A printer reduces the amount of ink wastefully consumed by purging bubbles from the ink supply path. An interface between the two layers of material at which the layers of material are to be separated, or a region in the vicinity of the interface, is exposed to electromagnetic radiation through one of the two layers of material. Use of the present invention increases the ability of persons to achieve restful sleep by enabling convenient control of the air surrounding the person to a comfortable level. Thus, even in a state in which the number of pieces of image data, the amount of the management information thereof, etc. The polarization analyzer is configured to receive the detection light from the NMR cell and pass a portion of the detection light to a processor for determination of angular rate information.