Effective Illumination Control for an Active Spectral Imaging System

摘要

A high-speed spectral imaging system using an active spectral illumination has a big potential in the spectral color imaging field. However, it has been difficult to produce an accurate target illuminant because the basis illuminants are not ideal narrow-band spectra. Therefore, we need a mechanism of appropriate adjustments for emitting the desired illuminants from the light source. This paper proposes a control method for producing an arbitrary target illuminant precisely from the active spectral light source by combining the light source with a measurement device. We construct two types of illuminant control systems. The first system uses a high-speed monochrome camera as the measurement device. In this system, we determine the desired sequence of the camera outputs in advance. Then we adjust the light source system for generating the target camera outputs by a feedback control. The second system uses a spectroradiometer as the measurement device. In this system, the target is the spectral-power distribution determined by multiplying the surface-spectral reflectance to the illuminant. The system adjusts the light source for producing the optimum illuminant with the target spectrum by the feedback control. We consider two applications of the illuminant control system to (1) accurate generation of a target illuminant and (2) estimation of surface-spectral reflectances without knowing the camera spectral sensitivity function.