Optical Sensor Skin Detection Temperature Compensation
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Solution Overview
Problem
Existing optical devices for detecting human skin are sensitive to temperature fluctuations and lack the ability to accurately differentiate skin from other materials, particularly in terms of spectral remission and pigmentation, leading to variable and unreliable results.
Innovation Solution
The use of a single broad-band source or multiple narrow-band sources with corresponding detectors to measure spectral remission, allowing for calibration to determine absolute remission values and detect skin presence and pigmentation levels, while minimizing temperature sensitivity through temperature compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If LED sources are used as optical sources, then the device can detect skin presence, but the output power varies with temperature causing measurement errors
Solution Approach 1:
The system uses a feedback mechanism where the detected remitted light intensity is used to dynamically adjust the LED drive current. The controller monitors the light remission and automatically compensates for temperature-induced power variations by adjusting the drive current to maintain consistent output, thereby eliminating temperature sensitivity effects on measurement accuracy.
2Loss of information
If prior art skin sensors are used, then skin presence can be detected, but only broad indication is provided without spectral remission data
Solution Approach 1:
The optical detection is segmented into multiple wavelength bands using either multiple LEDs with different peak wavelengths or a single broadband LED with spectral filtering. Each wavelength band provides independent remission measurements, enabling spectral analysis that distinguishes skin from other materials based on their unique spectral signatures, thereby preventing loss of spectral information.
Solution Approach 2:
The system transitions from single-dimensional intensity detection to multi-dimensional spectral detection by measuring remission across multiple wavelength bands. This dimensional expansion allows the system to capture spectral remission characteristics that provide additional information for more precise skin detection and pigmentation assessment.
3Measurement precision
If prior art devices are used, then skin detection is provided, but the degree of pigmentation cannot be ascertained
Solution Approach 1:
The spectral range is segmented into multiple wavelength bands that are sensitive to different pigmentation levels. By comparing remission ratios across these segmented bands, the system can quantify pigmentation degree, as melanin absorption characteristics vary systematically with wavelength, enabling precise pigmentation measurement that was previously unavailable.
4Measurement precision
If multiple narrow-band sources and detectors are used, then spectral remission can be measured, but device complexity and cost increase
Solution Approach 1:
The system merges multiple narrow-band detection channels into a single broadband detector by using sequential illumination with different wavelength bands. Instead of requiring simultaneous multi-wavelength detection capability, the system combines temporal sequencing with spectral filtering, allowing a single detector to capture spectral remission data across multiple bands, thereby reducing device complexity while maintaining measurement precision.
Solution Approach 2:
The system employs periodic action by sequentially activating different LED wavelength bands or filtering mechanisms in alternating cycles. This temporal periodicity allows a single broadband detector to measure spectral remission at different wavelengths at different times, achieving multi-wavelength spectral analysis without requiring multiple simultaneous detection channels, thus simplifying the device architecture.
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 enables precise differentiation of human skin from other materials, reduces temperature-related errors, and allows for safe and appropriate operation of dermatological treatment devices by ensuring skin presence and pigmentation levels meet predetermined criteria.
Implementation Method 1
a light source that emits light onto the skin and a photodetector that detects light remitted by the skin
Implementation Method 2
the sensitivity of the phototransistor used to detect the remitted light may depend on the temperature of the phototransistor
Data Source
AI summary
Apparatus and methods are provided to control a device, such as a light emitting dermatologic or cosmetic treatment device, and ensure that the device is in contact with skin while also determining the pigmentation level of skin. One or more light sources contact the skin and one or more detectors measure spectral remission from the skin. The obtained remission measurements are compared with known skin spectral remission values, and calibration allows measurements of absolute remission to be converted to fractional remission values. Skin pigmentation levels are compared to known base-line levels to determine and control appropriate treatment parameters. A temperature sensor allows correction for temperature variations. The apparatus may or may not be incorporated into the treatment device.