Compact Imaging Lens with Diffractive Optical Element
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Solution Overview
Problem
The existing imaging lenses for small mobile products, such as mobile phones, face challenges in reducing optical total length while maintaining aberration correction, especially when incorporating high pixel imaging elements, due to the use of negative refractive power lenses, which also increase production errors and costs.
Innovation Solution
The proposed imaging lens configuration includes a first lens with positive refractive power and a diffractive optical element, a second meniscus lens with positive refractive power, and a third lens with negative refractive power, satisfying specific conditional expressions to balance refractive power and correct aberrations, allowing for a compact, cost-effective design compatible with high pixel imaging elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a lens with negative refractive power is used for the second lens to correct chromatic aberration, then chromatic aberration correction is improved, but the optical total length cannot be further reduced
Solution Approach 1:
The patent changes the refractive power parameter of the second lens from negative to positive, and introduces a diffractive optical element on the first lens to achieve chromatic aberration correction. This parameter change allows the system to maintain aberration correction while reducing the optical total length, as the positive refractive power lens combined with the diffractive element creates a more compact optical path.
Solution Approach 2:
The patent combines a refractive lens (first lens with positive refractive power) and a diffractive optical element to form a composite optical system. The diffractive optical element is integrated on the first lens, creating a hybrid structure that leverages both refractive and diffractive properties to correct chromatic aberration while enabling compact design.
2Length of stationary object
If the first lens or second lens has large power relative to the focal length of the entire optical system to achieve compact design, then the optical total length is reduced, but the impact of production errors such as decentering on aberration increases
Solution Approach 1:
The patent optimizes the refractive power distribution by making the second lens have positive refractive power with a focal length ratio f2/f within 0.7-1.1, and the third lens have negative refractive power with a focal length ratio f3/f within -0.8 to -0.6. This balanced parameter distribution reduces aberration sensitivity while maintaining compact size.
Solution Approach 2:
The patent applies different optical properties to different lenses in the system: the first lens has positive refractive power with a diffractive element for light convergence and chromatic correction, the second lens has positive refractive power for intermediate focusing, and the third lens has negative refractive power for field flattening. This localized optimization of optical properties reduces overall system sensitivity to manufacturing errors.
3Ease of manufacture
If plastic lenses are used for all lenses to reduce cost, then manufacturing cost is reduced, but it is difficult to achieve further reduction in optical total length
Solution Approach 1:
The patent specifies precise focal length ratios for each lens (f1/f: 0.9-1.3, f2/f: 0.7-1.1, f3/f: -0.8 to -0.6) and combines them with a diffractive optical element to achieve compact design using plastic lenses. This parameter optimization enables cost-effective plastic lens implementation while achieving reduced optical total length.
Solution Approach 2:
The patent integrates a diffractive optical element on the plastic first lens, creating a composite structure that enables compact optical design using inexpensive plastic materials. The diffractive element compensates for the limitations of plastic lens materials, allowing achieving both cost reduction and compact size.
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 results in a high-performance imaging lens that is compact, cost-effective, and capable of correcting various aberrations, making it compatible with high pixel imaging elements in small mobile products, such as mobile phones, while reducing production costs through the use of plastic lenses.
Implementation Method 1
a first lens having positive refractive power whose lens surface facing the image surface side is provided with a diffractive optical element
Data Source
AI summary
The present invention provides an imaging lens composed of three lenses that can be made compact (downsized, thinned), allows a reduction in cost and can be made compatible with a high pixel imaging element having a megapixel or more incorporated in a small mobile product such as a mobile phone. The imaging lens 6 includes, in order from the object side to the image surface side: an aperture stop 4; a first lens 1 having positive refractive power whose lens surface facing the image surface side is provided with a diffractive optical element; a second lens 2 composed of a meniscus lens having positive refractive power whose lens surface facing the image surface side is convex; a third lens 3 having negative refractive power. When f denotes the focal length of the entire optical system, f1 denotes the focal length of the first lens 1, f2 denotes the focal length of the second lens 2, f3 denotes the focal length of the third lens 3 and φDOE denotes refractive power of the diffractive optical element, conditional expressions (1) to (4) are satisfied:0.9<f1/f<1.3 (1)0.7<f2/f<1.1 (2)−0.8<f3/f<−0.6 (3)−0.3<f·φDOE<0.5 (4).