JP2009234146A - Birefringence pattern certification device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a birefringence pattern certification device capable of exactly certificating even a birefringence pattern in which a plurality of colors excluding black can be recognized visually through a polarizing plate. <P>SOLUTION: The certification device which has a light source, a polarizer converting the light of the light source into polarized light, a polarizer which transmits reflected light or transmitted light produced by irradiating an object to be certified with the polarized light to convert the light into detected light, and a means for observing the detected light and in which the light source includes a means for emitting single wavelength light of a certain specified wavelength, or a filter including a part selectively transmitting only single wavelength light of the following wavelength is installed in the means for observing the detected light is constituted. The certain specified wavelength, when the birefringence pattern includes a domain X and a domain Y indicating different colors when observed through the polarizing plate, is selected from a visual light wavelength domain in which (polarized light reflectance of domain X)/(polarized light reflectance of domain Y), (polarized light transmittance of domain X)/(polarized light transmittance of domain Y), or (polarized light reflectance of domain Y)/(polarized light transmittance of domain X) is at least 1.5. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to a birefringence pattern authentication device.

The birefringence pattern in which the pattern is visually recognized through the polarizing plate is difficult to forge or alter, and is useful as a means for determining authenticity. If a birefringence pattern authentication apparatus is used for authenticity determination, more accurate authenticity determination is possible.
If the birefringence pattern latent image is a multicolor latent image, forgery or alteration is more difficult and preferable, but the conventional birefringence pattern authentication apparatus does not particularly take into consideration the correspondence to the multicolor latent image. For this reason, it is limited to a device using a monochromatic light source or a device combining a white light source and an image sensor without a color filter, and depending on the color of the latent image, the image may be difficult to visually recognize. In addition, if the support is colored, the authenticity determination is hindered, so the color of the support is limited.

Patent Document 1 discloses a birefringence pattern authentication system having a light source, a light receiving unit, and a polarizing plate. Further, Patent Document 2 describes an authentication apparatus that includes a polarization irradiating unit, a polarizing plate disposed on an optical path of reflected light from an object to be authenticated, and a unit that observes the light that has passed through. In either case, however, there is no description about a method for selecting the wavelength of light emitted from a light source or the use of two or more single-wavelength lights as a light source.
JP 2007-1130 A JP 2004-354430 A

  It is an object of the present invention to provide a birefringence pattern authentication apparatus capable of accurate authentication even in a birefringence pattern in which a plurality of colors other than black are visible in observation through a polarizing plate.

As a result of diligent research for solving the above-mentioned problems, the present inventors have selected the wavelength of light irradiated to the object to be authenticated and performed measurement via a polarizer to thereby determine the S / N ratio in color discrimination. Found to improve. A more accurate birefringence pattern can be obtained by using a light source that can irradiate a single wavelength of a selected wavelength, or by using an image sensor provided with a color filter that can selectively detect a selected wavelength. We found that authentication is possible. And based on this knowledge, this invention was completed. That is, the present invention provides the following [1] to [14].

[1] An apparatus for authenticating a birefringence pattern having a region X and a region Y that show different colors when observed through a polarizing plate,
The authentication apparatus includes a light source, a polarizer that transmits light from the light source to be polarized, and a polarizer that transmits reflected light or transmitted light generated by irradiating an object to be authenticated with the polarized light and detects the light. And means for observing the detection light, and the light source includes means for emitting single-wavelength light having the following wavelength, or the means for observing the detection light selectively includes only single-wavelength light having the following wavelength. Authentication device provided with a filter including a part to be transmitted:
(Polarization reflectance of region X) / (polarization reflectance of region Y) or (polarization transmittance of region X) / (polarization transmittance of region Y) or (polarization reflectance of region Y) / (of region X) A wavelength selected from a visible light wavelength region in which (polarized reflectance) or (polarized transmittance of region Y) / (polarized transmittance of region X) is 1.5 or more.

[2] The authentication device according to [1] or [2] according to [1], wherein each of the region X and the region Y exhibits a color other than black when observed through a polarizing plate. An authentication apparatus, wherein the light source includes at least one of means for emitting single-wavelength light of the wavelength and means for emitting single-wavelength light of another wavelength.
[4] A birefringence pattern authentication device,
A light source, a polarizer that transmits light from the light source to be polarized light, a polarizer that transmits reflected light or transmitted light generated by irradiating the object to be authenticated with transmitted light, and detects the light, and the detection light. Means for observing,
An authentication apparatus including two or more means for emitting single wavelength light having different wavelengths from each other.

[5] The authentication device according to [3] or [4], wherein the light source includes two or more types of light emitting diodes.
[6] The authentication device according to any one of [3] to [5], wherein the light source includes two or more types of semiconductor lasers.
[7] The light source includes means for emitting two or more single-wavelength light selected from the group consisting of light having a wavelength of 400 nm to 500 nm, light having a wavelength of 500 nm to 600 nm, and single wavelength light having a wavelength of 600 nm to 700 nm. ] The authentication apparatus as described in any one of [6].
[8] The authentication device according to any one of [1] to [7], wherein the means for observing the detection light is an image sensor.

[9] The authentication apparatus according to [1] or [2], wherein the means for observing the detection light selectively selects only a part that selectively transmits only light having the wavelength and light having another wavelength. An authentication apparatus, which is an image sensor provided with a filter including at least one of the parts to be transmitted.
[10] A birefringence pattern authentication device,
A light source, a polarizer that transmits light from the light source to be polarized light, a polarizer that transmits reflected light or transmitted light generated by irradiating the object to be authenticated with transmitted light, and detects the light, and the detection light. An image sensor for receiving light,
An authentication apparatus in which the imaging device is provided with a filter including two or more portions that selectively transmit only light having different wavelengths.

[11] A part of the filter provided in the image sensor selectively transmits light having a wavelength of 400 nm to 500 nm, a part selectively transmitting light having a wavelength of 500 nm to 600 nm, and single wavelength light having a wavelength of 600 nm to 700 nm. The authentication device according to [9] or [10], wherein the authentication device is a filter including two or more parts selected from the group consisting of parts that selectively transmit light.
[12] A part provided in the image sensor selectively transmits light with a wavelength of 500 nm to 700 nm, a part selectively transmits light with a wavelength of 400 nm to 500 nm and 600 nm to 700 nm, and a wavelength of 400 nm to 600 nm. The authentication device according to [9] or [10], which is a filter including two or more parts selected from the group consisting of parts that selectively transmit single-wavelength light.

[13] The authentication device according to any one of [1] to [12], which includes means for rotating a polarizer.
[14] The apparatus according to any one of [1] to [13];
Means for storing an image obtained by observing a true birefringence pattern using the apparatus;
Means for acquiring an image using the apparatus for the object to be authenticated and means for determining whether the stored image matches or does not match the acquired image;
Including means for displaying matches as true and mismatches as false,
A system that authenticates birefringence patterns.

According to the present invention, there is provided a birefringence pattern authentication apparatus capable of accurate authentication even in a birefringence pattern in which a plurality of colors other than white or black are visually recognized through the polarizing plate.

Hereinafter, the present invention will be described in detail.
In the present specification, “to” is used to mean that the numerical values described before and after it are included as a lower limit value and an upper limit value.

  In the present specification, retardation or Re represents in-plane retardation. In-plane retardation (Re (λ)) is measured by making light having a wavelength of λ nm incident in the normal direction of the film in KOBRA 21ADH or WR (manufactured by Oji Scientific Instruments). Retardation or Re in this specification means those measured at wavelengths of 611 ± 5 nm, 545 ± 5 nm, and 435 ± 5 nm for R, G, and B, respectively. It means that measured at a wavelength of 5 nm or 590 ± 5 nm. In the present specification, “visible light” refers to light having a wavelength of 400 to 700 nm.

In the present specification, the birefringence pattern means an article including a plurality of regions having different birefringence. Specifically, it means an article including a plurality of regions showing two or more different colors when observed through the polarizing plate from the normal direction. This “different color” usually means that it is not recognized in the absence of a polarizing plate, but is recognized through the polarizing plate. At this time, the polarizing plate means a linear polarizing plate, and the direction of the transmission axis of the polarizing plate is arranged in a direction in which “different colors” are recognized. The regions showing different colors may be regions having different retardation and / or optical axis directions. In this specification, “optical axis” means “slow axis” or “transmission axis”. In this specification, “having two or more regions having different retardation and / or optical axis directions” means “having retardation and / or optical axis directions in a pattern” or “retardation and / or optical axis directions” May be patterned ". More preferably, the birefringence pattern has three or more regions exhibiting different colors. Individual regions having the same color may be continuous or non-continuous. The birefringence pattern only needs to have a planar (film or sheet) shape. Further, since the above-mentioned region is recognized when the birefringence pattern is observed from the normal direction of the plane, it is a region divided by a plane parallel to the normal line of this plane.

In the authentication apparatus of the present invention, the region X in which the birefringence pattern exhibits a non-black color when observed as a region through the polarizing plate, preferably from the normal direction through the polarizing plate. And a region Y (color latent image), it is particularly useful. However, when the birefringence pattern is observed through a polarizing plate, it is composed of only one color other than black and black (monochrome latent image). ) May use the authentication device of the present invention.

In this specification, “authentication” includes the meanings of “identification”, “presence / absence confirmation”, or “authentication determination”.
In this specification, single-wavelength light means light having a spectral peak that stands out at one wavelength. The half width of the peak is preferably 100 nm or less, and more preferably 50 nm or less. Further, in this specification, when indicating the wavelength of single wavelength light, there may be an error of ± 50 nm. Also, in the case of selectively transmitting only light of a specific wavelength in the filter, the wavelength of light to be transmitted May have the same width and error as above.

  Examples of the birefringence pattern include an article including retardation and / or an optically anisotropic layer whose optical axis direction is patterned in the plane. An example of a birefringence pattern is shown in FIG. FIG. 1A shows an example in which the retardation is patterned. In the example shown in FIG. 1A, the retardations indicated by a nm, b nm, c nm, and d nm are different from each other. FIG. 1B shows an example in which the optical axis direction is patterned. In FIG. 1B, the arrow indicates the optical axis direction.

Such a birefringence pattern can be used for brand protection by being provided on tags of various products such as pharmaceuticals, home appliances, and clothing. Alternatively, forgery prevention effects are expected when used for securities such as ID cards such as credit cards and entrance / exit management cards, banknotes, checks and gift certificates.
The optically anisotropic layer in which the retardation is patterned in the plane can be produced, for example, by the following method. First, a solution containing a liquid crystalline compound is applied and dried to form a liquid crystal phase, and then pattern exposure is performed using a concentration mask, or pattern exposure under different irradiation conditions is performed a plurality of times, followed by baking. It can be produced by performing treatment. The optically anisotropic layer whose optical axis direction is patterned in the plane can be obtained by, for example, the method described in JP-T-2001-52580.

  An authentication apparatus according to the present invention includes a light source, a polarizer that transmits light from the light source and converts the light into polarized light, and polarized light that transmits reflected light or transmitted light generated by irradiating the object to be authenticated and transmits the detected light as detection light. And a means for observing the detection light. The authentication apparatus may have a sample table for placing an object to be authenticated.

  As the light source, a light source having means for emitting single wavelength light selected as described below is used. As a light source having means for emitting single wavelength light, a light source provided with a filter in a white light source such as a fluorescent lamp, an incandescent lamp, a cold cathode tube, a light source including a light emitting diode having a peak wavelength in the visible light range, or a visible light range A light source including a semiconductor laser having a peak wavelength can be preferably used. Further, it is also preferable that the light source can emit two or more single-wavelength lights having different wavelengths (peak wavelengths). As such a light source, a light source provided with a filter including two or more parts that selectively transmit only a specific wavelength to a white light source may be used, but two types having different peak wavelengths in the visible light region. The above light emitting diodes or two or more types of semiconductor lasers having different peak wavelengths in the visible light region can be preferably used. A light source (such as an LED array) having an array structure may be used so that different single wavelength lights can be emitted at one time. As will be described later, when an imaging device having two or more color filters is used as a means for observing detection light, the light source need not be able to emit single-wavelength light. Good. In addition, when the birefringence pattern to be authenticated has few colors visible when observed through a polarizing plate (for example, a white and red two-color pattern), a single wavelength of a wavelength selected as described below If it is light, you may use the light source containing only the means to emit only one single wavelength light.

Further, when two or more means are used as the light source, it is preferable that they can be switched on and off independently. In the case of an apparatus used for visual authentication (an apparatus that does not include an image sensor or the like), a diffusion surface light source is preferable so that the birefringence pattern of the object to be authenticated can be illuminated uniformly. As the diffusion surface light source, a fluorescent lamp surface light source, a cold cathode tube suitably used for a display or the like, an LED, or the like can be used. Furthermore, you may combine a diffusion sheet, a condensing sheet, a brightness improvement sheet, etc. with these light sources. By installing a color filter on these surface light sources, the spectral distribution can be adjusted. Alternatively, when an LED light source is used, a plurality of types of LED elements having different emission wavelengths may be arranged. In an apparatus having an image sensor or the like, the light source may be scanned in a linear or point manner using a linear light source or a point light source and scanned. As the line light source, a light source in which LEDs and lasers are arranged in a line shape can be suitably used. In addition, line lighting that combines a known technique such as a fluorescent lamp, a halogen, xenon, or a metal halide with a color filter and a slit, a cylindrical lens, or the like may be used as appropriate. An optical fiber may be used as a line light source. A condensing lens or an imaging lens is preferably disposed between the light source and the subject as appropriate.

The polarizer that transmits light from the light source to be polarized and the polarizer that transmits reflected light or transmitted light to be detected light are the same or different (including the same type). May be. As will be described later, a separate type is used in the case of a transmission type. As will be described later, the reflection type can be the same, but a separate type may be used. When the same device is used, there is an advantage that the apparatus has a simple structure, and when a separate device is used, there is an advantage that the optimum transmission axis direction can be adjusted individually.
As the polarizer, a commercially available sheet-like polarizer can be preferably used.
The authentication device of the present invention may include a mechanism for rotating each polarizer so that the angle formed by the optical axis of the polarizer and the optical axis of the object to be authenticated can be adjusted.

Schematic diagrams of examples of the authentication device of the present invention are shown in FIGS. 2 and 3, arrows indicate the traveling direction of light. Means for observing the detection light is provided at the tip of the arrow.
FIG. 2 shows a reflection type invention comprising a light source and a polarizer that transmits light from the light source to make polarized light, and transmits reflected light generated by irradiating the object to be authenticated with transmitted light to detect light. The schematic of the example of this authentication apparatus is shown. Such an apparatus can be used when the object to be authenticated has a reflective support as shown in the figure. The light source is arranged so that the emitted light is efficiently irradiated on the object to be authenticated and reflected to the means for observing the detection light. The polarizing plate is disposed between the object to be authenticated and the light source, and the polarizing plate and the object to be authenticated are disposed so as to polarize light from the light source in a desired direction for identifying the birefringence pattern. Usually, it is preferable that the optical axis direction of each region of the birefringence pattern (object to be authenticated) and the optical axis direction of the polarizing plate are 45 °. Therefore, particularly when performing authentication of a birefringence pattern having two or more regions having different optical axis directions, the authentication device preferably includes a mechanism for rotating the polarizer.

For example, in an object to be authenticated having a birefringence pattern in which the reflected light not passing through the polarizing plate is white, the optical axis direction of at least one region in the birefringence pattern and the optical axis direction of the polarizing plate are 45 °. When the retardation of the region is around 0 nm, the reflected light luminance is the highest and is observed as “white”. On the other hand, when the retardation of the region is λ / 4 (usually around 137.5 nm), the reflected light luminance is low and is observed as “black”, and the contrast becomes clear. Further, in the arrangement as described above, a reflection color of blue is observed when the retardation is around 200 nm, green when the retardation is around 500 nm, and red when the retardation is around 650 nm.

FIG. 3 illustrates a light source, a polarizer that transmits light from the light source to be polarized light, and a detection light that transmits reflected light generated by irradiating an object to be authenticated with the polarized light different from the polarizer. 1 is a schematic view of an example of a transmission type authentication device of the present invention composed of polarizers that perform the same. Such an apparatus can be used when the object to be authenticated has a transparent support as shown in the figure. The light source is arranged so that the emitted light is efficiently irradiated to the polarizing plate and the object to be authenticated and reflected to the means for observing the detection light. The two polarizing plates are arranged so that the object to be authenticated is between them, and the polarizing plate and the object to be authenticated are arranged so as to polarize light from the light source in a desired direction for identifying the birefringence pattern. Usually, it is preferable to arrange so that the optical axis direction of each region of the birefringence pattern (object to be authenticated) and the optical axis direction of the polarizing plate are 45 °, and the two polarizers are arranged in a crossed Nicol or Paranicol pattern. Preferably it is.

For example, in an object to be authenticated that has a birefringence pattern in which the transmitted light that does not pass through the polarizer is white, when the two polarizers are arranged in a crossed Nicol state, the transmitted light has a retardation of about 0 nm in the birefringence pattern. The light intensity is the lowest and is observed as “black”. When the retardation is in the vicinity of λ / 2, the transmitted light luminance is maximized and is observed as “white”. For example, when the retardation is around 450 nm, 730 nm, and 580 nm, red, green, and blue are observed, respectively.
On the other hand, when two polarizers are arranged in paranicol, the transmitted light luminance is the highest and observed as “white” when the retardation in the birefringence pattern is around 0 nm. When the retardation is in the vicinity of λ / 2, the transmitted light luminance is minimized and can be suitably used as “black”. Other than that, for example, when the retardation is in the vicinity of 680 nm, 490 nm, and 290 nm, red, green, and blue are exhibited, respectively, but the vividness of the color is inferior as compared with the case where they are arranged in crossed Nicols.

The means for observing the detection light may be a light display portion (simple window) for visual observation. A filter may be provided in the window. Further, an image sensor may be used as a means for observing the detection light.
As the image sensor, a CMOS image sensor, a CCD, or the like can be suitably used. In addition to using a two-dimensional array, a two-dimensional image may be acquired as an imaging element by scanning a line sensor or a single light receiving element. A photodiode or the like can be used as the light receiving element.
In particular, when a light source having means for emitting single-wavelength light is not used, an image sensor provided with a filter may be used. Here, the filter means a filter (so-called color filter) including a portion that selectively transmits only a specific wavelength. It is also preferable that a filter including two or more of the above-described parts (sites that transmit light having different wavelengths) is provided. The filter may be provided in a detachable form.
It is preferable to appropriately arrange a lens on the incident side of the image sensor.

The authentication device is preferably shielded from light except for the observation unit in order to prevent reflection of external light.
The authentication device may be a fixed type or a handy type. In the case of the fixed type, a sample insertion port may be provided.

A method for selecting the wavelength of single-wavelength light included in the light source used in the authentication apparatus of the present invention will be described below.
FIG. 4 shows an example of a birefringence pattern together with the retardation value of each region and the observed color. Hereinafter, R, G, B, K, and W represent red, green, blue, black, and white.
In this birefringence pattern, an optically anisotropic layer composed of five regions having different retardations is provided on an aluminum sheet. The birefringence pattern A cannot be identified by normal visual observation. However, when the polarizing plate is overlaid on the birefringence pattern A so that the angle formed by the slow axis of the optically anisotropic layer and the absorption axis of the polarizing plate is 45 °, each region is shown in the figure. Color developed. FIG. 5 shows the reflection spectrum of each region in the state where the polarizing plates are stacked.

When there is K in the background of W, or there is a W pattern in the background of K, the reflectance difference is large at any wavelength, so that the pattern can be identified with good contrast. However, for example, when an R pattern is applied to the background of W, it is preferable to read with G light in order to identify the pattern with a high S / N ratio. Note that “reading” with G light means that an object to be authenticated is irradiated with G single-wavelength light (wavelength 500 to 600 nm) or only G light is detected. Specifically, the birefringent pattern is irradiated with a light emitting diode that emits green light, and is visually observed or photographed with an image sensor, or white light is irradiated onto the birefringent pattern and photographed with a color CCD, and green. Luminance information can be extracted. The same applies to R light (wavelength 600 to 700 nm) and B light (wavelength 400 to 500 nm).
Similarly, the color of light to be read can be selected in accordance with the background color and the pattern color. Table 1 summarizes typical background and pattern colors and appropriate light colors to read them.

As described above, the wavelength of light emitted from the light source or the wavelength selected by the image sensor is preferably selected according to the color of the latent image. For example, in the birefringence pattern shown in FIG. 4, in order to read a red pattern (R on the left half) drawn on a white background, single wavelength light having a wavelength near 535 nm or 430 nm with a large reflectance difference is used. And easy to read. Conversely, to read a red pattern (R on the right half) drawn on a black background, it is easy to read using single-wavelength light having a wavelength near 630 nm or 475 nm. Thus, the readability is improved by selecting the wavelength used for the light source according to the latent image. When the latent image is a multi-color latent image including two or more colors other than black and white, the three primary colors of light are red, green, and blue, the light wavelength of the light source, or a filter used in the image sensor. It is preferably used as the wavelength to be selected. For example, a light source including three kinds of means for coloring red, green, and blue can be used. In this case, as a light source, a method using an array of red, green, and blue light-emitting diodes, a method of irradiating an object to be authenticated from three surface light sources that generate red, green, and blue colors can be given.

Thus, it is preferable to select the wavelength of the light irradiated to the object to be authenticated according to the color (color in the latent image) included in the authenticated birefringence pattern. As described above, it is possible to compare the reflection spectrum or transmission spectrum for each region (measured through a polarizing plate) in the visible light region, and select a wavelength having a large polarization reflectance or polarization transmittance ratio between the regions. preferable. The polarized light reflectance or the polarized light transmittance means the reflectance or transmittance of two regions when passing through the polarizing plate from the normal direction. Specifically, the polarized light reflectance or polarized light transmittance of the above two regions is a value measured by a measurement performed under the same conditions as those when authentication is performed by the authentication apparatus of the present invention, or the same Any value calculated as a condition may be used. As a wavelength having a large ratio of polarized light reflectance or polarized light transmittance, specifically, a ratio of polarized light reflectance or a ratio of polarized light transmittance (a value obtained by dividing a larger value by a smaller value) is 1.5 or more. It is preferable that the wavelength is selected from a wavelength region (visible light region), and more preferable is a wavelength selected from a wavelength region of 2.0 or more. That is, when two regions having different birefringence in the birefringence pattern are defined as region X and region Y, (polarization reflectance of region X) / (polarization reflectance of region Y) or (polarization transmittance of region X) / (Polarization excess ratio of region Y), or (polarization emissivity of region Y) / (polarization reflectance of region X) or (polarization transmittance of region Y) / (polarization transmittance of region X) is 1.5 or more The wavelength region is preferably 2.0 or more.
The wavelength can be selected using either the ratio of polarization reflectance or the ratio of polarization transmittance, usually the ratio of polarization transmittance for transmissive devices and the ratio of polarization reflectance for reflective devices. What is necessary is just to judge using ratio.

For example, when the birefringence pattern is observed through a polarizing plate, in the case of a monochrome latent image that is substantially composed of only black and “white” , the ratio of the polarization reflectance or the polarization transmittance is any wavelength. Large (polarized reflectance of region X) / (polarized reflectance of region Y) or (polarized transmittance of region X) / (polarized transmittance of region Y) or (polarized reflectance of region Y) / (region It can be considered that (polarized light reflectance of X) or (polarized light transmittance of region Y) / (polarized light transmittance of region X) is 1.5 or more. On the other hand, when the birefringence pattern is a color latent image including a region showing a color other than black and white when the birefringence pattern is observed through the polarizing plate, or when the birefringence pattern includes a colored support For example, the birefringence pattern can be authenticated or the accuracy can be improved by selecting the wavelength as described above.
Note that the observed region may include, in addition to the region X and the region Y, a black region in which light to be observed is shielded and a region that exhibits a color other than the region X and the region Y.

Even if the specific wavelength is not selected, each region of the birefringence pattern can be obtained by configuring the authentication apparatus including two or more means for emitting single-wavelength light having different wavelengths from each other. It is possible to select a wavelength having a larger reflectance or transmittance ratio between them, and to improve the accuracy of authentication of the birefringence pattern. Also, more complex birefringence patterns can be authenticated by combining two or more reflectances or transmittances.

The birefringence pattern may include a colored support. That is, the birefringence pattern may be a pattern that can be visually recognized without passing through the polarizing plate. When a birefringence pattern is read with a specific color, it is not affected by other colors, so that a colored support can be used with other colors. For example, as in the previous example, when a birefringence pattern is read with G light, it is not affected by red or blue, so the support may have red or blue coloring.
Alternatively, a reflective support colored on the entire surface may be used. For example, when a red reflective support is used, the reading light needs to be red. In this case, K, G, or B has a low reflectivity, and W or R has a high reflectivity. Therefore, the latent image can be turned on / off using this.

An advantage of using the authentication device of the present invention is that the SN ratio of the latent image can be improved. In addition, there is an advantage that the choices of colors (reflection color or transmission color) used for the latent image of the birefringence pattern used as a means for authenticity determination can be expanded. It is also possible to use a support that is colored as described above.

Example of birefringence pattern authentication device (birefringence pattern authentication device example A: FIG. 6)
In this example, a light source including means for emitting two or more types of single wavelength (visible light region) light is used as the light source. One polarizer is provided, and the reflected light from the object to be authenticated irradiated from the light source through the polarizer to the object to be authenticated is visually observed as a latent image in the observation unit through the polarizer, and a birefringence pattern is formed. It is an example of an apparatus to authenticate. In such an example, a diffusion surface light source is preferable so that the birefringence pattern of the object to be authenticated can be illuminated uniformly.

(Birefringence pattern authentication device B: FIG. 7)
In this example, a light source including means for emitting two or more types of single wavelength (visible light region) light is used as the light source. This is an example of an apparatus that authenticates a birefringence pattern by visually observing, as a latent image, a light through a polarizer, which is irradiated on an object to be authenticated from a light source and transmitted through the object to be authenticated. A diffusing surface light source is preferable so that the birefringence pattern of the object to be authenticated can be illuminated uniformly. When a single layer of polarizer is laminated on the birefringence pattern in advance (the left diagram in FIG. B), the authentication device only needs to have one polarizer. When the polarizer is not provided, it is necessary to arrange two polarizers so as to sandwich the birefringence pattern (the right diagram in FIG. B). In general, the two polarizers are preferably installed so as to be crossed Nicols from the viewpoint of contrast, but the optical axis angle of the polarizer can be selected according to the birefringence pattern. For this reason, it is preferable to make the optical axis angle of the polarizer variable. Further, it is preferable that two polarizers can be arranged, and at least one of the polarizers is detachable.

(Birefringence pattern authentication device C: FIG. 8)
In this example, a light source including means for emitting two or more types of single wavelength (visible light region) light is used as the light source. An apparatus for providing a single polarizer, authenticating a birefringence pattern by receiving reflected light from an object to be authenticated irradiated from the light source through the polarizer through the polarizer, and then receiving the light with an image sensor It is an example. In this example, an LED array is condensed by a cylindrical lens as an illumination light source to illuminate an object to be authenticated, and the illuminated light is imaged by a cylindrical lens to guide the light to a white CCD and acquire image data. As the LED light source, the reference color (FUJITSU.52, 3, p.253-259 (05, 2001)), the primary LED array shown in Fig. 1 may be used. By switching and scanning each color, data corresponding to each color can be acquired.

In this device example, an image sensor is installed instead of the observation unit of the authentication device example A. As the light source, it is preferable to use a line light source in which two or more types of light sources are arranged. Alternatively, it is also preferable to use a scanning optical system that scans the entire sample surface by combining two or more types of point light sources with a galvanometer mirror or a polygon mirror. Further, as the type of light source, a semiconductor laser or the like may be used in addition to those mentioned above.

In order to scan the entire surface, it is preferable to move the imaging system including the light source and the imaging device relative to the object to be authenticated. In this case, either the object to be authenticated or the imaging system may be moved. A flat bed type in which an object to be authenticated is fixed and a light source and an image sensor are scanned, or a handy scan type in which a small body in which a light source and an image sensor are integrated are manually scanned. In the case of the handy scan type, the object to be authenticated need not be a sheet. When the object to be authenticated is like paper or plastic film, the light source / image sensor can be fixed and the object to be authenticated can be conveyed by an automatic document feeder or a drum scanner.

(Birefringence pattern authentication device D: FIG. 9)
In this example, a light source including means for emitting two or more types of single wavelength (visible light region) light is used as the light source. This is an example of an apparatus for authenticating a birefringence pattern by receiving light that is irradiated to an object to be authenticated through a polarizer from a light source and transmitted through the object to be detected, and then received by an image sensor through the polarizer. It is suitable for authenticating a birefringence pattern formed on a transparent support. The details of the other devices are the same as those of the birefringence pattern authentication device C.

(Birefringence pattern authentication device E: FIG. 10)
The birefringence pattern authentication apparatus E can be manufactured with the same apparatus configuration as that of the birefringence pattern authentication apparatus C except that the image sensor includes a color filter. The light source may be one kind, and is preferably white light. As a sensor, a color CCD provided with two or more color filters is used. The color filter preferably includes a filter that selectively transmits only R light, a filter that selectively transmits only G light, and a filter that selectively transmits only B light.

(Birefringence pattern authentication device F: FIG. 11)
The birefringence pattern authentication apparatus F can be manufactured with the same apparatus configuration as the birefringence pattern authentication apparatus D except that the image sensor includes a color filter. The light source may be one kind, and is preferably white light. The sensor is characterized by using a color CCD provided with two or more color filters. The color filter preferably includes a filter that selectively transmits only R light, a filter that selectively transmits only G light, and a filter that selectively transmits only B light.

The birefringence pattern authentication apparatus can also be used as part of a system for birefringence pattern authentication (authentication discrimination).
In order to perform authenticity determination, first, it is necessary to digitize an image signal obtained from a true birefringence pattern to be authenticated through an image sensor. After that, it is preferable to remove noise or perform corrections such as enlargement, reduction, and rotation as necessary. The acquired image may be displayed on a display or the like. In this way, an image of the true birefringence pattern is stored in the system.
Thereafter, it is determined whether the image obtained by similarly authenticating the object to be authenticated matches the image of the stored true birefringence pattern. This determination is performed by the pattern matching function of the system.
As a pattern matching method, template matching is preferably used in which authenticity determination is performed from the correlation of luminance data in each pixel between an image of an object to be authenticated and a true image (template).
In this way, it is possible to make a true / false determination obtained as true when the images match, or as false when the images do not match. In order to enable display of the result, the system preferably has a display or display means such as a lamp or a buzzer.

If the birefringence pattern latent image contains character data, the system may have an optical character recognition (OCR) function. In this case, the recognized character may be displayed on the display or the like as it is. Or you may display only the authenticity determination result whether the recognized character corresponded with the true character inputted beforehand by the above-mentioned method.

Depending on the birefringence pattern, it is necessary to adjust the angle between the optical axis of the polarizing plate and the optical axis of the birefringence pattern (optically anisotropic layer). Although these optical axes may be adjusted to have an appropriate relationship by using a width-shifting roller or the like, this may be difficult depending on the shape of the object to be authenticated. Alternatively, when the birefringence pattern is updated, the optical axis of the polarizing plate may be desired to be changed.
Also from this viewpoint, it is preferable that the polarizing plate has a rotation mechanism as described above. Furthermore, you may have the fixing mechanism of a polarizing plate. These mechanisms may be manual or automatic. When performing automatically, it is preferable that the optical axis of the polarizer is detected and adjusted so as to have an appropriate angle in combination with the pattern matching described above.

A commercially available CCD type scanner was prepared, and a polarizing plate was attached to a glass table. The birefringence pattern surface of the birefringence pattern A was placed on the reading surface side. At this time, the optical axis of the birefringence pattern and the optical axis of the polarizing plate were arranged to be approximately 45 degrees. As a result of scanning in this state, it was confirmed that each character was read in a desired color.

It is a figure which shows the example of a birefringence pattern. It is the schematic of the example of the authentication apparatus (reflection type) of this invention. It is the schematic of the example of the authentication apparatus (transmission type) of this invention. It is a figure which shows the example of a birefringence pattern with the retardation value of each part, and the color observed. It is a figure which shows the reflection spectrum of each area | region of the example of the birefringence pattern shown in FIG. It is a figure which shows the example (birefringence pattern authentication apparatus A) of a birefringence pattern authentication apparatus. It is a figure which shows the example (birefringence pattern authentication apparatus B) of a birefringence pattern authentication apparatus. It is a figure which shows the example (birefringence pattern authentication apparatus C) of a birefringence pattern authentication apparatus. It is a figure which shows the example (birefringence pattern authentication apparatus D) of a birefringence pattern authentication apparatus. It is a figure which shows the example (birefringence pattern authentication apparatus E) of a birefringence pattern authentication apparatus. It is a figure which shows the example (birefringence pattern authentication apparatus F) of a birefringence pattern authentication apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Birefringence pattern 2 Light source 3 Polarizer 4 To-be-authenticated object 5 Observation part 6 Line light source 7 Line sensor 8 Handle 9 Cylindrical lens 10 Image data acquisition part 11 Emission color switching signal 12 RGB image data acquisition part

Claims (14)

A birefringence pattern authentication device having a region X and a region Y exhibiting different colors when observed through a polarizing plate,
The authentication apparatus includes a light source, a polarizer that transmits light from the light source to be polarized, and a polarizer that transmits reflected light or transmitted light generated by irradiating an object to be authenticated with the polarized light and detects the light. And means for observing the detection light, and the light source includes means for emitting single-wavelength light having the following wavelength, or the means for observing the detection light selectively includes only single-wavelength light having the following wavelength. Authentication device provided with a filter including a part to be transmitted:
(Polarization reflectance of region X) / (polarization reflectance of region Y) or (polarization transmittance of region X) / (polarization transmittance of region Y) or (polarization reflectance of region Y) / (of region X) A wavelength selected from a visible light wavelength region in which (polarized reflectance) or (polarized transmittance of region Y) / (polarized transmittance of region X) is 1.5 or more. The authentication device according to claim 1, wherein the region X and the region Y exhibit colors other than black when observed through a polarizing plate. 3. The authentication apparatus according to claim 1, wherein the light source includes at least one of means for emitting single-wavelength light having the wavelength and means for emitting single-wavelength light having another wavelength. A birefringence pattern authentication device,
A light source, a polarizer that transmits light from the light source to be polarized light, a polarizer that transmits reflected light or transmitted light generated by irradiating the object to be authenticated with transmitted light, and detects the light, and the detection light. Means for observing,
An authentication apparatus including two or more means for emitting single wavelength light having different wavelengths from each other. The authentication device according to claim 3 or 4, wherein the light source includes two or more types of light emitting diodes. The authentication device according to any one of claims 3 to 5, wherein the light source includes two or more types of semiconductor lasers. The light source includes means for emitting two or more single-wavelength lights selected from the group consisting of light having a wavelength of 400 nm to 500 nm, light having a wavelength of 500 nm to 600 nm, and single wavelength light having a wavelength of 600 nm to 700 nm. The authentication device according to any one of the above. The authentication device according to any one of claims 1 to 7, wherein the means for observing the detection light is an image sensor. The authentication apparatus according to claim 1 or 2, wherein the means for observing the detection light includes at least a part that selectively transmits only light having the wavelength and a part that selectively transmits light having another wavelength. An authentication device, which is an image sensor provided with a filter including one of them. A birefringence pattern authentication device,
A light source, a polarizer that transmits light from the light source to be polarized light, a polarizer that transmits reflected light or transmitted light generated by irradiating the object to be authenticated with transmitted light, and detects the light, and the detection light. An image sensor for receiving light,
An authentication apparatus in which the imaging device is provided with a filter including two or more portions that selectively transmit only light having different wavelengths. A filter provided in the imaging element selectively selects a part that selectively transmits light having a wavelength of 400 nm to 500 nm, a part that selectively transmits light having a wavelength of 500 nm to 600 nm, and a single wavelength light having a wavelength of 600 nm to 700 nm. The authentication device according to claim 9 or 10, wherein the authentication device is a filter including two or more parts selected from the group consisting of parts to be transmitted through. A filter provided in the imaging element selectively transmits light having a wavelength of 500 nm to 700 nm, a part selectively transmitting light having a wavelength of 400 nm to 500 nm and 600 nm to 700 nm, and a single wavelength having a wavelength of 400 nm to 600 nm. The authentication device according to claim 9 or 10, which is a filter including two or more parts selected from the group consisting of parts that selectively transmit light. The authentication device according to any one of claims 1 to 12, further comprising means for rotating a polarizer. An apparatus according to any one of claims 1 to 13;
Means for storing an image obtained by observing a true birefringence pattern using the apparatus;
Means for acquiring an image using the apparatus for the object to be authenticated and means for determining whether the stored image matches or does not match the acquired image;
Including means for displaying matches as true and mismatches as false,
A system that authenticates birefringence patterns.

Images