Coordinate Detection Apparatus Ambient Light Compensation
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Solution Overview
Problem
Existing coordinate detection apparatuses using the light-shielding method are prone to errors and malfunctions due to changes in the installation environment, such as ambient light, which can alter the base data and reference data used for calculating the light-shielded position, leading to inaccurate coordinate detection.
Innovation Solution
The apparatus includes light projecting and receiving means, with detection mechanisms to identify abnormal light sources and adjust calculations based on outputs from both states where the light projecting means is on and off, allowing for precise detection of light-shielded positions even in environments with changing light conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If base data and reference data are acquired upon power ON to eliminate individual differences of CCD pixels and ambient light influence, then measurement precision is improved, but reliability deteriorates because changes in installation environment during use cause coordinate detection errors
Solution Approach 1:
The patent applies preliminary action by acquiring base data and reference data not only upon power ON but also at multiple points during operation. The system proactively updates calibration data before environmental changes cause detection errors, rather than waiting for errors to occur. This is implemented through periodic re-acquisition of base data and reference data during device operation, ensuring the calibration reflects current environmental conditions.
Solution Approach 2:
The patent implements feedback by continuously monitoring coordinate detection results and comparing them against expected ranges. When anomalies are detected that suggest environmental changes have affected accuracy, the system triggers re-acquisition of base and reference data. This closed-loop feedback mechanism ensures reliability is maintained by adapting to environmental changes dynamically.
2Measurement precision
If light receiving units detect light amount distributions to calculate light-shielded position, then measurement precision is improved, but object-affected harmful factors worsen due to sensitivity to ambient light changes
Solution Approach 1:
The patent converts the harmful effect of ambient light into a beneficial calibration reference. By acquiring base data that includes the ambient light components present at the time of calibration, and using this base data to subtract environmental influences from subsequent measurements, the system transforms ambient light from a source of error into a reference that enables compensation. The ambient light that would normally cause detection errors is instead captured and used to correct future measurements.
3Measurement precision
If coordinate detection is performed by detecting light-shielded position using light projecting and receiving means, then measurement precision is improved, but reliability deteriorates due to detection errors from environmental changes
Solution Approach 1:
The system performs preliminary calibration by acquiring base data and reference data before coordinate detection begins. This preliminary action establishes a baseline that accounts for environmental conditions, device characteristics, and optical path properties. The base data is acquired in a known good state, and subsequent coordinate measurements are calculated by comparing against this pre-established baseline, ensuring reliable and accurate detection.
Solution Approach 2:
The patent applies beforehand cushioning by storing multiple sets of base data and reference data acquired at different times and environmental conditions. This creates a buffer or cushion of reference data that can be selected based on current conditions, protecting the system from errors that would occur if only a single baseline were available. The system can switch between different baseline datasets to maintain accuracy despite environmental variations.
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 approach ensures accurate and reliable coordinate detection by accounting for environmental changes, reducing errors and malfunctions caused by ambient light or other external factors, and providing a stable operation by informing the user of abnormal conditions.
Implementation Method 1
a retroreflecting member 4 is arranged outside a coordinate input effective region 3... illumination units 1L, 1R for illuminating light and light receiving units 1L, 1R for receiving light... detect angles between the light receiving units and an object such as a finger or the like, which shields light
Implementation Method 2
a retroreflecting sheet is provided outside a coordinate input surface of this type and reflects light coming from illumination units that illuminate light, and light receiving units detect light amount distributions
Data Source
AI summary
A coordinate detection apparatus has a light projecting unit and light receiving unit, detects abnormal light based on the output from the light receiving unit in a state in which the light projecting unit does not project any light, and detects the coordinates of a light-shielded position based on the output from the light receiving unit in a state in which the light projecting unit projects light.