Apparatus, system, and method for adjusting head-mounted-display straps

1. A head-mounted-display adjustment apparatus comprising:

a strap comprising a distal section coupled to a distal area of a head-mounted display;

a pinion rotatably coupled to a proximal area of the head-mounted display in a manner that holds the head-mounted display against a user's face when a user is wearing the head-mounted display;

a rack that is coupled to a proximal section of the strap and comprises a plurality of teeth in mesh with the pinion such that:

rotation of the pinion repositions the rack relative to the head-mounted display; and

repositioning the rack adjusts an area between the strap and the head-mounted display; and

a constant-force spring that:

comprises a ribbon having a rolled portion and a protracted section that extends from the rolled portion; and

is coupled to the rack and that is configured to provide a tension on the strap in a manner that holds the head-mounted display against the user's face when the user is wearing the head-mounted display.

2. The head-mounted-display adjustment apparatus of claim 1 , wherein the pinion:

drives a gear train that comprises a set of gears; and

couples the rack to a slide such that rotation of the pinion moves the rack along the slide.

3. The head-mounted-display adjustment apparatus of claim 2 , wherein the gear train:

is housed by the slide; and

increases a range of motion of the rack such that the rack is extendable beyond the pinion.

4. The head-mounted-display adjustment apparatus of claim 2 :

wherein the rack is coupled to the proximal section of the strap such that the proximal section of the strap moves in tandem with the rack; and

further comprising a graspable knob coupled to the pinion such that rotation of the knob rotates the pinion.

5. The head-mounted-display adjustment apparatus of claim 4 , wherein the graspable knob is configured to adjust a distance of the head-mounted display to a user's face when a user is wearing the head-mounted display.

6. The head-mounted-display adjustment apparatus of claim 1 , wherein the constant force spring comprises resilient spring steel having a restoring force that is substantially a result of an extended portion of the ribbon that is nearest the rolled portion.

7. The head-mounted-display adjustment apparatus of claim 2 , wherein the rolled portion of the ribbon is housed by the slide such that, when the rack moves away from the pinion, the ribbon unrolls and the strap extends away from the head-mounted display.

8. The head-mounted-display adjustment apparatus of claim 1 , wherein the protracted section of the ribbon is anchored to the rack.

9. A head-mounted-display system comprising:

a head-mounted display;

a strap comprising a distal section coupled to a distal area of the head-mounted display; and

a rack-and-pinion assembly coupled to a proximal section of the strap and a proximal area of the head-mounted display such that, when a user is wearing the head-mounted display, the strap holds the head-mounted display against the user's face, the rack-and-pinion assembly comprising:

a pinion rotatably coupled to the proximal area of the head-mounted display; and

a rack in mesh with the pinion such that rotation of the pinion repositions the rack relative to the head-mounted display, wherein repositioning the rack adjusts an area between the strap and the head-mounted display, wherein:

the distal section of the strap is coupled to the distal area of the head-mounted display via an additional rack-and-pinion assembly comprising:

an additional pinion rotatably coupled to the head-mounted display; and

an additional rack in mesh with the additional pinion such that rotation of the additional pinion repositions the additional rack relative to the head-mounted display.

10. The head-mounted-display system of claim 9 , wherein:

the rack-and-pinion assembly is connected to a first section of the head-mounted display that is dimensioned to be positioned at a right side of the user's head; and

the additional rack-and-pinion assembly is connected to a second section of the head-mounted display that is dimensioned to be positioned at a left side of the user's head.

11. The head-mounted-display system of claim 9 , wherein:

the rack-and-pinion assembly further comprises:

a graspable knob coupled to the pinion such that rotation of the knob rotates the pinion; and

a constant-force spring that provides a tension holding the head-mounted display against the user's face when the user is wearing the head-mounted display; and

the additional rack-and-pinion assembly further comprises:

an additional graspable knob coupled to the additional pinion such that rotation of the additional knob rotates the additional pinion; and

an additional constant-force spring that provides an additional tension holding the head-mounted display against the user's face when the user is wearing the head-mounted display.

12. The head-mounted-display system of claim 11 , wherein rotation of the knob to reposition the rack relative to the head-mounted display adjusts the area between the strap and the head-mounted display separately from rotation of the additional knob to reposition the additional rack relative to the head-mounted display.

13. The head-mounted-display system of claim 11 , wherein:

the constant-force spring comprises a ribbon having:

a rolled portion that is housed by a slide coupled to the rack such that, when the rack moves away from the slide, the ribbon unrolls and the strap extends away from the head-mounted display; and

a protracted section anchored to the rack that extends from the rolled portion; and

the additional constant-force spring comprises an additional ribbon having:

an additional rolled portion that is housed by an additional slide coupled to the additional rack such that, when the additional rack moves away from the additional slide, the additional ribbon unrolls and the strap extends away from the head-mounted display; and

an additional protracted section anchored to the additional rack that extends from the additional rolled portion.

14. The head-mounted-display system of claim 11 , wherein the tension of the constant-force spring at least approximates the additional tension of the additional constant-force spring.

15. The head-mounted-display system of claim 9 , wherein the strap comprises a medial section coupled to a third section of the head-mounted display that is dimensioned to be positioned at a forehead of the user.

16. A method comprising:

coupling a distal section of a strap to a distal area of a head-mounted display;

rotatably coupling a pinion to a proximal area of the head-mounted display in a manner that holds the head-mounted display against a user's face when a user is wearing the head-mounted display; and

coupling a rack with a plurality of teeth in mesh with the pinion to a proximal section of the strap such that:

rotation of the pinion repositions the rack relative to the head-mounted display;

repositioning the rack adjusts an area between the strap and the head-mounted display; and

anchoring a constant-force spring to the rack such that the spring provides tension on the strap for holding the head-mounted display against the user's face when the user is wearing the head-mounted display, wherein the constant-force spring comprises a ribbon having a rolled portion and a protracted section that extends from the rolled portion.

17. The method of claim 16 , wherein:

coupling the pinion to the proximal area of the head-mounted display comprises:

coupling a slide to the rack such that rotation of the pinion moves the rack along the slide;

coupling the rack to the proximal section of the strap such that the proximal section of the strap moves in tandem with the rack;

housing a gear train, driven by the pinion, at the slide; and

the method further comprises housing the rolled portion of a constant-force spring at the slide such that, when the rack moves away from the slide, the constant-force spring unrolls and the strap extends away from the head-mounted display.

18. The method of claim 16 , further comprising coupling a graspable knob to the pinion such that rotation of the knob rotates the pinion.

19. The head-mounted-display adjustment apparatus of claim 1 , wherein the spring, when deflected, does not at least approximately follow Hooke's law.

20. The method of claim 16 , wherein a restoring force of the spring is substantially disproportional to a deflection of the spring.