Passive ranging using a filter-based non-imaging method based on oxygen absorption

Abstract

To solve the problem of poor real-time measurement caused by a hyperspectral imaging system and to simplify the design in passive ranging technology based on oxygen absorption spectrum, a filter-based non-imaging ranging method is proposed. In this method, three bandpass filters are used to obtain the source radiation intensities that are located in the oxygen absorption band near 762 nm and the band's left and right non-absorption shoulders, and a photomultiplier tube is used as the non-imaging sensor of the passive ranging system. Range is estimated by comparing the calculated values of band-average transmission due to oxygen absorption, τ , against the predicted curve of τ versus range. The method is tested under short-range conditions. Accuracy of 6.5% is achieved with the designed experimental ranging system at the range of 400 m.

Monocular passive ranging through a PQ:PMMA holographic wavelength division demultiplexer

“…Finally, due to the third issue, it will be necessary to consider band-averaged values throughout the calculations. For this reason, it is not possible to reorder equation ( 1) to obtain a mathematical expression for the distance, L. Instead, an Elsasser band model is typically used to fit a curve to known distance measurements; 1,4,5 this model yields an equation with adjustable parameters that assumes equal spacing of equal-strength absorption lines. Due to these assumptions, the model is only accurate when averaged over a spectral band, which is the case for MPR.…”

“…More specifically, MPR as first proposed by M. R. Hawks 1 observes the optical spectrum of an emissive target around the 762 nm absorption band of O2 as well as the non-absorbing 750 nm and 780 nm bands in order to calculate the total transmissivity of this particle species, from which a range estimate can be obtained. This method has been used to estimate distance for rockets, fighter jets, and reference lamp sources [2][3][4][5][6] , yielding errors below 7% and 3% for long and short distance experiments, respectively. However, most of these experiments have been performed either with a Fourier transform spectrometer or by switching between three bandpass filters in series, significantly impacting the feasibility of the systems.…”

Absorption-Based Ranging from Ambient Thermal Radiation without Known Emissivities

“…Short-range [26] and long-range [17] demonstrations of the method were shown by tracking a hot lamp and a Falcon 9 rocket, respectively. Following the work on O 2 absorption, a cheaper optical system was developed with three spectral filters [18], [27]. The system was later tested with a jet engine [28].…”