JP2004290535A - Eye fundus camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an eye fundus camera capable of easily performing visual confirmation of a focal index and nicely performing focal matching of the eye fundus. <P>SOLUTION: The eye fundus camera for imaging the eye fundus to be examined is equipped with an illumination optical system for illuminating the eye fundus by an infrared ray for observation, an index board for focusing arranged on the optical path of the illumination optical system and having a wavelength characteristic by which the index part shields the infrared region, an imaging optical system having an imaging means for imaging the illuminated eye fundus and a focal index image projected on the eye fundus, a display means for displaying an imaged observation image, a judging means for judging whether or not the difference between brightness levels of the focal index image of the imaged image and the eye fundus is less than a prescribed level, and an image compensating means for compensating the contrast of the image to be displayed on the display means when the difference between the brightness levels is judged to be the prescribed level or less. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a fundus camera for photographing a fundus.
[0002]
[Prior art]
As a projection method of a focus index in a non-mydriatic retinal camera using infrared light as observation illumination light, a method of placing a focus index plate in an observation illumination optical path is known (see Patent Document 1). With this fundus camera, the focus index image can be confirmed as a black shadow on the fundus observation image projected on the monitor, and the examiner moves the focusing lens so that the focus index image is in focus, and thereby focuses the fundus. Perform alignment.
[0003]
[Patent Document 1]
Japanese Patent Application Laid-Open No. H10-127584
[Problems to be solved by the invention]
However, when observing the focus index image projected on the fundus, it may be difficult to visually confirm the focus index image due to the luminance level of the fundus, and the focusing may not be properly performed.
[0005]
The present invention has been made in consideration of the above-described problems of the conventional apparatus, and it is an object of the present invention to provide a fundus camera that facilitates visual confirmation of a focus index and can perform good focusing of the fundus.
[0006]
[Means for Solving the Problems]
In order to solve the above problems, the present invention is characterized by having the following configuration.
[0007]
(1) In a fundus camera for photographing a fundus of a subject's eye, an illumination optical system for illuminating the fundus with infrared light for observation, and an index plate for focusing disposed in an optical path of the illumination optical system, An index plate having a wavelength characteristic of which part shields an infrared region, an imaging optical system having an imaging unit for imaging a fundus illuminated by the illumination optical system and a focus index image projected on the fundus, and imaging by the imaging unit Display means for displaying the obtained observation image; determining means for determining whether a difference between the focus index image of the image captured by the imaging means and the luminance level of the fundus is below a predetermined level; And an image correcting means for correcting the contrast of an image displayed on the display means when it is determined that the difference between the luminance level of the fundus and the luminance level of the fundus is below a predetermined level. You.
[0008]
(2) In the fundus camera according to (1), after the image correcting unit offsets a luminance signal level of an image captured by the imaging unit so as to decrease the luminance signal level, the image correcting unit increases at least one of a gain and a gamma value of the signal. It is characterized in that the contrast of the image displayed on the display means is enhanced.
[0009]
(3) The fundus camera according to (1), further comprising switching means for switching the image corrected by the image correction means to an image before correction.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a schematic configuration of a non-mydriatic retinal camera according to the present invention.
[0011]
The fundus camera according to the embodiment includes a photographing unit 1 in which an optical system for observation and photographing is housed in a housing suitable for hand-held operation, and a control unit 2 which controls the photographing unit 1 and in which a photographing light source is arranged. A color display monitor 3 having a touch panel function, which is roughly divided and provided with a touch panel function, is provided in the control unit 2. The monitor 3 uses a liquid crystal type. Illumination light from the photographing flash light source of the control unit 2 is guided to the optical system in the photographing unit 1 via the fiber bundle 4.
[0012]
FIG. 2 is a diagram showing an optical system of the fundus camera. The optical system includes an observation illumination optical system, a photography illumination optical system, and an observation / photography optical system.
[0013]
<Observation illumination optical system> 11 is an observation illumination light source such as an infrared light emitting diode, 12 is a diffusing plate, 13 is a dichroic mirror, and the dichroic mirror 13 reflects infrared light and is visible light for photography. Has the property of transmitting light. Reference numeral 14 denotes a condenser lens, and reference numeral 15 denotes a slit plate, which has a pinhole opening and a ring slit opening centered on the optical axis at the center. Reference numeral 10 denotes a focus chart, which is made of a member that transmits visible light and infrared light, and has a double ring index mark formed on the chart surface. The index mark of the double ring is made of a coating having a wavelength characteristic of transmitting visible light and blocking infrared light. The focus chart 10 moves in the optical axis direction (the direction of the arrow) in conjunction with a focusing lens 23 of an observation / photographing optical system described later, and is placed at a position conjugate with the fundus. Reference numeral 16 denotes a light projecting lens, and 17 denotes a half mirror, which makes an illumination / index projection optical axis coaxial with an optical axis of an observation / photographing optical system described later. Reference numeral 19 denotes a black absorber, which absorbs an illumination light beam transmitted through the half mirror 17 to prevent unnecessary noise light from entering the observation / photographing optical system. Reference numeral 18 denotes an eye to be examined.
[0014]
<Imaging Illumination Optical System> 31 is a flash light source for imaging, 32 is a condenser lens, and an illumination light beam for imaging is guided to the imaging unit 1 via the fiber bundle 4. The photographing illumination optical system in the photographing unit 1 shares an optical path from the dichroic mirror 13 to the half mirror 17 of the observation illumination optical system.
[0015]
<Observation / Photographing Optical System> Reference numeral 21 denotes an observation objective lens, and reference numeral 22 denotes a photographing stop arranged at a position conjugate with the pupil of the subject's eye 18. Reference numeral 23 denotes a focusing lens, which can be moved in the optical axis direction by a lens moving mechanism (not shown) in order to perform adjustment according to the refractive power of the eye to be inspected. Reference numeral 24 denotes an imaging lens, 25 denotes a dichroic mirror, and the dichroic mirror 25 has a characteristic of reflecting infrared light and transmitting visible light. Reference numeral 26 denotes a CCD camera for photographing. 27 is a relay lens for extending the optical path, 28 is a mirror for returning mirror image inversion, and 29 is an infrared CCD camera for observation.
[0016]
FIG. 3 shows a block diagram of a control system of the present apparatus. Reference numeral 41 denotes an image control unit, which receives video signals from the CCD camera 29 and the CCD camera 26 and switches an analog video signal to be output to the monitor 3. The image control unit 41 superimposes characters, marks, and the like on the video signal of the eye image to be inspected. When it is difficult to visually confirm the fundus image and the index image of the focus chart 10, the image control unit 41 corrects the luminance level of the image by performing offset and gamma correction.
[0017]
Further, a touch panel 42 is provided on the screen of the monitor 3, and a touch position of the touch panel 42 is detected by a touch panel control unit 43. The system control unit 40 includes an image control unit 41, a touch panel control unit 43, a flash lamp 31, a light source 11, a photographing switch 45, a non-volatile memory 46 for storing set values of display conditions of the monitor 3, and a large number of image data. Is connected.
[0018]
The operation of the fundus camera having the above configuration will be described below. The photographing environment is such that the eyes of the subject's eye are wide open in a natural mydriatic state in a dark place where the brightness of the newspaper is barely readable. During observation, the light source 11 is turned on. The infrared light emitted from the light source 11 illuminates the subject's eye via the diffusion plate 12, the dichroic mirror 13, the condenser lens 14, the slit plate 15, the focus chart 10, and the half mirror 17.
[0019]
The reflected light from the subject's eye passes through the half mirror 17, the objective lens 21, the photographing stop 22, the focusing lens 23, and the imaging lens 24, is reflected by the dichroic mirror 25, and is reflected by the relay lens 27 on the image sensor of the CCD camera 29. Image. The image captured by the CCD camera 29 is displayed on the screen of the monitor 3. When the apparatus is activated, the observation mode is set to the alignment mode in which the observation image is displayed on the monitor 3, and the monochrome (black and white) image from the CCD camera 29 is projected on the monitor 3 as shown in FIG. Since the focus chart 10 is projected on the fundus, the index mark 50 that is the index image of the focus chart 10 is projected on the monitor 3 as a black shadow. The examiner observes the fundus image and the index mark 50, and moves the focusing lens 23 so that the index mark 50 is in focus, thereby performing focusing on the fundus.
[0020]
Here, the image control unit 41 detects the index mark 50 and the luminance level of the fundus in the image signal output from the CCD camera 29, and corrects the contrast of the image displayed on the monitor 3 based on the detection result. The index mark 50 and the luminance level of the fundus are detected by one horizontal scanning line L passing through the center of the index mark 50 (image center). Note that a plurality of horizontal scanning lines for detecting the luminance level may be set around the center of the image.
[0021]
FIG. 5 is a diagram of a voltage level waveform indicating luminance on the horizontal scanning line L detected by the image control unit 41. FIG. 5A shows a case where the contrast between the index mark 50 and the luminance level of the fundus is relatively high. FIG. 5B is an example in the case where the contrast is low. The image control unit 41 determines whether the voltage level of the fundus of the portion of the index mark 50 on the horizontal scanning line L is equal to or lower than a predetermined level A stored in the memory 46. If the fundus voltage level is equal to or lower than the predetermined level A, the contrast with the index mark 50 is low, and the index mark 50 is difficult to see. The predetermined level A is set within the range of 2 to 3 V, for example, assuming that the voltage value of the image displayed on the monitor 3 is in the range of 2 to 3 V. Note that the voltage level detection region on the horizontal scanning line L is preferably performed for a region B that is slightly larger than the region including the index mark 50 in order to reduce the calculation time.
[0022]
As shown in FIG. 5B, when the luminance level (voltage level) of the fundus of the index mark 50 portion is equal to or lower than a predetermined level A, the contrast of the index mark 50 with respect to the fundus is low. It becomes hard to do. In this case, the image control unit 41 performs a correction process of offset, gain adjustment, and gamma correction on the luminance signal output from the CCD camera to correct the image luminance displayed on the monitor 3.
[0023]
The correction of the luminance of the image displayed on the monitor 3 will be described with reference to FIG. FIG. 6A shows voltage values when a gray scale (NTSC 5 Step) is input as an image signal. In this state, since the difference in brightness between the intermediate portions is not well understood, as shown in FIG. 6B, the signal level is offset downward by a certain amount as a whole, and then the gain and gamma value of the signal are reduced. increase. Note that either the gain or the gamma value may be changed. As a result, the brightness at the intermediate luminance portion of the image captured by the CCD camera 29 is amplified, and the index mark 50 with enhanced contrast can be observed on the monitor 3.
[0024]
In the above description, it is determined whether or not to correct the image luminance by comparing the luminance level of the fundus oculi and the predetermined level A without calculating the difference between the index mark 50 and the luminance level of the fundus oculi in order to shorten the calculation time. However, a difference between the luminance level of the index mark 50 and the luminance level of the fundus may be directly calculated, and if the difference is equal to or less than a predetermined level, the image luminance may be corrected.
[0025]
Note that the saturation enhancement may increase the saturation portion of the luminance, making it difficult to confirm the portion of the fundus image. In this case, by pressing a contrast changeover switch (not shown) on the touch panel of the monitor 3, it is possible to return to the initial setting state before the contrast enhancement. Therefore, it is possible to observe a screen in which the contrast is enhanced at the time of focusing, and to observe the screen returned to the initial setting state when emphasis is placed on observing the fundus image. When the contrast switch is pressed again, the screen is switched to a screen in which the contrast is enhanced.
[0026]
After the focusing is completed, the photographing switch 45 is pressed to cause the flash light source 31 to emit light. By the emission of the flash light source 31, the visible reflected light beam from the fundus illuminated with visible light passes through the objective lens 21, the photographic stop 22, the focusing lens 23, and the imaging lens 24 in the same manner as the fundus reflected light beam by infrared light. Incident on the dichroic mirror 25. Since the dichroic mirror 25 transmits the visible light beam, the visible fundus reflected light beam is incident on the imaging element surface of the CCD camera 26 by the imaging lens 24 to form a fundus image. When the fundus image is obtained by the CCD camera 26, the captured image is temporarily stored in the memory 41a in the image control unit 41, and the screen of the monitor 3 is displayed by the image control unit 41 from the display of the alignment image to the color image which is the captured image. Is displayed. The image switching signal at this time is output from the system control unit 40 in response to a signal input of the photographing switch 45. In addition, the obtained color fundus image is stored in the storage unit 47 by pressing a SAVE button (not shown) on the touch panel 42.
[0027]
【The invention's effect】
As described above, according to the present invention, it is easy to visually check the focus index, and the focus of the fundus can be favorably adjusted.
[Brief description of the drawings]
FIG. 1 is a diagram showing a schematic configuration of a non-mydriatic retinal camera according to the present invention.
FIG. 2 is a diagram showing an optical system of a fundus camera.
FIG. 3 is a control block diagram of a fundus camera.
FIG. 4 is a view showing a screen in an alignment mode.
FIG. 5 is a diagram showing a luminance level on a horizontal scanning line.
FIG. 6 is a diagram showing voltage values when a gray scale (NTSC 5 Step) is input.
FIG. 7 is a diagram showing a luminance level on a horizontal scanning line.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 shooting unit section 2 control unit section 3 monitor 10 focus chart 11 illumination light source for observation 29 infrared CCD camera for observation 40 system control section 41 image control section 50 index mark

Claims (3)

A fundus camera for photographing a fundus of a subject's eye, comprising an illumination optical system for illuminating the fundus with infrared light for observation, and a focus indicator plate disposed in an optical path of the illumination optical system, wherein the indicator portion is red. An index plate having a wavelength characteristic for shielding an external region, an imaging optical system having an imaging unit for imaging the fundus illuminated by the illumination optical system and a focus index image projected on the fundus, and observation captured by the imaging unit Display means for displaying an image, determining means for determining whether or not the difference between the luminance level of the focus index image and the fundus of the image captured by the image capturing means is equal to or less than a predetermined level, and An image correcting unit for correcting a contrast of an image displayed on the display unit when it is determined that the difference between the luminance levels is equal to or less than a predetermined level. Mera. 2. The fundus camera according to claim 1, wherein the image correction unit offsets a luminance signal level of an image captured by the imaging unit so as to reduce the luminance signal level, and then increases at least one of a gain and a gamma value of the signal to the display unit. A fundus camera characterized by enhancing the contrast of an image to be displayed. 2. The fundus camera according to claim 1, further comprising a switching unit that switches an image corrected by the image correction unit to an image before correction.

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