Patent Application
20100252747
This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2009-093217, filed Apr. 7, 2009, the entire contents of which are incorporated herein by reference.
1. Field of the Invention
This invention relates to a fluorescence detection device configured to detect a fluorescent substance attached to an inspected medium, such as a sheet of paper, and authenticate the inspected medium.
2. Description of the Related Art
In recent years, fluorescent printing for authentication has been done on some sheets of paper, such as paper money. A security information medium reader disclosed in Jpn. Pat. Appln. KOKAI Publication No. 2007-193387 is proposed as a device for detecting the fluorescent printing on the sheets of paper. In this security information medium reader, an information medium is irradiated successively by infrared, ultraviolet, and visible-light LEDs. Fluorescence emitted from the information medium is captured by a CCD camera, and a fluorescence pattern image and fine high-definition pattern are displayed on a monitor of a personal computer. According to this device, a fluorescence that glows at a specific wavelength is detected by a light receiving element through a filter that transmits light of the specific wavelength only.
A novel method and device for identifying printed matter are proposed in Jpn. Pat. Appln. KOKAI Publication No. 2006-275578. According to this method or device, two or more light emission characteristics and/or afterglow characteristic spectra emitted from a fluorescent substance and/or phosphor attached to printed matter are captured. The captured spectra are measured to detect a specific pattern of the fluorescent substance and/or phosphor, whereby the printed matter is identified.
In the security information medium reader disclosed in Jpn. Pat. Appln. KOKAI Publication No. 2007-193387, the phosphor is detected by the light receiving element through the filter that transmits light of the specific wavelength only. In this case, phosphors that glow at some other wavelengths in a wider frequency band that includes the specific wavelength can also be detected, so that it is difficult to perform valid authentication.
Although the identification method and device disclosed in Jpn. Pat. Appln. KOKAI Publication No. 2006-275578 can solve the above problem, the identification based on spectrometry or measurement of light emission characteristic spectra requires complex equipment and processing.
This invention has been made in consideration of these circumstances, and its object is to provide a fluorescence detection device capable of accurately detecting a fluorescent substance that glows at one or more specific wavelengths and easily performing authentication processing.
According to an aspect of the invention, there is provided a fluorescence detection device for detecting a fluorescent substance which is attached to an inspected medium and glows at a specific wavelength, comprising: an illumination device configured to apply excitation light for exciting the fluorescent substance to the inspected medium; a first photoreceptor configured to receive excited light from the fluorescent substance of the inspected medium and detect only light of the specific wavelength; a second photoreceptor configured to receive excited light from the fluorescent substance of the inspected medium and detect light in a wider frequency band including the specific wavelength; and an authentication section configured to authenticate the fluorescent substance based on detection signals from the first and second photoreceptors.
According to another aspect of the invention, there is provided a fluorescence detection device for detecting a fluorescent substance which is attached to an inspected medium and glows at a plurality of different specific wavelengths, comprising: an illumination device configured to apply a plurality of excitation light components of different wavelengths for individually exciting the fluorescent substance to the inspected medium; a first photoreceptor configured to receive excited light from the fluorescent substance of the inspected medium and detect only light of a first one of the different specific wavelengths; a third photoreceptor configured to receive excited light from the fluorescent substance of the inspected medium and detect only light of a second one of the different specific wavelengths; a second photoreceptor configured to receive excited light from the fluorescent substance of the inspected medium and detect light in a wider frequency band including the first and second specific wavelengths; and an authentication section configured to authenticate the fluorescent substance based on detection signals from the first, third, and second photoreceptors.
According to this arrangement, there is provided a fluorescence detection device capable of accurately detecting a fluorescent substance that glows at one or more specific wavelengths and easily performing authentication processing.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.
The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention, and together with the general description given above and the detailed description of the embodiments given below, serve to explain the principles of the invention.
Fluorescence detection devices according to embodiments of this invention will now be described with reference to the accompanying drawings.
As shown in
The conveying mechanism 10 includes a plurality of conveyor rollers 7, which nip and convey the sheet of paper 8, a belt, guides (not shown), etc. The standard-size sheet of paper 8 is conveyed in the direction of arrow B by the conveyor rollers 7. Although the sheet of paper 8 is designed to be conveyed by the conveying mechanism 10, it may alternatively be located at rest in a predetermined inspection position.
The fluorescent printing element 11 on the sheet of paper 8 is assumed to include a fluorescent substance, which is excited by light of an excitation wavelength λx1 and emits light of a specific wavelength λm1, for example. Illumination device L1 is located in a predetermined angular position with respect to the sheet of paper 8 and serves to apply the excitation light to the entire fluorescent printing element 11 on the sheet of paper 8. The light emitted from illumination device L1 includes a frequency band in which the printing element 11 is excited, that is, a frequency band for at least excitation wavelength λ.
The fluorescent printing element 11, which is excited by the illumination light, emits fluorescent light of specific wavelength λml, and the emitted light is detected by the light receiving system 14.
As shown in
The first photoreceptor 16 characterized in this manner is not limited to the combination of the optical sensor and filter and may also be easily realized by means of an alternative optical member. Although the optical sensor may be a photosensor, CCD, etc., it may be any other suitable type that is sensitive to specific wavelength λm1.
The second photoreceptor 18 has such a characteristic that it broadly receives light components of wavelengths in a wider frequency band that includes specific wavelength λm'. In this case, the second photoreceptor 18 includes an optical sensor S2 and optical filter f2 located between the sensor S2 and inspected medium 8. The optical filter f2 has such a characteristic that it transmits light components of wavelengths in a wide frequency band including specific wavelength λml. The second photoreceptor 18 characterized in this manner is not limited to the combination of the optical sensor and filter and may also be easily realized by means of an alternative optical member. Although the optical sensor may be a photosensor, CCD, etc., it may be any other suitable type that is sufficiently sensitive to broadly receive light components of wavelengths in a wide frequency band for transmission through the optical filter f2.
The fluorescent light of specific wavelength λml emitted from the fluorescent printing element 11 is incident on and received by the first and second photoreceptors 16 and 18. The light received by the first photoreceptor 16 is converted into an electrical signal, which is sent to the authentication section 20. The light received by the second photoreceptor 18 is converted into an electrical signal, which is sent to the authentication section 20.
As shown in
The following is a description of the detection operation of the fluorescence detection device constructed in this manner.
When the sheet of paper 8 is conveyed to a predetermined detection position by the conveying mechanism 10, as shown in
The optical sensor S1 of the first photoreceptor 16 receives only light of specific wavelength λm1 transmitted through optical filter f1 and converts the received fluorescent light of specific wavelength λnil into an electrical signal and outputs it. The output signal from the optical sensor S1 is sent to the CPU 24 and compared with the normal data at wavelength λm1 stored in the memory 25, whereby it is authenticated.
If the output signal from the first photoreceptor 16 is different from the normal data at wavelength λm1, the fluorescent printing element 11 is determined to be counterfeit, that is, the sheet of paper 8 is determined to be counterfeit. If the output signal from the first photoreceptor 16 is identical with the normal data at wavelength λm1, it is input to the comparator 22.
On the other hand, the optical sensor S2 of the second photoreceptor 18 receives light in a wide frequency band including specific wavelength λm1 transmitted through the optical filter f2 and converts the received fluorescent light of specific wavelength λm1 into an electrical signal and outputs it. The output signal from optical sensor S2 is input to the comparator 22, which comparatively computes the respective output levels of optical sensors S1 and S2. As shown in
The following is a description of a case where the fluorescent printing element 11 is a fluorescent substance that has a fluorescence emission characteristic λm1-2 with a wider frequency band including the specific wavelength λml.
Fluorescent light of wavelength λm1-2 emitted from the fluorescent printing element 11 by excitation light from illumination device L1 is incident on the first and second photoreceptors 16 and 18. The optical filter f1 of the first photoreceptor 16, by its transmission characteristic, transmits only light of specific wavelength λm1, so that optical sensor S1 receives only the light of wavelength λm1. The output level of the electrical signal converted by the optical sensor S1 represents only a portion transmitted through the optical filter f1, that is, a portion corresponding to the light of specific wavelength λm1.
The optical filter f2 of the second photoreceptor 18 has such a characteristic that it transmits light in a wider frequency band including specific wavelength λm1. Therefore, all light components with the fluorescence emission characteristic λm1-2 are incident on the optical sensor S2 of the second photoreceptor 18, so that the output level of the electrical signal converted by the optical sensor S2 represents the fluorescence emission characteristic λm1-2.
Consequently, the respective signal output levels of the first and second photoreceptors 16 and 18, which are comparatively computed by the comparator 22, are not equal, that is, the output level of the second photoreceptor 18 is higher.
Thus, if the fluorescence emission from the fluorescent printing element 11 is at the normal specific wavelength λm1, the signal output levels S1 and S2 of the first and second photoreceptors 16 and 18 are equal. In the case of fluorescence emission wavelength λm1-2 having a wider frequency band including specific wavelength λm1, the signal output levels S1 and S2 are different, that is, S1<S2.
If the compared signal output levels S1 and S2 are equal, the authentication section 20 determines that the fluorescent substance is a desired one. If not, the fluorescent substance is determined to be an undesired one.
According to the first embodiment, as described above, there is obtained a fluorescence detection device of simple construction capable of accurately detecting a fluorescent substance that glows at a specific wavelength and easily determining the presence of a desired fluorescent substance.
In the present embodiment, (1) the output signal from the first photoreceptor 16 is input to the CPU 24 to authenticate the received fluorescence emission, and (2) the output signals from the first and second photoreceptors 16 and 18 are then compared by the comparator 22. Alternatively, however, process 1 may be omitted so that the fluorescence emission is authenticated in process 2 only.
The following is a description of a fluorescence detection device according to a second embodiment. This fluorescence detection device detects a sheet of paper 8 to which a fluorescent printing element 11 that glows at different specific wavelengths is attached. For example, the fluorescent printing element 11, an object to be detected, is formed by mixing or superposing a fluorescent substance that is excited by light of an excitation wavelength λx1 and glows at a specific wavelength λm1 and a fluorescent substance that is excited by light of an excitation wavelength λx2 and glows at a specific wavelength λm2.
As shown in
The conveying mechanism 10 includes a plurality of conveyor rollers 7, which nip and convey the sheet of paper 8, a belt, guides (not shown), etc. The standard-size sheet of paper 8 is conveyed in the direction of arrow B by the conveyor rollers 7. Although the sheet of paper 8 is designed to be conveyed by the conveying mechanism 10, it may alternatively be located at rest in a predetermined inspection position.
The illumination device L2 is located in a predetermined angular position with respect to the sheet of paper 8 and serves to apply the excitation light to the entire fluorescent printing element 11 on the sheet of paper 8. The light emitted from the illumination device L2 includes a frequency band for excitation wavelength λx2 in which the printing element 11 is excited. The printing element 11 excited by this illumination light emits fluorescent light of specific wavelength λm2, which is detected by the light receiving system 14.
Although laser sources or LEDs may be used as the illumination devices L1 and L2, the invention is not limited to this arrangement.
As shown in
The first photoreceptor 16 characterized in this manner is not limited to the combination of the optical sensor and filter and may also be easily realized by means of an alternative optical member. Although the optical sensor may be a photosensor, CCD, etc., it may be any other suitable type that is sensitive to specific wavelength λm1.
The third photoreceptor 28 has such a characteristic that it receives only light of specific wavelength (second specific wavelength) λm2. In this case, the third photoreceptor 28 includes an optical sensor S3 and optical filter f3 located between the sensor S3 and inspected medium. The optical filter f3 has such a characteristic that it transmits only light of specific wavelength λm2.
The third photoreceptor 28 characterized in this manner is not limited to the combination of the optical sensor and filter and may also be easily realized by means of an alternative optical member. Although the optical sensor S3 may be a photosensor, CCD, etc., it may be any other suitable type that is sensitive to specific wavelength λm2.
The second photoreceptor 18 has such a characteristic that it broadly receives light components of wavelengths in a frequency band that includes specific wavelengths λm1 and λm2 or a wider frequency band. In this case, the second photoreceptor 18 includes an optical sensor S2 and optical filter f2 located between the sensor S2 and inspected medium. The optical filter f2 has such a characteristic that it transmits light components of wavelengths in a wide frequency band including specific wavelengths λm1 and λm2.
The second photoreceptor 18 characterized in this manner is not limited to the combination of the optical sensor and filter and may also be easily realized by means of an alternative optical member. Although the optical sensor S2 may be a photosensor, CCD, etc., it may be any other suitable type that is sufficiently sensitive to broadly receive light components of wavelengths in a wide frequency band for transmission through the optical filter f2.
The fluorescent light of specific wavelength λm1 emitted from the fluorescent printing element 11 is incident on and received by the first and second photoreceptors 16 and 18. The fluorescent light of specific wavelength λm2 emitted from the fluorescent printing element 11 is incident on and received by the third and second photoreceptors 28 and 18. The light components received by the first and second photoreceptors 16 and 18 are converted individually into electrical signals, which are sent to the authentication section 20.
As shown in
The following is a description of the detection operation of the fluorescence detection device constructed in this manner.
When the sheet of paper 8 is conveyed to a predetermined detection position by the conveying mechanism 10, as shown in
The light of wavelength λx2 emitted from the illumination device L2 is applied at a predetermined angle to the fluorescent printing element 11, whereupon the element 11 emits the fluorescent light of specific wavelength λm2. This fluorescent light is received by the third and second photoreceptors 28 and 18.
The optical sensor S1 of the first photoreceptor 16 receives only light of specific wavelength λm1 transmitted through the optical filter f1 and converts the received fluorescent light of wavelength λm1 into an electrical signal and outputs it. The optical sensor S3 of the third photoreceptor 28 receives only light of specific wavelength λm2 transmitted through the optical filter f3 and converts the received fluorescent light of wavelength λm2 into an electrical signal and outputs it. The optical sensor S2 of the second photoreceptor 18 receives light components in a wide frequency band including specific wavelengths λm1 and λm2 transmitted through the optical filter f2 and converts the received fluorescent light components of wavelengths λm1 and λm2 into electrical signals and outputs them.
Output signals from the first and third photoreceptors 16 and 28 are added together, and a sum output level is input to the comparator 22. Further, an output signal from the second photoreceptor 18 is input to the comparator 22, in which it is computed in comparison with the sum output signal. A signal output level can be regarded as the area of light transmitted through each filter shown in
Data on the comparative computation by the comparator 22 is sent to the CPU 24. Since the sensor output levels are equal, the CPU 24 determines that the fluorescent printing element 11 and hence the sheet of paper 8 are real. If the sum output level, obtained by adding up the respective outputs of the optical sensors S1 and S3, and the output level of the optical sensor S2 are different, the CPU 24 determines that the fluorescent printing element 11 is counterfeit.
The following is a description of a case where the fluorescent printing element 11 is a fluorescent substance that has a fluorescence emission characteristic λm1-2 with a wider frequency band including specific wavelengths λm1 and λm2.
Fluorescent light of wavelength λm1-2 emitted from the fluorescent printing element 11 by excitation light components of wavelengths λm1 and λm2 from illumination devices L1 and L2 is incident on the first, third, and second photoreceptors 16, 28 and 18. The optical filter f1 of the first photoreceptor 16, by its transmission characteristic, transmits only light of specific wavelength λm1, so that the optical sensor S1 receives only light of specific wavelength λml. The output level of the electrical signal converted by the optical sensor S1 represents only a portion transmitted through the optical filter f1, that is, a portion corresponding to the light of specific wavelength λm1. The optical filter f3 of the third photoreceptor 28, by its transmission characteristic, transmits only light of specific wavelength λm2, so that the optical sensor. S3 receives only the light of specific wavelength λm2. The output level of the electrical signal converted by the optical sensor S3 represents only a portion transmitted through the optical filter f3, that is, a portion corresponding to the light of specific wavelength λm2.
The optical filter f2 of the second photoreceptor 18 has such a characteristic that it transmits light components in a wider frequency band including specific wavelengths λml and λm2. Therefore, the optical sensor S2 of the second photoreceptor 18 receives light at a portion where the transmission characteristic of the optical filter f2 and the fluorescence emission characteristic λm1-2 overlap each other, so that the output level of the electrical signal converted by the optical sensor S2 represents this overlapping portion.
Consequently, the sum output level of the first and third photoreceptors 16 and 28 and the output level of the second photoreceptor 18, which are comparatively computed by the comparator 22, are not equal, that is, the output level of the optical sensor S2 of the second photoreceptor 18 is higher.
Thus, if the fluorescence emission from the fluorescent printing element 11 is at specific wavelength λm1 or λm2 only, the output level S2 of the second photoreceptor 18 and an output level (S1+S3), that is, the sum of the respective outputs of the first and third photoreceptors 16 and 28, are equal. In the case of fluorescence emission wavelength λm1-2 having a wider frequency band including specific wavelengths λm1 and λm2, the output levels of the first and second photoreceptors are defined by (S1+S3)<S2.
If the compared signal output levels are equal, the authentication section 20 determines that the fluorescent printing element 11 is a desired one. If not, the printing element is determined to be an undesired one.
According to the second embodiment, as described above, there is obtained a fluorescence detection device of simple construction capable of accurately detecting a fluorescent substance that glows at a plurality of different specific wavelengths and easily determining the presence of a desired fluorescent substance.
Although the detection of the fluorescence that glows at two different specific wavelengths has been described in connection with the second embodiment, the invention is not limited to this detection and is also applicable to the detection of a fluorescent substance that glows at three or more different emission wavelengths. The number of detection wavelengths can be increased if a photoreceptor having such a characteristic as to transmit only light components of additional wavelengths is added, and in addition, if the second photoreceptor is configured to receive light components in a frequency band including the additional wavelengths.
The following is a description of a fluorescence detection device according to a third embodiment. This fluorescence detection device detects a sheet of paper 8 to which a fluorescent printing element 11 that glows at different specific wavelengths is attached. For example, the fluorescent printing element 11, an object to be detected, is formed by mixing or superposing a fluorescent substance that is excited by light of an excitation wavelength λx1 and glows at a specific wavelength λm1 and a fluorescent substance that is excited by light of an excitation wavelength λx2 and glows at a specific wavelength λm2.
The fluorescence detection device according to the third embodiment is constructed in the same manner as the device of the second embodiment. Specifically, as shown in
As shown in
The CPU 24 authenticates the fluorescent printing element 11 based on an output from the comparator 22. The CPU 24 is connected with a memory 25, which stores predetermined data, e.g., the output levels of the correct wavelengths λm1 and λm2. Further, the CPU 24 functions as a light emission control section, which outputs lamp control signals to the illumination devices L1 and L2, thereby controlling devices L1 and L2 by means of a driver (not shown). Furthermore, the authentication section 20 includes a transfer switch 30 that connects the optical sensors S1 and S3 alternatively to the comparator 22. The transfer switch 30 is changed in association with the lamp control signals from the CPU 24.
The following is a description of the detection operation of the fluorescence detection device constructed in this manner.
When the sheet of paper 8 is conveyed to a predetermined detection position by the conveying mechanism 10, as shown in
The light of specific wavelength λm1 incident on the first photoreceptor 16 and received by the optical sensor S1 is converted into an electrical signal. Since the third photoreceptor 28 is not sensitive to specific wavelength λm1, the electrical signal cannot be output. The light of specific wavelength λm1 incident on the second photoreceptor 18 is received by the optical sensor S2 and converted into an electrical signal.
When the illumination device L1 is turned on in response to the lamp control signal from the CPU 24, as shown in
Then, the illumination devices L2 and L1 are turned on and off, respectively, under the control of the CPU 24, as shown in
The light of specific wavelength λm2 incident on the third photoreceptor 28 and received by the optical sensor S3 is converted into an electrical signal. Since the first photoreceptor 16 is not sensitive to specific wavelength λm2, the electrical signal cannot be output. The light of specific wavelength λm2 incident on the second photoreceptor 18 is received by the optical sensor S2 and converted into an electrical signal.
When the illumination device L2 is turned on in response to the lamp control signal from the CPU 24, as shown in
Data on the comparative computation by the comparator 22 is sent to the CPU 24. If the respective output levels of the optical sensors S1 and S2 are equal and if those of the optical sensors S3 and S2 are equal, the CPU 24 determines that the fluorescent printing element 11 and hence the sheet of paper 8 are real. If the output levels of the optical sensors S1 and S2 are different or if those of the optical sensors S3 and S2 are different, the CPU 24 determines that the fluorescent printing element 11 and hence the sheet of paper 8 are counterfeit.
The following is a description of a case where the fluorescent printing element 11 is a fluorescent substance that has a fluorescence emission characteristic λm1-2-1 with a wider frequency band including specific wavelength λml or a fluorescent substance that has a fluorescence emission characteristic λm1-2-2 with a wider frequency band including specific wavelength λm2.
First, the illumination devices L1 and L2 are turned on and off, respectively, as shown in
Since the second photoreceptor 18 has such a characteristic that it broadly transmits light components in a frequency band that includes the optical filters f1 and f2 or a wider frequency band, it receives light of wavelength λm1-2-1 transmitted through the optical filter f2. The output level of the electrical signal converted by the optical sensor S2 represents a portion where wavelength λm1-2-1 and the optical filter f2 overlap each other.
When the respective output levels of the first and second photoreceptors 16 and 18 are comparatively computed by the comparator 22, the output level of the second photoreceptor 18 is found to be higher.
Then, the illumination devices L1 and L2 are turned off and on, respectively, as shown in
Since the second photoreceptor 18 has such a characteristic that it broadly transmits light components in a frequency band that includes the optical filters f1 and f3 or a wider frequency band, its optical sensor S2 receives light of wavelength λm1-2-2 transmitted through the optical filter f2. The output level of the electrical signal converted by the optical sensor S2 represents a portion where wavelength λm1-2-2 and the optical filter f2 overlap each other.
When the respective output levels of the optical sensors S3 and S2 of the third and second photoreceptors 28 and 18 are comparatively computed by the comparator 22, the output level of the second photoreceptor 18 is found to be higher.
Thus, if the fluorescence emission from the fluorescent printing element 11 is at the normal specific wavelengths λm1 and λm2 only, the respective output levels of the first and second photoreceptors 16 and 18 are equal, and those of the third and second photoreceptors 28 and 18 are equal. If the fluorescence emission from the fluorescent printing element 11 is at fluorescence emission wavelength λm1-2-1 or λm1-2-2 having the wider frequency band including specific wavelengths λm1 and λm2, on the other hand, the output levels of the first, third, and second photoreceptors 16, 28 and 18 are defined by S1<S2 and S3<S2. If the compared output levels are equal, the authentication section 20 determines that the fluorescent substance is a desired one. If not, the fluorescent substance is determined to be an undesired one.
According to the third embodiment, as described above, there is obtained a fluorescence detection device of simple construction capable of accurately detecting a fluorescence that glows at a plurality of different specific wavelengths and easily determining the presence of a desired fluorescent substance. By separately detecting and comparing the plurality of specific wavelengths λm1 and λm2, moreover, the fluorescence emission from the fluorescent printing element can be detected more accurately than in the second embodiment.
Although the detection of the fluorescent substance that glows at two different specific wavelengths has been described in connection with the third embodiment, the invention is not limited to this detection and is also applicable to the detection of a fluorescent substance that glows at three or more different emission wavelengths. The number of detection wavelengths can be increased if a photoreceptor having such a characteristic as to transmit only light components of additional wavelengths is added, and in addition, if the second photoreceptor is configured to receive light in a frequency band including the additional wavelengths.
The present invention is not limited directly to the embodiments described above, and its components may be embodied in modified forms without departing from the scope or spirit of the invention. Further, various inventions may be made by suitably combining a plurality of components described in connection with the foregoing embodiments. For example, some of the components according to the foregoing embodiments may be omitted. Furthermore, components according to different embodiments may be combined as required.
For example, the inspected medium as an object of inspection is not limited to the sheet of paper and may alternatively be a card, gift certificate, securities, etc.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2009-093217 | Apr 2009 | JP | national |
