Abstract:
A system for authenticating an object ( 12 ) includes an object having fluorescent indicia ( 14 ), wherein the indicia includes at least two different types of particles which fluoresce upon exposure to light ( 15 ) and which have different decay rates, a lamp ( 32 ) for exposing the indicia to light and causing the plurality of particles to fluoresce, a sensor ( 22 ) for capturing at least a first image of the indicia at a first time and a second image of the indicia at a second time different from the first time, means for analyzing the images to determine decay rates of the at least two types of particles, and means for authenticating the object if the decay rates match stored information.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    Reference is made to commonly-assigned copending U.S. patent application Ser. No. 13/755,296 (now U.S. Publication No. 2014/0210998), filed Jan. 31, 2013, entitled METHOD FOR AUTHENTICATING AN OBJECT, by Pawlik et al.; U.S. patent application Ser. No. ______ (Attorney Docket No. K001867), filed herewith, entitled SYSTEM FOR DETECTING UV-FLUORESCENT INDICIA WITH A CAMERA, by Pawlik et al.; U.S. patent application Ser. No. ______ (Attorney Docket No. K001868), filed herewith, entitled METHOD OF AUTHENTICATING AN OBJECT, by Pawlik et al.; U.S. patent application Ser. No. ______ (Attorney Docket No. K001317), filed herewith, entitled DETECTING UV-FLUORESCENT MATERIALS WITH A CAMERA, by Pawlik et al.; the disclosures of which are incorporated herein. 
       FIELD OF THE INVENTION 
       [0002]    This invention relates in general to authentication of objects having fluorescent indicia and in particular to authentication of objects using a cell phone. 
       BACKGROUND OF THE INVENTION 
       [0003]    Applying invisible covert marks and indicia to products, product packaging, documents and printed materials is a well established method for authenticating products and thus combating counterfeiting. In addition, when variable invisible information is printed, batch-level and item-level tracking of products can be accomplished in a covert manner. Common covert marking materials are ultraviolet (UV) fluorescent inks. The security information is invisible under normal, visible lighting but is revealed when a UV light source is used, such as a UV flashlight. The product or document of interest is authenticated by revealing the invisible indicia with the UV flashlight and visually verifying the image or human-readable text or code that is revealed. While this can be an effective security feature, the authentication process has limitations. 
         [0004]    When authenticating products and documents in the field, it is desirable for investigators to perform their audits in a covert manner, often without handling the item to be authenticated or using extraneous or unusual devices to reveal the covert indicia. It is therefore useful to be able to authenticate an item from some distance, not require the revealing device be in close proximity to the product, and to use revealing devices that are commonplace and inconspicuous. 
         [0005]    During investigations, it is often the case that many items need to be authenticated sequentially, and the results of the authentication audit transmitted to another location. It is therefore useful to be able to automate the method for recording and storing the results and to have a convenient means for transmitting the results once collected. In these cases, a UV flashlight alone is not adequate to support the required workflow. 
         [0006]    It is also sometimes desirable to have an immediate response to a positive or negative authentication audit. It is therefore useful to have a system that can not only transmit the results of an authentication audit, but also receive a response to the authentication. 
         [0007]    Because acquiring information in the field is frequently a requirement, mobile devices are extremely useful when conducting investigations. It is also useful to be able to acquire images of indicia, display such images and analyze them with mobile devices. For example, smart phones include useful sensors, flashes for light exposures, and microprocessors for processing data and images. However, such devices are designed to detect visible indicia and are not suitable for detecting covert invisible indicia. 
         [0008]    It is also often desirable to encode a large amount of data in invisible indicia, for example an item-level serialized number. To reduce the amount of space required to print the data or to speed up reading the printed information, the data can be printed in the form of a machine-readable code rather than a human-readable code, for example a linear or two-dimensional bar code. It is therefore useful to be able to quickly and conveniently decode a revealed, covert machine-readable code to be able to quickly authenticate the item. Again, in these cases, a UV flashlight is insufficient to support the required workflow. 
         [0009]    In addition to fluorescent materials, phosphorescent materials can be used to create invisible indicia. Phosphorescent materials not only have a signature wavelength of light that is emitted, they also have a signature rate of decay of that emission. It is well known that rates of decay can be determined by measuring the intensity of emission at varying time points. It is also well known that the wavelength of emission and rate of decay of emission are characteristics that can be used to identify phosphorescent materials. 
       SUMMARY OF THE INVENTION 
       [0010]    Briefly, according to one aspect of the present invention, a system for authenticating an object includes an object having fluorescent indicia, wherein the indicia includes at least two different types of particles which fluoresce upon exposure to light and which have different decay rates, a lamp for exposing the indicia to light and causing the plurality of particles to fluoresce, a sensor for capturing at least a first image of the indicia at a first time and a second image of the indicia at a second time different from the first time, means for analyzing the images to determine decay rates of the at least two types of particles, and means for authenticating the object if the decay rates match stored information. 
         [0011]    In another embodiment of the present invention the conversion device comprises a photovoltaic device that converts the visible light emitted by the camera flash to electrical power, and a UV lamp that converts the electric power to UV light. The conversion device can also contain a capacitor. 
         [0012]    The conversion device can be affixed to the camera in any of a number of ways including via adhesives, mechanical hardware, and magnets. The conversion device can also be incorporated into a case or a shell that is attached to the camera, for example in a manner similar to cases and shells that are used with mobile phones (also referred to as cell phones and smart phones) or tablet devices. 
         [0013]    According to another aspect of the present invention, the method can further involve analyzing the captured image with a microprocessor, using the microprocessor to compare the analyzed image to stored, reference, or standard information to determine a match, and then authenticating the image if there is a match. By association, if the image is authentic then so is the item having the image. 
         [0014]    According to another aspect of the present invention, the method can further involve displaying the captured image with a display on the camera and comparing the displayed image to a stored or reference or standard image and authenticating the image (and therefore item) if there is a match. 
         [0015]    According to another aspect of the present invention, the method can further involve transmitting the captured image from the camera to a remote computer for comparison to a stored, reference or standard image and authenticating the image (and therefore item) if there is a match. The result of the authentication audit can then be transmitted back to the camera. 
         [0016]    In one embodiment of the present invention the camera, flash, sensor, microprocessor and memory are components of a cell phone or smart phone. 
         [0017]    According to one aspect of the present invention a method of authenticating an object includes mounting a visible-to-UV light conversion device over a flash on a camera or cell phone; activating the camera to initiate a visible-light flash exposure; converting visible light from the flash to UV light with the conversion device; capturing an image of indicia on the object with the sensor on the camera or cell phone; analyzing the captured image; comparing the analyzed image to stored information to determine a match; and authenticating the object if the captured image matches the stored information. 
         [0018]    According to an aspect of the present invention the UV-light-fluorescent indicia comprise a plurality of UV-responsive materials that can differ in their characteristic response to UV illumination. The response characteristic can be color of emitted light, brightness (or luminance) of emitted light, or rate of decay of emitted light. The indicia can be an image, text, a graphic element, a bar code, or a logo. 
         [0019]    In a method of the present invention an object is authenticated by applying indicia to the object, for example a product or document. The indicia comprises at least two different types of particles that fluoresce upon exposure to light and have different decay rates. The method further includes exposing the indicia to light from a lamp causing the plurality of particles to fluoresce; capturing at least a first image of the indicia with a sensor at a first time and a second image of the indicia at a second time different from the first time; analyzing the images to determine decay rates of the at least two types of particles; and authenticating the object if the decay matches stored or reference information. 
         [0020]    The invention and its objects and advantages will become more apparent in the detailed description of the preferred embodiment presented below. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]      FIG. 1  is a schematic representation of a camera comprising a flash, a sensor, a microprocessor and memory; 
           [0022]      FIG. 2  is a schematic representation of the visible-to-UV light conversion device; 
           [0023]      FIG. 3  is a plot showing the transient voltage obtained from a specific photo cell connected to a resistive load of 3.3 kOhm over time; 
           [0024]      FIG. 4  is a representation of a code captured with a smart phone with attached visible-to-UV light conversion device; 
           [0025]      FIG. 5  is a schematic representing a variant of the visible-to-UV light conversion device that incorporates control electronics and energy storage in addition to the components shown in  FIG. 2 ; 
           [0026]      FIG. 6  is a schematic representation of the front and back sides of a smart phone indicating the display, camera and flash; 
           [0027]      FIG. 7  is a schematic of the visible-to-UV light conversion device placed over the flash of a smart phone; 
           [0028]      FIG. 8  is a schematic representation of an object wherein the indicia consist of two UV-responsive materials and that are spatially arranged in a pattern; 
           [0029]      FIG. 9  is a schematic representation of an object wherein the indicia consist of two UV-responsive materials that are randomly distributed; 
           [0030]      FIG. 10  is a schematic representation of an object wherein the indicia consist of two UV-responsive materials printed to form parts of a text string; 
           [0031]      FIG. 11  is a schematic representation of a sequence of image captures of the object in  FIG. 10  wherein the first and third images are captured with the sensor when the camera flash is not operated, and the second image is captured when the flash is operated; 
           [0032]      FIG. 12  is a schematic representation of a sequence of image captures of the object of  FIG. 10  where the first image is captured with the sensor when the camera flash is not operated and the second and third images are captured when the flash is operated; and 
           [0033]      FIG. 13  is a plot of the time behavior of the emission of two UV responsive materials undergoing two sequential flash exposures and representations of the corresponding images captured at specified times. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0034]    The present invention will be directed in particular to elements forming part of, or in cooperation more directly with the apparatus in accordance with the present invention. It is to be understood that elements not specifically shown or described may take various forms well known to those skilled in the art. 
         [0035]      FIG. 1  shows a schematic representation of a camera  18  comprising a flash  20 , a sensor  22 , a microprocessor  26 , and a memory  28 . Mounted in front of the flash is a visible-to-UV light conversion device  24 . This device transforms the incident visible light  15  from the flash  20  into UV light  16 . The conversion device  24  can be attached to the camera  18  by way of a clamp, magnet, adhesive, shell, or sleeve or other methods of attachment. The emitted UV light  16  exposes an object  12  with invisible indicia  14 . The indicia  14  absorb UV light and emit visible light  17 . The visible light is captured by the sensor  22  thus capturing a digital image of the indicia  14 . The digital image is read by the microprocessor  26  and stored in the memory  28 . 
         [0036]    The microprocessor  26  can, for example, be used to compare the captured image to a stored reference image of an authentic object and the authentication process is based on the similarity of the captured image and the stored reference image. The invisible indicia could also be printed in the form of a machine readable code, for example a one or two-dimensional barcode. Examples of these barcodes are Data Matrix barcodes, QR-codes, linear barcode formats like 2 of 5 or code-128. The microprocessor analyzes the image of the invisible indicia and decodes the barcode using a decoding algorithm. Barcode decoding algorithms are well known and widely available. The decoded data are used to authenticate the object, by, for example, comparing the code value to stored values of valid codes. Thus, indicia (and objects) can be authenticated by comparing a captured image of the indicia to a stored reference image. Alternatively, the captured image can be analyzed, for example by processor  26 , to extract information from the captured image and the extracted information compared to reference information to authenticate the indicia if a match is found. 
         [0037]    The emission of light by a material or substance that has absorbed light, usually of a different wavelength, is referred to as luminescence. Two categories of luminescence are fluorescence and phosphorescence. Fluorescence is characterized by nearly immediate reradiation that ceases instantly when the incident light stops. Reradiation that continues for a noticeable time after the incident light has stopped is referred to as phosphorescence. Certain materials can also change color upon exposure to light. This effect is called photochromism. Copper-activated zinc sulfide or rate earth-doped strontium aluminates are examples of materials that exhibit phosphorescence with long phosphorescence lifetimes. 
         [0038]      FIG. 2  shows a schematic representation of the visible-to-UV light conversion device  24 . It includes a photovoltaic device  30  that converts the incident visible light  15  into electrical energy. This photovoltaic device  30  is connected via electrical connections  34  to a UV lamp  32 . The UV lamp  32  uses the electrical energy supplied by the photovoltaic device  30  to generate UV light. A light shield  36  blocks visible light and prevents it from reaching the object  12 . An example of a UV lamp is the UV LED, part number XSL-370-3E, supplied by Roithner Lasertechnik GmbH, Vienna, Austria. This LED emits UV light of 370 nm wavelength when supplied with a typical voltage of 3.3 V at a current of 1 mA. 
         [0039]    In an embodiment, a typical single silicon photocell used as a photovoltaic device  30  has an output voltage of just 0.6 V (open circuit). At peak power, output voltages are typically 15-20% lower. Therefore, in such an embodiment the output voltage of a single silicon photocell is insufficient to operate the UV LED. Mechanisms exist to increase voltages at the expense of current by employing voltage multipliers. These circuits first convert the supply DC voltage to a pulsed or AC voltage and then use charge pumps made of diodes and rectifiers, or transformers to generate the higher voltage. The use of a voltage multiplier, however, adds complexity and size to the visible-to-UV conversion device  24 . 
         [0040]    Another way to increase the voltage of a photovoltaic cell is to connect several photovoltaic cells in series. While most of the serially connected photovoltaic devices are large area solar cells and therefore unsuitable to collect the light in close proximity from the small flash of a camera  18 , a few devices exist that consist of serially connected photovoltaic devices with a small active area. One example of such a device is a 4V output photo cell, part number CPC1842N, by Clare Inc, Beverly, Mass. This device is rated to produce 4V/0.1 mA under direct sunlight. It has an active area of 3.5 mm by 2.7 mm, which is comparable in size to the active area of a white LED flash used in most smart phone cameras. Tests were conducted using this device mounted in front of and facing the flash LED of a Samsung Galaxy S3 smart phone (Samsung Electronics, South Korea) in order to determine the electrical voltage and current that can be obtained during the image capture using the smart phone flash.  FIG. 3  shows the transient voltage obtained from CPC1842N connected to a resistive load of 3.3 kOhm. Prior to image capture the flash operates at a reduced current (torch mode) to assist focusing. During image capture, the flash operates at a higher current for a duration of 40 milliseconds. During this flash, the voltage measured at the output of the photovoltaic device is 3.45V. This equates to a current of 1.04 mA flowing through the 3.3 kOhm load resistor. This experiment demonstrates that the voltage and current output of the photovoltaic device is sufficient to operate the UV LED XSL-370-3E. 
         [0041]      FIG. 4  shows a representation of a code captured with the Samsung Galaxy S3 smart phone with attached visible-to-UV light conversion device  24 . The object  12  is a piece of paper with indicia printed with a UV-to-red fluorescent ink available as KODAK NEXPRESS Red Fluorescing Dry Ink from Eastman Kodak, Rochester, N.Y. The indicia are invisible under normal, visible light, but fluoresce under UV light to emit red light that can be detected by the sensor  22  in the camera  18 . The captured image can be analyzed and decoded by a QR decoder. The result of the decoding of the image in  FIG. 4  is the string http://www.kodak.com/go/nexpress. 
         [0042]      FIG. 5  shows a variant of the visible-to-UV light conversion device  24  that incorporates control electronics  38  and energy storage  40  (capacitor or rechargeable battery) in addition to the components shown in  FIG. 2 . The purpose of this addition is to capture the light of the flash that is emitted during the focusing operation, convert it to electrical energy using the photovoltaic device  30  and store the converted electrical energy in the energy storage device  40 . During image capture, this energy is added to the energy that is available from the flash during image capture and used to power the UV lamp. The control electronics control energy capture, storage and release. The difference in the light intensities of the flash and torch mode, when translated into voltage or current by the photovoltaic device can be used to distinguish the energy collection and storage from the energy release phases of the focusing and image capture process. 
         [0043]      FIG. 6  shows the front side  100  and back side  101  of a smart phone. A display  110  is located on the front side. The back side comprises camera  18  and flash  20 . The captured image of the object  12  containing invisible indicia  14  can be displayed on the display  110  in order to enable the operator to compare the displayed image to an expected standard and to ensure that converted light from the flash  20  reaches the object  12 . The smart phone also contains a wireless transmitter and receiver allowing bidirectional wireless data transmission  120  with a remote computer  122 , for example via a local area network, Bluetooth connection, or a cellular telephony network. This network connection allows the device to transmit the captured image to a remote computer where it is analyzed and compared to a standard to determine a match. Alternatively, if the invisible indicia comprise a machine readable code, it can be decoded by the microprocessor of the smart phone and the decoded data is sent via the wireless network to the remote computer to be compared to stored values of authentic objects. The result of the analysis by the remote computer can be transmitted back to the smart phone and displayed to the operator. In another embodiment, the local microprocessor  26  in the camera  18  performs the comparison to reference data stored in the local memory  28  to authenticate the object. 
         [0044]      FIG. 7  shows the visible-to-UV light conversion device  24  placed over the flash  20 . 
         [0045]      FIG. 8  is a schematic representation of an object  12  wherein the indicia consist of two UV-responsive materials  130  and  132  that are each spatially arranged in a pattern. The two materials  130  and  132  have a different response to the incident UV light and can differ in their color of emission, brightness of emission, rate of decay of emission, or a combination of these properties. Brightness of emission is also referred to as luminance. For example, material  130  could be a UV-to-green emissive material with a long lifetime of emission whereas material  132  could be a UV-to-red emissive material with a short lifetime of emission. UV-responsive materials can be in the form of inks, dyes, pigments, molecules, or particles. 
         [0046]      FIG. 9  is a schematic representation of an object  12  wherein the indicia consist of two UV-responsive materials  130  and  132  that are randomly distributed. 
         [0047]      FIG. 10  is a schematic representation of an object  12  wherein the indicia consist of two UV-responsive materials  130  and  132  printed to form parts of a text. 
         [0048]    Thus, in various embodiments, the UV-responsive materials in the indicia can form an image, a color image, a pattern, graphic element, random arrangement, or text. 
         [0049]      FIG. 11  is a schematic representation of a sequence of image captures of the object  12  in  FIG. 10  wherein the first image  150  is captured with the sensor when the flash is not operated. The second image is captured when the flash is operated and the third image is captured after the second image capture when the flash is not operated. The three images are acquired at regular intervals, although they could be acquired at irregular intervals. Many cameras have a mode of operation that allows image capture to occur in a burst mode, that is, multiple images are captured in rapid succession. As used herein, a burst mode can apply to either the flash (multiple flashes in rapid succession) or to image capture (multiple images captured in rapid succession). The flash burst mode can control the flash  20  to operate at regular intervals or at irregular intervals. Likewise, the image burst mode can control the sensor  22  to operate at regular intervals or at irregular intervals. In the first image  150 , the indicia are invisible because there is no incident UV light from the visible-to-UV light conversion device  24  (because the flash  20  was not operated). In the second image  152 , the indicia  14  are visible because the flash  20  is operated and the visible-to-UV light conversion device  24  is illuminating the object  12  with UV light. In the last image  154  that is acquired without flash, the indicia  14  are partly visible, because one of the UV-responsive materials  130  has an emission lifetime that is longer than the time between the capture of images  152  and  154  whereas the other UV-responsive material  132  has an emission lifetime that is shorter than the time between the capture of images  152  and  154 . Examples of UV-responsive materials with a long emission lifetime are rare-earth-doped strontium aluminates or copper-activated zinc sulfide. Examples of materials with a short emission lifetime include UV fluorescent dyes such as 7-hydroxycoumarin, CAS RN 93-35-6 or Disodium 2,2′-([1,1′-biphenyl]-4,4′-diyldivinylene)bis(benzenesulphonate) CAS RN 27344-41-8. Materials with intermediate emission lifetimes include europium chelates such as Eu[(3-thenoyltrifluoroacetonate) 3 (H 2 O) 2 ] CAS RN 21392-96-1. 
         [0050]    FIG. 12 is a schematic representation of a sequence of image captures of the object  12  in  FIG. 10  where the first image  160  is captured with the sensor when the flash  20  is not operated. The second and third images  162 ,  164  are captured when the flash  20  is operated. In the first image  160 , the indicia  14  are invisible because there is no incident UV light from the visible-to-UV light conversion device  24 . In the second and third image  162  and  164  the indicia  14  are visible because the flash  20  is operated, and the visible-to-UV light conversion device  24  is illuminating the object  12  with UV light. However, the two UV light responsive materials  130 ,  132  differ in their response to UV illumination. Material  130  reacts instantly to the exciting UV radiation reaching a stationary value of brightness in images  162  and  164 . In contrast, UV light responsive material  132  reacts slowly to the incident UV radiation and builds up emission intensity over time. Therefore the brightness of UV-responsive material  132  is higher in captured image  164  than image  162 . In  FIG. 12  brightness (or emission intensity) differences are depicted by representing the indicia  14  with a normal font for the less bright state of the characters “R”, “T”, and the first “E” in image  162  and a bold font for those same characters in the brighter state of image  164 . 
         [0051]      FIG. 13  shows the time behavior of the emission of two UV-responsive materials undergoing two sequential flash exposures. Illustrated are the moments in time corresponding to the first flash exposure  140 , the first image acquisition  141 , the second flash exposure  142 , the second image acquisition  143 , and a third image acquisition  145 . On the emission intensity axis, a threshold value  136  indicates the emission intensity level above which the pixel is considered in the on or 1 state and below which the pixel is considered to be in the off or 0 state. A microprocessor (e.g. microprocessor  26  in  FIG. 1 ) with appropriate software can analyze the image for emission intensity and determine the binary value, 1 or 0, for example by comparing the pixel emission intensity level to the threshold value  136 . In the image corresponding to the first image acquisition  141  after the first flash  140  the pixels that represent material  132  are on whereas the pixels that represent material  130  are off. In the image corresponding to the second image acquisition  143  the pixels that represent both material  132  and  130  are on because material  130  with the long emission lifetime retains some emission intensity from the first flash exposure  140  and consequently the second flash exposure  142  increases the emission intensity above the threshold level  136 . In the image corresponding to the third image acquisition  145  the pixels that represent material  130  are on because material  130  with the long emission lifetime retains some emission intensity from the first and second flash exposures  140 ,  142 . In contrast, the material  132  has decayed below the threshold level  136 . A comparison of the pixels in the three images makes it possible to distinguish indicia on an object that contain both types of UV-responsive materials from an object with indicia that are composed of just one of the UV-responsive materials or none at all. Authentication can depend on the location of the pixels of material  130  and pixels of material  132  in all three images. Thus, both the location and the temporal sequence of pixels form an authentication code dependent upon the sequence and timing of the flashes and the image captures. Note that, in this example, the image captures are at irregular intervals. 
         [0052]    In further embodiments, more than two flashes are used in sequence and more than two or more than three image captures are employed to authenticate an object  12 . For example material  130  could require three flashes to emit light with an intensity greater than the threshold level  136 . 
         [0053]    Thus, in various embodiments of the present invention, authentication can depend upon the presence of the different UV-responsive material, their rate of decay in response to UV-light exposure, to a pre-determined sequence of UV-light exposures, and to a pre-determined sequence of image captures. The UV-light exposures and image captures can be at regular intervals or irregular intervals. Image captures can be made immediately after a flash or independently of a flash. The sequence and timing of flashes and image captures can be used to control temporal material emission and thus to determine authenticity. 
         [0054]    The different materials can be located at spatially distinct locations, as in  FIGS. 8-12 . In another embodiment, the different materials are located in a visually common location. As the materials acquire energy or decay at different rates, the light emission at the visually common location can change color. For example, referring to  FIG. 12 , if material  130  emits red light and material  132  emits green light in response to UV illumination, the visually common location would change over time from green (green material  132  only) to yellow (both red and green materials  130 ,  132 ) to red (only red material  130 ). 
         [0055]    In another embodiment, the first captured image can be used to determine the number and timing of subsequent flash exposures and image captures. The first image can be analyzed to determine information that is then used to find flash and image capture timing information for subsequent flashes and image captures and to find authentication information, for example in a lookup table in memory  28 . Thus, the time until a second flash or image capture can depend upon information extracted from an image capture with a flash at a first time. 
         [0056]    An evaluation of images of a plurality of flash and non-flash exposures is not only useful for UV responsive materials, it can be applied to visible and IR responsive materials as well. Certain phosphors such as rare earth-doped strontium aluminates or copper-activated zinc sulfide exhibit phosphorescence upon exposure with visible light. In this situation, the image sequences described in  FIGS. 11-13  can be acquired using a visible flash exposure without a need for a visible-to-UV light conversion device. Other examples of materials that show a time variant change in appearance upon light exposure are photochromic materials. Such materials change their light absorption characteristics when exposed to a high intensity of light and revert back to their original state after some time in the absence of high intensity light. For these materials, the camera captures the change in the color of the reflected ambient light after flash exposure instead of capturing the luminescence from UV responsive materials. 
         [0057]    The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the scope of the invention. 
       PARTS LIST 
       [0000]    
       
           12  object 
           14  UV light fluorescent indicia 
           15  visible light 
           16  incident UV light 
           17  reflected visible light 
           18  camera 
           20  flash 
           22  sensor 
           24  visible-to-UV light conversion device 
           26  microprocessor 
           28  memory 
           30  photovoltaic device 
           32  UV lamp 
           34  electrical connection 
           36  light shield 
           38  control electronics 
           40  energy storage (capacitor or rechargeable battery) 
           100  mobile device with digital camera (smart phone)—front side 
           101  mobile device with digital camera (smart phone)—back side 
           110  display 
           120  data transmission (external communication, local area network communication, or cellular telephony communication) 
           122  remote computer 
           130  UV responsive particle with first response 
           132  UV responsive particle with second response 
           136  threshold emission intensity level 
           140  first flash exposure 
           141  first image acquisition 
           142  second flash exposure 
           143  second image acquisition 
           145  third image acquisition 
           150  first image when the flash is not operated 
           152  second image when flash is operated 
           154  third image when flash is not operated 
           160  first image when the flash is not operated 
           162  second image when flash is operated 
           164  third image when flash is operated