What is disclosed is a system and method for estimating tidal chest volume using 3D surface reconstruction based on an analysis of captured reflections of structured illumination patterns from the subject with a video camera. The imaging system hereof captures the reflection of the light patterns from a target area of the subject's thoracic region. The captured information produces a depth map and a volume is estimated from the resulting 3D map. The teachings hereof provide a non-contact approach to patient respiration monitoring that is particularly useful for infant care in a neo-natal intensive care unit (NICU), and can aid in the early detection of sudden deterioration of physiological condition due to detectable changes in respiratory function. The systems and methods disclosed herein provide an effective tool for tidal chest volume study and respiratory function analysis.