Mirror Driving Circuit Offset Compensation for Waveform Distortion
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Solution Overview
Problem
Existing optical scanning apparatuses experience distortion in driving voltage waveforms due to dead zones in operational amplifiers and Integral Non-Linearity (INL) errors in Digital-to-Analog Converters (DACs), leading to undesired resonant oscillations and ringing in scanned images.
Innovation Solution
An optical scanning apparatus with a mirror driving circuit that includes a digital-to-analog converter and an amplifier, configured to generate driving signals based on digital waveform data, using a reference waveform generator and offset setting circuit to compensate for dead bands and INL errors, thereby reducing waveform distortion and resonant oscillations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a dead zone exists in the operational amplifier, then the amplifier can operate with simpler circuit design, but the driving voltage waveform becomes distorted and resonant oscillation occurs
Solution Approach 1:
The patent applies preliminary action by pre-calculating and pre-storing compensation values in a lookup table before actual operation. The offset setting circuit uses pre-computed compensation data to adjust the driving voltage waveform in advance, eliminating the need for complex real-time correction circuits while preventing waveform distortion and resonant oscillation.
Solution Approach 2:
The patent changes the parameter of the driving voltage waveform by introducing an offset value that shifts the waveform to avoid the dead zone of the operational amplifier. The offset setting circuit dynamically adjusts the waveform parameters (amplitude and phase) to compensate for the dead zone effect, maintaining waveform accuracy without requiring changes to the amplifier's basic circuit design.
2Device complexity
If INL error is present in the DAC, then the converter can be simpler and cheaper, but periodic resonant oscillation and ringing are generated
Solution Approach 1:
The patent converts the harmful periodic INL error into a beneficial pattern by using the same periodicity to create compensation. The offset setting circuit detects the periodic nature of the INL error and applies a compensating offset that is equal in magnitude but opposite in phase, transforming the harmful periodic distortion into a controlled correction that eliminates resonant oscillation.
Solution Approach 2:
The patent implements feedback by continuously monitoring the actual output of the DAC and comparing it with the expected waveform. The offset setting circuit uses this feedback information to adjust the compensation values in real-time, creating a closed-loop system that automatically corrects for INL errors and prevents resonant oscillation without requiring complex error correction circuitry.
3Reliability
If offset value is adjusted to compensate for dead zone and INL error, then waveform distortion is reduced, but additional circuit complexity is introduced
Solution Approach 1:
The patent applies preliminary action by pre-calculating and pre-storing compensation values in a lookup table before actual operation. The offset setting circuit uses pre-computed compensation data to adjust the driving voltage waveform in advance, eliminating the need for complex real-time correction circuits while preventing waveform distortion and resonant oscillation.
Solution Approach 2:
The patent uses copying by creating a simplified model of the distortion characteristics and storing it in a lookup table. Instead of implementing complex correction circuitry, the system copies the essential distortion patterns into memory and uses them to generate corrected waveforms through simple table lookup and offset addition, significantly reducing circuit complexity.
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
The solution effectively minimizes waveform distortion and resonant oscillations, reducing the generation of ringing artifacts in scanned images while maintaining minimal power consumption by setting offset values to specific values that align INL errors and avoid dead zones.
Implementation Method 1
The optical scanner includes a Micro Electro Mechanical System (MEMS) that drives a mirror by a piezoelectric element. The mirror deflects the laser beam by oscillating when a periodic driving voltage, such as a sinusoidal wave or the like, generated by a driving circuit is applied to the piezoelectric element.
Data Source
AI summary
An optical scanning apparatus that oscillates a mirror in at least one direction, includes a mirror driving circuit including a digital-to-analog converter and an amplifier and generating a pair of driving signals for driving the mirror based on digital driving waveform data, a reference waveform data generator generating a reference waveform data, and an offset setting circuit setting an offset value of the reference waveform data, based on a dead band of the amplifier and a periodic integral non-linearity error of the digital-to-analog converter, to generate the driving waveform data.