Abstract: A method and apparatus for providing non-linear, passive quenching of avalanche currents in Geiger-mode avalanche photodiodes (APDs) is provided. A non-linear, passive, current-limiting device is connected in series with the APD and a bias source. The non-linear, passive, current-limiting device rapidly quenches avalanche currents generated by the APD in response to an input photon and resets the APD for detecting additional photons, using a minimal number of components. The non-linear, passive, current-limiting device could comprise a field-effect transistor (FET), as well as a junction FET (JFET) a metal-oxide semiconductor FET (MOSFET), or a current-limiting diode (CLD) connected in series with the APD and the bias source.

Abstract: A method and apparatus for providing non-linear, passive quenching of avalanche currents in Geiger-mode avalanche photodiodes (APDs) is provided. A non-linear, passive, current-limiting device is connected in series with the APD and a bias source. The non-linear, passive, current-limiting device rapidly quenches avalanche currents generated by the APD in response to an input photon and resets the APD for detecting additional photons, using a minimal number of components. The non-linear, passive, current-limiting device could comprise a field-effect transistor (FET), as well as a junction FET (JFET) a metal-oxide semiconductor FET (MOSFET), or a current-limiting diode (CLD) connected in series with the APD and the bias source.

Abstract: A method and apparatus for providing non-linear, passive quenching of avalanche currents in Geiger-mode avalanche photodiodes (APDs) is provided. A non-linear, passive, current-limiting device is connected in series with the APD and a bias source. The non-linear, passive, current-limiting device rapidly quenches avalanche currents generated by the APD in response to an input photon and resets the APD for detecting additional photons, using a minimal number of components. The non-linear, passive, current-limiting device could comprise a field-effect transistor (FET), as well as a junction FET (JFET) a metal-oxide semiconductor FET (MOSFET), or a current-limiting diode (CLD) connected in series with the APD and the bias source.

Abstract: Methods for detecting the presence or absence of ice or liquid water on surfaces are provided. In a first embodiment of the invention, a reflectance spectrum from a surface to be tested is measured using any suitable near-infrared optical system. The midpoint wavelength of the transition or step of the measured reflectance spectrum near 1.4 microns is calculated, and compared to a decision threshold wavelength. If the midpoint wavelength is less than the decision threshold wavelength, the presence of liquid water on the surface is indicated. If the midpoint wavelength is greater than the decision threshold wavelength, the presence of ice is indicated on the surface. In a second embodiment of the invention, at least three reflectance levels are measured at three wavelengths, and a dimensionless decision function is applied to the measured reflectance levels. Output of the decision function is compared to at least two pre-defined ranges.

Abstract: An electrical discharge measurement device for non-contact measurement of an electrical discharge having a discharge magnitude. The electrical discharge causes a corresponding emission of optical radiation. The electrical discharge measurement device has a light-collecting device for forming an image from the optical radiation from the electrical discharge, and an optical filter operatively coupled to the light-collecting device for preferentially selecting wavelengths at which the electrical discharge emits relatively intense optical radiation. An optical detector receives light from the light-collecting device and filtered by the optical filter for converting the filtered light to an electrical signal. An electronic signal-processing device provides, based on the electrical signal, a quantitative discharge measurement related to the magnitude of the electrical discharge.

Abstract: A corona detector for detecting a corona associated with a remote object under outdoor daylight conditions. A selective optical filter filters light from the remote object, wherein the optical filter passes one or more of the corona emission bands centered at wavelengths below approximately 290 nanometers (nm) and rejects radiation at wavelengths above approximately 290 nm. A operatively coupled to the optical filter forms an image of the remote object, the lens having high transmissivity in the ultraviolet spectrum.

Abstract: A corona detector for detecting a corona associated with a remote object. In one embodiment, the corona detector employs an optical filter having at least one passband centered at a wavelength corresponding with one of the molecular nitrogen emission spectrum second positive emission lines in the visible spectrum for filtering light from the remote object. A lens operatively coupled to the optical filter forms an image of the remote object, the lens having high transmissivity in the visible spectrum.

Abstract: A corona detector for detecting a corona associated with a remote object. In one embodiment, the corona detector employs an optical filter having at least one passband centered at a wavelength corresponding with one of the molecular nitrogen emission spectrum second positive emission lines for filtering light from the remote object. A lens operatively coupled to the optical filter forms an image of the remote object, the lens having high transmissivity in the ultraviolet spectrum.

Abstract: An apparatus and method for sorting documents is provided. A document transport on the apparatus conveys documents along a selected path of movement from an input bin to a series of output bins. An optical scanner, such as a video camera, is positioned along the selected path to capture images of the documents. The captured images are displayed on a display monitor to permit an operator to inspect portions of the documents for a desired characteristic. The operator activates a push button on a selector switch depending on the presence of the desired characteristic. Bins are provided for stacking and separating documents having the desired characteristic from those documents lacking the desired characteristic. Gates are provided for directing the documents to the appropriate output bin.

Abstract: An electro-optic sampler utilizes a Pockels cell comprising an electro-optic crystal and a separate, removable sample carrier having an electrical transmission line affixed thereto to provide an electric field accessible to the optical sampling pulses. In the present system, a device under test is bonded to the removable sample carrier. The electro-optic crystal is not bonded to the carrier. Rather, means are provided for the electro-optic crystal to releasably engage the sample carrier and its affixed electrical transmission lines. Upon completion of a test, the carrier may be removed from the system with the device-under-test affixed thereto, and the same electro-optic crystal may be utilized in conjunction with another removable sample carrier having another device under test affixed thereto.