Through focus retinal image capturing

1. A non-mydriatic fundus imaging apparatus, comprising:

an illumination unit including a near-infrared component and a visible component;

a camera including an adjustable lens;

a processing unit; and

system memory, the system memory including instructions that, when executed by the processing unit, cause the apparatus to:

cause the illumination unit to illuminate near-infrared light using the near-infrared component;

obtain frames during illumination of near-infrared light;

estimate a first focus position based on the frames;

adjust a focus of the adjustable lens to a plurality of different diopter settings, with at least one of the plurality of different diopter settings being greater than or lesser than a diopter of the first focus position;

cause the illumination unit to illuminate visible light using the visible component; and

capture a plurality of images of a fundus at each of the plurality of different diopter settings during illumination of visible light.

2. The non-mydriatic fundus imaging apparatus according to claim 1 , wherein the instructions further cause the apparatus to: determine an estimated optimal focus, the estimated optimal focus being different from the first focus position.

3. The non-mydriatic fundus imaging apparatus according to claim 2 , the estimated optimal focus being a frame having a sharpest contrast.

4. The non-mydriatic fundus imaging apparatus according to claim 2 , the plurality of different diopter settings including the estimated optimal focus.

5. The non-mydriatic fundus imaging apparatus according to claim 3 , the first focus position being −6 diopters relative to the estimated optimal focus.

6. The non-mydriatic fundus imaging apparatus according to claim 1 , the plurality of images being captured in a time no greater than 150 milliseconds.

7. The non-mydriatic fundus imaging apparatus according to claim 1 , the frames being captured during a scan of the fundus wherein the focus of the adjustable lens is adjusted from −21 diopters to +12 diopters.

8. The non-mydriatic fundus imaging apparatus according to claim 1 , each subsequent diopter setting of the plurality of different diopter settings differing by 3 diopters.

9. The non-mydriatic fundus imaging apparatus according to claim 8 , the plurality of different diopter settings including −6 diopters, −3 diopters, 0 diopters, +3 diopters, and 6 diopters relative to an optimal starting focus being a frame having a sharpest contrast.

10. The non-mydriatic fundus imaging apparatus according to claim 1 , further comprising a display unit coupled to the system memory and to the processing unit, the display unit configured to display a representative image of the fundus.

11. A method of capturing a non-mydriatic image of a fundus, comprising:

causing illumination using near-infrared light;

scanning the fundus during illumination of near-infrared light;

capturing frames during scanning;

analyzing each frame;

determining a first focus based on analyzing each frame;

adjusting a lens to the first focus;

causing illumination using visible light; and

capturing images at a plurality of focus ranges during illumination of visible light, with at least one of the plurality of focus ranges being greater than or lesser than a diopter of the first focus.

12. The method according to claim 11 , wherein scanning the fundus includes adjusting lens focus to a plurality of diopter settings.

13. The method according to claim 12 , further comprising determining an estimated optimal focus based on analyzing each frame.

14. The method according to claim 13 , wherein capturing images includes adjusting the lens to a different plurality of diopter settings and capturing an image at each diopter setting, and

wherein no more than five images are captured within the plurality of focus ranges.

15. The method according to claim 13 , further comprising:

determining a representative image of the fundus from the images; and

displaying the representative image of the fundus.

16. A non-mydriatic imaging system, comprising:

a housing;

an image capture device coupled to the housing, including an adjustable lens, and configured to capture images of an eye fundus of a subject;

an illumination unit including a visible component and a near-infrared component;

a processing unit; and

system memory, the system memory including instructions that, when executed by the processing unit, cause the system to create a control module programmed to:

cause the illumination unit to illuminate near-infrared light using the near-infrared component;

obtain frames during illumination of near-infrared light;

estimate a first focus position based on the frames;

starting at the first focus position, adjust a focus of the adjustable lens to a plurality of different diopter settings;

determine an estimated optimal focus, the estimated optimal focus being different from the first focus position;

cause the illumination unit to illuminate visible light using the visible component; and

capture a plurality of images of a fundus at each of the plurality of different diopter settings during illumination with visible light.

17. The non-mydriatic imaging system according to claim 16 , wherein the system memory includes further instructions that, when executed by the processing unit, cause the control module to:

instruct the image capture device to capture an image in a second image capture mode when a position of a pupil is substantially aligned with an optical axis of the image capture device,

wherein the position of the pupil is substantially aligned with the optical axis of the image capture device when an angle formed between the optical axis and a vector formed between the adjustable lens of the image capture device and the pupil is less than fifteen degrees; and

wherein the second image capture mode includes:

a visible light illumination of a visible light source in the illumination unit; and

a plurality of adjustments of a lens of the image capture device such that the image capture device captures an image at each of the plurality of adjustments in a depth of field focus range.

18. The non-mydriatic imaging system according to claim 17 , the estimated optimal focus being a frame having a sharpest contrast;

the first focus position being −6 diopters relative to the estimated optimal focus; and

the plurality of images being captured in a time no greater than 151 milliseconds.

19. The non-mydriatic imaging system according to claim 18 , wherein the illumination unit includes a visible light component configured to illuminate during capture of the plurality of images;

the frames being captured during a scan of the fundus wherein the focus of an adjustable lens is adjusted from −21 diopters to +12 diopters; and

each subsequent diopter setting of the plurality of different diopter settings differing by 3 diopters.