Optical Interference Tomography for Ink State Detection in Recording Heads

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Solution Overview

Problem

Ink jet recording apparatuses face challenges in evaluating the state of ink inside the recording head, particularly in detecting thickening and uneven distribution of ink and scattering particles, which can lead to ejection abnormalities.

Innovation Solution

A recording apparatus equipped with a light source, irradiation optical device, coupling optical device, detector, and arithmetic device that captures optical interference tomographic images of the ink inside the recording head, allowing for the evaluation of ink state and distribution of scattering particles.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If conventional image capture methods are used to evaluate ink state, then the apparatus structure remains simple, but the measurement precision is insufficient to detect thickening and uneven distribution of ink and scattering particles

Engineering Contradiction:
Improvedetection accuracy of ink stateVSAvoidoptical system complexity
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The patent introduces an optical interference measurement system as an intermediary between the light source and detector, using interference patterns to indirectly measure ink properties. The interference fringes created by coupling reference light with light reflected/scattered from ink inside the recording head provide precise information about ink state, thickness, and particle distribution without requiring direct contact or complex mechanical measurement devices

Inventive Principle:
Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent replaces conventional mechanical or direct optical measurement methods with an optical interference-based measurement system. Instead of using physical probes or simple imaging to assess ink state, the system uses light interference phenomena to non-contactly detect changes in ink refractive index, thickness, and particle distribution, achieving higher precision without mechanical complexity

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If optical interference tomographic imaging is implemented to evaluate ink state, then the measurement precision improves for detecting ink abnormalities, but the device complexity increases due to multiple optical components

Engineering Contradiction:
Improvestability of ink ejectionVSAvoidnumber of optical components
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The optical interference system acts as an intermediary that translates complex ink state information (viscosity, particle distribution, thickness) into measurable interference patterns. The reference light path and sample light path interfere to create fringes that encode information about ink abnormalities, enabling reliable detection of conditions that would otherwise require multiple separate measurement devices

Inventive Principle:
Principle #24Intermediary (Mediator)

Solution Approach 2:

The optical interference measurement system performs multiple evaluation functions simultaneously: it detects ink thickness variations, particle distribution uniformity, and refractive index changes all through a single integrated optical path. The same interference pattern provides information about multiple ink parameters, making the system universally applicable for comprehensive ink state monitoring without requiring separate specialized devices for each measurement type

Inventive Principle:
Principle #6Universality (Multi-functionality)

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 accurate assessment of ink state and distribution, facilitating the detection of abnormalities and enabling restoration processes to maintain stable ink ejection, thereby improving printing quality and reliability.

Implementation Method 1

a light source 150 configured to emit light

Methodology Applied
Scientific EffectLight emission: Light

Implementation Method 2

an irradiation optical device 110 configured to irradiate the recording head 160 with an irradiation light being at least a part of the light emitted from the light source 150

Methodology Applied
Scientific EffectLight irradiation: Light

Implementation Method 3

The coupling optical unit causes reflected light reflected by the liquid ejection head to interfere with reference light not reflected by the liquid ejection head. The imaging unit images interference fringes that are generated due to the interference between the reflected light and the reference light.

Methodology Applied
Scientific EffectOptical interference: Interference

Implementation Method 4

a detector 130 configured to detect the coupled light formed by the coupling optical device 120

Methodology Applied
Scientific EffectLight detection: Photoelectric Effect

Implementation Method 5

The arithmetic device is configured to acquire an optical interference tomographic image of the inside of the liquid inside the recording head based on the coupled light.

Methodology Applied
Scientific EffectOptical tomography: Tomography

Data Source

PatentEP3626462B1Recording apparatus
Publication Date: 2022.03.30 RICOH CO LTD
  • EP3626462B1 patent drawingFigure 1
  • EP3626462B1 patent drawingFigure 2~3
  • EP3626462B1 patent drawingFigure 4~5

AI summary

A recording apparatus (250, 250a, 250b) includes a recording head (160, 160a), a light source (150), an irradiation optical device (110), a coupling optical device (120), a detector (130), and an arithmetic device (140). The recording head (160, 160a) is configured to eject liquid containing scattering particles. The irradiation optical device (110) is configured to irradiate the recording head (160, 160a) with an irradiation light being at least a part of light emitted from the light source (150). The coupling optical device (120) is configured to couple reflected or scattered light with reference light to from a coupled light. The detector (130) is configured to detect the coupled light formed by the coupling optical device (120). The arithmetic device (140) is configured to acquire an optical interference tomographic image of the liquid inside the recording head (160, 160a) based on the coupled light.