Abstract
To achieve high-resolution and wide field-of-view, digital holographic imaging techniques need to tackle two major challenges: phase recovery and spatial undersampling. Previously, these challenges were separately addressed using phase retrieval and pixel super-resolution algorithms, which utilize the diversity of different imaging parameters. Although existing holographic imaging methods can achieve large space-bandwidth-products by performing pixel super-resolution and phase retrieval sequentially, they require large amounts of data, which might be a limitation in high-speed or cost-effective imaging applications. Here we report a propagation phasor approach, which for the first time combines phase retrieval and pixel super-resolution into a unified mathematical framework and enables the synthesis of new holographic image reconstruction methods with significantly improved data efficiency. In this approach, twin image and spatial aliasing signals, along with other digital artifacts, are interpreted as noise terms that are modulated by phasors that analytically depend on the lateral displacement between hologram and sensor planes, sample-to-sensor distance, wavelength, and the illumination angle. Compared to previous holographic reconstruction techniques, this new framework results in five- to seven-fold reduced number of raw measurements, while still achieving a competitive resolution and space-bandwidth-product. We also demonstrated the success of this approach by imaging biological specimens including Papanicolaou and blood smears.
Highlights
To achieve high-resolution and wide field-of-view, digital holographic imaging techniques need to tackle two major challenges: phase recovery and spatial undersampling
Twin image and spatial aliasing signals, along with other digital artifacts, are interpreted as noise terms that are modulated by phasors that analytically depend on the lateral displacement between hologram and sensor planes, sample-to-sensor distance, wavelength, and the illumination angle
The propagation phasor approach of this manuscript relies on the fact that in the digital hologram of a specimen, the twin image noise and spatial aliasing signals vary under different imaging configurations
Summary
To achieve high-resolution and wide field-of-view, digital holographic imaging techniques need to tackle two major challenges: phase recovery and spatial undersampling. For wide-field implementations of high-resolution holographic microscopy, another limitation is posed by pixelation of the holograms since high magnification optics (e.g., objective lenses) or fringe magnification in the form of large distance wave propagation would both result in a significant reduction in the imaging volume and the field-of-view of the microscope These challenges of spatial aliasing (i.e., undersampling) and twin image noise in digital holography have been addressed by pixel super-resolution and phase retrieval techniques, implemented sequentially to reconstruct images of the specimen with ultra-large space-bandwidth-products[16,25,36,37,38]. In a multi-height configuration (i.e., using multiple sample-to-sensor distances)[25,36,37,44], if 4 × 4 pixel super-resolution is implemented at eight different heights, the total number of raw holograms to be captured becomes 128, which could be a limitation for e.g., high-speed imaging applications
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