Systems and methods for controlling strobe illumination

• US 8,045,002 B2
• Filed: 07/29/2005
• Issued: 10/25/2011
• Est. Priority Date: 07/29/2005
• Status: Active Grant

• Current Assignee: Mitutoyo Corporation
• Original Assignee: Mitutoyo Corporation
• Inventors: Gladnick, Paul G., Tobiason, Joseph D.
• Primary Examiner(s): Lee; Young
• Assistant Examiner(s): PONTIUS, JAMES M
• Application Number:
  US11/191,969
• Publication Number:
  US 20070025709A1
• Time in Patent Office: 2,279 Days
• Field of Search: 348/132, 396/4, 396/429, 359/290, 385/17, 382/149
• US Class Current: 348/132
• CPC Class Codes: G01N 2021/8838 Stroboscopic illumination; synchronised illumination
• CPC Class Codes: G01N 21/8806 Specially adapted optical and illumination features
• CPC Class Codes: H04N 23/74 by influencing the scene brightness using illuminating means

Abstract

Various exemplary embodiments may provide systems and methods for strobe illumination of a workpiece. The systems may include an illumination source, an image acquisition device and a control system. The illumination source may emit visible, UV, or near-IR light as a transient flash to the workpiece, the transient flash occurring in response to a lamp trigger. The illumination source may emit the light at an illumination intensity that rises from a begin threshold to a peak and afterwards diminishes to an end threshold during a flash duration. The image acquisition device may capture the light associated with the workpiece for an exposure duration starting from an exposure trigger. The control system may control the illumination source and the image acquisition device to synchronize the lamp trigger so that the exposure duration ends during the flash duration, such that a remaining portion of the flash does not affect the image exposure.

Claims

1. A system for controlling image exposure strobe illumination used to illuminate a workpiece such that the workpiece may be imaged by a camera in a machine vision system, the system comprising:

a camera operable to provide a camera image of the workpiece;

a strobe light generator that emits radiation usable by the camera for imaging;

a controllable spatial light modulator configured to provide a first controllable light channel aperture positioned to receive a first portion of the emitted radiation and to control an amount of the first portion of the emitted radiation which it outputs as first channel light, and a second controllable light channel aperture positioned to receive a second portion of the emitted radiation and to control an amount of the second portion of the emitted radiation which it outputs as second channel light;

a control system portion that controls the spatial light modulator; and

at least first and second light channel light cables,

wherein;

the first light channel light cable comprises a first optical fiber bundle, and has an input end positioned to receive the first channel light through the first light channel aperture, and is configured to output the first channel light through a first light source that projects first channel illumination from a first position relative to the workpiece;

the second light channel light cable comprises a second optical fiber bundle, and has an input end positioned to receive the second channel light through the second light channel aperture, and is configured to output the second channel light through a second light source that projects second channel illumination from a second position relative to the workpiece;

the first light channel aperture comprises a first portion of the spatial light modulator that is controllable to provide at least three respective configurations which respectively minimally attenuate at a minimal attenuation level, partially attenuate at a partial attenuation level that is greater than the minimal attenuation level, and substantially block at a full attenuation level, the amount of emitted radiation which it outputs as first channel light during a strobe flash; and

the second light channel aperture comprises a second portion of the spatial light modulator that is controllable to provide at least three respective configurations which respectively minimally attenuate at a minimal attenuation level, partially attenuate at a partial attenuation level that is greater than the minimal attenuation level, and substantially block at a full attenuation level, the amount of emitted radiation which it outputs as second channel light during a strobe flash.

2. The system according to claim 1, wherein the first and second light sources are configured such that the first channel illumination and the second channel illumination each illuminate an entire camera image of the workpiece.

3. The system according to claim 1, wherein the controllable spatial light modulator is configured to provide the first and second controllable light channel apertures at a first time, and is configured at a second time to provide a structured light pattern positioned to receive the emitted radiation, and to output the emitted radiation in a form of a corresponding structured light which is transmitted to illuminate the workpiece.

4. The system according to claim 1, wherein the first portion of the spatial light modulator comprises at least one transmissive element that is controllable to provide at least three respective levels of attenuation corresponding to the minimal, partial and full attenuation levels.

5. The system according to claim 4, wherein the at least one transmissive element comprises an LCD element.

6. The system according to claim 4, wherein the at least one transmissive element comprises a plurality of elements.

7. The system according to claim 6, wherein the respective configuration that provides the partial attenuation level comprises controlling some of the plurality of elements at the full attenuation level to, in effect, reduce the size of the first light channel aperture that outputs the first channel light.

8. The system according to claim 7, wherein the respective configuration that provides the partial attenuation level comprises controlling some of the plurality of elements at the partial attenuation level to, in effect, partially attenuate transmission through the reduced size of the first light channel aperture that outputs the first channel light.