Refraction Measurement of the Human Eye with a Reverse Wavefront Sensor

Abstract

A wavefront sensor measures the phase distribution of a beam of light perpendicular to its axis of propagation. The Shack-Hartmann (S-H) wavefront sensor is based on segmentation of the incident light beam into small, spatially distributed, parts. Each of these parts is then incident on a lens, and the deviation of the focal spot from the lens optical axis is measured in two dimensions, usually by a camera or detector array. An array of lenses is used to characterize the wavefront of the entire beam.

Claims

1. An optical device, comprising: a. a lenslet array, the lenslet array having a baffle disposed between each lens; and b. a de-magnifier comprising a first lens disposed in a first position (f1) and a second lens disposed in a second position (f2) with the distance between the first lens and second lens known as (d).

2. The system of claim 1 wherein a magnification between a display image H and an output image of the optical device h is M=h/H, with M being the magnification of the de-magnifier.

3. The system of claim 2 wherein the magnification of the de-magnifier is used to enhance the resolution of the output image.

4. The system of claim 1 wherein each lens of the lenslet array may accept a segment of a view, wherein each segmented view is presented by a display screen.

5. The system of claim 4 wherein a center lens of the lenslet array accepts a static reference image from the display screen and wherein a different lens of the lenslet array accepts a test image from the display screen and wherein alignment of the test image to the static image produces two dimensions of measured movement.

6. The system of claim 5 wherein the two dimensions of measured movement are fitted to Zernike polynomials to derive defocus and astigmatism values of a measured system.

7. The system of claim 6 wherein a plurality of two dimensional values are obtained by using a plurality of test images aligned to the static image and the plurality of two dimensional values are fitted to Zernike polynomials to derive defocus and astigmatism values of the measured system.

8. The system of claim 1 compressing two optical devices used a binocular device.

9. The system of claim 8 used to generate values of accommodation of a measured system.

10. The system of claim 8 used to present a three dimensional/stereoscopic image to a measured system to measure or induce accommodation.

11. The system of claim 1 wherein the optical device is used with a camera to facilitate retinal imaging.

12. The system of claim 2 using a display screen of a smartphone to produce the display image.

13. The system of claim 2 using an integrated display screen to produce the display image.

14. The system of claim 1 using a see through display to measure accommodation of a measured system.

15. The system of claim 1 using filters in place of baffles, the filters used to prevent cross talk between display segments.

16. A method for measuring optical distortion of a measured system, the method comprising the steps of: a) using an optical device to present a static image and a test image to the measured system; b) the measured system moving the test image to the static image with the movement data fitted to Zernike polynomials to derive defocus and astigmatism values of the measured system.

17. The method of claim 16 further comprising the step of a) the optical device accepting segmented views from a display and the optical device using a lenslet array, the lenslet array comprising a plurality of lenses with the lenslet array having a baffle disposed between each lens; b) using a de-magnifier to enhance resolution of the images received by the measured system.

18. The method of claim 17 further comprising the step of using filters in place of baffles, the filters used to prevent cross-talk between the segmented views.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by the Office upon request and payment of the necessary fee.

[0030] FIG. 1 describes a first set of tasks in obtaining eye care in the prior art

[0031] FIG. 2 describes a second set of tasks in obtaining eye care in the prior art

[0032] FIG. 3 depicts entity management in the prior art

[0033] FIG. 4 depicts a disclosed system of optical measurement

[0034] FIG. 5 depicts a disclosed system of optical measurement

[0035] FIG. 6 depicts images used in a disclosed system

[0036] FIG. 7 depicts a disclosed demagnification system

[0037] FIG. 8 depicts the use of a central image to create a 3D implementation for accommodation

REFERENCE NUMBERS

[0038] 100 a disclosed system in general

[0039] 110 pixelated detector

[0040] 120 lenslet array

[0041] 130 plane wave

[0042] 140 aberrated wave front

[0043] 150 screen

[0044] 155 baffles

[0045] 160 33 lenslet array

[0046] 170 de-magnifier

[0047] 200 prior art methods of eye care

[0048] 300 prior art entity management for eye care

[0049] 400 images sometimes used for optical measurements

[0050] 500 central image system to create a 3D implementation for accommodation

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

[0051] The following detailed description is directed to certain specific embodiments of the invention. However, the invention can be embodied in a multitude of different ways as defined and covered by the claims and their equivalents. In this description, reference is made to the drawings wherein like parts are designated with like numerals throughout.

[0052] Unless otherwise noted in this specification or in the claims, all of the terms used in the specification and the claims will have the meanings normally ascribed to these terms by workers in the art.

[0053] Unless the context clearly requires otherwise, throughout the description and the claims, the words comprise, comprising and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in a sense of including, but not limited to. Words using the singular or plural number also include the plural or singular number, respectively. Additionally, the words herein, above, below, and words of similar import, when used in this application, shall refer to this application as a whole and not to any particular portions of this application.

[0054] The above detailed description of embodiments of the invention is not intended to be exhaustive or to limit the invention to the precise form disclosed above. While specific embodiments of, and examples for, the invention are described above for illustrative purposes, various equivalent modifications are possible within the scope of the invention, as those skilled in the relevant art will recognize. For example, while steps are presented in a given order, alternative embodiments may perform routines having steps in a different order. The teachings of the invention provided herein can be applied to other systems, not only the systems described herein. The various embodiments described herein can be combined to provide further embodiments. These and other changes can be made to the invention in light of the detailed description.

[0055] Any and all the above references and U.S. patents and applications are incorporated herein by reference. Aspects of the invention can be modified, if necessary, to employ the systems, functions and concepts of the various patents and applications described above to provide yet further embodiments of the invention.

[0056] Referring to FIG. 1 and FIG. 2 a prior art system of eye care management 200 is described.

[0057] Referring to FIG. 3 a prior art system of entity management 300 for eye care is described.

[0058] Referring to 4 a disclosed system is depicted and may comprise a pixelated detector 110, a lenslet array, a lenslet optical axis 125, a plane wave 130 and an aberrated wave front 140.

[0059] Referring to FIG. 5, a disclosed embodiment may include a screen 150, baffles 155, a 33 lenslet array 160 and a de-magnifier 170.

[0060] FIG. 6 depicts images 600 sometimes used for optical measurements.

[0061] The central segment of the display 600 presents an image of a red cross. In the subsequent steps of the measurement, this central image is static. The first step of the measurement includes a presentation of a green cross at one of the adjacent segments. The measured system detector is used to align the two crosses in two dimensions so that they overlap. The location of the green cross is recorded. The process is repeated for other segments of the display. Each step is independent from the other steps; thus, the green cross image is displayed on only one segment at a time. The collection of recorded locations is then used in the analysis to determine the Zernike profile of the measured system and could be used to determine the required correction of such system. Correction in this respect means providing a uniform wavefront.

[0062] FIG. 7 depicts a de-magnifier 170. In one disclosed de-magnifier, the following equations should be met:

f_1+f_2=d

Magnification=h/H=f_2/f_1

[0063] The de-magnifier is comprised of a positive and a negative lens, the de-magnifier is comprised of two positive lenses, the de-magnifier is built to cover the entire pupil of the measured system, the de-magnifier is built to cover a portion of the pupil of the measured system. The de-magnifier is built to combine the beams from the individual lenslets. The de-magnifier is built to create a collimated beam space. The de-magnifier is used to improve the resolution of the device.

[0064] The image presented can be of a cross, a star, an Asterix, or any other image. The central image can be overlaid on a background image. The color of the image could be any color. The image could have motion included in it (the measurement reference must be stationary). The central image could be overlaid on the actual environment using the see-through screen (as in augmented reality devices). The central image can be static while the other images are controlled for the alignment, alternatively, in another embodiment of the invention the other image would be static, and the central image would be controlled for the alignment.

[0065] The measured system could be the human eye. The measured system could be an optical system with an array sensor (e.g. CCD or CMOS camera).

[0066] The cross alignment could be done simultaneously for the image as a whole, alternatively, in another embodiment of the invention, the two lines comprising the cross could be moved independently.

[0067] The collection of recorded locations could be used to fit the data to the Zernike polynomials or any other representation that could yield useful information about the measured system (e.g. Fourier series/transform).

[0068] FIG. 8 depicts a central image system to create a 3D implementation for accommodation

[0069] Benefits of the Invention

[0070] Ease of Use

[0071] The optical design of the device allows for a relatively large FoV (no slits or other restricting components).

[0072] Industrial design will allow for ease of control and intuitive interaction (graphical and voice commands, UI and controls).

[0073] Speed

[0074] This measurement is relatively simple. Furthermore, the use of 2 dimensional marks allows the user to essentially perform two measurements at once, thus reducing the total number of required measurements. The user mental focus and ability to align in two dimensions is expected to be similar to that of one-dimensional alignment.

[0075] The device has no moving parts thus negating the need for wait or distraction between steps in the measurement.

[0076] Robustness

[0077] The proposed design alleviates, to some extent, the sensitivity of alignment of the measurement system with the measured system. Many of the degrees of freedom are captured in the measurement and thus are self-referenced. An example to that would be misalignment of the measured system laterally in a direction perpendicular to the optical axis of the system. This type of misalignment will be represented in a tip/tilt terms in the Zernike polynomials which are independent of the defocus and astigmatism terms for example.

[0078] Higher Order Aberration Measurement

[0079] As the measurement is based on the S-H wavefront sensor physical principles, the same rules apply as for the relation between the number of lenslets to the order of Zernike polynomials the could be represented by the measured data. Therefore, the more, lenslets and steps of measurement used, the higher the order of aberrations that can be represented.

[0080] Accommodation

[0081] Due to the static nature of the central image, in some embodiment, as well as the large FoV, it could be used as a reference image, and could be used for display as described above. Furthermore, the device could be replicated to create a binocular device. In which case, the correlation between vergence and accommodation could be used to create stereoscopic images that trigger depth perception and enable the user to direct and maintain accommodation of their eyes and vision to infinity. Thus, enabling control of the accommodation error present in the measurement. An implementation of this concept could be seen in FIG. 8.

[0082] The central segment image presented to each eye is shifted to allow for placing the measurement mark at a very far distance. Moreover, a real image, e.g. landscape, mountains, fields, could be used to further enhance the user depth perception. In an alternative embodiment, the marks are overlaid on the real environment using a see-through screen. At this case, the user would be requested to look at a far object. This has the advantage of real life, familiar, accommodation target which might improve the depth perception and thus the accommodation. The other image marks are only presented to the measured eye to enable monocular measurement for accounting for the different in refraction between the eyes.

[0083] Alternative Constructions

[0084] The device can be built such that the display could be replaced by a camera to allow for retinal imaging.

[0085] The baffles in the device, are used to prevent cross-talk between segments of the display. This can also be achieved by use of filters (each lens has a different filter) and different colors on the display (each mark/cross has a different color corresponding to the lens in front of it).