Ghost Image Correction via Digital Subtraction for Partially-Silvered Reflectors
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Solution Overview
Problem
Beam-splitter systems in image display devices often produce secondary reflections, known as 'ghost images,' which distort the intended image by creating a faint, spatially offset version of the displayed image, interfering with the accuracy of the reflected image.
Innovation Solution
An image processing method that subtracts a shifted and attenuated copy of the intended image from the original image data to correct for the ghost image artifact, using a partially-silvered finite-thickness reflector, where the shift and attenuation match those of the ghost image, effectively eliminating the ghost image from the displayed output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a partially-silvered glass element is used as a beam splitter, then image reflection is provided, but secondary reflections (ghost images) appear due to the finite thickness of the glass
Solution Approach 1:
The patent applies preliminary action by processing the image data before it reaches the beam splitter. The system predicts and subtracts the ghost image component from the original image in advance, so that when the image passes through the beam splitter, the ghost image artifact is already compensated for. This involves calculating the expected ghost image position and attenuation factor, then removing that component from the displayed image to eliminate the harmful secondary reflection effect.
2Object-generated harmful factors
If coatings are applied to minimize reflections, then some ghost images are reduced, but multiple image artifacts still appear due to the finite-thickness reflector
Solution Approach 1:
The patent replaces the purely optical solution (coatings) with a digital signal processing approach. Instead of relying solely on physical coatings to minimize reflections, the system uses computational methods to calculate and subtract the ghost image component from the image data. This substitution allows for more precise control over the ghost image elimination by using digital processing rather than physical optimization alone.
Solution Approach 2:
The patent changes the parameters of the image data through digital processing. By adjusting the attenuation factor and spatial offset parameters to match the physical characteristics of the beam splitter, the system creates a corrected image that compensates for the finite-thickness reflector effects. This parameter-based correction allows the system to adapt to different glass thicknesses and material properties without changing the physical hardware.
3Object-generated harmful factors
If the ghost image is subtracted from the image data, then the ghost image artifact is eliminated, but the complexity of image processing increases
Solution Approach 1:
The patent uses copying by creating a digital copy of the original image and then manipulating this copy to remove the ghost image component. The system creates a corrected version of the image data by subtracting the calculated ghost image from the original, effectively working with a copy rather than the original physical light path. This copying approach simplifies the processing by allowing flexible digital manipulation without affecting the physical beam splitter hardware.
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 method significantly reduces or eliminates the ghost image artifact, ensuring that the viewer sees only the intended image, with minimal distortion, by accurately accounting for the secondary reflection's shift and attenuation.
Implementation Method 1
Beam splitters typically use a partially-silvered glass element so that one image is transmitted through the glass, and another is reflected by the partially-silvered surface, typically the front surface
Implementation Method 2
there is a chance that there is also reflection by the back surface of the glass
Data Source
AI summary
An apparatus, a method and a computer program product for correcting image data for the presence of a ghost image. The image data is for acceptance by a device that includes a partially-silvered finite-thickness reflector or similar element to provide a reflection of an image for display. The ghost image is a shifted, attenuated version of the image data. The method includes subtracting a first correction term from the image data, the first correction term being a shifted and attenuated version of the image data, the shift being the same as that between the image data and the ghost image, and the attenuation matching the attenuation of the ghost image caused by the device. The processed image data is input to the device. For a small enough attenuation of the ghost image, substantially no ghost image of the image data is displayed by the device.