Method and apparatus for detection of patterns and edges with un-calibrated devices

摘要

Methods of determining a known location of a sensor head in a scanner without the use of contact sensors are described. Upon initialization of a scanner, the sensor head is moved rapidly to quickly detect a known pattern at a known location in the scanner. As the scan head is moved, windows moving along lines of pixels detected by the sensor head are used to perform pixel averaging to detect the known pattern in the scanner. Parameters associated with the windows custom fit the windows to the known pattern to facilitate rapid detection of the known pattern and determine a known location of the scan head to facilitate calibration of the scanner.

主权项

1. A method for determining a position of a scan head in a scanning unit, wherein the method comprises determining that the scan head is positioned at a known location in the scanning unit based at least in part on:
adjusting parameters of a first window and a second window to correspond to edges of a known pattern at the known location; moving, in accordance with the adjusted parameters, (i) the first window in steps along a line of pixels detected by the scan head and (ii) the second window in the steps along the line of pixels detected by the scan head; at each of the steps, determining (i) an average value of pixels of the line of pixels in the first window and (ii) an average value of pixels of the line of pixels in the second window; in at least a subset of the steps, determining edges in the line of pixels detected by the scan head based at least in part on a difference between the average value in the first window and the average value in the second window being greater than or equal to a predetermined threshold; and determining a correlation between (i) the edges in the line of pixels detected by the scan head and (ii) the edges of the known pattern, wherein the correlation between (i) the edges in the line of pixels detected by the scan head and (ii) the edges of the known pattern corresponds to the scan head being positioned at the known location in the scanning unit.