Calibration based Minimalistic Multi-Exposure Digital Sensor Camera Robust Linear High Dynamic Range Enhancement Technique Demonstration

TL;DR

This paper introduces a calibration-based minimalistic multi-exposure HDR imaging method for digital sensors, demonstrating robust high dynamic range recovery with only two images and limited exposure adjustments.

Contribution

It presents a novel calibration technique for CRF estimation and a minimal exposure multi-image HDR recovery method that outperforms prior algorithms in robustness and efficiency.

Findings

Achieved robust HDR recovery with only 2 images over a 78 dB range.

Demonstrated stability of HDR recovery over 20-fold illumination changes.

Outperformed prior multi-exposure HDR algorithms using 16 images.

Abstract

Demonstrated for a digital image sensor based camera is a calibration target optimized method for finding the Camera Response Function (CRF). The proposed method uses localized known target zone pixel outputs spatial averaging and histogram analysis for saturated pixel detection. Using the proposed CRF generation method with a 87 dB High Dynamic Range (HDR) silicon CMOS image sensor camera viewing a 90 dB HDR calibration target, experimentally produced is a non-linear CRF with a limited 40 dB linear CRF zone. Next, a 78 dB test target is deployed to test the camera with this measured CRF and its restricted 40 dB zone. By engaging the proposed minimal exposures, weighting free, multi-exposure imaging method with 2 images, demonstrated is a highly robust recovery of the test target. In addition, the 78 dB test target recovery with 16 individual DR value patches stays robust over a factor of 20 change in test target illumination lighting. In comparison, a non-robust test target image recovery is produced by 5 leading prior-art multi-exposure HDR recovery algorithms using 16 images having 16 different exposure times, with each consecutive image having a sensor dwell time increasing by a factor of 2. Further validation of the proposed HDR image recovery method is provided using two additional experiments, the first using a 78 dB calibrated target combined with a natural indoor scene to form a hybrid design target and a second experiment using an uncalibrated indoor natural scene. The proposed technique applies to all digital image sensor based cameras having exposure time and illumination controls. In addition, the proposed methods apply to various sensor technologies, spectral bands, and imaging applications.