InfoMarch 31, 2006 7:01 pm
As you requested, here is a schematics of adapter. There is nothing much to tell about it. If there is any questions, don’t hesitate to ask.
InfoMarch 29, 2006 4:36 pm
How polarizers remove surface reflections?
There is simple system by using two perpendicular polarization films. The angle on which light should fall is called Brusters angle. This is an angle on which incident polarized lights polarization plane is turned on 90 degrees when it is reflected.
The system of imaging looks as follows:
And here you can see a results where photos are made with polarizer system and without it;
1) Without polarizers:
2) With polarizers:
As you can see, polarizers remove surface reflections and it is better view of inner skin structure. This is necessary procedure when images are processed digitally.
Skin Image Processing 9:43 am
Imaging system with four different wavelengths obtained from LEDs
To evaluate skin pigmentation in different skin layers, there is special light adapter needed in order to take multispectral pictures of skin. As there are different optical properties of skin pigments, 4 different light sources have been chosen.
blue λ= 470 nm – highly absorbed by epidermal melanin
green λ= 576 nm – hemoglobin peak
red λ= 660nm – epidermal dermal boundary
IR λ= 865 nm – low absorption, sensitive to scattering to measure papillary dermis thickness.
There was lighting source for “Nikon Coolpix E3100” digital camera developed to take multispectral images of skin.
Making adapter
The drawing of lighting adapter
The lighting adapter isn’t very hard to build. You just need to make circular PCB and solder LEDs with protective resistors. The PCB image:
PCB Mask REAL view
Then soldered LEDs symmetrically to distribute the smooth light:
LED’s are in row: Red, Green, Blue, and IR, White. White LED is optional, to make normal pictures of skin.
Then I made a hole for camera optics. It also serves as holder of PCB. As you see in front of LEDs I put polarized filter (another is put on optics of camera with polarization axis crossed to this one). This filter is used to filter light reflections from surface layer of skin to remove flares. Then you get the image of deeper skin structure.
The nice shiny LEDs are working:
I had some problems to focus them to one spot. LEDs have not ideal characteristics and they weren’t ideally soldered to board. You can see my effort 
I only needed one square centimetter ofregion to be smooth lightened.
The finished adapter:
About skin modeling there are other topics created, you’re welcome to read them. There I will put few interesting results about taking photos of skin and lesions.
Here are the matrixes calculated for each color. They are substracted form every picture I made, to make a suggest, that lighting is equal to all points on 1x1cm region:
Lets make some test shoots:
Benign lesion:
Blue Green
Red White
I didntmake Infrared here, as this lession isbenign, and doesnt show any changes in skin structure.
Suspicious lesion as you can see Infrared (fig e) picture shows view from deeper skin layers:
And here you can see parametric maps generated using model with these images:
Here are images with hair and benign lesion:
As this light adapter is hand made and calibration is poor, there still can be good results obtained. This experiment was made to prove, that handheld digital camera and simple lighting adapter can be used to show relative diagnostic results while inspecting skin lesions.
