Abstract: Apparatus for producing an output signal responsive to a sensor signal having a unit for setting desired hysteresis values and desired reference values of the sensor signal, aunit for detecting whether the sensor signal has a positive or negative slope with respect to time, a unit for triggering one logical signal when the sensor signal has a positive slope and also exceeds one reference value minus a first hysteresis value, and a unit for triggering another logical signal when the sensor signal has a negative slope and also falls below the sum of a second reference value and a second hysteresis value. The apparatus and method may have more than two reference values and/or more than two hysteresis values simultaneously. The apparatus may be implemented by an embedded microcomputer of conventional type, programmed to perform the signal-processing disclosed. The steps of the process and initial values of the reference values and hysteresis values may be stored in a read-only memory.

Abstract: An authentication system combines a source of ultraviolet light (and optionally a scanning mechanism) with apparatus for capturing and recognizing either graphic images or characters or both, where the graphic images and/or characters have been previously made with fluorescent substances that may be invisible under ordinary visible light, but are rendered detectable by the ultraviolet light. As in conventional optical character recognition (OCR), the characters may be conventional alphanumeric characters readable by human readers once they are made visible. The authentication system has a housing enclosing its optical path, a source of UV light, a detector for detecting graphic images or characters, conversion of the detector signal to digital form, a memory storing predetermined indicia, recognition logic, and indicating means. The system may also include a scanning mechanism and optical filters to select predetermined wavelengths of fluorescent light.

Abstract: An authentication system combines a source of ultraviolet light (and optionally a scanning mechanism) with apparatus for capturing and recognizing either graphic images or characters or both, where the graphic images and/or characters have been previously made with fluorescent substances that may be invisible under ordinary visible light, but are rendered detectable by the ultraviolet light. As in conventional optical character recognition (OCR), the characters may be conventional alphanumeric characters readable by human readers once they are made visible. The authentication system has a housing enclosing its optical path, a source of UV light, a detector for detecting graphic images or characters, conversion of the detector signal to digital form, a memory storing predetermined indicia, recognition logic, and indicating means. The system may also include a scanning mechanism and optical filters to select predetermined wavelengths of fluorescent light.

Abstract: An improved laser printer or photocopier toner for authentication is made by mixing conventional toner particles with submicron ultraviolet sensitive particles that exhibit detectable characteristics in response to ultraviolet radiation. A document printed using the improved toner can be authenticated using a UV scanner.

Abstract: Proposed is a grain boundary-free crystalline body of a perovskite structure having a chemical composition of the formula Pr.sub.1-x M.sub.x MnO.sub.3, in which M is calcium or strontium and the subscript x is a number of 0.3 to 0.5, which exhibits a magnetoresistance behavior with a phase transition between an insulator phase and a ferromagnetic metallic phase accompanied by the phenomenon of hysteresis. This grain boundary-free crystalline body can be obtained by subjecting a sintered body of a powder blend consisting of the oxides of praseodymium, manganese and calcium or strontium to a crystal growing treatment by the floating zone-melting method in an atmosphere of oxygen.

Abstract: A multiple-reader system for authentication of articles uses a first reader (400) which employs predetermined modulated illuminating light (20) and a multiplicity of discriminating variables, such as wavelengths (110), amplitudes (120), and time delays (140) relative to the modulated illuminating light (20) to characterize fluorescent light (70) detected from fluorescent indicia on the articles. The fluorescent indicia may also incorporate spatial distributions such as bar codes as discriminating features. Additional readers (410 and 420), which may be readers of fluorescent marks and/or readers of other indicia, are synchronized with the fluorescence reader by timing signals. The discriminating features may be re-programmed by the user of the authentication system. Thus the discriminating features define a user-determined and programmable encryption of the articles' authentic identity.

Abstract: A release agent is first applied to a target article and on top of the release agent is applied an ultraviolet radiation fluorescent material to enable fraud detection. To prevent fraud, a security label may also be used comprising a label substrate, a release layer, a layer of ultraviolet radiation fluorescent material, and an adhesive layer for adhering to a target article. When the substrate is peeled off, part of the ultraviolet sensitive material will be peeled off also to enable detection.

Abstract: A multiple-reader system for authentication of articles uses a first reader (400) which employs predetermined modulated illuminating light (20) and a multiplicity of discriminating variables, such as wavelengths (110), amplitudes (120), and time delays (140) relative to the modulated illuminating light (20) to characterize fluorescent light (70) detected from fluorescent indicia on the articles. The fluorescent indicia may also incorporate spatial distributions such as bar codes as discriminating features. Additional readers (410 and 420), which may be readers of fluorescent marks and/or readers of other indicia, are synchronized with the fluorescence reader by timing signals. The discriminating features may be re-programmed by the user of the authentication system. Thus the discriminating features define a user-determined and programmable encryption of the articles' authentic identity.

Abstract: Accessory apparatus for authenticating articles is used in conjunction with existing readers or scanners of articles bearing stored data, such as credit cards or identification cards. The accessory apparatus is disposed before, after, on, under, inside, or adjacent to existing reader apparatus, to have a view of the article whose data is to be read. Information in addition to the stored data is coded on the article in non-visible indicia and is detected by the accessory authenticating apparatus. This coded additional information may be related to identification data stored in the article by the article's normal storage mechanism, such as a magnetic stripe or an embedded memory IC chip. The additional information may be coded in various combinations of predetermined characteristics of light emitted by the article to be authenticated when the article is irradiated with non-visible light from the accessory apparatus.

Abstract: A system for authentication of articles uses a multiplicity of discriminating variables to characterize light detected from the articles after predetermined illumination. Articles are tested which have been marked with substances such as dye or ink that fluoresce in a region of the optical spectrum when illuminated with light in another region of the spectrum, such as the ultraviolet region. The authentication system illuminates the articles with light modulated at a frequency of more than about 50 kHz, and secondary fluorescent light returned from the articles is synchronously detected. A programmable microcomputer digitizes the synchronously detected signal and analyzes it to compare the signal with predetermined standard digital signals. The standard signals incorporate a number of discriminating features, for example the fluorescent light's wavelengths, amplitudes, and time delays relative to the modulated illuminating light.

Abstract: The response of a fluorescence detector is calibrated using apparatus and methods for both static and dynamic calibrations. The apparatus and methods are especially suited for portable use in field calibration of fluorescence detectors of authentication systems that use non-visible light. The calibration apparatus incorporates standard target elements (20) comprising predetermined fluorescent substances with known emission spectra, and either non-fluorescent substances or fluorescent substances with other known emission spectra. The substances are either mixed in predetermined proportions, or one substance is arranged in a predetermined pattern (170), such as a bar code, on the other substances. An aperture (30) exposes a predetermined surface area of a standard target element to the view of the fluorescence detector. The distance of the standard target element from the optical front end (70) of the fluorescence detector to be calibrated is adjustable (50).