Transient imaging provides a direct view of how light travel in the scene, which leads to exciting applications such as
looking around corners. Low-budget transient imagers, adapted from Time-of-Fight (ToF) cameras, reduce the barrier of
entry for performing research of this new imaging modality. However, the image quality is far from satisfactory due to
the limited resolution of PMD sensors. In this paper, we improve the resolution of transient images by modulating the
illumination. We capture the scene under three linearly independent lighting conditions, and derive a theoretical model
for the relationship between the time-profile and the corresponding 3D details of each pixel. Our key idea is that the light
flight time in each pixel patch is proportional to the cross product of the illuminating direction and the surface normal.
First we capture and reconstruct transient images by Fourier analysis at multiple illumination locations, and then fuse the
data of acquired low-spatial resolution images to calculate the surface normal. Afterwards, we use an optimization
procedure to split the pixels and finally enhance the image quality. We show that we can not only reveal the fine
structure of the object but may also uncover the reflectance properties of different materials. We hope the idea of
utilizing spatial-temporal relations will give new insights to the research and applications of transient imaging.