Segmented Photodetector for Compact Motion and Gesture Detection

Solution Overview

Problem

Existing optical motion and gesture recognition sensors require a large footprint and multiple light sources, making them unsuitable for integration into portable devices like mobile phones and tablets, and are prone to interpreting unintended contacts as touch events.

Innovation Solution

A compact optoelectronics apparatus with a single light source and four closely arranged photodetector segments, which uses signal processing to detect motion in multiple directions and distinguish between active and retrace motions, reducing the need for multiple light sources and minimizing the sensor's footprint.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If multiple spatially dispersed light sources are used to detect motion in multiple directions, then motion detection accuracy is improved, but device footprint and complexity increase

Engineering Contradiction:

Improvemotion detection accuracyVSAvoiddevice footprint

Core Design Contradiction:

Measurement precisionVSArea of stationary object

Solution Approach 1:

The photodetector is divided into multiple segments (e.g., four quadrants) that are spatially dispersed. Each segment detects light from a different angular direction, enabling the system to distinguish motion in multiple directions using a single light source rather than multiple light sources

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent transitions from dispersing light sources in space to dispersing photodetector segments in space. By segmenting the detector and using signal processing to analyze light intensity differences across segments, the system achieves multi-directional motion detection capability without requiring multiple light sources spaced tens of millimeters apart

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Measurement precision

If multiple spatially dispersed light sources are used to detect motion in multiple directions, then motion detection accuracy is improved, but device complexity increases

Engineering Contradiction:

Improvemotion detection accuracyVSAvoidsensor complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The photodetector is divided into multiple segments (e.g., four quadrants) that are spatially dispersed. Each segment detects light from a different angular direction, enabling the system to distinguish motion in multiple directions using a single light source rather than multiple light sources

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Multiple photodetector segments are integrated into a single detector component. The segments work together with a single light source, and their signals are processed collectively to determine motion direction and velocity, reducing the number of separate components needed

Inventive Principle:

Principle #5Merging (Combining)

3Measurement precision

If larger aperture is used above light sources, then angular resolution is improved, but device footprint increases

Engineering Contradiction:

Improveangular resolutionVSAvoidaperture size

Core Design Contradiction:

Measurement precisionVSArea of stationary object

Solution Approach 1:

The photodetector is divided into multiple segments (e.g., four quadrants) that are spatially dispersed. Each segment detects light from a different angular direction, enabling the system to distinguish motion in multiple directions using a single light source rather than multiple light sources

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent changes the spatial arrangement parameters by placing photodetector segments very close to the light source (millimeters or less) rather than spacing light sources tens of millimeters apart. This parameter change enables adequate angular resolution with a compact aperture size

Inventive Principle:

Principle #35Parameter changes

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

Enables efficient gesture recognition with reduced size and complexity, improving the accuracy of motion detection and reducing false touch events, thereby enhancing the usability of portable devices.

Implementation Method 1

The IR-LEDs are pulsed one at a time, sequentially, such that the detected reflected light signals can be associated with the correct light source

Methodology Applied

Scientific EffectLight reflection: Reflection

Implementation Method 2

one existing sensor includes a photodetector that is flanked on both sides by infrared light emitting diodes

Methodology Applied

Scientific EffectPhotoelectric effect: Photoelectric Effect

Data Source

PatentUS8907264B2Motion and simple gesture detection using multiple photodetector segments

Publication Date: 2014.12.09 INTERSIL AMERICAS INC

AI summary

An optoelectronics apparatus selectively drives a light source, and includes four electrically isolated photodetector (PD) segments that detect light that has reflected off an object. Each of the four PD segments produces a corresponding signal, referred to as signals A, B, C and D, indicative of the light detected by the respective PD segment. Circuitry is used to produce a first motion signal indicative of a sum of the signals A plus B minus a sum of the signals C plus D, i.e., the first motion signal is indicative of (A+B)−(C+D). Further circuitry produces a second motion signal indicative of (B+C)−(A+D). Additional circuitry produces a signal and/or data that is indicative of a direction and/or rate of motion of an object, in dependence on the first and second motion signals.