JP2005021316A - Fundus camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fundus camera capable of performing an efficient illumination corresponding to the difference of a pupil diamete and obtaining a satisfactory fundus image while keeping viewing angles in respective photographings constant. <P>SOLUTION: The fundus camera is provided with: an illumination optical system having a ring illumination forming means of a variable inner diameter which forms a ring-formed illumination luminous flux at nearly a conjugate position with the pupil of the eye to be examined for illuminating the fundus of the eye to be examined; a photographing optical system having a photographing means for photographing the fundus of the eye to be examined through a focus lens movable in the photographing means; and a display control means for varying the display area of the fundus image to be displayed on the display means based on the moving information of the focusing lens and the inner diameter variable information of the ring-formed illumination luminous flux. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fundus camera that photographs the fundus of a subject's eye.
[0002]
[Prior art]
In the fundus camera, the fundus is illuminated by illuminating the fundus with an illumination light beam formed in a ring shape at the pupil position, and the fundus reflected light is extracted from the central region of the pupil. If the mydriatic of the eye to be examined is not sufficient, it is not possible to sufficiently illuminate the imaging range with illumination light, and the reflected light from the fundus cannot be used efficiently. For this reason, when the mydriatic of the eye to be examined is not sufficient, the inner diameter of the ring slit that forms the ring-shaped illumination light beam is made smaller to allow more illumination light to enter, and in accordance with the change in the inner diameter of the ring slit, There has been proposed a fundus camera in which the diameter of an aperture stop provided at a position substantially conjugate with the fundus to be examined in the system is changed, or the fundus image display area is limited (see Patent Document 1).
[0003]
In addition, as a fundus camera, a mydriatic type that takes an image of the fundus in a state in which the pupil is opened by instilling the mydriatic agent before photographing, and an infrared light is used as the observation illumination light, There is a non-mydriatic type that takes an image without instillation, and there is also a mydriatic / non-mydriatic integrated fundus camera that combines both functions in one apparatus (see Patent Document 2).
[0004]
[Patent Document 1]
Japanese Patent Laid-Open No. 2002-51985
[Patent Document 2]
JP-A-2001-353128 [0006]
[Problems to be solved by the invention]
By the way, in photographing with a fundus camera, focusing on the fundus is performed by moving the focus lens in order to correct the refractive error of the eye to be examined. For this reason, as in the above-mentioned Patent Document 1, just changing the aperture size of the aperture stop and the mask size that limits the display area of the fundus image in accordance with the change of the inner diameter of the ring-shaped illumination light beam, The shooting area expands outside or enters inside. That is, even if the mask size corresponding to the change in the inner diameter of the ring-shaped light beam is determined based on the eye to be examined in the stationary state 0D, the fundus image in the myopic state has a photographing field angle area extending outside the mask, Inside is a fundus image with a narrow angle of view. On the other hand, in a farsighted state fundus image, the imaging angle of view is maintained, but the fundus image enters the inside of the mask region, and the periphery of the fundus image becomes a blurred image.
[0007]
The present invention provides a fundus camera that can efficiently illuminate corresponding to the difference in pupil diameter and can obtain a good fundus image while keeping the angle of view in each photographing constant in view of the above-described conventional technology. This is a technical issue.
[0008]
[Means for Solving the Problems]
In order to solve the above problems, the present invention is characterized by having the following configuration.
[0009]
(1) An illumination optical system having a ring illumination forming means with a variable inner diameter that forms a ring-shaped illumination light beam at a position substantially conjugate with the pupil of the eye to be examined to illuminate the fundus of the eye to be examined, and a focus movable in the optical axis direction An imaging optical system having an imaging unit that images the fundus of the eye to be examined via a lens, a display unit that displays a fundus image captured by the imaging unit, and a display area of the fundus image displayed on the display unit is the focusing lens. Display control means for changing the movement information based on the movement information and the inner diameter variable information of the ring-shaped illumination light beam.
[0010]
(2) In the fundus camera of (1), an observation illumination optical system capable of switching the observation illumination light to the mydriatic visible light and the non-mydriatic infrared light via the ring illumination forming means; Mode switching means for switching the observation illumination light to a mydriatic mode for making the visible illumination light for mydriasis and a non-mydriatic mode for making the infrared light, and the inner diameter variable information of the ring-shaped illumination light beam of the mode switching means It is characterized by being given by a mode switching signal.
[0011]
(3) The display control means of (1) determines the photographing field angle of the display area of the fundus image based on the inner diameter variable information of the ring-shaped illumination light beam by the ring illumination forming means, and includes the movement information of the focus lens. A fundus image display area in which the imaging angle of view is maintained constant is determined based on the above.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram of an optical system of a fundus camera of the mydriatic / non-mydriatic photographing type according to the embodiment. The optical system includes an illumination optical system 1, a photographing optical system 2, an observation optical system 3, a fixation target projection optical system 35, and a focus index projection optical system 45.
[0013]
<Illumination Optical System> The light beam emitted from the halogen lamp 10 serving as the observation light source illuminates the ring slit 16a having a ring-shaped opening after passing through the infrared filter 11 and the condenser lenses 12 and 14. The infrared filter 11 is inserted into and removed from the optical path of the illumination optical system by the infrared filter solenoid 11a. At the time of non-mydriatic photographing, the infrared filter 11 is inserted to make the illumination light infrared light, and at the time of mydriatic photographing, the infrared filter 11 is removed to switch the illumination light to visible and infrared light.
[0014]
Further, the visible light beam emitted from the flash lamp 13 that is a photographing light source illuminates the ring slit 16a disposed at a position substantially conjugate with the pupil of the eye to be examined after passing through the condenser lens 14.
[0015]
The ring slit 16 a is replaced with the ring slit 16 b by a ring slit solenoid 28. The ring slit 16a has a small annular inner diameter for forming an annular illumination light, and the ring slit 16b has a large annular inner diameter. The ring slit 16a is inserted into the illumination optical path during non-mydriatic imaging, and the ring slit 16b is inserted during mydriatic imaging. In addition, the change of the inner diameter of the ring slit may be configured to change the light shielding region of the inner diameter.
[0016]
The luminous flux of the ring slit 16a or 16b forms an intermediate image near the opening of the perforated mirror 21 via the relay lens 17a, the mirror 18, the black spot plate 19 having a small black spot at the center, the beam splitter 48, and the relay lens 17b. After being formed, it is reflected so as to be coaxial with the optical axis of the photographing optical system 2. The ring slit light beam reflected by the perforated mirror 21 is once converged in the vicinity of the pupil of the eye E by the objective lens 20, and then diffused to uniformly illuminate the fundus of the eye to be examined. At this time, since some reflected light generated when the ring slit light beam is incident on the objective lens 20 becomes harmful light for observing and photographing the fundus image, a small black spot provided at the center of the black spot plate 19 causes the relay lens 17b. Through which the harmful light is absorbed. The illumination optical system for observation shares the lens 14 to the objective lens 20 of the illumination optical system for photographing.
[0017]
<Shooting Optical System> The reflected light beam from the fundus passes through the relay lens 26 via the objective lens 20, the opening of the perforated mirror 21, the photographing aperture 22, the focus lens 23 movable in the optical axis direction, and the imaging lens 24. After passing, the light enters the color CCD camera 27 for photographing having sensitivity in the visible range, and forms a fundus image on the surface of the image sensor.
[0018]
<Observation Optical System> The observation optical system 3 shares the objective lens 20 to the imaging lens 24 of the photographing optical system 2. The reflected light beam from the fundus is reflected by the flip-up mirror 25 that is inserted into and removed from the optical path by the mirror solenoid 29. The light beam reflected by the flip-up mirror 25 is transmitted through the relay lens 30, and then reflects infrared light as a light splitting member, reflects part of visible light, and transmits most of visible light. The light enters the dichroic mirror 31 (dichroic prism). The visible light beam transmitted through the dichroic mirror 31 is incident on the observation CCD camera 32 having sensitivity in the visible region, and forms a fundus image on the imaging element surface. The infrared light reflected from the dichroic mirror 31 is incident on a dichroic mirror 33 having infrared transmission characteristics and visible light reflection characteristics. The infrared light beam transmitted through the dichroic mirror 31 is incident on the observation CCD camera 34 having sensitivity in the infrared region, and forms a fundus image on the surface of the imaging device.
[0019]
Note that the focus lens 23 can move on the optical axis of the shared optical path of the photographing optical system 2 and the observation optical system 3, and can adjust the refractive error in accordance with the refractive power of the eye to be examined. The focus lens 23 is fixed to a rack 42, and the rack 42 meshes with a pinion 41 fixed to the rotating shaft of the stepping motor 40. The focus lens 23 moves on the optical axis through the pinion 41 and the rack 42 by the rotation of the stepping motor 40, and the fundus of the eye to be examined is focused on the imaging device surfaces of the imaging CCD camera 27 and the observation CCD cameras 32 and 34. Adjust.
[0020]
<Focus Index Projection Optical System> The focus index projection optical system 45 includes an index plate 47, an infrared filter 49, an illumination lamp 46, and a beam splitter 48. The index plate 47, the infrared filter 49, and the lamp 46 are the focus lens 23. It is configured to be movable in conjunction with. The infrared filter 49 is inserted into and removed from the optical path by an infrared filter solenoid 49a. The index projection infrared light beam or visible light beam emitted from the index plate 47 is reflected by the perforated mirror 21 and once formed on the fundus conjugate surface (not shown), and then the eye fundus to be examined is passed through the objective lens 20. Projected on. The focus index image projected on the fundus of the subject's eye passes through the optical path of the observation optical system and is picked up by the observation CCD cameras 32 and 34 together with the fundus image of the eye to be examined.
[0021]
<Fixation Target Projection Optical System> The fixation target projection optical system 35 is disposed on the observation optical system 3 side, includes a fixation lamp 36 that emits visible light, and shares the dichroic mirror 33. The dichroic mirror 33 divides the optical path of the observation optical system 3, and a fixation lamp 36 is disposed on the divided optical path side. Further, the fixation lamp 36 is provided at the tip of the knob 37 and is configured such that its position can be changed within a plane substantially conjugate with the fundus of the eye to be examined and the imaging surface of the observation CCD camera 34. When the examiner operates the knob 37, the fixation lamp 36 is moved in a plane perpendicular to the projection optical axis, whereby the position of the fixation target presented to the eye to be examined changes and the eye fundus of the eye to be examined is desired. It can be guided to the imaging region.
[0022]
The visible light beam emitted from the fixation lamp 36 reflects the dichroic mirror 33. Although the dichroic mirror 31 transmits most of the visible light, but reflects a part (about 10%), about 10% of the visible light beam emitted from the fixation lamp 36 reflects the dichroic mirror 31 and the relay lens 30. Then, the flip-up mirror 25 is reflected.
[0023]
Next, the operation of the fundus camera of the present embodiment will be described based on the schematic diagram of the control system shown in FIG.
[0024]
First, the examiner presses the non-mydriatic switch 57 or the mydriatic switch 58 to select the non-mydriatic mode or the mydriatic mode. In the mydriatic mode, the fundus is photographed in a state where the pupil is opened by applying a mydriatic agent before photographing. In the non-mydriatic mode, the eye fundus is photographed after illuminating the eye to be examined with infrared light and observing the fundus without applying a mydriatic agent.
[0025]
First, the non-mydriatic mode will be described. The non-mydriatic switch 57 is pressed to select the non-mydriatic mode. When the non-mydriatic mode is selected, the system control unit 50 inserts the infrared filters 11 and 49 into the optical path by the infrared filter solenoids 11a and 49a, respectively. In this initial state, the flip-up mirror 25 is in a state of descending on the optical path of the photographing optical system 2, and reflected light from the fundus is directed to the observation optical system 3. When the non-mydriatic mode is selected, the system control unit 50 switches the ring slit to an annular slit 16a having a small inner diameter. When the non-mydriatic mode is selected, the system control unit 50 switches the image output to the LCD 53 to the observation camera 34 for infrared light.
[0026]
The examiner performs alignment between the eye to be examined and the optical system as preparation for photographing the eye to be examined. The optical system housed in the casing is placed on a movable table, and moves relative to the fixed table by a sliding mechanism (not shown). The reflected light beam from the fundus due to the illumination of the infrared light is reflected by the flip-up mirror 25, and the eye image to be examined is picked up by the observation CCD camera 34. An image signal from the observation CCD camera 34 is input to the image control unit 51. A liquid crystal display (LCD) 53 is connected to the image control unit 51, and a moving image observation image is displayed thereon. The examiner observes the eye image displayed on the LCD 53 and also observes the alignment bright point formed by the alignment optical system (not shown) to align the working distance between the eye and the optical system and the optical axis adjustment.
[0027]
After completing the alignment, the examiner operates the focus switch 56 to move the focus lens 23 so that the imaging surfaces of the CCD cameras 27 and 34 are conjugate with the fundus. The system control unit 50 moves the focus lens 23 on the optical axis of the photographing optical system 2 by rotating the stepping motor 40 in accordance with an operation signal from the focus switch 56. This is to correct a focus position shift due to a refractive error of the eye to be examined, focus on the fundus, and obtain a clear fundus image. As described above, the visible light beam emitted from the fixation lamp 36 is reflected by the flip-up mirror 25 and projected onto the fundus of the eye to be examined, so that it can be clearly confirmed when the refractive error of the subject is corrected. In this state, the subject is made to fixate this.
[0028]
For focusing by moving the focus lens 23, a focus index image (an image of the index plate 47) captured by the observation CCD camera 34 together with the fundus image is used. The examiner operates the focus switch 56 so as to focus the focus index image while observing the infrared fundus image and the focus index image captured by the observation CCD camera 34 on the LCD 53, thereby refraction of the subject. The deviation of the focal position due to the abnormality (the amount of fluctuation of the eye refractive power diopter) is corrected.
[0029]
When the examiner presses the photographing switch 55 in a state where the fundus image to be photographed can be observed after the focusing is completed, the flip-up mirror 25 jumps up by the mirror solenoid 29, and the flash lamp 13 emits light, The fundus of the eye to be examined is illuminated with visible light. The visible reflected light from the fundus enters the photographing CCD camera 27 along the optical path described above. The video signal from the CCD camera 27 is input to the image control unit 51, and a still image is stored in the image memory 51a of the image control unit 51 in synchronization with the light emission of the flash lamp 13.
[0030]
When the fundus image is stored in the image memory 51a, the image displayed on the LCD 53 is switched to the stored image under the control of the image control unit 51. Here, the display area size (mask size) of the fundus image displayed on the LCD 53 is changed based on the mode switching signal of the non-mydriatic mode / mydriatic mode and the movement position information of the focus lens 23.
[0031]
First, based on the non-mydriatic mode switching signal using the ring slit 16a having a small inner diameter, the image control unit 51 has a field angle size of 45 ° that defines the visual field range of the fundus image, as shown in FIG. For example, a mask screen 80 having a circular opening is generated as a graphic, and the mask screen 80 is combined with the fundus image stored in the image memory 51 a and displayed on the LCD 53. On the other hand, FIG. 4 shows an example in the case of a non-mydriatic mode using a ring slit 16a having a small inner diameter and a 50 ° mask screen 80 ′ used in the mydriatic mode. When the angle of view is set to 50 ° using the ring slit 16a having a small inner diameter, the reflected light from the crystalline lens or cornea appears as flare light or ghost light in the peripheral portion of the fundus image, which makes it difficult to observe. . Therefore, in the non-mydriatic mode, the field angle size is reduced to 45 ° as shown in FIG.
[0032]
Further, the image control unit 51 changes the mask size of the mask screen 80 displayed on the LCD 53 based on the position information of the focus lens 23. The position information of the focus lens 23 at the time of shooting is detected by the control unit 50 from the number of rotation pulses of the motor 40. The image control unit 51 obtains the variation information of the photographing magnification (diopter variation) based on 0D from the position information of the focus lens 23, that is, the fundus image size corresponding to this. The fundus image size is obtained by programming in advance the correlation between the angle of view setting (45 °) in the non-mydriatic mode and the position of the focus lens 23 and the magnification variation calculated from the optical design surface based on this. be able to. The moving position of the focus lens 23 may be detected by an encoder or the like.
[0033]
FIG. 5 is a diagram showing the relationship between the movement position of the focus lens 23 and the fundus image displayed on the LCD 53. FIG. 5A shows a case where the eye to be examined is in a normal vision state (0D). FIG. 5B shows a case where the eye to be examined is in a myopic state (−D), and the fundus image size is enlarged as compared with FIG. FIG. 5C shows a state in which the eye to be examined is in a hyperopic state (+ D), and the fundus image size is reduced with respect to the normal vision state of the eye to be examined. The LCD 53 displays a black background mask screen 80 as a graphic, and the aperture size is also changed in accordance with the fundus image size due to the movement of the focus lens 23, so that the shooting angle of view of 45 ° is kept constant. .
[0034]
As for the display of the observation image at the time of alignment, the mask screen 80 is graphically displayed in the same manner as described above so that the fundus image without flare or ghost can be observed.
[0035]
Connected to the control unit 50 is an image storage unit 60 such as an MO (magneto-optical disk) or a memory card capable of storing a large number of image data. When the image storage switch 54a provided in the input unit 54 is pressed, the fundus image data stored in the image memory 51a is stored on the image storage unit 60 side. At this time, the size data of the mask screen 80 used for display is also associated and stored. Further, the image data stored in the image storage unit 60 and the size data attached thereto can be transmitted and output to the external computer 70 connected by a communication cable by pressing the data transmission switch 54b.
[0036]
As for the control of the display area of the fundus image, instead of displaying the black frame mask screen 80 as a graphic, the captured fundus image data is trimmed according to the angle of view and the fundus image size and combined with a black background. The case where it processed is also included. The storage of the image storage unit 60 also includes the case of storing a trimmed image.
[0037]
Next, the mydriatic mode will be described. Hereinafter, description of the same parts as the non-mydriatic mode will be omitted. In mydriatic mode, the pupil is opened by instilling mydriatic before photographing. The examiner presses the mydriatic switch 58 to select the mydriatic mode, and when the mydriatic mode is selected, the system control unit 50 moves the infrared filters 11 and 49 from the optical path by the infrared filter solenoids 11a and 49a, respectively. remove. When the mydriatic mode is selected, the system control unit 50 switches the ring slit to an annular slit 16b having a large annular inner diameter.
[0038]
When the mydriatic mode is selected, the image control unit 50 switches the observation camera to the observation camera 32. Further, the image control unit 51 generates the mask screen 80 ′ shown in FIG. 3A as a graphic so that the angle of view becomes 50 °, and the fundus image obtained by photographing the mask screen 80 ′ with the observation camera 32. Are combined and displayed on the LCD 53. In the mydriatic mode, the fundus can be observed in a wide range by setting the angle of view to 50 °.
[0039]
The fundus of the eye to be examined is illuminated with visible light emitted from the halogen lamp 10. The reflected light beam from the fundus is reflected by the flip-up mirror 25, and an eye image to be examined is captured by the observation CCD camera 32 for visible light. The image from the observation CCD camera 32 is displayed on the LCD 53, and the examiner observes the alignment bright spot to perform alignment of the working distance between the eye to be examined and the optical system and optical axis adjustment.
[0040]
After completing the alignment, the examiner operates the focus switch 56 to move the focus lens 23 so that the imaging surfaces of the CCD cameras 27 and 32 are conjugate to the fundus so that the fundus image to be photographed can be observed. In this state, the examiner presses the photographing switch 55. When the photographing switch 55 is pressed, the flip-up mirror 29 jumps up, the flash lamp 13 emits light, and the fundus of the eye to be examined is illuminated with visible light. Visible reflected light from the fundus enters the photographing CCD camera 27. The video signal from the CCD camera 27 is input to the image control unit 51, and a still image is stored in the image memory 51a of the image control unit 51 in synchronization with the light emission of the flash lamp 13.
[0041]
The fundus image stored in the image memory 51 a is displayed on the LCD 53. Similar to the non-mydriatic mode, the size of the fundus image at this time is also changed according to the angle of view setting by the mode switching signal of the mydriatic mode and the moving position of the focus lens 23, and a mask with an angle of view setting of 50 °. A screen 80 'is displayed graphically.
[0042]
【The invention's effect】
As described above, according to the present invention, efficient fundus illumination corresponding to the difference in pupil diameter can be performed as in mydriatic photography / non-mydriatic photography, and the angle of view in each photography can be kept constant. A good fundus image can be obtained.
[Brief description of the drawings]
FIG. 1 is a schematic diagram of an optical system of a fundus camera according to an embodiment.
FIG. 2 is a schematic diagram of a control system.
FIG. 3 is a diagram showing the mask size in the mydriatic / non-mydriatic mode.
FIG. 4 is a diagram showing a fundus image obtained by photographing a non-mydriatic state at an angle of view of 50 °.
FIG. 5 is a diagram illustrating a state of a fundus image obtained when a focus lens is moved.
[Explanation of symbols]
1
2
10 Halogen lamp 11 Infrared filter 11a Infrared filter solenoid 16a Ring slit 16b Ring slit 23 Focus lens 27 Imaging CCD camera 28 Ring slit solenoid 32 Observation CCD camera 34 Observation CCD camera 40 Stepping motor 41 Pinion 42 Rack 50 System control unit 51 Image control unit 53 Liquid crystal display 57 Non-mydriatic switch 58 Mydriatic switch

Claims (3)

Via an illumination optical system having a ring illumination forming means with a variable inner diameter that forms a ring-shaped illumination light beam at a position substantially conjugate with the pupil of the eye to be examined to illuminate the fundus of the eye to be examined, and a focus lens movable in the optical axis direction An imaging optical system having an imaging unit that images the fundus of the subject to be examined, a display unit that displays the fundus image captured by the imaging unit, and a display area of the fundus image displayed on the display unit is information on movement of the focusing lens And a display control means for changing the information based on the inner diameter variable information of the ring-shaped illumination light beam. The fundus camera according to claim 1, wherein the observation illumination optical system is capable of switching the observation illumination light between the mydriatic visible light and the non-mydriatic infrared light via the ring illumination forming means, and the observation illumination light. Mode switching means for switching between a mydriatic mode for making mydriatic visible light and a non-mydriatic mode for making infrared light, and the inner diameter variable information of the ring-shaped illumination light beam is a mode switching signal of the mode switching means. A fundus camera characterized by being given by: The display control unit according to claim 1 determines a shooting field angle of a display area of the fundus image based on the inner diameter variable information of the ring-shaped illumination light beam by the ring illumination forming unit, and shoots based on the movement information of the focus lens. A fundus camera characterized by defining a display area of a fundus image with a constant angle of view.

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