Absorbance measuring photometer
AssigneeThe Perkin-Elmer Corporation
InventorsJohn G. Atwood, Hamilton W. Marshall, Jr., Charles F. DE Mey, II
Life of this patent
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Abstract
An absorbance measuring photometer, for measuring the absorbance of a sample in a sample cell, in which light of preselected wavelengths from one of two alternately utilizable sources of different wavelengths is formed into a beam and the etendu of the beam defined. The beam is then split into two separate beams one of which is directed through the sample cell onto a first detector and the other of which is passed directly onto a reference detector. The beam is so directed though the sample cell that it does not touch the cell walls and both beams are imaged on their respective detectors so as to be wholly within the photosensitive area thereof.
Claims11
A method of measuring the photo-absorbance of a translucent reaction mixture comprising:
- a. placing the reaction mixture in a sample cell
- b. forming a first beam of light containing predetermined wavelengths;
- c. defining the etendu of said first beam with a field stop and aperture stop;
- d. splitting said first beam into second and third contemporaneous beams while preserving uniformity of illumination over both said second and third beams;
- e. passing said second beam through said sample cell so as to symmetrically image said field stop near the entrance of said cell and said aperture stop near the exit of said cell, both said images being located so that said second beam does not touch the walls of said cell;
- f. forming an image of said aperture stop wholly within the sensitive area of a first detector using large angle optical means to capture a major portion of light scattered by the reaction mixture in the cell;
- g. imaging one of said field and aperture stops in said third beam wholly within the sensitive area of a second detector;
- and
- h. using the output of said second detector to cancel out any flucutations in the output of said first detector resulting from changing brightness in said first beam of light.
Apparatus for measuring the absorbance of a reaction mixture in a photometer sample cell comprising:
- a. a light source emitting predetermined wavelengths;
- b. means for forming the light from said source into a first beam;
- c. means for defining the etendu of said first beam including a field stop and an aperture stop;
- d. means for splitting said first beam into second and third contemporaneous beams while preserving the uniformity of illumination over both second and third beams and directing said second beam through said cell;
- e. lens means to symmetrically image said field stop near the entrance of said cell and said aperture stop near the exit of said cell in such manner that, when passing through said cell, said second beam does not touch the sides thereof;
- f. a first detector;
- g. means forming an image of said aperture stop wholly on the sensitive area of said first detector;
- h. a second detector in the path of said third beam;
- i. means forming an image of one of said field and aperture stops wholly on the sensitive area of said second detector;
- and
- j. signal amplifying means including means to cause the signal from said second detector to cancel out any variations in the signal from said first detector resulting from light source fluctuations.
Dependencies are inferred from the claim text.