tailieunhanh - An advanced logarithmic phase mask for extending depth of field of hybrid optical systems

In this paper, an advanced logarithmic phase mask is proposed and its performance is investigated. The essential performance characteristics of phase masks are shown, including the defocused modulation transfer functions (MTF), integral area of the MTF, Hilbert space angle, non-axial Strehl ratio, and decoded images. The results have demonstrated that our phase mask is highly beneficial to extend the depth of field of hybrid optical systems. The advantages of the proposed phase mask in comparison to some other masks are also pointed out. | Communications in Physics, Vol. 27, No. 1 (2017), pp. 45-53 DOI: AN ADVANCED LOGARITHMIC PHASE MASK FOR EXTENDING DEPTH OF FIELD OF HYBRID OPTICAL SYSTEMS LE VAN NHU, PHAN NGUYEN NHUE, LE HOANG HAI † Le Quy Don Technical University, 236 Hoang Quoc Viet, Bac Tu Liem, Hanoi, Vietnam † E-mail: haiktq@ Received 27 February 2017 Accepted for publication 31 March 2017 Abstract. In this paper, an advanced logarithmic phase mask is proposed and its performance is investigated. The essential performance characteristics of phase masks are shown, including the defocused modulation transfer functions (MTF), integral area of the MTF, Hilbert space angle, non-axial Strehl ratio, and decoded images. The results have demonstrated that our phase mask is highly beneficial to extend the depth of field of hybrid optical systems. The advantages of the proposed phase mask in comparison to some other masks are also pointed out. Keywords: extended depth of field, hybrid imaging system, phase mask, wavefront coding. Classification numbers: , . I. INTRODUCTION Hybrid imaging systems, in which a phase mask is placed in the pupil plane to make the modulation transfer function (MTF) or the point spread function (PSF) less sensitive to defocus, can be used in many applications, such as aberrations reduction [1, 2], thermal imaging [3, 4], iris recognition [5,6]. In a hybrid imaging system, the incident wavefront is intentionally coded with a phase mask and the optically blurred images will be deblurred and decoded by a digital processing. The essential part of hybrid imaging systems is the phase mask that is designed suitably to obtain invariant image quality with defocus. During the last years, a large number of researchers over the world have been keeping their eyes on the development of hybrid imaging system and many kinds of phase mask have been reported, such as cubic phase mask [1], logarithmic phase mask [7–10], exponential phase