Method and device for measuring a person's eyesight

Abstract

Methods and devices for measuring the visual acuity of a person (42) are provided. The method includes determining a distance (d) between a measuring device and the person (42). The distance is determined by communication between a first wireless communication interface of the measuring device and a second wireless communication interface of a portable device (43, 44) located at the person. Then, the method includes performing a visual acuity measurement based on the distance.

Description

[0001] The present application relates to methods and devices for measuring a person's visual acuity.

[0002] The measurement of a person's visual acuity (referred to as visual acuity measurement for short) is generally used to determine eye characteristics related to vision. These characteristics characterize a person's ability to perceive his or her surrounding environment. For example, visual acuity measurements performed by, for example, an optician or a doctor can determine the refraction of the eye in terms of spherical power, cylindrical power, and axis (see 11.2, 12.5, and 12.6 of DIN EN ISO 13666:2013-10) and visual acuity, which is a measure of the spatial resolution or color perception of at least one eye.

[0003] There are known subjective refraction methods that rely on the feedback of the person being examined and objective refraction methods that operate without feedback. For example, in common subjective refraction methods, the person being examined views optotypes of various sizes printed on paper or displayed on a screen and provides feedback on which optotypes he or she can still distinguish (e.g., how small). In this context, an optotype refers to any symbol, letter, number, or light that a person has to distinguish in such a test. Examples of optotypes are Snellen letters or Landolt C rings.

[0004] Examples of objective refraction include isotropic photorefraction and eccentric photorefraction. These methods are described, for example, in the following document: W. Wesemann and H. I. Wesemann, “Fotorefraktion - ein objektives Screening - Verfahren zur Refraktionsbestimmung”, DOZ - Deutsche Optiker Zeitung 11 / 92, Seiten 50–54 [“Photorefraction - an objective screening method for determining refraction”, DOZ - German Optician's Newspaper 11 / 92, pages 50 - 54].

[0005] Generally, these methods are performed by an optician or a doctor using specific devices and components constructed for the respective measurements.

[0006] In recent years, it has become a trend to use home computers, laptops, and mobile devices (such as smartphones or tablet PCs) for refractive and visual acuity measurements, aiming to enable people to measure their own eye refraction or visual acuity without the help of opticians or doctors, although these methods can also be performed by opticians or doctors. For example, for subjective refraction, US10314475 B2 and US 8702238 B2 describe corresponding methods where the test chart is displayed on a computer screen. For objective refraction using eccentric photorefraction, WO2018 / 002332A2 discloses various methods for performing eccentric photorefraction using a smartphone.

[0007] For both types of measurements (subjective or objective), the distance from the person to the measuring device is important. For subjective refraction methods, it is easy to understand that the closer the person is to the test chart, the easier it is usually to distinguish them. In addition, it may be necessary to distinguish between near vision (i.e., the person's eyes are close to the test chart, such as 1 meter or less) and far vision (i.e., the person's eyes are far from the test chart, such as 2 meters or more, or 3 meters or more). Therefore, each of the above-cited references includes a method for determining and correcting the distance. For example, US10314475 B2 uses a computer that displays the test chart and a portable device held by the user. The camera of the portable device takes a picture of the computer screen, and based on the size of the screen (in pixels) in the captured image, the distance can be determined. Based on this information, the size of the displayed test chart can be adjusted. Various methods for distance determination are mentioned in US 8702238 B2, including the input of information by the user. In other methods, the subject needs to take a predetermined number of steps away from the screen. Obviously, the distance obtained thereby depends on the size of the steps taken by the person.

[0008] For eccentric photorefraction, based on the measurement, the distance is directly used for calculating the refraction, as described in WO 2018 / 002332A2. In addition, WO 2018 / 002332 A2 discusses various possibilities for distance measurement, including the input of information, measurements by the camera (such as measuring an object with a known size, such as a credit card), etc.

[0009] The methods for distance measurement disclosed in these documents may be relatively inaccurate (e.g., if the user needs to estimate the distance or needs to take a predetermined number of steps) and may be difficult to repeat or perform continuously. For example, if a person needs to hold an object with a known size (such as a credit card) next to his / her head, he / she will usually do so once for the distance measurement and then take the object away. Then, if the distance changes during the measurement (e.g., due to the inadvertent movement of the person), the change will not be recognized.

[0010] Accordingly, starting from the above-cited literature, a basic object of the present application is to provide methods and devices for vision measurement with improved distance measurement, which are accurate enough and can be repeated for substantially continuous monitoring.

[0011] This object is achieved by the method as defined in claim 1 and the device as defined in claim 9. The dependent claims define further embodiments of the method and the device and systems comprising such a device. In addition, a method for manufacturing lenses based on vision measurement is provided.

[0012] According to one aspect of the present invention, there is provided a method for measuring a person's vision, comprising:

[0013] determining a distance between a measurement device and the person; and

[0014] measuring the vision based on the distance.

[0015] The method is characterized in that determining the distance comprises determining the distance by communication between a first wireless communication interface of the measurement device and a second wireless communication interface of a portable device located at the person.

[0016] The measurement of a person's vision, abbreviated as vision measurement as described herein, refers to a non-invasive measurement method for determining the characteristics (such as refraction, visual acuity, contrast sensitivity, astigmatism, color sensitivity, dynamic acuity, or a combination thereof) of one or both eyes of a person. Measuring the vision based on the distance means that the distance affects the measurement in some way. Examples will be given further below.

[0017] Different from the traditional method explained above, according to the above method, the distance is determined by communication between the first and second wireless interfaces.

[0018] As used herein, a wireless communication interface refers to a component capable of wireless data transmission between devices. Most computers, laptops, smartphones, tablet PCs, smartwatches, etc. include one or more wireless communication interfaces. Examples of such wireless communication interfaces include Bluetooth specified in various versions at www.bluetooth.com, wireless local area networks (WLANs) (such as b, g, m, ac, ax, ad) specified in the standard series IEEE 802.11, or ultra-wideband (UWB) communication specified in IEEE 802.15.4a and IEEE 802.15.4z. Distance measurement using Bluetooth is based on the so-called "received signal strength indication" (RSSI). Distance measurement regarding LAN technologies is generally described in the following literature: A. Günther and C. Proc. of Networking 2005 [Proceedings of the Networking 2005 Conference], Waterloo, Canada, May 2005. For the 60 gigahertz band used, for example, by IEEE 802.11ad, distance measurements are described in: V. Sark et al., "Achieving Millimeter Precision Distance Estimation using Two-Way Ranging in the 60GHz Band", DOI: 10.1109 / EuCNC.2019.8801999 ["Achieving Millimeter Precision Distance Estimation using Two-Way Ranging in the 60GHz Band", DOI: 10.1109 / EuCNC.2019.8801999].

[0019] For example, distance determination using ultra-wideband technology is described in US 7962150 B2 or EP 3651410 A1. General methods for distance estimation using a wireless communication interface are described in: C.L. Sang et al., "Numerical and Experimental Evaluation of Error Estimation for Two-Way Ranging Methods" Sensors 2019, vol. 19, 616 ["Numerical and Experimental Evaluation of Error Estimation for Two-Way Ranging Methods", Sensors 2019, vol. 19, 616].

[0020] The methods described above utilize the fact that, as mentioned above, many devices include a corresponding wireless communication interface. For example, many people today carry a smartphone or even a smartwatch, which can be used as a portable device located at the person and communicate with a correspondingly programmed measurement device (such as a computer or laptop) to determine the distance. In this way, distance measurement does not require specific hardware, but only corresponding programming of the devices.

[0021] Among the wireless communication interfaces described above, ultra-wideband interfaces are preferred because they offer high precision.

[0022] Preferably, the determination of the distance is repeated such that substantially continuous monitoring of the distance becomes possible. "Substantially continuous" means that the distance measurements are repeated one after another at very short intervals (e.g., 1 second or less, 100 ms or less or shorter intervals). In this way, unlike in some traditional solutions where the distance is only measured once, for example, at the start of the measurement, it is also possible to take into account changes in the distance during the measurement (e.g., due to the movement of a person).

[0023] Depending on the type of measurement for a particular application, distance-based vision measurements can be performed in various ways.

[0024] For example, for subjective refraction measurements, a target can be displayed on the screen of the measurement device, where the size of the target is set according to the distance, and as such, is described in US 10314475B2 with another type of distance measurement. In other examples, a vision measurement may require a specific distance, and if the determined distance does not match the required distance, the measurement device, the portable device, or both can output instructions to a person to move to the correct distance. In yet some other methods, such as the eccentric photorefraction mentioned initially, the calculation of the measurement result itself can use the distance as a parameter.

[0025] For example, to measure a vision parameter such as contrast vision, the contrast of the target is varied while keeping the distance fixed. However, the distance measurement described herein, particularly the substantially continuous monitoring mentioned above, provides an active control mechanism to check whether the distance used for the contrast test during the test execution is still correct. To evaluate color vision, the color of the target is varied. To evaluate astigmatism, the orientation of the target is varied. To evaluate dynamic acuity, the speed of the target is non-zero but varied. In all tests, the distance measurement can be used to control the distance (e.g., maintain a predetermined distance), to adjust the target parameters (such as size) according to the distance measurement, or both.

[0026] Preferably, the measurement device can be controlled by a portable device using the first and second communication interfaces. In this way, a person can use the portable device to send commands to the measurement device, such as starting the measurement. This can be done, for example, by pressing a button on the portable device (such as a button displayed on the touch screen of the portable device), or by using an audio input of the microphone of the portable device. Conventional portable devices (such as smartphones, tablets, or smartwatches) include such input methods.

[0027] In some preferred embodiments, the method further includes determining the orientation between the portable device and the measuring device, wherein the vision measurement is further based on the orientation. Using the above wireless communication standards, such orientation measurement is possible. The orientation measurement is substantially based on the signal strength received by the receiving device (if the measuring device is the transmitter, it is the portable device; if the portable device is the transmitter, it is the measuring device), and the signal strength depends on the mutual antenna orientation of the two devices. For example, in this way, the orientation of a person's head can be determined by holding the portable device in a specific way on the head. This is particularly preferred if the portable device includes earphones, which also often include ultra-wideband wireless communication interfaces nowadays. In this way, the person does not have to hold the portable device in a specific way, but only needs to wear the earphones in a normal way. The orientation of the head is important for measurements involving astigmatism because the eye refraction here is not rotationally symmetric. In other cases, for example, when the portable device is a smartwatch, the orientation of a person's hand or arm can be measured. The orientation of the hand or arm can be used to control the measurement, as a kind of gesture control.

[0028] For example, performing a vision measurement based on the determined orientation includes at least one of the following:

[0029] - Displaying an optotype with an orientation based on the determined orientation. For example, the orientation of the optotype can be adapted to the orientation of the head or controlled by the orientation of the hand or arm.

[0030] - Calculating a measurement value based on the determined orientation. For example, the calculation of the astigmatism axis can be performed based on the orientation of the head or the orientation of the hand (if the hand in turn controls the orientation of the optotype), or

[0031] - If the determined orientation does not correspond to the target orientation, outputting a rotation instruction to the person (42), such as correcting the orientation of the head, or receiving an instruction or command from the person by changing the orientation of the hand or arm.

[0032] In another embodiment, a method for manufacturing spectacle lenses is provided, including measuring a person's vision based on any of the above methods, and

[0033] manufacturing spectacle lenses based on the measurement results of the vision. For example, when the vision measurement is a refractive measurement, spectacle lenses for correcting eye refraction can be manufactured.

[0034] In addition, a measuring device for measuring a person's vision is provided, including:

[0035] a distance determination component configured to determine the distance between the measuring device and the person, and

[0036] a measurement component configured to measure the person's vision based on the distance.

[0037] The device is characterized in that the distance determination component includes a first wireless interface configured to determine the distance by communicating with a second wireless communication interface of a portable device located at the person.

[0038] The above explanation of the method also applies to the measuring device, including its variants. For example, the measuring component may include a display for displaying visual targets for subjective optometry measurements, or may include a camera and a processor for performing objective optometry measurements (such as eccentric photorefraction).

[0039] Furthermore, a system including a measuring device and a portable device is provided. The measuring device may include, for example, a personal computer (PC) or a laptop, a computer, or a mobile device (such as a tablet or a smartphone). In this case, a computer program may be provided to be executed on the measuring device such that any of the methods discussed above is executed. The portable device as described above may include, for example, a smartphone, a smartwatch, a tablet PC or may also include devices such as headphones. Therefore, the techniques discussed herein can also be used for smartphones or tablet PCs and smartphones.

[0040] Embodiments will now be discussed with reference to the accompanying drawings.

[0041] Figure 1 is a block diagram of a system according to an embodiment.

[0042] Figure 2 is a flowchart showing a method according to an embodiment.

[0043] Figure 3 is a diagram showing distance measurement using a wireless communication interface.

[0044] Figure 4 shows a measurement scenario according to an embodiment.

[0045] Figure 5A and 5B shows a measurement scenario according to an embodiment.

[0046] Figure 1 is a system according to an embodiment, including a measuring device 10 and a portable device 11. The measuring device 10 is schematically shown as including at least a processor 12 and a first wireless interface 13. The measuring device 10 may be, for example, a computer, such as a laptop or a desktop computer with a monitor. The portable device 11 is schematically shown as including at least a processor 14 and a second wireless interface 15, which communicates with the first wireless interface 13 (as shown by line 16). The first wireless interface 13 and the second wireless interface 15 may be ultra-wideband (UWB) interfaces as described above. The portable device 11 may be a smartphone, a tablet PC, a smartwatch or may be a pair of headphones.

[0047] A system using Figure 1 can perform a method according to an embodiment as Figure 2 shown. In step 20, the method includes determining the distance between the measuring device 10 and the portable device 11 through communication between the wireless interfaces 13, 15. During the measurement, the portable device 11 is located at the person to be examined (e.g., worn by the person), so that the determined distance corresponds to the distance between the measuring device 10 and the person. In step 21, the method includes performing a vision measurement based on the distance. Optionally, the orientation between the measuring device 10 and the portable device 11 can also be determined in step 20, and in this case, a vision measurement can also be performed based on the orientation in step 21. Examples of the measurement have been described in the above Summary of the Invention section and will be further described below.

[0048] The determination of the distance can be performed by measuring the time of flight of the signal exchanged between the wireless interfaces. Details are described in the above-cited publication by C.L. Sang et al. and will be briefly described with reference to Figure 3 it.

[0049] At the first transmission time ts1, the first wireless interface 13 transmits a signal 30 to the second wireless interface 15, which receives the signal at the first reception time tr1. After the internal processing time, the second wireless interface 15 replies with a signal 31 at the second transmission time ts2, and this signal is received by the first wireless interface 13 at the second reception time tr2. After the internal processing time, the first wireless interface 13 transmits another signal 32 at the transmission time ts3, and this signal is received by the second wireless interface 15 at the time tr3.

[0050] The round-trip time is the time between one of the wireless interfaces transmitting a signal and the same wireless interface receiving the signal again. Therefore, Figure 3 the first round-trip time in tof is tr2–ts1, and the second round-trip time is tr3–ts2. Each round-trip time is twice the time of flight T tof (i.e., the time it takes for the electromagnetic wave to travel from one of the wireless interfaces 13, 15 to the other of the wireless interfaces 13, 15) plus the processing time of the other device. Therefore, tr2–ts1 = 2xT tof +ts2–tr1, and tr3–ts2 = 2xT tof, and the distance can be determined by multiplying by the speed of light (electromagnetic waves propagate at the speed of light). As mentioned before, more details about these calculations can be found in the above-mentioned publication by C.L.Sang et al.

[0051] Figure 4 FIG. shows an application scenario of a system according to an embodiment. The screen 40 of the measuring device is shown as displaying a visual target, here a circle with an opening, a so-called Landolt C-ring, 41. The subject 42 has a smart phone 44 in his / her pocket and wears a smart watch 43. Both the smart watch 43, the smart phone 44, and a combination of both can be used as portable devices. By communicating between the measuring device and the smart phone 44 or the smart watch 43, the test distance d can be measured as described above. In addition, the user can use the smart watch 43 or the smart phone 44 to control the measurement. For example, the person can start the measurement in this way, switch to the next visual target displayed, or give feedback on whether he / she can distinguish the visual target. As Figure 4 shown, in this example, the visual target is additionally displayed on the smart phone 44.

[0052] Figure 5A and 5B FIG. shows an example of how to perform a measurement based on distance. In this case, a laptop 50 is used as the measuring device for displaying the visual target 41 as in Figure 4 , and the person 42 has a smart phone 44 as an example of a portable device. As described above, the corresponding wireless communication interface is used to measure the distance between the laptop 50 and the smart phone 44.

[0053] In Figure 5A , the test distance d1 is less than Figure 5B the test distance d2 in Figure 5A . Therefore, in this example, in Figure 5B , the visual target 41 is displayed as the visual target 41A, while in the case of Figure 5B , the visual target 41 is displayed as a visual target 41B that is larger than the visual target 41A. In other words, in this case, the size of the displayed visual target is adapted to the test distance, and for a larger test distance, a larger visual target is displayed.

Claims

1. A method for measuring the visual acuity of a person (42), comprising: determining the distance (d, d1, d2) between the measuring device (10; 50) and the person (42), and using the measuring component (12) of the measuring device (10; 50) to measure the visual acuity based on the distance (d, d1, d2), characterized in that, determining the distance (d, d1, d2) includes determining the distance (d, d1, d2) by communicating between a first wireless communication interface (13) of the measuring device (10; 50) and a second wireless communication interface (15) of a portable device (11; 43, 44) located at the person (42), the method further includes determining the orientation between the measuring device (10; 50) and the portable device (11; 43, 44) by communicating between the first wireless communication interface (13) and the second wireless communication interface (15), wherein measuring the visual acuity further includes measuring the visual acuity based on the orientation.

2. The method according to claim 1, characterized in that The first wireless communication interface (13) and the second wireless communication interface (15) are ultra-wideband communication interfaces.

3. The method according to claim 1, characterized in that The orientation indicates the orientation of a body part selected from the group consisting of the head, hand, and arm of the person (42).

4. The method according to claim 1 or 3, characterized in that Measuring the visual acuity based on the determined orientation includes at least one of the group consisting of: - displaying optotypes with an orientation based on the determined orientation, - calculating a measurement value based on the determined orientation, - if the determined orientation does not correspond to a target orientation, outputting a rotation instruction to the person (42), and - controlling the measurement based on the determined orientation.

5. The method according to any one of claims 1 to 3, wherein, Repeating the determination of the distance.

6. The method according to any one of claims 1 to 3, characterized in that, Measuring the visual acuity based on the distance (d, d1, d2) includes at least one of the group consisting of: - displaying optotypes with a size based on the distance, - calculating a measurement value based on the distance, or - if the distance does not correspond to a target distance, outputting a movement instruction to the person (42).

7. The method according to any one of claims 1 to 3, characterized in that, The portable device controls the measuring device (10; 50).

8. A method for manufacturing spectacle lenses, the method comprising: measuring the visual acuity of a person according to the method of any one of claims 1 to 6, and manufacturing the spectacle lenses based on the result of the measurement.

9. A measuring device (10; 50) for measuring the visual acuity of a person (42), comprising: a distance determination component configured to determine the distance (d, d1, d2) between the measuring device (10; 50) and the person (42), and a measuring component (12) configured to measure the visual acuity of the person based on the distance, characterized in that the distance determination component includes a first wireless interface (13) configured to determine the distance by communicating with a second wireless communication interface (15) of a portable device (11; 43, 44) located at the person (42), The measurement component (12) is further configured to determine an orientation between the measurement device (10; 50) and the portable device (11; 43, 44) through communication between the first wireless communication interface (13) and the second wireless communication interface (15), wherein performing the vision measurement further includes performing the vision measurement based on the orientation.

10. The measuring device (10; 50) according to claim 9, characterized in that, The first wireless communication interface (13) and the second wireless communication interface (15) are ultra-wideband communication interfaces.

11. The measuring device (10; 50) according to any one of claims 9 to 10, wherein, The measurement component (12) is configured to repeatedly determine the distance.

12. A system comprising a measurement device (10; 50) and a portable device (11; 43; 44) according to any one of claims 9 to 11.

13. A computer program product comprising a computer program for a measurement device according to any one of claims 9 to 11, the computer program when executed on the measurement device causing the method according to any one of claims 1 to 8 to be performed.

14. A computer-readable storage medium having stored thereon a computer program for a measurement device according to any one of claims 9 to 11, the computer program when executed on the measurement device causing the method according to any one of claims 1 to 8 to be performed.

Images