Apparatus for measuring curvatures of a spherical surface

An actuating means for an ophthalmoscopic instrument wherein the adjustment knobs and handle are relatively located such that the knobs can be conveniently actuated by fingers of a hand gripping the handle.

The present invention relates to an apparatus for measuring curvature of 
spherical surface. More particularly, the present invention pertains to 
scale projecting means for such curvature measuring apparatus. The present 
invention is particularly applicable an apparatus for measuring the 
curvature of an eyeball of a patient or of a contact lens. 
An apparatus for measuring the curvature of an eyeball is in general 
designed to observe through an observing optical system a target image 
projected on the surface of the cornea. The observing optical system 
generally comprises a vertical deflection prism and a horizontal 
deflection prism so that the light bundle which has been reflected at the 
cornea surface is deflected in both vertical and horizontal directions 
before it is focused on an image plane. The deflecting prisms are movable 
along the optical axis of the apparatus for placing the deflected target 
images at predetermined positions with respect to an undeflected target 
image which has not been passed through any of the deflecting prisms. The 
positions of the deflecting prisms are then indicated in terms of the 
curvature or radius of curvature. 
In conventional apparatus, separate scale projecting optical systems have 
been provided for the vertical and horizontal deflecting prisms so that 
two different scales are projected on the same plane. In the conventional 
apparatus, however, it has been quite difficult to project the two scales 
with substantially the same brightness, substantially the same 
magnification and substantially the same focus. Further, it has also been 
difficult to eliminate any inclination between the two scales. 
The present invention has therefore an object to eliminate the above 
problems and provide a structure which can readily be assembled and 
adjusted. 
Another object of the present invention is to provide a curvature measuring 
apparatus which is easy to handle. 
According to the present invention, the above and other objects can be 
accomplished by a curvature measuring apparatus comprising a target 
projecting system for projecting a target image on a spherical surface, an 
observing optical system including an image plane, a first lens system for 
focusing a light bundle as reflected at the spherical surface on the image 
plane and a second lens system for observing an image produced on the 
image plane, said observing optical system further including first 
deflecting means for deflecting the light bundle from the spherical 
surface in a first direction to produce a first deflected image and second 
deflecting means for deflecting the light bundle in a second direction 
which is perpendicular to the first direction to produce a second 
deflected image, said first and second deflecting means being movable 
along an optical axis of the observing optical system, adjusting means for 
moving the first and second deflected means along the optical axis so that 
said first and second deflected images are placed at predetermined 
positions with respect to an undeflected image, scale means including a 
first and second scales which are disposed adjacent to each other and 
adapted for designating the positions of the first and second deflecting 
means, respectively, scale projecting means for projecting said scale 
means, said scale projecting means including a single source of 
illumination for illuminating the first and second scales simultaneously 
and a scale projecting optical system for projecting light bundles from 
the scales. 
Thus, the present invention is characterized by the fact that the scales 
for the first and second deflecting means are disposed adjacent to each 
other and illuminated by the same light source. In a preferable 
arrangement, the scales are projected on the image plane where the target 
images are projected. The scales may be provided on transparent plates so 
that they are projected by the lights which have passed through the 
transparent plates. 
Preferably, said apparatus includes a body having a handle extending 
downwardly from a lower surface thereof, and said adjusting means includes 
a pair of adjusting knobs located one on each side of the handle, said 
adjusting knobs being provided at free ends thereof with means for 
removably attaching an extension knob, said extension knob being attached 
to one of said adjusting knobs. The arrangement provides convenient means 
for actuation by a single hand. For example, when it is desired to actuate 
by a right hand, the extension knob may be attached to the left side 
adjusting knob. On the other hand, for an actuation by a left hand, the 
extension knob may be attached to the right side adjusting knob.

Referring now to the drawings, particularly to FIGS. 1 and 2, the optical 
system shown therein includes a target projecting system A, an observing 
optical system B and a scale projecting system C. The target projecting 
system A comprises an illuminating light source 1, a condensing mirror 2 
provided at the backside of the light source 1 and a target plate 3 
located in front of the light source 1. The target plate 3 has a 
transparent target pattern so that the light from the source 1 is passed 
through the target pattern to produce a target image on a patient's eye E. 
When it is desired to measure the curvature of a contact lens, it may be 
located in the place of the eye E. The target plate 3 has an aperture 3a 
at the center thereof so that the light bundle of the target image as 
reflected at the cornea surface is passed through the aperture 3a into the 
observing optical system B. 
The observing optical system B includes an objective lens 4 and an aperture 
plate 5 located behind the objective lens 4. The aperture plate 5 has four 
apertures 5a, 5b, 5c and 5d as shown in FIG. 3 so that the light from the 
lens 4 is passed through the apertures along the optical axis 6 and 
focused on an image plate 7. The image on the plate 7 is observed by an 
eye lens 8. 
Between the aperture plate 5 and the image plate 7, there are disposed a 
vertical deflecting prism 9 and a horizontal deflecting prism 10 which 
respectively correspond to the apertures 5c and 5d of the plate 5. The 
prisms 9 and 10 functions to deflect the light bundles which have passed 
through the apertures 5c and 5d respectively in vertical and horizontal 
directions. The prisms 9 and 10 are movable along the optical axis 6 so 
that any movements of the prisms 9 and 10 cause changes in positions on 
the image plate 7 of the light bundles which have passed through the 
apertures 5c and 5d. As well known in the art, the curvatures of the 
cornea surface of the eye E are measured in terms of the positions of the 
prisms 9 and 10 with respect to the images of the light bundles which have 
passed through the apertures 5a and 5b. 
The scale projecting system includes a vertical scale plate 11 connected 
with the vertical deflecting prism 9 and a horizontal scale plate 12 
connected with the horizontal deflecting prism 10. The scale plates 11 and 
12 are positioned adjacent and parallel with each other and movable in the 
longitudinal directions together with the prisms 9 and 10, respectively. 
In order to project the scales on the scale plates 11 and 12, there is 
provided a light source 13 in such a manner that the light from the light 
source 13 is directed through a filter 14, a first condenser lens 15, a 
reflecting mirror 16 and a second condenser lens 17 to the scale plates 11 
and 12. The light which has passed through the scale plates 11 and 12 are 
then reflected by a prism 18 to a projecting lens 19 which projects the 
light through prisms 20 and 21 to the image plate 7. The projected images 
of the scales are then observed through the eye lens 8. It should be noted 
that, in the above scale projecting system C, the two scales are 
illuminated by the same light source so that there will be no problem of 
adjusting the brightness and the focus of the scale images and of 
correcting the inclinations of the scale images. 
FIGS. 4 through 6 show a specific embodiment having the aforedescribed 
optical system. The eye curvature measuring apparatus shown therein 
includes a case 100 having a front end portion which houses an 
illuminating light source 101, a condensing reflector 102 and a target 
plate 103 provided with a central aperture 103a. Behind the target 
projecting system, there is provided an objective lens 104 having an 
optical axis 106 and, along the optical axis 106, there is an aperture 
plate 105 which is secured to the tube of the objective lens 104. At the 
rear portion of the case 100, there are disposed an image plate 107 and an 
eye lens 108. 
At one side of the optical axis 106, there is a vertical deflecting prism 
109 and at the other side a horizontal deflecting prism 110. The prism 109 
is carried on a support member 203 which is movable between paired guide 
rails 200 and 201 in a direction parallel with the optical axis. The 
support member 203 has a transversely extending arm 203a which carries a 
vertical deflection scale plate 111. Similarly, the prism 110 is carried 
by a support member 205 which is movable between paired guide rails 201 
and 204 in a direction parallel with the optical axis 106. The member 205 
has an arm 205a which extends transversely above the optical axis 106 and 
a horizontal scale plate 112 is attached to the arm 205a. 
As shown in FIG. 5, the case 100 is provided at a side with a cover 100a 
and inside of the cover 100a there are provided a scale projecting light 
source 113, a condenser lens 115 and a reflector 116 so that the light 
from the source 113 is reflected by the reflector 116 and then passed 
through the scale plates 111 and 112 to a prism 118 in the case 100. The 
light is then reflected by the prism 118 and passed through a projecting 
lens 119, prisms 120 and 121 to the image plate 107. 
Referring to FIG. 6, the support member 203 for the deflecting prism 109 is 
formed at its side surface with a rack 206 which is engaged with a pinion 
207 having a shaft 208 extending downwardly beyond the lower surface of 
the case 100. An adjusting knob 209 is secured to the lower end of the 
shaft 208. It will therefore be noted that a rotation of the knob 209 
causes a movement of the prism 109 in the direction parallel with the 
optical axis 106. 
Similarly, the support member 205 for the deflecting prism 110 is formed 
with a rack 210 which is engaged with a pinion 211 having a shaft 212 
extending downwardly beyond the lower surface of the case 100. An 
adjusting knob 213 similar to the knob 209 is secured to the lower end of 
the shaft 212. The adjusting knobs 209 and 213 are respectively formed 
with axially extending threaded bores 214 and, in the case shown in FIG. 
6, an extension knob 215 is threaded at its screw shaft 216 into the 
threaded bore 214 of the knob 213. Between the adjusting knobs 209 and 
213, there is a handle 217 which is secured to the case 100. 
FIGS. 7 and 8 show a single hand operation by using a right hand. The 
operator grips the handle 217 and actuates the knob 209 by the thumb and 
the forefinger as shown in FIG. 7. When it is desired to the knob 213 with 
the handle gripped by the same hand, the operator may actuate the 
extension knob 215 as shown in FIG. 8. It is thus unnecessary to change 
the grip for actuating both of the knobs 209 and 213. 
When it is intended to perform a single hand actuation by using a left 
hand, the extension knob 215 is removed from the adjusting knob 213 and 
attached instead to the adjusting knob 209. 
The invention has thus been shown and described with reference to a 
specific embodiment, however, it should be noted that the invention is in 
no way limited to the details of the illustrated structures but changes 
and modifications may be made without departing from the scope of the 
appended claims.