Position Detection Combining Optical and Non-Optical Detectors
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Solution Overview
Problem
Optical position detection systems face inaccuracies due to unclean optical scales with smudges or dust, and temperature-induced expansions/contractions, which affect position detection accuracy, and manual zoom operations in power-off states lead to unclear backlash direction, hindering zoom tracking control.
Innovation Solution
A position detection apparatus combining optical and non-optical position detectors, using multiple periodic patterns on the optical scale and a potentiometer to generate detection signals, normalizing and combining them to produce an absolute position signal, and incorporating temperature correction and foreign substance detection to ensure accurate positioning and backlash direction determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an optical encoder uses multiple paired periodic patterns with long and short periods to calculate absolute position, then position detection accuracy is improved, but noise from unclean optical scales (smudges, dust) is amplified by the multiplying process
Solution Approach 1:
The patent applies preliminary action by detecting the presence of foreign substances on the optical scale before performing the multiplying process. The system checks for smudges or dust on the optical scale and, when detected, prevents the multiplying operation that would amplify noise, thereby maintaining position detection accuracy without propagating errors.
2Measurement precision
If an optical encoder performs multiplying process to combine upper and lower level signals, then absolute position calculation is enabled, but temperature-induced expansion and contraction of the optical scale significantly affects position detection
Solution Approach 1:
The patent applies preliminary action by detecting temperature changes before performing the multiplying process. The system monitors temperature variations that cause optical scale expansion or contraction and, when significant changes are detected, prevents the multiplying operation that would amplify thermal errors, thereby maintaining accurate absolute position calculation.
3Ease of operation
If manual zoom operation is performed in power-off state, then zoom ring rotation is possible, but backlash direction becomes unclear hindering zoom tracking control upon power-on
Solution Approach 1:
The patent applies self-service by using the encoder to automatically detect the backlash direction upon power-on. The system performs a detection operation where the zoom ring is rotated in both directions and the encoder measures the actual backlash direction, then stores this information for use in zoom tracking control, eliminating the need for manual backlash direction specification.
Solution Approach 2:
The patent applies feedback by using the encoder to detect the actual backlash direction and feed this information back to the control system. The detected backlash direction is used to adjust the zoom tracking control parameters, ensuring accurate focus lens movement in response to zoom ring rotation regardless of the direction in which backlash occurred during manual operation.
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 enhances position detection accuracy by mitigating noise from unclean scales and temperature variations, and enables immediate and accurate zoom tracking control upon power-on by determining the correct backlash direction.
Implementation Method 1
The optical scale is provided with a periodic pattern reflecting or transmitting light
Implementation Method 2
Detecting the light from the periodic pattern by the light-receiving sensor with a movement of the movable member provides a detection signal
Data Source
AI summary
The position detection apparatus includes the first optical position detector used with an optical scale having periodic patterns. The first position detector receives lights from the periodic patterns when moving relatively to the optical scale with a movement of a movable member to generate first detection signals respectively changing at periods corresponding to periods of the periodic patterns. The second non-optical position detector generates a second detection signal changing with the movement of the movable member. The calculator produces a first position signal by using the first detection signals, produces a second position signal whose resolution is different from that of the first position signal, by using the second detection signal, and performs a calculation for combining the first and second position signals together to produce an absolute position signal.