Photopyroelectric  As known that Photopyroelectric can be regarded as –Photo +Pyroelectric，which means any optical systems using a pyroelectric detector or imaging system, In addition, pyroelectricity could be depicted as the capability of the components formulating the transient voltage when heated or cooled. Once the temperature on which they depend changes, the position of the atom will change slightly in the crystal structure. This process of change can also be referred to as the polarization of the material. As a result, the voltage across the crystal will be triggered by this change in polarization. To further explain, when the temperature in the engine is kept constant for a period of time, the voltage in the photovoltage will gradually disappear due to the leakage current. In this sense, leakage is mainly caused by several ways, for example, electrons going through the crystal, ions going through the air, or current leaking through a voltmeter connected to the crystal.<br />