ophthalmic devices

Abstract

To propose techniques that make it possible to suitably emit light beam onto a fundus of a subject eye regardless of an eye axis length of the subject eye.SOLUTION: An ophthalmic device comprises: a measurement optical system that includes a light-emitting optical system, which has a light source configured to emit a light beam in a spot shape onto a fundus of a subject eye, and a light-receiving optical system, which has a light receiving element configured to receive reflected light from the fundus of the subject eye; an arithmetic device configured to calculate an eye refractive power of the subject eye based on an output of the light receiving element; a light beam deflecting member arranged in an optical path of the measurement optical system and configured to deflect the light beam emitted from the light source; and a driving device configured to drive the light beam deflecting member so that the subject eye is scanned in a ring shape with the light beam emitted from the light source. The light beam deflecting member is disposed such that traveling directions of the light beam emitted from the light source intersect with each other between the subject eye and the light beam deflecting member when the light beam deflecting member is driven by the driving device.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The technology disclosed in this specification relates to an ophthalmic device.

[0002] Patent Document 1 discloses an ophthalmic device for measuring ocular refractive power. This device includes a measurement optical system having a light-projecting optical system and a light-receiving optical system, a calculation means, a light beam deflector, and a rotation means. The light-projecting optical system projects a spot-shaped light beam onto the fundus of the subject's eye. The light-receiving optical system extracts reflected light from the fundus of the subject's eye and receives it with a light-receiving element. The calculation means measures ocular refractive power based on the output of the light-receiving element. The light beam deflector is disposed in the optical path of the measurement optical system, at a position away from a position conjugate with the pupil. The rotation means rotates the light beam deflector around the optical axis. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-185523 Summary of the Invention [Problem to be solved by the invention]

[0004] In Patent Document 1, a light beam projected in a spot shape is deflected by a light beam deflector that rotates around the optical axis, and the light beam scans the fundus in a ring shape. The light beam deflected by the light beam deflector may travel at an angle with respect to the optical axis of the ophthalmic device inside the subject's eye. Therefore, the scanning diameter of the light beam irradiated onto the fundus may change depending on the axial length of the subject's eye. As a result, depending on the axial length of the subject's eye, the light beam irradiated onto the fundus may scan a position far from the fovea, resulting in a deviation from the test value of subjective refractive power. This specification proposes a technology that can appropriately project a light beam onto the fundus of the subject's eye, regardless of the axial length of the subject's eye. [Means for solving the problem]

[0005] The ophthalmologic apparatus disclosed in the present specification includes a measurement optical system including a light-projecting optical system having a light source that projects a spot-shaped light beam onto a fundus of an eye to be examined and a light-receiving optical system having a light-receiving element that receives light reflected from the fundus of the eye to be examined, a calculation device that calculates the ocular refractive power of the eye to be examined based on an output of the light-receiving element, a light beam deflector that is disposed in an optical path of the measurement optical system and deflects the light beam projected from the light source, and a drive device that drives the light beam deflector so that the light beam projected from the light source scans the eye to be examined in a ring shape. The light beam deflector is disposed so that, when driven by the drive device, the traveling direction of the light beam projected from the light source intersects between the eye to be examined and the light beam deflector.

[0006] In the above-described ophthalmic apparatus, when the light beam deflecting member is driven by the driving device, the light beam scans the subject's eye in a ring shape, and the traveling direction of the light beam intersects between the subject's eye and the light beam deflecting member. That is, in this ophthalmic apparatus, the light beam deflected by the light beam deflecting member enters the subject's eye at an angle away from the optical axis of the ophthalmic apparatus. Therefore, when the light beam scanned in a ring shape passes through the ocular lens of the subject's eye (i.e., the lens when the subject's eye is considered as a single lens), the traveling direction of the light beam is refracted in a direction approaching parallel. Therefore, in this ophthalmic apparatus, even if the axial length of the subject's eye is relatively long or short, the scanning diameter of the light beam irradiated onto the fundus of the subject's eye does not change significantly, and the light can be suitably scanned in a ring shape onto the fundus of the subject's eye. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 2 is a schematic diagram illustrating the configuration of an optical system of the ophthalmic apparatus according to the first embodiment. [Figure 2] 2 is a diagram for explaining a light projection optical system of a refractive power measurement optical system of the ophthalmic apparatus according to the first embodiment. FIG. [Figure 3] FIG. 2 is a diagram for explaining a light receiving optical system of a refractive power measuring optical system of the ophthalmic apparatus according to the first embodiment. [Figure 4] FIG. 2 is a diagram illustrating the configuration of a ring lens. [Figure 5]FIG. 2 is a diagram schematically showing the optical path of light in a projection optical system of a refractive power measurement optical system. [Figure 6] FIG. 2 is a diagram for explaining a front monitor optical system of the ophthalmologic apparatus according to the first embodiment. [Figure 7] 2 is a diagram for explaining a position detection light projection optical system of the ophthalmologic apparatus according to the first embodiment. FIG. [Figure 8] FIG. 2 is a diagram for explaining a position detecting light receiving optical system of the ophthalmologic apparatus according to the first embodiment. [Figure 9] FIG. 2 is a diagram for explaining a fixation target optical system of the ophthalmologic apparatus according to the first embodiment. [Figure 10] FIG. 2 is a diagram schematically illustrating the path of light in a projection optical system of a refractive power measurement optical system. [Figure 11] FIG. 2 is a diagram schematically illustrating the path of light in a light-receiving optical system of a refractive power measurement optical system. [Figure 12] FIG. 10 is a diagram for calculating the conditional formula for the pivot position and the deflection angle of the light beam in a short-axis eye. [Figure 13] FIG. 10 is a diagram for calculating the conditional formula for the pivot position and the deflection angle of the light beam in a long-axis eye. [Figure 14] 10 is a graph showing a range in which the pivot position and the deflection angle of the light beam satisfy the conditions. [Figure 15] 11A and 11B are diagrams each showing a schematic diagram of a light path of a light receiving optical system of a refractive power measuring optical system of an ophthalmic apparatus according to a second embodiment; [Figure 16] FIG. 2 is a diagram illustrating the configuration of a lens array. [Figure 17] 6 is a diagram corresponding to FIG. 5 and schematically showing the optical path of light in a projection optical system of a refractive power measurement optical system of an ophthalmic apparatus according to a third embodiment. [Figure 18] 6 is a diagram corresponding to FIG. 5 and schematically showing the optical path of light in a projection optical system of a refractive power measurement optical system of an ophthalmic apparatus according to a fourth embodiment. [Figure 19] 6 is a diagram corresponding to FIG. 5 and schematically showing the optical path of light in a projection optical system of a refractive power measurement optical system of an ophthalmic apparatus according to a fifth embodiment.

[0008] The technical elements disclosed in this specification are listed below. Note that each of the following technical elements is independently useful.

[0009] In an embodiment of the present technology, the light beam deflecting member may be disposed at a position conjugate with a crossing position where the traveling directions of the light beams cross each other.

[0010] With this configuration, the traveling direction of the light beam can be easily made to intersect between the eye to be examined and the light beam deflecting member.

[0011] In one embodiment of the present technology, the light receiving optical system is positioned at a position conjugate with the fundus of the test eye, and may further have an optical element that focuses the reflected light in a ring shape onto the light receiving element.

[0012] According to this configuration, the ring image formed on the light receiving element is analyzed by approximating it to an ellipse, thereby making it possible to calculate the spherical power and cylindrical power of the subject's eye.

[0013] In one embodiment of the present technology, the light receiving optical system may further include an optical element having a plurality of lenses arranged in a grid pattern at a position conjugate with the fundus of the test eye, each of the plurality of lenses focusing the reflected light onto the light receiving element in a grid point pattern.

[0014] With this configuration, it is possible to measure the wavefront distortion caused by the eyeball of the subject's eye (that is, the total aberration of the eyeball) based on the position coordinates of the reflected light input to the light receiving element in the form of lattice points.

[0015] In an embodiment of the present technology, the drive device may drive the light beam deflection member so that the traveling direction of the light beam incident on the subject's eye becomes approximately parallel inside the subject's eye.

[0016] With this configuration, the light beam can be irradiated onto the fundus of the subject's eye with high precision, regardless of the axial length of the subject's eye.

[0017] In one embodiment of the present technology, when the diameter of the fovea of the eye to be examined is 1.5 mm, the focal length of the eye lens of the eye to be examined is 17.1 mm, the distance from the corneal apex of the eye to be examined to the intersection position where the traveling direction of the light beam intersects is a', and the angle formed by the light beam incident on the eye lens of the eye to be examined from the intersection position and the optical axis of the ophthalmic device is θ, when a > f, the following formula;

Equation

Equation

[0018] According to such a configuration, regardless of the axial length of the eye to be examined of the subject, the light beam can be scanned in a ring shape with a scanning diameter smaller than the diameter of the fovea of the eye to be examined.

[0019] (Example 1) Hereinafter, the ophthalmic device 10 according to Example 1 will be described. The ophthalmic device 10 of this example is an eye refractive power measuring device that objectively measures the refractive power of the eye to be examined E. The ophthalmic device 10 includes an optical system 20 shown in FIG. 1. The optical system 20 includes a refractive power measuring optical system, a front monitor optical system, a position detection light projecting optical system, a position detection light receiving optical system, a fixation target optical system, and an observation optical system (not shown) for observing the eye to be examined E. Since the observation optical system can use those used in known ophthalmic devices, its detailed description will be omitted. First, the ideal optical arrangement set for the ideal eye to be examined E (for example, Gullstrand model eye) will be described below.

[0020] As shown in FIG. 2, the projection optical system of the refractive power measurement optical system is composed of a light source 120, a lens 122, a polarizing beam splitter 124, a two-dimensional scanner 108 (an example of a light beam deflection member), a dichroic mirror 110, a dichroic mirror 126, and an objective lens 128.

[0021] The light source 120 is an infrared point light source such as an SLD (super luminescent diode), an LD (laser diode), or an LED (light emitting diode). The light source 120 emits light with a central wavelength of 0.83 μm. The light output from the light source 120 passes through a lens 122 and a polarizing beam splitter 124 and enters the two-dimensional scanner 108. The two-dimensional scanner 108 is driven by a driving device (not shown) to scan the incident light beam in two directions, the x direction and the y direction, over the fundus of the subject's eye E. In this embodiment, a galvanometer scanner is used for the two-dimensional scanner 108. However, the two-dimensional scanner 108 may be configured to use a device other than a galvanometer scanner. For example, a MEMS mirror capable of biaxial scanning may be used. The light emitted from the two-dimensional scanner 108 passes through the dichroic mirror 110, is reflected by the dichroic mirror 126, and enters the objective lens 128. The light incident on the objective lens 128 passes through the objective lens 128 and is irradiated onto the fundus of the subject's eye E (for example, the fovea centralis, etc.).

[0022] As shown in Figure 3, the light receiving optical system of the refractive power measurement optical system is composed of an objective lens 128, a dichroic mirror 126, a dichroic mirror 110, a two-dimensional scanner 108, a polarizing beam splitter 124, a lens 130, a mirror 132, an aperture 134, a lens 136, a ring lens 138 (an example of an optical element), a two-dimensional sensor 140 (an example of a light receiving element), a focus adjustment mechanism 142, and a fogging mechanism (not shown).

[0023] 2 and 3, the path of the light scattered at the fundus of the subject's eye E is the same as that of the light projection optical system from the objective lens 128 to the polarizing beam splitter 124. Only the S-polarized component of the light scattered at the fundus of the subject's eye E is reflected by the polarizing beam splitter 124, and is irradiated onto a mirror 132 via a lens 130. The light irradiated onto the mirror 132 passes through an aperture 134, a lens 136, and a ring lens 138.

[0024] As shown in FIG. 4, the ring lens 138 is composed of a lens portion 138a, which is a cylindrical lens formed in a ring shape on a flat plate, and a light-shielding portion 138b, which is coated with a light-shielding coating on the area excluding the lens portion 138a. The ring lens 138 is positioned so that the light-shielding portion 138b is conjugate with the fundus of the subject's eye E. This allows reflected light from the fundus to be extracted in a ring shape from the pupil periphery, with a size corresponding to the light-shielding portion 138b. When the reflected light is incident on the ring lens 138, a ring-shaped image of the same size as the ring lens 138 is formed on the detection surface of the two-dimensional sensor 140. The refractive power of the subject's eye E is calculated based on the ring image formed by the two-dimensional sensor 140. For example, the spherical power and cylindrical power of the subject's eye E can be calculated by analyzing the ring image formed by the two-dimensional sensor 140 using an ellipse approximation.

[0025] Here, scanning of the measurement light beam in the refractive power measurement optical system will be described with reference to Fig. 5. Fig. 5 shows the optical path along which light emitted from the light source 120 is irradiated to the subject's eye E, and only some optical components arranged on the optical path (i.e., the lens 122, the two-dimensional scanner 108, and the objective lens 128) are illustrated, with the other optical components not being illustrated. Furthermore, the two-dimensional scanner 108 is arranged at a position conjugate with the range between the subject's eye E and the objective lens 128 in the optical path L1. Therefore, in the refractive power measurement optical system, the light scanned by the two-dimensional scanner 108 intersects with the optical axis (optical path L1) of the ophthalmic apparatus 10 in the range between the objective lens 128 and the subject's eye E. That is, in the refractive power measurement optical system, scanning is performed with a pivot just before the subject's eye E. Furthermore, in the refractive power measurement optical system, a pivot position (intersection position) P is set so that light that intersects between the objective lens 128 and the subject's eye E becomes parallel to the optical axis of the ophthalmic apparatus 10 when it enters the subject's eye E. That is, in the refractive power measurement optical system, the pivot position P is set so as to coincide with the front focal point of the subject's eye E when the subject's eye E is considered to be a single lens. Therefore, in the refractive power measurement optical system, light scanned by the two-dimensional scanner 108 reaches the fundus approximately parallel to the optical axis of the ophthalmic apparatus 10. That is, in the refractive power measurement optical system, telecentric scanning is performed, and the measurement light beam is circularly scanned inside the subject's eye E while maintaining a position a predetermined distance from the measurement optical axis, and reaches the fundus.

[0026] The refractive power measurement optical system also includes a focus adjustment mechanism 142. The focus adjustment mechanism 142 includes a moving device (not shown) that integrally moves the light source 120, the aperture 134, the lens 136, the ring lens 138, and the two-dimensional sensor 140 in the direction of the optical axis (optical paths L2, L3). By driving the moving device, the focus adjustment mechanism 142 can move the position of the light source 120 and the position of the two-dimensional sensor 140 to positions conjugate with the fundus of the subject's eye E according to the refractive power of the subject's eye E, thereby enabling refractive power measurement to be performed with high accuracy.

[0027] Next, the front monitor optical system will be described. As shown in Figure 6, the front monitor optical system is composed of LEDs 144 and 146, objective lens 128, dichroic mirror 126, dichroic mirror 110, aperture 148, lens 150, and two-dimensional sensor 152.

[0028] The LEDs 144 and 146 are disposed diagonally in front of the subject's eye E and illuminate the anterior segment of the subject's eye E. The LEDs 144 and 146 emit light with a central wavelength of 0.76 μm. The light reflected by the subject's eye E passes through the objective lens 128, is reflected by the dichroic mirrors 126 and 110, passes through the aperture 148 and the lens 150, and a front image of the anterior segment is formed on the two-dimensional sensor 152. The anterior segment image of the subject's eye E captured by the two-dimensional sensor 152 is displayed on a display device (not shown). The aperture 148 is disposed at the rear focal point of the objective lens 128 so that the image magnification does not change even if the anterior segment image is defocused.

[0029] Next, the position detecting light projection optical system will be described. As shown in Fig. 7, the position detecting light projection optical system is composed of an LED 154, a lens 156, a dichroic mirror 158, a dichroic mirror 126, and an objective lens 128. The LED 154 emits light with a central wavelength of 0.94 µm. The light emitted from the LED 154 passes through the lens 156, the dichroic mirrors 158 and 126, and the objective lens 128, and illuminates the cornea of ​​the subject's eye E. The light illuminated on the subject's eye E is specularly reflected by the corneal surface of the subject's eye E, and a virtual image of the light-emitting surface of the LED 154 is formed on an extension of the corneal vertex.

[0030] Next, the position detection light receiving optical system will be described. The position detection light receiving optical system detects the corneal vertex position in the direction (horizontal direction) perpendicular to the optical axis (optical path L1) and also detects the corneal vertex position in the optical axis direction (depth direction). As shown in FIG. 8, the position detection light receiving optical system is composed of a lens 160 and a two-dimensional sensor 162, and a lens 164 and a two-dimensional sensor 166. The lens 160 and the two-dimensional sensor 162 are disposed diagonally in front of the subject's eye E. The lens 164 and the two-dimensional sensor 166 are also disposed diagonally in front of the subject's eye E. The lens 164 and the two-dimensional sensor 166, and the lens 160 and the two-dimensional sensor 162 are disposed symmetrically with respect to the optical axis (optical path L1). Light reflected at a position slightly offset from the corneal vertex of the subject's eye E is reflected obliquely and passes through the lens 160, and a virtual image of the light-emitting surface of the LED 154 is projected onto the two-dimensional sensor 162. Similarly, light reflected at a position slightly shifted from the corneal apex of the subject's eye E passes through the lens 164, and a virtual image of the light-emitting surface of the LED 154 is projected onto the two-dimensional sensor 166. In the ophthalmologic apparatus 10 of this embodiment, based on the virtual image of the light-emitting surface of the LED 154 detected by the two-dimensional sensors 162 and 166, the corneal apex position in the direction (lateral direction) perpendicular to the optical axis (optical path L1) and the corneal apex position in the optical axis direction (depth direction) are detected.

[0031] Next, the fixation target optical system will be described. As shown in Fig. 9, the fixation target optical system is composed of an LED 168, a lens 170, a mirror 172, dichroic mirrors 158 and 126, an objective lens 128, and a dichroic mirror 116. The LED 168 emits white light. The light from the LED 168 passes through an image film on which a symbol for the subject to fixate is printed, and is reflected by the mirror 172. The light reflected by the mirror 172 is reflected by the dichroic mirror 158, passes through the dichroic mirror 126, the objective lens 128, and the dichroic mirror 116, and is irradiated toward the subject's eye E. The LED 168 and the image film are movable in the optical axis direction (direction along the optical path L4), and their positions are adjusted according to the refractive power of the subject's eye E.

[0032] Next, a process for measuring the ocular refractive power of the subject's eye E using the ophthalmic apparatus 10 will be described. First, when the examiner inputs an instruction to start the examination into an operation unit (e.g., a touch panel monitor) of the ophthalmic apparatus 10, a calculation device (not shown) aligns the subject's eye E with the ophthalmic apparatus 10. The alignment is performed using a position detection optical system (FIGS. 7 and 8) provided in the ophthalmic apparatus 10. Note that the alignment method is well known, and therefore a detailed description thereof will be omitted.

[0033] Once the alignment of the subject's eye E and the ophthalmologic apparatus 10 is complete, the arithmetic device performs refractive power measurement. The refractive power measurement is performed in the following procedure. First, the arithmetic device adjusts the two-dimensional scanner 108. At this time, the arithmetic device adjusts the scanning diameter and the irradiation position on the subject's eye E based on a predetermined setting value range. The setting value range will be described in detail later.

[0034] After the adjustment of the two-dimensional scanner 108 is completed, the calculation device turns on the light source 120. FIG. 10 shows the optical path of the light beam emitted from the light source 120 to the eye E in the light projection optical system, illustrating only some optical components arranged on the optical path (i.e., the lens 122, the two-dimensional scanner 108, and the objective lens 128), while omitting the other optical components. FIG. 10 also shows a simplified view of the two-dimensional scanner 108 scanning with light. As shown in FIG. 10, the light beam emitted from the light source 120 passes through the lens 122, the two-dimensional scanner 108, and the objective lens 128 to form a spot-shaped point light source image on the fundus of the eye E. At this time, when the two-dimensional scanner 108 is driven by the driving device, the light beam from the light source 120 scans the eye E in a ring shape, and the spot-shaped point light source image is irradiated in a ring shape on the fundus of the eye E.

[0035] FIG. 11 shows the optical path of the light beam reflected from the fundus in the light receiving optical system until it is imaged on the two-dimensional sensor 140. Only some optical components arranged on the optical path (i.e., the objective lens 128, the two-dimensional scanner 108, the lens 130, the aperture 134, the lens 136, the ring lens 138, and the two-dimensional sensor 140) are illustrated, and the other optical components are not illustrated. The point light source image projected on the fundus is reflected and scattered, exits the subject's eye E, passes through the objective lens 128, the two-dimensional scanner 108, and the lens 130, passes through the aperture 134, and is imaged in a ring shape on the two-dimensional sensor 140 by the lens 136 and the ring lens 138. As shown in FIG. 11, the reflected light beam from the fundus is reverse-scanned in the subsequent optical systems by the two-dimensional scanner 108, which is the same as the light projection optical system, as if the light beam had not been deflected relative to the subject's eye E.

[0036] The arithmetic device measures the refractive power by capturing an image output from the two-dimensional sensor 140 and analyzing the image. At this time, a fogging mechanism (not shown) may be used to measure the refractive power in a state where the refractive accommodation power of the crystalline lens of the subject's eye E is eliminated. Note that the fogging mechanism may be one used in known ophthalmic devices, and therefore a detailed description thereof will be omitted.

[0037] The light source 120 is disposed at a position conjugate with the fundus of the subject's eye E. This allows the light emitted from the light source 120 to be focused on the fundus of the subject's eye E. The two-dimensional scanner 108 also scans the measurement light beam in a ring shape around the optical axis on the pupil of the subject's eye E. This makes it possible to perform measurements while avoiding opacified areas caused by cataracts or the like, and suppresses deterioration of measurement accuracy due to speckle noise.

[0038] The above description describes the ideal arrangement of each optical member relative to an ideal subject's eye E when measuring eye refractive power using the ophthalmic apparatus 10. However, it is known in the technical field that eye refractive power can be objectively measured with sufficient accuracy if the scanning diameter of the ring-shaped light beam irradiated onto the fundus of the subject's eye E is equal to or less than the diameter of the fovea centralis of the subject's eye E. Therefore, the present inventors have studied conditions under which eye refractive power can be measured with high accuracy (i.e., with small deviation from the value of subjective refractive power) using the ophthalmic apparatus 10.

[0039] In the above description, the light scanned by the two-dimensional scanner 108 intersects at a predetermined pivot position P and enters the subject's eye E, thereby reaching the fundus parallel to the optical axis of the ophthalmologic apparatus 10. However, in reality, even if the light entering the subject's eye E is not completely parallel to the optical axis, the scanning diameter of the light beam irradiated onto the fundus may be equal to or smaller than the diameter of the fovea centralis of the subject's eye E, depending on the axial length of the subject's eye E. In other words, when the light entering the subject's eye E is not parallel to the optical axis, the scanning diameter may be larger or smaller than the diameter of the fovea centralis, depending on the axial length of the subject's eye E.

[0040] Below, we will explain the conditions corresponding to the axial length of the pivot position P and the deflection angle θ of the light beam by the two-dimensional scanner 108 (the angle (hereinafter sometimes referred to as the incident angle) between the light beam incident on the ocular lens of the subject's eye E from the pivot position P and the optical axis of the ophthalmic device 10) so that the scanning diameter is equal to or smaller than the diameter of the fovea centralis (i.e., the maximum value of the scanning diameter is equal to or smaller than the diameter of the fovea centralis).

[0041] 12 shows the path of a light beam when the pivot position P is set at a position farther from the cornea than the focal point (front focal point) of the ocular lens OL of the eye E (i.e., the lens when the eye E is considered as one lens). If the focal length of the ocular lens OL (the distance from the principal point to the front focal point) is f, the distance from the principal point of the ocular lens OL to the pivot position P is a, and the distance from the principal point of the ocular lens OL to the conjugate position Q of the pivot position P with respect to the eye lens OL is b, the following equation (1) holds true from paraxial approximation.

[0042]

number

[0043] When the pivot position P is set as shown in FIG. 12, a>f, so b becomes a positive value, and the light transmitted through the ocular lens OL is refracted and travels so as to converge on the center of the fundus (i.e., approach the center of the fundus). Therefore, the scanning diameter of the light beam becomes maximum immediately after passing through the ocular lens. In other words, the scanning diameter of the light beam irradiated on the fundus of the subject's eye E becomes larger as the axial length of the subject's eye E becomes shorter. Therefore, when a>f is set, the conditions for each value are calculated so that the maximum value of the scanning diameter is equal to or less than the diameter of the fovea for the subject's eye E, which has a shorter than average axial length (i.e., a so-called short-axial eye).

[0044] Here, the height of the light beam irradiated to the principal point of the eyeball lens OL (the distance from the optical axis of the ophthalmic device 10) is h0, and the air-equivalent distance from the principal point to the fundus of the short-axis eye is AL. S Then, the scanning radius of the light beam at the fundus (the distance from the center of the fundus) h S can be expressed by the following equation (2).

[0045]

number

[0046] The deflection angle θ of the light beam can be expressed by the following equation (3).

[0047]

number

[0048] As described above, in order to measure the eye refractive power with high accuracy using the ophthalmic device 10, the scanning diameter must be equal to or smaller than the diameter of the fovea centralis. Therefore, when the diameter of the fovea centralis is d, the following equation (4) must be satisfied.

[0049]

Number

[0050] From formulas (1) to (4), the condition of the distance a from the principal point of the ocular lens OL to the pivot position P and the swing angle θ of the light beam can be expressed as in the following formula (5).

[0051]

Number

[0052] Figure 13 shows the path of the light beam when the pivot position P is set at a position closer to the cornea than the focal point (front focal point) of the ocular lens OL of the eye to be examined E. When the pivot position P is set as shown in Figure 13, since a < f, b becomes a negative value, and the light transmitted through the ocular lens OL is refracted and travels so as to diverge (i.e., move away from the center of the fundus) around the fundus. Therefore, the scanning diameter of the light beam increases as it moves away from the ocular lens OL. That is, the scanning diameter of the light beam irradiated on the fundus of the eye to be examined E increases as the axial length of the eye to be examined E increases. Therefore, when a < f is set, the conditions of each value for the maximum value of the scanning diameter to be less than or equal to the diameter of the fovea are calculated in the eye to be examined E having an axial length longer than the general axial length (i.e., a so-called long axial length eye).

[0053] Similar to formula (2), the air equivalent distance from the principal point to the fundus of the long axial length eye is AL L Then, the scanning radius h of the light beam at the fundus L can be expressed by the following formula (6) from Figure 13. As described above, since b has a negative value, in Figure 13, the distance from the principal point of the ocular lens OL to the conjugate position Q is taken as "-b" to derive the following formula (6).

[0054]

Number

[0055] Therefore, from equations (1), (3), (4), and (6), the condition for the distance a from the principal point of the eyeball lens OL to the pivot position P and the deflection angle θ of the light beam can be expressed as the following equation (7).

[0056]

number

[0057] Here, the values ​​of the diameter d of the fovea and the focal length f of the eyeball lens are the air-equivalent distance AL from the principal point of the eye E to the fundus. S , A.L. L The variation between subjects is smaller than that of the above formulas (5) and (7). That is, in the above formulas (5) and (7), the diameter d and the focal length f can be set as fixed values. Specifically, the diameter d can be set to approximately 1.5 mm, which is the diameter of a typical fovea known in the technical field. Furthermore, since the total refractive power of the Gullstrand model eye is 58.64 D, the focal length f can be set to 1000 / 58.6 = 17.1 (mm).

[0058] On the other hand, the air equivalent distance AL in the above formula (5) S For (7), the lower limit of the short axial length (i.e., the shortest axial length to be considered) is calculated. Specifically, from +15D, which is the upper limit of the refractometer measurement range defined in the international standard ISO10342:2010 by the International Organization for Standardization, and the focal length f, it can be set as 1 / (1 / 17+15 / 1000)=13.6 (mm). Also, the air equivalent distance AL in the above formula (7) L For (a), the upper limit of the axial length (i.e., the longest axial length to be considered) is calculated. Specifically, using -15D, the lower limit of the refractometer measurement range defined in the international standard ISO10342:2010, and the focal length f, it can be set as 1 / (1 / 17-15 / 1000) = 22.9 (mm). By substituting these values ​​into equations (5) and (7), the conditional expressions for the distance a and the oscillation angle θ can be calculated. Specifically, it can be determined that the range satisfies the following equations (8) and (9).

[0059]

number

[0060]

number

[0061] When actually measuring the ocular refractive power of the subject's eye E, the pivot position P is set as the distance a' from the corneal apex of the subject's eye E. However, since the principal point of the ocular lens OL exists inside the subject's eye E, the actual distance from the corneal apex of the subject's eye E to the front focal point does not coincide with the focal length of 17.1 mm. Therefore, when actually calculating the conditions, the distance a in the above formulas (8) and (9) is corrected to a = a' - 15.7 + 17.1 = a' + 1.4 (mm) based on the fact that the distance from the corneal apex to the front focal point of the Gullstrand model eye is 15.7 mm, and the conditions are calculated.

[0062] FIG. 14 is a graph showing the range (hatched area) that satisfies Equations (8) and (9). By setting the distance a' and the incident angle θ to values ​​within the hatched area shown in FIG. 14, the scanning diameter of the ring-shaped scanning light beam can be made equal to or smaller than the diameter of the fovea of ​​the subject's eye E, regardless of the axial length of the subject's eye E. In other words, the eye refractive power can be measured with high accuracy. In this embodiment, the light beam deflected by the two-dimensional scanner 108 is set to form a pivot just before the subject's eye E. For this reason, the vertical and horizontal axes (i.e., a' = 0 mm, θ = 0°) are not included in the conditions in FIG. 14.

[0063] Example 2 In the first embodiment, the ring lens 138 was used to form a ring-shaped image of light scattered at the fundus of the subject's eye E on the light-receiving surface of the two-dimensional sensor 140. In the second embodiment, as shown in FIG. 15, a lens array 238 (an example of an optical element) is arranged instead of the ring lens 138. As shown in FIG. 16, the lens array 238 is composed of a plurality of lenses 238a arranged in a lattice pattern on a flat plate and light-shielding portions 238b on which a light-shielding coating is applied to the area excluding each lens 238a. Similar to the ring lens 138 of the first embodiment, the lens array 238 is arranged so that the light-shielding portions 238b are conjugate with the fundus of the subject's eye E. As a result, reflected light from the fundus is extracted from the pupil periphery in the form of lattice points corresponding to the light-shielding portions 238b. When reflected light is incident on the lens array 238, a dot pattern image corresponding to each lens 238a is formed on the detection surface of the two-dimensional sensor 140. In this embodiment, the refractive power of the subject's eye E is calculated based on the dot pattern imaged by the two-dimensional sensor 140. For example, by detecting the position coordinates of each dot imaged on the two-dimensional sensor 140, it is possible to measure the wavefront distortion caused by the eyeball of the subject's eye E (i.e., the total aberration of the eyeball).

[0064] Example 3 In the ophthalmic apparatus of Example 3, as shown in FIG. 17 , a relay lens 208 is arranged instead of the two-dimensional scanner 108 of Example 1. Like the two-dimensional scanner 108 of Example 1, the relay lens 208 is arranged at a position conjugate with the pivot position P. The relay lens 208 is driven by a driving device (e.g., a hollow motor, a voice coil motor (VCM) or the like) (not shown) in a ring shape around the optical axis of the ophthalmic apparatus on a plane perpendicular to the optical axis of the ophthalmic apparatus. In this example, the relay lens 208 is decentered in a ring shape with respect to the optical axis of the ophthalmic apparatus, thereby deflecting the light beam incident on the relay lens 208 and enabling ring-shaped scanning of the fundus of the subject's eye E. In this example, by combining the relay lens 208 with a driving device such as a VCM, ring-shaped scanning of the light beam can be achieved at low cost.

[0065] Example 4 In the ophthalmologic apparatus of Example 4, as shown in FIG. 18 , a wedge-shaped prism 308 is arranged instead of the two-dimensional scanner 108 of Example 1. The prism 308 is arranged at a position conjugate with the pivot position P, similar to the two-dimensional scanner 108 of Example 1. The prism 308 is driven to rotate about the optical axis by a driving device (e.g., a hollow motor) (not shown). In this example, the prism 308 rotates about the optical axis, thereby deflecting the light beam incident on the prism 308 and enabling ring-shaped scanning of the fundus of the subject's eye E. In this example as well, the combination of the prism 308 and the hollow motor enables ring-shaped scanning of the light beam at low cost.

[0066] Example 5 In the ophthalmologic apparatus of Example 5, as shown in FIG. 19 , a plane-parallel plate 408 is disposed instead of the two-dimensional scanner 108 of Example 1. In this example, the thickness and inclination angle of the plane-parallel plate 408 are adjusted so that the pivot is formed at a position corresponding to the focal length of the objective lens 128. The plane-parallel plate 408 is driven to rotate about the optical axis by a driving device (e.g., a hollow motor) (not shown). In this example, as the plane-parallel plate 408 rotates about the optical axis, a light beam incident on the plane-parallel plate 408 is output from the periphery of the optical axis in the same traveling direction as the incident light beam (i.e., the optical axis direction). In other words, as the plane-parallel plate 408 rotates, a light beam scanned in a ring shape parallel to the optical axis is output from the plane-parallel plate 408. Therefore, in this example as well, the light beam emitted from the light source 120 can scan the fundus of the subject's eye E in a ring shape.

[0067] Although the embodiments have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and variations of the specific examples exemplified above. The technical elements described in this specification or drawings exhibit technical utility alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Furthermore, the technology exemplified in this specification or drawings simultaneously achieves multiple objectives, and achieving one of these objectives itself has technical utility. [Explanation of symbols]

[0068] 10: Ophthalmology equipment 20:Optical system 108: 2D scanner 120: Light source 128: Objective lens 138: Ring lens 140: 2D sensor

Claims

1. 1. An ophthalmic device comprising: a measurement optical system including a light projecting optical system having a light source that projects a spot-shaped light beam onto the fundus of the subject's eye, and a light receiving optical system having a light receiving element that receives reflected light from the fundus of the subject's eye; a calculation unit that calculates the ocular refractive power of the subject's eye based on an output of the light receiving element; a light beam deflecting member disposed in an optical path of the measurement optical system and deflecting the light beam projected from the light source; a driving device that drives the light beam deflecting member so that the light beam projected from the light source scans the subject's eye in a ring shape; It is equipped with the light beam deflecting member is provided such that, when driven by the driving device, a traveling direction of the light beam projected from the light source intersects with an optical axis of the ophthalmic apparatus between the eye to be examined and the light beam deflecting member, The driving device drives the light beam deflecting member so that the traveling direction of the light beam incident on the subject's eye becomes approximately parallel inside the subject's eye.

2. The ophthalmic apparatus according to claim 1 , wherein the light beam deflecting member is disposed at a position conjugate with a crossing position where the traveling directions of the light beams cross each other.

3. 3. The ophthalmologic apparatus according to claim 1, wherein the light receiving optical system is arranged at a position conjugate with the fundus of the subject's eye, and further includes an optical element that focuses the reflected light in a ring shape onto the light receiving element.

4. 3. The ophthalmic apparatus according to claim 1, wherein the light receiving optical system further includes an optical element having a plurality of lenses arranged in a grid pattern at positions conjugate with the fundus of the test eye, each of the plurality of lenses focusing the reflected light onto the light receiving element in a grid point pattern.

5. When the diameter of the fovea of ​​the eye to be examined is 1.5 mm, the focal length of the ocular lens of the eye to be examined is 17.1 mm, the distance from the corneal vertex of the eye to the intersection position where the traveling directions of the light beams intersect is a', the distance from the principal point of the ocular lens of the eye to be examined to the intersection position is a, and the angle formed by the light beam incident on the ocular lens of the eye to be examined from the intersection position and the optical axis of the ophthalmic apparatus is θ, When a>17.1, the following formula: [0012] Fulfilling When a<17.1, the following formula: [0013] 5. The ophthalmologic apparatus according to claim 1, wherein the position of the light beam deflector or the deflection angle of the light beam is set so as to satisfy the following condition.

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