Lensless Optical Navigation Using Light Pipe and Aperture
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Solution Overview
Problem
Conventional optical navigation devices face challenges in reducing their thickness below 2.5 mm due to the complexity of molding imaging lenses and tight tolerances, which affects accuracy and increases production costs, making them unsuitable for handheld devices like cellular telephones and small portable computing peripherals.
Innovation Solution
A user input device design that includes a light source, a sensor array, and a light shield with an aperture, eliminating the need for an optical lens by using a light pipe and total internal reflection, allowing for a reduced optical track height of less than 2 mm and improved manufacturing simplicity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If conventional optical lenses are used to direct light from the finger interface surface to the sensor, then the device can achieve proper imaging function, but the optical height cannot be reduced below about 2.5 mm due to molding difficulties and tight tolerances
Solution Approach 1:
The patent removes the imaging lens from the optical navigation device package, eliminating the need for complex lens molding and tight tolerances. The light guide structure directly directs light to the sensor without requiring a separate imaging lens component, thereby reducing optical height while maintaining manufacturing simplicity.
Solution Approach 2:
The light guide structure serves multiple functions: it transports light from the LED to the finger interface surface, directs reflected light to the sensor array, and replaces the traditional imaging lens function. This multi-functionality eliminates the need for a separate lens component and reduces overall optical height.
2Length of stationary object
If the optical height is reduced below 2.5 mm, then the device thickness is reduced for handheld applications, but the manufacturing complexity and cost increase due to tight tolerances
Solution Approach 1:
The patent extracts the imaging lens from the device architecture, eliminating the need for complex molding processes and tight tolerances associated with lens manufacturing. The simplified light guide structure can be manufactured with standard tolerances, reducing manufacturing complexity and cost.
Solution Approach 2:
The patent changes the optical parameters by using a light guide with specific refractive index and geometric configuration to achieve proper light direction without a lens. This parameter change allows for relaxed tolerances in manufacturing while maintaining the required optical performance at reduced optical height.
3Measurement precision
If conventional optical navigation devices are designed with proper imaging lenses, then navigation accuracy is maintained, but the device package becomes too thick for some handheld implementations
Solution Approach 1:
The light guide structure performs multiple optical functions including light transport, light direction, and imaging, replacing the traditional separate lens component. This maintains navigation accuracy through proper light focusing while reducing optical height to enable thinner handheld device implementations.
Solution Approach 2:
The patent uses specific parameter optimization in the light guide design, including refractive index selection and geometric configuration, to achieve proper light focusing and imaging performance without requiring a traditional lens, thereby maintaining navigation accuracy at reduced optical height.
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
Enables accurate navigation signals with reduced device thickness, suitable for spatially constrained systems, and lowers manufacturing complexity and costs, facilitating implementation in handheld devices.
Implementation Method 1
The light source includes a laser in optical communication with the finger interface surface to provide light to the finger interface surface
Implementation Method 2
Lensless user input device with optical interference based on diffraction with a small aperture
Implementation Method 3
optical interference based on diffraction with a small aperture
Data Source
AI summary
An optical navigation device which uses optical interference to generate navigation images. The optical navigation device includes an optical element, a light source, a sensor array, a navigation engine, and a light shield. The optical element includes a finger interface surface. The light source includes a laser in optical communication with the finger interface surface to provide light to the finger interface surface. The sensor array detects light reflected from the finger interface surface in response to contact between a finger and the finger interface surface. The navigation engine is coupled to the sensor array. The navigation engine generates lateral movement information based on lateral movement of the finger relative to the sensor array. The light shield is between the optical element and the sensor array. The light shield includes an aperture linearly aligned with the sensor array.