Patent ID: 7489402

Claim:
Optical system for the stimulation and collection of fluorescent signals emitted by a target fluorophore comprising: i) a frequency modulated optical source which emits excitation light of a wavelength which will stimulate at least one target fluorophore to emit a fluorescent signal when illuminated by said excitation light; ii) a first optical filter interposed between said optical source and said target fluorophore, said first optical filter substantially preventing radiation emitted by said optical source having a wavelength which will not stimulate said target fluorophore from impinging on said target fluorophore; iii) a second optical filter interposed between said fluorophore and a photo-detector positioned to receive said emitted fluorescent signal, said second optical filter substantially preventing radiation other than said fluorescent signal from impinging on said photo-detector; and wherein said target fluorophore's cross sectional area is at least π mm 2 , wherein the beam path of at least one of the excitation light and the fluorescent signal is transmitted substantially through free space and wherein the collection efficiency provided by the optical system to said photo-detector is at least 50%.