Variable Optical Low-Pass Filter for Dynamic MTF Control
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Solution Overview
Problem
Conventional optical low-pass filters in cameras exert a double low-pass effect when image blurring occurs due to changes in the relative position or angle between the subject and camera, leading to excessive degradation in image quality, especially during continuous image shooting.
Innovation Solution
A filter control device and method that dynamically adjust the low-pass characteristics of the optical low-pass filter based on changes in the image shooting range, using a variable optical low-pass filter with a liquid crystal layer and birefringent plates to control the low-pass effect in response to image movement and zooming, thereby compensating for changes in MTF characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a fixed optical low-pass filter is used, then aliasing is suppressed, but image sharpness is excessively degraded when image blurring occurs
Solution Approach 1:
The patent applies a variable optical low-pass filter that can dynamically change its low-pass characteristics in real-time. The filter's birefringence properties are adjusted based on detected image blurring conditions, allowing the system to adapt between suppressing aliasing and maintaining sharpness. This dynamic adjustment resolves the contradiction by making the filter characteristics changeable rather than fixed.
Solution Approach 2:
The patent changes the optical parameters of the low-pass filter based on image blurring conditions. By detecting relative position changes and angle variations that cause blurring, the system adjusts the filter's birefringence parameters to optimize the balance between aliasing suppression and sharpness preservation for each shooting condition.
2Adaptability or versatility
If mechanical switching of the optical low-pass filter is performed, then two states (with/without low-pass effect) are available, but continuous adjustment of MTF characteristics is insufficient
Solution Approach 1:
The patent replaces the mechanical switching system with an optical control mechanism using a variable birefringent filter. Instead of physically moving or switching filter elements, the system uses electrically controllable liquid crystal technology to continuously adjust the optical properties, eliminating mechanical complexity while achieving continuous MTF adjustment.
Solution Approach 2:
The patent enables continuous variation of the low-pass filter characteristics by changing the birefringence parameters through electrical control. This allows smooth transition between different MTF characteristics without mechanical switching, providing continuous adaptability while simplifying the device structure.
3Adaptability or versatility
If a variable optical low-pass filter is used, then low-pass characteristics can be optimized for different shooting modes, but image blurring-induced MTF changes are not compensated
Solution Approach 1:
The patent implements a feedback control system that detects image blurring conditions (relative position changes, angle variations) and uses this information to adjust the variable optical low-pass filter characteristics. The detection unit monitors shooting conditions and feeds this information to the control unit, which compensates for MTF changes by adjusting the filter's birefringence properties in real-time.
Solution Approach 2:
The patent applies preliminary anti-action by detecting potential image blurring conditions before they significantly degrade image quality. The system proactively adjusts the filter characteristics to counteract the expected MTF reduction from blurring, preventing excessive sharpness degradation rather than reacting after the damage is done.
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
This approach ensures high image quality by adaptively managing the low-pass effect, preventing excessive reduction in MTF and maintaining sharpness, even during hand movement, panning, or zooming operations, and is effective for both still and moving image shooting.
Implementation Method 1
an optical low-pass filter comprising birefringent plates arranged to face each other and a liquid crystal layer sandwiched between the plates
Implementation Method 2
a variable optical low-pass filter with a liquid crystal layer and birefringent plates to control the low-pass effect
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A filter control device of the present disclosure includes a filter controller that performs control to cause low-pass characteristics of an optical low-pass filter mounted in an imaging device to be changed in accordance with change in an image shooting range.