Nested Prism Unit for Projector Miniaturization
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Solution Overview
Problem
Existing projector systems face challenges in miniaturizing the optical system, including the prism unit, which affects the device's thickness and overall size, especially in portable projectors.
Innovation Solution
A prism unit configuration that includes multiple prisms with specific optical surfaces and a reflective film, allowing for efficient illumination and projection light management, including a second prism that forms air gaps to align the optical axes of illumination and projection light, and using materials with varying refractive indices to optimize light transmission and reflection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a conventional prism configuration is used in the projector, then the optical system can guide illumination light and projection light, but the projector's thickness and overall size increase
Solution Approach 1:
The patent implements nesting by placing the second prism inside the first prism and the third prism inside the second prism, creating a nested configuration where smaller optical components are housed within larger ones. This nested arrangement allows multiple prisms to occupy overlapping spatial volumes, significantly reducing the overall projector size while maintaining the complete optical path for both illumination and projection light
Solution Approach 2:
The patent utilizes the depth dimension (z-axis) by forming air gaps between optical surfaces of nested prisms, allowing light to propagate through three-dimensional space rather than requiring larger two-dimensional footprints. The air gaps enable optical paths to be stacked vertically, transforming the spatial arrangement from a planar layout to a compact volumetric configuration
2Use of energy by moving object
If the number of prisms is increased to manage light paths, then light transmission efficiency improves, but the optical system size increases
Solution Approach 1:
The nested prism configuration allows three separate prisms (first, second, and third) to be arranged in a space-efficient manner, with each prism performing specific light management functions. The nesting enables complete separation of illumination and projection light paths through multiple total internal reflections, maximizing light transmission efficiency without requiring a proportional increase in overall optical system volume
Solution Approach 2:
The patent utilizes air gaps (effectively thin film spaces) between the optical surfaces of nested prisms to enable light reflection and path separation. These air gaps act as optical interfaces that facilitate total internal reflection, allowing efficient light management with minimal additional material volume, thereby improving light transmission efficiency without significantly increasing optical system size
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 enables the miniaturization of the optical system, reducing the projector's size and weight while ensuring efficient light transmission and separation of ON and OFF light, thereby enhancing the projector's compactness and performance.
Implementation Method 1
a second optical surface totally reflecting the illumination light having entered through the first optical surface
Implementation Method 2
a fourth optical surface forming a first air gap with the second optical surface and allowing the illumination light having exited through the second optical surface to enter the prism
Implementation Method 3
an eighth optical surface allowing projection light to exit the prism, the projection light being the illumination light exiting through the seventh optical surface, incident on and reflected by an externally provided reflective image display device, entering the prism through the seventh optical surface, and totally reflected by the sixth optical surface
Data Source
AI summary
A prism unit includes a first prism and a second prism. The first prism includes a first optical surface that allows the illumination light to enter the prism, a second optical surface that reflects the illumination light that entered through the first optical surface, and a third optical surface that allows the illumination light reflected by the second optical surface to exit the prism. The second prism includes a fourth optical surface that forms a first air gap with the second optical surface and allows the illumination light that exited through the second optical surface to enter the prism, and a fifth optical surface that allows the illumination light that entered through the fourth optical surface to exit the prism.