JP7476617B2 - Ophthalmic device and program for the same - Google Patents

Description

This disclosure relates to an ophthalmic device that measures a subject's eye, and a program for the ophthalmic device.

Conventional ophthalmic devices include OCT (Optical coherence tomography) devices equipped with an interference optical system that measures intraocular distances such as the axial length of the subject's eye and captures tomographic images. OCT includes TD (Time Domain)-OCT and FD (Fourier Domain)-OCT, and FD-OCT includes SS (Swept Source)-OCT, which uses a wavelength-swept light source. In SS-OCT, the characteristics of the measurement light change due to aging of the light source, which can reduce the measurement sensitivity. For this reason, a calibration mechanism (e.g., a calibration optical system) must be installed inside or outside the device to perform periodic corrections.

JP 2012-183152 A

However, in conventional ophthalmic devices, installing a calibration mechanism leads to problems such as increased costs and larger equipment.

In view of the problems inherent in the prior art, the technical objective of this disclosure is to provide an ophthalmic device and an ophthalmic device program that can perform calibration with a simple configuration.

To solve the above problems, the present disclosure is characterized by having the following configuration:

(1) An ophthalmic device for measuring a subject's eye, comprising: an interference optical system for obtaining a first interference signal by causing a first reflected light of measurement light emitted from a light source and reflected by the subject's eye to interfere with a reference light corresponding to the measurement light; a calculation means for correcting a measurement result based on the first interference signal using a second interference signal obtained by interference between a second reflected light of the measurement light reflected by an optical component constituting the interference optical system and the reference light; an optical path length adjustment means for adjusting the optical path length of the interference optical system; and a control means for controlling the optical path length adjustment means so that the second reflected light from the optical component falls within a coherent region of the interference optical system during calibration and so that the second reflected light does not fall within the coherent region during measurement .
(2) A program for an ophthalmic device executed in an ophthalmic device that measures a subject's eye, the program being executed by a processor of the ophthalmic device to cause the ophthalmic device to execute the following steps: an acquisition step of acquiring a first interference signal by an interference optical system by causing a first reflected light of measurement light emitted from a light source and reflected by the subject's eye to interfere with a reference light corresponding to the measurement light; a calculation step of correcting a measurement result based on the first interference signal using a second interference signal obtained by interference between a second reflected light of the measurement light reflected by an optical component constituting the interference optical system and the reference light; and an optical path length adjustment step of adjusting the optical path length of the interference optical system so that the second reflected light from the optical component falls within a coherence region of the interference optical system during calibration and so that the second reflected light does not fall within the coherence region during measurement .

According to this disclosure, calibration can be performed with a simple configuration.

FIG. 2 is a schematic diagram showing an optical system inside the device. This is an interference signal detected during the initial calibration before shipment. FIG. 13 is a flowchart showing the procedure for measuring axial length. This is an interference signal detected in the calibration mode before measurement. This is an interference signal detected in normal mode during measurement.

<Embodiment>
An embodiment according to the present disclosure will be described. An ophthalmic device (for example, an ophthalmic device 1) of this embodiment measures a subject's eye. The ophthalmic device includes, for example, an interference optical system (for example, an interference optical system 100) and a calculation unit (for example, a control unit 70). The interference optical system, for example, causes a first reflected light (for example, a measurement reflected light) of a measurement light emitted from a light source (for example, a light source 102) reflected by the subject's eye to interfere with a reference light corresponding to the measurement light, thereby acquiring a first interference signal (a measurement interference signal). The calculation unit corrects a measurement result based on the first interference signal using a second interference signal (for example, a calibration interference signal) of a second reflected light (for example, an internally reflected light) of the measurement light reflected by an optical component constituting the interference optical system and an interference between the reference light. By including the above configuration, the ophthalmic device of this embodiment does not need to provide an optical system dedicated to calibration, and can achieve low cost, small size, weight, and the like.

The optical components constituting the interference optical system are, for example, optical components that guide the measurement light to the test eye. In other words, the optical components constituting the interference optical system are, for example, optical components through which the measurement light irradiated to the test eye passes. The optical components constituting the interference optical system are, for example, optical components that guide the reflected light of the measurement light reflected by the test eye to a light receiving element. In other words, the optical components constituting the interference optical system are, for example, optical components through which the reflected light from the test eye passes and is received by the light receiving element.

The optical component is at least one of the multiple optical components that make up the interference optical system.

The optical component may be an objective lens of the interference optical system (e.g., objective lens 125). The objective lens is, for example, the lens closest to the subject's eye. Since the objective lens is close to the subject's eye, it is easy to include it in the coherence region (also called the OCT imaging range or depth range) of the interference optical system, and is easy to realize.

The calculation unit may correct the measurement results by correcting the measurement distance conversion data or the interference signal interpolation data (also called dispersion correction data or mapping data). In this case, the calculation unit indirectly corrects the measurement results by correcting the data used to calculate the measurement results.

The ophthalmic device may include an optical path length adjustment unit (e.g., optical path length adjustment unit 126) and a control unit (e.g., control unit 70). The optical path length adjustment unit adjusts the optical path length of the interference optical system, for example. The control unit may control the optical path length adjustment unit so that the second reflected light from the optical component falls within the coherence region during calibration, and so that the second reflected light does not fall within the coherence region of the interference optical system during measurement. This makes it possible to prevent the second reflected light from being detected as noise during measurement.

The second reflected light may be positioned within the coherence region during measurement. For example, when the second reflected light is present within the coherence region, it may be positioned at a position where it does not overlap with the first reflected light. In other words, it may be positioned at a position where there is no signal peak of the measurement object (e.g., the cornea or retina). This makes it easier to detect the peak position of the measurement object.

The processor (e.g., control unit 70) of the ophthalmic device may execute a program for the ophthalmic device stored in a storage unit (e.g., storage unit 74) or the like. The program for the ophthalmic device includes, for example, an acquisition step and a calculation step. The acquisition step is, for example, a step of acquiring a first interference signal by an interference optical system by interfering a first reflected light, which is a measurement light emitted from a light source and reflected by the subject's eye, with a reference light corresponding to the measurement light. The calculation step is a step of correcting the measurement result based on the first interference signal by using a second interference signal, which is an interference between a second reflected light, which is a measurement light reflected by an optical component constituting the interference optical system, and the reference light.

<Example>
An ophthalmic device 1 according to the present disclosure will be described below with reference to the drawings. FIG. 1 is a schematic diagram showing the optical system of the ophthalmic device 1 according to this embodiment. The optical system described below is built into a housing (not shown). The housing is moved three-dimensionally with respect to the subject's eye E by driving a well-known alignment driving mechanism. The subject's face is supported by a face support unit (not shown). In the following description, the optical axis direction of the subject's eye E is the Z direction, the horizontal direction is the X direction, and the vertical direction is the Y direction. The surface directions of the fundus may be considered as the XY directions.

The ophthalmic apparatus of this embodiment includes an interference optical system 100 and is used to measure the axial length of the subject's eye E. The interference optical system 100 irradiates the eye E with measurement light. The interference optical system 100 detects the interference state between the measurement light reflected from the anterior segment or fundus of the subject's eye and the reference light by a light receiving element (detector) 120. The control unit 70 acquires a spectral interference signal by the light receiving element 120.

The interference optical system 100 has the device configuration of a so-called ophthalmic optical coherence tomography (OCT). The interference optical system 100 splits light emitted from a light source 102 into measurement light (sample light) and reference light by a coupler (light splitter) 104. The interference optical system 100 then guides the measurement light to the subject's eye by a measurement optical system 106, and also guides the reference light to a reference optical system 110. The interference light resulting from the combination of the measurement light reflected by the subject's eye and the reference light is then received by a light receiving element 120.

The light emitted from the light source 102 is split into a measurement beam and a reference beam by the coupler 104. The measurement beam then passes through the optical fiber and is emitted from the fiber end 122 into the air. The beam is focused on the anterior segment via the optical components of the measurement optical system 106, such as the collimator lens 123, focus lens 124, and objective lens 125. The light reflected by the test eye is then returned to the optical fiber via a similar optical path.

The collimator lens 123 converts the measurement light beam emitted from the optical fiber into parallel light. The focus lens 124 adjusts the focus position of the measurement optical system 106. The focus lens 124 may be movable in the optical axis direction by a drive unit (not shown). The objective lens 125 guides the measurement light to the test eye.

The optical path length adjustment unit 126 changes the optical path length difference between the measurement light and the reference light. The optical path length adjustment unit 126 is disposed in the measurement optical path of the measurement optical system 106. The optical path length adjustment unit 126 includes, for example, a drive unit 127, and moves the fiber end 122 and the collimator lens 123 integrally in the optical axis direction. The optical path length adjustment unit 126 may be provided in the reference optical system 110, which will be described later. In this case, for example, the reference mirror may be configured to be moved in the optical axis direction by the drive unit.

The reference optical system 110 generates a reference light to be combined with the reflected light obtained by reflection of the measurement light at the eye E. The reference optical system 110 may be of a Michelson type or a Mach-Zehnder type. The reference optical system 110 is formed, for example, by a reflective optical system (e.g., a reference mirror), and reflects the light from the coupler 104 back to the coupler 104 by the reflective optical system, and guides it to the light receiving element 120. As another example, the reference optical system 110 is formed by a transmission optical system (e.g., an optical fiber), and guides the light from the coupler 104 to the light receiving element 120 by transmitting it instead of returning it.

The light receiving element 120 detects the interference state between the measurement light and the reference light. In the case of Fourier domain OCT, the spectral intensity of the interference light is detected by the light receiving element 120, and a depth profile (OCT data) in a predetermined range is obtained by performing a Fourier transform on the spectral intensity data. The OCT data is stored in the memory unit 74.

The interference optical system 100 of this embodiment employs SS (Swept Source)-OCT. In the case of SS-OCT, a wavelength-swept light source (tunable light source) that changes the emission wavelength at high speed over time is used as the light source 102. The light source 102 is composed of, for example, a light source, a fiber ring resonator, and a wavelength selection filter. Examples of the wavelength selection filter include a combination of a diffraction grating and a polygon mirror, and a Fabry-Perot etalon.

The ophthalmic device 1 may also include a keratoprojection optical system 50, an alignment projection optical system 40, an anterior segment imaging optical system 30, etc.

The keratoprojection optical system 50 has a ring-shaped light source 51 centered on the measurement optical axis O1, and is used to project a ring index onto the cornea of the test eye to measure the corneal shape (curvature, astigmatism axis angle, etc.). The light source 51 is, for example, an LED that emits infrared light or visible light. The projection optical system 50 may have at least three or more point light sources arranged on the same circumference centered on the optical axis O1, and may be an intermittent ring light source. Furthermore, it may be a placido index projection optical system that projects multiple ring indexes.

The alignment projection optical system 40 is disposed inside the light source 51, has a projection light source 41 that emits infrared light, and is used to project an alignment index onto the cornea Ec of the test eye. The alignment index projected onto the cornea Ec is used for positioning the test eye (e.g., automatic alignment, alignment detection, manual alignment, etc.). In this embodiment, the projection optical system 50 is an optical system that projects a ring index onto the cornea Ec of the test eye, and the ring index also serves as a Mayer ring. The light source 41 of the projection optical system 40 also serves as an anterior segment illumination that illuminates the anterior segment from an oblique direction with infrared light. Note that the projection optical system 40 may further include an optical system that projects parallel light onto the cornea Ec, and front-to-back alignment may be performed by combining this with the finite light from the projection optical system 40.

The anterior eye imaging optical system 30 is used to capture (obtain) a front image of the anterior eye. The anterior eye imaging optical system 30 includes a two-dimensional imaging element 31, an imaging lens 32, a filter 33, a dichroic mirror 34, a lens 35, and a dichroic mirror 36, and is used to capture a front image of the anterior eye of the subject's eye. The two-dimensional imaging element 31 is positioned at a position approximately conjugate with the anterior eye of the subject's eye.

The light reflected from the anterior eye by the projection optical system 40 and the projection optical system 50 is imaged on the two-dimensional image sensor 31 via the dichroic mirror 36, the lens 35, the dichroic mirror 34, the filter 33, and the imaging lens 32.

The light source 37 is a fixation light. The light source 37 is provided, for example, in the transmission direction of the dichroic mirror 34. For example, a portion of the anterior segment reflected light obtained by reflection of the light emitted from the light source 37 at the anterior segment is reflected by the dichroic mirror 36 and is imaged by the front imaging optical system 30.

Next, the control system will be described. The control unit 70 controls the entire device and calculates the measurement results. The control unit 70 is connected to each component of the interference optical system 100, a memory unit 74, a display unit 75, an operation unit 76, etc. In addition to various control programs, the memory unit 74 stores analysis programs and the like for the control unit 70 to perform analysis. Furthermore, the operation unit 76 may use a general-purpose interface such as a mouse as an operation input unit, or may also use a touch panel.

<About proofreading>
The characteristics of the light source 102 may change due to temperature changes or aging. In this case, even if the same object is measured, the measurement result will change due to the change in characteristics. Therefore, in this embodiment, the measurement result is corrected using the optical components constituting the interference optical system 100. Specifically, the conversion data used to calculate the measurement result is corrected using a calibration interference signal obtained by interference between the internally reflected light reflected by the optical components constituting the interference optical system 100 and the reference light. The conversion data is, for example, a value for converting the length on the interference signal obtained by analysis into an actual distance. For example, the control unit 70 obtains the length of the optical component using the calibration interference signal, and corrects the conversion data using this length as a reference. The length of the optical component is stored in the storage unit 74 as reference data, and the control unit 70 uses the reference data stored in the storage unit 74 to correct the conversion data during measurement or when the device is started.

Next, the acquisition of the reference data will be described. The length of the optical component used as the reference data is measured, for example, before the shipment of the device and stored in the memory unit 74. The length of the optical component is obtained, for example, by measuring an optical member (plate glass, model eye, plastic plate, etc.) with a known thickness. In this embodiment, the thickness T1 on the optical axis of the objective lens 125 is acquired as the length of the optical component. FIG. 2 shows an interference signal detected when the objective lens 125 and a plate glass with a thickness T2 are measured by the interference optical system 100. When measuring the objective lens 125, the control unit 70 moves the Zerodelay position to the vicinity of the objective lens 125 by the optical path length adjustment unit 126. This causes the objective lens 125 to enter the coherent region of the interference optical system 100, and the reflected light from the objective lens 125 can be detected as an interference signal. The Zerodelay position is, for example, a position where the measurement optical path length and the reference optical path length match. As shown in FIG. 2, the interference signal detects peaks P1 and P2 due to front and rear reflections when the objective lens 125 is viewed from the light source 102 side, and peaks P3 and P4 due to front and rear reflections of the glass plate.

The control unit 70 detects the position of each peak by signal analysis processing, and obtains the interval D1 between peak P1 and peak P2, and the interval D2 between peak P3 and peak P4. For example, the control unit 70 obtains the interval D1 by subtracting the position of peak P2 from the position of peak P1, and obtains the interval D2 by subtracting the position of peak P4 from the position of peak P3. Here, the interval D1 on the interference signal corresponds to the thickness T1 on the optical axis of the objective lens 125, and the interval D2 corresponds to the thickness T2 of the plate glass. Since the thickness T2 of the plate glass is known, the thickness T1 of the objective lens 125 can be obtained by multiplying this thickness T2 by the ratio of the interval D1 to the interval D2. For example, if the thickness T2 of the plate glass is 14 mm, the interval D1 is 40 pixels, and the interval D2 is 100 pixels, the thickness T1 of the objective lens 125 is T1 = T2 × D1 / D2 = 5.6 mm. The actual value of the thickness T1 of the objective lens 125 obtained in this manner is stored in the memory unit 74 as reference data.

Of course, the method of obtaining the length of an optical component is not limited to the above. For example, it may be measured using a measuring instrument such as a caliper or a micrometer, or may be obtained based on the design value of the lens.

The length of the optical component used as the reference data is not limited to the thickness of the objective lens 125. For example, it may be an optical component other than the objective lens that can be measured by the interference optical system 100. There may also be multiple optical components. For example, the distance between multiple optical components may be used as the reference data.

<Control operation>
The control operation when measuring the intraocular distance in the device having the above configuration will be described with reference to Fig. 3. Fig. 3 is a flow chart showing the flow of axial length measurement.

(Step S1: Calibration)
First, the control unit 70 calibrates the ophthalmic device 1. Calibration may be performed for each measurement, each time the device is started, or at an appropriately set timing. The control unit 70 sets the measurement mode to the calibration mode. In the calibration mode, the Zerodelay position is set near the reference optical component (the objective lens in this embodiment). The control unit 70 moves the Zerodelay position near the optical component by adjusting the optical path length with the optical path length adjustment unit 126. For example, the control unit 70 moves the fiber end 122 and the collimator lens 123 to extend the optical path length of the measurement light, and moves the Zerodelay position near the optical component.

Figure 4 shows the calibration interference signal acquired in the calibration mode. As shown in Figure 4, a peak P5 due to front reflection of the objective lens 125 and a peak P6 due to rear reflection are detected. The control unit 70 detects the positions of the peaks, obtains the distance D3 between them, and corrects the conversion data using the thickness T1 of the objective lens 125 stored as reference data.

For example, suppose that due to a change in the characteristics of the light source 102, the spacing D3 corresponding to the thickness T1 of the objective lens 125 on the interference signal has changed from the spacing D1 when the reference data was acquired to 28 pixels. Since the thickness T1 of the objective lens 125 before shipment stored in the memory unit 74 is 5.6 mm, it is found that the distance per pixel is 5.6 mm/28 pixels = 0.2 mm/pixel. After calculating the distance per pixel, the control unit 70 stores it in the memory unit 74 as corrected converted data.

(Step S2: Mode switching)
The control unit 70 switches the measurement mode to the normal mode. In the normal mode, the control unit 70 measures the axial length and the like by measuring the subject's eye. The control unit 70 adjusts the optical path length by the optical path length adjustment unit 126 and moves the Zerodelay position to the vicinity of the subject's eye. At this time, if the objective lens 125 enters the coherent region, the reflected light of the objective lens 125 enters the measurement interference signal and becomes noise, so the control unit 70 adjusts the optical path length so that it is not captured as much as possible (does not enter the coherent region). For example, the control unit 70 may adjust the optical path length so that the Zerodelay position is located at a position slightly shifted from the front surface of the cornea toward the light source, or may adjust the optical path length so that the Zerodelay position is located at the vitreous position (a position slightly shifted from the retina toward the light source).

(Step S3: Alignment)
First, while viewing the alignment state of the subject's eye displayed on the display unit 75, the examiner uses the operation unit 76 to move the ophthalmic apparatus 1 up, down, left, right, and front to back, and places the ophthalmic apparatus 1 in a predetermined positional relationship with the subject's eye E. At this time, the examiner has the subject fixate the fixation target.

During alignment, light source 41 and light source 51 are turned on. For example, the examiner performs vertical and horizontal alignment so that the reticle electronically displayed on the display unit 75 and the ring index generated by light source 41 are concentric. This results in alignment in the XY direction so that the optical axis O1 of the ophthalmic device 1 passes through the corneal apex of the subject's eye. The examiner also performs front-to-back alignment so that the ring index is in focus. The control unit 70 may perform alignment automatically based on a frontal image of the anterior segment captured by the front imaging optical system 30.

(Step S4: Measurement)
When the alignment is completed, the control unit 70 starts measuring the intraocular distance. For example, the control unit 70 irradiates the subject's eye with measurement light while changing the wavelength by the light source 12, and causes the light receiving element 120 to receive the measurement reflected light reflected at each part of the subject's eye. The control unit 70 obtains a measurement interference signal by performing a Fourier transform on the signal obtained by the light receiving element 120.

(Step S5: Calculate intraocular distance)
The control unit 70 calculates the intraocular distance from the acquired interference signal. For example, the control unit 70 detects the positions of various parts of the subject's eye (e.g., the anterior surface of the cornea, the posterior surface of the cornea, the anterior surface of the lens, the posterior surface of the lens, and the retina) based on the peak positions of the interference signal, and calculates the intraocular distance (e.g., the corneal thickness, the anterior chamber depth, the lens thickness, the axial length, etc.).

Figure 5 shows an interference signal obtained when the test eye is measured in normal mode. The control unit 70 detects the positions of the corneal peak P7 and the retinal peak P8 of the test eye, and obtains the distance D4 between them. The control unit 70 reads the distance per pixel obtained by calibration from the storage unit 74, and calculates the axial length by multiplying it by the distance D4. For example, if the distance D4 is 80 pixels, the axial length = 80 x 0.2 = 16 mm. The control unit 70 may calculate the intraocular distance taking into account the optical members (such as plate glass), the objective lens 125, and the refractive index of the test eye at the time of acquiring the reference data. The control unit 70 causes the display unit 75 to display the calculation result of the intraocular distance or an OCT image, etc., and ends the intraocular distance measurement.

As in the ophthalmic device 1 of this embodiment, by correcting the measurement results using reflected light from the optical components that make up the interference optical system 100, the device can be calibrated without providing an optical system dedicated to calibration. This allows for cost reduction and miniaturization.

Note that any reflective surface (e.g., lens, cover glass, etc.) may be used as long as the reflected light is from an optical component constituting the interference optical system 100. However, by using the reflected light from the objective lens 125, which is closest to the Zerodelay position in the interference optical system 100 as in this embodiment, it is easier to obtain a highly sensitive interference signal. In addition, the amount of driving of the optical path length adjustment unit 126 can be reduced.

As described above, the control unit 70 drives the optical path length adjustment unit 126 during calibration to move the reflected light of the objective lens into the coherence region of the interference optical system 100, and during measurement, moves it out of the coherence region, thereby preventing noise due to the reflected light of the objective lens from appearing during measurement.

In the above embodiment, the positional relationship between the coherence region of the interference optical system 100 and the objective lens (an optical component that constitutes the interference optical system 100) is adjusted by adjusting the optical path length using the optical path length adjustment unit 126, but this is not limited to the above. For example, the ophthalmic device 1 may be provided with a drive unit that drives the objective lens in the optical axis direction. In this case, the control unit 70 may adjust the positional relationship between the coherence region of the interference optical system 100 and the objective lens by driving the objective lens using the drive unit.

In the above description, the control unit 70 corrects the converted data, but the control unit 70 may also directly correct the measurement results. For example, in the examples of Figures 2, 4, and 5, the control unit 70 may correct the distance D4 according to the ratio (rate of change) of the distance D1 to the distance D3. In this way, the control unit 70 may correct the interference signal itself obtained by measuring the subject's eye.

In the above embodiment, the ophthalmic device 1 is an axial length measuring device that measures the axial length, and the thickness of the objective lens 125 is used to correct the measurement distance conversion data for axial length measurement, but this is not limited to the above. The ophthalmic device may be, for example, a tomographic imaging device that captures a tomographic image of the anterior part or fundus of the subject's eye using an interference optical system. In this case, the thickness of the objective lens may be used to correct the mapping data for tomographic imaging. For example, the control unit 70 samples an interference signal based on the reflected light of the objective lens 125 input from the light receiving element 120 at equal time intervals, and creates mapping data based on the sampled data. For example, the control unit 70 performs a Fourier transform on the interference signal to decompose it into frequency components, and then extracts only the frequency components of the reflected light from the front surface (or rear surface) of the objective lens 125. The control unit 70 then performs an inverse Fourier transform on the extracted frequency components to obtain an interference signal containing only the interference light of the reflected light from the front surface (or rear surface) of the objective lens 125, and creates mapping data (for example, see JP 2010-014459 A). Because the mapping data provides the relationship between frequency and time, it is possible to convert the interference signal obtained by sampling at equal time intervals into an interference signal with equal frequency intervals. In other words, it is possible to reduce distortion of the tomographic image caused by the wavelength of the light output from the swept-wavelength light source not changing linearly with time.

When capturing a tomographic image, the ophthalmic apparatus may be equipped with an optical scanner. The optical scanner scans the measurement light in the XY directions (transverse directions) on the eye E. The optical scanner is, for example, two galvanometer mirrors, and the reflection angle is arbitrarily adjusted by a drive mechanism. This changes the reflection (traveling) direction of the light beam emitted from the light source, and scans the subject's eye E in an arbitrary direction. In other words, the imaging position on the subject's eye is changed. The optical scanner may be configured to deflect light. For example, in addition to a reflecting mirror (galvanometer mirror, polygon mirror, resonant scanner), an acousto-optical element (AOM) that changes the traveling (deflection) direction of light may be used.

The control unit 70 may obtain a tomographic image by scanning the measurement light in a predetermined transverse direction on the test eye using an optical scanner. For example, by scanning in the X or Y direction, a tomographic image in the XZ or YZ plane of the test eye can be obtained. Furthermore, it is also possible to obtain a three-dimensional image of the anterior segment of the test eye by scanning the measurement light two-dimensionally in the X and Y directions.

When an optical scanner or the like is provided and a tomographic image of the test eye can be captured, the measurement results may be corrected in the calibration mode based on cross-sectional images of the optical components that make up the interference optical system 100. For example, the control unit 70 may detect the vertices of the front and rear surfaces of the objective lens 125 from the cross-sectional image of the objective lens 125, and correct the measurement results based on the distance between the vertices.

The technical elements described in this disclosure exert technical utility either alone or in various combinations, and are not limited to the above combinations. Furthermore, the technologies illustrated in this specification or drawings achieve multiple objectives simultaneously, and achieving one of those objectives is itself technically useful.

Note that the present disclosure is not limited to the above-described embodiments, and various modifications are possible. For example, software (programs) that realize the functions of the above-described embodiments may be supplied to a system or device via a network or various storage media, so that the computer (or CPU, MPU, etc.) of the system or device can read and execute the program.

Reference Signs List 1 Ophthalmic apparatus 30 Anterior eye front imaging optical system 40 Alignment projection optical system 50 Kerato projection optical system 70 Control unit 74 Storage unit 75 Display unit 76 Operation unit 100 Interference optical system

Claims (4)

An ophthalmic apparatus for measuring an eye to be examined,
an interference optical system that causes a first reflected light, which is a measurement light emitted from a light source and reflected by the subject's eye, to interfere with a reference light corresponding to the measurement light, to obtain a first interference signal;
a calculation means for correcting a measurement result based on the first interference signal by using a second interference signal obtained by interference between the reference light and a second reflected light that is reflected by an optical component constituting the interference optical system of the measurement light;
an optical path length adjusting means for adjusting an optical path length of the interference optical system;
a control means for controlling the optical path length adjustment means so that the second reflected light from the optical component falls within a coherence region of the interference optical system during calibration and so that the second reflected light does not fall within the coherence region during measurement;
An ophthalmic apparatus comprising: The ophthalmic device of claim 1, wherein the optical component is an objective lens of the interference optical system. The ophthalmic device of claim 1 or 2, characterized in that the calculation means corrects the measurement result by correcting the measurement distance conversion data or the interference signal interpolation data. A program for an ophthalmic device executed in an ophthalmic device for measuring a subject's eye, the program being executed by a processor of the ophthalmic device,
an acquisition step of acquiring a first interference signal by an interference optical system by causing interference between a first reflected light obtained by reflecting a measurement light emitted from a light source by the subject's eye and a reference light corresponding to the measurement light;
a calculation step of correcting a measurement result based on the first interference signal by using a second interference signal obtained by interference between the reference light and a second reflected light of the measurement light reflected by an optical component constituting the interference optical system;
an optical path length adjustment step of adjusting an optical path length of the interference optical system during calibration so that the second reflected light from the optical component falls within a coherence region of the interference optical system, and adjusting an optical path length of the interference optical system during measurement so that the second reflected light does not fall within the coherence region;
The ophthalmic apparatus according to claim 1, further comprising: a computer program for performing the above-mentioned program on the ophthalmic apparatus.

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