Image analysis using modulated light sources

With the development of high-speed CMOS imagers, it is possible to acquire and process multiple images within the imager, prior to output. We refer to an imaging architecture that acquires a collection of images and produces a single result as multiple capture single image (MCSI). In this paper we describe some applications of the MCSI architecture using a monochrome sensor and modulating light sources. By using active (modulating) light sources, it is possible to measure object information in a manner that is independent of the passive (ambient) illuminant. To study this architecture, we have implemented a test system using a monochrome CMOS sensor and several arrays of color LEDs whose temporal modulation can be precisely controlled. First, we report on experimental measurements that evaluate how well the active and passive illuminant can be separated as a function of experimental variables, including passive illuminant intensity, temporal sampling rate and modulation amplitude. Second, we describe two applications of this technique: (a) creating a color image from a monochrome sensor, and (b) measuring the spatial distribution of the passive illuminant.