Liquid Lens Assembly with Integrated Feedback Control
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Solution Overview
Problem
Liquid lenses used in machine vision systems face challenges with focus variation due to thermal drift and other factors, requiring significant processing time to maintain focus, which can burden the system's processor and slow response times.
Innovation Solution
A lens assembly with a membrane-based liquid lens and a feedback control circuit that uses a position sensor and current-driven annular bobbin assembly, along with a controller that adjusts the actuator position to maintain focus, incorporating temperature and orientation corrections to compensate for variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a liquid lens assembly is used for automatic focusing, then response time is reduced and mechanical complexity is eliminated, but focus variation occurs due to thermal drift and calibration changes
Solution Approach 1:
The patent implements a feedback control system that continuously monitors the actual bobbin position using a linear Hall sensor and compares it with the target position. The controller automatically adjusts the bobbin position by applying correction currents to maintain accurate focus, compensating for thermal drift and calibration variations without requiring manual intervention.
Solution Approach 2:
The patent replaces mechanical position sensing and adjustment mechanisms with an electromagnetic field-based system. A linear Hall sensor detects the bobbin's magnetic field to determine its position, and electromagnetic coils apply correction forces to the bobbin, eliminating the need for mechanical encoders or manual focus adjustment mechanisms.
2Reliability
If a feedback control system is implemented to correct focus variation, then focus stability is improved, but processing time increases and processor burden increases
Solution Approach 1:
The patent extracts the focus control functionality from the camera's main processor and implements it as an independent controller within the lens assembly. This dedicated controller handles all feedback control operations locally, freeing the camera processor from continuous focus adjustment tasks and reducing overall system processing time and computational burden.
Solution Approach 2:
The lens assembly's integrated controller autonomously manages focus correction by continuously reading sensor data, calculating position errors, and applying correction currents without requiring intervention from the camera processor. The system serves itself by maintaining focus stability through self-contained control logic and execution.
3Device complexity
If the camera processor handles focus control tasks, then system integration is simplified, but productivity decreases due to processor preoccupation with lens-control tasks
Solution Approach 1:
The patent segments the control system into two independent parts: the camera processor handles high-level vision processing tasks, while a dedicated controller in the lens assembly handles low-level focus control. This segmentation allows each component to specialize in its specific function, improving overall system productivity without significantly increasing integration complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution enables rapid and accurate focus control, reducing processing burdens on the camera's processor and maintaining focus stability, even under thermal and orientation changes, with correction times as fast as 1 millisecond.
Implementation Method 1
the position sensor comprises at least one Hall sensor
Implementation Method 2
the actuator comprises a current-driven annular bobbin assembly with a magnetic coil
Data Source
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AI summary
This invention provides a removably mountable lens assembly for a vision system camera that includes an integral auto-focusing liquid lens unit, in which the lens unit compensates for focus variations by employing a feedback control circuit that is integrated into the body of the lens assembly. The feedback control circuit receives motion information related to the bobbin of the lens from a position sensor (e.g. a Hall sensor) and uses this information internally to correct for motion variations that deviate from the lens setting position at a desired lens focal distance setting. Illustratively, the feedback circuit can be interconnected with one or more temperature sensors that adjust the lens setting position for a particular temperature value. In addition, the feedback circuit can communicate with an accelerometer that reads a direction of gravity and thereby corrects for potential sag in the lens membrane based upon the spatial orientation of the lens.