An imaging spectrophotometer for measuring the two-dimensional distribution of spectral reflectance

Abstract

We present a novel instrumentation scheme for measuring the two-dimensional distribution of spectral reflectance based on the spectral imaging technique. It takes digital spectral images of a test sample using a LED-based monochromatic integrating sphere source and a monochrome CCD camera. We developed a calibration algorithm to assign the digital counts of the images to the reflectance values at each wavelength. The measurement uncertainty is evaluated to be less than 1.5% (k = 2) for high-reflectance samples (with reflectance ⩾0.4) and less than 3% (k = 2) for low-reflectance samples (with reflectance <0.4). For a validity test, we demonstrate an agreement with the results of a reference spectrophotometer within 1% for high-reflectance samples or within 2% for low-reflectance samples. This scheme of ‘imaging spectrophotometer’ is promising to measure the spatially resolved spectral reflectance of complex samples only by a single wavelength scan.