WO2017030194A1

WO2017030194A1 - Observation system

Info

Publication number: WO2017030194A1
Application number: PCT/JP2016/074265
Authority: WO
Inventors: 深臼杵; 智裕 ▲高▼田
Original assignee: 国立大学法人静岡大学
Priority date: 2015-08-19
Filing date: 2016-08-19
Publication date: 2017-02-23
Also published as: JP6714917B2; JPWO2017030194A1

Abstract

The purpose of the present invention is to provide an inexpensive system whereby a correct high-resolution image can be stably obtained even when a disturbance occurs. The present invention is provided with a light source 2 having a coherence length in a predetermined range, first and second light paths 3, 4 leading first and second lights from the light source 2 to an observation object S, an interference fringe generating part 6 for generating a first interference fringe resulting from the first and second lights, a measurement part 12 for measuring the light intensity distribution of a second interference fringe resulting from first and second reflected lights reflected by the observation object S in the first and second lights, and a computation part 13 for calculating an amount of phase shift in the first interference fringe on the basis of an amount of displacement of the light intensity distribution of the second interference fringe.

Description

Observation system

The present invention relates to an observation system.

Conventionally, as a microscopic method that realizes high spatial resolution using an optical microscope, a modulated illumination microscopic method (SIM) is known. In the modulated illumination microscope, when observation such as measurement, appearance inspection, etc. is performed on an observation object, the observation object is irradiated with light having a light intensity distribution in a striped pattern (modulation illumination). Information of spatial frequency higher than the diffraction limit of the optical microscope is shifted to the low frequency side. Then, an image distribution having the information is acquired by an optical microscope, and signal processing is performed on the image distribution to reproduce high-frequency information. In this way, a high resolution image can be obtained using the modulated illumination microscope.

As an observation system using the modulated illumination microscope, for example, Non-Patent Document 1 discloses a laser light source, an optical path for guiding a part of laser light emitted from the laser light source to the observation target, and the remainder of the laser light as the observation target. An observation system is disclosed that includes another optical path that leads to an optical path and a stage that expands and contracts the optical path length of the optical path. In this observation system, an interference fringe is generated on an observation object by causing a part and the remainder of the laser light to interfere, and the light scattered by the observation object is imaged, and the observation object is based on the captured image distribution. The shape distribution is calculated.

By the way, this observation system operates the stage to increase or decrease the optical path length difference between the optical paths in order to generate interference fringes having different phases. However, since this observation system uses a laser light source having a long coherent length as the light source, it is difficult to distinguish between the interference fringes and the interference fringes generated each time the phase shifts by one wavelength (wavelength). Uncertainty for each). On the other hand, in order to correctly calculate the shape distribution of the observation object, it is necessary to accurately detect the phase shift amount of the interference fringes. Therefore, this observation system uses a piezo actuator to drive the stage so that the stage can be precisely driven with a small amount of displacement, and the phase of the interference fringes is accurately controlled to accurately detect the amount of phase shift. is doing.

By the way, since the modulated illumination microscope method is an observation method using an optical microscope, it has the advantages that the time required for observation is shorter than other microscope methods and that non-destructive inspection is possible. Therefore, it is desired to be carried out, for example, at a factory production site. However, in production sites and the like, disturbances such as vibrations and temperature changes are more likely to occur than in laboratories and the like. For this reason, in the above observation system, for example, the optical path difference of each optical path may fluctuate due to vibration, or a temperature drift may occur due to a temperature change. In such a case, the interference fringe and the observation object move relatively, and it becomes difficult to accurately detect the phase shift amount of the interference fringe due to the uncertainty for each wavelength. It becomes difficult to stably obtain a correct high-resolution image. For these reasons, the modulated illumination microscopy is only performed in fluorescence observation in the biological field in laboratories where disturbances are unlikely to occur.

In addition, the modulation illumination microscope generally requires a high-precision positioning mechanism such as a piezo actuator in order to detect the phase of the interference fringes with high accuracy, so that it is generally expensive and is desired to be provided at a lower cost. .

One embodiment of the present invention has been made in view of the above problems, and provides an observation system that is inexpensive and can stably obtain a correct high-resolution image even when a disturbance occurs. With the goal.

In order to solve the above-described problem, an observation system according to one aspect of the present invention includes a light source having a coherent length in a predetermined range, a first light having a first optical path length and part of light emitted from the light source. A first optical path that guides the light from the light source to the observation object, a second optical path that has a second optical path length and guides the second light that is the remainder of the light from the light source to the observation object, and the first light And an interference fringe generator for causing the second light to interfere with each other to generate a first interference fringe on the observation object, a first reflected light reflected by the observation object in the first light, A measuring unit that measures the light intensity distribution of the second interference fringe generated by the interference with the second reflected light reflected by the observation object of the two lights, and an arithmetic unit connected to the measuring unit, The computing unit includes a phase in the first interference fringe based on the amount of displacement of the light intensity distribution in the second interference fringe. And calculates the shift amount.

According to such an observation system, the first light guided from the light source to the observation target by the first optical path and the second light guided from the light source to the observation target by the second optical path interfere with each other. A first interference fringe is generated by interference by the fringe generation unit. On the other hand, the first reflected light reflected by the observation object in the first light and the second reflected light reflected by the observation object in the second light interfere with each other to cause the second interference. A fringe is generated, and the light intensity distribution of the second interference fringe is measured by the measurement unit. Since the light source has a coherent length in a predetermined range, the light intensity distribution of the second interference fringe has one peak in its envelope. The amount of displacement of the light intensity distribution of the second interference fringe is obtained by measuring the amount of displacement of the peak of the envelope. Therefore, even when the phase of the first interference fringe is shifted by one wavelength or more, the envelope in the light intensity distribution of the second interference fringe is not affected by the uncertainty of each wavelength in the first interference fringe. The phase shift amount of the first interference fringes can be detected based on the displacement amount of the line peak. Further, even when a disturbance such as vibration or temperature change occurs, the phase shift amount of the first interference fringes can be detected with high accuracy. Thereby, the calculating part can calculate correctly the shape distribution of an observation object. Furthermore, this observation system does not require a high-precision positioning mechanism such as a piezo actuator in order to accurately detect the phase shift amount of the first interference fringes, and as an example, a relatively high-speed actuator such as an actuator using a stepping motor. Since a positioning mechanism with low accuracy can be used, it is provided at low cost. As described above, an inexpensive system can stably obtain a correct high-resolution image even when a disturbance occurs.

According to one aspect of the present invention, an inexpensive system can stably obtain a correct high-resolution image even when a disturbance occurs.

It is a schematic structure figure showing an observation system concerning an embodiment of the present invention. It is a schematic side view which shows the interference fringe production | generation part of FIG. It is a schematic side view which shows the interference fringe production | generation part of FIG. It is a figure which shows the shape characteristic of the 1st interference fringe by low coherence light. It is the elements on larger scale of FIG. It is a figure which shows the light intensity distribution measured by the measurement part. It is a figure which shows the pass band of the microscope in frequency space. It is a figure which shows the pass band which moved to 3 directions in the frequency space by modulated illumination. It is a figure which shows an example of an observation target object. It is a figure which shows the image distribution imaged by the imaging part. It is a figure which shows the image which performed the Fourier-transform with respect to the image distribution of FIG. It is a figure which shows the image which frequency-separated by the interference type information with respect to the image of FIG. It is a figure which shows the high-resolution image which performed image reconstruction. It is a schematic block diagram which shows the conventional observation system.

Hereinafter, preferred embodiments of the observation system according to the present invention will be described in detail with reference to the drawings. In the description of the drawings, the same or corresponding parts are denoted by the same reference numerals, and redundant description is omitted.

FIG. 1 is a schematic configuration diagram showing an observation system according to an embodiment of the present invention, and FIGS. 2 and 3 are schematic side views showing an interference fringe generation unit of FIG. As shown in FIG. 1, the observation system 1 is a modulation illumination microscope capable of obtaining a high-resolution image of the observation object S using a modulation illumination microscope. The observation system 1 includes a light source 2, a first optical path 3 and a second optical path 4 that guide light emitted from the light source 2, and a first optical path length adjustment unit 5 provided in the middle of the second optical path 4. The interference fringe generator 6 provided at the end of the first optical path 3 and the second optical path 4, the turntable 7 on which the observation object S is placed, and the observation object S placed on the turntable The third optical path 9 and the fourth optical path 10 for guiding the light output from the interference fringe generator 6, and the second optical path length adjustment provided in the middle of the fourth optical path 10 Unit 11, measurement unit 12 provided at the end of third optical path 9 and fourth optical path 10, and calculation unit that calculates the shape distribution of observation object S based on information from imaging unit 8 and measurement unit 12 13.

The light source 2 is a low coherence light source. Light (low coherence light) emitted from a low coherence light source has a wider spectral width and a shorter coherence distance (coherent length) than, for example, laser light. That is, the light source 2 is a light source having a short coherent length (for example, 1 μm or more and 100 μm or less) compared to a laser light source having a long (for example, about several tens of meters) coherent length. The light source 2 can be, for example, an SLD (Super Luminescent Diode) light source, an LED (Light Emitting Diode) light source, or the like. In the present embodiment, the light source 2 is an SLD having a wavelength of 669 nm, a full width at half maximum of 7 nm, and a coherent length of 32 μm.

The first optical path 3 is an optical path that has a first optical path length and guides the first light, which is a part of the light emitted from the light source 2, from the light source 2 to the observation object S. The second optical path 4 has a second optical path length and is an optical path that guides the second light, which is the remainder of the light emitted from the light source 2, from the light source 2 to the observation object S. The first light and the second light are emitted from the light source 2 and branched from each other by the beam splitter 20 provided on the optical path, and reach the interference fringe generation unit 6. The first light and the second light have the same optical path between the light source 2 and the beam splitter 20 without being distinguished from each other. Here, the first light is light that passes through the beam splitter 20, and the second light is light that is reflected by the beam splitter 20. The first optical path 3 and the second optical path 4 include a collimating lens 21 between the light source 2 and the beam splitter 20. Thereby, the first light and the second light traveling respectively in the first optical path 3 and the second optical path 4 are converted into parallel light by the collimating lens 21.

In the first optical path 3, another beam splitter 22 is provided on the exit side of the beam splitter 20. The first optical path 3 has an optical path 3 a of light reflected by the beam splitter 22 on the emission side of the beam splitter 22. Thus, the first light traveling in the first optical path 3 is transmitted through the beam splitter 20, reflected by the beam splitter 22, and then input to the interference fringe generator 6.

The second light traveling in the second optical path 4 reaches the first optical path length adjustment unit 5 on the emission side of the beam splitter 20, is turned back by the first optical path length adjustment unit 5, and is again beam splitter 20. To reach. The second optical path 4 has an optical path 4 a of the second light transmitted through the beam splitter 20 on the light output side of the folded beam of the beam splitter 20. As a result, the second light traveling in the second optical path 4 is reflected once by the beam splitter 20, turned back by the first optical path length adjusting unit 5, then transmitted through the beam splitter 20, and then interfered. Input to the fringe generator 6. As described above, since the first light and the second light are both transmitted through the beam splitter and reflected once, when reaching the interference fringe generator 6, the light intensity is substantially equal to each other. Yes.

The first optical path length adjustment unit 5 includes a mirror 23 and a modulator 24 that moves the mirror 23. The first optical path length adjustment unit 5 reflects the second light traveling in the second optical path 4 by the mirror 23 and folds it, and moves the mirror 23 by the modulator 24 to expand and contract the second optical path length. Mechanism.

The modulator 24 reciprocates the mirror 23 along the second optical path 4. As a result, the modulator 24 expands and contracts the distance between the beam splitter 20 and the mirror 23, and as a result, expands and contracts the second optical path length. The modulator 24 is not limited to a modulator capable of controlling the displacement amount with extremely high accuracy, such as a piezo actuator, but may be an actuator using a stepping motor whose displacement control accuracy is lower than that of the piezo actuator or the like. it can. The modulator 24 is not limited to an actuator using a stepping motor, and may be any mechanism that can move the mirror 23 along the second optical path 4.

The turntable 7 includes a stage that holds the observation object S, and is configured so that the stage is positioned in a horizontal plane (XY plane in the drawing). The turntable 7 holds the observation object S on the stage so that the surface of the observation object S to be observed faces upward. The turntable 7 allows the stage to rotate about the axis A in the vertical direction (Z-axis direction in the drawing). Therefore, the observation object S placed on the stage is held by the stage so as to be rotatable around the axis A in the vertical direction. Note that the axis A is not necessarily limited to the vertical direction, and may be any direction from the observation object S toward the imaging unit 8. In this case, the turntable 7 may be arranged so that the stage is positioned on a plane perpendicular to the axis A and the surface of the observation object S to be observed faces the imaging unit 8 side.

The interference fringe generation unit 6 causes the first light and the second light to interfere with each other to generate a first interference fringe on the observation object S. The first interference fringes generated by the interference fringe generator 6 are used as modulated illumination in the observation system 1 (that is, standing wave illumination using light interference). FIG. 4 is a diagram showing the shape characteristics of the first interference fringes due to the low coherence light, and FIG. 5 is a partially enlarged view of FIG. Here, since a low-coherence light source is used as the light source 2, the first interference fringes are generated in a range of about the coherent length of the low-coherence light source (for example, a range of about 30 μm) (see FIG. 4). The intensity changes at a constant period (see FIG. 5). The interference fringe generation unit 6 includes a first light projecting unit 30, a first light receiving unit 31, a second light projecting unit 32, and a second light receiving unit 33 arranged so as to surround the turntable 7.

The first light projecting unit 30 is provided at the end of the first optical path 3 and projects the first light to the observation object S from obliquely above. The first light projecting unit 30 includes a mirror 30a and a mirror 30b. The first light traveling in the substantially horizontal direction is reflected upward in the substantially vertical direction by the mirror 30a and then reflected obliquely downward by the mirror 30b. And light is projected onto the observation object S. As an example, the first light projecting unit 30 has an incident angle with respect to the observation object S (that is, an angle formed between the optical path of the first light projected onto the observation object S and the axis A). The first light is projected so as to be 45 deg. The lower limit of the incident angle of the first light is the smallest angle in a range where the optical path of the first light is not hindered by the objective lens 34. Moreover, the 1st light projection part 30 is not limited to the structure using a mirror, For example, the structure which light-projects from the diagonally upper direction with respect to the observation object S by bending the 1st optical path 3 with an optical fiber. It is good.

The first light receiving unit 31 is provided at the start end of a third optical path 9 (details will be described later), and the first reflected light reflected by the observation object S in the first light is used as an observation target. Light is received obliquely above the object S. The first light receiving unit 31 is arranged at a position facing the first light projecting unit 30 with the observation object S interposed therebetween. The first light receiving unit 31 includes a mirror 31a and a mirror 31b. After the first reflected light received from the observation object S is reflected downward in the substantially vertical direction by the mirror 31a, the first light receiving unit 31 is substantially horizontal by the mirror 31b. And output to the third optical path 9. Note that the first light receiving unit 31 is not limited to a configuration using a mirror. For example, the first light receiving unit 31 receives the first reflected light obliquely upward with respect to the observation object S, and bends it with an optical fiber, thereby forming the third light receiving unit 31. It is good also as a structure output to the optical path 9 of this.

The second light projecting unit 32 is provided at the end of the second optical path 4 and projects the second light to the observation object S from obliquely above. The second light projecting unit 32 includes a mirror 32a and a mirror 32b. The second light traveling in the substantially horizontal direction is reflected upward in the substantially vertical direction by the mirror 32a and then reflected obliquely downward by the mirror 32b. And light is projected onto the observation object S. As an example, the second light projecting unit 32 has an incident angle with respect to the observation object S (that is, an angle formed between the second light projected on the observation object S and the axis A) is 45 deg. The second light is projected so as to be. Note that the lower limit of the incident angle of the second light is the minimum angle in a range where the optical path of the second light is not hindered by the objective lens 34. Moreover, the 2nd light projection part 32 is not limited to the structure using a mirror, For example, the structure which light-projects from the diagonally upper direction with respect to the observation object S by bending the 2nd optical path 4 with an optical fiber. It is good.

The second light receiving unit 33 is provided at the start end of the fourth optical path 10 (details will be described later), and the second reflected light reflected by the observation target S in the second light is used as the observation target. Light is received obliquely above the object S. The second light receiving unit 33 is disposed at a position facing the second light projecting unit 32 with the observation object S interposed therebetween. The second light receiving unit 33 includes a mirror 33a and a mirror 33b. The second reflected light received from the observation object S is reflected substantially downward in the vertical direction by the mirror 33a, and then substantially horizontal by the mirror 33b. And output to the fourth optical path 10. Note that the second light receiving unit 33 is not limited to a configuration using a mirror. For example, the second light receiving unit 33 receives the second reflected light obliquely upward with respect to the observation object S, and bends it with an optical fiber. It is good also as a structure output to the optical path 10 of this.

In the interference fringe generation unit 6, a first direction in which the first light travels from the first light projecting unit 30 to the first light receiving unit 31 (X-axis direction in the drawing), and a second light projecting unit 32. The second direction (Y-axis direction in the figure) in which the second light travels from the second light receiving unit 33 to the second light-receiving unit 33 is substantially perpendicular to the observation object S in a plan view (Z-axis direction view in the figure). . In the interference fringe generator 6, the

mirrors

30a, 30b, 31a, 31b, 32a, 32b, 33a, 33b provided in each light projecting unit and each light receiving unit are movable, and the optimum position of the observation object S is set. In addition, it is possible to project the first light and the second light.

The first light and the second light projected onto the observation object S by the first light projecting unit 30 and the second light projecting unit 32 respectively cause the first interference fringes on the observation object S. Generate. The first optical path 3 and the second optical path 4 have a first optical path length and a second optical path length, respectively, and the first interference fringes are the first optical path length and the second optical path length. The phase differs depending on the optical path length difference. Accordingly, when the second optical path length is expanded and contracted by the operation of the first optical path length adjusting unit 5, the optical path length difference between the first optical path length and the second optical path length is expanded and contracted, and the phase of the first interference fringe is shifted. To do.

The imaging unit 8 captures an image distribution of light scattered by the observation object S in the first light and the second light presenting the first interference fringes. The imaging unit 8 is disposed above the turntable 7 in the Z-axis direction, and images the observation object S from above. The imaging unit 8 includes an objective lens 34 and an optical microscope 35 for enlarging an image of scattered light, and a detector 36 that detects the enlarged image of scattered light as an image distribution. As the objective lens 34, for example, an objective lens of 10 times (NA 0.28), 20 times (NA 0.28), 50 times (NA 0.42), 100 times (NA 0.55) or the like can be suitably used. As the detector 36, for example, a CCD camera or the like can be used.

The third optical path 9 has a third optical path length, and is an optical path that guides the first reflected light reflected by the observation object S in the first light to the measurement unit 12. The fourth optical path 10 has a fourth optical path length, and is an optical path that guides the second reflected light reflected by the observation object S in the second light to the measurement unit 12.

In the third optical path 9, a first light receiving portion 31 is provided at the start end, and a beam splitter 26 is provided on the exit side. The third optical path 9 has an optical path 9 a for the first reflected light reflected by the beam splitter 26 on the emission side of the beam splitter 26. The third optical path 9 is provided with another beam splitter 27 on the emission side of the beam splitter 26. The third optical path 9 has an optical path of the first reflected light transmitted through the beam splitter 27 on the emission side of the beam splitter 27. As a result, the first reflected light traveling in the third optical path 9 is reflected by the beam splitter 26, passes through the beam splitter 27, and is then input to the measuring unit 12.

In the fourth optical path 10, a second light receiving portion 33 is provided at the start end, and a beam splitter 27 is provided on the emission side. The fourth optical path 10 has an optical path 10 a of second reflected light that has passed through the beam splitter 27 on the emission side of the beam splitter 27. Further, the second reflected light traveling in the fourth optical path 10 reaches the second optical path length adjustment unit 11 on the emission side of the beam splitter 27, is turned back by the second optical path length adjustment unit 11, and again. It reaches the beam splitter 27. The fourth optical path 10 has an optical path of the second reflected light reflected by the beam splitter 27 on the light output side of the folded beam splitter 27. As a result, the second reflected light traveling in the fourth optical path 10 is transmitted once through the beam splitter 27, turned back by the second optical path length adjusting unit 11, then reflected by the beam splitter 27, and then Are input to the measurement unit 12. As described above, since both the first reflected light and the second reflected light are once transmitted through the beam splitter and reflected once, when reaching the measurement unit 12, the light intensity is substantially equal to each other. Yes.

The second optical path length adjusting unit 11 has a movable mirror 25. The second optical path length adjusting unit 11 is a mechanism for reflecting the second reflected light traveling in the fourth optical path 10 by the mirror 25 and turning it back, and moving the mirror 25 to expand and contract the fourth optical path length. is there. The second optical path length adjusting unit 11 expands and contracts the distance between the beam splitter 27 and the mirror 25 by moving the mirror 25, and as a result, expands and contracts the fourth optical path length. Note that the second optical path length adjustment unit 11 may be configured to manually move the mirror 23 or may be configured to be electrically performed using an actuator using a stepping motor or the like.

The measurement unit 12 is provided at the end of the third optical path 9 and the fourth optical path 10, and measures the light intensity distribution of the second interference fringes generated by the interference of the first reflected light and the second reflected light. To do. In the present embodiment, the measurement unit 12 is an area sensor that can two-dimensionally measure the light intensity distribution of the second interference fringes.

The second interference fringe has a light intensity according to the optical path difference between the optical path length from the light source 2 to the measurement unit 12 in the first light and the optical path length from the light source 2 to the measurement unit 12 in the second light. The distribution is displaced in the phase direction (that is, the direction orthogonal to each stripe). Therefore, when a change occurs in the optical path difference between the optical path length from the light source 2 to the measurement unit 12 in the first light and the optical path length from the light source 2 to the measurement unit 12 in the second light, the amount of change Can be calculated based on the amount of displacement from the reference position of the light intensity distribution of the second interference fringes. FIG. 6 is a diagram illustrating the light intensity distribution measured by the measurement unit. FIG. 6 shows the displacement of the light intensity distribution of the second interference fringes when the second optical path length is expanded and contracted by the first optical path length adjustment unit 5. 6A shows the light intensity distribution of the second interference fringes when the second optical path length is an arbitrary value (initial value). FIG. 6B shows the second optical path length. FIG. 6C shows the light intensity distribution of the second interference fringe when the first optical path length adjustment unit 5 is operated so that the optical path length changes by 0.1 μm from the initial value. 2 shows the light intensity distribution of the second interference fringes when the first optical path length adjustment unit 5 is operated so that the optical path length changes by 0.2 μm from the initial value.

As described above, when the third optical path length and the fourth optical path length do not change, the optical paths having the first optical path length and the second optical path length based on the displacement amount of the light intensity distribution of the second interference fringes. The change amount of the length difference can be calculated. Further, the phase of the first interference fringe is shifted according to the amount of change in the optical path length difference between the first optical path length and the second optical path length. As described above, an accurate shift amount of the phase of the first interference fringe can be obtained by measuring the displacement amount of the light intensity distribution of the second interference fringe.

The calculation unit 13 is connected to the imaging unit 8 and the measurement unit 12 and acquires the image distribution captured by the imaging unit 8 and the light intensity distribution of the second interference fringe measured by the measurement unit 12. Then, the calculation unit 13 calculates the phase shift amount in the first interference fringe based on the displacement amount of the light intensity distribution in the second interference fringe. The computing unit 13 also includes a phase corresponding to the calculated phase shift amount in the first interference fringe, and an observation target of the first light and the second light presenting the first interference fringe having the phase. Based on the image distribution of the light scattered by the object S, the shape distribution of the observation object S is calculated.

Specifically, the calculation unit 13 performs the following process to calculate the shape distribution of the observation object S based on the modulated illumination microscope. FIG. 7 is a diagram showing the passband of the microscope in the frequency space, and FIG. 8 is a diagram showing the passband moved in three directions in the frequency space by the modulated illumination. In FIG. 7, k _x and k _y are frequency space coordinate systems, and conceptually indicate that the inside of a circle is a frequency that can be resolved with a microscope. FIG. 7A shows the pass band of the microscope at a spatial frequency, and shows that resolution can be performed up to a frequency separated by k ₁ from the origin. FIG. 7B shows the movement of the pass band due to the modulated illumination. When the first interference fringe generated by the interference fringe generation unit 6 is irradiated onto the observation object S, the passband is from the origin of the frequency space coordinate system in the image distribution of the light scattered by the observation object S. It has been moved to the k ₂ apart position. Thus, the resolution of the microscope, while so that the resolution k _{1 +} k ₂ in the arrow positive direction of k ₂ is increased, resolution k ₁ -k ₂ in the arrow negative direction k ₂ is lowered. As described above, when only a striped pattern in one direction is used as the first interference fringe, only the pass band moves and a high-resolution image cannot be obtained as a whole. Therefore, as shown in FIG. 8, in the observation system 1, a stripe pattern in a plurality of directions (here, three directions) is used as the first interference fringe, and the pass band is moved in both positive and negative directions. As a result, the passband is expanded in almost all directions in the frequency space coordinate system, and the resolution of the microscope is improved.

However, the image distribution obtained in this way is a moire signal obtained by the moire effect, and a high-frequency component cannot be obtained directly from this image distribution. Therefore, image reconstruction processing is performed by solving the following equation (1). Here, k is the spatial frequency, _{f m} is the spatial frequency of the modulation _{_{lighting, θ 1, θ 2, θ}} 3 are mutually different three phases of the modulation illumination, D (k) is an imaging zone, OFT (k) Represents an optical transfer function, and S (k) represents an observation object band. OFT (k) represents a point spread function determined by the objective lens 34 of the microscope, the light source wavelength, and the like in the frequency space by Fourier transform. According to the following formula (1), information of the observation target band was translated by ± f _m to the high frequency side is obtained. Since the following equation (1) includes three unknowns S (k), S (k−f _m ), and S (k + f _m ), three image distributions corresponding to the three modulated illuminations are acquired. Thus, D ₁ (k), D ₂ (k), and D ₃ (k) are obtained, and the three equations are simultaneous. By appropriately weighting and adding S (k), S (k−f _m ), and S (k + f _m ) thus obtained, a high resolution image is reconstructed by numerical calculation. From the above, it can be seen that it is necessary to correctly detect the phase of the first interference fringe (modulated illumination) in order to obtain a high resolution image using the modulated illumination microscope.

As described above, in order to solve the above equation (1), three different phases θ ₁ , θ ₂ , and θ ₃ of the modulated illumination are necessary. The measurement unit 12 continues to measure the light intensity distribution until the calculation unit 13 calculates the shift amounts of the first interference fringes corresponding to the _three different phases θ ₁ , θ ₂ , and θ ₃ of the modulated illumination. Do (repeat). Thus, for example, even when a plurality of the _three phases θ ₁ , θ ₂ , θ ₃ corresponding to the shift amounts calculated by the calculation unit 13 are in the same phase, the equation (1) is solved. The measurement unit 12 continues to measure the light intensity distribution until three different phases necessary for the above are aligned.

Subsequently, a specific example of the observation result of the observation object S by the observation system 1 will be described.

FIG. 9 is a diagram showing an example of the observation object S. As shown in FIG. 9, the observation object S was observed using a group of square dots having two kinds of pitches. This observation object S is obtained by periodically arranging protrusions on a flat plate. Each protrusion has a cubic shape with one side indicated by L1, L2, etc. in the figure of 0.2 μm. The protrusions form dot pairs (a pair of dots) whose pitch indicated by L3 in the figure is 0.4 μm, and these dot pairs have a pitch indicated by L4 and L5 in the figure of 2.2 μm. Are arranged.

As the first optical path length adjustment unit 5, an actuator using a stepping motor was used. An actuator using this stepping motor has one pulse of 2 μm and can be divided into pulses. Here, the pulse was divided into 20 to make one pulse 0.1 μm. The wavelength λ of the light source 2 was 669 nm, and the incident angle θ was 45 deg. As described above, when the actuator using the stepping motor is operated so that the actuator using the stepping motor changes by one pulse (0.1 μm) and two pulses (0.2 μm) from the initial value, the first interference The operation value (indicated value) of the shift amount of the fringe phase was calculated as 1.33 rad and 2.66 rad, respectively. On the other hand, the phase shift amounts of the first interference fringes detected based on the displacement amount of the light intensity distribution of the second interference fringes at this time were 6.33 rad and 4.98 rad, respectively. Thus, it was confirmed that the actual movement amount of the actuator using the stepping motor is different from the operation value.

In order to perform image reconstruction, it is only necessary to know the phase of the first interference fringes when the imaging unit 8 captures the image distribution of scattered light. However, in order to stably calculate the correct shift amount of the phase of the first interference fringe based on the operation value of the first optical path length adjustment unit 5, the first optical path length and the second optical path length are increased. It can be seen that it is necessary to maintain accuracy and to eliminate disturbances such as vibration of the support table.

On the other hand, in the observation system 1, the phase of the first interference fringes when the image distribution of scattered light is captured can be calculated by the measurement unit 12. Therefore, in the observation system 1, if the imaging of the scattered light image distribution by the imaging unit 8 and the measurement of the light intensity distribution of the second interference fringe by the measurement unit 12 are synchronized, image reconstruction is performed. be able to. Here, “synchronization” means that the measurement unit 12 measures the light intensity distribution of the second interference fringes when the image distribution of the scattered light is imaged by the imaging unit 8. That is, the exposure (shutter) timing of the measurement unit 12 is aligned.

Therefore, the observation system 1 does not require a high-precision positioning mechanism such as a piezo actuator in order to accurately detect the phase shift amount of the first interference fringes, and eliminates the influence of disturbance such as vibration and temperature change. Easy to do. As described above, the observation system 1 is inexpensive and can stably obtain a correct high-resolution image even when a disturbance occurs.

FIG. 10 is a diagram showing an image distribution imaged by the imaging unit. FIG. 10 divides the low coherence light emitted from the light source 2 into a first light traveling in the first optical path 3 and a second light traveling in the second optical path 4, and an interference fringe generation unit 6 generates a first interference fringe on the observation object S, and captures an image distribution of the light scattered by the observation object S among the first light and the second light presenting the first interference fringe. The image is taken by the unit 8. FIG. 10A shows an image distribution when the second optical path length is an arbitrary value (initial value) (that is, the state of FIG. 6A). FIG. 10B shows an image when the first optical path length adjustment unit 5 is operated so that the second optical path length changes by 0.1 μm from the initial value (that is, the state of FIG. 6B). Distribution. FIG. 10C shows an image when the first optical path length adjustment unit 5 is operated so that the second optical path length changes by 0.2 μm from the initial value (that is, the state of FIG. 6C). Distribution. In FIG. 10, the dots can be partially resolved by the moire effect, but the overall resolution is not improved. FIG. 11 is a diagram showing an image obtained by performing Fourier transform on the image distribution of FIG. (A) to (c) in FIG. 11 are images corresponding to (a) to (c) in FIG. 10, respectively.

FIG. 12 is a diagram illustrating an image obtained by performing frequency separation on the image of FIG. 11 based on interference system information. That is, FIG. 12 is calculated from the image distributions shown in FIG. 11 and the phase of the first interference fringes calculated based on the displacement amount of the light intensity distribution of the second interference fringes corresponding to these image distributions. These frequency separated images correspond to S (k), S (k−f _m ), and S (k + f _m ) in the above equation (1). (A) to (c) in FIG. 12 are images corresponding to (a) to (c) in FIG. 11, respectively. Compared with the image of FIG. 11, the image of FIG. 12 is clearly observed with the high frequency components separated in FIGS. 12B and 12C, while the light intensity near the origin is reduced. .

FIG. 13 is a diagram showing a high-resolution image that has undergone image reconstruction. That is, the image of FIG. 13 is an image obtained by adding the images of (a), (b), and (c) of FIG. In the image of FIG. 13, for the observation object S shown in FIG. 9, the dot pairs indicated by L3 are correctly separated, and the pitches indicated by L4 and L5 are also correctly represented. Therefore, it can be seen that a correct high-resolution image was obtained.

Here, a conventional observation system will be described. FIG. 14 is a schematic configuration diagram showing a conventional observation system. As shown in FIG. 14, in the conventional observation system, a laser light source having a long coherent length is used as the light source 102, and the optical path length adjusting unit 105 that expands and contracts the optical path length of the second optical path 4 is used by the piezo actuator 124. A mechanism for reciprocating the mirror 23 along the second optical path 4 is used.

In such a conventional observation system, the piezo actuator 124 is used for the optical path length adjustment unit 137 in order to accurately detect the phase shift amount of the first interference fringes. However, in production sites and the like, disturbances such as vibrations and temperature changes are more likely to occur than in laboratories and the like. For example, optical path differences between optical paths may vary due to vibrations, and temperature drifts may occur due to temperature changes. In this case, the interference fringe and the observation object move relatively, and it becomes difficult to detect the amount of phase shift of the interference fringe with high accuracy due to uncertainty for each wavelength. Therefore, it has been difficult for the conventional observation system to stably obtain a correct high-resolution image.

In the conventional observation system, as the interference fringe generation unit 106, a light projecting unit 130 that projects the first light onto the observation object S and a position that faces the light projecting unit 130 via the observation object S are provided. A mechanism provided with a light projecting unit 132 that is disposed and projects the second light onto the observation object S is used. Further, in the conventional observation system, a mirror 128 and an optical path length adjusting unit 137 that expands and contracts the first optical path length are added to the first optical path 3 with respect to the observation system 1, and a mirror 129 is added to the second optical path 4. Has been added. The optical path length adjustment unit 137 is a mechanism that expands and contracts the first optical path length by moving the mirror 138. Further, the conventional observation system includes a fixed base for fixing and holding the observation object S instead of the turntable 7.

In the observation system 1 according to the present embodiment, the first light guided from the light source 2 to the observation target S by the first optical path 3 and the second light path 4 from the light source 2 to the observation target S are guided. The second light interferes with the interference fringe generation unit 6 to generate a first interference fringe. Then, the image distribution of the light scattered by the observation object S out of the first light and the second light presenting the first interference fringes is imaged by the imaging unit 8. On the other hand, the first reflected light reflected by the observation object S in the first light and guided by the third optical path 9 is reflected by the observation object S in the second light and the fourth light. The second reflected light guided by the optical path 10 interferes to generate a second interference fringe. Then, the light intensity distribution of the second interference fringe is measured by the measurement unit 12. Here, when the second optical path length is expanded or contracted by the first optical path length adjusting unit 5, the phase of the first interference fringe is shifted and the light intensity distribution of the second interference fringe is displaced. Since the light source 2 has a coherent length within a predetermined range, the light intensity distribution of the second interference fringe has one peak in its envelope. The amount of displacement of the light intensity distribution of the second interference fringe is obtained by measuring the amount of displacement of the peak of the envelope. Therefore, even when the phase of the first interference fringe is shifted by one wavelength or more, the envelope in the light intensity distribution of the second interference fringe is not affected by the uncertainty of each wavelength in the first interference fringe. The phase shift amount of the first interference fringes can be detected based on the displacement amount of the line peak. Further, even when a disturbance such as vibration or temperature change occurs, the phase shift amount of the first interference fringes can be detected with high accuracy. Thereby, the calculating part 13 can calculate the shape distribution of the observation object S correctly. Furthermore, the observation system 1 does not require a high-precision positioning mechanism such as a piezo actuator in order to accurately detect the phase shift amount of the first interference fringes, and as an example, a relatively high degree of actuator such as an actuator using a stepping motor. Since a positioning mechanism with low accuracy can be used, it is provided at low cost. As described above, it is possible to stably obtain a correct high-resolution image at low cost even when a disturbance occurs.

In addition, the calculation unit 13 calculates the shape distribution of the observation object S based on the three different phases and the three image distributions corresponding to the three first interference fringes each having these phases. As a result, the above equation (1) can be solved by the information on the three phases and the image distribution. As a result, in addition to information that can be resolved with a conventional optical microscope in the frequency space, information obtained by translating the band of the observation object S to the high frequency side by the spatial frequency of the first interference fringes can be acquired. Accordingly, the calculation unit 13 can correctly calculate the shape distribution of the observation object S. Since one period of the first interference fringes is 2π rad, three different phases can be set to 0 rad, 2π / 3 rad, 4π / 3 rad obtained by dividing 2π into three equal parts, for example. In order to stabilize the calculation when solving the above equation (1), the larger the difference between these three phases, the better. For this reason, the three different phases are set to 0 rad, 2π / 3 rad, 4π / 3 rad. Sometimes it is possible to best perform image reconstruction. However, the three phases different from each other do not necessarily divide 2π into three equal parts as described above. The degree to which the shape distribution of the observation object S is correctly calculated (extracted) differs depending on these three phase values.

Further, the measurement unit 12 continues to measure the light intensity distribution until the calculation unit 13 calculates shift amounts corresponding to at least three phases different from each other. For this reason, in the case where the shift amount of the first interference fringe is calculated a plurality of times by the calculation unit 13, even when a plurality of phases corresponding to each shift amount are the same phase, a predetermined simultaneous equation is solved. It is possible to prevent a lack of information on at least three phases and image distributions required for the above. Accordingly, the calculation unit 13 can correctly calculate the shape distribution of the observation object S.

The interference fringe generation unit 6 is provided at the end of the first optical path 3, and the first light projecting unit 30 that projects the first light onto the observation object S and the beginning of the third optical path 9. Provided at a position facing the first light projecting unit 30 via the observation object S, and a first light receiving unit 31 that receives the first reflected light, and at the end of the second optical path 4 A second light projecting unit 32 that projects the second light onto the observation object S, and a second light projecting unit that is provided at the beginning of the fourth optical path 10 and that passes through the observation object S. And a second light receiving portion 33 that receives the second reflected light. For this reason, the first light and the second light can be reliably irradiated to appropriate positions on the observation object S, and the first reflected light and the second reflected light are respectively applied to the third optical path 9 and the fourth light path. Can be reliably output to the optical path 10.

Further, the first light travels from the first light projecting unit 30 to the first light receiving unit 31 and the second light travels from the second light projecting unit 32 to the second light receiving unit 33. The traveling second direction is substantially orthogonal to the observation object S in plan view. For this reason, since the 1st light projection part 30, the 1st light-receiving part 31, the 2nd light projection part 32, and the 2nd light-receiving part 33 can be arrange | positioned in the position which does not mutually interfere, the interference fringe production | generation part 6 is provided. A simple configuration can be obtained.

Further, a second optical path length adjusting unit 11 that expands or contracts the third optical path length or the fourth optical path length is further provided. The second interference fringe is a light intensity distribution according to the optical path difference between the optical path length from the light source 2 to the measurement unit 12 in the first light and the optical path length from the light source 2 to the measurement unit 12 in the second light. Is displaced. For this reason, the second interference fringes need to be adjusted so that the peak of the envelope of the light intensity distribution approaches the center of the measurement range of the measurement unit 12 by adjusting the optical path length. However, in order to fit the second interference fringe in the measurement range of the measurement unit 12, the displacement amount of the light intensity distribution of the second interference fringe can be reduced only by the expansion and contraction of the second optical path length by the first optical path length adjustment unit 5. It may be insufficient. Therefore, the second interference fringes can be sufficiently displaced by expanding and contracting the fourth optical path length by the second optical path length adjustment unit 11. Thus, in the preparation stage for observation, the operation of bringing the peak of the envelope of the light intensity distribution in the second interference fringe closer to the center of the measurement range of the measurement unit 12 is facilitated, so that the operability is improved.

Also, the coherent length of the predetermined range is shorter than the coherent length of the laser light source. For this reason, the width of the peak of the envelope in the light intensity distribution of the second interference fringes is sufficiently narrow, and it is easy to measure the displacement amount of the peak. For this reason, since the displacement amount of the light intensity distribution of the second interference fringe can be easily obtained, it is easy to detect the shift amount of the phase of the first interference fringe with high accuracy.

Further, the coherent length in a predetermined range is 1 μm or more and 100 μm or less. For this reason, the width of the peak of the envelope in the light intensity distribution of the second interference fringes is sufficiently narrow, and it is easy to measure the displacement amount of the peak. For this reason, since the displacement amount of the light intensity distribution of the second interference fringe can be easily obtained, it is easy to detect the shift amount of the phase of the first interference fringe with high accuracy.

The light source 2 is an SLD light source. For this reason, the width of the peak of the envelope in the light intensity distribution of the second interference fringes is sufficiently narrow, and it is easy to measure the displacement amount of the peak. For this reason, since the displacement amount of the light intensity distribution of the second interference fringe can be easily obtained, it is easy to detect the shift amount of the phase of the first interference fringe with high accuracy.

Further, the observation system 1 includes a turntable 7 that holds the observation object S so as to be rotatable about an axis A from the observation object S toward the imaging unit 8. In this observation system 1, it is possible to calculate the shape distribution of the observation object S with higher resolution in the direction in which the phase of the first interference fringes is shifted compared to a conventional optical microscope. Therefore, by observing the observation object S and the first interference fringes in a plurality of relative angles obtained by relatively rotating around the axis A, the shape of the observation object S is obtained in each direction perpendicular to the axis A. A high-resolution image with a correct distribution can be obtained stably. Here, in the case of the above configuration, since the operation of relatively rotating the observation object S and the first interference fringe around the axis A becomes easy, the operability is improved.

As described above, the observation system 1 uses the first interference fringes by the low coherence light as the modulated illumination to irradiate the observation object S. The first interference fringes due to the low coherence light have a narrower range of interference fringes than the interference fringes due to the high coherence light. For this reason, in order to observe a wide range by the observation system 1, it is necessary to scan the first interference fringe on the observation object S. However, since the piezo actuator used in the conventional observation system has a short stroke, it is difficult to observe a wide range with the conventional observation system. Further, since the piezo actuator has a slow stroke speed, the conventional observation system requires a long time for observation. On the other hand, the observation system 1 can use an actuator using a stepping motor having a longer stroke and a higher stroke speed than a piezo actuator. For this reason, the observation system 1 can easily observe a wide range in a short time compared to the conventional observation system.

Note that the present invention is not limited to the embodiment described above. For example, the measurement unit 12 may be a line sensor that can measure the light intensity distribution of the second interference fringes one-dimensionally along the phase direction. In the measurement of the displacement amount of the envelope peak in the light intensity distribution of the second interference fringes, it is not always necessary to measure the second interference fringes two-dimensionally. It only needs to be able to measure one-dimensionally along. Therefore, the measurement unit 12 can be a line sensor. In this case, when calculating the phase shift amount in the first interference fringe based on the displacement amount of the light intensity distribution in the second interference fringe, The amount of calculation in the calculating part 13 can be reduced. Further, the measurement unit 12 requires a higher frame rate than the imaging unit 8. Since the measurement unit 12 is a line sensor and easily increases the frame rate, a higher frame rate than that of the imaging unit 8 can be easily realized.

Moreover, in the said embodiment, although the 1st optical path length adjustment part 5 is provided in the middle of the 2nd optical path 4, and expands / contracts the 2nd optical path length, it is provided in the middle of the 1st optical path 3. The first optical path length may be expanded and contracted.

In the above embodiment, the second optical path length adjustment unit 11 is provided in the middle of the fourth optical path 10 to expand and contract the fourth optical path length, but is provided in the middle of the third optical path 9. The third optical path length may be expanded and contracted.

Here, an observation system according to another aspect of the present invention provides a light source having a coherent length within a predetermined range and a first light having a first optical path length and a part of light emitted from the light source. A first optical path that leads to the observation object, a second optical path length, and a second optical path that guides the second light that is the remainder of the light from the light source to the observation object, and the first optical path length or the first optical path length A first optical path length adjustment unit that expands and contracts the optical path length of 2, an interference fringe generation unit that causes the first light and the second light to interfere with each other to generate a first interference fringe on the observation object, and a first An imaging unit that captures an image distribution of the light scattered by the observation object in the first light and the second light that exhibit the interference fringes, and a third optical path length, A third optical path for guiding the first reflected light reflected by the observation object, and a fourth optical path length, which are reflected by the observation object in the second light. A fourth optical path that guides the second reflected light, and a third optical path that is provided at the end of the third optical path and the fourth optical path, and that is generated by interference between the first reflected light and the second reflected light. A measurement unit that measures the light intensity distribution of the interference fringes, and a calculation unit connected to the imaging unit and the measurement unit, wherein the calculation unit is based on the amount of displacement of the light intensity distribution in the second interference fringes. The phase shift amount in the interference fringes is calculated, and the shape distribution of the observation object is calculated based on the phase corresponding to the shift amount and the image distribution corresponding to the first interference fringe having the phase.

According to such an observation system, the first light guided from the light source to the observation target by the first optical path and the second light guided from the light source to the observation target by the second optical path interfere with each other. A first interference fringe is generated by interference by the fringe generation unit. Then, the image distribution of the light scattered by the observation object in the first light and the second light presenting the first interference fringes is imaged by the imaging unit. On the other hand, the first reflected light reflected by the observation target in the first light and guided by the third optical path, and the first reflected light reflected by the observation target in the second light and guided by the fourth optical path. The second reflected light thus interfered to generate a second interference fringe. Then, the light intensity distribution of the second interference fringe is measured by the measurement unit. Here, when the first optical path length or the second optical path length is expanded or contracted by the first optical path length adjusting unit, the phase of the first interference fringe is shifted and the light intensity distribution of the second interference fringe is displaced. To do. Since the light source has a coherent length in a predetermined range, the light intensity distribution of the second interference fringe has one peak in its envelope. The amount of displacement of the light intensity distribution of the second interference fringe is obtained by measuring the amount of displacement of the peak of the envelope. Therefore, even when the phase of the first interference fringe is shifted by one wavelength or more, the envelope in the light intensity distribution of the second interference fringe is not affected by the uncertainty of each wavelength in the first interference fringe. The phase shift amount of the first interference fringes can be detected based on the displacement amount of the line peak. Further, even when a disturbance such as vibration or temperature change occurs, the phase shift amount of the first interference fringes can be detected with high accuracy. Thereby, the calculating part can calculate correctly the shape distribution of an observation object. Furthermore, this observation system does not require a high-precision positioning mechanism such as a piezo actuator in order to accurately detect the phase shift amount of the first interference fringes, and as an example, a relatively high-speed actuator such as an actuator using a stepping motor. Since a positioning mechanism with low accuracy can be used, it is provided at low cost. As described above, an inexpensive system can stably obtain a correct high-resolution image even when a disturbance occurs.

In the above-described embodiment, the calculation unit calculates the shape distribution of the observation object based on at least three phases different from each other and at least three image distributions corresponding to at least three first interference fringes each having these phases. May be calculated. As a result, it is possible to solve a predetermined simultaneous equation based on information on at least three phases and image distributions. As a result, in addition to information that can be resolved with a conventional optical microscope in the frequency space, information obtained by translating the band of the observation object to the high frequency side by the spatial frequency of the first interference fringes can be acquired. Therefore, the calculation unit can correctly calculate the shape distribution of the observation object.

Further, the measurement unit may continue measuring the light intensity distribution until shift amounts corresponding to at least three phases different from each other are calculated by the calculation unit. In this case, when the shift amount of the first interference fringe is calculated a plurality of times by the calculation unit, even when a plurality of phases corresponding to each shift amount are the same phase, in order to solve a predetermined simultaneous equation It is possible to prevent a shortage of necessary information on at least three phases and image distributions. Therefore, the calculation unit can correctly calculate the shape distribution of the observation object.

The interference fringe generation unit is provided at the end of the first optical path, and is provided at the first light projecting unit for projecting the first light onto the observation target and the start end of the third optical path for observation. The first light receiving unit that is disposed at a position facing the first light projecting unit via the object, receives the first reflected light, and is provided at the end of the second optical path, and observes the second light. A second light projecting unit that projects light onto the object and a second reflected light that is provided at the start of the fourth optical path and that is disposed at a position facing the second light projecting unit through the observation object. And a second light receiving portion that receives light. In this case, the first light and the second light can be reliably radiated to appropriate positions on the observation object, and the first reflected light and the second reflected light are respectively applied to the third optical path and the fourth optical path. Can be output reliably.

In addition, a first direction in which the first light travels from the first light projecting unit to the first light receiving unit, and a second direction in which the second light travels from the second light projecting unit to the second light receiving unit. These directions may be substantially orthogonal in a plan view with respect to the observation object. In this case, since the first light projecting unit, the first light receiving unit, the second light projecting unit, and the second light receiving unit can be arranged at positions that do not interfere with each other, the interference fringe generating unit has a simple configuration. be able to.

Further, a second optical path length adjustment unit that expands or contracts the third optical path length or the fourth optical path length may be further provided. In this case, in the preparatory stage for observation, the operation of bringing the peak of the envelope of the light intensity distribution in the second interference fringe closer to the center of the measurement range of the measurement unit is facilitated, and the operability is improved.

Further, the coherent length in the predetermined range may be shorter than the coherent length of the laser light source. In this case, since the peak width of the envelope in the light intensity distribution of the second interference fringes is sufficiently narrow, it is easy to measure the displacement amount of the peak. For this reason, since the displacement amount of the light intensity distribution of the second interference fringe can be easily obtained, it is easy to detect the shift amount of the phase of the first interference fringe with high accuracy.

Further, the coherent length in a predetermined range may be 1 μm or more and 100 μm or less. In this case, since the peak width of the envelope in the light intensity distribution of the second interference fringes is sufficiently narrow, it is easy to measure the displacement amount of the peak. For this reason, since the displacement amount of the light intensity distribution of the second interference fringe can be easily obtained, it is easy to detect the shift amount of the phase of the first interference fringe with high accuracy.

The light source may be an SLD light source or an LED light source. In this case, since the peak width of the envelope in the light intensity distribution of the second interference fringes is sufficiently narrow, it is easy to measure the displacement amount of the peak. For this reason, since the displacement amount of the light intensity distribution of the second interference fringe can be easily obtained, it is easy to detect the shift amount of the phase of the first interference fringe with high accuracy.

Further, the measurement unit may be a line sensor. In the measurement of the displacement amount of the envelope peak in the light intensity distribution of the second interference fringes, it is not always necessary to measure the second interference fringes two-dimensionally. It only needs to be able to measure one-dimensionally along. That is, a line sensor can be used as the measurement unit. In this case, when calculating the amount of phase shift in the first interference fringe based on the amount of displacement of the light intensity distribution in the second interference fringe, the amount of computation in the computing unit can be reduced. Further, the measurement unit requires a higher frame rate than the imaging unit. Since the measurement unit is a line sensor, it is easy to increase the frame rate. Therefore, a higher frame rate than that of the imaging unit can be easily realized.

Further, a turntable for holding the observation object so as to be rotatable around an axis line from the observation object to the imaging unit may be further provided. In this observation system, it is possible to calculate the shape distribution of the observation object with higher resolution in the direction in which the phase of the first interference fringe is shifted compared to a conventional optical microscope. Therefore, by performing observation in a plurality of relative angle states in which the observation object and the first interference fringes are relatively rotated around the axis, the shape distribution of the observation object can be accurately increased in each direction perpendicular to the axis. A resolution image can be obtained stably. Here, in the case of the above configuration, an operation for relatively rotating the observation object and the first interference fringe around the axis is facilitated, so that the operability is improved.

One aspect of the present invention is that an observation system is used, and a low-cost system can stably obtain a correct high-resolution image even when a disturbance occurs.

DESCRIPTION OF SYMBOLS 1 ... Observation system, 2 ... Light source, 3 ... 1st optical path, 4 ... 2nd optical path, 5 ... 1st optical path length adjustment part, 6 ... Interference fringe production | generation part, 7 ... Turntable, 8 ... Imaging part, DESCRIPTION OF SYMBOLS 9 ... 3rd optical path, 10 ... 4th optical path, 11 ... 2nd optical path length adjustment part, 12 ... Measurement part, 13 ... Calculation part, 30 ... 1st light projection part, 31 ... 1st light-receiving part 32 ... 2nd light projection part, 33 ... 2nd light-receiving part, A ... axis line, S ... observation object.

Claims

A light source having a coherent length in a predetermined range;
A first optical path having a first optical path length and guiding the first light, which is a part of the light emitted from the light source, from the light source to the observation object;
A second optical path having a second optical path length and guiding the second light, which is the remainder of the light, from the light source to the observation object;
An interference fringe generator that causes the first light and the second light to interfere with each other to generate a first interference fringe on the observation object;
It is generated by the interference between the first reflected light reflected by the observation object in the first light and the second reflected light reflected by the observation object in the second light. A measurement unit for measuring the light intensity distribution of the second interference fringes,
A calculation unit connected to the measurement unit;
With
The computing unit is
Calculating a phase shift amount in the first interference fringe based on a displacement amount of the light intensity distribution in the second interference fringe;
Observation system.
A first optical path length adjustment unit that expands or contracts the first optical path length or the second optical path length;
An imaging unit that captures an image distribution of the light scattered by the observation object in the first light and the second light presenting the first interference fringes;
A third optical path having a third optical path length and guiding the first reflected light;
A fourth optical path having a fourth optical path length and guiding the second reflected light, and
The measurement unit is provided at the end of the third optical path and the fourth optical path,
The computing unit is also connected to the imaging unit, and the shape of the observation object is based on the phase according to the shift amount and the image distribution corresponding to the first interference fringe having the phase. Calculate the distribution,
The observation system according to claim 1.
The computing unit is
Calculating the shape distribution of the observation object based on at least three different phases from each other and at least three image distributions corresponding to the at least three first interference fringes each having the phases.
The observation system according to claim 2.
The observation system according to claim 3, wherein the measurement unit continues the measurement of the light intensity distribution until the shift amounts corresponding to at least three different phases are calculated by the calculation unit.
The interference fringe generator is
A first light projecting unit provided at an end of the first optical path and projecting the first light onto the object to be observed;
A first light receiving unit that is provided at a start end of the third optical path, is disposed at a position facing the first light projecting unit via the observation object, and receives the first reflected light;
A second light projecting unit provided at an end of the second optical path and projecting the second light onto the object to be observed;
A second light receiving unit that is provided at a start end of the fourth optical path, is disposed at a position facing the second light projecting unit via the observation object, and receives the second reflected light;
Having
The observation system according to any one of claims 2 to 4.
The first light travels from the first light projecting unit to the first light receiving unit, and the second light travels from the second light projecting unit to the second light receiving unit. The traveling second direction is substantially perpendicular to the observation object in plan view,
The observation system according to claim 5.
A second optical path length adjustment unit that expands or contracts the third optical path length or the fourth optical path length;
The observation system according to any one of claims 2 to 6.
The coherent length of the predetermined range is shorter than the coherent length of the laser light source,
The observation system according to any one of claims 1 to 7.
The coherent length of the predetermined range is 1 μm or more and 100 μm or less,
The observation system according to any one of claims 1 to 8.
The light source is an SLD light source or an LED light source.
The observation system according to any one of claims 1 to 9.
The measurement unit is a line sensor.
The observation system according to any one of claims 1 to 10.
The observation system according to any one of claims 2 to 7, further comprising a turntable that holds the observation object so as to be rotatable about an axis from the observation object toward the imaging unit.