JP2016174978A - Optical image measuring apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical image measuring apparatus having high transverse resolution and capable of obtaining a sharp image as a whole.SOLUTION: An optical system of the optical image measuring apparatus according to the present embodiment, includes: a scanning part for changing an irradiation position of a signal light to an object; and a focal position change part for changing a focal position of the signal light, and detects interference light between return light of each signal light and reference light. An image forming part forms a tomographic image from a plurality of detection results of interference light corresponding to a plurality of irradiation positions of the signal light. A control part controls the optical system and repetitively irradiates the plurality of irradiation positions with the signal light, while changing the focal position. A synthetic tomographic image forming part forms one synthetic tomographic image from two or more tomographic images formed on the basis of the repetitive irradiation results of the signal light. The synthetic tomographic image forming part includes a partial image specification part that specifies, for each tomographic image, a partial image of the tomographic image including an image area equivalent to the corresponding focal position, and synthesizes two or more specified partial images to form a synthetic tomographic image.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an optical image measurement technique for acquiring an image of an object using optical coherence tomography (OCT).

  In recent years, OCT that forms an image representing a surface form or an internal form of an object using a light beam from a laser light source or the like has attracted attention. 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 device irradiates a target with a beam of low coherence light, superimposes the reflected light and reference light to generate interference light, acquires the spectral intensity distribution of this interference light, and performs Fourier transform Is used to image the form of the object in the depth direction (z direction). 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. ing. 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. A spectral domain type OCT apparatus is also disclosed in Patent Document 2.

  In Patent Document 3, the wavelength of light irradiated on an object is scanned (wavelength sweep), and interference intensity obtained by superimposing reflected light of each wavelength and reference light is detected to obtain a spectral intensity distribution. An OCT apparatus is described that obtains an image of the form of an object by performing Fourier transform on the acquired image. Such an OCT apparatus is called a swept source type. The swept source type is a kind of Fourier domain type. Patent Document 4 discloses a configuration in which OCT is applied to the ophthalmic field.

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

JP 11-325849 A JP 2007-101250 A JP 2007-24677 A JP 2008-73099 A

  A conventional OCT apparatus uses an optical system having a large NA (Numerical Aperture) in order to improve the lateral resolution. However, when the value of NA is increased, the depth of focus becomes shallow, and blurring tends to occur in the image. That is, the lateral resolution and the sharpness of the entire image are in a trade-off relationship, and it has been difficult to achieve both of them with the conventional technology.

  An object of the present invention is to provide a technique capable of acquiring an image having a high lateral resolution and an overall sharp image.

  In order to achieve the above object, the invention according to claim 1 includes a scanning unit that changes the irradiation position of the signal light on the object, and a focusing position changing unit that changes the focusing position of the signal light, An image that forms a tomographic image based on an optical system that detects interference light between the return light from the object of each signal light and the reference light and a plurality of interference light detection results corresponding to a plurality of irradiation positions of the signal light A control unit that repeatedly irradiates the plurality of irradiation positions with the signal light while changing the in-focus position by controlling the optical system, and a result of the repeated signal light irradiation; Based on two or more tomographic images formed by the image forming unit, and a combined tomographic image forming unit that forms one synthetic tomographic image, wherein the synthetic tomographic image forming unit includes: , For each of the two or more tomographic images, A partial image specifying unit that specifies a partial image of the tomographic image including an image region corresponding to a position is formed, and the combined tomographic image is formed by combining two or more specified partial images. .

  According to the present invention, it is possible to acquire an image having high lateral resolution and sharp overall.

It is a schematic diagram showing an example of composition of an optical image measuring device (fundus observation device) concerning an embodiment. It is a schematic diagram showing an example of composition of an optical image measuring device (fundus observation device) concerning an embodiment. It is a schematic block diagram showing an example of composition of an optical image measuring device (fundus observation device) concerning an embodiment. It is a schematic block diagram showing an example of composition of an optical image measuring device (fundus observation device) concerning an embodiment. It is the schematic for demonstrating the structure of the optical image measuring device (fundus observation device) concerning an embodiment. It is the schematic for demonstrating the structure of the optical image measuring device (fundus observation device) concerning an embodiment. It is the schematic for demonstrating the structure of the optical image measuring device (fundus observation device) concerning an embodiment. It is the schematic for demonstrating the structure of the optical image measuring device (fundus observation device) concerning an embodiment. It is a flowchart showing the operation example of the optical image measuring device (fundus observation device) concerning an embodiment. It is a timing chart for demonstrating the operation example of the optical image measuring device (fundus observation device) concerning an embodiment. It is a schematic block diagram showing an example of composition of an optical image measuring device (fundus observation device) concerning a modification. It is a timing chart for demonstrating the operation example of the optical image measuring device (fundus observation device) concerning a modification. It is the schematic for demonstrating the operation example of the optical image measuring device (fundus observation device) concerning a modification. It is the schematic for demonstrating the operation example of the optical image measuring device (fundus observation device) concerning a modification. It is a timing chart for demonstrating the operation example of the optical image measuring device (fundus observation device) concerning a modification. It is a schematic block diagram showing an example of composition of an optical image measuring device (fundus observation device) concerning a modification. It is the schematic for demonstrating the operation example of the optical image measuring device (fundus observation device) concerning a modification. It is the schematic for demonstrating the operation example of the optical image measuring device (fundus observation device) concerning a modification.

  An example of an embodiment of an optical image measurement device according to the present invention will be described in detail with reference to the drawings. The optical image measurement device according to the present invention forms a tomographic image or a three-dimensional image of an object 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. Also, various configurations described in the following embodiments and modifications can be arbitrarily combined.

  In the following embodiments, a fundus oculi observation device that performs OCT measurement of the fundus by applying Fourier domain type OCT with the object to be examined (fundus) as an object will be described. In particular, the fundus oculi observation device according to the embodiment can acquire both an OCT image and a fundus image of the fundus using a spectral domain OCT technique. Note that the configuration according to the present invention can be applied to an optical image measurement apparatus using a type other than the spectral domain, for example, a swept source OCT technique. In this embodiment, an apparatus combining an OCT apparatus and a fundus camera will be described. However, a fundus imaging apparatus other than the fundus camera, for example, an SLO, a slit lamp, an ophthalmic surgical microscope, and the like has a configuration according to this embodiment. It is also possible to combine OCT apparatuses. In addition, the configuration according to this embodiment can be incorporated into a single OCT apparatus.

[Constitution]
As shown in FIGS. 1 and 2, the fundus oculi observation device (optical image measurement device) 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.

  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 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. In addition, when the focus (focus) of the photographing optical system is adjusted to 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 perforated mirror 21, and reaches the dichroic mirror 46. And is projected onto the cornea of the eye E by the objective lens 22.

  The corneal reflection 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, is reflected by the mirror 32, and is half mirror 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 and 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 combines the optical path for fundus imaging and the optical path for OCT measurement. The dichroic mirror 46 reflects light in a wavelength band used for OCT measurement and transmits light for fundus photographing. In the 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. ing. The members arranged in the optical path for OCT measurement and the members included in the OCT unit 100 are examples of the “optical system”.

  The collimator lens unit 40 turns the light (signal light LS) emitted from the optical fiber 107 into a parallel light flux. Further, the collimator lens unit 40 causes the return light of the signal light LS from the eye E to be incident on the optical fiber 107. The collimator lens unit 40 is provided with a numerical aperture changing unit 40A that changes the numerical aperture (NA) in OCT measurement by changing the beam diameter of the parallel light flux. The numerical aperture changing unit 40A is configured by, for example, a unit capable of selectively arranging a plurality of lenses having different refractive powers in the optical path, or a unit capable of moving the lenses along the optical axis direction. The numerical aperture in OCT measurement is changed by changing the beam diameter of the signal light LS.

  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.

  The focusing lens 43 is movable in the direction of the arrow shown in FIG. 1, and changes the focus position (focus position) in OCT measurement.

[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 (return 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.

  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, operation control of the numerical aperture changing unit 40A, 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 fundus oculi observation device 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 cases. It may be.

[Control system]
The configuration of the control system of the fundus oculi observation device 1 will be described with reference to FIGS.

(Control part)
The control system of the fundus oculi observation device 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 numerical aperture changing unit 40A, the optical path length changing unit 41, the galvano scanner 42, and the focusing driving unit 43A of the fundus camera unit 2. The main control unit 211 also controls the light source unit 101, the optical attenuator 105, and the polarization adjuster 106 of the OCT unit 100.

  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. Under the control of the main control unit 211, the focusing drive unit 43A moves the focusing lens 43 along the optical axis. Thereby, the focus position of the optical system for OCT measurement is changed. The in-focus position defines the amount of the signal light LS incident on the optical fiber 107 via the collimator lens unit 40. That is, the optimum focusing position is realized by arranging the focusing lens 43 at a position where the fiber end of the optical fiber 107 on the collimator lens unit 40 side and the fundus oculi Ef are optically conjugate. Each of the focusing driving unit 31A and the focusing driving unit 43A includes an actuator such as a pulse motor and a mechanism for transmitting the driving force generated by the actuator to the focusing lens 43.

  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.

(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 fundus oculi observation device 1.

(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, dispersion compensation, and FFT (Fast Fourier Transform) as in the conventional spectral domain type optical coherence tomography. 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. In this specification, “image data” and “image” based thereon may be identified.

(Image processing unit)
The image processing unit 230 performs various types of image processing and analysis processing on the image formed by the image forming unit 220. For example, the image processing unit 230 executes various correction processes such as image brightness correction. 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 a layer thickness calculation unit 231, an iteration number determination unit 232, a numerical aperture determination unit 233, and a synthetic tomographic image formation unit 234.

(Layer thickness calculator)
The layer thickness calculation unit 231 calculates the thickness of the predetermined layer of the fundus oculi Ef by analyzing the tomographic image of the fundus oculi Ef. This process includes a process of specifying a boundary (upper end and lower end) of a predetermined layer of the fundus oculi Ef and a process of obtaining a distance between the specified upper end and lower end.

  The predetermined layer indicates a layer of the fundus oculi Ef to be observed. The layer tissue of the fundus oculi Ef includes the retina, choroid and sclera. In addition, the retina has a multi-layered structure, including inner boundary membrane, nerve fiber layer, ganglion cell layer, inner plexiform layer inner granular layer, outer reticular layer, outer granular layer, outer boundary membrane, photoreceptor layer and retinal pigment Has an epithelial layer. As the predetermined layer, the retina, choroid or sclera, or one or more layer tissues included in the retina are applied. The predetermined layer is set in advance. Further, the predetermined layer may be arbitrarily set.

  The process of specifying the boundary of the predetermined layer is a process called so-called segmentation. Segmentation is image processing for specifying an image region in a tomographic image corresponding to the layer structure of the fundus oculi Ef. This process is performed based on the pixel value (luminance value) of the tomographic image. Each layer structure of the fundus oculi Ef has a characteristic reflectance, and an image region of the layer structure also has a characteristic luminance value. In segmentation, a target image area is specified based on such characteristic luminance values. It is also possible to specify the surface of the fundus oculi Ef (the boundary between the retina and the vitreous body) and specify the target image area based on the distance from the surface position.

  When the boundary (upper end and lower end) of the predetermined layer is specified in this way, the layer thickness calculation unit 231 obtains, for example, the number of pixels between the upper end and the lower end, and determines the thickness of the predetermined layer based on the number of pixels. Ask. The information indicating the thickness of the predetermined layer (layer thickness information) may be the number of pixels itself, or distance information obtained from the number of pixels (e.g., conversion to a distance in real space). Further, the layer thickness information may be information indicating a thickness distribution in a predetermined layer, or information statistically obtained from the thickness distribution (average value, mode value, median value, maximum value, minimum value, etc.) Good. Further, the thickness of a predetermined position of a predetermined layer (for example, a position in a straight line passing through the center of the frame) may be used as layer thickness information.

(Iteration number determination part)
The iteration number determination unit 232 determines the number of scan iterations in OCT measurement based on the layer thickness information acquired by the layer thickness calculation unit 231. Although details will be described later, the OCT measurement of this embodiment is to repeatedly scan the same portion of the fundus oculi Ef while changing the focus position. The number of iterations determined by the iteration number determination unit 232 corresponds to the number of tomographic images obtained by such OCT measurement. Further, when the focus position is changed stepwise in such OCT measurement, the number of repetitions corresponds to the number of focus positions to be changed.

  An example of processing for determining the number of iterations will be described. As shown in FIG. 5, as the layer thickness information, the retinal thickness d, that is, between the retina surface (boundary between the inner limiting membrane and the vitreous body) L1 and the retina bottom (boundary between the retinal pigment epithelial layer and the choroid) L2 Is obtained. Further, the frame height of the tomographic image G (distance in the depth direction (z direction) of the fundus oculi Ef) is defined as H.

  A first processing example will be described. The iteration number determination unit 232 divides the frame height H by the retinal thickness d. When the quotient H / d is an integer, the quotient H / d is the number of iterations. When the quotient H / d is not an integer, the smallest value among the integers greater than the quotient H / d is set as the number of iterations.

  A second processing example will be described. The number-of-repetitions determination unit 232 obtains a value d1 that is less than or equal to the retinal thickness d and is an integer fraction of the frame height H: d1 ≦ d, H / d1 = integer. This integer may be the maximum value that satisfies this relationship, or a value less than that. This integer value is used as the number of iterations.

  A third processing example will be described. The iteration number determination unit 232 arbitrarily sets a value d2 less than the retinal thickness d: d2 <d. When the quotient H / d2 obtained by dividing the frame height H by this value d2 is an integer, the quotient H / d2 is set as the number of iterations. When the quotient H / d2 is not an integer, the smallest value among the integers greater than the quotient H / d2 is set as the number of iterations. The method for obtaining the value d2 is, for example, a value obtained by dividing the retinal thickness d by a predetermined number e: d2 = d / e. Moreover, although it is substantially the same value, the value obtained by multiplying the retinal thickness d by a predetermined ratio f (%) may be d2: d2 = d × f.

  When a so-called “margin” is provided in the composite tomographic image forming process described later, the number of iterations corresponding to “margin” is added to the number of iterations obtained in the above processing example. Also, as will be described later, the number of iterations can be determined based on the depth of focus.

(Numerical aperture determination part)
As described above, the numerical aperture in the OCT measurement is changed by the numerical aperture changing unit 40A. The numerical aperture determination unit 233 determines the numerical aperture value so that the depth of focus (or depth of field) in OCT measurement is less than the thickness of the predetermined layer.

In general, there is a relationship between the depth of focus D and the numerical aperture NA as follows: D = λ / (2 × NA ² ). Here, λ is the (center) wavelength of the signal light LS, which is a fixed value.

In the case shown in FIG. 5, the numerical aperture determining unit 233 determines the value of the numerical aperture NA so that the depth of focus D is less than the retinal thickness d. That is, the numerical aperture determining unit 233 determines the numerical aperture NA so as to satisfy the following relational expression: d> D = λ / (2 × NA ² ), that is, NA> √ (λ / 2d).

  As a numerical example, if NA = 0.088 and λ = 840 nm, D≈50 μm. Since the general retinal thickness d is 200 to 300 μm, the focal depth D <the retinal thickness d.

  The number of iterations can be determined based on the depth of focus D obtained as described above. For example, the iteration number determination unit 232 divides the frame height H by the focal depth D. When the quotient H / D is an integer, the quotient H / D is set as the number of iterations. When the quotient H / D is not an integer, for example, the smallest value among the integers larger than the quotient H / D is set as the number of iterations.

(Synthetic tomographic image forming part)
In the OCT measurement of this embodiment, the same portion of the fundus oculi Ef is repeatedly scanned while changing the focus position. As a result, the tomographic images having different in-focus positions can be obtained for the scan location by the number corresponding to the number of repetitions. The synthetic tomographic image forming unit 234 forms one synthetic tomographic image based on the two or more tomographic images obtained in this way.

  In order to perform such processing, the composite tomographic image forming unit 234 includes a partial image specifying unit 2341, a position adjusting unit 2342, a partial image forming unit 2345, and a composite processing unit 2346. The position adjustment unit 2342 includes a feature image area specifying unit 2343 and an image position adjustment unit 2344.

(Partial image identification part)
As described above, in this embodiment, the same portion of the fundus oculi Ef is repeatedly scanned while changing the focus position. Therefore, the focus position differs for each tomographic image. The partial image specifying unit 2341 specifies a partial image including an image area corresponding to the corresponding in-focus position for each tomographic image. The image area corresponding to the in-focus position indicates the depth position (z coordinate) of the frame corresponding to the in-focus position.

  An example of processing for specifying a partial image will be described. One of a plurality of tomographic images obtained by repetitive scanning is shown in FIG. The straight line FPi indicates the in-focus position when the tomographic image Gi is acquired. Pixels located on the straight line FPi form an image area corresponding to the in-focus position. For example, the partial image specifying unit 2341 specifies a range Ri that extends by an equal distance from each other in the depth direction (z direction) of the fundus oculi Ef with the image region formed by the pixels located on the straight line FPi as the center. An image region composed of pixels located in the range Ri is a partial image of the tomographic image Gi.

  The range Ri covers, for example, a distance obtained by dividing the frame height of the tomographic image Gi by the number of repetitions. This distance is, for example, the above-mentioned depth of focus. In addition, when “margin” is used in the composition processing described later, the range Ri includes a distance corresponding to “margin”.

(Position adjuster)
The position adjustment unit 2342 adjusts the relative positions of the partial images by analyzing the partial images specified by the partial image specifying unit 2341. In order to perform this processing, the position adjustment unit 2342 includes, for example, a feature image area specifying unit 2343 and an image position adjustment unit 2344.

(Feature image area specifying part)
The feature image region specifying unit 2343 specifies the feature image region corresponding to the feature part of the fundus oculi Ef by analyzing each partial image specified by the partial image specifying unit 2341. The characteristic sites are the macular region (fovea), the optic disc, and the lesion. An image area corresponding to a predetermined layer structure may be used as the feature image area. The process of specifying the feature image area is performed, for example, by specifying a predetermined image area in the same manner as the layer thickness calculation unit 231 and specifying the feature image area based on the shape of the image area.

  As a specific example, when a feature image region corresponding to a macular portion (fovea) is specified, a concave portion characteristic to the macular portion is detected. Further, when a feature image region corresponding to the optic nerve head is specified, an inclination in the depth direction (z direction) characteristic of the optic nerve head is detected. Further, when a feature image region corresponding to edema (lesioned portion) is specified, a convex portion characteristic to edema is detected. A cavity corresponding to edema can also be detected.

(Image position adjustment unit)
The image position adjustment unit 2344 adjusts the relative positions of the plurality of partial images specified by the partial image specification unit 2341 based on the feature image region specified by the feature image region specification unit 2343. In this process, for example, adjacent partial images are aligned so that the feature image areas match. When the “margin” is provided, adjacent partial images can be aligned so that the feature image regions overlap. When the “margin” is not provided, the adjacent partial images can be aligned so that the feature image area is smoothly connected.

(Partial image forming unit)
The partial image forming unit 2345 forms a partial image by trimming a tomographic image obtained by repetitive scanning. In this trimming process, for example, pixel information (pixel position and pixel value) of pixels located in the range in the tomographic image specified by the partial image specifying unit 2341 is extracted.

(Composition processing part)
The composition processing unit 2346 composes a plurality of partial images formed by the partial image forming unit 2345 to form one tomographic image (composite tomographic image). For example, this combination processing is to convert pixel information of a plurality of partial images into single image data. The composite tomogram is an image in which a cross section of the fundus oculi Ef that has been repeatedly scanned is drawn. Furthermore, since each partial image includes an image region corresponding to the in-focus position at the time of OCT measurement, the combined tomographic image is an image that is in focus as a whole.

  An example of synthesis processing in this embodiment will be described with reference to FIGS. 7A and 7B. In the synthesis process, partial images PG1 to PGn of the plurality of tomographic images G1 to Gn shown in FIG. 7A are synthesized. The partial images PG1 to PGn are images corresponding to the range Ri of the tomographic image Gi shown in FIG. In this embodiment, for example, the focus position is changed in stages in repetitive scanning. In that case, as shown in FIGS. 6 and 7A, rectangular partial images PG1 to PGn can be applied. The composition processing unit 2346 composes these rectangular partial images PG1 to PGn to form a composite tomographic image CG shown in FIG. 7B. The composite tomographic image CG is obtained by arranging rectangular partial images PG1 to PGn in the depth direction (z direction).

  The composition processing unit 2346 can form a composite tomogram by combining these partial images based on the adjustment result of the relative position of the partial image by the position adjusting unit 2342. Here, the result of the position adjustment may be always reflected, or may be reflected according to circumstances. As an example of the latter, it is possible to determine the position shift of the partial image based on the displacement of the feature image area, and to perform the composition processing by reflecting the position adjustment result only when the position shift is equal to or greater than a threshold value.

  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 fundus oculi observation device 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 images]
Here, the scanning of the signal light LS and the OCT image will be described.

  Examples of scanning modes of the signal light LS by the fundus oculi observation device 1 include horizontal scanning, vertical scanning, cross scanning, radiation scanning, circular scanning, concentric scanning, and spiral (vortex) scanning. 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 helical scan, the signal light LS is scanned along a spiral (spiral) trajectory while gradually reducing (or increasing) the radius of rotation.

  Since the galvano scanner 42 is configured to scan the signal light LS in directions orthogonal to each other, it can independently scan the signal light LS 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.

  A region on the fundus oculi Ef to be scanned with the signal light LS as described above, that is, a region on the fundus oculi Ef to be subjected to OCT measurement is referred to as a scanning region. The scanning area in the three-dimensional scan is a rectangular area in which a plurality of horizontal scans are arranged. The scanning area in the concentric scan is a disk-shaped area surrounded by the locus of the circular scan with the maximum diameter. In addition, the scanning area in the radial scan is a disk-shaped (or polygonal) area connecting both end positions of each scan line.

[Operation]
The operation of the fundus oculi observation device 1 will be described. FIG. 8 illustrates an example of the operation of the fundus oculi observation device 1. It is assumed that alignment and focus are made.

(S1: A tomographic image for preprocessing is acquired)
First, a tomographic image using prior writing is acquired. The pre-processing is processing for determining the number of scan repetitions and the numerical aperture. The tomographic image acquired here is, for example, a live tomographic image obtained by repeatedly scanning the same cross section of the fundus oculi Ef.

(S2: Find layer thickness information)
The layer thickness calculation unit 231 analyzes the tomographic image acquired in step 1 and obtains layer thickness information indicating the thickness of the predetermined layer of the fundus oculi Ef.

(S3: Determine the numerical aperture)
The numerical aperture determining unit 233 determines the numerical aperture value so that the depth of focus is less than the thickness indicated in the layer thickness information acquired in Step 2. The main control unit 211 controls the numerical aperture changing unit 40A to set the numerical aperture to the determined value.

(S4: Determine the number of iterations)
The repetition number determination unit 232 determines the number of repetitions in the repeated scanning of the signal light LS based on the thickness indicated in the layer thickness information acquired in Step 2. At this time, the in-focus position can also be determined. For example, the position at which the frame height of the tomographic image is equally divided by the number of iterations can be set as the in-focus position.

(S5: Perform repetitive scanning)
In response to a predetermined trigger, the main control unit 211 performs repetitive scanning while changing the focus position. This iterative scan is performed with the numerical aperture set in step 3 and the number of iterations determined in step 4. The number of focus positions to be changed is the same as the number of repetitions.

  The repetitive scan control is executed by, for example, the timing chart shown in FIG. In the scan of the signal light LS, the irradiation position of the signal light LS is changed according to a graph indicated by a sawtooth shape. The shaded portion TS in this graph indicates the scanning operation of the signal light LS for a plurality of different irradiation positions. Further, the vertical portion TR of the graph shows an operation (return operation) of changing the irradiation position of the signal light LS from the last irradiation position to the first irradiation position among the plurality of irradiation positions. On the other hand, the in-focus position is changed stepwise as shown in the stepped graph TF1. The focus position is changed simultaneously with the operation of returning the irradiation position of the signal light LS (vertical portion TR).

(S6: forming a plurality of tomographic images)
The image forming unit 220 forms a plurality of tomographic images based on the data obtained by repetitive scanning in Step 5. The number of tomographic images formed here is equal to the number of iterations determined in step 4. Each tomographic image is formed from data collected during one hatched portion TS in the scan timing chart shown in FIG.

(S7: Specify a partial image)
The partial image specifying unit 2341 specifies, for each tomographic image formed in Step 6, a partial image including an image region corresponding to the corresponding in-focus position.

(S8: Specify the feature image area)
The feature image area specifying unit 2343 specifies the feature image area corresponding to the feature part of the fundus oculi Ef by analyzing each partial image specified in step 7.

(S9: Adjust the relative position of the partial image)
The image position adjustment unit 2344 adjusts the relative position of the partial image based on the feature image area specified in step 8.

(S10: forming a partial image)
The partial image forming unit 2345 trims the partial image specified in step 7 from the tomographic image. Thereby, a partial image is formed from each tomographic image. Note that the process of step 10 can be performed at any timing after step 7.

(S11: A composite tomographic image is formed)
The composition processing unit 2346 forms a composite tomographic image of the fundus oculi Ef by synthesizing the partial images formed in step 10 based on the relative position adjustment result in step 9. The formed composite tomogram is stored in the storage unit 212 by the main control unit 211. In addition, the composite tomogram can be displayed on the display unit 240A. Thus, this operation example ends.

[Action / Effect]
The operation and effect of the optical image measurement device (fundus observation device 1) according to this embodiment will be described.

  The fundus oculi observation device 1 includes an optical system, an image forming unit, a control unit, and a synthetic tomographic image forming unit. The optical system includes a scanning unit (galvano scanner 42) that changes the irradiation position of the signal light on the object (fundus Ef), and a focusing position changing unit (the focusing lens 43, the focusing point) that changes the focusing position of the signal light. Drive unit 43A). Further, the optical system detects interference light between the return light from the object of each signal light and the reference light. That is, the optical system performs OCT measurement of the object. The image forming unit 220 forms a tomographic image based on detection results of a plurality of interference lights corresponding to a plurality of signal light irradiation positions. The control unit (main control unit 211) controls the optical system to repeatedly irradiate the plurality of irradiation positions with the signal light while changing the focus position. The synthetic tomographic image forming unit (234) forms one synthetic tomographic image based on two or more tomographic images formed by the image forming unit based on the result of repetitive signal light irradiation.

  According to such a configuration, a single tomographic image (composite tomographic image) can be formed by synthesizing a plurality of tomographic images obtained by scanning the same cross section of the object a plurality of times while changing the focus position. An image in focus over the entire frame is obtained. In addition, OCT measurement can be performed by applying an arbitrary setting to factors (such as numerical aperture) that affect the lateral resolution. Therefore, it is possible to acquire an image with high lateral resolution and sharp overall.

  The combined tomographic image forming unit may include a partial image specifying unit (2341) for specifying a partial image including an image region corresponding to the corresponding in-focus position for each tomographic image formed by the image forming unit. In that case, the combined tomographic image forming unit can form a combined tomographic image by combining the specified partial images. By applying this configuration, it is possible to synthesize a partial image including the in-focus position in the tomographic image, so that it is possible to reliably and automatically acquire an image that is entirely in focus.

  The synthetic tomographic image forming unit may include a position adjusting unit (2342) that adjusts the relative position of the partial images by analyzing the partial images specified by the partial image specifying unit. In that case, the composite tomographic image forming unit can form a composite tomographic image by combining the partial images whose relative positions have been adjusted. By applying this configuration, even if a positional shift occurs between tomographic images due to eye movement or pulsation during repetitive scanning, it is possible to correct this positional shift and form a composite tomographic image. .

  The position adjustment unit may include a feature image region specifying unit (2343) that specifies a feature image region corresponding to a feature part of the target object by analyzing each partial image. In that case, the position adjustment unit (2344) can adjust the relative position of the partial image based on the identified feature image region. By applying this configuration, position adjustment with high accuracy and high accuracy is possible based on the feature image region.

  The fundus oculi observation device 1 may include an iterative number determination unit (232) that determines an iterative number of repetitive signal light irradiations based on the thickness of a predetermined layer of an object acquired in advance. By applying this configuration, the number of repetitions in repetitive scanning can be automatically determined. Moreover, it is possible to obtain an appropriate number of repetitions by referring to the thickness of the predetermined layer.

  The fundus oculi observation device 1 may include a layer thickness calculation unit (231) that calculates the thickness of a predetermined layer by analyzing a tomographic image acquired before repetitive signal light irradiation. By applying this configuration, it is possible to refer to the thickness of the predetermined layer obtained by actually measuring the object, so that the optimum number of iterations can be obtained.

  A numerical aperture changing section (40A) for changing the numerical aperture is provided in the optical system, and a numerical aperture determining section (233) for determining the numerical aperture value so that the depth of focus is less than the thickness of the predetermined layer is provided. Also good. In that case, the control unit can set the numerical aperture to the determined value by controlling the numerical aperture changing unit. By applying this configuration, OCT measurement of a predetermined layer can be performed with high resolution, and a high-quality composite tomographic image can be acquired. The numerical aperture is preferably determined in consideration of the influence on the lateral resolution.

  In the repetitive signal light irradiation, the control unit can change the in-focus position step by step for each repetition of the signal light irradiation with respect to a plurality of irradiation positions (see FIG. 9). In this case, the synthetic tomographic image forming unit can form a synthetic tomographic image based on the rectangular partial image of the tomographic image including the image region corresponding to the in-focus position. This configuration provides a specific example of repetitive scanning and image composition processing.

  The composite tomographic image forming unit trims each tomographic image to form a partial image, and a composite image processing unit (2346) that forms a composite tomographic image by tiling these partial images. And may be included. Tiling refers to an image composition process that forms a single image by pasting together a plurality of images. In the tiling of this embodiment, there may or may not be a “margin”. This configuration provides a specific example of image composition processing.

[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. Hereinafter, examples of such modifications will be described. In addition, the same code | symbol is attached | subjected and demonstrated about the component similar to the said embodiment.

(Modification 1)
As described above, when eye movements, pulsations, and body movements occur during repetitive scanning, misalignment occurs in a plurality of acquired tomographic images. When this positional deviation is large, the plurality of tomographic images become images in which different cross sections are drawn, which is inappropriate for forming a composite tomographic image. This modification deals with such a situation.

  An example of the configuration of this modification is shown in FIG. The optical image measurement device (fundus observation device) according to this modification has substantially the same configuration as that of the above embodiment (see FIG. 3), but is different in that a displacement detection unit 235 is provided in the image processing unit 230. . Note that the image processing unit 230 of this modification may include a layer thickness calculation unit 231, an iterative number determination unit 232 and / or a numerical aperture determination unit 233 similar to those in the above embodiment. In addition, the synthetic tomographic image forming unit 234 of this modification may have the same configuration as that of the above-described embodiment (see FIG. 4) or may have a different configuration.

  The displacement detection unit 235 detects the displacement between the optical system for OCT measurement and the object (fundus Ef) during repetitive scanning. This displacement detection processing includes at least one of detection of displacement in the xy direction and detection of displacement in the z direction. The displacement detection process is preferably executed before the process for forming the composite tomographic image.

  The displacement in the xy direction is detected by, for example, acquiring an observation image (real-time infrared fundus image) of the fundus oculi Ef in parallel with repetitive scanning, and the position of the characteristic part of the fundus oculi Ef in a frame acquired in time series. This can be done by detecting changes over time. The same processing can also be performed by using an observation image of the anterior segment of the eye E. Such processing is also executed in the tracking described above.

  It is also possible to detect displacement in the xy direction by analyzing a plurality of tomographic images obtained by repetitive scanning. Note that these tomographic images are time-sequential tomographic images in which the repetition frequency of repetitive scanning is used as a frame rate. By detecting a temporal change in the form (position (x coordinate, y coordinate), shape, size, etc.) of the characteristic part of the fundus oculi Ef in the frame of these tomographic images, it is possible to detect a displacement in the xy direction.

  The detection of the displacement in the z direction can be performed, for example, by analyzing a plurality of tomographic images obtained by repetitive scanning. As an example, similarly to the displacement detection in the xy direction, it is possible to detect the displacement in the z direction by detecting the temporal change of the position (z coordinate) of the characteristic part of the fundus oculi Ef in the frame of these tomographic images. is there.

  Based on the displacement detected by the displacement detection unit 235, the main control unit 211 newly performs a repetitive scan of the fundus oculi Ef. This process is, for example, a process of determining whether or not to perform a new repetitive scan based on the detected displacement (maximum displacement value or the like). In addition, this process may include a process of determining a new repetitive scan control content (scanning mode, scanning position, etc.) based on the detected displacement.

  The new repetitive scan is performed, for example, in the same scan mode as the previous time. Note that a scanning mode different from the previous time can also be applied. For example, when a horizontal scan is applied in the previous repetitive scan, two adjacent horizontal scans can be applied as a scan mode of a new repetitive scan to reduce the possibility of redoing again.

  The image forming unit 220 forms a plurality of new tomographic images based on the detection signal obtained by the newly executed repetitive scan. The synthetic tomographic image forming unit 234 forms a synthetic tomographic image based on these new tomographic images.

  It is also possible to execute a displacement detection process similar to the above on a plurality of new tomographic images formed by the image forming unit 220. For example, it can be determined whether to perform a further iterative scan based on the newly detected displacement. In this case, when the number of repetitive scans reaches a predetermined number, a message to that effect can be displayed on the display unit 240A.

  According to such a modification, it is possible to perform a new scan based on the displacement between the optical system and the object during repetitive scanning. For example, re-measurement can be automatically performed when repetitive scanning is not suitably performed.

(Modification 2)
This modification deals with the same situation as the first modification. In Modification 1, a new scan is performed based on the displacement between the optical system and the object during repetitive scanning. In this modification, notification is performed based on this displacement.

  The configuration of this modification is the same as that of Modification 1 (see FIG. 10). Similar to the first modification, the displacement detection unit 235 detects the displacement between the OCT measurement optical system and the object (fundus Ef) during repetitive scanning.

  The main control unit 211 causes the notification unit to output notification information based on the displacement detected by the displacement detection unit 235. Examples of the notification unit include a display unit 240A, a voice output unit (not shown), and the like. The notification information varies depending on the configuration of the notification unit, and is, for example, visual information (character string information, image information, etc.) or auditory information (warning message, warning sound, etc.).

  The main control unit 211 can obtain, for example, a statistical value (maximum value, standard deviation, etc.) of the detected displacement and perform notification control based on this statistical value. As a specific example, when the statistical value of displacement is greater than or equal to a predetermined value, a message indicating that can be output. Further, the statistical value of displacement itself can be notified. In these cases, a GUI for the user to instruct the presence or absence of remeasurement can be displayed on the display unit 240A.

  According to such a modification, notification can be performed based on the displacement between the optical system and the object during repetitive scanning. Therefore, it is possible to inform the user that the repetitive scanning has not been suitably performed and that remeasurement should be performed.

(Modification 3)
In the above embodiment, the focus position is changed stepwise in repetitive scanning (see FIG. 9), but the manner of changing the focus position is not limited to this. For example, the focus position can be continuously changed in repeated scanning. An example of a timing chart in this case is shown in FIG.

  The scanning of the signal light LS is executed in the same manner as in the above embodiment. The shaded portion TS in this graph indicates the scanning operation of the signal light LS for a plurality of different irradiation positions. The vertical portion TR indicates the returning operation of the irradiation position of the signal light LS. On the other hand, the in-focus position is continuously changed as shown in the linear graph TF2 unlike the above embodiment.

  When the focus position is changed stepwise as in the above-described embodiment, the focus position is the same in each of the scan repetitions (that is, in each hatched portion TS), and the focus corresponding to each repetition. There is one position. However, in this modification, the focus position is continuously changed. Therefore, as shown in FIG. 6 of the above-described embodiment, if the range Ri of the tomographic image Gi used for forming the composite tomographic image is rectangular, the in-focus position may deviate from the range Ri. Further, if the range Ri is widened so that the in-focus position is not deviated, the focus becomes undesirably in a portion far from the in-focus position.

  In view of such circumstances, in this modification, a composite tomogram is formed using a parallelogram-shaped partial region in the tomogram. An example is shown in FIG. 12A. A plurality of tomographic images J1 to Jn shown in FIG. 12A are formed based on data obtained by repetitive scanning executed in accordance with the timing chart shown in FIG. Here, each tomographic image Ji (i = 1 to n) is based on data collected in a scan corresponding to the i-th shaded portion TS of this timing chart.

  In this example, the partial image PJi of the tomographic image Ji is used for the synthesis process. Each partial image PJin is an image area having an equal distance in the ± z direction with respect to the graph (corresponding image area) TF2 of the in-focus position in the period of the corresponding shaded portion TS. Since the graph TF2 is a monotonous straight line graph (that is, a graph having a constant inclination), each partial image PJi is an image region having a parallelogram shape. Each partial image PJi is an example of a parallelogram-shaped partial image.

  The synthetic tomographic image forming unit 234 forms a synthetic tomographic image by synthesizing such parallelogram-shaped partial images PJ1 to PJn. Although not shown in the figure, this composite tomographic image is obtained by arranging parallelogram-shaped partial images PJ1 to PJn in the depth direction (z direction). In this example, “margin” is provided in each partial image PJi, and the synthesis is performed such that a part of the adjacent partial images PJi and Pj (i + 1) is superimposed on each other. It is also possible to perform the combining process without providing a “margin” like the partial images PK1 to PKn of the tomographic images K1 to Kn shown in FIG. 12B.

  For the triangular areas at the upper and lower ends of the frame of the composite tomographic image, the tomographic image Ji including the partial image PJi closest to the frame, that is, the image of the triangular area in the tomographic images J1 and Jn can be used. Further, by extending the graph TF2 shown in FIG. 11 back and forth over time, it is also possible to acquire images of these triangular regions separately.

  FIG. 13 shows another example when the focus position is continuously changed. In this example, the composition processing is performed using the rectangular partial image as in the above-described embodiment while performing the repetitive scanning by continuously changing the focus position.

  Since the main control unit 211 controls the in-focus position, it recognizes the in-focus position (z coordinate) at an arbitrary timing of repetitive scanning. Note that the focus position may be recognized by providing a sensor for detecting the position of the focus lens 43 during repetitive scanning.

  The main control unit 211 acquires a representative in-focus position during each period for each shaded portion TS in the scan of the signal light LS. As this typical in-focus position, for example, as shown in FIG. 13, in-focus positions at intermediate times t1 to tn in the shaded portion TS can be applied.

  The composite tomographic image forming unit 234 includes, for each tomographic image, an image region (consisting of pixels on a line segment orthogonal to the z direction) corresponding to a representative in-focus position corresponding to the hatched portion TS. A rectangular partial image is specified. Then, the composite tomographic image forming unit 234 forms a composite tomographic image by combining the specified rectangular partial images. It is also possible to set a rectangular partial image so as to include an image region TF2 corresponding to the in-focus position shown in FIG. 12A.

  In the above modification, since the focus position is continuously changed, the configuration and control of the focus drive unit 43A can be simplified as compared with the case where the focus position is changed stepwise.

(Modification 4)
In the above embodiment, a composite tomographic image is formed by trimming and bonding a plurality of tomographic images, but the synthesis process is not limited to this. For example, a composite tomographic image can be formed by superimposing a plurality of tomographic images using a layer function.

  An example of the configuration of this modification is shown in FIG. The optical image measurement device (fundus observation device) according to this modification has substantially the same configuration as that of the above embodiment (see FIG. 3), but is different in that a weighting unit 2347 is provided in the image processing unit 230. Note that the image processing unit 230 of this modification may include a layer thickness calculation unit 231, an iterative number determination unit 232 and / or a numerical aperture determination unit 233 similar to those in the above embodiment. In addition, the synthetic tomographic image forming unit 234 of this modification may have the same configuration as that of the above-described embodiment (see FIG. 4) or may have a different configuration.

  The weighting unit 2347 weights the pixels of each tomographic image used for the synthesis process. This weighting is performed, for example, by adding transparency information (alpha value) to the alpha channel of the pixel of the tomographic image. The weighting unit 2347 gives the transparency information so that the opacity of the pixels constituting the partial image of the above embodiment is relatively high. Specific examples thereof are shown in FIGS. 15A and 15B.

  It is assumed that a plurality of tomographic images Mi (i = 1 to n) are obtained by repetitive scanning. The opacity graph α1 shown in FIG. 15A provides transparency information to the alpha channel of the pixels of the tomographic image Mi so that the opacity of the partial image PMi of the tomographic image Mi is relatively high. The tomographic image Mi to which the opacity graph α1 is applied is an image in which the opacity of the partial image PMi is high, and the opacity gradually decreases with distance from the partial image PMi.

  The opacity graph α2 shown in FIG. 15B is created so that the opacity of the partial image PMi of the tomographic image Mi takes the maximum value and the opacity of the other parts takes the minimum value. The tomographic image Mi to which the opacity graph α2 is applied is an image in which a portion other than the partial image PMi is transparent.

  The combined tomographic image forming unit 234 forms a combined tomographic image by superimposing a plurality of tomographic images M1 to Mn whose pixels are weighted by the weighting unit 2347. Here, when aligning a plurality of tomographic images Mi, it can be performed in the same manner as in the above embodiment.

(Other variations)
In the above embodiment, 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, but this optical path length difference is changed. The method 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 target is not a living body part, the optical path length difference can be changed by moving the target 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.

1 Fundus observation device (optical image measurement device)
2 fundus camera unit 40A numerical aperture changing unit 41 optical path length changing unit 42 galvano scanner 43 focusing lens 43A focusing drive unit 100 OCT unit 200 arithmetic control unit 210 control unit 211 main control unit 212 storage unit 220 image forming unit 230 image processing Unit 231 layer thickness calculating unit 232 iteration number determining unit 233 numerical aperture changing unit 234 composite tomographic image forming unit 2341 partial image specifying unit 2342 position adjusting unit 2343 feature image region specifying unit 2344 image position adjusting unit 2345 partial image forming unit 2346 synthesis processing Unit 2347 weighting unit 235 displacement detection unit 240A display unit 240B operation unit E eye Ef fundus LS signal light LR reference light LC interference light

Claims (12)

Interference light between the return light of each signal light from the object and the reference light, including a scanning part that changes the irradiation position of the signal light on the object and a focusing position changing part that changes the focusing position of the signal light An optical system for detecting
An image forming unit that forms a tomographic image based on detection results of a plurality of interference lights corresponding to a plurality of signal light irradiation positions;
A controller that repeatedly irradiates the plurality of irradiation positions with signal light while changing the in-focus position by controlling the optical system;
A combined tomographic image forming unit that forms one combined tomographic image based on two or more tomographic images formed by the image forming unit based on the result of repetitive signal light irradiation;
The synthetic tomographic image forming unit is
For each of the two or more tomographic images, including a partial image specifying unit that specifies a partial image of the tomographic image including an image region corresponding to a corresponding in-focus position,
The composite tomographic image is formed by synthesizing two or more specified partial images. An optical image measuring device. The synthetic tomographic image forming unit is
A position adjusting unit that adjusts a relative position of the two or more partial images by analyzing the two or more partial images;
The optical image measurement apparatus according to claim 1, wherein the combined tomographic image is formed by combining the two or more partial images that have been adjusted in relative position. The position adjusting unit is
A feature image region specifying unit that specifies a feature image region corresponding to a feature part of the object by analyzing each of the two or more partial images;
The optical image measurement device according to claim 2, wherein a relative position of the two or more partial images is adjusted based on the identified characteristic image region. A displacement detection unit for detecting displacement between the optical system and the object during repetitive signal light irradiation;
Based on the detected displacement, the control unit newly performs repetitive signal light irradiation,
The synthetic tomographic image forming unit forms the synthetic tomographic image on the basis of two or more new tomographic images formed based on a result of newly executed repetitive signal light irradiation. The optical image measuring device according to any one of claims 1 to 3. A displacement detection unit for detecting displacement between the optical system and the object during repetitive signal light irradiation;
The optical control unit according to any one of claims 1 to 3, wherein the control unit causes the notification unit to output notification information based on the detected displacement.   6. The apparatus according to claim 1, further comprising an iterative number determining unit that determines an iterative number of repetitions of signal light irradiation based on a thickness of a predetermined layer of an object acquired in advance. The optical image measuring device described in 1.   The optical image measurement according to claim 6, further comprising: a layer thickness calculation unit that calculates a thickness of the predetermined layer by analyzing a tomographic image acquired before repetitive signal light irradiation. apparatus. The optical system includes a numerical aperture changing unit that changes the numerical aperture,
A numerical aperture determining unit that determines a numerical aperture value so that a depth of focus is less than the thickness of the predetermined layer;
The optical image measurement device according to claim 6, wherein the control unit controls the numerical aperture changing unit to set the numerical aperture to a determined value. The control unit, in repetitive signal light irradiation, changes the in-focus position step by step for each repetition of signal light irradiation to the plurality of irradiation positions,
The synthetic tomographic image forming unit forms the synthetic tomographic image based on a rectangular partial image including an image region corresponding to a corresponding in-focus position in each tomographic image. Item 9. The optical image measurement device according to any one of Items 8 to 8. The control unit continuously changes the in-focus position in repeated signal light irradiation,
The synthetic tomographic image forming unit forms the synthetic tomographic image based on a parallelogram partial image including an image region corresponding to a corresponding in-focus position in each tomographic image. The optical image measurement device according to claim 8. The synthetic tomographic image forming unit is
A partial image forming unit that trims each of the two or more tomographic images to form a partial image;
The composition processing part which forms the synthetic tomographic image by tiling the two or more partial images obtained from the two or more tomographic images. The optical image measurement device according to one item. The synthetic tomographic image forming unit is
For each of the two or more tomographic images, a weighting unit that weights the pixels of the tomographic image;
The composition processing part which forms the synthetic tomographic image by superimposing the two or more tomographic images weighted to the pixel, The method according to any one of claims 1 to 10 characterized by things. Optical image measuring device.

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