Lens Barrel Sensor Arrangement for Backlash-Resistant Position Detection
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Solution Overview
Problem
Conventional lens barrel systems face challenges in accurately detecting the absolute position of a movable lens due to mechanical backlash, which affects the position detection accuracy, especially when using two sensors, and are prone to errors from deviations in sensor alignment and interference issues.
Innovation Solution
A lens barrel design incorporating a first sensor unit with a monotonic signal output and a second sensor unit with a periodic signal output, where the first sensor is arranged closer to the main guide bar to minimize backlash effects, allowing for high-accuracy absolute position detection without origin position detection, even when mechanical backlash occurs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If two position sensors are arranged to detect absolute position of the movable lens, then position detection accuracy is improved, but mechanical backlash causes deviation in positional relation between sensors and reduces detection accuracy
Solution Approach 1:
The patent applies local quality by differentiating the functional characteristics of two sensor units: the first sensor unit provides monotonic position information for absolute position detection, while the second sensor unit provides periodic position information for fine position resolution. Each sensor unit is optimized for its specific detection role, and their outputs are combined to achieve high-accuracy absolute position detection that overcomes mechanical backlash effects.
Solution Approach 2:
The patent uses a composite sensing approach by combining outputs from two different sensor units with distinct signal characteristics (monotonic and periodic signals). This composite detection system integrates the advantages of both sensor types to achieve robust absolute position measurement that is insensitive to mechanical backlash, effectively creating a hybrid sensing solution that overcomes the limitations of individual sensor types.
2Measurement precision
If contact potentiometer is used as position sensor, then absolute position detection is achieved, but slider connection to movable lens group adds movement load and reduces durability
Solution Approach 1:
The patent replaces the mechanical contact potentiometer system with a non-contact optical sensing system. The first and second sensor units use optical methods to detect position without physical contact with the movable lens group, eliminating the slider that would add movement load and reduce durability. This substitution maintains absolute position detection capability while significantly improving reliability and durability.
3Reliability
If noncontact optical sensor with shading plate is used, then durability is improved, but mechanical backlash causes deviation between shading plate and photo interrupter leading to detection errors
Solution Approach 1:
The patent changes the detection parameter approach by using two different signal types (monotonic and periodic) from the two sensor units. This parameter differentiation allows the system to detect absolute position through the monotonic sensor while using the periodic sensor for fine position resolution, creating a combined measurement that is robust against mechanical backlash-induced deviations in either individual sensor.
4Measurement precision
If origin position detection is implemented before camera start, then absolute position can be detected, but detection time is extended
Solution Approach 1:
The patent implements preliminary action by having the first sensor unit continuously provide monotonic position information that establishes absolute position reference without requiring origin detection procedures before camera operation. This allows the system to be ready for immediate position detection upon startup, eliminating the time-consuming origin detection step while maintaining accurate absolute position measurement capability.
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 design enables precise detection of the absolute position of the movable lens with high accuracy, reducing detection errors and maintaining miniaturization and cost-effectiveness by optimizing sensor placement and signal processing.
Implementation Method 1
a first detection unit that outputs a signal that continuously increases or decreases according to movement of the movable part by reading the pattern of the first scale
Implementation Method 2
a second detection unit that outputs a periodic signal corresponding to movement of the movable part by reading the pattern of the second scale
Data Source
AI summary
A lens barrel that is capable of detecting an absolute position of a movable part with high accuracy. A first guide guides the movable part with an optical lens. A first sensor unit includes a first scale and first detection unit. The first scale in the movable part has a pattern that makes a signal output from the first detection unit monotonically increase. The first detection unit outputs the signal that continuously varies according to the movement. A second sensor unit includes a second scale in the movable part that has a periodic repeated pattern and a second detection unit that outputs a periodic signal by reading the second scale. A controller detects a position of the movable part based on the signals output from the first and second detection units. The first sensor unit is arranged nearer to the first guide in comparison with the second sensor unit.