Experimental demonstration of continuously variable optical encoding in a hybrid imaging system

Abstract

We demonstrate an experimental method to obtain a continuously variable hybrid imaging system that uses two generalized cubic phase masks, to enable real-time optimization of the trade between extended depth-of-field and noise gain. We obtain point-spread functions as a function of the rotation angle and show an example of optimization based on recovered image quality.

Adaptive phase plates for optical encoding systems invariant to second-order aberrations

“…has been experimentally demonstrated [19]. In both cases, terms (x 3 + y 3 ) and (x 2 y + xy 2 ) do not vary independently but with a fixed ratio 1:-3.…”

“…One plate of the first pair encodes a phase that can be described by A(x 3 − 3xy 2 ) or equivalently in polar coordinates, by Ar 3 cos(3θ), and the other encodes A(y 3 − 3yx 2 ) or equivalently −Ar 3 sin(3θ) (Zernike polynomials Z 3 − 3 (r, θ) and Z 3 3 (r, θ) respectively, or trefoils). If only this pair of plates is used, it is impossible to independently control both phase profiles (x 3 + y 3 ) and (x 2 y + xy 2 ) [19], control being limited to a proportion of 1:-3 as mentioned above, thus indicating that a second pair will be needed. For this latter pair, the first element encodes B(x 3 + xy 2 ) or equivalently Br 3 cos(θ) and the second one −B(y 3 + yx 2 ) or −Br 3 sin(θ) (or coma).…”

“…Phase plates in the shape of R(r) * cos(nθ) can be effectively shaped in both refractive [12,16,19] and diffractive structures [22]. Besides, experimental generation of trefoil by rotation of only one pair of phase plates has been already reported for wavefront coding purposes [19] and the experimental generation of several Zernike aberrations has been experimentally demonstrated for correction of eye aberrations [16].…”

“…Besides, experimental generation of trefoil by rotation of only one pair of phase plates has been already reported for wavefront coding purposes [19] and the experimental generation of several Zernike aberrations has been experimentally demonstrated for correction of eye aberrations [16]. Therefore, the practical implementation of the plates here proposed should be straightforward.…”

Effect of spherical aberration in trefoil phase plates on color wavefront coding

“…24) In practice, the phase at the pupil can be modified using spatial light modulators 25) or phase plates. 26,27) Phase plates represent a cheap and robust option for WFC-based optical systems. The experimental performance of fabricated phase plates trefoil-shaped has been demonstrated.…”