Methods and apparatus for determining the relative amount of substance present in a transparent medium

Claim 1

A method of determining the relative amount of substance present in a transparent medium comprising the steps of generating a first beam of radiation, separately polarizing portions of said first beam of radiation into a second and third beam of radiation, said second and third beams of radiation being along mutually polarized perpendicular planes, fIltering said second beam of radiation and passing a first beam component exhibiting a narrow band of frequencies within an absorption band of said substance and filtering said third beam of radiation and passing a second beam component exhibiting a band of frequencies which are substantially unabsorbed by said substance, periodically rotating the plane of polarization of said first and second beam components through an angle of rotation of 90* selectively passing said first and said second beam components alternately, projecting said first and said second beam components into said medium along a substantially common path through said medium, and detecting the difference of intensities of said first and said second beam components whereby said first and second beam components have a similar genesis but because of said filtering said first beam component is absorbed by said substance and said second beam component is not affected by said substance and said first and second beam components being polarized along mutually perpendicular planes are differentiated and the difference in the intensity of said first and second beam components is detected to indicate the amount of said substance present in said transparent medium as a function of the difference in the intensity of said first and second beam components.

Claim 2

A method of determining the relative amount of substance present in a transparent medium comprising the steps of generating a first beam of radiation, separately polarizing portions of said first beam of radiation into a second and third beam of radiation, said second and third beams of radiation being along mutually polarized perpendicular planes, fIltering said second beam of radiation and passing a first beam component exhibiting a narrow band of frequencies within an absorption band of said substance and filtering said third beam of radiation and passing a second beam component exhibiting a band of frequencies which are substantially unabsorbed by said substance, periodically rotating the plane of polarization of said first and second beam components through an angle of rotation of 90* selectively passing said first and said second beam components alternately, projecting said first and said second beam components into said medium along a substantially common path through said medium, and detecting the difference of intensities of said first and said second beam components whereby said first and second beam components have a similar genesis but because of said filtering said first beam component is absorbed by said substance and said second beam component is not affected by said substance and said first and second beam components being polarized along mutually perpendicular planes are differentiated and the difference in the intensity of said first and second beam components is detected to indicate the amount of said substance present in said transparent medium as a function of the difference in the intensity of said first and second beam components.

Claim 7

An apparatus for determining the relative amount of a substance present in a transparent medium comprising means for generating radiation, means for forming from said generated radiation first and second plane polarized beams having planes of polarization substantially mutually perpendicular, said means for forming being disposed within the path of said generated radiation from said means for generating radiation, means for filtering said first plane polarized beam to pass a first filtered beam having a narrow band of frequencies within an absorption band of said substance, means for filtering said second plane polarized beam to pass a second filtered beam having a band of frequencies which are substantially unabsorbed by said substance, means for periodically rotating the plane of polarization of said first and second filtered beams between two substantially perpendicular orientations, means for selectively passing said first and said second filtered beams alternately, means for projecting said first and said second filtered beams into said medium along a substantially common path through said medium, and means disposed in the path of said first and second filtered beams after said first and second filtered beams pass through said medium for receiving said first and second filtered beams, which means includes means for detecting the difference of intensities of said first and said second filtered beams.

Claim 8

An apparatus for determining the relative amount of a substance present in a transparent medium comprising means for generating radiation, means for forming from said generated radiation first and second plane polarized beams having planes of polarization substantially mutually perpendicular, said means for forming being disposed within the path of said generated radiation from said means for generating radiation, means for filtering said first plane polarized beam to pass a first filtered beam having a narrow band of frequencies within an absorption band of said substance, means for filtering said second plane polarized beam to pass a second filtered beam having a band of frequencies which are substantially unabsorbed by said substance, means for periodically rotating the plane of polarization of said first and second filtered beams between two substantially perpendicular orientations, means for selectively passing said first and said second filtered beams alternately, means for projecting said first and said second filtered beams into said medium along a substantially common path through said medium, and means disposed in the path of said first and second filtered beams after said first and second filtered beams pass through said medium for receiving said first and second filtered beams, which means includes means for detecting the difference of intensities of said first and said second filtered beams.