On the figure of merit of uncooled bolometers fabricated at INO

Abstract

This paper reports the NETD values of various uncooled bolometers fabricated at INO. They are measured using an external readout circuit that emulates the readout scheme of a commercial ROIC. The measured NETD values range between 6 and 75 mK, depending on the pixel pitch and response time. Pixel pitches of 12, 17 and 35 µm are considered. The figure of merit of the characterized detectors is below 350 mK*ms.

Per-Pixel Time Constant Measurement of Bolometer Cameras

“…Collected data is "folded" back into one period, as shown in Figure 1, allowing data collected at the camera's frame rate to populate a curve. Either a shutter must be thrown with a set of specific time differences in relation to the camera frame rate f fr [12], or a shutter must be thrown periodically with a period that is not phase-synchronized with f fr [13]. The consequences of synchronization can be seen in Figure 2: data is captured at the same time relative to the camera frame time and overlaps when folded back, not allowing for enough unique points to fit a curve.…”

“…In this case, the value at the beginning and end of the period must be equal (y B (0) = y D (p)), and the value at the boundary of regions B ○ and D ○ must be equal (y B (t − 2 ) = y D (t + 2 )). Incorporating these conditions into (12) and (13) yields the system:…”

“…Without direct electrical control as assumed above, the pixel must be excited optically, typically with a large blackbody target and shutter. There are many variations on this method, including a slow chopper [8,9], an aperture mounted on a linear motion stage (LMS) [10,11], and a "fast" shutter (transition < 25 % of τ ) [9,[12][13][14]. In all cases, the pixels are excited by the blackbody when the aperture is open and cool when it is closed.…”