CMOS Image Sensor Pixel Readout Mode Switching for Focus and Exposure

Solution Overview

Problem

In image capturing apparatuses with CMOS-type image sensors, the division of photodiodes into multiple units leads to increased readout time, reducing frame rate and causing uneven light exposure during live view or moving image shooting due to differing accumulation times between rows used for focus point detection and those not used.

Innovation Solution

An image capturing apparatus with a switching unit that allows for two readout modes: one where signals from multiple photoelectric conversion portions are read out through separate column output lines and another where they are combined and read out through a single column output line, ensuring uniform light exposure and reduced readout time.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If photodiodes of a unit pixel are divided into multiple photodiodes for focus point detection, then focus detection capability is improved, but readout time increases and frame rate decreases

Engineering Contradiction:

Improvefocus detection capabilityVSAvoidreadout time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The pixel array is segmented into first pixels and second pixels with different readout paths. First pixels have their divided photodiode signals read out separately through different column output lines for focus detection, while second pixels have their signals summed and read out through a single column output line for image generation, thereby reducing overall readout time while maintaining focus detection capability

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The system dynamically switches between different readout modes: a first readout mode where divided photodiode signals are read out separately for focus detection, and a second readout mode where signals are summed for image generation. This dynamic switching optimizes the balance between focus detection accuracy and readout speed

Inventive Principle:

Principle #15Dynamics

2Measurement precision

If photodiodes are divided and read out at different times for focus detection, then focus point detection is enabled, but uniform light exposure across pixels is compromised

Engineering Contradiction:

Improvefocus point detectionVSAvoiduniform light exposure

Core Design Contradiction:

Measurement precisionVSStability of the object's composition

Solution Approach 1:

The pixel array is segmented into first pixels and second pixels with different readout paths. First pixels have their divided photodiode signals read out separately through different column output lines for focus detection, while second pixels have their signals summed and read out through a single column output line for image generation, thereby reducing overall readout time while maintaining focus detection capability

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The system dynamically switches between different readout modes: a first readout mode where divided photodiode signals are read out separately for focus detection, and a second readout mode where signals are summed for image generation. This dynamic switching optimizes the balance between focus detection accuracy and readout speed

Inventive Principle:

Principle #15Dynamics

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 solution enables uniform light exposure across all pixels while maintaining high frame rates by optimizing readout operations, addressing the issue of increased readout time and uneven accumulation times in previous technologies.

Implementation Method 1

a plurality of unit pixels that each have a plurality of photoelectric conversion portions

Methodology Applied

Scientific EffectPhotoelectric conversion: Photoelectric Effect

Data Source

PatentUS9930279B2Image capturing apparatus and control method thereof, and storage medium

Publication Date: 2018.03.27 CANON KK

AI summary

An image capturing apparatus includes a plurality of unit pixels that each have a plurality of photoelectric conversion portions, and are arranged in a matrix; a plurality of column output lines arranged for each column of the unit pixels; and a switching unit configured to switch between a first read out mode where signals that have been accumulated in the plurality of photoelectric conversion portions of a unit pixel are read out from respectively different column output lines, and a second read out mode where signals that have been accumulated in the plurality of photoelectric conversion portions of a unit pixel are combined and then read out from a single column output line.