Micromirror Optical Scanning Using One-Dimensional Light Detection

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Solution Overview

Problem

Existing optical scanning devices using micromirror devices face challenges in accurately detecting the motion of the mirror portion due to temperature dependence and high manufacturing costs associated with anti-reflection processing or the use of expensive two-dimensional position detection elements.

Innovation Solution

An optical scanning device with a micromirror device that includes a mirror portion driven by first and second actuators, and uses first and second photodetection elements to detect the mirror's motion in one-dimensional directions, allowing for accurate amplitude and phase difference calculations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a strain sensor is used to detect mirror portion motion, then the detection method is simple, but detection accuracy deteriorates due to temperature dependence and material deterioration

Engineering Contradiction:

Improvedetection method complexityVSAvoidmotion detection accuracy

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The patent replaces the mechanical/physical strain sensor with an optical detection system. A light source emits light through the mirror portion's back surface, and a photodetector measures light intensity changes caused by mirror inclination. This optical measurement method eliminates temperature dependence and material deterioration issues inherent in strain sensors, achieving high-accuracy motion detection without complex sensor structures.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Measurement precision

If anti-reflection processing is applied to the back surface of the mirror portion, then light beam detection capability is improved, but manufacturing complexity and cost increase

Engineering Contradiction:

Improvelight beam detection capabilityVSAvoidmanufacturing steps

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent extracts the essential function of anti-reflection processing (improving light transmission) while eliminating the complex manufacturing steps required to achieve it. Instead of applying anti-reflection coating, the invention uses the natural light transmission properties of the mirror portion's back surface material, combined with photodetector-based detection, to achieve sufficient detection capability without additional manufacturing complexity.

Inventive Principle:

Principle #2Taking out (Extraction)

3Measurement precision

If a two-dimensional position detection element is used to detect reflected light beam position, then motion detection accuracy is improved, but device cost increases significantly

Engineering Contradiction:

Improvemotion detection accuracyVSAvoiddevice cost

Core Design Contradiction:

Measurement precisionVSEase of manufacture

Solution Approach 1:

The patent extracts only the necessary one-dimensional position detection capability from the complex two-dimensional position detection element. By using a simple photodetector that measures light intensity changes along a single axis, the system achieves sufficient motion detection accuracy for the application while dramatically reducing component cost and system complexity.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent replaces the expensive two-dimensional position detection element with a inexpensive photodetector. The photodetector, being a simple and cost-effective component, provides the necessary detection functionality without the high cost associated with two-dimensional position detection elements, making the overall device more economically viable.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

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 low-cost and high-accuracy detection of the mirror portion's motion, maintaining scanning precision with feedback control.

Implementation Method 1

a light source that emits a light beam, a first photodetection element and a second photodetection element that detect a position in a one-dimensional direction of the light beam reflected by the mirror portion

Methodology Applied

Scientific EffectLight reflection: Reflection

Implementation Method 2

a first photodetection element and a second photodetection element that detect a position in a one-dimensional direction of the light beam reflected by the mirror portion

Methodology Applied

Scientific EffectPhotoelectric effect: Photoelectric Effect

Data Source

PatentUS20250231398A1Optical scanning device

Publication Date: 2025.07.17 FUJIFILM CORP

AI summary

An optical scanning device of the present disclosure includes a micromirror device that includes a mirror portion, a first actuator allowing the mirror portion to swing around a first axis, and a second actuator allowing the mirror portion to swing around a second axis orthogonal to the first axis, a light source that emits a light beam, a first photodetection element and a second photodetection element that detect a position in a one-dimensional direction of the light beam reflected by the mirror portion, and a processor that calculates, based on detection signals output from the first photodetection element and the second photodetection element, an amplitude of the mirror portion around the first axis, an amplitude of the mirror portion around the second axis, and a phase difference between the swing of the mirror portion around the first axis and the swing of the mirror portion around the second axis.