An optical switch having an insulator under a heater element is disclosed. The electric power signal further is undergone constant voltagecurrent control to achieve voltage overshoot protection. At least one feature point is identified within the cardiac cycles. The first interference pattern is created by interference of light components of the collected light that propagated within a first periphery region of an optical axis of the focusing optics and light components of the collected light that propagated within a paraxial region of the optical axis. The central lens and the peripheral lens share a common focal point at which the LED may be positioned.