Pinhole Layer Optical Filter for Under-Display Fingerprint Sensing
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Solution Overview
Problem
Conventional biometric fingerprint sensors integrated into the active area of a display face challenges in compactness, reliability, and interference with the display image, especially when sensing through thick glass or cover layers, and struggle to accurately detect fine fingerprint features.
Innovation Solution
The integration of a pinhole layer with an array of pinhole apertures and a blocking portion that includes an optical filter, positioned between the display layer and the detector, allows for illumination and light conditioning to pass through the pinhole apertures while blocking light from the illuminator, enabling accurate fingerprint sensing without distorting the display image.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the fingerprint sensor is integrated into the active area of the display using conventional techniques, then the biometric sensing function is achieved, but the display image is distorted and the appearance is interfered with
Solution Approach 1:
The sensor array is divided into multiple independently addressable sensor elements corresponding to display pixels, allowing selective activation and independent control of sensing regions, thereby enabling fingerprint detection without compromising overall display integrity
Solution Approach 2:
A light guide layer is introduced as an intermediary component between the illuminator and the cover glass, directing illuminator light to illuminate the sensing region through the cover glass while preventing direct visibility of the illuminator, thus enabling sensing without display distortion
2Volume of moving object
If the fingerprint sensor is integrated into the active area of the display, then compactness is achieved, but fine fingerprint features cannot be reliably sensed through thick glass cover layers
Solution Approach 1:
The system changes the wavelength parameter of illumination by using an illuminator that emits at a wavelength different from the display layer, enabling effective penetration through the cover glass thickness while maintaining detection precision of fine fingerprint features
Solution Approach 2:
The light guide layer serves as a mediator that directs and concentrates illuminator light through the cover glass to the sensing region, enhancing light delivery efficiency and enabling reliable detection through thick glass layers while maintaining compact form factor
3Reliability
If an illuminator is used to illuminate the sensing region, then fingerprint sensing is enabled, but light from the illuminator interferes with the display image
Solution Approach 1:
The light guide layer directs illuminator light to a specific local sensing region through the cover glass while preventing light propagation to other areas, creating localized illumination that enables sensing without interfering with the overall display image visibility
Solution Approach 2:
The system uses wavelength differentiation where the illuminator emits at a wavelength different from the display layer, and the optical filter selectively transmits display wavelengths while blocking illuminator wavelengths, enabling simultaneous operation without interference
4Ease of operation
If conventional sensing technologies are used, then the sensor can be placed on the front face, but additional device real estate is consumed
Solution Approach 1:
The fingerprint sensor array is merged with the display structure by integrating sensor elements with display pixels and sharing common components such as the cover glass and light guide layer, eliminating the need for separate sensor real estate while maintaining front-face accessibility
Solution Approach 2:
The cover glass and light guide layer serve multiple functions: protecting the display, guiding illuminator light to the sensing region, and enabling both display and sensing functions through the same physical structure, thereby maximizing space utilization
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 configuration enhances the ability to reliably sense fine fingerprint features while maintaining the display's appearance, allowing for compact and efficient biometric authentication in portable devices.
Implementation Method 1
the blocking portion has an optical filter configured to pass the light from the display layer and block the light from the illuminator
Implementation Method 2
the pinhole layer has an array of pinhole apertures and a blocking portion between the pinhole apertures
Implementation Method 3
the illuminator is configured to illuminate a sensing region of the cover layer with the wavelength of light
Implementation Method 4
The detector is configured to be sensitive to a wavelength of light
Data Source
AI summary
An electronic device including an optical sensor for optically sensing an image of an input object such as a user's fingerprint is provided. The electronic device includes a display layer, a detector, a pinhole layer, a cover layer and an illuminator. The display layer is configured to generate light within a visible light spectrum. The detector is configured to be sensitive to a wavelength of light. The pinhole layer is located above both the display layer and the detector. The cover layer is located above the pinhole layer, and the illuminator is configured to illuminate a sensing region of the cover layer with the wavelength of light. Further, the pinhole layer has an array of pinhole apertures formed in a material substantially transparent to the light generated by the display layer and substantially opaque to the wavelength of light from the illuminator.