Image Sensor Lens Array Shift Compensation for Pixel Defect Detection

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Solution Overview

Problem

Existing image reading apparatuses face challenges in accurately determining defective pixels due to lens unevenness, which is affected by the positional shift between the lens array and image sensor caused by environmental changes such as temperature and humidity, making it difficult to distinguish between pixel defects from foreign matter and lens unevenness.

Innovation Solution

The apparatus includes a control unit that acquires and interpolates background image data to detect the shift amount between the image sensor and lens array, allowing for the comparison of shifted pixel ranges to determine if pixels are defective, thereby isolating the influence of lens unevenness and identifying abnormal pixel values.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If lens array and image sensor are fixed to members made of various materials, then the apparatus can be manufactured with standard materials, but heat contraction and expansion cause positional shifts that change lens unevenness and make defect detection inaccurate

Engineering Contradiction:

ImprovemanufacturabilityVSAvoiddefect detection accuracy

Core Design Contradiction:

Ease of manufactureVSMeasurement precision

Solution Approach 1:

The patent performs preliminary actions by: (1) detecting the positional shift between lens array and image sensor before defect detection, (2) calculating the lens unevenness based on the detected shift, and (3) correcting the pixel values by removing the calculated lens unevenness influence. This preliminary correction enables accurate defect detection despite environmental changes.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent implements feedback by using the detected positional shift information to adjust the defect detection process. The system continuously monitors the positional relationship and uses this feedback to dynamically correct lens unevenness, ensuring accurate defect detection under varying environmental conditions.

Inventive Principle:

Principle #23Feedback

2Device complexity

If positional shift between lens array and image sensor is not detected, then the defect detection process is simple, but lens unevenness cannot be distinguished from actual pixel defects

Engineering Contradiction:

Improvedetection process complexityVSAvoidpixel defect detection accuracy

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The patent segments the defect detection process into distinct steps: (1) positional shift detection, (2) lens unevenness calculation, and (3) defect determination after correction. This segmentation allows the system to handle the complex task of distinguishing lens unevenness from actual defects through a structured, multi-stage approach.

Inventive Principle:

Principle #1Segmentation

3Adaptability or versatility

If environmental conditions change, then the apparatus can operate in various environments, but the positional relationship between lens array and image sensor changes causing lens unevenness variation

Engineering Contradiction:

Improveenvironmental adaptabilityVSAvoidlens unevenness consistency

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The patent applies dynamics by making the lens unevenness correction adaptive rather than fixed. The system dynamically adjusts the correction based on the currently detected positional shift, allowing it to operate accurately across various environmental conditions while compensating for thermal expansion and contraction effects.

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 method enables accurate detection of defective pixels affected by foreign matter while accounting for lens unevenness, even when the image sensor is displaced relative to the lens array, by increasing the resolution of background image data and comparing shifted pixel ranges, thus improving the reliability of defect detection.

Implementation Method 1

a lens array having a plurality of arranged lenses for guiding light to the image sensor

Methodology Applied

Scientific EffectLight guidance through lens: Lens

Data Source

PatentUS11240383B2Image reading apparatus, defect detection method, and storage medium

Publication Date: 2022.02.01 SEIKO EPSON CORP

AI summary

An image reading apparatus acquires first image data of a background portion stored in advance and read by a reading unit, acquires second image data by reading the background portion, generates third image data by increasing resolution of the first image data and fourth image data by increasing resolution of the second image data, detects an amount of shift of an image sensor relative to a lens array in a predetermined direction by shifting a specific pixel range of the fourth image data relative to the third image data and comparing the specific pixel range with the third image data, and compares fifth image data obtained by shifting the fourth image data in accordance with the shift amount with the third image data, so as to determine whether each of pixels included in the fifth image data is a defective pixel having an abnormal value.