Multi-spot modulator using a laser diode

DETAILED DESCRIPTION Referring now to FIG.
1, the preferred embodiment consists of a laser diode 1, a focussing lens 2 placed to project the magnified image of the laser diode emitting apperture onto an acousto-optic modulator 3.
The undiffracted beam 4 from the acousto-optic modulator is not used while the diffracted beam 5 is focussed by a second lens 6 to form an image of the acoustic field inside the modulator 3 onto a light sensitive material 7.
The distances between the components are such that the image of laser diode 1 is formed inside modulator 3 and the image of the acoustic wave inside modulator 3 is formed on the light sensitive material 7.
The focal length and size of the first lens 2 is chosen to capture the radiated light from the laser diode and illuminate the desired portion of the acousto-optic modulator 3.
The focal length of the second lens is chosen to reduce the image of the acoustic wave by the desired amount.
In the preferred embodiment diode 1 will be a pulsed laser diode of about 10 W peak power, such as available from RCA or Sanders Associateds (USA).
Lens 2 will magnify the 20.
times.
200 .
mu.
m exit aperture of this laser diode by about a factor of 10, the forming an image of about 200.
times.
2000 .
mu.
m in the acousto-optic modulator.
The modulator is of standard construction, such as available from Isomet (USA) or Crystal Technology (USA) operating at 200 MHz.
The laser diode driver and modulator driver are items well known to those versed in the art.
The laser diode 1 is of the pulsed type.
The laser-diode driver 8 generates a narrow current pulse of about 1 nS duration.
The AM modulator 9 converts the input data 10 to an amplitude modulated carrier at the operating frequency of the acousto-optic cell, in this case 200 MHz.
The data rate is selected such that a single bit is longer than the exposure pulse from the laser diode.
In this embodiment one data bit is about 10 nS.
Since the acoustic wave travels in the acousto-optics modulator at a velocity of about 3