Adjusting Lens-Sensor Distance for Downscaled Image Depth of Field
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Solution Overview
Problem
Digital imaging devices face a disparity between the captured image at the sensor and the displayed or recorded image due to differences in resolution, which affects the depth of field, leading to suboptimal focus when images are downscaled for viewing or storage.
Innovation Solution
The solution involves dynamically adjusting the optical distance between the lens and the digital sensing surface based on the downscaling ratio between the captured and displayed images, optimizing the hyperfocal distance for the displayed or recorded image resolution to enhance depth of field.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the lens is focused at the hyperfocal distance for the sensor resolution, then the depth of field is maximized for the captured image, but the displayed or recorded image (after downscaling) exhibits suboptimal focus and reduced depth of field
Solution Approach 1:
The patent changes the focusing parameter (hyperfocal distance) based on the downscaling ratio. When downscaling is applied, the system calculates a new hyperfocal distance that is shorter than the original, allowing the lens to be focused at a distance that maximizes depth of field in the downscaled displayed or recorded image rather than the original sensor-resolution image
Solution Approach 2:
The system uses feedback from the downscaling ratio to adjust the focusing distance. The processor determines the appropriate hyperfocal distance based on the calculated downscaling ratio, creating a closed-loop system where the output (downscaled image) quality feeds back into the input (focusing distance) optimization
2Measurement precision
If dynamic focusing adjustment is implemented to optimize depth of field for different downscaling ratios, then focus accuracy for displayed images is improved, but device complexity increases
Solution Approach 1:
The system performs preliminary calculation of the downscaling ratio and determines the optimal hyperfocal distance before capturing the image. By pre-calculating the appropriate focusing distance based on the intended downscaling, the system avoids the need for complex real-time focusing adjustments during image capture or processing
Solution Approach 2:
The patent introduces an intermediary processing step where the processor calculates the downscaling ratio and determines the optimal hyperfocal distance. This intermediary computation layer translates between the downscaling parameter and the physical focusing distance, simplifying the overall control logic
3Loss of information
If the lens is focused at a shorter hyperfocal distance to accommodate downscaling, then depth of field in displayed images is increased, but the captured image at sensor resolution may have reduced depth of field
Solution Approach 1:
The system dynamically adjusts the hyperfocal distance based on the downscaling ratio rather than using a fixed focusing distance. This dynamic adaptation allows the system to optimize for the actual output medium (displayed or recorded image) while maintaining flexibility to handle different downscaling scenarios
Solution Approach 2:
The patent applies different focusing strategies for different output scenarios. When downscaling is applied, the system optimizes locally for the downscaled image quality rather than the original sensor-resolution image, recognizing that the final viewing experience occurs at the lower resolution
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 results in a deeper depth of field for the displayed or recorded images, reducing the need for auto focus and lowering power consumption, while being relatively easy to implement by adjusting the lens position according to stored data related to the downscaling ratio.
Implementation Method 1
focus a camera lens at a hyperfocal distance of a scene in order that the resulting image exhibit a greater depth of field
Data Source
AI summary
A digital camera apparatus has a sensing surface that captures images at a first resolution. A derivative of the captured image is displayed at a viewfinder or stored in a memory, after encoding, with a second, generally lower resolution. The resolutions are related by a downscale ratio. A method for digitally imaging a scene includes providing an imaging lens and a digital image sensing surface such as a CCD sensing surface, and changing a focusing of the lens with respect to the sensing surface in correspondence with a variance of a parameter that relates a captured image at the sensing surface and another image deriving from the captured image. Preferably, the variance of the parameter is the downscale ratio. The focusing of the lens with respect to the sensing surface may be changed by changing the physical distance or by changing a shape of the lens, for example. Apparatus and computer program products are also detailed.