Enhancing form factor and light collection of multiplex imaging systems by using a cubic phase mask

Abstract

The bulky form factor of traditional optical sensors limits their utility for certain applications. Flat multiplex imaging-sensor architectures face the light-gathering challenges inherent with small collection apertures. We examine a wavefront-coding approach wherein a cubic phase mask is used to increase the aperture sizes of multiplex imaging systems while maintaining the distance from the lens to the detector array. The proposed approach exploits the ability of cubic-phase-mask systems to operate over a large range of misfocus values. An exact expression for the optical transfer function of cubic-phase-mask systems is presented, and its misfocus-dependent spatial-filtering properties are described. Criteria for form-factor enhancement are assessed and trade-offs encountered in the design process are evaluated.

Applications of the phase transfer function of digital incoherent imaging systems

“…This extension was realized through the inclusion of a cubic phase mask at the pupil plane to achieve an MTF that was largely invariant to defocus. It was subsequently shown that the exact OTF of this wavefront coding imager for a given phase mask strength α and defocus parameter ψ is given by [7] Hu; ψ…”

“…where C and S represent the Fresnel cosine integral and Fresnel sine integral, respectively, whose operands au and bu have been described in [7]. The parameters α and ψ may be expressed in multiples of wavelength.…”

“…These systems routinely defy the traditional philosophy pertaining to PTF characteristics of a well-designed imaging system. Often, systems based on such techniques purposely compromise contrast so that a large part of the operating MTF remains below 0.2, in exchange for other benefits such as, say, an enhanced depth of field [5][6][7][8][9]. Meanwhile, their PTFs could exhibit parametric variations and magnitudes much larger than π∕4, and would hence need to be taken into account if optimal imaging performance is to be achieved [9].…”

Complex Amplitude Filters for Extended Depth of Field

“…(5) can be expressed in terms of a Fresnel integrals, as was first recognized in radar engineering [17], and later on in optics [18]- [19]. In Fig.…”

Beam shaping with multiple-powered phase masks

“…Cubic phase mask has been demonstrated to generate finite energy Airy beam by modulating a Gaussian beam [1], to extend the depth of imaging field [2] and to increase the aperture sizes of multiplex imaging systems [3]. Based on the concept of cubic phase mask, we present multiple-powered phase masks to convert a plane wave beam into different shaped beams by using different power exponents.…”