Wrist-worn input device

1. A wrist-worn input device measuring a biopotential for use in inputting a gesture, comprising:

a band that forms at least part of a tubular structure having a first opening and a second opening at two ends thereof in an axial direction thereof;

one or more electrodes open to an internal surface of the band;

a first position determiner that is located close to the first opening and has a shape to be engaged with at least part of a periphery of the styloid process of ulna of a user;

a measurer that measures the biopotential of the user using the one or more electrodes; and

an outputter that outputs the biopotential of the user measured by the measurer,

wherein the one or more electrodes include at least one measurement electrode, and

wherein the at least one measurement electrode is located at a center point between the first opening and the second opening along the axial direction or located at a point closer to the second opening than to the center point along the axial direction.

2. The wrist-worn input device according to claim 1 , wherein the one or more electrodes comprise at least one reference electrode,

wherein the at least one reference electrode is located in alignment with the first position determiner along the axial direction and measures a reference potential that is used to normalize the biopotential measured using the at least one measurement electrode, and

wherein the first position determiner and the reference electrode are aligned in the axial direction.

3. The wrist-worn input device according to claim 1 , wherein the one and more electrodes further comprises at least one ground electrode, and

wherein the at least one ground electrode is located in alignment with the first position determiner along the axial direction.

4. The wrist-worn input device according to claim 1 , wherein the first position determiner is a cutout formed in an end edge portion of the band at the first opening.

5. The wrist-worn input device according to claim 1 , wherein the first position determiner is a recess formed on the internal surface of the band.

6. The wrist-worn input device according to claim 5 , wherein the recess is a through-hole penetrating through the band, and

wherein the first position determiner comprises a cap closing the through-hole on an external surface of the band.

7. The wrist-worn input device according to claim 6 , wherein at least part of the cap is transparent.

8. The wrist-worn input device according to claim 6 , wherein the cap detachably closes the through-hole.

9. The wrist-worn input device according to claim 1 , wherein the band comprises a first band portion and a second band portion lower in flexibility than the first band portion, and

wherein the first position determiner is formed in the first band portion.

10. The wrist-worn input device according to claim 1 , further comprising a second position determiner that is located closer to the second opening, and has a shape to be engaged with at least part of the periphery of the styloid process of ulna of the user.

11. The wrist-worn input device according to claim 10 , wherein the at least one measurement electrode is located at the center point.

12. The wrist-worn input device according to claim 1 , wherein the one or more electrodes further comprise a plurality of reference electrodes,

wherein each of the reference electrodes is used to measure a reference potential that is used to normalize the biopotential measured using the at least one measurement electrode, and

wherein the measurer normalizes the biopotential measured using the at least one measurement electrode by selectively using one of a plurality of reference potentials measured using the reference electrodes.

13. The wrist-worn input device according to claim 1 , further comprising on an external surface of the tubular structure a display having a width in a lateral direction and a height in a vertical direction,

wherein the first position determiner is located above a center of the display.

14. The wrist-worn input device according to claim 1 , further comprising a display on an external surface of the tubular structure,

wherein the display displays a screen in alignment such that the first position determiner is located above a center of the screen.

15. A wrist-worn input device measuring a biopotential for use in inputting a gesture, comprising:

a band that forms at least part of a tubular structure having a first opening and a second opening at two ends thereof in an axial direction thereof;

one or more electrodes open to an internal surface of the band;

a first position determiner that is located close to the first opening and has a shape to be engaged with at least part of the periphery of the styloid process of ulna of a user;

a sensor that measures the biopotential of the user using the one or more electrodes; and

a communication device that transmits the biopotential of the user measured by the sensor,

wherein the one or more electrodes include at least one measurement electrode, and

wherein the at least one measurement electrodes is located at a center point between the first opening and the second opening along the axial direction or located at a point closer to the second opening than to the center point along the axial direction.

16. A wrist-worn input device, comprising:

a band in a rectangular development shape, except a cutout, extending along a first longitudinal line and a second longitudinal line, and having the cutout extending along the first longitudinal line; and

a plurality of electrodes including one or more measurement electrodes, one or more reference electrodes, and one or more ground electrodes, each of the electrodes open to an internal surface of the band,

wherein a center line extends along the internal surface between the first longitudinal line and the second longitudinal line,

wherein the one or more measurement electrodes are located in an area between the center line and the second longitudinal line,

wherein one or more potentials measured by using the one or more measurement electrodes are normalized by using one or more potentials measured by the one or more reference electrodes,

wherein a longest distance between the cutout and the one or more reference electrodes is shorter than a shortest distance between the cutout and the one or more measurement electrodes, and

wherein the one or more reference electrodes and the one or more ground electrodes are located in an area between a line running from a first intersection of the cutout and the first longitudinal line in perpendicular to the second longitudinal line and a line running from a second intersection of the cutout and the first longitudinal line in perpendicular to the second longitudinal line.