Optical Lens Position Sensing via Image Sensor Spot Tracking
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Solution Overview
Problem
Auto-focus optical systems require high precision in position sensing, typically achieved by counting stepper motor steps, but existing methods are limited by mechanical wear and size constraints, especially in small devices like mobile phones, where non-contact, high-accuracy, and cost-effective solutions are needed.
Innovation Solution
A light beam is used to illuminate a spot on a lens element, with the reflected light beam detected on an image sensor, allowing the signal processor to determine the lens position, and a control module adjusts the lens position for focusing or zooming, using a pulsed light source synchronized with frame capture to optimize data transfer and reduce mechanical wear.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If stepper motor steps are counted for position determination, then position sensing can be achieved, but mechanical wear occurs and precision is limited
Solution Approach 1:
The patent replaces the mechanical stepper motor position encoding system with an optical sensing system. A light source projects light through the lens element to the image sensor, and the position of the light spot on the image sensor indicates the lens position. This optical method eliminates mechanical contact and wear while achieving higher precision position sensing.
Solution Approach 2:
The patent creates an optical copy of the lens position information by projecting a light spot through the lens element onto the image sensor. The position of this light spot copy on the sensor plane directly reflects the lens element's position along the optical axis, enabling non-contact position measurement with high precision.
2Volume of moving object
If miniature piezoelectric motors are used to reduce size, then device size is reduced, but separate position sensors are required increasing complexity
Solution Approach 1:
The patent makes the image sensor serve dual functions: capturing image data and detecting lens position through light spot analysis. By utilizing the existing image sensor for both imaging and position sensing, the system eliminates the need for separate position sensors, reducing component count and system complexity while maintaining compact size.
Solution Approach 2:
The patent merges the position sensing function with the image capture function by using the same image sensor for both purposes. The light spot position information is extracted from the image data, combining two measurement functions into a single sensor and processing pipeline, thereby simplifying the overall system architecture.
3Measurement precision
If continuous light beam is used for position sensing, then position information is continuously available, but energy consumption increases
Solution Approach 1:
The patent employs periodic or pulsed illumination instead of continuous light beam for position sensing. The light source is activated only when position measurement is required (e.g., during focus adjustment or before image capture), reducing energy consumption while maintaining the ability to obtain position information when needed.
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 method provides improved accuracy and reduced mechanical wear, achieving over 3× improvement in precision for lens position determination, suitable for small devices and mass production, while minimizing component size and cost.
Implementation Method 1
The light beam is arranged such that the reflected light beam from the lens element encounters a spot on the image sensor
Data Source
AI summary
A light beam is used to illuminate a spot on a lens element which is shifted along the optical axis of an imaging system for auto-focus or optical zoom purposes. The light beam is arranged such that the reflected light beam from the lens element encounters a spot on the image sensor. The spot location on the image sensor is determined by a signal processor. As the lens element is shifted along the optical axis, the spot location changes accordingly. Based on the moving distance of the spot, the signal processor determines the shifting distance of the lens element and hence the position of the lens element. Based on the shifting distance of the lens element, a control module is used to adjust the lens position along the optical axis to achieve the desired focusing or zooming effects.