JP2009037418A - Discrimination apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a small discrimination apparatus for irradiating a phosphor with exciting light beams of different wavelengths. <P>SOLUTION: The discrimination apparatus has a current-driven light emission means (10, 11) for emitting a first light beam, and a light receiving means (15, 16) for processing as an electric signal a second light beam emitted from the phosphor by the first light beam. The light emission means is designed to emit a light beam whose central wavelength is made different by the shift of a driving current value as the first light beam. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a discrimination device that analyzes light emitted from a phosphor and performs authenticity determination, and particularly relates to a discrimination device that includes a light emitting unit that irradiates phosphor with excitation light.

  In order to prevent the distribution of these counterfeit goods, such a device as to allow the authenticity determination to be made later is applied to valuables such as paper sheets represented by banknotes. One of them is a discrimination mark by fluorescent fiber or fluorescent ink on valuables printed matter. For example, in Japanese banknotes, special fluorescent ink that emits fluorescence when exposed to ultraviolet rays is printed, so that humans can visually determine the discrimination mark formed by the light emitted from the special fluorescent ink on the banknote. It has become.

There are the following techniques for performing authenticity determination later based on light emitted from such fluorescent fibers, fluorescent inks, etc. (hereinafter collectively referred to as phosphors).
Two or more fluorescent materials having different light absorption spectrum patterns are mixed at a predetermined mixing ratio, and the mixed fluorescent material is attached to a sample such as a bill as a discrimination mark. Then, by using a plurality of light sources or by switching between a plurality of optical filters, two or more specific wavelengths of excitation light are selectively applied to the sample, and the phosphors generated by the excitation light of the respective wavelengths The fluorescence spectrum from is measured. Then, at the time of authenticity determination, the fluorescence spectrum pattern obtained by irradiating the sample to be determined with the excitation light having the same specific wavelength as described above is displayed on a monitor or the like, By comparing these two, a human determines the authenticity of the sample visually. According to this method, fluorescence having a spectral pattern specific to the type and mixing ratio of the fluorescent material is emitted from the phosphor on the sample corresponding to the wavelength of the excitation light (hereinafter referred to as excitation wavelength). Examining the light spectrum intensity distribution makes it possible to determine whether a bill is authentic or not, and makes it difficult to counterfeit it. (For example, refer to Patent Document 1).
JP 2001-356589 A

  As described in Patent Document 1, in order to make it difficult to counterfeit bills, it is effective to use a mixture of two or more types of fluorescent materials having different absorption spectra at a predetermined mixing ratio as a discrimination mark. is there.

  However, when the discrimination mark is formed of a plurality of fluorescent materials as described above, a plurality of excitation light sources are required as described in Patent Document 1. On the other hand, when a mercury vapor discharge ultraviolet lamp or the like is used as the excitation light source, a plurality of optical filters and a switching mechanism for them are required to extract light having a specific excitation wavelength therefrom.

  Thus, in the case where a plurality of excitation light sources or a plurality of optical filters and their switching mechanisms are provided, a space for that purpose must be provided and the apparatus becomes large, which is a problem. In addition, in the case of using a plurality of optical filters, the optical filter is expensive, so that the cost increases depending on the number of excitation wavelengths, which is a problem.

  Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to provide a small discrimination device that can separately irradiate phosphors with excitation light having different wavelengths.

In order to solve the above problems, the present invention is configured as follows.
One of the aspects of the discrimination apparatus of the present invention includes a current-driven light emitting unit that emits first light and a light receiving unit that performs electrical signal processing on the second light emitted from the phosphor by the first light. The light-emitting means is configured to emit light having a different center wavelength by shifting the drive current value as the first light.

The light emitting means may be configured to have means for driving a direct current pulse as means for shifting the drive current value.
Further, the light emitting means may be configured to include an ultraviolet LED as an element that emits the first light.

  According to the present invention, the center wavelength of the first light applied to the phosphor can be changed by shifting the drive current value. Therefore, it becomes possible to irradiate two or more types of excitation light having different center wavelengths to the phosphor separately with a configuration that keeps the number of light sources or optical filters small, thereby reducing the size and cost. Is possible.

Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.
The discrimination device according to the embodiment of the present invention reads a discrimination mark made of a phosphor printed, applied or dyed on a valuable printed matter such as a paper sheet by light irradiation to determine the authenticity of the valuable printed matter. Is. Here, as the discrimination device, a light emitting diode (LED) is used to irradiate light on the valuable printed matter, and the fluorescence emitted from the phosphor is read by the light.

FIG. 1 is an explanatory diagram of the discrimination device.
As shown in the figure, the discrimination apparatus includes an LED 10 as a light emitting means and a pulse current generator 11 that drives the LED 10.

  The LED 10 is of a type in which the center wavelength of the emitted light changes due to the shift of the drive current value. For example, it is an ultraviolet LED that emits light in the ultraviolet region of 400 nm or less.

  The pulse current generator 11 is a part that drives the LED 10 with a pulse current. This portion is configured by, for example, electrically connecting a pulse signal generation circuit that outputs a pulse signal between a direct current (DC) power source and the input portion of the LED 10. Under such a configuration, a current in which a pulse current from the pulse signal generation circuit is superimposed on a DC current, that is, a pulse current is input to the LED 10 as a drive current.

  The LED 10 emits light of a predetermined center wavelength when the pulse signals do not overlap (hereinafter referred to as a steady state) due to the pulse current drive from the pulse current generator 11, while the pulse signals overlap. Since the drive current value is shifted from the steady-state value, light having a central wavelength different from that is emitted.

Further, in this discrimination apparatus, a photodiode (PD) 15 and a signal amplifying unit 16 are configured as light receiving means in the same figure.
The PD 15 is, for example, a silicon photodiode or the like, and converts light emitted from a phosphor on a valuable printed matter, that is, fluorescence, into an electric quantity.

The signal amplifying unit 16 includes a current / voltage conversion circuit using an operational amplifier and a current conversion resistor, and amplifies the output from the PD 15 and outputs a signal of the fluorescence amount to the subsequent stage.
The signal is output from the signal amplifying unit 16 to an electric signal processing unit (not shown), where it is used to determine the authenticity of the valuables printed matter.

  In the figure, a light emitting side optical filter 12 and a light receiving side optical filter 17 are further configured. These optical filters 12 and 17 are provided here as noise cut filters for removing unnecessary light components based on the characteristics of phosphors A and B described later.

Then, under the configuration as described above, the light of the LED 10 is irradiated to a predetermined position or over the whole while sending the valuable printed matter by the conveying means.
As the transport means, the transport means 19 is simply shown in the figure. The conveying means 19 is constituted by a conveying roller or the like on the conveying path so that the valuable printed matter is conveyed in the right direction between the two optical filters 12 and 17 shown at the upper and lower positions in this case.

The printed valuables are shown as medium M in FIG. In this medium M, two phosphors A and B having different fluorescence spectrum characteristics are dyed at predetermined positions.
FIG. 2 is an example of a characteristic graph of fluorescence spectra of the phosphors A and B.

  As is apparent from the characteristic graph of FIG. 6, here, as the phosphor A and the phosphor B, green phosphors having similar light intensity with the highest light intensity at wavelengths of 520 nm and 510 nm, respectively, are used.

FIG. 3 is a graph showing the relationship between the wavelength of excitation light (excitation wavelength) and the fluorescence intensity of the phosphors A and B shown as an example above.
In the graph of the figure, the slopes of the graphs of phosphor A and phosphor B are opposite to each other such that the slopes of the phosphor A and the phosphor B are positive and negative in the wavelength region from around the excitation wavelength of 330 nm to around 380 nm. Specifically, in the wavelength region, the fluorescence intensity of the phosphor A increases and the fluorescence intensity of one phosphor B decreases as the excitation wavelength becomes longer.

  Therefore, from the relationship of the above graph, at least two wavelengths included in the wavelength region from around the excitation wavelength exceeding 330 nm to around 380 nm are switched as the central wavelengths of the excitation light irradiated to the phosphors A and B. If used, the intensity of the light emitted from the phosphors A and B can be changed in accordance with the switching so as to be mutually contradictory.

  Therefore, when the phosphors A and B shown as an example above are targeted, the LED 10 is selected that shifts within the range from the center wavelength exceeding 330 nm to exceeding 380 nm. . Here, an ultraviolet LED that emits light having a center wavelength of 375 nm by a driving current of 20 mA and a center wavelength of 370 nm by a driving current of 100 mA is used. Further, the pulse signal generation circuit 11 is set so as to output a pulse signal having a pulse width of 1 ms and a duty ratio of 1/10 every 10 ms, and the LED 10 is driven by superimposing the pulse signal on a DC drive current of 20 mA. .

In this case, as the light-emitting side optical filter 12, for example, a visible light block filter having a transmission center wavelength of 360 nm and a full width at half maximum of about 45 nm is used.
As the light receiving side filter 17, for example, an interference filter having a transmission center wavelength of 515 nm and a full width at half maximum of about 10 nm is used.

FIG. 4 shows the waveform of the drive current at that time.
As shown in the figure, the drive current level is shifted from 20 mA (LOW level) output in the steady state to 100 mA (HIGH level) for a moment when the pulse signal is output from the pulse signal generation circuit 11.

FIG. 5 is a change graph of the emission center wavelength of the LED 10 that changes in accordance with the drive current waveform of FIG.
As shown in the figure, when the drive current of FIG. 4 is in a steady state (LOW level), light having a center wavelength of 375 nm is output from the LED 10, and when the drive current of FIG. 4 is shifted from the LOW level to the HIGH level, the light is linked. LED 10 outputs light having a center wavelength of 370 nm.

  Under the above configuration, the drive current value takes two values alternately by time division. Therefore, due to the shift of the drive current value, the light having the center wavelength of 370 nm and the light having the center wavelength of 375 nm are alternately radiated to the phosphors A and B from the LED 10, and when the center wavelength is switched from 370 nm to 375 nm The fluorescence intensity of A increases and the fluorescence intensity of phosphor B decreases. On the other hand, when the light is switched from the central wavelength of 375 nm to 370 nm, the fluorescent intensity of the phosphor A decreases and the fluorescent intensity of the phosphor B increases. Specifically, as shown in FIG. 3, when the phosphor A is irradiated with light having a central wavelength of 375 nm, the relative fluorescence intensity is 82%, but when irradiated with light having a central wavelength of 370 nm, the relative fluorescence intensity is Is -10% lower, like 72%. On the other hand, in the same manner, in phosphor B, the relative fluorescence intensity is 72% when irradiated with light having a central wavelength of 375 nm, whereas the relative fluorescence intensity is 74% when irradiated with light having a central wavelength of 370 nm. 2% higher. Thus, under the above configuration, a large difference is generated between the light intensities of various phosphors with respect to a slight change in excitation wavelength, which is suitable for use in authenticity determination.

When used for authenticity determination, for example, the following is performed.
Suppose that phosphor A and phosphor B are each stained with a predetermined pattern on the medium M. In this case, the entire surface of the medium M is scanned by the light of the LED 10 while being fed by the transport means 19. At the time of this scanning, each region on the medium M is selectively irradiated with the excitation light of the two central wavelengths as the light of the LED 10 and the fluorescence amount at that time is output from the PD 15. After the signal is amplified in the subsequent circuit, the electric signal processing unit compares whether or not the signal indicating the amount of fluorescence exceeds a predetermined threshold value. If it exceeds, the phosphor A or B is present. judge. Next, increase / decrease in the amount of fluorescence is compared from the continuous signal, and it is determined that the phosphor is A or B depending on the increase and decrease. The determination result is recorded in the memory in association with each other by, for example, acquiring the position coordinate information of the irradiation position of the light on the medium M from the transport unit 19. Then, after scanning the entire surface of the medium M, a person can monitor the screen by displaying the symbols of the phosphors A and B on the monitor based on the position coordinate information associated with the memory and the identification information of the phosphor A or B. Authenticate true or false from

  This authenticity determination method is only an example. Therefore, for example, as described in Japanese Patent Application Laid-Open No. 2001-356589, the light of the phosphor is dispersed by a spectroscope and then input to the PD for each wavelength of light, and the output is input to the data processing computer. Then, it may be arbitrarily combined with other authenticity determination methods such as performing appraisal.

In the above example, the LED is used, but it may be replaced with another configuration as long as the center wavelength of the output light is changed by the shift of the drive current value.
In addition, as the wavelength of the excitation light, two of the wavelength regions in which the light intensity increase rates of the phosphor A and the phosphor B are opposite to each other such as positive and negative are selected, but the wavelength is limited to this range. If there is a wavelength that causes a difference between the light intensities of the phosphors A and B due to the wavelength shift, a certain effect can be obtained even if other ranges are used.

Further, although the binary drive current value is obtained by pulse driving the drive current, a square wave signal or the like may be used as the drive current as long as the drive current value can be varied. .

  Further, the phosphor is not limited to two types, and three or more types may be used. In that case, a light emitting element that emits light of three or more central wavelengths is introduced according to the number of current values, and this is controlled so that the drive current value takes three or more values.

  As described above, in the identification device according to the embodiment of the present invention, the center wavelength of the light (first light) applied to the phosphor can be changed by shifting the drive current value. Therefore, it is possible to irradiate two or more types of excitation light having different center wavelengths to the phosphor separately with a configuration in which the number of light sources or optical filters is kept small. Further, miniaturization and cost reduction are realized by reducing the number of light sources or optical filters. In addition, since light in the ultraviolet region is used for authenticity determination, it is difficult to forge the light emitter.

It is explanatory drawing of the discrimination apparatus by embodiment of this invention. It is an example of the characteristic graph of the fluorescence spectrum of fluorescent substance A and B. It is the graph which showed the relationship between an excitation wavelength and fluorescence intensity. It is a drive current waveform. It is a change graph of the light emission center wavelength of LED10 which changes corresponding to the drive current waveform of FIG.

Explanation of symbols

10 LED
11 Pulse current generator 15 Photodiode (PD)
16 Signal Amplifier 12 Light-Emitting Side Optical Filter 17 Light-Receiving Side Optical Filter 19 Conveying Means A, B Phosphor M Medium

Claims (3)

A discrimination apparatus having a current-driven light-emitting means that emits first light and a light-receiving means that performs electrical signal processing on second light emitted from the phosphor by the first light,
The light emitting means emits light having a different center wavelength by shifting the drive current value as the first light.
A discrimination device characterized by that.   2. The identification device according to claim 1, wherein the light emitting means includes means for pulse driving a direct current as means for shifting the drive current value.   The discrimination device according to claim 1, wherein the light emitting unit includes an ultraviolet LED as an element that emits the first light.

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