Current generation analog and photon counting flash lidar approaches suffer from limitation in waveform depth,
dynamic range, sensitivity, false alarm rates, optical acceptance angle (f/#), optical and electronic cross talk, and pixel
density. To address these issues Ball Aerospace is developing a new approach to flash lidar that employs direct coupling
of a photocathode and microchannel plate front end to a high-speed, pipelined, all-digital Read Out Integrated Circuit
(ROIC) to achieve photon-counting temporal waveform capture in each pixel on each laser return pulse. A unique
characteristic is the absence of performance-limiting analog or mixed signal components. When implemented in 65nm
CMOS technology, the Ball Intensified Imaging Photon Counting (I<sup>2</sup>PC) flash lidar FPA technology can record up to
300 photon arrivals in each pixel with 100 ps resolution on each photon return, with up to 6000 range bins in each pixel.
The architecture supports near 100% fill factor and fast optical system designs (f/#<1), and array sizes to 3000×3000
pixels. Compared to existing technologies, >60 dB ultimate dynamic range improvement, and >104 reductions in false
alarm rates are anticipated, while achieving single photon range precision better than 1cm. I<sup>2</sup>PC significantly extends
long-range and low-power hard target imaging capabilities useful for autonomous hazard avoidance (ALHAT),
navigation, imaging vibrometry, and inspection applications, and enables scannerless 3D imaging for distributed target
applications such as range-resolved atmospheric remote sensing, vegetation canopies, and camouflage penetration from
terrestrial, airborne, GEO, and LEO platforms. We discuss the I<sup>2</sup>PC architecture, development status, anticipated
performance advantages, and limitations.
Intensified Imaging Photon Counting (I<sup>2</sup>PC) is a new approach to flash lidar that employs direct coupling of a
photocathode and microchannel plate front end to a high-speed, pipelined, all-digital ASIC to achieve photon-counting
temporal waveform capture in each pixel on each laser return pulse. A unique characteristic of the Ball architecture is the
absence of analog components that limit temporal resolution and dynamic range. Implemented in 65nm CMOS
technology, the current generation I<sup>2</sup>PC is expected to record up to 300 photon arrivals in each pixel with 100 ps
resolution on each pulse return, and with up to 6000 range bins in each 55 μm pixel. Additional advantages of this
architecture are operation at any wavelength where photocathodes are available, intrinsically low f/# and high fill factor
capability, array sizes to >3000×3000 pixels with COTS components, extremely high dynamic range, and extremely low
false alarm rates. In addition to long-range and low-power hard target imaging, I<sup>2</sup>PC extends the scannerless capabilities
of flash lidar to distributed target applications such as
range-resolved waveform captures for atmospheric aerosol and
chemistry sensing, vegetation canopies, and camouflage penetration. As a passive imager, I2PC also brings
unprecedented speed and dynamic range to low-light and UV imaging applications.
We discuss the architecture and performance of compact, robust, alignment-free, homodyne vibrometers using telecom
diode lasers as the illumination source. The technical challenges and performance of implementations using conventional
macroscopic optical components are compared with ultra-miniature micro-bench components and assembly methods.
Focused sensitivity exceeding 4.6 pm/SQRT(Hz) at 1m range, 23 pm/SQRT(Hz) at 5m range, and useful operation to
>20m have been demonstrated with COTS 1550 nm sources, 1.5 cm transmit/receive beam diameter and 32 mW
transmitted power. Vibrometer measurement bandwidth exceeds 100 kHz with current electronics. Demonstrated
performance is suitable for a variety of defense, security, and inspection applications.
Optical Autocovariance Wind Lidar (OAWL) is a new direct-detection interferometric Doppler lidar approach that
inherently enables simultaneous acquisition of multiple-wavelength High Spectral Resolution Lidar calibrated aerosol
profiles (OA-HSRL). Unlike other coherent and direct detection Doppler systems, the receiver is self referencing; no
specific optical frequency lock is required between the receiver and transmitter. This property facilitates frequency-agile
modalities such as DIAL. Because UV laser wavelengths are accommodated, a single transmitter can simultaneously
support winds, Raman, fluorescence, DIAL, and HSRL receiver channels, each sampling identical spatial and temporal
volumes. LOS species flux measurements are acquired without the usual spatial and temporal sampling errors (or cost,
volume, mass, power, and logistical issues) incurred by separate lidar systems, or lidars in combination with other
remote or in-situ sensors. A proof of concept (POC) OAWL system has been built and demonstrated at Ball, and OAHSRL
POC is in progress. A robust multi-wavelength, field-widened OAWL/OA-HSRL system is under development
with planned airborne demonstration from a WB-57 in late 2010. Detailed radiometric and dynamic models have been
developed to predict performance in both airborne and space borne scenarios. OA theory, development, demonstration
status, advantages, limitations, space and airborne performance, and combined measurement synergies are discussed.
Coherent Technologies, Inc. has recently designed and developed an airborne Differential Absorption Lidar (DIAL) sensor that can rapidly and economically locate, identify, and quantitatively map hazardous chemical releases. The lidar was built under contract from Eastman Kodak Company and is capable of filling a broad range of chemical measurement needs. Topographic returns are used to provide simultaneous column content measurement of two (possibly three) chemical species with absorption features between approximately 2.4 microns and 3.5 microns. The system incorporates platform attitude correction and is optimized for mapping surface-source chemical plumes within swaths exceeding 50 m. This system can provide ground resolution better than 1 m at flight speeds in excess of 75 m/s. The 14-month transceiver design-and-build effort is currently in the final integration phase, and flight-testing is scheduled to begin this summer. A recently developed species-specific plume model developed by Kodak, enables reconstruction of the altitude distribution of the chemical plume and estimation of the source release rate, as well as providing realistic species-specific sensor performance predictions under differing environmental conditions. The paper discusses the system architecture, performance modeling, technology trades, and current status, and demonstrates the system measurement capabilities using modeled HCl plumes.
The University of Wisconsin High Spectral Resolution Lidar (UW HSRL) produces direct measurements of cloud and aerosol optical depth, extinction cross section, backscatter cross section, and backscatter phase
function. The HSRL uses a multietalon interferometer to separate the backsctter return into a component due to particle scattering and a component due to scattering from air molecules. The molecular backscatter component is affected by extinction but not by particle backscatter. Because the molecular backscatter cross section is determined by the known atmospheric density, the atmospheric extinction can be directly calculated from the measured decrease in molecular backscatter signal with range. The
separation of aerosol from molecular scattering is possible because the backscatter component from air is Doppler-broadened by the thermal yelocities
of the molecules, while the backscatter from more massive, slower moving particles remains spectrally unbroadened. Although the HSRL was originally designed for airborne nadir observation of boundary layer aerosol optical properties, increases in transmitted power, receiver improvements, and modified calibration techniques have allowed it to measure cirrus cloud optical properties. A continuously pumped, Q-switched, 4 kHz pulse repetition frequency, injection seeded, frequency doubled Nd:YAG laser, still under development, has recently been installed and has reduced cirrus cloud measurement averaging times by a factor of '-10.