Scanimage 2017 : Optimization of Scanned Images Aspect Ratio


Optimizing image aspect ratios for X/Y scanner pairs requires correct settings for the angular range of each scanner.

These must be specified in the Machine Data File (MDF).

This guide provides information about:

  • (left) the relevant MDF settings 
  • (right) typical MDF values for various market-available scanners

Machine Data File (MDF) Settings

The following key Machine Data File settings affect the image aspect ratio

  • %% ResScan Section

    • xGalvoAngularRange

    • yGalvoAngularRange

    • galvoVoltsPerOpticalDegreeX

    • galvoVoltsPerOpticalDegreeY

    • resonantAngularRange

    • rScanVoltsPerOpticalDegree


  • %% LinScan Section
    • xGalvoAngularRange
    • yGalvoAngularRange
    • galvoVoltsPerOpticalDegreeX
    • galvoVoltsPerOpticalDegreeY


The Volts Per Optical Degree values specify the amount of control voltage required to drive each scanner to a specified angle deflection from the center

The Angular Range values specify the peak-to-peak angular range of each scanner
(of which a specified Fill Fraction is imaged, as configured within ScanImage)

(tick) These values are in optical degrees - which is 2x the mechanical angular range of the scanner, because of the laser reflection

Angular Ranges at Zoom=1

Zoom 1 is automatically defined as a square scan of the smaller of the two scanner angular ranges

 (tick) BUT - it is permissible to use the full angular range of the larger of the two angular ranges, via the ROI/Stimulus Group Editor dialog


Typical MDF Settings

Sutter Res Scanner Systems

Typical Sutter resonant scanner system

Optical Angular Range
Volts per Optical Degrees
Resonant (X)26 degrees0.1923
Galvo (Y)20 degrees1.0

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Cambridge Technologies OEM Resonant Scanners


Optical Angular Range
Volts per Optical Degrees
CRS-8 (new driver board)260.1923 
CRS-8 (old driver board)150.33 


Cambridge Technologies OEM Galvo Scanners

The specifications for galvo scanners from Cambridge Technologies are listed on specific order sheets when purchased

Below are typical Angular Range & VoltsPerOpticalDegree values for standard X/Y scanner sizes and configurations 


Aperture Size
Optical Angular Range
Volts per Optical Degrees
3mmStandard60 degrees0.33Matched to smaller objective lenses (back focal aperture < 10mm). Typical for slice & fly applications.
5mmStandard40 degrees0.5 
5mmReduced Angle20 degrees1.0 
6mmStandard40 degrees0.5 



Cambridge has 2 types of X/Y scanner configurations

Reduced AngleX & Y scanners are the same size, achieving the best and most uniform speed.
The tradeoff is somewhat reduced angular range for the scanner pair.
StandardY scanner elongated compared to X scanner. 
This ensures full X scanner range is incident on Y scanner.