Modeling the light of LED's for position detection with an optical sensor

Abstract

The optical systems are increasingly used to determine the motion. The optical systems use a light source like a LED and an optical sensor, they are based on the object view on the optical sensor. One parameter measured in building management is building movement. The accuracy is critical in building safety, the requirements is ±150 μm. The geometrical principle of measurements considers the LED's as a point and a uniform light source. The emitted light is affected by the refraction on LED and on the optical sensor surface. The optical phenomenon and the erroneous position of LED on the PCB affect the geometry of measurement. All these introduce an error in object position calculation having the magnitude of mm. These phenomena can be modeled by a calibration equation which is established by interpolating the measured value with the object position measured with a high accuracy position system. For increasing the accuracy of measurement the calibration equation is determinate on areas. The measurement system use a microcontroller as a central processing unit, the complexity of calibration equation is limited by the power calculus of microcontroller. Using the modeling equation the accuracy of measurement is essential improved. On 0X direction the accuracy is of ±50 μm and on direction 0Y is ±150 μm.