Collimated LED Light Source With Blue-Light Recycling for HUDs
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Solution Overview
Problem
Existing light source devices for display devices, such as head-up displays (HUDs) and ultra-small projectors, face inefficiencies in light utilization and uniform illumination due to the shape of the optical system, particularly when using LEDs and collimators, leading to suboptimal performance in miniaturization and cost-effectiveness.
Innovation Solution
A light source device incorporating a collimating optical system with high-luminance LEDs, a light guide, and a reflective film to reflect blue and ultraviolet light, combined with a polarization conversion element to align light polarization, enhancing light utilization efficiency and uniformity, while maintaining cost-effectiveness by eliminating the need for additional reflective films.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a conventional LED and collimator optical system is used, then the light source device can be miniaturized, but the light utilization efficiency and uniform illumination characteristics are insufficient
Solution Approach 1:
The patent converts the harmful reflection loss of blue and ultraviolet light from the light guide into a beneficial effect by adding a reflective film. This reflective film reflects the previously lost blue and ultraviolet light back toward the light guide, transforming the energy loss into useful illumination, thereby improving light utilization efficiency while maintaining the miniaturized structure
Solution Approach 2:
The patent applies a reflective film with specific optical characteristics (reflecting blue and ultraviolet light) to a specific location (one of the optical elements in the collimating optical system or between the collimating optical system and light guide). This localized application of specialized material properties addresses the light utilization efficiency problem without requiring changes to the entire optical system
2Volume of moving object
If a conventional LED and collimator optical system is used, then the light source device can be miniaturized, but the uniform illumination characteristics are insufficient
Solution Approach 1:
The polarization conversion element is applied to a specific optical element in the collimating optical system, converting light in specific regions to a unified polarization state. This localized intervention improves the uniformity of illumination characteristics without requiring redesign of the entire miniaturized optical system
Solution Approach 2:
The patent changes the polarization state parameter of light by introducing a polarization conversion element. This parameter change (from unpolarized or randomly polarized light to uniformly polarized light) directly improves illumination uniformity while maintaining the compact device structure
3Loss of energy
If additional reflective films are added to improve light utilization efficiency, then light output increases, but manufacturing cost increases
Solution Approach 1:
The reflective film is integrated as part of the optical element itself or positioned between existing optical elements, serving multiple functions: reflecting blue and ultraviolet light, maintaining structural integrity, and potentially serving as a mounting interface. This multi-functionality reduces the need for separate additional components, thereby controlling manufacturing costs while improving light utilization efficiency
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 achieves a miniaturized, highly efficient, and reliable light source device suitable for HUDs and other electronic devices, improving light output and uniformity while reducing manufacturing costs.
Implementation Method 1
A reflective film is provided so as to have an optical characteristic of reflecting a part of blue light and ultraviolet light to the LED side
Implementation Method 2
A polarization conversion element is provided to reflect a part of light emitted from the LED to the LED side by an action of the reflective film, and to align a polarization direction of light emitted from the light guide in one direction
Data Source
AI summary
A light source device which is miniaturized, can be manufactured at low cost, and is suitable as an illumination light source of a display device of an electronic device such as an HUD and an aerial floating image display apparatus is provided. The light source device includes: a light source configured to generate white light by irradiating a phosphor with light emitted from a solid-state light source; a collimating optical system (15) configured to convert a divergent light flux of the white light emitted from the light source into parallel light; a light guide configured to cause the light emitted from the collimating optical system (15) to be incident as incident light and emit the incident light in a direction different from an incident direction; and a filter configured to reflect light in a blue region of the parallel light to irradiate the phosphor.