Fingerprint identification device, electronic device and fingerprint identification method

A fingerprint identification device includes a fingerprint identification element configured to identify fingerprint and a capacitive touch sensor configured to continuously detect whether an object is touching the fingerprint identification element. A controller is electrically connected to the fingerprint identification element and the capacitive touch sensor. The controller is configured to control the capacitive touch sensor to stop detecting and the fingerprint identification element to start working when the capacitive touch sensor detects that an object is touching the fingerprint identification element.

FIELD

The subject matter herein generally relates to a fingerprint identification device, an electronic device using the fingerprint identification device, and a fingerprint identification method.

BACKGROUND

To perform certain functions an electronic device may require authentication or a password. One may provide authentication by using fingerprint identification devices. Many electronic devices include fingerprint identification devices.

DETAILED DESCRIPTION

FIG. 1andFIG. 2illustrate a fingerprint identification device100according to a first exemplary embodiment. The fingerprint identification device100may be applied in an electronic device500such as a mobile phone as shown inFIG. 8. The fingerprint identification device100comprises a fingerprint identification element110, a capacitive touch sensor120, and a controller130. The capacitive touch sensor120is configured to continuously detect whether an object (such as a finger) is touching the fingerprint identification element110. The fingerprint identification element110is configured for identifying fingerprint. The controller130is electrically connected to the fingerprint identification element110and the capacitive touch sensor120. When the capacitive touch sensor120detects that an object (such as a finger, not shown) is touching the fingerprint identification element110, the controller130controls the capacitive touch sensor120to stop detecting, and controls the fingerprint identification element110to start working.

The fingerprint identification element110may be an area-array sensor defining a fingerprint identification area (not shown). The capacitive touch sensor120is positioned on the fingerprint identification element110and located around the fingerprint identification area. When an object (such as a finger) is touching the fingerprint identification device100, the object (not shown) can cover the whole of the fingerprint identification area and at least a portion of the capacitive touch sensor120. For example, when the fingerprint identification device100is used in a mobile phone in the form of a button (such as the Home button) of the mobile phone, the total size of the fingerprint identification area and a surface area occupied by capacitive touch sensor120is not bigger in surface area than a size of a regular button, ensuring that the object can cover the whole of the fingerprint identification area and at least a portion of the capacitive touch sensor120.

In at least one embodiment, the fingerprint identification element110is an ultrasonic area-array sensor for fingerprint identification. The fingerprint identification element110comprises a signal sending layer19and a signal receiving layer18stacked over the signal sending layer19. The signal sending layer19comprises a first electrode layer11, a second electrode layer12, and a piezoelectric layer13sandwiched between the first electrode layer11and the second electrode layer12. In at least one embodiment, the piezoelectric layer13is made of polyvinylidene fluoride. The first electrode layer11and the second electrode layer12are configured to apply a voltage to the piezoelectric layer13. The piezoelectric layer13is able to vibrate and emit ultrasonic signals when a voltage is applied to the piezoelectric layer13.

The signal receiving layer18comprises a glass substrate17, a receiving array16, and a readout circuit15. Both the receiving array16and the readout circuit15are formed on a surface of the glass substrate17adjacent to the signal sending layer19. In other words, both the receiving array16and the readout circuit15are formed between the signal sending layer19and the glass substrate17. The receiving array16is configured to receive ultrasonic signals reflected by the object when the object is touching the fingerprint identification device100. The readout circuit15is configured for converting the reflected ultrasonic signals to electrical signals.

The capacitive touch sensor120comprises a sensing electrode layer21. In the illustrated embodiment, the sensing electrode layer21is formed on a surface of the glass substrate17far away from the signal sending layer19. The sensing electrode layer21is located around the receiving array16. The sensing electrode layer21is made of an electrically conductive material, such as indium tin oxide. The sensing electrode layer21is electrically connected to the controller130. The sensing electrode layer21and ground form a capacitor. When an object touches the glass substrate17and the sensing electrode layer21, capacitance between the sensing electrode layer21and the ground is changed, thus the object can be detected.

The controller130can be a central processing unit (CPU), a microprocessor, or other data processor chip that performs functions of the fingerprint identification device100. The controller130is electrically connected to the first electrode layer11, the second electrode layer12, the readout circuit15, and the sensing electrode layer21, respectively. When the capacitance between the sensing electrode layer21and ground changes, the controller130controls the sensing electrode layer21to allow the capacitive touch sensor120to stop working, the controller130also controls the first electrode layer11and the second electrode layer12to apply a voltage to the piezoelectric layer13, and allow the fingerprint identification element110to start working. The fingerprint identification element110continuously scans the finger until output a readout signal to the controller130. The controller130analyzes the readout signal to acquire a grayscale fingerprint image, and can control the first electrode layer11and the second electrode layer12to stop applying a voltage to the piezoelectric layer13. Meanwhile, the controller130controls the sensing electrode layer21to allow the capacitive touch sensor120to start working.

If the fingerprint identification element110detects that the object is not a finger, the fingerprint identification element110outputs a sensing signal to the controller130via the readout circuit15, and the controller130controls the fingerprint identification element110to stop working and the capacitive touch sensor120to start working. When the fingerprint identification element110detects that the object is a finger, the fingerprint identification element110continuously scans the finger and outputs the readout signal to the controller130.

As shown inFIG. 2, the capacitive touch sensor120is located around the fingerprint identification element110and substantially has a “U” shape. In other embodiments, the capacitive touch sensor120shown inFIG. 3Ais in the shape of a circular ring which is located around the fingerprint identification element110. The capacitive touch sensor120shown inFIG. 3Bis in the shape of a rectangular frame which is located around the fingerprint identification element110. The capacitive touch sensor120shown inFIG. 3Cis in the shape of a pentagonal frame which is located around the fingerprint identification element110. The capacitive touch sensor120can be other shapes. In other embodiments, the fingerprint identification device100comprises more than one capacitive touch sensor120, and the plurality of capacitive touch sensors120is also located around the fingerprint identification element110.

The capacitive touch sensor120shown inFIG. 2is attached to the glass substrate17. In other embodiments, the capacitive touch sensor120may formed on other portions of the fingerprint identification element110. The capacitive touch sensor120may also be separate from the fingerprint identification element110. It is understood that the fingerprint identification element110is not limited to the above-described structure, but can have other structures. For example, the signal sending layer19and the signal receiving layer18may be located in a same layer instead of being two stacked layers.

The capacitive touch sensor120continuously detects whether an object is touching the fingerprint identification element110. When the capacitive touch sensor120detects that an object (such as a finger) is touching the fingerprint identification element110, the capacitive touch sensor120stops detecting and the fingerprint identification element110starts working. Power consumption of the capacitive touch sensor120is much lower than power consumption of the fingerprint identification element110, thus usage of electrical power can be saved.

FIG. 4illustrates a fingerprint identification device200according to a second exemplary embodiment. The fingerprint identification device200is similar to the fingerprint identification device100except that sensing electrode layer21of the fingerprint identification device200is formed on a flexible printed circuit board150. The capacitive touch sensor120of the fingerprint identification device200comprises a sensing electrode layer21which is made of an electrically conductive material (such as indium tin oxide) and is formed on the flexible printed circuit board150. The flexible printed circuit board150is configured to transmit sensing signals from the sensing electrode layer21to the controller130.

FIG. 5illustrates a fingerprint identification device300according to a third exemplary embodiment. The fingerprint identification device300is similar to the fingerprint identification device100except that a capacitive touch sensor320of the fingerprint identification device300comprises a sending sensing electrode layer28and a receiving sensing electrode layer29formed on the fingerprint identification element110. Both the sending sensing electrode layer28and the receiving sensing electrode layer29are made of an electrically conductive material (indium tin oxide for example). Both the sending sensing electrode layer28and the receiving sensing electrode layer29are in the shape of a strip. The electrode layer28is opposite to and parallel to the receiving electrode layer29.

The electrode layer28and the receiving sensing electrode layer29may form a capacitor. When an object touches fingerprint identification device300, capacitance between the electrode layer28and the receiving sensing electrode layer29changes, thus the object can be detected. The controller130is electrically connected to the electrode layer28and the receiving electrode layer29. When capacitance between the electrode layer28and the receiving sensing electrode layer29is changed, the controller130controls the electrode layer28and the receiving sensing electrode layer29to allow the capacitive touch sensor320to stop working. If the fingerprint identification element110continuously scans the object, and then outputs a readout signal to the controllers130, the controller130controls the electrode layer28and the receiving sensing electrode layer29to allow the capacitive touch sensor320to start working.

FIG. 6illustrates a fingerprint identification device400according to a fourth exemplary embodiment. The fingerprint identification device400is similar to the fingerprint identification device300except that both the sending sensing electrode layer28and the receiving sensing electrode layer29of the fingerprint identification device400are formed on a flexible printed circuit board160. Both the sending sensing electrode layer28and the receiving sensing electrode layer29of the fingerprint identification device300are formed on the fingerprint identification element110.FIG. 7illustrates a flow chart of a method for identifying a fingerprint. The example method is provided by way of example, as there are a variety of ways to carry out the method. The example method described below can be carried out using the configurations illustrated inFIGS. 2, 4, 5 and 6, for example, and various elements of these figures are referenced in explaining example method. Each block shown inFIG. 7represents one or more processes, methods, or subroutines, carried out in the exemplary method. Furthermore, the illustrated order of blocks is by example only and the order of the blocks can change. The exemplary method can begin at block701according to the present disclosure. Depending on the embodiment, additional steps can be added, others removed, and the ordering of the steps can be changed.

At block701, the capacitive touch sensor starts working when the capacitive touch sensor is powered on.

At block703, the capacitive touch sensor continuously detects whether an object is touching the fingerprint identification element. If yes, the process goes to block705, if no, the processes goes back to block703.

At block705, the controller powers on the fingerprint identification element to start working and powers off the capacitive touch sensor to stop working.

At block707, the fingerprint identification element determines whether the object is a finger. If yes, the process goes to block709, if no, the process goes back to block711.

At block709, the fingerprint identification element continuously scans the object (the finger) until output a readout signal to the controller.

At block711, the controller powers off the fingerprint identification element to stop working and powers on the capacitive touch sensor to start working.

FIG. 8illustrates an electronic device500using the fingerprint identification device100. The electronic device500is a mobile phone. The electronic device500also comprises an optical sensor600electrically connected to the fingerprint identification device100. In this embodiment, the fingerprint identification device100forms a button (such as Home button) of the electronic device500. The optical sensor600and the fingerprint identification device100are mounted at a same surface of the electronic device500, but the optical sensor600is far away from the fingerprint identification device100. In this embodiment, the optical sensor600is mounted adjacent to the top end of the electronic device500, and the fingerprint identification device100is mounted adjacent to the bottom end of the electronic device500.

When the capacitive touch sensor120detects an object is touching the fingerprint identification element110, the optical sensor600detects whether the object is an erroneous object, such as face of a user or pocket of a user touching the fingerprint identification element110. In this disclosure, the correct object is finger; other things except finger are erroneous objects. If the optical sensor600detects an erroneous object, the capacitive touch sensor120continuously detects whether a new object is touching the fingerprint identification element110. If the optical sensor600detects a correct object, the fingerprint identification element110would be powered on and the capacitive touch sensor320would be powered off.

FIG. 9illustrates a flow chart of a method for preventing erroneously touching the electronic device ofFIG. 8during fingerprint identification. The example method is provided by way of example, as there are a variety of ways to carry out the method. The example method described below can be carried out using the configurations illustrated inFIGS. 2, 4, 5, and 8, for example, and various elements of these figures are referenced in explaining example method. Each block shown inFIG. 9represents one or more processes, methods, or subroutines, carried out in the exemplary method. Furthermore, the illustrated order of blocks is by example only and the order of the blocks can change. The exemplary method can begin at block901according to the present disclosure. Depending on the embodiment, additional steps can be added, others removed, and the ordering of the steps can be changed.

At block901, the capacitive touch sensor of the fingerprint identification device starts working when the capacitive touch sensor is powered on.

At block903, the capacitive touch sensor continuously detects whether an object is touching the fingerprint identification element110. If yes, the process goes to block905, if no, the process goes back to block903.

At block905, the optical sensor detects whether the object is an erroneous object. If yes, the process goes to block903, if no, the process goes back to block907.

At block907, the controller powers on the fingerprint identification element of the fingerprint identification device to start working and powers off the capacitive touch sensor to stop working.

At block909, the fingerprint identification element continuously scan the object (a finger) until outputs a readout signal to the controller; and then the controller powers off the fingerprint identification element.