The design of typical microbolometer is described.According to optical admittance matrix method

the optical characteristics of multilayer film structure is simulated by Matlab software.The optimal thickness of absorbor film and height of vacuum are obtained when infrared absorptivity rate is maximal

and their values are 0.1 μm and 2 μm respectively.It is reported the infrared absorptivity variation with incident angle’s increasing by theoretic calculating in oblique incidence.Compared with the infrared absorptivity in normal incidence

which is different from the conventional method

this method is closer to the actual situation and can obtain a better simulation result.The results indicate the microbolometer has an infrared absorptivity of more than 80 % in 8

1

4 μm spectral range.

Meanwhile

even when the strain of micro-bridge is very small

the device still has a high infrared absorptivity

either.The simulation result of this paper offered reliable evidence to study microbolometers.