Skin Tone Sensor Temperature Control for Stable IPL Detection

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Solution Overview

Problem

The temperature dependence of light emitted by LEDs in skin treatment apparatuses, such as IPL devices, leads to inaccurate skin tone characterization due to changes in the ratio of reflected wavelengths, affecting the accuracy of skin type detection.

Innovation Solution

A heat control system maintains the detection unit at a desired temperature by providing additional heat, using a thermally conductive body and heating device to stabilize the temperature of the sensor system, ensuring accurate skin characterization.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If the detection unit is allowed to heat up during IPL treatment, then energy efficiency is improved, but measurement precision deteriorates due to temperature-dependent LED wavelength shifts

Engineering Contradiction:
Improveenergy efficiencyVSAvoidskin tone detection accuracy
Core Design Contradiction:
Use of energy by moving objectVSMeasurement precision

Solution Approach 1:

The detection unit is thermally isolated from the treatment light source through spatial separation and thermal management systems. The LED sensors are positioned in a separate detection unit that can be thermally managed independently from the high-power IPL light source, allowing the detection unit to remain at stable temperatures while the treatment source operates at high power.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

A thermal management system acts as an intermediary between the treatment light source and the detection unit. This system includes thermal pathways, heat sinks, and temperature control mechanisms that mediate the thermal interaction, preventing heat from the treatment source from affecting the detection unit's temperature-stable LED sensors.

Inventive Principle:
Principle #24Intermediary (Mediator)

2Adaptability or versatility

If LED wavelength is used for skin tone detection, then adaptability to different skin types is improved, but measurement precision deteriorates due to temperature-induced wavelength changes

Engineering Contradiction:
Improveskin type coverageVSAvoidwavelength ratio accuracy
Core Design Contradiction:
Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The system performs preliminary temperature stabilization of the detection unit before skin tone measurement. The detection unit is pre-cooled or pre-heated to a target temperature range, and temperature maintenance is continued during measurement to ensure the LED wavelengths remain stable and accurate for detecting different skin types.

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

Temperature sensors monitor the detection unit temperature in real-time, and the system adjusts power delivery or activation timing based on temperature feedback. This feedback mechanism ensures that measurements are taken when the detection unit is at the optimal temperature range, maintaining wavelength stability across different skin type assessments.

Inventive Principle:
Principle #23Feedback

3Measurement precision

If temperature stabilization is implemented through active cooling, then measurement precision is improved, but device complexity increases

Engineering Contradiction:
Improvedetector signal accuracyVSAvoidthermal management system complexity
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The detection unit incorporates self-regulating thermal characteristics, such as thermally conductive materials and passive heat dissipation structures that automatically maintain optimal temperatures without requiring complex active cooling systems. The unit serves its own thermal management needs through inherent thermal pathways and materials.

Inventive Principle:
Principle #25Self-service

Solution Approach 2:

The system changes operational parameters based on temperature conditions rather than using complex active cooling. This includes adjusting the timing of light pulses, modifying power delivery levels, or changing detection activation based on detected temperature ranges, thereby maintaining precision through parameter adaptation rather than thermal active management.

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

The solution maintains the detection unit at a stable temperature, improving the accuracy of skin characterization and enabling precise control of the light-based skin treatment apparatus.

Implementation Method 1

a heat control system adapted to control a temperature of the detection unit at a desired temperature above an ambient temperature

Methodology Applied
Scientific EffectHeating: Heating

Implementation Method 2

The light of these two LEDs is emitted towards the skin and a detector measures the reflected light

Methodology Applied
Scientific EffectLight reflection: Reflection

Implementation Method 3

A method of skin type detection in IPL apparatus uses reflectance spectroscopy

Methodology Applied
Scientific EffectAbsorption spectroscopy: Absorption Spectroscopy

Implementation Method 4

Hairs and follicles that are in their anagen phase of the growth cycle absorb the light's energy

Methodology Applied
Scientific EffectLight absorption: Absorption (EM radiation)

Data Source

PatentEP4647026A1Light-based skin treatment apparatus, sensor system, and method for operating the apparatus
Publication Date: 2025.11.12 KONINKLIJKE PHILIPS NV
  • EP4647026A1 patent drawingFigure 1~2
  • EP4647026A1 patent drawingFigure 3~4
  • EP4647026A1 patent drawingFigure 5~6

AI summary

There is provided light-based skin treatment apparatus, comprising a treatment light source adapted to provide treatment light to a skin, and a sensor system for measuring a characteristic of the skin. The sensor system comprises a detection unit having a detector and at least one sensor light source. The at least one sensor light source is adapted to emit sensor light to the skin. The detector is adapted to generate a detector signal in response to receiving at least a portion of the sensor light after interaction of the sensor light with the skin. The sensor system comprises a heat control system adapted to control a temperature of the detection unit at a desired temperature above an ambient temperature.