Identification of foreign object debris
AssigneeDMetrix, Inc.
InventorsPixuan Zhou, Lu Ding, Xuemeng Zhang
Life of this patent
Estimating the term…
Abstract
System and method for identification of foreign object debris, FOD, in a sample, based on comparison of edge features identified in images of the sample takes at a reference point in time and at a later time (when FOD may be already present). The rate of success of identification of the FOD is increased by compensation for relative movement between the imaging camera and the sample, which may include not only processing the sample's image by eroding of imaging data but also preceding spatial widening of edge features that may be indicative of FOD.
Claims13
A method for determining a foreign object debris (FOD) associated with a sample, the method comprising:
- a) with a detector of an imaging system, acquiring reference image data representing the reference sample to form a reference gradient image, of the reference sample, each pixel of which represents a value of a two-dimensional (2D) gradient of irradiance distribution associated with the reference sample;
- b) determining reference edge image data representing a position of an edge associated with the reference sample based on the reference gradient image data;
- c) forming a reference binary image data by
- assigning a first value to first pixels of the reference gradient image data that correspond to the edge associated with the reference sample, and
- assigning a second value to the remaining pixels of the reference gradient image, the second value being different from the first value;
- d) forming an inverted reference binary image by defining a negative of the reference binary image created from the reference binary image data.
- e) based on acquisition of an image of a stale sample with the imaging system and determination of a 2D gradient of irradiance distribution associated with said image, forming an image of the stale sample that displays an edge associated with the stale sample;
- f) combining, with a processing unit, the inverted reference binary image with the image of the stale sample to form a comparison image, said comparison image being devoid of an edge that is associated with both the reference sample and the stale sample.
A method for determining a foreign object debris (FOD) associated with a sample, the method comprising:
- a) with a detector of an imaging system, acquiring reference image data representing a reference sample to form a reference image;
- b) forming an image of the reference sample representing a position of an edge associated with the reference sample based on (i) a first image of said reference sample representing a first change of irradiance distribution associated with said reference sample and (ii) a second image of said reference sample representing a second change of irradiance distribution associated with said reference sample, the first and second changes occurring in mutually transverse directions;
- c) converting the image of the reference sample representing a position of an edge associated with the reference sample into a binary image of the reference sample, said binary image containing edges associated with said reference sample on a uniform background;
- d) forming an image of a stale sample representing a position of an edge associated with the stale sample based on (i) a first image of the stale sample and (ii) a second image of the stale sample, the first image representing a first change of irradiance distribution associated with the stale sample and the second image representing a second change of irradiance distribution associated with the stale sample, the first and second changes occurring in mutually transverse directions;
- e) forming a comparison image of the sample, which comparison image is devoid of an edge that is associated with both the reference sample and the stale sample, based on the binary image of the reference sample and the image of the stale sample;
- f) determining if the FOD is present at the stale sample by compensating the comparison image for a relative movement between the stale sample and the imaging system and comparing pixel irradiance values of the comparison image with a predetermined threshold value.
Dependencies are inferred from the claim text.