Variable-Transmittance ND Filter Control for Focus Lag Reduction
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Solution Overview
Problem
The response speed of liquid crystal ND filters decreases at low temperatures, leading to delayed exposure control and increased focus lag in compact digital cameras when the shutter button is pressed halfway, activating auto focus before imaging.
Innovation Solution
An action control device with a variable-transmittance ND filter that adjusts transmittance based on applied voltage, including an applied voltage control unit and a diaphragm control unit, where minimum voltage is applied during monitoring and a certain voltage during imaging preparation or imaging to control transmittance and diaphragm opening, respectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a liquid crystal ND filter is used to control exposure by changing transmittance, then exposure control is improved, but response speed decreases at low temperatures causing focus lag
Solution Approach 1:
The patent applies a minimum voltage to the liquid crystal ND filter in advance during the monitoring state, before autofocus is activated. This preliminary action ensures that when the shutter button is pressed halfway and autofocus begins, the filter is already in a state ready for rapid transmittance adjustment, thereby reducing focus lag caused by low-temperature slow response.
2Illumination intensity
If the diaphragm is opened or closed during monitoring, then illuminance control is achieved, but it interferes with autofocus operation
Solution Approach 1:
The patent segments the illuminance control function into two distinct control mechanisms: the diaphragm is used for illuminance control during the monitoring state, while the liquid crystal ND filter is used for transmittance control during autofocus and imaging. This segmentation allows each component to operate independently in its optimal state, preventing diaphragm movement from interfering with autofocus operation.
3Illumination intensity
If transmittance is controlled during monitoring, then exposure is optimized, but response time increases due to liquid crystal viscosity
Solution Approach 1:
The patent applies a minimum voltage to the liquid crystal ND filter during the monitoring state to maintain it in a ready state. This preliminary action reduces the viscosity effect and prepares the filter for rapid response when autofocus is activated, thereby optimizing exposure while minimizing response time delays.
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 solution reduces focus lag by optimizing transmittance control and diaphragm operation to maintain image quality and reduce response time delays.
Implementation Method 1
a liquid crystal ND filter is used to reduce a drastic change in exposure and thus reduce an observer's fatigue by changing a transmittance
Data Source
AI summary
Provided is an action control device, including a variable-transmittance ND filter configured to have transmittance that varies according to an applied voltage, an applied voltage control unit configured to control a voltage to be applied to the variable-transmittance ND filter, and a diaphragm control unit configured to control illuminance through a diaphragm. At a time of monitoring, the illuminance is controlled such that the applied voltage control unit applies a substantially minimum voltage to the variable-transmittance ND filter, and the diaphragm control unit opens or closes the diaphragm, and at a time of imaging preparation or imaging, the illuminance is controlled such that the applied voltage control unit applies a certain applied voltage to the variable-transmittance ND filter in a state of the substantially minimum voltage, and controls transmittance, and the diaphragm control unit performs control such that the diaphragm enters a fully opened state or substantially fully opened state.