Device for measuring eye length

Abstract

With particular regard to the problem of identifying a device that can measure ocular length simply and robustly without hardware modifications to the camera, an optical device for use in an instrument (13) for performing optical coherence tomography (OCT) is characterized in that it comprises a cylindrical optical channel (1) for guiding and refracting light, the optical channel (1) having a first diameter (1a) and a first length (1b), the first channel (1) being partially surrounded in an annular and concentric manner by a second optical channel (2) for guiding and refracting light, the second channel (2) having a larger diameter (2a) and a shorter length (2b) than the first channel (1).

Description

[Technical Field]

[0001] The invention relates to an optical device according to the preamble of claim 1 . [Background technology]

[0002] Optical Coherence Tomography (usually abbreviated as OCT) is an imaging method that allows obtaining two-dimensional and three-dimensional images of light-scattering structures. In this method, light of a given bandwidth is usually split into two partial beams by a beam splitter. The first partial beam strikes the sample or object to be examined, while the second partial beam travels through a reference optical path. The light reflected by the sample or object interferes with the reference beam. The signal resulting from this interference can be used to examine the sample with depth resolution, i.e., at the optical axis depth of the first partial beam, by so-called A-scans. OCT images can also be obtained by scanning the sample in the plane or transverse direction with the first partial beam. A B-scan is made up of several A-scans.

[0003] It is known how to measure or estimate the eye length by the above-mentioned OCT techniques.

[0004] Some of these methods require a relatively broad OCT spectrum, others require additional optical components, and many are time consuming or subject to errors caused by eye movements. Summary of the Invention [Problem to be solved by the invention]

[0005] Therefore, an object of the present invention is to provide a device that can measure eye length simply and robustly, especially without modifying the hardware of the camera. [Means for solving the problem]

[0006] The present invention achieves the above-mentioned object by means of the features of claim 1.

[0007] In accordance with the present invention, it has been discovered that by providing two optical channels with different diameters and lengths, two focal planes as well as two OCT reference planes with the same optical path length can be generated. Using these planes, ocular length measurements can be performed arbitrarily without the use of beam splitters, particularly conventional beam splitters, in the optical device or the instrument in which the device is installed. The described device does not require a broad OCT spectrum and can be used with many existing OCT instruments. Furthermore, no hardware modifications to the camera of existing OCT instruments are required, particularly for performing ocular length measurements with the device. Furthermore, both the optical device and the ocular length measurements performed with it are highly robust and accurate. The retina and cornea can be clearly imaged simultaneously during use of the optical device or during ocular length measurements performed with it.

[0008] The two optical channels may be formed by a plurality of lenses arranged in series, collinear and concentric with respect to their respective optical axes, with at least one lens having a larger diameter than the other lenses and contributing to the second channel as a portion of material protruding annularly from the other lenses, thereby forming an annular channel. The lenses are robust and can be easily connected to each other mechanically or materially, or optically connected in series. Furthermore, the optical properties of the lenses are well-defined by their refractive behavior and are substantially unaffected by system heating, cooling, or other factors. In such an optical device, the central ray of light passes through all lenses, while the outer ray of light passes only through the larger-diameter lenses.

[0009] A plurality of lenses having the same second diameter may be arranged as a cluster between at least two lenses having the same first diameter, the first diameter being smaller than the second diameter. By using multiple lenses as a cluster, the refractive behavior of the entire cluster can be tailored.

[0010] The optical device may have two focal planes: a first focal plane for light passing through the inner first channel and a second focal plane for light passing only through the annular second channel. The central or outer light beam is focused at the respective focal plane. The optical device may be designed so that the focal plane for the central beam is located on the cornea and the focal plane for the outer light beam is located on the retina.

[0011] The optical device may have two reference surfaces, each preferably with the same total optical path length: a first reference surface for light passing through the inner first channel, which forms the long optical path, and a second reference surface for light passing only through the annular second channel, which forms the short optical path. Ultimately, the optical path lengths to the two reference surfaces are identical, with only the partial optical path, i.e., the first length, being significantly longer for the central ray, depending on the refractive index of the glass. The significantly longer optical path length for the central ray results in different reference surfaces. The optical device can be designed so that the reference surface for the central ray is located on the cornea and the reference surface for the outer ray is located on the retina.

[0012] The division into two focal or reference regions is preferably achieved through concentric optics of different diameters, with the central rays of the scan field passing through all the optics and the peripheral rays not passing through all the optics.

[0013] The optical device can be configured as an objective or an exchangeable objective. The objective forms a prefabricated structural unit. The exchangeability of the objective allows the OCT device to be adapted. Such an objective can be used for measuring the ocular length. In particular, such an objective can be configured as a multifocal objective.

[0014] In a method of measuring the distance between two structures, in which an optical device of the type described herein is used, a first structure is recorded in a first focal plane and / or a first reference plane of the optical device, and a second structure is recorded in a second focal plane and / or a second reference plane of the optical device, in which case the distance between the structures may be measured from the recorded data and / or from image representations of the two structures.

[0015] The first structure may be the cornea or a region of the cornea of ​​the eye, and the second structure may be the retina or a region of the retina of the eye, thereby providing a method for measuring ocular length using OCT techniques.

[0016] An apparatus for performing optical coherence tomography (OCT) having an optical device of the type described herein may have electronics, particularly as hardware with corresponding software, that perform the method for measuring the distance between two structures described herein.

[0017] The electronic device controls the optical system of the instrument, in particular the interferometer, and records the distance between the structures using the optical device. The electronic device then measures the recorded distance between the structures automatically or in a user-defined manner using an algorithm. The electronic device may display the recorded structures in an image. The image can be used by a user to identify information useful for diagnosis. The image can be stored and / or processed in the memory of the electronic device. [Brief explanation of the drawings]

[0018] [Figure 1] 1 shows a schematic diagram of an optical setup using an optical device for measuring eye length by OCT technology. [Figure 2] 1 shows a cross-sectional image showing that the cornea is clearly imaged in the central region and the retina is clearly imaged in the peripheral region. DETAILED DESCRIPTION OF THE INVENTION

[0019] 1 depicts an optical device for use in an instrument 13 for performing optical coherence tomography. The optical device has or forms a cylindrical optical channel 1 for directing and refracting light, the optical channel 1 having a first diameter 1 a and a first length 1 b. The first channel 1 is partially surrounded in an annular and concentric manner by a second optical channel 2 for directing and refracting light, the second channel 2 having a larger diameter 2 a and a shorter length 2 b than the first channel 1.

[0020] The two channels 1 and 2 are formed by a plurality of lenses 3a-3d, which are arranged in series and collinearly and concentrically with respect to the respective optical axes 4a-4d. Specifically, a single optical axis is provided that coincides with the optical axes 4a-4d. At least one of the lenses 3b and 3c has a larger diameter than the other lenses 3a and 3d, and thus contributes to the second channel 2 as a material portion that protrudes annularly from the other lenses, thereby forming an annular channel.

[0021] Specifically, two lenses 3b, 3c having the same second diameter 2a are arranged as a cluster between two lenses 3a, 3d having the same first diameter 1a, where the first diameter 1a is smaller than the second diameter 2a.

[0022] The optical device has two focal planes 5, 6, i.e. a first focal plane 5 for light passing through the inner first channel 1 and a second focal plane 6 for light passing only through the annular second channel 2.

[0023] The optical device has two reference surfaces 7, 8: a first reference surface 7 for light passing through the inner first channel 1, which forms a long optical path for the light, and a second reference surface 8 for light passing only through the annular second channel 2, which forms a short optical path. The device is designed as an objective or an exchangeable objective.

[0024] Figure 1 also shows a method for measuring the distance 9 between two structures using the above arrangement, in which an optical device of the type described above is used, where a first structure is recorded in a first focal plane 5 and a first reference plane 7 of the optical device, and a second structure is recorded in a second focal plane 6 and a second reference plane 8 of the optical device, and the distance 9 between the structures is measured from the recorded data and / or from an image representation of the two structures.

[0025] In a specific, but non-limiting, exemplary embodiment, the first structure is the cornea 10 of the eye 11 or a region of the cornea 10 and the second structure is the retina 12 of the eye 11 or a region of the retina 12.

[0026] In this regard, FIG. 1 illustrates the optical structure of an objective lens, specifically an OCT objective lens for measuring ocular length in a human eye 11. The objective lens is composed of multiple lenses 3a-3d arranged concentrically in a row and each having different diameters. Therefore, as shown in FIG. 1, the central ray passes through all optical systems, while the outer rays pass only through the optical systems with larger diameters. This results in different focal planes 5 and 6 for the central and outer rays. Furthermore, because the optical path length of the central ray is significantly longer, different reference planes 7 and 8, each with the same total optical path length, are also generated. The objective lens is designed so that the focal plane 6 and reference plane 8 for the outer rays are located on the retina 12. The focal plane 5 and reference plane 7 for the central ray are located on the cornea 10.

[0027] FIG. 1 shows a schematic representation of an apparatus 13 for performing optical coherence tomography (OCT), comprising the optical device and electronics 14 for carrying out the method described above.

[0028] In OCT, light is typically split into two partial beams. The first partial beam strikes the sample to be examined, e.g., the cornea 10 or the retina 12, while the second partial beam travels through a reference optical path. Specifically, each first partial beam is directed to a respective focal plane 5, 6. Each second partial beam travels through a finite-length reference optical path. The position of the reference plane, at which the OCT image is displayed, is defined by the reference arm length. Since the "optical path lengths" of RE1 (reference plane 7) and RE2 (reference plane 8) are the same, two regions can be displayed simultaneously in the OCT image. Specifically, each reference plane 7, 8 coincides with the respective focal plane 5, 6. The light beam reflected by the sample interferes with the reference beam. Using the signal resulting from this interference, the sample can be examined with depth resolution, i.e., at the optical axial depth of the first partial beam, by a so-called A-scan.

[0029] FIG. 2 shows the result of applying the method described with reference to FIG. 1 to a human eye, where the first structure is the cornea 10 of the eye 11 or a region of the cornea 10, and the second structure is the retina 12 of the eye 11 or a region of the retina 12. FIG. 2 shows that an electronic device 14 displays the structures in an image 15. In FIG. 2, the image 15 is shown as a cross-sectional image. Radial linear scanning (OCT B-scan) of the optical axes 4a-4d of the objective lens or optical device produces the cross-sectional image shown in FIG. 2. The cornea 10 is clearly imaged in the central region, and the retina 12 is clearly imaged in the peripheral region. From the spacing 9 between the structures in the cross-sectional image, the distance between the cornea 10 and the retina 12 can be accurately calculated.

[0030] Accurate measurement of ocular length offers several advantages: for example, knowing the ocular length allows for more accurate scale calculations and allows for more accurate dimensional representation of ocular structures. [Explanation of symbols]

[0031] 1. Cylindrical optical channel 1a First diameter 1b First Length 2 Second Optical Channel 2a Short length 2b Large diameter 3a~d lenses 4a~d Optical axis 5 First Focal Plane 6 Second Focal Plane 7 First Reference Plane 8 Second Reference Plane 9 intervals 10 Cornea 11 eyes 12 Retina 13 OCT equipment 14 Electronic equipment 15 images

Claims

1. 1. An optical device for use in an apparatus (13) for performing optical coherence tomography (OCT), comprising: A cylindrical light channel (1) for guiding and refracting light, the light channel (1) having a first diameter (1a) and a first length (1b); the first channel (1) being partially surrounded in an annular and concentric manner by a second optical channel (2) for guiding and refracting light; The optical device is characterized in that the second channel (2) has a larger diameter (2a) and a shorter length (2b) than the first channel (1).

2. 2. The device according to claim 1, characterized in that the two channels (1, 2) are formed by a plurality of lenses (3a-3d) arranged in series, collinear and concentric with respect to their respective optical axes (4a-4d), and at least one lens (3b, 3c) has a larger diameter than the other lenses (3a, 3d) and therefore contributes to the second channel (2) as a material portion protruding annularly from the other lenses, thereby forming an annular channel.

3. 3. The device according to claim 2, characterized in that a plurality of lenses (3b, 3c) having the same second diameter (2a) are arranged as a cluster between at least two lenses (3a, 3d) having the same first diameter (1a), said first diameter (1a) being smaller than said second diameter (2a).

4. 4. The device according to claim 3, characterized by two focal planes (5, 6): a first focal plane (5) for light passing through the inner first channel (1) and a second focal plane (6) for light passing only through the annular second channel (2).

5. 4. The device according to claim 3, characterized by two reference surfaces (7, 8): a first reference surface (7) for light passing through the inner first channel (1) forming a long optical path for light, and a second reference surface (8) for light passing only through the annular second channel (2) forming a short optical path.

6. 4. The device according to claim 3, characterized in that it is configured as an objective or an exchangeable objective.

7. 4. A method for measuring a distance (9) between two structures, in which an optical device according to claim 3 is used, comprising the steps of: the first structure is recorded in a first focal plane (5) and / or a first reference plane (7) of the optical device, the second structure is recorded in a second focal plane (6) and / or a second reference plane (8) of the optical device, A method in which the spacing (9) between said structures is measured from the recorded data and / or from a pictorial representation of said two structures.

8. 8. The method of claim 7, wherein the first structure is a cornea (10) or a region of the cornea (10) of an eye (11), and the second structure is a retina (12) or a region of the retina (12) of the eye (11).

9. The optical device according to claim 3; an electronic device (14) for carrying out the method according to claim 7 or 8; An apparatus (13) for performing optical coherence tomography (OCT), comprising:

10. 10. The device according to claim 9, characterized by an electronic device (14) for displaying said structure in an image (15).

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