초록 ▼

An edge detection system for measuring lateral position in the presence of height variations such as found in gauging the edge position of a wafer uses first and second capacitive probes formed of passive elements with the active components kept outside the probe and at a distance that permits a sma

An edge detection system for measuring lateral position in the presence of height variations such as found in gauging the edge position of a wafer uses first and second capacitive probes formed of passive elements with the active components kept outside the probe and at a distance that permits a smaller, stabler and more economical probe to be located at the location of the wafer. The probes are instrumented in an electronic circuit having plural operational amplifiers that drive the probes to compensate the edge detection for wafer height effects.

대표청구항 ▼

A system for capacitive edge detection of a supported member comprising: a member where the position of an edge of said member is to be detected; a first probe positioned proximate to said member near the edge thereof and having a parameter varying as a function both of a distance from said probe to

A system for capacitive edge detection of a supported member comprising: a member where the position of an edge of said member is to be detected; a first probe positioned proximate to said member near the edge thereof and having a parameter varying as a function both of a distance from said probe to said member and displacement of a portion of said probe beyond the edge of said member; a second probe positioned near said first probe and closer to an interior location of said member than said first probe, said second probe having a parameter varying with distance of said second probe from said member; a first operational amplifier having the capacitance sensed by the electrode of the first probe in a feedback loop thereof; a second operational amplifier having the capacitance sensed by the electrode of the second probe in an input circuit thereof and; a source of A.C. excitation driving said first operational amplifier.