Thin Light Guide Film for Compact Optical Finger Navigation
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Solution Overview
Problem
Conventional optical navigation devices are too thick for handheld devices due to the thickness of traditional light guides, which limits their implementation in smaller form factors like cellular telephones and portable personal computing peripherals.
Innovation Solution
A finger navigation device utilizing a thin light guide film (LGF) with non-planar elements that exhibit total internal reflection (TIR), allowing for a thinner form factor and enhanced light scattering, reducing the overall device thickness and increasing light detection intensity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a traditional light guide is used to channel light from the light source to the navigation surface, then light transmission is achieved, but the device thickness increases to about 2.5 mm
Solution Approach 1:
The patent replaces the traditional discrete light guide element with a thin film light guide structure that has a thickness of approximately 100 micrometers or less. This thin film approach maintains the light transmission function while dramatically reducing the overall device thickness from 2.5 mm to a much thinner profile, enabling integration into handheld devices.
Solution Approach 2:
The patent transitions from a bulk three-dimensional light guide structure to a two-dimensional thin film structure. By flattening the light guide into a planar configuration, the vertical thickness is eliminated while light transmission continues through the thin film layer, achieving space efficiency in the vertical dimension.
2Length of stationary object
If a thin light guide film is used to reduce device thickness, then device compactness is improved, but light scattering intensity may be reduced
Solution Approach 1:
The patent incorporates curved or non-planar surface features on the light guide film to enhance light scattering. By introducing surface curvature or three-dimensional surface structures, the film maintains effective light scattering intensity despite its thin profile, preventing the loss of illumination effectiveness that would otherwise occur with a flat thin film.
Solution Approach 2:
The patent uses composite material structures for the light guide film, combining different materials with complementary optical properties. This composite approach enables the thin film to achieve both thinness and effective light scattering, as the combined materials provide both light transmission and scattering functions that a single material could not achieve alone.
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
The thin light guide film and non-planar elements enable a more compact optical finger navigation device with improved light detection, reducing battery power consumption and allowing for more efficient navigation signals, suitable for smaller electronic devices.
Implementation Method 1
at least a portion of the LGF exhibits total internal reflection (TIR). The light source is in optical communication with the LGF to provide light from the light source to the finger interface surface
Data Source
AI summary
An optical finger navigation device. Embodiments of the optical finger navigation device include a light guide film (LGF) including a finger interface surface, a light source in optical communication with the LGF to provide light from the light source to the finger interface surface, a sensor, and a navigation engine. At least a portion of the LGF exhibits total internal reflection (TIR). The sensor detects light from the LGF in response to contact between a finger and the finger interface surface which modifies reflection of light out of the LGF to the sensor. The light detected by the sensor is changed over at least a portion of the sensor in response to the contact between the finger and the finger interface surface. The navigation engine is configured to generate lateral movement information indicative of lateral movement of the finger relative to the sensor, in response to the detected light.