An imager for obtaining an image of an object includes a substrate including a plurality of electrical emitting units for emitting electromagnetic waves and a plurality of electrical detecting units for detecting the electromagnetic waves reflected by the object. Each emitting unit includes an electrical emitter, a first antenna, a first metallic reflector, and a first dielectric element between the first antenna and the first metallic reflector. Each detecting unit includes an electrical detector, a second antenna, a second metallic reflector, and a second dielectric element between the second antenna and the second metallic reflector.