Per-Pixel Coded Exposure for Image Sensor Dynamic Range Extension
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Solution Overview
Problem
Conventional image sensors have a limited dynamic range, allowing them to capture either bright or dark scenes but not both simultaneously, and existing high-dynamic-range (HDR) techniques often introduce additional complexity, reduce image resolution, or suffer from optical distortion.
Innovation Solution
The method and system employ per-pixel coding of pixel parameters, such as exposure time and signal gain, using coded-exposure pixels and coded-gain pixels to extend the dynamic range by programmably controlling each pixel's exposure time and gain, allowing for arbitrary temporal codes to be applied to each pixel or group of pixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional image sensors are used, then the device structure is simple, but the dynamic range is limited and cannot capture both bright and dark scenes simultaneously
Solution Approach 1:
The image sensor array is divided into multiple independently controllable pixel groups, where each group can be assigned different exposure times or signal gains through per-pixel coding. This segmentation allows simultaneous capture of bright and dark scenes with different illumination requirements, extending the overall dynamic range without requiring complex external optical devices
Solution Approach 2:
The patent implements dynamic control of pixel parameters by providing different pixel codes to different pixel groups for each subframe. The exposure time and signal gain are made programmably adjustable and can be changed adaptively between subframes based on scene requirements, enabling the sensor to dynamically optimize performance across varying illumination conditions
2Illumination intensity
If existing HDR techniques are used, then the dynamic range is extended, but additional complexity is introduced or image resolution is reduced
Solution Approach 1:
The patent achieves HDR functionality using the existing photodetector array and readout circuitry by implementing per-pixel coding control. The same hardware infrastructure is made multi-functional through software/control-based differentiation of pixel parameters, eliminating the need for additional dedicated HDR hardware components and maintaining system simplicity
Solution Approach 2:
Instead of changing hardware configuration, the patent extends dynamic range by changing operational parameters (exposure time, signal gain) of existing pixels through coded control signals. This parameter-based approach allows flexible HDR implementation without physical modifications to the sensor structure, avoiding additional complexity
3Illumination intensity
If existing HDR techniques are used, then the dynamic range is extended, but optical distortion occurs
Solution Approach 1:
The patent removes the need for external optical devices (such as beam splitters, mirrors, or variable focus lenses) that are typically used in HDR systems. By extracting the HDR functionality from the optical domain and implementing it at the pixel control level through coding, the system eliminates sources of optical distortion while maintaining dynamic range extension capability
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 extends the image sensor's dynamic range, enabling the capture of both bright and dark scenes in a single frame with improved signal-to-noise ratio and reduced noise, while maintaining a compact and cost-effective design without external optical devices.
Implementation Method 1
a photodetector array to convert an incoming light signal into a photo-generated electronic signal
Data Source
AI summary
There is provided a method and system for extending image sensor dynamic range using coded pixels. The method including: providing pixel codes to pixels in the photodetector array for each subframe of a frame; receiving a sensor readout of each of the pixels in the photodetector array for each subframe; for each subframe, based on the pixel code, routing each sensor readout value for collection at one or more taps or to a drain; combining the collected sensor readout values at each of the taps to determine a single pixel value for the frame; and outputting the single pixel value for each pixel for the frame.