Sequential beam switching of acousto-optic modulator

DETAILED DESCRIPTION It is a novel feature of the present invention that simultaneous multiple-beam operation of a laser recording or display system is provided by sequential application of the various modulated carrier frequencies.
In this way, the high conversion efficiencies appertaining to the use of a single drive frequency are achieved and there are no cross-channel interference effects as only a single carrier frequency is applied at a time.
Simultaneous multiple-beam operation is achieved in two ways.
First, the various carrier frequencies are represented as separate but contiguous regions in the acoustic wave that passes through the acousto-optic cell.
As each of these regions pass through the acousto-optic cell, it will eventually interact with the entire incident laser beam to form an output beam at the angle corresponding to the frequency used.
The carrier frequency repetition rate is sufficiently high so that successive beam deflections corresponding to a particular carrier frequency will have sufficient overlap in the horizontal (or scanning) direction to yield an essentially continuous scan line.
Tilting of the recorded information produced by the interaction of the non-simultaneous beam deflections and the horizontal scanning motion is compensated for by an appropriate rotation of the acoustic axis of the acousto-optic cell.
Another novel feature of the present invention is that the peak drive power requirement for the acousto-optic cell is much lower for sequential as compared to simultaneous application of the various carrier frequencies.
In fact, the peak power for simultaneous operation is larger than that for sequential operation by a factor equal to the number of carrier frequencies used.