Flash Lens Fresnel Collimator and Array for Uniform Illumination
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Solution Overview
Problem
Existing optical designs for flash devices, particularly in smartphones and miniature cameras, fail to provide a highly uniform light output and color temperature while maintaining a compact form factor, which is essential for effective flash photography.
Innovation Solution
A flash device comprising a light source, a Fresnel lens, and a lens array with optical elements arranged on a substrate, where the Fresnel lens collimates light and the lens array mixes the collimated light to produce a uniform color temperature and illuminance distribution, matching the aspect ratio and shape of the imaging sensor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a Fresnel lens is used to collimate light from LED flash, then the light directionality is improved, but the uniformity of light output deteriorates
Solution Approach 1:
The optical system is divided into two distinct functional components: a Fresnel lens for collimation and a lens array for uniformity. The lens array consists of multiple discrete optical elements (lenslets) that segment the collimated light into multiple sub-beams, which are then overlaid to create uniform illumination. This segmentation resolves the contradiction by separating the directionality function from the uniformity function.
Solution Approach 2:
The patent combines the Fresnel lens and lens array into an integrated optical system where the output of one becomes the input of the other. The collimated light from the Fresnel lens is merged with the light-shaping function of the lens array, creating a unified optical path that achieves both directionality and uniformity simultaneously.
2Volume of moving object
If the optical system is made compact to fit in smartphones, then the form factor is improved, but the light mixing capability deteriorates
Solution Approach 1:
The lens array is positioned in a plane perpendicular to the optical axis, creating a two-dimensional array of lenslets that process light in the transverse dimension. This dimensional approach allows compact packaging while maintaining effective light mixing, as the lenslets work in parallel to achieve uniformity without requiring long propagation distances.
Solution Approach 2:
The optical elements of the lens array are arranged in a compact, nested configuration on a substrate, with each lenslet occupying a specific position in the array. This nested arrangement maximizes the use of available space while maintaining the optical functionality, allowing the entire system to fit within the constrained volume of a smartphone.
3Illumination intensity
If multiple LEDs are used as light source, then the brightness is improved, but the uniformity of color temperature deteriorates
Solution Approach 1:
The lens array segments the light from multiple LEDs into separate beams that are spatially distributed. By carefully designing the lenslet positions and focal lengths, the system creates overlapping illumination patterns that mix the light from different LEDs, thereby uniformizing the color temperature across the illuminated area while maintaining high brightness.
Solution Approach 2:
The lens array acts as an intermediary between multiple LEDs with different color temperatures and the final illumination field. It mediates the light from each LED by creating specific beam patterns that overlap and mix, resulting in a unified illumination with uniform color temperature. This intermediary function resolves the color temperature non-uniformity caused by multiple LEDs.
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 achieves highly uniform color temperature and illuminance distribution, enhancing image quality by ensuring the illumination spot matches the camera's field of view, resulting in improved photographic outcomes.
Implementation Method 1
a Fresnel lens, and a lens array. The Fresnel lens is disposed upstream from the light source to collimate light output by the light source
Implementation Method 2
The lens array is disposed upstream from the Fresnel lens to mix collimated light that is output from the Fresnel lens
Data Source
Figure 1A
Figure 1B~1C
Figure 2
AI summary
An apparatus is disclosed including: a light source; a Fresnel lens, and a lens array. The Fresnel lens is disposed upstream from the light source to collimate light output by the light source. The lens array is disposed upstream from the Fresnel lens to mix collimated light that is output from the Fresnel lens. The lens array includes a plurality of optical elements arranged on a substrate. Each optical element includes a respective first planar surface arranged to face towards a different respective portion of the Fresnel lens and a second convex surface arranged to face away from the Fresnel lens.