Fundus photography device

Abstract

To provide a fundus imaging apparatus which can obtain a high-resolution fundus image.SOLUTION: A fundus imaging apparatus comprises: an imaging optical system which includes an irradiation optical system that irradiates a fundus of a subject eye with imaging light from a light source, a light reception optical system that has a light reception element for receiving fundus reflection light of the imaging light, and a refractive error correction unit that corrects a refractive error of the subject eye and which acquires a fundus image on the basis of a light reception signal from the light reception element; and control means. The refractive error correction unit has a variable focus lens which can change a frequency for at least a spherical surface component and regular astigmatism component by changing the refractive state of a lens part. The control means corrects at least the spherical surface component and regular astigmatism component of the subject eye by controlling the variable focus lens.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to a fundus imaging apparatus for imaging the fundus of a subject's eye. [Background technology]

[0002] A typical fundus imaging device is a fundus camera (see, for example, Patent Document 1). Also, a device having adaptive optics has been proposed as a fundus imaging device. For example, Patent Document 2 proposes a device equipped with adaptive optics having a wavefront sensor that measures the wavefront aberration of the subject's eye and a wavefront compensation device such as a deformable mirror. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2009-240625 A [Patent Document 2] JP 2014-110825 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the fundus camera shown in Patent Document 1, only the spherical component of the refractive error of the test eye is corrected by moving the focusing lens, and if the test eye has a regular astigmatism component and high-order aberration of the refractive error, a high-resolution fundus image in which the details of the fundus are focused cannot be obtained. On the other hand, according to the fundus photography device shown in Patent Document 2, by using a focusing lens and an adaptive optical system, a high-resolution fundus image in which the details of the fundus are focused can be obtained even if the test eye has a regular astigmatism component and high-order aberration in addition to the spherical component of the refractive error.

[0005] However, in Patent Document 2, a focusing lens is also required in addition to the adaptive optics system, which complicates the photographing optical system, resulting in problems of increased size and cost of the device.

[0006] An object of the present disclosure is to provide a fundus imaging device capable of obtaining higher resolution fundus images without complicating the imaging optical system. [Means for solving the problem]

[0007] In order to solve the above problems, the present disclosure is characterized by having the following configuration. (1) Fundus photography equipment Objective optical system Shooting light from the light source and a light scanner for scanning the imaging light scanned by the light scanner through the objective optical system. an illumination optical system that illuminates the fundus of the subject's eye; and a light receiving optical system having a light receiving element that receives the fundus reflection light of the photographing light; an optical path branching member that branches an optical path between the irradiation optical system and the light receiving optical system; and , disposed between the optical scanner and the optical path branching member; a refractive error correction unit that corrects a refractive error of the subject's eye, an imaging optical system that acquires a fundus image based on a light receiving signal from the light receiving element, and a control means, the refractive error correction unit having a variable focus lens that can change the power of at least a spherical component and a regular astigmatism component by changing the refractive state of a lens unit; The control means corrects at least a spherical component and a regular astigmatism component of a refractive error of the subject's eye by controlling the variable-focus lens. [Brief description of the drawings]

[0008] [Figure 1] 1 is a diagram showing an example of the appearance of a fundus imaging apparatus according to an embodiment of the present invention; [Diagram 2] 1 is a diagram showing an example of an optical system of a fundus imaging apparatus according to an embodiment of the present invention; [Diagram 3] 1A and 1B are diagrams illustrating an example of the structure of a liquid lens. [Figure 4] 1A and 1B are diagrams illustrating the shape of a liquid lens when a spherical component of a refractive error of a test eye is corrected. [Diagram 5] 11A and 11B are diagrams illustrating a case where the focal position of the liquid lens in the 0°-180° direction is changed in order to correct a regular astigmatism component of the refractive error of the subject's eye. [Figure 6] FIG. 2 is a diagram showing an example of a control system of the fundus imaging apparatus according to the present embodiment. [Figure 7] FIG. 4 is a flowchart of the control performed by the control unit in the present embodiment. [Figure 8] 11 is a flowchart showing an example of control performed by a control unit when correcting regular astigmatism components and higher-order aberrations of refractive errors of a subject's eye. FIG. [Figure 9] 11A and 11B are diagrams illustrating an example of an increase and decrease in pressure of an actuator when correcting a regular astigmatism component and higher-order aberrations among refractive errors of a subject's eye in this embodiment. [Figure 10] FIG. 2 is a diagram showing an example of an optical system in a fundus imaging apparatus including a refractive error acquisition optical system. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] [overview] An embodiment of a fundus imaging device according to the present disclosure (for example, a fundus imaging device 1) will be described. The items grouped in <> below can be used independently or in conjunction with each other.

[0010] In the present disclosure, for example, a fundus imaging device includes at least an imaging optical system (eg, imaging optical system 30) for imaging the fundus of a subject's eye, and a control unit (eg, control unit 70).

[0011] <Photographic optical system> For example, the imaging optical system includes an irradiation optical system (eg, an irradiation optical system 10), a light receiving optical system (eg, a light receiving optical system 20), and a refractive error correction unit (eg, a refractive error correction unit 40).

[0012] For example, the irradiation optical system irradiates the fundus of the subject's eye with imaging light from a light source (for example, a laser light source 11).

[0013] For example, the light receiving optical system has a light receiving element (for example, the light receiving element 29) that receives fundus reflected light of the photographing light. For example, the photographing optical system is used to obtain a fundus image based on a light receiving signal from the light receiving element.

[0014] For example, the fundus photographing device has an image processing means (for example, a control unit 70). The signal from the light receiving element is input to the image processing means. The image processing means generates (forms) a fundus image of the subject's eye based on the signal from the light receiving element.

[0015] For example, the refractive error correction unit has a variable focus lens. For example, the variable focus lens changes the refractive state of a lens unit (for example, lens unit 42). This changes the focal position of the lens unit (in this embodiment, the focal position of the lens unit is used to include the position of the image point where the light ray emitted from the off-axis object point, etc. is imaged on the image surface in addition to the on-axis object point of the lens unit) and changes the power of at least the spherical component and the regular astigmatism component. That is, the refractive error correction unit is, for example, a variable focus lens that has the function of a focus lens that corrects the spherical component (defocus) of the refractive error and the function of correcting at least the regular astigmatism component.

[0016] In the present disclosure, the spherical component is the component represented by S in the S (Sphere), C (Cylinder), and A (Axis) values ​​that represent the degree of refractive error of the subject's eye. Also, the regular astigmatism component is the component represented by C (and A) in the S, C, and A values.

[0017] For example, the variable-focus lens can correct the entire correction range of the refractive error of the subject's eye with respect to the spherical component and regular astigmatism component of the refractive error without using a focus lens and an astigmatism correction lens. For example, when the correction range of the spherical component of the refractive error of the subject's eye is set to -10D to +10D (D is a symbol indicating diopter of refractive power), the variable-focus lens can correct at least the range of the spherical component of the refractive error from -10D to +10D. Also, for example, the variable-focus lens can correct at least the range of the regular astigmatism component of the refractive error from -6D to +6D. This makes it possible to acquire a fundus image in which at least the spherical component and regular astigmatism component of the refractive error of the subject's eye are corrected without complicating the photographing optical system, as compared with the case of using a focus lens, an astigmatism correction lens, and an adaptive optical system.

[0018] Furthermore, for example, the variable-focus lens is designed to be capable of correcting at least coma among higher-order aberrations, thereby enabling a fundus image with higher resolution to be obtained.

[0019] Furthermore, for example, if there is a misalignment between the photographing optical system and the subject's eye (alignment in a direction perpendicular to the optical axis of the photographing optical system), this will appear as a pseudo coma aberration of the refractive error of the subject's eye on the fundus image. In this case, since the variable-focus lens is capable of correcting coma aberration, it is possible to obtain a fundus image with higher resolution in which the coma aberration caused by the misalignment has been corrected. Furthermore, even if there is a manufacturing error in the arrangement of each optical element of the photographing optical system in the direction perpendicular to the optical axis of the photographing optical system, since the variable-focus lens is capable of correcting coma aberration, it is possible to correct the manufacturing error and obtain a fundus image with higher resolution.

[0020] For example, the variable focus lens is a liquid lens (liquid lens 41). For example, the shape of the lens part of the liquid lens is changed by applying pressure to the periphery of the lens part, and the refraction state of light passing through the lens part is changed. This changes the focal position of the lens part. For example, the liquid lens may contain a first liquid and a second liquid having a refractive index different from that of the first liquid in the lens part, and the shape of the interface between the first liquid and the second liquid may be changed by adjusting the magnitude of the voltage applied to the contained liquid, thereby changing the refractive index of the lens part.

[0021] For example, the variable-focus lens may be a liquid crystal lens, which has a liquid crystal layer in a lens portion and changes the refractive index of the liquid crystal layer by adjusting the voltage applied to the liquid crystal layer, thereby changing the focal position of the lens portion.

[0022] <Control Means> For example, the control unit corrects at least the spherical component and the regular astigmatism component of the refractive error of the subject's eye by controlling the variable-focus lens, thereby making it possible to obtain a higher-resolution fundus image without complicating the photographing optical system.

[0023] For example, the control means controls the variable-focus lens to correct at least the regular astigmatism component after correcting the spherical component of the refractive error of the subject's eye. When the spherical component of the refractive error is large, correcting the spherical component first allows the refractive error to be corrected more efficiently and accurately than correcting the spherical component and the regular astigmatism component simultaneously.

[0024] The control means may have a function of controlling each part of the fundus imaging apparatus and performing calculation processing.

[0025] <Evaluation methods> For example, the fundus photographing device includes an evaluation means (e.g., a control unit 70). For example, the evaluation means evaluates the correction state of the refractive error of the subject's eye by the variable-focus lens based on the light receiving signal of the light receiving element of the photographing optical system. For example, the evaluation means acquires a fundus image based on the light receiving signal of the light receiving element, and evaluates the correction state of the refractive error of the subject's eye by the variable-focus lens based on the acquired fundus image. For example, the evaluation means evaluates the correction state of a spherical component of the refractive error of the subject's eye, and for example, the evaluation means evaluates the correction state of a regular astigmatism component and higher-order aberrations of the refractive error of the subject's eye.

[0026] For example, the control means corrects the refractive error of the subject's eye by controlling the variable-focus lens based on the evaluation result of the evaluation means, which makes it possible to control the variable-focus lens without providing a special detector such as a wavefront sensor in the fundus imaging device and without complicating the device configuration.

[0027] <Refractive error acquisition means, refractive error detection unit> For example, the fundus imaging device may include a refractive error acquisition means (e.g., a refractive error acquisition optical system 50, a control unit 70). For example, the control means controls the variable-focus lens based on the refractive error data acquired by the refractive error acquisition means, and then controls the variable-focus lens based on the evaluation result of the evaluation means. This makes it possible to efficiently obtain a fundus image with improved resolution.

[0028] For example, the refractive error acquisition means includes a refractive error acquisition optical system (e.g., a refractive error acquisition optical system 50). For example, the refractive error acquisition optical system 50 includes an irradiation optical system (e.g., an irradiation optical system 10) that irradiates the fundus with measurement light. The refractive error acquisition optical system 50 includes a measurement light receiving optical system (e.g., a measurement light receiving optical system 51) having a detector (e.g., a CCD sensor 55) that receives fundus reflected light of the measurement light. For example, the detector is placed at a conjugate position with the fundus. The refractive error acquisition means obtains refractive error data of the test eye by the spread of the measurement light on the fundus based on the light receiving signal from the detector.

[0029] For example, the refractive error acquisition means may acquire refractive error information (e.g., information including at least spherical power, astigmatism power, and astigmatism axis angle) of the test eye obtained by a separate device (e.g., an eye refraction measuring device) other than the fundus imaging device by inputting the information through an input means (e.g., an input interface 75).

[0030] Furthermore, for example, the fundus photographing device may include a refractive error detection unit (for example, a refractive error acquisition optical system 50). For example, the refractive error detection unit detects the refractive error of the subject's eye based on the fundus reflection light of the photographing light. In this case, the variable-focus lens is controlled based on the detection result of the refractive error detection unit to correct the refractive error.

[0031] <Selection method> For example, the fundus photographing device may include a selection means (for example, an input interface 75, a control unit 70). For example, the selection means is capable of selecting between a first photographing mode in which at least a spherical component and a regular astigmatism component of the refractive error of the subject's eye are corrected to obtain a fundus image, and a second photographing mode in which only a spherical component of the refractive error of the subject's eye is corrected to obtain a fundus image. In this case, for example, the control means controls the variable-focus lens based on the selection result by the selection means. For example, when the first photographing mode is selected, the control means controls the variable-focus lens so as to correct at least a spherical component and a regular astigmatism component of the refractive error of the subject's eye. For example, when the second photographing mode is selected, the control means controls the variable-focus lens so as to correct only the spherical component of the refractive error without correcting the regular astigmatism component and high-order aberrations of the refractive error. As a result, for example, when it is not necessary to obtain a fundus image in which even the finest blood vessels are in focus (for example, when a fundus image of the conventional SLO level is sufficient), by selecting the second imaging mode, imaging can be completed in a shorter time than in the first imaging mode, which also reduces the burden on the subject.

[0032] The control means may also function as the selection means. For example, the control means selects whether to execute the first photography mode or the second photography mode. Also, for example, when the conditions for fundus photography are input or set, the control means may select whether to execute the first photography mode or the second photography mode based on the conditions.

[0033] [Example] A fundus photographing device according to an embodiment of the present disclosure will now be described with reference to Figures 1 to 6. For example, in Figure 1, the fundus photographing device 1 is a scanning laser ophthalmoscope (SLO) device that photographs a front image of the fundus.

[0034] In this embodiment, for convenience of explanation, a scanning laser ophthalmoscope (SLO) device will be described as an example, but the fundus imaging device to which the present disclosure can be applied is not limited to this. For example, the present disclosure can also be applied to a fundus camera and an optical coherence tomography (OCT).

[0035] <Appearance> 1, in this embodiment, the device body includes an imaging unit 4, an alignment mechanism 5, a base 6, and a face support unit 7. The imaging unit 4 houses an imaging optical system 30 (see FIG. 2) for imaging the subject's eye E.

[0036] The alignment mechanism 5 is used to align the imaging unit 4 with respect to the subject's eye E. In this embodiment, the alignment mechanism 5 moves the imaging unit 4 three-dimensionally with respect to the base 6. The imaging unit 4 may be movable in each of the Y direction (up-down direction), X direction (left-right direction), and Z direction (front-back direction).

[0037] 1, the face support unit 7 supports the face of the subject with the eye E facing the imaging unit 4. In this embodiment, the face support unit 7 is fixed to the base 6.

[0038] <Optical system configuration> The photographing optical system 30 provided in the fundus photographing device 1 will be described with reference to Fig. 2. As shown in Fig. 2, the photographing optical system 30 has an irradiation optical system 10 and a light receiving optical system 20. The fundus photographing device 1 photographs a fundus image using the photographing optical system 30.

[0039] The irradiation optical system 10 includes a laser light source 11, which is an example of a light source of the imaging light, and a refraction error correction unit 40. The refraction error correction unit 40 has a liquid lens 41, which is an example of a variable focus lens. As shown in FIG. 2, the irradiation optical system 10 may further include a collimating lens 12, a holey mirror 13, a lens 15, a scanning unit 16, and an objective optical system 17.

[0040] The laser light source 11 may be formed to include, for example, a laser diode (LD) and a superluminescent diode (SLD).

[0041] In this embodiment, the laser light from the laser light source 11 passes through the collimating lens 12, an opening formed in the perforated mirror 13, and then passes through the liquid lens 41 and lens 15, before heading toward the scanning unit 16. The laser light reflected by the scanning unit 16 passes through the objective optical system 17, and is then irradiated onto the fundus Er of the subject's eye E. As a result, the laser light is reflected and scattered by the fundus Er. This light (i.e., the reflected and scattered light) is emitted from the pupil as return light.

[0042] The scanning unit 16 (also called "optical scanner") is a unit for scanning the fundus with the laser light emitted from the laser light source 11. In the following description, unless otherwise specified, the scanning unit 16 includes two optical scanners with different scanning directions of the laser light. That is, the scanning unit 16 includes an optical scanner 16a for main scanning (for example, for scanning in the X direction) and an optical scanner 16b for sub-scanning (for example, for scanning in the Y direction). As an example, the optical scanner 16a for main scanning may be a resonant scanner, and the optical scanner 16b for sub-scanning may be a galvanometer mirror. However, other optical scanners may be applied to each of the optical scanners 16a and 16b. For example, an acousto-optical element (AOM) that changes the traveling (deflection) direction of light may be applied to each of the optical scanners 16a and 16b in addition to other reflection mirrors (galvanometer mirrors, polygon mirrors, resonant scanners, MEMS, etc.).

[0043] The objective optical system 17 is included in the imaging optical system 30. The objective optical system 17 is used to guide the laser light scanned by the scanning unit 16 to the fundus Er. The objective optical system 17 forms a rotation point P at the position of an exit pupil (first exit pupil) of the objective optical system 17. In detail, the position of the rotation point P is on the optical axis L1 of the irradiation optical system 10, and is a position optically conjugate with the scanning unit 16 with respect to the objective optical system 17. At the rotation point P, the laser light that has passed through the scanning unit 16 is rotated.

[0044] In the present disclosure, "conjugate" is not necessarily limited to a perfect conjugate relationship, but includes "approximate conjugate." In other words, "conjugate" in the present disclosure also includes a position that is shifted from a perfect conjugate position within an allowable range in relation to the intended use of the fundus image (e.g., observation, analysis, etc.).

[0045] The laser light that has passed through the scanning unit 16 passes through the objective optical system 17 and is then irradiated onto the fundus Er via the rotation point P. The laser light is rotated around the rotation point P, causing the laser light to scan the fundus Er two-dimensionally. The laser light irradiated onto the fundus Er is reflected by the fundus. The fundus reflected light is emitted from the pupil as parallel light.

[0046] Next, the light receiving optical system 20 will be described. The light receiving optical system 20 has one or more light receiving elements. For example, as shown in FIG. 2, the light receiving optical system 20 has a light receiving element 29. In this case, fundus reflection light due to the laser light irradiated by the irradiation optical system 10 is received by the light receiving element 29.

[0047] 2, the light receiving optical system 20 in this embodiment shares each component arranged from the objective optical system 17 to the perforated mirror 13 with the irradiation optical system 10. In this case, light from the fundus is guided back along the optical path of the irradiation optical system 10 to the perforated mirror 13. The perforated mirror 13 guides the fundus reflected light to an independent optical path of the light receiving optical system 20 while removing at least a part of noise light caused by reflection on the cornea of ​​the subject eye and the optical system inside the device (e.g., the lens surface of the objective optical system, etc.). Note that the optical path branching component that branches the irradiation optical system 10 and the light receiving optical system 20 is not limited to the perforated mirror 13, and other beam splitters may be used.

[0048] The light receiving optical system 20 of this embodiment has a lens 21 and a pinhole plate 23 in the reflected light path of the perforated mirror 13. The pinhole plate 23 is disposed on a fundus conjugate plane, and functions as a confocal aperture in the photographing optical system 30. That is, when the refractive error of the subject's eye is properly corrected by the refractive error correction unit 40, the light from the fundus Er that has passed through the lens 21 is focused at the opening of the pinhole plate 23. The pinhole plate 23 removes light from positions other than the focal point (or focal plane) of the fundus Er, and the remaining light (light from the focal point) is guided to the light receiving element 29.

[0049] <Refractive error correction section> 2, the refraction error correction unit 40 of this embodiment has a liquid lens 41, which is an example of a variable-focus lens. In the optical system of this embodiment, the liquid lens 41 is disposed between the holed mirror 13 and the lens 15.

[0050] For example, as shown in FIG. 3, liquid lens 41 has lens portion 42 and actuator 43 as an example of a driving unit that changes the refractive state of lens portion 42. Actuator 43 applies pressure to the periphery of lens portion 42 under the control of control unit 70 (see FIG. 6). This changes the shape of lens portion 42 and changes the focal position. Note that actuator 43 is an example of a driving unit that changes the refractive state of lens portion 42 and changes the focal position. For example, the driving unit may be configured to change the refractive state of lens portion 42 and change the focal position by passing electricity through lens portion 42.

[0051] The liquid lens 41 shown in FIG. 3 is an example of a variable-focus lens, and is not limited thereto. For example, the liquid lens 41 may contain a first liquid and a second liquid having a refractive index different from that of the first liquid in a lens portion, and the shape of the interface between the first liquid and the second liquid may be changed by adjusting the magnitude of the voltage applied to the contained liquid. Also, for example, a liquid crystal lens may be used as the variable-focus lens. For example, a liquid crystal lens may have a liquid crystal layer in a lens portion, and the refractive index of the liquid crystal layer may be changed by adjusting the voltage applied to the liquid crystal layer.

[0052] In the liquid lens 41 of this embodiment, a plurality of (e.g., eight) actuators 43 (43a, 43b, 43c, 43d, 43e, 43f, 43g, 43h) are arranged on the periphery of the lens portion 42. In this embodiment, among the actuators 43, 43a and 43e, 43b and 43f, 43c and 43g, and 43d and 43h are arranged symmetrically with respect to the central axis C of the lens portion 42. For convenience, in the following description, the direction passing through the center of the actuator 43a is defined as the 0 degree direction, the direction passing through the center of the actuator 43c is defined as the 90 degree direction, the direction passing through the center of the actuator 43e is defined as the 180 degree direction, and the direction passing through the center of the actuator 43g is defined as the 270 degree direction, with the central axis C of the lens portion 42 as the center, and correspond to the angle notation of the astigmatism axis in the regular astigmatism component of the refractive error.

[0053] In this embodiment, the control unit 70 changes the magnitude of the voltage applied to each of the actuators 43a to 43h. Note that the magnitude of the voltage applied to each of the actuators 43a to 43h may be different from each other.

[0054] The lens unit 42 changes its shape and focal position in response to pressure applied from the actuator 43. This corrects the refractive error of the subject's eye (spherical component, regular astigmatism component, and higher-order aberrations).

[0055] First, the shape of the lens portion 42 when the spherical component of the refractive error is corrected will be described with reference to FIG.

[0056] For example, when the pressure applied to the lens unit 42 by each of the actuators 43a to 43h is increased uniformly as shown in Fig. 4(b) from the state of the lens unit 42 shown in Fig. 4(a) (a state in which no pressure is applied by each actuator 43, or a state in which a slight uniform pressure is applied), the focal position of the entire lens unit 42 moves in the direction of the optical axis L1 according to the magnitude of the pressure. This corrects the spherical components (i.e., myopic and hyperopic components) of the refractive error of the subject's eye.

[0057] Next, a case where the regular astigmatism component of the refractive error is corrected will be described. For the sake of explanation, for example, the shape of the lens portion 42 when correcting the astigmatism component for an examinee's eye with regular astigmatism whose steepest meridian is oriented in the direction of 90°-270° will be described.

[0058] For example, the actuator 43 is driven so that the focal position of the lens unit 42 in the direction perpendicular to the intensive meridian direction moves. That is, among the actuators 43a to 43h, the actuators 43c and 43g positioned in the 90°-270° direction do not apply pressure to the lens unit 42, and the actuators 43a and 43e positioned in the 0°-180° direction apply pressure to the lens unit 42 evenly. The actuators 43b and 43f positioned in the 45°-225° direction and the actuators 43d and 43h positioned in the 135°-315° direction may apply pressure to the lens unit 42 so as to interpolate between the intensive meridian direction and the intensive meridian direction. In this case, as shown in FIG. 5, the focal position of the lens unit 42 in the 0°-180° direction moves in the direction of the optical axis L1. This allows correction of the regular astigmatism component in the 90°-270° direction perpendicular to the 0°-180° direction. In this way, the pressure applied to the lens unit 42 is changed for each combination of actuators 43 (actuators 43a and 43e, 43b and 43f, 43c and 43g, and 43d and 43h) that are symmetrically arranged around the central axis C of the lens unit 42, so that the focal position in a predetermined direction of the lens unit 42 moves toward the optical axis L1. This corrects the regular astigmatism component of the subject's eye.

[0059] Next, a case where the higher-order aberration of the refractive error is corrected will be described. For example, when the coma aberration of the higher-order aberration is corrected, the lens unit 42 may be deformed so that the coma aberration occurs in a direction 180 degrees opposite to the coma aberration of the refractive error. That is, in order to correct the coma aberration of the refractive error, the shape of the lens unit 42 is deformed so that the curve shape of the lens unit 42 has a bias with respect to the optical axis L1. For example, when the coma aberration of the refractive error occurs biased toward the 0° side in the 0°-180° direction, the actuator 43e located in the 180° direction applies a larger pressure to the lens unit 42 than the actuator 43a located in the 0° direction. As a result, the curve shape of the lens unit 42 in the 180° direction is largely deformed with respect to the 0° direction, and the focal position of the lens unit 42 is changed so as to correct the coma aberration of the refractive error.

[0060] In addition, for higher-order aberrations other than coma aberration, the curve shape of the lens portion 42 can be deformed to have a bias by applying different voltages to the actuators 43a to 43h depending on the higher-order aberration, thereby making it possible to correct the higher-order aberration of the refractive error.

[0061] The number and arrangement of the actuators 43 are merely examples and are not limited to these. The method of correcting high-order aberrations by changing the focal position of the liquid lens 41 is not limited to the above, and the method described in Japanese Patent Application Laid-Open No. 2009-37711 can be used, for example.

[0062] As described above, the refractive error correction unit 40 corrects the refractive error (spherical component, regular astigmatism component, and higher-order aberration) of the subject's eye by changing the focal position of the liquid lens 41. This enables the fundus imaging device 1 to obtain a higher-resolution fundus image.

[0063] <Control system> The control system of the fundus photographing device 1 will be described with reference to Fig. 6. Fig. 6 is a block diagram showing the control system of the fundus photographing device 1. Each part of the fundus photographing device 1 is controlled by a control unit 70. The control unit 70 is a processing device (processor) having electronic circuits that perform control processing of each part of the fundus photographing device 1 and arithmetic processing. The control unit 70 is realized by a CPU (Central Processing Unit), memory, etc. The control unit 70 is electrically connected to a storage unit 71 via a bus, etc.

[0064] The control unit 70 is electrically connected to the actuators 43a to 43h of the liquid lens 41. The control unit 70 changes the focal position of the liquid lens 41 by driving the actuators 43a to 43h to correct the refractive error of the subject's eye. In this embodiment, the control unit 70 controls the actuators 43a to 43h in at least one of a first correction control for correcting a spherical component of the refractive error of the subject's eye and a second correction control for correcting at least an astigmatism component of the refractive error of the subject's eye (details will be described later).

[0065] The control unit 70 is also electrically connected to each of the laser light source 11, the light receiving element 29, the scanning unit 16, the input interface 75, the monitor 80, and the like.

[0066] The storage unit 71 stores various control programs, fixed data, etc. Temporary data, etc. may also be stored in the storage unit 71. Images obtained by the fundus photographing device 1 may be stored in the storage unit 71. However, this is not necessarily limited to this, and images obtained by the fundus photographing device 1 may also be stored in an external storage device (for example, a storage device connected to the control unit 70 via a LAN and a WAN).

[0067] In this embodiment, the control unit 70 also serves as an image processing unit (image forming unit). As an image processing unit, the control unit 70 forms a fundus image based on, for example, a light receiving signal output from the light receiving element 29. More specifically, the control unit 70 forms a fundus image in synchronization with the optical scanning by the scanning unit 16. For example, the control unit 70 forms at least one frame (in other words, one) of a fundus image (for each light receiving element) every time the optical scanner 16b for sub-scanning makes one round trip (n is an integer equal to or greater than 1). In the following description, for the sake of convenience, it is assumed that one frame of a fundus image is formed every time the optical scanner 16b for sub-scanning makes one round trip, unless otherwise specified.

[0068] The control unit 70 may display a plurality of frames of fundus images formed sequentially as observation images on the monitor 80 in chronological order. The observation images are moving images consisting of fundus images acquired in approximately real time. The control unit 70 also takes in (captures) some of the plurality of fundus images formed sequentially as photographed images (captured images). At that time, the photographed images are stored in the storage unit 71. The storage unit 71 in which the photographed images are stored may be a non-volatile storage medium (e.g., a hard disk, a flash memory, etc.). In this embodiment, for example, after a trigger signal (e.g., a release operation signal, etc.) for starting photographing is output, a fundus image formed at a predetermined timing (or period) is captured.

[0069] The control unit 70 also has a function of evaluating the correction state of the refractive error of the subject's eye by the liquid lens 41, based on the light receiving signal of the light receiving element 29. For example, the control unit 70 evaluates the correction state of the refractive error of the subject's eye, based on an index indicating the brightness of the entire fundus image formed based on the light receiving signal of the light receiving element 29, or an index indicating the contrast of an image obtained by applying image processing to the fundus image.

[0070] In this embodiment, the control unit 70 executes one of two imaging modes, a high image quality mode and a standard image quality mode. For example, the high image quality mode is a mode in which the control unit 70 controls the liquid lens 41 to perform at least a correction of the spherical component of the refractive error (first correction control described later) and a correction of the regular astigmatism component (second correction control described later) to obtain a fundus image. In the high image quality mode, a high-resolution fundus image is obtained. For example, the standard image quality mode is a mode in which the control unit 70 controls the liquid lens 41 to perform a correction of only the spherical component of the refractive error to obtain a fundus image.

[0071] For example, the selection between the high-image-quality mode and the standard-image-quality mode is performed by the examiner inputting a selection signal via the input interface 75. The control unit 70 may also serve as a selection means for selecting the imaging mode to be executed. For example, the control unit 70 may select the imaging mode based on the imaging conditions input via the input interface 75. Alternatively, the control unit 70 may allow the examiner to select the imaging mode via the input interface 75. Of course, the fundus imaging device 1 may be provided with a configuration (e.g., a switch) for allowing the examiner to select the imaging mode.

[0072] The input interface 75 is an operation unit that receives the examiner's operations. For example, the input interface 75 may be a touch panel. In that case, the monitor 80 and the input interface 75 may be used in common. Of course, a mouse, a keyboard, etc. may be used as the input interface 75. Such an input interface 75 may be a device separate from the fundus imaging apparatus 1. The control unit 70 controls each of the above-described members based on an operation signal output from the input interface 75 (operation unit). Any of, for example, an operation for selecting a shooting mode, an operation for release, etc. may be input to the input interface 75. Also, for example, a refractive error of the eye to be examined (that is, a spherical power, a cylindrical power, and a cylindrical axis) may be input to the input interface 75 from the outside.

[0073] [Operation] The operation of the fundus imaging apparatus 1 having the above-described configuration will be described.

[0074] First, the operation of the fundus imaging apparatus 1 in the high image quality mode will be described with reference to FIG. 7. Note that FIG. 7 is a flowchart diagram of the control performed by the control unit 70 in the present embodiment.

[0075] <S101: Align the eye to be examined and the imaging optical system> The control unit 70 controls the drive of the alignment mechanism 5 and changes the positional relationship between the eye to be examined and the imaging optical system 30. For example, by driving the alignment mechanism 5 by the control unit 70, the XY-direction positions of the optical axis L1 and the pupil center are adjusted so that the fundus can be imaged, and the Z-direction position is adjusted so as to obtain an operating distance suitable for fundus imaging. For example, as a method for adjusting the positional relationship between the eye to be examined and the imaging optical system 30, the method described in Japanese Patent Application Laid-Open No. 2013-179978 can be used. In that case, the fundus imaging apparatus 1 may include an alignment optical system for adjusting the positional relationship between the eye to be examined and the imaging optical system 30.

[0076] Of course, the examiner may manually adjust the positional relationship between the eye to be examined and the imaging optical system 30.

[0077] <S102: First correction control> When the alignment is completed and the operation start signal of the refractive error correction unit 40 is input (for example, the examiner inputs the operation start signal through the input interface 75 or the like), the laser light source 11 of the irradiation optical system 10 is turned on. Further, the scanning unit 16 is driven, and the laser light is scanned on the fundus Er of the eye to be examined. Further, the fundus reflected light is received by the light receiving element 29 of the light receiving optical system 20. For example, the light receiving element 29 outputs the intensity of the received fundus reflected light. The control unit 70 forms a fundus image based on the driving of the scanning unit 16 and the intensity of the fundus reflected light output by the light receiving element 29.

[0078] The control unit 70 controls the refractive error correction unit 40 based on the formed fundus image, and first performs first correction control to correct the spherical component of the refractive error of the eye to be examined. An example of the first correction control will be described below.

[0079] For example, the control unit 70 changes the voltage applied to the actuator 43 of the liquid lens 41 from the minimum to the maximum within the changeable range. As a result, the pressure applied by the actuator 43 to the lens unit 42 changes from the minimum to the maximum. That is, the focal position of the lens unit 42 moves from one end of the moving range to the other end in the direction of the optical axis L1.

[0080] In parallel with changing the voltage, the control unit 70 scans the optical scanner 16b to capture a fundus image. That is, while changing the voltage, the control unit 70 sequentially forms a fundus image as an image processing unit. Note that the sequentially formed fundus images may be displayed on the monitor 80 as a moving image.

[0081] Further, the control unit 70 performs image processing on each of the sequentially formed fundus images. Then, the control unit 70 obtains an evaluation value (hereinafter referred to as evaluation value B) for evaluating whether the spherical component is corrected by the refractive error correction unit 40 based on the fundus image. For example, the control unit 70 obtains the evaluation value B based on the brightness of the entire fundus image. If the value of the brightness of the entire fundus image is high, the evaluation value B is set to a high value.

[0082] Of course, the evaluation value B is not limited to this example. As the evaluation value B, an index indicating the contrast of the fundus image may be used. For example, the value indicating the contrast of the fundus image can be the intensity of the edge extracted by image processing of the fundus image. The intensity of the edge can be obtained by processing the fundus image with a Laplacian filter and obtaining the average value of the luminance of the entire obtained image.

[0083] The control unit 70 associates and stores in the storage unit 71 the obtained evaluation value B and the voltage applied to the actuator 43 when the light reception signal serving as the basis of the image was acquired (that is, the pressure applied by the actuator 43 to the lens unit 42) for each sequentially formed fundus image.

[0084] Thereafter, the control unit 70 changes the voltage applied to the actuator 43 so that the evaluation value B becomes maximum. As a result, the focal position of the liquid lens 41 is changed so that the spherical component of the refractive error of the eye to be examined is corrected.

[0085] Note that the method for correcting the spherical component of the refractive error of the eye to be examined is not limited to this. For example, the examiner may adjust the focal position of the liquid lens 41 via the input interface 75 while checking the fundus image displayed on the monitor 80. For example, the examiner changes the focal position of the liquid lens 41 so that the fundus image becomes the brightest. For example, the control unit 70 changes the pressure of the actuator 43 based on the signal input from the input interface 75 by the examiner.

[0086] <S103: Determination of shooting mode> When the high-quality mode is selected by the control unit 70 (an example of the selection means), the control unit 70 proceeds to step S104 (second correction control). When the standard-quality mode is selected, the control unit 70 proceeds to step S105 (shooting).

[0087] <S104: Second correction control> When the high image quality mode is selected, when the spherical component of the refractive error of the subject's eye is corrected, the control unit 70 controls the refractive error correction unit 40 to perform the second correction control. The second correction control corrects the regular astigmatism component and high-order aberration of the refractive error of the subject's eye. In this embodiment, as the second correction control, the control unit 70 changes the pressure of the actuators 43a to 43h so that the evaluation value B becomes higher, and changes the shape of the lens portion 42 of the liquid lens 41 as described above, thereby correcting the regular astigmatism component and high-order aberration of the subject's eye.

[0088] In the second correction control, the evaluation value B for evaluating the correction state of the refractive error of the subject eye is preferably an index of contrast extracted by image processing of the fundus image, rather than an index of brightness of the entire fundus image, because the index of contrast of the fundus image has better sensitivity in evaluating subtle changes in the regular astigmatism component of the refractive error and the higher-order aberrations.

[0089] For example, a known simultaneous perturbation optimization method can be used as the second correction control. In the control using the simultaneous perturbation optimization method, for example, the pressures of the actuators 43a to 43h are randomly increased or decreased simultaneously to change the shape of the lens unit 42 so that the evaluation value B is increased (i.e., the refractive error of the regular astigmatism component and the higher-order aberrations is corrected).

[0090] An example of the second correction control using the simultaneous perturbation optimization method will be described below with reference to Fig. 8 and Fig. 9. Fig. 8 is a flow chart showing an example of control performed by the control unit 70 when correcting the regular astigmatism component and higher-order aberrations of the refractive error of the subject's eye based on the simultaneous perturbation optimization method.

[0091] It should be noted that the pressure change of the actuators 43a to 43h in the correction of the regular astigmatism component of the refractive error and the higher-order aberrations is additionally performed after the correction of the spherical component of the refractive error.

[0092] First, the control unit 70 increases or decreases the pressure applied by each of the actuators 43a to 43h to the lens unit 42 by Δd (S11). For example, the initial Δd is set to a pressure equivalent to the amount of correction for 2.0 D (diopter) of the regular astigmatism component of the refractive error.

[0093] Also, whether each of the actuators 43a to 43h increases or decreases the pressure is determined randomly. For example, for the sake of explanation, it is assumed that the actuators 43a, 43c, 43e, and 43g increase the pressure by Δd (+Δd), and the actuators 43b, 43d, 43f, and 43h decrease the pressure by Δd (-Δd) (see FIG. 9). Of course, this combination is just one example.

[0094] After changing the pressure of each of the actuators 43a to 43h, the control unit 70 forms a fundus image based on the light receiving signal output from the light receiving element 29, and obtains an evaluation value B (b11) of the fundus image (S12).

[0095] Next, the control unit 70 changes the pressure of the actuator 43 to be the opposite of the increase or decrease in pressure performed in S11 (reverses the + / - sign of the increase or decrease) (S13). That is, for example, the actuators 43a, 43c, 43e, and 43g decrease the pressure by Δd (-Δd), and the actuators 43b, 43d, 43f, and 43h increase the pressure by Δd (+Δd) (see FIG. 9).

[0096] Thereafter, the control unit 70 obtains an evaluation value B (b12) of the fundus image in the same manner as in S11 (S14). Next, the control unit 70 compares the evaluation value b11 with the evaluation value b12. Then, the control unit 70 changes the pressure of the actuator 43 so that a fundus image having a larger evaluation value is obtained from the pressure set in step S11 and the pressure set in step S13 (S15). For example, for the sake of explanation, it is assumed that the evaluation value b11 is larger than the evaluation value b12. In this case, the control unit 70 changes the pressure so that the actuators 43a, 43c, 43e, and 43g increase the pressure by Δd, and the actuators 43b, 43d, 43f, and 43h decrease the pressure by Δd.

[0097] Next, the control unit 70 determines whether the evaluation value B of the fundus image in step S15 (i.e., the evaluation value b11 in this description) exceeds a reference value Ba of a predetermined level (S16). For example, the reference value Ba is a value that is experimentally determined in advance.

[0098] If the evaluation value B of the fundus image exceeds the reference value Ba, the control unit 70 ends step S104 (second correction control) and proceeds to step S105 (photographing).

[0099] If the evaluation value B of the fundus image does not exceed the reference value Ba, the control unit 70 returns to step S11 and continues the second correction control. That is, steps S11 to S15 (for the sake of explanation, referred to as flow F) are repeatedly executed until the evaluation value B of the fundus image exceeds the reference value Ba. Note that, for example, the control unit 70 adjusts the pressure Δd to be increased or decreased before executing step S11. For example, the control unit 70 makes the pressure Δd to be increased or decreased in flow F smaller than the pressure Δd increased or decreased when executing the previous flow F (for example, the pressure Δd is set to be 20% smaller than the pressure Δd used in the previous flow F). That is, the pressure Δd to be increased or decreased becomes smaller each time flow F is repeated.

[0100] In the above description, an example has been described in which the evaluation value B of a fundus image is calculated each time the fundus image is acquired by changing the pressure, but this is not limiting. That is, the control unit 70 may obtain two fundus images for which evaluation values ​​B are compared, and then calculate the evaluation value B for each fundus image, and compare the magnitude of the evaluation value B. In other words, for example, steps S12 and S14 may be performed after step S13 is completed.

[0101] Furthermore, for example, the pressure Δd that is increased or decreased by the actuators 43a to 43h may be different for each of the actuators 43a to 43h.

[0102] Further, for the end determination of the second correction control, instead of using the reference value Ba, the difference between the evaluation value b11 and the evaluation value b12 before and after inverting the + / − sign of the pressure of the actuator 43 may be obtained, and it may be determined based on whether or not the difference is equal to or less than a predetermined value. If the difference between the evaluation value b11 and the evaluation value b12 becomes equal to or less than the predetermined value, it can be regarded that the correction of the refractive error has converged approximately.

[0103] As described above, the control unit 70 can change the focal position of the liquid lens 41 so that the evaluation value B becomes a certain value or more. Therefore, the control unit 70 can consequently obtain a fundus image in which the refractive error component and the higher-order aberration of the eye to be examined are corrected. That is, the control unit 70 can obtain a fundus image with higher resolution by correcting the refractive error of the eye to be examined based on the result of the image processing.

[0104] Of course, the method of changing the focal position of the liquid lens 41 so as to correct the refractive error component and the higher-order aberration of the eye to be examined is not limited to this. For example, a hill climbing method may be used for the method of changing the pressure of the actuator 43 so that the evaluation value B becomes higher. The method using the hill climbing method is, for example, a method in which the pressure of each of the actuators 43a to 43h is increased or decreased so that the evaluation value B becomes higher, and the pressure is determined when the evaluation value B becomes the highest.

[0105] Further, for example, the control unit 70 may control the actuator 43 based on the input information on the refractive error of the eye to be examined (astigmatism degree, astigmatism axis), and change the focal position of the liquid lens 41. In that case, for example, information on the refractive error of the eye to be examined is input from the outside through the input interface 75.

[0106] <S105: Imaging> In the present embodiment, for example, when a shooting trigger signal (for example, a release operation signal or the like) is input from an examiner, a fundus image formed at a predetermined timing (or period) is captured by the control unit 70.

[0107] According to the configuration and operation of the fundus photographing device 1 described above, it is possible to obtain a higher-resolution fundus image without complicating the photographing optical system.

[0108] <Standard image quality mode> When the standard image quality mode is selected, the second correction control (step S104) is not executed, and the correction of the refractive error ends when the first correction control (correction of the spherical component of the refractive error) of step S102 ends. Therefore, in the standard image quality mode, it is possible to acquire a fundus image in a shorter time than in the high image quality mode because step S104 is not executed.

[0109] <Mode selection> In this embodiment, the selection between the standard image quality mode and the high image quality mode is performed before step S103. For example, the selection between the standard image quality mode and the high image quality mode may be performed after the operation is started and before step S101 is performed. Of course, the configuration may be such that the standard image quality mode and the high image quality mode are selected in step S103. For example, a message prompting the examiner to select either the standard image quality mode or the high image quality mode may be displayed on the monitor 80 to prompt the examiner to select the imaging mode.

[0110] For example, the standard image quality mode is selected when it is not necessary to obtain a fundus image in which even fine blood vessels are in focus (for example, when a fundus image of a conventional fundus camera is sufficient). The standard image quality mode may also be selected when it is known in advance that the subject's eye does not contain regular astigmatism components and high-order aberrations.

[0111] On the other hand, for example, the high image quality mode is selected when obtaining a fundus image in which even minute tissues (for example, retinal veins and retinal arteries) contained in the fundus Er of the subject's eye are in focus.

[0112] For example, when the high-image-quality mode is selected, the control unit 70 may control the operation of the scanning unit 16 to make the range (angle of view) for obtaining a fundus image smaller than the angle of view in the standard imaging mode. For example, when the scanning time for obtaining one fundus image is constant, the smaller the angle of view, the smaller the range of the fundus Er scanned by the laser light per unit time. Therefore, when the scanning time is constant, the smaller the angle of view, the higher the resolution of the fundus image can be obtained. For example, the fundus imaging device 1 may be provided with an optical system or attachment for changing the magnification. For example, the method for changing the angle of view may use the technology described in JP-A-2019-195422.

[0113] [Example of transformation] The present disclosure is not necessarily limited to the above-described embodiments, and various modifications are possible.

[0114] For example, the lens unit 42 and the actuators 43a to 43h are arranged at a fixed angle in accordance with the angle notation of the astigmatism axis, but are not limited to this. For example, a rotation mechanism that rotates the liquid lens 41 (lens unit 42 and actuators 43a to 43h) around the central axis C may be provided in the refractive error correction unit 40. The rotation mechanism is controlled by the control unit 70 based on the result of the evaluation value B. In this way, when the subject's eye has a regular astigmatism component of the refractive error, the rotation angle of the liquid lens 41 can be controlled according to the astigmatism axis of the regular astigmatism component so that the regular astigmatism component is more accurately corrected. This makes it possible to obtain a fundus image with higher resolution.

[0115] For example, the photographing optical system 30 may include a refractive error acquisition optical system 50 for acquiring the refractive error of the subject's eye. For example, as shown in FIG. 10, the refractive error acquisition optical system 50 shares the irradiation optical system 10 as a measurement light irradiating optical system that irradiates the fundus of the subject's eye with measurement light. The refractive error acquisition optical system 50 also shares the optical path from the objective optical system 17 of the light receiving optical system 20 to the lens 21 as a measurement light receiving optical system 51 that receives the fundus reflected light of the measurement light, and includes a beam splitter 53 that splits the fundus reflected light from the subject's eye, and a CCD sensor 55 that receives the fundus reflected light. For example, the beam splitter 53 is disposed between the lens 21 and the pinhole plate 23. For example, the CCD sensor 55 is disposed at a conjugate position with the retina.

[0116] For example, the control unit 70 obtains the refractive error of the subject's eye based on the light receiving signal of the fundus reflected light output by the CCD sensor 55. For example, the control unit 70 may obtain the refractive error of the subject's eye by obtaining how the reflected light received by the CCD sensor 55 spreads (for example, by using a point spread function (PSF)). In this case, the control unit 70 may control the liquid lens 41 based on the obtained refractive error of the subject's eye to change the focal position so that the refractive error is corrected. Note that, as a method for obtaining the refractive error of the subject's eye using the PSF, for example, the method described in JP-A-2007-526808 can be used.

[0117] This makes it possible to efficiently correct the refractive error of the subject's eye and shorten the time required to adjust the focal position of the liquid lens 41. Therefore, even when obtaining a fundus image with a higher resolution, an increase in the imaging time can be suppressed.

[0118] In the present embodiment, the fundus imaging device 1 is described as an SLO device, but is not limited thereto. The fundus imaging device 1 may be a device integrated with other ophthalmic devices such as an optical coherence tomography (OCT) or a perimeter. For example, when the fundus imaging device 1 is an optical coherence tomography, the high image quality mode may be used when angiography (OCT angiography) is performed. [Explanation of symbols]

[0119] 1 Fundus photography device 10 Irradiation optical system 20 Light receiving optical system 30. Photographing Optical System 40 Refractive error correction unit 41 Liquid Lens 42 Lens section 43 Actuator 70 Control section

Claims

1. An imaging optical system including an objective optical system and an optical scanner that scans imaging light from a light source, and which irradiates the imaging light scanned by the optical scanner onto the fundus of the test eye via the objective optical system, a light receiving optical system having a light receiving element that receives fundus reflected light of the imaging light, an optical path branching member that branches the optical paths between the illumination optical system and the light receiving optical system, and a refractive error correction unit that is arranged between the optical scanner and the optical path branching member and corrects refractive error of the test eye, and which acquires a fundus image based on a light receiving signal from the light receiving element; A control means, the refractive error correction unit has a variable-focus lens capable of changing the power of at least a spherical component and a regular astigmatism component by changing the refractive state of a lens unit; The fundus photographing apparatus according to claim 1, wherein the control means corrects at least a spherical component and a regular astigmatism component of a refractive error of the subject's eye by controlling the variable focus lens.

2. 2. The fundus imaging apparatus according to claim 1, wherein said control means controls said variable-focus lens to correct at least a regular astigmatism component of a refractive error of the subject's eye after correcting a spherical component of the refractive error.

3. the fundus photographing apparatus further comprises an evaluation means for evaluating a correction state of a refractive error of the subject's eye by the variable-focus lens based on a light receiving signal of the light receiving element, 3. The fundus photographing apparatus according to claim 1, wherein the control means corrects a refractive error of the subject's eye by controlling the variable-focus lens based on the evaluation result of the evaluation means.

4. 4. The fundus imaging apparatus according to claim 1, wherein the variable focus lens is further capable of correcting at least coma aberration.

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