David Z Li

6567337, May 20, 2003

Jun 30, 2000

09/607897

Milo D. Sprague - Hudson MA
David K. Li - Portland OR
Robert J. Murray - Portland OR

Intel Corporation - Santa Clara CA

G11C 800

365233, 36518905, 36518912

A pulsed circuit topology to perform a memory array write operation. A write enable pulse width control circuit is responsive to a pulsed clock signal to generate a pulsed write enable signal and a write data path circuit is provided to output a write data signal. The write enable pulse width control circuit and the write data path circuit together control a write operation to a memory cell.

8442304, May 14, 2013

Dec 29, 2008

12/345130

Cyril C. Marrion - Acton MA, US
Nigel J. Foster - Natick MA, US
Lifeng Liu - Arlington MA, US
David Y. Li - West Roxbury MA, US
Guruprasad Shivaram - Chestnut Hill MA, US
Aaron S. Wallack - Natick MA, US
Xiangyun Ye - Framingham MA, US

Cognex Corporation - Natick MA

G06K 9/00

382154, 382190, 382294

This invention provides a system and method for determining the three-dimensional alignment of a modeled object or scene. A 3D (stereo) sensor system views the object to derive a runtime 3D representation of the scene containing the object. Rectified images from each stereo head are preprocessed to enhance their edge features. 3D points are computed for each pair of cameras to derive a 3D point cloud. The amount of 3D data from the point cloud is reduced by extracting higher-level geometric shapes (HLGS), such as line segments. Found HLGS from runtime are corresponded to HLGS on the model to produce candidate 3D poses. A coarse scoring process prunes the number of poses. The remaining candidate poses are then subjected to a further more-refined scoring process. These surviving candidate poses are then verified whereby the closest match is the best refined three-dimensional pose.

20110157373, Jun 30, 2011

Dec 24, 2009

12/647192

Xiangyun Ye - Framingham MA, US
David Y. Li - West Roxbury MA, US
Guruprasad Shivaram - Chestnut Hill MA, US
David J. Michael - Wayland MA, US

COGNEX CORPORATION - Natick MA

H04N 17/00

348187, 348E07085

This invention provides a system and method for runtime determination (self-diagnosis) of camera miscalibration (accuracy), typically related to camera extrinsics, based on historical statistics of runtime alignment scores for objects acquired in the scene, which are defined based on matching of observed and expected image data of trained object models. This arrangement avoids a need to cease runtime operation of the vision system and/or stop the production line that is served by the vision system to diagnose if the system's camera(s) remain calibrated. Under the assumption that objects or features inspected by the vision system over time are substantially the same, the vision system accumulates statistics of part alignment results and stores intermediate results to be used as indicator of current system accuracy. For multi-camera vision systems, cross validation is illustratively employed to identify individual problematic cameras. The system and method allows for faster, less-expensive and more-straightforward diagnosis of vision system failures related to deteriorating camera calibration.

20130313312, Nov 28, 2013

May 22, 2012

13/477351

Lei Wang - Wayland MA, US
Gang Liu - Natick MA, US
David Li - West Roxbury MA, US

G06F 17/00

235375

An apparatus for associating codes on parts with part spaces on a conveyor wherein each part has a leading edge and a trailing edge that define a part space and each part is to be marked with at least one code, the apparatus comprising an area scan camera having a two dimensional field of view (FOV), the camera supported adjacent the conveyor so that parts conveyed by the conveyor pass through the FOV, a processor linked to the area scan camera, the processor programmed to perform the steps of receiving images from the area scan camera, identifying the locations of codes on parts in at least one of the images wherein a code located is a located code, identifying the locations of leading and trailing edges of parts wherein the leading and trailing edges define part spaces and associating each located code with a part space that includes the location of the located code.

57420378, Apr 21, 1998

Mar 7, 1996

8/612032

Joseph R. Scola - Medfield MA
David Y. Li - West Roxbury MA

Cognex Corp. - Natick MA

G06K 710

235454

A method and apparatus for identifying an object having an identifying feature includes a two step process for detecting the identifying feature. The process involves locating the feature based upon a first characteristic of the feature and then verifying that feature is the identifying feature based upon a second characteristic of the feature. Preferably, the first step of the process is less discriminating and substantially faster than the second step. This permits the process to be performed rapidly without reducing accuracy.

20210291376, Sep 23, 2021

Mar 11, 2021

17/198333

Yukun Bian - Suzhou, CN
Li Sun - Sudbury MA, US
David Y. Li - West Roxbury MA, US

B25J 9/16
G06T 7/80

This invention provides a system and method for calibration of a 3D vision system using a multi-layer 3D calibration target that removes the requirement of accurate pre-calibration of the target. The system and method acquires images of the multi-layer 3D calibration target at different spatial locations and at different times, and computes the orientation difference of the 3D calibration target between the two acquisitions. The technique can be used to perform vision-based single-plane orientation repeatability inspection and monitoring. By applying this technique to an assembly working plane, vision-based assembly working plane orientation repeatability, inspection and monitoring can occur. Combined with a moving robot end effector, this technique provides vision-based robot end-effector orientation repeatability inspection and monitoring. Vision-guided adjustment of two planes to achieve parallelism can be achieved. The system and method operates to perform precise vision-guided robot setup to achieve parallelism of the robot's end-effector and the assembly working plane.

20200005069, Jan 2, 2020

Jun 6, 2019

16/433602

- Natick MA, US
Vivek Anand - Chelmsford MA, US
Lowell D. Jacobson - Grafton MA, US
David Y. Li - West Roxbury MA, US

G06K 9/46
G06K 9/62
G06N 3/08

This invention provides a system and method for finding patterns in images that incorporates neural net classifiers. A pattern finding tool is coupled with a classifier that can be run before or after the tool to have labeled pattern results with sub-pixel accuracy. In the case of a pattern finding tool that can detect multiple templates, its performance is improved when a neural net classifier informs the pattern finding tool to work only on a subset of the originally trained templates. Similarly, in the case of a pattern finding tool that initially detects a pattern, a neural network classifier can then determine whether it has found the correct pattern. The neural network can also reconstruct/clean-up an imaged shape, and/or to eliminate pixels less relevant to the shape of interest, therefore reducing the search time, as well significantly increasing the chance of lock on the correct shapes.

20190378254, Dec 12, 2019

Dec 10, 2018

16/215485

- Natick MA, US
Lowell D. Jacobson - Grafton MA, US
David Y. Li - West Roxbury MA, US

G06T 5/20
G06T 7/13
G06T 7/143

This invention provides a system and method for finding multiple line features in an image. Two related steps are used to identify line features. First, the process computes x and y-components of the gradient field at each image location, projects the gradient field over a plurality subregions, and detects a plurality of gradient extrema, yielding a plurality of edge points with position and gradient. Next, the process iteratively chooses two edge points, fits a model line to them, and if edge point gradients are consistent with the model, computes the full set of inlier points whose position and gradient are consistent with that model. The candidate line with greatest inlier count is retained and the set of remaining outlier points is derived. The process then repeatedly applies the line fitting operation on this and subsequent outlier sets to find a plurality of line results. The process can be exhaustive RANSAC-based.