Cypress Perform

Optical sensors based on detection of light beam interruption by moving objects are widely used in automatic door opening systems and are also used in various industrial applications for measuring liquids level in the tanks, goods quantity calculation and movable parts position. These sensors typically consist of a light source and a photodiode and signal detection circuit, which compares photodiode signal level with a reference signal. The main drawbacks of this approach lie in high sensor noise and sensitivity characteristics which can cause false detection. This drawback can be eliminated by using modulated light instead of constant light and using correlation techniques to make decisions about presence or absence of an object between the light source and the photo diode. This approach is demonstrated in this application note using PSoC® Programmable Systems On Chip.