Dynamic Phase-contrast Microscopy Research Articles

Smart optical measurement probe for autonomously detecting nano-defects on bare semiconductor wafer surface: highly sensitive observation system using phase-contrast microscopy with a spatial light modulator

Nowadays, the yield rate of semiconductor process is strongly affected even by nanoscale defects on bare Si wafer surfaces. Therefore, a non-destructive and high-speed method for detection of nanoparticle contamination is highly demanded. In this research, a nanoparticle detection method is proposed based on the fact that the volatilization process of the volatile inert liquid behaves as an autonomous nanoparticle search probe. Dynamic phase contrast microscopy (Dynamic PCM) is proposed to detect small thickness changes of a thin liquid film with high sensitivity. The dynamic PCM is expected to have double sensitivity compared to normal PCM and it is experimentally verified. Based on previous results, 4% intensity change is expected for 10 nm particles and even over 1.5% intensity change is expected for 5 nm particles by using this proposed dynamic PCM.

Multimodal biophotonic workstation for live cell analysis

A reliable description and quantification of the complex physiology and reactions of living cells requires a multimodal analysis with various measurement techniques. We have investigated the integration of different techniques into a biophotonic workstation that can provide biological researchers with these capabilities. The combination of a micromanipulation tool with three different imaging principles is accomplished in a single inverted microscope which makes the results from all the techniques directly comparable. Chinese Hamster Ovary (CHO) cells were manipulated by optical tweezers while the feedback was directly analyzed by fluorescence lifetime imaging, digital holographic microscopy and dynamic phase-contrast microscopy.

Depth-resolved velocimetry of Hagen–Poiseuille and electro-osmotic flow using dynamic phase-contrast microscopy

We quantitatively investigate the axial imaging properties of dynamic phase-contrast microscopy, with a special focus on typical combinations of tracer particles and magnifications that are used for velocimetry analysis. We show, for the first time, that a dynamic phase-contrast microscope, which is the integration of an all-optical novelty filter in a commercially available inverted microscope, can visualize three-dimensional velocity fields with a significantly reduced optical sectioning depth. The depth of field for dynamic phase-contrast microscopy is extracted from the three-dimensional response function and compared with the respective values for incoherent bright-field illumination. These results are then used to perform a depth-resolved particle image velocimetry analysis of Hagen–Poiseuille as well as electro-osmotically actuated flows in a microchannel.

Label-free analysis of microfluidic mixing processes by dynamic phase contrast microscopy

We demonstrate a dynamic phase contrast microscope based on photorefractive holographic interferometry. This system allows us to quantify concentration changes during micro-mixing processes by measuring the change of the optical path length. Therefore, no labelling processes with dyes or tracers are needed. The obtained interferograms are evaluated by an intensity analysis of every pixel, resulting in a high lateral resolution of about one micrometre, and the possibility of real-time phase determination. Due to the interferometric nature of the method the phase measurement is unambiguous for optical phase changes in the interval of zero to π radians. We present the expansion of the phase measurement range by a two-wavelength method, allowing us to resolve concentration changes down to 4 × 10−6 mol cm−3 and quantify concentrations up to 10−3 mol cm−3. The result is an optimization of the resolution by a factor of two and of the dynamic range by a factor of six in comparison to the single-wavelength technique.

A study of demyelination of nerve fibers using dynamic phase contrast microscopy.

Dynamic phase microscopy was used for evaluation of changes in myelinated axon segment in the paranodal region of nerve fibers during demyelination. Normally paranodal myelin sheath is characterized by regular oscillations of the optical path difference with frequences of 4.2 and 6.7 Hz. Demyelination decreased the amplitude and conduction velocity in nerve fibers and shifted the characteristic frequencies of optical path difference oscillations to 2.8, 3.2, and 11 Hz. These shifts of optical path difference frequencies probably resulted from disturbances in the state of charged phospholipids and a decrease in the level of bound Ca(2+)during demyelination of nerve fiber.