Optical SSB Modulator Frequency Shift Control for Laser Distance Measurement

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Solution Overview

Problem

Frequency-shifted feedback lasers using acousto-optic elements face difficulties in easily changing the frequency shift amount and direction due to limitations in ultrasonic transducer capabilities and refractive index modulation, making it challenging to adjust the frequency shift effectively.

Innovation Solution

The use of an optical single-sideband (SSB) modulator as a frequency shifter, controlled by a control part to adjust the frequency shift amount and direction, allows for flexible frequency modulation in frequency-shifted feedback lasers.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If acousto-optic elements are used as frequency shifters in the laser cavity, then frequency shifting capability is achieved, but the ability to easily change frequency shift amount and direction is limited

Engineering Contradiction:

Improvefrequency shift adjustment capabilityVSAvoidfrequency shifter structure

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent replaces the acousto-optic frequency shifter (which uses ultrasonic mechanical vibrations) with an electro-optic phase modulator that uses electrical signals to achieve frequency shifting. This substitution eliminates the need for complex ultrasonic transducers and allows for easier electronic control of the frequency shift amount and direction, directly resolving the technical contradiction between adaptability and device complexity.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Ease of operation

If acousto-optic elements are used for frequency shifting, then frequency modulation is achieved, but easy adjustment of shift direction is not possible

Engineering Contradiction:

Improvefrequency shift direction controlVSAvoidfrequency shift flexibility

Core Design Contradiction:

Ease of operationVSAdaptability or versatility

Solution Approach 1:

The patent enables easy adjustment of frequency shift direction by changing the sign of the frequency shift parameter in the electro-optic phase modulator. By simply inverting the sign of the control voltage applied to the modulator, the frequency shift direction can be reversed without any mechanical reconfiguration, thereby improving both ease of operation and adaptability simultaneously.

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

This solution enables easy adjustment of frequency shift amount and direction without altering the output angle, improving accuracy and functionality in optical distance measurements.

Implementation Method 1

an optical SSB modulator for shifting a frequency of the light amplified by the gain medium

Methodology Applied

Scientific EffectPhase modulation: Phase Modulation

Implementation Method 2

a gain medium for amplifying a light to be input

Methodology Applied

Scientific EffectStimulated emission: Laser

Implementation Method 3

outputting a frequency-modulated laser beam with a plurality of modes

Methodology Applied

Scientific EffectLaser oscillation: Laser

Implementation Method 4

generates a beat signal by mixing the reference light and a reflected light

Methodology Applied

Scientific EffectOptical interference: Interference

Data Source

PatentUS11415406B2Single sideband frequency modulated laser measurement for detecting a difference in a propagation distance

Publication Date: 2022.08.16 MITUTOYO CORP

AI summary

A laser apparatus, a measurement apparatus, and a measurement method are provided in which the laser apparatus outputs a frequency-modulated laser beam with a plurality of modes and includes: an optical cavity that has a gain medium for amplifying a light to be input, and an optical SSB modulator for shifting a frequency of the light amplified by the gain medium: and a control part that controls the optical SSB modulator to shift a frequency of a light to be input to the optical SSB modulator.