Image Sensor Detecting Blinking Light Sources via Interlaced Sub-Periods
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Solution Overview
Problem
Conventional high dynamic range image sensors struggle to reliably detect blinking light sources due to their limited ability to capture the full illumination range, especially when the blinking frequency matches or exceeds the sensor's acquisition frequency, leading to missed detection of light sources with low on-state periods and potential saturation during longer exposure times.
Innovation Solution
The proposed solution involves an image sensor design with multiple photodiodes and capacitive elements, where the integration periods are divided into sub-periods that are interlaced and distributed across a longer period, allowing for more consistent measurement and increased chances of detecting blinking light sources by ensuring that at least part of the integration periods coincide with the light source's on phase, even in high ambient luminosity conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the sensor uses a single long integration period to capture dark areas, then the dynamic range is improved, but blinking light sources are missed or incorrectly detected
Solution Approach 1:
The patent divides the integration period into multiple segments (first integration period and second integration period with sub-periods) to simultaneously capture both dark and bright areas. This segmentation allows the sensor to record blinking light sources during specific sub-periods while maintaining long exposure capability for dark areas through the first integration period.
Solution Approach 2:
The patent implements periodic sampling through multiple integration periods, where the second integration period is divided into multiple sub-periods that periodically sample the scene. This periodic action increases the probability of capturing blinking light sources at their active states while the first integration period provides continuous long-exposure capture.
2Illumination intensity
If the sensor uses multiple integration periods to capture high dynamic range, then the illumination range is improved, but the acquisition time increases
Solution Approach 1:
The first integration period performs preliminary capture of the dark areas and ambient illumination before the second integration period samples the bright areas and blinking light sources. This preliminary action allows the sensor to prepare the first image data early, reducing the effective acquisition time by overlapping operations.
Solution Approach 2:
The patent dynamically adjusts the integration strategy by using a first continuous integration period followed by a second integration period with multiple sub-periods. This dynamic approach adapts to different scene conditions, allowing flexible capture of both static and transient illumination elements without requiring excessive total acquisition time.
3Reliability
If the sensor uses a short integration period to detect blinking light sources, then the detection reliability is improved, but the dynamic range capability is reduced
Solution Approach 1:
The patent merges the results of the first integration period (capturing dark areas with long exposure) and the second integration period with sub-periods (capturing bright areas and blinking sources). By combining these complementary measurements, the sensor achieves both high dynamic range capability and reliable blinking light source detection within a unified acquisition framework.
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 design enhances the reliability of detecting blinking light sources by ensuring that part of the light emitted during the acquisition phase is captured, improving the dynamic range and reducing the likelihood of saturation, thereby providing a more accurate representation of the scene's illumination levels.
Implementation Method 1
each comprising a photodiode and a control circuit capable of delivering an output signal representative of the illumination level received by its photodiode
Data Source
AI summary
An image sensor including: a plurality of pixels each including a photodiode coupled to first and second capacitive elements by first and second transistors; a control circuit provided to acquire, for each pixel, a first and second value V_S and V_M representative of illumination levels of the photodiode during the first second periods, the first period being divided into a plurality of first sub-periods and the second period being divided into a plurality of second sub-periods, the first and second sub-periods sub-periods being interlaced; and a sum circuit capable of calculating, for each pixel, a value V_MS=C_S*V_S+C_M*V_M, C_S et C_M being first and second coefficients such that values C_S*V_S and C_M*V_M are substantially equal when the illumination of the photodiode is continuous.