| 摘要 |
A transport (11) for a laser writing and reading system in which a carriage (15) is propelled by a falling mass, either its own or an auxiliary mass. The falling mass works against a hydraulic cylinder (23) and piston in which hydraulic fluid is displaced from the cylinder. An adjustable valve limits the flow of hydraulic fluid out of the cylinder so that the fall of the mass, and hence the carriage is braked to a uniform velocity. The system also includes a laser (33) having a beam (31) for scanning in a line transverse to the direction of motion of the carriage. A photosensitive medium (18) is disposed to receive the scanning radiation. Either the laser or the photosensitive medium may be mounted on the carriage, with the other mounted in the fixed position in optical communication therewith. A servo system (Fig. 7) receives a signal representing velocity of the carriage and compares it to a first reference signal representing desired carriage velocity. The comparison yields an error signal which is used to adjust the adjustable valve (28) acting as a variable brake for the transport. A second selectable reference signal is provided so that the first reference signal can be bypassed when the carriage is reset at high velocity or is at rest. By controlling the rate of fluid flow through the valve, the mass will fall with uniform velocity, thereby propelling the carriage at a uniform, vibration-free rate. |
