Abstract
We present a high-speed transport-of-intensity equation (TIE) quantitative phase microscopy technique, named TL-TIE, by combining an electrically tunable lens with a conventional transmission microscope. This permits the specimen at different focus position to be imaged in rapid succession, with constant magnification and no physically moving parts. The simplified image stack collection significantly reduces the acquisition time, allows for the diffraction-limited through-focus intensity stack collection at 15 frames per second, making dynamic TIE phase imaging possible. The technique is demonstrated by profiling of microlens array using optimal frequency selection scheme, and time-lapse imaging of live breast cancer cells by inversion the defocused phase optical transfer function to correct the phase blurring in traditional TIE. Experimental results illustrate its outstanding capability of the technique for quantitative phase imaging, through a simple, non-interferometric, high-speed, high-resolution, and unwrapping-free approach with prosperous applications in micro-optics, life sciences and bio-photonics.
Highlights
Many objects of interest in material and life science research are phase objects
The defocus distance was controlled from −15μm to 15μm in steps of 1 μm at a switching rate of 15 Hz, and the image stack was captured within two seconds with the TL-transport-of-intensity equation (TIE) system
The flexibility offered by the TL-TIE system allows for the rapid recording of intensity images at different defocus distances with constant magnification, simple and straightforward implementation on conventional microscope at low cost without altering its original high imaging quality
Summary
Many objects of interest in material and life science research are phase objects. These objects are visualized well by techniques such as Zernike phase contrast [1] and differential interference contrast microscopy [2], but neither of these methods provide quantitative phase information, which makes data interpretation difficult. TIE phase imaging have been increasingly investigated during recent years due to its unique advantages over interferometric techniques [9, 10]: it is non-interferometric, works with partially coherent illumination, computationally simple, no need to phase unwrapping, and does not require a complicated optical system Despite these evident merits and great improvements, TIE has still not gained so much attention and widespread applications as interferometric techniques in the field of quantitative phase microscopy. One important reason is TIE typically requires a series of images captured at different focal depths, which is usually realized by translating the camera or the object manually or mechanically This complicates the image acquisition process, and prolongs the measurement time, precluding real-time observation of dynamic process. The phase blurring in traditional TIE is corrected by the deconvolution based on the defocused phase optical transfer function [18, 19], allowing high-resolution, dynamic TIE phase imaging with only three intensity recordings
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