Distance-measuring device with increased signal-to-noise ratio and method thereof
View Patent ↗A method of increasing signal-to-noise ratio of a distance-measuring device includes a light-emitting component emitting a detecting light to a measured object during an emitting period for generating a reflected light, a delay period after the light-emitting component emitting the detecting light, a light-sensing component sensing the energy of the reflected light to generate a light-sensing signal, and obtaining a measured distance between the distance-measuring device and the measured object according to the energy of the detecting light and the light-sensing signal. Since the measured distance is longer than a predetermined shortest measured distance, the method can accordingly calculate a proper delay period for ensuring that the reflected light reaches the light-sensing component after the delay period. In this way, the light-sensing component does not sense the background light during the delay period, so that the signal-to-noise ratio of the light-sensing signal is improved.
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 first 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, switching the first shutter periodic signal to represent turning-on during a first sensing period for the first light-sensing component to sense and accumulate energy of the reflected light to generate the first 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 first 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;
wherein the delay period is calculated according to the following formula:
T DELAY =2 ×D MIN /C;
wherein T DELAY represents the delay period; D MIN represents the predetermined shortest measured distance; and C represents speed of light;
wherein relationship between the predetermined longest measured distance and the first sensing period is represented by the following formula:
D MAX =2×( T SEN1 +T Delay )/ C;
wherein D MAX represents the predetermined longest measured distance; and T SEN1 represents the first sensing period.
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 first 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 first sensing period is equal to period length of the emitting period.
5. 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, a first light-sensing component for sensing and accumulating energy of light according to a first shutter periodic signal to generate a first light-sensing signal, and a second light-sensing component for sensing and accumulating energy of light according to a second shutter periodic signal to generate a second 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, switching the first shutter periodic signal to represent turning-on during a first sensing period for the first light-sensing component to sense and accumulate energy of the reflected light to generate the first light-sensing signal;
switching the second shutter periodic signal to represent turning-on during a second sensing period for the second light-sensing component to sense and accumulate energy of the reflected light to generate the second light-sensing signal when the first light-sensing component stops sensing the reflected light;
obtaining a time of flight of light going back and forth between the distance-measuring device and the measured object according to a ratio of the first light-sensing signal and the second light-sensing signal; and
obtaining the measured distance according to the time of flight;
wherein the delay period is calculated according to the predetermined shortest measured distance;
wherein the delay period is calculated according to the following formula:
T DELAY =2 ×D MIN /C;
wherein T DELAY represents the delay period; D MIN represents the predetermined shortest measured distance; and C represents speed of light;
wherein relationship between the predetermined longest measured distance and the first sensing period is represented by the following formula:
D MAX =2×( T SEN1 +T DELAY )/ C;
wherein D MAX represents the predetermined longest measured distance; and T SEN1 represents the first sensing period.
6. The method of claim 5 , 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.
7. The method of claim 5 , wherein period length of the first sensing period is equal to period length of the second sensing period.
8. 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 according to a light-emitting periodic signal, and a light-sensing group for sensing and accumulating energy of light according to a first shutter periodic signal to generate a first light-sensing signal, and sensing and accumulating energy of light according to a second shutter periodic signal to generate a second light-sensing signal, the method comprising:
switching the light-emitting periodic signal between representing turning-on and turning off with a detecting frequency, for the light-emitting component to emit the detecting light to the measured object to generate a reflected light during an emitting period, and not emit the detecting light during a non-emitting period;
a delay period after every time the light-emitting component starts to emit the detecting light, switching the first shutter periodic signal to represent turning-on during a first sensing period for the light-sensing group to sense and accumulate energy of the reflected light to generate the first light-sensing signal;
wherein the light-emitting periodic signal and the first shutter periodic signal are substantially in phase;
switching the second shutter periodic signal to represent turning-on during a second sensing period for the light-sensing group to sense and accumulate energy of the reflected light to generate the second light-sensing signal after the first sensing period;
wherein phase of the light-emitting periodic signal is substantially opposite to phase of the second shutter periodic signal;
obtaining a time of flight of light going back and forth between the distance-measuring device and the measured object according to a ratio of the first light-sensing signal and the second light-sensing signal; and
obtaining the measured distance according to the time of flight;
wherein the delay period is calculated according to the predetermined shortest measured distance;
wherein the delay period is calculated according to the following formula:
T DELAY =2 ×D MIN /C;
wherein T DELAY represents the delay period; D MIN represents the predetermined shortest measured distance; and C represents speed of light;
wherein relationship between the predetermined longest measured distance and the first sensing period is represented by the following formula:
D MAX =2×( T SEN1 +T DELAY ) /C;
wherein D MAX represents the predetermined longest measured and T SEN1 represents the first sensing period.
9. The method of claim 8 , 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.
10. The method of claim 8 , further comprising:
switching the first shutter periodic signal to represent turning-on during a background-measuring phase, for the light-sensing group to sense and accumulate energy of a background light to generate the first light-sensing signal; and
generating a background signal according to the first light-sensing signal generated by the light-sensing group during the background-measuring phase and period length of the first shutter periodic signal representing turning-on during the background-measuring phase.
11. The method of claim 10 , wherein obtaining the time of flight of light going back and forth between the distance-measuring device and the measured object according to the ratio of the first light-sensing signal and the second light-sensing signal comprises:
calibrating the ratio between the first light-sensing signal and the second light-sensing signal according to the background signal; and
obtaining the time of flight of light going back and forth between the distance-measuring device and the measured object according to the calibrated ratio between the first light-sensing signal and the second light-sensing signal.
12. The method of claim 11 , wherein obtaining the time of flight of light going back and forth between the distance-measuring device and the measured object according to the calibrated ratio between the first light-sensing signal and the second light-sensing signal comprises:
calculating the time of flight according to the following formula:
T TOF =T DELAY +T SEN1 −[( S LS1 −S B ×T SEN1 )/( S LS1 −S B ×T SEN1 +S LS2 −S B ×T SEN2 )]× T LD ;
wherein T TOF represents the time of flight; T DELAY represents the delay period; T SEN1 represents the first light-sensing period; T SEN2 represents the second light-sensing period; S B represents the background signal; S LS1 represents the first light-sensing signal; S LS2 represents the second light-sensing signal; and T LD represents the emitting period.
13. 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 first light-sensing component, for sensing and accumulating energy of light according to a first shutter periodic signal to generate a first light-sensing signal;
a light-emitting/sensing 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, the light-emitting/sensing controlling circuit switching the first shutter periodic signal representing turning-on during a first sensing period for the first light-sensing component to sense and accumulate energy of the reflected light to generate the first light-sensing signal;
wherein the light-emitting/sensing controlling circuit calculates the delay period according to the predetermined shortest measured distance; and
a distance-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 first 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 light-emitting/sensing controlling circuit calculates the delay period according to the following formula:
T DELAY =2 ×D MIN /C;
wherein T DELAY represents the delay period; D MIN represents the predetermined shortest measured distance; and C represents speed of light;
wherein relationship between the predetermined longest measured distance and the first sensing period is represented by the following formula:
D MX =2×( T SEN1 +T DELAY )/ C;
wherein D MAX represents the predetermined longest measured distance; and T SEN1 represents the first sensing period.
14. The distance-measuring device of claim 13 , 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.
15. The distance-measuring device of claim 13 , wherein a sum of period lengths of the first sensing period and the delay period is equal to period length of the emitting period.
16. The distance-measuring device of claim 13 , wherein period length of the first sensing period is equal to period length of the emitting period.
17. The distance-measuring device of claim 13 , further comprising:
a focusing module, for focusing the reflected light onto the first light-sensing component.
18. 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 first light-sensing component, for sensing and accumulating energy of light according to a first shutter periodic signal to generate a first light-sensing signal;
a second light-sensing component, for sensing and accumulating energy of light according to a second shutter periodic signal to generate a second light-sensing signal;
a light-emitting/sensing 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, the light-emitting/sensing controlling circuit switching the first shutter periodic signal representing turning-on during a first sensing period for the first light-sensing component to sense and accumulate energy of the reflected light to generate the first light-sensing signal, and when the first light-sensing component stops sensing the reflected light, the light-emitting/sensing controlling circuit switching the second shutter periodic signal representing turning-on during a second sensing period for the second light-sensing component to sense and accumulate energy of the reflected light to generate the second light-sensing signal;
wherein the light-emitting/sensing controlling circuit calculates the delay period according to the predetermined shortest measured distance; and
a distance-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 a ratio between the first light-sensing signal and the second light-sensing signal, and generating an output signal representing length of the measured distance according to the time of flight;
wherein the light-emitting/sensing controlling circuit calculates the delay period according to the following formula:
T DELAY =2× D MIN /C;
wherein TDELAY represents the delay period; DMIN represents the predetermined shortest measured distance; and C represents speed of light;
wherein relationship between the predetermined longest measured distance and the first sensing period is represented by the following formula:
D MAX =2×( T SEN1 +T DELAY )/ C;
wherein D MAX represents the predetermined longest measured distance; and T SEN1 represents the first sensing period.
19. The distance-measuring device of claim 18 , 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.
20. The distance-measuring device of claim 18 , wherein period length of the first sensing period is equal to period length of the second sensing period.
21. The distance-measuring device of claim 18 , further comprising:
a focusing module, for focusing the reflected light onto the first light-sensing component and the second light-sensing component.
22. 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 group, for sensing and accumulating energy of light according to a first shutter periodic signal to generate a first light-sensing signal, and sensing and accumulating energy of light according to a second shutter periodic signal to generate a second light-sensing signal;
a light-emitting/sensing controlling circuit, for switching the light-emitting periodic signal between representing turning-on and turning off with a detecting frequency, for the light-emitting component to emit the detecting light to the measured object to generate a reflected light during an emitting period, and not emit the detecting light during a non-emitting period;
wherein a delay period after every time the light-emitting component starts to emit the detecting light, the light-emitting/sensing controlling circuit switches the first shutter periodic signal to represent turning-on during a first sensing period for the light-sensing group to sense and accumulate energy of the reflected light to generate the first light-sensing signal, and after the first sensing period, the light-emitting/sensing controlling circuit switches the second shutter periodic signal to represent turning-on during a second sensing period for the light-sensing group to sense and accumulate energy of the reflected light to generate the second light-sensing signal;
wherein the light-emitting periodic signal and the first shutter periodic signal are substantially in phase, and phase of the light-emitting periodic signal is substantially opposite phase of the second shutter periodic signal;
wherein the light-emitting/sensing controlling circuit calculates the delay period according to the predetermined shortest measured distance; and
a distance-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 a ratio between the first light-sensing signal and the second light-sensing signal, and generating an output signal representing length of the measured distance according to the time of flight;
wherein the light-emitting/sensing controlling circuit calculates the delay period according to the following formula:
T DELAY =2 ×D MIN /C;
wherein T DELAY represents the delay period; D MIN represents the predetermined shortest measured distance; and C represents speed of light;
wherein relationship between the predetermined longest measured distance and the first sensing period is represented by the following formula:
D MAX =2×( T SEN1 +T DELAY )/ C;
wherein D MAX represents the predetermined longest measured distance; and T SEN1 represents the first sensing period.
23. The distance-measuring device of claim 22 , 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.
24. The distance-measuring device of claim 22 , further comprising:
a focusing module, for focusing the reflected light onto the light-sensing group.
25. The distance-measuring device of claim 22 , further comprising:
a background-calculating circuit, the light-emitting/sensing controlling circuit switching the first shutter periodic signal to represent turning-on during a background-measuring phase for the light-sensing group to sense and accumulate energy of a background light to generate the first light-sensing signal, the background-calculating circuit generating a background signal according to the first light-sensing signal generated by the light-sensing group during the background-measuring phase and period length of the first shutter periodic signal representing turning-on during the background-measuring phase.
26. The distance-measuring device of claim 25 , wherein the distance-calculating circuit calibrates the ratio between the first light-sensing signal and the second light-sensing signal according to the background signal, and obtains the time of flight of light going back and forth between the distance-measuring device and the measured object according to the calibrated ratio between the first light-sensing signal and the second light-sensing signal.
27. The distance-measuring device of claim 26 , wherein the distance-calculating circuit calculates the time of flight according to the following formula:
T TOF =T DELAY +T SEN1 −[( S LS1 −S B ×T SEN1 )/( S LS1 −S B ×T SEN1 +S LS2 −S B ×T SEN2 )]× T LD ;
wherein T TOF represents the time of flight; T DELAY represents the delay period, T SEN1 represents the first light-sensing period; T SEN2 represents the second light-sensing period; S B represents the background signal; S LS1 represents the first light-sensing signal; S LS2 represents the second light-sensing signal; and T LD represents the emitting period.
28. 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 according to a light-emitting periodic signal, and a light-sensing group for sensing and accumulating energy of light according to a first shutter periodic signal to generate a first light-sensing signal, and sensing and accumulating energy of light according to a second shutter periodic signal to generate a second light-sensing signal, the method comprising:
switching the light-emitting periodic signal between representing turning-on and turning off with a detecting frequency, for the light-emitting component to emit the detecting light to the measured object to generate a reflected light during an emitting period, and not emit the detecting light during a non-emitting period;
a delay period after every time the light-emitting component starts to emit the detecting light, switching the first shutter periodic signal to represent turning-on during a first sensing period for the light-sensing group to sense and accumulate energy of the reflected light to generate the first light-sensing signal;
wherein the light-emitting periodic signal and the first shutter periodic signal are substantially in phase;
switching the second shutter periodic signal to represent turning-on during a second sensing period for the light-sensing group to sense and accumulate energy of the reflected light to generate the second light-sensing signal after the first sensing period;
wherein phase of the light-emitting periodic signal is substantially opposite to phase of the second shutter periodic signal;
obtaining a time of flight of light going back and forth between the distance-measuring device and the measured object according to a ratio of the first light-sensing signal and the second light-sensing signal;
obtaining the measured distance according to the time of flight;
switching the first shutter periodic signal to represent turning-on during a background-measuring phase, for the light-sensing group to sense and accumulate energy of a background light to generate the first light-sensing signal; and
generating a background signal according to the first light-sensing signal generated by the light-sensing group during the background-measuring phase and period length of the first shutter periodic signal representing turning-on during the background-measuring phase;
wherein the delay period is calculated according to the predetermined shortest measured distance.
29. The method of claim 28 , wherein obtaining the time of flight of light going back and forth between the distance-measuring device and the measured object according to the ratio of the first light-sensing signal and the second light-sensing signal comprises:
calibrating the ratio between the first light-sensing signal and the second light-sensing signal according to the background signal; and
obtaining the time of flight of light going back and forth between the distance-measuring device and the measured object according to the calibrated ratio between the first light-sensing signal and the second light-sensing signal.
30. The method of claim 29 , wherein obtaining the time of flight of light going back and forth between the distance-measuring device and the measured object according to the calibrated ratio between the first light-sensing signal and the second light-sensing signal comprises:
calculating the time of flight according to the following formula:
T TOF =T DELAY +T SEN1 −[( S LS1 −S B ×T SEN1 )/( S LS1 −S B ×T SEN1 +S LS2 −S B ×T SEN2 )]× T LD ;
wherein T TOF represents the time of flight; T DELAY represents the delay period; T SEN1 represents the first light-sensing period; T SEN2 represents the second light-sensing period; S B represents the background signal; S LS1 represents the first light-sensing signal; S LS2 represents the second light-sensing signal; and T LD represents the emitting period.
31. 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 group, for sensing and accumulating energy of light according to a first shutter periodic signal to generate a first light-sensing signal, and sensing and accumulating energy of light according to a second shutter periodic signal to generate a second light-sensing signal;
a light-emitting/sensing controlling circuit, for switching the light-emitting periodic signal between representing turning-on and turning off with a detecting frequency, for the light-emitting component to emit the detecting light to the measured object to generate a reflected light during an emitting period, and not emit the detecting light during a non-emitting period;
wherein a delay period after every time the light-emitting component starts to emit the detecting light, the light-emitting/sensing controlling circuit switches the first shutter periodic signal to represent turning-on during a first sensing period for the light-sensing group to sense and accumulate energy of the reflected light to generate the first light-sensing signal, and after the first sensing period, the light-emitting/sensing controlling circuit switches the second shutter periodic signal to represent turning-on during a second sensing period for the light-sensing group to sense and accumulate energy of the reflected light to generate the second light-sensing signal;
wherein the light-emitting periodic signal and the first shutter periodic signal are substantially in phase, and phase of the light-emitting periodic signal is substantially opposite phase of the second shutter periodic signal;
wherein the light-emitting/sensing controlling circuit calculates the delay period according to the predetermined shortest measured distance;
a distance-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 a ratio between the first light-sensing signal and the second light-sensing signal, and generating an output signal representing length of the measured distance according to the time of flight; and
a background-calculating circuit, the light-emitting/sensing controlling circuit switching the first shutter periodic signal to represent turning-on during a background-measuring phase for the light-sensing group to sense and accumulate energy of a background light to generate the first light-sensing signal, the background-calculating circuit generating a background signal according to the first light-sensing signal generated by the light-sensing group during the background-measuring phase and period length of the first shutter periodic signal representing turning-on during the background-measuring phase.
32. The distance-measuring device of claim 31 , wherein the distance-calculating circuit calibrates the ratio between the first light-sensing signal and the second light-sensing signal according to the background signal, and obtains the time of flight of light going back and forth between the distance-measuring device and the measured object according to the calibrated ratio between the first light-sensing signal and the second light-sensing signal.
33. The distance-measuring device of claim 32 , wherein the distance-calculating circuit calculates the time of flight according to the following formula:
T TOF =T DELAY +T SEN1 −[( S LS1 −S B ×T SEN1 )/( S LS1 −S B ×T SEN1 +S LS2 −S B ×T SEN2 )]× T LD ;
wherein T TOF represents the time of flight; T DELAY represents the delay period, T SEN1 represents the first light-sensing period; T SEN2 represents the second light-sensing period; S B represents the background signal; S LS1 represents the first light-sensing signal; S LS2 represents the second light-sensing signal; and T LD represents the emitting period.