By Josh Perry, Editor
Researchers at Tohoku University (Sendai, Japan) recently presented a new capacitance imaging sensor that has a high enough resolution and sensitivity that it can display not only the swirls of a fingerprint but also the sweat pores between the ridges.
Researchers developed a high-res capacitance imaging sensor. (Tohoku University)
According to a report from the university, a prototype sensor was first presented at the 2018 IEEE International Electron Devices Meeting in December and researchers released new materials and experimental data in March.
“Many touch screen phones and computer track pads use a less sensitive capacitance sensor, where the differences in electrical properties between a sensor and a conductive tool (such as a finger) allow the device to react to scrolling or double clicking,” the report explained. “The capacitance increases when the object is closer - the double-click versus lighter scrolling.”
This new sensor boosts the sensitivity to another level thanks to new noise reduction technology that eliminate background thermal noise or noise from the variability of electrical components of the pixels.
“The sensor chip contains pixels to detect the capacitance between the sample and detection electrodes,” the report continued. “Each pixel has one detection electrode attached to it that's capacitively coupled with a ground wire. These electrical signals are converted into images of the samples.”
Scientists used reset switched to the detection electrodes and a voltage pulse to create a circuit that follows the source of the noise, with the switched detecting the noise and the voltage pulses effectively cancelling it out.
“It's the equivalent of removing the white and black snow from a television without signal input into a smooth, grey screen,” the article noted. “It's much easier to sense any deviation on a solid background.”
Researchers hope to tailor the sensor to specific applications, such as the inspection of PCB.