Presence sensing method, presence sensing device and light system

1. A presence sensing method for a light, comprising:

detecting a presence of a user by a sensing module having a first sensitivity while the light is off;

turning on the light when identifying the presence of the user and keeping the light on for a delay time period which has a preset length;

increasing a sensitivity of the sensing module to a second sensitivity after turning on the light;

detecting actions of the user by the sensing module having the second sensitivity while the light is on;

determining a length of a next delay time period based on the actions of the user during the previous delay time period immediately prior to the next delay time period; and

keeping the light on for the next delay time period.

2. The method according to claim 1 , further comprising turning off the light if no action is detected during the last delay time period.

3. The method according to claim 2 , further comprising decreasing a luminance of the light before turning off the light.

4. The method according to claim 1 , wherein the determining the length of the next delay time period comprises determining the length of the next delay time period based on times and amplitudes of the actions of the users during the previous delay time period.

5. The method according to claim 1 , wherein increasing the sensitivity of the sensing module comprises decreasing a sensing threshold of the sensing module.

6. A presence sensing device for a light, comprising:

a sensing module, configured to detect a presence of a user with a first sensitivity while the light is off, and detect actions of the user with a second sensitivity higher than the first sensitivity while the light is on; and

a controller, coupled with the sensing module and configured to:

turn on the light if the sensing module identifies the presence of the user while the light is off and set a preset length for a delay time period during which the light is on,

determine a length of a next delay time period based on the actions of the user during the previous delay time period immediately prior to the next delay time period, and

set the delay time period as the determined length.

7. The device according to claim 6 , wherein the controller is configured to turn off the light if no action is detected during the last delay time period.

8. The device according to claim 6 , further comprising: a timer, coupled with the controller and configured to send an end signal to the controller when the current delay time period ends.

9. The device according to claim 6 , wherein the sensing module comprises a first sensing unit having the first sensitivity and a second sensing unit having the second sensitivity.

10. The device according to claim 9 , wherein the first sensing unit has a first sensing threshold, and the second sensing unit has a second sensing threshold which is lower than the first sensing threshold.

11. The device according to claim 6 , wherein the controller is configured to determine the length of the next delay time period based on times and amplitudes of the actions during the previous delay time period.

12. A light system, comprising:

a light; and

a presence sensing device coupled with the light, the presence sensing device comprising:

a sensing module, configured to detect a presence of a user with a first sensitivity while the light is off, and detect actions of the user with a second sensitivity higher than the first sensitivity while the light is on, and

a controller, coupled with the sensing module and configured to:

turn on the light if the sensing module identifies the presence of the user while the light is off and set a preset length for a delay time period during which the light is on,

determine a length of a next delay time period based on the actions of the user during the previous delay time period immediately prior to the next delay time period, and

set the delay time period as the determined length.