Stabilizing operation of a high speed variable focal length tunable acoustic gradient lens in an imaging system

Abstract

A method is provided for operating an imaging system to maintain a tunable acoustic gradient (TAG) lens at a desired operating state. In a first step, the TAG lens operates using a standard imaging drive control configuration (e.g., a standard drive voltage and duration) during a plurality of imaging drive mode time periods, to achieve a standard imaging state of the TAG lens. In a second step, the TAG lens operates using a regulating adaptive drive control configuration during a plurality of regulating adaptive drive mode time periods, wherein at least one of a different respective TAG lens drive voltage and a different respective TAG lens drive duration is used for different respective regulating adaptive drive mode time periods, based on a monitoring signal that is indicative of a difference between the standard imaging state and a current operating state of the TAG lens.

Description

BACKGROUNDTechnical Field[0001]This disclosure relates to precision metrology using a high speed variable focal length lens (e.g., in a machine vision inspection system) and, more particularly, to monitoring and stabilizing operation of a high speed variable focal length lens in an imaging system.Description of the Related Art[0002]Precision non-contact metrology systems such as precision machine vision inspection systems (or “vision systems” for short) may be utilized to obtain precise dimensional measurements of objects and to inspect various other object characteristics, and may include a computer, a camera and optical system, and a precision stage that moves to allow workpiece traversal and inspection. One exemplary prior art system is the QUICK VISION® series of PC-based vision systems and QVPAK® software available from Mitutoyo America Corporation (MAC), located in Aurora, Ill. The features and operation of the QUICK VISION® series of vision systems and the QVPAK® software are...

AI Technical Summary

Benefits of technology

The patent describes a method and system for calibrating and stabilizing an imaging system that uses a TAG lens. The system uses known operating conditions to calibrate the lens's focal length or position. However, these conditions may drift due to factors such as temperature changes, leading to small measurement errors. The method and system described in the patent can monitor and stabilize the lens and imaging system, reducing or eliminating these errors.

Problems solved by technology

In operation, however, the operating conditions of a TAG lens may drift due to various factors, and may fail to precisely match the operating conditions used for calibration.

This may result in small, but non-negligible, measurement errors.

Any such change in the electro-mechanical response of the lens and / or its fluid properties necessarily changes the optical power (or focal length) response of the lens to the drive signal, resulting in the aforementioned measurement errors.

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