Diffractive Optical Element with Stepwise Grating for Thin LIDAR Systems
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Solution Overview
Problem
Existing diffractive optical elements face challenges in reducing thickness while maintaining high light utilization efficiency and minimizing unnecessary outgoing light, particularly in applications like remote sensing and LIDAR systems, where thinning the optical system is required without compromising beam quality or increasing processing difficulties.
Innovation Solution
A diffractive optical element with a diffraction unit and a lens unit, where the lens unit includes a substrate with a periodic structure of relief-protrusion portions and stepwise gratings, allowing for efficient conversion of incident light into parallel light and reducing 0th-order light efficiency, while maintaining high diffraction efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a collimating lens is used to convert scattered light into parallel light, then the light can be effectively collimated, but the thickness of the optical system increases
Solution Approach 1:
The patent combines the collimating lens and diffractive optical element into a single integrated structure. The diffractive optical element is formed directly on the collimating lens surface, merging two separate optical components into one, thereby achieving both collimation and diffraction functions while reducing overall system thickness
Solution Approach 2:
The collimating lens is given multiple functions by adding diffractive optical element patterns to its surface. This allows the single component to perform both collimation (converging scattered light into parallel beams) and diffraction (creating specific light patterns), eliminating the need for separate optical elements
2Length of stationary object
If a Fresnel zone plate is used to reduce thickness, then the optical system becomes thinner, but the beam quality deteriorates due to diffraction effects
Solution Approach 1:
The diffractive optical element is divided into multiple stepwise levels (e.g., 2-level, 4-level, or more) that approximate the ideal continuous relief shape. This segmentation allows the structure to be manufactured with current molding technology while maintaining effective diffraction control and beam quality
Solution Approach 2:
The diffractive optical element structure is optimized for specific regions: the central region has different step configurations compared to the peripheral region. This local optimization ensures that beam quality is maintained across the entire aperture while accommodating manufacturing constraints
3Loss of energy
If the number of steps in the stepwise grating is increased to improve light utilization efficiency, then the manufacturing precision requirements increase
Solution Approach 1:
Instead of using a large number of steps (e.g., 8-level or more) that would require extremely high manufacturing precision, the patent achieves satisfactory light utilization efficiency with a smaller number of steps (2-level, 4-level, or 8-level). This partial action approach balances performance requirements with manufacturing capabilities
Solution Approach 2:
The patent optimizes parameters such as step height, step width, and refractive index to achieve high light utilization efficiency with a limited number of steps. By carefully adjusting these parameters, the system compensates for the reduced number of steps while maintaining effective light control
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 results in a thinner, more processable diffractive optical element with increased light utilization efficiency and reduced unnecessary outgoing light, addressing the challenges of thickness reduction and processing complexity.
Implementation Method 1
a lens unit configured to convert incident light into parallel light, the lens unit including: a substrate; and a protrusion and recess portion disposed on a side opposite to a light incident side of the substrate
Implementation Method 2
a diffraction unit configured to split light by using a diffraction effect
Data Source
AI summary
A diffractive optical element includes: a diffraction unit; and a lens unit disposed on a light incident side of the diffraction unit. The lens unit includes: a substrate; and a protrusion and recess portion disposed on a side opposite to a light incident side of the substrate. The protrusion and recess portion includes: a periodic structure of a relief-protrusion portion disposed in a central part, a periodic structure of a stepwise grating disposed in a central part simulating the relief-protrusion portion, or a combination thereof; and a grating disposed in a portion other than the central part. The number of steps of the stepwise grating disposed in the central part is larger than the number of steps of the grating disposed in the portion other than the central part.