How to implement bidirectional scanning?

[hwuscut]

I implement a bidirectional scanning, but the performance is not good. How to improve it? Thanks very much.

[raacampbell]

In what sense is performance not good? There is a simple bidi scanner implemented here: DAQ_ToolBox_Scanners/scanAndAcquire_Polished.m

[hwuscut]

@raacampbell Thanks very much for your replay. I use the DAQmx_Scanners/polishedScanner.m.
In the function generateScanWaveforms(obj) part, I modify the xWaveform
xWaveform = repmat(xWaveform, 1, length(yWaveform)/length(xWaveform));
as
num = length(yWaveform)/length(xWaveform);
if mod(obj.imSize,2) == 1
xWaveform_tmp = xWaveform;
xWaveform = [xWaveform fliplr(xWaveform)];
xWaveform = repmat(xWaveform, 1, (num-1)/2);
xWaveform = [xWaveform, xWaveform_tmp];
else
xWaveform = [xWaveform fliplr(xWaveform)];
xWaveform = repmat(xWaveform, 1, num/2);
end

These can generate a bidirectional scanning signal.

In the function readAndDisplayLastFrame(obj,src,evnt) part, I add new codes as

obj.lastFrame = reshape(obj.lastFrame, obj.correctedPointsPerLine, obj.imSize); % The following is added newly.

obj.flipIndex = 2:2:obj.imSize;
obj.lastFrame(:,obj.flipIndex) = flipud(obj.lastFrame(:,obj.flipIndex));

The performance means the image resolution. The resolution is lower than unidirectional scanning method. What is wrong with the modifications?

Thanks for your help.

[hwuscut]

I will carefully read DAQ_ToolBox_Scanners/scanAndAcquire_Polished.m.

[raacampbell]

Looks like you are missing the phase correction when rebuilding the image. You'll see that in the link I sent, above.

[hwuscut]

Sorry to trouble you again. I find the phase correction part now. But how to determine the delayed phase?
%Flip the even rows if data were acquired bidirectionally
im(2:2:end,:) = fliplr(im(2:2:end,:));

		im(1:2:end,:) = circshift(im(1:2:end,:),-bidiPhaseDelay,2);
		im(2:2:end,:) = circshift(im(2:2:end,:), bidiPhaseDelay,2);

		im = fliplr(im); %To keep it in the same orientation as the uni-directional scan

		im = im(:,1+bidiPhaseDelay:end-bidiPhaseDelay); %Trim the turnaround on one edge (BADLY)
		set(h(chan).imAx,'XLim',[1,size(im,2)]);

[raacampbell]

Empirically whilst you image. The image will go from looking crappy to sharp as you change the value.

[hwuscut]

I use DAQ_ToolBox_Scanners/scanAndAcquire_Polished.m to try the bidirectionally scanning. The result is not good as the unidirectional scanning. I modify the codes, the results are not improved. The phase correction is added. The results are still not improved. May be other improvements are needed.

[raacampbell]

The phase correction is pretty sensitive and some scanners need to be run slower. The object-oriented version of the code allows you to change the scan phase whilst it's running, which is much easier to work with. You can run it without the GUI (see help in scanAndAcquire_OO.m). Scan slowly and play with the phase offset in small increments. Then see how much faster you can scan and still have it work well. If you scan too fast uni-directionally (beyond what the control loop can do), then scanners will produce a distorted image but it will look more reasonable than a bidirectional image that is too fast.