Quasi-physical phase compensation in digital holographic microscopy

Abstract

In digital holographic microscopy, if an optical setup is well aligned, the phase curvature introduced by the microscope objective (MO) together with the illuminating wave to the object wave is a spherical phase curvature. It can be physically compensated by introducing the same spherical phase curvature in the reference beam. Digital holographic microscopy setups based on the Michelson interferometric configuration with MO and an adjustable lens are presented, which can well perform the quasi-physical phase compensation during the hologram recording. In the reflection mode, the adjustable lens serves as both the condensing lens and the compensation lens. When the spatial frequency spectra of the hologram become a point spectrum, one can see that the phase curvature introduced by imaging is quasi-physically compensated. A simple plane numerical reference wavefront used for the reconstruction can give the correct quantitative phase map of the test object. A theoretical analysis and experimental demonstration are given. The simplicity of the presented setup makes it easy to align it well at lower cost.

High-speed transport-of-intensity phase microscopy with an electrically tunable lens

“…The corresponding threedimensional (3D) profile is shown by converting the phase to the physical height of the lens [the refractive index of lens material (fused silica) is 1.46]. For comparison, the same sample was also measured using a digital holographic microscopy (DHM) system (laser wavelength 650 nm, magnification 43x), described in detail in [37]. Figure 4(g) shows the digital hologram captured and the high-frequency carrier fringes due to the off-axis geometry are clearly visible in the enlarged area.…”

Further investigation on the phase stitching and system errors in digital holography

“…1(b), we assume that the reference wave is generated by a point source located at x r ; y r ; z r , and the object wave is also generated by a point source located at x o ; y o ; z o , where z r is the distance between the point source of the reference wave and hologram plane; similarly, z o is the distance between the point source of the object wave and hologram plane. Thus, the reference wave Rx H ; y H and object wave Ox H ; y H in the hologram plane can be, respectively, expressed as follows [20]:…”

“…(4)] by the frequency filtering method for numerical reconstruction. Throughout this paper, the reconstructed holographic image ψ I can be calculated from ψ F H by the angular spectrum method [20] as in Eq. (5)…”

Tomographic diffractive microscopy and multiview profilometry with flexible aberration correction

“…Aberration compensation usually relies on the optimization of a quality criterium (usually the Strehl ratio combined to an aberration model [23], or the maximization of the specular component in Fourier space [24]), or a reference hologram allowing for the measurement of any departure from a perfect reference wave (i.e., plane or spherical). This reference hologram is obtained by double exposition [25], or by selecting a profile (for example, a line profile) in a flat area of the sample [26].…”