JPH08317906A - Ophthalmology photographic device - Google Patents

Abstract

PURPOSE: To enable the prevention of focal deviation and the change in magnification by shifting/controlling, depending upon the change in focal distance of a field lens and in the light axial direction, a relay lens which relays an image- forming light beam, once image-formed near the field lens, onto a photographic surface of an image pickup element. CONSTITUTION: Through an objective lens 31, a reflected light flux from an eyeground 33 forms the first eyeground image 45 at an intermediate image- forming point M1. Its main light beam passes the center of a hole 43 of a perforated mirror 30, which functions as an aperture diaphragm, and is conducted by an focus-adjusting lens 34 and an image-forming lens 35. Then, the second eyeground image 46 is formed at an intermediate image-forming point M2 in front of a field lens 38. The main light, which is of the image-forming light flux forming the second eyeground image 46 and is conducted by an image pickup element of a TV camera, is made by the relay lens 40 to be light fluxes P1 and P2 parallel to a photographic light axis O1. Then, the image-forming light flux is made telecentric on the side of the image pickup element. And then, the third eyeground image 47 is formed on a photographic surface 42a of the image pickup element as a final image-forming surface.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an objective lens for guiding an image forming light beam forming an image of an eye to be examined to an image forming lens by an image taking optical system, and an intermediate image forming point near the field lens by the image forming lens. A relay lens for relaying the formed image-forming light flux to the image pickup surface of the image pickup device; and a lens that is inserted into or removed from the optical path of the photographing optical system or is moved along the optical path,
The field lens relates to an improvement of the ophthalmic photographing apparatus in which the focal length of the field lens is changed in order to keep the incident condition of the image forming light flux which is changed by the lens on the relay lens, and more specifically, the lens is For example, the present invention relates to an ophthalmologic photographing apparatus which is a variable magnification lens for changing photographing magnification, an anterior segment lens, and a diopter correction lens.

[0002]

2. Description of the Related Art Conventionally, a fundus camera having a structure shown in FIG. 1 has been known as an ophthalmologic photographing apparatus. In FIG. 1, 1 is an illumination optical system for illuminating the fundus 4 of the eye 3 to be inspected, and 2 is a photographing optical system. The photographic optical system 2 is the subject's eye 3
An objective lens 5 facing the aperture, a perforated mirror 6 having a hole portion 7 for passing an image forming light beam forming a fundus image as an eye image to be inspected, and a focusing lens 8 provided behind the perforated mirror 6. , An image forming lens 9 for forming an image forming light flux passing through the focusing lens 8 on an intermediate image forming point 16 near a field lens 11 which will be described later, and an electronic image capturing mode provided behind the image forming lens 9. Sometimes a quick return mirror 10 that reflects the image forming light beam toward the field lens 11.
A relay lens 13 for relaying an image forming light flux, which is once focused by the imaging lens 9 to an intermediate image forming point 16 near the field lens 11, to an image pickup surface 14a of an image pickup device 14 of a TV camera; Relay lens 1
3, a reflecting mirror 12 existing between the reflecting mirror 12 and the film 3, a film 15 disposed behind the quick return mirror 10, and a variable magnification lens 18 that can be inserted into and removed from the optical path of the photographing optical system 2. The variable-magnification lens 18 is for changing the photographing magnification, and is inserted in the optical path of the photographing optical system 2 when the angle of view of 20 degrees is selected with reference to the angle of view of 45 degrees, for example. The field lens 11 is located in the optical path of the photographing optical system 2 when the angle of view of 45 degrees is selected.
8 is inserted in the optical path of the photographing optical system 2 (that is, when the angle of view of 20 degrees is selected), the photographing optical system 2
Of the zoom lens 1 is retracted from the optical path of the field lens 11 and a field lens 11 ′ having a focal length different from that of the field lens 11 is inserted in the optical path instead of the field lens 11.
When 8 is inserted in the optical path of the photographing optical system 2, the incident condition of the image forming light flux on the relay lens 13 is not changed (for example, refer to Japanese Patent Laid-Open No. 4-295333).

Further, as shown in FIG. 2, when an angle of view of 20 degrees is selected on the basis of an angle of view of 45 degrees, the auxiliary lens 11 is provided in the optical path behind the field lens 11 of the photographing optical system 2.
a is inserted and the incident condition of the image forming light beam is set to the relay lens 13
There is also known a configuration that does not fluctuate.

A field stop 16 'is conventionally provided near the intermediate image forming point 16 shown in FIGS.
The reason for disposing the field lens 11 in the vicinity of the intermediate image formation point 16 so as to be displaced is to avoid image deterioration due to foreign matter such as dust and dirt attached to the field lens 11.

[0005]

However, in the case of the ophthalmic photographing apparatus shown in FIG. 1, since the field lens is provided in the vicinity of the intermediate image forming point 16 so that the focal length is short, There is a problem of focus shift and change of magnification due to replacement of the field lenses 11 and 11 'having different focal lengths.

On the other hand, also in the case of the ophthalmologic photographing apparatus shown in FIG. 2, the field lens is also provided in the vicinity of the intermediate image forming point 16 while being displaced, and the auxiliary lens 11 is inserted and removed to assist the field lens. Since the main plane due to the combination with the lens 11a also moves, the focus shift due to the insertion / removal of the auxiliary lens 11a into / from the optical path of the photographing optical system 2,
A change in magnification occurs.

The present invention has been made in view of the above circumstances. An object of the present invention is to provide an objective lens for guiding an image forming light flux forming an eye image by an image pickup optical system to an image forming lens, and A relay lens for relaying an image-forming light beam, which is once formed by an imaging lens at an intermediate image forming point near the field lens, to an image pickup surface of an image pickup element; and a relay lens which can be inserted into or removed from an optical path of the photographing optical system. And a lens that is movable along the optical path of the field lens in order to maintain the incident condition of the image forming light flux, which changes due to insertion or removal of the lens into or from the optical path, into the relay lens. In an ophthalmic imaging device whose focal length is changed,
Changing the focal length of the field lens in order to keep the incident condition on the relay lens of the image forming light flux that changes by inserting the lens into the optical path of the photographing optical system or moving the lens along the optical path. Provided is an ophthalmic photographing apparatus capable of preventing a focus shift and a change in magnification caused by the above.

[0008]

In order to solve the above-mentioned problems, an optical system of an ophthalmic photographing apparatus according to the present invention has an objective lens for guiding an image forming light beam forming an image of an eye to be examined to an imaging lens by the photographing optical system. A relay lens for relaying an image-forming light beam, which is once formed by the image forming lens at an intermediate image forming point near the field lens, to an image pickup surface of an image pickup element; Alternatively, a lens that is movable along the optical path is provided, and in order to maintain the incident condition on the relay lens of the image forming light flux that changes due to the insertion or removal of the lens to or from the optical path, An ophthalmic photographing apparatus in which the focal length of a field lens is changed, wherein the relay lens is an optical axis of the photographing optical system according to a change in the focal length of the field lens. A control means for controlling the movement of the image pickup device in the optical axis direction of the photographing optical system according to the change of the focal length of the field lens is provided. According to the third aspect of the present invention, the optical path length correcting optical element is inserted into and removed from the optical path of the photographing optical system behind the field lens according to the change of the focal length of the field lens.

[0009]

According to the first aspect of the invention, the relay lens is controlled to move in the optical axis direction of the photographing optical system according to the insertion / removal of the lens into the optical path of the photographing optical system or the movement along the optical path. According to the invention described in claim 2, the image pickup device is controlled to move in the optical axis direction of the photographing optical system, and according to the invention described in claim 3, the lens is inserted into or removed from the optical path of the photographing optical system or the optical path. The optical element for correcting the optical path length is inserted into or removed from the optical path according to the movement along the optical path.

[0010]

【Example】

(First Embodiment) In FIG. 3, 20 is an illumination optical system, and 21
Is a photographing optical system. The illumination optical system 20 is generally composed of a concave mirror 22, a halogen lamp 23 for illumination, a relay lens 24, a xenon lamp 25 for photographing, a condenser lens 26, a reflecting mirror 27, a ring slit 28, and a relay lens 29. The photographing optical system 21 includes an objective lens 31, a perforated mirror 30, a focusing lens 34, an imaging lens 35, a quick return mirror 37, a field lens 38, a reflection mirror 39, a relay lens 40, an image pickup element 42 of a TV camera, and a quick lens. The film 41 is generally arranged behind the return mirror 37. The perforated mirror 30 and the objective lens 31 are shared by the illumination optical system 20 and the photographing optical system 21, and the illumination light is reflected by the perforated mirror 30 toward the objective lens 31, whereby the fundus 33 of the eye 32 to be inspected. Illuminated. The reflected light flux from the fundus 33 is an objective lens 31 as an image-forming light flux that forms a fundus image.
It is guided to the focusing lens 34 through the hole 43 of the perforated mirror 30. The photographing optical system 21 includes the fundus 3 of the eye 32 to be inspected.
3 to the image pickup surface 42a of the image pickup element 42 as the final image formation surface
At least two intermediate imaging points M1, M in the optical path between
2 Between the image forming lens 35 and the quick return mirror 37, a variable power lens 36 for changing the photographing magnification is provided so that it can be inserted into and removed from the optical path of the photographing optical system 21. The field lens 38 is arranged near the intermediate image forming point M2 and immediately after the intermediate image forming point M2, and the field diaphragm 44 is arranged at the intermediate image forming point M2. An auxiliary lens 45 is inserted / removed in the optical path of the photographing optical system 21 between the relay lens 38 and the reflection mirror 39 according to the insertion / removal of the variable power lens 36 in / from the photographing optical system 21. This auxiliary lens 45 prevents the variation of the incident condition of the image forming light flux on the relay lens 40 (variation of the position of the entrance pupil of the relay lens 40) due to the insertion of the variable power lens 36 into the optical path of the photographing optical system 21. It serves to change the focal length of the field lens 38. The auxiliary lens 45 is automatically provided in response to the insertion of the variable power lens 36 into the optical path of the photographing optical system 21.
It is desirable to insert it in the optical path of
The examiner may manually insert the photographing optical system 2 according to the insertion of the photographing optical system 2 into the optical path. The relay lens 40 is an auxiliary lens 45.
The fine movement is adjusted along the optical axis O1 of the photographing optical system 21 in accordance with the amount of shift of the focus position due to the insertion / removal into / from the optical path. This fine movement adjustment is automatically performed by a pulse motor (not shown), but the examiner may manually adjust it while looking at the display of the TV camera.

Next, the operation of this embodiment will be described.

FIG. 4 is a schematic optical diagram of the photographing optical system 21, showing principal rays when photographing the fundus 33 at an angle of view of 45 degrees. The reflected light flux from the fundus 33 is the objective lens 3
1 forms a first fundus image 45 at the intermediate image formation point M1.
The chief ray forming the first fundus image 45 passes through the center 43 ′ of the hole portion 43 of the perforated mirror 30, which functions as an aperture stop, and is guided to the focusing lens 34 and the imaging lens 35, and the field lens 38. The second fundus image 46 is formed at the intermediate image formation point M2 in the foreground. The chief ray that is an image forming light flux forming the second fundus image 46 and is guided to the image pickup element 42 of the TV camera is made into parallel light fluxes P1 and P2 with respect to the photographing optical axis O1 by the relay lens 40. That is, the image forming light flux is image-side telecentric on the side of the image pickup device 42, and the third fundus image 4 is formed on the image pickup surface 42a of the image pickup device 42 as the final image forming surface.
7 is formed. An exit pupil 48 (an entrance pupil of the relay lens 40) as an image of the aperture stop is formed at a point M between the field lens 38 and the relay lens 40.

FIG. 5 is an optical diagram schematically showing the photographing optical system as in FIG. 4, and shows the chief ray when photographing the fundus 33 at an angle of view of 20 degrees. In this case, the variable magnification lens 35 is inserted in the optical path of the photographing optical system 21, and the auxiliary lens 4 is inserted as the variable magnification lens 35 is inserted in the optical path of the photographing optical system 21.
5 is inserted in the optical path of the photographing optical system 21. By inserting the auxiliary lens 45, the position of the exit pupil 48 can be prevented from shifting from the point M. In this case, the insertion of the auxiliary lens 45 changes the combined focal length of the field lens 46 and the auxiliary lens 45. Since the field lens 38 is displaced from the intermediate image formation point M2 in order to avoid image deterioration due to foreign matter such as dust and dirt attached to the field lens 38, the focus position on the final image formation plane is displaced. However, in order to eliminate this focus shift, the relay lens 40 is moved along the photographing optical axis O1. For example, when the auxiliary lens 45 having a positive power is used, the focus position moves to the right in FIG. 3, so the relay lens 40 is moved to the right,
When the auxiliary lens 45 having a negative power is used, the focus position moves to the left in FIG. 3, so the relay lens 40 is moved to the left.

In the first embodiment, the auxiliary lens 4
By inserting No. 5 into the optical path of the photographing optical system 21, fluctuations in the incident condition of the image forming light flux to the relay lens 40 due to the insertion of the variable power lens 36 into the optical path of the photographing optical system 21 are prevented. Instead of inserting the lens 45 into the optical path of the photographing optical system 21, the variable magnification lens 36 is used.
When it is inserted into the optical path of No. 1, the field lens 38 is retracted from the optical path, and the field lens 38 having a focal length shorter than the focal length of the field lens 38 is inserted.
It is also possible to prevent the fluctuation of the incident condition of the image forming light flux on the relay lens 40 due to the insertion of the variable magnification lens 36 into the optical path of the photographing optical system 21 by inserting ′ in the optical path of the photographing optical system 21.

Although the relay lens 40 is moved along the photographing optical axis O1 of the photographing optical system 21 in the first embodiment, the image pickup element 42 may be moved along the photographing optical axis O1. good.

(Second Embodiment) In the second embodiment, instead of moving the relay lens 40 along the photographing optical axis O1 in accordance with the insertion of the correction lens 45 into the optical path of the photographing optical system 21, FIG. As shown in FIG. 1, the optical path length correction lens 49 is provided between the relay lens 40 and the reflection mirror 39.
Of the field lens 3 according to the change in the focal length of the field lens 38.
By inserting the optical element for correcting the optical path length in the optical path of the photographing optical system 21 at the rear of 8, the focus shift on the final image plane is prevented.

Since the relay magnification of the relay lens 40 is generally smaller than 1 (about 0.2 times), a parallel plane plate is used as the optical path length correcting optical element instead of the optical path length correcting lens 49. You may use.

(Third Embodiment) The third embodiment will be described with reference to FIGS.

In the third embodiment, as shown in FIG. 7, a variable field stop 44 'is provided at the intermediate image forming point M2, and the other configurations are the same as those shown in FIG. The focus deviation can be corrected by moving the relay lens 40 along the photographing optical axis O1 as the correction lens 45 is inserted into the optical path of the photographing optical system 21.
However, only by moving the relay lens 40 along the photographing optical axis O1, it is not possible to correct the magnification change of the fundus image due to the insertion of the correction lens 45 into the optical path of the photographing optical system 21. That is, as shown in FIG. 8, it is assumed that the fundus image indicated by the reference numeral 51 and the field stop image indicated by the reference numeral 52 are displayed on the display 50 of the TV camera when the angle of view is 45 degrees. When it is inserted into the optical path of the optical system 21 and the angle of view is changed to 20 degrees, the field stop image 52 is shown in FIG.
In some cases, as shown by reference numeral 52 ', the projection 50 may be projected from the display 50, and in order to avoid this, the aperture diameter of the field stop 44' is adjusted.

(Fourth Embodiment) This fourth embodiment is shown in FIG.
As shown in FIG.
a, 40b, 40c, and moves at least two lenses of the three relay lenses 40a, 40b, 40c along the photographing optical axis O1 according to the insertion of the correction lens 45 into the optical path of the photographing optical system 21. In this configuration, both the focus shift and the magnification change due to the change in the focal length of the field lens 38 are prevented. In this embodiment, it is not necessary to change the field stop 44 and move the image pickup element 42 of the TV camera.

By the way, in the first to fourth embodiments, the variable power lens 36 changes the condition of incidence on the relay lens 40, but the same applies to the anterior segment lens and the diopter correction lens. Further, the focusing lens or the variable power lens that moves on the optical axis may be a zoom lens.

[0022]

[Effect] Since the present invention is configured as described above,
An objective lens that guides an image forming light beam, which forms an image of the eye to be inspected, to an image forming lens by a photographing optical system, and an image forming light beam that is once formed by the image forming lens at an intermediate image forming point in the vicinity of a field lens. A relay lens that relays to the imaging surface,
A lens which is inserted into or removed from the optical path of the photographing optical system or is moved along the optical path, and the incident condition to the relay lens of the image forming light flux which changes due to the insertion and removal of the lens is maintained substantially constant. In the ophthalmic photographing apparatus in which the focal length of the field lens is changed in order to maintain the incident condition on the relay lens of the image forming light flux which is changed by the insertion / removal / movement of the lens in the optical path of the photographing optical system, is kept constant. Therefore, there is an effect that it is possible to prevent out-of-focus and change in magnification due to changing the focal length of the field lens.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of an optical system of a conventional ophthalmic imaging apparatus.

FIG. 2 is a diagram showing another example of an optical system of a conventional ophthalmic imaging apparatus.

FIG. 3 is a diagram showing a first embodiment of the optical system of the ophthalmologic photographing apparatus according to the present invention.

FIG. 4 is a schematic diagram of a photographing optical system according to a first embodiment,
It is a figure for demonstrating the effect | action of a photography optical system in case an angle of view is 45 degrees.

FIG. 5 is a schematic view of the taking optical system according to the first embodiment,
It is a figure for explaining the operation of the photographing optical system when the angle of view is 20 degrees.

FIG. 6 is a diagram showing a second embodiment of the optical system of the ophthalmic photographing apparatus according to the present invention.

FIG. 7 is a diagram showing a third embodiment of the optical system of the ophthalmologic photographing apparatus according to the present invention.

FIG. 8 is an explanatory diagram of a fundus image on the display when the image is captured at an angle of view of 45 degrees.

FIG. 9 is an explanatory diagram of a fundus image on the display when the image is captured at an angle of view of 20 degrees.

FIG. 10 is a diagram showing a fourth embodiment of the optical system of the ophthalmologic photographing apparatus according to the present invention.

[Explanation of symbols]

 21 ... Shooting optical system 31 ... Objective lens 32 ... Eye image 36 ... Variable-magnification lens 38 ... Field lens 40 ... Relay lens O1 ... Shooting optical axis M2 ... Intermediate imaging point

Claims (7)

[Claims] 1. An objective lens for guiding an image forming light flux forming an image of a subject's eye to an image forming lens by a photographing optical system, and an image forming image once formed by the image forming lens at an intermediate image forming point near a field lens. A relay lens that relays the light flux to the image pickup surface of the image pickup device; and a lens that can be inserted into and removed from the optical path of the photographing optical system or that can be moved along the optical path,
In an ophthalmic imaging apparatus in which the focal length of the field lens is changed in order to maintain the incident condition of the image forming light flux that changes by inserting or removing the lens into or from the optical path to the relay lens, An ophthalmic photographing apparatus provided with control means for controlling movement of a relay lens in the optical axis direction of the photographing optical system according to a change in focal length of the field lens. 2. An objective lens, which guides an image forming light flux forming an image of an eye to be examined, to an image forming lens by a photographing optical system, and an image forming image once formed by the image forming lens at an intermediate image forming point near a field lens. A relay lens that relays the light flux to the image pickup surface of the image pickup device; and a lens that can be inserted into and removed from the optical path of the photographing optical system or that can be moved along the optical path,
In the ophthalmic photographing apparatus in which the focal length of the field lens is changed in order to maintain the incident condition of the image forming light flux, which is changed by inserting or removing the lens into or from the optical path, to the relay lens, An ophthalmic photographing apparatus provided with control means for controlling movement of the image pickup element in the optical axis direction of the photographing optical system according to a change in the focal length of the field lens. 3. An objective lens for guiding an image forming light flux forming an image of an eye to be inspected to an imaging lens by an imaging optical system, and an image formation once formed by the imaging lens at an intermediate imaging point near a field lens. A relay lens that relays the light flux to the image pickup surface of the image pickup device; and a lens that can be inserted into and removed from the optical path of the photographing optical system or that can be moved along the optical path,
In an ophthalmic imaging apparatus in which the focal length of the field lens is changed in order to maintain the incident condition of the image forming light flux that changes by inserting or removing the lens into or from the optical path to the relay lens, An ophthalmologic image taking apparatus in which an optical element for correcting an optical path length is inserted into and removed from an optical path of the taking optical system behind the field lens according to a change in a focal length of the field lens. 4. The method according to claim 1, wherein the focal length of the field lens is changed by an auxiliary lens that is inserted into and removed from the optical path of the photographing optical system behind the field lens. The ophthalmic imaging device described. 5. The auxiliary lens inserted into and removed from the optical path between the field lens and the optical element for correcting the optical path between the field lens and the optical element for correcting the optical path to change the focal length of the field lens. The ophthalmic imaging device described. 6. A field diaphragm is provided at an intermediate image forming point near the field lens, and an aperture diameter of the field diaphragm is changed according to a change in a focal length of the field lens. To any one of claims 3 to 3
The ophthalmic imaging device according to the item. 7. The ophthalmic photographing apparatus according to claim 1, wherein the lens is a variable power lens that changes a photographing magnification.