Sub-pixel Tracking Engine Linear Compensation

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Solution Overview

Problem

Conventional optical navigation devices face errors due to re-referencing, especially in absolute referencing, where cumulative errors exceed acceptable limits, and sub-pixel approximation techniques like 3-point peak approximation can skew results non-linearly, affecting accuracy and increasing errors.

Innovation Solution

An optical navigation device with a tracking engine that includes a sub-pixel approximation engine and a linear approximation engine, which generates intermediate and final sub-pixel displacement values based on non-linear and compensation distributions respectively, to compensate for non-linear sub-pixel distributions, reducing cumulative errors and improving accuracy.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Duration of action of stationary object

If re-referencing is performed to maintain correlation when navigation array approaches boundary conditions, then the navigation tracking can continue, but cumulative error exceeds acceptable limits

Engineering Contradiction:

Improvetracking continuityVSAvoidtracking accuracy

Core Design Contradiction:

Duration of action of stationary objectVSMeasurement precision

Solution Approach 1:

The patent applies preliminary action by using sub-pixel approximation to predict and compensate for boundary conditions before they cause significant tracking errors. The system continuously calculates sub-pixel displacement values to anticipate when the navigation array will approach image boundaries, allowing smooth re-referencing without cumulative errors.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent changes the parameter of reference image selection by using sub-pixel analysis to identify optimal re-referencing points. Instead of fixed boundary-based re-referencing, the system dynamically determines when to switch reference images based on sub-pixel displacement calculations, maintaining correlation quality while minimizing cumulative error.

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If sub-pixel approximation techniques are used to increase movement sensitivity, then resolution and accuracy improve, but non-linear distribution skews results and increases error

Engineering Contradiction:

Improvemovement sensitivityVSAvoidapproximation accuracy

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent implements feedback by continuously monitoring the distribution of sub-pixel approximation values and comparing them against expected linear distributions. When non-linear skewing is detected, the system adjusts the approximation calculations to compensate, ensuring long-term accuracy and reliability of movement measurements.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent applies partial action by using a modified version of sub-pixel approximation that applies correction only where non-linear skewing occurs. Rather than completely redesigning the approximation algorithm, the system selectively adjusts calculations in regions where boundary effects and non-linear distributions become significant.

Inventive Principle:

Principle #16Partial or excessive action

3Measurement precision

If 3-point peak approximation is used for absolute referencing, then sub-pixel displacement can be calculated, but cumulative error quickly exceeds acceptable limits due to non-linear skewing

Engineering Contradiction:

Improvesub-pixel displacement measurementVSAvoiderror accumulation rate

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The patent introduces an intermediary correction mechanism that mediates between the 3-point peak approximation results and the final displacement measurement. This intermediary layer detects and compensates for non-linear skewing, allowing the system to maintain accurate cumulative measurements over extended tracking periods.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS8315434B2Absolute tracking in a sub-pixel range

Publication Date: 2012.11.20 PIXART IMAGING INC

AI summary

An optical navigation device for absolute tracking in a sub-pixel range. The optical navigation device includes an image sensor and a tracking engine. The image sensor includes a pixel array to generate a plurality of tracking images. The tracking images correspond to incident light at the pixel array. The tracking engine determines a sub-pixel displacement value of a tracking surface based on a comparison of at least two of the tracking images. The tracking engine includes a sub-pixel approximation engine and a linear approximation engine. The sub-pixel approximation engine generates an intermediate sub-pixel displacement value based on a sub-pixel approximation according to a non-linear sub-pixel distribution. The linear approximation engine generates a final sub-pixel displacement value from the intermediate sub-pixel displacement value.