One of the non-trivial challenges of real time stereo is being able to acquire simultaneous synchronized images from two camera positions.

It is not widely recognized that this can be accomplished with a single camera and one mirror element arranged in a very simple geometry:

Look Down Stereo

Because obstacles and objects of interest will not usually be located above a mobile robot, mounting a camera near the top, immediately below a downward facing mirror, can provide an unobstructed stereo view of the navigation space.

This arrangement can have the additional benefit of shielding the camera from the glare of overhead lighting or the sky, possibly resulting in a larger image intensity range for surrounding objects.

It should also minimize any obscuration from the accumulation of dirt on the surface of the mirror.

With more than one camera a single mirror can also be used to provide simultaneous real time stereo views in multiple directions: