Image Sensor Light Shielding for External Interference
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Solution Overview
Problem
Conventional image reading apparatuses face challenges in maintaining image quality due to external light interference during light intensity adjustment, especially when using low-illuminance light sources, leading to image degradation such as darkening or blurring.
Innovation Solution
The implementation of light-shielding plates around the image sensor and a control unit that adjusts light intensity based on the open or closed state of the document pressing member, using reference members for accurate light intensity and output adjustments, prevents external light from influencing the image reading process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a light source with low illuminance is used to enhance sensitivity of the image sensor, then energy consumption is reduced, but external light interference increases causing image degradation
Solution Approach 1:
A light-shielding plate is introduced as an intermediary element between the external environment and the image sensor. This plate selectively blocks external light from reaching the sensor while allowing the light source to illuminate the document normally, thereby mediating the harmful effect of external light without compromising the low-illuminance operation
Solution Approach 2:
The internal lighting space is segmented into a light-shielded region and a non-shielded region. The light-shielding plate creates a distinct zone around the image sensor that is isolated from external light, while the document reading area remains accessible to both the light source and external environment
2Ease of operation
If the document pressing member is opened to allow document placement, then ease of operation is improved, but external light enters the document placing table causing image degradation
Solution Approach 1:
The light-shielding plate serves as a permanent intermediary structure within the document placing table that continuously blocks external light paths to the image sensor, regardless of whether the document pressing member is open or closed. This allows the pressing member to remain open for easy document placement without compromising image quality
3Device complexity
If light intensity adjustment is performed on the reference member with external light present, then the adjustment process is simplified, but the measured light intensity becomes inaccurate causing image degradation
Solution Approach 1:
The light-shielding plate creates a controlled measurement environment by blocking external light during the light intensity adjustment process. This intermediary structure ensures that the reference member is illuminated only by the light source, allowing accurate measurement of the light source's actual output intensity without contamination from external light
Solution Approach 2:
The light-shielding plate creates a localized dark environment around the reference member and image sensor during adjustment, while the rest of the document reading area remains normally lit. This local modification of lighting conditions enables precise measurement without affecting the overall system operation
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 solution ensures high-quality image reading by maintaining optimal light intensity and output adjustments regardless of external light conditions, preventing image degradation when the document pressing member is open or closed.
Implementation Method 1
light is emitted from a light source toward the platen glass 93, transmits the platen glass 93, and is reflected from the surface of the document. And then, reflected light is converted into an electrical signal by a light-receiving element
Implementation Method 2
a light-shielding plate 57 which shields external light from entering into a document placing table 94
Data Source
AI summary
An image reading apparatus includes a document placing table having a transparent member, a document pressing member, an image reading unit, a scanning unit that is disposed on a side opposite to a document placing surface of the transparent member and reciprocates in a predetermined direction along the transparent member with the image reading unit mounted thereon, an open/closed state detecting unit that detects open and closed states of the document pressing member, a control unit that controls an image reading operation of the image reading unit and a reciprocation movement of the scanning unit, and a reference member that serves as a luminance reference of the image reading unit. When the open/closed state detecting unit detects the open state of the document pressing member, the control unit set a predetermined light intensity set value to a light intensity value of light irradiated from the light source at the time of image reading.