Single Element Aspherical Lens Optical Position Sensor
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Solution Overview
Problem
Conventional optical position sensing systems are bulky, expensive, and prone to mechanical instability due to the use of multi-element lens systems, which are not necessary for touch detection and are susceptible to vibrations and contaminants, especially in compact devices like small touch screens.
Innovation Solution
The optical position sensing system employs a single element aspherical lens with an f-theta characteristic, a retroreflective material like prismatic film, and a flexible light path separator, allowing for compact, robust, and cost-effective design with improved immunity to dust and contaminants, and focusing adjustments without moving lens elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple refractive elements (multi-element lens systems) are used, then image clarity and aberration correction are improved, but device size and depth increase
Solution Approach 1:
The patent extracts and removes the unnecessary multiple refractive elements from the optical system, retaining only a single refractive element (lens) while achieving sufficient imaging quality for touch detection applications. This extraction principle directly reduces device size and complexity while maintaining functional requirements.
Solution Approach 2:
Instead of using multiple lenses to correct aberrations (conventional approach), the patent inverts the approach by using a single lens with specific optical characteristics (aspherical surfaces, specific focal lengths) that inherently provide the needed performance without requiring correction through multiple elements.
2Measurement precision
If multiple refractive elements are used, then aberration correction is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent extracts and eliminates the complex multi-element lens system, retaining only a single refractive element. This dramatically simplifies the optical system while maintaining sufficient aberration correction through careful selection of the single lens's optical properties.
Solution Approach 2:
The patent changes the parameters of the single lens (aspherical surfaces, specific focal length, specific material properties) to achieve the aberration correction that would otherwise require multiple spherical lenses. This parameter optimization allows a single element to replace a multi-element system.
3Ease of operation
If lens elements are physically moved for focusing, then focus adjustment is achieved, but mechanical stability and vibration resistance decrease
Solution Approach 1:
The patent replaces the mechanical focusing system (physical movement of lens elements via threaded lens barrels) with a fixed optical design where the lens elements remain stationary. Focus and imaging are achieved through optical design parameters rather than mechanical adjustment, eliminating vibration sensitivity and mechanical failure points.
4Measurement precision
If multi-element lens systems are used, then image quality is improved, but susceptibility to dust and contaminants increases
Solution Approach 1:
The patent extracts and removes the multiple lens elements that create multiple surfaces susceptible to dust and contaminants. By using a single lens element with fewer optical surfaces, the system reduces the points where contaminants can accumulate and interfere with optical performance.
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 design results in a more accurate, compact, and cost-efficient optical position sensing system suitable for small devices like mobile phones and tablets, with enhanced mechanical stability and reduced susceptibility to vibrations and contaminants.
Implementation Method 1
The reflectors may comprise retroreflective material, such as a prismatic film or tape
Implementation Method 2
The optical position sensor assembly may include a single element aspherical lens with an f-theta characteristic
Implementation Method 3
a single element aspherical lens with an f-theta characteristic
Data Source
AI summary
An optical position sensing system includes a bezel surrounding a display, a position sensor assembly, and a processor for calculating touch locations. Prismatic film may be applied to the bezel. Each optical position sensor assembly includes a body. A lens holder holds an imaging window on a first side and a single element aspherical lens on a second side. The imaging window has an inside face shaped to form a shallow convex surface. The lens holder is mounted to a front face of the body such that the lens is aligned with an opening in the body. An optical sensor is mounted to a rear face of the body and aligned with the opening. A radiation source is positioned within the body above the lens holder and behind an illumination window. A light path separator is positioned between the illumination window and the imaging window.