This is a workshop to introduce the Public Lab community to members of Citizens without Borders and Science has no Borders meetup groups. It the first in a series of activities on environmental monitoring. We will introduce near infrared sensing and the PL approach, including the development of tools and application.
The follow-up workshops include NIR image processing using infragram.org and discussion and calibration as well as DIY aerial mapping using kites.
Where: London, UK University College London
When: Monday 14th Nov 18:30
More information at www.sciencehasnoborder.org
What we would like to try at this workshop
Once cameras have been converted, we will compare reflectance from halogen bulbs and growing lamps using red and blue LEDs; we will also photograph different types of indoor plants (too dark to take photos outside!)
Some light passes through human skin, and near infrared light (especially around 800 nm) passes through more readily than visible light. Skin also scatters near infrared light after it has entered the skin, so near infrared photos of skin can appear whitish, waxy, glowing, and ghostly. Near infrared light is absorbed strongly by blood, so veins look dark in near infrared photos. So near infrared photos of skin can highlight veins that are not too deep under the skin.
The best results for highlighting veins might be pure infrared photos. Such photos can be taken by either illuminating the scene with pure infrared light or by using a filter which passses only near infrared light. Cameras converted by replacing the IR cut filter with a blue filter will capture infrared and red light mixed in the red channel. Using a red filter instead will allow capture of rather pure infrared light in the blue channel. Using exposed developed color slide film or a Wratten 87 filter will allow all three channels to capture only near infrared light. Using a narrow band filter which passes only light near 850 nm might be best.
Above: Black and white photos of the top surface of the right foot of a normal healthy caucasian (and otherwise not unattractive) male taken with a normal visible light camera (left) and with a camera modified to capture only light between 850 nm and about 1000 nm (right). The foot was illuminated with an incandescent lamp.