LED Current Control for Image Seam Prevention
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Solution Overview
Problem
Image reading apparatuses face issues with luminance reduction in LEDs due to temperature increases during temporary stops in reading operations, leading to noticeable image seams and increased costs from requiring temperature sensors, heating elements, and control circuits.
Innovation Solution
An image reading apparatus with a control unit that adjusts the current flowing through the light emitting element, setting a higher current during active reading and a lower current during temporary stops to maintain LED temperature and prevent luminance decrease.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the read operation is temporarily stopped when the buffer memory is full, then the reading apparatus can process data, but the LED temperature increases and luminance decreases causing image seams
Solution Approach 1:
The patent changes the electrical parameter (current) flowing through the LED based on the operational state. During temporary stops, the current is reduced to a maintenance level rather than being completely cut off or maintained at full reading level. This dynamic parameter adjustment prevents temperature-induced luminance shifts that would cause image seams, while still allowing the LED to remain functional for immediate resumption of reading operations.
Solution Approach 2:
The patent implements dynamic current control that adapts to the real-time operational state of the reading apparatus. The control unit dynamically switches between high current during active reading and low maintenance current during temporary stops. This dynamic approach allows the system to optimize both productivity (by enabling temporary stops when buffer is full) and image quality consistency (by preventing LED temperature drift during stops).
2Reliability
If a temperature sensor and heating element are added to maintain LED temperature, then image quality consistency is improved, but device complexity and cost increase
Solution Approach 1:
The patent extracts and eliminates the complex temperature control subsystem (temperature sensor, heating element, and associated control circuits) from the LED temperature management system. Instead of actively controlling temperature through these components, the invention uses a simplified approach of adjusting electrical current based on operational state. This extraction removes the harmful complexity while maintaining the essential function of preventing image seams through current-based temperature management.
Solution Approach 2:
The patent enables the LED to self-regulate its temperature characteristics through electrical current adjustment rather than requiring external active control systems. By reducing current during temporary stops, the LED naturally maintains a stable temperature without needing external heating elements or temperature sensors. The reading apparatus's control unit already present for operational control is sufficient to implement this self-service temperature management.
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 maintains consistent image quality by controlling the LED current, reducing the need for additional components and minimizing cost while preventing luminance differences and image seams.
Implementation Method 1
when the temperature of a light-emitting diode (LED) generally used in a reading unit of an image reading apparatus is increased, the luminance of the LED is decreased
Data Source
AI summary
An image reading apparatus capable of reading documents includes a reading unit including a light emitting element, a mechanism configured to move the reading unit, and a control unit configured to control the reading unit and the mechanism both to carry out reading by turning on the light emitting element and moving the reading unit and to temporarily stop moving the reading unit upon occurrence of a predetermined factor. The control unit sets a first current value which is caused to flow through the light emitting element when reading is carried out and sets a second current value which is less than the first current value and which is caused to flow through the light emitting element when the reading unit is temporarily stopped.