Camera Timing Marker with Dual Spark and Neon Light Sources

Abstract

Efficient camera timing marker blocks with dual light sources, one spark and one neon lamp, for installation in 16 and 35mm high-speed cameras have been designed and produced. These timing-light sources can be operated continuously in short bursts or pulsed at cycling times of 1,000 to 50,000 cps. They are positioned to produce intense timing marks with sharp leading edges outside and between the perforations on either side of 16mm and 35mm film. They are designed with small dimensions for fitting into most high-speed cameras. — The rear source consists of a small spark-gap assembly designed to fire from a 5,000- to 10,000-v d-c pulse. This spark gap produces an intense spot of light at pulse frequencies of from 1,000 to 10,000 cps with the pulse duration of 12 to 30μsec. The resulting high-contrast image is readily observable and measurable on medium-speed black-and-white and color films, with the cameras operating at at 16mm frame rates of 8,000 frames/sec (200 ft/sec) and higher. — The neon source utilizes the NE2J or BA1C neon lamps which, when pulsed with short-duration pulses at input voltages of 200 to 300 v, produce bright images at frequencies of 1,000 to 50,000 cps. Extremely sharp edges and light intensities of an order of magnitude over conventional systems are obtained with a special f/1.3 illuminating and projection lens system designed to collect the light from the neon electrode and produce a bright image of a slit on the film.