Collecting hemispherical attachment for spectrophotometry

• US 4,853,542 A
• Filed: 06/08/1987
• Issued: 08/01/1989
• Est. Priority Date: 06/08/1987
• Status: Expired due to Fees

• Current Assignee: Croton Dam Rd., Ossining, Ny. Nicolas James Harrick
• Original Assignee: Nicolas J. Harrick
• Inventors: Milosevic, Milan, Harrick, Nicolas J.
• Primary Examiner(s): Fields, Carolyn E.
• Assistant Examiner(s): NOT, DEFINED
• Application Number:
  US07/059,323
• Time in Patent Office: 785 Days
• Field of Search: 250/353, 250/341, 250/372, 250/228, 250/339, 356/446, 356/236
• US Class Current: 250/353
• CPC Class Codes: G01N 2021/516 Multiple excitation of scattering medium, e.g. by retro-reflected or multiply reflected excitation rays
• CPC Class Codes: G01N 2021/6469 Cavity, e.g. ellipsoid
• CPC Class Codes: G01N 21/474 Details of optical heads therefor, e.g. using optical fibres

Abstract

An attachment or accessory for performing diffuse reflectance spectroscopy on a conventional UV-VIS-IR spectrophotometer. The attachment includes a removable body having a hemispherical mirrored interior surface positioned over the sample, and containing windows for entrance and exit of radiation. Multiple sampling of the same sample area enhances the quality of the spectrophotometer output.

Claims

1. A method for improving the spectroanalysis of a sample of a material by diffuse reflectance spectrometry in a spectrometer providing a sampling compartment in the optical path of a radiation beam to a detector, comprising the steps:

a. supporting the sample in a fixed position within the sampling compartment,

b. redirecting the radiation beam so it is incident upon a surface of the sample at an angle between 20 and 70 degrees,

c. providing a hollow body having an interior hemispherical reflecting surface and windows for entrance of a radiation beam and for allowing radiation to exit,

d. surrounding the sample with the hemispherical reflecting surface in such a manner that the redirected incident beam will pass through the entrance window and impinge upon the sample and such that the center of curvature of the hemisphere substantially coincides with the impingement area on the sample of the incident beam,

e. redirecting radiation exiting through the exit window of the hollow body toward the detector, and

f. detecting the redirected radiation exiting from the body and using the detected radiation to determine a characteristic of the sample,

g. said entrance and exit windows being spaced from one another, and the exit window being located in a position to allow predominantly diffusely reflected radiation from the sample to exit through it.

2. The method of claim 1 wherein the sample is provided with a reflecting medium.

3. A method as set forth in claim 1, wherein the sample is a diffuse reflector, the radiation is UV, VIS, or IR, and the incident radiation beam is focussed at substantially a point of the sample located substantially at the center of curvature of the hemispherical reflecting surface.

4. A method as set forth in claim 3 wherein the entrance and exit windows are offset at an angle of about 120°

to prevent specular radiation from exiting.

5. An attachment for use with an accessory for carrying out diffuse reflectance spectroscopy in a spectrometer wherein the accessory provides first means for focussing an incident radiation beam received from the spectrometer onto the surface of a sample to be analyzed and supported by the accessory and second means for collecting diffused reflections from the sample surface and redirecting it back into the spectrometer for detection and processing of the resultant signal;

the attachment comprising a hollow body having an interior hemispherical reflecting surface, an entrance window for receiving the incident beam and an exit window for allowing diffused reflections from the sample to exit from the body, the entrance and exit windows being spaced openings in the body located offset from the hemispherical peak, said attachment being positioned over the sample such that the area of impingement of the incident beam on the sample surface substantially coincides with the center of curvature of the interior reflecting surface.

6. An accessory for performing diffuse reflectance analysis of a sample in an UV, VIS, or IR spectrometer comprising:

a. a base member configured to fit within the sampling compartment of the spectrometer,

b. means on the base member for supporting a sample in a fixed position,

c. optical means for receiving an incident radiation beam from the spectrometer and focussing the beam onto substantially an impingement point of the sample surface such that diffuse reflectance occurs producing diffuse reflectance rays carrying information about a characteristic of the sample in many directions,

d. a removable body having an interior hemispherical reflecting surface provided over the sample such that the center of curvature of the reflecting surface substantially coincides with the impingement point on the sample of the incident beam, those reflected rays which are intercepted by the reflecting surface being reimaged at substantially the same impingement point,

e. an entrance window in the body for allowing the incident beam to impinge upon the sample,

f. an exit window in the body for allowing predominantly diffuse reflectance radiation to exit from the body,

g. optical means on the base member for collecting radiation exiting from the body and redirecting same back into the spectrometer for detection and processing of the resultant signals therein.

7. An accessory as claimed in claim 6 wherein the entrance window is located on the body so as to allow the incident beam to impinge upon the sample at an angle of incidence between 20°

and 70°

, and the exit window is offset from the entrance window and is located so as to allow to exit diffused reflections, but not specular radiation, from the body at an angle of incidence between 20° and

70°

.

8. An accessory as claimed in claim 7 wherein the entrance and exit windows occupy approximately one-thrid of the surface of the hemispherical reflector.

9. An accessory as claimed in claim 8 wherein the hemispherical surface has a diameter of about 25 mm, and the windows are circular openings each having a diameter of about 15 mm.