Abstract: A method of marking and identifying an object (10) by the marking consists of applying to an object (10) an up-conversion material (12), then irradiating the object (10) with infrared electromagnetic radiation (16) and, finally, observing the irradiated object to detect the spectrum of emitted electromagnetic radiation (18). A suitable up-conversion material (12) is selected from a group of up-conversion materials consisting of CaF2, BaF2, CdF2, LaF2 and SrF2 doped with erbium, praseodymium, neodymium or dysprosium. The objects (10) may be observed to detect emitted electromagnetic radiation (18) from that part of the electromagnetic spectrum that is visible to the naked eye. The objects (10) may also be observed to detect specific wavelengths of electromagnetic radiation which are known to be emitted by the up-conversion material (12) when the up-conversion material (12) is irradiated by designated wavelengths of infrared electromagnetic radiation.

Abstract: A large area image detecting apparatus made by arranging a plurality of small area sensors in a stepped arrangement so that the inactive regions of the small sensors are covered by a active area of another small sensor. The apparatus may be used to detect light or radiation. A fiber optic assembly may be used to guide light from a flat scintillator plate onto the small sensors.

Abstract: A threshold detector circuit (2) suitable for use with a nuclear event detector for sensing an ionising radiation pulse has a high tolerance to ambient temperature fluctuations. The threshold detector (2) comprises an amplifier stage (3) which includes a pair of complementary transistors (Q2, Q3) and a comparator stage (6) which includes a third transistor (Q4) and a voltage reference (7). Temperature compensation is achieved by the addition of a feedback loop (5) in the amplifier stage (3) including a fourth transistor (Q1) whose temperature coefficient is closely matched to that of the third transistor (Q4).

Abstract: A method for quantitative verification of line-wise scanning geometry in a digital radiographic read out system. An x-ray transparent phantom substrate with an embedded ruler having a number of equidistant parallel strips that are opaque on top of a photostimulable phosphor screen so that the ruler is parallel with the direction of line-wise scanning. After x-ray exposure and scanning, the position in the scanning direction of the center of each ruler strip is computed. At least one of the following parameters is determined: average pixel sampling distance, geometric distortion value, and total scanned width.

Abstract: A fluorescent microscope includes a laser scanning unit having a stage for supporting a fluorescent sample, a laser beam generator and a beam scanning unit for causing a laser beam from the generator to spot scan a sample to cause fluorescence generated by multi-photon absorption. A first detector detects fluorescence emitted from a side of the sample on which the laser beam is incident to output a first signal corresponding to detected fluorescence. A second detector detects fluorescence emitted from a side of the sample from which the laser beam, having been transmitted through the sample, is emitted from the sample. The second detector produces a second signal corresponding to the detected fluorescence. The first and second signals are summed and amplified. A display is provided for a microscopic image of the sample in synchronization with the scanning of the laser beam, based on the amplified summed signals.

Abstract: An integrated charge monitor for measuring a level of cumulative radiation exposure includes semiconductor devices having characteristics that change with a cumulative level of radiation to which the devices are exposed, different amounts of radiation shielding associated with each of the devices, and circuitry operable to separately address each of the devices to measure a change in the characteristic of the selected device due to radiation exposure. The monitor may be implemented on a single integrated circuit chip. The monitor may also be employed in performing a spectrometric analysis of radiation based on the affect of the radiation on characteristics of multiple, differently-shielded semiconductor devices.

Abstract: A scintillation camera is provided with a scintillation crystal assembly having multiple crystal layers for interacting with various photon energy levels. The camera performs imaging of conventional nuclear medicine radioisotopes as well imaging of high energy isotopes used in PET (Positron Emission Tomography) applications. The multiple crystal layers have the effect of doubling the sensitivity of the camera to high energy photons, while retaining the performance characteristics needed for conventional low energy photon imaging.

Abstract: A latent image is formed on a stimulable phosphor plate (10) by irradiating the phosphor plate with x-rays from an x-ray source (14). To develop the stimulable phosphor plate, the plate is irradiated with light of a different wavelength from developer light source (32). The light from the developer light source causes the stimulable phosphor plate to give off light of yet another characteristic wavelength. Light from the stimulable phosphor plate is filtered (38) to remove the wavelength of the developer light and focused (42) on a light sensing element (46) of a time delay and integration video camera (34). The stimulable phosphor plate and the video camera are moved relative to each other and the rate of movement is monitored (60).

Abstract: Contaminants are detected optically at concentrations below 1 part-per-million (ppm) and extending to a level approaching 1 part-per-trillion (ppt) by using intracavity laser spectroscopy (ILS) techniques. A diode laser-pumped solid-state laser (the ILS laser) is employed as a detector. The ILS laser comprises an ion-doped crystal medium contained in a laser cavity optically pumped by a diode laser pump laser. A gas sample containing gaseous contaminant species is placed inside the laser cavity and on one side of the ion-doped crystal. The output signal from the ILS laser is detected and analyzed to identify the gaseous species (via its spectral signature). The concentration of the gaseous species can be determined from the spectral signature as well. Advantageously, the diode laser pump laser is relatively small and compact in comparison to other sources of optical pumping.

Abstract: The invention relates to a radiation dosimeter comprising a sensor arranged in a dosimeter casing and including at least one measuring field and a calibrating zone (64). To provide a dosimeter which can be readily manufactured and comprises a wide measuring range with high precision, it is provided, according to the invention, that the calibrating zone (64) of the sensor (56) is inserted into a radiation-shielded clearance (66) of a double-wall element (68) being formed by folding a radiation-proof web-like material.

Abstract: The specification describes pulse generators and detectors for the far infra-red and operating at frequencies of the order of 10.sup.10 to 10.sup.13 Hz (the Terahertz range). These devices rely on electric field interactions with optical beams in biased metal semiconductor microstructures. The electric field is created between metal electrodes on the semiconductor surface and the electric field is enhanced, according to the invention, by configuring the electrode gap geometry with sharp electrode features.

Abstract: A low cost night vision system for use in connection with law enforcement vehicles, marine vessels, and other nonmilitary surface vehicles. The invention includes a night vision camera having an array of uncooled detectors. A mechanism is provided for adjusting the pointing angle of the night vision camera in response to scan control signals. Output signals from the uncooled detectors are further processed into a standard video format and displayed on a conventional display located, for example, within a vehicle or marine vessel.

Abstract: An x-ray imaging device. One surface of a flat single crystal CsI crystal is supported on an optically transparent support plate. The opposite surface, i.e. an x-ray illumination surface of the crystal is coated with an x-ray transparent optical reflector to provide an x-ray scintillation sandwich having an optical mirror at the x-ray illumination surface of the CsI crystal. An optical camera is preferably focused on the illumination surface of the CsI crystal. In a preferred embodiment an index of refraction matched optical adhesive is used at the x-ray illumination surface to attach the reflector and to reduce Fresnel reflections.

Abstract: Contaminants are detected optically at concentrations below 1 part-per-million (ppm) and extending to a level approaching 1 part-per-trillion (ppt) by using intracavity laser spectroscopy (ILS) techniques. An optically-pumped solid-state laser (the ILS laser) is employed as a detector. The ILS laser comprises an ion-doped crystal medium contained in a linear laser cavity which may be optically pumped by a diode laser pump laser. A gas sample containing gaseous contaminant species is placed inside the laser cavity and on one side of the ion-doped crystal. The output signal from the ILS laser is detected and analyzed to identify the gaseous species (via its spectral signature). The concentration of the gaseous species can be determined from the spectral signature as well. Advantageously, the linear cavity is relatively small and compact in comparison to other ILS systems.

Abstract: Multichannel infrared detector assemblies for use in the detection and monitoring of gas concentrations are provided.

Abstract: A gamma ray detection and locating system comprising an array of scintillator crystals connected to a multichannel photomultiplier tube by discrete optical fibers, each fiber connecting a single crystal to a corresponding specific location on the face of the photomultiplier tube. Also described is an improved system for identifying the location of specific electrodes in the photomultiplier tube receiving electrons generated by photons flowing from the crystal along the fiber to the tube.

Abstract: An apparatus for detecting the presence of a target material such as a multicomponent gas is disclosed. The apparatus includes a source of electromagnetic radiation and a device for dispersing the radiation into different frequency bands for targeting the material at different wavelengths corresponding to absorption bands in the material. Spaced apart optoelectric transducers detect the different frequency bands. A processor detects the changes in the output of the transducers occasioned by partial absorption of the electromagnetic radiation from the source by the target material. Processing means also compensates for temperature variations in the source.

Abstract: A method for monitoring the properties of a coating comprising the steps of adding a fluorescence probe to a coating composition which has the ability to undergo microscopic changes in viscosity, the ratio of the intensity of the fluorescence emission of said probe at two wavelengths changing in response to said changes in said viscosity of said coating composition; curing said coating; causing said compound to fluoresce; measuring the fluorescence of said compound; calculating the ratio of the intensities of fluorescence emission of said compound at two or more wavelengths; relating said ratio to the monitored property of said coating.

Abstract: A rotating gantry (20) is rotatably mounted to a stationary gantry for rotation around an axis of rotation. Gamma camera detector heads (22a, 22b, 22c) are mounted to the rotating gantry for rotation about a patient receiving region (14). A patient is supported on a first, cantilevered patient support portion (10) which is adjustable in height, and which selectively extends toward and away from a slab defined by the detector heads. In one mode of use, the first patient support portion (10) is supported on a second support surface (16) when fully cantilevered to minimize vibration and movement. In a second mode, the first patient support portion (10) is separated by a gap from the second support portion (16) and the region of interest of the patient is positioned over the gap. In this manner, radiation passing from the region of interest of the patient to the detector heads is not attenuated by a patient support structure. Further, the detector heads are mounted on tracks (30, 32) by rollers (44, 46).

Abstract: An electronic apparatus comprising a material having photoconductivity, an energy bandgap, and trap levels. The material is typified by a thin film of polycrystalline diamond. The material is illuminated with first light having photon energies smaller than the energy bandgap of the material. Then, the material is illuminated with second light having photon energies greater than the energy bandgap of the material to thereby induce a photocurrent. The amount of the first light can be known by measuring the induced photocurrent.