Concave Mirror Projector Lens Group Brightness Optimization
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Solution Overview
Problem
Ultra-close-range projectors using convex or concave mirrors face issues with dust protection, where convex mirrors require large dust-proof glass to prevent dust and fingerprints, leading to increased weight and cost, while concave mirrors result in low brightness at image edges due to sharp light angles and reduced transmittance.
Innovation Solution
A projection optical system with a concave mirror and a dust-proof glass on the image side, incorporating a refractive optical system with a lens group having positive refractive power and low field curvature, which focuses light intensely onto the entrance pupil, increasing peripheral image brightness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a dust-proof glass is used to protect the concave mirror, then the mirror is protected from dust, but the glass becomes excessively large due to the enlarged imaging luminous flux diameter
Solution Approach 1:
A lens is introduced as an intermediary optical element between the concave mirror and the dust-proof glass. This lens serves as a mediator that transforms the enlarged imaging luminous flux into a smaller, more manageable beam diameter, allowing for a compact dust-proof glass while still protecting the mirror effectively.
2Reliability
If a dust-proof glass is used to protect the concave mirror, then the mirror is protected from dust, but the transmittance and brightness are reduced, especially at the image edges
Solution Approach 1:
The lens acts as an intermediary that optimizes light transmission through the dust-proof glass. By properly designing the lens parameters, it ensures that light from the concave mirror passes through the glass with minimal loss, maintaining high transmittance and brightness even at the edges of the projected image.
Solution Approach 2:
The lens parameters (focal length, diameter, curvature) are carefully optimized to change the light beam characteristics. This transformation allows the dust-proof glass to be smaller while maintaining adequate light transmission, thereby preserving image brightness and reducing edge darkening effects.
3Area of stationary object
If the imaging luminous flux diameter is enlarged to cover the projection area, then the projection coverage is improved, but the dust-proof glass must be larger and light transmittance decreases
Solution Approach 1:
The lens serves as a mediator that decouples the relationship between projection coverage area and dust-proof glass size. It allows the imaging luminous flux to cover a large projection area while transforming the beam to pass through a smaller, more efficient dust-proof glass, thereby reducing light energy loss.
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 effectively increases brightness in the peripheral parts of the projected image by optimizing light distribution and reducing the need for large dust-proof glass, while maintaining a compact projector size.
Implementation Method 1
a lens group that is arranged between the image display element and the aperture, has a positive refractive power, and has low field curvature with respect to the image display element
Implementation Method 2
which focuses light intensely onto the entrance pupil, increasing peripheral image brightness
Implementation Method 3
a mirror optical system that has a concave mirror arranged on an opposite side from the image display element across the refractive optical system, the aperture, and the lens group
Data Source
AI summary
A projection optical system that is used for an image display device having an image display element, includes a refractive optical system that includes a plurality of lenses; an aperture that limits a quantity of light led to the refractive optical system from the image display element; a lens group that is arranged between the image display element and the aperture, has a positive refractive power, and has low field curvature with respect to the image display element; and a mirror optical system that has a concave mirror arranged on an opposite side from the image display element across the refractive optical system, the aperture, and the lens group.