Recent Patents on Color Demosaicing

Abstract

Single-sensor technology is a popular imaging approach used in image-enabled consumer electronic devices such as digital still and video cameras, mobile phones, personal digital assistants, and visual sensors for surveillance and automotive applications. Cameras make use of an electronic sensor (Charge Coupled Device -CCD -or Complementary Metal-Oxide-Semiconductor -CMOS) to acquire the spatial variations in light intensity and then use image processing algorithms to reconstruct a color picture from the data provided by the sensor. Acquisition of color images requires the presence of different sensors for different color channels. Manufacturers reduce the cost and complexity by placing a color filter array (CFA) on top of a single image sensor, which is basically a monochromatic device, to acquire color information of the true visual scene. Typical imaging pipelines implemented in single-sensor cameras are usually designed to find a trade-off between sub-optimal solutions (devoted to solve imaging acquisition) and technological problems (e.g., color balancing, thermal noise, etc.) in a context of limited hardware resources. In this paper we review the existing patent solutions devoted to demosaicing and able to generate a color image from a single-sensor reading. Demosaicing solutions can be basically divided into four main categories: inter-channel (spectral) correlation, edge based, pattern based and iterative together with alternative techniques also present in literature. Discussion about pro and cons of each technique will be briefly reported.

Watermarking of Raw Digital Images in Camera Firmware: Embedding and Detection

“…Although demosaicking can be solved by standard image interpolation techniques such as e.g., bilinear or edge-directed interpolation 11) , exploiting the intra and inter color channel dependencies can significantly improve the visual appearance of the full resolution image. Note that the actual implementation in digital cameras is generally not known and might be covered by patents 1) . Most demosaicking methods belong to the class of sequential interpolation algorithms 10) where first the luminance (green) channel is reconstructed which then aids in recovering the chrominance channels.…”