Welcome to the LED-BRDF Wiki!


This site is a repository for a summer job with the Rochester Institute of Technology's Color Science department. My task is to create a device that uses only LEDs to measure the BRDF (bi-directional reflectance distribution function) of an object, as seen here.

It is a little-known fact that LEDs (light-emitting diodes) are actually bi-directional devices. Normally we see them in applications like flashlights, headlamps, and automobile headlights/taillights, as emitters of light. However, LEDs can also be used as receivers of light. This can be done with very little or no additional hardware, and it is simple to implement in terms of software. The challenge here is to get the LED functioning as a scientific device, with repeatable and highly accurate results.

Changes to the Project

In the world of science (and in the world in general) things may happen that require you to change your plans a little. The same has happened here. The following is a list of changes made to this project:
  • We are changing the functions our device, from a BRDF measurement device to a materials measurement device that can accurately measure the glossiness of a surface. This was done because of the complexity of capturing and creating the BRDF, which would take significant time to implement in processing.
  • LED sensing is now out of the picture. After experimenting with, learning about, testing, and characterizing LEDs for the past four weeks, I have been unable to recreate highly accurate and precise results from emitter-receiver pairs of LEDs.
  • While I will be moving away from LED sensing in the project, I still intend to create a device to measure the surface glossiness of materials. Though the methods for sensing will be different, I will use the same general parameters for my new device as I had set out previously for my original design. This device must meet the following specifications:
    • Inexpensive - the device must cost significantly less than current products. Gloss meters are available, but they cost around $5,000.
    • Accurate - the device must be able to output accurate, reproducible results on a consistent basis for a variety of materials.
    • Fast - the device must be able to take measurements, perform all necessary calculations, and output a final glossiness value that is easily interpreted by users.
    • Portable - existing gloss meters are portable; this should also be. I intend to base my device on a simple, lightweight plastic or aluminum hemisphere, a microcontroller (perhaps two microcontrollers), LEDs, inexpensive sensors, and a laptop computer. This should be a device that users can easily take outside of a laboratory and use for real-world materials classification.