Variable polarization and skin depth analysis methods and apparatuses
Methods and apparatuses are disclosed for capturing and analyzing images of tissue, such as human skin, using variable polarization. Exemplary devices are described having a detection polarizer via which an area of tissue is imaged and one or more light sources whose emitted light is polarized with one or more source polarizers. In a first such device, one or more of the detection polarizer and a source polarizer is rotatable so as to allow the angle between their polarizations to be varied. An area of tissue can be imaged as the angle is varied. Another device has multiple fixed source polarizers of different polarization orientations, each source polarizer polarizing the light emitted by a corresponding group of light sources which can be selectively activated, thereby enabling the device to illuminate an area of tissue with polarized light of different orientations relative to the orientation of the detection polarizer. Images of an area of tissue captured with different polarizations provide information from different depths, allowing visualization of superficial as well as subsurface features.
1. A skin analysis method comprising:
obtaining at least three images from at least three respective depths of an area of skin, at least two of the depths being below a surface of the area of skin, each image having been captured through a detection polarization and with illumination of a source polarization, the detection and source polarizations having respective orientations defining a polarization angle therebetween, the polarization angle being different for each of the at least three images; and
processing the at least three images to generate at least one further image or further information derived from the at least three images, including:
determining a relative depth of at least two of the images based on the polarization angles with which the images were captured and on skin type.
2. The method of claim 1 , wherein obtaining the at least three images includes:
illuminating the skin with the illumination having the source polarization,
capturing each of the images through the detection polarization, and
changing at least one of the source polarization orientation or the detection polarization orientation between capturing each image.
3. The method of claim 1 , wherein processing the at least three images includes generating an image indicating one or more features in at least one of the images.
4. The method of claim 1 , wherein processing the at least three images includes generating a three-dimensional image.
5. A non-transitory computer-readable storage medium having stored thereon a computer program comprising instructions for causing a skin analysis apparatus to perform the method of claim 1 .
6. A skin analysis apparatus comprising:
circuitry configured to:
obtain at least three images from at least three respective depths of an area of skin, at least two of the depths being below a surface of the area of skin, each image having been captured through a detection polarization and with illumination of a source polarization, the detection and source polarizations having respective orientations defining a polarization angle therebetween, the polarization angle being different for each of the at least three images; and
process the at least three images to generate at least one further image or further information derived from the at least three images, including:
determining a relative depth of at least two of the images based on the polarization angles with which the images were captured and on skin type.
7. The apparatus of claim 6 , wherein obtaining the at least three images includes:
illuminating the skin with the illumination having the source polarization,
capturing each of the images through the detection polarization, and
changing at least one of the source polarization orientation or the detection polarization orientation between capturing each image.
8. The apparatus of claim 6 , wherein processing the at least three images includes generating an image indicating one or more features in at least one of the images.
9. The apparatus of claim 6 , wherein processing the at least three images includes generating a three-dimensional image.