Image capturing device for capturing a shape of a measurement subject

• US 6,822,681 B1
• Filed: 06/30/1999
• Issued: 11/23/2004
• Est. Priority Date: 07/02/1998
• Status: Expired due to Fees

• Current Assignee: PENTAX RICOH IMAGING COMPANY, LTD.
• Original Assignee: Pentax Corporation (Hoya Corporation)
• Inventors: Aoki, Harumi
• Primary Examiner(s): Christensen, Andrew
• Assistant Examiner(s): TRAN, NHAN T
• Application Number:
  US09/343,392
• Time in Patent Office: 1,973 Days
• Field of Search: 348/295, 348/296, 356/5.01, 356/5.02, 356/5.03, 356/5.04, 356/5.07, 356/5.08, 356/5.09
• US Class Current: 348/296
• 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: H04N 13/254 in combination with electromagnetic radiation sources for illuminating objects

Abstract

A three-dimensional image capturing device comprises a light source and an imaging device, such as a CCD, having a plurality of photo-diodes. The light source outputs a pulsed distance measuring light beam simultaneously with a discharge of unwanted charges from the photo-diodes due to an electric charge discharging signal. A reflected light beam, generated by a measurement subject due to the distance measuring light beam, is received by the photo-diodes. When a predetermined time has elapsed since the output of the distance measuring light beam, an electric charge transfer signal is output so that electric charge, i.e. signal charge accumulated in each of the photo-diodes, is transferred to the vertical transfer unit. The electric charge and the electric charge discharging signal are repeatedly output, so that the signal charge is integrated in the vertical transfer unit. Numbers of the electric discharging signals and the electric charge transfer signals are adjusted such that a level of the signal charge has a proper value.

Claims

1. A three-dimensional image capturing device, comprising:

a light source that radiates a distance measuring light beam irradiating a measurement subject, said measurement subject reflecting said distance measuring light beam to generate a reflected light beam;

a plurality of photoelectric conversion elements that receive said reflected light beam, so that electric charge corresponding to an amount of said received reflected light beam is accumulated in each of said photoelectric conversion elements;

a signal charge holding unit disposed adjacent to each of said photoelectric conversion elements;

an electric charge discharging processor that discharges unwanted charge accumulated in each of said photoelectric conversion elements, so that an accumulating operation of signal charge is started in each of said photoelectric conversion elements;

a signal charge transfer processor that transfers said signal charge accumulated in said photoelectric conversion elements to said signal charge holding unit;

a signal charge integrating processor that outputs control pulse signals to drive said electric charge discharging processor and said signal charge transfer processor alternately, in accordance with a number of said control pulse signals, for a predetermined period, so that said signal charge is integrated in said signal charge holding unit; and

a signal level adjusting processor that controls said number of said control pulse signals to adjust a level of said signal charge, said signal level adjusting processor configured to;

obtain distance information from said signal charge; and

adjust, in accordance with a level assessment value that indicates whether the number of said control pulse signals is proper, the number of said control pulse signals.

2. A device according to claim 1, further comprising an assessment value obtaining processor that obtains an assessment value in accordance with which said number of said control pulse signals is adjusted, said assessment value being a mean value of levels of said signal charge generated by at least a portion of said photoelectric conversion elements.

3. A device according to claim 2, wherein said mean value is obtained by weighting said levels of said signal charge generated by a part of said portion of said photoelectric conversion elements.

4. A device according to claim 1, further comprising an assessment value obtaining processor that obtains an assessment value in accordance with which said number of said control pulse signals is adjusted, said assessment value being a maximum value of levels of said signal charge generated by at least a portion of said photoelectric conversion elements.

5. A device according to claim 1, wherein said photoelectric conversion elements are formed on a substrate, and said electric charge discharging processor discharges said unwanted charge to said substrate.

6. A device according to claim 1, wherein said signal charge holding unit is provided in a vertical transfer unit that outputs said signal charge from said image capturing device.

7. A device according to claim 1, wherein said photoelectric conversion elements and said signal charge holding units are formed as a vertical overflow drain type of interline CCD.

8. A device according to claim 1, wherein said electric charge discharging processor outputs an electric charge discharging signal to discharge said unwanted charge, and said signal charge holding processor outputs an electric charge transfer signal to transfer said signal charge to said signal charge holding unit, said electric charge discharging signal and said electric charge transfer signal being pulse signals.

9. A device according to claim 8, wherein said distance measuring light beam is a pulsed beam having a predetermined pulse width, a first accumulating period, which is from an output of said electric charge discharging signal to an output of said electric charge transfer signal, being set such that an amount of said reflected light beam received corresponds to a distance between said measurement subject and said image capturing device, so that said signal charge corresponding to distance information regarding said measurement subject is integrated in said signal charge holding unit.

10. A device according to claim 9, wherein a second accumulating period, which is from an output of said electric charge discharging signal to an output of said electric charge transfer signal, is set such that said reflected light beam is received in entirety, so that signal charge, corresponding to reflectance information related to a reflectance of said measurement subject, is integrated in said signal charge holding unit, and said distance information is normalized by said reflectance information, so that an influence of a reflectance contained in said distance information is reduced.

11. A device according to claim 10, wherein distance correction information is sensed by said three-dimensional image capturing device using said first accumulating period when said light source is turned OFF, and said distance information is normalized using said distance information corrected by said distance correction information and said reflectance information.

12. A device according to claim 11, wherein:

distance correction information is sensed by said three-dimensional image capturing device using said first accumulating period when said light source is turned OFF;

reflectance correction information is sensed by said three-dimensional image capturing device using said second accumulating period when said light source is turned OFF; and

said distance information is normalized using said distance information corrected by said distance correction information, and said reflectance information corrected by said reflectance correction information.

13. A device according to claim 1, wherein said signal charge corresponds to a distance from the device to said measurement subject.

14. A three-dimensional image capturing device, comprising:

a light source that radiates a distance measuring light beam irradiating a measurement subject, said measurement subject reflecting said distance measuring light beam to generate a reflected light beam;

a plurality of photoelectric conversion elements that receive said reflected light beam, so that electric charge corresponding to an amount of said received reflected light beam is accumulated in each of said photoelectric conversion elements;

a signal charge holding unit disposed adjacent to each of said photoelectric conversion elements;

an electric charge discharging processor that discharges unwanted charge accumulated in each of said photoelectric conversion elements, so that an accumulating operation of signal charge is started in each of said photoelectric conversion elements;

a signal charge transfer processor that transfers said signal charge accumulated in said photoelectric conversion elements to said signal charge holding unit;

a signal charge integrating processor that drives said electric charge discharging processor and said signal charge transfer processor alternately, so that said signal charge is integrated in said signal charge holding unit; and

a signal level adjusting processor that controls a number of operations by which said signal charge integrating processor drives said electric charge discharging processor and said signal charge transfer processor alternately, so that a level of said signal charge is adjustable, said signal level adjusting processor configured to;

obtain distance information from said signal charge; and

adjust, in accordance with a level assessment value that indicates whether the number of said control pulse signals is proper, the number of said control pulse signals.