×

Method and device for electrostatically investigating surface and sub-surface structures

  • US 5,485,092 A
  • Filed: 01/31/1994
  • Issued: 01/16/1996
  • Est. Priority Date: 08/01/1991
  • Status: Expired due to Fees
First Claim
Patent Images

1. An electrostatic sensing device for investigating a surface and/or sub-surface structure presenting a permittivity to an electric field which is a function of at least one characteristic of said structure, comprising:

  • at least one first electrically conductive sensor plate that can be placed in the proximity of the structure under investigation, said first sensor plate comprising a first edge;

    at least one second electrically conductive sensor plate comprising a second edge spaced apart from said first edge;

    means for electrically charging said first and second plates at different rates, a charging rate of at least one of said first and second plates being affected by said permittivity of said structure to said electric field produced by said first and second plates being charged; and

    a detecting and generating circuit for detecting a difference between respective electric voltages on said first and second plates as said first and second plates charge, and for generating an output signal representative of an amplitude of said voltage difference which is affected by said charging rates of said first and second plates, said first and second plates being affected by said permittivity of the structure, whereby said output signal is a function of said permittivity and is therefore indicative of at least one characteristic of said structure under investigation;

    wherein said detecting and generating circuit comprises;

    a differential amplifier having a first input connected to said first plate and a second input connected to said second plate for amplifying said voltage difference between said first and second plates; and

    a peak detector for detecting a highest amplitude of an amplified voltage difference from said differential amplifier and for generating said output signal in proportion to said highest amplitude.

View all claims
  • 0 Assignments
Timeline View
Assignment View
    ×
    ×