Profile measurement of a partially specular object using spatial light modulation

When specular objects are imaged on visual sensors, the acquired images usually suffer from saturation and blooming problem of imaging sensors. These problems are critical to apply optical profiling methods based on structured light to specular surface objects. In this paper, a structured-light-based profiling system combined with a spatial light modulator in the pattern projection side is proposed to obtain the profile of partially specular surfaces. As each pixel's transmittance can be independently and selectively controlled, the spatial light modulator can project a series of coded patterns, and prevent the image sensor from being saturated by controlling the lighting intensity. In this way, a series of projected pattern is well imaged on image sensors, and the pattern correspondence is correctly extracted based on images with good quality. Finally 3-D profile is obtained from the correspondence. The system configuration and transmittance control scheme are explained. This idea is verified on experimental results, in which both the pattern correspondence and 3-D shape are successfully extracted from the partial specular areas which are not normally measurable due to saturation.