ophthalmic devices

Abstract

To allow an operator to set a reference position calculated by reference light to an arbitrary position.SOLUTION: An ophthalmologic device includes a light source, a measurement optical system for generating measurement light by applying light from the light source to a subject's eye, a reference optical system using the light from the light source to generate reference light, a base optical system using the light from the light source to generate base light for calculating a base position, and an interference optical system for generating measurement interference light by multiplexing the measurement light and the reference light and generating base interference light by multiplexing the base light and the reference light. The base optical system has an optical path branched from the measurement optical system. The measurement optical system includes a changeover part for changing over between a first state for applying the light from the light source to the subject's eye and a second state for guiding the light from the light source to the base optical system. A control part controls the changeover part such that when the subject's eye is measured, the interference signal is detected by a detector as the first state and the base interference signal is detected by the detector as the second state.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The technology disclosed in this specification relates to an ophthalmic device that uses the interference phenomenon of light to capture a tomographic image of an eye to be examined.

Background Art

[0002] In an ophthalmic device that uses the interference phenomenon of light, reference light and measurement light are combined to generate measurement interference light, and position information in the depth direction of the eye to be examined is calculated from the generated measurement interference light (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In this type of ophthalmic device, in order to accurately calculate the position information in the depth direction, it is necessary to accurately adjust the optical path lengths of the optical systems that generate the reference light and the measurement light. For this reason, calibration of the optical system is performed during the manufacture of the ophthalmic device, and then it is shipped (that is, calibration processing is performed at the time of shipment (specifically, at the time of optical system calibration preset in the manufacturing process)). However, due to changes over time after shipment and the measurement environment (for example, temperature, etc.), the optical path lengths of the optical systems change, and it may be difficult to measure under the same conditions as when the calibration processing was performed. Therefore, it is conceivable to branch a part of the light of the interference optical system to generate reference light, and use this reference light to correct the position information in the depth direction of the eye to be examined.

[0005] However, in such ophthalmic devices, a portion of the light from the measuring optical system is directed onto the eye under examination to generate measurement light, while simultaneously branching off a portion of the light from the measuring optical system to generate reference light. The depth-direction position information of the eye under examination, calculated from the measurement light, is then corrected using the reference position calculated from the reference light. Therefore, there is a constraint that the reference position calculated from the reference light must be set to a position different from the depth-direction position information of the eye under examination calculated from the measurement light. This specification discloses a technique for an ophthalmic device that corrects the depth-direction position information of the eye under examination using reference light, in which the reference position calculated by the reference light can be set to an arbitrary position. [Means for solving the problem]

[0006] The first ophthalmic apparatus disclosed herein comprises a light source; a measuring optical system that generates measurement light by irradiating the eye under examination with light from the light source; a reference optical system that generates reference light using light from the light source; a reference optical system that generates reference light for calculating a reference position using light from the light source; an interference optical system that generates measurement interference light by combining the measurement light and the reference light, and generates reference interference light by combining the reference light and the reference light; a detector that detects the measurement interference light and outputs a measurement interference signal, and detects the reference interference light and outputs a reference interference signal; and a control unit that calculates depth-direction position information of the eye under examination based on the measurement interference signal and calculates a reference position based on the reference interference signal. The reference optical system has an optical path branched from the measuring optical system. The measuring optical system includes a switching unit that switches between a first state in which light from the light source is irradiated onto the eye under examination and a second state in which light from the light source is directed to the reference optical system. The control unit controls the switching unit to detect the measurement interference signal with the detector in the first state and to detect the reference interference signal with the detector in the second state when measuring the eye under examination.

[0007] The ophthalmic device described above can switch between a first state, in which light from a light source is shone onto the eye under examination, and a second state, in which light from the light source is guided to a reference optical system. When measuring the eye under examination, the detector detects the measurement interference signal in the first state, and the detector detects the reference interference signal in the second state. In other words, the period for detecting the measurement interference signal and the period for detecting the reference interference signal are different. Therefore, the reference position calculated by the reference interference signal can be set to an arbitrary position, regardless of the depth-direction position information of the eye under examination calculated by the measurement interference signal.

[0008] Furthermore, the second ophthalmic apparatus disclosed herein includes a first OCT for measuring a first position in the depth direction of a first part of the eye under examination, a second OCT for measuring a second position in the depth direction of a second part of the eye different from the first part, and a control unit for calculating the depth dimension from the first part to the second part based on the first position measured by the first OCT and the second position measured by the second OCT. The first OCT comprises a first light source, a first measurement optical system that generates a first measurement light by irradiating a first part of the eye under examination with light from the first light source, a first reference optical system that generates a first reference light using light from the first light source, a first reference optical system that generates a first reference light for calculating a first reference position using light from the first light source, a first interference optical system that generates a first measurement interference light by combining the first measurement light and the first reference light, and generates a first reference interference light by combining the first reference light and the first reference light, and a first detector that detects the first measurement interference light and outputs a first measurement interference signal, and also detects the first reference interference light and outputs a first reference interference signal. The first reference optical system has an optical path branched from the first measurement optical system. The first measurement optical system includes a first switching unit that switches between a first state in which light from the first light source is irradiated onto the eye under examination and a second state in which light from the first light source is guided to the first reference optical system. During the measurement of the eye under examination, the first switching unit detects the first measurement interference signal with the first detector as the first state, and the first switching unit also detects the first reference interference signal with the first detector as the second state.

[0009] In the ophthalmic device described above, the first measurement interference signal is detected by the first detector in the first state, and the first reference interference signal is detected by the first detector in the second state. Therefore, the first reference position calculated by the first reference interference signal can be set to any position, regardless of the depth-direction position information of the eye being examined, which is calculated by the first measurement interference signal. [Brief explanation of the drawing]

[0010] [Figure 1] A diagram showing the configuration of the optical system of the ophthalmic device according to Example 1. [Figure 2] This figure shows the relationship between the measurement ranges of the eye under examination measured by the two OCTs provided in the ophthalmic device according to Example 1. [Figure 3] A block diagram showing the configuration of the control system for the ophthalmic device according to Example 1. [Figure 4] A flowchart showing the procedure for measuring the axial length of the eye under examination using the ophthalmic device according to Example 1. [Figure 5] A diagram showing the configuration of the optical system of the ophthalmic device according to Example 2. [Figure 6] A diagram showing the optical system configuration of the ophthalmic device according to Example 2 (during optical system calibration). [Figure 7] A diagram showing the optical system configuration of the ophthalmic device according to Example 2 (during eye examination measurement). [Figure 8] A block diagram showing the configuration of the control system for the ophthalmic device according to Example 2. [Figure 9] A flowchart showing the procedure for measuring the axial length of the eye under examination using the ophthalmic device according to Example 2. [Modes for carrying out the invention]

[0011] The main embodiments of the first and second ophthalmic devices described above are listed below. Note that the technical elements described below are independent technical elements that exhibit technical usefulness individually or in various combinations, and are not limited to the combinations described in the claims at the time of filing.

[0012] (First Embodiment) In the first ophthalmic apparatus disclosed herein, the control unit may control the switching unit to detect a reference interference signal with the detector as a second state before or after detecting the measurement interference signal with the detector as a first state. With such a configuration, a reference position is obtained before and after acquiring the depth-direction position information of the eye under examination. Therefore, the depth-direction position information of the eye under examination can be corrected by appropriately considering the conditions at the time of measurement.

[0013] (Second Embodiment) The first ophthalmic apparatus or first embodiment disclosed herein may further include a storage unit that stores a specific time reference position indicating a reference position adjusted at a specific time. The specific time reference position may be a position calculated from a reference interference light generated by combining a reference light generated by a reference optical system and a reference light generated by a reference optical system at a specific time. The control unit may be configured to correct the depth-direction position information of the eye under examination, calculated based on the measurement interference signal output from the detector at the time of measurement, based on the difference between the measurement time reference position, which is a reference position calculated based on the reference interference signal output from the detector at the time of measurement, and the specific time reference position stored in the storage unit. With such a configuration, the depth-direction position information of the eye under examination is corrected based on the reference position acquired at the time of measurement and the reference position acquired at a specific time (for example, at the time of factory calibration or repair calibration). This makes it possible to consider the change in the optical system over time from the time of specification to the time of measurement.

[0014] (Third Embodiment) In a second embodiment of the first ophthalmic apparatus disclosed herein, the memory unit may further store a conversion formula for converting the depth-direction position information of the eye to be examined, calculated based on the measurement interference signal, into the actual dimensions of the eye to be examined. The control unit may be configured to further calculate the actual dimensions of the eye to be examined by converting the depth-direction position information of the eye to be examined, calculated based on the measurement interference signal, using the conversion formula. The conversion formula may be obtained using (A) depth-direction position information of two reflective surfaces obtained from calibration interference light generated by combining calibration measurement light, which is generated by irradiating a calibration tool having at least two reflective surfaces having a known optical path length difference with light from a light source through a measurement optical system, and reference light generated by a reference optical system, and (B) the optical path length difference of the two reflective surfaces. With such a configuration, the actual dimensions of the eye to be examined can be calculated with high accuracy.

[0015] (Fourth aspect) In a third aspect of the first ophthalmic apparatus disclosed herein, the timing of the specific time and the timing of measuring the calibration interference light using a calibration tool to obtain the conversion formula may be approximately simultaneous. With this configuration, the timing of measuring the specific time reference position and the timing of measuring to obtain the conversion formula are approximately simultaneous, thereby improving the measurement accuracy of the eye under examination.

[0016] (Fifth Embodiment) The first ophthalmic apparatus disclosed herein may further include a storage unit that stores a specific reference position indicating a reference position adjusted at a specific time. The specific reference position may be a position calculated from a reference interference light generated by combining a reference light generated by a reference optical system and a reference light generated by a reference optical system at a specific time. The reference optical system may include an adjustment unit that adjusts the optical path length of the reference light. The control unit may calculate a measurement reference position, which is a reference position calculated based on the reference interference signal output from the detector at the time of measurement, and may control the adjustment unit so that the measurement reference position calculated at the time of measurement becomes the specific reference position stored in the storage unit. With such a configuration, by adjusting the optical path length of the reference light, the eye under examination can be measured in a state substantially the same as the state at a specific time.

[0017] (Sixth Aspect) In the fifth aspect of the first ophthalmic device disclosed in this specification, the storage unit may further store a conversion formula for converting the depth direction position information of the eye under examination calculated based on the measurement interference signal into the actual size value of the eye under examination. The control unit may be configured to further calculate the actual dimensions of the eye under examination by converting the depth direction position information of the eye under examination calculated based on the measurement interference signal using the conversion formula. The conversion formula may be obtained using (A) the depth direction position information of the two reflecting surfaces obtained from the calibration interference light generated by combining the calibration measurement light irradiated from the light source to a calibration tool having at least two reflecting surfaces with known optical path length differences by the measurement optical system and the reference light generated by the reference optical system, and (B) the optical path length differences of the two reflecting surfaces. With such a configuration, the actual dimensions in the depth direction of the eye under examination can be accurately calculated.

[0018] (Seventh Aspect) In the sixth aspect of the first ophthalmic device disclosed in this specification, the specific time and the time of measuring the calibration interference light using the calibration tool to obtain the conversion formula may be substantially the same time. With such a configuration, since the specific time and the time of measurement for obtaining the conversion formula are substantially the same time, the measurement accuracy of the eye under examination can be improved.

[0019] (Eighth Aspect) In any of the fifth to seventh aspects of the first ophthalmic device disclosed in this specification, the control unit detects the reference interference signal with the detector with the switching unit in the second state, controls the adjustment unit so that the measurement reference position calculated based on the detected reference interference signal becomes the specific reference position stored in the storage unit, and after the optical path length of the reference light is adjusted by the adjustment unit, may detect the measurement interference signal with the switching unit in the first state. With such a configuration, after adjusting the optical path length of the reference light to be in the same state as the specific time, the measurement of the eye under examination is performed. For this reason, the measurement of the eye under examination can be performed under the same conditions as the specific time (for example, at the time of shipment calibration, at the time of repair calibration, etc.).

[0020] (9th aspect) In the second ophthalmic apparatus disclosed herein, the second OCT may include a second light source, a second measurement optical system that generates a second measurement light by irradiating a second part of the eye under examination with light from the second light source, a second reference optical system that generates a second reference light using light from the second light source, a second reference optical system that generates a second reference light for calculating a second reference position using light from the second light source, a second interference optical system that generates a second measurement interference light by combining the second measurement light and the second reference light, and generates a second reference interference light by combining the second reference light and the second reference light, and a second detector that detects the second measurement interference light and outputs a second measurement interference signal, and detects the second reference interference light and outputs a second reference interference signal. The second reference optical system may have an optical path branched from the second measurement optical system. The second measurement optical system may include a second switching unit that switches between a third state in which light from the second light source is irradiated onto the eye under examination and a fourth state in which light from the second light source is directed to the second reference optical system. During the measurement of the eye under examination, the second switching unit may detect the second measurement interference signal with the second detector as a third state, and the second switching unit may also detect the second reference interference signal with the second detector as a fourth state. With this configuration, the second reference position can be set to any position in the second OCT, just as in the first OCT.

[0021] (Tenth aspect) In the ninth aspect of the second ophthalmic device disclosed herein, when the first switching unit is in the first state, the second switching unit is in the third state, and when the first switching unit is in the second state, the second switching unit is in the fourth state, and the first switching unit and the second switching unit may be used interchangeably. With such a configuration, since the first switching unit and the second switching unit are used interchangeably, the configuration of the optical system can be simplified and the switching of each switching unit can be easily performed.

[0022] (11th aspect) In the 9th or 10th aspect of the second ophthalmic device disclosed herein, the ophthalmic device may further include a storage unit that stores the distance in the depth direction between the measurement range of the first OCT and the measurement range of the second OCT adjusted at a particular time, a first reference position at a particular time indicating a first reference position adjusted at a particular time, and a second reference position at a particular time indicating a second reference position adjusted at a particular time. The control unit may calculate the depth dimension from the first part to the second part using: (1) the difference between the first reference position at measurement, calculated based on the first reference interference signal output from the first detector during measurement, and the first reference position at a specific time stored in the memory unit; (2) the first position of the eye under examination, calculated based on the first measurement interference signal output from the first detector during measurement; (3) the difference between the second reference position at measurement, calculated based on the second reference interference signal output from the second detector during measurement, and the second reference position at a specific time stored in the memory unit; (4) the second position of the eye under examination, calculated based on the second measurement interference signal output from the second detector during measurement; and (5) the distance in the depth direction between the measurement range of the first OCT and the measurement range of the second OCT stored in the memory unit. With such a configuration, the depth dimension from the first part to the second part can be calculated with high accuracy.

[0023] (Twelfth Embodiment) In the eleventh embodiment of the second ophthalmic apparatus disclosed herein, the storage unit may further store a first conversion formula for converting depth-direction position information of the eye to be examined, calculated based on a first measurement interference signal, into the actual dimensions of the eye to be examined within the measurement range of the first OCT, and a second conversion formula for converting depth-direction position information of the eye to be examined, calculated based on a second measurement interference signal, into the actual dimensions of the eye to be examined within the measurement range of the second OCT. The control unit may be configured to further calculate the actual dimensions of the eye to be examined within the measurement range of the first OCT by converting the depth-direction position information of the eye to be examined, calculated based on the first measurement interference signal, using the first conversion formula, and to further calculate the actual dimensions of the eye to be examined within the measurement range of the second OCT by converting the depth-direction position information of the eye to be examined, calculated based on the second measurement interference signal, using the second conversion formula. The first conversion formula may be obtained using (A1) positional information in the depth direction of the two reflective surfaces obtained from a first calibration interference light generated by combining a first calibration measurement light, which is generated by irradiating a first calibration tool having at least two reflective surfaces with a known optical path length difference from a first measurement optical system, with light from a first light source and a first reference light generated by a first reference optical system, and (B) the optical path length difference of the two reflective surfaces. The second conversion formula may be obtained using (A) positional information in the depth direction of the two reflective surfaces obtained from a second calibration interference light generated by combining a second calibration measurement light, which is generated by irradiating a second calibration tool having at least two reflective surfaces with a known optical path length difference from a second measurement optical system, with light from a second light source and a second reference light generated by a second reference optical system, and (B) the optical path length difference of the two reflective surfaces. With such a configuration, the actual depth dimension of the eye under examination can be calculated with high accuracy.

[0024] (13th aspect) In a 12th aspect of the second ophthalmic apparatus disclosed herein, the first reference position at a specific time may be a position calculated from the first reference interference light generated by combining the first reference light generated by the first reference optical system and the first reference light generated by the first reference optical system at a specific time. The second reference position at a specific time may be a position calculated from the second reference interference light generated by combining the second reference light generated by the second reference optical system and the second reference light generated by the second reference optical system at a specific time. The time at which a specific time occurs, the time when the first measurement light is shone on the first calibration tool to obtain the first conversion formula, and the time when the second measurement light is shone on the second calibration tool to obtain the second conversion formula may be approximately simultaneous. With such a configuration, the time at which a specific time occurs and the time when measurement is performed to obtain the conversion formula are approximately simultaneous, thereby improving the measurement accuracy of the eye under examination.

[0025] (14th aspect) In the 9th or 10th aspect of the second ophthalmic apparatus disclosed herein, the ophthalmic apparatus may further include an adjustment unit provided in at least one of the first reference optical system and the second reference optical system for adjusting the optical path length. The control unit may control the adjustment unit so that the distance between the first reference position at measurement, calculated from the first reference interference signal at measurement, and the second reference position at measurement, calculated from the second reference interference signal at measurement, is a preset distance. With this configuration, the relationship between the optical path lengths of the two reference optical systems is adjusted to a preset distance before measuring the eye under examination. This makes it possible to accurately calculate the depth dimension from the first part to the second part of the eye under examination.

[0026] (15th aspect) In the 14th aspect of the second ophthalmic device disclosed herein, the preset distance may be the distance between a first reference position at a specific time calculated from a first reference interference signal at a specific time and a second reference position at a specific time calculated from a second reference interference signal at a specific time. With such a configuration, the eye under examination can be measured under the same conditions as at a specific time (for example, during factory calibration, during repair calibration, etc.).

[0027] (16th aspect) In the 14th or 15th aspect of the second ophthalmic apparatus disclosed herein, the control unit may set the first switching unit to a second state and detect a first reference interference signal with the first detector, set the second switching unit to a fourth state and detect a second reference interference signal with the second detector, control the adjustment unit so that the difference between the first reference position and the second reference position at measurement, calculated based on the detected first and second reference interference signals, becomes a preset distance, and after the optical path length has been adjusted by the adjustment unit, the first switching unit may set the first switching unit to a first state and detect a first measurement interference signal, and the second switching unit may set the second switching unit to a third state and detect a second measurement interference signal. [Examples]

[0028] (Example 1) The ophthalmic device 10 according to Example 1 will now be described. The ophthalmic device 10 includes an anterior segment OCT (an example of a first OCT) that captures a tomographic image of the anterior segment of the eye under examination (an example of a first segment), and a fundus OCT (an example of a second OCT) that captures a tomographic image of the fundus of the eye under examination (an example of a second segment). By using different OCTs for the anterior segment and the fundus to capture tomographic images, the ophthalmic device 10 enables the acquisition of clear tomographic images for both the anterior segment and the fundus.

[0029] In other words, as shown in Figure 2, the ophthalmic device 10 acquires a tomographic image of the anterior segment 202 of the eye under examination 200 using an anterior segment OCT, and acquires a tomographic image of the fundus 204 using a fundus OCT. In order to clearly image both the anterior segment 202 and the fundus 204, the imaging range 202a (length B in the depth direction) of the anterior segment OCT and the imaging range 204a (length C in the depth direction) of the fundus OCT are set so as not to overlap. Therefore, for example, when trying to measure the axial length (length from the corneal surface of the anterior segment 202 (an example of the first position) to the retinal surface of the fundus 204 (an example of the second position)), it is necessary to know the positional relationship in the depth direction between the imaging range 202a of the anterior segment OCT and the imaging range 204a of the fundus OCT. For example, the distance (length A) from the deepest part of the imaging range 202a of the anterior segment OCT to the shallowest part of the imaging range 204a of the fundus OCT is required. Therefore, the optical system configuration of the ophthalmic device 10 is designed so that the positional relationship in the depth direction between the imaging range 202a of the anterior segment OCT and the imaging range 204a of the fundus OCT is a predetermined positional relationship, and the optical system of the ophthalmic device 10 is calibrated when it is shipped. However, the optical system of the ophthalmic device 10 changes over time after shipment and due to the environment during measurement (e.g., temperature), and it is not possible to measure under the conditions calibrated by the calibration process. Therefore, the ophthalmic device 10 calculates the axial length of the eye by correcting for changes in the optical path length of the optical system.

[0030] First, the optical system configuration of the ophthalmic device 10 will be explained. As shown in Figure 1, the ophthalmic device 10 is equipped with an anterior segment OCT (12, 18a~18e, 20, 22, 26, 24, 28, 32, 34, 36, 38, 40, 43) and a fundus OCT (14, 16, 30a~30d, 32, 33, 36, 38, 41, 42).

[0031] The anterior segment OCT is a Fourier domain type optical tomography system (so-called SS-OCT) equipped with a wavelength-swept light source 12 (an example of a first light source), and comprises an anterior segment measurement optical system (an example of a first measurement optical system), an anterior segment reference optical system (an example of a first reference optical system), an anterior segment reference optical system (an example of a first reference optical system), an anterior segment interference optical system (an example of a first interference optical system), and an anterior segment detector 28 (an example of a first detector).

[0032] The anterior segment measurement optical system comprises optical fibers 18a, 18b, and 18d, a coupler 20, a circulator 22, a lens 34, and a galvanoscanner 36. Light emitted from the light source 12 passes through optical fiber 18a and is input to the coupler 20. The coupler 20 splits the light from the light source 12 into measurement light and reference light. The measurement light split by the coupler 20 (an example of the first measurement light) is output to optical fiber 18b. A circulator 22 is located on optical fiber 18b. The measurement light output to optical fiber 18b passes through the circulator 22 and is emitted from the tip of optical fiber 18b towards lens 34. The measurement light emitted to lens 34 is emitted to a two-axis galvanoscanner 36. The galvanoscanner 36 is configured to tilt by a drive device (not shown), and by tilting the galvanoscanner 36, the irradiation position of the measurement light onto the eye under examination 200 is scanned. The reflected light from the eye under examination 200 is input to the lens 34 via the galvanoscanner 36, in the opposite direction to the above. The reflected light input to the lens 34 is input to the circulator 22 through the optical fiber 18b. The reflected light input to the circulator 22 is input to the coupler 26 through the optical fiber 18d. Note that in Figure 1, the optical system configuration is simplified, and the optical fiber 18b is shown as penetrating the lens 32, but in reality, the optical fiber 18b does not penetrate the lens 33. Also, in Figure 1, the circulator 22 is shown as being located on the optical fiber 30c, which will be described later, but in reality, the circulator 22 is not located on the optical fiber 30c.

[0033] The anterior segment reference optical system comprises optical fibers 18a, 18c, and 18e, a coupler 20, a circulator 24, a lens 43, and a reference mirror 40. As described above, light emitted from the light source 12 passes through optical fiber 18a and is input to coupler 20, where it is split into measurement light and reference light. The reference light output from coupler 20 (an example of the first reference light) is input to optical fiber 18c, passes through circulator 24, and is emitted from the tip of optical fiber 18c toward lens 43. The reference light emitted from lens 43 is reflected by reference mirror 40 and input to lens 43 again. The reference light input to lens 43 passes through optical fiber 18c and is input to circulator 24. The reflected light input to circulator 24 passes through optical fiber 18e and is input to coupler 26.

[0034] The anterior segment reference optical system has an optical path branched from the anterior segment measurement optical system and includes a reference mirror 38 positioned on this optical path. The galvanoscanner 36 described above switches between a first state in which light from the light source 12 is irradiated onto the eye under examination 200 and a second state in which light from the light source 12 is irradiated onto the reference mirror 38 by tilting with a drive device (not shown). The galvanoscanner 36 functions as a "first switching unit" that switches between the first and second states. In this embodiment, when light from the light source 12 is irradiated onto the eye under examination 200, the light from the light source 12 is not directed to the reference mirror 38. On the other hand, when light from the light source 12 is directed to the reference mirror 38, the light from the light source 12 is not irradiated onto the eye under examination 200. That is, all the light directed from the light source 12 to the anterior segment measurement optical system is irradiated onto either the eye under examination 200 or the reference mirror 38. The light irradiated onto the reference mirror 38 (an example of the first reference light) is reflected by the reference mirror 38 and input to the circulator 22 through the galvanometer scanner 36, lens 34, and optical fiber 18b. The light input to the circulator 22 is input to the coupler 26 through the optical fiber 18d.

[0035] The anterior segment interference optical system is equipped with a coupler 26. The coupler 26 combines the light reflected from the eye under examination 200 (first measurement light) and the light reflected from the reference mirror 40 (first reference light) to generate interference light (an example of first measurement interference light), and also combines the light reflected from the reference mirror 38 (first reference light) and the light reflected from the reference mirror 40 (first reference light) to generate interference light (an example of first reference interference light). The interference light generated by the coupler 26 is input to the anterior segment detector 28. The anterior segment detector 28 is a balance detector that detects the interference light input from the coupler 26 and outputs an interference signal (electrical signal). The interference signal output from the anterior segment detector 28 is input to a control device 44 (shown in Figure 3), which will be described later.

[0036] The fundus OCT is a spectral domain type optical tomography imaging device (so-called SD-OCT) equipped with a broadband wavelength light source 14 (an example of a second light source), and comprises a fundus measurement optical system (an example of a second measurement optical system), a fundus reference optical system (an example of a second reference optical system), a fundus reference optical system (an example of a second reference optical system), a fundus interference optical system (an example of a second interference optical system), and a fundus detector 16 (an example of a second detector).

[0037] The fundus measurement optical system comprises optical fibers 30a and 30c, a coupler 32, a lens 33, and a galvanoscanner 36. Light emitted from the light source 14 is input to the coupler 32 through optical fiber 30a. The coupler 32 splits the light from the light source 14 into measurement light (an example of second measurement light) and reference light. The measurement light split by the coupler 40 is output to the optical fiber 30c and emitted from the tip of the optical fiber 30c toward the lens 33. The measurement light emitted by the lens 33 is emitted to the two-axis galvanoscanner 36, similar to the anterior segment OCT described above. The galvanoscanner 36 is driven by a drive device (not shown) and scans the irradiation position of the measurement light onto the eye under examination 200. The reflected light from the eye under examination 200 is input to the coupler 32 through the galvanoscanner 36, lens 34, and optical fiber 30c, in the reverse direction to the above.

[0038] As is clear from the above explanation, the optical path from the galvanoscanner 36 to the eye under examination 200 is common to both the fundus measurement optical system and the anterior segment measurement optical system, and the galvanoscanner 36 is used for both the fundus measurement optical system and the anterior segment measurement optical system. In Figure 1, the measurement light emitted from the tip of the optical fiber 30c toward the lens 33 is shown to pass through the lens 34, but in reality, it does not pass through the lens 34. Also, as shown in Figure 1, the optical path length from the tip of the optical fiber 30c toward the eye under examination 200 in the fundus measurement optical system is longer than the optical path length from the tip of the optical fiber 18b toward the eye under examination 200 in the anterior segment measurement optical system. That is, in the fundus measurement optical system, the section from the tip of the optical fiber 30c to the position corresponding to the tip of the optical fiber 18b is composed of a bulk optical system, whereas in the anterior segment measurement optical system, it is composed of the optical fiber 18b. For this reason, the change in optical path length of the anterior segment measurement optical system due to temperature changes is not the same as the change in optical path length of the fundus measurement optical system. Furthermore, since the temperature inside the ophthalmic device 10 is non-uniform, the temperature of each optical system is not uniform across the entire optical path length. This also results in non-uniform changes in the optical path length of each optical system due to temperature.

[0039] The fundus reference optical system comprises optical fibers 30a and 30b, a coupler 32, a lens 41, and a reference mirror 42. As described above, light emitted from the light source 14 passes through optical fiber 30a and is input to coupler 32, where it is split into measurement light and reference light. The reference light output from coupler 32 (an example of a second reference light) passes through optical fiber 30b and is emitted from the tip of optical fiber 30b toward lens 41. The reference light emitted from lens 41 is reflected by reference mirror 42 and input to coupler 32 through lens 41 and optical fiber 30b.

[0040] The fundus reference optical system has an optical path branched from the fundus measurement optical system and is equipped with a reference mirror 38 positioned on this optical path. As is clear from Figure 1, the reference mirror 38 is used for both the fundus reference optical system and the anterior segment reference optical system, and the fundus reference optical system has the same configuration as the anterior segment reference optical system. Therefore, by driving the galvanoscanner 36, it is possible to switch between a third state in which light from the light source 14 is irradiated onto the eye under examination 200 and a fourth state in which light from the light source 14 is irradiated onto the reference mirror 38. In other words, the galvanoscanner 36 functions as a "second switching unit" that switches between the third and fourth states. As will be described later, since the anterior segment OCT and fundus OCT simultaneously capture tomographic images of the eye under examination 200, if the galvanoscanner 36 sets the anterior segment OCT to the first state, the fundus OCT will be in the third state. Also, if the galvanoscanner 36 sets the anterior segment OCT to the second state, the fundus OCT will be in the fourth state. In fundus OCT, all the light guided from the light source 14 to the fundus measurement optical system is directed onto the eye under examination 200 or the reference mirror 38. The light directed onto the reference mirror 38 (an example of a second reference light) is reflected by the reference mirror 38 and input to the coupler 32 via the galvanoscanner 36 and optical fiber 30b.

[0041] The fundus interference optical system is equipped with a coupler 32. The coupler 32 combines the light reflected from the eye under examination 200 (second measurement light) and the light reflected from the reference mirror 40 (second reference light) to generate interference light (an example of second measurement interference light), and also combines the light reflected from the reference mirror 38 (second reference light) and the light reflected from the reference mirror 40 (second reference light) to generate interference light (an example of second reference interference light). The interference light generated by the coupler 26 is input to the fundus detector 16. The fundus detector 16 is a spectrometer that spectrally analyzes the input interference light, detects it, and outputs an interference signal (electrical signal). The interference signal (spectral information of the interference light) output from the fundus detector 16 is input to a control device 44 (shown in Figure 3), which will be described later.

[0042] Next, the configuration of the control system of the ophthalmic device 10 will be described. As shown in Figure 3, the ophthalmic device 10 is controlled by a control device 44. The control device 44 is composed of a microcomputer (microprocessor) consisting of a CPU, ROM, RAM, etc., and functions as a calculation unit 46 that calculates the axial length of the eye under examination 200 and a storage unit 48 that stores various information. The control device 44 is connected to light sources 12 and 14, an anterior segment detector 28, a fundus detector 16, and a galvanoscanner 36. The control device 44 controls the on / off state of the light sources 12 and 14 and drives the galvanoscanner 36. The control device 44 also generates a tomographic image of the anterior segment 202 of the eye under examination 200 from the interference signal input from the anterior segment detector 28, and generates a tomographic image of the fundus 204 of the eye under examination 200 from the interference signal input from the fundus detector 16. The tomographic images generated by the control device 44 are displayed on a monitor (not shown).

[0043] Furthermore, the calculation unit 46 of the control device 44 calculates the axial length of the eye under examination 200 (the length from the anterior surface of the cornea to the surface of the retina of the eye under examination 200) based on the interference signal input from the anterior segment detector 28 (positional information in the depth direction of the anterior segment 202a) and the interference signal input from the fundus detector 16 (positional information in the depth direction of the fundus 204). As described above, in order to calculate the axial length of the eye under examination 200, the positional relationship in the depth direction of the imaging range 202a of the anterior segment OCT and the imaging range 204a of the fundus OCT (for example, the distance (length A) from the deepest part of the imaging range 202a of the anterior segment OCT to the shallowest part of the imaging range 204a of the fundus OCT) is required. Therefore, the storage unit 48 of the control device 44 stores the positional relationship in the depth direction (length A) of the imaging range 202a of the anterior segment OCT and the imaging range 204a of the fundus OCT at the time of shipment of the ophthalmic device 10. More specifically, the system stores a conversion formula (an example of a first conversion formula) to convert the depth-direction position information of the eye 200, calculated from the interference signal measured by the anterior segment OCT, into the actual size of the eye, and a conversion formula (an example of a second conversion formula) to convert the depth-direction position information of the eye 200, calculated from the interference signal measured by the fundus OCT, into the actual size of the eye. In addition, it stores the depth-direction positional relationship (e.g., length A) between the imaging range 202a of the anterior segment OCT and the imaging range 204a of the fundus OCT at the time of shipment of the ophthalmic device 10. These conversion formulas and positional relationships are acquired when the optical system calibration process is performed at the time of shipment of the ophthalmic device 10.

[0044] Even if the optical system of the ophthalmic device 10 is calibrated at the time of shipment and the positional relationship in the depth direction between imaging range 202a and imaging range 204a at the time of shipment (conversion formula (length A)) is stored, the optical path length of the optical system changes due to changes over time after shipment and the environment at the time of measurement (e.g., temperature). As a result, the positional relationship in the depth direction between imaging range 202a and imaging range 204a changes, and the axial length cannot be calculated correctly as is. Therefore, in this embodiment, the storage unit 48 of the control device 44 further stores the position of the reference mirror 38 in the anterior segment OCT at the time of shipment (an example of a specific first reference position) and the position of the reference mirror 38 in the fundus OCT at the time of shipment (an example of a specific second reference position).

[0045] Here, we will describe an example of the optical system calibration process performed when the ophthalmic device 10 is shipped, and the process of obtaining a conversion formula for calculating the axial length of the eye. When performing the optical system calibration process, a calibration tool (glass block) having at least two reflective surfaces with a known difference in optical path length is used. That is, the front and back surfaces of the glass block are reflective surfaces, and the length from the front to the back surface (the thickness of the glass block) is known. For this reason, a glass block can be used as a calibration tool.

[0046] The specific procedure involves placing a calibration tool (glass block) at the anterior segment of eye 200, measuring the calibration tool using anterior segment OCT, and obtaining the anterior and posterior positions of the calibration tool. As mentioned above, the difference in optical path length between the anterior and posterior positions of the calibration tool is known, so a conversion formula (first conversion formula) is obtained to convert the values ​​measured by anterior segment OCT into actual dimensions. Similarly, a calibration tool (glass block) is placed at the retinal position of eye 200, measuring the calibration tool using fundus OCT, and obtaining the anterior and posterior positions of the calibration tool. This allows for obtaining a conversion formula (second conversion formula) to convert the values ​​measured by fundus OCT into actual dimensions. Next, the calibration tool is positioned such that its front surface is within the imaging range 202a of the anterior segment OCT and its posterior surface is within the imaging range 204a of the fundus OCT. The position of the front surface of the calibration tool is obtained using the anterior segment OCT, and the position of the posterior surface is obtained using the fundus OCT. This allows the positional relationship (e.g., length A) between the imaging range 202a of the anterior segment OCT and the imaging range 204a of the fundus OCT to be obtained. These measurements provide a conversion formula for calculating the axial length (actual size) of the eye under examination 200, and the obtained conversion formula is stored in the memory unit 48.

[0047] Simultaneously with the measurement to acquire the conversion formula described above, the position of the reference mirror 38 in the anterior segment OCT and the position of the reference mirror 38 in the fundus OCT are measured. That is, when measuring the calibration tool with the anterior segment OCT, after the measurement is completed, the galvanoscanner 36 is driven to illuminate the reference mirror 38 with light from the light source. Then, the position of the reference mirror 38 in the anterior segment OCT is obtained from the reference interference light obtained by combining the reference light and reference light reflected by the reference mirror 38. Similarly, when measuring the calibration tool with the fundus OCT, after the measurement is completed, the galvanoscanner 36 is driven to illuminate the reference mirror 38 with light from the light source. Then, the position of the reference mirror 38 in the fundus OCT is obtained from the reference interference light obtained by combining the reference light and reference light reflected by the reference mirror 38. These two reference positions are then stored in the memory unit 48. By storing the above conversion formula and reference positions in the memory unit 48, the factory calibration process for the ophthalmic device 10 is completed. Furthermore, the above calibration process can be performed at various times, not just when the ophthalmic device 10 is shipped. For example, it may be performed when the ophthalmic device 10 is repaired or maintained. Also, in the above example, the process of measuring the reference position was performed after the measurement to obtain the conversion formula, but conversely, the process of measuring the reference position may be performed first, followed by the measurement to obtain the conversion formula.

[0048] Next, the operation of the ophthalmic device 10 when measuring the axial length of the eye 200 after shipment will be described. To measure the axial length of the eye 200, first, the optical systems of the anterior segment OCT and fundus OCT are positioned (aligned) with respect to the eye 200. Next, the control device 44 turns on the light sources 12 and 14 (S10), as shown in Figure 4. As a result, light is output from each of the light sources 12 and 14, and the output light is irradiated onto the eye 200. That is, the light emitted from each of the light sources 12 and 14 is irradiated onto the eye 200 simultaneously.

[0049] Next, the control device 44 takes tomographic images of the anterior segment 202 and fundus 204 of the eye under examination 200 (S12). Specifically, the control device 44 drives the galvanoscanner 36 to scan the measurement range of the eye under examination 200 with light from the light sources 12 and 14 (S12). As a result, interference light from the light reflected from the anterior segment 202 of the eye under examination 200 is detected by the anterior segment detector 28, and at the same time, interference light from the light reflected from the fundus 204 of the eye under examination 200 is detected by the fundus detector 16. Therefore, the control device 44 generates a tomographic image of the anterior segment 202 of the eye under examination 200 based on the interference signal input from the anterior segment detector 28, and generates a tomographic image of the fundus 204 of the eye under examination 200 based on the interference signal input from the fundus detector 16.

[0050] Next, the control device 44 irradiates the reference mirror 38 with light from the light sources 12 and 14 and measures the position of the reference mirror 38 (S14). Specifically, the control device 44 drives the galvanoscanner 36 to guide the light from the light sources 12 and 14 to the reference optical system and irradiates the reference mirror 38 with the light from the light sources 12 and 14. As described above, in the state of S14, the light from the light sources 12 and 14 does not irradiate the eye under examination 200. For this reason, the anterior segment detector 28 detects only the interference light between the light irradiated by the reference mirror 38 (first reference light) and the first reference light, and the fundus detector 16 detects only the interference light between the light irradiated by the reference mirror 38 (second reference light) and the second reference light. Based on these detected interference lights, the control device 44 calculates the position of the reference mirror 38 in the anterior segment OCT and the position of the reference mirror 38 in the fundus OCT.

[0051] Next, the control device 44 calculates the axial length of the eye 200 based on the measurement results of the eye 200 measured in S12 and the measurement results of the reference mirror 38 measured in S14 (S16). That is, in S12, a tomographic image of the anterior segment 202 of the eye 200 is taken using the anterior segment OCT, and a tomographic image of the fundus 204 of the eye 200 is taken using the fundus OCT. Therefore, the control device 44 can determine the position of the corneal surface of the eye 200 from the tomographic image of the anterior segment 202 and the position of the retinal surface of the eye 200 from the tomographic image of the fundus 204. Here, the memory unit 48 of the control device 44 stores the positional relationship (length A) and conversion formula between the imaging range 202a of the anterior segment OCT and the imaging range 204a of the fundus OCT. Therefore, if there is no change in the optical path length of the anterior segment OCT and fundus OCT optical systems, the control device 44 can calculate the axial length from the identified corneal surface position and retinal surface position, as well as the conversion formula (length A) and positional relationship.

[0052] However, as already explained, the optical path length of the optical system of the ophthalmic device 10 changes over time after shipment and due to environmental factors during measurement (e.g., temperature). For this reason, the control device 44 uses the position of the reference mirror 38 calculated in S14 to correct the positions of the corneal surface and retinal surface identified from the tomographic image taken in S12. That is, the memory unit 48 of the control device 44 stores the position of the reference mirror 38 in the anterior segment OCT and the position of the reference mirror 38 in the fundus OCT at the time of shipment. Therefore, in both the anterior segment OCT and the fundus OCT, the position of the corneal surface and retinal surface identified from the tomographic image taken in S12 is corrected based on the difference (i.e., change in optical path length) between the position of the reference mirror 38 measured in S14 and the position of the reference mirror 38 stored in the memory unit 48. Next, the axial length is calculated from the corrected positions of the corneal surface and retinal surface and the positional relationship (length A) between the imaging range 202a and the imaging range 204a. This allows for accurate calculation of the axial length of the eye under examination (200). The axial length calculated in S16 is displayed on a monitor (not shown).

[0053] In the ophthalmic device 10 of the above-described Example 1, both the anterior segment OCT and fundus OCT are equipped with a reference optical system, and the measurement results of the anterior segment OCT and fundus OCT are corrected based on the reference position (position of the reference mirror 38) measured by the reference optical system. Therefore, even if the optical path length of the optical system of the ophthalmic device 10 changes over time or due to temperature, the measurement results of the anterior segment OCT and fundus OCT are corrected to take into account the change in optical path length. As a result, the axial length of the eye under examination 200 can be calculated with high accuracy.

[0054] Furthermore, after illuminating the eye 200 under test and measuring it, illuminating the reference mirror 38 with light is performed to measure the position (reference position) of the reference mirror 38. In other words, the measurement of the eye 200 under test and the measurement of the reference mirror 38 are not performed simultaneously. Therefore, the reference mirror 38 can be set to any position, and there is no problem even if the positions of each part of the eye 200 (cornea, lens, retina) and the position of the reference mirror 38 are the same. Although the measurement of the eye 200 under test and the measurement of the reference mirror 38 are not performed simultaneously, the measurement of the reference mirror 38 is performed immediately after the measurement of the eye 200. Therefore, there is almost no effect on the accuracy of the calculation of the axial length of the eye. Note that in the above example, the measurement of the reference mirror 38 was performed immediately after the measurement of the eye 200, but conversely, the measurement of the eye 200 may be performed immediately after the measurement of the reference mirror 38.

[0055] (Example 2) Next, the ophthalmic device 50 according to Example 2 will be described. The ophthalmic device 50 according to Example 2 is equipped with an anterior segment OCT and a fundus OCT, and each OCT is equipped with a reference optical system for acquiring a reference position, and in this respect it is the same as the ophthalmic device 10 according to Example 1. However, in the ophthalmic device 50 according to Example 2, the configuration of the reference optical system is different, and the configuration for correcting the change in the optical path length of the optical system of the ophthalmic device 50 based on the reference position acquired by the reference optical system is different from that of the ophthalmic device 10 in Example 1. Below, the parts of the ophthalmic device 50 of Example 2 that have the same configuration as the ophthalmic device 10 of Example 1 will be briefly described, and the parts that have a different configuration from Example 1 will be described in detail.

[0056] As shown in Figures 5-7, the ophthalmic device 10 includes an anterior segment OCT 54 (another example of a first OCT) for acquiring tomographic images of the anterior segment of the eye under examination, and a fundus OCT 52 (another example of a second OCT) for acquiring tomographic images of the fundus of the eye under examination. The anterior segment OCT 54 is an optical tomography device (SS-OCT) equipped with a wavelength-swept light source 82, and includes an anterior segment measurement optical system (86a, 86c, 59, 60, 62, 63, 76, 68), an anterior segment reference optical system (86a, 86d, 88, 94, 90, 96, 92), an anterior segment reference optical system (80, 74), an anterior segment interference optical system 88, and an anterior segment detector 84.

[0057] The anterior segment measurement optical system comprises optical fibers 86a and 86c, a coupler 88, a lens 59, a beam splitter 60, a galvanoscanner 62, a mirror 63, a lens 76, and a mirror 68. Light emitted from the light source 82 passes through the optical fiber 86a and is split into measurement light and reference light at the coupler 88. The measurement light split at the coupler 88 is emitted from the tip of the optical fiber 86c towards the lens 59. The measurement light emitted from the lens 59 passes through the beam splitter 60, galvanoscanner 62, mirror 63, lens 76, and mirror 68 before illuminating the eye under test 200 (see Figures 6 and 7). In Figure 5, a calibration tool 72 (e.g., a simulated eye) used at the time of product shipment is shown instead of the eye under test 200. The calibration tool 72 has one glass block placed at the corneal position and one glass block placed at the retinal position. The thickness of each glass block (optical path length difference) and the distance between the two glass blocks (optical path length difference) are known. In Example 2, the galvanometer scanner 62 is driven to scan the light irradiated onto the eye under examination 200. The light reflected from the eye under examination travels in the reverse direction along the path described above and is input to the coupler 88.

[0058] The anterior segment reference optical system comprises optical fibers 86a and 86d, a coupler 88, a lens 94, a beam splitter 90, a lens 96, and a reference mirror 92. The reference light, delimited by the coupler 88, is emitted from the tip of the optical fiber 86d to the lens 94, passes through the beam splitter 90 and lens 96, and illuminates the reference mirror 92. The light reflected by the reference mirror 92 travels in the reverse direction along the above path and is input to the coupler 88.

[0059] The anterior segment reference optical system has an optical path branched from the anterior segment measurement optical system (specifically, the galvanoscanner 62), and includes a lens 80 and a reference mirror 74 positioned on this optical path. The reference mirror 74 has the same configuration as the calibration tool 72 used at the time of product shipment, and is positioned so that the optical path length from the galvanoscanner 62 to the calibration tool 72 (more precisely, the reflective surface of the glass block corresponding to the front surface of the cornea of ​​the calibration tool 72) is the same as the optical path length from the galvanoscanner 62 to the reflective surface of the reference mirror 74 (more precisely, the reflective surface of the glass block corresponding to the front surface of the cornea of ​​the reference mirror 74). Therefore, if the optical path length of the anterior segment OCT 54 optical system does not change, the depth-direction position of the reflective surface of the calibration tool 72 and the depth-direction position of the reference mirror 74 will be the same. Similar to Example 1, by driving the galvanoscanner 62, the state in which light from the light source 82 is irradiated onto the eye under examination (calibration tool 72) and the state in which light from the light source 82 is irradiated onto the reference mirror 74 are switched. The light irradiated onto the reference mirror 74 is reflected toward the galvanoscanner 62 and input to the coupler 88 through the beam splitter 60, lens 59 and optical fiber 86c.

[0060] The anterior segment interference optical system includes a coupler 88. The coupler 88 generates interference light by combining light reflected from the calibration tool 72 (or the eye under examination 200) and light reflected from the reference mirror 92, and also generates interference light by combining light reflected from the reference mirror 74 and light reflected from the reference mirror 72. The interference light generated by the coupler 88 is input to the anterior segment detector 84. The anterior segment detector 28 detects the interference light and outputs the interference signal to the control device 100 (shown in Figure 8).

[0061] The fundus OCT 52 is an optical tomography (SD-OCT) device equipped with a broadband wavelength light source 54, and includes a fundus measurement optical system (58a, 58e, 60, 62, 63, 66, 70, 78, 68), a fundus reference optical system (58a, 58c, 58d, 60, 61, 58d, 64), a fundus reference optical system (58f, 90, 96, 92), a fundus interference optical system 60, and a fundus detector 56.

[0062] The fundus measurement optical system comprises optical fibers 58a and 58e, a coupler 60, a beam splitter 60, a galvanoscanner 62, mirrors 63, 66, and 70, a lens 76, and a mirror 68. Light emitted from the light source 54 passes through the optical fiber 58a and is split into measurement light and reference light at the coupler 60. The measurement light split at the coupler 60 is emitted from the tip of the optical fiber 58e towards the beam splitter 60. The light emitted from the optical fiber 58e is reflected by the beam splitter 60 and emitted to the galvanoscanner 62. The light reflected by the galvanoscanner 62 is reflected by mirrors 63, 66, and 70 respectively, passes through the lens 76, is reflected by mirror 68, and illuminates the eye under examination 200 (calibration tool 72 in Figure 5). The reflected light from the eye under examination 200 travels in the reverse direction and is input to the coupler 60.

[0063] The fundus reference optical system comprises optical fibers 58a, 58c, and 58d, a coupler 61, and a reference mirror 64. The reference light, decoupled by the coupler 60, passes through the optical fiber 58d and is input to the coupler 61. The coupler 61 decouples the light input from the optical fiber 58d into reference light and reference light (for example, reference light:reference light = 99:1). The reference light decoupled by the coupler 61 travels through the optical fiber 58d and is emitted from the tip of the optical fiber 58d to the reference mirror 64. The light emitted to the reference mirror 64 and reflected by the reference mirror 64 travels in the reverse direction along the above path and is input to the coupler 60.

[0064] The fundus reference optical system has an optical path branched from the coupler 61 of the fundus reference optical system, and comprises the coupler 61, an optical fiber 58f, a beam splitter 90, a lens 96, and a reference mirror 92 (the reference mirror 92 in the anterior segment OCT 54). In other words, the reference mirror 92 of the fundus reference optical system and the reference mirror 92 of the anterior segment reference optical system are common. The reference light branched by the coupler 61 is irradiated onto the reference mirror 92 via the optical fiber 58f, beam splitter 90, and lens 96, and is reflected by the reference mirror 92. The reference light reflected by the reference mirror 92 is input to the lens 96, beam splitter 90, optical fiber 58f, and coupler 61. At the coupler 61, the reference light reflected by the reference mirror 64 and the reference light reflected by the reference mirror 92 are combined.

[0065] The fundus interference optical system is equipped with a coupler 60. The coupler 60 combines the light input from the optical fiber 58c (i.e., the reference light reflected by the reference mirror 64 and the reference light reflected by the reference mirror 92) and the light input from the optical fiber 58e (the measurement light reflected from the eye under examination). This generates interference light between the reference light reflected by the reference mirror 64 and the measurement light reflected from the eye under examination 200, interference light between the reference light reflected by the reference mirror 64 and the reference light reflected by the reference mirror 92, and interference light between the reference light reflected by the reference mirror 92 and the measurement light reflected from the eye under examination 200. The generated interference light is input to the fundus detector 56 via the optical fiber 58b. Here, the intensity of the reference light is set to be negligibly small compared to the intensity of the reference light. Therefore, the fundus detector 56 detects the interference light between the reference light reflected by the reference mirror 64 and the measurement light reflected from the eye under examination, and the interference light between the reference light reflected by the reference mirror 64 and the reference light reflected by the reference mirror 92, and outputs the interference signals of these interference lights to the control device 100 (shown in Figure 8), which will be described later.

[0066] Next, the configuration of the control system for the ophthalmic device 50 will be described. As shown in Figure 8, the ophthalmic device 50 is controlled by a control device 100. The control device 100 is composed of a microcomputer (microprocessor) consisting of a CPU, ROM, RAM, etc., and functions as an arithmetic unit 102 and a storage unit 104, similar to Embodiment 1. The control device 100 is connected to light sources 54 and 82, detectors 56 and 84, and a galvanometer scanner 62. The control device 100 controls the on / off state of the light sources 54 and 82 and also drives the galvanometer scanner 62. The control device 100 also generates a tomographic image of the eye under examination 200 based on interference signals input from the detectors 56 and 84.

[0067] In Embodiment 2, the control device 100 is further connected to an anterior segment reference optical path length adjustment unit 106 and a fundus reference optical path length adjustment unit 108. That is, in Embodiment 2, the length from the tip of the optical fiber 86d to the reference mirror 92 is adjustable, and the length from the tip of the optical fiber 58d to the reference mirror 64 is adjustable. The control device 100 drives the anterior segment reference optical path length adjustment unit 106 to move the lens 94, beam splitter 90, lens 96, and reference mirror 92 in the optical axis direction relative to the tip of the optical fiber 86d. The control device 100 also drives the fundus reference optical path length adjustment unit 108 to move the lens reference mirror 64 in the optical axis direction relative to the tip of the optical fiber 58d.

[0068] Furthermore, the memory unit 104 of the control device 100 stores various information used when measuring the axial length of the eye under examination 200. That is, in the ophthalmic device 50 of Example 2, as shown in Figure 5, calibration processing is performed using the calibration tool 72 at the time of shipment, and the various information acquired at that time is stored in the memory unit 104. Specifically, the calibration tool 72 is placed at the position of the eye under examination 200, and the positions of the anterior and posterior surfaces of the glass block placed in front of the calibration tool 72 (corresponding to the corneal surface) and the anterior and posterior surfaces of the glass block placed on the posterior surface of the calibration tool 72 (corresponding to the retinal surface) are measured. That is, the anterior segment OCT 54 measures the positions of the anterior and posterior surfaces of the glass block in front of the calibration tool 72 (corresponding to the corneal surface), and the fundus OCT 52 measures the positions of the anterior and posterior surfaces of the glass block on the posterior surface of the calibration tool 72 (corresponding to the retinal surface). At this time, the anterior segment OCT 54 measures the position of the reflective surface of the reference mirror 74 of the anterior segment reference optical system. Furthermore, the fundus OCT 52 measures the reference mirror 92 of the fundus reference optical system (i.e., the position of the reference mirror 92 in the anterior segment OCT 54).

[0069] Here, since the length of the calibration tool 72 from the front to the back is known, similar to Example 1, the calculation unit 102 of the control device 100 calculates a conversion formula and positional relationship (length A) for calculating the axial length (actual size) of the eye under examination 200 from the position of the anterior surface of the cornea identified from the image acquired by the anterior segment OCT 54 and the position of the retinal surface identified from the image acquired by the fundus OCT 52. The storage unit 104 of the control device 100 then stores the calculated conversion formula and positional relationship (length A). The storage unit 104 of the control device 100 also stores the position of the front of the measured calibration tool 72 (i.e., the position of the reference mirror 74 of the anterior segment reference optical system) and the position of the measured reference mirror 92 (i.e., the position of the reference mirror 92 of the fundus reference optical system).

[0070] Next, the operation of the ophthalmic device 50 when measuring the axial length of the eye under examination 200 will be described. First, when the optical systems of the anterior segment OCT 54 and the fundus OCT 52 are positioned relative to the eye under examination 200, the control device 100 turns on the light sources 12 and 14 (S20), as shown in Figure 9.

[0071] Next, the control device 100 measures the positions of the reference mirror 74 and the reference mirror 92 (S22). Specifically, as shown in Figure 6, the light from the light source 54 is shone onto the reference mirror 92, and the galvanometer scanner 62 is driven to shone the light from the light source 82 onto the reference mirror 74. As a result, the fundus detector 56 detects the interference light between the reflected light reflected by the reference mirror 92 and the reference light (reference light of the fundus reference optical system), and the control device 50 calculates the position of the reference mirror 92 (reference mirror 92 of the anterior segment reference optical system) from the interference light detected by the fundus detector 56. In addition, the anterior segment detector 84 detects the interference light between the reflected light reflected by the reference mirror 74 and the reference light (reference light of the anterior segment reference optical system), and the control device 50 calculates the position of the reference mirror 74 from the interference light detected by the anterior segment detector 84.

[0072] Next, the control device 100 adjusts the optical path length of the anterior segment reference optical system and the optical path length of the fundus reference optical system (S24) based on the positions of the reference mirrors 74 and 92 stored in the memory unit 104 and the positions of the reference mirrors 74 and 92 measured in S22. As already explained, the position of the front surface of the calibration tool 72 (i.e., the position of the reference mirror 74) and the position of the reference mirror 92 are measured and stored in the memory unit 104 during the calibration process at the time of shipment. The optical path length of the optical system of the ophthalmic device 50 has changed since shipment (when the calibration process was performed) due to aging since shipment and the ambient temperature of the ophthalmic device 50. For this reason, in S24, the position of the reference mirror 92 (reference mirror 92) is adjusted by the anterior segment reference optical path length adjustment unit 106 so that the position of the reference mirror 92 measured in S22 becomes the position of the reference mirror 92 stored in the memory unit 104. Next, the position of the reference mirror 64 is adjusted by the fundus reference optical path length adjustment unit 108 so that the position of the reference mirror 74 measured in S22 is the position of the front surface of the calibration tool 72 stored in the memory unit 104. At this time, since the position of the reference mirror 92 has been adjusted, the position of the reference mirror 74 measured in S22 has changed by the same amount. Therefore, the position of the reference mirror 64 is adjusted based on the adjustment of the position of the reference mirror 92 and the position of the reference mirror 74 measured in S22. As a result, the positional relationship in the depth direction between the imaging range 202a of the anterior segment OCT 54 and the imaging range 204a of the fundus OCT 52 becomes the same as the positional relationship during the calibration process.

[0073] Next, as shown in Figure 7, the control device 100 measures the position of the corneal surface of the eye under examination 200 using the anterior segment OCT 54 and the position of the retinal surface using the fundus OCT 52 (S26). Then, the control device 100 calculates the axial length of the eye under examination 200 using the measurement results from S26 (position of the corneal surface and position of the retinal surface) and the conversion formula and positional relationship (length A) stored in the memory unit (S28). Here, as shown in S24, the positional relationship in the depth direction between the imaging range 202a of the anterior segment OCT 54 and the imaging range 204a of the fundus OCT 52 is the same as the positional relationship during calibration processing. Therefore, the axial length can be calculated using the conversion formula and positional relationship (length A) stored in the memory unit without correcting the positions of the corneal surface and retinal surface measured in S26.

[0074] In the ophthalmic device 50 of Example 2 described above, the axial length of the eye under examination 200 can be measured under the same conditions as during calibration by adjusting the optical path lengths of the reference optical systems of the anterior segment OCT 54 and the fundus OCT 52. As a result, the axial length of the eye under examination 200 can be measured accurately even with the ophthalmic device 50 of Example 2.

[0075] Furthermore, in the ophthalmic device 50 of Example 2, for the anterior segment OCT 54, the measurement of the eye under examination 200 is performed after the measurement of the reference mirror 74 is completed. In other words, since the measurement of the reference mirror 74 and the measurement of the eye under examination 200 are not performed simultaneously, the position of the reference mirror 74 can be set to any position.

[0076] In the ophthalmic device 50 of Example 2 described above, the positional relationship between the anterior segment OCT 54 and the fundus OCT 52 was made the same as the positional relationship during calibration by adjusting the reference optical path length of both the anterior segment OCT 54 and the fundus OCT 52. However, the technology disclosed herein is not limited to such examples. For example, the positional relationship between the anterior segment OCT 54 and the fundus OCT 52 may be made the same as the positional relationship during calibration by adjusting only the reference optical path length of the anterior segment OCT 54. Alternatively, the positional relationship between the anterior segment OCT 54 and the fundus OCT 52 may be made the same as the positional relationship during calibration by adjusting only the reference optical path length of the fundus OCT 52.

[0077] Furthermore, in the ophthalmic device 50 of Example 2, the reference light from the fundus OCT 52 is branched to generate a reference light, and the generated reference light is irradiated onto the reference mirror 92 of the anterior segment OCT 54. However, the technology disclosed herein is not limited to such examples. Conversely to the above example, the reference light from the anterior segment OCT may be branched to generate a reference light, and the generated reference light may be irradiated onto the reference mirror of the fundus OCT.

[0078] Furthermore, although the ophthalmic devices of Examples 1 and 2 described above were equipped with both fundus OCT and anterior segment OCT, the technology disclosed herein can also be applied to ophthalmic devices equipped with only fundus OCT or anterior segment OCT. In this case, for example, a galvanometer scanner can be used to switch between illuminating a reference mirror with light from a light source and illuminating the eye under examination with light from a light source, thereby allowing the reference mirror to be set at any desired position.

[0079] The specific examples of the technology disclosed herein have been described in detail above, but these are merely illustrative and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes to the specific examples described above. Furthermore, the technical elements described herein or in the drawings exhibit technical usefulness individually or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology illustrated herein or in the drawings achieves multiple objectives simultaneously, and achieving even one of these objectives itself constitutes technical usefulness. [Explanation of symbols]

[0080] 10: Ophthalmology equipment 12, 14: Light source 18a~18e, 30a~30c: Optical fiber 16,28: Detector 36: Galvanometer Scanner 40,42: Reference mirror 44: Control device

Claims

1. Light source and A measuring optical system that generates measurement light by irradiating the eye under examination with light from the aforementioned light source, A reference optical system that generates reference light using light from the aforementioned light source, A reference optical system that generates reference light for calculating a reference position using light from the aforementioned light source, An interference optical system that generates measurement interference light by combining the measurement light and the reference light, and generates reference interference light by combining the reference light and the reference light, A detector that detects the aforementioned measurement interference light and outputs a measurement interference signal, and also detects the aforementioned reference interference light and outputs a reference interference signal, The system includes a control unit that calculates the depth-direction position information of the eye under examination based on the measurement interference signal, and calculates the reference position based on the reference interference signal. The reference optical system has an optical path branched from the measurement optical system. The measuring optical system includes a switching unit that switches between a first state in which light from the light source is irradiated onto the eye under examination and a second state in which light from the light source is guided to the reference optical system. The control unit controls the switching unit so that, when measuring the eye under examination, the detector detects the measurement interference signal in the first state and the detector detects the reference interference signal in the second state. The system further includes a storage unit that stores a specific time reference position indicating the reference position adjusted at a specific time, The aforementioned specific time reference position is a position calculated from the reference interference light generated by combining the reference light generated by the reference optical system and the reference light generated by the reference optical system at the aforementioned specific time. The control unit is configured to correct the depth-direction position information of the eye under examination, which is calculated based on the measurement interference signal output from the detector during the measurement, based on the difference between the measurement reference position, which is the reference position calculated based on the reference interference signal output from the detector during the measurement, and the specific reference position stored in the storage unit. The memory unit further stores a conversion formula to convert the depth-direction position information of the eye under examination, calculated based on the measurement interference signal, into the actual size of the eye under examination. The control unit is configured to further calculate the actual dimensions of the eye under examination by converting the depth-direction position information of the eye under examination, which is calculated based on the measurement interference signal, using the conversion formula. An ophthalmic device in which the conversion formula is obtained using (A) positional information in the depth direction of the two reflective surfaces obtained from calibration interference light generated by combining calibration measurement light, which is generated by irradiating a calibration tool having at least two reflective surfaces having a known optical path length difference with light from the light source through the measurement optical system, and the reference light generated by the reference optical system, and (B) the optical path length difference of the two reflective surfaces.

2. The ophthalmic apparatus according to claim 1, wherein the control unit controls the switching unit to detect the reference interference signal with the detector in a second state before or after detecting the measurement interference signal with the detector in a first state.

3. The ophthalmic apparatus according to claim 1, wherein the specified time and the time when the calibration interference light is measured using the calibration tool to obtain the conversion formula are substantially simultaneous.

4. A light source, A measuring optical system that generates measurement light by irradiating the eye under examination with light from the aforementioned light source, A reference optical system that generates reference light using light from the aforementioned light source, A reference optical system that generates reference light for calculating a reference position using light from the aforementioned light source, An interference optical system that generates measurement interference light by combining the measurement light and the reference light, and generates reference interference light by combining the reference light and the reference light, A detector that detects the aforementioned measurement interference light and outputs a measurement interference signal, and also detects the aforementioned reference interference light and outputs a reference interference signal, The system includes a control unit that calculates the depth-direction position information of the eye under examination based on the measurement interference signal, and calculates the reference position based on the reference interference signal. The reference optical system has an optical path branched from the measurement optical system. The measuring optical system includes a switching unit that switches between a first state in which light from the light source is irradiated onto the eye under examination and a second state in which light from the light source is guided to the reference optical system. The control unit controls the switching unit so that, when measuring the eye under examination, the detector detects the measurement interference signal in the first state and the detector detects the reference interference signal in the second state. The system further includes a storage unit that stores a specific time reference position indicating the reference position adjusted at a specific time, The aforementioned specific time reference position is a position calculated from the reference interference light generated by combining the reference light generated by the reference optical system and the reference light generated by the reference optical system at the aforementioned specific time. The aforementioned reference optical system includes an adjustment unit for adjusting the optical path length of the reference light, An ophthalmic apparatus comprising: a control unit that calculates a reference position during measurement, which is the reference position calculated based on the reference interference signal output from the detector during measurement, and controls the adjustment unit so that the reference position during measurement calculated during measurement becomes the specific reference position stored in the storage unit.

5. The memory unit further stores a conversion formula to convert the depth-direction position information of the eye under examination, calculated based on the measurement interference signal, into the actual size of the eye under examination. The control unit is configured to further calculate the actual dimensions of the eye under examination by converting the depth-direction position information of the eye under examination, which is calculated based on the measurement interference signal, using the conversion formula. The ophthalmic apparatus according to claim 4, wherein the conversion formula is obtained using (A) positional information in the depth direction of the two reflective surfaces obtained from calibration interference light generated by combining calibration measurement light, which is generated by irradiating a calibration tool having at least two reflective surfaces having a known optical path length difference with light from the light source through the measurement optical system, and the reference light generated by the reference optical system, and (B) the optical path length difference of the two reflective surfaces.

6. The ophthalmic apparatus according to claim 5, wherein the specified time and the time when the calibration interference light is measured using the calibration tool to obtain the conversion formula are substantially simultaneous.

7. The control unit, The switching unit is set to the second state, and the detector detects the reference interference signal. The adjustment unit is controlled so that the reference position at measurement, calculated based on the detected reference interference signal, becomes the reference position at a specific time stored in the storage unit. The ophthalmic apparatus according to any one of claims 4 to 6, wherein the optical path length of the reference light is adjusted by the adjustment unit, and the measurement interference signal is detected with the switching unit in the first state.

8. It is an ophthalmic device, A first OCT measures the first position in the depth direction of the first part of the eye under examination, A second OCT measures a second position in the depth direction of a second part of the eye to be examined that is different from the first part, The system includes a control unit that calculates the depth dimension from the first part to the second part based on the first position measured by the first OCT and the second position measured by the second OCT. The first OCT is, First light source and A first measurement optical system that generates a first measurement light by irradiating the first part of the eye to be examined with light from the first light source, A first reference optical system that generates a first reference light using light from the first light source, A first reference optical system that generates a first reference light for calculating a first reference position using light from the first light source, A first interference optical system that generates a first measurement interference light by combining the first measurement light and the first reference light, and generates a first reference interference light by combining the first reference light and the first reference light, The system includes a first detector that detects the first measurement interference light and outputs a first measurement interference signal, and also detects the first reference interference light and outputs a first reference interference signal. The first reference optical system has an optical path branched from the first measurement optical system. The first measuring optical system includes a first switching unit that switches between a first state in which light from the first light source is irradiated onto the eye under examination and a second state in which light from the first light source is guided to the first reference optical system. During the measurement of the eye under examination, the first switching unit detects the first measurement interference signal with the first detector as the first state, and the first switching unit detects the first reference interference signal with the first detector as the second state. The second OCT is, The second light source and A second measurement optical system that generates a second measurement light by irradiating the second part of the eye to be examined with light from the second light source, A second reference optical system that generates a second reference light using light from the second light source, A second reference optical system that generates a second reference light for calculating a second reference position using light from the second light source, A second interference optical system that generates a second measurement interference light by combining the second measurement light and the second reference light, and generates a second reference interference light by combining the second reference light and the second reference light, The system includes a second detector that detects the second measurement interference light and outputs a second measurement interference signal, and also detects the second reference interference light and outputs a second reference interference signal. The aforementioned second reference optical system has an optical path branched from the aforementioned second measurement optical system. The second measuring optical system includes a second switching unit that switches between a third state in which light from the second light source is irradiated onto the eye under examination and a fourth state in which light from the second light source is guided to the second reference optical system. During the measurement of the eye under examination, the second switching unit detects the second measurement interference signal with the second detector in the third state, and the second switching unit detects the second reference interference signal with the second detector in the fourth state. The ophthalmic device further includes a storage unit that stores the distance in the depth direction between the measurement range of the first OCT and the measurement range of the second OCT adjusted at a specific time, a specific time first reference position indicating the first reference position adjusted at the specific time, and a specific time second reference position indicating the second reference position adjusted at the specific time. The control unit, (1) The difference between the first reference position at measurement, calculated based on the first reference interference signal output from the first detector during measurement, and the first reference position at a specific time stored in the storage unit, (2) The first position of the eye under examination calculated based on the first measurement interference signal output from the first detector during measurement, (3) The difference between the second reference position at measurement, which is calculated based on the second reference interference signal output from the second detector during measurement, and the second reference position at a specific time stored in the storage unit, (4) The second position of the eye under examination, calculated based on the second measurement interference signal output from the second detector during measurement, (5) The distance in the depth direction between the measurement range of the first OCT and the measurement range of the second OCT stored in the memory unit, Using this method, the depth dimension from the first part to the second part is calculated. The aforementioned storage unit is A first conversion formula is used to convert the depth-direction position information of the eye under examination, calculated based on the first measurement interference signal, into the actual size of the eye under examination within the measurement range of the first OCT. The system further stores a second conversion formula for converting the depth-direction position information of the eye under examination, calculated based on the second measurement interference signal, into the actual size of the eye under examination within the measurement range of the second OCT. The control unit, The system is configured to further calculate the actual dimensions of the eye under examination within the measurement range of the first OCT by converting the depth-direction position information of the eye under examination, calculated based on the first measurement interference signal, using the first conversion formula. The system is configured to further calculate the actual dimensions of the eye under examination within the measurement range of the second OCT by converting the depth-direction position information of the eye under examination, which is calculated based on the second measurement interference signal, using the second conversion formula. The first conversion formula is obtained using (A1) positional information in the depth direction of the two reflective surfaces obtained from a first calibration interference light generated by combining a first calibration measurement light, which is generated by irradiating a first calibration tool having at least two reflective surfaces with a known optical path length difference, with light from the first light source from the first measurement optical system, and the first reference light generated by the first reference optical system, and (B) the optical path length difference of the two reflective surfaces. The second conversion formula is obtained using (A) positional information in the depth direction of the two reflective surfaces obtained from a second calibration interference light generated by combining a second calibration measuring light, which is generated by irradiating a second calibration tool having at least two reflective surfaces with a known optical path length difference, with light from the second light source from the second measuring optical system, and the second reference light generated by the second reference optical system, and (B) the optical path length difference of the two reflective surfaces, in an ophthalmic device.

9. When the first switching unit is in the first state, the second switching unit is in the third state, When the first switching unit is in the second state, the second switching unit is in the fourth state, The ophthalmic apparatus according to claim 8, wherein the first switching unit and the second switching unit are used for both purposes.

10. The aforementioned first reference position at a specific time is a position calculated from the first reference interference light generated by combining the first reference light generated by the first reference optical system and the first reference light generated by the first reference optical system at the aforementioned time, The aforementioned second reference position at a specific time is a position calculated from the second reference interference light generated by combining the second reference light generated by the second reference optical system and the second reference light generated by the second reference optical system at the aforementioned time. The ophthalmic apparatus according to claim 8, wherein the specified time, the time when the first measurement light is irradiated onto the first calibration tool to obtain the first conversion formula, and the time when the second measurement light is irradiated onto the second calibration tool to obtain the second conversion formula are substantially simultaneous.

11. It is an ophthalmic device, A first OCT measures the first position in the depth direction of the first part of the eye under examination, A second OCT measures a second position in the depth direction of a second part of the eye to be examined that is different from the first part, The system includes a control unit that calculates the depth dimension from the first part to the second part based on the first position measured by the first OCT and the second position measured by the second OCT. The first OCT is, First light source and A first measurement optical system that generates a first measurement light by irradiating the first part of the eye to be examined with light from the first light source, A first reference optical system that generates a first reference light using light from the first light source, A first reference optical system that generates a first reference light for calculating a first reference position using light from the first light source, A first interference optical system that generates a first measurement interference light by combining the first measurement light and the first reference light, and generates a first reference interference light by combining the first reference light and the first reference light, The system includes a first detector that detects the first measurement interference light and outputs a first measurement interference signal, and also detects the first reference interference light and outputs a first reference interference signal. The first reference optical system has an optical path branched from the first measurement optical system. The first measuring optical system includes a first switching unit that switches between a first state in which light from the first light source is irradiated onto the eye under examination and a second state in which light from the first light source is guided to the first reference optical system. During the measurement of the eye under examination, the first switching unit detects the first measurement interference signal with the first detector as the first state, and the first switching unit detects the first reference interference signal with the first detector as the second state. The second OCT is, The second light source and A second measurement optical system that generates a second measurement light by irradiating the second part of the eye to be examined with light from the second light source, A second reference optical system that generates a second reference light using light from the second light source, A second reference optical system that generates a second reference light for calculating a second reference position using light from the second light source, A second interference optical system that generates a second measurement interference light by combining the second measurement light and the second reference light, and generates a second reference interference light by combining the second reference light and the second reference light, The system includes a second detector that detects the second measurement interference light and outputs a second measurement interference signal, and also detects the second reference interference light and outputs a second reference interference signal. The aforementioned second reference optical system has an optical path branched from the aforementioned second measurement optical system. The second measuring optical system includes a second switching unit that switches between a third state in which light from the second light source is irradiated onto the eye under examination and a fourth state in which light from the second light source is guided to the second reference optical system. During the measurement of the eye under examination, the second switching unit detects the second measurement interference signal with the second detector in the third state, and the second switching unit detects the second reference interference signal with the second detector in the fourth state. The aforementioned ophthalmic device further includes, At least one of the first reference optical system and the second reference optical system is provided with an adjustment unit for adjusting its optical path length, The control unit controls the adjustment unit so that the distance between a first reference position calculated from the first reference interference signal during measurement and a second reference position calculated from the second reference interference signal during measurement becomes a preset distance, in this ophthalmic device.

12. The ophthalmic apparatus according to claim 11, wherein the preset distance is the distance between a first reference position at a specific time calculated from the first reference interference signal at a specific time and a second reference position at a specific time calculated from the second reference interference signal at a specific time.

13. The control unit, The first switching unit is set to the second state and the first detector detects the first reference interference signal. The second switching unit is set to the fourth state and the second reference interference signal is detected by the second detector. The adjustment unit is controlled so that the difference between the first reference position and the second reference position during measurement, calculated based on the detected first reference interference signal and the second reference interference signal, becomes the preset distance. The ophthalmic apparatus according to claim 11, wherein, after the optical path length is adjusted by the adjustment unit, the first switching unit is set to the first state to detect the first measurement interference signal, and the second switching unit is set to the third state to detect the second measurement interference signal.

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