Light scattering test apparatus

• US 4,043,669 A
• Filed: 05/28/1976
• Issued: 08/23/1977
• Est. Priority Date: 05/28/1976
• Status: Expired due to Term

• Current Assignee: United States Of America As Represented By The Secretary Of The Air Force
• Original Assignee: United States Of America As Represented By The Secretary Of The Air Force
• Inventors: Wiff, Donald R., Gehatia, Matatiahu
• Primary Examiner(s): Corbin, John K.
• Assistant Examiner(s): Koren, Matthew W.
• Application Number:
  US05/691,162
• Time in Patent Office: 452 Days
• Field of Search: 356/103, 356/104, 356/207, 356/208, 356/246, 250/574
• US Class Current: 356/340
• CPC Class Codes: G01N 21/51 inside a container, e.g. in an ampoule G01N21/53 takes precedence

Abstract

An apparatus for measuring light scattered at various angles from a sample of molecules in solution, having a plurality of conical reflectors mounted on a turret assembly. The turret assembly is positioned in a temperature controlled tank. A laser beam is directed through the tank with the polymer sample being positioned within one of said reflectors in the path of the laser beam. Light scattered at a particular angle is collected and directed to a detector. The unscattered light is also directed toward the detector along a second path. A light chopper is provided to alternately supply scattered light and the unscattered light beam to the detector. The laser beam path through the sample can be reversed to provide a measure of back scattered light. Each of the conical mirrors may be selectively locked in position for positioning the polymer sample in the light path.

Claims

1. An apparatus for obtaining data for determining the ratio of scattered light intensity to unscattered light intensity from a sample of molecules in solution;

comprising an elongated test cell containing the sample solution;

means for maintaining said sample at a substantially constant temperature;

means for passing a beam of monochromatic light in a longitudinal direction through said test cell;

a photomultiplier;

means for passing light scattered by said sample solution along a first light path toward said photomultiplier;

means for passing unscattered light passing through said sample solution along a second path toward said photomultiplier;

means for removing substantially all the scattered light from the sample solution, in said first path, except light scattered at a predetermined angle;

means in said first and said second light paths for alternately passing light from the first and second light paths to said photomultiplier;

a null indicating device connected to the output of said photomultiplier;

means for attenuating the light in the unscattered light path to provide a null reading on said null meter;

means for providing an indication of the attenuation needed to provide a null in the output of said photomultiplier, to thereby obtain data for determining the ratio of scattered light intensity to unscattered light intensity;

said means for maintaining said sample at a substantially constant temperature including a constant temperature tank;

a liquid coolant within said tank;

a heat exchanger in the wall of said tank;

means for supplying coolant to the heat exchanger;

a turret assembly within said tank;

a plurality of conical mirrors, each having a different cone angle, mounted on said turret assembly;

means for rotating said turret assembly to selectively position one of said conical mirrors around the beam path of light passing through the test cell;

each of said mirrors including means for holding the test cell.

2. The device as recited in claim 1 wherein said means for removing substantially all of the scattered light from the sample solution, in the first path, except light scattered at a predetermined angle, includes a collimater positioned adjacent the bottom of said tank;

a flat mirror for passing scattered light from the conical mirror toward said photomultiplier;

said flat mirror having a hole therein for passing unscattered light passing through the test cell along the second path;

a mask, having an aperture, between the flat mirror and the photomultiplier;

a condensing lens between said flat mirror and said mask for focusing light from said flat mirror on said aperture;

a collimating lens between said mask and said photomultiplier.

3. The device as recited in claim 2 wherein said means for attenuating the light in the unscattered light path includes a polarizer-analyzer attenuator;

said polarizer-analyzer including means for indicating the angle between the planes of transmission of the polarizer and the analyzer.

4. The device as recited in claim 3 including means for reversing the direction of the light beam path through the sample cell;

said means for reversing the direction of the light beam path through said sample includes means for directing unscattered light along a third beam path toward said photomultiplier;

a second polarizer-analyzer attenuator in said third beam path;

said second polarizer-analyzer attenuator including means for indicating the angle between the planes of transmission of the polarizer and analyzer.