An infrared sensor including an absorber for absorbing incident infrared power to produce a signal representing the temperature of a target object, a frame supporting a membrane which carries the absorber, the frame including a plurality of reflecting surfaces disposed about the circumference of an opening over which the membrane spans for reflecting incident infrared power toward the absorber. By concentrating incident infrared power through reflection, the temperature difference between the absorber and the surrounding frame is increased, thereby producing an increased electrical output from the sensor.