JP2016104304A - Ophthalmological imaging device and ophthalmological image processing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To quantitatively evaluate the degree of an error in follow-up imaging using OCT measurement.SOLUTION: An ophthalmological imaging device is used in follow-up imaging for acquiring a tomographic image by referring to a front image of a subject eye acquired in the past and scanning the same position as the past image with light, and comprises: an imaging part which acquires the front image of the subject eye; a tomographic image formation part which forms the tomographic image by scanning the subject eye with light; a storage part which stores the first front image of the subject eye and the second front image acquired in follow-up imaging performed by referring to the first front image; an information acquisition part which acquires positional deviation information between the front and second images by analyzing the first and second front images; and a calculation part which calculates an evaluation value of an error at the scanning position in the follow-up imaging on the basis of the positional deviation information. The storage part stores the front images obtained first and last in a period in which scanning with light is performed in the follow-up imaging as the second front images.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an ophthalmologic photographing apparatus and an ophthalmic image processing apparatus.

  In recent years, optical coherence tomography (OCT) has attracted attention as an apparatus for imaging an eye to be examined using light scanning. Since OCT has no invasiveness to the human body like X-ray CT, it is expected to be applied particularly in the medical field and the biological field. For example, in the field of ophthalmology, an apparatus for forming an image of the fundus oculi or cornea has been put into practical use.

  Patent Document 1 discloses an apparatus using a so-called “Fourier Domain OCT (Fourier Domain OCT)” technique. That is, this apparatus irradiates the object to be measured with a beam of low coherence light, superimposes the reflected light and the reference light to generate interference light, acquires the spectral intensity distribution of the interference light, and performs Fourier transform. By performing the conversion, the form of the object to be measured in the depth direction (z direction) is imaged. Further, this apparatus includes a galvanometer mirror that scans a light beam (signal light) in one direction (x direction) orthogonal to the z direction, thereby forming an image of a desired measurement target region of the object to be measured. It has become. An image formed by this apparatus is a two-dimensional tomographic image in the depth direction (z direction) along the scanning direction (x direction) of the light beam. Note that this technique is also called a spectral domain.

  In Patent Document 2, a plurality of horizontal two-dimensional tomographic images are formed by scanning signal light in the horizontal direction (x direction) and the vertical direction (y direction), and the measurement range is determined based on the plurality of tomographic images. A technique for acquiring and imaging three-dimensional tomographic information is disclosed. As this three-dimensional imaging, for example, a method of displaying a plurality of tomographic images side by side in a vertical direction (referred to as stack data or the like), volume data (voxel data) based on the stack data is rendered, and a three-dimensional image is rendered. There is a method of forming.

  Patent Documents 3 and 4 disclose other types of OCT apparatuses. In Patent Document 3, the wavelength of light irradiated to a measured object is scanned (wavelength sweep), and interference intensity obtained by superimposing reflected light of each wavelength and reference light is detected to detect spectral intensity distribution. And an OCT apparatus for imaging the form of an object to be measured by performing Fourier transform on the obtained image. Such an OCT apparatus is called a swept source type. The swept source type is a kind of Fourier domain type.

  In Patent Document 4, the traveling direction of light is obtained by irradiating the object to be measured with light having a predetermined beam diameter, and analyzing the component of interference light obtained by superimposing the reflected light and the reference light. An OCT apparatus for forming an image of an object to be measured in a cross-section orthogonal to is described. Such an OCT apparatus is called a full-field type or an en-face type.

  Patent Document 5 discloses a configuration in which OCT is applied to the ophthalmic field. Prior to the application of OCT, a fundus camera, a slit lamp, an SLO (Scanning Laser Ophthalmoscope), and the like were used as devices for observing the eye to be examined (for example, Patent Document 6, Patent Document 7, and Patent Document). 8). A fundus camera is a device that shoots the fundus by illuminating the subject's eye with illumination light and receiving the fundus reflection light. A slit lamp is a device that acquires an image of a cross-section of the cornea by cutting off a light section of the cornea using slit light. The SLO is an apparatus that images the fundus surface by scanning the fundus with laser light and detecting the reflected light with a highly sensitive element such as a photomultiplier tube.

  An apparatus using OCT has an advantage over a fundus camera or the like in that a high-definition image can be acquired, and further, a tomographic image or a three-dimensional image can be acquired.

  As described above, an apparatus using OCT can be applied to observation of various parts of an eye to be examined, and can acquire high-definition images, and thus has been applied to diagnosis of various ophthalmic diseases.

  By the way, in various medical fields, the same part of the subject is repeatedly examined (referred to as follow-up). Examples include follow-up and pre- and post-operative observations. There are problems specific to ophthalmology regarding follow-up. That is, it is difficult to inspect the same part due to the influence of eye movement (fixed eye movement, rotation, etc.) of the eye to be inspected. In particular, in an imaging apparatus that scans the eye to be examined with light, it is extremely difficult to reproduce the same scanning position as in the past.

  A technique described in Patent Document 9-11 is known as a technique applicable to such a problem of follow-up photography.

  An object of the invention described in Patent Document 9 is to smoothly detect a positional shift between fundus images including rotational movement. Therefore, the present invention is configured to detect the amount of positional deviation between fundus images by collating a plurality of small region images cut out from each fundus image.

  An object of the invention described in Patent Document 10 is to suitably detect the retinal intrinsic signal of the human eye by continuously measuring the same tomographic site on the fundus. For this purpose, the present invention detects the shift of the scanning position by irradiating the fundus with the second light beam and detecting it while scanning the fundus with the measurement light beam, and controls the second optical scanner based on the detection result. Thus, the scanning position of the measurement light beam is corrected as needed. In addition, it is also described that template matching based on a characteristic region in the fundus front image is used in detection of a scanning position shift.

  An object of the invention described in Patent Document 11 is to accurately irradiate a light beam at a predetermined position on the fundus regardless of the eye movement of the eye to be examined. Therefore, the present invention is configured to detect the angle-of-view information of the scanning light and the positional deviation information of the fundus based on the fundus front image, and correct the scanning position of the scanning light based on these information.

JP 11-325849 A JP 2002-139421 A JP 2007-24677 A JP 2006-153838 A JP 2008-73099 A JP-A-9-276232 JP 2008-259544 A JP 2009-11811 A JP 2011-50430 A JP 2011-115507 A JP 2011-212213 A

  In follow-up imaging, it is very important to know the degree of error (accuracy and accuracy), that is, the degree of deviation of the scanning position in imaging performed at different timings. That is, in order to accurately perform diagnosis, it is very important to know whether or not follow-up imaging has been performed properly, and to what degree of accuracy and accuracy the follow-up imaging has been performed. However, in the prior art, it was impossible to quantitatively evaluate the degree of error in follow-up photography.

  For example, with the technique described in Patent Document 9, it is possible to detect the amount of positional deviation between fundus images, but it is impossible to provide the user with the meaning of the positional deviation and the suitability of follow-up photography. . Therefore, the user has to make a judgment based on the positional deviation. However, the error of the scanning start point in follow-up imaging is usually on the order of millimeters or less, and it is difficult to visually determine whether or not follow-up imaging is appropriate. Moreover, although there are various modes of misalignment such as parallel misalignment and rotational misalignment, it is impossible to evaluate the misalignment at least from the viewpoint of appropriate / inappropriate follow-up photography.

  In the techniques described in Patent Documents 10 and 11, the scanning position is corrected by detecting a positional deviation while performing photographing. However, even if such correction is performed, a shift in scanning position, that is, an error in follow-up imaging still exists. These conventional techniques cannot quantitatively evaluate the error in follow-up photography.

  The present invention has been made to solve the above problems, and an object thereof is to provide a technique capable of quantitatively evaluating the degree of error in follow-up imaging.

  An embodiment is an ophthalmologic imaging apparatus capable of performing follow-up imaging for acquiring a tomographic image by scanning a light at the same position as the past with reference to a front image of a subject eye acquired in the past, An imaging unit that captures a subject eye and obtains a front image, a tomographic image formation unit that scans the subject eye with light to form a tomographic image, a first front image of the subject eye, and the first A storage unit that stores a second front image acquired in follow-up photography performed with reference to the front image, and the first front image and the second front image are analyzed, and these front images are analyzed. An information acquisition unit that acquires misalignment information between, and a calculation unit that calculates an evaluation value of a scanning position error in the follow-up imaging based on the misalignment information, and the storage unit As the second front image, the follower And to store the initially obtained front image and the last obtained front image in the period in which the scanning is performed of the light-flop shooting.

  According to the present invention, it is possible to quantitatively evaluate the degree of error in follow-up photography.

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 block diagram showing an example of composition of an ophthalmology photographing instrument concerning an embodiment. It is a schematic block 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 embodiment. It is the schematic for demonstrating operation | movement of the ophthalmologic imaging device which concerns on embodiment. It is the schematic for demonstrating operation | movement of the ophthalmologic imaging device which concerns on embodiment. It is the schematic for demonstrating operation | movement of the ophthalmologic imaging device which concerns on embodiment. It is the schematic for demonstrating operation | movement of the ophthalmologic imaging device which concerns on embodiment. It is the schematic for demonstrating operation | movement of the ophthalmologic imaging device which concerns on embodiment. It is the schematic for demonstrating operation | movement of the ophthalmologic imaging device which concerns on embodiment. It is the schematic for demonstrating operation | movement of the ophthalmologic imaging device which concerns on embodiment. It is the schematic for demonstrating operation | movement of the ophthalmologic imaging device which concerns on embodiment. It is the schematic for demonstrating operation | movement of the ophthalmologic imaging device which concerns on embodiment. It is a schematic block diagram showing an example of composition of an ophthalmology photographing instrument concerning an embodiment. It is a schematic block diagram showing an example of composition of an ophthalmology photographing instrument concerning an embodiment. It is a schematic block diagram showing an example of composition of an ophthalmology image processing device concerning an embodiment.

  An example of an embodiment of an ophthalmologic photographing apparatus and an ophthalmic image processing apparatus according to the present invention will be described in detail with reference to the drawings. The ophthalmologic photographing apparatus according to the present invention forms a tomographic image or a three-dimensional image of the fundus using OCT. In this specification, images acquired by OCT may be collectively referred to as OCT images. In addition, a measurement operation for forming an OCT image may be referred to as OCT measurement. In addition, it is possible to use suitably the description content of the literature described in this specification as the content of the following embodiment.

  In the following embodiment, a configuration to which Fourier domain type OCT is applied will be described in detail. In particular, the ophthalmologic imaging apparatus according to the embodiment can acquire both the OCT image and the fundus image of the fundus using the spectral domain OCT technique, as in the apparatus disclosed in Patent Document 5. The configuration according to the present invention can also be applied to an ophthalmologic photographing apparatus using a method other than the spectral domain, for example, a swept source OCT technique.

  In this embodiment, a fundus camera is applied as a configuration for capturing a front image of the eye to be examined. However, an imaging apparatus such as an SLO, a slit lamp, or an ophthalmic surgical microscope may be applied. The front image of the eye to be examined is an image obtained by photographing any part of the eye to be examined, such as the fundus or anterior eye portion, from a viewpoint facing the eye to be examined.

  Moreover, the ophthalmic image processing apparatus according to the present invention can be configured as a part of the ophthalmic imaging apparatus according to the present invention, or can be configured by a single computer, or can be connected via a network. It is also possible to configure with two or more computers.

<First Embodiment>
[Constitution]
As shown in FIGS. 1 and 2, 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 acquiring an OCT image of the fundus. 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, such as a fluorescein fluorescent image, an indocyanine green fluorescent image, a spontaneous fluorescent image, and the like. An arbitrary fundus image captured by the fundus camera unit 2 corresponds to a “front image”. The fundus camera unit 2 is an example of a “photographing unit”.

  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 signal light from the OCT unit 100 to the fundus oculi Ef and guides the signal light passing through the fundus oculi Ef to the OCT unit 100.

  The observation light source 11 of the illumination optical system 10 is constituted by a halogen lamp, for example. 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. An LED (Light Emitting Diode) can also be used as the observation light source.

  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 39A, 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 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 constituted by, for example, a xenon lamp. 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 39A, 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. As the fixation position of the eye E, for example, a position for acquiring an image centered on the macular portion of the fundus oculi Ef, or a position for acquiring an image centered on the optic disc as in the case of a conventional fundus camera And a position for acquiring an image centered on the fundus center between the macula and the optic disc. It is also possible to arbitrarily change the display position of the fixation target.

  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 fundus oculi Ef.

  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 39A, 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 measurement from the optical path for fundus photography. The dichroic mirror 46 reflects light in a wavelength band used for OCT measurement and transmits light for fundus photographing. In this optical path for OCT measurement, a collimator lens unit 40, an optical path length changing unit 41, a galvano 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. It has been.

  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 measurement. 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 galvano scanner 42 changes the traveling direction of light (signal light LS) passing through the optical path for OCT measurement. Thereby, the fundus oculi Ef can be scanned with the signal light LS. The galvano scanner 42 includes, for example, a galvano mirror that scans the signal light LS in the x direction, a galvano mirror that scans in the y direction, and a mechanism that drives these independently. Thereby, the signal 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 will be described with reference to FIG. The OCT unit 100 is provided with an optical system for acquiring an OCT image of the fundus oculi Ef. This optical system has the same configuration as a conventional spectral domain type OCT apparatus. That is, this optical system divides low-coherence light into reference light and signal light, and generates interference light by causing interference between the signal light passing through the fundus oculi Ef and the reference light passing through the reference optical path. It is configured to detect spectral components. This detection result (detection signal) is sent to the arithmetic control unit 200.

  In the case of a swept source type OCT apparatus, a wavelength swept light source is provided instead of a light source that outputs a low coherence light source, and an optical member that spectrally decomposes interference light is not provided. In general, for the configuration of the OCT unit 100, a known technique according to the type of optical coherence tomography can be arbitrarily applied.

  The light source unit 101 outputs a broadband low-coherence light L0. The low coherence light L0 includes, for example, a near-infrared wavelength band (about 800 nm to 900 nm) and has a temporal coherence length of about several tens of micrometers. Note that near-infrared light having a wavelength band that cannot be visually recognized by the human eye, for example, a center wavelength of about 1040 to 1060 nm, may be used as the low-coherence light L0.

  The light source unit 101 includes a light output device such as a super luminescent diode (SLD), an LED, or an SOA (Semiconductor Optical Amplifier).

  The low-coherence light L0 output from the light source unit 101 is guided to the fiber coupler 103 by the optical fiber 102 and split into the signal light LS and the reference light LR.

  The reference light LR is guided by the optical fiber 104 and reaches the optical attenuator (attenuator) 105. The optical attenuator 105 automatically adjusts the amount of the reference light LR guided to the optical fiber 104 under the control of the arithmetic control unit 200 using a known technique. The reference light LR whose light amount has been adjusted by the optical attenuator 105 is guided by the optical fiber 104 and reaches the polarization adjuster (polarization controller) 106. The polarization adjuster 106 is, for example, a device that adjusts the polarization state of the reference light LR guided in the optical fiber 104 by applying a stress from the outside to the optical fiber 104 in a loop shape. The configuration of the polarization adjuster 106 is not limited to this, and any known technique can be used. The reference light LR whose polarization state is adjusted by the polarization adjuster 106 reaches the fiber coupler 109.

  The signal light LS generated by the fiber coupler 103 is guided by the optical fiber 107 and converted into a parallel light beam by the collimator lens unit 40. Further, the signal light LS reaches the dichroic mirror 46 via the optical path length changing unit 41, the galvano scanner 42, the focusing lens 43, the mirror 44, and the relay lens 45. The signal light LS is reflected by the dichroic mirror 46, is refracted by the objective lens 22, and is applied to the fundus oculi Ef. The signal light LS is scattered (including reflection) at various depth positions of the fundus oculi Ef. The backscattered light of the signal light LS from the fundus oculi Ef travels in the same direction as the forward path in the reverse direction, is guided to the fiber coupler 103, and reaches the fiber coupler 109 via the optical fiber 108.

  The fiber coupler 109 causes the backscattered light of the signal light LS to interfere with the reference light LR that has passed through the optical fiber 104. The interference light LC generated thereby is guided by the optical fiber 110 and emitted from the emission end 111. Further, the interference light LC is converted into a parallel light beam by the collimator lens 112, dispersed (spectral decomposition) by the diffraction grating 113, condensed by the condenser lens 114, and projected onto the light receiving surface of the CCD image sensor 115. Although the diffraction grating 113 shown in FIG. 2 is a transmission type, other types of spectroscopic elements such as a reflection type diffraction grating may be used.

  The CCD image sensor 115 is a line sensor, for example, and detects each spectral component of the split interference light LC and converts it into electric charges. The CCD image sensor 115 accumulates this electric charge, generates a detection signal, and sends it to the arithmetic control unit 200.

  In this embodiment, a Michelson type interferometer is employed, but any type of interferometer such as a Mach-Zehnder type can be appropriately employed. Further, in place of the CCD image sensor, another form of image sensor such as a CMOS (Complementary Metal Oxide Semiconductor) image sensor can be used.

[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 CCD image sensor 115 and forms an OCT image of the fundus oculi Ef. The arithmetic processing for this is the same as that of a conventional spectral domain 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 control unit 200 displays an OCT image of the fundus oculi Ef on the display device 3.

  As the control of the fundus camera unit 2, the arithmetic control unit 200 controls the operation of the observation light source 11, the imaging light source 15 and the LEDs 51 and 61, the operation control of the LCD 39, the movement control of the focusing lenses 31 and 43, and the reflector 67. Movement control, movement control of the focus optical system 60, movement control of the optical path length changing unit 41, operation control of the galvano scanner 42, and the like are performed.

  As control of the OCT unit 100, the arithmetic control unit 200 performs operation control of the light source unit 101, operation control of the optical attenuator 105, operation control of the polarization adjuster 106, operation control of the CCD image sensor 115, and the like.

  The arithmetic control unit 200 includes, for example, a microprocessor, a RAM, a ROM, a hard disk drive, a communication interface, etc., as in a conventional computer. 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 may include various circuit boards, for example, a circuit board for forming an OCT image. 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 fundus camera unit 2, the display device 3, the OCT unit 100, and the calculation control unit 200 may be configured integrally (that is, in a single housing) or separated into two or more housings. It may be.

[Control system]
The configuration of the control system of the ophthalmologic photographing apparatus 1 will be described with reference to FIGS. 3 and 4.

  Incidentally, the ophthalmologic photographing apparatus 1 is configured to be able to perform follow-up photographing and subsequent processing. Follow-up imaging is an imaging technique for acquiring a tomographic image by scanning the same position as the past with light with reference to the front image of the eye to be examined acquired in the past. Further, the post-processing includes processing for evaluating an error in the light scanning position in follow-up imaging. In other words, the post-processing includes a process for evaluating a shift between a scanning position in past imaging and a scanning position in follow-up imaging based on the front image obtained in the past imaging. The ophthalmic image processing apparatus according to the embodiment executes this post-processing.

  Before explaining the control system, the follow-up shooting which is the premise thereof will be briefly explained. In follow-up imaging, control of each unit of the ophthalmologic imaging apparatus 1 is executed by the control unit 210 (particularly the main control unit 211).

  Follow-up shooting is to perform the current shooting while reproducing the scanning position in the previous shooting. As the preparation stage, a patient selection screen (not shown) is displayed on the display unit 240A. On the patient selection screen, a function for selecting a patient to be a subject for follow-up imaging (patient selection unit), a function for displaying patient information (patient information display unit), and a function for displaying imaging information (imaging) Information display section). Various operation units (software keys) are provided on the patient selection screen.

  The patient selection unit is provided with an input space for a search query, a calendar for selecting an imaging date (such as the last imaging date in the past), and the like. When input is made to the patient selection unit, the control unit 210 searches for patient information stored in the information storage device (the storage unit 212 of the ophthalmologic imaging apparatus 1, a database on the network, etc.), and the search result is displayed as It is displayed on the information display section. The displayed patient information includes patient ID, patient name, sex, date of birth, and the like. Note that a plurality of pieces of patient information are listed in the patient information display section when the shooting date is selected on the calendar. In that case, the user can select a desired patient from a plurality of pieces of patient information.

  When one patient is selected, the control unit 210 acquires imaging information related to the patient from the information storage device and causes the imaging information display unit to display the acquired imaging information. When a plurality of shootings have been performed in the past, shooting information for each shooting is listed in time series. The shooting information includes the shooting date, shooting time, data storage destination (file number, etc.), whether follow-up shooting is performed, OCT measurement scan mode (described later), left / right eye identification information, fixation position, analysis Information on processing (such as retinal thickness analysis).

  When the user selects shooting information to be referred to in this follow-up shooting, the control unit 210 acquires image data obtained by shooting corresponding to the selected shooting information from the information storage device, and an image based on the image data. (Front image and tomographic image) are displayed on the display 240A. At this time, the display screen is switched from the patient selection screen to an image display screen (not shown). The user observes the displayed image and determines whether to perform follow-up shooting with reference to the front image. When referring to another front image, the same determination is made by displaying another image obtained by the photographing or an image obtained by another photographing. When the front image to be referred to is determined by the user, the control unit 210 displays the front image (reference front image, first front image) on the display unit 240A, and shifts to a state for waiting for a follow-up shooting start instruction. To do.

  When a predetermined imaging start instruction is input, the control unit 210 acquires a near-infrared moving image of the eye E in real time. Then, the control unit 210 performs tracking described later while performing image matching between the frame of the near-infrared moving image (second front image, follow-up front image) and the reference front image. OCT measurement is performed in the same scan mode as the imaging. This OCT measurement is started, for example, at a timing when it is determined that tracking is suitably performed. In this OCT measurement, scanning in the same scan mode is repeated a predetermined number of times. The image forming unit 220 forms final image data by superimposing a plurality of image data acquired by this repeated scanning.

  The image data of the OCT image obtained by such follow-up imaging includes patient information, scanning position information in this follow-up imaging, a frame of the near-infrared moving image obtained by this follow-up imaging, The information is stored in the storage unit 212 in association with imaging information, information about past imaging referred to (scanning position information, imaging information, image data, and the like). Here, the frames of the near-infrared moving image to be stored are, for example, a frame acquired first and a frame acquired last in a period during which OCT measurement is performed.

  This is the end of the description of the example of processing executed in follow-up shooting, and the description returns to the description of the control system.

(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 aforementioned microprocessor, 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, the main control unit 211 controls the focusing drive unit 31A, the optical path length changing unit 41, and the galvano scanner 42 of the fundus camera unit 2, and further the light source unit 101, the optical attenuator 105, and the polarization adjuster 106 of the OCT unit 100. To do.

  The focusing drive 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 also move an optical system provided in the fundus camera unit 2 in a three-dimensional manner by controlling an optical system drive unit (not shown). This control is used in alignment and tracking. Tracking is to move the apparatus optical system in accordance with the eye movement of the eye E. When tracking is performed, alignment and focusing are performed in advance. Tracking is a function of maintaining a suitable positional relationship in which the alignment and focus are achieved by causing the position of the apparatus optical system to follow the eye movement.

  Further, the main control unit 211 performs processing for writing data into the storage unit 212 and processing for reading data from the storage unit 212. The main control unit 211 includes a display control unit 2111 that displays various types of information on the display unit 240A. The display control unit 2111 functions as an example of a “first display control unit” and a “second display control unit”. Processing executed by the display control unit 2111 will be described later.

(Memory part)
The storage unit 212 stores various data. Examples of the data stored in the storage unit 212 include OCT image image data, fundus image data, and examined eye information. 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.

  The storage unit 212 stores follow-up shooting information 2121. The follow-up shooting information 2121 is information related to follow-up shooting performed in the past. The follow-up imaging information 2121 includes a front image (first front image and reference front image) of the eye E to be referred to in the follow-up imaging performed in the past, and the eye E to be acquired acquired in the follow-up imaging. At least a front image (second front image, follow-up front image). The latter is a frame of a near-infrared moving image acquired in real time in this follow-up shooting. This frame is, for example, the first acquired frame and the last acquired frame in the period during which the OCT measurement is performed.

  Further, the follow-up imaging information 2121 includes reference scanning position information indicating the scanning position (first scanning position, reference scanning position) of the tomographic image formed together with the reference front image, and the follow-up front image in this follow-up imaging. And follow-up scanning position information indicating the scanning position (second scanning position, follow-up scanning position) of the tomographic image acquired together. The scanning position information includes, for example, control information of the galvano scanner 42 in the scanning, that is, information indicating the direction of the galvano scanner 42. Further, when the front image is acquired in real time during the OCT measurement, the scanning position information may include the coordinates of the scanning position (scanning trajectory) reflected in the front image.

(Image forming part)
The image forming unit 220 forms tomographic image data of the fundus oculi Ef based on the detection signal from the CCD image sensor 115. This process includes processes such as noise removal (noise reduction), filter processing, FFT (Fast Fourier Transform), and the like, as in the conventional spectral domain type optical coherence tomography.

  When scanning is continuously performed a predetermined number of times in the same scan mode, the image forming unit 220 performs processing for forming new image data by superimposing image data of a plurality of tomographic images obtained by the continuous scanning. . This superposition process is performed for the purpose of removing random noise mixed in the image data.

  In the case of another type of OCT apparatus, the image forming unit 220 executes a known process corresponding to the type. The image forming unit 220 includes, for example, the circuit board described above. The image forming unit 220 functions as a “tomographic image forming unit” together with an optical system used in OCT measurement. In this specification, “image data” and an “image” based on the “image data” may be identified.

(Image processing unit)
The image processing unit 230 performs various types of image processing and analysis processing on the OCT image formed by the image forming unit 220. For example, the image processing unit 230 executes various correction processes such as image brightness correction and dispersion correction. Further, the image processing unit 230 executes a layer thickness analysis process for analyzing the OCT image and acquiring a retinal thickness distribution. The image 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 image processing unit 230 executes known image processing such as interpolation processing for interpolating pixels between tomographic images to form image data of a three-dimensional image of the fundus oculi Ef. Note that the image data of a three-dimensional image means image data in which pixel positions are defined by a three-dimensional coordinate system. As image data of a three-dimensional image, there is image data composed of voxels arranged three-dimensionally. This image data is called volume data or voxel data. When displaying an image based on volume data, the image processing unit 230 performs rendering processing (volume rendering, MIP (Maximum Intensity Projection), etc.) on the volume data, and views the image from a specific gaze direction. Image data of a pseudo three-dimensional image is formed. This pseudo three-dimensional image is displayed on a display device such as the display unit 240A.

  It is also possible to form stack data of a plurality of tomographic images as image data of a three-dimensional image. The stack data is image data obtained by three-dimensionally arranging a plurality of tomographic images obtained along a plurality of scanning lines based on the positional relationship of the scanning lines. That is, stack data is image data obtained by expressing a plurality of tomographic images originally defined by individual two-dimensional coordinate systems by one three-dimensional coordinate system (that is, by embedding them in one three-dimensional space). is there.

  The image processing unit 230 includes an information acquisition unit 231, a calculation unit 232, and a photographing suitability determination unit 233. These perform post-processing of post-up photography. As described above, this post-processing is to evaluate an error in the light scanning position in follow-up imaging.

(Information acquisition unit)
The information acquisition unit 231 analyzes the front image (reference front image) referred to in the follow-up shooting and the front image (follow-up front image) obtained in the follow-up shooting, and positions between these front images. Get shift information. This positional shift information is information that quantitatively represents how much the drawing position of the fundus oculi Ef in the front image is shifted.

  The information acquisition unit 231 calculates, for example, a translational displacement and a rotational displacement between the reference front image and the follow-up front image as the positional deviation information. The translational shift corresponds to a displacement in the form of the fundus oculi Ef drawn on the front image in the spreading direction of the front image (in the xy plane). The rotational displacement is equivalent to the displacement in the rotational direction of the form centering on a predetermined position in the xy plane. The translational displacement and the rotational displacement are expressed as affine transformation between the coordinates of both front images, for example. Further, only one of the translational displacement and the rotational displacement may be calculated.

  An example of a method for calculating the parallel displacement and the rotational displacement will be described. First, the information acquisition unit 231 analyzes each front image and specifies an image position corresponding to a predetermined characteristic part of the fundus oculi Ef. Examples of the characteristic site include the center / edge of the optic nerve head, the macular center, specific blood vessels, blood vessel bifurcations, and lesions.

  Next, the information acquisition unit 231 obtains a displacement between the coordinates of the image position in the reference front image and the coordinates of the image position in the follow-up front image. In this process, for example, for each of the image positions of a plurality of feature parts, the coordinates of the image positions in both front images are substituted into a two-dimensional affine transformation conversion formula to determine the components of the affine transformation matrix. Note that the coordinates of the image position are address information assigned in advance to each pixel. The affine transformation matrix obtained in this way includes information on both translational displacement and rotational displacement between front images.

(Calculation unit)
The calculation unit 232 calculates the evaluation value of the error of the scanning position in follow-up imaging based on the positional deviation information acquired by the information acquisition unit 231. Examples of the evaluation value are calculated based on the area of a predetermined image area defined by the scanning position of the reference front image and the scanning position of the follow-up front image, and based on the displacement between these scanning positions. There is a thing. It is also possible to calculate the evaluation value based on factors other than these. Further, the evaluation value may be calculated by combining different factors.

  The calculation unit 232 includes a relative position calculation unit 2321, a determination unit 2322, an area calculation unit 2323, a displacement calculation unit 2324, and an evaluation value calculation unit 2325. The calculation of the evaluation value based on the area is executed by the relative position calculation unit 2321, the determination unit 2322, and the area calculation unit 2323. The calculation of the evaluation value based on the displacement is executed by the relative position calculation unit 2321, the displacement calculation unit 2324, and the evaluation value calculation unit 2325.

(Relative position calculation unit)
As described above, the follow-up imaging information 2121 stored in the storage unit 212 includes the reference scanning position information and the follow-up scanning position information. The relative position calculation unit 2321 calculates relative position information between the reference scanning position and the follow-up scanning position based on the positional deviation information acquired by the information acquisition unit 231.

  By the way, follow-up imaging reproduces a past scanning position and performs OCT measurement. Therefore, ideally, the reference scanning position and the follow-up scanning position are the same. However, it is practically difficult to completely reproduce the scanning position due to the influence of microscopic fixation and the like. On the other hand, since the reference scanning position and the follow-up scanning position match if there is no fixation fine movement or the like, the relative position between these scanning positions is the displacement of the eye E due to fixation fine movement or the like, that is, the reference front image. This corresponds to a positional shift between the follow-up front image. This positional deviation is acquired as positional deviation information by the information acquisition unit 231.

  For example, the relative position calculation unit 2321 displaces the reference scanning position by the amount of positional deviation indicated in the positional deviation information, so that the position corresponding to the reference scanning position in the follow-up front image, that is, the reference scanning position is completely reproduced. An ideal scanning position realized in this case is obtained. The relative position information indicates a relative position between this ideal scanning position and a scanning position (follow-up scanning position) executed in actual follow-up imaging. Thus, the relative position information is substantially the same value as the positional deviation information. That is, the displacement information represents the displacement between the front images, and the relative position information represents the displacement between the scanning positions. The relative position calculation unit 2321 sends the acquired relative position information to the determination unit 2322 and the displacement calculation unit 2324.

(Judgment part)
For example, the relative positions of the reference scanning position and the follow-up scanning position are as shown in FIGS. 5A to 5D. In these drawings, a symbol R indicates a follow-up scanning position in the follow-up front image. Reference sign R0 indicates a reference scanning position in the follow-up front image, that is, a reference scanning position displaced based on positional deviation information (relative position information). FIG. 5A shows an example where only a translational displacement is present. FIG. 5B shows an example in which only the rotational displacement is present and both scanning positions intersect in the vicinity of the center. FIG. 5C shows an example in which only the rotational displacement is present and both scanning positions intersect in the vicinity of the scanning start point. FIG. 5D shows an example in which both a translational displacement and a rotational displacement are present. In addition, the aspect of the relative position of the scanning position is not limited to these. The scan mode is not limited to line scan.

  The determination unit 2322 determines whether a shared position exists between the reference scanning position and the follow-up scanning position based on the positional deviation information (relative position information). The shared position represents a position (region) where the reference scanning position and the follow-up scanning position overlap.

  The shared position is a zero-dimensional area (point), a one-dimensional area (line), or a two-dimensional area (plane). In FIGS. 5A to 5D, since the reference scanning position and the follow-up scanning position are both line segments, the shared position is the intersection when they intersect, and the shared position is not intersected when they intersect. None. Although not shown, when the displacement direction of the reference scanning position and the follow-up scanning position is only the length direction and the displacement amount is less than the length, the shared position of these two scanning positions is It becomes a one-dimensional area. When a three-dimensional scan is used as the scan mode, both the reference scan position and the follow-up scan position are two-dimensional areas, and these shared positions are a zero-dimensional area, a one-dimensional area, or 2 according to the relative positional relationship. It becomes a dimension area.

  The process for determining whether or not the shared position exists is performed based on the coordinates of the reference scanning position and the coordinates of the follow-up scanning position in the follow-up front image. For example, the determination unit 2322 collates the coordinates of the reference scanning position with the coordinates of the follow-up scanning position, and determines that there is a shared position when there is a common coordinate between these scanning positions. Is determined to have no shared position. By this process, the coordinates of the shared position in the follow-up front image are also obtained. These coordinates are coordinates in a two-dimensional coordinate system defined in advance in the follow-up front image.

  The determination unit 2322 sends a determination result related to the shared position (presence / absence of existence, coordinates of the shared position, etc.) to the area calculation unit 2323.

(Area calculation part)
The area calculation unit 2323 calculates the area of the image region defined by the reference scanning position and the follow-up scanning position based on the positional deviation information (relative position information). Here, as described above, the positional deviation information and the relative positional information are substantially the same value. In addition, the image area whose area is to be calculated is a partial area of the follow-up front image. A method for defining the image area based on the two scanning positions is determined in advance. Further, the area calculation process can be performed in an arbitrary manner. The area calculation process may include, for example, a process for counting the number of pixels in the image area, a process for obtaining a mathematical expression (such as a mathematical expression) indicating the boundary area of the image area, and an integration operation. The area as the calculation result may be a numerical value that uniquely represents the two-dimensional size of the image region.

  In this area calculation process, the area calculation unit 2323 performs different calculation processes according to the determination result by the determination unit 2322. For example, the area calculation unit 2323 executes different calculation processes depending on whether the shared position exists between the reference scanning position and the follow-up scanning position or not. Specific examples will be described below. In the following specific example, when the two scanning positions are line segments, the case where these scanning positions intersect and the case where they do not intersect are considered separately. That is, the case where the shared position exists and the case where it does not exist are considered separately. Furthermore, regarding the case where two scanning positions intersect, the case where the intersection is the end point of the scanning position and the case where it is not the end point will be considered separately. Whether or not the intersection is an end point can be easily determined based on the coordinates of the two scanning positions and the coordinates of the intersection. Note that the end points of the scanning position indicate the scanning start point and the scanning end point of the line-shaped scanning position. Further, in the following specific examples, the scanning position is a line segment, so there is only one intersection, but when the scanning position is a curve, there may be two or more intersections.

  When the two scanning positions intersect as shown in FIGS. 5B and 5C, the area calculation unit 2323 obtains the area of the image area defined by the end points and the intersections of the two scanning positions. More specifically, the area calculation unit 2323 calculates the area of the triangle formed by the end points of the two scanning positions located on one side with respect to the intersection and the two scanning positions located on the other side. The sum of the area of the triangle formed by the end point and the intersection can be calculated and used as the area of the image region.

  For example, when an intersection exists at a position other than the end point of the scanning position as shown in FIG. 5B, the area calculation unit 2323 has two scanning positions R0 and R located on the right side with respect to the intersection C as shown in FIG. 6A. The area of the triangle TR1 having the vertexes of the end points (scan end points) R0E, RE and the intersection C is calculated. In addition, the area calculation unit 2323 calculates the area of the triangle TR2 having the two scanning positions R0 and R (end points of scanning) R0S and RS located on the left side of the intersection C and the intersection C as the vertices. Furthermore, the area calculation unit 2323 adds the area of the triangle TR1 and the area of the triangle TR2. This sum is the target area value.

  As another example, when two scanning positions intersect at an end point (scanning start point) as shown in FIG. 5C, the area calculation unit 2323, as shown in FIG. Point), the scanning end point of the reference scanning position R0 and the scanning end point of the follow-up scanning position R, the area of the triangle TR is obtained.

  When two scanning positions intersect at an end point of one scanning position and an end point other than the other scanning position, for example, the intersection, an end point on the opposite side of one scanning position, and the other scanning position The area of a triangle whose apex is one end point (for example, an end point located on the same side as the opposite end point) can be obtained.

  On the other hand, when the two scanning positions do not intersect as shown in FIGS. 5A and 5D, the area calculation unit 2323 calculates a square area defined by the two scanning positions and calculates the area of the target image region. To do. More specifically, when the two scanning positions do not intersect, the area calculation unit 2323 sets the reference scanning position R0 and the follow-up scanning position R as two sides as shown in FIGS. 6C and 6D, and The area of a quadrangle QU having two sides connecting two end points of these scanning positions is obtained.

  The area calculation unit 2323 sends the area obtained as described above to the evaluation value calculation unit 2325.

(Displacement calculation unit)
The displacement calculation unit 2324 calculates a displacement between the reference scanning position and the follow-up scanning position based on the positional deviation information (relative position information). The method for calculating this displacement is arbitrary. Hereinafter, a specific example of the displacement calculation process will be described with reference to FIG.

  FIG. 7 shows a line-segment reference scanning position R0 and a follow-up scanning position R, respectively. In calculating the displacement, it may be unquestioned whether or not the two scanning positions intersect.

  The displacement calculation unit 2324 first specifies a predetermined position on each of the scanning positions R0 and R. This specifying process can be performed based on the coordinates of the respective points of the line-shaped scanning positions R0 and R. Examples of the predetermined position include a scan start point, a scan end point, and a midpoint. When a scanning position other than a line segment is considered, a predetermined position corresponding to the form can be used. In addition, the same type of predetermined position is applied to the two scanning positions to be compared. For example, when the scan start point is used as the predetermined position, both scan start points are specified. Further, when a plurality of types of predetermined positions are specified, the types are associated with each predetermined position.

  Next, the displacement calculation unit 2324 calculates the displacement between the coordinates of the predetermined position at the reference scanning position R0 and the coordinates of the predetermined position at the follow-up scanning position R. This calculation process can be performed using a two-dimensional coordinate system defined in advance in the follow-up front image. Also, the displacement can be obtained by counting the number of pixels between two predetermined positions. The displacement calculated here is a displacement between predetermined positions of the same type. For example, this displacement is a displacement between the scanning start points, and is not a displacement between the scanning start point and the midpoint.

  FIG. 7 shows a case where three types of scanning start point, scanning end point, and middle point are applied as the predetermined position. In FIG. 7, the displacement between the scan start point R0S at the reference scan position R0 and the scan start point RS at the follow-up scan position R is indicated by the symbol DS. Further, the displacement between the scanning end point R0E at the reference scanning position R0 and the scanning end point RE at the follow-up scanning position R is indicated by a symbol DE. Further, the displacement between the middle point R0M of the reference scanning position R0 and the middle point RM of the follow-up scanning position R is indicated by a symbol DM.

  The displacement calculation unit 2324 sends the displacement obtained as described above to the evaluation value calculation unit 2325.

(Evaluation value calculator)
The evaluation value calculation unit 2325 calculates an evaluation value of a scanning position error in follow-up imaging. As information provided for this calculation process, the evaluation value calculation unit 2325 receives the area information obtained by the area calculation unit 2323 and the displacement information obtained by the displacement calculation unit 2324. Hereinafter, an example of the evaluation value calculation process based on the area, an example of the evaluation value calculation process based on the displacement, and an example of the evaluation value calculation process combining both will be described.

  In addition, although this embodiment demonstrates the case where both evaluation value calculation processes are executable, the structure which can implement only one side may be sufficient. Further, the evaluation value may be calculated based on other arbitrary information that reflects the error of the scanning position in follow-up imaging.

(Evaluation value calculation process based on area)
As an example of processing for obtaining an evaluation value from the area of the image region calculated by the area calculation unit 2323, the evaluation value calculation unit 2325 calculates a product of the area of the image region and a predetermined weight as a predetermined maximum value of the evaluation value. It is possible to perform arithmetic processing to subtract from. This arithmetic processing is expressed as, for example, the following equation.

Here, S ₁ represents the evaluation value based on the area, S _{1 and max} represent the maximum value of the evaluation value set in advance, a represents the weight set in advance, and Area is calculated by the area calculation unit 2323. Represents the area made. The maximum value S1 _{, max} and the weight a can be arbitrarily set. For example, the maximum values S _{1 and max} are set to 100, and the weight a is set based on the set value of the maximum value and the numerical value of the area.

According to such processing, as the area is smaller, i.e. as the error of the scanning position in the follow-up photography is small, the value of the evaluation values S ₁ becomes large.

(Evaluation value calculation process based on displacement)
As an example of processing for obtaining an evaluation value from the displacement calculated by the displacement calculation unit 2324, the evaluation value calculation unit 2325 performs arithmetic processing for subtracting the product of this displacement and a predetermined weight from a predetermined maximum value of the evaluation value. be able to. This arithmetic processing is expressed as, for example, the following equation.

Here, S ₂ represents the evaluation value based on the displacement, S _{2, max} represents the maximum value of the preset the evaluation value, b, c and d represents a weight which is set in advance, DM, DS and DE represents the displacement of the midpoint, the scan start point, and the scan end point calculated by the displacement calculator 2324, respectively. The maximum values S2 _{, max} and the weights b to d can be set arbitrarily. For example, the maximum values S _{2 and max} are set to 100, and the weights b to d are respectively set based on the set value of the maximum value and the numerical value of the area.

According to such processing, the more displacement is small, that is as the error of the scanning position in the follow-up photography is small, the evaluation value S ₂ is increased. In this example, the evaluation value is calculated in consideration of the three points of the middle point, the scanning start point, and the scanning end point. However, the evaluation value is calculated in consideration of one or two of these points. You can also It is also possible to calculate the displacement at points other than these and take this into account.

(Evaluation value calculation process based on area and displacement)
As an example of processing for obtaining an evaluation value based on the area of the image area calculated by the area calculation unit 2323 and the displacement calculated by the displacement calculation unit 2324, the evaluation value calculation unit 2325 is an operation that integrates the above cases. Equations can be used. This arithmetic expression is expressed as follows, for example.

Here, S represents an evaluation value based on the area and displacement, S _max represents a maximum value of the preset evaluation value, a to d represent preset weights, and Area is calculated by the area calculation unit 2323. The calculated area is represented, and DM, DS, and DE represent the displacement of the midpoint, the scan start point, and the scan end point calculated by the displacement calculation unit 2324, respectively. The maximum value S _max and the weights a to d can be set arbitrarily. For example, the maximum value S _max is set to 100, and the weights a to d are set based on the maximum value setting value, the numerical value of the area, and the like.

  According to such a calculation process, the evaluation value S increases as the area and / or displacement decreases, that is, as the error of the scanning position in follow-up imaging decreases.

  Information on the evaluation value calculated by the evaluation value calculation unit 2325 is sent to the photographing suitability determination unit 233.

(Shooting suitability determination unit)
The shooting suitability determination unit 233 determines whether the follow-up shooting is appropriate based on the evaluation value calculated by the evaluation value calculation unit 2325. This process is performed by, for example, comparing a preset numerical range with an evaluation value.

  A specific example of processing executed by the imaging suitability determination unit 233 will be described. When the evaluation value increases as the error decreases as described above, the imaging suitability determination unit 233 determines whether the calculated evaluation value is equal to or greater than a predetermined threshold value. When the evaluation value is greater than or equal to the threshold value, the imaging suitability determination unit 233 determines that the follow-up has been properly performed. Conversely, when the evaluation value is less than the threshold value, the imaging suitability determination unit 233 determines that the follow-up imaging has not been properly performed.

  In this example, one threshold is used, but the suitability of follow-up shooting may be determined step by step by using two or more thresholds.

  The imaging suitability determination unit 233 sends the determination result to the control unit 210. Further, arbitrary information used in the above process by the image processing unit 230 or information generated in the middle of the above process may be sent to the control unit 210. Further, when the suitability for follow-up photography is presented using the evaluation value itself, it is not necessary to provide the photography suitability determination unit 233.

  The image processing unit 230 that functions as described above includes, for example, the aforementioned microprocessor, RAM, ROM, hard disk drive, circuit board, and the like. In a storage device such as a hard disk drive, a computer program for causing the microprocessor to execute the above functions is stored in advance.

(User interface)
The user interface 240 includes a display unit 240A and an operation unit 240B. The display unit 240A includes the display device of the arithmetic control unit 200 and the display device 3 described above. The operation unit 240B includes the operation device of the arithmetic control unit 200 described above. The operation unit 240B may include various buttons and keys provided on the housing of the ophthalmologic photographing apparatus 1 or outside. For example, when the fundus camera unit 2 has a housing similar to that of a conventional fundus camera, the operation unit 240B may include a joystick, an operation panel, or the like provided on the housing. The display unit 240 </ b> A may include various display devices such as a touch panel provided on the housing of the fundus camera unit 2.

  The display unit 240A and the operation unit 240B 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 240B includes the touch panel and a computer program. The operation content for the operation unit 240B is input to the control unit 210 as an electrical signal. Further, operations and information input may be performed using a graphical user interface (GUI) displayed on the display unit 240A and the operation unit 240B.

(Signal light scanning and OCT image)
Examples of the scanning mode (scan mode) of the signal light LS by the ophthalmologic photographing apparatus 1 include a horizontal scan, a vertical scan, a cross scan, a radial scan, a circular scan, a concentric scan, and a spiral (spiral) scan. These scanning modes are selectively used as appropriate in consideration of the observation site of the fundus, the analysis target (such as retinal thickness), the time required for scanning, the precision of scanning, and the like.

  The horizontal scan scans the signal light LS in the horizontal direction (x direction). The horizontal scan also includes an aspect in which the signal light LS is scanned along a plurality of horizontal scanning lines arranged in the vertical direction (y direction). In this aspect, it is possible to arbitrarily set the scanning line interval. Further, the above-described three-dimensional image can be formed by sufficiently narrowing the interval between adjacent scanning lines (three-dimensional scanning). The same applies to the vertical scan.

  In the cross scan, the signal light LS is scanned along a cross-shaped trajectory composed of two linear trajectories (straight trajectories) orthogonal to each other. In the radiation scan, the signal light LS is scanned along a radial trajectory composed of a plurality of linear trajectories arranged at a predetermined angle. The cross scan is an example of a radiation scan.

  In the circle scan, the signal light LS is scanned along a circular locus. In the concentric scan, the signal light LS is scanned along a plurality of circular trajectories arranged concentrically around a predetermined center position. A circle scan is an example of a concentric scan. In the spiral scan, the signal light LS is scanned along a spiral (spiral) locus while the radius of rotation is gradually reduced (or increased).

  Since the galvano scanner 42 is configured to scan the signal light LS in directions orthogonal to each other, the signal light LS can be scanned independently in the x direction and the y direction, respectively. Further, by simultaneously controlling the directions of the two galvanometer mirrors included in the galvano scanner 42, the signal light LS can be scanned along an arbitrary locus on the xy plane. Thereby, various scanning modes as described above can be realized.

  By scanning the signal light LS in the above-described manner, a tomographic image on a plane stretched by the direction along the scanning line (scanning trajectory) and the fundus depth direction (z direction) can be acquired. In addition, the above-described three-dimensional image can be acquired particularly when the scanning line interval is narrow.

(About display control)
An example of display control according to this embodiment will be described. Display control is executed by the display control unit 2111.

  As the first display control, the display control unit 2111 causes the reference front image and / or the follow-up front image to be displayed on the display unit 240A, and is based on the positional deviation information acquired by the information acquisition unit 231. A reference scanning position image indicating the position and a follow-up scanning position image indicating the follow-up scanning position are displayed superimposed on the front image.

  Here, instead of the positional deviation information, relative positional information equivalent to this can be referred to. The reference scanning position image is an example of a “first scanning position image”, and the follow-up scanning position image is an example of a “second scanning position image”.

  When one of the reference front image and the follow-up front image is displayed, the reference scanning position image and the follow-up scanning position image are displayed over the one front image. When both front images are displayed, the reference scanning position image and the follow-up scanning position image may be displayed superimposed on each front image, or these scanning position images may be superimposed on only one front image. It may be displayed.

  The display control unit 2111 can display the reference scanning position image and the follow-up scanning position image in different modes. For example, two scanning position images can be displayed in different colors, displayed in different thicknesses, or displayed in different densities. Also, identification information (character string information, image information, etc.) can be attached to each scanning position image. Further, the two scanning position images may be always displayed in different modes, or may be switched to different display modes in response to a predetermined trigger.

  An example of information displayed by the first display control as described above is shown in FIG. FIG. 8 shows a state in which a reference scanning position image indicated by a broken line and a follow-up scanning position image indicated by a solid line are superimposed and displayed on a follow-up front image representing the fundus morphology. The follow-up scanning position image indicates the scanning position actually applied in this follow-up imaging. The reference scanning position image shows an ideal scanning position when follow-up shooting is performed without error. In the example shown in FIG. 8, the portion indicated by the solid line is scanned due to the influence of eye movement or the like, where the portion indicated by the broken line should be scanned.

  As the second display control, the display control unit 2111 can display information indicating an error in the scanning position in follow-up imaging. For example, the display control unit 2111 can cause the display unit 240A to display the evaluation value calculated by the evaluation value calculation unit 2325. The evaluation value may be displayed alone, or may be displayed together with the front image and display information by the first display control. In addition, the determination result by the imaging suitability determination unit 233 can be displayed instead of or together with the evaluation value. This determination result may be character string information such as “appropriate” or “inappropriate”, or may be image information.

[Action / Effect]
The operation and effect of the ophthalmologic photographing apparatus 1 will be described.

  The ophthalmologic photographing apparatus 1 can perform follow-up photographing. The photographing unit (fundus camera unit 2) photographs the eye E and acquires a front image. The tomographic image forming unit (OCT optical system, image forming unit 220) scans the eye E with light to form a tomographic image. The storage unit 212 stores a first front image of the eye E and a second front image acquired in follow-up imaging performed with reference to the first front image. The information acquisition unit 231 analyzes the first front image and the second front image and acquires positional deviation information between the front images; the calculation unit 232 performs the follow-up based on the positional deviation information. An evaluation value of a scanning position error in photographing is calculated. According to such an ophthalmologic photographing apparatus 1, it is possible to quantitatively evaluate the degree of error in follow-up photographing.

<Second Embodiment>
Follow-up shooting is performed with reference to a reference front image acquired in the past. Therefore, the accuracy and accuracy of follow-up shooting depend on the state of the reference front image. In this embodiment, in addition to the arbitrary configuration described in the first embodiment, an ophthalmologic imaging apparatus that can determine whether a reference front image used for follow-up imaging is appropriate will be described.

  A configuration example of the ophthalmologic photographing apparatus according to this embodiment is shown in FIG. The ophthalmologic photographing apparatus includes a candidate image determination unit 234 in addition to the configuration of the first embodiment (see FIGS. 1 to 4). Candidate image determination unit 234 is provided in image processing unit 230. Since the configuration other than this is the same as that of the first embodiment, the description is omitted unless otherwise specified.

  When follow-up shooting is performed, the storage unit 212 stores one or more images (candidate images) that are candidates for the reference front image (first front image). The candidate image determination unit 234 performs a process of determining whether or not the candidate image is appropriate as a reference front image by analyzing each candidate image. When there are two or more candidate images determined to be appropriate, for example, the most appropriate candidate image is selected as the reference front image.

  This determination process is executed based on, for example, predetermined information regarding the candidate image. This information includes information in real space and information in frequency space. Examples of information in real space include flare amount and contrast. Examples of information in the frequency space include a blur amount and frequency characteristics. These pieces of information are obtained by the candidate image determination unit 234.

  The flare amount is, for example, a distribution of pixels having a pixel value (such as a luminance value) equal to or greater than a predetermined threshold (such as a maximum value) in the candidate image. This distribution is, for example, the ratio of such pixels in all pixels. The candidate image determination unit 234 determines that the candidate image is appropriate as the reference front image when the obtained flare amount is equal to or less than a predetermined threshold value, for example. Here, it is determined that the smaller the flare amount is, the more suitable as the reference front image.

  Contrast is calculated | required by the arbitrary well-known techniques performed based on the pixel value (luminance value) of a candidate image, for example. Candidate image determination unit 234 determines that the candidate image is appropriate as the reference front image when the obtained contrast is equal to or greater than a predetermined threshold. Here, it is determined that the higher the contrast, the more appropriate as the reference front image.

  The amount of blur can be calculated, for example, based on the signal intensity of the spatial frequency component obtained by decomposing the candidate image into spatial frequencies. Candidate image determination unit 234 determines that the candidate image is appropriate as the reference front image, for example, when the obtained blur amount is equal to or less than a predetermined threshold value. Here, it is determined that the smaller the amount of blur, the more appropriate as the reference front image.

  The frequency characteristic is obtained, for example, by decomposing a candidate image into a spatial frequency and obtaining characteristics of the obtained spatial frequency component. Candidate image determination unit 234 determines that the candidate image is appropriate as a reference front image when the obtained frequency characteristics satisfy a predetermined condition, for example. Here, it is determined that the higher the degree of satisfaction of the condition is, the more appropriate as the reference front image.

  The control unit 210 performs notification control based on the determination result by the candidate image determination unit 234. The control unit 210 and the control target in the notification control function as an example of “notification unit”.

  As a specific example of the notification control, the display control unit 2111 displays information indicating the determination result on the display unit 240A. This display information is, for example, character string information or image information indicating whether or not the candidate image is suitable as a reference front image. In addition, one or more candidate images (its thumbnails) subjected to the determination process by the candidate image determination unit 234 may be displayed on the display unit 240A, and information indicating the determination result may be displayed in a list. Further, the photographing information of candidate images may be displayed as a list on the photographing information display section of the patient selection screen described in the first embodiment, and the determination result may be displayed in this list. When such notification control is performed, the display control unit 2111 functions as an example of a “notification control unit”.

  The notification control is not limited to such display control. For example, the control unit 210 controls a sound output unit (not shown) so that sound information indicating a determination result can be output.

  When a determination result that a certain candidate image is inappropriate as a reference front image is obtained, follow-up shooting based on the candidate image can be prohibited. As a specific example, the control unit 210 can prohibit scanning of light by the tomographic image forming unit in response to the determination result that the candidate image is inappropriate as the reference front image. . This prohibition refers to a control mode in which OCT measurement is not executed even if an operation for starting OCT measurement is performed. The control unit 210 that performs such control is an example of a “prohibition control unit”. For example, assuming that follow-up shooting is performed using a candidate image determined to be inappropriate, an operation for canceling this prohibited state can be performed.

  According to such an ophthalmologic photographing apparatus, it is possible to determine whether or not the reference front image used for follow-up photographing is appropriate. Therefore, it is possible to perform follow-up photographing using a suitable reference front image. Therefore, the degree of error in follow-up shooting can be quantitatively evaluated as in the first embodiment, and the accuracy and accuracy of follow-up shooting can be increased.

  It is possible to configure the ophthalmologic photographing apparatus so as to have the characteristics of the second embodiment and not to have the characteristics of the first embodiment. This ophthalmologic photographing apparatus has a configuration as shown in FIG. 10, for example.

  Specifically, this ophthalmic imaging apparatus is an ophthalmic imaging apparatus capable of performing follow-up imaging, and includes an imaging unit, a tomographic image forming unit, a storage unit, a candidate image determination unit, and a notification unit. Have The imaging unit (fundus camera unit 2) acquires a front image by imaging the eye to be examined. A tomographic image forming unit (an optical system for OCT measurement, the image forming unit 220) scans the eye to be examined with light to form a tomographic image. The storage unit (storage unit 212) stores one or more candidate images that are candidates for the front image referred to in follow-up shooting. The candidate image determination unit (candidate image determination unit 234) analyzes the candidate image to determine whether the candidate image is appropriate as a reference front image for follow-up shooting. The notification unit performs notification based on the determination result by the candidate image determination unit.

  According to such an ophthalmologic photographing apparatus, it is possible to determine whether or not the reference front image used for follow-up photographing is appropriate. Therefore, it is possible to perform follow-up photographing using a suitable reference front image. Therefore, it is possible to improve the accuracy and accuracy of follow-up shooting. Note that the process executed by the candidate image determination unit 234 may be the same as described above. Moreover, you may be comprised so that execution of said display control and alerting | reporting control is possible.

<Third Embodiment>
In this embodiment, an ophthalmic image processing apparatus that receives information from an ophthalmic imaging apparatus capable of performing follow-up imaging and processes the information will be described. The ophthalmologic image processing apparatus includes a computer, for example. A part of the ophthalmic image processing apparatus may be provided outside the computer. For example, a database on a network can be used as the storage unit.

  A configuration example of the ophthalmic image processing apparatus of this embodiment is shown in FIG. This ophthalmic image processing apparatus has the same configuration as that of the first embodiment (see FIG. 4). On the other hand, this ophthalmic image processing apparatus does not have an imaging unit (fundus camera unit 2) and a tomographic image forming unit (an optical system for OCT measurement, the image forming unit 220) as in the first embodiment. Further, this ophthalmic image processing apparatus does not have a computer program for controlling these excluded components. Hereinafter, the description of the constituent parts similar to those of the first embodiment is omitted unless otherwise mentioned.

  The ophthalmic image processing apparatus according to this embodiment processes an image obtained by follow-up imaging, and includes at least a storage unit, an information acquisition unit, and a calculation unit. The storage unit (storage unit 212) stores a first front image of the eye to be examined and a second front image acquired in follow-up imaging performed with reference to the first front image. The information acquisition unit (information acquisition unit 231) analyzes the first front image and the second front image, and acquires positional deviation information between these front images. The calculation unit (calculation unit 232) calculates an evaluation value of the error of the light scanning position in the follow-up imaging based on the positional deviation information. About the structure and operation | movement of another structure part, it applies to 1st Embodiment.

  According to such an ophthalmologic image processing apparatus, it is possible to quantitatively evaluate the degree of error in follow-up imaging performed by the ophthalmologic imaging apparatus.

[Modification]
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.

  In the first and second embodiments, the optical path length difference between the optical path of the signal light LS and the optical path of the reference light LR is changed by changing the position of the optical path length changing unit 41. The method for changing the difference is not limited to this. For example, it is possible to change the optical path length difference by disposing a reflection mirror (reference mirror) in the optical path of the reference light and moving the reference mirror in the traveling direction of the reference light to change the optical path length of the reference light. Is possible. Further, the optical path length difference may be changed by moving the fundus camera unit 2 or the OCT unit 100 with respect to the eye E to change the optical path length of the signal light LS. In particular, when the measured object is not a living body part, the optical path length difference can be changed by moving the measured object in the depth direction (z direction).

  A computer program for realizing the above embodiment can be stored in any recording medium readable by a computer. Examples of the recording medium include a semiconductor memory, an optical disk, a magneto-optical disk (CD-ROM / DVD-RAM / DVD-ROM / MO, etc.), a magnetic storage medium (hard disk / floppy (registered trademark) disk / ZIP, etc.), and the like. Can be used.

  It is also possible to transmit / receive this program through a network such as the Internet or a LAN.

DESCRIPTION OF SYMBOLS 1 Ophthalmic imaging device 2 Fundus camera unit 10 Illumination optical system 30 Imaging optical system 31 Focus lens 31A Focus drive part 41 Optical path length change part 42 Galvano scanner 50 Alignment optical system 60 Focus optical system 100 OCT unit 101 Light source unit 105 Light attenuation Device 106 polarization adjuster 115 CCD image sensor 200 arithmetic control unit 210 control unit 211 main control unit 2111 display control unit 212 storage unit 2121 follow-up imaging information 220 image forming unit 230 image processing unit 231 information acquisition unit 232 calculation unit 2321 relative Position calculation unit 2322 Determination unit 2323 Area calculation unit 2324 Displacement calculation unit 2325 Evaluation value calculation unit 233 Imaging suitability determination unit 234 Candidate image determination unit 240A Display unit 240B Operation unit E Eye to be examined Ef Fundus LS Signal light LR Reference light LC Interference light

Claims (7)

An ophthalmologic imaging apparatus capable of performing follow-up imaging for acquiring a tomographic image by scanning a light at the same position as the past with reference to a front image of a subject eye acquired in the past,
A photographing unit for photographing the eye to be examined and obtaining a front image;
A tomographic image forming unit that scans the eye with light to form a tomographic image;
A storage unit that stores a first front image of the eye to be examined and a second front image acquired in follow-up imaging performed with reference to the first front image;
An information acquisition unit that analyzes the first front image and the second front image and acquires positional deviation information between the front images;
A calculation unit that calculates an evaluation value of an error of a scanning position in the follow-up imaging based on the positional deviation information, and
The storage unit stores, as the second front image, a front image obtained first and a front image obtained last in a period in which the light scan is performed in the follow-up photography. Ophthalmic imaging device. When the follow-up shooting is done,
The storage unit stores one or more candidate images that are candidates for the first front image,
A candidate image determination unit that determines whether the candidate image is appropriate as the first front image by analyzing the candidate image;
The ophthalmologic photographing apparatus according to claim 1, further comprising: a notification unit that performs notification based on a determination result by the candidate image determination unit.   The ophthalmologic photographing apparatus according to claim 2, wherein the candidate image determination unit performs the determination based on a pixel value of the candidate image.   The ophthalmologic photographing apparatus according to claim 2, wherein the candidate image determination unit obtains a spatial frequency component of the candidate image and performs the determination based on the spatial frequency component.   The ophthalmologic photographing apparatus according to any one of claims 2 to 4, wherein the notification unit includes a notification control unit that displays information indicating the determination result on a display unit.   And a prohibition control unit that prohibits scanning of the light by the tomographic image forming unit in response to the determination result that the candidate image is inappropriate as the referenced front image. The ophthalmologic photographing apparatus according to any one of claims 2 to 5. An ophthalmic image processing apparatus that processes an image obtained by follow-up imaging for scanning a light at the same position as the past with reference to a front image of the eye to be examined acquired in the past and acquiring a tomographic image,
A storage unit that stores a first front image of the eye to be examined and a second front image acquired in follow-up imaging performed with reference to the first front image;
An information acquisition unit that analyzes the first front image and the second front image and acquires positional deviation information between the front images;
A calculation unit that calculates an evaluation value of an error in the scanning position of the light in the follow-up imaging based on the positional deviation information;
The storage unit stores, as the second front image, a front image obtained first and a front image obtained last in a period in which the light scan is performed in the follow-up photography. An ophthalmic image processing apparatus.

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