Document Scanner Infrared LED Intermittent Control
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Solution Overview
Problem
Existing document scanning systems face increased power consumption and processing load due to continuous CPU monitoring of infrared LED light emission for document detection, which hinders efficient power management and real-time detection capabilities.
Innovation Solution
A document scanning apparatus with a signal output unit providing pulse signals at predetermined intervals to control the infrared LED emission, offloading light-on and light-off operations to a low-power module, allowing the CPU to focus on detection signal monitoring without continuous LED illumination, thereby reducing processing load and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the infrared LED is caused to emit light at all times for continuous document detection, then the detection capability is maintained, but the power consumption increases correspondingly
Solution Approach 1:
The patent applies periodic action by controlling the infrared LED to emit light only at specific intervals rather than continuously. The light emitting unit is driven intermittently based on timing signals from the control unit, enabling document detection at periodic moments while reducing overall power consumption compared to continuous operation.
2Speed
If the CPU monitors the detection signal simultaneously with light-on timing of the infrared LED, then real-time detection is achieved, but the processing load on the CPU increases
Solution Approach 1:
The patent extracts the timing control function from the CPU and assigns it to a dedicated control unit or timer circuit. This separate component generates timing signals independently to control the light emitting unit's operation, freeing the CPU from simultaneous monitoring tasks and reducing its processing load while maintaining real-time detection capability.
3Use of energy by moving object
If control over light-on and light-off operations of the infrared LED is off-loaded to a low power consumption module, then power consumption is reduced, but the CPU may monitor detection signal at wrong timing
Solution Approach 1:
The patent implements feedback mechanisms where the control unit that manages LED timing also coordinates with the CPU to ensure detection signals are read at appropriate moments. The system uses timing synchronization and signal coordination to ensure that even with off-loaded control, the CPU receives accurate detection signals at the correct timing, preventing information loss.
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 approach enables real-time document detection without increasing CPU load, even in power-saving modes, by intermittently controlling the infrared LED emission, thus optimizing power usage and maintaining efficient detection capabilities.
Implementation Method 1
an infrared light emitting diode (infrared LED) may be used as such a light emitting unit in a photo interrupter
Implementation Method 2
a photo interrupter and a movable flag as a document detection unit configured to detect whether a document bundle is set on a document platen or not. The movable flag may shield or transmit light from a light emitting unit in the photo interrupter
Data Source
AI summary
A document scanning apparatus reading an image of a document includes a signal output unit configured to output a pulse signal at predetermined intervals, a sensor configured to detect a document set on a platen glass, the sensor having a light emitting unit configured to emit light in response to a pulse signal output from the signal output unit and a light receiving unit configured to output a detection signal in accordance with light output from the light emitting unit, and a control unit configured to receive the detection signal output from the light receiving unit. In this case, the signal output unit outputs the pulse signal at a different time point from the predetermined intervals in response to a request from an external apparatus.