We address a multi-spectral holographic imaging of optically transparent objects widely used in biomedical studies and industrial inspection. Instead of complicated optomechanical systems based on several light sources, our setup is based on acousto-optic tunable filter (AOTF) coupled with a broadband light source, which enables fast and highly effective spectral selection within a wide wavelength range. The filtered light enters the Mach-Zehnder interferometer and produces the interference pattern captured by camera and processed in the spatial frequency domain to extract amplitude and phase information about the inspected sample. We compare successive acquisition of several single-wavelength holograms and two single-shot modes for obtaining wavelength-multiplexed holograms using either sequential tuning to several wavelengths during the exposure time of the sensor or multi-frequency AOTF driving. The effectiveness of AOTF-based setup for multi-spectral digital holographic microscopy in all modes is demonstrated by the quantitative phase imaging of red blood cells smear specimens. The results of the study may be helpful to choose the optimal mode based on several criteria, such as required spatial and spectral resolution, field of view and image acquisition time, as well as for the optimization of AOTF-based setups for digital holography.
We address the problem of single-shot color multiplexed digital holography and propose its new technical realization. To acquire a three-wavelength interference pattern, we propose to implement spectral filtration of wide-band light by means of acousto-optical tunable filter (AOTF) providing three-band operation. We describe digital image processing procedure for amplitude and phase information extraction, and confirm its effectiveness experimentally. Proposed approach may be effective for the detection and classification of structural elements without spectral or mechanical scanning.
We address the problem of differential diagnostics of chronic spontaneous urticaria and urticarial vasculitis. The clinical pictures of these two allergy diagnoses are similar, however a well-trained pathologist can see the differences in skin tissue on the microscopic level, and thus the histological study of skin biopsy is usually performed to prescribe the right treatment. To increase the throughput and quality of the histological study and differential diagnostics of chronic spontaneous urticaria and urticarial vasculitis, we propose an imaging system with neural-network-based classification of skin tissue structures. The capabilities of a hyperspectral microscopic visualization system with acousto-optical module for increasing the efficiency of neural network training are also being considered.
Quantitative phase imaging is widely used in biomedical and industrial applications for morphology and dynamics characterization of various unstained samples with nanoscale sensitivity. Registration of phase images in multiple narrow wavelength bands enables analysis of spectral properties as well as extending the dynamic range and increasing the accuracy of quantitative phase measurements. In this paper, we present a new scheme for hyperspectral quantitative phase imaging, based on acousto-optic filtration of light in lens-in-lens common-path interferometer. It may be implemented as a PC-controlled compact add-on module for light microscope, has a robust and vibration insensitive design, and allows a quantitative phase imaging of various samples. Acousto-optic filtration provides fast and arbitrary wavelength tuning within a wide range with high spectral resolution. Choosing proper parameters of the interferometer and acousto-optical filter allows adapting the proposed scheme to many microscopy applications.
We propose to use an acousto-optic tunable image filtration to implement spectral and phase measurements in nearcommon-path interferometric module based on Michelson interferometer with artificial reference light source. In such two-beam interferometer, reference beam is formed via spatial filtration from one of the light beams. The module may be placed at the output of the imaging device for obtaining wideband images of the inspected object, such as, for example, camera port of transmitted light microscope. Acousto-optical tunable imaging filter is necessary to enable spectral measurements as well as quantitative phase retrieval.
A compact and cost-effective lens-in-lens common-path interferometer for quantitative phase imaging of objects in white light as well as in narrow spectral bands is proposed. The optical system of the interferometer includes three lenses. The first component of the interferometer consists of two lenses with the same focal length, but different diameters. The lens with the smaller diameter is installed inside the hole in the bigger diameter lens. The light wave is thus divided into two beams. The second component is a single lens. A pinhole is placed between the first and the second components in their joint focal plane. The pinhole serves as a spatial filter to form a reference wavefront from one of the beams passed through the first component. The reference and the object beams are collected by the second component, and the digital holographic pattern resulting from their interference is registered by the camera. The performance of the system is demonstrated by quantitative phase imaging of red blood cells, onion cells and nylon fiber with use of green and red laser light sources.
Multi-spectral imaging techniques are widely used in microscopy for many applications. One of the most widespread spectral elements for this purpose is an imaging acousto-optic tunable filter (AOTF). AOTF-based contrast visualization is especially effective when used together with other imaging techniques. Simultaneous utilization of two or more imagers requires optical coupling to provide point-to-point matching of the obtained images. Small linear and angular aperture of AOTF additionally hampers the development of multi-sensor imaging systems for microscopy. In this paper, we present a compact optical system which allows to integrate AOTF-based spectral imager into the schemes of conventional microscopes and provide high-quality spectral image of the same scale as in another, for example, wideband channel. The effectiveness of the proposed approach is demonstrated experimentally.
Endoscopic instrumentation is widely used for diagnostics and surgery. The imaging systems, which provide the hyperspectral information of the tissues accessible by endoscopes, are particularly interesting and promising for in vivo photoluminescence diagnostics and therapy of tumour and inflammatory diseases. To add the spectral imaging feature to standard video endoscopes, we propose to implement acousto-optical (AO) filtration of wide-band illumination of incandescent-lamp-based light sources. To collect maximum light and direct it to the fiber-optic light guide inside the endoscopic probe, we have developed and tested the optical system for coupling the light source, the acousto-optical tunable filter (AOTF) and the light guide. The system is compact and compatible with the standard endoscopic components.
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