Video frame synthesizing method for HDR video capturing system with four image sensors

Abstract

High Dynamic Range (HDR) imaging has recently been applied to video systems, including the next-generation ultrahigh definition television (UHDTV) format. This format requires a camera with a dynamic range of over 15 f-stops and an S/N ratio that is the same as that of HDTV systems. Current UHDTV cameras cannot satisfy these conditions, as their small pixel size decreases the full-well capacity of UHDTV camera image sensors in comparison with that of HDTV sensors. We propose a four-chip capturing method combining threechip and single-chip systems. A prism divides incident light into two rays with intensities in the ratio m:1. Most of the incident light is directed to the three-chip capturing block; the remainder is directed to a single-chip capturing block, avoiding saturation in high-exposure videos. High quality HDR video can then be obtained by synthesizing the high-quality image obtained from the three-chip system with the low saturation image from the singlechip. Herein, we detail this image synthesis method, discuss the smooth matching method between spectrum characteristics of the two systems, and consider the modulation transfer function (MTF) response differences between the three- and single-chip capturing systems by means of analyzing using human visual models.