JP2805040B2 - Eye refractive power measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an eye-refractive-power measuring apparatus, and more particularly to an eye-refractive-power measuring apparatus capable of measuring a change in eye refractive power in real time.

[0002]

2. Description of the Related Art Hitherto, as a multilateral eye refractive power measuring apparatus, an apparatus such as a so-called auto-refractometer as disclosed in JP-A-2-154732 has been known.

[0003]

However, in the auto-refractometer, it is necessary to fix the position of the subject's eyeball at a certain fixed position with respect to the apparatus, and the measurement must be performed not only during continuous measurement but also during operation. Measurement was not possible.

[0004] In view of the above circumstances, the present invention is small and lightweight so that measurement can be performed with the measurement unit attached to the head, and it is not necessary for the subject to maintain a fixed posture, for example, a front view state, for measurement. It is an object of the present invention to provide an eye-refractive-power measuring device capable of continuously obtaining eye-refractive-power data in real time.

[0005]

An eye refractive power measuring apparatus according to the present invention is provided with a light projecting system for illuminating a test eye and forming a light source image on a fundus, and at a position optically conjugate with a pupil of the test eye. Having a light receiving system for detecting the reflected light flux distribution from the fundus of the test eye,
The light receiving system is composed of two photographing optical systems that are divided into two on both sides of the optical axis by a dividing unit that is placed at a position conjugate with the light source of the light projecting system, and the two optical systems detect the light. means for determining the light amount difference comrades points corresponding to each other of the reflected light flux distribution, the hand for obtaining the light amount difference for that two or more points
And a means for measuring the eye refractive power of the subject's eye using the ratio of the light amount difference as a parameter.

In the eye-refractive-power measuring apparatus of the present invention, the width of the light source is extended in a direction perpendicular to the optical axis.

In the eye-refractive-power measuring apparatus according to the present invention, the dividing means for dividing the light receiving system into two parts comprises a two-sided mirror having a ridge on the optical axis.

In the eye-refractive-power measuring apparatus of the present invention, in a portion conjugate with the pupil of the subject's eye on the detector, the light amount difference is not zero according to the eye-refractive power of the subject's eye in most of the region. This value corresponds to the eye refractive power, and the eye refractive power can be measured based on a parameter obtained by a ratio of a light amount difference between at least two points. Except for a portion conjugate with the pupil, the light source light amount can be set to approximately zero by setting the light source light amount to an appropriate value.

[0009]

Embodiments of the present invention will be described below with reference to the drawings.

In the first embodiment of the present invention, as shown in FIG. 1, a light projecting system 2 and a light receiving system 3 are arranged opposite to a subject's eye 1 via a common half mirror 4, respectively. The test eye 1 is illuminated by a linear or rectangular uniform light source 5 having a certain size through 2 to form a light source image on the fundus 6. This light source image acts on the light receiving system 3 as a secondary light source for illuminating the pupil 7 from the back. The light source may be either visible light or near-infrared light that does not affect the subject.

The light receiving system 3 is constituted by photographing optical systems 9 and 9 'having the same aperture area and divided by a prism type two-surface mirror 8 having a ridge on the optical axis. ′ Is constituted by detectors 10 and 10 ′ comprising photoelectric conversion elements such as a two-dimensional imager such as a CCD, a photographic tube or a plurality of light amount sensors, and lenses 11 and 11 ′, and the detectors 10 and 10 ′ are the lens 11,
11 'is placed at a position conjugate with the pupil 7 of the eye under test.

The outputs from the detectors 10 and 10 'are used in addition to a subtractor 12 to determine the difference in the amount of light incident on the photographing optical systems 9 and 9' from the subject's eye 1 as described later. Then, a parameter based on the ratio of the light quantity difference is calculated, and the eye refractive power D (diopter) is obtained using the parameter, and the value is displayed on the display unit 14.

[0013] Figure 2, when the eye is looking near, i.e. be a diagram when viewing distance L from the subject eye pupil 7 to the retina conjugate point O is shorter than the distance L ₀ to the crest of the secondary mirror 8 Pupil 7
Is illuminated with the light source image formed on the fundus 6 as a secondary light source, passes through the retinal conjugate point O, and then enters the two-sided mirror 8.
, And guided to the photographing optical systems 9 and 9 ′, and condensed by the lenses 11 and 11 ′.
This leads to points Q and Q '.

The light amounts on the points Q and Q 'are different from each other as shown in FIGS. 3A and 3B due to the fact that the position of the point P is deviated from the center of the pupil 7 and the action of the two-sided mirror 8. become.

In FIGS. 3A and 3B, the horizontal axis indicates the light amount, and the vertical axis indicates the positions of the detectors 10 and 10 '.

A point R other than the pupil 7 is a point on the diffusion surface which is directly illuminated by the light source. Since the aperture areas of the photographing optical systems 9, 9 'are equal, the points S and S on the detectors 10, 10' are equal. The light amounts of S 'are equal to each other, and this relationship does not change even if the position of the point R changes with respect to the optical axis.

From the relationship between the light amounts, the result of the subtraction by the subtractor 12 is as shown in FIG. 3C, and all parts other than the pupil 7 become zero. In addition, as is clear from FIG. 3C.
3A and 3B, the noise in the pupil 7 appears.
N, N 'is canceled each other _and, (Q 1 _-Q' 1)
From the difference between the light quantity at the point and the light quantity at the point (Q ₂ −Q ′ ₂ ), 2
Twice the amount of light change, and the detection resolution is doubled.
Swell.

[0018] FIG. 4 is an explanatory view of a light receiving optical path when time, i.e. viewing distance L is longer than the distance L ₀ to the crest of the dihedral mirror 8 which eye is looking at distant place, similar to the above description, the detection 5A and FIG. 5B, the output of the subtracter 12 is zero in the parts other than the pupil 7 as shown in FIG. 5C, and the distribution of the light quantity difference inside the pupil 7 is The opposite is the case with FIG. 3C.

FIG. 6 is a diagram for explaining a method of obtaining the eye refractive power D (diopter) from the parameters calculated by the calculator 13.

The size of the light source image formed on the fundus 6 is determined by the angle at which the subject's eye 1 watches the light source 5. Depending on the change in the eye refractive power D of the eye to be examined 1, the light source image is blurred and the image is enlarged. However, for the purpose of the following light amount evaluation, the effect of the blur is removed by integration, so the light source without blur is used. There is no problem if we proceed with the image.

Since the position of the retinal conjugate point O is conjugate with the fundus 6 at the viewing position, when the light source image of the fundus 6 is considered as a secondary light source, an image of this secondary light source is formed here. Eye refractive power D
And the viewing distance L are shown by Equation 1.

[0022]

(Equation 1)

Obtaining the eye refractive power results in obtaining the viewing distance L. The diameter C of the light beam incident on the light receiving system 3 from the center point Pc of the pupil 7 at the edge of the two-sided mirror 8
Is a unique value determined by the size of the light source 5 of the light projecting system 2, and is equally divided by the two-sided mirror 8 in the light receiving system 3, so that one half of the total luminous flux is always in one photographing optical system. Will be incident.

As shown in FIG. 6, the light flux from the point P having a height a from the optical axis in the pupil 7 enters the light receiving system 3 via the retinal conjugate point O as shown in FIG. At the position, the distance between the center of the light beam and the optical axis is b.

The relationship among a, b, L, and L ₀ is shown by _{equation (} 2).

[0026]

(Equation 2)

The above value b is obtained from the ratio of the light beam incident on one of the photographing optical systems 9 and 9 'to the total light beam _IO incident on both of them. The amount of light incident on one of the photographing optical systems from the point Pc is (1/2) I _O , and (1/2) I _O = k ·
C / 2 (where k is a proportional coefficient) and the point P
Let I and I 'denote the amounts of light incident on the two photographing optical systems 9 and 9', respectively, and I = k [(1/2) Cb],
I '= k [(1/2) C + b]. Therefore, when the ratio of the light amount difference (I-I ') to the total luminous flux I _O is obtained, Expression 3 is obtained.

[0028]

(Equation 3)

Here, (II ') / I _O is a measured value, and C is a predetermined value as described above.

[0030]

(Equation 4)

When Equations 1 to 4 are put together, Equation 5 for obtaining the eye refractive power D is obtained.

[0032]

(Equation 5)

The light amount I _O is obtained from the signal before input to the subtractor 12 by the light amount at the center of the pupil plane of the subject eye.
It is also obtained from a value obtained by integrating and averaging the light amounts in the pupil range. Alternatively, it may be obtained from the sum (I + I ′) of the amounts of light incident on the two photographing optical systems 9 and 9 ′.

In the second embodiment of the present invention, as shown in FIG. 7, the width of the light source 5 is extended in a direction perpendicular to the optical axis, for example, to the left by half the width of the light source 5. Extended light source 15
And the light from the extended light source 15 is
To bend into the eye 1 to be examined.

In this case, the luminous flux from the extended portion of the light source 5 generates a secondary light source indicated by oblique lines on the fundus 6 and the extended light source 15
Is separated from the optical axis, the reflected light from the fundus 6 enters only one of the two photographing optical systems 9 and 9 'in the light receiving system 3.

In this case, the light quantity distribution of the two photographing optical systems 9, 9 'is as shown in FIGS. 8A and 8B, and the output of the subtractor 12 is as shown in FIG. 8C.

As shown in FIG. 8C, the light quantity difference at the central portion of the pupil is (1/2) I _O , and I _O is obtained from this value.
In this way, since all the measured values can be obtained from the output of the subtractor 12, the number of signal processing systems can be reduced, and the process of extracting the pupil portion to be processed in the signal processing can be performed by a simple binarizing circuit. There is also an advantage.

The extended light source 15 may be a point light source independent of the light source 5, and its position may be any position as long as the fundus reflected light is incident on only one of the detectors.

The division of the light receiving system 3 may be realized by two mirrors 8a and 8b as shown in FIG. 9 in addition to the above-described prism type two-sided mirror 8.

If the detectors 10 and 10 'are capable of supporting a left-right inverted image, one mirror 8 as shown in FIG.
It can also be realized by c.

[0041]

As described above, in the eye-refractive-power measuring apparatus of the present invention, the parameters are calculated by focusing only on the portion where the light amount difference of the detector is not zero, and the eye-refractive power is obtained. Since the amount of processing is small, the eye refractive power can be measured in real time, and the repetition rate of the measurement can be increased, so that the temporal change of the eye refractive power can be continuously measured, thereby exhibiting an excellent effect.

Even when the eye to be examined is not directly facing the apparatus, there is an individual difference between the measured eye refractive power and the true eye refractive power depending on the azimuth and angle between the optical axis of the apparatus and the viewing direction. Since there is a certain relationship determined by the eyes of the subject, if this relationship is determined in advance, the subject can perform continuous measurement without looking at the optical axis of the device each time without looking in any direction .

Further, the pupil diameter can be easily obtained in the above-described detection process, and a virtual image of the light source is generated near the pupil of the subject's eye due to the reflection of the illumination light by the cornea, and the virtual image changes the visual direction of the eyeball. In addition, since the position is changed at the same time, if the processing device for detecting the position of the virtual image is used together, it is possible to simultaneously measure the visual direction of the subject's eye.

Therefore, according to the present invention, there can be obtained many effects that accommodation, eye movement, and pupil reaction, which are said to be the three major functions of the eye, can be simultaneously measured in real time.

The output waveform of the detector 10 'is
0 output is almost the same level, but the slope is reversed,
The output waveform after the arithmetic processing has a slope of 2 only in the pupil by subtraction.
Doubled and almost zero level outside the pupil, so detection resolution
The performance is improved twice. The outside of the pupil is almost at zero level.
As a result, the pupil part, which is a necessary detection part, can be extracted in a short time
And image processing is simplified, so high-speed image processing is possible.
Becomes Furthermore, external light other than the detection light source becomes detection noise.
Although this may cause a decrease in measurement accuracy, the device according to the present invention
For example, there are various benefits such as removal of detection noise and maintenance of high precision measurement .

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a basic configuration of an eye refractive power measuring device according to the present invention.

FIG. 2 is an explanatory diagram showing a state of a light beam when the subject's eye is looking near in the eye refractive power measuring device of the present invention.

FIG. 3A is an explanatory diagram of a light amount distribution on a detector in the eye refractive power measuring device of the present invention.

FIG. 3B is an explanatory diagram of a light amount distribution on a detector in the eye refractive power measuring device of the present invention.

FIG. 3C is an explanatory diagram of a difference between light amount distributions shown in FIGS. 3A and 3B.

FIG. 4 is an explanatory diagram showing a state of a luminous flux when the subject's eye is looking far in the eye refractive power measuring device of the present invention.

FIG. 5A is an explanatory diagram of a light amount distribution on a detector in the eye refractive power measuring device of the present invention.

FIG. 5B is an explanatory diagram of a light amount distribution on a detector in the eye refractive power measuring device of the present invention.

FIG. 5C is an explanatory diagram of the difference between the light amount distributions shown in FIGS. 5A and 5B.

FIG. 6 is an explanatory diagram in a case where an eye refractive power is calculated from a state of a light beam in the eye refractive power measuring device of the present invention.

FIG. 7 is an explanatory view of a second embodiment of the eye-refractive-power measuring apparatus of the present invention.

FIG. 8A is an explanatory diagram of a light amount distribution on a detector in a second embodiment of the eye refractive power measuring device of the present invention.

FIG. 8B is an explanatory diagram of a light amount distribution on a detector in a second embodiment of the eye refractive power measuring device of the present invention.

FIG. 8C is an explanatory diagram of a difference between light amount distributions shown in FIGS. 8A and 8B.

FIG. 9 is an explanatory diagram in the case where two mirrors are used instead of the two-sided mirror in the eye refractive power measuring device of the present invention.

FIG. 10 is an explanatory diagram in the case where one mirror is used instead of the two-sided mirror in the eye refractive power measurement device of the present invention.

[Explanation of symbols]

 Reference Signs List 1 test eye 2 light projecting system 3 light receiving system 4 half mirror 5 light source 6 fundus 7 pupil 8 prism type two-sided mirror 8a mirror 8b mirror 8c mirror 9 photographing optical system 9 'photographing optical system 10 detector 10' detector 11 lens 11 ′ Lens 12 subtractor 13 arithmetic unit 14 display 15 extended light source

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int.Cl. ⁶ , DB name) A61B 3/103

Claims (3)

(57) [Claims] 1. A light projecting system for illuminating a subject's eye and forming a light source image on the fundus, and a light receiving system located at a position optically substantially conjugate with a pupil of the subject's eye and detecting a distribution of a light beam reflected from the fundus of the subject's eye And the light receiving system is arranged on both sides of the optical axis by dividing means placed at a position conjugate with the light source of the light projecting system.
It consists divided two imaging optical system, and means for determining the light amount difference of each other corresponding points comrades reflected light flux distribution detected by the two optical systems, the light amount difference for that two or more points
An eye-refractive-power measuring apparatus, comprising: a means for determining the light-refractive-power difference ; 2. The eye refractive power measuring device according to claim 1, wherein the width of the light source is extended in a direction perpendicular to the optical axis. 3. The splitting means for splitting the light receiving system into two parts comprises a two-sided mirror having a ridge on an optical axis.
An eye refractive power measurement device as described in the above.