Stepping Motor Diaphragm Control with Position Feedback
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Solution Overview
Problem
Conventional diaphragm control mechanisms in interchangeable lens SLR camera systems allow only single-direction diaphragm control, preventing f-number adjustments during live-view or moving-image shooting, and suffer from positional errors due to mechanical and assembly inaccuracies, leading to incorrect stepping motor operation.
Innovation Solution
A diaphragm control apparatus with a slide member driven by a lead screw and a stepping motor, incorporating a position detector to adjust the excitation phase of the stepping motor, ensuring precise control and compensation for initial positional errors, and including an elastic biasing member and reset mechanism for accurate diaphragm operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a conventional diaphragm control mechanism with a ratchet is used, then the diaphragm can be controlled in a single direction (stop-down direction), but the f-number cannot be adjusted afterwards during live-view or moving-image shooting
Solution Approach 1:
The patent replaces the conventional ratchet mechanism that allows only stop-down movement with a stepping motor that can drive the diaphragm control rod in both directions (stop-down and opening directions). This inversion of the control mechanism enables bidirectional adjustment of the diaphragm during exposure, allowing f-number changes during live-view and moving-image shooting operations.
2Adaptability or versatility
If a stepping motor is used as a driving source, then continuous diaphragm control during exposure becomes possible, but the stepping motor rotates from the initial detent position causing uncertain stop position and f-number control errors
Solution Approach 1:
The patent introduces a position detector that detects the initial position of the diaphragm control rod before stepping motor operation. Based on this detected initial position, the control system calculates and sets the appropriate excitation phase for the stepping motor, ensuring that the motor starts from the correct reference position. This preliminary position detection and phase setting eliminates the uncertainty of the stop position and prevents f-number control errors.
Solution Approach 2:
The patent employs a position detector to continuously monitor the position of the diaphragm control rod and provides feedback to the control system. This feedback mechanism allows the control system to adjust the excitation phase of the stepping motor based on the actual position, ensuring precise f-number control and correcting any deviations from the intended position.
3Adaptability or versatility
If the open-aperture reference position of the diaphragm operatively-associated rod varies depending on lens type, then the amount of movement of the diaphragm control rod varies, but the stepping motor is forced to rotate in association with these movements causing initial position deviation
Solution Approach 1:
The patent uses the position detector to detect the initial position of the diaphragm control rod for each specific lens attachment. Based on this detected initial position, the control system sets the appropriate excitation phase before stepping motor operation. This preliminary detection and phase setting compensates for variations in open-aperture reference positions across different lens types, ensuring accurate initial positioning regardless of lens compatibility variations.
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 and precise diaphragm control during exposure, allowing f-number adjustments even with stepping motors, improving operational accuracy and reliability by detecting and correcting initial positional errors.
Implementation Method 1
a lead screw which is driven to rotate by the stepping motor, wherein the slide member is moved by rotation of the lead screw
Implementation Method 2
a position detector for detecting a position of the slide member
Implementation Method 3
a diaphragm drive mechanism including a stepping motor and a lead screw which is driven to rotate by the stepping motor
Data Source
AI summary
A diaphragm control apparatus incorporated in a camera body, to which an interchangeable lens equipped with a diaphragm apparatus is detachably attached, the diaphragm apparatus including a diaphragm operatively-associated rod for driving an adjustable diaphragm to open and shut the adjustable diaphragm, and the diaphragm control apparatus including a slide member that is driven to move the diaphragm operatively-associated rod, the diaphragm control apparatus includes a diaphragm drive mechanism including a stepping motor and a lead screw which is driven to rotate by the stepping motor, wherein the slide member is moved by rotation of the lead screw, a position detector for detecting a position of the slide member, and a controller for adjusting an excitation phase of the stepping motor based on a stop position of the slide member detected by the position detector.