Systems and methods for thermophotonic dynamic imaging

摘要

Systems and methods for improved thermophotonic imaging are provided in which both amplitude and phase image information is obtained with a high signal to noise ratio and depth-resolved capabilities. Image data obtained from an imaging camera is dynamically averaged and subsequently processed to extract amplitude and/or phase image data. The system may be configured for a wide range of imaging modalities, including single frequency modulation (thermophotonic lock-in imaging), Thermal-Wave Radar imaging or Thermophotonic Radar imaging involving chirp modulation, and Binary Phase Coded Modulation. Such imaging modalities may find application in many diverse areas, including non-destructive testing and biomedical diagnostic imaging including the imaging of teeth and monitoring changes in the tooth over time which are due to pathology such as dental caries or erosion.

主权项

1. A method of performing thermophotonic imaging, said method comprising the steps of:
providing a sample; providing an optical source having a wavelength selected to generate photothermal radiation within said sample; providing an imaging camera with an optical bandwidth selected for detection of said photothermal radiation; generating a reference waveform comprising a plurality of modulation cycles, wherein said reference waveform comprises multiple frequency components; producing a modulated optical beam by modulating an intensity of an optical beam emitted by said optical source according to said reference waveform; illuminating said sample with said modulated optical beam; imaging said photothermal radiation with said imaging camera; recording a plurality of averaged image frames at time offsets corresponding to different values of said reference waveform; and processing said averaged image frames and said reference waveform to obtain an image relating to said photothermal radiation, wherein said image is a cross-correlation image obtained by calculating a complex cross-correlation of said reference waveform and each pixel of said averaged image frames, thereby obtaining a complex cross-correlation signal for each pixel, and processing the complex cross-correlation signals to obtain the cross-correlation image; wherein said cross-correlation image is one of:
(i) a cross-correlation peak amplitude image obtained by determining, for each said pixel, a peak amplitude value of a peak in a real part of said cross-correlation signal;(ii) a cross-correlation peak delay image obtained by determining, for each said pixel, a delay of a peak in a real part of said complex cross-correlation signal; and(iii) a cross-correlation phase image obtained by the steps of:
obtaining a second complex cross-correlation signal of a quadrature waveform and each pixel of said averaged image frames, wherein said quadrature waveform is based on said reference waveform;forming a complex quantity comprising a real portion of first complex cross-correlation signal and a real portion of said second complex cross-correlation signal; andobtaining said phase image by determining, for each pixel, a phase angle of said complex quantity at a pre-selected time delay.