Optical system and method for sample analyzation

• US 5,019,715 A
• Filed: 03/02/1990
• Issued: 05/28/1991
• Est. Priority Date: 03/02/1990
• Status: Expired due to Term

• Current Assignee: Thermo Electron Scientific Instruments LLC (Thermo Fisher Scientific Incorporated)
• Original Assignee: Spectra-Tech, Inc. (Thermo Fisher Scientific Incorporated)
• Inventors: Messerschmidt, Robert G., Sting, Donald W., Reffner, John A.
• Primary Examiner(s): Nelms, David C.
• Assistant Examiner(s): Allen, Stephone B.
• Application Number:
  US07/487,550
• Time in Patent Office: 452 Days
• Field of Search: 250/216, 250/237 G, 250/571, 250/572, 356/317-319, 356/445-448
• US Class Current: 250/559.16
• CPC Class Codes: G01N 21/4738 Diffuse reflection precedence is given to G01N21/55 - G01N21/57 if specular component is taken into consideration, e.g. also for testing fluids, fibrous materials
• CPC Class Codes: G01N 21/55 Specular reflectivity

Abstract

An optical system, apparatus and method for analyzing samples includes a radiant energy source, a first mask, a first mirror system, a sample plane, a second mirror system, a second mask and a detector. The first and second masks are respectively positioned along the optical path of the system in the same or different Fourier planes and/or conjugate planes thereof. The first mask has at least one inlet aperture with the relative position thereof in the first mask determining the angle of the energy incidence onto the sample. The second mask has at least one outlet aperture therein passing radiant energy therethrough which has been reflected from or transmitted through the sample at a preselected angle determined by the relative position of the second aperture in the second mask. Numerous first and second masks respectively having inlet and outlet apertures at different radial and/or circumferential positions may be used in the optical system to perform many types of analyses without moving or specially preparing the sample.

Claims

1. An optical system for analyzing samples comprising:

a source of radiant energy emitting radiant energy along an optical path of the optical system;

a sample plane in the optical path;

a sample to be analyzed having a surface thereof placed at the sample plane;

means for directing the incident radiant energy to the sample surface including first mask means removably positioned approximately at a Fourier plane or conjugate thereof of the optical system to selectively allow only certain radiant energy to pass therethrough to target that radiant energy at preselected angles of incidence to the sample surface;

means for collecting energy reflected, emitted or transmitted from the sample including second mask means removably positioned approximately at a Fourier plane or conjugate thereof of the optical system to selectively allow only certain reflected, emitted and/or transmitted radiant energy to pass therethrough which has emanated from the sample at preselected angles of reflection, emission or transmission, and

a detector in the optical path receiving the radiant energy passing through the second mask means to analyze selected aspects of the sample.

2. The optical system of claim 1 wherein the means for directing includes one-half of a Cassegrain mirror objective positioned between the first mask and the sample plane and the means for collection includes the other half of the Cassegrain mirror objective positioned between the sample plane and the second mask.

3. The optical system of claim 1 wherein the means to target includes a first mirror system to direct incident radiant energy from the first mask means to the sample surface and the means to collect includes a second mirror system to direct radiant energy reflected, emitted or transmitted from the sample surface to the second mask means.

4. The optical system of claim 1 wherein the first mask means includes a plurality of first masks respectively having at least one inlet aperture therein variably positioned from one first mask to another for different calibrated angles of energy beam incidence, the first masks being respectively selected and removably mounted in the optical path in accordance with the desired angle of incidence for the type of sample analysis being performed.

5. The optical system of claim 4 wherein the inlet apertures are arcuate, the radius of the arcuate inlet aperture from the center line of the optics can be varied from one first mask to another and the arcuate extent of the respective inlet apertures can be varied from one first mask to another.

6. The optical system of claim 4 wherein the second mask means includes a plurality of second masks respectively having at least one outlet aperture therein variably positioned from one second mask to another for different calibrated angles of energy beam reflectance, transmission and/or emission, the second masks being respectively selected and removably mounted in the optical path in accordance with the desired angle of reflectance, transmission and/or emission for the type of sample analysis being performed.

7. The optical system of claim 6 wherein the outlet apertures are arcuate, the radius of the arcuate outlet aperture from the centerline of the optics can be varied from one second mask to another, and the arcuate extent of the outlet aperture can be varied from one second second mask to another.

8. The optical system of claim 6 wherein the number of inlet and outlet apertures in the first and second masks, respectively, is equal.

9. The optical system of claim 8 wherein the inlet and outlet apertures are equally radially spaced from the center line of the optics.

10. The optical system of claim 9 wherein the inlet and outlet apertures are not diametrically opposed from one another.

11. The optical system of claim 8 wherein the inlet and outlet apertures are unequally radially spaced from the center line of the optics.

12. The optical system of claim 6 wherein the number of inlet and outlet apertures in the first and second masks, respectively, is unequal.

13. The optical system of claim 6 wherein the inlet and outlet apertures in the first and second masks, respectively, are unequally radially spaced from the center line of the optics.

14. The optical system of claim 13 wherein the inlet and outlet apertures are not diametrically opposed from one another.

15. The optical system of claim 12 wherein the outlet apertures outnumber the inlet apertures.

16. The optical system of claim 1 wherein the first and second masks are common to a single disc body.

17. The optical system of claim 2 wherein the first and second masks are both positioned in the Fourier plane most closely adjacent the Cassegrain mirror objective.

18. The optical system of claim 17 wherein the first and second masks are positioned in a conjugate plane of the Fourier transfer plane.

19. The optical system of claim 1 further including slide means having at least two receptacles therein, at lease one of such receptacles at least partially containing a first and a second mask.

20. The optical system of claim 19 wherein the slide means has two receptacles and either of such receptacles can be selectively slid into the optical path of the system.

21. The optical system of claim 20 wherein the other receptacle has a viewing mask at least partially positioned therein.

22. The optical system of claim 20 wherein the other receptacle has a different first and second mask at least partially embedded therein.

23. The optical system of claim 1 wherein the first and second masks are positioned in different Fourier planes on opposite sides of the sample plane for performing transmission studies.

24. A method for analyzing a sample at a sample plane of a radiant energy optical path comprising:

positioning a first mask inlet means at a Fourier plane of the optical path, the first mask means having at least one inlet aperture therein;

passing radiant energy through said first aperture;

reflecting the radiant energy passed by said first aperture through a first mirror system;

directing the radiant energy from the first mirror system to the sample at a preselected angle of incidence determined by the relative position of the first aperture in the first mask means;

reflecting or transmitting energy from said sample to a second mirror system,

directing radiant energy from said second mirror system to a second mask means positioned at a Fourier plane, said second mask means having at least one outlet aperture;

passing radiant energy through said outlet aperture which has been reflected from or transmitted through the sample at preselected angles of reflection or transmission determined by the relative position of the outlet aperture in the second mask means; and

analyzing the radiant energy passed through said second mask means at a detector.

25. The method of claim 24 including the further steps of:

running at least two different analyses on the same sample using different sets of inlet and outlet masks having differently positioned and/or configured inlet and outlet apertures therein;

comparing the detected results of the different analyses to obtain the differences therebetween; and

using the differences in the test results in conjunction with mathematical algorithms to more precisely quantify the components of the same being analyzed and/or its optical constants.

26. An optical system for analyzing samples comprising:

a sample positioned at a sample plane of the optical system emitting radiant energy;

means for collecting the radiant energy emitted from the sample including an outlet mask means removably positioned approximately at a Fourier plane or conjugate thereof of the optical system to selectively allow only certain emitted energy to pass therethrough which has been emitted at a preselected angle of emission, and

a detector in the optical path receiving radiant energy passing through the outlet mask means to analyze selected aspects of the sample.