Sensor interpixel correlation analysis and reduction for color filter array high dynamic range image reconstruction

Abstract

High dynamic range imaging (HDRI) by bracketing of low dynamic range (LDR) images is demanding, as the sensor is deliberately operated at saturation. This exacerbates any crosstalk, interpixel capacitance, blooming and smear, all causing interpixel correlations (IC) and a deteriorated modulation transfer function (MTF). Established HDRI algorithms exclude saturated pixels, but generally overlook IC. This work presents a calibration method to estimate the affected region from saturated pixels for a color filter array (CFA) sensor, using the native CFA as a matched filter. The method minimizes color crosstalk given a set of candidates for proximity regions, and requires no special setup. Results are shown for a 21‐bit HDR output image with improved color fidelity and reduced noise. The calibration reduces IC in the LDR images and is performed only once for a given sensor. The improvement is applicable to any HDRI algorithm based on CFA image bracketing, irrespective of sensor technology. Generalizations to subsaturated and supersaturated pixels are described, facilitating a suggested irradiance‐exposure dependent point spread function charge repatriation strategy.

Color Sensing and Image Reconstruction Using Intelligent Machine Learning Algorithm with PINIP Radial Junction Imager

“…Nowadays, image sensors usually comprise an array of pixels on siliconbased charge-coupled devices (CCDs) or complementary metal-oxide semiconductors (CMOSs), which convert light to electrical signals. To obtain color images, an array of color filters are employed and deposited on top of the image sensor, typically a two dimensional symmetric mosaic Beyer filter array with the unit pattern of RGGB (two Gs for green, one R for red, and one B for blue) [3][4][5][6]. Dramatic progress has been achieved for this kind of pixelated image sensor.…”

Bias-selected full Red/Green/Blue color sensing and imaging based on inversely stacked radial PINIP junctions

“…Blue/Green/Red (RGB) color sensing is prevalent in a wide range of applications, including imaging, charge-coupled device (CCD) camera, environmental surveillance and biological sensing [1][2][3][4][5][6], which are always in pursuit of more compact and more efficient color sensing configuration to achieve higher imaging resolution, faster detection and more flexibility, catering to the needs of wearable and soft electronics. Conventional RGB color sensors in CCD camera use Bayer mosaic matrix array with 4 photodetectors and 4 filters (2 for green, 1 for red and 1 for blue) for a single color unit, as depicted schematically in figure 1(a), which is a fundamental limit to shrink the unit size further, reduce the cost and adapt to flexible or curved surfaces [7][8][9][10][11]. To break this limit, also to avoid color aliasing in mosaic imaging [12][13][14], filter-less stacked PIN/PIN junction sensors were proposed, where the different incident wavelengths get absorbed at different penetration depths in stacked PIN junctions (see figure 1(b)) [15][16][17][18].…”

Optical Document Security: Measurement, Characterization and Visualization: in the Light of Visual Evaluation

“…For this reason a new sensor-level IC limiting algorithm was developed and implemented that significantly reduces the IC, color crosstalk as well as increase the MTF and the signal-to-noise ratio (SNR). (Paper IV) [5] and (Paper V) [6] cover a literature review and details on the implemented algorithm respectively.…”