Optical Pickup for Stringed Instruments Using Bridge Grating Modulation

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Solution Overview

Problem

Current acoustic string instrument amplification methods, such as piezo and magnetic pickups, and microphones, fail to accurately reproduce tonal quality and are prone to feedback, necessitating an improved transducer that modulates light with grates to enhance frequency and intensity capture.

Innovation Solution

An optical electro-acoustic transducer with a pair of gratings positioned on the instrument bridge, utilizing a light emitting diode and photodetector to modulate light and produce an electronic signal corresponding to note frequency, intensity, and tonal quality, with associated circuitry for connection to standard amplifiers or recording devices.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If piezo or magnetic pickups are used for amplification, then the instrument can be electrically amplified, but the tonal quality reproduction is inaccurate

Engineering Contradiction:

Improvetonal quality reproduction accuracyVSAvoidamplification accuracy

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent replaces mechanical/electromagnetic pickup systems with an optical system. A light source emits light through a bridge grating that vibrates with the string, modulating the light intensity. A photodetector converts the modulated light into electrical signals, accurately capturing the vibration characteristics and tonal quality without the limitations of piezo or magnetic pickups.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces light as an intermediary between the vibrating string and the detection system. The bridge grating acts as a mechanical intermediary that converts string vibrations into light modulation, which is then detected by the photodetector, providing accurate tonal reproduction.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If microphones are used to amplify the full sound, then both acoustic and electrical characteristics are captured, but feedback problems occur

Engineering Contradiction:

Improvesound capture accuracyVSAvoidfeedback susceptibility

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent replaces the acoustic microphone system with an optical detection system. Instead of capturing sound waves that can cause feedback, the system directly detects the mechanical vibrations of the bridge grating through light modulation, eliminating the feedback loop between speaker and microphone.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent extracts the vibration detection function from the acoustic field and places it in the optical domain. By detecting bridge vibrations directly through optical means rather than capturing radiated sound, the system removes the feedback pathway while preserving accurate sound capture.

Inventive Principle:

Principle #2Taking out (Extraction)

3Reliability

If contact pickups are mounted under the saddle or on the body, then vibrations can be sensed, but the tonal quality and transient motions are not accurately captured

Engineering Contradiction:

Improvevibration sensing capabilityVSAvoidtransient motion detection accuracy

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The patent places the optical detection system specifically at the bridge location where the grating is mounted. This strategic positioning allows direct observation of the bridge vibrations that are most representative of the string instrument's tonal characteristics and transient motions, providing superior measurement precision compared to generic contact pickup locations.

Inventive Principle:

Principle #3Local quality

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

The transducer provides accurate tonal reproduction and significantly reduces feedback, capturing subtle and fast transient motions with high sensitivity and fidelity, maintaining signal purity and dynamic range without introducing sound artifacts.

Implementation Method 1

The patterns formed on the gratings modulate the frequency and intensity of the light from the LED impinging on the photodetector to produce an electronic signal

Methodology Applied

Scientific EffectPhotoelectric Effect: Photoelectric Effect

Implementation Method 2

The grating can vibrate freely in sync with the instrument

Methodology Applied

Scientific EffectMechanical Vibration: Vibration

Data Source

PatentUS20210065667A1Acoustical optical pickup for use in stringed musical instruments

Publication Date: 2021.03.04 TAFF OPTICAL

AI summary

An optical head assembly for sue with a stringed musical instrument, the vibrations of the strings causing a light beam to be modulated in accordance with the frequency of the vibrating strings. The modulated light output, produced by the relative motion between two adjacent grates, is coupled to a device with converts the modulated light beam to a corresponding modulated electrical signal which, in turn, is coupled to an amplifier associated with the instrument.