Diffractive Optical Element for Uniform Laser Illumination
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Solution Overview
Problem
Projection type image display devices face challenges in achieving uniform illuminance distribution with laser light, leading to potential image quality issues, increased device complexity, and higher costs due to the need for complex optical systems.
Innovation Solution
Incorporating a diffractive optical element that generates diffracted light from a laser light source, ensuring the incidence face is positioned to avoid zero-order light and utilizing a spatial light modulation device with a liquid crystal panel for efficient illumination, thereby maintaining image quality while reducing device size and cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a predetermined optical system is used to realize uniform illuminance distribution, then uniform illuminance distribution is achieved, but the device becomes larger and more complex
Solution Approach 1:
The patent extracts the illuminance uniformization function from a complex multi-element optical system and implements it using a single diffractive optical element. This DOE is designed with specific phase modulation patterns that directly generate uniform illuminance distribution when illuminated by laser light, eliminating the need for additional uniformizing optics and reducing overall system complexity.
Solution Approach 2:
The patent replaces a mechanical/optical system requiring multiple lenses and mirrors for illuminance uniformization with a diffractive optical element that achieves the same effect through diffraction-based phase modulation. This substitution reduces the number of optical components and simplifies the overall optical path while maintaining uniform illuminance distribution.
2Illumination intensity
If a complex optical system is configured to achieve uniform illuminance distribution, then desired image quality is obtained, but device cost increases
Solution Approach 1:
The patent extracts the expensive uniformization optics from the system and replaces them with a diffractive optical element that can be manufactured using standard diffractive optics fabrication techniques. This single component performs the function of multiple expensive optical elements, significantly reducing device cost while maintaining uniform illuminance distribution.
Solution Approach 2:
The patent changes the approach from using multiple optical elements with complex alignment requirements to a single diffractive optical element with fixed diffraction parameters. The DOE is designed with specific groove patterns and phase profiles that inherently produce uniform illuminance, eliminating the need for costly precision alignment and reducing manufacturing complexity.
3Illumination intensity
If a complex optical system is used for illuminating the incidence face, then uniform illuminance distribution is achieved, but light utilization efficiency decreases
Solution Approach 1:
The patent replaces a multi-element optical system with multiple optical interfaces that cause reflection and transmission losses with a single diffractive optical element. The DOE directly modulates the phase of incident laser light to create uniform illuminance distribution, minimizing light loss at optical interfaces and improving overall light utilization efficiency.
Solution Approach 2:
The patent ensures continuous useful action by designing the diffractive optical element to efficiently redirect nearly all incident laser light into the desired diffraction orders that illuminate the incidence face uniformly. The DOE structure minimizes stray light and unused diffraction orders, maximizing the utilization of incident laser energy for the intended illumination purpose.
4Illumination intensity
If zero-order light from the diffractive optical element is allowed to incident on the first face, then illumination is provided, but a desired image cannot be obtained
Solution Approach 1:
The patent extracts the problematic zero-order light from the illumination path by positioning the first face (spatial light modulation device) at a location where zero-order light does not incident. The diffractive optical element is designed to direct zero-order light in a different direction, separating it from the useful diffracted light that illuminates the incidence face uniformly. This spatial separation eliminates image quality degradation while maintaining effective illumination.
Solution Approach 2:
The patent segments the light path into different spatial regions: one for useful diffracted light that illuminates the incidence face uniformly, and another for zero-order light that is directed away from the first face. This spatial segmentation allows the system to utilize the diffractive optical element's output effectively while avoiding the harmful effects of zero-order light on image quality.
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 the formation of a desired image with uniform illumination distribution, suppressing the increase in device size, complexity, and cost, while enhancing light utilization efficiency and preventing speckled patterns.
Implementation Method 1
a diffractive optical element on which the laser light emitted from the laser light source device is incident, generating diffracted light from the incident laser light, and illuminating the first face with the diffracted light
Data Source
AI summary
An image display device includes: a first face; a laser light source device emitting laser light; and a diffractive optical element on which the laser light emitted from the laser light source device is incident, generating diffracted light from the incident laser light, and illuminating the first face with the diffracted light, the first face is provided at a position on which zero-order light emitted from the diffractive optical element is not incident, and an image is displayed by light via the first face.