JP3109818B2 - Fundus camera - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a fundus camera capable of automatic focusing.

[Prior Art] Various automatic focusing devices for a fundus camera have been proposed. An active type, which projects a focusing luminous flux and receives light reflected by the fundus of the eye, is generally used. On the other hand, a passive type, which uses an image itself, has also been proposed.

[Problem to be Solved by the Invention] However, in such an automatic focusing apparatus for a fundus camera, when reflection from the eyelid or the cornea of the eye to be inspected is received by a photoelectric sensor for focus detection, malfunction occurs, resulting in malfunction. It will put time and burden on the examiner.

Means for Solving the Problems The present invention provides an illumination system for illuminating the fundus of the eye to be inspected, and an imaging unit for imaging an image of the fundus of the eye to be illuminated by the illumination system via an optical system having a focusing lens. A signal processor that detects a focus state with respect to the fundus by a video signal of the imaging unit, and a controller that controls driving of the focusing lens based on the detection by the signal processor to perform a focusing operation. The signal processor, when the signal level of the video signal is higher than the signal level due to fundus reflection light set according to the illumination conditions of the illumination system or the magnification of the optical system, or the video signal A focusing operation performed by the controller when the temporal change rate of the signal level is equal to or higher than a predetermined value.

Embodiment FIG. 1 shows an embodiment of the present invention.

The light source 1 is an incandescent lamp used for focusing on television observation. The light source 1 is conjugated to a strobe 3 used for photographing via a lens 2, conjugated to a perforated mirror 5 via a lens 4, and conjugated to a pupil Ep of an eye E via an objective lens 6. It is.

The reflected light from the fundus Er passes through the objective lens 6, the perforated mirror 5, the focusing lens 7, the imaging lens 8, the flip-up mirror 9, and the lens 11, and forms a fundus image on the television camera 12. The fundus image is displayed on the monitor 13, and the video signal is processed by the signal processor.
Enter 14.

As shown in FIG. 2, the signal processor 14 determines whether the signal is from the bottom surface or from the eyelid or the cornea. The signal level of the light from the eyelids and the cornea is higher than the light from the fundus, and can be determined based on the faster change speed.

That is, since the signal level from the fundus is almost fixed, if the signal level deviates greatly from this, it is not taken in as a focus signal.

Regarding the change speed, a change in the temporal level at a predetermined position is detected. If the change is equal to or more than a predetermined value, it is determined that ghost light has entered, and the change is not taken in as a focus signal.

In addition, regarding at least one of the signal level and the change speed, it is determined whether or not the signal is caused by light from the fundus.

Although the reflectance of the fundus varies slightly between individuals, it can be considered to be considerably constant compared to the reflectance of the eyelids and the cornea. However, if the illumination conditions change, the detected fundus reflection light quantity also changes. Therefore, when judging the level of the video signal related to the fundus reflection light of the television camera, it is necessary to take into account the observation conditions including the illumination conditions. That is, as shown in FIG. 3, the magnification of the observation lens system, the size of the aperture of the illumination system or the observation system, the transmittance of the filter including the light receiving filter,
Conditions such as the brightness of the illumination lamp are taken into account.

The signal processor 14 also detects the degree of blur. Specifically, a process of detecting the inclination of a signal from an edge or the like through a differentiating circuit can be considered.

That is, the degree of the blur is determined by the fact that the more the blur is, the lower the slope signal output through the differentiating circuit is.

The tilt signal output is stored, and the focusing lens 7 is driven by a predetermined amount in order to determine the direction. That is, the controller 16 controls the motor 16 to drive the focusing lens 7 in the direction in which the tilt signal output increases.

When the focusing lens 7 is adjusted to the in-focus position, the strobe light is emitted and a clear fundus image is formed on the film 10.
Form on top.

When processing a fundus image, ghost light is likely to appear in the peripheral portion of the screen, and it is desirable to make a focus determination based on a video signal in a portion excluding the peripheral portion as much as possible.

Further, the processing in FIG. 2 may be performed in parallel instead of being performed in series.

[Effects] As described above, according to the present invention, it is possible to provide a fundus camera in which malfunction of automatic focusing is less likely to occur due to light from the eyelids and the cornea.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of the present invention, FIG. 2 is a diagram showing a signal processing system, FIG. 3 is an explanatory diagram of determination of a fundus reflection signal level in consideration of illumination conditions, and 1 is a light source (incandescent light). Lamp, 3 is a strobe, 10 is a film, 12 is a television camera, 14 is a signal processor, 15 is a controller, and 16 is a motor.

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Claims (1)

(57) [Claims] An illumination system for illuminating the fundus of the eye to be inspected, imaging means for imaging an image of the fundus of the eye illuminated by the illumination system via an optical system having a focusing lens, and a video signal of the imaging means A signal processor that detects a focus state with respect to the fundus, and a controller that controls the driving of the focusing lens based on the detection in the signal processor to perform a focusing operation, and the signal processor includes: When the signal level of the video signal is higher than the signal level due to the fundus reflection light set according to the illumination conditions of the illumination system or the magnification of the optical system, or a temporal change in the signal level of the video signal A fundus camera, wherein a focusing operation by the controller is not performed when the speed is equal to or higher than a predetermined value.