OLED Display Fingerprint Sensing via Pixel Frequency Modulation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing fingerprint sensors in smartphones and wearable devices face challenges in reducing size while maintaining high recognition performance and improving signal-to-noise ratio (SNR) for effective fingerprint sensing.
Innovation Solution
The implementation of an OLED display device with a fingerprint management method that adjusts the driving frequency of pixels in the fingerprint sensing area to reduce noise, using a combination of self-capacitance and mutual capacitance methods for fingerprint recognition, and integrating a sensing controller within the display driver IC to enhance SNR.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the display scan frequency is reduced during fingerprint identification, then the signal-to-noise ratio for fingerprint sensing is improved, but the display refresh performance deteriorates
Solution Approach 1:
The display area is segmented into a fingerprint sensing area and a non-sensing area. The controller selectively reduces the scan frequency only for pixels in the fingerprint sensing area during fingerprint identification, while maintaining normal scan frequency for other display areas. This segmentation allows simultaneous optimization of fingerprint sensing precision and overall display refresh performance.
2Volume of moving object
If the fingerprint sensor size is reduced to fit smartphone and wearable devices, then the device compactness is improved, but the fingerprint recognition performance deteriorates
Solution Approach 1:
The controller dynamically changes the operating parameters of display pixels in the fingerprint sensing area by adjusting the scan frequency. During fingerprint identification, the scan frequency is reduced to minimize noise generation from pixel switching, thereby improving the signal-to-noise ratio and fingerprint recognition accuracy despite the small sensor size.
3Speed
If pixels in the fingerprint sensing area are continuously driven at high frequency, then the display refresh performance is maintained, but noise increases and fingerprint sensing precision deteriorates
Solution Approach 1:
The controller implements periodic action by temporarily reducing the scan frequency of pixels in the fingerprint sensing area during fingerprint identification periods, then restoring normal scan frequency for regular display operations. This periodic modulation of scan frequency minimizes noise during sensing while maintaining display performance during normal operation.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A display device has a display area with a first area in which a fingerprint is recognized and a second area in which a fingerprint is not recognized, and a non-display area. A fingerprint sensing unit is disposed to overlap with the first area. A first pixel set is disposed to overlap with the first area, and a second pixel set is disposed to overlap with the second area, each set including a plurality of pixels. A first voltage signal is provided to the first pixel set as a variable frequency signal, and includes a first period during which the first voltage signal is a first frequency signal, a second period during which the first voltage signal is a second frequency signal having a lower frequency than the first frequency signal, and a third period during which the first voltage signal is the first frequency signal.