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To stack or not to stack

Started Sep 26, 2019 | Polls thread
mawyatt2002
mawyatt2002 Contributing Member • Posts: 502
Re: Larger DOF with larger sensors (not a typo)
1

DoF is unfortunately not a precise well defined "scientific parameter" based upon an arbitrary circle of confusion (good name!) and up to lots of interpretation and "confusion"!

Outside macro work it's usually defined based upon the acceptable in-focus longest position minus the closest position acceptable in-focus regions. Calculation involves the Hyperfocal distance and such which you can find with Google.

At macro and below it's usually best to consider a different approach to DoF and use Numerical Aperture, or NA.

From my notes:

NA= (M/(M+1))*(1/(2F))

Physics based "wave optics" results in a relatively simple definition for a quarter wavefront error:

DoF = lambda/NA^2,

where lambda is wavelength of light, usually assumed to be 550nm ( Green).

Another definition which augments the wavefront definition to include pixel size, not sensor size though, for small NA:

DoF = lambda/NA^2 + e/(M*NA)

where e is the pixel size.

So DoF does depend somewhat on pixel size.

For example with a NA of 0.28 at 5X DoF = ~7um, using a pixel of 4um results in DoF of ~9.9um. At 5X NA of 0.038 (F11, Feff of 66), DoF = ~ 383um, and considering a 4um pixel DoF = ~404um. At 2X with a NA of 0.055 results in DoF of ~182um and ~218um when 4um pixel is considered.

Best,

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Research is like a treasure hunt, you don't know where to look or what you'll find!
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