Cam Curve Focus Control for Moving Lens AF Precision

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Solution Overview

Problem

Existing camera systems face challenges in achieving high-precision auto focus (AF) processing, especially when the focus lens is moving, as the accuracy of contrast or phase difference detection information is unclear, and adjusting for zoom lens movements complicates the focus positioning, leading to inefficiencies in high-speed AF operations.

Innovation Solution

An interchangeable lens device and imaging system that utilize a cam curve to correlate zoom lens and focus lens positions with subject distance, allowing for precise focus control by calculating defocus amounts and referencing points on the cam curve to determine the target focus lens position, even during zoom adjustments.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If contrast detection or phase difference detection is performed while the focus lens is moving, then high-speed auto focusing can be achieved, but the measurement precision of focus position becomes unclear

Engineering Contradiction:

Improveauto focusing speedVSAvoidfocus position detection accuracy

Core Design Contradiction:

SpeedVSMeasurement precision

Solution Approach 1:

The system performs preliminary acquisition of focus lens position information during the exposure time period, before final focus calculation. Multiple position data points are collected in advance while the lens is moving, then processed after exposure to determine the accurate focus position corresponding to the detection information acquisition timing.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent introduces an intermediary calculation process that uses the acquired focus lens position information and zoom lens position information, combined with stored cam curve data, to interpolate or calculate the precise focus position at the moment detection information was acquired. This intermediary step bridges the gap between continuous lens movement and discrete detection moments.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Adaptability or versatility

If zoom lens position is adjusted during auto focus processing, then versatility of operation is improved, but the reliability of focus position detection deteriorates

Engineering Contradiction:

Improvezoom adjustment capability during AFVSAvoidfocus position detection reliability

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The system continuously acquires and updates focus lens position information and zoom lens position information during the exposure time period. This feedback mechanism allows the system to track changing conditions in real-time and use the most current position data for focus calculation, maintaining reliability even as zoom adjustments occur.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent makes the focus control system dynamic by allowing continuous acquisition of lens position information during exposure rather than requiring static positions. The system adapts to changing zoom positions and focus lens movements during the exposure time period, calculating focus based on the dynamic state of the lens system at detection moments.

Inventive Principle:

Principle #15Dynamics

3Measurement precision

If multiple focus lens positions are measured to improve precision, then measurement precision improves, but the time required for focus adjustment increases

Engineering Contradiction:

Improvefocus position measurement accuracyVSAvoidfocus adjustment time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The system performs continuous acquisition of focus lens position information throughout the exposure time period rather than taking discrete measurements before and after. This continuous data collection ensures that detection information is always paired with accurate, up-to-date focus lens position data, maintaining high precision without requiring additional time for separate measurement steps.

Inventive Principle:

Principle #20Continuity of useful action

Data Source

PatentUS12105401B2Imaging device, imaging system, focus control method, and non-transitory computer-readable medium with cam curve

Publication Date: 2024.10.01 SONY GROUP CORP

AI summary

Provided are a device and a method by which high-precision auto focus (AF) processing can be performed while a focus lens or a zoom lens is being operated. An interchangeable lens acquires position information regarding a focus lens and a zoom lens at a predetermined time interval during an exposure time period of detection information acquisition pixels for use in calculation of a defocus amount (DF), and outputs the position information to an imaging device. The imaging device calculates the defocus amount (DF) by using information regarding the detection information acquisition pixels, calculates a reference focus lens position (Ref_fc) by using points, on a cam curve, corresponding to the inputted lens position information, calculates a target focus lens position (Tgt_fc) in an in-focus position, from the reference focus lens position (Ref_fc) and the defocus amount (DF), and outputs the target focus lens position (Tgt_fc) to the interchangeable lens.