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3.17. Understanding Software Autofocus Functionality

Software autofocus in Volocity is designed to find the optimal focal point by maximizing the signal-to-noise ratio (SNR) within the autofocus range. This means the algorithm identifies the point where the brightest point in the image divided by the darkest point in the image is greatest. By focusing on this ratio, the system ensures sharp and clear imaging.

Method Used: Golden Section Search

• Volocity uses the golden section search method to determine the optimal focus point.
• This mathematical optimization algorithm minimizes the number of sample exposures required, making the autofocus process faster and more efficient.
• More details on the golden section search can be found here.

Key Considerations:

1. Autofocus Limits:

   • It is crucial to set the autofocus range limits appropriately.
   • Incorrect or overly broad limits can cause the autofocus to be "thrown off" by local maxima—bright areas that may not represent the actual focal plane.

2. Region of Interest (ROI):

   • If a region of interest (ROI) is drawn on the live preview, the autofocus algorithm will restrict its calculations to this specific area.
   • This ensures that the autofocus is applied to the most relevant part of the image and avoids distractions from less important areas.

Advantages of Software Autofocus:

• It reduces manual adjustments, saving time during image acquisition.
• By using a mathematical approach to maximize SNR, the process is highly repeatable and precise, ideal for quantitative imaging tasks.
• The use of the golden section method minimizes unnecessary exposures, preserving the sample and improving workflow efficiency.

By setting the autofocus limits carefully and utilizing the ROI feature when necessary, Volocity's software autofocus can deliver highly accurate results, ensuring optimal imaging quality.