Infrared Imaging Assembly With Region-Based Pulse Exposure Control
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Solution Overview
Problem
Existing depth map generation techniques using uniform infrared illumination result in inaccurate depth maps due to variations in scene brightness and object distances, particularly when using segmented IR emitters, which can degrade phase detection accuracy.
Innovation Solution
An infrared imaging assembly with individually addressable LEDs and a pulse train adjusting unit that analyzes preliminary images to adjust illumination levels for each scene region, ensuring optimal exposure through switching pulse trains, thereby improving depth map accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the current of an array segment is increased to increase illumination of a corresponding scene region, then the illumination intensity is improved, but the waveform alteration decreases the accuracy of phase detection
Solution Approach 1:
The patent applies periodic switching pulse trains to control the illumination of scene regions. By using periodic pulsed illumination instead of continuous or variable current illumination, the system maintains consistent waveform characteristics for phase detection while achieving variable exposure through pulse duration control. This resolves the contradiction by decoupling illumination intensity control from waveform distortion.
Solution Approach 2:
The patent changes the parameter being controlled from current amplitude to pulse duration (duty cycle). By adjusting the duration of switching pulse trains rather than the current magnitude, the system achieves variable illumination intensity without altering the waveform shape or frequency, thereby maintaining phase detection accuracy while controlling exposure levels.
2Device complexity
If uniform infrared light is directed at the scene, then the device complexity is reduced, but the depth map accuracy deteriorates due to varying scene brightness and object distances
Solution Approach 1:
The patent segments the scene into multiple regions, each illuminated by a specific IR-LED. This allows independent control of illumination for each scene region, enabling optimized exposure for different distances and brightness conditions without requiring a completely different uniform illumination system. The segmentation approach maintains relative simplicity while achieving variable illumination control.
Solution Approach 2:
The patent applies local quality control by assigning different exposure levels to different scene regions based on their specific requirements. Each scene region receives customized illumination through its corresponding IR-LED with adjusted pulse train parameters, ensuring optimal exposure locally rather than applying a single uniform illumination level across the entire scene.
3Manufacturing precision
If switching pulse trains with adjusted parameters are applied to control illumination, then the exposure accuracy is improved, but the device complexity increases due to additional control mechanisms
Solution Approach 1:
The patent implements feedback control by analyzing a preliminary infrared image to determine required exposure levels for different scene regions, then using this information to adjust the switching pulse train parameters for subsequent imaging. This feedback mechanism enables automatic exposure optimization without requiring complex manual control systems or additional hardware components.
Solution Approach 2:
The system performs self-adjustment by automatically analyzing the preliminary image and determining the appropriate pulse train parameters for each scene region. The driver circuitry self-configures the illumination parameters based on the exposure requirements identified in the preliminary image, eliminating the need for external complex control systems.
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
The solution enables the generation of accurately exposed infrared images, leading to more precise depth maps that are less affected by stray light, enhancing applications like face recognition and autonomous vehicles.
Implementation Method 1
an image of the illuminated scene is captured by an infrared-sensitive sensor array
Implementation Method 2
an array of individually addressable semiconductor light sources such as vertical-cavity surface-emitting lasers (VCSELs) or light-emitting diodes (LEDs) that emit in the near-infrared range
Implementation Method 3
The accuracy of the depth map will depend (among others) on how well the scene is illuminated. A scene including bright and dark objects as well as near and remote objects may result in an inaccurate depth map if the light directed at the scene is uniform
Data Source
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AI summary
The invention describes an infrared imaging assembly (1) for capturing an infrared image (M0, M1) of a scene (S), comprising an infrared-sensitive image sensor (14); an irradiator (10) comprising an array of individually addressable infrared-emitting LEDs, wherein each infrared-emitting LED is arranged to illuminate a scene region (S1,..., S9); a driver (11) configured to actuate the infrared irradiator (10) by applying a switching pulse train (T1,..., T9) to each infrared-emitting LED; an image analysis module (13) configured to analyse a preliminary infrared image (M0) to determine the required exposure levels (130) for each of a plurality of image regions (R1,..., R9); and a pulse train adjusting unit (12) configured to adjust the duration (L1,..., L9) of a switching pulse train (T1,..., T9) according to the required exposure levels (130). The invention also described a method of generating a depth map (D) for a scene (S); a depth map generator comprising an embodiment of the inventive infrared imaging assembly (1); and a camera comprising such a depth map generator (2).