As a demonstration and verification, we create a hybrid light source (which consists of two monochromatic LEDs) to shift the location of the distinctive feature away from the zero OPD location. The hybrid light source is made out of blue (LXHL– LB5C) and green (LXHL–LM5C) LEDs to create an effective spec- trum as shown in Fig. 4. The dominant wavelengths are 528 nm
(11.9 rad/mm) and 458 nm (13.71 rad/mm) , and the blue–green ratio is 0.78:1.