Atmospheric scattering and turbulence modulation transfer function for CCD cameras on CBERS-02b and HJ-1A/1B

Atmospheric turbulence and aerosol scattering can produce the blurring of the remotely sensed image. The degrading effect is usually quantified by atmospheric modulation transfer function (MTF). However, this effect behaves differently with different remote sensors. The effort of this article is to study the different degrading effects of aerosol MTF and turbulence MTF between charge-coupled device (CCD) camera on China–Brazil Earth Resources Satellite-02b (CBERS-02b) and on Huan Jing-1A/1B satellite (HJ-1A/1B). Specifically, a corrected aerosol MTF model is established based on classical solution of small-angle approximation (SAA) model by considering the MTF and the effective instantaneous field of view (EIFOV) of CCD cameras. By assuming many different atmospheric conditions, the aerosol MTF and turbulence MTF for two CCD cameras are evaluated. It is found that the output aerosol MTF of CCD camera on HJ-1A/1B causes more degrading effect than that of CBERS-02b under the same atmospheric condition. However, the situation reverses for the turbulence MTF. Furthermore, CCD images acquired over Beijing, China, by CBERS-02b and HJ-1A/1B on four different dates are selected. The overall atmospheric MTF for these images are determined based on the aerosol products from Aerosol Robotic Network (Aeronet) and radiosounding data. Results indicate that the overall atmospheric MTF of CBERS-02b CCD camera reduces image quality more seriously than that of HJ-1A/1B CCD camera. Additionally, the atmospheric MTF compensation is performed and evaluated for these CCD images based on the overall atmospheric MTF.     

In‐field evaluation of the modulation transfer function and the signal‐to‐noise ratio of electronic‐display devices

Abstract— This paper describes a charged‐coupled device (CCD) camera, which was developed for in‐field evaluation of the image quality of electronic‐display devices [such as cathode‐ray tubes (CRTs) and liquid‐crystal displays (LCDs)] used for medical applications. Contrary to traditional cameras for display‐image‐quality evaluation, this CCD camera does not require a sophisticated x‐y‐z translation stage for mounting and adjustment. Instead, it is handheld and pressed by gentle pressure against the display screen. It is controlled by a software package which was originally developed for display calibration according to the DICOM 14 gray‐scale standard display function (GSDF). This software package controls the camera gain when measurements are made at different display luminance, display test patterns, performs image analysis and displays the results of the measurements and calculations. The work concentrated on the measurement of modulation transfer function (MTF) and of signal‐to‐noise ratio (SNR) per display pixel. The MTF is derived from the Fourier transform of the line spread function (LSF). The single‐display‐pixel SNR is derived from the integration of the noise power spectrum (NPS) of a camera image taken of a display with a uniform luminance. It is demonstrated that the device can produce repeatable results in terms of MTF and SNR. MTFs were measured on three monochrome CRTs and five monochrome LCDs in order to study repeatability and similar quantities. The MTF was measured on a 5‐Mpixel LCD yielding values that lie within 3.5% of the average MTF at the Nyquist frequency and 4.0% of the maximum total sharpness (∫ MTF² df). The MTF was also measured on a 9‐Mpixel LCD, yielding values that lie within 9.0% of the average MTF at the Nyquist frequency and 8.0% of the maximum total sharpness. The SNR was measured eight times on a 3‐Mpixel monochrome LCD at nine digital driving levels (DDLs). At a DDL of 185, the mean SNR was 15.694 and the standard deviation (Stdv) was 0.587. At a DDL of 65, the mean SNR was 5.675 and Stdv was 0.120.     

Validation of HJ-1 B charge-coupled device vegetation index products with spectral reflectance of Hyperion

To validate the HJ-1 B charge-coupled device (CCD) vegetation index (VI) products, spectral reflectance data from EO-1 Hyperion of a close date were used to simulate the band reflectance of the HJ-1 B CCD camera. Four vegetation indices (the normalized difference vegetation index (NDVI), the ratio vegetation index (RVI), the soil adjusted vegetation index (SAVI) and the enhanced vegetation index (EVI)) were computed from both simulated and actual HJ-1 B CCD band reflectance data. Comparisons between simulated and actual HJ-1 B CCD band reflectance data, as well as that between simulated and actual HJ-1 B CCD vegetation indices were implemented to validate the VI products of the HJ-1 B CCD camera. The correlation coefficients between simulated and actual HJ-1 B CCD band reflectance data were 0.836, 0.891, 0.912 and 0.923 for the blue, green, red and near infra-red bands, and the correlation coefficients between simulated and actual HJ-1 B CCD VIs were 0.943, 0.926, 0.939 and 0.933 for SAVI, RVI, NDVI and EVI. The standard deviation of differential images between actual and simulated HJ-1 B CCD VIs are 0.052, 0.527, 0.073 and 0.133. The results show that the VI products from the HJ-1 B CCD camera are consistent with the simulated VIs from Hyperion, which proves the reliability of HJ-1 B CCD VI products.     

遥感图像恢复与遥感器MTF 在轨检测技术

遥感成像过程受到大气和成像系统中的光学、探测器和电子学子系统等的影响, 引起成像退化作用, 造成图像模糊, 降低了图像中信息的提取能力。图像恢复技术可以改善图像的质量, 提高图像信息提取能力。依据图像恢复技术的要求, 高精度成像系统调制传递函数(MTF) 是高质量图像恢复的基本条件。针对不同遥感器之间、同一遥感器不同时期存在的成像性能变化, 所引起成像系统MTF 变化的实际情况, 介绍了成像过程中系统MTF 在轨运检测方法。着重于介绍刃边法, 对刃边法的原理、刃边法检测对地物景观的要求等进行了详细分析, 对这一方法中有关图像景物的行扫描采样、扫描行的配准以及对所获得的边扩散函数的拟合等关键技术进行了详细介绍, 这些技术是保证较高精度获取遥感图像MTF 的基础。文章在介绍基于成像系统MTF 图像恢复技术后, 通过实验检验了方法的可行性, 结果表明以MTF 在轨检测为基础的图像恢复技术, 可以明显地提高遥感图像质量。     

MTF measurement method for medical displays by using a bar‐pattern image

Abstract— A modulation‐transfer‐function (MTF) measurement method that uses a bar‐pattern image for medical displays such as liquid‐crystal displays (LCDs) and cathode‐ray tubes (CRTs) has been investigated. A specific bar‐pattern image on the display was acquired with a high‐resolution single‐lens reflex‐type digital camera equipped with a close‐up lens. The MTF was calculated from the amplitudes of the fundamental‐frequency components, which were extracted from the profile data across the bar patterns by using Fourier analysis. Actual comparisons with the conventional line technique were performed for a medical CRT. The adequate accuracy and excellent reproducibility of the method were confirmed. Furthermore, unlike the line method, an advantageous feature which can use an input signal with sufficient amplitude was theoretically proved. Horizontal and vertical MTFs at the central position of the display area were measured up to the Nyquist frequency for several medical displays. From these measurements, this method has the capability to detect slight differences between the displays measured. This proposed method is useful in understanding and quantifying the medical display's performance due to excellent reproducibility and accuracy.     

CPU-GPU协同计算的遥感仿真图像MTF退化并行算法

在遥感图像仿真中,为了定量模拟并分析平台抖动、探测器电子特性、大气衰减等因素对遥感成像质量的影响,需要有效计算遥感系统的调制传递函数MTF,并将其快速作用到仿真图像上。然而,由于遥感仿真图像的大数据量特性以及MTF退化包含多个计算密集型算法,使得计算效率成为一个瓶颈问题。为此,根据已有研究提出的MTF计算模型,分析了遥感仿真图像MTF退化的一般流程及主要环节的算法复杂度。在此基础上,提出了一种CPU-GPU协同计算的遥感仿真图像MTF退化并行算法。实验结果表明,该并行算法有效地发挥了GPU并行计算能力,并明显提高了MTF退化处理效率。     

基于HJ-1卫星数据反演长江三角洲地区气溶胶光学厚度

探索利用我国HJ-1卫星CCD数据,运用深蓝算法开展长江三角洲地区气溶胶光学厚度反演的可行性,并将结果与其他气溶胶光学厚度产品进行比较。针对HJ-1A和HJ-1B数据,反演结果分别与MODIS气溶胶光学厚度产品以及AERONET地基观测数据进行对比验证。结果表明:深蓝算法得到A星、B星的反演结果与MODIS气溶胶产品呈显著相关,但在数值上普遍高于MODIS产品;反演结果与AERONET站点数据之间的误差介于0.008~0.364之间,研究时段内站点数据缺乏,未对误差进行严格的统计分析。基于深蓝算法的HJ-1卫星数据反演结果虽然在数值上与MODIS气溶胶光学厚度产品存在系统性偏差,但在空间上能够较好地反映长江三角洲地区大气气溶胶分布状况,且具有空间分辨率高的优势。     

资源三号卫星在轨MTF测量与图像复原

随着高分辨率遥感卫星发射数量的增多,高分辨率遥感图像数据应用需求也日益增强,而遥感数据的质量直接影响到其数据应用的可靠性和精确性。为此,对高分辨率遥感图像数据进行图像复原是非常有必要的。针对资源三号卫星电荷耦合装置相机遥感图像高空间分辨率的特点,分析在仅有图像信息的情况下系统调制传递函数（MTF）的在轨测量方法,验证双边缘法的可行性。探讨双边缘线状地物选取方法,同时推导证明二维MTF矩阵的构建方法,并借助二维MTF矩阵对原图像进行修正反转滤波实现图像复原。试验结果表明,复原后的图像质量明显提高。     

基于MTF理论的遥感图像复原

由于遥感图像成像过程中受传感器性能下降、大气扰动等因素影响，致使图像质量退化。为了改善遥感图像质量，从图像质量退化原理分析，提出了一种基于调制传递函数（modulation transfer function，MTF）理论的图像复原方法。该方法主要包括去噪和MTF拉伸两部分。针对遥感图像的特点，给出了一种有效的基于频域的去噪方法。为了能够调节频谱拉伸的程度，还给出了一种指数调节MTF曲线的方法。中巴（中国和巴西）卫星红外遥感图像的实验结果表明：该新方法有效地提高了图像的对比度（对于实验图像来说，较复原前图像对比度提高了7倍多，方差也由原来的8．77提高到17．37）、熵等图像要素，从而改善了图像的质量。     

MTF driven adaptive multiscale bilateral filtering for pansharpening

The recently proposed Bilateral Filter Luminance Proportional (BFLP) method extracts the high-frequency details from panchromatic (Pan) image via a multiscale bilateral filter and adds them proportionally to the multispectral (MS) image. Although this approach seems similar to other multiresolution (MRA) based schemes such as Additive Wavelet proportional Luminance (AWLP) or Generalized Laplacian (GLP) methods, multiscale bilateral filter obtains the detail planes to be injected to MS image by the combination of two Gaussian kernels controlling the transfer of details and performing successively in spatial and range domains, thus it has two parameters to be defined, namely spatial and range parameters. Since the parameter determination step considerably affects the efficiency of the method, in this paper we propose a single parameter bilateral filter by approximating the Gaussian kernel with the bicubic kernel of à trous wavelet transform (ATWT) or modulation transfer function (MTF). Moreover, we adopt an adaptive injection scheme where the range parameter is determined adaptively so as to follow the statistics of the images to be fused. The pansharpening results are compared with ATWT-based methods, as well as some state-of-the-art methods and BFLP. The visual and quantitative comparisons for Système Pour l’Observation de la Terre 7 (SPOT 7) and Pléiades 1A images, field studies supported with UAV (Unmanned Aerial Vehicle) images and digitization results of the chosen areas in Istanbul Technical University (ITU) Maslak campus confirm the superiority of the proposed detail injection approach.     

基于 MTF 和变分的全色与多光谱图像融合模型

Pan-sharpening将高分辨率图像全色(Panchromatic, Pan)波段的空间细节注入多光谱(Multispectral, MS)波段, 以生成同时具有高光谱和高空间分辨率的多光谱图像. 为改善融合效果, 需要考虑多光谱和全色波段的调制传输函数(Modulation transfer function, MTF). 本文提出了一个新的基于MTF和变分的Pan-sharpening模型. 该模型的能量泛函包括两项, 第1项为细节注入项, 基于高通滤波器从Pan波段中提取细节信息并注入融合图像;第2项为光谱保真项, 基于MTF设计多孔小波的低通滤波器以保持MS波段的多光谱信息. 在QuickBird、IKONOS和GeoEye数据集上的融合结果表明, 该模型可以生成同时具有高空间和高光谱质量的融合图像, 融合效果优于AWLP、IHS_BT、HPM-CC-PSF、NAWL、快速变分等算法.     

基于生成逆推的大气湍流退化图像复原方法

大气湍流是影响远距离成像质量的重要因素。虽然已有的深度学习模型能够较好地抑制大气湍流引起的图像像素几何位移与空间模糊,但是这些模型需要大量的参数和计算量。为了解决该问题,提出了一种轻量化的基于生成逆推的大气湍流退化图像复原模型,该模型包含了去模糊、去偏移和湍流再生成三个核心模块。其中,去模糊模块通过高维特征映射块、细节特征抽取块和特征补充块,抑制湍流引起的图像模糊;去偏移模块通过两层卷积,补偿湍流引起的像素位移;湍流再生成模块通过卷积等操作再次生成湍流退化图像。在去模糊模块中,设计了基于注意力的特征补充模块,该模块融合了通道注意力机制与空间混合注意力机制,能在训练过程中聚焦关注图像中的重要细节信息。在公开的Heat Chamber与自建的Helen两个数据集上,所提模型分别取得了19.94 dB、23.51 dB的峰值信噪比和0.688 2、0.752 1的结构相似性。在达到当前最佳SOTA方法性能的同时,参数量与计算量分别减少了20倍与1.8倍。实验结果表明,该方法对大气湍流退化图像复原有良好的效果。     

HJ-1A/B卫星CCD影像大气订正

大气订正是遥感信息定量化研究中必不可少的一步,目前已有一些成熟的方法,但由于HJ-1A/B卫星CCD相机波段设置特点,常规的大气订正方法基本不适合于HJ-1A/BCCD影像.本文在大量分析HJ-1A/BCCD影像中不同地物的多种指数基础上,提出了改进暗目标法实现HJ-1A/BCCD影像的大气订正,该方法采用比值植被指数(RVI)、土壤调整植被指数(SAVI)和归一化水体指数(NDWI)的综合分析法确定暗像元自动提取,使之适用于环境减灾卫星CCD影像数据.为了客观地验证该方法的精度,本文选取地表平坦均一的敦煌校正场作为实验区,通过多次测量卫星过境时的地表反射率进行分析验证.     

基于气象数据估计大气MTF的遥感影像去模糊算法

针对直接解卷积算法没有充分利用影像成像过程中模糊函数先验信息的缺陷,利用成像时刻局部区域的气象参数来估计大气MTF,并用估计的大气MTF对直接解卷积算法进行了改进。利用中巴资源卫星所获取的遥感影像,及其对应区域成像时刻的气象数据,对改进后直接解卷积算法进行了验证,各种影像质量评价指标均表明,改进后直接解卷积算法性能相对原有算法有了大幅度提高,进而验证了论文改进思路的可行性与合理性。     

Aerosol optical depth spatio-temporal characterization over the Canadian BOREAS domain

A complete set of Advanced Very High Resolution Radiometer (AVHRR) data (75 images) is used to retrieve aerosol optical depth (AOD) over dense vegetation and over lake water in the visible AVHRR channel. The present approach for remote sensing of aerosols from the National Oceanic and Atmospheric Administration (NOAA)-11 AVHRR sensor is based on the detection of atmospherically dominated signals over dark surface covers such as dense dark vegetation (DDV). Such targets were identified using the reflective portion of the middle-wave AVHRR channel 3 signal. When a fixed DDV surface reflectance is subtracted from the observed reflectance after correction for all other atmospheric effects, the remaining part, which is due to aerosols, is inverted to derive aerosol optical thickness using a look-up table (LUT) similar to that used in water surface inversion. The algorithm was applied to the daily afternoon NOAA-11 AVHRR (1?km×1?km) data acquired from the end of May to mid-August 1994 over the Canadian 1000?km×1000?km Boreal Ecosystem Atmosphere Study (BOREAS) domain. A validation analysis using five ground-based Sun photometers within the studied area shows the good performance of the retrieval algorithm. The approach allows detailed analysis of the AOD spatio-temporal behaviour at the regional scale useful for climate and transport model validation.     

HJ-1A/1B卫星远程播报系统的实现

基于环境与灾害监测预报小卫星星座中的HJ-1A、1B卫星遥感数据,提出一种卫星影像数据与矢量数据在远程播报系统中快速叠加匹配的方法与技术流程。在此基础上,实现了HJ-1A、1B卫星宽覆盖CCD相机的数据远程播报。系统测试表明,远程播报系统对HJ-1A、1B卫星数据空间定位准确,数据处理速度快,满足远程播报实时显示数据的要求。     

An automatic geometric precision correction system based on hierarchical registration for HJ-1 A/B CCD images

On 6 September 2008, two optical satellites, HJ-1 A and B (HJ-1 A/B), were successfully launched from China. However, the system geometric correction products of the HJ-1 A/B charge-coupled device (HJ-1 images) have low geometric precision and need to be corrected. The HJ-1 images have a large aspect angle, a wide swath width, and a large image size. Furthermore, the local geometric distortions are too complex in one scene. Given these characteristics of HJ-1 images, geometric correction is still a challenging work. This article proposes an automatic geometric precision correction system (GPCS) based on the automatic registration between HJ-1 images and Landsat Thematic Mapper images. First, the coarse image matching method based on geometric-restricted scale-invariant feature transform (SIFT) is used to determine the coarse global transformation between the HJ-1 image and the reference image. Second, inspired by the hierarchical method of non-rigid registration for medical images, a hierarchical image matching approach is proposed based on the combination of SIFT feature points and template matching. This approach decomposes a matching problem of a whole image into numerous matching problems of image blocks and can overcome the impact of local distortions in HJ-1 images. Hierarchical random sample consensus (RANSAC) based on digital elevation model (H-RANSAC) is used to remove incorrect control points. Third, an HJ-1 image is rectified using a triangulated irregular network. Finally, the automatic evaluation method based on automatic image matching between the corrected HJ-1 image and the reference image is adopted to evaluate the geometric precision. On the one hand, experiments on eight HJ-1 images demonstrate the efficiency and accuracy of the different steps of GPCS. On the other hand, experiments on 1000 HJ-1 images also demonstrated the robustness, accuracy, and suitability for batch processing.     

经MTF修正的骨X射线图象二维谱估计

根据骨X射线图象的谱特征分析来决定骨质疏松的程度,也许可为识别个体的高骨折风险提供一种自动诊断工具,还可作为监控治疗有效性的客观依据。因为各向异性骨小梁在骨X射线图象中表现为弱纹理,其对二维功率谱只贡献很小一部分,从而导致其功率谱被成象系统的调制传递函数和噪声所遮蔽,这里也许可以将发现骨小梁模式的谱特征视为一种反演问题。由于成象系统的调制传递函数和噪声可视为各向同性,并可统一以合成调制传递函数来表达,且各向同性函数在所有的角度上具有相同的投影。因此可在重构骨X射线图象二维功率谱的过程中,利用滤波反投影方法和傅立叶切片定理,并用合成MTF除以投影功率谱,来准确地将骨小梁模式的功率谱提出。在骨X射线图象和合成图象上进行的实验结果表明,由于各向异性的骨小梁,在重构的二维功率谱中有差异显著的峰,因此一旦获得骨小梁的功率谱,就可定位最大峰值频率,以用于估计骨小梁间距和角度,以及其他纹理特征,进而用来描述其各向异性的程度。由于这些纹理特征与骨结构直接相关,因此可用于预测骨折风险。     

HJ-1星CCD相机场地辐射定标与真实性检验研究

为了满足HJ-1星遥感数据定量化应用的需求,2008年10月中旬,以敦煌定标实验场为地面目标,采用反射率基法对HJ-1A和HJ-1B星的CCD相机开展场地绝对辐射定标,以确定CCD相机响应的变化,并对得到的定标结果进行了误差分析。同时利用非定标同日的敦煌场和贡格尔实验场的CCD星地同步数据得到的表观辐亮度作为标准值,对定标系数进行真实性检验研究。结果表明,定标系数模拟出的CCD表观辐亮度与标准值非常接近,误差均小于3%。研究表明:此次定标实验的结果精度高,并将两次同步数据的定标系数平均值作为定标系数结果,为CCD相机定量化应用研究奠定了良好基础。     

图像采集系统的面阵CCD驱动电路设计

详细介绍了基于面阵CCD器件的图像采集系统的构成,通过对CCD图像传感器ICX424AQ的驱动时序及数模转换芯片AD9943转换时序的分析,设计了用于图像采集的CCD驱动电路,并采用FPGA进行了实现。采用双线性插值算法,从表面覆盖Bayer彩色滤波阵列的CCD图像传感器获得全彩图像,图像数据以DVI格式实时发送到LCD屏上显示。