Light Guide Unit Scattering for Uniform Illumination
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Solution Overview
Problem
Image reading apparatuses experience non-uniformity in light brightness due to attenuated peripheral light intensity, affecting the uniformity of light received by CCD sensors.
Innovation Solution
An image reading apparatus with a light source having arrayed light emitting elements, a light guide unit that scatters light to increase intensity at the end portions, and an optical system guiding light to a detection unit, ensuring uniform light distribution across the reading area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a lens is used to form reflected light from light irradiated onto an original as an image on a CCD sensor, then the image formation function is achieved, but the brightness at the peripheral edge portions of the lens is more attenuated compared to the brightness in the vicinity of the center, leading to non-uniform brightness on the CCD sensor
Solution Approach 1:
The light guide unit is designed with spatially varying scattering properties: the scattering power is made higher at the end portions (corresponding to peripheral regions) and lower at the central portion. This local differentiation of scattering characteristics compensates for the lens's peripheral attenuation, ensuring uniform light intensity distribution across the entire CCD sensor surface.
Solution Approach 2:
The invention changes the scattering parameter of the light guide unit along its length. By making the scattering power variable (higher at ends, lower at center) rather than uniform, the light intensity distribution is adjusted to counteract the lens's inherent peripheral attenuation, achieving overall brightness uniformity on the sensor.
2Illumination intensity
If light is guided through a conventional light guide unit with uniform scattering, then light is distributed across the reading area, but non-uniformity in light intensity remains due to lens peripheral attenuation
Solution Approach 1:
The light guide unit incorporates non-uniform scattering characteristics along its length, with end portions having higher scattering power than the central portion. This local quality variation is specifically designed to compensate for lens peripheral attenuation, achieving uniform light intensity distribution across the CCD sensor and improving manufacturing precision of the imaging system.
3Manufacturing precision
If the light guide unit increases scattering power at end portions, then light intensity at peripheral regions is enhanced, but the overall light distribution uniformity is improved
Solution Approach 1:
The light guide unit achieves the desired non-uniform light distribution through localized scattering modifications at specific regions (higher scattering at ends, lower at center). This approach improves image signal uniformity without requiring complex additional components, as the scattering variation is integrated into the light guide unit's structure itself.
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 suppresses non-uniformity in light intensity, enhancing the quality of the image signal by maintaining higher light intensity at the edges, thus reducing attenuation and improving image reading performance.
Implementation Method 1
a light guide unit that scatters light emitted from the light source such that the light intensity is greater at end portions than at the central portion in the array direction of the light emitting elements
Implementation Method 2
an optical system that guides the light reflected at the reading position to a light detection unit that detects the light intensity
Data Source
AI summary
There is provided an image reading apparatus including: a light source with arrayed light emitting elements; a light guide unit that scatters light emitted from the light source such that the light intensity is greater at end portions than at the central portion in the array direction of the light emitting elements, and guides the light to a reading position of a medium to be read; and an optical system that guides the light reflected at the reading position to a light detection unit that detects the light intensity.