Patent ID: 7289195
Filing Date: 2007-10-30
Classification: F41J,G01N,G01S

Abstract:
1. A method of determining, within a predetermined atmosphere exhibiting an atmospheric electromagnetic-absorption profile, a relative direction of change in distance between an electromagnetic-energy emitting source and a predetermined location, the method comprising: providing reference-profile data indicative of an electromagnetic-absorption profile associated with a model atmosphere and including indications as to the absorption behavior, within the model atmosphere, of each wavelength of a selected set of wavelengths as a function of transmission distance; selecting a wavelength range within which to measure the relative intensity of detectable energy emitted from the emitting source, the selected wavelength range including wavelengths for which absorption behavior as a function of transmission distance is represented in the reference-profile data; selecting from within the wavelength range first and second energy sub-ranges such that (i) the first energy sub-range includes wavelengths whose average length is shorter than the average length of the wavelengths included in the second energy sub-range, (ii) the average wavelength within the first energy sub-range and the average wavelength within the second energy sub-range are disparately absorbed as a function of transmission distance in the predetermined atmosphere and (iii) each of the first and second sub-ranges includes at least one wavelength for which absorption behavior as a function of transmission distance is represented in the reference-profile data; measuring, from the predetermined location at each of first and second times, the relative intensity of detectable energy emitted from the emitting source within each of the first and second energy sub-ranges and associating relative-energy values to each of the first and second sub-ranges, each relative-energy value associated with one of the first and second sub-ranges corresponding to the intensity of energy detected in that sub-range at one of the first and second times; computing first and second ratios comparatively indicative of the intensity of energy detected, as represented by the assigned relative-energy values, within the first and second sub-ranges at each of the first and second times; and rendering, with reference to the reference-profile data, a determination as to whether the distance between the electromagnetic-energy emitting source and the predetermined location one of (a) decreased, (b) increased and (c) remained constant in the time elapsed between the first and second times based on a comparison between the first and second ratios.