JPH09197282A - Object observation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a phase difference microscope which enables a pure phase distribution image to excellently be observed with simple optical constitution and is not affected by intensity variation. SOLUTION: A rotatable polarizer 18 and a 1/4-wavelength plate 20 adjust the phase difference between the orthogonal polarized components of light from a phase object 14. Then a ring-zone polarizing plate 22 and an analyzer 24 extract polarized light components which are coherent in different polarizing directions from the light after the adjustment and find difference images from images of the respective polarizing directions. Those difference images and 0th-order light intensity signal of the object are used to perform operation for adjusting the relative intensity of the difference images and operation for composing an adjusted image, respectively. The operation results include no intensity component of the light and only pure phase components are obtained. Consequently, the phase distribution image is observed excellently.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an object observation device,
For example, the present invention relates to reduction of the influence of a change in the amplitude of light by an observation object in a phase contrast microscope.

[0002]

2. Description of the Related Art A phase contrast microscope converts a phase difference of light into a difference between light and dark so that a difference in thickness or refractive index of an object can be visually observed. . The basic configuration is, for example, as shown in FIG. 13, in which a ring-shaped diaphragm (ring diaphragm) 102 is provided at the front focal position of the condenser lens 100, and a ring diaphragm is provided at the rear focal position of the objective lens 104. Polarizing plate (phase plate) 1
06 is provided.

The ring-shaped light transmitted through the ring diaphragm 102 is condensed by the condenser lens 100 and then enters the phase object 108 to be observed. The light transmitted through the phase object 108 enters the ring-shaped polarizing plate 106, but the ring-shaped polarizing plate 1
Reference numeral 06 denotes a size in which the image is overlapped with the ring diaphragm 102, and a phase change of a constant size (λ / 4, λ is the wavelength of light) is given to the light directly transmitted through the phase object 108. Directly transmitted light (0th order light) that has undergone this phase change and diffracted light diffracted by the phase object 108 enter the eyepiece lens 110, and a bright and dark image is formed by the interference between the two. As a result, the phase difference of the light generated by the phase object 108 becomes the amplitude difference of brightness and darkness, and can be observed with the naked eye 112.

By the way, p. 90 to 93, a phase contrast microscope using a variable annular polarizing plate made of liquid crystal instead of the fixed annular polarizing plate 106 described above is described. Figure 14 (A)
Shows the side surface of the variable annular polarization plate 120, and FIG. Variable annular polarization plate 120
Has a liquid crystal cell structure as a whole, and the ring-shaped transparent electrodes 122a and
2b is formed. As the liquid crystal 124 in the cell,
A nematic liquid crystal with a homogeneous alignment is used. When a voltage is applied between the transparent electrodes, the molecular orientation of the liquid crystal 124 changes and its refractive index changes. As a result, of the incident light from the objective lens 104 (see FIG. 13) side,
Phase modulation is applied only to the 0th order light.

However, in the background art as described above, the change in the intensity (absolute value of the amplitude) of the light from the object side affects the image, so that it is impossible to purely observe only the phase distribution. That is, since the phase distribution image and the intensity distribution image are observed in an overlapping manner, it is not always clear what the obtained image means.

The present invention focuses on the above points,
It is an object of the present invention to provide an object observing apparatus that can observe a pure phase distribution image satisfactorily with a simple optical configuration and is not affected by intensity changes.

[0007]

In order to achieve the above object, the present invention provides an objective lens (16) for collecting light from an object to be observed; illuminating the object and near the pupil of the objective lens. An illuminating means (10, 30, 32, 34, 36, 38) for obtaining a light image that can be selectively filtered; the phase difference between the 0th-order light component and the diffracted light component of the incident light from the objective lens is arbitrarily set. Phase difference adjusting means (18,20) for adjusting; Image pickup means (42,46) for photoelectrically converting the intensity distribution of the image formed by the light from the phase difference adjusting means and outputting an image signal; The difference between the intensities of the respective image signals obtained by the image pickup means in the state of the first phase difference that is an integral multiple of π and the second phase difference obtained by adding an odd multiple of π to the first phase difference by the phase difference adjusting means. And a first difference image signal that is Third with / 2 added
A difference for obtaining a second difference image signal which is a difference in their intensities from the image signals obtained by the image pickup means in the state of the fourth phase difference obtained by adding an odd multiple of π to the phase difference and the third phase difference. And an image signal generating means (48); for forming an object phase image using the first and second difference image signals and the 0th order light intensity signal of the object.

Another invention is an objective lens (16) for collecting light from an object to be observed; for illuminating the object to obtain a light image that can be selectively filtered near the pupil of the objective lens. Illumination means (10, 30, 32, 34, 36, 38); phase difference adjusting means (18, 20) for arbitrarily adjusting the phase difference between two orthogonal linearly polarized light components of incident light from the objective lens First filter means (22) for extracting the linearly polarized light components of the 0th order light and diffracted light of the incident light from the phase difference adjusting means in different directions; the light from the first filter means Second filter means (24) for polarization splitting; Image pickup means (42) for photoelectrically converting the intensity distribution of the image formed by the light of each polarization component polarization-split by the second filter means and outputting an image signal. , 46); the phase difference is an integral multiple of π by the phase difference adjusting means. From two image signals obtained by the imaging means in a coordinated state, the obtaining a first difference image signal is the difference in their intensity,
By the phase difference adjusting means, the phase difference becomes an integral multiple of π / π /
From the two image signals obtained by the image pickup means in the state of the value obtained by adding 2
Difference image signal generation means (48) for obtaining the difference image signal of
First and second obtained by the difference image signal generating means
And a calculation means (58) for respectively performing calculation of adjustment of the relative intensity of the difference image signal and calculation of combination of the adjusted images from the difference image signal and the 0th order light intensity signal of the object. To do.

Still another invention is an objective lens (16) for collecting light from an object to be observed; illuminating the object,
Illumination means (10, 30, 32, 34, 36, 38) for obtaining a light image that can be selectively filtered in the vicinity of the pupil of the objective lens; two orthogonal linear polarization components of incident light from the objective lens Phase difference adjusting means (18, 2) for adjusting the phase difference arbitrarily
0); First filter means (22) for extracting linearly polarized light components of the 0th order light and diffracted light of the incident light from the phase adjusting means in different directions; Incident from the first filter means Third for extracting linearly polarized light component from light
A filter means (26); an image pickup means (42) for converting the intensity distribution of the image formed by the polarized component light extracted by the third filter means into an optical signal, and outputting an image signal; The first phase difference, which is an integer multiple of π, and the first phase difference, which is the difference between the first phase difference and the second phase difference obtained by adding an odd multiple of π to the first phase difference, are obtained. In addition to obtaining the difference image signal, the imaging is performed in the state of the third phase difference obtained by adding π / 2 to an integer multiple of π and the fourth phase difference obtained by adding an odd multiple of π to the third phase difference by the phase difference adjusting means. Difference image signal generating means (50, 58) for obtaining a second difference image signal which is a difference between the respective image signals obtained by the means; first and first difference image signal generating means From the difference image signal of 2 and the 0th order light intensity signal of the object, An arithmetic means (58) for performing an arithmetic operation for adjusting the relative intensity of the image signal and an arithmetic operation for combining the adjusted images, respectively.

According to a main aspect, a zero-order light intensity measuring means for measuring the zero-order light intensity of an object and obtaining its intensity signal is provided. According to the third aspect of the invention, the 0th-order light intensity is measured by rotating the third filter means. According to another aspect, the phase difference adjusting unit includes a rotatable polarizer and a quarter-wave plate. Further, the phase difference adjusting means is a liquid crystal whose refractive index can be controlled by a voltage.

Another invention is an objective lens (16) for collecting light from an object to be observed; for illuminating the object to obtain a light image which can be selectively filtered near the pupil of the objective lens. Illuminating means (10, 30, 32, 34, 36, 38); including a polarizer (18) and a quarter wave plate (20), and a phase difference between two linearly polarized light components of the incident light from the objective lens which are orthogonal to each other. Phase difference adjusting means for arbitrarily adjusting the linearly polarized light components of the 0th order light and diffracted light of the incident light from the phase difference adjusting means in different directions (21). ); Second filter means (26) for polarization-splitting the light from the first filter means; Imaging means (42, 46) for obtaining images of the respective polarization components polarization-split by the second filter means ); The azimuth angle of the polarizer is set to the light of the quarter wavelength plate. When the first azimuth of the two azimuths corresponding to the axis is set, a first difference image, which is the difference between the two azimuths obtained by the image pickup means, is obtained, and a second azimuth is obtained. Difference image generating means (4) for obtaining a second difference image which is the difference between the two images obtained by the image pickup means when
8); secondary difference image means (51) for generating a secondary difference image from the first and second difference images obtained by the difference image generating means.

Yet another invention is an objective lens (16) for collecting light from an object to be observed; illuminating the object,
Illumination means (10, 30, 32, 34, 36, 38) for obtaining a light image that can be selectively filtered in the vicinity of the pupil of the objective lens; including incident light from the objective lens, including a polarizer and a quarter wave plate Difference adjusting means (18, 20) for arbitrarily adjusting the phase difference between two linearly polarized light components orthogonal to each other; the straight lines of the incident light from the phase difference adjusting means with respect to the 0th order light and the diffracted light. First filter means (21) for extracting polarization components in different directions; Second filter means (2) for extracting linear polarization components from incident light from the first filter means (2)
6); Imaging means (42) for obtaining an image of the polarization component extracted by the second filter means; The azimuth angle of the polarizer or the second filter means corresponds to the optical axis of the quarter wavelength plate. Image storage means (50) for storing four images respectively obtained by the image pickup means in four azimuth directions; from the four images stored therein to the optical axis of the quarter wavelength plate. Corresponding first and second
Difference image generating means (58) for obtaining the difference image of the second difference image means (58) for generating a second difference image from the first and second difference images obtained by the difference image generating means.
1); is provided.

According to a main aspect, said illuminating means comprises a condenser lens (12) for collecting the illuminating light;
The polarizer is arranged in the vicinity of the pupil of the condenser lens.

Further, the following are the main aspects of the present invention. (1) Illuminating means for illuminating an object, and an objective lens arranged along an optical axis for collecting light rays from the object and generating a spatial frequency spectrum that can be selectively filtered in the vicinity of a pupil plane. , A rotatable polarizer for converting a light beam passing near the pupil plane into a linearly polarized light of a polarization plane in a first direction with respect to the optical axis, and the linearly polarized light which is located near the pupil plane and can pass therethrough Includes only a quarter-wave plate, a wavefront splitting device that splits a light beam transmitted through the quarter-wave plate into a first light beam and a second light beam, and a spatial frequency component of the first light beam that is not diffracted by an object. Have a possible area,
A first spatial filter that transmits only the linearly polarized light component of the plane of polarization in the second direction, and an area that can include spatial frequency components that are not included in the first filter in the first light beam, The second spatial filter that transmits only the linearly polarized light component of the polarization plane of the third azimuth direction orthogonal to each other, and the linearly polarized light of the polarization plane of the fourth azimuth direction among the light rays that have passed through the first spatial filter and the second spatial filter. And a polarization beam splitter that transmits only linearly polarized light having a polarization plane in a fifth azimuth direction orthogonal thereto and a first object image that photoelectrically converts the first object image by the linearly polarized light beam having a polarization plane in the fourth azimuth direction. A photoelectric conversion element, a second photoelectric conversion element for photoelectrically converting a second object image by a linearly polarized light beam having a polarization plane in the fifth direction, and a straight line having a polarization plane in the second direction among the second light rays. A that transmits only polarized light A riser, and a third photoelectric conversion element for photoelectrically converting a light beam transmitted through the analyzer, the first,
It is data showing a differential circuit for generating a difference image signal which is a difference in intensity of image signals of the second photoelectric conversion element, and a difference image signal obtained when the first direction is matched with the fifth direction. First difference image storage means for storing first difference image data,
A second difference image storage means for storing second difference image data, which is data indicating a difference image signal of an object obtained when the first direction is matched with the sixth direction, and the third photoelectric conversion element. A first signal storage means for storing data indicating a first signal, the first difference image storage means, the second difference image storage means, and the first signal storage means from the first difference image, the second difference image, and the first difference image.
After the signals are taken out and their relative intensities are adjusted, a composite image generation means for generating a composite image based on these image data and an image display means for displaying the composite image are provided, and the 1/4 wavelength plate The azimuth of the optical axis and the second azimuth form an angle obtained by adding 45 ° to an integer multiple of 90 °, and the fourth azimuth formed by the polarization beam splitter is ¼ the azimuth.
An angle obtained by adding 45 to the azimuth of the optical axis of the wave plate is added to 45, and the fifth azimuth is an integer multiple of 90 degrees relative to the azimuth of the optic axis of the quarter wave plate to 45. The object observing device is characterized in that the sixth azimuth forms an angle that is an integral multiple of 90 ° with respect to the method of the optical axis of the quarter wavelength plate.

(2) The composite image generating means in (1) is a composite representing the arctangent of the result of dividing the second difference image data by the image obtained by subtracting the first signal data from the first difference image data. It is characterized by generating an image.

(3) The illumination means, the objective lens, the polarizer, and the quarter-wave plate in (1) above are included, and only the spatial frequency component that is not diffracted by the object is included among the light rays that have passed through the quarter-wave plate. A first spatial filter that has a possible area and transmits only the linearly polarized light component of the polarization plane of the second direction, and the first of the light rays that have passed through the quarter wavelength plate
A second spatial filter having an area capable of including a spatial frequency component that is not included in the spatial filter, and transmitting only a linearly polarized component of a polarization plane of a third azimuth orthogonal to the second azimuth;
Of the light rays that have passed through the first spatial filter and the second spatial filter, only the linearly polarized light of the polarization plane of the fourth azimuth is transmitted, and the object image of the linearly polarized light of the polarization plane of the fourth azimuth. Photoelectric conversion element which outputs an image signal, and an image signal which shows the intensity distribution of an optical image obtained when the first azimuth is matched with the fifth azimuth and is converted into data. With the first image storage means for storing as a first image data and an image signal indicating the intensity distribution of the optical image obtained when the first azimuth is aligned with the sixth azimuth orthogonal to the fifth azimuth as data. Second image storage means for converting and storing this as second image data, and an image signal indicating the intensity distribution of the optical image obtained when the first azimuth is matched with the seventh azimuth, This is the third image data And a third image storing means for storing the same, and an image signal showing the intensity distribution of the optical image obtained when the first azimuth is orthogonal to the seventh azimuth and coincident with the eighth azimuth, and converted into data. Fourth image storing means for storing as fourth image data, and the first image data and the second image data are taken out from the first image storing means and the second image storing means, and a first difference indicating a difference between these intensities. Generate an image,
A first difference image generating means, the third image data and the fourth image data from the third image storing means and the fourth image storing means, and a second difference image showing a difference between these intensities is generated. Two-difference image generation means, first difference image storage means for converting the first difference image into storable data, and storing this, and second difference image storage means for converting the second difference image into storable data, and storing this Second difference image storage means, first signal storage means for converting the first signal obtained when the fourth orientation is parallel to the second orientation into storable data, and storing the data. The data of the first difference image, the data of the second difference image, and the data of the first signal are taken out from the first difference image storage means, the second difference image storage means, and the first signal storage means, and their relative intensities are adjusted. And then create a composite image of these images. A generating means and an image displaying means for displaying the composite image, wherein the azimuth of the optical axis of the quarter-wave plate and the second azimuth form an angle obtained by adding 45 ° to an integer multiple of 90 °. The fourth azimuth formed by the polarization analyzer is an integral multiple of 90 ° with respect to the azimuth of the optical axis of the quarter wavelength plate when storing the first, second, third, and fourth images. And the fifth azimuth is ¼
An angle obtained by adding 45 ° to an azimuth of the optical axis of the wave plate is added to the azimuth of 90 °, and the seventh azimuth is an integer multiple of 90 ° with respect to the method of the optic axis of the ¼ wave plate. An object observation device characterized by forming an angle.

(4) The composite image generation means in (3) above calculates the arc tangent of the result of dividing the data of the second difference image by the image obtained by subtracting the data of the first signal from the data of the first difference image. Is generated.

(5) Illuminating means for illuminating an object, arranged along the optical axis for collecting light rays from the object and generating a spatial frequency spectrum which can be selectively filtered near the pupil plane, An objective lens, a rotatable polarizer for converting a light beam passing near the pupil plane into a linearly polarized light in a polarization plane of a first azimuth with respect to the optical axis, and a linearly polarized light located near the pupil plane, A quarter wave plate that can pass through,
A first spatial filter having an area capable of containing only spatial frequency components that are not diffracted by an object among the light rays transmitted through the quarter-wave plate, and transmitting only linearly polarized light components of a polarization plane in the second direction; , A linearly polarized light of a polarization plane in a third azimuth direction orthogonal to the second azimuth having an area capable of including a spatial frequency component not included in the first spatial filter among the light rays that have passed through the ¼ wavelength plate. A second spatial filter that transmits only the component, and a fifth azimuth that passes only the linearly polarized light of the polarization plane of the fourth azimuth among the rays that have passed through the first spatial filter and the second spatial filter and is orthogonal thereto , A first photoelectric conversion element for photoelectrically converting the first object image by the linearly polarized light of the polarization plane of the fourth direction, and a straight line of the polarization plane of the fifth direction. By polarized light Second for photoelectrically converting the second object image
A photoelectric conversion element and a differential circuit that generates a difference signal of the signals of the first and second photoelectric conversion elements, the first difference image is formed using the difference signal, and the quarter wavelength plate is formed. The azimuth of the optical axis and the second azimuth form an angle obtained by adding 45 ° to an integer multiple of 90 °, and the fourth azimuth formed by the analyzer is relative to the azimuth of the optic axis of the quarter wavelength plate. A plurality of first difference images corresponding to the plurality of first azimuths, the observation means having an angle obtained by adding 45 ° to an integral multiple of 90 °. The first azimuth is paired with an azimuth symmetrical with respect to the azimuth of the optical axis of the quarter-wave plate.
An object observation apparatus characterized by calculating a mutual difference image of a pair of first difference images and displaying the calculated difference image.

(6) Illumination means, objective lens, polarizer, quarter wave plate, first spatial filter,
A second spatial filter, the first spatial filter and the second spatial filter
Of the light rays that have passed through the spatial filter, an analyzer that transmits only linearly polarized light of the polarization plane of the fourth azimuth, a photoelectric conversion element that photoelectrically converts an object image of the linearly polarized light of the polarization plane of the fourth azimuth, and A first image storage unit for storing a first image of the object obtained when the first azimuth coincides with the fifth azimuth, and a sixth image orthogonal to the fifth azimuth.
Second image storage means for storing a second image of the object obtained when the orientation is matched, the first image storage means, and the second image storage means
The first image and the second image are taken out from the image storing means, and a first difference image generating means for generating a first difference image which is a difference image between them is provided, and the azimuth of the optical axis of the quarter wavelength plate. And the second azimuth is an integer multiple of 90 ° plus 45 °, and the fourth azimuth formed by the analyzer is an integer of 90 ° with respect to the azimuth of the optical axis of the quarter wavelength plate. The first difference image is formed in plural corresponding to the plurality of first orientations, and the first orientation corresponding to the plurality of first orientations is formed. An object observation apparatus, which calculates a mutual difference image of a pair of first difference images which forms a pair with an azimuth that is symmetric with respect to the azimuth of the optical axis of the quarter wave plate, and displays the difference image. .

(7) Illuminating means, objective lens, polarizer, quarter wave plate, first spatial filter,
Having a second spatial filter, an analyzer, a photoelectric conversion element,
A first image storing means for storing a first image of an object obtained when the fourth azimuth coincides with the fifth azimuth, and the fourth azimuth coincides with a sixth azimuth orthogonal to the fifth azimuth. The second image storage means for storing the second image of the object obtained when the first image storage means, the first image storage means and the second image storage means,
A first difference image generating means for extracting the first image and the second image and generating a first difference image which is a difference image between them;
The azimuth of the optical axis of the quarter-wave plate and the second azimuth are 90
An angle obtained by adding 45 ° to an angle that is an integral multiple of °, and the first azimuth formed by the polarizer is an integer multiple of 90 ° with respect to the azimuth of the optical axis of the ¼ wavelength plate, and 45 ° is added. The first difference image has a plurality of the fourth difference images.
One first difference image formed in plural corresponding to the azimuth, and a corresponding fourth azimuth of the first difference image is paired with an azimuth symmetrical to the azimuth of the optical axis of the quarter wavelength plate. An object observing device, which calculates a difference image between the pairs of and displays the difference image.

[0021]

According to the present invention, the phase difference of the orthogonal polarization components of the light from the phase object is adjusted by the rotatable polarizer and the quarter-wave plate. Then, a coherent polarization component in different polarization directions is extracted from the adjusted light by the filter means, and a difference image is obtained from the image in each polarization direction. Then, from the difference image and the 0th-order light intensity signal of the object, the calculation of the relative intensity of the difference image and the calculation of the combination of the adjusted images are performed. Or,
The interference components are extracted in two predetermined azimuths, for example, two azimuths corresponding to the azimuths of the optical axes of the quarter-wave plate to generate difference images, and the quadratic difference images are calculated. The calculation result does not include the light intensity component, but only the pure phase component. Thereby, the phase distribution image can be satisfactorily observed.

The above and other objects, features and advantages of the present invention will be apparent from the following detailed description and the accompanying drawings.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to Examples.

[0024]

First Basic Mode of Embodiment First, a first basic mode will be described with reference to FIG. The light output from a light source (not shown) is focused into a ring shape by the ring diaphragm 10 and then enters the condenser lens 12. Then, the light transmitted through the condenser lens 12 is incident on the phase object 14, and the light transmitted through the phase object 14 is incident on the objective lens 16.

In the vicinity of the pupil position of the objective lens 16, a rotatable polarizer 18 for obtaining linearly polarized light of an arbitrary polarization plane from the incident light and always having the same amplitude, linearly polarized light is transmitted 1 / 4 wavelength plate 20, 0 of incident light that is not diffracted by the phase object 14
A ring-shaped polarizing plate 22 for separating the next spectrum component and other spectrum components into orthogonal linearly polarized light, which reflects 50% of the amplitude intensity of the incident light and the remaining 5
A half mirror 23 that transmits 0% and splits it, and an analyzer (polarization beam splitter) 24 that extracts coherent light of the same polarization direction from incident light are provided in that order along the optical axis AX. ing. Also,
On the reflection optical axis AX2 of the half mirror 23, a linearly polarized light having a plane of polarization parallel to the x axis, that is, an analyzer 25 for transmitting and extracting the 0th order light in the incident light is provided.

The orthogonal coordinates (X1, Y1) to (X5, Y5) of these elements are set so as to be orthogonal to the optical axis AX and have the same orientation. Similarly, the Cartesian coordinates (X6, Y6), (X7, Y7) are calculated by the analyzer 2
It is set so as to be orthogonal to the reflection-side optical axes AX1 and AX2 obtained by folding back the optical axis AX of No. 4 and have the same azimuth as the orthogonal coordinates (X1, Y1) to (X5, Y5). That is, the ring diaphragm 10
The coordinates are set so that the coordinate axes overlap when viewed from the side. Hereinafter, those directions will be simply expressed as (x, y).

Next, the relationship between these coordinate axes and the polarization direction of each element will be described. First, the polarizer 18 is shown in FIG.
As shown in (A), the azimuth angle θ1 with respect to the x-axis is the polarization direction of the transmitted light, and this angle θ1 is the polarization direction of the polarizer 18.
It can be changed by rotating. As shown in FIG. 2B, the quarter-wave plate 20 has a fast axis ne as an optical axis and a slow axis no orthogonal to the fast axis ne, and the azimuth angle of the fast axis ne is 45 with respect to the x axis.゜, slow axis no azimuth is x
It is set at -45 ° to the axis. Of the incident light
The linear polarization component of the plane of polarization parallel to the slow axis no is fast axis ne
1/4 wavelength (9
0 °) phase delay occurs.

For example, the azimuth angle θ1 of the polarizer 18 is 1
When it coincides with the fast axis ne of the / 4 wave plate 20, the polarized light in the fast axis ne direction of the transmitted light of the objective lens 16 enters the annular polarization plate 22 as it is. Polarizer 18
When the azimuth angle .theta.1 of the object coincides with the slow axis no of the quarter-wave plate 20, the slow axis n of the transmitted light of the objective lens 16 is transmitted.
The polarized light in the o direction is incident on the annular polarization plate 22 after a phase delay of 90 ° due to the quarter-wave plate 20. In this way,
By the polarizer 18 and the quarter-wave plate 20, the object 1
The phase difference between the two linearly polarized light components orthogonal to each other out of the light from 4 can be arbitrarily adjusted, and the phase difference α given to the output light of the quarter wavelength plate 20 is α = 2θ1−π / 2. Represented.

The ring-shaped polarizing plate 22 is composed of a ring-shaped portion 22a and a portion 22b other than that. Zone 22
As indicated by an arrow in FIG. 2 (C), a transmits only the linearly polarized light component of the plane of polarization parallel to the x-axis, and the other part 2
2b transmits only the linearly polarized component of the plane of polarization parallel to the y-axis. Further, the size of the ring portion 22a of the ring-shaped polarizing plate 22 is set so that when there is no object other than the light-transmissive parallel flat plate such as a slide glass having a predetermined thickness, which is designed at the position of the phase object 14, there is no objective. The size of the aerial image of the ring diaphragm 10 formed near the pupil position of the lens 16 is made to match. That is, the magnitude of the direct light (0th-order light) that is not diffracted by the phase object 14 is matched. With this configuration, the linearly polarized light component X0 parallel to the x direction is extracted for the 0th order light, and the linearly polarized light component Yd parallel to the y direction is extracted for the diffracted light.

Next, as shown in FIG. 2D, the analyzer 24 transmits the ray i1 of the linearly polarized light component of the plane of polarization parallel to the analyzer angle θ2 in the direction of the optical axis AX, and the anti-analyzer angle θ3 = It has a function of reflecting a light ray i2 of a linearly polarized component having a plane of polarization parallel to θ2 + 90 ° in the direction of the optical axis AX1. For example, the analyzer angle θ2 is set to 45 °,
The anti-analyzer angle θ3 is set to 45 + 90 = 135 °. The coherent ray i1 that passes through the analyzer 24 is an interference image Ii1 (x, y, α) = Iθ2 on the image plane of the objective lens 16.
Form (x, y, θ1). The coherent ray i2 reflected by the analyzer 24 forms Ii2 (x, y, α) = Iθ3 (x, y, θ2 = θ1 + π / 2) on the image plane of the objective lens 16.

The analyzer 24 extracts coherent polarized components forming two interference images having a phase difference of π added between the 0th-order spectral component of the object and the other spectral components. More specifically, as shown in FIG. 2C, the annular polarization plate 22 outputs a polarization component X0 in the x direction for the 0th order light and a polarization component Yd in the y direction for the diffracted light. . On the other hand, in the analyzer 24, the polarized component in the i1 direction shown in FIG. 2D is transmitted and the polarized component in the i2 direction is reflected. Therefore,
As for the 0th-order light, as shown in FIG. 3A, the i1 direction component X01 is transmitted and the i2 direction component X02 is reflected. The same applies to diffracted light, as shown in FIG.
The i1 direction component Yd1 is transmitted and the i2 direction component Yd2 is reflected.

The transmission component in the i1 direction is X01 in FIG. 3 (A) and Yd1 in FIG. 3 (B), both of which are parallel linearly polarized light. For this reason, the two interfere with each other and a bright and dark image is observed. The transmission component in the i2 direction is X02 in FIG. 3 (A) and Yd2 in FIG. 3 (B), both of which are parallel linearly polarized light. For this reason, the two interfere with each other and a bright and dark image is observed. In this case, when the polarizer 18 is rotated to select the plane of polarization of the linearly polarized light that enters the quarter-wave plate 20, the elliptically-polarized light having various major and minor diameter ratios depending on the orientation is converted into the quarter-wave plate. Emit from 20. In this elliptically polarized light, the major axis and the minor axis are orthogonal to each other regardless of the value of θ1, and the orientation is 45 ° in the x and y coordinates. Also, θ1 =
At 0 ° or 90 °, the light beam emitted from the quarter-wave plate 20 becomes circularly polarized light, and at θ1 = ± 45 °, it becomes linearly polarized light. That is, elliptically polarized light including these circularly polarized light and linearly polarized light is equivalent to that the phase difference α between two linearly polarized lights that are parallel to the x and y directions and have the same amplitude is determined by the polarizer angle θ1.

Next, a method for obtaining a pure phase distribution image using the above optical system will be described using mathematical expressions. The description will be made without considering the transfer function of the phase contrast microscope. Optics, Vol. 20, No. 9 (September 1991) p590
~ P591 "Consideration on image contrast of phase contrast microscope" According to Hirofumi Oki, or Proc. Is easily removed by image processing to remove the influence of halo and the like. The transmitted light distribution O (x, y) of the phase object 14 that is the observation target is expressed by the following equation (1), for example.

[0034]

[Equation 1]

This equation (1) is a complex representation, and ρ (x, y)
Represents an amplitude component, and exp [jφ (x, y)] represents a phase component. "J" is an imaginary unit. Where phase object 1
If the magnitude of 4 is (x, y) = (2g, 2h), the average amplitude b of the object can be integrated in these ranges and divided by the total area. It is shown by the formula.

[0036]

[Equation 2]

Next, in the annular portion 22a of the annular polarizing plate 22, a constant amplitude change a1 and a constant phase change α are given to the incident light, so that its transmission characteristic is expressed by the equation (3).

[0038]

(Equation 3)

Next, the intensity distribution Ii1 corresponding to the ray i1
(X, y, α) = Iθ2 (x, y, θ1) is expressed by the equation (4). Substituting equation (1) into this and rearranging it yields equation (5).

[0040]

(Equation 4)

(Equation 5)

Further, a1 = a2 = 1 / √2, α = 2θ1−π / 2
Therefore, substituting this gives equation (6). Further, by substituting θ2 = θ1 + π / 2, the intensity distribution Ii2 (x, y, α) = Iθ3 (x, y, θ1) corresponding to the light ray I2 is obtained as in the equation (7).

[0042]

(Equation 6)

(Equation 7)

Here, when the difference image between the two is obtained, the following equation (8) is obtained. By substituting equations (6) and (7) into this, equation (9) is obtained.

[0044]

(Equation 8)

[Equation 9]

Here, the azimuth angle θ1 of the polarizer 18 is π /
4, the operating output when the phase difference α obtained by the polarizer 18 and the quarter-wave plate 20 is 0 is S1 (x, y), θ1 is 0, in other words, the phase difference is 0. α is π / 2
Let S2 (x, y) be the operation output at (10), (11)
It looks like an expression.

[0046]

(Equation 10)

[Equation 11]

On the other hand, the ray i extracted by the analyzer 25
The intensity Ib of b is expressed by equation (12), and is proportional to the square of the absolute value of the average amplitude of the intensity of the 0th-order optical spectrum of the object 14.
If the average intensity of the light transmitted (or reflected) from the object 14 is known in advance, that value may be used. In this case, it is not necessary to provide the half mirror 23 and the analyzer 25.

[0048]

(Equation 12)

From the above equations (10), (11) and (12), the evaluation amount Sr is defined as the equation (13). The right side of this equation (13) can be measured. If the arctangent of the equation (13) is taken, the phase distribution image of the object 14 is obtained as the following equation (14). That is, even if the light from the object 14 has an intensity distribution, only the phase distribution can be observed without being affected by the intensity distribution. It should be noted that the expression (13) can be considered as an operation for adjusting the relative intensity of the difference image and combining the adjusted images.

[0050]

(Equation 13)

[Equation 14]

As described above, an extremely simple optical element from the polarizer 18 to the analyzer 24 and a predetermined calculation for the obtained difference image can be used to obtain a pure phase distribution image without being affected by the intensity change. Can be observed.

[0052]

[Basic Form 2] Next, a second basic form will be described with reference to FIG. This form is an example in which it is not necessary to perform polarization division by the polarization beam splitter and generation of a difference image by two detectors, and the device configuration is further simplified. Returning to the equations (3) and (4), considering the phase difference α between the operation outputs S1 (x, y) and S2 (x, y),
It can be expressed by equations (5) and (16). Also, the above (12)
The formula is expressed as formula (17).

[0053]

(Equation 15)

(Equation 16)

[Equation 17]

FIG. 4 shows a device configuration using these mathematical expressions. An analyzer 26 is provided on the output side of the annular polarizing plate 22 so that the light ray i1 can be extracted. When the polarizer 18 is rotated, the light ray i1
The phase α of can be changed, and two pairs of polarizer angles θ1 (θ1 = π can be used as shown in Eqs. (15) and (16).
/ 4, θ1 = 3π / 4), and (θ1 = 0, θ1 = π / 2), four angles can be set to obtain four images. Predetermined calculation is performed on these four image data to obtain the difference image shown in equations (15) and (16). On the other hand,
As shown in the equation (17), the intensity Ib of the light ray ib is θ2 = 0.
Is the intensity of the light ray i1 at the time, and can be detected by rotating the analyzer 26. From the two difference image data S1 and S2 and the intensity data Ib thus obtained, the phase distribution image of the object can be obtained by the equations (13) and (14).

[0055]

First Embodiment Next, a first embodiment will be described with reference to FIG. This embodiment corresponds to the basic form of FIG. In FIG. 5, a mercury lamp is used as the light source 30. The light beam emitted from the light source 30 enters the interference filter 32, and the light of the optimum wavelength is selected thereby. The light transmitted through the interference filter 32 enters the ring diaphragm 10 through the collector lens 34, the first relay lens 36, and the second relay lens 38 in this order. The ring diaphragm 10 is located near the pupil position of the condenser lens 12. Through the ring diaphragm 10,
The light refracted by the condenser lens 125 transmits and illuminates the phase object 14 on the slide glass 13.

The light ray transmitted through the phase object 14 is incident on the objective lens 16 and is refracted. Near the pupil position of the objective lens 16, a rotatable polarizer 18 and a quarter-wave plate 2 are provided.
0, an annular polarizing plate 22, and a half mirror 23 are arranged in that order. The ring-shaped polarizing plate 22 is formed by the ring-shaped portion Rp and the other portion Ro. The ring zone Rp is x
Only the linearly polarized light component of the plane of polarization parallel to the axis, that is, the component having the azimuth of 45 ° with respect to the optical axis of the quarter wave plate 20 is transmitted. The other part Ro transmits only the linearly polarized light component of the polarization plane perpendicular to the polarization plane of the linearly polarized light component that passes through the annular zone Rp (see FIG. 2C).

The light emitted from the objective lens 16 and sequentially transmitted through the polarizer 18, the quarter-wave plate 20, and the annular polarizing plate 22 enters the half mirror 23, where the amplitude of 50 is applied.
Polarization beam splitter 2 which is an analyzer that transmits%
It advances on the optical axis AX toward 4. 50 of remaining amplitude
% Is reflected by the half mirror 23 and travels toward the analyzer 25 on the optical axis AX2. Of the light that has traveled on the optical axis AX and has entered the polarization beam splitter 24, the light that has passed through the polarization beam splitter 24 becomes i1, and the rest is reflected and becomes i2.

Here, the optical axis azimuth of the quarter-wave plate 20 is an azimuth of 45 ° with the Y direction being positive with respect to the X axis (FIG. 2).
(See (B)). The analyzer angle of the polarization beam splitter 24 is 45 ° with the Y direction being positive with respect to the X axis (see FIG. 2D). That is, the analyzer angle is 1/4
It is assumed that it is parallel to the optical axis of the wave plate 20. Then, the light ray i1 becomes linearly polarized light having a plane of polarization parallel to the analyzer angle of the polarization beam splitter 24, and the light ray i2 becomes linearly polarized light having a plane of polarization perpendicular to the analyzer angle of the polarization beam splitter 24.

The ray i1 is refracted by the lens 40,
An interference image is formed on an image plane conjugate with the object plane of the objective lens 16. The interference image is photoelectrically converted by the two-dimensional image pickup device 42 whose light detection surface is located on this image plane, and a video signal is output from the two-dimensional image pickup device 42. On the other hand, the ray i2 is
The light is refracted by the lens 44, and an interference image is formed on an image plane conjugate with the object plane of the objective lens 16. The interference image is photoelectrically converted by the two-dimensional image pickup device 46 whose light detection surface is located on this image plane, and a video signal is output from the two-dimensional image pickup device 46.

The two video signals output from the two-dimensional image pickup devices 42 and 46 are input to the differential amplifier 48, and the differential signal is output from the differential amplifier 48. This differential signal is input to and stored in the image storage unit 50. It should be noted that an object point at an arbitrary position within the field of view of the objective lens 16 and a conjugate point 2
Information on the position in the video signal corresponding to one image point, for example, so that the number of clock pulses is exactly the same, that is, if the object is represented by only the amplitude distribution, the differential signal becomes zero, The positions of the two two-dimensional image pickup devices 42 and 46 in the direction crossing the optical axis, the signal output timing, and the like are adjusted.

By the way, the rotatable polarizer 18 is
The azimuth angle is switched by the actuator 56 to two azimuths of 0 ° and 45 ° with the Y direction being positive with respect to the X axis. When the actuator 56 operates based on the instruction from the computer 58, two difference images corresponding to the two directions of the polarizer 18 are generated by the differential amplifier 4.
Obtained in 8. These are the differential outputs S1 (x,
y) and the differential output S2 (x, y) of the equation (11), respectively.

On the other hand, the light reflected by the half mirror 23 passes through the analyzer 25 and is a linearly polarized light ray ib.
Becomes The analyzer angle of the analyzer 25 is set so that only the linearly polarized light of the plane of polarization that passes through the ring zone Rp of the ring polarization plate 22 is transmitted. The light passing through the analyzer 25 passes through the lens 52 and the two-dimensional image pickup device 54.
And is photoelectrically converted here. This signal is a DC signal that does not change depending on the azimuth angle of the polarizer 18,
It is the intensity Ib represented by the formula (12). This is stored in the image storage unit 50.

In this way, the two difference images S1 (x, y) and S2 (x, which are necessary for calculating the phase distribution image of the phase object 14 are obtained.
y) and the intensity Ib of one DC signal are stored in the image storage unit 50 in a readable state. The computer 58 reads out these three data and
The equation (14) is calculated to calculate the phase distribution image, which is displayed on the display unit 60. The observer can input necessary information to the computer 58 through the interface 62, for example, an instruction to capture an image and a call to stored image data.

[0064]

Second Embodiment Next, a second embodiment will be described with reference to FIG. This embodiment corresponds to the basic form of FIG. That is, this is an example in which the polarization beam splitter does not split the polarized light and the two detectors do not generate the difference image by photoelectric conversion. The phase difference α of the light ray i1 is changed according to the equations (15) and (16) to obtain four images. It is obtained and stored once in the memory, and two difference images are obtained from these four image data. Note that the intensity Ib of the light ray ib represented by the equation (17) is also detected and stored in the memory as the fifth image data. Then, from the two difference image data and one DC signal strength Ib, (14)
The phase distribution image of the object is obtained by the formula.

The components from the light source 30 to the annular polarizing plate 22 are the same as those in the first embodiment. In this embodiment,
The polarizer 18 and the analyzer 26 make the actuator 5
6 and 57, and only the two-dimensional image pickup element 42 is provided.

First, two difference images S1 (x, y) and S2 (x,
The procedure for obtaining y) will be described. The analyzer angle of the rotatable analyzer 26 is set to 45 ° by the actuator 57 with the Y direction being positive with respect to the X axis. That is, the analyzer angle is made parallel to the optical axis of the quarter-wave plate 20. Then, the ray i1 is transmitted to the analyzer 26.
Linearly polarized light with a plane of polarization parallel to the analyzer angle of. The light ray i1 is refracted by the lens 40 as described above, and an interference image is formed on the image plane conjugate with the object plane of the objective lens 16. Then, the interference image is photoelectrically converted by the two-dimensional image pickup device 42 whose light detection surface is located on this image plane, and a video signal is output from the two-dimensional image pickup device 42.

By the way, the azimuth of the polarizer angle θ1 of the polarizer 18 can be switched by the actuator 56. Set the polarizer angle θ1 to “0”,
By switching between “π / 4”, “π / 2”, and “3π / 4”, four image signals can be obtained corresponding to four polarizer angles. These four image signals are A / D converted,
The image data is stored in the image storage unit 50 as image data. On the computer 58 ,. θ1 = π / 4 and θ1 = 3π / 4
A pair of images of is read from the image storage unit 50, and (15)
The difference image data is calculated according to the formula and stored in the image storage unit 50. Next, a pair of images of θ1 = 0 and θ1 = π / 2 is read from the image storage unit 50, difference image data is calculated according to the equation (16), and stored in the image storage unit 50.

Next, the procedure for obtaining one DC signal strength Ib will be described. In this case, the analyzer angle of the analyzer 26 is made parallel to the X axis by the actuator 57. Incidentally, the azimuth of the polarizer angle θ1 of the polarizer 18 may be arbitrary. The intensity Ib of the light ray ib, which is the signal intensity at this time, is represented by the equation (17), and is represented by the two-dimensional image pickup device 4
Detected by 2. The DC signal intensity data photoelectrically converted by the two-dimensional image sensor 42 is stored in the image storage unit 50 as the fifth image data in a readable state.

The two difference image data and one DC signal intensity Ib obtained by the above procedure are read out to the computer 58 and the operation of the equation (14) is performed. Then, the calculated phase distribution image is output and displayed on the display unit 60. It is to be noted that the observer can input necessary information, for example, an instruction to capture an image or a call to stored image data to the computer 58 through the interface 62, as in the first embodiment.

[0070]

Third Embodiment Next, a third embodiment will be described with reference to FIG. The configuration is almost the same as that of the second embodiment, but the installation location of the polarizer 18 is different. That is, in this embodiment, the polarizer 18 is arranged near the pupil plane of the condenser lens 12. Although it is optically equivalent to the second embodiment, this embodiment is effective when the flatness of the polarizer 18 is not good or when the rotation axis of the polarizer 18 is not completely perpendicular to the optical axis AX. Even when the polarizer 18 is rotated by the actuator 56 in such a situation, the image does not move on the image plane, and four images whose positions are completely matched can be obtained in correspondence with the four polarizer angles. . Also, one DC signal strength Ib
Is also obtained by rotating the analyzer 26. Therefore, a difference image can be easily obtained.

[0071]

Fourth Embodiment FIG. 8 shows a fourth embodiment of the present invention. This embodiment was made in view of Hiroshi Oki (hereinafter referred to as "reference"), which is an optical "consideration regarding image contrast of a phase contrast microscope". According to said document, the phase contrast microscope image of a phase object (a pure phase object with a uniform amplitude distribution) is:
For an object having an intensity distribution proportional to the phase, the product (Ka (x) Kb) of the Fourier transform (Ka (x)) of the annular zone part of the annular phase plate and the Fourier transform (Kb (x)) of the other zone It is stated that it is the convolution integral of (x)). That is, this is the structure of halo. The effect of this halo is
It can be removed by deconvolution processing. Therefore, it is possible by calculation to make the differential output S ₂ (x, y) of the equation (11) an image without the influence of halo.

As described in Examples 1 to 3, b ² is (1
It is obtained by the equation (7), and if the square root of this is calculated, a signal proportional to b is obtained. Further, the following method can be considered to obtain ρ (x, y). (1) In FIG. 8, the analyzer 26 is retracted by the actuator 57 according to the instruction of the computer 58,
Take the square root of the image proportional to [ρ (x, y)] ² formed on the image plane. (2) The polarizer angle is set so that α = 0, the image at this time is photoelectrically converted, and the square root is obtained. (3) The annular polarizing plate 22 is retracted from the optical axis by the actuator 70, an image proportional to [ρ (x, y)] ^{2 formed} on the image plane is used, and a square root of this is obtained to obtain ρ ( x, y)
Form an image proportional to.

In such processing, the electric signal photoelectrically converted by the photoelectric conversion element 42 is converted into data that can be stored by the signal / data conversion unit (generally an analog / digital converter) in the image storage unit 50. By calculating the square root of the data with a computer, ρ (x, y)
Generate image data proportional to. INDUSTRIAL APPLICABILITY The present invention is effective for measuring the step of an object, inspecting defects such as a magnetic head, a wafer, and a reticle, and measuring the position in consideration of the shape of the object.

[0074]

[Basic Form 3] Next, a third basic form will be described with reference to FIG. This form is shown in FIG.
From the basic form of the half mirror 23 and the analyzer 2
The difference is that 5 is excluded.

Next, the operation of this mode will be described. First,
The equations (1) to (9) are the same as in the case of FIG. That is, when the azimuth angle of the polarizer 18 is θ1, the intensity distributions Iθ ₂ (x, y, θ1, Iθ ₃ (x, y, θ1) of the images formed on the transmission side and the reflection side of the analyzer 24, respectively.
Are expressed by equations (6) and (7), respectively. Then, when the difference image S (x, y, θ1) is obtained, (8), (9)
It looks like an expression.

In the case of FIG. 1, here, θ1 is set to "π /
The difference image when 4 "and" 0 "was obtained. However, in the case of FIG. 9, a pair is paired with the polarizer angle θ1.
Another polarizer angle θ11 is defined by the following equation (18). Azimuth of this pair (θ1, θ11)
Corresponds to the azimuth of the optical axis of the quarter-wave plate 20.
The difference image S (x, y, θ11) at the polarizer angle θ11 is
It becomes like the formula (19). The difference image S (x, y, θ1) at the polarizer angle θ1 is as shown in the equation (9).

[0077]

(Equation 18)

[Equation 19]

Next, these polarizer angles (θ1, θ11)
The difference signal between the respective difference images in is defined as the second-order difference image as in the following expression (20), and when this is obtained, the following expression (21) is obtained. Looking at this equation (21), the image signal is proportional to the phase distribution. As described above, even with the configuration shown in FIG. 9, it is possible to observe only the phase distribution as in FIG. The secondary difference image of the equation (21) becomes maximum when the polarizer angle θ1 is represented by the equation (22).

[0079]

(Equation 20)

(Equation 21)

(Equation 22)

[0080]

Fifth Embodiment Next, a fifth embodiment will be described with reference to FIG. This embodiment corresponds to the basic form of FIG. As in the first embodiment of FIG. 5, the two video signals output from the two-dimensional image pickup devices 42 and 46 are input to the differential amplifier 48, and the differential image (differential signal) is output from the differential amplifier 48. It

First, a differential signal (Equations (8) and (9)) corresponding to the first difference image S (x, y, θ1) when the azimuth angle of the polarizer 18 is θ1 is obtained, It is stored in the secondary difference image calculation unit 51. After that, the azimuth angle of the polarizer 18 is set to θ11 = π / 2−θ1, and the second difference image S (x, y,
A differential signal (equation (19)) corresponding to θ11) is obtained and similarly stored in the secondary difference image calculation unit 51. In the secondary difference image calculation unit 51, the secondary difference image SS shown in the equations (20) and (21) is calculated and calculated from the accumulated first and second difference images, and this is D / A converted. Is output to the display unit 60 after.

[0082]

Sixth Embodiment Next, a sixth embodiment will be described with reference to FIG. This embodiment corresponds to the second embodiment shown in FIG. That is, this is an example in which the polarization beam splitter does not split the polarization and the two detectors do not generate a difference image by photoelectric conversion, and four images are obtained by changing the azimuth angle of the polarizer 18. Then, they are stored once in the memory, two difference images are obtained from the four image data, and a secondary difference image is obtained.

The components from the light source 30 to the annular polarizing plate 22 are the same as those in the fifth embodiment. An analyzer 26 is provided instead of the polarization beam splitter, the polarizer 18 is driven by an actuator 56, and only the two-dimensional image pickup element 42 is provided.

First, the azimuth angle of the polarizer 18 is set to θ1 and the first image is captured by the two-dimensional image sensor 42, and then the azimuth angle is set to θ1 + π / 2 and the second image is similarly captured. . The data of the first and second images are stored in the image storage unit 50, respectively. In the computer 58, the first and second stored in the image storage unit 50
Image data of the first difference image ((8),
(Corresponding to equation (9)) is calculated, and this is stored in the secondary difference image calculation unit 51.

Next, the azimuth angle of the polarizer 18 is π / 2-
The third image is captured by the two-dimensional image sensor 42 after being set to θ1, and the fourth image is similarly captured after setting the azimuth angle to π−θ1. The data of the third and fourth images are stored in the image storage unit 50, respectively. In the computer 58, the data of the second difference image from the third and fourth image data stored in the image storage unit 50 (the above (19)
(Corresponding to the equation) is calculated, and this is stored in the secondary difference image calculation unit 51.

Then, the secondary difference image calculation unit 51 calculates the secondary difference image ((2) above from the two accumulated difference image data.
0) and (corresponding to equation (21)) are calculated and calculated, and this is output to the display unit 60.

[0087]

Seventh Embodiment Next, a seventh embodiment will be described with reference to FIG. This corresponds to the third embodiment shown in FIG. The configuration is almost the same as that of the sixth embodiment, but the installation location of the polarizer 18 is different. That is, in this embodiment,
The polarizer 18 is arranged near the pupil plane of the condenser lens 12. Optically equivalent to the sixth embodiment,
This embodiment is effective when the flatness of the polarizer 18 is not good or when the rotation axis of the polarizer 18 is not completely perpendicular to the optical axis AX. Even when the polarizer 18 is rotated by the actuator 56 in such a situation, the image does not move on the image plane, and four images whose positions are completely matched can be obtained corresponding to four polarizer angles. . Therefore, a difference image can be easily obtained.

[0088]

Other Embodiments The present invention has many embodiments and can be variously modified based on the above disclosure. For example, the following is also included. (1) In the above embodiment, the rotatable polarizers 18 and 1
Although the phase difference adjusting means for the 0th-order light and the diffracted light is constituted by the / 4 wavelength plate 20, another method, for example, a phase difference adjustment for the 0th-order light and the diffracted light is performed by using a variable refractive index element such as liquid crystal. May be performed.

(2) In the above embodiment, the DC signal intensity Ib was obtained in the same manner as the image signal, but it is not necessary to measure it if it is known beforehand. Further, the signal intensity obtained by electrically integrating the light ray i1 with the analyzer angle of the analyzer kept at 45 ° may be used as a substitute value for the DC signal intensity Ib.

(3) In the above embodiment, a two-dimensional image pickup device such as a CCD was used, but any image pickup means may be used. A larger number of image pickup means may be provided to perform a predetermined calculation without requiring an image storage section. In addition, a relay optical system or a mirror may be used if necessary. As the light source, various ones other than the mercury lamp may be used.

(4) In Examples 1 to 4, one or both of the ring-to-polarizer and the analyzer are evacuated, and in this state, a bright field image and a difference image obtained by the photoelectric conversion element are used to synthesize a composite image. The same effect can be obtained by calculating Also, a good result can be obtained by performing a signal strength calculation in which the signal strength of the difference image generated by the differential amplifier is divided by the square root of the signal strength of the bright field image by the computer as the calculation means. be able to. Further, the computer may be provided with a spatial frequency filter representing an inverse function of the spatial frequency characteristic of the object observation apparatus, and the difference image and the bright field image may be passed through the filter prior to the calculation of the signal intensity. (5) In the above embodiments, the present invention is mainly applied to a microscope, but the present invention can be applied to all object observing apparatuses.

[Brief description of drawings]

FIG. 1 is a perspective view showing a first basic configuration of an embodiment of the present invention.

FIG. 2 is a diagram showing a basic operation of each component of FIG.

FIG. 3 is a diagram showing a basic operation of the apparatus of FIG.

FIG. 4 is a perspective view showing a second basic configuration of the embodiment of the present invention.

FIG. 5 is a diagram showing a first embodiment of the present invention.

FIG. 6 is a diagram showing a second embodiment of the present invention.

FIG. 7 is a diagram showing Embodiment 3 of the present invention.

FIG. 8 is a diagram showing Embodiment 4 of the present invention.

FIG. 9 is a perspective view showing a third basic configuration of the embodiment of the present invention.

FIG. 10 is a diagram showing Embodiment 5 of the present invention.

FIG. 11 is a diagram showing a sixth embodiment of the present invention.

FIG. 12 is a diagram showing Embodiment 7 of the present invention.

FIG. 13 is a diagram showing a general configuration of a phase contrast microscope.

FIG. 14 is a diagram showing a configuration of a phase plate of the background art.

[Explanation of symbols]

10 ... Ring diaphragm 12 ... Condenser lens 14 ... Phase object 16 ... Objective lens 18 ... Polarizer 20 ... Quarter wavelength plate 22 ... Ring zone polarizing plate 22a ... Ring zone part 22b ... Other part 24, 25, 26 ... Analyzer ( Polarization beam splitter) 30 ... Light source 32 ... Interference filter 34 ... Collector lens 36 ... First relay lens 38 ... Second relay lens 40, 44, 52 ... Lens 42, 46, 54 ... Two-dimensional imaging element 48 ... Differential amplifier 50 Image storage unit 51 Second-order difference image calculation unit 56, 57 Actuator 58 Computer 60 Image display unit 62 Interface

Claims (13)

[Claims] 1. An objective lens for condensing light from an object to be observed; illumination means for illuminating the object to obtain a light image that can be selectively filtered in the vicinity of the pupil of the objective lens; Phase difference adjusting means for arbitrarily adjusting the phase difference between the 0th-order light component and the diffracted light component of the incident light from; the image pickup means for photoelectrically converting the light from this phase difference adjusting means; A first phase difference which is an integral multiple of the first phase difference and a second phase difference obtained by adding the first phase difference by an odd multiple of π In addition, it is obtained by the image pickup means in a state of a third phase difference obtained by adding π / 2 to an integer multiple of π and a fourth phase difference obtained by adding an odd multiple of π to the third phase difference by the phase difference adjusting means. The second difference image, which is their difference, is obtained from the images Difference image generation means; and a, the first object observation apparatus characterized by imaging the object phase image by using the 0 order light intensity signal from the second differential image and the object. 2. An objective lens for collecting light from an object to be observed; an illumination means for illuminating the object to obtain a light image that can be selectively filtered in the vicinity of the pupil of the objective lens; Phase difference adjusting means for arbitrarily adjusting the phase difference between two orthogonal linearly polarized light components of the incident light from
First filter means for extracting linearly polarized light components of the 0th order light and diffracted light of the incident light from the phase difference adjusting means in different directions; for polarization splitting of the light from the first filter means Second filter means; image pickup means for obtaining images of respective polarization components polarized by the second filter means; the image pickup in a state where the phase difference is adjusted to an integral multiple of π by the phase difference adjusting means. A first difference image, which is the difference between the two images obtained by the means, is obtained, and the phase difference is adjusted by the phase difference adjusting means to a value obtained by adding π / 2 to an integral multiple of π. Difference image generation means for obtaining a second difference image which is the difference between the two images obtained by the image pickup means; first and second difference images obtained by the difference image generation means
Object observation apparatus comprising: a difference image and a 0th-order light intensity signal from the object; calculation means for calculating the relative intensity of the difference image, and calculation means for combining the adjusted images, respectively. . 3. An objective lens for collecting light from an object to be observed; illumination means for illuminating the object to obtain a light image that can be selectively filtered in the vicinity of the pupil of the objective lens; Phase difference adjusting means for arbitrarily adjusting the phase difference between two orthogonal linearly polarized light components of the incident light from
First filter means for extracting the linearly polarized light components of the 0th order light and the diffracted light of the incident light from the phase difference adjusting means in different directions; the linearly polarized light component from the incident light from the first filter means A third filter means for extracting the image; an image pickup means for obtaining an image of the polarization component extracted by the third filter means; a first phase difference and a first position which are integer multiples of π by the phase difference adjusting means. A first difference image, which is the difference between the images obtained by the image pickup means in the state of the second phase difference obtained by adding an odd multiple of π to the phase difference, is obtained, and the phase difference adjustment means makes an integer of π. The third phase difference obtained by adding π / 2 to the second phase and the fourth phase difference obtained by adding an odd multiple of π to the third phase difference are obtained from the respective images obtained by the image pickup means. Difference image to get the difference image Generating means; calculation of adjustment of relative intensity of the difference image and calculation of composition of the adjustment image from the first and second difference images obtained by the difference image generating means and the 0th-order light intensity from the object, respectively. An object observing apparatus comprising: a computing unit for performing the operation. 4. The object observing device according to claim 1, further comprising: a 0th order light intensity measuring means for measuring a 0th order light intensity of the object to obtain an intensity signal thereof. 5. The difference image generation means or the calculation means has a spatial frequency filter representing an inverse function of the spatial frequency characteristic of the object observation device, and the image output by the image pickup means or the difference image generation means outputs the image. The difference image is
The object observing device according to claim 1, wherein the object observing device is filtered by passing through the spatial frequency filter. 6. An objective lens for collecting light from an object to be observed; illumination means for illuminating the object to obtain a light image that can be selectively filtered in the vicinity of the pupil of the objective lens; Phase difference adjusting means for arbitrarily adjusting the phase difference between two orthogonal linearly polarized light components of the incident light from
First filter means for extracting linearly polarized light components of the 0th order light and diffracted light of the incident light from the phase difference adjusting means in different directions; for polarization splitting the light from the first filter means Second filter means; image pickup means for obtaining images of respective polarization components polarization-divided by the second filter means; filter saving means for saving one or both of the first filter means and the second filter means; To obtain a second difference image, which is the difference between the two images obtained by the image pickup unit in a state where the phase difference becomes a value obtained by adding π / 2 to an integer multiple of π by the phase difference adjustment unit. Difference image generating means; a composite image using the bright-field image and the second difference image obtained by the image pickup means in a state where the filter means is retracted by the filter retracting means. An object observing device, comprising: a calculating means for calculating an image. 7. The calculation means executes a signal strength calculation for dividing the signal strength of the second difference image by the square root of the signal strength of the bright field image.
The object observation device described. 8. The calculation means has a spatial frequency filter representing an inverse function of the spatial frequency characteristic of the object observation device,
8. The object observation apparatus according to claim 7, wherein the second difference image and the bright field image pass through this filter prior to the calculation of the signal intensity. 9. The object observation according to claim 1, 2, 3, 4, 5, 6, 7 or 8, wherein the phase difference adjusting means includes a rotatable polarizer and a quarter wave plate. apparatus. 10. The object observing device according to claim 1, wherein the phase difference adjusting means is a liquid crystal whose refractive index is controllable by a voltage. . 11. An objective lens for collecting light from an object to be observed; an illumination means for illuminating the object to obtain a light image that can be selectively filtered in the vicinity of the pupil of the objective lens; a polarizer and a polarizer. Phase difference adjusting means including a quarter-wave plate for arbitrarily adjusting the phase difference between two linearly polarized light components of the incident light from the objective lens which are orthogonal to each other; zero-order light of the incident light from the phase difference adjusting means And first filter means for extracting the linearly polarized light components of the diffracted light in different directions; second filter means for polarization splitting the light from the first filter means; polarization by the second filter means Imaging means for respectively obtaining images of the respective divided polarization components; when the azimuth angle of the polarizer is a first azimuth of two azimuths corresponding to the optical axis of the quarter wavelength plate, The above A first difference image, which is the difference between them, is obtained from the two images obtained by the image pickup means, and when the second azimuth is set, the difference between them is obtained from the two images obtained by the image pickup means. Difference image generating means for obtaining a certain second difference image; secondary difference image means for generating a secondary difference image from the first and second difference images obtained by the difference image generating means; An object observation device characterized by being provided. 12. An objective lens for collecting light from an object to be observed; illumination means for illuminating the object to obtain a light image that can be selectively filtered in the vicinity of the pupil of the objective lens; a polarizer and Phase difference adjusting means including a quarter-wave plate for arbitrarily adjusting the phase difference between two linearly polarized light components of the incident light from the objective lens which are orthogonal to each other; zero-order light of the incident light from the phase difference adjusting means And a first filter means for extracting the linearly polarized light components of the diffracted light in different directions; a second filter means for extracting the linearly polarized light component from the incident light from the first filter means; Imaging means for obtaining an image of the polarization component extracted by the filter means; when the azimuth angle of the polarizer or the second filter means is set to four azimuths corresponding to the optical axis of the quarter wave plate Image storage means for storing four images respectively obtained by the image pickup means; first and second difference images corresponding to the optical axis of the quarter wavelength plate from the four images stored therein A difference image generating means for obtaining a secondary difference image from the first and second difference images obtained by the difference image generating means; Object observation device. 13. The object according to claim 9, 11 or 12, wherein the illuminating means includes a condenser lens for condensing illumination light; and the polarizer is arranged in the vicinity of the pupil of the condenser lens. Observation device.