Method and apparatus for projecting a target pattern onto a modified retinal region of a human eye

Abstract

The present invention relates to a method for projecting a target pattern (6) onto a modified retinal area (5) of a human eye, comprising the steps of: providing a pulsed input beam (20), modulating and dividing the pulsed input beam (20) into a pulsed modulated light pattern of modulated pulsed sub-beams (40) based on the target pattern (6), wherein the modulated light pattern forms a pulsed output beam (4) reflecting the target pattern (6), wherein individual pulse width modulation is performed on the modulation duty cycle (32) of the individual modulated sub-beams (40) forming the output beam (4), and adapting the device accordingly.

Description

Technical Field

[0001] The present invention relates to a method for projecting a target pattern onto a region of the human retina that has been modified, for example, by an implanted retinal implant to restore its photosensitive properties, and to a corresponding device. Background Art

[0002] Retinal dysfunction, especially caused by degenerative retinal diseases, is a major cause of impaired vision and even blindness.

[0003] To at least partially restore the visual function of a patient, it is known to utilize the modification of a region of the human retina, for example, by using a retinal implant or, in other words, a retinal prosthesis. In this regard, several different types of retinal implants are known, which are based on different operating principles.

[0004] The common feature of retinal implants is that they are typically placed in the patient's eye under the retina, on the retina, or in the choroid, so that they can effectively replace damaged photoreceptors. In this regard, information about the visual scene is captured by a camera and then transmitted to an electrode array implanted in the retina.

[0005] In common retinal implants, it is known that the implants include wires that penetrate the skin. These wires pose a risk of infection and scarring. Therefore, more modern implants use different wireless technologies, such as transmitting power and visual information through induction coils. In addition, it is known to transmit power inductively and visual information optically through the pupil of the eye, or to transmit visual information and power optically.

[0006] A particularly beneficial wireless information transmission to a retinal implant is based on projecting a stimulation pattern, preferably infrared light, into the eye. When the gaze direction is such that certain parts of the implant are illuminated by the partial pattern, the implant converts the signal of that part into an electric current, thereby stimulating the retina accordingly.

[0007] A retinal implant is an array composed of stimulation electrodes or pixels. Each pixel has one or several photodiodes, which are used to capture the light emitted by a visual processor and convert it into an electric current for stimulation.

[0008] Several implant arrays can be placed in the subretinal space, usually in or near the foveal region.

[0009] Optionally, a method called optogenetics has been proposed to treat residual retinal cells to restore their photosensitive behavior through gene therapy. Optogenetics refers to the combination of genetics and optics to control well-defined events within specific cells of living tissue. Optogenetics includes (i) genetically modifying target cells to make them light-sensitive by expressing exogenous light-responsive proteins in the cell membrane, and (ii) providing an illumination device capable of providing light to the light-responsive proteins.

[0010] In the following paragraphs of this patent, such a retinal region of the human eye that has been modified to restore photosensitive behavior by implanting a retinal prosthesis or by optogenetics will also be referred to as the "modified retinal region".

[0011] To project light or a light beam into the human eye respectively, it is known to use a projector device, such as augmented reality goggles. The projector unit of the projector device, such as projector optics, projects a pulsed light beam onto the human eye and at least partially into the human eye. That is, the picture to be transmitted is transmitted through the pupil of the eye into the eye and towards the retina.

[0012] Although a target illumination pattern can be provided to the patient thereby, the patient can only perceive a single light-dark contrast because the irradiation for each pulse of the pulsed light beam is constant.

[0013] However, safety issues are associated with the use of such a projector device. For example, the projector device and the method of use must ensure that the irradiation on the retina complies with a specific duty cycle, such as less than 0.5, and may require ensuring the proper safety of the modified retinal region, such as a retinal implant, for example to ensure proper discharge between the implanted pulsed electrical function and electrical pulses.

[0014] Similarly, for optical safety, it may also be required that the projector device and the method of use must ensure that the irradiation on the retina complies with the duty cycle, so as to ensure that the average light irradiance does not reach the safety threshold. In this way, high light irradiance can be acceptable if it is modulated at a sufficiently low duty cycle. This can be achieved by providing commands to the light source to regularly turn off between pulses of a specific duty cycle. It can also be achieved by ensuring that the micromirror regularly turns off between pulses of a specific duty cycle. However, for medical applications, it is generally required that safety and the relevant duty cycle should be ensured even under single-fault conditions. Summary of the Invention

[0015] The object of the present invention is to provide an improved method for projecting a target pattern onto the modified retinal region of the human eye, and a corresponding device for projecting a target pattern onto the modified retinal region.

[0016] The above object is solved by a method for projecting a target pattern onto a modified retinal area of a human eye, comprising the features of claim 1. Further preferred embodiments are presented in the dependent claims, the description and the drawings.

[0017] Thus, in a first aspect, there is provided a method for projecting a target pattern onto a modified retinal area of a human eye or a method of operating a device for projecting a target pattern as described herein, the method comprising the steps of: providing a pulsed input beam, preferably comprising coherent or incoherent light and / or preferably light having a wavelength in the near-infrared field, and modulating and dividing the pulsed input beam into pulses of modulated pulsed sub-beams and a modulated light pattern based on the target pattern, wherein the modulated light pattern forms a pulsed output beam reflecting the target pattern. The method is characterized by the step of performing single pulse width modulation on the modulation duty cycle of the modulated individual sub-beams forming the output beam.

[0018] Since the modulation duty cycle of each sub-beam can be adjusted separately and individually, the irradiation duration of each sub-beam can be controlled separately by single pulse width modulation of the individual sub-beams. That is, for each period of the pulsed output beam, the irradiation duration at the retinal implant to which the output beam is directed can vary within the output beam, since each sub-beam can comprise a single duty cycle. Thus, the photodiodes of the retinal implant may be exposed to different irradiation durations, which in turn results in different stimulation currents and / or different retinal stimulation durations. Thereby, it is possible to achieve a perception of the gray level of the projected pattern irradiated via the output beam. In other words, thus, it is possible to illuminate the retina with a pattern that is converted into different perceived gray levels within one pulse period. Thus, a patient equipped with a corresponding photosensitive retinal implant may be able to sense or perceive at least a basic gray-scale image. The latter can improve or facilitate the patient's orientation and can increase visual ability.

[0019] The target pattern here can be based on a picture or image that is captured and to be projected, wherein the picture or image can comprise dark and bright areas, preferably pixels with different brightness values.

[0020] Preferably, the modified retinal area can be provided via an implanted retinal prosthesis.

[0021] According to a further exemplary embodiment, the input beam comprises a constant peak irradiance. Thereby, the irradiance hitting the retinal implant can be accurately identified, determined and / or calculated. Thus, reliable operation of the retinal implant can be achieved and retinal damage due to unknown excessive irradiance can be prevented.

[0022] Optionally or alternatively, the input beam may substantially comprise the form of a pulsed wave, since the beam thus formed may have the advantage of substantially constant irradiation during each duty cycle.

[0023] Preferably, the input beam comprises a constant period.

[0024] According to another preferred embodiment, the input beam comprises a constant duty cycle. Optionally, the duty cycle of the input beam is controlled.

[0025] According to yet another preferred embodiment, when the modulation period is synchronized with the period of the pulsed input beam, an optimal adaptation of the gray-scale distribution inside the output beam can be achieved. In other words, the period of the pulse width modulation corresponding to the modulation period and thus the period of the sub-beams are synchronized with the period of the pulsed input beam.

[0026] According to another preferred embodiment, the method can be optimized in that the maximum individual modulation duty cycle of a single sub-beam corresponds to the duty cycle of the pulsed input beam.

[0027] In order to prevent damage to the retina due to excessive irradiation, the duty cycle of the pulsed input beam may preferably be equal to or less than 0.5, preferably 0.4, particularly preferably 0.3 of the period of the pulsed input beam, and / or the maximum possible duty cycle of the sub-beams may preferably be equal to or less than 0.5, preferably 0.4, particularly preferably 0.3 of the period of the pulsed input beam.

[0028] According to another preferred embodiment, a target pattern is obtained by capturing visual information, preferably an image, and dividing the captured visual information, preferably the captured image, into a pixel pattern forming the target pattern, wherein the pixels reflect at least different brightness values within the visual information, preferably within the image, if any.

[0029] Preferably, the captured image is optionally processed before assigning brightness values to the pixels or regions of the processed image.

[0030] Furthermore, the above object is also solved by a device for projecting a target pattern onto a modified retinal region of a human eye preferably comprising a retinal implant, the device comprising the features described in claim 7. Further preferred embodiments are presented in the dependent claims, the description and the drawings.

[0031] Accordingly, in a second aspect, there is provided an apparatus for projecting a target pattern onto a modified retinal region of a human eye, which includes a light source for providing a pulsed input beam, preferably, the pulsed input beam is a beam of preferably coherent or incoherent light, preferably, light having a near-infrared field wavelength, and a modulation micromirror array for modulating and dividing the pulsed input beam into modulated pulsed sub-beams, wherein the orientation of each micromirror of the micromirror array is independently controllable based on the target pattern, such that the sub-beams form a pulsed output beam reflecting the target pattern. The apparatus is also configured and adapted to perform individual pulse width modulation of the sub-beams forming the output beam by independently controlling the modulation duty cycle of individual micromirrors.

[0032] With this apparatus, the effects and advantages described in the above method can be achieved.

[0033] According to a preferred embodiment, the apparatus is further adapted to synchronize the modulation period of the orientation control of the micromirrors with the period of the pulsed input beam.

[0034] For the synchronization of the modulation by the micromirror array and the input beam pulses, the maximum individual modulation duty cycle of the micromirrors can preferably correspond to the duty cycle of the pulsed input beam.

[0035] To prevent damage to the retina by the output beam, the duty cycle of the pulsed input beam relative to the period of the pulsed input beam can preferably be set to be equal to or less than 0.5, preferably 0.4, particularly preferably 0.3, and / or the maximum possible modulation duty cycle of the sub-beams relative to the period of the pulsed input beam can preferably be equal to or less than 0.5, preferably 0.4, particularly preferably 0.3.

[0036] According to another preferred embodiment, the apparatus may further include a camera for capturing visual information, preferably an image, and / or a processing unit for dividing the captured visual information, preferably the captured image, into a pixel pattern forming the target pattern, wherein the pixels reflect at least different brightness values within the visual information, preferably within the image, if any.

[0037] Furthermore, it is important to note that for wearable electronic devices such as projector devices, the battery life must be as long as possible to ensure the longest running time between battery or power charging. Therefore, for a given reasonable battery size, the power consumption of the device must be minimized. Advantageously, the light source modulation proposed according to the present invention allows the power supply to be regularly turned off between pulses, thereby significantly reducing its power consumption. In addition, the fact that it only operates for a small part of the time reduces the power consumption required to cool the laser source, for example, by operating a Peltier element or a fan. Therefore, pulsing the laser source at a specific duty cycle can significantly increase the battery life. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] When considered in conjunction with the accompanying drawings, the present disclosure will be more readily understood by reference to the following detailed description, in which:

[0039] Figure 1 Schematically shows an apparatus for projecting a target pattern onto a photosensitive modified retinal region of a human eye;

[0040] Figure 2 Schematically shows Figure 1 a detailed view of the target pattern that is the illuminated area of the modified retinal region;

[0041] Figure 3 Schematically shows a pulsed input beam including a pulse wave shape and corresponding modulated pulsed sub - beams;

[0042] Figure 4 Schematically shows another input beam that substantially has the form of a pulse wave and mirror pulses corresponding to three different micromirrors, thereby generating three different sub - beams; and

[0043] Figure 5 Schematically shows an example of the target pattern area projected onto a retinal implant via Figure 5 the sub - beams. DETAILED DESCRIPTION

[0044] Hereinafter, the present invention will be explained in more detail with reference to the drawings. In the figures, the same elements are denoted by the same reference numerals and their repeated description may be omitted to avoid redundancy.

[0045] Figure 1 Schematically shows an apparatus 1 for projecting a target pattern 6 onto a modified retinal region 5 of a human eye. The apparatus 1 includes a light source 2 that provides a pulsed input beam 20, and the pulsed input beam 20 includes light having a wavelength in the near - infrared field.

[0046] The input beam 20 is directed onto a modulating micromirror array 3 including a plurality of micromirrors 30 that can be operated independently, so that the orientation of each micromirror 30 can be adjusted and / or controlled independently. The modulating micromirror array 3 according to this specific embodiment is provided in the form of a digital micromirror device known per se.

[0047] Via the micromirror array 3, the input beam 20 is reflected to form an output beam 4. The output beam 4 consists of a plurality of sub - beams 40 that are formed when the input beam 20 hits individual micromirrors 30 of the micromirror array 3. The orientation of the micromirrors 30 is adjusted independently such that the target pattern 6 to be projected onto the modified retinal region 5 is reflected by the plurality of sub - beams 40.

[0048] In this regard, the target pattern 6 is based on an image captured by a camera (not shown), which has been processed into a digital pattern of pixels, where the pixels include gray values corresponding to the luminance values of the respective regions of the image. This data processing is known per se.

[0049] That is, only those micromirrors 30 corresponding to pixels including luminance values above a predetermined threshold are controlled to reflect the input beam 20, while the micromirrors 30 corresponding to pixels including luminance values below the predetermined threshold are oriented such that they do not contribute to the formation of the output beam 4.

[0050] Optionally, the modified retinal region 5 may include a retinal implant, preferably a photosensitive retinal implant.

[0051] Thus, the output beam 4 substantially reflects the target pattern 6. When the output beam 4 hits the modified retinal region 5, only those parts of the modified retinal region 5 including the retinal implant are illuminated by the output beam 4, or in particular by the sub-beam 40, which reflects the target pattern at the retinal implant. Thus, only those photodiodes of the retinal implant that convert light into current are arranged in the projected target pattern 6. Thus, a person including the retinal implant can perceive the target pattern 6.

[0052] Figure 2 A detailed view of the target pattern 6, which is the illumination region of the modified retinal region 5, is schematically shown.

[0053] The input beam 20 is pulsed into a waveform including a pulse wave shape, as can be obtained from Figure 3 Since the light source 2 includes a constant illumination 23 that is irradiated during each duty cycle 22 in each period 21 of the wave of the beam 20, the beam 20 is pulsed by the light source 2.

[0054] Thus, since the output beam 4 is substantially based on the input beam 20, the output beam 4 is also pulsed, where the period of the output beam 4 and the duty cycle of the output beam 4 generally correspond to the period 21 and the duty cycle 22 of the input beam 20. Thus, the target pattern 6 includes a uniform illumination over its entire surface, as depicted in Figure 2

[0055] To enable the ability to also provide gray-scale information to the output beam 4, the device 1 is also formed and adapted to perform pulse-width modulation independently for each sub-beam 40. The latter is achieved by independently controlling the modulation duty cycle 32 of each individual micromirror 30.

[0056] ​In other words, each micromirror 30 is oriented in a position such that it reflects the input beam 20, and thus the time of the sub-beam 40 that will contribute to the output beam 4 is set independently for each micromirror 30 to be different, depending on the corresponding gray level of the pixel in the target pattern 6 associated with the respective micromirror 30.

[0057] In this regard, pulse width modulation is performed such that for each micromirror pulse period, the modulation duty cycle 32 can be adjusted independently. That is, when the camera continuously captures images, changes in the pixel brightness level may cause the modulation duty cycle 32 to change. Therefore, when the brightness level increases, the modulation duty cycle 32 also increases accordingly, and vice versa.

[0058] Preferably, as Figure 3 shown, the modulation period 31 of the micromirror pulse 33 corresponding to the output beam period 41 is synchronized with the period 21 of the input beam 20. Additionally, optionally, the maximum possible modulation duty cycle 32 of the micromirror 30 is set to correspond to a constant duty cycle 22 of the input beam 20.

[0059] Thus, when the light source 2 does not provide irradiance, the operation of the micromirror 30 can be achieved without performing. Therefore, this can ensure the safe operating power of the device 1.

[0060] In Figure 3 two subsequent micromirror pulse periods of a single micromirror 30 are shown, and thus the sub-beam 40 is shown. The first modulation duty cycle 32 shown is less than the second modulation duty cycle 32', where for each modulation duty cycle 32, 32', the irradiance 42 is constant. Therefore, the patient including the retinal implant will perceive the corresponding area of the image to become brighter.

[0061] Furthermore, it can be seen in this figure that both the modulation duty cycles 32, 32' are shorter than the duty cycle 22. Therefore, the brightness level perceived by the patient is lower than the maximum possible perceivable brightness. For safety reasons, the duty cycle 22 is limited to 30% of the period 21, thus preventing retinal damage due to excessive irradiation.

[0062] To provide a redundant safety system, the duty cycle 32 of the micromirror 30 is also respectively limited to 30% of the period 21 or the modulation period 31. Therefore, in the case where the light source erroneously emits a constant beam, the maximum possible duty cycle of the output beam 4 is limited to the duty cycle 32 of the micromirror 30.

[0063] Therefore, even if the safety setting of the light source 2 fails, it can be achieved that no excessive irradiance hits the retina. Additionally, if the micromirror 30 cannot pulse and / or gets stuck in the "ON" position, the source pulse prohibits the pulse duration of the output beam 4 from being higher than the source pulse duration, that is, higher than the duty cycle 22.

[0064] Figure 4 Shows an exemplary embodiment of the waveform of the input beam 20, which substantially has the form of a pulsed wave, including a constant source irradiance 23, a constant duty cycle 22 of the pulse 24, and a constant period 21.

[0065] Below the waveform of the input beam 20, the mirror pulses 33, 33', 33" of three different mirrors 30 are shown, thereby generating three different sub-beams 40, 40', 40".

[0066] The mirror pulses 33, 33', 33" differ from each other in the duty cycles 32, 32', 32" of their respective pulses 34, 34', 34".

[0067] That is, the radiant power of each of the sub-beams 40, 40', 40" is different from that of the other sub-beams, where the first sub-beam 40 includes a lower radiant power than the second and third sub-beams 40', 40", and the second sub-beam 40' includes a lower irradiation power than the third sub-beam 40".

[0068] Thus, for example, when the first region 61 of the target pattern 6 is irradiated by the sub-beam corresponding to the sub-beam 40, the patient including the retinal implant perceives a darker gray value than the second region 62 irradiated by the sub-beam corresponding to the sub-beam 40' and the third region 63 irradiated by the sub-beam corresponding to the sub-beam 40", where the latter includes the brightest gray value.

[0069] Can be obtained from Figure 5 Examples of the above regions 61, 62, 63 of the target pattern 6 projected onto the modified retinal region 5 including the retinal implant are obtained.

[0070] Thus, through the above device 1 and the corresponding method, a photosensitive retinal implant including a pattern with different gray levels can be provided for the patient.

[0071] In addition, through the above, the power consumption for operating the method and / or the device 1 can be reduced and / or optimized, because the light source can be turned off between pulses and thus consume less energy between pulses and thus reduce the power consumption.

[0072] It is obvious to those skilled in the art that these embodiments and items only describe examples of various possibilities. Therefore, the embodiments shown herein should not be understood as forming a limitation on these features and configurations. Any possible combination and configuration of the described features can be selected according to the scope of the present invention.

[0073] List of reference numerals

[0074] 1. Device

[0075] 2. Light source

[0076] 20. Input light beam

[0077] 21. Period

[0078] 22. Duty cycle

[0079] 23. Irradiance

[0080] 24. Pulse

[0081] 3. Micromirror array

[0082] 30. Micromirror

[0083] 31. Modulation period

[0084] 32. Modulation duty cycle

[0085] 33. Micromirror pulse

[0086] 34. Pulse

[0087] 4. Output light beam

[0088] 40. Sub - beam

[0089] 41. Output light beam period

[0090] 42. Irradiance

[0091] 5. Modified retinal area

[0092] 6. Target pattern

[0093] 61. First zone

[0094] 62. Second zone

[0095] 63. Third zone

Claims

1. A method for projecting a target pattern (6) onto a modified retinal region (5) of a human eye, comprising: - providing a pulsed input beam (20), - modulating and dividing the pulsed input beam (20) into pulses of modulated pulsed sub-beams (40) and a modulated light pattern based on the target pattern (6), wherein the modulated light pattern forms a pulsed output beam (4) reflecting the target pattern (6), characterized in that performing single pulse width modulation on the modulation duty cycle (32) of the modulated individual sub-beams (40) forming the output beam (4), wherein the modulation period (31) is synchronized with the period (21) of the pulsed input beam (20), wherein the maximum single modulation duty cycle (32) of the individual sub-beams (4) corresponds to the duty cycle (22) of the pulsed input beam (20), wherein the duty cycle (22) of the pulsed input beam (20) relative to the period (21) of the pulsed input beam (20) is equal to or less than 0.5, and / or the maximum possible modulation duty cycle of the sub-beams (40) relative to the period (21) of the pulsed input beam (20) is equal to or less than 0.

5.

2. The method according to claim 1, wherein the input beam (20) comprises a constant peak irradiance (23), and / or the input beam (20) substantially comprises the form of a pulsed wave, and / or the input beam (20) comprises a constant period (21), and / or the input beam (20) comprises a constant duty cycle (22) or controls the duty cycle (22) of the input beam (21).

3. The method according to claim 1, wherein the duty cycle (22) of the pulsed input beam (20) relative to the period (21) of the pulsed input beam (20) is equal to or less than 0.4, and / or the maximum possible modulation duty cycle of the sub-beams (40) relative to the period (21) of the pulsed input beam (20) is equal to or less than 0.

4.

4. The method according to claim 3, wherein the duty cycle (22) of the pulsed input beam (20) relative to the period (21) of the pulsed input beam (20) is equal to or less than 0.3, and / or the maximum possible modulation duty cycle of the sub-beams (40) relative to the period (21) of the pulsed input beam (20) is equal to or less than 0.

3.

5. The method according to any one of claims 1-4, wherein the target pattern (6) is obtained by capturing visual information and dividing the captured visual information into a pixel pattern forming the target pattern (6), wherein the pixels reflect at least different brightness values within the visual information, if any.

6. The method according to claim 5, wherein the visual information is an image.

7. A device (1) for projecting a target pattern (6) onto a modified retinal region (5) of a human eye, comprising: - a light source (2) for providing a pulsed input beam (20), - A modulation micromirror array (3) for modulating and dividing the pulsed input beam (20) into a modulated light pattern of modulated pulsed sub - beams (40), wherein the orientation of each micromirror (30) of the micromirror array (3) can be independently controlled based on a target pattern (6) such that the sub - beams form a pulsed output beam (4) reflecting the target pattern (6). Characterized in that the device (1) forms and is adapted to perform individual pulse - width modulation of the sub - beams (40) forming the output beam (4) by independently controlling the modulation duty cycle (32) of individual micromirrors (30). the device (1) is further adapted to synchronize the modulation period (31) of the orientation control of the micromirrors (30) with the period (21) of the pulsed input beam (20). wherein the maximum individual modulation duty cycle (32) of the micromirrors (30) corresponds to the duty cycle (22) of the pulsed input beam (20); and wherein the duty cycle (22) of the pulsed input beam (20) relative to the period (21) of the pulsed input beam (20) is equal to or less than 0.5, and / or the maximum possible modulation duty cycle (32) of the sub - beams (40) relative to the period (21) of the pulsed input beam (20) is equal to or less than 0.

5.

8. The device (1) according to claim 7, wherein the duty cycle (22) of the pulsed input beam (20) relative to the period (21) of the pulsed input beam (20) is equal to or less than 0.4, and / or the maximum possible modulation duty cycle (32) of the sub - beams (40) relative to the period (21) of the pulsed input beam (20) is equal to or less than 0.

4.

9. The device (1) according to claim 8, wherein the duty cycle (22) of the pulsed input beam (20) relative to the period (21) of the pulsed input beam (20) is equal to or less than 0.3, and / or the maximum possible modulation duty cycle (32) of the sub - beams (40) relative to the period (21) of the pulsed input beam (20) is equal to or less than 0.

3.

10. The device (1) according to any one of claims 7 - 9, further comprising a camera for capturing visual information, and / or a processing unit for dividing the captured visual information into a pixel pattern forming the target pattern (6), wherein the pixels reflect at least different brightness values within the visual information, if any.

11. The device (1) according to claim 10, wherein the visual information is an image.

Images