ToF Ranging Module Layout for Light Leakage Suppression
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Solution Overview
Problem
Conventional ranging modules using the time of flight (ToF) method suffer from irradiation light leakage to the light receiving side due to gaps formed to prevent thermal expansion of the light blocking wall from affecting the substrate, which compromises sensing performance.
Innovation Solution
A ranging module design with a sensor chip featuring first and second pixel regions, a light blocking wall, and a support substrate with openings to guide reflected light, reducing light leakage by ensuring the light blocking wall is narrower than the pixel region distance and eliminating gaps at the light blocking wall's lower end.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a gap is formed between the light blocking wall and the substrate to prevent thermal expansion effects, then sensing performance is enhanced, but irradiation light leaks to the light receiving side through the gap
Solution Approach 1:
The patent introduces a support substrate with openings as an intermediary structure between the light blocking wall and the sensor chip. The openings guide reflected light to the pixel regions while the support substrate itself blocks direct light leakage paths, thus maintaining the gap's thermal benefits while eliminating its optical drawbacks
Solution Approach 2:
The support substrate is segmented with multiple openings (first opening for measurement pixels, second opening for reference pixel) that are spatially separated. This segmentation allows different regions of the sensor chip to receive light through dedicated pathways, preventing cross-contamination of light signals while maintaining structural integrity
2Object-generated harmful factors
If the light blocking wall is made wider to block light leakage, then light shielding improves, but reflected light may be blocked and sensing performance deteriorates
Solution Approach 1:
The light blocking wall is designed with non-uniform width characteristics - wider in regions where light blocking is needed and narrower or absent in regions where light transmission is required. The openings in the support substrate create local variations in light blocking properties, allowing simultaneous light leakage prevention and signal transmission
Solution Approach 2:
The patent moves the light blocking function from a two-dimensional planar structure to a three-dimensional configuration by introducing vertical separation between the light blocking wall and sensor chip through the support substrate. This dimensional change allows light to be blocked from certain directions while permitting transmission from other directions
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 effectively reduces irradiation light leakage, enhances sensing performance, and allows for wider short-distance measurement ranges while minimizing occlusion and calculation costs.
Implementation Method 1
a support substrate to which the sensor chip is connected, the support substrate having an opening through which the reflected light is guided to the first pixel region and the second pixel region
Implementation Method 2
a light blocking wall that is disposed between the first pixel region and the second pixel region
Implementation Method 3
the first pixels receiving reflected light of irradiation light from a light source
Data Source
AI summary
Leakage of irradiation light to the light receiving side is to be reduced in a ranging module that uses the time of flight (ToF) method. A first pixel region in which a plurality of first pixels that receive reflected light of irradiation light from a light source is provided, and a second pixel region in which a second pixel is provided between the first pixel region and the light source are formed on the light receiving surface of a sensor chip. A light blocking wall is disposed between the first pixel region and the second pixel region. The sensor chip is connected to a support substrate, and openings that guide the reflected light to the first pixel region and the second pixel region are formed in the support substrate.