Zoom Lens Miniaturization via Segmented Group Movement
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Solution Overview
Problem
Current projector units using DMDs face limitations in miniaturization due to constraints on the f-number and light loss when using a DMD as a light valve, requiring a long back focal length and large lens aperture, which contradicts the goal of creating a compact and portable projector unit with high image quality.
Innovation Solution
A zoom lens configuration comprising a first lens group with positive or negative refractive power, a second lens group with negative refractive power, and a third lens group with positive refractive power, where the second and third lens groups move along the optical axis to adjust magnification, while satisfying specific conditional expressions to balance power distribution and aberration correction, thereby optimizing the optical system for miniaturization and image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a long back focal length is provided for the projection lens to capture valid light from DMD, then the f-number can be optimized for brightness, but the overall length of the projection lens increases, contradicting miniaturization goals
Solution Approach 1:
The projection lens is divided into multiple lens groups (first lens group with positive/negative refractive power, second lens group with negative refractive power, third lens group with positive refractive power). This segmentation allows each group to be optimized for specific functions: the first group captures valid light from DMD, the second group corrects aberrations, and the third group controls the back focal length, thereby reducing the overall lens length while maintaining brightness performance.
Solution Approach 2:
The patent positions the pupil of the projection lens on the light valve side at the rear of the lens rather than at the front. This dimensional repositioning of the pupil allows the optical path to be folded back, enabling a shorter overall lens length while maintaining the required back focal length for capturing valid light from the DMD.
2Manufacturing precision
If a large number of lenses are combined to improve image quality and correct aberrations, then aberration correction performance improves, but the overall length of the projection lens increases, making miniaturization difficult
Solution Approach 1:
The lens system is segmented into three functional groups with specific refractive power assignments. The first lens group (positive or negative) handles light capture, the second lens group (negative) primarily corrects aberrations, and the third lens group (positive) controls focal length. This segmentation achieves effective aberration correction with fewer total lenses compared to a conventional multi-element design, thereby reducing overall lens length.
Solution Approach 2:
The patent employs specific refractive index and Abbe number parameters for the lens materials in each group. By carefully selecting materials with appropriate optical parameters, the aberration correction capability is enhanced without requiring additional lens elements, thus maintaining a compact lens structure.
3Adaptability or versatility
If the pupil position of the zoom lens moves during zooming, then the optical system can maintain focus across different focal lengths, but light loss occurs corresponding to the distance the pupil has moved
Solution Approach 1:
The first lens group acts as an intermediary element that tracks and follows the moving pupil position during zooming. As the pupil moves to maintain focus across different focal lengths, the first lens group compensates by adjusting its position accordingly, thereby minimizing light loss that would otherwise occur due to pupil displacement.
4Volume of moving object
If the lens aperture is reduced to achieve a compact and portable projector unit, then the overall size and weight of the projector are reduced, but the ability to capture sufficient light for bright image projection is compromised
Solution Approach 1:
The projection lens is divided into multiple lens groups with optimized refractive powers. This segmentation allows the use of smaller individual lens elements with smaller aperture, while the collective optical power of all groups maintains the light-gathering capability. The first lens group with positive or negative refractive power efficiently captures and directs light, compensating for the reduced aperture size.
Solution Approach 2:
The patent utilizes lens materials with high refractive indices to increase the optical power of each lens element. This allows smaller aperture lenses to achieve the same light-gathering capability as larger aperture lenses made from conventional materials, thereby enabling projector miniaturization without sacrificing image brightness.
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 enables the creation of a compact, high-image-quality projector unit that can project enlarged images on large screens with a small lens aperture, suitable for portable applications, while maintaining a thin and lightweight design.
Implementation Method 1
a first lens group having a positive or negative refractive power as a whole, a second lens group having a negative refractive power as a whole, and a third lens group having a positive refractive power as a whole
Data Source
AI summary
To provide a compact, high-performance zoom lens having a small lens aperture for enlarging an image from a light valve such as a DMD for forming an image by changing a reflecting direction of light and projecting the image so enlarged on to a screen or the like, the zoom lens includes, in order from a magnifying side, a first lens group having a positive or negative refractive power as a whole, a second lens group having a negative refractive power as a whole and a third lens group having a positive refractive power as a whole, wherein changing the magnification of a whole lens system thereof is attained by configuring such that while a magnification varying operation is in effect, the first lens group is left fixed, and the second lens group and the third lens group are made to move on the optical axis.