External Optical Viewfinder Parallax Correction
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Solution Overview
Problem
Existing optical viewfinders for cameras with interchangeable lenses face challenges such as high cost, large size, limited angle of view, and difficulty in correcting optical axis shifts, leading to poor visual recognition and followability of moving objects.
Innovation Solution
An external optical viewfinder with a Keplerian viewfinder optical system, a drive source for adjusting objective lenses, a control circuit for parallax correction, and a display device that shows a wider visual field frame than the photographing frame, allowing for real-time adjustment of magnification and parallax correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a traditional single-lens reflex camera design with OVF/EVF switching is used, then the camera can capture images, but the device becomes complex, expensive, and large in size
Solution Approach 1:
The patent extracts the viewfinder function from the camera body and places it in a separate external device. This external optical viewfinder contains only the essential components (objective lens, prism, eyepiece) needed for viewing, eliminating the need for complex mirror mechanisms and electronic components within the camera body itself.
Solution Approach 2:
The viewfinder system is segmented into independent functional modules: the external optical viewfinder unit with its own objective lens and optical path, and the camera body with its imaging sensor. This segmentation allows each component to be optimized independently and reduces overall system complexity.
2Ease of operation
If the visual field frame is wider than the photographing frame, then the periphery can be observed for predicting movement, but the photographing frame may not be centered
Solution Approach 1:
The patent incorporates a display unit that shows real-time feedback of the photographing frame position within the wider visual field. This allows the user to see both the extended field of view for predicting object movement and the precise framing information needed for accurate composition, with the display updating as the user adjusts the viewfinder.
3Measurement precision
If parallax correction is implemented, then optical axis shift errors are reduced, but the device complexity increases
Solution Approach 1:
The patent employs adjustable optical elements including a movable prism and variable focal length objective lens. These dynamic components can be adjusted to compensate for parallax and optical axis misalignment, allowing the system to adapt to different shooting conditions without requiring complex fixed correction mechanisms.
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
Enhances visual recognizability and followability of moving objects, enabling prediction of object movement and accurate framing while reducing the complexity and cost associated with traditional single-lens reflex camera designs.
Implementation Method 1
a Keplerian viewfinder optical system including a scalable objective lens group
Implementation Method 2
an image is formed by reflecting, on a mirror, a subject image transmitted through a taking lens
Implementation Method 3
a drive source configured to drive at least one objective lens of the objective lens group along an optical axis
Implementation Method 4
a visual field frame disposed on a focal plane of the objective lens group
Data Source
AI summary
An optical viewfinder is configured to be attached to a camera body with an interchangeable lens. The optical viewfinder includes: a Keplerian viewfinder optical system 301 including a scalable objective lens group 330; a stepping motor 305 configured to drive the objective lens group 330 along an optical axis; and a control circuit configured to control driving of the stepping motor 305 based on a result of detection by a PI 306. When a variable focal length lens (an interchangeable lens) is attached to a camera body, the control circuit controls driving of the stepping motor 305 in accordance with a focal length of the variable focal length lens and displays at least a photographing frame on an EVF panel 307.