JPH09138350A - Surface observing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily adjust a contrast according to the phase change rate of a phase object by simple optical constitution. SOLUTION: The phase difference of two linearly polarized light components orthogonal with each other among the light rays from an object 14 are arbitarily made adjustable by a polarizer 18 and a quarter-wave plate 20. The phase difference α applied to the output light of this quarter-wave plate 20 is expressed by α=201-π/2. The linearly polarized light component parallel with a y- direction is extracted with respect to zero order light in a ring band polarizing plate 22 and the linearly polarized light component parallel with an x-direction is extracted for the diffracted light in this plate. Coherent rays i1 transmit an analyzer 24 respectively from the zero order light and the diffracted light and the coherent rays i2 transmit the analyzer. The bright and dark images are observed by these coherent rays.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface observation device such as a phase contrast microscope, and more specifically, to improvement of its contrast adjusting function.

[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 thereof is, for example, as shown in FIG. 8, 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) 10
6 are 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 annular polarization plate (phase plate) 106, and the annular polarization plate 106 has such a size that the image overlaps with the ring diaphragm 102, and the light directly transmitted through the phase object 108. A phase change of a certain magnitude (λ / 4, λ is the wavelength of light) is given to. 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, 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. 9A shows the side surface of the variable annular polarizing plate 120, and FIG. 9B shows the plane thereof. 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.

However, in the background art as described above, a liquid crystal cell having a complicated structure is required as a variable annular polarizing plate, and a control system thereof is also required to be complicated. The present invention focuses on the above points, and provides a surface observation device such as a phase contrast microscope capable of easily performing contrast adjustment according to the phase change amount of a phase object by a simple optical configuration. , That is the purpose.

[0006]

[Means for Solving the Problems]

DISCLOSURE OF THE INVENTION In order to achieve the above object, one of the inventions is to provide an objective lens (16) for condensing light from an object (14) to be observed; Illuminating means (12,40,42,44,46,48) for obtaining a selectively filterable light image near the pupil; including a rotatable polarizer (18) and a quarter wave plate (20), Phase difference adjusting means (18, 20) for arbitrarily adjusting the phase difference between two orthogonal linearly polarized light components of the incident light from the objective lens; 0th order light and diffracted light of the incident light from the phase difference adjusting means To extract those linearly polarized light components in different directions.
Filter means (22); second filter means (24,5, respectively) for obtaining coherent polarization components in the first and second different directions from the incident light from the first filter means.
0); first image pickup means (5) for photoelectrically converting the intensity distribution of the first image based on the coherent polarization component in the first direction obtained by the second filter means to obtain an image signal.
4); Second image pickup means (58) for photoelectrically converting the intensity distribution of the second image based on the coherent polarization component in the second direction obtained by the second filter means to obtain an image signal. ;
Difference image signal generation means (6) for obtaining a difference image signal of the first and second image signals obtained by these image pickup means (6
0); is provided.

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 (12,40,42,44,46,48); including a rotatable polarizer (18) and a quarter-wave plate (20), and two linearly polarized components of incident light from the objective lens which intersect at right angles. Phase difference adjusting means (18, 2) for adjusting the phase difference of
0); First filter means (22) for extracting the linearly polarized light components of the incident light from the phase difference adjusting means in different directions, and the incident light from the filter means. From the second to obtain coherent polarization components from
Filtering means (24, 50); Imaging means (54) for photoelectrically converting the intensity distribution of the image formed by the polarization component obtained by the second filtering means to obtain an image signal; the polarizer or the second filter The image signal of the first image taken when the means is set to the first polarization direction, and the polarizer or second filter means for setting the second polarization direction different from the first polarization direction.
Difference image signal generation means (60, 7) for obtaining a difference image signal from the image signal of the second image captured when the polarization direction is set to
0,72,74) ;.

Still another invention is the invention of the above (1) or (2), wherein the illuminating means includes a condenser lens (12) for converging illumination light; the polarizer (18).
Is arranged near the pupil of the condenser lens (12).

The present invention also includes the following aspects. (1) Illuminating means for illuminating an object, an objective lens arranged along the optical axis, which collects light rays from the object and generates a spatial frequency spectrum that can be selectively filtered in the vicinity of the pupil plane, A rotatable polarizer that converts 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 that is located near the pupil plane and can pass through 1 / 4 wavelength plate and an area that can include only spatial frequency components that are not diffracted by the object among the light rays that have passed through the ¼ wavelength plate, and transmit only the linearly polarized component of the polarization plane in the second direction. The first spatial filter and the polarization plane of the third azimuth orthogonal to the second azimuth having an area capable of including the spatial frequency component not included in the first filter among the rays that have passed through the quarter wavelength plate. Transmits only linearly polarized light component Of the light rays that have passed through the second spatial filter, the first spatial filter, and the second spatial filter, only linearly polarized light in the polarization plane of the fourth direction is transmitted,
A polarization beam splitter that reflects linearly polarized light having a polarization plane in a fifth azimuth direction orthogonal thereto, and a second photoelectric conversion element that photoelectrically converts the first object image by the light beam of linearly polarized light having a polarization plane in the fourth azimuth, A differential circuit that generates a difference signal between the signals of the first and second photoelectric conversion elements is provided, and an image is formed using the difference signal. The two azimuths form an angle obtained by adding 45 ° to an integer multiple of 90 °, and the fourth azimuth formed by the analyzer is an integer multiple of 90 ° with respect to the azimuth of the optical axis of the quarter wavelength plate. A surface observation device characterized by forming an angle with the addition of °.

(2) Illuminating means for illuminating an object and an objective arranged along the optical axis for condensing light rays from the object and generating a spatial frequency spectrum which can be selectively filtered near the pupil plane. A lens, a rotatable polarizer for converting a light beam passing near the pupil plane into a linearly polarized light in a polarization plane in a first azimuth with respect to the optical axis, and a linearly polarized light located near the pupil plane and passing through the linearly polarized light. And a possible quarter wave plate, and an area that can include only the spatial frequency component that is not diffracted by the object in the light beam that has passed through the quarter wave plate, and only the linearly polarized light component of the polarization plane in the second direction. Through the first
Linear polarization of a polarization plane of a third azimuth direction orthogonal to the second azimuth having an area capable of including the spatial frequency component not included in the first filter among the light rays that have passed through the spatial filter and the ¼ wavelength plate. A second spatial filter that transmits only the component of the first spatial filter, an analyzer that transmits only the linearly polarized light of the polarization plane of the fourth direction among the light rays that have passed through the first spatial filter and the second spatial filter, The intensity distribution of the object image by the linearly polarized light of the azimuth polarization plane is photoelectrically converted,
A photoelectric conversion element that outputs an image signal and an image signal indicating the intensity distribution of an optical image obtained when the first azimuth direction is matched with the fifth azimuth direction are converted into data and stored as first image data. The first image storage means and the first orientation,
Second image storing means for converting an image signal, which is orthogonal to the fifth azimuth and showing the intensity distribution of the optical image obtained when the sixth azimuth is matched, into data and storing the data as second image data; A difference image generation unit that extracts the first image data and the second image data from the first image storage unit and the second image storage unit, and generates a difference image indicating the difference between these intensities, and an image using the difference image. An image display means for displaying is provided, and 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 °. Is an integer multiple of 90 ° plus 45 ° with respect to the azimuth of the optical axis of the quarter-wave plate.

(3) Illuminating means for illuminating an object, and an objective arranged along the optical axis for collecting light rays from the object and generating a spatial frequency spectrum which can be selectively filtered in the vicinity of the pupil plane. A lens and a polarizer that converts a light beam that passes 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, and a polarizer that is located near the pupil plane and that can pass the linearly polarized light 1 / 4 wavelength plate and 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 ¼ wavelength plate, and transmits only the linearly polarized light component of the polarization plane in the second direction. The first spatial filter and the first of the light rays that have passed through the quarter-wave plate.
A second spatial filter having an area capable of including a spatial frequency component not included in the filter and transmitting only a linearly polarized component of a polarization plane of a third azimuth orthogonal to the second azimuth; Among the light rays that have passed through the second spatial filter, a rotatable analyzer that transmits only the linearly polarized light of the polarization plane of the fourth azimuth and the intensity distribution of the object image by the linearly polarized light of the polarization plane of the fourth azimuth Photoelectric conversion,
A photoelectric conversion element that outputs an image signal and an image signal indicating the intensity distribution of the optical image obtained when the fourth azimuth are matched with the fifth azimuth are converted into data and stored as first image data. The first image storage means and the fourth orientation,
An image signal showing the intensity distribution of the optical image obtained when the sixth azimuth orthogonal to the fifth azimuth is matched is converted into data,
Second image storage means for storing this as the second image data, and the first image data and the second image data are taken out from the first image storage means and the second image storage means, and a difference indicating a difference between these intensities is obtained. It has a difference image generating means for generating an image and an image display means for displaying the image using the difference image, and the azimuth of the optical axis of the quarter wavelength plate and the second azimuth are angles that are integral multiples of 90 °. And the first azimuth formed by the polarizer is an angle obtained by adding 45 ° to an integer multiple of 90 ° with respect to the azimuth of the optical axis of the quarter wavelength plate. Surface observation device.

[0012]

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. The contrast of the difference image changes according to the amount of phase change of the phase object, and changes by adjusting the phase difference. This makes it possible to obtain a surface observation device such as a phase contrast microscope whose contrast can be adjusted with a simple optical 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.

[0014]

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

[0015]

First, the basic form 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. The light condensed and transmitted 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 (X1, Y1) to (X5, Y5) are set so as to be orthogonal to the optical axis AX and have the same orientation. Similarly, the Cartesian coordinates (X6, Y6) are set to the optical axis AX of the analyzer 24.
Is set so as to be orthogonal to the reflection-side optical axis AX1 folded back and to have the same orientation as the orthogonal coordinates (X1, Y1) to (X5, Y5). That is, the coordinates are set so that the coordinate axes overlap when viewed from the ring diaphragm 10 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,
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 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 forms an interference image Iθ2 (x, y, θ1) on the image plane of the objective lens 16. The coherent ray i2 reflected by the analyzer 24 is an interference image Iθ3 (x, y, θ) on the image plane of the objective lens 16.
2 = θ1 + π / 2) is formed.

The analyzer 24 extracts coherent polarization 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 components in the i1 direction are 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.

[0024]

(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. Here, the phase object 14
If the magnitude of is (x, y) = (2g, 2h), the average amplitude b of the object can be integrated in these ranges and divided by the total area. Indicated by.

[0026]

(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 the transmission characteristic is expressed by the equation (3).

[0028]

(Equation 3)

Next, the intensity distribution Iθ2 corresponding to the ray I1
(X, y, θ1) is represented by the following equation (4) (for example, see Tokai Univ., "Principle of Optics II" P.639). In the equation, A is the amplitude transmittance, C is C1 * b, and C1 is a constant.
Substituting equation (1) into equation (4) and rearranging
Equation (5) is obtained.

[0030]

(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 Iθ3 (x, y, θ2 = θ1 + π / 2) corresponding to the light ray i2 can be obtained by the equation (7).

[0032]

(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.

[0034]

(Equation 8)

(Equation 9)

This equation (9) shows the inner product of the two vectors, and the intensity of the difference image S is maximized when the polarizer angle θ1 that satisfies the equation (10). On the contrary, the polarizer angle θ
When 1 deviates from the value of the expression (10) by π / 4, the intensity of the difference image S becomes the minimum (zero). Therefore, when the polarizer 18 is rotated, the intensity of the difference image is increased or decreased every 45 °.

[0036]

(Equation 10)

By the way, in general, the amplitude distribution of the phase object 14 is flat and can be regarded as ρ (x, y) ≈b. Substituting this into the equation (9) gives the following equation (11).

[0038]

[Equation 11]

Focusing on the term of cos in this equation, the differential output S is maximized when the polarizer angle θ1 satisfies the condition of equation (12). Also, from the angle satisfying the expression (12), π / 4 (4
The differential output S becomes the minimum (zero) at an angle deviated by 5 °.
In this way, the contrast of the difference image of the phase object 14 can be adjusted by adjusting the polarizer angle. Further, from the value of the analyzer angle θ1 at this time, the amount of phase change φ (x, y) caused by the phase object 14 can be obtained from the equation (12).

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, a polarizer and a quarter wavelength plate which are very general optical elements are used. The variable phase means is easily realized only by using the element.

[0041]

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 passing through the ring diaphragm 10 is refracted by the condenser lens 12 and illuminates the phase object 14 on the slide glass 13 by 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 a polarization beam splitter 50 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 further the polarization beam splitter 50.
Incident on. Then, a part of the light passes through the polarization beam splitter 50 to become a light ray i1 and the rest is reflected to become a light ray i2.

The azimuth angle (θ1) of the polarizer 18 is variable, and the analyzer angle of the polarization beam splitter 50 is 1 /.
The azimuth is 45 ° with respect to the optical axis of the four-wave plate 20. The ring-shaped polarizing plate 22 includes the ring-shaped portion Rp and the other portion Ro.
And the annular zone Rp is a quarter wavelength plate 2
Only the linear polarization component of the polarization plane parallel to the optic axis of 0 with respect to the optical axis of 0 is transmitted, and the other part Ro is the polarization plane of the polarization plane perpendicular to the polarization plane of the linear polarization component transmitted through the annular zone Rp. Only the linearly polarized light component is transmitted.

The light ray i1 is linearly polarized light having a plane of polarization parallel to the analyzer angle of the polarization beam splitter 50.
Reference numeral 2 is linearly polarized light having a plane of polarization perpendicular to the analyzer angle of the polarization beam splitter 50.

The ray i1 is refracted by the lens 52,
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 54 whose light detection surface is located on the image plane, and a video signal is output from the two-dimensional image pickup device 54. On the other hand, ray i2
Is refracted by the lens 56, 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 58 whose light detection surface is located on the image plane, and a video signal is output from the two-dimensional image pickup device 58.

The two video signals output from the image pickup devices 54 and 58 are input to the differential amplifier 60, and the differential amplifier 6
A differential signal is output from 0. This differential signal is output to the image display unit 62, 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 elements 54 and 58 in the direction crossing the optical axis, the signal output timing, and the like are Has been adjusted. Image display section 6
The second observer can adjust the magnitude of the differential output by adjusting the orientation of the rotatable polarizer 18 with respect to the optical axis AX.

[0047]

Second Embodiment Next, a second embodiment will be described with reference to FIG. The part from the light source 40 to the objective lens 16 is the same as in the first embodiment. In this embodiment, the polarizer angle of the polarizer 18 can be switched by the actuator 70 between the azimuth of θ1 and the azimuth (θ1 + 90 °) perpendicular thereto. Also, analyzer 5
The analyzer angle of 0 has an azimuth of 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 first embodiment is used.
Is output from the polarization beam splitter 50, and when the polarizer angle becomes 135 °, the linearly polarized light i 2 of the first embodiment is output from the analyzer 50.

The light ray i1 or the light ray i2 is transmitted to the lens 52.
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 54 whose light detection surface is located on the image plane, and a video signal is output from the two-dimensional image pickup device 54. The two image signals obtained corresponding to the two polarizer angles are A / D converted by the image storage unit 72 and stored as two image data. These image data are
It is supplied to the computer 74.

In the computer 74, difference image data equal to the difference between the two images is calculated from the two image data in the image storage section 72, and after this D / A conversion, the difference image data is output to the image display section 62 to obtain the difference image. Is displayed. The observer can instruct the computer 74 through the interface 76 about necessary information, for example, an instruction to capture an image and a call to stored image data.

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

[0052]

Third Embodiment Next, a third embodiment will be described with reference to FIG. Although the configuration is almost the same as that of the second 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. Although it is optically equivalent to the second embodiment, when the flatness of the polarizer 18 is not good,
This embodiment is effective 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 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.

[0053]

Fourth Embodiment Next, a fourth embodiment will be described with reference to FIG. The fourth embodiment is a modification of the second embodiment. In the second embodiment, the polarizer 70 is rotated by the actuator 70, but in this embodiment, the analyzer 50 is rotated.
Is configured to rotate. That is, the analyzer angle is 45 °, 135 ° with respect to the optical axis of the quarter-wave plate 20.
The analyzer 50 is rotationally driven by the actuator 70 so that Then, the two images corresponding to the respective analyzer angles are captured by the two-dimensional image pickup device 54 by photoelectric conversion. The azimuth of the polarizer 18 is set to 45 °.

[0054]

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-described embodiment, the present invention is mainly applied to a microscope, but the present invention is applicable to all object surface observing apparatuses. For example, step measurement of an object, magnetic head,
It is effective for defect inspection of wafers, reticles, etc., and position measurement taking into consideration the surface shape of the object.

[Brief description of the drawings]

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

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

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

FIG. 7 is a diagram showing a fourth embodiment of the present invention.

FIG. 8 is a diagram showing a general configuration of a phase contrast microscope.

FIG. 9 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 wavelength plate 22 ... Ring zone deflector 22a ... Ring zone 22b ... Other part 24 ... Analyzer 40 ... Light source 42 ... Interference filter 44 ... Collector lens 46 ... First relay lens 48 ... Second relay lens 50 ... Polarization beam splitter (analyzer) 52, 56 ... Lens 54, 58 ... Two-dimensional imaging device 60 ... Differential amplifier 62 ... Image display unit 70 ... Actuator 72 ... Image storage 74 ... Computer 76 ... Interface

(Equation 12)

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[Procedure amendment]

[Submission date] November 28, 1995

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0038

[Correction method] Change

[Correction contents]

S = ² | C | ² [sin2θ ₁ −sin {2θ ₁ −φ (x, y))}] = ² | C | ² [sin φ (x, y) / 2} cos {2θ ₁ −φ (X, y) / 2}] (11) 2θ ₁ -φ (x, y) / 2 = nπ [| n | = 0, 1, 2, 3, ...] (12)

Claims (3)

[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 the linearly polarized light components in different directions; second for obtaining coherent polarized light components in the first and second different directions from the incident light from the first filter means, respectively. Filter means; first imaging means for obtaining a first image based on the coherent polarization component in the first direction obtained by the second filter means;
Second image pickup means for obtaining a second image based on the coherent polarization component in the second direction obtained by the second filter means; first and second image pickup means obtained by these image pickup means
Image observation means for obtaining a difference image of the image of the surface observation device. 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 those linearly polarized light components in different directions; from incident light from this filter means,
Second filter means for obtaining a coherent polarization component; image pickup means for obtaining an image by the polarization component obtained by the second filter means; when the polarizer or the second filter means is set to the first polarization direction Memory means for storing the first image captured in the second image and the second image captured when the polarizer or the second filter means has a second polarization direction different from the first polarization direction; A surface observation apparatus comprising: a difference image generating means for obtaining a difference image of the first and second images stored in the memory means. 3. The surface observation apparatus according to claim 1, wherein the illuminating unit includes a condenser lens for condensing illumination light; and the polarizer is arranged near a pupil of the condenser lens. .