Ophthalmic observation apparatus

An apparatus for observing an eye of an examinee by imaging the eye, includes an irradiation optical system; an imaging optical system; a monitor; and a display control part, wherein the imaging optical system includes a wavefront detector which receives the beam reflected by the objective part to detect wavefront aberration thereof and a wavefront compensator adapted to compensate the wavefront aberration based on a detection result of the wavefront detector, the wavefront compensator being placed within an optical path of the imaging optical system excepting a common optical path with the irradiation optical system.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an ophthalmic observation apparatus for observing an eye of an examinee by imaging the eye.

2. Description of Related Art

There is an apparatus constructed to irradiate and scan a laser beam in two dimensions over an objective part to be observed such as a fundus and receives the beam reflected by the objective part by a photo-receiving element (a photo-detector) to produce an image of the objective part. The apparatus of this type can produce high resolution images as compared with a conventional fundus camera or the like. However, a further improved apparatus has been demanded to produce higher resolution images of the objective part.

BRIEF SUMMARY OF THE INVENTION

The present invention has been made in view of the above circumstances and has an object to provide an ophthalmic observation apparatus capable of producing a high-resolution image of an objective part to be observed.

To achieve the purpose of the invention, there is provided an apparatus for observing an eye of an examinee by imaging the eye,  comprising: an irradiation optical system including a laser source which emits a laser beam and a scanning unit which two-dimensionally scans the beam onto an objective part of the examinee's eye to be observed, the irradiation optical system being adapted to irradiate the beam to the objective part; an imaging optical system including a photo-receiving element which receives the beam reflected by the objective part; a monitor; and a display control part which produces an image of the objective part based on an output signal from the photo-receiving element, and causes the monitor to display the image; wherein the imaging optical system includes a wavefront detector which receives the beam reflected by the objective part to detect wavefront aberration thereof and a wavefront compensator adapted to compensate the wavefront aberration based on a detection result of the wavefront detector, the wavefront compensator being placed within an optical path of the imaging optical system excepting a common optical path with the irradiation optical system.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A detailed description of a preferred embodiment of the present invention will now be given referring to the accompanying drawings.FIG. 1is a schematic structural view of an optical system of a fundus observation apparatus in the present embodiment.

A laser beam emitted from a laser source1passes through a center opening (hole) of a perforated mirror2and a lens3and is reflected by plane reflecting mirrors4and5and a concave reflecting mirror6, and falls on a polygon mirror7. The beam reflected by the polygon mirror7is then reflected by a concave reflecting mirror8, and falls on a galvano-mirror9. The beam reflected by the galvano-mirror9is reflected by a concave reflecting mirror10and is concentrated (condensed) on an objective part to be observed of a fundus Ef of an examinee's eye E. The mirrors4and5are synchronously movable in a direction indicated by an arrow A to change an optical path length of the beam for diopter correction (for focusing) of the eye E. The polygon mirror7is rotated in a direction indicated by an arrow B in order to scan the beam in a horizontal direction (an X-direction). The galvano-mirror9is swung (oscillated) in a direction indicated by an arrow C to scan the beam in a vertical direction (a Y-direction). With this structure, the beam is irradiated onto the objective part of the fundus Ef while scanning it in two dimensions (in the X- and Y-directions). These optical members constitute an irradiation optical system (a light projecting optical system).

In the present embodiment, used as the laser source1is a semiconductor laser source which emits an infrared laser beam of linear polarized light having a predetermined polarization direction.

The beam reflected from the objective part of the fundus Ef travels back along the irradiation optical system and is reflected by a portion surrounding the opening of the perforated mirror2.

The beam reflected by the perforated mirror2is reflected by a plane reflecting mirror11and enters a wavefront compensator12.

The wavefront compensator12is disposed within an optical path of an imaging optical system excepting a common optical path with the irradiation optical system. This makes it possible to achieve a downsized apparatus as compared with a case where the wavefront compensator12is disposed in the common optical path. For this wavefront compensator12, for example, a liquid-crystal spatial phase modulator, typified by e.g. PPM (a programmable phase modulator) made by Hamamatsu Photonics K.K. is used. In the wavefront compensator12, an aligning direction of liquid crystal molecules in a liquid crystal layer is nearly parallel to a polarization plane of the incident beam. Further, in the wavefront compensator12, a predetermined plane, relative to which liquid crystal molecules will rotate in response to changes in applied voltage to the liquid crystal layer, is nearly parallel to a plane including an incident optical axis and a reflecting optical axis of the beam and the normal to a mirror layer of the wavefront compensator12.

The beam is reflected by a reflecting plane of the wavefront compensator12in which wavefront aberration is compensated. Successively, the beam partly passes through a half mirror13and a lens15in order and then is focused on a center pinhole of a pinhole plate16. The beam focused on the pinhole passes through a lens17and then is received by a photo-receiving element (a photo-detector)18. The opening of the perforated mirror2is substantially conjugated with the pupil of the eye E with respect to the lens3. The pinhole of the pinhole plate16is substantially conjugated with the objective part of the fundus Ef with respect to the lens15. These optical members constitute the imaging optical system (a photo-receiving optical system).

Further, part of the beam of which wavefront aberration has been compensated is reflected by the half mirror13and then enters a wavefront detector14. The wavefront detector14detects the wavefront aberration to obtain information on the wavefront aberration to be compensated by the wavefront compensator12. For this wavefront detector14, for example, a Hartmann-Shack sensor, a wavefront curvature sensor for detecting a change in light intensity, and others are used. The reflecting plane of the wavefront compensator12and a light receiving plane of the wavefront detector14may be conjugated with the pupil of the eye E. In this case, a needful optical member has to be disposed in the imaging optical system.

In the present embodiment, used as the photo-receiving element18is an Avalanche Photodiode (APD).

In the present embodiment, the laser source1is placed so that the beam of the linear polarized light enters the wavefront compensator12as a P-polarized beam, but not limited thereto. A ½ wave plate for changing a polarization direction of P waves may be placed in the optical path of the imaging optical system between the perforated mirror2and the wavefront compensator12. Such ½ wave plate is rotated to provide the polarization direction of appropriately producing an image of the objective part (the polarization direction of efficiently reflecting the beam to the wavefront compensator12). This ½ wave plate is preferably located within the optical path of the imaging optical system excepting the common optical path with the irradiation optical system.

FIG. 2is a schematic block diagram of a control system of the apparatus. Connected to a control part20which controls the entire apparatus are the laser source1, the polygon mirror7, the galvano-mirror9, the wavefront compensator12, the wavefront detector14, the photo-receiving element18, a moving unit21for moving the mirrors4and5, an input part22, an image processing part (a display control part)23, a monitor24, a memory part25, and others. The input part22is provided with switches and others for inputting data on refractive power of the eye E in order to correct diopter. The image processing part23produces an image based on an output signal from the photo-receiving element18, and causes the monitor24to display the image. The memory part25stores various setting information, captured images, etc.

Operations of the apparatus constructed as above will be described below.

An examiner inputs data on the refractive power of the eye E, which is a previously measured result through an eye refractive power measurement apparatus or the like, with the input part22. The control part20stores the inputted refractive power data in the memory part25and also causes the moving unit21to move the mirrors4and5based on the data, thus correcting the diopter. Successively, the examiner manipulates a joystick or the like not shown to move the apparatus after the diopter correction to make alignment with respect to the eye E so that the image of the objective part of the fundus Ef appears on the monitor24.

The beam irradiated to and reflected by the objective part of the fundus Ef is reflected by the reflecting plane of the wavefront compensator12. The beam reflected by the wavefront compensator12is partially reflected by the half mirror13and received by the wavefront detector14. The control part20performs a Fourier transform of an optical distribution (a photo-receiving signal) detected by the wavefront detector14and, based on the result, dynamically controls the phase of pupil function of a compensating optical system. In the present embodiment, a liquid crystal layer of the wavefront compensator12is used for phase modulation of the pupil function. The aligning direction of liquid crystal molecules in the liquid crystal layer is changed by voltage control, thereby controlling a phase distribution so that a spreading range of a diffraction pattern of the beam reflected by the objective part of the fundus Ef is reduced to a minimum. With the above structure, the beam reflected by the wavefront compensator12whereby the wavefront aberration is compensated is received by the photo-receiving element18.

The image processing part23produces an image of the objective part based on the output signal from the photo-receiving element18, and causes the monitor24to display that image. In the present embodiment, because the objective part of the fundus Ef and the pinhole of the pinhole plate16are conjugated with each other, only the beam from the objective part of the fundus Ef is allowed to pass through the pinhole and be received by the photo-receiving element18. Accordingly, a clear image of the objective part can be obtained. For ensuring an adequate light quantity of the beam or others, an additional system for changing the diameter of the pinhole of the pinhole plate16may be provided.

In the above embodiment, a reflection-type wavefront compensator is used as the wavefront compensator12, but other types may also be adopted. A transmission-type wavefront compensator which allows the beam reflected by the objective part to pass therethrough to thereby compensate wavefront aberration may be adopted.

As the wavefront compensator12, furthermore, any well known device may also be used; for example, micro-electro-machined (MEMs) membrance mirrors, MEMs segmented mirrors, bimorph deformable mirrors, electrostatic membrance deformable mirrors. The liquid crystal spatial phase modulator is easy to control and capable of compensating wavefront aberration with high accuracy.

Although the above embodiment was explained using the fundus observation apparatus, the present invention may also be applied to an apparatus for imaging and observing an anterior segment of an eye and so on.