Structured illumination for resolution enhancement and autofocusing in digital holographic microscopy

Abstract

In this Letter we show how resolution enhancement and autofocusing in digital holographic microscopy is obtained by using structured illumination generated by a spatial light modulator, which enables it to project fringes of different orientations and phase shift without mechanical movement. The image plane is numerically determined by searching for the minimal deviation between the reconstructed images carried by different diffraction orders of the structured illuminations.

Enhancing spatial resolution in digital holographic microscopy by biprism structured illumination

“…The methodology of SIM has been recently adopted in DHM to improve the spatial resolution as transparent samples are imaged [8,11]. The needed multiple images to synthesize the extended transfer functions are obtained either by using a spatial light modulator [8] or by the interference of two diffracted waves from a diffraction grating [11]. In this Letter, we also present the enhancement of the spatial resolution in DHM by using a SIM-like methodology.…”

“…To increase the resolving power either shorter wavelengths can be utilized [4] or the NA can be increased [1,[5][6][7]. The enlargement of the NA, namely, the increasing of the capability of gathering spatial frequencies, can be achieved either in the space [5] or in the spatial frequency-domain [1,7,8]. The latter methods can be categorized as those that synthesize an enlarged transfer function.…”

“…Perhaps the most notable architecture that improves the spatial resolution by this way is the structured illumination microscopy (SIM) [9,10]. The methodology of SIM has been recently adopted in DHM to improve the spatial resolution as transparent samples are imaged [8,11]. The needed multiple images to synthesize the extended transfer functions are obtained either by using a spatial light modulator [8] or by the interference of two diffracted waves from a diffraction grating [11].…”

“…In this Letter, we also present the enhancement of the spatial resolution in DHM by using a SIM-like methodology. The main differences with the recently reported advances in this direction [8,11] are: (1) the use of a Fresnelś biprism [2] to produce periodic illumination pattern over the object plane; (2) the use of unknown phase-shifting to synthesize the enlarged transfer function; and (3) the optimized utilization of the space bandwidth of the recording device.…”

“…SIM-like strategies illuminate the sample with a periodic wave, field to improve the lateral resolution [8][9][10][11]. As illustrated in Fig.…”