JPH066112B2 - Eye movement measuring device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an eye movement measuring apparatus, and is particularly used for medical examinations in ophthalmology and neuropsychiatry, and for visual psychological experiments in psychological engineering and image engineering. Eye movement measuring device.

[Problems to be Solved by Conventional Techniques and Inventions] Generally, in an eye movement measuring apparatus, it is necessary to perform calibration between a gazing point of a subject and a gazing point detected by the apparatus before measurement so that they correspond to each other. In the conventional device, prepared in advance,
Have the subject gaze at multiple indices whose positional relationship is known,
From each eyeball rotation angle at that time, the actual eyeball rotation angle of the subject and the eyeball rotation angle detected by the device were calibrated.

However, when a human gazes at one point, the index is captured at the fovea with the highest visual acuity, but the fovea diameter is about 1 ° 20 'in terms of viewing angle, and at any position within this range The subject can perceive a clear image even by capturing the index.
For this reason, such a subjective method has a problem in that it is difficult to detect with a precision better than about 1 ° 20 ', no matter how high the precision of the device is increased.

Therefore, a main object of the present invention is to provide an eye movement measuring device capable of obtaining a true eye rotation angle with a relatively simple structure.

[Means for Solving the Problems] The present invention is an eye movement measuring device that measures eye movement by irradiating the eye with light and photographing reflected light from the eye, and an index presenting means that presents an index to a subject. Eye movement detection means that detects the reflected light of the light source presented to the eyeball and outputs the amount of movement of the reflection position of the reflected light due to the movement of the gazing point, photographing means that photographs the fundus image from the eyeball, and photographing Image processing means for image-processing the selected fundus image and extracting the pattern of the index presented on the eyeball from the fundus image, and output of the pattern movement amount of the index set on the extracted fundus image from the eye movement detection means And a calculation unit that calibrates the calculated eyeball rotation angle and calculates and outputs the true eyeball rotation angle.

[Effect] The eye movement measuring apparatus according to the present invention captures the fundus image of the subject when the index is presented to the subject by the image capturing means, and detects the reflected light of the light source applied to the eye,
Calculate the amount of reflection position movement of the reflected light that accompanies the movement of the gazing point,
An index pattern is extracted from the fundus image, an absolute eyeball rotation angle is obtained thereby, a reflection position movement amount of reflected light is configured, and a true eyeball rotation angle is calculated and output.

[Embodiment of the Invention] FIG. 1 is a diagram showing a configuration of an embodiment of the present invention. Referring to FIG. 1, the light from the irradiation light source 1 that irradiates the fundus is reflected by the half mirror 2, passes through the lens system 3, and the eye 30.
Is input to the fundus of. The image reflected by the fundus travels backward in this optical path, passes through the lens system 3 and the half mirror 2, and becomes an input image of the fundus photographing camera 4. The lens system 3 focuses the light from the irradiation light source 1 on the fundus and also focuses the fundus image on the fundus photographing camera 4. The image captured by the fundus imaging camera 4 is stored in the memory included in the image processing unit 12.

An infrared LED 6 is provided to detect eye movements,
The spot light from the infrared LED 6 is imaged on the cornea surface via the lens system 5, and the reflected light is focused on the area sensor 9 via the mirror 7 and the lens system 8. The eye movement detecting unit 10 detects the eye rotation angle from the image on the area sensor 9 by means of an eye movement detecting unit, which will be described later, and inputs the rotation angle of the eye to the calculating unit 11 together with the output of the image processing unit 12. The calculation unit 11 outputs the true eyeball rotation angle corrected by the absolute eyeball rotation angle on the retina.

As a method of detecting eye movement, a method of irradiating the eye with weak infrared light to detect the difference between the reflected light of the black eye and the white eye, or a method of detecting the movement of the light spot imaged on the cornea, , There are various methods such that a subject is equipped with a contact lens incorporating a coil and the eye movement is detected from an induced electromotive force associated with the eye movement in a magnetic field.

2 and 3 are views for explaining the detection principle of eye movement. In FIG. 2 and FIG. 3, infrared LE
The virtual image 33 is formed on the crystalline lens 31 using D13. Since the rotation center 0 of the eyeball and the rotation center 0'of the crystalline lens 31 are different, the virtual image 33 moves in parallel with the rotation of the eyeball. This translation amount 34 corresponds to the rotation angle of the eyeball,
Using the area sensor 9 such as the video camera shown in FIG. 1, an image 3 obtained by moving the virtual image 33 in parallel as shown in FIG.
It is detected by photographing 3 '.

FIG. 4 is a diagram showing an example of a fundus image obtained by an embodiment of the present invention. The example shown in FIG. 4 is an example of the fundus image when the image of the mermaid is shown, and the blood vessel 39 is running in a mesh shape. As shown in FIG. 4, the image observed by the subject can be reproduced on the fundus image. The brightest part from the center of Fig. 4 to the right is the yellow patch 3.
7 and has a diameter of 3-5 mm. There is a central fossa with particularly high visual acuity in the macula 37, the diameter of which is about 1.5 mm and 25
Includes 00 foveal cones.

FIG. 5 is a diagram showing a relationship between a pattern used for calibration of eye movement and vision. As shown in FIG. 5 (a), the light emitting diodes P ₁₁ , P ₁₂ , P ₁₃ , P ₁₃ ,
It is arranged at the positions of P ₂₁ , P ₂₂ , P ₂₃ , P ₃₁ , P ₃₂ , and P ₃₃ . The distance between the respective light emitting diodes is known in advance, and by knowing the distance d between the subject and the pattern, the visual angle θ on the retina between the patterns can be obtained.

FIG. 6 is a diagram showing an example of projection of the calibration pattern onto the retina when the subject is gazing at the center P ₂₂ of the pattern.
The image captured by the fundus photographing camera 4 shown in FIG. 1 is appropriately binarized by the image processing unit 12, and the projected calibration pattern is extracted. By the way, the retina is concave, and the presented lattice pattern is distorted and projected on the retina, but the origin of the projected lattice pattern is already known, and the image processing unit 12 uses this value.
Can generate a correspondence table between the internal coordinates in the image processing unit 12 and the visual sense.

7 and 8 are diagrams showing an example of projection of a calibration pattern onto the retina during eye movement calibration, in particular, FIG. 7 shows a case of gazing at P _31, and FIG. 8 shows P _32. It shows when gazing at. If the internal coordinates in each image processing unit 12 are (X _p31 , Y _p31 ), (X _p32 , Y _p32 ), the difference (Δx, Δy) in the internal coordinates is as follows.

(Δx, Δy) = (X _p32 , Y _p32 ) − (X _p31 , Y _p31 ) If the subject gazes at the indices P ₃₁ and P ₃₂ at the same position in the fovea, (Δx, Δy) = ( Although it should be 0,0), there is a centrality of 1 ° 20 'as described above, and generally (Δx, Δy) ≠ (0, 0). The image processing unit 12 outputs this (Δx, Δy) to the calculation unit 11. When the subject is gazing at the calibration index, the calculation unit 11 uses the eye movement detection outputs (Xe, Ye) and (Δx, Δy) of the eye movement detection unit 10 at that time to determine the true eye rotation angle (X, Y) to obtain the functional expression φ or the conversion table Txy.

After the calibration is completed, the measurement can be performed, and the true eyeball rotation angle can be obtained by performing the following calculation on any eye movement data without using the output of the image processing unit 12. it can.

In the case of a functional expression: (X, Y) = φ (Xe, Ye) In the case of a conversion table: (X, Y) → Txy (Xe, Ye) As described above, it is difficult to avoid when calibrating by a subjective method. An error in the size of the fovea can be removed by an objective calibration method, and an eye movement measuring apparatus that can obtain a true eye rotation angle can be realized.

[Effects of the Invention] As described above, according to the present invention, by using the index image projected on the fundus image at the time of calibration, the size of the fovea which is difficult to avoid by the conventional subjective method can be obtained. An error can be removed by an objective calibration method, a true eyeball rotation angle can be obtained, and a highly accurate eye movement measurement device can be realized in a clinical examination of eye movement or a visual experiment.

[Brief description of drawings]

FIG. 1 is a diagram showing the configuration of an embodiment of the present invention. 2 and 3 are views for explaining the detection principle of eye movement. FIG. 4 is a diagram showing an example of a fundus image obtained by an embodiment of the present invention. FIG. 5 is a diagram showing the relationship between the eye movement calibration pattern and vision. FIG. 6 is a diagram showing an example of projection of the calibration pattern onto the retina when gazing at the center P _{22 of the} subject pattern. 7 and 8 are diagrams showing an example of projection of a calibration pattern onto the retina during eye movement calibration. In the figure, 1 is a fundus irradiation light source, 2 is a half mirror,
3, 5 and 8 are lens systems, 4 is a fundus photographing camera, 6 is an infrared LED, 7 is a mirror, 9 is an area sensor, 10 is an eye movement detecting section, 11 is a calculating section, and 12 is an image processing section.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A 1-312902 (JP, A) JP-A 2-140136 (JP, A) JP-A 3-215243 (JP, A)

Claims (1)

[Claims] 1. An eye movement measuring apparatus for irradiating an eye with light and photographing reflected light from the eye to measure eye movement, an index presenting means for presenting an index to a subject, and a light source presented to the eye. Detecting the reflected light, an eye movement detecting means for outputting the amount of movement of the reflection position of the reflected light accompanying the movement of the gazing point, a photographing means for photographing a fundus image from the eyeball, a fundus image photographed by the photographing means Image processing,
Image processing means for extracting the pattern of the index presented on the eyeball from the fundus image, and the pattern movement amount of the index set on the fundus image extracted by the image processing means was output from the eye movement detecting means. An eye movement measuring device comprising an arithmetic means for calibrating an eye rotation angle and calculating and outputting a true eye rotation angle.