  In some applications, the object space of light field imaging system is
restrictive, such as industrial and medical endoscopes. If the traditional
light field imaging system is used in the restrictive object space (ROS)
directly but without any specific considerations, the ROS will lead to severe
microlens image distortions and then affects light field decoding, calibration
and 3D reconstruction. The light field imaging in restrictive object space
(ROS-LF) is complicated but significant. In this paper, we first deduce that
the reason of the microlens image deviation is the position variation of the
angular plane, then we propose the flexible angular plane for ROS-LF, while in
the traditional light field the angular plane always coincides with the main
lens plane. Subsequently, we propose the microlens image non-distortion
principle for ROS-LF and introduce the ROS-LF imaging principle. We demonstrate
that the difference is an aperture constant term between the ROS-LF and
traditional light field imaging models. At last, we design a ROS-LF simulated
system and calibrate it to verify principles proposed in this paper.
