Proximity Imaging Filter Angle Limiting Noise Reduction
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Solution Overview
Problem
Proximity-type image scanners face challenges in capturing fine images due to obliquely transmitted light through the imaging filter and external light interference, which disrupts the one-to-one correspondence between subject and pixel areas, leading to noise and reduced image quality.
Innovation Solution
A proximity-type imaging device with an imaging filter featuring a transparent substrate and a light shielding film with openings corresponding to pixels, where the incidence angle of light is limited by satisfying specific refractive index and thickness conditions, and optionally accompanied by a wavelength limiting filter and intermediate layer, to ensure that light is only incident to the corresponding pixel, thereby reducing noise and external interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a light shielding film with openings is provided on a glass substrate to limit incidence angle, then image quality improves, but obliquely transmitted light through the substrate causes noise
Solution Approach 1:
An intermediate layer with refractive index n2 is introduced between the glass substrate (n1) and the image sensor to act as an optical intermediary. This layer modifies the light transmission path and reduces oblique light transmission through the substrate by utilizing refractive index differences, thereby decreasing noise while preserving the angle-limiting function of the imaging filter
Solution Approach 2:
The patent changes the optical parameters of the system by selecting specific refractive indices for the intermediate layer (n2) that satisfy the condition n1 < n2 > n3. This parameter optimization controls the refraction and transmission of oblique light, reducing harmful light transmission while maintaining effective angle limitation for normal incident light
2Length of stationary object
If the image sensor is brought into close contact with the subject, then device thickness decreases, but light from peripheral areas incident to the image sensor degrades image quality
Solution Approach 1:
The imaging filter segments the light paths by providing openings that correspond one-to-one with pixel areas. This segmentation ensures that light from specific subject portions is directed to corresponding pixels only, preventing peripheral light from degrading image quality while maintaining the thin proximity-type configuration
3Manufacturing precision
If the light receiving areas are made small for fine capturing, then image resolution improves, but it becomes difficult to provide through holes or rod lenses of the same size
Solution Approach 1:
The patent uses a light shielding film pattern that copies the pixel arrangement on the glass substrate, creating openings that correspond to each pixel area. This approach avoids the need for complex through holes or rod lenses, enabling fine resolution through a manufacturable planar filter structure
Solution Approach 2:
The patent replaces complex mechanical structures (through holes, rod lenses) with a planar light shielding film pattern on a glass substrate. This substitution achieves the same angle-limiting function through optical design rather than mechanical structures, enabling finer pixel dimensions while maintaining ease of manufacture
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 effectively decreases obliquely passing light, establishes accurate one-to-one correspondence between subject and pixel areas, and enhances image quality by limiting incidence angles and wavelengths, resulting in a finer image capture without external interference.
Implementation Method 1
where n1 denotes a refractive index of the substrate, T1 denotes a thickness of the substrate
Implementation Method 2
a light shielding film formed with openings having one-to-one correspondence with the pixels
Implementation Method 3
an image sensor that performs photoelectric conversion for light transmitted from a subject that is in proximity thereto using a plurality of pixels
Data Source
AI summary
A proximity-type imaging device includes an image sensor and an angle limiting filter. The image sensor performs photoelectric conversion for light transmitted from a subject using plural pixels, so as to capture the subject. The angle limiting filter includes a transparent glass substrate and a light shielding film which is formed with openings having one-to-one correspondence with the pixels and which is provided on the glass substrate. The angle limiting filter is disposed on the image sensor and limits an incidence angle of light incident to the image sensor to such an angle range that the light is incident from each opening to the corresponding pixel. The conditionLā„T1(n12-1)1/2is satisfied, where n1 denotes a refractive index of the substrate, T1 denotes a thickness of the substrate, and L denotes a shortest distance between a contour of one opening and a contour of the pixel corresponding to an opening adjacent.