Inclined Aperture Light Shielding for Stray Light Control
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Solution Overview
Problem
Conventional image reading apparatuses face issues with stray light entering the photoelectric conversion element, leading to defects such as ghosting, flare, and decreased color density due to incomplete light shielding, which degrades image quality.
Innovation Solution
An image reading apparatus with a light shielding member having inclined wall surfaces around the aperture, ensuring that only convergent light reaches the CCD sensor, effectively blocking stray light by positioning the aperture's hypothetical extension planes to avoid intersecting with the optical axis, thereby preventing stray light from entering the sensor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a light shielding member is disposed between the optical system and the photoelectric converter to cover the entire optical path, then external light and stray light can be blocked to some extent, but it is difficult to completely prevent stray light that passes through the lens via the vicinity of the proper optical path from entering the photoelectric conversion element
Solution Approach 1:
The light shielding member is designed with an aperture portion that has specific local properties: the inner peripheral surface is formed with an inclined surface having a predetermined slope angle. This localized structural modification at the aperture region enables the member to both block stray light and prevent reflection into the sensor, resolving the contradiction between light blocking and image quality
Solution Approach 2:
The inclined surface on the inner peripheral surface of the aperture portion introduces a dimensional change in how light interacts with the shielding member. By angling the surface rather than using a flat perpendicular wall, the structure redirects stray light away from the sensor in a different spatial dimension, effectively preventing reflection while maintaining blocking functionality
2Object-affected harmful factors
If the aperture portion of the light shielding member is narrowed to ensure an interval close to the width of the proper optical path, then stray light may be blocked, but the stray light may be reflected from the wall surfaces of the light shielding member so that it enters the sensor, degrading image quality
Solution Approach 1:
The light shielding member is designed with an aperture portion that has specific local properties: the inner peripheral surface is formed with an inclined surface having a predetermined slope angle. This localized structural modification at the aperture region enables the member to both block stray light and prevent reflection into the sensor, resolving the contradiction between light blocking and image quality
Solution Approach 2:
Instead of simply blocking stray light which may cause reflection from the wall surfaces, the inclined surface design converts the potentially harmful reflection into a beneficial redirection. The angled surface actively directs stray light away from the sensor, transforming what would be a harmful reflective path into a controlled light management solution that improves image quality
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 ensures that only proper convergent light reaches the CCD sensor, resulting in improved image quality with higher contrast ratio and reduced occurrence of image defects like ghosting and faint colors.
Implementation Method 1
a light shielding member having an aperture portion, in which inner peripheral surfaces are formed with inclined surfaces having a predetermined slope angle... ensuring that only convergent light reaches the CCD sensor, effectively blocking stray light
Implementation Method 2
the aperture's hypothetical extension planes to avoid intersecting with the optical axis, thereby preventing stray light from entering the sensor
Implementation Method 3
an optical system configured to condense and image the light reflected from the reflection member
Implementation Method 4
a photoelectric converter configured to receive the light passing through the optical system and convert the light into electric charge
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
An image reading apparatus, including: a light source; a reflection member changing a traveling direction of the light reflected from an original; an optical system imaging the light; a photoelectric converter receiving the light from the optical system to convert the light into an electric signal; and a light passing and blocking member disposed between the optical system and the photoelectric converter, and provided with an aperture through which the light from the optical system imaged on the photoelectric converter passes, the blocking member blocking non-convergent light which is not imaged on the photoelectric converter, wherein the blocking member has an inclined surface surrounding the aperture so that the aperture gets smaller from the optical system toward the photoelectric converter, and a hypothetical extension plane extending from the inclined surface toward the photoelectric converter intersects with an optical axis of the optical system without intersecting with photoelectric converter.