Photon counting ladar work at FOI, Sweden

Abstract

Photon counting techniques using direct detection has recently gained considerable interest within the laser radar community. The high sensitivity is of special importance to achieve high area coverage in surveillance and mapping applications and long range with compact systems for imaging, profiling and ranging. New short pulse lasers including the super continuum laser is of interest for active spectral imaging. A special technique in photon counting is the "time correlated single photon counting" (TCSPC). This can be utilized together with short pulse (ps) lasers to achieve very high range resolution and accuracy (mm level). Low average power lasers in the mW range enables covert operation with respect to present laser warning technology.By analyzing the return waveform range and shape information from the target can be extracted. By scanning the beam high resolution 3D images are obtained. At FOI we have studied the TCSPC with respect to range profiling and imaging. Limitations due to low SNR and dwell times are studied in conjunction with varying daylight background and atmospheric turbulence. Examples of measurements will be presented and discussed with respect to some system applications.

Simulating the performance of laser imaging and range profiling of small surface vessels

“…For the 8 km data the main peak location were also in good correspondence with the "true" values from the CAD models except for 3 cases where the peaks at larger depth were missed due to low SNO and occlusion. We can also conclude that it would be valuable if the range resolution could be improved for example using TCSPC techniques [25]. The simple peak finding algorithm will also give larger range errors a compared with other techniques such as constant fraction detection, Gauss fitting, correlation and others [26].…”

Time-correlated single-photon counting range profiling and reflectance tomographic imaging

“…In addition to laterally unresolved range profiling and reflectance tomographic imaging, TCSPC laser radar can generate high resolution 3D data using a step-andstare mode, although this scheme has the disadvantage of long scanning times with the present TCSPC setup [35]. However, point-to-point high-resolution range-resolved studies are of importance in several applications.…”

“…In addition, high-resolution 3D datasets could be generated by mechanically scanning the FOV of the TCSPC system [35]. This feature was implemented in a LabView application allowing low speed scanning.…”

Simulation and modeling of laser range profiling and imaging of small surface vessels

“…An overview of the TCSPC work at FOI was recently presented at SPIE. 22 This allowed us to use small toy models of ships to study range profiling and convert the results to real targets and systems by scaling about a factor of 10 to 100 in size. Our laboratory TCSPC ladar system had a time response of 54 ps corresponding to a range resolution of 0.8 cm.…”