JPH0511191A - Optical device for microscope - Google Patents

Abstract

PURPOSE:To hold an entrance pupil position invariably constant by providing an optical means which holds an entrance pupil for a relay optical system at the same position for a shift in exit pupil position due to variation in the magnification of an objective optical system. CONSTITUTION:A parallel plane plate 2 and a visual field lens 3 are provided in a mutually replaceable state at or nearby the position of a spatial image I1 formed by the objective optical system and the relay optical system 1 is so constituted that the side of an image I1 is telecentric. Further, a main light beam Lp from a pupil center position P1 indicating the entrance pupil position of the relay optical system 1 is passed through the parallel plane plate 2 and relay optical system 1 and made incident vertically on an image pickup element arranged on the re-formed image I2. A main light beam L'p from the center position P'1 of the exit pupil of the objective optical system which shifts as the magnification of the objective optical system is varied, on the other hand, is refracted by the visual field lens 3 arranged at or nearby the position of the spatial image I1 formed by the objective optical system.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical device for a microscope used for relaying an aerial image by an objective optical system of a microscope to a detection surface and photographing it with a TV camera or the like.

[0002]

2. Description of the Related Art When an image of an object to be examined by a microscope is observed by a television camera (TV camera) or the like, a method of directly forming an image by an objective optical system on a detection surface of the TV camera or the like, and an objective optical system There is a method of re-imaging the image by the image on a detection surface of a TV camera or the like via a relay optical system. In the latter case, the relay optical system is required to be a telecentric optical system due to the characteristics of TV.

[0003]

However, the exit pupil of the objective optical system changes with the polarization of the magnification of the objective optical system. That is, the exit pupil of the objective optical system is changed by changing the magnification by exchanging the objective lens of the objective optical system, or by an intermediate variable power system in which lenses having different focal lengths are exchangeably provided in the objective optical system. . As a result, the pupil position of the relay system also changes, and the telecentric condition cannot be maintained. Such a change amount of the pupil position is inversely proportional to the square of the magnification of the relay optical system.

In recent years, the image quality of TV cameras has improved considerably due to the development of HD (high-definition) cameras, and even during microscope observation, the high image quality and wide screen due to the large screen are being used while the frequency of use of the TV camera is increasing. The demand for visual field images is increasing. In addition, the size of the image sensor is in the direction of miniaturization,
The magnification of the relay system is in the direction of reduction.

However, since the variation amount of the exit pupil position of the relay optical system is inversely proportional to the square of the magnification of the relay optical system as described above, the magnification can be changed by exchanging any objective lens or the magnification of the intermediate variable power system. It has been difficult to realize a low-magnification relay optical system that can sufficiently accommodate changes.

In view of the above, the present invention solves the above problems and maintains a constant telecentric condition for the entrance pupil position of the relay optical system even if the magnification of the objective optical system is changed. Aim to get.

[0007]

In order to achieve the above object, in the microscope optical apparatus according to the invention described in claim 1, a microscope equipped with a telecentric relay optical system for relaying an aerial image by an objective optical system to a detection surface. Optical device for
Optical means for maintaining the entrance pupil to the relay optical system at the same position with respect to the change of the exit pupil position due to the change of the magnification of the objective optical system is provided at the aerial image or a position in the vicinity thereof.

According to a second aspect of the present invention, there is provided a microscope optical apparatus according to the first aspect, wherein the optical means has an exit pupil of the objective optical system at a position of the aerial image. The first optical element disposed in the optical path in the first magnification state when the distance is relatively far from, and the second optical element when the exit pupil of the objective optical system is relatively close to the position of the aerial image.
And a second optical element disposed in the optical path in the magnification state, the first optical element and the second optical element are configured to be interchangeably disposed in the optical path.

According to a third aspect of the present invention, there is provided a microscope optical device according to the second aspect, wherein one of the first and second optical elements is a plane parallel plate. The other is a field lens, the principal point interval of the field lens is S, the distance from the front principal point of the field lens to the aerial image formed by the objective optical system is D ₀ , and the focal length of the field lens is f, where the thickness of the plane-parallel plate is d, and the refractive index of the plane-parallel plate is n, the following formula is substantially satisfied. S-D ₀ ² / (f + D ₀ ) = d (1-1 / n)

[0010]

According to the present invention, the aerial image of the objective optical system or the aerial image of the objective optical system is changed according to the change of the magnification accompanying the exchange of the objective lens and the change of the exit pupil position accompanying the change of the magnification of the intermediate variable power system in the objective optical system. Since the optical means for keeping the entrance pupil position of the relay optical system constant is arranged in the vicinity thereof, the imaging device side is always kept telecentric without changing the magnification of the relay optical system. be able to.

Further, in the present invention, as the optical means, a field lens and a parallel plane plate for optical path length correction are arranged so as to be interchangeable, and the parallel plane plate has an appropriate refractive index and thickness according to the field lens. By setting the height to H, it is possible to prevent the position variation of the image due to the relay optical system.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An optical device for a microscope according to an embodiment of the present invention will be described below with reference to FIG. In the microscope optical apparatus of the present embodiment, the aerial image I ₁ by the objective optical system (not shown) is used.
1 is re-imaged by the relay optical system 1 via the plane-parallel plate 2 or the field lens 3 as shown by the light ray L in FIG. 1, and the image I ₁ is taken by the image pickup device by this optical system 1.

At the position of the aerial image I ₁ formed by the objective optical system or in the vicinity thereof, the plane parallel plate 2
And the field lens 4 are provided interchangeably,
The relay optical system 1 is configured such that the image I ₂ side (detection surface side) is telecentric.

In FIG. 1, (a) shows a state where the exit pupil position of the objective optical system is relatively far from the position of the aerial image I ₁ . A pupil center position P ₁ indicating the exit pupil position formed by the objective optical system and indicating the entrance pupil position of the relay optical system _1.
The principal ray L _P from the laser beam passes through the plane-parallel plate 2 and the relay optical system 1 and is vertically incident on the image pickup device (not shown) arranged on the re-formed image I ₂ . Since the principal ray reaching the image sensor is parallel (telecentric) to the optical axis, the exit pupil P ₂ of the relay optical system 1 is located at infinity.

On the other hand, FIG. 1B shows a state in which the position of the exit pupil of the objective optical system is relatively close to the position of the spatial image I ₁ . The chief ray L _P ′ from the center position P ₁ ′ of the exit pupil of the objective optical system in a displaced state due to the change of the magnification of the objective optical system is the position of the aerial image I ₁ formed by the objective optical system or It is refracted by the refracting action of the field lens 3 arranged in the vicinity thereof.

As a result, the entrance pupil of the relay optical system 1 is positioned at the position P ₁ which is substantially equal to that in the case of FIG. Therefore, the chief ray passing through the field lens 3 is
In the same manner as in (a) above, the light is vertically incident on the image pickup element arranged on the re-formed image I ₂ via the relay optical system 1. Therefore, even when the exit pupil of the objective optical system changes, the telecentricity of the relay optical system 1 is always maintained.

When switching to the field lens 3,
The magnification of the relay optics does not change. Also, the field lens 3
By appropriately setting the refractive index and the thickness of the plane-parallel plate 2 according to the above, the position of the image 5 does not change.

Next, the conditions under which the image I ₂ detected by the image pickup device or the like does not change due to the arrangement of the plane-parallel plate 2 and the field lens 3 will be described with reference to FIGS. FIG. 2 is a diagram showing an image formation relationship in a state where the field lens 3 is arranged near the position where the aerial image is formed by the objective optical system.

As shown in FIG. 2, the movement to the image plane due to the arrangement of the field lens 3 is due to the object point of the telecentric relay system 1 moving from the aerial image I ₁ (primary image plane) by ΔD _0. . At this time, the axial distance from the front principal point H _{0 of the} field lens 3 to the aerial image (the object point of the field lens 3) is D
₀ , the axial distance from the rear principal point H ₁ of the field lens 3 to the image point of the field lens 3 is D ₁ , and the focal length of the field lens 3 is f
Then, in the field lens 3, the imaging relationship as shown in the following equation is established.

1 / D ₁ = 1 / f + 1 / D ₀ ... (1) Then, the formula (1) is transformed into the following formula (2). D ₁ = fD ₀ / (f + D ₀ ) ... (2) Further, when the principal point interval of the field lens 3 is S, the following equation (3) is established from FIG. ΔD ₀ = −D ₀ + S + D ₁ (3) Then, by substituting the equation (3) into the equation (2) and transforming, the following equation (4) can be introduced. ΔD ₀ = S−D ₀ ² / (f + D ₀ ) (4)

On the other hand, FIG. 3 shows the aerial image I ₁ by the objective optical system.
It is a figure which shows the imaging relationship in the state in which the plane parallel plate 2 is arrange | positioned in the vicinity of the position where is formed. As shown in FIG. 3, the movement of the image plane due to the arrangement of the plane-parallel plate 2 is such that the object point of the telecentric relay optical system 1 is Δ from the aerial image I ₁ (primary image plane).
This is due to movement by X ₀ .

At this time, assuming that the thickness of the plane-parallel plate 2 is d and the refractive index of the plane-parallel plate 2 is n, the following equation (5) holds. ΔX ₀ = d (1-1 / n) (5) Therefore, in order to simultaneously correct the image plane movement due to the respective arrangements of the field lens 3 and the plane parallel plate 2, ( From equations (4) and (5), it is desirable to satisfy the following equation (6). S−D ₀ ² / (f + D ₀ ) = d (1-1 / n) (6)

In the above embodiment, the plane-parallel plate is arranged when the exit pupil of the objective optical system is relatively far from the aerial image formed by the objective optical system, and the exit pupil of the objective optical system is Although the field lens is arranged when it is relatively close to the aerial image formed by the objective optical system, the present invention is not limited to this. That is, depending on the case, when the exit pupil of the objective optical system is relatively far from the aerial image formed by this objective optical system, the field lens is arranged, and the exit pupil of the objective optical system is formed by this objective optical system. A plane-parallel plate may be arranged when it is relatively close to the aerial image.

[0024]

As described above, according to the present invention, even if the position of the exit pupil of the objective optical system changes, the plane-parallel plate and the field of view that are exchangeably arranged in the spatial image of the objective optical system or in the vicinity thereof. With the lens, the position of the entrance pupil to the relay optical system can be made constant, and the imaging device side can be always kept telecentric without changing the magnification of the relay optical system.

Further, by setting the plane-parallel plate to have an appropriate refractive index and thickness according to the field lens, it is possible to prevent the position variation of the image due to the relay optical system. Therefore, a lower magnification relay optical system can be achieved and a wider field of view image can be provided. Further, since it is not necessary to worry about the variation of the pupil of the aerial image, there is an advantage that the degree of freedom in designing the objective lens and the intermediate magnification is improved.

[Brief description of drawings]

FIG. 1 is a schematic optical path diagram of a microscope optical device according to an embodiment of the present invention.

FIG. 2 is a schematic optical path diagram showing a case where a field lens is arranged in the optical system of the embodiment shown in FIG.

FIG. 3 is a schematic optical path diagram showing a case where a plane parallel plate is arranged in the optical system of the embodiment shown in FIG.

[Explanation of symbols]

1: relay optical system 2: plane parallel plate 3: field lens P ₁ : entrance pupil of relay optical system P ₂ : exit pupil of relay optical system I ₁ : aerial image of objective optical system I ₂ : relay of microscope optical device Image by optical system

Claims (3)

[Claims] 1. An optical device for a microscope comprising a telecentric relay optical system for relaying an aerial image by an objective optical system to a detection surface, wherein the aerial image or a position in the vicinity thereof is provided.
An optical device for a microscope, comprising optical means for keeping the entrance pupil of the relay optical system at the same position with respect to the change of the exit pupil position due to the change of the magnification of the objective optical system. 2. The first optical element, wherein the optical means is disposed in the optical path in the first magnification state when the exit pupil of the objective optical system is relatively far from the position of the aerial image; A second optical element disposed in the optical path in the second magnification state when the exit pupil of the objective optical system is relatively close to the position of the aerial image, and these first and second optical elements are included. The optical device for a microscope according to claim 1, wherein the optical device for a microscope is configured so as to be interchangeably arranged in the optical path. 3. One of the first and second optical elements is a plane-parallel plate and the other is a field lens, and the principal point interval of the field lens is S, from the front principal point of the field lens. The distance to the aerial image formed by the objective optical system is D
_0, focal length f of the field lens, the thickness d of the parallel flat plate, the refractive index of the parallel flat plate when the n, according to claim 2, characterized in that substantially satisfies the following equation Optical device for microscope. S-D ₀ ² / (f + D ₀ ) = d (1-1 / n)