An access control apparatus includes a processor. Said body consists of a substrate, a cover with a suction hole, and a base with an exhaust hole. The concave side of the leaf spring exhibits a plurality of transverse ribs. As such, no additional half-wave plates and quarter-wave plates are needed. The use of non-selective excitation pulses reduces the sensitivity to off-resonance and allows excitation to be achieved in a shorter time compared to selective excitation, thereby shortening the time between echoes and minimizing slice profile issues.