Diffuse reflectance monitoring apparatus

• US 5,935,062 A
• Filed: 06/09/1997
• Issued: 08/10/1999
• Est. Priority Date: 08/09/1995
• Status: Expired due to Term

• Current Assignee: Rio Grande Medical Technologies Incorporated
• Original Assignee: Rio Grande Medical Technologies Incorporated
• Inventors: Robinson, Mark Ries, Messerschmidt, Robert G.
• Primary Examiner(s): O'Connor, Cary
• Assistant Examiner(s): WINAKUR, ERIC FRANK
• Application Number:
  US08/871,366
• Time in Patent Office: 792 Days
• Field of Search: 600/310, 600/322, 600/323, 600/344, 600/336, 600/340, 600/473, 356/446, 250/339.11, 250/341.8
• US Class Current: 600/322
• 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 21/474 Details of optical heads therefor, e.g. using optical fibres
• CPC Class Codes: G01N 21/49 within a body or fluid

Abstract

An improved method and apparatus for diffuse reflectance spectroscopy. A specular control device is provided that can discriminate between diffusely reflected light that is reflected from selected depths or layers within the tissue. The specular control device permits a spectroscopic analyzer to receive the diffusely reflected light that is reflected from, for example, a first layer or depth within the tissue, while preventing the remaining diffusely reflected light from reaching the spectroscopic analyzer. Furthermore, the specular control device may prevent the specularly reflected light (e.g. surface reflected light) from reaching the spectroscopic analyzer.

Claims

1. An apparatus for obtaining a diffuse reflectance spectra from human skin tissue for the non-invasive measurement of blood analytes, the human skin tissue having an epidermis layer and a dermis layer, comprising:

(a) generating means for generating infrared energy;

(b) directing means for directing said infrared energy to said tissue;

(c) collecting means for collecting infrared energy that is reflected by said tissue;

(d) discrimination means for discriminating between infrared energy that is diffusely reflected from the epidermis layer within said tissue from infrared energy that is diffusely reflected from the dermis layer, said discrimination means specifically sized for substantially preventing said infrared energy that is diffusely reflected from the epidermis layer from reaching said collecting means; and

(e) determining means for determining the concentration of a selected blood analyte by analyzing the infrared energy collected by said collecting means.

2. The apparatus of claim 1 wherein said discrimination means comprises a blocker blade adapted to be positioned on or adjacent to a surface of said tissue.

3. The apparatus of claim 2 wherein said blocker blade is adapted to extend substantially perpendicular to the surface of said tissue, and has two opposing surfaces including a front surface and a back surface defining a thickness thereof.

4. The apparatus of claim 3 wherein said directing means directs said infrared energy to form an illuminated portion of the surface of said tissue.

5. The apparatus of claim 4 wherein the back surface of said blocker blade is laterally spaced a predetermined distance from said illuminated portion of said tissue such that infrared energy that is diffusely reflected from the epidermis layer within said tissue is substantially prevented from reaching said collecting means.

6. The apparatus of claim 5 wherein the front surface of said blocker blade is adjacent to said illuminated portion of said tissue.

7. The apparatus of claim 3 wherein said blocker blade thickness defined by said front surface and said back surface is sufficient to prevent infrared energy that is diffusely reflected from the epidermis layer from reaching said collecting means.

8. The apparatus of claim 3 wherein said blocker blade absorbs diffusely reflected infrared energy incident thereon.

9. An apparatus for obtaining a diffuse reflectance spectra from human tissue for the non-invasive measurement of blood analytes, comprising:

(a) generating means for generating infrared energy;

(b) directing means for directing said infrared energy to said tissues

(c) collecting means for collecting infrared energy that is reflected by said tissue; and

(d) discrimination means for discriminating between infrared energy that is diffusely reflected from a first selected depth within said tissue from infrared energy that is diffusely reflected from a second selected depth, said discrimination means specifically sized for substantially preventing said infrared energy that is diffusely reflected from said first selected depth from reaching said collecting means; and

(e) said discrimination means comprises a blocker blade adapted to be positioned on or adjacent to the surface of said tissue, wherein at least part of said blocker blade reflects diffusely reflected infrared energy incident thereon.

10. An apparatus for obtaining a diffuse reflectance spectra from human tissue for the non-invasive measurement of blood analytes, comprising:

(a) generating means for generating infrared energy;

(b) directing means for directing said infrared energy to said tissue;

(c) collecting means for collecting infrared energy that is reflected by said tissue; and

(d) discrimination means for discriminating between infrared energy that is diffusely reflected from a first selected depth within said tissue from infrared energy that is diffusely reflected from a second selected depth, said discrimination means specifically sized for substantially preventing said infrared energy that is diffusely reflected from said first selected depth from reaching said collecting means; and

(e) said discrimination means comprises a blocker blade adapted to be positioned on or adjacent to the surface of said tissue, said directing means including an immersion lens, with said blocker blade positioned within said immersion lens.

11. An apparatus for obtaining a diffuse reflectance spectra from human skin tissue for the non-invasive measurement of blood analytes, the human skin tissue having a top surface, an epidermis layer and a dermis layer, the apparatus comprising:

(a) generating means for generating infrared energy;

(b) directing means for directing said infrared energy to said tissue;

(c) collecting means for collecting infrared energy that is reflected by said tissue; and

(d) discrimination means for discriminating between infrared energy that is diffusely reflected from the epidermis layer from infrared energy that is diffusely reflected from the dermis layer, said discrimination means substantially preventing said infrared energy that is diffusely reflected from said epidermis layer from reaching said collecting means; and

(e) determining means for determining the concentration of a selected blood analyte by analyzing the infrared energy collected by said collecting means using infrared spectroscopy.

12. The apparatus of claim 11 wherein said discrimination means further prevents the infrared energy that reflects specularly from the top surface of the tissue from reaching said collecting means.

13. A method for obtaining a diffuse reflectance spectra from human skin tissue for the non-invasive measurement of blood analytes, the human skin tissue having an epidermis layer and a dermis layer, the method comprising the steps of:

(a) generating infrared energy;

(b) directing said infrared energy to said tissue;

(c) collecting the infrared energy that is reflected from the dermis layer while rejecting the infrared energy that is reflected from the epidermis layer with a discriminating means; and

(d) determining the concentration of a selected blood analyte by analyzing the collected infrared energy.

14. The method of claim 13 wherein the directing step directs said infrared energy to a top surface of said tissue.

15. A method for obtaining a diffuse reflectance spectra from human tissue for the non-invasive measurement of blood analytes, said human tissue having a top surface, an epidermis layer and a dermis layer, the method comprising the steps of:

(a) generating infrared energy;

(b) directing said infrared energy to said tissue; and

(c) collecting the infrared energy that is reflected from said dermis layer, and rejecting the infrared energy that is reflected from said epidermis layer with a discriminating means which thereby discriminates between infrared energy diffusely reflected from such layers; and

(d) determining the concentration of a selected blood analyte by analyzing the collected infrared energy using infrared spectroscopy.

16. An apparatus for obtaining a diffuse reflectance spectra from human tissue for the non-invasive measurement of blood analytes, the human tissue having a top surface, an epidermis layer and a dermis layer, the apparatus comprising:

(a) generating means for generating infrared energy;

(b) directing means for directing said infrared energy to said tissue;

(c) collecting means for collecting infrared energy that is reflected by said tissue; and

(d) discrimination means for discriminating between infrared energy that reflects specularly from the top surface of the tissue from infrared energy that is diffusely reflected, said discrimination means having a thickness great enough to prevent light from leaking under the discrimination means due to the roughness of said tissue top surface to said collecting means; and

(d) determining means for determining the concentration of a selected blood analyte by analyzing the collected infrared energy.

17. The apparatus of claim 16 wherein said discrimination means comprises a blocker blade adapted to be positioned adjacent to a surface of said tissue.

18. The apparatus of claim 17 wherein said blocker blade is adapted to extend substantially perpendicular to the surface of said tissue, and has two opposing surfaces including a front surface and a back surface.