WO2014097489A1

WO2014097489A1 - Spectral sensor

Info

Publication number: WO2014097489A1
Application number: PCT/JP2012/083347
Authority: WO
Inventors: 佐藤　剛
Original assignee: グローリー株式会社
Priority date: 2012-12-21
Filing date: 2012-12-21
Publication date: 2014-06-26

Abstract

In the present invention, a spectral sensor for irradiating light from a light source toward a conveyed paper sheet and measuring a spectrum generated from light obtained from the paper sheet is configured from: a prism for generating interference fringes from light received from the paper sheet; a sensor unit for measuring the interference fringes generated by the prism; a lens arranged by adjusting the focal distance thereof so that focal points of interference fringes generated from light of a predetermined wavelength on the sensor unit coincide between the prism and the sensor unit; and a composite filter having a shape formed by combining a plurality of filter regions molded by adjusting the material and/or the thickness thereof, in which the position of a corresponding filter region is controlled so that light is transmitted in accordance with the wavelength of light that is to be measured, in order to realize filtering of light in a predetermined wavelength region and/or adjustment of focal point misalignment caused by a wavelength difference.

Description

Spectrum sensor

The present invention relates to a spectrum sensor for measuring optical characteristics of paper sheets and the like, and more particularly to a spectrum sensor for measuring a spectrum using a plurality of lights in different wavelength ranges as measurement targets.

In recent years, in order to identify authenticity with paper sheets such as banknotes, ink in which anti-Stokes light emission having a higher frequency of light than irradiation light is observed has been used. When the ink that emits anti-Stokes light is irradiated with excitation light having a predetermined wavelength, a light emission phenomenon is observed even during irradiation and after the irradiation is stopped. Specifically, anti-Stokes light emission, which is visible light emission, and Stokes light emission, which is infrared light emission, are observed during excitation light irradiation, and infrared light emission is continued for a while after the excitation light irradiation is stopped. A phosphorescence emission is observed. If a mark or the like is printed on a paper sheet using such ink, the mark or the like can be made to emit visible light by irradiating the paper sheet with excitation light. Since phosphorescence is observed even after the excitation light irradiation is stopped, the authenticity of the paper sheet can be identified from the relationship between the excitation light irradiation timing and the light emission state.

For example, Patent Document 1 discloses an apparatus for measuring both fluorescence emission and phosphorescence emission. This apparatus distinguishes and detects fluorescence and phosphorescence from the relationship between the irradiation timing of excitation light and the timing at which emitted light is measured. Further, it is possible to detect each of fluorescence and phosphorescence having different wavelength ranges by using two sensors. Specifically, while measuring light in the entire wavelength range with one sensor, the other sensor measures only fluorescence in a predetermined wavelength range using a filter. And phosphorescence is detected from the difference of the result of having measured the light of all the wavelength ranges, and the result of having measured only fluorescence.

JP-T-2001-506001

However, according to the above-described conventional technology, it is possible to detect whether there is fluorescence emission or phosphorescence emission, but there is a problem that it is difficult to accurately measure a spectrum related to each emission. Specifically, a spectrum sensor that measures a spectrum as an optical characteristic of a paper sheet is affected by the chromatic aberration of the optical system if the wavelength range of light to be measured is different.

The spectrum sensor generates interference light due to polarized light using an optical system including a Wollaston prism and a polarizing plate. After generating interference fringes of two polarization components obtained from paper sheets and imaging the interference fringes with an image sensor such as a CCD, a spectrum can be obtained by Fourier transform. At this time, if the wavelength range of the light to be measured is different, the focal length shifts due to chromatic aberration. For example, if a lens for focus adjustment is placed between the Wollaston prism and the image sensor, and the lens position is adjusted so that the image sensor is focused in the wavelength range when fluorescent light is emitted, in a wavelength range different from that of fluorescence. When phosphorescent light is emitted, focusing is not possible due to chromatic aberration. For this reason, the image is captured with the interference fringes on the CCD blurred, and an accurate spectrum cannot be obtained.

Defocus due to chromatic aberration can be corrected, for example, by combining multiple lenses of different materials, but the use of multiple lenses increases the complexity of the structure and increases manufacturing costs, and increases the size of the spectrum sensor. End up. A method of adjusting the focal length of each image sensor to each wavelength region by using a plurality of image sensors as in the apparatus disclosed in Patent Document 1 can be considered. It is preferable to use one image sensor.

When using a single image sensor, in addition to the effects of chromatic aberration, there are problems with filters. For example, depending on the wavelength range of light to be measured, it may be necessary to prepare a plurality of types of filters that cut off light that is not to be measured. Further, in this case, it is necessary to replace a plurality of filters according to the light to be measured, and it takes time for measurement.

The present invention has been made to solve the above-described problems caused by the prior art, and an object of the present invention is to provide an inexpensive and small-sized spectrum sensor capable of accurately measuring a plurality of light spectra having different wavelength ranges. And

In order to solve the above-described problems and achieve the object, the present invention irradiates light from a light source toward a transported paper sheet and generates a spectrum from the light obtained from the paper sheet and measures it. A prism for generating an interference fringe from light received from a paper sheet, a sensor unit for measuring the interference fringe generated by the prism, and the prism and the sensor unit. And a lens arranged by adjusting a focal length so that an interference fringe generated from light of a predetermined wavelength is focused on the sensor unit, and a focus caused by filtering of light in a predetermined wavelength region and a wavelength difference In order to realize at least one of the adjustment of displacement, it has a shape formed by combining a plurality of filter regions formed by adjusting at least one of material (refractive index depending on material) and thickness. , Characterized in that it comprises a composite filter that is controlling the position so as to transmit the corresponding filter regions according to the wavelength of the light to be measured.

Further, the present invention is the above invention, wherein the composite filter has a rotating disk shape in which a plurality of filter regions are arranged in a circumferential direction around a rotation axis, and the composite filter has a shape corresponding to the wavelength of light to be measured. The rotational position of the rotary shaft is controlled.

Further, in the present invention, in the above invention, the timing of irradiation of light from the light source, position control of the composite filter, and measurement of the interference fringes by the sensor unit is controlled in accordance with the conveyance timing of the paper sheet. It is characterized by that.

In the invention described above, the composite filter may include a first filter region for first wavelength light and a second filter region for second wavelength light having a wavelength different from that of the first wavelength light. When measuring the first wavelength light, the lens focuses the first wavelength light transmitted through the first filter region on the sensor unit and measures the second wavelength light. The second wavelength light is focused on the sensor by transmitting the second filter region that absorbs the defocus generated between the first wavelength light and the second wavelength light. And

Further, the present invention is characterized in that, in the above invention, at least one of the first filter region and the second filter region has a filtering function of cutting light in a predetermined wavelength region.

Further, the present invention is the above invention, wherein the first wavelength light is visible light emission observed while irradiating the anti-Stokes ink used in the paper sheet with infrared light, and the second light The wavelength light is infrared light emission observed after the irradiation of the infrared light to the anti-Stokes ink is stopped.

In the present invention, in the above invention, when controlling the position of the composite filter, the measurement by the sensor unit is interrupted while the light to be measured passes through a predetermined region including the boundary of the filter region. It is characterized by that.

According to the present invention, by controlling the position of the composite filter composed of a plurality of filter regions and selecting the filter region according to the wavelength of the light to be measured, light in unnecessary wavelength regions can be cut or chromatic aberration Therefore, it is not necessary to use a plurality of lenses for exchanging a plurality of filters or correcting a defocus due to chromatic aberration. Further, it is not necessary to change the lens position for focus adjustment in order to correct the defocus. Therefore, it is possible to easily and accurately measure a plurality of lights having different wavelengths while using an inexpensive and small sensor.

Further, according to the present invention, the composite filter is formed by arranging a plurality of filter regions in the circumferential direction around the rotation axis. Therefore, by rotating the composite filter, the filter region to be used can be quickly and easily made. Can be changed.

In addition, according to the present invention, the irradiation of light to the conveyed paper sheet, the change of the filter area, and the measurement of light are controlled in accordance with the conveyance timing of the paper sheet. The measurement can be performed accurately in accordance with the timing of passing through. Further, by controlling the light irradiation from the light source, not only reflected light and fluorescence but also phosphorescence can be measured.

Further, according to the present invention, in a state where the position of the focus adjustment lens is fixed in accordance with the first wavelength light, the second wavelength light having a wavelength different from the first wavelength causes a defocus due to chromatic aberration. By controlling the position of the composite filter and correcting the defocus by the optical characteristics of the second filter region used for the measurement of the second wavelength light, the second wavelength light can also be measured in a focused state. it can.

In addition, according to the present invention, for example, in the case where accurate measurement cannot be performed due to the influence of light not measured, such as light from a light source, extra light can be provided by providing a filtering function in the filter region. Can be cut.

In addition, according to the present invention, the light emitted from the anti-Stokes ink is used as a measurement object, and the infrared light is irradiated to measure the anti-Stokes light emission obtained as visible light by focusing on the sensor unit with the focus adjustment lens. can do. Moreover, it can avoid that a sensor part is saturated by cut | disconnecting infrared light by a 1st filter area | region. In addition, after the irradiation of excitation light is stopped, the second filter region that corrects the defocus due to chromatic aberration can be used to measure phosphorescence emission, which is infrared emission, while focusing on the sensor unit.

Further, according to the present invention, in the predetermined area including the boundary of the filter area, the measurement by the sensor unit is interrupted, so that only the light transmitted through the corresponding filter area can be measured and an accurate measurement result can be obtained. .

FIG. 1 is a schematic diagram for explaining an outline of the configuration of the spectrum sensor according to the present embodiment. FIG. 2 is a schematic cross-sectional view illustrating a schematic configuration of the optical system unit according to the present embodiment. FIG. 3 is a schematic diagram for explaining the operation of the composite filter according to the present embodiment. FIG. 4 is a schematic diagram for explaining defocus due to chromatic aberration. FIG. 5 is a schematic cross-sectional view illustrating filtering and defocus correction performed by the composite filter according to the present embodiment. FIG. 6 is a diagram for explaining the light emission phenomenon observed with the anti-Stokes ink. FIG. 7 is a diagram illustrating an example of a measurement method performed using the composite filter according to the present embodiment. FIG. 8 is a timing chart for explaining the control timing of each part in the measurement performed using the composite filter according to the present embodiment. FIG. 9 is a diagram for explaining the relationship between the rotational position of the composite filter according to the present embodiment and the measurement timing. FIG. 10 is a diagram illustrating an example of a method for detecting and controlling the rotational position of the composite filter according to the present embodiment. FIG. 11 is a diagram for explaining an example of light to be measured by the spectrum sensor according to the present embodiment, a wavelength range filtered by a composite filter to measure this light, and excitation light. FIG. 12 is a diagram for explaining an example of a different structure of the composite filter according to the present embodiment.

Hereinafter, preferred embodiments of a spectrum sensor according to the present invention will be described in detail with reference to the accompanying drawings. First, an outline of the spectrum sensor 100 will be described with reference to FIG. The spectrum sensor 100 generates interference fringes from light obtained from a measurement object by a prism or the like, and Fourier transforms the interference fringes to measure light intensity with respect to frequency.

The spectrum sensor 100 includes a light guide 10, an optical coupling device 1, an optical system unit 20, and a sensor unit 30, and converts light indicating the optical characteristics of the paper sheet 3 into an electrical signal. It has a function of outputting to an external signal processing unit. As shown in FIG. 1C, the spectrum sensor 100 irradiates light on the paper sheet 3 from the light source 2 and reflects the light reflected from the paper sheet 3 into 16 light receiving sections 212a to 212a of the light guide 10. Light is received at 212p.

As shown in FIGS. 1A and 1B, the light guide 10 is formed of four light guide plates 10a to 10d formed of a transparent member such as acrylic resin. The light guide plate 10a has four light receiving portions 212a to 212d provided so as to face the paper sheet 3, and each of the light receiving portions 212a to 212d has an X height so that the height from the paper sheet 3 is the same. They are arranged at equal intervals in one row in the axial direction. The light received by the four light receiving portions 212a to 212d is guided in the X-axis direction while being totally reflected inside and is emitted from the emitting portion 212q toward the optical system portion 20. The other light guide plates 10b to 10d have the same function. As shown in FIG. 1B, in the state where the four light guide plates 10a to 10d are arranged so that the end portions on the optical coupling device 1 side are aligned in the Y-axis direction, each of the sixteen light receiving portions 212a to 212p. Are arranged at equal intervals in the X-axis direction. As shown in FIG. 1B, by transporting the paper sheet 3 in the Y-axis direction on the transport path 4, the entire surface of the paper sheet 3 is received by the light receiving portions 212a to 212p arranged in a line in the X-axis direction. Can be measured. Light emitted from the four light guide plates 10a to 10d becomes incident light to the optical coupling device 1.

The optical coupling device 1 has a function of optically coupling between the light guide 10 and the optical system unit 20. Specifically, the light emitted from the four light guide plates 10a to 10d is received by the incident surface, and the light is condensed while being uniformed and emitted from the emission surface having a smaller area than the incident surface. The light emitted from the optical coupling device 1 becomes incident light to the optical system unit 20.

The optical system unit 20 has a function of generating an interference fringe indicating the optical characteristics of the paper sheet 3 from incident light and focusing the image to capture the interference fringe with the sensor unit 30. FIG. 2 is a schematic diagram illustrating a schematic configuration of the optical system unit 20. The optical system unit 20 includes a diffusion plate 21 for diffusing the light 101 incident from the optical coupling device 1,

polarizing plates

22a and 22b and a prism 23 for generating interference fringes, light filtering and defocusing. A composite filter 24 for realizing at least one of the corrections and a lens 25 for focusing the generated interference fringes on the sensor unit 30 are provided. As the prism 23, for example, a Wollaston prism is used.

The sensor unit 30 has a function of imaging the interference fringes generated by the optical system unit 20. The sensor unit 30 includes an image sensor such as a CCD, and a substrate for performing a process of generating a spectrum by performing Fourier transform on the control of the image sensor and the measurement result of interference fringes obtained by the image sensor. Yes. The spectrum sensor 100 is used in, for example, a paper sheet identification device that identifies the paper sheet 3. In the paper sheet identification device, for example, a process of identifying the type, authenticity, and the like of the paper sheet 3 from the features appearing in the spectrum generated by the sensor unit 30 is performed.

Conventional optical filters are mainly used for cutting light in a predetermined wavelength range. However, the composite filter 24 according to the present embodiment has one feature in that the defocus due to chromatic aberration can be corrected by adjusting the optical path length. Hereinafter, functions and operations of the composite filter 24 will be described in detail.

FIG. 3 is a schematic diagram for explaining the operation of the composite filter 24. The composite filter 24 has a disk shape formed by a plurality of

filter regions

24a and 24b, and is rotatably supported by a rotation shaft 24f. The rotation of the composite filter 24 can be controlled in accordance with the incident timing of the incident light 102 so that the incident light 102 passes through a region selected from the plurality of

filter regions

24a and 24b. The light 102 that has passed through the composite filter 24 passes through the lens 25 for adjusting the focal length and is imaged by the image sensor of the sensor unit 30. Note that, in the optical system unit 20, the distance L1 between the lens 25 and the sensor unit 30 is adjusted and fixed in advance so that the light is focused on the sensor unit 30 when light in a predetermined wavelength region is incident. ing.

FIG. 4 is a diagram for explaining the relationship between the distance L1 from the lens 25 to the sensor unit 30 and the optical path lengths of a plurality of lights having different wavelengths. As shown in FIG. 4A, the distance L1 from the lens 25 to the sensor unit 30 is adjusted so that the sensor unit 30 is focused when the light 102 having the wavelength α is irradiated. For this reason, in the light of the wavelength (beta) and the light of the wavelength (gamma) from which a wavelength differs, a focus shift | offset | difference arises by a chromatic aberration, and a sensor part 30 becomes unable to focus. For example, as shown in FIG. 4B, a defocus due to chromatic aberration occurs according to the wavelength, but the defocus due to this chromatic aberration can be corrected by the composite filter 24.

Next, the defocus correction function and the filtering function by the composite filter 24 will be described. FIG. 5 is a schematic cross-sectional view for explaining the function of the composite filter 24. When defocusing occurs due to chromatic aberration due to different wavelengths of light, for example, as shown in FIG. 5 (a), the in-focus position shifts between light of wavelength α, light of wavelength β, and light of wavelength γ. . In FIG. 5A, the distance L <b> 1 from the lens 25 to the sensor unit 30 is adjusted and fixed so as to be focused on the sensor unit 30 with light of wavelength α. That is, in the state of FIG. 5A, the sensor unit 30 cannot measure the light with the wavelength β and the light with the wavelength γ in focus.

For example, light 102 including light of wavelength α, light of wavelength β, and light of wavelength γ is incident. However, when it is desired to measure only light of wavelength α, as shown in FIG. However, the rotational position of the composite filter 24 shown in FIG. 3 is controlled so as to pass through the filter region 24a for cutting light of wavelength β and light of wavelength γ. Thereby, since the focal distance L1 is adjusted according to the wavelength (alpha), the light of the wavelength (alpha) which permeate | transmitted the filter area | region 24a can be measured in a focused state.

For example, when the light 102 is strong and an attempt is made to measure all the light, an image pickup device such as a CCD may be saturated and accurate measurement may not be performed. In such a case, by setting a part of the composite filter 24 as a filter region 24a that cuts light of a predetermined wavelength, only light in a desired wavelength region can be measured.

In addition, for example, when light 102 having a wavelength β is incident but accurate measurement cannot be performed due to defocusing, the light 102 is used for adjusting the optical path length as shown in FIG. The rotational position of the composite filter 24 is controlled so as to pass through the filter region 24b. The filter region 24b is formed by calculating the material and thickness so that the optical path length is changed by the light having the wavelength β refracted therein and the sensor unit 30 is focused. As a result, it becomes possible to measure the light of wavelength β in a focused state. A method for determining the material and thickness for correcting defocus will be described later.

In addition, for example, when light 102 including light having wavelength α and light having wavelength γ is incident, when only light having wavelength γ is to be measured, as shown in FIG. The rotational position of the composite filter 24 is controlled so as to pass through the filter region 24c for cutting α light. At this time, if the light of wavelength α is simply cut, defocus due to chromatic aberration occurs and accurate measurement cannot be performed. For this reason, the filter region 24c cuts light in the predetermined wavelength region as in the case of FIG. 5B, and adjusts the optical path length of the light of wavelength γ as in the case of FIG. 5C. It is molded by calculating its material and thickness. As a result, it is possible to measure in a state where only the light of wavelength γ is transmitted and in focus.

As described above, the composite filter 24 realizes at least one of a filtering function that cuts light in a predetermined wavelength region and a defocus correction function that adjusts the optical path length of light having a predetermined wavelength to correct defocus. It is formed including filter regions 24a to 24c. By selecting any one of the filter regions 24a to 24c according to the type of incident light and the purpose of measurement, a plurality of lights having different wavelengths can be accurately measured at the same sensor position. Further, since the composite filter 24 has a rotatable disk shape, the rotational position can be easily controlled so that the composite filter 24 is rotated and light is transmitted through the selected filter regions 24a to 24c. Can do.

Next, as a measurement example of light using the composite filter 24, a method for measuring light emission from the anti-Stokes ink used in the paper sheet 3 will be specifically described. FIG. 6 is a diagram for explaining the light emission phenomenon of the anti-Stokes ink. In anti-Stokes ink, infrared light is used as excitation light. As shown in FIG. 1C, this excitation light is emitted from the light source 2 toward the paper sheet 3. Specifically, as shown in FIG. 6A, infrared light irradiation from the light source 2 is started at time t1, and infrared light irradiation is stopped at time t2. In the paper sheet 3, as shown in FIG. 6B, light emission by the anti-Stokes ink starts from the time t1 when the irradiation of the excitation light from the light source 2 is started, and gradually becomes brighter, and eventually reaches a saturated state. And when irradiation of the excitation light from the light source 2 is stopped at time t2, phosphorescence emission is observed as afterglow thereafter. The phosphorescence emission gradually becomes dark and disappears at time t3.

FIG. 7 is a diagram for explaining a method of measuring emitted light by irradiating infrared light from the light source 2 toward the paper sheet 3 as shown in FIG. 6A. 7A and 7B are diagrams illustrating the wavelength distribution of the observed light, and the right diagram is a diagram illustrating the function of the composite filter 24 when measuring this light. FIG. 7C is a diagram for explaining the structure of the composite filter 24. 2, the interference fringes generated by the prism 23 and the

polarizing plates

22a and 22b are imaged by the sensor unit 30 via the composite filter 24 and the lens 25, as shown in FIG. Hereinafter, the interference fringes are simply referred to as “light”.

As shown in FIG. 6B, excitation light (infrared light) 43 is observed in addition to the visible light emission 41 and the infrared light emission 42 during the time t1 to t2 after the light emission by the anti-Stokes ink starts. Is done. If all the light is received by the sensor unit 30 in this state, the image sensor becomes saturated and accurate measurement cannot be performed. In addition, since both the infrared light emission 42 and the excitation light 43 are in the infrared light region, there is a possibility that even if the infrared light is measured in this state, the infrared light emission 42 cannot be accurately measured due to the influence of the excitation light. is there.

Therefore, from time t1 to t2, the infrared light emission 42 and the excitation light 43 indicated by the broken line in the left diagram of FIG. 7A are cut, and only the visible light emission 41 indicated by the solid line is measured. Specifically, the focal length L1 from the lens 25 to the sensor unit 30 is adjusted in advance so that the visible light emission 41 can be measured in a state where the sensor unit 30 is focused. Moreover, let the filter area | region 24a of the composite filter 24 shown to Fig.7 (a) right figure and the same figure (c) be an infrared-light cut filter. Then, during the time t1 to t2 when the visible light emission 41 is observed, the rotational position of the composite filter 24 is controlled so that the light received from the paper sheet 3 passes through the filter region 24a and reaches the sensor unit 30. .

As a result, at the time of measurement, the infrared light emission 42 and the excitation light 43 indicated by broken lines in the left diagram of FIG. 7A are cut by the filter region 24a of the composite filter 24, and only the visible light emission 41 indicated by the solid line is detected by the sensor unit 30. It can measure in the state focused on. Thereby, it is possible to accurately measure the visible light emission 41 while avoiding that the sensor unit 30 is saturated.

Thus, after measuring the visible light emission 41, the infrared light emission 42 is measured. As shown as afterglow in FIG. 6B, infrared light emission 42 is observed as phosphorescence emission during a period of time t2 to t3 after irradiation of excitation light from the light source 2 is stopped. Specifically, as shown in the left diagram of FIG. 7B, the excitation light 43 disappears, the visible light emission 41 disappears, and the infrared light emission 42 is observed. Thereby, the infrared emission 42 can be measured during the time t2 to t3.

The visible light 41 of anti-Stokes light emission is visible light in the wavelength range of green to red with a wavelength of 550 to 650 nm, whereas the infrared light emission 42 is infrared light with a wavelength range of 950 to 1100 nm. In the optical system unit 20 of the spectrum sensor 100, the focal length L1 is adjusted and fixed in advance so that the visible light emission 41 is focused on the sensor unit 30 as shown in the right diagram of FIG. For this reason, simply removing the filter region 24a and allowing the light emitted from the infrared light emission 42 to reach the sensor unit 30 causes a distance ΔP due to chromatic aberration as indicated by a dashed line 44 in the right diagram of FIG. Therefore, the sensor unit 30 cannot be focused. In the spectrum sensor 100 according to this embodiment, this defocus is corrected by the composite filter 24.

Specifically, as shown in the right diagram and FIG. 7C of FIG. 7B, the filter region 24b of the composite filter 24 is an infrared light focus adjustment filter. When the filter region 24a is formed of a material having a refractive index n1 and having a thickness D1, the filter region 24b having a material having a refractive index n2 and a thickness D2 is corrected by D1 × It is molded so as to satisfy the relational expression of n1 = D2 × n2-ΔP. That is, if the filter region 24b is made of a material having a refractive index n2 through which infrared light is transmitted, the thickness D2 is determined according to the previous equation based on the refractive index n1 and the thickness D1 of the filter region 24a and the defocus amount ΔP. Defocus due to chromatic aberration can be corrected.

During the time t2 to t3 in FIG. 6B where only the infrared light emission 42 is observed, the light received from the paper sheet 3 and passing through the prism 23 and the like passes through the filter region 24b and reaches the sensor unit 30. Thus, the rotational position of the composite filter 24 is controlled. The defocus is corrected by the filter region 24b, and infrared light is emitted in the focused state without changing the distance L1 from the lens 25 to the sensor unit 30 as shown by the solid line in FIG. 42 can be measured. Further, the change from the filter region 24a to the filter region 24b is performed by reading the interference fringes of the light in the target wavelength region by synchronizing the filter position with the measurement of the composite filter 24 that is rotatably provided in the optical system unit 20. By rotating in this manner, it can be performed easily and at high speed.

In FIG. 7, for example, a method of measuring the visible light emission 41 and the infrared light emission 42 by irradiating the excitation light 43 from the light source 2 to a mark or the like printed using anti-Stokes ink has been described. For example, as shown in FIG. 1, it is performed in accordance with the conveyance timing of the paper sheet 3 conveyed on the conveyance path 4.

FIG. 8 is a timing chart showing the relationship between the transport timing of the paper sheet 3 and the measurement timing of visible light emission and infrared light emission. As shown in FIG. 8, the mechanical clock of the transport mechanism that drives the transport path 4 that transports the paper sheet 3 is used as the transport timing of the paper sheet 3. This mechanical clock is a signal output according to the transport distance of the paper sheet 3 by the transport path 4. Based on this signal and a signal from a passage sensor provided to detect the passage of the paper sheet 3 on the conveyance path 4, the position of the paper sheet 3 can be specified.

As shown in FIG. 1B, when the paper sheet 3 conveyed through the conveyance path 4 is detected by a passage sensor installed at a predetermined position in front of the light guide 10 (time t3 in FIG. 8), thereafter The irradiation of the excitation light from the light source 2 toward the paper sheet 3 is started at a timing when a predetermined time has elapsed (time t4 in FIG. 8). After the detection by the passage sensor, the mechanical clock is counted and the measurement is started at the timing when it passes under the light guide 10. When the irradiation of excitation light is started, visible light emission and infrared light emission by the anti-Stokes ink start on the paper sheet 3.

When the irradiation of the excitation light is started, the light emitted from the anti-Stokes ink is received by the light guide 10 and enters the optical system unit 20 through the optical coupling device 1. The rotation position of the composite filter 24 is adjusted to the rotation position A shown in FIG. 9A so that this light passes through the prism 23 and passes through the filter region 24a which is an infrared light cut filter. Specifically, the rotation position A of the composite filter 24 shown in FIG. 8 is a position where light passes through the filter region 24a on the front side in the rotation direction in the filter region 24a, as shown in FIG. 9A. Become. A rectangular area 45 indicated by a broken line in FIG. 9 indicates an optical path area through which light passes in the optical system unit 20.

The composite filter 24 rotates counterclockwise around the rotation shaft 24f from the rotation position A. As shown in FIG. 9A, while the areas E to F of the composite filter 24 pass through a rectangular area 45 (light path area) through which light passes, that is, the composite filter 24 moves from the rotation position A to the rotation position B. During the rotation, the visible light emission 41 is measured by cutting the excitation light, which is infrared light, as shown in FIG. This measurement is a measurement performed in the region of the infrared light cut filter at the composite filter rotation position shown in FIG. 8, and corresponds to the visible light emission measurement of the sensor unit measurement shown in FIG.

After the measurement of the visible light emission 41 is completed, the measurement by the sensor unit 30 is interrupted while rotating counterclockwise from the rotational position B shown in FIG. 9A to the rotational position C shown in FIG. That is, the measurement is interrupted in the boundary region (time t5 to t6 in FIG. 8) indicated at the composite filter rotation position shown in FIG. In the vicinity of the boundary between the two

filter regions

24a and 24b forming the composite filter 24, there is a possibility that the transmitted light cannot be measured accurately, so the measurement is interrupted.

As shown in FIG. 8, at the timing of stopping the irradiation of the excitation light (time t6 in FIG. 8), the light incident on the optical system unit 20 is transmitted through the filter region 24b, which is an infrared light focus adjustment filter, and red. The rotational position of the composite filter 24 is adjusted so that the external light emission 42 can be measured.

When the irradiation of excitation light is stopped, the visible light emission 41 is reduced, and the infrared light emission 42 is observed (time t6 in FIG. 8), the infrared light emission 42 is measured. As shown in FIG. 9 (b), while the regions G to H of the composite filter 24 pass through the optical path region 45, that is, while the composite filter 24 rotates counterclockwise from the rotation position C to the rotation position D, Infrared emission 42 is measured. Specifically, as shown in FIG. 7B, the measurement is performed after adjusting the optical path length of the infrared light emission 42 to correct the defocus. This measurement is performed in the region of the infrared light focus adjustment filter at the composite filter rotation position shown in FIG. 8, and corresponds to the infrared emission (phosphorescence) measurement of the sensor unit measurement shown in FIG.

When the measurement of the infrared light emission 42 is completed, the measurement by the sensor unit 30 is interrupted while rotating counterclockwise from the rotational position D shown in FIG. 9B to the rotational position A shown in FIG. That is, the measurement is interrupted in the boundary region (time t7 to t9 in FIG. 8) indicated at the composite filter rotation position shown in FIG. Then, while the measurement is interrupted, the light source 2 is turned on again and irradiation of excitation light is started (time t8 in FIG. 8). After the irradiation of the excitation light is started and the boundary region of the composite filter 24 passes through the optical path region 45 (time t9 in FIG. 8), the light incident on the optical system unit 20 is a filter region 24a that is an infrared light cut filter. Then, the visible light emission 41 can be measured again.

Thus, while the paper sheet 3 is conveyed by the conveyance path 4, the visible light emission measurement in the filter region 24a which is an infrared light cut filter and the infrared light emission in the filter region 24b which is an infrared light focus adjustment filter. Repeat the measurement. Specifically, as illustrated in FIG. 9, the composite filter 24 rotates so that the rotation positions become A, B, C, and D, and then the rotation position returns to A again. For this reason, the visible light emission measurement and the infrared light emission measurement are continuously repeated by continuously rotating the composite filter 24 in synchronization with the conveyance of the paper sheet 3 and the excitation light irradiation timing from the light source 2. Can be done.

As shown in FIGS. 8 and 9, the measurement controls the irradiation of excitation light, the rotational position of the composite filter 24, and the timing of measurement by the sensor unit 30 in accordance with the passage of the paper sheet 3 below the light guide 10. Done. The positional relationship between the paper sheet 3 transported on the transport path 4 and the light guide 10 and the irradiation timing of the excitation light to the paper sheet 3 are conventionally performed on the paper sheet on the transport path 4. 3 and a mechanical clock of the transport mechanism that is output in accordance with the driving of the transport path 4 can be controlled. Specifically, the light source 2 and the sensor unit 30 are controlled using position information of the paper sheet 3 obtained based on the detection result of the paper sheet 3 by the passage sensor and the mechanical clock of the transport mechanism. . In addition to this, in the spectrum sensor 100, the rotational position of the composite filter 24 in the optical system unit 20 is detected, and the rotational position of the composite filter 24 is controlled by rotating the rotary shaft 24f based on the detection result. Is done.

FIG. 10 is a schematic diagram for explaining an example of a method for detecting and controlling the rotational position of the composite filter 24. For example, as shown in FIG. 10A, the rotational position of the rotary shaft 24f of the composite filter 24 is detected using a rotary encoder 51 connected to the rotary shaft 24f. Specifically, the composite filter position detection unit 52 detects the rotational position of the composite filter 24 based on a signal output from the rotary encoder 51. Based on the detected rotational position information and the positional information on the transport path 4 of the paper sheet 3 input from the outside, the composite filter position control unit 53 rotates the rotational position and rotational speed of the composite filter 24. To control. The rotational position and rotational speed of the composite filter 24 are performed by controlling a composite filter drive unit 54 such as a motor connected to the rotary shaft 24f.

Further, for example, as shown in FIG. 10B, a light projecting unit 55a and a light receiving unit 55b installed to detect light transmitted through the composite filter 24 are used. Since the

filter regions

24a and 24b forming the composite filter 24 are different in material and thickness, the rotational position of the composite filter 24 can be detected by detecting a change in light transmitted through the composite filter 24. For example, when the filter region 24a is made of a material that cuts infrared light and the filter region 24b is made of a material that transmits infrared light, the light projecting unit 55a emits infrared light, and this is received by the light receiving unit. By detecting at 55b, the rotational position of the composite filter 24 can be detected. If the composite filter position detection unit 52 detects the rotational position of the composite filter 24 from the change in the wavelength or light quantity of the light received by the light receiving unit 55b, the composite filter position control unit is the same as in FIG. 53 and the composite filter drive unit 54 can control the rotational position of the composite filter 24. In addition, without providing a dedicated light source as the light projecting unit 55a, the light source 2 provided in the spectrum sensor 100 is turned on, and light incident on the optical system unit 20 through the light guide 10 and the optical coupling device 1 is projected. The aspect utilized as a partial light source may be sufficient.

Further, for example, as shown in FIG. 10C, the rotation shaft 24 f of the composite filter 24 and the rotation shaft 59 of the drive mechanism of the conveyance path 4 that conveys the paper sheet 3 are configured by a plurality of gears. The transmission mechanism 58 may be connected by hardware. If the composite filter 24 and the transport path 4 are connected in hardware, the positional relationship between the rotational position of the composite filter 24 and the transport path 4 is fixed. Thereby, the drive of the drive part 57 is controlled by the control part 56, and the rotational position of the composite filter 24 can be recognized from the positional information of the paper sheet 3 on the conveyance path 4, and measurement can be performed. In this case, the position information of the sheet 3 is input from the control unit 56 to the signal reading unit 60, and the signal reading unit 60 detects a sensor such as a CCD based on the signal input from the control unit 56. Signal reading from the unit 30 (light measurement) is performed.

In addition, the material and shape of each filter region forming the composite filter 24 are not limited to the example of this embodiment. Depending on the light to be measured, each filter region may have a mode in which only the thickness is changed as the same material, or may be a mode in which only the material is changed as the same thickness. It is possible to change both thicknesses.

Moreover, although this embodiment demonstrated the example which measures different light emission on the sheet | seat 3 of 1 sheet, this embodiment is not limited to this, A plurality of paper sheets 3 and paper sheets It may be an aspect in which measurement is performed by changing the rotational position of the composite filter 24 every time.

In the present embodiment, as illustrated in FIG. 2, the example in which the composite filter 24 is disposed between the polarizing plate 22b disposed on the rear stage side of the prism 23 and the focus adjustment lens 25 has been described. The present embodiment is not limited to this. The arrangement position of the composite filter 24 is not particularly limited as long as it is between the prism 23 where the interference fringes are generated and the sensor unit 30.

In the present embodiment, an example in which infrared light is emitted from the light source 2 as excitation light has been described. However, the excitation light is determined according to light to be measured or light emitted from the paper sheet 3. Is. FIG. 11 shows an example of the light to be measured, the filtering performance required for the composite filter 24 for measuring this light, and the wavelength of the light emitted from the light source 2 at the time of measurement.

In the present embodiment, the example of measuring the visible light emission (a) and the infrared light emission (phosphorescence) (b) observed with the anti-Stokes ink shown in FIG. 11 has been described. As shown in FIG. 11B, when measuring infrared light emission, the material of the filter region 24b is not particularly limited as long as it is a material that transmits infrared light to be measured. Is used. In addition, since no excitation light is required when measuring infrared emission, the light source 2 is used only for excitation light irradiation that excites visible light emission.

However, for example, when the reflected light shown in FIGS. 11 (c) and 11 (d) is to be measured, the visible light is irradiated to measure the visible light ((c) in the figure), and the infrared light is In order to measure infrared light by irradiation ((d) in the figure, the light source 2 capable of irradiating a plurality of visible light and infrared light is used. In this case, for example, the material of the composite filter 24 is used. By changing the thickness of the filter region 24a for measuring visible light in FIG. 11 (c) and the filter region 24b for measuring infrared light in FIG. 11 (d) as transparent glass, defocus due to the difference in wavelength. Adjust.

In addition to this, if the wavelength range of light emitted from the light source 2 and the material and thickness of each

filter region

24a and 24b are determined according to the light to be measured and the wavelength range to be filtered, one composite filter 24 can be accurately measured in a state where each light exemplified as the measurement object in FIG. 11 is focused.

The number of filter regions forming the composite filter 24 is not particularly limited. For example, as shown in FIG. 12A, it may be formed of four filter regions 24a to 24d, or may be formed of five or more filter regions. It does not matter even if it is a mode. Further, as shown in FIG. 12B, a shape in which a part of the region 24e forming the composite filter 24 is cut away may be used so that a glass material, a filter material, or the like is not used in this region. Absent. The number, material, and shape of the filter regions are appropriately determined according to the type of light obtained from the paper sheet 3 and the light to be measured.

As described above, according to the present embodiment, the rotational position of the composite filter 24 is controlled even when defocusing occurs due to the measurement of a plurality of lights having different wavelengths as the optical characteristics of the paper sheet 3. By changing the positions of the filter regions 24a to 24e through which light is transmitted, at least one of a filtering function for cutting light in a predetermined wavelength region and a defocus correction function for correcting and eliminating defocus is realized. Each light to be measured can be accurately measured in a focused state.

At this time, the composite filter 24 has a structure in which a plurality of plate-like filter regions 24a to 24e are arranged around the rotation axis, and the composite filter 24 is rotated and arranged in the optical path region 45 through which the light to be measured is transmitted. The filter regions 24a to 24e to be changed can be changed easily and at high speed. By controlling and using the rotational position of the composite filter 24, it is not necessary to correct a defocus due to chromatic aberration by combining a plurality of optical lenses, or to replace the filter in accordance with the light to be measured. Further, it is not necessary to change the position of the lens 25 for focus adjustment. Thereby, the structure of the spectrum sensor 100 is not complicated, and the manufacturing cost can be suppressed and the size can be reduced.

As described above, the present invention is a spectrum sensor that measures the optical characteristics of paper sheets, and is a useful technique for accurately measuring the spectra of a plurality of lights having different wavelength ranges.

DESCRIPTION OF SYMBOLS 1 Optical coupling device 2 Light source 3 Paper sheet 4 Conveyance path 10 Light guide 10a-10d Light guide plate 20 Optical system part 21

Diffusing plate

22a, 22b Polarizing plate 23 Prism 24 Composite filter 24a-24d Filter area | region 24f Rotating shaft 25 Lens 30 Sensor unit 51 Rotary encoder 52 Composite filter position detection unit 53 Composite filter position control unit 54 Composite filter drive unit 55a Light projection unit 55b Light reception unit 56 Control unit 57 Drive unit 58 Transmission mechanism 59 Rotating shaft 60 Signal reading unit 100 Spectrum sensor

Claims

A spectrum sensor that irradiates light from a light source toward a conveyed paper sheet and generates a spectrum from the light obtained from the paper sheet, and measures the spectrum.
A prism for generating interference fringes from light received from paper sheets;
A sensor unit for measuring the interference fringes generated by the prism;
Between the prism and the sensor unit, a lens arranged by adjusting a focal length so that an interference fringe generated from light of a predetermined wavelength is focused on the sensor unit;
In order to realize at least one of filtering of light in a predetermined wavelength range and adjustment of defocus due to wavelength difference, a plurality of filter regions formed by adjusting at least one of material and thickness are combined. A spectrum sensor comprising: a composite filter having a shape and whose position is controlled so as to transmit a corresponding filter region in accordance with a wavelength of light to be measured.
The composite filter has a rotating disk shape in which a plurality of filter regions are arranged in the circumferential direction around the rotation axis, and the rotation position of the rotation axis is controlled according to the wavelength of light to be measured. The spectrum sensor according to claim 1.
The timing of irradiation of light from the light source, position control of the composite filter, and measurement of the interference fringes by the sensor unit is controlled in accordance with the conveyance timing of the paper sheet. The spectrum sensor described in 1.
The composite filter is formed including a first filter region for first wavelength light and a second filter region for second wavelength light having a wavelength different from that of the first wavelength light,
When measuring the first wavelength light, the lens focuses the first wavelength light transmitted through the first filter region with the lens, and
When measuring the second wavelength light, the second wavelength light is transmitted by passing through the second filter region that absorbs the defocus generated between the first wavelength light and the second wavelength light. 4. A spectral sensor according to claim 1, 2 or 3, characterized in that it focuses on the sensor.
The spectrum sensor according to claim 4, wherein at least one of the first filter region and the second filter region has a filtering function of cutting light in a predetermined wavelength region.
The first wavelength light is visible light emission observed while irradiating the anti-Stokes ink used in the paper sheet with infrared light, and the second wavelength light is red to the anti-Stokes ink. 6. The spectrum sensor according to claim 5, wherein the spectrum sensor is an infrared light emission observed after the external light irradiation is stopped.
The measurement by the sensor unit is interrupted while the light to be measured passes through a predetermined region including the boundary of the filter region when controlling the position of the composite filter. The spectrum sensor according to any one of the above.