Distance measuring device with increased signal-to-noise ratio and method thereof

1. A method of increasing signal-to-noise ratio of a distance-measuring device, the distance-measuring device being utilized for measuring a measured distance between the distance-measuring device and a measured object, the measured distance being longer than a predetermined shortest measured distance and shorter than a predetermined longest measured distance, the distance-measuring device having a light-emitting component for emitting a detecting light, and a first light-sensing component for sensing and accumulating energy of light according to a first shutter periodic signal to generate a light-sensing signal, the method comprising:

the light-emitting component continuously emitting the detecting light to the measured object to generate a reflected light during an emitting period;

a delay period after the light-emitting component starts to emit the detecting light, the first light-sensing component sensing and accumulating energy of the reflected light during a sensing period to generate the light-sensing signal;

obtaining a time of flight of light going back and forth between the distance-measuring device and the measured object according to the light-sensing signal and energy of the detecting light emitted by the light-emitting component during the emitting period; and

obtaining the measured distance according to the time of flight;

wherein:

the delay period is calculated according to the predetermined shortest measured distance;

a relationship between the predetermined longest measured distance and the sensing period is represented by D MAX =2×(T SEN1 +T DELAY )/C;

D MAX represents the predetermined longest measured distance;

T SEN1 represents the sensing period;

T DELAY represents the delay period; and

C represents speed of light.

2. The method of claim 1 , wherein obtaining the measured distance according to the time of flight comprises:

calculating the measured distance according to the following formula:

D M =T TOF ×C/ 2;

wherein D M represents the measured distance; T TOF represents the time of flight; and C represents speed of light.

3. The method of claim 1 , wherein a sum of period lengths of the sensing period and the delay period is equal to period length of the emitting period.

4. The method of claim 1 , wherein period length of the sensing period is equal to period length of the emitting period.

5. The method of claim 1 , further comprising calculating the delay period according to T DELAY =2×D MIN /C, wherein D MIN represents the predetermined shortest measured distance.

6. A distance-measuring device with increased signal-to-noise ratio, the distance-measuring device being utilized for measuring a measured distance between the distance-measuring device and a measured object, the measured distance being longer than a predetermined shortest measured distance and shorter than a predetermined longest measured distance, the distance-measuring device comprising:

an emitting component, for emitting a detecting light;

a light-sensing component, for sensing and accumulating energy of light to generate a light-sensing signal;

a controlling circuit, for controlling the emitting component to continuously emit the detecting light to the measured object to generate a reflected light during an emitting period, and a delay period after the light-emitting component starts to emit the detecting light, for controlling the light-sensing component to sense and accumulate energy of the reflected light during a sensing period to generate the light-sensing signal; and

a calculating circuit, for obtaining a time of flight of light going back and forth between the distance-measuring device and the measured object according to the light-sensing signal and energy of the detecting light emitted by the light-emitting component during the emitting period, and generating an output signal representing length of the measured distance according to the time of flight; wherein:

the delay period is calculated according to the predetermined shortest measured distance;

a relationship between the predetermined longest measured distance and the sensing period is represented by D MAX =2×(T SEN1 +T DELAY )/C;

D MAX represents the predetermined longest measured distance;

T SEN1 represents the sensing period;

T DELAY represents the delay period; and

C represents speed of light.

7. The distance-measuring device of claim 6 , wherein the distance-calculating circuit calculates the measured distance according to the following formula:

D M =T TOF ×C /2;

wherein D M represents the measured distance; T TOF represents the time of flight; and C represents speed of light.

8. The distance-measuring device of claim 6 , wherein a sum of period lengths of the sensing period and the delay period is equal to period length of the emitting period.

9. The distance-measuring device of claim 6 , wherein period length of the sensing period is equal to period length of the emitting period.

10. The distance-measuring device of claim 6 , further comprising:

a focusing module, for focusing the reflected light onto the-light-sensing component.

11. The distance-measuring device of claim 6 , wherein the calculating circuit is configured to calculate the delay period according to T DELAY =2×D MIN /C, wherein D MIN represents the predetermined shortest measured distance.