Optical Sensor Location Shift Measurement in Display Devices
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Solution Overview
Problem
Display devices with sensors attached to their rear surfaces, such as fingerprint sensors, face challenges in accurately measuring and updating the location of these sensors due to unintentional shifts, which affects the calibration data and overall sensor functionality.
Innovation Solution
A display device with an optical sensor system that measures location shifts and directions in both integer and decimal units using sensor pixels, where a pattern with markers is displayed, imaged, and processed to calculate representative coordinates, allowing for precise determination of shift amounts and directions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the optical sensor location is measured only in integer units based on sensor pixels, then the measurement process is simple, but the measurement precision is insufficient to detect fine location shifts
Solution Approach 1:
The patent segments the coordinate measurement into two parts: integer part (in sensor pixel units) and decimal part (in sub-pixel units). The integer part is obtained by rounding the centroid coordinates, while the decimal part is calculated by comparing brightness values between current and reference images. This segmentation allows precise measurement without requiring complex measurement systems.
Solution Approach 2:
The patent uses brightness comparison as an intermediary method to achieve sub-pixel precision. By comparing the brightness values of corresponding pixels between the current sensor image and the reference image, the system can determine decimal part coordinates without directly measuring sub-pixel positions, thus maintaining measurement simplicity while achieving high precision.
2Reliability
If the sensor location is updated frequently to account for unintentional shifts, then the sensor functionality is maintained, but the calibration data becomes invalid and requires re-calibration
Solution Approach 1:
The patent replaces the mechanical approach of physical re-calibration with an optical/image processing approach. By capturing an image of the sensor's field of view and calculating the centroid position of reference markers, the system can digitally update the sensor location without physical re-calibration, thus maintaining reliability while avoiding time loss.
Solution Approach 2:
The patent performs preliminary action by storing reference images and marker positions in advance. When location shifts occur, the system compares current images against these pre-stored references to quickly determine location changes, eliminating the need for time-consuming re-calibration procedures while maintaining sensor functionality.
3Measurement precision
If the measurement system uses only integer pixel coordinates, then the calculation is straightforward, but it cannot detect location shifts smaller than one pixel width
Solution Approach 1:
The patent changes the measurement parameter from discrete integer pixel coordinates to continuous coordinates with decimal parts. By introducing brightness values as a new parameter and comparing them between current and reference images, the system can determine sub-pixel position shifts, achieving high measurement precision while keeping the calculation process manageable through systematic brightness comparison.
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 measurement and correction of sensor location shifts, ensuring proper calibration and functionality even in fine movements, enhancing the reliability of sensors like fingerprint sensors.
Implementation Method 1
a fingerprint sensor... may recognize ridges and valleys of a fingerprint based on information of a carrier (for example, light or ultrasound) passing through the display panel
Data Source
AI summary
A display device having an optical sensor includes a display panel including display pixels; and a sensor controller; and sensor pixels, wherein the sensor pixels include an optical sensor located on a first area of the display panel, the display pixels display a pattern including a plurality of markers in the first area, the sensor pixels image the pattern to generate a first image, the sensor controller divides the first image into sub-images corresponding to the markers, the sensor controller calculates first representative coordinates obtained by adding an integer part and a decimal part with respect to the sub-images, a unit of the integer part is the number of the sensor pixels, and each of the integer part and the decimal part independently includes a first dimensional value for a first direction and a second dimensional value for a second direction orthogonal to the first direction.