Whenever a pyroelectric crystal undergoes a change of temperature, surface charge is produced in a particular direction as a result of the change in its spontaneous polarization with temperature. This effect has been known as a physically observable phenomenon for many centuries, being described by Theophrastus in 315 BC [1]. Its name “pyroelectricity” was introduced by Brewster [2]. The concept of using the pyroelectric effect for detecting radiation was proposed very early by Ta [3], however in practice, a little progress was made due to the lack of suitable materials. The importance of the pyroelectric effect in infrared detection was becoming obvious about 50 years ago, due to scientic activity from such authors as Chynoweth [4], Cooper [5,6], Hadni et al. [7], and others [8-13]. A widely acclaimed review of work up to 1969 has been published by Putley [14], and further developments have been reported by Baker et al. [15], Putley [16], Liu and Long [17], Marshall [18], Porter [19], Joshi and Dawar [20], Whatmore [21,22], Ravich [23], Watton [24], and Robin et al. [25]. More recently published papers have been shown that the pyroelectric micromachining version of uncooled thermal detectors reach fundamental limits [26-33].