Method and apparatus for predicting the direction of movement in machine vision

In a machine vision system including a video camera having an input lens for viewing an area of interest and producing an analog signal at an output thereof reflecting a 2-dimensional area of interest being viewed by the input lens, an analog to digital converter connected to the output of the video camera for converting the analog signal into a binary signal, a digital buffer for storing the binary signal, and logic for analyzing the binary signal at times t1 and t2 to provide information about the contents of the area of interest, the method for determining movement in the area of interest comprising the steps of:

• a) filtering the binary signal from the digital buffer at times t.sub.1 and t.sub.2 to produce enhanced 2-dimensional binary representations of the area of interest at the times;
• b) producing smoothed versions of the enhanced 2-dimensional binary representations;
• c) processing the enhanced 2-dimensional binary representations to provided the spatial gradients of components thereof comprising a background frame of reference and components identified with objects moving against the background frame of reference;
• d) producing the temporal gradients of the enhanced 2-dimensional binary representations;
• and,
• e) comparing the spatial and temporal gradients at times t.sub.1 and t.sub.2 to one another to determine any motion parallax existing in the area of interest, whereby movement of objects in the area of interest is determined.

In a machine vision system including a video camera having an input lens for viewing an area of interest and producing an analog signal at an output thereof reflecting a 2-dimensional area of interest being viewed by the input lens, an analog to digital converter connected to the output of the video camera for converting the analog signal into a binary signal, a digital buffer for storing the binary signal, and logic for analyzing the binary signal at times t.sub.1 and t.sub.2 to provide information about the contents of the area of interest, the method for determining movement in the area of interest by establishing the 2-dimensional velocity of objects and converting them into a 3-dimensional position and depth map comprising the steps of:

• a) horizontally scanning the area of interest to create a sequence of video images taken at small distance intervals so as to measure motion parallax or translational movement taking place in the area of interest;
• and,
• b) constructing the depth map by scene analysis using paired even- and odd-symmetric filters that are normalized Gabor filters, that comprise a cosine times a Gaussian and a sine times a Gaussian, the even- and odd-symmetric filters being oriented filters that compute both the smoothed contrast and the corresponding spatial gradient at each spatial position to provide two independent measures of the contrast differences in the area of interest, the paired filters being computed at several orientations and resolutions using a coarse-to-fine matching procedure;
• wherein said step of scanning the area of interest includes the step of:
• dividing the area of interest into rectangular windows of attention determined by different object widths wherein closer occluding objects determine a maximum window of attention that can be used to view more distant object;
• wherein;
• a) within each window of attention, the location that produces the maximum output of the paired even- and odd-symmetric filters at low resolutions that is above a pre-established threshold is used to determine the width of objects that are used to partition the area of interest into different depth regions with those objects being verified at higher resolution spatial scales;
• b) constructing the depth map using regions of constant velocity to construct each moving object's height and width and changes in the direction of movement relative to the video camera and other objects in the scene to infer the position of the objects in a three-dimensional scene such that the closer an object is to the video camera, the larger the distance transversed by the object in each video image of the scene;
• and,
• c) updating the depth map by minimizing deviations from expected changes in object boundaries at different depths over time.