| 摘要 |
PURPOSE:To prevent malfunction caused by a stained light receiving part and prevent deterioration of the light receiving part to improve a reliability in operation by a method wherein a heat-resistant optical guiding rod is arranged out of a room in proximity with an opening part of a wall of a heating chamber is provided, and an optical energy from a heated item is received and transmitted to an optical sensor through an optical fiber. CONSTITUTION:In order to perform a defreezing and a cooking, an infrared ray detector 9b is set as an optical sensor 9, an electrical power is supplied through a power supply device 5, a shape memory alloy spring 50 is extended and a shutter 55 is opened. At the same time an infrared ray corresponding to a temperature of a heated item 2 is detected through a heat-resistant optical transmitting rod 7 and an optical fiber 8 installed out of a heating chamber. When a strength of the infrared ray of an optical sensor reaches a predetermined value, electric heaters 4a,..., 4d capable of heating the heated item 2 up to such a degree as one having a scorch are operated through a power supply device and changed over to a visual sensor 9a. When a visual light strength reaches a predetermined condition, biasing of the electric heater and the shape memory alloy spring 50 is terminated. With this arrangement, the shutter 55 may close the opening 18a at the wall surface of the heating chamber. Then, a control device 12 may heat the heater 10, the stained material adhered to a light receiving part 7a is removed by heating within a desired temperature and time.
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