Apparatus and method for measuring the included angle of a reflective cone

• US 4,758,729 A
• Filed: 08/28/1987
• Issued: 07/19/1988
• Est. Priority Date: 08/28/1987
• Status: Expired due to Fees

• Current Assignee: Spectra Precision Inc. (Trimble Inc.)
• Original Assignee: Spectra-Physics Incorporated (MKS Instruments Incorporated)
• Inventors: Monnin, Douglas B.
• Primary Examiner(s): Nelms, David C.
• Assistant Examiner(s): Allen, Stephone B.
• Application Number:
  US07/090,944
• Time in Patent Office: 326 Days
• Field of Search: 250/560, 250/561, 356/376, 356/388, 356/391-393
• US Class Current: 250/559.22
• CPC Class Codes: G01B 11/26 for measuring angles or tapers; for testing the alignment of axes

Abstract

An apparatus and method are provided for measuring the included angle of a reflective cone between opposite sides of the reflective cone. The apparatus includes means for illuminating the curved surface of the reflective cone with a collimated beam of light, the beam of light being generally parallel to the axis of the cone. A lens receives directly a portion of the light reflected from a first side of the cone, and focuses the portion of the light so received in a reference plane. A retro-reflective mirror arrangement, positioned on the side of the cone opposite the lens, receives directly a portion of the light reflected from a second side of the cone and redirects the light to the lens in a direction parallel to the light reflected from the second side of the cone. The second side of the cone is opposite to the first side of the cone. A light detection arrangement at the focal point of the lens displays the light received by the lens, whereby the spacing between the light received from the retro-reflective mirror arrangement and the light received directly from the cone is related to the included angle between the first and second sides of the reflective cone.

Claims

1. Apparatus for measuring the included angle of a reflective cone between opposite sides of said reflective cone, comprising:

means for illuminating the curved surface of said reflective cone with a collimated beam of light, said beam of light being generally parallel to the axis of said cone,

lens means for receiving directly a portion of the light reflected from a first side of said cone, and for focusing the portion of the light so received in a reference plane,

retro-reflective means, positioned on the side of said cone opposite said lens means, for receiving directly a portion of the light reflected from a second side of said cone and redirecting said light to said lens means substantially parallel to the light reflected from said second side of said cone, said second side of said cone being opposite to said first side of said cone, and

light detection means at the focal point of said lens means for displaying the light received by said lens means, whereby the spacing between the light received from said retro-reflective means and the light received directly from said cone is related to said included angle between said first and second sides of said reflective cone.

2. The apparatus of claim 1 for measuring the included angle of a reflective cone between opposite sides of said reflective cone in which said light detection means comprises a screen.

3. The apparatus of claim 1 for measuring the included angle of a reflective cone between opposite sides of said reflective cone in which said means for illuminating the curved surface of said reflective cone with a collimated beam of light comprises a source of laser light.

4. The appratus of claim 1 for measuring the included angle of a reflective cone between opposite sides of said reflective cone in which said lens means and said light detection means comprise portions of an auto-collimator.

5. The apparatus of claim 1 for measuring the included angle of a reflective cone between opposite sides of said reflective cone in which said retro-reflective means comprises a pair of mirrors having their mirrored surfaces oriented at a 90 degree included angle.

6. The apparatus of claim 1 for measuring the included angle of a reflective cone between opposite sides of said reflective cone in which said light detection means at the focal point of said lens means for displaying the light received by said lens means comprises a reticle screen in said plane.

7. The appratus of claim 1 for measuring the included angle of a reflective cone between opposite sides of said reflective cone in which the included angle is equal to ninety degrees minus one half the angle of divergence between the light reflected by the first side of the cone and the light reflected from the retro-reflective means.

8. The appratus of claim 5 for measuring the included angle of a reflective cone between opposite sides of said reflective cone in which said pair of mirrors in said retro-reflective means are oriented so as to reflect light received from said cone to said lens means along a path which is parallel to the path of the light received from the second side of the cone, but offset with respect thereto, such that the light reflected from said retro-reflective means to said lens means does not strike said cone.

9. The apparatus of claim 6 for measuring the included angle of a reflective cone between opposite sides of said reflective cone further comprises an eyepiece for viewing said reticle screen.

10. The apparatus of claim 7 for measuring the included angle of a reflective cone between opposite sides of said reflective cone in which said spacing in said reference plane between the light received from said retro-reflective means and the light received directly from said cone is equal to said angle of divergence multiplied by the focal length of said lens means.

11. A method for measuring the included angle of a reflective cone between opposite, first and second sides of said reflective cone, comprising the steps of:

illuminating the curved surface of said reflective cone with a collimated beam of light, said beam of light being generally parallel to the axis of said cone,

receiving a portion of the light reflected from said second side of said cone and redirecting said light in a direction generally parallel to the light reflected from said second side of said cone,

positioning a lens so as to focus in a reference plane a portion of the light reflected from a first side of said cone, and a portion of the redirected light from the second side of said cone, and

displaying in the reference plane the light received by said lens, whereby the spacing between the light received from said first and second sides of said cone is related to said included angle.

12. The method of claim 11 for measuring the included angle of a reflective cone between opposite sides of said reflective cone in which said step of displaying includes the step of displaying the light on a screen.

13. The method of claim 11 for measuring the included angle of a reflective cone between opposite sides of said reflective cone in which said collimated beam of light comprises a beam of laser light.

14. The method of claim 11 for measuring the included angle of a reflective cone between opposite sides of said reflective cone in which said lens forms a portion of an auto-collimator.

15. The method of claim 11 for measuring the included angle of a reflective cone between opposite sides of said reflective cone in which the step of receiving and redirecting a portion of the light reflected from said second side of the cone is accomplished by means of a pair of mirrors having their mirrored surfaces oriented at a 90 degree included angle.

16. The method of claim 11 for measuring the included angle of a reflective cone between opposite sides of said reflective cone in which a reticle screen is positioned in said plane.

17. The method of claim 11 for measuring the included angle of a reflective cone between opposite sides of said reflective cone in which the included angle is equal to ninety degrees minus one half the angle of divergence between the light reflected by the first side of the cone and the light reflected from the second side of the cone and subsequently redirected.

18. The method of claim 15 for measuring the included angle of a reflective cone between opposite sides of said reflective cone in which said pair of mirrors are oriented so as to reflect light received from said cone to said lens along a path which is parallel to the path of the light received from the second side of the cone, but offset with respect thereto, such that the light reflected from said mirrors to said lens does not strike said cone.

19. The method of claim 16 for measuring the included angle of a reflective cone between opposite sides of said reflective cone in which an eyepiece is provided for viewing said reticle screen.

20. The method of claim 17 for measuring the included angle of a reflective cone between opposite sides of said reflective cone in which said spacing in said reference plane between the light received from said first and second sides of said cone is equal to said angle of divergence multiplied by the focal length of said lens.