Theoretical approach on a galvanometric scanner with an enhanced duty cycle

The paper explores the possibilities of achieving a galvanometric scanner with an enhanced, as close as possible to 100%, duty cycle (eta) even for high scan, i.e. high oscillation, frequencies. Nowadays solutions provide high eta, but up to certain frequencies. The study of this limit frequency, of its relationship with the duty cycle, and the ascertainment of the scanning and command functions that may produce better results, is the final scope of this work. The scanning device is considered in a setup characteristic to the dimensional, usually on-line, industrial measurements. A detailed theoretical study is performed, starting with the equation of the mobile element of the galvoscanner. The expressions of the active torque and of the necessary command function that has to be used are obtained, with regard to the desired scanning function. This is considered linear and symmetrical on its active portions and with non-linear returning portions that have to be performed as fast as possible. Two such functions for the returning portions are considered and studied: parabolic and sinusoidal. The best scanning function, with regard to achieving the objectives of the device (high duty cycle for high frequencies), is obtained and the way the necessary command function has to be deduced is discussed.