Reflective Lens Aperture Data for Accurate Defocus
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Solution Overview
Problem
Existing focus detecting methods for image pickup apparatuses with reflective telephoto lenses fail to accurately calculate defocus amounts due to changes in the shielding of AF light beams, leading to focus detecting errors.
Innovation Solution
A lens apparatus with a reflective optical system that includes a memory for storing aperture information based on optical conditions and a transmitter to send this information to the camera body, allowing an image pickup apparatus with an image sensor and receiver to calculate accurate defocus amounts by using the received aperture information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If phase difference AF is used with reflective telephoto lens, then focus detection can be performed, but defocus amount calculation becomes inaccurate due to shielding way changes
Solution Approach 1:
The lens apparatus preliminarily calculates and stores aperture information (including exit pupil diameter, exit pupil position, and baseline length) based on optical conditions before focus detection is needed. This preliminary preparation allows the camera body to accurately calculate defocus amounts without needing to recalculate during focus detection, resolving the accuracy issue caused by shielding way changes in reflective telephoto lenses
2Measurement precision
If aperture information is stored in lens apparatus memory and transmitted to camera body, then accurate defocus detection is enabled, but device complexity increases
Solution Approach 1:
The system is segmented into two functional parts: the lens apparatus that performs optical calculations and stores aperture information in its own memory, and the camera body that receives and uses this information for focus detection. This segmentation allows each component to have specialized functionality, reducing overall system complexity while enabling accurate defocus detection
Solution Approach 2:
Aperture information acts as an intermediary data element that bridges the lens apparatus and camera body. By transmitting this pre-calculated information from the lens to the camera, the system avoids the need for complex real-time calculations during focus detection, simplifying the overall system architecture while maintaining high measurement precision
Data Source
AI summary
A lens apparatus attachable to and detachable from a camera body includes a reflective optical system, a memory configured to store aperture information based on an optical condition of the lens apparatus, and a transmitter configured to transmit the aperture information acquired from the memory to the camera body.