Field Curvature, also known as “curvature of field” or “Petzval field curvature”, is a common optical problem that causes a flat object to appear sharp only in a certain part(s) of the frame, instead of being uniformly sharp across the frame.
This happens due to the curved nature of optical elements, which project the image in a curved manner, rather than flat.
And since all digital camera sensors are flat, they cannot capture the entire image in perfect focus.
This especially becomes an issue when capturing topographic images, which may tend to have an unwanted curvature.
The compensation – which is approximated by a parabola – id the difference is focus from center of image towards image corners.
Example of adding a compensation value of 10um to the 0.5x objective.
Example of a motorized Navitar 6x motorized objective with virtual-fixed objectives at the objectives click-stops.
Using the click-stop position will activate the designated compensation values.
The field curvature compensation will automatically appear in the 3D topography. I a compensation value is not available, the a slider will appear, for manual compensation.
References:
•https://photographylife.com/what-is-field-curvature
•https://www.coursera.org/lecture/design-high-performance-optical-systems/what-is-petzval-radius-Yy2ya