Ophthalmic optical systems and ophthalmic devices

Abstract

To provide a compact ophthalmic optical system and ophthalmic device that allows for fundus observation even without a large observation space and enables small pupil photography. [Solution] The ophthalmic optical system and ophthalmic apparatus include a light source for illuminating the fundus and an optical system that forms an image conjugate to the pupil of the eye under examination. The optical system forms an image of the light beam emitted from the cornea of ​​the eye under examination, with the fundus of the eye under examination as the object point, in a straight line from the eye under examination side to the observation side. It comprises a lens group G1 with a common positive refractive power for fundus imaging and fundus illumination, a lens group G2 with a positive refractive power that re-images the image point of lens group G1 as the object point, a lens group G3 that emits the image point of lens group G2 as the object point in a substantially afocal manner, a field diaphragm ST located between lens group G1 and lens group G2, and a field diaphragm ST2 located between lens group G2 and lens group G3. The optical path for fundus imaging and fundus illumination does not have an optical path splitting element or an optical path bending element.

Description

[Technical Field]

[0001] The present invention relates to an ophthalmic optical system and an ophthalmic apparatus capable of observing and imaging the fundus of a subject's eye with a small pupil diameter, which is used in ophthalmology clinics, internal medicine clinics, physical examinations and the like. [Background Art]

[0002] Conventional fundus observation apparatuses each have drawbacks. For example, a direct ophthalmoscope has a high observation magnification but an observation viewing angle of only about 5 degrees, so that only the optic disc or the fovea centralis can be observed. Furthermore, it is necessary to get very close to the subject. In contrast, an indirect ophthalmoscope has a wide observation field of view, and can observe retinal capillaries in addition to the optic disc and fovea centralis. However, with an indirect ophthalmoscope, the examiner holds the indirect mirror and the condenser lens with separate hands, and must observe the fundus of the subject while adjusting the distance and angle between the two hands, as well as the axes of the condenser lens and the indirect mirror, and the axes of the examiner and the indirect mirror. In addition, the fundus image of the subject is an inverted image, so training is required. [Prior Art Documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Laid-Open Publication No. 50-136023 [Patent Document 2] Japanese National Publication of International Patent Application No. 2019-526346 [Summary of the Invention] [Problem to be Solved by the Invention]

[0004] For example, Patent Document 1 discloses a system in which a ring slit is used for fundus illumination light flux to project an annular light flux onto a subject's eye, and the fundus reflected light flux passes through the central part of the annular light flux for fundus illumination and is received by a fundus camera, thereby suppressing the generation of ghost and flare caused by corneal reflected light and obtaining a clear fundus image.

[0005] However, in such optical systems, the light source of the illumination system is significantly bent by a mirror, making the entire system large and difficult to carry. It also requires a large observation and diagnostic space. Although it is used in tabletop fundus cameras, it is not suitable for observing the fundus of certain special subjects, such as infants, bedridden patients, and people with disabilities.

[0006] Furthermore, observing the eye in a dilated state requires the use of pupil-dilating drugs, which presents problems such as side effects and prolonged discomfort until the effects of the drugs wear off. On the other hand, fundus photography in a naturally dilated state is sometimes performed by shading the area around the eye being examined to induce natural pupil dilation, focusing on the fundus with infrared light, and flashing a strong light source instantaneously (so-called strobe light), but this causes discomfort for the patient. In addition, if the relationship between the pupil diameter of the eye being examined and the entrance pupil diameter of the imaging system is not efficient, the intensity of the illumination light source can be too strong, causing discomfort for the patient.

[0007] Furthermore, Patent Document 2 describes a method in which a smartphone with a camera (hereinafter referred to as "smartphone") is used as the observation device, and is directly attached to the observation optical system, and the fundus image is displayed and captured using its display function.

[0008] However, because the fundus camera optical system only has a primary image-forming point, it is necessary to process the image in the smartphone to convert it to an upright image. Furthermore, when the smartphone is removed and the image is observed with the naked eye, there is a problem of an inverted image.

[0009] This invention has been made in view of the above circumstances, and aims to provide an ophthalmic optical system and ophthalmic device that overcomes the aforementioned drawbacks, is compact, allows observation of the fundus even without a large observation space, enables small pupil imaging for fundus photography of eyes with only small pupils, appropriately maintains the pupil diameter of the eye under examination and the entrance pupil diameter of the imaging system, allows direct observation of an upright image without image conversion even when attached to observation devices such as human eyes or smartphones, and satisfies the optical arrangement for efficiently acquiring reflected light beams from the fundus, thereby reducing the luminosity of the illumination light source so as not to cause discomfort to the subject. [Means for solving the problem]

[0010] To achieve the above-mentioned objectives, the present invention provides an ophthalmic optical system that includes a light source for illuminating the fundus and an optical system that forms an image conjugate to the pupil of the eye under examination. The optical system is arranged in a straight line and, in order from the eye under examination side to the observation side, images the light beam emitted from the cornea of ​​the eye under examination with the fundus of the eye under examination as the object point. It comprises a lens group G1 with a common positive refractive power for fundus imaging and fundus illumination, a lens group G2 with a positive refractive power that re-images the image point of lens group G1 as the object point, a lens group G3 that emits the image point of lens group G2 as the object point in a substantially afocal manner, a field diaphragm ST located between lens group G1 and lens group G2, and a field diaphragm ST2 located between lens group G2 and lens group G3. The optical system is characterized in that it does not have optical path splitting elements or optical path bending elements in the optical path for fundus imaging and fundus illumination.

[0011] Furthermore, the ophthalmic apparatus according to the present invention is characterized by comprising an observation device and the above-mentioned ophthalmic optical system. [Effects of the Invention]

[0012] According to the present invention, these configurations make it possible to prevent overlap between unwanted ghosting light from corneal reflection of illumination light and observation light from fundus reflection, even when the pupil of the eye being examined is constricted, without increasing the overall size of the system or dilating the pupil of the eye being examined with a pupil-dilating drug. Furthermore, even when the eye being examined is nearsighted or farsighted, observation similar to that of an emmetropic eye becomes possible by moving the focus group in the optical system to an appropriate position. [Brief explanation of the drawing]

[0013] [Figure 1] A schematic diagram illustrating the principle of an ophthalmic optical system and ophthalmic device, which is one embodiment of the present invention. [Figure 2] A schematic diagram showing an example of the shape of lens group G2A as viewed from the eye side and the positional relationship of the light source. [Figure 3]FIG. 1 is a lens configuration diagram of an optical system in the ophthalmic optical system of the present invention. [Figure 4(a)] Longitudinal aberration diagram of the optical system of Example 1 at an infinite imaging distance. [Figure 4(b)] Longitudinal aberration diagram of the optical system of Example 1 at an infinite imaging distance when the G2IF group is shifted by 1 mm in a direction orthogonal to the optical axis. [Figure 5(a)] Lateral aberration diagram of the optical system of Example 1 at an infinite imaging distance. [Figure 5(b)] Lateral aberration diagram of the optical system of Example 1 at an infinite imaging distance when the G2IF group is shifted by 1 mm in a direction orthogonal to the optical axis. [Figure 6] FIG. 2 is a lens configuration diagram of an optical system in the ophthalmic optical system of the present invention. [Figure 7(a)] Longitudinal aberration diagram of the optical system of Example 2 at an infinite imaging distance. [Figure 7(b)] Longitudinal aberration diagram of the optical system of Example 2 at an infinite imaging distance when the G2IF group is shifted by 1 mm in a direction orthogonal to the optical axis. [Figure 8(a)] Lateral aberration diagram of the optical system of Example 2 at an infinite imaging distance. [Figure 8(b)] Lateral aberration diagram of the optical system of Example 2 at an infinite imaging distance when the G2IF group is shifted by 1 mm in a direction orthogonal to the optical axis. [Figure 9] FIG. 3 is a lens configuration diagram of an optical system in the ophthalmic optical system of the present invention. [Figure 10(a)] Longitudinal aberration diagram of the optical system of Example 3 at an infinite imaging distance. [Figure 10(b)] Longitudinal aberration diagram of the optical system of Example 3 at an infinite imaging distance when the G2IF group is shifted by 1 mm in a direction orthogonal to the optical axis. [Figure 11(a)] Lateral aberration diagram of the optical system of Example 3 at an infinite imaging distance. [Figure 11(b)] Lateral aberration diagram of the optical system of Example 3 at an infinite imaging distance when the G2IF group is shifted by 1 mm in a direction orthogonal to the optical axis. [Figure 12] FIG. 4 is a lens configuration diagram of an optical system in the ophthalmic optical system of the present invention. [Figure 13(a)]Longitudinal aberration diagram of the optical system of Example 4 at an infinity shooting distance. [Figure 13(b)] This diagram shows the longitudinal aberration of the optical system in Example 4 when the shooting distance is infinity and the G2IF group is shifted by 1 mm in a direction perpendicular to the optical axis. [Figure 14(a)] Transverse aberration diagram of the optical system of Example 4 at an infinity shooting distance. [Figure 14(b)] This diagram shows the lateral aberration of the optical system in Example 4 when the shooting distance is infinity and the G2IF group is shifted by 1 mm in a direction perpendicular to the optical axis. [Figure 15] Lens configuration diagram of Embodiment 5 of the optical system in the ophthalmic optical system of the present invention. [Figure 16(a)] Longitudinal aberration diagram of the optical system of Example 5 at an infinity shooting distance. [Figure 16(b)] This diagram shows the longitudinal aberration of the optical system in Example 5 when the shooting distance is infinity and the G2IF group is shifted by 1 mm in a direction perpendicular to the optical axis. [Figure 17(a)] Transverse aberration diagram of the optical system of Example 5 at an infinity shooting distance. [Figure 17(b)] This diagram shows the lateral aberration of the optical system in Example 5 when the shooting distance is infinity and the G2IF group is shifted by 1 mm in a direction perpendicular to the optical axis. [Modes for carrying out the invention]

[0014] The following describes the ophthalmic optical system and ophthalmic apparatus of this embodiment. Note that the following description of the embodiment illustrates an example of the ophthalmic optical system and ophthalmic apparatus of the present invention, and the present invention is not limited to this embodiment without departing from its spirit.

[0015] Figure 1 shows a schematic diagram illustrating the principle of an ophthalmic optical system and ophthalmic device, which is one embodiment of the present invention. As shown in this figure, the ophthalmic optical system is attached to an observation device and together constitutes an ophthalmic device.

[0016] The ophthalmic optical system embodying the present invention includes a light source composed of one or more visible light-emitting diode light sources that illuminate the fundus of the eye under examination, and the optical path for fundus imaging and fundus illumination does not have optical path splitting elements such as beam splitters, or optical path bending elements such as mirrors or prisms.

[0017] As shown in this figure, in the ophthalmic optical system embodying the present invention, the eye under examination is positioned to the left of lens group G1, and the position of the cornea and pupil area of ​​the eye under examination is approximately aligned with the aperture diaphragm of the ophthalmic optical system. As a result, information from the fundus of the eye under examination is read by the ophthalmic optical system and observed by the observer's own eye or by an observation device attached behind the ophthalmic optical system. An example of an observation device is a smartphone with a camera (hereinafter referred to as a smartphone).

[0018] The optical system in the ophthalmic optical system consists of, in order from the eye being examined to the observation side, a lens group G1 with positive refractive power, a lens group G2 with positive refractive power, and a lens group G3 with positive refractive power. A field diaphragm ST is located between lens group G1 and lens group G2, and a field diaphragm ST2 is located between lens group G2 and lens group G3.

[0019] Lens group G1 forms an image of the light beam emitted from the cornea of ​​the eye under examination, using the fundus of the eye under examination as the object point, and is used for fundus imaging and fundus illumination. Lens group G2 re-images using the image point of lens group G1 as the object point. Lens group G3 emits an image approximately afocal, using the image point of lens group G2 as the object point. The light source is positioned between the field diaphragm ST and lens group G2, and shifted perpendicular to the optical axis. In this figure, it is shifted downward.

[0020] In systems that have optical path splitting elements such as beam splitters or optical path bending elements such as mirrors and prisms in the optical path for fundus imaging and illumination, the illumination light source is significantly eccentric from the imaging optical path, resulting in a larger overall system size. By configuring the system without using optical path splitting elements or optical path bending elements, as in the present invention, it is possible to miniaturize the entire system and reduce the causes of astigmatism. Furthermore, the optical system is an afocal optical system that images the light beam emitted from the cornea of ​​the eyeball with the fundus as a point by lens group G1, then re-images that image point by lens group G2, and then emits the re-imaged image point approximately afocal by lens group G3. Because it is an afocal optical system that images twice within the system, the fundus can be observed as an upright image when viewed with the human eye or a smartphone, improving visibility. In addition, by having a field diaphragm ST2 between lens group G2 and lens group G3, it is possible to eliminate unwanted light and efficiently observe the light reflected from the fundus of the subject.

[0021] Furthermore, in the ophthalmic optical system implementing the present invention, lens group G2 includes lens group G2A, which emits the light beam from lens group G1 approximately afocally towards the eye being examined, and focus group G2IF, which focuses for fundus imaging. In this figure, the left and right arrows shown below focus group G2IF indicate that it has the function of focusing for fundus imaging in accordance with the refractive power of the eye being examined.

[0022] By positioning lens group G2A, which makes the light beam from lens group G1 approximately afocal, on the side of lens group G2 closest to the eye being examined, the focusing conditions of the subsequent focusing group G2IF are met. This allows the focusing function of focusing group G2IF, which moves back and forth in the optical axis direction, to compensate for the shift in the position of the fundus object due to the strength of the subject's visual acuity, thereby enabling the observation image to be brought into focus.

[0023] Furthermore, the ophthalmic optical system embodying the present invention satisfies the following condition (1). (1) 0.25 <M<1.0 however, M: Afocal magnification of the optical system

[0024] Condition (1) defines the afocal magnification of the optical system and is a condition for efficiently directing the light beam into the entrance pupil of the observation device, such as a smartphone, even when the eye under examination is in a constricted pupil state, and furthermore, a condition that enables effective utilization of the optical performance of the smartphone. In addition, the value of the afocal magnification M of the optical system is set to positive in order to observe the image as an upright image.

[0025] If the axial light beam diameter emitted from the optical system is Φe', then Φe' is equal to the pupil diameter of the eye under examination when constricted, and M is the afocal magnification of the optical system. Φe' = Φe / M Therefore, when the pupil diameter Φe of the eye under examination is kept constant, the axial light beam diameter Φe' emitted from the optical system varies depending on the afocal magnification M.

[0026] Here, if we denote the entrance pupil diameter of the observation device as Φod, then Φod is determined by the image sensor size, focal length, and F-number of the observation device. Therefore, the diameter of the light beam emitted from the optical system, Φe', must take this into account for effectiveness. For example, the specifications of lenses and image sensors installed in recent smartphones include a 35mm equivalent focal length of 26mm, an F-number of 1.6, and an image sensor size of 1 / 1.56 inch (such as the wide-angle lens of Apple's iPhone (registered trademark, hereafter the same) 15), with a diagonal length of 10.24mm.

[0027] Therefore, the actual focal length fi of a smartphone lens is calculated from the ratio of the actual image sensor size to the diagonal length of a 35mm format, which is 43.26mm. fi=26mm×(10.24mm / 43.26mm)=6.15mm Therefore, the entrance pupil diameter Φod calculated from the F-number 1.6 is, Φod=fi / F=3.84mm This is the result.

[0028] Furthermore, the specifications of the lens and image sensor installed in another smartphone include a 35mm equivalent focal length of 26mm, an f / 1.6 aperture, and an image sensor size of 1 / 1.88 inch (such as the wide-angle lens in Apple's iPhone 13), with a diagonal length of 8.5mm.

[0029] Therefore, the actual focal length fi of a smartphone lens is calculated from the ratio of the actual image sensor size to the diagonal length of a 35mm format, which is 43.26mm. fi=26mm×(8.5mm / 43.26mm)=5.11mm Therefore, the entrance pupil diameter Φod calculated from the F-number 1.6 is, Φod=fi / F=3.19mm That is the case.

[0030] Here, the relationship between the on-axial light beam diameter Φe' emitted from the optical system and the entrance pupil diameter Φod of the observation device is as follows: Φe'<Φod In this case, the on-axial light beam diameter emitted from the optical system is relatively small, so the observation device is used with a narrowed F-number, which reduces the resolution that the observation device can inherently possess due to diffraction. In addition, the tolerance for misalignment between the observation device and the optical axis becomes stricter, making the field of view more prone to vignetting.

[0031] On the other hand, the relationship between the on-axial light beam diameter Φe' emitted from the optical system and the entrance pupil diameter Φod of the observation device is, Φe'≧Φod In this case, since the on-axial light beam diameter emitted from the optical system is equal to or greater than that of the observation device, the tolerance for misalignment between the observation device and the optical axis of the optical system becomes looser, making observation easier. Also, since the observation device can be used with its f-number wide open, higher resolution observation becomes possible as the performance of the observation device approaches that of a diffraction-limited system. Furthermore, since the observation device can be used in a wide-open state, the field of view becomes brighter.

[0032] Therefore, the relationship between the on-axial light beam diameter Φe' emitted from the optical system and the entrance pupil diameter Φod of the observation device is Φe'≧Φod It is desirable that this be the case.

[0033] Based on the above, when the entrance pupil diameter Φod of the observation device is set to be the same as the diameter of the light beam Φe' emitted from the optical system, and the pupil diameter of the eye under examination when constricted is Φe = 2.0, the afocal magnification M can be calculated as follows. M = 2.0 / 3.84 = 0.52 M = 2.0 / 3.19 = 0.63 Furthermore, assuming that the pupil diameter of the eye under examination when constricted is Φe = 3.0, M = 3.0 / 3.84 = 0.78 M = 3.0 / 3.19 = 0.94 Therefore, the afocal magnification M is, M<1.0 That is the case.

[0034] When the afocal magnification of the optical system decreases beyond the lower limit, the power of lens group G3 decreases, the effective diameter increases, and the on-axial light beam diameter emitted from the optical system must also increase, resulting in a larger optical system. Furthermore, the entrance pupil diameter of the observation device must be increased, making it difficult to realize a compact lens that can be mounted on a smartphone. On the other hand, when the afocal magnification increases beyond the upper limit, the on-axial light beam diameter emitted from the optical system decreases, and the observation device is used with a narrowed F-number, so the resolution that the observation device inherently possesses decreases due to the effects of diffraction. In addition, the tolerance for misalignment between the observation device and the optical axis of the optical system becomes stricter, and the field of view is more prone to vignetting.

[0035] Furthermore, regarding condition (1), it is more desirable to further limit its lower limit to 0.38, as this will suppress the need to enlarge the optical system. Also, it is more desirable to further limit its upper limit to 0.75, as this will make it easier to relax the tolerance for misalignment between the observation device and the optical axis of the optical system.

[0036] Furthermore, in the ophthalmic optical system embodying the present invention, the light source is positioned between the field diaphragm ST and the lens group G2, and is shifted upward and downward relative to the optical axis. This light source is imaged near the cornea of ​​the eye being examined by the lens group G1, and then diverges, passing through the pupil and illuminating the fundus.

[0037] This separates the optical paths of the light used for fundus observation and the light reflected from the cornea, making it easier to observe the fundus.

[0038] Furthermore, the ophthalmic optical system embodying the present invention satisfies the following condition (2). (2) 1.6mm <|S·M1| < 5.0mm however, M1: Lateral magnification of lens group G1, with the light source as the object point and the cornea of ​​the eye being examined as the image point. S: Amount of shift (mm) from the optical axis of a light source that has been shifted perpendicular to the optical axis.

[0039] The illumination system for illuminating the fundus of the eye under examination utilizes lens group G1, which alone forms an image of the light source onto the cornea of ​​the eye under examination. The illumination beam formed on the cornea of ​​the eye under examination passes through the pupil and diverges according to the aperture angle of lens group G1 and the light distribution angle of the light source, illuminating the fundus of the eye under examination. The fundus illumination light that reaches the fundus of the eye under examination travels backward through the ocular optical system as reflected light (fundus information) and is emitted from the cornea of ​​the eye under examination. After that, it passes through the optical system and reaches the observation device.

[0040] In the ophthalmic optical system implementing the present invention, the optical path for fundus imaging and fundus illumination does not have optical path splitting elements such as beam splitters, or optical path bending elements such as mirrors or prisms. Therefore, in order to illuminate the fundus, the light source must be positioned at a location shifted perpendicular to the optical axis. Furthermore, the light source must be placed in a position that does not interfere with the optical path for observing the fundus image after illumination, and the condition for this is given by condition (2).

[0041] If the product of the lateral magnification of lens group G1, with the light source illuminating the fundus as a point object, and the amount of shift of the light source from the optical axis in a direction perpendicular to the optical axis becomes small beyond the lower limit, the light source approaches the observation light path and interferes with the observation light path, which is undesirable. On the other hand, if the product of the lateral magnification of lens group G1, with the light source illuminating the fundus as a point object, and the amount of shift of the light source from the optical axis in a direction perpendicular to the optical axis becomes large beyond the upper limit, the light source image on the cornea is significantly deviated from the optical axis, preventing the light beam of the light source image intended to illuminate the fundus from passing through the pupil of the constricted eye being examined, and thus the fundus cannot be illuminated.

[0042] Furthermore, regarding condition (2), it is more desirable to further limit the lower limit to 2.5, as this makes it possible to suppress the approach of the light source to the observation light path. Also, it is more desirable to further limit the upper limit to 4.1, as this makes it easier to reduce the deviation of the light source image on the cornea from the optical axis.

[0043] Furthermore, the light source is capable of shifting in a direction perpendicular to the optical axis during fundus observation using a known mechanism. The up and down arrows shown adjacent to the light source in this figure indicate that the amount of shift of the light source in a direction perpendicular to the optical axis is variable during fundus observation.

[0044] By changing the amount of shift during fundus observation, it is possible to reduce the overlap between corneal ghosting and the fundus observation light.

[0045] Furthermore, the ophthalmic optical system embodying the present invention satisfies the following condition (3). (3) 0.7mm <|DL·M1| < 2.8mm however, DL: Light source diameter (mm) M1: Lateral magnification of lens group G1, with the light source as the object point and the cornea of ​​the eye being examined as the image point.

[0046] As mentioned above, the illumination system for illuminating the fundus of the eye under examination utilizes lens group G1, and this lens alone forms a light source image onto the cornea of ​​the eye under examination. The illumination beam formed on the cornea of ​​the eye under examination passes through and diverges through the pupil according to the aperture angle of lens group G1 and the light distribution angle of the light source, illuminating the fundus of the eye under examination. Therefore, the size of the light source image formed on the cornea is an important value that affects the tolerance of the position through which the illumination beam passes when it passes through the constricted pupil of the eye under examination.

[0047] If the lower limit is exceeded and the diameter of the light source illuminating the fundus becomes smaller, or if the lateral magnification of lens group G1, with the light source as the object point and the cornea of ​​the eye under examination as the image point, becomes smaller, the image of the light source on the cornea becomes smaller, making it difficult to pass the illumination light through the constricted pupil. Also, as the distance between the objective lens and the eye under examination decreases, the objective lens is more likely to interfere with the eye under examination, making it difficult to safely observe the eye under examination. On the other hand, if the upper limit is exceeded and the diameter of the light source becomes larger, or if the lateral magnification of lens group G1, with the light source as the object point and the cornea of ​​the eye under examination as the image point, becomes larger, the reflected ghost from the cornea becomes larger, and the reflected light from the fundus overlaps with this ghost, making it difficult to observe the fundus.

[0048] Furthermore, regarding condition (3), it is more desirable to further limit the lower limit to 1.1, as this makes it easier for illumination light to pass through the constricted pupil. Also, it is more desirable to further limit the upper limit to 2.1, as this makes it easier to suppress reflective ghosting from the cornea.

[0049] Furthermore, in the ophthalmic optical system that embodies the present invention, the lens group G2A closest to the eye being examined within the lens group G2 is non-circular, and has a notched or perforated shape. Figure 2 shows a schematic diagram illustrating an example of the relationship between the shape of this lens group G2A as seen from the eye side and the position of the light source.

[0050] Lens group G2A needs to have the largest possible diameter to guide the divergent light beam from lens group G1 as approximately afocal light to the subsequent focusing group G2IF. However, since a light source shifted relative to the optical axis is placed nearby, interference with the light source is likely. Furthermore, since the image of the light source itself is formed near the cornea of ​​the eye being examined by lens group G1, it is desirable to increase the distance from lens group G1 to the light source in order to make the image of the light source as small as possible. However, the distance to the light source is naturally limited by the presence of lens group G2A.

[0051] Therefore, the shape of lens group G2A is made non-circular, or more specifically, it is made by cutting out an arc shape from the outer edge of lens group G2A at a position close to the optical axis by the diameter of the light source, or by drilling a hole from the outer edge of lens group G2A at a position close to the optical axis by the diameter of the light source. The light source is then placed in this cutout or hole. This allows the light source to be positioned without interfering with lens group G2A, thus increasing the degree of freedom in the lateral magnification of lens group G1, where the light source illuminating the fundus of the eye under examination is the object point and the cornea of ​​the eye under examination is the image point. The amount by which the cutout or hole approaches the outer edge of lens group G2A in the direction of the optical axis is set to a maximum of the diameter of the light source and a minimum of zero. A minimum of zero means that the light source is in contact with lens group G2A.

[0052] Furthermore, in the ophthalmic optical system implementing the present invention, the focus group G2IF is positioned shifted perpendicular to the optical axis in the same direction as the shift direction of the light source. In Figure 1, it is shifted downwards.

[0053] By positioning the G2IF focus group in the same direction as the light source and shifted perpendicular to the optical axis, it becomes possible to efficiently observe the reflected light from the subject's fundus while avoiding corneal reflection. Furthermore, by changing the amount of this shift during fundus observation, it is possible to reduce the overlap between corneal ghosting and the fundus observation light.

[0054] Furthermore, the ophthalmic optical system embodying the present invention satisfies the following condition (4). (4) 0.25mm <|G2IFS·M2| <3.0mm however, G2IFS: The amount of shift (mm) from the optical axis of the G2IF focus group, which is shifted perpendicular to the optical axis. M2: Lateral magnification of lens group G2 when an infinite ray of light is incident on lens group G1.

[0055] Conditional equation (4) defines the amount by which the focus group G2IF is shifted relative to the optical axis in the same direction as the light source, and is a condition for efficiently receiving reflected light from the fundus when the eye under examination is shifted relative to the optical axis. As described above, in the ophthalmic optical system that embodies the present invention, the light source is positioned at a location shifted perpendicular to the optical axis, so the image of the light source is formed at a position shifted from the center of the eye under examination due to the lateral magnification of lens group G1. Therefore, in order to pass the light beam through the constricted pupil diameter, it is desirable to shift the eye under examination perpendicular to the optical axis to match the image of the light source.

[0056] On the other hand, if the eye under examination is shifted orthogonally, the eye will be offset from the optical axis center relative to the observation system, preventing the light beam from the observation system from efficiently reaching the observation side. To avoid this, the G2IF focus group is shifted orthogonally to the optical axis in the same direction as the light source. However, if the amount of this shift is too large, the amount of corneal reflection ghosting superimposed on the fundus observation light will increase, which is undesirable. In order to properly illuminate the fundus and observe it well, it is necessary to set the amount of shift of the G2IF focus group appropriately.

[0057] If the product of the shift amount of the focus group G2IF from the optical axis and the lateral magnification of lens group G2 when an infinity ray is incident on lens group G1 becomes small beyond the lower limit, the light beam of the fundus observation system does not efficiently reach the observation side, resulting in a decrease in the illuminance of the observation light, which is undesirable. On the other hand, if the product of the shift amount of the focus group G2IF from the optical axis and the lateral magnification of lens group G2 when an infinity ray is incident on lens group G1 becomes large beyond the upper limit, the amount of corneal reflection ghosting superimposed on the fundus observation light increases, which is undesirable. Note that the shift amount of the focus group G2IF perpendicular to the optical axis may be changed within the above condition range during fundus observation.

[0058] Furthermore, regarding condition (4), further limiting its lower limit to 0.37 is preferable because it allows the light beam from the fundus observation system to reach the observation side more efficiently. Also, further limiting its upper limit to 1.5 is preferable because it suppresses the amount of corneal reflection ghosting that overlaps with the fundus observation light.

[0059] Furthermore, the ophthalmic optical system that embodies the present invention has a light source that has a filter in front of the light source that cuts out the short wavelength side (500 nm or less, 520 nm half value). Furthermore, a polarizing filter may be placed in front of the light source, and a second polarizing filter with a polarization axis rotated 90 degrees relative to the polarizing filter may be provided behind the observation-side surface of lens group G3, or between the focus group G2IF and the eye-side surface of the final lens of lens group G3. It is also possible to change the aperture of the field diaphragm ST during fundus observation. In addition, the light source comprises one or more visible light-emitting diode light sources, the luminous intensity of which is 10 cd or less at a rated current of 20 mA.

[0060] The light source has a filter in front of it that cuts out short wavelengths (below 500nm, half-power at 520nm), intentionally cutting out ghosting, especially on the short wavelength side, of the reflected light from the cornea, thereby improving the visibility of the light used for fundus observation.

[0061] Furthermore, by placing a polarizing filter in front of the light source and illuminating the fundus of the eye under examination with only the polarized light, the corneal reflection ghost maintains its polarization state. By placing a second polarizing filter, which has a polarization axis rotated 90 degrees relative to that polarization state, behind the observation-side surface of lens group G3, the corneal reflection ghost can be reduced by its polarization effect. However, while placing the second polarizing filter behind the observation-side surface of lens group G3 makes adjustment during installation easier, it exposes the polarizing filter when the observation device is removed, making it prone to handling scratches. By positioning it between the focus group G2IF and the eye-side surface of the final lens of lens group G3, the occurrence of handling scratches when using the fundus camera can be avoided.

[0062] Furthermore, by changing the aperture of the field diaphragm ST during fundus observation, the observation range of the fundus field of view is narrowed, but the generation of corneal reflected light can be suppressed. In addition, by specifying the luminous intensity of the visible light-emitting diode light source that constitutes the light source, it is possible to ensure that the subject does not find the illumination uncomfortable.

[0063] When observing the fundus, it is also possible to use lens group G3 instead of focus group G2IF for focusing. While simultaneously focusing both focus group G2IF and lens group G3 can reduce the amount of focus movement for each and increase the flexibility for aberration correction, this would increase the weight due to the increased number of mechanical parts required to move multiple lens groups.

[0064] Furthermore, even when it is difficult to move the G2IF focus group back and forth in the optical axis direction, moving the G3 lens group back and forth in the optical axis direction allows this focusing function to compensate for the shift in the position of the fundus object caused by the strength of the subject's visual acuity, thereby enabling the observed image to be in focus.

[0065] Next, the lens configuration of the optical system in the ophthalmic optical system of the present invention will be described for each example. In the following description, the lens configuration will be described in order from the eye side to the observation side.

[0066] The optical system in the ophthalmic optical system of the present invention is an afocal optical system, and therefore, imaging is achieved by placing an observation device, which is an imaging system, on the observation side. In the lens configuration described below, an ideal lens with a focal length of 6.15 mm is added as an example of an observation device. The same applies to the various numerical data described later.

[0067] Furthermore, in the lens configuration diagrams of each embodiment, the light source L is omitted for simplification, and the focusing lens group G2IF is positioned on the optical axis, but in reality, each is shifted by a predetermined amount in the same direction from the optical axis. [Examples]

[0068] Figure 3 is a lens configuration diagram of Embodiment 1 of the optical system of the present invention. Starting from the eye side, it consists of a first lens group G1 with positive refractive power, a field diaphragm ST, a lens group G2A and a focusing lens group G2IF, and as a whole, a second lens group G2 with positive refractive power, a field diaphragm ST2, a third lens group G3 with positive refractive power, and an ideal lens IL as an observation device.

[0069] The first lens group G1 consists of biconvex lenses with aspherical shapes on both sides. The second lens group G2 consists of lens group G2A, which consists of positive meniscus lenses with aspherical shapes on both sides and the convex surface facing the eye being examined, and focusing lens group G2IF, which consists of a negative meniscus lens with the convex surface facing the eye being examined and a biconvex lens, and is a cemented lens with an overall positive refractive power. The third lens group G3 consists of biconvex lenses with aspherical shapes on both sides, biconcave lenses, biconcave lenses, biconcave lenses and biconvex lenses, and is a cemented lens with an overall positive refractive power.

[0070] The G2IF focusing lens group within the second lens group G2 compensates for the displacement of the fundus object position due to the subject's visual acuity by moving the G2IF focusing lens group back and forth along the optical axis, thereby focusing the observed image. Similarly, if the third lens group G3 is used as the focusing lens group, it is possible to compensate for the displacement of the fundus object position due to the subject's visual acuity by moving the focusing lens group back and forth along the optical axis, thereby focusing the observed image.

[0071] Furthermore, the light source, which is not shown in this figure, is shifted in a direction perpendicular to the optical axis. Also, the focusing lens group G2IF within the second lens group G2 is shifted in a direction perpendicular to the optical axis in the same direction as the light source, but for simplification purposes, it is shown as being on the optical axis in this figure. [Examples]

[0072] Figure 6 is a lens configuration diagram of Embodiment 2 of the optical system of the present invention. Starting from the eye side, it consists of a first lens group G1 with positive refractive power, a field diaphragm ST, a lens group G2A and a focusing lens group G2IF, and as a whole, a second lens group G2 with positive refractive power, a field diaphragm ST2, a third lens group G3 with positive refractive power, and an ideal lens IL as an observation device.

[0073] The first lens group G1 consists of biconvex lenses with an aspherical shape on the observation side. The second lens group G2 consists of lens group G2A, which consists of biconvex lenses with an aspherical shape on the eye side, and focusing lens group G2IF, which is a cemented lens with a positive refractive power overall, consisting of a negative meniscus lens with a convex surface facing the eye side and a biconvex lens. The third lens group G3 consists of a positive meniscus lens with an aspherical shape on the observation side and a concave surface facing the eye side, a negative meniscus lens with an aspherical shape on the eye side and a concave surface facing the eye side, and a positive meniscus lens with a concave surface facing the eye side.

[0074] The G2IF focusing lens group within the second lens group G2 compensates for the displacement of the fundus object position due to the subject's visual acuity by moving the G2IF focusing lens group back and forth along the optical axis, thereby focusing the observed image. Similarly, if the third lens group is used as the focusing lens group, it is possible to compensate for the displacement of the fundus object position due to the subject's visual acuity by moving the focusing lens group back and forth along the optical axis, thereby focusing the observed image.

[0075] Furthermore, the light source, which is not shown in this figure, is shifted in a direction perpendicular to the optical axis. Also, the focusing lens group G2IF within the second lens group is shifted in the same direction as the light source, perpendicular to the optical axis, but for simplification purposes, it is shown as being on the optical axis in this figure. [Examples]

[0076] Figure 9 is a lens configuration diagram of Embodiment 3 of the optical system of the present invention. Starting from the eye side, it consists of a first lens group G1 with positive refractive power, a field diaphragm ST, a lens group G2A and a focusing lens group G2IF, and as a whole, a second lens group G2 with positive refractive power, a field diaphragm ST2, a third lens group G3 with positive refractive power, and an ideal lens IL as an observation device.

[0077] The first lens group G1 consists of biconvex lenses with an aspherical shape on the observation side. The second lens group G2 consists of lens group G2A, which consists of biconvex lenses with an aspherical shape on the eye side, and focusing lens group G2IF, which is a cemented lens with a positive refractive power overall, consisting of a negative meniscus lens and a biconvex lens with the convex surface facing the eye side. The third lens group G3 consists of a positive meniscus lens with the concave surface facing the eye side, a positive meniscus lens with an aspherical shape on the observation side and the convex surface facing the eye side, a biconcave lens with an aspherical shape on the eye side, and a biconvex lens.

[0078] The G2IF focusing lens group within the second lens group G2 compensates for the displacement of the fundus object position due to the subject's visual acuity by moving the G2IF focusing lens group back and forth along the optical axis, thereby focusing the observed image. Similarly, if the third lens group is used as the focusing lens group, it is possible to compensate for the displacement of the fundus object position due to the subject's visual acuity by moving the focusing lens group back and forth along the optical axis, thereby focusing the observed image.

[0079] Furthermore, the light source, which is not shown in this figure, is shifted in a direction perpendicular to the optical axis. Also, the focusing lens group G2IF within the second lens group is shifted in the same direction as the light source, perpendicular to the optical axis, but for simplification purposes, it is shown as being on the optical axis in this figure. [Examples]

[0080] Figure 12 is a lens configuration diagram of Embodiment 4 of the optical system of the present invention. Starting from the eye side, it consists of a first lens group G1 with positive refractive power, a field diaphragm ST, a lens group G2A and a focusing lens group G2IF, and as a whole, a second lens group G2 with positive refractive power, a field diaphragm ST2, a third lens group G3 with positive refractive power, and an ideal lens IL as an observation device.

[0081] The first lens group G1 consists of biconvex lenses with an aspherical shape on the observation side. The second lens group G2 consists of lens group G2A, which consists of biconvex lenses with an aspherical shape on the eye side, and focus group G2IF, which is a cemented lens with a positive refractive power overall, consisting of a negative meniscus lens with a convex surface facing the eye side and a positive meniscus lens with a convex surface facing the eye side. The third lens group G3 consists of a positive meniscus lens with a concave surface facing the eye side, a negative meniscus lens with an aspherical shape on the observation side and a convex surface facing the eye side, a negative meniscus lens with an aspherical shape on the eye side and a convex surface facing the eye side, and a biconvex lens.

[0082] The G2IF focusing lens group within the second lens group G2 compensates for the displacement of the fundus object position due to the subject's visual acuity by moving the G2IF focusing lens group back and forth along the optical axis, thereby focusing the observed image. Similarly, if the third lens group is used as the focusing lens group, it is possible to compensate for the displacement of the fundus object position due to the subject's visual acuity by moving the focusing lens group back and forth along the optical axis, thereby focusing the observed image.

[0083] Furthermore, the light source, which is not shown in this figure, is shifted in a direction perpendicular to the optical axis. Also, the focusing lens group G2IF within the second lens group is shifted in the same direction as the light source, perpendicular to the optical axis, but for simplification purposes, it is shown as being on the optical axis in this figure. [Examples]

[0084] Figure 15 is a lens configuration diagram of Embodiment 5 of the optical system of the present invention. Starting from the eye side, it consists of a first lens group G1 with positive refractive power, a field diaphragm ST, a lens group G2A and a focusing lens group G2IF, and as a whole, a second lens group G2 with positive refractive power, a field diaphragm ST2, a third lens group G3 with positive refractive power, and an ideal lens IL as an observation device.

[0085] The first lens group G1 consists of biconvex lenses with an aspherical shape on the observation side. The second lens group G2 consists of a biconvex lens group G2A and a focus group G2IF, which is a cemented lens with a positive refractive power overall, consisting of a negative meniscus lens with a convex surface facing the eye being examined and a biconvex lens. The third lens group G3 consists of a positive meniscus lens with a concave surface facing the eye being examined, a negative meniscus lens with a convex surface facing the eye being examined, a biconcave lens, and a biconvex lens.

[0086] The G2IF focusing lens group within the second lens group G2 compensates for the displacement of the fundus object position due to the subject's visual acuity by moving the G2IF focusing lens group back and forth along the optical axis, thereby focusing the observed image. Similarly, if the third lens group G3 is used as the focusing lens group, it is possible to compensate for the displacement of the fundus object position due to the subject's visual acuity by moving the focusing lens group back and forth along the optical axis, thereby focusing the observed image.

[0087] Furthermore, the light source, which is not shown in this figure, is shifted in a direction perpendicular to the optical axis. Also, the focusing lens group G2IF within the second lens group is shifted in the same direction as the light source, perpendicular to the optical axis, but for simplification purposes, it is shown as being on the optical axis in this figure.

[0088] The following shows specific numerical data for each embodiment of the optical system in the ophthalmic optical system of the present invention described above.

[0089] In the [surface data], the surface number is the number of the lens surface or aperture diaphragm counted from the side of the eye being examined, r is the radius of curvature of each surface, d is the spacing between each surface, nd is the refractive index for the d line (wavelength 587.56 nm), and vd is the Abbe number for the d line.

[0090] The asterisk (*) next to the lens surface number indicates that the lens surface is aspherical. BF represents the back focus.

[0091] The (aperture) appended to the face number indicates that an aperture is located at that position. The radius of curvature relative to a plane or aperture is indicated with ∞ (infinity).

[0092] The [Aspherical Data] section shows the coefficient values ​​that give the aspherical shape of the lens surface marked with an asterisk (*) in the [Surface Data] section. The aspherical shape is defined as follows, where y is the displacement from the optical axis in the direction perpendicular to the optical axis, z is the displacement (sag) in the direction of the optical axis from the intersection of the aspherical surface and the optical axis, r is the radius of curvature of the reference sphere, K is the conic coefficient, and A4, A6, A8, and A10 are the 4th, 6th, 8th, and 10th order aspherical coefficients, respectively, and the coordinates of the aspherical surface are expressed by the following formula.

[0093] TIFF0007919783000002.tif18128

[0094] The [Various Data] section shows various values ​​for an INF shooting distance and for -20 diopters and +20 diopters when focusing with either the G2IF or G3 lens group.

[0095] The [Variable Interval Data] shows the variable interval and BF values ​​at -20 diopters and +20 diopters when focusing with either the G2IF or G3 lens group, and when the shooting distance is INF.

[0096] The [Lens Group Data] shows the face number closest to the eye being examined and the combined focal length of the entire group for each lens group.

[0097] In addition, for all the specifications listed below, the units of focal length f, radius of curvature r, lens plane spacing d, and other lengths are millimeters (mm) unless otherwise specified. However, since equivalent optical performance can be obtained in both proportional magnification and proportional reduction in the optical system, this is not the only unit of measurement.

[0098] Furthermore, a list of corresponding values ​​for the conditional expressions in each of these examples is provided.

[0099] Furthermore, in the aberration diagrams corresponding to each embodiment, d, g, and C represent the d line, g line, and C line, respectively, and △S and △M represent the sagittal image plane and meridional image plane, respectively.

[0100] Numerical Example 1 Unit: mm [Surface data] Face number rd nd vd Object surface ∞ (d0) 1 (aperture) ∞ 0.0000 2 ∞ 30.5000 3* 26.5800 14.0000 1.53503 55.71 4* -20.9600 20.0000 5 (Field of View Aperture) ∞ 50.6500 6* 9.7300 2.5000 1.53503 55.71 7* 17.8100 (d7) 8 19.8100 1.0000 1.98612 16.48 9 9.4300 4.5000 1.83481 42.72 10 -145.3500 (d10) 11 (Field of View Aperture) ∞ 7.4000 12* 8.3600 6.2000 1.53503 55.71 13* -8.5800 4.2000 14 -6.9000 1.0000 1.65844 50.86 15 6.9000 3.6000 16 -17.0700 1.0000 1.92119 23.96 17 17.0700 4.0000 1.88300 40.81 18 -7.6700 (d18) 19 (Ideal lens) ∞ 0.0000 20 ∞ (BF) Image plane ∞ [Aspherical data] 3 sides 4 sides 6 sides 7 sides 12 sides K 0.00000 0.00000 0.00000 0.00000 0.00000 A4 -1.58970E-05 3.19800E-05 -1.56980E-05 1.69100E-04 -3.00000E-04 A6 -2.27510E-07 -1.80060E-07 1.18450E-06 -2.23240E-06 2.74620E-06 A8 1.17250E-09 7.16260E-10 2.95270E-07 6.43290E-07 -1.84050E-07 A10 -1.62780E-12 -5.61670E-13 -3.77500E-09 -7.75920E-09 1.39760E-09 13 sides K 0.00000 A4 7.00000E-04 A6 -6.78310E-06 A8 7.97630E-08 A10 0.00000E+00 [Various Data] G2IF G2IF G3 G3 INF -20 diopters +20 diopters -20 diopters +20 diopters Focal length 3.20 3.22 3.18 3.12 3.19 F-number 0.92 0.92 0.93 0.92 0.93 Full angle of view 2ω 36.00 36.00 36.00 36.00 36.00 Image height Y 0.99 0.97 1.01 0.95 1.02 Lens length 193.50 193.50 193.50 193.50 193.50 [Variable interval data] G2IF G2IF INF -20 diopters +20 diopters d0 ∞ -50.0000 50.0000 d7 13.5000 16.4640 10.4697 d10 18.3000 15.3360 21.3303 BF 6.1491 6.1483 6.1482 G3 G3 INF -20 diopters +20 diopters d0 ∞ -50.0000 50.0000 d10 18.3000 15.5660 21.3091 d18 5.0000 7.7334 1.9909 BF 6.1491 6.1491 6.1490 [Lens group data] Group Starting plane Focal length G1 3 24.41 G2A 6 36.18 G2IF 8 25.48 G3 12 22.99

[0101] Numerical Example 2 Unit: mm [Surface data] Face number rd nd vd Object surface ∞ (d0) 1 (aperture) ∞ 0.0000 2 ∞ 35.1200 3 253.8400 10.0000 1.77250 49.46 4* -19.9453 24.0000 5 (Field of view aperture) ∞ 43.7000 6* 31.4428 2.9757 1.43700 95.10 7 -20.3840 (d7) 8 23.8229 1.0000 1.89286 20.36 9 8.7976 4.8382 1.74400 44.90 10 -30.9279 (d10) 11 (Field of View Aperture) ∞ 7.5869 12 -17.4352 2.7000 1.66059 20.40 13* -8.4927 14.8906 14* -6.9383 1.0000 1.66059 20.40 15 -21.2909 0.6493 16 -10.6492 3.4284 1.74400 44.90 17 -6.3895 (d17) 18 (Ideal lens) ∞ 0.0000 19 ∞ (BF) Image plane ∞ [Aspherical data] 4 sides 6 sides 13 sides 14 sides K 0.00000 0.00000 0.00000 0.00000 A4 4.23425E-05 1.06511E-05 6.34843E-04 -7.62921E-04 A6 -2.57085E-07 -2.79691E-06 -4.27388E-05 -3.63390E-05 A8 1.55145E-09 7.69032E-08 1.77781E-06 1.27674E-06 A10 -2.92885E-12 -6.56904E-10 -2.58687E-08 -1.68296E-07 [Various Data] G2IF G2IF G3 G3 INF -20 diopters +20 diopters -20 diopters +20 diopters Focal length 2.77 3.04 2.57 2.87 2.62 F-number 0.93 0.93 0.92 0.93 0.92 Full angle of view 2ω 32.00 32.00 32.00 32.00 32.00 Image height Y 0.75 0.81 0.72 0.76 0.74 Lens length 193.15 193.15 193.15 193.15 193.15 [Variable interval data] G2IF G2IF INF -20 diopters +20 diopters d0 ∞ -50.0000 50.0000 d7 15.0000 18.3618 12.2773 d10 15.1109 11.7491 17.8336 BF 6.1500 6.1500 6.1500 G3 G3 INF -20 diopters +20 diopters d0 ∞ -50.0000 50.0000 d10 15.1109 12.2984 17.7677 d17 5.0000 7.8125 2.3431 BF 6.1500 6.1500 6.1500 [Lens group data] Group Starting plane Focal length G1 3 24.33 G2A 6 28.80 G2IF 8 23.21 G3 12 25.97

[0102] Numerical Example 3 Unit: mm [Surface data] Face number rd nd vd Object surface ∞ (d0) 1 (aperture) ∞ 0.0000 2 ∞ 32.6200 3 253.8400 10.0000 1.77250 49.46 4* -19.9453 24.0000 5 (Field of view aperture) ∞ 43.7000 6* 31.0057 2.9402 1.43700 95.10 7 -22.4083 (d7) 8 24.9575 1.0000 2.00272 19.32 9 10.1507 7.0000 1.87070 40.73 10 -55.1062 (d10) 11 (field of view aperture) ∞ 3.0404 12 -10.0769 2.7000 2.00272 19.32 13 -8.6929 3.5506 14 6.2440 3.1207 2.00272 19.32 15* 6.2978 4.4261 16* -4.4811 1.0000 1.66059 20.40 17 22.1069 0.4112 18 77.7309 4.0464 1.82080 42.71 19 -6.1380 (d19) 20 (Ideal lens) ∞ 0.0000 21 ∞ (BF) Image plane ∞ [Aspherical data] 4 sides 6 sides 15 sides 16 sides K 0.00000 0.00000 0.00000 0.00000 A4 1.79529E-05 -4.53369E-05 1.60763E-03 -1.51981E-03 A6 1.13888E-07 2.03006E-06 -2.02591E-04 -2.23823E-04 A8 -4.50507E-10 -1.01708E-07 1.71772E-05 2.05513E-05 A10 9.39207E-13 1.55120E-09 -6.49617E-07 -2.98334E-06 [Various Data] G2IF G2IF G3 G3 INF -20 diopters +20 diopters -20 diopters +20 diopters Focal length 4.92 5.68 4.42 5.07 4.40 F-numbers: 1.23, 1.36, 1.19, 1.26, 1.21 Full angle of view 2ω 34.00 34.00 34.00 34.00 34.00 Image height Y 1.44 1.51 1.48 1.38 1.51 Lens length: 193.15 193.16 193.15 193.15 193.15 [Variable interval data] G2IF G2IF INF -20 diopters +20 diopters d0 ∞ -50.0000 50.0000 d7 23.6705 28.1535 20.1229 d10 14.7739 10.2989 18.3215 BF 6.1500 6.1489 6.1500 G3 G3 INF -20 diopters +20 diopters d0 ∞ -50.0000 50.0000 d10 14.7739 11.1365 18.2690 d19 5.0000 8.6374 1.5049 BF 6.1500 6.1500 6.1500 [Lens group data] Group Starting plane Focal length G1 3 24.33 G2A 6 30.27 G2IF 8 24.22 G3 12 16.69

[0103] Numerical Example 4 Unit: mm [Surface data] Face number rd nd vd Object surface ∞ (d0) 1 (aperture) ∞ 0.0000 2 ∞ 35.1200 3 253.8400 10.0000 1.77250 49.46 4* -19.9453 24.0000 5 (field of view aperture) ∞ 46.4092 6* 33.0274 2.9364 1.43700 95.10 7 -21.0374 (d7) 8 15.6341 1.0000 2.00272 19.32 9 8.1480 7.0000 1.83481 42.72 10 1181.9400 (d10) 11 (field of view aperture) ∞ 5.4257 12 -9.5594 2.7000 1.98612 16.48 13 -8.1848 0.3000 14 5.5485 3.0000 2.00069 25.46 15* 3.5534 10.1551 16* 104.3760 1.0000 1.77047 29.74 17 9.5597 0.9754 18 15.5880 4.6703 1.48749 70.44 19 -7.1289 (d19) 20 (Ideal lens) ∞ 0.0000 21 ∞ (BF) Image plane ∞ [Aspherical data] 4 sides 6 sides 15 sides 16 sides K 0.00000 0.00000 0.00000 0.00000 A4 2.49746E-05 -1.65634E-05 9.71950E-04 1.83194E-05 A6 4.16958E-08 -1.65714E-06 -1.81499E-04 3.05521E-07 A8 -1.21503E-10 5.31088E-08 2.19616E-05 1.51697E-07 A10 4.14796E-13 -5.66590E-10 -9.69567E-07 -9.85412E-11 [Various Data] G2IF G2IF G3 G3 INF -20 diopters +20 diopters -20 diopters +20 diopters Focal length 2.46 2.70 2.29 2.58 2.33 F number 0.89 0.89 0.89 0.89 0.89 Full angle of view 2ω 34.00 34.00 34.00 34.00 34.00 Image height Y 0.78 0.80 0.78 0.76 0.80 Lens length 193.15 193.15 193.15 193.15 193.15 [Variable interval data] G2IF G2IF INF -20 diopters +20 diopters d0 ∞ -50.0000 50.0000 d7 15.0000 17.7620 12.7428 d10 12.3080 9.546 14.5653 BF 6.1500 6.1500 6.1500 G3 G3 INF -20 diopters +20 diopters d0 ∞ -50.0000 50.0000 d10 12.3080 9.9331 14.5036 d19 5.0000 7.3750 2.8044 BF 6.1500 6.1500 6.1500 [Lens group data] Group Starting plane Focal length G1 3 24.33 G2A 6 29.90 G2IF 8 22.92 G3 12 26.70

[0104] Numerical Example 5 Unit: mm [Surface data] Face number rd nd vd Object surface ∞ (d0) 1 (aperture) ∞ 0.0000 2 ∞ 35.1200 3 25.7632 10.0000 1.77250 49.46 4* -55.5412 24.0000 5 (field of view aperture) ∞ 44.8118 6 31.5894 2.5471 1.43700 95.10 7 -35.3309 (d7) 8 18.5598 1.0000 2.00272 19.32 9 9.7796 4.3913 1.88300 40.81 10 -511.7055 (d10) 11 (field of view aperture) ∞ 4.5184 12 -12.4166 2.7000 1.98612 16.48 13 -8.7641 0.3000 14 5.2242 3.0000 2.00100 29.13 15 3.4080 12.0626 16 -20.6001 1.0000 2.00272 19.32 17 24.1609 1.2068 18 89.3375 3.1974 1.88300 40.81 19 -9.4257 (d19) 20 (Ideal lens) ∞ 0.0000 21 ∞ (BF) Image plane ∞ [Aspherical data] 4 sides K 0.00000 A4 2.23701E-05 A6 7.95301E-08 A8 -6.77013E-10 A10 1.57459E-12 [Various Data] G2IF G2IF G3 G3 INF -20 diopters +20 diopters -20 diopters +20 diopters Focal length 2.46 2.51 2.41 2.46 2.42 F number 0.79 0.79 0.80 0.79 0.80 Full angle of view 2ω 34.00 34.00 34.00 34.00 34.00 Image height Y 0.76 0.76 0.76 0.75 0.78 Lens length 193.15 193.15 193.15 193.15 193.15 [Variable interval data] G2IF G2IF INF -20 diopters +20 diopters d0 ∞ -50.0000 50.0000 d7 15.0000 17.3926 12.7019 d10 17.1446 14.7521 19.4427 BF 6.1500 6.1500 6.1500 G3 G3 INF -20 diopters +20 diopters d0 ∞ -50.0000 50.0000 d10 17.1446 14.8771 19.4411 d19 5.0000 7.2676 2.7035 BF 6.1500 6.1500 6.1500 [Lens group data] Group Starting plane Focal length G1 3 24.07 G2A 6 38.61 G2IF 8 22.92 G3 12 26.70

[0105] [Conditional expression corresponding value] Conditional Expression / Examples EX1 EX2 EX3 EX4 EX5 (1) 0.52 0.45 0.80 0.40 0.40 (2) 3.38 4.64 3.92 4.64 3.76 (3) 1.45 1.99 1.68 1.99 1.61 (4) 0.49 0.48 0.55 0.44 0.44 [Explanation of Symbols]

[0106] G1 lens group G1 G2 lens group G2 G2A lens group G2A G2IF Focus Group G2IF G3 lens group G3 ST Field Diameter ST2 Field of View Aperture S aperture IL Ideal Lens I. Image point

Claims

1. It includes a light source for illuminating the fundus and an optical system that forms a conjugate image with the pupil of the eye being examined. The optical system is arranged in a straight line, from the eye being examined to the observation side, The fundus of the eye under examination is used as the object point to form an image of the light beam emitted from the cornea of ​​the eye under examination, and a lens group G1 with a common positive refractive power for fundus imaging and fundus illumination, A lens group G2 with positive refractive power that re-images the image point of the aforementioned lens group G1 as an object point, A lens group G3 that projects the image point of the aforementioned lens group G2 as an object point in a substantially afocal manner, A field aperture ST is located between the lens group G1 and the lens group G2, It has a field aperture ST2 located between the lens group G2 and the lens group G3, The optical path for fundus imaging and fundus illumination does not contain any optical path splitting elements or optical path bending elements. Ophthalmic optical systems.

2. The aforementioned lens group G2 includes a lens group G2A that emits the light beam from lens group G1 in a substantially afocal direction, and a focus group G2IF that focuses for fundus imaging, located closest to the eye being examined. The ophthalmic optical system according to claim 1.

3. An ophthalmic optical system according to claim 1, satisfying the following conditions. (1) 0.25<M<1.0 however, M: Afocal magnification of the optical system.

4. The light source is located between the field aperture ST and the lens group G2, and is shifted in a direction perpendicular to the optical axis. An ophthalmic optical system according to claim 1 that satisfies the following condition. (2) 1.6mm<|S・M1|<5.0mm however, M1: The lateral magnification of the lens group G1, with the light source as the object point and the cornea of ​​the eye under examination as the image point. S: The amount of shift (mm) from the optical axis of the light source, which is shifted in a direction perpendicular to the optical axis.

5. The aforementioned light source is capable of changing the amount of shift in a direction perpendicular to the optical axis during fundus observation. The ophthalmic optical system according to claim 4.

6. An ophthalmic optical system according to claim 1 that satisfies the following condition. (3) 0.7mm<|DL・M1|<2.8mm however, DL: Diameter of the light source (mm) M1: The lateral magnification of the lens group G1, with the light source of the aforementioned light source as the object point and the cornea of ​​the eye under examination as the image point.

7. The lens group G2 has a lens group G2A on the side closest to the eye being examined that emits the light beam from the lens group G1 in a substantially afocal manner, The lens group G2A has a shape in which an arc-shaped notch is cut out from the outer periphery of the lens group G2A at a position close to the optical axis by the diameter of the light source, or a shape in which a hole is cut out from the outer periphery of the lens group G2A at a position close to the optical axis by the diameter of the light source. The ophthalmic optical system according to claim 4.

8. The aforementioned focus group G2IF is shifted perpendicular to the optical axis in the same direction as the light source, An ophthalmic optical system according to claim 4, satisfying the following conditional expression. (4) 0.25mm<|G2IFS・M2|<3.0mm however, G2IFS: The amount of shift (mm) of the focus group G2IF from the optical axis, which is shifted in a direction perpendicular to the optical axis. M2: Lateral magnification of lens group G2 when an infinity ray is incident on lens group G1.

9. The light source has a filter in front of the light source that cuts off the short wavelength side (below 500 nm, half-power at 520 nm). The ophthalmic optical system according to claim 4.

10. The light source has a polarizing filter in front of it, The lens group G3 has a second polarizing filter located behind the observation-side surface, with a polarization axis rotated 90 degrees relative to the polarizing filter. The ophthalmic optical system according to claim 4.

11. The lens group G2 has a focus group G2IF that focuses for fundus imaging, The light source has a polarizing filter in front of it, Between the eye-side surface of the final lens of lens group G3 from lens group G2IF, there is a second polarizing filter having a polarization axis rotated 90 degrees relative to the polarizing filter. The ophthalmic optical system according to claim 4.

12. The aforementioned field diaphragm ST is capable of changing its aperture during fundus observation. The ophthalmic optical system according to claim 1.

13. The light source comprises one or more visible light-emitting diode light sources, and the luminous intensity of the visible light-emitting diode light sources is 10 cd or less at a rated current of 20 mA. The ophthalmic optical system according to claim 1.

14. The aforementioned lens group G3 performs focusing for fundus imaging. The ophthalmic optical system according to claim 1.

15. Observation device, The system comprises an ophthalmic optical system according to any one of claims 1 to 14. Ophthalmology equipment.

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