Image Reading Apparatus Restart Position Control
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Solution Overview
Problem
In high-resolution image reading apparatuses, the buffer overflow during image processing leads to temporary stops and restarts in image reading operations, causing image distortion and uneven density due to inferior encoder resolution, increasing manufacturing costs with higher-performance encoders.
Innovation Solution
An image reading apparatus with a conveyance mechanism, reading control device, stop control device, encoder, position detection device, elapsed time measuring device, time setting unit, position setting unit, and retreat control device, which measures elapsed time and adjusts the restart position based on positional information from the encoder to synchronize the reading unit's position accurately.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a DC motor is used as a drive source to reduce noise and power consumption, then noise and power consumption are reduced, but position control accuracy deteriorates compared to pulse motors
Solution Approach 1:
An encoder is introduced as an intermediary device to detect the position of the reading unit. The encoder provides positional feedback that enables accurate position control despite using a DC motor instead of a pulse motor, thus resolving the contradiction between reduced power consumption and maintained position control accuracy.
2Reliability
If the reading operation is temporarily stopped when buffer free space becomes small, then buffer overflow is prevented, but image distortion and uneven density occur at restart points due to inferior encoder resolution
Solution Approach 1:
The system performs preliminary actions by measuring elapsed time from encoder signals before stopping the reading operation. This time measurement is stored and used to calculate the correct restart position, ensuring that the reading operation can be restarted without causing image distortion or uneven density, thus maintaining image quality while preventing buffer overflow.
Solution Approach 2:
The system uses feedback from the encoder to detect position and provides feedback through elapsed time measurement. This feedback mechanism enables the system to accurately determine the restart position even with inferior encoder resolution, preventing image quality degradation at restart points while maintaining buffer overflow prevention.
3Measurement precision
If a higher-performance encoder is used to accurately recognize reading restart position, then position recognition accuracy is improved, but manufacturing cost increases
Solution Approach 1:
Instead of using a high-performance encoder, the system creates a copy of the necessary positional information by measuring elapsed time from lower-resolution encoder signals. This time-based copy of position data achieves the required accuracy for restart position recognition without the cost of a high-performance encoder.
Solution Approach 2:
The system changes the parameter used for position recognition from direct encoder resolution to elapsed time measurement. By measuring the time interval between encoder signals and using this time parameter to calculate position, the system achieves accurate restart position recognition with a lower-performance, less expensive encoder.
Data Source
AI summary
In an image reading apparatus, a retreat control device moves a conveyance target through a conveyance mechanism, when a stop operation is performed by a stop control device, in an opposite direction to an image reading direction to a position further from a restart reference position set by a position setting unit. A reading control device again moves the conveyance target, which has been moved by the retreat control device, at a constant speed in the image reading direction under a predetermined condition; inputs a line start signal to a reading unit when an offset time set by a time setting unit has elapsed from a time point when the conveyance target reaches the restart reference position; and periodically inputs a line start signal to thereby cause the reading unit to perform a reading operation from a point; where the reading unit is located when the offset time has elapsed.