Solid-State Imaging Device Using Photochromic White Pixels
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Solution Overview
Problem
Existing solid-state imaging devices face challenges in expanding their dynamic range without introducing unnatural image effects, particularly due to time lags in moving and continuous imaging, and materials-based solutions face issues with wavelength-dependent transmittance and slow photochromic reaction rates.
Innovation Solution
The use of a photochromic material with a half period shorter than one frame in white pixels, integrated into a solid-state imaging device, allows for dynamic range expansion without unnatural image generation, utilizing a hexaarylbisimidazole derivative photochromic film that rapidly changes transmittance in response to light intensity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If photochromic materials are used to expand dynamic range, then the dynamic range is improved, but time lags occur during moving picture imaging and continuous imaging
Solution Approach 1:
The imaging device divides pixels into multiple types (first pixels without photochromic material, second pixels with photochromic material, third pixels for reference) to handle different lighting conditions separately. This segmentation allows the system to process images without time lags by using appropriate pixel types for different scenes, resolving the contradiction between dynamic range expansion and time lag elimination.
Solution Approach 2:
Photochromic material is applied selectively to only certain pixels (second pixels) rather than all pixels, creating local quality differences. This allows the patent to expand dynamic range in specific regions while maintaining fast response in other regions, thus resolving the time lag issue in moving picture imaging.
2Adaptability or versatility
If mechanical shutters are used to control light exposure, then the dynamic range is improved, but time lags occur depending on positions
Solution Approach 1:
The patent replaces mechanical shutters with a photochromic material-based optical system. The photochromic material changes transmittance in response to light intensity, eliminating mechanical moving parts and their associated position-dependent time lags, thus resolving the contradiction between dynamic range expansion and time lag elimination.
3Adaptability or versatility
If photochromic materials are used for dynamic range expansion, then the dynamic range is improved, but the photochromic reaction rate is too slow to satisfy signal processing speed requirements
Solution Approach 1:
The patent segments the pixel array into multiple types with different characteristics. First pixels provide fast response for normal imaging, while second pixels with photochromic material provide extended dynamic range for bright conditions. This segmentation allows the system to achieve both fast reaction rates and expanded dynamic range by using appropriate pixel types for different lighting conditions.
Solution Approach 2:
The patent applies photochromic material to only a portion of pixels (second pixels) rather than all pixels, using partial action. This reduces the overall time lag impact while still providing dynamic range expansion where needed, resolving the contradiction between reaction rate and dynamic range.
4Adaptability or versatility
If photochromic materials are used to expand dynamic range, then the dynamic range is improved, but transmittance becomes wavelength dependent
Solution Approach 1:
The patent creates local quality differences by applying photochromic material selectively to second pixels while leaving first pixels without the material. This allows different parts of the image sensor to have different spectral characteristics, enabling the system to handle wavelength-dependent transmittance by using appropriate pixel types for different wavelength regions.
Solution Approach 2:
The patent changes the optical parameters (transmittance characteristics) of specific pixels by applying photochromic material, creating a heterogeneous pixel array with varying spectral responses. This parameter change allows the system to expand dynamic range while managing wavelength dependence through selective pixel usage.
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 effectively expands the dynamic range of the imaging device by adjusting light transmittance based on incident light intensity, preventing saturation and enhancing image quality without introducing time lags or unnatural effects.
Implementation Method 1
a photochromic film 23 which contains a photochromic material and has a light transmittance varying in response to incident light intensity in a predetermined wavelength region
Implementation Method 2
the light entering the sensor part is photoelectrically converted by the photodiode, the incident light is converted into electric charge
Data Source
Figure 1A~1C
Figure 2A~2B
Figure 3A~3B
AI summary
A solid-state imaging device includes: a semiconductor substrate having a light receiving surface sectioned for red, green, blue, and white pixels arranged in a matrix with photodiodes formed thereon; color filters formed on the semiconductor substrate in light incident paths to the photodiodes of the respective formation regions of the red, green, and blue pixels and respectively transmitting lights in red, green, and blue wavelength regions; and photochromic films formed on the semiconductor substrate in the light incident path to the photodiodes in the formation regions of at least some of the white pixels, and containing a photochromic material having light transmittance varying in response to incident light intensity in a predetermined wavelength region, wherein a half period of the light transmittance of the photochromic films is shorter than one frame as a period in which pixel signals obtained in the pixels are read out with respect to all pixels.