Method of measuring in three-dimensions at high speed

• US 4,630,910 A
• Filed: 02/16/1984
• Issued: 12/23/1986
• Est. Priority Date: 02/16/1984
• Status: Expired due to Term

• Current Assignee: Robotic Vision Systems, Inc. (Acuity Brands, Inc.)
• Original Assignee: Robotic Vision Systems, Inc. (Acuity Brands, Inc.)
• Inventors: Ross, Joseph, DiMatteo, Paul
• Primary Examiner(s): Adams, Russell E.
• Application Number:
  US06/580,653
• Time in Patent Office: 1,041 Days
• Field of Search: 354/75-80, 354/112, 354/113, 354/292, 354/354
• US Class Current: 396/334
• CPC Class Codes: G03B 29/00 Combinations of cameras, projectors or photographic printing apparatus with non-photographic non-optical apparatus, e.g. clocks or weapons; Cameras having the shape of other objects combinations with flash apparatus G03B15/03

Abstract

An apparatus with a common aperture and multiple image recording surfaces with individual filters and/or controlled shutters enables the implementation of several methods of 3-D measurement systems. The parallel nature of the device lends to short measurement times suitable for measuring moving objects. A similar apparatus may be constructed to project multiple images simultaneously or in rapid succession. Elimination of mechanical motion within the projectors and cameras of the prior art reduce the measurement time significantly. A new method of 3-D measurement employing a sweeping light plane and time encoded image recording uses the apparatus. An alternate method maintains a stationary projected light plane through which an object moves as it is measured in 3-D. Another method uses simultaneous projection of light patterns at different frequencies. Another method employs the time of flight of a light pulse and time encoded recording of the reflected energy.

Claims

1. An arrangement for recording a scene with a common aperture and multiple cameras comprising:

a lens for imaging the scene on N light-sensitive surfaces;

N beam splitters for dividing light from said lens into N equal intensity paths;

N shutters operated by a controller, one controller being in each said path;

N said light-sensitive surfaces following each said shutter; and

means for independently adjusting the path length to each said light-sensitive surface;

each shutter blocking incident light of its path until commanded by said controller to pass said light for the duration of a coded pattern projected during said duration.

2. An arrangement for projecting a plurality of patterns onto a common area without moving parts comprising:

a plurality of light sources;

each light source being imaged by a lens via separate light paths into a common light path and projection lens;

the light of each said light source fully illuminating a pattern forming mask;

means for independently adjusting each separate light path;

a partially reflecting mirror for each separate light path for combining the separate paths into said one common path with reflecting ratios selected such that equal intensity of said light sources result in equal intensities at said projection lens;

each light source providing illumination only during an interval determined by a controller;

said projection lens imaging said mask patterns on a common area.

3. A method for obtaining 3-D measurements on a moving subject comprising the steps of:

projecting a stationary plane of light upon said subject as said subject moves through said plane of light;

synchronizing a view angle of multiple cameras to the motion of said subject;

recording reflected light of said stationary plane of light from said subject with said multiple cameras via controlled shutters blocking said reflected light from said shutter'"'"'s respective camera except when commanded by a controller;

said controller commanding said shutters to record portions of reflected light in a time encoded sequence enabling identification of the said camera view angle and said subject location as a result of identifying the time of the recording.

4. A method for reducing the time to obtain 3-D measurements comprising the steps of:

projecting a plurality of light patterns on a surface to be measured;

said light patterns being projected simultaneously;

each pattern being projected in a different color (frequency); and

recording the reflected light from said patterns with a plurality of cameras;

each camera receiving said reflected light via a filter having low attenuation for one of the said colors projected, a different color corresponding for each camera.

5. An arrangement for obtaining 3-D measurements comprising:

a projector for projecting a pulse of light upon a subject and producing a scene thereof;

a lens for imaging the scene on N light-sensitive surfaces;

N beam splitters for dividing the light from said lens into N equal intensity paths;

N shutters operated by a controller, one said shutter in each said path;

N said light-sensitive surfaces following each said shutter; and

means for independently adjusting the path length to each said light-sensitive surface;

each shutter blocking incident light of its path until commanded by said controller;

said controller commanding said shutters to record portions of the image in a time-encoded sequence enabling identification of the said light pulse location as a result of identifying the time of the recording.

6. A method for obtaining 3-D measurements comprising the steps of:

sweeping a plane of light as a precise function of time across a subject to be measured;

imaging the subject onto multiple light-sensitive surfaces via controlled shutters blocking said image from said shutter'"'"'s respective light-sensitive surfaces except when commanded by a controller;

said controller commanding said shutters to record portions of the image in a time-encoded sequence enabling identification of the said light plane location as a result of identifying the time of the recording, whereby sweeping said plane across said subject N light-sensitive surfaces behind N shutters can time-encode 2^N -1 positions of the plane of light.

7. A method for obtaining 3-D measurements comprising the steps of:

sweeping a plane of light as a precise function of time across a subject to be measured;

imaging the subject onto a light-sensitive surface via a controlled shutter blocking said image from said light-sensitive surface except when commanded by a controller;

said controller commanding said shutter to record portions of the image in a time-encoded sequence enabling the identification of the said light plane location as a result of identifying the time of the recording; and

repeating said steps for the number of codes required to obtain a predetermined resolution, said steps being repeated N times to define 2^N -1 positions of said sweeping plane.

8. A method for reducing the time to obtain three-dimensional measurements comprising the steps of:

projecting a sequence of patterns on a surface to be measured, three-dimensional measurements being obtained uniquely by said patterns when taken as a group; and

recording reflected radiation from said patterns with multiple cameras, said cameras being sequenced to record one pattern by each camera, said recording step having a minimum time dependent on time needed to record reflected light intensity patterns and speed of the camera shutter.