Lenslet Array for Uniform LED Irradiance Distribution
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Solution Overview
Problem
Current UV LEDs operating at 280 nanometers for fluorescence sensors have low output power, leading to sensitivity issues and a trade-off between power and uniformity in irradiance distribution, which is costly and reduces LED lifetime.
Innovation Solution
A lenslet array is used to form images of individual LEDs or optical fibers, creating a uniform irradiance distribution by matching the pitch of the lenslet array to the LED array, allowing for higher power excitation energy while maintaining uniformity without gaps in illumination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If more input electrical current is supplied to the LED junction to increase output power, then the output power increases, but the thermal load increases and LED lifetime reduces
Solution Approach 1:
The invention segments the illumination function by using an array of multiple LEDs instead of a single high-power LED. Each LED operates at a lower current level, distributing the thermal load across multiple junctions. The lenslet array further segments the light output, with each lenslet collecting light from a corresponding LED and directing it to a specific region in the illumination plane, thereby maintaining uniform irradiance while avoiding excessive thermal concentration in any single LED.
2Temperature
If the emitting area of the diode is increased to distribute thermal load, then thermal distribution improves, but current depletion occurs in regions leading to non-uniform projected spot distribution
Solution Approach 1:
The lenslet array serves as an intermediary optical element between the LED array and the illumination plane. Each lenslet acts as a mediator that collects light from its corresponding LED emitting area and focuses it to form a uniform spot in the illumination plane. This intermediary system decouples the relationship between LED emitting area size and uniformity of the projected spot, allowing large emitting areas for thermal management while maintaining uniform illumination through the optical transformation provided by the lenslets.
3Power
If larger arrays of LEDs are manufactured to increase total power, then output power increases, but maintaining spatial uniformity becomes more difficult
Solution Approach 1:
The invention scales the system by segmenting it into repeating units: each LED is paired with a corresponding lenslet, and each combination illuminates a specific region in the illumination plane. This modular segmentation allows the array size to be increased while maintaining uniformity, as each unit independently contributes to the overall uniform irradiance distribution. The lenslet pitch is matched to the LED array pitch, ensuring that as more units are added, the uniform illumination pattern scales proportionally without degradation.
4Measurement precision
If YAG lasers and photomultiplier tube detectors are used for fluorescence sensing, then detection sensitivity is achieved, but system cost increases significantly
Solution Approach 1:
The invention replaces expensive, long-lived components (YAG lasers and photomultiplier tubes) with cheaper alternatives (UV LEDs and simplified detectors). While LEDs have shorter operational lifetimes compared to lasers, their significantly lower cost makes them economically viable for applications where ultimate long-term durability is not the primary constraint. The array configuration and lenslet optics compensate for the lower individual LED power output, maintaining adequate detection sensitivity at a fraction of the cost of laser-based 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
This approach enhances the sensitivity of fluorescence sensing by providing a uniform and repeatable signal, reducing the need for costly lasers and extending LED lifetime by optimizing power distribution without compromising uniformity.
Implementation Method 1
Each of the lenslets is configured to focus the one or more rays of light and transmit the focused rays of light
Implementation Method 2
one or more light emitting diodes (LEDs) arranged in one or more rows and columns of an LED array, each LED being configured to emit one or more rays of light
Data Source
AI summary
An apparatus and method for producing a spatially uniform irradiance in an image plane are provided. The apparatus includes an array of light emitting diodes (LEDs) which generate light (i.e., an image). The apparatus combines the outputs of an array of the LEDs in such a way as to produce a spatially uniform irradiance in an image plane some distance away. The apparatus includes an array of lenslets to form images of the emitting areas of the individual LEDs. The lenslets have a magnification, size and spacing such that the images produced by the respective LEDs are adjacent to one another and not overlapping. The irradiance distribution in the image plane is equivalent to an image of an LED whose emitting area is equal to the total area of the LED array, and whose total power is equal to the total power of the LEDs in the LED array.