JP6619203B2 - Ophthalmic imaging equipment - Google Patents

Description

  The present invention relates to an ophthalmologic photographing apparatus.

  Optical coherence tomography (hereinafter referred to as OCT) is used to form an image representing the surface form and internal form of a measured object. In an OCT image acquired using OCT, artifacts due to reflection from an object other than the object to be measured and a coherence revival phenomenon may appear. These artifacts may appear overlapping the site of interest or may affect the results of image processing such as segmentation processing.

  For example, an artifact caused by reflection from an object other than the object to be measured may be removed by applying an anti-reflection coating to an optical member constituting an interference optical system for acquiring an OCT image. In addition, there is known a technique for removing artifacts by performing phase modulation on light from a light source so that the occurrence of a coherence revival phenomenon is suppressed (Patent Document 1).

US Patent Application Publication No. 2014/0029015

  However, even when an anti-reflection coating is applied to the optical member, it is difficult to completely suppress reflection. Further, the technique disclosed in Patent Document 1 requires a design according to the optical conditions such as the type of optical members constituting the optical system and the arrangement thereof, and the design of the optical system and the control system is complicated.

  In general, the longer the coherence length, the more likely artifacts due to reflection from an object other than the object to be measured appear in the OCT image. Further, as the coherence revival interval becomes shorter, artifacts due to the coherence revival phenomenon are more likely to appear in the OCT image. Accordingly, when a light source having a long coherence length or a light source having a short coherence revival interval is used, the image quality of the OCT image is likely to be deteriorated, and a new technique for removing the above-described artifact is required.

  The present invention has been made to solve such a problem, and an object thereof is to provide a new technique for removing artifacts appearing in an image acquired using an interference optical system. .

The ophthalmologic photographing apparatus according to the embodiment includes an objective lens, an interference optical system, an image forming unit, an analysis unit, a moving mechanism, and a control unit . The interference optical system divides the light from the light source into measurement light and reference light, makes the measurement light incident on the subject's eye via the objective lens, and returns the measurement light that has exited the subject eye and passed through the objective lens. Detect interference light with reference light. The image forming unit forms an image of the eye to be examined based on the detection result of the interference light acquired by the interference optical system. The analysis unit analyzes two or more images based on two or more detection results acquired by the interference optical system in a state where the relative positions of the objective lens and the eye to be examined are different, thereby corresponding positions in the two or more images. Remove the noise drawn in. The moving mechanism moves the objective lens and the interference optical system integrally. The control unit controls the moving mechanism to cause the interference optical system to acquire the above two or more detection results.
The ophthalmologic photographing apparatus according to the embodiment includes an objective lens, an interference optical system, an image forming unit, and an analysis unit. The interference optical system divides the light from the light source into measurement light and reference light, makes the measurement light incident on the subject's eye via the objective lens, and returns the measurement light that has exited the subject eye and passed through the objective lens. Detect interference light with reference light. The image forming unit forms an image of the eye to be examined based on the detection result of the interference light acquired by the interference optical system. The analysis unit analyzes two or more images based on two or more detection results acquired by the interference optical system in a state where the relative positions of the objective lens and the eye to be examined are different, thereby corresponding positions in the two or more images. Remove the noise drawn in. The analysis unit determines whether each pixel value of the corresponding pixel in the two or more images is equal to or greater than a first threshold value, and a fluctuation range of these pixel values is equal to or less than a second threshold value. Identify the noise based on the results.

  According to the present invention, it is possible to provide a new technique for removing artifacts appearing in an image acquired using an interference optical system.

It is a schematic diagram showing an example of composition of an ophthalmology photographing instrument concerning an embodiment. It is a schematic diagram showing an example of composition of an ophthalmology photographing instrument concerning an embodiment. It is a schematic diagram showing an example of composition of an ophthalmology photographing instrument concerning an embodiment. It is the schematic for demonstrating operation | movement of the ophthalmologic imaging device which concerns on the comparative example of embodiment. It is a flowchart showing the flow of the operation example of the ophthalmologic imaging device which concerns on embodiment. It is a flowchart showing the flow of the operation example of the ophthalmologic imaging apparatus which concerns on the 1st modification of embodiment. It is the schematic for demonstrating the ophthalmologic imaging device which concerns on the 2nd modification of embodiment.

  An example of an embodiment of the present invention will be described in detail with reference to the drawings. The ophthalmologic imaging apparatus according to the present invention has a function of an optical coherence tomography and performs OCT on the eye to be examined. This OCT is performed on any part of the eye to be examined, such as the fundus or the anterior segment.

  In this specification, images acquired by OCT may be collectively referred to as OCT images. In some cases, noise is described as being the same as an artifact. Moreover, it is possible to use the description content of the literature referred in this specification as the content of the following embodiment.

  In the following embodiment, an ophthalmologic imaging apparatus capable of executing Fourier domain type OCT will be described. In particular, the ophthalmologic photographing apparatus according to the embodiment can apply a swept source type OCT technique. Note that the configuration according to the present invention can also be applied to an ophthalmic imaging apparatus capable of executing a type other than the swept source type, for example, a spectral domain type OCT. In the following embodiments, an apparatus combining an OCT apparatus and a fundus camera will be described. However, it is also possible to combine the OCT apparatus having the configuration according to the embodiment with a modality other than the fundus camera, for example, SLO (Scanning Laser Ophthalmoscope), slit lamp, ophthalmic surgical microscope, photocoagulation apparatus, and the like. In addition, the configuration according to the embodiment can be incorporated into a single OCT apparatus.

[Constitution]
As shown in FIG. 1, the ophthalmologic photographing apparatus 1 includes a fundus camera unit 2, an OCT unit 100, and an arithmetic control unit 200. The retinal camera unit 2 has almost the same optical system as a conventional retinal camera. The OCT unit 100 is provided with an optical system for executing OCT. The arithmetic control unit 200 includes a computer that executes various arithmetic processes and control processes.

[Fundus camera unit]
The fundus camera unit 2 shown in FIG. 1 is provided with an optical system for obtaining a two-dimensional image (fundus image) representing the surface form of the fundus oculi Ef of the eye E to be examined. The fundus image includes an observation image and a captured image. The observation image is, for example, a monochrome moving image formed at a predetermined frame rate using near infrared light. The captured image may be, for example, a color image obtained by flashing visible light, or a monochrome still image using near infrared light or visible light as illumination light. The fundus camera unit 2 may be configured to be able to acquire images other than these, for example, a fluorescein fluorescent image, an indocyanine green fluorescent image, a spontaneous fluorescent image, and the like.

  The retinal camera unit 2 is provided with a chin rest and a forehead support for supporting the subject's face. Further, the fundus camera unit 2 is provided with an illumination optical system 10 and a photographing optical system 30. The illumination optical system 10 irradiates the fundus oculi Ef with illumination light. The photographing optical system 30 guides the fundus reflection light of the illumination light to an imaging device (CCD image sensor (sometimes simply referred to as a CCD) 35, 38). The imaging optical system 30 guides the measurement light from the OCT unit 100 to the eye E and guides the measurement light passing through the eye E to the OCT unit 100.

  The observation light source 11 of the illumination optical system 10 is composed of, for example, a halogen lamp or an LED (Light Emitting Diode). The light (observation illumination light) output from the observation light source 11 is reflected by the reflection mirror 12 having a curved reflection surface, passes through the condensing lens 13, passes through the visible cut filter 14, and is converted into near infrared light. Become. Further, the observation illumination light is once converged in the vicinity of the photographing light source 15, reflected by the mirror 16, and passes through the relay lenses 17 and 18, the diaphragm 19 and the relay lens 20. Then, the observation illumination light is reflected at the peripheral portion (region around the hole portion) of the aperture mirror 21, passes through the dichroic mirror 46, and is refracted by the objective lens 22 to illuminate the fundus oculi Ef.

  The fundus reflection light of the observation illumination light is refracted by the objective lens 22, passes through the dichroic mirror 46, passes through the hole formed in the central region of the perforated mirror 21, passes through the dichroic mirror 55, and is a focusing lens. It is reflected by the mirror 32 via 31. Further, the fundus reflection light passes through the half mirror 33A, is reflected by the dichroic mirror 33, and forms an image on the light receiving surface of the CCD image sensor 35 by the condenser lens. The CCD image sensor 35 detects fundus reflected light at a predetermined frame rate, for example. On the display device 3, an image (observation image) based on fundus reflection light detected by the CCD image sensor 35 is displayed. When the photographing optical system 30 is focused on the anterior segment, an observation image of the anterior segment of the eye E is displayed.

  The imaging light source 15 is configured by, for example, a xenon lamp or an LED. The light (imaging illumination light) output from the imaging light source 15 is applied to the fundus oculi Ef through the same path as the observation illumination light. The fundus reflection light of the imaging illumination light is guided to the dichroic mirror 33 through the same path as that of the observation illumination light, passes through the dichroic mirror 33, is reflected by the mirror 36, and is reflected by the condenser lens 37 of the CCD image sensor 38. An image is formed on the light receiving surface. On the display device 3, an image (captured image) based on fundus reflection light detected by the CCD image sensor 38 is displayed. Note that the display device 3 that displays the observation image and the display device 3 that displays the captured image may be the same or different. In addition, when similar imaging is performed by illuminating the eye E with infrared light, an infrared captured image is displayed. It is also possible to use an LED as a photographing light source.

  An LCD (Liquid Crystal Display) 39 displays a fixation target and an eyesight measurement index. The fixation target is an index for fixing the eye E to be examined, and is used at the time of fundus photographing or OCT measurement.

  A part of the light output from the LCD 39 is reflected by the half mirror 33A, reflected by the mirror 32, passes through the focusing lens 31 and the dichroic mirror 55, passes through the hole of the perforated mirror 21, and reaches the dichroic. The light passes through the mirror 46, is refracted by the objective lens 22, and is projected onto the fundus oculi Ef. By changing the display position of the fixation target on the screen of the LCD 39, the fixation position of the eye E can be changed.

  Further, the fundus camera unit 2 is provided with an alignment optical system 50 and a focus optical system 60 as in a conventional fundus camera. The alignment optical system 50 generates an index (alignment index) for performing alignment (alignment) of the apparatus optical system with respect to the eye E. The focus optical system 60 generates an index (split index) for focusing on the eye E to be examined.

  The light (alignment light) output from the LED 51 of the alignment optical system 50 is reflected by the dichroic mirror 55 via the apertures 52 and 53 and the relay lens 54, passes through the hole of the aperture mirror 21, and reaches the dichroic mirror 46. And is projected onto the cornea of the eye E by the objective lens 22.

  The cornea-reflected light of the alignment light passes through the objective lens 22, the dichroic mirror 46, and the hole, part of which passes through the dichroic mirror 55, passes through the focusing lens 31, and is reflected by the mirror 32. The light passes through 33A, is reflected by the dichroic mirror 33, and is projected onto the light receiving surface of the CCD image sensor 35 by the condenser lens. The light reception image (alignment index) by the CCD image sensor 35 is displayed on the display device 3 together with the observation image. The user performs alignment by performing the same operation as that of a conventional fundus camera. Further, the arithmetic control unit 200 may perform alignment by analyzing the position of the alignment index and moving the optical system (auto-alignment function).

  When performing the focus adjustment, the reflecting surface of the reflecting rod 67 is obliquely provided on the optical path of the illumination optical system 10. The light (focus light) output from the LED 61 of the focus optical system 60 passes through the relay lens 62, is separated into two light beams by the split indicator plate 63, passes through the two-hole aperture 64, and is reflected by the mirror 65. The light is focused on the reflecting surface of the reflecting bar 67 by the condenser lens 66 and reflected. Further, the focus light passes through the relay lens 20, is reflected by the perforated mirror 21, passes through the dichroic mirror 46, is refracted by the objective lens 22, and is projected onto the fundus oculi Ef.

  The fundus reflection light of the focus light is detected by the CCD image sensor 35 through the same path as the cornea reflection light of the alignment light. A light reception image (split index) by the CCD image sensor 35 is displayed on the display device 3 together with the observation image. The arithmetic control unit 200 analyzes the position of the split index and moves the focusing lens 31 and the focus optical system 60 to perform focusing as in the conventional case (autofocus function). Alternatively, focusing may be performed manually while visually checking the split indicator.

  The dichroic mirror 46 branches the optical path for OCT from the optical path for fundus imaging. The dichroic mirror 46 reflects light in a wavelength band used for OCT and transmits light for fundus photographing. In this OCT optical path, a collimator lens unit 40, an optical path length changing unit 41, an optical scanner 42, a focusing lens 43, a mirror 44, and a relay lens 45 are provided in this order from the OCT unit 100 side. ing.

  The optical path length changing unit 41 is movable in the direction of the arrow shown in FIG. 1, and changes the optical path length of the optical path for OCT. This change in the optical path length is used for correcting the optical path length according to the axial length of the eye E or adjusting the interference state. The optical path length changing unit 41 includes, for example, a corner cube and a mechanism for moving the corner cube.

  The optical scanner 42 is disposed at a position optically conjugate with the pupil of the eye E. The optical scanner 42 changes the traveling direction of the light (measurement light LS) passing through the optical path for OCT. Thereby, the eye E can be scanned with the measurement light LS. The optical scanner 42 includes, for example, a galvanometer mirror that scans the measurement light LS in the x direction, a galvanometer mirror that scans in the y direction, and a mechanism that drives these independently. Thereby, the measurement light LS can be scanned in an arbitrary direction on the xy plane.

[OCT unit]
An example of the configuration of the OCT unit 100 is shown in FIG. The OCT unit 100 is provided with an optical system for acquiring an OCT image of the eye E. This optical system has the same configuration as a conventional swept source type OCT apparatus. That is, this optical system divides the light from the wavelength sweep type (wavelength scanning type) light source into the measurement light and the reference light, and returns the return light of the measurement light from the eye E and the reference light via the reference light path. An interference optical system that generates interference light by causing interference and detects the interference light. The detection result (detection signal) of the interference light by the interference optical system is a signal indicating the spectrum of the interference light, and is sent to the arithmetic control unit 200.

  The light source unit 101 is configured to include a wavelength sweep type (wavelength scanning type) light source capable of sweeping (scanning) the wavelength of emitted light, as in a general swept source type OCT apparatus. The wavelength sweep type light source includes a laser light source including a resonator. The light source unit 101 temporally changes the output wavelength in the near-infrared wavelength band that cannot be visually recognized by the human eye.

  The light L0 output from the light source unit 101 is guided to the polarization controller 103 by the optical fiber 102 and its polarization state is adjusted. The polarization controller 103 adjusts the polarization state of the light L0 guided through the optical fiber 102, for example, by applying stress from the outside to the looped optical fiber 102.

  The light L0 whose polarization state is adjusted by the polarization controller 103 is guided to the fiber coupler 105 by the optical fiber 104, and is divided into the measurement light LS and the reference light LR.

  The reference light LR is guided to the collimator 111 by the optical fiber 110 and becomes a parallel light beam. The reference light LR that has become a parallel light beam is guided to the corner cube 114 via the optical path length correction member 112 and the dispersion compensation member 113. The optical path length correction member 112 functions as a delay unit for matching the optical path length (optical distance) of the reference light LR and the optical path length of the measurement light LS. The dispersion compensation member 113 functions as a dispersion compensation means for matching the dispersion characteristics between the reference light LR and the measurement light LS.

  The corner cube 114 folds the traveling direction of the reference light LR that has become a parallel light beam by the collimator 111 in the reverse direction. The optical path of the reference light LR incident on the corner cube 114 and the optical path of the reference light LR emitted from the corner cube 114 are parallel. The corner cube 114 is movable in a direction along the incident optical path and the outgoing optical path of the reference light LR. By this movement, the length of the optical path of the reference light LR is changed.

  1 and 2, the optical path length changing unit 41 for changing the length of the optical path (measurement optical path, measurement arm) of the measurement light LS and the optical path (reference optical path, reference) of the reference light LR. Both corner cubes 114 for changing the length of the arm) are provided, but either one of them may be provided. It is also possible to change the difference between the measurement optical path length and the reference optical path length using optical members other than these.

  The reference light LR that has passed through the corner cube 114 passes through the dispersion compensation member 113 and the optical path length correction member 112, is converted from a parallel light beam into a focused light beam by the collimator 116, enters the optical fiber 117, and is guided to the polarization controller 118. Accordingly, the polarization state of the reference light LR is adjusted.

  For example, the polarization controller 118 has the same configuration as the polarization controller 103. The reference light LR whose polarization state is adjusted by the polarization controller 118 is guided to the attenuator 120 by the optical fiber 119, and the light quantity is adjusted under the control of the arithmetic control unit 200. The reference light LR whose light amount has been adjusted by the attenuator 120 is guided to the fiber coupler 122 by the optical fiber 121.

  On the other hand, the measurement light LS generated by the fiber coupler 105 is guided by the optical fiber 127 and converted into a parallel light beam by the collimator lens unit 40. The measurement light LS converted into a parallel light beam reaches the dichroic mirror 46 via the optical path length changing unit 41, the optical scanner 42, the focusing lens 43, the mirror 44, and the relay lens 45. Then, the measurement light LS is reflected by the dichroic mirror 46, refracted by the objective lens 22, and irradiated to the eye E. The measurement light LS is scattered (including reflection) at various depth positions of the eye E. The return light of the measurement light LS including such backscattered light travels in the reverse direction on the same path as the forward path, is guided to the fiber coupler 105, and reaches the fiber coupler 122 via the optical fiber 128.

  The fiber coupler 122 combines (interferes) the measurement light LS incident through the optical fiber 128 and the reference light LR incident through the optical fiber 121 to generate interference light. The fiber coupler 122 branches the interference light between the measurement light LS and the reference light LR at a predetermined branching ratio (for example, 1: 1), thereby generating a pair of interference lights LC. The pair of interference lights LC emitted from the fiber coupler 122 are guided to the detector 125 by optical fibers 123 and 124, respectively.

  The detector 125 is, for example, a balanced photodiode that includes a pair of photodetectors that respectively detect a pair of interference lights LC and outputs a difference between detection results obtained by the pair of photodetectors. The detector 125 sends the detection result (detection signal) to a DAQ (Data Acquisition System) 130. The clock 130 is supplied from the light source unit 101 to the DAQ 130. The clock KC is generated in synchronization with the output timing of each wavelength swept (scanned) within a predetermined wavelength range by the wavelength sweep type light source in the light source unit 101. For example, the light source unit 101 optically delays one of the two branched lights obtained by branching the light L0 of each output wavelength, and then generates a clock KC based on the result of detecting these combined lights. Generate. The DAQ 130 samples the detection result of the detector 125 based on the clock KC. The DAQ 130 sends the sampled detection result of the detector 125 to the arithmetic control unit 200. The arithmetic control unit 200 performs a Fourier transform or the like on the spectrum distribution based on the detection result obtained by the detector 125 for each series of wavelength scans (for each A line), for example, thereby obtaining a reflection intensity profile in each A line. Form. Furthermore, the arithmetic control unit 200 forms image data by imaging the reflection intensity profile of each A line.

[Calculation control unit]
The configuration of the arithmetic control unit 200 will be described. The arithmetic control unit 200 analyzes the detection signal input from the detector 125 and forms an OCT image of the eye E. The arithmetic processing for this is the same as that of a conventional swept source type OCT apparatus.

  The arithmetic control unit 200 controls each part of the fundus camera unit 2, the display device 3, and the OCT unit 100. For example, the arithmetic and control unit 200 displays an OCT image of the eye E on the display device 3.

  The arithmetic control unit 200 includes, for example, a processor, a RAM (Random Access Memory), a ROM (Read Only Memory), a hard disk drive, a communication interface, and the like. The arithmetic control unit 200 may include an operation device (input device) such as a keyboard and a mouse, and a display device such as an LCD. The processor is, for example, a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), an ASIC (Application Specific Integrated Circuit), a programmable logic device (for example, SPLD (Simple Programmable LD). (Field Programmable Gate Array)) or the like. A computer program for controlling the ophthalmologic photographing apparatus 1 is stored in a storage device such as a hard disk drive. The arithmetic control unit 200 implements the functions according to the embodiment by reading and executing a program stored in a storage circuit or a storage device, for example.

[Control system]
The configuration of the control system of the ophthalmologic photographing apparatus 1 will be described with reference to FIG. In FIG. 3, some components of the ophthalmologic photographing apparatus 1 are omitted, and components particularly necessary for explaining this embodiment are selectively shown.

(Control part)
The control system of the ophthalmologic photographing apparatus 1 is configured around the control unit 210. The control unit 210 includes, for example, the above-described processor, RAM, ROM, hard disk drive, communication interface, and the like. The control unit 210 is provided with a main control unit 211 and a storage unit 212.

(Main control unit)
The main control unit 211 performs the various controls described above. In particular, as shown in FIG. 3, the main control unit 211 includes the imaging focus drive unit 31A, the CCD image sensors 35 and 38, the LCD 39, the optical path length change unit 41, the optical scanner 42, and the OCT focus drive of the fundus camera unit 2. The unit 43A, the moving mechanism driving unit 80A, and the like are controlled. The main control unit 211 controls the light source unit 101, the reference driving unit 114A, the detector 125, the DAQ 130, and the like of the OCT unit 100.

  The moving mechanism drive unit 80A drives the moving mechanism 80. The moving mechanism 80 moves the optical system shown in FIGS. 1 and 2 integrally. The movement mechanism 80 includes a first movement mechanism for moving the optical system in the x direction, a second movement mechanism for moving the optical system in the y direction, and a movement of the optical system in the z direction. And a third moving mechanism. The x direction is a direction (left-right direction) orthogonal to the optical axis direction of the objective lens 22. The y direction is a direction (vertical direction) orthogonal to the optical axis direction of the objective lens 22. The z direction is the optical axis direction of the objective lens 22. The moving mechanism driving unit 80A includes a first driving unit that drives the first moving mechanism, a second driving unit that drives the second moving mechanism, and a third driving unit that drives the third moving mechanism.

  The photographing focus driving unit 31A moves the focusing lens 31 in the optical axis direction. Thereby, the focus position of the photographic optical system 30 is changed. The main control unit 211 can move the optical system provided in the fundus camera unit 2 three-dimensionally by the movement mechanism 80 by controlling the movement mechanism driving unit 80A. This control is used in alignment and tracking. Tracking refers to moving the apparatus optical system in accordance with the movement of the eye E. When tracking is performed, alignment and focusing are performed in advance. Tracking maintains a suitable positional relationship in which alignment and focus are achieved by moving the apparatus optical system in real time according to the position and orientation of the eye E based on an image obtained by taking a moving image of the eye E. It is a function.

  The OCT focusing drive unit 43A moves the focusing lens 43 along the optical axis of the measurement optical path. Thereby, the focus position of the measurement light LS is changed. The focus position of the measurement light LS corresponds to the depth position (z position) of the beam waist of the measurement light LS.

  The reference driving unit 114A moves the corner cube 114 provided in the reference optical path. Thereby, the length of the reference optical path is changed. As described above, the optical path length changing unit 41 and only one of the corner cube 114 and the reference driving unit 114A may be provided.

(Memory part)
The storage unit 212 stores various data. Examples of the data stored in the storage unit 212 include image data of an OCT image, image data of a fundus image, and eye information to be examined. The eye information includes information about the subject such as patient ID and name, and information about the eye such as left / right eye identification information. The storage unit 212 stores various programs and data for operating the ophthalmologic photographing apparatus 1.

(Image forming part)
The image forming unit 220 forms image data of a cross-sectional image of the fundus oculi Ef based on the detection signal from the detector 125 (DAQ 130). That is, the image forming unit 220 forms image data of the eye E based on the detection result of the interference light LC by the interference optical system. This process includes processes such as filter processing and FFT (Fast Fourier Transform) as in the case of the conventional swept source type OCT. The image data acquired in this way is a data set including a group of image data formed by imaging reflection intensity profiles in a plurality of A lines (paths of the measurement light LS in the eye E). is there.

  In order to improve the image quality, it is possible to superimpose (addition average) a plurality of data sets acquired by repeating scanning with the same pattern a plurality of times.

  The image forming unit 220 includes, for example, the circuit board described above. In this specification, “image data” and “image” based thereon may be identified. Moreover, the part of the eye E to be examined and the image thereof may be identified.

(Data processing part)
The data processing unit 230 performs various types of data processing (image processing) and analysis processing on the OCT image formed by the image forming unit 220. For example, the data processing unit 230 executes correction processing such as image luminance correction and dispersion correction. Further, the data processing unit 230 performs various types of image processing and analysis processing on the image (fundus image, anterior eye image, etc.) obtained by the fundus camera unit 2.

  The data processing unit 230 includes an analysis unit 231. The analysis unit 231 executes the analysis process described above. For two or more images based on the detection results of two or more interference lights acquired by the interference optical system under the same measurement condition, the position of the measurement site on the fundus is not affected by the position of the artifact and the eye movement is fixed. Changes. Thus, the analysis unit 231 analyzes the two or more images in a state where the relative positions of the objective lens 22 and the eye E are different, thereby removing noise depicted at corresponding positions in the two or more images. To do. That is, the analysis unit 231 determines the image and artifact of the measurement site of the subject eye based on the detection result of two or more interference lights acquired by the interference optical system in a state where the relative position between the objective lens 22 and the subject eye E is different. And only the determined artifact is removed from the image of the eye to be examined.

  In this embodiment, two or more OCT measurements are performed on the eye E with a predetermined time by the interference optical system to which the same setting is applied. The setting for the interference optical system includes the position of the focusing lens 43, the scan length and scan pattern by the optical scanner 42, the change state of the optical path length by the optical path length changing unit 41 and the corner cube 114, and the polarization state by the polarization controllers 103 and 118. There is a setting to determine. By repeatedly executing the OCT measurement at a predetermined time interval, it is possible to obtain the two or more detection results described above in a state where the relative positions of the objective lens 22 and the eye E are different due to fixation fine movement.

  The analysis unit 231 includes a specifying unit 231A and a removing unit 231B. The specifying unit 231A specifies an artifact (noise) in two or more images acquired by the interference optical system. The artifact is specified as an area having a strength (luminance) equal to or higher than a predetermined threshold and having a small intensity fluctuation range with a corresponding area in another image that has been relatively moved. For example, the specifying unit 231A specifies a corresponding pixel that is a pixel in the same part of the eye to be examined in the two or more acquired images, each pixel value of the specified corresponding pixel is equal to or greater than a first threshold value, and Then, it is determined whether or not the fluctuation range of these pixel values is equal to or smaller than the second threshold value. The specifying unit 231A specifies, as an artifact, a corresponding pixel in which each pixel value of the corresponding pixel is equal to or greater than the first threshold value and the variation range of these pixel values is equal to or smaller than the second threshold value.

  The removing unit 231B generates a noise-free (artifact-free) image by removing the artifact specified by the specifying unit 231A for any of the two or more images already acquired.

  Further, the analysis unit 231 identifies the position of the characteristic part of the eye to be examined such as macular by analyzing each of the two or more images acquired by the interference optical system, and extracts two or more images having different positions of the characteristic part. The above artifacts may be removed using two or more selected images.

  The data processing unit 230 can form volume data (voxel data) of the eye E by performing known image processing such as interpolation processing for interpolating pixels between cross-sectional images. When displaying an image based on volume data, the data processing unit 230 performs a rendering process on the volume data to form a pseudo three-dimensional image when viewed from a specific viewing direction.

  The data processing unit 230 can perform alignment between the fundus image and the OCT image. When the fundus image and the OCT image are acquired in parallel, since both optical systems are coaxial, the optical axis of the imaging optical system 30 is used to (substantially) simultaneously acquire the fundus image and the OCT image. Can be aligned with reference to. Regardless of the acquisition timing of the fundus image and the OCT image, the front image obtained by projecting at least a part of the image area corresponding to the fundus oculi Ef of the OCT image onto the xy plane is aligned with the fundus image. By doing so, it is possible to align the OCT image and the fundus image. This alignment method is applicable even when the fundus image acquisition optical system and the OCT optical system are not coaxial. Even if both optical systems are not coaxial, if the relative positional relationship between both optical systems is known, the same alignment as in the coaxial case is executed with reference to this relative positional relationship. It is possible.

  The data processing unit 230 that functions as described above includes, for example, a processor, a RAM, a ROM, a hard disk drive, a circuit board, and the like. A storage device such as a hard disk drive stores in advance a computer program that causes the processor to execute the above functions.

(User interface)
The user interface 240 includes a display unit 241 and an operation unit 242. The display unit 241 includes the display device of the arithmetic control unit 200 and the display device 3 described above. The operation unit 242 includes the operation device of the arithmetic control unit 200 described above. The operation unit 242 may include various buttons and keys provided on the housing of the ophthalmologic photographing apparatus 1 or outside. Further, the display unit 241 may include various display devices such as a touch panel provided in the housing of the fundus camera unit 2.

  The display unit 241 and the operation unit 242 do not need to be configured as individual devices. For example, a device in which a display function and an operation function are integrated, such as a touch panel, can be used. In that case, the operation unit 242 includes the touch panel and a computer program. The operation content for the operation unit 242 is input to the control unit 210 as an electrical signal. Further, operations and information input may be performed using the graphical user interface (GUI) displayed on the display unit 241 and the operation unit 242.

  The OCT unit 100, the collimator lens unit 40, the optical path length changing unit 41, the optical scanner 42, the focusing lens 43, the mirror 44, and the relay lens 45 are examples of the “interference optical system” according to this embodiment.

[Operation example]
The operation of the ophthalmologic photographing apparatus 1 will be described.

  FIG. 4 is an explanatory diagram of a comparative example of the embodiment. FIG. 4 schematically shows an OCT image obtained by the ophthalmologic imaging apparatus in the comparative example.

  In the ophthalmologic photographing apparatus in the comparative example, the center of the polarization control of the measurement light by the optical scanner 42 (the origin of the scanner coordinate system) is provided so as to coincide with the optical axis of the objective lens 22. Such position adjustment is performed in a design stage, a shipping process, or a maintenance process. Thereby, in the ophthalmologic photographing apparatus according to this comparative example, alignment is performed so that the target region of the eye E to be examined is arranged at the position of the optical axis of the objective lens 22, and the photographing frequency by the scan including the optical axis increases. .

  However, in the OCT image IMG1 acquired by scanning including the optical axis of the objective lens 22, reflected light from the apex of the lens surface of the objective lens 22 may appear as an artifact N1 as shown in FIG. For example, as shown in FIG. 4, although the image is taken for the purpose of observing a tomographic image with the foveal CF as a target region, an artifact N1 appears near the target region, and the vicinity of the target region in the image is observed. It becomes difficult. In this phenomenon, the longer the coherence length, the more likely artifacts caused by the reflection of the optical system of the ophthalmic imaging apparatus appear in the OCT image.

  Therefore, in the embodiment, as described above, two or more images based on the detection result of two or more interference lights acquired by the interference optical system in a state where the relative positions of the objective lens 22 and the eye E to be examined are different are analyzed. As a result, noise drawn at corresponding positions in two or more images is removed. This makes it possible to acquire an OCT image in which noise such as artifacts caused by the coherence revival phenomenon as well as reflection of the optical system is not depicted. In particular, in an OCT image having a high imaging frequency (an OCT image acquired by scanning including the optical axis of the objective lens 22), it is possible to perform detailed observation near the region of interest.

  FIG. 5 shows a flowchart of an operation example of the ophthalmologic photographing apparatus 1. This operation example includes a process of aligning the eye E to be examined and the apparatus optical system based on an image, and a scan area setting process based on the image. The alignment processing includes alignment for OCT measurement (auto alignment), focusing (auto focus), and tracking (auto tracking).

(S1)
First, acquisition of a near-infrared moving image of the fundus oculi Ef is started by continuously illuminating the fundus oculi Ef with illumination light from the observation light source 11 (which becomes near-infrared light by the visible cut filter 14). This near-infrared moving image is obtained in real time until the continuous illumination ends. The image of each frame composing the moving image is temporarily stored in the frame memory (storage unit 212) and sequentially sent to the data processing unit 230.

  Note that an alignment index by the alignment optical system 50 and a split index by the focus optical system 60 are projected onto the eye E to be examined. Therefore, the alignment index and the split index are depicted in the near-infrared moving image. These indices can be used for alignment and focusing. A fixation target by the LCD 39 is also projected onto the eye E. The subject is instructed to stare at the fixation target.

(S2)
The data processing unit 230 sequentially analyzes frames obtained by taking a moving image of the eye E with the optical system, obtains the position of the alignment target, and calculates the movement amount of the optical system. The control unit 210 performs auto-alignment by controlling the moving mechanism driving unit 80A based on the movement amount of the optical system calculated by the data processing unit 230.

(S3)
The data processing unit 230 sequentially analyzes frames obtained by taking a moving image of the eye E with the optical system, obtains the position of the split target, and calculates the movement amount of the focusing lens 31. The control unit 210 performs autofocus by controlling the photographing focus driving unit 31A based on the movement amount of the focusing lens 31 calculated by the data processing unit 230.

(S4)
Subsequently, the control unit 210 starts auto-tracking. Specifically, the data processing unit 230 analyzes in real time frames obtained sequentially by taking a moving image of the eye E with the optical system, and monitors the movement (position change) of the eye E. The control unit 210 controls the moving mechanism driving unit 80A so as to move the optical system in accordance with the position of the eye E to be sequentially acquired. As a result, the optical system can follow the movement of the eye E in real time, and it is possible to maintain a suitable positional relationship in which the alignment is in focus.

(S5)
The control unit 210 displays the near-infrared moving image on the display unit 241 in real time. The user sets a scan area on the near-infrared moving image by using the operation unit 242. The scan area to be set may be a one-dimensional area or a two-dimensional area.

  When the scan mode of the measurement light LS and the region of interest (optic nerve head, macula, lesion, etc.) are set in advance, the control unit 210 sets the scan area based on these settings. It is also possible to configure. Specifically, a region of interest is identified by image analysis by the data processing unit 230, and the control unit 210 defines a region of a predetermined pattern so as to include the region of interest (for example, the region of interest is located at the center). Set.

(S6)
The control unit 210 controls the light source unit 101 and the optical path length changing unit 41, and controls the optical scanner 42 based on the scan area set in S5, thereby performing the first OCT measurement on the fundus oculi Ef. The image forming unit 220 forms a tomographic image (image) based on the collected data obtained by sampling the detection signal obtained by the detector 150 based on the clock KC as described above.

(S7)
When the predetermined time has elapsed, the control unit 210 performs the second OCT measurement on the fundus oculi Ef under the same measurement conditions as in S6. The image forming unit 220 forms a tomographic image based on the collected data obtained by sampling the detection signal obtained by the detector 150 in S7 as in S6.

(S8)
The data processing unit 230 identifies an artifact from the two tomographic images acquired in S6 and S7 by the analysis unit 231, removes the identified artifact from one of the tomographic images, and creates a new artifact-free tomographic image. Is generated. This is the end of this operation example (end).

  In S6 and S7, when the scan mode is a three-dimensional scan, the data processing unit 230 can form a three-dimensional image of the fundus oculi Ef based on a plurality of tomographic images formed by the image forming unit 220. It is.

[Modification]
(First modification)
In the above-described embodiment, the case where the objective lens 22 and the eye E to be examined are relatively moved by fine fixation is described, but the configuration according to the embodiment is not limited to this. For example, the objective lens 22 and the eye E may be relatively moved by integrally moving the objective lens 22 and the interference optical system by the moving mechanism 80. In this case, the main control unit 211 may control the moving mechanism so as to move the interference optical system in the optical axis direction (z direction) of the objective lens 22, or in a direction orthogonal to the optical axis of the objective lens 22 ( The movement mechanism 80 may be controlled to move the interference optical system in the xy direction).

  The configuration of the ophthalmic imaging apparatus according to the first modification is the same as the configuration of the ophthalmic imaging apparatus 1 according to the above-described embodiment. Below, a 1st modification is demonstrated centering around difference with embodiment.

  FIG. 6 shows a flowchart of an operation example of the ophthalmologic photographing apparatus according to the first modification. In FIG. 6, the same steps as those in FIG. 5 are denoted by the same reference numerals, and description thereof will be omitted as appropriate. The flow shown in FIG. 6 is different from the flow shown in FIG. 5 in that S11 is added between S6 and S7.

  In S11, after the end of the first OCT measurement, the main control unit 211 controls the moving mechanism driving unit 80A so as to move the interference optical system in the optical axis direction of the objective lens 22 (or the direction orthogonal thereto). The objective lens 22 and the eye E to be examined are relatively moved. The amount of movement in S11 may be a minute amount that is within the imaging range of the OCT image.

  In S7, the control unit 210 performs the second OCT measurement on the fundus oculi Ef with the objective lens 22 and the interference optical system moved relative to the eye E in S11 under the same measurement conditions as in S6. The image forming unit 220 forms a tomographic image based on the collected data obtained by sampling the detection signal obtained by the detector 150 in S7 as in S6.

  As described above, by changing the working distance of the ophthalmologic photographing apparatus or moving the optical system in the xy direction, the relative movement between the objective lens 22 and the eye E to be examined is more reliable as compared with the fixation fine movement. As a result, an artifact-free image can be acquired with high accuracy.

(Second modification)
In FIG. 7, the principal part of a structure of the ophthalmologic imaging device in the 2nd modification of embodiment is shown. In FIG. 7, only the portion between the eye E and the objective lens 22 of FIG. 1 is illustrated.

  The ophthalmologic photographing apparatus according to the second modification includes a front lens 23 that can be disposed between the objective lens 22 and the eye E to be examined. The front lens 23 can be manually or automatically disposed between the objective lens 22 and the eye E. When the front lens 23 is disposed between the objective lens 22 and the eye E, the present invention is applied by replacing the “object lens” in the above-described embodiment with the “front lens” in the above-described relative movement control. It is possible. For example, when the front lens 23 is disposed between the objective lens 22 and the eye E, the analysis unit is in a state where the relative positions of the front lens (or the front lens and the objective lens) and the eye to be examined are different. By analyzing two or more images based on the detection result of two or more interference lights acquired by the interference optical system, it is possible to remove noise depicted at corresponding positions in the two or more images.

[effect]
The effect of the ophthalmologic photographing apparatus according to this embodiment will be described.

  An ophthalmic imaging apparatus (ophthalmic imaging apparatus 1) according to the embodiment includes an objective lens (objective lens 22), an interference optical system (an optical system from the OCT unit 100 to the relay lens 45), and an image forming unit (image forming unit 220). ) And an analysis unit (analysis unit 231). The interference optical system divides light (light L0) from the light source (light source unit 101) into measurement light (measurement light LS) and reference light (reference light LR), and the measurement light passes through the objective lens ( Interference light (interference light LC) between the return light of the measurement light that has entered the eye E), exited from the eye and passed through the objective lens, and the reference light is detected. The image forming unit forms an image of the eye to be examined based on the detection result of the interference light acquired by the interference optical system. The analysis unit analyzes two or more images based on two or more detection results acquired by the interference optical system in a state where the relative positions of the objective lens and the eye to be examined are different, thereby corresponding positions in the two or more images. Remove the noise drawn in.

  According to such a configuration, using the fact that the position of noise caused by the optical system does not change in two or more acquired images, the position of noise in the image is identified by image processing, and the identified noise Can be removed from the image. Thereby, not only the artifacts caused by the reflected light of the objective lens but also the artifacts caused by the coherence revival phenomenon generated according to the state of the optical system can be removed.

  In addition, the ophthalmologic photographing apparatus according to the embodiment acquires, in the interference optical system, two or more detection results by controlling the movement mechanism (movement mechanism 80) that integrally moves the objective lens and the interference optical system. Control units (control unit 210, main control unit 211).

  According to such a configuration, for example, the objective lens and the eye to be examined can be relatively moved by a moving mechanism used for alignment or the like, and a noise-free image can be acquired with a simple configuration.

  In the ophthalmologic photographing apparatus according to the embodiment, the control unit may control the moving mechanism so as to move the interference optical system in the optical axis direction of the objective lens.

  According to such a configuration, the certainty of relative movement between the objective lens and the eye to be examined is increased, and a noise-free image can be acquired with high accuracy.

  In the ophthalmologic photographing apparatus according to the embodiment, the control unit may control the moving mechanism so as to move the interference optical system in a direction orthogonal to the optical axis of the objective lens.

  According to such a configuration, the certainty of relative movement between the objective lens and the eye to be examined is increased, and a noise-free image can be acquired with high accuracy.

  In the ophthalmologic photographing apparatus according to the embodiment, two or more detection results may be acquired by an interference optical system to which the same setting is applied.

  According to such a configuration, since it becomes possible to acquire two or more detection results by the interference optical system under the same conditions, it is possible to determine the noise portion and the other portions with high accuracy, It becomes possible to acquire noise-free high-quality images.

  In the ophthalmologic photographing apparatus according to the embodiment, the analysis unit has a pixel value of each of corresponding pixels in two or more images that is equal to or greater than a first threshold value, and a fluctuation range of these pixel values is equal to or less than a second threshold value. It may be determined whether or not, and noise may be specified based on the determination result.

  According to such a configuration, it is possible to specify noise with high accuracy by simple control.

  The configuration described above is merely an example for favorably implementing the present invention. Therefore, arbitrary modifications (omitted, replacement, addition, etc.) within the scope of the present invention can be made as appropriate. The configuration to be applied is selected according to the purpose, for example. In addition, depending on the configuration to be applied, a function and effect obvious to those skilled in the art and the function and effect described in this specification can be obtained.

  In the modified example of the above-described embodiment, the case where the object to be measured by OCT is the eye to be examined (fundus) has been described. However, the modified example of the above-described embodiment performs OCT on the measured object other than the eye to be examined. Applicable to things. The object to be measured need not be a living body part.

DESCRIPTION OF SYMBOLS 1 Ophthalmic imaging device 2 Fundus camera unit 22 Objective lens 23 Prefix lens 100 OCT unit 200 Arithmetic control unit 210 Control part 211 Main control part 212 Storage part 220 Image formation part 230 Data processing part 231 Analysis part E Eye to be examined

Claims (6)

An objective lens;
Splitting light from a light source into measurement light and reference light, causing the measurement light to enter the eye to be examined via the objective lens, and returning light of the measurement light that has exited from the eye to be examined and passed through the objective lens; An interference optical system for detecting interference light with the reference light;
An image forming unit that forms an image of the eye to be examined based on a detection result of the interference light acquired by the interference optical system;
Corresponding positions in the two or more images by analyzing two or more images based on two or more detection results acquired by the interference optical system in a state where the relative positions of the objective lens and the eye to be examined are different. An analysis unit that removes the noise depicted in
A moving mechanism for integrally moving the objective lens and the interference optical system;
A control unit that causes the interference optical system to acquire the two or more detection results by controlling the moving mechanism;
Ophthalmologic imaging device. The ophthalmologic photographing apparatus according to claim 1, wherein the control unit controls the moving mechanism so as to move the interference optical system in an optical axis direction of the objective lens. The ophthalmologic photographing apparatus according to claim 1, wherein the control unit controls the moving mechanism so as to move the interference optical system in a direction orthogonal to an optical axis of the objective lens. The ophthalmologic photographing apparatus according to any one of claims 1 to 3, wherein the two or more detection results are acquired by the interference optical system to which the same setting is applied. The analysis unit determines whether each pixel value of the corresponding pixel in the two or more images is equal to or greater than a first threshold value, and a fluctuation range of these pixel values is equal to or less than a second threshold value. The ophthalmic imaging apparatus according to any one of claims 1 to 4, wherein the noise is specified based on a result. An objective lens;
Splitting light from a light source into measurement light and reference light, causing the measurement light to enter the eye to be examined via the objective lens, and returning light of the measurement light that has exited from the eye to be examined and passed through the objective lens; An interference optical system for detecting interference light with the reference light;
An image forming unit that forms an image of the eye to be examined based on the detection result of the interference light acquired by the interference optical system;
Corresponding positions in the two or more images by analyzing two or more images based on two or more detection results acquired by the interference optical system in a state where the relative positions of the objective lens and the eye to be examined are different. An analysis unit that removes the noise depicted in
Including
The analysis unit determines whether each pixel value of the corresponding pixel in the two or more images is equal to or greater than a first threshold value, and a fluctuation range of these pixel values is equal to or less than a second threshold value. An ophthalmologic photographing apparatus that identifies the noise based on a result.

Images