Visibility meter, street light device and operation method thereof

1. A visibility meter, configured to sense a fog to determine a visibility, the visibility meter comprising:

a controller;

an optical transmitter, coupled to the controller, the optical transmitter being configured to transmit a visible laser;

an optical sensor, coupled to the controller, the optical sensor receiving the visible laser to generate a sensed result; and

a hygrometer, coupled to the controller and configured to sense an ambient humidity, wherein

the controller calculates the visibility according to the sensed result and a reference value of a luminous intensity, wherein

the controller updates the reference value according to the ambient humidity being lower than a first humidity threshold.

2. The visibility meter according to claim 1 , wherein the visible laser is a blue light laser.

3. The visibility meter according to claim 1 ,

wherein the optical transmitter is activated according to the ambient humidity being higher than a second humidity threshold, so as to transmit the visible laser.

4. The visibility meter according to claim 1 , wherein the optical sensor receives an ambient light to calculate an ambient brightness, and the controller updates the reference value according to the ambient brightness being lower than a brightness threshold.

5. The visibility meter according to claim 1 , wherein a path length of the visible laser between the optical transmitter and the optical sensor is greater than or equal to 50 cm.

6. The visibility meter according to claim 5 , wherein a shape of an optical path of the visible laser between the optical transmitter and the optical sensor comprises an 8 shape, a bow-tie shape, a triangle-like shape, an S shape, or a pentagram shape.

7. The visibility meter according to claim 5 , further comprising:

a housing, the optical transmitter and the optical sensor being disposed on the housing; and

at least one optical path changing element, disposed on the housing to change a path of the visible laser between the optical transmitter and the optical sensor.

8. A street light device, comprising:

an illumination light source;

a driving circuit, coupled to the illumination light source, wherein the driving circuit is configured to drive the illumination light source; and

a visibility meter, comprising:

an optical transmitter, configured to transmit a visible laser;

an optical sensor, configured to receive the visible laser to generate a sensed result;

a hygrometer, configured to sense an ambient humidity; and

a controller, coupled to the optical transmitter, the optical sensor, the hygrometer, and the driving circuit, wherein the controller calculates a visibility according to the sensed result and a reference value of a luminous intensity, configures the driving circuit according to the visibility to adjust a color temperature of the illumination light source, and updates the reference value according to the ambient humidity being lower than a first humidity threshold.

9. The street light device according to claim 8 , wherein the illumination light source comprises a first light source and a second light source, wherein the first light source emits light with a first color temperature, the second light source emits light with a second color temperature, and the first color temperature is lower than the second color temperature.

10. The street light device according to claim 9 , wherein a first driving current value of the first light source is inversely proportional to the visibility, and a second driving current value of the second light source is directly proportional to the visibility.

11. The street light device according to claim 8 , further comprising:

a wireless transceiver, coupled to the controller, wherein the controller transmits a message comprising the visibility or a color temperature configuration corresponding to the visibility to an external electronic device through the wireless transceiver.

12. An operation method of a street light device, comprising:

transmitting a visible laser through an optical transmitter;

receiving the visible laser through an optical sensor to generate a sensed result

sensing an ambient humidity through a hygrometer;

calculating a fog-based visibility according to the sensed result and a reference value of a luminous intensity; and

updating the reference value according to the ambient humidity being lower than a first humidity threshold.

13. The operation method of the street light device according to claim 12 , further comprising:

adjusting a color temperature of light emitted by the street light device according to the fog-based visibility.