Light-Emitting Array Layout for Low-Inductance Optical Sensing
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Solution Overview
Problem
In light-emitting device configurations, it is challenging to bring a drive unit and a light-emitting element array close to each other when circuit elements of different sizes are involved, leading to increased inductance and difficulty in optimizing the placement of light diffusing and temperature detecting elements.
Innovation Solution
A light-emitting device structure is implemented with a wiring substrate, a base member, a light-emitting element array, a drive unit, and circuit elements where the light diffusing member overlaps the light-emitting and receiving elements, and temperature detecting elements are strategically positioned to reduce inductance and enhance light distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a larger circuit element is disposed at the side close to the drive unit, then the circuit element can be properly positioned, but it becomes difficult to bring the drive unit and the light-emitting element array close to each other, increasing inductance
Solution Approach 1:
The patent transitions from a two-dimensional planar arrangement to a three-dimensional stacked configuration. Circuit elements are disposed on both the upper and lower surfaces of the base member, allowing the light receiving element to be positioned close to the light-emitting element array vertically while the drive unit remains accessible on the lower surface. This vertical stacking resolves the contradiction by utilizing the third dimension to accommodate both requirements simultaneously.
2Reliability
If circuit elements are disposed on both sides of the light-emitting element array, then inductance is reduced and light reception is improved, but the device complexity increases
Solution Approach 1:
The base member serves multiple functions: it provides mechanical support, electrical insulation, thermal management, and a mounting platform for circuit elements on both surfaces. The light receiving element on the upper surface performs both light detection and serves as a reference for alignment. This multi-functionality reduces device complexity by consolidating multiple roles into existing components rather than adding separate dedicated structures.
3Length of moving object
If the light diffusing member is made smaller to improve alignment, then the drive unit and light-emitting element array can be brought closer, but the light distribution efficiency decreases
Solution Approach 1:
The light diffusing member acts as an intermediary optical element positioned between the light-emitting element array and the light receiving element. It has a specific refractive index and thickness designed to diffuse light effectively while maintaining a compact form factor. The light receiving element's position on the upper surface allows it to capture diffused light efficiently even with a smaller diffusing member, resolving the contradiction between size and efficiency.
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 configuration allows for easier alignment of the drive unit and light-emitting element array, increases the light reception by the light receiving element, and reduces the size of the light diffusing member while maintaining efficient heat dissipation and high-intensity light emission.
Implementation Method 1
a light diffusing member that diffuses light emitted from the light-emitting element array toward an outer side
Implementation Method 2
Vertical Cavity Surface Emitting Laser (VCSEL) having a large area terminal
Implementation Method 3
a thermoelectric element that heats or cools the laser diode device
Implementation Method 4
a light receiving element and a temperature detecting element may need to be disposed close to the side surfaces
Data Source
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AI summary
A light-emitting device includes a wiring substrate, a base member provided on the wiring substrate, a light-emitting element array that has a first side surface and a second side surface facing each other, that has a third side surface and a fourth side surface facing each other and connecting the first side surface and the second side surface, and that is provided on the base member, a drive unit that is provided on the wiring substrate at a side of the first side surface and drives the light-emitting element array, a first circuit element that is provided on the base member at the side of the first side surface, a second circuit element that is provided on the base member at a side of the second side surface and has a larger occupation area on the base member than the first circuit element, and wiring members that are provided at a side of the third side surface and at a side of the fourth side surface and extend from an upper surface electrode of the light-emitting element array toward an outer side of the light-emitting element array.