Abstract: A nuclear spectrometer employs asymmetrical weighting functions to optimize energy resolution and throughput. Photons striking a semi-conductor detector generate current which is amplified, converted to a voltage step, and fed to a fast analog-to-digital converter (ADC) for pile-up rejection and a slow ADC whose output is examined for low-energy pile-up, slope corrected, and buffered for photon energy measurement. Pile-up is detected with a unique pair of leading and trailing weighting functions whose outputs have sharp rising and falling edges respectively, nearly independent of photon energy. Digital triangular shaping is used to locate the step in the buffer. Asymmetry of the triangular response is used to reject very low-energy pile-up. The step is also rejected if the average noise nearby exceeds a threshold.

Abstract: A computer graphics apparatus and a method for allowing the comparison of two or more digitally-stored images on a raster-scan display device, such as a cathode ray tube (CRT), by use of arithmetic or Boolean logic operations performed on the picture elements (pixels) in each image which are to be superimposed at a given display pixel on the CRT. The invention provides the features of color lookup tables, continuous zoom and roam logic and high-speed processing in a computer graphics apparatus for digital image comparison.