JPH05253188A - Optic axial length measuring instrument - Google Patents

Abstract

PURPOSE:To provide the optic axial length measuring instrument which corrects the refracting power of an eye to be examined and can correctly focus luminous fluxes for measurement to the eye ground. CONSTITUTION:This measuring instrument has an optical system 3 for irradiation which is constituted to focus the luminous fluxes for measurement and to irradiate the eye ground 28 with the focused flux, a photodetecting optical system 4 which has a diaphragm installed in the position approximately conjugate with the eye ground 28 in order to remove the luminous fluxes reflected from parts exclusive of the eye ground and introduces the luminous fluxes reflected from the eye ground 28 to a photodetecting part 14 and a visual index projecting member 19 for judging the focusing state in order to judge the state of the luminous fluxes for measurement focused to the eye ground 28. The instrument has a visual index projecting optical system 15 for judging the focusing state which projects the visual index for judging the focusing state to the eye ground 28 and an optical member 8 for correcting the refracting power of the eye to be inspected which displaces the focusing point of the luminous fluxes for measurement in correspondence to the movement of the visual index for judging the focusing state according to the refracting power of the eye 2 to be inspected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an axial length measuring device for optically measuring the axial length of an eyeball.

[0002]

2. Description of the Related Art As an axial length measuring device, a device for optically measuring the axial length from the apex of the cornea to the fundus of the eye is known.
As this type of axial length measuring device, a device utilizing an interference phenomenon and a device utilizing a phase difference are known. When measuring the fundus position, any of the eye axial length measuring devices irradiates the fundus with a measurement light beam and observes a light beam reflected from the fundus.

Here, if the quantity of light reflected from the fundus of the eye is weak, the measurement accuracy deteriorates. In order to increase the amount of the reflected light flux, it is possible to increase the amount of the measurement light beam with which the eye to be inspected is irradiated.However, the light amount of the measurement light beam with which the eye is inspected has an upper limit from the viewpoint of safety. In the axial length measuring device, by focusing and irradiating the measurement light beam on the fundus,
The amount of the reflected light flux is increased. When the measurement light beam is guided to the fundus, it is scattered by the cornea and the crystalline lens, and the measurement light beam scattered by the fundus is scattered by the crystalline lens when it is guided to the outside as a reflected light beam, and the reflected light beam from the fundus is received by the light receiving unit. A scattered light flux from the crystalline lens, cornea, and other components of the visual system enters the light receiving optical system that guides it.In particular, when measuring the axial length of a patient such as a cataract patient, the measured luminous flux and the reflected luminous flux due to opacity of the crystalline lens. Since it is largely scattered to pass through the crystalline lens, the light amount of the reflected light flux from the fundus becomes weak, so the reflected light flux from the fundus is guided to the light receiving part at a position substantially conjugate with the fundus in the light receiving optical system, and the light from other than the fundus. A diaphragm for removing the reflected light flux is provided to extract the reflected light flux from the fundus as much as possible.

[0004]

By the way, in order to increase the light quantity of the reflected light flux as much as possible, it is desired to correct the refractive power of the eye to be inspected and focus the measurement light flux properly on the fundus.
Since the reflected light flux is weak, it is not easy to determine whether or not the measurement light flux is focused on the fundus, and it is difficult to increase the amount of the reflected light flux.

The present invention has been made in view of the above circumstances. An object of the present invention is to correct the refractive power of the eye to be inspected and to appropriately focus the measurement light beam on the fundus of the eye. It is to provide a length measuring device.

[0006]

In order to achieve the above object, an axial length measuring apparatus according to claim 1 of the present invention comprises an irradiation optical system for focusing and irradiating a measurement light beam on the fundus of the eye. A light receiving optical system that is installed at a position substantially conjugate with the fundus and removes a reflected light beam from a portion other than the fundus, guides a reflected light beam from the fundus to a light receiving unit, and a focusing of the measurement light beam to the fundus. Having a focusing state determination index projection member for determining the state, a focusing state determination index projection optical system for projecting a focusing state determination index on the fundus, and the refractive power of the eye to be inspected provided in the irradiation optical system. And an optical member for correcting refractive power of the eye to be inspected for displacing the focus point of the measurement light beam in response to the movement of the focus state determination index.

[0007]

[Operation] According to the axial length measuring device according to claim 1,
The irradiation optical system focuses and irradiates the measurement light beam on the fundus of the eye to be inspected. On the other hand, the focused state determination index projection optical system projects a focused state determination index for determining the focused state of the measurement light beam on the fundus onto the fundus. The subject or the examiner determines whether or not the measurement light beam is properly focused on the fundus based on the focus state determination index. When it is determined that the measurement light flux is not properly focused on the fundus, the refractive power correction optical member is moved in the direction in which the focus point of the measurement light flux is properly positioned on the fundus while looking at the focusing state determination index. With this, when the focusing state determination index is set in a state in which it can be viewed well, the focusing point of the measurement light beam is located at the fundus.

[0008]

1 is an external view of an axial length measuring device according to a first embodiment of the present invention, and FIGS. 2 to 4 are optical diagrams thereof.

2 to 4, reference numeral 1 is a measuring optical system for measuring the axial length of the eye 2 to be inspected. The measurement optical system 1 includes an irradiation optical system 3 and a light receiving optical system 4. Measuring optical system 1
Is provided with a reflection prism 5, relay lenses 6 and 7, a refractive power correction lens 8 and an objective lens 9. These optical elements 5 to 9 are shared by the irradiation optical system 3 and the light receiving optical system 4. The measurement optical system 1 is aligned by a known optical means such that the optical axis O of the measurement optical system 1 is located at the corneal vertex M of the eye 2 to be inspected, and the distance from the corneal vertex M in the optical axis direction (working distance). ) W is set. The position of the point at the working distance W from the corneal apex M is set as the reference position K.

The irradiation optical system 3 has a laser light source 10 and a condenser lens 11 which have almost no coherence. The laser light source 10 emits a measurement light beam P in the infrared wavelength range. The measurement light beam P is intensity-modulated by a modulator (not shown).
As shown in FIG. 2, the measurement light beam P is reflected by the reflecting surface of the reflecting prism 5.
It is reflected by 5a, guided to the refractive power correction lens 8 via relay lenses 6 and 7, and is focused and irradiated on the cornea C of the eye 2 to be examined by the refractive power correction lens 8 and the objective lens 9.

The light receiving optical system 4 has a diaphragm member 12, a condenser lens 13, and a light receiver 14. The measurement light beam P reflected by the cornea C is reflected light beam R as a reflected light beam R via the objective lens 9, the refractive power correction lens 8, and the relay lenses 7 and 6.
Is reflected by the reflecting surface 5b, passes through the diaphragm member 12, and is guided to the light receiver 14. The diaphragm member 12 is optically conjugate with the corneal vertex M with respect to the objective lens 9 and the refractive power correction lens 8 when the refractive power correction lens 8 is positioned so that the measurement light beam P is focused on the corneal vertex M. The reflected light flux other than the cornea C is blocked from reaching the light receiver 14. The light reception output of the light receiver 14 is input to a calculation means (not shown).

The calculating means counts the reference pulses from the emission of the modulated measuring light beam P to the reflection of the corneal apex M until the light is received by the light receiver 14. As a result, the time (phase difference) from the emission of the measurement light beam P to the light reception by the light receiver 14 is obtained, and the distance from the reference position K to the corneal apex M and the time and the modulation frequency are constant. Therefore, the distance from the corneal apex M to the reference position K can be obtained (for signal processing and arithmetic means for obtaining the distance from the reference position K to the corneal apex M by this phase difference, Japanese Patent Application No. 1-251286). See).

When the optical axis O is aligned with the eye 2 to be inspected, a focusing state determination index described later is used as a fixation target.

The measurement optical system 1 has a focusing state determination index projection optical system 15. The focusing state determination index projection optical system 15 includes a light source 16, a condenser lens 17, a split prism 18, a focusing state determination index projection optical member 19, a relay lens 20, and a pupil diaphragm 21. The light source 16 emits a visible light beam Q. The visible light flux Q is condensed by the condenser lens 17 and guided to the split prism 18. The split prism 18 is composed of a prism 18a and a prism 18b as shown in FIG. The prism 18a has a function of deflecting the visible light beam Q toward the left side. The prism 18b has a function of deflecting the visible light beam Q toward the right side. In FIG. 3, the visible light beam Q deflected to the left is shown by a solid line, and the visible light beam Q deflected to the right is shown by a broken line. Both visible light beams Q are guided to the focused state determination index projection optical member 19. The focusing state determination index projection optical member 19 has a rectangular opening 22 as shown in FIG.
Have.

The visible light beam Q deflected to the left has a rectangular aperture.
After passing through 22, it is guided to the upper half of the relay lens 20 and forms an upper focused state determination index projection light beam Q ′. The visible light beam Q deflected to the right passes through the rectangular aperture 22 and is guided to the lower half of the relay lens 20 to form a lower focusing state determination index projection beam Q ″. Upper focusing state determination index projection beam Q ′
And the lower focused state determination index projection light beam Q ″ are refracted and guided to the pupil diaphragm 21. The pupil diaphragm 21 is provided at a position optically conjugate with the pupil 23 with respect to the objective lens 9.
Serves to prevent the harmful reflected light flux from entering the light receiving optical system 4. As shown in FIG. 7, the pupil stop 21 is an upper aperture that allows the upper focusing state determination index projection light beam Q'to pass.
24 and a lower opening 25 that allows passage of the lower focusing state determination index projection light beam Q ″. The respective focusing state determination index projection light beams Q ′ and Q ″ pass through the pupil stop 21 and then the dichroic mirror 26. Be led to. The dichroic mirror 26 is provided between the objective lens 9 and the refractive power correction lens 8 and plays a role of reflecting light in the visible wavelength range and transmitting light in the infrared wavelength range.

The focused state determination index projection light beams Q'and Q "are focused at a point Z on the optical axis O. The objective lens 9 has a focal point at the point Z. The focused state determination index projection light beams Q'and Q" are objectives. It is converted into a parallel light flux by the lens 9 and guided to the eye 2 to be inspected,
It is refracted by the crystalline lens 27 and guided to the fundus 28 to form a focusing state determination index described later.

The focus state determination index projection optical member 19 is movable along the optical axis O'of the focus state determination index projection optical system 15. The focusing state determination index projection optical member 19 is connected to the refractive power correction lens 8. The fundus 28 and the focusing state determination index projection optical member 19 are located at an optically conjugate position with respect to the objective lens 2 when the focusing state determination index projection optical member 19 is at the reference position and the eye 2 is an emmetropic eye. Yes, as shown in FIG. 10, the upper focusing state determination index 29 and the lower focusing state determination index
An image is formed on the fundus 28 in a state of being in focus and in alignment with 30. When detecting the position of the apex M of the cornea,
Focusing state determination index projection optical member 19 and refractive power correction lens 8
Focusing state determination index projection optical member
Fix 19 at the reference position and do not use the focusing state judgment index.

When the eye 2 to be inspected is nearsighted, as shown in FIG. 8, when the focusing state determination index projection optical member 19 is at the reference position, the eye 2 will be in focus and matched on the front side of the fundus 28. When the optometry 2 is hyperopia, when the focusing state determination index projection optical member 19 is at the reference position as shown in FIG.
In 28, the upper focusing state determination index 29 and the lower focusing state determination index 30 are separated as shown in FIGS. 11 and 12, and the subject separates the focusing state determination indexes 29 and 30 from each other. You can see the separation. In the case of a cataract patient, it is difficult to clearly see the focusing state determination indexes 29 and 30 due to the opacity of the lens, but this separation / non-separation can be confirmed. The refractive power correction lens 8 is movable along the optical axis O. The focusing state determination index projection optical member 19 is moved along the optical axis O ′ in conjunction with the movement of the refractive power correction lens 8 when detecting the position of the fundus 28.

A dichroic mirror 31 is provided between the refractive power correction lens 8 and the relay lens 7. The dichroic mirror 31 plays a role of reflecting light in the visible wavelength range and transmitting light in the infrared wavelength range. The reflected light flux forming the image of the fundus 28 and the focus state determination indexes 29, 30 is reflected by the dichroic mirror 31, guided to the imaging lens 32, and imaged on the image receiving element 33. The output of the image receiving element 33 is processed into a video signal and input to the monitor 34. The monitor 34 and the fundus image 35 together with the focusing state determination indicators 29, 30
Is displayed.

The refractive power correction lens 8 is moved along the optical axis O, and is moved from the position where the measurement light beam P is focused at the point Z'to the position where it is focused at the point Z. Then, the measurement light beam P is emitted as a parallel light beam from the objective lens 9 toward the subject's eye 2 as shown in FIG. When the eye 2 to be inspected is an emmetropic eye, the focal point of the measurement light beam is located at the fundus 28. When the eye 2 to be inspected is nearsighted, the focal point of the measurement light beam P is located on the front side of the fundus 28. In this case, the subject moves the refractive power correction lens 8 so that the point Z moves in the direction away from the objective lens 9. The knob 36 shown in FIG. 1 is used to move the refractive power correction lens 8. Then, the focused state determination indexes 29 and 30 are changed from the split visible state to the consistent visible state. On the other hand, the measurement light beam P becomes a divergent light beam when emitted from the objective lens 9 toward the eye 2 to be inspected, so that the focal point of the measurement light beam P is located at the fundus 28.

When the eye 2 to be inspected is hyperopic, the focal point of the measurement light beam P is located on the inner side of the fundus 28. In this case, the subject moves the refractive power correction lens 8 so that the point Z approaches the objective lens 9. Then, the focused state determination indexes 29 and 30 are changed from the split visible state to the consistent visible state. On the other hand, the measurement light beam P slightly becomes a focused light beam when it is emitted from the objective lens 9 toward the eye 2 to be inspected, so that the focus point of the measurement light beam P is located on the fundus 28.

The measurement light beam reflected by the fundus 28 is a reflected light beam and is a lens 27, an objective lens 9, a dichroic mirror 26, a refractive power correction lens 8, and a dichroic mirror 3.
1, led to the prism 5 via the relay lenses 7 and 6,
It is reflected by the reflecting surface 5b and guided to the diaphragm member 12. Fundus
When detecting the reflected light flux from 28, the fundus 28 and the diaphragm member 12 are substantially conjugate with respect to the objective lens 9 and the refractive power correction lens 8. The diaphragm member 12 removes the reflected light flux from other than the fundus 28 and guides the reflected light flux from the fundus 28 to the light receiver 14. The distance from the reference position K to the fundus 28 is obtained based on the light reception output of the light receiver 14, and the axial length is obtained from the distance from the reference position K to the corneal vertex M and the distance from the reference position K to the fundus 28. Be done.

In the case of mild cataract patients, the examiner operates the knob 36 to move the refractive power correction lens 8 while checking the focusing index 29, 30 of the monitor 34, and the fundus The focal point of the measurement light beam P can be located at 28.

FIG. 13 shows a structure in which the focusing state determination index projection optical member 19 and the refractive power correction lens 8 are automatically driven, and the operation unit 37 has switches 38 to 41. Switch 38
Has a function of turning on the light source 16, and the switch 39 has a function of turning on the laser light source 10. The output of the operation unit 37 is input to the control calculation unit 42. The control calculation unit 42 is the laser light source 1
0, ON / OFF control of the light source 16, a function of calculating the axial length based on the output of the light receiver 14, a focusing state determination index projection optical member
It has a function of performing drive control of 19 and drive control of the refractive power correction lens 8. 43 is the focusing state determination index projection optical member
Focusing state determination index projection optical member driving unit for driving 19
Is a refractive power correction lens drive unit for driving the refractive power correction lens 8. When the switch 40 is operated, the focusing state determination index projection optical member drive unit 43 and the refractive power correction lens drive unit 44
Is driven, and the focusing state determination index projection optical member 19 is driven correspondingly with the movement of the refractive power correction lens 8.
When the subject operates the response unit 45, the refractive power correction lens 8 and the focusing state determination index projection optical member 19 are stopped based on the response.

Although the embodiment has been described above, the present invention is not limited to this, and includes the following.

In these embodiments, the back side of the focusing state determination index projection optical member 19 is illuminated to form the focusing state determination index on the fundus 28. The focusing state determination index may be formed on the fundus 28.

Further, even if the focus state determination index is blurred, a mark visible to the subject is provided in the center of the focus state determination index, and when the subject gazes at this mark, the measurement light flux P is covered. If the measurement optical system 1 and the focusing state determination index projection optical system 15 are coaxially arranged so as to coincide with the visual axis of the optometry 2, the axial length can be measured more accurately.

Further, the focus state determination index may not be based on the split image.

In addition, the focusing state determination index projection optical system of the eye axial length measuring apparatus according to the present invention is disclosed in Japanese Patent Application No. 1465 of 1990.
No. 31 (Title of invention; Length measuring device; Application date June 4, 1990)
1), the optical system shown in FIG. 1 and FIG.
Optical system shown in FIGS. 1 and 9 of 657 (name of invention; axial length measuring method and axial length measuring device; filing date: April 15, 1991), 1991 patent application No. 90877 ( Figure of invention title; axial length measurement method and device; filing date April 22, 1991)
It can also be applied to the interference optical system shown in 11.

[0030]

According to the axial length measuring apparatus of the first aspect, it is possible to correct the refractive power of the eye to be inspected and properly focus the measurement light beam on the fundus.

[Brief description of drawings]

FIG. 1 is an external view of an axial length measuring device according to the present invention.

FIG. 2 is an optical diagram for detecting the position of a corneal apex using the apparatus for measuring an axial length according to the present invention.

FIG. 3 is an optical diagram for explaining a state in which a focusing state determination index is projected on the fundus using the axial length measuring device according to the present invention.

FIG. 4 is an optical diagram for detecting the position of the fundus of the eye by using the axial length measuring device according to the present invention.

FIG. 5 is a perspective view of a split prism.

FIG. 6 is a plan view of a focusing state determination index projection optical member.

FIG. 7 is a plan view of a pupil stop.

FIG. 8 is a diagram showing an image formation point of a focus state determination index when the eye to be inspected is myopic.

FIG. 9 is a diagram showing an imaging point of a focus state determination index when the eye to be inspected is hyperopic.

FIG. 10 is an explanatory diagram showing a matching state of a focusing state determination index.

FIG. 11 is a diagram showing a separation state of a focus state determination index when the eye to be inspected has myopia.

FIG. 12 is a diagram showing a separated state of a focus state determination index when the eye to be inspected is hyperopic.

FIG. 13 is a control circuit diagram for controlling the refractive power correction lens and the focusing state determination index projection optical member.

[Explanation of symbols]

 2 Eye to be inspected 3 Irradiation optical system 4 Light receiving optical system 15 Focusing state judgment index projection optical system 28 Fundus P Measurement luminous flux

Claims (3)

[Claims] 1. An irradiation optical system for converging and irradiating a measurement light beam to the fundus, and a diaphragm installed at a position substantially conjugate with the fundus for removing a light beam reflected from other than the fundus. A light receiving optical system that guides the reflected light flux to a light receiving unit, and a focusing state determination index projection member for determining the focusing state of the measurement light beam to the fundus, and a focusing state determination index that projects onto the fundus. A state determination index projection optical system, and an eye to be inspected refractive power correction optical which is provided in the irradiation optical system and displaces a focal point of the measurement light beam in response to movement of the focusing state determination index according to the refractive power of the eye to be inspected. An axial length measuring device comprising: a member; 2. A driving means for driving the focusing state determination index projection member and the refractive power correction optical member, wherein the subject is capable of satisfactorily visually recognizing the focusing state determination index. The eye axial length measuring device according to claim 1, wherein driving of the focused state determination index projection member and the refractive power correction optical member is stopped. 3. A fundus image observation optical system provided in the middle of the light receiving optical system for observing a fundus image including the focus state determination index, the focus state determination index projection member, and the refractive power correction optical member. A driving unit that drives the focusing state determination index projection member and the refractive power correction optical member by determining whether or not the subject can visually recognize the focusing state determination index in good condition. The axial length measuring device according to claim 1, which is stopped.