Optical image measuring device

Abstract

Optical image measuring device with: an optical system comprising a scanner configured to change the irradiation position of signal light on an object, a focus position change section configured to change the focus position of the signal light, and a numerical aperture change section configured to change a numerical aperture and configured to detect interference light from light returning from the object of the corresponding signal light and reference light; an image generation section configured to produce a cross-sectional image based on the acquisition results of multiple interference light beams corresponding to multiple irradiation positions of the signal light; a control device configured to control the optical system to repeatedly shine the signal light onto the multiple irradiation positions while the focus position is changed; and a section for generating a composite cross-sectional image, configured to produce a composite cross-sectional image based on two or more cross-sectional images generated by the image generation section based on results of repeated irradiation of the signal light; a layer thickness calculation section configured to analyze a cross-sectional image obtained before repeated irradiation with the signal light in order to calculate the thickness of the specified layer; a section for determining the numerical aperture, configured to determine a value of the numerical aperture such that the imaging depth becomes smaller than the thickness of the specified layer; and a repetition determination section configured to determine the number of repetitions during repeated irradiation of the signal light based on the imaging depth; the control device controls the section for changing the numerical aperture in order to set the numerical aperture to the specified value.

Description

Technical field

[0001] The present invention relates to an optical image measurement technique for capturing images of an object using optical coherence tomography (OCT). Technical background

[0002] In recent years, optical coherence tomography (OCT) has gained increasing attention. It generates images depicting the surface and / or internal morphology of objects using light beams from laser light sources and similar devices. Unlike X-ray CT, OCT is non-invasive to the human body, and therefore its applications are expected to be particularly strong in the medical and biological fields. For example, in ophthalmology, devices for generating images of the fundus, cornea, and other structures of the eye are already in practical use.

[0003] JP H11 325849 A describes a device that uses a technique called "Fourier Domain OCT." Specifically, this device shines a low-coherence light beam onto an object, superimposes its reflected light and reference light to generate interference light, determines the spectral intensity distribution of the interference light, and applies a Fourier transform to it to image the morphology of the object in a depth direction (z-direction). Furthermore, this device includes a galvanic mirror for scanning light beams (signal light) in a direction (x-direction) perpendicular to the z-direction, producing an image of a desired target area of ​​the object. An image produced by this device is a two-dimensional cross-sectional image along the depth direction (z-direction) and the scan direction (x-direction) of the light beam. This technique is specifically referred to as spectral domain OCT.JP 2007-101250 A also describes an OCT device of the spectral domain type.

[0004] JP 2007-24677 A describes an OCT device that scans wavelengths of light directed at an object (wavelength sweeping), captures interference light obtained by superimposing reflected light beams of the respective wavelengths onto reference light to obtain a spectral intensity distribution, and applies a Fourier transform to this to map the morphology of the object. Such an OCT technique is called swept-source or similar. A swept-source type is a type of Fourier domain. JP2008-73099 A describes a configuration in which OCT is applied in ophthalmology.

[0005] OCT devices have advantages in that high-resolution images, cross-sectional images, and three-dimensional images can be obtained, and the like.

[0006] Further state of the art is disclosed in US 2012 / 0 044 455 A1, US 2012 / 0 249 962 A1, US 2012 / 0 249 956 A1, US 2012 / 0 092 615 A1, DE 10 2006 053 118 A1, US 2010 / 0 165 291 A1 and JP 2005-111 053 A. Brief description of the invention Problem to be solved by the invention

[0007] Conventional OCT devices employ optical systems with a large numerical aperture (NA) to improve lateral resolution. However, a large numerical aperture value results in a shallow depth of field, which can easily introduce bokeh (haze) into images. This means that lateral resolution and overall image sharpness are in a trade-off, and achieving optimal values ​​for both parameters simultaneously is challenging with conventional techniques.

[0008] It is an object of the present invention to provide a technique suitable for obtaining images with high lateral resolution and global sharpness. Means to solve the problem

[0009] To solve the above problem, the present invention provides an optical image measuring device as described in claim 1.

[0010] The device according to the invention described in claim 2 corresponds to the optical image measuring device according to claim 1, wherein the section for generating a composite cross-sectional image has a partial image specification section configured to specify a partial image having an image area corresponding to a corresponding focus position for each of the two or more cross-sectional images, and combines the specified two or more partial images to generate the composite cross-sectional image.

[0011] The device according to the invention described in claim 3 corresponds to the optical image measuring device according to claim 2, wherein the section for generating a composite cross-sectional image has a position setting section configured to analyze the two or more partial images in order to set the relative positions between the two or more partial images, and to combine the two or more partial images whose relative positions have been set in order to generate the composite cross-sectional image.

[0012] The device according to the invention described in claim 4 corresponds to the optical image measuring device according to claim 3, wherein the position setting section has a section for specifying a characteristic image area, which is configured to analyze each of the two or more partial images in order to specify a characteristic image area corresponding to a characteristic location of the object, and sets the relative positions between the two or more partial images based on the specified characteristic image areas.

[0013] The device according to the invention described in claim 5 corresponds to the optical image measuring device according to any one of claims 1 to 4, further comprising an offset detection section configured to detect an offset between the optical system and the object during repeated irradiation of the signal light, wherein the control device performs a further repeated irradiation of the signal light on the basis of the detected offset, and wherein the section for generating a composite cross-sectional image generates the composite cross-sectional image based on two or more new cross-sectional images generated on the basis of results of the further repeated irradiation of the signal light.

[0014] The device according to the invention described in claim 6 corresponds to the optical image measuring device according to any one of claims 1 to 4, further comprising an offset detection section configured to detect an offset between the optical system and the object during repeated irradiation with the signal light, wherein the control unit has a communication section for outputting communication information based on the detected offset.

[0015] The device according to the invention described in claim 7 corresponds to the optical image measuring device according to any one of claims 1 to 6, wherein the control device incrementally changes the focus position for each repetition of the irradiation of the signal light to the multiple irradiation positions when the repeated irradiation of the signal light is performed, and wherein the section for generating a composite cross-sectional image generates the composite cross-sectional image based on a rectangular partial image containing an image area corresponding to a corresponding focus position in each cross-sectional image.

[0016] The device according to the invention described in claim 8 corresponds to the optical image measuring device according to any one of claims 1 to 6, wherein the control device continuously changes the focus position when the repeated irradiation of the signal light is performed, and wherein the section for generating a composite cross-sectional image generates the composite cross-sectional image on the basis of a parallelogram-shaped partial image which has an image area corresponding to a corresponding focus position in each cross-sectional image.

[0017] The device according to the invention described in claim 9 corresponds to the optical image measuring device according to any one of claims 1 to 8, wherein the section for generating a composite cross-sectional image comprises a partial image generation section configured to crop each of the two or more cross-sectional images to generate a partial image, and a composition processor configured to perform tiling processing of the two or more partial images obtained from the two or more cross-sectional images to generate the composite cross-sectional image.

[0018] The device according to the invention described in claim 10 corresponds to the optical image measuring device according to any one of claims 1 to 8, wherein the section for generating a composite cross-sectional image has a weighting section configured to perform weighting of pixels of each of the two or more cross-sectional images, and a composition processor configured to perform superimposition processing of the two or more cross-sectional images with the weighted pixels to generate the composite cross-sectional image. Effect of the invention

[0019] According to the present invention, it is possible to capture images with high lateral resolution and global sharpness. Brief description of the drawings Fig. Figure 1 shows a schematic diagram illustrating a configuration example of an optical image measuring device (fundus observation device) according to one embodiment; Fig. Figure 2 shows a schematic diagram illustrating a configuration example of an optical image measuring device (fundus observation device) according to one embodiment; Fig. Figure 3 shows a schematic block diagram illustrating a configuration example of an optical image measurement device (fundus observation device) according to one embodiment; Fig. Figure 4 shows a schematic diagram illustrating a configuration example of an optical image measuring device (fundus observation device) according to one embodiment; Fig. Figure 5 shows a schematic representation to explain a configuration of an optical image measuring device (fundus observation device) according to one embodiment; Fig. Figure 6 shows a schematic diagram to explain a configuration of an optical image measuring device (fundus observation device) according to one embodiment; Fig. Figure 7A shows a schematic diagram to explain a configuration of an optical image measuring device (fundus observation device) according to one embodiment; Fig. Figure 7B shows a schematic diagram to explain a configuration of an optical image measuring device (fundus observation device) according to one embodiment; Fig. Figure 8 shows a flowchart illustrating an example of the processing of an optical image measurement device (fundus observation device) according to one embodiment; Fig. Figure 9 shows a time diagram to illustrate an operating example of an optical image measuring device (fundus observation device) according to one embodiment; Fig. Figure 10 shows a schematic block diagram illustrating a configuration example of an optical image measurement device (fundus observation device) according to a modification; Fig. Figure 11 shows a time diagram to illustrate an operating example of an optical image measuring device (fundus observation device) according to a modification; Fig. Figure 12A shows a schematic diagram to illustrate an operating example of an optical image measuring device (fundus observation device) according to a modification; Fig. Figure 12B shows a schematic diagram to illustrate an operating example of an optical image measuring device (fundus observation device) according to a modification; Fig. Figure 13 shows a time diagram to illustrate an operating example of an optical image measuring device (fundus observation device) according to a modification; Fig. Figure 14 shows a schematic block diagram illustrating a configuration example of an optical image measuring device (fundus observation device) according to a modification; Fig. Figure 15A shows a schematic diagram to illustrate an operating example of an optical image measuring device (fundus observation device) according to a modification; and Fig. Figure 15B shows a schematic diagram to illustrate an operating example of an optical image measuring device (fundus observation device) according to a modification. Technique for implementing the invention

[0020] Examples of embodiments of optical image measurement devices according to the invention are described in more detail below with reference to the drawings. The optical image measurement devices according to the invention generate cross-sectional images and / or three-dimensional images of objects. In this description, images acquired by OCT are sometimes referred to as OCT images. Measurement methods for generating OCT images are also sometimes referred to as OCT (measurement). The content presented in the documents cited in this description can be applied to the following embodiments. Furthermore, various configurations described in connection with the following embodiments and modifications can be combined in any way.

[0021] In the following embodiments, it is assumed that an object is an eye (fundus), and fundus observation devices are described that apply Fourier-domain OCT to perform OCT of a fundus. In particular, fundus observation devices of embodiments are capable of obtaining OCT images of a fundus using spectral-domain OCT and of obtaining fundus images. Configurations of the present invention can be applied to optical imaging devices of any type other than a spectral-domain type (for example, swept-source OCT). The following embodiments describe devices as combinations of OCT devices and retinal cameras; however, various ophthalmic imaging devices (such as SLO, slit-lamp microscope, ophthalmic surgical microscope, etc.) can be used instead of retinal cameras.) can be combined with OCT devices that have configurations of embodiments. Configurations of embodiments can also be integrated into single-function OCT devices. Configurations

[0022] As in Fig. 1 and in Fig. As shown in Figure 2, a fundus observation device (optical image measuring device) 1 comprises a retinal camera unit 2, an OCT unit 100, and a computing and control unit 200. The retinal camera unit 2 has virtually the same optical system as a conventional retinal camera. The OCT unit 100 has optical systems for capturing fundus OCT images. The computing and control unit 200 includes a computer that performs various calculations, control operations, etc. Retinal camera unit

[0023] The in Fig. The retinal camera unit 2, as depicted, has optical systems for obtaining two-dimensional images (fundus images) that represent the surface morphology of the fundus Ef of an eye E. Fundus images include, for example, observational images, photographic images, etc. The observational image is, for example, a monochromatic moving image generated at a predetermined frame rate using near-infrared light. The photographic image can be, for example, a color image captured by flash in the visible wavelength range, or a monochromatic still image captured using near-infrared light or visible light as illumination. The retinal camera unit 2 can also acquire other types of images, such as fluorescence angiography images, indocyanine green fluorescence images, and autofluorescence images.

[0024] The retinal camera unit 2 has a chin rest and a forehead rest for supporting a person's face. Furthermore, the retinal camera unit 2 has an optical illumination system 10 and an optical imaging system 30. The optical illumination system 10 shines illumination light onto the fundus Ef. The optical imaging system 30 directs light reflected from the fundus of the eye from the illumination light to imaging devices (CCD image sensors 35, 38 (sometimes simply referred to as CCDs)).

[0025] An observation light source 11 of the optical illumination system 10, for example, comprises a halogen lamp. Light (observation illumination light) emitted by the observation light source 11 is reflected by a reflecting mirror 12 with a curved reflective surface, passes through a condenser lens 13, and becomes near-infrared light after passing through a blocking filter 14 for visible light. The observation illumination light is then convergently directed near an imaging light source 15, reflected by a mirror 16, and passes through relay lenses 17 and 18, an aperture 19, and a relay lens 20. Finally, the observation illumination light is reflected on a peripheral part (area around an aperture section) of an aperture mirror 21, transmitted through a dichroic mirror 46, and refracted by an objective lens 22, thus illuminating the fundus Ef.An LED (light-emitting diode) can be used as an observation light source.

[0026] The light from the observation illumination, reflected by the fundus of the eye, is refracted by the objective lens 22, transmitted by the dichroic mirror 46, passes through the aperture section formed in the central region of the diaphragm mirror 21, is transmitted by a dichroic mirror 55, passes through a focusing lens 31, and is reflected by a mirror 32. Additionally, the light reflected by the fundus is transmitted by a semi-transparent mirror 39A, reflected by a dichroic mirror 33, and, via a condenser lens 34, forms an image on a light-receiving surface of the CCD 35. The CCD 35 captures the light reflected from the fundus, for example, at a predetermined frame rate. An image (observation image) based on the light reflected from the fundus and captured by the CCD 35 is displayed on a display device 3.When the optical imaging system 30 is focused on an anterior segment of the eye, the observation image of the anterior segment of eye E is displayed.

[0027] The imaging light source 15, for example, comprises a xenon lamp. Light emitted by the imaging light source 15 (imaging illumination light) is directed onto the fundus Ef via the same path as the observation illumination light. The light of the imaging illumination light reflected from the fundus is guided to the dichroic mirror 33 via the same path as the observation illumination light, transmitted through the dichroic mirror 33, reflected by a mirror 36, and forms an image on the light-receiving surface of the CCD 38 via a condenser lens 37. An image (photographed image) based on the light reflected from the fundus and captured by the CCD 38 is displayed on the display unit 3. The display unit 3 for displaying the observation image and the display unit 3 for displaying the photographed image can be the same or different.If a similar photograph is taken by illuminating eye E with infrared light, the image photographed by infrared light is displayed. An LED can be used as the imaging light source.

[0028] An LCD (liquid crystal display) 39 displays fixation targets, target specifications for visual acuity measurement, etc. The fixation target is a visual target (index) for fixating the eye E and is used in fundus photography, OCT, etc.

[0029] Part of the light emitted by the LCD display 39 is reflected by the semi-transparent mirror 39A, reflected by the mirror 32, passes through the focusing lens 31 and the dichroic mirror 55, passes through the aperture section of the aperture mirror 21, is transmitted through the dichroic mirror 46, refracted by the objective lens 22 and projected onto the fundus Ef.

[0030] By changing the display position of the fixation target on the LCD screen 39, the fixation position of the eye E can be changed. Examples of fixation positions of the eye E are a position to capture an image centered on the macula, a position to capture an image centered on the optic nerve head, a position to capture an image centered on the fundus (at a point between the macula and the optic disc), etc., as with conventional retinal cameras. The display positions of the fixation targets can be changed as desired.

[0031] As with conventional retinal cameras, the retinal camera unit 2 features an optical alignment system 50 and an optical focusing system 60. The optical alignment system 50 generates a target (index, alignment target) for adjusting the position of the optical system relative to the eye E (that is, for performing an alignment). The optical focusing system 60 generates a target (index, split target) for focusing on the fundus Ef.

[0032] Light emitted by an LED 51 of the optical alignment system 50 (alignment light) passes through apertures 52 and 53 and the relay lens 54, is reflected by the dichroic mirror 55, passes through the aperture section of the aperture mirror 21, is transmitted through the dichroic mirror 46 and is projected onto the cornea of ​​the eye E by the objective lens 22.

[0033] Light from the alignment light, reflected from the cornea, passes through the objective lens 22, the dichroic mirror 46, and the aperture section. A portion of the light reflected from the cornea is then transmitted through the dichroic mirror 55, passes through the focusing lens 31, is reflected by the mirror 32, transmitted through the semi-transparent mirror 39A, reflected by the dichroic mirror 33, and projected by the condenser lens 34 onto the light-receiving surface of the CCD 35. An image captured by the CCD 35 (alignment target, alignment index) is displayed on the display unit 3 along with the observation image. The user performs alignment by carrying out operations similar to those used with conventional retinal cameras. Alternatively, the computer and control unit 200 can analyze the position of the alignment target and move the optical system accordingly (automatic alignment).

[0034] To adjust the focus, the reflective surface of a reflector bar 67 is positioned obliquely in an optical path of the optical illumination system 10. Light emitted by an LED 61 of the optical focusing system 60 (focusing light) passes through a relay lens 62, is split into two light streams by a split-target plate 63, passes through a two-hole aperture 64, is reflected by a mirror 65, forms an image on the reflective surface of the reflector bar 67 by a condenser lens 66, and is then reflected. The focusing light then passes through the relay lens 20, is reflected at the aperture mirror 21, is transmitted through the dichroic mirror 46, is refracted by the objective lens 22, and is projected onto the fundus Ef.

[0035] Light from the focusing light, reflected from the fundus of the eye, follows the same path as the light from the alignment light reflected from the cornea and is captured by the CCD 35. An image captured by the CCD 35 (split target, split index) is displayed on the display unit 3 together with the observation image. Similar to conventional techniques, the computing and control unit 200 analyzes the position of the split target and moves the focusing lens 31 and the optical focusing system 60 to perform a focusing operation (automatic focusing). Focusing can also be performed manually while the split target is being observed.

[0036] The dichroic mirror 46 couples the optical path for fundus photography and the optical path for OCT. The dichroic mirror 46 reflects light of wavelength bands for OCT and transmits the light for fundus photography. The optical path for OCT includes a collimator lens unit 40, a section 41 for changing the optical path length, a galvanic scanner 42, a focusing lens 43, a mirror 44, and a relay lens 45. The components arranged in the optical path for OCT and the components arranged in the OCT unit 100 form an example of an “optical system”.

[0037] The collimator lens unit 40 converts light (signal light LS) emitted from an optical fiber 107 into a parallel luminous flux. The collimator lens unit 40 also couples the signal light LS returning from the eye E back into the optical fiber 107. The collimator lens unit 40 has a numerical aperture changing section 40A, which varies the beam diameter of the parallel luminous flux to change the numerical aperture (NA) for OCT. The numerical aperture changing section 40A can be configured as a unit with multiple lenses of different powers that can be selectively positioned in the optical path, or as a unit with one or more lenses that are movable along the optical axis. Changing the beam diameter of the signal light LS changes the numerical aperture for OCT.

[0038] Section 41, concerning the modification of the optical path, is found in the text provided by a [unclear text]. Fig. The prism shown in arrow 1 can be moved in the direction indicated to change the optical path length for OCT. Changing the optical path length can be used to correct the optical path length according to the axial length of the eye E, to adjust the interference state, etc. Section 41, for example, shows a prism and a mechanism for moving the prism.

[0039] The Galvanoscanner 42 changes the direction of propagation of light (signal light LS) guided along the optical path for OCT. Therefore, the fundus Ef is scanned by the signal light LS. The Galvanoscanner 42 features a galvanic mirror for scanning signal light LS in the x-direction, a galvanic mirror for scanning in the y-direction, and a mechanism for independently driving these components. This allows the signal light LS to be scanned in any direction on the xy-plane.

[0040] The focusing lens 43 is movable in directions indicated by an arrow. Fig. 1 are shown, and changes the focus position for OCT. OCT unit

[0041] Below is a configuration example of the OCT unit 100 with reference to Fig. Section 2 explains. The OCT unit 100 has an optical system for acquiring OCT images of the fundus Ef. This optical system has a configuration similar to a conventional spectral-domain OCT device. That is, this optical system is configured to split low-coherence light into signal light and reference light, superimpose the signal light returning from the fundus Ef onto the reference light that has traveled an optical reference path to generate interference light, and acquire spectral components of the interference light. The acquisition result (acquisition signal) is transmitted to the computing and control unit 200.

[0042] When swept-source OCT is used, a variable-wavelength light source (wavelength sweeping) is employed instead of a low-coherence light source, and an optical element for spectral decomposition of interference light is not included. In general, any known technique of the OCT type can be used for a configuration of the OCT Unit 100.

[0043] A light source unit 101 emits broadband light L0 with low coherence. This low-coherence light L0 contains, for example, a wavelength band in the near-infrared (approximately 800–900 nm) and has a temporal coherence length of a few tens of micrometers. It is possible to use wavelength bands invisible to the human eye, such as near-infrared light with a center wavelength of approximately 1040–1060 nm, as low-coherence light L0.

[0044] The light source unit 101 includes a light emission device, such as an SLD (superluminescent diode), an LED, an SOA (semiconductor optical amplifier), etc.

[0045] The light L0 emitted by the light source unit 101 with low coherence is fed to a fiber coupler 103 via an optical fiber 102 and split into signal light LS and reference light LR.

[0046] The reference light LR is fed to an optical attenuator 105 via an optical fiber 104. Using any known technique, the computing and control unit 200 controls the optical attenuator 105 to automatically adjust the amount of light (light intensity) of the reference light LR guided through the optical fiber 104. The reference light LR, whose light intensity has been adjusted by the optical attenuator 105, is guided through the optical fiber 104 and reaches a polarization control device 106. The polarization control device 106, for example, exerts a load on the optical fiber 104, which is configured in a loop, to adjust the polarization states of the reference light LR guided in the optical fiber 104. However, the configuration of the polarization control device 106 is not limited to this; any known technique can be used.The reference light LR, whose polarization state has been set by the polarization control device 106, is supplied to an optical coupler 109.

[0047] The signal light LS generated by the fiber coupler 103 is guided through the optical fiber 107 and converted into a parallel luminous flux by the collimator lens unit 40. The signal light LS then passes through the optical path changer 41, the electrotype scanner 42, the focusing lens 43, the mirror 44, and the relay lens 45, reaching the dichroic mirror 46. The signal light LS is reflected by the dichroic mirror 46, refracted by the objective lens 22, and projected onto the fundus Ef. The signal light LS is scattered (reflected) at various depth positions within the fundus Ef. Light scattered back from the fundus Ef (returning light) of the signal light LS travels along the same path, but in the opposite direction, back to the fiber coupler 103 and reaches the fiber coupler 109 via an optical fiber 108.

[0048] The fiber coupler 109 superimposes the backscattered light of the signal light LS and the reference light LR, which has passed through the optical fiber 104. The resulting interference light LC is guided through an optical fiber 110 and emitted from the exit end 111. Furthermore, the interference light LC is converted into a parallel luminous flux by a collimator lens 112, spectrally split (spectrally decomposed) by a diffraction grating 113, convergently aligned by a condenser lens 114, and projected onto a light-receiving surface of a CCD (image sensor) 115. Although the in Fig. 2. Diffraction grating 113 shown is a grating of the transmission type, any other type of spectrally decomposing elements (for example, of the reflection type) can be used.

[0049] The CCD 115, for example, is a line sensor that detects the respective spectral components of the spectrally decomposed interference light LC and converts these components into electrical charges. The CCD 115 accumulates these electrical charges, generates detection signals, and transmits them to the processing and control unit 200.

[0050] Although a Michelson-type interferometer is used in the present embodiment, any interferometer type can be used as required, such as a Mach-Zehnder-type interferometer. Instead of the CCD, other types of image sensors can be used, such as CMOS (Complementary Metal Oxide Semiconductor) image sensors. Computing and control unit

[0051] The following describes a configuration of the Computing and Control Unit 200. The Computing and Control Unit 200 analyzes acquisition signals supplied by the CCD 115 to generate OCT images of the fundus Ef. The computational processing for this can be the same as in a conventional spectral-domain OCT device.

[0052] The Computing and Control Unit 200 controls each component under the Retinal Camera Unit 2, the Display Unit 3, and the OCT Unit 100. For example, the Computing and Control Unit 200 displays OCT images of the fundus Ef on the Display Unit 3.

[0053] The computer and control unit 200 performs the following controls for the retinal camera unit 2: operational controls of the observation light source 101, the imaging light source 103 and the LEDs 51 and 61, an operational control of the LCD 39, movement controls of the focusing lenses 31 and 43, a movement control of the reflection bar 67, a movement control of the optical focusing system 60, an operational control of section 40A for changing the numerical aperture, a movement control of section 41 for changing the optical path, an operational control of the electrotype scanner 42, etc.

[0054] The computing and control unit 200 performs the following controls for the OCT unit 100: an operational control of the light source unit 101, an operational control of the optical attenuator 105, an operational control of the polarization control device 106, an operational control of the CCD 115, etc.

[0055] The Computing and Control Unit 200 features a microprocessor, RAM, ROM, a hard drive, a communication interface, etc., similar to conventional computers. Storage media, such as a hard drive, store computer programs for controlling the fundus observation device 1. The Computing and Control Unit 200 may include various circuit boards, such as circuit boards for OCT image generation. The Computing and Control Unit 200 may include operating devices (input devices), such as a keyboard, a mouse, and / or a display device, such as an LCD display.

[0056] The retinal camera unit 2, the display unit 3, the OCT unit 100 and the computing and control unit 200 can be integrally designed (i.e., arranged in a single housing) or arranged separately in two or more housings. tax system

[0057] The following describes a configuration of a control system for the fundus observation device 1 with reference to the Fig. 3 and Fig. 4 described. Control unit

[0058] A control unit 210 forms the central part of the control system of the fundus observation device 1. The control unit 210 includes, for example, the microprocessor, RAM, ROM, hard disk drive, and communication interface, etc. The control unit 210 includes a main control unit 211 and a memory 212. Main control unit

[0059] The main control unit 211 performs various controls, as described above. In particular, the main control unit 211 controls a focus drive 31A, a numerical aperture changing section 40A, a variable optical path length changing section 41, a galvanic scanner 42, and a focus drive 43A in the retinal camera unit 2. Furthermore, the main control unit 211 controls the light source unit 101, the optical attenuator 105, and the polarization control unit 106 in the OCT unit 100.

[0060] The focus drive 31A moves the focusing lens 31 along the optical axis. This changes the focus position of the optical imaging system 30. The focus drive 43A moves the focusing lens 43 along an optical axis under the control of the main control unit 211. This changes the focus position of the optical OCT system. This focus position controls the amount of light LS entering the optical fiber 107 via the collimator lens unit 40. Therefore, an optimal focus position is achieved by positioning the focusing lens 43 at a location where one fiber end of the optical fiber 107 on the side of the collimator lens unit 40 is optically conjugated with the fundus Ef. Each of the focus drives 31A and 43A has an actuator, such as a stepper motor, and a mechanism that transmits the driving force generated by this actuator to the focusing lens 31 or 43.

[0061] The main control unit 211 can be configured to control a drive mechanism of the optical system (not shown) for the three-dimensional movement of the optical systems 2 provided in the retinal camera unit 2. Such control is used for alignment and tracking. Tracking is an operation to move the optical system in accordance with an eye movement of the eye E. When tracking is performed, an alignment and a focusing operation are carried out beforehand. Tracking is a function for maintaining a suitable positional relationship, whereby the alignment and focus are adjusted by causing the position of the optical system to follow the eye movement.

[0062] The main control unit 211 performs processing to write data to memory 212 and processing to read data from memory 212. memory

[0063] Memory 212 stores various types of data. The data stored in memory 212 can include, for example, OCT image data, fundus image data, eye information, etc. The eye information contains information about individuals, such as a patient ID and name, and information about the eyes, such as left / right eye identification. Memory 212 stores various programs and data for the operation of the fundus observation device 1. Image generation section

[0064] An image generation section 220 generates cross-sectional image data of the fundus Ef based on acquisition signals from the CCD 115. Similar to conventional spectral-domain OCT, this processing includes noise reduction, filtering, dispersion compensation, fast Fourier transform (FFT), etc. For other types of OCT devices, the image generation section 220 performs known processing according to the type used.

[0065] The image generation section 220 can, for example, comprise the aforementioned printed circuit boards. According to the invention, “image data” and an “image” based on this image data can be assigned to one another. Image processor

[0066] An image processor 230 performs various image processing operations and analyses on images generated by the image generation section 220. For example, the image processor 230 performs various corrections, such as brightness correction of images, etc. Furthermore, the image processor 230 performs various image processing operations and analyses on images obtained by the retinal camera unit 2 (fundus images, anterior segment images, etc.).

[0067] The 230 image processor performs familiar image processing operations, such as interpolation, in which pixels are interpolated between cross-sectional images to generate three-dimensional image data of the fundus (Ef). Three-dimensional image data refers to image data whose pixel positions are defined by a three-dimensional coordinate system. Three-dimensional image data can be image data composed, for example, of three-dimensionally arranged voxels. Such image data is referred to as volume data, voxel data, etc. To display an image based on volume data, the 230 image processor performs rendering processing (e.g., volume rendering, maximum intensity projection (MIP), etc.) on the volume data to generate image data of a pseudo-three-dimensional image taken from a specific viewing angle.This pseudo three-dimensional image is displayed on a display device, such as a Display 240A.

[0068] It is also possible to generate batch data of cross-sectional images as three-dimensional image data. Batch data is image data obtained by three-dimensionally arranging cross-sectional images captured along scan lines, where the arrangement is based on a positional relationship of the scan lines. That is, batch data is image data obtained by representing cross-sectional images in a three-dimensional coordinate system, which are originally defined in their respective two-dimensional coordinate systems (i.e., by embedding the image data in a three-dimensional space).

[0069] The image processor 230 has a layer thickness calculation section 231, a repetition determination section 232, a section 233 for determining the numerical aperture and a section 234 for generating a composite cross-sectional image. Layer thickness calculation section

[0070] The layer thickness calculation section 231 analyzes a cross-sectional image of the fundus Ef to calculate the thickness of a specified layer of the fundus Ef. This processing includes a process to specify the boundaries (upper and lower margins) of the specified fundus layer Ef and a process to determine the distance between the specified upper and lower margins.

[0071] The specified layer can be one or more layers of the fundus (Ef) being observed. The layered tissues of the fundus (Ef) include the retina, the choroid, and the sclera. The retina has a multilayered structure with an inner limiting membrane, a nerve fiber layer, a ganglion cell layer, an inner plexiform layer, an inner nuclear layer, an outer plexiform layer, an outer nuclear layer, an outer limiting membrane, a photoreceptor layer, and a retinal pigment epithelium. The specified layer can be the retina, the choroid, or the sclera, or one or more of the layered tissues contained within the retina. The specified layer is predetermined. The specified layer can be chosen arbitrarily.

[0072] The processing used to define the boundaries of the specified layer is generally referred to as segmentation. Segmentation is an image processing technique used to specify an image area within a cross-sectional image corresponding to a layer of the fundus tissue Ef. This processing is performed based on pixel values ​​(brightness values) of the cross-sectional image. The respective layers of the fundus tissue have characteristic reflectances, so their image areas have characteristic brightness values. Segmentation defines a target image area based on these characteristic brightness values. It should be noted that the configuration can be such that a surface of the fundus Ef (the boundary between the retina and the vitreous) is specified, and a target image area is specified based on distances from the positions of this surface.

[0073] Once the boundaries (upper and lower edges) of the specified layer are defined, the layer thickness calculation section 231, for example, counts the number of pixels between the upper and lower edges and determines the thickness of the specified layer based on this number of pixels. Information (layer thickness information) indicating the thickness of the specified layer can be the number of pixels itself or distance information derived from the number of pixels (conversion to distances in real space, etc.). Furthermore, the layer thickness information can be information indicating the thickness distribution of the specified layer or information statistically derived from this thickness distribution (mean, mode, median, maximum, minimum, etc.).Furthermore, the layer thickness information can display the thickness of the specified layer at a specified position (for example, at a position on a line that runs through the center of a frame). Repetition determination section

[0074] The repetition determination section 232 determines the number of repetitions of the OCT scan based on the slice thickness information obtained by the slice thickness calculation section 231. Although details will be explained later, in the OCT in the present embodiment, a scan is repeatedly performed with respect to the same location of the fundus Ef while the focus position is changed. The number of repetitions determined by the repetition determination section 232 corresponds to the number of cross-sectional images acquired by the OCT performed in this way. If the focus position is changed incrementally in such an OCT, the number of repetitions corresponds to the number of focus positions changed in this way.

[0075] The following are examples of a process for determining the number of repetitions. As in Fig. As shown in Figure 5, the retinal thickness d is assumed to be obtained as the layer thickness information, where the retinal thickness d is a distance between a retinal surface L1 (boundary between the inner limiting membrane and the vitreous body) and a retinal underside L2 (boundary between the retinal pigment epithelium and the choroid). Furthermore, the height of a frame of a cross-sectional image G (distance along the depth direction (z-direction) of the fundus Ef) is denoted by H.

[0076] A first example is described below. Section 232 of the repetition determination divides the frame height H by the retinal thickness d. If the quotient H / d is an integer, it is set as the number of repetitions. Conversely, if the quotient H / d is not an integer, the minimum value among integers greater than the quotient H / d is set as the number of repetitions.

[0077] A second example is described below. The repetition determination section 232 determines a value d1 that is less than or equal to the retinal thickness d and is 1 / (integer) of the frame height H: d1 = d or d1 < d and H / d1 = (integer). This integer can be a maximum value that satisfies the preceding relationship or a value smaller than the maximum value. This integer value is used as the number of repetitions.

[0078] A third example is described below. The repetition determination section 232 arbitrarily sets a value d2 that is less than the retinal thickness d: d2 < d. If the quotient H / d2, obtained by dividing the frame height H by the value d2, is an integer, the quotient H / d2 is set as the number of repetitions. If, on the other hand, the quotient H / d2 is not an integer, the minimum value among integers greater than the quotient H / d2 is set as the number of repetitions. Here, the value d2 can be obtained by dividing the retinal thickness d by a given value e: d2 = d / e. Essentially equivalently, it is possible to obtain the value d2 by multiplying the retinal thickness d by a given ratio f (%): d2 = d × f.

[0079] If an "overlap width (margin dimension for piecing)" is used in the processing to generate a composite cross-sectional image (described later), the number of repetitions corresponding to the "overlap width" is added to the number of repetitions obtained in the processing examples mentioned above. Additionally, the number of repetitions can be determined based on the image depth, as described later. Section on determining the numerical aperture

[0080] As described above, the numerical aperture in OCT is modified by Section 40A, which describes how to change the numerical aperture. Section 233, which describes how to determine the numerical aperture, specifies a value such that the image depth (or depth of field) in OCT becomes less than the thickness of the specified slice.

[0081] In general, the following relationship between the imaging depth D and the numerical aperture NA is known: D = λ / (2×NA) 2 ). Here, λ denotes a (center) wavelength of the signal light LS and is a fixed value.

[0082] In a Fig. In the case shown in Figure 5, Section 233 determines the numerical aperture by setting a value for the numerical aperture NA such that the depth of field D is less than the retinal thickness d. That is, Section 233 determines the numerical aperture by setting a value for the numerical aperture NA such that the following relationship is satisfied: d > D = λ / (2×NA) 2 ), i.e., NA > √(λ / 2d).

[0083] According to a numerical example, if NA = 0.088 and λ = 840 nm, D will be approximately 50 µm. Because the retinal thickness d is generally 200 to 300 µm, the imaging depth D is less than the retinal thickness d.

[0084] The number of repetitions is determined based on the resulting image depth D. For example, Section 233, for determining the numerical aperture, divides the frame height H by the image depth D. If the quotient H / D is an integer, the quotient H / D is set as the number of repetitions. Conversely, if the quotient H / D is not an integer, the minimum value among integers greater than the quotient H / D is set as the number of repetitions. Section on creating a composite cross-sectional image

[0085] In OCT measurements of the present embodiment, the same area of ​​the fundus Ef is repeatedly scanned while the focus position is changed. This yields cross-sectional images for different focus positions of this scanned area, the number of cross-sectional images corresponding to the number of repetitions. Section 234 for generating a composite cross-sectional image generates a composite cross-sectional image based on two or more such acquired cross-sectional images.

[0086] To perform such processing, section 234 for generating a composite cross-sectional image includes a sub-image specification section 2341, a position setting section 2342, a sub-image generation section 2345, and a composition processor 2346. Furthermore, the position setting section 2342 includes a section 2343 for specifying a characteristic image area and an image position setting section 2344. Sub-image specification section

[0087] As described above, in the present embodiment the same area of ​​the fundus Ef is repeatedly scanned while changing the focus position. Therefore, cross-sectional images correspond to different focus positions. Partial image specification section 2341 specifies a partial image that contains an image area corresponding to a given focus position. The image area corresponding to a focus position indicates a depth position (z-coordinate) of a frame corresponding to that focus position.

[0088] Examples of processing for specifying a sub-image are described below. Fig. Figure 6 shows one of a multitude of cross-sectional images obtained by repeated scanning. A line FPi represents a focus position when a cross-sectional image Gi is acquired. Pixels arranged on the line FPi form an image region corresponding to this focus position. For example, sub-image specification section 2341 specifies a region Ri that extends the same distance in both the +z and -z directions from the image region formed by the pixels arranged on the line FPi. An image region formed by the pixels contained in the region Ri is defined as a sub-region of the cross-sectional image Gi.

[0089] The area Ri can, for example, have a width (spacing) obtained by dividing the frame height of the cross-sectional image Gi by the number of repetitions, as described above. This spacing corresponds, for example, to the image depth described above. If the "overlap width" is used in the compositing process (described later), the area Ri can have a spacing corresponding to the "overlap width". Position setting section

[0090] The position setting section 2342 analyzes sub-images specified by the sub-image specification section 2341 to set relative positions between these sub-images. To perform this processing, the position setting section 2342 includes, for example, section 2343 for specifying a characteristic image area and image position setting section 2344. Section for specifying a characteristic image area

[0091] Section 2343, for specifying a characteristic image area, analyzes each of the partial images specified by the partial image specification section 2341 to specify a characteristic image area corresponding to a characteristic location in the fundus Ef. The characteristic location can be a macula (fovea centralis), an optic disc, a lesion site, etc. The characteristic image area can be an image area corresponding to a given layer of tissue. The processing to specify a characteristic image area can be performed, for example, by specifying a given image area in the same way as in the layer thickness calculation section 231 and specifying the characteristic image area based on the shape of the specified image area.

[0092] As a specific example, if a characteristic image area corresponding to a macula (fovea centralis) is to be specified, a characteristic depression (bulge) of the macula can be captured. If a characteristic image area corresponding to an optic disc is to be specified, a characteristic rise in the depth direction (z-direction) of the optic disc can be captured. If a characteristic image area corresponding to an edema (lesion) is to be specified, a characteristic protrusion of the edema is captured. Alternatively, a cavity corresponding to the edema can be captured. Image Position Adjustment Section

[0093] The image position setting section 2344 sets relative positions between the multiple sub-images specified by the sub-image specification section 2341, based on the characteristic image areas specified by section 2343 for specifying a characteristic image area. This processing is, for example, a position adjustment of adjacent sub-images such that the characteristic image areas coincide. If the "overlap width" is provided, the position adjustment of adjacent sub-images can be performed such that the characteristic image areas overlap. If the "overlap width" is not provided, the position adjustment of adjacent sub-images can be performed such that the characteristic image areas are smoothly joined. Sub-image generation section

[0094] The sub-image generation section 2345 crops cross-sectional images obtained through repeated scanning to generate sub-images. This cropping process extracts, for example, pixel information (pixel positions and pixel values) from pixels located in the areas of the cross-sectional images specified by the sub-image specification section 2341. Composition processor

[0095] The composition processor 2346 combines the multiple partial images generated by the partial image generation section 2345 to produce a cross-sectional image (composite cross-sectional image). During this composition processing, the pixel information of the multiple partial images can, for example, be treated as a single image data element. The composite cross-sectional image is an image representing a cross-section of the fundus Ef over which the repeated scanning process has been applied. Furthermore, because each of the partial images has an image area corresponding to a focus position for a corresponding OCT scan, the composite cross-sectional image is a globally focused image.

[0096] Examples of the composition processing of the present embodiment are given below with reference to the Fig. 7A and Fig. 7B described. The composition processing combines partial images PG1 to PGn from several cross-sectional images G1 to Gn, as described in Fig. 7A is shown. The sub-images PG1 to PGn are images that correspond to the areas Ri of the in Fig. The cross-sectional images Gi shown in 6 correspond to the following. In the present embodiment, the focus position is changed stepwise for the repeated scanning process. In this case, as shown in the Fig. 6 and Fig. As shown in Figure 7A, rectangular sub-areas PG1 to PGn are used. The composition processor 2346 combines the rectangular sub-areas PG1 to PGn to create a composite cross-sectional image CG, as shown in Figure 7A. Fig. Figure 7B shows the composite cross-sectional image CG, which is created by arranging the rectangular sub-areas PG1 to PGn in the depth direction (z-direction).

[0097] The compositing processor 2346 can combine sub-images based on the result of the relative position settings between the sub-images, as determined by the position setting section 2342, to generate a composite cross-sectional image. The result of the position setting can be used every time or depending on the situation. As an example of the latter, it is possible to determine a misalignment of sub-images based on offsets of characteristic image areas and use the result of the position setting to execute the compositing process only if the misalignment is equal to or greater than a threshold value.

[0098] The 230 image processor, which functions as described above, includes, for example, the aforementioned components, namely a microprocessor, RAM, ROM, hard disk, circuit boards, etc. Computer programs that instruct the microprocessor to perform the aforementioned functions are pre-stored in storage devices, such as the hard disk. User interface

[0099] A user interface 240 comprises a display 240A and a control unit 240B. The display 240A includes a display unit in the computing and control unit 200 and / or a display unit 3. The control unit 240B includes operating devices in the computing and control unit 200. The control unit 240B may include various buttons, keys, etc., which are provided on or outside the housing of the fundus observation device 1. For example, if the retinal camera unit 2 has a housing similar to conventional retinal cameras, a joystick, control panel, etc., located on that housing may be located in the control unit 240B. The display 240A may include various display devices, such as a touch panel, etc., which are located on the housing of the retinal camera unit 2.

[0100] The display 240A and the control unit 240B are not necessarily separate components. For example, a combined device similar to a touch panel can be used for display and control functions. In this case, the control unit 240B includes the touch panel and computer programs. Control inputs from the control unit 240B are supplied to the control unit 210 as electrical signals. Furthermore, control and / or information inputs can be executed via a graphical user interface (GUI) displayed on the display 240A and the control unit 240B. Signal light scanning process and OCT images

[0101] The scanning of signal light (LS) and OCT images is explained below.

[0102] The scan modes of the signal light LS provided by the fundus observation device 1 can include, for example, horizontal, vertical, crosswise, radial, circular, concentric, spiral scans, etc. These scan modes are used selectively with regard to the observation site of the fundus, the analysis mode (retinal thickness, etc.), the time required for the scan, the scan density, etc.

[0103] The horizontal scan process is a scanning operation for signal light (LS) in the horizontal direction (x-direction). The horizontal scan process includes a mode for scanning signal light (LS) along multiple scan lines extending horizontally and arranged vertically (y-direction). In this mode, the distance between scan lines can be set as desired. By setting the distance between adjacent scan lines sufficiently small, a three-dimensional image can be generated (three-dimensional scan). The vertical scan process is performed similarly.

[0104] The cross-scan operation is a scanning operation for signal light LS along a cross-shaped trajectory consisting of two mutually orthogonal straight trajectories (linear trajectories). The radial scan operation is a scanning operation for signal light LS along a radial trajectory consisting of several linear trajectories arranged at predefined angles. The cross-scan operation is an example of a radial scan operation.

[0105] The circular scan is a scan for scanning signal light LS along a circular trajectory. The concentric scan is a scan for scanning signal light LS along multiple circular trajectories arranged concentrically around a predetermined center position. The circular scan is an example of the concentric scan. The spiral scan is a scan for scanning signal light LS along a spiral trajectory while the curve radius is gradually decreased (or increased).

[0106] Because the electroplating scanner 42 is configured to scan signal light LS in mutually orthogonal directions, it is capable of scanning signal light LS independently in the x and y directions. The signal light LS can be scanned along any trajectory on the xy plane by simultaneously controlling the orientations of two electroplating mirrors arranged in the electroplating scanner 42. As a result, the various scan modes described above can be implemented.

[0107] By scanning signal light LS according to the modes described above, it is possible to obtain a cross-sectional image in a plane defined by the direction along a scan line (scan trajectory) and the depth direction (z-direction) of the fundus. Furthermore, if the interval between scan lines is small, a three-dimensional image can be obtained.

[0108] An area of ​​the fundus Ef to be scanned by signal light LS, i.e., an area of ​​the fundus Ef subjected to OCT, is called a scan area. A scan area of ​​a three-dimensional scan is a rectangular area containing multiple horizontal scans. A scan area of ​​a concentric scan is a disk-shaped area enclosed by a trajectory of the circular scan with maximum diameter. A scan area of ​​a radial scan is a disk-shaped (or polygonal) area connecting the ends of scan lines. Processes

[0109] The following describes the processing of the fundus observation device 1. Fig. Figure 8 shows an example of processing the fundus observation device 1. It is assumed that alignment and focusing have already been performed. S1: Capturing a cross-sectional image for preprocessing

[0110] Initially, a cross-sectional image is acquired for preprocessing. This preprocessing includes determining the number of scan repetitions, the numerical aperture, and so on. The cross-sectional image acquired here is a live cross-sectional image, obtained, for example, by repeatedly scanning the same cross-section of the fundus Ef. S2: Obtaining layer thickness information

[0111] The layer thickness calculation section 231 analyzes the cross-sectional image acquired in step S1 to obtain layer thickness information that indicates the thickness of a given layer of the fundus Ef. S3: Determination of the numerical aperture

[0112] Section 233, for determining the numerical aperture, sets a numerical aperture value such that the imaging depth becomes less than the thickness indicated in the layer thickness information obtained in step S2. The main control unit 211 controls section 40A, for changing the numerical aperture, to set the numerical aperture to the determined value. S4: Determining the number of repetitions

[0113] The repetition determination section 232 determines the number of repetitions for repeatedly scanning the signal light LSs based on the layer thickness displayed in the layer thickness information obtained in step S2. The focus positions can also be determined here. For example, the focus positions can be set as positions that divide the frame height of a cross-sectional image into N equal parts, where N represents the number of repetitions. S5: Performing a repeating scan

[0114] Upon receiving a predefined trigger signal, the main control unit 211 performs successive scans while changing the focus positions. The repeated scanning is performed with the numerical aperture specified in step S3 and for the number of times (number of repetitions) determined in step S4. The number of focus positions to be changed is equal to the number of repetitions.

[0115] The repeated scanning process can be achieved, for example, using a [missing information - likely a specific tool or method]. Fig. The process is controlled by the timing diagram shown in Figure 9. Scanning the signal light LS involves changing its irradiation position according to a sawtooth-shaped graph. A slanted line segment TS of the diagram indicates a scanning operation of the signal light LS with respect to different irradiation positions. A vertical segment TR of the graph indicates an operation whereby the irradiation position of the light signal LS is changed from the last irradiation position among several irradiation positions to the first irradiation position (reset operation). Otherwise, the focus position is changed stepwise, as shown by a step-shaped graph TF1. The change in focus position is performed simultaneously with the reset operation of the irradiation position of the light signal LS (vertical segment TR). S6: Generating cross-sectional images

[0116] Image generation section 220 generates multiple cross-sectional images based on data acquired by repeated scanning in step S5. The number of cross-sectional images generated is equal to the number of repetitions determined in step S4. Each cross-sectional image is generated from data acquired during an oblique line segment TS in the Fig. The scanning process is captured as shown in the time diagram 9. S7: Specifying sub-images

[0117] For each of the cross-sectional images generated in step S6, the sub-image specification section 2341 specifies a sub-image that contains an image area corresponding to a corresponding focus position. S8: Specifying a characteristic image area

[0118] Section 2343, for specifying a characteristic image area, analyzes each of the partial images specified in step S7 to specify a characteristic image area that corresponds to a characteristic location of the fundus Ef. S9: Setting relative positions between sub-images

[0119] The image position setting section 2344 sets relative positions between the sub-images based on the characteristic image areas specified in step S8. S10: Generating partial images

[0120] The partial image generation section 2345 extracts the partial images specified in step S7 from the cross-sectional images. Therefore, partial images are generated from the corresponding cross-sectional images. It should be noted that the processing of step S10 can be executed at any time after step S7. S11: Generating a composite cross-sectional image

[0121] The compositing processor 2346 combines the partial images generated in step S10, based on the results of the relative position adjustment in step S9, to produce a composite cross-sectional image of the fundus Ef. The resulting composite cross-sectional image is stored in memory 212 by the main control unit 211. The composite cross-sectional image can be displayed on the display 240A. This concludes this processing example. Effects and impacts

[0122] The following describes the effects and properties of an optical image measurement device of the present embodiment (fundus observation device 1).

[0123] The fundus observation device 1 comprises an optical system, an image generation section, a control unit, and a section for generating a composite cross-sectional image. The optical system includes: a scanner (galvanic scanner 42) configured to change the irradiation position of signal light on an object (fundus Ef), and a focus position change section (focusing lens 43, focus drive 43A) configured to change the focus position of the signal light. Furthermore, the optical system detects interference light from the light returning from the object, both the signal light and the reference light. That is, the optical system performs an OCT measurement of the object. The image generation section 220 generates a cross-sectional image based on the detection results of multiple interference light beams corresponding to multiple irradiation positions of the signal light.The control unit (main control unit 211) controls the optical system to repeatedly illuminate the signal light to the multiple irradiation positions while the focus position is changed. Section 234 for generating a composite cross-sectional image produces a composite cross-sectional image based on two or more cross-sectional images generated by the image generation section based on the results of repeated irradiation of the signal light.

[0124] With such a configuration, a single cross-sectional image (composite cross-sectional image) is generated by combining multiple cross-sectional images acquired by repeatedly scanning the same cross-section of the object while changing the focus position, resulting in an image that is in focus overall. Furthermore, OCT can be performed by applying arbitrary settings to factors (e.g., the numerical aperture) that affect lateral resolution. Therefore, it is possible to obtain images with high lateral resolution and global sharpness.

[0125] The section for generating a composite cross-sectional image can include a sub-image specification section 2341, which is configured to specify a sub-image containing an image area corresponding to a focus position for each of the cross-sectional images generated by the image generation section. In this case, the section for generating a composite cross-sectional image can combine two or more such specified sub-images to produce the composite cross-sectional image. With this configuration, sub-images corresponding to focus positions in cross-sectional images are combined, ensuring that an overall focused image is obtained reliably and automatically.

[0126] The section for generating a composite cross-sectional image can include a position setting section 2342, which is configured to analyze the sub-images specified by the sub-image specification section in order to set relative positions between the sub-images. In this case, the section for generating a composite cross-sectional image can combine the sub-images whose relative positions have been set to generate the composite cross-sectional image. With this configuration, even if misalignment occurs between cross-sectional images during a repeated scan due to eye movement, pulse, etc., this misalignment can be corrected to generate the composite cross-sectional image.

[0127] The position setting section can include a section 2343 for specifying a characteristic image area, which is configured to analyze each of the sub-images to specify a characteristic image area corresponding to a characteristic location of the object. In this case, the position setting section 2342 can perform the adjustment of the relative positions between the sub-images based on the specified characteristic image areas. With this configuration, it is possible to achieve position setting with high precision and a high degree of accuracy based on the characteristic image areas.

[0128] The fundus observation device 1 can have a repetition determination section 232 configured to determine the number of repetitions for repeated irradiation of the signal light based on a pre-established thickness of a predetermined layer of the object. With this configuration, the number of repetitions for the repeated scanning process can be determined automatically. Furthermore, the appropriate number of repetitions can be derived with reference to the thickness of the predetermined layer.

[0129] The fundus observation device 1 can include a layer thickness calculation section 231 configured to analyze a cross-sectional image obtained before repeated irradiation with signal light in order to calculate the thickness of the specified layer. With this configuration, the optimal number of repetitions can be derived by actually measuring the object to obtain and reference the thickness of the specified layer.

[0130] The optical system can include a numerical aperture change section 40A, configured to change the numerical aperture, and a numerical aperture determination section 233, configured to determine a numerical aperture value such that the imaging depth becomes less than the thickness of the specified slice. In this case, the control unit can control the numerical aperture change section to set the numerical aperture to the specified value. With this configuration, a high-resolution OCT measurement of the specified slice can be performed, and a composite cross-sectional image with high image quality can be acquired. It is also desirable to determine the numerical aperture with respect to its influence on the lateral resolution.

[0131] The control unit can incrementally change the focus position for each repetition of the signal light illumination to the multiple illumination positions when the repeated illumination of the signal light is performed (cf. Fig. 9) In this case, the section for generating a composite cross-sectional image can create the composite cross-sectional image based on rectangular sub-images that contain image areas corresponding to the focus positions in the cross-sectional images. This configuration represents a concrete example of repeated scanning and image compositing processing.

[0132] The section for generating a composite cross-sectional image can include a sub-image generation section 2345, configured to crop each of the cross-sectional images to generate sub-images, and a composition processor 2346, configured to perform tiling processing of the sub-images to generate the composite cross-sectional image. Tiling is an image composition processing technique for generating a single image by combining multiple images. In the present embodiment, tiling does not require the use of an "overlap width." This configuration represents a specific example of image composition processing. Modification examples

[0133] The configurations described above serve only to illustrate advantageous implementations of the present invention. Therefore, within the scope of protection of the present invention, it is possible to implement any modifications (by omission, substitution, addition, etc.). Examples of such modifications are presented below. It should be noted that components similar to those of the preceding embodiment are designated by the same reference numerals. Modification example 1

[0134] As described above, misalignment between cross-sectional images occurs when eye movement, pulse, body movement, etc., takes place during repeated scanning. If the misalignment is large, multiple cross-sectional images will represent different cross-sections and are therefore unsuitable for generating a composite cross-sectional image. The present modification example is used to solve such a problem.

[0135] Fig. Figure 10 shows an example of the present modification. An optical image measuring device (fundus observation device) of the present modification has almost the same configurations as the embodiment described above (cf. Figure 10). Fig. 3), however, it differs in that the image processor 230 has an offset detection section 235. It should be noted that the image processor 230 of the present modification example may have at least one component below the layer thickness calculation section 231, the repetition determination section 232, and the section 233 for determining the numerical aperture of the embodiment described above. Furthermore, the section 234 for generating a composite cross-sectional image of the present modification example may have similar configurations to the embodiment described above or different configurations (cf. Fig. 4).

[0136] The offset detection section 235 detects an offset between the optical OCT system and the object (fundus Ef) during the repeated scanning process. This offset detection includes offset detection in the xy-direction and / or offset detection in the z-direction. It is desirable that the offset detection be performed before processing to generate a composite cross-sectional image.

[0137] Displacement detection in the xy direction can be performed, for example, by: acquiring an observational image of the fundus Ef (real-time infrared fundus image) simultaneously with the repeated scanning process, and capturing a chronological change in the position of a characteristic point of the fundus Ef in frames acquired in chronological sequence. Alternatively, similar processing can be performed using an observational image of the anterior segment of the eye E. Such processing can be performed during the tracking described above.

[0138] Displacement detection in the xy-direction can be performed by analyzing multiple cross-sectional images acquired through repeated scanning. It should be noted that these cross-sectional images are chronological, with a frame rate corresponding to the repetition frequency of the scan. The xy-direction displacement can be detected by identifying chronological changes in the morphology (position (x-coordinate, y-coordinate), shape, size, etc.) of a characteristic location in the fundus Ef within the frames of the cross-sectional images.

[0139] Displacement detection in the z-direction can be performed, for example, by analyzing multiple cross-sectional images acquired through repeated scanning. As an example, the z-direction displacement can be detected, similar to displacement detection in the xy-direction, by recording a chronological change in the position (z-coordinate) of a characteristic point in the fundus Ef within the frame of the cross-sectional images.

[0140] The main control unit 211 performs a new repeated scan of the fundus Ef based on the offset detected by the offset detection section 235. This processing involves deciding whether or not to perform the repeated scan, for example, based on the detected offset (e.g., a maximum offset value). Furthermore, this processing may include determining control parameters for the new repeated scan (scan mode, scan positions, etc.) based on the detected offset.

[0141] The new repeated scan will be performed in the same scan mode as the last one. Alternatively, it's possible to use a different scan mode than the one used last time. For example, if the last repeated scan used a horizontal scan, the new scan could use two adjacent horizontal scans to reduce the risk of needing to scan again.

[0142] Image generation section 220 generates several new cross-sectional images based on acquisition signals obtained through the newly executed repeated scanning process. Section 234, for generating a composite cross-sectional image, creates a composite cross-sectional image based on these new cross-sectional images.

[0143] The offset detection described above can be performed with respect to several new cross-sectional images generated by the image generation section 220. For example, based on the newly detected offset, it can be determined whether or not a further repeat scan should be performed. In this case, when the number of repetitions of the repeat scan reaches a predetermined number, a message indicating this fact can be displayed on the display 240A.

[0144] According to the present modification example, a new scan can be performed based on the offset between the optical system and the object during the repeated scan. For example, re-measurements can be performed automatically if the repeated scan is performed in an unsuitable manner. Modification example 2

[0145] The present modification example solves the same problem as modification example 1. While modification example 1 performs a new scan based on an offset between the optical system and the object during the repeated scan, the present modification example provides a message based on the offset.

[0146] One configuration of the present modification example can be the same as that of modification example 1 (see below). Fig. 10) same. As in modification example 1, the offset detection section 235 is configured to detect an offset between the optical OCT system and the object (fundus Ef) during the execution of the repeated scan.

[0147] The main control unit 211 controls a message section to output message information based on the offset detected by the offset detection section 235. Examples of the message section include the display 240A, an audio output section (not shown), etc. The type of message information depends on the configuration of the message section, and examples include visual information (string information, image information, etc.), audio information (alarm messages, alarm signals, etc.), and the like.

[0148] The main control unit 211 can calculate a statistical value (maximum value, standard deviation, etc.) of the measured offsets and use this value for message control. For example, if a statistical value of the offsets is greater than a predetermined value, a message indicating this can be issued. It is also possible to display the statistical value of the offsets directly. In these cases, a GUI can be displayed on the display 240A to allow the user to determine whether or not to perform a remeasurement.

[0149] According to one such modification example, a message can be provided based on offsets between the optical system and the object during the repeated scanning process. Therefore, it is possible to inform the user that the repeated scanning process was not performed correctly, that a new measurement should be taken, and so on. Modification example 3

[0150] The embodiment described above changes the focus positions incrementally during repeated scanning, but aspects of changing the focus positions are not limited to this. For example, focus positions can be changed continuously during repeated scanning. Fig. Figure 11 shows an example of a time diagram for such a case.

[0151] The scanning of the signal light LS is performed in the same manner as in the embodiment described above. A slanted line segment TS of the diagram indicates a scanning process of the signal light LS with respect to different irradiation positions. A vertical segment TR of the graph indicates a reset process of the irradiation positions of the signal light LS. On the other hand, focus positions are continuously changed, as represented by a linear graph TF2, which differs from the embodiment described above.

[0152] If focus positions are changed stepwise as in the embodiment described above, the focus positions are the same for each repetition of the scan (i.e., for each of the oblique line segments TS), and each repetition corresponds to a single focus position. On the other hand, the present modification example changes focus positions continuously. Therefore, if the areas Ri of the cross-sectional images provided to generate a composite cross-sectional image are rectangular, as in Fig. As illustrated in Figure 6 of the embodiment described above, there is a risk that focus positions may deviate from the areas Ri. Furthermore, if the areas Ri are defined as large areas so that focus positions do not deviate from them, sections far from the focus positions will be slightly out of focus.

[0153] Taking such situations into account, the present modification example uses parallelogram-shaped sub-areas in cross-sectional images to create a composite cross-sectional image. Fig. 12A shows an example of this. Several in Fig. The cross-sectional images J1 to Jn shown in Figure 12A are generated based on data obtained through repeated scanning operations carried out according to the procedure described in Figure 12A. Fig. The process is carried out as shown in the time diagram 11. Each of the cross-sectional images Ji (i = 1 to n) is generated from data captured by scanning according to the i-th oblique line segment TS in the time diagram.

[0154] In this example, a sub-image PJi of the cross-sectional image Ji is used for compositing. Each sub-image PJi is an image region with a width that extends the same distance in both the +z and -z directions from graph TF2 (an image region corresponding to graph TF2) at the focus position during the period of the corresponding oblique line segment TS. Since graph TF2 is a monotonic, linear graph (i.e., a graph with a constant slope), each sub-image PJi becomes a parallelogram-shaped image region. Each sub-image PJi is an example of a parallelogram-shaped sub-image.

[0155] Section 234, on generating a composite cross-sectional image, combines such parallelogram-shaped sub-images PJ1 to PJn to create a composite cross-sectional image. This composite cross-sectional image is obtained by arranging the parallelogram-shaped sub-images PJ1 to PJn in the depth direction (z-direction) (not shown). In the present example, each of the sub-images PJi has an "overlap width," and the composition processing is performed such that sections of adjacent sub-images PJi, PJ(i+1) overlap each other. It is also possible to perform composition processing without an "overlap width," as in sub-images PK1 to PKn of cross-sectional images K1 to Kn in Fig. 12B is shown.

[0156] Regarding triangular areas at the top and bottom edges of a frame of the composite cross-sectional image, it is possible to use images of triangular areas in the cross-sectional images that contain sub-images PJi which are closest to them (i.e., cross-sectional images J1 and Jn). Alternatively, such images of the triangular areas can be obtained by the in Fig. The graph TF2 shown in section 11 is extended chronologically forwards and backwards.

[0157] Fig. Figure 13 shows another example of the case where the focus position is continuously changed. In this example, the compositing processing is performed as in the embodiment above, using rectangular sub-images, and a repeated scan is performed while the focus position is continuously changed.

[0158] The main control unit 211 is capable of detecting the focus position (z-coordinate) at any point during the repeated scanning process because it performs the focus position control. Alternatively, the focus position can be detected using a sensor that detects the position of the focusing lens 43 during the repeated scanning process.

[0159] The main control unit 211 receives a representative focus position for a duration corresponding to the respective inclined line segments TS when scanning the signal light LS. The representative focus positions can, for example, be focus positions at midpoints t1 to tn for durations corresponding to the inclined line segments TS.

[0160] Section 234, for generating a composite cross-sectional image, specifies rectangular sub-images such that they contain image areas (consisting of pixels on line segments extending perpendicular to the z-direction) corresponding to the representative focus positions that correspond to the oblique line segments TS for the cross-sectional images. Section 234 then assembles the specified rectangular sub-images to generate a composite cross-sectional image. It is also possible to define rectangular sub-images such that they contain the Fig. The focus positions shown in 12A contain corresponding image areas TF2.

[0161] The present modification example continuously changes focus positions, thus simplifying the configuration and control of the focus drive 43A compared to the case of stepwise movement. Modification example 4

[0162] The embodiment described above generates a composite cross-sectional image by cropping and joining several cross-sectional images, but the composite processing is not limited to this. For example, a composite cross-sectional image can be generated by superimposing several cross-sectional images using a layer function.

[0163] Fig. Figure 14 shows an example of a configuration of the present modification example. An optical image measuring device (fundus observation device) of the present modification example has almost the same configurations as the embodiment described above (cf. Figure 14). Fig. 3), however, it differs in that the image processor 230 has a weighting section 237. It should be noted that the image processor 230 of the present modification example may have at least one component under the layer thickness calculation section 231, the repetition determination section 232, and the section 233 for determining the numerical aperture of the embodiment described above. Furthermore, the section 234 for generating a composite cross-sectional image of the present modification example may have similar configurations to the embodiment described above (cf. Fig. 4) or different configurations thereof.

[0164] Weighting section 237 performs a weighting of pixels of each cross-sectional image to be processed for compositing. The weighting can be performed, for example, by assigning transparency information (alpha values) to the alpha channels of pixels in a cross-sectional image. Weighting section 237 assigns the transparency information in such a way that the opacity of pixels forming sub-images in the embodiment described above becomes relatively higher. Fig. 15A and Fig. Section 15B shows specific examples of this.

[0165] It is assumed that several cross-sectional images Mi (i = 1 to n) are obtained by repeated scanning. A in Fig. The opacity graph α1 shown in Figure 15A provides transparency information to the alpha channels of pixels in cross-sectional images Mi, such that the opacity of pixels in sub-images PMi becomes relatively higher in the cross-sectional images Mi. The cross-sectional images Mi to which the opacity graph α1 is applied are images in which the opacity of the sub-images PMi is high and the opacity gradually decreases with increasing distance from the sub-images PMi.

[0166] In a Fig. In the opacity graph α2 shown in Figure 15B, the opacity assumes a maximum value in sub-images PMi of the cross-sectional images Mi and a minimum value in other areas. The cross-sectional images Mi, to which the opacity graph α2 is applied, are images in which different areas of the sub-images PMi are transparent.

[0167] Section 234 for generating a composite cross-sectional image overlays the cross-sectional images M1 to Mn, whose pixels have been weighted by weighting section 237, to generate a composite cross-sectional image. If a positional adjustment is performed with respect to the cross-sectional images M1 to Mn, the processing can be carried out in the same way as in the embodiment described above. Other modification examples

[0168] In the embodiments described above, the difference in optical path length between the optical paths of the signal light LS and the reference light LR is changed by altering the position of section 41 to change the optical path length; however, the methods for changing the difference in optical path length are not limited to this. For example, the difference in optical path length can be changed by placing a reflective mirror (reference mirror) in the optical path of the reference light and moving the reference mirror in the direction of propagation of the reference light to change the optical path length of the reference light. Furthermore, the difference in optical path length can be changed by moving the retinal camera unit 2 and / or the OCT unit 100 relative to the eye E to change the optical path length of the signal light LS.If an object is not a part of a living body or the like, the difference in optical path length can be changed by moving the object in the depth direction (z-direction).

[0169] Computer programs for implementing the embodiments described above can be stored on any computer-readable storage media. Examples of such storage media include an optical disk, a semiconductor memory, a magneto-optical disk (CD-ROM, DVD-RAM, DVD-ROM, MO, etc.), a magnetic storage medium (a hard disk, a floppy disk (TM), ZIP, etc.), etc.

[0170] The programs can be transmitted over networks such as the Internet, a local area network (LAN), etc. Explanation of reference symbols 1 Fundus observation device (optical image measuring device) 2 Retinal camera unit 40A Section for changing the numerical aperture Section 41 on changing the optical path length 42 electroplating scanners 43 Focusing lens 43A Focus Drive 100 OCT units 200 computing and control units 210 Control unit 211 Main control unit 212 storage 220 Image generation section 230 image processor 231 Layer thickness calculation section 232 Repetition Determination Section 233 Section on determining the numerical aperture 234 Section on generating a composite cross-sectional image 2341 Sub-image specification section 2342 Position setting section 2343 Section on specifying a characteristic image area 2344 Image Position Adjustment Section 2345 Sub-image generation section 2346 Composition Processor 2347 Weighting section 235 Offset detection section 240A Display 240B Control Unit E eye Ef fundus of the eye LS signal light LR Reference Light LC interference light

Claims

[1] Optical image measuring device with: an optical system comprising a scanner configured to change the irradiation position of signal light on an object, a focus position change section configured to change the focus position of the signal light, and a numerical aperture change section configured to change a numerical aperture and configured to detect interference light from light returning from the object of the corresponding signal light and reference light; an image generation section configured to produce a cross-sectional image based on the acquisition results of multiple interference light beams corresponding to multiple irradiation positions of the signal light; a control device configured to control the optical system to repeatedly shine the signal light onto the multiple irradiation positions while the focus position is changed; and a section for generating a composite cross-sectional image, configured to produce a composite cross-sectional image based on two or more cross-sectional images generated by the image generation section based on results of repeated irradiation of the signal light; a layer thickness calculation section configured to analyze a cross-sectional image obtained before repeated irradiation with the signal light in order to calculate the thickness of the specified layer; a section for determining the numerical aperture, configured to determine a value of the numerical aperture such that the imaging depth becomes smaller than the thickness of the specified layer; and a repetition determination section configured to determine the number of repetitions during repeated irradiation of the signal light based on the imaging depth; the control device controls the section for changing the numerical aperture in order to set the numerical aperture to the specified value. [2] Device according to claim 1, wherein the section for generating a composite cross-sectional image comprises a sub-image specification section configured to specify a sub-image having an image area corresponding to a corresponding focus position for each of the two or more cross-sectional images, and combines the specified two or more sub-images to generate the composite cross-sectional image. [3] Device according to claim 2, wherein the section for generating a composite cross-sectional image comprises a position setting section configured to analyze the two or more partial images in order to set the relative positions between the two or more partial images, and to combine the two or more partial images whose relative positions have been set in order to generate the composite cross-sectional image. [4] Device according to claim 3, wherein the position setting section has a section for specifying a characteristic image area, which is configured to analyze each of the two or more partial images in order to specify a characteristic image area corresponding to a characteristic location of the object, and sets the relative positions between the two or more partial images based on the specified characteristic image areas. [5] Device according to any one of claims 1 to 4, further comprising an offset detection section configured to detect an offset between the optical system and the object during repeated irradiation with the signal light, wherein The control unit performs a repeated irradiation of the signal light based on the detected offset, and The section on generating a composite cross-sectional image generates the composite cross-sectional image based on two or more new cross-sectional images, which are generated based on the results of repeated irradiation of the signal light. [6] Device according to any one of claims 1 to 4, further comprising an offset detection section configured to detect an offset between the optical system and the object during repeated irradiation of the signal light, wherein the control unit controls a communication section to output communication information based on the detected offset. [7] Device according to any one of claims 1 to 6, wherein the control device incrementally changes the focus position for each repetition of the irradiation of the signal light to the multiple irradiation positions when the repeated irradiation of the signal light is performed, and wherein the section for generating a composite cross-sectional image generates the composite cross-sectional image based on a rectangular partial image containing an image area corresponding to a corresponding focus position in each cross-sectional image. [8] Device according to any one of claims 1 to 6, wherein the control device continuously changes the focus position when the repeated irradiation of the signal light is performed, and wherein the section for generating a composite cross-sectional image generates the composite cross-sectional image on the basis of a parallelogram-shaped partial image having an image area corresponding to a corresponding focus position in each cross-sectional image. [9] Device according to any one of claims 1 to 8, wherein the section for generating a composite cross-sectional image comprises a sub-image generation section configured to crop each of the two or more cross-sectional images to generate a sub-image, and a composition processor configured to perform tiling processing of two or more sub-images obtained from the two or more cross-sectional images to generate the composite cross-sectional image. [10] Device according to any one of claims 1 to 8, wherein the section for generating a composite cross-sectional image comprises a weighting section configured to perform weighting of pixels of each of the two or more cross-sectional images, and a composition processor configured to perform overlay processing of the two or more cross-sectional images with the weighted pixels to generate the composite cross-sectional image.

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