1. A distance detecting method for use with a stereoscopical imaging apparatus for imaging an object from a plurality of different directions and for obtaining a plurality of pictures of an image of the object, and a picture processing unit for processing said pictures and for outputting distance distribution information for said image, the method comprising the steps of: dividing one of said pictures of said image into a plurality of zones; determining an average brightness for at least one of said zones; determining a correction level for a present shutter speed of said stereoscopical imaging apparatus based upon said average brightness of said at least one of said zones; correcting said present shutter speed based on said determined correction level; performing a high-speed calculation of coincidence between at least two of said pictures for each of a plurality of small regions of each picture, and determining deviation amounts of brightness corresponding to said at least two pictures on the basis of a minimum value of a brightness difference between said at least two pictures; detecting a minimum value and maximum value of a degree of said coincidence between said at least two of said pictures; and determining a deviation amount of each picture element corresponding to said at least two pictures with respect to a minimum value and a maximum value for said degree of said coincidence when a minimum value is equal to or less than a first predetermined value, when a difference between said maximum value and said minimum value is equal to or larger than a second predetermined value, and when a brightness change of a small portion of a required image out of said at least two pictures is a third predetermined value.