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US 4,056,716 AGranted
Defect inspection of objects such as electronic circuits
AssigneeInternational Business Machines Corporation
InventorsDuane Willard Baxter, Richard Edward Shipway
Life of this patent
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Abstract
Successive areas of a high-resolution object image are compared with corresponding areas of a low-resolution master pattern to produce signals representing the quality of the object. Comparison is effected by detecting which of a set of features occurs in each area of the object image, detecting which feature of the same set occurs in a larger area of the master pattern, and determining whether these two features are the same.
Claims8
A method of inspecting an object for defects, comprising the steps of:
- a. producing a high-resolution electronic representation of an object, said representation having a plurality of cells each corresponding to a first amount of area on said object;
- b. storing a low-resolution master pattern having a plurality of cells each representing a second, substantially larger amount of area on said object;
- c. detecting a first of a predetermined set of features in a first window comprising a plurality of said cells of said high-resolution representation;
- d. detecting a second feature of said set in a second window comprising a plurality of said cells of said low-resolution master pattern, said second window representing a substantially larger total area on said object than the area represented by said first window;
- e. comparing said first feature with said second feature;
- and
- f. repeating steps (c), (d) and (e) for different ones of said windows, representing further areas on said object.
4 more elements
Comparison means for an automatic inspection device, comprising:
- a high-resolution register for receiving and shifting an image of an object to be inspected, said first register having a plurality of cells each representing different first areas on said object;
- a low-resolution register for receiving and shifting a master pattern of an ideal form of said object, said low-resolution register being divided into a plurality of cells each representing different second areas on said object, each of said second areas corresponding to a plurality of said first areas on said object;
- a first feature detector coupled to a group of said cells of said high-resolution register for detecting the presence of absence of a predetermined set of features;
- a second feature detector coupled to a group of said cells of said low-resolution register for detecting the presence or absence of said set of features;
- gating means coupled to said feature detectors for producing a signal indicating whether or not the particular features found by said first and second detectors are the same.
2 more elements
Dependencies are inferred from the claim text.