JP2002117431A - Paper sheet discriminating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a paper sheet discriminating device for precisely discriminating a discoloring element with a small-sized inexpensive structure. SOLUTION: This device comprises a light source for emitting light to the discoloring element of a paper sheet; a moving means for generating first and second detecting lights differed in wavelength and emitting angle to the transmitted or reflected light of the discoloring element by changing the relative position between the light source and the paper sheet; a transmission type first diffraction optical element for deflecting the first and second detecting light to emit first and second transmitted light; a transmission type second diffraction optical element for deflecting the first and second transmitted lights to different directions according to the differed wavelengths to emit third and fourth transmitted light; a position detecting element for receiving the third and fourth transmitted light and outputting a detection signal according to the light receiving position; and a discrimination processing part for determining that the paper sheet is true when the light receiving position of the third and fourth transmitted light by the detection signal is matched to a prescribed position.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet discriminating apparatus for discriminating the authenticity of a sheet.

[0002]

2. Description of the Related Art In recent years, paper sheets such as banknotes, securities, and gift certificates, or plastic cards such as credit cards and cash cards (hereinafter, collectively referred to simply as paper sheets) are forged. Cases are increasing. As a countermeasure, letters, figures, and symbols printed on these papers by OVI (Optical Variable Ink) or the like, whose brightness and color change depending on the viewing angle, and letters, figures, and symbols (hereinafter referred to as holograms) In some cases, paper sheets may be provided with different colors depending on the viewing angle.

[0003] It is difficult to forge paper sheets provided with these discoloration elements, and providing discoloration elements on a large number of paper sheets is an effective means for preventing forgery. The discrimination of the discoloration element includes discrimination by a human and discrimination by a machine. When a person tries to discriminate a paper sheet, observing the discolored element while tilting the paper sheet, the color of the discolored element changes depending on the viewing direction, so that the authenticity can be easily confirmed. on the other hand,
When automatically discriminating paper sheets (especially banknotes) inserted in a vending machine, a currency exchange machine, or a depositing / dispensing machine of an unmanned store, etc., a point different from a discoloring element depending on a viewing angle is used. A color from a direction is detected to detect the presence or absence of a discoloration element.

A prior art of a discriminating apparatus (hereinafter, referred to as a sheet discriminating apparatus) for realizing the operation of detecting a discoloration element provided on such a sheet will be described. 18 and 19
1 is a configuration diagram of a conventional paper sheet discriminating apparatus. For example,
In the conventional sheet discriminating apparatus shown in FIG.
And two sets of lenses 8, two sets of filters 9 as optical bandpass filters, and two sets of light receiving elements 10, which detect colors from two different directions. Further, in the conventional sheet discriminating apparatus shown in FIG. 19, one CCD (Charge C
oupled Device) Camera 11 and CCD camera 11
Have detected the color of paper sheets in a wide range.

[0005]

FIG. 18 shows a configuration of a conventional sheet discriminating apparatus for detecting a discolored element.
It is necessary to adopt a configuration using at least two or more sets of lenses 8, filters 9, and light receiving elements 10, which are expensive optical components as shown in FIG. 1, and a configuration using an expensive CCD camera 11 as shown in FIG. Therefore, any of these becomes a high-cost paper sheet discriminating apparatus, and a cost problem arises in an apparatus such as a vending machine where cost reduction is desired.

In the prior art shown in FIG. 18, two or more sets of lenses 8, filters 9, and light receiving elements 10 are provided, so that the overall size is large. In the prior art shown in FIG. 11 also has a problem in that these technologies cannot be used in vending machines and the like that are required to be miniaturized because of their large shape. As described above, the problem of the related art is to reduce the cost and size of the paper sheet discriminating apparatus that detects the discoloration element.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and an object of the present invention is to provide a paper sheet discriminating apparatus which has a small shape, is inexpensive, and can accurately identify a discoloration element. It is in.

[0008]

According to a first aspect of the present invention, there is provided an apparatus for discriminating the authenticity of a sheet having a discoloration element. A light source that irradiates light or light having a predetermined wavelength, and a wavelength and an emission angle that are different in the wavelength or emission angle of the transmitted or reflected light of the color changing element by changing a relative position between the light source and the paper sheet. Moving means for generating the second detection light, and deflecting the first and second detection lights after the incidence;
A transmission-type or reflection-type first diffractive optical element that emits second transmitted light or first and second reflected light, and a first or second transmitted light that is emitted from the first diffraction-type optical element; A transmissive or reflective second diffractive optic that deflects the first and second reflected lights in different directions according to different wavelengths and emits third or fourth transmitted light or third and fourth reflected light. An element, a position detecting element that receives the third or fourth transmitted light or the third or fourth reflected light emitted from the second diffractive optical element, and outputs a detection signal according to a light receiving position; The light receiving position of the third or fourth transmitted light or the third and fourth reflected light is determined based on the detection signal output from the position detection element, and the third or fourth transmitted light or the third or fourth reflected light is detected. A discriminating processing unit that determines that the paper sheet is genuine when the light receiving position matches the predetermined position. And it features.

Further, in the invention according to claim 2, claim 1
In the paper sheet discriminating apparatus according to the above, the first transmission type or reflection type diffraction optical element deflects the first and second detection lights after being incident, and deflects the first and second transmission lights or the first and second detection lights. And a diffraction grating surface having a surface shape realizing a composite function of emitting the second reflected light.

[0010] In the invention according to claim 3, according to claim 1,
In the paper sheet discriminating apparatus described in the above, the first transmission type or reflection type diffraction optical element deflects the first detection light after being incident, and emits the first transmitted light or the first reflected light. A first portion of a transmission type or a reflection type, and a second portion of a transmission type or a reflection type that deflects the second detection light after being incident and emits the second transmission light or the second reflection light. A diffraction grating surface having a surface shape is provided.

In the invention according to claim 4, claim 1 is
4. The sheet discriminating apparatus according to claim 3, wherein the second transmission-type or reflection-type diffractive optical element is configured to output the first and the second diffractive optical elements from the first diffractive optical element. 5. The second transmitted light or the first and second reflected lights are deflected in different directions according to different wavelengths, and the third and fourth transmitted lights or the third and fourth reflected lights are deflected.
It is characterized by having a diffraction grating surface having a surface shape realizing a composite function of emitting the fourth reflected light.

Further, in the invention according to claim 5, according to claim 1,
The sheet discriminating apparatus according to any one of claims 1 to 3, wherein the first transmitted light or the first reflected light emitted from the second diffractive optical element is directed in different directions according to different wavelengths. A transmission-type or reflection-type first portion that deflects and emits a third transmission light or a third reflection light is different from a second transmission light or a second reflection light emitted from the first diffractive optical element. And a transmission-type or reflection-type second portion that deflects light in a different direction according to the wavelength to be emitted and emits fourth transmitted light or fourth reflected light. I do.

According to a sixth aspect of the present invention, in the device for discriminating the authenticity of a sheet having a color changing element, the color changing element of the sheet is irradiated with white light or light having a predetermined wavelength. A light source, and moving means for generating first and second detection lights having different wavelengths and emission angles in the transmitted or reflected light of the color changing element by changing the relative positions of the light source and the paper sheet, A third transmission-type or reflection-type third light that deflects the first and second detection lights in different directions according to different wavelengths after the incidence, and emits fifth, sixth transmitted light, or fifth, sixth reflected light. A diffractive optical element, and fifth or sixth transmitted light or fifth or fifth transmitted light emitted from the third diffractive optical element.
A position detecting element that receives the sixth reflected light and outputs a detection signal in accordance with the light receiving position; and a fifth or sixth transmitted light or a fifth and sixth reflected light based on the detection signal output from the position detecting element. The light receiving position is determined, and when the light receiving positions of the fifth and sixth transmitted lights or the fifth and sixth reflected lights match the predetermined position,
And a discrimination processing unit that determines that the paper sheet is genuine.

In the invention according to claim 7, claim 6
In the paper sheet discriminating apparatus described in the above, the third transmission-type or reflection-type diffraction optical element deflects the first and second detection lights after being incident, and reflects the fifth, sixth transmitted light, or fifth light. And a diffraction grating surface having a surface shape realizing a composite function of emitting the sixth reflected light.

[0015] In the invention according to claim 8, claim 6 is provided.
In the paper sheet discriminating apparatus according to the above, the third transmission type or reflection type diffraction optical element deflects the first detection light after incidence, and emits fifth transmission light or fifth reflection light. A first portion of a transmission type or a reflection type, and a second portion of a transmission type or a reflection type that deflects the second detection light after being incident and emits a sixth transmission light or a sixth reflection light. A diffraction grating surface having a surface shape is provided.

According to the ninth aspect of the present invention, in the first aspect,
The paper sheet discriminating apparatus according to any one of claims 1 to 8, wherein, when designing the shape of each diffractive optical element, an interference pattern on a diffractive optical element surface when a light beam is incident on the diffractive optical element. The maximum value and the minimum value of the phase distribution are searched from the rate of change of the phase distribution along a plurality of lines virtually drawn on the surface of the diffractive optical element, and the virtual line In the case where the two maximum values adjacent to each other or the minimum values are sequentially selected and the two maximum values are selected, the two maximum values are selected between the two maximum values. A slope is formed such that the difference between one and the minimum value sandwiched between these two maximum values becomes a step, and furthermore, the transmitted light or the reflected light emitted from the diffractive optical element goes in a predetermined direction. So that the phase distribution is sawtooth By approximating with a pattern, using a transmission-type or reflection-type diffractive optical element whose surface shape is determined, and when the two minimum values are selected, between those two minimum values, An inclined surface such that the difference between one of the two minimum values and the maximum value sandwiched between the two minimum values becomes a step, and furthermore, the transmitted light or the reflected light from the diffractive optical element goes in a predetermined direction. A transmission or reflection type diffractive optical element whose surface shape is determined by approximating the phase distribution with a saw-tooth pattern so as to form a phase difference is formed.

According to the tenth aspect of the present invention, in the paper sheet discriminating apparatus according to the ninth aspect, the paper is virtually drawn on the surface of the diffractive optical element so as to intersect with the diffraction grating formed by the phase distribution. Along several parallel straight lines
A transmissive or reflective diffractive optical element whose surface shape is determined by searching for a maximum value and a minimum value of the phase distribution is used.

According to the eleventh aspect of the present invention, in the paper sheet discriminating apparatus according to the ninth aspect, the surface of the diffractive optical element is radiated from the vicinity of the center of curvature determined from the shape of the diffraction grating constituted by the phase distribution. A transmission type or reflection type diffractive optical element whose surface shape is determined by searching for the maximum value and the minimum value of the phase distribution along a plurality of virtual lines extending in the direction is used.

According to a twelfth aspect of the present invention, in the paper sheet discriminating apparatus according to the ninth aspect, there is provided a paper sheet discriminating apparatus in which a plurality of virtual spots are provided on the surface of the diffractive optical element so as to intersect with the diffraction grating formed by the phase distribution. Using a transmissive or reflective diffractive optical element whose surface shape is determined by retrieving the maximum value and the minimum value of the phase distribution along the plurality of polygonal lines or curves. It is characterized by.

According to a thirteenth aspect of the present invention, in the paper sheet discriminating apparatus according to any one of the first to eighth aspects, when designing the shape of each diffractive optical element, a light beam is diffracted. Obtain the phase distribution of the interference pattern on the diffractive optical element surface when incident on the optical element, and calculate the phase distribution from the rate of change of the phase distribution along a plurality of lines virtually drawn on the diffractive optical element surface. The local maximum and minimum of the distribution are searched, and two local maximums (A, B) adjacent along the virtually drawn line are selected, and the two local maximums (A, B) are selected.
B) (C ₁ , C ₂ ,..., C _i ,..., C _N : i is a natural number from 1 to N) along a plurality of virtual lines connected to one of the B (maximum value A) Considering the curve to be formed, along the normal of the curve at each local maximum (C _i ) position of the local maximum, the local maximum (C _i ) Another maximum value (D _i ) was detected, and the maximum value (C _i ) was sandwiched between the two maximum values (C _i , D _i ) between the maximum value (C _i ) and the another maximum value (D _i ). The phase distribution has a sawtooth pattern so that the difference from the minimum value is a step, and furthermore, a slope is formed such that transmitted light or reflected light emitted from the diffractive optical element goes in a predetermined direction. Characterized by using a transmissive or reflective diffractive optical element whose surface shape is determined by approximating .

According to a fourteenth aspect of the present invention, in the paper sheet discriminating apparatus according to any one of the _ninth to _{thirteenth aspects} , a maximum value I _maxo and a minimum value I _{mino of the} entire phase distribution are set. And the difference (I _maxo -I _mino ) between the maximum value I _maxo and the minimum value I _mino is divided into N intervals ((I _maxo −I _mino ) / N),
By quantizing the approximated phase distribution,
A transmissive or reflective diffractive optical element whose surface shape is determined is used.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a paper sheet discriminating apparatus according to the present invention will be described. First, a first embodiment will be described. FIG. 1 is a configuration diagram of the present embodiment, FIG. 2 is an explanatory diagram illustrating a color changing element, FIG. 3 is an explanatory diagram of a first diffractive optical element as a component of the present embodiment, and FIG. 4 is a configuration of the present embodiment. FIG. 5 is a diagram illustrating a second diffractive optical element as an element, and FIG. 5 is a diagram illustrating an output example of a position detection element (PSD and PD array) as a component according to the present embodiment.

First, a first embodiment of a paper sheet discriminating apparatus will be described with reference to FIG. The paper sheet discriminating apparatus includes a light source 2, a first diffractive optical element 4, a second diffractive optical element 5, and a position detecting element 6. Although not shown, a moving unit that changes the relative position between the sheet 1 and the light source 2 (in this embodiment, a moving unit that conveys the sheet).
And a discrimination processing unit that performs discrimination processing using a detection signal output from the position detection element 6. The paper sheet 1 conveyed into the paper sheet discriminating apparatus is provided with a color changing element 31 having a different color appearance depending on a viewing direction. The discoloring element 32 indicates a state in which the discoloring element 31 has moved when the sheet 1 has been transported in the transport direction by a transport device (not shown). In other words, the discoloring element 31 and the discoloring element 32 have different signs. Are the same.

Next, the color changing element will be described with reference to FIG. FIG. 2A shows a case in which illumination light is applied to a printed character or the like of a normal paper sheet, and FIG. 2B shows a case where the illumination light is applied to a color changing element 31 (32) on the paper sheet. Each case is illustrated. In ordinary paper sheets, as shown in FIG. 2A, when illuminated with white light (assuming wavelengths λ1 and λ2), the wavelength of light reflected by the color of the printed ink is determined. A normal diffuse reflection surface diffuses in all directions and looks the same color from any direction.

On the other hand, the discoloration element 3 provided on the sheet 1
When the illumination light is applied to 1 (32), as shown in FIG. 2B, the wavelength of the light reflected from the color changing element 31 (32) varies depending on the angle of reflection. Therefore, as shown in FIG. 1, if the light is reflected from the color-changing element 31 at the angle θ1, the light becomes the first detection light with the wavelength λ1. . As described above as a specific example of the discoloration element, the character
There are symbols / graphics and characters / symbols / graphics using holograms.

Next, each configuration of the paper sheet discriminating apparatus will be described. The discoloration element 31 (3
2) is provided by printing or the like. The light source 2 is disposed in the paper sheet discriminating apparatus at a position above the conveyance path on which the paper sheet 1 is conveyed and at a position where the color changing element 31 (32) of the paper sheet 1 can be illuminated. The light source 2 is a discoloring element 31 (32) of the paper sheet 1 inserted into the paper sheet discriminating apparatus.
Are irradiated with white light or light rays having predetermined wavelengths (λ1 and λ2).

As shown in FIG. 3, the first diffractive optical element 4 includes a first detection light having a wavelength λ1 and an incident angle θ1, and
When the second detection light having the wavelength λ2 and the incident angle θ2 enters,
The wavelength is maintained as it is, but the angle is deflected so that both angles become the emission angle θ3, and the first transmitted light and the second
Emitted as transmitted light. As shown in FIG. 1, the position where the first detection light is incident is defined as a first portion, and
The position where the detection light is incident is referred to as a second portion, and the first portion and the second portion are configured to have different diffraction gratings and the like. As will be described later, this configuration is common to the first, second, and third diffractive optical elements that appear below.

Although FIG. 3 illustrates the transmission type first diffraction optical element 4, the wavelength λ1 and the incident angle θ
When the first reflected light of 1 enters the first portion, and the second reflected light of wavelength λ2 and the incident angle θ2 enters the second portion,
The wavelength is maintained as it is, but the output angle θ
The first diffractive optical element 4 may be a reflective first diffractive optical element 4 that emits the first reflected light and the second reflected light by being deflected to 3. Whether it is a transmission type or reflection type first diffraction optical element 4 is appropriately designed and selected.

As shown in FIG. 4, the second diffractive optical element 5 has a function of changing the deflection angle according to the wavelength of the incident light, and the first transmitted light (wavelength λ1 and angle θ4). When the first reflected light) and the second transmitted light (second reflected light) having the wavelength λ2 and the angle θ4 are incident, the light is deflected to angles θ5 and θ6, respectively, and the third transmitted light having the wavelength λ1 and the angle θ5 and The fourth transmitted light having the wavelength λ2 and the angle θ6 is emitted. Also in this case, as shown in FIGS. 1 and 4, the position where the first transmitted light (first reflected light) is incident is defined as the first portion, and the position where the second transmitted light (second reflected light) is incident. Is a second portion, and the first portion and the second portion are configured to have different diffraction gratings and the like.

Although FIG. 4 illustrates the transmission type second diffractive optical element 5, the first transmitted light (first reflected light) having the wavelength λ1 and the angle θ4 is transmitted to the first portion, and When the second transmitted light (second reflected light) having the wavelength λ2 and the angle θ4 is incident on the second portion, the light is deflected to angles θ5 and θ6, respectively, and the third reflected light having the wavelength λ1 and the angle θ5 and Wavelength λ2
The reflection type second diffractive optical element 5 that emits the fourth reflected light at the angle θ6 may be used. Transmissive or reflective second
The design of the diffraction optical element 5 is appropriately selected.

The position detecting element 6 is a semiconductor position detecting element (PSD: Position Sensitive Detector) or a multi-division position detecting element (PD array: Photo Diode).
Array, etc., as is clear from FIG. 1, the PSD has a light receiving surface that is long in one direction and can obtain an electric output according to the position where light is incident.
The PD array includes a plurality of PDs, and an output is obtained from the PD on which light is incident.

Next, the discriminating process by the sheet discriminating apparatus will be described. As shown in FIG. 1, when a sheet 1 is inserted into a sheet discriminating apparatus and is conveyed on a conveying path in a conveying direction, the sheet 1 is illuminated by a light source 2. First, discoloration element 3
At 1, the first detection light having the wavelength λ1 is emitted from the color changing element at an angle θ1, and the position is detected via the first portion of the first diffractive optical element 4 and the first portion of the second diffractive optical element 5. The light enters the device 6.

Subsequently, when the sheet 1 advances on the transport path and the color changing element 31 comes to the position of the color changing element 32, the incident position on the first diffractive optical element 4 becomes the second portion, and the wavelength λ2 The second detection light is reflected from the color changing element at an angle θ2,
The light enters the position detecting element 6 via the second part of the first diffractive optical element 4 and the second part of the second diffractive optical element 5.

In the position detecting element 6, the light detection position differs depending on whether the incident light beam is the third transmitted light (third reflected light) or the fourth transmitted light (fourth reflected light). As a result, the detection signals are different, and the wavelength can be determined based on the detection position. The third transmitted light (third reflected light) from the color changing element 31 is received as light of the wavelength λ1, and after a short time, the fourth transmitted light (fourth reflected light) from the color changing element 32 is converted to light of the wavelength λ2. Since the light is received, the detection signal of the position detection element 6 becomes a signal as shown in FIG. If such a detection signal is output to a discrimination processing unit (not shown), the discrimination processing unit stores the detection signal in a memory unit (not shown), compares the detection signal with a genuine signal pattern registered in advance, and matches the signal pattern. Then, it can be determined that the light is reflected light from the color changing element, and the paper sheet 1 has a color changing element, that is, is distinguished from a true paper sheet.

On the other hand, when fake paper sheets such as counterfeit bills have no discoloration element, the detection light of the discoloration element is not emitted, and the wavelength of the reflected light is any one of λ1 and λ2. Or there is no reflected light of both wavelengths. For this reason, the third transmitted light (third transmitted light) shown in FIG.
One or two of the two waveforms indicating the reflected light) or the fourth transmitted light (fourth reflected light) disappear. The discrimination processing unit stores the detection signal in a memory unit (not shown), compares it with a genuine signal pattern registered in advance, and if it does not match, can determine that the light is not reflected light from the color changing element. Has no discoloration element, that is, is distinguished from fake paper sheets.

The first diffractive optical element 4 described above is
As shown in FIG. 1 and FIG. 3, in addition to the configuration having the diffraction grating surface separating the first portion and the second portion, as shown in FIG. Diffraction grating surfaces that are not divided can also be used. Specifically, a surface shape that realizes a composite function described later is designed, and the first diffraction optical element 4 having a diffraction grating surface having this surface shape is obtained. Here, having a composite function refers to a function of deflecting a plurality of incident lights having different wavelengths and incident angles in arbitrary directions, respectively. A method of designing a surface shape that realizes such a composite function will be described later. This diffraction grating surface converts the first and second detection lights into the first and second light beams at arbitrary emission angles.
Since the light is deflected into two transmitted lights (first and second reflected lights), the light does not need to be divided into the first part and the second part. As described above, whether to use the diffraction grating surface having the first and second portions or the diffraction grating surface having the composite function is appropriately selected.

The second diffractive optical element 5 described above is
As shown in FIG. 1 and FIG. 4, in addition to the configuration having the diffraction grating surface separating the first portion and the second portion, as shown in FIG. Diffraction grating surfaces that are not divided can also be used. The diffraction grating surface may be a normal (for example, a simple sawtooth diffraction grating surface) diffraction grating surface.
The first and second transmitted light (first and second transmitted light) having the same incident angle and different wavelengths are incident on the diffractive optical element having such a normal diffraction grating surface.
It is well known that when the reflected light is incident, the emission angle can be made different while maintaining the wavelength.
And the second part need not be divided.

Further, a surface shape having a composite function may be designed and the second diffraction optical element 5 having a diffraction grating surface having this surface shape may be used. The diffraction grating surface converts the first and second transmitted lights (first and second reflected lights) having different wavelengths and incident angles into third and fourth transmitted lights (third and fourth reflected lights) having arbitrary output angles, respectively. ), And need not be deliberately divided into the first portion and the second portion. As described above, whether to use the diffraction grating surface having the first and second portions or the diffraction grating surface having the composite function is appropriately selected. Furthermore, in the above embodiment, the first and second detection lights are described as the reflected light of the color changing element 31, but the transmitted light of the color changing element may be used as the first and second detection light.

FIG. 22 is a configuration diagram of a sheet discriminating apparatus in which both the first diffractive optical element 4 and the second diffractive optical element 5 have a diffraction grating surface having a composite function, and FIG. Is a configuration diagram of a paper sheet discriminating apparatus having a composite function or a normal diffraction grating surface, while the diffractive optical element 4 has first and second portions. As described above, the above-described first diffractive optical element 4 and second diffractive optical element 5 can be appropriately combined and configured.

Next, a second embodiment of the paper sheet discriminating apparatus of the present invention will be described with reference to the drawings. FIG. 6 is a configuration diagram of the present embodiment, and FIG. 7 is an explanatory diagram of a third diffractive optical element as a component of the embodiment. In the first embodiment, the first diffractive optical element 4 and the second diffractive optical element 5 are provided. However, in the present embodiment, as shown in FIG. 7 is different. In addition, the sheet 1, the discoloring element 31, the discoloring element 32, the light source 2, and the position detecting element 6 are the same as those in the first embodiment, and the detailed description is omitted.

Third Diffractive Optical Element 7 Having Composite Function
Is designed to have both functions of the first diffractive optical element 4 and the second diffractive optical element 5 of the first embodiment. As shown in FIG. 7, the wavelength λ1 and the incident angle θ
When the first first detection light and the second detection light having the wavelength λ2 and the incident angle θ2 enter, the third diffraction optical element 7
It has the function of changing the deflection angle according to the wavelength and angle of the incident light, and deflects it to angles θ5 and θ6, respectively.
Fifth transmitted light at wavelength λ1, angle θ5, and wavelength λ2
The sixth transmitted light having the angle θ6 is emitted. As also shown in FIGS. 6 and 7, the position where the first detection light is incident is defined as a first part, the position where the second detection light is incident is defined as a second part, and the first part and the first part are separated. The second part has a configuration in which a diffraction grating and the like are different.

Although FIGS. 6 and 7 show the third diffractive optical element 7 of the transmission type, the first detection light having the wavelength λ1 and the incident angle θ1 and the wavelength λ2 and the incident angle θ
When the second second detection light is incident, the third diffractive optical element 7 has a function of changing the deflection angle in accordance with the wavelength of the incident light, and deflects the light to angles θ5 and θ6, respectively. The reflection type third diffractive optical element 7 that emits the fifth reflected light having the wavelength λ1 and the angle θ5 and the sixth reflected light having the wavelength λ2 and the angle θ6 may be used. Whether it is a transmission type or reflection type third diffraction optical element 7 is appropriately designed and selected. The light emitted from the third diffractive optical element 7 is detected by the position detection element 6, which is a PD array or PSD, and a detection signal is output.

Next, the discriminating operation according to the second embodiment will be described. In FIG. 6, when the sheet 1 is inserted into the sheet discriminating apparatus and is conveyed on the conveying path in the conveying direction, the sheet 1 is illuminated by the light source 2. First, the wavelength λ1
Is emitted from the color changing element at an angle θ1, and the third detection light
Of the position detecting element 6 through the first portion of the diffractive optical element 7
Incident on. The paper sheet 1 advances on the transport path, and the discoloration element 31
Comes to the position of the color-changing element 32, the incident position on the third diffractive optical element 7 is different, the second detection light of wavelength λ2 is reflected from the color-changing element at an angle θ2, and the third diffractive optical element 7 The light enters the position detection element 6 via the second portion.

In the position detecting element 6, the light detection position differs depending on whether the incident light beam is the fifth transmitted light (fifth reflected light) or the sixth transmitted light (sixth reflected light). As a result, the detection signals are different, and the wavelength can be determined based on the detection position. The fifth transmitted light (fifth reflected light) from the color changing element 31 is received as light of wavelength λ1, and after a short time, the sixth transmitted light (sixth reflected light) from color changing element 32 is converted to light of wavelength λ2. Since the light is received, the detection signal of the position detection element 6 becomes a signal as shown in FIG. 5 as in the first embodiment. If such a detection signal is output to a discrimination processing unit (not shown), the discrimination processing unit can determine that the light is reflected light from the discoloration element, and the sheet 1 has a discoloration element. That is, it is discriminated from a true paper leaf, and if there is no one or two of the two waveforms shown in FIG. 5, it is discriminated from a fake leaf.

The third diffractive optical element 7 described above is
As shown in FIGS. 6 and 7, in addition to the configuration having a diffraction grating surface separating the first portion and the second portion, FIGS.
As shown by 5, the first portion and the second portion can be formed as a diffraction grating surface which is not separated. More specifically, a surface shape that realizes a composite function described later is designed, and a third diffraction optical element 7 having a diffraction grating surface having this surface shape is obtained.
This diffraction grating surface is a grating surface that deflects the first and second detection lights into fifth and sixth transmitted lights (fifth and sixth reflected lights) having an arbitrary emission angle, respectively. It does not have to be divided into parts. As described above, whether to use the diffraction grating surface having the first and second portions or the diffraction grating surface having the composite function is appropriately selected.

Subsequently, common to the first and second embodiments,
The first, second and third diffractive optical elements having a surface shape realizing a composite function and having high accuracy will be described. As a specific example of the first, second, and third diffractive optical elements having the functions described in the first and second embodiments, a hologram for recording interference fringes by disposing an actual optical system is provided. There are graphic optics. As an example of a holographic optical element, for example, as shown in FIG. 8, the same function as that of the first diffractive optical element 4 can be provided, but there are many noise components such as transmitted light and high-order diffracted light, and The efficiency of light incident on the detection element 6 is low. For example, an element is manufactured with a pattern in which the phase distribution is binarized, and the element has a diffraction efficiency of about 40%.

In order to improve the diffraction efficiency, the present inventors invented a design method for improving the diffraction efficiency, and filed a patent application as Japanese Patent Application No. 11-327080 (Title of Invention: Design Method for Diffractive Optical Element). I came to. In the present embodiment, a diffraction type optical element is obtained by a design method for improving diffraction efficiency, and the diffraction efficiency is improved by using this diffraction type optical element for a paper sheet discriminating apparatus.

First, a first design method of the first diffractive optical element 4, the second diffractive optical element 5, and the third diffractive optical element 7 will be described with reference to the drawings. The first
Is a common method for designing the diffractive optical element 4, the second diffractive optical element 5, and the third diffractive optical element 7. The description will be made with reference to the element 50.

FIG. 9 is a flowchart showing the procedure of the first design method of the diffractive optical element 50, FIG. 10 is an explanatory diagram of the direct phase calculation method, and FIG. 11 is an explanatory diagram of a process approximating a sawtooth pattern. 12 is a diagram showing a sawtooth pattern in one section of the diffractive optical element, FIG. 13 is a diagram showing an example in which the sawtooth pattern is quantized, and FIG. 14 is a diagram showing a case where the sawtooth pattern is formed based on the minimum value. is there. The design of the diffractive optical element in the present embodiment is performed by executing a program stored in an electronic computer. When the process is started, first, in step 101, a phase distribution is calculated. You.

The method of calculating the phase distribution in step 101 is not particularly limited. For example, a conventionally known direct phase calculation method can be applied. The direct phase calculation method has been published as a "Computer Hologram for Free-Space Optical Interconnection" in the Transactions of the Japan Society of Applied Physics (S. Kawai and Y. Kohga, Compu
ter-Generated Holograms for Free-Space Optical
Interconnections, Japanese Journal of Applied
Physics, Vol. 30, PP. L210-2103 (1991)).

The outline of the direct phase calculation method will be briefly described with reference to FIG. 10. First, a plane A on which a diffractive optical element 50 to be designed is placed, and the diffractive optical element 50
Consider a light source S ₀ and a focal point S ₁ for each ray deflected by The coordinates (x, y, 0) are coordinates representing a point on the plane A. The coordinate origin is a point on the plane A. The position coordinates of the light source _{S 0} is _{(X s, Y s, Z} s). Focus S
Position coordinates of _a is _{(X m, Y m, Z} m). And
The intensity of the interference wave I (x, y) on the plane A when emitted light rays from the light sources S _0, calculates according to equation 1.

[0052]

(Equation 1)

[0053] Here, _{r m} and _{r s} are defined as follows.

[0054]

(Equation 2)

[0055] In the above formula, A _s is the amplitude of the input wave, A _m is the amplitude of the light when the light is emitted from the focal point S ₁ of the focal point, i is the imaginary unit, lambda is the wavelength of light, k (= 2π / λ) is the wave number of the light, and x and y are the coordinates (x = 0, 1,
2,..., N: y = 0, 1, 2,. I (x, y) is the phase distribution on the diffractive optical element 50. Note that the direction orthogonal to the diffractive optical element 50 is
The direction is the z direction.

The phase distribution I (x,
When y) is obtained, the process proceeds to step 102, and the respective values of the counters i, j, k, l are set to 0 as an initial setting.
Set to. Note that i is x of the phase distribution I (x, y).
A counter for moving the position on the coordinate, j is a counter for moving the position on the y coordinate of the phase distribution I (x, y), and k is a counter for storing the position of the maximum value at y = j. , L are counters for storing the position of the local minimum at y = j.

Then, the processing shifts to step 103, where y = j
, The i-th phase distribution I (i, j) and the (i + 1) -th phase distribution I (i + 1, j) based on the magnitude relationship between the i-th phase distribution I (i, j) and the (i + 1) -th phase distribution I (i, j) It is determined whether it is increasing or decreasing toward (i + 1, j). In step 103, the phase distribution I
Is determined to have decreased (I (i, j)> I
In (1 + 1, j)), the process proceeds to step 104, where the flag F (i) is set to −1. Then, the process proceeds to step 105 to determine whether the previously set flag F (i−1) is 1. Is determined.

That is, the flag F is set to 1 in step 104 when it is determined in step 103 that the phase distribution I is decreasing, whereas the flag F is set in step 104 when it is determined that it is decreasing. Since the flag is set to −1 in step 108 described later, if the determination in step 105 is “YES”, it can be determined that the phase distribution I has turned from an increase to a decrease. Can be determined to have been searched.

Therefore, the determination in step 105 is "YE
In the case of “S”, the process proceeds to step 106, where N _max (k,
j) stores the current value of the counter i. Then, the process proceeds to step 107, where the counter k is incremented by one. If the determination in step 105 is “NO”,
Steps 106 and 107 are not executed.

On the other hand, if it is determined in step 103 that the phase distribution I has increased (I (i, j) <I (i +
At 1, j)), the process proceeds to step 108, where the flag F
(I) is set to 1, and then the routine proceeds to step 109, where it is determined whether or not the previously set flag F (i-1) is -1. If the determination in step 109 is "YE
In the case of "S", it can be determined that the phase distribution I has turned from a decrease to an increase, and thus it can be determined that the minimum value has been searched.

Therefore, the determination in step 109 is "YE
S ”, go to step 110 and store N _min (1,
j) stores the current value of the counter i. Then, the process proceeds to step 111, and the counter 1 is incremented by one. If the determination in step 109 is "NO",
Steps 110 and 111 are not executed.

When the processing in step 107 or 111 is completed, or when the determination in step 106 or 109 is “NO”, the flow proceeds to step 112, the counter i is incremented, and the flow proceeds to step 113.
It is determined whether or not the counter i has exceeded the maximum value m. If the counter i has not exceeded the maximum value m, the process returns to step 103 to execute the above-described processing again. If the determination in step 113 is “YES”, In step 114, the counter i is cleared to 0, and the counter j is incremented.

Next, the routine proceeds to step 115, where it is determined whether or not the counter j has exceeded the maximum value n. If not, the routine returns to step 103 to execute the above processing again. Is "YES"
, All the phase distributions I obtained in step 101
It is determined that the search processing of the maximum value and the minimum value for (i, j) has been completed, and the process proceeds to step 116.

That is, when the processing of steps 102 to 115 is completed, the phase distribution I (i) is drawn along the mutually parallel lines in the x-axis direction virtually drawn on the plane on which the diffractive optical element 50 is placed. , J) have been found. Then, the process proceeds to step 116 to execute a process of approximating the phase distribution I (i, j) with a sawtooth pattern using the local maximum value and the local minimum value searched in the processes of steps 102 to 115 described above. The details of the sawtooth processing executed in step 116 are as shown in FIG.

That is, steps 106 and 110 in FIG.
And N_max(K, j) and N_{m in}Write (1, j)
From this, what phase distribution I at y = j is
It is known whether (i, j) is a maximum value or a minimum value.
Therefore, those N_max(K, j) and N_min(1,
j), the maximum value I_max(P, j) and minimum I
_min(P, j) can be selected. And
Due to the nature of the maxima and minima, they appear alternately.

In FIG. 11, after the p-th local maximum value I _max (p, j) at y = j, the p-th local minimum value I _min
(P, j) appears, and then the (p + 1) -th local maximum I
_max (p + 1, j), then the p + 1st local minimum I
_min (p + 1, j), then the p + 2nd local maximum I
_The appearance of _max (j, p + 2) is shown. The black circles arranged on the curve indicate the phase distribution I (x, y) before the execution of the sawtooth processing in step 116.

[0067] In the present embodiment, the two maxima _I max (p, j) of adjacent and in units of _{I ma x (p + 1,} j) and the part sandwiched by to perform a serrated process And the whole is a repetition of the saw-tooth processing, so that any two adjacent maxima I
The saw-tooth processing of a portion sandwiched between _max (p, j) and I _max (p + 1, j) will be described.

First, the intervals and steps of the sawtooth pattern are determined. Note that these intervals and steps are individually determined for each of the sawtooth patterns. The interval Wp of the sawtooth pattern is determined by two adjacent maximum values I _max (p,
j) and I _max (p + 1, j) in the direction along the x-axis. Specifically, N _max (k, j) −N
_max (p, j).

The step Ap of the sawtooth pattern has a maximum value I
_max(P, j) and the local minimum I_min(P,
j) and the difference (I_max(P, j) -I_min(P,
j)). Note that the step of the sawtooth pattern has a maximum value.
I_max(P + 1, j) and the minimum value I _min(P, j)
It is possible to use the difference between
The shape of the slope of the tooth pattern is opposite to that of FIG.
become. In other words, as the shape of the slope of the sawtooth pattern
Is opposite to the left-downward one as shown in FIG.
There are two types, one that descends to the right, and one is used.
Is appropriately selected.

Next, the slope of the sawtooth pattern is determined so as to pass through the local maximum value I _max (p, j) based on the interval Wp and the step Ap. In the example of FIG.
A thick solid line that passes through _max (p, j) and slopes down to the left
The slope is determined. Then, the maximum value I _max (p,
Each phase distribution I (i, j) between j) and I _max (p + 1, j) is moved to the point on the slope determined as described above. In the example of FIG. 11, a white circle indicates the phase distribution I (i, j) after the movement.

If the above-described saw-tooth processing is performed on the whole of y = j, a saw-tooth pattern shown by a broken line in FIG. 12 is obtained, and the same processing is performed for all of y = 0 to n. If executed, the entire phase distribution I (x, y) is approximated by a sawtooth pattern. It is desirable that the phase distribution I (x, y) after being approximated to the sawtooth pattern be quantized, for example, as shown in FIG. As the quantization process, for example, the maximum value I of the entire phase distribution I (x, y)
_maxO and a minimum value I _minO are obtained, and the maximum value I
The difference between _maxO and the minimum value I _minO (I _maxO −I
_minO ) is divided into N intervals ((I _maxO −I
_{minO 2} ) / N) and the approximated phase distribution I (x, y)
Is effective.

Thus, the processing of FIG. 9 is completed. And the final approximation (or approximation and quantization)
The diffractive optical element 50 is manufactured using the phase distribution I (x, y). In the diffractive optical element 50 designed and manufactured according to the procedure as in the present embodiment,
Since the phase distribution I is blazed, the diffraction efficiency is greatly improved as compared with a conventional diffractive optical element in which the phase distribution I is not performed. Further, in the present embodiment, the processing approximating the sawtooth pattern is performed by the phase distribution I
Since the processing is performed along a virtual line parallel to the x-axis, which is a direction in which (x, y) are arranged, there is also an advantage that the saw-tooth processing is simple.

When quantizing the phase distribution I (x, y) approximated to the sawtooth pattern, the phase distribution I (x, y)
(X, y) Maximum value I _maxO and minimum value I _{minO of the whole}
, The quantization can be performed with respect to all of y = 0 to n using the same reference, and there is an advantage that there is little possibility that a problem occurs when the diffractive optical element 50 is actually manufactured. There is also.

In this embodiment, as shown in FIG. 11, the interval Wp between the tooth-like patterns is set to two adjacent maximum values I _max (p, j) and I _max (p + 1,
j), but is not limited to this, and two adjacent minimum values I _min (p, j)
And the distance between I _min (p + 1, j) may be defined as the interval Wp of the sawtooth pattern. In such a case, actually, as shown in FIG. 14, a saw-tooth pattern similar to that of FIG. 12 is obtained. That is, as can be seen from a comparison between FIG. 14 and FIG. 12, the sawtooth patterns of both have the same shape and are only shifted in position by a half cycle.

In this embodiment, the processing approximating the saw-tooth pattern is performed along a line parallel to the x-axis which is the direction in which the phase distributions I (x, y) are arranged. However, the present invention is not limited to this. For example, a center of curvature is obtained from the shape of the diffraction grating included in the phase distribution I (x, y), and a plurality of radially extending from the center of curvature along the diffractive optical element 50 are obtained. May be searched for the maximum value and the minimum value along the line, and a process approximating the sawtooth pattern may be performed. Such processing has the advantage that the sawtooth pattern can be more three-dimensionally approximated.

The line for searching for the maximum value and the minimum value is not limited to a straight line as in this embodiment, but may be a curve or a polygonal line. Then, such a curve or a polygonal line is oriented so that the gradient in the phase distribution I (x, y) faces a steep direction and does not cross each other.
A plurality may be selected, a maximum value and a minimum value may be searched along the curve or the polygonal line, and a process of approximating the sawtooth pattern may be performed. Even with such processing, there is an advantage that the sawtooth pattern can be more three-dimensionally approximated.

Next, a diffractive optical element according to another design method will be described with reference to FIG. FIG.
FIG. 4 is an explanatory diagram for describing a design method of FIG. Looking at the original phase distribution I (x, y) before approximation with a sawtooth pattern, it is composed of a mountain part and each part. Therefore, in the present design method, the peak portion or the valley portion is extracted, and each peak portion or the valley portion is approximated by a sawtooth pattern.

Here, in FIG. 15, reference numeral 60 indicates a series of local maximum values of the phase distribution. In FIG. 15, the local maximum value I _max (s, j) and the local minimum value I _min (p,
j), the local maximum value I _max (q, j) is detected. Indicated by an arrow in FIG. 15, to set the normal _{h j} at the maximum value _I max (s, j) the maximum value with respect to the curve of the series of maximum values, including the _I max (s, j), the first on the normal line The maximum value I _max (s,
j), the sequence of maxima including I _max (s, j) and I
_{The maximum} (s ′, P ′) and the minimum I _min (s ″, p ″) between these maximums are detected. These maxima I
_The phase distribution of _max (s, j), the minimum value I _min (s ″, p ″), and the maximum value I _max (s ′, p ′) is approximated by a slope as in the first design method.

Then, by a method similar to the above, approximation of the series of local maxima by the slope of the phase distribution is performed half a round for the series of local maxima. By such an operation, each part can be blazed. By operating the entire phase distribution and using the above-described method in the same manner as in the first design method, approximate blazing of the entire phase distribution is performed. The blazed valleys can be stored on a computer to avoid double operations.

According to the second design method described above, it is possible to design the diffractive optical element 50 whose diffraction efficiency is greatly improved. Next, a third design method of the present invention will be described with reference to FIGS. Here, FIG. 16 is a flowchart showing a processing procedure in the third design method, and FIG. 17 is an explanatory diagram of the third design method.

The third design method supplements a flow chart and the like in order to clarify the processing procedure of the second design method, and similarly to the second design method, obtains the phase distribution. A peak or a valley is extracted, and each peak or valley is approximated by a sawtooth pattern. In the third design method, as shown in FIG.
On a line virtually drawn on (x, y), a search process of the maximum value and the minimum value of the phase distribution is performed from the change rate of the phase distribution. This search process is a process corresponding to steps 101 to 115 of the flowchart in FIG. 9 in the first design method, and thus detailed description thereof will be omitted here.

In step 202, from one of the maximum values obtained in step 201, the maximum value along a plurality of virtual lines connected to the maximum value is detected, and a curve Cs in which the maximum values continue is extracted. . Specifically explaining with reference to FIG. 17, first, the maximum value _M ax I (s, j) begins, the maximum value _M ax I (s, j) the maximum continuous with value _M ax I (t,
j + 1) and the maximum value _Max I (t ', j-1),
A continuous curve of the maximum values including these is extracted. Note that reference numeral 60 in FIG. 17 indicates a series of local maximum values of the phase distribution.

In step 203, the temporary
Selected on the line drawn in step 202
Another maximum value adjacent to the maximum value and the minimum value
Is extracted as a continuous curve Cq of local maxima including. See FIG.
Specifically, the maximum value M_axI (s, j)
And the minimum value M_inMaximum value M adjacent to each other across I (r, j)
_axFor I (q, j), this maximum value M_axI (q,
The continuous curve of the maximum value including j) is extracted.

The portion between the two curves Cs and Cq obtained in this way has a minimum value as described above, and this portion becomes a valley portion of the phase distribution. Next, a method of blazing the valley portion of the phase distribution thus obtained will be described. First, in step 204, one point of the maximum value on the curve Cs is selected, and the normal line of the curve Cs at that point is drawn. In the next step 205, the maximum value of the intersection of the normal line and the curve Cq is obtained. Further, in step 206, a minimum value between the two curves Cs and Cq is detected on the normal line.

Each of the above steps 204 to 206 will be described with reference to FIG. First, the maximum value M
The normal h _{j of the} curve containing this local maximum on _ax I (s, j)
pull. Next, the normal h _j and the maximum value _Max I (q,
the maximum value of the intersection of the curve continuing the maximum value including j) M _ax
I (s ', p') is detected. Further, the two maximum values _Max I (s, j) and the maximum values _Max I (s ′, p ′)
, The minimum value M _in I (s ″, p ″) is detected.

Next, in step 207, step 20
The two adjacent maxima on each normal obtained in 4 to 206,
Saw-tooth processing is performed based on the position of the minimum value sandwiched between those maximum values and the intensity of the phase distribution. This sawtooth processing is performed in the first
This is the same as the saw-tooth processing described in the embodiment. In the third embodiment, the amounts corresponding to the interval Wp and the step Ap described in the first embodiment are two adjacent maximum values _Max I (s, j) and the maximum values _Max I ( s',
p,), and the horizontal distance between the positions where
_ax I (s, j) and its adjacent minimum value M _in I (s ″,
p ″) and the difference _ΔMax I (s, j) −M _in I (s ″,
p ")}.

Therefore, the slope of the sawtooth pattern is determined so as to pass through the maximum value _Max I (s, j) based on the amount corresponding to the interval Wp and the step Ap. Next, the local maximum value _Max I
Each phase distribution between (s, j) and the maximum value _Max I (s ′, p ′) is moved to a point on the slope in the same manner as described in the first design method. At this time, as in the case of the first design method, the saw-tooth processing has two types of surface inclinations. In this case, a highly efficient direction is selected each time by a method such as ray tracing.

At step 208, it is determined whether or not the processing at steps 204 to 207 has been completed at all points on the curve Cs. As a result of this determination, an affirmative determination (Ye
In the case of s), since the saw-tooth processing of the portion sandwiched between the curves Cs and Cq has been completed, the next step 2
Go to 09. In step 209, the curve C on the phase distribution
The portion surrounded by s and the curve Cq (the portion where the processing has been completed) is stored in the memory of the computer. This can prevent the processed portion from being reprocessed later.

In step 210, the presence or absence of an unprocessed portion on the phase distribution plane is determined with reference to the memory. If there is an unprocessed part, steps 202 to 20
9 is repeated, and when there is no more unprocessed part, the design ends. In the above description of the procedure of the design method, the saw-tooth processing of the valley portion sandwiched by the local maximum values is described as an example.However, the present invention is not limited to this, and the local maximum value and the local minimum value in the description, By exchanging the peaks and the valleys, the peaks sandwiched between the local minimums can be subjected to the sawtooth processing.

According to the third design method described above, the peaks or valleys of the phase distribution are extracted, and each peak or valley is approximated by a sawtooth pattern. A diffractive optical element 50 with significantly improved diffraction efficiency can be designed. In each of the first to third design methods described above, the case where the present invention is applied to the design of a transmission type diffractive optical element is described. However, the present invention is not limited to this. Naturally, the design of the present invention can be applied.

As described above, according to the first to third design methods, it is possible to design a diffractive optical element which can be blazed to improve the diffraction efficiency even in a complicated case where the diffraction gratings overlap. And a diffraction type optical element having high diffraction efficiency. In particular, according to the invention of claim 13, a diffractive optical element capable of more remarkably improving diffraction efficiency can be provided.

Using the first to third diffractive optical elements designed by the first to third design methods, the position detecting element 6 can detect the color changing element with high efficiency and low noise. This makes it possible to improve the accuracy of determining the authenticity of paper sheets.

[0093] Now, the intensity I (x, y) of the interference wave on a plane A represented by the number 1 above, the first light source _{S 0} and focal S
₁ assuming the input and output was formulas in the case of one-to-one. This assumes a case in which a first portion and a second portion corresponding to each other with a 1: 1 input and an output are designed. However, in order to obtain a surface shape that realizes a composite function of transmitting or reflecting the first detection light and the second detection light in different directions, it is necessary to make a plurality of outputs correspond to a plurality of inputs. For this purpose, Equation 1 used in the direct phase calculation method described above is modified.

Specifically, as shown in FIG. 26, first,
Plane A on which the diffractive optical element 50 to be designed is placed
And is deflected by the diffractive optical element 50
Light source S_0AAnd focus S_1Athink of. Coordinate
(X, y, 0) are coordinates representing a point on the plane A. seat
The target origin is a point on the plane A. Light source S_0APosition seat
The mark is (X_s, Y_s, Z_s). Focus S_1APosition of
The coordinates are (X_m, Y_m, Z _m). And plane A
Above the intensity of the interference wave I_A(X, y) is obtained. Similarly, light
Source S_0BAnd focus S_1Bthink of. Light source S_0BPosition of
The coordinates are (X_l, Y_l, Z_l). Focus S_1BRank
The coordinates are (X_q, Y_q, Z_q). And the plane
The intensity I of the interference wave on A_B(X, y) is obtained. like this
Strength I_A(X, y) and intensity I_B(X,
y) is synthesized to obtain the following equation.

[0095]

(Equation 3)

Here, r _m , r _s , r _l and r _q are defined as follows.

[0097]

(Equation 4)

In the above formula, A_s, A_lIs the light source S
_0A, Light source S_0BAmplitude of light emitted from_m, A_q
Is the focus S_1A, Focus S_1BEmitted light from
The amplitude of the light, i is the imaginary unit, λ1 and λ2 are the light
Source S_0A, Light source S_0BWavelength of light emitted from
_A(= 2π / λ1), k_B(= 2π / λ2) is light
Source S _0A, S_0BWave number of light radiated from
Coordinates (x = 0, 1, 2,..., N: y =
0, 1, 2, ..., n). And I_A(X, y)
And strength I_BI (x, y) obtained by adding (x, y) is
9 is a phase distribution on the diffractive optical element 50. In addition, diffraction type
The direction orthogonal to the optical element 50 is defined as the z direction. So
After that, by using the first to third design methods described above,
Because it is possible to obtain a surface shape with functions,
Description is omitted.

As described above, the first, second or third diffractive optical element having a composite function can be obtained by using the first to third design methods. These first and second
Alternatively, the third diffractive optical element is a diffractive optical element having a diffraction grating surface having a surface shape realizing a composite function, thereby deflecting incident light and outgoing light in an optimal direction in accordance with actual conditions. It can be a diffractive optical element.

[0100]

As described above, according to the present invention, one set of light receiving optical systems can detect light from two or more directions, and the diffractive optical element can be manufactured by molding. There is no thickness like the conventional lens, and the whole configuration can be reduced in size, and the number of parts is small, so that the cost is low. According to the fourth aspect of the present invention, the third diffractive optical element and the second optical element are integrated into a third optical element.
Therefore, the size and cost can be further reduced. Further, according to the inventions according to Claims 7 to 14, since a diffractive optical element capable of detecting the detection light reflected from the paper sheet to be discriminated with high efficiency and low noise is used, paper having high discrimination accuracy is provided. It can be a leaf discriminating device. As a whole, it is possible to provide a paper sheet discriminating apparatus having a small shape and an inexpensive configuration, and which can accurately determine a color changing element.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a first embodiment of a paper sheet discriminating apparatus of the present invention.

FIG. 2 is an explanatory diagram illustrating a color change element.

FIG. 3 is an explanatory diagram of a first diffractive optical element as a component of the first embodiment of the paper sheet discriminating apparatus of the present invention.

FIG. 4 is an explanatory diagram of a second diffractive optical element as a component of the first embodiment of the paper sheet discriminating apparatus of the present invention.

FIG. 5 is a diagram illustrating an output example of a position detecting element (PSD and PD array) as a component of the first embodiment of the paper sheet discriminating apparatus of the present invention.

FIG. 6 is a configuration diagram of a paper sheet discriminating apparatus according to a second embodiment of the present invention.

FIG. 7 is an explanatory diagram of a third diffractive optical element as a component of the second embodiment of the paper sheet discriminating apparatus of the present invention.

FIG. 8 is an explanatory diagram of a holographic optical element.

FIG. 9 is a flowchart showing a procedure of a first design method of the diffractive optical element 50.

FIG. 10 is an explanatory diagram of a direct phase calculation method.

FIG. 11 is an explanatory diagram of a process for approximating a sawtooth pattern.

FIG. 12 is a diagram showing a sawtooth pattern in one section of the diffractive optical element.

FIG. 13 is a diagram showing an example in which a sawtooth pattern is quantized.

FIG. 14 is a diagram when a sawtooth pattern is formed based on a minimum value.

FIG. 15 is an explanatory diagram for describing a second design method.

FIG. 16 is a flowchart showing a processing procedure in a third design method.

FIG. 17 is an explanatory diagram of a third design method.

FIG. 18 is a configuration diagram of a conventional paper sheet discriminating apparatus.

FIG. 19 is a configuration diagram of a conventional paper sheet discriminating apparatus.

FIG. 20 is an explanatory diagram of a first diffractive optical element as a component of the first embodiment of the paper sheet discriminating apparatus of the present invention.

FIG. 21 is an explanatory diagram of a second diffractive optical element that is a component of the first embodiment of the paper sheet discriminating apparatus of the present invention.

FIG. 22 is a configuration diagram of a paper sheet discriminating apparatus in which both first and second diffractive optical elements have a composite function.

FIG. 23 shows a configuration of a paper sheet discriminating apparatus in which a first diffractive optical element has first and second portions, while a second diffractive optical element 5 has a composite function or a normal diffraction grating surface. FIG.

FIG. 24 is a configuration diagram of a second embodiment of the paper sheet discriminating apparatus in which the third diffractive optical element has a composite function.

FIG. 25 is an explanatory diagram of a third diffractive optical element having a composite function.

FIG. 26 is an explanatory diagram of a direct phase calculation method.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Paper sheet 2 Light source 31 Discoloration element 32 Discoloration element 4 First diffractive optical element 5 Second diffractive optical element 6 Position detecting element 7 Third diffractive optical element 50 Diffractive optical element 60 Maximum of phase distribution Sequence of values

Claims (14)

[Claims] An apparatus for discriminating the authenticity of a paper sheet having a discoloring element, comprising: a light source for irradiating a white light or a light having a predetermined wavelength to the discoloring element of the paper sheet; Moving means for generating first and second detection lights having different wavelengths and emission angles in transmitted or reflected light of the color changing element by changing the relative position with the leaves; A first or second transmissive or reflective first diffractive optical element that deflects after incidence and emits first or second transmitted light or first and second reflected light, and is emitted from the first diffractive optical element The first and second transmitted lights or the first and second reflected lights are deflected in different directions according to different wavelengths, and the third and fourth transmitted lights or the third and fourth reflected lights are deflected.
A transmissive or reflective second diffractive optical element that emits reflected light; and a third or fourth transmitted light or a third or fourth reflected light that is emitted from the second diffractive optical element. A position detection element that outputs a detection signal according to the light receiving position, and a third signal based on the detection signal output from the position detection element.
The light receiving position of the fourth transmitted light or the third and fourth reflected light is determined, and when the light receiving position of the third, fourth transmitted light, or the third and fourth reflected light matches the predetermined position, the sheet And a discrimination processing unit that determines that the paper is authentic. 2. The paper sheet discriminating apparatus according to claim 1, wherein the first transmissive or reflective diffractive optical element deflects the first and second detection lights after being incident on the first and second detection lights. And a diffraction grating surface having a surface shape realizing a combined function of emitting the second transmitted light or the first and second reflected lights. 3. The paper sheet discriminating apparatus according to claim 1, wherein the first transmissive or reflective diffractive optical element deflects the first detection light after being incident thereon, and the first transmitted light. Alternatively, a transmissive or reflective first portion that emits first reflected light, and a transmissive or reflective type that deflects the second detection light after being incident and emits second transmitted light or second reflected light. A paper sheet discriminating apparatus comprising: a second portion; and a diffraction grating surface having a surface shape consisting of: 4. The paper sheet discriminating apparatus according to claim 1, wherein said second transmissive or reflective diffractive optical element comprises: said first diffractive optical element. The first and second transmitted lights or the first and second reflected lights emitted from the element are deflected in different directions according to different wavelengths, and the third and fourth transmitted lights or the third and fourth transmitted lights are deflected.
A paper sheet discriminating apparatus comprising a diffraction grating surface having a surface shape for realizing a composite function of emitting reflected light. 5. The paper sheet discriminating apparatus according to claim 1, wherein the first transmitted light or the first reflected light emitted from the second diffractive optical element is different. A first portion of a transmission type or a reflection type that deflects light in a different direction according to the wavelength to be emitted and emits a third transmitted light or a third reflected light, and a second transmission light emitted from the first diffractive optical element A second portion of a transmission or reflection type that deflects the light or the second reflected light in different directions according to different wavelengths and emits the fourth transmitted light or the fourth reflected light; A paper sheet discriminating apparatus comprising a lattice surface. 6. An apparatus for discriminating the authenticity of a paper sheet having a discoloration element, comprising: a light source for irradiating a white light or a light having a predetermined wavelength to the discoloration element of the paper sheet; Moving means for generating first and second detection lights having different wavelengths and emission angles in transmitted or reflected light of the color changing element by changing the relative position with the leaves; After the incidence, the light is deflected in different directions according to the different wavelengths, and the fifth or sixth transmitted light or the fifth or sixth light is transmitted.
A transmissive or reflective third diffractive optical element that emits reflected light, and receives the fifth, sixth transmitted light, or fifth and sixth reflected light emitted from the third diffractive optical element A position detection element that outputs a detection signal in accordance with a light receiving position, and a fifth signal based on the detection signal output from the position detection element.
The light receiving position of the sixth transmitted light or the fifth and sixth reflected light is determined, and if the light receiving position of the fifth, sixth transmitted light, or the fifth and sixth reflected light coincides with the predetermined position, the paper sheet And a discrimination processing unit that determines that the paper is authentic. 7. The paper sheet discriminating apparatus according to claim 6, wherein the third transmission type or reflection type diffraction type optical element deflects the first and second detection lights after being incident, and deflects the first and second detection lights. And a diffraction grating surface having a surface shape for realizing a combined function of emitting the sixth transmitted light or the fifth and sixth reflected lights. 8. The paper sheet discriminating apparatus according to claim 6, wherein the third transmission type or reflection type diffraction type optical element deflects the first detection light after being incident, and the fifth transmission light. Alternatively, a transmissive or reflective first portion that emits fifth reflected light, and a transmissive or reflective type that deflects the second detection light after being incident and emits sixth transmitted light or sixth reflected light. A paper sheet discriminating apparatus comprising: a second portion; and a diffraction grating surface having a surface shape consisting of: 9. The paper sheet discriminating apparatus according to claim 1, wherein, when designing the shape of each diffractive optical element, diffraction when a light beam is incident on the diffractive optical element. Determine the phase distribution of the interference pattern on the optical element surface, the maximum value and the minimum value of the phase distribution from the rate of change of the phase distribution along a plurality of lines virtually drawn on the diffractive optical element surface Searching, sequentially selecting two maxima or minima adjacent to each other along the virtual line, and if the two maxima are selected, between the two maxima The difference between one of the two maximum values and the minimum value sandwiched between the two maximum values is a step, and the transmitted light or the reflected light emitted from the diffractive optical element is directed in a predetermined direction. The slope that goes toward is formed By using a transmissive or reflective diffractive optical element whose surface shape is determined by approximating the phase distribution with a sawtooth pattern, when the two minimum values are selected, Between the two minimum values, so that the difference between one of the two minimum values and the maximum value sandwiched between the two minimum values becomes a step, and furthermore, the transmitted light or the reflected light from the diffractive optical element. By using a transmissive or reflective diffractive optical element whose surface shape is determined by approximating the phase distribution with a sawtooth pattern so that an inclined surface is formed in a predetermined direction. Paper sheet discriminating device. 10. The paper sheet discriminating apparatus according to claim 9, wherein a plurality of parallel straight lines are virtually drawn on the surface of the diffractive optical element so as to intersect the diffraction grating constituted by the phase distribution. Characterized in that a transmissive or reflective diffractive optical element whose surface shape is determined by searching for the maximum value and the minimum value of the phase distribution along is used. 11. The paper sheet discriminating apparatus according to claim 9, wherein a plurality of virtual lines radially extending on the surface of the diffractive optical element from near the center of curvature determined from the shape of the diffraction grating formed by the phase distribution. Characterized in that a transmissive or reflective diffractive optical element whose surface shape is determined by searching for the maximum value and the minimum value of the phase distribution along is used. 12. The paper sheet discriminating apparatus according to claim 9, wherein a plurality of broken lines or curves are virtually drawn on the surface of the diffractive optical element so as to intersect with the diffraction grating constituted by the phase distribution. A paper sheet discriminator characterized by using a transmissive or reflective diffractive optical element whose surface shape is determined by searching for a maximum value and a minimum value of the phase distribution along a plurality of polygonal lines or curves. apparatus. 13. The paper sheet discriminating apparatus according to claim 1, wherein, when designing the shape of each diffractive optical element, diffraction when a light beam is incident on the diffractive optical element. Determine the phase distribution of the interference pattern on the optical element surface, the maximum value and the minimum value of the phase distribution from the rate of change of the phase distribution along a plurality of lines virtually drawn on the diffractive optical element surface Searching, selecting two maxima (A, B) adjacent to each other along the virtually drawn line, and selecting those two maxima (A, B)
(C ₁ , C ₂ ,..., C _i ,..., C _N : i is a natural number from 1 to N) along a plurality of virtual lines that are continuous with one of the (maximum value A). Consider a curve, and along the normal line of the curve at each local maximum (C _i ) position of the local maximum value sequence, a different side from the local maximum (C _i ) on the side where the local maximum (B) exists. A local maximum value (D _i ) is detected, and a local minimum value sandwiched between the two local maximum values (C _i , D _i ) between the local maximum value (C _i ) and the another local maximum value (D _i ). The phase distribution is approximated by a sawtooth pattern so that a difference between the phase distribution and the transmitted light or the reflected light emitted from the diffractive optical element is directed toward a predetermined direction so that the difference is a step. Paper using a transmissive or reflective diffractive optical element whose surface shape is determined by Kind discriminating apparatus. 14. The sheet discriminating apparatus according to claim 9, wherein a maximum value I _maxo and a minimum value I of the entire phase distribution are set.
seeking a _mino, at their maximum _{I MAXO} and the minimum value _I difference _{mino (I} maxo _{-I mino)} the N divided intervals _{((I maxo -I mino) /} N), the approximated the phase distribution A paper sheet discriminating apparatus characterized by using a transmissive or reflective diffractive optical element whose surface shape is determined by quantization.