Patent Application
20230286299
The present application claims priority to Japanese Patent Application No. 2022-036177 filed on Mar. 9, 2022 under the Paris Convention and provisions of national law in a designated State. The entire contents of the application are hereby incorporated by reference.
The present disclosure relates to lighting units for an image sensor, image sensors, sheet recognition units, and sheet handling devices.
Some lighting units for an image sensor (optical line sensor) adopt a rod-shaped light guide to use point light sources as a line light source. The longitudinal end surfaces of the light guide each are provided with an incidence surface that the lights from the point light sources enter. The side surface of the light guide is provided with a band-shaped emission surface from which light is emitted toward the irradiation target.
For example, JP 2008-244985 A discloses a line illumination device including a reflection layer that is formed by printing white paint on the plane portion of a light-guiding member.
The present disclosure is directed to a lighting unit for an image sensor, the lighting unit including: a light source; a light guide extending in a main scanning direction; and a light diffusion area which diffuses light emitted from the light source and incident on the light guide, the light diffusion area including a first coating film formed on the light guide from a first paint containing metal powder.
A paint containing a white pigment, when applied by printing to a light guide, however, absorbs ultraviolet light (e.g., light having a wavelength of around 400 nm) from a light source. This decreases the ultraviolet reflectance of the light guide.
In response to the above current state of the art, an object of the present disclosure is to provide a lighting unit for an image sensor, an image sensor, a sheet recognition unit, and a sheet handling device that can have an increased reflectance of ultraviolet light from a light source.
The lighting unit for an image sensor, the image sensor, the sheet recognition unit, and the sheet handling device of the present disclosure can exhibit an increased reflectance of ultraviolet light from a light source.
Hereinafter, embodiments of the lighting unit for an image sensor, the image sensor, the sheet recognition unit, and the sheet handling device of the present disclosure are described with reference to the drawings. The lighting unit for an image sensor and the image sensor of the present disclosure can be used in various fields and are applicable to a lighting unit for an image sensor and an image sensor that scan a sheet to acquire the optical image information of the sheet. Thus, the following embodiments describe examples in which the concept of the present disclosure is applied to such lighting units for an image sensor and image sensors.
Components having the same or similar functions in the following description are commonly assigned with the same reference sign throughout the embodiments and drawings as appropriate, and description thereof is omitted as appropriate. The drawings showing a structure appropriately include the XYZ coordinate system where the XYZ axes are perpendicular to one another. The X axis direction, the Y axis direction, and the Z axis direction respectively correspond to the sub-scanning direction, the main scanning direction, and the height direction (depth direction) of the image sensor.
First, a lighting unit for an image sensor of Embodiment 1 is described.
As shown in
The light guide 10 guides light from each of the light sources 20 to apply linear light to a sheet P, which is an irradiation target (illumination target). The light guide 10 is an optical component that linearizes light from each of the light sources 20. The light guide 10 has a thin rod-like shape extending in the main scanning direction Y of an image sensor and is formed from, for example, a transparent resin such as an acrylic resin.
Each of the light sources 20 is adjacent to an end surface of the light guide 10 in the main scanning direction Y. Light from the light source 20 is incident on the end surface of the light guide 10 and propagates in the light guide 10. Each end surface on which the light from the light source 20 is incident functions as an incidence surface 11. In other words, a first end portion 15a and a second end portion 15b of the light guide 10 are adjacent to the respective light sources 20.
The light sources 20 are a plurality of light-emitting elements (not shown) such as light emitting diodes (LEDs) capable of emitting lights having different wavelength bands, for example, and these light sources 20 are capable of emitting lights having different wavelength bands (e.g., ultraviolet light, red light, green light, blue light, infrared light). The lighting unit 1 for an image sensor includes at least one light source 20 that emits ultraviolet light (which may hereinafter also be referred to as UV light source(s)). Each of the light-emitting elements is electrically connected to a lead frame to which a positive voltage is to be applied and a lead frame to which a negative voltage is to be applied (both of which are not shown).
Although
Meanwhile, although
Next, the light guide 10 is described in detail.
As shown in
The emission surface 12 emits light, incident on the light guide 10 from each of the light sources 20, toward a sheet. The emission surface 12 may be convex as shown in
The opposing surface 13 reflects light propagating inside the light guide 10 toward the emission surface 12. The opposing surface 13 may be flat as shown in
Also, as shown in
The light diffusion area A may be spaced from each end surface of the light guide 10 by a predetermined distance (see
As shown in
The first coating film 31 is formed on the light guide 10, in particular, the opposing surface 13, and is formed from a first paint containing metal powder.
As described above, the first coating film 31 is formed from a first paint containing metal powder. Containing the metal powder, the first coating film 31 has a higher ultraviolet reflectance and a lower ultraviolet absorbance than a coating film formed from a paint containing a white pigment (hereinafter, such a film may also be referred to as a white coating film). Thus, the light diffusion area A including the first coating film 31 has an increased reflectance of ultraviolet light from a UV light source. In other words, the lighting unit 1 for an image sensor has an increased reflectance of ultraviolet light from a UV light source.
The first coating film 31 may have any reflectance higher than the reflectance of a white coating film at least in an ultraviolet wavelength range. The first coating film 31 may have a reflectance of 60% or higher in the wavelength range of 360 nm to 410 nm. Herein, the expression “in the wavelength range of A to B” means “at all wavelengths between A and B inclusive”, unless otherwise specified.
The first coating film 31 may have a reflectance of 80% or lower or may have a reflectance of 70% or lower in the wavelength range of 360 nm to 410 nm. In other words, in the wavelength range of 360 nm to 410 nm, the reflectance of the first coating film 31 may be 60% or higher and 80% or lower or may be 60% or higher and 70% or lower.
In addition, the first coating film 31 may have any reflectance in a visible wavelength range, and may have a reflectance of 50% or higher and 80% or lower or may have a reflectance of 55% or higher and 70% or lower at all wavelengths longer than 410 nm and 710 nm or shorter.
As described above, the first coating film 31 may have a substantially flat reflectance spectrum in the wavelength range of 360 nm to 710 nm. Specifically, in the wavelength range of 360 nm to 710 nm, the fluctuation range of reflectance (the difference between the maximum reflectance and the minimum reflectance) of the first coating film 31 may be from 0% to 20%, may be from 0% to 10%, or may be from 0% to 5%.
As shown in
The first coating film 31 has a silver color with metallic luster and mainly specularly reflects the applied light.
The first coating film 31 lies on the opposing surface 13 of the light guide 10 from the first end portion 15a to the second end portion 15b of the light guide 10. The first coating film 31 may be spaced from each end surface of the light guide 10 by a predetermined distance (see
The first coating film 31 contains at least one type of metal powder evenly dispersed in a matrix (e.g., resin matrix) and is formed by, for example, applying the first paint to the light guide 10 by printing (e.g., screen printing).
The metal powder contained in the first paint, i.e., the metal powder contained in the first coating film 31, may contain at least one type of metal selected from the group consisting of aluminum, silver, and an alloy of these metals.
The mean particle size of the metal powder contained in the first coating film 31 may be any size greater than the ultraviolet to visible wavelength range (specifically, the wavelength range of 300 nm to 700 nm), i.e., greater than 700 nm. With such a mean particle size, as shown in
As shown in
Specifically, the second coating film 32 may have a reflectance of 70% or higher and 90% or lower or may have a reflectance of 75% or higher and 85% or lower in the wavelength range of 410 nm to 1000 nm.
As described above, the second coating film 32 may have a substantially flat reflectance spectrum in the wavelength range of 410 nm to 1000 nm. Specifically, in the wavelength range of 410 nm to 1000 nm, the fluctuation range of reflectance (the difference between the maximum reflectance and the minimum reflectance) of the second coating film 32 may be from 0% to 20%, may be from 0% to 10%, or may be from 0% to 5%.
The second coating film 32 has a white color and diffusely reflects light incident thereon as described above.
Meanwhile, the second coating film 32 may have a reflectance of 0% or higher and 20% or lower or may have a reflectance of 0% or higher and 10% or lower in the wavelength range of 300 nm to 350 nm.
The second coating film 32 lies on the opposing surface 13 of the light guide 10 from the first end portion 15a to the second end portion 15b of the light guide 10. The second coating film 32 may be spaced from each end surface of the light guide 10 by a predetermined distance (see
The second coating film 32 contains at least one type of white pigment evenly dispersed in a matrix (e.g., resin matrix) and is formed by, for example, applying the second paint to the light guide 10 by printing (e.g., screen printing).
The white pigment may be, for example, titanium oxide (TiO2), zinc oxide (ZnO), barium sulfate (BaSO4), or magnesium oxide (MgO).
As shown in
In this case, the predetermined angle θ to the axis Ay lying in the main scanning direction Y may be any angle. For example, the angle θ may be 20° or greater and 70° or smaller, may be 30° or greater and 60° or smaller, or may be 40° or greater and 50° or smaller. The first coating film 31 and the second coating film 32 may alternate each other in the main scanning direction Y to form stripes.
As shown in
In either case, print areas 33 arranged in the main scanning direction Y may each include a first coating film 31 and a second coating film 32. The print areas 33 are, for example, rectangular regions. The area of the regions may increase gradually (see
The light diffusion area A may include substantially no coating film other than the first coating film 31.
The first coating film 31 may be formed from a paint containing a white pigment as well as the metal powder.
As described above, the present embodiment can achieve the lighting unit 1 for an image sensor which can achieve an increased reflectance of ultraviolet light from the light sources 20.
Next, an image sensor of Embodiment 2 is described.
As shown in
As shown in
The lighting units 111b irradiate a banknote BN with lights having respective wavelengths. The light receiving units 113 each receive lights having respective wavelengths emitted from the lighting units 111b in the corresponding sensor unit and reflected by the banknote BN, and output reflection image data related to each of the lights having respective wavelengths.
The sensor unit 120 further includes one lighting unit 111a for transmission. The lighting unit 111a also corresponds to the lighting unit 1 for an image sensor of Embodiment 1 and includes a light guide 10 extending in the main scanning direction and a plurality of types of light sources 20 (light-emitting elements) each facing either one of the end surfaces of the light guide 10. The light sources 20 emit lights having respective wavelengths. The lighting unit 111a is disposed on the optical axis of the condensing lens 112 of the sensor unit 110. Part of light emitted from the lighting unit 111a is transmitted through a banknote BN, condensed by the condensing lens 112 of the sensor unit 110, and detected by the light receiving unit 113 of the sensor unit 110. The lighting unit 111a sequentially or simultaneously irradiates the surface B of the banknote BN with lights having different wavelength bands. The lighting unit 111a emits lights whose peak wavelengths are different from one another, for example, as the lights having respective wavelengths. Specifically, for example, infrared light (which may be a plurality of types of infrared lights whose peak wavelengths are different from one another), red light, green light, blue light, white light, ultraviolet light, and other light can be used.
The light receiving unit 113 of the sensor unit 110 receives lights having respective wavelengths emitted from the lighting unit 111a and transmitted through a banknote BN, and outputs reflection image data related to each of the lights having respective wavelengths.
The “lights having respective wavelengths” mean lights having different wavelength bands, and their peak wavelengths may be different from one another. The lights having respective wavelengths may be, for example, lights having different colors in the case of visible light, and lights having overlapping wavelength bands or lights having non-overlapping wavelength bands in the case of infrared light and ultraviolet light.
As shown in
Since including the lighting units 111a and 111b each corresponding to the lighting unit 1 for an image sensor of Embodiment 1, the image sensor 100 of the present embodiment can irradiate a banknote with more intense ultraviolet light to acquire image data of the banknote, and thus can acquire image data related to light based on ultraviolet light, such as fluorescence or phosphorescence with a higher degree of accuracy.
Next, a sheet recognition unit of the present embodiment is described. Various sheets such as banknotes, checks, vouchers, bills, business forms, documents of value, and card-like media are applicable as sheets used in the present disclosure. Devices for banknotes are used hereinbelow as examples to describe the present disclosure.
As shown in
The control unit 210 is defined by, for example, programs used to execute various processings stored in the storage unit 230, a central processing unit (CPU) used to execute the programs, and various hardware devices (e.g., field programmable gate array (FPGA)) controlled by the CPU. The control unit 210 is a controller that controls the components of the sheet recognition unit 200 following the programs stored in the storage unit 230. The programs stored in the storage unit 230 make the control unit 210 function as a recognition unit.
The detection unit 220 detects a variety of characteristics of a transported banknote, and may include a magnetic detection unit 221 and a thickness detection unit 222 as well as the image sensor 100 described above along the transport path of banknotes. The image sensor 100 captures an image of each banknote as described above and outputs an image signal (image data).
The storage unit 230 is defined by a nonvolatile storage device such as a semiconductor memory or a hard disk. The storage unit 230 stores programs and data for controlling the sheet recognition unit 200.
The control unit 210 uses various signals related to a banknote acquired from the detection unit 220 to execute recognition. The control unit 210 recognizes at least the denomination and authenticity of the banknote. The control unit 210 may function to determine the fitness of the banknote. In this case, the control unit 210 detects a stained/soiled portion, a folded portion, a torn portion, or other defective portions of the banknote, as well as, for example, tape attached to the banknote based on the thickness of the banknote, so as to determine whether the banknote should be handled as a fit note suitable for circulation or as an unfit note unsuitable for circulation.
At this time, the control unit 210 uses the image (image data) of the banknote captured by the image sensor 100 for recognition of the denomination, authenticity, and fitness, for example.
The sheet recognition unit 200 of the present embodiment, including the image sensor 100 of Embodiment 2, can execute banknote recognition with a higher degree of accuracy based on images captured using fluorescence and/or phosphorescence.
Next, a sheet handling device of the present embodiment is described.
The sheet handling device 300 of the present embodiment, including the sheet recognition unit of Embodiment 3, can handle banknotes with a higher degree of accuracy based on the recognition results from the sheet recognition unit.
Embodiments of the present disclosure have been described above with reference to the drawings. The present disclosure is not limited to the embodiments. Also, the structures of the embodiments may be combined or modified as appropriate within the range not departing from the gist of the present disclosure.
As described above, the present disclosure provides a technique useful in increasing the reflectance of ultraviolet light from light sources in a lighting unit for an image sensor.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2022-036177 | Mar 2022 | JP | national |
