Alexander L. Kalyanov

Polychromatic low-coherence interferometry of stratified structures with digital interferogram recording and processing

The processes of formation and digital recording of interference patterns arising in partially coherent polychromatic light in the course of interference monitoring of surface microrelief in objects having stratified volume structure are considered. The expressions for the intensity distribution in the interference pattern depending on the surface relief and the object structure are derived taking the spectral properties of the photodetector array into account. The results of numerical simulation of interference fringes in polychromatic light and experimentally measured digital white light microinterferograms are presented. These results demonstrate the agreement between the theoretical model and the experimental interferograms and the possibility of solving the direct problem of low-coherence interferometry using numerical simulation of the interference pattern.

White-light full-field OCT resolution improvement by image sensor colour balance adjustment: numerical simulation

The possibility of improving white-light full-field optical coherence tomography (OCT) resolution by image sensor colour balance tuning is shown numerically. We calculated the full-width at half-maximum (FWHM) of a coherence pulse registered by a silicon colour image sensor under various colour balance settings. The calculations were made for both a halogen lamp and white LED sources. The results show that the interference pulse width can be reduced by the proper choice of colour balance coefficients. The reduction is up to 18%, as compared with a colour image sensor with regular settings, and up to 20%, as compared with a monochrome sensor.

The Influence of the Spectral Properties of Human Skin on the Resolution of a Linnik Interference Microscope

We present the results of modeling a signal in low coherent microinterferometry for different broadband sources of radiation taking into account the spectral characteristics of the optical elements, including the controlled object. We show the influence of the spectral characteristics of the object under study, human skin in particular, on the resolution of a low coherent microinterferometer. The values of interference pulse width are obtained while studying human skin using a white light emitting diode and an incandescent lamp as light sources.

Change dynamics of RBC morphology after injection glucose for diabetes by diffraction phase microscope

Experimental setup of diffraction phase microscope (DPM) with double low-coherence lighting system is presented in the paper. Algorithm of interference picture processing and optical thickness, height, volume and mean cells volume (MCV) of RBC calculating is shown. We demonstrate results of experiments with blood smears and ability of the method to calculate 3D model of the biological cells shape. Investigation change dynamics of RBC morphology after injection glucose for diabetes by DPM is shown in the paper.

Formal theory of diffraction phase microscopy

Fourier optics approach is employed in the work do describe formal theory of diffraction phase microscope (DPM). Final expression for optical field in registration plain is given. Optimal spatial filter diameter and numerical aperture is calculated theoretically. DPM is used in the work for reconstruction of phase map of red blood cells in blood slide. The filter windows diameter influence on phase map reconstruction is shown experimentally.

Method for distant diagnostics of layered media inner structure

The method of autocorrelation low coherence interferometry is proposed for diagnostics of layered media inner structure. The possible applications of this method in technology and biomedicine are presented. In this method the low coherence optical field is reflected from the objects structure and then analyzed using the Michelson interferometer. Since the object is outside of the Michelson interferometer the axial position of the object is not important and thus the object can move during the measurements. The theoretical background of this autocorrelation method for a media with discrete and continuous optical structure modification is presented.

Full-field micro-interferometry of crystallized blood plasma

Study of a protein water solution dehydration processes gives rise to a novel diagnostics methods [1,2]. Self-assembly of a drying bioliquid depends on many physical and physicochemical parameters, the slightest changes of which induce essential changes in size, arrangement and symmetry of characteristic elements of observed patterns. Various pathological processes, being taking in human organism, cause alteration of the physicochemical state of explored bioliquid. Further investigation of this problem requires instrument making it possible to efficiently track in real time drop spatial formation that would allow study of dehydration dynamics and influence of chemical and physical parameters of the solution on it.

Autocorrelation low coherence interferometry for scattering media

Method of autocorrelation low coherence interferometry (LCI) is investigated in the work and proposed for diagnostic of layered media inner structure. The autocorrelation LCI is non reference beam method [1–3]. A sample beam directs to the interferometer where optical path difference between the waves reflected from different layers within the sample is compensated. In these methods an object is out of interferometer. So any distance to object is suitable and movements of object do not influence on interference signal. The output signal represents sample field autocorrelation function. Variable component of output signal Ĩ(2Δz<inf>M</inf>) is: given equation where Δt=2Δz<inf>M</inf>/c, Δt<inf>ij</inf>=2d<inf>ij</inf>n<inf>ij</inf>/c, d<inf>ij</inf>n<inf>ij</inf> - is the optical thickness of layer contained by i-th and j-th boundaries, λ<inf>0</inf>=2πc/ω<inf>0</inf> [4,5]. There is a central pulse which corresponds to zero path difference between two sample fields in the interferometer. The side pulses are located symmetrically about the central. Location of side pulses in interference signal shows optical thicknesses of layers and serial combinations of theirs within the sample. Total number of side pulses is N = 1/2*(m² − m), where m - is the number of reflecting boundaries. Several technical and biological objects (including skin abruption and nanorods of gold [6]) were investigated using the method. Result of scanning of skin abruption is shown on fig. 1. The scheme of the object (fig. 1a) and interference signal of it (fig. 1b) are presented.

Correlation technique for exploration of local features of emission spectrum of laser and superluminescence diodes

It is well known that the spectral properties of the light source relate explicitly to the correlation properties of the source field. Thus it is possible to have an action on the correlation function of the source affecting on emission spectrum. It is shown in this paper that correlation analysis of the light source field allows to perform control of the spectral properties of the source. Availability of Michelson interferometer for investigation of the thin structure of emission spectrum of superluminescent diodes (SLD) and appreciation of the use of its in low coherence interference schemes are discussed in this work.

Effects of spatial and temporal coherence of optical wide frequency and angle spectrum fields in Michelson interferometer

Effects of spatial coherence of optical field with wide frequency and angular spectra in the Michelson interferometer are studied. Manly effects of longitudinal spatial coherence are considered. It is shown that in classical configuration of the Michelson interferometer the effects of not temporal, but spatial coherence are taken place. Experimental data of observation of spatial and temporal coherence effects in image domain behind a lens at the output of the Michelson interferometer are shown.