JP2003116792A - Fundus camera with compensating optical device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively correct wave surface distortion of the imaging light due to an aberration of a cornea and a crystalline lens becoming a cause of impairing resolution of a fundus camera in real time with high resolution. SOLUTION: This fundus camera has a fundus camera optical system, and a compensating optical device composed of an optical writing spatial phase modulation element and a light wave interferometer. The phase distribution for generating wave surface distortion in the inverse direction to the wave surface distortion of the imaging light reflected from a retina caused by the complicated aberration existing in the cornea and the crystalline lens of a person's eye is formed on a phase modulation surface of the optical writing spatial phase modulation element by the compensating optical device. The wave surface distortion of the imaging light is offset by reflecting the imaging light on the phase modulation surface, and the resolution is improved by compensating for the wave surface distortion.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fundus camera, and more particularly, to a complex optic that exists in the cornea and lens of the human eye by utilizing an adaptive optics device composed of an optical writing type spatial phase modulator and a light wave interferometer. The present invention relates to a fundus camera with an adaptive optics device that prevents a reduction in resolution due to the influence of aberration and fluctuation.

[0002]

2. Description of the Related Art Research on adaptive optics technology for detecting and correcting wavefront distortion of light in real time has been conducted mainly for the purpose of improving a blurred celestial image due to atmospheric fluctuations. A typical example is a system that combines a wavefront sensor and a deformable mirror, and has been put to practical use mainly in the field of astronomy.

This prior art is shown in FIG. The wavefront 60 disturbed by the influence of the phase variation of the medium in the optical path is reflected by the variable shape mirror 61, a part of the reflected light is extracted by the beam splitter (BS) 62, and it is incident on the wavefront sensor 63. Here, the deformable mirror 61 is a device in which a large number of electrostrictive elements 65 are attached to the back surface of a thin mirror 64, and the shape of the mirror can be arbitrarily changed according to the voltage applied to each electrostrictive element 65. Is.

The wavefront sensor 63 measures the disturbance of the wavefront, and the data is guided to the control device 66. The controller 66 calculates the shape of the mirror necessary for correcting the wavefront, that is, the voltage applied to each electrostrictive element 65 based on the data, and changes the shape of the deformable mirror based on the calculated voltage. By performing this series of operations quickly, the wavefront of the reflected light can be corrected in real time. By incorporating the deformable mirror 61 in the image system, it is possible to improve the resolution of the image system which is lowered due to the disturbance of the wavefront.

On the other hand, in the field of fundus cameras, the wavefront of the imaging light obtained by being irradiated into the eyeball and reflected by the retina is distorted due to the influence of complicated aberrations existing in the cornea and crystalline lens of the human eye. It is known that the resolution of the retinal image captured is limited due to the above, and it is required to remove the influence of such aberrations to obtain a high-resolution retinal image.

[0006]

In order to meet the needs of such a fundus camera, it is possible to apply a conventional system combining a wavefront sensor and a deformable mirror to the fundus camera to correct the aberration. However, the conventional wavefront sensor and compensation system have not been widely used because of their large size, high cost, large power consumption, difficulty in controlling the wavefront with high precision, and enormous calculation by a computer. Particularly, in the field of precision medical equipment such as a fundus camera, the conventional system is too large to be applied.

An object of the present invention is to solve the conventional problems in such a fundus camera, and it is a small and inexpensive device which consumes less power and causes the resolution of the fundus camera to be impaired. It is an object of the present invention to realize a fundus camera with an adaptive optics device capable of effectively correcting the distortion of the cornea and the crystalline lens in high resolution and in real time without the need for calculation by a computer.

By the way, the inventors of the present invention aim to realize a general-purpose adaptive optical device applicable to various industrial measurements and the like, and a high-resolution optical writing type liquid crystal spatial phase modulator and a feedback interference method as its driving principle. A patent application has already been filed for an invention relating to a light-driven wavefront-corrected image method and apparatus using the above (Japanese Patent Application No. 2000-227874).
The present invention is an invention having novelty and inventive step in a specific configuration in which the preceding invention is applied to a fundus camera.

[0009]

In order to solve the above-mentioned problems, the present invention has a fundus camera optical system, and an adaptive optical device composed of an optical writing type spatial phase modulator and a light wave interferometer. The optical writing type spatial phase modulation is performed by the adaptive optics device to generate a phase distribution that produces a wavefront distortion in the opposite direction to the wavefront distortion of the imaging light reflected from the retina due to the complex aberrations existing in the cornea and lens of the human eye. A fundus camera with an adaptive optics device that is formed on a phase modulation surface of an element and reflects the imaging light on the phase modulation surface to cancel the wavefront distortion of the imaging light to compensate the wavefront distortion and improve the resolution. There, the fundus camera optical system, illuminating the illumination light into the eyeball, reflected light from the retina is reflected by the phase modulation surface of the optical writing type spatial phase changing element at a position conjugate with the pupil of the eye, The fundus observation optical system has an optical system for forming an image on the fundus observation camera. Further, the fundus camera optical system irradiates a laser beam for driving an adaptive optics device into the eyeball and converges it on a retina-shaped point and reflects it. An optical system for reflecting light on the phase modulation surface and introducing it to an adaptive optics apparatus, wherein the adaptive optics apparatus uses the optical wave interference to drive the adaptive optics device driving laser light reflected on the phase modulation surface. Introduced into the meter to obtain interference fringes that reflect the aberrations existing in the cornea and lens, and irradiate the writing surface of the above-mentioned optical writing type spatial phase modulator to cancel the aberrations existing in the cornea and lens. There is provided a fundus camera with an adaptive optics device, characterized in that a different phase distribution is formed on the phase modulation surface.

In the fundus camera with an adaptive optics device according to the present invention, the interference fringes are imaged by a high-sensitivity CCD camera, and the imaged data is written on the writing surface of the optical writing type spatial phase modulator by a projection device. May be

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a fundus camera device with an adaptive optics device according to the present invention will be described below with reference to the drawings. As shown in FIGS. 1 and 2, the present camera device is generally composed of a fundus camera optical system, an adaptive optical device including a phase modulator unit and a light wave interferometer. In addition,
The phase modulator unit includes a light-writing type liquid crystal spatial phase modulator, a projection device including an imaging lens system, a liquid crystal display, a light source and the like.

It is known that the fundus camera has a limited resolution due to the influence of complicated aberrations existing in the cornea and lens of the human eye. In the present invention, the influence of the aberration is removed to obtain a high resolution retinal image.

The basic principle is that the reflected light (imaging light) from the retina causes wavefront distortion of the light wave due to the effects of complicated aberrations and fluctuations existing in the cornea and crystalline lens of the human eye in the fundus camera. A phase distribution that causes wavefront distortion in the opposite direction to this wavefront distortion is formed on the phase modulation surface of the optical writing type liquid crystal spatial phase modulation element in the phase modulator unit by the adaptive optical device, and the imaging light is reflected by the phase modulation surface. As a result, the wavefront distortion of the imaging light is canceled to compensate for the wavefront distortion and the resolution is improved.

As described above, the camera device as a whole is composed of the fundus camera optical system and the adaptive optical device.
More specifically, this camera device includes a laser light source for driving an adaptive optics device, a halogen light source for fundus illumination, and a lens L.
1, beam splitter BS1, beam splitter B
S2, polarizing plate, lens L2, lens L3, beam splitter BS3, beam splitter BS4, lens L
4, a fundus observation camera, a lens L5, a lens L6, a high-sensitivity CCD camera, a Mach-Zehnder interferometer, and a phase modulator unit.

The light source for illuminating the fundus of the eye uses a spatially incoherent halogen light source, but a spatially coherent light source such as a laser beam may be used. Further, not only continuous light but also discontinuous light such as a flash light source may be used. The lenses L2 and L3 are arranged such that the pupil of the eye and the phase modulation surface of the optical writing type liquid crystal spatial phase modulation element are optically conjugate with each other, that is, in an image forming relationship.

The illumination light from the halogen light source is the lens L.
1, beam splitter BS1, beam splitter B
The light is irradiated into the eyeball through S2. This illuminating light is applied to the retina through the cornea and the crystalline lens, and its reflected light again exits from the eyeball through the crystalline lens and the cornea, passes through the beam splitter BS2, the polarizing plate, the lenses L2 and L3, the beam splitters BS3 and BS4, and the phase The light is reflected by the phase modulation surface of the optical writing type liquid crystal spatial phase modulator in the modulator unit. The reflected light is reflected by the beam splitter BS4, is focused on the fundus observation camera through the lens L4, and a retinal image is captured.

The laser light for driving the adaptive optics device is irradiated into the eyeball through the beam splitter BS1 and the beam splitter BS2 and is converged to one point on the retina through the cornea and the crystalline lens, and the reflected light from the retina is again reflected by the crystalline lens and the crystalline lens.
Through the cornea and out of the eye, the beam splitter BS2,
After passing through the polarizing plate, the lens L2, the lens L3, the beam splitter BS3, and the beam splitter BS4, the light is reflected by the phase modulation surface of the optical writing type liquid crystal spatial phase modulation element in the phase modulator unit.

The laser light for driving the adaptive optics device is linearly polarized light, and the polarizing plate is arranged so as to transmit only the light wave of the polarization component orthogonal to the polarization direction. As a result, the laser light reflected on the corneal surface can be blocked, and only the laser light reflected from a single point of the retina can be transmitted.

The laser light for driving the adaptive optics device reflected by the phase modulation surface passes through the beam splitter BS4 and is reflected by the beam splitter BS3, and the lens L5,
The light enters the Mach-Zehnder interferometer through the lens L6 and the reflecting mirror. Then, the optical writing type liquid crystal spatial phase modulator in the phase modulator unit, which will be described later, performs the phase modulation operation to cancel the wavefront distortion of the imaging light to compensate the wavefront distortion and improve the resolution.

The phase modulator unit will be described in more detail. The optical writing type liquid crystal spatial phase modulation element is an element in which the modulation phase of the phase modulation surface R on the back side thereof changes depending on the intensity of light applied to the writing surface W. However, the phase modulation has polarization dependency, and modulates only the phase of the light wave of the polarization component parallel to the alignment direction of the liquid crystal molecules. Further, since this element can arbitrarily perform phase modulation according to the intensity pattern irradiated on the writing surface W, it has a high resolution wavefront correction capability.

As described above, the cornea and lens of the human eye having an aberration that becomes a disturbing medium that disturbs the wavefront are arranged so as to form an image on the phase modulation surface R by the lenses L2 and L3.

In this optical system, when the phase of the phase modulation surface R of the optical writing type liquid crystal spatial phase modulator is opposite in direction to the aberration existing in the cornea and the crystalline lens and its size is half the distribution, the reflection process is performed. The two cancel each other out, and the influence of the aberration of the cornea and the crystalline lens in this camera device is removed. At this time, the image on the fundus observing camera, which was blurred due to the influence of the aberration of the cornea and the crystalline lens, changes to a clear image.

Next, the adaptive optics device will be described. As described above, the laser light for driving the adaptive optics device is reflected by the phase modulation surface R of the optical writing type liquid crystal spatial phase modulation element, passes through the beam splitter BS4, passes through the beam splitter BS3, and the lenses L5, L6 and the reflecting mirror. And enters the Mach-Zehnder interferometer via.

In this interferometer, the vertically polarized component of the light wave is reflected by the polarization beam splitter PBS, and the lens L7,
The light enters the high-sensitivity CCD camera through the reflecting mirror, the lens L8, the half-wave plate, and the beam splitter BS5.
On the other hand, the horizontal polarization component transmits through the polarization beam splitter PBS, the size of which is enlarged by the lenses L9 and L10 and a pseudo reference plane wave is formed from the disturbed wavefront, and the high sensitivity CCD is transmitted through the reflecting mirror and the beam splitter BS5.
It is incident on the camera. These two light waves form interference fringes that faithfully reflect the aberrations existing in the cornea and crystalline lens, and these interference fringes are photographed by a high-sensitivity CCD camera.

Since it is necessary to align the polarization directions of the two light waves to be superimposed in order to form the interference fringes, a half-wave plate is introduced to rotate the polarization direction of one light wave by 90 degrees and The polarization directions are aligned. Further, the polarization direction of the laser light source for driving this adaptive optics device and the polarizing plate arranged so as to transmit the light wave of the polarization component orthogonal to it are adjusted so that the two light waves to be superposed have the same intensity. .

The electrical image signal of the interference fringes photographed by the high sensitivity CCD camera as described above is displayed as a two-dimensional image on the liquid crystal display. The two-dimensional image on the liquid crystal display is projected by a light source to form an imaging lens system L11,
An image is formed on the writing surface W (the back side of the phase modulation surface R) of the optically writable liquid crystal spatial phase modulation element through L12.

The lenses L9 and L10 are determined according to the magnifying power for creating the reference plane wave (for example, to obtain a magnifying power of 5 times, the lenses L9 and L10 are determined).
The ratio of the focal lengths is 1 to 5). When the above is realized,
Due to the polarization dependence of the optical writing type liquid crystal spatial phase modulation element, the phase of only the light wave of the vertically polarized component of the incident light is modulated on the phase modulation surface of the element, and a feedback interferometer is realized. As a result, the phase distribution of the phase modulation surface of the optical writing type liquid crystal spatial phase modulation element becomes a distribution that cancels the aberrations and fluctuations existing in the cornea and the crystalline lens, and operates as an adaptive optical system.

Although the embodiments of the fundus camera device according to the present invention have been described based on the embodiments, the present invention is not limited to such embodiments and various modifications can be made within the scope of the claims. It goes without saying that there are examples.

[0029]

According to the present invention having the above-described structure, a small and inexpensive device which consumes less power and does not require calculation by a computer of distortion of the cornea and crystalline lens, which causes deterioration of resolution of the fundus camera. In addition, it is possible to realize a fundus camera with an adaptive optics device capable of effectively performing correction with high resolution and in real time.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an optical device mainly showing a fundus camera optical system in a basic configuration of the present invention.

FIG. 2 is a configuration diagram of an optical device showing a compensating optical device mainly including a phase modulator unit and a light wave interferometer in a basic configuration of the present invention.

FIG. 3 is a conceptual diagram of a conventional adaptive optics system using a deformable mirror.

[Explanation of symbols]

BS1, BS2, BS3, BS4, BS5 Beam splitters L1, L2, L3, L4, L5, L6, L7, L8, L
9, L10, L11, L12 Lens PBS Polarization beam splitter R Phase modulation surface of optical writing type liquid crystal spatial phase modulation element W Writing surface of optical writing type liquid crystal spatial phase modulation element

Claims (2)

[Claims] 1. A fundus camera optical system, and an adaptive optical device composed of an optical writing type spatial phase modulator and a light wave interferometer, which are caused by complicated aberrations existing in the cornea and lens of the human eye. A phase distribution that produces a wavefront distortion in a direction opposite to the wavefront distortion of the imaging light reflected from the retina is formed on the phase modulation surface of the optical writing type spatial phase modulation element by the adaptive optics device, and the imaging light is converted into the phase. A fundus camera with an adaptive optics device for compensating the wavefront distortion of the imaging light to improve the resolution by reflecting the wavefront distortion of the imaging light by reflecting the light on the inside of the eyeball. It has an optical system that irradiates the retina and reflects the reflected light from the retina on the phase modulation surface of the optical writing type spatial phase modulation element at a position conjugate with the pupil of the eye and forms an image on the fundus observation camera. Further, the fundus camera optical system irradiates the adaptive optics driving laser light into the eyeball, converges it on one point on the retina, reflects the reflected light on the phase modulation surface, and makes it the adaptive optics. And an optical system to be introduced, wherein the adaptive optics device reflects the aberration existing in the cornea and the crystalline lens by introducing the adaptive optics device driving laser beam reflected by the phase modulation surface into the light wave interferometer. By obtaining interference fringes and irradiating the writing surface of the optical writing type spatial phase modulation element with this, a phase distribution that cancels aberrations existing in the cornea and the crystalline lens is formed on the phase modulation surface. Fundus camera with adaptive optics. 2. The adaptive optics apparatus according to claim 1, wherein the interference fringes are imaged by a high-sensitivity CCD camera, and the imaged data is written on a writing surface of the optical writing type spatial phase modulator by a projection device. Fundus camera with.