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synchronized_zaxis_focus_sweeps

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documentation:synchronized_zaxis_focus_sweeps [2016/09/07 18:03] – ↷ Links adapted because of a move operation asiadminsynchronized_zaxis_focus_sweeps [2021/09/23 17:15] (current) – external edit 127.0.0.1
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 +====== Synchronized Z-axis Focus Sweeps ======
  
 +Focus sweeps provide a simple way to integrate many focal planes in a single image.   It is possible to generate accurate position and exposure control using some specialized scanning firmware and hardware encoder comparisons with the MS2000WK controller and an ASI Z-axis drive.  
 +
 +===== Required Configuration =====
 +
 +The following components are required:
 +  * MS2000WK controller with firmware** SCAN MODULE**
 +  * Mechanical Z-axis Drive
 +  * Camera with TTL gated exposure mode
 +
 +===== Procedure =====
 +
 +The user should familiarize themselves with the [[commands:scan|SCAN]], [[commands:scanr|SCANR]], [[commands:scanv|SCANV]] and [[commands:ttl|TTL commands]].  
 +
 +As an example, let us assume that we would like to take a 200ms exposure over a swept focal range of 10μm.  The exposure time will determine the sweep speed.
 +
 +\begin{equation} Speed = \frac{Focal Range}{Exposure Time} \\
 +
 +Speed = \frac{0.010 mm}{0.200 sec} = 0.05 mm/sec \end{equation}
 +
 +The following commands will set up the single Z-axis scan at the correct speed:
 +
 +''SCAN X=0 Y=0 Z=1'' X and Y axes not used; Z-axis is fast-scanned axis
 +
 +''SCANR X=0.0 Y=0.01'' sets the start and stop positions for the fast-scanned axis to 0.0 and 0.010 mm respectively
 +
 +''SCANV Z=100'' the scan will be repeated 100 times
 +
 +''SPEED Z=0.05'' set the scan speed to value calculated above
 +
 +''SCAN'' start the scan
 +
 +At this point the controller will begin successive scans of z-axis followed by rapid retraces.  To trigger a camera, some TTL exposure control is required.  There are two ways this can be accomplished.
 +
 +  - Use TTL OUT0 (internal SV1-2) and the command [[commands:ttl|TTL Y=5]] to select a gated output during the “uniform velocity” portion of the move as determined by the built in trajectory generator.  This provides a reasonably accurate gate pulse, with perhaps 3-6 ms jitter and 0.2 to 2m systematic position error compared to what is desired. 
 +  - Use the SCAN SYNC (internal SV1-7) output directly.  For this to work on the Z-axis, JP1 – Pin 2 must be connected to the Z-channel encoder flag output, pin 22 of IC24.  This is a special hardware modification that must be made for Z-axis synchronized sweeps.  This method has the advantage that the precise encoder locations of the start and stop positions (as defined by the SCANR command) determine the edges of the SYNC pulse.
 +
 +With either (or both) method(s), you should be able to display the TTL trigger pulses on an oscilloscope.  
 +
 +There may be some reason you wish to pause between successive sweeps.  An arbitrary time delay can be added using the [[commands:wait| WAIT command]].  For example[[commands:wait| WT Z=1000]] would add a one second delay time between successive sweeps.
 +
 +The basic setup parameters for your sweep can be stored into nonvolatile memory in the controller using the command [[commands:saveset|SS Z]].  
 +
 +A scan can be initiated, stopped, and restarted just by using the [[commands:scan|SCAN command]] without any other arguments.
 +
 +===== Overshoot Parameter =====
 +
 +The overshoot parameter is set using [[commands:scanv|SCANV F=overshoot]].   The stage will travel a distance on each side of the uniform-speed scan equal to the acceleration ramp distance multiplied by //overshoot//  The default value is ''overshoot=1.0'' so the ramp regions are exactly excluded from the uniform speed section of the move.  A value of ''overshoot > 1'' provides additional distance for the speed to settle into a constant velocity.  Scans with ''overshoot < 1'' will have non-uniform speed at the beginning and end of the scan.
 +
 +
 +{{tag>advanced_feature ms2000 scan_module tiger}}
Address: 29391 W Enid Rd. Eugene, OR 97402, USA | Phone: +1 (541) 461-8181