Control systems and methods for synchronizing diffuse illumination with a camera

• US 6,525,303 B1
• Filed: 09/23/1999
• Issued: 02/25/2003
• Est. Priority Date: 09/23/1999
• Status: Expired due to Term

• Current Assignee: Mitutoyo Corporation
• Original Assignee: Mitutoyo Corporation
• Inventors: Gladnick, Paul G.
• Primary Examiner(s): Le, Que T.
• Assistant Examiner(s): Luu, Thanh X.
• Application Number:
  US09/401,654
• Time in Patent Office: 1,251 Days
• Field of Search: 250/208.1, 250/204, 250/205, 250/234, 250/216, 250/559-6-5
• US Class Current: 250/208.1
• CPC Class Codes: G01N 2021/8835 Adjustable illumination, e.g. software adjustable screen
• CPC Class Codes: G01N 21/8806 Specially adapted optical and illumination features

Abstract

A light pattern controller generates a pattern of continuous wave, modulated and/or pulsed light onto a face of a collimating element. The light beam is collimated by the collimating element and extends to a focusing element which focuses the collimated light onto an illumination field. A controller controls the light pattern controller or the light source to determine a shape of the pattern on the face of the collimating element. The illumination field is imaged by an electronic or digital camera having first and second fields. Each field captures an image by integrating light received from the illumination field over an integration period. The controller controls the light pattern controller and the light source, and/or the camera to ensure an even amount of illumination from each element of the light pattern focused on the illumination field is integrated by each field of the camera. The controller also controls the frequency, phase angle and pulse width of the light source.

Claims

1. An apparatus for generating an image of a diffusely illuminated object, the apparatus comprising:

a light pattern generation system that controllably generates a pattern of light over a period of time, the pattern of light usable to illuminate the object and having at least one illumination area, each illumination area having an angle of incidence controlled independently of the illumination area for the corresponding light illuminating the object;

a camera that has at least a first camera field having a first integration period for accumulating received light signals and a second camera field having a second integration period for accumulating received light signals; and

a controller that synchronizes the pattern of light generated by the light pattern generation system and the at least first and second integration periods such that each camera field accumulates received light signals which correspond to a substantially identical spatial distribution and amount of the light illuminating the object.

2. The apparatus of claim 1, wherein the controller synchronizes at least one of a deflector and a modulation of a light source of the light pattern generation system with the integration periods for the at least first and second integration periods.

3. The apparatus of claim 1, wherein the controller synchronizes the at least first and second integration periods with at least one of a deflector and a modulation of a light source of the light pattern generation system.

4. The apparatus of claim 1, wherein the pattern of light is generated an integer number of times during each of the at least first and second integration periods.

5. The apparatus of claim 1, wherein the first and second integration periods at least partially overlap in time.

6. The apparatus of claim 5, wherein first and second camera fields captured during a single cycle comprising one first integration period and one second integration period are combined to generate images usable for high resolution observation and analysis of the illuminated object.

7. The apparatus of claim 1, wherein each illumination area further has at least one of a controlled phase angle and a controlled arc length of the pattern of light illuminating the object.

8. A machine vision system comprising:

a controllable light source that outputs a modulated light beam;

a controllable deflector that deflects the light beam from the light source to sweep out a pattern of at least one illumination area on a face of a collimating element that collimates the patterned light beam;

a focusing element that focuses the collimated patterned light beam to illuminate an object, each at least one illumination area thereby illuminating the object with a corresponding angle of incidence, phase angle and arc length;

a camera having at least first camera field having a first integration period for accumulating received light signals and a second camera field having a second integration period for accumulating received light signals, the camera capturing an image of the illuminated object; and

a controller that synchronizes integration periods for the at least first and second camera fields, modulation of the light beam and the deflector so that each of the first and second fields accumulates received light signals which correspond to a substantially identical spatial distribution and amount of the light illuminating the object such that first and second camera fields captured during a single cycle comprising one first integration period and one second integration period are combinable to generate images usable in the machine vision system for high resolution observation and analysis of the illuminated object.

9. The system of claim 8, wherein the controller synchronizes the deflector and the modulation of the light beam with the integration periods for the at least first and second fields.

10. The system of claim 8, wherein the controller synchronizes the integration periods for the at least first and second fields with the deflector and the modulation of the light beam.

11. The system of claim 8, wherein the pattern is swept by the deflector an integer number of times during each integration period of the at least first and second fields.

12. A method for generating an image of a controllably diffusely illuminated object, the method comprising:

controllably generating a pattern of light usable to illuminate the object, the pattern of light having at least one illumination area, each illumination area having an angle of incidence controlled independently of the illumination area for the corresponding light illuminating the object;

illuminating the object with the corresponding light and imaging the object onto a camera having at least first camera field having a first integration period for accumulating received light signals and a second camera field having a second integration period for accumulating received light signals; and

synchronizing at least the controlled angle of incidence of the corresponding light illuminating the object for each illumination area and the at least first and second integration periods so each of the at least first and second integration periods accumulates received light signals which correspond to a substantially identical spatial distribution and amount of the light illuminating the object.

13. The method of claim 12, wherein:

controllably generating the pattern of light comprises;

controllably operating a light deflector, and

controllably modulating a light beam; and

synchronizing at least one of the controlled angle of incidence, a controlled phase angle and a controlled arc length of the corresponding light illuminating the object and the at least first and second integration periods comprises synchronizing at least one of the light deflector and the modulation of the light beam with the at least first and second integration periods.

14. The method of claim 12, wherein:

controllably generating the pattern of light comprises;

controllably operating a light deflector, and

controllably modulating a light beam; and

synchronizing at least one of the controlled angle of incidence, a controlled phase angle and a controlled arc length of the corresponding light illuminating the object and the at least first and second integration periods comprises synchronizing the at least first and second integration periods with at least one of the light deflector and the modulation of the light beam.

15. The method of claim 12, herein each of the at least first and second integration periods accumulates received light signals which correspond to generating an integer number of each at least one illumination area during each of the first and second integration periods, respectively.

16. The method of claim 12, wherein the at least first and second integration periods overlap in time.

17. The method of claim 12, wherein first and second camera fields captured during a single cycle comprising one first integration period and one second integration period are combined to generate an image usable for high resolution observation and analysis of the illuminated object.

18. The method of claim 12, wherein each illumination area further corresponds to at least one of a controlled phase angle and a controlled arc length for the corresponding light illuminating the object and the step of synchronizing at least the controlled angle of incidence further comprises synchronizing at least one of the controlled phase angle and the controlled arc length of the corresponding light illuminating the object for each illumination area.

19. A method for generating an image by diffusely illuminating an object, comprising:

modulating a light beam;

deflecting the modulated light beam to sweep out an illumination pattern;

collimating the deflected light beam;

focusing the collimated light beam onto the object;

receiving the light reflected from the object with a camera having at least a first integration period for accumulating received light signals and a second integration period for accumulating received light signals; and

synchronizing each of the first and second integration periods with modulating the light beam and deflecting the modulated light beam so that each of the at least first and second integration periods accumulates received light signals which correspond to a substantially identical spatial distribution and amount of the light illuminating the object.

20. The method of claim 19, wherein each of the at least first and second integration periods accumulates received light signals which correspond to sweeping out the illumination pattern an integer number of times during each of the first and second integration periods, respectively.

21. The method of claim 19, wherein the at least first and second integration periods overlap in time.

22. The method of claim 19, wherein received light signals captured during a single cycle comprising one first integration period and one second integration period are combined to generate an image usable for high resolution observation and analysis of the illuminated object.