Under-screen Optical Fingerprint Sensor with Off-Normal Lens Axis
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional fingerprint sensors, particularly capacitive sensors, face limitations in compact design and high spatial image resolution, leading to conflicts in minimizing footprint and achieving reliable fingerprint sensing on mobile devices with limited space, while optical sensors can offer flexibility in placement but require separate components and complex optical paths.
Innovation Solution
The development of an under-display optical fingerprint sensor module that utilizes light from the display screen for illumination, employing a photodiode array, pinhole, and lens configuration to capture and process fingerprint patterns without the need for a separate sensing area, allowing for integration beneath the display screen and enhanced user experience.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If conventional capacitive fingerprint sensors are used, then fingerprint sensing function is achieved, but device footprint cannot be minimized due to space requirements for separate sensing areas
Solution Approach 1:
The patent combines the display screen and fingerprint sensor into a single integrated structure. The display screen serves dual purposes: visual output and fingerprint illumination/detection. The fingerprint sensor is positioned directly beneath the display screen, allowing the display to act as both the user interface and the sensing mechanism, thereby eliminating the need for separate sensing areas and reducing device footprint.
Solution Approach 2:
The display screen is designed to perform multiple functions simultaneously: it displays visual information to the user and serves as an optical illumination source for fingerprint sensing. The same display structure that presents information also provides the light necessary for capturing fingerprint patterns, making the system more versatile and space-efficient.
2Reliability
If separate optical components are added for under-screen fingerprint sensing, then fingerprint sensing is enabled, but device complexity increases
Solution Approach 1:
The patent extracts and utilizes the display screen's inherent light-emitting capability for fingerprint illumination, eliminating the need for separate illumination LEDs or complex optical guiding structures. By directly using the display pixels as the light source, the design removes unnecessary intermediate optical components and simplifies the overall system architecture.
Solution Approach 2:
The display screen serves itself by providing its own light output for fingerprint illumination. Instead of requiring external or dedicated illumination sources, the display's pixel elements directly illuminate the fingerprint area, and the same structure captures the reflected light, making the system self-sufficient and reducing component count.
3Device complexity
If display screen light is used for illumination, then component count is reduced, but light intensity control for fingerprint sensing becomes challenging
Solution Approach 1:
The patent divides the display screen into specific functional regions: certain pixels or pixel groups are designated for fingerprint illumination while others maintain display functions. This segmentation allows independent control of illumination intensity through software, enabling precise adjustment of light output for fingerprint capture without affecting the overall display performance.
Solution Approach 2:
The illumination intensity is made dynamically adjustable through software control of display pixel brightness. The system can adapt the light output level based on environmental conditions, fingerprint detection requirements, and power management needs, providing flexible and precise illumination control without hardware modifications.
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 solution enables robust and reliable fingerprint sensing with high spatial image resolution, minimizing device footprint, and integrates seamlessly with display screens, providing enhanced security and user interaction without additional hardware or significant design changes to existing devices.
Implementation Method 1
a lens positioned adjacent the pinhole and configured to focus the signal light transmitted through the pinhole onto the surface of the photodiode array
Implementation Method 2
The photodiode array is configured to convert the signal light incident thereon into electrical signals
Implementation Method 3
utilizes light from the display screen for illumination
Data Source
AI summary
An optical fingerprint sensor module includes a light source configured to provide illumination light directed toward a finger. A portion of the illumination light may be scattered or reflected off of the finger, thereby generating signal light. The optical fingerprint sensor module further includes a photodiode array that has a surface, a member defining a pinhole configured to receive and transmit the signal light, and a lens positioned adjacent the pinhole and configured to focus the signal light transmitted through the pinhole onto the surface of the photodiode array. An optical axis of the lens forms an angle with respect to a normal of the surface of the photodiode array that is between 45 degrees and 135 degrees. The optical fingerprint sensor module further includes electronic circuitries configured to process the electrical signals generated by the photodiode array to produce an image of a fingerprint pattern of the finger.