CIRTEMO, SCD and Pixelteq have co-developed a miniature short-wave infrared (SWIR) hyperspectral snapshot
imager utilizing Multivariate Optical Elements (MOEs). The resultant product may address many of the detection
challenges facing multiple markets including commercial, medical, security and defense. This paper highlights the
design process of developing MOEs for a targeted application, as well as the technological challenges faced and
solutions developed for successful integration of a micro-patterned mosaic array to an InGaAs focal plane array.
The benefits of multispectral imaging are well established in a variety of applications including remote sensing, authentication, satellite and aerial surveillance, machine vision, biomedical, and other scientific and industrial uses. However, many of the potential solutions require more compact, robust, and cost-effective cameras to realize these benefits. The next generation of multispectral sensors and cameras needs to deliver improvements in size, weight, power, portability, and spectral band customization to support widespread deployment for a variety of purpose-built aerial, unmanned, and scientific applications. A novel implementation uses micro-patterning of dichroic filters<sup>1</sup> into Bayer and custom mosaics, enabling true real-time multispectral imaging with simultaneous multi-band image acquisition. Consistent with color image processing, individual spectral channels are de-mosaiced with each channel providing an image of the field of view. This approach can be implemented across a variety of wavelength ranges and on a variety of detector types including linear, area, silicon, and InGaAs. This dichroic filter array approach can also reduce payloads and increase range for unmanned systems, with the capability to support both handheld and autonomous systems. Recent examples and results of 4 band RGB + NIR dichroic filter arrays in multispectral cameras are discussed. Benefits and tradeoffs of multispectral sensors using dichroic filter arrays are compared with alternative approaches – including their passivity, spectral range, customization options, and scalable production.
Previously real-time false-colored multispectral imaging was not available in a true snapshot single compact imager. Recent technology improvements now allow for this technique to be used in practical applications. This paper will cover those advancements as well as a case study for its use in UAV’s where the technology is enabling new remote sensing methodologies.
Multispectral imaging or imaging spectroscopy obtains spectral content of an object by dividing the image data, pixel by
pixel, into wavelength (color) bands. The resulting 3D data cube (x, y, λ) allows materials to be identified by their pixel
spectral content at multiple wavelengths in addition to their spatial characteristics. A new class of multispectral imaging
systems are being developed that utilizes lithographically patterned dichroic filter arrays integrated with standard CCD
and CMOS detector arrays. These new imagers offer the unique advantage of scalability to tens of Megapixel
resolutions, compact size, and no moving parts. Our multispectral imagers are much simpler to manufacture in volume
because the complexity is in the lithographically patterned dichroics rather than in the bulk optical system. The patterned
dichroic filter arrays are fabricated utilizing standard microlithography techniques and can incorporate up to 10 different
wavelength bands deposited onto a single substrate. Each channel is selectively patterned on the substrate with the
dichroic filter coating applied using standard thin film coating techniques. The technique is repeated for all of the
wavelength bands and then the final filter array is directly attached and aligned onto the CCD.
We measured the resonator insertion losses, slope efficiencies and output power of six Nd doped Y<sub>3</sub>Al<sub>5</sub>O<sub>12</sub> (YAG)laser crystals with and without chemical etching. It was found that chemical etching lowered the insertion losses and increased the slope efficiency. Point defects were investigated by positron annihilation spectroscopy (PAS). PAS depth profiles showed that the etching efficiently removed near surface atomic-scale defects. The results suggested that chemical etching is an effective means to improve lasing properties of Nd:YAG crystals, reduce the thermal loading and increase the strength.