Patent ID: 7265824

Claim:
A method for obtaining a low-noise optical signal in a two-slit spectroscopic device, comprising: (a) injecting into a first aperture of a two aperture scanning spectroscopic device a luminous beam emitted by a sample of said spectroscopic device; (b) detecting a first intensity of the luminous beam after the luminous beam passes through the first aperture; (c) generating, in response to said detecting a first intensity of the luminous beam after the luminous beam passes through the first aperture, a basic optical signal representative of said first intensity measured as a function of time, the basic optical signal comprising at least a first peak of intensity and having a full bandwidth at a half maximum; (d) injecting the luminous beam through a second aperture of said spectroscopic device; (e) detecting a second intensity of the beam after the beam passes through the second aperture; (f) generating a corrective optical signal representative of the second intensity measured as a function of time, the corrective optical signal comprising at least a second peak of intensity and the first and second peaks of intensity being spaced by a gap; and (g) subtracting the first and second optical signal to obtain a resulting signal, the resulting signal comprising an output low-noise optical signal suitable for detection, display, control or other use, the first and second apertures being spaced by a distance so that the gap between the first peak of intensity of the basic optical signal and the second peak of intensity of the corrective optical signal corresponds to 2 to 4 times the bandwidth.