Projection Optical System Compact Design via Lens Parameter Optimization
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Solution Overview
Problem
Existing projection optical systems face challenges in preventing distortion while enlarging the field angle, which often results in increased total lens length, making the system less compact.
Innovation Solution
A projection optical system with a first lens unit of positive power and a second lens unit of negative power, where specific conditional expressions are satisfied to control focal distances and lens lengths, and incorporating light path folding elements to maintain compactness and correct aberrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the field angle is enlarged to project the image in an enlarged manner even in the case of disposing the projection image display device at a position close to the screen, then the projection capability is improved, but a distortion becomes apt to occur on the projection field
Solution Approach 1:
The patent applies parameter changes by optimizing the focal distances of the first and second lens units relative to each other, and by controlling the total lens lengths of both units according to specific conditional expressions. This allows the system to achieve wide field angles while maintaining distortion correction through precise parameter optimization rather than simply increasing the number of lenses.
2Manufacturing precision
If the number of lenses is increased to suppress the distortion of the projection field, then the distortion correction is improved, but the total length of the lenses increases
Solution Approach 1:
The patent resolves this contradiction by changing the parameters of the existing lens units - specifically the focal distances and total lens lengths - to satisfy conditional expressions that enable effective distortion correction with a reduced number of lenses, thereby shortening the total lens length.
Solution Approach 2:
The patent employs dynamic adjustment mechanisms where the first and second lens units can move relative to each other along the optical axis. This dynamic configuration allows the system to maintain optimal distortion correction across different projection distances and field angles without requiring additional fixed lenses.
3Adaptability or versatility
If the focal distance of the first lens unit is increased to satisfy the lower limit of conditional expression (1), then the field angle can be enlarged, but the light beam becomes telecentric or beam diameter increases causing increased load on the first lens unit
Solution Approach 1:
The patent optimizes the focal distance of the first lens unit by establishing a specific range through conditional expression (1). This parameter optimization ensures that the field angle is sufficiently enlarged while preventing the light beam from becoming overly telecentric, thereby maintaining an acceptable load on the first lens unit.
4Adaptability or versatility
If the tilt of the light beam between the second lens unit and the intermediate image is increased to satisfy the lower limit of conditional expression (2), then the field angle is improved, but the field curvature deteriorates and the diameter of the lens becomes large
Solution Approach 1:
The patent controls the tilt of the light beam by optimizing the focal distance of the second lens unit according to conditional expression (2). This parameter optimization balances the field angle enhancement with maintaining acceptable field curvature and preventing excessive lens diameter.
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 system effectively prevents distortion and maintains a compact design by optimizing lens configurations and folding light paths, allowing for wider field angles without increasing the total lens length.
Implementation Method 1
the optical system is provided with a first lens unit for making the screen (a enlargement-side imaging surface) and the intermediate image conjugate with each other, and a second lens unit for making the intermediate image and a reduction-side imaging surface (the image of the image display element) conjugate with each other
Data Source
AI summary
A projection optical system includes a first lens unit adapted to make a enlargement-side imaging surface and an intermediate image conjugate with each other, a second lens unit adapted to make the intermediate image and a reduction-side imaging surface conjugate with each other. The first lens unit has positive power, and the second lens unit has negative power. Defining a focal distance of the first lens unit as fU1, a focal distance of the second lens unit as fU2, a total lens length of the first lens unit as LLU1, and a total lens length of the second lens unit as LLU2, the following expression (1) and expression (2) are satisfied:−0.3<fU1/fU2<−0.005 (1)0.5<LLU1/LLU2<0.9 (2).