Image Sensor Pixel Layout for Accurate Phase Difference Autofocus
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Solution Overview
Problem
Existing solid-state image-capturing devices face challenges in achieving high phase difference detection accuracy while maintaining a simple configuration, as techniques often result in increased production complexity, reflection loss, or reduced sensitivity due to thicker films and additional layers.
Innovation Solution
A solid-state image-capturing device with a pixel array unit featuring a phase difference pixel and an image-capturing pixel, where a layer between the light shielding layer and the micro lens in the image-capturing pixel has a higher refraction index than in the phase difference pixel, optimizing phase difference detection accuracy with a simpler configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the film thickness of the inter-layer film in the phase difference pixel is increased to improve phase difference detection accuracy, then the sensitivity becomes highly dependent on the angle, but the image-capturing pixels also become thicker and lose their diagonal incidence property
Solution Approach 1:
The patent applies local quality by making the inter-layer film thickness selective: the phase difference pixel has a thicker inter-layer film (second thickness) for high angle-dependent sensitivity, while the image-capturing pixel maintains a thinner inter-layer film (first thickness) to preserve diagonal incidence light reception. This localized differentiation resolves the contradiction by allowing each pixel type to have optimal film thickness for its specific function.
2Measurement precision
If different structures are employed for phase difference pixels and image-capturing pixels to improve phase difference detection accuracy, then detection accuracy improves, but the device complexity increases
Solution Approach 1:
The patent uses local quality to differentiate pixel structures only where necessary. Both phase difference pixels and image-capturing pixels share the same basic structure, but the inter-layer film thickness is locally adjusted: thicker in phase difference pixels for angle-dependent sensitivity, and thinner in image-capturing pixels for diagonal incidence reception. This minimal structural differentiation achieves high detection accuracy while avoiding excessive device complexity.
3Measurement precision
If additional layers such as inter-layer lenses and light guides are added to optimize phase difference pixels, then phase difference detection accuracy improves, but the number of production steps greatly increases
Solution Approach 1:
The patent applies parameter changes by modifying only the inter-layer film thickness parameter to achieve phase difference detection optimization. Instead of adding complex structures like inter-layer lenses and light guides, the invention changes the thickness parameter of the existing inter-layer film to be thicker in phase difference pixels, which provides sufficient angle-dependent sensitivity improvement while maintaining production process simplicity and avoiding excessive manufacturing steps.
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 approach enables high phase difference detection accuracy with reduced degradation of image-capturing pixel characteristics and minimized production complexity, enhancing the overall performance of the solid-state image-capturing device.
Implementation Method 1
a layer between a light shielding layer and a micro lens formed in the image-capturing pixel has a higher refraction index than a refraction index of a layer formed in the phase difference pixel
Data Source
AI summary
A high degree of phase difference detection accuracy can be obtained using a phase difference pixel with a simpler configuration. A solid-state image-capturing device includes a pixel array unit in which a plurality of pixels including a phase difference pixel which is a pixel for focal point detection and an image-capturing pixel which is a pixel for image generation are arranged in a two-dimensional array. In this case, a predetermined layer between a light shielding layer and a micro lens formed in the image-capturing pixel has a higher refraction index than a refraction index of the predetermined layer formed in the phase difference pixel. The technique of the present disclosure can be applied to, for example, a back-illuminated-type solid-state image-capturing device and the like.