Modern multi-camera computational imaging can enable new levels of performance beyond what is possible using conventional single-aperture imaging. We will report recent research that demonstrates how multi-camera computational imaging enables low-cost thermal-infrared imaging through 2pi steradians combined with three-dimensional imaging through obscurations. Modern consumer electronics commonly employ multiple cameras to provide multiple fields of view: we will describe how, for the first time, high-resolution imaging can be attained using an array of anamorphic cameras. Microscopy traditionally involves a trade of field of view, spatial resolution and depth of field: we show how multi-camera Fourier-ptychographic microscopy enables sub-micron gigapixel microscopy with a depth of field that is two orders-of-magnitude greater than using conventional microscopy.
The use of exotic optical modes is becoming increasingly widespread in microscopy. Particularly, propagation-invariant beams, such as Airy and Bessel beams and optical lattices, have been particularly useful in light-sheet fluorescence microscopy (LSFM) as they enable high-resolution imaging over a large field-of-view (FOV), possess a resistance to the deleterious effects of specimen induced light scattering, and can potentially reduce photo-toxicity.
Although these propagation-invariant beams can resist the effects of light scattering to some degree, and there has been some interest in adaptive-optical methods to correct for beam aberrations when they cannot, scattering and absorption of the illuminating light-sheet limit the penetration of LSFM into tissues and results in non-uniform intensity across the FOV.
A new degree of control over the intensity evolution of propagation-invariant beams can overcome beam losses across the FOV, restoring uniform illumination intensity and therefore image quality. This concept is compatible with all types of propagation-invariant beams and is characterised in the context of light-sheet image quality.
Another property to control is the wavelength of light used. Optical transmission through tissue is greatly improved at longer wavelengths into the near-infrared due to reduced Rayleigh scattering and two-photon excitation has proved beneficial for imaging at greater depth in LSFM. Three-photon excitation has already been demonstrated as a powerful tool to increase tissue penetration in deep brain confocal microscopy, and when combined with beam shaping can also be a powerful illumination strategy for LSFM.
Recent progress in shaping optical fields for LSFM will be presented.
We describe how the use of multiple-camera imaging systems provides an interesting alternative imaging modality to conventional single-aperture imaging, but with a different challenge: to computationally integrate diverse images while demonstrating an overall system benefit. We report the use of super-resolution with arrays of nominally identical longwave infrared cameras to yield high-resolution imaging with reduced track length, while various architectures enable foveal imaging, 4π and 3D imaging through the exploitation of integral imaging techniques. Strikingly, multi-camera spectral imaging using a camera array can uniquely demonstrate video-rate imaging, high performance and low cost.
Light-sheet microscopy (LSM) is an emergent fluorescence microscopy technique showing great promise for biomedical research. LSM enables rapid, high-contrast imaging of large specimens with high spatiotemporal resolution and minimal photo-damage. When imaging large specimens, the intensity of the light-sheet reduces across the field-of-view (FOV) due to absorption. This results in an image with spatially-variant intensity, affecting quantitative measurements, and ultimately limits the penetration depth of the illumination. Some existing approaches to alleviate this issue involve illuminating the sample from multiple directions or rotating the sample. These approaches are not always practical and restrict specimen choice.
Separately, propagation-invariant light modes have been used to develop high-resolution LSM techniques as they can overcome the natural divergence of a Gaussian beam, producing a thin and uniform light-sheet over long distances. Most notably, Bessel and Airy beam-based LSM techniques have been implemented.
For propagation-invariant beams, there exists a mapping between the transverse coordinate in the pupil plane of a lens, and the axial propagation in the focal plane. Spatially-variant amplitude modulation therefore offers control of the intensity of the beam with propagation.
In this paper, we report that such amplitude modulation in the pupil plane of an Airy LSM can yield a system which counteracts absorption of the light-sheet and gives uniform intensity across the FOV with a single acquisition and without restricting specimen choice. This technique is an alternative to, and may be complimented by, wavefront correction. We demonstrate this technique through numerical simulations and experimental validation in absorbing tissue phantoms.
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