# Patent

## Title
Fundus observation device

## Abstract

Highly reliable technology is provided with the capable of forming three-dimensional images of fundus oculi. The image forming part 220 of a computational control unit 200 forms images of the surface of fundus oculi Ef based on results of detecting fundus oculi catoptric light of light illuminated by a fundus camera unit 1A, in addition to forming tomographic images of the fundus oculi Ef based on results of detecting interference light LC from the OCT unit 150. The controlling part 210 synchronizes the timing of detecting fundus oculi catoptric light of light illuminated by the fundus camera unit 1A with the timing of detecting interference light LC from the OCT unit 150. The correction processing part 240 corrects the image positions of the tomographic images based on results of detecting interference light LC from the OCT unit 150 on the basis of two-dimensional images based on the results of detecting fundus oculi catoptric light of light illuminated from the fundus camera unit 1A. The image processing part 230 forms three-dimensional images of fundus oculi Ef based on tomographic images for which the image positions have been corrected.

## Background
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a fundus observation device, for observing the state of the fundus oculi of an eye to be examined.
2. Description of the Related Art
As a fundus observation device, conventionally a fundus camera has been widely used. FIG. 10 shows one example of the appearance of a conventional fundus camera in general, and FIG. 11 shows one example of an optical system composition to be internally accommodated therein (e.g. JP Patent laid-open No. 2004-350849). Furthermore, “observation” is intended to include at least a case in which produced fundus images are observed (fundus observations with the naked eye may be included).
First, referring to FIG. 10, an explanation is made regarding the appearance of a conventional fundus camera 1000. This fundus camera is provided with a platform 3 mounted on a base 2 slidably in the front and rear, right and left (horizontal direction) directions. On this platform 3, an operation panel 3a and a joystick 4 are installed for an examiner to conduct various operations.
The examiner may place the platform 3 on the base 2 to be moved 3-dimensionally by operating the joystick 4. On the top of the joystick 4, an operation button 4a is installed to be pressed down to form fundus oculi images.
On the base 2, a post 5 is installed standing upwards. On the post 5, ajaw rest 6 where the jaw of a patient is to be rested and an external fixation lamp 7 as a light source for fixing an eye to be examined E are provided.
On the platform 3, a main body part 8 is installed to accommodate various optical systems or control systems of the fundus camera 1000. Furthermore, the control system may be installed inside the base 2 or the platform, etc., or in an external device such as a computer, etc. connected to the fundus camera 1000.
On the side of the eye to be examined E of the main body part 8 (the left side of the page in FIG. 10), an objective lens part 8a disposed opposite the eye to be examined E is installed. Also, on the examiner's side of the main body part 8 (the right side of the page in FIG. 10), an objective lens part 8b for observing the fundus oculi of the eye to be examined E with the naked is installed.
Furthermore, connected to the main body part 8 is a still camera 9 for producing a still image of a fundus oculi of the eye to be examined E and an imaging device 10 such as a TV camera, etc. for producing still images or moving images of a fundus oculi. The still camera 9 and the imaging device 10 are formed removably with respect to the main body part 8.
As a still camera 9, in accordance with various conditions such as the purpose of an examination or the saving method of produced images, etc., a digital camera equipped with imaging elements such as CCD (Charge Coupled Device) or CMOS (Complementary Metal Oxide Semiconductor), a film camera, and an instant camera, etc. may interchangeably be used when it is appropriate. The main body part 8 is equipped with a mounting part 8c for interchangeably mounting such a still camera 9.
If the still camera 9 or the imaging device 10 is for taking digital images, the image data of the produced fundus image may be sent to a device such as a computer, etc. connected to the fundus camera 1000 and be observed as a fundus image by being displayed on the display. Also, the image data in an image storing device connected to the fundus camera 1000 can be sent to compile a database and be used as electronic data for creating medical charts, etc.
Furthermore, on the examiner's side of the main body part 8, a touch panel monitor 11 is installed. On this touch panel monitor 11, fundus images of the eye to be examined E created based on the picture signals output from the still camera 9 (a digital method thereof) or the imaging device 10 are displayed. Moreover, on the touch panel monitor 11, the xy coordinate system with the center of the screen as the origin is displayed overlapped with a fundus image. When the screen is touched by the examiner, the coordinate value corresponding to the touched position is displayed.
Next, referring to FIG. 11, a composition of an optical system of the fundus camera 1000 is described. The fundus camera 1000 is provided with an illuminating optical system 100 to light the fundus oculi Ef of an eye to be examined E, a imaging optical system 120 to guide the fundus reflection light of the illumination light to the eyepiece part 8b, a still camera 9, and an imaging device 10.
The illuminating optical system 100 comprises: an observation optical source 101, a condenser lens 102, an imaging light source 103, a condenser lens 104, an exciter filter 105 and 106, a ring transparent plate 107, a mirror 108, a liquid crystal display (LCD) 109, an illumination diaphragm 110, a relay lens 111, an aperture mirror 112, and an objective lens 113.
The observation optical source 101 consists of a light source such as a halogen lamp, etc. and emits fixed light (continuous light) for observing the fundus. The condenser lens 102 is an optical element that converges the fixed light (observation illumination light) emitted by the observation optical source 101 and substantially evenly irradiates the observation illumination light to the fundus oculi.
The imaging light source 103 consists of a light source such as a xenon lamp, etc. to be flashed when producing fundus oculi Ef images. The condenser lens 104 is an optical element that converges the flash light (imaging illumination light) emitted by the imaging light source 103 and irradiates the fundus oculi Ef evenly with the imaging illumination light.
The exciter filters 105 and 106 are the filters to be used when fluorography of ocular fundus images of a fundus oculi Ef takes a place. The exciter filters 105 and 106 respectively can be inserted and/or removed on the optical path by a drive mechanism such as a solenoid, etc. The exciter filter 105 is disposed on the optical path in the event of FAG (fluorescein angiography). Whereas, the exciter filter 106 is disposed on the optical path in the event of ICG (indocyanine green angiography). Furthermore, when color images are being obtained, both exciter filters 105 and 106 are retracted from the optical path.
The ring transparent plate 107 is disposed in a conjugating location with a pupil of the eye to be examined E, and is equipped with a ring transparent part 107a taking an optical axis of the illuminating optical system 100 as a center. The mirror 108 reflects the illumination light emitted by the observation optical source 101 or by the imaging light source 103 in the direction of the optical axis of the imaging optical system 120. The LCD 109 displays a fixation target (not illustrated) for fixing the eye to be examined E.
The illumination diaphragm 110 is a diaphragm member to shut out a part of the illumination light for flare prevention, etc. This illumination diaphragm 110 is composed movably in the light axial direction of the illuminating optical system 100, and is thus capable of changing the illuminating region of the fundus oculi Ef.
The aperture mirror 112 is an optical element to combine an optical axis of the illuminating optical system 100 and an optical axis of the imaging optical system 120. In the center region of the aperture mirror 112 an aperture part 112a is opened. The light axis of the illuminating optical system 100 and the light axis of the imaging optical system 120 are to be crossed at a substantially central location of this aperture part 112a. The objective lens 113 is installed in the objective lens part 8a of the main body part 8.
The illuminating optical system 100 having such a composition illuminates a fundus oculi Ef in the following manner. First, the observation illumination light is output when the observation optical source 101 is lit during fundus observation. This observation illumination light irradiates the ring transparent plate 107 through the condenser lenses 102 and 104. The exciter filters 105 and 106 are removed from the optical path. The light passed through the ring transparent part 107a of the ring transparent plate 107 is reflected by the mirror 108 and is reflected along the optical axial direction of the imaging optical system 120 due to the aperture mirror 112 through the LCD 109, the illumination diaphragm 110 and the relay lens 111. The observing illumination light reflected by the aperture mirror 112 advances in the optical axial direction of the imaging optical system 120 and is converged by the objective lens 113, to be made incident onto the eye to be examined E, and illuminates the fundus oculi Ef.
Then, the ring transparent plate 107 is disposed in a conjugating location with the pupil of the eye to be examined E, and on the pupil a ring shaped image of the entering observation illumination light is formed. The fundus reflection light of the entered observation illumination light is to be emitted from the eye to be examined E through a central dark part of the ring image on the pupil. As described, it is to protect the effect of observing illumination light entering the eye to be examined E with respect to the fundus reflection light of the observing illumination light.
On the other hand, when imaging the fundus oculi Ef, flush light is emitted from the imaging light source 103 and the imaging illumination light is irradiated onto the fundus oculi Ef through the same path. In the event of photofluographing, either the exciter filter 105 or the exciter filter 106 is disposed selectively on the optical path depending on whether FAG imaging or ICG imaging is required.
Whereas, imaging optical system 120 comprises: an objective lens 113, an aperture mirror 112 (an aperture part 112a thereof), an imaging diaphragm 121, a barrier filter 122 and 123, a variable magnifying lens 124, a relay lens 125, an imaging lens 126, a quick return mirror 127 and an imaging media 9a. Herein, the imaging media 9a is an arbitrary imaging medium (image pick-up elements such as CCD, camera film, instant film, etc.) used for a still camera 9.
The fundus reflection light of the illumination light emitted through the central dart part of the ring shaped image center formed on the pupil of the eye to be examined E, enters the imaging diaphragm 121 through the aperture part 112a of the aperture mirror 112. The aperture mirror 112 reflects cornea reflection light of the illumination light and acts so as not to mix the cornea reflection light into the fundus reflection light made incident onto the imaging diaphragm 121. As a result, the generation of flare on the observation images and/or produced images is prevented.
The imaging diaphragm 121 is a plate shaped member at which plural circular light transparent parts of different sizes are formed. The plural light transparent parts constitute different diaphragms with different diaphragm values (F value), and are to be disposed alternatively on the optical path by a drive mechanism not illustrated herein.
The barrier filters 122 and 123 can be inserted and/or removed on the optical path by a drive mechanism such as a solenoid, etc. In the event of FAG imaging, the barrier filter 122 is disposed on the optical path while in the event of ICG imaging the barrier filter 123 is inserted onto the optical path. Furthermore, when producing color images the barrier filters 122 and 123 are to be retracted from the optical path.
The variable magnifying lens 124 is to be movable in the light axial direction of the imaging optical system 120 by a drive mechanism not illustrated herein. This makes it possible to change the magnifying ratio of an observation and the magnifying ratio in imaging, and to focus images of a fundus oculi. The imaging lens 126 is a lens to form an image of the fundus reflection light from an eye to be examined E on the imaging media 9a. 
The quick return mirror 127 is disposed rotatably around a rotary shaft 127a by a drive mechanism not illustrated herein. In the event of imaging a fundus oculi Ef with the still camera 9, the fundus reflection light is supposed to be guided to the imaging media 9a by springing up the quick return mirror 127 that is obliquely mounted on the optical path. Whereas, in the event of imaging a fundus oculi with an imaging device 10 or of observing the fundus oculi with the naked eye of the examiner, the quick return mirror 127 is to be obliquely mounted on the optical path to upwardly reflect the fundus reflection light.
The imaging optical system 120 is further provided with a field lens (eye vision lens) 128 for guiding the fundus reflection light reflected by the quick return mirror 127, a switching mirror 129, an eyepiece 130, a relay lens 131, a reflection mirror 132, an imaging lens 133 and an image pick up element 10a. The image pick up element 10a is an image pick up element such as CCD, etc. installed internally in the imaging device 10. On the touch panel monitor 11 a fundus oculi image Ef imaged by the image pick up element 10a is be displayed.
The switching mirror 129 is to be rotatable around the rotary shaft 129a as well as the quick return mirror 127. This switching mirror 129 is obliquely disposed on the optical path during observation with the naked eye and guides reflected light on the fundus oculi to the eyepiece 130.
Also, when a fundus image is formed by the imaging device 10, the switching mirror 129 is retracted from the optical path, and the fundus reflection light is guided toward an image pick-up element 10a. In this case, the fundus reflection light is directed toward a relay lens 131, is reflected by the mirror 132, and is formed on the image pick-up element 10a by the imaging lens 133.
Such a fundus camera 1000 is a fundus observation apparatus to be used for observing the state of the surface of a fundus oculi Ef, that is, the retina. In other words, a fundus camera 1000 is a fundus observation apparatus to obtain a 2-dimensional fundus oculi image when it sees the fundus oculi Ef from the corneal direction onto the eye to be examined E. On the other hand, in the deep layer of retina tissues such as where the choroidea or sclera exist, technology for observing these deep layer tissues has been desired, but, in recent years, devices for observing these deep layer tissues have been practically implemented (e.g. JP Patent laid-open No. 2003-00543, JP Patent laid-open No. 2005-241464)□
The fundus observation apparatus disclosed in JP Patent laid-open No. 2003-00543 and JP Patent laid-open No. 2005-241464 are devices to which so called OCT (Optical Coherence Tomography) technology is applied. With such fundus observation devices, low coherence light is split into two, one of which (signal light) is guided to a fundus oculi and the other one (reference light) is guided to a given reference object, while at the same time this is a device to form tomographic images of the surface and the deep layer tissue of a fundus oculi by detecting and analyzing the interference light obtained by overlaying the signal light that has passed through the fundus oculi and the reference light that has been reflected by the reference object. Also, it is possible to form the 3-dimensional image of a fundus oculi from the tomographic images.
In order to capture the state of a fundus oculi (presence/absence of a disease, etc.) in detail, it is desirable to consider both the images obtained from a fundus camera and the images obtained from an optical image measuring device. This is because by just observing images of the fundus surface obtained from a fundus camera, it was difficult to capture the state of the deep layer tissues such as choroidea or sclera in detail, while, with tomographic images of the fundus oculi obtained from an optical image measuring device, it was difficult to capture the detailed state of the fundus surface or the entire retina.
Furthermore, in order to determine the state of fundus oculi comprehensively, it is considered to be desirable to determine the state of a disease by taking both the state of the retina and the state of deep layer tissues into consideration. That is, in order to improve the accuracy in determining the condition of a disease, etc., it is desirable to refer to more information and also to refer to information from multiple angles.
For this purpose, it is desirable to use a fundus observation device in order to obtain both a fundus image from a fundus camera and a fundus image from an optical image measuring device. In particular, if it is possible to simultaneously produce both images, it is possible to observe the condition of the fundus by another fundus image in forming one fundus image.
However, with conventional fundus observation devices, it was difficult to capture both a 2-dimensional surface image of the fundus of an eye to be examined by a fundus camera, a tomographic image of the fundus, and a 3-dimensional image by an optical image measuring device. In particular, it was difficult to capture both fundus images at the same time.
Furthermore, when the eye that is subject to examination moves while measuring a plurality of tomographic images presented in three-dimensional image formation, displacement of the measured positions of the tomographic images occurs, leading to a problem in which three-dimensional images cannot be formed with a high degree of reliability. Nevertheless, when measuring an organic eye to be examined, it is difficult to completely prevent eye movement, even using a fixation target or the like.
This invention was devised, with this kind of situation in view, for the purpose of providing a fundus observation device to make it possible to form highly reliable three-dimensional images of fundus oculi from a plurality of tomographic images, along with making it possible to simultaneously acquire images of the surface of the fundus oculi as well as tomographic images of the fundus oculi.
SUMMARY OF THE INVENTION
In order to achieve the above purpose, the present embodiment is constructed as follows: A fundus observation device comprising: a first image forming means having an illuminating optical system for emitting illumination light onto fundus oculi of an eye to be examined and a imaging optical system for detecting the illumination light passing through said fundus oculi by the first detecting means, wherein the first image forming means forms a 2-dimensional image of the surface of said fundus oculi based on the detection results by said first detecting means; a second image forming means having a light source which outputs light with a wavelength which is different from said illumination light; an interference optical generating means splitting said light output from said light source into the signal light directed towards said fundus oculi and the reference light directed towards a reference object and generating interference light by overlapping the signal light passing through said fundus oculi and the reference light passing through said reference object; and a second detecting means for detecting said interference light generated, wherein tomographic images of said fundus oculi are formed based on the detected results by said second detecting means; an optical path combination and separation means for combining the imaging optical path formed by said imaging optical system and the optical path of a signal light directed toward said fundus oculi and illuminate said signal light onto said fundus oculi through said imaging optical path, as well as separating said imaging optical path from the optical path of the signal light toward said fundus oculi and overlapping said signal light on said reference light by said interference optical generating means; a control means for synchronizing detection timing by said first detection means and detection timing by said second detection means; a correction means for correcting the image positions of said tomographic images based on two-dimensional images based on detection results by said first detection means; and a three-dimensional image formation means for forming three-dimensional images of said fundus oculi based on said tomographic images in which said image positions have been corrected.
Effects Of The Invention
The fundus observation device related to the present embodiment comprises a first image forming means for forming 2-dimensional images of the surface of the fundus oculi and a second image forming means for forming tomographic images of the fundus oculi. The imaging optical system of the first image forming means forms the imaging optical path. The second image forming means generates the interference light by overlapping the signal light passing through the fundus oculi to the reference light, and forms tomographic images of the fundus oculi based on this interference light.
Optical combination and separation means operates to combine the optical path of the signal light toward the fundus oculi and the imaging optical path. The signal light irradiates onto the fundus oculi through this imaging optical path. Also, optical combination and separation means are used for separating the signal light toward the fundus oculi from the imaging optical path. The separating signal light generates the interference light by overlapping the reference light.
Such optical combination and separation means permits to capture both 2-dimensional images of the surface of the fundus oculi and tomographic images of the fundus oculi. In particular, when the illumination light from the first image forming means irradiates and the illumination from the signal light by the second image forming means irradiate simultaneously, each light through the fundus oculi is separated by the optical path combination and separation means, each light is detected so that the image is formed. Therefore, by the fundus observation device related to the present invention, it is possible to capture both 2-dimensional images of the surface of the fundus oculi and tomographic images of the fundus oculi to be captured simultaneously.
Furthermore, the fundus observation device according to the present embodiment comprises the formation of three-dimensional images of the fundus oculi wherein the detection timing of the first detection means is synchronized with the detection timing of the second detection means, the image positions of the tomographic images based on detection results from the second detection means are corrected on the basis of the two-dimensional images based on the detection results from the first detection means, and the positions of these images are based on the corrected tomographic images.
Thus, even when the eye to be examined moves while detecting the interference light, which is the basis of the tomographic images, detection of this interference light is synchronized, and it becomes possible to form highly reliable three-dimensional images by correcting the image positions of the tomographic images using two-dimensional images of the surface of the fundus oculi based on illuminated light detected by the first detection means.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic diagram representing one example of the entire constitution in a favorable embodiment of the fundus observation device related to the present invention.
FIG. 2 is a schematic diagram representing one compositional example of a scanning unit installed in a fundus camera unit in a favorable embodiment of the fundus observation device related to the present invention.
FIG. 3 is a schematic diagram representing one compositional example of an OCT unit in a favorable embodiment of the fundus observation device related to the present invention.
FIG. 4 is a schematic block diagram representing one example of hardware configurations of an arithmetic and control unit in a favorable embodiment of the fundus observation device related to the present invention.
FIG. 5 is a schematic block diagram representing one compositional example of a control system in a favorable embodiment of the fundus observation device related to the present invention.
FIG. 6 is a schematic diagram representing one example of scanning features of signal light in a favorable embodiment of the fundus observation device related to the present invention. FIG. 6 (A) represents one example of the scanning features of signal light when a fundus oculi is seen from the incident side of the signal light with respect to an eye to be examined. In addition, FIG. 6 (B) represents one example of arrangement features of scanning points of each scanning line.
FIG. 7 is a schematic diagram representing one example of the scanning features of signal light and tomographic image features formed along each scanning line in a favorable embodiment of the fundus observation device related to the present invention.
FIG. 8 is a flow chart showing one example of the operation of forming three-dimensional images of fundus oculi by means of an optimal embodiment of the fundus observation device according to the present invention.
FIG. 9 is an outline explanatory drawing for describing the operation of forming three-dimensional images of the fundus oculi by means of the optimal embodiment of the fundus observation device according to the present invention.
FIG. 10 is a schematic side view representing an appearance constitution of a conventional fundus observation device (fundus camera).
FIG. 11 is a schematic diagram representing one example of an internal constitution (an optical system constitution) of a conventional fundus observation device (fundus camera).



DETAILED DESCRIPTION OF THE REFERENCE EMBODIMENT
One example of favorable embodiments of a fundus observation device related to the present invention is described in detail referring to figures. Furthermore, for compositional parts that are the same as conventional ones, the same numeric symbols used in FIG. 10 and FIG. 11 are used.
First, by referring to FIGS. 1 through 5, the composition of the fundus observation device related to the present embodiment is described. FIG. 1 shows the entire constitution of the fundus observation device 1 related to the present invention. FIG. 2 shows a composition of a scanning unit 141 in a fundus camera unit 1A. FIG. 3 shows a composition of an OCT unit 150. FIG. 4 shows a hardware configuration of an arithmetic and control unit 200. FIG. 5 shows a configuration of a control system of the fundus observation unit 1.
The Entire Constitution
As shown in FIG. 1, the fundus observation device 1 a component of a fundus camera unit 1A that functions as a fundus camera, an OCT unit 150 accommodating the optical system of an optical image measuring device (OCT device), and an arithmetic and control unit 200 that executes various control processes, etc.
This fundus camera unit 1A is a component of one example of the “first image forming means” with the arithmetic and control unit 200. Also, the OCT unit 150 is a configuration of one example of the “second image forming means” with the arithmetic and control unit 200. Further, this “second image forming means” also includes each optical element through the signal light such as a scan unit 141 provided in the fundus camera unit 1A, etc.
To the OCT unit 150, one end of a connection line 152 is attached. To the other end of this connection line 152, a connector part 151 is attached. This connector part 151 is attached to a mounting part 8c shown in FIG. 10. Furthermore, a conductive optical fiber runs through the inside of the connection line 152. The OCT unit 150 and the fundus camera unit 1A are optically connected through the connection line 152. The composition details of the OCT unit 150 are to be described later referring to FIG. 3.
Constitution of Fundus Camera Unit
The fundus camera unit 1A has substantially the same appearance as the conventional fundus camera 1000 shown in FIG. 10. Furthermore, as in the conventional optical system shown in FIG. 11, the fundus camera unit 1A is provided with an illuminating optical system 100 to light a fundus oculi Ef of an eye to be examined E, and a imaging optical system 120 for guiding the fundus reflection light of the illumination light to an eyepiece 8b, an imaging device 10, and an OCT unit 150.
In addition, although the details are to be described later, an imaging device 10 in a imaging optical system 120 of the present embodiment is used for detecting the illumination light with a wavelength in the near-infrared region. Furthermore, in this imaging optical system 120, an imaging device 12 for detecting the illumination light with wavelength in the visible region is provided separately. In addition, in this imaging optical system 120, it can guide the signal light from the OCT unit 150 to the fundus oculi Ef and the signal light through the fundus oculi Ef to the OCT unit 150.
Also, the illuminating optical system 100 is comprised as in conventional ones including: an observation optical source 101, a condenser lens 102, an imaging light source 103, a condenser lens 104, an exciter filter 105 and 106, a ring transparent plate 107, a mirror 108, an LCD 109, an illumination diaphragm 110, a relay lens 111, an aperture mirror 112, and an objective lens 113.
An observation optical source 101 outputs the illumination light of a wavelength in the visible region included within about 400 nm to 700 nm. Furthermore, an imaging light source 103 outputs the illumination light of a wavelength in the near-infrared region included within about 700 nm to 800 nm. The near-infrared light output from this imaging light source 103 is provided shorter than the wavelength of the light used by the OCT unit 150 (to be described later).
At the same time, the imaging optical system 120 comprises: an objective lens 113, an aperture mirror 112 (aperture part 112a thereof), an imaging diaphragm 121, a barrier filter 122 and 123, a variable magnifying lens 124, a relay lens 125, an imaging lens 126, a dichroic mirror 134, a field lens (eye vision lens) 128, a half mirror 135, a relay lens 131, a dichroic mirror 136, an imaging lens 133, an imaging device 10 (an image pick-up element 10a), a reflection mirror 137, an imaging lens 138, an imaging device 12 (an image pick-up element 12a), and a lens 139 and LCD (Liquid crystal Display) 140.
The imaging optical system 120 related to the present embodiment is different from the conventional imaging optical system 120 shown in FIG. 11 in that a dichroic mirror 134, a half mirror 135, a dichroic mirror 136, a reflection mirror 137, an imaging lens 138, and a lens 139 and LCD 140 are provided.
The dichroic mirror 134 reflects the fundus reflection light of the illumination light from the illuminating optical system 100 (with a wavelength included within about 400 nm to 800 nm), and transmits the signal light LS (with a wavelength included within about 800 nm to 900 nm; to be described later) from the OCT unit 150. This dichroic mirror 134 is the equivalent of one example of the “optical combination and separation means” of the present invention.
Furthermore, the dichroic mirror 136 transmits the illumination light with a wavelength in the visible region from the illuminating optical system 100 (the visible light of a wavelength within about 400 nm to 700 nm for outputting from the observation optical source 101), and refrects the illumination light with a wavelength in the near-infrared region (the near-infrared light of a wavelength within about 700 nm to 800 nm for outputting from the imaging light source 103).
The LCD 140 shows an internal fixation target, etc. The light from this LCD 140 is reflected by the half mirror 135 after being converged by the lens 139, and reflects the dichroic mirror 136 through the field lens 128. Further, it enters the eye to be examined E passing through the imaging lens 126, the relay lens 125, the variable magnifying lens 124, the aperture mirror 112 (aperture part 112a thereof), the objective lens 113, etc. As a result, an internal fixation target, etc. is displayed in a fundus oculi Ef of an eye to be examined E.
The image pick up element 10a is the image pick up element of CCD and CMOS, etc. installed internally in an imaging device 10 such as a TV camera, and is particularly used for detecting light of a wavelength in the near-infrared region (that is, the imaging device 10 is the infrared TV camera for detecting near-infrared light). The imaging device 10 outputs the image signal as a result of detecting near-infrared light. A touch panel monitor 11 displays a 2-dimensional image (fundus image Ef′) of the surface of the fundus oculi Ef based on this image signal. Also, this image signal is sent to the arithmetic and control unit 200, and the fundus oculi image is displayed on the display (to be described later). Furthermore, when the fundus oculi are being imaged by this imaging device 10, the illumination light output from the imaging light source 103 of the illuminating optical system 100, having a wavelength in the near-infrared region, is used. This imaging device 10 (of the image pick up element 10a) is the equivalent of one example of the “first detecting means”.
Also, The image pick up element 12a is the image pick up element of CCD and CMOS, etc. installed internally in an imaging device 12 such as a TV camera, and is particularly used for detecting light of a wavelength in the visible region (that is, the imaging device 12 is the TV camera for detecting visible light). The imaging device 12 outputs the image signal as a result of detecting visible light. A touch panel monitor 11 displays a 2-dimensional image (fundus image Ef′) of the surface of the fundus oculi Ef based on this image signal. Also, this image signal is sent to the arithmetic and control unit 200, and the fundus oculi image is displayed on the display (to be described later). Furthermore, when the fundus oculi are being imaged by this imaging device 12, the illumination light output from the observation optical source 101 of the illuminating optical system 100, having a wavelength in the visible region, is used. This imaging device 12 (of the image pick up element 12a) is the equivalent of one example of the “third detecting means”.
Furthermore, the imaging optical system 120 of the present embodiment is provided with a scanning unit 141 and a lens 142. The scanning unit 141 is equipped with a constitution to scan the light output (signal light LS; to be described later) from the OCT unit 150 on a fundus oculi Ef.
The lens 142 incidents the signal light LS from the OCT unit 150 in the form of parallel light flux onto the scanning unit 141. Furthermore, the lens 142 acts so as to converge the fundus reflection light of the signal light LS that has reached through the scanning unit 141.
In FIG. 2, one example of a concrete composition of the scanning unit 141 is shown. The scanning unit 141 is comprised including Galvanometer mirrors 141A, 141B, and reflection mirrors 141C, 141D.
The Galvanometer mirrors 141A and 141B are to be rotatable centering around rotary shafts 141a and 141b respectively. The rotary shaft 141a and 141b are arranged perpendicular to each other. In FIG. 2, the rotary shaft 141a of the Galvanometer mirror 141A is arranged parallel to the paper face on the same figure, while the rotary shaft 141b of the Galvanometer mirror 141B is arranged perpendicular to the paper face in the same figure. That is, the Galvanometer mirror 141B is to be rotatable in the directions indicated by an arrow pointing in both directions in FIG. 2, while the Galvanometer mirror 141A is to be rotatable in the directions perpendicular to the arrow pointing in both directions. As a result, this pair of Galvanometer mirrors 141A and 141B act so that the reflecting direction of the signal light LS changes to a direction perpendicular to each other. Furthermore, the rotary movement of the Galvanometer mirror 141A and 141B respectively is driven by a drive mechanism to be described later(see FIG. 5).
The signal light LS reflected by the Galvanometer mirrors 141A and 141B is to be reflected by reflection mirrors 141C and 141D, and is to advance in the same direction as having entered into the Galvanometer mirror 141A.
As described previously, a conductive optical fiber 152a runs inside the connection line 152, and the end face 152b of the optical fiber 152a is arranged opposing the lens 142. The signal light LS emitted from this end face 152b advances while gradually expanding its beam diameter toward the lens 142 until being converged to a parallel light flux by this lens 142. On the contrary, the fundus reflection light of the signal light LS is converged toward the end face 152b by this lens 142.
Constitution of OCT Unit
Next, referring to FIG. 3, the constitution of an OCT unit 150 is described. The OCT unit 150 shown in the same figure has substantially the same optical system as a conventional optical image measuring device, and is equipped with an interferometer that splits the light output from a light source into reference light and signal light, and generates interference light by the reference light that has passed through a reference object and by the signal light that has passed through an object to be measured (fundus oculi Ef), and at the same time, is configured to form images of the object to be measured by analyzing the detection result of this interference light.
A low coherence light source 160 is composed of a broad band light source such as super luminescent diode (SLD) that outputs low coherence light L0 or a light emitting diode (LED), etc. This low coherence light L0, for instance, has a wave length in the near-infrared region and is supposed to be light having a time wise coherence length of approximately several tens of micro-meters. The low coherence light L0 output from the low coherence light source 160 has a longer wavelength than the illumination light (wavelength: about 400 nm to 800 nm) of the fundus camera unit 1A, for example, a wavelength included within about 800 mn to 900 nm. This low coherence light source 160 corresponds to an example of the “light source” of the present invention.
The low coherence light L0 output from the low coherence light source 160 is guided to an optical coupler 162 through an optical fiber 161 composed of, e.g. a single mode fiber, or PM (Polarization maintaining) fiber, and then split into reference light LR and signal light LS.
Furthermore, the optical coupler 162 has both actions, i.e. a means for splitting the light (splitter), and a means for overlaying the light (coupler); however, herein conventionally referred to as an “optical coupler”.
The reference light LR generated by the optical coupler 162 is guided by an optical fiber 163 consisting of such as a single mode fiber, and emitted from the end face of the fiber. The emitted reference light LR is reflected by a reference mirror 174 (reference object) through a glass block 172 and a density filter 173 after having been converged into a parallel light flux by a collimator lens 171.
The reference light LR reflected by the reference mirror 174 is converged to the end face of the fiber of the optical fiber 163 by the collimator lens 171 again through the density filter 173 and the glass block 172. The converged reference light LR is guided to the optical coupler 162 through the optical fiber 163.
Furthermore, the glass block 172 and the density filter 173 act as a delaying means to match the optical path length (optical distance) between the reference light LR and the signal light LS, and as a means to match the dispersion characteristics of reference light LR and the signal light LS.
Furthermore, the reference mirror 174 is provided to be movable in the traveling direction of the reference light LR. As a result, it ensures the light path length of the reference light LR according to the length of the eyeball, etc. of an eye to be examined E. Moreover, shifting of the reference mirror 174 is operated to move by a drive mechanism including a motor, etc.
Whereas, the signal light LS generated by the optical coupler 162 is guided to the end part of the connection line 152 by an optical fiber 164 consisting of such as a single mode fiber. A conductive optical fiber 152a runs inside the connection line 152. Herein, the optical fiber 164 and the optical fiber 152a may be composed of a single optical fiber, or may be jointly formed by connecting each end. In either case, it is sufficient as long as the optical fiber 164 and 152a are composed so as to be capable of transferring the signal light LS between the fundus camera unit 1A and the OCT unit 150.
The signal light LS is guided within the connection line 152 to the fundus camera unit 1A. Then, the signal light LS enters into the eye to be examined E through the lens 142, the scanning unit 141, the dichroic mirror 134 the imaging lens 126, the relay lens 125, the variable magnifying lens 124, the imaging diaphragm 121, the aperture part 112a of an aperture mirror 112, and the objective lens 113 (then, as described later, the barrier filter 122 and 123 as well as the quick return mirror 127 are retracted from the optical path respectively).
The signal light LS that has entered into the eye to be examined E forms an image on a fundus oculi (retina) Ef and is then reflected. Then, the signal light LS is not only reflected on the surface of the fundus oculi Ef, but is also scattered at the refractive index boundary reaching the deep area region of the fundus oculi Ef. As a result, the signal light LS passed through the fundus Ef becomes a light containing the information reflecting the surface state of the fundus oculi Ef and the information reflecting the scattered state in the rear at the refractive index boundary of the deep area tissue. The light is simply referred as “fundus reflection light” (signal light LS thereof).
The fundus reflection light of the signal light LS advances reversely on the above route and converges at the end face 152b of the optical fiber 152a, then enters into the OCT unit 150 through this optical fiber 152, and returns to the optical coupler 162 through the optical fiber 164. The optical coupler 162 overlays this signal light LS and the reference light LR reflected at the reference mirror 174 to generate interference light LC. The generated interference light LC is guided into a spectrometer 180 through an optical fiber 165 consisting of such as a single mode fiber.
Herein, the “interference light generating means” in the present embodiment is comprised of an interferometer including at least an optical coupler 162, an optical fiber 163 and 164, and a reference mirror 174. Furthermore, although a Michelson type interferometer has been adopted in the present embodiment, for instance, a Mach Zender type, etc. or any optional type of interferometer may be adopted appropriately.
The spectrometer 180 is comprised of a collimator lens 181, a diffraction grating 182, an image forming lens 183, and a CCD (Charge Coupled Device) 184. The diffraction grating 182 in the present embodiment is a transmission type diffraction grating; however, needless to say, a reflection type diffraction grating may also be used. Furthermore, needless to say, in place of CCD 184, it is also possible to adopt other photo-detecting elements. This photo-detecting element is the equivalent of one example of the “second detecting means” of the present invention.
The interference light LC made incident onto the spectrometer 180 is to be split (spectral resolution) by the diffraction grating 182 after having been converged into a parallel light flux by the collimator lens. The split interference light LC forms an image on the image pick up surface of the CCD 184 by the image forming lens 183. The CCD 184 receives this interference light LC that is to be converted to an electrical detection signal, and outputs this detection signal to the arithmetic and control unit 200.
Constitution of Arithmetic and Control Unit
Next, the configuration of the arithmetic and control unit 200 is described. This arithmetic and control unit 200 analyzes the detection signal input from the CCD 184 of the spectrometer 180 of the OCT unit 150, and performs a process of forming tomographic images of a fundus oculi Ef of an eye to be examined E. The analysis technique then is the same technique as the conventional Fourier domain OCT technique. Furthermore, the arithmetic and control unit 200 executes the control of each part of the fundus camera unit 1A and the control of each part of the OCT unit 150.
Also, the arithmetic and control unit 200 operates to form a 2-dimensional image showing the state of the surface of a fundus oculi Ef (retina) based on the image signal output from the imaging device 10 and 12 of the fundus camera unit 1A.
Furthermore, the arithmetic and control unit 200 executes the control of each part of the fundus camera unit 1A and the control of each part of the OCT unit 150.
As for the control of the fundus camera unit 1A, to be controlled is, for example: controlling the output of illumination light by the observation light source 101 or the imaging light source 103; controlling the insertion/retraction operation of the exciter filters 105, 106, or the barrier filters 122, 123 on the optical path; controlling the display operation of the liquid crystal display 109; controlling the shift of the illumination diaphragm 110 (controlling the diaphragm value); controlling the diaphragm value of the imaging diaphragm 121; controlling the shift of the variable magnifying lens 124 (controlling the magnification), etc. Furthermore, the arithmetic and control unit 200 performs a control of rotary operations of the Galvanometer mirrors 141A, 141B within the scanning unit 141.
Whereas, as for the control of the OCT unit 150, output control of the low coherence light by a low coherence light source 160, control of accumulated time of the CCD 184, or movement control of reference mirror 174, etc. are to be performed.
The hardware configuration of the arithmetic and control unit 200 that acts as described above is explained referring to FIG. 4. The arithmetic and control unit 200 is provided with a hardware configuration that is the same as conventional computers. To be specific, the configuration includes: a microprocessor 201 (CPU,MPU, etc.), a RAM202, a ROM203, a hard disk drive (HDD) 204, a key board 205, a mouse 206, a display 207, an image forming board 208, and a communication interface (I/F)209. Each part of these is connected through a bus 200a. 
The microprocessor 201 executes operations characteristic to the present embodiment by rolling out a control program 204a that has been stored in the hard disk drive 204, on the RAM 202.
Furthermore, the microprocessor 201 executes control of each part of the devices that have previously been described and various arithmetic processes, etc. Moreover, control of each part of the devices that respond to an operation signal from the key board 205 or the mouse 206, control of display processes by the display 207, and control of transmitting/receiving processes of various types of data or control signals, etc. are executed by the communication interface 209.
The key board 205, the mouse 206 and the display 207 are used as a user interface of the fundus observation device 1. The key board 205 is used as a device for entering letters or figures, etc. by typing. The mouse 206 is used as a device to perform various entry operations with respect to the display screen of the display 207.
Furthermore, the display 207 being an optional display device such as LCD (Liquid Crystal Display) or CRT (Cathode Ray Tube), etc. displays images of a fundus oculi Ef formed by the fundus observation device 1 and displays various operation screens or set up screens, etc.
Furthermore, the user interface of the fundus observation device 1 is not limited to such a configuration but may be configured by using an optional user interface means equipped with a function to display and output various information such as track ball, joystick, touch panel type LCD, control panel for ophthalmology examinations, and with a function to input various information.
An image forming board 208 is a dedicated electronic circuit for operating the treatment forming the image of the fundus oculi Ef of an eye to be examined E. In this image forming board 208, the fundus image forming board 208a and OCT image forming board 208b are installed. The fundus image forming board 208a is a dedicated electronic circuit for operating in order to form the image of the fundus oculi based on the image signal from the imaging device 10 and the imaging device 12 of the fundus camera unit 1A. Furthermore, the OCT image forming board 208b is a dedicated electronic circuit for operating in order to form fundus images (tomographic images) based on the detecting signal from CCD 184 of the spectrometer 180 in the OCT unit 150. In addition, three-dimensional images of the fundus oculi Ef may be formed by an OCT image formation board 208b. The image forming board 208 allows the processing speed for forming fundus images to improve.
A communication interface 209 operates to send the control signal from a microprocessor 201 to the fundus camera unit 1A and OCT unit 150. Also, the communication interface 209 operates to receive the image signal from the imaging device 10 and 12 in the fundus camera unit 1A and the detecting signal from CCD 184 in the OCT unit 150, and it operates to input the image forming board 208. At this time, the communication interface 209 operates to input the image signal from the imaging device 10 and 12 to the fundus image forming board 208a, and it operates to input the detecting signal from CCD 184 to OCT image forming board 208b. 
Moreover, when the arithmetic and control unit 200 is connected to a network such as LAN (Local Area Network) or Internet, etc., the communication interface 209 may be configured to be equipped with a network adopter such as LAN card, etc. or a communication equipment such as modem, etc. so as to be able to perform data communication through the network. In this case, a server accommodating the control program 204a may be installed, and at the same time, the arithmetic and control unit 200 may be configured as a client terminal of the server.
Control System Configuration
The configuration of the control system of the fundus observation device 1 having the configuration described above is explained referring to FIG. 5. FIG. 5 shows a part related to the operations or processes of the present invention that has been particularly selected from among constituents composing the fundus observation device 1.
The control system of the fundus observation device 1 is configured mainly having a controlling part 210 of the arithmetic and control unit 200. The controlling part 210 is comprise including: the microprocessor 201, the RAM202, the ROM203, the hard disk drive 204 (control program 204a), and. the communication interface 209.
A controlling part 210 executes various control processes by a microprocessor 201 that runs based on a control program 204a. In particular, the controlling part 210 controls the detection timing of the fundus oculi catoptric light of the illuminated light, or in other words, controls the radiographic timing of the fundus oculi image by the imaging devices 10, 12 of the fundus camera unit 1A. Similarly, the controlling part 210 controls the timing of the radiogram of the fundus oculi image by the CCD 184 of the spectrometer 180 on the OCT unit 150, or in other words, controls the timing of detection of the interference light LC.
Control of this imaging timing can be executed by controlling the electronic shutter as well as controlling the storage time of the imaging sensor element 10a, 12a and the CCD 184, and by controlling the frame rate of the imaging devices 10, 12 and the CCD 184 similar to before, for example. Then, the controlling part 210 controls the low-coherence light source 160 of the OCT unit 150, and outputs the low-coherence light L0 according to the imaging timing of the CCD 184.
The controlling part 210 variously controls both the image device 10 (or image device 12) and the CCD 184, and synchronizes the imaging timing (timing of the detection of light) of these. Then, the controlling part 210 controls the frame rate of the imaging device 10 (or imaging device 12) as well as the frame rate of the CCD 184 at a ratio of about 10:1 to 1:1, for example. The controlling part 210 acting in this way is equivalent to one example of the “control means” according to the present invention.
The controlling part 210 executes said controlling processes by the microprocessor 201 that is operated based on the control program 204a. Particularly, by controlling the mirror drive mechanisms 241, 242 of the fundus camera unit 1A respectively, the Galvanometer mirrors 141A, 141B respectively may be operated independently.
Furthermore, the controlling part 210 executes control for displaying two kinds of images produced by the fundus observation device 1: that is, a 2-dimensional image (fundus image Ef′) of the surface of a fundus oculi Ef by the fundus camera unit 1A, and an image(sectional image, 3-dimensional image, etc.) of a fundus oculi Ef formed based on the detection signal obtained by the OCT unit 150, parallel to each other on the display 207 of the user interface 250. These fundus images are simultaneously displayed on the display 207 respectively.
An image forming part 220 is intended to operate the process forming the fundus image based on the image signal from the imaging device 10 and 12 of the fundus camera unit 1A and to operate the process forming the fundus image based on the detecting signal from CCD 184 in the OCT unit 150 including the image forming board 208.
The image processing part 230 is used for various image processes to the fundus images formed by the image forming part 220. For example, it operates to form a 3-dimensional image of the fundus oculi Ef based on the tomographic images of the fundus oculi Ef corresponding to the detection signal from the OCT unit 150 and various corrections, such as brightness adjustment. This image processing part 230 may be comprised with the inclusion of a microprocessor 201, and may be comprised with the inclusion of an OCT image formation board 208b. This image processing part 230 is equivalent to one example of the “three-dimensional image formation means” according to the present invention.
The correction processing part 240 performs the process of correcting image positions of the tomographic images of fundus oculi Ef based on results of detecting interference light LC from the CCD 184 on the OCT unit 150 based on two-dimensional images of the surface of the fundus oculi Ef based on results of detecting fundus oculi catoptric light from the light illuminated by the imaging device 10 (or imaging device 12) on the fundus camera unit 1A. This correction processing part 240 is equivalent to one example of “correction means” according to the present invention and consists of the inclusion of a microprocessor 201 or the like.
The process of correcting the image positions of the tomographic images executed by the correction processing part 240 will now be described more specifically. An extraction processing part 240a is built into the correction processing part 240. This extraction processing part 240a analyzes the two-dimensional images of the surface of the fundus oculi Ef based on results of detection from the imaging device 10 (or imaging device 12) and extracts the characteristic part among these two-dimensional images. The characteristic parts subject to extraction are, for example, the optic papilla, macula lutea, a specific blood vessel or vascular bifurcation. The extraction processing part 240a extracts the characteristic parts that are subject to extraction by analyzing the luminance and color of the two-dimensional images of the fundus oculi Ef, for example. This extraction processing part 240a is equivalent to an example of the “extraction means” according to the present invention.
The correction processing part 240 acquires the image positions of the characteristic part extracted by the extraction processing part 240a. These coordinate positions are expressed by an xycoordinate system shown, for example, in FIG. 1. In addition, the xy coordinate system is connected in advance to the two-dimensional coordinate system defined on the detection side of the imaging sensor element 10a (or imagine sensor element 12a of the imaging device 12) on the imagining device 10. The correction processing part 240 acquires the image positions of the relevant characteristic part by converting the image positions of the characteristic part expressed by the two-dimensional coordinate system on this detection surface to the image positions by means of the relevant xy coordinate system.
The correction processing part 240 corrects the image positions of the tomographic images of the fundus oculi Ef using the image positions of the characteristic part acquired in this way. Details of this correction process are described below.
The user interface (UI)250 is equipped with operational devices such as a key board 205 or a mouse 206, etc. and with a display device such as a display 207, etc.
The controlling feature of the scanning signal light LS by the controlling part 210 and the process feature to the detecting signal from the OCT unit 150 by the image forming part 220 and the image processing part 230 are respectively described below. Furthermore, an explanation regarding the process of the image forming part 220, etc., to the image signal from the fundus camera unit 1A is omitted because it is the same as the conventional process.
Regarding the Signal Light Scanning
Scanning of signal light LS is performed by changing the facing direction of the reflecting surfaces of the Galvanometer mirrors 141A and 141B of the scanning unit 141 in the fundus camera unit 1A. By controlling the mirror drive mechanisms 241 and 242 respectively, the controlling part 210 changes the facing direction of the reflecting surfaces of the Galvanometer mirror 141A and 141B, and scans the signal light LS on the fundus oculi Ef.
Once the facing direction of the reflecting surface of the Galvanometer mirror 141A is changed, the signal light LS is scanned in a horizontal direction (x-direction in FIG. 1) on the fundus oculi Ef. Whereas, once the facing direction of the reflecting surface of the Galvanometer mirror 141A is changed, the signal light LS is scanned in a vertical direction (y-direction in FIG. 1) on the fundus oculi Ef. Furthermore, by changing the facing direction of the reflecting surfaces of both Galvanometer mirrors 141A and 141B simultaneously, the signal light LS may be scanned in the combined x-direction and y-direction. That is, by controlling these two Galvanometer mirrors 141A and 141B, the signal light LS may be scanned in an arbitrarily direction on the xy plane.
FIG. 6 represents one example of scanning features of signal light LS for forming images of a fundus oculi Ef. FIG. 6 (A) represents one example of scanning features of the signal light LS, when the signal light LS sees the fundus oculi Ef from an incident direction onto the eye to be examined E (that is, +direction of z is seen from −direction of z in FIG. 1). Furthermore, FIG. 6 (B) represents one example of arrangement features of scanning points (positions at which image measurement is carried out) on each scanning line on the fundus oculi Ef.
As shown in FIG. 6 (A), the signal light LS is scanned within a rectangular shaped scanning region R that has been preset. Within this scanning region R, plural (m number of) scanning lines R1 through Rm have been set in the x-direction. When the signal light LS is scanned along each scanning line Ri (i=1 through m), detection signals of interference light LC are to be generated.
Herein, the direction of each scanning line Ri is referred as the “main scanning direction” and the orthogonally crossing direction is referred as the “sub-scanning direction”. Therefore, the scanning of the signal light LS in a main scanning direction is performed by changing the facing direction of the reflecting surface of the Galvanometer mirror 141A, and the scanning in a sub-scanning direction is performed by changing the facing direction of the reflecting surface of the Galvanometer mirror 141B.
On each scanning line Ri, as shown in FIG. 6 (B), a plurality (n number of) of scanning points Ri1 through Rin have been preset.
In order to execute the scanning shown in FIG. 6, the controlling part 210 controls the Galvanometer mirrors 141A and 141B to set the incident target of the signal light LS with respect to a fundus oculi Ef at a scan start position RS(scanning point R11) on the first scanning line R1. Subsequently, the controlling part 210 controls the low coherence light source 160 to flush the low coherence light L0 for emitting the signal light LS to the scan start position RS. The CCD 184 receives the interference light LC based on the fundus reflection light of this signal light LS at the scan start position RS, and outputs detection signals to the controlling part 210.
Next, by controlling the Galvanometer mirror 141A the controlling part 210 scans the signal light LS in a main scanning direction and sets the incident target at a scanning point R12, triggering a flush emission of the low coherence light L0 for making the signal light LS incident onto the scanning point R12. The CCD 184 receives the interference light LC based on the fundus reflection light of this signal light LS at the scanning point R12, and then outputs the detection signal to the controlling part 210.
Likewise, the controlling part 210 obtains detection signals output from the CCD 184 responding to the interference light LC with respect to each scanning point, by flush emitting the low coherence light L0 at each scanning point while shifting the incident target of the signal light LS from scanning point R13, R14, - - - , R1 (n−1), R1n in order.
Once the measurement at the last scanning point R1n of the first scanning line Ri is finished, the controlling part 210 controls the Galvanometer mirrors 141A and 141B simultaneously and shifts the incident target of the signal light LS to the first scanning point R21 of the second scanning line R2 following a line switching scan r. Then, by conducting the previously described measurement with regard to each scanning point R2j (j=1 through n) of this second scanning line R2, a detection signal corresponding to each scanning point R2j is obtained.
Likewise, by conducting a measurement with respect to the third scanning line R3, - - - , the m−1th scanning line R (m−1), the mth scanning line Rm respectively to obtain the detection signals corresponding to each scanning point. Furthermore, the symbol RE on a scanning line Rm is a scan end position in accordance with a scanning point Rmn.
As a result, the controlling part 210 obtains m×n number of detection signals corresponding to m×n number of scanning points Rij (i=1 through m, j=1 through n) within the scanning region R. Hereinafter, a detection signal corresponding to the scanning point Rij may be represented as Dij.
Such interlocking control of such shifting of scanning points and the output of the low coherence light L0 may be realized by synchronizing, for instance, the transmitting timing of control signals with respect to the mirror drive mechanisms 241, 242 and the transmitting timing of control signals (output request signal) with respect to the low coherence light source 160.
As described, when each Galvanometer mirror 141A and 141B is being operated, the controlling part 210 stores the position of each scanning line Ri or the position of each scanning point Rij (coordinate on the xy coordinate system) as information indicating the content of the operation. This stored content (scan positional information) is used in an image forming process as was conducted conventionally.
Regarding Image Processing
Next, the process according to OCT images by the image forming part 220 and the image processing part 230 is described by example. Only the process of forming tomographic images of the fundus oculi Ef and the process of forming three-dimensional images based on tomographic images are explained here, and the process of forming three-dimensional images including image position correction of tomographic images by the correction processing part 240 on the arithmetic and control device 200 will be described later.
Forming Process of Tomographic Images
The image forming part 220 executes the formation process of tomographic images of a fundus oculi Ef along each scanning line Ri (main scanning direction). The image processing part 230 executes the formation process of a 3-dimensional image of the fundus oculi Ef based on these tomographic images formed by the image forming part 220.
The formation process of a tomographic image by the image forming part 220, as was conventionally done, includes a 2-step arithmetic process. In the first step of the arithmetic process, based on a detection signal Dij corresponding to each scanning point Rij, an image in the depth-wise direction (z-direction in FIG. 1) of a fundus oculi Ef at the scanning point Rij is formed.
FIG. 7 represents a feature of a tomographic image formed by the image forming part 220. In the second step of the arithmetic process, with regard to each scanning line Ri, based on the images in the depth-wise direction at the n number of scanning points Ri1 through Rin thereon, a tomographic image Gi of a fundus oculi Ef along this scanning line Ri is formed. Then, the image forming part 220 determines the arrangement and the distance of each scanning point Ri1 through Rin while referring to the positional information (said scan positional information) of each scanning point Ri1 through Rin, and forms this scanning line Ri. Due to the above process, m number of tomographic images G1 through Gm at different positions of the sub-scanning direction (y-direction) are obtained.
Formation Process of 3-Dimensional Images
Next, the formation process of a 3-dimensional image of a fundus oculi Ef by the image processing part 230 is explained. A 3-dimensional image of a fundus oculi Ef is formed based on the m number of tomographic images (at least a plurality of these images) obtained by the above arithmetic process. The image processing part 230 forms a 3-dimensional image of the fundus oculi Ef by performing a publicly known interpolating process to interpolate an image between the adjacent tomographic images Gi and G (i+1).
Then, the image processing part 230 determines the arrangement and the distance of each scanning line Ri while referring to the positional information of each scanning line Ri to form this 3-dimensional image. For this 3-dimensional image, a 3-dimensional coordinate system (x,y,z) is set up, based on the positional information (said scan positional information) of each scanning point Rij and the z coordinate in the images of the depth-wise direction.
Furthermore, based on this 3-dimensional image, the image processing part 230 is capable of forming a tomographic image of the fundus oculi Ef at a cross-section in an arbitrary direction other than the main scanning direction (x-direction). Once the cross-section is designated, the image processing part 230 determines the position of each scanning point (and/or an image in the depth-wise direction that has been interpolated) on this designated cross-section, and extracts an image (and/or image in the depth-wise direction that has been interpolated) in the depth-wise direction at each determined position to form a tomographic image of the fundus oculi Ef at the designated cross-section by arranging plural extracted images in the depth-wise direction.
The image Gmj in FIG. 7 represents an image in the depth-wise direction (z-direction) at the scanning point Rmj on the scanning line Rm. Likewise, an image in the depth-wise direction at each scanning point Rij on the scanning line Ri formed by the arithmetic process of said first step may be represented as “image Gij”.
In addition, the process of forming three-dimensional images of fundus oculi Ef described here is assumed to be when m number of tomographic images G1-Gm are displaced in the xy direction, or in other words, when eye movement of the eye subject to examination E occurs during image measurement of the tomographic images G1-Gm. The following [Operation] section describes operation of the fundus observation device 1 for optimally forming three-dimensional images even if eye movement of the eye subject to examination E occurs during image measurement of the tomographic images G1-Gm.
Operation
Operation of the fundus observation device 1 is described with reference to FIG. 8 and FIG. 9. The flow chart in FIG. 8 shows one example of operation of the process of forming three-dimensional images of the fundus oculi Ef by means of this fundus observation device 1. Furthermore, the fundus oculi image shown in FIG. 9 is an outline explanatory drawing for describing the operation shown in FIG. 8.
Also described is the case in which the ratio of the frame rate when the fundus camera unit 1A detects fundus oculi catoptric light of the illuminated light to the frame rate when the OCT unit 150 detects interference light LC is 2:1 in the operation of the fundus observation device 1 described below. However, even when the ratio of these frame rates is other than 2:1, it is possible for a similar process to be executed.
Detection: Steps S1, S2
First, the controlling part 210 controls the CCD 184 and low-coherence light source 160 on the OCT unit 150 along with illuminating the observation optical source 101 of the fundus camera unit 1A and controlling the imaging device 12 so as to detect the fundus oculi catoptric light of the light illuminated from this observation optical source 101 by means of frame rate f1 (frames/second) (S1), and detects the interference light LC by the frame rate f2 (frames/second) in the CCD 184 (S2). At this time, the frame rate f1 of the imaging device 12 and the frame rate f2 of the OCT unit 150 are mutually synchronized by the controlling part 210.
Surface Images, Formation of Tomographic Images: Steps S3, S4
The image forming part 220 of the arithmetic and control device 200 sequentially forms (S4) tomographic images of fundus oculi Ef based on detection signals input sequentially from the CCD 184, along with sequentially forming (S3) surface images of the fundus oculi based on image signals sequentially output from the imaging device 12.
FIG. 9 shows one example of the formation of surface images and tomographic images of the fundus oculi Ef formed in steps S3, S4. The same figure shows surface images and tomographic images of the fundus oculi Ef sequentially formed by the image forming part 220 when the ratio of the frame rate f1 of the imaging device 12 to the frame rate of the CCD 184 is f1:f2=2:1.
FIG. 9 (A), (B), (C), and (D) show the image formed based on the interference light LC and fundus oculi catoptric light of the illuminated light variously detected at times t=t1, t2, t3, and t4. In addition, these images show only some of the images formed in the process of forming a series of images. Furthermore, the intervals of detection times t (k+1)−Tk(k=1, 2, 3, . . . )=Δt are constant.
In time t=t1, both the imaging device 12 and the CCD 184 are controlled so as to detect light, and the surface image Ef1′ and the tomographic image G1 of the fundus oculi Ef (See FIG. 6 and FIG. 7) are formed (See FIG. 9 (A)) based on each of the detected results.
In time t=t2, only the imaging device 12 is controlled so as to detect light, and the surface image Ef2′ of the fundus oculi Ef is formed (See FIG. 9 (B)) based on these detected results.
In time t=t3, both the imaging device 12 and the CCD 184 are controlled so as to detect light similar to the case with time t=t1, and based on each of the detected results, the surface image Ef3′ and the tomographic images G2 of the fundus oculi Ef (See FIG. 6 and FIG. 7) are formed (See FIG. 9 (C)).
In time t=t4, only the imaging device 12 is controlled so as to detect light similar to the case with time t2, and the surface image Ef2′ of the fundus oculi Ef is formed based on the detected results (See FIG. 9 (D)).
Below, fundus oculi images are similarly formed for t=t5, t6, t7, etc. In other words, when the ratio of the frame rate f1 of the imaging device 12 to the frame rate f2 of the CCD 184 is 2:1, both the imaging device 12 and the CCD 184 detect light at time t=tk (k=odd number), and a surface image Efk′ and tomographic image G((k+1)/2) of the fundus oculi Ef are acquired, and only the imaging device 12 detects light at time t=tk (k=even number) and only the surface image Efk′ on the locus oculi Ef is acquired.
The surface images Ef1′-Ef4′ of the fundus oculi Ef shown in FIG. 9 differ in the positions of the images of optic papilla and blood vessels among the frames and show the occurrence of eye movement of the eye subject to examination E during the examination. Described below is the process for optimally forming three-dimensional images under such circumstances.
Image Position Correction for Tomographic Images: Steps S5-S8
The extraction processing part 240a on the correction processing part 240 extracts the characteristic part of various surface images produced at the same time as the tomographic images (S5). In the example shown in FIG. 9, the correction processing part 240 analyzes each of the surface images Efk′ (k=odd number) and extracts the image area equivalent to the optic papilla in the fundus oculi Ef by extracting the image area of an approximate round shape having a roughly equal luminance value.
The correction processing part 240 finds the coordinate values of the characteristic part (S6). As an example of this process, the correction processing part 240 finds the coordinate values (x coordinate, y coordinate) of predetermined positions in the image areas of the extracted optic papilla, such as the coordinate values of pixels having the greatest luminance value.
Next, the correction processing part 240 calculates the deviation of coordinate value for the characteristic part obtained from another surface image Efk′ (k=odd number) for coordinate values of a characteristic part obtained from one of the surface images Efk′ (k=odd number) (S7). For example, deviation (Δxk=xk−x1, Δyk=yk−y1) of the coordinate values (xk, yk) of the characteristic part of each surface image Efk′ (k=3, 5, 7, etc.) is calculated for the coordinate values (x1, y1) of the characteristic part of the surface image Ef1′. In other words, the correction processing part 240 calculates the relative deviation of image positions of a plurality of extracted characteristic part.
Furthermore, the correction processing part 240 corrects image positions of the tomographic images using the deviation of the coordinate values of the characteristic part calculated in Step S7 (S8). In the example mentioned above, for each of k=3, 5, 7, etc. (odd numbers), only the image position (−Δxk, −Δyk) of the tomographic image G((k+1)/2) is moved, correcting it so as to match the image position of the tomographic image G1.
Formation of Three-Dimensional Images: Step S9
Finally, the image processing 230 forms three-dimensional images of fundus oculi Ef (S9) based on the tomographic image G((k+1)/2) (k=odd number) for which the image position was corrected in Step S8. Thereby, the process of forming three-dimensional images of the fundus oculi Ef by means of this fundus observation device 1 is finished.
Action and Effect
The action and effect of the fundus observation device 1 related to the present embodiment having the constitution as above is explained.
This fundus observation device 1 comprises the fundus camera unit 1A for operating as the fundus camera in order to capture 2-dimensional images showing the state of the surface of the fundus oculi Ef and the OCT unit 150 for operating as an optical image measuring device in order to capture tomographic images (and 3-dimensional images) of the fundus oculi Ef.
The optical path of the signal light used for image forming by the OCT unit 150 is guided to an eye to be examined E by combining the optical path (the imaging optical path) for forming by the imaging optical system 120 of the fundus camera unit 1A. The combining of this optical path is performed by the dichroic mirror 134.
In addition, the fundus reflection light of the signal light LS is guided to the dichroic mirror 134 along the imaging path, and goes to the OCT unit 150 by being separated from the imaging optical path via this dichroic mirror 134.
As a result, by setting the dichroic mirror 134 for operating in order to combine and separate the imaging optical path of the fundus camera unit 1A and the optical path of the signal light LS, it is possible to capture both 2-dimensional images of the surface of the fundus oculi Ef and tomographic images of the fundus oculi Ef (and 3-dimensional images).
In particular, to an eye to be examined E, if illumination of the illumination light by the fundus camera unit 1A and illumination of the signal light LS by the OCT unit 150 are simultaneously operated, each fundus reflection light can be separated via the dichroic mirror 134 and images formed by detecting each of them, making it possible to simultaneously produce both 2-dimensional images of the surface of the fundus oculi Ef and tomographic images of the fundus oculi Ef.
At this time, the signal light LS from the OCT unit 150 and the simultaneously illuminated light may be near-infrared light from the imaging light source 103 and also visible light from the observation optical source 101.
Furthermore, according to the fundus observation device 1 related to this embodiment, even if the eye subject to examination E moves while measuring the tomographic images of the fundus oculi Ef, the image positions of the tomographic images can be corrected using the surface images of the fundus oculi Ef produced at the same time as detecting the interference light LC that forms the base of the tomographic images, and it is possible to form highly reliable three-dimensional images based on the tomographic images for which the image positions have been corrected.
Modified Example
The constitution described above is merely one example to preferably implement the fundus observation device related to the present invention. Therefore, optional modifications may be implemented appropriately within the scope of the present invention.
The embodiment mentioned above is comprised so as to correct the image positions of the tomographic images using the surface images of the fundus oculi Ef produced while detecting interference light LC that forms the base of the tomographic images, but it is not limited to this. For example, if the degree of discrepancy between the time when the interference light LC is detected and the time when the surface images are produced can be ignored regarding movement of the eye subject to examination E, it is possible to compose the embodiment so as to correct the image positions of the relevant tomographic images using the relevant surface images.
For example, it is possible to correct the image positions of the relevant tomographic images using surface images produced with frames before and after the relevant tomographic images such as correcting the image positions of a tomographic image G2 using the surface image Ef4′ in FIG. 9.
Furthermore, it is not necessary for the timing of obtaining the surface images of fundus oculi Ef and the timing of detecting the interference light LC to always coincide. For example, it is allowable for the difference in timing of movement of the eye subject to examination E to be an ignorable degree. However, it is possible to improve the precision of correction of the tomographic images based on the relevant interference light LC by simultaneously obtaining the surface images and detecting the interference light LC as in the embodiment mentioned above.
Furthermore, in the embodiment mentioned above, the ratio of the frame rate of the fundus camera unit 1A and the frame rate of the OCT unit 150 is set to about 1:1 to 10:1, but it is not limited to this range. However, in order to secure surface images for correction of image positions of all of tomographic images, it is preferable to set the frame rate of the fundus camera unit 1A above the frame rate of the OCT unit 150. In particular, by setting the ratio of frame rates at 1:1, it is possible to perform an effective and efficient correction process by synchronizing the timing of imaging surface images with the timing of detecting the interference light LC.
For example, in the above embodiment, as the low coherence light L0, near-infrared light with a wavelength of about 800 nm to 900 nm is used, but light of longer wavelengths can be used to measure images in the deeper region of the fundus oculi Ef. For example, near-infrared light of a wavelength within about 900 nm to 1000 nm is used, and also near-infrared light of a wavelength within about 1000 nm to 1100 nm can be used.
Moreover, when low coherence light L0 of a wavelength within about 900 nm to 1000 nm is used, the near-infrared light of a wavelength within about 700 nm to 900 nm can be used as the illumination light for the fundus camera unit 1A. Moreover, when the low coherence light L0 of a wavelength within about 1000 nm to 1100 nm is used, near-infrared light of a wavelength within about 850 nm to 1000 nm can be used as the illumination light for the fundus camera unit 1A. Herein, in each case, it is desirable to set a longer wavelength for the low coherence light L0 than the wavelength of the illumination light of the fundus camera unit 1A, but it is possible to adapt the composition such that the relationship of short and long wavelengths is reversed.
A first image forming means of the fundus observation device related to the present embodiment is not limited to a fundus camera (unit), an arbitrary ophthalmologic device capable of forming a 2-dimensional image of a fundus surface may also be applied. For example, a slit lamp (slit lamp microscopic device) may be used as a first image forming means.
Moreover, in the above embodiment, the forming process of the fundus image by the image forming part 220 (image forming board 208) and each controlling process are operated by the controlling part 210 (microprocessor 201, etc.), but it can be composed to operate these two processes by one or several computers.

## Claims

1. A fundus observation device comprising:
a first image forming means having an illuminating optical system for emitting illumination light onto fundus oculi of an eye to be examined and a imaging optical system for detecting the illumination light passing through said fundus oculi by the first detecting means, forming a 2-dimensional image of the surface of said fundus oculi based on the detection results by said first detecting means;
a second image forming means having a light source which outputs light with a wavelength which is different from said illumination light; an interference optical generating means splitting said light output from said light source into the signal light directed towards said fundus oculi and the reference light directed towards a reference object and generating interference light by overlapping the signal light passing through said fundus oculi and the reference light passing through said reference object; and a second detecting means for detecting said interference light generated, forming tomographic images of said fundus oculi based on the detected results by said second detecting means;
an optical path combination and separation means for combining the imaging optical path formed by said imaging optical system and the optical path of a signal light directed toward said fundus oculi and illuminate said signal light onto said fundus oculi through said imaging optical path, as well as separating said imaging optical path from the optical path of the signal light toward said fundus oculi and overlapping said signal light on said reference light by said interference optical generating means;
a control means for synchronizing detection timing by said first detection means and detection timing by said second detection means;
a correction means for correcting the image positions of said tomographic images based on two-dimensional images based on detection results by said first detection means; and
a three-dimensional image formation means for forming three-dimensional images of said fundus oculi based on said tomographic images in which said image positions have been corrected.

2. A fundus observation device according to claim 1, wherein said control means synchronizes detection timing by said first detection means and detection timing by said second detection means.

3. A fundus observation device according to claim 1, wherein said correction means comprises:
an extraction means for extracting characteristic part from two-dimensional images based on detection results by said first detection means; and
corrects the image positions of said tomographic images based on the image positions of said extracted characteristic part.

4. A fundus observation device according to claim 3, wherein said second image formation means sequentially forms a plurality of said tomographic images,
and said first image formation means sequentially forms said plurality of two-dimensional images of the surface of said fundus oculi,
and said correction means extracts various characteristic part of said two-dimensional images by said extraction means and corrects the various image positions of said plurality of tomographic images based on the relative deviation of said image positions of said plurality of said extracted characteristic part.