Compact Zoom Lens for DMD Projectors
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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 pupil position, leading to increased size and weight, and require a large image circle and variable power ratio for high image quality and portability.
Innovation Solution
A compact zoom lens configuration comprising a first lens group with negative refractive power, a second lens group with positive refractive power, and a third lens group with positive refractive power, where the first lens group moves along the optical axis from the wide angle end to the telephoto end, and the second lens group moves from the wide angle end to the telephoto end, while maintaining the third lens group fixed, to achieve variable magnification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the f number of the projection lens is reduced to capture more light, then the brightness is improved, but the lens aperture size increases leading to larger projector unit size
Solution Approach 1:
The patent changes the f-number parameter from conventional values to a specific range (F1.7-F2.0) to optimize the balance between brightness and size. By precisely controlling the f-number within this range, the patent achieves sufficient light capture for bright images while keeping the lens aperture size manageable for compact projector design.
Solution Approach 2:
The patent employs a movable lens group configuration where the first lens group moves along the optical axis during zooming operations. This dynamic arrangement allows optimization of the pupil position and light path at different focal lengths, enabling compact design while maintaining adequate brightness across the zoom range.
2Illumination intensity
If the pupil position of the zoom lens moves to optimize brightness at wide angle end, then the brightness is improved, but light quantity loss occurs due to pupil movement distance
Solution Approach 1:
The patent pre-positions the pupil at a specific location (near the rear of the projection lens) that is optimized for wide-angle performance. By establishing this fixed reference position in advance, the patent minimizes unnecessary pupil movement during operation, thereby reducing light quantity loss while maintaining optimal brightness at the wide angle end.
3Volume of moving object
If the image circle of the projection lens is decreased to miniaturize the projector unit, then the projector unit size is reduced, but the adaptability for DMD is limited
Solution Approach 1:
The patent optimizes the image circle diameter to a specific range (4.0-4.8mm) that is tailored for DMD compatibility. This precise parameter control ensures the projection lens works effectively with DMD technology while maintaining a compact form factor, achieving both miniaturization and adaptability goals simultaneously.
4Manufacturing precision
If a large number of lenses are combined to increase projection lens performance, then the image quality is improved, but the overall length of the projection lens increases
Solution Approach 1:
The patent divides the projection lens into multiple functional groups (first lens group, second lens group, third lens group) with specific refractive power distributions. This segmentation allows each group to perform specialized functions for aberration correction and image quality enhancement, achieving high performance without requiring a uniformly long lens structure.
Solution Approach 2:
The patent arranges lens groups in a three-dimensional configuration along the optical axis, with specific spacing and positioning. By utilizing the axial dimension effectively and creating a compact folded optical path, the patent achieves high image quality through multiple lens elements while keeping the overall lens length minimized.
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 a compact, high-image-quality projector unit with a small lens aperture, suitable for DMDs, enabling miniaturization and improved portability without compromising image quality or brightness.
Implementation Method 1
a first lens group having a negative refractive power as a whole
Implementation Method 2
a second lens group having a positive refractive power as a whole, and a third lens group having a positive refractive power as a whole
Implementation Method 3
the angle at which micromirrors tilt to represent their ON and OFF positions in producing an image is +/−12°, and by tilting the micromirrors in that way, reflected lights are switched between valid reflected light (valid light) and invalid reflected light (invalid light)
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, and a zoom lens so provided includes, in order from a magnifying side, a first lens group having a negative refractive power as a whole, a second lens group having a positive 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 third lens group is left fixed, the first lens group and the second lens group are made to move on the optical axis.