Optical Fingerprint Sensing Ambient Light Interference
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Solution Overview
Problem
Ambient light interference causes fingerprint signal drifting and recognition failures in optical fingerprint sensing apparatuses, especially in strong ambient conditions, due to the combination of reflected and transmissive light components.
Innovation Solution
The optical fingerprint sensing apparatus captures multiple fingerprint images under different transmitted and reflected light intensities, processed to generate a single fingerprint image that minimizes the impact of ambient light, using a driver apparatus with a display driving device and a fingerprint sensing driving device to adjust light frames and capture images.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If optical fingerprint sensing is performed in strong ambient light, then the display panel can capture light signals, but the strong ambient light penetrates the finger and interferes with the reflected light component, causing fingerprint signal drifting
Solution Approach 1:
The patent segments the light signal into two distinct components: reflected light component (from the fingerprint ridges and valleys) and transmissive light component (from ambient light penetrating the finger). By capturing multiple images under different lighting conditions and separating these components through image processing, the system can extract the pure reflected light component for accurate fingerprint recognition, thus resolving the interference problem in strong ambient light
Solution Approach 2:
The patent converts the harmful effect of strong ambient light into a useful signal. By intentionally capturing images with both reflected and transmissive light components, and then using image processing to subtract the transmissive component (which can be captured separately when the display panel does not emit light), the system transforms the interfering ambient light into a removable background signal, leaving the pure fingerprint information
2Measurement precision
If the display panel displays different frames with different luminances to generate different light intensities, then multiple fingerprint images can be captured for processing, but the device complexity increases
Solution Approach 1:
The patent makes the display panel serve multiple functions: it acts as both the display device and the light source for fingerprint sensing. By controlling the display panel to show different frames with different luminances, the system generates the necessary varied lighting conditions for capturing multiple fingerprint images without requiring separate lighting devices, thus reducing overall device complexity while maintaining measurement precision
Solution Approach 2:
The patent merges the display driving device and fingerprint sensing driving device into a coordinated system that controls the same display panel. By combining the control functions and using the same hardware component (display panel) for both display and sensing illumination, the system achieves multiple imaging functions without proportionally increasing device complexity
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 effectively reduces the negative effects of ambient light on fingerprint sensing, allowing for accurate fingerprint recognition even in strong ambient conditions by subtracting transmissive light components from the processed image.
Implementation Method 1
the display panel may display a speckle to supply a light source (incident light) to the finger of the user
Implementation Method 2
The reflected light of the finger may be sensed by the display panel. Generally, in a fingerprint, the luminance of the reflected light of the ridges is greater than the luminance of the reflected light of the valleys
Implementation Method 3
the strong ambient light may penetrate the finger and may be sensed by the display panel
Data Source
AI summary
An optical fingerprint sensing apparatus, a driver apparatus, and an operation method are provided. The driver apparatus includes a display driving device and a fingerprint sensing driving device. The display driving device drives the display panel to display different frames with different luminances, and the different frames are used to generate at least one of different transmitted light intensities and different reflected light intensities. The fingerprint sensing driving device drives the display panel to perform a fingerprint capturing operation to capture a plurality of different fingerprint images of a finger under the at least one of the different transmitted light intensities and the different reflected light intensities. The different fingerprint images are processed to generate a processed fingerprint image.