device for calibrating brightness of rooms to spark;

摘要

Circuitry is disclosed for calibrating the brightness level of the cathode ray tube associated with a scintillation camera. The apparatus disclosed includes circuitry for generating a raster over a small area of the cathode ray tube face. A photodiode is mounted closely adjacent that face area and produces an output voltage related to the brightness of the emitted light. That voltage is amplified and applied to a comparator circuit which compares the amplitude thereof with that of a reference voltage. The cathode ray tube beam intensity is altered until the comparator output achieves a desired state. The raster is chopped to produce a series of dots on the cathode ray tube face and minimize problems of aging of the tube phospher. In one embodiment, the output of the photodiode is processed to minimize the effects of light and electrical noise.