Depth measurement by the multi-focus camera

In this paper, we first introduce the multi-focus camera, a new image sensor used for depth from defocus (DFD) range measurement. It can capture three images with different focus values simultaneously. We then propose two different depth measurement methods using the camera. The first method, an augmented version of the one proposed by N. Asada et al. (1998), employs a noniterative optimization process to compute depth values on edge points. The second one incorporates a coded aperture with the camera; and applies model-based pattern matching to estimate depth values of textured surfaces. Here we propose two types of coded apertures and corresponding analysis algorithms: 1D Fourier analysis to acquire a depth map and a blur-free image from three defocused images taken with a pair of pinholes, and 2D convolution based model matching for the fast and precise depth measurement using a coded aperture with four pinholes. Experimental results showed that the multi-focus camera works well as a practical DFD range sensor and that the coded apertures much improve its range estimation capability for real world scenes.