Stepping Motor Lens Control with Detent Torque Correction
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Solution Overview
Problem
Stepping motors used in imaging devices for lens movement in the optical axis direction face instability due to variations in rotation angle caused by detent torque, leading to wobbling operations and pulsation in focusing, which destabilizes the focusing process.
Innovation Solution
A lens control apparatus and method that utilize a stepping motor with a controller to calculate and correct the drive amount by obtaining a first drive amount to the current position and a second drive amount to the target position, resulting in a third drive amount for precise rotational positioning, thereby stabilizing the focusing process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the stepping motor is driven in micro steps to achieve precise positioning, then the positioning precision is improved, but the rotation angle varies due to detent torque causing focusing instability
Solution Approach 1:
The patent implements feedback control by detecting the actual rotational position of the stepping motor and comparing it with the target position. The controller adjusts the drive pulses based on the detected position deviation, ensuring the lens reaches the accurate target position despite detent torque variations. This closed-loop feedback mechanism resolves the contradiction by maintaining both precision and stability.
Solution Approach 2:
The patent changes the control parameter from simple pulse counting to actual position detection. By using a position detection mechanism to monitor the real rotational position and adjusting drive accordingly, the system adapts to detent torque variations. This parameter change enables the system to maintain focusing stability while preserving micro-step positioning precision.
2Ease of operation
If the stepping motor follows the input target position directly without correction, then the control simplicity is maintained, but detection deviations occur leading to reduced stop accuracy
Solution Approach 1:
The patent introduces position detection feedback to identify actual stop positions and compares them with target positions. The controller calculates detection deviations and applies correction values to subsequent positioning operations. This feedback mechanism improves stop accuracy without significantly complicating the control system, as the correction is automatically applied based on detected deviations.
Solution Approach 2:
The patent performs preliminary position detection and deviation calculation before actual positioning operations. By detecting the position deviation in advance and pre-calculating correction values, the system prepares compensation data that is applied during subsequent positioning. This preliminary action improves stop accuracy while maintaining control simplicity through automated correction.
Data Source
AI summary
A lens control apparatus for moving a lens in an optical axis direction, including: a stepping motor for driving the lens; a controller for obtaining a drive amount on the basis of an input target position, instructing a rotational position of the stepping motor to perform drive control, wherein the controller obtains, in accordance with a first drive amount when the stepping motor is driven to a current position, a second drive amount from the current position to a target position, a third drive amount obtained by correcting the second drive amount, and instructs a rotational position on the basis of the third drive amount.