5 – X-series Camera Controller
X-series User’s Manual
62
5.4.3.8 Misc Tab
5.4.3.9 Lockin Tab
The lockin feature is designed for a non-destructive testing technique, where a periodic thermal
excitation is applied to a part under test. An electrical signal that is synchronous with the excitation
mechanism is also sent into the lockin input port on the camera’s Auxiliary connector. This signal has
its mean amplitude value and its period measured by the camera, and the results are stored in the
image header metadata. An image sequence is acquired with this lockin metadata stored in the
image header for each frame. This metadata is used for a post-acquisition analysis that can pull very
weak signals out of the IR images and reveal defects in the part that are impossible to detect with
conventional IR imaging techniques.
The signal period is determined by measuring the time interval between signal crossings of the
digitizer midpoint value of 8192 counts, which is half of the 14-bit scale. The signal does not have to
have any particular shape to get its period measured – it just has to be periodic. The lockin input has
a 1.25 MHz sampling rate at 14 bits of depth, and selectable AC/DC coupling, with latency less than 1
microsecond. The input signal range is 0-5 volts. The frame period is the effective latency if it is
used as a regular input, since it is only updated once per frame. When not used as a lockin input, this
port still stores a value for each new image frame.
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