Wide-angle pupil relay for cellphone-based fundus camera
An optical imaging system includes a first lens system housed in a body of a mobile telecommunication device, the first lens system having a first optical axis, a first entrance pupil fixed in space in a reference plane associated with said body, and a first focal length; and an optical telescope providing a diffraction-limited imaging within a spectral range from at least 486 nm to at least 656 nm. The optical imaging system is configured to image, when the optical telescope is inserted between the first lens system and an entrance pupil of a visual system of an eye (EPE), the EPE onto the first entrance pupil and vice versa with a substantially unit magnification.
1. A portable handheld relay optical system for forming an image of a fundus of a subject eye to be examined, said relay optical system being configured as an attachment optical system to be disposed between a portable handheld imaging device and the subject eye, the relay optical system, comprising:
a first positive lens group G 1 and a second positive lens group G 2 , wherein:
the first positive lens group G 1 and the second positive lens group G 2 form an afocal system having an identical optical axis, and are configured to form a conjugate relationship between a pupil of the subject eye and a pupil of the imaging device when the relay optical system is inserted between the imaging device and the subject eye, and
the first positive lens group G 1 and the second positive lens group G 2 substantially form an afocal relay system, and the following condition is satisfied:
0.9 <f 2 /f 1>2.2,
in which f1 is a focal length of the first positive lens group G 1 , and f2 is a focal length of the second positive lens group G 2 .
2. The relay optical system of claim 1 , wherein:
when the relay optical system is disposed between the subject eye and the imaging device, the relay optical system is configured such that a focal position, at a side of the subject eye, of the first positive lens group G 1 is aligned with a pupil position of the subject eye, and such that a focal position, at a side of the imaging device, of the second positive lens group G 2 is aligned with a pupil position of the imaging device, and
an image of an eye fundus of the subject eye is formed between the first positive lens group G 1 and the second positive lens group G 2 and also formed in the imaging device.
3. The relay optical system of claim 2 , wherein,
when D is a principal plane interval of both of the lens groups, the following condition is substantially satisfied:
f 1 +f 2 =D.
4. The relay optical system of claim 3 , wherein:
the first positive lens group G 1 includes, in order from a side of the subject eye, a positive meniscus lens having a concave surface facing the side of the subject eye, and a positive lens; and
the second positive lens group G 2 includes, in order from the side of the subject eye, a positive lens and a meniscus lens having a convex surface facing the side of the subject eye.
5. The relay optical system of claim 4 , wherein the positive meniscus lens of the first positive lens group G 1 is formed as a composite positive meniscus lens composed of a positive meniscus lens element having a concave surface facing the side of the subject eye and a meniscus lens having a concave surface facing the side of the subject eye.
6. The relay optical system of claim 4 , wherein a meniscus lens element of the second positive lens group G 2 is formed as a composite meniscus lens composed of a biconvex lens and a biconcave lens.
7. The relay optical system of claim 1 , wherein the following conditions are satisfied:
30 mm< f 1<50 mm
30 mm< f 2<60 mm.
8. The relay optical system of claim 1 , wherein:
an angle of view of the second positive lens group G 2 of the relay optical system at a side of the imaging device includes an angle of view of the imaging device; and
an image of an eye fundus of the subject eye corresponding to an angle of view of the first positive lens group G 1 is transferred to the imaging device via the second positive lens group G 2 .
9. The relay optical system of claim 8 , wherein the imaging device comprises an image capture lens of a portable camera.