Stacked Photoelectric Conversion Sections for High Sensitivity Imaging
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Solution Overview
Problem
Solid-state imaging devices, such as CCD and CMOS image sensors, face challenges in achieving high sensitivity and resolution due to reduced photon entry per pixel and color filter absorption, leading to lowered sensitivity and false color issues.
Innovation Solution
The imaging element stacks a first organic photoelectric conversion section and two inorganic photoelectric conversion sections, with the inorganic sections disposed at a narrower pitch than the organic section, allowing for selective detection and conversion of different wavelength bands without phase shift, enabling high-sensitivity mode operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pixel size is reduced to increase pixel count, then spatial resolution is improved, but sensitivity and S/N ratio are lowered due to decreased photon entry per pixel
Solution Approach 1:
The patent transitions from a two-dimensional pixel array to a three-dimensional stacked architecture with multiple photoelectric conversion sections at different depths. This vertical stacking allows each pixel position to capture multiple wavelength bands simultaneously, maintaining spatial resolution while improving sensitivity through increased light capture volume.
Solution Approach 2:
The imaging device is segmented into multiple specialized photoelectric conversion sections, each optimized for specific wavelength bands. This segmentation allows different sections to detect different colors (e.g., red, green, blue, infrared) independently, improving overall sensitivity without requiring larger pixel areas.
2Loss of information
If color filters are used for colorization, then color information is obtained, but sensitivity is lowered due to absorption of green and blue light in red pixels and other wavelength blocks
Solution Approach 1:
Instead of using color filters in the lateral dimension, the patent uses vertical stacking of multiple photoelectric conversion sections to achieve color separation. Each section is optimized for specific wavelength bands, allowing simultaneous detection of multiple colors without mutual absorption losses.
Solution Approach 2:
Different photoelectric conversion sections are designed with locally optimized characteristics for specific wavelength bands. For example, certain sections have enhanced sensitivity to red light while others are optimized for blue or green, allowing each region to perform its specialized function without interfering with other wavelength detections.
3Measurement precision
If interpolation processing is performed between pixels for color signal generation, then false color occurs, but color accuracy is compromised
Solution Approach 1:
The patent segments the detection function across multiple vertical layers, with each layer dedicated to specific wavelength bands. This allows direct measurement of color information at each pixel position without requiring interpolation, thereby eliminating false color artifacts while maintaining color accuracy.
4Reliability
If multiple photoelectric conversion sections are stacked vertically, then sensitivity is improved, but device complexity increases
Solution Approach 1:
The patent implements a nested structure where multiple photoelectric conversion sections are stacked vertically within a compact footprint. Each section is integrated into the same pixel column, allowing high sensitivity to be achieved without proportionally increasing the overall device size or lateral complexity.
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 enhances resolution and granular feeling by acquiring color signals without phase shift, improving sensitivity and reducing color noise in dark states.
Implementation Method 1
a first photoelectric conversion section and a second photoelectric conversion section that are stacked in order from light incident side and that selectively detect and photoelectrically convert light beams of different wavelength bands
Data Source
AI summary
An imaging element according to an embodiment of the present disclosure includes a first photoelectric conversion section and a second photoelectric conversion section that are stacked in order from light incident side and that selectively detect and photoelectrically convert light beams of different wavelength bands, and the second photoelectric conversion section is disposed at an interval narrower than a pixel pitch of the first photoelectric conversion section.