Zoom Lens with Intermediate Image for Telecentric Projection
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Solution Overview
Problem
Existing projection display devices require a zoom lens with a wide angle of view and compact size, while being telecentric on the reduction side to accommodate larger screen sizes and shorter projection distances, but existing lens systems fail to meet these demands in terms of angle of view and minimization of total lens length.
Innovation Solution
A zoom lens configuration that forms an intermediate image and re-images it on a magnification side imaging plane, comprising a stationary first lens group, movable lens groups that adjust spacings, and a final stationary lens group with positive refractive power, satisfying specific conditional expressions to achieve telecentricity and wide angle of view.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the lens system is configured to be telecentric on the reduction side, then the entrance pupil position is sufficiently far, but the total lens length increases and cannot be minimized
Solution Approach 1:
The lens system is divided into multiple lens groups (first lens group with positive power, second lens group with negative power, third lens group with positive power) that can move independently during zooming. This segmentation allows each group to contribute differently to the overall optical path, enabling telecentricity on the reduction side while controlling the total lens length through coordinated movement of segments.
Solution Approach 2:
The lens groups are configured to move along the optical axis during zooming operations. The first lens group moves to adjust the entrance pupil position for telecentricity, while the second and third lens groups move to maintain focal length and image quality. This dynamic adjustment allows the system to achieve telecentricity without excessive lens length.
2Adaptability or versatility
If the angle of view is widened to satisfy larger screen size requirements, then the projection distance is shortened, but the lens system becomes more complex and larger in size
Solution Approach 1:
The lens groups move relative to each other during zooming to dynamically adjust the angle of view. The first lens group's movement controls the entrance pupil position, while the second and third lens groups move to maintain focus and image quality across different field angles. This dynamic configuration enables wide angle of view without excessive complexity.
Solution Approach 2:
The system changes optical parameters (focal length, entrance pupil position, field angle) through coordinated movement of lens groups. By varying the positions of the first, second, and third lens groups, the system achieves different angles of view and maintains telecentricity, adapting to different projection requirements without requiring fundamentally different optical designs.
3Length of moving object
If the lens system is made compact to reduce size, then the total lens length is minimized, but the angle of view becomes insufficient for recent demands
Solution Approach 1:
The compact lens system is segmented into three functional groups with alternating positive and negative powers. This segmentation allows the negative-powered second lens group to act as a telephoto element, effectively extending the optical path and increasing the angle of view without proportionally increasing the physical lens length. The compact form is maintained while achieving the required angular coverage.
Solution Approach 2:
The lens groups have asymmetric power distribution (positive-negative-positive) rather than symmetric configuration. This asymmetry, particularly the placement of the negative-powered second lens group, creates a telephoto effect that increases the angle of view for a given physical length, allowing the system to be compact while meeting wide-angle requirements.
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 zoom lens achieves a small size with favorable optical performance and a wide angle of view while maintaining telecentricity on the reduction side, suitable for projection display devices and imaging apparatuses, effectively addressing the limitations of previous lens systems.
Implementation Method 1
a zoom lens forming an intermediate image at a position conjugate to a reduction side imaging plane and imaging the intermediate image on a magnification side imaging plane
Data Source
AI summary
The zoom lens is a lens system that forms an intermediate image, and includes, in order from the magnification side: a first lens group that remains stationary during zooming; a plurality of movable lens groups that move during zooming; and a final lens group that has a positive power and remains stationary during zooming. Two or more movable lens groups are positioned to be closer to the reduction side than the intermediate image. The lens system closer to the reduction side than the intermediate image includes, in order from the magnification side, a front group and a rear group. The zoom lens satisfies predetermined conditional expressions (1) and (2) relating to the rear group.