Multiple internal reflectance spectroscopy system

• US 4,730,882 A
• Filed: 02/10/1986
• Issued: 03/15/1988
• Est. Priority Date: 02/10/1986
• Status: Expired due to Term

• Current Assignee: Spectra-Tech, Inc. (Thermo Fisher Scientific Incorporated)
• Original Assignee: Spectra-Tech, Inc. (Thermo Fisher Scientific Incorporated)
• Inventors: Messerschmidt, Robert G.
• Primary Examiner(s): Lee, John
• Assistant Examiner(s): NGO, HUNG NHAT
• Application Number:
  US06/827,367
• Time in Patent Office: 764 Days
• Field of Search: 350/96.10, 350/96.15, 350/96.28, 356/300
• US Class Current: 385/146
• CPC Class Codes: G01N 21/552 Attenuated total reflection
• CPC Class Codes: G02B 6/10 of the optical waveguide type G02B6/02, G02B6/24 take precedence; devices or arrangements for the control of light by electric, magnetic, electro-magnetic or acoustic means G02F1/00; transferring the modulation of modulated light G02F2/00; optical logic elements G02F3/00; optical analogue/digital converters G02F7/00

Abstract

A multiple internal reflectance crystal has a sample surface and a bottom surface and reflective beveled ends such that energy may enter normal to the bottom surface, reflect off one beveled end to the bottom surface, from the bottom surface to the top surface, down the length of the crystal, and exit the crystal normal to the bottom surface by reflecting off of another beveled end. The crystal may be optically linked with light pipes and positioned at a location remote from the source and receiver of energy.

Claims

1. An internal reflectance spectroscopy system, especially for the spectroscopic analysis of a surface, wherein radiant energy undergoes internal reflection at a constant angle of incidence and reflection in an internal reflectance crystal, comprising:

a first side;

a second side;

a first beveled edge oriented at an acute angle with respect to said first side;

a second beveled edge on said crystal being oriented at an acute angle to said first side;

first radiation transfer means for condensing a beam of the radiant energy into the crystal to form an optical path extending directly through said first side to said first beveled edge, from said beveled edge directly back to said first side, from said first side directly to said second side, from said second side directly to said first side, from said first side directly to said second beveled edge, and from said second beveled edge directly through said first side, said first radiation transfer means defining an entrance for the radiant energy; and

second radiation transfer means for receiving a diverging beam of the radiant energy that is reflected from said second beveled edge through said first side of the crystal, said second radiation transfer means defining an exit for the radiant energy.

2. An internal reflectance spectroscopy system as claimed in claim 1, wherein said first and second beveled edges are separated by a predetermined distance such that the radiant energy internally reflects in said crystal a plurality of times between said first and second sides.

3. An internal reflectance spectroscopy system as claimed in claim 1 wherein said first and second beveled edges are coated with a material that reflects the radiant energy.

4. An internal reflectance spectroscopy system as claimed in claim 1, wherein:

said first radiation transfer means comprises a first light pipe for directing the radiant energy through said surface to said first beveled edge; and

said second radiation transfer means comprises a second light pipe for receiving said diverging beam of radiant energy reflected from said second beveled edge through said first side.

5. An internal reflectance spectroscopy system as claimed in claim 4, wherein:

said first light pipe has tapered sides that condense the radiant energy; and

said second light pipe has tapered sides that diverge the radiant energy.

6. An internal reflectance spectroscopy system as claimed in claim 4, wherein said first and second light pipes are purged of gasses that attenuate the radiant energy.

7. An internal reflectance spectroscopy system as claimed in claim 1, wherein said first side and said second side are parallel.

8. An internal reflectance spectroscopy system as claimed in claim 7, wherein:

said first side comprises a flat, contiguous surface; and

said second side comprises a flat, contiguous surface.

9. A method of reflecting radiant energy in an internal reflectance spectroscopy system for use in spectroscopy, especially in the spectroscopic analysis of a surface, wherein radiant energy undergoes internal reflection at a constant angles of incidence and reflection in an internal reflectance crystal, comprising the steps of:

receiving the radiant energy at an entrance;

condensing the radiant energy from the entrance into the crystal through a first side to a first beveled edge;

directing the radiant energy from said first beveled edge directly to said first side;

reflecting the radiant energy from said first side directly to a second side of said crystal;

reflecting the radiant energy from said second side directly to said first side;

reflecting the radiant energy from said first side directly to a second beveled edge, said second beveled edge being oriented at an acute angle relative to said first side;

directing the radiant energy from said second beveled edge directly through said first side to form a diverging beam of radiant energy; and

discharging the radiant energy forming said diverging beam to an exit.

10. A method as claimed in claim 9, wherein:

the radiant energy enters the crystal normal to said first side; and

the radiant energy is discharged from the crystal normal to said first side.

11. A method as claimed in claim 9, further comprising the steps of reflecting the radiant energy between said first and second sides a plurality of times.