Imaging Apparatus Focus Lens Control for Minute Point Light Sources
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Solution Overview
Problem
Existing imaging apparatuses face challenges in achieving high accuracy for focus adjustment, particularly when capturing minute point light sources like stars, due to the limitations of phase difference AF in detecting clear phase differences and the variability caused by temperature and attitude changes.
Innovation Solution
A control method for an imaging apparatus that performs phase-difference focus detection by calculating defocus amounts and controlling the focus lens, using a point-away calculation to enhance reliability by shifting the focus detection from the initial focus position to a predetermined depth, thereby improving focus accuracy on minute point light sources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If phase difference AF is used for focus adjustment, then the time for automatic focus adjustment is shorter, but detection accuracy deteriorates when capturing minute point light sources like stars
Solution Approach 1:
The patent applies preliminary action by performing focus detection at a predetermined point-away (a position away from the reference focus position) before final focus adjustment. This preliminary detection at a known offset position allows the system to calculate the reference focus position more accurately, thereby improving focus detection accuracy for minute point light sources while maintaining the speed advantages of phase difference AF
2Device complexity
If focus adjustment is performed at a fixed reference position, then the adjustment process is simple, but focus accuracy deteriorates under temperature and attitude changes
Solution Approach 1:
The patent performs preliminary focus detection at a point-away (a predetermined position away from the reference focus position) to calculate the actual reference focus position. This preliminary action compensates for temperature and attitude changes by establishing an accurate reference point before final focus adjustment, thereby improving reliability without significantly increasing device complexity
Solution Approach 2:
The patent implements feedback by using the detection result from the point-away position to calculate and adjust the reference focus position. The system feeds back the calculated defocus amount to determine the correct reference focus position, creating a closed-loop control that maintains focus accuracy under varying temperature and attitude conditions
3Ease of operation
If focus detection is performed at the reference focus position, then the detection process is straightforward, but variance in defocus detection increases for minute point light sources
Solution Approach 1:
The patent performs preliminary focus detection at a point-away (a predetermined position away from the reference focus position) rather than directly at the reference position. This preliminary detection provides more reliable phase difference information for minute point light sources, reducing variance in defocus detection while maintaining operational simplicity through automated calculation of the reference position
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 allows for high-accuracy focus adjustment on minute point light sources by reducing the variance in defocus detection and improving reliability, even under conditions of temperature and attitude changes.
Implementation Method 1
having multiple pixels capable of performing photoelectric conversion of light fluxes that have passed through different pupil regions of an imaging optical system
Implementation Method 2
imaging optical system including a focus lens
Data Source
AI summary
An imaging apparatus includes a storage unit configured to store beforehand a focus position serving as a reference for a predetermined subject, and a unit configured to drive a focus lens at a position away by a predetermined depth from the focus position serving as a reference that is stored, and calculate a defocus amount.