WO2010116237A1 - Appareil pour déterminer la densité optique d'un échantillon liquide - Google Patents

Appareil pour déterminer la densité optique d'un échantillon liquide Download PDF

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Publication number
WO2010116237A1
WO2010116237A1 PCT/IB2010/000766 IB2010000766W WO2010116237A1 WO 2010116237 A1 WO2010116237 A1 WO 2010116237A1 IB 2010000766 W IB2010000766 W IB 2010000766W WO 2010116237 A1 WO2010116237 A1 WO 2010116237A1
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WO
WIPO (PCT)
Prior art keywords
lens
light source
cuvette
predetermined distance
liquid sample
Prior art date
Application number
PCT/IB2010/000766
Other languages
English (en)
Inventor
Amit Bhatnagar
Original Assignee
Amit Bhatnagar
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Amit Bhatnagar filed Critical Amit Bhatnagar
Publication of WO2010116237A1 publication Critical patent/WO2010116237A1/fr

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/59—Transmissivity
    • G01N21/5907—Densitometers

Definitions

  • the present invention relates to an apparatus for determining the optical density of a liquid sample.
  • Colorimeters are devices for accurately measuring the concentration of a liquid sample. As is conventionally known, the concentration of a liquid sample is proportional to the absorbance (optical density) of that sample. It is also known that, colorimeters determine the concentration of a liquid sample based on the measured value of the absorbance (optical density). The accurate measurement of absorbance (optical density) of a liquid sample by a colorimeter is often limited by errors caused due to refraction of light.
  • a divergent light beam from a light source such as a light emitting diode (I JvD) is passed through a cuvette holding a liquid sample, depending on the concentration of the sample, some amount of light is absorbed and the rest is transmitted.
  • the transmitted light is incident onto a sensor or detector such as a photo detector for determining the intensity of transmitted light beam.
  • the absorbance (optical density) of the sample can also be determined.
  • the accurate measurement of transmittance and thus absorbance (optical density) is affected by the refraction of light beam which takes place as the light beam enters the liquid sample. An error is introduced due to refraction of light beam.
  • the conventional or prior existing colorimeters suffer from the above mentioned disadvantage.
  • the divergent light beam gels refracted as it enters the cuvette.
  • the light beam emerging out of the cuvette i.e. the transmitted light beam is a dense light beam having a distance shift.
  • the dense light beam is incident on sensor or detector for determining the intensity of the transmitted beam.
  • the sensor or detector gives an error reading, which is a combination of transmittance of light and the refraction of light.
  • the distance shift varies with the variation in the concentration of the sample, because the refractive index of the medium varies with the variation in the concentration of the sample.
  • An object of the present invention is to accurately determine the optical density of a liquid sample.
  • the present invention provides an apparatus for determining the optical 0 density of a liquid sample comprising a light source for emitting a divergent beam, a photo detector for detecting a measuring beam, a cuvette positioned between said light source and said photo detector for holding a liquid sample optical density of which is to be measured and an optical assembly placed in an optical path between said light source and said cuvette for receiving the divergent beam and directing an illuminating 5 beam onto the said cuvette, said illuminating beam being at a zero degree angle of incidence with respect to the cuvette.
  • Figure 1 is an exemplary illustration of the apparatus for determining the optical density of a liquid sample according to the first embodiment of present invention.
  • Figure 2 shows the apparatus for determining the optical density of a liquid sample according to the second embodiment of present invention.
  • the present invention provides an apparatus for determining the optical density of a liquid sample, said apparatus comprising: a light source for emitting a divergent beam; a photo detector for detecting a measuring beam; a cuvette positioned between said light source and said photo detector for holding a liquid sample, optical density of which is to be measured; and an optical assembly placed in an optical path between said light source and said cuvette for receiving the divergent beam and directing an illuminating beam onto the said cuvette, said illuminating beam being at a zero degree angle of incidence with respect to the cuvette.
  • the present invention provides an apparatus for determining the optical density of a liquid sample wherein the optical assembly comprises: a pinhole located at a first predetermined distance from the light source for creating an artillcial point light source at a central position thereof; and a lens located at a second predetermined distance from the pinhole for generating the illuminating beam and directing the same onto the cuvette.
  • the present invention provides an apparatus for determining the optical density of a liquid sample wherein the lens is supported by a lens supporting means, said lens supporting means being arranged to eliminate the effect of spherical aberration created by the lens.
  • the present invention provides an apparatus lor determining the optical density of a liquid sample wherein the optical assembly further comprises: a pinhole located at a third predetermined distance from the lens for eliminating the effect of spherical aberration created by the lens.
  • the present invention provides an apparatus for determining the optical density of a liquid sample wherein the second predetermined distance equals the focal length of the lens.
  • the present invention provides an apparatus for determining the optical density of a liquid sample wherein the lens is a convex lens.
  • the present invention provides an apparatus for determining the optical density of a liquid sample wherein the optical assembly comprises: a first lens located at a first predetermined distance from the light source for receiving the divergent beam and converging the same to form an artificial point light source; a pinhole located at a second predetermined distance from the first lens for controlling the size of the artificial point light source; and a second lens located at a third predetermined distance from a location at which the artificial point light source is formed for generating the illuminating beam and directing the same onto the cuvette.
  • the present invention provides an apparatus for determining the optical density of a liquid sample wherein the first and second lenses are supported by respective lens supporting means.
  • the present invention provides an apparatus for determining the optical density of a liquid sample wherein the lens supporting means for the second lens is arranged to eliminate the effect of spherical aberration created by the second lens.
  • the present invention provides an apparatus for determining the optical density of a liquid sample wherein the optical assembly further comprises: a pinhole located at a fourth predetermined distance from the second lens for eliminating the effect of spherical aberration created by the second lens.
  • the present invention provides an apparatus lor determining the optical density of a liquid sample wherein the third predetermined distance equals the focal length of the second lens.
  • the present invention provides an apparatus lor determining the optical density of a liquid sample wherein the first and second lenses are convex lenses.
  • the present invention provides an apparatus lor determining the optical density of a liquid sample wherein the first and second lenses have same or different focal lengths.
  • the present invention provides an apparatus for determining the optical density of a liquid sample wherein the light source is a monochromatic source of light.
  • the present invention provides an apparatus for determining the optical density of a liquid sample wherein the light source is a white light source.
  • the present invention provides an apparatus for determining the optical density of a liquid sample wherein an optical filter is located between the optical assembly and the cuvette for selecting a predetermined wavelength of the illuminating beam.
  • Figure 1 shows the apparatus for determining the optical density of a liquid sample according to the first embodiment of present invention.
  • the said apparatus (10) comprises of a light source (20), an optical assembly (40), a cuvette (70) for holding a liquid sample optical density of which is to be measured and a photo detector (80).
  • the light source (20) when energized by a constant voltage power source (30) emits a divergent light beam which is incident onto the optical assembly (40).
  • the optical assembly (40) is arranged in an optical path between the light source (20) and the cuvette (70) for receiving the divergent light beam and directing an illuminating beam onto the said cuvette (70).
  • the illuminating beam emerging out of the optical assembly (40) is at a zero degree angle of incidence with respect to the cuvette (70).
  • the illuminating beam enters the cuvette (70) with intensity Io and leaves the cuvette (70) with intensity I. In other words, some amount of light is absorbed by the liquid sample in the cuvette (70) and the rest is transmitted.
  • the measuring beam with intensity I after leaving the cuvette (70) is incident onto the photo detector (80).
  • the photo detector (80) is arranged to detect the intensity of the measuring beam or transmitted beam.
  • the transmittance of liquid sample in the cuvette (70) can be determined by determining by the intensity of measuring beam or transmitted beam.
  • the said optical assembly (40) comprises of a pinhole (50) and a lens (60).
  • the said pinhole (50) is located at a first predetermined distance from the light source (20) for receiving the divergent light beam and creating an artificial point light source at a central position thereof.
  • the lens (60) is located at a second predetermined distance from the pinhole (50) or at a second predetermined distance from the location at which the artificial point light source is formed for generating the illuminating beam.
  • the second predetermined distance equals the focal length of the lens (60).
  • the lens (60) is arranged to generate the illuminating beam and direct the same onto the cuvette (70).
  • the illuminating beam generated by the lens (60) is at a zero degree angle of incidence with respect to the cuvette (70). Since, the illuminating beam is at a zero degree angle of incidence with respect to the cuvette (70) it does not undergo refraction as it enters the cuvette (70). In other words, the illuminating beam does not under go a distance shift when it enters the cuvette (70). As no refraction of illuminating beam takes place, errors caused due to refraction of light are minimized i.e. the optical assembly (40) is arranged in a way that it minimi/cs the errors caused due to refraction of light. Since, no errors are introduced the transmittance of the liquid sample in the cuvette (70) can be determined accurately.
  • Transmittance or transmissvity (T) of the liquid sample in the cuvette (70) is given by:
  • I is the intensity of light that has passed through the liquid sample i.e. the intensity of measuring beam
  • Io is the intensity of light before it enters the liquid sample i.e. the intensity of illuminating beam.
  • optical density or absorbance (A) of the liquid sample in the cuvette (70) is given by:
  • A - log,o (T)
  • concentration of the liquid sample in the cuvette (70) is determined based on the calculated value of the optical density (A) using conventionally known techniques.
  • the lens (60) for generating the illuminating beam is a convex lens.
  • the lens (60) may be a Plano-convex lens or a Bi-convex lens. In this embodiment of the present invention the lens (60) is selected as a Bi-convex lens.
  • the light source (20) for emitting the divergent light beam may be a monochromatic source of light or a white light source.
  • the light source (20) may be a light emitting diode (LED) or any other source of light emitting a divergent light beam.
  • the lens (60) may be supported by a lens supporting means.
  • Figure 1 shows the lens (60) supported by a lens supporting means (90).
  • the primary objective of the lens supporting means (90) is to hold or support the lens (60).
  • the lens supporting means (90) may be any lens supporting means (90)
  • the size of the lens supporting means (90) may be so adjusted that it only allows the light rays incident near the center of lens (60) to pass through and block rest of the light rays. More particularly, the lens supporting means (90) is dimensioned to block the light rays emanating from area near the lens (60).
  • the optical assembly (40) may further comprise a pinhole for eliminating the effect of spherical aberration created by the lens (60).
  • This aspect of the first embodiment provides an alternative way of 0 eliminating the effect of spherical aberration without adjusting the size of the lens supporting means (90).
  • Figure 1 shows the optical assembly (40) equipped with a pinhole ( 100).
  • the said pinhole ( 100) is located at a third predetermined distance from the lens (60) and allows the light rays emerging out from the center of the lens (60) to pass through and blocks rest of the light rays. 5
  • the apparatus ( 10) may comprise an optical filter. If the light source (20) is selected as a white light source, an optical filter is required for converting white light to monochromatic light or to select a predetermined wavelength of light. As shown in figure I , an optical filter ( 1 10) is 0 located between the optical assembly (40) and the cuvette (70).
  • the optical filter ( 1 10) may be a monochromatic filter that allows only a narrow range of wavelengths (that is a single color to pass) and blocks rest of the wavelengths. Depending on the wavelength of light to be measured a suitable monochromatic filter may be used. The following paragraphs describe the second embodiment of present invention with reference to figure 2.
  • Figure 2 shows the apparatus for determining the optical density of a liquid sample according to the second embodiment of present invention.
  • the said apparatus (120) comprises of a light source ( 130), an optical assembly ( 150), a cuvette (190) for holding a liquid sample optical density of which is to be measured and a photo detector (200).
  • the light source ( 130) when energized by a constant voltage power source ( 140) emits a divergent light beam which is incident onto the optical assembly ( 150).
  • the optical assembly ( 1 50) is arranged in an optical path between the light source (130) and cuvette ( 190) for receiving the divergent light beam and directing an illuminating beam onto the cuvette ( 190).
  • the illuminating beam emerging out of the optical assembly ( 150) is at a zero degree angle of incidence with respect to the cuvette ( 190).
  • the illuminating beam enters the cuvette ( 190) with intensity Io and leaves the cuvette ( 190) with intensity I. In other words, some amount of light is absorbed by the liquid sample in the cuvette ( 190) and the rest is transmitted.
  • the measuring beam with intensity I after leaving the cuvette ( 190) is incident onto the photo detector (200).
  • the photo detector (200) is arranged to detect the intensity of the measuring beam or transmitted beam.
  • the transmittance of liquid sample in the cuvette ( 190) can be determined by determining by the intensity of measuring beam or transmitted beam.
  • the said optical assembly ( 150) comprises of a first lens ( 160), a pinhole ( 170) and a second lens (180).
  • the first lens ( 160) is located at a first predetermined distance from the light source ( 130) for receiving the divergent light beam.
  • the said first lens ( 160) converges or focuses the divergent light beam incident onto it to a point on its axis and at a certain distance behind it.
  • the first lens ( 160) is arranged to form an artificial point light source.
  • the convergence of the divergent light beam by the first lens ( 160) forms an arti ficial point source which is of the order of 1 or 2 mm.
  • a pinhole ( 1 70) is located at a second predetermined distance from the first lens ( 160) for controlling the size of the artificial point light source i.e. the pinhole ( 170) is positioned to create a dense artificial point light source which is of the order of 50- 100 microns.
  • the second predetermined distance is selected such that the location of pinhole ( 170) eliminates the effect of spherical aberration created by the first lens ( 160) and forms a proper artificial point light source.
  • a second lens (180) is located at a third predetermined distance from the location at which the artificial point source is formed for generating the illuminating beam.
  • the third predetermined distance equals the focal length of the second lens ( 180).
  • the second lens ( 180) is arranged to generate the illuminating beam and direct the same onto the cuvette ( 190).
  • the illuminating beam generated by the second lens ( 180) is at a zero degree angle of incidence with respect to the cuvette ( 190).
  • the illuminating beam is at a zero degree angle of incidence with respect to the cuvette ( 190) it does not undergo refraction as it enters the cuvette ( 190). In other words, the illuminating beam does not under go a distance shift when it enters the cuvette ( 190). As no refraction of illuminating beam takes place, errors caused due to refraction of light are minimized i.e. the optical assembly ( 150) is arranged in a way that it minimizes the errors caused due to refraction of light. Since, no errors arc introduced the transmittance of liquid sample in the cuvette ( 190) can be measured accurately.
  • Transmittance or transmissvity (T) of the liquid sample in the cuvette ( 190) is given by:
  • I is the intensity of light that has passed through the liquid sample i.e. the intensity of measuring beam and Io is the intensity of light before it enters the liquid sample i.e. the intensity of illuminating beam.
  • optical density or absorbance (A) of the liquid sample in the cuvette ( 190) is given by:
  • the concentration of the liquid sample in the cuvette ( 190) is determined based on lhc calculated vale of the optical density (A) using conventionally known techniques.
  • the said first and second lenses ( 160, 180) are convex lenses.
  • the first and second lenses ( 160, 180) may be Plano-convex lenses or Bi-convex lenses.
  • the first and second lenses ( 160, 180) may have same or different focal lengths. In this embodiment of the present invention the lenses ( 160, 180) are selected as Bi-convex lenses.
  • the light source (130) for emitting the divergent light beam may be a monochromatic source of light or a white light source.
  • the light source ( 130) may be a light emitting diode (LED) or may be any other source of light emitting a divergent light beam.
  • the first lens ( 160) and the second lens ( 180) may be supported by respective lens supporting means.
  • Figure 2 shows the first lens ( 160) supported by a lens supporting means (210) and the second lens (180) supported by a lens supporting means (220).
  • the primary objective of the lens supporting means (210,220) is to hold or support the lenses ( 160, 180).
  • the lens supporting means (220) for the second lens ( 180) may be arranged to eliminate the effect of spherical aberration created by the second lens ( 180).
  • the size of the lens supporting means (220) may be so adjusted that it only allows the light rays incident near the center of second lens ( 180) to pass through and block rest of the light rays. More particularly, the lens supporting means (220) is dimensioned to block the light rays emanating from area near the periphery of the second lens ( 1 80).
  • the optical assembly ( 150) may further comprise a pinhole for eliminating the effect of spherical aberration created by the second lens ( 180).
  • This aspect of the second embodiment provides an alternative way of eliminating the spherical aberration without adjusting the length of the lens supporting means (220).
  • Figure 2 shows the optical assembly ( 1 50) equipped with a pinhole (230). The said pinhole (230) is located at a fourth predetermined distance from
  • the apparatus ( 120) may comprise an optical filter. If the light source ( 130) is selected as a white light source, an
  • optical filter is required for converting white light to monochromatic light or to select a predetermined wavelength of light.
  • an optical filter (240) is located between the optical assembly (150) and the cuvette ( 190).
  • the optical filter (240) may be a monochromatic filter that allows only a narrow range of wavelengths (that is a single color to pass) and blocks rest of the wavelengths. Depending on the 0 wavelength of light to be measured a suitable monochromatic filter is used.
  • Table I shows the measurement results for the concentration of Potassium dichromalc. measured using the conventionally known spectrophotometer provided by Simatzu.
  • Table 2 shows the measurement results for the concentration of Potassium dichromalc, measured using the conventionally known colorimeter such as DTL 1005 provided by DTL Pro, Elico, Alpine.
  • Table 3 shows the measurement results for the concentration of Potassium dichromatc. measured using the apparatus provided by the present invention.

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  • Physics & Mathematics (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Biochemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Investigating Or Analysing Materials By Optical Means (AREA)
  • Optical Measuring Cells (AREA)

Abstract

La présente invention concerne un appareil pour déterminer avec précision la densité optique d'un échantillon liquide. L'appareil selon la présente invention comprend une source lumineuse (20) pour émettre un faisceau divergent, un photodétecteur (80) pour détecter un faisceau de mesure, une cuve (70) positionnée entre ladite source lumineuse (20) et ledit photodétecteur (80) pour retenir un échantillon liquide dont la densité optique doit être mesurée, et un ensemble optique (40) placé dans un chemin optique entre ladite source lumineuse (20) et ladite cuve (70) pour recevoir le faisceau divergent et diriger un faisceau d'éclairage sur ladite cuve (70), l'angle d'incidence entre ledit faisceau d'éclairage et la cuve (70) étant nul.
PCT/IB2010/000766 2009-04-08 2010-04-08 Appareil pour déterminer la densité optique d'un échantillon liquide WO2010116237A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
IN721/DEL/2009 2009-04-08
IN721DE2009 2009-04-08

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WO2010116237A1 true WO2010116237A1 (fr) 2010-10-14

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2015118043A (ja) * 2013-12-19 2015-06-25 ブラザー工業株式会社 検査装置

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS57168144A (en) * 1982-03-26 1982-10-16 Olympus Optical Co Ltd Colorimetric measuring method
JPH0650885A (ja) * 1992-07-29 1994-02-25 Tafuto:Kk 光電比色計
JPH0720038A (ja) * 1993-06-23 1995-01-24 Olympus Optical Co Ltd デンシトメータ
US5455177A (en) * 1992-02-05 1995-10-03 Boehringer Mannheim Gmbh Method for analysis of a medical sample
US5717494A (en) * 1995-11-15 1998-02-10 Nihon Medi-Physics Co., Ltd. Method of optically measuring liquid in porous material
JP2005291726A (ja) * 2004-03-31 2005-10-20 Fujifilm Techno Products Co Ltd 生化学分析装置

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS57168144A (en) * 1982-03-26 1982-10-16 Olympus Optical Co Ltd Colorimetric measuring method
US5455177A (en) * 1992-02-05 1995-10-03 Boehringer Mannheim Gmbh Method for analysis of a medical sample
JPH0650885A (ja) * 1992-07-29 1994-02-25 Tafuto:Kk 光電比色計
JPH0720038A (ja) * 1993-06-23 1995-01-24 Olympus Optical Co Ltd デンシトメータ
US5717494A (en) * 1995-11-15 1998-02-10 Nihon Medi-Physics Co., Ltd. Method of optically measuring liquid in porous material
JP2005291726A (ja) * 2004-03-31 2005-10-20 Fujifilm Techno Products Co Ltd 生化学分析装置

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2015118043A (ja) * 2013-12-19 2015-06-25 ブラザー工業株式会社 検査装置

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