Optical Linear Encoder Force Transducer for Input Pen
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Solution Overview
Problem
Conventional force transducers in computer input pens require strict mechanical tolerances and precise calibration, making them impractical for use in touchscreen devices due to their sensitivity to mechanical shock and misalignment, and they struggle with providing fine-step digital resolution over larger axial deflections.
Innovation Solution
A linear encoder force transducer that uses a light emitting diode (LED) and an encoder strip with reflective surfaces and etched lines, detected by an array of photo transistors, which generates a digital signal through a digital counter, eliminating the need for analog-to-digital conversion and allowing for increased assembly tolerances and reduced calibration requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional force transducers are used in computer input pens, then force measurement capability is provided, but the device requires strict mechanical tolerances and precise calibration, making it sensitive to mechanical shock and misalignment
Solution Approach 1:
The patent replaces the conventional mechanical force transducer with an optical encoding system. The mechanical deflection of a cantilever beam is converted into optical signal modulation through etched lines on the encoder strip that move relative to gradated slots in the encoder component. This substitution eliminates direct mechanical contact and friction between measurement components, making the system immune to mechanical shock and misalignment while requiring no calibration.
Solution Approach 2:
The patent creates an optical copy of the mechanical displacement. The physical movement of the encoder strip is replicated as an optical pattern through the etched lines, which are detected by photo transistors. This optical copying allows the measurement of mechanical deflection without direct mechanical sensing, eliminating the need for precise mechanical tolerances and calibration while maintaining measurement accuracy.
2Measurement precision
If conventional force transducers are used, then force measurement is achieved, but they struggle to provide fine-step digital resolution over larger axial deflections
Solution Approach 1:
The patent transitions from direct linear measurement to angular/optical pattern detection. The etched lines on the encoder strip create a Moiré pattern when viewed through the gradated slots, converting linear displacement into a detectable optical interference pattern. This dimensional transformation enables fine-step digital resolution (detecting sub-micron movements) over larger axial deflections (millimeter range) by measuring the phase shift of the optical pattern rather than direct position.
Solution Approach 2:
The patent changes the measurement parameter from direct displacement to optical path difference. By using the Moiré effect created by the interaction between etched lines and gradated slots, the system measures changes in optical phase rather than direct mechanical position. This parameter change enables high-resolution measurement over extended ranges, as the optical interference pattern provides amplified sensitivity to small displacements while accommodating larger overall movements.
3Device complexity
If conventional force transducers are used, then analog force signals are obtained, but analog-to-digital conversion is required which complicates the system
Solution Approach 1:
The patent replaces the analog measurement system with a direct digital measurement system. Instead of using an analog force transducer that requires signal conversion, the system uses an optical encoder that directly generates digital signals through the detection of the Moiré pattern by an array of photo transistors. The encoder module processes the optical signals and outputs digital data, eliminating the need for analog-to-digital conversion and simplifying the overall system architecture.
Solution Approach 2:
The patent introduces an optical intermediary (the encoder strip with etched lines) that mediates between the mechanical deflection and the digital output. The mechanical movement is first converted into an optical pattern, which is then detected and converted into digital signals by the photo transistor array and encoder module. This intermediary transformation sequence (mechanical → optical → digital) eliminates the need for direct analog-to-digital conversion of force signals, simplifying the system while enabling direct digital output.
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 linear encoder force transducer provides fine-step digital resolution over larger axial deflections, is immune to mechanical shock and misalignment, and simplifies calibration, enabling accurate force measurement in computer input pens.
Implementation Method 1
The encoder component includes a light emitting diode (LED) that generates light
Implementation Method 2
Reflective surfaces of the encoder strip include light dispersal particles that disperse and reflect the light internally within the encoder strip
Implementation Method 3
The encoder component has gradated slots through which the emitted light from the encoder strip is detected by an array of photo transistors
Implementation Method 4
The digital counter registers incremental steps of digital resolution as the etched lines of the encoder strip move relative to the gradated slots of the encoder component in a Moiré pattern
Data Source
AI summary
In implementations of a linear encoder force transducer, an encoder component generates light that enters a light input window of an encoder strip, and reflective surfaces disperse the light internally within the encoder strip. The encoder strip has etched lines formed cross-width of the encoder strip for emitted light that exits the encoder strip. The encoder component has gradated slots through which the emitted light from the encoder strip is detected by an array of photo transistors, each of the gradated slots corresponding to one of the photo transistors in the array of photo transistors. An encoder module can determine a linear displacement, such as representative of a force applied to a pen tip of a computer input pen, based on one or more of the photo transistors detecting the emitted light as the etched lines of the encoder strip move relative to the gradated slots of the encoder component.