Optimization of image-forming optics for transmission optical projection tomography.

A new optical system for transmission optical projection tomography (TOPT) is presented to reduce the divergence of the projection data from the true parallel projections. This is performed by introducing an iris at the back focus of the objective lens. The influence of the defocusing on TOPT is demonstrated by computational simulations and experiments. We compare the performances of the new and conventional TOPT systems in order to optimize the optical system for three-dimensional imaging of the embryos of small animals. The optimal imaging performance is given by the new system with numerical apertures between 0.007 and 0.014, with which the spatial resolution of 25 microm is achieved. The optimal configuration is validated by TOPT of a phantom sample and a fixed five-day chick embryo.