Method and apparatus for distance measurement

• US 7,645,974 B2
• Filed: 03/27/2008
• Issued: 01/12/2010
• Est. Priority Date: 03/27/2007
• Status: Active Grant

• Current Assignee: Stanley Electric Company Limited
• Original Assignee: Stanley Electric Company Limited
• Inventors: Kubo, Fumio, Ikeno, Ryohei, Kawata, Tadashi
• Primary Examiner(s): PYO, KEVIN K
• Application Number:
  US12/057,370
• Publication Number:
  US 20080237445A1
• Time in Patent Office: 656 Days
• Field of Search: 250/205, 250/206.1, 250/559.38, 356/4.01, 356/4.07, 356/5.01, 356/5.09
• US Class Current: 250/205
• CPC Class Codes: G01S 17/32 using transmission of continuous waves, whether amplitude-, frequency-, or phase-modulated, or unmodulated
• CPC Class Codes: G01S 17/89 for mapping or imaging
• CPC Class Codes: G01S 17/931 of land vehicles

Abstract

The disclosed subject matter relates to a method and distance measurement apparatus for measuring a distance to an object, which can include a light source, a solid state camera, a controller and a distance data generator. The light source can be configured to emit a modulated light towards an object, and the solid state camera can convert the light reflected from the object into charges. The distance data generator can be configured to calculate the distance based on the charges, and the controller can be configured to adjust the modulated light to be more favorable under various circumstances. Thus, the method of the disclosed subject matter can accurately measure distance under various circumstances and can result in providing a distance measurement apparatus with a simple configuration and at low cost, and can be used as a sensor for distance measurement of an obstacle and the like in a vehicle, security system, robot, etc.

Claims

1. A method for measuring a distance from a measurement apparatus to an object, comprising:

emitting a modulated light having a predetermined frequency and period towards a space in which measurement of the distance from the measurement apparatus to the object is desired;

receiving an incoming light including a reflex light reflected from the object;

converting the incoming light into a plurality of charges during each of four terms in one period of the modulated light;

calculating each phase difference between the modulated light and the incoming light based on each of the plurality of charges during and corresponding to each of the four terms in the one period of the modulated light;

calculating a distance from the measuring apparatus to the object using information related to the plurality of charges and each phase difference; and

adjusting a light intensity of the modulated light in accordance with information related to the plurality of charges converted from the incoming light.

2. The method for measuring a distance according to claim 1, wherein adjusting the light intensity of the modulated light includes adjusting the light intensity when a number of charges are less than a predetermined threshold in the plurality of charges converted from the incoming light during at least one of the four terms in the one period of the modulated light and/or when a number of charges are greater than another predetermined threshold in the plurality of charges converted from the incoming light during at least one of the four terms in the one period of the modulated light.

3. The method for measuring a distance according to claim 1, wherein adjusting the light intensity of the modulated light includes adjusting the light intensity when an amplitude of a number of charges in the plurality of charges converted from the incoming light is out of a range of at least one predetermined amplitude during at least the one period of the modulated light.

4. The method for measuring a distance according to claim 2, wherein adjusting the light intensity of the modulated light includes adjusting the light intensity when an amplitude of a number of charges in the plurality of charges converted from the incoming light is out of a range of at least one predetermined amplitude during at least the one period of the modulated light.

5. The method for measuring a distance according to claim 1, further comprising:

at least one of calculating a mean value of amplitudes of the modulated light and calculating a standard deviation of amplitudes of the modulated light,

wherein adjusting the light intensity includes adjusting the light intensity of the modulated light to fall within at least one of the mean value and the standard deviation of amplitudes when the plurality of charges converted from the incoming light during at least the one period of the modulated light is within a range of a definite value.

6. The method for measuring a distance according to claim 2, further comprising:

at least one of calculating a mean value of amplitudes of the modulated light and calculating a standard deviation of amplitudes of the modulated light,

wherein adjusting the light intensity includes adjusting the light intensity of the modulated light to fall within at least one of the mean value and the standard deviation of amplitudes when the plurality of charges converted from the incoming light during at least the one period of the modulated light is within a range of a definite value.

7. The method for measuring a distance according to claim 3, further comprising:

at least one of calculating a mean value of amplitudes of the modulated light and calculating a standard deviation of amplitudes of the modulated light,

wherein adjusting the light intensity includes adjusting the light intensity of the modulated light to fall within at least one of the mean value and the standard deviation of amplitudes when the plurality of charges converted from the incoming light during at least the one period of the modulated light is within a range of a definite value.

8. The method for measuring a distance according to claim 4, further comprising:

at least one of calculating a mean value of amplitudes of the modulated light and calculating a standard deviation of amplitudes of the modulated light,

wherein adjusting the light intensity includes adjusting the light intensity of the modulated light to fall within at least one of the mean value and the standard deviation of amplitudes when the plurality of charges converted from the incoming light during at least the one period of the modulated light is within a range of a definite value.

9. The method for measuring a distance according to claim 2, further comprising:

extracting a plurality of charges corresponding to the object from each of the plurality of charges used for calculating the distance to the object, wherein adjusting the light intensity includes adjusting the light intensity of the modulated light when a number of charges are less than a predetermined threshold in the plurality of charges corresponding to the object extracted from each of the plurality of charges used for calculating the distance to the object and/or when a number of charges are more than another predetermined threshold in the plurality of charges corresponding to the object extracted from each of the plurality of charges used for calculating the distance to the object.

10. The method for measuring a distance according to claim 3, further comprising:

extracting a plurality of charges corresponding to the object from each of the plurality of charges used for calculating the distance to the object, wherein adjusting the light intensity includes adjusting the light intensity of the modulated light when a number of charges are less than a predetermined threshold in the plurality of charges corresponding to the object extracted from each of the plurality of charges used for calculating the distance to the object and/or when a number of charges are more than another predetermined threshold in the plurality of charges corresponding to the object extracted from each of the plurality of charges used for calculating the distance to the object.

11. The method for measuring a distance according to claim 4, further comprising:

extracting a plurality of charges corresponding to the object from each of the plurality of charges used for calculating the distance to the object, wherein adjusting the light intensity includes adjusting the light intensity of the modulated light when a number of charges are less than a predetermined threshold in the plurality of charges corresponding to the object extracted from each of the plurality of charges used for calculating the distance to the object and/or when a number of charges are more than another predetermined threshold in the plurality of charges corresponding to the object extracted from each of the plurality of charges used for calculating the distance to the object.

12. The method for measuring a distance according to claim 9, wherein the plurality of charges corresponding to the object extracted from each of the plurality of charges used for calculating the distance to the object corresponds to an object positioned within a range of at least one predetermined distance from the measurement apparatus.

13. The method for measuring a distance according to claim 10, wherein the plurality of charges corresponding to the object extracted from each of the plurality of charges used for calculating the distance to the object corresponds to an object positioned within a range of at least one predetermined distance from the measurement apparatus.

14. The method for measuring a distance according to claim 11, wherein the plurality of charges corresponding to the object extracted from each of the plurality of charges used for calculating the distance to the object corresponds to an object positioned within a range of at least one predetermined distance from the measurement apparatus.

29. A distance measurement apparatus configured to use the method for measuring a distance according to claim 1, comprising:

a light source configured to emit the modulated light having the predetermined frequency towards the space in which the measurement of the distance to the object is desired;

a solid state camera configured to receive the incoming light including the reflex light reflected from the object and to convert the incoming light into the plurality of charges during each of the four terms in the one period of the modulated light;

a distance data generator configured to calculate each phase difference between the modulated light and the incoming light based on each of the plurality of charges converted during each of the four terms in the one period of the modulated light and to calculate the distance to the object corresponding to each of the plurality of charges in accordance with each phase difference; and

a controller configured to synchronize both the light source and the solid state camera and to adjust the light intensity of the modulated light emitted from the light source.

30. The distance measurement apparatus according to claim 29, wherein the controller is configured to count at least one of,

the number of charges that are less than a predetermined threshold in the plurality of charges converted from the incoming light during at least one of the four terms in the one period of the modulated light, and

the number of charges that are more than another predetermined threshold in the plurality of charges converted from the incoming light during at least one of the four terms in the one period of the modulated light,

the controller further configured to count a number of amplitudes that are out of the range of at least one predetermined amplitude in the plurality of charges converted from the incoming light during at least the one period of the modulated light;

and

the controller further configured to calculate at least one of the mean value and the standard deviation of amplitudes calculated in accordance with the plurality of charges converted from the incoming light during at least the one period of the modulated light.

31. The distance measurement apparatus according to claim 29, wherein the controller is configured to:

extract a plurality of charges corresponding to the object from each of the plurality of charges used for calculating the distance to the object; and

calculate a number of amplitudes out of a range of at least one predetermined amplitude in the plurality of charges corresponding to the object extracted from each of the plurality of charges used for calculating the distance to the object.

32. The distance measurement apparatus according to claim 29, wherein the controller is configured to extract a plurality of charges corresponding to the object from each of the plurality of charges used for calculating the distance to the object when the object is positioned within a range of at least one predetermined distance between the measurement apparatus and the object.

15. A method for measuring a distance from a measurement apparatus to an object, comprising:

emitting a plurality of modulated light rays each having a predetermined frequency and period, the light rays being divided into a plurality of emitting areas and directed towards a space in which a measurement of the distance from the measurement apparatus to the object is desired;

receiving incoming light rays including reflex light rays transmitted from the plurality of emitting areas and reflected from the object and onto each of a plurality of detecting areas of the measurement apparatus;

converting each of the incoming light rays into a plurality of charges during each of four terms in one period of the plurality of modulated light rays;

calculating a phase difference between the plurality of modulated light rays and each corresponding incoming light ray based on each of the plurality of charges converted during each of the four terms in the one period of the plurality of modulated light rays;

calculating a distance from the measuring apparatus to the object using information related to the plurality of charges and each phase difference; and

adjusting a light intensity of the plurality of modulated light rays in each of the plurality of emitting areas in accordance with information related to each of the plurality of charges converted from each of the incoming light rays.

16. The method for measuring a distance according to claim 15, wherein adjusting each light intensity of the plurality of modulated light rays in each of the plurality of emitting areas includes adjusting the light intensity when a number of charges are less than a predetermined threshold for each of the plurality of charges converted from each incoming light ray during at least one of the four terms in the one period of the plurality of modulated light rays and/or when a number of charges are greater than another predetermined threshold for each of the plurality of charges converted from each incoming light ray during at least one of the four terms in the one period of the plurality of modulated light rays.

17. The method for measuring a distance according to claim 15, wherein adjusting each light intensity of the plurality of modulated light rays in each of the plurality of emitting areas includes adjusting the light intensity when an amplitude associated with a number of charges is out of a range of at least one predetermined amplitude, the number of charges taken from the plurality of charges converted from each incoming light ray during at least the one period of the plurality of modulated light rays.

18. The method for measuring a distance according to claim 16, wherein adjusting each light intensity of the plurality of modulated light rays in each of the plurality of emitting areas includes adjusting the light intensity when an amplitude associated with a number of charges is out of a range of at least one predetermined amplitude, the number of charges taken from the plurality of charges converted from each incoming light ray during at least the one period of the plurality of modulated light rays.

19. The method for measuring a distance according to claim 15, further comprising:

at least one of calculating a mean value of amplitudes of the modulated light rays and calculating a standard deviation of amplitudes of the modulated light rays, wherein

adjusting light intensity includes adjusting light intensity of the plurality of modulated light rays in each of the plurality of emitting areas so as to fall within at least one of the mean value and the standard deviation of amplitudes when each of the plurality of charges converted from each incoming light ray during at least the one period of the plurality of modulated light rays is within a range of a definite value.

20. The method for measuring a distance according to claim 16, further comprising:

at least one of calculating a mean value of amplitudes of the modulated light rays and calculating a standard deviation of amplitudes of the modulated light rays, wherein

adjusting light intensity includes adjusting light intensity of the plurality of modulated light rays in each of the plurality of emitting areas so as to fall within at least one of the mean value and the standard deviation of amplitudes when each of the plurality of charges converted from each incoming light ray during at least the one period of the plurality of modulated light rays is within a range of a definite value.

21. The method for measuring a distance according to claim 17, further comprising:

at least one of calculating a mean value of amplitudes of the modulated light rays and calculating a standard deviation of amplitudes of the modulated light rays, wherein

adjusting light intensity includes adjusting light intensity of the plurality of modulated light rays in each of the plurality of emitting areas so as to fall within at least one of the mean value and the standard deviation of amplitudes when each of the plurality of charges converted from each incoming light ray during at least the one period of the plurality of modulated light rays is within a range of a definite value.

22. The method for measuring a distance according to claim 18, further comprising:

at least one of calculating a mean value of amplitudes of the modulated light rays and calculating a standard deviation of amplitudes of the modulated light rays, wherein

adjusting light intensity includes adjusting light intensity of the plurality of modulated light rays in each of the plurality of emitting areas so as to fall within at least one of the mean value and the standard deviation of amplitudes when each of the plurality of charges converted from each incoming light ray during at least the one period of the plurality of modulated light rays is within a range of a definite value.

23. The method for measuring a distance according to claim 16, further comprising:

extracting each of a plurality of charges corresponding to the object from each of the plurality of charges used for calculating each distance from each of the plurality of emitting areas to the object, wherein adjusting the light intensity of the plurality of modulated light rays includes adjusting the light intensity in each of the plurality of emitting areas when a number of charges is less than a predetermined threshold in each of the plurality of charges corresponding to the object extracted from each of the plurality of charges used for calculating each distance from each of the plurality of emitting areas to the object and/or when a number of charges is more than another predetermined threshold in each of the plurality of charges corresponding to the object extracted from each of the plurality of charges used for calculating each distance from each of the plurality of emitting areas to the object.

24. The method for measuring a distance according to claim 17, further comprising:

extracting each of a plurality of charges corresponding to the object from each of the plurality of charges used for calculating each distance from each of the plurality of emitting areas to the object, wherein adjusting the light intensity of the plurality of modulated light rays includes adjusting the light intensity in each of the plurality of emitting areas when a number of charges is less than a predetermined threshold in each of the plurality of charges corresponding to the object extracted from each of the plurality of charges used for calculating each distance from each of the plurality of emitting areas to the object and/or when a number of charges is more than another predetermined threshold in each of the plurality of charges corresponding to the object extracted from each of the plurality of charges used for calculating each distance from each of the plurality of emitting areas to the object.

25. The method for measuring a distance according to claim 18, further comprising:

extracting each of a plurality of charges corresponding to the object from each of the plurality of charges used for calculating each distance from each of the plurality of emitting areas to the object, wherein adjusting the light intensity of the plurality of modulated light rays includes adjusting the light intensity in each of the plurality of emitting areas when a number of charges is less than a predetermined threshold in each of the plurality of charges corresponding to the object extracted from each of the plurality of charges used for calculating each distance from each of the plurality of emitting areas to the object and/or when a number of charges is more than another predetermined threshold in each of the plurality of charges corresponding to the object extracted from each of the plurality of charges used for calculating each distance from each of the plurality of emitting areas to the object.

26. The method for measuring a distance according to claim 23, wherein each of the plurality of charges corresponding to the object extracted from each of the plurality of charges used for calculating each distance from each of the plurality of emitting areas to the object corresponds to an object positioned within a range of at least one predetermined distance from the measurement apparatus to the object.

27. The method for measuring a distance according to claim 24, wherein each of the plurality of charges corresponding to the object extracted from each of the plurality of charges used for calculating each distance from each of the plurality of emitting areas to the object corresponds to an object positioned within a range of at least one predetermined distance from the measurement apparatus to the object.

28. The method for measuring a distance according to claim 25, wherein each of the plurality of charges corresponding to the object extracted from each of the plurality of charges used for calculating each distance from each of the plurality of emitting areas to the object corresponds to an object positioned within a range of at least one predetermined distance from the measurement apparatus to the object.

33. A distance measurement apparatus configured to use the method for measuring distance according to claim 15, further comprising:

a plurality of light sources configured to be divided into a plurality of emitting areas and to emit a plurality of the modulated light rays having the predetermined frequency towards the space in which a distance from the measurement apparatus to the object is desired;

a solid state camera configured to include a plurality of detecting areas, to receive each incoming light ray including each reflex light from the plurality of emitting areas reflected from the object and onto each of the plurality of detecting areas of the measurement apparatus and to convert each incoming light ray into each of the plurality of charges during each of the four terms in the one period of the plurality of modulated light rays;

a distance data generator configured to calculate each phase difference between the plurality of modulated light rays and each corresponding incoming light ray based on each of the plurality of charges converted during each of the four terms in the one period of the plurality of modulated lights and to calculate each distance from each of the plurality of emitting areas to the object using information associated with the plurality of charges and each phase difference; and

a controller configured to synchronize both the plurality of light sources in each of the plurality of emitting areas and the solid state camera and to adjust each light intensity of the plurality of modulated light rays in each of the plurality of emitting areas.

34. The distance measurement apparatus according to claim 33, wherein the controller is configured to:

count at least one of

a number of charges that are less than a predetermined threshold in each of the plurality of charges converted from each incoming light ray during at least one of the four terms in the one period of the plurality of modulated light rays and

a number of charges that are more than another predetermined threshold in each of the plurality of charges converted from each incoming light ray during at least one of the four terms in the one period of the plurality of modulated light rays;

the controller also configured to count a number of amplitudes of charges out of a range of at least one predetermined amplitude in each of the plurality of charges converted from each incoming light during at least the one period of the plurality of modulated lights; and

the controller configured to calculate at least one of a mean value and a standard deviation of amplitudes in accordance with each of the plurality of charges converted from each incoming light ray during at least the one period of the plurality of modulated lights.

35. The distance measurement apparatus according to claim 33, wherein the controller is configured to:

extract each of a plurality of charges corresponding to the object from each of the plurality of charges used for calculating each distance; and

calculate at least one of

a number of charges that are less than a predetermined threshold in each of the plurality of charges corresponding to the object extracted from each of the plurality of charges used for calculating each distance, and

a number of charges that are more than another predetermined threshold in each of the plurality of charges corresponding to the object extracted from each of the plurality of charges used for calculating each distance.

36. The distance measurement apparatus according to claim 34, wherein the controller is configured to extract each of the plurality of charges corresponding to the object from each of the plurality of charges used for calculating each distance when the object is positioned within a range of at least a predetermined distance from the measurement apparatus.