Image Signal Processing for Accurate Focus on Low-Res Viewfinders
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Solution Overview
Problem
4K-resolution cameras often use viewfinders with lower HD-resolution, limiting the display of high-frequency edge information, making it difficult for users to achieve accurate focus due to the sampling theorem constraints.
Innovation Solution
An image signal processing apparatus that down-converts 4K-resolution images to HD-resolution, extracts high-frequency edge components, and combines them with down-converted images to display edge information at a higher resolution than the viewfinder, allowing for accurate focus on the camera.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a 4K-resolution camera uses an HD-resolution viewfinder, then the imaging apparatus becomes easier to move and place, but the viewfinder cannot display edge information in frequency bands higher than the Nyquist frequency, making accurate focus difficult
Solution Approach 1:
The patent segments the edge detection process into two distinct frequency bands: low-frequency band edge detection performed on the HD-resolution viewfinder image, and high-frequency band edge detection performed on the 4K-resolution captured image. This segmentation allows the system to overcome the Nyquist frequency limitation by separately processing different frequency components, thereby resolving the contradiction between using a lower-resolution viewfinder and achieving accurate focus.
Solution Approach 2:
The patent introduces an intermediary processing system that includes a frequency separation unit, a low-frequency-band edge detection unit, and a high-frequency-band edge detection unit. This intermediary system acts as a bridge between the HD-resolution viewfinder and the 4K-resolution captured image, enabling the combination of edge information from both sources to achieve accurate focus despite the resolution mismatch.
2Loss of information
If edge information from 4K-resolution image is obtained from a source other than the image outputted to the viewfinder, then higher frequency edge information can be accessed, but the sampling theorem prevents the HD-resolution viewfinder from displaying this edge information
Solution Approach 1:
The patent applies segmentation by dividing the edge detection process into two separate pathways: one for low-frequency band edges detected from the HD-resolution viewfinder image, and another for high-frequency band edges detected from the 4K-resolution captured image. This segmentation enables the system to preserve high-frequency edge information while acknowledging the display resolution limitation, as the high-frequency edges are processed separately and can be used for focus determination without requiring to be displayed on the HD viewfinder.
Solution Approach 2:
The patent transitions from a single-dimension approach (displaying all edge information on the HD viewfinder) to a multi-dimensional approach by separating edge detection into different frequency bands and processing them through different pathways. This dimensional change in the processing architecture allows high-frequency edge information to be preserved and utilized for focus control, even though it cannot be directly displayed on the HD-resolution viewfinder.
3Device complexity
If only HD-resolution edge information is displayed on the HD-resolution viewfinder, then the display device operates within its resolution limits, but the user has difficulty achieving accurate focus on the 4K-resolution camera
Solution Approach 1:
The patent segments the focus assistance system into two independent but complementary parts: low-frequency band edge detection for the HD-resolution viewfinder display, and high-frequency band edge detection for the 4K-resolution captured image. This segmentation allows the system to maintain simplicity in the display portion while enhancing focus accuracy through the additional high-frequency information processed separately.
Solution Approach 2:
The system implements self-service by having the high-frequency band edge detection unit independently process the 4K-resolution captured image to extract high-frequency edge information, which complements the low-frequency edge information from the HD viewfinder. This self-service mechanism enables the system to automatically overcome the resolution limitation without requiring external intervention or complex display modifications.
Data Source
AI summary
An image signal processing apparatus includes a down-converter unit configured to down-convert an image signal having a first resolution into an image signal having a second resolution lower than the first resolution, a high-frequency-band-edge detection unit configured to perform filtering on the image signal having the first resolution to extract components in a higher frequency band than a frequency corresponding to the second resolution and to perform down-conversion on an edge detection signal obtained through the filtering to obtain an edge detection signal having the second resolution, and a combination unit configured to combine the edge detection signal obtained by the high-frequency-band-edge detection unit with the image signal having the second resolution generated by the down-converter unit so as to obtain an image signal having the second resolution and being to be displayed.