To image an object off-axis, you simply need to tilt the focal plane, as shown in my design below. In this example, the system has 0.5x magnification and the optical axis is tilted 45 degrees. According to the Scheimpflug rule, the image plane should be tilted by 26.6 degrees and that is indeed a good estimate of the optimal tilt angle for any system of this magnification and orientation.
Scheimpflug Rule
θimg = atan(mag*tan(θobj))
