APPARATUS FOR CONTROLLING A BEAM OF COHERENT ELECTRO-MAGNETIC WAVES

• US 3,705,758 A
• Filed: 12/30/1969
• Issued: 12/12/1972
• Est. Priority Date: 12/30/1969
• Status: Expired due to Term

• Current Assignee: Haim Haskal
• Original Assignee: Haim Haskal
• Inventors: Haskal, Haim
• Primary Examiner(s): Wibert, Ronald L.
• Assistant Examiner(s): McGraw, V. P.
• Application Number:
  US04/889,054
• Time in Patent Office: 1,078 Days
• Field of Search: 350/160,175GN 331/94.5 356/160
• US Class Current: 359/239
• CPC Class Codes: G02F 1/0121 Operation of devices; Circuit arrangements, not otherwise provided for in this subclass
• CPC Class Codes: G02F 1/0327 Operation of the cell; Circuit arrangements G02F1/05 takes precedence

Abstract

Focusing means in the path of a beam of coherent electromagnetic waves focus the beam on a focal plane. The beam intensity varies across the diameter. First transparent refractive means in the path of the more intense portion of the beam transmits the waveforms but retards their phase. Second transparent refractive means in the path of the less intense portion of the beam transmits the less intense waveforms but retards their phase an amount different from that of the first refractive means. Interference at the focal plane between the phase changed waveforms alters the original intensity profile of the waveforms. By controlling the relative phase changes the intensity pattern can be altered to be substantially uniform across the beam with only small loss of energy.

Claims

1. Apparatus for controlling a beam of coherent electromagnetic waves whose intensity varies across the beam comprising, first transparent refractive means in the path of the more intense portion of the beam for transmitting the waveforms in the more intense portion but changing their phase, second transparent refractive means in the path of the less intense portion of the beam for transmitting the waves in the less intense portion of the beam and changing their phase an amount different from that of said first refractive means, and focusing means other than said first or second refractive means located in the path of both the more intense and less intense portion of the beam for focusing the beam on a focal plane, whereby interference at the focal plane between the phasechanged waveforms alters the intensity pattern of the waveforms.

2. Apparatus as in claim 1 wherein each of said refractive means transmit substantially all the energy in the waveforms passing through the respective refractive means and any energy absorbed by said refractive means is absorbed in virtually the same proportion in both of said refractive means.

3. Apparatus as in claim 1 wherein the beam of coherent electromagnetic waves is a laser beam and wherein said refractive means each includes a transparent material, said materials having different refractive indices with respect to the laser beam.

4. An apparatus as in claim 3 wherein one of said materials comprises an electro-optic material whose refractive index varies according to an electric field, and further comprising electrode means for forming an electric field in said electro-optic material, whereby the refractive index and hence the phase change of said material can be controlled on the basis of the electric field and whereby the cross-sectional intensity pattern of the waveform at the focal plane can be varied to achieve a given intensity pattern.

5. Apparatus as in claim 4 wherein the more intense portion of the beam is in the center and one of said materials is aligned with the center of the beam and the other of said materials surrounds the first of said materials, the first of said materials being electro-optic, said electrode means including an electrode at the interface between said materials, and control means for controlling the voltage of said electrode.

6. Apparatus as in claim 5 further comprising compensating means in the path of said beam, said compensating means having a center refractive portion and a surrounding refractive portion, said refractive portions having respective indices of refraction to reverse the phase changes imparted by said first refractive means and said second refractive means so that in the unenergized condition of the electrodes said refractive means and said compensating means impart no net phase change to said waveforms.

7. Apparatus as in claim 5 wherein said control means include sensing means extending in the path of the bean for sensing the relative intensities of two points in the beam, and means connected to said sensing and said electrode means for adjusting the voltage of said electrode means in response to the relative intensities sensed by said sensing means.

8. The method of controlling a beam of coherent electromagnetic waves whose intensity varies across the beam, which comprises changing the phase of waveforms in the more intense portion of the beam with first refractive means, changing the phase of the waveforms in another portion of the beam an amount different from that of the first refractive means with second refractive means, and then focusing the so changed beam onto a focal plane by means other than said refractive means so that interference at the focal plane between the phase changed waveforms alters the intensity pattern of the waveforms.

9. The method as in claim 8 further comprising the step of varying the refractive index of one of the refractive means so as to change the interference pattern at the focal plane and produce a predetermined intensity pattern.

10. The method as in claim 8 further comprising the step of sensing the relative intensities of two points in the beam and on the basis of the relative intensities controlling the refractive index of one of said refractive means so as to change the phase of the beams of the waveforms passing therethrough to produce a predetermined intensity pattern.

11. Apparatus for controlling a beam of coherent electromagnetic waves whose intensity varies across the beam comprising:

first transparent refractive means in the path of the more intense portion of the beam for transmitting the waveforms in the more intense portion but changing their phase, second transparent refractive means in the path of the less intense portion of the beam for transmitting the waves in the less intense portion of the beam and changing their phase an amount different from that of said first refractive means, at least one of said refractive means comprising an electro-optic material whose refractive index varies according to an electric field, electrode means for forming an electric field in said electro-optical material, whereby the refractive index and hence the phase change of said material can be controlled on the basis of the electric field, compensating means in the path of said beam, said compensating means having a center refractive portion and a surrounding refractive portion, said refractive portions having respective indices of refraction to reverse the phase changes imparted by said first refractive means and said second refractive means so that in the unenergized condition of the electrode means said first and second refractive means and said compensating means impart no net phase change to said waveforms, and focusing means in the path of both the more intense and less intense portion of the beam for focusing the beam on a focal plane.

12. Apparatus as in claim 11 further including control means having sensing means extending in the path of the beam for sensing the relative intensities of two points in the beam, and means connected to said sensing and said electrode means for adjusting the voltage of said electrode means in response to the relative intensities sensed by said sensing means.