JP2019205822A - Imaging device and control method thereof - Google Patents

Abstract

To provide a method to optimize AO control of AO-SLO and AO-OCT mounted devices without complicating a device configuration.SOLUTION: An imaging device includes: a common optical system for irradiating the ocular fundus with a first measurement light from a first light source and a second measurement light from a second light source whose wavelengths are different from each other; first generation means for generating a tomographic image of the ocular fundus on the basis of an interference light obtained by causing a return light of the first measurement light from the ocular fundus through the common optical system and a corresponding reference light to interfere with each other; second generation means for generating an ocular fundus image of the ocular fundus on the basis of a return light of the second measurement light from the ocular fundus through the common optical system; wavefront detection means disposed in the common optical system for detecting a wavefront aberration of at least one of the lights of the wavefront aberration of the return light of the first measurement light and the wavefront aberration of the return light of the second measurement light; and selection means for selecting at least one of the lights of the return light of the first measurement light and the return light of the second measurement light. The wavefront detection means measures the wavefront aberration of the selected light.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an imaging apparatus and a control method thereof, and more particularly to an imaging apparatus that acquires a tomographic image of a fundus retina of a subject eye and a control method thereof.

  A tomographic imaging apparatus (OCT: Optical Coherence Tomography) that captures a tomographic image of the fundus retina of the eye to be examined by analyzing the frequency of the interference fringes obtained by causing the reflected light (sample light) from the fundus retina to interfere with the reference light A tomographic image is generated.

  In particular, in such an ophthalmic imaging apparatus, in recent years, higher resolution has been promoted by increasing the NA of an irradiation laser. However, when imaging the fundus, the image must be captured through the optical tissue of the eye such as the cornea or the crystalline lens. For this reason, as the resolution increases, the aberrations of the cornea and the crystalline lens greatly affect the image quality of the captured image.

  Therefore, there is a technique for imaging a fine structure by correcting the wavefront of measurement light and reflected light disturbed by the optical tissue of the eye such as the cornea and the crystalline lens of the eye to be examined, using adaptive optics (AO: Adaptive Optics) technology. Are known. In OCT, OCT having a resolution capable of resolving photoreceptor cells using AO technology has been developed.

Japanese Patent Laying-Open No. 2015-221091 Japanese Patent No. 5641744

  When capturing a high-definition OCT image that can resolve a photoreceptor cell, it is more susceptible to motion artifacts due to the movement of the eye to be examined than an OCT image with a normal resolution. Also, in order to generate a tomographic image in which a plurality of B-scan images are superimposed in order to improve image quality, a plurality of B-scan images captured by scanning the same line with measurement light accurately are required. Highly accurate tracking is required.

  In this case, the same resolution as that of the AO-OCT image is also required for the motion detection image captured for tracking when capturing the AO-OCT image. Therefore, it is necessary to use an AO-SLO image captured by an AO-SLO (Scanning Laser Ophthalmoscope). Patent Document 1 discloses a technique for simultaneously capturing images by slightly shifting an optical path in an AO-SLO or AO-OCT mounted machine using light sources having overlapping wavelength ranges. However, in this case, tracking is difficult due to different shooting areas, and there is a problem that the apparatus becomes complicated. In addition, the apparatus of Patent Document 2 does not simultaneously perform AO-SLO and AO-OCT imaging, and cannot use an AO-SLO image for tracking during AO-OCT imaging.

  Therefore, it is desirable to simultaneously capture the same region by using light of different wavelengths for capturing an AO-SLO image and capturing an AO-OCT image and branching by a wavelength separation mirror. However, even when an AO-SLO image and an AO-OCT image can be acquired simultaneously, a suitable AO control method differs depending on the chromatic aberration and the depth of penetration of each light, and it was difficult to optimize. .

  An object of the present invention is to provide a method of optimizing AO-SLO image capturing and AO control during AO-OCT image capturing without complicating the apparatus configuration.

  In order to solve the above-described problem, an imaging apparatus according to the present invention includes a first measurement light from a first light source and a second measurement light from a second light source having a wavelength different from that of the first measurement light. By causing a common optical system for irradiating the fundus, a return light of the first measurement light from the fundus via the common optical system, and a reference light corresponding to the first measurement light to interfere with each other A fundus image of the fundus is generated based on a first generation unit that generates a tomographic image of the fundus based on the interference light and a return light of the second measurement light from the fundus through the common optical system. And a second generation means that is disposed in the common optical system and has a wavefront aberration of at least one of the wavefront aberration of the return light of the first measurement light and the wavefront aberration of the return light of the second measurement light. Wavefront detection means for detecting, return light of the first measurement light and second measurement light; Ri and selection means for selecting at least one light of the light, the wavefront sensing means measures the wavefront aberration of the light selected by said selecting means.

  According to the present invention, it is possible to optimize AO-SLO image capturing and AO control at the time of capturing an AO-OCT image without complicating the apparatus configuration.

It is a figure which shows the structure of the imaging device in one Embodiment of this invention. It is a figure which shows the display screen displayed on the monitor at the time of imaging | photography in one Embodiment of this invention. It is a figure for demonstrating the relationship between the acquisition position of the AO-OCT image and AO-SLO image in one Embodiment of this invention. It is a figure for demonstrating fundus tracking in one embodiment of the present invention. It is a figure for demonstrating the imaging range at the time of volume data acquisition in one Embodiment of this invention. It is a figure for demonstrating the imaging range at the time of volume data acquisition in one Embodiment of this invention. It is a figure for demonstrating the imaging range at the time of volume data acquisition in one Embodiment of this invention. It is a figure for demonstrating the imaging range at the time of volume data acquisition in one Embodiment of this invention. It is a figure for demonstrating the imaging range at the time of volume data acquisition in one Embodiment of this invention. It is a figure for demonstrating the drive waveform of the scanner at the time of the imaging in one Embodiment of this invention. It is a figure for demonstrating the drive waveform of the Y scanner at the time of tracking of one Embodiment of this invention. It is a figure for demonstrating the drive waveform of the X scanner at the time of tracking of one Embodiment of this invention. It is a figure for demonstrating the structure of the X direction scanning part in one Embodiment of this invention. It is a flowchart at the time of the imaging in one Embodiment of this invention. It is a flowchart at the time of tracking in one Embodiment of this invention.

  An embodiment of the present invention will be described in detail below with reference to the drawings. The following description is merely illustrative and exemplary in nature and is not intended to limit the present disclosure and its application or uses in any way. The relative configurations of components shown in the embodiments, and the steps, numerical expressions, and numerical values do not limit the scope of the present disclosure unless specifically indicated otherwise. Techniques, methods and devices well known by those skilled in the art may not have been discussed in detail as those skilled in the art do not need to know these details to enable the embodiments discussed below.

[First Embodiment]
What can be imaged by the apparatus of this embodiment is, for example, a tomographic image of the retina of the fundus of the eye to be examined.

(Device configuration)
An example in which the Fourier domain optical coherence tomography according to the present embodiment is applied to a fundus tomographic imaging apparatus will be described with reference to the imaging apparatus shown in FIG.

  FIG. 1 illustrates an imaging apparatus according to the present embodiment, which includes an AO-OCT unit, an AO-SLO unit, an anterior ocular segment observation unit, and a fixation lamp unit. A sample optical system that is a common optical system for the AO-OCT section and the AO-SLO section is also included.

  The light source 1 of AO-OCT is a light source that generates low coherence light as AO-OCT measurement light. In the present embodiment, an SLD (Super Luminescent Diode) light source having a center wavelength of 855 nm and a wavelength width of 100 nm is used as the light source 1.

  The light emitted from the light source 1 is branched to the sample optical system 101 and the reference optical system 102 by the fiber coupler 2, and the light branched to the sample optical system 101 side is supplied to the sample optical system 101 via the adapter 3 and the fiber 4. Led. The sample optical system 101 includes a collimator lens 5, a BS (beam splitter) 6 that is a wavelength separation mirror that branches off from the AO-SLO optical system, and a BS (beam splitter) 7 that is a half mirror that branches an optical path to the wavefront detection optical system 105. , Mirror 8, concave mirror 9, shape-variable mirror, wavefront correction device DM (Deformable Mirror) 10 used for wavefront correction, concave mirror 11, wavelength branching mirror that branches and merges OCT measurement light and SLO measurement light BS (beam splitter) 12, fixed mirror 13, concave mirror 14, galvano mirror scanning in X direction, X scanner 15 such as MEMS mirror, concave mirror 16, mirrors 17a and 17b, mirror 19, lens 20, and scanning in Y direction An anterior ocular segment observation optical system 1 including a Y scanner 21, a concave mirror 22, and a wavelength selection mirror 6, constituted by BS (beam splitter) 23 for branching the fixation lamp optical system 107. The mirrors 17a and 17b are integrated and configured to be movable in the optical axis direction by the stage 18, and perform focus adjustment of the sample optical system.

  The light source 24 is a light source such as an LD (Laser Diode) light source, an SLD light source, or an LED (Light Emitting Diode) light source that emits AO-SLO measurement light, and has a wavelength different from that of the AO-OCT measurement light. In this embodiment, an SLD light source having a center wavelength of 760 nm and a wavelength width of 10 nm is used. The light emitted from the light source 24 is guided to the fiber 26 through the fiber adapter 25 and is guided to the AO-SLO projection optical system 103. The AO-SLO projection optical system 103 passes through the collimator lens 27, BS28, the focus adjustment lenses 29 and 30, the mirror 31, and BS6, and merges with the AO-OCT optical path of the sample optical system 101 via the above-described path. To BS12.

  The BS 28 is a half mirror that transmits 10% light and reflects 90% light in order to branch the optical paths of the AO-SLO projection optical system and the AO-SLO light receiving optical system. BS6 is a wavelength branching mirror that transmits AO-SLO measurement light and reflects AO-OCT measurement light.

  As will be described later, the BS 12 is a wavelength branching mirror that reflects AO-OCT measurement light and transmits AO-SLO measurement light, and transmits AO-SLO measurement light and reflects it by a high-speed scanner 32 that is a high-speed scanner. The light is again merged with the AO-OCT measurement light by the BS 12. Thereafter, the AO-OCT sample optical system and the BS (beam splitter) 23 constitute the AO-SLO projection optical system. The AO-SLO light receiving optical system 104 is arranged in the reflection direction of the BS 28, and includes a light receiving element 35 including a lens 33, a confocal stop 34, and an APD (Avalanche Photo Diode). The light receiving element 35 receives the return light from the fundus via the confocal stop 34.

  As the high-speed scanner 32, a resonance scanner or a MEMS (Micro Electro Mechanical System) scanner that can perform reciprocal scanning at about 8 kHz to 16 kHz can be used. However, these high-speed scanners can adjust the swing angle, but cannot change the center angle of scanning. Therefore, a separate scanner needs to be prepared for tracking or moving the imaging range.

  Further, the irradiation position of the AO-OCT measurement light imaged on the fundus is substantially the same as the irradiation position of the AO-SLO measurement light imaged on the fundus when the swing angle is 0. It has been adjusted.

  The reference optical system 102 includes a collimator lens 36, a density variable filter 37, mirrors 38, 39, 40, and 41, a CQ 42 that is a corner cube mirror, and a mirror 43. The CQ 42 is composed of three surfaces whose reflecting surfaces are orthogonal to each other, is disposed on the stage 44, and is movable about ± 100 mm. This corresponds to the difference in the optical axis length due to the focus adjustment of the AO-OCT measurement light caused by the difference in the axial length of the eye to be examined and the movement of the stage 18 of the sample optical system.

  In the optical system of the spectroscope 108, interference light is imaged on the line sensor 49 by a collimator lens 46, a spectral member 47 such as a grating, and an imaging lens 48.

  The wavefront detection optical system 105 includes a mirror 55, a lens 56, a fundus conjugate diaphragm 57, a lens 58, a turret unit 60 configured to allow insertion and removal of a plurality of optical filters having different characteristics, a Hartmann Shack sensor that is a wavefront detection unit, and the like. The wavefront sensor 61 of FIG. The diaphragm 57 prevents unnecessary light other than the return light from the fundus from entering the wavefront sensor 61.

  The anterior ocular segment observation optical system 106 includes a camera 51 and captures an anterior ocular segment image illuminated by the anterior ocular segment illumination light source 52.

  The fixation lamp projection optical system 107 includes a fixation lamp presentation unit 54 such as an organic EL or a liquid crystal display device. By displaying an index on the fixation lamp presentation unit 54, the lens 53 and a wavelength branch that transmits visible light are displayed. A fixation target is presented to the eye to be examined via the mirrors BS50 and BS23.

  Reference numeral 62 denotes a PC which controls the above-described units as will be described later.

(X direction scanning part)
FIG. 13 shows the configuration of the X-direction scanning unit. The same components as those in FIG. BS12 is a wavelength branching mirror, which reflects AO-OCT measurement light having a wavelength of 805 nm to 905 nm and transmits AO-SLO measurement light having a wavelength of 750 nm to 770 nm. This transmission characteristic can be obtained by vacuum-depositing a plurality of types of dielectric multilayer films having different refractive indexes by about 30 to 70 layers by a known method. This multilayer film is applied to the surface on the incident side.

  The AO-OCT measurement light reaching the multilayer film in the region 141 on the surface 12a of the BS 12 is reflected upward in FIG. A known antireflection film is deposited on the surface 13a of the mirror 13, and the reflectance is 0.3% or less. Accordingly, the AO-OCT measurement light is refracted by the front surface 13a, enters the substrate, and reaches the back surface 13b. The substrate of the mirror 13 is quartz glass, optical glass BK7, or the like, and has a refractive index of about 1.5. A metal film such as silver, gold, and aluminum is deposited on the back surface 13b.

  The AO-OCT measurement light is reflected by this film, passes through the substrate again, exits from the mirror surface 13a into the air, reaches the multilayer film in the region 142 of the surface 12a of the BS 12, and is reflected and merged with the AO-SLO measurement light. To do. The AO-OCT measurement light is refracted by the surface 13a of the mirror 13 and is transmitted through the substrate, thereby being affected by astigmatism.

  The AO-SLO measurement light is transmitted through and refracted through the multilayer film in the region 141 of the surface 12a and enters the BS 12 substrate. This substrate is also made of quartz glass, optical glass BK7, or the like, similar to the mirror 13. And it is refracted again from the back surface 12b and comes out in the air. A known antireflection film is applied to the back surface 12b. This antireflection film has a reflectance of 0.3% or less for the AO-SLO measurement light and the AO-OCT measurement light. Thereby, generation | occurrence | production of a ghost and flare can be reduced.

  Further, the transmitted light is affected by astigmatism by being obliquely transmitted through the BS 12 which is also a parallel plate. The AO-SLO measurement light emitted into the air is reflected by the mirror of the movable part of the high-speed scanner 32 and scanned in different directions depending on the angle of the mirror of the movable part. The mirror of the movable part of the high-speed scanner 32 is a plane mirror, and a metal film such as silver, copper, or aluminum is applied on the surface, and a protective film of a dielectric multilayer film is applied thereon. The AO-SLO measurement light is reflected by this metal film surface. Then, the light is refracted again by the antireflection surface 12b of the region 142 of the BS 12, passes through the substrate, and travels out of the multilayer film on the surface 12a. In this way, since the light passes through the BS 12 twice, it is affected by astigmatism for two times. The traveling direction of the return light from the fundus is also opposite or affected by the same aberration.

  At this time, the substrate thicknesses of the BS 12 and the mirror 13 are equal, and the refractive indexes of the substrates are made equal by using the same glass material. With such a configuration, the astigmatism of the AO-OCT measurement light and the AO-SLO measurement light becomes substantially equal, and high-precision aberration correction can be performed under the same wavefront correction conditions using a common DM. .

  The incident light paths of the AO-OCT measurement light and the AO-SLO measurement light to the X-direction scanning unit are the return light of the AO-OCT measurement light and the output light of the return light of the AO-SLO measurement light from the X-direction scanning unit. It becomes a road. Further, the outgoing optical paths of the AO-OCT measurement light and the AO-SLO measurement light from the X direction scanning unit are incident on the return light of the AO-OCT measurement light and the return light of the AO-SLO measurement light to the X direction scanning unit. It becomes an optical path.

  Further, with respect to the AO-OCT measurement light and the AO-SLO measurement light, the DM 10, the wavefront sensor 61, the X scanner 15, the Y scanner 21, and the pupil of the eye to be examined are conjugated, and the projection position of the fundus coincides with the high speed. The intervals and angles of the scanner 32, BS12, and mirror 13 are adjusted. Thereby, the aberration of the AO-OCT measurement light and the AO-SLO measurement light can be corrected satisfactorily with one DM10.

  With the above configuration, a frontal image of the fundus centered on the imaging range of the AO-OCT image can be obtained without affecting the luminous flux of the AO-OCT measurement light. It can be performed.

(Imaging method)
Next, a method of acquiring and acquiring an AO-OCT image for scanning the same region of the fundus Er of the eye E to be examined a plurality of times and creating a superimposed image using the apparatus having the above-described configuration is illustrated in FIG. 2 and FIG. FIG. 2 is a diagram showing a display screen displayed on the monitor 70 of the PC 62 during imaging, and FIG. 14 is a flowchart during imaging.

  The eye E to be examined is placed in front of this apparatus. The reflected light from the anterior segment of the subject's eye illuminated by the anterior segment illumination light source 52 is reflected by the BS 50, captured by the anterior segment observation camera 51, and displayed in the anterior segment image display area 80 of the monitor 70 of the PC 62. Is displayed. The imager instructs the center of the display area 80 so that the center of the pupil image of the eye to be inspected and the iris pattern become clear while viewing the anterior segment image. The PC 62 drives an alignment mechanism (not shown) according to the instruction, and aligns the optical system with the pupil of the eye to be examined (step S151).

  When the alignment is completed, the photographer operates the AO-SLO image capturing start switch 71 on the monitor. The PC 62 that has detected this switch input automatically starts operation in the AO-SLO mode. Here, the AO-SLO mode is a mode in which the light from the AO-SLO light source 24 reaches the wavefront sensor 61 and the wavefront aberration is measured. Although details will be described later, in the present embodiment, wavefront aberration is caused by light from both the AO-SLO light source 24 and the AO-OCT light source 1 in the AO-OCT mode in which wavefront aberration is measured by light from the AO-OCT light source 1. The mixing mode for measuring the temperature can be selected. That is, the wavefront sensor 61 detects the wavefront aberration of at least one of the AO-SLO measurement light and the AO-OCT measurement light. The AO-SLO light source 24 is turned on, the high-speed scanner 32 and the Y scanner 21 are driven, and the fundus raster scan with the AO-SLO measurement light is started (step S152).

  The reflected and scattered light from the fundus Er illuminated in this way returns to the AO-SLO sample optical system, and 10% of the light passes through the BS 7 and reaches the wavefront sensor 61 via the fundus conjugate diaphragm 57. 90% of the light reflected by BS7 is transmitted through BS6, 90% of the light is reflected by BS28, condensed by the lens 33 onto the confocal stop 34, and the light passing through the confocal stop 34 is APD, The light reaches the light receiving element 35 such as PMT. Based on a voltage signal corresponding to the amount of light received by the light receiving element 35, the PC 62 generates image data and displays it as a front image of the fundus in the AO-SLO image display area 81 on the monitor 70.

  The photographer operates the focus switch 72 to instruct focus adjustment while viewing this image. The PC 62 that has detected the input to the focus switch 72 controls the drive unit of the stage 18 in order to move the mirrors 17a and 17b together in the optical axis direction. As a result, the fundus conjugate position in the optical system changes and the focus can be adjusted to a desired depth position (step S153). This is called a Badal optical system, and the imaging relationship of the pupil is maintained. As a result, an AO-SLO image having a desired depth is displayed in the display area 81.

  Further, the imager operates the fixation lamp operation switch 73 to guide fixation of the eye to be inspected so that a fundus image of a desired region is captured (step S154).

(Aberration correction)
When the PC 62 detects that an AO-SLO image having a signal intensity of a certain level or more is stably obtained, an aberration correction (AO) operation is started. Part of the return light from the fundus passes through the BS 7 and reaches the wavefront sensor 61, and the output data of the wavefront sensor 61 is sent to the PC 62. Since the wavefront sensor 61 has a lens array disposed in front of the light receiving element, the output image is an image in which spots are arranged in a grid pattern (grid shape). If there is aberration in the eye to be examined, these spot positions change. The PC 62 analyzes the deviation direction and the amount of deviation of each spot to determine the wavefront aberration of the return light of the AO-SLO measurement light (step S155).

  In order to correct the wavefront aberration, the PC 62 obtains a pattern for displacing the micromirrors that constitute the DM 10 that is an aberration correction device. The PC 62 controls the driving of the micro mirror of the DM 10 according to this pattern, and corrects the aberration of the AO-SLO measurement light and its return light (step S156).

  By correcting the aberration of the AO-SLO measurement light, the spot diameter projected onto the fundus is reduced, and at the same time, the spot diameter formed on the confocal stop is also reduced, so that the amount of light received by the light receiving element 35 is increased. Thereby, a high-resolution photoreceptor cell image is clearly displayed in the display area 81 of the AO-SLO image on the monitor 70 of the PC 62. A line 81a indicates the imaging position of the AO-OCT image.

(Alignment readjustment)
In step S151, the alignment based on the anterior ocular segment observation is performed. If a part of the pupil is covered by the eyelashes or the eyelids, or the aberration of the entire pupil cannot be measured due to the disease, the alignment is readjusted (step S180). The photographer instructs the luminance value and contrast of the AO-SLO image to be the highest while viewing the AO-SLO image displayed in the display area 81. The PC 62 drives an alignment mechanism (not shown) according to an instruction to perform alignment adjustment. By using the AO-SLO image, the return light from the reflective layer having a high reflectivity such as the photoreceptor layer reaches the wavefront sensor 61. Therefore, even when the optical path of the return light is partially blocked, a good AO operation is maintained. It is possible to readjust the alignment in the above state. Further, since the AO-SLO image configuration does not require time-consuming calculation processing such as FFT, it is possible to update the AO-SLO image at a video rate or higher without using a high-performance PC. Since the AO-SLO image in the display area 81 is updated at a sufficient speed, the photographer can easily check the brightness value and the contrast.

(Alignment end judgment)
An indicator 94 indicating the image quality of the AO-SLO image is displayed on the monitor 70. In addition to the brightness value and contrast of the AO-SLO image, the photographer can determine whether to end alignment readjustment based on the display of the indicator 94. The indicator 94 represents a numerical value calculated based on the histogram distribution of the luminance value of the AO-SLO image with a scaled bar, and updates the display in comparison with a reference numerical value set in advance. Operate. In the present embodiment, when the numerical value exceeds the reference value, the PC 62 highlights the scale display of the indicator 94 in blue so that the photographer can easily determine that it is in an appropriate alignment state.

(AO-OCT imaging)
After performing the alignment readjustment, the imager operates the switch 74 to start the AO-OCT mode and instructs the start of imaging of the AO-OCT image (step S157). The PC 62 that has detected the input to the switch 74 turns on the AO-OCT light source 1. As a result, the AO-OCT measurement light branched to the sample optical system side by the coupler 2 enters the sample optical system from the fiber 4. The AO-OCT measurement light entering the sample optical system is collimated by the collimator lens 5 and reaches the BS 12. As described above, the AO-OCT measurement light is reflected by the BS 12, further reflected by the fixed mirror 13, and again reflected by the BS 12, thereby joining the optical path of the AO-SLO measurement light. Thereby, the AO-OCT measurement light reaches the eye to be examined without being affected by the high-speed scanner 32. The return light reflected by the fundus of the AO-OCT measurement light travels back through the sample optical system, is reflected by the BS 12, is reflected by the mirror 13, is reflected again by the BS 12, and reaches the half mirror BS7. BS7 has a transmission characteristic of reflecting 90% light and transmitting 10% light. 10% of the return light from the BS 7 is transmitted to the wavefront sensor 61, and the remaining 90% of the return light is reflected by the BS 7 and the BS 6, and is imaged on the end face of the fiber 4 by the collimator lens 5. As a result, the fiber coupler 2 is reached.

(AO-OCT wavefront detection)
When the AO-OCT mode is started, the turret unit 60 is automatically driven by the PC 62, and a filter for cutting the return light of the AO-SLO measurement light is inserted in front of the wavefront sensor 61. Therefore, the light reaching the wavefront sensor 61 is only the AO-OCT measurement light, and the light whose wavefront is detected is switched from the AO-SLO measurement light to the AO-OCT measurement light, and the wavefront aberration of the AO-OCT measurement light is detected. (Step S158). However, the AO-SLO projection optical system has focus adjustment lenses 29 and 30, and when the focus is adjusted based on the AO-OCT measurement light due to the difference in wavelength between the AO-SLO measurement light and the AO-OCT measurement light. The difference in position where the AO-SLO measurement light is focused is automatically corrected by the focus adjustment lenses 29 and 30. Based on the detected wavefront aberration, the driving amount of each mirror of DM10 is calculated as described above, and the wavefront aberration is corrected by driving DM10 (step S159). Thereby, the AO-OCT image displayed in the display area 82 is brighter and the contrast is improved.

(Mode switching judgment)
Depending on the state of the optical tissue of the eye E and the imaging position of the fundus Er, there are problems such as a decrease in the amount of light reaching the wavefront sensor 61 and a lack of a spot on the wavefront sensor 61. Sometimes. In that case, if the wavefront aberration is detected only by the light from the light source 1 in the AO-OCT mode, the AO does not operate normally, and the desired image quality of the AO-OCT image cannot be obtained. In step S160, the photographer determines whether or not the AO operation, that is, aberration correction is appropriately performed. If appropriate, the process proceeds to steps S161 and S162. If not determined, the process proceeds to step S170. An operation based on the selection instruction is performed.

  The mode selection procedure in step S170 will be described below with reference to FIG. The switch 77 is a toggle switch that superimposes and displays an image of a spot group (hereinafter referred to as a Hartmann image) acquired by the wavefront sensor 61 in the anterior segment image display area 80. FIG. 2 schematically shows a state in which the spot 85 of the Hartmann image is superimposed and displayed. Note that the spot 85 can display the image data itself output from the wavefront sensor 61 in a translucent manner, or can display a graphic generated by software based on the spot shift amount and the luminance value. In the latter case, it is desirable to highlight a spot whose luminance value is lower than the surrounding area so that the photographer can easily determine the state of aberration correction. In the case of observing the anterior segment, the spot 85 can be hidden by pressing the switch 77, and the photographer can use the spot 85 properly according to the situation.

  The photographer can select the AO-SLO mode or the AO-OCT mode from the mode selection menu 78 based on the images in the anterior segment image display area 80 and the display areas 81 and 82. The imager can further select a mixed mode that uses both AO-SLO and AO-OCT light for aberration measurement, and the PC 62 automatically drives the turret unit 60 based on the imager's selection. For example, when switching to the AO-SLO mode at the time of imaging with AO-OCT, a filter for cutting the light of AO-OCT is inserted. Further, the PC 62 is configured to automatically switch the highlight frames 91, 92, and 93 based on the mode selection of the photographer, and easily determine in which mode the wavefront aberration is currently detected. . For example, in the case of the AO-SLO mode, the highlight frames 91 and 92 are highlighted and the display frame 93 is made transparent so that the photographer can clearly see that the light of AO-SLO is used for aberration measurement. Present. That is, it is identified whether the selected light for aberration measurement is the return light of the AO-SLO measurement light, the return light of the AO-OCT measurement light, or the return light of both measurement lights. Displayed as possible.

  The mixed mode is an effective mode because it is possible to increase the luminance value of the spot of the Hartmann image when the return light from the eye E is small. However, since light having different wavelengths is simultaneously used for aberration measurement, chromatic aberration and depth of penetration are different. In particular, since the defocus amount is different, there is a case where the intended focus position is not captured. This phenomenon becomes prominent when the nerve fiber layer around the optic nerve head becomes thick. In the mixed mode, the PC 62 stores in advance the focus correction value based on the wavelengths of the AO-SLO and AO-OCT light, and automatically corrects the DM control amount and the adjustment amounts of the focus adjustment lenses 29 and 30. Is configured to do. As a result, imaging can be performed within a desired range even in the mixed mode.

  It should be noted that the mode switching is preferably a method in which the focus adjustment lenses 29 and 30 are automatically adjusted by sequentially transitioning to the AO-SLO mode and the AO-OCT mode as in this embodiment. However, it is also possible for the photographer to select a different sequence in advance using a menu (not shown). With this method, for example, it is possible to focus on the photoreceptor layer with AO-SLO and stably image AO-OCT while maintaining the state in which AO is optimally controlled. The mode selection menu 78 is configured to automatically switch display according to the current mode.

  In the present embodiment, the photographer instructs the mode selection in step S170. However, the present invention is not limited to this configuration, and the PC 62 may analyze the Hartmann image and automatically switch the mode.

(Reference optical system)
The reference light branched to the reference optical system side by the fiber coupler 2 is subjected to polarization adjustment by the polarization adjuster 45 so that the polarization state matches the return light of the sample optical system. Then, the polarization-adjusted reference light enters the reference optical system 102 and is adjusted to an appropriate light amount by an ND (Neutral Density) filter 37 for adjusting the reference light amount. The reference light reflected by the mirrors 38, 39, 40 and 41 and reflected by the retro reflector 42 is reflected by the mirrors 41, 40, 39 and 38 and reaches the mirror 43. The light vertically reflected by the mirror 43 travels back along the optical path and returns to the coupler 2.

  The reference light from the reference optical system 102 and the return light from the fundus of the eye of the sample optical system are combined (combined) by the coupler 2 and guided to the spectroscope 108 as interference light. The interference light guided to the spectroscope 108 is collimated by the lens 46, is split by the spectroscopic means 47 such as a diffraction grating, and an interference wave is imaged on the line sensor 49 by the lens 48. The output of the line sensor 49 is sent to the PC 62, converted into digital data by the A / D converter 62a, and stored in the memory 62b. This data is computed by a known method such as frequency analysis after removal of fixed pattern noise and wave number conversion to generate tomographic image data.

(Gate adjustment)
The imager adjusts the optical path length of the reference optical system 102 using the optical path length adjustment switch 76 shown in FIG. 2 so that a desired tomographic image is displayed in the display area. The PC 62 that has detected the input to the optical path length adjustment switch 76 drives the stage 44 in a direction corresponding to the input. Thereby, the retro reflector 42 moves in the optical axis direction, and the optical path length changes. When the optical path length of the sample system and the optical path length of the reference system substantially coincide with each other, a tomographic image of a photoreceptor cell is displayed in the display area 82 (step S160).

(scan)
At this time, an AO-SLO image captured at the same time is displayed in the display area 81. Since the high-speed scanner 32 is disposed around the OCT optical system, the AO-OCT measurement light is only line-scanned by the Y scanner 21 in the Y direction (horizontal direction in FIG. 3). The AO-SLO measurement light is scanned in the Y direction by the Y scanner 21 and in the X direction (the vertical direction in FIG. 3) by the high speed scanner 32. Therefore, as shown in FIG. 3, an AO-SLO image of the imaging range 301 with the scanning line 302 that is the acquisition position of the AO-OCT image as the center in the vertical direction is acquired (step S161).

  A waveform 111 shown in FIG. 10 represents the scanning angle of the mirror of the high-speed scanner 32, the horizontal axis is time, and the vertical axis is the angle. That is, the high-speed scanner 32 reciprocates at high speed in the X direction. At the same time, the Y scanner 21 is scanned at a cycle slower than that of the waveform 111 as indicated by the waveform 112. Image acquisition is performed for both the forward and backward passes of the high-speed scanner.

  Periods P1 and P3 shown in FIG. 10 are periods in which one frame of an AO-OCT image and one frame of an AO-SLO image are acquired. P2 is a blanking period of the Y scanner 21. I will not. That is, the Y scanner 21 continuously changes from θ2 to −θ2 in the periods P1 and P3, and in the period P2, from −θ2 to + θ2 at an angular velocity faster than the angular velocity in the periods P1 and P3. Scanned. By repeating such scanning, a two-dimensional region is imaged by the AO-SLO unit and a line is imaged by the AO-OCT unit.

(tracking)
Tracking of eye movement detection and imaging range correction will be described with reference to the flowchart of FIG.

  When the imaging of the AO-OCT image is started, an AO-SLO image is recorded as one frame as a tracking reference image 301 (step S1621). The image size at this time is 400 × 400 pixels, and the image is composed of 400 lines in length. When the scanning frequency of the high-speed scanner 32 is 16 kHz, an image is acquired in a reciprocating manner. Therefore, it takes 12.5 msec to acquire an image of 400 lines, and an image of about 70 frames per second is obtained.

  As shown in FIG. 4, at the time of imaging the next frame, every time an image of a predetermined line is acquired, a correlation calculation is performed with the reference image to detect the movement of the eye to be examined. For example, in the present embodiment, the tracking image 402 is created with signals for 20 lines (step S1622). This makes it possible to detect the position 20 times (= 400/20) during one line scanning of the AO-OCT image. That is, the movement of the eye to be examined can be detected and corrected in a time of 1 msec or less. For this reason, it is possible to track fixation fine movement that moves at a speed of about 1 mm per second with an accuracy of 1 μm or less, and to obtain sufficient accuracy for an OCT line scan with a line width of 3 μm.

  As soon as each tracking image is acquired, a correlation operation is performed with the reference image 301 to obtain a shift amount (sf302_X, SF302_Y) (step S1623). If there is no movement of the eye to be examined, the shift amount of the Nth tracking image is (x, y) = (20 × (n−1), 0), and therefore the movement of the eye to be examined obtained from the Nth tracking image. The amount is (sf302_x-20N, SF302_y).

  Based on this movement amount, the mirror rotation angle of the X scanner 15 and Y scanner 21 is calculated (step S1631), and the X scanner 15 and Y scanner 21 are driven so as to follow the movement of the eye to be examined as described above. Since the Y scanner 21 is being driven with a predetermined waveform, the drive center is offset. The X scanner 15 performs only the obtained amount of offset (step S1632).

  A waveform 121 in FIG. 11 shows a change in angle of the Y scanner 21, and a waveform 131 in FIG. 12 shows a change in angle of the X scanner 15. The horizontal axis is the time vertical axis, and the vertical axis is the scanning angle. As described above, since the angle shift amount for correcting the movement amount of the eye to be examined is calculated at regular intervals, the scan angle is shifted as indicated by the waveform 122. Thereafter, scanning is performed at a normal angular velocity as indicated by a waveform 123. A solid line indicates a mirror angle to which an angle shift is applied, and a broken line indicates a mirror angle when there is no angle shift. A waveform 131 in FIG. 12 shows an angle change of the X scanner 15, and the horizontal axis is time. Since the X scanner 15 is used only for tracking for correcting the movement of the eye to be examined, the angle changes only by the calculated offset amount.

  Although the AO-SLO image is acquired even while the X scanner 15 is driven as shown by the waveform 132, the correlation calculation is performed on the image excluding the portion. By continuing such tracking control, the AO-OCT unit can obtain a plurality of tomographic images on the same line, a predetermined number, for example, about 100 (step S1633). These tomographic images are strictly the same region, and an AO-OCT image with high contrast can be created by superimposing these images.

(Alignment state)
An indicator 95 indicating the image quality of the AO-OCT image is displayed on the monitor 70. The indicator 95 represents a calculation result of sensitivity based on the A scan profile of the AO-OCT image by a bar with a scale, and operates to update the display in comparison with a preset reference numerical value.

  The display method of the indicator 95 is changed according to the alignment state and the AO-OCT adjustment state. When the alignment state is good and the image quality of AO-OCT is good, the indicator 95 is highlighted in blue. In addition, when the alignment state is good but the focus and gate adjustment are insufficient and a good AO-OCT image cannot be obtained, the indicator 95 is highlighted in orange. By switching the display method, the photographer can easily determine a position to be adjusted in order to obtain a good image.

  In addition, when it is necessary to readjust the alignment during imaging in the AO-OCT mode, the indicator 95 is highlighted in red. By this display, it is possible to prompt the photographer to switch to the AO-SLO mode or the mixed mode and perform alignment readjustment.

(OCT volume scan)
When the AO-OCT volume scan switch 75 is operated, scanning in the volume scan mode is started.

  When the photographer operates the AO-OCT volume scan switch 75 and an imaging range is set using a cursor not shown, the PC 62 causes the X scanner 15 to shift the AO-OCT line scan line in the Y direction. The Y scanner 21 is also driven in synchronization.

  A frame 501 on the fundus image in FIG. 5 indicates an imaging range of the AO-OCT volume scan. A region corresponding to the frame 501 on the fundus image is scanned with AO-OCT measurement light to acquire AO-OCT volume data. A frame 601 in FIG. 6 shows the imaging range of the AO-SLO image when the uppermost line 502 of the imaging range in FIG. 5 is scanned with the AO-OCT measurement light. As shown in FIG. 5, the imaging range of the AO-SLO image is a rectangular area centered on the imaging line 502 of the AO-OCT image. The AO-SLO image obtained here is stored as a tracking reference image. Next, the X scanner 15 is driven, and the AO-OCT measurement light starts scanning the next imaging line indicated by the line 503 in FIG. The imaging range of the AO-SLO image at that time is shown in a frame 701 in FIG. With respect to the imaging range 601, the imaging range of the AO-SLO image moves downward by one line of the AO-OCT image. That is, when an AO-OCT image is captured on the line 504 in FIG. 5, the AO-SLO image is the imaging range shown in the frame 801 in FIG. 8, and the line 505 that is the lowest line is captured. In FIG. 9, a frame 901 is an imaging range of the AO-SLO image. As described above, the imaging range of the AO-SLO image moves with the movement of the scan line of the AO-OCT measurement light. As a result, image information in the vicinity region centered on the imaging range of the AO-OCT image is always obtained.

(Tracking during OCT volume scan)
As described above, tracking is performed using an AO-SLO image even during AO-OCT volume scanning. While scanning the line 503 in FIG. 7, an image of the 20-line range indicated by the broken line is extracted while acquiring the image of the imaging range 701 of the AO-SLO image, and the image of the imaging range 601 of the AO-SLO image captured last time is extracted. To calculate the shift amount. As described above, the shift amounts of the X scan 15 and the Y scanner 16 are calculated from this shift amount, and the X scanner 15 and Y scanner 21 are immediately driven on the fundus of the AO-OCT measurement light and the AO-SLO measurement light. Fundus tracking is performed to correct the irradiation position.

  The AO-OCT image (volume data) in the imaging range 501 of the AO-OCT image is acquired by repeating the line scan while performing tracking in this way. Thereby, the three-dimensional information of the area 501 in FIG. 5 is obtained.

  The AO-SLO image used for tracking is generated as a single reference image with the shift amount corrected, and may be used as a reference image for line scanning of the AO-OCT image in the next row. As a result, the reference image can be constantly updated, so that more accurate tracking can be performed.

[Other Embodiments]
In the above-described embodiment, the case where the object to be inspected is an eye is described. However, the present invention can also be applied to an object to be inspected other than the eye, such as skin or organ. In this case, the present invention has an aspect as a medical device such as an endoscope other than the imaging device. Therefore, it is preferable that the present invention is grasped as an image processing apparatus exemplified by the imaging apparatus, and the eye to be examined is grasped as one aspect of the inspection object.

  The present invention can also be achieved by configuring the apparatus as follows. That is, a recording medium (or storage medium) that records software program codes (computer programs) that implement the functions of the above-described embodiments may be supplied to the system or apparatus. In addition to the form of the recording medium, a computer-readable recording medium may be used. Then, the computer (or CPU or MPU) of the system or apparatus reads and executes the program code stored in the recording medium. In this case, the program code itself read from the recording medium realizes the functions of the above-described embodiment, and the recording medium on which the program code is recorded constitutes the present invention. The embodiment can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

Claims (11)

A common optical system for irradiating the fundus with first measurement light from a first light source and second measurement light from a second light source having a wavelength different from that of the first measurement light;
A tomographic image of the fundus is obtained based on interference light obtained by causing the return light of the first measurement light from the fundus through the common optical system to interfere with the reference light corresponding to the first measurement light. First generating means for generating;
Second generating means for generating a fundus image of the fundus based on the return light of the second measurement light from the fundus through the common optical system;
A wavefront detection unit that is disposed in the common optical system and detects the wavefront aberration of at least one of the wavefront aberration of the return light of the first measurement light and the wavefront aberration of the return light of the second measurement light; Selecting means for selecting at least one of the return light of the first measurement light and the return light of the second measurement light;
The imaging apparatus according to claim 1, wherein the wavefront detection unit detects a wavefront aberration of the light selected by the selection unit. It further comprises wavefront correction means for correcting and emitting wavefront aberration of incident light,
The first generation unit generates the tomographic image based on the return light of the first measurement light corrected by the wavefront correction unit,
The imaging apparatus according to claim 1, wherein the second generation unit generates the fundus image based on a return light of the second measurement light corrected by the wavefront correction unit.   The imaging apparatus according to claim 1, further comprising a display unit configured to display the light selected by the selection unit together with the tomographic image and the fundus image in a distinguishable manner. After the return light of the second measurement light is selected by the selection means, and the fundus image is generated based on the return light of the second measurement light corrected by the wavefront correction means by the second generation means ,
The return light of the first measurement light is selected by the selection means, and the tomographic image is generated based on the return light of the first measurement light corrected by the wavefront correction means by the first generation means. The imaging apparatus according to claim 1, further comprising a control unit. Adjusting means provided in the optical path of the second measurement light, for adjusting the focus of the second measurement light;
When the return light of the first measurement light is selected by the selection means, a focus position shift due to the wavelength difference of the second measurement light corrected by the wavefront correction means is caused by the adjustment means. The imaging apparatus according to claim 2, further comprising an adjusting unit. Means for determining a state of measurement of the return light of the first measurement light detected by the wavefront detection means when the return light of the first measurement light is selected by the selection means;
When the measurement state does not satisfy the standard, the wavefront aberration of the return light of the first measurement light and the return light of the second measurement light is detected from the detection of the wavefront aberration of the return light of the first measurement light. 6. The imaging apparatus according to claim 1, further comprising means for changing to detection. A common optical system for irradiating the fundus with first measurement light from a first light source and second measurement light from a second light source having a wavelength different from that of the first measurement light;
A tomographic image of the fundus is obtained based on interference light obtained by causing the return light of the first measurement light from the fundus through the common optical system to interfere with the reference light corresponding to the first measurement light. First generating means for generating;
Second generating means for generating a fundus image of the fundus based on the return light of the second measurement light from the fundus through the common optical system;
Wavefront detecting means that is disposed in the common optical system and detects wavefront aberration of at least one of the wavefront aberration of the return light of the first measurement light and the wavefront aberration of the return light of the second measurement light. A method for controlling an imaging apparatus,
Selecting at least one of the return light of the first measurement light and the return light of the second measurement light;
And a step of causing the wavefront detection means to detect the wavefront aberration of the light selected in the selection step. Adjusting means for adjusting alignment based on the return light of the second measurement light;
An instruction means for instructing the end of the alignment,
The imaging apparatus according to claim 1, wherein the selection unit selects a return light of the first measurement light based on an instruction from the instruction unit. Means for displaying a first indicator indicating the state of the alignment;
The imaging apparatus according to claim 8, wherein when the alignment state satisfies a preset criterion, the display form of the first indicator is changed and displayed. Means for displaying a second indicator indicating the image quality of the tomographic image of the fundus oculi generated by the first generator;
The imaging apparatus according to claim 9, wherein the second indicator updates the display based on the display of the first indicator and a selection state by the selection unit. The fundus via a common optical system for irradiating the fundus with the first measurement light from the first light source and the second measurement light from the second light source having a wavelength different from that of the first measurement light A first generation step of generating a tomographic image of the fundus oculi based on interference light generated by causing the return light of the first measurement light from the reference light to interfere with the reference light corresponding to the first measurement light;
A second generation step of generating a fundus image of the fundus based on the return light of the second measurement light from the fundus via the common optical system;
Detection step of detecting wavefront aberration of at least one of the wavefront aberration of the return light of the first measurement light and the wavefront aberration of the return light of the second measurement light by the wavefront detection means arranged in the common optical system And a selection step of selecting at least one of the return light of the first measurement light and the return light of the second measurement light,
The wavefront detection means detects a wavefront aberration of the light selected in the selection step.

Images