Image sensing device and fingerprint sensing method

1. An image sensing device suitable for being installed in an electronic device, wherein the image sensing device comprises:

a light sensor; and

a controller coupled to the light sensor,

wherein, in response to the electronic device being operated in a sleep mode, the controller operates the light sensor in a light sensing mode, and the controller determines whether a number of signal intensity changes of a photosensitive signal output by the light sensor exceeds a predetermined number of intensity changes within a predetermined length of time to switch operation of the light sensor in a fingerprint sensing mode,

wherein the controller determines whether signal intensity of the photosensitive signal first becomes less than a first signal intensity threshold value and then greater than a second signal intensity threshold value to calculate the number of the signal intensity changes of the photosensitive signal, and

wherein the second signal intensity threshold value is greater than the first signal intensity threshold value.

2. The image sensing device according to claim 1 , wherein, in response to the light sensor being in the light sensing mode, it is determined whether a light source is lit up to illuminate a finger according to whether a current sensing environment is a dark state environment or a light state environment, and in response to the controller switching the operation of the light sensor in the fingerprint sensing mode, the controller outputs a waking signal to a processor of the electronic device to wake the electronic device.

3. The image sensing device according to claim 2 , wherein in response to the electronic device being woken and the light sensor performing fingerprint sensing, the electronic device simultaneously lights up the light source so that the controller obtains a fingerprint image of the finger through the light sensor.

4. The image sensing device according to claim 3 , wherein the controller provides the fingerprint image to the electronic device so that the electronic device performs fingerprint verification on the fingerprint image, and in response to the fingerprint image passing the fingerprint verification, the electronic device turns off the image sensing device and the light source.

5. The image sensing device according to claim 1 , wherein the controller determines whether signal intensity of the photosensitive signal first becomes less than a third signal intensity threshold value and then greater than the third signal intensity threshold value to calculate the number of the signal intensity changes of the photosensitive signal.

6. The image sensing device according to claim 1 , wherein, in response to the light sensor being operated in the light sensing mode, the light sensor continuously detects a light signal intensity change through at least one of a plurality of sensing pixels.

7. The image sensing device according to claim 1 , wherein in response to the light sensor being operated in the fingerprint sensing mode, the light sensor performs fingerprint sensing through all of a plurality of sensing pixels to obtain a fingerprint image.

8. The image sensing device according to claim 1 , wherein the light sensing mode is a light fidelity mode.

9. The image sensing device according to claim 1 , wherein the light sensing mode is an illumination detection mode.

10. A fingerprint sensing method, comprising:

in response to an electronic device being operated in a sleep mode, operating a light sensor in a light sensing mode; and

determining whether a number of signal intensity changes of a photosensitive signal output by the light sensor exceeds a predetermined number of intensity changes within a predetermined length of time to switch operation of the light sensor in a fingerprint sensing mode,

wherein determining the number of the signal intensity changes of the photosensitive signal output by the light sensor comprises:

determining whether signal intensity of the photosensitive signal first becomes less than a first signal intensity threshold value and then greater than a second signal intensity threshold value to calculate the number of the signal intensity changes of the photosensitive signal, and

wherein the second signal intensity threshold value is greater than the first signal intensity threshold value.

11. The fingerprint sensing method according to claim 10 , further comprising:

in response to the light sensor being in the light sensing mode, determining whether a light source is lit up to illuminate a finger according to whether a current sensing environment is a dark state environment or a light state environment; and

in response to the operation of the light sensor being switched in the fingerprint sensing mode, outputting a waking signal to a processor of the electronic device to wake the electronic device.

12. The fingerprint sensing method according to claim 11 , further comprising:

in response to the electronic device being woken and the light sensor performing fingerprint sensing, simultaneously lighting up the light source so that the light sensor obtains a fingerprint image of the finger.

13. The fingerprint sensing method according to claim 12 , further comprising:

providing the fingerprint image to the electronic device so that the electronic device performs fingerprint verification on the fingerprint image; and

in response to the fingerprint image passing the fingerprint verification, turning off the light sensor and the light source.

14. The fingerprint sensing method according to claim 10 , wherein determining the number of the signal intensity changes of the photosensitive signal output by the light sensor comprises:

determining whether signal intensity of the photosensitive signal first becomes less than a third signal intensity threshold value and then greater than the third signal intensity threshold value to calculate the number of the signal intensity changes of the photosensitive signal.

15. The fingerprint sensing method according to claim 10 , wherein, in response to the light sensor being operated in the light sensing mode, the light sensor continuously detects a light signal intensity change through at least one of a plurality of sensing pixels.

16. The fingerprint sensing method according to claim 10 , wherein in response to the light sensor being operated in the fingerprint sensing mode, the light sensor performs fingerprint sensing through all of a plurality of sensing pixels to obtain a fingerprint image.

17. The fingerprint sensing method according to claim 10 , wherein the light sensing mode is a light fidelity mode.

18. The fingerprint sensing method according to claim 10 , wherein the light sensing mode is an illumination detection mode.