  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.
