JPS6259580B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a focus detection device for a fundus camera, in particular a reflector having a through hole in the center, which is diagonally installed across the optical axis between an objective lens and an imaging lens. A focus detection device for a fundus camera that illuminates the subject's eye with illumination light for observation or photography, and switches the reflected light from the fundus to either observation or photography using an observation optical system installed behind an imaging lens. It is related to.

Conventionally, when observing or photographing the subject's eye using a fundus camera, the position of the subject's face is determined,
The eye to be examined is fixed directly on the optical axis of the objective lens of the fundus camera, and after illumination light is irradiated to focus on the fundus, observation and photography are performed.
Since the subject is a human being, various adjustments on the fundus camera side, especially focus adjustment, must be made within a short period of time so that the subject's eye does not move.

In order to quickly and easily adjust the focus, a dual-image matching type is used for fundus cameras that are operated while viewing the image on a TV monitor equipped with a TV camera. Therefore, there is a desire for the development of a fundus camera that can perform observation or photography in a shorter period of time.

The present invention has been made in view of the above points, and an object of the present invention is to provide a focus detection device for a fundus camera that facilitates focus adjustment with a simple configuration and can perform the adjustment in a short time. .

The purpose of this is to irradiate illumination light onto the subject's eye through the objective lens using a reflecting mirror installed diagonally across the optical axis between the objective lens and the imaging lens, and to use the reflected light from the fundus to form the image. In a fundus camera that can be switched to either observation or photography using an observation optical system installed behind the lens, apart from the illumination light, there are two symmetrical critical flickers with a phase difference of 180° from a position off the optical axis. The in-focus state of the imaging lens is detected by projecting a beam of light that blinks at a frequency equal to or less than the frequency of the imaging lens onto the subject's eye through an aperture, and visually observing or photoelectrically detecting the reflected light through the imaging lens. This is achieved by providing a focus detection device for a fundus camera characterized by the following configuration.

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1A is a cross-sectional view of the main part mainly showing an optical system showing an embodiment of the present invention. When the respective optical axes intersect at an angle 2α towards the provided pinhole 3a and the light emitting diodes 1 and 2 are turned on, the narrow beams passing through the pinhole 3a will each have an angle of α with respect to the optical axis L ₄ . The light passes through the two-hole diaphragm ₄ at an angle to the optical axis _L1 perpendicular to the optical axis L4, and reaches the obliquely disposed half mirror 5 through the intersection point. This half mirror 5 has a light emitting diode 1
It may be replaced with a partial reflection mirror that reflects only the part that the thin light beam emitted from 2 and 2 reaches and has no reflective layer for the rest, but in the following explanation, we will proceed with the explanation as a half mirror, and use the partial reflection mirror as a half mirror. The explanation as follows will be omitted.

On the optical axis _L1 , an imaging lens 6 is disposed adjacent to the half mirror 5 so as to be movable along the optical axis L1 in the direction of arrow B, and an aperture diaphragm is disposed at right angles to the optical axis L1. 7 and diagonally installed perforated mirror 8,
Further, the objective lenses 9 are arranged on the optical axis L at predetermined intervals.
They are arranged on 1.

As shown in FIG. 1B, the diaphragm 7 has a center hole 7a provided at the center and small holes 7b and 7c provided above and below the center hole 7a in opposing positions. The light beams emitted from 1 and 2 pass through a pinhole 3a and a two-hole diaphragm 4, are reflected by a half mirror 5, and are converged as they pass near the periphery of an imaging lens 6, resulting in a small hole 7, respectively.
b and 7c. The small holes 7b and 7c of the diaphragm 7 may be provided at positions facing each other laterally or diagonally, corresponding to the positions of the light emitting diodes 1 and 2.

Reference numeral 10 denotes a subject's eye to be observed or photographed, and is disposed on the optical axis L1 facing the objective lens 9.

A movable mirror 11 is installed obliquely with respect to the optical axis L1 close to the rear of the half mirror 5 adjacent to the imaging lens 6, and is installed so as to be able to rotate in the direction shown by arrow A. The movable mirror 11 and the optical axis
On the optical axis L ₂ which passes through the intersection of L ₁ and intersects perpendicularly, there is an imaging plane 1 formed by the imaging lens 6 in close proximity to the movable mirror 11.
2, and its focal point is the intersection _F1 with the optical axis _L2 . Next, a half mirror 13 is installed obliquely on the optical axis L ₂ and divides the light beam arriving from the imaging lens 6 via the movable mirror 11 into two, one of which passes through the half mirror 13 and is photoelectrically converted by the relay lens 16. reaches the surface of the element 17, and the other half mirror 1
3, the light passes through the eyepiece 14 along the optical axis _L3 and reaches the examiner's eye 15.

Reference numeral 18 denotes a photosensitive film, and when the movable mirror 11 is rotated in the direction of arrow A and is at the position indicated by the chain line, illumination light, which will be described later, is irradiated onto the eye 10 to be examined, and the reflected light passes through the objective lens 9 and the imaging lens 6. The structure is such that the lever reaches the photosensitive film 18 and photographs are taken. F ₀ is the focal point of the imaging lens 6.

Reference numeral 19 denotes an illumination lamp for illuminating the eye 10 to be examined.By lighting this lamp, preparations can be made in advance so that the position and direction of the eye to be examined are directly facing the objective lens 9. Condenser lenses 20 and 22 are disposed at a predetermined interval close to the illumination lamp 19 disposed on the optical axis _L8 , and these condenser lenses are formed by a xenon lamp disposed between the illumination lamp 19 and the condenser lenses 20 and 22. They are arranged so that the light emitted from each of them is reflected by a reflecting mirror 23 and then focused onto a ring slit 24. The ring slit 24 is provided with a ring-shaped portion that transmits light, and the portion other than the ring-shaped portion is covered with an opaque portion that does not transmit light.

On the optical axis L ₉ whose optical path is bent by the reflector 23 , there is a projection for connecting the image of the ring slit 24 to the position of the perforated mirror 8 and projecting it onto the cornea of the eye 10 through the objective lens 9 . optical lens 25,
26 is disposed, and the optical axis L ₉ and the optical axis L ₁ intersect approximately at the center of the perforated portion of the perforated mirror 8 described above.

The illumination light from the projecting lenses 25 and 26 is reflected by the reflective mirror portion of the perforated mirror 8 excluding the perforated portion, and passes through the objective lens 9 to irradiate a ring-shaped illumination light onto the cornea of the eye 10 to be examined. do.

Next, the operation of this embodiment configured as above will be explained.

In FIG. 1A, light emitting diodes 1 and 2 are
They are blinked with a phase difference of 180 degrees below the critical flicker frequency (for example, 30 Hz) that is perceived as flicker by the human eye, and the light beam is transmitted through the pinhole 3a,
It passes through a two-hole aperture 4, is reflected by a half mirror 5, is focused by an imaging lens 6, passes through small holes 7b and 7c of an aperture 7, and is reflected by a perforated mirror 8.
The light passes through the perforated part, converges at the intersection _F4 on the optical axis _L1 , then turns to a divergent direction, is made into a nearly parallel light beam by the objective lens 9, passes through the cornea of the eye 10 to be examined, and reaches the vicinity of the fundus of the eye. It is convergent.

The light flux that irradiated the fundus becomes a reflected light beam, passes through the objective lens 9 again, passes through the hole in the center of the perforated mirror 8, passes through the center hole 7a of the diaphragm 7, passes through the imaging lens 6, and enters the movable mirror 11. After being reflected, it reaches the vicinity of the center _F1 of the imaging plane 12.

This is passed through the half mirror 13 to the eyepiece lens 1.
4 and observed with the examiner's eye 15. If photoelectric detection is not used, the half mirror 13 may be a total reflection mirror.

In that case, if the focus adjustment by the imaging lens 6 is not performed correctly, the image shown in FIG.
As shown in Figure A, the two upper and lower beams of light are separated on the fundus of the eye, and as shown in Figure 5B or Figure 6B, the two spots appear to be separated, and the separate individual spots As shown in FIG. 5C or FIG. 6C, two spots of blinking light with a frequency of approximately 30 Hz, that is, flickering, are recognized separately.

Next, when the imaging lens 6 is moved back and forth along the optical axis _L1 in the direction of the arrow B, either manually or by the motor M, as shown in FIG.
At that time, as shown in Figure 7B, it is visible that the two light beams overlap into one, and at the same time, as shown in Figure 7C, they are 180 degrees shifted from each other. Due to the phase difference S, each light-emitting part, that is, the lighting part, overlaps with the non-lighting part of the luminous flux of the other side, and only the continuous lighting part with a frequency of approximately 60Hz, which is twice the aforementioned 30Hz, is visible, and flickering occurs. I can't feel it anymore.

At this time, the focus point is on the film 18 of the imaging lens 6 and on the photoelectric conversion element 17, and the light emitting diodes 1 and 2 are immediately turned off by operating the photographing operation section (not shown), and the movable mirror 11 is moved to the arrow A.
Then, the xenon lamp 21 is caused to emit light, and an image of the fundus of the eye 10 to be examined is photographed on the film 18.

Another embodiment for illuminating the blinking of two light emitting diodes with a phase difference of 180° uses a mechanical chopper in the form of three fan-shaped rotating mirrors 34, as shown in FIG. be able to. In this case, a lamp, a light emitting diode, or a laser diode can be used as the irradiation light source, but the light emitting diode will be discussed here. The light emitting diode 1 is arranged on the axis at an angle α from the optical axis L ₄ and from behind the rotating mirror 34 toward one hole of the two-hole diaphragm 4 , and the other light emitting diode 2 is arranged on the axis at an angle α from the optical axis L 4 The reflected light beam is directed toward the intersection of the surface and the light beam emitted from the light-emitting diode 1 at an angle α to the optical axis L ₄ on the opposite side of the light beam from the light-emitting diode 1, and the two-hole diaphragm 4
is arranged so as to irradiate the other hole.

In this embodiment, the light emitting diodes 1 and 2 are kept lit continuously during the focusing operation.

When the mirror 34 is rotated by a motor (not shown) in the direction of the arrow D or the opposite direction about the rotation axis 33 of the rotation mirror 34, the light beam emitted from the light emitting diode 1 is transmitted to the rotation axis 33 of the rotation mirror 34. When facing the portion θ ₂ , the mirror 3
4, passes through the opposing holes of the two-hole diaphragm 4, and is reflected by the half mirror 5 to form the imaging lens 6 and one small part of the diaphragm 7, as in the first embodiment described above. The eye 10 to be examined is irradiated through the hole 7c, the perforated portion of the perforated mirror 8, and the objective lens 9.

At this time, the light beam emitted from the other light emitting diode 2 is transmitted through the mirror θ of the rotating mirror 34.
Since the part ₂ is to be irradiated and is not facing the direction of the half mirror 5, the light emitting diode 1
Only the light beam emitted from the eye illuminates the eye to be examined.

As the rotation of the rotating mirror 34 progresses, the luminous flux emitted from the light emitting diode 1 is transferred to the rotating mirror 34.
When facing θ ₁ of the mirror portion of the rotating mirror 34, the light beam emitted from the light emitting diode 2 is blocked and the light beam emitted from the light emitting diode 2 is blocked, and the light beam emitted from the light emitting diode 1 of the rotating mirror 34 is blocked.
₁ , passes through one hole of the two-hole diaphragm 4, is reflected by the half mirror 5, and is reflected by the imaging lens 6, the other small hole 7b of the diaphragm 7, the hole of the perforated mirror 8, and the objective lens. 9 and irradiates the eye 10 to be examined.

In the embodiment shown in FIG. 2, the luminous flux from light emitting diode 1 blinks three times during one rotation, and the light flux from light emitting diode 2
The phase of the light beam from the light beam is shifted by 180 degrees, and it blinks three times in the same way. Therefore, when the rotating mirror 34 is rotated 10 times per second about its rotation axis 33, the light beams emitted from the light emitting diodes 1 and 2 will each flicker at a frequency of 30 Hz.

The operations performed subsequent to the above operations are the same as those in the first embodiment described above, so the explanation thereof will be omitted.

Since the light emitting diodes 1 and 2 shown in the above explanation were treated as having the same electrical and optical characteristics, they were not specified specifically, but
As another example, a combination of different colors may be considered, such as the light emitting diode 1 emitting red light and the light emitting diode 2 emitting green light.

In this case, if the focus adjustment by the imaging lens 6 is not performed correctly, one of the two separate upper and lower spots shown in FIG. 5B or FIG. 6B will turn red and the other will turn green. It is visually recognized as blinking, and by focusing operation of the imaging lens 6, two images are displayed on the fundus as shown in FIG. 7A.
When the two light beams coincide and are in focus, the spot of the overlapping light beams shown in Figure 7B is visually recognized as a yellow spot, which is a mixture of red and green light. With the addition of the discrimination power based on color sensation, it becomes possible to visually recognize the in-focus or out-of-focus state even more clearly, and it becomes possible to further improve the detection accuracy.

FIG. 3 shows a second embodiment according to the invention,
In the figure, the same parts as those shown in FIGS. 1A, B and 2 are denoted by the same reference numerals, and the explanation thereof will be omitted.

1' and 2' are infrared emitters, replacing the light emitting diodes 1 and 2 in FIG. 1A, which have a phase difference of 180° from each other;
It is configured to blink at approximately 30Hz, and the blinking light flux passes through the pinhole 3a, passes through the hole of the two-hole diaphragm 4, and is on the optical axis _L5 that is approximately parallel to the optical axis _L1 . Imaging lens 6 along optical axis L ₅ in the direction of arrow B'
It is converged by a projection lens 27 arranged to move in conjunction with the projection lens 27, reflected by a reflecting mirror 28 in a direction along the optical axis _L6 , further reflected by a half mirror 29, and then small holes 7b, 7
c (see Figure 1B), passes through the hole in the holed mirror 8, converges at _F4 on the optical axis _L1 , and then diverges.
The objective lens 9 turns the light into almost parallel rays, and the eye to be examined 10
It passes through the cornea of the eye and reaches the fundus of the eye.

The reflected light is transmitted to the objective lens 9, the perforated portion of the perforated mirror 8, the center hole 7a of the aperture 7, and the half mirror 2.
9. The light passes through the imaging lens 6, is reflected by the movable mirror 11, passes through the wavelength selection mirror 13' along the optical axis _L2 , and reaches the imaging surface 35a of the TV camera 35.
The arrived image is observed on the TV monitor 36, and the suitability of the focus is determined as shown in FIGS. 5 to 7, as in the case of the first embodiment described above.
The enlarged image can be viewed on the TV monitor 35.

The above-mentioned half mirror 29 may be replaced with a reflective surface only in the vicinity of the light beam reflecting surface, and the rest remaining as a transmitting surface, or the wavelength selection mirror 13'
is configured to transmit infrared light and reflect visible light.

In this embodiment, as in the first embodiment, the light beam can be flickered by the mechanical chopper shown in FIG. 2.

FIG. 4 shows a third embodiment of the present invention, in which the light emitting diodes 1 and 2 are tilted at an angle α with respect to the optical axis L ₇ to illuminate the pinhole 3a of the pinhole plate 3. The two-hole diaphragm 4, the projection lens 31, and the small mirror 32 are arranged on the optical axis _L7 , and the small mirrors 32 are arranged obliquely with respect to the optical axis _L9 perpendicular to the optical axis _L7 . projection unit 3
0 is provided, and the unit 30 moves in the direction of arrow C,
It is configured to be movable along the optical axis _L9 . When the imaging lens 6 is moved in the direction of arrow B along the optical axis _L1 , the projection unit 30 is moved in the direction of arrow C in conjunction with the movement.

In this case, the light beams from the light emitting diodes 1 and 2 are reflected at the intersection point F ₇ on the small mirror 32, converged by the projection lens 26, reflected by the outer peripheral reflective surface of the perforated portion of the perforated mirror 8, and then The light converges at an intersection point _F4 on the optical axis _L1 , diverges from that point, becomes a parallel light beam by the objective lens 9, passes through the cornea of the eye 10 to be examined, and reaches the fundus. The reflected light reaches the examiner's eye 15 and the photoelectric conversion element 17 as in the case of the first embodiment, so a description thereof will be omitted.

FIG. 8 is a block diagram showing the circuit configuration of an embodiment in which the focusing operation of the present invention is automatically performed by a motor. Photoelectric conversion element 1
7, the right side light receiving section 101 and the left side light receiving section 102 are integrally configured, and the output signal from the right side light receiving section 101 is sent to the right side preamplification circuit 103, and then to the left side light receiving section 1.
The output signal from 02 is sent to the left preamplifier circuit 104.
The respective outputs are input to the discrimination circuit 105 and the differential amplifier circuit 106, and then input to the motor control circuit 107.
Until the in-focus point is reached, it is determined whether the motor rotation direction is forward or reverse, and a rotation output signal is used as an output signal to the motor M. When the in-focus point is reached, a stop signal is issued to stop the motor M. Further, the rotation signal from the motor M is fed back to the motor control circuit 107 to prevent hunting phenomenon and improve the accuracy of motor rotation.

The oscillation tuning signal generated by the oscillation tuning control circuit 109 is input to the discrimination circuit 105, motor control circuit 107, and drive circuit 108, respectively. The driving circuit 108 generates output signals of approximately 30 Hz with a 180° phase difference to drive the light emitting diodes 1 and 2 so that a flashing light beam is emitted by the light emitting diodes 1 and 2.

As is clear from the above description, the present invention projects two light fluxes having a phase difference of 180° from each other symmetrically with respect to the optical axis from a position off the optical axis onto the fundus of the eye to be examined, and then reflects the reflected light. Since it is configured to perform visual observation or photoelectric detection through an imaging lens, it is possible to easily perform focusing operations in a short time, and focusing operations can be performed not only manually but also automatically. Because it is structured like this, the effect is great.

[Brief explanation of the drawing]

1 to 8 show embodiments according to the present invention. FIG. 1A is a cross-sectional view of the main part of the first embodiment mainly consisting of an optical system, and FIG. 1B is a sectional view of the irradiation light beam. Figure 2 is a plan view of a diaphragm with two small holes through which light passes through and a central hole through which reflected light from the subject's eye passes. A side view showing the relationship and a plan view of the mirror, FIG. 3 is a sectional view of the main part of the second embodiment, FIG. 4 is a sectional view of the main part of the third embodiment, and FIGS. 5A, B, and C are A cross-sectional view of the eye to be examined showing a state in which two light beams intersect on the front side of the fundus, a plan view of the state of the visual field, a waveform diagram of the two light beams, and FIG. 6A.
B and C are a cross-sectional view of the eye to be examined, a plan view of the state of the visual field, a waveform diagram of the two light beams, and FIG.
B and C are cross-sectional views of the subject's eye showing the state in which the two light beams match in the fundus, a plan view of the field of view showing focusing, a waveform diagram showing the state in which the two light beams overlap, and Figure 8 shows the automatic focus. FIG. 2 is a block diagram of a circuit for emitting a modulating and flashing beam; 1, 2...Light emitting diode, 1', 2'...Infrared emitter, 3...Pinhole plate, 4...2 hole diaphragm,
5... Half mirror, 6... Imaging lens, 7...
Aperture, 8... Hole mirror, 9... Objective lens,
10... Eye to be examined, 13... Half mirror, 14...
...Eyepiece lens, 16...Relay lens, 17...
Photoelectric conversion element, 27... Projection lens, 30... Projection unit, 34... Rotating mirror, 35... TV
camera.

Claims (1)

[Scope of Claims] 1. A reflector disposed diagonally across the optical axis between an objective lens and an imaging lens, which irradiates illumination light to the eye to be examined through the objective lens and reflects light from the fundus of the eye. In a fundus camera that can be switched to either observation or photography using an observation optical system provided behind the imaging lens, in addition to the illumination light, two symmetrical beams with a phase difference of 180° are emitted from a position off the optical axis. The focusing state of the imaging lens is determined by projecting a beam of light that is reduced at a frequency below a certain critical flicker frequency onto the subject's eye via an aperture, and visually observing or photoelectrically detecting the reflected light through the imaging lens. A focus detection device for a fundus camera, characterized in that it is configured to perform focus detection. 2. The focus detection device for a fundus camera according to claim 1, wherein one of the two light beams is red light and the other one is green light. 3. The light flux is infrared light, and a TV camera is provided behind the imaging lens to receive the infrared light reflected from the eye to be examined, and the eye is observed on a TV monitor. A focus detection device for the fundus camera described in 2. 4. A patent characterized in that the luminous flux is projected onto the subject's eye through an objective lens via a diaphragm using a partial reflecting mirror or a semi-transparent mirror disposed obliquely across the optical axis behind the imaging lens. Claim 1
A focus detection device for a fundus camera according to any one of items 1 to 3. 5. A partial reflecting mirror or a semi-transparent mirror installed diagonally across the optical axis between the objective lens and the imaging lens is configured to project the light flux through the objective lens and onto the subject's eye via a diaphragm. A focus detection device in a fundus camera according to any one of claims 1 to 3. 6. The light flux is configured to be projected from the illumination light side to the eye to be examined through the objective lens by a reflecting mirror obliquely installed between the objective lens and the imaging lens across the optical axis. A focus detection device for a fundus camera according to any one of claims 1 to 3.