THORLABS WFS20-14AR, Operation Manual

Page: 27 / 153

© 2007 - 2018 Thorlabs
5 Operating Instruction
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Camera Settings Tab
Trigger Mode allows the synchronization mode to be selected. Three modes are available:
·
Continuous - this is the default mode. The images are acquired auto-
matically and continuously by the camera - the camera operates in free
running mode, and the software displays the last available image, which
might be buffered in the camera or in the driver. This mode provides the
fastest measurement speed, but the internal buffering causes a delay of
several frames between the exposure and the appropriate wavefront result.
·
Slope H
g
L (L
g
H) - this mode enables image acquisition to be syn-
chronized to an external trigger signal, which may be a pulsed laser source or an electrical
function generator. See chapter
Trigger Input for a detailed specification of this input. The
trigger slope can be selected. In addition, a trigger delay can be programmed. The possible
delay range depends on the connected instrument. As soon as a trigger slope is selected,
the WFS waits for the trigger event at the electrical input. Until the trigger is
received, no wavefront measurement or screen update take place. This
state is indicated by the 'Awaiting hardware trigger...' message in the status
bar at the bottom.
·
Software: The WFS application controls the image acquisition. All buffered images are de-
leted at the start of each new exposure, and new images acquired by the camera are trans-
ferred to the PC. This operating mode is somewhat slower than Continuous mode, but it is
advantageous if a fixed correlation between exposure start and retrieved image is required,
e.g., in control loops.
Camera Image Size defines the active area of the camera that is used for wavefront measure-
ment. This setting should be adapted to the beam size that is applied to the instrument. Limiting
the active image size will reduce the unused sensor area, resulting in an increase of measure-
ment speed by saving the time that is required to transfer data from the sensor head and evalu-
ate the spotfield images.
·
Large image sizes allow the chosen pupil diameter to be large, which supports a high Zernike
resolution (Zernike order).
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