JP2009031229A - Measurement signal noise processing method - Google Patents

Abstract

An object of the present invention is to solve measurement variations caused by the structure and material of an object to be measured, and to reduce measurement errors such as the thickness of the object to be measured.
In normal measurement, data is measured repeatedly, and its distribution is obtained to obtain a true value with an average. However, since the data value itself is small near zero, it is buried in the original measurement noise. Since the measurement data cannot be detected at the zero point, the distribution becomes zero, or the data distribution is actually empirically smooth, so it spreads asymmetrically around the true value. The value cannot be estimated, but in order to estimate the true value of the observed signal with unknown random noise superimposed and not symmetric, the maximum value of the observed signal is taken, and measurement in the minute (observed) signal region is performed. Improve accuracy.
[Selection] Figure 3

Description

  The present invention relates to a noise processing method for a measurement signal used in a measuring instrument (eg, an optical coherence tomography apparatus or the like).

  Conventionally, as one of non-destructive tomographic measurement techniques for various objects to be measured, there is an optical tomographic imaging apparatus “optical coherence tomography” (OCT) (see Patent Document 1). Since OCT uses light as a measurement probe, it has the advantage that it can measure the refractive index distribution, spectral information, polarization information (birefringence distribution), etc. of the measured object.

  The basic OCT 43 is based on a Michelson interferometer, and its principle will be described with reference to FIG. The light emitted from the light source 44 is collimated by the collimator lens 45 and then divided into reference light and object light by the beam splitter 46. The object light is condensed on the measurement object 48 by the objective lens 47 in the object arm, scattered and reflected there, and then returns to the objective lens 47 and the beam splitter 46 again.

  On the other hand, the reference light passes through the objective lens 49 in the reference arm, is reflected by the reference mirror 50, and returns to the beam splitter 46 through the objective lens 49 again. The object light and the reference light that have returned to the beam splitter 46 in this way are incident on the condensing lens 51 together with the object light and are collected on the photodetector 52 (photodiode or the like).

  The light source 44 of the OCT uses a light source of light having low temporal coherence (light emitted from the light source at different times is extremely difficult to interfere with each other). In a Michelson interferometer using temporally low coherence light as a light source, an interference signal appears only when the distance between the reference arm and the object arm is approximately equal. As a result, when the intensity of the interference signal is measured by the photodetector 52 while changing the optical path length difference (τ) between the reference arm and the object arm, an interference signal (interferogram) for the optical path length difference is obtained.

  The shape of the interferogram shows the reflectance distribution in the depth direction of the measurement object 48, and the structure in the depth direction of the measurement object 48 can be obtained by one-dimensional axial scanning. Thus, in the OCT 43, the structure in the depth direction of the measurement object 48 can be measured by optical path length scanning.

  In addition to the scanning in the axial direction, a two-dimensional cross-sectional image of the object to be measured can be obtained by performing a two-dimensional scanning by adding a horizontal mechanical scanning. The scanning device that performs the horizontal scanning includes a configuration in which the object to be measured is directly moved, a configuration in which the objective lens is shifted while the object is fixed, and a pupil of the objective lens while the object to be measured and the objective lens are fixed. The structure etc. which rotate the angle of the galvanometer mirror in the surface vicinity are used.

JP 2002-310897 A JP 11-325849 A JP 2004-028970 A

  Conventionally, an OCT apparatus measures the structure of a sample having birefringence, and also requires various technical fields that require high-precision resolution in the depth direction of the sample, such as industrial fields such as semiconductor product manufacturing, animal Research and observation field of animals and plants such as biological observation and plant structure observation, field of analysis and appraisal technology of various cultural assets, robot technology field (observing each part organ such as plants, insects, animals, etc. This is useful for applications to robot technology).

  However, the difference in structure, material, and thickness at each part of the object to be measured has a variation in measurement, and there is a problem that measurement errors such as thickness increase.

  The present invention reduces measurement variations and errors caused by noise of measurement signals, particularly minute measurement signals, which occur when measurement is performed by a measuring instrument such as an OCT apparatus as described above, and enables precise measurement. It is an object to realize a noise processing method for a measurement signal.

  In order to solve the above-described problems, the present invention provides a measurement signal obtained by a measuring instrument, and a maximum signal of a measurement signal is measured in a minute signal region having a distribution curve in which a noise signal superimposed on the measurement signal is near 0 and is not symmetric. A noise processing method for a measurement signal, characterized in that a value is used as a true value.

  In order to solve the above-described problems, the present invention provides a measurement signal from a measuring instrument in which the signal region of the measurement signal is limited, or when the true value is a value close to the end of the signal region, a noise signal superimposed thereon. For a signal region having a distribution curve in which a minute measurement signal is not symmetric, the maximum value of the measurement signal is used as a true value, and a noise processing method for a measurement signal having a limited signal region is provided.

  In order to solve the above-described problems, the present invention provides a measurement signal obtained by a measuring instrument that has a distribution curve in which the measurement signal is not symmetrical due to a noise signal superimposed on the true value. The present invention provides a noise processing method for a measurement signal, which is characterized by being utilized.

  According to the measurement signal noise processing method according to the present invention having the above-described configuration, measurement variations and errors caused by noise of measurement signals, particularly minute measurement signals, that occur during measurement by various measuring devices. And precise measurement is possible.

  For example, when applied to an image processing apparatus for optical coherence tomography, it is possible to obtain clear OCT images by reducing phase noise in measurement for structural analysis of various organs of animals and plants obtained by optical coherence tomography. is there.

  The best mode for carrying out the noise processing method for measurement signals according to the present invention will be described below with reference to the drawings based on the embodiments.

  In the first embodiment, the measurement signal noise processing method according to the present invention is applied to a polarization-sensitive optical coherence tomography apparatus.

  As described in the “Background Art” section, in the optical coherence tomography apparatus (OCT), the beam from the light source is sent separately to the reference arm and the sample arm, and in the sample arm, the depth direction (A The sample is irradiated in a direction perpendicular to (direction) (B-scan), and an AB image is obtained from the interference spectrum between the reflected light and the reference light reflected from the reference arm (performs OCT measurement). The present invention is applied to FD-OCT (Fourier domain OCT) and the like.

  Supplementally, scanning in the depth (optical axis) direction of the sample (this scanning is referred to as “A-scan”, and this direction is also referred to as “A-direction”, “A scan direction”) is performed once. This is possible by acquiring backscattering data in the depth direction by light irradiation. Scanning in the lateral direction (direction perpendicular to the A direction) by a galvano mirror (this scanning is called “B-scan”). By performing “B-direction” and “B-scan direction”), a two-dimensional tomographic image (polarization-sensitive OCT image) can be obtained.

  The polarization-sensitive optical coherence tomography apparatus to which the noise processing method of the measurement signal according to the present invention is applied is a EO-converted polarization beam (a beam linearly polarized by a polarizer) from a light source simultaneously (synchronously) with a B-scan. The light is continuously modulated by a modulator (polarization modulator, electro-optic modulator), the polarization beam is continuously modulated, and the sample is scanned as an incident beam to irradiate the sample, and the reflected light ( (Object light) and OCT measurement by spectral interference between the two using the other as reference light.

  Of the spectral interference components, the vertical polarization component (H) and the horizontal polarization component (V) are simultaneously measured by two photodetectors, thereby obtaining a Jones vector representing the polarization characteristics of the sample (H image and V). Image) structure.

  FIG. 1 is a diagram showing an overall configuration of an optical system of a polarization-sensitive optical coherence tomography apparatus to which a measurement signal noise processing method according to the present invention is applied. 1 includes optical elements such as a light source 2, a polarizer 3, an EO modulator 4, a fiber coupler (optical coupler) 5, a reference arm 6, a sample arm 7, a spectroscope 8, and the like. ing. The optical system of this polarization-sensitive received light image measuring apparatus 1 may have a structure of a type (free space type) in which optical elements are coupled to each other by a fiber 9 but not coupled to a fiber.

  The light source 2 uses a super luminescent diode (SLD) having a broadband spectrum. The light source 2 may be a pulse laser. The light source 2 includes a collimating lens 11, a polarizer 3 that linearly polarizes light from the light source 2, an EO modulator 4 with a fast axis set in a 45 ° direction, and a condenser lens 13 (in some cases, a further lens 13 ′ is used) and the fiber coupler 5 are connected in sequence.

  The EO modulator 4 fixes the fast axis in a 45 ° direction and modulates the voltage applied to the EO modulator 4 sinusoidally, so that the phase between the fast axis and the slow axis orthogonal thereto is obtained. The phase difference (retardation) is continuously changed. As a result, when light that has been emitted from the light source 2 and changed into (longitudinal) linearly polarized light by the polarizer 3 is incident on the EO modulator 4, the light is linearly changed at the above-described modulation period. Polarized light → elliptical polarized light → linearly polarized light, etc. As the EO modulator 4, a commercially available EO modulator may be used.

  A reference arm 6 and a sample arm 7 are connected to the fiber coupler 5 via a branching fiber 9. The reference arm 6 is sequentially provided with a polarization controller 10, a collimating lens 11, a polarizer 12, a condenser lens 13, and a reference mirror (fixed mirror) 14. The polarizer 12 of the reference arm 6 is used to select a direction in which the intensity of light returning from the reference arm 6 does not change even when the polarization state is modulated as described above. Adjustment of the direction of the polarizer 12 (polarization direction of linearly polarized light) is performed as a set with the polarization controller 10.

  In the sample arm 7, a polarization controller 15, a collimator lens 11, a fixed mirror 24, a galvano mirror 16, and a condenser lens 13 are sequentially provided, and an incident beam from the fiber coupler 5 is scanned by a biaxial galvano mirror 16. The sample 17 is irradiated. The reflected light (backscattered light) from the sample 17 returns to the fiber coupler 5 again as object light, is superimposed on the reference light, and sent to the spectrometer 8 as an interference beam.

  The spectroscope 8 includes a polarization controller 18, a collimator lens 11, a (polarization-sensitive volume phase holographic) diffraction grating 19, a Fourier transform lens 20, a polarization beam splitter 21, and two photodetectors 22 and 23 that are sequentially connected. I have. In this embodiment, a line CCD camera (one-dimensional CCD camera) is used as the photodetectors 22 and 23. The interference beam sent from the fiber coupler 5 is collimated by the collimating lens 11 and dispersed into an interference spectrum by the diffraction grating 19.

  The interference spectrum beam split by the diffraction grating 19 is Fourier transformed by a Fourier transform lens 20 and divided into horizontal and vertical components by a polarization beam splitter 21 and detected by two line CCD cameras (photodetectors) 22 and 23, respectively. The Since the two line CCD cameras 22 and 23 are used to detect the phase information of both the horizontal and vertical polarization signals, the two line CCD cameras 22 and 23 do not contribute to the formation of the same spectrometer. must not.

  The light source 2, the reference arm 6, the sample arm 7, and the spectrometer 8 are provided with polarization controllers 10, 15, and 18, respectively. The initial polarization state of each beam sent to the device 8 is adjusted so that the polarization state continuously modulated by the EO modulator 4 has a constant amplitude and a constant relative polarization state in the reference light and the object light. The relationship is maintained, and the spectroscope 8 connected to the fiber coupler 5 is controlled so as to maintain a constant amplitude and a constant relative polarization state.

  When the spectroscope 8 including the two line CCD cameras 22 and 23 is calibrated, the EO modulator 4 is stopped. The reference light is blocked, and the slide glass and the reflecting mirror are placed on the sample arm 7. This arrangement ensures that the positions of the peaks of the horizontal and vertical polarization components are the same. The OCT signals from the rear surface of the slide glass and the reflecting mirror are detected by the two spectrometers 8. The phase difference of the peak of the OCT signal is monitored.

  This phase difference should be zero at all optical axis depths. The signal is then windowed and inverse Fourier transformed to obtain a complex spectrum with a spectrometer 8 that includes two line CCD cameras 22,23. Since this phase difference should be zero at all frequencies, by monitoring these values, the physical positions of the two line CCD cameras 22, 23 are aligned so that the phase difference is minimized.

  The operation of the polarized light-sensitive received image measuring device is as follows. The light from the light source 2 is linearly polarized, and the linearly polarized beam is continuously modulated in the polarization state by the EO modulator 4. That is, the EO modulator 4 fixes the fast axis in a 45 ° direction and modulates the voltage applied to the EO modulator 4 sinusoidally, so that the phase between the fast axis and the slow axis orthogonal thereto is obtained. The phase difference (polarization angle: retardation) of the light is continuously changed, so that when the light that has been emitted from the light source 2 and converted into (longitudinal) linearly polarized light by the linear polarizer enters the EO modulator 4, In a cycle, the light is modulated as follows: linearly polarized light → elliptical polarized light → linearly polarized light.

  The linearly polarized polarized beam is continuously modulated in the polarization state by the EO modulator 4, and at the same time, the B scan is performed in synchronization. That is, during one B scan, the EO modulator 4 continuously modulates the polarization for a plurality of periods. Here, one period is a period during which the polarization angle (retardation) φ changes from 0 to 2π. In short, during this one cycle, the polarization of light from the polarizer is continuously modulated as linearly polarized light (vertical polarized light) → elliptical polarized light → linearly polarized light (horizontal polarized light).

  In this way, while continuously modulating the polarization of the polarized beam, the sample arm 7 scans the incident beam on the sample 17 by the galvano mirror 16 to perform the B scan, and the spectroscope 8 performs the object light as the reflected light. As for the interference spectrum of the reference light, the horizontal polarization component and the vertical polarization component are detected by the two line CCD cameras 22 and 23. Thus, two AB scan images corresponding to the horizontal polarization component and the vertical polarization component are obtained by one B scan.

  As described above, during one B-scan, continuous modulation of the polarization of the polarized beam is performed for a plurality of periods, but the two line CCD cameras 22 and 23 are continuously modulated during each period (one period). The polarization information of each of the horizontal polarization component and the vertical polarization component detected in step 1 becomes polarization information for one pixel. Polarization information is synchronized with the detection timing signal by two line CCD cameras 22 and 23 during one period of continuous modulation, and the number of detections (number of acquisitions) is four times, eight times, etc. What is necessary is just to decide suitably.

  Two-dimensional AB scan image data obtained during one B scan in this way is subjected to a one-dimensional Fourier transform in the B scan direction. Then, 0th, 1st and −1st order peaks appear. Here, when 0th-order peaks are extracted and inverse Fourier transform is performed using only the data, H0 and V0 images are obtained. Similarly, H1 and V1 images are obtained by extracting primary peaks and performing inverse Fourier transform using only the data.

  From the H0 and H1 images, J (1,1) and J (1,2) can be obtained from the Jones matrix components of the equation (see equation (18) below) which is the polarization characteristic of the sample 17. From the V0 and V1 images, J (2,1) and J (2,2) among the components of the Jones matrix of the expression (1), which is the polarization characteristic of the sample 17, can be obtained.

  In this way, information including four polarization characteristics can be obtained for one B-scan. Then, when these four pieces of information are Fourier-transformed in the A-scan direction in the same manner as in ordinary FD-OCT, the primary peak has information in the depth direction of the sample 17, and each 4 corresponds to the polarization characteristic. A sheet of AB image is obtained.

  By the way, in the polarization-sensitive optical coherence tomography apparatus, the polarization state of incident light is such as linearly polarized light (vertical polarized light) → elliptical polarized light → linearly polarized light (horizontal polarized light) in order to embed the polarization information during the horizontal B scan. Continuously or three-step modulated.

  OCT signals including phase information are obtained by Fourier transforming the respective light intensity signals detected by the two CCD cameras 22 and 23. The 0th-order and 1st-order frequency components of this OCT signal are taken out and inverse Fourier transformed respectively. Using these values, all the elements of the Jones matrix representing the polarization properties of the sample are obtained. Finally, the phase retardation amount (birefringence amount), the relative orientation distribution (direction) of birefringence, and dichroism, which are values representing the physical polarization dependence of the sample, are calculated.

(Measurement signal noise processing method)
In polarization-sensitive optical coherence tomography, the amount of phase delay (phase information) of a sample is generally represented by a phase angle, and the value (signal) is calculated as a positive value such as 0 to 180 degrees. In the case of a signal distributed in this way, in a minute signal region near 0 degrees or 180 degrees, the measurement signal is not a target even if the noise distribution superimposed on it is symmetric (for example, Gaussian distribution). This is because, for example, an observation signal such as phase information obtained by polarization-sensitive optical coherence tomography can take only a positive limited value (greater than 0 degrees and smaller than 180 degrees).

  2 and 3 show true values (see FIGS. 2 (a) and 3 (a)) and noise distribution (see FIGS. 2 (b) and 3 (b)) in a general measurement of signal intensity with respect to phase. ) And the relationship between the observed values (see FIGS. 2C and 3C) (graph). As shown in FIG. 2A, when the true value is not a minute signal near 0 degrees or 180 degrees, unknown random noise (see FIG. 2B) is added to the true signal value. In this case, the observed signal spreads symmetrically with respect to the true signal (see FIG. 2C). Therefore, since the random noise is averaged and canceled by a simple moving average, the true value of the signal can be estimated.

  However, as shown in FIG. 3, in the case of a minute signal whose true value is 0 degree or in the vicinity of 180 degrees (see FIG. 3A), an observation signal on which random noise (see FIG. 3B) is superimposed. Since the distribution (see FIG. 3C) is not symmetric with respect to the true signal, the true value cannot be estimated with such a moving average.

  That is, in normal measurement, data is repeatedly measured, its distribution is obtained, and an average is obtained as a true value. However, since the data value itself is small near zero, it is buried in the original measurement noise and the measurement data cannot be detected at the zero point, so the distribution becomes zero. In addition, since the data distribution is actually empirically smooth, it spreads asymmetrically around the true value, and the true value cannot be simply estimated by the moving average.

  By applying the measurement signal noise processing method of the present invention, in the polarization-sensitive optical coherence tomography apparatus, in order to estimate the true value of the observation signal superimposed with such unknown random noise, FIG. ), The maximum value (mode value) of the observation signal is taken. Thereby, the resolution of the image in a minute (observation) signal region can be increased.

  The noise processing method of the minute measurement signal in such a minute signal region will be further described below. In this embodiment, a signal processing device (specifically, a computer) that acquires a phase delay amount from an image signal obtained by a polarization-sensitive optical coherence tomography device has a phase delay amount as described below. By performing the processing, it is possible to avoid the inappropriateness that “the phase delay amount is higher than the actual value”.

  By the way, polarization sensitive optical coherence tomography can measure the amount of phase delay of a sample. The phase delay amount at a specific position of the three-dimensional measurement object has two parameters, one is “the size of the phase delay amount itself” and the other is “the direction of the axis of the phase delay amount”. It is.

  “The magnitude of the phase delay amount itself” is a phase delay amount in a specific direction, or a maximum value or a minimum value of the phase delay amount. The phase delay amount is set to 360 degrees (2π) for one period, and the amount of deviation is expressed in units of angles and has a property of turning back at 180 degrees, so the range is 0 to 180 degrees.

  “Axis direction of phase delay amount” is an axis direction in which the delay amount is maximized or minimized, and is represented by an angle of 0 to 180 degrees. This axis is called “fast axis” or “slow axis”.

  In the following, the polarization-sensitive optical coherence tomography measures the phase extension of the sample. For the noise processing methods of the two measurement measurement signals, “the size of the phase delay itself” and “the direction of the axis of the phase delay”, respectively. The above will be described with reference to FIGS. 2 and 3 as well as FIG.

(Noise processing method for measurement signals with large phase delay)
Since the phase delay amount itself is calculated as an angle, it takes a positive value such as 0 to 180 degrees. On the other hand, unknown noise generally has a target distribution (see FIG. 2B). The observed value is obtained by superimposing noise on the true value (see FIG. 2C).

  When the true value is away from 0 or 180 degrees (see Fig. 2 (a)), the observed value is measured in contrast to the true value due to noise (see Fig. 2 (b)). (See FIG. 2 (c)). Therefore, a true value can be obtained by taking a simple moving average of the observed values (see FIG. 2C).

  When the true value is small and near 0 degrees (or around 180 degrees) (see FIG. 3A), the observed value spreads asymmetrically due to noise (see FIG. 3B) (see FIG. 3C). ). In this case, the simple moving average is higher than the true value. In this case, the true value is preferably determined from the position of the peak (mode, mode value) of the observed value (see FIG. 3C).

  Specifically, appropriate discretization is performed, and the observed values are converted into a histogram. The center value of the highest histogram is set as a true value (histogram method) (see FIG. 4).

  The signal processing method is not limited to the processing of the OCT signal, and is generally applied as a signal processing method when the data value is small for data that can only take a positive value.

(Measurement signal noise processing method in the direction of the axis of phase delay)
As described above, the polarization-sensitive optical coherence tomography can measure the maximum (or minimum) direction (fast axis or slow axis direction) of the phase delay amount of the sample. The fast axis direction is generally expressed as an angle, and the value is calculated as a positive value such as 0 to 180 degrees.

  In the case of a signal distributed in this way, in the signal region near 0 degree or 180 degrees, the measurement signal is not symmetric even if the distribution of unknown noise superimposed thereon is symmetric (for example, Gaussian distribution). This is because, for example, angle information such as the fast axis direction obtained by polarization-sensitive optical coherence tomography can take only a limited positive value (greater than 0 degrees and smaller than 180 degrees).

  As described above, in the measurement in the fast axis direction (angle) in the polarization-sensitive optical coherence tomography apparatus, the present invention relates to the case of estimating the true value of a non-symmetric signal generated by superimposing unknown random noise as described above. An example of applying the measurement signal noise processing method will be described below with reference to FIGS. 2 to 4, similarly to the measurement signal noise processing method of the phase delay amount itself.

  In this embodiment, a signal processing apparatus (specifically, a computer) that acquires a signal, for example, a fast axis direction (angle) from an image signal obtained by a polarization-sensitive optical coherence tomography apparatus will be described below. By performing the processing, it is possible to avoid the inappropriateness that “the angle in the fast axis direction is higher than the actual value”.

  For example, since the fast axis direction is calculated as an angle, it takes a positive value such as 0 to 180 degrees. On the other hand, unknown noise generally has a target distribution (see FIG. 2B). The observed value is obtained by superimposing noise on the true value (see FIG. 2C).

  When the true value is away from 0 or 180 degrees (see Fig. 2 (a)), the observed value is measured in contrast to the true value due to noise (see Fig. 2 (b)). (See FIG. 2 (c)). Therefore, a true value can be obtained by taking a simple moving average of the observed values (see FIG. 2C).

  When the true value is close to the edge of the signal region and near 0 degrees (or near 180 degrees) (see FIG. 3A), the observed value spreads asymmetrically due to noise (see FIG. 3B) (see FIG. 3B). 3 (c)). In this case, the simple moving average is higher than the true value. In this case, the true value is preferably determined from the position of the peak (mode, mode value) of the observed value (see FIG. 3C). As shown in FIG. 3C, by adopting a configuration that takes the maximum value (mode value) of the signal, the resolution of the image in the signal region where the signal region is limited can be increased.

  Specifically, appropriate discretization is performed, and the observed values are histogrammed. The center value of the highest histogram is set as a true value (histogram method) (see FIG. 4).

  The signal processing method is not limited to the OCT signal processing, and is generally applied as a signal processing method when the data value is small for data dealing with only a limited signal region.

  The signal processing method is not limited to the processing of a minute signal with a limited signal area, and is generally applied as a signal processing method for data whose noise distribution is asymmetric when the data value is small. It is what is done.

  The best mode for carrying out the measurement signal noise processing method according to the present invention has been described above based on the embodiments. However, the present invention is not limited to such embodiments, and the scope of the claims is described. It goes without saying that there are various embodiments within the scope of the technical matters.

  Since the measurement signal noise processing method according to the present invention has the above-described configuration, it can be applied not only to optical tomographic image acquisition OCT but also as a measurement signal noise processing method for various measuring instruments.

It is a figure explaining the whole structure of the polarization sensitive optical coherence tomography apparatus to which the noise processing method of the measurement signal which concerns on this invention is applied. It is a figure (graph) explaining the influence of the noise with respect to a true value when the true value is a value away from 0 ° in a general measurement of the signal intensity with respect to the phase, (a) is the true value, (B) shows a noise distribution and (c) shows an observed value. It is a figure (graph) explaining the influence of the noise with respect to a true value when the true value is a minute value near 0 ° in a general measurement of signal intensity with respect to a phase, and (a) is a true value. , (B) shows the noise distribution, and (c) shows the observed value. It is a figure explaining the histogram method which makes a true value a histogram in the general measurement of the signal intensity with respect to a phase, and makes the observed value a histogram and makes the center value of the highest histogram etc. a true value. It is a figure explaining the prior art example (the principle of OCT).

Explanation of symbols

1 Polarized light receiving image measuring device
2 Light source
3, 12 Polarizer
4 EO modulator (polarization modulator, electro-optic modulator)
5 Fiber coupler (optical coupler)
6 Reference arm
7 Sample arm
8 Spectrometer
9 Fiber
10, 15, 18 Polarization controller
11 Collimating lens
13 Condensing lens
14 Reference mirror (fixed mirror)
16 Galvano mirror
17 samples
19 Diffraction grating
20 Fourier transform lens
21 Polarizing beam splitter
22, 23 Photodetector (Line CCD camera)
24 fixed mirror

Claims (3)

  The measurement signal from the measurement device is characterized in that the maximum value of the measurement signal is used as a true value for a minute signal region having a distribution curve in which the noise signal superimposed on the measurement signal is near 0 and not symmetric. A noise processing method for measurement signals.   The measurement signal from the measuring instrument has a distribution curve in which the minute measurement signal is not symmetrical due to the noise signal superimposed on it when the signal area of the measurement signal is limited or the true value is close to the end of the signal area. For a signal region having the signal region, the maximum value of the measurement signal is used as a true value.   The measurement signal from the measurement device is a noise of the measurement signal characterized by using the maximum value of the measurement signal as a true value for a signal having a distribution curve in which the measurement signal is not symmetrical due to a noise signal superimposed on the true value. Processing method.

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