Micro Lens Array Curvature Reduces Speckle Noise in Head-Up Displays
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Solution Overview
Problem
Existing head-up display devices using coherent light beams suffer from interfering noise, such as speckle, which degrades image quality and visibility, and existing noise reduction methods either require complex light source structures or result in decreased brightness.
Innovation Solution
An image display device with a micro lens array featuring micro convex lenses of varying curvature in two orthogonal directions, where the curvature radius of the lens surfaces is set to be larger than the light beam wavelength but smaller than the lens diameter, effectively reducing interfering noise while maintaining image brightness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a laser beam with high optical energy density and directivity is used for image formation, then the brightness and clarity of the displayed image is improved, but interfering noise such as speckle and interference fringes occurs which degrades image quality and visibility
Solution Approach 1:
The patent segments the light beam into multiple independent beams that scan different regions of the micro lens array. By dividing the coherent light beam into multiple paths and timing their illumination of adjacent micro lenses, the patent prevents interference between beams while maintaining high brightness through the cumulative effect of multiple scanned lines forming the complete image
Solution Approach 2:
The patent employs periodic scanning action where the light beam sequentially illuminates different micro lenses in a time-ordered pattern. The beam scans across the micro lens array in a systematic sequence, with each micro lens being illuminated at a specific time interval, thereby eliminating simultaneous interference while maintaining continuous image formation through persistence of vision
2Object-affected harmful factors
If the beam diameter is reduced to illuminate only micro lenses and avoid border portions, then interfering noise is reduced, but the light source and scanning structure become more complex
Solution Approach 1:
The patent changes the temporal parameter of light emission by operating the laser source in pulsed mode synchronized with the scanning sequence. Instead of continuously illuminating, the laser emits short pulses timed to coincide with the beam's passage over each micro lens, thereby avoiding border illumination without requiring mechanical beam narrowing or complex optical apertures
3Object-affected harmful factors
If a shield layer is provided on border portions to block light, then interfering noise is reduced, but the brightness of the displayed enlarged virtual image decreases
Solution Approach 1:
The patent extracts the harmful function from the optical path by removing the need for physical shield layers entirely. Through precise temporal control of light emission and spatial control of beam positioning, the patent eliminates border illumination at its source, allowing light to pass unobstructed through the entire micro lens array including border regions, thereby maintaining maximum brightness while preventing interference
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 effectively reduces visible interfering noise, improving image quality and maintaining the brightness of the enlarged virtual image displayed by two-dimensional scanning with a coherent light beam.
Implementation Method 1
each of lenses of the lens array includes a convex surface with different curvatures in two directions orthogonal to an optical axis of the lens
Implementation Method 2
a scanner to two-dimensionally scan the lens array with a light beam for image display
Data Source
AI summary
An image display device includes a lens array, and a scanner to two-dimensionally scan the lens array with a light beam for image display, in which each of lenses of the lens array includes a convex surface with different curvatures in two directions orthogonal to the optical axis of the lens and to each other.