Relay optical system, and attachment

Abstract

To provide a handheld-type fundus imaging device at low cost.SOLUTION: A relay optical system is provided in an attachment attached to a portable camera and forms a fundus image of a subject eye by the portable camera. The relay optical system includes a positive first lens group G1 and a positive second lens group G2 which are aligned in an order from the other end toward the one end, the other end being opposite to the one end at which the attachment is attached to the portable camera. The positive first lens group G1 and the positive second lens group G2 has the same optical axis and forms an afocal system, and relays a pupil of the subject eye to a pupil position of the imaging lens of the portable camera.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] This invention is technically related to U.S. Provisional Patent Application No. 62 / 381,768, filed August 31, 2016, and U.S. Provisional Patent Application No. 62 / 539,733, filed August 1, 2017, the disclosures of which are incorporated herein by reference.

[0002] The present invention relates generally to ophthalmic diagnostic imaging devices, and more particularly to a portable, handheld, smartphone-based retinal camera configured to capture high-quality, wide-field fundus images. The use of a mobile phone platform creates a fully integrated system capable of acquiring, storing, and analyzing fundus images that can be transmitted directly from the phone via a wireless communication system for remote evaluation. [Background technology]

[0003] Fundus imaging is widely used in the diagnosis, monitoring, and management of many retinal diseases. One limitation found in current imaging systems is the bulky, stationary nature of the imaging equipment. Traditional fundus cameras are cumbersome tabletop devices that are not easily portable due to their fragility, large size, and heavy weight. In fact, such fundus cameras also force patients to sit upright, which can be difficult for sick and hospitalized patients. In addition to size constraints, fundus cameras require a power source to power the lighting, imaging screen, and data processing unit. Often, this power is provided by a central wall-mounted power plug, and continuous power is required for the fundus camera to function properly.

[0004] While digital fundus cameras have been considered (some of which are based on mobile devices, generally mobile devices such as iPhones® or similar devices), such cameras have substantial operational limitations caused by any of the following: (i) a lack of optical conjugation between the optics of the mobile device used and the visual system being imaged; (ii) an insufficient field of view (FOV) associated with imaging selected surfaces of the visual system, which results in the need for multiple computational "stitching" of the acquired images; (iii) significant residual aberrations that impair the resulting images; and (iv) combinations of the above. Summary of the Invention [Problem to be solved by the invention]

[0005] Therefore, there remains a need for a low-cost handheld device configured to serve as an alternative to high-cost medical devices, which allows for recording digital images of a surface(s) of the visual system during an ophthalmic examination of the visual system, while at the same time avoiding the operational drawbacks that characterize currently known imaging system solutions. [Means for solving the problem]

[0006] A first aspect of the present invention is a relay optical system that is arranged within an attachment that is attached to a portable camera and that forms an image of the fundus of the test eye using the portable camera. The relay optical system comprises a positive first lens group G1 and a positive second lens group G2 that are arranged in order from the end opposite to the end where the attachment is attached to the portable camera toward the end, and the positive first lens group G1 and the positive second lens group G2 have the same optical axis to form an afocal system that relays the pupil of the test eye to the pupil position of the image-taking lens of the portable camera.

[0007] The present invention will be more fully understood from the following detailed description of specific embodiments taken in conjunction with the drawings, which are not to scale. [Brief explanation of the drawings]

[0008] [Figure 1] This figure shows a mobile phone 20 equipped with an image capturing unit (camera sensor) 214 that captures an image of the fundus of the subject's eye through a window 214W and an optical system (image capturing lens system (camera lens)) not shown, and an attachment 22 that can be attached to the mobile phone 20. [Figure 2] 1 is a schematic diagram of a first embodiment optical train that complements the handheld device's exit pupil and relays the image of the cell phone camera pupil onto the eye pupil. [Figure 3] 3 includes spot diagrams characterizing the diffraction-limited quality of imaging using the first embodiment of FIG. 2 for various field heights. [Figure 4] 5 shows a second embodiment of an optical train 500 representing an afocal relay system constructed in accordance with the teachings of the present invention and shown in combination with the Navarro model of the human eye. [Figure 5] 5 shows spot diagrams for the second embodiment of FIG. 4 for various field heights. [Figure 6A] 10 is a diagram showing the relationship in size between the image capturing field of view of the fundus and the image sensor in the first embodiment. FIG. [Figure 6B] 10 is a diagram showing the relationship in size between the image capturing field of view of the fundus and the image sensor in the second embodiment. FIG. [Figure 7] FIG. 10 is a schematic view showing the configuration of an attachment 22 according to a third embodiment. [Figure 8] FIG. 10 is a schematic view showing the configuration of an attachment 22 according to a fourth embodiment. [Figure 9] FIG. 10 is a schematic view showing the configuration of an attachment 22 according to a fifth embodiment. [Figure 10] FIG. 2 is a diagram showing the electrical configuration of a mobile phone 20. [Figure 11]1 is a flowchart illustrating a method of using the attachment 22 and the mobile phone 20. In general, the sizes and relative scales of elements in the drawings may be different from their actual sizes in order to appropriately promote conciseness, clarity, and understanding of the drawings. For the same reason, not all elements present in one drawing are necessarily shown in another drawing. DETAILED DESCRIPTION OF THE INVENTION

[0009] Figure 1 shows a mobile phone 20 equipped with an image capturing unit (camera sensor) 214 that captures an image of the fundus of the subject's eye through a window 214W and an optical system (image capturing lens system (camera lens)) not shown, and an attachment 22 that can be attached to the mobile phone 20. In the description of the present invention, a mobile phone is the same as a device called a mobile communication device, a mobile phone (portable terminal), or a wireless communication system, and a fundus camera is the same as a device called a portable handheld smartphone-based retinal camera or an inexpensive handheld device.

[0010] A mobile phone camera lens is an imaging lens on a camera sensor, which of course is already provided by the mobile phone manufacturer.

[0011] The inventors take advantage of a very useful property of cell phone camera lenses: they are nearly diffraction limited, and the entrance pupil is at the front of the lens, inside the cell phone camera window.

[0012] If a mobile phone has both a wide-angle camera and a telephoto camera, they have the pupils in the same position, meaning that either mobile phone camera can be used by mechanically shifting the phone laterally. Simple zooming is possible without significant loss of pixel count between the 40-degree and 80-degree field-of-view fundus cameras.

[0013] Another useful feature of a cell phone camera lens is that the field of view is similar to that required for a fundus camera, so the pupil relay has a magnification close to 1x (1x) magnification, meaning that lateral chromatic aberration and distortion are small. The optical design is relatively simple.

[0014] Coarse focusing is the mechanical adjustment of the spacing between lens group G1 and second lens group G2 to accommodate different patient diopter settings. Fine focusing is the built-in autofocus system of the cell phone camera.

[0015] According to a disclosed embodiment of the present invention, a modular device and method of use are disclosed for a handheld ocular imaging device supplemented with an imaging optical detection system (camera) and a programmable processor in a mobile phone (or tablet or other smart device) operably coupled to optical and illumination elements configured to image one or more structures of the eye (e.g., the retina) in a non-clinical location. The modular device provides multiple functions (fluorescein imaging, fluorescence, brightfield, infrared (IR) imaging, near-infrared (NIR) imaging) and multi-region imaging of the eye (e.g., retina, cornea, exterior) with additional capabilities of image processing, storage, and wireless data transmission for remote storage and evaluation. Acquired ocular images can also be transmitted directly from the device to a patient's electronic medical record without an intermediate computer system.

[0016] The retinal field of view (FOV) is a technical specification for fundus imaging and is an important consideration in the development of fundus cameras. FOV represents the angle through the pupil of the eye at which the retina is imaged. Illuminating light from the device enters the retina, and reflected light from the retina is used to form an image on the device's sensor. A typical fundus camera has an FOV of approximately 40 to 45 degrees.

[0017] for example<peekvision.org / what-it-does> In the digital imaging system disclosed in (herein referred to as the Peek system), a cell phone camera is used to take a picture of a user's retina by placing it as close as possible to the user's eye. In this situation, the entrance pupil (EP) of the cell phone optics (which is typically located in the front lens element just inside its front window) is not optically conjugate with the EP or iris of the user's eye (i.e., the EP of the visual system being tested). (Devices similarly limited in construction and operation are<www.d-eyecare.com> (See, e.g., the "Peak System," disclosed in the same application note.) As a result—as will be readily understood by those skilled in the art—the image of the retina formed by the employed optical system inevitably contains many aberrations, which, under normal uncorrected / unaddressed circumstances, do not allow the user to properly assess the condition / state of the imaged retina as intended. In particular, the FOV associated with retinal imaging using a Peak system is therefore substantially limited by the ratio of the eye's pupil size to the dimensions of the foveal and macular regions around the optic nerve, resulting in poor image quality. While this solution provides useful, low-cost diagnostic information for some retinal pathologies, it would be advantageous to image a larger area of ​​the retina at a higher resolution so that other, more subtle retinal pathologies could be observed.

[0018] <bosch-eyecare.com / en / eyecare / products / fundus_imaging / fundus_imaging.html> The Bosch fundus camera described in is also limited to imaging within a + / - 40 degree FOV. Jedmed describes a similar system:<jedmed.com / products / portable-fundus-camera> The solution offered by Volk Optical is another example of a system that is operationally limited for imaging the retinal surface ( <veatchinstruments.com / Volk-Pictor-Plus-Portable-Reti nal-Camera>).

[0019] The operational problems associated with existing fundus cameras of the related art (having a low FOV, which results in the need for multiple computational "stitching" of optical data acquired from the retina, and having substantial residual aberrations, which result in a detrimental reduction in the overall quality of the resulting "stitched" image) are resolved by providing a compact, low-cost fundus camera with a wide 80-degree (full-angle) FOV configured as an achromatic afocal relay (telescope) operating at a magnification level approaching 1x, to achieve diffraction-limited resolution imaging of a 2mm diameter (non-mydriatic) eye pupil into a spatially fixed EP of a mobile device's optics.

[0020] An embodiment of the present invention utilizes the parameters of a typical built-in imaging optics for a mobile phone (or another mobile device) with a full-angle FOV of approximately 75-80 degrees, assumed to have no aberrations or vignetting (a reasonable assumption given the nominal diffraction-limited performance of such optics known in the art), and an EP size of approximately 2 mm in diameter (EP of the mobile device fixed in space) to provide an approximately 1x optical relay system for imaging the EP of the eye onto the EP of the mobile device.

[0021] Taking into account the dimensional match typically achieved between the EP of a non-mydriatic eye and the EP of a typical mobile device optical system, the afocal relay of the present invention is configured to provide imaging with a magnification of approximately 1x, thereby ensuring a full-angle FOV at the entrance of the eye of approximately 80 degrees. This is approximately twice the FOV of a typical fundus camera in the related art and approximately half the total horizontal field of view of the human eye. Thus, a single imaging exposure using the lens of the present invention covers a substantially larger area of ​​the retina than a typical fundus camera. Furthermore, if spatial stitching of several (e.g., four) image shots of the retina acquired using the lens system of the present invention is attempted, not only will the "stitched" image cover the entire retina, but the stitching will be achieved while maintaining approximately 50% overlap between the stitched individual fields of view. Those skilled in the art will readily understand that such spatial overlap of the constituent individual images is impossible to achieve using the systems described in the related art. Because existing systems have a much smaller field of view, less than 40 degrees, many more individual images (acquired with existing systems) must overlap or have a smaller overlap in order to cover the entire retina (approximately 160 degrees). However, it is recognized in the art that the greater the overlap between constituent images, the better the quality of the resulting stitched image will be, since there will be more features (primarily blood vessels in the case of retinal imaging) to use for alignment. An advantage of this embodiment is that each individual constituent image covers more of the retinal surface, and therefore there may be room to increase the area of ​​overlap between the constituent images when forming the resulting stitched image.

[0022] FIG. 2 shows a YZ cross section through the lens system implementation of the first embodiment—here configured as a rotationally symmetric refractive afocal relay (telescope). For convenience, as shown, light rays are traced from the cell phone camera EP on the right side of FIG. 2, through the optics in attachment 22, and to the Navarro model eye on the left side of FIG. 2. The lens element closest to the cell phone camera pupil is labeled element 1 in FIG. 2, the next lens element is element 2, and so on, with the retinal surface referred to as the image plane. This design includes two cemented doublets (320 near the eye EP and 310 near the cell phone camera lens EP), with a single positive biconvex lens 3 having the highest light-gathering power of the optical elements present in this embodiment. The cemented doublet lens 320 is composed of a meniscus lens element 6 that is concave toward the eye side, cemented with a meniscus lens element 6 that is concave toward the eye side. The first lens group G1 is composed of a cemented doublet lens 320. The second lens group G2 includes a doublet lens 310 and a positive meniscus lens element 4 that is concave toward the eye side. The cemented doublet lens 310 is composed of a biconvex positive lens element 2 and a biconcave negative lens element 1 cemented together. The second lens group G2 includes the cemented doublet lens 310 and a positive biconvex lens element 3.

[0023] Operation near 1x magnification is desirable and offers a distinct operational advantage over related art systems because such an optical configuration facilitates correction of lateral chromatic aberration and distortion, in stark contrast to related art systems. The optical design of Figure 2 is configured to compensate for the aberrations of the eye (Navarro model) (at a 2mm eye pupil diameter; healthy human eyes are nearly diffraction-limited) and to provide near diffraction-limited resolution throughout the entire 80-degree FOV. Evidence of this operational feature is shown in Figure 3, which shows ray aberrations (spot diagrams) in a plane locally tangent to a spherical retina at three identified wavelengths: 643.85nm, 546.1nm, and 479.99nm. As shown in Figure 3, and convincingly evidenced by the spot diagrams that fall within the Airy disk curve for each wavelength, aberrations are substantially corrected across the entire visible spectrum, but even less at the red end of the spectrum (where backscattered light from the retina is about five times stronger than in the blue, which is operationally preferred during retinal imaging). Such diffraction-limited performance across the entire visible spectrum critically and advantageously distinguishes the proposed invention from that in the related art. In fact, the proposed design of the optical system is such that, by balancing optical aberrations typical of the average eye with those of the ocular portion of an embodiment of the present invention, diffraction-limited imaging of the retina is achieved.

[0024] A few notes regarding the objective lenses utilized in embodiments of the inventive system: Tables 1, 2, and 3 provide data representing the optical sequence of lens elements for the first embodiment of FIG. 2, and Tables 4, 5, and 6 provide data representing the optical sequence of lens elements for the second embodiment of FIG. 4, which form a lens system constructed in accordance with the concepts of the present invention. Design prescriptions for the embodiments were generated using Code V and are described with reference to the corresponding drawings. In these tables, the optical elements, and in some cases the media separating some of the elements, are numbered in a "backward" fashion, starting with those closest to the object / target plane (shown in FIG. 4) and working toward the retinal surface of the eye. This approach to optical element numbering makes it easier to define the NA and parameters that characterize the system's behavior in image space—i.e., in eye space—during the optical design process, as will be appreciated by those skilled in the art. The lens element closest to the object is labeled as element 1 in both Table 4 and Figure 4, the next lens element is element 2, and so on, with the retinal surface referred to as the image plane. In particular, a combination with the Navarro model of the human eye was chosen, whose general optical and geometric characteristics must be included in the design of the relay system of the present invention for proper evaluation of the system.

[0025] A positive radius value for a given surface indicates that the center of curvature of that surface is to the left of that surface, and a negative radius value indicates that the center of curvature is to the right of that surface. Dimensions are shown in millimeters. Thickness is defined as the axial distance from a given surface to the next surface. The image diameters shown are paraxial values, not ray-trace values. Additionally, with regard to describing chromatic aberrations—if present—the decrease in the Strehl ratio between monochromatic and polychromatic designs represents the contrast loss from chromatic aberrations over the specified spectral band, and the change in best individual focus indicates residual field curvature.

[0026] For purposes of this disclosure and the appended claims, use of the terms "substantially," "approximately," "about," and similar terms with respect to descriptors of present values, elements, properties, or characteristics is intended to be indicative of the extent to which the present invention is applicable. It is intended to emphasize that the values, elements, properties, or characteristics described herein are, for practical purposes, to be considered as described by one of ordinary skill in the art, even if not necessarily exactly as stated. These terms, when applied to specified characteristics or characteristic descriptors, mean "largely," "mainly," "substantially," "generally," "essentially," "to a large or considerable extent," "almost the same, but not necessarily exactly the same," etc., to reasonably indicate approximation language and to describe the specified characteristics or descriptors so that their scope is understood by those of ordinary skill in the art. When used in reference to numerical values, these terms represent a range of plus or minus 20% from the specified value, more preferably plus or minus 10%, even more preferably plus or minus 5%, and most preferably plus or minus 2% from the specified value.

[0027] The use of these terms in describing selected features or concepts does not imply or provide any basis for uncertainty or for imposing numerical limitations on the specified features or descriptors. As will be understood by those skilled in the art, actual deviations of the exact values ​​or characteristics of such values, elements, or properties from those stated will fall within and may vary within numerical ranges defined by typical experimental measurement error when using measurement methods accepted in the art for such purposes. In some specific cases within the scope of the present invention, the terms "approximately" and "about," when used in reference to numerical values, represent a range of plus or minus 20% based on the specified value, more preferably plus or minus 10%, even more preferably plus or minus 5%, and most preferably plus or minus 2% based on the specified value. [Table 1] Note - A positive radius indicates that the center of curvature is to the right A negative radius indicates that the center of curvature is to the left - Dimensions are given in millimeters -Thickness is the axial distance to the next surface - The Navarro eye model is described in "Accommodation-dependent model of the human eye with aspherics," by Navarro R., Santamaria J., and Bescos J., J Opt Soc Am A, August 1985, 2(8), pp. 1273-81. [Table 2] [Table 3] Note: EFL is measured from side 1 -BFL is measured from the final face [Table 4] Note - A positive radius indicates that the center of curvature is to the right A negative radius indicates that the center of curvature is to the left - Dimensions are given in millimeters -Thickness is the axial distance to the next surface - The Navarro eye model is described in "Accommodation-dependent model of the human eye with aspherics," by Navarro R., Santamaria J., and Bescos J., J Opt Soc Am A, August 1985, 2(8), pp. 1273-81. [Table 5] [Table 6]

[0028] A second embodiment 500 of the inventive relay system, constructed as described above in Tables 4, 5, and 6, is shown in FIG. 4 and has an effective focal length of 30.67 mm (modulus value), resulting in the formation of an image with a (paraxial) height of approximately 10.6 mm and good correction for lateral chromatic aberration(s). This embodiment of the lens system according to the inventive concepts includes only one single aspheric surface A(1), which provides practical advantages (such as reduced cost). As shown in FIG. 4, the second embodiment includes a first lens group G1 and a second lens group G2. The first lens group G1 includes lens elements 4 and 5, and the second lens group G2 includes lens elements 1, 2, and 3. The Navarro model of the eye is also shown in combination with the relay system 500. The second lens group G2 includes a first meniscus lens element 1 having negative refractive power and in optical contact with a biconvex positive lens element 2, and an element 3 having positive optical power and an aspheric surface A(1) and spatially separated from the combination of elements 1 and 2. The second lens group G2 has an overall positive optical power and neutralizes the negative optical power of element 1. The first lens group G1 includes a positive lens element 4 and a second meniscus lens element 5 that is concave toward the eye and has an overall positive optical power. The first lens group G1 is positioned near the eye to be examined, which is shown by the Navarro model of the eye in FIG. 4.

[0029] FIG. 5 includes spot diagrams illustrating the effects of defocus as a function of field position (expressed in degrees) during imaging of an object using a second embodiment 500 of the present invention. The second embodiment is also shown to compensate for aberrations in the eye (Navarro model) (at a 2 mm eye pupil diameter; a healthy human eye is nearly diffraction-limited) and provide near-diffraction-limited resolution throughout the entire 80-degree FOV. As convincingly evidenced by the spot diagrams falling within the Airy disk curve for each wavelength, aberrations are substantially corrected across the entire visible spectrum, but even less at the red end of the spectrum (where backscattered light from the retina is approximately five times stronger than in the blue, which is operationally preferred during retinal imaging). Such diffraction-limited performance throughout the visible spectrum critically and advantageously distinguishes the proposed invention from related art. In fact, the proposed design of the optical system is such that diffraction-limited imaging of the retina is achieved by balancing optical aberrations typical of the average eye with those of the eyepiece portion of an embodiment of the present invention. In each of the first and second embodiments, the first lens group G The values ​​for the focal lengths of the first and second lens groups G1 and G2 are shown below. Embodiment 1 Focal length of group 1 (eyepiece): f1 = 32.3 Focal length of group 2 (objective lens): f2 = 34.4 Paraxial magnification: f2 / f1=1.07 Embodiment 2 Focal length of group 1 (eyepiece): f1 = 38.0 Focal length of group 2 (objective lens): f2 = 53.0 Paraxial magnification: f2 / f1=1.4 Regarding the relationship between the wide-angle retinal image size and the image sensor size, two cases can be considered. In Case 1, as shown in FIG. 6A, the magnification is selected so that the 80-degree field of view entering the eye is imaged onto the camera to fill the diagonal of the screen (i.e., the size of the image sensor). This has the advantage that all camera pixels are used, but the disadvantage is that some of the 80-degree field of view is lost at the top, bottom, and sides. In Case 2, as shown in FIG. 6B, the magnification is selected so that the 80-degree field of view entering the eye is imaged onto the camera screen (i.e., the size of the image sensor) to fill the short dimension of the rectangular screen. This has the advantage that the entire 80-degree field of view is seen, but the disadvantage is that not all camera pixels are used. This is the more common fundus camera situation, but these two cases demonstrate that the present invention can be applied to either situation by selecting a magnification close to 1.0 within the range of 1.0 to 2.0.

[0030] Certain implementations of the present invention may also be configured to utilize fundus imaging using a dual-lens (or generally multiple-lens) cell phone camera. For example, if a cell phone has a second camera lens with a different focal length (e.g., twice the focal length of the cell phone's first lens)—if the cell phone is shifted laterally or transversely relative to the afocal relay of the present invention so that the second lens is optically (axially) aligned with the afocal relay—a central angular portion of the retina (corresponding to the cell phone lens with a smaller FOV compared to the FOV of the cell phone's other lenses) can be imaged with higher resolution. This is advantageous for examining the foveal region and optic nerve in more detail, while still maintaining the ability to image the entire retina by switching to a shorter focal length camera. Alternatively, in this case, image stitching using a longer focal length lens may be used to cover a field of view of 80 degrees or more with higher resolution.

[0031] The scope of the present invention advantageously includes situations in which a mobile device has multiple lenses (optical systems) arranged adjacent to one another (e.g., as a 1D or 2D array of lenses) and with different focal lengths (and therefore different FOVs). Here, the embodiment of Fig. 1 may be integrated with the back of the mobile device via a mechanism or positioner (mechanically or otherwise, for example, driven using an electric motor) configured to laterally reposition the embodiment in a plane perpendicular to the optical axes of such lenses while maintaining a working (axial) distance between the embodiment and the plane in which the lenses are arranged. When the embodiment is translated so as to be coaxially arranged with the first lens of a mobile phone camera, an optical conjugate between the EP of the eye and the EP of the first lens is established, advantageously enabling 1x imaging of the retina using the telescope of the present invention and the first lens. In a next operational step, when the embodiment is translated so as to be coaxially positioned with a second lens of a cell phone camera, an optical conjugate between the EP of the eye and the EP of the second lens is established, enabling 1x imaging of the retina using the telescope and the second lens of the present invention. As a result of multiple repositioning steps (e.g., N>1), an N-position-zoom imaging system is actually implemented. During such configured imaging of the retina, when a cell phone lens with a smaller FOV is optically and mechanically cooperated with the afocal relay embodiment, It is understood that imaging of the retina with higher resolution is achieved (in the center of the stitched image).

[0032] Additionally, since the user is typically not wearing eyeglasses when the photograph is taken, a + / - 10 diopter adjustment can be provided by focusing the lens closest to the eye - the eyepiece - based on the user's prescription, and the camera's focusing system adjusts for fine focus.

[0033] The above-described embodiment enables a simple, compact, and inexpensive fundus camera. It is clear that superior fundus images can be obtained over a field of view approximately twice as wide and over a broad wavelength range as compared to conventional fundus cameras using attachment lenses. Furthermore, the use of a multi-lens mobile phone camera improves the freedom of view and resolution performance.

[0034] The disclosed aspects, or portions of those aspects, may be combined in ways not shown above, and therefore the present invention should not be considered limited to the disclosed embodiments.

[0035] Next, a third embodiment will be described with reference to FIG. 7, the attachment 22 is a relay optical system that relays the pupil of the subject's eye 150 to the pupil position of the optical system of the image capturing unit 214 of the mobile phone 20, and includes a first positive lens group G1 and a second positive lens group G2. The first positive lens group G1 and the second positive lens group G2 have the same optical axis and essentially form an afocal system. The first positive lens group G1 and the second positive lens group G2 relay the pupil of the subject's eye 150 to the pupil of the optical system of the image capturing unit 214 of the mobile phone 20.

[0036] The afocal relay of the present invention as an afocal attachment is in front of the cell phone camera lens, in this case serving to relay the cell phone camera pupil to the patient's iris (pupil).

[0037] When the positive first lens group G1 and the positive second lens group G2 are arranged between the subject's eye 150 and the optical system arranged in front of the image capturing unit 214 of the mobile phone 20 (the position shown in FIG. 7), the first lens group G1 is arranged so that the focal position of the first lens group G1 on the subject's eye side coincides with the pupil position of the subject's eye 150, and the focal position of the second lens group G2 on the mobile phone 20 side coincides with the pupil position of the image capturing optical system of the mobile phone 20. According to the above arrangement, a conjugate relationship is formed between the pupil of the subject's eye and the pupil of the external optical system by the combination of the positive first lens group G1 and the positive second lens group G2.

[0038] When the attachment 22 having the first lens group G1 and the second lens group G2 is positioned so that its optical axis coincides with the optical axis of the image capturing optical system of the mobile phone 20, as shown in Figure 7, an image FI of the fundus of the test eye 150 is formed between the first lens group G1 and the second lens group G2.

[0039] The first lens group G1 has, in order from the test eye side, a positive meniscus lens 320 with its concave surface facing the test eye side, and a positive lens 340, and the second lens group G2 has, in order from the test eye side, a positive lens 330 and a meniscus lens 310 with its convex surface facing the test eye side.

[0040] The positive meniscus lens 320 with its concave surface facing the test eye is not limited to the configuration shown in FIG. 7, but may have the configuration shown in FIG. 2, or may be a cemented lens made up of a positive meniscus lens 6 with its concave surface facing the test eye and a meniscus lens 5 with its concave surface facing the test eye.

[0041] The meniscus lens 310 in the second lens group G2, whose convex surface faces the test eye side, may be a cemented lens consisting of a biconvex positive lens 310A and a biconcave lens 310B, as shown in Fig. 7. The lens surface may be aspherical as appropriate, and in the second embodiment, an aspherical surface is provided on the convex surface facing the test eye of the biconvex positive lens in the second lens group G2.

[0042] When the focal length of the first lens group G1 is f1, the focal length of the second lens group G2 is f2, and the distance between the principal planes of both lens groups G1 and G2 is D, it is preferable to substantially satisfy the following condition. f1+f2=D

[0043] When the first lens group G1 and the positive second lens group G2 substantially form an afocal system as described above, it is preferable that the following condition be satisfied. 0.9 <f2 / f1<2.2 In addition, in practice, it is preferable to satisfy the condition 1.0≦f2 / f1<2.0.

[0044] The focal length f1 of the first lens group G1 and the focal length f2 of the second lens group G2 satisfy the following condition. 30mm <f1<50mm、 30mm <f2<60mm

[0045] The angle of view of the second lens group G2 on the optical system side of the mobile phone 20 includes, and preferably coincides with, the angle of view of the optical system of the mobile phone 20. An image of the imaging field of view (FOV) of the fundus of the subject's eye, which corresponds to the angle of view of the first lens group G1, is transferred to the optical system of the mobile phone 20 via the second lens group G2.

[0046] In all of the above examples, the 1x magnification of the relay optics (G1, G2) of attachment 22 is optimal for aberration correction. By introducing a smaller magnification, a larger field of view than that of a cell phone camera can be achieved, and the design can still achieve good aberration correction. The larger field of view is beneficial in that many retinal pathologies can be seen within 80°, and it is possible to switch to a cell phone telephoto lens camera to view more detail in the central 40° of the retina.

[0047] The attachment 22 also includes a power supply 380, a light source 362 powered by the power supply 380, and a beam splitter 372 that reflects light emitted from the light source 362 toward the second lens group G2 and transmits the reflected light from the subject's eye 150 via the second lens group G2 to the mobile phone 20.

[0048] In an image capturing mode, which will be described later, light emitted from the light source 362 is reflected by the beam splitter 372 toward the second lens group G2, and reaches the fundus of the eye 150 via the first lens group G1. The light that reaches the fundus of the eye 150 is reflected by the fundus, and the reflected light reaches the beam splitter 372 via the first lens group G1 and the second lens group G2, passes through the beam splitter 372, and reaches the mobile phone 20. The positive first lens group G1 and the positive second lens group G2 relay the pupil of the eye 150 to the pupil of the optical system of the image capturing unit 214 of the mobile phone 20.

[0049] Next, a fourth embodiment will be described. The fourth embodiment shown in Fig. 8 has some similar parts to the third embodiment, so the same reference numerals will be used to designate the similar parts, and their description will be omitted. Only the different parts will be described. As shown in Figure 8, the attachment 22 has a light source 362 and a power supply 380 for it, in addition to the first lens group G1 and the second lens group G2. Divergent light from the light source 362 is converted into parallel light by a condenser lens 364, enters a diffuser 366, and becomes divergent light, illuminating an annular diaphragm 368 having a ring-shaped opening. The light passing through this ring-shaped opening is converted into a beam. The light is reflected by the splitter 372, passes through the second lens group G2 and the first lens group G1, and is guided to the subject's eye 150. Then, an image of the ring-shaped opening of the ring diaphragm 368 is formed on the cornea of ​​the subject's eye by the action of the second lens group G2 and the first lens group G1, and illuminates the fundus of the subject's eye.

[0050] Next, a fifth embodiment will be described. The fifth embodiment shown in FIG. 9 has similar parts to the third embodiment, so the same reference numerals will be used to designate similar parts, and their description will be omitted. Only the differences will be described. As shown in FIG. 9, the attachment 22 has a contact 382 connected to the light source 362. The mobile phone 20 has a contact 20C connected to a battery (not shown) of the mobile phone 20. When the attachment 22 is attached to the mobile phone 20, the contact 382 of the attachment 22 and the contact 20C of the mobile phone 20 are connected. As described above, the contact 382 is connected to the light source 362, and the battery (not shown) of the mobile phone 20 is connected to the contact 20C of the mobile phone 20. Therefore, power from the battery (not shown) of the mobile phone 20 is supplied to the light source 362 via the contact 20C and the contact 382.

[0051] In the fourth embodiment (see FIG. 8), power supply 380 may be omitted, and contact 382 may be provided on attachment 22 and contact 20C may be provided on mobile phone 20. When attachment 22 is attached to mobile phone 20, contact 382 on attachment 22 and contact 20C on mobile phone 20 are connected, and power from a battery (not shown) of mobile phone 20 is supplied to light source 362 via contact 20C and contact 382.

[0052] In all the above examples, the beam splitter 372 is used, but in order to efficiently use the light from the light source 362, a polarizing beam splitter may be provided instead of the beam splitter 372, a polarizer may be placed between the light source 362 and the polarizing beam splitter, and an analyzer may be provided between the polarizing beam splitter and the mobile phone 20. It is also possible to insert a quarter wave plate between the second lens group G2 and the polarizing beam splitter to provide circularly polarized light to the subject's eye.

[0053] Next, the electrical configuration of the mobile phone 20 in all of the above examples will be described with reference to Fig. 10. As shown in Fig. 10, the mobile phone 20 includes a computer 200. The computer 200 includes a CPU 202, a ROM 204, a RAM 206, and an input / output (I / O) port 208. The CPU 202, the ROM 204, the RAM 206, and the input / output (I / O) port 208 are connected to one another via a bus 210. The input / output (I / O) port 208 is connected to an auxiliary storage device 212, an image capturing unit 214, a speaker 216, a display unit 218, a communication unit 220, a home button 222, an image capturing button 224, and an autofocus mechanism 226.

[0054] Next, with reference to FIG. 11, a method of using the attachment 22 and the mobile phone 20 will be described. In step 402, the user attaches the attachment 22 to the mobile phone 20. When the power switch of the mobile phone 20 is turned on, the fundus photography application starts in step 404. In step 406, the user holds his or her eye at the image capturing position of the image capturing unit 214.

[0055] In step 408, the home button 222 of the mobile phone 20 is turned on, and the CPU 202 starts the image capturing mode. When the image capturing mode starts, the image capturing unit 214 captures a fundus image via the attachment 22.

[0056] In step 410, the CPU 202 adjusts the autofocus mechanism 226 to automatically adjust the focus, and when the focus is automatically adjusted, it determines whether the fundus photographing range of the image photographing unit 214 is appropriate. Specifically, it determines whether the image photographing range of the fundus image is appropriate based on the pixel values ​​of the image data of the fundus image and whether the image is of the pupil or the surrounding area. The position of the pupil of the subject's eye 150 within the fundus photographing range of the image photographing unit 214 is detected based on a threshold value for distinguishing between the pupil position and the photographing range. By determining whether the detected pupil position is within the photographing range, it is determined whether the photographing range is appropriate.

[0057] If it is determined in step 410 that the fundus imaging range is not appropriate, then in step 412, CPU 202 issues an audio instruction via speaker 216 to change the holding position of mobile phone 20. For example, if the pupil position is located above the imaging range of image capturing unit 214, an audio message saying "Please lift your mobile phone" is output via speaker 216. Note that instead of or together with the audio output of "Please lift your mobile phone," the message "Please lift your mobile phone" may be displayed on display unit 218.

[0058] If it is determined that the position of the user's fundus is appropriately located within the imaging range of the image capturing unit 214, then in step 414 the CPU 202 displays an image capturing instruction on the display unit 218. The user, upon seeing the image capturing instruction displayed on the display unit 218, turns on the image capturing button 224. Note that the image capturing instruction is not limited to being displayed on the display unit 218, and the image capturing instruction may be output as audio via the speaker 216 instead of or in addition to the display. When the image capturing button 224 is turned on, then in step 416 the CPU 202 detects that the image capturing button 224 has been turned on. When it is detected that the image capturing button 224 has been turned on, then in step 418 the CPU 202 records the fundus image captured by the image capturing unit 214 in the auxiliary storage device 212, and in step 420 the CPU 202 transmits an image signal of the fundus image to the fundus image server 250 via the communication unit 220.

[0059] If the CPU 202 determines that the position of the user's fundus is appropriately located within the photographing range of the image photographing unit 214, the processing of steps 414 and 416 is omitted, and in step 418, the CPU 202 records the fundus image photographed by the image photographing unit 214 in the auxiliary storage device 212, and in step 420, transmits the image signal of the fundus image to the fundus image server 250 via the communication unit 220.

[0060] In all the examples described above, the mobile phone 20 is provided with one optical system (image capturing lens system (camera lens)), but the technology of the present disclosure is not limited to this, and the mobile phone 20 may be provided with multiple optical systems corresponding to multiple angles of view. For example, in order to handle cases where not only the central portion of the fundus but also the peripheral portion of the portion peripheral to the central portion is captured, the mobile phone 20 may be provided with a first optical system for a wide angle and a second optical system for a standard angle of view having a smaller angle of view than the wide angle. In a first mode in which the central and peripheral portions of the fundus are captured, images of the central and peripheral portions of the fundus are formed on the image capturing unit 214 via the first optical system. In a second mode in which only the central portion is captured, an image of only the central portion of the fundus is formed on the image capturing unit 214 via the second optical system.

[0061] 20. Mobile Phones 22 Attachment G1 First lens group G2 Second lens group 320 Meniscus Lens 320A Meniscus Lens 320B Meniscus Lens 340 positive lens 330 positive lens 310 Meniscus Lens 310A Biconvex positive lens 310B biconcave lens 320 Positive meniscus lens 320A Positive Meniscus Lens 320B Meniscus Lens

Claims

1. a relay optical system disposed in an attachment attached to a portable camera for forming an image of a fundus of an eye to be examined by the portable camera, the relay optical system includes a positive first lens group G1 and a positive second lens group G2, which are arranged in this order from an end opposite to an end where the attachment is attached to the portable camera toward the end, The positive first lens group G1 and the positive second lens group G2 have the same optical axis to form an afocal system, and relay the pupil of the test eye to the pupil position of the image capturing lens of the portable camera.

2. 2. The relay optical system according to claim 1, wherein an image of the fundus of the subject's eye is formed between the first positive lens group G1 and the second positive lens group G2.

3. 3. The relay optical system according to claim 1, wherein the first positive lens group G1 includes, in order from the test eye side, a positive meniscus lens having a concave surface facing the test eye side, and a positive lens, and the second positive lens group G2 includes, in order from the test eye side, a positive lens and a meniscus lens having a convex surface facing the test eye side.

4. 4. The relay optical system according to claim 3, wherein the positive meniscus lens of the positive first lens group G1 is formed as a positive compound meniscus lens composed of a positive meniscus lens element having a concave surface facing the test eye side, and a meniscus lens having a concave surface facing the test eye side.

5. 5. The relay optical system according to claim 4, wherein the meniscus lens of the second positive lens group G2 is formed as a compound meniscus lens of a biconvex positive lens and a biconcave lens.

6. The relay optical system according to any one of claims 1 to 5, wherein the following condition is substantially satisfied, where f1 is the focal length of the positive first lens group G1, f2 is the focal length of the positive second lens group G2, and D is the distance between the principal planes of both lens groups: f1 + f2 = D

7. 7. The relay optical system according to claim 1, wherein the first positive lens group G1 and the second positive lens group G2 substantially form an afocal relay system, and the following condition is satisfied: 0.9<f2 / f1<2.2

8. 8. The relay optical system according to claim 7, which satisfies the following conditions: 30mm < f1 < 50mm, 30mm < f2 < 60mm

9. a relay optical system according to any one of claims 1 to 8; A light source and a beam splitter that reflects light emitted from the light source toward the second lens group G2 and transmits reflected light from the subject's eye via the second lens group G2 to an image capturing lens of the portable camera; An attachment comprising:

10. Further, the portable camera further includes a power source, or a contact that is connected to a contact that is connected to a battery of the portable camera when the portable camera is attached to the portable camera; The light source is supplied with power from the power source or the contacts.

10. The attachment according to claim 9.

11. the light source emits divergent light; The attachment is a condenser lens that converts divergent light from the light source into parallel light; a diffuser that converts the parallel light into divergent light; a ring diaphragm having a ring-shaped opening that allows the divergent light from the diffuser to pass to the beam splitter; 11. The attachment of claim 9 or claim 10, further comprising:

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