Martin Antos

Off-axis setup taking full advantage of incoherent illumination in coherence-controlled holographic microscope.

Coherence-controlled holographic microscope (CCHM) combines off-axis holography and an achromatic grating interferometer allowing for the use of light sources of arbitrary degree of temporal and spatial coherence. This results in coherence gating and strong suppression of coherent noise and parasitic interferences enabling CCHM to reach high phase measurement accuracy and imaging quality. The achievable lateral resolution reaches performance of conventional widefield microscopes, which allows resolving up to twice smaller details when compared to typical off-axis setups. Imaging characteristics can be controlled arbitrarily by coherence between two extremes: fully coherent holography and confocal-like incoherent holography. The basic setup parameters are derived and described in detail and experimental validations of imaging characteristics are demonstrated.

Coherence-controlled holographic microscope

In the paper a new off-axis achromatic interferometer configuration of a digital holographic microscope is presented. The proposed configuration uses a reflective diffraction grating and ensures a high-contrast interference pattern in the output plane of the microscope using illumination of an arbitrary degree of temporal and spatial coherence. The concept of this optical system brings a significant improvement of microscope parameters, enables implementation of conventional observing techniques and is more user-friendly in comparison with the previous generation of the microscope. The functionality of the microscope has been proved experimentally.

Tomographic system for 3D temperature reconstruction

The novel laboratory system for the optical tomography is used to obtain three-dimensional temperature field around a heated element. The Mach-Zehnder holographic interferometers with diffusive illumination of the phase object provide the possibility to scan of multidirectional holographic interferograms in the range of viewing angles from 0 deg to 108 deg. These interferograms form the input data for the computer tomography of the 3D distribution of the refractive index variation, which characterizes the physical state of the studied medium. The configuration of the system allows automatic projection scanning of the studied phase object. The computer calculates the wavefront deformation for each projection, making use of different methods of Fourier-transform and phase-sampling evaluations. The experimental set-up together with experimental results is presented.

System for optical tomography

A basic description of the system for optical tomography with diffusive illumination of the phase object is presented. The configuration of the system allows automatic projection scanning of the studied phase object (such as a burner flame or temperature fields around heated elements) in the range of viewing angles from 0 deg to 90 deg. The object’s projections are obtained using multidirectional holographic interferometry and consequently digitized by a CCD camera. A computer then calculates the wavefront deformation for each projection, and the subsequent tomographic reconstruction of each horizontal slice of the object is processed. Finally, all slices are interpolated and displayed. Here we present the experimental setup along with some experimental results.

System for coherence-controlled holographic microscopy of living cells

Coherence Controlled Holographic Microscopy (CCHM) is a novel holographic technique for quantitative-phasecontrast (QPC) biological observations particularly of living cells. Owing to the ordinary (low coherence) illumination source, the CCHM images are of low noise, deprived of coherence noise (speckles) and the lateral resolution is improved by a factor of 2 compared to classic holographic microscopes. Long-lasting time-lapse experiments require elimination of the CCHM optical system instability in order to achieve precise QPC measurement and to maintain correct CCHM adjustment for its low-coherence operation. The critical part of CCHM is the interferometer, which is very sensitive to temperature fluctuations and air turbulences. The temperature stabilization of the whole microscope without air turbulences is therefore required to provide stability for long-term observations of living cells. Novel heated microscope box and stage designed and constructed for this purpose are described in the paper. The system maintains a constant temperature of both the microscope and of the sample set to 37 °C thus providing optimal living conditions for living human and animal cells. The system is completed with a novel flow-chamber for living-cells accommodation during observation. A service of the system to CCHM is demonstrated by a series of pictures of growing cells.

Coherence-Controlled Holographic Microscopy for Coherence-Gated Quantitative Phase Imaging

We show that the use of incoherent illumination in coherence-controlled holographic microscopy (CCHM) enables coherence-gated quantitative phase imaging of objects through turbid media. Also high lateral resolution and strong suppression of coherence noise is demonstrated.

The design of 3D optical system for multidirectional phase tomography

The design of 3D optical system for multidirectional phase tomograph is presented in detail. The suggested tomograph uses a multidirectional holographic interferometer with diffusive light. The method of dividing of the laser-beam to object and reference beams is described. The optimisation of geometrical dimensions of the testing area and optical parameters of projection beams was done in order to increase the number of obtainable angular projections. Finally, projecting properties of the scanning system of the tomograph are presented.

Multidirectional holographic interferometer with dodecagon geometry

A proposed design of the multidirectional holographic interferometer (MHI) with diffusive illumination in 3D dodecagon geometry for optical tomography is presented. The beam from Nd-YAG laser is divided and transformed to six object beams that incident to diffusors and illuminate the cross section area. The optical axes of reference beams lie in six vertical planes that are turned 30 degrees to each other, which is the specific of our design. Next is discussed the constructional design of mechanical realization of filtering and collimating optics as well as the ways of traction of the rotationally embedded scanning system of CCD cameras. Finally, optical and mechanical properties of interferometer are digestedly summarized.