Defocus-based three-dimensional particle location with extended depth of field via color coding

A color-coded lens system is designed and built for three-dimensional (3D) particle location. As it has wavelength-dependent focal length, it can obtain a series of multifocus images in a single snapshot by separating the red, green, and blue channels of the image captured by a color camera. A light source consisting of red, green, and blue LEDs is customized to provide narrowband illumination. In this way, the depth of field can be extended. A three-pinhole aperture is introduced into the system to produce defocus-based triangular patterns that help to encode the particle depth. The accurate 3D particle position can finally be obtained by fusing the information from the three color channels. Experimental results demonstrate that the system is well suited for applications where particles may be irregular or extended depth of field is needed.