Curved Dichroic Mirror for Projection Light Source Uniformity
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Solution Overview
Problem
In projection type display apparatuses, the nonuniformity of incident angles on dichroic mirrors due to diverging fluorescence leads to color irregularity and reduction in light amount, which is costly to address with conventional solutions like wedge filters.
Innovation Solution
A light source device featuring a surface-curved dichroic mirror with a curved surface that causes one of the excitation light and fluorescence to pass through while reflecting the other, and a converging lens positioned between the dichroic mirror and phosphor, maintaining uniform transmission and reflection characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a flat dichroic mirror is used to separate excitation light and fluorescence, then the optical path can be simply configured, but the incident angle of fluorescence varies across the mirror surface causing color irregularity and light amount reduction
Solution Approach 1:
The patent applies a curved surface to the dichroic mirror instead of a flat surface. The curved dichroic mirror is designed with a specific radius of curvature that matches the focal properties of the condenser lens, ensuring that diverging fluorescence rays from different positions on the phosphor strike the mirror at substantially the same incident angle. This curvature transformation resolves the color uniformity problem while maintaining optical path simplicity.
2Manufacturing precision
If a wedge filter is used to correct color irregularity, then color uniformity can be improved, but the device complexity and cost increase significantly
Solution Approach 1:
Instead of adding a separate wedge filter to correct color irregularity, the patent integrates the correction function directly into the dichroic mirror by giving it a curved surface. This single-component solution achieves both the beam splitting function and the incident angle uniformization function, avoiding the need for additional optical elements like wedge filters and thereby reducing device complexity and cost.
3Device complexity
If the phosphor is held at a fixed position for illumination, then the structure is simple, but temperature increases and light-emitting efficiency decreases
Solution Approach 1:
The patent employs periodic action by rotating the phosphor plate continuously during illumination. This rotation ensures that no single point on the phosphor remains illuminated for an extended period, allowing heat to dissipate and preventing temperature buildup that would reduce light-emitting efficiency. The periodic movement of the phosphor surface relative to the stationary excitation light source maintains high efficiency while keeping the mounting structure simple.
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 configuration reduces the difference in incident angles, minimizing color irregularity and light loss, thereby providing high-quality illumination at a lower cost.
Implementation Method 1
a surface-curved dichroic mirror with a curved surface that causes one of excitation light from the excitation light source and fluorescence from the phosphor to pass through the curved surface and that causes the other to be reflected on the curved surface
Implementation Method 2
a converging lens that causes light for exciting the phosphor to converge
Implementation Method 3
A phosphor is excited by output light of the semiconductor laser, and light that is wavelength-converted by the phosphor is used as a light source
Data Source
AI summary
A light source device for a projection display apparatus includes a phosphor, an excitation light source, a surface-curved dichroic mirror, and a converging lens. The excitation light source is configured to output excitation light for exciting the phosphor. The surface-curved dichroic mirror has a curved surface and is configured to cause one of the excitation light from the excitation light source and fluorescence from the phosphor to pass through the curved surface and to cause the other of the excitation light and the fluorescence to be reflected on the curved surface. The surface-curved dichroic mirror is configured to cause the one of the excitation light and the fluorescence that passes through, neither to substantially converge, nor to substantially diverge, but converge the other of the excitation light and the fluorescence that is reflected.