Liquid Crystal Shutter
Chapter 5: Operation
Rev D, January 8, 2020
Page 5
Chapter 5
Operation
Ensure that the input beam is linearly polarized and that the polarization axis is aligned with the marking
on the front of the shutter. A polarizer or wave plate can be used to ensure the polarization axis is aligned
to the shutter. For best performance, ensure the beam is at normal incidence to the shutter and is aligned
straight through the center of the LC cell.
Connect the power supply to the shutter.
The shutter may operate either as an on/off shutter or a variable attenuator. A slide switch on the top of
the shutter (see Figure 4) allows the user to select one of these two modes of operation. When the
“SHUTTER” mode is selected, the potentiometer is used to simply to block or transmit the beam. In this
operational mode, when the potentiometer is turned fully counterclockwise, the shutter is in the off
position, which is indicated by a red LED. Turning the potentiometer will eventually switch the shutter from
off to on. When in the on position, light is transmitted through the shutter, which is indicated by a green
LED. When the “ATTENUATOR” mode is selected, the potentiometer is used as an adjustable attenuator.
Turning the potentiometer clockwise will increase the power transmitted through the shutter. The green
LED light is always lit in “ATTENUATOR” mode.
The LCC1620 (/M) is also designed to be controlled by an external signal. The external signal is a 0 – 5 V
DC signal input into the “EXT. INPUT” SMC connector. To use an external input in “SHUTTER” mode, the
potentiometer must be in the turned fully clockwise. Whereas, in “ATTENTUATOR” mode, the “EXT
INPUT” adds an offset to the level set by the potentiometer. Thus if the potentiometer is fully
counterclockwise, the “EXT INPUT” has no effect. The “EXT INPUT” starts to take effect when the
potentiometer is turned clockwise and takes the full effect when the potentiometer is fully clockwise.
Note: under “ATTENUATOR” mode, if the potentiometer is not turned clockwise fully, the “EXT INPUT” voltage
will not achieve full transmission. Instead it can vary from off to the attenuation level set by the potentiometer.
Figure 4
Top View of the Shutter
