JP2021029477A - Model eye and method for adjusting optical coherence tomography device - Google Patents

Abstract

To provide a mechanism that can create an appropriate profile for OCT photography.SOLUTION: A model eye 600 is used for adjustment of an optical coherence tomography device (OCT device) for photographing an eye E to be examined. The model eye includes: a reflective member 610 arranged in a position separated from an object lens 101-1 contained in the OCT device by a total distance of a working distance W based on a distance from the object lens 101-1 to the eye E to be examined and a predetermined distance A, and reflecting the measurement light being incident on through the object lens 101-1; and a light volume adjustment member 620 arranged between the object lens 101-1 and the reflective member 610, and having a thickness t of 1/10 of a predetermined distance A or less and adjusting the light quantity of the measurement light. The predetermined distance A is in a range of 15 mm or more and 55 mm or less.SELECTED DRAWING: Figure 6

Description

The present invention relates to a model eye configured to be attached to an optical interference tomography apparatus for photographing an eye to be inspected, and a method for adjusting the optical interference tomography apparatus.

Currently, various ophthalmic devices using optical instruments are known. For example, as an ophthalmic apparatus for observing an eye to be inspected, various devices such as an anterior ocular segment imaging device, a fundus camera device, and a scanning laser optical ophthalmoscope (SLO) device are used. Among them, an optical coherence tomography apparatus (OCT apparatus) by optical coherence tomography (OCT) utilizing multi-wavelength optical wave interference is an apparatus capable of acquiring a tomographic image of a subject with high resolution. For this reason, the OCT device is becoming an indispensable device as an ophthalmic device in a specialized outpatient department of the retina of the eye to be inspected.

In the OCT device, the measurement light is irradiated to the subject (for example, the eye to be inspected), and the backward scattered light from the subject and the reference light corresponding to the measurement light are combined by using an interference system or an interference optical system. And the combined wave light (interference light) is obtained. Then, in the OCT apparatus, high-sensitivity measurement can be performed by performing a high-speed Fourier transform of the combined wave light to obtain information in the depth direction of the subject. The low-coherent light used as the measurement light has a feature that a high-resolution tomographic image can be obtained by widening the wavelength width thereof. Further, in the OCT apparatus, by scanning the measurement light on the subject, information in a plurality of depth directions can be obtained, and these can be combined to obtain a three-dimensional tomographic image.

Conventionally, efforts have been made to further increase the resolution in order to improve the image quality of the tomographic image obtained by the OCT apparatus. The resolution in OCT is divided into vertical resolution, which is the resolution in the optical axis direction of the measurement light, and horizontal resolution, which is the resolution in the direction perpendicular to the optical axis. The vertical resolution is important for identifying the layer structure in the measurement by the tomographic image of the fundus of the eye to be inspected using the OCT device, and the thickness of the layer is very important in the judgment of the eye disease. And the resolution in the vertical direction is determined by the performance of light in OCT. When the wavelength spectrum of light has a Gaussian distribution, the vertical resolution is expressed by the following equation (1).

In this equation (1), lc is the vertical resolution expressed as the half width of the coherence function, λ ₀ is the center wavelength of light, Δλ is the wavelength width of light, and ΔGD is the OCT apparatus. Represents the difference in the amount of dispersion between the reference optical system and the measurement optical system in. The light used in the OCT apparatus for ophthalmology generally uses the near infrared region. Since most of the components of the eye are composed of water, a light source in the 1 μm band having a relatively high water transmittance is used. From equation (1), in order to improve the vertical resolution lc (to reduce the value of the vertical resolution lc), the central wavelength λ ₀ of the light is shortened, the wavelength width Δλ of the light is widened, and the reference optical system is used. It can be seen that this is achieved by aligning the dispersion between the light and the measurement optical system.

FIG. 8 shows a point image distribution function (hereinafter, “PSF”) on a certain reflecting surface when the variances of the reference optical system and the measurement optical system of the optical coherence tomography device (OCT device) are uniform and not uniform. It is a schematic diagram which shows (described). In FIG. 8, the dotted line 810 is a PSF when the variances are not uniform, and the solid line 820 is a simplified PSF when the variances are uniform. In FIG. 8, if the variances are not uniform, the signal strength of the PSF indicating the resolution of the subject (for example, the eye to be inspected) in the depth direction is lowered, the half width is widened, and the vertical resolution is deteriorated. Is shown. Here, combining the dispersions of the reference optical system and the measurement optical system is called dispersion compensation.

In addition, the OCT imaging profile for correcting the polarization and phase of the reference optical system and the measurement optical system is stored in the OCT device, and the OCT imaging profile is reflected at the time of imaging of the eye to be inspected. Methods are being used to obtain tomographic images with higher longitudinal resolution. At this time, it is conceivable to take a model eye imitating the eye to be inspected to acquire an OCT imaging profile. As a conventional technique relating to a model eye, for example, Patent Document 1 describes a model eye in which a chart for focusing adjustment is arranged on a surface corresponding to the retina that imitates the eye. Further, for example, Patent Document 2 describes a model eye in which a plurality of layers having different scattering intensities are arranged on a surface corresponding to the retina that imitates the eye.

JP-A-2002-165759 Japanese Unexamined Patent Publication No. 2011-23584

However, the model eyes described in Patent Document 1 and Patent Document 2 are insufficient as a technique for creating an appropriate profile for OCT imaging.

The present invention has been made in view of such problems, and an object of the present invention is to provide a mechanism capable of creating an appropriate OCT imaging profile.

The model eye of the present invention is a model eye used for adjusting an optical interference tomography apparatus for photographing an eye to be inspected, from an objective lens included in the optical interference tomography apparatus to the objective lens to the eye to be inspected. It is arranged at a position separated by the total distance of the working distance based on the distance and the predetermined distance, and is arranged between the objective lens and the reflecting member and a reflecting member that reflects the measurement light incident through the objective lens. The thickness is 1/10 or less of the predetermined distance, and the light amount adjusting member for adjusting the light amount of the measurement light is provided, and the predetermined distance is in the range of 15 mm or more and 55 mm or less.
Another aspect of the model eye of the present invention is a model eye used for adjusting an optical interference tomography apparatus for photographing an eye to be examined, from an objective lens included in the optical interference tomography apparatus, from the objective lens to the said. A reflective member that is arranged at a position separated by a total distance of an operating distance based on the distance to the eye to be inspected and a predetermined distance and that reflects the measurement light incident through the objective lens, and the objective lens and the reflective member. It has a light amount adjusting member which is arranged between them and has a thickness of 1/10 or less of the predetermined distance and adjusts the light amount of the measurement light, and the measurement light of the optical interference tomography apparatus is 1000 nm to 1120 nm. The light is in the wavelength range, and no member other than the light amount adjusting member is arranged in the optical path of the measured light between the objective lens and the reflecting member.
The present invention also includes a method for adjusting an optical interference tomography apparatus using the above-mentioned model eye.

According to the present invention, it is possible to create an appropriate profile for OCT imaging.

It is a figure which shows an example of the schematic structure of the optical coherence tomography apparatus (OCT apparatus) which concerns on embodiment of this invention. The figure which shows the embodiment of this invention shows the state which irradiates the fundus of the eye under test shown in FIG. 1 with the measurement light, and controls the X scanner shown in FIG. 1 to scan the fundus of the eye under test in the X direction. Is. It is a figure which shows the embodiment of this invention and shows an example of the fundus tomography image which is the anterior eye part observation image, the fundus two-dimensional image and the B scan image displayed on the display part shown in FIG. It is a characteristic diagram of the dispersion value of water which is a main component of the eye to be inspected with respect to light of the wavelength range of 0.7 μm to 1.2 μm (700 nm to 1200 nm). It is a characteristic diagram of the dispersion value of a general glass with respect to the light of the wavelength range of 0.7 μm to 1.2 μm (700 nm to 1200 nm). It is a figure which shows the 1st example of the schematic structure of the model eye which concerns on embodiment of this invention. It is a figure which shows the 2nd example of the schematic structure of the model eye which concerns on embodiment of this invention. It is a schematic diagram which shows the point image distribution function on a certain reflection plane when the variance of a reference optical system and a measurement optical system of an optical coherence tomography apparatus (OCT apparatus) is uniform and not uniform.

Hereinafter, embodiments (embodiments) for carrying out the present invention will be described with reference to the drawings. It should be noted that the embodiments of the present invention described below do not limit the invention according to the claims, and all combinations of features described in the embodiments of the present invention are the means for solving the present invention. It is not always essential for.

<Outline configuration of ophthalmic equipment>
FIG. 1 is a diagram showing an example of a schematic configuration of an optical coherence tomography apparatus (OCT apparatus) 10 according to an embodiment of the present invention. FIG. 1 shows a view of the OCT device 10 from the side, and further, the depth direction of the eye E to be inspected is the Z direction, and an XYZ coordinate system representing the X direction and the Y direction orthogonal to the Z direction is shown. Shown. The OCT device 10 is based on the light obtained by combining the return light from the eye E to be inspected, which is irradiated with the measurement light via the OCT light scanning unit 122, and the reference light corresponding to the measurement light. It is a device to acquire the tomographic image of.

The OCT device 10 is an ophthalmic device that photographs and inspects the eye E to be inspected. As shown in FIG. 1, the OCT device 10 includes an optical head unit 11, an image generation unit 12, a control unit 13, an input unit 14, and a display unit 15. It is configured to have.

First, the internal configuration of the optical head unit 11 will be described.
The optical head portion 11 is for capturing an anterior segment observation image in the anterior segment Ea of the eye E, a fundus two-dimensional image in the fundus Ef of the eye E, and a fundus tomographic image in the fundus Ef of the eye E. It is configured to have a measurement optical system. In the optical head portion 11, the objective lens 101-1 is arranged so as to face the eye E to be inspected. The optical path from the eye E to be examined is the measurement optical path OP1 of the OCT optical system, the optical path OP2 of the fundus observation optical system, and the anterior segment observation optical system by the first dichroic mirror 102 and the second dichroic mirror 103, which are optical path branching portions. It is branched into the optical path OP3 of the above for each optical wavelength band.

≪Optical path OP2: Optical path of fundus observation optical system≫
The optical path OP2 is an optical path located in the reflection direction of the second dichroic mirror 103, and the optical path of the fundus observation optical system is wavelength-separated from the measurement light of the OCT optical system in the measurement optical path OP1 by the second dichroic mirror 103. Is. Specifically, in the optical path OP2, a lens 101-2, an observation light scanning unit 117, a focusing lens 111, a lens 112, and a hollow prism 118 are arranged in this order from the second dichroic mirror 103. Here, among these lenses, the focusing lens 111 is indicated by a bidirectional arrow 191 by a driving mechanism (not shown) such as a motor (not shown) for adjusting the focusing of the fixation lamp (not shown) and the light for observing the fundus. Driven in the indicated optical axis direction. The hollow prism 118 transmits the illumination light for observing the fundus from the light source 115, and reflects the reflected light from the fundus Ef of the eye E to be inspected in the direction of the single detector 116. The hollow prism 118 has a hole for transmitting the illumination light, and the reflected light is reflected by a metal mirror or the like. Further, a perforated mirror may be arranged instead of the hollow prism 118.

The light source 115 (SLO light source) for observing the fundus of the eye produces light having a wavelength of, for example, 780 nm. Further, the observation light scanning unit 117 scans the light emitted from the light source 115 for observing the fundus on the fundus Ef of the eye E to be inspected in the X direction and the Y direction, respectively. It is configured to have -2. The lens 101-2 is arranged so that the focal position is near the center position of the X scanner 117-1 and the Y scanner 117-2. The X scanner 117-1 is configured by, for example, a polygon mirror in order to scan in the X direction at high speed. The X scanner 117-1 may be composed of, for example, a resonance type mirror. The single detector 116 is composed of, for example, an APD (avalanche photodiode), and detects the light scattered / reflected from the fundus Ef of the eye E to be inspected and returned. The hollow prism 118 is, for example, a prism on which a perforated mirror or a hollow mirror is deposited, and separates the illumination light from the light source 115 for observing the fundus and the return light from the fundus Ef of the eye E to be inspected. Further, a dichroic mirror may be further arranged on the optical path OP2, and an LED or the like may be further provided as a light source of a fixed-view lamp (not shown). At this time, the light source of the fixation lamp is arranged closer to the light source 115 than the observation light scanning unit 117. Thereby, by sharing the observation light scanning unit 117 as a scanning means for fixation, a scanning type fixation lamp can be configured. In this case, the control unit 13 may control the light source of the fixation lamp to be turned on when the light from the light source of the fixation lamp is scanned at a position desired by the examiner. The light source of the fixation lamp may be turned on and off by further arranging a shutter on the optical path OP2 and opening and closing the shutter.

In the present embodiment, as the configuration of the fundus observation optical system, a point scanning type SLO optical system that two-dimensionally scans the spot-shaped measurement light to acquire a two-dimensional image of the fundus is used. Further, as a configuration of the fundus observation optical system, a line scanning type SLO optical system (line SLO optical system) that scans a line-shaped beam in one direction using a cylindrical lens or the like may be used. Further, the optical path OP2 may be configured to perform infrared observation with a two-dimensional CCD sensor instead of using the observation light scanning unit 117 described above. Specifically, in this case, instead of using the X scanner 117-1 and the Y scanner 117-2, a two-dimensional CCD sensor for observing the fundus is arranged instead of the single detector 116, and a two-dimensional image of the fundus of the eye E to be inspected. May be configured to obtain. At this time, the two-dimensional CCD sensor is used having a sensitivity in the wavelength of the illumination light for fundus observation (not shown), specifically in the vicinity of 780 nm.

Further, the fixation lamp in the optical path OP2 generates visible light by a display for fixation such as a liquid crystal, and by changing the lighting position on the display side for fixation, the examiner can move the subject to a desired position. It may be configured to encourage fixation. At this time, the display for fixation is arranged closer to the second dichroic mirror 103 than the observation light scanning unit 117. The drive mechanism (not shown), the observation light scanning unit 117, and the single detector 116 are each controlled by the control unit 13 that collectively controls the OCT device 10.

≪Optical path OP3: Optical path of anterior segment observation optical system≫
The optical path OP3 is an optical path located in the transmission direction of the first dichroic mirror 102. A lens 131 and an infrared CCD 132 for observing the anterior segment of the eye are arranged in the optical path OP3. The infrared CCD 132 has a sensitivity in the wavelength of the illumination light from a light source for observing the anterior segment (not shown) arranged at a position where the anterior segment Ea can be illuminated, specifically in the vicinity of 970 nm. The infrared CCD 132 is connected to the control unit 13, and the output signal of the infrared CCD 132 is sent to the control unit 13.

≪Measurement optical path OP1: Measurement optical path of OCT optical system≫
An OCT optical system for taking a tomographic image of the fundus Ef of the eye E to be inspected is arranged in the measurement optical path OP1. More specifically, this OCT optical system obtains an interference signal for forming a tomographic image of the fundus Ef of the eye to be examined E by using the return light of the measurement light applied to the eye to be inspected E from the eye to be inspected E. It is a measurement optical system. The measurement optical path OP1 is an optical path located in the reflection direction of the first dichroic mirror 102 and the transmission direction of the second dichroic mirror 103. A lens 101-3, a mirror 121, and an OCT optical scanning unit 122 are arranged in this measurement optical path OP1 in order from the second dichroic mirror 103. Here, the OCT optical scanning unit 122 includes an X scanner 122-1 and a Y scanner 122-2. The X scanner 122-1 is a scanner for scanning the measurement light on the fundus Ef of the eye E to be inspected in the X direction (main scanning direction), which is an example of the first direction. Further, the Y scanner 122-2 is a scanner for scanning the measurement light in the Y direction (sub-scanning direction), which is an example of the second direction intersecting the first direction on the fundus Ef of the eye E to be inspected. .. In the present embodiment, the OCT optical scanning unit 122 constitutes a scanning means for scanning the measurement light on the measurement target. In FIG. 1, the optical path between the X scanner 122-1 and the Y scanner 122-2 is arranged in the direction parallel to the paper surface, but is actually arranged in the direction perpendicular to the paper surface.

In the measurement optical path OP1, the focusing lens 123, the lens 124, and the fiber emitted by the OCT optical system as a configuration on the light source 130 side of the X scanner 122-1 and the Y scanner 122-2 which are the OCT optical scanning units 122. The end 125 is arranged. In the optical head unit 11, when the OCT optical scanning unit 122 and the anterior eye portion Ea of the eye to be inspected E are optically coupled, the fiber end 125 and the fundus of the eye to be inspected E are adjusted by focusing. It is designed so that it has an optically conjugate relationship with Ef. The focusing lens 123 is driven in the direction of the optical axis indicated by the bidirectional arrow 192 by a driving mechanism such as a motor (not shown) for focusing adjustment. The focusing adjustment is performed by adjusting the measurement light emitted from the fiber end 125 so as to form an image on the fundus Ef of the eye E to be inspected. The focusing lens 123, which is an example of the focusing means, is arranged between the fiber end 125 and the X scanner 122-1 and the Y scanner 122-2, which are OCT optical scanning units 122 of the measurement light. This eliminates the need to move the larger lens 101-3 or the optical fiber 141-2 connected to the fiber end 125. The drive mechanism of the focusing lens 123 and the OCT optical scanning unit 122 are connected to the control unit 13, and the drive control is performed by the control unit 13.

By the focusing adjustment described above, the measurement light emitted from the fiber end 125 can be imaged on the fundus Ef of the eye E to be inspected. Further, the return light of the measurement light from the fundus Ef of the eye E to be inspected can be efficiently returned to the optical fiber 141-2 through the fiber end 125. In the optical path OP2 when observing the anterior segment of the eye, focusing adjustment is performed in the same manner using the focusing lens 111.

Subsequently, the configuration of the optical path of the light emitted from the light source 130 in FIG. 1, the interference system including the reference optical system, and the like will be described. In this embodiment, the interference optical system is composed of a light source 130, mirrors 152 and 153, optical couplers 126 and 127, optical fibers 141-1 to 4 and 142-1 to 3, and collimator lenses 151 and 154. Optical fibers 1411-1-4 and 142-1-3 are single-mode optical fibers that are connected and integrated with the optical couplers 126 and 127, respectively. Further, the optical fiber 141-4 is connected to the optical coupler 127.

The light emitted from the light source 130 is guided to the optical coupler 126 through the optical fiber 141-1. As an optical branching member, the optical coupler 126 branches the guided light into a measurement light emitted to the optical fiber 141-2 side and a reference light emitted to the optical fiber 141-3 side. The measurement light is applied to the fundus Ef of the eye E to be measured through the optical system such as the OCT optical scanning unit 122 described above. The measurement light applied to the fundus Ef of the eye E to be inspected passes through the same optical path as return light due to reflection and scattering by the retina, passes through the fiber end 125, passes through the optical coupler 126, and passes through the optical fiber 141-4. It reaches the optical coupler 127. On the other hand, the reference light reaches the mirror 152 and is reflected through the optical fiber 141-3 and the collimator lens 151. After that, the reference light is reflected by the mirror 153, collected by the collimator lens 154, incident on the end face of the optical fiber 142-1 and reaches the optical coupler 127. Here, the focal position of the collimator lens 151 coincides with the end face of the optical fiber 141-3, and the focal position of the collimator lens 154 coincides with the end face of the optical fiber 142-1. Further, in the present embodiment, the mirror 152 and the mirror 153 are integrated and move in the optical axis direction so as to maintain this positional relationship.

Since the measurement light described above reaches the optical fiber 141-4 and the reference light passing through the reference optical path reaches the optical fiber 142-1, it is combined by the optical coupler 127 of FIG. 1 to become interference light. Here, interference occurs when the optical path length of the measurement light and the optical path length of the reference light are almost the same. As shown in FIG. 1, the mirrors 152 and 153, which are reference mirrors, are arranged between the collimator lens 151 and the collimator lens 154. The positional relationship between the mirror 152 and the mirror 153 is fixed, and the positions of the mirrors 152 and 153 can be adjusted and held in the optical axis direction (direction indicated by the bidirectional arrow 193) by a drive mechanism composed of a motor or the like (not shown). Will be done. The operation of the drive mechanism 193 is performed by the control unit 13. Therefore, it is possible to match the optical path length of the reference light with the optical path length of the measurement light that differs depending on the eye E to be inspected. The interference light that is combined by the optical coupler 127 and obtained by matching the optical path lengths is guided to the differential detector 160 that detects the combined light via the optical fibers 142-2 and 142-3. The differential detector 160 converts the interference signal into an electrical signal. The image generation unit 12 generates a tomographic image of the fundus Ef of the eye E to be inspected by performing a general reconstruction process on each electric signal output from the differential detector 160.

Next, the light source 130 will be described.
As the light source 130, for example, a wavelength sweep type (Swept Source) light source capable of changing the wavelength is used. In this case, the central wavelength of the light emitted from the light source 130 is set to 1050 nm, and the light is emitted while sweeping at a sweep width of about 100 nm. Here, as the center wavelength, near-infrared light is suitable in view of measuring the eye to be inspected. The wavelength bandwidth is an important parameter because it affects the resolution of the obtained tomographic image in the optical axis direction. Specifically, in the present embodiment, the light source 130 is a light source that emits light in the wavelength range of 1000 nm to 1120 nm.

The image generation unit 12 generates a fundus tomographic image related to the fundus Ef of the eye E to be inspected by performing a general reconstruction process on each electric signal output from the differential detector 160.

The control unit 13 comprehensively controls the operation of the OCT device 10 based on the information input from the input unit 14, for example, and performs various processes. For example, the control unit 13 controls the optical head unit 11 to observe an anterior segment observation image of the anterior segment Ea of the eye to be inspected E based on the output signal of the infrared CCD 132, or an eye to be inspected based on the output signal of the single detector 116. A two-dimensional image of the fundus related to the fundus Ef of E is generated and acquired. Further, for example, the control unit 13 acquires the fundus tomographic image generated by the image generation unit 12. Then, for example, the control unit 13 controls to display these acquired images on the display unit 15.

The input unit 14 inputs various information to the control unit 13.

The display unit 15 displays various images and various information based on the control of the control unit 13. For example, the display unit 15 displays an anterior ocular segment observation image, a fundus two-dimensional image, and a fundus tomographic image acquired by the control unit 13, and also displays information indicating the state of the OCT device 10.

<How to take a tomographic image>
Next, a method of photographing a fundus tomographic image relating to the fundus Ef of the eye E to be inspected will be described.
By controlling the X scanner 122-1 and the Y scanner 122-2 by the control unit 13, the OCT device 10 can scan the measurement light at a desired site in the fundus Ef of the eye E to be inspected, and the fault at the desired site. You can take an image.

FIG. 2 shows an embodiment of the present invention, in which the fundus Ef of the eye E to be inspected is irradiated with the measurement light 201 and the fundus Ef of the eye E to be inspected is controlled by controlling the X scanner 122-1 shown in FIG. It is a figure which shows the state of performing the scan in the X direction. In FIG. 2, the same reference numerals are given to the configurations similar to those shown in FIG. 1, and detailed description thereof will be omitted. Further, FIG. 2 illustrates an XYZ coordinate system corresponding to the XYZ coordinate system shown in FIG. Specifically, the XYZ coordinate system shown in FIG. 2 is obtained by rotating the XYZ coordinate system shown in FIG. 1 by 90 degrees with respect to the XY plane.

The OCT apparatus 10 controls the X scanner 122-1 shown in FIG. 1 to scan the fundus Ef of the eye E to be examined in the imaging range in the X direction, and differentially transmits a predetermined number of imaging information from the return light. Acquired by the detector 160. Then, the signal output from the differential detector 160 is output to the image generation unit 12. The image generation unit 12 performs FFT (Fast Fourier Transform) on the interference signal obtained at a certain position in the X direction, and converts it into signal information in order to show the calculation result by FFT on the display unit 15. In the present embodiment, the image generation unit 12 generates a tomographic image of the eye to be inspected E (more specifically, the fundus Ef of the eye to be inspected E) based on the interference signal. In the present embodiment, the image obtained by this signal processing is referred to as an A-scan image. Further, in the present embodiment, a two-dimensional image in which the plurality of A-scan images are arranged in the X direction is referred to as a B-scan image. Further, in the OCT apparatus 10, after taking a plurality of A scan images for constructing one B scan image, the scanning position of the measurement light is moved in the Y direction and the measurement light is scanned again in the X direction. Therefore, a three-dimensional tomographic image can be generated by obtaining a plurality of B-scan images. Then, the OCT device 10 displays a plurality of B-scan images or an EnFace image constructed from the plurality of B-scan images on the display unit 15.

FIG. 3 shows an embodiment of the present invention, and is a diagram showing an example of an anterior segment observation image 310, a fundus two-dimensional image 320, and a fundus tomographic image 330 which are B scan images displayed on the display unit 15 shown in FIG. Is.

The anterior segment observation image 310 is a two-dimensional image of the anterior segment Ea of the eye to be inspected E obtained by processing the output signal of the infrared CCD 132. The fundus two-dimensional image 320 is a two-dimensional image of the fundus Ef of the eye E to be inspected obtained by processing the output signal of the single detector 116. The fundus tomographic image 330 is a tomographic image of the fundus Ef of the eye E to be inspected output from the differential detector 160 with respect to the line 321 illustrated in the fundus two-dimensional image 320. Further, for example, the control unit 13 can also generate an EnFace image having a high resolution of the fundus two-dimensional image 320 constructed from a plurality of fundus tomographic images 330 (B scan images).

The OCT device 10 (optical head unit 11) makes it possible to diagnose the eye E to be inspected by using the fundus tomographic image 330 and the EnFace image thus taken by the examiner. In the present embodiment, an OCT imaging profile is created using a model eye that imitates the eye to be inspected E, and correction and evaluation are performed using the OCT imaging profile so that an accurate image of the eye to be inspected E can be obtained. .. Hereinafter, the model eye according to the present embodiment will be described.

<First example of model eye>
Here, first, the dispersion of incident light (measured light) in the model eye is considered. FIG. 4 is a characteristic diagram of the dispersion value of water, which is the main component of the eye E to be inspected, with respect to light in the wavelength range of 0.7 μm to 1.2 μm (700 nm to 1200 nm). Further, FIG. 5 is a characteristic diagram of the dispersion value of general glass with respect to light in the wavelength range of 0.7 μm to 1.2 μm (700 nm to 1200 nm). As shown in FIG. 4, the dispersion value of water when the wavelength of light is around 1050 nm (more specifically, around 1030 nm) is almost 0, and the influence of light dispersion is small in the air. Since the dispersion can be ignored, it can be seen that it is almost equivalent to that in air. That is, as a model eye corresponding to the light in the vicinity of 1050 nm included in the light in the wavelength range of 1000 nm to 1120 nm emitted from the light source 130 of the present embodiment, glass or the like should not be formed as much as possible (in the air). Is the best. On the other hand, the dispersion value of the general glass shown in FIG. 5 has a constant dispersion value that is not 0 even in the vicinity of 1050 nm, and in a model eye composed of such general glass, the main component of the eye E to be inspected. It is difficult to create an appropriate profile for OCT imaging due to the difference from the dispersion value of water. In this case, the captured image of the eye E to be inspected becomes a factor that causes deterioration of the vertical resolution.

FIG. 6 is a diagram showing a first example of a schematic configuration of a model eye according to an embodiment of the present invention. In the following description, the model eye of the first example shown in FIG. 6 will be referred to as "model eye 600". In FIG. 6, the same reference numerals are given to the configurations similar to those shown in FIG. 1, and the XYZ coordinate system corresponding to the XYZ coordinate system shown in FIG. 1 is illustrated.

The model eye 600 shown in FIG. 6 is a model eye configured so as to be attached to the optical head portion 11 of the optical coherence tomography apparatus (OCT apparatus) 10 for photographing the eye to be inspected E shown in FIG. As shown in FIG. 6, the model eye 600 includes a reflection member 610, a light amount adjusting member 620, and a housing 630.

The reflection member 610 is a member whose reflecting surface is arranged perpendicular to the optical axis K of the objective lens 101-1 included in the OCT device 10 and reflects the measurement light incident on the objective lens 101-1. For example, it is composed of a reflection mirror. Here, there is a relationship as shown by the following equation (2) between the optical path length of the measurement light and the optical path length of the reference light in the OCT apparatus 10.
Lr = Ls + W + A ... (2)
In the equation (2), Lr is the optical path length of the reference light, and Ls is the optical path length of the measurement light. Further, as shown in FIG. 6, in the equation (2), W is the working distance based on the objective lens 101-1 to the cornea of the eye E to be inspected, and A is the optical length of the axial length of the eye E to be inspected. It is a predetermined distance representing a distance. In the present embodiment, as shown in FIG. 6, the reflecting member 610 is arranged at a position separated from the objective lens 101-1 by the total distance of the operating distance W and the predetermined distance A. Then, in the present embodiment, the reflective member 610 is arranged within a range of a predetermined distance A of 35 mm ± 20 mm (a range of 15 mm or more and 55 mm or less) in consideration of the distribution of the axial length.

The light amount adjusting member 620 is arranged between the objective lens 101-1 and the reflecting member 610, and has a thickness t of 1/10 or less (for example, 3 mm or less) of a predetermined distance A and adjusts the light amount of the measured light. Is. The light amount adjusting member 620 is removable with respect to the optical axis K of the objective lens 101-1, and when it is inserted and arranged in the optical axis K of the objective lens 101-1, it is arranged at the arrangement position 621. As shown, it can be obliquely provided with respect to the optical axis K of the objective lens 101-1. For example, the light amount adjusting member 620 is composed of an ND filter in which a portion through which the measurement light is transmitted is a dimming filter having a variable transmittance. In the OCT device 10, the optical path length of the measurement light and the optical path length of the reference light at the time of photographing the eye E to be inspected can be matched by moving the mirror 152 and the mirror 153 by the drive mechanism 193. The reflectance of the eye E to be inspected at the time of photographing is as low as less than 1%, and the reflectance of a general reflection mirror is several tens of percent, which causes a discrepancy when the model eye 600 is photographed. Therefore, in the present embodiment, an ND filter is inserted as the light amount adjusting member 620 in order to dimming the light equivalent to the reflectance at the time of photographing the eye to be inspected E in order to evaluate the sensitivity corresponding to the time of photographing the eye to be inspected E. The dimming by this ND filter is about OD3 (transmittance 0.01%) in the evaluation corresponding to the sensitivity of the eye E to be inspected at the time of photographing. Further, in the present embodiment, in order to evaluate the interference waveform by combining the transmission efficiencies of the reference optical system and the measurement optical system of the OCT apparatus 10, in order to obtain the optimum transmission characteristics, the ND having a variable transmittance as the light amount adjusting member 620. A filter may be used to make the ND filter rotatable. Further, as described above, when the ND filter applied as the light amount adjusting member 620 is inserted into the measurement optical path of the model eye 600, the objective is set so that the surface reflected light of the ND filter does not enter the measurement optical system. It is obliquely provided at an appropriate angle with respect to the optical axis K of the lens 101-1.

The housing 630 is a housing of the model eye 600 that stores the reflection member 610 and the light amount adjusting member 620 at predetermined positions inside.

In the model eye 600 shown in FIG. 6, first, the defect caused by the difference between the dispersion value of water, which is the main component of the eye E to be inspected, and the dispersion value of general glass described with reference to FIGS. 4 and 5 is avoided. Therefore, as much as possible, it is decided not to construct general glass (in the air). Then, in the model eye 600 shown in FIG. 6, the reflective member 610 is arranged at a position separated from the objective lens 101-1 by the total distance of the working distance W and the predetermined distance A, and the eye axis of the eye E to be inspected. Considering the distribution of lengths, the predetermined distance A is set to a range of 15 mm or more and 55 mm or less. Further, in the model eye 600 shown in FIG. 6, the thickness t of the ND filter applied as the light amount adjusting member 620 is set to 1/10 or less of the predetermined distance A representing the optical distance of the axial length of the eye E to be inspected, and the residual dispersion is achieved. In consideration of the influence of the above, the deterioration of the vertical resolution, which is considered to be no problem in actual use of the obtained image, can be suppressed to about several percent. Further, in the model eye 600 shown in FIG. 6, in the optical path of the measured light between the objective lens 101-1 and the reflecting member 610, in addition to the light amount adjusting member 620, another member (that is, a member other than the light amount adjusting member) Is not placed.
By using the model eye 600 shown in FIG. 6, it is possible to create an appropriate profile for OCT imaging.

<Second example of model eye>
FIG. 7 is a diagram showing a second example of a schematic configuration of a model eye according to an embodiment of the present invention. In the following description, the model eye of the second example shown in FIG. 7 will be referred to as "model eye 700". In FIG. 7, the same reference numerals are given to the configurations similar to those shown in FIGS. 1 and 6, and the XYZ coordinate systems corresponding to the XYZ coordinate systems shown in FIGS. 1 and 6 are illustrated. There is. Further, in the description of the model eye 700 shown in FIG. 7 described below, the matters common to the model eye 600 shown in FIG. 6 will be omitted, and the matters different from the model eye 600 shown in FIG. 6 will be described. ..

The model eye 700 shown in FIG. 7 is a model eye configured to be attached to the optical head portion 11 of the optical coherence tomography apparatus (OCT apparatus) 10 for photographing the eye to be inspected E shown in FIG. As shown in FIG. 7, the model eye 700 includes a reflection member 610, a light amount adjusting member 720, and a housing 630.

Also in the model eye 700 shown in FIG. 7, the reflecting member 610 is arranged at a position separated from the objective lens 101-1 by the total distance of the operating distance W and the predetermined distance A. At this time, in the model eye 700 shown in FIG. 7, the predetermined distance A is set to a range of 35 mm ± 1 mm (a range of 34 mm or more and 36 mm or less), which is the center value of the axial length distribution. By setting the predetermined distance A in the range of 35 mm ± 1 mm (the range of 34 mm or more and 36 mm or less), which is the center value of the axial length distribution, the mirror 152 and the mirror 153 of the OCT device 10 have the axial length distribution. The center value and the optical path length are the same position, and the reference position of the mirror 152 and the mirror 153, that is, the reference length of the reference optical path can be determined.

The light amount adjusting member 720 is a convex lens arranged on the optical axis K of the objective lens 101-1 and having the characteristics of an ND filter (dimming filter) applied as the light amount adjusting member 620 shown in FIG. More specifically, the light amount adjusting member 720 is arranged between the objective lens 101-1 and the reflecting member 610, and the thickness t is 1/10 or less (for example, 3 mm or less) of the predetermined distance A and the measurement light. It is a member that adjusts the amount of light. In the model eye 700 shown in FIG. 7, in addition to the light amount adjusting member 720, another member (that is, a member other than the light amount adjusting member) is arranged in the optical path of the measured light between the objective lens 101-1 and the reflecting member 610. It has not been.

In the model eye 700 shown in FIG. 7, the position of the focusing lens 123 that adjusts the focusing in the optical head portion 11 in order to set the predetermined distance A within the range of 35 mm ± 1 mm, which is the center value of the axial length distribution. Needs to be set to + 28.5D, which is equivalent to the diopter of the eye E to be inspected. Depending on the specifications of the optical head unit 11, it may be out of the adjustment range of the focusing lens 123. Therefore, in the model eye 700 shown in FIG. 7, the distance S between the reflecting member 610 and the light amount adjusting member 720 is determined so that the reflecting member 610 is arranged at the focal position of the light amount adjusting member 720. As a result, the position of the focusing lens 123 can be set to the position of 0D of the eye to be inspected, which is equivalent to the diopter of the eye to be inspected E, so that the position can be easily kept within the diopter range of the specifications of the optical head portion 11.

By using the model eye 700 shown in FIG. 7, it is possible to create an appropriate profile for OCT imaging.

<Adjustment method of OCT device using model eyes>
When constructing an OCT tomographic image with the optical coherence tomography apparatus (OCT apparatus) 10 shown in FIG. 1, the profile for OCT imaging is calculated and created using the model eye 600 shown in FIG. 6 or the model eye 700 shown in FIG. To do. At this time, a method of creating an OCT imaging profile using the phase information of the interference signal obtained by the OCT apparatus 10 and constructing a tomographic image will be described.

The return light of the measurement light reflected by the reflection member 610 in the model eye 600 or 700 placed in the measurement optical path and the reference light propagating in the reference optical system interfere with each other to generate interference light, and the interference light is differentiated. The light is received by the detector 160, and the optical spectrum is acquired. Then, for example, the image generation unit 12 extracts the phase information of the real signal interference signal from the intensity distribution of the optical spectrum obtained by the differential detector 160, and the phase information of the real signal interference signal and the phase information of the ideal interference signal. Based on the difference from the above, a profile for OCT imaging is created and a tomographic image is constructed. By performing the above phase correction, only the information of the tomographic image of the eye excluding the influence of the device is extracted, the vertical resolution can be improved, and the tomographic image with high resolution can be displayed. At this time, if the residual dispersion remains with respect to the model eye, the residual dispersion appears at the time of phase correction, and as a result, it becomes a factor that the vertical resolution deteriorates. In this regard, since the model eye 600 shown in FIG. 6 and the model eye 700 shown in FIG. 7 adopt a configuration in consideration of this residual dispersion, deterioration of the vertical resolution can be suppressed.

By using the model eye 600 or 700 described in the present embodiment, it is possible to create an appropriate profile for OCT imaging, so that it is possible to acquire a tomographic image having an improved vertical resolution equivalent to that of the eye to be inspected E. Become.

It should be noted that the above-described embodiments of the present invention merely show examples of embodiment in carrying out the present invention, and the technical scope of the present invention should not be construed in a limited manner by these. Is. That is, the present invention can be implemented in various forms without departing from the technical idea or its main features.

10: Optical interference tomography device (OCT device), 11: Optical head unit, 12: Image generation unit, 13: Control unit, 14: Input unit, 15: Display unit, 101-1: Objective lens, 600: Model eye , 610: Reflective member, 620: Light amount adjusting member, 630: Housing, E: Eye to be inspected, K: Optical axis of objective lens

Claims (8)

A model eye used to adjust an optical coherence tomography device that photographs the eye to be inspected.
The objective lens included in the optical interference tomography apparatus is arranged at a position separated by a total distance of a predetermined distance and an operating distance based on the distance from the objective lens to the eye to be inspected, and is incident through the objective lens. A reflective member that reflects the measurement light and
A light amount adjusting member arranged between the objective lens and the reflecting member and having a thickness of 1/10 or less of the predetermined distance and adjusting the amount of the measured light.
Have,
A model eye characterized in that the predetermined distance is in the range of 15 mm or more and 55 mm or less. The model eye according to claim 1, wherein the predetermined distance is in a range of 34 mm or more and 36 mm or less. The model eye according to claim 1 or 2, wherein the light amount adjusting member has a thickness of 3 mm or less. Any one of claims 1 to 3, wherein the light amount adjusting member is obliquely provided with respect to the optical axis of the objective lens, and a portion through which the measured light is transmitted is a dimming filter having a variable transmittance. The model eye described in the section. The model eye according to any one of claims 1 to 3, wherein the light amount adjusting member is a convex lens arranged on the optical axis of the objective lens and having the characteristics of a dimming filter. The optical interference tomography apparatus
A light source that emits light in the wavelength range of 1000 nm to 1120 nm,
An optical branching member that splits the light from the light source into the measurement light and the reference light.
The model eye according to any one of claims 1 to 5, wherein the model eye is configured to include. A model eye used to adjust an optical coherence tomography device that photographs the eye to be inspected.
The objective lens included in the optical interference tomography apparatus is arranged at a position separated by a total distance of a predetermined distance and an operating distance based on the distance from the objective lens to the eye to be inspected, and is incident through the objective lens. A reflective member that reflects the measurement light and
A light amount adjusting member arranged between the objective lens and the reflecting member and having a thickness of 1/10 or less of the predetermined distance and adjusting the amount of the measured light.
Have,
The measurement light of the optical interference tomography apparatus is light in the wavelength range of 1000 nm to 1120 nm.
A model eye characterized in that no member other than the light amount adjusting member is arranged in the optical path of the measured light between the objective lens and the reflecting member. A method for adjusting an optical interference tomography apparatus, which comprises correcting the phase of an interference signal obtained by the optical interference tomography apparatus by using the model eye according to any one of claims 1 to 7.