JP2003070741A - Measurement unit for optical characteristics of eye - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a correct simulation image to observe a subject corresponding to characteristics of the eyeground and the simulation image can be easily obtained in real time, even when the light flux for measurement on the subject eyeground is in an arbitrary focusing condition, by only measuring light quantity distribution characteristics of the light flux on the eyeground of the subject in the condition. SOLUTION: This measurement unit for optical characteristics of an eye has a simulation image calculating part 26 comprising a projecting optical system 2 to project the light flux for measurement in an arbitrary focusing condition to the eyeground of the subject and a light intercepting optical system 3 to guide an image formed almost only by the light flux of a mirror-reflected component in the reflected light flux from the eyeground onto a photoelectric detector 21 to detect characteristics of light quantity distribution of the image by signals from the photoelectric detector 21 and the calculate a target image formed when a specific target 15 is projected on the eyeground in the focusing condition from the light quantity intensity distribution characteristics and a display part to display the target image based on signals in the simulation image calculating part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention detects a light amount distribution characteristic of a measuring light beam projected on a fundus of an eye to be examined, and determines from the light amount distribution characteristic what kind of image a subject can observe. The present invention relates to an eye-optical characteristic measuring device that can be known.

[0002]

2. Description of the Related Art Conventionally, in a device for measuring the optical characteristics of an eyeball optical system to be inspected, a measuring light beam is projected so that a point light source image or the like is formed on the fundus of the eye to be inspected, The light amount distribution characteristic of the formed image is photoelectrically detected, an image that can be observed by the subject is calculated from the light amount distribution characteristic, and the state in which the subject can observe is easily simulated. Recognizable devices have been proposed.

[0003]

However, in the conventional eye optical characteristic measuring apparatus, sufficient consideration is not given to the optical characteristics of the fundus of the human eye, and an accurate simulation image cannot be obtained. It had the drawback that

Further, in the conventional eye optical characteristic measuring apparatus, the refractive power of the eye to be inspected is corrected and the light beam for measurement is focused on the fundus of the eye to be inspected, or the fundus to be inspected by moving the focusing lens. Based on the measurement result of the light amount distribution characteristic in the state where the measurement light flux is focused on, it is necessary to calculate the simulation image of the target image on the eye to be examined, and from the light amount distribution characteristic in any focused state However, it had a drawback that a simulation image in that state could not be obtained in real time.

In view of such circumstances, the present invention makes it possible to obtain an accurate simulation image in which the subject is observed according to the characteristics of the fundus of the eye, and the luminous flux for measurement on the fundus of the eye to be examined is arbitrary. Even in the focused state, it is possible to easily obtain a simulation image in real time only by measuring the light amount distribution characteristic of the light flux on the fundus of the eye to be examined in that state.

[0006]

According to the present invention, a projection optical system for projecting a projection light beam for measurement on the fundus of the eye to be examined in an arbitrary focused state, and a light beam reflected from the fundus of the eye to be examined are substantially specularly reflected. A light receiving optical system that guides an image formed from only the light flux of the component onto the photoelectric detector, detects the light intensity distribution characteristic of the image by the signal from the photoelectric detector, and detects the light intensity distribution characteristic from the light intensity distribution characteristic. A simulation image calculation unit that calculates a target image formed when a specific target is projected on the fundus of the eye to be examined in a focused state, and the target image is displayed based on a signal from the simulation image calculation unit. For measuring the optical characteristics of the eye, and the measuring light beam for measuring the optical characteristics of the eye to form a point light source image on the fundus of the eye to be inspected. Optical characteristic measurement of eye It relates to the location.

[0007]

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

First, the fundus tissue of the human eye will be briefly described.

FIG. 1 is a schematic view of the fundus tissue of the human eye, where 31 is a photoreceptor layer, 32 is a retinal pigment epithelium layer, 33 is a choroid, and 34 is a sclera.

The photoreceptor layer 31 is the retinal pigment epithelium layer 3
It is a collection of fibrous photoreceptor cells perpendicular to 2. The light flux that has passed through the photoreceptor cell layer 31 (visual cells) is specularly reflected by the retinal pigment epithelium layer 32, while part of the light flux passes through the retinal pigment epithelium layer 32 and the choroid 3 behind it.
3. Scattered and reflected by the sclera 34. However, this scattered reflected light has almost no effect on an image recognized by a person.

Here, it has been experimentally confirmed that, when the light flux incident on the photoreceptor cell layer 31 passes through the photoreceptor cell, it is repeatedly transmitted through the photoreceptor cell by substantially total reflection.

FIG. 2 shows the basic configuration of the eye optical characteristic measuring apparatus according to this embodiment.

In the figure, 1 is an eye to be inspected, 2 is a projection optical system, and 3 is a light receiving optical system.

The projection optical system 2 includes a light source 5, a projection lens 6 for condensing a projection light beam emitted from the light source 5, a half mirror 7 arranged on the optical axis of the projection lens 6, and a half mirror 7. The projection light beam that has passed through the
The linearly polarized light component (P linearly polarized light) of the polarization direction of is reflected and projected, and the polarization direction is different from the P linearly polarized light by 90 °.
Polarization beam splitter 8 that transmits linearly polarized light, relay lens 9 disposed on the projection optical axis of polarization beam splitter 8 from the side of polarization beam splitter 8, objective lens 1
1. A correction optical system 12, which is arranged between the objective lens 11 and the eye 1 to be inspected and is formed of a spherical lens, and a quarter wavelength plate 13. Further, a fixation target system 17 having a fixation target 15 and a condenser lens 16 is arranged facing the half mirror 7. The light source 5 and the fixation target 15 are located at a position conjugate with the fundus of the eye 1 to be inspected, and as will be described later, the light source 5,
The fixation target 15 forms an image on the fundus. The light source 5 and the projection lens 6 are integrally formed, and are movable in the optical axis direction in conjunction with a focusing lens 19 described later.

The light receiving optical system 3 includes the polarization beam splitter 8, the relay lens 9 arranged on the projection optical axis of the polarization beam splitter 8, the objective lens 11, the correction optical system 12, and the quarter wavelength plate 13. Is shared with the projection optical system 2.

A focusing lens 1 which is movable along the reflection optical axis on the reflection optical axis passing through the polarization beam splitter 8.
9. An image forming lens 20 is provided, and the image forming lens 20 forms an image of the reflected light flux on the photoelectric detector 21 located at a position conjugate with the fundus of the eye 1 to be inspected.

The received light signal from the photoelectric detector 21 is stored in the storage unit 27 via the signal processing unit 26. The writing of data from the signal processing unit 26 to the storage unit 27 is controlled by the control unit 28, which controls the storage unit 2
Required calculation is performed based on the data stored in 7, and the calculation result is displayed on the display unit 29.

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

The focusing lens 19 is used as a reference position, and the eye 1 to be examined is focused on the fixation target 15. At this time, the correction optical system 12 sets the correction amount to zero.

The projection optical system 2 projects a projection light beam onto the fundus of the eye to be examined while the eye 1 to be examined is gazing at the fixation target 15, and a point light source image is formed on the fundus of the eye to be examined.
Note that visible light is used for the fixation target 15, and infrared light is used for the projection light flux.

A projection light beam (infrared light) from the light source 5 passes through the projection lens 6 and the half mirror 7 to reach the polarization beam splitter 8, and the P linear polarization component is reflected by the polarization beam splitter 8. After passing through the relay lens 9, the objective lens 11 and the correction optical system 12 pass through the quarter-wave plate 13 to project the light onto the fundus of the eye 1 to be inspected, and a first optotype image is formed on the fundus.

When the P linearly polarized light passes through the quarter wavelength plate 13, it becomes right circularly polarized light. The projected light flux is totally reflected by the fundus of the eye 1 to be examined, and the totally reflected light flux is reflected by the fundus to be left circularly polarized light. Further, the totally reflected light flux passes through the quarter-wave plate 13 to become S linearly polarized light whose polarization direction is different from that of the P linearly polarized light by 90 °.

The S linearly polarized light is guided to the polarization beam splitter 8 by the correction optical system 12, the objective lens 11 and the relay lens 9. Since the polarization beam splitter 8 reflects P linearly polarized light and transmits S linearly polarized light, the totally reflected light beam passes through the polarization beam splitter 8, and the focusing lens 19 and the imaging lens 20 cause the photoelectric detector. A second target image is formed on 21.

By the way, the projection light beam projected on the fundus of the eye 1 is not entirely specularly reflected on the fundus surface, but a part thereof penetrates into the surface layer from the fundus surface and is scattered and reflected. Reflection occurs. When this scattered reflected light flux is received by the photoelectric detector 21 together with the specular reflected light flux, it becomes noise in the light amount intensity distribution of the second target 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 linearly polarized light is transmitted through the quarter-wave plate 13 and coincides with the S linearly polarized light, it is limited to a limited portion, and the polarized beam splitter 8 scatters and reflects the S linearly polarized light. All but those that match are reflected. Therefore, the ratio of the S linearly polarized light component that is specularly reflected by the fundus of the eye 1 to be inspected to the S linearly polarized light component due to the scattered reflected light flux becomes negligibly small.

Therefore, the photoelectric detector 21 receives the specularly reflected light flux from which the scattered and reflected light flux is substantially removed. By using the quarter-wave plate 13 as a constituent element of the projection optical system 2 and the light receiving optical system 3, it is possible to accurately measure the eye optical characteristics of the eyeball optical system. The signal processing unit 26 calculates the light intensity distribution characteristic based on the received light signal from the photoelectric detector 21, as described later, and further calculates the simulation image.

The optical characteristics of the fundus of the eye can be measured by the following procedure.

Here, FIG. 3A shows a state in which the light beam is focused on the fundus, and FIG. 3B shows a state in which the light beam is out of focus on the fundus. Due to the influence, the amplitude transmittance of the eyeball optical system of the eye 1 to be examined is P (x, y) in any state, and the retinal pigment epithelium layer 32 is
The amplitude transmittance of photoreceptor cells including the reflection characteristics at R (x,
y), if the two-dimensional light intensity distribution on the two-dimensional detector calculated and measured based on the received light signal from the two-dimensional detector (photoelectric detector 21) is I (x, y), the following formula is established. . P (x, y) * R (x, y) * P (x, y) = I (x, y) (1) where * means convolution integration.

Next, Fourier transform is performed on both sides of the equation (1). Here, the optical transfer function of the eyeball optical system is p (u, v),
When the light transfer function of the photoreceptor cell is r (u, v) and the two-dimensional light transfer function on the two-dimensional detector is i (u, v), the following equation holds. FT [P (x, y)] = p (u, v) FT [R (x, y)] = r (u, v) FT [I (x, y)] = i (u, v) Therefore, When Fourier transform is performed on the equation (1), p (u, v) × r (u, v) × p (u, v) = i (u, v) (2) Here, since r (u, v) is experimentally close to about 1, the following formula is substantially established. [P (u, v)] ² = i (u, v) (3) Therefore, p (u, v) = √ [i (u, v)] (4). Since | FT [I (x, y)] | = i (u, v) (5), the two-dimensional light intensity distribution I (x, y) on the measured two-dimensional detector is Fourier Convert and use i in equation (5)
(U, v) is obtained and substituted into the equation (4) to calculate the optical transfer function p (u, v) of the eyeball optical system.

Next, the calculated p (u, v) is inverse-Fourier-transformed to obtain the amplitude transmittance P (x, y) of the eyeball optical system.
To calculate. IFT [p (u, v)] = P (x, y) (6)

The calculated amplitude transmittance P of the eyeball optical system
(X, y) and the desired light intensity distribution function O (x, y) of the visual acuity test target are subjected to convolution integration to obtain a simulation image S (x, y) can be calculated by the following equation. S (x, y) = P (x, y) * O (x, y) (7)

FIG. 4 is a simulation image S of an image obtained by convolution integration of the amplitude transmittance P (x, y) and the light intensity distribution function O (x, y).
(X, y) is illustrated. In the figure, the jagged edges around the simulation image S (x, y) indicate that the figure is blurred. In FIG. 4, the Landolt ring target is described as the target for the visual acuity test. However, if the light intensity distribution function of various targets for the visual acuity test such as characters and figures is selected, various visual targets can be selected as necessary. The simulation image S (x, y) on the mark can be calculated and displayed.

Therefore, even if the correction optical system 12 corrects a predetermined amount or the focusing lens 19 is moved by a predetermined amount, that is, the measuring light beam on the fundus is focused at an arbitrary position. Even in the state, an accurate simulation image S (x, y) can be calculated in real time only by detecting the light amount distribution characteristic of the light flux on the fundus in that state. Therefore, even if the correction amount is adjusted arbitrarily or the focus is adjusted arbitrarily, the image actually recognized by the subject in that state can be displayed in real time. It is possible to objectively and accurately grasp the image observed by the subject.

[0034]

As described above, according to the present invention, the projection optical system for projecting the projection light beam for measurement on the fundus of the eye to be examined in an arbitrary focus state, and the light flux reflected from the fundus of the eye to be examined are substantially mirror surfaces. It consists of a light receiving optical system that guides the image formed only from the light flux of the reflected component onto the photoelectric detector, detects the light intensity distribution characteristic of the image by the signal from the photoelectric detector, and from the light intensity distribution characteristic A simulation image calculation unit that calculates a target image formed by projecting a specific target onto the fundus of the eye to be examined in the focused state, and the target image based on the signal of the simulation image calculation unit. Since it has a display unit for displaying, it exhibits an excellent effect that the examiner can objectively and accurately grasp the image observed by the examinee during the measurement.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a fundus of a human eye.

FIG. 2 is a basic configuration diagram of an eye optical characteristic measuring device according to the present embodiment.

3 (A) and 3 (B) are explanatory views showing a reflection state at a fundus of an eye to be examined in the eye optical characteristic measuring apparatus.

FIG. 4 is an explanatory diagram of a simulation image calculated as a visual acuity test target.

[Explanation of symbols]

1 Eye to be examined 2 Projection optical system 5 light sources 12 Corrective optics 13 1/4 wave plate 15 fixation target 17 fixation target system 19 Focusing lens 21 Photoelectric detector 26 Signal processing unit 29 Display

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Masahiro Shibuya             75-1 Hasunumacho, Itabashi-ku, Tokyo             In Pucon (72) Inventor Hiromi Takahashi             75-1 Hasunumacho, Itabashi-ku, Tokyo             In Pucon

Claims (3)

[Claims] 1. A projection optical system for projecting a projection light flux for measurement on the fundus of the eye to be examined in an arbitrary focused state, and a light flux of a component which is substantially specularly reflected among the light flux reflected from the fundus of the eye to be examined. And an optical receiving system that guides the image onto the photoelectric detector,
The light intensity distribution characteristic of the image is detected by a signal from the photoelectric detector, and a target image formed when a specific target is projected on the fundus of the eye to be examined in the focused state from the light intensity distribution characteristic. An eye-optical characteristic measuring device comprising: a simulation image calculation section calculated by calculation; and a display section for displaying the optotype image based on a signal from the simulation image calculation section. 2. The eye optical characteristic measuring device according to claim 1, wherein the measuring light beam forms a point light source image on the fundus of the eye to be examined. 3. The eye optical characteristic measuring device according to claim 1, wherein the specific optotype is a visual acuity test optotype.