Method and apparatus for adjusting illumination angle

• US 6,788,411 B1
• Filed: 07/10/2000
• Issued: 09/07/2004
• Est. Priority Date: 07/08/1999
• Status: Active Grant

• Current Assignee: Cedar Lane Technologies Inc.
• Original Assignee: PPT Vision, Inc. (Datalogic S.p.A.)
• Inventors: Lebens, Gary A.
• Primary Examiner(s): Font, Frank G.
• Assistant Examiner(s): Punnoose, Roy M.
• Application Number:
  US09/612,763
• Time in Patent Office: 1,520 Days
• Field of Search: 356/394, 356/364, 356/369, 382/141-150
• US Class Current: 356/394
• CPC Class Codes: G01N 2021/8825 Separate detection of dark field and bright field
• CPC Class Codes: G01N 2021/8835 Adjustable illumination, e.g. software adjustable screen
• CPC Class Codes: G01N 2021/8848 Polarisation of light
• CPC Class Codes: G01N 21/21 Polarisation-affecting properties G01N21/19 takes precedence
• CPC Class Codes: G01N 21/8806 Specially adapted optical and illumination features
• CPC Class Codes: G01N 21/95684 Patterns showing highly reflecting parts, e.g. metallic elements
• CPC Class Codes: G01N 2201/062 LED's
• CPC Class Codes: G01N 2201/0626 Use of several LED's for spatial resolution

Abstract

In a machine-vision system for inspecting a part or either object, the invention provides a method and apparatus providing illumination with high-speed changing and/or automatic adjustment of not only the illumination'"'"'s angle, but also the dispersion, intensity, and/or color. Optionally, a light source emits polarized light, a machine-vision imager obtains an image, and a processor receives the image and generates a quality parameter based on the image. One or more of the various means described selectively direct the light in a predetermined pattern based on its polarization and based on the quality parameter of the image. A machine-vision method includes setting one or more illumination parameters, illuminating the object based on the one or more illumination parameters, obtaining an image of the illuminated object, generating a quality parameter based on an image quality of a predetermined region of interest in the image, and iterating using a different illumination parameter.

Claims

1. A machine-vision system having an optical axis, comprising:

a light source emitting light having a polarization;

a machine-vision imager that obtains an image of an object illuminated by the light;

a processor coupled to receive an image from the imager, and operative to generate a quality parameter based on the image; and

means for selectively directing the light in a predetermined pattern based on its polarization and based on the quality parameter of the image.

2. The system of claim 1, wherein the means for selectively directing the light include a liquid-crystal device.

3. The system of claim 1, wherein the means for selectively directing the light further include a polarized reflector.

4. The system of claim 1, wherein the means for selectively directing the light include

means for selectively polarizing the light; and

means for selectively directing the light based on its polarization.

5. The system of claim 1, wherein the means for selectively directing provides two or more different angles of illumination.

6. The system of claim 1, wherein the means for selectively directing includes means for selectively reflecting based on polarization.

7. The system of claim 1, wherein the means for selectively polarizing includes means for electronically driving a liquid-crystal device.

8. The system of claim 1, wherein the means for selectively directing further includes means for blocking light of one polarization and refracting light of another polarization.

9. The system of claim 1, wherein the light director include a liquid-crystal device.

10. The system of claim 1, wherein the light director further include a polarized reflector.

11. A machine-vision system having an optical axis, comprising:

a machine-vision imager located along the optical axis;

a controllable light source;

a first optical element that selectively directs light in a first predetermined pattern relative to the optical axis based on light characteristics;

a second optical element that directs light in a second predetermined pattern relative to the optical axis; and

an electronic controller operatively coupled to the imager and the controllable light source to control the light characteristics and thereby selecting one or more of the first and second predetermined patterns.

12. The system of claim 11, wherein the controllable light source comprises:

a light source;

a controllable polarizer for setting a polarity of the light, wherein the electronic controller is operatively coupled to the controllable polarizer to control the light polarization characteristics and thereby selecting one or more of the first and second predetermined patterns.

13. The system of claim 12, wherein the first optical element includes a polarized reflector that reflects light polarized on one direction and transmits light polarized in another direction.

14. The system of claim 11, wherein the controllable light source comprises:

a light source;

a liquid crystal device (LCD) having two or more areas that are each controllable to selectively transmit light.

15. The system of claim 14, wherein the first optical element includes a prism refractor that refracts light in the first pattern when a first one of the two or more LCD areas transmits light.

16. The system of claim 15, wherein the second optical element includes a prism refractor that refracts light in the second pattern when a second one of the two or more LCD areas transmits light.

17. The system of claim 11, wherein the controllable light source comprises:

a light source having two or more banks each having one or more LEDs and each operatively coupled to be activated by the electronic controller, wherein one or more of the banks can be simultaneously activated.

18. The system of claim 17, wherein

the first optical element is a ring reflector situated to reflect only light from a first one of the banks;

and

the second optical element is a ring reflector situated to reflect only light from a second one of the banks.

19. The system of claim 17, wherein the electronic controller further selects a region of interest of an image, determines an image quality within the region of interest, and selectively controls the first and second light pattern based on the image quality.

20. The system of claim 11, further comprising:

a support station that supports an object being inspected by the machine vision system; and

a selector that rejects that object based on an analysis of the image.

21. A machine-vision system having an optical axis, comprising:

a light source emitting light having a polarization;

a machine-vision imager that obtains an image of an object illuminated by the light;

a processor coupled to receive an image from the imager, and operative to generate a quality parameter based on the image; and

a light director operatively controlled by the processor that selectively directs the light in a predetermined pattern based on its polarization and based on the quality parameter of the image.