Abstract
We report a multilayer lensless in-line holographic microscope (LIHM) with improved imaging resolution by using the pixel super-resolution technique and random sample movement. In our imaging system, a laser beam illuminated the sample and a CMOS imaging sensor located behind the sample recorded the in-line hologram for image reconstruction. During the imaging process, the sample was moved by hand randomly and the in-line holograms were acquired sequentially. Then the sample image was reconstructed from an enhanced-resolution hologram obtained from multiple low-resolution in-line holograms by applying the pixel super-resolution (PSR) technique. We studied the resolution enhancement effects by using the U.S. Air Force (USAF) target as the sample in numerical simulation and experiment. We also showed that multilayer pixel super-resolution images can be obtained by imaging a triple-layer sample made with the filamentous algae on the middle layer and microspheres with diameter of 2 μm on the top and bottom layers. Our pixel super-resolution LIHM provides a compact and low-cost solution for microscopic imaging and is promising for many biomedical applications.
Highlights
Lensless in-line holographic microscope (LIHM)[1,2,3,4,5,6] provides a promising alternative to conventional microscope in application areas such as personal healthcare and telemedicine that requires compact and low-cost microscopic imaging systems
We built a prototype system to demonstrate the capability of our technique in acquiring microscopic pixel super-resolution (PSR) images of the U.S air force (USAF) target and a triple-layer biological samples consisting of filamentous algae and microsphere with a field of view of 5.7 * 4.3 mm
We observed that the movement of the sample should be smooth enough to adapt for the exposure time of the imaging sensor, and the moving range of the sample should be limited for better PSR reconstruction
Summary
Lensless in-line holographic microscope (LIHM)[1,2,3,4,5,6] provides a promising alternative to conventional microscope in application areas such as personal healthcare and telemedicine that requires compact and low-cost microscopic imaging systems. To achieve compactness in LIHM, short sample-to-sensor distance is usually required in the process of recording the holograms In this case, the resolution of the reconstructed sample image is limited by the finite pixel size of the imaging sensors instead of the numerical aperture of the imaging system. In LIHM, PSR technique has been successfully applied to reconstruct sub-pixel resolution image from multiple holograms acquired with different light illumination angles[9,10]. A high-resolution hologram was first obtained from multiple low-resolution holograms by the PSR technique, the high-resolution sample image can be reconstructed from the high-resolution holograms This technique requires multiple illumination sources and corresponding control circuits which increase the complexity of the system.
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