Imaging Device Light Guide Specular Reflection Suppression
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Solution Overview
Problem
Conventional imaging devices face challenges in reducing the effects of specular reflection from the surface of target objects, particularly in compact configurations, which hampers the accuracy of biometric authentication by increasing the specular reflection component and decreasing the signal component used for authentication.
Innovation Solution
The imaging device incorporates a light guide and imaging optical system with a diffusing surface, where light from multiple LEDs is reflected and diffused, and the second surface has a concave shape to minimize specular reflection by uniformly illuminating the target object and improving the signal-to-noise ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If polarizing plates are provided on both LED emitting surface side and imaging device incident plane side to reduce specular reflection, then the effects of specular reflection component are reduced, but transmittance becomes 1/4 or less and light utilization efficiency considerably deteriorates
Solution Approach 1:
The patent extracts and removes the polarizing plates from the optical path, eliminating the harmful specular reflection component through alternative means (illumination geometry and optical design) rather than using polarizing filters, thereby recovering light transmittance while still suppressing specular reflection effects
Solution Approach 2:
The patent introduces an intermediary illumination optical system consisting of a diffuser and specific lighting geometry that mediates between the light source and target object, transforming direct specular-reflecting illumination into diffuse illumination that reduces specular reflection effects without requiring polarizing plates
2Object-affected harmful factors
If polarizing plates are provided on both LED emitting surface side and imaging device incident plane side to reduce specular reflection, then the effects of specular reflection component are reduced, but the number of parts increases and cost increases
Solution Approach 1:
The patent removes the polarizing plates from the system, reducing the number of optical components and simplifying the device structure while achieving specular reflection suppression through alternative illumination and optical design approaches
Solution Approach 2:
The illumination optical system with diffuser and specific geometry serves multiple functions simultaneously: it provides uniform illumination, reduces specular reflection effects, and eliminates the need for separate polarizing plate components, thereby reducing overall device complexity
3Volume of moving object
If the size of the imaging device is reduced for portable electronic apparatus, then the imaging device becomes more compact, but characteristics of the illuminating optical system become closer to point light source and effects of specular reflection increase
Solution Approach 1:
The patent employs curved or diffusing surfaces in the illumination optical system that maintain effective illumination area and diffuse lighting characteristics even in compact configurations, preventing the illumination from degrading to point-source behavior that would increase specular reflection
Solution Approach 2:
The patent uses a diffuser element that transforms point-source or directional light into area-source illumination by distributing light in multiple dimensions, effectively reducing specular reflection effects while maintaining a compact overall device form factor
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 effectively reduces the impact of specular reflection, enhancing the reliability of biometric authentication by improving the signal component while maintaining a compact and cost-effective design suitable for portable electronic devices.
Implementation Method 1
a light guide (15, 16, 172) configured to reflect and diffuse light from a plurality of light sources (13) received by a first surface
Implementation Method 2
a light guide (15, 16, 172) configured to reflect and diffuse light from a plurality of light sources (13) received by a first surface
Data Source
Figure 1
Figure 2A~2C
Figure 3A~3B
AI summary
An imaging device may include an illuminating optical system that forms a light guide, and an imaging optical system that is arranged on an inner side of the illuminating optical system. Light from a light sources received by a first surface is reflected and diffused, and light from a second surface opposite to the first surface illuminates a target object. The illuminating optical system receives reflected light from the target object, and an image corresponding to at least a part of the target object is imaged on an imaging element. The second surface of the illuminating optical system may have a concave shape.