are linearized by the light guide member 22. The cover member 13 is disposed so as to cover the emission surface 221 of the light guide member 22 and the incident surface 171 of the rod lens array 17. The rod lens array 17 and the photoelectric conversion module 141 mounted on the sensor substrate 14 are arranged so that their longitudinal directions are substantially parallel. Then, the exit surface 172 of the rod lens array 17 and the photoelectric conversion module 141 face each other.

  Next, the operation of the image sensor unit 1a will be described. Visible light and infrared rays emitted from the light emitting elements of the light emitting module 21 are linearized by the light guide member 22 and irradiated to the banknote S. Visible light and infrared light reflected on the surface of the banknote S are incident on the inside from the incident surface 171 of the rod lens array 17 and are emitted from the emission surface 172 toward the photoelectric conversion module 141 of the sensor substrate 14. Visible light emitted from the exit surface 172 of the rod lens array 17 passes through the wavelength conversion layer 15 and forms an image on the light receiving portion of the photoelectric conversion module 141. The photoelectric conversion module 141 receives visible light that has been imaged and converts it into an electrical signal. On the other hand, the infrared rays emitted from the emission surface 172 of the rod lens array 17 reach the wavelength conversion layer 15 provided on the surface of the photoelectric conversion module 141. The wavelength conversion layer 15 emits visible light when excited by infrared rays (that is, converts infrared rays into visible light). The photoelectric conversion module 141 receives visible light emitted from the wavelength conversion layer 15 and converts it into an electrical signal.

  Then, the image sensor unit 1a has a short operation for detecting the reflected light by irradiating the banknote S with visible light and an operation for detecting the visible light excited by the infrared ray reflected by irradiating the banknote S with infrared light. Repeat alternately in time. By such an operation, the image sensor unit 1a reads a predetermined pattern (for example, a hologram) provided on the banknote S as a visible light image and reads the banknote S as an infrared image.

  Details of the reading operation using infrared rays are as follows. FIG. 3 is a graph showing the relationship between the sensitivity characteristics of the photoelectric conversion module 141 and the fluorescence characteristics (= wavelength conversion characteristics) of the wavelength conversion layer 15. As shown in FIG. 3A, the photoelectric conversion module 141 has sensitivity in the region of 400 to 700 nm, and has a sensitivity peak in the vicinity of 530 nm. On the other hand, as shown in FIG.3 (b), the wavelength conversion layer 15 will be excited when infrared rays with a wavelength of 1000-1500 nm are irradiated, and will emit visible light with a wavelength of 500-750 nm. Thus, the wavelength conversion layer 15 emits visible light in a wavelength region near the sensitivity peak of the photoelectric conversion module 141 when irradiated with infrared rays. For this reason, the infrared image of the banknote S can be read as a visible light image by the photoelectric conversion module 141 having sensitivity in the visible light region. Therefore, the photoelectric conversion module 141 can be shared by the image sensor unit 1a and a general image scanner.

  Moreover, the structure provided with the filter 16 which interrupts | blocks the visible light converted by the wavelength conversion layer 15, and permeate | transmits visible light and infrared rays of a wavelength range other than that may be sufficient. Accordingly, the image sensor unit 1b including the filter 16 will be described with reference to FIGS. FIG. 4 is a cross-sectional view schematically showing the configuration of the image sensor unit 1 b including the filter 16. FIG. 5 is an exploded perspective view schematically showing the configuration of the image sensor unit 1 b including the filter 16. In addition, about the structure which is common in the image sensor unit 1a which is not provided with the filter 16, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  As shown in FIG. 4, the image sensor unit 1 b is provided with a filter 16 on a visible light and infrared ray path L between the wavelength conversion layer 15 and the bill S. For example, as shown in FIG. 4, the filter 16 is provided between the wavelength conversion layer 15 provided on the surface of the photoelectric conversion module 141 and the rod lens array 17. The filter 16 only needs to block visible light converted by the wavelength conversion layer 15 and transmit visible light and infrared light in other wavelength regions, and the configuration is not limited. For example, various known band cut filters can be applied to the filter 16.

  The operation of the image sensor unit 1b including the filter 16 is basically the same as that of the image sensor unit 1a including no filter. The filter 16 blocks visible light emitted from the wavelength conversion layer 15 so as not to reach the banknote S. Specifically, the filter 16 can block visible light near 530 nm and transmit visible light and infrared rays in other wavelength regions. For this reason, the filter 16 can prevent visible light emitted from the wavelength conversion layer 15 from returning to the banknote S and reaching the photoelectric conversion module 141. Therefore, the photoelectric conversion module 141 can detect only visible light that reaches directly from the wavelength conversion layer 15 and convert it into an electrical signal. With such a configuration, it is possible to prevent a decrease in reading accuracy using infrared rays.

  That is, the visible light emitted from the wavelength conversion layer 15 is omnidirectional, so if the filter 16 is not provided, a part of the visible light emitted from the wavelength conversion layer 15 is reflected back to the banknote S and then photoelectrically converted. Module 141 is reached. Then, the photoelectric conversion module 141 receives visible light obtained by adding visible light reflected by the banknote S to visible light directly reaching from the wavelength conversion layer 15. As a result, the photoelectric conversion module 141 may not be able to accurately measure the level of infrared light reflected by the banknote S. In particular, since visible light reflected by the banknote S is added, the level of visible light detected by the photoelectric conversion module 141 may increase. On the other hand, when the filter 16 is provided, the filter 16 can prevent the visible light emitted from the wavelength conversion layer 15 from reaching the photoelectric conversion module 141 after being reflected back to the banknote S. Therefore, the level of infrared rays reflected by the banknote S can be accurately measured. That is, if it is such a structure, the infrared rays reflected on the surface of the banknote S are measured using the photoelectric conversion module 141 having sensitivity in the infrared region without having the wavelength conversion layer 15 and the filter 16 and Similar results are obtained.

  The positions of the wavelength conversion layer 15 and the filter 16 described above are examples, and are not limited to these positions. For example, the wavelength conversion layer 15 and the filter 16 may be configured to be provided at the positions shown in FIGS. 6 and 7 show a configuration in which the wavelength conversion layer 15 is provided on the surface of the photoelectric conversion module 141 and the filter 16 is disposed between the rod lens array 17 and the cover member 13. FIG. 8 shows a configuration in which the wavelength conversion layer 15 is formed on the surface of the exit surface 172 of the rod lens array 17 and the filter 16 is disposed between the rod lens array 17 and the cover member 13. FIG. 9 shows a configuration in which the wavelength conversion layer 15 is formed on the surface of the incident surface 171 of the rod lens array 17 and the filter 16 is disposed between the rod lens array 17 and the cover member 13. In any of the configurations shown in FIGS. 6 to 9, the wavelength conversion layer 15 is provided between the photoelectric conversion module 141 and the banknote S, and the filter 16 is provided between the wavelength conversion layer 15 and the banknote S. Is done. Similarly, the wavelength conversion layer 15 may be configured integrally on the surface of the photoelectric conversion module 141 or the rod lens array 17, or may be configured as a separate member. 6 to 9 illustrate a configuration in which both the wavelength conversion layer 15 and the filter 16 are provided, a configuration in which the filter 16 is not provided may be used.

  As described above, the wavelength conversion layer 15 may be provided between the photoelectric conversion module 141 and the banknote S. Furthermore, what is necessary is just the structure by which the filter 16 is provided between the wavelength conversion layer 15 and the banknote S. And if it is a structure like these, there can exist the same effect.

  In addition, about the part which abbreviate | omitted illustration and description among image sensor units 1a and 1b, the same structure as a conventionally well-known image sensor unit is applicable.

  In the above-described embodiment, the configuration in which the image sensor units 1a and 1b read visible light and infrared light reflected by the banknote S is shown. However, the configuration may be such that visible light and infrared light that passes through the banknote S are read. Furthermore, the structure which can read the visible light and infrared rays which the image sensor units 1a and 1b reflect with the banknote S, and the visible light and infrared rays which permeate | transmit the banknote S may be sufficient.

  The structure which can read the visible light and infrared rays which permeate | transmit the banknote S is demonstrated with reference to FIG. FIG. 10 is a diagram illustrating a configuration in which visible light and infrared light that pass through the banknote S are read by the image sensor unit 1b. 10 shows a configuration in which the image sensor unit 1b including the filter 16 is applied, a configuration in which the image sensor unit 1a not including the filter 16 is applied may be used. As shown in FIG. 10, the light source unit 5 is disposed facing the image sensor units 1 a and 1 b, and the bill S can be passed between the image sensor units 1 a and 1 b and the light source unit 5. The light source unit 5 includes a light source 6 that can irradiate the bill S with visible light and infrared light. The same configuration as the light source 2 of the image sensor units 1 a and 1 b can be applied to the light source 6 of the light source unit 5. For example, the light source 6 of the light source unit 5 includes a light emitting module 61 that functions as a point light source by mounting a light emitting element that emits visible light and an element that emits infrared light, and linearizes visible light and infrared light emitted from the light emitting module 61. A light guide member 62. And the light source unit 5 can irradiate the banknote S with visible light and infrared rays. Visible light and infrared rays irradiated from the light source unit 5 pass through the banknote S and enter the incident surface 171 of the rod lens array 17 of the image sensor units 1a and 1b. The operation in which the image sensor units 1a and 1b read the visible light and the infrared light transmitted through the banknote S is the same as the operation for reading the visible light and the infrared light reflected by the banknote S.

  The image sensor units 1a and 1b perform an operation for detecting visible light transmitted from the light source unit 5 to the banknote S and an operation for detecting infrared light transmitted from the light source unit 5 to the banknote S for a short time. Repeat alternately with. By such an operation, the image sensor units 1a and 1b can read visible light and infrared rays that pass through the banknote S. Furthermore, the image sensor units 1a and 1b have these two operations, an operation of irradiating the bill S with visible light to detect reflected light, and visible light excited by the infrared rays reflected by irradiating the bill S with infrared rays. The operation of detecting the above may be repeated periodically in a short time. By such an operation, the image sensor units 1a and 1b can read visible light and infrared rays that pass through the bill S and visible light and infrared rays that are reflected by the bill S.

  Next, the paper sheet identification device 3 to which the image sensor units 1a and 1b are applied will be described with reference to FIG. The paper sheet identification device 3 irradiates a paper sheet such as the banknote S with light to read the reflected light, and identifies the paper sheet using the read reflected light. As shown in FIG. 11, the paper sheet identification device 3 includes an image sensor unit 1 a (or 1 b) and a transport roller 31 that transports the banknote S. And the paper sheet identification device 3 conveys the image sensor unit 1a (or 1b) on the image sensor unit 1a (or 1b) in the reading direction (sub-scanning direction) via the cover member 13 with the banknote S between the conveyance rollers 31. A conveyance path A is set for this purpose. At this time, the focal point on the banknote S side of the rod lens array 17 is set at the approximate center of the transport path A. The operation of the paper sheet identification device 3 having such a configuration is as follows. The image sensor units 1a and 1b applied to the paper sheet identification device 3 read the predetermined pattern provided on the banknote S as the paper sheet as a visible light image and the banknote S as an infrared image by the operation described above. read. Thereafter, the paper sheet recognition device 3 is visible to the bill S image obtained by irradiating the bill S, which is a genuine bill prepared in advance, with visible light and infrared rays, and the bill S to be determined at the time of authenticity determination. The authenticity determination of the banknote S is performed by comparing with the image obtained by irradiating light and infrared rays. This is because the bill S, which is a genuine note, is provided with regions in which images obtained from visible light and infrared light are different from each other. In addition, about the part which abbreviate | omitted description and illustration, the same structure as the conventional paper sheet identification device is applicable.

  As mentioned above, although embodiment of this invention was described with reference to drawings, this invention is not limited to these embodiment at all. The present invention can be variously modified without departing from the spirit of the invention. For example, in the above-described embodiment, the light source includes a light emitting module that is a point light source and a light guide member that converts the point light source into a linear light source. However, the light source is limited to such a structure. It is not a thing. The light source may be a linear light source in which light emitting elements of point light sources are arranged in series. In short, the light source may be configured to irradiate visible light and infrared light onto the surface of the object to be illuminated. Further, in the above-described embodiment, the configuration in which the image sensor unit includes a set of light sources is shown, but the number of light sources is not limited. For example, the image sensor unit may include two sets of light sources.

  Moreover, in embodiment mentioned above, although the structure to which a banknote is applied as a to-be-illuminated body was shown, the kind of to-be-illuminated body is not limited. For example, various securities or an ID card can be applied as the object to be illuminated. Any paper sheet that reacts with infrared rays can be applied.

  The present invention is a technique effective as an image sensor unit and a paper sheet identification device.

1a, 1b: Image sensor unit, 11: casing, 13: cover member, 14: sensor substrate, 141: photoelectric conversion module, 15: wavelength conversion layer, 16: filter, 17: rod lens array, 2: light source, 21: Light emitting module, 22: light guide member, 3: paper sheet identification device

Claims (8)

An image sensor unit that irradiates light to an illuminated body and reads the illuminated body,
A light source that emits infrared light;
A wavelength conversion layer for converting infrared light into visible light;
A photoelectric conversion module that receives light and converts it into an electrical signal;
The image sensor unit, wherein the wavelength conversion layer is provided between the object to be illuminated and the photoelectric conversion module.   The image sensor unit according to claim 1, wherein the wavelength conversion layer is provided on a surface of the photoelectric conversion module. An image forming element that forms an image of the reflected light from the object to be illuminated on the surface of the photoelectric conversion module;
The image sensor unit according to claim 1, wherein the wavelength conversion layer is provided between the photoelectric conversion module and the imaging element.   The image sensor unit according to claim 3, wherein the wavelength conversion layer is provided on a surface of the imaging element. An imaging element that forms an image of reflected light from the object to be illuminated on the surface of the photoelectric conversion module; and a cover member that covers the imaging element;
The image sensor unit according to claim 1, wherein the wavelength conversion layer is provided between the imaging element and the cover member.   The image according to claim 1, wherein a filter that blocks visible light converted by the wavelength conversion layer is provided between the wavelength conversion layer and the object to be illuminated. Sensor unit. A paper sheet identifying apparatus for irradiating a paper sheet with light to identify the paper sheet,
A light source that emits infrared light; a photoelectric conversion module that receives light and converts it into an electrical signal; and a wavelength conversion layer that is provided between the paper sheet and the photoelectric conversion module and converts infrared light into visible light. A paper sheet identification apparatus comprising an image sensor unit.   The paper sheet identification apparatus according to claim 7, wherein a filter that blocks visible light converted by the wavelength conversion layer is provided between the wavelength conversion layer and the paper sheet.

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