Separating Reflective and Fluorescent Components Using High Frequency Illumination in the Spectral Domain

Abstract

Hyperspectral imaging is beneficial to many applications but current methods do not consider fluorescent effects which are present in everyday items ranging from paper, to clothing, to even our food. Furthermore, everyday fluorescent items exhibit a mix of reflectance and fluorescence. So proper separation of these components is necessary for analyzing them. In this paper, we demonstrate efficient separation and recovery of reflective and fluorescent emission spectra through the use of high frequency illumination in the spectral domain. With the obtained fluorescent emission spectra from our high frequency illuminants, we then present to our knowledge, the first method for estimating the fluorescent absorption spectrum of a material given its emission spectrum. Conventional bispectral measurement of absorption and emission spectra needs to examine all combinations of incident and observed light wavelengths. In contrast, our method requires only two hyperspectral images. The effectiveness of our proposed methods are then evaluated through a combination of simulation and real experiments. We also demonstrate an application of our method to synthetic relighting of real scenes.

Reflectance and Fluorescent Spectra Recovery Based on Fluorescent Chromaticity Invariance under Varying Illumination

“…To allow for the fairest comparison under ideal conditions for both methods, we performed synthetic tests. Compared against [4], which requires a hyperspectral camera and specialized illuminants, we achieve competitive results ( Figure 6). Similar results were observed for other spectra as well.…”

“…Lam and Sato [10] provided a method for recovering the full spectral reflectance and fluorescence absorption and emission spectra of scenes but they require a multiband camera and multiple narrowband illuminants. Fu et al [4] also recovered the full spectral reflectance and fluorescence spectra of scenes by using high frequency light spectra but they require a hyperspectral camera and a programmable light source: a device that can be programmed to produce arbitrary light spectra. While effective, these methods require specialized equipment so their use in applications is limited.…”

“…The recovered spectral reflectance ( Figure 5 (a) and (b)), absorption spectra ( Figure 5 (c) and (d)) and emission spectra ( Figure 5 (e) and (f)) of both fluorescent sheets approximate the ground truth well. We also compared our method against previous work [4]. To allow for the fairest comparison under ideal conditions for both methods, we performed synthetic tests.…”

“…Zhang and Sato [20] proposed a method that uses a RGB camera and ICA to separate reflective and fluorescent components but their method does not capture spectral distributions. In recent work, methods for hyperspectral imaging of reflective-fluorescent scenes have been proposed [10,4]. These methods are effective but require specialized cameras and specialized illuminants such as narrowband light or high frequency light spectra.…”

“…This is because fluorescence can provide additional information about scenes and has been applied to problems in camera spectral sensitivity estimation [5], 3D reconstruction [16,18], immersion range scanning [6], and color relighting [10,4] to name a few. In particular, hyperspec- tral images of reflective-fluorescent scenes provides a rich amount of data.…”