JPH1185384A - Visual acuity input method and device using cornea retina potential - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a visual acuity input method and a device capable of inputting by visual acuity at a gazing position in real time, which is easily set up, which gives less fatigue accompanying use of the device, capable of being used for a long time, which is less in malfunction by the change of environmental light and a motion of a subject capable of performing stable measurement, and by which natural sight is hardly obstructed. SOLUTION: The gazing position 3 of a subject 1 is calculated from a potential detector 12 to detect cornea retina potential 2 of the subject 1 and the cornea retina potential 2 detected by the potential detector 12 in real time by this operation controller 14. The relation between the cornea retina potential 2 and plural gazing positions is preliminarily calibrated and stored as an approximated straight line with fixed inclination and the gazing position 3 is calculated from the relation and the cornea retina potential 2 in real time by the operation controller 14. In addition, a fluctuated value of the cornea retina potential 2 at the same gazing position is found for every fluctuation and the cornea retina potential 2 is compensated by differentiating the fluctuated value. Furthermore, a fluctuation waveform of the cornea retina potential 2 is smoothed and rapid change of the gazing position due to a blink and rapid motion of an eyeball is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method and an apparatus for inputting visual acuity using corneal retinal potential.

[0002]

2. Description of the Related Art For a "severely physically handicapped person" having a severe dysfunction having difficulty in communication by conversation, writing, sign language, etc., a communication support device utilizing the remaining motor function is required. As such a device, a visual acuity input interface utilizing “eye movement” has recently attracted attention.

Hitherto, an eyesight input interface using an eye movement measuring method called "corneal reflected light method" or "scleral reflected light method" has been proposed (for example, "Document creation and peripheral device control by eye movement"). Device ”, IEICE Transactions (D), Vol. 69, No. 7, 1986,“ Head-mounted display device ”, JP-A-8-160345, etc.).

[0004]

However, such a conventional visual acuity input means is difficult to set up the apparatus, causes fatigue in use of the apparatus, is unstable in measurement (many malfunctions), hinders natural vision, and has a long time. There was a problem that it could not be used. In other words, "corneal reflection method"
In the eyesight input means using, the eye movement is measured by capturing the movement of the reflected light of the infrared light radiated to the eyes with a sensor,
The sensor must be strictly fixed at the position where the reflected light can be obtained, and there is a problem that it takes time and effort to set up and calibrate the apparatus.

In the visual acuity input means using the "scleral reflection light method", the eye movement is measured by detecting the difference between the reflection ratio of the black eye and the white eye of the eye with a light receiving element such as a photodiode fixed in front of the eye. Therefore, there has been a problem that the measurement accuracy is affected by changes in ambient light. Further, in these visual acuity input means, there is a problem that a large error occurs in the measurement accuracy even if the sensor moves about several millimeters from the fixed position. Therefore, in order to obtain practical measurement accuracy, it is necessary to firmly fix the sensor to the head (referred to as "immobilization"), resulting in a feeling of oppression, fatigue, dizziness, vomiting, etc. It is pointed out that it is not suitable for long-time use.

The present invention has been made to solve the various problems described above. That is, an object of the present invention is to input a gaze position in real-time visual acuity, and to easily set up the apparatus, reduce the fatigue associated with the use of the apparatus, enable long-term use, change environmental light, It is an object of the present invention to provide a visual acuity input method and apparatus in which malfunction due to movement is small, stable measurement can be performed, and natural vision is hardly hindered.

[0007]

Means for Solving the Problems The inventors of the present invention have:
We studied the relationship between eye movement and corneal retinal potential, and found that this corneal retinal potential was almost proportional to eye movement. In addition, the corneal retinal potential changes with time and changes drastically due to "blinking" and rapid movement of the eyeball, and a solution to this has been devised. The present invention is based on such new findings and ideas.

According to the present invention, the relationship between the corneal retinal potential and the plurality of gaze positions is calibrated in advance and stored.
A visual acuity input method using a corneal retinal potential is provided, wherein a gaze position is obtained in real time from the relationship and the corneal retinal potential. According to this method, visual acuity input can be performed only by detecting two corneal retinal potentials by attaching two electrodes to, for example, a temple with the subject's eyes interposed therebetween. Since the corneal retinal potential can be detected without applying any voltage or current between the electrodes, there is no influence on the user. Therefore, as compared with the conventional method, the apparatus is easy to set up, has less fatigue due to the use of the apparatus, can be used for a long time, has less malfunction due to a change in ambient light and the movement of the subject, and is stable. Measurement is possible and natural vision is hardly obstructed.

According to a preferred embodiment of the present invention, the relation is stored as an approximate straight line having a constant gradient. The inventors measure the relationship between eye movement and corneal retinal potential with the cooperation of a plurality of subjects, and even when subjects differ, the corneal retinal potential is almost always proportional to eye movement and the relationship is constant with a constant gradient. It has been found that a straight line can be approximated exactly. Therefore, by storing and using this relationship, visual acuity input can be performed with a simpler algorithm.

Further, a fluctuation value of the corneal retinal potential at the same gaze position is obtained as needed, and the corneal retinal potential is compensated by subtracting the fluctuation value. Many test results have revealed that the absolute value of the corneal retina potential changes with time, and the degree of the change differs depending on the subject. However, as described above, even if the subject is different, the corneal retinal potential is always almost proportional to the eye movement, so that the fluctuation value of the corneal retinal potential at the same gaze position (for example, the front) is obtained as needed. The corneal retinal potential can be accurately compensated by making a difference between the values at other gaze positions.

Furthermore, the fluctuation waveform of the corneal retina potential is smoothed, and a sudden change in the gaze position due to blinking and rapid eye movement is reduced. The change of the corneal retina potential due to blinking or rapid eye movement (impulsive eye movement) is severe, and if this is displayed as the gaze position as it is, the cursor jumps in a new direction, making it difficult to input visual acuity. Therefore, the corneal retinal potential is smoothed by signal processing having a delay element to reduce a sudden change in the gaze position, so that visual acuity input can be performed more easily and comfortably.

Further, according to the present invention, a potential detector for detecting a corneal retinal potential of a subject, and a relationship between a corneal retinal potential detected by the potential detector and a plurality of gaze positions are calibrated and stored in advance. An eyesight input device using a corneal retinal potential is provided, comprising: an arithmetic and control unit for obtaining a gaze position in real time from the relationship and the corneal retinal potential.

According to the configuration of the present invention, the corneal retinal potential can be detected by the potential detector, and the gaze position can be obtained in real time by the arithmetic and control unit. The potential detector is, for example, two electrodes stuck to the subject's eyes, for example, attached to a temple, and detects a corneal retinal potential from a potential (voltage) generated between the electrodes without applying any voltage or current between the electrodes. it can. The arithmetic and control unit is, for example, a computer having a CRT (display). The gaze position is displayed on the CRT and the subject gazes at the gaze position, thereby preliminarily calibrating the relationship between the corneal retinal potential and the plurality of gaze positions. The gaze position can be determined in real time from the detected corneal retinal potential based on this relationship.

According to a preferred embodiment of the present invention, the arithmetic and control unit is configured to store the relationship as an approximate straight line having a constant gradient, and to obtain a fluctuation value of a corneal retinal potential at the same gaze position as needed. Compensation means for compensating the corneal retinal potential by differentiating the fluctuation value, and signal processing means for smoothing the fluctuation waveform of the corneal retinal potential and reducing a sudden change in the gaze position due to blinking and fast eye movements.

With this configuration, the relationship between the corneal retinal potential and the plurality of gaze positions can be stored as an approximate straight line having a constant gradient by the storage means (for example, a memory). Can compensate for changes in the absolute value of the corneal retinal potential that differ, and the signal processing means prevents the cursor from jumping in unexpected directions, reduces sudden changes in the gaze position, and makes eyesight input easier and more comfortable. It can be carried out.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. In each of the drawings, common portions are denoted by the same reference numerals, and redundant description will be omitted. FIG. 1 is a diagram schematically showing a visual acuity input method of the present invention. As shown in this figure, in the visual acuity input method of the present invention, the corneal retinal potential 2 of the subject 1 is detected, and the gaze position 3 of the subject 1 is obtained from the corneal retinal potential 2 in real time.

In the eyes of humans and animals, the cornea, which is the anterior surface thereof, is positively charged with respect to the retina on the rear side. The potential between the electrodes fluctuates. This potential is referred to as corneal retinal potential 2
(corneoretinal potential), and the method of measuring eye movements in this way is EOG (Electro Oculo Grap
h). This EOG method has been conventionally used as one method of eye diagnosis in medical practice, but quantitative measurement and long-time use have not been performed due to large differences between individuals. The inventors of the present invention focused on the relationship between eye movements and corneal retinal potentials, accurately measured corneal retinal potentials of a plurality of subjects over a long period of time, and obtained many useful findings. The present invention is based on such new findings and ideas. Hereinafter, the present invention will be described in conjunction with test results.

FIG. 2 is a diagram showing changes in corneal retinal potential at the same gaze position obtained by the system of FIG. This result indicates that a subject has a CRT (display)
3 shows the corneal retinal potential 2 plotted with respect to the elapsed time after application of the electrode when the visual indicator at the center of FIG. Thus, the fact that the corneal retinal potential of the same subject fluctuates with time has been conventionally known as "drift phenomenon".

As is apparent from FIG. 2, the potential (corneal retinal potential) fluctuates greatly with the passage of time. In particular, the fluctuation fluctuates remarkably within 20 to 30 minutes after the application of the electrode, and the fluctuation thereafter becomes small. ing. A similar tendency was observed for all subjects (7
Name) was commonly accepted. In other respects, the state of fluctuation varied from subject to subject, and there was no common point regarding the drift phenomenon.

FIG. 3 is a test result showing the relationship between the corneal retinal potential and a plurality of gaze positions. This figure shows the corneal retinal potential for each visual index when the subject gazes at the visual index 3 presented at various positions in the display. This figure shows the results of a test performed on a certain subject, in the order of 5 minutes, 26 minutes, and 72 minutes after electrode application from the bottom. In addition,
In this test, 21 visual indices were facilitated every 3 degrees from the left 30 degrees to the right 30 degrees in the display, and were randomly presented one by one for one second.

In FIG. 3, the baseline of the graph fluctuates over time due to the drift phenomenon described above.
On the other hand, at each time, it can be seen that the corneal retinal potential (vertical axis) linearly changes with respect to each presentation position of the visual index (horizontal axis: deviation angle of the eyeball). That is, it is clear that the drift phenomenon does not become a significant problem in a short-time measurement. Furthermore, the point sequence at each time is arranged almost in parallel,
It can be seen that the linear relationship between the deviation angle of the eyeball and the corneal retina potential is almost the same regardless of the passage of time.

FIGS. 4A and 4B are graphs showing the gradient of the change in the corneal retinal potential at the same gaze position. FIG. 4A is for a single subject, and FIG. 4B is for 7 subjects. Note that, in this figure, the vertical axis represents the slope of an approximate straight line obtained by the least square method for the relationship between the deviation angle and the corneal retinal potential at each elapsed time. From FIG. 4 (A), it is clear that the slope of the approximate straight line is almost constant immediately after the application of the electrode, and the change becomes smaller as the elapsed time becomes longer. Also, from FIG. 4 (B), all of the seven subjects
It was found that the slope became substantially constant after at least 15 minutes had elapsed.

FIG. 5 is an overall configuration diagram of a visual acuity input device according to the present invention. As shown in this figure, a visual acuity input device 10 of the present invention includes a potential detector 12 for detecting a corneal retinal potential 2 of the subject 1, and a gaze position of the subject 1 based on the corneal retinal potential 2 detected by the potential detector 12. And an arithmetic and control unit 14 for obtaining the number 3 in real time.

The potential detector 12 includes, for example, a pair of electrodes arranged so as to hold an eye (eyeball) therebetween, and a signal line for inputting a potential generated between the electrodes to the arithmetic and control unit 14. In addition to the pair of electrodes, an electrode for measuring the potential of another portion for measuring the reference potential may be used. The electrode is formed by applying a conductive electrode paste, and is preferably attached to the skin around the eyes of the subject. Further, a conductive adhesive sheet may be used as a material. Further, depending on the position where the electrode is attached, the myoelectricity of the facial muscles that make up the facial expression may be mixed into the corneal retinal potential. Therefore, it is preferable to attach the electrode to the "temple" which is less affected. Further, since the measurement accuracy of the eye movement in the vertical direction is inferior to that in the horizontal direction, it is preferable to arrange the visual indices in the horizontal direction and arrange the electrodes so as to measure the horizontal direction. It is to be noted that the attachment of the electrodes is not necessarily indispensable. For example, an electrode embedded in a nose pad or the like of “glasses” may be used. Further, the electrodes may be brought into contact with each other when looking through a finder or the like to measure the corneal retinal potential.

The arithmetic and control unit 14 stores a relation between the corneal retinal potential and the plurality of gaze positions as an approximate straight line having a constant gradient, and obtains a fluctuation value of the corneal retinal potential at the same gaze position as needed. Compensation means 16 for compensating the corneal retinal potential by differentiating the fluctuation value, and signal processing means 17 for smoothing the fluctuation waveform of the corneal retinal potential and reducing a sudden change in the gaze position due to blinking and fast eye movement, The relationship between the corneal retinal potential and the plurality of gaze positions is calibrated and stored in advance, and the gaze position is determined in real time from this relationship and the corneal retinal potential.

Specifically, the arithmetic and control unit 14 includes a computer having a sufficient memory and a display device (C).
RT). The computer executes an algorithm described later by a predetermined program.

FIG. 6 is a flowchart showing a compensating means for compensating a corneal retinal potential according to the present invention. In this figure, the multi-point calibration is a step (step) of calibrating and storing a relationship between a corneal retinal potential 2 and a plurality of gaze positions 3 in advance, and using a computer at various positions in a display. The visual indices are sequentially presented, the subject is gazed at this, and the corneal retinal potential at that time is measured and stored. As described above, the drift phenomenon varies depending on the subject, but the drift phenomenon does not matter in a short measurement. The linear relationship between the deviation angle of the eyeball and the corneal retinal potential is independent of the passage of time and can be approximated as an approximate straight line having a constant gradient. Therefore, by performing the multi-point calibration, the linear relationship between the deviation angle of the eyeball and the corneal retinal potential is determined, and at least for a short time, the deviation angle is determined from the corneal retinal potential to obtain the gaze position of the subject. Can be.

The one-point calibration in FIG. 6 is a step (step) of measuring the corneal retinal potential 2 at a specific (eg, center) gaze position 3, and this step performs the corneal retinal potential at the same gaze position. The corneal retinal potential can be compensated by obtaining the fluctuation value of the variance from time to time and subtracting the fluctuation value. Therefore, the influence of the drift phenomenon is avoided by performing the one-point calibration at a sufficiently short time interval so that the influence of the drift phenomenon does not occur.
The gaze position can always be obtained accurately in real time.

On the other hand, the corneal retina potential changes drastically due to blinking of eyes and rapid eye movement, and it may be difficult to use the above-mentioned visual acuity input means alone for practical use. That is, "blinks" are mixed into the corneal retinal potential as electrical noise,
If the gaze position of the subject is obtained as it is from the corneal retinal potential and displayed by the cursor, the cursor jumps in an unexpected direction due to the effect of blinking. FIG. 7 shows the measurement result of the corneal retinal potential showing this state, and it can be seen that the corneal retinal potential is suddenly changed in a spike shape by “blinking” indicated by an arrow.

Similarly, when changing the point of gaze to look at another object (arbitrarily) suddenly, rapid eye movement called "impulsive eye movement (saccade movement)" may occur. Since this impulsive eye movement has a high angular velocity of several hundred degrees / second, it has been found from experiments that if the cursor is moved in accordance with this velocity, it is difficult or impossible to move the cursor as desired with the line of sight. .

FIG. 8 is a block diagram showing signal processing means for smoothing the fluctuation waveform of the corneal retinal potential according to the present invention. This signal processing means 17 solves the above-mentioned problem, and smoothes the fluctuation waveform of the corneal retinal potential, and reduces sudden changes in the gaze position due to blinking and rapid eye movement. That is, in FIG. 8, u (n) is the corneal retinal potential, y (n) is the “final” display position of the cursor, a is a parameter representing the slope of the approximate straight line obtained by the multi-point calibration, b is a parameter representing the drift variation correction obtained by the one-point calibration, D is a delay element, and k is a parameter for determining the amount of movement of the cursor.

In the signal processing means 17 of FIG. 8, the corneal retinal potential u (n) measured by the potential detector 12 is converted into a cursor display position x (n) by (Equation 1).

[0033]

(Equation 1)

If the display position x (n) is displayed on the display as it is, the above-mentioned problem occurs due to the effects of blinking and impulsive eye movement. Therefore, the signal processing unit 17 in FIG. 8 reduces the cursor movement amount to 1 / k when signal processing is not performed using a first-order delay element as shown in (Equation 2).

[0035]

(Equation 2)

FIG. 9 shows the result of applying the signal processing means of FIG. 8 to the corneal retinal potential of FIG. k = 1 indicates a case where the delay element is not considered, and k = 30 indicates 1/30 of the case.
The case where the cursor is moved at the speed of is shown. As is clear from this figure, if the delay element is not considered (k =
1) While the cursor jumps under the influence of blinking or the like, considering the delay element (k = 30), a spike-like waveform due to blinking or the like can be smoothed, and the cursor can be moved as desired with a line of sight. be able to.

FIG. 10 shows test results obtained by the above-mentioned visual acuity input device of the present invention. In this test, seven subjects were asked a simple question and asked to answer it by visual acuity input. In this figure, the horizontal axis is the number of tests and the vertical axis is the correct answer rate. (A) is for k = 1, (B) is for k =
30. From this figure, it is necessary to use the "sighting" means of the present invention in order to completely utilize the visual acuity input means, but in particular, by setting the delay element k in the signal processing means appropriately according to preference, In a short period of time, the accuracy rate is dramatically improved (that is, can be learned),
For example, it is understood that the correct answer rate reaches 90% or more in about four times.

In other words, in FIG. 10, the moving speed of the cursor is different between k = 1 and k = 30, and the former moves faster and the latter moves slowly. And the signal processing method according to the present invention was found to be effective.

It should be noted that the present invention is not limited to the above-described embodiment, and it goes without saying that various modifications can be made without departing from the spirit of the present invention. In the above description,
Although described with respect to a person having severe dysfunction, the present invention is not limited to this, and can be similarly applied to animals having similar eyes.

[0040]

As described above, according to the visual acuity input method and apparatus of the present invention, visual acuity input can be performed in real time only by detecting the corneal retinal potential from the subject, and the corneal retinal potential is determined by the distance between the electrodes. Can be detected without applying any voltage or current to the device, so that there is no effect on the user. Therefore, as compared with the conventional means, the setup of the device is easy, the fatigue associated with the use of the device is small, the device can be used for a long time, the malfunction due to the change of ambient light and the movement of the subject is small, and the device is stable. It has the effect that measurement can be performed and natural vision is hardly hindered.

Further, in the visual acuity input using the corneal retinal potential, drift phenomena that differ for each subject, blinking of the subject and rapid eye movement cannot be avoided. According to the present invention, these effects are avoided or compensated. Thus, accurate visual acuity input can be performed in real time. Therefore, the visual acuity input method and device of the present invention can be utilized as a communication support device for “severely physically handicapped” having severe dysfunction, in which communication by conversation, writing, and sign language is difficult.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing a visual acuity input method of the present invention.

FIG. 2 is a diagram showing a change in corneal retinal potential at the same gaze position.

FIG. 3 is a diagram showing a relationship between a corneal retinal potential and a plurality of gaze positions.

FIG. 4 is a diagram showing a gradient of a change in corneal retinal potential at the same gaze position.

FIG. 5 is an overall configuration diagram of a visual acuity input device according to the present invention.

FIG. 6 is a flowchart showing a compensating means for compensating for a drift of a corneal retinal potential according to the present invention.

FIG. 7 is a diagram showing changes in corneal retina potential due to blinking and fast eye movement.

FIG. 8 is a block diagram showing a signal processing means for smoothing a fluctuation waveform of a corneal retinal potential according to the present invention.

FIG. 9 is a similar diagram in which the corneal retinal potential of FIG. 7 is processed by a signal processing unit.

FIG. 10 is a test example using the apparatus of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 subject 2 corneal retina potential 3 gaze position (visual index) 10 visual acuity input device 12 potential detector 14 arithmetic and control unit 15 storage means 16 compensation means 17 signal processing means

Claims (6)

[Claims] 1. A corneal retinal potential, wherein a relationship between a corneal retinal potential and a plurality of gaze positions is previously calibrated and stored, and a gaze position is obtained in real time from the relationship and the corneal retinal potential. Eyesight input method. 2. The visual acuity input method according to claim 1, wherein the relation is stored as an approximate straight line having a constant gradient. 3. The visual acuity input method according to claim 1, wherein a fluctuation value of the corneal retinal potential at the same gaze position is obtained as needed, and the corneal retinal potential is compensated by subtracting the fluctuation value. 4. The visual acuity input method according to claim 1, wherein a fluctuation waveform of a corneal retina potential is smoothed, and a sudden change in a gaze position due to blinking and fast eye movement is reduced. 5. A potential detector for detecting a corneal retinal potential of a subject, and a relationship between a corneal retinal potential detected by the potential detector and a plurality of gaze positions is calibrated and stored in advance, and the relationship is stored in the cornea. A visual acuity input device using a corneal retinal potential, comprising: an arithmetic and control unit for obtaining a gaze position in real time from a retinal potential. 6. The arithmetic and control unit obtains a fluctuation value of a corneal retinal potential at the same gaze position as needed from a storage unit that stores the relation as an approximate straight line having a constant gradient, and calculates a difference between the fluctuation values. Compensating means for compensating corneal retinal potential;
The visual acuity input device according to claim 5, further comprising signal processing means for smoothing a fluctuation waveform of a corneal retina potential and reducing a sudden change in a gaze position due to blinking and fast eye movement.