The frequency-modulated reflective color sensor

In this paper frequency-modulated sensor for color detection based on reflective color sensing is proposed. Sensor consists of an RGB LED and a phototransistor. Red, green and blue LEDs are excited at different frequencies. In this way detection of the reflected signal is achieved with only one photodetector and three bandpass filters. Color information from the sensor is obtained using digital signal processing of frequency modulated signal on personal computer (PC). The signal is transferred to PC using analog to digital converter on PC sound card.