Optometric apparatus

An optometric apparatus for measuring optical characteristics of an eye to be examined comprising moving device for moving measuring section to adjust alignment with the eye to be examined, first and second deviation amount detecting devices for detecting deviation amount of the measuring section in a lateral and a vertical directions relatively to the eye at the time of measuring each of a left eye and a right eye to be examined, and correcting device for correcting data about an angle of astigmatic axis of the eye measured by the measuring section or interpupilary distance, based on the detected result obtained by the first deviation detecting device and the second deviation detecting device.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to an optometric apparatus including an eye 
refractive measuring apparatus and a cornea shape measuring apparatus and 
others. 
2. Description of Related Art 
Generally, an eye refractive measurement apparatus and a cornea shape 
measuring apparatus are for measuring a direction of axis of an eye to be 
examined, such as astigmatic axis and principal meridian, and therefore 
need precise alignment between an eye to be examined and the apparatus 
unit. If the alignment between an eye to be examined and the apparatus 
unit is not precise, it will be inavoidable that the measured data 
obtained with such apparatus have errors therein. 
In a conventional eye refractive measurement apparatus and the like, to 
effect alignment with an eye to be examined, utilized is a method of 
fixedly supporting the head of the examinee on a head or forehead support 
member so as to correspond with a direction of a reference axis of a 
measuring system. 
The recent optometric apparatus utilizes a monitor to project image of the 
anterior part of the eye to be examined, accordingly, the alignment 
situation can be partially found based on the monitored image. For 
instance, U.S. Pat. No. 4,755,041 discloses such measuring apparatus. 
There is also known an eye refractive power measuring apparatus with a 
system for measuring interpupilary distance which is a distance between 
each visual axes of a right and a left eyes of an examinee. For instance, 
U.S. Pat. No. 5,152,067 discloses such eye refractive power measurement 
apparatus in which the interpupilary distance is detected by measuring the 
moving distance of the measuring optical system from an alignment position 
with respect to an eye to another alignment position with another eye. 
In apparatuses mentioned above, although at least the examinee's head is 
fixed on the head support member, there is no assurance that the right and 
left eyes of the examinee are certainly in a horizontal and, if anything, 
strictly, these eyes are commonly inclined off the horizontal. And 
further, according to differences among individuals, there are quite a few 
instances that the inclination of the eyes is remarkable. It is, 
therefore, difficult to obtain accurate data about astigmatic axis and 
principal meridian by the conventional apparatuses. 
In the apparatus shown in U.S. Pat. No. 4,755,041, the anterior part of an 
eye is to be observed on a monitor, but it is just only a part around the 
pupil of the eye and therefore the examiner can find that both eyes are 
not in a horizontal only if an eye is extremely inclined. 
And also, in the measurement of interpupilary distance taught in U.S. Pat. 
No. 5,152,067, when both eyes of the examinee are not in a horizontal, 
results obtained must include errors. 
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 optometric 
apparatus capable of measuring accurately optical characteristics of the 
an eye, for instance, an eye refractive power and a cornea shape and 
others, even if the examinee's head inclines to either side thereof 
relatively to the apparatus unit, namely, a right and a left eyes of the 
examinee are not positioned in a horizontal. 
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 optometric apparatus for 
measuring optical characteristics of an eye to be examined of this 
invention comprises moving means for moving measuring section to adjust 
alignment with an eye to be examined, first deviation amount detecting 
means for detecting deviation amount of the measuring section in a lateral 
direction relatively to the eye at the time of measuring each of a left 
eye and a right eye to be examined, second deviation amount detecting 
means for detecting deviation amount of the measuring section in a 
vertical direction relatively to the eye to be examined at the time of 
measuring each of a left eye and a right eye to be examined, and 
correcting means for correcting data about an angle of astigmatic axis of 
the eye measured by the measuring section, based on the result detected by 
the first deviation detecting means and the second deviation detecting 
means. 
In the above apparatus, it is preferable to find an inclination angle of 
both eyes off a horizontal direction on the basis of deviation amount in a 
horizontal direction and a vertical direction between a right eye and a 
left eye of the examinee based on detected signals transmitted from the 
first deviation amount detecting means and the second deviation amount 
detecting means, thereby to calculate correctively an astigmatic axis 
angle. 
In a second aspect of the present invention, an optometric apparatus for 
measuring optical characteristics of an eye to be examined comprises 
moving means for moving measuring section to adjust alignment with an eye 
to be examined, first deviation amount detecting means for detecting 
deviation amount of the measuring section in a lateral direction 
relatively to the eye to be examined at the time of measuring each of a 
left eye and a right eye to be examined, second deviation amount detecting 
means for detecting deviation amount of the measuring section in a 
vertical direction relatively to the eye to be examined at the time of 
measuring each of a left eye and a right eye to be examined, and 
arithmetic means for calculating interpupilary distance of the eyes to be 
examined based on the results detected by the first and the second 
deviation amount means respectively. 
In the second construction, it is preferable to calculate interpupilary 
distance with Pythagoras' theorem formula on the basis of the deviation 
amount in the right and left and the vertical directions between a right 
and a left eyes, the deviation amount which is found based on the detected 
signal at the first and the second deviation amount detecting means. 
In a third aspect, which is a more specific construction of the present 
invention, an optometric apparatus for measuring optical characteristics 
including eye refracting power and cornea shape and others of an eye to be 
examined, the apparatus comprises an apparatus unit disposed on a base, 
movably in the back and forth direction, in the right and left direction 
relatively to an examiner thereof, in which measuring optical system for 
measuring the optical characteristics of the eye to be examined is 
equipped, the measuring optical system being arranged movably in a 
vertical direction, a head support member and a forehead support member 
installed on the base to fixedly support the examinee's head, monitor 
means, installed in the apparatus unit, for projecting image of the 
anterior part of the eye to be examined and, at the same time, displaying 
results about eye refracting power, interpupilary and others, a first 
deviation amount detecting means for detecting moving amount of the 
apparatus unit in the lateral direction, a second deviation amount 
detecting means for detecting moving amount of the measuring optical 
system in the vertical direction, and an arithmetic means for finding an 
angle of the astigmatic axis and the interpupilary distance based on the 
deviation amount between a right and left eyes of the examinee obtained on 
the basis of the detected signals respectively at the first and the second 
deviation amount detecting means. 
In the above construction, it is preferable that to find an angle of 
astigmatic axis and an interpupilary distance of the eye based on the 
detected signal at the first and second deviation detecting means. 
According to the present invention, optical characteristics of the eye to 
examined including refractive power and cornea shape can be precisely 
measured even if the examinee's head inclined to one side thereof, namely, 
a right eye and a left eye of the examinee are not positioned in a 
horizontal.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
A detailed description of one preferred embodiment of an optometric 
apparatus embodying the present invention will now be given referring to 
the accompanying drawings. 
In FIG. 1, the optometric apparatus comprises mainly a base 1 and an 
apparatus unit 2 which internally has a measuring optical system (an upper 
unit 17 and a lower unit 18 mentioned below) for measuring optical 
characteristic of an eye to be examined. Specifically, on the base 1, a 
head support member 3 and a forehead support member 4 are fixed at an end 
side of the base 1, both of which are for fixedly supporting the 
examinee's head opposing to the apparatus unit 2, and a printing section 5 
is provided in another end side of the base 1. The apparatus unit 2 is 
provided with a joystick 6 to be used for operation to slidingly move the 
apparatus unit 2 in the back and forth and in the right and left 
directions along on the base 1, a television monitor 7 to project image of 
the anterior part of the eye to be examined and display measured results 
about interpupilary distance and others, a display screen 8 to display the 
value of refractive power of the eye to be examined, and a knob 19 to move 
up and down an optical axis of a measuring optical system. The sliding 
moving system with the joystick 6 and the vertical moving system with the 
knob 19 will be explained below. 
In FIG. 3, the measurement optical system equipped inside the apparatus 
unit 2 is shown in a block diagram. The measurement optical system, as 
shown in FIG. 3, comprises an alignment light projecting system A, a 
fixation index projecting system B, an index projecting system C, an index 
detecting system D and an observing system E to which the television 
monitor 7 is connected. In such construction of the measuring optical 
system, the anterior part of the eye is photographed with a camera of the 
observing system and projected on the television monitor 7. And light beam 
emitted from the alignment light projecting system A is reflected by the 
cornea of the eye to be examined and then forms a cornea reflecting image 
thereon. Based on the cornea reflecting image, the examiner operates then 
the joystick 6 to move the apparatus unit 2 so that the eye to be examined 
and the cornea reflecting image are positioned with a predetermined 
relation on the monitor 7. 
Next, the moving system to move the measuring section of the apparatus unit 
2 will be explained hereinafter, referring to FIG. 4 and FIG. 5. 
As shown in FIGS. 4 and 5, a groove 10 is formed on the surface of the base 
1, into which a fixed block 11 is fitted movably along a longitudinal 
direction of the groove 10. The fixed block 11 also supports axially two 
bars 12 through some bearings (not shown) so that the two bars 12 fixed at 
a bottom of the apparatus unit 2 may move through the fixed block 11 in 
the right and left direction of the apparatus unit 2. Accordingly, based 
on operation of the joystick 6, the above moving system consisting of the 
groove 10, the fixed block 11 and the two bars 12 can move the apparatus 
unit 2 slidingly on the base 1 in the back and force direction and in the 
right and left direction. 
And further, as shown in FIG. 5, two pulleys 13 and 14 are installed on the 
bottom surface of the apparatus unit 2 and a wire 15 is put over the two 
pulleys 13 and 14. The wire 15 is partially fixed to the fixed block 11, 
and the two pulleys 13 and 14 are accordingly rotated through the wire 15 
when the apparatus unit 2 is moved in the right and left direction 
relatively to the base 1. Then, a rotary encoder 16 provided in a rotating 
shaft of the pulley 13 detects the rotary number of the pulley 13, and 
based on which a moved distance of the apparatus unit 2 in the right and 
left direction is detected. 
An upper unit 17 of the apparatus unit 2 in which the measuring optical 
system is equipped is supported on the lower unit 18 comprising a monitor 
and others so as to be movable in a vertical direction. Specifically, 
turning of the knob 19 installed to the lower unit 18 first rotates a 
driving shaft 20 and a bevel gear 21 fixed to the shaft 20, and further, 
the bevel gear 21 engaging with a bevel gear 23 fixed to a feed screw 22, 
the feed screw 22 rotates therewith in a female screw portion 24 formed at 
a bottom of the upper unit 17. The feed screw 22 and the female screw 
portion 24 of the upper unit 17 engage with each other, accordingly, the 
upper unit 17 is moved vertically to the lower unit 18. 
A gear 25 is also fixed to the driving shaft 20, which engages with a gear 
26 connected to a rotary encoder 27. When rotary of the gear 25 is 
transmitted to the gear 26, the rotary encoder 27 detects the rotary 
number of the gear 26 and thereby the moved distance of the upper unit 17 
in a vertical direction. 
Control operation of detecting the moved distance of the apparatus unit 2 
in the right and left direction and in the vertical direction. 
Numeral 30 is an input section to which measurement mode and trigger signal 
and others are input. The input section 30, after received the trigger 
signal about an eye of the examinee, transmits an initial set signal to 
the rotary encoders 16 and 27. After that, pulse signals are output from 
the rotary encoders 16 and 27 respectively according to the movement of 
the apparatus unit 2, and counted through the processing circuit of 
arithmetic processing section 31. The deviation amount is thus detected 
based on the counted signals and then stored in a memory. 
Measuring section 32 transmits picture data of the examinee's eye to a 
display section 33 and, at the same time, measured data to the arithmetic 
processing section 31 to process the data with the predetermined 
arithmetic operation. 
In the optometric apparatus of the present embodiment, the optical 
measurement is performed to the eyes to be examined one each and the 
obtained result about a first eye is provisionally displayed at the 
display section 33. And, after measuring both eyes, the above result is 
corrected in accordance with the following process. 
Assuming that X is a horizontal distance and Y is a vertical distance 
between a right and a left eyes, both distances which are detected at the 
rotary encoders 16 and 27, an inclined angle Z between the both eyes off 
the horizontal direction is characterized by the following formula (I); 
##EQU1## 
Based on the obtained inclined angle Z, an angle of the astigmatic axis of 
the eye which has been first obtained is corrected, for example, if the 
initial measured value is 90 degree and the value of Z is +10 degree, the 
angle of the astigmatic axis is corrected into 80 degree. 
Measurement operation with the apparatus of above construction will be 
described as follow. 
The head of the examinee, first, is fixedly supported on the head support 
member 3 and the forehead support member 4. While observing image of the 
anterior part of the eye to be examined displayed on the monitor 7, an 
examiner operates the knob 19 and the joystick 6 so that an alignment 
reticle and a cornea reflecting image are positioned with a determined 
relation with each other on the monitor 7. After alignment is completed, 
when a trigger button 6a provided at a top of the joystick 6 is pushed, 
refractive power of the examinee's eye is accordingly measured by the 
measuring section 32. The refractive power is then processed at the 
arithmetic processing section 31, and then displayed on the display 
section 33. 
Following the above measurement of one eye, refractive power of another eye 
of the examinee is measured. Also in this measurement, same alignment 
operation as the former is performed with the knob 19 and the joystick 6. 
The rotary encoders 16 and 27 receive the initial set signals following 
the first trigger signal. And the rotary encoders 16 and 27 detect the 
subsequent deviation amount in a lateral and in a vertical directions 
respectively. When such alignment operation is completed, the trigger 
button 6a is pushed and thereby refractive power of the eye is measured. 
The measured value of the refractive power is similarly processed in the 
arithmetic processing section 31 and displayed on the display section 33. 
The rotary encoders 16 and 27 detect the deviation amount in the lateral 
and the vertical directions between the trigger signals generated by the 
trigger button 6a with respect to the right and left eyes of the examinee 
respectively. If the deviation amount in the vertical direction exceeds 
the designated range, indication of necessity to correct the measured 
value is displayed on the monitor 7 in order to call the examiner's 
attention. And the data of refractive power, which is corrected in 
accordance with the above formula (I), is displayed on the display section 
33. Instead of being displayed on the display section 33, the corrected 
data may be displayed only on the printing section. 
The interpupilary distance PD is found based on the deviation amount in the 
vertical and the lateral directions as the following formula (II); 
##EQU2## 
Such calculating the above interpupilary distance PD may be processed only 
if the deviation amount in the vertical direction exceeds the designated 
range. 
The present invention may be embodied in other specific forms without 
departing from the spirit or essential characteristics thereof. In the 
above embodiment, the present invention is applied to an objective 
refractive power measurement apparatus, and further, it may be utilized to 
correct principal meridian direction in a cornea shape measuring apparatus 
as disclosed in U.S. Pat. No. 5,212,507. 
The above embodiment embodying the present invention may also be varied. 
Specifically, various means may be applied as means for detecting the 
deviation amount, for instance, positions of eyes to be examined are 
detected through two-dimensional CCD and the like and then, based on the 
detected position, position of measuring optical, axis is moved by pulse 
motor and the like, thereby the deviation amount is moved based on the 
moved amount of the measuring optical axis. And, in a measurement 
apparatus in which both eyes can be synchronously measured, the deviation 
amount may be detected by-detecting each position of measurement optical 
axes of the eyes. 
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.