Light Intensity Control Device with Segmented ND Filter
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Solution Overview
Problem
Existing light intensity control devices for imaging devices, which use both aperture blades and ND filters, fail to adequately reduce diffractive influence and wave aberration, and may introduce increased wave aberration when using ND filters.
Innovation Solution
A light intensity control device with an aperture stop, a light extinction part, and a light intensity aperture part, where the light extinction part and aperture blades can move independently to control light intensity, with a phase difference of less than 0.2 μm between transmission wavefronts, reducing diffractive influence and wave aberration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If aperture blades are used to control light intensity, then light intensity can be adjusted, but diffractive influence increases and dust/scratches are imaged as shadows
Solution Approach 1:
The light extinction part is divided into a first area with high transmissivity and a second area with low transmissivity, allowing different regions to serve different functions. The first area maintains good light transmission with minimal diffraction, while the second area provides additional light intensity control when needed.
Solution Approach 2:
Different areas of the light extinction part have different optical properties - the first area has high transmissivity for minimal interference with light, while the second area has low transmissivity for strong light blocking. This local differentiation allows the system to achieve light intensity control while minimizing diffractive influence in the primary transmission path.
2Illumination intensity
If ND filter is used to control light intensity, then light intensity can be adjusted, but wave aberration increases
Solution Approach 1:
The light extinction part segments the light control function into two areas: the first area with high transmissivity that maintains wavefront quality, and the second area with low transmissivity that provides additional attenuation. By using the first area as the primary light control mechanism, the system achieves light intensity adjustment while preserving wave aberration performance.
Solution Approach 2:
The light extinction part acts as an intermediary between the aperture blades and the pickup device, providing an additional layer of light control that does not introduce significant wave aberration. The first area with high transmissivity serves as a quality intermediary that maintains optical performance while enabling light intensity control.
3Illumination intensity
If aperture step-down is performed for correct exposure, then exposure can be controlled, but dusts and scratches on cover glass are imaged as shadows
Solution Approach 1:
The light extinction part extracts the light control function from the aperture mechanism alone, providing an additional independent means of light attenuation. This allows the aperture to maintain a larger opening (reducing shadow effects from dust and scratches) while the light extinction part provides the necessary light intensity reduction for correct exposure.
4Measurement precision
If both aperture blades and ND filter are used together, then light intensity control accuracy is improved, but diffractive influence is not sufficiently reduced
Solution Approach 1:
The light extinction part is segmented into two functional areas that work together: the first area with high transmissivity that maintains minimal diffraction for accurate light control, and the second area with low transmissivity that provides additional attenuation capability. This segmentation allows the system to achieve high light intensity control accuracy while the primary transmission path through the first area minimizes diffractive influence.
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
The solution allows for easy control of light intensity, reduces diffractive influence, and minimizes wave aberration in imaging devices, even when using ND filters, thereby improving image quality.
Implementation Method 1
a light extinction part (25) having a first area (253) whose transmissivity for incident light is more than a first value and a second area (254) whose transmissivity for incident light is a second value smaller than the first value
Implementation Method 2
the diffractive influence of narrowed aperture on the image formation by pickup lens becomes increased
Implementation Method 3
a phase difference of transmission wavefront between light transmitted through the first area 253 and light transmitted through the second area 254 is less than 0.2 μm with a wavelength of 0.55 μm
Data Source
AI summary
A light intensity control device includes a fixed opening 261, an aperture stop part 26 for controlling a light flux of incident light, a light intensity aperture part 24 for changing the size of an opening by moving a plurality of aperture blades to limit a light intensity of transmitted light and a ND filter 25 having a transparent area 253 and a light blocking area 254, which is arranged to be movable between a first light blocking state where the transparent area 253 faces the fixed opening 261 of the aperture stop part 26 and a second light blocking state where the light blocking area 254 faces the fixed opening. The moving of the ND filter 25 is carried out when the opening area of the light intensity aperture part 24 is a maximum.