Spread Spectrum Clock Timing Correction for Image Reading Devices
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Solution Overview
Problem
Image reading devices face challenges in maintaining consistent analog signal acquisition timing due to environmental variations and frequency changes in spread spectrum clocks, leading to variations in acquired signal values.
Innovation Solution
An image reading device is configured with a spread spectrum clock generation unit, an acquisition timing setting unit, and an acquisition timing correction unit to adjust the analog signal acquisition timing based on the spread spectrum clock frequency, using a timing adjustment circuit with delay elements and a select signal holding circuit to correct the timing and prevent signal shifts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an analog delay-unit is used to define the acquiring timing independently of the spread spectrum clock, then the acquiring timing can be defined with a predetermined delay time, but the delay time varies depending on environmental variation such as temperature variation
Solution Approach 1:
The patent replaces the analog delay-unit (mechanical/electronic circuit) with a digital timing adjustment circuit that uses a spread spectrum clock and correction unit. The timing adjustment circuit calculates the actual frequency of the spread spectrum clock and dynamically adjusts the acquiring timing in the digital domain, eliminating the environmental sensitivity of analog delay circuits while maintaining precise delay control.
Solution Approach 2:
The patent implements a feedback mechanism where the timing adjustment circuit continuously monitors the actual frequency of the spread spectrum clock and dynamically adjusts the acquiring timing accordingly. This closed-loop control ensures that the acquiring timing remains accurate despite frequency variations, resolving the contradiction between reliability and measurement precision.
2Adaptability or versatility
If the acquiring timing is defined based on the spread spectrum clock, then the acquiring timing can be synchronized with the clock, but the acquiring timing shifts on a time axis depending on the current frequency of the spread spectrum clock
Solution Approach 1:
The patent makes the acquiring timing dynamic by introducing a timing adjustment circuit that continuously adapts to the actual frequency of the spread spectrum clock. Instead of using a fixed timing relationship, the system dynamically calculates and adjusts the acquiring timing based on the current clock frequency, maintaining both synchronization and accuracy.
Solution Approach 2:
The patent changes the parameter of acquiring timing from a fixed value to a dynamically adjustable value. The timing adjustment circuit modifies the acquiring timing parameter in real-time based on the spread spectrum clock frequency, allowing the system to maintain accurate timing despite frequency variations while preserving synchronization flexibility.
3Manufacturing precision
If the acquiring timing is defined with the analog delay-unit, then the predetermined delay time can be established, but it becomes impossible to freely define the delay time in accordance with an operation mode
Solution Approach 1:
The patent transforms the delay time from a fixed analog parameter to a dynamically configurable digital parameter. The timing adjustment circuit allows the delay time to be freely defined and adjusted according to different operation modes, while the feedback mechanism ensures consistent and accurate delay execution regardless of the selected configuration.
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 configuration allows for flexible and stable analog signal acquisition timing, reducing the impact of environmental variations and frequency changes, resulting in precise digital data reflection of the original image and improved electromagnetic immunity.
Implementation Method 1
a spread spectrum clock generation unit configured to generate a spread spectrum clock by executing frequency-modulation on a reference clock having a constant frequency
Implementation Method 2
a photoelectric conversion device that outputs an analog signal corresponding to an image read from a document
Data Source
AI summary
An image reading device including: a photoelectric conversion device that outputs an analog signal corresponding to an image read from a document; an A-D converter that converts the analog signal into a digital signal; a spread spectrum clock generation unit configured to generate a spread spectrum clock by executing frequency-modulation on a reference clock having a constant frequency; an acquisition timing setting unit configured to set an acquiring timing of the analog signal with reference to the spread spectrum clock; and an acquisition timing correction unit configured to execute a delay correction for the acquiring timing of the analog signal set by the acquisition timing setting unit in accordance with a frequency of the spread spectrum clock defined when the analog signal is outputted. The analog signal acquired at the corrected acquiring timing corrected by the acquisition timing correction unit is converted into the digital signal.