Infrared Imaging Pixel Optics Using Fresnel Zone Plates for Focus Detection
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Solution Overview
Problem
Existing infrared sensors face challenges in acquiring parallax information and focus detection due to the weak light-condensing capability of on-chip lenses for short-wavelength infrared rays, making it difficult to manufacture lenses with sufficient thickness for effective light focusing.
Innovation Solution
The imaging device incorporates a Fresnel zone plate with alternating light shielding and light transmitting zones, disposed alternately in a concentric circle pattern, to diffract and focus infrared rays at the photoelectric conversion layer, enabling effective parallax information acquisition and focus detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If on-chip lenses are used for short-wavelength infrared rays, then light focusing is achieved, but the light-condensing capability is insufficient due to weak refractive power
Solution Approach 1:
The optical member is segmented into multiple regions with different refractive indices (first refractive index portions and second refractive index portions) arranged in a specific pattern. This segmentation creates effective phase difference and improves light-condensing capability without requiring thick lens structures, resolving the contradiction between focus detection precision and light-condensing capability for short-wavelength infrared rays.
Solution Approach 2:
The invention changes the refractive index parameter distribution within the optical member by creating regions with different refractive indices. This parameter change enables effective light focusing and phase difference generation for short-wavelength infrared rays, improving both focus detection precision and light-condensing capability simultaneously.
2Reliability
If lens thickness is increased to improve light focusing, then light-condensing capability is enhanced, but manufacturing difficulty increases
Solution Approach 1:
Instead of increasing lens thickness in the vertical dimension, the invention transitions to a planar dimension solution by creating a two-dimensional pattern of regions with different refractive indices. This dimensional change achieves effective light focusing without requiring thick lens structures, thereby improving manufacturing feasibility while maintaining light-condensing capability.
Solution Approach 2:
The optical member is divided into multiple segments with different refractive indices arranged in a specific pattern. This segmentation approach achieves light focusing functionality without requiring thick monolithic lenses, making the device easier to manufacture while maintaining effective light-condensing capability.
3Adaptability or versatility
If phase difference pixels are formed for focus detection, then focus detection function is achieved, but parallax information acquisition becomes difficult
Solution Approach 1:
The optical member with alternating refractive index regions serves multiple functions simultaneously: it creates phase differences for focus detection and generates parallax information for depth perception. This multi-functionality resolves the contradiction by enabling both focus detection and parallax information acquisition through the same structural configuration.
Solution Approach 2:
Different regions of the optical member have different refractive indices, creating local quality variations that produce both phase difference effects for focus detection and parallax effects for depth information. This local quality differentiation enables the system to achieve both functions without sacrificing either.
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 allows for the formation of image plane phase difference pixels that can acquire parallax information and provide a focus detection function, even for short-wavelength infrared rays, improving the light-condensing capability and manufacturing feasibility.
Implementation Method 1
The imaging device incorporates a Fresnel zone plate with alternating light shielding and light transmitting zones, disposed alternately in a concentric circle pattern, to diffract and focus infrared rays at the photoelectric conversion layer
Implementation Method 2
an optical member in which a first refractive index portion and a second refractive index portion having mutually different refractive indices are disposed alternately from a central part to an outer peripheral part
Data Source
AI summary
An imaging device of an embodiment of the present disclosure includes: a pixel array part in which a plurality of pixels is disposed in a row direction and a column direction; a photoelectric conversion layer including a compound semiconductor; and an optical member in which a first refractive index portion and a second refractive index portion having mutually different refractive indices are disposed alternately from a central part to an outer peripheral part. The optical member is disposed on side of a light entering surface of the photoelectric conversion layer to straddle the plurality of pixels adjacent at least in the row direction or the column direction.