WO2009101696A1

WO2009101696A1 - Method for operating eye ball movement tracking device with visual axis and light beam projection axis aligned

Info

Publication number: WO2009101696A1
Application number: PCT/JP2008/052468
Authority: WO
Inventors: Hidekazu Hirokawa
Original assignee: Hidekazu Hirokawa
Priority date: 2008-02-14
Filing date: 2008-02-14
Publication date: 2009-08-20
Also published as: DE112008003724T5

Abstract

An eye ball movement tracking device with the visual axis of the patient aligned with the light beam projection axis. The device is capable of projecting a beam of light aligned with the visual axis of a patient from the front under a cornea refraction correction operation toward a desired position on the cornea at all times even if the eye ball moves. While observing the position on a plane of the anterior ocular segment of the patient, the deflection angle of the visual axis of the patient and a desired position on the cornea are determined. According to the determination, a light guide unit using a concave mirror for directing the beam to the eye ball and two two-axis galvanometer mirrors is controlled. Thus, a projected beam aligned with the visual axis of the patient can be directed to the desired position on the cornea at all times.

Description

Actuation method of eye-coaxial tracking axis device for eye movement

The present invention relates to an operating method of a visual axis irradiation axis coaxial tracking device for eye movement.

In surgery to correct refractive errors that cannot normally connect images on the retina, surgery is currently being performed to shape the cornea into an appropriate shape by shaving the center of the cornea of the patient's eye with an irradiation device such as a therapeutic laser. May be.

An apparatus for performing refractive correction surgery is provided with a device for tracking the movement of the patient's eyeball in order to correct the deviation of the irradiation position of the therapeutic laser due to the movement of the patient's eye during treatment. For example, the center position of the pupil of the patient's eye is detected from the eyeball image captured by a video camera or the like, and the patient's eye is tracked (for example, see Patent Document 1) There has also been proposed a method for measuring an eyeball position by detecting a potential difference between the cornea side and the retina side (this is called electro-oculography = EOG method) (see, for example, Patent Document 2).

Japanese Patent Laid-Open No. 9-149914 Japanese Patent Laid-Open No. 2001-276111

However, the conventional eyeball tracking device (for example, Patent Document 1 or Patent Document 2) only captures the patient's eye movement in a plane, and when the visual axis of the patient's eye rotates in three dimensions, an actual therapeutic laser is used. There has been a problem (eccentric irradiation) that a deviation occurs between the irradiation position and the intended laser irradiation position and a deviation between the two axial directions.

An object of the present invention is to make the actual laser irradiation position and irradiation axis direction coincide with the visual axis of the patient's eye even when the visual axis of the patient's eye rotates in three dimensions in view of the problems of the above-described conventional technology. It is to provide a method of operating a possible visual axis irradiation axis coaxial tracking device.

The operation method of the visual axis irradiation axis coaxial tracking device according to the present invention is based on a detection unit for specifying the planar position of the anterior segment of the patient's eye and the planar position information of the anterior segment acquired by the detection unit. An arithmetic unit for calculating the rotation angle of the visual axis of the patient's eye, a beam irradiation light source, two sets of two-axis galvanomirrors disposed on the optical axis of the beam irradiation light source, and a galvanomirror disposed in front of the patient's eyes Comprising a concave mirror for guiding a beam passing through the patient's eye, and a control unit for controlling two sets of two-axis galvanomirrors based on the calculation result calculated by the calculation unit. Based on the control, two sets of two-axis galvanometer mirrors are controlled to generate an apparent displacement of the light source position with respect to the concave mirror and a deflection of the beam irradiation direction, and thereby the beam irradiation direction irradiated by the beam irradiation light source is determined by the patient. Move in the direction of the visual axis of the eye And it said that to Itasa.

According to the operating method of the visual axis irradiation axis coaxial tracking device of the present invention, even if the visual axis of the patient's eye rotates in three dimensions and the intended irradiation position and axial direction change, the optical axis of the beam irradiation light source The light guiding means placed above controls the axis of the beam irradiation side to move and rotate in accordance with the rotation of the visual axis of the patient's eye, and the actual laser irradiation position and irradiation direction completely match the visual axis of the patient's eye. Will do.

It is the image which image | photographed the anterior eye part of a patient's eye with the video camera etc. of the detection member 6. FIG. It is the figure which looked at the eyeball from the cross-sectional direction cut by the plane parallel to the Z-axis including the visual axis. It is a figure explaining the visual axis rotation angle determination method: Principle 2. FIG. Visual axis rotation angle and corneal vertex position determination method: FIG. 3 is a configuration diagram of a visual axis irradiation axis coaxial tracking device according to principle 1. FIG. 5 is an optical calculation drawing of a light guide unit using two biaxial galvanometer mirrors and a concave mirror half mirror in FIG. 4. It is an optical calculation drawing inside the beam irradiation light source 4 of the visual axis tracking device to which defocus cancellation means is added. It is optical calculation drawing of the light guide part of the visual axis tracking device which added the defocus cancellation | release means. Visual axis rotation angle determination method: It is a block diagram of a visual axis irradiation axis coaxial tracking device according to principle 2. It is an optical calculation drawing regarding the light guide part and the detection part in the apparatus of FIG.

Explanation of symbols

1 Patient's anterior eye image 2 Pupil
3 Iris 4 Beam irradiating light source 5 having inherent irradiation direction deflecting device 5

Mirrors

6 and 30 Detection member 7 such as video camera Calculation unit 8 Control unit 9 Observation member 10 such as observation telescope First biaxial galvanometer mirror 11 Second biaxial galvanometer mirror 12 Concave mirror half mirror 13 Light guide 14 Unique imaging optical system lens 15 in the beam irradiation light source 15 Parallel vibration plane mirror 16 Aiming light source 17 Fixation lamp 20 Eyeball α of patient Visual axis rotation angle r Distance between the rotation point of the eyeball and the center of the pupil R Distance between the rotation point and the corneal apex c Radius of curvature of the cornea surface d Center of gravity of the corneal portion / Distance between the corneal vertices FC Rotation point K1, K2 Corneal apex A1 Center of gravity position L1 (1) Conjugate point of rotation point F1
L1 '(1) Conjugate point L2 (1) of corneal ring center of gravity B1 Conjugate point L2 (2) of corneal vertex K1 Conjugate point of corneal vertex K2
Lm Curved surface G formed by the locus of the “virtual image of the fulcrum of the first two-axis galvano mirror” created by the second two-axis galvano mirror. Point where the extension of the visual axis intersects the concave mirror half mirror. Relative misalignment angle between axis and beam direction

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

<Visual axis rotation angle and corneal vertex position determination method: Principle 1>
One method (principle 1) for determining the visual axis rotation angle and the corneal apex position will be described. This is two data sets obtained from a detection member placed coaxially with the observation member for the operator, ie, (a set of pupil center position and eyeball rotation point position) or (corneal ring center position and eyeball rotation point) This is a method of calculating using any one of a pair with a position). Regardless of which set is used, the calculation principle is exactly the same. In the following description, a case where a set of a pupil center position and an eyeball rotation point position is used will be described.

FIG. 1 shows an image of an anterior segment of a patient's eye taken by a video camera or the like of the detection member 6 shown in FIG. 4. In order to obtain plane position information, the central portion (plane position information of the pupil) and the periphery The region of interest is divided into two parts (plane plane position information). Furthermore, in order to facilitate the detection of the face position, marks may be attached to two positions on the face that are symmetrical across the eyeball. The face position measurement is a substitute for the planar position of the eyeball rotation point, which is the original purpose. Therefore, the face position information is obtained by obtaining position information of two symmetrical points across the eyeball, and by setting the midpoint of the two points to F, the twist / rotation component of the face is canceled and only the translation component is obtained. This F is used as a substitute for the rotation point position.

The rotation point F and the pupil center position P at the tracking start time are set as F ₀ (0,0) and P ₀ (0,0), respectively. Further, when the rotation point position when the eyeball moves after a certain elapsed time t after the start of tracking is Ft (f _xt , f _yt ) and the pupil center position is Pt (p _xt , p _yt ), the elapsed time t The vector direction of (pupil center position Pt−rotation point position Ft) is the rotation direction of the visual axis.

FIG. 2 is a cross-sectional view taken along the visual axis rotation direction in FIG. Each of the pupil center position and the corneal apex position rotates with a visual axis rotation angle (α) with respect to the Z axis. Here, r (constant) is the distance between the rotation point and pupil center of the patient's eye, and R (constant) is the distance between the rotation point and corneal apex, and the visual axis rotation angle of the patient's eye and The corneal apex position (K) is calculated.
Formula 1: r * sin α = (PF)
Formula 2: (K−F) = (R / r) * (PF)

<Visual axis rotation angle determination method: Principle 2>
Next, a method for determining the relative deviation angle between the visual axis of the eyeball and the irradiation beam direction using the deviation amount from the center of the corneal reflection light from the center of gravity of the corneal ring will be described with reference to FIG.

FIG. 3A shows a state observed by the detection member 30 placed coaxially with the irradiation beam when the aiming light source 16 shown in FIG.
When the visual axis of the patient's eye is deflected, a relative shift is observed in the movement of the corneal contour of the patient's eye and the movement of the reflected light on the corneal surface.

FIG. 3B is a cross-sectional view taken along a plane including the visual axis of the patient's eyeball 20 and parallel to the irradiation beam, and the radius of curvature of the corneal surface of the patient's eye is c (constant), Assuming that the distance between the center of gravity and the apex of the cornea is d (constant) and the visual axis of the patient's eye is deflected by an angle of Ω relative to the irradiation beam direction, irradiation from the corneal ring center of gravity of the cornea reflection center of the patient's eye The shift amount Q projected in the plane perpendicular to the beam axis can be obtained by Equation 3.
Formula 3: Q = (cd) * sinΩ
Therefore, by measuring the deviation amount Q from the corneal ring center of gravity of the corneal reflection center of the patient's eye, the relative deviation angle of the visual axis of the patient's eye can be obtained.

<Visual axis irradiation axis coaxial tracking device according to Principle 1>
FIG. 4 shows a configuration of an example of the visual axis rotation axis and corneal apex position determining method: the visual axis irradiation axis coaxial tracking device according to Principle 1. The visual axis irradiation axis coaxial tracking device of the present embodiment is a light guide 4 comprising a beam irradiation light source 4 such as a gas laser, a first two-axis galvanometer mirror 10, a second two-axis galvanometer mirror 11, and a concave mirror half mirror 12. The light unit 13, the detection member 6 such as a video camera, the calculation unit 7 for calculating the visual axis rotation angle and the corneal apex position of the patient's eye, and the control unit 8 for controlling the beam irradiation light source 4 and the light guide unit 13. And an observation member 9 such as an observation telescope for observing the patient's eyes.

The concave mirror half mirror 12 is provided on the Z axis.

The detection member 6 such as a video camera is installed on the Z axis between the concave mirror half mirror 12 and the observation member 9.

The beam irradiated from the beam irradiation light source 4 is reflected by the first two-axis galvanometer mirror 10 having a fulcrum on its axis, and is installed so as to face the first two-axis galvanometer mirror 10. Head to the biaxial galvanometer mirror 11.

The beam further reflected by the second biaxial galvanometer mirror 11 is directed to the concave mirror half mirror 12 and finally guided to the eyeball 20 of the patient.

The calculation unit 7 is connected to the detection member 6, receives position information from the detection member 6, and calculates the visual axis rotation angle and the corneal apex position.

The control unit 8 connected to the calculation unit 7 controls the beam irradiation light source 4 and the light guide unit 13 based on the information obtained from the calculation unit 7.

Next, the tracking mechanism of the visual axis of the patient's eye using the two biaxial galvanometer mirrors and the concave mirror half mirror according to the present embodiment as light guiding means will be described with reference to FIG.

FIG. 5 shows an optical calculation drawing of the light guide unit using two biaxial galvanometer mirrors and a concave mirror half mirror.

When the eyeball tracking is started and the rotation point of the eyeball at a certain elapsed time is at F1, let G be the point where the extension of the visual axis intersects the concave mirror half mirror 12. A curved surface Lm formed by the extension of the line connecting G and the conjugate point L1 (1) of F1 is formed by the locus of the virtual image of the fulcrum of the first biaxial galvanometer mirror 10 that is copied by the second biaxial galvanometer mirror 11. Let Lm (1) be the intersection with.

The deflection angle of the second two-axis galvanometer mirror 11 is determined so that the image of the fulcrum of the first two-axis galvanometer mirror 10 is at Lm (1), and is driven like that.

At this time, there is only one deflection angle of the first biaxial galvanometer mirror 10 such that the beam emitted from the irradiation light source 4 passes through the point G, and it is driven as such. This beam passes through K1 and also through F1.
That is, the beam hits the apex of the cornea from the direction that coincides with the visual axis.

The conjugate point L2 (1) of the corneal vertex K1 exists on the extension of the line segment G → Lm (1).

Next, it is assumed that the visual axis rotates and the pupil position is displaced to P while F1 remains unchanged. The corresponding visual axis rotation angle is determined. At this time, a point J at which the extension of the new visual axis intersects the concave mirror half mirror 12 is obtained. A point Lm (2) at which the extension of the line segment from J to L1 (1) intersects the curved surface Lm is determined.

The conjugate point L2 (2) of the corneal vertex K2 at this time is obtained on the extension of the line segment J → Lm (2). L2 (1, 2,..., N) appropriately drives the first biaxial galvanometer mirror 10 and the second biaxial galvanometer mirror 11 and continues the tracking operation described above, whereby the beam irradiation device 4. On the optical axis connecting the fulcrum of the first two-axis galvanometer mirror 10. As a result, the conjugate point L2 (n) is distributed in a narrow range W (L2) on the optical axis of the beam corresponding to the locus of the corneal apex position K.

From the above, when a slight defocus is allowed with respect to the image formation of the light source on the corneal surface, the position of the light source image created by the beam irradiation device is placed at the center of W (L2), so that the irradiation beam has the minimum defocus. The visual axis can be tracked three-dimensionally from the coaxial direction.

The visual axis rotation angle and the corneal apex position of the patient's eye are calculated by the calculation unit 7 based on the position information acquired by the detection member 6. The information calculated by the calculation unit 7 is transmitted to the control unit 8, and the control unit 8 controls the light source 4 for beam irradiation and the light guide unit 13 for guiding the beam to the patient's eye.

That is, even when the patient's eyeball 20 is rotated with the visual axis rotation angle α, the light guide unit 13 including the first biaxial galvano mirror 10, the second biaxial galvano mirror 11, and the concave mirror half mirror 12 is controlled. By adjusting the irradiation direction of the beam so as to coincide with the visual axis rotation angle α, it is possible to always irradiate the apex of the cornea coaxially with the visual axis of the patient's eyeball 20.

By repeating a series of processes from the detection member 6 to the control of the beam irradiation light source 4 and the light guide unit 13 by the control unit 8, the intended irradiation position and the visual axis direction on the patient's cornea are always accurately identified. In addition, it becomes possible to track three-dimensionally.

The light source 4 for beam irradiation may be a semiconductor light emitting element such as a light emitting diode using spontaneous emission light or a semiconductor laser using stimulated emission light.

In FIG. 4, two biaxial galvanometer mirrors and a concave mirror half mirror are used as a light guide for guiding the beam irradiated from the beam irradiation light source 4 to the eyeball 20 of the patient. In order to suppress interference due to light, a half mirror with a wedge-shaped angle may be used. In addition to the light guiding means, a convex lens may be used instead of the concave mirror, or the beam from the beam irradiation light source 4 may be guided to the patient's eyeball 20 using a polygon mirror, a prism, or the like.

If a defocus is not allowed for the image formation of the light source on the corneal surface, a device for changing the image formation position of the light source 4 for beam irradiation is added.

For example, as shown in FIG. 6, the imaging optical system lens 14 inside the beam irradiation light source 4 is moved in the optical axis direction to adjust the imaging position of the beam.

Further, as shown in FIG. 7, a half mirror is provided between the beam irradiation light source 4 and the first galvanometer mirror 10, and a parallel vibration plane mirror 15 is installed on the reflection optical axis of the half mirror, and the optical path is reciprocated. The optical path length of the beam may be adjusted to eliminate the defocus.

<Visual axis irradiation axis coaxial tracking device based on Principle 2>
FIG. 8 shows a configuration of an example of the visual axis irradiation axis coaxial tracking device according to the visual axis rotation angle determination method: Principle 2. The visual axis irradiation axis coaxial tracking device in this embodiment is a light guide comprising a beam irradiation light source 4 such as a gas laser, a first two-axis galvanometer mirror 10, a second two-axis galvanometer mirror 11, and a concave mirror half mirror 12. Unit 13, a detection member 30 such as a video camera, a calculation unit 7 that calculates a deviation Q from the geometric center of gravity of the corneal ring part and the center of corneal reflection light from the corneal ring part, and a beam irradiation light source 4 A control unit 8 that controls the light guide unit 13 and an observation member 9 such as an observation telescope for observing the aiming light source 16 and the patient's eye are provided.

The concave mirror half mirror 12 is provided on the Z axis.

On the other hand, the detection member 30 such as a video camera is installed on the optical axis between the beam irradiation light source 4 and the first two-axis galvanometer mirror 10.

As shown in FIG. 8, the aiming light source 16 is provided on the optical axis connecting the first two-axis galvanomirror 10 and the detection member 30.

The light emitted from the aiming light source 16 follows the same optical path from the beam irradiation light source 4 to the patient's eyeball 20, is reflected by the eyeball 20, and then travels the same optical path in reverse to be detected by the detection member 30. Will be detected.

The calculation unit 7 is connected to the detection member 30 and receives positional information from the detection member 30 to calculate the displacement amount of the corneal ring center of gravity and the shift amount between the corneal reflection light center and the corneal ring center of gravity. .

By adopting the above-described configuration, the present embodiment forms a Feedback-Loop as a whole.

Next, the tracking mechanism of the visual axis of the patient's eye using the two biaxial galvanometer mirrors and the concave mirror half mirror according to the present embodiment as light guiding means will be described with reference to FIG. In FIG. 9, the same reference numerals as those in FIG.

FIG. 9 is an optical functional diagram of a light guide unit using two biaxial galvanometer mirrors and a concave mirror half mirror. It is assumed that the locus L1 ′ (n) of the conjugate point of the corneal ring center of gravity and the Lm curved surface formed by the second biaxial galvanometer mirror 11 are designed to overlap as much as possible. At the start of tracking, the patient first fixes the fixation lamp 17 in the telescope direction on the Z axis, and the measurement position of the corneal ring center of gravity at this time by the detection member 30 is B0, and the corneal reflection light. Let Q0 be the amount of deviation between the center and B0.

Assume that the center of gravity of the corneal ring portion is located at B1 at a certain time t.
At this time, the angle of the second biaxial galvanometer mirror 11 can be appropriately driven so that the center of gravity of the corneal limbus looks the same as B0 before the start of tracking when viewed from the detection member 30.

In this case, since the fulcrum of the first biaxial galvanometer mirror 10 exists at or near the conjugate point of B1 in the concave mirror half mirror 12, the angle of the first biaxial galvanometer mirror 10 has an arbitrary value. Even so, the tracking of the center of gravity of the limbus by the second biaxial galvanometer mirror 11 is hardly affected.

This is because the irradiation beam that has passed through the center of the optical axis passes through the fulcrum of the first biaxial galvanometer mirror 10, and thus passes through B1 that is the conjugate point or a point in the vicinity thereof, and the first 2 It will proceed from a certain direction where it is made by the axial galvanometer mirror 10, and the tracking of the point B1 by the second biaxial galvanometer mirror 11 will be performed without any problem regardless of the deflection angle of the first biaxial galvanometer mirror 10. Because it will be executed.

Next, the first biaxial galvanometer mirror 10 is driven using the Q value = Q1 calculated by the detection member 30 and the calculation unit 7, and control is performed so that Q = Q0. At this time, the corneal reflection light center and the corneal apex coincide with each other, and the irradiation beam continues to be irradiated while the positional relationship between the corneal apex and the corneal ring portion center of gravity is kept the same as the tracking start time.

If the observation position of the center of gravity of the corneal ring portion on the detection member 30 is shifted due to the drive / deflection of the first biaxial galvanometer mirror 10, the second biaxial galvanometer mirror 11 is additionally driven. And make corrections.

By continuing the above, a Closed Loop type visual axis irradiation axis coaxial tracking function for irradiating a beam from the direction coaxial with the visual axis of the patient's eye toward the apex of the cornea is realized.

In FIG. 8, a light guide unit composed of two biaxial galvanometer mirrors and a concave mirror half mirror is used as a light guide means for guiding the beam irradiated from the beam irradiation light source 4 to the eyeball 20 of the patient. In order to suppress interference caused by reflected light other than the reflecting surface, a half mirror with a wedge-shaped angle may be used. In addition to the light guiding means, a convex lens may be used instead of the concave mirror, or the beam from the beam irradiation light source 4 may be guided to the patient's eyeball 20 using a polygon mirror, a prism, or the like.

In addition, in order to facilitate the process of obtaining the barycentric position information of the reflected light intensity distribution, for example, infrared light may be used for corneal ring detection, and a wavelength with visible light may be used for corneal reflection detection.

Each embodiment described above is a preferred embodiment of the present invention, but the present invention is not limited to this, and various modifications can be made without departing from the gist of the present invention.

Claims

A detection unit for specifying the planar position of the anterior segment of the patient's eye;
A calculation unit that calculates a rotation angle of the visual axis of the patient's eye based on the planar position information of the anterior segment acquired by the detection unit;
A light source for beam irradiation;
Two sets of two-axis galvanometer mirrors arranged on the optical axis of the beam irradiation light source and a concave mirror arranged in front of the patient's eyes and guiding the beam passing through the two sets of two-axis galvanometer mirrors to the patient's eyes. A light guide means characterized by:
A control unit that controls the two sets of two-axis galvanometer mirrors based on a calculation result calculated by the calculation unit;
Based on the control of the control unit, the two sets of two-axis galvanometer mirrors are controlled to generate a deviation of the apparent light source position with respect to the concave mirror and a deflection of the beam irradiation direction. A method of operating a visual axis irradiation axis coaxial tracking device, characterized in that the beam irradiation direction is moved to coincide with the visual axis direction of the patient's eye.