Exposure Shutter settings

Shutter control is an element that controls digital output hardware. In general, shutters allow to turn on or off secondary connected hardware and to control timing of ON-OFF cycle either directly by its duration or in synchronization with other steps in the acquisition cycle.

There are several types of shutters that are used in xDSoft. The type of shutter that is used in spectral acquisition cycle is Exposure Shutter. Whenever shutter hardware is found on startup of Acquisition window, Shutter tab will appear in the Settings area and provide control over parameters of supported hardware. At the same time, Acquisition control steps that require Shutter for proper operation will be enabled. On the opposite, when shutter hardware is not found, Shutter tab and dependent Acquisition modes are hidden.

In the acquisition cycle, Shutter is implemented as a separate step that actually starts the acquisition cycle. For practical purposes, however, Shutter typically skips at least one cycle at the beginning of Acquisition to allow for measurement of reference values (spectra). 

Not all Acquisition modes use Shutter. For example cycles of monitoring, Single, and Continuous modes do not include Shutter operation steps. The cycles that use Shutter control will operate Shutter once or more over acquisition, depending on shutter occurrence mode. These cycles include:

• Exposure – cycle defined in exposure-time domain;
• Flash-continuous – continuous cycle that involves Shutter at one or more cycles;
• Stop-watch – a utility cycle that allows direct, simple, and straight-forward operation of Shutter for a given duration. 

The basic Exposure Shutter control has several settings that control timing parameters. These parameters include:

• Blank – number of acquisition cycles that are skipped before Shutter operation starts; typically at least one cycle is left blank for reference measurement;
• Exposure time – initial exposure on the first cycle that Shutter is activated;
• Cycle factor – change in shutter exposure time from one cycle to the next, does not apply to blank cycles;
• Occurrence mode – determines periodicity of Shutter operation over successive acquisition cycles;
• Synchronization mode – specifies how Shutter ON-OFF operation is synchronized to other steps of acquisition cycle.

Depending on the specific shutter hardware interface, additional control parameters can be present:

• Channel – specifies which channel is used for interfaces supporting multiple shutters; one instance of Shutter control can support one physical shutter, although it may be possible to add support for second, parallel or sequential, shutter in acquisition cycle.
• Pre- and post-roll – for controllers with multiple I/O channels and two-level shutters specifies delay between rise of first and second shutter levels and delay after fall.