Modulation transfer function measurement of microbolometers with small pixel pitch

Today, military and civilian applications require miniaturized and cheap optical systems. Both the optics and the detector tend to decrease their size, weight, power, and cost, which is known as the SWAP-C challenge. One way to achieve this goal consists of decreasing the pixel pitch of the focal plane array (FPA). Pixel sizes become smaller and are now close to the wavelength. A common figure of merit used to assess the quality of the whole system is the modulation transfer function (MTF). However, measuring the MTF of small pixels is challenging because it leads to high cut-off frequencies. Experimental methods and data processing have to be adapted to reach these high spatial frequencies. Some years ago, we proposed an interferometric method based on Llyod's mirror setup. Since the first implementation, both the test bench and the image processing method to extract relevant data from experimental images have been improved. In this paper, we apply this method to several microbolometer FPAs with pixel pitches of 17, 12, and 8.5 µm. Experimental results are shown and fitted with an analytical model to deduce technological parameters of the pixels, such as their size and cross-talk information.