Ophthalmic apparatus

An ophthalmic apparatus for measuring and operating a subject's eye, which includes an ophthalmic operation apparatus, provides an alignment mechanism including a slit image projecting system for projecting an alignment slit image on the subject's eye, a slit image observing system for observing the slit image projected on the subject's eye, wherein a plurality of the slit image projecting system are arranged so as to project the slit image from at least two directions on the subject's eye, the directions putting the optical axis of the slit image observing system therebetween, and an alignment moving device by which an apparatus body including the slit image observing system is moved relatively to the subject's eye in three-dimensional direction.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to an ophthalmic apparatus, and more 
particularly to an alignment mechanism of the ophthalmic apparatus for 
aligning an operation apparatus and a measuring apparatus with a patient's 
eye. 
2. Description of Related Art 
FIG. 1 shows a typical alignment mechanism used in a known ophthalmic 
operation apparatus and a known measuring apparatus. 
In the alignment mechanism, which provides a light source 2 arranged at the 
oblique above position of an examinee's eye 1, lenses 3, 4 and a light 
detector 5, a light beam emitted from the light source 2 is condensed 
through the lens 3 on an apex of cornea of the examinee's eye 1, and 
reflected thereon. The reflected light is again focused through the lens 4 
toward the light detector 5 arranged at a focus position of the lens 4, 
and detected thereby. 
This alignment method, although being able to obtain satisfactory alignment 
precision thereby, has only a very limited detectable scope. Accordingly, 
the alignment light may be focused out of the light detector 5 if the 
position (of the apparatus) is even slightly dislocated. 
In addition to the above problem, this alignment method needs a display 
means to display a detected result by the light detector 5 on an observing 
system including a microscope or a TV monitor or the like, whereby the 
alignment mechanism may become complicated. 
Another alignment mechanism shown in FIG. 2 has also been proposed. In the 
alignment mechanism, lasers 6a and 6b are arranged respectively at right 
and left oblique above positions of an examinee's eye 1. The respective 
laser beams emitted from the two lasers 6a and 6b irradiate the examinee's 
eye 1 and form laser spots thereon, the laser spots are then observed 
through an observing system 7 arranged on the optical axis of the 
examinee's eye 1. Thus, the alignment is adjusted so as to correspond the 
laser spots each other on the examinee's eye 1, namely, the focus position 
(alignment) is correct when laser spots by the two lasers 6a and 6b become 
one laser spot 8 as shown in FIG. 3(a), the examinee's eye 1 is too near 
than a proper focus position when two laser spots 8a and 8b are separate 
spots as shown in FIG. 3(b), and the examinee's eye 1 is too far than a 
proper focus position when two laser spots 8a and 8b are changed places 
with each other as shown in FIG. 3(c). 
The alignment method needs corresponding two small laser spots formed on 
the examinee's eye, however, the reflected plane on which the light beams 
are reflected toward the observing system is the curved cornea surface of 
the examinee's eye. Accordingly the small spots are even difficult to 
observe. And further, when the examinee's eye 1 is positioned either too 
near (b) or far (c) than a proper focus position, the operator may observe 
the two spots in a same view, thereby can not judge whether a distance 
between the examinee's eye and the apparatus is too short or long to 
determine an alignment direction to which the apparatus should be moved. 
SUMMARY OF THE INVENTION 
The present invention has been made in view of the above circumstances and 
has an object to overcome the above problems and to provide an ophthalmic 
apparatus provided with an alignment mechanism capable of easily aligning 
the apparatus with the examinee's eye by a simple construction. 
Additional objects and advantages of the invention will be set forth in 
part in the description which follows and in part will be obvious from the 
description, or may be learned by practice of the invention. The objects 
and advantages of the invention may be realized and attained by means of 
the instrumentalities and combinations particularly pointed out in the 
appended claims. 
To achieve the objects and in accordance with the purpose of the invention, 
as embodied and broadly described herein, an ophthalmic apparatus of this 
invention comprises an alignment mechanism including a slit image 
projecting system for projecting an alignment slit image on the subject's 
eye, a slit image observing system for observing the slit image projected 
on the subject's eye, wherein a plurality of the slit image projecting 
system are arranged so as to project the slit image from at least two 
directions on the subject's eye, the directions putting the optical axis 
of the slit image observing system therebetween, and an alignment moving 
means for moving an apparatus body comprising the slit image observing 
system, relatively to the subject's eye, in three-dimensional direction. 
In the second aspect of the present invention, an ophthalmic operation 
apparatus comprises an operation laser source, an operation laser optical 
system for projecting an operation laser beam emitting from the laser 
source on the patient's eye, a pair of slit image projecting systems, each 
for projecting an alignment slit image on the patient's eye, a slit image 
observing system for observing a slit image projected on the patient's eye 
through the slit image projecting system, and an alignment moving means 
for moving the operation laser optical system, relative to the patient's 
eye, in three-dimensional direction, based on the slit image on the 
patient's eye observed through the slit image observing system. 
According to the present invention, an alignment for the apex of a cornea 
can be easily achieved with a simple mechanism in which two slit light 
beams are projected from oblique above positions on the cornea and the 
operator adjusts the alignment based on the slit image observed by the 
observing system.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
A detailed description of one preferred embodiment of an ophthalmic 
apparatus embodying the present invention will now be given referring to 
the accompanying drawings. 
In FIG. 4, a cornea operation apparatus for correcting refractive error of 
a patient's eye is shown. The laser transmitting optical system of the 
apparatus has little relation to the present invention, accordingly the 
detail description thereof, having been mentioned in Japanese Patent Appl. 
No. HEI 2(1990)-416767 which corresponds to U.S. Appl. No. 812,819, is 
omitted in this specification. The only brief explanation thereof will be 
here described referring to FIG. 5. 
As shown in FIG. 5, an optical system includes an ablating laser source 20 
(preferably an excimer laser), plane mirrors 21, 22, 24, 25 and 27 for 
deflecting the laser beam emerging from the laser source 20, an aperture 
23 located in the optical path between the mirrors 21, 22, 24, 25 and a 
projection lens 26, the projection lens 26 which is arranged in the 
optical path and for projecting the laser beam passing through the 
aperture 23 to a cornea of the examinee's eye 1 via mirror 27. The 
aperture 23 has a variable diameter which is changed by an aperture drive 
motor 29 in accordance with an instruction signal of a control device 28. 
The projection lens 26 is conjugated with the aperture 23 and the cornea of 
the examinee's eye 1, and the laser beam passing through the aperture 23 
in a confined space is projected on the surface of the cornea through the 
lens 26 such that an ablation area of the cornea is restricted. Then, the 
laser beam passing through the projection lens 26 is deflected toward the 
examinee's eye 1 by the mirror 27. 
The examinee's eye 1 is provided at a position having a predetermined 
positioning relation for the apparatus. 
In an alignment driving mechanism of the optical system of the cornea 
operation apparatus shown in FIG. 5, the optical system including the 
aperture 23, the plane mirrors 24, 25, 27 and the projection lens 26 is 
movable parallel to the x-axis by a driving motor 30, the above optical 
system including further the plane mirror 22 is movable parallel to the 
y-axis by a driving motor 31. In this moving operation, the projection 
lens 26 keeps a conjugating relation with the aperture 23 and the 
examinee's eye 1. 
The optical system including the plane mirror 25, the projection lens 26 
and the plane mirror 27 is movable parallel to the z-axis by a driving 
motor 32, then the aperture 23 is moved according to the movement of the 
optical system by a link device 33 so that the projection lens 26 may keep 
as always a conjugating relation with the aperture 23 and the eye 1. 
FIG. 6 shows an optical arrangement of an alignment light projecting system 
and an alignment observing system provided in relation with the alignment 
driving mechanism shown in FIG. 5. 
The alignment observing system provides a microscope 10 for observing the 
cornea 11 of the examinee's eye. 
The alignment light projecting optical systems 12a and 12b are disposed 
symmetrically at both sides of the optical axis of the microscope 10, 
which are provided respectively with illumination lamps 13a, 13b, 
condenser lenses 14a, 14b for condensing the light emerging from the 
illumination lamps 13a, 13b, linear slit diaphragms 15a, 15b, and 
projection lenses 16a, 16b for projecting the light beam passing through 
the slit diaphragms 15a, 15b to the cornea 11. The projection lenses 16a, 
16b are conjugated with the respective slit diaphragms 15a, 15b and the 
cornea 11. 
The light beam passing through the slit diaphragm 15a in the slit space is 
projected on the surface of the cornea 11 such that the slit image by the 
slit diaphragm 15a is always formed at a focus point on the optical axis 
of the microscope 10. The light beam passing through the slit diaphragm 
15b is similarly projected to the cornea 11. 
The alignment operation with the apparatus including the above optical 
system will be explained as below. 
For the alignment in the optical axis direction, the slit light beam 
emerging from the slit projecting optical system 12a (left side system in 
FIG. 6), although substantially passes through the cornea 11, is partially 
diffused by the cornea 11 toward the microscope 10, and thereby a slit 
line image 17a of circular arc shape is observed through the microscope 10 
as shown in FIGS. 7(a) through 7(c). Similarly, the light beam emerging 
from the slit projecting optical system 12b (right side system in FIG. 6) 
is observed as a slit line image 17b of circular arc shaped through the 
microscope 10. 
When the apex of the cornea 11 is placed at a focus position of the 
microscope 10, as shown in FIG. 7(a), the slit line image 17a and the slit 
line image 17b partially overlap each other at the apical point of the 
cornea. But then, when the cornea 11 is positioned below the position 
shown in FIG. 6, that is, far from the microscope 10 than the focus 
position of the microscope 10, two slit line images 17a and 17b are apart 
from each other as shown in FIG. 7(b). When the cornea 11 is positioned 
above the position shown in FIG. 6, that is, near the microscope 10 than 
the position on which the microscope 10 is focused, two slit line images 
17a and 17b intersect as shown in FIG. 7(c). 
Accordingly, when the two slit line images 17a and 17b are observed as FIG. 
7(b), the apparatus is moved downward (to the z-axis direction in FIG. 5) 
or the cornea 11 upward so that a distance between the microscope 10 and 
the cornea 11 is made shorter, and, when the two slit line images 17a and 
17b are observed as FIG. 7(c), the apparatus 10 is moved upward or the 
cornea 11 downward so that the distance is made longer. Thus, if adjusting 
the distance between the apparatus 10 and the cornea 11 such that the two 
slit line images 17a and 17b may be observed as FIG. 7(a), the alignment 
to focus the microscope 10 on the cornea 11 is accordingly completed. 
Next, in the alignment operation in the longitudinal and lateral 
directions, the two slit line images 17a and 17b are observed as in either 
FIG. 8(a) or FIG. 8(b) when the apex of the cornea is dislocated in the 
longitudinal direction of the visual field, and the two slit images 17a 
and 17b are observed as in either FIG. 9(a) and FIG. 9(b) when dislocated 
in the lateral direction. For this alignment, the cornea 11 and the 
optical axis of the microscope 10 are relatively moved so that the two 
slit line images 17a and 17b are placed at respective correct positions in 
the visual field as shown in FIG. 7(a). 
More specifically, when the apex of cornea is dislocated in the 
longitudinal direction of the visual field, the apparatus is moved 
parallel to the y-axis of FIG. 5 or the cornea is moved in the 
longitudinal direction thereof. When the apex of cornea is dislocated in 
the lateral direction of the visual field, the apparatus is moved parallel 
to the x-axis of FIG. 5 or the cornea is moved in the lateral direction 
thereof. 
The present invention may be embodied in other specific forms without 
departing from the spirit or essential characteristics thereof. For 
instance, although the slit diaphragms 15a, 15b each provides a linear 
slit therein in the above embodiment, at least either slit diaphragm may 
further provide an across line in the center, referring to FIG. 10, which 
make the recognition which portion should be adjusted to a center of the 
visual field clearly and accordingly the alignment between the visual 
field and the cornea easily. Additionally, if the observing system is 
given a reticle indicating a position at which the across line should be 
placed, the alignment is made more easily. 
If, in addition to two linear slit line images, one or more slit line 
images are provided so as to overlap each other at a point as shown in 
FIGS. 11(a) and 11(b), the alignment can be easy achieved. 
And further, the slit diaphragm in the present invention can have various 
slit forms without limited to a linear slit form. 
The foregoing description of the preferred embodiment of the invention has 
been presented for purposes of illustration and description. It is not 
intended to be exhaustive or to limit the invention to the precise form 
disclosed, and modifications and variations are possible in light of the 
above teachings or may be acquired from practice of the invention. The 
embodiment chosen and described in order to explain the principles of the 
invention and its practical application to enable one skilled in the art 
to utilize the invention in various embodiments and with various 
modifications as are suited to the particular use contemplated. It is 
intended that the scope of the invention be defined by the claims appended 
hereto, and their equivalents.