Analysis of positioning errors for LED

We present the research conducted to find what possibilities are to minimize the errors of positioning LEDs, when the LEDs are used as source of light in a measurement instrument. In such a case where the position of the light source enters in computation of the measured value, errors in the LED position are a source of errors for the measurement value. We analyze different types of LED packages and different mounting technologies to find the best way to minimize the positioning errors of the LEDs. We found an important factor that affects the positioning errors indirectly when the light ray is coming out from the LED at a big angle. The refraction of light ray at the package-air interface manifests itself as a position error and should be taken into account because of its magnitude. An effective technique to compensate for the refraction errors that intervene here is to compute in the microcontroller the exact value of the offset produced by the refraction and then subtract that from the position.