Large arrays of bolometer elements offer uncooled and simple operation, and a thermal imaging performance which challenges the cooled semiconductor (photon) detectors. A hybrid array technology, exploiting the pyroelectric property of ferroelectric ceramic materials in the bolometer elements, is the basis of a successful range of linear and 2-D arrays. However, other technologies will compete for cost effectiveness in large area devices. Direct integration of ferroelectric thin films onto suitable thermal microstructures on the silicon readout IC is attractive if deposition processes which are compatible with the silicon IC are established. Deposited lead based perovskite films show considerable potential. Thin film resistance bolometers will also compete, and have some advantages of compatibility in fabrication.