1. A machine vision system comprising: a first image capture device configured to image a first portion of a target surface from a first viewpoint; a second image capture device configured to image a second portion of the target surface from a second viewpoint, wherein the first portion of the target surface at least partially overlaps the second portion of the target surface; a machine vision processor connected to the first image capture device and the second image capture device, the machine vision processor configured to: acquire a first image of the target surface from the first image capture device; acquire a second image of the target surface from the second image capture device; rectify the first image to form a first rectified image and rectify the second image to form a second rectified image; retrieve a disparity field that provides mappings from a first plurality of coordinates in the first rectified image to a second plurality of coordinates in the second rectified image; generate difference data by comparing, based on the mappings of the disparity field, a first plurality of image elements in the first rectified image to a second plurality of image elements in the second rectified image; and determine whether the difference data is indicative of an object on the target surface.