Figure 7: Flow chart and compensated signal at each step of the NREA (Noise reduction by Ensemble Averaging) algorithm.
From: Smartphone-based low light detection for bioluminescence application
To verify and quantify the effect of the algorithm, a green LED (light intensity measured 2.08 μW at 60 mm from the camera, using a commercial power meter) with ND filter (OD 5.133) is used as a light source. The light intensity in front of the camera after the ND filter is computed as 20 pW. (A) Flow chart of the algorithm and cross-section near the center of the LED (center x axis: 1011 pixel) on the tested sample image sets for (B) gray-scaled image Ig, (C) after applying a circular averaging filter, (D) compensation done (slant, curve, zero crossing, and intensity level normalized) of a single image, and (E) after accumulation of ten images. (F) Progressive accumulation result of 20 images using NREA, which effectively enhances the signal without increasing the noise level.
