Narcissus: reflections on retroreflections in thermal imaging systems

Abstract

Narcissus, a composite of self-images of a cryogenically cooled detector array, is an effect peculiar to scanning thermal imaging systems. It occurs when the detectors sense variations in the amount of background radiation reaching them via reflections from lens surfaces. Paraxial surface-contribution formulas derived from Lagrange invariants, coupled with the system spectral response, determine narcissus in terms of its equivalent scene temperature difference (NARCDeltaT). The equations give the intensity and size of the narcissus ghost in terms of paraxial ray data at the contributing surfaces and the system f/No. This Gaussian formulation has sufficient radiometric accuracy to make extensive ray tracing unnecessary.

Thermal imaging and power mapping at IBM

“…The columns of the A matrix represent the point spread function of a single unit of power applied at the corresponding row of the power vector. In the SIMP method, we measure the chip backside temperature and mathematically solve equation (2) for the power distribution.…”

“…The Narcissus Effect can be a factor when the emissivity of the objects in the scene are less than 1, and the object and camera are on axis [2]. The Narcissus effect reduces the measured radiance in portions of the image, often the center, since what is essentially a distorted, reflected image of the cold image sensor is observed in the scene.…”

Infrared temperature sensor system for mobile devices

“…Since the fieldof-view of the sensor has to be restricted in a practical mobile application, the sensor also detects a surface which is typically not at the same temperature as the surface to be measured. In idealised conditions, it is possible to calibrate the detector to compensate for this Narcissus effect [7] using an internal compensation circuit that measures the temperature of the sensor element itself. Fig.…”

Improved infrared temperature sensing system for mobile devices

“…Since the field of view of the sensor has to be restricted in a practical mobile application the sensor also sees a surface which typically is not at the same temperature as the surface to be measured. In idealized conditions, this Narcissus effect [7] can be calibrated away using an internal compensation circuit that measures the temperature of the sensor element itself. A traditional optomechanical design for IR sensing, showing the Narcissus effect is shown in Fig.…”