Variable Retardation Plate Optical Apparatus Stray Light Reduction
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Solution Overview
Problem
Conventional image pickup apparatuses struggle to distinguish and reduce stray light, such as ghost and flare, which interfere with polarization information of objects, especially due to multiple reflections in image display devices and optical systems, leading to erroneous recording of stray light as object information.
Innovation Solution
An optical apparatus configuration that includes a first retardation plate, a variable retardation plate, a polarizer, and a quarter waveplate, arranged in a specific order to control the retardation and polarization of light, allowing the image pickup element to receive only the polarization information of the object while minimizing stray light influence, using a retardation setter to adjust the variable retardation plate based on the object's polarization component.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If a polarizer is used to obtain polarization information, then polarization information of the object can be extracted, but stray light cannot be distinguished from object information
Solution Approach 1:
The patent segments the polarization information acquisition into multiple stages by inserting retardation plates before and after the polarizer. The first retardation plate converts linearly polarized light from the object into circularly polarized light, allowing the polarizer to distinguish between object light and stray light based on their different polarization transformations. This segmentation enables separate handling of object information and stray light information.
Solution Approach 2:
The retardation plates act as intermediary elements that mediate between the object light and the polarizer. By introducing these intermediary optical elements, the system can transform the polarization state of object light differently from stray light, enabling the polarizer to selectively pass or block each type based on their transformed polarization states.
2Productivity
If multiple reflections occur in the optical system, then light can be guided through the system, but polarization-dependent stray light is generated that cannot be distinguished from object information
Solution Approach 1:
The patent applies preliminary anti-action by placing a retardation plate before the polarizer that pre-transforms the polarization state of object light. This preliminary transformation ensures that when light undergoes multiple reflections in the optical system, the object light and stray light acquire different polarization characteristics, allowing the subsequent polarizer to differentiate and reject stray light while maintaining object light transmission.
3Object-generated harmful factors
If a polarizer is placed in the optical path to reduce stray light, then some stray light can be reduced, but concurrent stray light fluxes at different angles cannot be effectively reduced
Solution Approach 1:
The patent transitions from a single-dimension polarization filtering approach to a multi-dimensional solution by incorporating retardation plates that operate in the polarization state space. The combination of retardation plates and polarizer creates a more complex polarization transformation pathway that can handle stray light from multiple angles simultaneously, as the retardation plates affect different polarization components differently regardless of incident angle.
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 configuration effectively reduces the impact of stray light on polarization information, enabling precise acquisition and processing of object polarization data, even in scenarios with concurrent stray light fluxes at different angles, thereby improving image quality by distinguishing object and stray light polarization components.
Implementation Method 1
a first retardation plate configured to provide a retardation of π/2 between a polarization component in a slow axis direction and a polarization component in a fast axis direction
Implementation Method 2
a second retardation plate configured to change a retardation to be provided between a polarization component in a slow axis direction and a polarization component in a fast axis direction
Implementation Method 3
a third retardation plate configured to provide a retardation of π/2 between a polarization component in a slow axis direction and a polarization component in a fast axis direction
Implementation Method 4
a polarizer configured to extract a polarization component to be introduced to the image pickup element
Data Source
AI summary
An optical apparatus is configured to introduce light from an object to an image pickup element, and includes first, second, and third retardation plates, a polarizer, and a setter. The first retardation plate, the second retardation plate, and the polarizer are arranged in this order from a side of the object to a side of the image pickup element. The slow axis direction or the fast axis direction of the second retardation plate tilts to the slow axis direction or the fast axis direction of the first retardation plate. The setter sets the retardation of the second retardation plate according to the polarization component of the light from the object.