Optical Displacement Sensing System Utilizing Edge Diffraction

Reference #: 01113

The University of South Carolina is offering licensing opportunities for novel edge diffraction-based displacement sensor with nanometer accuracy that can be easily implemented in high precision stage applications for machine tool metrology.

Invention Description:

The subject invention describes an inexpensive sensor that has a simple and non-contact sensing configuration while providing a high resolution. The proposed sensor showed a high linearity within 60µm range and the resolution 5.2nm. The electronic bandwidth of the sensor can easily exceed 1MHz. 

Potential Applications:

• Interferometer and two-segmented one-dimensional position sensitive detector
• Compact high precision stage applications

Advantages and Benefits:

1. Sensor target does not have to be conductive like capacitive sensors used in current displacement measurement.
2. Provides a gap-free application that a PSD-based measurement system cannot achieve

Background:

In a current displacement measurement technology for precision stage applications, expensive capacitive type sensors are most widely used because these can detect motion at sub-nanometer levels directly and provide accuracy, linearity, resolution, and stability. However, with this method, the target must be conductive, and attractive force between the target and the sensor probe should be canceled. PSDs are commonly used because these are inexpensive and capable of measuring lateral displacement in one or two dimensions. They consist of two, four or more segmented photodiodes positioned symmetrically around the center of the detector and separated by a narrow gap, which brings about many issues with the position accuracy and resolution.