The treatment and diagnostic method known in medicine as PhotoDerm is actually based in a concept in physics known as photometric stereo, which gives the ability to estimate local surface orientation by using several images of the same surface taken from the same viewpoint but under illumination from different directions. Woodham first introduced it. The light sources are ideally point sources some distance away in different directions, so that in each case there is a well-defined light source direction from which to measure surface orientation. Therefore, the change of the intensities in the images depends on both local surface orientation and illumination direction.
Photometric stereo is a way in which the ill-posed problems in shading from shading can be resolved. It uses several images of the same surface under different illumination directions. The advantages of photometric stereo are:
1) Unlike single image shape from shading algorithms, photometric stereo makes no assumption of the smoothness of the surface, which it makes it quite useful in determining surfaces so individual as the skin.
The system triggers up to 16 lights, one at a time, synchronized with a high-speed video camera to capture views of a surface under various lighting directions. Photometric stereo is used to extract surface normals, and reflectance transformations to relight objects by introducing specular highlights.
In the past,
In the past, PhotoDerm has been the recommended treatment for patients who have extensive broken blood vessels, chronic facial redness or who have severe, long lasting facial blushing. It can be as a result of an abnormal functioning of blood vessels (altered responsiveness to substances delivered via the blood stream, altered responsiveness to neurotransmitters released from nerves, altered responsiveness to substances released from the epidermis or dermis) or in the chronic stages, structural damage to blood vessels and abnormal blood vessel growth in response to the chronic inflammatory environment. In mild cases, there are mild abnormalities in blood vessel function and structure. In more severe cases, there is extensive damage and dysfunction of these blood vessels. As the blood vessels become more abnormal and more leaky, one experiences more triggers. When the blood vessels are irritated and damaged, it changes the resting state of the blood vessel (length tension characteristic of the muscle layer of the blood vessel) making it much more responsive to many substances and triggers (i.e., able to open up much more easily to deliver more blood to the facial skin). Photoderm treatments act in a way that they remove the damaged and functionally abnormal blood vessels. These blood vessels will be replaced by smaller, stronger blood vessels. When treatment with PhotoDerm, several guidelines should be followed:
1. A patient should never stop the treatment after only the