JPH05127097A - Microscope optical system - Google Patents

Abstract

PURPOSE:To remove ghost images out of sight and to observe clear images by arranging the beam splitter prism tilting at the prescribed angles. CONSTITUTION:A beam splitter prism 6 with a beam splitter surface 6a to divide light flux is arranged in the area of parallel light flux between objective lens 1 and image formation lens 3. A light flux incident surface 6b of the beam splitter prism 6 is flat and tilted by the angle theta against the plane crossed orthogonally to the optical axis of the incident light flux from the objective lens 1. In this case, the focusing distance of the image formation lens is taken as 'F' and the number of sights as 'S', the angle theta whose light flux incident surface is vertical to the incident light flux shall be a formula I. Further, when the distance between the transparent light emitting surface and the light flux incident surface is taken as '1', the image formation lens is located at the position where the light axis is deviated by distance (d) represented by formula II against the incident light flux.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microscope optical system in which a beam splitter prism having a beam splitter surface for splitting a parallel light beam into a transmitted light beam and a reflected light beam is arranged in a parallel light beam region of a microscope. Regarding

[0002]

2. Description of the Related Art An example of a conventional microscope optical system of this type is shown in FIG. In this optical system, the object plane O
The light flux of is a parallel light flux via the objective lens 1. The beam splitter prism 2 having the beam splitter surface 2a arranged in front of the beam splitter surface 2a
b forms a plane perpendicular to the incident optical axis of the parallel light flux, and the light flux incident from the light flux incidence surface 2b is partially reflected by the beam splitter surface 2a and emitted from the reflected light emission surface 2c. And the rest of the light flux is the beam splitter surface 2
After passing through a, the light is emitted from the transmitted light exit surface 2d, passes through the imaging lens 3, and an image I is formed on the imaging surface.

However, in such an optical system, the light beam reflected by the light beam incident surface 2b of the beam splitter prism 2 is reflected on the object plane O and again enters the objective lens 1 to form the beam splitter prism 2 and an image. A 1 × ghost image is formed through the lens 3 at a position symmetrical with respect to the normal image point I with respect to the center of the visual field. Therefore, the contrast of the image I to be observed becomes poor, and it becomes impossible to observe a clear image. In order to prevent such ghost images, some prisms have a multilayer film coating, but due to the spectral characteristics of the multilayer film, a specific color appears in the ghost image, and the ghost image must be sufficiently removed. Was difficult.

As a microscope optical system intended to improve this problem, there is one disclosed in Japanese Patent Laid-Open No. 54-123044. As shown in FIGS. 9 and 10, this optical system is configured to remove the ghost image outside the field of view by arranging the beam splitter prism 4 at a predetermined angle θ ′ with respect to the incident optical axis. is there.

[0005]

However, this microscope optical system only describes tilting the beam splitter prism 4 to remove ghosts, and does not mention the light flux reflected by the beam splitter surface 4a. Absent. Therefore, in the optical system of FIG. 8, instead of the beam splitter prism 2, as shown in FIGS. 9 and 10, the light beam incident surface 4b is inclined by a certain angle θ ′ with respect to the surface orthogonal to the incident optical axis. When the beam splitter prism 4 is provided, a part of the light flux reflected by the beam splitter surface 4a is refracted by the reflected light exit surface 4c and is 90 ° + 2θ ′ or 90 ° −2θ ′ with respect to the incident optical axis. Eject at an angle. Therefore, the light flux is not perpendicular to the incident optical axis.

By the way, when the reflected light flux is not perpendicular to the incident optical axis in this way, for example, in a discussion microscope apparatus or the like in which a plurality of examiners can observe the same image at the same time, the reflected light flux traveling to the sub-inspector side. Since the optical axis of is not horizontal, extra space is required inside the device, and it is necessary to incline the mounting part and the joint part, which complicates the manufacturing process and increases the manufacturing cost. There is a problem that the system performance also deteriorates.

In view of the above problems, the present invention can split the parallel light flux of the optical system into a light flux parallel to the incident optical axis to the beam splitter prism and a light flux perpendicular to the beam splitter prism, and remove the ghost. It is an object of the present invention to provide a microscope optical system capable of observing a clear image.

[0008]

In a microscope optical system according to the present invention, a beam splitter prism having a beam splitter surface for splitting a parallel light beam is arranged in a parallel light beam region between an objective lens and an imaging lens. In a microscope optical system with infinity correction, the beam splitter prism is
When the beam splitter surface has an angle of 45 ° with respect to the incident optical axis of the light beam incident on the light beam incident surface, the focal length of the imaging lens is f, and the field number of the microscope is S, the light beam incident surface is The angle θ formed by the plane perpendicular to the incident optical axis is θ ≧ (1/2) tan ⁻¹ (S / f) (1), and the angle formed by the reflected light exit surface with the incident optical axis is the above-mentioned θ.
And the transmitted light exit surface is parallel to the light incident surface, and the distance between the transmitted light exit surface and the light incident surface is l, the optical axis of the imaging lens is as follows with respect to the incident optical axis. It is characterized in that it is arranged at a position deviated by a distance d shown by the formula (1).

[0009]

Further, in the microscope optical system according to the present invention, with respect to the beam splitter prism, when the focal length of the imaging lens is f and the field number of the microscope is S, the light beam incident surface is the incidence of the incident light beam on this surface. The angle θ with respect to the plane perpendicular to the optical axis is θ ≧ (1/2) tan ⁻¹ (S / f) (1), and the beam splitter surface is {45 ° -sin ^{−1 with} respect to the light beam incident surface. Has an angle of [(1 / n) sin θ]}, the reflected light exit surface is perpendicular to the light flux entrance surface, the transmitted light exit surface is parallel to the light flux entrance surface, and the transmitted light exit surface and the light flux entrance surface Assuming that the distance from the surface is l, the optical axis of the image forming lens is a distance d with respect to the incident optical axis expressed by the following formula.
It is characterized in that it is disposed at a position shifted by only.

[0011]

[0012]

The parallel light flux passing through the objective lens enters the light flux entrance surface of the beam splitter prism at an incident angle θ and is refracted at a certain angle, but the reflected light reflected by the beam splitter surface is the same as the reflected light exit surface. The light beam that is incident at an angle of θ and refracted at an angle θ when exiting this surface becomes a light beam that is perpendicular to the incident optical axis and that is transmitted through the beam splitter surface. Then, since it is displaced from the incident optical axis by the distance d, the optical axis of the imaging lens coincides with that optical axis, and an object image is formed on the imaging surface. Moreover, since the ghost image is formed outside the visual field, it is removed.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION A first embodiment of the present invention will be described below with reference to FIGS. 1 to 4. The same members as those in the above-mentioned conventional art are designated by the same reference numerals and the description thereof is omitted. FIG. 1 shows a configuration diagram of a microscope optical system. In the figure, a beam splitter surface 6a for splitting a light beam into two is provided in a region of a parallel light beam between an objective lens 1 and an imaging lens 3. A beam splitter prism 6 is provided.
The light beam incident surface 6b of the beam splitter prism 6 forms a plane and is inclined by an angle θ with respect to the plane orthogonal to the optical axis (incident optical axis) of the incident light beam from the objective lens 1.

Here, the angle θ will be considered with the microscope optical system in FIG. FIG. 2 is a principle diagram showing the image forming optical paths of an observation image and a ghost image when the beam splitter prism is tilted. In the figure, a parallel plate prism 7 inclined by an angle θ ″ with respect to the incident optical axis is arranged in a parallel light flux region between the objective lens 1 and the imaging lens 2. This optical system As indicated by the solid line, the light flux on the surface O passes through the objective lens 1 to become a parallel light flux, and then passes through the prism 7 to be imaged as an observation image I on the imaging surface by the imaging lens 3. Further, among the parallel light fluxes that enter the prism 7 through the objective lens 1, the light flux incidence surface 7a.
When the luminous flux reflected at is represented by a broken line, the reflected light is inclined by 2θ ″ with respect to the optical axis and passes through the objective lens 1, and the object plane O
Is imaged as a ghost image O'on the extended surface of. And
The light flux of this ghost image reverses the optical path of the broken line as it is, passes through the objective lens 1 and the prism 7, and is incident at an angle 2θ ″ with respect to the optical axis of the imaging lens 2. Assuming that the distance is f, the broken line light flux passes through the imaging lens 2 and is located on the imaging plane at a position (f · tan2θ ″) away from the optical axis of the imaging lens 2 by a ghost image I ′. Will be imaged.

Considering this, returning to FIG. 1 and considering the area of the angle θ, θ ≧ (1/2) in order to form all ghost images of the field number S outside the field of view. tan ^-1 (S / f) (1).

Further, as shown in FIG. 3, the beam splitter surface 6a has an angle of 45 ° with respect to the incident optical axis, and the light beam reflected by the beam splitter surface 6a exits the prism 6. The reflected light exit surface 6c is inclined by an angle θ with respect to the incident optical axis. The beam splitter surface 6a is formed at a position facing the light beam incident surface 6b.
The transmitted light exit surface 6d from which the light flux that passes through is emitted is formed parallel to the light flux entrance surface 6b. Also, the imaging lens 3
Is provided at a position where its optical axis is displaced by a distance d with respect to the incident optical axis of the light flux that has passed through the objective lens 1 to the light flux incident surface 6b.

The distance d will be described with reference to FIG. If the distance between the light beam incident surface 6b of the beam splitter prism 6 and the transmitted light exit surface 6d is l, and the optical path length of the light beam from the light beam incident surface 6b in the beam splitter prism 6 to the transmitted light exit surface d is l ', d = l'sin {θ-s
in ⁻¹ [(1 / n) sin θ]}. here, Therefore, It is represented by.

Since the present embodiment is configured as described above, among the light fluxes that exit the object plane O and pass through the objective lens 1, the light fluxes reflected by the light flux incidence surface of the beam splitter prism 6 are as shown in FIG. As described above, the incident light beam is reflected at an angle of 2θ, and a ghost image O ′ is formed at a position on the extension surface of the object plane O. Then, the light flux of this ghost image goes through the same optical path backwards and passes through the objective lens 1, the beam splitter prism 6 and the imaging lens 3,
An image is formed outside the visual field number S on the extension surface of the image plane. Thereby, the ghost can be removed.

On the other hand, the light beam entering the beam splitter prism 6 from the light beam incident surface 6b enters at an incident angle θ with respect to the normal line of the light beam incident surface 6b, is refracted at a refraction angle φ, and then is shown in FIG. As described above, a part of the beam splitter surface 6a is reflected and enters the reflected light exit surface 6c. Here, the light beam entrance surface 6b and the reflected light exit surface 6c of the beam splitter prism 6 are the beam splitter surface 6
Since the other two sides of the isosceles triangle whose base is a are formed and the angle of the incident light with respect to the beam splitter surface 6a and the angle of the reflected light are equal to each other, the light flux incident on the reflected light exit surface 6c is The incident angle is also φ. Therefore,
The refraction angle of the light beam emitted from the reflected light emission surface 6c is also θ. Therefore, the light flux emitted from this surface 6c is perpendicular to the light flux incident on the light flux incident surface 6b.

The rest of the light flux passing through the beam splitter surface 6a is incident on the transmitted light exit surface 6d. Since the transmitted light exit surface 6d is parallel to the light flux entrance surface 6b, refraction at the light flux entrance surface 6b is performed. The angle and the incident angle at the transmitted light exit surface 6d are equal. Therefore, the optical axis of the light flux emitted from the transmitted light exit surface 6d is emitted parallel to the incident optical axis to the light flux entrance surface 6b. At this time, since this light beam is refracted in the beam splitter prism 6, the optical axes of the incident light and the emitted light deviate in the direction orthogonal to the optical axis by a distance d, but the imaging lens 3 is previously aligned with the incident optical axis. On the other hand, since the centers are arranged so as to be displaced by the distance d, the optical axis of the emitted light is the imaging lens 3
Will coincide with the center of.

As described above, according to this embodiment, the ghost image can be removed out of the visual field by tilting the light beam incident surface 6b of the beam splitter prism 6 by an angle θ, and a clear image can be observed. In addition, the parallel light flux that has passed through the objective lens 1 can be split into two light fluxes, which are perpendicular to the incident optical axis and parallel to the incident optical axis, by the beam splitter prism 6. Therefore, with respect to a microscope apparatus having this microscope optical system, it is not necessary to incline the mounting portion or the joint portion for receiving the reflected light flux, and it is very convenient in terms of space and ease of manufacturing and processing. There is an advantage that the system property is improved. Further, in this embodiment, the two light-exiting surfaces 6c and 6 are incident on the light-incident surface 6b.
Since the optical path length of the light beam emitted from d in the beam splitter prism 6 is constant regardless of the light beam passing anywhere, there is also an advantage that it is unlikely to be affected by aberration or the like.

Next, a second embodiment of the present invention will be described with reference to FIGS.
It will be explained based on. FIG. 5 shows a configuration diagram of the microscope optical system. A beam splitter prism 8 for splitting a light beam into two beams by a beam splitter surface 8a is arranged in a parallel light beam region between the objective lens 1 and the imaging lens 3. There is.
The light beam incident surface 8b of the prism 8 is inclined with respect to the plane perpendicular to the incident optical axis by the same angle θ as in the first embodiment shown in the equation (1). Also, the beam splitter surface 8a
Is an angle of {45 °-
sin ^-1 [(1 / n) sin θ]} is inclined, and the reflected light exit surface 8c is formed perpendicularly to the light beam entrance surface 8b (see FIG. 6). Further, the transmitted light exit surface 8d is formed parallel to the light flux entrance surface 8b.

Further, as shown in FIG. 7, the imaging lens 3 is
The optical axis is arranged so as to be displaced from the incident optical axis to the beam splitter prism 8 by a distance d in a direction orthogonal to the optical axis. This distance d is equal to the light beam entrance surface 8b and the transmitted light exit surface 8d of the beam splitter prism 8.
Is 1 and the optical path length of the light flux passing between the light flux incident surface 8b and the transmitted light exit surface 8d is 1 ', the above equation (2) is obtained.

Is the present embodiment constructed as described above?
Light flux that has entered the beam splitter prism 8
Is an angle with respect to the normal line of the light beam entrance surface 8b as shown in FIG.
Degree {sin^-1Refraction by [(1 / n) sin θ]}
However, between the light beam incident surface 8b and the beam splitter surface 8a
The angle formed is {45 ° -sin^-1[(1 / n) sin
θ]}, the light beam is incident on the beam splitter surface 8a.
The angle of the luminous flux is 45 with respect to the beam splitter surface 8a.
It becomes °. Therefore, it is incident on the beam splitter surface 8a.
Light that is reflected and reflected by the beam splitter surface 8a
A part of the light flux toward the exit surface 8c is at a right angle. Only
Also, the light beam incident surface 8b and the reflected light emitting surface 8c are orthogonal to each other.
Therefore, the reflected light from the beam splitter surface 8a is
Is {sin to the normal to the reflected light exit surface 8c.
^-1Incident at an angle of [(1 / n) sin θ]},
It is emitted from this surface 8c at a refraction angle. Therefore, the beam
The incident light on the light beam incident surface 8b of the splitter prism 8
The light emitted from the reflected light emitting surface 8c should be orthogonal to each other.
become.

Further, since the transmitted light exit surface 8d of the light beam transmitted through the beam splitter surface 8a is parallel to the light beam entrance surface 8b, the refraction angle at the light beam entrance surface 8b and the transmitted light exit surface 8d.
The incident angle becomes equal to, and the light emitted from the transmitted light emission surface 8d is emitted parallel to the incident optical axis. In this case, the optical axis of the emitted light is displaced from the incident optical axis by a distance d in the direction orthogonal to the optical axis as shown in FIG. 7, but the imaging lens 3 is also displaced by the distance d. Therefore, the optical axis of the emitted light flux passes through the optical axis of the imaging lens 3,
A clear image I is formed on the image plane.

In the present embodiment, the angle formed by the light beam entrance surface 8b and the reflected light exit surface 8c of the beam splitter prism 8 and the angle of one corner facing the angle are formed at right angles, so the beam splitter prism 8 Is easy to manufacture and process, and the manufacturing cost can be further reduced.

[0027]

As described above, in the microscope optical system according to the present invention, the ghost image can be removed out of the field of view by arranging the beam splitter prism at an angle θ, and a clear image can be observed. Moreover, when splitting a parallel light flux by the beam splitter prism, it can be split into a light flux perpendicular to the incident optical axis and a light flux parallel to the incident optical axis, which facilitates the manufacturing and processing of the microscope apparatus having this optical system, thereby reducing the manufacturing cost. It is possible to reduce costs and improve system performance.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a microscope optical system according to a first embodiment of the present invention.

FIG. 2 is a principle diagram showing imaging optical paths of an observation image and a ghost image when a prism is tilted in a microscope optical system.

FIG. 3 is a diagram showing the optical paths of reflected light and transmitted light by a beam splitter prism in the first embodiment, with their optical axes respectively.

FIG. 4 is a diagram showing the optical paths of incident light and transmitted light with respect to the beam splitter prism in the first example, with their optical axes.

FIG. 5 is a diagram showing a configuration of a microscope optical system according to a second embodiment of the present invention.

FIG. 6 is a diagram showing the optical paths of reflected light and transmitted light by a beam splitter prism in the second example, with their optical axes.

FIG. 7 is a diagram showing the optical paths of incident light and transmitted light with respect to the beam splitter prism in the embodiment of FIG. 1, respectively.

FIG. 8 is a diagram showing a configuration of a conventional microscope optical system.

9 is a configuration diagram of another conventional technique in which a beam splitter prism is arranged to be inclined in the optical system of FIG.

10 is a view similar to FIG. 9 in which the tilt directions of the beam splitter prisms are opposite.

[Explanation of symbols]

 1 Objective Lens 3 Imaging Lens 7,8 Beam Splitter Prism 7a, 8a Beam Splitter Surface 7b, 8b Light Beam Incident Surface 7c, 8c Reflected Light Emission Surface 7d, 8d Transmitted Light Emission Surface

Claims (2)

[Claims] 1. A microscope optical system for infinity correction, wherein a beam splitter prism having a beam splitter surface for splitting a parallel light flux is arranged in a parallel light flux region between an objective lens and an imaging lens. In the splitter prism, the beam splitter surface has an angle of 45 ° with respect to the incident optical axis of the light beam incident on the light beam incident surface, the focal length of the imaging lens is f, and the field number of the microscope is S. At this time, the angle θ formed by the light flux incident surface with respect to the surface perpendicular to the incident optical axis is θ ≧ (1/2) tan ⁻¹ (S / f), and the angle formed by the reflected light emitting surface with the incident optical axis. Is θ, and the transmitted light exit surface is parallel to the light flux entrance surface, and when the distance between the transmitted light exit surface and the light flux entrance surface is l, the optical axis of the imaging lens is the incident light Distance shown below with respect to axis Microscope optical system characterized in that it is arranged in a position shifted by. 2. A microscope optical system for infinity correction, wherein a beam splitter prism having a beam splitter surface for splitting the parallel light flux is arranged in a parallel light flux region between an objective lens and an imaging lens. In the splitter prism, when the focal length of the imaging lens is f and the field number of the microscope is S, the angle θ formed by the light beam incident surface with the plane perpendicular to the incident light axis of the light beam incident on the light beam incident surface is , Θ ≧ (1/2) tan ⁻¹ (S / f), and the beam splitter surface is {45
The angle of the angle is −−sin ⁻¹ [(1 / n) sin θ]}, the reflected light exit surface is perpendicular to the light flux entrance surface, and the transmitted light exit surface is parallel to the light flux entrance surface. When the distance between the transmitted light exit surface and the light beam entrance surface is l, it is determined that the optical axis of the imaging lens is displaced from the incident light axis by a distance d represented by the following formula. Characteristic microscope optical system.