Structured-light imaging systems and methods for determining sub-diffuse scattering parameters

Abstract

A method for determining sub-diffuse scattering parameters of a material includes illuminating the material with structured light and imaging remission by the material of the structured light. The method further includes determining, from captured remission images, sub-diffuse scattering parameters of the material. A structured-light imaging system for determining sub-diffuse scattering parameters of a material includes a structured-light illuminator, for illuminating the material with structured light of periodic spatial structure, and a camera for capturing images of the remission of the structured light by the material. The structured-light imaging system further includes an analysis module for processing the images to quantitatively determine the sub-diffuse scattering parameters. A software product includes machine-readable instructions for analyzing images of remission of structured light by a material to determine sub-diffuse scattering parameters of the material.

What is claimed is: 
     
         1 . A system for determining sub-diffuse scattering parameters of a material, the system comprising:
 a structured light illuminator comprising a light source and a structured-light modulator configured to modulate light from the light source under control of a digital imaging processor;   projection apparatus configured to illuminate the material with structured light from the structured light illuminator, the structured light having spatial wavelengths between 0.1 and 1 lines per millimeter; and   a digital camera configured to image the material as illuminated with the structured light and to provide images to the digital imaging processor;   the digital imaging processor configured to use the structured light modulator to illuminate the material with structured light of a plurality of spatial frequencies, each spatial frequency at a plurality of phase shifts, and to determine, in an analysis module, from images captured by the digital camera of remission from the material for each of the plurality of spatial phase shifts associated with each of the plurality of spatial frequencies, sub-diffuse scattering parameters of the material.   
     
     
         2 . The system of  claim 1  where the digital imaging processor is configured to use the structured light illuminator to illuminate the material with monochromatic light at each of a plurality of wavelengths, and the digital imaging processor is configured to determine wavelength-specific values of the sub-diffuse scattering parameters at each of the plurality of wavelengths by fitting a wavelength dependent model for demodulated remission to the plurality of images, the wavelength dependent model sensitive to (a) the wavelength-specific values of the sub-diffuse scattering parameters and (b) spatial frequency of the periodic structure, to intensities in the demodulated images, to ascertain the wavelength-specific values of the sub-diffuse scattering parameters. 
     
     
         3 . The system of  claim 2  wherein the sub-diffuse scattering parameters include reduced scattering coefficient and backscatter likelihood. 
     
     
         4 . The system of  claim 2 , the fitting being performed independently for each of at least some of all spatial locations represented by the demodulated images, to produce a spatial map of the wavelength-specific values of the sub-diffuse scattering parameters. 
     
     
         5 . The system of  claim 4  configured with firmware in the digital imaging processor to use the spatial map of the wavelength-specific values of the sub-diffuse scattering parameters to assess tissue. 
     
     
         6 . The system of  claim 5  wherein the tissue incorporates a wound. 
     
     
         7 . The system of  claim 5  wherein the firmware for assessing tissue comprises firmware for diagnosing cancer. 
     
     
         8 . A system for determining sub-diffuse scattering parameters of a material,
 a structured light illuminator comprising a light source and a structured-light modulator configured to modulate light from the light source under control of a digital imaging processor;   projection apparatus configured to illuminate the material with structured light from the structured light illuminator, the structured light having spatial wavelengths between 0.1 and 1 lines per millimeter; and   a digital camera configured to image the material as illuminated with the structured light and to provide images to the digital imaging processor;   the digital imaging processor configured to perform a method comprising:   illuminating the material with structured light of a plurality of phase shifts from the structured light illuminator;   imaging remission by the material of the structured light with the digital camera; and   determining, in an analysis module, from images captured during the imaging, sub-diffuse scattering parameters of the material;   wherein the illuminating comprises, at a spectral wavelength of the structured light, temporally varying periodic structure of the structured light to produce each of a plurality of spatial frequencies and, for each of the plurality of spatial frequencies, a plurality of spatial phase shifts;   the imaging comprising capturing a plurality of images including an image of the remission for each of the plurality of spatial phase shifts associated with each of the plurality of spatial frequencies; and   the determining comprising processing the plurality of images to deduce wavelength-specific values of the sub-diffuse scattering parameters;   the determining comprises:   generating demodulated images respectively associated with the plurality of spatial frequencies, each of the demodulated images being generated from the plurality of images captured for a respective one of the plurality of spatial frequencies; and   fitting a wavelength dependent model for demodulated remission to the plurality of images, the wavelength dependent model sensitive to (a) the wavelength-specific values of the sub-diffuse scattering parameters and (b) spatial frequency of the structured light, to intensities in the demodulated images, to ascertain the wavelength-specific values of the sub-diffuse scattering parameters;   the fitting being performed independently for each of at least some of all spatial locations represented by the demodulated images, to produce a spatial map of the wavelength-specific values of the sub-diffuse scattering parameters;   the fitting comprising ascertaining a wavelength-specific value of backscatter likelihood as γ=(1−g2)/(1−g1), wherein g1 and g2 are first and second Legendre moments, respectively, of a scattering phase function of the material; and   in the fitting, the wavelength dependent model specifying remission as a function of γ and product between (a) a wavelength-specific value of the reduced scattering coefficient and (b) spatial frequency of the structured light.   
     
     
         9 . A method for determining sub-diffuse scattering parameters of a material, comprising:
 illuminating the material with structured light at a sequence of wavelengths, the structured light incorporating periodic patterns of light and dark at a same wavelength of the sequence of wavelengths;   imaging remission by the material of the structured light; and   determining, from images captured in the imaging, sub-diffuse scattering parameters of the material;   the sub-diffuse scattering parameters including reduced scattering coefficient and backscatter likelihood;   the illuminating comprising temporally varying the patterns to produce a plurality of spatial frequencies and, at each of the plurality of spatial frequencies a plurality of spatial phase shifts;   the imaging comprising capturing a plurality of images including an image of the remission for each of the spatial phase shifts associated with each of the plurality of spatial frequencies;   the determining comprising processing the plurality of images to deduce wavelength-specific values of the reduced scattering coefficient and the backscatter likelihood;   the determining comprising:   for each of the plurality of sequence of wavelengths, generating demodulated images respectively associated with the plurality of spatial frequencies, from t the plurality of images; and   fitting a wavelength-dependent model for demodulated remission, sensitive to (a) the wavelength-specific values of the reduced scattering coefficient and the backscatter likelihood and (b) spatial frequency of the periodic structure, to intensities in the demodulated images associated with all of the plurality of spectral wavelengths, to determine the wavelength-specific values of the reduced scattering coefficient and the backscatter likelihood for each of the plurality of spectral wavelengths.   
     
     
         10 . The method of  claim 9 ,
 the fitting comprising ascertaining, for each of the plurality of spectral wavelengths, the wavelength-specific value of the backscatter likelihood as γ=(1−g2)/(1−g1), wherein g1 and g2 are first and second Legendre moments, respectively, of scattering phase function of the material; and   in the step of fitting, the model specifying remission as a function of y and product between (a) the wavelength-specific value of the reduced scattering coefficient and (b) spatial frequency of the structured light.   
     
     
         11 . The method of  claim 10  wherein the illuminating is performed using a spatial modulator comprising a light source providing light to a spatial modulator selected from the group consisting of a liquid crystal display and a digital multimirror device. 
     
     
         12 . The method of  claim 9  wherein the sub-diffuse scattering parameters include reduced scattering coefficient and backscatter likelihood. 
     
     
         13 . The method of  claim 9  further comprising using a spatial map of the wavelength-specific values of the sub-diffuse scattering parameters to assess tissue. 
     
     
         14 . The method of  claim 13  wherein the assessing tissue comprises assessing tissue incorporating a wound. 
     
     
         15 . The method of  claim 13  wherein the assessing tissue comprises diagnosing cancer. cm  16 . The method of  claim 13  wherein the assessing tissue comprises assessing brain tissue.