Electro-oculography estimating device, electro-oculography calculating method, eye-gaze tracking device, wearable camera, head-mounted display, and electronic eyeglasses

1. An electro-oculography estimating device which estimates an electro-oculography theoretical value that is a theoretical value of an electro-oculogram generated in a living body, said electro-oculography estimating device comprising:

a distance obtaining unit configured to obtain (i) a right-eye corneal distance and a right-eye retinal distance each of which is a distance to an arbitrary three-dimensional spatial position from a corresponding one of a right eye cornea and a right eye retina, and (ii) a left-eye corneal distance and a left-eye retinal distance each of which is a distance to the arbitrary three-dimensional spatial position from a corresponding one of a left eye cornea and a left eye retina; and

an electro-oculography theoretical value calculating unit configured to calculate the theoretical value of the electro-oculogram generated at the arbitrary three-dimensional spatial position, using, as input into an electro-oculography model, the right-eye corneal distance, the right-eye retinal distance, the left-eye corneal distance, and the left-eye retinal distance obtained by said distance obtaining unit, the electro-oculography model being a function for calculating the electro-oculography theoretical value generated at the arbitrary three-dimensional spatial position.

2. The electro-oculography estimating device according to claim 1 ,

wherein, based on an assumption that a right eye and a left eye are gazing at a same gaze point, said distance obtaining unit is configured to calculate the right-eye corneal distance, the right-eye retinal distance, the left-eye corneal distance, and the left-eye retinal distance, based on a parallel movement component of both eyes, and a depth distance from both of the eyes to the same gaze point or a vergence movement component of both of the eyes.

3. The electro-oculography estimating device according to claim 1 ,

wherein the electro-oculography model includes predetermined coefficients each of which is individually settable for a corresponding one of the right-eye corneal distance, the right-eye retinal distance, the left-eye corneal distance, and the left-eye retinal distance.

4. The electro-oculography estimating device according to claim 3 ,

wherein, in the electro-oculography model, when: r 1 , r 2 , r 3 , and r 4 represent, respectively, the right-eye corneal distance, the right-eye retinal distance, the left-eye corneal distance, and the left-eye retinal distance; f 1 , f 2 , f 3 , and f 4 represent, respectively, a function for converting the right-eye corneal distance, the right-eye retinal distance, the left-eye corneal distance, and the left-eye retinal distance into the electro-oculogram; and α 1 , α 2 , α 3 , and α 4 represent, respectively, the predetermined coefficients each of which is settable for the corresponding one of the right-eye corneal distance, the right-eye retinal distance, the left-eye corneal distance, and the left-eye retinal distance, and when the electro-oculography theoretical value is represented by

{circumflex over (ν)},  [Math 1]

α 1 and α 2 are not zero at the same time, and α 3 and α 4 are not zero at the same time, in accordance with:

{circumflex over (ν)}=α 1 f 1 ( r 1 )+α 2 f 2 ( r 2 )+α 3 f 3 ( r 3 )+α 4 f 4 ( r 4 ).  [Math 2]

5. The electro-oculography estimating device according to claim 4 , wherein the electro-oculography model is represented by:

{circumflex over (ν)}=α 1 /r 1 +α 2 /r 2 +α 3 /r 3 +α 4 /r 4 .  [Math 3]

6. The electro-oculography estimating device according to claim 4 , further comprising

a model parameter estimating unit configured to estimate the predetermined coefficients α 1 , α 2 , α 3 , and α 4 each of which is obtained for a corresponding one of a plurality of gaze positions so that a difference between a theoretical voltage and an observation voltage is smallest, the theoretical voltage being generated at a corresponding one of a plurality of electrodes provided at different positions and calculated using the electro-oculography model, and the observation voltage being observed at the plurality of electrodes.

7. The electro-oculography estimating device according to claim 6 ,

wherein, when, for each of the plurality of electrodes i (i=1, . . . , N): Δv i =(Δv i, 1 , . . . , Δv i, M) t represents the observation voltage at a corresponding one of M different gaze positions θ j (j=1, . . . , M); α i =(α i, 1 , α i, 2 , α i, 3 , α i, 4 ) t represents the predetermined coefficients each of which is settable for the corresponding one of the right-eye corneal distance, the right-eye retinal distance, the left-eye corneal distance, and the left-eye retinal distance; r i, j, 1 , r i, j, 2 , r i, j, 3 , and r i, j, 4 , represent, respectively, the right-eye corneal distance, the right-eye retinal distance, the left-eye corneal distance, and the left-eye retinal distance; and f i, 1 , f i, 2 , f i, 3 , and f i, 4 represent, respectively, the function for converting the right-eye corneal distance, the right-eye retinal distance, the left-eye corneal distance, and the left-eye retinal distance, and when a matrix A i is represented by

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and when, for a reference electrode R: α R =(α R, 1 , α R, 2 , α R, 3 , α R, 4 ) t represents the predetermined coefficients each of which is settable for the corresponding one of the right-eye corneal distance, the right-eye retinal distance, the left-eye corneal distance, and the left-eye retinal distance at the corresponding one of the M different gaze positions θ j (j=1, . . . , M); r R, 1, 1 , r R, i, 2, r R, i, 3 , and r R, i, 4 represent, respectively, the right-eye corneal distance, the right-eye retinal distance, the left-eye corneal distance, and the left-eye retinal distance; and f R, 1 , f R, 2 , f R, 3 , and f R, 4 represent, respectively, the function for converting the right-eye corneal distance, the right-eye retinal distance, the left-eye corneal distance, and the left-eye retinal distance, and when a matrix A R is represented by

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said model-parameter estimating unit is configured to calculate each of the predetermined coefficients α i and α R for the plurality of electrodes and the reference electrode, in accordance with:

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(However, B i =A i (A i t A i ) −1 A i t −I, where I is a unit matrix).

8. The electro-oculography estimating device according to claim 6 ,

wherein said model-parameter estimating unit is configured to estimate the predetermined coefficients α 1 , α 2 , α 3 , and α 4 , using the observation voltage at the plurality of electrodes, the observation voltage being observed during eyeball movement that moves in a front-rear direction with respect to the living body from which the electro-oculogram is to be measured.

9. The electro-oculography estimating device according to claim 6 ,

wherein said model-parameter estimating unit is configured to estimate the predetermined coefficients α 1 , α 2 , α 3 , and α 4 , using the observation voltage at the plurality of electrodes, the observation voltage being obtained by saccadic movement.

10. The electro-oculography estimating device according to claim 1 ,

wherein the electro-oculography model is configured using a look-up table indicating a correspondence relationship between the electro-oculography theoretical value and a gaze direction of a user.

11. The electro-oculography estimating device according to claim 1 , further comprising

at least one electrode which is provided between both eyes of a user, measures the electro-oculogram, and outputs an electro-oculography original signal.

12. The electro-oculography estimating device according to claim 11 ,

wherein said at least one electrode is incorporated in a frame of eyeglasses, and includes a plurality of electrodes each of which is provided at a position at which the eyeglasses contact skin.

13. The electro-oculography estimating device according to claim 1 , further comprising

a plurality of electrodes each of which is positioned in front and back of an ear, measures the electro-oculogram, and outputs an electro-oculography original signal.

14. An electro-oculography calculating method for calculating, by an electro-oculography calculating device, a theoretical value of an electro-oculogram generated in a living body, said electro-oculography calculated method comprising:

obtaining (i) a right-eye corneal distance and a right-eye retinal distance each of which is a distance to an arbitrary three-dimensional spatial position from a corresponding one of a right eye cornea and a right eye retina, and (ii) a left-eye corneal distance and a left-eye retinal distance each of which is a distance to the arbitrary three-dimensional spatial position from a corresponding one of a left eye cornea and a left eye retina; and

calculating the theoretical value of the electro-oculogram generated at the arbitrary three-dimensional spatial position, using, as input into an electro-oculography model, the right-eye corneal distance, the right-eye retinal distance, the left-eye corneal distance, and the left-eye retinal distance obtained in said obtaining, the electro-oculography model being function for calculating the theoretical value of the electro-oculogram generated at the arbitrary three-dimensional spatial position.

15. An eye-gaze tracking device which detects a gaze direction of a user based on an electro-oculogram, said eye-gaze tracking device comprising:

an electro-oculography measuring unit configured to measure the electro-oculogram generated by eyeball movement, and outputs an electro-oculography original signal;

a calibration index presenting unit configured to present a calibration index to the user;

a saccade detecting unit configured to detect saccadic movement and output an electro-oculography change amount that is an amount of change in the electro-oculogram before and after the saccadic movement, the saccadic movement being rapid eyeball movement that occurs when a gaze position of the user moves to the calibration index presented by said calibration index presenting unit;

a calibration parameter calculating unit configured to calculate predetermined coefficients of an electro-oculography model based on a position of the calibration index presented by said calibration index presenting unit and the electro-oculography change amount that is output from said saccade detecting unit, using (i) a right-eye corneal distance and a right-eye retinal distance each of which is a distance to an arbitrary three-dimensional spatial position from a corresponding one of a right-eye cornea and a right-eye retina, (ii) a left-eye corneal distance and a left-eye retinal distance each of which is a distance to the arbitrary three-dimensional spatial position from a corresponding one of a left-eye cornea and a left-eye retina; and (iii) the predetermined coefficients, the electro-oculography model being a function for calculating the theoretical value of the electro-oculogram generated at the arbitrary three-dimensional spatial position, and the predetermined coefficients being individually settable for a corresponding one of the right-eye corneal distance, the right-eye retinal distance, the left-eye corneal distance, and the left-eye retinal distance; and

a calibration unit configured to detect the gaze direction of the user from the electro-oculogram, based on the electro-oculography model.

16. The eye-gaze tracking device according to claim 15 ,

wherein said saccade detecting unit includes:

a delayed signal generating unit configured to delay the electro-oculography original signal for a predetermined delay time and output a delayed signal;

a subtraction unit configured to generate an output signal obtained by subtracting the delayed signal from the electro-oculography original signal; and

a saccade determination unit configured to determine that a signal larger than a predetermined threshold is a saccade signal representing the saccadic movement, the signal being included in the output signal, and

the predetermined delay time is shorter than a period of time for which the user is gazing at the calibration index.

17. A wearable camera which captures an image in a gaze direction of a user, said wearable camera comprising:

an imaging unit;

the eye-gaze tracking device according to claim 15 ; and

an imaging control unit configured to cause said imaging unit to capture the image in the gaze direction detected by said eye-gaze tracking device.

18. A head-mounted display which moves a mouse pointer in a gaze direction of a user, said head-mounted display comprising:

a display unit configured to display an image and the mouse pointer;

the eye-gaze tracking device according to claim 15 ; and

a display control unit configured to move the mouse pointer in the gaze direction detected by said eye-gaze tracking device, the mouse pointer being displayed on the display unit.

19. Electronic eyeglasses which change a focal point of each of lenses according to a gaze position of a user, said electronic eyeglasses comprising:

lenses each having a changeable focal point;

the eye-gaze tracking device according to claim 15 ; and

a focus control unit configured to change the focal point of each of said lenses according to the gaze position detected by said eye-gaze tracking device.

20. A non-transitory computer readable medium having stored thereon a program for calculating a theoretical value of an electro-oculogram generated in a living body, said program causing a computer to execute:

obtaining (i) a right-eye corneal distance and a right-eye retinal distance each of which is a distance to an arbitrary three-dimensional spatial position from a corresponding one of a right eye cornea and a right eye retina, and (ii) a left-eye corneal distance and a left-eye retinal distance each of which is a distance to the arbitrary three-dimensional spatial position from a corresponding one of a left eye cornea and a left eye retina; and

calculating the theoretical value of the electro-oculogram generated at the arbitrary three-dimensional spatial position, using, as input into an electro-oculography model, the right-eye corneal distance, the right-eye retinal distance, the left-eye corneal distance, and the left-eye retinal distance obtained in the obtaining, the electro-oculography model being a function for calculating the theoretical value of the electro-oculogram generated at the arbitrary three-dimensional spatial position.