| 摘要 |
A preset temperature, which is an optimum control temperature for a semiconductor light-receiving element corresponding to the temperature of a space A, in which an analog circuit board 5 having a semiconductor light-receiving element 43 mounted thereon is disposed, is measured in advance, and is stored in an optimum-preset-temperature storage element 605. Then, the temperature of the space A is measured by a space temperature sensor 9, and by referring to the optimum-preset-temperature storage element 605, information concerning the preset temperature corresponding to the measured temperature of the space A is obtained. Then, the semiconductor light-receiving element 43 is cooled by using an electronic cooling element 49 so that the temperature of the semiconductor light-receiving element 43 to be measured by a temperature sensor for the semiconductor light-receiving element 43 will be the preset temperature indicated by the obtained information. With this arrangement, even if the environmental temperature, such as the temperature of a board, is changed, it is possible to control the temperature of the semiconductor light-receiving element 43 with higher precision, thereby suppressing a variation in the dark current value. |
