Abstract
Up to now photoelectric devices using photoconductive, photovoltaic, photoemissive and pyroelectric effects have been put to practical use. These photo detectors are devices using electrical properties of semiconductor or ceramics, while the amorphous magnetic photo detector (AMPD) is a pyro-magnetic film utilizing temperature dependence of a magnetic reluctance. The amorphous magnetic substance with an excellent magnetic property are used in electrical and electronic apparatuses, however application to a photo device has not yet been approached. The AMPD with a thickness of 20μm is made by an amorphous magnetic material with low Curie temperature and its surface is painted with a radiant flux absorbent. When the visible rays are radiated to the AMPD, the radiant flux absorbent captures the light energy and transfers thermal energy to the amorphous, which causes the reluctance change of the amorphous. The reluctance change of an AMPD can be read out as an output voltage by a Hall element. Therefore the AMPD acts as a photo-magnetic transducer. The pyro-photo detector such as an AMPD need the large reluctance change and a quick response with temperature rise. The thick film AMPD with a low Curie point agrees with this purpose and the coating of a radiant flux absorbent brings about an effective conversion of light energy. Moreover, a Hall element can read out a light signal in non-contact with the AMPD, so that an influence due to a conversion circuit does not occur. The AMPD is excepted to be used as a photo-sensor, a photo relay, a photo chopper and an exposure meter. The construction, the pyro-magnetic characteristics and the techniques of the light signal read out on the AMPD, are discussed here.
