Aberration correction in ophthalmic imaging devices

Abstract

The present invention provides an ophthalmic imaging device that suppresses or eliminates any image artifacts related to back reflection of the scanning beam while maintaining the system complexity at an acceptable level. [Solution] The ophthalmic imaging device comprises a light source that emits a light beam, a polygon scanning mirror having a plurality of reflective facets, a drive device configured to rotate the polygon scanning mirror so that each facet reflects the light beam at a changing angle during operation, an optical system configured to guide the beam reflected by the polygon scanning mirror towards the fundus of the eye through the cornea of ​​the subject's eye and to guide the reflected light towards the polygon scanning mirror, an aberration correction element disposed between the polygon scanning mirror and the optical system and having an elongated portion with a changing thickness supported by a carrier, and a mask disposed on the carrier and configured to block light from the peripheral portion of the elongated portion of the aberration correction element.

Description

[Technical Field]

[0001] The present invention relates to aberration correction in ophthalmic imaging devices. More specifically, but not limited to, the present invention relates to an aberration correction element that guides a light beam reflected from and to a polygon scanning mirror, and to reducing the acquisition of undesirable beam components by a photodetector in an ophthalmic imaging device. [Background technology]

[0002] Ophthalmic imaging devices are widely used to image a patient's eye in order to assess the health of their eye. Such devices comprise a light source and a controller configured to control the light source to generate a light beam with a target optical power. The light beam is deflected by one or more scanning relay elements, and the imaging area is typically covered by multiple parallel scanning lines. The scanning relay elements typically consist of a polygon scanning mirror and one or more scanning galvanometer mirrors. The former, the polygon scanning mirror, has multiple reflective facets arranged along the outer circumference of a rotating body. A drive mechanism is capable of rotating the polygon scanning mirror body, causing each facet to sequentially reflect the incident light beam at a changing angle. Thus, while passing through one individual facet, the light beam is deflected over a changing angle. Once such a deflection cycle is complete, the next facet substantially repeats this process, and all other facets operate similarly.

[0003] The repeated deflection by the polygon scanning mirror provides multiple scanning lines, forming the basis for at least one scanning direction. Further scanning elements, such as the galvanometer mirror mentioned above, can deflect the beam in another direction, thereby shifting the scanning lines relative to each other on the target, ultimately covering a two-dimensional scanning area. In at least some imaging modalities, light from the scanning beam is backscattered from the target tissue. In ophthalmic imaging, the target tissue includes major parts of the human eye, such as the fundus and retina. Generally, the light thus returns along the incident path and is finally detected by a detector in the form of an optical sensor, converted into an intensity signal, and processed to form an image. The latter signal processing, in particular, is performed by computational resources that generate individual images from the corresponding set of line scans. [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] When the target tissue is the fundus of the eye, light from the scanning beam passes through the cornea of ​​the eye to reach the retina, which is the target of imaging. The light is reflected by the retina and guided towards the detector with the help of optical elements in the device. However, the light reflected by the retina first exits the eye through the patient's pupil. This pupil forms a larger exit aperture in some respects compared to the incident beam, which is typically a laser beam with a relatively small spot size. In addition, the cornea (e.g., the outer surface of the cornea) specularly reflects some of the scanning beam back towards the detector, which can cause artifacts in the image. Similarly, some of the scanning beam specularly reflecting back from the optical elements in the device can form other image artifacts. Ultimately, this results in the cross-sectional area of ​​the incident beam (to the detector) being larger than the cross-sectional area of ​​the exit scanning beam (from the light source). In particular, this incident beam may contain undesirable components as a result of reflections at interfaces other than the primary target of imaging. This can be especially problematic if optical elements with dimensions similar to the cross-section of the guiding light beam are included.

[0005] Therefore, improved structures and configurations for ophthalmic imaging devices are needed that take into account the effect of beam cross-sectional dimensions on the properties of the included optical elements. For this reason, it is particularly necessary to suppress or eliminate any image artifacts related to the back reflection of the scanning beam, as described above, while maintaining the system complexity at an acceptable level. [Means for solving the problem]

[0006] The subject matter of the independent claim solves the problem and achieves the objective. Further preferred embodiments are defined in the dependent claims.

[0007] According to one embodiment of the present invention, an ophthalmic imaging device is provided. The ophthalmic imaging device comprises a light source that emits a light beam; a polygon scanning mirror having a plurality of reflective facets; a drive device configured to rotate the polygon scanning mirror such that each facet reflects the light beam at a changing angle during operation; an optical system configured to guide the beam reflected by the polygon scanning mirror towards the fundus of the eye through the cornea of ​​the subject's eye and to guide the reflected light towards the polygon scanning mirror; an aberration correction element disposed between the polygon scanning mirror and the optical system and having an elongated portion with a changing thickness supported by a carrier; and a mask disposed on the carrier and configured to block light from the peripheral portion of the elongated portion of the aberration correction element.

[0008] The embodiments of the present invention are presented to provide a clearer understanding of the concept of the present invention and should not be considered as limiting the invention. Embodiments of the present invention will be described below with reference to the following drawings. [Brief explanation of the drawing]

[0009] [Figure 1] A schematic diagram of an ophthalmic imaging device according to a general embodiment of the present invention is shown. [Figure 2] A schematic diagram of an ophthalmic imaging device according to an embodiment of the present invention is shown. [Figure 3A] It is a schematic front view of an aberration correction element including an elongated portion having a changing thickness as part of an ophthalmic imaging device according to an embodiment of the present invention. [Figure 3B] It is a schematic side view of an aberration correction element including an elongated portion having a changing thickness as part of an ophthalmic imaging device according to an embodiment of the present invention. [Figure 4A] It is a schematic diagram of an aberration correction element combined with a carrier as part of an ophthalmic imaging device according to an embodiment of the present invention. [Figure 4B] [[ID=IO]]It is a schematic diagram of an aberration correction element combined with a carrier as part of an ophthalmic imaging device according to an embodiment of the present invention. [[ID=II]] [Figure 5] It is a schematic diagram of an aberration correction element combined with a mask as part of an ophthalmic imaging device according to an embodiment of the present invention. [Figure 6] It is a schematic diagram of the arrangement and position of an aberration correction element as part of an ophthalmic imaging device according to an embodiment of the present invention.

MODE FOR CARRYING OUT THE INVENTION

[0010] It should be understood that, unless otherwise specified, a part of the drawings is not necessarily to scale. In certain cases, details that are not necessarily required for understanding the present disclosure or that make it difficult to understand other details may be omitted. Of course, it should be understood that the present invention is not necessarily limited to the specific examples or embodiments described and illustrated in this specification.

[0011] Note: In the original text, there is a misspelling in line . It should be "It is a schematic diagram of an aberration correction element combined with a carrier as part of an ophthalmic imaging device according to an embodiment of the present invention." instead of "It is a schematic diagram of an aberration correction element combined with a carrier as part of an ophthalmic imaging device according to an embodiment of the present invention. " with an extra closing tag. The above translation has corrected this error. Also, in the translation, "IO" in line [ID=IO] should be "10" for better clarity.The inventors have noticed that when the cross-section of the light beam retroreflected from the imaging target expands, a part of the beam components may enter a part of the optical element, resulting in an undesirable stray light effect. For example, the problematic optical element may be an aberration correction element having an elongated portion with a varying thickness. In this way, this elongated portion may project from the carrier or form a recess within the carrier to form a sidewall. Therefore, a part of the expanded beam cross-section may enter such a sidewall, and the sidewall may act as an additional surface that reflects the incident beam components in an undesirable manner. Therefore, the inventors have devised a mask that blocks such parts of the beam from reaching the detector of the ophthalmic imaging device. This mask can at least partially suppress the image artifacts in the fundus image that may occur in the detection of the retroreflection of these beams. As a result, the quality of the image generated by the ophthalmic imaging device can be significantly improved.

[0012] Next, exemplary embodiments of the present specification will be described with reference to the accompanying drawings.

[0013] Figure 1 shows a schematic diagram of an ophthalmic imaging device 102 according to a general embodiment of the present invention. Specifically, it shows an ophthalmic imaging system 112 including an ophthalmic imaging device 102 that provides at least one imaging modality 121. For example, the ophthalmic imaging device 102 may take the form of a scanning laser ophthalmoscope (SLO) or an optical coherence tomography (OCT) imaging device. The imaging modality 121 can be understood as the operating mode in which each device is operated. Generally, the ophthalmic imaging device 102 can operate in multiple modes and can provide multiple corresponding imaging modalities. The ophthalmic imaging system 112 may include a computing resource 106 comprising a processing unit 108 and a memory unit 110, or it may be accessible to the computing resource (e.g., via a wired or wireless connection). The components of the ophthalmic imaging system 112, including the ophthalmic imaging device 102 and the computing resource 106, are housed in a common housing so that the system 112 can form an ophthalmic imaging device 102, such as an ophthalmoscope. Thus, the ophthalmic imaging device 102 has access to the computing resources 106, or the ophthalmic imaging device 102 itself has the computing resources 106. In some embodiments, the computing resources 106 are located outside the device 102 and may be housed in different enclosures. In some embodiments, any one component may be housed in a different enclosure from the other components.

[0014] The computing resource 106 controls the ophthalmic imaging device 102 to operate with the selected imaging modality 121. The computing resource also includes at least one processing unit 108, such as a central processing unit (CPU) and / or a graphics processing unit (GPU), and a memory unit 110 that stores instructions, when executed on at least one processing unit 108, causing the processing unit 108 to perform one or more methods and functions described herein. In embodiments of a local computing resource or a local physical component of a computer device, the resource may include a processor such as a CPU and / or GPU, system memory, and a system bus connecting the system memory to the CPU / GPU. The system memory may include random access memory ("RAM") and read-only memory ("ROM").

[0015] The basic input / output ("I / O") system includes basic routines that assist in the transfer of information between elements within the computer device, such as during startup, and is stored in ROM. The computing resource may further include a mass storage device capable of storing software instructions and data. The mass storage device can be connected to the CPU / GPU via a mass storage device controller connected to the system bus. The mass storage device and its associated computer-readable data storage medium can provide non-volatile, non-temporary storage to the computing resource 106. The computer-readable data storage medium as used herein refers to a mass storage device such as a hard disk or CD-ROM drive, but it will be understood by those skilled in the art that the computer-readable data storage medium may be any available non-temporary physical device or product from which the device can read data and / or instructions. The mass storage device is an example of a computer-readable storage device.

[0016] Computer-readable data storage media include volatile and non-volatile, removable and non-removable media implemented in any way or technique for storing information such as computer-readable software instructions, data structures, program modules, or other data. Exemplary types of computer-readable data storage media include, but are not limited to, RAM, ROM, EPROM, EEPROM, flash memory, or other solid-state memory technologies, CD-ROM, digital versatile disks ("DVD"), other optical storage media, magnetic cassettes, magnetic tapes, magnetic disk storage devices, or other magnetic storage devices, or any other media that can be used to store desired information and are accessible by a computer device.

[0017] The computing resource 106 can operate in a network environment using a logical connection to a remote network device via a network such as a local network, the Internet, or other types of networks. The computing resource 106 can connect to a network via a network interface unit connected to a system bus. The network interface unit can also connect to other types of networks and remote computing systems. The computing resource 106 may include an input / output controller for receiving and processing input from multiple other devices, including a touch user interface display screen and other types of input devices. Similarly, the input / output controller may provide output to a touch user interface display screen, a printer, or other types of output devices. As described above, the mass storage and RAM can store software instructions and data. The software instructions may include an operating system suitable for controlling the operation of the computing resource 106. The mass storage and / or RAM may further store software instructions that, when executed by the CPU / GPU, cause the computing resource 106 to provide the functions described herein, including the methods described and illustrated herein.

[0018] In some embodiments, the imaging modality 121 may be provided as an operating mode of the SLO described above, which allows the use of confocal laser scanning microscopy for diagnostic imaging of the retina of the eye. The imaging may be two-dimensional (2D) imaging, in which the retina is scanned in a raster pattern using a laser beam, and sequential elements of the retina can be illuminated point by point. The light reflected from each point on the retina is captured by a photomultiplier tube. The output of the photomultiplier tube can be recorded and displayed in digital format. In this way, the imaging modality of the SLO can produce high-contrast, detailed images of the retina. In some embodiments, the images are acquired sequentially by one imaging modality and at least one further imaging modality.

[0019] Figure 2 shows a schematic diagram of an ophthalmic imaging device 102 according to an embodiment of the apparatus of the present invention. As shown, the ophthalmic imaging device 102 includes a light source 200 configured to emit a light beam 201 as a scanning beam. A polygon scanning mirror 202 functions as a first scanning element (or, in other words, a first scanning relay element) comprising a plurality of reflective facets 2021, 2022, ... In some embodiments, the beam 201 may have a cross-sectional area corresponding to a portion of the area of ​​the reflective facets (e.g., less than 0.1% or less than 1% of the area of ​​each reflective facet).

[0020] As will be described later, the polygon scanning mirror 202 reflects the beam 201 toward the optical system 220, and the light L returning from eye E is reflected. RThe beam is configured to reflect toward the detector 205. As shown in the figure, when the beam 201 is incident on the polygon scanning mirror 202, it may propagate with a component opposite to the positive y-direction. In this embodiment, the polygon scanning mirror is a convex polygon having 12 rectangular facets, each facet having a length defined by the lengths of two edges parallel to the plane of rotation of the polygon scanning mirror 202 and a width (i.e., width in the x-direction) defined by the lengths of two edges perpendicular to the plane of rotation. However, other numbers of facets (e.g., 16, or at least 4 or 5), other facet shapes, or other polygon shapes may be used instead.

[0021] The drive unit 203 is configured to rotate the polygon scanning mirror 202 during operation (in the plane of rotation of the polygon scanning mirror 202, i.e., the yz plane), and to reflect the light beam 201 at an angle α in which each facet 2021, 2022, ... changes (if the facet rotates over a predetermined angular position range). The drive unit 203 may be, for example, an electric motor connected to the polygon scanning mirror 202 and controlled by a controller of the ophthalmic imaging device 102 (which may be a computing resource 106). As shown in the figure, the optical path of the scanning beam 201 is shown in a one-dimensional (1D) scan generated during an exemplary counterclockwise rotation of the polygon scanning mirror 202 (indicated by a curved arrow). Optical path "A" is an example of the scanning beam 201 reflected from facet 2021 of the polygon scanning mirror 202 at the starting point of the rotation, i.e., when facet 2021 has moved and entered the optical path of the beam 201 from the light source 200. Optical path "B" is an example of the scanning beam 201 reflected from facet 2021 of the polygon scanning mirror 202 at a point in time after the rotation has progressed further and its facet 2021 has moved out of the optical path of the beam 201 from the light source 200.

[0022] Thus, the polygon scanning mirror 202 reflects the beam 201 at an angle α that changes from the effective facet (i.e., the facet currently reflecting the beam 201) (or over the changing angle α) as the beam 201 moves from one edge defining the facet length to the other. When facet 2021 moves out of the reach of the beam 201, the adjacent facet 2022 (i.e., the facet adjacent to / tangential to facet 2021, in the opposite direction to the rotation of the polygon scanning mirror 202) substantially repeats the reflection process described above. As a result, each facet sequentially reflects the beam 201 at the changing angle α. This changing angle α changes as defined by the length and rotation of each facet, since the orientation of each facet relative to the incident beam 201 determines the reflection angle. The ophthalmic imaging device 102 further includes an optical system 220 configured to guide a light beam 201 reflected from a polygon scanning mirror 202 (i.e., a beam 201 reflected at a changing angle α) through the cornea C of the eye E toward the fundus F of the subject's eye E. Examples of components and optical elements within the optical system 220 will be described later with reference to Figure 4.

[0023] The optical system 220 further receives the reflected light L from the fundus F. R It is configured to guide the light towards the polygon scanning mirror 202. R This could be, for example, light scattered by the eye E in a color (red-green) or color (red-green-blue) imaging modality, or reflected light L. R This may be, for example, light emitted from the eye E in an AF imaging modality, or may include such light. (Reflected light L) R It follows the same optical path as beam 201, and therefore, as will be described later, the reflected light L R The reflected light L can be guided by the optical system 220 along an optical path corresponding to the reflection of the beam 201 at a changing angle α toward the polygon scanning mirror 202. R Thus, the light is guided by the optical system 220 towards the effective facet, and this effective facet is then reflected by the light L RBy reflecting it along the optical path of the beam 201 towards the detector 205, an image 210 of the eye E is formed. As already described, the return light beam L R usually has a larger cross-section than the (incident) light beam 201 as a result of being reflected mainly from the imaging target (e.g., the retina) and then exiting through a relatively large exit aperture (the pupil).

[0024] When the current effective facet moves outside the reach of the beam 201, an adjacent facet becomes the effective facet, and the return light L R substantially repeats the above-described reflection process, and each facet sequentially reflects the return light L R along the optical path of the beam 201 towards the detector 205. As a result, for example, by using an orthogonal scanning element described later, continuous scanning lines in the image 210 can be formed. In some embodiments, the return light L R from the eye E may be a light beam having a diameter larger than that of the beam 201 and larger than the larger of the width and length of each facet. However, it will be understood by those skilled in the art that this depends, for example, on the components and optical elements of the optical system 220, the characteristics of the beam 201, and the imaging modality 121.

[0025] The ophthalmic imaging device 102 further includes an aberration correction element 230 positioned between the polygon scanning mirror 202 and the optical system 220. This aberration correction element 230 is generally provided to at least partially compensate for aberrations caused by light passing through the patient's pupil. For example, the aberration correction element 230 can take the form of a phase mask that is substantially conjugate to the patient's pupil. Since the cross-section (spot size) of the return beam on the aberration correction element 230 is usually larger than the cross-section of the incident scanning beam, it is possible to distinguish between cases where only the incident beam is compensated and cases where both the incident beam and the return beam are compensated. Assuming that the cross-section of the return beam is approximately equal to the dimensions of the patient's pupil, a phase mask having an elongated portion that alters the aberration can substantially compensate only the incident beam. This is because virtually all of the incident beam, which has a relatively small cross-section, passes through the relatively narrow slot of such an elongated section, while most of the reflected light, which has a relatively large cross-section, passes through the outer portion of the effective elongated section of the phase mask (see also exemplary sections 2001 and 2002, which are illustrated and described in conjunction with Figure 3A).

[0026] At this stage of the optical path, it should be noted that the direction of the light beam changes over time as the polygon scanning mirror periodically scans the light beam emitted from the light source. Furthermore, the reflected light beam incident on the polygon scanning mirror also propagates along substantially the same optical path as the incident beam, so the reflected light beam also changes direction. However, this change is only compensated for by the polygon scanning mirror so that the reflected light beam is directed towards the detector in substantially a constant direction. As a result, the light beam can be incident on the optical elements of the optical system at a changing position and / or angle, thereby causing the aberration of the light beam to change according to its direction of propagation. Therefore, as described above, the aberration correction element 230 includes an elongated portion 231 that covers the trajectory of the intersection with the light beam as the direction and / or angle of propagation of the light beam changes. Such an elongated portion 231 may have a varying thickness, and the change in thickness changes the optical depth, which in turn changes the phase shift and compensates for the aberration. A more detailed embodiment of such an aberration correction element is disclosed in relation to Figures 4A and 4B.

[0027] The ophthalmic imaging system further includes a mask 233 positioned on the carrier 232 and configured to block light in the peripheral area of ​​the elongated portion 231 of the aberration correction element 230. Note that in the side view of Figure 2, the mask 233 is shown with a dashed line, so as not to block the light that is expected to be guided toward and returning from the imaging target (eye). The returned light, which has a substantially large beam cross-section, may enter part of the aberration correction element 230, which can cause further reflection and deviation from the target optical path within the optical system. Since such stray light can eventually reach the detector 205 and form image artifacts in the image 210, the ophthalmic imaging system includes a mask (or light shield) configured to block part of the light beam that is adversely affected by the peripheral area or part of the elongated portion of the aberration correction element.

[0028] Figures 3A and 3B are schematic front and side views, respectively, of an aberration correction element having a slender section with varying thickness, as part of an ophthalmic imaging device according to one embodiment of the present invention. Specifically, the aberration correction element 230 is shown in the front view and is positioned in a plane that is substantially perpendicular to the light beam in at least one dimension. That is, the light beam 201(A) is substantially perpendicular to the surface of the element 230 at 90°, as shown in Figure 3A, while it may propagate at a varying angle β relative to the surface of the element 230 due to scanning at a varying angle α, as shown in Figure 3B. The varying angle α is given by the rotation of a polygon scanning mirror, each of which facets reflects the light beam incident from the light source and the object to be imaged at a varying angle.

[0029] The aberration correction element 230 includes an elongated portion 231 within the carrier 232, which covers a similarly elongated region that the light beam covers when it intersects the plane of the aberration correction element 230. That is, the elongated region 231 corresponds to the target trajectory of the point where the light beam intersects the plane of the aberration correction element 230. For example, the first end 231-1 of the elongated portion 231 is positioned so that the light beam at one end of the scanning motion is still guided through the elongated portion 231. This may correspond to the light beam 201(B) described in relation to Figure 2. The second end 231-2 of the elongated portion 231 is positioned so that the light beam at the other end of the scanning motion is still guided through the elongated portion 231. This may correspond to the light beam 201(A) described in relation to Figure 2.

[0030] As already explained, the light beam 201 initially propagates toward the subject's eye (E) as emitted beams 201(A) and 201(B), is reflected by the eye (E) as the imaging target, and then the reflected light beam L R (A), L R This leads to returning as (B). However, the cross-section of the outgoing beam and the cross-section of the incident beam may differ. Typically, the outgoing light beam 201(A / B) has a relatively small first cross-section 2001 in the plane of the aberration correction element 230, while the incident light beam L R(A / B) may have a relatively large second cross-section 2002 in the plane of the aberration correction element 230. The first cross-section 2001 fits well within the elongated region 231, but the second cross-section 2002 may include a portion that overlaps with the elongated region 231 and overlapping beam components. As a result, as will be explained in detail in relation to Figures 4A and 4B, light may be incident on a portion of the aberration correction element 230, which may cause further undesirable reflections and deviations from the target propagation path. This may result in the detection of undesirable beam components by the detector, ultimately leading to image artifacts and distortions.

[0031] To avoid such inclusion and substantially suppress the generation of stray light related to the effects described above, a mask is provided on the carrier 232. This mask may be placed in the peripheral portion 233 of the elongated portion 231 of the aberration correction element 230. In the schematic diagram shown in Figure 3A, reference numeral 233 can refer to both the peripheral portion and the mask, because the mask is located in the peripheral portion. The peripheral portion 233 of the elongated portion 231 may comprise at least regions 233-1 and 233-2 adjacent to the longitudinal side of the elongated portion 231. These regions may overlap with the longitudinal side of the elongated portion 231, or they may extend only on the carrier 232, separate from the elongated portion 231. In other words, at least the side of the aberration correction element 230 along its major axis (i.e., the length direction, or the y direction) can be considered a region where a mask is placed to shield light. However, the peripheral region may include an area covering the sidewall along the longitudinal side of the elongated portion 231, preferably an area covering the sidewall of the elongated portion 231 that protrudes from and / or forms a recess within the carrier 232. In other words, if the longitudinal side of the elongated portion also includes a sidewall by protruding from or forming a recess within the carrier, the edges and / or sidewalls related to the elongated portion can be suitable regions and areas for which a mask that blocks reflected light is provided. These regions 233-1 and 233-2 are generally located in the central region along the longitudinal direction of the elongated portion, thereby accommodating any coating, blocking element, or other form of mask. Thus, the important central region is covered, and its central arrangement may facilitate the formation, placement, and / or fixing of the mask to the carrier.

[0032] The mask may comprise one or more blocking elements or shadowing and / or opaque coatings positioned on the relevant regions, portions, and surfaces of the carrier 232. The latter coatings, such as anti-reflective coatings, may be applied particularly to the aforementioned edges and / or sides relating to portions that protrude from or form recesses in the carrier. Thus, light incident on the periphery of the elongated portion 231, for example, a portion of the large optical cross-section 2002, is effectively absorbed to prevent the occurrence of undesirable reflections, thereby preventing the generation of stray light that could eventually reach the detector and cause image artifacts and distortions. However, the mask 233 preferably extends only to the peripheral region of the elongated portion, so as not to block the remainder of the reflected light having a relatively large cross-section (i.e., light is allowed to return through region 2022).

[0033] Figures 4A and 4B are schematic diagrams of an aberration correction element combined with a carrier as part of an ophthalmic imaging device according to an embodiment of the present invention. Specifically, the aberration correction element 230 is shown in an exemplary form of a static aberration correction element comprising a substantially rectangular transmissive phase mask 2310 that covers a corresponding elongated portion 231. The elongated portion 231 is shown having a major axis along its length direction (y direction) and a minor axis along its width direction (x direction). The shape of the transmissive phase mask 231 is generally such that its thickness varies, and the phase mask is supported by or within the carrier 232. The thickness, i.e., depth S, of the mask 2310 varies spatially along the major and minor axes and can be defined by at least one predetermined mathematical function, the mathematical function including:

[0034] JPEG2026108548000002.jpg2080

[0035] Here, N is the number of polynomial coefficients in the series, and a i The i-th term is p i These are the coefficients. This polynomial is a power series in terms of x and y. The first term is x, the next is y, and the next is x.* x, x * y, y * y, etc. In one example, N=20, and the coefficients (which are dimensionless because they are divided by the normalization radius R=100mm) are as follows: a1=0, a2=1.515, a3=9.981, a4=0, a5=15.486, a6=0, a7=-2342.830, a8=0, a9=-635.766, a 10 =1026163.828, a 11 =0, a 12 =-30279.492, a 13 =0, a 14 =-5695.243, a 15 =0, a 16 =23929093.583, a 17 =0, a 18 =-145044.106, a 19 =0, a 20 = -14564.76025249. This changing thickness is schematically shown as a plot in Figure 4B and represents the changing thickness relative to a reference thickness shown as plane P. This plane P may not coincide with the carrier surface. That is, the elongated portion can be sufficiently etched into the carrier so that even the thickest part remains within the carrier thickness, and no portion of the elongated portion extends beyond the surface of carrier 232.

[0036] In this embodiment, the depth (thickness) of the transmissive phase mask 2310 varies along the long axis, i.e., the length direction, and the maximum sag (depth from peak to valley) of the mask is approximately 110 μm. The transmissive phase mask 2310 has a width of approximately 1.5 mm and a length of approximately 12 mm. The transmissive phase mask 2310 may comprise optical glass having spectral transmittance from the visible to near-infrared region of the electromagnetic spectrum. Generally, the phase mask can be formed from a transparent material, preferably optical glass. Thus, the transmissive phase mask 2310 can be formed within the carrier 232 in the form of a glass substrate. The transmissive phase mask 2310 and the elongated portion having a generally varying thickness can not only be supported by the carrier 232 but can also be integrally formed within the carrier 232. The latter configuration substantially facilitates the efficient and reproducible manufacturing of the aberration correction element 230, and the elongated portion with varying thickness can be formed by etching within the substrate of the carrier 232.

[0037] The transmissive phase mask 2310 has a depth that varies along the long and short axes of the mask. Therefore, it provides a spatially varying depth along the long and short axes of the mask and corresponding spatially varying optical properties (including refraction). As the incident light beam is scanned through the transmissive phase mask, the mask modulates the phase of the light beam by refraction. The phase properties of the mask, resulting from the mask's depth, are imparted to the phase of the light beam. As the mask's depth varies along the long and short axes, the phase modulation of the incident light beam changes along two mutually orthogonal axes of the light beam. This change in phase modulation during the scanning of the incident light beam can be advantageous in addressing at least some of the fluctuating aberrations that the scanning of the light beam experiences as it passes through the rest of the optical system and the ophthalmic imaging device.

[0038] As an example, the scanning compensation element of the optical system may be configured, for example, in the form of a curved slit mirror, which can produce aberrations that vary along their respective major and minor axes. As will be explained in more detail in relation to Figure 5, by defining the varying depth of the transmissive phase mask and arranging the major axis of the mask substantially parallel to the major axis of such a scanning compensation element, the mask can provide correction for these varying aberrations. Thus, the shape of this transmissive phase mask 2310 modulates the scanning phase of the light beam, and as a result, after propagating through the ophthalmic imaging device, a substantially collimated and aberration-free light beam is introduced into the eye (E) at an apparent point source at the pupil position of the eye, and is focused by the eye into sharp spots (about 20 μm or less) at almost all scanning points in the field of view and on the imaging surface. Thus, aberrations that cause blurring and attenuation can be reduced or avoided, and as a result, desired spatial information can be retained in substantially all parts of the image.

[0039] In this embodiment, the mask is provided in the form of a coating on the relevant surface. Specifically, a coating 233-1 and / or a coating 233-2 may be provided on the carrier 232 around the periphery of the elongated portion 231. These regions represent two opposing faces of the carrier 232, with coating 233-1 provided to block and absorb light incident from one side (the side facing upward in the figure), and coating 233-2 provided to block and absorb light incident from the other side (the side facing backward in the figure). Furthermore, a coating 233-3 may be provided on either of the side walls relating to the elongated portion 231 to similarly avoid or at least reduce light reflection. Preferably, the mask in the form of a coating and / or a shielding element extends only in the longitudinal direction of the elongated portion, i.e., in the y direction as shown in Figure 4A.

[0040] Figure 5 is a schematic diagram of an aberration correction element combined with a mask as part of an ophthalmic imaging device according to one embodiment of the present invention. In this embodiment, an aberration correction element 230 similar to or identical to the element 230 described in relation to Figures 4A and 4B is shown. However, the mask in this embodiment consists of one or more shielding elements 2330 arranged around the elongated portion, more specifically near or adjacent to the sides of the elongated portion 231 (note that only a portion of the elements 2330 are shown in order to allow other relevant elements in the figure to be seen). The shielding elements 2330 may be provided in the form of rods or plates and are preferably made of a light-absorbing material. However, the shielding elements 2330 may have an opaque, anti-reflective and / or light-absorbing coating. It should be noted that the blocking element 2330 (and generally the peripheral portion of the elongated portion as well) does not need to extend along the entire length of the elongated portion, as shown by ends 2330-1 and 2330-2, and the mask may extend only along a length shorter than the elongated portion in the longitudinal direction. This allows for effective blocking of undesirable light components, while allowing a larger portion of the light returning from the eye E to the detector to pass through carriers that may be transparent in all areas other than the peripheral portion covered by the mask or individual mask elements. In one embodiment, blocking elements 2330-1 and 2330-2 may take the form of covering the side wall 2313 of the elongated portion 231, the corner / edge 2311 toward the main surface of the carrier 232, and the corner / edge 2311 toward the bottom surface of the elongated portion 231. The bottom surface can be formed by the elongated portion 231 being recessed in a trough-like manner within the carrier 232, as can be seen from the inset showing the cross-sections of the elongated portion 231 and the blocking elements 2330-1 and 2330-2 in surface (A). In a sense, the blocking elements 2330-1 and 2330-2 can have a cross-section that includes two L-shaped portions, which can be effectively combined to form a shape similar to an S-shape or Z-shape. This makes it possible to manufacture and mold the blocking elements separately as simple components using efficient techniques such as die casting or extrusion molding. They can then be attached to the phase mask and the relevant parts of its elongated portion.

[0041] Figure 6 is a schematic diagram of the arrangement and position of an aberration correction element as part of an ophthalmic imaging device according to one embodiment of the present invention. In each embodiment, the aberration correction element 230 is positioned between the polygon scanning mirror and the optical system of the ophthalmic imaging device. Therefore, in this particular embodiment as well, the position of the aberration correction element 230 in the ophthalmic imaging device, for example in the form of a transmissive phase mask, is between the polygon scanning mirror 202 and the optical system 220. As shown, the polygon scanning mirror 202 is housed in a mirror housing 208, which not only protects the mirror from dust but also from other stray light that could cause undesirable image artifacts if it reaches the detector. The mirror housing 208 may be provided with an opening 2080 in which the aberration correction element 230 is positioned, and this opening 2080 may be the sole optical access to the mirror facets 2021, ... Preferably, a mask 233 further restricts this access to an elongated portion 231 as an active optical element for aberration correction.

[0042] The optical system 220 may include one or more scanning compensation elements, for example, in the form of a curved slit mirror 204. Such scanning compensation elements can provide an extended range that takes into account the changing direction of propagation of the incident light beam. In the illustrated embodiment, the polygon scanning mirror 202 deflects the light beam 201 in a first plane indicated by line D1. The scanning compensation element 204 is located in a second plane indicated by line D2. Preferably, lines D1 and D2 are located in the same plane. Preferably, the major axis D3 of the aberration correction element 230 is also located in the same plane. For example, the major axis D3 coincides with the major axis in the y-direction described in relation to Figures 4A and 4B.

[0043] While this specification includes details of many specific embodiments, these should not be considered as limiting the scope of any invention or claimed invention, but rather as descriptions of features specific to the particular embodiments described herein. Certain features described herein in the context of separate embodiments can also be combined and implemented in a single embodiment. Conversely, various features described in the context of a single embodiment can also be implemented separately in multiple embodiments, or in any appropriate partial combination (subcombination). Furthermore, even if features are described above as acting in a particular combination and are initially claimed as such, it may be possible to remove one or more features from the claimed combination, and the claimed combination may be directed towards a partial combination or a variation of a partial combination.

Claims

1. An ophthalmic imaging device (102, 120), A light source (200) that emits a light beam (201), A polygon scanning mirror (202) having multiple reflective facets (2021, 2022, ...), A drive device (203) is configured to rotate the polygon scanning mirror (202) during operation so that each facet reflects the light beam at a changing angle (α), The light beam (201) reflected by the polygon scanning mirror (202) is guided through the cornea (C) of the subject's eye (E) towards the fundus (F) of the eye (E), and the reflected light (L Ｒ An optical system (220) configured to guide the ) toward the polygon scanning mirror (202), An aberration correction element (230) is positioned between the polygon scanning mirror (202) and the optical system (220) and has an elongated portion (231) with a varying thickness that is supported by a carrier (232), A mask (233-1, 233-2, ...) is placed on the carrier and configured to block light from the peripheral portion of the elongated portion (231) of the aberration correction element (230), An ophthalmic imaging device (102, 120) equipped with the following.

2. The peripheral portion of the elongated portion (231) comprises a region adjacent to the longitudinal side of the elongated portion (231) and / or a region covering the side wall along the longitudinal side of the elongated portion (231), preferably a region covering the side wall of the elongated portion (231) that protrudes from the carrier (232) and / or forms a recess within the carrier (232), according to claim 1 (102, 120).

3. The ophthalmic imaging device (102, 120) according to claim 1 or claim 2, wherein the elongated portion (231) having a varying thickness is integrally formed with the carrier (232).

4. The ophthalmic imaging device (102, 120) according to any one of claims 1 to 3, wherein the elongated portion (231) having a changing thickness is equipped with a transmission-type phase mask.

5. The mask extends only along the longitudinal direction of the elongated portion, as described in any one of claims 1 to 4 (102, 120).

6. The ophthalmic imaging apparatus (102, 120) according to claim 5, wherein the mask extends over a length shorter than the elongated portion in the longitudinal direction.

7. The ophthalmic imaging apparatus (102, 120) according to any one of claims 1 to 6, wherein the mask comprises a coating on a portion of the carrier (232), preferably on the edges and / or side walls related to the elongated portion.

8. The ophthalmic imaging device (102) according to any one of claims 1 to 7, wherein the mask is provided with a coating on the side wall of the elongated portion (231) having a varying thickness.

9. The mask comprises one or more blocking elements, as described in the ophthalmic imaging apparatus (102, 120) according to any one of claims 1 to 8.

10. The ophthalmic imaging apparatus (102, 120) according to claim 9, wherein the blocking element comprises a portion that covers the side wall (2313) of the elongated portion (231), the main surface edge (2313) of the carrier (232), and the bottom surface edge (2312) of the elongated portion (231).

11. The ophthalmic imaging device (102, 120) according to claim 10, wherein the blocking element has a cross-section that includes two L-shaped portions.

12. The blocking element is arranged in the central region in the longitudinal direction of the elongated portion, as described in any one of claims 9 to 11 (102, 120).

13. The ophthalmic imaging apparatus (102, 120) according to any one of claims 1 to 12, wherein the polygon scanning mirror (202) is housed in a housing (208) having an opening (2080), and the opening (2080) is covered by the aberration correction element (230).

14. The reflected light (L) from the polygon scanning mirror (202) Ｒ ) detects the detection signal (S ｄ A detector (205) configured to generate ), The detection signal (S ｄ An access unit (207) to a computing resource (106) configured to generate an image (210) of the fundus (F) of the eye (E) using ), Furthermore, The image (210) of the fundus (F) of the eye (E) is obtained by the reflected light (L) reflected by all facets (2021, 2022, ...) during the rotation of the polygon scanning mirror (202). Ｒ The detection signal (S) generated from ) ｄ An ophthalmic imaging device (102, 120) according to any one of claims 1 to 13, which is generated using ).

15. The ophthalmic imaging device (102, 120) is a scanning laser ophthalmoscope, according to any one of claims 1 to 14.

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