Distance-measuring-device

1. A method for determining the distance (d) from a distance-measuring-device ( 50 ) to an object ( 24 ), said method comprising:

a) sending a light-pulse ( 62 ) from a light-emitting component ( 60 ) to the object ( 24 ) by passing a current (I1) through the light-emitting component ( 60 );

b) measuring a value indicative of the current (I1) through the light-emitting component ( 60 ) or a voltage (V1) across the light-emitting component ( 60 ), determining a reference-time T0 when the value exceeds a pre-determined first threshold-value THL1, and determining a first-time T1 when the value is reduced to a pre-determined second threshold-value THL2;

c) using the time first-time T1 to define an end point and a start point of two adjacent time-slots;

d) receiving a reflected light-pulse ( 72 ) from said object ( 24 ) at said distance-measuring-device ( 50 ) by a light sensor ( 26 );

e) integrating a measure of the intensity of reflected light-pulse ( 72 ) in said light sensor ( 26 ) during the two time-slots to provide two values (Q1/Q3 and Q2/Q4); and

f) determining a time of flight from the two values of step e), a difference in time between T0 and T1 (T1−T0), and the speed of light, c.

2. The method in accordance with claim 1 , wherein said measure of the intensity of reflected light-pulse ( 72 ) is a current (Ipd) through the light sensor ( 26 ).

3. The method in accordance with claim 1 , wherein the value of (T1−T0) is determined by charging a first capacitor ( 73 ) of value C1 by a constant current Ic between times T0 and T1 to a voltage value VC1 and where T1−T0=(VC1*C1)/Ic.

4. The method in accordance with claim 1 , wherein the thresholds THL1 and THL2 are equal.

5. A method for determining the distance (d) from a distance-measuring-device ( 50 ) to an object ( 24 ), said method comprising:

a) sending a light-pulse ( 62 ) from a light-emitting component ( 60 ) to said object ( 24 ) by means of passing a current pulse (I1) sent through said light-emitting component ( 60 );

b) measuring a value indicative of the current (I1) through or a voltage (V1) across said light-emitting component ( 60 ), determining the reference-time T0 when the value exceeds a pre-determined first threshold-value THL1, and determining the first-time T1 when the value is reduced to a pre-determined second threshold-value THL2;

c) receiving a reflected light-pulse ( 72 ) from said object ( 24 ) at said distance-measuring-device ( 50 ) by a light sensor ( 26 );

d) integrating a measure of the intensity of the reflected light-pulse ( 72 ) in said light sensor ( 26 ) between time T0 and T1 to provide a value Q1;

e) integrating a measure of the intensity of a reflected light-pulse ( 72 ) in said light sensor ( 26 ) between time T1 and T2, where T2 is the time-interval equal to T0−F(2*(T1−T0)) to provide a value Q2; and

f) determining the distance (d) from the formula d=½*c*(T1−T0)*(Q1/(Q1+Q2)).

6. The method in accordance with claim 5 , wherein said measure of the intensity of the reflected light-pulse ( 72 ) is current (Ipd) through the light sensor ( 26 ).

7. The method in accordance with claim 5 , wherein the value of (T1−T0) is determined by charging a first capacitor ( 73 ) of value C1 by a constant current Ic between times T0 and T1 to a voltage value VC1 and where T1−T0=(VC1*C1)/Ic.

8. The method in accordance with claim 5 , wherein the thresholds THL1 and THL2 are equal.

9. A method for determining the distance (d) from a distance-measuring-device ( 50 ) to an object ( 24 ), said method comprising:

a) sending a light-pulse ( 62 ) from a light-emitting component ( 60 ) to said object ( 24 ) by means of passing ( 70 ) a current pulse (I1) sent through said light-emitting component ( 60 );

b) measuring a value indicative of the current (I1) through or a voltage (V1) across said light-emitting component ( 60 ), determining the reference-time T0 when the value exceeds a pre-determined first threshold-value THL1, and determining the first-time T1 when the value is reduced to a pre-determined second threshold-value THL2;

c) receiving a reflected light-pulse ( 72 ) from said object ( 24 ) at said distance-measuring-device ( 50 ) by a light sensor ( 26 );

d) measuring the current (Ipd) through or voltage across said light sensor ( 26 ), determining the point TA when the value exceeds a pre-determined third threshold-value THL3, and determining the point TB when the value is reduced to a pre-determined fourth threshold-value THL4;

e) integrating a measure of the intensity of a reflected light-pulse ( 72 ) in said light sensor ( 26 ) between time TA and T1 to provide a value Q3;

f) integrating a measure of the intensity of a reflected light-pulse ( 72 ) in said light sensor ( 26 ) between time T1 and TB to provide a value Q4;

g) determining the distance (d) from the formula d=½*c*(T1−T0)*(Q3/(Q3+Q4)).

10. The method in accordance with claim 9 , wherein said measure of the intensity of the reflected light-pulse ( 72 ) is current (Ipd) through the light sensor ( 26 ).

11. The method in accordance with claim 9 , wherein the value of (T1−T0) is determined by charging a first capacitor ( 73 ) of value C1 by a constant current Ic between times T0 and T1 to a voltage value VC1 and where T1−T0=(VC1*C1)/Ic.

12. The method in accordance with claim 9 , wherein the thresholds THL1 and THL2 are equal.

13. An apparatus for determining the distance (d) from a distance-measuring-device ( 50 ) to an object ( 24 ) comprising:

a) means to send a light-pulse ( 62 ) from a light-emitting component ( 60 ) to said object ( 24 ) by passing a current pulse (I1) through said light-emitting component ( 60 );

b) means to measure the current (I1) through or voltage (V1) across said light-emitting component ( 60 ), determine a reference-time T0 when the value exceeds a pre-determined first threshold-value THL1, and determine a first-time T1 when the value is reduced to a pre-determined second threshold-value THL2;

c) means to using the time first-time T1 to define two time-windows;

d) means to receive a reflected light-pulse ( 72 ) from said object ( 24 ) at said distance-measuring-device ( 50 ) by a light sensor ( 26 );

e) means to integrate a measure of an intensity of the reflected light-pulse ( 72 ) in said light sensor ( 26 ) during the two time-windows to provide two values (Q1/Q3 and Q2/Q4); and

f) means to determine a time of flight from the two values (Q1/Q3 and Q2/Q4), a difference between T0 and T1 (T1−T0), and the speed of light, c.

14. The apparatus in accordance with claim 13 , wherein the thresholds THL1 and THL2 are equal.

15. The apparatus in accordance with claim 13 , wherein said means of measuring the intensity of the reflected light-pulse ( 72 ) comprises means to measure current (Ipd) through the light sensor ( 26 ).

16. The apparatus in accordance with claim 13 , wherein the means of determining the value of (T1−T0) comprises a first capacitor of value C1 charged by a constant current Ic between times T0 and T1 to a voltage value VC1 such that T1−T0=(VC1*C1)/Ic.

17. The apparatus in accordance with claim 13 , wherein the means for determining the reference-time T0 and for determining the first-time T1 comprises a voltage comparator ( 80 ) having an adjustable threshold voltage input.

18. An apparatus for determining the distance (d) from a distance-measuring-device ( 50 ) to an object ( 24 ) comprising:

a) means for sending ( 84 ) a light-pulse ( 62 ) from a light-emitting component ( 60 ) to said object ( 24 ) by means of passing ( 70 ) a current pulse (I1) sent through said component;

b) means for measuring ( 80 ) a value indicative of the current (I1) through or a voltage (V1) across said light-emitting component ( 60 );

c) means for determining ( 80 ) a reference-time T0 when the values exceeds a pre-determined first threshold-value THL1 and means for determining ( 80 ) the first-time T1 when the value is reduced to a pre-determined second threshold-value THL2;

d) means for determining the point T2 where T2 is the time-interval equal to T0−F(2*(T1−T0));

e) light sensor means ( 26 ) for receiving a reflected light-pulse ( 72 );

f) means for integrating a measure of the intensity of the reflected light-pulse ( 72 ) in said light sensor ( 26 ) between time T0 and T1 to provide a value Q1 and for integrating a measure of the intensity of the reflected light-pulse ( 72 ) in said light sensor ( 26 ) between time T1 and T2, where T2 is the time-interval equal to T0+( 2 *(T1−T0)), to provide a value Q2;

g) means for determining the distance (d) from the formula d=½ *c*(T1−T0)*(Q1/(Q1+Q2)).

19. The apparatus in accordance with claim 18 , wherein the thresholds THL1 and THL2 are equal.

20. The apparatus in accordance with claim 18 , wherein said means of measuring the intensity of the reflected light-pulse ( 72 ) comprises means to measure current (Ipd) through the light sensor ( 26 ).

21. The apparatus in accordance with claim 18 , wherein the means of determining the value of (T1−T0) comprises a first capacitor of value C1 charged by a constant current Ic between times T0 and T1 to a voltage value VC1 such that T1−T0=(VC1*C1)/Ic.

22. The apparatus in accordance with claim 18 , wherein the means for determining the reference-time T0 and for determining the first-time T1 comprises a voltage comparator ( 80 ) having an adjustable threshold voltage input.

23. An apparatus for determining the distance (d) from a distance-measuring-device ( 50 ) to an object ( 24 ) comprising:

a) means for sending ( 84 ) a light-pulse ( 62 ) from a light-emitting component ( 60 ) to said object ( 24 ) by means of passing ( 70 ) a current pulse (I1) sent through said light-emitting component ( 60 );

b) means for measuring a value indicative of the current (I1) through or voltage (V1) across said light-emitting component ( 60 );

c) determining ( 80 ) a reference-time T0 when the value exceeds a pre-determined first threshold-value THL1 and means for determining ( 80 ) a first-time T1 when the value is reduced to a pre-determined second threshold-value THL2;

d) light sensor means ( 26 ) for receiving the reflected pulse of light from said object;

e) means for measuring the current (Ipd) through or voltage across said light sensor means ( 26 ), means for determining ( 82 ) the point TA when the values of said current (Ipd) through the light sensor exceeds a pre-determined third threshold-value THL3, and means for determining the point TB when the values of said current is reduced to a pre-determined fourth threshold-value THL4;

f) means for integrating a measure of the intensity of reflected light in said light sensor between time TA and T1 to provide a value Q3 and means for integrating a measure of the intensity of reflected light in said light sensor between time T1 and TB; and

g) means for determining the distance from the formula d=½ *c*(T1−T0)*(Q3/(Q3+Q4)).

24. The apparatus in accordance with claim 23 , wherein the thresholds THL1 and THL2 are equal.

25. The apparatus in accordance with claim 23 , wherein said means of measuring the intensity of the reflected light-pulse ( 72 ) comprises means to measure current (Ipd) through the light sensor ( 26 ).

26. The apparatus in accordance with claim 23 , wherein the means of determining the value of (T1−T0) comprises a first capacitor of value C1 charged by a constant current Ic between times T0 and T1 to a voltage value VC1 such that T1−T0=(VC1*C1)/Ic.

27. The apparatus in accordance with claim 23 , wherein the means for determining the reference-time T0 and for determining the first-time T1 comprises a voltage comparator ( 80 ) having an adjustable threshold voltage input.