Segmented Illumination Synchronization for High Frame Rate Imaging
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Solution Overview
Problem
In actively illuminated imaging systems, synchronizing the illumination of all photodetector elements with the image sensing period is challenging, especially at high frame rates, leading to image distortion and inefficiency in light usage due to the need to balance sensitivity, frame rate, and eye safety constraints.
Innovation Solution
The system synchronizes the illumination of a segmented scene with the image sensing period by dividing the scene into portions and illuminating them sequentially based on the imager's active collection periods, using multiple light sources to create a uniform irradiance pattern that redistributes intensity from the center to the periphery, optimizing sensitivity and reducing light emission during non-detection periods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the illumination is synchronized with the image sensing period for all photodetector elements, then the image sensor sensitivity is maximized, but the device complexity increases due to the need for precise timing control and segmentation
Solution Approach 1:
The scene is divided into multiple segments corresponding to different photodetector elements or groups. Each segment is illuminated independently and synchronously with its corresponding photodetector's active sensing period. This segmentation allows precise timing control for each detector element, maximizing sensitivity without requiring complex global illumination control for the entire array simultaneously.
Solution Approach 2:
The illumination sources are activated in periodic pulses that correspond to the active sensing periods of the photodetector elements. Each photodetector element has a specific integration time window during which it collects photons, and the illumination is provided periodically during these windows. This periodic synchronization ensures maximum photon collection efficiency while maintaining manageable control complexity through rhythmic, predictable timing patterns.
2Productivity
If the frame rate is increased, then the productivity is improved, but the illumination synchronization becomes more difficult and image distortion increases
Solution Approach 1:
By segmenting the scene and corresponding photodetector elements, the system can handle high frame rates more effectively. Each segment's illumination and sensing are synchronized independently, allowing the system to process multiple segments in quick succession. This reduces the timing constraints on any single segment, enabling higher overall frame rates while maintaining synchronization accuracy and minimizing distortion within each segment.
Solution Approach 2:
The illumination timing and duration are dynamically adjusted for each segment based on its specific sensing window and the overall frame rate requirements. This dynamic control allows the system to optimize the illumination pulse width and timing for each segment, ensuring proper synchronization even at high frame rates where fixed timing schemes would fail and cause distortion.
3Measurement precision
If the irradiance of illumination sources is increased to overpower ambient lighting, then the sensitivity is improved, but eye safety constraints are violated
Solution Approach 1:
Instead of using continuous high-intensity illumination that would exceed eye safety limits, the system uses periodic pulsed illumination synchronized with the photodetector sensing windows. The illumination is delivered in short bursts only when needed for detection, reducing the total energy exposure to safe levels while maintaining high peak intensity during the pulse to ensure adequate sensitivity for overpowering ambient lighting during the brief sensing period.
Solution Approach 2:
The illumination is provided precisely when the photodetector elements are actively sensing, before the integration window closes. This timing ensures that the full benefit of the illumination pulse is captured during the sensing period, maximizing detection sensitivity without requiring excessive total energy. The preliminary timing of illumination relative to the sensing window allows efficient use of minimal light energy.
4Measurement precision
If the detector area is increased to improve sensitivity, then the measurement precision is improved, but the cost increases
Solution Approach 1:
The system segments the detection task across multiple smaller photodetector elements rather than using a single large detector. Each element has its own synchronized illumination source or shares illumination in a coordinated manner. This segmentation achieves the required total sensitivity by combining the output of multiple elements, avoiding the need for a single large-area detector that would be more expensive. The segmented approach maintains cost-effectiveness while achieving the necessary sensitivity through coordinated operation of multiple standard-sized detectors.
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 maximizes image sensor sensitivity, reduces light requirements, enhances eye safety, and improves signal-to-noise ratio while maintaining high frame rates without modifying the imager chip, making it suitable for applications like automotive imaging and security systems.
Implementation Method 1
A first light source transmits light to a first segment of the segmented lens to illuminate the first scene portion, and a second light source transmits light to a second segment of the segmented lens to illuminate the second scene portion
Implementation Method 2
The first scene portion is illuminated when an imager is actively collecting photogenerated charge from the first scene portion
Data Source
AI summary
In an actively illuminated imaging system, illumination of a segmented scene is synchronized with an image sensing period. A scene is segmented into a plurality of scene portions utilizing a segmented lens. In an aspect, a first scene portion is illuminated when an imager is actively collecting photogenerated charge from the first scene portion, and a second scene portion is illuminated when an imager is actively collecting photogenerated charge from the second scene portion. The sensitivity of an image sensor is maximized, while simultaneously minimizing the amount of light that must be supplied to illuminate a scene. An irradiance pattern is varied allowing a more uniform distribution of light. Bands of varying wavelength, polarization, and light intensity may be variously applied to illuminate individual scene segments, as needed to enhance an identification of an object in the scene. The present invention is particularly useful with high frame rate imaging systems.