Relief Pattern Detection Using Inclined Fiber Optic Plate
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Solution Overview
Problem
Fingerprint detection devices using fiber optic plates face reduced image contrast when detecting relief patterns on thick objects, such as palmprints, due to the need for light transmission through the object, which affects detection reliability.
Innovation Solution
A relief pattern detection device with a fiber optic plate having inclined optical axes and a light irradiation system that scatters or absorbs light at object surface projections, allowing for image detection without transmitting light through the object, thereby maintaining image contrast and improving detection reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If light is transmitted through the object to detect relief patterns, then the detection can be performed on thick objects, but the image contrast decreases according to object thickness
Solution Approach 1:
Instead of transmitting light through the object from one surface to the other, the invention inverts the approach by illuminating the second surface and detecting light that reflects off the first surface. This inversion eliminates the need for light to traverse the entire object thickness, thereby maintaining image contrast while enabling detection on thick objects.
Solution Approach 2:
The invention changes the optical path parameters by tilting the optical axes of the fiber optic plate at a specific angle (e.g., 45 degrees) relative to the first surface. This parameter change allows the light to reflect off the object surface at an optimized angle, improving both the contrast and the ability to detect relief patterns on thick objects.
2Measurement precision
If the optical axes of optical fibers are inclined to detect relief patterns through reflection, then image contrast is maintained, but light may not efficiently enter the core of the optical fiber
Solution Approach 1:
The invention optimizes the inclination angle of the optical axes as a critical parameter. By setting the angle to approximately 45 degrees and coordinating it with the illumination angle, the design ensures that reflected light from the object surface enters the fiber core efficiently while maintaining high image contrast for relief pattern detection.
Solution Approach 2:
The invention applies different angular parameters to different components: the optical axes are tilted at a specific angle relative to the first surface, while the illumination is directed at a coordinated angle relative to the second surface. This local optimization of angular parameters ensures both efficient light coupling and high image contrast.
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
The solution ensures high reliability in detecting relief patterns with sufficient contrast, reducing the impact of object thickness and enhancing detection accuracy, while also simplifying the device structure and reducing costs through the use of a reinforcing member for durability.
Implementation Method 1
a fiber optic plate having a first surface which is formed of first end faces of a plurality of optical fibers... and a second surface which is formed of second end faces of the optical fibers
Implementation Method 2
light is propagated from the second surface toward the first surface
Implementation Method 3
the light is scattered or absorbed at projections on the object surface that are in contact with the first surface
Implementation Method 4
the light is scattered or absorbed at projections on the object surface that are in contact with the first surface
Implementation Method 5
the light is reflected by the first surface at recesses that are out of contact with the first surface
Data Source
AI summary
The present invention aims to provide a highly reliable relief pattern detection device 1, including a slant FOP 3 having an input end surface 4 with which an object surface makes contact and an output end surface 5 substantially parallel to the input end surface 4, an irradiation light source 10 disposed on the output end surface 5 side of the slant FOP 3, for irradiating the output end surface 5 with light, and a CCD camera 11 disposed on the output end surface 5 side of the slant FOP 3, for detecting a relief pattern based on light emitted from the output end surface 5, in which optical axes Rf of optical fibers are inclined so as to create a first angle α less than 90° in one direction from the output end surface 5 within a predetermined plane substantially perpendicular to the output end surface 5, the irradiation light source 10 irradiates the output end surface 5 with light in a direction to create a second angle β less than 90° in the other direction from the output end surface 5 within the predetermined plane, and the first angle α and the second angle β are set so that light made incident from the output end surface 5 into a core 8 of the optical fiber 6 enters into a cladding 9.