EP-4742201-A1 - SHEET RECOGNITION UNIT AND SHEET RECOGNITION METHOD

EP4742201A1EP 4742201 A1EP4742201 A1EP 4742201A1EP-4742201-A1

Abstract

Provided are a sheet recognition unit and a sheet recognition method capable of simultaneously acquiring visible range data and infrared range data without using a filter configuration that is difficult to manufacture. A sheet recognition unit includes a light source capable of emitting light having a specific wavelength to a sheet to be recognized, a light receiving unit that receives light coming from the sheet to be recognized, based on the light from the light source and outputs a light detection signal, and a recognition unit that recognizes the sheet to be recognized, using the light detection signal output from the light receiving unit. The light receiving unit includes a first light receiving element including a color filter that transmits blue light and infrared light, a second light receiving element including a color filter that transmits green light and infrared light, a third light receiving element including a color filter that transmits red light and infrared light, and a fourth light receiving element including a color filter that transmits only one of blue light, green light, red light, or infrared light.

Inventors

SATO, TAKESHI
BOGAKI, Akira
SHIMAOKA, FUMIAKI
MORIMOTO, TAKAAKI

Assignees

GLORY LTD.

Dates

Publication Date: 20260513
Application Date: 20251030

Claims (15)

A sheet recognition unit, comprising: a light source capable of emitting light having a specific wavelength to a sheet to be recognized; a light receiving unit that receives light coming from the sheet to be recognized, based on the light from the light source and outputs a light detection signal; and a recognition unit that recognizes the sheet to be recognized, using the light detection signal output from the light receiving unit, the light receiving unit including a first light receiving element including a color filter that transmits blue light and infrared light, a second light receiving element including a color filter that transmits green light and infrared light, a third light receiving element including a color filter that transmits red light and infrared light, and a fourth light receiving element including a color filter that transmits only one of blue light, green light, red light, or infrared light.
The sheet recognition unit according to claim 1, wherein the recognition unit subtracts an output value of the fourth light receiving element from at least one of an output value of the first light receiving element, an output value of the second light receiving element, or an output value of the third light receiving element, and recognizes the sheet to be recognized, using a subtraction result.
The sheet recognition unit according to claim 2, wherein the color filter of the fourth light receiving element transmits only infrared light, and wherein the recognition unit subtracts the output value of the fourth light receiving element from at least one of the output value of the first light receiving element, the output value of the second light receiving element, or the output value of the third light receiving element to calculate at least one of an amount of blue light, an amount of green light, or an amount of red light as the subtraction result.
The sheet recognition unit according to claim 2, wherein the color filter of the fourth light receiving element transmits only blue light, and wherein the recognition unit subtracts the output value of the fourth light receiving element from the output value of the first light receiving element to calculate an amount of infrared light as the subtraction result.
The sheet recognition unit according to claim 2, wherein the color filter of the fourth light receiving element transmits only green light, and wherein the recognition unit subtracts the output value of the fourth light receiving element from the output value of the second light receiving element to calculate an amount of infrared light as the subtraction result.
The sheet recognition unit according to claim 2, wherein the color filter of the fourth light receiving element transmits only red light, and wherein the recognition unit subtracts the output value of the fourth light receiving element from the output value of the third light receiving element to calculate an amount of infrared light as the subtraction result.
The sheet recognition unit according to claim 6, wherein the recognition unit subtracts the amount of the infrared light from at least one of the output value of the first light receiving element or the output value of the second light receiving element to further calculate at least one of an amount of blue light or an amount of green light as the subtraction result.
The sheet recognition unit according to any one of claims 1 to 7, wherein the first light receiving element, the second light receiving element, the third light receiving element, and the fourth light receiving element are arranged in a row in a main scanning direction.
The sheet recognition unit according to any one of claims 1 to 7, wherein the first light receiving element, the second light receiving element, and the third light receiving element are arranged in a row along a first reference line parallel to a main-scanning direction, and wherein the fourth light receiving elements are arranged in a row along a second reference line parallel to the main-scanning direction, the second reference line being at a position shifted from the first reference line to a sub-scanning direction.
The sheet recognition unit according to any one of claims 1 to 9, wherein the light having specific wavelength emitted by the light source is ultraviolet light, wherein the light receiving unit receives photoluminescence emitted from the sheet to be recognized, the sheet being irradiated with the ultraviolet light, and outputs a photoluminescence detection signal as the light detection signal, and wherein the recognition unit recognizes the sheet to be recognized, using the photoluminescence detection signal output from the light receiving unit.
The sheet recognition unit according to claim 10, wherein the recognition unit recognizes the sheet to be recognized, based on whether a visible photoluminescence emission amount and an infrared photoluminescence emission amount of the sheet to be recognized are within an allowable range with respect to reference data relating to a visible photoluminescence emission amount and an infrared photoluminescence emission amount in a genuine sheet.
The sheet recognition unit according to claim 11, wherein the reference data includes a ratio between the visible photoluminescence emission amount and the infrared photoluminescence emission amount, and wherein the recognition unit calculates the ratio between the visible photoluminescence emission amount and the infrared photoluminescence emission amount of the sheet to be recognized, and recognizes the sheet to be recognized, based on whether the ratio is within an allowable range with respect to the ratio included in the reference data.
The sheet recognition unit according to claim 11 or 12, wherein the light receiving unit receives photoluminescence of at least one color among blue, green, or red as the visible photoluminescence and outputs a photoluminescence detection signal of the at least one color, wherein the reference data relates to a photoluminescence emission amount of the at least one color and an infrared photoluminescence emission amount, and wherein the recognition unit recognizes the sheet to be recognized, based on whether the photoluminescence emission amount of the at least one color and the infrared photoluminescence emission amount of the sheet to be recognized are within an allowable range with respect to the reference data.
The sheet recognition unit according to claim 13, wherein the light receiving unit receives green photoluminescence as the visible photoluminescence and outputs a green photoluminescence detection signal, wherein the reference data relates to a green photoluminescence emission amount and an infrared photoluminescence emission amount, and wherein the recognition unit recognizes the sheet to be recognized, based on whether the green photoluminescence emission amount and the infrared photoluminescence emission amount of the sheet to be recognized are within an allowable range with respect to the reference data.
A sheet recognition method, comprising: emitting light having a specific wavelength to a sheet to be recognized from a light source; receiving, with a light receiving unit, light coming from the sheet to be recognized, based on the light from the light source and outputting a light detection signal; and recognizing the sheet to be recognized, using the light detection signal output from the light receiving unit, the light receiving unit including a first light receiving element including a color filter that transmits blue light and infrared light, a second light receiving element including a color filter that transmits green light and infrared light, a third light receiving element including a color filter that transmits red light and infrared light, and a fourth light receiving element including a color filter that transmits only one of blue light, green light, red light, or infrared light.

Description

TECHNICAL FIELD The present disclosure relates to a sheet recognition unit and a sheet recognition method. BACKGROUND ART Conventionally, a photoluminescent compound is known as a security element attached to a sheet such as a banknote. The photoluminescent compound is excited by ultraviolet light to generate fluorescence emission or phosphorescence emission. As a method for detecting these characteristics, for example, those described in the following literature are known. JP 6469370 B describes a device that acquires IR information in addition to visible color information (RGB). During emission of visible light, light (infrared light or ultraviolet light) other than the visible light is simultaneously emitted. As a result, visible color information is acquired, and IR information is acquired as phosphorescence after all lights are turned off. In this way, the color information about the visible light and light other than the visible light is acquired with a small number of lighting times. JP 6469370 B describes a second embodiment in which four light receiving elements are linearly arranged per pixel of a light receiving unit. Among the four light receiving elements, a first light receiving element is covered with a red color filter (R), a second light receiving element is covered with a green color filter (G), a third light receiving element is covered with a blue color filter (B), and a fourth light receiving element is covered with an infrared color filter (IR). The color filter (R) transmits red light, the color filter (G) transmits green light, and the color filter (B) transmits blue light, but the color filters (R), (G), and (B) do not transmit ultraviolet light and infrared light. The color filter (IR) used here transmits infrared light but does not transmit ultraviolet light. JP 7473677 B discloses an optical sensor that detects light from a sheet on which at least one type of monochromatic ink among n types of monochromatic ink is printed. The optical sensor includes a light source, a light receiving unit having first to (n-1)-th light receiving elements, a storage unit, and a correction processing unit. The storage unit stores a correction value based on reference data acquired by the light receiving unit independently receiving light emitted from the first to n-th monochromatic ink for each type of monochromatic ink. The correction processing unit executes correction processing on detection data acquired by the light receiving unit receiving light emitted from the sheet irradiated with light from the light source, using a correction value based on an inverse matrix of a matrix obtained by normalizing a predetermined matrix A with n rows and n columns acquired in advance. SUMMARY The filter configuration used in the second embodiment in JP 6469370 B enables visible light and infrared light coming from a banknote to be separated and then to be independently and simultaneously received (detected). However, this filter configuration is difficult to manufacture, and has problems in terms of thickness and cost. The present disclosure has been made in view of the above circumstances, and an object thereof is to provide a sheet recognition unit and a sheet recognition method capable of simultaneously acquiring visible range data and infrared range data without using a filter configuration that is difficult to manufacture. In order to solve the above-described problems and achieve the object, (1) a sheet recognition unit from a first aspect of the present disclosure includes a light source capable of emitting light having a specific wavelength to a sheet to be recognized, a light receiving unit that receives light coming from the sheet to be recognized, based on the light from the light source and outputs a light detection signal, and a recognition unit that recognizes the sheet to be recognized, using the light detection signal output from the light receiving unit. The light receiving unit includes a first light receiving element including a color filter that transmits blue light and infrared light, a second light receiving element including a color filter that transmits green light and infrared light, a third light receiving element including a color filter that transmits red light and infrared light, and a fourth light receiving element including a color filter that transmits only one of blue light, green light, red light, or infrared light. (2) In the sheet recognition unit described in (1), the recognition unit may subtract an output value of the fourth light receiving element from at least one of an output value of the first light receiving element, an output value of the second light receiving element, or an output value of the third light receiving element, and recognize the sheet to be recognized, using a subtraction result.(3) In the sheet recognition unit described in (2), the color filter of the fourth light receiving element may transmit only infrared light, and the recognition unit may sub