Lambda SRS SR475, Руководство по эксплуатации

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1 – 2 Operation
1.1 Introduction to the Instrument
The SR475 and SR476 Laser Shutters are high performance instru-
ments designed to provide fast, versatile, and reliable mechanical
blocking of a free-space laser beam while minimizing vibration and
acoustic noise.
The shutters are suitable for low-power beam switching and pulse
selection applications. They are also particularly suited to provide
additional extinction to optical systems incorporating fast optoelec-
tronic shutters.
1.1.1 Overview
The basic function of the laser shutter, or “shutter head” is to block
or unblock a laser beam when commanded to do so.
The shutter head is normally operated in conjunction with a shutter
driver or controller that provides power, a serial communications
interface, and a control input. Details about this interface are given
in
§
1.7.
1.1.2 Design and theory of operation
Mechanical laser shutters have traditionally been electronic descen-
dants of camera shutters, consisting of a solenoid-driven blade (or
set of blades) with a return spring. The shutter’s open and closed
positions are then determined by physical stops that limit the blade
travel.
By contrast, the SR475 and SR476 Laser Shutters do not use physical
stops to control the blade position. Instead, the blade position is
precisely measured in real time and a digital servo loop is used to
hold the blade in the desired location. During a transition between
the open and closed states, the shutter blade is guided along a pre-
determined trajectory such that it arrives at its final position with
zero velocity, without encountering a physical stop.
This design reduces or eliminates many of the less desirable char-
acteristics of conventional solenoid-based mechanical laser shutters.
Most importantly, it removes the high impulse that is encountered
when a solenoid or a return spring drives a shutter blade into a hard
stop. This high impulse is responsible for the bulk of vibration and
mechanical noise associated with shutters, but is also a contributing
factor in the limited lifetime of such devices.
A typical shutter with a solenoid and return spring necessarily has
a defined
normal state—either open or closed—and expends energy
not only to reach but also to hold in the normal state. By using an
SR475 and SR476 Laser Shutters