G-Channel Restoration for RWB CFA with Double-Exposed W Channel

• Published in: Sensors (Basel, Switzerland) Vol. 17; no. 2; p. 293
• Main Authors: Park, Chulhee, Song, Ki Sun, Kang, Moon Gi
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 05.02.2017; MDPI
• Subjects: Algorithms; Channels; Color; Exposure; G-channel restoration; Image filters; multispectral image sensor; Pixels; red–white–blue color filter array; Restoration; Sampling; Sampling techniques; Sensitivity; Sensor arrays; Sensors; Signal to noise ratio; red–white–blue color filter array; multispectral image sensor; G-channel restoration
• ISSN: 1424-8220; 1424-8220
• DOI: 10.3390/s17020293

In this paper, we propose a green (G)-channel restoration for a red-white-blue (RWB) color filter array (CFA) image sensor using the dual sampling technique. By using white (W) pixels instead of G pixels, the RWB CFA provides high-sensitivity imaging and an improved signal-to-noise ratio compared to the Bayer CFA. However, owing to this high sensitivity, the W pixel values become rapidly over-saturated before the red-blue (RB) pixel values reach the appropriate levels. Because the missing G color information included in the W channel cannot be restored with a saturated W, multiple captures with dual sampling are necessary to solve this early W-pixel saturation problem. Each W pixel has a different exposure time when compared to those of the R and B pixels, because the W pixels are double-exposed. Therefore, a RWB-to-RGB color conversion method is required in order to restore the G color information, using a double-exposed W channel. The proposed G-channel restoration algorithm restores G color information from the W channel by considering the energy difference caused by the different exposure times. Using the proposed method, the RGB full-color image can be obtained while maintaining the high-sensitivity characteristic of the W pixels.