Date of Completion
Qing zhu, Kazunori Hoshino
Field of Study
Master of Engineering
Fourier ptychographic (FP) imaging is a recently developed technique to get high-resolution high-throughput imaging. FP iteratively stitches together many variably illuminated, low-resolution intensity images in the Fourier space to expand the frequency passband and recover a high-resolution sample image.
There are several latest developments of the Fourier ptychographic imaging scheme. FP scheme can be used as adaptive imaging method. An image-quality metric is defined as a guide star for the optimization process, and system corrections are then performed to maximize such a guide star. The adaptive FP scheme performs system correction by modifying the complex transfer function in the recovery process, which can be used to recover the unknown pupil function, perform system correction and recover unknown system parameters.
To shorten the acquisition time of the FP platform, sparsely sampled FP, which uses a sparse-sampled mask to filter the captured intensity images, is developed and it reduced the acquisition time by ~ 50%. In addition, the application of sub-sampled Fourier ptychography solved the pixel aliasing problem.
State-multiplexed FP, which allows the illumination of at most 4 LEDs at the same time, is able to shorten the acquisition time and the number of frames for 2~4 times. Similar reconstruction procedure is used to decompose R/G/B data and recovery a colorful high-resolution image, which can also be used to replace spectral filter, gratings or other optical components for spectral multiplexing and demultiplexing.
Pattern-illuminated FP extends the original FP from coherent imaging to incoherent imaging. Instead of using coherent light with different incident angles, pattern-illuminated FP uses different structured pattern to illuminate sample, and then recover a high resolution image.
Finally, based on the FP algorithm, a field-portable high-resolution microscope using a cellphone lens was design for low-cost imaging. It uses a cellphone lens in a reverse manner and a LED array as illumination. The FPscope can get a maximum synthetic numerical aperture (NA) of 0.5 and depth-of-focus of 0.1mm, which is longer than that of a conventional microscope objective with a similar NA.
DONG, SIYUAN, "Developments of Gigapixel Microscopy" (2014). Master's Theses. 687.