Thermal Fingerprint Sensor Pixel Heating Method
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Solution Overview
Problem
Active thermal fingerprint sensors face limitations due to diathermy effects, where heat transfer between adjacent pixels reduces the effectiveness of thermal pattern capture, leading to inefficient heating and signal degradation.
Innovation Solution
The method involves simultaneously heating both the target pixel and adjacent pixels during reading, utilizing diathermy to enhance heat injection into the target pixel, thereby increasing the reading signal while minimizing heat loss to neighboring pixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If heating elements are used to heat target pixels during reading, then the reading signal strength is improved, but heat transfer to adjacent pixels (diathermy) causes signal degradation and reduces heating efficiency
Solution Approach 1:
The method applies preliminary heating to adjacent pixels before reading the target pixel. By pre-heating the adjacent pixels, the diathermy effect is converted into a beneficial source of heat for the target pixel, improving the reading signal while reducing the energy required from the target pixel's heating element.
Solution Approach 2:
The invention converts the harmful diathermy effect (unwanted heat transfer to adjacent pixels) into a beneficial effect by intentionally heating adjacent pixels. The heat that would otherwise be considered a loss is now used to supplement the heating of the target pixel, improving signal strength while reducing overall energy consumption.
2Measurement precision
If higher heating current is applied to target pixels, then the thermal pattern capture quality is improved, but circuit damage risk increases
Solution Approach 1:
By converting the diathermy effect from harmful to beneficial, the system can achieve the required thermal pattern capture quality using lower heating currents. The adjacent pixels serve as additional heat sources, reducing the burden on the target pixel's heating element and eliminating the need for high currents that could damage the circuit.
Solution Approach 2:
The invention changes the thermal parameters of the system by heating adjacent pixels to different temperatures than the target pixel. This creates a controlled thermal gradient that improves heat transfer to the target pixel while maintaining safe operating temperatures for all circuit components.
3Use of energy by moving object
If only target pixels are heated during reading, then energy consumption is reduced, but signal strength is insufficient due to diathermy heat loss
Solution Approach 1:
The invention transforms the energy loss from diathermy into a useful resource. By heating adjacent pixels, the system recovers what would have been wasted heat and uses it to strengthen the reading signal, achieving better signal strength without proportionally increasing energy consumption.
Solution Approach 2:
The method merges the heating functions of adjacent pixels to support the target pixel reading. The adjacent pixels are heated and their thermal energy is combined with the target pixel's heating, creating a synergistic effect that improves signal strength while keeping total energy consumption manageable.
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 approach allows for increased heating current without risking circuit damage, reduces unwanted heat transfer, and improves the quality of thermal pattern capture by maintaining temperature differences between pixels, resulting in enhanced signal strength and reduced diathermy effects.
Implementation Method 1
The pixels of such a sensor are coupled to heating elements generally using the Joule effect which dissipate heat from a resistive element through which a current flows
Implementation Method 2
A fingerprint sensor includes thermal sensing means. These thermal sensing means may be pyroelectric elements, diodes, thermistors, or any other temperature-sensitive element capable of converting a temperature variation into a variation in electrical potential or current
Implementation Method 3
Active thermal fingerprint sensors face limitations due to diathermy effects, where heat transfer between adjacent pixels reduces the effectiveness of thermal pattern capture
Data Source
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AI summary
Method of capturing a thermal pattern by a sensor (100) comprising a matrix of several rows and columns of pixels (102) and a plurality of heating elements (111) each associated with a pixel or a group of pixels, and capable of heating a thermosensitive measuring element (106) of the pixel or of each pixel of the group of pixels independently of the other heating elements when reading the pixel or at least one of the pixels of said group, wherein, when reading a first pixel or first group of pixels, heating of this first pixel or each pixel of the first group by the associated heating element and heating of a second pixel or second group of pixels by at least one other associated heating element are implemented, the second pixel or second group of pixels being read before or after the first pixel or first group of pixels.