Interactive Input System Modulated Illumination Synchronization

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Solution Overview

Problem

Existing interactive input systems face challenges in accurately detecting and distinguishing between active and passive pointers, particularly in environments with ambient light interference, leading to misidentification and reduced accuracy in capturing pointer coordinates.

Innovation Solution

The system employs a synchronization method using modulated illumination to synchronize image frame capture with the timing of an active pointer's illumination, allowing for precise detection of active and passive pointers by processing image frames both when the illumination is on and off, and utilizing a light curtain that is modulated to synchronize active pointer illumination with image frame capture.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If conventional projection units and image sensors are used to detect pointer interaction, then the system can capture pointer coordinates, but ambient light interference reduces detection accuracy and causes misidentification between active and passive pointers

Engineering Contradiction:

Improvepointer detection accuracyVSAvoidambient light interference

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent applies periodic action by modulating the illumination source at a specific frequency (e.g., 1kHz) and synchronizing the image sensor to capture frames at the same frequency. This periodic modulation creates distinct temporal signatures for active pointers (which reflect modulated light) versus passive pointers (which do not), enabling accurate differentiation and eliminating ambient light interference through frequency-based filtering.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The patent changes the temporal parameter of the illumination by modulating its intensity at a specific frequency rather than using continuous or unmodulated lighting. This parameter change creates a detectable signal pattern that distinguishes active pointers from passive pointers and filters out ambient light, thereby improving measurement precision.

Inventive Principle:

Principle #35Parameter changes

2Productivity

If image frames are captured continuously to track pointer movement, then pointer coordinates can be captured, but synchronization issues arise between illumination timing and image capture timing

Engineering Contradiction:

Improvepointer tracking capabilityVSAvoidsynchronization timing offset

Core Design Contradiction:

ProductivityVSLoss of time

Solution Approach 1:

The patent implements feedback by using the modulated illumination signal itself as a synchronization reference. The image sensor is triggered to capture frames based on the illumination modulation signal, creating a closed-loop synchronization system. This feedback mechanism ensures that each captured frame corresponds to a known illumination state, eliminating timing offsets and enabling accurate pointer tracking.

Inventive Principle:

Principle #23Feedback

3Illumination intensity

If the illumination source remains continuously on to illuminate the display surface, then the display is visible, but active pointer detection is obscured by the continuous illumination

Engineering Contradiction:

Improvedisplay surface illuminationVSAvoidactive pointer detection accuracy

Core Design Contradiction:

Illumination intensityVSMeasurement precision

Solution Approach 1:

The patent resolves this contradiction by applying periodic modulation to the illumination source. The illumination alternates between on and off states at a specific frequency, creating temporal windows where the display is illuminated and windows where it is not. Active pointers reflecting the modulated illumination can be detected during the off periods or by analyzing the modulated reflection pattern, while maintaining overall display visibility during on periods.

Inventive Principle:

Principle #19Periodic action

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 approach enhances the accuracy of pointer detection, reduces ambient light interference, and allows for the differentiation between active and passive pointers, improving the overall precision of capturing pointer coordinates and interactions.

Implementation Method 1

a light curtain LC that reflects off the display surface 116 and impinges on one or more pointers

Methodology Applied

Scientific EffectReflection: Reflection

Implementation Method 2

generating a synchronization signal based on modulated illumination; and synchronizing image frame capture of at least one image sensor using the synchronization signal with the illumination timing of an active pointer

Methodology Applied

Scientific EffectModulation: Phase Modulation

Data Source

PatentUS9582119B2Interactive input system and method

Publication Date: 2017.02.28 SMART TECH INC (CA)

AI summary

An image capture method comprises generating a synchronization signal based on modulated illumination; and synchronizing image frame capture of at least one image sensor using the synchronization signal with the illumination timing of an active pointer within a region of interest in the field of view of the at least one image sensor.