An electrical interface between a scene to be imaged and a bolometer type sensor is disclosed. Efficiency is improved by means of a thermal energy concentrator including a lens and an antenna. Where a plurality of bolometer pixels are located in an array, a microantenna is provided for each pixel in the array with a common lens being provided to focus and channel incoming radiation to each microantenna. Radiation from a scene is further coupled by means of a lens and microantenna to the absorbing element of each bolometer through an AC coupling circuit including an electronic chopper implemented by means of a PIN diode, the conductivity of which is varied so as to affect the reflection coefficient of the input signal supplied through the microantenna.