Projection Zoom Lens Wide Angle Design
Solution Overview
Problem
Current projection zoom lenses have insufficient angles of view to meet the demand for wider angles, particularly in applications requiring large image projection with short projection distances, and there is a need for cost reduction in projection lenses due to market price competition.
Innovation Solution
A projection zoom lens configuration consisting of a first lens group with negative refractive power, a second lens group with positive refractive power that moves during magnification changes, and additional lens groups, optimized with specific refractive index temperature coefficients and focal lengths to achieve a wider angle of view while maintaining high optical performance at a lower cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional zoom lens configurations (5-6 lens groups with negative lead group) are used to achieve telecentricity at the reduction side, then optical performance is maintained, but the angle of view remains insufficient for wide-angle projection applications
Solution Approach 1:
The patent applies parameter changes by modifying the refractive index temperature coefficients (dn1/dt and dn2/dt) of the first two lenses to satisfy specific conditional formulas. This allows achieving wide angle of view (95° or more) while maintaining telecentricity and optical performance, resolving the contradiction between angle of view expansion and lens configuration complexity
Solution Approach 2:
Instead of adding more lens groups to widen the angle of view (conventional approach), the patent inverts the approach by using a simplified 4-lens configuration with specific aspherical surfaces and refractive index characteristics. This reduces device complexity while achieving the desired wide angle of view through unconventional parameter optimization
2Measurement precision
If more lens groups are added to widen the angle of view for large-screen projection, then projection capability is improved, but manufacturing cost increases
Solution Approach 1:
The patent changes material parameters by selecting lenses with specific refractive index temperature coefficients that satisfy conditional formulas (1) and (2). This allows achieving wide angle of view with only 4 lenses instead of 5-6 lens groups, significantly reducing manufacturing cost while maintaining optical performance
Solution Approach 2:
The patent employs inexpensive aspherical lenses with specific refractive index characteristics rather than expensive multi-group lens configurations. The first and second lenses are designed as single aspherical elements, reducing manufacturing complexity and cost compared to conventional cemented lens groups
3Ease of manufacture
If the first lens has a convex surface toward the magnification side, then manufacturing is simplified, but distortion correction becomes difficult at wide angles
Solution Approach 1:
The patent changes the surface configuration parameter by making the first lens surface toward the magnification side concave (negative curvature). Combined with specific aspherical coefficients and refractive index temperature characteristics, this configuration effectively corrects distortion at wide angles (95° or more) while maintaining manufacturing feasibility
Solution Approach 2:
The patent uses composite optical design by combining aspherical surfaces with specific refractive index temperature coefficient characteristics. The first lens integrates both aspherical shape and thermal-optical properties to simultaneously achieve distortion correction and manufacturing practicality
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 provides a projection zoom lens with a wider angle of view and reduced costs, suitable for applications like home theater systems, while maintaining high optical performance and telecentricity at the reduction side.
Implementation Method 1
a first lens, which is a single lens having an aspherical surface with a concave surface toward the magnification side in the paraxial region and a negative refractive power in the paraxial region
Implementation Method 2
both the first lens and the second lens are aspherical lenses
Data Source
AI summary
A projection zoom lens is essentially constituted by, in order from the magnification side: a negative first lens group, which is fixed when changing magnification; a positive second lens group, which moves when changing magnification; a plurality of other lens groups; and a final lens group, which is fixed when changing magnification. The distances among all adjacent lens groups change when changing magnification. The first through third lenses from the magnification side within the first lens group are a first single lens having an aspherical surface with a concave surface toward the magnification side and a negative refractive power in the paraxial region, a second single lens having an aspherical surface, and a third lens. A first lens group front group constituted by the first through third lenses has a negative refractive power. Predetermined conditional formulae are satisfied.