Optics: eye examining – vision testing and correcting – Eye examining or testing instrument – Subjective type
Reexamination Certificate
2002-04-19
2004-06-15
Manuel, George (Department: 3762)
Optics: eye examining, vision testing and correcting
Eye examining or testing instrument
Subjective type
Reexamination Certificate
active
06749303
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an optometry apparatus having an optical element by which targets can be seen as if they were dispersed in a plane orthogonal to an optical axis and presented simultaneously at a different distance or position in a direction of an optical axis through examined eyes to be subjected to optometry, and a diffraction grating plate as an optical element used in the same.
Conventionally, an optometry apparatus makes a precise decision of an astigmatic axis of examined eyes to be subjected to optometry and of an astigmatic degree by use of a cross cylinder lens. As a method for deciding the astigmatic axis and astigmatic degree precisely using this cross cylinder lens, a cross cylinder method and an auto-cross cylinder method are known.
In any method, firstly a spherical degree S, a cylindrical degree C, and an axial angle A of a cylindrical axis O are roughly measured, thereafter, the astigmatic axis of the examined eyes to be subjected to optometry and the astigmatic degree are precisely measured.
For example, it is assumed that a spherical degree S (=−1.00D), a cylindrical degree C (=−0.50D) and an axial angle A of a cylindrical axis O (=90 degree) are set as a result of the optical characteristic of one lens of eyeglasses in use currently by a lens meter.
At the time of optometry, first of all, in order to remove accommodation power of eyes, as shown in
FIG. 1
, a spherical lens
2
whose the spherical degree S is, for example, +3.00D, which is higher than a prospective degree, is set to an optometric window of a correction optical system
1
by fogging, and an eyesight-test chart is shown to a subject. In the case of the spherical degree S (=−1.00D), the spherical lens
2
with the spherical degree S (=+2.00D) is set to the optometric window, and the spherical degree S of the spherical lens
2
to be set to the optometric window is reduced by −0.25D so as to increase eyesight.
Then, an astigmatic test chart
3
illustrated in
FIG. 2
is shown to the subject at the stage which is one step before desirable eyesight, and the subject is asked how the astigmatic test chart
3
is seen.
In a case where the astigmatic test chart
3
is blurredly seen uniformly, it can be judged that the subject is not a person with astigmatism. Here, it is assumed that the subject is a person with astigmatism. For example, if an answer “I can see the direction at 3 o'clock clearly” is received in response to a question “which direction at a clockwise can you see?”, a cylindrical lens
4
is set to the optometric window of the correction optical system
1
and the cylindrical axis O is set in a direction orthogonal to a direction where clear vision can be obtained. Namely, the axial angle A of cylindrical axis O is set to 90 degrees.
After that, the cylindrical degree C of the cylindrical lens
4
to be set to the optometric window is increased 0.25 by 0.25, and the approximate measurement is completed when the degree of the cylindrical lens
4
reaches a value where the astigmatic test chart
3
is clearly seen uniformly.
Additionally, in
FIG. 1
, reference numeral O
1
denotes an optical axis of the correction optical system
1
.
Next, precise measurement of the cylindrical axis O and cylindrical degree C is performed.
In case of the cross cylinder method, a cross cylindrical lens
5
is inserted in the correction optical system
1
. This cross cylinder lens
5
is structured such that the axis of (−) axial cylindrical lens is orthogonal to that of (+) axial cylindrical lens as shown in FIG.
1
.
Then, an intermediate axis
6
of the cross cylindrical lens
5
is allowed to conform to the cylindrical axis O of the cylindrical lens
4
. Next, the cross cylindrical lens
5
is reversed using the intermediate axis
6
of the cross cylindrical lens
5
as a central axis. Then, the subject is allowed to look at a point group chart
7
of FIG.
3
.
Before and after the cross cylindrical lens
5
is reversed at the time of showing this point group chart
7
, the cylindrical lens
4
and cross cylindrical lens
5
are integrally rotated in a direction where a clear view is obtained by, for example 5 degrees to measure the axial angle A of the cylindrical lens
4
precisely.
Sequentially, as illustrated in
FIG. 4
, any one of (+) axis and (−) axis of the cross cylindrical lens
5
is confirmed to the cylindrical axis O of the cylindrical lens
4
.
FIG. 4
shows a state in which (+) is confined to the cylindrical axis O. Then, the point group chart of
FIG. 3
is shown to the subject. Next, the cross cylinder lens
5
is reversed using the intermediate axis
6
as a central axis and the (−) axis is conformed to the cylindrical axis O. Then, the point group chart of
FIG. 3
is shown to the subject. After asking the subject a question about which way the chart can be clearly seen before or after the cross cylindrical lens
5
is reversed, the cylindrical degree C of the cylindrical lens
2
is set to a direction where a clear view can be obtained.
Thus, precise measurement of the subject's astigmatic axis and astigmatic degree is completed.
In case of the auto-cross cylinder method, an auto cross cylindrical lens
8
shown in
FIG. 5
is used. This auto cross cylindrical lens
8
includes a triangular prism
9
and cross cylindrical lenses
10
,
11
. The cross cylindrical lenses
10
and
11
have the degree of, for example, ±0.25D or ±0.5D, and plus and minus axes of the cross cylindrical lenses
10
and
11
are orthogonal with respect to each other.
The precise measurement of the astigmatic axis and astigmatic degree using this auto cross cylindrical lens
8
is carried out, for example, as follows:
The approximate measurement of the spherical degree S, cylindrical degree C, and axial angle A of cylindrical axis O is the same as the case of the cross cylinder method.
After the approximate measurement of the spherical degree S, cylindrical degree C, and axial angle A of cylindrical axis O, an intermediate axis
12
of the auto cross cylindrical lens
8
is conformed to the cylindrical axis O of the cylindrical lens
4
as shown in FIG.
6
. Consequently, the plus axis (+) of the upper-side cross cylinder lens
10
is set to a direction at 45 degrees with respect to the cylindrical axis O and the minus axis (−) thereof is set to a direction at 135 degrees. Moreover, the minus axis (−) of the lower-side cross cylinder lens
11
is set to a direction at 45 degrees with respect to the cylindrical axis O and the plus (+) thereof is set to a direction at 135 degrees.
Then, the point group chart
7
of
FIG. 3
is similarly shown to the subject so that the subject is allowed to perform comparison between the point group chart
7
seen through the upper-side cross cylinder lens
10
and the point group chart
7
seen through the lower-side cross cylinder lens
11
simultaneously to check which chart can be clearly seen. Then, the cylindrical lens
4
is rotated integrally with the auto cross cylinder
8
in the direction where a good view can be obtained. Thus, the axial angle A of the cylindrical axis O is decided.
After that, the cross cylinder lenses
10
and
11
are rotated so that the plus axis (+) of the cross cylinder lens
10
is conformed to the cylindrical axis O and the minus (−) of the cross cylinder lens
11
is conformed to the cylindrical axis O as illustrated in FIG.
7
. After performing comparison between the point group chart
7
seen through the cross cylinder lens
10
and the point group chart
7
seen through the cross cylinder lens
11
simultaneously to check which chart can be clearly seen, the cylindrical degree C of the cylindrical lens
4
, which is inserted in the optical path of the correction optical system
1
, is changed to the direction where the good view can be obtained.
Thus, precise measurement of the axial angle A of the cylindrical axis and cylindri
Fujino Makoto
Fukuma Yasufumi
Kato Yasuo
Chapman and Cutler LLP
Kabushiki Kaisha TOPCON
Manuel George
LandOfFree
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