External Optical Fingerprint Device Using Flat Refractor Plate
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Solution Overview
Problem
Existing optical fingerprint recognition devices are bulky due to their triangular prism design, making them unsuitable for thin mobile devices, and existing solutions that embed fingerprint input devices in terminals cannot accommodate the trend of thinner devices or be retrofitted into existing ones.
Innovation Solution
An external optical fingerprint input device using a plate-shaped optical refractor with a first mirror to reflect the fingerprint image towards a camera and a second mirror to direct light from an LED onto the refractor, along with a light blocking part and light incident part, allowing for a compact setup that can be attached to a portable terminal equipped with a camera and LED.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a triangular prism is used for optical fingerprint recognition, then fingerprint image quality is improved, but device volume increases
Solution Approach 1:
The patent divides the optical system into separate functional components: a flat optical refractor plate for light refraction, a mirror for light reflection, and a camera for image capture. This segmentation allows each component to be optimized independently, replacing the monolithic triangular prism with a compact assembled system that maintains imaging quality while reducing volume.
Solution Approach 2:
The patent embeds the mirror within the optical refractor plate structure, with the mirror positioned at the bottom surface of the plate. This nesting arrangement allows the light reflection function to be integrated into the refraction component, maximizing space utilization and minimizing the overall device volume while maintaining the necessary optical path length for high-quality fingerprint imaging.
2Adaptability or versatility
If an optical fingerprint input device is embedded in a terminal, then authentication function is improved, but terminal thickness increases
Solution Approach 1:
The patent extracts the light source function from the terminal body and implements it as an external optical device that can be attached to the terminal. The external device includes the optical refractor plate, mirror, and camera, while the terminal only needs to provide the light source and housing space, significantly reducing the thickness requirement for the terminal itself while maintaining full authentication functionality.
Solution Approach 2:
The patent transitions from a three-dimensional embedded prism structure to a two-dimensional flat plate configuration. The optical refractor plate is designed as a thin flat component with the mirror integrated at its bottom surface, allowing the optical system to function in a planar arrangement that minimizes thickness while maintaining the necessary optical path for fingerprint image capture.
3Length of stationary object
If a plate-shaped optical refractor is used, then device thickness is reduced, but light path control becomes more complex
Solution Approach 1:
The patent introduces a mirror as an intermediary element within the flat optical refractor plate to control the light path. The mirror is positioned at the bottom surface of the plate and reflects light upward through the plate to form the fingerprint image. This intermediary reflection mechanism simplifies the overall light path control compared to complex prism geometries, allowing precise optical path management in a thin flat structure.
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
Enables fingerprint image generation using an external optical system without increasing the thickness of the portable terminal, allowing for secure fingerprint authentication on devices without embedded optical systems and accommodating various terminal designs.
Implementation Method 1
a plate-shaped optical refractor... Light emitted from the light source 1 is incident into the prism 3, forms a fingerprint picture while being reflected, absorbed, or scattered at valleys and ridges of a fingerprint
Implementation Method 2
the first mirror is provided over the camera part to reflect a fingerprint picture emitted from the emitting surface toward the camera part
Implementation Method 3
the second mirror is provided to an outer space portion of both side surfaces and a rear surface of the optical refractor to reflect the light emitted from the LED toward the optical refractor
Data Source
AI summary
Disclosed is a fingerprint input device using a portable terminal equipped with a camera, and an external optical device for inputting a fingerprint. According to the present invention, a fingerprint image may be generated by an optical fingerprint input method by using the external optical device of the present invention even when an existing portable terminal does not have a configuration for an optical fingerprint input. To this end, the external optical device is provided as an external type to be mounted in the existing portable terminal provided with a camera, and has an optical refractor and a mirror. The external optical device may generate a user's fingerprint image by an optical fingerprint input method, in accordance with circumstances, without interrupting the main use of a camera and an LED of the existing portable terminal.