Classifications

• • 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
  • G01J3/2803—Investigating the spectrum using photoelectric array detector
• • 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
  • G01J3/30—Measuring the intensity of spectral lines directly on the spectrum itself
  • G01J3/36—Investigating two or more bands of a spectrum by separate detectors
• • 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
  • G01J3/46—Measurement of colour; Colour measuring devices, e.g. colorimeters
  • G01J3/50—Measurement of colour; Colour measuring devices, e.g. colorimeters using electric radiation detectors
  • G01J3/51—Measurement of colour; Colour measuring devices, e.g. colorimeters using electric radiation detectors using colour filters
• • 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
  • G01J3/0262—Constructional arrangements for removing stray light

Definitions

• the present invention relates to a measuring system and a method for determining spectrometric measurement results with high accuracy.
• detectors which are sensitive in the entire spectral range detected by the spectrometer are usually used to detect the light at the output of multichannel spectrometers.
• the multichannel detectors consist of several line or matrix-shaped detector elements, which can also be referred to as pixels.
• Each of the pixels is assigned a specific subarea of the entire spectral range whose light output is to be measured. Since the separation of the light into its spectral components never takes place completely, such a broadband detector always captures a certain amount of light from another spectral range, not assigned to the pixel, in the form of so-called false light. This leads to inaccurate measurement results.
• US Pat. No. 6,181,418 B1 describes a concentric spectrometer which has a special surface called “light trap” for reducing scattered light, this "light trap” being integrated into the design of the imaging optic and designed as a bevelled surface.
• the "light trap” is a specially designed surface to eliminate or attenuate the stray light generated by the entrance slit. light including light of different diffraction orders is not imaged on the detector.
• the "light trap” is a beveled surface, with non-reflecting, absorbing or dissipating properties.
• the bevelled surface of the imaging optics is roughened and additionally coated with an optically absorbing material Surface is formed according to the inner surface of the housing of the concentric spectrometer, wherein for the selection of the material whose mechanical properties, such as elasticity, strength and heat resistance are crucial.
• US Pat. No. 6,700,664 B1 describes a device with which light beams are selectively split by linearly variable filters (LVF) and directed to a photodetector row in order to be able to determine the spectral properties of the transmitted light.
• Linear variable filters (LVF) are formed by optical thin film layers on a substrate, whereby the thickness of the individual layers can vary.
• the LVF can be designed either as a gradient bandpass filter or as a "high / low-cut” filter, and the width of the selectively split light beams can be matched to the detector to approximately match the pixel width that the LVF can not be applied to the surface of the detector array, since this is difficult to realize because of the sensitive surface and the wiring of the detector array.
• the different LVF elements are therefore placed on a carrier disk, which is located at a distance of a few millimeters from
• micro-lenses are used which focus the optical light beams on the pixels of the detector row.
• the device becomes more complex and expensive in its construction - on the other hand, the micro-lenses can in turn add extra Cause light scattering.
• MMS Metal Multilithic Miniature Spectrometer
• the present invention has for its object to develop a spectrometric measuring system and a method with which the measurement results can be compensated in terms of stray light, without requiring an increased equipment expense is required.
• the object is achieved according to the invention in that a detector with pixels arranged in a linear or matrix form and a regular distribution of different wavelength-selective filters (color filters) on the pixels is used to detect the light at the spetrometer output.
• the detector may be a known from photo and video applications color camera, which are very inexpensive because of the very high numbers in which they are made, u. This may be cheaper than corresponding black and white cameras, which are only manufactured for special applications.
• the application of the invention is not limited to the visible spectral range. If necessary, in the final step of color camera production, the color filters on the pixels may be partially omitted or modified to optimize them for the required spectral range. However, it is also possible to use other types of detectors in which the wavelength-selective filters and the associated detectors are arranged in several levels one behind the other, as in the so-called X3 image converter of the American company Foveon, Inc. In contrast to conventional image converters each color pixel is the full color information available here.
• FIG. 1 shows a color camera sensor with a regular distribution of four different wavelength-selective filters
• FIG. 2 a spectrometric arrangement with three entrance slits aligned parallel to the grid lines
• Figure 3 a spectrometric arrangement with three parallel to the grid lines, but offset to each other aligned entrance columns and
• FIG. 4 shows a representation of the relative sensitivity of the color filters k as a function of the (useful) wavelength ⁇ j assigned to the pixel i.
• the spectrometric measuring system according to the invention with compensation for stray light consists of at least one radiation source, at least one entrance slit, a dispersion element and a detector, with linear or matrix-shaped detector elements arranged in one or more planes.
• the detector has a regular distribution, at least two different, wavelength-selective filters on its detector elements.
• Figure 1 shows a color camera sensor with a regular distribution of four different wavelength-selective filters, which are arranged in a square scheme. For example, the detector uses the colors cyan (Cy), yellow (Ye), green (Gn), and magenta (Mg).
• the detector is followed by a control unit (not shown) for determining, evaluating or storing the signal values of the differently colored detector elements.
• a diffraction grating or a dispersion prism is provided in a known manner, wherein the entry column or are aligned parallel to the grating lines or the roof edge of the dispersion prism, so that the partial spectra imaged on the detector have the same wavelength assignment (see Figure 2).
• the entrance column (s) are offset relative to a parallel to the grating lines or to the roof edge of the dispersion prism so that the partial spectra of each entrance slit imaged on the detector can detect different partial areas of an entire spectral range (see FIG. 3).
• the control unit downstream of the detector is able to determine spectral intensity values Ii of the detector elements present with the same color filters transversely to the dispersion direction as weighted sums, optionally with or without compensation of the crosstalk.
• the light from at least one radiation source is imaged via at least one entrance slit and a dispersion element onto a detector with detector elements arranged linearly or matrix-like in one or more planes, using a detector which has a regular distribution of different wavelength-selective filters on the detector elements.
• a dispersing element a diffraction grating or a dispersion prism is preferably used.
• the detector has a regularly distributed arrangement of at least two wavelength-selective filters and corresponds, for example, to the color camera sensor known from photo and video applications.
• FIGS. 2 and 3 each show a variant of a spectrometer arrangement with an imaging grating.
• a control unit downstream of the detector assumes the determination, evaluation or storage of the signal values of the differently colored detector elements.
• the entrance column (s) is aligned parallel to the grid lines or to the roof edge of the dispersion prism.
• each of the partial spectra 4, 4 'and 4 has the same wavelength scale:
• the partial spectra are assigned to the individual radiation sources. With the same radiation source, the partial spectra can be added up for noise reduction.
• the entrance gaps are offset relative to a parallel to the grid lines or to the roof edge of the dispersion prism.
• FIG. 3 shows a spectrometric arrangement with three entrance slits aligned parallel to the grid lines, with the result that the light 2 coming from the three entrance slits 1, 1 'and 1 "passes over the dispersive slit.
• the control unit (not shown) separates the partial spectra 4, 4' and 4" depicted on the detector 5 and summarized to a spectrum covering the entire wavelength range.
• a prism perpendicular to the diffraction grating in its dispersion direction may be used. Since the diffraction grating is dimensioned so that several diffraction orders of the spectral range to be imaged hit the detector, the additional prism, according to the solution described in DE 1 909 841 C2, serves to separate the diffraction orders.
• the control unit determines the net signal values S 1 of each detector element as the difference between the light and dark signals, and the sum of the spectral intensity values I i; determined for detector elements with the same color filter transversely to the dispersion direction.
• the determination of the net signal values Sy occurs under otherwise identical conditions for each pixel of the detector, where i characterizes the column number and j the line number.
• the control unit uses the spectral intensity values Ij of the detector elements present with the same color filter transversely to the direction of dispersion as a weighted sum n
• Sj 1Ic corresponds to the net signal value of the color filter k in column i, k of the number of the color filter and n to the number of color filters.
• control unit determines the spectral intensity values Ij of the detector elements present with the same color filter transversely to the direction of dispersion as a weighted sum without compensation of crosstalk, by the following weighting factors
• FIG. 4 shows a representation of the relative sensitivity of the color filters k as a function of the (useful) wavelength ⁇ j assigned to the pixel i.
• the signal with the lowest sensitivity at the useful wavelength ⁇ , - is suitable for compensation of crosstalk.
• the corresponding weight factor must then become negative.
• the height of the negative compensation value must be optimized for different spectrometry specimens and the application using different scattered light sensitive specimens.
• the spectrometer be optimized for maximum signal-to-noise ratio or minimal mutual crosstalk.
• each entrance slit creates a spectral trace on the detector.
• the calculation of the spectral intensity values is carried out as described, separated for each track.
• the summation in the column direction is then limited to the area of each track.
• the summation limits can be adjusted if the grid lines are not perfectly aligned with the detector or if wavelength-dependent stigmatism depends on the column number i. This makes the result less sensitive to manufacturing tolerances and aberrations.

Landscapes

• Physics & Mathematics (AREA)
• Spectroscopy & Molecular Physics (AREA)
• General Physics & Mathematics (AREA)
• Spectrometry And Color Measurement (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=38024326

Family Applications (1)

Country Status (5)

Families Citing this family (5)

Family Cites Families (13)

• 2006
  • 2006-04-01 DE DE102006015269A patent/DE102006015269A1/de not_active Withdrawn
• 2007
  • 2007-03-12 WO PCT/EP2007/002128 patent/WO2007115628A1/de active Application Filing
  • 2007-03-12 JP JP2009501890A patent/JP2009532666A/ja active Pending
  • 2007-03-12 US US12/225,904 patent/US8111396B2/en not_active Expired - Fee Related
  • 2007-03-12 EP EP07723178A patent/EP2002225A1/de not_active Withdrawn
• 2012
  • 2012-01-03 US US13/342,317 patent/US20120105847A1/en not_active Abandoned

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events