Department of Electrophysics, National Yang Ming Chiao Tung University, No. 1001 University Road, Hsinchu 30010, Taiwan.
Department of Electrical Engineering, Yuan Ze University, No. 135 Yuan-Tung Road, Taoyuan 320, Taiwan.
Sensors (Basel). 2022 Aug 21;22(16):6288. doi: 10.3390/s22166288.
The recovery of surface spectral reflectance using the quadcolor camera was numerically studied. Assume that the RGB channels of the quadcolor camera are the same as the Nikon D5100 tricolor camera. The spectral sensitivity of the fourth signal channel was tailored using a color filter. Munsell color chips were used as reflective surfaces. When the interpolation method or the weighted principal component analysis (wPCA) method is used to reconstruct spectra, using the quadcolor camera can effectively reduce the mean spectral error of the test samples compared to using the tricolor camera. Except for computation time, the interpolation method outperforms the wPCA method in spectrum reconstruction. A long-pass optical filter can be applied to the fourth channel for reducing the mean spectral error. A short-pass optical filter can be applied to the fourth channel for reducing the mean color difference, but the mean spectral error will be larger. Due to the small color difference, the quadcolor camera using an optimized short-pass filter may be suitable as an imaging colorimeter. It was found that an empirical design rule to keep the color difference small is to reduce the error in fitting the color-matching functions using the camera spectral sensitivity functions.
使用四色相机恢复表面光谱反射率的数值研究。假设四色相机的 RGB 通道与尼康 D5100 三色相机相同。使用滤色片定制第四信号通道的光谱灵敏度。使用孟塞尔色标作为反射面。当使用插值法或加权主成分分析（wPCA）方法重建光谱时，与使用三色相机相比，使用四色相机可以有效地降低测试样本的平均光谱误差。除了计算时间外，插值法在光谱重建方面优于 wPCA 法。可以将长通光学滤波器应用于第四通道以减小平均光谱误差。可以将短通光学滤波器应用于第四通道以减小平均颜色差异，但平均光谱误差会更大。由于颜色差异较小，使用优化的短通滤波器的四色相机可能适合用作成像比色计。研究发现，保持色差小的经验设计规则是减小使用相机光谱灵敏度函数拟合颜色匹配函数时的误差。
