JPS6223574B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fundus camera that performs automatic focus adjustment, and particularly to prevention of malfunctions that occur when a subject is not performing an examination.

Fundus cameras with automatic focusing have been proposed for some time, and the present applicant has published Japanese Patent Application No. 54-3734 (Japanese Unexamined Patent Publication No. 55-96138) and Japanese Patent Application No. 107729 (Sho 56-1983) 31732), etc., for an automatic focusing fundus camera. When using these fundus cameras in practice, there is no problem as long as the power supply to the automatic focusing mechanism is turned on and off frequently. It is common to use the switch with the switch turned on even before the subject's face is removed from the table, or even before alignment between the subject and the objective lens is achieved. In such a case, since the output signal of the focus detection element of the automatic focus adjustment mechanism is absent or very small, the adjustment mechanism repeatedly drives the focusing lens over the entire movement range in search of a predetermined signal.

However, unnecessary movement of the focusing lens when the subject's eye is not present or during camera positioning is considered to be troublesome and is particularly undesirable from the standpoint of affecting the lifespan of the automatic focusing mechanism.

On the other hand, when operating a fundus camera, the optical axis of the eye being examined and the objective lens are aligned and the working distance is adjusted before performing focus adjustment. This is done by pulling the body far away from the subject, allowing the anterior segment of the eye to be seen through the viewfinder, and adjusting the camera position so that the subject's pupils are in the center of the viewfinder field of view. Push it toward the examiner, observe the state of the illumination light hitting the cornea, and adjust the working distance (distance between the eye to be examined and the fundus camera) to the optimum value so that no flare occurs in the viewfinder field of view.

However, recently, a method has been proposed in Japanese Patent Publication No. 52-48440, in which an auxiliary lens is inserted into the photographing/observation optical path to forcibly move the focal point to the anterior segment of the eye so that the pupil can be seen. In addition, a method for adjusting the working distance by projecting a detection mark onto the anterior segment of the eye and observing the reflected image was disclosed in Japanese Patent Application Laid-Open No. 53.
-Known as No. 49890.

An object of the present invention is to prevent malfunctions in focus adjustment in a fundus camera equipped with an automatic focus adjustment mechanism. Note that the means referred to herein as an automatic focus adjustment mechanism includes a detection unit that detects the focus state on the fundus, and a drive unit that moves, for example, a focus adjustment lens of a fundus camera in the optical axis direction to adjust the focus. , disabling the automatic focus adjustment mechanism includes disabling both the detection section and the drive section and disabling only the drive section. This is because the detection section can be composed only of electronic circuits, and in that case, even if the circuit is activated, there will be almost no actual harm.

First, a fundus camera equipped with an automatic focus adjustment mechanism will be described below.

In Figure 1A, E is the eye to be examined, Ea is the fundus,
Eb is the iris. 1 is the objective lens, D is the aperture,
3 is a photographing lens, 2 is a focusing lens, 5 is a film, and 4 is a shutter, and the above members constitute a photographing system. Further, 18 is a mirror with a hole, which is installed obliquely with respect to the optical axis x of the photographing system, and 16 and 17 are relay lenses. 15 is a ring slit, which is a light shielding plate having an annular opening. 14 is a light source for photography; 13 is a xenon flash tube; 13 is a filter that passes light in the infrared and near-infrared wavelength ranges and blocks visible light;
2 is a reflecting mirror, 11 is a condenser lens, 1
0 is an observation light source. The above members and the objective lens 1 constitute a fundus illumination system. Here, the aperture of the perforated mirror 18 may be used as a photographic aperture, or a separate aperture may be provided, and the photographic aperture is approximately conjugate with the iris Eb with respect to the objective lens 1.

Further, the ring slit 15 is almost conjugate with the iris Eb with respect to the relaying optical system.

The bright line (detection mark) projection unit 20 will be explained below. 21 is a bright line projection light source, 22 is a viewing field limiting slit, and 23 is a condenser lens.
24 is a split prism (or bi-
prisw), consisting of mutually oppositely sloped optical wedges with boundaries perpendicular to the drawing. 25 is a linear slit,
Its longitudinal direction is parallel to the drawing. 26 is a reflective mirror. 27 is a two-hole slit with a fan-shaped opening 2.
7a and 27b. Apertures 27a and 27b are horizontally aligned and are aligned with the iris with respect to the relay optics.
It is conjugate with Eb. 28 is a projection lens, 29 is an infrared transmission/visible cutoff filter, and 31 is a small flip-up mirror rod, one end of which is formed with an oblique mirror, and the other end of which is attached to the rotating shaft of a rotary solenoid. The rotary solenoid 30 is magnetically excited during photographing, and the mirror rod 31 is moved out of the optical path. At this time, the unit 20 is movable in the optical axis direction, and the mirror surface of the mirror rod 31 is aligned with the film surface 5.
is equivalent, and both surfaces are focused on the fundus at the same time. Further, the light beam that has been refracted and split by the split prism 24 and then passed through the slit 25 is split into two from the center of the slit 25, refracted in opposite directions, and sent to the aperture 27a.
or 27b, the image of the slit 25 is reconstructed on the mirror surface of the mirror rod 31 by the action of the imaging lens 28, and is reflected there and split into two beams again. The light enters the eye E through the perforated mirror 18 and the objective lens 1, and forms half images (bright lines) of the slit at the fundus or in front and behind it, respectively, as oblique light beams with opposite gradients.

The bright line projection unit 20 works together with the focusing lens 2 to make the slit 25 and the film 5 conjugate with the fundus according to the rotation of the drive shaft 32. Also, observation light source 1
The emitted light passes through a condenser lens 11, a reflecting mirror 12, and an infrared filter 13, and illuminates a ring slit 15. Further, the light exiting the ring slit 15 passes through relay lenses 16 and 17 to form an image on the perforated mirror 18, and then passes through the objective lens 1.
The image is refocused near the iris Eb of the eye and illuminates the fundus Ea. On the other hand, the split bright line emitted from the bright line projection unit 20 is transmitted through the relay lens 17 and the perforated mirror 1.
8. An image is formed on the fundus Ea through the objective lens 1. The light reflected from the fundus Ea passes through the objective lens 1, the hole of the perforated mirror 18, the focusing lens 2, and the photographing lens 3, and forms an image on the film surface 5.
During observation, the image is projected via a flip-up mirror 6 onto the imaging surface of a television camera 8 having a relay lens 7 and sensitive to the infrared region.
will be displayed on the screen. 6, 8, and 9 constitute a fundus observation section. The image on the monitor image receptor 9 is a fundus image with bright lines superimposed thereon. By rotating the drive shaft 32 while watching the image receptor 9 so that the bright line images on the image receptor 9 have a predetermined positional relationship, manual focusing can be easily performed. Now, in the fundus camera, we newly added a bright line receiving system and a signal processing circuit 3.
6, a motor 37 and manual/automatic switching means are provided. The bright line light receiving system is composed of a light splitting member 33, a cylindrical lens 34 (FIG. 1B), and a linear photosensor array 35, and the light receiving surface of the linear photosensor array 35 is connected to the cylindrical lens 34.
coincides with the focal plane of The light splitting member 33 is arranged between the photographic lens 3 and the flip-up mirror 6, and partially reflects the infrared light in a fundus camera that observes with infrared light, and partially reflects the infrared light with a fundus camera that observes with visible light. For example, it is an interference thin film mirror that reflects all visible light and transmits all visible light. In addition, linear photosensor array 3
5 is placed at a position conjugate with the fundus Ea of a normal eye with respect to the relay optical system. The motor 37 is the bright line projection system 2
0 and the focusing lens 2 are connected via a connecting arm 31 to a drive shaft 32 through gears 38 and 39, and the drive shaft 32 is rotated in accordance with the output of a signal processing circuit 36.

A part of the fundus image and the bright line light reflected by the light splitting member 33 are bent in a direction perpendicular to the plane of the paper, and are imaged on the linear photosensor array 35 via the cylindrical lens 34. Here, the scanning direction of the linear photosensor array is a direction perpendicular to the longitudinal direction of the bright line, in other words, a direction that is parallel to the optical axis of the imaging system when guiding a luminous flux by one reflection, and a direction parallel to the optical axis of the imaging system. They are arranged so that the bright lines coincide at specific positions.

In the above configuration, a bright line is projected onto the fundus of the eye, one of the bright lines reflected from the fundus is received by the linear photosensor array 35, and when the position on the array where the bright line is formed deviates from the normal position, , determines the direction in which the circuit 36 is deviated and drives the motor 37;
The shaft 32 is rotated via the gears 38 and 39, and the connecting arm 31 is swung to adjust the positions of the focusing lens 2 and the bright line projection unit 20, and this operation is performed to form the bright lines on the array in the normal position. will continue until

Next, the positioning operation according to the present invention will be described. As an example, a device for aligning the optical axis by inserting an auxiliary lens described in Japanese Patent Publication No. 52-48440 will be used.

In Fig. 1A, 40 is an auxiliary lens for observing the anterior segment of the eye, which is inserted behind the objective lens 1 with its optical axis aligned, and is removed from the optical path when its role is finished. indicates the attachment/detachment mechanism. In FIG. 2, reference numeral 41 denotes a support arm of the auxiliary lens 40, which is fixed to the rotating shaft of the rotary solenoid 52 and is constantly pulled in a direction outside the optical path by a tension spring 42.
Normally, the auxiliary lens 40 is placed outside the optical path, and when the solenoid 52 is energized, the rotation of the rotation axis is caused by the support arm 4.
1 to place the auxiliary lens 40 in the optical path. To explain the function of the auxiliary lens, first, in the optical system for photographing the fundus, when the focusing lens is in the neutral position, it emits the fundus of a normal eye of zero diopters, and exits the subject's eye as a parallel light beam. Since the power arrangement is such that the light is focused on the film surface, it is not possible to focus on the anterior part of the eye, such as the iris, just by adjusting the focusing lens. Therefore, the auxiliary lens 40 is inserted to strengthen the power of the objective lens 1, thereby bringing the system into focus on the anterior segment of the eye. In addition,
If you move the fundus camera far away from the subject's eye and adjust the focusing lens, you can see a blurred anterior segment, but if you insert an auxiliary lens, you can see a sharp anterior segment without moving the camera back and forth. Eye images can be observed.

FIG. 3 shows an electrical circuit connected to the means used for alignment shown in FIG. 2;
47 is the electric circuit of the fundus camera, and the observation light source 1
0 includes a photographing light source 14, a television camera 8, and an image receiver 9; 61 is an electric circuit for an automatic focusing mechanism; an illumination light source 21; a rotary solenoid 3
0, linear sensor array 35, processing circuit 36,
A motor 37 is included. 48 is a power source, 49 is a power switch, 50 is an anterior segment observation switch, and 56 is an automatic/manual selection switch.

When the power switch 49 and the selection switch 56 are closed and the power is input, when the anterior segment observation switch 50 is closed in order to align the eye to be examined and the fundus camera, the electromagnetic relay 51 is excited, and as a result, the relay contact 51a is closed, the solenoid 52 is driven, and the auxiliary lens 40 is inserted into the optical path.

At that time, the contact 51a is closed in synchronization with the closing of the contact 51a.
b switches from d to e, capacitor 62 is charged through resistor 53, and when the voltage reaches a certain value it is applied to the base of transistor 54 through resistor 57, making it conductive. This corresponds to the storage state of the storage unit that stores the setting of the anterior segment observation system.

In this state, when the positioning is completed and the switch 50 is opened, the contact 51a opens and the solenoid 5
Since the power supply to lens 2 is cut off and the rotating shaft becomes free, the auxiliary lens 40 is housed in a position outside the optical path by the force of the tension spring 42. Therefore, the focus of the optical system moves from the anterior segment of the eye to the vicinity of the fundus, and enters the detection range of the automatic focus detection mechanism.

At the same time as the contact 51a is opened, the contact 51b is also switched from e to d, and after this switching, the electromagnetic relay 55 is driven during the period when the transistor 54 is on (period _T1 in FIG. 4). Note that the period 51 is set by a discharge time constant via the resistor 56 and resistor 57 of the capacitor 62 and the transistor 54.

When the contact 55a is closed by driving the electromagnetic relay 55, the potential of the conductor 58 is at a low level as shown in FIG. 4, and the transistor 59 is in a conductive state, so the electromagnetic relay 60 is driven. The electromagnetic relay 60 closes the contact 60a, energizes the circuit 61, and the automatic focus adjustment mechanism becomes operational. In other words, the automatic focus adjustment mechanism is activated only when there is an output from both the storage unit that stores the setting of the anterior segment observation system and the switch unit that switches from the anterior segment observation system to the fundus observation system. .

When the contact 60a is closed, the contact 60b is also closed, and the electromagnetic relay 60a remains driven even after the contact 55a is opened after the period _T1 . However, period T ₁
After switching from e to d of contact 51b, contact 6
Set it to be longer than the time Td until 0a is closed.

While the circuit 61 of the automatic focus adjustment mechanism is energized, when imaging of the fundus is completed, the circuit 61 sets the conductor 58 to a high level, turns off the transistor 59, and stops energizing the electromagnetic relay 60. cut, open contacts 60a and 60b, and open circuit 6.
The automatic focus adjustment mechanism is rendered inactive by stopping the power supply to 1. In addition, since this example is applied to a non-mydriatic fundus camera, we are considering only one shot, and to put the automatic focus adjustment mechanism into operation again, the anterior segment observation operation must be performed again. However, since a mydriatic fundus camera takes several images, a separate time-limited circuit is installed to keep the automatic focus adjustment mechanism energized for several minutes after each image is taken. It is also possible to update the operating status. In addition, by embedding a pressure-sensitive, heat-sensitive, photoelectric, or other proximity switch in the face holder or chin rest of the fundus camera face fixation table, or by providing a switch to detect the movement of the fundus camera to switch between the left and right eyes, it is possible to It is also possible to detect the absence of the person, the switching movement of the camera, or a combination of both to stop the power supply to the automatic focusing mechanism.

As described above, according to the present invention, the inconvenience of shortening the life of the adjustment mechanism due to activation of the adjustment mechanism at a time when the focus adjustment operation is unnecessary can be avoided, and the focus adjustment operation can be performed during positioning. This has the effect of not making alignment difficult. Even if the fundus camera is powered on with the fundus observation system set, the automatic focus adjustment mechanism is prevented from operating immediately, and the automatic focus adjustment mechanism is activated when the alignment is good. .

[Brief explanation of the drawing]

FIG. 1a is an optical sectional view of the embodiment, and FIG. 1b is a view seen from - in FIG. Figure 2 is a partial front view.
Figure 3 is an electrical circuit diagram. Figure 4 is a waveform diagram. In the figure, 2 is a focusing lens, 30 is a bright line projection unit, 35 is a photo sensor array, 40 is an auxiliary lens, 52 is a rotary solenoid, 51,
55 and 60 are electromagnetic relays, 54 and 59 are transistors, 53, 56 and 57 are resistors, and 62 is a capacitor.

Claims (1)

[Scope of Claims] 1. A fundus camera equipped with an anterior segment observation system, a fundus observation system, and an automatic focus adjustment system for the fundus of the eye to be examined, comprising: a memory unit that stores the setting of the anterior segment observation system; A fundus camera, comprising: a switch section that switches from an anterior segment observation system to a fundus observation system; and a control section that operates an automatic focus adjustment system only when there is an output from the storage section and the switch section. 2. When the auxiliary lens is inserted into the optical path of the fundus observation system, the anterior segment observation system is set, and when the auxiliary lens is moved out of the optical path, the anterior segment observation system is switched to the fundus observation system. A fundus camera according to scope 1.