Systems and methods for controlling strobe illumination

• US 20070025709A1
• Filed: 07/29/2005
• Published: 02/01/2007
• Est. Priority Date: 07/29/2005
• Status: Active Grant

• Current Assignee: Mitutoyo Corporation
• Original Assignee: Mitutoyo Corporation
• Inventors: Gladnick, Paul, Tobiason, Joseph
• Granted Patent: US 8,045,002 B2
• Time in Patent Office: Days
• US Class Current: 396/4
• 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 provided by a plurality of respective light channels in a machine vision system, comprising:

a camera;

a strobe illumination source that emits radiation usable by the camera for imaging;

a controllable spatial light modulator that provides a plurality of controllable respective light channel apertures positioned to receive the emitted radiation;

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

a plurality of respective light cables corresponding to the plurality of respective lighting channels, the respective light cables positioned to receive radiation transmitted from respective light channel apertures,

wherein the spatial light modulator is controlled to determine which of the plurality of controllable respective light channel apertures transmits the emitted radiation to their corresponding respective light cable.

2. The system according to claim 1, comprising at least one respective structured light channel, wherein the controllable spatial light modulator is controlled to provide a structured light pattern positioned to receive the emitted radiation and transmit the emitted radiation in the form of a corresponding structured light to the at least one structured light channel.

3. The system according to claim 1, wherein the spatial light modulator is further controlled to determine respective attenuations provided by the respective light channel apertures before transmitting the emitted radiation to their corresponding respective light cables thereby further controlling the image exposure strobe illumination.

4. The system according to claim 3, wherein the respective attenuations are determined by at least one of gray-level control of the respective light channel apertures and size control of the respective light channel apertures.

5. The system according to claim 3, wherein the control system portion further controls at least one timing relationship between an image integration period of the camera and a timing of a pulse profile of the radiation emitted by the strobe illumination source to further control the image exposure strobe illumination.

6. The system according to claim 5, wherein the timing relationship causes the image integration period to end during the pulse profile of the radiation emitted by the strobe illumination source, such that a remaining portion of the pulse profile does not affect the image exposure.

7. The system according to claim 3, wherein the control system portion further controls an operating voltage of the strobe illumination source to further control the image exposure strobe illumination.

8. The system according to claim 1, wherein the spatial light modulator comprises an LCD pixel array.

9. The system according to claim 1, wherein the strobe illumination source comprises a Xenon flash lamp.

10. The system according to claim 1, wherein a location of at least some of the plurality of controllable respective light channel apertures is adjusted using software parameters, such that the at least some of the plurality of controllable respective light channel apertures are aligned to a desired degree with corresponding respective light cables.

11. A method for controlling image exposure strobe illumination provided by a plurality of respective light channels in a machine vision system, comprising:

emitting radiation from a strobe illumination source, the radiation usable for imaging by a camera of the machine vision system; and

operating a control system portion of the machine vision inspection system to control a spatial light modulator that provides a plurality of controllable respective light channel apertures positioned to receive the emitted radiation,

wherein;

the machine vision system comprises a plurality of respective light cables corresponding to the plurality of respective lighting channels;

the respective light cables are positioned to receive radiation transmitted from respective light channel apertures, and

the step of operating the control system portion of the machine vision inspection system to control the spatial light modulator comprises determining which of the plurality of controllable respective light channel apertures transmits the emitted radiation to their corresponding respective light cable.

12. The method according to claim 11, wherein the machine vision system comprises at least one respective structured light channel, and the method further comprises operating the control system portion of the machine vision inspection system to control the spatial light modulator to provide a structured light pattern positioned to receive the emitted radiation and transmit the emitted radiation in the form of a corresponding structured light to the at least one structured light channel.

13. The method according to claim 11, wherein the step of operating the control system portion of the machine vision inspection system to control the spatial light modulator further comprises controlling the spatial light modulator to determine respective attenuations provided by the respective light channel apertures before transmitting the emitted radiation to their corresponding respective light cables thereby further controlling the image exposure strobe illumination.

14. The method according to claim 13, wherein the respective attenuations are determined by controlling at least one of a gray-level of the respective light channel apertures and a size of the respective light channel apertures.

15. The method according to claim 13, further comprising operating the control system portion of the machine vision inspection system to control at least one timing relationship between an image integration period of the camera and a timing of a pulse profile of the radiation emitted by the strobe illumination source to further control the image exposure strobe illumination.

16. The method according to claim 15, wherein the timing relationship is controlled to cause the image integration period to end during the pulse profile of the radiation emitted by the strobe illumination source, such that a remaining portion of the pulse profile does not affect the image exposure.

17. The method according to claim 13, furter comprising operating the control system portion of the machine vision inspection system to control an operating voltage of the strobe illumination source to further control the image exposure strobe illumination.

18. The method according to claim 11, wherein the spatial light modulator comprises an LCD pixel array.

19. The method according to claim 11, wherein the strobe illumination source comprises a Xenon flash lamp.

20. The method according to claim 11, further comprising operating the control system portion of the machine vision inspection system to adjust a location of at least some of the plurality of controllable respective light channel apertures using software parameters, such that the at least some of the plurality of controllable respective light channel apertures are aligned to a desired degree with corresponding respective light cables.