APPARATUS FOR MEASURING CHANGES IN THE OPTICAL REFRACTIVE INDEX OF FLUIDS

• US 3,680,963 A
• Filed: 09/04/1970
• Issued: 08/01/1972
• Est. Priority Date: 09/04/1970
• Status: Expired due to Term

• Current Assignee: Bruce D. Hopkins, Dennis D. Rice, Louis J. Edwards
• Original Assignee: Bruce D. Hopkins, Dennis D. Rice, Louis J. Edwards
• Inventors: Edwards, Louis J., Hopkins, Bruce D., Rice, Dennis D.
• Primary Examiner(s): Wibert, Ronald L.
• Assistant Examiner(s): Clark, Conrad
• Application Number:
  US05/069,639
• Time in Patent Office: 697 Days
• Field of Search: 356/106-113
• US Class Current: 356/517
• CPC Class Codes: G01N 21/45 using interferometric methods; using Schlieren methods

Abstract

Apparatus for measuring changes in the optical refractive index of fluids including an interferometer cell having compartments for the fluids. Coherent light is split and separate beams thereof are passed through each of the fluid compartments and then combined to form a single optical beam which is projected on to matched light detectors to measure the difference in the optical refractive index of the fluids in the compartments.

Claims

1. Apparatus for measuring changes in the optical refractive index of fluids, said apparatus comprising in combination:

a. a coherent light source;

b. a refractometer cell comprising a reference fluid compartment for a fluid having a known index of refraction, said compartment having a light entry-end and a moveable retroreflector positioned at the end of said compartment opposite the light entry-end, and a sample fluid compartment having a light entry-end and a retroreflector positioned at the end of said compartment opposite the light entry-end, said sample fluid having an unknown index of refraction;

c. means for moving the retroreflector within the reference fluid compartment;

d. means for splitting the coherent light and passing separate beams through each of the fluid compartments and then combining the separate beams to form a single optical beam;

e. means for spreading the single optical beam and projecting part of the fringe pattern thereof onto matched light detectors; and

f. means for comparing and displaying the outputs from the matched light detectors to measure the difference in the optical refractive index of fluids in the compartments.

2. Apparatus as in claim 1 wherein the single optical beam is spread by optical means to form a more useful fringe pattern.

3. Apparatus as in claim 1 wherein the light detectors comprise a plurality of matched photocells.

4. Apparatus as in claim 3 wherein the photocells are matched and one pair is positioned on the opposite sides of at least one fringe pattern and another pair is positioned at the edges of the beam pattern.