Apparatus and method for measuring visual acuity by using focus-tunable lens

1 . An apparatus configured to measure a visual acuity (VA) by a focus-tunable lens, the apparatus comprising:

a display engine configured to project light comprising a VA measuring image;

an image combiner configured to guide the light projected from the display engine;

the focus-tunable lens provided on a path of the light guided by the image combiner;

an input device configured to receive a user's input with respect to the VA measuring image;

a storage configured to store one or more instructions; and

a processor configured to execute the one or more instructions to:

control the focus-tunable lens to assign a first optical power to a first lens region and a second optical power that is different from the first optical power to a second lens region, the first lens region and the second lens region being included in a lens surface of the focus-tunable lens;

control the display engine to display the VA measuring image through a first output region and a second output region of the image combiner, which respectively correspond to the first lens region and the second lens region of the focus-tunable lens;

control the input device to receive the user's input;

specify one optical power of the first optical power and the second optical power based on the user's input; and

determine a VA of a user based on the specified optical power,

wherein the focus-tunable lens comprises a first liquid crystal lens comprising a first strip electrode array and divided into a plurality of first zones, and a second liquid crystal lens comprising a second strip electrode array and divided into a plurality of second zones,

wherein the first strip electrode array comprises a plurality of first strip electrodes having a linear shape extending along a first direction, and the second strip electrode array comprises a plurality of second strip electrodes having a linear shape extending along a second direction perpendicular to the first direction,

wherein the plurality of first strip electrodes and the plurality of second strip electrodes overlap each other orthogonally,

wherein the processor is further configured to assign the first optical power to the first lens region by setting a first voltage profile applied to at least one first strip electrode included in a first zone among the plurality of first zones corresponding to the first lens region and at least one second strip electrode included in a second zone among the plurality of second zones corresponding to the first lens region, and assign the second optical power to the second lens region by setting a second voltage profile applied to at least one first strip electrode included in a first zone among the plurality of first zones corresponding to the second lens region and at least one second strip electrode included in a second zone among the plurality of second zones corresponding to the second lens region,

wherein the first optical power has a first cylindrical lens optical power with the first direction, placed on the lens surface of the focus-tunable lens, as an axial direction, and the second optical power has a second cylindrical lens optical power with the second direction, placed on the lens surface of the focus-tunable lens and orthogonal to the first direction, as the axial direction based on measuring astigmatism of the user, and

wherein the measuring of the VA of the user comprises determining an astigmatism direction of the user based on the axial direction of each of the first cylindrical lens optical power and the second cylindrical lens optical power.

2 . The apparatus of claim 1 , wherein a first VA measuring image displayed through the first output region and a second VA measuring image displayed through the second output region are same images having same sizes.

3 . The apparatus of claim 1 , wherein the focus-tunable lens comprises a pixel electrode liquid crystal lens comprising a pixel electrode array, and

wherein the processor is further configured to:

apply a voltage to first pixel electrodes of the pixel electrode array, which pass by the first lens region, such that the first lens region has the first optical power; and

apply a voltage to second pixel electrodes of the pixel electrode array, which pass by the second lens region, such that the second lens region has the second optical power.

4 . The apparatus of claim 1 , wherein the input device comprises at least one of a gaze tracking sensor, a microphone, a button, and a gesture recognition sensor.

5 . The apparatus of claim 1 , wherein the image combiner is further configured to guide the light projected from the display engine to a target region and project light of a real scene, and

wherein the focus-tunable lens is provided on a path of the light guided from the image combiner to the target region.

6 . The apparatus of claim 5 , wherein the image combiner comprises one of a waveguide, multiple mirrors, and a reflective mirror.

7 . The apparatus of claim 1 , wherein information with respect to the measured VA of the user is stored in the storage.

8 . The apparatus of claim 1 , wherein the apparatus comprises an augmented reality (AR) device.

9 . A method of measuring a visual acuity (VA) by a focus-tunable lens, the method comprising:

assigning a first optical power to a first lens region and a second optical power that is different from the first optical power to a second lens region, the first lens region and the second lens region being included on a lens surface of the focus-tunable lens;

displaying a VA measuring image through a first output region and a second output region of an image combiner, which respectively correspond to the first lens region and the second lens region of the focus-tunable lens;

receiving a first input of a user with respect to the VA measuring image;

specifying one optical power of the first optical power and the second optical power based on the first input of the user; and

determining a VA of the user based on the specified optical power,

wherein the focus-tunable lens comprises a first liquid crystal lens comprising a first strip electrode array and divided into a plurality of first zones, and a second liquid crystal lens comprising a second strip electrode array and divided into a plurality of second zones,

wherein the first strip electrode array comprises a plurality of first strip electrodes having a linear shape extending along a first direction, and the second strip electrode array comprises a plurality of second strip electrodes having a linear shape extending along a second direction perpendicular to the first direction,

wherein the plurality of first strip electrodes and the plurality of second strip electrodes overlap each other orthogonally,

wherein method further comprises:

assigning the first optical power to the first lens region by setting a first voltage profile applied to at least one first strip electrode included in a first zone among the plurality of first zones corresponding to the first lens region and at least one second strip electrode included in a second zone among the plurality of second zones corresponding to the first lens region; and

assigning the second optical power to the second lens region by setting a second voltage profile applied to at least one first strip electrode included in a first zone among the plurality of first zones corresponding to the second lens region and at least one second strip electrode included in a second zone among the plurality of second zones corresponding to the second lens region,

wherein the assigning of the first optical power and the second optical power to the focus-tunable lens comprises applying a voltage to electrodes of the focus-tunable lens such that the first optical power has a first cylindrical lens optical power with the first direction, placed on the lens surface of the focus-tunable lens, as an axial direction, and the second optical power has a second cylindrical lens optical power with the second direction, placed on the lens surface of the focus-tunable lens and orthogonal to the first direction, as the axial direction based on measuring astigmatism of the user, and

wherein the measuring of the VA of the user comprises determining an astigmatism direction of the user based on the axial direction of each of the first cylindrical lens optical power and the second cylindrical lens optical power.

10 . The method of claim 9 , wherein a first VA measuring image displayed through the first output region and a second VA measuring image displayed through the second output region are same images having same sizes.

11 . The method of claim 9 , further comprising:

changing the first optical power and the second optical power based on the specified optical power and re-assigning the changed first optical power and the changed second optical power to the focus-tunable lens;

displaying the VA measuring image and receiving a second input of the user;

re-specifying one optical power of the changed first optical power and the changed second optical power based on the second input of the user; and

determining the VA of the user based on the re-specified optical power.

12 . The method of claim 9 , further comprising:

after changing the first direction in a range of greater than 0 degree to 90 degree, assigning the changed first optical power and the second optical power to the focus-tunable lens;

displaying the VA measuring image;

receiving a third input of the user;

re-specifying one optical power of the changed first optical power and the changed second optical power based on the third input of the user; and

re-measuring the VA of the user based on the re-specified optical power.

13 . The method of claim 9 , wherein the first input of the user is input by at least one of a gaze tracking sensor, a microphone, a button, and a gesture recognition sensor.

14 . The method of claim 9 , further comprising storing the measured VA of the user in a storage of an apparatus.

15 . A non-transitory computer-readable recording medium for executing a method of measuring a visual acuity (VA) by a focus-tunable lens on a computer, the method comprising:

assigning a first optical power to a first lens region and a second optical power that is different from the first optical power to a second lens region, the first lens region and the second lens region being included on a lens surface of the focus-tunable lens;

displaying a VA measuring image through a first output region and a second output region of an image combiner, which respectively correspond to the first lens region and the second lens region of the focus-tunable lens;

receiving a first input of a user with respect to the VA measuring image;

specifying one optical power of the first optical power and the second optical power based on the first input of the user; and

determining a VA of the user based on the specified optical power,

wherein the focus-tunable lens comprises a first liquid crystal lens comprising a first strip electrode array and divided into a plurality of first zones, and a second liquid crystal lens comprising a second strip electrode array and divided into a plurality of second zones,

wherein the first strip electrode array comprises a plurality of first strip electrodes having a linear shape extending along a first direction, and the second strip electrode array comprises a plurality of second strip electrodes having a linear shape extending along a second direction perpendicular to the first direction,

wherein the plurality of first strip electrodes and the plurality of second strip electrodes overlap each other orthogonally,

wherein method further comprises:

assigning the first optical power to the first lens region by setting a first voltage profile applied to at least one first strip electrode included in a first zone among the plurality of first zones corresponding to the first lens region and at least one second strip electrode included in a second zone among the plurality of second zones corresponding to the first lens region; and

assigning the second optical power to the second lens region by setting a second voltage profile applied to at least one first strip electrode included in a first zone among the plurality of first zones corresponding to the second lens region and at least one second strip electrode included in a second zone among the plurality of second zones corresponding to the second lens region,

wherein the assigning of the first optical power and the second optical power to the focus-tunable lens comprises applying a voltage to electrodes of the focus-tunable lens such that the first optical power has a first cylindrical lens optical power with the first direction, placed on the lens surface of the focus-tunable lens, as an axial direction, and the second optical power has a second cylindrical lens optical power with the second direction, placed on the lens surface of the focus-tunable lens and orthogonal to the first direction, as the axial direction based on measuring astigmatism of the user, and

wherein the measuring of the VA of the user comprises determining an astigmatism direction of the user based on the axial direction of each of the first cylindrical lens optical power and the second cylindrical lens optical power.