Illumination device with microlouver for illuminating an object with continuous diffuse light

• US 5,761,540 A
• Filed: 02/14/1997
• Issued: 06/02/1998
• Est. Priority Date: 10/31/1994
• Status: Expired due to Term

• Current Assignee: Microscan Systems Inc (Omron Corporation)
• Original Assignee: Northeast Robotics, Inc. (Acuity Brands, Inc.)
• Inventors: White, Timothy P.
• Primary Examiner(s): Gray, David M.
• Application Number:
  US08/821,961
• Time in Patent Office: 473 Days
• Field of Search: 396/4, 396/429, 362/16, 362/17
• US Class Current: 396/4
• CPC Class Codes: G01N 21/8806 Specially adapted optical and illumination features
• CPC Class Codes: G03B 15/03 Combinations of cameras with lighting apparatus; Flash units
• CPC Class Codes: G03B 27/323 Copying cameras G03B27/34 - G03B27/70 take precedence
• CPC Class Codes: H04N 23/56 provided with illuminating means
• CPC Class Codes: H05K 13/0812 the monitoring devices being integrated in the mounting machine, e.g. for monitoring components, leads, component placement

Abstract

An illumination device for illuminating an object to be observed, by a machine vision camera or the like for example, with a continuous diffuse wide angle light which is supplied along the observation axis of the machine vision camera. The diffuser is mounted parallel to the observation axis but separated from the beam splitter by a microlouver filter so that the microlouver filter prevents diffused light from the diffuser from directly illuminating any point of interest on the surface of the object to be observed. The microlouver filter only allows indirect illumination of the object to be observed by the diffuser and provides improved uniform illumination of the object to be observed.

Claims

1. An illumination device for illuminating an object to be observed by a camera along an observation axis extending from the camera to the object, said illumination device comprising:

a housing having at least a first aperture therein alignable with an observation axis;

a partially reflective beam splitter being supported by said housing and being positioned obliquely relative to the observation axis adjacent said at least first aperture;

a light source being arranged to cast light on a first surface of said beam splitter;

a diffuser being positioned between said beam splitter and said light source for diffusing light from said light source as the light passes through said diffuser to said first surface of said beam splitter; and

a louver filter being positioned between said beam splitter and said diffuser to prevent direct illumination of an object to be observed by said diffuser whereby said diffuser is only able, during use, to indirectly illuminate a desired portion of the object to be observed, via said louver filter and said beam splitter, when the object is positioned along the observation axis.

2. The illumination device according to claim 1, wherein said louver filter is formed from a plastic film and contains a plurality of closely spaced and parallelly arranged microlouvers members;

and

the angle and spacing of the microlouver members is selected such that any light from the microlouver filter which directly illuminates the object to be observed is matched to be substantially equal or less than an intensity and in character to light reflected by said beam splitter to the object to be observed.

3. The illumination device according to claim 2, wherein said louver filter has parallel light receiving and light transmission surfaces and said plurality of closely spaced and parallelly arranged microlouvers members extend in planes lying substantially perpendicular to said light receiving and light transmission surfaces.

4. The illumination device according to claim 1, wherein said housing has a second aperture therein which is also alignable with said observation axis and said beam splitter is located between said first aperture and said second aperture.

5. The illumination device according to claim 1, wherein said light source comprises one of a bulb, an incandescent fiber optic, at least one LED, a fluorescent light and an array of lights.

6. The illumination device according to claim 1, wherein said illumination device includes a light trap and said light trap is positioned such that unreflected diffused light, from said light source, which passes through said louver filter and said beam splitter is absorbed by said light trap.

7. The illumination device according to claim 1, wherein the inner surface of the housing is coated with a substance which reflects a sufficient amount of light so as to match a brightness of the diffused light reflected by said beam splitter from said diffuser and said louver filter toward the object to be observed.

8. The illumination device according to claim 1, wherein said illumination device is used in combination with an inspection camera, and said inspection camera is positioned along said observation axis and adjacent a second aperture of said housing to sense light reflected by the object to be observed and passing through said beam splitter.

9. The combination according to claim 8 wherein the combination further includes a computer and assembly equipment, and the computer is connected with said inspection camera and the assembly equipment to control and manipulate the object to be observed, as desired.

10. An inspection system for illuminating an object to be observed by a camera along an observation axis extending from the camera to the object, said inspection system including an illumination device in combination with a camera, said illumination device comprising:

a housing having at least a first aperture therein aligned with an observation axis;

a partially reflective beam splitter being supported by said housing and being positioned obliquely relative to the observation axis adjacent said at least first aperture;

a light source being arranged to cast light on a first surface of said beam splitter;

a diffuser being positioned between said beam splitter and said light source for diffusing light from said light source as the light passes through said diffuser to said first surface of said beam splitter; and

a louver filter being positioned between said beam splitter and said diffuser to prevent direct illumination of an object to be observed by said diffuser whereby said diffuser is only able, during use, to indirectly illuminate a desired portion of the object to be observed, via said louver filter and said beam splitter, when the object is positioned along the observation axis defined by the camera thereby facilitating determination by the camera of one of a desired feature and characteristic of the object to be observed.

11. The inspection system according to claim 10, wherein said housing has a second aperture therein also aligned with said observation axis and said beam splitter is located between said first aperture and said second aperture;

and

said light source comprises one of a bulb, an incandescent fiber optic, at least one LED and a fluorescent light.

12. The inspection system according to claim 10, wherein said louver filter is formed from a plastic film and contains a plurality of closely spaced and parallelly arranged microlouvers members;

and

said louver filter has parallel light receiving and light transmission surfaces and said plurality of closely spaced and parallelly arranged microlouvers members extend in planes lying substantially perpendicular to said light receiving and light transmission surfaces.

13. The inspection system according to claim 10, wherein said illumination device includes a light trap and said light trap is positioned such that unreflected diffused light, from said light source, which passes through said louver filter and said beam splitter is absorbed by said light trap.

14. The inspection system according to claim 10, wherein the inner surface of the housing is coated with a substance which reflects a sufficient amount of light so as to match a brightness of the diffused light reflected by said beam splitter from said diffuser and said louver filter toward the object to be observed.

15. A method of illuminating an object to be observed by a camera along an observation axis extending from the camera to the object, said method comprising the steps of:

utilizing a housing having two aligned apertures therein which are both aligned with an observation axis;

supporting a partially reflective beam splitter within said housing between said apertures and along the observation axis;

arranging a light source to cast light on a first surface of said beam splitter;

positioning a diffuser between said beam splitter and said light source for diffusing light from said light source as the light passes through said diffuser toward said beam splitter;

positioning a louver filter between said beam splitter and said diffuser to prevent direct illumination an object to be observed by said diffuser;

supplying light, from said light source, through said diffuser and said louver filter;

reflecting a portion of said light, via said beam splitter, toward the object to be observed;

allowing a portion of light reflected back by said object to be observed to pass through said beam splitter and be sensed by said camera whereby said diffuser is only able, during use, to indirectly illuminate a desired portion of the object to be observed when the object is positioned along the observation axis.

16. The method according to claim 15, further comprising the steps of forming said louver filter from a plastic film and providing a plurality of closely spaced and parallelly arranged microlouvers members within said plastic film.

17. The method according to claim 15, further comprising the step of providing said louver filter with parallel light receiving and light transmission surfaces and arranging said plurality of closely spaced microlouvers members parallel to one another and extending in planes lying substantially perpendicular to said light receiving and light transmission surfaces.

18. The method according to claim 15, further comprising the step of utilizing one of a bulb, an incandescent fiber optic, at least one LED and a fluorescent light as said light source.

19. The method according to claim 15, further comprising the steps of providing a light trap and positioning said light trap such that unreflected diffuse light which passes through said beam splitter is absorbed by said light trap.

20. The method according to claim 15, further comprising the steps of coating an inner surface of the housing with a substance which reflects a sufficient amount of light so as to match a brightness of the diffused light reflected by said beam splitter from said diffuser and said louver filter toward the object to be observed.