Experimental validation of hybrid optical–digital imaging system for extended depth-of-field based on co-optimized binary phase masks

Abstract

We experimentally investigate the performance of co-optimized hybrid optical-digital imaging systems based on binary phase masks and digital deconvolution for extended depth of field (DoF) under narrow-band illumination hypothesis. These systems are numerically optimized by assuming a simple generic imaging model. Using images of DoF targets and real scenes, we experimentally demonstrate that in practice, they actually reach the DoF range for which they have been optimized. Moreover, they are shown to be robust against small mask manufacturing errors and residual spherical aberration in the optical system. These results demonstrate that the optical/digital optimization protocol based on generic imaging model can be safely used to design DoF-enhanced imaging systems aimed at real-world applications.

What is the depth of field reachable in practice with generic binary phase masks and digital deconvolution?

“…(1) and Ref. [9]). In order the final image to be sharp and devoid of artifact after deconvolution, the CTF should be constant and large enough within this range.…”

“…In this paper, we study the DoF reachable in practice by generic binary phase masks associated with digital deconvolution based on the average Wiener filter [7]. Their performance has already been demonstrated by simulation [8] and we have reported a first experimental study under narrow-band illumination [9].…”

Theoretical and experimental analysis of co-designed binary phase masks for enhancing the depth of field of panchromatic cameras

“…We model the object PSD S oo (ν) by the function ∝ ν −2.5 , which is a realistic model of natural scenes. 15,16,28,29 In addition, we will consider in the remainder of the paper that, unless otherwise stated, the PSD of the noise S nn (ν) is white and adjusted so that the signal-to-noise ratio (SNR) is 34 dB. The goal of co-design is to find the deconvolution filter w φ λ 0 (r) and the mask parameters φ that minimize MSE (φ, ψ) over the targeted range of defocus parameters.…”

“…14 We consider here annular binary phase masks co-optimized with a unique Wiener deconvolution algorithm. Their performance and robustness have been characterized theoretically 15 and experimentally 16 in the case of monochromatic illumination. It was shown that nearly optimal performance can be obtained with a limited number of rings and that this performance is robust to small amounts of optical aberrations.…”

End-to-end optimization of optical systems with extended depth of field under wide spectrum illumination

“…Among the many existing types of DOF extending masks, annular binary phase masks are easy to manufacture, and can be co-optimized with a simple Wiener deconvolution filter. Their performance and robustness have been characterized theoretically and experimentally in the case of monochromatic illumination [9,11,12]. However, the question remains of their efficiency under wide spectrum illumination [19,18,8].…”