Lens Control Apparatus Focus Shift Correction
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Solution Overview
Problem
Existing optical apparatuses face challenges in reducing focus shift while minimizing aberrations such as spherical aberration and distortion during focusing, as large movements of higher-resolution focus lenses can degrade in-focus accuracy and imaging quality.
Innovation Solution
A lens control apparatus that includes processors to control the movement of both first and second optical elements, calculating correction values based on positional differences and focus sensitivities, with a correction limit set to prevent aberrations, allowing precise positioning and movement of the second focus lens to maintain image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the second focus lens is moved by a large amount to correct focus shift, then the focus shift is reduced, but spherical aberration and distortion increase, degrading in-focus accuracy and imaging quality
Solution Approach 1:
The patent changes the parameter of correction value by introducing an upper limit (correction limit value) on the movement amount of the second focus lens. The correction value calculation task calculates the movement amount needed to correct focus shift, but this value is constrained by the correction limit value to prevent excessive movement that would cause aberrations. This parameter change resolves the contradiction by finding an optimal balance between focus correction and aberration suppression.
2Manufacturing precision
If the correction value for the second focus lens is increased to reduce focus shift, then focus accuracy improves, but the movable range is exceeded and aberrations are generated
Solution Approach 1:
The patent modifies the correction value parameter by establishing an upper bound (correction limit value) that represents the maximum safe movement amount of the second focus lens. The correction value calculation task computes the required correction amount, but this value is capped at the correction limit value to maintain imaging quality. This parameter constraint resolves the contradiction between achieving high in-focus accuracy and maintaining stable imaging quality.
Data Source
AI summary
A lens control apparatus that controls moving of each of the first optical element and the second optical element during focusing includes a first controller that controls driving of the first optical element to move the first optical element to a first target position according to an object distance, a second controller that controls driving of the second optical element to move the second optical element to a second target position according to the object distance, and a correction value calculator that calculates a correction value for the second target position using a difference between an actual position of the first optical element and the first target position, and focus sensitivities of the first and second optical elements and calculates the correction value using a correction limit value smaller than a maximum movable amount of the second optical element from the second target position.