Monitor Sensor Arrangement for Phase-Difference Focus Detection

Solution Overview

Problem

In Single Reflex Lens (SRL) cameras using phase-difference Auto Focus (AF) mechanisms, the peripheral region of the projected area receives insufficient light due to optical characteristics, leading to inaccurate light monitoring by monitor sensors, which affects the precision of focus detection.

Innovation Solution

The arrangement of monitor sensors adjacent to line sensors, with at least the endmost monitor sensor positioned along the center-facing side of the endmost line sensor, ensures precise light monitoring and charge accumulation, allowing for effective focus detection across the projected area without modifying the optical image-forming system.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Area of stationary object

If monitor sensors are arranged at the peripheral region to monitor line sensors, then the projected area is utilized more effectively, but the light monitoring precision deteriorates due to insufficient light reaching the peripheral region

Engineering Contradiction:

Improveprojected area utilizationVSAvoidlight monitoring precision

Core Design Contradiction:

Area of stationary objectVSMeasurement precision

Solution Approach 1:

The patent applies local quality by making the endmost monitor sensor smaller than other monitor sensors. This size differentiation is specifically tailored to the peripheral region where light intensity is lower, allowing the reduced sensor to effectively monitor the corresponding line sensor without requiring excessive light intensity, thus resolving the contradiction between utilizing peripheral area and maintaining monitoring precision.

Inventive Principle:

Principle #3Local quality

2Area of stationary object

If the endmost monitor sensor is positioned at the periphery, then the focus detection coverage is expanded, but the accuracy of focus detection deteriorates due to insufficient light

Engineering Contradiction:

Improvefocus measurement areaVSAvoidfocus detection accuracy

Core Design Contradiction:

Area of stationary objectVSMeasurement precision

Solution Approach 1:

The patent applies local quality by making the endmost monitor sensor smaller than other monitor sensors. This size differentiation is specifically tailored to the peripheral region where light intensity is lower, allowing the reduced sensor to effectively monitor the corresponding line sensor without requiring excessive light intensity, thus resolving the contradiction between utilizing peripheral area and maintaining monitoring precision.

Inventive Principle:

Principle #3Local quality

3Area of stationary object

If line sensors are arranged at the periphery to maximize projected area, then the focus detection coverage is improved, but the light reception capability deteriorates due to vignetting

Engineering Contradiction:

Improveprojected area coverageVSAvoidlight reception capability

Core Design Contradiction:

Area of stationary objectVSIllumination intensity

Solution Approach 1:

The patent applies local quality by making the endmost monitor sensor smaller than other monitor sensors. This size differentiation is specifically tailored to the peripheral region where light intensity is lower, allowing the reduced sensor to effectively monitor the corresponding line sensor without requiring excessive light intensity, thus resolving the contradiction between utilizing peripheral area and maintaining monitoring precision.

Inventive Principle:

Principle #3Local quality

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 configuration enhances the precision of focus detection and prevents light overflow, enabling accurate phase difference detection and effective Auto Focus adjustments, while allowing for a larger focus-measurement area without altering the optical design.

Implementation Method 1

an optical image-forming system that forms an object image with a plurality of line sensors arranged on a projected area

Methodology Applied

Scientific EffectRefraction: Refraction

Implementation Method 2

Each line-sensor outputs image-pixel signals by photoelectric conversion

Methodology Applied

Scientific EffectPhotoelectric conversion: Photoelectric Effect

Data Source

PatentUS8305449B2Apparatus for detecting focus

Publication Date: 2012.11.06 RICOH IMAGING COMPANY

AI summary

An apparatus for detecting a focus state has an optical image-forming system that forms an object image, a plurality of line sensors that is arranged on a projected area of the optical image-forming system; a plurality of monitor sensors that is arranged on the projected area along the direction of a line-sensor array, each monitor sensor being adjacent to a corresponding line sensor and monitoring an amount of light incident on the corresponding line sensor; and a signal processor that outputs image-pixel signals corresponding to the object image on the basis of electric charges accumulated in the plurality of line sensors. At least an endmost monitor sensor corresponding to an endmost line sensor is arranged on the center-facing side of the endmost line sensor.