JP2003111729A - Method and instrument for measuring ocular optical property - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure the light transfer function of a retina by a mirror surface reflected luminous flux which gives influence to the characteristic of an image which can be recognized by a subject and to objectively recognize the property of the image which is recognized by the subject in ocular optical property measurement. SOLUTION: A light source image is projected to the retina 2 of the eye to be tested to obtain the light transfer function of the retina 2 of the eye to be tested by the mirror surface reflected luminous flux based on a light quantity distribution property obtained from the mirror surface reflected components in a reflected luminous flux from the retina and wave surface property obtained by a luminous flux emitted from the retina of the eye to be tested.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an eye optical characteristic measuring method and apparatus for measuring an optical characteristic of an eye to be examined.

[0002]

2. Description of the Related Art As a conventional device for measuring the optical characteristics of an eye to be inspected, a minute point light source is projected on the retina of the eye to be inspected, and the wavefront of a light beam emitted from the cornea of the eye to be inspected is, for example, a wavefront using a Hartmann diaphragm. There is known an apparatus that detects optical characteristics including a high-order aberration of an eyeball optical system from a cornea to a retina by detecting with a sensor or the like.

However, when the subject's eye observes the image, the characteristics of the image recognized by the subject are affected not only by the optical system of the eye from the cornea to the retina but also by the light transfer function of the retina. On the other hand, in the retina, there are scattered reflections that can be seen when a part of the retina penetrates into the surface layer of the retina and specular reflections that are reflected on the retina surface, and the subject recognizes the light transfer function of the light flux scattered and reflected by the retina. It has been experimentally confirmed by the applicant that the optical transfer function of the light flux specularly reflected by the retina affects the characteristics of the image that can be recognized by the subject without affecting the characteristics of the image that can be obtained. is there.

[0004]

However, in the conventional method and apparatus for measuring the optical characteristics of the eye, the optical transfer function of the retina with the light beam specularly reflected by the retina cannot be measured. Therefore, it was not possible to objectively and accurately recognize the characteristics of the image recognized by the subject.

In view of such circumstances, the present invention makes it possible to measure the optical transfer function of the retina that influences the characteristics of the image that can be recognized by the subject, and objectively determine the characteristics of the image that the subject recognizes. It enables accurate recognition.

[0006]

According to the present invention, a light source image is projected on a retina of an eye to be inspected, and a light amount distribution characteristic obtained from a specular reflection component in a light flux reflected from the retina and a light flux emitted from a cornea of an eye to be inspected. According to the eye optical characteristic measurement method for obtaining the light transfer function of the retina of the eye by the specularly reflected light flux based on the wavefront characteristics obtained by, the light source image is projected on the retina of the eye, and the specular reflection component of the light flux reflected from the retina Based on the light amount distribution characteristics obtained from the eye cornea and the optical characteristics of the eye from the cornea to the retina, the method of determining the optical transfer function of the retina of the eye by the specular reflection light flux is related to the method for determining the optical characteristics of the eye, and the light source image is placed on the retina of the eye. A means for projecting, a light receiving element for receiving the reflected light flux of the light source image, an optical system for forming a light source image on the light receiving element by a light flux of a specular reflection component of the reflected light flux of the light source image, and the light receiving element of A light quantity distribution characteristic detecting means for detecting a light quantity distribution characteristic of the light source image based on a signal, a means for detecting a wavefront characteristic of a light flux emitted from the cornea of the eye to be examined by a light flux from the light source image projected on the retina of the eye to be examined, The present invention relates to an eye-optical characteristic measuring device comprising a calculation unit for calculating a light transfer function of a retina by a specular reflection light flux from the light amount distribution characteristic and the wavefront characteristic, and further, means for projecting a light source image on a retina of an eye to be examined, A light receiving element for receiving a reflected light flux of a light source image, an optical system for forming a light source image on the light receiving element by a light flux of a specular reflection component of the reflected light flux of the light source image, and the light source based on a signal from the light receiving element A light quantity distribution characteristic detecting means for detecting a light quantity distribution characteristic of the image, and a light transfer function of the retina by the specular reflected light flux is calculated from the known wavefront characteristic measured for the eye to be examined and the detected light quantity distribution characteristic. Those of the eye's optical characteristic measuring apparatus comprising an arithmetic unit.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

First, the principle of the present invention will be described with reference to FIGS.

According to the present invention, the single-pass eye optical characteristic (MTF) and spread function (PSF) of the eye optical system from the cornea to the retina, which are obtained by the wavefront detection mechanism, are used.
The optical characteristic (MTF) of the retina of the eye to be examined is obtained based on the double-pass eye optical characteristic (MTF) including the characteristics of the retina and the eyeball optical system obtained by the detection mechanism.

An outline of the wavefront detecting mechanism will be described with reference to FIG.

In FIG. 1, 1 is an eye to be inspected and 2 is a retina.

A light beam 4 emitted from the projection optical system 3 is directed to an eye 1 to be examined by a deflecting member 5 such as a half mirror.
A sufficiently small point light source is projected on the retina 2. The reflected light flux reflected by the retina 2 passes through the cornea 6 and the deflecting member 5, and the two-dimensional light receiving element 8 such as CCD is received by the light receiving optical system 7.
Be led to. The light receiving optical system 7 includes a lens array 10 in which microlenses 9 are arranged in a grid pattern, and the reflected light flux that has passed through the cornea 6 and the deflecting member 5 passes through the lens array 10, It is divided into a plurality of small luminous fluxes 11, and each small luminous flux 11 is individually imaged on the light receiving element 8. The image forming position of the small light flux 11 is affected by the characteristics of the eyeball optical system from the cornea to the retina.

Therefore, when the shape of the cornea 6 is normal, the original position on the light receiving element 8 where the small light beam 11 is imaged and the small light beam 11 from the retina 2 of the eye 1 to be inspected.
The deviation δ from the image forming position of is detected, and based on the information of the deviation δ,
When a point light source is placed on the retina 2 of the eyeball optical system, the wavefront shape of the light flux emitted from the cornea is measured. Note that this measurement result is purely due to the eyeball optical system and not due to the characteristics of the retina.

Further, the measurement result is (x,
y) Wavefront aberration that indicates how much the wavefront is deviated in the z-axis direction from the coordinate. Letting this be the pupil function W (x, y), the autocorrelation of the pupil function W is the optical transfer function (OFT: OFT).
optical Transfer Function)
Therefore, the absolute value becomes the single-pass eye optical characteristic (MTF) of the eyeball optical system.

E (U, V) = | ∫∫ _−∞ ^∞ w (x + U / 2, y + V / 2) × w ^* (x−U / 2, y−V / 2) dxdy | (1)

However, w ^* represents a complex conjugate of w. Further, in FIG. 1, R (U, V) represents the MTF of the retina. still,
In FIG. 1, the three center wavy lines schematically represent the wavefront of the light beam emitted from the cornea 6.

Next, referring to FIG. 2, an outline of the spread function (PSF) detection mechanism will be described.

In FIG. 2, the same parts as those shown in FIG. 1 are designated by the same reference numerals.

A projection light beam emitted from a sufficiently small point light source o is guided to an eye 1 to be examined by a projection optical system 3 and forms an image on a retina 2. The reflected light beam specularly reflected by the retina 2 is guided to the light receiving element 8 by the light receiving optical system 7 and forms an image. Further, the specularly reflected light beam is affected by the optical characteristics of the eyeball optical system and the optical characteristics of the retina.

Here, the point light source o (x, y), the amplitude transmittance p1 (x, y) of the outward path of the eyeball optical system, the amplitude transmittance r (x, y) of the retina, and the amplitude of the return path of the eyeball optical system. Transmittance p2
If (x, y), the reflected light flux obtained on the light receiving element 8 has passed through the eye 1 to be inspected twice, and therefore the double-pass PSF image i (x, y) obtained on the light receiving element 8 is obtained. ) Is the point light source o (x, y), the amplitude transmittance p1 (x, y) of the outward path of the eyeball optical system, the amplitude transmittance r (x, y) of the retina due to the specular reflected light flux, and Return path amplitude transmittance p2 (x, y) is expressed as the result of convolution integration of all of these.

I (x, y) = o (x, y) * p1 (x,
y) * r (x, y) * r (x, y) * p2 (x, y) When Fourier transform is performed on both sides, double-pass eye optical characteristics (MTF) (I (U, V))
Is obtained.

[0022]   I (U, V) = O (U, V) × P1 (U, V) × R (U, V) × R (U, V) × P2 (U, V) (2)

Since the point light source o is sufficiently small, O (U, V) = 1 can be set, and P1 can be set.
(U, V) and P2 (U, V) are equal, so P1 (U, V
V) = P2 (U, V) = P (U, V), the above formula (2) is: I (U, V) = {P (U, V) × R (U, V)} ² Therefore, R (U, V) = √ {I (U, V)} / P (U, V) (3)

Further, P (U, V) is a single-pass eye optical characteristic (MTF) of the eyeball optical system which does not include the optical characteristic of the retina 2 obtained by the wavefront detection mechanism, that is, E (U, V).
V), P (U, V) = E (U, V) (4)

Therefore, from the equations (3) and (4),   R (U, V) = √ {I (U, V)} / E (U, V) (5)

That is, the MTF of the retina due to the specularly reflected light beam can be obtained by MTF of the retina = √ (double-pass MTF obtained by the PSF detection mechanism) / (single-pass MTF obtained by the wavefront detection mechanism) (6)

Next, an embodiment of the present invention will be described with reference to FIG. In FIG. 3, the same components as those shown in FIGS. 1 and 2 are designated by the same reference numerals.

The projection optical system 3 has a light source 21, a projection lens 22 for condensing a projection light beam emitted from the light source 21, and an insertable / removable optical axis of the projection lens 22. A first polarizing plate 26 that transmits a linearly polarized light component (S linearly polarized light), a half mirror 23 disposed on the optical axis of the projection lens 22, and a projection light flux that has passed through the half mirror 23 is reflected toward the subject's eye 1. And the half mirror 5 for projecting, the relay lens 24 disposed from the half mirror 5 side to the projection optical axis of the half mirror 5, the objective lens 12, the objective lens 12, and being removable from the optical axis. 1/4 provided
The wavelength plate 13 and an aperture stop 14 which is arranged at a position (including a position conjugate) which is substantially conjugate with the pupil 18 of the eye 1 to be inspected and which can be inserted and removed with respect to the projection optical axis. The aperture stop 14 defines the portion of the light flux passing through the eye 1 to be inspected.

Further, a fixation target system 17 having a fixation target 15 and a condenser lens 16 is arranged facing the half mirror 23. The light source 21 and the fixation target 15 are the eye 1 to be examined.
The light source 2 is located at a position conjugate with the retina of the
1. The fixation target 15 forms an image on the retina 2. The light source 21
The projection lens 22 and the projection lens 22 are integrally formed, and are movable in conjunction with a focusing lens 19 described later along the optical axis direction and in a plane orthogonal to the optical axis.

The light receiving optical system 7 shares the half mirror 5, the relay lens 24 disposed on the projection optical axis of the half mirror 5, the objective lens 12, and the quarter wavelength plate 13 with the projection optical system 3. is doing.

A focusing lens 19 movable along the reflected light axis is provided on the reflected light axis passing through the half mirror 5, and the polarization direction is 90 ° different from that of the S linearly polarized light.
A second polarizing plate 27 that transmits linearly polarized light is detachably provided, and an imaging lens 20 is further disposed on the reflection optical axis, and the imaging lens 20 is at a position conjugate with the retina of the eye 1 to be inspected. The reflected light beam is imaged on the light receiving element 8 at. Further, the imaging lens 20 is replaceable with the lens array 10, and when replaced with the lens array 10, the lens array 10 splits the reflected light beam from the retina 2 into a predetermined small light beam 11. , Each of the small luminous fluxes 11 is imaged on the light receiving element 8.

The light reception signal from the light receiving element 8 is stored in the storage unit 31 via the signal processing unit 30. The writing of data from the signal processing unit 30 to the storage unit 31 is performed by the control unit 3.
2, the control section 32 performs a required calculation based on the data stored in the storage section 31 and displays the calculation result on the display section 33.

The operation of the above optical system will be described below.

The focusing lens 19 is set to a reference position (a state where an emmetropic eye is in focus), and the eye 1 is made to gaze at the fixation target 15. Here, if the fixation target 15 is placed on the optical axis, measurement is performed in the fovea centralis of the fundus retina. or,
By changing the line-of-sight direction of the eye to be inspected by moving the fixation target 15 out of the optical axis in a plane orthogonal to the optical axis, it is possible to measure at a desired site on the retina.

The projection optical system 3 projects a projection light beam onto the retina 2 while the eye 1 to be examined is gazing at the fixation target 15. Note that visible light is used for the fixation target 15, and infrared light or visible light is used for the projection light flux.

First, the quarter wavelength plate 13 and the aperture stop 1
4, imaging lens 20, first polarizing plate 26, second polarizing plate 27
And the lens array 10 is inserted, the single-pass eye optical characteristic (MTF) of the eyeball optical system is required.

The projection light beam from the light source 21 passes through the projection lens 22 and the half mirror 23, reaches the half mirror 5, is reflected by the half mirror 5, passes through the relay lens 24, and is passed through the objective lens 12 to be reflected by the objective lens 12. The image is projected onto the retina 2 of the eye 1 to be inspected, and is formed on the retina 2 as a substantially point light source image.

The light flux emitted from the point light source image of the retina 2 passes through the objective lens 12, the relay lens 24, the half mirror 5, and the focusing lens 19, and the lens array 1
It is incident on 0. The lens array 10 causes a predetermined number of small luminous fluxes 1
It is divided into 1 and further imaged on the light receiving element 8.

As described above, the image forming position of each of the small light fluxes 11 is displaced from the reference position due to the characteristics of the eyeball optical system of the subject eye 1. The light receiving signal of the light receiving element 8 is stored in the storage unit 31 via the signal processing unit 30, and further the deviation δ of each image forming position is obtained by the control unit 32.
Further, a single-pass eye optical characteristic (MTF) of the eyeball optical system, that is, E (U, V) is calculated from the shift δ.

Next, the double-pass eye optical characteristics (MTF) including the characteristics of the retina and the eyeball optical system are obtained.

When the double-pass eye optical characteristic (MTF) is detected, the light flux specularly reflected by the retina 2 is used as described above.

The quarter wavelength plate 13, the aperture stop 14, the first polarizing plate 26, and the second polarizing plate 27 are inserted in the optical axis, and the lens array 10 is replaced with the imaging lens 20.

The focusing lens 19 is set under the same conditions as the single-pass eye optical characteristics (MTF) of the eyeball optical system, for example, at the same reference position as described above, and the fixation target 15 is focused on the eye 1 to be inspected. Let

The projection optical system 3 projects a projection light beam onto the retina 2 while the eye 1 to be examined is gazing at the fixation target 15. The fixation target 15 uses visible light as described above, and the projection light flux uses infrared light or visible light.

The projection light beam from the light source 21 passes through the projection lens 22, the first polarizing plate 26 and the half mirror 23 and reaches the half mirror 5. The first polarizing plate 26 is S
By transmitting the linearly polarized light, the S linearly polarized light is reflected by the half mirror 5, and passes through the relay lens 24, the aperture stop 14 and the objective lens 12 through the quarter wavelength plate 13 and the retina of the eye 1 to be inspected. 2 and the first index image is formed on the retina 2.

The S linearly polarized light passes through the quarter-wave plate 13 to become right circularly polarized light. The projection light flux is specularly reflected by the retina 2 of the eye 1 to be examined, and the specular reflection light flux is reflected by the retina 2 to become left circularly polarized light. Further, the specularly reflected light flux is transmitted through the quarter-wave plate 13 to become P linearly polarized light having a polarization direction different by 90 ° from the S linearly polarized light.

The P linearly polarized light is guided to the half mirror 5 by the objective lens 12 and the relay lens 24, passes through the half mirror 5 and the focusing lens 19, and reaches the second polarizing plate 27. Since the second polarizing plate 27 transmits P linearly polarized light, the specularly reflected light flux is imaged on the light receiving element 8 by the imaging lens 20 as a secondary index image.

By the way, the projection light flux projected on the retina 2 of the eye 1 is not all specularly reflected by the retina 2, but a part thereof penetrates from the surface of the retina 2 into the surface layer and is scattered and reflected. So-called bleeding reflection occurs. When this scattered reflection light beam is received by the light receiving element 8 together with the specular reflection light beam, it becomes noise in the light intensity distribution of the secondary index image, and accurate eye optical characteristics of the eyeball optical system cannot be measured.

The polarization state of the light beam due to such scattering reflection is a random state. Therefore, when the light is transmitted through the quarter-wave plate 13 and becomes linearly polarized light, what is matched with P linearly polarized light is limited to a limited part, and the half mirror 5 converts the scattered reflected light into P linearly polarized light. Anything that does not match is reflected. Therefore, the ratio of the P linearly polarized light component due to the scattered reflected light flux to the P linearly polarized light component totally reflected by the retina 2 of the subject's eye 1 becomes negligibly small.

Therefore, the light receiving element 8 receives the specular reflection light flux from which the scattered reflection light flux is substantially removed.
By using the ¼ wavelength plate 13 as a constituent element of the projection optical system 3 and the light receiving optical system 7, it is possible to accurately measure the eye optical characteristics of the eyeball optical system.

The light intensity distribution of the secondary index image received by the light receiving element 8 is a double-pass eye optical characteristic (MTF) including the characteristics of the retina 2 and the eyeball optical system.
The double-pass eye optical characteristic (MTF) is detected from the received light signal of.

Thus, double-pass eye optical characteristics (MTF)
The MTF of the retina due to the specularly reflected light flux is calculated by the following formula (6): MTF of the retina = √ (double-pass MTF obtained from the PSF detection mechanism) / (single-pass M obtained from the wavefront detection mechanism)
TF).

In the above embodiment, the single-pass ocular optical characteristic (MTF) is measured by the wavefront detecting mechanism, but the ocular optical characteristic of the ocular optical system calculated by the psychophysical subjective measuring method or the like ( The calculation may be performed using the MTF) value.

Further, in the above embodiment, the wavefront detection mechanism and the spread function detection mechanism are incorporated in the same eye optical characteristic measuring device, but only one of them is provided, and the other is used as the computing device. May have a function of calculating the MTF of the retina by inputting known data. Alternatively, the PC (personal computer) has a function of calculating the MTF of the retina based on the double-pass MTF obtained from the spread function detection mechanism and the single-pass MTF obtained from the wavefront detection mechanism, and the data individually obtained from each detection mechanism is used. The MTF of the retina may be obtained by inputting it to a PC (personal computer).

[0055]

As described above, according to the present invention, the light source image is projected on the retina of the eye to be examined, and the light amount distribution characteristic obtained from the specular reflection component of the light flux reflected from the retina and the light emitted from the cornea of the eye to be examined. Since the light transfer function of the retina of the eye to be inspected by the specularly reflected light beam is obtained based on the wavefront characteristic obtained by the light flux of the retina, it is possible to measure the light transfer function of the retina that affects the characteristics of the image that the subject can recognize. It has an excellent effect of being able to objectively grasp what kind of image the optometry can recognize.

[Brief description of drawings]

FIG. 1 is a schematic view of a wavefront detection mechanism.

FIG. 2 is a schematic diagram of a spread function (PSF) detection mechanism.

FIG. 3 is a basic configuration diagram showing an embodiment of the present invention.

[Explanation of symbols]

1 Eye to be examined 2 retina 3 Projection optical system 7 Light receiving optical system 8 Light receiving element 10 lens array 11 small luminous flux 13 1/4 wave plate 15 fixation target 21 light source 26 First Polarizing Plate 27 Second polarizing plate 30 signal processor 32 control unit

Claims (4)

[Claims] 1. A mirror surface based on a light amount distribution characteristic obtained by projecting a light source image on a retina of an eye to be examined, which is obtained from a specular reflection component of a light flux reflected from the retina, and a wavefront characteristic obtained by a light flux emitted from a cornea of an eye to be examined. A method for measuring optical characteristics of an eye, which comprises obtaining a light transfer function of a retina of an eye to be examined by a reflected light beam. 2. The light source image is projected on the retina of the eye to be examined, and the light quantity distribution characteristic obtained from the specular reflection component of the reflected light flux from the retina and the eyeball optical characteristic from the cornea of the eye to the retina are used to generate the specular reflected light flux. A method for determining the optical characteristics of an eye, characterized by obtaining a light transfer function of a retina of an eye to be examined. 3. A means for projecting a light source image on a retina of an eye to be examined,
A light receiving element that receives the reflected light flux of the light source image, an optical system that forms a light source image on the light receiving element by a light flux of a specular reflection component of the reflected light flux of the light source image, and the optical system based on a signal from the light receiving element Light amount distribution characteristic detecting means for detecting the light amount distribution characteristic of the light source image, means for detecting the wavefront characteristic of the light beam emitted from the cornea of the eye to be inspected by the light beam from the light source image projected on the retina of the eye, and the light amount distribution characteristic, An ocular optical characteristic measuring device comprising: a calculation unit that calculates a light transfer function of the retina based on a specularly reflected light flux based on the wavefront characteristic. 4. A means for projecting a light source image on a retina of an eye to be examined,
A light receiving element that receives the reflected light flux of the light source image, an optical system that forms a light source image on the light receiving element by a light flux of a specular reflection component of the reflected light flux of the light source image, and the optical system based on a signal from the light receiving element A light amount distribution characteristic detecting means for detecting the light amount distribution characteristic of the light source image, and a calculation for calculating the light transfer function of the retina by the specular reflected light flux from the known wavefront characteristic measured for the eye to be examined and the detected light amount distribution characteristic. And an optical optical characteristic measuring device.