Imaging Sensor Double Bandpass Filter Infrared Control
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Solution Overview
Problem
In imaging devices using double bandpass filters, infrared light passing through the second wavelength band affects color reproduction, making it difficult to achieve color reproducibility equivalent to that with an infrared cut filter.
Innovation Solution
An imaging sensor with a filter array that includes multiple filter regions with different spectral transmission characteristics, allowing for the removal of infrared components from visible light images, similar to an infrared cut filter, by using an optical filter with a transmission characteristic in the visible-light band and a second wavelength band on the infrared side, which blocks light between the visible and infrared bands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a double bandpass filter is used to enable both visible light and infrared light photography, then the imaging device can perform both types of photography without manual filter attachment/detachment, but infrared light passes through the second wavelength band and affects color reproduction in visible light images
Solution Approach 1:
The imaging sensor is divided into two distinct types of pixels: first type pixels for visible light photography and second type pixels for infrared light photography. This segmentation allows each pixel type to be optimized for its specific function, with the visible light pixels using a color filter array for accurate color reproduction and infrared pixels using a different filter configuration for infrared detection, thereby resolving the color reproduction issue while maintaining dual photography capability
Solution Approach 2:
A microlens array is introduced as an intermediary component positioned between the optical system and the imaging sensor. The microlenses are configured to direct visible light primarily to first type pixels and infrared light primarily to second type pixels, acting as a spatial mediator that separates the light paths before they reach the sensor, thus preventing infrared light from contaminating visible light images while enabling both photography modes
2Manufacturing precision
If an infrared cut filter is used to block infrared light and improve color reproduction, then color accuracy is enhanced, but the imaging device cannot perform infrared light photography without manual filter removal
Solution Approach 1:
The imaging sensor employs a dynamic pixel configuration where each pixel can be electronically configured to function as either a visible light pixel or an infrared pixel based on operational requirements. This dynamic adaptability eliminates the need for manual filter attachment/detachment, as the sensor itself can switch between modes by activating different pixel types, thereby maintaining both color accuracy and operational convenience
Solution Approach 2:
The imaging sensor is designed with universal pixels that can perform multiple functions - the same physical pixel structure can detect both visible light and infrared light depending on which filter configuration is active. This multi-functionality allows the device to switch between visible light and infrared photography modes without requiring separate hardware components or manual filter changes, resolving the contradiction between color accuracy and operational ease
3Loss of information
If a color filter with red, green, and blue regions is used for color photography, then color information is captured, but infrared light passing through these filters increases electron generation and degrades image quality
Solution Approach 1:
The color filter array is segmented into distinct regions: color filter regions (red, green, blue) for visible light pixels and a separate infrared cut filter region for infrared pixels. This spatial segmentation ensures that infrared light is blocked at the filter level before reaching visible light pixels, preventing the harmful effect of increased electron generation while preserving color information capture in dedicated color pixels
Solution Approach 2:
The infrared transmission characteristic is extracted and assigned exclusively to second type pixels, while first type pixels are given the property of infrared blocking through their color filter configuration. This extraction of the infrared function to a separate pixel type eliminates infrared interference from visible light images while maintaining color photography capability in the first type pixels
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 enables improved color reproducibility by controlling the influence of infrared light in visible light images, allowing for both visible and infrared photography with enhanced color accuracy.
Implementation Method 1
each of the plurality of kinds of filter regions has an infrared-light transmission wavelength band, which passes light, on a long-wavelength side of the visible-light band and has a light-blocking wavelength band, which blocks light, between the visible-light band and the infrared-light transmission wavelength band
Implementation Method 2
an imaging sensor main body in which a light-receiving element is arranged in each pixel
Data Source
AI summary
An imaging sensor includes a color filter, and DBPF that has a transmission characteristic in a visible-light band, a blocking characteristic in a first wavelength band adjacent to a long-wavelength side of the visible-light band, and a transmission characteristic in a second wavelength band that is a part of the first wavelength band. A transmission characteristic of DBPF and a transmission characteristic of each filter part of the color filter are set in such a manner that the second wavelength band of DBPF is included in a third wavelength band that is a wavelength band in which transmittance of the filter parts in colors is approximate to each other on a long-wavelength side of the visible-light band and a fourth wavelength band that is a wavelength band in which a filter part for infrared light has a transmission characteristic.