Lens Array with Dual-Period Structure for Head-Up Display Brightness
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Solution Overview
Problem
The challenge is to suppress irregular brightness in head-up displays without degrading the resolution, as both small and large lens array pitches have limitations in achieving this goal.
Innovation Solution
A lens array with a two-dimensional basic periodic structure and a secondary periodic structure, where the period of the secondary structure is an integer multiple of the basic structure, is used to diffuse diffracted light and fill light intensity distribution clearances, maintaining resolution by generating optical path length differences and controlling diffraction efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a small pitch of the lens array is used, then the resolution is improved, but irregular brightness occurs
Solution Approach 1:
The lens array is segmented into multiple lens types with different optical path lengths (first, second, and third lens types). This segmentation creates multiple diffraction orders that fill in the intensity clearances between diffracted beams, thereby suppressing irregular brightness while maintaining the fine pitch required for high resolution.
Solution Approach 2:
The invention changes the optical path length parameter by introducing lenses with different thicknesses or refractive indices. Specifically, some lenses have an optical path length that is an integer multiple of a reference value, while others have a different integer multiple. This parameter variation controls diffraction efficiency across different orders, filling intensity gaps without requiring a larger pitch that would degrade resolution.
2Illumination intensity
If a large pitch of the lens array is used, then irregular brightness is suppressed, but resolution deteriorates
Solution Approach 1:
The lens array employs a periodic pattern of different lens types arranged in a systematic manner. The first, second, and third lens types are periodically distributed according to specific rules (e.g., alternating patterns or block patterns), creating a periodic modulation of diffraction efficiency that fills intensity clearances while maintaining a compact pitch for high resolution.
3Illumination intensity
If the pitch of the lens array is expanded to prevent irregular brightness, then brightness uniformity is improved, but the resolution of the intermediate image deteriorates
Solution Approach 1:
The invention introduces intermediate diffraction orders (first-order, second-order, etc. diffracted lights) as mediators to fill the intensity clearances between zero-order diffracted beams. These intermediate orders act as fillers that suppress irregular brightness without requiring an increased pitch, thereby preserving the resolution of the intermediate image while achieving uniform brightness distribution.
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 effectively suppresses irregular brightness while preventing resolution deterioration, ensuring even light intensity distribution and maintaining image quality across different wavelengths.
Implementation Method 1
A lens array with a two-dimensional basic periodic structure and a secondary periodic structure, where the period of the secondary structure is an integer multiple of the basic structure, is used to diffuse diffracted light and fill light intensity distribution clearances
Implementation Method 2
plural lenses configured to have the same effective diameter and to have a structure that generates an optical path length difference in transmission light or reflective light
Data Source
AI summary
There is provided a lens array and an lens array capable of suitably preventing irregular brightness without reducing resolution. A micro lens array of a screen includes upper-level microlenses and lower-level microlenses which are formed on the incidence surface of the screen, which have the same effective diameter, and which have a structure that generates an optical path length difference Δ in transmission light. By disposing the upper-level microlenses and the lower-level microlenses at an interval based on the effective diameter, the basic periodic structure of a lens period is formed. Further, the upper-level microlenses and the lower-level microlenses form a basic block comprising a combination of the lenses having a structure that generates the optical path length difference. A concave-and-convex period PC based on the basic block is an integer multiple of the lens period.