Stepping Motor Diaphragm Control with Hall Sensor Position Detection
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Solution Overview
Problem
Conventional interchangeable lens SLR camera systems have limitations in diaphragm control, particularly when using a stepping motor, as the stop position of the stepping motor becomes uncertain due to mechanical errors or varying interchangeable lens types, leading to inaccurate f-number adjustments during live-view or movie shooting operations.
Innovation Solution
A diaphragm control apparatus with a slider driven by a lead screw and a stepping motor, incorporating a position detector and controller to initialize the stepping motor's origin position and excitation pattern, ensuring precise stepping-drive control by using a resilient biaser to move the slider to the initial position and detecting the position via a Hall sensor and magnet system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a stepping motor is used as a driving source of the diaphragm control mechanism, then the diaphragm can be controlled in both directions (open and shut), but the stop position of the stepping motor becomes uncertain due to mechanical errors or varying interchangeable lens types, leading to inaccurate f-number adjustments
Solution Approach 1:
The system performs preliminary actions by detecting the stop position of the stepping motor before actual diaphragm control operations. The controller detects where the stepping motor stops when power is cut off, stores this position information, and uses it to calculate the correct excitation pattern sequence for accurate f-number adjustments. This preliminary detection and storage of position data ensures subsequent precision control despite mechanical variations.
Solution Approach 2:
The system implements feedback by continuously monitoring the stop position of the stepping motor and using this information to adjust control commands. The controller detects the actual stop position, compares it with expected positions, and modifies the excitation pattern sequence accordingly to achieve accurate f-number settings. This closed-loop feedback mechanism compensates for mechanical errors and lens variations.
2Ease of operation
If the stepping motor is forced to rotate in association with movements of the diaphragm control rod, then the diaphragm control mechanism can function, but the amount of rotation of the stepping motor varies depending on the type of interchangeable lens attached, making the stop position uncertain
Solution Approach 1:
The system employs self-service by allowing the stepping motor to naturally stop at its own position when power is cut off, rather than forcing it to stop at a predetermined location. The controller detects this natural stop position and uses it as the basis for subsequent control operations. This self-determined stop position approach accommodates variations in lens types and mechanical conditions while maintaining reliable control.
3Adaptability or versatility
If the open-aperture reference position of the diaphragm operatively-associated rod varies depending on the f-number at open aperture, then the system can accommodate different lens types, but the amount of movement of the diaphragm control rod varies, causing the stepping motor to rotate from the initial detent position
Solution Approach 1:
The system performs preliminary detection of the stepping motor's stop position when the interchangeable lens is attached and the diaphragm is at open aperture. This preliminary position detection occurs before any control operations, allowing the controller to establish the correct reference point and excitation pattern sequence specific to each lens type, ensuring both adaptability and precision.
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
Enables continuous diaphragm control and precise f-number adjustments during exposure, even with interchangeable lenses of different types, by accurately setting the stepping motor's origin position and excitation pattern, thus stabilizing the diaphragm control mechanism.
Implementation Method 1
the slider being biased to move toward an initial position by a resilient biaser
Implementation Method 2
detecting the position via a Hall sensor and magnet system
Data Source
AI summary
A diaphragm control apparatus is provided in a camera body, in which a controller drives a stepping motor to move the slider away from an origin position, thereafter drives the stepping motor in the opposite direction toward the origin position, and thereafter detects the slider position after holding the stepping motor for a first waiting time upon a distance from the slider to the origin position becoming less than slider-moving distance for one step of the stepping motor. The controller causes the stepping motor to enter a free state upon a lapse of the first waiting time and detects the slider position upon a lapse of a second waiting time to set an initial excitation pattern from a difference between the slider position detected during the first waiting time and the slider position detected in the free state thereof and from the moving distance of the slider.