Multi-mode ophthalmic imaging device capable of operating in multiple imaging modes

Abstract

(There is a need for an improved output control mechanism in an ophthalmic imaging device that allows flexibility while maintaining safety, while keeping system complexity at an acceptable level.). ) SOLUTION: Wherein the ophthalmic imaging device comprises a plurality of light sources that provide light beams, a controller configured to control the light sources that generate the light beams to provide a plurality of imaging modes in which respective contributions of the light sources to a light output projected toward the subject's eye vary in each of the imaging modes, an optical path comprising one or more scanning elements and one or more directing elements configured to project the light beams onto the subject's eye (E), and a shutter mechanism configured to block the light beams from reaching the subject's eye (E); The controller is configured to operate the shutter mechanism to block the light beam when switching between the first imaging mode and the second imaging mode.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a multi-mode ophthalmic imaging device operable in multiple imaging modes in which the contribution of the corresponding light source to the light beam is varied. More particularly, but not exclusively, the present invention relates to switching between a first imaging mode and a second imaging mode in which the contribution of the light source to the light beam directed toward the eye of a subject is varied. [Background technology]

[0002] Ophthalmic imaging devices are widely used to image patients' eyes to assess ocular health. Such systems include one or more light sources and a controller configured to control the light sources and device to generate a light beam that scans the target tissue. The optical path of such devices includes one or more scanning elements configured to project the light beam onto the subject's eye and one or more steering elements. For example, one or more polygonal scanning mirrors and one or more galvanometer scanning mirrors perform the beam scanning. Furthermore, a beam splitter is typically provided to split the light beam into two, with one partial beam propagating toward the subject's eye and the other partial beam directed toward a detector. The measured optical power is then converted into some signal indicative of the optical power incident on the detector. Assuming a well-defined, constant splitting ratio of the beam splitter, the optical power actually directed toward the eye can be controlled by controlling the light source output based on a signal indicative of the optical power of the partial beam incident on the detector.

[0003] In ophthalmic imaging, where the subject's eye is the object of imaging, proper power control can be an important aspect. On the one hand, the optical power incident on the eye must not exceed a predetermined power budget at any time, otherwise the tissue may be damaged by the light. However, on the other hand, the optical power must be sufficiently high to obtain sufficient imaging quality. It is noteworthy that if the optical power of the incident beam is too weak, the signal-to-noise ratio will be unduly low. Therefore, typical ophthalmic imaging devices are equipped with a control mechanism that maintains the optical power within an acceptable power band, i.e., below a maximum threshold to prevent damage to the subject's eye and above a minimum threshold to provide the desired imaging quality. Such a control mechanism typically shuts off the light source or prevents light from reaching the subject's eye by other means whenever the optical beam power falls outside the acceptable band.

[0004] Furthermore, modern ophthalmic imaging devices can operate in multiple imaging modes, allowing clinicians to select the imaging mode most suitable for imaging a particular region or disease of a patient's eye. Each imaging mode enables the ophthalmic imaging system to acquire different types of ophthalmic images, helping clinicians obtain images containing the most relevant information for diagnosing ocular diseases. For example, a color imaging mode can be used to acquire fundus images of a patient's eye, including a portion of the retina. In this imaging mode, a combination of red, green, and blue laser light is delivered to the patient's eye to acquire a fundus image. Infrared (IR) retinal imaging and autofluorescence (AF) imaging are examples of other imaging modes that can be used to image a patient's eye. IR imaging delivers light from an infrared laser to the patient's eye and can be used to detect retinal pathologies such as intraretinal fluid and retinal pigment epithelial tears. AF imaging typically uses a monochromatic light beam from a single laser to excite fluorescent materials for imaging. Because the incident light and the fluorescent response have different wavelengths, it is possible to distinguish the response from the actual tissue from the illumination light. Summary of the Invention [Problem to be solved by the invention]

[0005] Although power control is essential under changing imaging conditions or modes, existing power control mechanisms often cannot accommodate both sufficient and reliable control of light beam power and the desired flexibility. Therefore, there is a need for an improved power control mechanism in an ophthalmic imaging device that allows flexibility while maintaining safety, while keeping system complexity at an acceptable level. [Means for solving the problem]

[0006] The problem is solved and the object is achieved by the subject matter of the independent claims. Further preferred embodiments are defined in the dependent claims.

[0007] According to one embodiment of the present invention, there is provided an ophthalmic imaging device comprising: a plurality of light sources providing light beams; a controller configured to control the light sources generating the light beams to provide a plurality of imaging modes, the controller varying the light sources' corresponding contributions to a light output projected toward an eye of a subject in each of the imaging modes; an optical path comprising one or more scanning elements and one or more steering elements configured to project the light beams toward the eye of the subject; and a shutter mechanism configured to block the light beams from reaching the eye of the subject, wherein the controller is configured to operate the shutter mechanism to block the light beams when switching between a first imaging mode and a second imaging mode.

[0008] According to a method embodiment of the present invention, there is provided a method of operating an ophthalmic imaging device comprising a plurality of light sources providing light beams, an optical path comprising one or more scanning elements and one or more steering elements configured to project the light beams toward a subject's eye, and a shutter mechanism configured to block the light beams from reaching the subject's eye, the method comprising: controlling the light sources to generate the light beams and providing a plurality of imaging modes, wherein a corresponding contribution to the light output projected from the light sources toward the subject's eye varies for each imaging mode; and operating the shutter mechanism to block the light beams when switching between a first imaging mode and a second imaging mode.

[0009] BRIEF DESCRIPTION OF THE DRAWINGS An embodiment of the present invention, which is presented for a clearer understanding of the concept of the present invention and should not be considered as limiting the present invention, will now be described with reference to the following drawings. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 shows a schematic diagram of an ophthalmic imaging device according to a general apparatus embodiment of the present invention. [Figure 2A] FIG. 2A shows a schematic implementation of a blocking mechanism for an ophthalmic imaging device, in accordance with a more specific device embodiment of the present invention. [Figure 2B] FIG. 2B shows a schematic implementation of a blocking mechanism for an ophthalmic imaging device, in accordance with a more specific device embodiment of the present invention. [Figure 3] FIG. 3 shows a schematic diagram of an ophthalmic imaging device providing two or more imaging modes, according to an embodiment of the device of the present invention. [Figure 4] FIG. 4 shows a schematic diagram of the light output and other associated drive signals for the individual light beams in different imaging modes, according to one embodiment of the present invention. [Figure 5] FIG. 5 shows a flow diagram of a general method embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] FIG. 1 shows a schematic diagram of an ophthalmic imaging device according to a general apparatus embodiment of the present invention. The illustrated ophthalmic imaging device is for imaging a subject's (patient's) eye, e.g., for assessing eye health. This embodiment relates particularly, but not exclusively, to controlling the optical output of one or more light sources that contribute to a light beam used to image the subject's eye. The illustrated ophthalmic imaging device 1 includes multiple light sources 11-1, 11-2, ..., each providing a separate light beam B-1, B-2, .... For example, the ophthalmic imaging device 1 may include multiple light sources in the form of laser light sources, such as red (R), green (G), and blue (B) lasers. Other types of light sources include one or more infrared (IR) lasers and one or more ultraviolet (UV) lasers. The individual light beams B-1, B-2, ... can be combined by combining optics 15, which is configured to combine, e.g., collimate, the individual beams into a single beam, with each color component according to its respective individual contribution from the individual light sources. The multiple light sources are thus configured to provide a light beam in the form of a scanned beam B that is directed towards the eye E of the subject.

[0012] The ophthalmic imaging device 1, as in this exemplary embodiment, is provided in the form of an ultra-wide field of view (UWF) ophthalmic imaging device, which has a larger field of view (FoV) than a wide field of view (WF) device, enabling acquisition of a UWF image of the fundus that covers a wider portion of the fundus. A UWF image of the fundus is defined as a single image centered on the fovea of ​​the eye E and capturing anatomical features of the peripheral retina anterior to the vortex vein ampulla in all four quadrants. Thus, a UWF ophthalmic imaging device is defined as being capable of acquiring a single UWF image covering the retinal region extending from the fovea to the anterior edge of the vortex vein ampulla and down to the pars plana, and having a field of view (expressed in eye angles) ranging from 110 degrees to 220 degrees. As an example, the Optos Daytona® can capture UWF images (so-called Optomap® images) covering up to 200 degrees of the fundus (i.e., approximately 82% of the retina) in a single exposure.

[0013] The techniques described herein are not limited to WF and UWF ophthalmic imaging devices, but also apply to small FoV (field of view) ophthalmic imaging devices, and may be beneficial to any scanning ophthalmic imaging device that uses one or more elliptical mirrors to scan light over a portion of the eye E for partial imaging.

[0014] The illustrated ophthalmic imaging device 1 includes a controller 140 configured to control light sources 11-1, 11-2, ... to generate light beams B and provide multiple imaging modes, where the corresponding contribution of the light sources 11-1, 11-2, ... to the light power projected toward the subject's eye E is different for each imaging mode. As part of this power control, a configuration of one or more respective beam splitters 12-1, 12-2, ... and power detectors 13-1, 13-2, ... can be provided. In such a configuration, one partial beam B-1a propagates toward the subject's eye, while the other partial beam B-1b is directed toward a detector, e.g., detector 13-1, which converts the incident light power into a signal representative of that detector. Assuming beam splitters with well-defined, constant splitting ratios, the actual light power directed toward the eye can be controlled by respective feedback control loops 14-1, 14-2, ... These individual output controls can be used to provide respective target light outputs for the light sources 11-1, 11-2, . . . to provide multiple imaging modes.

[0015] For example, the controller can be configured to control a first number of light sources to provide a first imaging mode and a second number of light sources different from the first number to provide a second imaging mode. In such an example with multiple light sources, each laser can emit red (R), green (G), and blue (B) light, and the first imaging mode can be provided by activating only one light source and using the available optical window for allowable output. This imaging mode can be a green autofluorescence (G-AF) imaging mode, in which only green light is used. In the second imaging mode, all three light sources R, G, and B are active, allowing each light source to use only a portion of the light output budget. For example, each light source can be operated to provide only one-third of its light output to provide a full-color, or RGB, imaging mode in which white light is used.

[0016] The ophthalmic imaging device 1 further includes an optical path 150 configured to irradiate the subject's eye E with a light beam B. The optical path 150 includes one or more scanning elements. Thus, the light beam B can be deflected by one or more scanning relay elements to cover the imaging area with multiple parallel scan lines. The reflective relay element or scanning relay element can include a polygonal scanning mirror 16 and one or more scanning galvanometer mirrors 18 (hereinafter referred to as "galvos" 18). The former polygonal scanning mirror 16 can include multiple reflective facets arranged around the circumference of a rotating body. The driver is configured to rotate the polygonal scanning mirror body during operation, allowing the incident light beam to be reflected at varying angles. While passing through one individual facet, the light beam is deflected through a corresponding range of angular change. After such a deflection cycle is completed, the next facet essentially repeats the process, and so on for all other facets.

[0017] This repeated deflection by such a polygonal scan mirror 16 provides multiple parallel scan lines, thereby forming the basis for at least one scan direction. Additional scanning elements, such as the aforementioned galvo 18, allow the beam to be further deflected in other directions, offsetting the scan lines on the target to ultimately cover a two-dimensional scan area. In at least some imaging modes, light from the scanning beam is backscattered from the target tissue. In the case of ophthalmic imaging, this includes key areas of the human eye, such as the retina. Generally, this light B' returns along the incident optical path and is ultimately detected by an image detector in the form of a photosensor, converted into an intensity signal, and processed to form an image. This latter signal processing, in particular, is performed by a digital processor that generates individual images from the corresponding sets of line scans. The optical path 150 further includes one or more steering elements, e.g., in the form of elliptical mirrors 17, 19. Other examples of steering elements include lenses, mirrors, waveguides, etc. Generally, the components and elements of the optical path 150 are configured to guide a light beam B to the subject's eye E, scan an imaging area of ​​the target tissue, and guide a light beam B' back from the eye E for detection.

[0018] The ophthalmic imaging device 1 further comprises a shutter mechanism 20 configured to block the light beam B from reaching the subject's eye E. This shutter mechanism 20 can, in principle, be located at any suitable position in the imaging device 1, including the entire optical path from each of the individual light sources through the common optical path 150 to the position of the ophthalmic imaging device 1, leaving room for effective control of the scanning beam B before it finally reaches the target. Preferably, the shutter mechanism 20 is located in the optical path after the combining optics 15, which facilitates controlling all of the partial and contributing beams at one location with a single element. Also preferably, the shutter mechanism 20 is located in the optical path before the first scanning element, where the light beam B can follow a fixed path without changing its direction and propagation angle. In this way, the beam can be blocked by blocking its propagation path at a local fixed point corresponding to the beam cross-section, without having to consider changes in direction or angle, thereby enabling the shutter mechanism to have small dimensions and low structural complexity.

[0019] Furthermore, in the ophthalmic imaging device 1, the controller 140 is configured to operate the shutter mechanism 20 to block the light beam B when switching between the first and second imaging modes. Specifically, the second imaging mode may use one or more additional light sources compared to the first imaging mode. This means that switching from the first imaging mode to the second imaging mode involves activating one or more of the light sources, which may result in output fluctuations, especially immediately after activation. For example, a light source may require some time to reach a stable output control state, i.e., a state in which the light output fluctuates only within a tolerance band between the nominal minimum light output and the nominal maximum light output. However, as mentioned above, light output plays an important role in scanning laser ophthalmoscopy (SLO) because (human) tissues in general, and the eye in particular, are subject to more or less strict output tolerances. In a sense, there is a maximum power tolerance allowed during an examination, which relates to both the maximum instantaneous output and the power tolerance as the integral amount of optical power applied over the entire examination time. Therefore, any power fluctuations may exceed the instantaneous light output tolerance applied and / or may create significant uncertainty regarding the calculation of and ultimately compliance with the light output tolerance.

[0020] Thus, the light beam is preferably blocked by the controller before one or more light sources are activated as part of switching between the first and second imaging modes. However, the light beam can also be blocked by the controller before one or more light sources are deactivated as part of switching between the first and second imaging modes. This is because powering down the light sources can also result in unpredictable and fluctuating output behavior, particularly including output spikes as a result of deactivating any power control loops, which may include switching power supplies underlying light-emitting elements such as lasers or diodes. By way of example, the light beam can be blocked at least 0.5 seconds before one or more light sources are activated and / or at least 0.5 seconds before one or more light sources are deactivated.

[0021] FIG. 2A shows a schematic implementation of a blocking mechanism for an ophthalmic imaging device according to a more specific device embodiment of the present invention. In this embodiment, it is initially assumed that the light beam to be blocked propagates in a fixed direction and angle, which can be advantageous in terms of the size and complexity of the device configuration. Such an arrangement can be achieved by locating the shutter mechanism upstream of a first scanning element, such as a scanning polygon mirror or a scanning mirror in the form of a galvo, in the optical path. In this embodiment, a mechanical shutter mechanism is shown. This can provide high reliability as well as an additional safety feature, since a physical shutter can interact with a switch, sensor, light barrier, etc. to provide confirmation feedback, as described below. As shown, a light beam B is incident from one or more light sources and propagates toward a first scanning element, such as a scanning polygon mirror 16, which provides multiple reflective facets 161-1, 161-2, ... Mirror driver 160 is typically configured, in operation, to rotate the body of polygon scan mirror 16 so that each facet 161-1, 161-2, ... can reflect an incident light beam at a varying angle α. During passage through one individual facet, the light beam is deflected through a corresponding range of varying angles. Upon completion of such a deflection cycle, the next facet essentially repeats the process, and so on for all other facets.

[0022] The illustrated blocking mechanism 21 comprises a frame 211 and a movable shield 212 that is positionable relative to the frame 211 by an actuator 213. Specifically, the shutter mechanism 21 may include the movable shield 212, which, upon actuation by the actuator 213, may close an opening 216 in the shutter mechanism to block the light beam in response to a blocking signal. In the illustrated example, the opening 216 is defined by the frame 211. The actuator 213 may be implemented with any suitable mechanical actuation mechanism, such as a magnet, electromagnet, spring, piezoelectric element, or the like, that moves the shield 212 into the path of the light beam B in response to a blocking signal SS. Such mechanisms are known and can provide reliable operation even on time scales in the millisecond range.

[0023] The shield 212 is an opaque element capable of blocking the optical beam and preventing the beam from propagating toward the patient's eye when the shield 212 is in the beam-blocking position. Preferably, the shield 212 includes a section 214 configured to interact with a confirmation sensor 215 to provide a confirmation signal Cf. The confirmation sensor 215 may comprise any of a mechanical switch, a pair of electrical contacts, a light barrier consisting of a light source and a photodetector, a reflective surface, a magnet and Hall sensor, an amplifier, or a threshold circuit such as a Schmitt trigger. Thus, the confirmation sensor 215 can be configured to provide a confirmation signal Cf when the shield 212 is in the blocking position in response to detecting the actual position of the shield 212 and therefore the actual blocking of the beam by the shield 212. This confirmation signal Cf can be used by the controller 140 to confirm the blocking of the beam in response to issuing a blocking signal SS. For example, the controller 140 may be configured to proceed to change the imaging mode only if the confirmation signal Cf confirms that the propagation path of the light beam B has been blocked.

[0024] Although this embodiment primarily assumes that the light beam to be blocked propagates in a constant direction and angle, modifications can also be provided for light beams propagating in varying directions and angles of incidence, such as in the case of a scanning beam that has already been deflected upstream in the optical path. For such modifications, the frame 211 and the shielding body 212 can be configured to have an aperture size with sufficient spread ev and eh in one or two dimensions so that in the open, non-shielding state they can accommodate an applicable angular range, and in the closed, shielding state they can block beams from all directions and angles that occur.

[0025] FIG. 2B shows a schematic implementation of a shutter mechanism for an ophthalmic imaging device according to a more specific embodiment of the present invention. In this embodiment, it is initially assumed that the light beam to be blocked propagates in a fixed direction and angle, which can be advantageous in terms of the size and complexity of the device configuration. Such an implementation can be achieved by placing the shutter mechanism upstream of a first scanning element, such as a scanning polygon mirror or a scanning mirror in the form of a galvo, in the optical path. In this embodiment, an optical shutter mechanism is shown, which provides high reliability by not relying on any moving parts. As shown in the figure, a light beam B enters from one or more light sources and propagates toward the first scanning element, as shown in FIG. 2 for the example of the scanning polygon mirror 16. The illustrated shutter mechanism 22 includes a frame 221 and a light shield 222, which is driven by a shield signal SS to shield the light. In this embodiment, the light shield 222 can be switched between a transparent state and an opaque state by a control signal SS applied to the light shield 222. Such a shield can be implemented as either a polarizer or a polarizing filter. There, a control signal SS, for example in the form of a voltage, changes the polarization properties of the layer of the light blocking device 222, setting it to one of a transparent state and an opaque state, respectively. In one embodiment, the polarization properties of a liquid crystal layer can be changed by the control signal SS, which can be combined with a polarizing filter to form a light blocking device switchable between a transparent state and an opaque state. Another possible implementation is a Pockels cell. Preferably, the blocking mechanism 22 also includes a confirmation sensor in the form of a light barrier having a light-emitting element 225A and a light-receiving element 225B, which can provide a confirmation signal Cf. In the case of a light blocking mechanism, the confirmation sensor 225 is thus implemented in the form of a light barrier, where light shares an opening with the light beam B, indicating that the light barrier does not transmit light, meaning that the light beam B is blocked.

[0026] FIG. 3 shows a schematic diagram of an ophthalmic imaging device providing two or more imaging modes, according to an embodiment of the device of the present invention. The ophthalmic imaging device 1′ will be described with reference to an imaging mode in which a light beam is generated by one or more light sources 200-1, 200-2, ..., directed toward a patient's eye E, reflected by the tissue thereof, and directed back to a detector 218. The device 1′ therefore includes a light source that emits a light beam that is formed into a scanning beam by a plurality of scanning relay elements. The scanning relay elements include a first scanning element in the form of a polygonal scanning mirror 202, a second scanning element 206, and optical elements positioned and configured to direct the scanning beam B. In some embodiments, the optical elements include an optical element 204, which may be a scanning compensation element such as an elliptical mirror (referred to as a slit mirror), and a second optical element 208, which may also be an elliptical mirror scanning transfer element.

[0027] Optical elements 204, 208 are positioned and configured to direct scanning beam B. Second scanning element 206 can be or include an oscillating planar scanning mirror or a planar scanning mirror coupled to a galvanometer motor. Optical element 204 can be a curved mirror, such as an elliptical mirror. Second optical element 208 can be an aspherical mirror. It should be understood that the first and second optical elements can have alternative forms. Scanning elements 202, 206 can be referred to as a scanning device or multiple individual scanning devices. It should be understood that the functionality illustrated here is merely an example of configurations that can be used in the embodiments described herein. In some embodiments, one or more scanning elements can include, for example, one or more of an oscillating planar mirror, a galvanometer mirror, a MEMS mirror, a rotating mirror, a prism or polygon scanner, and / or a resonant mirror. It should be understood that other suitable scanning elements can be used, such as a line scan generated by a laser line source or its equivalent. Line scans can be used as an effective alternative to point scans. A line source can illuminate a line on the retina, which is scanned in an orthogonal direction by a slow scanner. The line illumination can be detected by a linear pixel array, and a 2D image can be constructed by rotating the slow scanner.

[0028] In some embodiments, each of the first scanning element 202 or the second scanning element 206 may be a single element or an arrangement of two or more elements suitable for providing a scan at a respective focal point F1, F2 at which the scanning element is located, as shown. Focal point F1 or F2 is the focal point of the optical element 204, and focal point F2 or F3 is the focal point of the optical element 208. The first scanning element 202 is located at focal point F1, the second scanning element 206 is located at focal point F2, and the eye E is located at focal point F3 (also referred to as a virtual scanning point). The resulting scan may be a 2D scan, or scan pattern, of the scanning beam 201 as light is swept through the virtual scanning point (e.g., through F3) within the eye E.

[0029] In some embodiments, the first scanning element 202 provides either a vertical scan, a horizontal scan, or a pattern scan that is incident on the optical element 204 and, through the optical element 204, to a point on the scanning element 206. The scan may be, for example, a one-dimensional (1D) or two-dimensional (2D) optical scan. The axes of the first scanning element 202 and the second scanning element 206 can be arranged to generate a 2D optical scan, such as in the form of a raster scan pattern of the scanned beam 201. The alignment of the first and second scanning elements 202, 206 can be arranged to generate orthogonal, substantially orthogonal, or any arbitrary scan shape with respect to the optical elements 204 and 208.

[0030] In some embodiments, the second scanning element 206 provides multiple scans, for example, 1D or 2D optical scans, which may include horizontal scans, vertical scans, or arbitrary patterns of the scanned beam 201. The scans provided by the first scanning element 202 and the second scanning element 206 differ from each other, for example, in the direction of the scans. In some examples, one scanning element may provide a vertical scan of the retina and another scanning element may provide a horizontal scan of the retina. The scanned beam 201 is directed to the patient's eye E via scanning elements 202 and 206 and optical elements 204 and 208, achieving an ultra-wide field of view scan angle at the pupil plane of the eye E.

[0031] In some embodiments, the first scanning element 202 can be used to scan the retina in a first direction to generate multiple line scans, and the multiple line scans can be repositioned in a second direction using the second scanning element 206, which is orthogonal to the first direction. As shown in FIG. 4 , the path of the scanning beam B is depicted as a 1D scan generated by the oscillation or rotation (indicated by the curved arrow) of the first scanning element 202. Path "a" is an example of scanning beam B reflecting off the polygonal scanning mirror when the reflective facets are oriented in one direction during rotation, while paths "b" and "c" are examples of scanning beam B reflecting off different orientations of the facets during rotation.

[0032] The components of the ophthalmic imaging device 1′ may be arranged such that the rotation axis of the first scanning element 202 is substantially parallel to a line connecting the two focal points (i.e., F2 and F3) of the optical element 208, such that the scanning beam B can be scanned across the second axis of the optical element 204. Furthermore, the first scanning element 202 is capable of generating a 1D or 2D scan, which is incident on the optical element 204. The optical element 204 is therefore also capable of generating a 1D or 2D scan. The components of the ophthalmic imaging device 1′ may be arranged such that the line connecting the two focal points (i.e., F2 and F3) of the optical element 208 substantially lies on a plane defined by the scan (e.g., a 1D vertical scan) generated by the optical element 204. The first and second scanning elements are therefore capable of together generating an optical scan in the form of a raster scan pattern, e.g., a 2D scan, from a point in space at or near the focal point F3 on or in the patient's eye E. The first and second scanning elements can have operating parameters including oscillation amplitude and oscillation rotational offset. The operating parameters can also include oscillation speed. Any of these operating parameters can be selected to control the direction and pattern of the light scan from the apparent point source. In some embodiments, the first and second scanning elements can be housed on a rotation stage (not shown) that can adjust the centering (or decentering) of the scanning beam B on the retina of the eye E, thereby allowing the imaging field of view to be "moved" across the retina.

[0033] In this embodiment, the ophthalmic imaging device 1′ comprises a blocking mechanism 20 arranged to block a light beam B incident from one or more light sources from propagating further along the optical path, in particular before it propagates further towards a first scanning relay element in the form of a scanning polygon mirror 202. The light beam B will eventually be used to form a scanning beam covering some finite imaging area, at which point the light beam B propagates at a substantially constant direction and angle and the shutter mechanism 20 can advantageously block the light beam B. For further implementation details of this embodiment, please refer to the disclosure provided in connection with FIGS. 2A and 2B .

[0034] FIG. 4 shows a schematic diagram of the optical output and other associated drive signals for the individual light beams in different imaging modes, according to an embodiment of the present invention. Specifically, the different imaging modes are illustrated by the respective optical outputs for three light sources R, G, and B. Such light sources may include respective lasers emitting red (R), green (G), and blue (B) light. The lasers mentioned above may be implementations of the multiple light sources 11-1, 11-2, ... of FIG. 1 or the multiple light sources 200-1, 200-2, ... of FIG. 3. In a first imaging mode, only one light source is activated and provides an optical output power Po, denoted as 1 / 1, thereby utilizing the full optical output power budget. This imaging mode may be a green autofluorescence (G-AF) imaging mode, in which only green light is used. In such a mode, the gain can be set to generate any desired output power, e.g., 1 V, at a predetermined target optical output power of the green light, e.g., 2 mW. In a second imaging mode, all three light sources R, G, and B can be activated, with each light source using only a portion of its light output allowance. For example, each light source can be operated to provide only one-third of its light output (denoted as 1 / 3). This imaging mode can be a full-color, or RGB, imaging mode in which white light is used.

[0035] The possible changes in actual light output associated with activating and deactivating a light source are illustrated and explained by the example of the operation of a red laser R between the imaging modes G-AF and RGB, and between the imaging modes RGB and B-AF, respectively (see inset). In this example, switching from the first imaging mode G-AF to the second imaging mode RGB involves activating (switching on) a light source in the form of a red laser R. This may result in power fluctuations F and / or power spikes S, as shown in the inset on the left. To avoid these adverse effects, a blocking mechanism can be activated by a blocking signal SS, as described in connection with this disclosure. Specifically, the blocking signal SS can be controlled to block the light beam propagating toward the subject's eye until time tSS0-1, at which it can be safely assumed that the power fluctuations F have disappeared or that further power spikes S are at least unlikely to occur. The same, or at least similar, considerations apply to the blocking signal SS at time tSS0-2 for switching from the RGB imaging mode to the imaging mode B-AF.

[0036] However, power fluctuations and / or power spikes may occur not only in association with the activation of the light source but also when the light source is deactivated (switched off). To take such effects into account, the blocking signal SS can be controlled so that the blocking mechanism blocks the light beam propagating toward the subject's eye from time tSS1-1, which may be even earlier than the time when the light source is deactivated. In this way, power fluctuations F' and / or power spikes S' can be safely blocked. The same or at least a similar consideration applies to the blocking signal SS at time tSS1-2 related to switching from the RGB imaging mode to the imaging mode B-AF. Therefore, the controller can be configured to operate the shutter mechanism to block the light beam when switching between the first imaging mode and the second imaging mode, particularly before activating the light source and / or before deactivating the light source.

[0037] As a further option, a confirmation signal Cf may be considered, which may originate from a confirmation sensor as described elsewhere in this disclosure. Specifically, such a confirmation signal may represent confirmation that the light beam propagating toward the subject's eye is effectively and actually blocked. For example, such a signal may be received at time tSS11-1 with some delay in response to the issuance of a close signal at time tSS1-1. This is because the blocking signal controls the shutter mechanism to close, and the confirmation signal (with its delay) registers and confirms the closure of the light path. Specifically, the controller may first control the blocking mechanism to block the light beam propagating toward the subject's eye by issuing a corresponding blocking signal SS (e.g., set to a relatively high logic level H), wait until the confirmation signal Cf responds (e.g., transitions to a relatively high logic level H), and only then proceed to activate and / or deactivate the light source associated with switching from the first imaging mode to the second imaging mode.

[0038] FIG. 5 shows a flow diagram of a general method embodiment of the present invention. Specifically, this embodiment relates to a method of operating an ophthalmic imaging device. For example, a method is provided for scanning an ophthalmic imaging device 1, the method comprising: a plurality of light sources 11-1, ... providing light beams; an optical path configured to project the light beams toward a subject's eye (E), the optical path comprising one or more scanning elements 16, 18 and one or more guiding elements 17, 19; and a shutter mechanism configured to block the light beams from reaching the subject's eye. The method includes a step S100 of controlling the light sources to generate the light beams and providing multiple imaging modes, each of which varies a corresponding contribution to the light output projected from the light sources toward the subject's eye. The method further includes a step S200 of operating a shutter mechanism to block the light beams when switching between a first imaging mode and a second imaging mode. Note that these steps S100 and S200 can be performed sequentially, iteratively, and / or simultaneously, depending on the actual implementation.

[0039] In some embodiments, the shutter mechanism is operated to block the light beam in step S201 prior to step S101 of deactivating the light source in connection with the end of the first imaging mode. Furthermore, the shutter mechanism can be operated to block the light beam at least until a delay time after activating the light source in connection with the start of the second imaging mode. Specifically, a respective sequence can involve a first step S102 of activating at least one light source, a second step S103 of waiting a predetermined time (e.g., a delay time) until any fluctuations or spikes in the actual light output are deemed to have subsided, and then a step S202 of emitting the light beam by opening the shutter mechanism so that the light beam is no longer blocked.

[0040] The foregoing has provided embodiments and details thereof as part of the present invention that may provide one or more advantages through an improved power control mechanism in an ophthalmic imaging device. The device allows for the flexibility of providing multiple imaging modes, while maintaining safety without requiring an increase in system and / or implementation. While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example and not by way of limitation. Various changes in form and detail will be apparent to those skilled in the relevant art. Accordingly, the exemplary embodiments set forth above are not intended to be limiting.

Claims

1. An ophthalmic imaging device (1), a plurality of light sources (11-1, 11-2, 11-3) for providing light beams (B); a controller (140) configured to control the light sources (11-1, 11-2, 11-3) generating the light beams (B) to provide a plurality of imaging modes, wherein the controller (140) varies the corresponding contribution of the light sources (11-1, 11-2, 11-3) to a light output projected toward the subject's eye (E) in each of the imaging modes; an optical path (150) configured to project the light beam (B) onto the subject's eye (E), the optical path (150) comprising one or more scanning elements (16, 18) and one or more guiding elements (17, 19); a shutter mechanism (20) configured to block the light beam (B) from reaching the subject's eye (E); Equipped with The ophthalmic imaging device (1), wherein the controller (140) is configured to operate the shutter mechanism (20) to block the light beam when switching between a first imaging mode and a second imaging mode.

2. 2. The ophthalmic imaging device (1) of claim 1, further comprising a combining optical system (15) configured to combine light beams (B-1a, B-2a, B-3a) from each of a plurality of light sources (11-1, 11-2, 11-3) to provide said light beam (B).

3. 3. The ophthalmic imaging device (1) of claim 2, wherein the shutter mechanism (20) is located in the optical path (150) downstream from the coupling optics (15).

4. The ophthalmic imaging device (1) of any one of claims 1 to 3, wherein the shutter mechanism (20) is arranged in the optical path (150) upstream from a first scanning element (16).

5. 5. The ophthalmic imaging device (1) of claim 1, wherein the controller (140) is configured to control a first number of light sources to provide a first imaging mode and to control a second number of light sources different from the first number to provide a second imaging mode.

6. The ophthalmic imaging device (1) of any one of claims 1 to 5, wherein the controller (140) is configured to activate at least one of the light sources (11-1, 11-2, 11-3) or deactivate at least one of the light sources (11-1, 11-2, 11-3) when switching from the first imaging mode to the second imaging mode.

7. 7. The ophthalmic imaging device (1) of claim 6, wherein the controller (140) is configured to operate the shutter mechanism (20) to block the light beam (B) before at least one light source is activated when switching between the first imaging mode and the second imaging mode.

8. 8. The ophthalmic imaging device (1) of claim 6 or claim 7, wherein the controller (140) is configured to operate the shutter mechanism (20) to block the light beam (B) after at least one light source is stopped when switching between the first imaging mode and the second imaging mode.

9. An ophthalmic imaging device (1) as described in any one of claims 1 to 8, wherein the shutter mechanism (20) comprises a movable shield (212) and a driver (213) configured to close an opening (216) of the shutter mechanism (20) to shield the light beam (B) in response to a blocking signal (SS).

10. An ophthalmic imaging device (1) as described in any one of claims 1 to 8, wherein the shutter mechanism (22) comprises an optical shutter (222) configured to block the light beam (B) in response to a blocking signal (SS).

11. 11. An ophthalmic imaging device (1) according to any one of claims 1 to 10, further comprising a confirmation detector (215, 225A / B) configured to provide a confirmation signal (Cf) in response to the light beam (B) being blocked by the shutter mechanism (20, 21, 22).

12. 12. The ophthalmic imaging device (1) of claim 11, wherein the controller (140) is configured to operate the shutter mechanism (20) to block the light beam (B), receive the confirmation signal (Cf), and control the light sources (11-1, 11-2, 11-3) to switch between the first imaging mode and the second imaging mode in response to receiving the confirmation signal (Cf).

13. a plurality of light sources (11-1, 11-2, 11-3) for providing light beams; an optical path (150) comprising one or more scanning elements (16, 18) and one or more guiding elements (17, 18) configured to project the light beam (B) onto the subject's eye (E); a shutter mechanism (20) configured to block the light beam (B) from reaching the subject's eye (E); 1. A method of operating an ophthalmic imaging device (1) comprising: a step (S100) of controlling the light sources (11-1, 11-2, 11-3) to generate light beams (B) and to provide a plurality of imaging modes, wherein a corresponding contribution to the light output projected from the light sources (11-1, 11-2, 11-3) towards the subject's eye (E) is varied for each of the imaging modes; a step (S200) of operating the shutter mechanism to block the light beam (B) when switching between a first imaging mode and a second imaging mode; 1. A method of operating an ophthalmic imaging device (1), comprising:

14. controlling a first number of light sources to provide a first imaging mode; controlling a second number of light sources, different from the first number, to provide a second imaging mode; A step (S102) of activating at least one of the light sources (11-1, 11-2, 11-3) or stopping at least one of the light sources (11-1, 11-2, 11-3) when switching from the first imaging mode to the second imaging mode; The method of operating an ophthalmic imaging device (1) according to claim 13, further comprising:

15. 15. The method of operating an ophthalmic imaging device (1) of claim 14, further comprising the step of operating a shutter mechanism to block the light beam before at least one light source is activated when switching between the first and second imaging modes.

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