Non-contact high resolution displacement measurement technique
US4827436A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Apr 22, 1987 |
| Grant date | May 2, 1989 |
| Priority date | — |
| Expiry date | Apr 22, 2007 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH05K13/0813
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
Apparatus is disclosed for optically detecting the position of an edge of a workpiece (such as an IC lead tip) in a sensing plane, involving the emission of electromagnetic energy from a known source region in the sensing plane such as to cause the edge to create a shadow having a penumbra in the sensing plane. Two detectors determine the amount of energy which reach two known detection regions in the sensing plane and wholly within the penumbra. The amount of energy detected by one detector determines a first curve in the sensing plane on which the edge must lie, and the amount of energy detected by the other determines a second such curve. The intersection of these two curves fully determines the position of the edge in the sensing plane. Preferably, the source region and both detector regions are all essentially line segments oriented parallel to a z-axis, the two detection regions being disposed axially but spaced from each other. Apparatus is also disclosed for determining a profile of edges on one side of the workpiece. Algorithms are disclosed for interrelating measurements taken on four sides of the workpiece, calculating coplanarity of the lead tips, and calculating tweezi…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.