Lee Min Seok, Park Sang Wook, Kang Moon Gi
School of Electrical and Electronics Engineering, Yonsei University, 50 Yonsei-Ro, Seodaemun-Gu, Seoul 03722, Korea.
Medical Device Development Centre, Daegu-Gyeongbuk Medical Innovation Foundation, 80 Cheombok-Ro, Dong-gu, Daegu 41061, Korea.
Sensors (Basel). 2017 May 28;17(6):1236. doi: 10.3390/s17061236.
In this paper, a spatio-spectral-temporal filter considering an inter-channel correlation is proposed for the denoising of a color filter array (CFA) sequence acquired by CCD/CMOS image sensors. Owing to the alternating under-sampled grid of the CFA pattern, the inter-channel correlation must be considered in the direct denoising process. The proposed filter is applied in the spatial, spectral, and temporal domain, considering the spatio-tempo-spectral correlation. First, nonlocal means (NLM) spatial filtering with patch-based difference (PBD) refinement is performed by considering both the intra-channel correlation and inter-channel correlation to overcome the spatial resolution degradation occurring with the alternating under-sampled pattern. Second, a motion-compensated temporal filter that employs inter-channel correlated motion estimation and compensation is proposed to remove the noise in the temporal domain. Then, a motion adaptive detection value controls the ratio of the spatial filter and the temporal filter. The denoised CFA sequence can thus be obtained without motion artifacts. Experimental results for both simulated and real CFA sequences are presented with visual and numerical comparisons to several state-of-the-art denoising methods combined with a demosaicing method. Experimental results confirmed that the proposed frameworks outperformed the other techniques in terms of the objective criteria and subjective visual perception in CFA sequences.
本文提出了一种考虑通道间相关性的时空频谱滤波器，用于对电荷耦合器件（CCD）/互补金属氧化物半导体（CMOS）图像传感器采集的彩色滤光片阵列（CFA）序列进行去噪。由于CFA模式的交替欠采样网格，在直接去噪过程中必须考虑通道间的相关性。所提出的滤波器应用于空间、频谱和时间域，考虑了时空频谱相关性。首先，通过考虑通道内相关性和通道间相关性，执行基于块差异（PBD）细化的非局部均值（NLM）空间滤波，以克服交替欠采样模式导致的空间分辨率下降。其次，提出了一种采用通道间相关运动估计和补偿的运动补偿时间滤波器，以去除时间域中的噪声。然后，运动自适应检测值控制空间滤波器和时间滤波器的比例。从而可以获得无运动伪影的去噪CFA序列。给出了模拟和真实CFA序列的实验结果，并与几种结合去马赛克方法的最新去噪方法进行了视觉和数值比较。实验结果证实，所提出的框架在CFA序列的客观标准和主观视觉感知方面优于其他技术。
