Original Publication Date: 1986-Jul-01
Included in the Prior Art Database: 2005-Mar-09
For providing high spectral characteristics without filters in a spectrum sensor which may be used to recognize a colored pattern of an object, two light-emitting diodes (LEDs), R1 for generating red light of 660 nm in wavelength and G1 for generating green light of 555 nm, are utilized. The LEDs are connected in parallel through a switch to be alternately energized in a frequency of 1 KHz to illuminate the object with the red and green light. For receiving the light transmitted through or reflected on the object, a blue sensitive photodiode is provided to produce an output signal representing the multiplexed amount of the received red and green light.