In digital holography, the image sensor must have a sufficient pixel density. The book New Techniques in Digital Holography by Pascal Picart and others, the following condition is given:
Considering the maximum angle $\theta_{max}$ between the two waves, the micro fringes locally produced by the two tilted wavefronts must be sampled so that the sampling pitch is at least equal to two times the fringe period. Thus, this leads to the maximum acceptable angle for the setup, according to the following equation: $\theta_{max} < 2sin^{-1}(\frac{\lambda}{4max(p_x,p_y)})$
Here, $p_x$ and $p_y$ denote the pixel pitch of the sensor, $\lambda$ the illumination wavelength and $\theta_{max}$ the maximum incident angle on the sensor like this:
Does this formula translate at all to an in-line setup like the following? How is the maximum angle between reference and object light determined? Considering the following drawing, it could approximate something like 85 degrees:
I'm sure the above beam interaction has a minimal influence on reconstruction, so how useful is the formula here?