Systems and methods for rapidly automatically focusing a machine vision inspection system
First Claim
1. A method for operating a precision machine vision inspection system to determine an estimated best focus position that is at least approximately a best focus position usable for inspecting a region of interest of a workpiece, the precision machine vision inspection system comprising:
- an imaging system comprising;
a camera having a pixel set corresponding to a full field of view of the camera, the camera operable to output the pixel values of at least one configuration of a reduced readout pixel set, the at least one configuration of a reduced readout pixel set corresponding to substantially less than the full field of view of the camera along at least one dimension of the field of view of the camera, andat least one lens configuration;
a plurality of controllable motion axes including a focus axis, the focus axis including a focus axis position sensor;
a control system portion; and
a workpiece stage that carries the workpiece, wherein at least one of the workpiece stage and the imaging system is movable to provide relative motion with respect to the other at least along the focus axis, the method comprising;
overlapping at least a majority of the region of interest and at least part of a reduced readout pixel set in the field of view of the camera;
providing a motion, the motion including traversing a focus image range along the focus axis direction using continuous motion;
inputting an auto focus image into the camera during the continuous motion, the auto focus image having a respective effective exposure time and exposure duration;
outputting the pixel values of the reduced readout pixel set of the auto focus image to the control system portion during the continuous motion, the output pixel values of the auto focus image corresponding to substantially less than the full field of view of the camera along at least one dimension of the field of view of the camera;
repeating the inputting and outputting steps to provide data for a plurality of reduced readout pixel sets corresponding to a plurality of auto focus images distributed along the focus image range;
determining respective positions along the focus axis for at least some of the plurality of auto focus images; and
determining an estimated best focus position that is at least approximately the best focus position usable for inspecting a region of interest of a workpiece based on at least some of the data for a plurality of reduced readout pixel sets and at least some of the respective positions along the focus axis for at least some of the plurality of auto focus images, wherein;
the output pixel values of the outputting operation are output in a time that is substantially less than a time required for outputting the full pixel set corresponding to a full field of view of the camera;
repeating the inputting and outputting steps is performed within a reduced time that is less than a standard time that corresponds to inputting an input image and outputting a pixel set corresponding to a full field of view of the camera;
the plurality of auto focus images are distributed along the focus image range in a manner depending at least partially on the reduced time and the provided motion such that a maximum spacing along the focus axis between the respective positions of adjacent auto focus images is operational for determining the estimated best focus position that is at least approximately the best focus position to a desired level of accuracy; and
the motion over at least a part of the focus image range is substantially faster than a fastest motion allowable in combination with the standard time in order to hypothetically produce adjacent auto focus images that are spaced apart along the focus axis direction by that maximum spacing between the respective positions of adjacent auto focus images.
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Abstract
Auto focus systems and methods for a machine vision metrology and inspection system provide high speed and high precision auto focusing, while using relatively low-cost and flexible hardware. One aspect of various embodiments of the invention is that the portion of an image frame that is output by a camera is minimized for auto focus images, based on a reduced readout pixel set determined in conjunction with a desired region of interest. The reduced readout pixel set allows a maximized image acquisition rate, which in turn allows faster motion between auto focus image acquisition positions to achieve a desired auto focus precision at a corresponding auto focus execution speed that is approximately optimized in relation to a particular region of interest. In various embodiments, strobe illumination is used to further improve auto focus speed and accuracy. A method is provided for adapting and programming the various associated auto focus control parameters.
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Citations
48 Claims
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1. A method for operating a precision machine vision inspection system to determine an estimated best focus position that is at least approximately a best focus position usable for inspecting a region of interest of a workpiece, the precision machine vision inspection system comprising:
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an imaging system comprising; a camera having a pixel set corresponding to a full field of view of the camera, the camera operable to output the pixel values of at least one configuration of a reduced readout pixel set, the at least one configuration of a reduced readout pixel set corresponding to substantially less than the full field of view of the camera along at least one dimension of the field of view of the camera, and at least one lens configuration; a plurality of controllable motion axes including a focus axis, the focus axis including a focus axis position sensor; a control system portion; and a workpiece stage that carries the workpiece, wherein at least one of the workpiece stage and the imaging system is movable to provide relative motion with respect to the other at least along the focus axis, the method comprising; overlapping at least a majority of the region of interest and at least part of a reduced readout pixel set in the field of view of the camera; providing a motion, the motion including traversing a focus image range along the focus axis direction using continuous motion; inputting an auto focus image into the camera during the continuous motion, the auto focus image having a respective effective exposure time and exposure duration; outputting the pixel values of the reduced readout pixel set of the auto focus image to the control system portion during the continuous motion, the output pixel values of the auto focus image corresponding to substantially less than the full field of view of the camera along at least one dimension of the field of view of the camera; repeating the inputting and outputting steps to provide data for a plurality of reduced readout pixel sets corresponding to a plurality of auto focus images distributed along the focus image range; determining respective positions along the focus axis for at least some of the plurality of auto focus images; and determining an estimated best focus position that is at least approximately the best focus position usable for inspecting a region of interest of a workpiece based on at least some of the data for a plurality of reduced readout pixel sets and at least some of the respective positions along the focus axis for at least some of the plurality of auto focus images, wherein; the output pixel values of the outputting operation are output in a time that is substantially less than a time required for outputting the full pixel set corresponding to a full field of view of the camera; repeating the inputting and outputting steps is performed within a reduced time that is less than a standard time that corresponds to inputting an input image and outputting a pixel set corresponding to a full field of view of the camera; the plurality of auto focus images are distributed along the focus image range in a manner depending at least partially on the reduced time and the provided motion such that a maximum spacing along the focus axis between the respective positions of adjacent auto focus images is operational for determining the estimated best focus position that is at least approximately the best focus position to a desired level of accuracy; and the motion over at least a part of the focus image range is substantially faster than a fastest motion allowable in combination with the standard time in order to hypothetically produce adjacent auto focus images that are spaced apart along the focus axis direction by that maximum spacing between the respective positions of adjacent auto focus images. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21)
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22. A method of training mode operation for a precision machine vision inspection system in order to determine set of machine control instructions usable to automatically determine an estimated best focus position that is at least approximately a best focus position usable for inspecting a region of interest of a workpiece, the precision machine vision inspection system comprising:
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an imaging system comprising; a camera having a pixel set corresponding to a full field of view of the camera, the camera operable to output the pixel values of at least one configuration of a reduced readout pixel set, the at least one configuration of a reduced readout pixel set corresponding to substantially less than the full field of view of the camera along at least one dimension of the field of view of the camera, and at least one lens configuration; a plurality of controllable motion axes including a focus axis, the focus axis including a focus axis position sensor; a control system portion; a workpiece stage that carries the workpiece, wherein at least one of the workpiece stage and the imaging system is movable to provide relative motion with respect to the other at least along the focus axis; and a graphical user interface comprising a display portion usable to display workpieces images, and a plurality of user interface elements comprising at least one auto focus tool, the method comprising; defining a region of interest and a reduced readout pixel set overlapping with at least a majority of the region of interest, wherein; at least the region of interest is defined using an auto focus widget associated with the operation of an auto focus tool, the auto focus widget positionable on a displayed image of the workpiece, the output pixel values correspond to substantially less than the full field of view of the camera along at least one dimension of the field of view of the camera, and the pixel values of the reduced readout pixel set of an auto focus image can be output to the control system portion in a time that is substantially less than a time required for outputting the full pixel set corresponding to a full field of view of the camera; defining a set of auto focus parameters usable to determine a set of auto focus operations for the region of interest; determining a set of auto focus operations for the region of interest, comprising; determining a run mode focus image range, determining a run mode auto focus motion;
the auto focus motion including traversing the focus image range along the focus axis direction using continuous motion, anddetermining a run mode illumination level and exposure duration usable for inputting an auto focus image into the camera during the continuous motion; providing operations to determine a repetitive inputting of respective auto focus images and outputting of respective data for a plurality of reduced readout pixel sets corresponding to a plurality of auto focus images distributed along the focus image range during the continuous motion, each of the respective auto focus images having an effective exposure time and exposure duration; providing operations to determine respective positions along the focus axis for at least some of the plurality of auto focus images; and providing operations to determine the estimated best focus position that is at least approximately the best focus position usable for inspecting a region of interest of a workpiece based on at least some of the data for a plurality of reduced readout pixel sets and at least some of the respective positions along the focus axis for at least some of the plurality of auto focus images, wherein; the determined repetitive inputting of respective auto focus images and outputting of respective data for a plurality of reduced readout pixel sets is performed within a reduced time that is less than a standard time that corresponds to inputting an input image and outputting a pixel set corresponding to a full field of view of the camera; the plurality of auto focus images are distributed along the focus image range in a manner depending at least partially on the reduced time and the auto focus motion such that a maximum spacing along the focus axis between the respective positions of adjacent auto focus images is operational for determining the estimated best focus position that is at least approximately the best focus position to a desired level of accuracy; and the auto focus motion is substantially faster along the focus axis over at least a part of the focus image range than a fastest motion allowable in combination with the standard time in order to hypothetically produce that maximum spacing between the respective positions of adjacent auto focus images. - View Dependent Claims (23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48)
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Specification