JPH11258057A - Complex signal detecting method, complex microscope and complex diffraction device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect a complete complex signal by detecting a real number component microscopic image of a sample and an imaginary number component microscopic image by shifting a phase by π/2 on only the sample transmitted light, and taking the complex sum of these real number component microscopic image and imaginary number component microscopic image. SOLUTION: First of all, the light passing through a sample is detected by using a lens system to measure a square of the amplitude, that is, an intensity value (energy per unit time and area). Next, a π/2 phase plate is arranged on the focal surface on the rear side of a lens to shift a phase by π/2 on only the 0 order diffracted light (the focus condensed light of the unscattered irradiating light) of this transmitted light. This transmitted irradiating light is mixed with the object light having an image signal at image forming time as a reference signal to detect an intensity value of the sum of both. The complex sum of a detecting intensity value (a real number component signal) of the front stage and a detecting intensity value (an imaginary component signal) of the rear stage is calculated to thus detect a complex signal composed of the real number component signal and the imaginary number component signal of a bright field image sample, that is, a sample original image.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting a complex signal, a complex microscope, and a complex diffraction device. More specifically, the present invention relates to an optical device using electromagnetic waves such as microwaves, infrared rays, visible light, ultraviolet rays, X-rays and γ-rays, and an optical device using material waves such as electron beams, neutron beams and muons. The present invention relates to a new method for detecting a complex signal that enables phase detection in a device, and a complex microscope and a complex diffraction device using the method.

[0002]

2. Description of the Related Art Conventionally, various optical devices have been developed as optical devices for detecting the square of the amplitude of an electromagnetic wave or a matter wave (that is, intensity = energy value per unit time, unit area). For example, transmission electron microscopes, transmission optical microscopes, reflection optical microscopes, X-ray diffraction, holography, and spectrometers are known.

However, each of these various optical devices has a problem to be solved as described below. i) Transmission electron microscope A transmission electron microscope is a microscope that uses an electron wave, which is a material wave, and has two fundamental problems.

One problem is that the spatial resolution is 1/20 or less, and sometimes 1/100, worse than the wavelength of the electron wave used. For example, 1
The wavelength of an electron beam having an acceleration voltage of 00 kV is about 0.04 °, but the current maximum resolution for this electron wave is about 1 °.
And a very low resolution of 25 times the wavelength is obtained. The optical microscope detects 1 /
Compared to a resolution of 3 obtained, the performance of the electron microscope is only about 1/75 of the theoretical limit of Abbe.

Another problem is the inherent distortion of the image obtained through the lens system from the electron waves transmitted through the sample.
This image distortion is caused by blurring due to aberration of the lens system of the electron microscope, and is said to be a problem of the contrast transfer function. For example, in the case of a metal sample having electron beam absorption, the aberration appears as a high-frequency component deterioration of the spatial frequency of the image function, and the resolution deteriorates. On the other hand, in the case of an object that does not absorb electron beams, such as a biological sample, the contrast transfer function works even worse, and the aberration appears as deterioration of both the low frequency component and the high frequency component of the spatial frequency of the image function, and the In addition to the blur, the image is distorted. This means that the shape of the image greatly depends on how to focus, and it is impossible to obtain a correct image with high resolution from a biological sample.

[0006] Both the reduction in resolution and the intrinsic distortion of the image as described above are due to the large spherical aberration of the electron microscope lens and the resulting contrast transfer function. In order to solve this problem, various attempts have been made in the past to produce concave lenses for electron beams, but none of them have achieved a satisfactory effect. On the other hand, aberration removal or contrast transfer function correction by computer image processing
It is known that it can be realized if an image can be correctly reproduced as a complex image.

First, as a method of reproducing a complex image, that is, a complex signal, holography by Gabor is known ("A New Microsopic Principle", D. Gabor, Nature
No. 4098 (1948)). In the method according to Gabor, since a real number signal is essentially obtained, two complex images of complex conjugate (Ψ and Ψ ^* ) are overlapped. Therefore, two methods have been proposed to eliminate this difficulty. One is to extend conventional electron microscopy and combine two measurements and detections using two complementary semicircular apertures ("Single-Sideband Holography", O. Bryngdahl an.
d A. Lohmann, Journal of the Optical Society of Ame
rica Vol.58 No.5 (1968), "An alternative to Holograp
hy for Determining Phase from Image Intensity Meas
urements in Optics ", DLMisell, REBurge and A.
H. Greenaway, Nature Vol.247 (1974)). the other one is,
This is an off-axis holography using an oblique reference beam ("Reconstructed Wavefronts and Communicatio").
n Theory ", ENLeith and J. Upatnieks, Journal of t
he Optical Society of America Vol. 52No.10 (1962)
). The application of this method to electron optics will be described later.

In the method using the complementary semicircular aperture, two images are subjected to a Fourier transform, and then synthesized by removing unnecessary portions.
Fourier transform is performed again. Thus, a non-overlapping complex image Ψ is obtained. However, this method is essentially applicable only to weak optical objects, and has the disadvantage that the sensitivity is reduced by half with a semicircular stop. The aberration problem of the lens system appears in the image through the contrast transfer function, and in order to avoid this in hardware, electron microscopes have made the numerical aperture of the lens extremely small (1/100 or less). This causes the resolution to be reduced to 1/75 of the theoretical limit. Furthermore, the small numerical aperture means that
Contrast is not sufficient to eliminate most of the electron waves scattered from the object, which causes a light source system that is extremely dark compared to an optical microscope.

On the other hand, in an optical microscope, aberrations are eliminated by a combination of lenses, and the numerical aperture is increased to realize a high resolution and a high contrast that are almost equal to the wavelength of light. This is not possible with an electron microscope because the absence of a concave lens, both in hardware and software, does not eliminate the effect of aberrations, which can distort the image through the contrast transfer function. It is.

This problem can be solved if the complex signal of the electron wave can be correctly extracted as an image. ii) Transmission type and reflection type optical microscopes Compared with electron microscopes, optical microscopes using electromagnetic waves have a long history and can be said to have been completed to some extent. This is because the optical microscope has both a convex lens and a concave lens, so that aberration correction is possible, and performance close to the logical limit of Abbe is achieved.

However, the intensity of the image obtained by the optical microscope is detected as long as the image is recorded by a human eye, a photograph, a CCD camera, various kinds of image pickup tubes, and the like. It is incomplete because the original complex signal constituting it cannot be recorded. In order to obtain the intensity and the out-of-phase of a complex signal as a microscopic image, a method of making an interference by adding an external reference signal to an image signal as an application of an interferometer and creating an image corresponding to a real component signal and an imaginary component signal is a method. Known ("Digital Wavefront Measuring I
nterferometer for Testing Optical Surfaces and Len
ses ", JHBruning et al., Applied Optics Vol.13 N
o.11 (1974), "New Common-Path Phase ShiftingInterf
erometer using a Polarization Technique ", H. Kadono
et al., AppliedOptics Vol.26 No.5 (1987), "Phase
Shifting Common Path Interferometer using a Liquid
-crystal ", H.Kadono et al., Optics Communications
110 (1994) 391-400). Generally, four reference signals having phases different by π / 2 are prepared, interference with an image signal is obtained, detected, and the result is combined to extract a complex signal. Therefore, even with this method, at least four measurement detections are required. Further, since the relative phase between the image signal and the reference signal is not known in advance, the phase of the image signal leaves the constant term uncertain. Therefore, the problems of this method are that an external reference signal is required, that measurement and detection are required at least four times, and that the relative phase is uncertain in the phase image.

Further, depending on the optical properties of the target object, for example, a light absorbing object, a reflecting object, a transparent object, a transmission microscope, a reflection microscope,
There are optical microscopes such as a phase contrast microscope. Each of these optical microscopes sees some of the properties of the object to light. That is, the light absorption coefficient, reflectance,
They are looking at the refractive index.

Although such optical information originally appears at once as a complex signal in an electromagnetic wave, a complex signal can be obtained only by the square of the absolute value in ordinary intensity value detection.
A device has been devised to extract each optical property individually by changing the device. This is why various optical microscopes exist. If there is a method for correctly extracting complex signals and an optical microscope, these types of microscopes are unnecessary, and results equivalent to the results obtained with various microscopes can all be simulated by processing complex signals. become.

Iii) X-ray diffraction X-ray diffraction has conventionally been used as a means for analyzing the structure of molecules that cannot be seen with a microscope. Instead of using a lens to enlarge the shape of a substance as in a microscope, X-ray diffraction has been used. ,
A diffraction image of a crystal is obtained, and the crystal structure and molecular structure are enlarged as a diffraction pattern.

However, since the diffraction image obtained in this manner is still the intensity value of the diffracted electromagnetic wave, even if this diffraction image is Fourier-transformed, the original crystal structure and molecular structure cannot be obtained. Although the diffracted wave itself has this phase information, the phase information is lost because the recording of the diffraction pattern is the square detection of the electromagnetic wave. In the case of structural analysis of small molecules, a direct method is used in which phase information is obtained while estimating phase information only from intensity information.

In the case of a macromolecule such as a protein, this direct method cannot be applied because the calculation amount becomes enormous. Instead, heavy atoms are adsorbed and introduced into the molecule to determine the phase, but many crystals are broken during this process. For this reason, even if a crystal is obtained, the crystal analysis often fails due to the failure of heavy atom substitution.

This phase problem, that is, crystal analysis using only one crystal, can be solved if a complex signal can be detected from electromagnetic waves. iv) Holographic holograms record the interference pattern between the diffracted light from the object and the reference light. In order to generate an image from the hologram, reproduction of the image is performed in the reverse process of recording. However, in order to complete reproduction imaging, recording of interference fringes with extremely high resolution and reference light whose angle has been adjusted are required. The hologram itself is a complex interference fringe pattern without an image when viewed without a reference beam for reproduction.

Although holography is currently used for displaying a stereoscopic image, it is also used for improving the resolution of an electron microscope which Gabor originally aimed at. It is off-axis
As an application of holography, it separates the overlap (Ψ and Ψ ^* ) of complex conjugated complex images. That is,
One of Ψ and Ψ ^* is shifted to the high frequency side and the other is shifted to the low frequency side for separation. In this method, a hologram is Fourier-transformed, for example, a signal component shifted to a low frequency.

[0019]

(Equation 1)

And a squared signal

[0021]

(Equation 2)

And the signal component shifted to high frequency

[0023]

(Equation 3)

Take out only Next, multiply the inverse function,

[0025]

(Equation 4)

Then, the Fourier-transformed elephant is returned to the origin once again, is set to Ψ _k, and is again Fourier-transformed to extract one of the complex images （(“Electron Holography App”).
roaching Atomic Resolution ", H. Lichte, Ultramicros
copy 20 (1986) 293-304). The problem with this method is that some of the signals contained in the Fourier transform image in the frequency space,
That only one-third of the whole can be used, that the image must be band-limited in order to guarantee separation by frequency shift of the complex image, and off-axis
This is because holography requires two coherent illuminations which are at an angle to each other.

Although holography uses an image hologram, which uses the same image forming system as a photograph, it requires a reference light whose angle is adjusted for image reproduction, a real image, a virtual image,
Separating the transmitted light only optically is the same as a general hologram. If the complex signal can be extracted, the image itself is imaged like a photograph, and a pure intensity image and a phase image are separated. Here, the intensity image corresponds to the extinction coefficient image, and the phase image corresponds to the refractive index image.

Accordingly, the present invention has been made in view of the above circumstances, and solves the above-mentioned problems of the conventional method and reduces the brightness and sensitivity of the optical system. It is not necessary to use a complex signal component, and there is no need to limit the measurement sample to a weak optical absorber or a weak phase object because only the complex signal component is extracted.Therefore, it has wide applicability and internal reference. Since a signal is used, an external reference signal is not required, and coherence between an image and a reference signal required when an internal reference signal is used can be automatically guaranteed. A new complex signal detection method capable of realizing complete complex signal detection without previously requesting a band limitation for an image signal, and a complex microscope and a complex diffraction device using the method. It is intended to be subjected.

[0029]

Means for Solving the Problems The invention of this application is a first invention for solving the above-mentioned problems, and is a real component microscopic image of a sample and an imaginary component microscopic image obtained by shifting only the sample transmitted light by π / 2 phase. By detecting the complex sum of the real component microscopic image and the imaginary component microscopic image, to provide a complex signal detection method characterized by obtaining a complex microscopic image consisting of a real component signal and an imaginary component signal, In this method, a square microscopic image in which only the sample transmitted light is shielded is detected,
By taking the complex sum of the squared microscopic image, the real component microscopic image, and the imaginary component microscopic image, it is possible to obtain a complex microscopic image including a real component signal and an imaginary component signal, and not including a square signal. By converting each microscopic image into a numerical value and calculating a complex sum, detecting an imaginary component microscopic image using a π / 2 phase plate provided behind the lens, and using a light shielding plate provided behind the lens Detecting the squared microscopic image of the sample by using it, and irradiating the sample with parallel irradiation light and oblique light irradiation, obtaining interference between the parallel irradiation light and oblique light irradiation, and using this interference Perform spatial frequency shift to shift high spatial frequency components to near the frequency origin, increase cutoff spatial frequency by performing spatial frequency shift many times, Correction of defocus caused by lens aberration and focus shift using an inverse function of the contrast transfer function, obtaining an intensity image and a phase image from the corrected complex microscopic image, and converting the intensity and phase from the complex microscopic image into functions. For example, obtaining a real number image having unique information to be performed is also provided as an aspect thereof.

As a second invention, a real component interference diffraction image of a sample transmitted light and a sample diffracted light, an imaginary component interference diffraction image of a sample transmitted light and a sample diffracted light shifted by π / 2 phase, and a sample diffraction A complex signal detection method characterized by detecting a square diffraction image by only light and obtaining a complex diffraction image by taking a complex sum of a real component interference diffraction image, an imaginary component interference diffraction image, and a square diffraction image. In this method, obtaining a complex image from the complex diffraction image by Fourier transform,
Detecting an imaginary component interference diffraction image using a π / 2 phase plate provided in front of a compound lens having a lens area and a non-lens area, and shielding light in front of a compound lens having a lens area and a non-lens area Detecting a square diffraction image of a sample using a plate is also provided as an embodiment thereof.

Further, as third and fourth inventions, there are also provided a complex microscope and a complex diffraction apparatus characterized by using each of the above complex signal detecting methods.

[0032]

DESCRIPTION OF THE PREFERRED EMBODIMENTS i) Complex optics First, complex optics, which is a basic concept of the present invention, will be described. The complex optics mixes a target coherent signal (Z) with a coherent and strong reference signal and detects the intensity value of the sum of the two signals. At this time, a cross term of the complex signal and the reference signal occurs, and an amount proportional to the complex signal is extracted.

However, due to the nature of the intensity value detection, the value extracted in this manner is the real component (Re
(Z)), not the complex signal itself. Therefore,
In order to extract the imaginary component (Im (Z)) of the crossover term, the same detection as described above is performed by mixing a complex signal with a coherent and strong reference signal for extracting the imaginary component. Then, when the real component and the imaginary component extracted in this manner are added in a complex manner (that is, a complex sum), Re (Z) + iIm (Z)
= Z, and an original complex signal is obtained.

Therefore, complex optics essentially requires two or three measurement detections, as described below, and its implementation requires that the reference be orthogonal to each other in complex space, eg, 1 and i. A device that produces the signal is essential. The detection of the real number component in the first stage is similar to the above-described principle of holography, but is more general in that a reference signal itself is extracted from a complex signal when a lens system is used.

This series of operations is possible because the focal plane on the rear side of the lens gives a Fourier transform to the object and separates the complex signal from the reference signal for optical processing. The principle of the complex signal detection method of the present invention based on such complex optics will be described below.

Ii) Detection of Complex Image Signal Here, a case will be described in which a complex signal having two-dimensional spatial information, that is, a complex image signal is detected by the complex signal detection method of the present invention. In addition, the electromagnetic wave and the material wave as the irradiation signal applied to the object sample are monochromatic,
Further, it is assumed that they are coherent (that is, coherent).

A) Complex image signal detection utilizing interference with 0th-order diffracted light When a bright-field image is used, that is, when the object sample is translucent and the transmission of irradiation light is large, and both the object light and the irradiation light are observed. Or when the reflection of the illuminating light at the reflector is large (this is the halation condition of the photograph), the complex signal is given by the following equation.

[0038]

(Equation 5)

Since a and b both vary depending on the location (image), they are functions of spatial dependence. | Z | << 1
The condition (1) indicates that the transmission of irradiation light is greater than that of absorption or scattering. The constant term 1 in the complex signal equation (Equation 5) is a reference signal that is not affected by the object. First, as a first stage detection, light transmitted through the sample is detected using a lens system. At this time, the square of the amplitude, that is, the intensity value (energy per unit time and unit area) is measured.

This intensity value is given by the following equation.

[0041]

(Equation 6)

The above equation is given by considering the condition of | Z | << 1.

[0043]

(Equation 7)

Is approximated. As is apparent from this equation, in the first stage detection, only the real number component signal of the sample is detected. Therefore, in order to reproduce a correct complex image signal Z of the sample, that is, a complex image signal composed of a real component signal and an imaginary component signal, it is necessary to obtain an imaginary part projection Im.

Therefore, as a second stage detection, for example, a small π / 2 phase plate is provided on the focal plane on the rear side of the lens, and the 0th-order diffracted light of the transmitted light (that is, the focal point The phase of only light is shifted by π / 2. The transmitted irradiation light shifted by π / 2 is used as a reference signal, mixed with object light having an image signal at the time of image formation, and the intensity value of the sum of the two is detected. The mixing of the transmitted irradiation light and the object light is automatically performed by the imaging of the lens.

The complex image signal Σ _S ^C including the imaginary component detection reference signal, that is, the complementary complex image signal Σ _S ^C is represented by the following equation.

[0047]

(Equation 8)

The intensity value of this complementary complex image signal is expressed by the following equation.

[0049]

(Equation 9)

Considering the condition of | Z | << 1 shown in Equation 5, Equation 9 is similar to Equation 7,

[0051]

(Equation 10)

Can be approximately expressed as Then, the detected intensity value of Expression 7 (that is, a signal including a real component) and Expression 10
Is calculated with the detected intensity value (i.e., a signal including an imaginary component). The calculation result is as follows.

[0053]

[Equation 11]

In this equation, the complex signal Z (r) can be obtained correctly except for the constant term (1 + i). To remove this constant term (1 + i), a Fourier transform is applied to Equation 11, and
The Fourier transform may be performed again with the vicinity of the origin set to 0. As described above, when the sample is a bright-field image, the complex signal composed of the real component signal and the imaginary component signal of the bright-field image sample, that is, the original image of the sample is detected by the complex signal detection method of the present invention. Can be.

FIGS. 1 (a) and 1 (b) exemplify the main components of a complex image signal detecting optical system corresponding to equations (7) and (10), respectively. FIG.
In the complex image signal detection optical system illustrated in (a), a signal Σ _S Σ _S ^* including a real component signal is detected. However,
The transmitted irradiation light after the focal plane = 1 and the object light = Z.

In the complex image signal detecting optical system illustrated in FIG. 1B, a signal Σ _S ^C Σ _S ^{C *} including an imaginary component signal is detected. However, the transmitted irradiation light after the focal plane = i and the object light = Z. Although the transmitted light in FIG. 1 is shown as coming only to the origin, it actually spreads on the image plane as background light of the image. This situation is clear when the spread of the illuminating light beam is considered as shown in FIG.

In the present invention, the first stage image signal Σ_Sdetection
And the second stage image signal Σ_S ^CIn detection, each
In the second stage image signal
Signal detection, a small position that shifts the phase of the irradiated transmitted light by π / 2
The imaginary component can be obtained simply by inserting only the phase plate at the center of the focal plane.
The signal can be detected. Then, | Z | << 1
ZZ in a general complex image without the condition^*= | Z | ^Two
Discusses the addition of a third measurement detection to eliminate the term
I will tell. For example, when the sample is opaque and the light is hard to pass,
The direct reflection of illumination light like a photo or movie
0), the zero-order diffracted light becomes weaker | Z |^Two
The term becomes relatively strong. This | Z |^TwoTerm is first-order term of Z
Need to be erased.

In the above equation 7, ZZ ^* in the image data
However, since this term is not a constant term, it cannot be eliminated by zeroing around the origin after Fourier transform. Therefore, first, the term of (1 + i) is eliminated by zeroing, and then the term of | Z | ² can be completely eliminated as follows. The original detection signal including | Z | ² is expressed by the following equation.

[0059]

(Equation 12)

In order to obtain the signal of | Z | ² , as shown in FIG. 1C, it is sufficient to place a small light shielding plate, which is the same as the π / 2 phase plate, at the focal point on the rear focal plane of the lens. As a result, the zero-order diffracted light disappears, and the complex image signal Σ _S ^{S at} that time is expressed by the following equation.

[0061]

(Equation 13)

As can be seen from Expression 13, the square signal of Σ _S ^S is detected, and the following image is obtained.

[0063]

[Equation 14]

Using the Z ₀ (r) of Equation 12 and the squared image signal | Z | ² of Equation 14, the following equation that gives a pure complex image is obtained.

[0065]

(Equation 15)

In the case of such a complex signal detection method comprising three measurement detections (which can also be referred to as a three measurement detection method), the same optical system and the same sample are used, and only three types of apertures are used. A normal one, a π / 2 phase plate at the focal point, and a light shielding plate at the focal point) are prepared, and each diaphragm is replaced, for example, to perform measurement and detection three times. Next, the three detected image signals obtained from the respective measurement detections are digitized, and the following complex sum is obtained in the computer.

[0067]

(Equation 16)

In order to remove the 0th-order diffracted light (that is, 1 + i) in this complex sum signal, it is sufficient to perform Fourier transform and set the origin to zero. However, in general, the value of the origin (the value of the 0th-order diffracted light) is adjusted during Fourier transform so that Z (r) takes a correct background value. Finally, a pure complex image represented by the following equation is extracted.

[0069]

[Equation 17]

Once the above complex image is obtained, two methods are available for displaying a two-dimensional image. That is, i) an intensity image and ii) a phase image represented by the following equations.

[0071]

(Equation 18)

[0072] Moreover, various combinations of R _e (Z) and I _m (Z), it is also possible to make a special image for information extraction. B) Frequency shift complex image signal detection due to interference between parallel-irradiated 0th-order diffracted light and oblique-light-irradiated scattered light When the irradiated monochromatic light obliquely strikes an object or when the irradiated light is not a plane wave, the 0th-order diffracted light is reflected on the rear focal plane. Since it is not at the center, the operation of the zero-order diffracted light cannot be performed.
Therefore, in this case, for example, FIGS.
As illustrated in (c), parallel irradiation light is applied to the object in the same manner as in A), and oblique light irradiation from the same light source is applied to the object. The optical signal from the object by the parallel irradiation light and the oblique irradiation light which are given at the same time can be expressed by the following equation.

[0073]

[Equation 19]

As shown in Expression 19, the image signal does not include the 0th-order diffracted light (corresponding to 1 in Expression 19), but the reference signal includes the 0th-order diffracted light. Can be obtained. Note that, in Equation 19, there is no relative phase difference between the two signals, but there is actually a constant phase difference, and this phase difference remains as an indefinite phase of the reproduced image.

The intensity of Σ _W in Equation 19 is detected, and two complementary signals Σ _w ^C and Σ shown in Equation 20 below are obtained.
_When the intensity of _w ^S is detected and the complex sum of the three intensity values is calculated, a correct complex signal of the object light can be obtained as described in A).

[0076]

(Equation 20)

The complex sum of the three intensity values is given by:

[0078]

(Equation 21)

Equation 21 includes the parallel irradiation light image Z (r) and the oblique light irradiation light image Z _ob (r). When Z (r) stops oblique light irradiation and applies only parallel irradiation light, 1 + i as described in A)
+ 2Z (r) can be obtained.
Can be excluded from Note that the relationship between Z _ob (r) and Z (r) is given by the following equation when oblique light irradiation is inclined in the x direction.

[0080]

(Equation 22)

Equation 22 indicates that Z _ob (r) is the spatial frequency sin
This indicates that the frequency is shifted by sin θ / λ in the kx-axis direction of the frequency space corresponding to x because of the complex modulation at θ / λ. This frequency shift provides the basis for a super-resolution microscope that observes the fine structure of objects beyond the Abbe wavelength limit given by 1 / λ. C) Complex image signal detection when the reference light (signal) for obtaining the complementary pair (Σ, Σ ^c ) is not completely orthogonal. The complementary pair of Σ and 、 ^c has the phase of the reference light (signal) of π. / 2 offset and orthogonal. The error when the orthogonality of the reference light is poor or when the intensities are not equal can be corrected as follows.

Here, in order to simplify the explanation,
The case of the reference light pair 1 and i will be described. | Z
| << 1.

[0083]

(Equation 23)

[0084]

(Equation 24)

[0085]

(Equation 25)

[0086]

(Equation 26)

[0087]

[Equation 27]

The sum of a plurality of equations (25) and (26) is obtained by taking the conditions shown in equation (24) into consideration and calculating as follows.

[0089]

[Equation 28]

In such an operation, knowledge about a and θ is required in advance. Using a standard object whose shape can completely predict Z,

[0091]

(Equation 29)

In order to predict, the following is performed. Since a and θ are device constants, this determination need only be made once. Z + Z ^* is created using the known Z, and a constant term 1 is estimated from Equation 25. When Equation 26 is subtracted by the estimated value, the following equation remains.

[0093]

[Equation 30]

Using the value of the place where Z is a real number,
0 is

[0095]

(Equation 31)

Then, when this is divided by 2Z, a cos
θ is obtained. Using the value of the location where Z is an imaginary number,

[0097]

(Equation 32)

When this is divided by -2 | Z |, a
sin θ is obtained. From the results of Equations 31 and 32,
^{[(Acosθ) 2 + (asinθ} ) 2] 1/2 than a
From the sum of cos θ and isin θ

[0099]

[Equation 33]

Is obtained. As described above, according to the complex image detection method of the present invention, a complex image signal composed of a real component signal and an imaginary component signal of a sample, that is, an original image of an object can be detected. D) Detection of Complex Image Signal in Diffraction Image In the case of a diffraction image, since no imaging lens is used, the 0th-order diffracted light (that is, transmitted irradiation light) does not interfere with higher-order diffracted light (that is, object light) as it is.

The problem of non-interference between the transmitted irradiation light and the object light has been solved by, for example, the well-known off-axis holography that obtains a diffraction image using reference light obliquely incident from the outside. However, this off-a
The hologram obtained in xi holography is a real component of a diffraction image, and an imaginary component cannot be obtained. Therefore, attempts to detect the real component and the imaginary component have been made by various methods, for example, a double measurement detection method and an optical operation method on a focal plane.
The number of measurement detections is combined in real numbers (that is, sum of real numbers), and is not realized. This conventional method is so-called real holography.

The complex signal detection method of the present invention can realize detection of such real and imaginary components of a diffraction image, that is, detection of a complex signal. Here, detection of a complex signal in a diffraction image of an X-ray crystal by the method of the present invention will be described. X-rays have lower coherence of electromagnetic waves than electron beams and laser beams, and therefore cannot essentially use external reference light, so that interference between transmitted light and diffracted light as described in A) occurs. Special devices are required. That is, an optical system using a lens as illustrated in FIG. 3 is used. In the case of complex reconstruction of a diffracted image, the lens (complex lens in the example of FIG. 3) is placed in front of the object (crystal in the example of FIG. 3) instead of behind.

FIGS. 3 (a), 3 (b) and 3 (c) show a diffraction image real component detection optical system, a diffraction image imaginary component detection optical system, and a diffraction image square signal detection, respectively, using the complex signal detection method of the present invention. 2 illustrates an example of a configuration of a main part of an optical system. FIG.
In each of the optical systems (b) and (c), the π / 2 phase plate and the light shielding plate placed in front of the lens are replaced while keeping all the optical systems the same. Then, a complex sum of the three images obtained by these three optical systems is obtained to obtain a complex signal of the diffraction image.

Here, a mechanism for generating a coherent and divergent reference signal that can interfere with the divergent diffracted light coming from the crystal using the diffracted image real number component detection optical system of FIG. 3A will be described. The lens consists of a non-lens area near the center and a lens area near the center. The diffraction signal from the crystal results from parallel illumination through a central non-lens area, which gives a diffraction image. On the other hand, the reference signal passes through the lens area around the parallel irradiation light and converges toward the lens focal point where the crystal is placed. The feature of this optical system is that both the parallel light passing through the central non-lens area and the parallel light passing through the peripheral lens area have the same phase at the focal point due to the function of the lens.

Here, an arbitrary point r ′ =
Let the diffraction image at (x ′, y ′) be Z (r ′). The reference light that converges on the crystal through the peripheral lens area and passes therethrough becomes a signal given by the following equation on the diffraction image plane.

[0106]

(Equation 34)

In Expression 34, θ _k (r ′) represents the phase difference of the optical signal arriving from the focal point on the diffraction image plane. σ _R is diffuse scattering in which the divergent reference light hits the crystal,

[0108]

(Equation 35)

It is extremely weak as compared with the above. In equation 34, |
Considering paraxial light of r ′ | <f, the distance from a point on the diffraction image plane to the focal point was set substantially constant. Considering θ _k (r '), the diffracted light generated by the parallel light

[0110]

[Equation 36]

[0111] Therefore, the square signal of the interference (sum) between this and the reference light, that is, the real number component detection signal of the diffraction image is represented by the following equation.

[0112]

(37)

The signal of equation 37_DΣ_D ^*At σ
_RIs diffuse scattering, and its intensity | σ _R| Is | Z (r ') |
Σ_R|^TwoAnd

[0114]

(38)

The term is ignored. Next, in order to detect an imaginary component of the diffraction image, as shown in FIGS. 3B and 3C, a π / 2 phase plate or a light shielding plate is set in front of the lens area of the compound lens, and The phase of the light is shifted to π / 2 or the light is shielded. Accordingly imaginary component detection of a diffraction image (sigma _D ^c) and the diffraction image square detection (sigma _D ^s) is expressed by the following equation.

[0116]

[Equation 39]

Then, the real component intensity value of Expression 37 and Expression 3
The complex sum of the imaginary component intensity value of 9 and the squared signal value is calculated.
This complex sum is given by the following equation.

[0118]

(Equation 40)

From this equation (40), it can be understood that a diffraction image can be extracted as a complex signal by using the three measurement detection method (in the case of using the three measurement detections described above) in the complex signal detection method of the present invention illustrated in FIG. . The constant term of 1 + i is
The correction can be performed in the same manner as in the case of the microscopic image by the Fourier transform of Z (r '). | Σ _R | <assumed when deriving Equation 40
The relationship | Z (r ′) | <1 is satisfied in ordinary X-ray crystallography and photocrystal analysis using microcrystals.

In FIG. 3, the diaphragm immediately before the crystal is
This is for preventing stray light of the compound lens system, and is particularly effective for X-ray crystal analysis. In addition, as a method of producing a compound lens, in the case of visible light, it is usually sufficient to polish the vicinity of the center of the lens in parallel. Regarding the electron beam, a small electric field type thin film lens may be placed as a concave lens at the center of the electromagnetic lens. With respect to X-rays, in the case of a Fresnel type lens, it is sufficient to pass through dozens of annular zones at the center. Also, Wolte
When an r-type total reflection lens is used, the vicinity of the optical axis automatically becomes a non-reflective non-lens area, and thus can be used as it is as a compound lens in the present invention.

Iii) Specific requirements for the π / 2 phase plate [0121] For an optical microscope, a known Zernike phase-contrast microscope uses π / 2.
A phase plate is used. However, since the optical microscope uses conical (that is, conical) irradiation light without parallel irradiation to improve the resolution, the 0th-order diffracted light spreads in a ring shape on the rear focal plane, and the phase plate also has a ring shape. take.

The phase contrast microscope has a weak absorption but a refractive index of 1
In order to observe a substance different from that described above, the phase is shifted by π / 2 with respect to the 0th-order diffracted light, and the phase difference, which is an imaginary signal, is converted to a real number and observed. However, when there is absorption, the image is not simply a function of the phase difference, as shown in Expression 48 below. Further, the transmitted light becomes strong background light, on which the phase of the image is converted into a contrast as a phase difference from the background light. That is, the absorption component, the phase component, and the transmitted light component are all inseparable.

In the method of the present invention, in order to clarify such a complicated situation and take out the imaginary image with respect to the real number image with less error, the zero-order diffracted light is focused on an extremely narrow space of the rear focal plane by parallel irradiation. By covering only that part with a small π / 2 phase plate, the scattered light other than the zero-order diffracted light is not affected. Therefore, as long as the parallelism (coherence) of the parallel irradiation is good, the size of the π / 2 phase plate is 1/10 to 1/1 / that of the object to be observed.
Since it can be as large as 100, it does not affect the scattered light from other objects.

At this time, as illustrated in FIG. 4, there is a slight difference in the path passing through the π / 2 phase plate between the transmitted convergent lights, which may degrade the orthogonality between the real number image and the imaginary number image. Can be Assuming that the light flux is 2d and the focal length is f, there is an angle difference between the optical path perpendicular to the lens and the optical path oblique to the following equation.

[0125]

[Equation 41]

This gives an optical path difference between the two π / 2 phase plates, which serves to increase π / 2 by about 1 / cos Δθ. When this is approximated, the difference between the vertical optical path and the oblique optical path is as follows.

[0127]

(Equation 42)

If, for example, Δθ = 1/10, this only gives an error of 1/100. Next, a method for avoiding damage to the π / 2 phase plate due to the passage of strong transmitted light such as an electron beam or a laser beam will be described. Such damage can be avoided by, for example, putting the π / 2 phase plate on the scattered light side instead of the irradiated transmitted light as illustrated in FIG.

That is, the phase may be shifted by π / 2 by inserting a π / 2 phase plate on the side of the weak scattered light, and the strong transmitted light may be passed through the focal plane as it is in the real image observation. As a result, Σ ^c is given by the following equation, but its intensity value is the same as that in the normal case of FIG.

[0130]

[Equation 43]

In this case, the complex sum becomes a complex difference as shown in the following equation.

[0132]

[Equation 44]

The following is the same as the procedure described above. iv) Aberration correction in a complex electron microscope using the complex signal detection method of the present invention As described above, blurring occurs due to aberrations peculiar to the lens system and out-of-focus in images of various microscopes as well as the electron microscope. . This
In an electron microscope, it is expressed that a contrast transfer function is applied to an image function. However, this contrast transfer function is
A so-called wave number vector space (k
In space, the image function is multiplied, so that it is generally very difficult to understand. This has made it difficult to understand the principle of the electron microscope, and has been a factor that hinders improvement in resolution. At first glance, the contrast transfer function appears to be an inherent problem derived from hardware such as an electron microscope, but in fact, it is derived from a defect in the conventional optical measurement, that is, an electromagnetic wave cannot be correctly detected as a complex signal.

Therefore, the problem of the above-described contrast transfer function is solved by the complex signal detection method of the present invention, and the resolution of the electron microscope is improved. First, the wave function of the scattered electrons from the sample after the parallel irradiation of an electron beam having good monochromaticity (same as a plane wave) can be expressed by the following equation.

[0135]

[Equation 45]

An electron microscope uses a thin sample to prevent multiple scattering. Therefore, there is transmitted light (incident electron beam itself) that is transmitted without being scattered from the object, and the scattered electron wave in Equation 45 is expressed by the following equation using this transmitted light, similarly to the complex signal in Equation 5: . Where the object function z
(R) represents the optical properties of the object to be finally converted to the image function Z (r). Although the assumption of | z | ≪1 is made, as described above, in the three-measurement detection method of the complex signal detection method of the present invention, this condition is removed, and the present invention can be applied to any optical object.

[0137]

[Equation 46]

The scattered electron wave, that is, the scattered light is condensed by the objective lens to form an image. On the focal plane behind the lens, a diffraction image of the object, that is, a Fourier transform image is formed. Put aperture. In an optical system having a fixed optical path length, image focusing is performed by adjusting the focal length. The shift of the focal position from the stop fixing surface is defined as a defocus amount.

The Fourier transform O (k) of the scattered light ψ (r)
Is expressed in the approximate range as follows.

[0140]

[Equation 47]

[0141] [psi [psi ₀ in (r) is a constant term, since a ^{_{1 (ψ 0 ψ 0 * =}} 1) when the intensity detection, omitted here. The function derived from the aperture, aberration, and defocus described above is applied to this function O (k) (hereinafter, referred to as an object function in k space). Aperture, aberration, and defocus can all be expressed as the following equation as a shift of the phase of an electron wave or an attenuation effect of a wave vector resulting from integration thereof.

[0142]

[Equation 48]

Here, exp [ε (k)] is the limitation of the wave vector due to the aperture, chromatic aberration, and spread of the light source, that is, the limitation of the resolution, and is generally a monotonically decreasing function of k. Exp [iγ (k)] is a phase shift effect dependent on k derived from spherical aberration, coma, and defocus. H (k) is called an object transfer function (OTF) in an optical microscope.

When only spherical aberration and defocus are considered, Equation 48 can be assumed as in the following equation.

[0145]

[Equation 49]

K _s is uniquely determined by the wave number k ₀ and the spherical aberration of the electron wave, and K _d is uniquely determined by the wave number k ₀ and defocus (see FIG. 6). FIG.
[Iγ (k)] phase γ (k), real part = cos (γ
(K)) = − 2 sin γ (k) and imaginary part = sir
(Γ (k)) = − 2 cosγ (k) wave number k (that is, 2
This is an example of the (absolute value of a dimensional wave number vector) dependency. In FIG. 6, the wave number k uses a normalized wave number.

In FIG. 6, each value is represented by the following equation.

[0148]

[Equation 50]

The image formation of the objective lens, that is, the reproduced image function of the object is obtained by subjecting O (k) to H (k) to another Fourier transform. That is, it is given by the following equation.

[0150]

(Equation 51)

Here, m is a magnification, and the sign indicates that the image is reversed. Reproduced image [psi _i, which is recorded and stored as an image in various image recording apparatus, an image to be detected is in the form of the following equation in response to the intensity value.

[0152]

(Equation 52)

Hereinafter, the relationship between the object function z (r) and the image function Z (r) will be considered without considering the magnification m and the inversion of the image. [psi _i itself originally but complex signal, as described above, (see Equation 7) that is a real part that obtained by the intensity values detected. When O (k) in Equation 47 and H (k) in Equation 48 are put in Equation 40 and a Fourier transform is performed, the image function I (r) becomes (Fourier that multiplication in k space becomes convolution in real space). From the formula of conversion, it is expressed by the following equation (see Equation 7).

[0154]

(Equation 53)

In the above equation, cosγ (k) and si
nγ (k) is the contrast transfer function (C
TF) are the real and imaginary parts. The term | z | ² is omitted (the same applies hereinafter). This I (r) is | α | << | β | when the object is transparent like a biological sample.
Further, it is expressed by the following equation.

[0156]

(Equation 54)

In this case, sinγ (k) is calculated as shown in FIG.
As shown in the example, the function vibrates violently at 0 where k = 0 and where k is large, which is extremely inconvenient for image reproduction. In particular, since image information is essentially lost near sinγ (k) = 0, even if an attempt is made to perform a Fourier transform on the reproduced image and correct the multiplication of H (k) by division, the image information cannot be restored. (It does not break at 0).

This can be avoided by creating a complex image using the principle of complex spectroscopy. That is, H
It is necessary to create a reconstructed image in which H (k) is multiplied as it is, instead of the image function I (r) of Equation 53 or Equation 54 in which a part of (k) is multiplied. As described above, this method is a method of detecting an imaginary component of an image separately from a real component, and taking a complex sum of the real component and the imaginary component. That is, the scattered electron wave obtained by converting the portion of the transmitted light 1 in Expression 46 into i using the π / 2 phase plate may be obtained.

The scattered electron wave is represented by the following equation.

[0160]

[Equation 55]

The image I ^c (r) given by the electron wave is finally given by the following equation.

[0162]

[Equation 56]

Although the term of | z | ² has been neglected so far, in the three-measurement detection method of the complex signal detection method of the present invention, FIG.
The square signal detection I ^s (r) as shown in (c) is performed, and a complex sum of the square signal detection I ^s (r) and I ^c (r) is obtained.
| ² can be subtracted. Therefore, the final complex image is

[0164]

[Equation 57]

Is obtained. This equation is Fourier transformed and exp
Multiplying by (−iγ (k)) gives the following equation.

[0166]

[Equation 58]

The above operation is essentially a multiplication of cosγ (k) and sinγ (k), and is not division.
No point problems occur. The first term (1 + i) δ in Expression 58
(K) Since exp (−iγ (k)) is a function concentrated on k = 0, it can be set to 0. Further, exp (ε
If the attenuation term of (k)) is processed, the aberration will be completely removed. What remains after all is O (k) exp (ε (k))
, This Fourier transform will give the complex image Z (r). exp (ε (k)) determines the resolution,
The largest contributor is the aperture, that is, the numerical aperture.
The method of the present invention, which can eliminate the influence of the contrast transfer function exp [iγ (k)], uses a conventional electron microscope in which k
The aperture is set small, and the numerical aperture of the objective lens is reduced to 0.01 because of fear of CTF of sinγ (k) vibrating violently at a high value of
Since the effect can be eliminated as compared with the case where it is set to ~ 0.001, the numerical aperture can be increased to about 0.1. In a microscope, since the reciprocal of the numerical aperture is proportional to the resolution, it is possible to achieve about 10 times the resolution as compared with the conventional one. When the numerical aperture is increased by a factor of ten, more electron scattered waves can be collected, so that the contrast is automatically improved.

FIG. 7 exemplifies a flow of a simulation of image formation and image reproduction of a complex electron microscope using the complex signal detection method of the present invention and a result image. The present invention uses the principle that the diffraction phenomenon in optics can be replaced by a numerical calculation called Fourier transform when a lens system is used. For this reason, various optical measurement detections can be simulated using a computer before the actual device is manufactured.

The simulation was performed as follows. First, one portrait is prepared and a two-dimensional image z
(R) is read by a computer as a digital signal. Since this is a real number signal, this real number image is converted into a complex object function e ^{iZ (r)} assuming a perfect phase object. This means that the phase shift from the object has a spatial distribution like a portrait. Here, in order to show that the method of the present invention can be applied to a strong optical body (absorption, phase), the maximum value π of the phase shift is made to correspond to the darkest part.

Complex object function e assuming this phase object
^{By performing a} Fourier transform on ^{iZ (r)} , a k-space object function, that is, a diffraction image is obtained, and the obtained k-space image is subjected to CTF to obtain a k-space CTF modulated image. The k-space CTF modulated image is subjected to Fourier transform without a plate, Fourier transform with a phase plate, and Fourier transform with a light shield plate.

Up to this point, the simulation corresponding to the three image forming processes based on the three measurement detections has been described. The simulation images in which the images (a), (b), and (c) at the middle stage in FIG. (A) (b) (c)
Is an image obtained by The parameters of the image simulation at this time are

[0172]

[Equation 59]

[0173] As illustrated in FIG. 6, normalized defocus

[0174]

[Equation 60]

In the case of (Scherze Focus)
r Focus). As is clear from the phase CTF in FIG. 6B, at a small k, the CTF takes a constant value (approximately −2) over a wide range, and the degree of modulation applied to the image is small. This was found by Scherzer ("The Theoretical Resolution Limit of the Elect
ron Microscopy ", O. Scherzer, Journal Applied Physic
s 20 (1949) 20-29). In general,

[0176]

[Equation 61]

A large deep defocus, for example, 9 /
√ (2π) is used. This allows CT near the origin of k
F rises abruptly, and the low-frequency signal that determines the shape of the object recovers. Therefore, in this simulation,

[0178]

(Equation 62)

[0179] The three real number images thus obtained have different contrasts from the original two-dimensional image Z (r), and the boundaries are blurred due to CTF modulation. Next, after taking a complex sum from these three real images according to Equation 55 and applying a Fourier transform to them, the obtained k-space C
The reciprocal (inverse filter) of CTF already known in the TF modulation image, that is,

[0180]

[Equation 63]

[0181] By applying the correction, the CTF modulation is eliminated to correct the aberration and defocus, and the Fourier transform is performed again to obtain a CTF unmodulated image. And
By adjusting the background level of the CTF unmodulated image, the constant term σ ₀
To obtain a pure complex elephant e ^{iZ (r)} . The phase image tan ⁻¹ {I _m [e ^{iZ (r)} ] / R _e [e ^{iZ (r)} ]} of this pure complex image
(The lower part in FIG. 7) is a reproduced image Z (r) of the portrait.
give. A real number image obtained by three measurement detections (the middle part of FIG. 7) and a real phase image Z (r) obtained by excluding the CTF modulation (FIG. 7)
Comparing with (lower), it can be seen that the resolution and contrast can be improved very well and complete reproduction in detail is realized by the complex signal detection method of the present invention.

V) Improvement of resolution in complex optical microscope using complex signal detection method of the present invention In general, the spatial resolution of an optical microscope given by Abbe theory is defined by the following equation.

[0183]

[Equation 64]

Λ is the wavelength of the light to be used, n is the refractive index of the space where the sample is placed, θ is 開 き of the opening angle of the objective lens with respect to the sample, and nsin θ is the numerical aperture.
Α is a value obtained when conical (conical) irradiation light obtained by collecting light with a condenser lens is used, and becomes 1 in the case of parallel irradiation (coherent parallel light) perpendicular to the sample surface.

Here, the complex optical microscope uses parallel irradiation conditions, and δ adopts λ / nsin θ.
Expressing this as a diffraction image of the focal plane, in the case of parallel irradiation, it means that a diffraction pattern can be obtained only up to the reciprocal of δ, that is, the value of k corresponding to n sin θ / λ.

Θ = π / 2 is the limit of the opening angle, and in the case of parallel irradiation, λ / n is the theoretical limit of the resolution. Therefore,
There is no way to break this Abbe limit in hardware. In terms of software, where k is high, i
As described in the complex electron microscope of v), since the aberration is generally large, the contrast transfer function appears on the surface and cannot be corrected. As an optical lens system for correcting this aberration, a larger number of aberration-correcting compound lenses have been developed than in the past, but none of them can completely correct the aberration.
Has not been achieved.

According to the composite signal detection method of the present invention, since the aberration can be completely corrected, the resolution of the optical microscope can be improved, and an optical microscope having a resolution of several 64 can be realized. Further, in order to realize a super-resolution exceeding this limit, the aperture function A (k) (= 1, | k | ≦ k _c ; = 0) included in the aforementioned attenuation function exp (ε (k))
| K |> k _c ) is substantially expanded in k-space and the cutoff frequency k
_c must be greatly increased. By the way, as described above, the microscope cannot be expanded due to physical limitations (Abe's limit). Thus, a synthetic solution that repeats the frequency shift complex image signal detection proposed in ii-B) many times many times and sequentially covers the frequency (k) space in the same way as aperture synthesis is conceivable.

The frequency shift complex image detection is performed as shown in FIG.
, The cutoff frequency (k_x ^c, K_y
^c) To the observation band near the origin.
A way to bring it. Referring to Equation 22, frequency
Fourier transform of shifted image O ^ob(K) is the object function z
Using the Fourier transform O (k) of (r) (here, Equation 4
Δ (k) in O (k) shown in FIG. 7 is omitted.)
It is represented by an expression.

[0189]

[Equation 65]

In this equation, O^ob(K) is the original k sky
The interim image (diffraction image) O (k) is expressed in k-space (−k_x ^ob, -K_y
^ob). k_x ^ob, K_y ^ob
Is the inclination of the oblique light with respect to the optical axis (θ_x, Θ_yRelated to)
It is a kutor component. O^ob(K) to (-k_x ^ob, −
k_y ^ob) Returns to the opposite direction and returns O^ob(K_x+
k_x ^ob, K _y+ K_y ^ob) Is obtained, which is shown in FIG.
This is the original high-frequency signal function illustrated. Note here
All we have to do is perform the reverse shift operation

[0191]

[Equation 66]

Is multiplied by O ^ob (k). Therefore, if only this real or imaginary component is performed,
This creates an impossible problem of dividing by zero experienced in electron microscopy. Therefore, it is necessary to always generate a complex image and perform an inverse shift on it. This is a decisive difference from the conventional aperture synthesis method using real number images. By the way, what is actually observed is not the Fourier transform O (k) of the object function z (r) itself, but the field of view (in k space) to which the aperture function A (k) is applied. _{^{Therefore, O ob (k x -k x}} ob, k y -k y ob) For actual observation is expressed by the following equation.

[0193]

[Equation 67]

A (k_x-K_x ^ob, K_y-K_y ^ob)
Function A (k) to (k_x ^ob, K_y ^ob)
Function. This situation is shown in FIG.
This opens the window for observing high-frequency components.
It has been done. FIG. 8 (b) is an enlarged view.
The oblique light irradiation is changed regularly so that the window function becomes
Such measurement is performed many times (in the example of FIG.
(Two measurement detections or three measurement detections) 9 times. Soshi
O^ob(K_x-K_x ^ob, K_y-K_y
^obTake the sum of

Thus, according to the following equation, the complex image is _converted into a wide aperture function A exceeding the normal cutoff frequency k _c.
^It is equivalent to the observation by ^U (k).

[0196]

[Equation 68]

[0197] ^{_{Here, I j, I j c,}} I j s is a different frequency shifts _{^{(-k xj ob, -k yj o}} b) the real component detection signal with the imaginary component detection signal, the square detection signal, the complex After taking the sum, an inverse shift operation is performed in k-space to return to a higher frequency and combined with other observations. Care must be taken in the order of this procedure. As a result, a coupling aperture function A ^U (k) is obtained, and its cutoff frequency is mk _c , and an improvement in resolution by a factor of m is guaranteed.

By the way, oblique light irradiation is performed through the air.
Mk_cThe value of m does not exceed a maximum of 2. frequency
The shift is 1 / λ as shown in Equation 61 even if the oblique light is tilted to the maximum.
= K _cIs not exceeded. To improve this,
Both light and parallel light can pass through a medium with a high refractive index (n)
I just need. This is, for example, as illustrated in FIG.
Use a substrate with a high refractive index (n) as the light incident side substrate of
It can be done by doing. At this time, the frequency k is n
And therefore frequency shift for oblique light with the same tilt angle.
The shift is also n times. This allows a maximum (1 + n) times resolution
Performance improvement. n is 1.7 for oil and 5 for metal
The degree is known. Especially in the case of metal, the traveling wave on the surface
(Surface plasmon) to excite large frequency
Can be realized.

[0199]

As described above in detail, according to the present invention, a real component signal, an imaginary component signal, and a squared signal can be easily detected separately. A new method for detecting a complex signal is provided in which a complex signal can be obtained without interference of other image signals. Further, the method for detecting a complex signal according to the present invention can realize the correction of the aberration of the microscope and the improvement of the resolution, and can also determine the phase of the diffraction image. Furthermore, using the above-described method of detecting a complex signal according to the present invention, a complex microscope capable of completely obtaining the original complex signal of the object, particularly a complex microscope capable of realizing a resolution exceeding the Abbe wavelength limit, A complex diffraction apparatus capable of obtaining a complex diffraction image is also provided.

[Brief description of the drawings]

FIGS. 1A, 1B, and 1C show an image detection optical system using a lens that detects a real component signal, an image detection optical system that uses a lens that detects an imaginary component signal, and a square signal, respectively. FIG. 2 is a configuration diagram of a main part illustrating an image detection optical system using a lens for detecting the image.

FIGS. 2A, 2B, and 2C are main configuration diagrams of frequency shift complex image signal detection due to interference between zero-order diffracted light and oblique light scattered light, respectively. 1 illustrates an optical system for use, a lens optical system for detecting an imaginary component signal, and a lens optical system for detecting a square signal.

FIGS. 3 (a), (b) and (c) are optical systems for detecting a real component of a diffracted image, an imaginary component for detecting a imaginary component of a diffracted image, and a system for detecting a squared signal of a diffracted image using the complex signal detecting method of the present invention, FIG. 2 is a configuration diagram of a main part, illustrating the example.

FIG. 4 is a conceptual diagram illustrating an optical path difference in a π / 2 phase plate of irradiation transmitted light on a focal plane.

FIG. 5 is a main part configuration diagram illustrating another imaginary component detection optical system using the complex signal detection method of the present invention.

6 (a), (b) and (c) show the phase γ (k) of the contrast transfer function exp [iγ (k)] and the real part [cos
(Γ (k))] and the normalized wave number k of the imaginary part [sir (γ (k))] (that is, the absolute value of the two-dimensional wave vector)
It is a figure which illustrated dependency.

FIG. 7 is a diagram exemplifying a flow of a simulation of image formation and image reproduction of a complex electron microscope using a complex signal detection method of the present invention and a result image.

FIGS. 8A and 8B are a conceptual diagram illustrating a shift of a spatial frequency in a super-resolution microscope using the complex signal detection method of the present invention, and a concept illustrating an expansion of an aperture function by frequency synthesis, respectively. FIG.

FIG. 9 is an explanatory view exemplifying the concept of oblique light / parallel irradiation when the light incident side substrate of the sample is changed to one having a high refractive index in order to increase the frequency shift due to interference between parallel irradiation and oblique light irradiation. is there.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI H01J 37/22 501 G06F 15/66 A

Claims (16)

[Claims] 1. A real component microscopic image of a sample and an imaginary component microscopic image obtained by phase-shifting only the sample transmitted light by π / 2 and detecting the complex sum of the real component microscopic image and the imaginary component microscopic image. A complex microscopic image comprising a real component signal and an imaginary component signal. 2. A real component signal and an imaginary component are detected by detecting a square microscopic image in which only light transmitted through a sample is shielded, and taking a complex sum of the square microscopic image, the real component microscopic image, and the imaginary component microscopic image. 2. The complex signal detection method according to claim 1, wherein a complex microscopic image composed of signals and not including a square signal is obtained. 3. The complex signal detecting method according to claim 1, wherein each microscopic image is digitized by a computer to calculate a complex sum. 4. An imaginary component microscopic image is detected by using a π / 2 phase plate provided behind the lens.
Any of the complex signal detection methods. 5. The complex signal detection method according to claim 2, wherein a square microscopic image of the sample is detected using a light shielding plate provided behind the lens. 6. irradiating the sample with parallel irradiation light and oblique light irradiation light, obtaining interference between the parallel irradiation light and oblique light irradiation light,
2. A spatial frequency shift for shifting a high spatial frequency component in a sample to a vicinity of a frequency origin by using the interference.
5. The method for detecting a complex signal according to any one of items 5 to 5. 7. The complex signal detection method according to claim 6, wherein the cut-off spatial frequency is increased by performing the spatial frequency shift many times. 8. The complex signal detection method according to claim 1, wherein defocus caused by a lens aberration and a focus shift of the complex microscope image is corrected using an inverse function of a contrast transfer function. 9. The complex signal detecting method according to claim 1, wherein an intensity image and a phase image are obtained from the corrected complex microscope image. 10. A real number image having singular information as a function of intensity and phase from a complex microscope image.
Any of the complex signal detection methods. 11. A real component interference diffraction image of sample transmitted light and sample diffracted light, an imaginary component interference diffraction image of π / 2 phase shifted sample transmitted light and sample diffracted light, and a squared diffraction image of only sample diffracted light And obtaining a complex diffraction image by calculating a complex sum of a real component interference diffraction image, an imaginary component interference diffraction image, and a square diffraction image. 12. The method according to claim 11, wherein a complex image is obtained from the complex diffraction image by Fourier transform. 13. The complex signal detection method according to claim 11, wherein an imaginary component interference diffraction image is detected using a π / 2 phase plate provided in front of a compound lens having a lens area and a non-lens area. 14. The complex signal detecting method according to claim 11, wherein a square diffraction image of the sample is detected using a light shielding plate provided in front of a compound lens having a lens area and a non-lens area. 15. A complex microscope using the complex signal detection method according to any one of claims 1 to 10. 16. A complex diffraction apparatus using the complex signal detection method according to claim 11.