Head-Up Display LED Array Luminance Uniformity
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Solution Overview
Problem
Conventional head-up displays in vehicles experience non-uniform brightness across the virtual image due to varying light output from LEDs, with central areas being brighter than outer areas, as individual LEDs do not emit the same amount of light when passed with the same current.
Innovation Solution
The solution involves adjusting the current through each LED and varying the spacing between them to optimize luminance uniformity, with outer LEDs drawing more current and having greater spacings to compensate for individual LED variations, ensuring a direct or inverse relationship between current and distance from the center, and current and gap, respectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If LEDs are evenly spaced and passed with the same current, then the manufacturing process is simple, but the luminance uniformity across the display deteriorates
Solution Approach 1:
The patent applies local quality by varying the current through each LED based on its position in the array. LEDs closer to the center receive lower current while outer LEDs receive higher current, creating a non-uniform current distribution that compensates for the geometric illumination pattern. This local differentiation in electrical parameters achieves uniform luminance output across the entire display area.
Solution Approach 2:
The patent changes the electrical parameter (current) through each LED individually based on its position. By adjusting the current magnitude for each LED according to a predetermined pattern that accounts for geometric illumination variations, the system transforms the uniform current input into a position-dependent current distribution that produces uniform luminance output.
2Use of energy by moving object
If multiple LEDs illuminate central areas from different directions, then the central areas receive sufficient illumination, but the brightness uniformity deteriorates due to over-illumination
Solution Approach 1:
The patent addresses the over-illumination of central areas by applying local quality through position-dependent current control. Central LEDs that contribute to multiple illuminated zones have their current reduced, while outer LEDs that primarily illuminate their local region maintain or increase their current. This local differentiation prevents the accumulation of excessive light in central areas while maintaining adequate illumination coverage.
Solution Approach 2:
The patent applies preliminary anti-action by pre-calculating and compensating for the geometric illumination pattern before the display operates. The system anticipates the non-uniform luminance distribution that would result from uniform LED illumination and applies the opposite correction through differentiated current control, thereby preventing brightness non-uniformity before it occurs.
3Ease of manufacture
If individual LED variations are not compensated, then the manufacturing cost is lower, but the luminance uniformity deteriorates
Solution Approach 1:
The patent applies parameter changes by adjusting the electrical current through each LED based on its position and individual characteristics. This approach compensates for LED variations without requiring expensive precision manufacturing or selection processes. By modifying the operational parameter (current) rather than the physical characteristics of the LEDs themselves, the system achieves uniform luminance while maintaining cost-effective manufacturing.
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 approach reduces luminance variation across the display to less than 25% of the mean value, providing a more uniform brightness experience for the driver across the entire field-of-view.
Implementation Method 1
A plurality of light emitting devices are substantially aligned in a row and each emits light
Implementation Method 2
At least one mirror reflects the light emitted by the light emitting devices toward a windshield of the motor vehicle such that the light is reflected by the windshield and is visible to the human driver as the virtual image
Data Source
AI summary
A head up display system presents a virtual image to a human driver of a motor vehicle. A plurality of light emitting devices are substantially aligned in a row and each emits light. There is a direct relationship between an electrical current drawn by each individual light emitting device and a distance each individual light emitting device is disposed from a center of the row. At least one mirror reflects the light emitted by the light emitting devices toward a windshield of the motor vehicle such that the light is reflected by the windshield and is visible to the human driver as the virtual image.