Lensless microscopy, also known as computational or holographic microscopy, is an imaging technique that captures and reconstructs microscopic images without the use of traditional lenses. Instead of relying on conventional lenses to magnify and focus light, lensless microscopy employs computational methods to reconstruct images from the diffraction patterns or holograms generated by the interaction of light with the specimen.
Key features and principles of lensless microscopy:
Digital holography: Lensless microscopy often involves digital holography, where the entire wavefront of light interacting with the specimen is recorded. This recorded hologram contains information about both the amplitude and phase of the light, enabling the reconstruction of a high-resolution image of the specimen.
Inline holography: In inline holography, the specimen is illuminated by coherent light, and the resulting interference pattern is directly recorded on a digital sensor, such as a charge-coupled device (CCD) or a complementary metal-oxide-semiconductor (CMOS) sensor.
Off-axis holography: Off-axis holography involves introducing a slight angle between the reference and object beams, which simplifies the hologram recording process and aids in the reconstruction of the specimen image.
Computational reconstruction: After capturing the holographic data, sophisticated algorithms and computational techniques are applied to reconstruct the image of the specimen. These computational methods can recover both intensity and phase information, providing quantitative data about the sample.
Wide field of view: Lensless microscopy often offers a wide field of view because it doesn't rely on physical lenses, allowing for the imaging of larger sample areas in a single acquisition.
Applications: Lensless microscopy has applications in various fields, including biology, medicine, and material science. It can be particularly useful for studying transparent or phase-sensitive specimens without the need for staining or labeling.
Portable and compact: Lensless microscopy setups can be more compact and portable than traditional microscope systems since they do not require complex optics. This makes them potentially suitable for point-of-care diagnostics or field applications.
Quantitative phase imaging: Lensless microscopy is capable of providing quantitative phase information, allowing researchers to study dynamic processes, such as cell migration or division, in addition to capturing the morphology of the specimen.