Pico-projector Lens Array Height Reduction
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Solution Overview
Problem
Conventional projection lenses for pico-projectors face challenges in reducing the height and full length while maintaining high performance, as the reduction of lens array elements is limited by the constraints of lens diameter and back focus length.
Innovation Solution
A projection lens unit for pico-projectors is designed with a 6-lens array, where the 1st lens acts as an aperture stop, and the lenses are arranged with specific refractive powers and focal distances to minimize height and full length, using aspherical lenses and a doublet lens configuration to reduce distortion and chromatic aberration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the lens array is reduced in size to fit pico-projector requirements, then the full length and height are reduced, but the number of lenses must be increased to maintain optical performance
Solution Approach 1:
The patent combines multiple lens functions into fewer lens elements. Specifically, the first lens integrates both aperture stop and field lens functions, and the third and fourth lenses form a doublet configuration that handles multiple optical corrections simultaneously. This merging approach reduces the total lens count from 7 to 6 elements while maintaining optical performance in the compact 13mm form factor.
Solution Approach 2:
Lens elements are designed to perform multiple functions. The first lens serves dual purposes as both aperture stop and field lens, while the doublet configuration of the third and fourth lenses provides both focusing and aberration correction capabilities. This multi-functionality allows the reduced lens array to maintain high optical performance despite having fewer elements.
2Weight of stationary object
If the lens diameter is reduced to decrease height, then the lens array becomes more compact, but optical performance and aberration control become more difficult
Solution Approach 1:
The patent employs aspherical lens surfaces to correct optical aberrations in the compact lens design. The aspherical shapes enable precise control of light paths despite the reduced lens diameter and tight spacing, maintaining high optical performance and minimizing distortion and chromatic aberration in the shortened optical path.
Solution Approach 2:
The patent optimizes specific optical parameters including the refractive powers and focal distances of each lens element. The carefully selected parameter combinations (positive powers for lenses 1, 2, 4, 5, 6 and negative power for lens 3, with specific focal distance relationships) enable effective aberration control and high optical performance within the constrained compact geometry.
3Length of moving object
If the number of lenses is decreased to reduce full length, then the lens array becomes more compact, but aberration control and image quality may deteriorate
Solution Approach 1:
The patent segments the optical system into functional groups: the first lens handles aperture and field control, the second lens provides additional positive power, the third and fourth lenses form a doublet for aberration correction, and the fifth and sixth lenses complete the focusing system. This strategic segmentation allows six lenses to perform the work that would traditionally require seven or more separate elements.
Solution Approach 2:
The patent uses a composite lens configuration where the third and fourth lenses form a doublet, combining different refractive power elements (negative and positive) in close proximity. This composite arrangement enables sophisticated aberration control and image quality optimization within the reduced lens count, maintaining high reliability despite the compact six-element design.
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 reduces the height and full length of the lens unit while maintaining high performance by optimizing the arrangement of lenses and their refractive powers, achieving a full length of 13 mm or less and minimizing aberrations, thus enhancing the compactness and functionality of pico-projectors.
Implementation Method 1
the 1st lens includes a stop side formed on a 1st side of the 1st lens, the stop side stops the passage of light, thereby performing the function of an aperture stop
Implementation Method 2
the 1st lens has a positive (+) refractive power, the 2nd lens has the positive (+) refractive power, the 3rd lens has a negative (−) refractive power
Data Source
AI summary
There is provided a projection lens unit for a pico-projector which comprises a lens array, a color composition prism, a cover glass and an image panel, the projection lens unit characterized in that: the lens array includes 1st to 6th lenses sequentially arrayed from a screen on which an image is projected, the 1st lens includes a stop side formed on a 1st side of the 1st lens, the stop side stops the passage of light, to perform the function of a diaphragm aperture, light passing from the 1st lens to the 6th lens travels in only one direction of the lens sides based on the diaphragm aperture, and parts of the lens sides through which the light does not pass are cut so that the whole height of the lens array is reduced.