JP2003225208A - Fundus camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fundus camera which can advantageously utilize taken images in diagnosis by obtaining fundus images that allow eyes to be examined to maintain a fixed angle at which pictures are taken even in others than OD. <P>SOLUTION: In the fundus camera for photographing the eyegrounds of eyes to be examined, there are provided a photographing optical system which has a focus lens and an image sensor for photographing the eyegrounds of the eyes to be examined through the focus lens, a display means for displaying the images of the eyegrounds taken by the image sensor, a moving means for moving the focus lens in the direction of optical axis in photographing, a detection means for detecting the moving positions of the focus lens and a display control means which performs a graphic display of a screen frame for determining the ranges of visual fields with respect to fundus images to be displayed on the display means while the size of the screen frame is changed based on the results of the detection by the detection means. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fundus camera for photographing a fundus of a subject's eye.

[0002]

2. Description of the Related Art 35 mm film has historically been used as a basic medium for imaging with a fundus camera.
In this case, the screen frame (mask, field stop) on the film surface, which is the image forming surface of the image, was fixed. Even in recent electronic image pickup, the screen frame provided in the case of 35 mm film is relayed and used as it is as an image.

[0003]

In a normal fundus camera, the focus lens is moved to focus on the fundus of the eye in order to correct the refractive error of the eye to be examined. However, when the focus lens is moved, the photographing magnification changes, and the image circle of the fundus image itself spreads outside the screen frame or enters the inside of the screen frame.

FIG. 4 is a diagram showing a state of a fundus image obtained when the focus lens is moved in accordance with correction of refractive error. Reference numeral 100 is an objective lens, 101 is a focus lens that moves in the photographing optical axis direction, 102 is an imaging lens, and 103 is a fixedly arranged screen frame. Figure 4
The fundus image in the myopia state (-D) shown in FIG. 4B has the image circle (the portion indicated by the dotted line) outside the screen frame with reference to 0D (diopter) in the normal vision state shown in (a). It becomes an expanded shape. On the other hand, the fundus image in the hyperopic state (+ D) shown in FIG. 4C has a shape in which the image circle is inserted inside the screen frame, and a blurred image circle appears.

As described above, the fixed screen frame determines the actual photographing range of the fundus. However, the photographing angle of view can be accurately supported only when the eye to be inspected is 0D. It was In order to deal with this problem, the screen frame is set as small as possible within the range of the specified standard (shooting angle of view) so that a blurry image circle does not appear on the far-sighted (+ D) side. There was no choice but to take.

The present invention has been made in view of the above problems of the prior art.
It is a technical object to provide a fundus camera that can obtain a fundus image with a constant angle of view even if the eye to be inspected is other than 0D and can advantageously use the image for diagnosis.

[0007]

In order to solve the above problems, the present invention is characterized by having the following configuration.

(1) In a fundus camera for photographing a fundus of an eye to be inspected, a photographing optical system having a focus lens and an image pickup device for picking up an image of the fundus of the eye to be examined through the focus lens, and a fundus imaged by the image pickup device. Display means for displaying an image, moving means for moving the focus lens in the photographing optical axis direction, detecting means for detecting the moving position of the focus lens, and visual field range for the fundus image displayed on the display means. And a display control unit for changing the size of the screen frame on the basis of the detection result of the detection unit. (2) In the fundus camera of (1), an observation optical system having an observation image pickup device for picking up an image of the fundus of the eye to be inspected illuminated by the observation illumination light through the focus lens, and an image pickup by the observation image pickup device. And a second display means for displaying the observed image, and a screen frame for defining the visual field range with respect to the observed image displayed on the second display means are displayed graphically, and the size of the screen frame is determined by the detecting means. A second display control unit that changes based on the detection result. (3) In the fundus camera of (1), a storage unit is provided that stores the fundus image data captured by the image sensor and stores the size data of the screen frame in association with the fundus image data. And the fundus image are reproducible.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram of an optical system of a non-mydriasis type fundus camera as an 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.
Equipped with.

<Illumination Optical System> The luminous flux emitted from the halogen lamp 10 which is a light source for observation is an infrared filter 11.
Is converted into an infrared light flux by the condenser lens 12 and then reflected by a dichroic mirror 15 having infrared light reflection and visible light transmission characteristics to illuminate a ring slit 16 having a ring-shaped opening. The visible light flux emitted from the flash lamp 13, which is a light source for photographing, passes through the condenser lens 14, then passes through the dichroic mirror 15, and is combined with the infrared light flux for observation coaxially with the case, and the ring slit 16 Illuminate. An infrared light source such as an infrared LED may be used instead of the halogen lamp 10, and in this case, the infrared filter 11 is unnecessary.

The light flux of the ring slit 16 passes through a relay lens 17a, a mirror 18, a black spot plate 19 having a small black spot in the center, a beam splitter 48, and a relay lens 17b, and an intermediate image near the opening of the perforated mirror 21. 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 flux reflected by the perforated mirror 21 is once converged by the objective lens 20 in the vicinity of the pupil of the eye E to be examined, and then diffused to uniformly illuminate the fundus of the eye E to be examined. At this time, since a small amount of reflected light generated when the ring slit light flux enters the objective lens 20 becomes harmful light for observing and photographing the fundus image, a small black dot provided at the center of the black dot plate 19 causes the relay lens 17b to pass through. It is configured to be projected through and absorb harmful light.

<Photographing optical system> The reflected light flux from the fundus is
A dichroic mirror (dichroic mirror) having the characteristics of infrared light reflection and visible light transmission through the objective lens 20, the aperture of the perforated mirror 21, the photographing diaphragm 22, the focus lens 23 movable in the optical axis direction, and the imaging lens 24. It enters the prism 25. The visible light flux that has passed through the dichroic mirror 25 passes through a relay lens 26 that relays the light flux from the imaging lens 24 in accordance with the purpose, and then enters a color CCD camera 27 for photographing that has sensitivity in the visible region, and captures the image. A fundus image is formed on the element surface.

<Observation Optical System> The observation optical system 3 includes the objective lens 20 of the photographing optical system 2 through the dichroic mirror 25.
The light path is split only in the infrared region by the dichroic mirror 25 as a light splitting member. The infrared reflected light flux from the fundus reflected by the dichroic mirror 25, after passing through the relay lens 30, is further reflected by the dichroic mirror 31 as a light splitting member having the same optical characteristics as the dichroic mirror 25 to reach the infrared region. It is incident on an observation CCD camera 32 having high sensitivity,
A fundus image is formed on the surface of the image sensor.

The focus lens 23 is movable on the optical axis of the optical path shared by the taking optical system 2 and the observing optical system 3, and makes it possible to adjust the refractive error according to the refractive power of the eye to be examined.
The focus lens 23 is fixed to the rack 42,
The rack 42 meshes with a pinion 41 fixed to the rotation shaft of the stepping motor 40. By the rotation of the stepping motor 40, the focus lens 23 moves on the optical axis via the pinion 41 and the rack 42, and the photographing C
The fundus of the eye to be examined is focused on the image pickup element surfaces of the CD camera 27 and the observation CCD camera 32.

<Focus Index Projection Optical System> The focus index projection optical system 45 includes an index plate 47, an illumination LED 46 for emitting infrared light, and a beam splitter 48, and the index plate 47 and the LED 46 are linked with the focus lens 23. It is configured to be movable. The light beam for projecting an index emitted from the index plate 47 is reflected by the perforated mirror 21 and once focused on a fundus conjugate plane (not shown), and then projected onto the fundus of the eye to be examined via the objective lens 20. Since the focus index image projected on the fundus of the eye to be examined is projected by infrared light, the reflected light is reflected by the dichroic mirrors 25 and 31, and is taken by the observation CCD camera 32 together with the fundus image of the eye to be examined.

<Fixation Target Projection Optical System> The fixation target projection optical system 35 is disposed on the side of the observation optical system 3 whose optical path is separated from that of the photographing optical system 2 by the dichroic mirror 25, and includes a fixation lamp 36 which emits visible light. It is provided and shares the dichroic mirror 31. The dichroic mirror 31 further divides the optical path of the observation optical system 3, and a fixation lamp 36 is arranged on the side of the optical path divided from the observation optical system 3. Further, the fixation lamp 36 is provided at the tip of the knob 37, and the fundus of the eye to be inspected and the observation CCD are used.
The position of the camera 32 can be changed within a plane substantially conjugate with the image pickup surface of the camera 32. The examiner operates the knob 37 to move the fixation lamp 36 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 to be examined is desired. It is possible to guide the user to the imaging site.

The visible light flux emitted from the fixation lamp 36 passes through the dichroic mirror 31 and enters the dichroic mirror 25 via the relay lens 30. The visible fixation target light flux that has entered the dichroic mirror 25 is efficiently reflected by only about 10% at most, but it is sufficient to be visually recognized by the eye to be examined by following the optical path of the photographing optical system 2. The sight is done.

Next, the operation of the fundus camera of this embodiment will be described with reference to the schematic diagram of the control system shown in FIG.

First, as a preparation for photographing an eye to be inspected, the eye to be inspected and the optical system are aligned. The optical system housed in the casing is placed on a movable base and moves relative to the fixed base by a sliding mechanism (not shown). After fixing the subject to the chin rest on the fixed base side, the halogen lamp 10 is turned on to illuminate the subject's eye with infrared light. The reflected light flux from the fundus due to the illumination of infrared light is reflected by the dichroic mirror 25, and the CC for observation is used.
An image of the eye to be inspected is captured by the D camera 32. The image signal from the observation CCD camera 32 is input to the image controller 51. The image control unit 51 includes a color liquid crystal display (L
A CD) 53 is connected to which a moving image observation image is displayed. The examiner observes the image of the eye to be inspected (in this case, a monochrome moving image) displayed on the LCD 53, and also observes the alignment bright point formed by the alignment optical system (not shown) to determine the working distance between the eye to be inspected and the optical system. And alignment for optical axis adjustment.

After the alignment is completed, the examiner operates the focus switch 56 to move the CCD cameras 27 and 32.
The focus lens 23 is moved so that the image pickup surface of is at a position 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 according to the operation signal from the focus switch 56. This is to correct the shift of the focal position due to the refractive error of the eye to be inspected, focus on the fundus and obtain a clear fundus image. As described above, the visible light flux emitted from the fixation lamp 36 is reflected by the dichroic mirror 25 and projected on the fundus of the eye to be inspected, so that it can be clearly confirmed when the refractive error of the subject is corrected, In this state, the subject should fixate on this.

For focusing by moving the focus lens 23, a focus index image (image of the index plate 47) taken by the observation CCD camera 32 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 32 on the LCD 53, thereby refracting the subject. The focus position shift (variation of diopter of refractive power of the eye to be examined) due to abnormality is corrected.

When the examiner presses the photographing switch 55 in a state where focusing is completed and the fundus image to be photographed can be observed, the flash lamp 13 emits light and the fundus of the eye to be examined is illuminated with visible light. The visible reflected light from the fundus of the eye follows the above-mentioned optical path and 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.

The size of the fundus image picked up by the CCD camera 27 differs depending on the moving position of the focus lens 23. The control unit 50 detects the position information of the focus lens 23 at the time of shooting from the number of rotation pulses of the motor 40,
From the position information, the variation information of the imaging magnification (diopter variation), that is, the fundus image size corresponding to this is obtained. The fundus image size can be obtained by programming in advance the correlation between the position of the focus lens 23 and the magnification variation calculated from the optical design surface based on the position. The moving position of the focus lens 23 may be detected by an encoder or the like.

The image controller 51 graphically generates a screen frame (reference numeral 80 in FIG. 3) having a circular opening for defining the visual field range, synthesizes the screen frame with the fundus image stored in the image memory 51a, and LCD 53. To display. At this time, the image control unit 51 changes the size of the screen frame displayed graphically on the LCD 53 so as to correspond to the fundus image size data obtained by the system control unit 50, that is, so that the photographing angle of view becomes constant. It should be noted that although the same LCD 53 is used here for displaying the observation image and for displaying the still image, they may be displayed by dedicated displays.

FIG. 3 is a diagram showing the relationship between the moving position of the focus lens 23 and the fundus image displayed on the LCD 53. FIG. 3A shows the case where the eye to be inspected is in the stereoscopic state (0D). FIG. 3B shows the case where the eye to be inspected is in the myopia state (-D), and the fundus image size is enlarged compared to FIG. 3A. FIG. 3C shows the case where the eye to be inspected is in the hyperopia state (+ D), and the fundus image size is reduced with respect to the emmetropic state of the eye to be inspected. A black screen frame 80 with a background is graphically displayed on the LCD 53, and its aperture size is also changed corresponding to the fundus image size due to the movement of the focus lens 23. The opening of the screen frame 80 is sized to cut the blurred portion around the image circle of the captured fundus image. With such a display, the examiner can observe a fundus image with a constant angle of view regardless of the difference in refractive power of the subject's eye (regardless of what kind of fundus of the subject's eye). .

The graphic display of the screen frame 80 also includes the case where the captured fundus image data is trimmed in accordance with the above-described fundus image size and is combined with a background such as black. The shape of the screen frame 80 is not limited to a circular shape, but may be a quadrangular shape or a horizontally elongated oval shape.
Further, a notch may be provided at the upper right of the opening so that the left, right, top, and bottom are asymmetrical so that the left, right, top, and bottom can be identified even when the display image is printed out.

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 is connected to the control unit 50. 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 in the image storage unit 60 side. At this time, the size data of the screen frame 80 used for display is also attached (stored in association).

The image data stored in the image storage section 60 and the size data attached thereto can be transmitted and output to the external computer 70 side connected by the communication cable by pressing the data transmission switch 54b. . When a memory card is used as the image storage unit 60, the data in the memory card can be read and transmitted by the external computer 70 side. When the fundus image is displayed on the display 71 on the external computer 70 side, the size data of the screen frame 80 attached is used to display the fundus image having the same screen frame 80 as the LCD 53. Further, even when printing is performed by the printer 72, the one having the screen frame 80 is printed. of course,
It is also possible to display and print in a raw image state at the time of shooting.

If a raw image at the time of photographing is not particularly required, the fundus image having the screen frame 80 combined (this is obtained by the image control unit 52 by image processing) is stored in the image storage unit 60. May be.

With the screen frame 80 as described above, it is possible to obtain an image of the fundus field maintaining a constant photographing field angle regardless of the diopter of the eye to be examined. Therefore, it is advantageous not only in imaging the posterior pole of the fundus but also in the context of peripheral imaging because there is no influence of the conventional fixedly provided screen frame. In addition, it is possible to effectively use the imaging result in terms of diagnosis. For example, it is easy to create a panoramic image in which fundus images are joined together, and the joining can be improved.

In the above, the screen frame 80 is displayed for the color still image picked up by the photographing CCD camera 27, but it is convenient to perform this also when the observation image is displayed by the observation CCD camera 32 during alignment. Is good. The image control unit 51 graphically displays a screen frame 80 having an opening on the live image (moving fundus image) displayed on the LCD 53 based on the fundus image size obtained from the position information of the focus lens 23 as described above. indicate. In this case, the screen frame 80 is combined and displayed on the live image. As a result, it is possible to avoid a mismatch in the angle of view with a still image obtained by shooting.

[0032]

As described above, according to the present invention,
By accurately grasping the magnification (size) of the fundus image that fluctuates due to the movement of the focus lens without complicating the device configuration, it is possible to achieve high visibility in accordance with the size of the captured image even with the eye to be inspected with different refractive power. Image data can be obtained with a screen frame and the same angle of view.

[Brief description of drawings]

FIG. 1 is a schematic diagram of an optical system of a fundus camera that is an embodiment.

FIG. 2 is a schematic diagram of a control system.

FIG. 3 is a diagram illustrating a relationship between a position of a focus lens and a fundus image displayed on an LCD.

FIG. 4 is a diagram showing a state of a fundus image obtained when a focus lens is moved in the related art.

[Explanation of symbols]

23 Focus lens 27 CCD camera for photography 32 CCD camera for observation 40 stepping motor 50 System control unit 51 Image control unit 53 LCD display 60 image storage 80 screen frames

Claims (3)

[Claims] 1. A fundus camera for photographing a fundus of an eye to be examined, and a photographing optical system having a focus lens and an image pickup device for photographing the fundus of the eye to be examined through the focus lens.
Display means for displaying the fundus image captured by the image sensor, moving means for moving the focus lens in the photographing optical axis direction, detecting means for detecting the moving position of the focus lens, and display means for displaying on the display means. A fundus camera, comprising: a display frame that graphically displays a screen frame that defines a visual field range for the fundus image and that changes the size of the screen frame based on the detection result of the detection unit. 2. The fundus camera according to claim 1, wherein the observation optical system has an observation image pickup device for picking up an image of the fundus of the eye to be inspected illuminated by the observation illumination light through the focus lens, and the observation image pickup device. Second display means for displaying the captured observation image, and a screen frame for defining a visual field range for the observation image displayed on the second display means are displayed graphically, and the size of the screen frame is detected. A second display control unit that changes based on the detection result of the unit. 3. The fundus camera according to claim 1, further comprising a storage unit that stores the fundus image data captured by the image sensor and stores the size data of the screen frame in association with the fundus image data. A fundus camera characterized in that a screen frame and a fundus image can be reproduced.