Off-Axis Projection Distortion Correction via Keystone Tilting
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Solution Overview
Problem
Off-axis projection display systems suffer from increased distortion due to the placement of digital micromirror devices (DMDs), leading to issues like astigmatism and lateral color variations, which are typically corrected using expensive and complex optics.
Innovation Solution
The system corrects distortion by intentionally inducing keystone distortion through tilting the display plane, projection lens, or spatial-light modulator, compensating for pincushion or barrel distortions without requiring precise and costly optics, thereby maintaining a normal viewing angle and reducing overall distortion noticeability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the DMD is placed off axis to achieve a shorter throw distance and thinner cabinet form factor, then the physical dimension between light source and display plane is shortened, but the projection lenses' instantaneous FOV increases and distortion aberrations worsen
Solution Approach 1:
The patent applies preliminary anti-action by intentionally introducing keystone distortion through optical design that counteracts the pincushion distortion caused by off-axis DMD placement. This pre-compensation approach allows the system to achieve both short throw distance and acceptable image quality without requiring complex corrective optics.
Solution Approach 2:
The patent changes optical parameters by adjusting the projection lens design to accommodate off-axis DMD placement while managing distortion characteristics. By modifying lens parameters and optical configuration, the system achieves short throw performance while controlling aberrations through parameter optimization rather than complex structural solutions.
2Manufacturing precision
If complicated and expensive optics with specific specifications are used to correct image distortion, then image quality improves, but production cost becomes exceedingly high and the system becomes uncompetitive
Solution Approach 1:
The patent employs standard, commercially available optical components rather than custom-designed expensive optics. By using off-the-shelf projection lenses and standard DMD devices, the system achieves cost-effective distortion correction without requiring precision-machined custom optics, thereby maintaining competitiveness with other display technologies.
Solution Approach 2:
The patent uses software-based image processing to create a corrected version of the distorted image. By capturing the distorted output and applying digital correction algorithms, the system compensates for optical aberrations without requiring expensive physical optics, effectively creating a corrected copy of the original image.
3Volume of moving object
If the DMD is placed off axis to achieve shorter throw distance, then the cabinet form factor becomes thinner, but the field of view increases and distortion effects become more pronounced
Solution Approach 1:
The patent converts the harmful distortion effect into a beneficial characteristic by intentionally designing the optical system to produce controlled keystone distortion that counteracts the unwanted pincushion distortion. The off-axis configuration, which initially causes problems, is leveraged to create compensating distortion patterns that improve overall image quality.
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 approach effectively compensates for third-order residual distortions, particularly pincushion and barrel distortions, resulting in a more uniform and less noticeable image, without the need for expensive optics, making it a cost-effective solution for off-axis projection systems.
Implementation Method 1
one or more folding mirrors positioned to reflect light from the projection system to the display within a shorter distance
Data Source
AI summary
A system and method for correcting optical distortion in an off-axis system is provided. The offset between the center of a display plane and the optical axis of the projection lens system is configured such that the offset is greater than half the vertical dimension of the display plane. In this manner, the distortion, such as a pincushion-type or barrel-type of distortion, is not symmetrical about the horizontal axis. In this scenario, the display plane, the projection lens system, a folding mirror, and/or the spatial light modulator may be tilted such that a keystone effect is induced. This keystone effect may be used to offset the distortion, particularly the pincushion-type or barrel-type of distortions.