Sensors & Transducers

Vol. 249, Issue 2, February 2021, pp. 36-44

1, * Maxime CARRE and 2 Michel JOURLIN

1 NT2I Company, 10 rue Jean Servanton, 42000 Saint-Etienne, France

2 Hubert Curien Laboratory, 18 rue du Pr Lauras, 42000 Saint-Etienne, France


Received: 15 October 2020 /Accepted: 31 January 2021 /Published: 28 February 2021

Abstract: The LIP (Logarithmic Image Processing) model is recognized as an efficient framework to process images acquired in transmitted and reflected light, and to take into account the human visual system. Several image enhancement algorithms have been developed in the LIP framework. Some of them exploit an important property of the LIP model consisting in simulating exposure time variations. Applied to very low light images, our LIP algorithms enhance not only the signal, but also the noise and lead to quantized grey levels. Noise reduction based on Deep Convolutional Neural Networks is performed on these enhanced noisy images. The combination of LIP enhancement and DCNN denoising transforms low light images into well-balanced images with low noise level. In addition to classical PSNR evaluation, we propose an estimation of image noise based on LIP contrasts computed at a local scale. The use of LIP contrast results in a noise evaluation consistent with human vision.

Keywords: LIP model, Exposure time simulation, Image enhancement, Low light images, Noise reduction, Deep convolutional neural networks.