Digital Camera Focus Range Extension via Aperture Control
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Solution Overview
Problem
Digital cameras with fixed focus lenses face challenges in capturing images of subjects closer than the near focus position, as they lack adjustable focus settings, making it difficult for amateur photographers to achieve acceptable focus and depth of field.
Innovation Solution
A method for controlling a digital camera system by varying the F/# of the optical system between a minimum and maximum setting, capturing evaluation images, and adjusting the F/# until the subject is acceptably focused, thereby determining the optimal capture F/# for capturing archival images.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fixed focus lens is used to reduce costs and simplify the system, then device complexity is reduced, but the focus range is limited and cannot capture subjects closer than the near focus position
Solution Approach 1:
The patent changes the F/# parameter of the optical system to extend the focus range. By varying the aperture size (F/# setting), the system can capture subjects at different distances including those closer than the near focus position, while maintaining a fixed focus lens design.
2Adaptability or versatility
If the F/# is increased to extend the depth of field for closer subjects, then the focus range is extended, but the image noise increases and motion blur occurs due to longer exposure time
Solution Approach 1:
The patent uses flash illumination to provide additional light, allowing the use of higher F/# settings without excessive exposure time. The flash provides sufficient illumination for close subjects, enabling the system to achieve extended focus range while minimizing motion blur and noise through the combination of aperture control and supplemental lighting.
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 method extends the focus range of digital cameras, allowing for focused images of subjects closer than the near focus position and adaptively controlling the depth of field based on subject position, providing a tradeoff between focus, noise, and motion blur.
Implementation Method 1
Digital cameras use a lens to focus a scene onto an image sensor
Implementation Method 2
the depth of field for a lens will depend on the F/# of the lens. A smaller F/# (corresponding to a larger aperture diameter) will have a smaller depth of field, while a larger F/# (corresponding to a smaller aperture diameter) will have a larger depth of field
Data Source
AI summary
A method for controlling a digital camera system having an optical system with an F/# that can be varied between a minimum F/# and a maximum F/#, comprising: setting the optical system F/# to a first F/#; capturing an evaluation image of the scene; analyzing the evaluation image to determine whether a subject is acceptably focused; if the subject is acceptably focused setting a capture F/# to be equal to the first F/#, otherwise the optical system F/# is iteratively increased until the subject is determined to be acceptably focused, or until a maximum F/# is reached; determining a capture F/# responsive to the F/# where the subject is acceptably focused; setting the optical system to use the capture F/#; capturing an archival image of the scene using the image sensor; and storing the captured archival image in a storage memory.