Magneto-optical colloidal cell and device

• US 4,267,509 A
• Filed: 11/01/1978
• Issued: 05/12/1981
• Est. Priority Date: 11/01/1978
• Status: Expired due to Term

• Current Assignee: Graham W. Gordon
• Original Assignee: Graham W. Gordon
• Inventors: Graham, W. Gordon
• Primary Examiner(s): Strecker, Gerard R.
• Assistant Examiner(s): Snow, Walter E.
• Application Number:
  US05/956,565
• Time in Patent Office: 923 Days
• Field of Search: 324/96, 324/214, 324/244, 324/260, 356/336-343
• US Class Current: 324/244.1
• CPC Class Codes: G01C 17/28 Electromagnetic compasses with north seeking magnetic elements and having electric pick-offs G01C17/26
• CPC Class Codes: G01R 33/0052 Manufacturing aspects; Manufacturing of single devices, i.e. of semiconductor magnetic sensor chips devices based on galvano-magnetic effect or the like H10N50/85
• CPC Class Codes: G01R 33/032 using magneto-optic devices, e.g. Faraday or Cotton-Mouton effect
• CPC Class Codes: G02F 1/091 based on magneto-absorption or magneto-reflection

Abstract

A magneto-optical device which is responsive to magnetic fields by means of a Tyndall Effect in a particular direction exhibited by aligned magnetic colloidal particles suspended in an illuminated liquid medium. The liquid medium is contained in a transparent vessel and has magnetic particles in a very low density, such that the liquid is substantially transparent to the naked eye. A light source is positioned to illuminate the liquid medium and a light-sensing device or photocell is positioned to receive light scattered by the magnetic particles. The light-sensing device is positioned at a predetermined angle from the paraxial direction of the light source. All colloidal solutions, when illuminated by a beam of light, exhibit the Tyndall Effect, i.e. a visible scattering of light by the colloidal particles. When the magnetic colloidal solution of this device is brought into the presence of a magnetic field, the magnetic particles become aligned, causing the directed scattering of light called herein the Directional Tyndall Effect, which scattering can be detected by the photocell. In order to minimize the effects of surrounding light, the vessel containing the liquid medium can be enclosed in an opaque container with the photocell and light source mounted in appropriate apertures. For use in varying applications, two photocells can be provided, with the photocells and light source in an orthogonal arrangement.

Claims

1. A magneto-optical apparatus comprising:

a container having at least portions transparent;

a transparent liquid medium in said container;

a plurality of magnetic particles suspended in said liquid medium thereby forming a substantially transparent colloidal solution;

a light source positioned to illuminate said colloidal solution;

said magnetic particles in said colloidal solution adapted to produce a directional scattering of light under the influence of a magnetic field;

light-sensing means positioned at a predetermined angle with respect to the central axis of said light source;

said directional scattering of light produced by said magnetic particles being toward said light-sensing means;

whereby said light-sensing means senses variations in intensity of scattered light from said magnetic particles caused by the magnetic field.

2. The apparatus according to claim 1 including means for indicating the variations in intensity of light detected by said light-sensing means.

3. The apparatus according to claim 2 wherein said indicating means comprises a galvanometer.

4. The apparatus according to claim 1 wherein said magnetic particles are irregular in shape.

5. The apparatus according to claim 4 wherein said irregular particles have one long axis.

6. The apparatus according to claim 1 wherein said substantially transparent colloidal solution is a stabilized colloidal suspension of ferromagnetic material.

7. The apparatus according to claim 1 wherein said substantially transparent colloidal solution is a stabilized colloidal suspension of ferrimagnetic material.

8. The apparatus according to claim 1 wherein the magnetic particles'"'"' size is less than the wave length of the incident light.

9. The apparatus according to claim 1 wherein the particle size is between approximately 1000 Angstroms and 50 Angstroms.

10. The apparatus according to claim 1 wherein the concentration of magnetic particles in the liquid medium is less than about 5×

10¹² particles per cubic centimeter.

11. The apparatus according to claim 1 wherein the concentration of magnetic particles is in the range of about 5×

10⁹ to 5×

10¹¹ particles per cubic centimeter.

12. The apparatus according to claim 1 wherein said container comprises:

a transparent vessel;

an opaque cover over said transparent vessel; and

a plurality of openings in said opaque cover providing access to said transparent vessel.

13. The apparatus according to claim 12 wherein there are two openings in said opaque cover;

said light source being positioned adjacent to one of said openings; and

said light-sensing means being positioned adjacent to said second opening.

14. The apparatus according to claim 12 wherein said light-sensing means is positioned substantially perpendicular to said light source.

15. The apparatus according to claim 13 including:

a third opening in said opaque cover;

second light-sensing means positioned adjacent said third opening; and

said second light-sensing means is at a predetermined angle with respect to said light source and said first light-sensing means.

16. The apparatus according to claim 15 wherein the respective positions of said light source and said first and second light-sensing means are orthogonal.

17. The apparatus according to claim 14, including:

a pair of coils at each end of said container connected to amplifying means whereby said magneto-optical apparatus can detect and amplify small currents.

18. The apparatus according to claim 17 wherein said coils have ferrite cores.

19. The apparatus according to claim 17 wherein the respective positions of said light source and said first and second light-sensing means are orthogonal.

20. The apparatus according to claim 19 wherein said coils have ferrite cores.

21. The apparatus according to claim 17 wherein said coils are positioned to produce a uniform magnetic field.

22. The apparatus according to claim 17 including:

sensitivity adjusting means for adjusting the sensitivity of said magnetic particles to a magnetic field.

23. The apparatus according to claim 22 wherein said sensitivity adjusting means comprises a permanent magnet positioned proximate said colloidal solution.

24. The apparatus according to claim 23 including means for varying the position of said permanent magnet with respect to said colloidal solution whereby the sensitivity of said magnetic particles may be varied.

25. A magnetometer comprising:

a resistance bridge circuit having a balancing resistor in one leg and a device as in claim 1 in another leg;

a pair of operational amplifiers parallel connected to the outputs of said resistive bridge;

a differential amplifier connected to the outputs of the operational amplifiers;

rectifying means for rectifying the output of said differential amplifier; and

indicating means for indicating the output of said rectifying means.

26. The magnetometer according to claim 25 wherein said indicating means is a digital current meter.

27. The magnetometer according to claim 25 wherein said indicating means is a digital voltmeter.

28. An optical amplifier comprising:

a resistance bridge circuit having a balancing resistor in one leg and a device as in claim 1 in another leg;

at least one coil positioned proximate said magneto-optical device for applying an electro-magnetic field; and

a galvanometer connected across the resistance bridge for measuring the effect of the electro-magnetic field.

29. The optical amplifier according to claim 28 including:

modifying means for modifying the effect of the electro-magnetic field by aligning the magnetic particles whereby the sensitivity is increased or decreased.

30. The optical amplifier according to claim 29 wherein said modifying means comprises:

a permanent magnet adjustably positioned proximate said magneto-optical device for increasing or decreasing the effect of the electro-magnetic field on the magnetic particles.