SUMMARY
UCLA researchers have developed a new high-resolution color microscopy technique termed Demosaiced Pixel Super-Resolution (D-PSR), which significantly improves the performance of holographic high-resolution color imaging.
BACKGROUND
Digital holography refers to the acquisition and processing of holograms with a digital sensor array, typically a CCD camera or a similar device. Digital holography has became one of the most widely explored computational microscopy techniques because it permits high-throughput 3D imaging of phase and amplitude information of specimen To achieve color imaging in digital holography various methods have been employed. One of the most commonly used approaches sequentially captures three holograms at different wavelengths and then digitally cross-registers and combines these holograms to reconstruct a color image of the specimen.
As an alternative to this sequential color illumination method, simultaneous multi-wavelength illumination of the sample has also been utilized in combination with a color imager chip (e.g., with a Bayer color-filter array, CFA) to digitize the resulting multi-color hologram in one snap-shot. Compared to sequential color illumination, this simultaneous illumination approach saves experimental time. However, the reconstructed color images are lower resolution and exhibit color artifacts.
To better handle these artifacts, different Bayer demosaicing approaches have been proposed. However these methods are still short of creating an artifact-free de-multiplexing of holographic high frequency fringes created by multi-wavelength illumination.
INNOVATION
UCLA researchers have developed a new high-resolution color microscopy technique, which solves Bayer CFA related spatial sampling limitations and color artifacts of previous color de-multiplexing approaches, significantly improving the performance of holographic high-resolution color imaging. This D-PSR approach first captures a plurality of raw holograms on a Bayer color sensor chip using simultaneous multi-wavelength illumination, where the sensor plane is shifted by small increments. Then it performs pixel super-resolution based on these sub-pixel shifted raw holograms to digitally synthesize smaller pixels (e.g., by a factor of ~3 fold) for each element of the Bayer CFA. Using the pre-calibrated spectral cross-talk matrix of each filter of the Bayer CFA at the selected illumination wavelengths, this approach de-multiplex three color channels, each of which is also pixel super-resolved.
POTENTIAL APPLICATIONS
- Wavelength-multiplexing
- High-resolution holographic color imaging
- Microscopy
ADVANTAGES
- D-PSR significantly alleviates Demosaicing induced holographic color artifacts through the digital synthesis of spatially overlapping and much smaller effective pixels in each color channel.
- In D-PSR, the pixel-level spectral cross-talk of a Bayer CFA is compensated by digital de-multiplexing.
- Compared to holographic color imaging using sequential multi-wavelength illumination, D-PSR takes 3-fold less number of raw holograms/measurements while also achieving a very similar color imaging performance.
RELATED MATERIALS
PATENT STATUS
United States Of America Published Patent Application 20200393793 12/17/2020