Trapezoidal PBS Ghosting Elimination in Projection Systems
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Solution Overview
Problem
Conventional projection systems suffer from ghosting issues due to non-uniform light distribution and shape mismatch between the light source and screen, leading to loss of light intensity and uneven illumination.
Innovation Solution
A projection system incorporating a Polarizing Beam Splitter (PBS) with a wider width facing the projection lenses than the area perpendicular to them, along with a body tube structure that absorbs image light components hitting the PBS's lateral surface, preventing these components from entering the exit pupil and thus eliminating ghosting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional PBS with square pillar shape is used, then the structure is simple, but ghosting occurs due to non-uniform light distribution and shape mismatch
Solution Approach 1:
The patent applies asymmetry by changing the PBS shape from a conventional square pillar to a trapezoidal prism. The trapezoidal cross-section with different width dimensions (first width larger than second width) creates an asymmetric structure that better matches the light distribution pattern, thereby eliminating ghosting while maintaining manufacturing feasibility
Solution Approach 2:
The patent implements local quality by creating different width dimensions at different regions of the PBS. The first width (facing projection lenses) is made larger than the second width (perpendicular area), providing locally optimized light interaction in different spatial zones to prevent ghosting without requiring complete structural redesign
2Object-affected harmful factors
If the PBS width is increased to match light distribution, then ghosting is reduced, but the device complexity increases
Solution Approach 1:
The asymmetric trapezoidal prism design achieves ghosting removal through geometric asymmetry rather than complex multi-component structures. The single integrated trapezoidal PBS maintains structural simplicity while the asymmetric geometry provides the necessary light distribution control to eliminate ghosting
Solution Approach 2:
The trapezoidal PBS structure serves multiple functions simultaneously: it acts as a beam splitter, a light distributor, and a ghosting prevention element. This multi-functionality is achieved through the geometric shape itself rather than requiring separate components, thereby reducing overall device complexity
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 removes ghosting by ensuring that image light components hitting the PBS's lateral surface are absorbed, maintaining uniform light distribution and intensity on the screen, thereby enhancing image quality.
Implementation Method 1
a PBS (Polarizing Beam Splitter) reflecting the light from the illumination unit, transmitting an image light
Implementation Method 2
the image light component hitting a lateral surface of the PBS is absorbed by the body tube and fails to be included in the image light projected to the screen
Data Source
AI summary
A projection system is disclosed, the projection system including: an illumination unit; a PBS (Polarizing Beam Splitter) reflecting the light from the illumination unit, transmitting an image light, having a width larger than that of entrance pupil through which the image light is incident, and having a structure in which a width of an area facing projection lenses is larger than that of an area perpendicular to an area facing the projection lenses; a display device receiving the light reflected from the PBS and outputting the light as an image light; and a projection unit mounted with the projection lenses for projecting the image light outputted from the display device to a screen.