Patent ID: 7084409

Claim:
An apparatus to measure emission time delay during irradiation of targeted samples by utilizing digital signal processing to determine the emission phase shift caused by the sample, said apparatus comprising: a source of electromagnetic radiation adapted to irradiate a target sample; means for generating first and second digital input signals of known similar frequency and phase offset; means for generating a third digital input signal having a frequency different from said first and second digital input signals; means for converting said first, second and third digital input signals to analog sinusoidal signals; means for directing said first input signal to said electromagnetic radiation source to modulate said electromagnetic radiation source by the frequency thereof to irradiate said target sample and generate a target sample emission; means for detecting said target sample emission and producing a corresponding first intermediate signal having a phase shift relative to the phase of said first input signal, said phase shift being caused by the irradiation time delay in said sample; means for producing a known phase shift in said second input signal to create a second intermediate signal; first signal down conversion means for combining the frequency of said third input signal with the frequency of said first intermediate signal to produce a first output signal representing the sum and difference frequencies between said first intermediate and said third input signals; second signal down conversion means for combining the frequency of said third input signal with the frequency of said second intermediate signal to produce a second output signal representing the sum and difference frequencies between said second intermediate and said third input signals; means for filtering out the sum frequency of each said first and second output signals; means for converting said filtered first and second analog output signals to digital first and second output signals; means for generating a fourth digital signal having a frequency the same as said second output signal; means for mixing said second digital output signal with said fourth digital signal to create a feedback signal to said fourth signal generation means to adjust the phase of said fourth digital signal until it is in quadrature with said second digital output signal; means for generating a fifth digital signal having a frequency substantially the same as said fourth digital signal; means for mixing said fifth digital signal with said first digital output signal and generating an adjustment output signal therefrom; and means for varying the phase of said fifth digital signal based on said adjustment output signal to place said fifth digital signal and said first digital output signal in quadrature to determine the phase shift caused by the emission time delay of said targeted sample.