APPLICATIONS OF TECHNOLOGY:
- Food inspection
- Biomedical imaging, diagnostic screening
- Flame chemistry
- Remote sensing — astronomy, space, earth observation
- Machine vision
- Camera manufacturers
- Captures changing spatio-spectral information over time
- Compact and lightweight, with few external optics required
- Fast and highly sensitive, works with low light
- Configurable resolution
- Tunable to specific bandpasses of interest (including multiple narrowbands)
- Lower cost, can be bulk manufactured
Scientists have developed a compact and lightweight optical device that can perform spatially resolved spectroscopy at low levels of visible light. The team — led by Joshua Bloom, a Berkeley Lab physicist and UC Berkeley professor, and UC Davis physicist John Tyson — designed a “hyperspectral” imaging system to harvest specific bands of visible light as it shines through a thin stack of precision optical filters. These microfabricated filters divert photons of selected wavelengths to a parallel and adjacent stack of tiny photon detectors. Using this simple architecture, arrays of these devices laid out on a focal plane can rapidly capture the color and intensity of a changing scene at high spatial and moderate spectral resolution.
Each “dichroic” filter is coated to reflect one specific wavelength while letting the rest of the spectrum pass through unimpeded; this allows for customized designs in which selected multiple bands of light can be captured. Berkeley Lab’s device is designed to pick off a succession of spectral bands as photons descend a gauntlet of miniaturized dichroic filters, each one tuned to reflect a different wavelength from near-red to ultraviolet. Reflected photons are directed to a charged-couple device (CCD) that records the light intensity of that particular band. A stack of CCDs linked to its companion stack of dichroic filters records the spectral signature of each column of light. Thousands of these micro-scale stacks can be arrayed in a grid to form a focal plane for collection of spatially resolved hyperspectral images in real time.
The current generation of hyperspectral imaging equipment is large, cumbersome, and costly, so the scientific and commercial potential of hyperspectral imaging has been sharply limited. The Berkeley Lab technology overcomes that limitation by tapping fabrication techniques developed in the microelectronics and digital camera industries. It is lightweight, solid state, and if manufactured at significant scale, potentially inexpensive to produce. This could significantly expand the market for hyperspectral imaging equipment to other domains where the return on investment has not yet created an obvious need.
Hyperspectral imaging equipment is used today throughout industry. For example, in machine vision systems, hyperspectral imaging devices identify contamination of fruits and vegetables: The multiple bands of an image can resolve the signature of bacteria or fruit bruising in surface anomalies otherwise invisible to the human eye. Because the imaging is in real time, large numbers of objects in motion can be scrutinized, such as food being sorted on a high-speed inspection line, or the images can produce a dynamic picture for analysis of processes as fast and complex as combustion.
Future commercial digital cameras could also use this device for enhanced post-processing because they could capture more bands of light than the three bands currently used. The technology could be applied to new generations of medical diagnostic equipment or in laboratories to monitor biological activity at the cellular or inter-cellular level. Because of the exquisite sensitivity of CCD detectors, the devices could also be used in low-light remote sensing instruments on Earth or aboard spacecraft.
DEVELOPMENT STAGE: Early stage research.
STATUS: Issued U. S. Patent 9,257,478. Available for licensing or collaborative research.
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REFERENCE NUMBER: IB-3163