Projector Optical System Diffractive Element Miniaturization
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Solution Overview
Problem
High-performance projector optical systems face challenges in miniaturization due to increased lens count, which hinders size reduction and portability.
Innovation Solution
A projector optical system utilizing a diffractive optical element with a multilayer-type diffractive optical surface, combined with a first lens group and a final lens group, to achieve good image forming performance while minimizing the number of lenses, thus reducing the overall size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If high-performance projector optical systems use more lenses to achieve high resolution and sufficient correction of various aberrations, then image forming performance is improved, but device size increases and miniaturization is hindered
Solution Approach 1:
The patent combines refractive and diffractive optical functions into a single integrated optical element. The diffractive optical surface is formed on at least one lens surface of the lens group, merging the functions of multiple separate optical components into one unified structure. This integration reduces the total number of lenses while maintaining both high-resolution imaging and aberration correction capabilities, thereby solving the contradiction between image quality and device size.
Solution Approach 2:
The patent employs a composite optical design that combines refractive optics (traditional lenses) with diffractive optics (diffractive optical surface with diffraction gratings). This composite approach allows the single lens group to simultaneously perform multiple optical functions including focusing, chromatic aberration correction, and spherical aberration correction, eliminating the need for multiple separate lenses and reducing overall device volume.
2Volume of moving object
If the number of lenses is reduced to enable miniaturization, then device size is reduced, but image forming performance and aberration correction capability deteriorate
Solution Approach 1:
The diffractive optical surface performs multiple optical functions simultaneously within a single element. It provides chromatic aberration correction through its dispersive properties, spherical aberration correction through its wavefront modulation capability, and maintains focusing function. This multi-functionality allows a reduced number of lenses to achieve the same overall optical performance that would traditionally require multiple specialized lenses, enabling miniaturization without sacrificing image quality.
Solution Approach 2:
The patent utilizes the wavelength-dependent diffraction efficiency of the diffractive optical surface to correct chromatic aberrations. By carefully designing the diffraction grating parameters and optimizing the diffractive structure for specific wavelength ranges, the system achieves broad-spectrum chromatic correction with a single element. Additionally, the diffractive optical parameters are optimized to maintain high diffraction efficiency while correcting various aberrations, enabling compact design without performance loss.
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 compact and lightweight projector optical systems with effective chromatic aberration correction and reduced flare, allowing for smaller and more portable devices.
Implementation Method 1
a diffraction optical surface formed by a multilayer-type diffractive optical element in which diffraction gratings formed on two diffractive element components are arranged facing each other
Data Source
AI summary
A projector optical system for forming a real image by projecting an image of a display element is constituted by, sequentially from a projection side, an aperture diaphragm; and a first lens group having positive refractive power and having, in the interior thereof or on a lens surface at a projection side or at a display element side, a diffraction optical surface formed by a multilayer-type diffractive optical element in which diffraction gratings formed on two diffractive element components are arranged facing each other. The projector optical system is configured so as to satisfy the following expression0.1<K/L<1.5wherein L is a total length on an optical axis, and K is a distance on the optical axis from the aperture diaphragm to a surface of the first lens group that is closest to the projection side, and satisfy also the following expression0.01<ΔNd<0.45wherein ΔNd is a difference between refractive indices of the two diffractive element components for a main wavelength (d-line).