[en] This research introduces an improved version of a spectroscopic imaging reflectometer to secure reliable measurement performance in the reconstruction of spatially resolved thin film thickness. Due to its simple structure, the rotating-type filter has the advantage of robustness, but it has a limitation of spectral resolution. To improve the spectral resolution, a multi-reflectance method was applied. The angle of incidence can be adjusted by changing the diameter of the tunable aperture. By combining multiple spectral reflectance signals obtained at different incident angles, one integrated signal with improved spectral resolution can be obtained. The effect of the improved spectral resolution on the measurement performance was evaluated. (paper)