Variable Transmittance Filter for Frame Rate Brightness Control
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Solution Overview
Problem
When the frame rate of an imaging apparatus changes during shooting, existing methods to maintain brightness, such as adjusting shutter speed or diaphragm, result in intermittent motion or degradation of image quality, and mechanical ND filter switching is impractical.
Innovation Solution
A control apparatus and method that includes a frame rate control unit and a transmittance control unit for a filter to adjust the transmittance of light incident on the imaging element, maintaining subject brightness without causing strangeness or image quality changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If shutter speed is changed in accordance with change of the frame rate so that brightness is maintained, then brightness is maintained, but the moving image becomes intermittent
Solution Approach 1:
The patent replaces the mechanical shutter system with an optical filter (ND filter) system. Instead of mechanically opening and closing the shutter at different speeds, the invention uses a variable transmittance filter that can be adjusted continuously to control light amount, thereby maintaining brightness without creating intermittent motion effects.
Solution Approach 2:
The invention changes the transmittance parameter of the optical filter in accordance with frame rate changes. By adjusting the filter's light transmission property rather than the shutter's temporal opening/closing behavior, the system maintains brightness while preserving continuous motion capture.
2Illumination intensity
If a diaphragm is adjusted in accordance with change of a frame rate so that brightness is maintained, then brightness is maintained, but image quality changes due to change of a depth of field
Solution Approach 1:
The patent substitutes the diaphragm (aperture) mechanism with an ND filter mechanism. The diaphragm adjustment changes both brightness and depth of field, while the ND filter only affects brightness by absorbing light, leaving the optical path and depth of field characteristics unchanged.
3Illumination intensity
If a pixel value is multiplied by a gain in accordance with change of the frame rate, then brightness is adjusted, but image quality degrades due to decrease in a dynamic range of a signal
Solution Approach 1:
The patent replaces digital signal processing (gain multiplication) with optical processing (ND filter transmittance control). By adjusting the amount of light entering the sensor through the filter rather than amplifying the digital signal afterward, the invention maintains the full dynamic range and avoids noise amplification associated with digital gain.
4Illumination intensity
If a mechanical ND filter is used to control transmittance, then brightness can be adjusted, but the filter cannot be switched quickly and mechanically switching is impractical
Solution Approach 1:
The patent replaces the mechanical ND filter switching mechanism with an electronic control system that adjusts filter transmittance without mechanical movement. This electronic adjustment mechanism achieves rapid transmittance changes without the inertia and wear limitations of mechanical systems.
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 allows for seamless brightness adjustment with frame rate changes without causing a feeling of discontinuity or image quality degradation, ensuring continuous and high-quality imaging.
Implementation Method 1
a filter which transmits light incident on an imaging element
Data Source
AI summary
A control apparatus according to the present disclosure includes a frame rate control unit configured to control a frame rate of imaging, and a transmittance control unit configured to control transmittance of a filter which transmits light incident on an imaging element according to change of the frame rate so that brightness of an imaged subject is maintained. According to this configuration, even when the frame rate changes, it is possible to maintain fixed brightness according to change of the frame rate without causing change in imaging quality.