Optical Fingerprint Module Backlight Angle Design
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Solution Overview
Problem
Existing optical fingerprint modules suffer from blurred fingerprint images due to the use of light guiding plates, which scatter light and result in mixed signal angles, leading to reduced image clarity and increased costs.
Innovation Solution
An optical fingerprint module design featuring a backlight source positioned under the pixel area, forming a right or near-right angle with the protective layer, allowing for more focused light reflection onto the fingerprint, eliminating the need for a light guiding plate and enhancing image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a light guiding plate is used in the optical fingerprint module, then the light can be distributed across the sensor area, but the light becomes scattered and produces mixed signal angles resulting in blurred fingerprint images
Solution Approach 1:
The patent removes the light guiding plate from the optical fingerprint module structure. By extracting this component, the patent eliminates the light scattering effect that caused blurred images, while maintaining adequate light distribution through direct illumination from the backlight source to the sensor.
Solution Approach 2:
Instead of using a light guiding plate to distribute light (converging approach), the patent inverts the approach by positioning the backlight source directly beneath the sensor area, allowing light to illuminate the fingerprint from below without intermediate guiding components, thus achieving both distribution and clarity.
2Illumination intensity
If a light guiding plate is used in the optical fingerprint module, then light can be directed to the sensor, but the module structure becomes more complex and production costs increase
Solution Approach 1:
The patent extracts and removes the light guiding plate from the module structure, simplifying the overall design. The light direction function is achieved directly through the backlight source positioning, eliminating the need for intermediate guiding components and reducing structural complexity.
Solution Approach 2:
The patent merges the backlight source directly with the sensor assembly, eliminating the separate light guiding plate component. This integration simplifies the module structure by combining light generation and light direction functions into a more compact arrangement.
3Illumination intensity
If the backlight source is positioned close to the optical fingerprint sensor, then light can reach the sensor effectively, but the light does not form the correct angle with the protective layer resulting in poor image quality
Solution Approach 1:
The patent adjusts the positional parameters of the backlight source, specifically setting it at a predetermined distance below the sensor surface. This parameter change ensures that light travels the appropriate distance and forms the correct angle (substantially perpendicular) with the protective layer, achieving both effective illumination and high image quality.
Solution Approach 2:
The patent positions the backlight source in the vertical dimension below the sensor surface rather than placing it adjacent to the sensor in the horizontal plane. This dimensional change allows light to travel upward through the protective layer at the correct angle, improving image quality while maintaining effective illumination.
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 design improves fingerprint image recognition by capturing clear images with reduced distortion and lower production costs, simplifying the module structure while maintaining high accuracy.
Implementation Method 1
each of the plurality of pixels includes a non-opaque region and a light blocking region, the light blocking region includes a photosensitive element, and the non-opaque region allows light to penetrate through the pixel area of the device layer
Implementation Method 2
a right angle or a near-right angle is formed between light emitted from the backlight source and an upper surface of the protective layer
Implementation Method 3
Circuits (not shown in FIG. 1) inside the optical fingerprint sensor 120 perform photoelectric conversion and signal processing to realize acquisition of the fingerprint image
Data Source
AI summary
An optical fingerprint module comprises: an optical fingerprint sensor, the optical fingerprint sensor having a non-opaque substrate and a device layer located on a surface of the non-opaque substrate, the device layer having a pixel area, the pixel area having a plurality of pixels, each pixel having a non-opaque area and a light blocking area, the light blocking area having a photosensitive element, the non-opaque area enabling lights to transmit through the pixel area of the device layer; a protection layer located above the entire optical fingerprint sensor; and a backlight source located right under the pixel area, the backlight source and the optical fingerprint sensor being disposed with an interval, an included angle formed between light emitted from the backlight source and an upper surface of the protection layer being mainly a right angle or a near-right angle. The optical fingerprint module has an improved structure and enhanced performance.