Stepping Motor Diaphragm Control with Hall Sensor Position Initialization
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Solution Overview
Problem
Conventional interchangeable lens SLR camera systems have limitations in diaphragm control, particularly during live-view operations and movie shooting, as the f-number cannot be adjusted once set, and the stepping motor's position is uncertain due to mechanical errors or varying lens attachments, leading to inaccurate f-number control.
Innovation Solution
A diaphragm control apparatus with a stepping motor, lead screw, position detector, and controller that initializes the stepping motor's position precisely by using a resilient biaser and Hall sensor to detect the slider's position, allowing for continuous diaphragm control and precise stepping-drive control, even with varying lens attachments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a stepping motor is used as a driving source of the diaphragm control mechanism, then the diaphragm can be controlled in a single direction with mechanical simplicity, but the stop position of the stepping motor becomes uncertain due to variations in lens attachment and mechanical errors
Solution Approach 1:
The system performs preliminary actions by detecting the initial stop position of the stepping motor when the lens is first attached, storing this position information in memory, and using it as a reference for subsequent diaphragm control operations. This preliminary detection and storage of position data resolves the uncertainty caused by mechanical variations in lens attachment.
Solution Approach 2:
The system implements feedback by continuously monitoring the relationship between the stepping motor's excitation patterns and the actual diaphragm position, comparing expected positions with actual positions, and correcting any deviations. This feedback mechanism ensures accurate diaphragm control despite uncertainties in the initial stepping motor stop position.
2Ease of operation
If the stepping motor is forced to rotate in association with movements of the diaphragm control rod, then the diaphragm control is simplified, but the stop position of the stepping motor deviates from the preset initial position due to mechanical errors
Solution Approach 1:
The system performs preliminary detection of the actual open-aperture reference position when the lens is attached, stores this detected position information, and uses it as the basis for subsequent diaphragm control operations. This preliminary action compensates for manufacturing errors in the open-aperture reference position by using the actual measured position rather than a theoretical preset position.
Solution Approach 2:
The system changes the reference parameter for diaphragm control from a fixed preset value to a dynamically detected actual position. By detecting the real position of the diaphragm control rod and using this detected position as the control reference, the system adapts to manufacturing variations and ensures accurate diaphragm operation.
3Measurement precision
If the stepping motor is brought into a free state by cutting off power, then the initial excitation pattern of the stop position can be detected, but the stop position becomes unstable due to deformation of diaphragm control mechanism components
Solution Approach 1:
The system performs preliminary detection of the stop position when the stepping motor is in a stable energized state, stores this position information, and uses it as a reference. This preliminary detection avoids the instability problem that occurs when the motor is in a free state, while still enabling accurate position detection.
Solution Approach 2:
The system compensates for the instability that will occur when the stepping motor enters a free state by detecting and storing the position information beforehand, while the motor is still in a stable energized state. This beforehand cushioning prevents the stability problem from affecting the position detection accuracy.
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 precise and continuous diaphragm control during exposure, allowing for f-number adjustments during live-view operations and movie shooting, ensuring accurate aperture settings regardless of lens type or mechanical errors.
Implementation Method 1
Hall sensor to detect the slider's position
Implementation Method 2
resilient biaser to allow the diaphragm operatively-associated rod to move to the initial position
Data Source
AI summary
A diaphragm control apparatus in a camera body includes a stepping motor, a lead screw thereof, wherein a slider is driven by the lead screw, a position detector, and a controller. When the stepping motor is in a free state, the slider allows a diaphragm operatively-associated rod to move to an initial position. The controller detects the slider origin position when the stepping motor is in the free state and drives the stepping motor stepwise to move the slider away from the origin position against a biasing force of a resilient biaser, and drives the stepping motor stepwise to move the slider toward the origin position while detecting the slider position; and sets an initial excitation pattern of the stepping motor upon a distance from the detected slider position to the origin position becoming less than a slider moving distance for one step of the stepping motor.