JP3048267B2 - Microscope optics - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND 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 transmitted light and reflected light is provided in a parallel light beam region of the microscope. About.

[0002]

2. Description of the Related Art FIG. 8 shows an example of a conventional microscope optical system of this kind. In this optical system, the object plane O
Becomes a parallel light beam through the objective lens 1. The beam splitter prism 2 having the beam splitter surface 2a disposed in front of the beam splitter prism 2
b forms a plane perpendicular to the incident optical axis of the parallel light beam, and the light beam incident from the light beam incident surface 2b is partially reflected by the beam splitter surface 2a and emitted from the reflected light exit surface 2c. And the remaining beam is beam splitter surface 2
a, and exits from the transmitted light exit surface 2d, passes through the imaging lens 3, and forms an image I on the imaging surface.

However, in such an optical system, the light beam reflected on the light beam incident surface 2b of the beam splitter prism 2 is reflected on the object surface O and re-enters the objective lens 1, where the beam splitter prism 2 A ghost image of the same size is formed at a position symmetrical with the normal image point I with respect to the center of the visual field via the lens 3. For this reason, the contrast of the image I to be observed is deteriorated, and a clear image cannot be observed. In order to prevent such ghost images, some prism surfaces are coated with a multilayer film.However, 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.

A microscope optical system which has attempted to solve this problem is disclosed in Japanese Patent Application Laid-Open No. Sho 54-123044. In this optical system, as shown in FIGS. 9 and 10, the ghost image is removed from the visual field 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 discloses that the ghost is removed by inclining the beam splitter prism 4, and the light beam reflected by the beam splitter surface 4a is mentioned. 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 a surface orthogonal to the incident optical axis. When the beam splitter prism 4 is provided, a part of the light beam 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. Inject at an angle. For this reason, the light beam is not perpendicular to the incident optical axis.

[0006] Incidentally, when the reflected light beam thus is not perpendicular to the incident optical axis, for example, in the discussion microscope apparatus such as a plurality of observer can observe the same image at the same time, progress to Fukuken mirror side Since the optical axis of the reflected light beam is not horizontal, extra space is required in the device, and the mounting and joining parts need to be inclined, which complicates processing during manufacturing and increases manufacturing costs. And
There is a problem that the system performance is deteriorated.

The present invention has been made in view of the above-described problems, and it is possible to split a parallel light beam of an optical system into a light beam parallel to a light beam incident on a beam splitter prism and a light beam perpendicular to an optical axis incident on the beam splitter prism, and to remove ghosts. An object of the present invention is 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 disposed in a parallel light beam region between an objective lens and an imaging lens. In the microscope optics for 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 incident surface is The angle θ formed by a 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 and the incident optical axis is θ described above.
When 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 imaging lens has an optical axis with respect to the incident optical axis as follows. Is disposed at a position shifted by a distance d shown by the following equation.

[0009]

In the microscope optical system according to the present invention, when the focal length of the imaging lens is f and the number of fields of view of the microscope is S with respect to the beam splitter prism, the light incident surface is incident on the surface. The angle θ formed with 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. [(1 / n) sin θ]｝, the reflected light exit surface is perpendicular to the light incident surface, the transmitted light exit surface is parallel to the light incident surface, and the transmitted light exit surface and the light incident Assuming that the distance from the plane is l, the optical axis of the imaging lens is the distance d represented by the following equation with respect to the incident optical axis.
It is characterized in that it is disposed at a position shifted only by.

[0011]

[0012]

The parallel light beam that has passed through the objective lens enters the light beam incident surface of the beam splitter prism at an incident angle θ and is refracted at an angle, but the light reflected by the beam splitter surface is the same as the reflected light exit surface. Incident at an angle, and further refracted by an angle θ when exiting this surface, the beam becomes perpendicular to the incident optical axis, and the light beam transmitted through the beam splitter surface is refracted by an angle θ when exiting from the transmitted light exit surface. As a result, the optical axis of the imaging lens is shifted from the incident optical axis by the distance d, so that the optical axis coincides with the optical axis, and an object image is formed on the imaging plane. In addition, the ghost image is formed outside the visual field, and is therefore removed.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 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 prior art are denoted by the same reference numerals, and description thereof will be omitted. FIG. 1 shows a configuration diagram of a microscope optical system. In FIG. 1, a beam splitter surface 6a for dividing the light beam into two is provided in a region of a parallel light beam between the objective lens 1 and the imaging lens 3 in the figure. 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 a 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 shown in FIG. FIG. 2 is a principle diagram showing an optical path for forming an observation image and a ghost image when the beam splitter prism is inclined. In the figure, a parallel plate prism 7 inclined at an angle θ ″ with respect to an incident optical axis is disposed in a parallel light beam region between the objective lens 1 and the imaging lens 2. In this optical system, an object is formed. The luminous flux on the surface O passes through the objective lens 1 to become a parallel luminous flux as shown by a solid line, then passes through the prism 7, and is formed as an observation image I on the imaging plane by the imaging lens 3. Also, of the parallel light beams that enter the prism 7 via the objective lens 1, the light beam incident surface 7a
Is represented by a broken line, the reflected light passes through the objective lens 1 at an angle of 2θ ″ with respect to the optical axis, and
Is formed as a ghost image O 'on the extension surface of. And
The luminous flux of this ghost image travels in the reverse direction along the dashed optical path, 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 dashed light beam passes through the imaging lens 2 and is located at a position (f · tan2θ ″) away from the optical axis of the imaging lens 2 on the imaging surface by a ghost image I ′. Will be imaged.

In consideration of this, returning to FIG. 1 and considering the area of the angle θ, in order to form all the ghost images of the number of fields S outside the field of view, θ ≧ (1/2) 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 beam passing through is emitted is formed in parallel with the light beam incident surface 6b. Also, the imaging lens 3
Is provided at a position whose optical axis is shifted by a distance d with respect to the optical axis of the light beam passing through the objective lens 1 and incident on the light beam incident surface 6b.

The distance d will be described with reference to FIG. Assuming that 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, Because It is represented by

Since the present embodiment is configured as described above, of the light beams that exit the object plane O and pass through the objective lens 1, the light beams reflected by the light beam incident surface of the beam splitter prism 6 are shown in FIG. As described above, an 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 luminous flux of the ghost image passes through the objective lens 1, the beam splitter prism 6, and the imaging lens 3 in the same optical path in the reverse direction.
An image is formed outside the visual field of the number of visual fields S on the extension surface of the image forming surface. Thereby, a 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 the beam splitter prism 6 at an incident angle θ with respect to the normal to the light beam incident surface 6b, and is refracted at a refraction angle φ, as shown in FIG. As described above, a part of the light is reflected by the beam splitter surface 6a and enters the reflected light exit surface 6c. Here, the light beam incidence surface 6b and the reflected light emission surface 6c of the beam splitter prism 6 are connected to the beam splitter surface 6c.
Since the other two sides of the isosceles triangle having the base 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 formed. The incident angle is also φ. Therefore,
The refraction angle of the light beam emitted from the reflected light exit surface 6c is also θ. Therefore, the light beam emitted from the surface 6c becomes perpendicular to the light beam incident on the light beam incident surface 6b.

The remaining light beam 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 beam incident surface 6b, refraction at the light beam incident surface 6b. The angle is equal to the angle of incidence on the transmitted light exit surface 6d. Therefore, the optical axis of the light beam emitted from the transmitted light exit surface 6d is emitted in parallel with the optical axis incident on the light beam incident surface 6b. At this time, since this light beam is refracted in the beam splitter prism 6, the optical axis of the incident light and the emitted light is shifted by a distance d in a direction orthogonal to the optical axis. On the other hand, since the center is displaced by the distance d, the optical axis of the emitted light is
Will match the center of

As described above, according to the present embodiment, the ghost image can be removed from the visual field by tilting the light incident surface 6b of the beam splitter prism 6 by an angle θ, and a clear image can be observed. Moreover, the parallel light beam that has passed through the objective lens 1 can be split into two by the beam splitter prism 6 into a light beam perpendicular to the incident optical axis and a light beam parallel to the incident light axis. Therefore, with respect to the microscope apparatus having this microscope optical system, it is not necessary to incline the mounting portion and the joining portion for receiving the reflected light beam, which is very convenient from the viewpoint of space and ease of manufacturing and processing, There is an advantage that the system performance is improved. Further, in this embodiment, the light is incident from the light beam incident surface 6b and the two exit surfaces 6c and 6c.
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 therethrough, there is also an advantage that the light beam is hardly affected by aberration and the like.

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

As shown in FIG. 7, the imaging lens 3 is
The optical axis is disposed so as to be shifted from the optical axis incident on the beam splitter prism 8 by a distance d in a direction orthogonal to the optical axis. The distance d is equal to the distance between the light incident surface 8b of the beam splitter prism 8 and the transmitted light exit surface 8d.
Is 1 and the optical path length of a light beam passing between the light beam incident surface 8b and the transmitted light exit surface 8d is l ', the above expression (2) is obtained.

Is this embodiment configured as described above?
, The light beam incident on the beam splitter prism 8
Is an angle with respect to a normal to the light beam incident surface 8b as shown in FIG.
Degree @ sin^-1Refraction by [(1 / n) sin θ]｝
Needless to say, the light incident surface 8b and the beam splitter surface 8a
The angle to make is $ 45-sin^-1[(1 / n) sin
θ]｝, the light is incident on the beam splitter surface 8a.
The angle of the luminous flux is 45 degrees with respect to the beam splitter surface 8a.
°. Therefore, it is incident on the beam splitter surface 8a.
And the reflected light reflected by the beam splitter surface 8a
A part of the luminous flux toward the exit surface 8c is at a right angle. Only
The light incident surface 8b and the reflected light exit surface 8c are orthogonal to each other.
Therefore, the reflected light from the beam splitter surface 8a
Is Δsin on the reflected light exit surface 8c with respect to the normal line.
^-1[(1 / n) sin θ] incident at an angle of｝
The light exits from this surface 8c at a refraction angle. Therefore, the beam
The light incident on the light incident surface 8b of the splitter prism 8 and
Light emitted from the reflected light exit surface 8c should be orthogonal to each other
become.

The light beam transmitted through the beam splitter surface 8a has a refraction angle at the light beam incident surface 8b and a transmitted light exit surface 8d because the transmitted light exit surface 8d is parallel to the light beam incident surface 8b.
Are equal to each other, and the light emitted from the transmitted light exit surface 8d is emitted in parallel with the incident optical axis. In this case, as shown in FIG. 7, the optical axis of the emitted light is shifted by a distance d from the incident optical axis in a direction orthogonal to the optical axis, but the imaging lens 3 is also shifted by the distance d. Therefore, the optical axis of the emitted light beam passes through the optical axis of the imaging lens 3,
A clear image I is formed on the image plane.

In this embodiment, the angle formed by the light beam incident surface 8b and the reflected light emitting surface 8c of the beam splitter prism 8 and the angle of one corner opposed thereto are formed at right angles, so that the beam splitter prism 8 Is easy to manufacture and process, and the manufacturing cost can be 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 and the clear image can be observed by arranging the beam splitter prism at an angle θ. In addition, when the parallel light beam is split by the beam splitter prism, it can be split into a light beam that is perpendicular to the incident optical axis and a light beam that is parallel to the light beam. It is possible to reduce the cost and improve the system performance.

[Brief description of the 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 an image forming optical path 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, respectively, with their optical axes.

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

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 by their optical axes in the second embodiment.

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

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

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

FIG. 10 is a view similar to FIG. 9, in which the tilt direction of the beam splitter prism is reversed.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 objective lens 3 imaging lens 6 , 8 beam splitter prism 6 a, 8 a beam splitter surface 6 b, 8 b light beam incident surface 6 c, 8 c reflected light exit surface 6 d, 8 d transmitted light exit surface

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G02B 21/00 G02B 21/06-21/36

Claims (2)

(57) [Claims] In a microscope optical system for infinity correction, a beam splitter prism having a beam splitter surface for splitting a parallel light beam is disposed in a parallel light beam 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 between the light incident surface and the surface perpendicular to the incident optical axis is θ ≧ (1/2) tan ⁻¹ (S / f), and the angle formed by the reflected light exit surface with the incident optical axis a is the theta, with the transmitted light exit plane is parallel to the light incident surface, whereupon the distance between the transmitted light exit surface and the light beam incident surface l, the imaging lens, enter the optical axis before The distance shown in the following formula with respect to the emission axis Microscope optics, characterized in that disposed on the d shifted position. 2. A microscope optical system for infinity correction, wherein a beam splitter prism having a beam splitter surface for splitting a parallel light beam is disposed in a parallel light beam region between an objective lens and an imaging lens. When the focal length of the imaging lens is f and the field of view of the microscope is S, the splitter prism has an angle θ between the light incident surface and a surface perpendicular to the incident optical axis of the light incident on the light incident surface. , Θ ≧ (1/2) tan ⁻¹ (S / f), and the beam splitter surface is ｛45 with respect to the light beam incident surface.
° -sin ^-1 [(1 / n) sin θ]｝, the reflected light exit surface is perpendicular to the light incident surface, and the transmitted light exit surface is parallel to the light incident surface. Assuming that the distance between the transmitted light exit surface and the light beam incident surface is l , the imaging lens is disposed at a position where its optical axis is displaced from the incident optical axis by a distance d represented by the following equation. A microscope optical system.