Abstract: The state of an object such as a presence or absence of the object in a sensor visual field is detected with accuracy. For this end, a DC output Sdc that is a direct current component of a temperature sensor output value S is operated. Based on this, a fluctuation level representing whether a fluctuation is caused by a user or someone else who passes by is acquired. When the DC output Sdc is lower than a DC output threshold THdc, an absence determination counter is incremented when the fluctuation is not caused by either the user or the someone else who passes by, and the state of absence is determined when the absence determination counter reaches the upper limit. When the fluctuation is caused by either the user or someone else who passes by, the absence determination counter is reset.

Abstract: The state of an object such as a presence or absence of the object in a sensor visual field is detected with accuracy. For this end, a DC output Sdc that is a direct current component of a temperature sensor output value S is operated. Based on this, a fluctuation level representing whether a fluctuation is caused by a user or someone else who passes by is acquired. When the DC output Sdc is lower than a DC output threshold THdc, an absence determination counter is incremented when the fluctuation is not caused by either the user or the someone else who passes by, and the state of absence is determined when the absence determination counter reaches the upper limit. When the fluctuation is caused by either the user or someone else who passes by, the absence determination counter is reset.

Abstract: When an amount of a change of a temperature sensor output value is greater than a threshold, the occupation ratio is updated. When the amount of the change of the temperature sensor output value is equal to or smaller greater than the threshold, the occupation ratio is not updated and the background temperature is updated by using the occupation ratio at the time one sampling period before. When a difference between the temperature sensor output value and the background temperature calculated in this way becomes equal to or smaller than a threshold for an absence stated determination, it is determined an user is in an absence state.