JPH10232204A - Device for measuring refractive index - Google Patents

Abstract

PROBLEM TO BE SOLVED: To exactly measure a distribution of refractive indexes even a medium of high scattering and large refractive index change, by relatively adjusting optical paths of an object light-beam and a reference light-beam. SOLUTION: A light beam 11a is divided into an object light-beam 11b and reference light-beam 11c with a beam splitter 12. The beam 11b is transmitted through a measured sample 10 on an X-Y stage 13 movable in X-Y directions, and reflected by a reflector 14 and further by the splitter 12. On the other hand, the beam 11c is reflected by a reflector 16 on a Z stage 15 movable in a Z direction. An interfering light-beam 11d, consisting of beam 11c and 11b superposed each other, is inputted to a data processing part 19 as digital data through a light-reception element 17 and a signal processing part 18. The processing part 19 scans the beam 11b by moving the stage 13, and finds the phase zero point of each scanning point. The stage 15 is moved then, the optical paths of both beams 11b and 11c are relatively changed, the phase zero point of each scanning point of the sample 10 is found, and the distribution of refractive indexes within the X-Y plane is fond on the basis of the distribution of the point.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a refractive index measuring device for measuring a refractive index distribution or a refractive index of a sample.

[0002]

2. Description of the Related Art Interferometry is a technique capable of observing a difference in optical path length between a reference optical path and a sample optical path on which a sample is placed, that is, a phase difference between lights passing through these two optical paths as a difference in light intensity. It is possible to observe a refractive index distribution of a phase object in a straight line or a plane intersecting the sample optical path as a light intensity distribution, and to obtain meaningful information different from a simple light intensity image representing a transmittance distribution. . A phase contrast microscope and a differential interference microscope are devices that apply such a principle.

There is also known a technique of measuring the above-mentioned refractive index distribution while rotating the sample, and measuring the three-dimensional refractive index distribution of the sample by using a so-called CT reconstruction algorithm. FIG. 20 is a configuration diagram showing an example of a conventional refractive index measuring device. The laser light 100a emitted from the laser light source 100 is reflected by the mirror 101 and is incident on the Kesta prism 102,
Is divided into object light 100b and reference light 100c, and object light 1
Only the light beam 00b passes through the sample 10 in the sample cell 103, the object light 100b and the reference light 100c are superimposed by another Kester prism 104, and the superimposed light is
And is photographed by the CCD camera 106. The image obtained by this shooting is recorded on the video recorder 108 via the image memory 107. Sample cell 103
Rotates at a predetermined slow rotation speed, and during that rotation, images are repeatedly picked up by the CCD turtle 106, and a number of images are recorded on the video recorder 108. The image recorded in the video recorder 108 in this manner is read out to the workstation 109 via the image memory 107, and the workstation 109 uses the CT reconstruction algorithm to perform the tertiary ordering of the sample 10 in the sample cell 103. The original refractive index distribution is calculated. CCD camera 106
And the refractive index distribution obtained by the workstation 109 are displayed on the CRT display 110.

[0004]

In the above-mentioned prior art, a "phase object" which is relatively ideal is used, and a sample whose spatial refractive index change is extremely small is used. However, in recent years, the scattering inside is extremely large,
It is considered to apply the interference measurement to a biological sample or the like having a large spatial refractive index change. To make this application possible, it is necessary to: (a) use a substantially linear medium in a high scattering medium such as a biological sample; It is necessary to selectively collect only the light that has been transmitted and has low scattering.

(B) It is necessary to perform accurate phase measurement even when the spatial refractive index change is large. In view of the above circumstances, the present invention provides a refractive index measuring device that can accurately measure a refractive index distribution even in a highly scattering medium such as a biological sample and a medium having a large refractive index change. The purpose is to:

In some cases, it is necessary to measure not only the refractive index distribution but also the absolute refractive index of a sample such as a high scattering medium. In view of this point, an object of the present invention is to provide a refractive index measuring device capable of easily measuring a refractive index even for a sample such as a high scattering medium.

[0007]

According to the present invention, there is provided a refractive index measuring apparatus comprising: (1_1) a light source for emitting a predetermined low coherence light beam (1_2) Beam splitting means for splitting a light beam emitted from a light source into an object light beam and a reference light beam. (1_3) Sample placement section in which a sample to be measured is detachably arranged on the optical path of the object light beam. (1_4) Object Scanning means for scanning the sample placed on the sample placement unit with the light beam in a direction intersecting the optical path of the object light beam. (1_5) The reference light beam and the object light beam passing through the sample placement unit are superimposed on each other. (1_6) Optical path for relatively adjusting the optical path lengths of the object light beam and the reference light beam before being superimposed on each other by the beam superimposing means By receiving the adjusting means (1_7) the interference light beam, a represents the state of interference between the reference light beam and object light beam 1
(1_8) During scanning by the scanning unit when the optical path length is adjusted by the optical path length varying unit so that the first interference signal is kept in the same phase state And a refractive index calculating means for calculating a refractive index distribution or a refractive index of the sample placed in the sample placement section based on the adjustment amount of the optical path length.

Here, in the first refractive index measuring device, the scanning means (1_4) moves the sample placed in the sample placement section in a direction crossing the optical path of the object light beam. The scanning means may move the object light beam incident on the sample placed in the sample placement section in a direction intersecting the optical path of the object light beam. Reflecting means for returning the object light beam passing through the portion on the same optical path as the outward path, wherein the scanning means constitutes a descan on the return path where the object light beam is returned by the reflecting means. preferable.

In the first refractive index measuring apparatus, there is provided a frequency shift means for making the frequency of the object light beam and the frequency of the reference light beam relatively different from each other.
It is preferable that the optical path length adjusting means of (6) adjusts the optical path length so as to obtain an interference signal maintained in a predetermined phase state during scanning by the scanning means of (1_4).

Further, in the first refractive index measuring device, the (1_1) light source may be polarized in a direction intersecting with each other and have a predetermined low coherence of 2 different in frequency from each other.
A light source that emits a light beam formed by superimposing two light beams, wherein the beam splitting unit (1_2) splits the light beam emitted from the light source into an object light beam and a reference light beam having different frequencies from each other. And (1_
It is also a preferable embodiment that the optical path length adjusting means of (6) adjusts the optical path length so as to obtain an interference signal maintained in a predetermined phase state during scanning by the scanning means of (1_4).

Further, in the first refractive index measuring device provided with each of the above-mentioned constituent elements (1_1) to (1_8), further: (1_9) the object light beam when passing through the sample placement part from the object light beam; Second beam splitting means for splitting the comparison light beam having the same frequency as the frequency of the reference light beam. (1_10) The frequency of the reference light beam when superimposed on the object light beam by the first beam superimposing means from the reference light beam Third beam splitting means for splitting a second reference light beam having the same frequency. (1_11) A second beam splitting means for generating a second interference light beam by superimposing the comparison light beam and the second reference light beam.
(1_12) a second light receiving means for receiving the second interference light beam to obtain a second interference signal indicating an interference state between the comparison light beam and the second reference light beam Wherein the refractive index calculating means according to (1_8) maintains the same phase state of the first interference signal with respect to the second interference signal during scanning by the scanning means; It is a more preferable embodiment that the refractive index distribution or the refractive index of the sample placed in the sample placement section is obtained based on the adjustment amount of.

In the case of this embodiment, the above (1_)
The scanning means of 4) moves the object light beam incident on the sample placed on the sample placement section in a direction intersecting the optical path of the object light beam.
A first reflection unit that turns the object light beam that has passed through the sample placement unit onto the same optical path as the outward path, and the scanning unit includes:
It is preferable that a descan is formed on the return path where the object light beam is turned back by the first reflecting means.

[0013] In this case, further, in the above (1_10), the second
May include an optical plate that divides the object light beam incident on the sample placement part into a transmitted light beam and a reflected light beam. In the above aspect, the scanning means (1_4) moves the object light beam incident on the sample placed on the sample placement section in a direction intersecting the optical path of the object light beam. A comparison light beam split from the object light beam by the second beam splitting means in a direction intersecting the optical path of the comparison light beam. The comparison light beam passing through the scanning means is moved on the same optical path as the forward path. A second reflecting means turned back to the scanning means, and the scanning means constitutes a descan on the return path of the object light beam obtained by turning the object light beam back by the first reflecting means, and the comparison light beam is turned to a second light. It is further preferable that a descan is formed on the return path of the comparison light beam folded by the reflection means.

Further, in the first refractive index measuring apparatus of the present invention comprising the above components (1_1) to (1_8),
The light source (1_1) is a light source that emits a light beam that is polarized in two directions that intersect with each other and is formed by superimposing two lights of predetermined low coherence having different frequencies from each other,
The beam splitting means (1_2) splits the light beam emitted from the light source into an object light beam and a reference light beam having different frequencies from each other, and further includes a comparison light having the same frequency as the frequency of the object light beam. The first and second reference light beams are split into a second reference light beam having the same frequency as the frequency of the reference light beam and the reference light beam. Second beam superimposing means for generating a light beam, and (1_4)
(1_8) a second light receiving means for receiving a second interference light beam to obtain a second interference signal indicating an interference state between the comparison light beam and the second reference light beam;
Is based on the amount of adjustment of the optical path length by the optical path length varying means during which the first interference signal with respect to the second interference signal is kept in the same phase during scanning by the scanning means. It is also a preferable embodiment to obtain the refractive index distribution or the refractive index of the sample placed in the sample placement section.

In this embodiment, the above (1_)
The scanning means of 4) moves the object light beam incident on the sample placed on the sample placement section in a direction intersecting the optical path of the object light beam.
A first reflection unit that turns the object light beam that has passed through the sample placement unit onto the same optical path as the outward path, and the scanning unit includes:
It is preferable that a descan is formed on the return path where the object light beam is turned back by the first reflecting means.

In this case, the scanning means (1_4) moves the object light beam incident on the sample placed on the sample placement section in a direction crossing the optical path of the object light beam. The comparison light beam split from the object light beam by the second beam splitting means is moved in a direction intersecting the optical path of the comparison light beam. A second reflecting means for turning back on the road, wherein the scanning means constitutes a descan on the return path of the object light beam obtained by folding the object light beam by the first reflecting means, and the comparison light beam is provided for the second light means; It is a further preferable embodiment that the descanning is configured on the return path of the comparison light beam folded back by the second reflection means.

The second refractive index measuring device of the refractive index measuring device of the present invention that achieves the above object is: (2_1) a light source that emits a predetermined low coherence light beam; Beam splitting means for splitting the light beam into an object light beam and a reference light beam. (2_3) a sample placement section in which a sample to be measured is detachably disposed on the optical path of the object light beam; (2_4) the object light beam Scanning means for scanning the sample placed on the sample placement section in a direction intersecting the optical path of the object light beam. (2_5) Interference by overlapping the reference light beam and the object light beam passing through the sample placement section with each other Beam superimposing means for generating a light beam (2_6) A first light beam representing the interference state between an object light beam and a reference light beam by receiving the interference light beam.
(2_7) Refraction for obtaining a refractive index distribution or a refractive index of a sample placed in the sample placement section based on a phase change of the first interference signal during scanning by the scanning means. It is characterized by having a rate calculating means.

Here, in the second refractive index measuring device, as in the first refractive index measuring device, (2_4)
The scanning means may move the sample placed in the sample placement section in a direction crossing the optical path of the object light beam, but the scanning means enters the sample placed in the sample placement section. The object light beam is moved in a direction intersecting the optical path of the object light beam, and the refraction index measuring device includes a reflection unit that folds the object light beam that has passed through the sample placement unit on the same optical path as the outward path. The scanning means comprises:
It is preferable that a descan is formed on the return path where the object light beam is turned back by the reflection means.

In the second refractive index measuring apparatus, it is preferable that the apparatus further comprises a frequency shift means for making the frequency of the object light beam and the frequency of the reference light beam relatively different. Alternatively, the light sources are polarized in directions intersecting each other and have predetermined low coherence 2 different in frequency from each other.
A light source that emits a light beam formed by superimposing two light beams, wherein the beam splitting unit (2_2) splits the light beam emitted from the light source into an object light beam and a reference light beam having different frequencies from each other. Is also a preferred embodiment.

Further, in the second refractive index measuring apparatus provided with each of the above-mentioned components (2_1) to (2_7), the apparatus further comprises: (2_8) converting the object light beam from the object light beam when passing through the sample placement section Second beam splitting means for splitting the comparison light beam having the same frequency as the frequency. (2_9) The same frequency as the frequency of the reference light beam when being superimposed on the object light beam by the first beam superimposing means from the reference light beam A third beam splitting unit that splits a second reference light beam having a frequency of (2_10). A second interference light beam that is generated by superimposing the comparison light beam and the second reference light beam.
(2_11) a second light receiving means for receiving a second interference light beam to obtain a second interference signal representing an interference state between the comparison light beam and the second reference light beam;
The refractive index calculating means according to (2_7), based on a phase change of the first interference signal with respect to the second interference signal during scanning by the scanning means, a refractive index of the sample placed in the sample placement part. It is a more preferable embodiment to obtain the distribution or the refractive index.

In the case of this embodiment, the above (2_)
The scanning means of 4) moves the object light beam incident on the sample placed on the sample placement section in a direction intersecting the optical path of the object light beam.
A first reflection unit that turns the object light beam that has passed through the sample placement unit onto the same optical path as the outward path, and the scanning unit includes:
It is preferable that a descan is formed on the return path where the object light beam is turned back by the first reflecting means.

In this case, the second beam splitting means of (2_8) may further include an optical plate for splitting the object light beam incident on the sample placement portion into a transmitted light beam and a reflected light beam. . In the above aspect, the scanning means (2_4) moves the object light beam incident on the sample placed on the sample placement section in a direction intersecting the optical path of the object light beam. 2
The comparison light beam split from the object light beam by the beam splitting means is moved in a direction intersecting the optical path of the comparison light beam, and the comparison light beam passing through the scanning means is placed on the same optical path as the outward path. A second reflecting unit that is turned back, wherein the scanning unit forms a descan on the return path of the object light beam obtained by turning the object light beam back by the first reflecting unit; It is further preferable that a descan is formed on the return path of the comparison light beam folded by the reflection means.

Further, in the second refractive index measuring apparatus of the present invention comprising the above components (2_1) to (2_7),
The light source (2_1) is a light source that emits a light beam that is polarized in two directions that intersect with each other and is superimposed with two lights of predetermined low coherence having different frequencies.
The beam splitting means of (2_2) splits the light beam emitted from the light source into an object light beam and a reference light beam having different frequencies from each other, and furthermore, a comparison light having the same frequency as the frequency of the object light beam. And (2_12) superimposing the comparison light beam and the second reference light beam to form the second interference light beam. Second to generate light beam
And (2_13) second light receiving means for receiving a second interference light beam to obtain a second interference signal indicating an interference state between the comparison light beam and the second reference light beam. Prepared,
The refractive index calculating means according to (2_7), based on a phase change of the first interference signal with respect to the second interference signal during scanning by the scanning means, a refractive index of the sample placed in the sample placement part. It is also a preferable embodiment to obtain the distribution or the refractive index.

Also in this embodiment, the above (2_)
The scanning means of 4) moves the object light beam incident on the sample placed on the sample placement section in a direction intersecting the optical path of the object light beam.
A first reflection unit that turns the object light beam that has passed through the sample placement unit onto the same optical path as the outward path, and the scanning unit includes:
It is preferable that a descan is formed on the return path where the object light beam is turned back by the first reflection means.

In this case, the scanning means (2_4) is
The object light beam incident on the sample placed on the sample placement part is moved in a direction intersecting the optical path of the object light beam, and the object light beam is split from the object light beam by the second beam splitting means. Moving the light beam in a direction intersecting the optical path of the comparison light beam,
A second reflecting means for returning the comparative light beam having passed through the scanning means on the same optical path as the outward path, wherein the scanning means comprises an object light beam obtained by returning the object light beam by the first reflecting means; It is a further preferred embodiment that the descanning is configured on the return path of the above and that the descanning is configured on the return path of the comparison light beam that is folded back by the second reflection means.

The refractive index measuring apparatus of the present invention includes a light source for emitting a predetermined low coherence light beam, for example, an SLD or an LSD, and uses a low coherence light beam emitted from the light source. Only light that has transmitted almost linearly in such a high scattering medium can be separated from light scattered in the medium and used for interference measurement. Further, in the first refractive index measuring device of the refractive index measuring device of the present invention, the optical path length is adjusted by the optical path length varying means while scanning the sample,
Since the refractive index distribution is obtained based on the optical path length adjustment amount in which the phase of the interference signal is kept constant, the second refractive index measuring device of the refractive index measuring device according to the present invention uses a sample. Since the amount of change in the phase of the interference signal is determined while scanning, in any case, the change in the phase between adjacent scanning points is within a small range (for example, within 1/20 of the wavelength λ). By defining the scanning interval, even if there is a large phase change that is many times the wavelength over the entire scanning range, the refractive index distribution can be obtained with high accuracy, for example, a fraction of the wavelength or less. Therefore, the refractive index can be determined with high accuracy even when the refractive index is determined.

[0027]

Embodiments of the present invention will be described below. Hereinafter, first, various optical systems for obtaining the relative refractive index distribution of each part of the sample will be mainly described,
Then, a method of obtaining the absolute refractive index of the sample from the relative refractive index distribution will be described. FIG. 1 is a block diagram showing a configuration of a first embodiment of the refractive index measuring device of the present invention, and FIG. 2 is a block diagram showing one configuration example of a signal processing unit in the first embodiment shown in FIG.

The first embodiment is an example in which a Michelson-type interferometer is employed, and a so-called homodyne type in which the interference signal intensity does not change with time when the optical system is stopped. SLD, a type of low coherence light source
(Super Luminescent Diode)
The light beam 11a emitted from the light beam 11 is split into an object light beam 11b and a reference light beam 11c by a beam splitter 12, and the object light beam 11b is
The light passes through the sample to be measured 10 placed on an XY stage 13 movable in two directions, x and y, perpendicular to the optical axis direction b (z direction) of b. The reflected light is transmitted through the sample 10 again, and the beam splitter 1
The light is reflected by 2 and goes to the light receiving element 17. On the other hand, the other reference light beam 11c split by the half mirror 12
Is reflected by a reflection mirror 16 fixed to a Z stage 15 movable in the optical axis direction (z direction) of the reference light beam 11c, passes through the beam splitter 12, and travels toward the light receiving element 17.

In this way, the beam splitter 12 outputs the interference light beam 11d in which the reference light beam 11c and the object light beam 11b transmitted through the sample 10 are superimposed.
Goes to the light receiving element 17 and is received by the light receiving element 17. In the present embodiment, the beam splitter 12
Serve both as a beam splitting means and a beam superimposing means according to the present invention.

In the signal processing section 18, as shown in FIG.
High-frequency noise is cut by the low-pass filter 18_1, amplified by the DC amplifier 18_2, converted into digital data by the A / D converter 18_3, and input to the data processing unit 19. The data processing unit 19 controls the stage driver 20 to set the XY stage 13 to x
The object light beam 11 by moving in the
While scanning the sample 10 by b, the phase zero of each scanning point is obtained.

FIG. 3 is a schematic diagram showing the behavior of the object light beam 11b passing through the sample 10. The object light transmitted through the sample 10 is light transmitted through the sample 10 without being scattered much as shown by the light ray a, or transmitted light emitted forward after being multiply scattered inside the sample 10 as shown by the light ray b. There is light included in the later object light beam 11b, and further light such as the light ray c that has deviated from the object light beam 11b as a result of being scattered.

Here, it is necessary to make the light ray c out of the question and to detect only the light ray a from the light ray b. Therefore, in this embodiment, the SLD 11 which emits a light beam with low coherence is adopted as the light source. ing. That is, SL
Since the light emitted from D11 has a short coherence distance, the light beam b
The object light beam 11 after multiple scattering as shown in FIG.
The light mixed in b does not contribute to the interference, and only the light a that causes the interference can be extracted as a signal.

FIG. 4 is an explanatory view of the measurement principle in the first embodiment shown in FIG. The horizontal axis in FIG.
Position of upper reflecting mirror 16 (right side is beam splitter 1)
2, the vertical axis indicates the interference signal.
The broken line in the figure is the envelope of the interference signal. Here, first, the object light beam 11b is set at one point (measurement start point) of the sample.
In the state but irradiated, the beam splitter 12 to the reflecting mirror 16 on the Z stage 15, the position at which the amplitude does not change in the interference signal even move the reflecting mirror 16 (the position of the Z ₀ on the horizontal axis in FIG. 4) And then the reflection mirror 1
6 is moved away from the beam splitter 12. Then
The change (the width between envelopes) of the interference signal gradually increases while the amplitude changes. Therefore the variation is placed in the first after exceeding the predetermined value A _t, the midpoint of the change amount (phase zero) (Z _lo the horizontal axis in FIG. 4).
The data processing unit 19 stores this position _Zlo .

Next, the stage driver 20 is controlled to
The sample 10 is moved in the x direction or y direction by one scanning point interval. Then, the phase of the interference signal is shifted as shown by a dotted line in FIG. Therefore, the Z stage 15 is moved to the position Z.
_About half of the wavelength λ of the light beam 11a with _respect to _lo (±
(approximately λ / 4) to obtain a new phase zero Z ₁₁ .
The data processing unit 19 records the new phase zero _Z11 .

Next, the stage driver 20 is controlled to
The sample 10 is further moved in the x direction or y direction by one scanning point interval, and then the Z stage is moved about ± λ / 4 about the position Z _l1 to obtain and record a new phase zero. . By repeating this, the phase zero for each scanning point of the sample 10 is obtained, and the data processing unit 19 calculates the phase zero based on the distribution of these phase zeros, that is, the optical path length adjustment amount distribution based on the measurement start point. Sample 10
, The refractive index distribution in the x or y direction or in the xy plane is determined. In addition, the phase zero point is obtained as described above, and the amplitude (width between envelopes) of the AC component of the interference signal is obtained for each scanning point, and the transmission of the sample is determined based on the amplitude distribution along with the refractive index distribution of the sample. The rate distribution may be obtained.

The first embodiment is an example in which a Michelson-type interferometer is employed, but a Mach-Zehnder interferometer may be employed as shown in a later embodiment. Also,
In the above embodiment, the phase zero at each scanning point of the sample is obtained, but the phase of the interference signal at each scanning point of the sample at the fixed position _Z10 may be obtained. However, in this case, for example, the phase changed by 2π is not the same as the original phase, and needs to be handled as a phase changed by 2π. When the phase distribution is obtained in this manner, the data processing unit 19 obtains the refractive index distribution based on the phase distribution.
This aspect corresponds to an embodiment of the second refractive index measuring device of the present invention.

FIG. 5 is a block diagram showing a configuration of a second embodiment of the refractive index measuring device of the present invention, and FIG. 6 is a block diagram showing an example of a configuration of a signal processing unit in the second embodiment shown in FIG. It is. The second embodiment is an example in which a Mach-Zehnder interferometer is employed, and a so-called heterodyne type in which an interference signal repeatedly changes with time even when an XY stage or a Z stage is stationary. is there.

Light beam 11a emitted from SLD 11
Is split by the beam splitter 12 into an object light beam 11b and a reference light beam 11c. Object light beam 11b
Is subjected to a frequency shift by an acousto-optic modulator (AOM) 24, and a part of the object light beam 11b is split by a beam splitter 26 as a comparison light beam 11e. Object light beam 11 reflected by beam splitter 26
b is reflected by the reflection mirror 16 fixed to the Z stage 15, passes through the beam splitter 26, passes through the sample 10 disposed on the XY stage 13, passes through the beam splitter 29, and passes through the light receiving element 17 Incident on.

On the other hand, the comparison light beam 11e split from the object light beam 11b by the beam splitter 26 passes through the beam splitter 27, is reflected by the reflection mirror 28,
The light passes through the beam splitter 30 and enters the light receiving element 31. Further, the other reference light beam 11c split by the beam splitter 12 is reflected by the beam splitter 22, reflected by the reflection mirror 23, and reflected by the beam splitter 22.
, And undergoes a frequency shift in the AOM 25. This A
The OM 25 is driven by a drive signal having a frequency slightly different from that of the AOM 24. Therefore, the frequency of the reference light beam 11c subjected to the frequency shift by the AOM 25 is lower than that of the object light beam 11b subjected to the frequency shift by the AOM 24. Somewhat different.

The reference light beam 11c having passed through the AOM 25
Reaches the beam splitter 29 and its reference light beam 1
Part of 1c is split as the second reference light beam 11f. Reference light beam 11 reflected by beam splitter 29
c forms a first interference light beam 11d by being superimposed on the object light beam 29, and the first interference light beam 11d enters the light receiving element 17 and is received to generate a first interference signal. . This first interference signal is input to the signal processing unit 18.

The second reference light beam split from the reference light beam 11c by the beam splitter 29 is reflected by the beam splitter 30 and superimposed on the comparison light beam 11e to generate a second interference light beam 11g. The second
Is incident on the light receiving element 31 and is received, and a second interference signal is generated. This second interference signal is also input to the signal processing unit 18.

In the signal processing section 18, the phase and the amplitude of the first interference signal with respect to the second interference signal are obtained as described below. Preamplifier 18_ shown in FIG.
The first interference signal and the second interference signal obtained by the light receiving elements 17 and 31 are input to and amplified by the light-receiving elements 17 and 31, respectively.
6, only the frequency components corresponding to the difference between the frequencies of the drive signals of the AOM 24 and the AOM 25 are extracted.

The output of the band-pass filter 18_2 is input to each of the multipliers 18_3 and 18_4. The output of the band-pass filter 18_6 is input to the multiplier 18_4, and the phase of the signal is advanced by π / 2. After passing through the phase shifter 18_7, it is input to the multiplier 18_3. The outputs of the multipliers 18_3 and 18_4 are input to the low-pass filters 18_8 and 18_10, and unnecessary high-frequency components are cut. Then, the output of each of these low-pass filters 18_8 and 18_10 indicates the ratio of the amplitude of the first interference signal to the amplitude of the second interference signal as A, and the phase of the first interference signal with respect to the phase of the second interference signal. When θ is set, the signals are proportional to Asin θ and Acos θ, respectively.

Each of these low-pass filters 18_8, 18
_10 are output from A / D converters 18_9, 18
_11, is converted into digital data, input to the digital operation unit 18_12,
In _12, the amplitude A and the phase θ are obtained. FIG. 7 is an explanatory view of the measurement principle in the second embodiment shown in FIG.

The horizontal axis in FIG. 7 is the position of the reflection mirror 16 on the Z stage 15 (the right side is away from the beam splitter 26), and the vertical axis is the amplitude of the interference signal (relative to the amplitude of the above-mentioned second interference signal). Ratio of amplitude of first interference signal) A
And the phase (the phase of the first interference signal with respect to the phase of the second interference signal) θ. Here, similarly to the case of the first embodiment described above, first, the reflecting mirror 16 on the Z stage 15 is moved while a certain point (measurement start point) of the sample is irradiated with the object light beam 11b. Then, the beam A is brought close to the beam splitter 26 to a position where the amplitude A is sufficiently small (the position of Z _{0 on} the horizontal axis in FIG. 7).
6 is moved away from the beam splitter 26. Then
The amplitude gradually increases. Therefore, the initial phase zero of the amplitude A later point reaches a predetermined value A _t (theta =
The reflection mirror 16 is arranged at (point 0) z ₁₀ . The data processing unit 19 stores the amplitude A ₀ at this position Z _l0, and its position Z _l0.

Next, the stage driver 20 is controlled to
The sample 10 is moved in the x direction or y direction by one scanning point interval. Then, the phase θ shifts as shown by the dotted line in the figure. Therefore, the data processing unit 19 that moves the Z stage 15 to the new phase zero position Z ₁₁ stores the new position Z ₁₁ and the amplitude A ₁ at the new position Z ₁₁ .

Next, by controlling the stage driver 20,
The sample 10 is moved in the x direction or y direction by one scanning point interval, and the Z stage 15 is moved in the same manner as described above.
To a new phase zero. By repeating this, the phase zero and the amplitude for each scanning point of the sample 10 are obtained, and the data processing unit 19 determines the distribution of the phase zero, that is, the optical path based on the position of the Z stage 15 at the measurement start point. The refractive index distribution of the sample 10 is obtained based on the length adjustment amount distribution, and the transmittance distribution of the sample 10 is obtained based on the amplitude distribution.

FIG. 8 shows another example of the second embodiment shown in FIG.
FIG. 4 is an explanatory diagram of one measurement method. Also in this case, similarly to the above, first, in a state where one point (measurement start point) of the sample is irradiated with the object light beam 11b, the Z stage 1
5 is moved close to the beam splitter 26 to a position Z ₀ where the amplitude A is sufficiently small.
Away the reflecting mirror 16 from the beam splitter 26, the amplitude A is disposed a predetermined (point theta = 0) value first phase zero after the point has been reached A _t reflected Z _l0 mirror 16. Up to this point, the measurement method is the same as the measurement method described with reference to FIG. 7, but in this measurement method, the reflecting mirror 16 is not moved while being fixed thereafter. When the XY stage 13 is moved in this state, the amplitude A and the phase θ change. The amplitude A is recorded as it is. The phase θ is monitored as to whether there is a transition from near π to near −π or from near −π to near π as shown in FIG. 7A, and as shown in FIG. 2 for every transition from near π to near −π
π is added, and −2π is added each time a transition from near −π to near π occurs. Thus, as shown in FIG. 8C, the phase distribution of the sample 10 having a phase change corresponding to the wavelength of the light beam is obtained, and the refractive index distribution of the sample 10 is obtained based on the phase distribution.

FIG. 9 is a block diagram showing a configuration of a third embodiment of the refractive index measuring apparatus according to the present invention. The second shown in FIG.
The differences from the embodiment will be described. The third embodiment shown in FIG. 9 differs from the second embodiment shown in FIG.
No optical path for the comparison light beam or an optical path for the second reference light beam is provided, so that no second interference signal to be used as a reference is generated. Instead, in the third embodiment, the signal of the difference frequency Δf = f ₁ −f ₂ between the frequencies f ₁ and f _{2 of the} drive signals of the two AOMs 24 and 25 is output from the explicitly illustrated AOM driver 32. Signal processing unit 1
8 is input. Alternatively, both signals of the frequencies f ₁ and f ₂ may be input to the signal processing unit 18 to generate a signal of Δf = f ₁ −f ₂ inside the signal processing unit 18. The signal processing unit 18 converts the signal of the frequency Δf of the difference into the light receiving element 1
6 is used as a reference for the amplitude and phase of the interference signal obtained.

FIG. 10 shows a fourth example of the refractive index measuring apparatus according to the present invention.
FIG. 2 is a block diagram illustrating a configuration of the embodiment. The difference from the third embodiment shown in FIG. 9 will be described. The fourth embodiment shown in FIG. 10 is different from the third embodiment shown in FIG. 9 in that AOM on the optical path of the object light beam 11b is omitted. In the herodyne method, the frequency of the object light beam and the frequency of the reference light beam need to be relatively different, but it is sufficient if they are relatively different. The AOM is based on the optical path of the object light beam 11b and the reference light beam. It is not necessary to provide both in the optical path of the beam 11c, and it may be provided in only one optical path (in the example of FIG. 10, the optical path of the reference light beam 11c).

However, at this time, since the frequency f of the drive signal for driving the AOM 25 becomes the frequency of the interference signal obtained by the light receiving element 17, the signal processing unit 18 does not need to process an extremely high frequency signal. AO
It is desirable that the drive signal for driving M25 is a signal with a frequency as low as possible. In the fourth embodiment shown in FIG. 10, a signal having the same frequency as the frequency f of the drive signal is input to the signal processing unit 18 and used as a reference for the amplitude and phase of the interference signal obtained by the light receiving element 17.

FIG. 11 shows a fifth embodiment of the refractive index measuring apparatus according to the present invention.
FIG. 2 is a block diagram illustrating a configuration of the embodiment. Each of the fifth and subsequent embodiments shown in FIG. 11 is an embodiment having a feature in the configuration of the optical system, and therefore, the block of the signal processing system is not shown. Each of the embodiments described so far includes an XY stage on which a sample is placed, and scans the sample by moving the XY stage. The fifth embodiment shown in FIG. The embodiment is an embodiment in which the sample is scanned by moving the object light beam.

Light beam 11a emitted from SLD 11
Is split by the beam splitter 12 into an object light beam 11b and a reference light beam 11c. Object light beam 11
b is frequency-shifted by the AOM 24, and a part of the object light beam 11b is split by the beam splitter 26 as a comparison light beam 11e. The object light beam 11b reflected by the beam splitter 26 deflects the object light beam 11b in the x direction perpendicular to the optical axis direction (z direction) of the object light beam 11b, for example, a galvanometer mirror or a polygon mirror. The x-axis scanner 35 deflects the object light 11b in the y-direction perpendicular to both the z-direction and the x-direction, and also includes a galvanometer mirror or a polygon mirror.
The light enters the sample 10 via the axis scanner 36. Thus, the sample 10 is scanned in the x direction and the y direction. The object light beam 11b transmitted through the sample 10 is
The sample 1 is reflected by the reflecting mirror 16 fixed to
0 is transmitted again, and reaches the beam splitter 26 via the same optical path as the outward path. That is, this object light beam 11
In the return path b, a so-called descan is configured, in which the light returns through the same optical path as the outward path regardless of the deflection of the object light beam by the x-axis scanner 35 and the y-axis scanner 36.

The object light beam 11b returned to the beam splitter 26 passes through the beam splitter 26, further passes through the beam splitter 29, and reaches the light receiving element 17. On the other hand, the object light beam 1 is
The comparison light beam 11e separated from 1b is reflected by the total reflection prism 37, reflected by the reflection mirror 38, transmitted through the beam splitter 30, and enters the light receiving element 31.

Further, the other reference light beam 11c split by the beam splitter 12 is
And reflected by the reflection mirror 34, and the AOM 25
, And reaches the beam splitter 29. In the beam splitter 29, the reference light beam 1
Part of 1c is split as the second reference light beam 11f. Reference light beam 11 reflected by beam splitter 29
c is superimposed on the object light beam 11b transmitted through the sample 10 to form a first interference light beam 11d, and the first interference light beam 11d enters the light receiving element 17 and is received,
A first interference signal is generated. This first interference signal is
A signal processing unit (not shown) (for example, the signal processing unit 1 shown in FIG. 5)
8).

The second reference light beam 11f split from the reference light beam 11c by the beam splitter 29.
Is the comparison light beam 11 transmitted through the beam splitter 30
A second interference light beam 11g is generated by being superimposed on e, and the second interference light beam 11g is incident on the light receiving element 31 and received, and a second interference signal is generated. This second interference signal is also input to the signal processing unit.

When the sample 10 is scanned by deflecting the object light beam as in the fifth embodiment shown in FIG. 11, high-speed scanning becomes possible. FIG. 12 is a block diagram showing a configuration of a sixth embodiment of the refractive index measuring device of the present invention. The differences from the fifth embodiment shown in FIG. 11 will be described. In the sixth embodiment shown in FIG. 12, the beam splitter 26 converts the comparison light beam 1 from the object light beam 11b.
1e is not divided, a part of the object light beam 11b deflected by the x-axis scanner 35 and the y-axis scanner 36 is reflected by the optical plate 39, and the light reflected by this optical plate is used as a comparison light beam 11e. Used. Both the object light beam reflected by the optical plate 39 and the object light beam transmitted through the sample and reflected by the reflection mirror 16 return to the beam splitter 26 through the same optical path as the outward path, and the beam splitter 26
And the beam splitter 40 transmits the object light beam 1
A part of 1b is split as a comparison light beam 11e.

The comparison light beam 11 e split from the object light beam 11 b by the beam splitter 40 includes not only the object light reflected by the optical plate 39 but also the object light transmitted through the sample 10 and reflected by the reflection mirror 16. However, by appropriately adjusting the optical path length of the comparison light beam 11e, only light reflected by the optical plate 39 can contribute to interference. The same applies to the object light beam 11b transmitted through the beam splitter 40.
Although the object light beam 11b that has passed through 0 includes the object light reflected by the optical plate 19, only the object light that has passed through the sample 10 and has been reflected by the reflection mirror 16 can contribute to interference.

Here, as shown in FIG. 12, the behavior of the object light beam when the object light beam 11b transmits through the sample 10 and is reflected by the reflection mirror 16 and again passes through the sample 10 will be described. FIG. 13 is a schematic diagram showing the behavior of the object light beam 11b passing through the sample 10.

Here, for the sake of explanation, it is assumed that an extremely short pulse beam of the object light is applied to the sample 10, and the temporal change of the intensity of the reflected object light in that case is shown in FIG.
Shown in First, as shown by a ray a in FIG. 13A, light reflected by the optical plate 39 is first observed as reflected light.
Next, the light beam b reflected on the surface 10A of the case in which the sample 10 is placed is observed, and thereafter, the light c that has been reflected multiple times within the sample 10 and returned has continued. Thereafter, the light d that is reflected by the reflecting mirror 16 that is transmitted through the sample 10 without being scattered, and that is transmitted through the sample 10 again without being scattered.
Then, the light scattered on the outward path and reflected by the reflection mirror 16 and returned, or the light e scattered on the return path after reflection on the reflection mirror 16 is observed.

Here, the light a is used as the comparison light as described above, and only the light d among the light b to the light e is extracted as the object light. Therefore, the distance between the sample 10 and the reflection mirror 16 shown in FIG. 12 needs to be longer than a certain distance so that the light c and the light d do not overlap. FIG. 14 is a block diagram showing the configuration of the seventh embodiment of the refractive index measuring device of the present invention. The differences from the fifth embodiment shown in FIG. 11 will be described.

The object light beam 11 is output from the beam splitter 26.
The comparison light beam 11e split from b passes through an optical diode 41 that propagates light only in one direction,
The x-axis scanner 35, which is reflected by the beam splitter 42,
The light is deflected by the y-axis scanner 36 together with the object light beam 11b, reflected by the reflection mirror 43, and returns to the beam splitter 42 again through the same optical path as the outward path. in this case,
The x-axis scanner 35 and the y-axis scanner 36 descan both the object light beam 11b and the comparison light beam 11e on the return path of the object light beam 11b and the comparison light beam 11e.

The comparison light beam 11e returned to the beam splitter 42 passes through the beam splitter 42, is superimposed on the second reference light 11f by the beam splitter 30, and enters the light receiving element 31 as a second interference light beam 11g. In the seventh embodiment, the x-axis scanner 35 and the y-axis scanner 36 are included in the optical path of the object light beam, and the same x-axis scanner 35 and y-axis scanner 36 are also included in the optical path of the comparison light beam. Therefore, a more stable signal can be obtained.

FIG. 15 shows an eighth embodiment of the refractive index measuring apparatus according to the present invention.
3 is a block diagram illustrating a configuration of the embodiment. In the eighth embodiment shown in FIG. 15, as a light source 50, a light beam 50 is formed by superimposing two predetermined low-coherence lights that are polarized in mutually intersecting directions and have different frequencies.
A light source that emits a (hereinafter, referred to as a “two-frequency orthogonally polarized light source”) is used.

FIG. 16 is a block diagram showing a configuration example of the light source 50 shown in FIG. The light source 50 includes an SLD
The polarization beam splitter 502 converts a light beam 501a emitted from the SLD 501 into two light beams 50 having polarization components orthogonal to each other.
1b and 501c. These two light beams 5
01b and 501c undergo frequency shifts different from each other by the AOMs 503 and 504, respectively, are superimposed by the polarization beam splitter 505, and are emitted from the light source 50 as one light beam 50a. In the eighth embodiment shown in FIG. 15, for example, a light source 50 in which the elements shown in FIG. 16 are modularized is used.

The light source 50 is not limited to the light source having the structure shown in FIG. 16. In short, the light source 50 is a light obtained by superimposing two low-interfering light beams which are polarized in mutually intersecting directions and have different frequencies. Any light source that emits a beam may be used. Returning to FIG. 15, the description of the eighth embodiment will be continued. Light beam 50a emitted from light source 50
Is partially split by the beam splitter 51 in intensity and reflected, and passes through an analyzer 58 arranged at an azimuth of 45 ° to generate interference light in which an S-polarized component and a P-polarized component interfere with each other, The light is received by the light receiving element 31.

On the other hand, the light beam 50a transmitted through the beam splitter 51 is split by the polarizing beam splitter 52 into an object light beam 11b and a reference light beam 11c.
Here, the object light beam 11b and the reference light beam 11c are lights having different frequencies from each other, and are lights polarized in directions orthogonal to each other. The optical path of the object light beam 11 b is turned back by the total reflection prism 54 fixed to the Z stage 15, passes through the sample 10 placed on the XY stage 13, and returns to the polarization beam splitter 52.

On the other hand, the reference light beam 11c emitted from the polarizing beam splitter 52 returns its optical path by the total reflection prism 55 and returns to the polarizing beam splitter 52. The object light beam 11b and the reference light beam 11c that have returned to the polarization beam splitter 52 are superimposed on each other, emitted from the polarization beam splitter 52, reflected by the reflection mirror 56, and passed through an analyzer 57 arranged at an azimuth of 45 °. Then, they interfere with each other and are received by the light receiving element 17 to generate an interference signal.

As shown in the eighth embodiment, the optical system can be simplified by using a two-frequency orthogonally polarized light source and combining it with a polarizing beam splitter. FIG.
FIG. 7 is a block diagram showing a configuration of a ninth embodiment of the refractive index measuring device of the present invention. The light beam 50a emitted from the two-frequency orthogonally polarized light source 50 is intensity-divided into two light beams 50b and 50c by the Kester prism 59 and enters the polarization beam splitter 52. The light beam 50b is split by the polarization beam splitter 52 into an object light beam 11b and a reference light beam 11c according to its polarization direction, and the light beam 50c is split by the polarization beam splitter 52 into a comparison light beam according to its polarization direction. 11e and 2nd
And the reference light beam 11f.

The object light beam 11b and the comparison light beam 11e emitted from the polarization beam splitter 52 are λ / 4
After passing through the plate 60, the light enters the x-axis scanner 35. The optical system on the right side of the x-axis scanner 35 in FIG.
This is the same as the optical system in the lower part of the x-axis scanner 35 shown in FIG. 14, and the duplicated description is omitted here. The object light beam 1 reflected by each of the reflecting mirrors 16 and 43 and returned
The light beam 1b and the comparative light beam 11f pass through the λ / 4 plate 60 again, and return to the polarization beam splitter 52 in a polarization state rotated by 90 ° as compared with the polarization state when emitted from the polarization beam splitter 52.

On the other hand, the reference light beam 11c and the second reference light beam 11c emitted from the polarization beam splitter 52
f is reflected by the reflection mirror 62 via the λ / 4 plate 61, and returns to the polarization beam splitter 52 again via the λ / 4 plate 61. The reference light beam 11c and the second reference light beam 11f that have returned to the polarization beam splitter 52 are also λ /
By passing through the four plates 61 twice, the polarization direction is rotated by 90 ° as compared with that at the time of emission from the polarization beam splitter 52.

The object light 11b and the reference light beam 11c returning to the polarization beam splitter 52 are superimposed on each other and exit from the polarization beam splitter 52, and are arranged at an azimuth of 45 ° and interfere with each other by passing through an analyzer 63. First
Is generated and received by the light receiving element 17. On the other hand, the comparison light beam 11e and the second reference light 11f that have returned to the polarization beam splitter 52 are also superimposed on each other and output from the polarization beam splitter 52, and
3, the light beams interfere with each other, become a second interference beam 11g, enter the light receiving element 31, and are received by the light receiving element 31. Even when the two-frequency orthogonally polarized light source 50 is used as in the ninth embodiment shown in FIG. 7, the light beam can be scanned.

In each of the above embodiments, the rotation of the sample 10 is not mentioned. However, the sample 10 is configured to be rotatable, a known CT reconstruction algorithm is employed, and the three-dimensional refractive index of the sample is used. The distribution may be determined. The method for obtaining the relative refractive index distribution of each part of the sample has been described above. Next, the method for obtaining the absolute refractive index of the sample will be described.

To determine the refractive index, any of the above-described embodiments can be employed. However, the sample is a homogeneous sample (the refractive index is constant regardless of the portion). Limited. FIG. 18 is a diagram showing each example of the measurement container. Here, a liquid sample will be described as an example of a homogeneous sample.

The measurement container 100A shown in FIG. 18A is a measurement container formed in a tapered shape in a direction perpendicular to the traveling direction of the object light beam, and is filled with a liquid sample 101. The object light beam is scanned relative to the sample in directions in which the lengths of the paths passing through the liquid sample 101 are different, such as the light beam A and the light beam B shown in FIG. FIG.
The measurement container 100B shown in (B) is divided into a room filled with the measurement sample 101 and a room filled with the standard sample 102, and the boundary between these rooms is defined by the scanning direction of the object light beam (FIG. (Up and down direction).

FIG. 19 is a schematic diagram showing the waveform of the object light beam passing through the measurement container shown in FIG. 18A along the optical path. FIGS. 19A and 19B are diagrams of FIG.
The waveforms of the light beams A and B are shown, and the solid line is
The waveform when the measurement container 100A is arranged, and the broken line is the waveform when the measurement container is removed.

The light beam A and the light beam B correspond to the measurement container 100A
Have different distances through the liquid sample and are therefore out of phase with each other. The refractive index of the surrounding (air) is n
₀ , the wavelength of the object light beam in the air is λ ₀ , the measurement container 1
When the refractive index of the liquid sample inside 00A is n _1, and the difference between the distances of light A and light B passing through the liquid sample is Δd, the phase difference between light A and light B is θ
Is θ = (2π · n ₁ Δd) / (n ₀ λ ₀ ).

In the case of the measuring container 100B shown in FIG. 18B, when the refractive index of the standard sample is n ₂ , θ = {2π · (n ₁ −n ₂ ) · Δd} / (n ₀ λ ₀₎ ). Therefore, as described in each embodiment, the phase difference θ, or the adjustment amount of the optical path length at which the phase is constant is obtained, and the absolute refractive index distribution of the liquid sample thus obtained is used as the absolute value. The refractive index can be determined.

Although a liquid sample has been described above as an example of a homogeneous sample, the invention is not limited to a liquid sample, but any other homogeneous sample may be used. For example, a fluid may be used. A solid or solidified sample may be used as long as it can be processed into a wedge shape as in 18 (A).

[0080]

As described above, according to the present invention,
Even in a medium having high scattering and a large refractive index change such as a biological sample, the refractive index distribution can be accurately measured.
If the medium is a homogeneous medium, the absolute refractive index of the medium can be accurately measured.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a first embodiment of a refractive index measuring device of the present invention.

FIG. 2 is a block diagram illustrating a configuration example of a signal processing unit according to the first embodiment illustrated in FIG.

FIG. 3 is a schematic diagram showing the behavior of an object light beam transmitted through a sample.

FIG. 4 is an explanatory view of a measurement principle in the first embodiment shown in FIG. 1;

FIG. 5 is a block diagram showing a configuration of a second embodiment of the refractive index measuring device of the present invention.

FIG. 6 is a block diagram illustrating a configuration example of a signal processing unit according to the second embodiment illustrated in FIG. 5;

FIG. 7 is an explanatory view of a measurement principle in the second embodiment shown in FIG.

8 is an explanatory diagram of another measurement method according to the second embodiment shown in FIG.

FIG. 9 is a block diagram showing a configuration of a third embodiment of the refractive index measuring device of the present invention.

FIG. 10 is a block diagram showing a configuration of a fourth embodiment of the refractive index measuring device of the present invention.

FIG. 11 is a block diagram showing a configuration of a fifth embodiment of the refractive index measuring device of the present invention.

FIG. 12 is a block diagram showing a configuration of a sixth embodiment of the refractive index measuring device of the present invention.

FIG. 13 is a schematic diagram showing the behavior of an object light beam transmitted through a sample.

FIG. 14 is a block diagram showing a configuration of a seventh embodiment of the refractive index measuring device of the present invention.

FIG. 15 is a block diagram showing a configuration of an eighth embodiment of the refractive index measuring device of the present invention.

FIG. 16 is a block diagram showing a configuration example of a light source according to the eighth embodiment shown in FIG.

FIG. 17 is a block diagram showing a configuration of a ninth embodiment of the refractive index measuring device of the present invention.

FIG. 18 is a diagram showing each example of a measurement container.

19 is a schematic diagram showing a waveform of an object light beam passing through the measurement container shown in FIG. 18A along an optical path.

FIG. 20 is a configuration diagram showing an example of a conventional refractive index measuring device.

[Explanation of symbols]

10 Sample to be measured 11 SLD 11a Light beam 11b Object light beam 11c Reference light beam 11d Interference light beam 11e Comparative light beam 11f Reference light beam 12,22,26,27,29,30,40,42
Beam splitter 13 XY stage 14 Reflecting mirror 15 Z stage 16 Reflecting mirror 17 Light receiving element 18 Signal processing section 19 Data processing section 20, 21 Stage driver 24, 25 AOM 31 Light receiving element 32 AOM driver 35 x-axis scanner 36 y-axis scanner Reference Signs List 39 optical plate 41 optical diode 52 beam splitter 57, 58 analyzer 59 Kester prism 60, 61 λ / 4 plate 63 analyzer 100A, 100B measuring container 101 liquid sample 102 standard sample

Claims (15)

[Claims] A light source for emitting a predetermined low coherence light beam; a beam splitting unit for splitting a light beam emitted from the light source into an object light beam and a reference light beam; A sample placement unit detachably disposed on an optical path of a light beam, and a scanning unit configured to scan, by the object light beam, a sample disposed on the sample placement unit in a direction intersecting the optical path of the object light beam; By superimposing the reference light beam and the object light beam that has passed through the sample placement unit on each other, a beam superimposing unit that generates an interference light beam, An optical path length adjusting means for relatively adjusting the optical path length of the reference light beam; and receiving the interference light beam to detect an interference state between the object light beam and the reference light beam. A light receiving unit that obtains a first interference signal to be passed, and an optical path length adjusted by the optical path length varying unit so that the first interference signal is kept in the same phase state.
A refractive index calculating means for calculating a refractive index distribution or a refractive index of a sample placed in the sample placement section based on an adjustment amount of an optical path length during scanning by the scanning means. measuring device. 2. The refractive index measuring apparatus according to claim 1, wherein said scanning means moves the sample placed on said sample placement section in a direction crossing the optical path of said object light beam. . 3. The scanning unit moves an object light beam incident on a sample placed on the sample placement unit in a direction crossing an optical path of the object light beam, and passes through the sample placement unit. Reflecting means for turning the object light beam back on the same optical path as the outward path, wherein the scanning means constitutes descanning on the return path where the object light beam is turned back by the reflecting means. 2. The refractive index measuring device according to 1. 4. A frequency shift means for relatively varying the frequency of the object light beam and the frequency of the reference light beam, wherein the optical path length adjusting means maintains a predetermined phase state during scanning by the scanning means. 2. The refractive index measuring device according to claim 1, wherein the optical path length is adjusted so as to obtain a tilted interference signal. 5. A second beam splitting unit for splitting, from the object light beam, a comparison light beam having the same frequency as the frequency of the object light beam when passing through the sample placement unit, Third beam splitting means for splitting a second reference light beam having the same frequency as the frequency of the reference light beam when being superimposed on the object light beam by the first beam superimposing means; A second beam superimposing unit configured to generate a second interference light beam by superimposing the second reference light beam; and receiving the second interference light beam, the comparison light beam and the second light beam. A second light receiving unit that obtains a second interference signal indicating an interference state with the second reference light beam, wherein the refractive index calculation unit performs the second interference signal during scanning by the scanning unit. Before The first interference signal is maintained in the same phase state, and the refractive index distribution or the refractive index of the sample placed in the sample placement section is obtained based on the adjustment amount of the optical path length by the optical path length variable unit. 2. The refractive index measuring device according to claim 1, wherein: 6. The scanning unit moves an object light beam incident on a sample placed on the sample placement unit in a direction intersecting the optical path of the object light beam, and passes through the sample placement unit. A first reflecting means for returning the object light beam on the same optical path as the outward path, wherein the scanning means constitutes a descan on a return path in which the object light beam is returned by the first reflecting means. The refractive index measuring device according to claim 5, characterized in that: 7. The apparatus according to claim 6, wherein the second beam splitting means includes an optical plate for splitting the object light beam incident on the sample placement portion into a transmitted light beam and a reflected light beam. Refractive index measuring device. 8. The light source, wherein the light source emits a light beam that is polarized in a direction intersecting with each other and superimposes two predetermined low-coherence lights having different frequencies from each other. Dividing the light beam emitted from the light source into the object light beam and the reference light beam having different frequencies from each other, and further, comparing the reference light beam and the reference light beam having the same frequency as the frequency of the object light beam. Splitting into a second reference light beam having the same frequency as the frequency of the beam, and generating a second interference light beam by superimposing the comparison light beam and the second reference light beam. A second beam superimposing means, and receiving a second interference light beam to generate a second interference signal indicating an interference state between the comparison light beam and the second reference light beam. A second light receiving means for obtaining, wherein the refractive index calculating means maintains the same phase state of the first interference signal with respect to the second interference signal during scanning by the scanning means, 2. The refractive index measuring device according to claim 1, wherein a refractive index distribution or a refractive index of a sample placed in the sample placement section is obtained based on an adjustment amount of an optical path length by an optical path length varying unit. 9. The scanning means for moving an object light beam incident on a sample placed on the sample placement section in a direction crossing an optical path of the object light beam, wherein the scanning means has passed the sample placement section. A first reflecting means for returning the object light beam on the same optical path as the outward path, wherein the scanning means constitutes a descan on a return path in which the object light beam is returned by the first reflecting means. The refractive index measuring device according to claim 8, wherein: 10. The scanning means for moving an object light beam incident on a sample placed on the sample placement section in a direction crossing an optical path of the object light beam,
Moving the comparison light beam split from the object light beam by the second beam splitting means in a direction intersecting the optical path of the comparison light beam; A second reflecting means which is turned back on the optical path of the object light beam scanning means, wherein the scanning means constitutes a descan on the return path of the object light beam obtained by turning the object light beam back by the first reflecting means, and the comparison light 10. The refractive index measuring device according to claim 6, wherein a descan is formed on the return path of the comparison light beam obtained by folding the beam by the second reflection means. 11. A light source for emitting a predetermined low coherence light beam, beam splitting means for splitting a light beam emitted from the light source into an object light beam and a reference light beam, and the sample to be measured is the object A sample placement unit detachably disposed on an optical path of a light beam, and a scanning unit configured to scan, by the object light beam, a sample disposed on the sample placement unit in a direction intersecting the optical path of the object light beam; By superimposing the reference light beam and the object light beam that has passed through the sample placement unit on each other, a beam superimposing unit that generates an interference light beam, and by receiving the interference light beam, the object light beam A light receiving unit that obtains a first interference signal representing an interference state with the reference light beam; and the sample based on a phase change of the first interference signal during scanning by the scanning unit. A refractive index calculating device for calculating a refractive index distribution or a refractive index of the sample disposed in the disposing portion. 12. The scanning unit moves an object light beam incident on a sample placed on the sample placement unit in a direction crossing an optical path of the object light beam, and passes through the sample placement unit. Reflecting means for turning the object light beam back on the same optical path as the outward path, wherein the scanning means constitutes descanning on the return path where the object light beam is turned back by the reflecting means. 12. The refractive index measuring device according to item 11. 13. A second beam splitting unit for splitting, from the object light beam, a comparison light beam having the same frequency as the frequency of the object light beam when passing through the sample placement unit, Third beam splitting means for splitting a second reference light beam having the same frequency as the frequency of the reference light beam when being superimposed on the object light beam by the first beam superimposing means; A second beam superimposing unit configured to generate a second interference light beam by superimposing the second reference light beam; and receiving the second interference light beam, the comparison light beam and the second light beam. A second light receiving unit that obtains a second interference signal indicating an interference state with the second reference light beam, wherein the refractive index calculation unit performs the second interference signal during scanning by the scanning unit. Against Serial based on a phase change of the first interference signal, the refractive index measuring apparatus according to claim 11, characterized in that to determine the refractive index distribution or a refractive index of the sample disposed in the sample placement part. 14. The scanning means moves an object light beam incident on a sample placed on the sample placement section in a direction intersecting the optical path of the object light beam, and passes through the sample placement section. A first reflecting means for returning the object light beam on the same optical path as the outward path, wherein the scanning means constitutes a descan on a return path in which the object light beam is returned by the first reflecting means. 14. The refractive index measuring device according to claim 13, wherein: 15. The apparatus according to claim 14, wherein the second beam splitting means includes an optical plate for splitting the object light beam incident on the sample placement portion into a transmitted light beam and a reflected light beam. Refractive index measuring device.