JP2022118395A - Optical measuring device and data operation method of optical measuring device - Google Patents

Abstract

To obtain an optical measuring device capable of not only simultaneously acquiring intensity and information of optical distance and accurately dividing both on the basis of a signal acquired from a light receiving element but also executing differential operation only of intensity, differential operation only of a phase and differential operation to polarization.SOLUTION: A laser light source 21, a two-dimensional scanning device 26, and the like are arranged in a line, and an objective lens 31 faces a measuring object G1. Signals from light receiving elements 29A, 29B receiving light from the measuring object G1 and a signal to be reference for scanning by the two-dimensional scanning device 26 are sent to a data processing part 34 through a signal comparator 33. The data processing part 34 creates a first data group obtained by adding a plurality of pieces of data and a second data group obtained by adding a plurality of pieces of data deviated from the plurality of pieces of data of the first data group. Not only intensity information and phase information but also differential operation only of intensity and differential operation only of a phase are executed from an output of difference between two kinds of the data groups.SELECTED DRAWING: Figure 1

Description

The present invention provides intensity information such as transmittance, reflectance, and absorbance for measurement of the profile of the surface state of an object to be measured, measurement and observation of the surface state and internal state of cells, etc. by irradiating laser light, and optical The present invention relates to an optical measuring device that simultaneously obtains distance information and accurately separates both, and is suitable for devices that improve the performance of optical instruments such as microscopes.

In conventional optical microscopes, three-dimensional measurement such as optical distance is difficult, and phase information and intensity information cannot be separated accurately. For example, in a phase-contrast microscope, a phase plate is used to convert phase information into intensity information for observation in order to clearly observe low-contrast biological cells and the like. Thus, although phase information could be visualized, intensity information was also observed.
Thus, the conventional phase-contrast microscope was not a microscope for purely separating and observing phase information or intensity information. The same applies to a differential interference contrast microscope that visualizes phase information. In particular, in order to enable three-dimensional measurement, it is necessary to clearly separate optical distance information and intensity information, which are phase information.

On the other hand, confocal microscopes, digital hologram microscopes, and the like are known as conventional means for detecting optical path differences.
In the former confocal microscope, the object to be measured is irradiated with spot light, and the objective lens or By moving the measurement object, height information and path difference information of the measurement object are acquired.

In addition, the latter digital hologram microscope irradiates a laser beam substantially parallel to the object to be measured, collects the light diffracted by the object with an objective lens, and uses a plane wave as a reference and an area such as a CCD A hologram is created by causing interference on the sensor. Then, by analyzing the interference fringes by calculation, the wavefront from the original object to be measured is restored, and path difference information is obtained.

However, in the former confocal microscope, if there is a phase distribution in the spot light, the beam is basically deformed, resulting in erroneous information. In particular, it must be said that the reliability of the value is poor when the measurement object is such that the wavefront changes in terms of phase, such as changes in the refractive index of cells or the like. Moreover, since it is necessary to move the objective lens and the object to be measured so as to maximize the amount of received light, real-time performance is lacking. Furthermore, if the object to be measured has intensity unevenness due to changes in absorptance or reflectance, the amount of light received will naturally change at the point where the intensity changes, so the amount of light passing through the pinhole will be , it is not possible to determine whether the intensity is increased at the in-focus point or due to unevenness in intensity, and an erroneous optical distance is calculated.

In the latter digital hologram microscope, the light diffracted by the objective lens is condensed and interfered with a reference plane wave, the light and dark pattern is taken in by a CCD or the like, and the wavefront is reproduced by a computer as information. However, since the reference plane wave is a plane wave that has passed through a number of optical elements, even though it is a plane wave, if viewed microscopically, there is unevenness within the plane for about 1/10 of the wavelength. Even if the uneven state of the wavefront is stored in some kind of calibration plane or the like, it will effectively fluctuate due to temperature fluctuations, air density fluctuations, and the like. Therefore, in a strict sense, it is difficult to say that the interference pattern between the plane wave and the object wave that have passed through different paths reproduces the object wave.

In addition, many conventional hologram microscopes use an imaging lens or the like, and the phase information and intensity information in the spatial frequency domain due to the NA of the lens vary depending on the MTF. was hard to say. Therefore, it was difficult to assume that the optical distance information also calculated a correct value.

On the other hand, in a conventional differential interference contrast microscope, by irradiating the measurement object with light beams having different polarizations with a slight spatial shift, there is no difference in path difference between the two polarized light beams irradiated onto the measurement object. Retardation is given to the polarized light as it occurs, and by synthesizing this again, a slight refractive index difference and a phase difference in height of the object to be measured can be visualized. The amount of shift when irradiating polarized light with this spatial shift is referred to as the amount of shear.

Japanese Patent Application Laid-Open No. 2020-27096 JP 2015-075340 A

An advantage of such a differential interference microscope is that it optically amplifies high spatial frequency components, so that the resolution appears to be high. However, when the object to be measured contains a substance with birefringence or optical rotation, the differential interference microscope has the drawback that the image appears to change as the plane of polarization rotates due to the birefringence, making it extremely difficult to handle. was

SUMMARY OF THE INVENTION The present invention has been made in view of the above background. It is an object of the present invention to provide an optical measuring device and a data computing method for the optical measuring device that can perform a differential operation of only the phase, a differential operation of only the phase, and a differential operation of the polarized light.

The optical measurement device according to claim 1 comprises a light source that emits coherent irradiation light,
a scanning element that scans the irradiation light from the light source and sends it to the measurement object;
At least two light-receiving elements positioned on each side with a boundary line perpendicular to the direction of the optical axis of the illuminating light, and receiving and photoelectrically converting the illuminating light modulated by the object to be measured during scanning. ,
The measurement values of the sum signal and the difference signal for the object to be measured are obtained from the signals of the basic basic data photoelectrically converted and output by these light receiving elements, and the basic data are obtained from the signals photoelectrically converted and output. A first data group obtained by adding values of data and a plurality of data extracted at predetermined intervals; a measuring unit that creates a second data group obtained by adding the values of a plurality of extracted data, and executes a differential operation on the object to be measured by outputting the difference between these two data groups;
including.

The operation of the optical measuring device according to claim 1 will be described below.
In the present invention, coherent illuminating light is emitted from a light source and a scanning element scans the illuminating light into a scanning beam onto a measurement object. Further, two light-receiving elements, one on each side of the boundary line perpendicular to the optical axis of the irradiated light, receive the irradiated light modulated by the object to be measured during scanning, Convert. Along with this, intensity information and phase information of the measurement object can be obtained from the measurement values of the sum signal and the difference signal for the measurement object obtained from the basic data signals photoelectrically converted by the two light receiving elements.

Then, a first data group obtained by adding the values of the basic data and a plurality of data extracted at predetermined intervals from the signals photoelectrically converted by these two light receiving elements, and the plurality of data of the first data group. A second data group obtained by adding a plurality of data values extracted by shifting a predetermined amount corresponding to the share amount from each other is created by the measurement unit. Furthermore, from the output of the difference between these two types of data groups, not only the measured values of the sum signal and the difference signal for the measurement object, but also the differential operation of only the intensity, the differential operation of only the phase, and the differential operation with respect to the polarization Each can perform an operation.

That is, in contrast to conventional differential interference microscopes that use retardation of polarized light to obtain differential information, the optical measuring device of the present invention obtains differential information based on electrical signals without using polarized light. Therefore, correct differential interference information can be generated even if the object to be measured has birefringence or optical rotation.

Therefore, to overcome the drawbacks of conventional differential interference microscopes, and in addition to the conventionally used method of obtaining the intensity and phase, the method of the optical measurement apparatus according to the present claim is added with the function of a differential interference microscope. As a result, it is possible to perform a differential operation of only intensity, a differential operation of only phase, and a differential operation of polarized light, and obtain new information that cannot be obtained by conventional devices and methods. Note that the differential operation of only the phase is almost synonymous with the conventional differential interference. However, it differs in that it is not affected by polarization.

As a result of the above, in a microscope or the like to which the present invention is applied, it is possible to obtain intensity information and optical distance information simultaneously subjected to a differential operation from the irradiation position of the scanning beam. Since it is possible to emphatically express a portion with a high spatial frequency such as a state change such as , intensity observation and phase observation of details can be easily performed. Moreover, since the information is obtained from the same observation point rather than multiple data obtained by a plurality of CCDs or the like, the processing is unrelated to alignment due to pixel deviation, and different information can be reliably obtained from the same location. .

Furthermore, when the present invention is applied to a transmission microscope, as the apparatus becomes simpler, live cells, micro-organisms, etc. are not fluorescently colored, and can be easily and quickly visualized with high resolution. Observable. In addition, since it is possible to perform differential calculations of only intensity, differential calculation of phase only, and differential calculation with respect to polarized light, it has a great feature that it is possible to emphasize the detailed structure of the observation object very easily. become.

As in claim 2, when the number of data extracted at predetermined intervals between basic data is k,
The data extracted from the first data group is obtained by adding the values of (k+1) pieces of data up to the k+(k+1)n-th sample point by shifting the extraction position one by one from the (k+1)n-th sample point,
The data extracted from the second data group is obtained by adding the values of (k+1) pieces of data up to the k+(k+1)n+m-th sample point by shifting the extraction position by one from the (k+1)n+m-th sample point,
By setting n to be a natural number including 0 and m to be a natural number not including 0, the optical measurement device according to claim 1 can reliably perform a differential operation of only intensity, a differential operation of only phase, and a differential operation of polarized light. will be able to run Note that the differential operation of only the phase is almost synonymous with the conventional differential interference. However, it differs in that it is not affected by polarization.

As in claim 3, the data extracted by the first data group is the sample point sx, and the values of the plurality of data are added, and the data extracted by the second data group is the sample point s(x+m). is the sum of the data values of
With s as the data extraction interval, x as the acquired data position within each data extraction interval, and m as the share amount, the optical measurement device of claim 1 can perform the differential operation of only the intensity, the differential operation of only the phase, and the polarization , can be reliably executed in the same manner as in claim 2.

In claim 4, two light receiving elements are added to the two light receiving elements, and the polarized light can be detected using the four light receiving elements. By performing calculations using the data group of , it is possible to obtain polarization differential interference information that cannot be obtained with an optical system such as a conventional differential polarization microscope.

On the other hand, as in claim 5, the scanning element is a two-dimensional scanning element that scans the irradiation light in two mutually orthogonal directions. It is conceivable that the irradiated illumination light is modulated. Further, as in claim 6, it is conceivable that a controller is connected to the scanning element and the controller operates the operation of the scanning element to adjust the scanning speed and scanning range. In this way, not only can a two-dimensional image be simply obtained, but measurement can be made with any modulation amount and any range by simply changing the settings of the controller.

According to a seventh aspect of the present invention, there is provided a data calculation method for an optical measurement device, comprising:
a scanning element that scans the irradiation light from the light source and sends it to the measurement object;
At least two light-receiving elements positioned on each side with a boundary line perpendicular to the direction of the optical axis of the illuminating light, and receiving and photoelectrically converting the illuminating light modulated by the object to be measured during scanning. ,
a measurement unit that obtains a measurement value of an object to be measured from signals of basic basic data photoelectrically converted and output by these light receiving elements;
A data calculation method for an optical measuring device comprising:
A first data group obtained by adding basic data and a plurality of data values extracted at predetermined intervals from a signal photoelectrically converted and output in a measurement unit; Creating a second data group obtained by adding the values of a plurality of data extracted by shifting each of the plurality of data by a predetermined amount,
In addition to obtaining measured values for the object to be measured, the measurement section executes differential operation for the object to be measured by outputting the difference between these two types of data groups.

The operation of the data calculation method for the optical measuring device according to claim 7 will be described below.
In the present invention, coherent illuminating light is emitted from a light source and a scanning element scans the illuminating light into a scanning beam onto a measurement object. Further, two light-receiving elements, one on each side of the boundary line perpendicular to the optical axis of the irradiated light, receive the irradiated light modulated by the object to be measured during scanning, Converting is the same as in claim 1.

Then, a first data group obtained by adding basic data and a plurality of data values extracted at predetermined intervals from signals photoelectrically converted by these two light receiving elements, and a plurality of data in the first data group. A second data group obtained by adding a plurality of data extracted by shifting a predetermined amount corresponding to each share amount is created by the measurement unit. Furthermore, from the output of the difference between these two types of data groups, not only the intensity information and phase information, but also the differential operation of only the intensity and the differential operation of only the phase based on the measured values of the sum signal and the difference signal for the measurement object Calculations and differential calculations with respect to polarized light can be executed.

As in claim 8, when the number of data extracted at predetermined intervals between basic data is k,
The data extracted from the first data group is obtained by adding the values of (k+1) pieces of data up to the k+(k+1)n-th sample point by shifting the extraction position one by one from the (k+1)n-th sample point,
The data extracted from the second data group is obtained by adding the values of (k+1) pieces of data up to the k+(k+1)n+m-th sample point by shifting the extraction position by one from the (k+1)n+m-th sample point,
By setting n to be a natural number including 0 and m to be a natural number not including 0, differential calculation of intensity only, differential calculation of phase only, and polarization calculation by the data calculation method of the optical measurement device according to claim 7 can be performed. It becomes possible to reliably execute differential calculations and the like.

As in claim 9, the data extracted by the first data group is the sample point sx, and the values of the plurality of data are added, and the data extracted by the second data group is the sample point s(x+m). is the sum of the data values of
By setting s as the data extraction interval, x as the acquired data position within each data extraction interval, and m as the share amount, the differential calculation of only the intensity and the calculation of only the phase are performed by the data calculation method of the optical measurement device according to claim 7. Differential calculation, differential calculation with respect to polarized light, etc. can be reliably executed in the same manner as in claim 8.

INDUSTRIAL APPLICABILITY As described above, in the optical measurement apparatus and the data calculation method of the optical measurement apparatus of the present invention, coherent irradiation light is irradiated from the light source, and the scanning element scans the irradiation light to form a scanning beam to be measured. Sending it to an object modulates this illuminating light.
Furthermore, the intensity information is obtained from the sum of the signals themselves photoelectrically converted by the light receiving elements positioned on each side of the boundary in the direction perpendicular to the optical axis direction of the irradiated light, and the difference between the signals is obtained. Phase information is obtained from the output Hilbert transformed signal. An output of the difference between the first data group and the second data group is then obtained. As a result, not only can the intensity information and phase information of the object to be measured be obtained at the same time and the two can be accurately separated, but also the differentiation operation of only the intensity, the differentiation operation of only the phase, the differentiation operation of the polarized light, etc. can be performed. It has an excellent effect of being able to Note that the differential operation of only the phase is almost synonymous with the conventional differential interference. However, it differs in that it is not affected by polarization.

1 is a block diagram of a device of a reflecting optical system as a first embodiment of an optical measuring device according to the present invention; FIG. FIG. 2 is an explanatory diagram showing a light irradiation region on a light receiving element of the reflective optical system of FIG. 1; It is a perspective view explaining repeated scanning of a laser beam. FIG. 4 shows graphs representing MTF curves for intensity and phase in Example 1, wherein FIG. 4A shows the MTF curve of normal intensity information, and FIG. 4B shows a method of adding differential information FIG. 4(C) shows the MTF curve of normal phase information, and FIG. 4(D) shows the MTF curve of phase information by the method of adding differential information. FIG. 10 is a block diagram of a transmission optical system as a second embodiment of the optical measuring device according to the present invention; FIG. 11 is a block diagram of a transmission optical system device as a modified example of the second embodiment; FIG. 11 is an explanatory diagram showing a light irradiation region on a light receiving element of an optical measuring device according to a third embodiment of the present invention; It is a block diagram of the optical system which shows Example 4 based on the optical measuring device of this invention. 10 shows the relationship between the 0th-order diffracted light and the 1st-order diffracted light with respect to the optical axis of the objective lens and the optical axis of the condensing lens in Example 4. FIG. FIG. 10A is a graph showing MTF curves for intensity and phase in Example 4, FIG. 10A shows the MTF curve for normal intensity information, and FIG. 10B is a method of adding differential information. FIG. 10(C) shows the MTF curve of the normal phase information, and FIG. 10(D) shows the MTF curve of the phase information by the method of adding differential information. It is a block diagram of the optical system which shows Example 5 based on the optical measuring device of this invention.

Embodiments 1 to 4 of the optical measuring device and the data calculation method for the optical measuring device according to the present invention will be described below in detail with reference to the drawings.

A first embodiment of an optical measuring device according to the present invention will be described below with reference to FIGS. 1 and 2. FIG. This embodiment is an apparatus of a reflecting optical system that reflects a scanning beam on an object to be measured. FIG. 1 is a block diagram showing the configuration of a reflective optical system apparatus according to an embodiment.

As shown in FIG. 1, a laser light source 21 is a light source that irradiates (emits) laser light, which is coherent light, and a collimator lens 22 is aberration-corrected so that parallel light can be obtained from the laser light. are arranged in order. Therefore, in this embodiment, the laser light emitted from the laser light source 21 is collimated by the collimator lens 22 .

Further, for this collimator lens 22, a pupil transmission lens system 25 consisting of two groups of lenses, a two-dimensional scanning device 26 which is a two-dimensional scanning element for two-dimensionally scanning the input laser light, and the input laser light A beam splitter 27, which is originally intended to separate and emit the light, is further arranged in series. As shown in FIG. 1, the optical axis L is the optical path of the laser beam toward the pupil transmission lens system 25 . The two-dimensional scanning device 26 is connected to a controller 23, which is control means for changing a scanning range for two-dimensional scanning with laser light and a voltage for adjusting the scanning speed.

Further, adjacent to the beam splitter 27, a pupil transfer lens system 30 consisting of two groups of lenses is positioned, and next to this, an objective lens 31 is arranged to face the object G1 to be measured. In other words, these members are also arranged along the optical axis L. As described above, the laser beam passes through the pupil transfer lens system 25, the two-dimensional scanning device 26, the beam splitter 27, the pupil transfer lens system 30, and the objective lens 31 in order along the optical axis L, and is irradiated onto the measurement object G1. be. At this time, the operation of the two-dimensional scanning device 26 causes this laser light to become a scanning beam and two-dimensionally scan the object G1 to be measured.

On the other hand, a light-receiving element group 29 composed of a plurality of optical sensors is arranged at a position adjacent to the beam splitter 27 in a direction perpendicular to the direction in which the optical axis L passes. The scanning beam reflected by the measurement object G1 shown in FIG. 1 becomes diffracted light, returns to the objective lens 31, the pupil transfer lens system 30 and the beam splitter 27 in that order, and becomes parallel light. Along with this, the light is reflected by the beam splitter 27 and is incident on the light receiving element group 29 along the optical axis L of the irradiation light orthogonal to the original optical axis L.

The light receiving element group 29 is not only arranged on the far field plane of the measurement object G1, but also consists of two light receiving elements 29A and 29B in this embodiment. However, as shown in FIG. 2, on a plane substantially perpendicular to the direction along the optical axis L, which is the center of the spot of the scanning beam LA, and across a boundary line S passing through the optical axis L, these Light receiving elements 29A and 29B are arranged respectively. That is, the light-receiving element 29A is positioned on one side of the boundary line S, and the light-receiving element 29B is positioned on the opposite side of the boundary line S. These light receiving elements 29A and 29B receive LA.

Furthermore, each of the light receiving elements 29A and 29B has a structure having a photoelectric conversion portion (not shown), and each of the light receiving elements 29A and 29B receives the scanning beam LA and photoelectrically converts it.
The light receiving elements 29A and 29B and the controller 23 that operates the two-dimensional scanning device 26 are connected to a signal comparator 33, respectively. Along with this, the signal comparator 33 obtains intensity information and phase information of the measuring object G1 from the signals from the light receiving elements 29A and 29B and the signal from the controller 23. FIG. This signal comparator 33 is connected to a data processing section 34 that finally processes the data to obtain measured values such as the profile of the measurement object G1. Therefore, in this embodiment, the signal comparator 33 and the data processing section 34 are used as the measurement section. Although not shown, the data processing unit 34 incorporates an AD converter for converting analog data into digital data.

The laser light source 21 is a semiconductor laser and generates coherent laser light. This laser beam is collimated by a collimator lens 22 and made incident on a pupil transmission lens system 25 . At this time, the incident beam diameter of the laser light is optimized by using a diaphragm mechanism (not shown) or the like in consideration of the pupil transmission lens system 25 .

Here, the pupil transmission lens system 25 arranged between the collimator lens 22 and the two-dimensional scanning device 26 conjugately transmits the output surface position of the collimator lens 22 to the next two-dimensional scanning device 26. is the optical system. The laser light passing through this pupil transmission lens system 25 passes through a two-dimensional scanning device 26 and is sent to a beam splitter 27 as a scanning beam. It enters the objective lens 31 via the pupil transfer lens system 30 which is conjugated to the position.

As described above, in this embodiment, although the laser light source 21 irradiates the laser light in a non-modulated state, the laser light converted into a scanning beam by the two-dimensional scanning device 26 is incident on the measurement object G1 to form a pattern. The light-receiving element group 29 finally detects the modulated signal of the Fourier transform of the measurement object G1 as a result of being substantially modulated by the intensity change and the optical distance change and reflected by the measurement object G1.

Further, as shown in FIG. 3, the two-dimensional scanning device 26 repeats the laser beam along the horizontal direction X to scan the measurement object G1 while moving the optical axis L. As shown in FIG. However, two-dimensional scanning is made possible by sequentially changing the scanning positions along the vertical direction Y as indicated by 1, 2, 3, 4, . . . in FIG. A controller 23 that adjusts the operation of the two-dimensional scanning device 26 can change the visual field range of the apparatus. In other words, the controller 23 changes the voltage for controlling the horizontal scanning range of the two-dimensional scanning device 26 and the vertical scanning range, thereby freely enlarging or reducing the three-dimensional image to obtain the visual field range. can be adjusted. At this time, the controller 23 can change only the visual field range while keeping the horizontal resolution constant.

Therefore, according to the present embodiment, as shown in FIG. 3, the surface of the object G1 to be measured has irregularities such as the presence of convex portions C, and shading such as the presence of high-concentration portions D. Even in this case, the convex portion C and the high-density portion D can be accurately reproduced by changing the amount of diffraction and the amount of reflection of the laser beam scanned and irradiated by the two-dimensional scanning device 26 .

In this way, the laser light source 21 emits an unmodulated laser beam, which is scanned by the two-dimensional scanning device 26 and converted into a scanning beam. diffracted light. Of these diffracted lights, the 0th order diffracted light and the 1st order diffracted light themselves are non-modulated lights, and the intensity signals of these diffracted lights are non-modulated signals.
On the other hand, the portion where the 0th-order diffracted light and the 1st-order diffracted light overlap is a signal in which the 1st-order diffracted light has a phase difference with respect to the 0th-order diffracted light, so that it becomes a modulated intensity signal. This is because each of the intensity and the optical distance can be regarded as an aggregate of a certain spatial frequency, and the overlapped portion of the 0th-order diffracted light and the 1st-order diffracted light due to the scanning of the irradiation light beam is the spatial frequency corresponding to the 1st-order diffracted light. is modulated by

The modulated light is converted by the light receiving elements 29A and 29B into a current having a frequency corresponding to the spatial frequency as an intensity signal. Convert to voltage. Therefore, the 0th-order diffracted light and the 1st-order diffracted light, which are non-modulated light, become a DC signal, and the overlapping portion of the 0th-order diffracted light and the 1st-order diffracted light, which are modulated light, becomes an AC signal.

Next, the data processing of the optical measuring device according to this embodiment will be specifically described below. However, since data processing is the same not only in the reflective optical system but also in the transmissive optical system, it will be collectively described below.

Each signal photoelectrically converted and output by each of the light receiving elements 29A and 29B is compared with the signal from the controller 23 in the signal comparator 33 to obtain the signal information of the measuring object G1. Then, in the data processing section 34 to which the signal information is sent from the signal comparator 33, Hilbert transform is performed. Then, the signal information itself and the Hilbert-transformed signal are processed by the data processing unit 34 into measurement data consisting of a plurality of discrete data.

For example, when the sampling frequency of the AD converter constituting part of the data processing unit 34 is 480 MHz and the scanning speed of the scanning beam is v=3.0 m/s, the frequency of 240 MHz is spaced at intervals of 12.5 nm. , and a frequency of 30 MHz corresponds to a spacing of 100 nm.
On the other hand, for example, if the laser wavelength of the laser light source 21 being used is 488 nm and the NA of the objective lens 31 is 0.95, the cutoff spatial frequency is 256 nm, so data is acquired at intervals of 100 nm. That would be enough. However, in the optical system for improving the lateral resolution as shown in the fourth embodiment of the present invention, the upper limit of the frequency to be acquired may be increased, for example, up to 60 MHz.

In the case of this embodiment, from the relationship with the scanning speed of the scanning beam on the measurement object G1, 16 measurement data at a frequency of 30 MHz are obtained as discrete data obtained by AD-converting the AC signal after the Hilbert transform. data will be obtained.

Next, how the signals detected by the light receiving elements 29A and 29B will be concretely described below. Since the signal processing is the same not only in the reflection optical system but also in the transmission optical system, and also in the transmission optical system with high resolution, it will be collectively described in the following embodiments.

The state of the measurement object G1 is generally represented by the product of the intensity pattern and the optical distance pattern, and the irradiation light is diffracted by the measurement object G1.
For simplicity, the complex amplitude E ₀ of the intensity pattern is assumed to be a cosine pattern of pitch di, and the phase Θ of the optical range pattern is assumed to be a sinusoidal pattern of pitch dp. Assuming that the wavelength of the irradiation light is λ, the intensity modulation is m, the refractive index difference between the medium and the object to be measured is δn, and the thickness is h, it can be expressed by the following formula.

These patterns are irradiated with light of wavelength λ and received by the light receiving elements 29A and 29B arranged on the far-field Fourier transform plane. On the Fourier transform plane of the complex amplitude E ₀ of the intensity pattern in the pattern of the measurement object G1 in the amplitude portion, the area on one side of the optical axis L where the 1st-order diffracted light and the −1st-order diffracted light do not overlap, that is, the spatial frequency Considering a region where is relatively high, the following formula is obtained on the side of the first-order diffracted light.

Similarly, on the Fourier transform surface of the phase portion, consider a portion on one side of the optical axis where the spatial frequency is relatively high where the 1st-order diffracted light and the −1st-order diffracted light do not overlap. On the 1st-order diffracted light side, a portion with a relatively high spatial frequency is given by the following formula.

Therefore, on the side of first-order diffracted light, the amplitude distribution E _R of light is expressed by the following formula.

Here, a represents the phase information of the optical distance, and b represents the ratio of the first-order Bessel function and the zeroth-order Bessel function of the phase information of the optical distance. Also, as described above, m represents the degree of intensity modulation. Therefore, the output I _R of the amount of light received on the 1st-order diffracted light side can be obtained by the following formula.

Similarly, consider a portion on one side of the optical axis L where the 1st-order diffracted light and the −1st-order diffracted light do not overlap and the frequency is relatively high. On the -1st order diffracted light side, the amplitude distribution E _L of the light is given by the following formula.

Therefore, the output I _L of the amount of light received on the -1st order diffracted light side is given by the following formula.

Considering the possibility that there is a slight difference in circuit gain between the 1st-order diffracted light side and the −1st _- order diffracted light _side , the signal levels A ₁ and A ₂ was generalized with a difference.

As described above, the intensity portion is in phase and the phase portion is in opposite phase.
Although the details are omitted, when using a light receiving element that receives light in the same area as the NA of the objective lens with the optical axis L as the boundary, and with respect to the spot diameter on the measurement object G1, the spot diameter For the same spatial frequency as the magnitude, the above formula is obtained.

Now, when the scanning beam is scanned at a speed v, a modulated signal corresponding to the spatial frequency is carried on the scanning beam. can be expressed as That is, the spatial frequency phase is modulated as follows.

Next, the signals obtained from the 1st-order diffracted light and -1st-order diffracted light at each light receiving element are used as the first signal, and the modulated signal of the AC component of the first signal is successively subjected to Hilbert transform twice. and At this time, the second signals after the first Hilbert transform are represented by H1( _IR ) and H1( _IL ), and the third signals after the second Hilbert transform are H2( _IR ) and H2( _IL ). shall be represented by Then, the Hilbert transform of the output obtained by the light-receiving element on the 1st-order diffracted light side and the signal obtained by the light-receiving element on the -1st-order diffracted light side is given by the following equation.

Here, first, the output of the sum of the first signal that is the current signal I _R and the current signal I _L of the light amount and the third signals H2(I _R ) and H2(I _L ) that have been Hilbert-transformed twice. , the current signals I _R and I _L are taken as follows.

In other words, the signal comparator 33 outputs the intensity information of the measurement object G1 based on the signal obtained by photoelectrically converting the scanning beam reflected by the measurement object G1 and the signal instructing the scanning of the controller 23, which is the basis of the scanning beam. Then, the intensity information and the phase information are sent to the data processing section 34 including a CPU, a memory, etc. connected to the signal comparator 33 .
Accompanying this, the data processing unit 34 records the intensity information and the phase information together with the scanning information for the plane, so that the measured values of the intensity information and the phase information such as the profile information about the surface of the measurement object G1 can be easily derived. be able to. In this case, the intensity information described above becomes information that reflects the reflectance.

Next, an optical measuring device to which the present embodiment is applied as a laser scanning differential interference microscope and a data calculation method of the optical measuring device will be described below.
When the sampling frequency of the AD converter forming part of the data processing unit 34 similar to the above is set to 30 MHz in consideration of the scanning speed of the scanning beam, the sampling interval is set to 90 nm.

However, if basic data sampled at intervals of 90 nm is used as basic data, oversampling is performed between samplings of each basic data, the actual sampling frequency is set to 480 MHz, and 16 data are acquired every 90 nm. At this time, the sampling interval of each data is 5.625 nm.

Based on the data obtained at a sampling frequency of 480 MHz, every 16 pieces of data are processed in the data processing unit 34. The procedure of the processing will be described below.
First, a first data group is obtained by adding the values of 16 data, which are the data of each sample point from the 16nth sample point to the 15+16nth sample point. A second data group is obtained by adding 16 data values of each sample point from the 16n+m-th sample point to the 15+16n+m-th sample point. At this time, n is a natural number including 0, and m is a natural number that does not include 0 but corresponds to the share amount of this method.

Then, as the sampling interval of each data is 5.625 nm, the two most distant data in each data group are separated by 15 data, so the separation is 84.375 nm. It means that Accordingly, for example, when the share amount is 2 and m=2, the sample points in the plurality of data in the first data group and the plurality of data in the second data group are shifted by two from each other. Each data group is the sum of these data. When m=1, the data are shifted by one, and when m=3, the data are shifted by three.

However, the above description is only an example, and in general, the number of data extracted at predetermined intervals is k, and the data extracted by the first data group is sampled from sample point (k+1)n-th to sample point k+(k+1). The data extracted by the second data group can be from the (k+1)n+mth sample point to the k+(k+1)n+mth sample point. In the above description, k is set to 15 and k+1 is set to 16 as 16 data are obtained every 90 nm.

Along with the above, intensity information and phase information of the measurement object G1 can be obtained from the measured values of the sum signal and the difference signal of the measurement object G1 obtained from the signals photoelectrically converted by the two light receiving elements 29A and 29B. , a first data group obtained by adding values of a plurality of data extracted at predetermined intervals from the signals photoelectrically converted by the two light receiving elements 29A and 29B, and a plurality of data in the first data group. On the other hand, the data processing unit 34 creates a second data group obtained by adding a plurality of data values extracted with a predetermined shift corresponding to the share amount.

Furthermore, from the output of the difference between these two types of data groups, not only the intensity information and phase information based on the measured values of the sum signal and the difference signal for the measurement object G1, but also the differential operation of only the intensity and the differential operation of only the phase are obtained. Calculations and differential calculations with respect to polarized light can be executed. Note that the differential operation of only the phase is almost synonymous with the conventional differential interference. However, it differs in that it is not affected by polarization.

On the other hand, optically, sufficient contrast cannot be produced unless the amount of shear is set to an appropriate size. If the S/N ratio is obtained, the contrast can be detected even with a slight change such as when the share amount is m=1. Further, for example, m can be easily adjusted by inputting a set numerical value to the optical measuring apparatus of this embodiment, so there is no need to perform shear adjustment by the optical system.

How to obtain specific values of the intensity pattern and the phase pattern will be described below.
In the case of the intensity pattern, if the profile of the measurement object G1 itself is f(x)=1+mcos(kx), the information obtained from the ratio of the AC signal to the DC signal of the output of the sum of the two light receiving elements 29A and 29B becomes mcos(kx).
In the case of the phase pattern, if the profile of the measurement object G1 itself is represented by the following equation (11), the information obtained from the ratio of the Hilbert transform of the AC signal output from the difference between the two light receiving elements 29A and 29B to the DC signal is When the phase is θ(x), the following equation (12) is obtained. Accompanying this, the output of the difference between adjacent data is given by the following formula (13) for intensity and given by the following formula (14) for phase.

Thus for each original pattern, k times the intensity and phase patterns can be obtained. That is, it is the differential of the pattern on the original measurement object G1. Therefore, in addition to the calculation of the intensity and phase on the Fourier transform plane derived using the output of the sum signal and the difference signal of the two light receiving elements 29A and 29B, as described above, oversampling and differentiation Intensity information and phase information proportional to the spatial frequency can be individually derived by performing a similar calculation. Furthermore, the polarizing optical system provides the same function as a differential polarizing microscope.

In other words, conventional differential interference microscopes use the retardation of polarized light to obtain differential information. As the surface is rotated, the image appears to change due to birefringence, making it very difficult to handle and difficult to obtain correct observation results.
On the other hand, according to the method using the optical measurement apparatus of the present embodiment, differential information can be obtained based on the electrical signal without using polarized light. correct DIC information can be generated even if

As described above, the method of the optical measuring device according to the present embodiment, which overcomes the drawbacks of the conventional differential interference microscope and adds the function of the differential interference microscope in addition to the method of obtaining the intensity and phase that have been used conventionally, is added. By doing so, it is possible to perform a differential operation of only intensity, a differential operation of only phase, and a differential operation of polarized light, and obtain new information that cannot be obtained by conventional devices and methods.

According to the present embodiment, the MTF curve M regarding intensity and phase becomes like each graph shown in FIG. In these graphs, y is the degree of modulation on the vertical axis, f is the spatial frequency on the horizontal axis, and fc is the cutoff frequency.
In the graph of FIG. 4A, which represents the MTF curve M of simple intensity information, the MTF curve M linearly decreases from the modulation degree 1 at the spatial frequency f of 0 as shown in the following equation (15). , the degree of modulation becomes 0 at the cutoff frequency fc.

On the other hand, according to the method of adding differential information of the present embodiment, the intensity information at the spatial frequency f is 0 as shown in the graph of FIG. 4B based on the above equation (16). The value of the degree of modulation becomes 0, and as the spatial frequency f increases, the degree of modulation increases curvilinearly, reaching a maximum value of 1 at the spatial frequency f half the cutoff frequency fc. After that, the degree of modulation decreases curvilinearly and becomes 0 at the cutoff frequency fc.

On the other hand, in the graph of FIG. 4C, which represents the MTF curve M of simple phase information, the MTF curve M is a straight line from the modulation degree 0 at the spatial frequency f of 0, as shown in the following equations (17) and (18). increases exponentially, and the degree of modulation reaches a maximum value of 1 at a frequency half the cutoff frequency fc. After that, the degree of modulation decreases linearly and becomes 0 at the cutoff frequency fc. In this case, the curve becomes an upwardly convex quadratic curve.

On the other hand, according to the method of adding differential information of the present embodiment, the spatial The value of the degree of modulation when the frequency f is 0 is 0, and the degree of modulation increases curvilinearly as the spatial frequency f increases. In this section, a downward convex quadratic curve is formed. Then, it has a maximum value of 1 at a spatial frequency f that is half the cutoff frequency fc. After that, the degree of modulation slowly decreases in a curvilinear manner until the degree of modulation becomes 0 at the cutoff frequency fc. In this section, a downward convex quadratic curve is formed.

That is, in both the intensity part and the phase part, if the method of adding differential information of the present embodiment is used, it is possible not only to obtain information with the maximum degree of modulation at 1/2 of the cutoff frequency fc, but also , the high frequency region will be emphasized.

Next, an optical measuring device to which the present embodiment is applied and a modified example of the data calculation method of the optical measuring device will be described below.
In this modified example, the following processing is performed in the data processing unit 34 based on every 16 pieces of data from the data obtained with the sampling frequency of 480 MHz in the same manner as described above.

First, the data of each sample point sx-th is taken as the first data group, and the data of the s(x+m)-th sample point is taken as the second data group. At this time, let s be the data extraction interval, x be the acquisition data position within each data extraction interval, and m be the share amount. Specifically, when acquiring, for example, a total of 10 pieces of data every 90 nm, s is 16, x is any acquired data position from 0 to 15, and m is 1, for example.

As a result, in the first data group, 10 pieces of sample data are obtained every 90 nm, and the values of the obtained sample data are added. Also, in the second data group, the sample data at the position next to the position of the sample data in the first data group is obtained. In other words, 10 pieces of sample data are obtained every 90 nm as in the above, and the values of the obtained sample data are added. However, if the share amount m is set to 2, for example, in the second data group, sample data at a position shifted by two from the position of the sample data in the first data group is acquired.

Along with the above, similarly to the first embodiment, a first data group obtained by adding a plurality of data at predetermined intervals from the signals photoelectrically converted by the two light receiving elements 29A and 29B, and this first data group The data processing unit 34 creates a second data group obtained by adding a plurality of data shifted by a predetermined amount corresponding to the share amount to the plurality of data of . Furthermore, from the output of the difference between these two types of data groups, not only is it possible to obtain intensity information and phase information based on the measured values of the sum signal and the difference signal for the measurement object G1, but also the differential operation of only the intensity, the phase It is possible to perform a differential operation of only , and a differential operation with respect to polarized light, respectively. Note that the differential operation of only the phase is almost synonymous with the conventional differential interference. However, it differs in that it is not affected by polarization.

Next, Embodiment 2 of the optical measuring device and the data calculation method for the optical measuring device according to the present invention will be described below with reference to FIG. This embodiment is a transmission optical system in which a scanning beam is transmitted through an object to be measured.
FIG. 5 is a block diagram showing a transmission optical system apparatus according to this embodiment. The main optical system is the same as that of the reflective optical system, so the explanation is omitted. will pass through.

In this embodiment, since the transmission optical system is used, the beam splitter 27 is not required, and accordingly, the light receiving element group 29 is arranged on the opposite side of the objective lens 31 with respect to the measurement object G2. ing. However, as in the first embodiment, the light receiving element group 29 is not only arranged on the far-field surface of the measurement object G2, but also has the same structure as the two light receiving elements 29A and 29B in the first embodiment. 29E and 29F.

That is, in the case of this device of a transmission optical system, the light receiving element group 29 is arranged on the extension line of the optical axis L of the objective lens 31 as shown in FIG. Furthermore, as in the first embodiment, light is received on a plane substantially perpendicular to the direction along the optical axis L, which is the center of the spot of the scanning beam LA, with a boundary line S passing through the optical axis L interposed therebetween. Elements 29E and 29F are located respectively. Accordingly, the light receiving element 29E is positioned on one side of the boundary line S, and the light receiving element 29F is positioned on the opposite side of the boundary line S. As a result, even in the transmission optical system apparatus shown in FIG. 5, the light beams are spatially substantially equiphase on the light receiving element group 29 in the same manner as in the reflection optical system apparatus shown in FIG.

Further, the signal comparator 33 outputs the intensity information of the measurement object G2 and the intensity information of the measurement object G2 based on the signal obtained by photoelectrically converting the scanning beam transmitted through the measurement object G2 and the signal for instructing the scanning of the controller 23 which is the basis of the scanning beam. Phase information is obtained, and this intensity information and phase information are sent to a data processing section 34 comprising a CPU, a memory, etc., connected to the signal comparator 33 . Along with this, the data processing unit 34 records the intensity information and the phase information along with the scanning information for the plane, and easily obtains the measured values of the intensity information and the phase information such as the profile information about the surface and inside of the measurement object G2. can lead to In this case, the intensity information described above becomes information that reflects the reflectance.

Therefore, as in the first embodiment, the signals photoelectrically converted by the light receiving elements 29E and 29F constituting the light receiving element group 29 and the signal from the controller 23 instructing the scanning by the two-dimensional scanning device 26 are used by the signal comparator 33. obtains the intensity information and phase information of the measuring object G2.
Then, as in the first embodiment, the original signal is subjected to Hilbert transform, and the data is finally processed, and the data processing unit 34 converts the optical distance, transmittance, transmittance, etc. of the profile of the object G2 to be measured. can be obtained substantially. As a result, this embodiment also makes it possible to completely separate the transmitted light intensity information and the optical distance information.

In addition, C ₀ and C ₁ shown in the above-described Example 1 are measured in the absence of the measurement object, and b is obtained in the presence of the measurement object G2, and then C ₀ and C ₁ are measured. , it is possible to effectively obtain intensity information related to the degree of modulation m of intensity. In this way, it becomes possible to convert this intensity information into a physical quantity such as transmittance.

In particular, in the apparatus of the transmission optical system as in this embodiment, changes in the state of unstained, non-invasive living cells can be separated into intensity information and optical distance information and observed in real time. It can play a major role in testing whether cells such as cells are normal or not, testing for the presence of cancer cells, and the like. This is a feature that is significantly different from a measuring instrument such as an electron microscope, which can only observe a living body in a dead state even at high magnification.
Furthermore, according to the method using the optical measurement apparatus of the present embodiment, differential information can be obtained based on the electrical signal without using polarized light. Even if an object has it, it can generate correct DIC information.

On the other hand, as a modification of this embodiment, a lens 40 is placed behind the measurement object G2 on the opposite side of the measurement object G2 to the objective lens 31 and in front of the light receiving element group 29 as shown in FIG. It is conceivable to place That is, the scanning beam, which is the diffracted light from the measurement object G2, is collimated by the lens 40, and then led to the light receiving element group 29. FIG. Therefore, in this modification, the Fourier transform pattern of the scanning beam transmitted through the measurement object G2 is collimated by the lens 40 and received by the light receiving element group 29 as shown in FIG. However, the scanning beam may be guided to the light receiving element group 29 by condensing the light with this lens 40 .

Next, Embodiment 3 of the optical measuring device and the data calculation method for the optical measuring device according to the present invention will be described below with reference to FIG. This embodiment can be applied to a reflective optical system device and a transmissive optical system device.

In Embodiments 1 and 2, the light receiving elements 29A and 29B or the light receiving elements 29E and 29F constituting the light receiving element group 29 are on a plane substantially perpendicular to the direction along the optical axis L of the scanning beam LA. A boundary line S passing through the optical axis L is interposed between them, and they are located in two divided areas. On the other hand, in this embodiment, the light receiving elements 29A to 29D divided into four shown in FIG. .

In other words, the light-receiving elements 29A to 29D are arranged in each area defined by the boundary line S and the intersecting boundary line KS that intersects the boundary line S on the optical axis L of the irradiation light. More detailed data can be obtained by individually acquiring information in the horizontal and vertical directions within the surfaces of the measurement objects G1 and G2 with these four light receiving elements 29A to 29D.

In addition to this, two of the four light receiving elements 29A to 29D facing each other across the boundary line S (for example, the light receiving element 29A and the light receiving element 29B), The intensity information and the optical distance information are obtained by the above-described calculations using two light receiving elements that form a pair (for example, the light receiving element 29A and the light receiving element 29C).

Specifically, the outputs of the paired light-receiving elements have the in-phase signal as the intensity information and the opposite-phase signal as the optical distance information, so that the intensity and the optical distance information can be separated as described above. Along with this, it is possible to use a smaller, lower-cost light receiving element, and even a small amount of phase information received by this small light receiving element can provide the necessary observation value for the measurement unit. In this embodiment, the area is divided into four areas, but the area may be divided into four or more areas and four or more light receiving elements may be employed.

Furthermore, when the polarization signals detected by these four light-receiving elements 29A to 29D are subjected to calculations using the two data groups as described above, polarized light that cannot be obtained by conventional optical systems such as differential polarizing microscopes can be obtained. Differential interference information can also be obtained.

A fourth embodiment of the optical measuring device and the data calculation method for the optical measuring device according to the present invention will be described below with reference to FIG. FIG. 8 is a schematic diagram showing the configuration of the optical measuring device of this embodiment.
As shown in FIG. 8, a laser light source 21, which is a light source for emitting light and is a semiconductor laser, is arranged to face an objective lens 31 via an optical device (not shown). The light emitted from the laser light source 21 is collimated by a collimator lens (not shown) and enters the objective lens 31 . Then, the light transmitted through the objective lens 31 converges and irradiates the sample S, which is the measurement object of the transmitted object.

In the present embodiment, as shown in FIG. 8, the condenser lens 36 for condensing the diffracted light flux through the sample S into a parallel light flux is tilted with respect to the optical axis L0 of the zero-order diffracted light. installed. This makes it possible to capture not only a portion of the 0th order diffracted light, but also a portion of the 1st order diffracted light having a higher spatial frequency than if the same lens were used. That is, in the present embodiment, the light irradiated onto the sample S is diffracted as it passes through the sample S into 0th-order diffracted light and 1st-order diffracted light. Further, a part of the 0th-order diffracted light and a part of the 1st-order diffracted light are inclined by the optical axis L3 having an inclination angle intermediate between the 0th-order diffracted light and the 1st-order diffracted light. is incident on This condenser lens 36 is substantially a Fourier transform lens, and the Fourier transform pattern of the sample S is transmitted by this condenser lens 36 .

Specifically, in this embodiment, as shown in FIG. 8, a condenser lens 36 having the same NA as that of the objective lens 31 is placed at a position centering on the terminal end of the 0th-order diffracted light of the objective lens 31 as described above. It is arranged with an intermediate tilt angle between the 0th-order diffracted light and the 1st-order diffracted light. Note that the condenser lens 36 is arranged in the far field sufficiently away from the sample S.

A beam splitter 38, which is a separation element for splitting the parallel light flux emitted from the condenser lens 36 in the right direction, is arranged below the condenser lens 36 on the optical axis L3. The beam splitter 38 splits the beam into two optical paths, an optical path B1 along which the light beam is sent straight and an optical path B2 along which the beam is bent at right angles.

A rhomboid prism 39 is arranged on the optical path B1 along the optical axis L3. One surface of the rhomboid prism 39 is a semi-transmissive mirror 39A, and the opposite surface to the semi-transmissive mirror 39A is a semi-transmissive mirror 39B. 40 and 41 are arranged. On the other hand, a rhomboid prism 49 similar to the rhomboid prism 39 is arranged on the optical path B2 perpendicular to the optical axis L3. One surface of the rhomboid prism 49 is a semi-transmissive mirror 49A, and the opposite surface to the semi-transmissive mirror 49A is a semi-transmissive mirror 49B. 50, 51 are also arranged.

Here, the semicircular beams BA and BB on the optical path B1 synthesized by the rhomboid prism 39 are sent to the light receiving element 40 which is the first light receiving element. The semicircular beams BC and BD synthesized by the rhomboid prism 49 are sent to a light receiving element 50 as a second light receiving element. The light receiving element 50 is a light receiving element corresponding to the light receiving element 40 on another optical path B2 branched by the beam splitter 38. FIG. On the other hand, the light-receiving element 40 is formed of divided light-receiving elements 40A and 40B which are divided into two in the direction perpendicular to the paper with the paper as a boundary. In other words, the upper portion of the light receiving element 40 is designated as the divided light receiving element 40A, and the lower portion is designated as the divided light receiving element 40B. Similarly, the upper portion of the light receiving element 50 is designated as a divided light receiving element 50A, and the lower portion is designated as a divided light receiving element 50B.

Further, the divided light receiving elements 40A and 40B and the divided light receiving elements 50A and 50B are connected to a comparator 7 for comparing the signals from the divided light receiving elements 40A and 40B and the divided light receiving elements 50A and 50B, respectively. . The comparator 7 is connected to a data processing section 8 that finally processes the data to obtain the profile of the sample S and the like. Therefore, the comparator 7 and the data processing unit 8 calculate the output sum and the output difference between the divided light receiving elements 40A and 40B of the light receiving element 40 and the output sum and output difference between the divided light receiving elements 50A and 50B of the light receiving element 50. It is an output sum/difference detection unit for detecting.

If the same data calculation method as in Example 1 is applied to the present example of the lateral resolution improving optical system shown in FIG. Specifically, FIG. 9 shows the relationship between the 0th-order diffracted light and the 1st-order diffracted light with respect to the optical axis X1 of the objective lens 31 and the optical axis X2 of the condenser lens .

Here, R1 is the spread range of the 0th-order diffracted light of the objective lens 31, and a represents the edge of the 0th-order diffracted light of the objective lens 31. FIG. R2 is the range in which diffracted light can be received by the aperture of the condenser lens 36, and 2a represents the edge of the 0th-order diffracted light of the condenser lens 36. FIG. Also, R3 is the range in which the first-order diffracted light is received by the aperture of the objective lens 31 itself, and 3a represents the edge of the first-order diffracted light of the objective lens 31. FIG. R4 is the range in which the first-order diffracted light is received by the aperture of the condenser lens 36 itself, and 4a represents the edge of the first-order diffracted light of the condenser lens 36. FIG.

Let f be the focal length of the objective lens 31 and NA be the numerical aperture. .

The relationship of the MTF between this spatial frequency fs and the intensity and phase is as follows.
Area 1 where 0th order diffracted light and ±1st order diffracted light overlap at 0<fs≦a/λ\ochf
Area 2 where the 0th order diffracted light and the +1st order diffracted light overlap at a/λ\ochf'<fs≤3a/λ\ochf'
The MTF represents the degree of modulation. In general, the MTF is determined by the degree of overlap between the 0th order diffracted light and the ±1st order diffracted light. In the case of the intensity pattern, the ±1st order diffracted lights have the same sign, and , and ±1st-order diffracted lights have opposite signs.

Therefore, in the case of the intensity pattern, in region 1, the -1st order diffracted light decreases as the +1st order diffracted light increases. In region 2, the 1st-order diffracted light linearly decreases at the aperture of the condenser lens 36, so the MTF decreases linearly.

On the other hand, in the case of the phase pattern, in region 1, the degree of overlapping of the ±1st-order diffracted lights decreases, and the overlap between the 1st-order diffracted lights and the 0th-order diffracted lights increases linearly, so the MTF increases linearly. In region 2, the +1st-order diffracted light gradually decreases linearly in the same way as the intensity pattern, so the MTF decreases linearly.

From the above, if the spatial frequency is plotted on the horizontal axis and the degree of modulation is plotted on the vertical axis, the cutoff frequency fc of the objective lens 31 is fc=2NA/λ, and the spatial frequency f is given by the following equation (22). However, in the following formula, y is the distance from the optical axis of the objective lens 31 .

According to the present embodiment, the MTF curve M regarding intensity and phase becomes like each graph shown in FIG. In these graphs, y is the degree of modulation on the vertical axis, f is the spatial frequency on the horizontal axis, and fc is the cutoff frequency.
In the graph of FIG. 10A representing the MTF curve of the intensity information, the MTF curve M is cut from the modulation degree 1 at the spatial frequency f of 0 as shown in the following equations (23) and (24). The degree of modulation is 1 as it is up to the off frequency fc/2. Then, it decreases linearly from here and becomes 0 at 3fc/2.

On the other hand, according to the method of adding differential information of the present embodiment, the intensity information is expressed as the graph shown in FIG. When the frequency f is 0, the value of the degree of modulation is 0, and as the spatial frequency f increases, the degree of modulation increases linearly up to the cutoff frequency fc/2. Furthermore, as the spatial frequency f increases, the modulation increases curvilinearly, reaching a maximum modulation of 1 at a spatial frequency of 3fc/4. After that, the degree of modulation decreases curvilinearly and becomes 0 at 3fc/2.

On the other hand, in the graph of FIG. 10(C) representing the MTF curve of the phase information, the MTF curve M linearly changes from the modulation degree 0 at the spatial frequency f of 0 as shown in the following equations (27) and (28). The degree of modulation reaches the maximum value of 1 at the cutoff frequency fc/2. After that, the modulation index decreases linearly and becomes 0 at 3fc/2.

On the other hand, according to the method of adding differential information of the present embodiment, the phase information is expressed as the graph shown in FIG. The value of the degree of modulation when the frequency f is 0 is 0, and the degree of modulation increases curvilinearly as the spatial frequency f increases. Although there is an inflection point at the cutoff frequency fc/2, the maximum modulation degree is 1 at the spatial frequency of 3fc/4. After that, the degree of modulation decreases curvilinearly and becomes 0 at 3fc/2.

As described above, by using the differential operation in the optical system for improving the lateral resolution according to the present embodiment, the contrast in the region with higher spatial frequency can be emphasized, so that the fine structure can be displayed more clearly. .

A fifth embodiment of the optical measuring device and the data calculation method for the optical measuring device according to the present invention will be described below with reference to FIG. This embodiment is an example of applying the present invention to an optical system having high resolution, and FIG. 11 is a schematic diagram showing the configuration of this embodiment.
In this embodiment, in order to improve the lateral resolution of the scanning beam that has passed through the measurement object G2, the tilted optical system shown in this figure is arranged below the apparatus of the transmission optical system of the second embodiment, for example. It is something to do. In FIG. 11, optical systems such as the collimator lens 22, the pupil transfer lens systems 25 and 30, and the two-dimensional scanning device 26 are omitted.

In the present embodiment, a lens 61 is installed at an angle to the optical axis L of the 0th-order diffracted light, which is the optical axis of the objective lens 31, and converts the light diffracted by the measurement object G2 into parallel light. there is As a result, part of the 0th-order diffracted light and part of the 1st-order diffracted light transmitted through the measurement object G2 are arranged at an intermediate tilt angle between the optical axis L of the 0th-order diffracted light and the optical axis L1 of the 1st-order diffracted light. A part of the 0th-order diffracted light and part of the 1st-order diffracted light transmitted through the measurement object G2 can be taken into the lens 61 tilted by the optical axis L3.

In this way, not only a part of the 0th-order diffracted light but also a part of the 1st-order diffracted light having a higher spatial frequency than when the same lens is used is taken in, and the 0th-order diffracted light and the 1st-order diffracted light are combined. achieves interference.

Also, as shown in FIG. 11, an optical element that receives a light beam passing through this lens 61 is arranged to face each other. That is, a set of the beam splitter 12, the polarizers 3 and 4, and the light receiving element groups 7 and 8 is arranged facing the lens 61. FIG. In this way, by tilting the lens 61, part of the 0th order diffracted light and part of the 1st order diffracted light are acquired, and the diffracted lights converted into parallel beams by the lens 61 are guided to a set of optical elements. there is

On the other hand, in this embodiment, the optical axis L2 of the −1st order diffracted light is located symmetrically with respect to the optical axis L of the objective lens 31 with respect to the optical axis L1. Then, the measurement object G2 is transmitted through the lens 61 arranged in a state inclined by the optical axis L4 having an inclination angle intermediate between the optical axis L of the 0th-order diffracted light and the optical axis L2 of the -1st-order diffracted light. A portion of the 0th order diffracted light and a portion of the −1st order diffracted light can be captured.

As a result, not only a part of the 0th-order diffracted light but also a part of the -1st-order diffracted light having a higher spatial frequency than when the same lens is used is taken in, and these 0th-order diffracted lights and Interference of −1st order diffracted light is realized.

Then, as shown in FIG. 11, a set of optical elements that receive the light beam passing through this lens 61 are arranged facing each other in the same manner as described above. However, a set of the beam splitter 11, the polarizers 1 and 2, and the light receiving element groups 5 and 6 is arranged facing the lens 61 on the optical axis L4. As a result, the tilted lens 61 obtains a part of the 0th order diffracted light and a part of the -1st order diffracted light, and the diffracted lights made into parallel beams by this lens 61 are guided to the sets of the respective optical elements. ing.

In this embodiment, the lenses 63 are inserted between the polarizers 3 and 4 and the light receiving element groups 7 and 8, respectively, so that the light receiving surfaces of the light receiving element groups 7 and 8 are positioned substantially at the focal point of the lens 63. so that However, the light-receiving surfaces of the light-receiving element groups 7 and 8 are not necessarily required to be the imaging surface of the object G2 to be measured. do not have.

Similarly, lenses 63 are also inserted between the polarizers 1 and 2 and the light receiving element groups 5 and 6 so that the light receiving surfaces of the light receiving element groups 5 and 6 are almost at the focal position of the lens 63 . However, the light-receiving surfaces of the light-receiving element groups 5 and 6 do not necessarily have to be the imaging surface of the measurement object G2. do not have.

As described above, in this embodiment, as in the first to fourth embodiments, the in-plane resolution is high, and the out-of-plane resolution for height and refractive index distribution is high. An optical measuring device is provided that can obtain three-dimensional information of a living biological sample having a thickness such as a cell in a living state in real time.

By doing so, it is possible to acquire information even in a region with a high spatial frequency in a very simple manner, and to improve the MTF characteristics. This makes it possible to measure the optical distance with high reliability even for the measuring object G2 that requires high lateral resolution. In the case of this embodiment, since the lens 63 is used, the phase difference between the 0th-order diffracted light and the 1st-order diffracted light and the phase difference between the 0th-order diffracted light and the -1st-order diffracted light incident on the lens 63 are reflected as they are. A certain amount of wavefront aberration is acceptable. Therefore, there is no need to use an expensive lens.

Also, although the optical system shown in FIG. 11 is drawn within the plane of the paper, a similar optical system may be additionally arranged in a direction perpendicular to the plane of the paper. By doing so, the polarization axes to be detected can be arranged in four directions different from each other, and directivityless detection can be performed. Moreover, it is preferable that the directions of the respective polarization axes are different from each other by 45 degrees in order to simplify the arrangement and calculation.

As a result of the above, in this embodiment, the light receiving element groups 7 and 8 and the light receiving element groups 5 and 6 can detect intensity information on four mutually different polarization axes. For this reason, as in the first to fourth embodiments, this embodiment also has a high in-plane resolution and a high out-of-plane resolution for height and refractive index distribution. An optical measuring device is provided that can obtain three-dimensional information of a living biological sample having a thickness such as a cell in a living state in real time. Furthermore, in this embodiment as well, from the output of the difference between the two types of data groups, not only the intensity information and phase information based on the measured values of the sum signal and the difference signal for the measurement object G2, but also the differential operation of only the intensity , phase only, and polarization.

However, in this embodiment, the polarization directions of the polarizers 1 and 2 of the optical system set on the optical axis L4 are different from the polarization directions of the polarizers 3 and 4 of the optical system set on the optical axis L3. is tilted 45 degrees. However, a polarizing beam splitter can be employed instead of the beam splitter and the polarizer. In this case, the other polarizing beam splitter can be arranged at an angle of 45 degrees with respect to the other polarizing beam splitter.

In each of the above embodiments, the end of the sample to be extracted is the k+(k+1)n-th sample point "sample point 15+16n" or the k+(k+1)n+m-th sample point "sample point 15+16n+m". Therefore, the number of data to be extracted is set to 16, but other number of data such as 4 or 8 may be used. Also, the share amount m may be a number other than 1 or 2.

Furthermore, the data extracted by the first data group is the sum of a plurality of data with sample point sx, and the data extracted by the second data group is the sum of a plurality of data with sample point s(x+m). , the number of data may be two or more as the plurality of data, and as the number of data increases, it becomes possible to generate more accurate differential interference-like information.

The optical measuring device of the present invention can measure not only the distance to the sample, which is the object to be measured, and the shape of the sample, but also the intensity information can be separated from the optical distance information. It is also possible to measure the physical quantity of In this way, the present invention can be applied to various types of measuring instruments such as microscopes.
In addition, the optical measuring apparatus of the present invention can be applied not only to microscopes but also to various types of optical instruments and measuring instruments using electromagnetic waves having waves. and three-dimensional profile information such as height can be separated.

21 laser light source (light source)
22 collimator lens 23 controller 25 pupil transfer lens system 26 two-dimensional scanning device (scanning element, two-dimensional scanning element)
27 beam splitter 29 light receiving element group 29A to 29D light receiving element 30 pupil transfer lens system 31 objective lens 33 signal comparator (measurement unit)
34 Data processing unit (measurement unit)
G1, G2 object to be measured L optical axis LA scanning beam S boundary line KS cross boundary line

Claims (9)

a light source that emits coherent illuminating light;
a scanning element that scans the irradiation light from the light source and sends it to the measurement object;
At least two light-receiving elements positioned on each side with a boundary line perpendicular to the direction of the optical axis of the illuminating light, and receiving and photoelectrically converting the illuminating light modulated by the object to be measured during scanning. ,
The measurement values of the sum signal and the difference signal for the object to be measured are obtained from the signals of the basic basic data photoelectrically converted and output by these light receiving elements, and the basic data are obtained from the signals photoelectrically converted and output. A first data group obtained by adding values of data and a plurality of data extracted at predetermined intervals; a measuring unit that creates a second data group obtained by adding the values of a plurality of extracted data, and executes a differential operation on the object to be measured by outputting the difference between these two data groups;
an optical metrology device including When the number of data extracted at predetermined intervals between basic data is k,
The data extracted from the first data group is obtained by adding the values of (k+1) pieces of data up to the k+(k+1)n-th sample point by shifting the extraction position one by one from the (k+1)n-th sample point,
The data extracted from the second data group is obtained by adding the values of (k+1) pieces of data up to the k+(k+1)n+m-th sample point by shifting the extraction position by one from the (k+1)n+m-th sample point,
2. The optical measuring device according to claim 1, wherein n is a natural number including 0 and m is a natural number not including 0. The values of a plurality of data with the data extracted by the first data group as the sample point sx are added, and the values of the plurality of data with the data extracted by the second data group as the sample point s(x+m) are added. shall be
2. The optical measuring device according to claim 1, wherein s is the data extraction interval, x is the acquisition data position within each data extraction interval, and m is the share amount. 4. The optical measuring device according to any one of claims 1 to 3, wherein two light receiving elements are added to the two light receiving elements so that polarized light can be detected with four light receiving elements. The scanning element is a two-dimensional scanning element that scans the irradiation light in two mutually orthogonal directions, and the irradiation light applied to the object to be measured is modulated by scanning in at least one of the two directions. The optical measuring device according to any one of claims 1 to 4. 6. An optical metrology apparatus according to any one of claims 1 to 5, wherein a controller is connected to said scanning element, said controller manipulating operation of said scanning element to adjust scanning speed and scanning range. a light source that emits coherent illuminating light;
a scanning element that scans the irradiation light from the light source and sends it to the measurement object;
At least two light-receiving elements positioned on each side with a boundary line perpendicular to the direction of the optical axis of the illuminating light, and receiving and photoelectrically converting the illuminating light modulated by the object to be measured during scanning. ,
a measurement unit that obtains a measurement value of an object to be measured from signals of basic basic data photoelectrically converted and output by these light receiving elements;
A data calculation method for an optical measuring device comprising:
A first data group obtained by adding values of basic data and a plurality of data extracted at predetermined intervals from a signal photoelectrically converted and output in a measurement unit; Creating a second data group obtained by adding the values of a plurality of data extracted by shifting a predetermined amount from each of the plurality of data,
A data calculation method for an optical measuring device, in which, in addition to obtaining measured values for the object to be measured, a differential operation is performed on the object to be measured by outputting a difference between these two types of data groups in a measurement unit. When the number of data extracted at predetermined intervals between basic data is k,
The data extracted from the first data group is obtained by adding the values of (k+1) pieces of data up to the k+(k+1)n-th sample point by shifting the extraction position one by one from the (k+1)n-th sample point,
The data extracted from the second data group is obtained by adding the values of (k+1) pieces of data up to the k+(k+1)n+m-th sample point by shifting the extraction position by one from the (k+1)n+m-th sample point,
8. The data calculation method for an optical measuring device according to claim 7, wherein n is a natural number including 0 and m is a natural number not including 0. The values of a plurality of data with the data extracted by the first data group as the sample point sx are added, and the values of the plurality of data with the data extracted by the second data group as the sample point s(x+m) are added. shall be
8. The data calculation method for an optical measuring device according to claim 7, wherein s is the data extraction interval, x is the acquisition data position within each data extraction interval, and m is the share amount.

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