JPH09281400A - Object observation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To adjust the contrast of the observed images of a phase object with simple constitution. SOLUTION: The phase difference of the two orthogonal linearly polarized light components of the light from an object 14 is made arbitrary adjustable by a polarizer 18 and a quarter-wave plate 20. The phase difference α applied to the output light of the quarter-wave plate 20 is expressed by α=2θ1-π/2. The linearly polarized light component parallel with a (y) direction as to zero order light is extracted by a ring band polarizing plate 22 and the linearly polarized light component parallel with an (x) direction as to diffracted light is extracted. Coherent rays are transmitted respectively from the zero order light and the diffracted light and the bright and dark images are observed by the coherent rays in an analyzer 24. The contrast of the observed images are easily adjusted by rotating the polarizer 18.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of an object observation apparatus suitable for observing a phase object.

[0002]

BACKGROUND ART A phase contrast microscope for observing a phase object is one that converts the phase difference of light into a difference between light and dark so that the difference in the thickness or refractive index of the object can be observed with the naked eye.
kon TECHNICAL JOURNAL ”1974, No.6.
The basic structure is as shown in FIG.
A ring-shaped diaphragm (ring diaphragm) 102 is provided at the front focus position of the condenser lens 100, and the objective lens 1
An annular polarizing plate (phase plate) 106 is provided at the back focus position 04.

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 annular polarization plate 106, but the annular polarization plate 1
06 is a size in which the image overlaps with the ring diaphragm 102, and a phase change of a constant size (λ / 4, λ is the wavelength of the light) with respect to the light (zero-order light) directly transmitted through the phase object 108. Given. The zero-order light that has undergone this phase change and the 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, and the naked eye 112 can observe it as bright and dark.

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 12 (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 122a and 122b, 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. 8) side, only the 0th-order light is phase-modulated.

[0005]

By the way, in order to obtain an observation image with a desired contrast in such a phase contrast microscope, it is necessary to replace the objective lens 104 and the annular polarizing plate 106 as a whole. In other words, there is an inconvenience that the objective lens 104 and the annular polarizing plate 106 must be prepared corresponding to a plurality of desired contrasts. Further, in the background art of FIG. 12, a liquid crystal cell having a complicated structure is required as a variable annular polarization plate, and a control system thereof is also required to be complicated.

The present invention focuses on the above points,
The purpose is to adjust the contrast of the observed image with a simple structure. Another object is to simply adjust the contrast according to the amount of phase change of the phase object with a simple optical configuration.

[0007]

[Means for Solving the Problems]

DISCLOSURE OF THE INVENTION To achieve the above object, the present invention provides:
Objective lens (16) for collecting light from the object to be observed; Illuminating means for illuminating the object to obtain a light image that can be selectively filtered near the pupil of the objective lens (1
0,12,40,42,44,46,48); rotatable polarizer and 1
Phase difference adjusting means (18, 20) for arbitrarily adjusting the phase difference between the two linearly polarized light components of the incident light from the objective lens, which include a / 4 wavelength plate, and the incident light from the phase difference adjusting means. Filter means (22) for extracting the 0th-order light and the diffracted light in the same and orthogonal directions with respect to the optical axis of the quarter-wave plate, respectively, and incident light from the first filter means. A second filter means (24) for obtaining a coherent polarization component from

In another invention, third filter means (5) for respectively obtaining coherent polarization components in the first and second different directions from the incident light from the first filter means.
2); first imaging means (56) for obtaining a first image based on the coherent polarization component in the first direction obtained by the third filter means; obtained by the third filter means Second image pickup means (60) for obtaining a second image based on the coherent polarization component in the second direction; a difference image between the first and second images obtained by these image pickup means is obtained. A difference image generating means (62);

In still another aspect of the invention, the number of the image pickup means is only one, and the first image picked up when the polarizer or the second filter means has the first polarization direction,
Memory means (76) for storing a second image captured when the polarizer or the second filter means is set to a second polarization direction different from the first polarization direction; A difference image generating means (74) for obtaining a difference image of the first and second images is provided.

[0010] Still another invention is, in any of the above,
The illumination means includes a condenser lens for condensing the illumination light, and the polarizer is arranged in the vicinity of the pupil of the condenser lens.

The main aspects of the present invention include the following:

(1) Illumination means (40, 42, 44, for illuminating an object
46,48,10,12), an objective lens (1) arranged along the optical axis that collects light rays from the object and produces a spatial frequency spectrum that can be selectively filtered near the pupil plane.
6), a rotatable polarizer (18) for converting a light beam passing near the pupil plane into a linearly polarized light having a plane of polarization at an arbitrary azimuth angle with respect to the optical axis, the linearly polarized light being located near the pupil plane. A quarter wave plate (20) that can pass through, and has an area that can include only the spatial frequency component that is not diffracted by the object among the light rays that have passed through the quarter wave plate, and the straight line of the polarization plane in the first direction. A first spatial filter (22) that transmits only a polarized component, has an area that can include a spatial frequency component that is not included in the first spatial filter among the rays that have passed through the quarter wavelength plate, and has a first azimuth direction. A second spatial filter (22) that transmits only the linearly polarized light component of the polarization plane of the second azimuth direction orthogonal to, and the polarization plane of the third azimuth direction among the rays that have passed through the first spatial filter and the second spatial filter. 3rd direction, which transmits only the linearly polarized light of And the first azimuth forms an angle that is an integral multiple of 90 degrees, and the third azimuth forming the analyzer is the ¼ 9 with respect to the azimuth of the optical axis of the wave plate
An object observation device characterized by forming an angle obtained by adding 45 degrees to an integral multiple of 0 degrees.

(2) A rotatable polarizer (18) including the illuminating means and the objective lens, which converts a light beam passing through the vicinity of the pupil plane into a linearly polarized light having a polarization plane in a first direction with respect to the optical axis, A quarter wavelength plate (20) that is located near the pupil plane and that can pass the linearly polarized light, and an area that can include only spatial frequency components that are not diffracted by an object among the rays that have passed through the quarter wavelength plate. And a first spatial filter (2 that transmits only the linearly polarized light component of the plane of polarization in the second direction
2), linearly polarized light having a plane of polarization in a third azimuth direction orthogonal to the second azimuth having an area capable of including a spatial frequency component that is not included in the first spatial filter among light rays that have passed through the ¼ wavelength plate The second spatial filter (2
2) Among 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 linearly polarized light of the polarization plane of the fifth azimuth orthogonal to this is reflected. A polarization beam splitter (52), a first photoelectric conversion element (56) for photoelectrically converting a first object image by a linearly polarized light beam having a polarization plane in the fourth azimuth, and a linear polarization having a polarization plane in the fifth azimuth. A second photoelectric conversion element (60) for photoelectrically converting a second object image formed by light rays, generates a difference signal between the signals of the first and second photoelectric conversion elements, and generates a difference image based on the difference signal. A difference image generating means (62) and an image display means (64) for displaying the difference image, wherein the azimuth of the optical axis of the quarter wavelength plate and the second azimuth form an angle that is an integral multiple of 90 °. , The fourth azimuth formed by the analyzer is the azimuth of the optical axis of the quarter wavelength plate. Object observation device, characterized in that an angle of plus 45 ° to 90 ° integral multiple with.

(3) Of the light rays passing through the first spatial filter and the second spatial filter, including the illuminating means, the objective lens, the polarizer, the quarter wavelength plate, the first spatial filter and the second spatial filter. An analyzer (72) that transmits only linearly polarized light of the plane of polarization of the fourth azimuth, a photoelectric conversion element (56) that photoelectrically converts an object image by the light of linearly polarized light of the plane of polarization of the fourth azimuth, the first azimuth ( Or a fourth orientation) stores the first image of the object obtained when the fifth orientation is matched with the fifth orientation, and the first orientation (or fourth orientation) is
An image storage means (76) for storing a second image of the object obtained when the object is matched with the sixth direction orthogonal to the fifth direction, and the first image and the second image stored in this image storage means are taken out. , Difference image generating means for generating these difference images (7
4) has an image display means (64) for displaying this difference image, and the azimuth of the optical axis of the quarter-wave plate and the second azimuth make an angle of an integral multiple of 90 °, The fourth azimuth is 9 with respect to the azimuth of the optical axis of the quarter-wave plate.
The fifth azimuth is an integer multiple of 0 ° plus 40 °, and the fifth azimuth is an integer multiple of 90 ° plus 45 ° with respect to the azimuth of the optical axis of the quarter wavelength plate. Characteristic object observation device.

According to the present invention, the following effects can be obtained. (1) The observer can rotate the polarizer and adjust the azimuth with respect to the optical axis to continuously change the contrast of the observed image from dark contrast to bright contrast. It is possible to observe the image by. According to the background art, a variable phase means having a complicated structure called a liquid crystal cell is required, whereas in the present invention, a polarizer and 1 /
The variable phase means is easily realized only by using a very general optical element called a four-wave plate. (2) Since the difference image between the two interference images is obtained, the intensity component (amplitude component) of the image is canceled well, and only the phase image can be observed with a simple configuration. The above and other objects, features, and advantages of the present invention will be apparent from the following detailed description and the accompanying drawings.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to Examples. The object observation device according to the present invention is particularly suitable for application as a phase contrast microscope for observing a phase image.

[0016]

Basic Mode 1 of Embodiment First, a basic mode 1 of the embodiment 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 condensed by the condenser lens 12 enters the phase object 14, and the light transmitted through the phase object 14 enters 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, 1/4 which transmits linearly polarized light Wave plate 20, out of incident light, not diffracted by phase object 14
An annular polarization plate 22 for separating the next spectral component and other spectral components into orthogonal linearly polarized light, an analyzer (polarizing beam splitter) 24 for extracting coherent light in the same polarization direction from the incident light, They are provided in that order along the optical axis AX.

For these elements, the Cartesian coordinates (X ₁ , Y ₁ ) to (X ₅ , Y ₅ ) are set so as to be orthogonal to the optical axis AX and have the same orientation. That is, the coordinates are set so that the coordinate axes overlap when viewed from the ring diaphragm 10 side. Hereafter, those directions are simply (x, y)
Express.

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 θ ₁ with respect to the x-axis is the polarization direction of the transmitted light, and this angle θ 1 is the polarizer 18.
It can be changed by rotating. As shown in FIG. 2B, the quarter-wave plate 20 has a fast axis n _e that is an optical axis and a slow axis n _o that is orthogonal to this, and the azimuth of the fast axis n _e is the y-axis. match is, the azimuth angle of the slow axis n _o is x
It is set to match the axis. Of the incident light, the slow axis n
linearly polarized light component of the polarization plane parallel to _o, the phase delay of 1/4 wavelength (90 degrees) occurs for linearly polarized light component in the polarization plane parallel to the fast axis n _e.

For example, the azimuth angle θ1 of the polarizer 18 is 1
When it coincides with the fast axis n _e of the / 4 wavelength plate 20, the polarized light in the fast axis n _e 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,
The object 14 is formed by the polarizer 18 and the quarter-wave plate 20.
It is possible to arbitrarily adjust the phase difference between the two linearly polarized light components orthogonal to each other out of the light from, and the phase difference α given to the output light of the quarter-wave plate 20 is represented by α = 2θ1−π / 2. Be done.

The ring-shaped polarizing plate 22 is composed of a ring-shaped portion 22a and a central portion 22b other than that. Zone 2
2a transmits only the linearly polarized light component of the polarization plane parallel to the y-axis, as shown by the arrow in FIG.
Transmits only the linearly polarized light component of the plane of polarization parallel to the x-axis. Further, the size of the ring portion 22a of the ring polarizing plate 22 is
When there is no object other than a light-transmissive parallel plate such as a slide glass having a predetermined thickness designed at the position of the phase object 14, the aerial image of the ring diaphragm 10 formed near the pupil position of the objective lens 16 is formed. Try to match the size. That is, the magnitude of the direct light (0th-order light) that is not diffracted by the phase object 14 is matched. With such a configuration, for the 0th-order light, the linearly polarized light component Y parallel to the y direction is generated.
0 is extracted, and the linearly polarized light component Xd parallel to the x direction is extracted from the diffracted light.

Next, as shown in FIG. 2D, the analyzer 24 has a function of transmitting the light ray i of the linearly polarized component of the plane of polarization parallel to the analyzer angle θ ₂ in the direction of the optical axis AX. There is. The analyzer angle θ ₂ is set to 45 °, for example. The coherent light ray i passing through the analyzer 24 forms an interference image 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. 2 (C), the annular polarization plate 22 outputs the y-direction polarization component Y0 for the 0th-order light and the x-direction polarization component Xd for the diffracted light. . On the other hand, in the analyzer 24, the polarized component in the i direction shown in FIG. That is, the i-direction component of each of the 0th-order light and the diffracted light passes through the analyzer 24. For this reason, the two interfere with each other and a bright and dark image is observed.

Next, the optical image obtained as described above will be described using mathematical expressions. In the following description, it is assumed that the influence of the OTF of the image forming system is not taken into consideration, and the width of the ring zone 22a of the ring polarization plate 22 is sufficiently small and there is no influence of halo or the like. Phase object 14 to be observed
The transmitted light distribution O (x, y) of is expressed by, for example, the following equation (1). This equation (1) is a complex representation, and exp [jφ (x,
y)] represents the phase component. "J" is an imaginary unit.

[0024]

[Equation 1]

Next, in the annular zone 22a of the annular polarization plate 22, a constant amplitude change a and phase change α are given to the incident light, so the transmitted light distribution is expressed by equation (2).

[0026]

[Equation 2]

Next, the intensity distribution I (x, y) on the image plane corresponding to the ray i is expressed by the following equation (3) (for example, Tokai Univ., "Principle of Optics II", P.639). reference). In the equation, A is the equation (2) and C is a constant. Substituting equations (1) and (2) into equation (3) and rearranging yields equation (4).

[0028]

(Equation 3)

(Equation 4)

Furthermore, this, dark-contrast images I _-
Rewriting for (x, y) and the bright contrast image I ₊ (x, y) gives the following equations (5) and (6), respectively. As described above, α = 2θ1−π / 2. As is clear from these equations (5) and (6), by changing the azimuth angle θ1 of the polarizer 18, it is possible to continuously change from dark contrast to bright contrast of the image. In addition, (5),
The ratio of the second term to the first term in equation (6) is determined by the phase object 14
The contrast of these images is shown, and these ratios can be similarly continuously changed by the azimuth angle θ1 of the polarizer 18.

[0030]

(Equation 5)

(Equation 6)

[0031]

First Embodiment Next, a first embodiment will be described with reference to FIG. A mercury lamp is used as the light source 40, and the optimum wavelength of the light beam emitted from this is selected by the interference filter 42. The light transmitted through the interference filter 42 is collected by the collector lens 44 and the first relay lens 4
6, through the second relay lens 48 in this order, and enters the ring diaphragm 10 located near the pupil position of the condenser lens 12.

The light that has passed through the ring diaphragm 10 is refracted by the condenser lens 12 and illuminates the phase object 14 on the slide glass 13 through transmission. The light transmitted through the phase object 14 enters the objective lens 16. A rotatable polarizer 18, a quarter-wave plate 20, an annular polarizing plate 22, and an analyzer 24 are arranged near the pupil position of the objective lens 16. The light refracted by the objective lens 16 sequentially passes through the polarizer 18, the quarter-wave plate 20, and the annular polarizing plate 22, and then enters the analyzer 24. Then, light of a predetermined polarization direction passes through the analyzer 24 and becomes a light ray i, which is transmitted through the eyepiece lens 50 to the naked eye (not shown).
Incident on. As a result, the image formed on the image plane of the objective lens 16 is observed through the eyepiece lens 50.

By adjusting the azimuth angle θ1 of the polarizer 18, the observer can adjust the image contrast as shown in the equations (5) and (6), and observe the image with the desired contrast. it can.

[0034]

Second Embodiment Next, a second embodiment will be described with reference to FIG. Although the configuration is almost the same as that of the first embodiment,
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. Since the pupil of the condenser lens 12 and the pupil of the objective lens 16 have a conjugate relationship, a similar image can be observed.

This embodiment is particularly 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 if the polarizer 18 is rotated in such a situation,
There is an advantage that the image does not move on the image plane.

[0036]

[Basic Form 2 of Embodiment] Next, a basic form 2 of the embodiment will be described with reference to FIG. In this example, a polarization beam splitter 52 is provided instead of the analyzer 24 in addition to the basic form 1 shown in FIG.
It should be noted that the polarization beam splitter 52 is orthogonal to the reflection-side optical axis AX1 where the optical axis AX is folded back, and the orthogonal coordinate (X
_{1, Y 1) ~ (X} 5, Y 5) so as to have the same orientation as, sets an orthogonal coordinate (X ^_6, Y _6).

The polarization beam splitter 52 is shown in FIG.
As shown in, the ray i1 of the linearly polarized component of the plane of polarization parallel to the analyzer angle θ ₂ is transmitted in the direction of the optical axis AX, and the linearly polarized component of the plane of polarization parallel to the anti-analyzer angle θ ₃ = θ ₂ + 90 ° It has a function of reflecting the light ray i2 in the direction of the optical axis AX1. For example, the analyzer angle θ ₂ is set to 45 ° and the anti-analyzer angle θ ₃ is set to 45 + 90 = 135 °. The coherent ray i1 that passes through the polarization beam splitter 52 forms a dark contrast interference image I ₋ (x, y) on the image plane of the objective lens 16. The coherent ray i2 reflected by the polarization beam splitter 52 is a bright contrast interference image I on the image plane of the objective lens 16.
Form ₊ (x, y).

With this polarization beam splitter 52,
A coherent polarization component 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 is extracted. More specifically, as shown in FIG. 2 (C), the annular polarization plate 22 outputs the y-direction polarization component Y0 for the 0th-order light and the x-direction polarization component Xd for the diffracted light. .
On the other hand, in the polarization beam splitter 52, as shown in FIG.
The polarized component in the i1 direction shown in (A) is transmitted, and the polarized component in the i2 direction is reflected. Therefore, regarding the 0th-order light, as shown in FIG.
As shown in (B), the i1 direction component Y01 is transmitted and i2
The directional component Y02 is reflected. The same applies to diffracted light. As shown in FIG. 7C, the i1 direction component Xd1 is transmitted and the i2 direction component XYd2 is reflected.

The transmission component in the i1 direction is Y01 in FIG. 6B and Xd1 in FIG. 6C, 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 Y02 in FIG. 6 (B) and Xd2 in FIG. 6 (C), 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.

Next, a method for obtaining a pure phase distribution image using the above interference image will be described using mathematical expressions. Note that the OTF of the imaging system is similar to the above case.
The influence of the above is not taken into consideration, and the width of the ring zone 22a of the ring polarization plate 22 is sufficiently small and there is no influence of halo or the like. The transmitted light distribution O (x, of the phase object 14 to be observed is
y) is represented by, for example, the following equation (7).

[0041]

(Equation 7)

Here, ρ (x, y) represents an amplitude component, and e
xp [jφ (x, y)] represents a phase component. Here, if the size of the phase object 14 is (x, y) = (2g, 2h), the average amplitude b of the object may be integrated in these ranges and divided by the total area. It is shown by the following equation (8).

[0043]

(Equation 8)

Next, as shown in the equation (2), the annular zone 22a of the annular polarizing plate 22 is given a constant amplitude change a1 and phase change α with respect to the incident light. Is given by equation (9).

[0045]

[Equation 9]

Next, the intensity distribution I (x, y) on each image plane corresponding to the rays i1 and i2 is expressed by the following equation (10) (for example, Tokai Univ. (See page 639). In the equation, A is the amplitude transmittance, C is C1 * b, C
1 is a constant. Substituting equation (8) into equation (10) and rearranging it yields equation (11).

[0047]

(Equation 10)

[Equation 11]

Here, a1 = sin θ1, a2 = cos θ1, α =
Since −π / 2 and θ ₂ = θ ₁ + π / 2, these are substituted into the equation (11) and the intensity distribution Ii1 (x, y on the image plane corresponding to the rays i1 and i2 is obtained. ) And Ii2 (x, y) are obtained, the following equations (12) and (13) are obtained.

[0049]

(Equation 12)

(Equation 13)

Then, these intensity distributions Ii1 (x, y), Ii
The relationship between 2 (x, y) and the dark contrast image I ₋ (x, y) and the bright contrast image I ₊ (x, y) is shown in the following equations (14) and (15), respectively. become.

[0051]

[Equation 14]

(Equation 15)

Here, when the difference image between the two is obtained, the following (1
6) It becomes like the formula. By substituting the equations (12) and (13) into this, the equation (17) is obtained.

[0053]

(Equation 16)

[Equation 17]

In this equation (17), assuming that the azimuth angle θ1 of the polarizer 18 is π / 4, the following equation (18) is obtained, and assuming that φ (x, y) is smaller, equation (19) Like As shown in these equations, the difference image is imaged only when a phase change occurs in the object.

[0055]

(Equation 18)

[Equation 19]

By the way, in general, the amplitude distribution of the phase object 14 is flat and can be regarded as ρ (x, y) ≈b. Then
The equation (19) becomes completely proportional to the phase distribution φ (x, y), and only the phase distribution image can be observed well. Even if the value of the amplitude distribution ρ (x, y) changes a little depending on the position of the phase object 14, the intensity distribution of the difference image of the equation (19) has the amplitude normalized by the average amplitude b of the phase object 14. Only the amount is modulated. Also, Polarizer 1
When 8 is rotated, the intensity of the difference image increases or decreases every 45 °. Furthermore, Polarizer 1
When the azimuth angle of 8 is θ1 ≠ π / 4, it is possible to observe an amplitude distribution image, and an object without a phase change can be imaged.

As described above, according to the background art, a variable phase means having a complicated structure called a liquid crystal cell is required, whereas in the present invention, an extremely general optical system including a polarizer and a quarter wave plate is used. The variable phase means is easily realized only by using the element.

[0058]

Third Embodiment Next, a third embodiment corresponding to the basic mode 2 will be described with reference to FIG. The configuration from the light source 40 to the polarization beam splitter 52 is the same as that in FIG. 5, and the azimuth angle θ ₁ of the polarizer 18 is 45 ° with respect to the optical axis of the ¼ wavelength plate 20, and the polarization beam splitter 52 has the same azimuth angle θ ₁ . The analyzer angle has an azimuth of 45 ° with respect to the optical axis of the quarter-wave plate 20.

The polarization beam splitter 52 transmits a linearly polarized light ray i1 having a plane of polarization parallel to the analyzer angle and a linearly polarized light ray i2 having a plane of polarization perpendicular to the analyzer angle. Among these, the light ray i1 is refracted by the lens 54, and an interference image is formed on an image plane conjugate with the object plane of the objective lens 16. Then, the optical image is photoelectrically converted by the two-dimensional image pickup device 56 whose light detection surface is located on the image plane, and a video signal is output from the two-dimensional image pickup device 56. On the other hand, the light ray i2 is refracted by the lens 58, and an interference image is formed on an image plane conjugate with the object plane of the objective lens 16.
Then, the optical image is photoelectrically converted by the two-dimensional image pickup device 60 having the light detection surface on the image plane, and the two-dimensional image pickup device 6
A video signal is output from 0.

The two video signals output from the image pickup devices 56 and 60 are input to the differential amplifier 62, and the differential amplifier 6
A differential signal is output from 2. This differential signal is output to the image display unit 64, where an image of the phase object is displayed. It should be noted that an object point at an arbitrary position within the field of view of the objective lens 16 and information on the position (for example, the number of clock pulses) in the video signal corresponding to the two image points conjugate with the object point are completely matched. (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 56 and 60 in the direction crossing the optical axis, the signal output timing, and the like are Has been adjusted. Image display section 6
The observer of No. 4 can adjust the magnitude of the differential output, in other words, the contrast by adjusting the azimuth angle θ1 of the rotatable polarizer 18 with respect to the optical axis AX.

Contrast indicates the relative intensity of light and dark.
In this image, light and dark are reversed due to the phase difference. For example,
Assuming that the gray level has no phase difference, black is on the negative side and white is on the positive side.
An image representing the side phase is formed. At this time, when the polarizer 18 is rotated, the contrast between the black part and the white part appears to be improved, but in reality, the gain is merely adjusted around the gray level.

[0062]

Fourth Embodiment Next, a fourth embodiment will be described with reference to FIG. The part from the light source 40 to the objective lens 16 is the same as that in the third embodiment. In the present embodiment, the polarizer angle of the polarizer 18 is switched by the actuator 70 between the azimuth of θ ₁ = 45 ° and the azimuth θ ₁ = 135 ° perpendicular to the azimuth. Further, the analyzer angle of the analyzer 72 is oriented at 45 ° with respect to the optical axis of the quarter-wave plate 20.

When the operation of the actuator 70 is controlled by the computer 74 and the polarizer angle of the polarizer 18 becomes 45 °, the linearly polarized light i1 of the third embodiment is obtained.
Is output from the analyzer 72 and the polarizer angle is 135
When the angle becomes 0, the linearly polarized light i2 of the third embodiment is output from the analyzer 72.

The light ray i1 or the light ray i2 is transmitted to the lens 54.
Is refracted by, and an interference image is formed on an image plane conjugate with the object plane of the objective lens 16. Then, the optical image is photoelectrically converted by the two-dimensional image pickup device 56 whose light detection surface is located on the image plane, and a video signal is output from the two-dimensional image pickup device 56. The two image signals obtained corresponding to the two polarizer angles are A / D converted by the image storage unit 76 and stored as two image data. These image data are
It is supplied to the computer 74.

In the computer 74, the difference image data equal to the difference between the two images is calculated from the two image data in the image storage section 76, and after this D / A conversion, it is output to the image display section 64 and the difference image data is outputted. Is displayed. The observer can instruct the computer 74 through the interface 78 about necessary information, for example, an instruction to capture an image and a call to stored image data.

According to the fourth embodiment, compared with the third embodiment, there is an advantage that a difference image can be obtained by using only one image pickup device.

[0067]

Fifth Embodiment Next, a fifth embodiment will be described with reference to FIG. Although the configuration is almost the same as that of the fourth embodiment,
The installation location of the polarizer 18 is different. That is, in the present embodiment, the polarizer 18 is arranged near the pupil plane of the condenser lens 12 as in the second embodiment. Although it is optically equivalent to the fourth embodiment, when the flatness of the polarizer 18 is not good, or the rotation axis of the polarizer 18 is the optical axis AX.
This embodiment is effective when it is not completely perpendicular to. Even when the polarizer 18 is rotated by the actuator 70 in such a situation, the image does not move on the image plane, and two images whose positions are completely matched can be obtained corresponding to two polarizer angles. . Therefore, a difference image can be easily obtained.

[0068]

Sixth Embodiment Next, a sixth embodiment will be described with reference to FIG. The sixth embodiment is a modification of the fourth and fifth embodiments. In the fourth and fifth embodiments, the polarizer 70 is rotated by the actuator 70, but in this embodiment, the analyzer 72 is rotated. That is, the analyzer angle is 45 with respect to the optical axis of the quarter-wave plate 20.
The analyzer 72 is rotationally driven by the actuator 70 so that the angle becomes 135 °. Then, the two images corresponding to the respective analyzer angles are captured by the two-dimensional image sensor 56 by photoelectric conversion. The azimuth of the polarizer 18 is set to 45 °.

[0069]

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, a two-dimensional image pickup device such as a CCD was used, but any image pickup means may be used. Also, the analyzer output may be optically observed.

(2) 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.

(3) In the above-mentioned embodiment, the present invention is mainly applied to a microscope, but the present invention can be applied to all surface observing devices for objects. For example, measuring the step of an object,
It is effective for defect inspection of magnetic heads, wafers, reticles, etc., and position measurement taking into consideration the surface shape of the object.

[Brief description of drawings]

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

FIG. 4 is a diagram showing a second embodiment of the present invention.

FIG. 5 is a perspective view showing a basic form 2 of the embodiment of the invention.

FIG. 6 is a diagram showing the basic operation of the main elements of FIG.

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 diagram showing a fifth embodiment of the present invention.

FIG. 10 is a diagram showing Embodiment 6 of the present invention.

FIG. 11 is a diagram showing a general configuration of a phase contrast microscope.

FIG. 12 is a diagram showing a configuration of a phase plate of the background art.

[Explanation of symbols]

 Reference numeral 10 ... Ring diaphragm 12 ... Condenser lens 14 ... Phase object 16 ... Objective lens 18 ... Polarizer 20 ... Quarter wave plate 22 ... Ring zone deflector 22a ... Ring zone 22b ... Center part 24 ... Analyzer 40 ... Light source 42 ... Interference Filter 44 ... Collector lens 46 ... First relay lens 48 ... Second relay lens 50 ... Eyepiece lens 52 ... Polarization beam splitter (analyzer) 54, 58 ... Lens 56, 60 ... Two-dimensional image sensor 62 ... Differential amplifier 64 ... Image Display unit 70 ... Actuator 72 ... Analyzer 74 ... Computer 76 ... Image storage unit 78 ... Interface

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location G01N 21/88 G01N 21/88 J G02B 21/00 G02B 21/00

Claims (4)

[Claims] 1. An objective lens for collecting light from an object to be observed; illumination means for illuminating the object to obtain a selectively filterable light image in the vicinity of the pupil of the objective lens; rotatable. Phase difference adjusting means for arbitrarily adjusting the phase difference between two linearly polarized light components orthogonal to each other of the incident light from the objective lens, including a polarizer and a quarter wave plate; For 0th order light and diffracted light,
First filter means for extracting in the same and orthogonal directions with respect to the optical axis of the quarter-wave plate respectively; second filter for obtaining coherent polarization components from the incident light from the first filter means An object observing apparatus comprising: means. 2. An objective lens for condensing light from an object to be observed; an illumination means for illuminating the object to obtain a selectively filterable optical image in the vicinity of the pupil of the objective lens; rotatable. Phase difference adjusting means for arbitrarily adjusting the phase difference between two linearly polarized light components orthogonal to each other of the incident light from the objective lens, including a polarizer and a quarter wave plate; For 0th order light and diffracted light,
First filter means for extracting in the same and orthogonal directions with respect to the optical axis of the quarter-wave plate respectively; coherent in first and second different directions from incident light from the first filter means Filter means for obtaining different polarization components respectively; first imaging means for obtaining a first image based on the coherent polarization components in the first direction obtained by the third filter means; 3 second image pickup means for obtaining a second image based on the coherent polarization component in the second direction obtained by the filter means; of the first and second images obtained by these image pickup means An object observation apparatus comprising: a difference image generating unit for obtaining a difference image. 3. 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 near the pupil of the objective lens; rotatable. Phase difference adjusting means for arbitrarily adjusting the phase difference between two linearly polarized light components orthogonal to each other of the incident light from the objective lens, including a polarizer and a quarter wave plate; For 0th order light and diffracted light,
First filter means for extracting in the same and orthogonal directions with respect to the optical axis of the quarter-wave plate respectively; second filter for obtaining coherent polarization components from the incident light from the first filter means Means; imaging means for obtaining an image by the polarization component obtained by the second filter means;
A first image taken when the polarizer or the second filter means is set to the first polarization direction, and an image when the polarizer or the second filter means is set to the second polarization direction different from the first polarization direction. Memory means for storing the stored second image; first and second stored in the memory means
Difference image generating means for obtaining a difference image of the image of the object. 4. The object according to claim 1, wherein the illuminating means includes a condenser lens for condensing illumination light, and the polarizer is arranged near a pupil of the condenser lens. Observation device.