The next generation of multispectral sensors and cameras needs to deliver significant improvements in size, weight, portability, and spectral band customization to support widespread commercial deployment for a variety of purposebuilt aerial, unmanned, and scientific applications.The benefits of multispectral imaging are well established for applications including machine vision, biomedical, authentication, and remote sensing environments -but many aerial and OEM solutions require more compact, robust, and cost-effective production cameras to realize these benefits. A novel implementation uses micropatterning of dichroic filters into Bayer and custom mosaics, enabling true real-time multispectral imaging with simultaneous multi-band image acquisition. Consistent with color camera image processing, individual spectral channels are de-mosaiced with each channel providing an image of the field of view. We demonstrate recent results of 4-9 band dichroic filter arrays in multispectral cameras using a variety of sensors including linear, area, silicon, and InGaAs. Specific implementations range from hybrid RGB + NIR sensors to custom sensors with applicationspecific VIS, NIR, and SWIR spectral bands. Benefits and tradeoffs of multispectral sensors using dichroic filter arrays are compared with alternative approaches -including their passivity, spectral range, customization options, and development path. Finally, we report on the wafer-level fabrication of dichroic filter arrays on imaging sensors for scalable production of multispectral sensors and cameras. CURRENT HYPERSPECTRAL & MULTISPECTRAL APPROACHESThe objective with spectral imaging is not only to acquire the spatial information of an object or scene, but also to extract the spectral information associated with each particular spatial location within the frame. By definition, a monochrome sensor -commonly employed in many scientific grade imaging systems -cannot distinguish between incoming light of different colors. Obtaining this spectral information requires dispersing the light across the sensor, sacrificing one axis of spatial information (hyperspectral imaging), or pre-filtering the light prior to reaching the detector and acquiring a series of spectrallyselective images (multispectral imaging).In a way, the spectral information can be considered a third data "dimension," similar to physical depth. With a single two-dimensional detector, gathering this information requires projecting acquisition into a third dimensiontime. In hyperspectral imaging, one spatial axis and the spectral information are acquired simultaneously, and the second spatial axis is obtained by acquiring sequential images. In multispectral imaging, both spatial axes are acquired simultaneously, while the spectral information is sequentially acquired over time.Each imaging methodology has drawbacks and tradeoffs, the relevance of which varies with application. Hyperspectral imaging can provide substantial spectral information and uninterrupted spatial information with sufficient image ac...
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