OPTICAL SHUTTER

• US 3,649,105 A
• Filed: 02/21/1968
• Issued: 03/14/1972
• Est. Priority Date: 02/21/1968
• Status: Expired due to Term

• Current Assignee: Robert L. Treuthart
• Original Assignee: Robert L. Treuthart
• Inventors: Treuthart, Robert L.
• Primary Examiner(s): Wibert, Ronald L.
• Assistant Examiner(s): Rothenberg, Jeff
• Application Number:
  US04/707,925
• Time in Patent Office: 1,483 Days
• Field of Search: 350/161,285
• US Class Current: 359/222.1
• CPC Class Codes: G02B 26/02 for controlling the intensity of light G02B26/004 takes precedence
• CPC Class Codes: H01S 3/121 using intracavity mechanical devices

Abstract

A wedge of transparent material having first and second angularly displaced faces is positioned in a controllable manner with respect to a right angle prism with one of the faces of the wedge parallel to the hypotenuse face of the prism. A piezoelectric element is positioned to drive the wedge relative to the prism between a first position wherein the wedge and prism are in near optical contact and a second position wherein the wedge and prism are spaced by a distance of about one wavelength of the light incident upon the prism so as to switch the optical path of the incident light beam from a condition of transmission to a condition of transmission to a condition of reflection at the hypotenuse face.

Claims

1. A shutter for switching the optical path of a beam of light comprising:

a prism of transparent material, said beam of light being internally incident on one face of said prism at an angle greater than the critical angle;

a wedge of transparent material having first and second angularly displaced faces, said first face being positioned parallel to said one face of said prism; and

means for driving said wedge relative to said prism between a first position wherein said first face of said wedge and said one face of said prism are in near optical contact and a second position wherein said first face of said wedge and said one face of said prism are spaced by a distance of at least lambda where lambda the wavelength of said light beam, said prism is a right angle prism and said one face is the hypotenuse Face of said right angle prism, said beam of light passing through one of the right angle faces of said prism and being incident on said hypotenuse face, said beam of light being totally internally reflected by said hypotenuse face when said wedge is in said second position, said beam of light passing through said hypotenuse face and being internally incident upon the second face of the wedge at an angle greater than the critical angle and being internally reflected by said second face of said wedge when said wedge is in said first position, the index of refraction of a material external the second face of the wedge being lower than the index of refraction of the wedge.

2. The shutter of claim 1 further comprising means for reflecting the light reflected by said hypotenuse face and said second face of said wedge back toward said hypotenuse face so that said beam of light emerges from said one right angle face along the same path as the incident beam when said wedge is in said second position and at an angle to said incident beam when said wedge is in said first position.

3. The shutter of claim 1 wherein the other of the right angle faces of said prism is totally reflective so that said beam of light is reflected back upon itself when said wedge is in said second position, said beam of light emerging from said one right angle face at an angle to the incident beam when said wedge is in said first position.

4. The shutter of claim 3 further comprising:

a block of material having first and second opposite faces, said first face being in optical contact with said second face of said wedge, the index of refraction of said block of material being less than that of said wedge so that light passing through said hypotenuse face of said prism when said wedge is in said first position is totally internally reflected by said second face of said wedge.

5. The shutter of claim 4 wherein said means for driving said wedge comprises:

a piezoelectric element having first and second opposite faces, said first face being in contact with said second face of said block of material, said first face of said piezoelectric element and said second face of said block of material being positioned parallel to said hypotenuse face of said prism and said first face of said wedge.

6. The shutter of claim 5 wherein said piezoelectric element has an annular groove therein so as to divide said piezoelectric element into a central section and a peripheral section, said second face of said block of material being in contact with said central section of said piezoelectric element, including means for supporting said block and said wedge relative to said prism being in contact with said peripheral section of said piezoelectric element, and wherein said means for driving said wedge further comprises:

a first electrical lead operatively coupled to said first face of said central section of said piezoelectric element; and

a second electrical lead operatively coupled to said second face of said piezoelectric element whereby a voltage pulse applied to said first and second leads causes said central section of said piezoelectric element to contract or expand to move said wedge relative to said prism.

7. The shutter of claim 6 further comprising:

a third electrical lead operatively coupled to said first face of said peripheral section of said piezoelectric element whereby a voltage pulse applied to said second and third leads of a polarity opposite to said first-mentioned voltage pulse causes said peripheral section of said piezoelectric element to contract or expand to provide an additional force to move said wedge relative to said prism.

8. The shutter of claim 7 wherein the voltage pulse applied to said first and second leads is delayed relative to the voltage pulse applied to said second and third leads.

9. The shutter of claim 1 further comprising:

a block of material having first and second opposite faces, said first face being in optical contact with saiD second face of said wedge, the index of refraction of said block of material being less than that of said wedge so that light passing through said one face of said prism when said wedge is in said first position is totally internally reflected by said second face of said wedge.

10. The shutter of claim 9 wherein said means for driving said wedge comprises:

a piezoelectric element having first and second opposite faces, said first face being in contact with said second face of said block of material.

11. The shutter of claim 10, including means for supporting said block and said wedge which are made of the same material.

12. The shutter of claim 11 wherein said prism is made of the same material as said means for supporting said block and said wedge.

13. The shutter of claim 12 wherein the side of said block of material adjacent said second face is cross-slotted to form a plurality of posts to prevent differential thermal expansion at the interface between said second face of said block of material and said first face of said piezoelectric element in a direction perpendicular to said interface.

14. The shutter of claim 10 wherein said first face of said piezoelectric element and said second face of said block of material are positioned parallel to said one face of said prism and said first face of said wedge.

15. The shutter of claim 14 wherein said means for driving said wedge further comprises:

a first electrical lead operatively coupled to said first face of said piezoelectric element; and

a second electrical lead operatively coupled to said second face of said piezoelectric element whereby a voltage pulse applied to said first and second leads causes said piezoelectric element to contract or expand to move said wedge relative to said prism.

16. The shutter of claim 15 wherein said piezoelectric element has an annular groove therein so as to divide said piezoelectric element into a central section and a peripheral section, said second face of said block of material being in contact with said central section of said piezoelectric element, said means for supporting said block and said wedge relative to said prism being in contact with said peripheral section of said piezoelectric element.

17. The shutter of claim 16 wherein said first electrical lead is operatively coupled to said central section of said piezoelectric element.

18. The shutter of claim 17 further comprising:

a third electrical lead operatively coupled to said first face of said peripheral section of said piezoelectric element whereby a voltage pulse applied to said second and third leads of a polarity opposite to said first-mentioned voltage pulse causes said peripheral section of said piezoelectric element to contract or expand to provide an additional force to move said wedge relative to said prism.

19. The shutter of claim 18 wherein the voltage pulse applied to said first and second leads is delayed relative to the voltage pulse applied to said second and third leads.

20. The shutter of claim 18 wherein said means for supporting said block and said wedge is made of the same material as said block of material whereby substantially all material between said first face of said piezoelectric element and said one face of said prism is identical and all material between said first face of said piezoelectric element and said second face of said piezoelectric element is identical to prevent differential thermal expansion in a direction perpendicular to said one face of said prism.