Ophthalmologic apparatus and control program of ophthalmologic apparatus

Abstract

To provide an ophthalmologic apparatus and a control program of an ophthalmologic apparatus capable of performing alignment between the cornea apex of an eye to be examined and a measurement optical axis more accurately.SOLUTION: A control part performs an alignment step for preforming relative positioning between a measurement optical axis which is a common optical axis of a light projection optical system and a light reception optical system, and the cornea of an eye to be examined on the basis of an observation image of the anterior eye part captured by an anterior eye part observation optical system. In the alignment step, the control part can perform a measurement reflection image alignment step. In the measurement reflection image alignment step, the control part performs relative positioning between the measurement optical axis and the cornea using both an alignment index image 42 projected on the cornea of the eye to be examined by an alignment index projection optical system and a reflection image 51 of the measurement light projected by the light projection optical system and reflected by the cornea of the observation images 20 of the anterior eye part.SELECTED DRAWING: Figure 9

Description

[Technical field]

[0001] The present disclosure relates to an ophthalmic apparatus that measures characteristics of a subject's eye by irradiating the subject's eye with measurement light, and an ophthalmic apparatus control program executed in the ophthalmic apparatus. [Background technology]

[0002] There is known an ophthalmic device that uses measurement light to measure the characteristics of a subject's eye. For example, an eye refractive power measuring device described in Patent Document 1 converts a reflected light beam from the fundus of the subject's eye into a measurement target image consisting of multiple ring images, receives the light on a light receiving element, and measures the eye refractive power of the subject's eye based on the measurement target image captured by the light receiving element. The light receiving optical system of the eye refractive power measuring device described in Patent Document 1 includes a hole mirror. The hole mirror reflects fundus reflected light required for measurement toward the light receiving element. On the other hand, the hole mirror passes corneal reflected light that is reflected by the cornea of ​​the subject's eye and travels toward the light receiving element along the optical axis of the light receiving optical system. In other words, the hole mirror in Patent Document 1 is an example of a corneal reflected light removing unit that removes corneal reflected light that travels toward the light receiving element.

[0003] The eye refractive power measuring device described in Patent Document 1 includes an alignment target projection optical system that projects an alignment target onto the cornea of ​​the subject's eye. In eye refractive power measurement, alignment between the measurement unit and the subject's eye is performed based on the alignment target that appears in an observation image of the anterior segment of the subject's eye. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2005-103103 A Summary of the Invention [Problem to be solved by the invention]

[0005] It is sometimes desirable to match the measurement optical axis (the optical axis of the measurement light and the optical axis of the light-receiving optical system) of an ophthalmic apparatus with the corneal apex of the subject's eye with higher accuracy.

[0006] For example, as described in Patent Document 1, when alignment in a direction intersecting the measurement optical axis is performed by an alignment index projected around the corneal apex, the measurement optical axis is aligned to a position predicted to be the corneal apex based on the alignment index image in the observation image. In this case, if the shape of the cornea of ​​the test eye is symmetrical around the corneal apex, the measurement optical axis is easily aligned to the vicinity of the corneal apex by performing alignment based on the alignment index image. As a result, the corneal reflected light of the measurement light reflected by the corneal apex and directed to the light receiving element is appropriately removed by the corneal reflected light removing unit. However, if the shape of the cornea of ​​the test eye is not symmetrical around the corneal apex, even if alignment is performed based on the alignment index projected around the corneal apex, the position of the corneal apex predicted by the alignment index image in the observation image will deviate from the actual corneal apex, making it difficult for the optical axis of the light receiving optical system to match the vicinity of the corneal apex. If the optical axis of the light receiving optical system does not coincide with the vicinity of the corneal apex, there is a high possibility that the corneal reflected light will be incident on the light receiving element without being removed by the corneal reflected light removing unit. As a result, the corneal reflected image may overlap with the measurement target image captured by the light receiving element, resulting in a decrease in measurement accuracy. If the range in which the corneal reflected light is removed by the corneal reflected light removing unit is widened in order to reduce the possibility that the corneal reflected light will be incident on the light receiving element, it becomes difficult to reflect the fundus reflected light passing near the measurement optical axis in the measurement result (i.e., the measurement area becomes narrow), and the quality of the measurement decreases. In addition, there are cases where it is desirable to improve the accuracy of the alignment between the corneal apex of the test eye and the measurement optical axis for other reasons.

[0007] A typical object of the present disclosure is to provide an ophthalmic apparatus and an ophthalmic apparatus control program capable of performing alignment between the corneal apex of a subject's eye and a measurement optical axis with higher accuracy. [Means for solving the problem]

[0008] An ophthalmic apparatus provided by a typical embodiment of the present disclosure includes a light projecting optical system that projects measurement light onto a fundus of a test eye via an objective lens, a light receiving optical system that causes a light receiving element to receive reflected light of the measurement light that is reflected by the fundus and passes through the objective lens, an alignment target projection optical system that projects an alignment target onto a cornea of ​​the test eye, an anterior segment observation optical system that captures an observation image of an anterior segment of the test eye, and a control unit, and the control unit determines, based on the observation image of the anterior segment captured by the anterior segment observation optical system, An alignment step is executed to perform relative alignment between a measurement optical axis, which is a common optical axis of the light-projecting optical system and the light-receiving optical system, and the cornea of ​​the test eye, and in the alignment step, a measurement reflection image alignment step can be executed to perform relative alignment between the measurement optical axis and the cornea by using both an alignment index image projected onto the cornea of ​​the test eye by the alignment index projection optical system and a reflected image of the measurement light projected by the light-projecting optical system and reflected by the cornea, among the observation images of the anterior segment.

[0009] An ophthalmic apparatus control program provided by a typical embodiment of the present disclosure is an ophthalmic apparatus control program executed by an ophthalmic apparatus, the ophthalmic apparatus including: a light projection optical system that projects measurement light onto a fundus of a test eye via an objective lens; a light receiving optical system that causes a light receiving element to receive reflected light of the measurement light that is reflected by the fundus and passes through the objective lens; an alignment target projection optical system that projects an alignment target onto a cornea of ​​the test eye; an anterior segment observation optical system that captures an observation image of an anterior segment of the test eye; and a control unit. The ophthalmic apparatus control program is executed by the control unit of the ophthalmic apparatus, whereby the anterior segment observation optical system and causing the ophthalmic device to execute an alignment step of performing relative alignment between a measurement optical axis, which is a common optical axis of the light-projecting optical system and the light-receiving optical system, and the cornea of ​​the test eye based on an observation image of the anterior eye captured by the light-projecting optical system. In the alignment step, the ophthalmic device is capable of executing a measurement reflection image alignment step of performing relative alignment between the measurement optical axis and the cornea by using both an alignment index image projected onto the cornea of ​​the test eye by the alignment index projection optical system and a reflected image of the measurement light projected by the light-projecting optical system and reflected by the cornea, among the observation images of the anterior eye.

[0010] According to the ophthalmic apparatus and ophthalmic apparatus control program according to the present disclosure, alignment between the corneal apex of the test eye and the measurement optical axis can be more easily performed with higher accuracy. [Brief description of the drawings]

[0011] [Figure 1] 1 is a side view showing the external configuration of an ophthalmologic apparatus 1 of the present embodiment. [Diagram 2] 1 is a schematic diagram of an optical system of an ophthalmic apparatus 1 of the present embodiment. [Diagram 3] 1A and 1B are a front view and a cross-sectional view of a ring lens 125 of the present embodiment. [Figure 4] 10 is an explanatory diagram for explaining a situation in which corneal reflected light is removed by a corneal reflected light removing portion; FIG. [Diagram 5]13 is an explanatory diagram for explaining a situation in which corneal reflected light is not removed by a corneal reflected light removing portion and is incident on a light receiving element 126. FIG. [Figure 6] 13 is a diagram showing an example of a ring image captured by the light receiving element 126 when corneal reflected light is incident on the light receiving element 126. FIG. [Figure 7] 4 is a flowchart of an alignment process executed by the ophthalmologic apparatus 1 of the first embodiment. [Figure 8] FIG. 11 is a diagram showing an example of an observation image 20 when alignment processing (target image alignment processing) of the first embodiment is started. [Figure 9] FIG. 2 is a diagram showing an example of an observation image 20 for calculating a relative relationship. [Figure 10] 13 is a diagram showing an example of the observed image 20 after the new reference position NBP is calculated. FIG. [Figure 11] 10 is a flowchart of an alignment process executed by an ophthalmic apparatus 1 according to a second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] <Summary> The ophthalmic apparatus exemplified in the present disclosure includes a light projecting optical system, a light receiving optical system, an alignment index projection optical system, an anterior segment observation optical system, and a control unit. The light projecting optical system projects measurement light onto the fundus of the subject's eye via an objective lens. The light receiving optical system causes a light receiving element to receive the reflected light of the measurement light that is reflected by the fundus of the subject's eye and passes through the objective lens. The alignment index projection optical system projects an alignment index onto the cornea of ​​the subject's eye. The anterior segment observation optical system captures an observation image of the anterior segment of the subject's eye. The control unit is responsible for controlling the ophthalmic apparatus. The control unit executes an alignment step of performing relative alignment between a measurement optical axis, which is a common optical axis of the light projecting optical system and the light receiving optical system, and the cornea of ​​the subject's eye based on the observation image of the anterior segment captured by the anterior segment observation optical system. In the alignment step, the control unit can execute a measurement reflection image alignment step. In the measurement reflected image alignment step, the control unit performs relative alignment between the measurement optical axis and the cornea using both the alignment index image projected onto the cornea of ​​the test eye by the alignment index projection optical system and the reflected image of the measurement light projected by the light projection optical system and reflected by the cornea, out of the observation images of the anterior segment.

[0013] Even if the alignment is not completed and the distance between the measurement optical axis and the corneal apex of the test eye is still far away, the alignment index projected onto the cornea by the alignment index projection optical system is likely to be clearly reflected in the observation image of the anterior eye. On the other hand, as described above, if the shape of the cornea of ​​the test eye is not symmetrical around the corneal apex, even if the alignment is performed based on the alignment index projected around the corneal apex, the position of the corneal apex predicted by the alignment index will be shifted from the actual corneal apex, and the measurement optical axis will be difficult to match with the vicinity of the corneal apex. On the other hand, the measurement light is emitted toward the test eye along the measurement optical axis. Therefore, when the distance between the measurement optical axis and the corneal apex approaches to a certain extent, the position of the reflection image of the measurement light (hereinafter, sometimes simply referred to as the "measurement light reflection image") reflected in the observation image is likely to match with the actual corneal apex position (the position of the cornea perpendicular to the measurement optical axis) with high accuracy, regardless of whether the shape of the cornea is symmetrical or not. Therefore, in the measurement reflection image alignment step, the control unit can properly perform alignment between the corneal apex of the test eye and the measurement optical axis with higher accuracy by using both the alignment index image, which is likely to be reflected in the observation image of the anterior eye, and the measurement light reflection image, which is likely to coincide with the position of the actual corneal apex.

[0014] In addition, by providing an additional optical system that irradiates light along the measurement optical axis in addition to the measurement light in the ophthalmic device, the position of the corneal reflection image of the light by the additional optical system in the observation image can be considered to be the actual position of the corneal apex. However, when the light emitted by the additional optical system is irradiated to the cornea through the objective lens along the measurement optical axis, the reflected light of the light by the objective lens appears as a bright spot in the observation image. Also, when the light emitted by the additional optical system is irradiated to the cornea along the measurement optical axis without passing through the objective lens, it is necessary to place an optical system between the objective lens and the test eye to make the optical axis of the additional optical system and the measurement optical axis coaxial. In this case, the distance between the device and the test eye (so-called working distance) becomes short, which may make the measurement difficult. In contrast, according to the technology disclosed herein, the measurement light reflection image is used, and alignment is performed with high accuracy without causing both the problem of the reflected light by the objective lens and the problem of the working distance becoming short.

[0015] The alignment index projection optical system may project an alignment index onto the cornea so that a reference position expected to be the corneal apex can be calculated based on the position of the alignment index image around the corneal apex of the cornea of ​​the subject eye shown in the observation image. For example, the alignment index projection optical system may project a finite index onto the cornea by a light source arranged in a ring shape around the measurement optical axis. In this case, a ring index (so-called Mayer ring) is projected onto the cornea as the alignment index. The control unit may calculate the center position of the ring index shown in the observation image as the reference position expected to be the corneal apex. The alignment index optical system may also project a finite index onto the cornea by at least three point light sources arranged symmetrically around the measurement optical axis. In this case, the control unit may calculate the center position of the three point-shaped alignment index images shown in the observation image as the reference position expected to be the corneal apex.

[0016] In the measurement reflection image alignment step, the control unit may execute a relative position calculation step of calculating the relative relationship between a reference position predicted to be the corneal apex by the alignment index image in the observation image of the anterior segment and the position of the measurement light reflection image (e.g., the center position of the measurement light reflection image, etc.). In this case, for example, at least one of the following is appropriately grasped by the calculated relative relationship: whether or not the reference position and the measurement light reflection image match, the amount of deviation (distance) when the reference position and the measurement light reflection image are deviated, the direction of deviation, and the relative relationship between the position of the alignment index image and the position of the measurement light reflection image. Therefore, it becomes easier to perform alignment more appropriately.

[0017] A specific method for calculating the relative relationship between the reference position and the position of the measurement light reflection image can be appropriately selected. For example, the control unit may directly calculate the relative relationship (direction and distance) between the reference position (e.g., the center position of the alignment index image, etc.) predicted to be the corneal apex by the alignment index image and the position of the measurement light reflection image. As described above, the reference position is calculated based on the position of the alignment index image shown in the observation image. Therefore, the control unit may calculate the relative relationship between the reference position and the position of the measurement light reflection image by calculating the relative relationship (direction and distance) between the position of the alignment index image shown in the observation image and the position of the measurement light reflection image.

[0018] In the measurement reflection image alignment step, the control unit may calculate the position of the reflection image (hereinafter referred to as "new reference position") that is to be reflected in the observation image when the measurement light is projected based on the position of the alignment index image reflected in the observation image and the relative relationship calculated in the relative position calculation step, and may align the position of the measurement optical axis to the calculated new reference position. In other words, the control unit may change the target position for aligning the position of the measurement light from the reference position to the new reference position based on the relative relationship between the alignment index image and the measurement light reflection image calculated in the relative relationship calculation step. In this case, if the control unit can detect the position of the alignment index image that is likely to be reflected in the observation image of the anterior segment, the control unit can match the position of the measurement optical axis with the position of the actual corneal apex with high accuracy by aligning the position of the measurement optical axis to the new reference position calculated based on the position of the detected alignment index image. As a result, regardless of whether the measurement light is emitted during alignment, it becomes easier to perform alignment appropriately with higher accuracy.

[0019] During the alignment step, the control unit may stop the emission of the measurement light by the light projection optical system when the photographing of the observation image of the anterior eye used for calculating the relative relationship in the relative position calculation step is completed. If the measurement light is emitted toward the subject's eye during alignment, when the subject's eye has cataracts, the measurement light may be reflected by the transillumination or the reflection from the crystalline lens in the observation image of the anterior eye, making it difficult to accurately detect the position of the Purkinje image (e.g., the alignment index image). In response to this, the control unit stops the emission of the measurement light when the photographing of the observation image of the anterior eye used for calculating the relative relationship between the reference position and the position of the measurement light reflection image is completed, thereby reducing the possibility that the position of the alignment index image is difficult to detect due to the influence of the transillumination or the reflection from the crystalline lens.

[0020] The control unit may emit the measurement light again to capture an observation image of the anterior eye when the alignment of the measurement optical axis with respect to the new reference position calculated based on the relative relationship between the reference position and the position of the measurement light reflection image is completed. The control unit may calculate the relative position of the measurement light reflection image and the measurement optical axis in the captured observation image. In this case, the control unit can confirm whether the position of the measurement optical axis has been aligned with high accuracy near the corneal apex based on the relative position of the measurement light reflection image and the measurement optical axis calculated after the alignment is completed. In addition, the control unit may execute the measurement reflection image alignment step again when the relative position of the measurement light reflection image and the measurement optical axis calculated after the alignment is completed does not satisfy the criteria (for example, when the distance between them is equal to or greater than a threshold value). In this case, the alignment can be performed more accurately.

[0021] However, in cases where continued irradiation of the measurement light does not affect the detection accuracy of the alignment index image, the control unit may emit the measurement light even after the capture of the observation image for calculating the relative relationship has been completed.

[0022] In the measurement reflection image alignment step, the control unit may align the final position of the measurement optical axis to the position of the measurement light reflection image captured in the observation image of the anterior segment (e.g., the center position of the measurement light reflection image, etc.). As described above, the position of the measurement light reflection image captured in the observation image of the anterior segment tends to accurately match the position of the actual corneal apex. Therefore, by aligning the final position of the measurement optical axis to the position of the measurement light reflection image captured in the observation image, it becomes easier to perform alignment with higher accuracy.

[0023] In addition, a specific control method for aligning the final position of the measurement optical axis with the position of the measurement light reflection image can be appropriately selected. For example, when the control unit starts the measurement reflection image alignment step, the control unit may first complete a process of aligning the position of the measurement optical axis with a reference position that is predicted to be the corneal apex by an alignment index image reflected in the observation image of the anterior eye. During this time, it is more preferable to stop the emission of the measurement light. Thereafter, the control unit may align the final position of the measurement optical axis with the position of the measurement light reflection image reflected in the observation image of the anterior eye. In this case, when the movement of the measurement optical axis to the reference position is completed, rough alignment is completed, so that the measurement light reflection image is easily reflected in the observation image. Thereafter, the final position of the measurement optical axis is aligned with the position of the measurement light reflection image reflected in the observation image, so that the position of the measurement optical axis is easily aligned with the corneal apex with high accuracy.

[0024] In the measurement reflection image alignment step, the control unit may align the position of the measurement optical axis with the position of the measurement light reflection image while continuously or intermittently emitting a measurement light having a smaller amount of light than the amount of light emitted during measurement of the subject's eye after the alignment is completed to the measurement optical system. If the amount of measurement light emitted during alignment is increased, when the subject's eye has cataracts, the measurement light may be easily reflected in the observation image of the anterior eye, and the position of the Purkinje image (e.g., the measurement light reflection image, etc.) in the observation image may be difficult to accurately detect. On the other hand, by making the amount of measurement light emitted during alignment smaller than the amount of light emitted during measurement of the subject's eye, the possibility that the position of the Purkinje image may be difficult to detect due to the influence of the reflection from the crystalline lens is reduced. Note that the measurement light reflection image is more difficult to detect than the alignment target image. Therefore, when it is necessary to detect the position of the measurement light reflection image from the observation image, it is more effective to reduce the amount of measurement light.

[0025] The control unit may set the amount of measurement light in the measurement reflection image alignment step to be smaller than the amount of light in the transillumination image observation mode in which the subject's eye is observed by the reflected light (transillumination) of the measurement light from the fundus. In the transillumination image observation mode, the amount of measurement light is generally set to be very large. If the measurement light is emitted in the measurement reflection image alignment step with an amount of light similar to that in the transillumination image observation mode, the transillumination of the measurement light or the reflection from the crystalline lens is likely to be captured in the observation image. In contrast, by setting the amount of measurement light in the measurement reflection image alignment step to be smaller than the amount of light in the transillumination image observation mode, the possibility that the position of the Purkinje image becomes difficult to detect due to the influence of the transillumination or the reflection from the crystalline lens is appropriately reduced. In addition, the control unit may set the amount of measurement light in the measurement reflection image alignment step to be smaller than the amount of light when measuring at least one of the ocular refractive power and aberration of the subject's eye. In this case, the possibility that the position of the Purkinje image becomes difficult to detect is further reduced.

[0026] Similarly, the control unit may set the amount of measurement light in the alignment steps other than the measurement reflection image alignment step (e.g., the relative position calculation step, etc.) to be smaller than the amount of light emitted during measurement of the subject's eye. In this case, too, the possibility that the position of the Purkinje image becomes difficult to detect is appropriately reduced.

[0027] A specific method for aligning the position of the measurement light axis with the position of the measurement light reflection image can be appropriately selected. For example, the control unit may continuously emit (i.e., turn on) the measurement light during the measurement reflection image alignment step. In this case, the control unit can always detect the position of the measurement light reflection image in the observation image, so that the alignment can be easily performed accurately in a short time. In addition, the control unit may intermittently emit (i.e., blink) the measurement light multiple times during the measurement reflection image alignment step. In this case, the possibility that the position of the measurement light reflection image becomes difficult to detect due to the influence of the above-mentioned transillumination or reflection from the crystalline lens is reduced compared to the case where the measurement light is constantly emitted.

[0028] The control unit may also store the position of the measurement light reflection image in the observation image captured by the anterior eye observation optical system when the measurement light is emitted at least once. The control unit may align the position of the measurement light axis to the position of the stored reflection image. In this case, the control unit may omit emission of the measurement light or reduce the number of emission times until the alignment is completed after storing the position of the measurement light reflection image. For example, after emitting the measurement light and capturing the observation image, the control unit may stop emitting the measurement light and move the position of the measurement light axis toward the position of the stored measurement light reflection image. When the movement of the measurement light axis to the position of the stored reflection image is completed, the control unit may emit the measurement light and capture the observation image again, and finely adjust the position of the measurement light axis to the position of the reflection image of the re-captured observation image. Furthermore, after emitting the measurement light and capturing the observation image, the control unit may also complete the alignment by aligning the position of the measurement light axis to the position of the stored measurement light reflection image without irradiating the measurement light. Therefore, the alignment can be performed appropriately while suppressing the influence of the above-mentioned transillumination or reflection from the crystalline lens.

[0029] In the alignment step, the control unit may selectively execute either an index image alignment step or an alignment step using a measurement light reflection image. In the index image alignment step, the control unit may detect an alignment index image projected onto the cornea of ​​the subject's eye by the alignment index projection optical system based on the observation image of the anterior eye, and align the position of the measurement optical axis to a reference position predicted to be the apex of the cornea by the detected alignment index image. As described above, even if the distance between the measurement optical axis and the corneal apex of the subject's eye is large, the alignment index image projected onto the cornea by the alignment index projection optical system is likely to be clearly reflected in the observation image of the anterior eye. In addition, the measurement light is often emitted by the projection optical system with a narrow beam diameter and nearly parallel. Therefore, the measurement light reflection image is unlikely to be reflected in the observation image unless the positions of the measurement optical axis and the corneal apex are close to each other by a certain amount. However, the position of the measurement light reflection image is likely to coincide with the actual corneal apex position with high accuracy, regardless of whether the corneal shape is symmetrical or not. As described above, there are advantages to both the target image alignment step and the alignment step using the measurement light reflection image. Therefore, by selectively executing the target image alignment step and the alignment step using the measurement light reflection image, it becomes easier to perform more appropriate alignment.

[0030] A specific method for selectively executing the target image alignment step and the alignment step using the measurement light reflection image can be appropriately selected. First, the method for the measurement reflection image alignment step may be a method of changing the target position of the measurement light calculated by the alignment target image from the reference position to a new reference position, or a method of aligning the position of the measurement light axis with the position of the measurement light reflection image captured in the observation image.

[0031] The control unit may also first execute the target image alignment step. After the target image alignment step is completed and the measurement light is emitted, the control unit may capture an observation image of the anterior eye using the anterior eye observation optical system, and calculate a difference (at least a distance) between a reference position predicted to be the corneal apex by the alignment target image in the captured observation image and the position of the measurement light reflection image. If the calculated difference is less than a threshold, the control unit may end the alignment step. On the other hand, if the calculated difference is equal to or greater than a threshold, the control unit may complete the alignment after executing an alignment step using the measurement light reflection image. In this case, if the alignment is performed with high accuracy by the target image alignment step, the alignment is completed without executing the alignment step using the measurement light reflection image. Also, if the accuracy of the alignment by the target image alignment step is low, the alignment is performed with high accuracy by the alignment step using the measurement light reflection image. Thus, the alignment is performed efficiently and with high accuracy. The threshold value for comparing the above-mentioned difference may be set in advance based on the design values ​​of various optical systems (e.g., the innermost diameter of the multiple ring images formed on the light receiving element, etc.). The threshold value may be changed based on the quality of the result of actually measuring the characteristics of the subject's eye (e.g., at least one of the ocular refractive power and the aberration, etc.) using the measurement light, and the accuracy of the alignment during the measurement. The threshold value may be set according to an instruction input by the user.

[0032] The control unit may also first execute an index image alignment step. After completing the index image alignment step, the control unit may execute a measurement process of the characteristics of the subject's eye using the measurement light, and evaluate the accuracy of the measurement result. The control unit may complete the alignment when the accuracy of the measurement result satisfies a standard, and may execute an alignment step using the measurement light reflection image when the accuracy of the measurement result does not satisfy the standard. In this case, whether to execute the alignment step using the measurement light reflection image is appropriately determined according to the accuracy of the measurement result.

[0033] The control unit may also acquire information on the corneal shape of the test eye measured by the corneal shape measuring unit. The control unit may execute an index image alignment step when the corneal shape of the test eye indicated by the acquired information satisfies a criterion, and execute an alignment step using a measurement light reflection image when the criterion is not satisfied. In this case, one of the index image alignment step and the alignment step using the measurement light reflection image is executed efficiently and appropriately. The corneal shape measuring unit may be included in the ophthalmic device itself that actually executes the alignment. The ophthalmic device may also acquire information on the corneal shape acquired by a corneal shape measuring unit of another device. The corneal shape information may be information acquired in a simple manner.

[0034] The ophthalmic device may further include a corneal reflection light removing unit that removes corneal reflection light that is reflected by the cornea of ​​the subject's eye and travels along the optical axis of the light receiving optical system to the light receiving element. When the alignment accuracy in the direction intersecting the measurement optical axis is reduced and measurement is performed in a state in which the optical axis of the light receiving optical system is separated from the vicinity of the corneal apex, the corneal reflection light may be incident on the light receiving element without being removed by the corneal reflection light removing unit. As a result, the corneal reflection image may overlap the measurement index image captured by the light receiving element, resulting in a decrease in measurement accuracy. In contrast, according to the technology disclosed herein, the alignment between the corneal apex of the subject's eye and the measurement optical axis is performed with higher accuracy. Therefore, the corneal reflection light of the measurement light that is reflected by the corneal apex and travels to the light receiving element is easily removed appropriately by the corneal reflection light removing unit. Therefore, it is easy to perform measurement with higher accuracy.

[0035] A specific configuration of the corneal reflected light removing unit can be appropriately selected. For example, at least one of a hole mirror and a mask may be adopted as the corneal reflected light removing unit. The hole mirror may reflect the reflected light of the measurement light from the test eye, which is necessary for measuring the characteristics of the test eye, toward the light receiving element. On the other hand, the hole mirror may pass the corneal reflected light that is reflected by the cornea of ​​the test eye and travels toward the light receiving element along the optical axis of the light receiving optical system. In this case, the corneal reflected light that travels toward the light receiving element is appropriately removed by the hole mirror. In addition, the mask may be disposed at a substantially conjugate position of the pupil of the test eye (for example, at the position of a ring lens that converts the reflected light from the fundus into a multiple ring image on the light receiving element, or a position near the ring lens, etc.) to block light within a predetermined range including the optical axis of the light receiving optical system.

[0036] However, the technology disclosed herein can also be applied to an ophthalmic device that does not have a corneal reflection removing unit. Even in this case, the alignment between the corneal apex of the test eye and the measurement optical axis is performed with high accuracy, making it easier to perform more appropriate measurements.

[0037] The ophthalmologic apparatus may measure the ocular refractive power at the central corneal region by forming a ring-shaped image of fundus reflected light at the central corneal region of the pupil of the subject's eye on a light receiving element. In this case, by adopting the technology disclosed herein, the ocular refractive power at the central corneal region is measured with high accuracy while preventing the corneal reflected light from being incident on the light receiving element.

[0038] <Embodiment> A typical embodiment according to the present disclosure will be described below. The ophthalmic apparatus 1 identifies characteristics of the subject's eye E. The ophthalmic apparatus 1 of this embodiment projects measurement light onto the fundus of the subject's eye E, and can measure the characteristics of the subject's eye E (e.g., at least one of ocular refractive power and aberration) by the measurement light reflected from the fundus. The characteristics of the subject's eye E are measured in a state where the subject's eye E and the measurement optical axis LA are relatively aligned.

[0039] <Appearance> 1, an example of the external configuration of an ophthalmic apparatus 1 will be described. The ophthalmic apparatus 1 of this embodiment includes a base 11, a measurement unit 12, an alignment drive unit 13, a face support unit 15, a monitor 16, an operation unit 17, and a control unit 50.

[0040] The base 11 supports the entire ophthalmic apparatus 1. The measurement unit 12 houses an optical system and the like used to measure the subject's eye E. The face support unit 15 is fixed to the base 11. The face support unit 15 fixes the position of the subject's eye E by supporting the subject's face. The alignment drive unit 13 changes the relative position of the measurement unit 12 (more specifically, the measurement optical axis LA (see FIG. 2) extending from the measurement unit 12 to the subject's eye E) with respect to the subject's eye E by moving the measurement unit 12 in the X direction (left-right direction), the Y direction (up-down direction), and the Z direction (front-back direction) with respect to the base 11. The monitor 16 can display various information (for example, at least one of an observation image of the anterior part of the subject's eye E and a measurement result of the characteristics of the subject's eye E). The operation unit 17 is operated by a user to input an instruction from the user to the control unit 50. As an example, a touch panel provided on the monitor 16 is used for the operation unit 17 of this embodiment. The control unit 50 is responsible for controlling the ophthalmic apparatus 1.

[0041] <Optical system> An example of a schematic configuration of an optical system included in the measurement unit 12 of the ophthalmic device 1 will be described with reference to FIG. 2 and FIG. 3. The "conjugate position" in the present disclosure includes an approximately conjugate position. "Approximately conjugate" means that the position is not necessarily completely conjugate, but may be conjugate with a required accuracy in relation to the measurement accuracy. Also, "nearby" means that the position is near with a required accuracy in relation to the measurement accuracy. The measurement unit 12 of the ophthalmic device 1 of this embodiment includes a measurement optical system 100, a fixation target presenting optical system 150, an anterior eye observation optical system 200, and an alignment target projection optical system 400. Also, the measurement unit 12 includes half mirrors 501 and 502 that branch and combine the optical paths of each optical system, an objective lens 505, and the like.

[0042] (Measurement optical system) The measurement optical system 100 is used to objectively measure the characteristics (e.g., ocular refractive power) of the subject's eye E. The measurement optical system 100 includes a light projecting optical system 110 and a light receiving optical system 120. The light projecting optical system 110 projects measurement light onto the fundus of the subject's eye E via an objective lens 505. As an example, the light projecting optical system 110 of this embodiment projects spot-shaped measurement light onto the fundus of the subject's eye E via the center of the pupil of the subject's eye E. The light receiving optical system 120 causes the light receiving element 126 to receive the reflected light of the measurement light that is reflected by the fundus and passes through the pupil and the objective lens 505.

[0043] The light projection optical system 110 includes a light source 111, a relay lens 112, a hole mirror 113, an objective lens 505, and the like on an optical axis L1. The light source 111 is disposed at a fundus conjugate position on the optical axis L1 of the light projection optical system 110, and emits measurement light for measuring the characteristics of the subject's eye E. The light source 111 may be any of various light sources, such as a superluminescent diode (SLD) light source and a light emitting diode (LED) light source. The light source 111 of this embodiment is an infrared light source that emits infrared light. As an example, the light source 111 of this embodiment emits near-infrared light having a peak between wavelengths of 800 nm and 900 nm as measurement light. The opening of the hole mirror 113 is disposed at a pupil conjugate position. The measurement light emitted by the light source 111 passes through the relay lens 112, the opening of the hole mirror 113, the half mirror 502, the half mirror 501, and the objective lens 505, and is projected onto the fundus of the eye E to be examined.

[0044] The light receiving optical system 120 includes an objective lens 505, a hole mirror 113, relay lenses 121 and 122, a light receiving aperture 123, a collimator lens 124, a ring lens 125, a light receiving element 126, and the like on an optical axis L2. The reflected light from the fundus required to measure the characteristics of the subject's eye E passes through the objective lens 505, a half mirror 501, and a half mirror 502, is reflected by the hole mirror 113, passes through the relay lens 121, the light receiving aperture 123, the collimator lens 124, and the ring lens 125, and is received by the light receiving element 126. The light receiving aperture 123 is disposed at a conjugate position with the fundus. The ring lens 125 is disposed at a conjugate position with the pupil (pupil) of the subject's eye E. The light receiving element 126 is disposed at a conjugate position with the fundus.

[0045] The hole mirror 113 passes the measurement light emitted by the light source 111 of the light projecting optical system 110 through an opening, and reflects the reflected light of the measurement light from the fundus. As a result, the optical axis L1 of the light projecting optical system 110 and the optical axis L2 of the light receiving optical system 120 are made coaxial by the hole mirror 113. In addition, the hole mirror 113 passes the corneal reflected light, which is reflected by the cornea of ​​the subject's eye E and travels toward the light receiving element 126 along the optical axis L2 of the light receiving optical system 120, through the opening. Therefore, the hole mirror 113 is an example of a corneal reflected light removing unit that removes the corneal reflected light that travels toward the light receiving element 126 along the optical axis L2 of the light receiving optical system 120.

[0046] The light receiving optical system 120 of this embodiment also includes a mask 130. The mask 130 is disposed at a conjugate position of the pupil of the subject's eye E, thereby blocking light within a predetermined range including the optical axis L2, among light traveling along the optical axis 2 of the light receiving optical system 120 toward the light receiving element 126. The mask 130 is an example of a corneal reflection light removing unit that removes corneal reflection light traveling along the optical axis L2 of the light receiving optical system 120 toward the light receiving element 126. The mask 130 of this embodiment is disposed at a conjugate position of the ring lens 125 or in the vicinity of the ring lens 125.

[0047] FIG. 3 is a diagram showing an example of the ring lens 125. The ring lens 125 is arranged at a conjugate position of the pupil (pupil) of the subject's eye E, and converts the reflected light from the fundus into multiple (multiple divided in the meridian direction) ring images on the light receiving element 126 and receives (forms) the light. Therefore, the ophthalmic device 1 of this embodiment measures the eye refractive power in the central cornea region by forming a ring-shaped image of the fundus reflected light in the central cornea region of the pupil of the subject's eye E on the light receiving element 126. The left side of FIG. 3 shows a front view of the ring lens 125 (a view seen from a direction along the optical axis L2), and the right side shows a cross-sectional view of the ring lens 125 (a cross-sectional view of a cross section including the optical axis L2). The ring lens 125 shown in FIG. 3 is made of a ring-shaped cylindrical lens portion and forms three or more multiple ring images on the light receiving element 126. In the ring lens 125 illustrated in FIG. 3, ring-shaped lens parts RL1, RL2, RL3, RL4, RL5, RL6, and RL7 are provided from the inside so as to form seven ring images on the light receiving element 126. For example, the diameter D1 (diameter at the center of the lens part) of the innermost lens part RL1 on the pupil is set as small as possible while reducing the influence of the corneal reflection light of the measurement light projected by the light projecting optical system 110. For example, the diameter D1 in pupil equivalent is set to 1.5 mm or less. For example, the diameter D7 (diameter at the center of the lens part) of the outermost lens part RL7 in pupil equivalent is set to a size that covers the expected large pupil diameter of the human eye. For example, the diameter D7 in pupil equivalent is set to 6 mm or more. In the example illustrated in FIG. 3, the lens parts RL1 to RL7 are formed with the same ring width W. Each ring area on the pupil corresponding to each ring area of ​​the lens parts RL1 to RL7 is set to the measurement area. Light-blocking portions 125B that block light are formed in the inner region of lens portion RL1, the regions between lens portions RL1 to RL7, and the outer region of lens portion RL7. The gaps between adjacent lens portions are preferably small and uniform. The number of rings in ring lens 125 is not limited to seven.

[0048] The measurement optical system 100 may include a light projecting optical system that projects measurement light onto the fundus of the subject eye, and a light receiving optical system that causes a light receiving element to receive the reflected light of the measurement light reflected by the fundus. Therefore, the configuration of the measurement optical system 100 of this embodiment can be changed. For example, the measurement optical system 100 may be an optical system that projects a spot index onto the fundus and detects the reflected light of the spot index on the fundus with a Shack-Hartmann sensor. In this case, a Hartmann plate may be disposed instead of the ring lens 125. The reflected light of the spot index is separated and converted into multiple light beams by the Hartmann plate. As a result, a large number of point images are captured by the light receiving element.

[0049] (Fixation target presentation optical system) The fixation target presenting optical system 150 presents a fixation target to the subject's eye E to fixate the eye E. The fixation target presenting optical system 150 may also be used to provide fogging and accommodation load to the subject's eye E. The fixation target presenting optical system 150 includes a light source 151, a fixation target plate 155, lenses 156, 157, and an objective lens 505. The light source 151 is disposed on the optical axis L4 of the fixation target presenting optical system 150. The fixation target plate 155 is disposed at a position conjugate with the fundus. The fixation light beam from the light source 151 passes through the fixation target plate 155, the lenses 156, and 157, then passes through the half mirror 502, is reflected by the half mirror 501, becomes coaxial with the optical axis L1, and then passes through the objective lens 505 to reach the fundus.

[0050] (Anterior segment observation optical system) The anterior-segment observation optical system 200 captures an observation image of the anterior segment of the subject's eye E. In this embodiment, the anterior-segment observation image captured by the anterior-segment observation optical system 200 is used to perform relative positioning (alignment) between the measurement optical axis LA, which is a common optical axis of the light projecting optical system 110 and the light receiving optical system 120, and the cornea of ​​the subject's eye E. The anterior-segment observation optical system 200 includes a light receiving element 201, a lens 202, and an objective lens 505. The light receiving element 205 is disposed at a pupil conjugate position. The anterior-segment observation optical system 200 also serves as a detection optical system that detects an alignment index image projected onto the cornea from the alignment index projecting optical system 400 and a measurement light reflection image projected onto the cornea from the light projecting optical system 110.

[0051] (Alignment target projection optical system) The alignment target projection optical system 400 projects an alignment target onto the cornea of ​​the subject's eye E. The alignment target projection optical system 400 includes a first target projection optical system 401 and a second target projection optical system 402.

[0052] The first index projection optical system 401 projects an alignment index onto the cornea from the front facing the subject's eye E. The first index projection optical system 401 includes a plurality of point light sources 410. Each point light source 410 projects an index at infinity by irradiating the cornea with a parallel light beam. The plurality of point light sources 410 are arranged symmetrically in the vertical direction and the horizontal direction with respect to the measurement optical axis LA. As an example, in this embodiment, two point light sources 410 are provided on the left and right. As a result, four point image indices are projected onto the cornea. Note that the number of indices projected onto the cornea by the first index projection optical system 401 may be three or more, and is not limited to four. In addition, the shape of the indices projected onto the cornea by the first index projection optical system 401 is not limited to a point shape, and may include an index having a linear shape or the like. Note that the ophthalmic apparatus 1 can also simply measure the corneal shape by the indices projected onto the cornea by the first index projection optical system 401.

[0053] The second target projection optical system 402 includes a ring-shaped light source 420. The ring-shaped light source 420 projects a finite target by irradiating the cornea with a diffused light beam. The ring-shaped light source 420 is arranged in a ring shape centered on the measurement optical axis LA. As a result, a ring target (so-called Mayer ring image) is projected onto the cornea. However, it is also possible to change the specific form of the finite target projected onto the cornea by the second target projection optical system 402. For example, multiple point target images arranged in a ring may be projected onto the cornea as the finite target. In this case, the number of point target images arranged in a ring may be three or more.

[0054] The control unit 50 of the ophthalmic apparatus 1 can perform alignment in the XYZ directions of the measurement unit 12 (specifically, the measurement optical axis LA extending from the measurement unit 12 toward the test eye E) with respect to the cornea of ​​the test eye E by detecting the alignment index shown in the observation image of the anterior eye. For example, the control unit 50 calculates the center of the finite index image (a ring index in this embodiment) projected onto the cornea by the second index projection optical system 402 and shown in the observation image as a reference position predicted to be the position of the corneal apex in a direction intersecting the measurement unit 12 (the XY direction in this embodiment), and can perform alignment in the XY directions by matching the position of the measurement optical axis LA (for example, the center position of the observation image, etc.) to the calculated reference position. In addition, the control unit 50 can perform alignment in the Z direction of the measurement unit 12 with respect to the test eye E based on the relative positional relationship between the finite index image and the infinite index image shown in the observation image. When the distance in the Z direction between the subject's eye E and the measurement unit 12 changes, the infinite target image hardly changes, but the finite target image changes. Therefore, by utilizing the relative positional relationship between the finite target image and the infinite target image shown in the observation image, the alignment in the Z direction is appropriately performed.

[0055] (Diopter correction section) The ophthalmic apparatus 1 of this embodiment includes a diopter correction unit. The diopter correction unit includes a drive unit 160 and a drive unit 161. The drive unit 160 can integrally move the light source 111, the ring lens 125, and the light receiving element 126 in the measurement optical system 100, and the light source 151 and the fixation target plate 155 in the fixation target presenting optical system 150 along the direction of the measurement optical axis LA. The drive unit 161 moves the drive unit 160. For example, the drive unit 160 is moved according to the ocular refractive power of the subject's eye E (i.e., the diopter of the subject's eye), thereby changing the presentation distance of the fixation target plate 155 relative to the subject's eye E (i.e., the presentation position of the fixation target). The ring lens 125 and the light receiving element 126 of the light receiving optical system 120 are moved together so that the light receiving element 126 is near a position conjugate with the fundus of the test eye E, and the imaging state (focus state) of the ring image received by the light receiving element 126 is adjusted according to the visibility of the test eye E.

[0056] (Control System) The control unit 50 includes a CPU (processor), a RAM, and a ROM. The CPU performs various controls in the ophthalmic apparatus 10. The RAM temporarily stores various information. The ROM stores various programs executed by the CPU. The control unit 50 may be configured with a plurality of processors. The control unit 50 is electrically connected to the alignment driving unit 13 (see FIG. 1), the monitor 16, the operation unit 17, a non-volatile memory 55 (hereinafter, memory 55), the light sources of the measurement unit 12, the light receiving elements, the driving units, and the like. The memory 55 is a non-transient storage medium that can retain the stored contents even if the power supply is cut off. For example, the memory 55 may be a hard disk drive, a flash ROM, a USB memory, or the like. The ophthalmic apparatus control program that controls the ophthalmic apparatus 1 may be stored in the memory 55.

[0057] <Light reflected from the cornea enters the light receiving element> A situation where the corneal reflected light is incident on the light receiving element 126 will be described with reference to Figs. 4 to 6. Fig. 4 is an explanatory diagram for explaining a situation where the corneal reflected light is removed by the corneal reflected light removing unit. Fig. 5 is an explanatory diagram for explaining a situation where the corneal reflected light is incident on the light receiving element 126 without being removed by the corneal reflected light removing unit. Figs. 4 and 5 are simplified diagrams in which only the hole mirror 113, the mask 130, the ring lens 125, and the light receiving element 126 are extracted from the actual optical system for the sake of simplicity. As described above, the hole mirror 113 and the mask 130 are an example of a corneal reflected light removing unit that removes the corneal reflected light traveling toward the light receiving element 126 along the optical axis L2 of the light receiving optical system 120. As described above, the measurement light emitted from the light projecting optical system 110 travels toward the subject's eye E along the measurement optical axis LA that is coaxial with the optical axis L2 of the light receiving optical system 120.

[0058] When alignment in the XY direction (direction intersecting the measurement optical axis LA) is performed using an alignment index projected around the corneal apex (in this embodiment, a ring index projected by the second index projection optical system 402) as in the ophthalmic apparatus 1 of this embodiment, the measurement optical axis is aligned to the position predicted to be the corneal apex based on the alignment index image appearing in the observation image of the anterior segment.

[0059] FIG. 4 shows a state where alignment is performed by an alignment indicator projected around the corneal apex when the shape of the cornea of ​​the test eye E is symmetrical around the corneal apex. If the shape of the cornea of ​​the test eye E is symmetrical around the corneal apex, alignment is performed based on the alignment indicator image, so that the measurement optical axis LA is easily aligned near the corneal apex. In this case, as shown in FIG. 4, the corneal reflected light of the measurement light reflected by the corneal apex of the test eye E and directed toward the light receiving element 126 is appropriately removed by the corneal reflected light removing unit. In the example shown in FIG. 4, the hole mirror 113, which is an example of the corneal reflected light removing unit, passes the corneal reflected light through an opening, thereby removing the corneal reflected light directed toward the light receiving element 126. Of course, the corneal reflected light may be removed by the mask 130.

[0060] FIG. 5 shows a state where alignment is performed by an alignment index projected around the corneal apex when the shape of the cornea of ​​the subject's eye E is not symmetrical around the corneal apex. When the shape of the cornea is not symmetrical, even if alignment is performed based on the alignment index projected around the corneal apex, the position of the corneal apex predicted by the alignment index image of the observation image is likely to deviate from the actual corneal apex. As a result, the optical axis L2 of the light receiving optical system 120 is unlikely to coincide with the vicinity of the corneal apex. As shown in FIG. 5, if the optical axis L2 of the light receiving optical system 120 does not coincide with the vicinity of the corneal apex, there is a high possibility that the corneal reflected light will be incident on the light receiving element 126 without being removed by the corneal reflected light removing unit. In the example shown in FIG. 5, the corneal reflected light is reflected toward the light receiving element 126 without passing through the opening of the hole mirror 113, and further, is incident on the light receiving element 126 without being blocked by the mask 130.

[0061] As shown in FIG. 6, in the ophthalmic apparatus 1 of the present embodiment, if the corneal reflected light is incident on the light receiving element 126, the corneal reflected image is superimposed on the ring image of the reflected light from the fundus captured by the light receiving element 126. In this case, the analysis accuracy of the ring image is reduced, and the measurement accuracy of the characteristics of the subject's eye E is reduced. In particular, as in the ophthalmic apparatus 1 of the present embodiment, the smaller the diameter of the innermost lens portion RL1 (see FIG. 3) of the ring lens 125 is made as small as possible to widen the measurement area, the more easily the corneal reflected light is incident on the light receiving element 126. Therefore, the ophthalmic apparatus 1 of the present embodiment performs an alignment process for matching the measurement optical axis LA with the corneal apex of the subject's eye E with higher accuracy, thereby reducing the possibility that the corneal reflected light is incident on the light receiving element 126 and the measurement accuracy is reduced.

[0062] (First embodiment) With reference to Figs. 7 to 10, the alignment process performed by the ophthalmic apparatus 1 of the first embodiment will be described. In the alignment process of this embodiment, the alignment target image 42 reflected in the observation image 20 of the anterior eye and the reflection image of the measurement light (hereinafter, sometimes simply referred to as "measurement light reflection image") 51 are used together to perform relative positioning (alignment) between the measurement optical axis LA and the corneal apex of the subject's eye E. Note that, in the alignment process, both alignment in the XY directions (directions intersecting the measurement optical axis LA) and alignment in the Z direction (direction along the measurement optical axis LA) are performed. However, in order to facilitate understanding of the description of the technology according to the present disclosure, the description of the alignment in the Z direction will be omitted below. The alignment process illustrated in Fig. 7 is performed by the control unit 50 of the ophthalmic apparatus 1 according to an ophthalmic apparatus control program stored in the non-volatile memory 55.

[0063] As shown in Fig. 7, the control unit 50 starts capturing an observation image 20 of the anterior segment of the subject's eye E by the anterior segment observation optical system 200 (S1). Furthermore, the control unit 50 starts projecting an alignment index onto the subject's eye E by the alignment index projecting optical system 400 (S2). As a result, as shown in Fig. 8, in addition to the anterior segment of the subject's eye E, the observation image 20 of the anterior segment also includes alignment index images projected onto the cornea of ​​the subject's eye E (an alignment index image 41 at infinity projected by the first index projecting optical system 401 and an alignment index image 42 at finite distance projected by the second index projecting optical system 402).

[0064] In this embodiment, the optical axis L3 of the anterior eye observation optical system 200 also coincides with the measurement optical axis LA (i.e., the optical axis L1 of the light projecting optical system 110 and the optical axis L2 of the light receiving optical system 120). On the observation image 20 captured by the anterior eye observation optical system 200, the measurement optical axis LA coincides with the center of the capturing range of the observation image 20. It is desirable for the ophthalmic apparatus 1 of this embodiment to coincide with the measurement optical axis LA and the corneal apex of the subject's eye E with higher accuracy. Therefore, in the alignment process, it is desirable for the control unit 50 to coincide the corneal apex of the subject's eye E with the center of the observation image 20.

[0065] Fig. 8 is an example of the observation image 20 when the alignment process is started (i.e., the observation image 20 before the alignment is completed). Therefore, in the example shown in Fig. 8, the corneal apex of the test eye E is separated in the XY direction from the center of the observation image 20 (i.e., the measurement optical axis LA). However, the alignment index image projected onto the cornea by the alignment index projecting optical system 400 (particularly, the finitely distant alignment index image 42 projected onto the cornea with a diverging light beam by the second index projecting optical system 402) is likely to be clearly reflected in the observation image 20 even if the distance between the corneal apex of the test eye E and the measurement optical axis LA is large. In the example shown in Fig. 8, the alignment index image 42 is also reflected in the observation image 20 even though the alignment is not completed.

[0066] The control unit 50 detects an alignment index image (in this embodiment, an alignment index image 42 at a finite distance projected by the second index projecting optical system 402) projected onto the cornea of ​​the test eye E by the alignment index projecting optical system 400 based on the observation image 20 of the anterior eye. The control unit 50 calculates a position predicted to be the corneal apex of the test eye E by the detected alignment index image 42 as a reference position BP (S3). If the shape of the cornea of ​​the test eye E is symmetrical with the corneal apex as the center, there is a high possibility that the center of the alignment index image 42 shown in the observation image 20 will be the corneal apex. Therefore, in this embodiment, the control unit 50 calculates the center position of the ring-shaped alignment index image 42 detected from the observation image 20, and sets the calculated center position as the reference position BP predicted to be the corneal apex of the test eye E.

[0067] The control unit 50 executes alignment in the XY directions by the alignment driving unit 13, using the reference position BP calculated in S3 as the target position for aligning the position of the measurement optical axis LA (i.e., the center of the observation image 20) (S4). As a result, the reference position BP in the observation image 20 approaches the center of the observation image 20. The control unit 50 repeats the processes of S3 to S5 until the position of the measurement optical axis LA coincides with the reference position BP (S5: NO). In this embodiment, the measurement light is not emitted from the light projection optical system 110 while the processes of S1 to S5 are being performed.

[0068] When the position of the measurement optical axis LA coincides with the reference position BP (S5: YES), the control unit 50 causes the light projecting optical system 110 to emit measurement light in order to detect the position of the measurement light reflection image 51 (see FIG. 9) reflected by the cornea of ​​the subject's eye E and captured in the observation image 20 (S7). The control unit 50 acquires the observation image 20 of the anterior segment captured by the anterior segment observation optical system 200 in a state in which the measurement light is emitted (S8). The measurement light is emitted toward the subject's eye E along the measurement optical axis LA. Therefore, the position of the measurement light reflection image 51 captured in the observation image 20 tends to coincide with the position of the actual corneal apex (the position of the cornea perpendicular to the measurement optical axis) with high accuracy, regardless of whether the shape of the cornea is symmetrical or not. Note that the measurement light is often emitted by the light projecting optical system with a narrow beam diameter and nearly parallel to the measurement optical axis LA. Therefore, the measurement light reflection image 51 is unlikely to be captured in the observation image 20 unless the positions of the measurement optical axis LA and the corneal apex are closer than a certain amount. However, after the alignment in the XY direction is performed using the alignment target image in S3 to S5, the measurement light reflection image 51 is also properly captured in the observation image 20 as shown in FIG. 9. The incident angle of the finitely far alignment target (illumination light) by the second target projection optical system 402 to the visual axis of the subject's eye E is large (about 20 degrees). On the other hand, the incident angle of the measurement light to the visual axis of the subject's eye E is relatively small (for example, 2 degrees or less). Therefore, on the observation image 20, the alignment target image 42 is formed in the peripheral part of the cornea, and the measurement light reflection image 51 is formed in the central part of the cornea. The measurement result of the characteristics of the subject's eye E is not affected by the asymmetry of the cornea. As described above, the measurement light emitted in S7 is not emitted to measure the characteristics of the subject's eye E.

[0069] Here, if the amount of measurement light emitted during alignment is increased, when the subject's eye E has cataracts, the measurement light may be easily reflected by the transillumination or the reflection from the crystalline lens in the observation image 20 of the anterior eye, and the position of the Purkinje image (e.g., the measurement light reflection image 51, etc.) in the observation image may be difficult to accurately detect. Therefore, in S7 of this embodiment, the control unit 50 makes the amount of measurement light emitted to the light projection optical system 110 smaller than the amount of light in the transillumination image observation mode in which the subject's eye E is observed by the reflection (transillumination) of the measurement light from the fundus. In the transillumination image observation mode, the amount of measurement light is generally made very large. In S7, if the measurement light is emitted with the same amount of light as in the transillumination image observation mode, the transillumination of the measurement light may be easily reflected in the observation image 20. In contrast, by making the amount of measurement light emitted in S7 smaller than the amount of light in the transillumination image observation mode, the possibility that the position of the Purkinje image becomes difficult to detect from the observation image 20 due to the influence of transillumination or reflection from the crystalline lens is appropriately reduced. In addition, in S7 of this embodiment, the control unit 50 emits measurement light with an amount of light smaller than the amount of light used when measuring at least one of the ocular refractive power and aberration of the subject's eye E. This further reduces the possibility that the position of the Purkinje image becomes difficult to detect.

[0070] Furthermore, when the observation image 20 of the anterior eye portion captured while the measurement light is emitted (i.e., the observation image 20 used in S10 described later) is captured, the control unit 50 stops the emission of the measurement light by the light projection optical system 110. As a result, the possibility that the position of the Purkinje image becomes difficult to detect due to the influence of transillumination or reflection from the crystalline lens is further reduced.

[0071] The control unit 50 calculates (S10) the relative relationship between the reference position BP, which is predicted to be the corneal apex by the alignment target image 42, and the position of the measurement light reflection image 51, among the observation image 20 acquired in S8 (see FIG. 9). As a result, at least one of the following is appropriately grasped from the calculated relative relationship, for example, whether or not the positions of the reference position BP and the measurement light reflection image 51 match, the amount of deviation (distance) when the positions of the reference position BP and the measurement light reflection image 51 are deviated from each other, the direction of deviation, and the relative relationship between the positions of the alignment target image 42 and the measurement light reflection image 51.

[0072] In S10, the control unit 50 may directly calculate the relative relationship (direction and distance) between the reference position BP predicted to be the corneal apex by the alignment index image 42 and the position of the measurement light reflection image 51. As described above, the reference position BP is calculated based on the position of the alignment index image 42 appearing in the observation image 20. Therefore, the control unit 50 may calculate the relative relationship (direction and distance) between the position of the alignment index image 42 appearing in the observation image 20 and the position of the measurement light reflection image 51, thereby calculating the relative relationship between the reference position BP and the position of the measurement light reflection image 51.

[0073] Based on the relative relationship calculated in S10, the control unit 50 judges whether the difference (at least the distance) between the reference position BP and the position of the measurement light reflection image 51 is less than a threshold value (S11). If the difference is less than the threshold value (S11: YES), it is highly likely that the position of the measurement optical axis LA is already close to the actual corneal apex of the subject's eye E. Therefore, the alignment process ends as it is.

[0074] On the other hand, if the difference is equal to or greater than the threshold (S11: NO), it is highly likely that the position of the measurement optical axis LA has not yet approached the actual corneal apex due to the influence of the asymmetric shape of the cornea of ​​the subject's eye E, etc. In this case, the control unit 50 calculates the position of the measurement light reflection image 51 that is expected to appear in the observation image 20 when the measurement light is emitted as a new reference position NBP based on the position of the alignment index image 42 appearing in the observation image 20 (see FIG. 9) acquired in S8 and the relative relationship calculated in S10 (S13). The new reference position NBP is calculated as a relative position with respect to the alignment index image 42 appearing in the observation image 20. Therefore, by calculating the new reference position NBP in S13, the control unit 50 can calculate the new reference position NBP based on the position of the alignment index image 42 that is likely to appear in the observation image 20 regardless of whether the measurement light is emitted during the subsequent alignment, and can bring the position of the measurement optical axis LA closer to the calculated new reference position NBP. That is, the control unit 50 changes the target position for aligning the measurement light from the reference position BP to the new reference position NBP based on the relative relationship between the position of the alignment target image 42 calculated in S10 and the position of the measurement light reflection image 51. As described above, the position of the measurement light reflection image 51 reflected in the observation image 20 is likely to match the position of the actual corneal apex with high accuracy, regardless of whether the shape of the cornea is symmetrical or not. The new reference position NBP is calculated based on the position of the measurement light reflection image 51 actually reflected on the observation image 20. Therefore, by matching the position of the measurement light axis LA to the new reference position NBP, the control unit 50 can match the position of the measurement light axis LA with the actual corneal apex with high accuracy, regardless of the shape of the cornea.

[0075] Based on the result of S13 and the position of the alignment target image 42 in the observation image 20, the control unit 50 calculates the position (new reference position NBP) of the measurement light reflection image 51 that is to be reflected in the observation image 20 when the measurement light is emitted (S14). The control unit 50 executes alignment in the XY directions by the alignment driving unit 13, using the new reference position NBP calculated in S14 as the target position for aligning the position of the measurement optical axis LA (i.e., the center of the observation image 20) (S15). As a result, the new reference position NBP in the observation image 20 approaches the center of the observation image 20. The control unit 50 repeats the processes of S14 to S17 until the position of the measurement optical axis LA coincides with the new reference position NBP (S17: NO). When the position of the measurement optical axis LA coincides with the new reference position NBP (S17: YES), the alignment process ends.

[0076] As described above, in the alignment process of the first embodiment, the target image alignment process (S3 to S5) for aligning the position of the measurement optical axis LA with the reference position BP predicted to be the corneal apex by the alignment target image 42 and the measurement reflected image alignment process (S13 to S17) based on the position of the measurement light reflection image 51 in the observation image 20 are selectively performed. As described above, even if the distance between the measurement optical axis LA and the corneal apex of the subject's eye E is large, the alignment target image is likely to be clearly reflected in the observation image 20 of the anterior eye. In addition, the measurement light is often emitted by the projection optical system with a narrow beam diameter and nearly parallel. Therefore, the measurement light reflection image 51 is unlikely to be reflected in the observation image 20 unless the positions of the measurement optical axis LA and the corneal apex are close to each other by a certain amount. However, the position of the measurement light reflection image 51 is likely to match the position of the actual corneal apex with high accuracy regardless of whether the shape of the cornea is symmetrical or not. As described above, there are advantages to both the target image alignment process and the measurement reflected image alignment process. Therefore, by selectively executing the target image alignment process and the measurement reflected image alignment process, it becomes easier to perform alignment more appropriately.

[0077] In addition, when the position of the measurement optical axis LA coincides with the new reference position NBP (S17: YES), the control unit 50 may emit the measurement light again to capture the observation image 20 of the anterior segment. The control unit 50 may calculate the relative position of the measurement light reflection image 51 and the measurement optical axis LA in the captured observation image 20. In this case, the control unit 50 can confirm whether the position of the measurement optical axis LA has been aligned with high accuracy near the corneal apex based on the relative position of the measurement light reflection image 51 and the measurement optical axis LA calculated after the alignment in S14 and S15 is completed. In addition, the control unit 50 may execute the processes of S14 to S17 again when the relative position of the measurement light reflection image 51 and the measurement optical axis LA calculated after the alignment in S14 and S15 does not satisfy the criteria (for example, when the distance between them is equal to or greater than a threshold). In this case, the alignment can be easily performed with higher accuracy.

[0078] Second embodiment The alignment process executed by the ophthalmologic apparatus 1 of the second embodiment will be described with reference to Fig. 11. In the alignment process of the second embodiment, the control unit 50 causes the projection optical system 110 to emit measurement light (continuous emission or intermittent emission), and aligns the final position of the measurement optical axis LA with the position of the measurement light reflection image 51 actually captured in the observation image 20. Note that, among the alignment process of the second embodiment (see Fig. 11), steps that can employ the same processes as those in the alignment process of the first embodiment (see Fig. 7) are given the same step numbers as those in the alignment process of the first embodiment, and their descriptions are omitted or simplified.

[0079] As shown in FIG. 11, the control unit 50 starts taking an observation image 20 of the anterior part of the eye E (S1) and starts projecting an alignment index onto the eye E (S2). The control unit 50 detects an alignment index image (in this embodiment, an alignment index image 42 at a finite distance projected by the second index projecting optical system 402) projected onto the cornea of ​​the eye E by the alignment index projecting optical system 400 based on the observation image 20 of the anterior part. The control unit 50 calculates a position predicted to be the corneal apex of the eye E by the detected alignment index image 42 as a reference position BP (S3). The control unit 50 executes alignment in the XY directions by setting the reference position BP calculated in S3 as a target position for aligning the position of the measurement optical axis LA (i.e., the center of the observation image 20) (S4). The processes of S3 to S5 are repeated until the position of the measurement optical axis LA coincides with the reference position BP (S5: NO).

[0080] When the position of the measurement optical axis LA coincides with the reference position BP (S5: YES), the control unit 50 causes the light projection optical system 110 to start emitting the measurement light (S19) in order to detect the position of the measurement light reflection image 51 (see FIG. 9) reflected by the cornea of ​​the subject's eye E and reflected in the observation image 20. After the alignment in the XY directions using the alignment target image is performed in S3 to S5, the measurement light reflection image 51 is also appropriately reflected in the observation image 20 as shown in FIG. 9. The control unit 50 performs alignment in the XY directions by setting the position of the measurement light reflection image 51 reflected in the observation image as the target position for aligning the measurement optical axis LA (the center of the observation image 20 in this embodiment) (S20). As described above, the position of the measurement light reflection image 51 reflected in the observation image 20 of the anterior eye portion is likely to accurately coincide with the position of the actual corneal apex. Therefore, alignment can be performed with higher accuracy by aligning the final position of the measurement optical axis LA with the position of the measurement light reflection image 51 captured in the observation image 20. The control unit 50 repeats the processes of S20 and S21 until the position of the measurement optical axis LA coincides with the position of the measurement light reflection image 51 (S21: NO). When the position of the measurement optical axis LA coincides with the position of the measurement light reflection image 51 (S21: YES), the alignment process ends.

[0081] As described above, if the amount of measurement light emitted during alignment is increased, when the subject's eye E has cataracts, the measurement light may be easily reflected by the transillumination or the reflection from the crystalline lens in the observation image 20 of the anterior part of the eye, and the position of the Purkinje image (e.g., the measurement light reflection image 51, etc.) in the observation image 20 may be difficult to accurately detect. Therefore, in S19 of this embodiment, the control unit 50 makes the amount of measurement light emitted to the light projection optical system 110 smaller than the amount of light in the transillumination image observation mode in which the subject's eye E is observed by the reflection (transillumination) of the measurement light from the fundus. In the transillumination image observation mode, the amount of measurement light is generally made very large. In S19, if the measurement light is emitted with the same amount of light as in the transillumination image observation mode, the measurement light may be easily reflected by the transillumination or the reflection from the crystalline lens in the observation image 20. In contrast, by making the amount of measurement light emitted in S19 smaller than the amount of light in the transillumination image observation mode, the possibility that the position of the Purkinje image becomes difficult to detect from the observation image 20 due to the influence of transillumination or reflection from the crystalline lens is appropriately reduced. In addition, in S19 of this embodiment, the control unit 50 emits measurement light with an amount of light smaller than the amount of light used when measuring at least one of the ocular refractive power and aberration of the subject's eye E. This further reduces the possibility that the position of the Purkinje image becomes difficult to detect.

[0082] The control unit 50 may also continuously emit (i.e., turn on) the measurement light while the processes of S20 to S21 are being performed. In this case, the control unit 50 can constantly detect the position of the measurement light reflection image 51 in the observation image 20, which makes it easier to perform accurate alignment in a short time. The control unit 50 may also intermittently emit (i.e., blink) the measurement light multiple times while the processes of S20 to S21 are being performed. In this case, the possibility that the position of the measurement light reflection image 51 becomes difficult to detect due to the influence of the above-mentioned transillumination or reflection from the crystalline lens is reduced compared to when the measurement light is constantly emitted.

[0083] In the alignment process of the second embodiment, similarly to the alignment process of the first embodiment, the target image alignment process (S3 to S5) and the measurement reflected image alignment process (S19 to S21) are selectively executed. As described above, there are advantages to both the target image alignment process and the measurement reflected image alignment process. Therefore, by selectively executing the target image alignment process and the measurement reflected image alignment process, it becomes easier to perform more appropriate alignment.

[0084] The techniques disclosed in the above embodiment are merely examples. Therefore, the techniques exemplified in the above embodiment can be modified. For example, the control unit 50 may store the position of the measurement light reflection image 51 in the observation image 20 captured by the anterior eye observation optical system 200 when the measurement light is emitted at least once. The control unit 50 may align the position of the measurement light axis LA with the position of the stored measurement light reflection image 51. In this case, after storing the position of the measurement light reflection image 51, the control unit 50 can omit emission of the measurement light or reduce the number of emission times until the alignment is completed. For example, after emitting the measurement light to capture the observation image 20, the control unit 50 may stop emitting the measurement light and move the position of the measurement light axis LA toward the position of the stored measurement light reflection image 51. When the control unit 50 has completed the movement of the measurement optical axis LA to the position of the stored measurement light reflection image 51, the control unit 50 may emit the measurement light to capture the observation image 20 again and fine-tune the position of the measurement optical axis LA to the position of the measurement light reflection image 51 of the recaptured observation image 20. Furthermore, after emitting the measurement light to capture the observation image 20, the control unit 50 may complete the alignment by aligning the position of the measurement optical axis to the position of the stored measurement light reflection image 51 without irradiating the measurement light. Thus, the alignment is appropriately performed in a state where the influence of the above-mentioned transillumination or reflection from the crystalline lens is suppressed.

[0085] 7 and 11 are examples of an "alignment step" and a "measurement reflected image alignment step". The process of calculating the relative relationship in S10 in FIG. 7 is an example of a "relative position calculation step". The target image alignment process executed in S3 to S5 in FIG. 7 and FIG. 11 is an example of a "target image alignment step". The measurement reflected image alignment process executed in S13 to S17 in FIG. 7 and S19 to S21 in FIG. 11 is an example of an "alignment step using a reflected image of the measurement light". [Explanation of symbols]

[0086] 1 Ophthalmology equipment 13 Alignment drive unit 20 Observation images 41 Alignment index image 51 Measurement light reflection image 50 Control section 55 Non-volatile memory 110 Projection optical system 113 Hall Mirror 120 Light receiving optical system 125 Ring Lens 126 Photodetector 130 Mask 200 Anterior segment observation optical system 400 Alignment target projection optical system 505 Objective Lens LA Measuring optical axis BP reference position NBP new reference position

Claims

1. 1. An ophthalmic device comprising: a light projection optical system that projects measurement light onto the fundus of the subject's eye through an objective lens; a light receiving optical system that receives the reflected light of the measurement light reflected by the fundus and passing through the objective lens, with a light receiving element; an alignment target projection optical system that projects an alignment target onto the cornea of ​​the subject's eye; an anterior ocular segment observation optical system that captures an observation image of an anterior ocular segment of the subject's eye; A control unit; Equipped with The control unit is performing an alignment step of performing relative alignment between a measurement optical axis, which is a common optical axis of the light projecting optical system and the light receiving optical system, and a cornea of ​​the subject's eye, based on an observation image of the anterior eye segment captured by the anterior eye observation optical system; In the alignment step, an alignment index image projected onto the cornea of ​​the test eye by the alignment index projection optical system and a reflected image of the measurement light projected by the light projection optical system and reflected by the cornea, among the observation images of the anterior segment, to perform a measurement reflection image alignment step of performing relative alignment between the measurement optical axis and the cornea.

2. 2. An ophthalmic apparatus according to claim 1, In the measurement reflected image alignment step, the control unit executes a relative position calculation step of calculating a relative relationship between a reference position predicted to be the apex of the cornea by the alignment target image in the observation image of the anterior segment and the position of the reflected image of the measurement light.

3. 3. An ophthalmic apparatus according to claim 2, The control unit, in the measurement reflection image alignment step, calculates the position of the reflection image that is expected to appear in the observation image when the measurement light is projected based on the position of the alignment index image appearing in the observation image and the relative relationship calculated in the relative position calculation step, and aligns the position of the measurement optical axis to the calculated position.

4. 4. An ophthalmic apparatus according to claim 2, The control unit is characterized in that, during execution of the alignment step, when capture of an observation image of the anterior eye portion to be used for calculating the relative relationship in the relative position calculation step is completed, the control unit stops the emission of the measurement light by the projection optical system.

5. 3. An ophthalmic apparatus according to claim 1, The ophthalmologic apparatus according to claim 1, wherein the control unit aligns the final position of the measurement optical axis to the position of a reflected image of the measurement light captured in the observation image of the anterior segment in the measurement reflected image alignment step.

6. 6. An ophthalmic apparatus according to claim 5, The control unit of the ophthalmic device is characterized in that, in the measurement reflection image alignment step, the control unit aligns the position of the measurement optical axis to the position of the reflection image of the measurement light while continuously or intermittently emitting the measurement light to the measurement optical system in an amount of light smaller than the amount of light emitted when measuring the test eye after alignment is completed.

7. 7. An ophthalmic apparatus according to claim 1, In the alignment step, the control unit an index image alignment step of detecting an alignment index image projected onto the cornea of ​​the subject's eye by the alignment index projection optical system based on the observation image of the anterior eye segment, and aligning the position of the measurement optical axis with a reference position predicted to be the apex of the cornea based on the detected alignment index image; an alignment step using a reflected image of the measurement light; An ophthalmic apparatus comprising:

8. An ophthalmic apparatus according to any one of claims 1 to 7, an optical axis of the light receiving optical system that is incident on the light receiving element and that is reflected by the cornea of ​​the subject's eye;

9. An ophthalmic device control program executed by an ophthalmic device, The ophthalmic device includes: a light projection optical system that projects measurement light onto the fundus of the subject's eye through an objective lens; a light receiving optical system that receives the reflected light of the measurement light reflected by the fundus and passing through the objective lens, with a light receiving element; an alignment target projection optical system that projects an alignment target onto the cornea of ​​the subject's eye; an anterior ocular segment observation optical system that captures an observation image of an anterior ocular segment of the subject's eye; A control unit; Equipped with The ophthalmic apparatus control program is executed by the control unit of the ophthalmic apparatus, an alignment step of performing relative alignment between a measurement optical axis, which is a common optical axis of the light projecting optical system and the light receiving optical system, and the cornea of ​​the subject's eye, based on an observation image of the anterior eye segment captured by the anterior eye observation optical system; causing the ophthalmic device to execute In the alignment step, the ophthalmic apparatus an alignment index image projected onto the cornea of ​​the test eye by the alignment index projection optical system and a reflected image of the measurement light projected by the light projection optical system and reflected by the cornea, among the observation images of the anterior segment of the eye, to perform a measurement reflection image alignment step of performing relative alignment between the measurement optical axis and the cornea.

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