WO2014129522A1

WO2014129522A1 - Fundus imaging device and retinal tissue characteristic value measurement method

Info

Publication number: WO2014129522A1
Application number: PCT/JP2014/053963
Authority: WO
Inventors: 中川　俊明; 篤志覺内
Original assignee: 興和株式会社
Priority date: 2013-02-21
Filing date: 2014-02-20
Publication date: 2014-08-28
Also published as: JPWO2014129522A1

Abstract

A fundus imaging device comprises: an electronic imaging means; an optical path dividing means; an imaging optical system which separates fundus images into left and right and forms an image on an imaging plane of the electronic imaging means; a first optical filter which is disposed on a first light path and substantially transmits only a first wavelength region; a second optical filter which is disposed on a second light path and substantially transmits only a second wavelength region; and a characteristic value calculation means which calculates a characteristic value of the retinal tissue of the subject's fundus from a first image which passes through the first optical filter and is imaged on the imaging plane of the electronic imaging means and a second image which passes through the second optical filter and is imaged on the imaging plane of the electronic imaging means.

Description

Fundus imaging apparatus and retinal tissue feature amount measuring method

The present invention relates to a fundus imaging apparatus that images a fundus of a subject's eye and measures a retinal tissue feature quantity such as oxygen saturation from the obtained image, and a feature quantity measurement method.

Patent Document 1 and Patent Document 2 describe an ophthalmologic photographing apparatus that divides light reflected from the fundus of an eye to be examined into two optical paths and generates a three-dimensional image of the fundus using parallax. Stereoscopic images of the fundus are useful for early detection of glaucoma and retinitis pigmentosa.

In recent years, early detection of glaucoma is expected by measuring oxygen saturation in the fundus. Patent Document 3 describes a fundus examination apparatus that can measure oxygen saturation. FIG. 7 shows the principle of a conventional oxygen saturation measurement method. The reflected light 101 from the fundus 100 is separated by, for example, a half mirror 102 and imaged on two imaging means 105 and 106 via

optical filters

103 and 104 that transmit light in different wavelength regions, and the same part of the fundus 100 Two images without parallax are captured. Then, the oxygen saturation is measured by performing arithmetic processing on these two images. Patent Document 4 also describes a retinal function camera that measures oxygen saturation by a similar method.

International Publication No. 2010/087046 International Publication No. 2010/140246 JP-A-8-71045 Japanese Patent No. 4197953

According to the devices described in

Patent Documents

3 and 4, the fundus oxygen saturation can be measured, but since the obtained image has no parallax, fundus stereoscopic photography must be performed by another imaging device. There wasn't. Therefore, shooting for oxygen saturation measurement and shooting for generating a 3D fundus image must be performed separately. Since the pupil contracts, there is an annoyance that it takes a certain amount of time to shoot the other. In addition, when the images are taken with different apparatuses, the magnification rate and the angle of view of the stereoscopic fundus image and the oxygen saturation measurement image are different, and thus it is necessary to integrate and diagnose the examination results in consideration of them.

In view of the above problems, the present invention provides a fundus imaging apparatus capable of both stereoscopic fundus imaging and retinal tissue feature quantity measurement, and a retinal tissue feature quantity measurement method that can be performed using an apparatus that performs stereoscopic fundus imaging. It is in.

The fundus imaging apparatus of the present invention that solves the above problems is as follows.
Electronic imaging means, optical path splitting means for dividing the reflected light beam from the fundus of the eye to be examined, which is arranged at the anterior eye conjugate position of the eye to be examined, into a pair of right and left light beams with parallax, and a pair of left and right fundus from the divided light flux In an ophthalmic imaging apparatus that shoots an image of the fundus of the eye to be examined, including an imaging optical system that separates the images into left and right and forms an image on the imaging surface of the electronic imaging means,
A first optical filter disposed in a first optical path in which one of the pair of right and left light beams travels and substantially transmits only the first wavelength range;
A second optical filter disposed in the second optical path through which one of the pair of right and left light beams travels and substantially transmits only the second wavelength region;
A first image that passes through the first optical filter and forms an image on the imaging surface of the electronic imaging means, and a second image that passes through the second optical filter and forms an image on the imaging surface of the electronic imaging means Characteristic amount calculating means for calculating a characteristic amount of the retinal tissue of the fundus of the eye to be examined by calculating an image signal obtained from the electronic imaging means.

The feature amount measuring method of the present invention includes:
The reflected light beam from the fundus of the eye to be examined is divided into a pair of right and left light beams with parallax by the optical path dividing means arranged at the anterior eye conjugate position of the eye to be examined,
A first image formed on the imaging surface of the electronic imaging means by passing through a first optical filter that substantially transmits only one of the pair of right and left light beams only in the first wavelength range;
An image signal obtained from the electronic imaging means for the second image formed on the imaging surface of the electronic imaging means through the second optical filter that substantially transmits only the other of the pair of left and right light beams only in the second wavelength range By calculating the feature amount of the retinal tissue of the fundus of the eye to be examined.

According to the fundus imaging apparatus of the present invention, the reflected light from the fundus divided into two parts is passed through an optical filter that passes through different wavelength regions, and is characterized based on two parallax images formed on the electronic imaging unit. The amount calculation means calculates the feature amount of the retina. Therefore, stereoscopic fundus imaging and retinal tissue feature quantity measurement can be performed using the same device.

1 is an optical diagram showing the overall configuration of a fundus imaging apparatus. (A) is a front view of a two-hole aperture stop. (B) is a front view of an imaging mask. It is a functional block diagram of a fundus imaging apparatus. (A) is an example of the fundus image imaged through the first optical filter. (B) is an example of a fundus image captured through the second optical filter. (C) is an example of a feature amount image. It is a figure which shows the principle of the measuring method of the feature-value in this invention. It is the figure which showed the result of having measured the feature-value in this invention. It is a figure which shows the principle of the measuring method of the conventional feature-value.

Hereinafter, the fundus imaging apparatus of the present invention will be described in detail based on examples with reference to the drawings.

FIG. 1 is an optical diagram showing the overall structure of a fundus imaging apparatus 10 capable of stereo photography (stereoscopic photography). In FIG. 1, a position conjugate with the fundus 1a of the eye 1 to be examined is indicated by R, and a position conjugate with the anterior eye part (particularly the pupil) is indicated by P.

FIG. 5 shows in principle the method of calculating the feature amount of the retinal tissue by the fundus imaging apparatus 10. A reflected light beam from the fundus 1a of the eye 1 to be examined is divided into a pair of left and

right light beams

110 and 111 having parallax, and passes through a first optical filter 53 that substantially transmits only one of the pair of left and right light beams 110 in a first wavelength region. The first image formed on the imaging surface of the electronic imaging means 57 and the second optical filter 54 that substantially transmits only the second wavelength band of the other 111 of the pair of left and right light beams is passed through the electronic imaging means. The feature amount of the retinal tissue of the fundus 1a of the eye 1 to be examined is calculated by calculating the image signal obtained from the electronic imaging means 57 for the second image formed on the imaging surface 57.

The fundus imaging apparatus 10 includes a main body 2 and an image processing apparatus 3. The main body 2 is provided with an illumination optical system that illuminates the fundus and an imaging optical system that forms an image of the illuminated fundus. In the illumination optical system, during stereo photography, light emitted from the light source 11 such as a halogen lamp and light reflected by the concave mirror 12 become infrared light through a visible cut infrared transmission filter 13 that can be inserted into and removed from the optical path. The light passes through the strobe 14, enters the diffusion plate 15, is diffused, and illuminates the ring slit 16 disposed at a position conjugate with the anterior eye portion (pupil) 1 b of the eye 1 to be examined.

At the time of measuring oxygen saturation, the visible cut infrared transmission filter 13 is removed from the optical path, and an optical filter 23 is inserted between the diffusion plate 15 and the ring slit 16 instead. The optical filter 23 is a filter having a characteristic that allows infrared light and light in a first wavelength range and a second wavelength range, which will be described later, to pass therethrough and blocks light in other wavelength ranges. As will be described later, since the

optical filters

53 and 54 are also provided in front of the electronic image pickup means 57, the blocking of other wavelength regions is not perfect, and there may be some passage.

The illumination light that has passed through the ring slit 16 passes through the lens 17, the black dot plate 18 for removing the reflection of the objective lens 22, the half mirror 19, and the relay lens 20, and has a perforated total reflection mirror 21 with a hole in the center. Reflected by. The black spot plate 18 is configured by depositing black spots on the center of a transparent square glass plate.

Further, the illumination optical system is provided with a focus dot light source 30, and a light beam from the light source 30 is incident on the fundus 1 a via the half mirror 19, and the focus dot position changes according to the movement of the focus lens 32. The examiner can focus on the fundus 1a to be examined by observing the focus dot.

The illumination light reflected by the perforated total reflection mirror 21 passes through the objective lens 22 and enters the fundus 1a from the anterior eye portion 1b of the subject eye 1 to illuminate the fundus 1a.

The reflected light from the fundus 1a is received through the objective lens 22, passes through the hole of the perforated total reflection mirror 21, and has two

circular holes

31a and 31b as shown in FIG. The light enters a two-hole diaphragm 31 as a photographing diaphragm. The two-hole aperture 31 is an example of an optical path dividing means, and is arranged at a position substantially conjugate with the anterior eye portion 1b of the eye 1 to be examined with its center 31c aligned with the imaging optical axis 48. , 31b divides the optical path of the reflected light from the fundus into left and right. A pair of right and left light beams with parallax from the fundus la with the optical path divided is movable along the imaging optical axis 48 and is incident on a focus lens 32 that corrects a shift in the fundus imaging position due to individual differences in the eye diopter. .

The fundus image that has passed through the focus lens 32 subsequently passes through the imaging lens 33, is reflected by the half mirror 34, is placed at a position conjugate with the fundus la, and is red via the imaging mask 42 that defines the fundus imaging range. The light enters the external transmission visible reflection mirror 36. The focus lens 32 and the imaging lens 33 constitute a first imaging optical system that forms a pair of left and right fundus images with parallax via the two-hole aperture 31 as intermediate images at the position of the photographing mask 42. .

As shown in FIG. 2B, the photographing mask 42 is a thin plate-shaped member comprising a square opening 42a, a circular area 42b that transmits only infrared light, and a light-shielding part 42c that does not transmit all wavelengths. It is. The photographing mask 42 is fixedly disposed on the optical path with its center 42d aligned with the photographing optical axis 48.

Returning to FIG. 1, the infrared light transmitted through the infrared transmission visible reflection mirror 36 is reflected by the mirror 38, passes through an optical path length adjusting means 39 constituted by a lens 37 and a glass plate, for example, and becomes infrared light. The light is incident on an electronic image pickup means 40 composed of an infrared CCD having sensitivity. The output signal of the electronic imaging means 40 is input to the monitor 41. When the fundus 1a is in focus, the monitor 41 displays a pair of fundus images formed at the position of the photographing mask 42 as a single fundus image. When the pair of fundus images are shifted and displayed as a double image, the focus lens 32 is adjusted to focus again so that the double image is eliminated.

In the initial stage of alignment, the anterior segment lens 44 is inserted into the optical path, so that the examiner can confirm the image of the anterior segment 1b of the subject eye 1 on the monitor 41. Further, during alignment or focusing operation, one of the internal fixation lamps 45 composed of a plurality of LED light sources 45a is turned on, and the examiner performs alignment by causing the subject to gaze at the fixation lamps. And focusing operation can be ensured.

The region 42 b of the imaging mask 42 is a region that transmits only infrared light, and the rectangular opening 42 a transmits light beams in all bands, so that an image captured by the image sensor 40 and displayed on the monitor 41 is displayed. As shown by A in the upper right of FIG. 1, a rectangular outline 43c corresponding to the rectangular opening 42a is displayed, and the examiner can confirm the extent of the imaging range during stereo imaging. it can.

A relay lens 47 is arranged to connect an exit pupil image of the first imaging optical system to a second imaging optical system described later. Visible light reflected by the infrared transmission mirror 36 is arranged at a conjugate position with the anterior segment 1b via the relay lens 47, and divides the reflected light beam from the fundus 1b to be examined into a pair of right and left light beams having parallax 2 The light enters the aperture stop 50. The two-hole stop 50 is a stop similar to the two-hole stop 31 shown in FIG. 2A, and is close to the two-hole stop 50 (that is, at a position almost conjugate with the two-hole stop 31).

Lenses

51 and 52 are arranged. The pair of optical

path dividing lenses

51 and 52 divides the optical path from the photographing mask 42 and separates a pair of left and right fundus images formed as intermediate images at the position of the photographing mask 42 so as not to overlap each other. A second imaging optical system for re-imaging is configured. Here, it is optimal that the optical

path dividing lenses

51 and 52 are arranged symmetrically with respect to the photographing optical axis 48.

A first optical filter 53 that substantially transmits only the first wavelength region is disposed after the optical path dividing lens 51, and a second optical filter 54 that substantially transmits only the second wavelength region is disposed after the optical path dividing lens 52, respectively. The Here, when measuring the oxygen saturation as a feature quantity, the first wavelength range is the visible green (495 to 570 nm) range, and the second wavelength range is the visible orange (590 to 620 nm) range. This is an area.

Chromatic aberration correction lenses 55 and 56 are arranged after the first optical filter 53 and the second optical filter 54 as optical elements for correcting chromatic aberration. Since this is for correcting chromatic aberration between the two optical paths, the chromatic aberration correcting lens may be arranged only after one of the first optical filter 53 and the second optical filter 54.

The first optical filter 53, the second optical filter 54, and the chromatic aberration correction lenses 55 and 56 are configured to be inserted into and removed from the optical path. These optical elements are detached from the optical path when observing the fundus oculi 1b with the display 41 or the eyepiece lens 62, and are inserted into the optical path when calculating the feature amount of the retinal tissue.

An imaging surface 57a of an electronic imaging means 57 composed of a visible CCD having sensitivity to visible light is disposed on the imaging surface of the second imaging optical system, and the optical

path dividing lenses

51 and 52 and the electronic imaging means 57 are arranged. A return mirror 60 is disposed between the two. The electronic imaging means 57 operates in conjunction with the shutter switch 46 provided on the housing of the main body 1. When the

optical filters

23, 53, 54 and the chromatic aberration correction lenses 55, 56 are detached from the optical path and the return mirror 60 is inserted into the optical path, the examiner displays a pair of left and right fundus images via the mirror 61. The eyepiece 62 can be observed with the naked eye. At this time, the observed fundus image is a separated pair of left and

right fundus images

1c and 1d as shown by B in the upper right of FIG. 1, and the examiner can stereoscopically view the fundus. .

The fundus image picked up by the electronic image pickup means 57 can be stored in the memory 54. The fundus image stored in the memory 54 is displayed on the monitor 41 or output to a printer (not shown). Further, the fundus image captured in a state where the

optical filters

23, 53, 54 and the chromatic aberration correction lenses 55, 56 are arranged in the optical path is taken into the image processing apparatus 3 configured by, for example, a personal computer, and the feature amount Used for calculation.

FIG. 3 shows a functional block diagram of the image processing apparatus 3. The control unit 70 is configured by a CPU and controls each hardware of the image processing apparatus 3. The display unit 72 is configured by a liquid crystal display device or the like, and displays an image generated by the image processing unit 80. The operation unit 73 includes a keyboard, a mouse, and the like, and serves as an interface for the examiner to operate the image processing apparatus 3. The storage unit 74 is configured by a storage device such as a semiconductor memory or a hard disk device, and stores an image generated by the image processing unit 80, a program executed by the control unit 71, and the like.

The image processing unit 80 includes a feature amount calculation unit 81, a stereoscopic image generation unit 82, and a feature amount image generation unit 83. The feature amount calculating unit 81 passes through the first optical filter 53 and forms a first image formed on the imaging surface 57a of the electronic imaging unit 57, and passes through the second optical filter 54 and passes through the second optical filter 54. By calculating an image signal obtained from the electronic imaging means 57 for the second image formed on the imaging surface 57a, a feature amount of the retinal tissue of the eye fundus 1a to be examined, for example, oxygen saturation is calculated.

4A shows an example of the first image, and FIG. 4B shows an example of the second image. A substantially circular macular portion 121 appears in the vicinity of the center, and the state in which the blood vessels 120 extend radially can be visually recognized. Although a schematic diagram is used here, the first image is actually obtained as a green grayscale image, and the second image is obtained as a red grayscale image. Due to the difference in transmittance of the retinal tissue between the light in the first wavelength region and the light in the second wavelength region, the shape of the blood vessel 120 is different between the two images. Moreover, since there is parallax, the position of the macular part 121 is slightly shifted between the two images.

When calculating the oxygen saturation, the feature amount calculating means 81 performs the following processing. The first image and the second image are images having a slight parallax. Therefore, first, alignment processing of both images is performed based on parallax information or the like. Although the transmittance to the retina is different between the first wavelength region and the second wavelength region, a blood vessel region that is commonly displayed in both images, for example, reference numeral 121a in FIGS. 4A and 4B is attached. If the alignment is performed based on the information of the part, the influence of the transmittance can usually be ignored. If it cannot be ignored, correction may be made based on the degree of chromatic aberration. Then, the oxygen saturation of the retinal tissue is calculated based on the intensity ratio of the image signals for both images after alignment. Other feature quantities such as macular tissue density can also be calculated by the same method as described above.

The stereoscopic image generating unit 82 generates a stereo image or a stereoscopic image of the fundus 1a to be examined by calculating an image signal obtained from the electronic imaging unit 57 for the first image and the second image. When the first image and the second image are viewed with the naked eye, they are grayscale images of different colors, but are basically images with parallax obtained by photographing the same part as in the conventional example. A stereo image that can be stereoscopically viewed with a stereoscope or the like, or a stereoscopic image that provides a stereoscopic effect when displayed on a display device, can be generated as a monochromatic grayscale image by calculating parallax.

The feature amount image generating means 83 generates a feature amount image in which the measurement result of the feature amount of the retinal tissue of the eye fundus 1a to be examined is associated with the stereoscopic image. FIG. 4C shows an example of the feature amount image. In this example, the oxygen saturation is indicated by the thickness of the line representing the blood vessel, and the portion indicated by the thick line as indicated by reference numeral 120 is a portion where the oxygen saturation is large. Here, the line thickness is set to two levels, but actually, it is better to divide and display in more stages. In addition, as a feature amount image, a stereoscopic image generated in black and white gray scale is displayed by color-coding corresponding to the magnitude of oxygen saturation, and an image showing the oxygen saturation of each part in a graph is superimposed on the stereoscopic image. Alternatively, an image displayed side by side with a stereoscopic image may be generated.

Each unit of the image processing unit 80 is realized by the above-described CPU executing a program stored in the storage unit 74.

In this embodiment, the image processing apparatus 3 is configured by a personal computer or the like in a separate housing from the main body 2. However, the image processing unit 80 is configured by a microcomputer built in the main body 2, and a generated stereoscopic image is generated. Etc. may be displayed on the display 41.

In the above-described embodiment, the feature amount calculation method focusing on a portion that can be recognized as a blood vessel on the retina has been described. However, as shown in FIG. May be performed. Note that FIG. 6 is a black and white grayscale image due to the limitation of the drawing style, but in reality, dark red, red, orange, yellow, green, It is displayed in seven colors, light blue and blue.

In the fundus imaging apparatus 10, the reflected light from the fundus 1 a is divided into a pair of left and right light beams by the two-hole aperture 31, passes through the first optical filter 53, and forms an image on the imaging surface 57 a of the electronic imaging unit 57. The feature amount calculating unit 81 calculates an image signal obtained from the electronic imaging unit 57 for the first image and the second image that has passed through the second optical filter 54 and formed on the imaging surface 57a of the electronic imaging unit 57. By processing, the feature amount of the retinal tissue of the eye fundus 1a to be examined is calculated. Therefore, according to the fundus imaging apparatus 10, it is possible to perform both the feature amount calculation and the stereoscopic image generation by one shooting.

Further, the stereoscopic image generating means 82 generates a stereoscopic image of the fundus from the same first image and second image used for calculating the feature amount. In other words, since the feature amount calculation and the stereoscopic image generation are performed based on the same image captured by the same device, the examiner can make a diagnosis without considering the difference in magnification and angle of view. it can.

In addition, since the first optical filter 53, the second optical filter 54, and the chromatic aberration correction lenses 55 and 56 are configured to be inserted into and removed from the optical path, the examiner can use the eyepiece 62 to form a stereoscopic image of the fundus as in the conventional case. Can be observed.

Since the chromatic aberration correction lenses 55 and 56 are provided between the optical

path splitting lenses

51 and 52 and the electronic image pickup means 57, the calculation accuracy of the feature amount can be increased.

In addition, since the feature amount image generating unit 83 generates a feature amount image in which the stereoscopic image and the feature amount are associated with each other, the examiner can observe this and use it for diagnosis. In particular, when the feature amount is oxygen saturation, it can be used for early detection of glaucoma.

DESCRIPTION OF SYMBOLS 1 Test eye 2 Main body 3 Image processing apparatus 10 Fundus imaging apparatus 11 Light source 12 Concave mirror 13 Visible cut infrared transmission filter 14 Strobe 15 Diffuser plate 16 Ring slit 17 Lens 18 Black spot plate 19 Half mirror 20 Relay lens 21 Perforated total reflection mirror 22 Objective lens 23 Optical filter 31 Two-hole aperture 32 Focus lens 33 Imaging lens 34 Half mirror 36 Infrared transmission visible reflection mirror 37 Lens 38 Mirror 39 Optical path length adjustment means 40 Electronic imaging means 41 Display 42 Shooting mask 46 Shutter switch 47 Relay lens 48 Optical axis 50 Two-

hole aperture

51, 52 Optical path splitting lens 53 First optical filter 54 Second optical filter 55, 56 Chromatic aberration correction lens 57 Electronic imaging means 58 Memory 60 Return mirror 61 Mirror 62 Eyepiece 71 Control Part 72 display unit 73 operating unit 74 storage unit 80 an image processing unit 81 feature calculating unit 82 three-dimensional image generating unit 83 characteristic amount image generating means

Claims

Electronic imaging means, optical path splitting means for dividing the reflected light beam from the fundus of the eye to be examined, which is arranged at the anterior eye conjugate position of the eye to be examined, into a pair of right and left light beams with parallax, and a pair of left and right fundus from the divided light flux In an ophthalmic imaging apparatus that shoots an image of the fundus of the eye to be examined, including an imaging optical system that separates the images into left and right images and forms an image on the imaging surface of the electronic imaging means.
A first optical filter disposed in a first optical path in which one of the pair of right and left light beams travels and substantially transmits only the first wavelength range;
A second optical filter that is disposed in a second optical path along which the other of the pair of right and left light beams travels and substantially transmits only the second wavelength range;
A first image that passes through the first optical filter and forms an image on the imaging surface of the electronic imaging means, and a second image that passes through the second optical filter and forms an image on the imaging surface of the electronic imaging means A feature amount calculating means for calculating a feature amount of the retinal tissue of the fundus of the eye to be examined by calculating an image signal obtained from the electronic imaging means;
A fundus imaging apparatus comprising:
2. The fundus imaging apparatus according to claim 1, wherein the optical path dividing means is a two-hole aperture.
The stereoscopic image generating means for generating a stereoscopic image of the fundus of the eye to be examined by calculating an image signal obtained from the electronic imaging means for the first image and the second image. Item 3. A fundus imaging apparatus according to Item 2.
4. The fundus imaging apparatus according to claim 1, wherein an optical element for correcting chromatic aberration is inserted into one or both of the first optical path and the second optical path.
The fundus imaging apparatus according to any one of claims 1 to 4, further comprising a feature amount image generation unit that generates a feature amount image in which a feature amount of a retinal tissue and a stereoscopic image are associated with each other.
The fundus according to any one of claims 1 to 5, wherein the first optical filter is configured to be inserted into and removed from the first optical path, and the second optical filter is configured to be inserted into and removed from the second optical path. Imaging device.
The fundus imaging apparatus according to any one of claims 1 to 6, wherein the feature amount of the retinal tissue is oxygen saturation.
The fundus imaging apparatus according to any one of claims 1 to 6, wherein the feature amount of the retinal tissue is macular pigment density.
The reflected light beam from the fundus of the eye to be examined is divided into a pair of right and left light beams with parallax by the optical path dividing means arranged at the anterior eye conjugate position of the eye to be examined,
A first image formed on the imaging surface of the electronic imaging means by passing through a first optical filter that substantially transmits only one of the pair of right and left light beams only in the first wavelength range;
An image signal obtained from the electronic imaging means for the second image formed on the imaging surface of the electronic imaging means through the second optical filter that substantially transmits only the other of the pair of left and right light beams only in the second wavelength range A feature amount measuring method for calculating a feature amount of the retinal tissue of the fundus of the eye to be examined by calculating.