Classifications

• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B21/00—Microscopes
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
  • G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
  • G01J3/28—Investigating the spectrum
  • G01J3/44—Raman spectrometry; Scattering spectrometry ; Fluorescence spectrometry
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
  • G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
  • G01J3/02—Details
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
  • G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
  • G01J3/02—Details
  • G01J3/0205—Optical elements not provided otherwise, e.g. optical manifolds, diffusers, windows
  • G01J3/0208—Optical elements not provided otherwise, e.g. optical manifolds, diffusers, windows using focussing or collimating elements, e.g. lenses or mirrors; performing aberration correction
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
  • G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
  • G01J3/02—Details
  • G01J3/0205—Optical elements not provided otherwise, e.g. optical manifolds, diffusers, windows
  • G01J3/0237—Adjustable, e.g. focussing
• • 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
  • G01N21/62—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light
  • G01N21/63—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light optically excited
  • G01N21/65—Raman scattering
• • 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
  • G01N21/62—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light
  • G01N21/63—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light optically excited
  • G01N21/65—Raman scattering
  • G01N2021/653—Coherent methods [CARS]
  • G01N2021/656—Raman microprobe
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B21/00—Microscopes
  • G02B21/02—Objectives

Definitions

• the present invention relates to a Raman microscope with excellent ratio of signal to noise, and more specifically to a user-friendly Raman microscope capable of obtaining a spectrum with excellent ratio of signal to noise (S /N), which includes an image selection device 6 selectively passing only a desired portion among the real images RI of a sample obtained from an objective lens 5 so as not to fit a size of a beam to the sample and further includes a variable double focus forming device forming a focus f2 of monochromatic light at a different position from a focus fl of the objective lens 5 so as not to control the intensity of the beam.
• S /N signal to noise
• a Raman spectroscopy is a device for qualitatively and quantitatively analyzing substances using a Raman scattering.
• Reviewing a measuring principle of the Raman spectroscopy when monochromatic light, such as laser light with a frequency VO, is irradiated to a molecular binding site vibrating at a frequency Vl, most light is scattered as it is without changing its frequency, but some light gives (VO-Vl) the frequency Vl corresponding to a binding energy of a molecule bound to the molecular binding site or receives (V0+V1) energy from the molecular binding so that it is scattered, thereby lengthening or shortening its wavelength.
• the change in the wavelength is referred to as a Raman scattering.
• a degree of the change in the wavelength corresponds to an infrared region and all substances have their inherent variations. Therefore, the qualitative and quantitative analysis can be performed on substances using the change in the wavelength in a similar way to a person's fingerprint.
• Raman spectroscopy qualitatively and quantitatively measures variations.
• the beam should be irradiated to only the sample or the Raman scattering light generated only from the sample should be measured. Also, in order to measure the small sample, the beam diameter of the monochromatic light should be reduced by use of an optical microscope.
• a size relation between an image and an objective lens of a microscope being a convex lens is as follows.
• an image with a size S 1 is formed at a position spaced by a apart from the front of the convex lens with a focal length f
• an image with a size S2 formed at the rear of the convex lens is formed at a place spaced apart by b obtained from the following equation (I) and the size S2 of the image depends on the following equation (II).
• l/a+l/b l/f (I)
• Sl/S2 b/a (II) Therefore, the beam diameter can be reduced by use of a high magnification objective lens.
• FIG. 2 is a schematic view showing a basic structure of the conventional Raman microscope.
• the monochromatic light, such as the laser light, etc. from the monochromatic light irradiating device 1 passes through a convex lens L6 and is then collected at a focus f5. Thereafter, it passes through a convex lens L7 via a primary pinhole 2 so that it becomes parallel light, which then passes through a beam splitter 4 and the objective lens 5 in order and is irradiated to the sample S at the Fl position being the focus of the objective lens 5.
• the Raman scattering is generated.
• the Raman scattered light passes through the objective lens 5 again so that it becomes the parallel light, which then passes through a convex lens L8 and is condensed into a focus f6. Thereafter, it enters a Raman spectroscopy 8 via a secondary pinhole 10 at the focus f6 position.
• the Raman scattered light is measured qualitatively and quantitatively.
• the conventional Raman spectroscopy shown in FIG. 2 has several problems associated with the size of the sample and the intensity (strength) of the monochromatic light.
• FIG. 3(a) is a diagram schematically showing a state where the monochromatic light with a wider beam diameter A than the area of the sample is irradiated to the sample S in a conventional Raman microscope.
• the beam diameter of the monochromatic light irradiated to the sample is larger than the sample, a very high magnification objective lens is needed to measure the small sample.
• the beam diameter of the laser light should primarily be reduced by the primary pinhole 2.
• the secondary pinhole 10 suitable for a size of the sample should be installed at the front end of the spectroscopy. In other words, it has a difficulty in that the primary pinhole 2 and the secondary pinhole 10 should have the same size and should be placed on the exactly same line in an optical path. Otherwise, since the focus of the objective lens 5 and the focus of the monochromatic light passing through the objective lens are the same, a severe degradation of the Raman signal for the sample occurs.
• FIG. 3(b) is a diagram schematically showing a state where the monochromatic light with a narrower beam diameter than the area of the sample is irradiated to the sample S in the conventional Raman microscope.
• FIG. 3(c) is a diagram schematically showing a state where the monochromatic light is irradiated to the sample S with severe surface roughness and is then scattered to the circumference, in the conventional Raman microscope.
• a size measurable with the conventional Raman microscope is limited to 10//m due to the aforementioned factors, so it is impossible to measure a sample with the size smaller than lO ⁇ m, except for a special case. In other words, the measuring limit is about 1 micron in theory but the measurement of a sample with a size of about 5 microns is actually not facilitated.
• the laser light used as the beam in the typical Raman is short-wavelength high energy light with a high integration degree
• the sample may be melted or pyrolyzed by the laser light concentrated through the high magnification objective lens.
• the conventional method lowers the current value of laser to lower the output of the laser.
• the intensity of the Raman scattering light being a signal is also lowered, thereby suddenly deteriorating the ratio of signal to noise (S/ N). Also, it is out of a range maintaining the output stability of laser so that the reproducibility of spectrum is deteriorated, thereby making the performance of the quantitative analysis difficult.
• the current value of about 60 to 90% relative to the maximum output should be applied.
• the condensed monochromatic light is too strong, thereby causing a decomposing phenomenon and a melting phenomenon of the sample.
• the maximum output is lowered so that the stability of the monochromatic light is degraded, thereby degrading the S/ N spectrum.
• the existing Raman microscope has undergone much trial and error to find the maximum output condition capable of maintaining the stability of the monochromatic light and preventing the decomposition of the sample.
• the size of the sample to be qualitatively analyzed is reaching 1 micron in the fields of electronics and semiconductors, which are rapidly developing to a nano size.
• a new concept fine sample measuring device is needed.
• the present invention provides a user friendly Raman microscope with excellent ratio of signal to noise (S/ N) while lowering the measurable size limit of a sample to l ⁇ m to 10 ⁇ m.
• the present invention includes an image selection device 6 selectively passing only a desired portion among the real images RI of a sample obtained from an objective lens 5 so as not to fit a size of a beam to the sample and further includes a variable double focus forming device forming a focus f2 of monochromatic light at a different position from a focus f 1 of the objective lens 5 by controlling a distance D3 between the focus f2 of the monochromatic light passing through the objective lens 5 and the objective lens 5 so as not to control the intensity of the beam, making it possible to obtain excellent ratio of signal to noise (S/ N) and a good S/ N spectrum for an ultrafine sample with a size of I ⁇ m.
• S/ N signal to noise
• the present invention can analyze an ultrafine sample in a range of single microns, which can only roughly be analyzed by the existing Raman microscope, so that it considerably meets a demand for the analysis of ultrafine samples required in the fields of electronics, semiconductors and material industry being developed to a nano size, etc.
• FIG. 1 is a schematic view of a basic structure of a Raman microscope according to the present invention.
• FIG. 2 is a schematic view of a basic structure of a conventional Raman microscope according to the present invention.
• FIG. 3 (a) is a diagram schematically showing a state where monochromatic light with a wider beam diameter A than an area of a sample is irradiated to a sample S in a conventional Raman microscope.
• FIG. 3(b) is a diagram schematically showing a state where monochromatic light with a narrower beam diameter A than an area of a sample is irradiated to a sample S in a conventional Raman microscope.
• FIG. 3(c) is a diagram schematically showing a state where monochromatic light is irradiated to a sample S with severe surface roughness and is then scattered to the circumference, in a conventional Raman microscope.
• FIG. 4 is a schematic view showing a state selectively passing only a desired portion among real images RI of a sample by an image selection device 6 according to the present invention.
• FIG. 5 is a diagram schematically showing a mutual connection state of a Raman microscope X and a Raman spectroscopy Y.
• FIG. 6 is a photograph of a Raman microscope according to the present invention.
• FIG. 7 is a photograph of a sample being a green pigment with a diameter of l ⁇ m used in a first embodiment of the present invention.
• FIG. 8 is a spectrum with excellent ratio of signal to noise (S/ N) of a sample measured in the first embodiment of the present invention.
• FIG. 9 is a photograph of a sample being polyester with a diameter of 2 ⁇ m used in a second embodiment of the present invention.
• FIG. 10 is a spectrum with excellent ratio of signal to noise (S/N) of a sample prior to the measurement of the sample in the first embodiment of the present invention.
• RI Real image of sample A : Beam diameter of monochromatic light
• S/ N which obtains real images RI by an objective lens 5 using monochromatic light as a beam and then transfers them to a selected one of a Raman spectroscopy 8 and a device 9 for visibly confirming a sample state, comprises an image selection device 6 selectively passing only desired portions among the real images RI of the sample obtained by the objective lens 5.
• the Raman microscope uses the monochromatic light as a beam as described above to obtain the real images RI of a sample and transfer them to the Raman spectroscopy 8 for measuring the S/ N spectrum or transfer them to the device 9 for visibly confirming the sample state.
• the present invention also uses the monochromatic light as a beam to obtain the real images RI of the sample by the objective lens 5 and transfer them to a selected one of a Raman spectroscopy 8 and a device 9 for visibly confirming the sample state.
• the Raman microscope comprises an image selection device 6 selectively passing only desired portions among the real images RI of the sample obtained by the objective lens 5.
• the image selection device 6 is an iris capable of changing the size continuously or stepwise, wherein the shape of the iris is a circle or a polygon, etc.
• the monochromatic light usually is laser light and its wavelength range is from an ultraviolet region to a near-infrared region.
• the device 9 for visibly confirming the sample state is a monitor or a camera, etc.
• the Raman microscope further comprises a variable double focus forming device that controls a distance D3 between a focus f2 of monochromatic light passing through the objective lens 5 and the objective lens 5 together with the image selection device 6 to form the focus f2 of the monochromatic light at a different position from the focus fl of the objective lens 5.
• the variable double focus forming device is a device, or the like that controls a distance Dl between a distal portion of a monochromatic light irradiating device 1 and a convex lens Ll first passing the monochromatic light irradiated from the monochromatic light irradiating device 1.
• a distance Dl between a distal portion of a monochromatic light irradiating device 1 and a convex lens Ll first passing the monochromatic light irradiated from the monochromatic light irradiating device 1.
• the laser light from the laser light irradiating device 1 is condensed passing through a first convex lens Ll or becomes parallel light. Meanwhile, visible rays from the visible rays irradiating device l?are condensed passing through the first convex lens L2 or become parallel light.
• a kind of irradiating light one of laser light and the visible rays, may be selected by a moving mirror 3, if necessary.
• the visible rays are selected and when intending to obtain the spectrum by Raman spectroscopy, the laser light is selected.
• the moving mirror 3 When intending to visibly confirm the sample state, the visible rays are selected and when intending to obtain the spectrum by Raman spectroscopy, the laser light is selected. At this time, the moving mirror
• the monochromatic light transmitted through the beam splitter 4 passes through the objective lens 5 to be formed at the position of the focus f2.
• the f2 is the focus of the monochromatic light passing through the objective lens.
• the position of the focus f2 is determined by a distance between the objective lens 5 and the focus Fl, wherein the focus Fl is determined according to the distance Dl between the monochromatic light irradiating device 1 and the convex lens Ll first passing the monochromatic light so that the position of the focus f2 can be controlled by the control of the distance Dl between the monochromatic light irradiating device 1 and the convex lens Ll first passing the monochromatic light.
• variable double focus forming device a device forming the position of the focus f2 at a different position from the focus fl of the objective lens 5 by the aforementioned control.
• the focus f2 and the focus fl are formed at different positions.
• the distance D3 between the objective lens 5 and the focus f2 is changed from a halfway point of the focus f 1 length of the objective lens 5 to infinity.
• the Raman scattering light from the monochromatic light irradiated on the sample S at the position of the focus f 1 is condensed by the objective lens 5 to form the expanded real images Rl of the sample on the position of the focus f3. Only the desired portion to be measured in the real images Rl remains and the remaining portions are covered by the image selection device 6 to input the signal (monochromatic light) from the desired portions into the Raman spectroscopy 8, thereby preparing the S/ N spectrum.
• FIG. 4 is a schematic view showing a state selectively passing only desired portions among the real images RI of the sample by the image selection device 6 according to the present invention.
• a path of the signal should be changed by the control of the moving mirror 7.
• FIG. 5 is a diagram schematically showing a mutual connection state of a Raman microscope X according to the present invention and a Raman spectroscopy Y, wherein the monochromatic light a from the Raman spectroscopy Y enters the Raman microscope X and the Raman scattering light b from the Raman microscope X enters the Raman microscope Y.
• FIG. 6 is a photograph of the Raman microscope according to the present invention.
• the Raman microscope according to the present invention includes the image selection device 6 and the variable double focus forming device together as shown in FIG. 1 to obtain a good S/ N spectrum.
• Forming of the double focus so as not to overlap the focus f 1 of the objective lens 5 and the focus f2 of the monochromatic light passing the objective lens 5 by the variable double focus forming device is very important in view of the following two aspects. As shown in FIG. 1, if the focus f2 is longer than the focus fl, the beam diameter A of the irradiated monochromatic light is larger than the sample size.
• the current value of about 60 to 90% with respect to the maximum output should be applied in order to maintain the stable output of the monochromatic light.
• the condensed monochromatic light is too strong so that the decomposition and melting phenomenon of the sample occurs.
• the Raman microscope according to the present invention changes the distance D3 of the f2 focus instead of lowering the maximum output of the monochromatic light to widen the beam diameter A of the monochromatic light and lower the density of the monochromatic light so that the decomposition or melting phenomenon of the sample is prevented, making it possible to maintain the output of the monochromatic light in a stable state.
• the existing Raman microscope has a problem of the degradation of the ratio of signal to noise (S /N), since the
• Raman scattering light from the sample as well as the Raman scattering light from the circumference of the sample enter the Raman spectroscopy.
• the beam diameter A of the monochromatic light passing through the objective lens 5 is larger than the sample size so that the Raman scattering light from the circumference is larger than the Raman scattering light reflected from the sample, thereby making a difficult problem to obtain the S/ N spectrum of only the sample severer.
• the image selection device 6 only the desired portions among the real images RI of the sample generated by the monochromatic light remain and the remaining portions are covered by the image selection device 6 to remove the Raman scattering light reflected from the circumference of the sample, making it possible to obtain the Raman scattering light of only the sample.
• the Raman microscope shown in FIG. 1 obtains the Raman scattering light of only the desired sample by the image selection device 6 and an optimal Raman scattering signal by the variable double focus forming device as described above, making it possible to obtain the spectrum of an ultrafine sample.
• the Raman microscope as shown in FIG. 1 obtains the Raman scattering light of the green pigment (sample) of a diameter of l ⁇ m as shown in FIG. 7 and then transfers it to the conventional Raman spectroscopy to measure the spectrum with excellent ratio of signal to noise S/ N, thereby obtaining the spectrum as shown in FIG. 8.
• the Raman microscope as shown in FIG. 1 obtains the Raman scattering light of polyester (sample) of a diameter of 2 ⁇ m as shown in FIG. 9 and then transfers it to the conventional Raman spectroscopy to measure the spectrum with excellent ratio of signal to noise S/ N as shown in FIG. 7, thereby obtaining the spectrum as shown in FIG. 10.
• the present invention can obtain a spectrum excellent ratio of signal to noise without controlling the intensity of the beam to provide a user-friendly device for qualitatively and quantitatively analyzing substances using Raman scattering.

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Citations (5)

• 2007
  • 2007-07-25 KR KR1020070074419A patent/KR100882490B1/ko active IP Right Grant
• 2008
  • 2008-05-06 WO PCT/KR2008/002525 patent/WO2009014306A1/en active Application Filing

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