A radiography apparatus comprises a radiation source which is arranged to supply radiation spectra of different energies. The apparatus also comprises a detector which can be adjusted for the radiation spectra so that a strong wavelength discrimination occurs in the measurement signals. In a detector comprising an ionization chamber, there is arranged an auxiliary electrode which can be adjusted in phase with the radiation source so that soft radiation of a soft source spectrum or hard radiation...

A light waveguide is formed by atomising under vacuum and deposition upon a substrate, of a metal such for example as tantalum, in an atomsphere comprising a gas capable, in association with the metal, of forming a chemical combination, oxygen in the case of tantalum. The deposit is a complex compound of the metal and of the gas if the gas pressure is insufficient to produce the desired chemical combination (tantalum pentoxide Ta.sub.2 O.sub.5); the assembly, after appropriate masking, is subjec...

A long wavelength photoemitter, for example a III-V semiconductor, having a work function reduction activation layer thereon, with means for overcoming the energy barrier between the semiconductor conduction band edge and the vacuum comprising means for thermally energizing the photoexcited electrons in the conduction band from a lower energy level therein to a higher "metastable" energy level in which they may reside for a sufficient time such that the electrons can pass with high probability f...

A photodetector useful at long wavelengths where silicon normally is transparent. It includes a photodiode stage which comprises a silicide layer forming a Schottky-barrier junction with a silicon substrate and which is integrated with an amplification stage which uses a silicon transistor adapted to amplify the photovoltaic voltage derived by the photodiode stage. In the preferred embodiment, the silicide layer forms the grid of a permeable base transistor.

A system for stabilizing the frequency of a laser employing the variation in position of interference patterns which results from a variation in laser beam frequency in passing through a Fabry Perot etalon filter. The system is particularly useful for maintaining strict frequency control at a particular frequency in the output of a tunable laser such as a dye laser for use in isotope separation.

A multi-wavelength optical filter, particularly useful for shielding against laser light, includes compounds incorporated into a glass base which produce Cu.sup.2.sup.+ ions, Er.sup.3.sup.+ ions, and Ce.sup.3.sup.+ ions, thereby providing a filter having desired optical densities at 488 nm, 515 nm, 530 nm, 671 nm, 694 nm, 1060 nm, 840-900 nm, 347 nm, and 337 nm.

A pulsed or CW laser is rapidly switched to operate at one or more selectable wavelengths by means of intracavity insertion of beam dispersion and focussing elements and an apertured focal plane mask and shutter assembly. The laser beam has an axis and is dispersed into components or sub-beams having different axes and representing different wavelengths, the sub-beams being focussed to substantially reduced diameters on the focal plane mask at points, respectively, at which apertures are formed....

A multiwavelength multiplexer-demultiplexer constructed from units each cble of multiplexing or demultiplexing two wavelengths. As many such units as required can be interconnected to form multiplexer-demultiplexers of any number of wavelengths. Each two-wavelength multiplexer-demultiplexer unit includes a four-port power divider, a four-port phase shifter having two ports connected to two ports of the power divider, and another four-port power divider having two ports connected to two ports of ...

A method and apparatus for determining the characteristics of a luminescent material using a monochromator to detect the intensity of a light emitted by the material at a single major spectral line as the material is scanned. The wavelength of a monochromator is adjusted such that the intensity being measured is the peak intensity. The fact that the intensity is the peak intensity is determined by taking the derivative of the intensity with respect to wavelength as the wavelength of the monochro...

A spectrofluorometer providing wavelength correction by means of an arbitrary function generator driven by a wavelength scanning element of the spectrofluorometer. The arbitrary function generator may be driven by the emission scanning monochromator to derive a wavelength-dependent voltage signal which is combined with the measure photomultiplier output to thereby provide a base-line compensated resultant output signal. Alternatively, the arbitrary function generator may be driven by the excitat...