A High-Dynamic-Range Optical Remote Sensing Imaging Method for Digital TDI CMOS

Abstract

Abstract:The digital time delay integration (digital TDI) technology of the complementary metal-oxide-semiconductor (CMOS) image sensor has been widely adopted and developed in the optical remote sensing field. However, the details of targets that have low illumination or low contrast in scenarios of high contrast are often drowned out because of the superposition of multi-stage images in digital domain multiplies the read noise and the dark noise, thus limiting the imaging dynamic range. Through an in-depth analysis of the information transfer model of digital TDI, this paper attempts to explore effective ways to overcome this issue. Based on the evaluation and analysis of multi-stage images, the entropy-maximized adaptive histogram equalization (EMAHE) algorithm is proposed to improve the ability of images to express the details of dark or low-contrast targets. Furthermore, in this paper, an image fusion method is utilized based on gradient pyramid decomposition and entropy weighting of different TDI stage images, which can improve the detection ability of the digital TDI CMOS for complex scenes with high contrast, and obtain images that are suitable for recognition by the human eye. The experimental results show that the proposed methods can effectively improve the high-dynamic-range imaging (HDRI) capability of the digital TDI CMOS. The obtained images have greater entropy and average gradients.

A Mixed Property-Based Automatic Shadow Detection Approach for VHR Multispectral Remote Sensing Images

“…With the development of aerospace techniques, an increasing number of very high-resolution (VHR) satellites have been launched in recent years, such as Ikonos, QuickBird, Pleiades, GeoEye, RapidEye, Skysat-1, WorldView-2, WorldView-3, Jilin-1, and Kompsat [1][2][3][4][5][6][7][8][9][10]. The VHR multispectral remote sensing images captured by these satellites can depict more details of typical land cover, including buildings, vegetation and roads.…”

“…Since shadows in VHR multispectral remote sensing images indicate additional information about ground objects, shadows may supply useful information for applications such as buildings reconstruction and height evaluation [11,12]. Notably, shadows always result in loss and distortion of land cover within shadow regions, because shadow regions always present low radiance and different spectral reflectivity properties from nonshadow areas [3,[13][14][15][16][17]. However, objects in shadow regions may contain significant information, especially in VHR multispectral remote sensing images.…”

A novel remote sensing detection method for buildings damaged by earthquake based on multiscale adaptive multiple feature fusion

“…Image preprocessing involved denoising and contrast enhancement. The images were denoised using Gaussian Denoiser and the contrast was enhanced with contrast limited adaptive histogram equalisation (CLAHE) (Lan et al 2017). The results are displayed in Figure 4.…”

HDR Synthesis Technology for Spaceborne CMOS Cameras Based on Virtual Digital TDI

“…In 1997, Paul E. Debevec and Jitendra Malik proposed a method to synthesize HDR images from multiple images with different exposures [13]. In recent years, in 2017, based on digital TDI technology, Taiji Lan et al [14]. proposed an adaptive histogram equalization algorithm with maximum entropy based on digital TDI technology to improve the ability of images to express dark or low-contrast target details, mainly focusing on the improvement of HDR synthesis technology; In 2018, Wu SUN [15] et al used digital TDI imaging technology for pushbroom cameras, simultaneously acquired images with different exposures in the same scene, and synthesized HDR images through image fusion method, mainly for HDR image synthesis with ideal conditions.…”