JP4126244B2 - Fundus camera - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fundus camera that photographs the fundus.
[0002]
[Prior art]
As a projection method of a focus index in a non-mydriatic fundus camera that uses infrared light as observation illumination light, a method of placing a focus index plate in the observation illumination optical path is known (see Patent Document 1). In 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, thereby focusing on the fundus. Align.
[0003]
[Patent Document 1]
Japanese Patent Laid-Open No. 10-127484 [0004]
[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 focus adjustment may not be performed satisfactorily.
[0005]
In view of the above-described problems of the conventional apparatus, it is an object of the present invention to provide a fundus camera that facilitates visual confirmation of a focus index and can favorably focus 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) An illumination optical system that illuminates the fundus with infrared light for observation, and a focus indicator plate disposed in the optical path of the illumination optical system, wherein the indicator portion has a wavelength characteristic that blocks the infrared region. An index plate, an imaging optical system having imaging means for capturing the fundus illuminated by the illumination optical system and a focus index image projected onto the fundus, and a display means for displaying an observation image captured by the imaging means It comprises, in a fundus camera for photographing a fundus with visible light, based on the captured image signal obtained by the imaging means, whether or not the difference between the focus index image and the fundus of the luminance level is below a predetermined level determination means for determining, when a difference in luminance level of the focus index image and the fundus is determined to be below a predetermined level by said determining means, con observation image to be displayed on said display means Correcting the last, characterized by comprising an image correcting means for obtaining a focus index image contrast is enhanced, the.
(2) The fundus camera of (1) is characterized by further comprising switching means for switching the image corrected by the image correction means to an image before correction.
[0010]
DETAILED DESCRIPTION OF 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 of the embodiment controls the photographing unit unit 1 in which an optical system for observation and photographing is housed in a housing suitable for hand-held operation, and the control unit unit 2 in which a photographing light source is arranged. The control unit section 2 is provided with a color display monitor 3 provided with a touch panel function. The monitor 3 is 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 photographing illumination optical system, and an observation / photographing optical system.
[0013]
<Observation Illumination Optical System> 11 is an illumination light source for observation such as an infrared light emitting diode, 12 is a diffusion plate, 13 is a dichroic mirror, and the dichroic mirror 13 reflects infrared light and is visible light for photographing. It has the property of transmitting through. 14 is a condenser lens, and 15 is a slit plate, which has a pinhole opening and a ring slit opening around the optical axis at the center. Reference numeral 10 denotes a focus chart, which is composed of a member that transmits visible light and infrared light, and a double ring index mark is formed on the chart surface. The double ring index mark is made of a coating having a wavelength characteristic that transmits light in the visible region and shields light in the infrared region. The focus chart 10 moves in the optical axis direction (arrow direction) in conjunction with a focusing lens 23 of an observation / photographing optical system, which will be described later, and is placed at a position conjugate with the fundus. Reference numeral 16 denotes a light projection lens, and reference numeral 17 denotes a half mirror. The illumination / index projection optical axis and the optical axis of an observation / photographing optical system, which will be described later, are coaxial. A black absorber 19 absorbs the illumination light beam that has passed 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]
<Photographing Illumination Optical System> 31 is a flash light source for photographing, 32 is a condenser lens, and the illumination light beam for photographing is guided to the photographing unit unit 1 through the fiber bundle 4. The photographing illumination optical system in the photographing unit unit 1 shares the optical path from the dichroic mirror 13 to the half mirror 17 of the observation illumination optical system.
[0015]
<Observation / Shooting Optical System> 21 is an objective lens for observation, and 22 is a photographing aperture arranged at a position conjugate with the pupil of the eye 18 to be examined. 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 in accordance with the refractive power of the eye to be examined. Reference numeral 24 denotes an imaging lens, and 25 denotes a dichroic mirror. The dichroic mirror 25 has characteristics 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 the mirror image inversion, and 29 is an infrared CCD camera for observation.
[0016]
FIG. 3 shows a block diagram of the control system of this apparatus. An image control unit 41 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. In addition, the image control unit 41 superimposes characters, marks, etc. on the video signal of the eye image to be examined. Further, when it is difficult to visually check 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 offset and gamma correction.
[0017]
Further, a touch panel 42 is provided on the screen of the monitor 3, and the touch position of the touch panel 42 is detected by the 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 that stores setting values for display conditions of the monitor 3, and a large number of image data. Is connected to the storage unit 47.
[0018]
The operation of the fundus camera having the above configuration will be described below. The shooting environment should be such that the pupil of the subject's eye opens widely in a natural mydriatic state in a dark place that is barely light enough to read newspaper characters. During observation, the light source 11 is turned on. The infrared light beam emitted from the light source 11 illuminates the eye to be examined through 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]
Reflected light from the eye to be examined passes through the half mirror 17, the objective lens 21, the imaging aperture 22, the focusing lens 23, and the imaging lens 24, is reflected by the dichroic mirror 25, and then is reflected on the image sensor of the CCD camera 29 by the relay lens 27. To form an image. An image captured by the CCD camera 29 is displayed on the screen of the monitor 3. When the apparatus is started, the observation image is displayed on the monitor 3 in an alignment mode, and a monochrome (monochrome) image from the CCD camera 29 is displayed on the monitor 3 as shown in FIG. Since the focus chart 10 is projected on the fundus, the index mark 50 that is an 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 focusing the fundus.
[0020]
Here, the image control unit 41 detects the brightness level of the index mark 50 and 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 brightness levels of the index mark 50 and the fundus are detected by a single horizontal scanning line L that passes 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 voltage level waveform diagram showing the 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 shows an example when the contrast is low. The image control unit 41 determines whether or not the fundus voltage level 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. For example, if the voltage value of the image displayed on the monitor 3 is in the range of 2 to 3V, the predetermined level A is set within the range of 2 to 3V. Note that the voltage level detection region on the horizontal scanning line L may be performed in a region B that is slightly larger than the region including the index mark 50 in order to shorten the calculation time.
[0022]
As shown in FIG. 5B, when the luminance level (voltage level) of the fundus of the index mark 50 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 difficult. In this case, the image control unit 41 performs correction processing of offset, gain adjustment, and gamma correction on the luminance signal output from the CCD camera, and corrects the luminance of the image 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 gray scale (NTSC 5Step) is input as an image signal. In this state, since the difference in brightness between the middle portions is not well understood, as shown in FIG. 6B, after the signal level is offset downward by a certain amount as a whole, the gain and gamma value of the signal are set. increase. Note that either the gain or the gamma value may be changed. Thereby, the darkness and darkness in 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, it is determined whether or not to correct the image luminance by comparing the luminance level of the fundus with a predetermined level A without obtaining the difference between the luminance level of the index mark 50 and the fundus in order to shorten the calculation time. However, the difference between the brightness level of the index mark 50 and the fundus may be obtained by direct calculation, and if the difference is less than a predetermined level, the image brightness may be corrected.
[0025]
Note that the above-described contrast enhancement increases the saturation portion of the luminance, which may make it difficult to confirm the fundus image portion. In this case, by pressing a contrast changeover switch (not shown) on the touch panel of the monitor 3, the initial setting state before contrast enhancement can be restored. Therefore, it is possible to observe a screen with enhanced contrast at the time of focusing, and to observe a screen that has been returned to the default state when emphasizing the observation of the fundus image. Press the contrast switch again to switch to a screen with enhanced contrast.
[0026]
After completing the focusing, the photographing switch 45 is pressed to cause the flash light source 31 to emit light. The visible reflected light beam from the fundus illuminated with visible light by the light emission of the flash light source 31 passes through the objective lens 21, the photographing aperture 22, the focusing lens 23, and the imaging lens 24 in the same manner as the fundus reflected light beam by infrared light. Then, the light enters the dichroic mirror 25. Since the dichroic mirror 25 transmits the visible light beam, the visible fundus reflected light beam is incident on the image sensor surface of the CCD camera 26 by the imaging lens 24 and forms 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 image control unit 41 causes the color image of the monitor 3 to be a captured image from the display of the alignment image. Is switched to the display. The image switching signal at this time is output from the system control unit 40 in response to a signal input from the photographing switch 45. 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, visual confirmation of the focus index is facilitated, and the fundus can be favorably focused.
[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 illustrating an optical system of a fundus camera.
FIG. 3 is a control system block diagram of a fundus camera.
FIG. 4 is a diagram showing a screen in an alignment mode.
FIG. 5 is a diagram illustrating a luminance level on a horizontal scanning line.
FIG. 6 is a diagram illustrating voltage values when gray scale (NTSC 5Step) is input.
FIG. 7 is a diagram illustrating a luminance level on a horizontal scanning line.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Shooting unit part 2 Control unit part 3 Monitor 10 Focus chart 11 Observation illumination light source 29 Observation infrared CCD camera 40 System control part 41 Image control part 50 Index mark

Claims (2)

An illumination optical system that illuminates the fundus with infrared light for observation, and an index plate for focusing disposed in the optical path of the illumination optical system, the index portion having a wavelength characteristic that blocks the infrared region If, comprising an imaging optical system having an imaging means for imaging the focus index image projected on the fundus and fundus illuminated by the illumination optical system, and display means for displaying an observation image captured by the image pickup means Determining whether or not the difference between the brightness level of the focus index image and the fundus is equal to or less than a predetermined level based on the captured image signal obtained by the imaging unit in a fundus camera that captures the fundus of the eye to be examined with visible light And a contrast of an observation image displayed on the display unit when the determination unit determines that the difference between the brightness level of the focus index image and the fundus is equal to or less than a predetermined level. A fundus camera comprising: an image correction unit that corrects the image and obtains a focus index image with enhanced contrast .   2. The fundus camera according to claim 1, further comprising switching means for switching the image corrected by the image correction means to an image before correction.

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