Patent ID: 7323673
Filing Date: 2008-01-29
Classification: G01C,G01J

Abstract:
1. A method for detecting a modulated light beam, said method comprising: (a) receiving an electromagnetic laser signal having at least one predetermined range of wavelengths and at least one predetermined first modulation frequency, and converting said electromagnetic laser signal into a first electrical signal; (b) converting said first electrical signal from said at least one predetermined first modulation frequency to a second signal having at least one predetermined second, different frequency that is related to said at least one predetermined first modulation frequency; (c) sampling, over a sampling time interval, said second signal at a rate that is an integer multiple of said at least one second frequency, and determining a substantially instantaneous magnitude of said sampled second signal, thereby deriving multiple values A that each represent the substantially instantaneous magnitude of said sampled second signal; (d) determining a Discrete Fourier Transform (DFT) value for each said sampled second signal A over at least one complete period of said second frequency, thereby deriving multiple DFT values B; (e) after all samples are taken for a predetermined sample period, determining real and imaginary components of said multiple DFT values B, thereby deriving multiple values C; (f) determining a magnitude of a spectral component of said multiple values C, thereby deriving multiple values D; and (g) using one of said values D to substantially represent a steady state signal magnitude that is used as a representation of a signal strength of said second signal over the sampling time interval, and thereby determining a relative strength of said received modulated electromagnetic signal.