Eye fundus camera

Details Eye fundus camera Eye fundus camera

2000-11-24

2002-09-24

Rutledge, D. (Department: 2851)

Photography

Body examination photography

Eye photography

C396S110000, C351S206000, C351S211000

Reexamination Certificate

active

06456787

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an eye fundus camera for photographing and recording an image of a subject's eye in a hospital of ophthalmology or the like. More particularly, this invention is concerned with an eye fundus camera suitable for fluorescence contrast photography.
2. Description of the Related Art
For performing fluorescence contrast photography using an eye fundus camera, a fluorescein that fluoresces in response to excitation light of specified wavelengths is intravenously injected into a patient. The fundus of the patient's eye is illuminated with the excitation light, and the fluorescent fundus is photographed. Indocyanine green or the like is employed as the fluorescein in infrared fluorescence photography in which infrared light that is invisible light is adopted as the excitation light.
FIG. 9
shows a typical configuration of a conventional eye fundus camera capable of performing infrared fluorescence photography. Since infrared light is utilized, an infrared television camera is used for observation or recording. A patient lying near a base
1
wears a face holder
2
. A fixation lamp
3
is mounted on the face holder
2
. A stage
4
whose position is adjustable back and forth, right and left, and up and down is placed on the top of the base
1
. A housing
6
for accommodating an optical system composed of optical elements including an exciter filter
5
for infrared fluorescence designed for eye fundus cameras, and an operator stick having a position adjustment lever
7
and a photography switch
8
are mounted on the stage
4
. A 35-mm film camera
9
, an optical finder
10
, and a relay lens unit
12
are fixed to the housing
6
. The 35-mm film camera
9
is employed in color photography or visible-light fluorescence photography. An operator observes a fundus with the naked eyes through the optical finder
10
. The relay lens unit
12
includes a barrier filter
11
used for infrared-fluorescence recording and enables mounting of a television camera. An infrared television camera
15
used for observation can be mounted on the optical finder
10
via a relay lens unit
14
that enables mounting of a television camera and includes a barrier filter
13
used for infrared-fluorescence observation. An output of the television camera
15
is fed to an observation display
16
over a cable. On the other hand, an infrared television camera
17
used for recording is mounted on the relay lens unit
12
. An output of the television camera
17
is fed to an image recording device
18
and a display
19
used to display a record image over a cable.
The foregoing conventional eye fundus camera has an optical path defined independently for observation and recording alike. Therefore, the relay lens unit
14
for observation, infrared television camera
15
for observation, and display
16
for displaying a view image must be arranged along an optical path different from an optical path along which the relay lens unit
12
for recording, infrared television camera
17
for recording, and display
19
for displaying a record image are arranged. This leads to a complex structure and a large number of parts, and poses a problem in that the eye fundus camera becomes large in size and expensive.
Moreover, the infrared television camera
15
is connected to the optical finder
10
via the relay lens unit
14
in order to produce a view image seen through the optical finder
10
. When an operator sees through the optical finder
10
for color photography or visible-light fluorescent photography, the operator must dismount the relay lens unit
14
. Moreover, the cable extending from the infrared television camera
15
mounted on the relay lend unit
14
can get entangled and thus interfere with the manipulation of the eye fundus camera. These factors pose a problem in that they hinder improvement in maneuverability of the eye fundus camera.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to solve the foregoing problems and to provide an eye fundus camera that is compact and low-cost and offers excellent maneuverability. According to one aspect, the present invention that achieves at least one of these objectives relates to an eye fundus camera comprising an illumination optical system configured to illuminate the fundus of a patient's eye with light of wavelengths falling within a first wavelength band, and a photography optical system configured and positioned to form an image of the fundus illuminated by the illumination optical system so that a fundus image will be produced by the camera. The photography optical system includes a first filter that exhibits a spectral characteristic of intercepting light of wavelengths falling within the first wavelength band and transmitting light of wavelengths falling within a second wavelength band of longer wavelengths than the first wavelength band, and a second filter that exhibits a spectral characteristic of transmitting light of wavelengths falling within a wavelength band that covers the second wavelength band and includes part of the first wavelength band and that is therefore wider than the second wavelength band including the wavelengths of the light transmitted by the first filter. At least the first filter is capable of being inserted into an optical path of the photography optical system and displaced therefrom. The camera also comprises a photography switch with which an operator gives instructions to photograph the fundus image as still images under strobe light, a controller for causing a strobe to produce the strobe light when the photography switch is pressed and the first filter is inserted into the optical path, and a display for displaying the fundus image produced by the photography optical system.
The illumination optical system includes an exciter filter that exhibits a spectral characteristic of transmitting light of wavelengths falling within the first wavelength band and intercepting light of wavelengths falling within the second wavelength band, and that is displaceable from the optical path. In addition, for enabling observation, the controller causes the first filter to be displaced from the optical path and causes the second filter to be inserted thereinto, and for enabling photography, the controller causes the first filter to be inserted into the optical path. Also, the photography switch can comprise a double switch, and in this case, the controller controls insertion of the second filter in response to pressing of a first-step switch of the double switch, and controls flashing of the strobe light in response to pressing of a second-step switch thereof. Further, when the time interval between the pressing of the first-step switch and the pressing of the second-step switch is smaller than a predetermined value, the controller disables insertion of the second filter. Moreover, in one embodiment, the eye fundus camera enables fluorescence photography of an eye fundus with fluorescein, the first wavelength band includes wavelengths suitable for excitation of the fluorescein, and the second wavelength band includes wavelengths of light produced by fluorescence of the excited fluorescein.
According to another aspect, the present invention that achieves at least one of these objectives relates to an eye fundus camera comprising an illumination optical system for illuminating a fundus of a patient's eye. The illumination optical system includes a first filter that exhibits a spectral characteristic of transmitting light of wavelengths falling within a first wavelength band and intercepting light of wavelengths falling within a second wavelength band of longer wavelengths than the first wavelength band, and a second filter that exhibits a spectral characteristic of transmitting light of wavelengths falling within a wavelength band which covers the first wavelength band and includes part of the second wavelength band and that is therefore wider than the first wavelength band including the wavelengths of the

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