Patent ID: 9726876
Date: 2017-08-08
CPC Classifications: G02B

Claim:
1. A method for operating an imaging system of a machine vision inspection system to provide at least one image that has a larger depth of field than the imaging system in a single focal position, the method comprising: (a) placing a workpiece in a field of view of the machine vision inspection system; (b) periodically modulating a focal length of a variable focal length tunable acoustic gradient index of refraction (TAG) lens included in the imaging system in order to periodically modulate a focus position of the imaging system without macroscopically adjusting the spacing between elements in the imaging system, wherein the focus position is periodically modulated over a plurality of focus positions along a focus axis direction in a focus range including a surface height of the workpiece at a frequency of at least 3 kHz; (c) exposing a first preliminary image during an image integration time while modulating the focus position in the focus range, comprising exposing the first preliminary image over an exposure duration comprising at least five periods of the periodically modulated focus position and providing illumination having an intensity variation synchronized with the periodically modulated focus position, such that it differently influences the respective exposure contributions for different respective focus positions within the focus range of the periodically modulated focus position; and (d) processing the first preliminary image to remove blurred image contributions occurring in the focus range during the image integration time to provide an extended depth of field (EDOF) image that is substantially focused throughout a larger depth of field than the imaging system provides at a single focal position.