Systems and methods for determining depth using shuttered light pulses

• US 7,095,487 B2
• Filed: 10/12/2004
• Issued: 08/22/2006
• Est. Priority Date: 10/09/2003
• Status: Active Grant

• Current Assignee: Honda Motor Co., Ltd. (Honda Motor Company)
• Original Assignee: Honda Motor Co., Ltd. (Honda Motor Company)
• Inventors: Davis, James E., Gonzalez-Banos, Hector H.
• Primary Examiner(s): Tarcza, Thomas H.
• Assistant Examiner(s): ALSOMIRI, ISAM A
• Application Number:
  US10/964,334
• Publication Number:
  US 20050280801A1
• Time in Patent Office: 679 Days
• Field of Search: 356/3.13, 356 401- 405, 356/4.07, 356/5.01, 356/5.07, 356/5.08, 356/6, 73/14.2, 73/15.6, 352/204
• US Class Current: 356/4.07
• CPC Class Codes: G01C 3/08 Use of electric radiation detectors
• CPC Class Codes: G01S 17/10 using transmission of interrupted, pulse-modulated waves determination of distance by phase measurements G01S17/32
• CPC Class Codes: G01S 17/18 wherein range gates are used
• 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: G02B 7/32 using active means, e.g. light emitter including both an active and a passive focus detecting device G02B7/285; using ultrasound G02B7/40
• CPC Class Codes: G03B 13/36 Autofocus systems

Abstract

Systems and methods are presented that use light sensors and computing devices to compute the depth of an object using shuttered light pulses. In one embodiment, depth is determined as follows: A light emitter emits a pulse of light that is directed toward an object. The pulse is reflected off the object and travels toward a beam splitter. The beam splitter splits the reflected pulse into multiple pulses, with each pulse directed to a shuttered sensor with a different shutter location. The shuttered sensors measure the integrated intensity of the light, and these values are used to determine the depth of the object. A method is presented which calibrates a system that has an arbitrary number of shutters and enables the system to determine the depth of an object, even in the presence of ambient illumination and scattered light.

Claims

1. A method for determining a distance to an object, the method comprising calculating the distance d in accordance with the equation:

$d=\frac{a_0+a_1<br><br>I_1+a_2<br><br>I_2+\mathrm{\dots <br><br>}<br><br><br><br>a_n<br><br>I_n}{b_0+b_1<br><br>I_1+b_2<br><br>I_2+\mathrm{\dots <br><br>}<br><br><br><br>b_n<br><br>I_n},$

wherein a₀ represents a first calibration bias, b₀ represents a second calibration bias, I_i represents a measurement of integrated intensity of light associated with a shutter location i, a_i represents a first calibration parameter for the shutter location i, and b_i represents a second calibration parameter for the shutter location i and where i=1, 2, . . . , n.

2. The method of claim 1, further comprising obtaining a plurality of measurements of integrated intensity of light prior to calculating the distance.

3. The method of claim 2, wherein obtaining the plurality of measurements of integrated intensity of light comprises using a shuttered sensor.

4. The method of claim 3, wherein the shuttered sensor comprises a physical barrier.

5. The method of claim 3, wherein the shuttered sensor comprises a time-gated sensor.

6. The method of claim 2, wherein obtaining the plurality of measurements of integrated intensity of light comprises splitting a beam of light.

7. The method of claim 2, wherein obtaining the plurality of measurements of integrated intensity of light comprises adjusting, over time, a shutter location of a sensor.

8. The method of claim 2, wherein obtaining the plurality of measurements of integrated intensity of light comprises interpolating measurements from a plurality of sensors.

9. The method of claim 8, wherein interpolating measurements from the plurality of sensors comprises interpolating measurements from a plurality of sensors that sample scene points that are in close proximity.

10. A system for determining a distance to an object, the system comprising means for calculating the distance d in accordance with the equation:

$d=\frac{a_0+a_1<br><br>I_1+a_2<br><br>I_2+\mathrm{\dots <br><br>}<br><br><br><br>a_n<br><br>I_n}{b_0+b_1<br><br>I_1+b_2<br><br>I_2+\mathrm{\dots <br><br>}<br><br><br><br>b_n<br><br>I_n},$

wherein a₀ represents a first calibration bias, b₀ represents a second calibration bias, I_i represents a measurement of integrated intensity of light associated with a shutter location i, a_i represents a first calibration parameter for the shutter location i, and b_i represents a second calibration parameter for the shutter location i and where i=1, 2, . . . , n.

11. The system of claim 10, further comprising means for obtaining a plurality of measurements of integrated intensity of light prior to calculating the distance.