SPAD Light Sensing Module Blind Zone Elimination
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Solution Overview
Problem
Conventional single photon avalanche diode (SPAD) light sensing modules suffer from blind zones due to peripheral circuits, leading to inefficient light collection and discontinuous sensing ranges, as reflected light is wasted and cannot be sensed, resulting in inaccurate distance measurement and environmental misjudgment.
Innovation Solution
A light sensing module incorporating a SPAD array substrate with a distance increasing layer and a light converging element array, where the light converging elements cover both the light sensing units and part of the circuit region, effectively redirecting reflected light onto the sensing units and minimizing irradiation onto the peripheral circuits, thereby eliminating blind zones and enhancing light collection efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a SPAD array substrate with peripheral circuits is used for light sensing, then the sensing function is achieved, but blind zones are formed in the external space due to light being blocked by the peripheral circuits
Solution Approach 1:
The patent introduces a distance increasing layer between the light sensing unit and the SPAD array substrate, effectively adding a depth dimension to the optical path. This allows light to travel a longer distance before reaching the sensing unit, enabling the light converging element to properly focus light from external space onto the sensing unit while avoiding the peripheral circuits, thus eliminating blind zones without changing the lateral arrangement of components
Solution Approach 2:
The patent introduces a light converging element as an intermediary optical component that mediates between the external light source and the light sensing unit. This intermediary element collects and converges light from external space, directing it precisely onto the light sensing unit while preventing light from reaching the peripheral circuits, thereby resolving the blind zone problem caused by the peripheral circuits blocking light paths
2Reliability
If the peripheral circuit width is reduced to minimize blind zones, then sensing coverage improves, but the circuit functionality and signal processing capability are compromised
Solution Approach 1:
The patent segments the optical path into distinct functional zones: a light collection region by the light converging element, a distance increasing layer, and a light sensing unit region. This segmentation allows the peripheral circuits to be positioned in a separate circuit region that does not interfere with the optimized optical path, enabling independent optimization of both circuit functionality and sensing coverage without compromising either
Solution Approach 2:
By introducing the distance increasing layer, the patent separates the optical function (light collection and sensing) from the electrical function (circuit processing) in the depth dimension. This vertical separation allows the peripheral circuits to maintain their required width and complexity for proper signal processing while the optical path is optimized above them, eliminating the need to reduce circuit width at the expense of functionality
3Loss of energy
If the light sensing unit area is increased to improve light collection, then the ratio of sensing area to circuit area decreases, but the overall module size increases
Solution Approach 1:
The light converging element acts as an intermediary that increases the effective light collection area without proportionally increasing the module size. By collecting light over a larger angular range and converging it onto the light sensing unit, the system achieves higher light collection efficiency while maintaining a compact form factor, as the light converging element is positioned close to the sensing unit in the depth dimension rather than laterally
Solution Approach 2:
The patent utilizes the depth dimension (vertical direction) to achieve light convergence rather than expanding the lateral area of the light sensing unit. The distance increasing layer and light converging element work together in the vertical dimension to focus light from a larger effective area onto the sensing unit, improving light collection efficiency without proportionally increasing the overall module footprint
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 effectively avoids blind zones and improves light collection efficiency, enabling continuous and accurate distance measurement by ensuring that reflected light is directed towards the sensing units, reducing misjudgment in environmental assessments.
Implementation Method 1
The reflected light from the outside is converged by the light converging elements on the light sensing units
Implementation Method 2
In LiDAR sensors or time-of-flight ranging sensors, there is a technology that uses a single photon avalanche diode (SPAD) array substrate to measure the flight time of light
Data Source
AI summary
A light sensing module including a photodiode array substrate, a distance increasing layer, and a light converging element array is provided. The photodiode array substrate includes a plurality of light sensing units arranged in an array and a circuit region. The circuit region is disposed on the periphery of the light sensing units. Each of the light sensing units includes a plurality of adjacent photodiodes arranged in an array. The distance increasing layer is disposed on the photodiode array substrate. The light converging element array is disposed on the distance increasing layer, and includes a plurality of light converging units arranged in an array. Reflected light from an outside is converged by the light converging elements on the light sensing units, respectively.