Apparatus for determining a substance by an optical radiation

Claim 2

Apparatus for determining the amount of a given component within a composition of matter to be investigated, said apparatus comprising: a laser radiation source (10) producing a beam (12) of electromagnetic radiation; a beam splitter (13) positioned in the path of said beam to derive therefrom a sample beam (12m) of said radiation and a reference beam (12r) of said radiation; sample positioning means (14) to position a sample of said substance in the path of said sample beam to modify the amplitude and phase of the radiation of said sample beam (12m) as a function of said component; first means (21) to produce first and second versions of said reference beam, said versions having first and second phases respectively; second means (29a, 29b) for producing first and second versions of said modified sample beam, said versions having third and fourth phases, respectively; third means (23) for combining said first reference beam version and said first modified sample beam version to produce a first combined beam; fourth means (27) for combining said second reference beam version with said second modified sample beam version to produce a second combined beam; first phase adjUstment means (25) located in the path of at least one of the versions of the reference beam to control the phasing of said beams to provide a phase difference between said first and third phases which differs by 90* from the difference between said second and fourth phases; second phase adjustment means (15) for adjusting the phase of both versions of said reference beam relative to both versions of said modified sample beam; and a first and second radiation detecting means (20a, 20b) receiving said first and second combined beams, respectively, to produce first and second output signals indicating the attenuation and phase shift, respectively, of the sample beam radiation caused by said substance.

Claim 3

The apparatus according to claim 1, comprising an amplitude modulator (11'') modulating the sample beam with a frequency (X) which is far lower than the frequency of the laser radiation, being placed in the path of the sample beam, and by a.c. voltage amplifiers being connected to the radiation detectors.

Claim 4

The apparatus according to claim 2, wherein the radiation detection means comprises an oscilloscope, the X- and Y-deflections of the oscilloscope being controlled by the first and second output signals, and the beam of the oscilloscope being briefly intensity modulated by the modulation frequency.

Claim 5

The apparatus according to claim 1 comprising a further beamsplitter (26) splitting the sample beam produced from the first-mentioned beam portion to form a second reference beam (12a); a comparison cuvette (14a) situated in the path of the second reference beam; the sample means (14b) being located in the path of the sample beam proper and a combining device (32) located in the paths of the beams to unite by superposition the beams issuing from the comparison and the sample cuvettes to pass the combined beam to said second means.

Claim 6

The apparatus according to claim 1, comprising adjustable means (15, 25, 28) to change the optical length of the path traversed by one beam with respect to the optical length of the path traversed by the second beam and being situated in the radiation path of at least one of the two beams.

Claim 7

Instrument according to claim 1, including an attenuator comprising an optical circular polariser being situated in the radiation path of the reference beam.

Claim 8

Apparatus according to claim 1 wherein the first means comprises a first semi-transparent mirror (21) which splits the reference beam (12r) into a transmitted portion and a reflected portion, said portions forming said versions of first and second phase; the third means comprises a second transparent mirror (23), the transmitted portion of the reference beam passing through said second transparent mirror (23) and falling on said first radiation detector (20a); the phase adjustment means comprises a mirror (25) which acts as a phase shifter and is movably mounted; the fourth means comprises a third semi-transparent mirror (27), the reflected portion of the reference beam being directed through said third semi-transparent mirror (27) on said second radiation detector (20b) by said phase adjustment mirror (25); said second means comprises a second mirror (29b) producing the first version of said modified sample beam and a third semi-transparent mirror (29a) producing said second version of said modified sample beam; said fourth means (27) comprises a fourth semi-transparent mirror (27); the modified sample beam being directed through said third semi-transparent mirror (29a), to be partially reflected thereby to said fourth semi-transparent mirror (27) and to be combined thereby with said second reference beam version, and to the extent that said modified sample beam, influenced by the sample, passes through said third semi-transparent mirror (29a), being reflected by said second mirror (29b) to be directed to said second semi-transparent mirror and to be combined with said first version of said referEnce beam; the length of the optical paths being of such dimensions that both portions of the sample beams reflected by said third semi-transparent mirror (29a) and by said second mirror (29b) interact with said first and said second versions of the reference beam in said third and fourth means, respectively, in phase differences which differ by 90* relative to each other.

Claim 9

Apparatus according to claim 1, wherein the sample of said substance positioned in said sample position means includes biological material having a Co2 content, wherein said laser is a Co2 laser.

Claim 10

Apparatus according to claim 8, wherein the laser and the radiation detection means are so positioned with respect to the biological material, that the radiation directed onto the biological material by the laser is reflected towards the radiation detection means.

Claim 11

Apparatus according to claim 1, wherein the laser is tunable to produce electromagnetic radiation of variable wavelength within a predetermined range; and the optical paths covered by said reference beam and by said sample beam from the beam splitter to said third and fourth means have exactly the same number of wavelengths of radiation from the laser.

Claim 12

Apparatus for determining the amount of a given component of a substance comprising: a laser radiation source producing a beam of electromagnetic radiation; a beam splitter positioned in the path of said beam to derive therefrom a sample beam of said radiation and a reference beam of said radiation; sample positioning means to position a sample of said substance in the path of said sample to produce a secondary sample beam modified by said substance; beam combining means to combine said reference beam and said modified sample beam and to produce therefrom a combined beam by superposition, and radiation detecting means receiving said combined beam and producing a first output signal indicating absorption caused by said substance; the laser radiation source being tunable to produce electromagnetic radiation the wavelength of which is variable within a predetermined range of wavelengths and being provided with means for causing said wavelength to be swept repetitively through a range of wavelength values; means for precisely equalizing the optical paths respectively covered by said sample and reference beams from the beam splitter to the beam combining means, said equalizing means including adjusting means for equalizing said paths in a standard condition, such as absence of a substance to be measured, and means automatically responsive to said radiation detecting means for maintaining such equalization in the presence of a substance to be measured even under wavelength variation of said radiation, said automatic equalization maintaining means being equipped to supply a second output signal indicating the phase shift caused by said substance; means for deriving, from said first output signal, a third output signal representative of the ratio of said first output signal to the intensity of said reference beam, and means synchronized with said wavelength sweep means for displaying the dependence of said second and third output signals on the wavelength.

Claim 13

Apparatus for determining the amount of a given component of a substance comprising: a laser radiation source producing a beam of electromagnetic radiation; a beam splitter positioned in the path of said beam to derive therefrom a sample beam of said radiation and a reference beam of said radiation; sample positioning means to position a sample of said substance in the path of said sample to produce a secondary sample beam modified by said substance; beam combining means to combine said reference beam and said modified sample beam and to produce therefrom a combined beam by superposition, and radiation detecting means receiving said combined beam and producing a first output signal indicating absorption caused by said substance; the laser radiation source being tunable to produce electromagnetic radiation the wavelength of which is variable within a predetermined range of wavelengths and being provided with means for causing said wavelength to be swept repetitively through a range of wavelength values; means for precisely equalizing the optical paths respectively covered by said sample and reference beams from the beam splitter to the beam combining means, said equalizing means including adjusting means for equalizing said paths in a standard condition, such as absence of a substance to be measured, and means automatically responsive to said radiation detecting means for maintaining such equalization in the presence of a substance to be measured even under wavelength variation of said radiation, said automatic equalization maintaining means being equipped to supply a second output signal indicating the phase shift caused by said substance; means for deriving, from said first output signal, a third output signal representative of the ratio of said first output signal to the intensity of said reference beam, and means synchronized with said wavelength sweep means for displaying the dependence of said second and third output signals on the wavelength.

Claim 14

The apparatus according to claim 11, characterized by a device being situated in the path of one of the reference and sample beams, by means of which the optical path length of the channel traversed by the pertaining beam may be changed, and by said detector being connected to a control arrangement which is joined to an adjusting device coupled with the device for changing the optical path and so acts upon this device that at the position of the device sensing the united beams an intensity maximum due to constructive interference is maintained.

Claim 15

The apparatus according to claim 12, characterized by a device for displaying a signal which is proportional to the adjusting signal.

Claim 16

Instrument according to one of the claims 11, characterized by A device for displaying the amplitude of the output signal of said detector sensing the united beams.

Claim 17

Instrument according to claim 14, characterized by a circuit arrangement being coupled to the output side of said detector sensing the united beams and to the output side of a device sensing a further reference beam, said circuit arrangement passing an output signal corresponding to the ratio of the two signals to an amplitude display- or recording device.