High performance CCD-based thermoreflectance imaging using stochastic resonance

A method of performing thermoreflectance measurements, comprising:

• modulating temperature of a sample at a selected modulation frequency (f),
• illuminating a portion of the sample with radiation having one or more selected wavelength components,
• utilizing a digital imaging system having a plurality of pixels to detect radiation reflected from the sample in response to said illumination to generate reflectance images of the sample, wherein said imaging system is triggered to obtain a selected number of reflectance images in one period of the temperature modulation,
• calculating from said images a map of relative reflectance changes of said sample, and
• iterating said step of acquiring reflectance images over a sufficient number of periods of said temperature modulation so as to obtain a sufficiently small uncertainty in the calculated relative reflectance such that signals smaller than a code width of said digital imaging system can be detected.

A method of performing thermoreflectance measurements, comprising

• adding noise having a known distribution about an average value to a digital detection system such that a root-mean-square of the noise is greater than a spacing between quantization levels of said detection system,
• utilizing said detection system to acquire digital images of radiation reflected from a surface of a sample in response to an illuminating radiation while a temperature modulation is applied to the sample,
• deriving a map of relative changes in reflectivity of said sample surface based on said images, and
• repeating acquisition of digital images until uncertainty in the reflectivity changes is reduced to a value less than said spacing between the quantization levels.

A method of performing thermoreflectance measurements, comprising:

• modulating temperature of sample at a selected modulation frequency f1,
• illuminating a portion of the sample with radiation modulated at a different frequency f2,
• utilizing a digital imaging system to detect radiation reflected from the sample, modulated at a difference frequency equal to a difference of said f1 and f2 frequencies in response to said illumination to generate reflectance images of the sample, wherein said imaging system is triggered to obtain a selected number of reflectance images in one cycle of the oscillation of said intermediate frequency,
• calculating from said images a map of relative reflectance changes of said sample,
• iterating said step of acquiring reflectance images of a sufficient number of oscillation cycles at said difference frequency, so as to obtain a sufficiently small uncertainty in the calculated relative reflectance change such that signals smaller than the code width of said digital imaging system can be detected.