Measuring instrument and method for optical measurement of velocity and direction of particles
Sensor chip, especially for measuring of structures in a finger surface, characterized in that it comprises an electronic ship being in a per se known way provided with a number of sensor electrodes for capacitance measurements, the chip being provided with a first layer comprising a metal or another electrically conducting material over and coupled to the sensor electrodes and a first dielectric layer substantially covering the first metal layer.
1. Sensor chip for measuring structures in a finger surface and including an electronic chip being provided with a number of interrogation electrodes for capacitance measurements, said sensor chip comprising:
a first electrically conductive layer, said first electrically conductive layer comprising sensor points defining positions of sensors in the sensor chip, said sensor points being coupled to the interrogation electrodes in the electronic chip,
a first dielectric layer substantially covering the first electrically conductive layer, and
an outer electrically conductive layer for electric contact with said structures in said finger surface, said outer electrically conductive layer comprising openings formed therein at least over the sensors points,
the electronic chip thus being adapted to measure the capacitance between the outer electrically conductive layer and said interrogation electrodes through the sensor points,
and wherein the sensor points form an essentially linear array with at least one sensor being adapted to measure relative movement between the array and the finger surface.
2. Sensor chip according to claim 1 , wherein the first electrically conductive layer is capacitively coupled to the interrogation electrodes.
3. Sensor chip according to claim 1 , wherein the outer electrically conductive layer is coupled to the electronic chip for application of a varying current or voltage to the outer electrically conductive layer.
4. Sensor chip according to claim 3 , wherein the outer electrically conductive layer is the only conductor applied with the varying current or voltage.
5. Sensor chip according to claim 1 , further comprising a second electrically conductive layer on the first dielectric layer and a second dielectric layer on said second electrically conductive layer, the outer electrically conductive layer being mounted on said second dielectric layer, said second electrically conductive layer constituting an earth plane.
6. Sensor chip according to claim 5 , wherein the second electrically conductive layer constitutes an essentially continuous layer with openings defined over the sensor points in the first electrically conductive layer.
7. Sensor chip according to claim 5 , wherein the thickness of the first and second dielectric layers is equal to or less than the distance between the centres of the sensor points in the first electrically conductive layer.
8. Sensor chip according to claim 1 , comprising a lower electrically conductive layer positioned under the electronic chip.
9. Sensor chip according to claim 1 , wherein the outer electrically conductive layer is electrically coupled to an electrical modulator in the electronic chip.
10. Sensor chip according to claim 1 , wherein the outer electrically conductive layer comprises a structure changing impedance or capacitance when coming close to an electrically conductive object, which together with a suitable electrical circuit is adapted to activate—the sensor chip when the surface to be measured approaches the sensor chip.