Pointer Inclination Derivation Using Electrode Position Lookup Tables
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Solution Overview
Problem
Existing position detection devices, such as those using active capacitive coupling type stylus pens, face challenges in precisely determining the inclination of a pointer due to the ring-shaped second electrode's large volume and distance from the sensor, leading to errors in detection coordinates and reduced precision in inclination calculation, especially in devices with limited processing capabilities like smartphones.
Innovation Solution
An inclination derivation device and method that employs a look-up table (LUT) to compensate for the differences in position detection values between the first and second electrodes, allowing for precise inclination calculation with reduced computational complexity by normalizing input values and using IIR filters to enhance signal processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a ring-shaped second electrode is used to increase detection range, then the detection range is improved, but the measurement precision deteriorates due to distributed small detection values
Solution Approach 1:
The second electrode is divided into multiple segments around the axis C, with each segment independently detected by the sensor. This segmentation allows the system to process detection values from multiple discrete points rather than treating the entire ring as a single distributed signal, thereby improving coordinate specification precision while maintaining the extended detection range provided by the ring structure.
2Reliability
If the second electrode is positioned at a distance from the axis to increase detection capability, then the detection capability is improved, but the manufacturing precision deteriorates due to inclination-dependent distance variations
Solution Approach 1:
The system dynamically adjusts the reference distance parameter based on the detected inclination angle of the pointer. By changing the distance parameter according to inclination, the system compensates for the variations caused by the second electrode's offset positioning, maintaining detection capability while reducing the impact of manufacturing tolerances on calculation accuracy.
3Measurement precision
If complex arithmetic operations are used to calculate inclination from electrode coordinates, then the measurement precision is improved, but the device complexity increases
Solution Approach 1:
The system pre-calculates and stores correction values in a lookup table (LUT) that corresponds to various inclination angles and electrode position combinations. During operation, instead of performing complex real-time arithmetic operations, the system simply queries the pre-computed LUT with the detected electrode coordinates to obtain the inclination angle, significantly reducing computational complexity while maintaining high precision.
4Volume of moving object
If the second electrode is formed with a large volume to improve detection range, then the detection range is improved, but the measurement precision deteriorates due to noise influence
Solution Approach 1:
The system uses only a portion of the detection signal from the large-volume second electrode by focusing on the maximum detection value location rather than averaging across the entire electrode volume. This partial action approach reduces the influence of distributed small detection values and noise while still utilizing the extended detection range provided by the large electrode volume.
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 solution enables high-precision inclination derivation with reduced calculation complexity, minimizing errors and enabling efficient operation even in devices with limited processing power, such as smartphones, by using a LUT to register corresponding relations between detection value differences and compensation values.
Implementation Method 1
an active capacitive coupling type stylus pen 101 includes a plurality of, for example, two electrodes that are a first electrode 101a and a second electrode 101b, and a driving power source to drive the first and second electrodes 101a and 101b. The first electrode 101a is installed at an end on an axis C of the stylus pen 101, and the second electrode 101b is installed with a ring shape around the axis C, for example, surrounding the axis C. A signal which each of the first and second electrodes 101a and 101b driven by the driving power source transmits is received by a sensor 100a of a position detection device 100
Data Source
AI summary
An inclination derivation device of a pointer of a pen shape, is discussed with the pointer including a first electrode installed at an end of an axis and a second electrode installed around the axis. The inclination derivation device includes a sensor of a plane shape that detects a position of the first electrode and a position of the second electrode, and a control portion. The control portion includes a look-up table (LUT) in which a corresponding relation of a value based on a difference between the position of the first electrode and the position of the second electrode, and a compensation value that becomes a base of an inclination of the axis of the pointer is registered; an input value calculation portion that calculates and inputs the value based on the difference to the LUT; and an inclination derivation portion that derives the inclination from the compensation value output from the LUT.