The Arb. Frames tab gives you important information about your scan, including the pixel dwell time and pixel size at the zoom you are working at. It also allows you to change between unidirectional and bidirectional scanning. Most of the fields are greyed out unless the arbitrary option is selected in the resolution drop down menu of the 2D Frame interface. If arbitrary is selected then the fields become editable and you can customise your scan parameters.
|A||X Resolution||The number of pixels per line|
|B||Y Resolution||The number of lines per frame|
|C||Pixel Dwell Time||the amount of time taken for the laser to scan over one pixel - line speed/number of pixels|
|D||x.pixel.sz||Width of a pixel in real world units|
|E||y.pixel.sz||Height of a pixel in real world units|
|F||Fill Fraction||Portion of the scanned area displayed - set to about 60% for unidirectional scans and 90% for bidirectional scanning. Decreasing fill fraction will eliminate artefacts caused by mirror instability due to velocity changes at mirror turn-around but will decrease line speed. (Minimum value - 60%, Maximum value - 100%)|
|G||Bidirectional options||Allows you to drive either mirror (x or y) with a triangle waveform rather than a unidirectional sawtooth waveform. Bidirectional scanning allows for faster mirror speeds (2kHz rather than 1kHz) due to the reduced changed in velocity at the end of each line.|
Bidirectional scanning runs the mirrors using a triangle wave rather than a sawtooth wave. For the X-Galvo this means that images are acquired from left to right for the first line and from right to left for the second line. This leads to faster scan times however also introduces a timing difference for image construction between every other line. The timing difference between lines can be corrected by adjusting the start.delay parameter in the Analogue Input (AI) Tab
For the Y-Galvo bidirectional scanning results in frames being acquired from top to bottom for the first frame and bottom to top for the second frame.