WO2026030321A1 - Multiwavelength optical sensor - Google Patents

Abstract

A multiwavelength optical sensor includes an illuminator (301, 501, 1001). The illuminator includes an illuminator housing, one or more light-emitting diodes (LEDs) (510, 1010) of different wavelengths disposed in the illuminator housing, and a light bar (509, 1000) disposed in the illuminator housing, the light bar including a light guide (505, 709, 1005) and a diffuser (518, 712, 1018) having a thickness, and a width corresponding to the shape of a bottom portion of the light guide, wherein light emitted by the one or more LEDs are reflected within the light guide and the light is scattered by the diffuser through the light guide for transmission. The multiwavelength optical sensor also includes a photodetector (303, 503) for being disposed opposite the illuminator. The photodetector includes a photodetector housing, a photodiode array (507) disposed within the photodetector housing, and a diaphragm array (529) having a plurality of vertical walls for controlling the scattered light transmitted by the illuminator and decreasing stray light effect.

Description

MULTIWAVELENGTH OPTICAL SENSOR

TECHNICAL FIELD

[0001] This disclosure relates generally to optical object detection systems. More specifically, this disclosure relates to a multiwavelength optical sensor.

BACKGROUND

[0002] Devices and machines, such as apparatuses for automatic processing of banknotes and other special securities, typically include optical sensors to provide measurements of the transparency of detected objects. Sensors or sensor arrays used in apparatuses for automatic processing of articles such as banknotes, securities, documents, and other items typically collect information about optical properties of processed objects, in particular, optical transmittance at various light wavelengths. However, existing optical sensors have various issues such as an unwanted stray light effect that reduces the accuracy of the optical sensors.

SUMMARY

[0003] This disclosure relates to a multiwavelength optical sensor.

[0004] In one aspect thereof, a multiwavelength optical sensor includes an illuminator for being disposed in an article detection area. The illuminator includes an illuminator housing, one or more lightemitting diodes (LEDs) of different wavelengths disposed in the illuminator housing, and a light bar disposed in the illuminator housing, the light bar including a light guide and a diffuser having a thickness, and a width corresponding to a shape of a bottom portion of the light guide, wherein light emitted by the one or more LEDs are reflected within the light guide and the light is scattered by the diffuser through the light guide for transmission outside the illuminator.

[0005] In some embodiments, the multiwavelength optical sensor also includes a photodetector for being disposed opposite the illuminator in the article detection area. The photodetector includes a photodetector housing, a photodiode array disposed within the photodetector housing, and a diaphragm array having a plurality of vertical walls for controlling the scattered light transmitted by the illuminator and decreasing stray light effects.

[0006] In another aspect thereof, a light bar for an optical device includes a light bar having ends having a shape for deflecting light into a central portion of the light bar. The light bar also includes a diffuser having a thickness, and a width corresponding to a shape of a bottom portion of the light guide. Light reflected within the light guide is scattered by the diffuser through the light guide for transmission. The light bar provides a stable indicatrix of illumination.

[0007] In another aspect thereof, a method includes detecting, by a multiwavelength optical sensor, an article in an article detection area of an apparatus, wherein the multiwavelength optical sensor includes an illuminator disposed in the article detection area. The illuminator includes an illuminator housing, one or more light-emitting diodes (LEDs) of different wavelengths disposed in the illuminator housing, and a light bar disposed in the illuminator housing, the light bar including a light guide and a diffuser having a thickness, and a width corresponding to a shape of a bottom portion of the light guide. The multiwavelength optical sensor also includes a photodetector disposed opposite the illuminator in the article detection area. The photodetector includes a photodetector housing, a photodiode array disposed within the photodetector housing, and a diaphragm array having a plurality of vertical walls. Detecting the article includes emitting light by the one or more LEDs, reflecting the emitted light within the light bar and scattering the light by the diffuser through the light bar for transmission outside the illuminator, receiving the scattered light, transmitted by the illuminator, by the photodetector and controlling the scattered light using the plurality of vertical walls of the diaphragm array and decreasing stray light effects.

[0008] Before undertaking the DETAILED DESCRIPTION below, it may be advantageous to set forth definitions of certain words and phrases used throughout this patent document. The term “couple” and its derivatives refer to any direct or indirect communication between two or more elements, whether or not those elements are in physical contact with one another. The terms “transmit,” “receive,” and “communicate,” as well as derivatives thereof, encompass both direct and indirect communication. The terms “include” and “comprise,” as well as derivatives thereof, mean inclusion without limitation. The term “or” is inclusive, meaning and/or. The phrase “associated with,” as well as derivatives thereof, means to include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, have a property of, have a relationship to or with, or the like. The term “controller” means any device, system or part thereof that controls at least one operation. Such a controller may be implemented in hardware or a combination of hardware and software and/or firmware. The functionality associated with any particular controller may be centralized or distributed, whether locally or remotely.

[0009] Moreover, various functions described below can be implemented or supported by one or more computer programs, each of which is formed from computer readable program code and embodied in a computer readable medium. The terms “application” and “program” refer to one or more computer programs, software components, sets of instructions, procedures, functions, objects, classes, instances, related data, or a portion thereof adapted for implementation in a suitable computer readable program code. The phrase “computer readable program code” includes any type of computer code, including source code, object code, and executable code. The phrase “computer readable medium” includes any type of medium capable of being accessed by a computer, such as read only memory (ROM), random access memory (RAM), a hard disk drive, a compact disc (CD), a digital video disc (DVD), or any other type of memory. A “non-transitory” computer readable medium excludes wired, wireless, optical, or other communication links that transport transitory electrical or other signals. A non-transitory computer readable medium includes media where data can be permanently stored and media where data can be stored and later overwritten, such as a rewritable optical disc or an erasable memory device.

[0010] As used here, terms and phrases such as “have,” “may have,” “include,” or “may include” a feature (like a number, function, operation, or component such as a part) indicate the existence of the feature and do not exclude the existence of other features. Also, as used here, the phrases “A or B,” “at least one of A and/or B,” or “one or more of A and/or B” may include all possible combinations of A and B. For example, “A or B,” “at least one of A and B,” and “at least one of A or B” may indicate all of (1) including at least one A, (2) including at least one B, or (3) including at least one A and at least one B. Further, as used here, the terms “first” and “second” may modify various components regardless of importance and do not limit the components. These terms are only used to distinguish one component from another. For example, a first user device and a second user device may indicate different user devices from each other, regardless of the order or importance of the devices. A first component may be denoted a second component and vice versa without departing from the scope of this disclosure.

[0011] It will be understood that, when an element (such as a first element) is referred to as being (operatively or communicatively) “coupled with/to” or “connected with/to” another element (such as a second element), it can be coupled or connected with/to the other element directly or via a third element. In contrast, it will be understood that, when an element (such as a first element) is referred to as being “directly coupled with/to” or “directly connected with/to” another element (such as a second element), no other element (such as a third element) intervenes between the element and the other element.

[0012] As used here, the phrase “configured (or set) to” may be interchangeably used with the phrases “suitable for,” “having the capacity to,” “designed to,” “adapted to,” “made to,” or “capable of’ depending on the circumstances. The phrase “configured (or set) to” does not essentially mean “specifically designed in hardware to.” Rather, the phrase “configured to” may mean that a device can perform an operation together with another device or parts. For example, the phrase “processor configured (or set) to perform A, B, and C” may mean a generic-purpose processor (such as a CPU or application processor) that may perform the operations by executing one or more software programs stored in a memory device or a dedicated processor (such as an embedded processor) for performing the operations.

[0013] The terms and phrases as used here are provided merely to describe some embodiments of this disclosure but not to limit the scope of other embodiments of this disclosure. It is to be understood that the singular forms “a,” “an,” and “the” include plural references unless the context clearly dictates otherwise. All terms and phrases, including technical and scientific terms and phrases, used here have the same meanings as commonly understood by one of ordinary skill in the art to which the embodiments of this disclosure belong. It will be further understood that terms and phrases, such as those defined in commonly- used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined here. In some cases, the terms and phrases defined here may be interpreted to exclude embodiments of this disclosure.

[0014] Definitions for other certain words and phrases are provided throughout this patent document. Those of ordinary skill in the art should understand that in many if not most instances, such definitions apply to prior as well as future uses of such defined words and phrases. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] For a more complete understanding of this disclosure, reference is now made to the following description, taken in conjunction with the accompanying drawings, in which:

[0016] FIGURE 1 illustrates an example banknote processing system in accordance with this disclosure;

[0017] FIGURE 2 illustrates a perspective view of a document processing system in accordance with this disclosure;

[0018] FIGURES 3A and 3B illustrate a general sensor operation showing ray traces during a presence and an absence of an object in the transportation path;

[0019] FIGURES 4A and 4B illustrate an example of a dependence of an output signal on an orientation of an object in a transportation path;

[0020] FIGURES 5A-5C illustrate an example multiwavelength optical sensor in accordance with this disclosure;

[0021] FIGURE 6 A illustrates an exploded view of an illuminator of the multi wavelength optical sensor of FIGURES 5A and 5B in accordance with this disclosure;

[0022] FIGURES 6B-6D illustrate views of a light bar of the illuminator of FIGURE 6A in accordance with this disclosure;

[0023] FIGURE 7 illustrates an example of how light can be reflected through a light bar;

[0024] FIGURE 8A illustrates an exploded view of a photodetector of the multiwavelength optical sensor of FIGURES 5A and 5B in accordance with this disclosure;

[0025] FIGURE 8B illustrates a view of a diaphragm array of the photodetector of FIGURE 8A in accordance with this disclosure;

[0026] FIGURE 8C illustrates a cross-sectional view of a single sensor in a sensor array in accordance with this disclosure;

[0027] FIGURE 8D illustrates the single sensor component of FIGURE 8C in accordance with this disclosure;

[0028] FIGURE 8E illustrates a cross sectional view of the photodetector of FIGURE 8 A in accordance with this disclosure;

[0029] FIGURE 9 illustrates an example of a stray light effect;

[0030] FIGURES 10A-10D illustrate various views of an example light bar in accordance with this disclosure;

[0031] FIGURE 10E illustrates an example illuminator including the light bar of FIGURES 10A-10D in accordance with this disclosure;

[0032] FIGURE 11 illustrates one example of a method for detecting an article using a multiwavelength optical sensor in accordance with this disclosure; and

[0033] FIGURE 12 illustrates an example electronic system in accordance with this disclosure. DETAILED DESCRIPTION

[0034] FIGURES 1 through 12, discussed below, and the various embodiments used to describe the principles of this disclosure in this patent document are by way of illustration only and should not be construed in any way to limit the scope of the disclosure. Those skilled in the art will understand that the principles of this disclosure may be implemented in any suitably arranged device or system.

[0035] As used throughout this specification, the terms currency denomination, denomination of currency, valuable document, currency bill, bill, banknote, note, check, bank check, paper money, paper currency, plastic money, plastic banknote, plastic currency, money order, coupon, ticket, and cash may be used interchangeably herein to refer to a type of a negotiable instrument or any other writing that evidences a right to the payment of a monetary obligation, typically issued by a central banking authority.

[0036] As described above, devices and machines, such as apparatuses for automatic processing of banknotes and other special securities, typically include optical sensors to provide measurements of the transparency of detected objects. Sensors or sensor arrays used in apparatuses for automatic processing of articles such as banknotes, securities, documents, and other items typically collect information about optical properties of processed objects, in particular, optical transmittance at various light wavelengths. However, existing optical sensors have various issues such as an unwanted stray light effect that reduces the accuracy of the optical sensors.

[0037] This disclosure provides embodiments of a multiwavelength optical sensor that provides for self-calibration of the rate between object transparency and sensor output signal, suppression of the difference of the sensor output signal at different orientation of object insertion (e.g., face up or face down), and a decrease in the effects of stray light which permeates through areas of the optical system that are not overlapped by the detected object.

[0038] The optical sensor and associated systems described in this disclosure can be implemented in a wide variety of article processing machines or apparatuses, such as ticketing machines, check scanning machines, automated teller machines, point-of-sale machines, banknote processing or recycling machines, document scanning machines, identity verification devices, etc. The optical sensor and associated systems of this disclosure can be integrated into such machines or apparatuses to provide for improved detection of articles the machine or apparatus is designed to process in order to provide for authentication/verification of such articles.

[0039] For example, FIGURE 1 illustrates an example banknote processing system 100 in accordance with this disclosure. The multiwavelength optical sensor and associated article detection systems of this disclosure can be implemented in the banknote processing system 100. However, it will be understood that the banknote processing system 100 is merely an example, and the multiwavelength optical sensor and associated article detection systems of this disclosure can be implemented in a wide variety of systems, machines, or apparatuses, as noted above.

[0040] The banknote processing system 100 may include a bezel, a chassis, an acceptor head, a banknote transport mechanism, a banknote transport path, one or more sensors to verify genuineness of inserted banknotes, a banknote storage section, and/or a banknote acceptor-dispenser module. The banknote processing system 100 of FIGURE 1 can also be used or incorporated in other systems, such as unattended payment systems, point-of-sale systems, or other currency processing apparatuses.

[0041] In various embodiments, the banknote processing system 100 is configured to verify the authenticity of an inserted banknote. The banknote processing system 100 generally has an acceptor head, a banknote transport system, and a removable banknote storage unit. Inserted banknotes are generally authenticated in a banknote accepting module using various sensors as further described in this disclosure. Once the banknote is deemed authentic and deemed acceptable, the banknote is transported further into the banknote acceptor using the banknote transport system into a banknote storage unit, which can be a removable banknote storage unit. If a banknote is rejected, it can be dispensed back out of the banknote processing system 100. When the optical sensor and systems of this disclosure are implemented in other types of machines or apparatuses, similar processes can be used to authenticate/verify articles, such as rejecting or accepting such articles based on outputs provided by the optical sensor and/or sensor systems. [0042] Although FIGURE 1 illustrates an example of a banknote processing system 100, various changes may be made to FIGURE 1. Various components of the banknote processing system in FIGURE 1 could be rearranged, omitted, combined, or further subdivided and additional components could be added according to particular needs. For example, the banknote processing system 100 could include any number of escrow, storage, or recycling modules. The banknote processing system 100 could be used in automatic ticket seller machines, automated payment systems, unattended payment systems, point-of-sale systems, customer assisted payment systems, automatic teller machines, vending machines and other kiosks, electronic gaming machines, or in other currency processing apparatuses/systems. In general, banknote processing systems can come in a variety of configurations, and FIGURE 1 does not limit the scope of this disclosure to any particular configuration.

[0043] As another example, FIGURE 2 illustrates a perspective view of a document processing system 200 in accordance with this disclosure. As shown in FIGURE 2, the document processing system 200 includes a document processing device 201 and an output portion 210a. The output portion 210a of the document processing system 200 includes a base module 202. That is, the document processing system 200 includes a document processing device 201 coupled to the output portion 210a, where the output portion 210a includes one or more modules (e.g., the base module 202). The document processing system 200 may include one or more output receptacles or pockets.

[0044] The multiwavelength optical sensor and associated article detection systems of this disclosure can be implemented in the document processing system 200. However, it will be understood that the document processing system 200 is merely an example, and the multiwavelength optical sensor and associated article detection systems of this disclosure can be implemented in a wide variety of systems, machines, or apparatuses, as noted above.

[0045] Although FIGURE 2 illustrates an example of a document processing system 200, various changes may be made to FIGURE 2. Various components of the document processing system in FIGURE 2 could be rearranged, omited, combined, or further subdivided and additional components could be added according to particular needs. For example, the document processing system 200 could include any number of escrow, storage, or recycling modules. In general, document processing systems can come in a variety of configurations, and FIGURE 2 does not limit the scope of this disclosure to any particular configuration. [0046] FIGURE 3A and 3B illustrate an example of a general sensor operation 300. The sensor includes an illuminator 301 irradiating the surface of an article 302, denoted using exemplary light rays 1- 7, from one side of the article transportation path, through which the article 302 is traveling through during its processing. The sensor also includes a photodetector 303 located on the other side of the article transportation path, which records light passing through the article transportation path.

[0047] Transparency determines what portion of incident light permeates to the opposite side of article 302. The photodetector 303 can collect a portion of illuminating light when there is no article 302 between the illuminator 301 and the photodetector 303, as shown in FIGURE 3A. When an article 302 passes between the illuminator 301 and the photodetector 303, the photodetector 303 can collect a portion of illuminating light permeating the article 302, as shown in FIGURE 3B. Each portion of the light rays 1-7 is transformed by the photodetector 303 to a proportional electrical signal.

[0048] However, problems can arise because the relation of these two signals cannot be used directly. It would be possible to use the relation of the two signals if the relative portions of the light incident on the photodetector 303 were the same, but, as shown in FIGURES 3A and 3B, that is not the case. Rather, the rays gathered by photodiodes of the photodetector 303 in FIGURES 3A and 3B originate from different initial rays emited by the illuminator 301 as the article 302 causes a redirection or bending of the light rays 1-7 such that different rays are incident on the photodetector 302 when the article is present between illuminator 301 and the photodetector 302.

[0049] Consequently, the practical way to overcome this situation is through calibration of the optical sensor. For example, by applying an article dummy having known transparency, a calibration value of the relation between the transparency and the ratio between rays gathered by the photodetector 303 can be obtained in the two scenarios shown in FIGURE 3A and 3B. That is, a calibration can be performed between the transparency and the output signal levels of the sensor during a presence and an absence of an object in the article transportation path.

[0050] The calibration value will be correct as far as a correlation among rays emited by the illuminator 301 in various directions stays the same. This correlation is usually described with respect to the concept of an indicatrix, which is produced by the illuminator 301. Due to manufacturing variations, there is variability between the indicatrices from illuminator to illuminator, requiring a calibration of each illuminator during or after manufacture. It is desirable to reduce or eliminate these manufacturing variations so that the indicatrices of each illuminator is replicable across illuminators so that calibration for a particular illuminator design is done once during sensor design, and need not be repeated for each illuminator of same design as part of the manufacturing process. [0051] As described herein, the optical sensor of this disclosure solves the above problems by providing an arrangement of the illuminator that provides a replicable indicatrix of illumination.

[0052] Another issue that can arise with optical sensors is that the illumination as well as the number of rays gathered by the photodetector 303 may depend on an orientation of the inserted object or article, e.g., whether the object or article is inserted face up or face down. FIGURES 4A and 4B illustrate this phenomenon. This issue stems from when a surface of the article 302 facing the illuminator 301 is illuminated not only by primary light 406 directly (as shown in FIGURE 4A) but also by additional light 407 that falls on the surface (as shown in FIGURE 4B).

[0053] For example, as shown in FIGURE 4B, if the surface of the article 302 facing the illuminator 301 is a light surface 404, a portion of the primary light is reflected in a direction of the illuminator 301. Illuminators consists of parts that are extremely transparent or extremely white. This is necessary for achieving a high efficiency of the illuminator, but this also creates conditions where the additional light 407 is redirected back to the illuminated surface, providing undesirable additional illumination. As a result, the photodetector 303 gathers additional light 408. As shown in FIGURE 4A, if the surface of the article 302 facing the illuminator 301 is a dark surface 405, the phenomenon shown in FIGURE 4B does not occur. Thus, signals from objects that have different images on different sides becomes dependent on which side is facing the illuminator 301, such as an article that has print-free and printed material.

[0054] As described herein, the optical sensor of this disclosure solves the above problems by providing an arrangement of the optical sensor that achieves an independence of the sensor signals no matter which side of the object is facing the illuminator.

[0055] Another issue is that in practical design, all single sensors, of which a sensor array consists, work simultaneously. That is, a portion of the sensors in the array tend to face the object, but some sensors can view the illuminator directly, because the object is usually smaller than the transportation path width and thus the article does not shade the light from the illuminator in some portions of the transportation path. This stray light flowing through non-overlapped areas of the transportation path is very strong, causing this light to be scattered by parts of the photodetector unit and thus illuminating the surface of object facing the photodetector, which in turn causes a foreign signal of the photodetector.

[0056] As described herein, the optical sensor of this disclosure solves the above problems by catching stray light rays to prevent their spread along the array line and to avoid the stray light rays hitting the surface of the article.

[0057] FIGURES 5A-5C illustrate an example multiwavelength optical sensor 500 in accordance with this disclosure. As shown in FIGURES 5A-5C, the multiwavelength optical sensor 500 includes two units, an illuminator 501 for being disposed on one side of a transportation path, such as a bill path in a currency processing apparatus, and a photodetector 503 for being disposed on an opposite side of the transportation path from the illuminator 501, such as demonstrated in FIGURES 3A and 3B, for example. As shown in FIGURES 5B and 5C, the photodetector 503 can include a photodiode array 507. [0058] FIGURE 6A illustrates an exploded view of the illuminator 501 in accordance with this disclosure, and FIGURES 6B-6D illustrates views of a light bar 509 of the illuminator 501 in accordance with this disclosure.

[0059] As shown in FIGURES 6A-6D, the illuminator 501 includes the light bar 509 into the end of which the feeding light of different wavelengths from light-emitting diodes (LEDs) 510 is injected for further measuring of article transparency in multiple regions of the light spectrum. The light bar 509 includes a transparent light guide 505 and a diffuser 518.

[0060] As shown in FIGURE 7, which illustrates an example 700 of how light 711 can be reflected through a light guide 709, this light 711 emitted by an LED 710 fills the volume of the light guide 709, because of repeated total internal reflection. A diffuser 712 is applied to the side of the light guide 709 opposite of an illuminated object 702 to scatter the light 711 in the direction of the illuminated object 702 as light rays 750. In previous designs, a layer of white paint is used as a diffuser. This causes there to be a low replicability of the irradiation indicatrix due to a weak replicability of parameters of the paint diffuser scattering. They are influenced by a presence of a total internal reflection at a transition through the layer between the light guide 709 and the diffuser 712 because of its complex structure and/or insufficient coverage of the paint, leading to variations in the degree of scattering depending on, among other things, the thickness of the paint layer, as well as because of a tendency of the paint to spread.

[0061] Referring again to FIGURES 6A-6D, the illuminator 501 includes an improved design that avoids the above issues. The illuminator 501 provides for replicability of indicatrices between illuminators in the manufacturing process, so that calibration is performed once, such as during sensor design, and does not need to be done for each illuminator during or after manufacture. The sensor 500 includes a housing 513 that is covered by a protective transparent cover 514, inside of which the light bar 509 is disposed. The transparent cover 514 may be made of plastic, glass, or other materials. The light bar 509 has a light guide 505 that has sloping ends 516 that direct the feeding light emitted by the LEDs 510 into the light guide 505. In various embodiments, the light guide 505 is transparent and can be made of plastic or other materials. The sloping ends 516 of the light guide 505 are covered by light shields 517 that prevent the light emitted by the LEDs from leaking from the light guide 505. In various embodiments, the light shields 517 are of white color and can be made of plastic. The light bar 509 also includes a diffuser 518 at a bottom portion of the light guide 505. The diffuser 518 can be an opaque bulk material, such as a plastic. The LEDs 510 are placed on a printed circuit board (PCB) 519.

[0062] As shown in FIGURES 6B-6D, replicability issues described in this disclosure with respect to indicatrices of illuminators is improved by the illuminator 501 for the following reasons. The diffuser 518 of the light bar 509 has a thickness, and a width that corresponds to a shape of a bottom portion of the light guide505. The thickness can be of bulk material, instead of a thin layer of paint as in prior designs. Such thin layers of paint can be applied in an inconsistent manner, resulting in variations of the thickness of the applied paint. The thickness and width of the diffuser 518 of the light bar 509 provides less relative variation of its size during manufacture. In some embodiments the bottom portion of the light guide 505 has a constant width over the entire length. In some embodiments that bottom portion of the light guide 505 varies in width over its length. As explained in this disclosure, previous designs used white paint as a diffuser. The white paint is typically applied as a single layer and causes the performance of prior diffusers to be less repeatable between illuminators due to manufacturing variations. While multiple layers of paint can be applied, there are practical manufacturing considerations to be able to apply enough layers of paint to potentially reduce indicatrix variations. The diffuser 518 of this disclosure has a thickness of bulk material, such as a plastic, such that the diffuser 518 is thick enough so that, at any wavelength of LED 710, the diffusion rate of the diffuser 518 is maximized and invariant to further increasing of thickness. If the diffuser were thinner like with previous designs such as those that used one or more layers of white paint, light might be transmitted through the diffuser and leak out the bottom.

[0063] The increased thickness of the bulk material of the diffuser 518 provides stability over the over prior designs such as paint stripes, since there is less control in coating a surface of the light guide with one or more layers of paint as opposed to molding a thick piece of plastic. Thus, the light bar 509 of this disclosure is calibrated by the design itself, and does not need calibration of individual light bars to account for manufacturing variations,

[0064] In various embodiments, the light guide 505 and diffuser 518 can be produced with injection molding technology to provide a higher stability and consistency in manufacturing of the light guide 505 and diffuser 518. In various embodiments, the same base plastic material can be used for both the light guide 505 and the diffuser 518, which makes a transition layer 520 between the light guide 505 and the diffuser 518 optically inactive after molding to provide an absence of light reflection. For the diffuser 518, the base material is doped such that the diffuser 518 appears opaque. In various embodiments the diffuser 518 is doped with a white pigment, such as titanium dioxide, zinc oxide, or calcium carbonate, among others. In various embodiments, the diffuser 518 may be injection molded before the light guide 505 during manufacturing. In other embodiments, the light guide 505 may be injection molded before the diffuser 518 during manufacturing.

[0065] As shown in FIGURE 6D, the width of the diffuser 518 can correspond to a shape of a bottom portion of the light guide 505 that, combined, make up the transition layer 520. As light from the LEDs is transmitted, the light is directed upwards, is reflected off the sloping ends 516 of the light guide 505, and then is scattered by the diffuser 518 as scattered light 550, the indicatrix of the scattered light also being affected by the interior sloping shape of the light guide 505. However, the bulk material thickness of the diffuser 518 increases the rate of the scattering and makes the scattering of the light strongly stable, avoiding the inefficiencies and unpredictability of scattered light over different wavelengths in previous illuminators. [0066] FIGURE 8 A illustrates an exploded view of the photodetector 503 in accordance with this disclosure, FIGURE 8B illustrates a view of a diaphragm array of the photodetector 503 in accordance with this disclosure, FIGURE 8C illustrates a cross-sectional view 801 of a single sensor in a sensor array in accordance with this disclosure, FIGURE 8D illustrates the single sensor component of FIGURE 8C in accordance with this disclosure, and FIGURE 8E illustrates a cross sectional view 802 of the photodetector 503 in accordance with this disclosure.

[0067] In various embodiments, the photodetector 303 contains a one-dimensional array of detectors, i.e., photodiodes. For example, FIGURES 8C and 8D show an arrangement and functionality of a single sensor that is part of the array. A single sensor in the array includes a photodiode 521. A portion of the surface of an illuminated object 502 is projected by a lens 522 onto a sensitive area 523 of the photodiode 521. To provide a desired quality of the optical system, a diaphragm 524 is disposed between the lens 522 and the photodiode 521. The diaphragm 524 includes a center cutout portion corresponding to the lens 522 that helps control light entering the photodiode 521 , such as by narrowing the beam of light as the light reaches the photodiode 521. Each photodiode 521 collects rays from a corresponding portion of a detection path or area, with each next sensor in the array collecting rays from a different portion of the detection area (and of a detectable object/article when present).

[0068] As shown in FIGURES 8A-8E, the components of the photodetector 503 are mounted on a PCB 525 placed into a housing 527 that is covered by protective transparent window 526 that is flush with the inner surface of the detection path or area. The transparent protective window 526 may be made of plastic, glass, or other materials. As shown in FIGURES 6A and 8A, each of the PCBs 519 and 525 include a flex cable connector for connecting each of the illuminator 501 and the photodetector 503 to an apparatus such as the apparatuses 100 or 200. As shown in FIGURES 8 A and 8B, the photodetector 503 includes an array of lenses 528 and a diaphragm array 529. The photodetector 503 also includes a light shield 530, which acts as an entrance to the photodetector 503. As shown in FIGURE 8A, the light shield 530 has a cutout portion corresponding to a light diffuser 531. In various embodiments, the light shield 530 can be made of plastic and in various embodiments can be a black color. In various embodiments, the light diffuser 531 can be made of plastic and in various embodiments can be a white color. The light shield 530, the light diffuser 531, and the diaphragm array 529 assist with avoiding the issues described in this disclosure by achieving independence of signals provided by the photodetector 503 from which side of the article or object is facing the illuminator, as well as catching stray light rays to prevent their spread along the array line and to avoid the stray light rays hitting the surface of the article.

[0069] Particularly, the light diffuser 531 provides for an independence of signals from the orientation of the object insertion. Particularly, equalization of signals of this disclosure is based on the fact that the signals at different orientations are to be equal by an equal light redirection ability of both the illuminator 501 and the photodetector 503. Because the initial issues arise due to a high redirection ability of an illuminator, the diffuser 531, being white, effectively redirects a part of the permeating rays back to the object/article surface to be collected by photodiodes once more. The desired rate of redirection can be determined by the form and location of the diffuser 531.

[0070] As shown in FIGURE 8E, the diaphragm array 529 is similar to the diaphragm 524, but diaphragm array 529 includes a set of lens hoods that prevent stray light from spreading along the photodiode array. For example, as shown in FIGURE 9, which illustrates an example 900 of a stray light effect, if the photodetector does not include the diaphragm array 529, light rays 950 emerging from the light bar 509 of the illuminator 501 can bypass the detected article 502 near its edge and illuminate the lens array 528. This can create extraneous additional illumination of a surface area 932 of the article 502, located near the edge of the article 502 and facing the photodetector, due to the reflection of the rays by the shiny lens array 528.

[0071] Referring again to FIGURE 8E, extraneous lighting is suppressed due to the vertical walls of the lens hoods of the diaphragm array 529. As shown in FIGURE 8E, light rays 850 emerging from the light bar 509 of the illuminator 501 are controlled by the vertical walls of the diaphragm array 529 to prevent the light rays 850 from bypassing the detected article 502 near its edge and also to direct the light rays 850 through the diaphragm array 529 and towards the appropriate lenses and photodiodes of the photodetector 503. Thus, the photodetector 503 provides for improved detection of articles in the detection area and improved signal accuracy.

[0072] Although FIGURES 5A-5C, 6A-6D, and 8A-8E illustrates example portions of a multiwavelength optical sensor 500, various changes may be made to FIGURES 5A-5C, 6A-6D, and 8A- 8E. For instance, various components of the illuminator 501 and/or the photodetector 503 shown in FIGURES 5A-5C, 6A-6D, and 8A-8E could be rearranged, omitted, combined, or further subdivided and additional components could be added according to particular needs. In general, FIGURES 5A-5C, 6A-6D, and 8A-8E do not limit the scope of this disclosure to any particular configuration.

[0073] For example, the light bar of the illuminator could be configured in a variety of ways. As a particular example, FIGURES 10A-10E illustrate various views of an example light bar 1000 in accordance with this disclosure. FIGURE 10A illustrates a perspective view of the light bar 1000, FIGURE 10B illustrates an exploded view of the light bar 1000 positioned over a PCB 1019, FIGURE 10C illustrates a top view of the light bar 1000 positioned over the PCB 1019, FIGURE 10D illustrates a side view of the light bar 1000 positioned over the PCB 1019, and FIGURE 10E illustrates an illuminator 1001 that incorporates the light bar 1000.

[0074] Rather than using sloping ends, such as the sloping ends 516 of the light guide 505, a light guide 1005 of the light bar 1000 includes ends 1016 that each have leg portions 1002 extending transversely from the ends 1016 and on either side of the body of the light guide 1005 and a diffuser 1018, as shown in FIG URES 10A-10D. The leg portions 1002 allow for LEDs 1010 of the illuminator to be situated on a PCB 1019 such that the LEDs 1010 are disposed on each side of the light guide 1005 and underneath the leg portions 1002, resulting in an overall reduction of the length of the sensor than other configurations, such as the illuminator 501 including the light bar 509 having sloping ends 516.

[0075] This reduction in length allows for the sensor to be made shorter so that it can be installed within machines that may have a smaller internal space. As shown in FIGURE 10E, it will be understood that the light bar 1000 can be used within an illuminator having similar features as the illuminator 501 of this disclosure. For example, the illuminator 1001 shown in FIGURE 10E can include the various other features described with respect to the illuminator 501, but can be at a reduced length compared to the length of the illuminator 501. This reduced length of the illuminator can also allow for a photodetector corresponding to the illuminator, such as the photodetector 503, to also be at a reduced length matching the length of the illuminator.

[0076] FIGURE 11 illustrates one example of a method 1100 for detecting an article using a multiwavelength optical sensor in accordance with this disclosure. At step 1102, a multiwavelength optical sensor, i.e., the multiwavelength optical sensor 500 of this disclosure, which includes an illuminator (e.g., illuminator 501) and a photodetector (e.g., photodetector 503) is disposed in an article detection area of an apparatus, such as within one of the apparatuses 100 or 200. At step 1104, light is emitted by one or more LEDs, such as LEDs 510, disposed in an illuminator housing of the illuminator. At step 1106, the emitted light is reflected within a light guide of a light bar disposed in the illuminator housing, such as the light guide 505 of the light bar 509, and the light reflected within the light guide is scattered using a diffuser of the light bar, such as the diffuser 518 of the light bar 509, for transmission outside the illuminator.

[0077] At step 1108, the scattered light transmitted by the illuminator is received by the photodetector, where the photodetector includes a photodetector housing and a photodiode array. At step 1110, the scattered light received by the photodetector is controlled using a plurality of vertical walls of a diaphragm array, such as the diaphragm array 529, to reduce further light scattering and direct the light to the photodiode array.

[0078] At step 1112, it is determined, such as by a processor or other processing device of the apparatus in which the multiwavelength optical sensor is installed, whether an article is detected. If not, the method 1100 moves back to step 1104. If so, the process moves to step 1114. At step 1114, the processor or other processing device of the apparatus performs an imaging, detection, and/or authentication operation in which an article can be imaged based on its detected optical characteristics, a detection status can be stored or otherwise transmitted or provided, and/or an authentication based on the measured optical characteristics of the article can be used to determine if the article is genuine can be performed. In such authentication operations, a result can be output and/or other apparatus functions can be triggered, such as accepting an article further into the apparatus, such as into a storage or escrow position, or rejecting an article and dispensing the article out of the apparatus. The method 1100 ends at block 1116.

[0079] Although FIGURE 11 illustrates one example of a method 1100 for detecting an article using a multiwavelength optical sensor, various changes may be made to FIGURE 11. For example, while shown as a series of steps, various steps in FIGURE 11 could overlap, occur in parallel, occur in a different order, or occur any number of times (including zero times).

[0080] FIGURE 12 illustrates an example electronic system 1200 in accordance with various embodiments of this disclosure. The system 1200 can be a portion of an article processing machine or apparatus, such as the banknote processing system 100 of FIGURE 1, the document processing system 200 of FIGURE 2, or of any other system, machine, or apparatus incorporating the multiwavelength optical sensor of the embodiments of this disclosure. The system 1200 includes a controller (e.g., a processor/central processing unit (“CPU”)) 1202, a memory unit 1204, and an input/output (“I/O”) device 1206. The system 1200 also includes at least one network interface 1208, or network interface controllers (NICs).

[0081] The system 1200 further includes one or more sensors 1210 for capturing and/or measuring data. In some embodiments, the system 1200 includes one or more multiwavelength optical sensors for detecting article presence and visual imaging of articles, as at least one of the sensors 1210, such that the imaging sensor is in communication with one or more of the other components of the system 1200.

[0082] The system 1200 also includes a storage drive 1212 used for storing content such as detected article data. In some embodiments, the components 1202, 1204, 1206, 1208, 1210, and 1212 are interconnected by a data transport system (e.g., a bus) 1214. In some embodiments, certain components, such as the sensors 1210, may not be connected to the data transport system 1214, and can be connected to the processor 1202 or an interface of the processor 1202, or another component via a wired or wireless connection. A power supply unit (PSU) 1216 provides power to components of the system 1200 via a power transport system 1218 (shown with data transport system 1214, although the power and data transport systems may be separate). It will be understood that the system 1200 may be differently configured and that each of the listed components may actually represent several different components. For example, the CPU 1202 can represent a multi-processor or a distributed processing system; the memory unit 1204 can include different levels of cache memory, and main memory; the I/O device 1206 can include monitors, keyboards, touchscreens, and the like; the at least one network interface 1208 can include one or more network cards providing one or more wired and/or wireless connections to a network 1220; and the storage drive 1212 can include hard disks and remote storage locations. Therefore, a wide range of flexibility is anticipated in the configuration of the system 1200, which may range from a single physical platform configured primarily for a single user or autonomous operation to a distributed multi-user platform such as a cloud computing system.

[0083] In some embodiments, the system 1200 can use an operating system (or multiple operating systems), including various versions of operating systems provided by MICROSOFT (such as WINDOWS), APPLE (such as Mac OS X), UNIX, RTOS, and LINUX, and may include operating systems specifically developed for handheld devices (e.g., iOS, ANDROID, RTOS, and/or BLACKBERRY), personal computers, servers, and other computing platforms depending on the use of the system 1200. The operating system, as well as other instructions (e.g., for telecommunications and/or other functions provided by the system 1200), may be stored in the memory unit 1204 and executed by the processor 1202. For example, the memory unit 1204 can include instructions for causing articles to be transported along a path within an apparatus, and for using data gathered from optical sensors to perform article identification and authentication.

[0084] The network 1220 may be a single network or may represent multiple networks, including networks of different types, whether wireless or wired. For example, the system 1200 may be coupled to external devices via a network that includes a cellular link coupled to a data packet network, or may be coupled via a data packet link such as a wide local area network (WLAN) coupled to a data packet network or a Public Switched Telephone Network (PSTN). Accordingly, many different network types and configurations may be used to couple the system 1200 with external devices.

[0085] One example embodiment of this disclosure can include a multiwavelength optical sensor that includes an illuminator for being disposed in an article detection area. The illuminator includes an illuminator housing, one or more light-emitting diodes (LEDs) of different wavelengths disposed in the illuminator housing, and a light bar disposed in the illuminator housing, the light bar including a light guide and a diffuser having a thickness, and a width corresponding to a shape of a bottom portion of the light guide, wherein light emitted by the one or more LEDs are reflected within the light guide and the light is scattered by the diffuser through the light guide for transmission outside the illuminator. The multiwavelength optical sensor also includes a photodetector for being disposed opposite the illuminator in the article detection area. The photodetector includes a photodetector housing, a photodiode array disposed within the photodetector housing, and a diaphragm array having a plurality of vertical walls for controlling the scattered light transmitted by the illuminator and decreasing stray light effects.

[0086] In one or more of the above examples, the thickness of the diffuser is of a bulk material.

[0087] In one or more of the above examples, the bulk material is a plastic.

[0088] In one or more of the above examples, the photodetector further includes a light diffuser disposed within the photodetector housing and between the diaphragm array and the illuminator.

[0089] In one or more of the above examples, the photodetector further includes a light shield for preventing stray light from entering the photodetector, and wherein the light shield includes a cutout within which the light diffuser of the photodetector is disposed.

[0090] In one or more of the above examples, the photodetector further includes a lens array disposed within the photodetector housing and between the photodiode array and the diaphragm array.

[0091] In one or more of the above examples, each photodiode of the photodiode array includes another diaphragm disposed between the photodiode and the lens array, and wherein the other diaphragm includes a cutout for controlling light passing through a lens of the lens array and to the photodiode.

[0092] In one or more of the above examples, at least a portion of the photodetector housing is covered by a protective transparent cover.

[0093] In one or more of the above examples, the light guide and the diffuser are made of a same base material.

[0094] In one or more of the above examples, at least a portion of the illuminator housing is covered by a protective transparent cover.

[0095] In one or more of the above examples, the light guide includes sloping sides for deflecting light emitted from the one or more LEDs into a central portion of the light bar.

[0096] In one or more of the above examples, each sloping side of the light guide is covered with a light shield attached thereto to prevent light from leaking outside the light guide.

[0097] In one or more of the above examples, the one or more LEDs of different wavelengths arranged in an LED array disposed below the sloping sides of the light guide. [0098] In one or more of the above examples, the width of the diffuser of the light bar corresponding to the shape of the bottom portion of the light guide forms a transition layer between the diffuser and the light guide that is optically inactive.

[0099] Another example embodiment of this disclosure can include a light bar for an optical device, comprising a light guide having ends having a shape for deflecting light into a central portion of the light guide and a diffuser having a thickness, and a width corresponding to a shape of a bottom portion of the light guide, wherein light reflected within the light guide is scattered by the diffuser through the light guide for transmission, and wherein the light bar provides a stable indicatrix of illumination.

[0100] In one or more of the above examples, the thickness of the diffuser is of a bulk material.

[0101] In one or more of the above examples, the bulk material is a plastic.

[0102] In one or more of the above examples, the shape of each end of the light guide is a sloping shape.

[0103] In one or more of the above examples, each end of the light guide is covered with a light shield attached thereto to prevent light from leaking outside the light bar.

[0104] In one or more of the above examples, each end of the light guide includes leg portions extending transversely from the respective end and on either side of a body of the light guide.

[0105] In one or more of the above examples, the width of the diffuser of the light bar corresponding to the shape of the bottom portion of the light guide forms a transition layer between the diffuser and the light guide that is optically inactive.

[0106] Another example embodiment of this disclosure can include a method that includes detecting, by a multiwavelength optical sensor, an article in an article detection area of an apparatus, wherein the multiwavelength optical sensor includes an illuminator disposed in the article detection area. The illuminator includes an illuminator housing, one or more light-emitting diodes (LEDs) of different wavelengths disposed in the illuminator housing, and a light bar disposed in the illuminator housing, the light bar including a light guide and a diffuser having a thickness, and a width corresponding to a shape of a bottom portion of the light guide. The multiwavelength optical sensor also includes a photodetector disposed opposite the illuminator in the article detection area. The photodetector includes a photodetector housing, a photodiode array disposed within the photodetector housing, and a diaphragm array having a plurality of vertical walls. Detecting the article includes emitting light by the one or more LEDs, reflecting the emitted light within the light guide and scattering the light by the diffuser through the light guide for transmission outside the illuminator, receiving the scattered light, transmitted by the illuminator, by the photodetector and controlling the scattered light using the plurality of vertical walls of the diaphragm array and decreasing stray light effect.

[0107] In one or more of the above examples, the thickness of the diffuser is of a bulk material.

[0108] In one or more of the above examples, the bulk material is a plastic.

[0109] In one or more of the above examples, the method further comprises preventing stray light from entering the photodetector using a light shield included in the photodetector and disposed between the diaphragm array and the illuminator, wherein the light shield includes a cutout within which a light diffuser of the photodetector is disposed and redirecting a portion of the scattered light back to the article using the light diffuser.

[OHO] In one or more of the above examples, the photodetector further includes a lens array disposed within the photodetector housing and between the photodiode array and the diaphragm array.

[0111] In one or more of the above examples, each photodiode of the photodiode array includes another diaphragm disposed between the photodiode and the lens array, and the method further includes controlling light passing through the lens of the lens array and to the photodiode using a cutout included in the other diaphragm.

[0H2] In one or more of the above examples, at least a portion of the photodetector housing is covered by a protective transparent cover, and wherein at least a portion of the illuminator housing is covered by a protective transparent cover.

[0H3] In one or more of the above examples, the method further comprises deflecting light emitted from the one or more LEDs into a central portion of the light guide using sloping sides of the light guide.

[0H4] In one or more of the above examples, the method further comprises preventing light from leaking outside the light guide using a light shield attached to each sloping side of the light guide.

[0H5] In one or more of the above examples, the one or more LEDs of different wavelengths arranged in an LED array disposed below the sloping sides of the light guide.

[0H6] In one or more of the above examples, the width of the diffuser of the light bar corresponding to the shape of the bottom portion of the light guide forms a transition layer between the diffuser and the light guide that is optically inactive.

[0H7] While this disclosure has described certain embodiments and generally associated methods, alterations and permutations of these embodiments and methods will be apparent to those skilled in the art. Accordingly, the above description of example embodiments does not define or constrain this disclosure. Other changes, substitutions, and alterations are also possible without departing from the spirit and scope of this disclosure, as defined by the following claims.

[0118] None of the description in this application should be read as implying that any particular element, step, or function is an essential element that must be included in the claim scope. The scope of patented subject matter is defined only by the claims. Moreover, none of the claims is intended to invoke 35 U.S.C. § 112(f) unless the exact words “means for” are followed by a participle.

Claims

WHAT IS CLAIMED IS:

1. A multiwavelength optical sensor comprising: an illuminator for being disposed in an article detection area, the illuminator including: an illuminator housing; one or more light-emitting diodes (LEDs) of different wavelengths disposed in the illuminator housing; and a light bar disposed in the illuminator housing, the light bar including: a light guide; and a diffuser having a thickness, and a width corresponding to a shape of a bottom portion of the light guide, wherein light emitted by the one or more LEDs are reflected within the light guide and the light is scattered by the diffuser through the light guide for transmission outside the illuminator.

2. The multiwavelength optical sensor of Claim 1, further comprising: a photodetector for being disposed opposite the illuminator in the article detection area, the photodetector including: a photodetector housing; a photodiode array disposed within the photodetector housing; and a diaphragm array having a plurality of vertical walls for controlling scattered light transmitted by the illuminator and decreasing stray light effects.

3. The multiwavelength optical sensor of Claim 2, wherein the photodetector further includes a light diffuser disposed within the photodetector housing and between the diaphragm array and the illuminator.

4. The multiwavelength optical sensor of Claim 3, wherein the photodetector further includes a light shield for preventing stray light from entering the photodetector, and wherein the light shield includes a cutout within which the light diffuser of the photodetector is disposed.

5. The multiwavelength optical sensor of Claim 2, wherein the photodetector further includes a lens array disposed within the photodetector housing and between the photodiode array and the diaphragm array.

6. The multiwavelength optical sensor of Claim 5, wherein each photodiode of the photodiode array includes another diaphragm disposed between the photodiode and the lens array, and wherein the other diaphragm includes a cutout for controlling light passing through a lens of the lens array and to the photodiode.

7. The multiwavelength optical sensor of Claim 2, wherein at least a portion of the photodetector housing is covered by a protective transparent cover.

8. The multiwavelength optical sensor of Claim 1, wherein the light guide and the diffuser are made of a same base material.

9. The multiwavelength optical sensor of Claim 1 , wherein at least a portion of the illuminator housing is covered by a protective transparent cover.

10. The multiwavelength optical sensor of Claim 1, wherein the light guide includes sloping sides for deflecting light emitted from the one or more LEDs into a central portion of the light guide.

11. The multiwavelength optical sensor of Claim 10, wherein each sloping side of the light guide is covered with a light shield attached thereto to prevent light from leaking outside the light guide.

12. The multiwavelength optical sensor of Claim 11 , wherein the one or more LEDs of different wavelengths are arranged in an LED array disposed below the sloping sides of the light guide.

13. The multiwavelength optical sensor of Claim 1, wherein the width of the diffuser of the light bar corresponding to the shape of the bottom portion of the light guide forms a transition layer between the diffuser and the light guide that is optically inactive.

14. A light bar for an optical device, comprising: a light guide having ends having a shape for deflecting light into a central portion of the light guide; and a diffuser having a thickness, and a width corresponding to a shape of a bottom portion of the light guide, wherein light reflected within the light guide is scattered by the diffuser through the light guide for transmission, and wherein the light bar provides a stable indicatrix of illumination.

15. The light bar of Claim 14, wherein the shape of each end of the light guide is a sloping shape.

16. The light bar of Claim 15, wherein each end of the light guide is covered with a light shield attached thereto to prevent light from leaking outside the light guide.

17. The light bar of Claim 14, wherein each end of the light guide includes leg portions extending transversely from the respective end and on either side of a body of the light guide.

18. The light bar of Claim 14, wherein the width of the diffuser of the light bar corresponding to the shape of the bottom portion of the light guide forms a transition layer between the diffuser and the light guide that is optically inactive.

19. A method comprising: detecting, by a multiwavelength optical sensor, an article in an article detection area of an apparatus, wherein the multi wavelength optical sensor includes: an illuminator disposed in the article detection area, the illuminator including: an illuminator housing; one or more light-emitting diodes (LEDs) of different wavelengths disposed in the illuminator housing; and a light bar disposed in the illuminator housing, the light bar including: a light guide; and a diffuser having a thickness, and a width corresponding to a shape of a bottom portion of the light guide; and a photodetector disposed opposite the illuminator in the article detection area, the photodetector including: a photodetector housing; a photodiode array disposed within the photodetector housing; and a diaphragm array having a plurality of vertical walls; wherein detecting the article includes: emitting light by the one or more LEDs; reflecting the emitted light within the light guide and scattering the light by the diffuser through the light guide for transmission outside the illuminator; and receiving scattered light, transmitted by the illuminator, by the photodetector and controlling the scattered light using the plurality of vertical walls of the diaphragm array and decreasing stray light effect.

20. The method of Claim 19, wherein the width of the diffuser of the light bar corresponding to the shape of the bottom portion of the light guide forms a transition layer between the diffuser and the light guide that is optically inactive.