TIME OF FLIGHT SYSTEM CAPABLE OF INCREASING MEASUREMENT ACCURACY, SAVING POWER AND/OR INCREASING MOTION DETECTION RATE AND METHOD THEREOF

• US 20110304842A1
• Filed: 03/10/2011
• Published: 12/15/2011
• Est. Priority Date: 06/15/2010
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: PixArt Imaging Incorporated
• Inventors: Kao, Ming-Tsan, Hsu, En-Feng, Wang, Chuan-Wei
• Granted Patent: US 9,618,610 B2
• Time in Patent Office: Days
• US Class Current: 356/5.01
• CPC Class Codes: G01S 17/894 3D imaging with simultaneous measurement of time-of-flight at a 2D array of receiver pixels, e.g. time-of-flight cameras or flash lidar
• CPC Class Codes: G01S 7/4918 Controlling received signal intensity, gain or exposure of sensor

Abstract

A light source is used for emitting an invisible light toward an object. The object reflects the invisible light and reflected light is formed, and a sensor is used for receiving the reflected light. A processor is coupled to the sensor for recording a time interval of the invisible light traveling from the light source to the object and reflected from the object to the sensor. Then, the processor estimates a measurement distance of the object according to the time interval, and adjusts an emission period of the light source, an exposure period of the sensor, intensity of the invisible light, and/or main sensing range of the sensor according to the measurement distance.

Claims

1. A method of time of flight capable of increasing measurement accuracy, the method comprising:

transmitting invisible light to detect an object;

recording a time interval of the invisible light traveling to the object, being reflected from the object, and traveling from the object to a sensor; and

adjusting an emission period of the invisible light and an exposure period of the sensor according to the time interval.

2. The method of claim 1, further comprising:

estimating a measurement distance of the object according to the time interval, wherein adjusting the emission period of the invisible light and the exposure period of the sensor according to the time interval is adjusting the emission period of the invisible light and the exposure period of the sensor according to the measurement distance of the object.

3. The method of claim 1, wherein adjusting the emission period of the invisible light and the exposure period of the sensor according to the time interval is adjusting the emission period of the invisible light and the exposure period of the sensor to be slightly longer than the time interval.

4. The method of claim 1, further comprising:

adjusting a duty cycle of the sensor according to a duty cycle of the invisible light, wherein the duty cycle of the invisible light is the same as the duty cycle of the sensor, and start-emission time of the invisible light precedes start-exposure time of the sensor, and a stop-emission time of the invisible light precedes a stop-exposure time of the sensor.

5. The method of claim 4, wherein the duty cycle of the invisible light is a percentage of the emission period of the invisible light in which a light source emitting the invisible light is on, and the duty cycle of the sensor is a percentage of the exposure period of the sensor in which a shutter of the sensor is turned on.

6. The method of claim 1, wherein the invisible light is an infrared (IR) light, and the sensor further comprises an IR filter for blocking light outside the IR range from entering the sensor.

7. A time of flight system capable of increasing measurement accuracy, comprising:

a light source for transmitting invisible light toward an object;

a sensor for receiving reflected light reflected by the object; and

a processor coupled to the sensor for recording a time interval of the invisible light traveling to the object, being reflected from the object, and traveling to the sensor, and adjusting an emission period of the invisible light and an exposure period of the sensor according to the time interval.

8. The time of flight system of claim 7, wherein the processor utilizes the time interval to estimate a measurement distance of the object and adjusts the emission period of the invisible light and the exposure period of the sensor according to the measurement distance of the object.

9. The time of flight system of claim 7, wherein the processor adjusts the emission period of the invisible light and the exposure period of the sensor to be slightly longer than the time interval.

10. The time of flight system of claim 7, wherein the processor adjusts a duty cycle of the sensor according to a duty cycle of the invisible light, the duty cycle of the invisible light is the same as the duty cycle of the sensor, start-emission time of the invisible light precedes start-exposure time of the sensor, and a stop-emission time of the invisible light precedes a stop-exposure time of the sensor.

11. The time of flight system of claim 10, wherein the duty cycle of the invisible light is a percentage of the emission period of the invisible light in which the light source emitting the invisible light is on, and the duty cycle of the sensor is a percentage of the exposure period of the sensor in which a shutter of the sensor is turned on.

12. The time of flight system of claim 7, wherein the light source is an IR light emitting diode (LED) or an IR laser source, and the sensor further comprises an IR filter for blocking light outside the IR range from entering the sensor.

13. A method of time of flight capable of saving power, comprising:

transmitting invisible light to detect an object;

recording a time interval of the invisible light traveling to the object, being reflected from the object, and traveling to a sensor; and

adjusting emission intensity of the invisible light according to the time interval.

14. The method of claim 13, further comprising:

estimating a measurement distance of the object according to the time interval, wherein adjusting the emission intensity of the invisible light according to the time interval is adjusting the emission intensity of the invisible light according to the measurement distance of the object.

15. The method of claim 13, wherein the invisible light is an infrared (IR) light, and the sensor further comprises an IR filter for blocking light outside the IR range from entering the sensor.

16. A time of flight system capable of saving power, comprising:

a light source for transmitting invisible light toward an object;

a sensor for receiving reflected light reflected by the object; and

a processor coupled to the sensor for recording a time interval of the invisible light traveling to the object, being reflected from the object, and traveling to the sensor, and adjusting emission intensity of the invisible light according to the time interval.

17. The time of flight system of claim 16, wherein the processor utilizes the time interval to estimate a measurement distance of the object and adjusts the emission intensity of the invisible light according to the measurement distance of the object.

18. The time of flight system of claim 16, wherein the light source is an IR LED or an IR laser source, and the sensor further comprises an IR filter for blocking light outside the IR range from entering the sensor.

19. A method of time of flight capable of increasing motion detection rate, comprising:

transmitting invisible light to detect an object;

recording a time interval of the invisible light traveling to the object, being reflected from the object, and traveling to a sensor; and

adjusting a main sensing range of the sensor according to the time interval.

20. The method of claim 19, further comprising:

adjusting an emission period of the invisible light, an exposure period of the sensor, and emission intensity of the invisible light according to the time interval.

21. The method of claim 19, further comprising:

estimating a measurement distance of the object according to the time interval, wherein adjusting the main sensing range of the sensor according to the time interval is adjusting the main sensing range of the sensor according to the measurement distance of the object.

22. The method of claim 19, wherein adjusting the main sensing range of the sensor according to the time interval is determining a size and motion range of the object according to the time interval, and determining the main sensing range of the sensor according to the size and the motion range of the object.

23. The method of claim 19, wherein number of pixels sensed by the sensor within the main sensing range is greater than number of pixels sensed by the sensor outside the main sensing range.

24. The method of claim 19, wherein the invisible light is an infrared (IR) light, and the sensor further comprises an IR filter for blocking light outside the IR range from entering the sensor.

25. A time of flight system capable of increasing motion detection rate, comprising:

alight source for transmitting invisible light toward an object;

a sensor for receiving reflected light reflected by the object; and

a processor coupled to the sensor for recording a time interval of the invisible light traveling to the object, being reflected from the object, and traveling to the sensor, and adjusting a main sensing range of the sensor according to the time interval.

26. The time of flight system of claim 25, wherein the processor utilizes the time interval to estimate a measurement distance of the object and adjusts the main sensing range of the sensor according to the measurement distance of the object.

27. The time of flight system of claim 25, wherein the processor determines a size and motion range of the object according to the time interval, and determines the main sensing range of the sensor according to the size and the motion range of the object.

28. The time of flight system of claim 25, wherein number of pixels sensed by the sensor within the main sensing range is greater than number of pixels sensed by the sensor outside the main sensing range.

29. The time of flight system of claim 25, wherein the light source is an IR LED or an IR laser source, and the sensor further comprises an IR filter for blocking light outside the IR range from entering the sensor.