System for carrying out a confocal ophthalmoscopy
Patent Information
- Application Number
- EP2023768810
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2022-11-22
- Filing Date
- 2023-09-07
- Publication Date
- 2025-10-01
AI Technical Summary
Conventional laser scanning ophthalmoscopy devices with classic scanners are expensive, have low light sensitivity, and produce non-confocal images due to the use of conventional CMOS and CCD camera chips, resulting in reduced image quality and slow frame rates.
A device utilizing a Digital Mirror Device (DMD) chip for both illumination and detection, allowing for a confocal structure with variable pinhole size and shape, achieved through individually movable mirrors, which enables high-resolution and high-frame-rate imaging with a compact and cost-effective design.
The device achieves excellent image quality with high frame rates, stability, and reduced noise, eliminating scanner drift and sinusoidal movements, while maintaining a confocal setup and being more cost-effective compared to traditional systems.
Smart Images
Figure 1.1
Abstract
Description
[0001] Device for performing confocal ophthalmoscopy
[0002] The invention relates to a device according to the preamble of claim 1.
[0003] Lasers are used in laser scanning ophthalmoscopy (SLO). A laser is passed over the back of the eye to examine it, emitting light onto it. The back of the eye reflects light, and this reflected light is analyzed and used to create an image. The laser typically scans the back of the eye, creating a grid pattern. The grid pattern typically runs from left to right and then vertically. This makes it possible to clearly image the area of the back of the eye under examination.
[0004] Laser scanning ophthalmoscopy is based on a similar principle to laser scanning microscopy. In contrast to laser scanning microscopy, laser scanning ophthalmoscopy uses the lens of the human eye as the objective lens. Laser scanning microscopy uses an artificial objective lens in a microscope. Conventional scanning technologies are often used for optical imaging in ophthalmology. These include line-scan systems or confocal scanning laser systems with two separate scanners for the X and Y directions.
[0005] Devices for performing laser scanning ophthalmoscopy with conventional scanners typically have relatively expensive components, such as line scan cameras or oscillating scanners. Conventional line scan cameras are less light-sensitive than single-detector cameras, and their imaging is confocal in only one axis. Oscillating resonant scanners are subject to adjustment, exhibit a sinusoidal motion, and can sometimes produce high levels of noise.
[0006] The invention is therefore based on the object of providing a device with which imaging with the best possible image quality is possible.
[0007] The present invention solves the above-mentioned problem by the features of claim 1.
[0008] According to this, the illumination device comprises a DMD chip, from which a light beam can be guided to a sample and from which a light beam reflected back to it by the sample can be guided to a detector.
[0009] According to the invention, it was first recognized that imaging systems that use so-called digital mirror devices (DMDs) as scanners are already known. It was then recognized that in these known concepts, the DMDs or DMD chips are used only as an illumination unit. Furthermore, it was recognized that in the prior art, the light returning from the eye, i.e., reflected or scattered, does not pass over the DMD chip again, but is first directed by beam splitters onto a high-resolution 2D camera chip, which then generates an image.
[0010] It has also been recognized that this setup is not confocal, which reduces image quality. Conventional high-resolution CMOS and CCD camera chips are significantly less light-sensitive than single detectors.
[0011] It has also been recognized that the frame rate for high-resolution images is relatively slow when the entire DMD chip is scanned pixel by pixel.
[0012] Finally, according to the invention, it was recognized that high frame rates with high resolution can be achieved using a confocal setup using DMD chips. Such a device is advantageously characterized by good image quality due to its confocal setup. The device advantageously has essentially no large moving parts, is optically absolutely stable, and is silent.
[0013] The use of DMD chips ensures the use of a long-lasting, robust technology. The device advantageously produces robust digital imaging that is free of scanner drift, sinusoidal waveforms, jitter, or similar phenomena.
[0014] A DMD chip is equipped with individual optical elements, namely very small mirrors or micromirrors. In order to direct or reflect light incident on a mirror from one direction into another direction, each individual mirror is movable, in particular tiltable, independently of the others. Against this background, a light beam or bundle of light beams could be guided along the same optical path from the DMD chip to the sample and from there back to the DMD chip as a reflected light beam or bundle of light beams, so that the same individual mirror of the DMD chip can be used to illuminate the sample with the light beam or bundle of light beams incident on it and to receive the light beam or bundle of light beams reflected by the sample. The device thus allows the realization of a variable pinhole size and shape by interconnecting individual mirrors of the DMD chip.Depending on the resolution, the device is cost-effective and compact and very affordable compared to alternative scanning systems.
[0015] The detector could be designed as an area detector and / or an MPPC array detector. This allows for a confocal setup with a DMD chip and digital scanning. On the object side, the DMD chip is imaged onto the retina when the human eye is used as the sample; on the detector side, the DMD chip is imaged onto a detector array.
[0016] The DMD chip could have a surface divided into a certain number of segments, with the detector having a surface also divided into a certain number of segments. The segments of the DMD chip optically correspond to the segments of the detector to generate an image. The DMD chip is thus optically imaged onto the detector array.
[0017] All segments of the DMD chip could be the same size, while all segments of the detector are the same size. Due to the large number of mirrors, the DMD chip can be configured to simulate individual segments, particularly their size, whereas the detector has real, spatially and physically limited segments. The DMD chip is therefore adjustable to the detector. Alternatively or additionally, the segments of the DMD chip could be the same size as the segments of the detector. Dividing the DMD chip and the detector into individual, equal segments allows them to be scanned in parallel.
[0018] Each segment of the DMD chip could be assigned exactly one segment of the detector, so that the DMD chip can be imaged or projected onto the sample area to be examined on the sample side and onto the detector surface on the detector side. This allows the light returning from the sample or the eye to pass over the DMD chip and be directed from there onto the segmented detector or a segmented detector array. The DMD chip is used for more than just illumination. The individual mirrors of the DMD chip function as pinholes, thus achieving a truly confocal effect. Therefore, the pinhole size and shape are variable.
[0019] The illumination device could comprise an illumination unit, with the light coming from the illumination unit being directed onto the DMD chip. The DMD chip can thus be used for illumination and is part of the illumination device. Alternatively, the light coming from the illumination unit can be directed onto the DMD chip using a TIR prism. A TIR prism typically consists of two laminated prisms that direct incident light onto a DMD chip in a particularly compact manner.
[0020] A beam splitter could be arranged between the illumination unit and the DMD chip and / or a TIR prism, from which a light beam reflected by the sample can be redirected to the detector. This allows the detector to be hit by reflected light, thus maintaining the confocal principle. A light beam emanating from the illumination unit could be guided through a first lens and a second lens before the light beam strikes the TIR prism and / or the DMD chip. This makes it possible to place a beam splitter between the two aforementioned lenses, which are axially spaced from each other.
[0021] Against this backdrop, a beam splitter could be arranged between a first lens and a second lens. This beam splitter can guide reflected light to the detector.
[0022] Light rays traveling from the DMD chip to the sample could be guided through an excitation lens or a third lens alone, or optionally further through a fourth lens and a fifth lens before impinging on the sample. Both lens configurations allow for a confocal setup in which the lens of the human eye functions as part of an optical arrangement. In one case, only a single lens is used to create a setup with few parts; in the other, three lenses are used, for example, to easily accommodate additional optical components.
[0023] A detector lens or sixth lens could be arranged between a beam splitter and the detector. This allows light to be focused onto the detector. The sample or the human eye is imaged on the DMD chip and the detector.
[0024] A single mirror of the DMD chip could function as a pinhole. Each individual mirror of the DMD chip thus acts as a so-called pinhole. This is how the confocal principle is realized. In an arrangement comprising a device of the type described here, the illumination device could have an illumination unit or swept-source OCT illumination unit, the emitted light of which can be split into a sample arm and a reference arm. The light signals from the sample arm and reference arm can be superimposed at the detector in such a way that they interfere, and OCT images can be generated from the interference signals using an evaluation device. Thus, a DMD chip is used for OCT imaging. The device used is characterized by a fixed image.
[0025] The light from the sample arm could be guided to the DMD chip via an injection lens, while the light from the reference arm could be guided to the DMD chip via a deflection mirror or reference beam splitter. When using a swept-source OCT illumination unit, this illuminates the DMD chip.
[0026] The device described here can be used for both confocal laser scanning 2D images and OCT imaging. In particular, the device described here can also be combined with swept-source OCT (SS-OCT).
[0027] Optical coherence tomography (OCT) is an imaging technique that can be used to obtain two- and three-dimensional images of light-scattering structures.
[0028] This description describes imaging of the retina of the human eye, but the device described can also be used for other applications. The drawing shows
[0029] Fig. 1 shows a device for performing confocal ophthalmoscopy with several lenses between the DMD chip or a TIR prism and the human eye,
[0030] Fig. 2 on the left, schematically shows a detector with a surface divided into segments, in the middle, schematically shows a DMD chip with a surface divided into simulated segments, where the size and number of segments correspond to those of the detector, and on the right, an image acquired with the DMD chip and the detector, which is composed of segments,
[0031] Fig. 3 shows a device for performing confocal ophthalmoscopy with only one lens between the DMD chip or a TIR prism and the human eye, and
[0032] Fig. 4 shows an arrangement for OCT imaging.
[0033] Fig. 1 shows a device for performing confocal ophthalmoscopy, comprising an illumination device for illuminating a sample 13, a lens arrangement with a plurality of lenses 6-11 for guiding light beams from the illumination device to the sample 13 and from there back to a detector 3. The illumination device has a DMD chip 2, from which a light beam can be guided to the sample 13 and from which a light beam reflected back onto it by the sample 13 can be guided to the detector 3. Fig. 1 schematically shows the function of a confocal optical arrangement for imaging the fundus of the eye, in particular the retina 12. The human eye serves as the sample 13. The arrangement comprises the device with an illumination device which has an illumination unit 1 and the DMD chip 2.
[0034] The device further comprises the detector 3, which is designed as an MPPC array detector, where MPPC stands for “multi pixel photon counter”, as well as various other optical components for beam guidance, namely a beam splitter 4, a TIR prism 5 and various optical lenses 6 to 11.
[0035] A light beam or light beam bundle is guided along the same optical path from the DMD chip 2 to the sample 13 and from there back to the DMD chip 2 as a returned light beam or light beam bundle, so that the same single mirror of the DMD chip 2 can be used to illuminate the sample 13 with the light beam or light beam incident thereon and to receive the light beam or light beam bundle reflected by the sample 13.
[0036] The detector 3 is designed as an area detector, namely as an MPPC array detector.
[0037] Fig. 2 shows, in the middle view, that the DMD chip 2 has a surface divided into a certain number of simulated segments 2a. Fig. 2 shows, in the left view, that the detector 3 also has a surface divided into a certain number of segments 3a. The segments 2a of the DMD chip 2 optically correspond to the segments 3a of the detector 3 to generate the image 15 shown on the right in Fig. 2. All segments 2a of the DMD chip 2 are the same size, and all segments 3a of the detector 3 are the same size. The segments 2a of the DMD chip 2 optically correspond to the segments 3a of the detector 3.
[0038] Each segment 2a of the DMD chip 2 is assigned exactly one segment 3a of the detector 3, so that the DMD chip 2 can be imaged or projected onto the area of the retina 12 of the sample 13 to be examined on the sample side and onto the surface of the detector 3 on the detector side. As a result, the retina 12 is imaged onto the DMD chip 2 and onto the detector 3.
[0039] The illumination device comprises the illumination unit 1, wherein the light coming from the illumination unit 1 can be guided to the DMD chip 2. Thus, the DMD chip 2 is used to illuminate the sample 13. Specifically, Fig. 1 shows that the light coming from the illumination unit 1 is guided to the DMD chip 2 by means of a TIR prism 5 and from there directed toward the sample 13.
[0040] A beam splitter 4 is arranged between the illumination unit 1 and the TIR prism 5, from which a light beam reflected by the sample 13 can be deflected onto the detector 3. A light beam emanating from the illumination unit 1 can be guided through a first lens 6 and a second lens 7 before the light beam strikes the TIR prism 5 and from there onto the DMD chip 2. The beam splitter 4 is arranged between the first lens 6 and the second lens 7.
[0041] Light rays traveling from the DMD chip 2 to the sample 13 are guided through a third lens 8, a fourth lens 9, and a fifth lens 10 before impinging on the sample 13. The sample 13 here is the human eye, whose lens 20 is used to redirect or focus light rays or light beam bundles onto the retina 12. A detector lens 11 or sixth lens 11 is arranged between the beam splitter 4 and the detector 3. A single mirror of the DMD chip 2 acts as a pinhole, limiting the amount of light.
[0042] Fig. 3 shows a further device which is constructed analogously to the device according to Fig. 1, but two lenses of the lens arrangement are omitted.
[0043] In both devices of Figs. 1 and 3, the detector 3, the DMD chip 2 and the retina 12 of an eye 13 are each optically imaged onto one another.
[0044] The DMD chip 2, which consists of many separately controllable mirrors, is imaged onto the retina 12 via the aforementioned optical components. Each individual mirror can correspond to a pixel of a generated image 15. The individual mirrors have very small surfaces. The diagonal of such a surface is approximately 10 μm.
[0045] The mirrors can be controlled and moved at very high speeds; typical movement frequencies are 30 kHz or higher.
[0046] Detection occurs by coupling the light-sensitive detector 3 into the illumination path 14 via the beam splitter 4 to detect light returning from the sample 13, namely the eye. The DMD chip 2 is imaged onto the surface of the detector 3 via optical components.
[0047] To generate image 15, the individual mirrors are switched individually at high speed, scanning the fundus point by point, similar to conventional laser scanning systems. The light is thus guided from a mirror via an optical path to the fundus. The light reflected or scattered at the fundus travels back along the same optical path and is guided to detector 3 via the currently active individual mirror and beam splitter 4.
[0048] The intensity at detector 3 is maximum when the light beam is reflected point-like from the focal plane; light from outside the focal plane is largely not reflected by the active mirror. This implements a confocal principle. Each individual point is assigned a measured value at detector 3, from which a two-dimensional image 15 can be composed.
[0049] Fig. 2 shows that instead of a single light-sensitive detector, an area detector with multiple segments or channels 3a, which can be read individually, is used as detector 3. Accordingly, the DMD chip 2 is also divided into segments 2a in the same way.
[0050] By using segments that work in parallel, the so-called pixel clock or the speed of image generation can be greatly increased.
[0051] Due to the spatial separation (or division and segments which scan in parallel) of the active mirrors of the DMD chip 2 or the pixels, the confocal principle is retained in contrast to a CCD or CMOS camera.
[0052] The illumination unit 1 provides homogeneous, planar illumination of the optically active DMD chip 2. An aperture stop is imaged onto the DMD chip 2. The beam is guided via a TIR prism 5 in Fig. 1 and Fig. 3, but can also be implemented without it. Since the light is distributed over the entire surface of the DMD chip 2 or the equivalent area of the retina 12, a high light output is required. This can be achieved, for example, with an IR LED.
[0053] Fig. 4 shows an arrangement which essentially comprises a device according to Fig. 1. The illumination device has an illumination unit T or swept-source OCT illumination unit T, the emitted light of which can be split into a sample arm 16 and a reference arm 17, wherein the light signals from the sample arm 16 and the reference arm 17 can be superimposed on the detector 3 in such a way that they interfere, and wherein OCT images can be generated from the interference signals by means of an evaluation device.
[0054] The light of the sample arm 16 can be guided via a feed lens 18 via the first lens 6 via the illumination path 14 to the DMD chip 2, wherein the light of the reference arm 17 can be guided via a deflection mirror or reference light beam splitter 19 via the excitation lens 8 to the DMD chip 2.
[0055] The light from the sample arm 16 travels from the DMD chip 2 to the sample 13. Light reflected from the sample 13 falls back onto the DMD chip 2 and from there via the TIR prism 5 and the beam splitter 4 to the detector 3.
[0056] The light of the reference arm 17 is guided by means of an output lens 21 and an input lens 22 to the reference light beam splitter 19 and from there through the excitation lens 8 in the direction of the DMD chip 2 and from there via the TIR prism 5 and the beam splitter 4 to the detector 3.
[0057] At detector 3, the light beams from sample arm 13 and reference arm 17 interfere. By analyzing the interference, OCT images can be generated. Figure 4 shows an extension of the device described here for use in optical coherence tomography (OCT).
[0058] Fig. 4 shows the optical setup for OCT images. The illumination unit T is designed as a swept-source light source and is divided into two arms, namely the sample arm 16 and the reference arm 17. At the detector 3, the light signals from the sample arm 16 and the reference arm 17 are superimposed again and interfere. The lengths of both arms 16 and 17 must be coordinated.
[0059] A frequency of 32 kHz, for example, could be achieved with a swept-source light source. With 64 channels, an effective A-scan rate of 2 MHz is achievable. This is eight times faster than a frequency of 250 kHz. 2D laser scanning, OCT, and a patient display could run on the same DMD chip. A binocular solution is also conceivable due to the compact dimensions.
[0060] List of reference symbols:
[0061] 1 , 1 ' lighting unit
[0062] 2 DMD chips
[0063] 3 Detector
[0064] 4 beam splitters
[0065] 5 TIR prism
[0066] 6 first lens
[0067] 7 second lens
[0068] 8 third lens
[0069] 9 fourth lens
[0070] 10 fifth lens
[0071] 11 Detector lens
[0072] 12 Retina
[0073] 13 Sample
[0074] 14 Lighting path
[0075] 15 images
[0076] 16 sample arms
[0077] 17 Reference arm
[0078] 18 Feed lens
[0079] 19 Reference light beam splitters
[0080] 20 lens of the human eye
[0081] 21 Output lens
[0082] 22 Coupling lens
Claims
Patent claims Device for carrying out confocal ophthalmoscopy, comprising an illumination device for illuminating a sample (13), a lens arrangement with a plurality of lenses (6-11) for guiding light beams from the illumination device to the sample (13) and from there back to a detector (3), characterized in that the illumination device has a DMD chip (2), from which a light beam can be guided to the sample (13) and from which a light beam reflected back onto it by the sample (13) can be guided to the detector (3).Device according to claim 1, characterized in that a light beam or light beam bundle can be guided along the same optical path from the DMD chip (2) to the sample (13) and from there back to the DMD chip (2) as a reflected light beam or reflected light beam bundle, so that the same individual mirror of the DMD chip (2) can be used to illuminate the sample (13) with the light beam or light beam bundle incident on it and to receive the light beam or light beam bundle reflected by the sample (13). Device according to claim 1 or 2, characterized in that the detector (3) is designed as an area detector and / or an M PPC array detector. Device according to one of the preceding claims, characterized in that the DMD chip (2) has an area that is divided into a specific number of segments (2a), wherein the detector (3) has an area that is also divided into a specific number of segments. (3a), and wherein the segments (2a) of the DMD chip (2) each optically correspond to the segments (3a) of the detector (3) in order to generate an image (15). Device according to claim 4, characterized in that all segments (2a) of the DMD chip (2) are of the same size, wherein all segments (3a) of the detector (3) are of the same size and / or that the segments (2a) of the DMD chip (2) are of the same size as the segments (3a) of the detector (3). Device according to claim 4 or 5, characterized in that each segment (2a) of the DMD chip (2) is assigned exactly one segment (3a) of the detector (3), so that the DMD chip (2) can be imaged or projected on the sample side onto the surface (12) of the sample (13) to be examined and on the detector side onto the surface of the detector (3).Device according to one of the preceding claims, characterized in that the illumination device comprises a lighting unit (1), wherein the light coming from the lighting unit (1) can be guided to the DMD chip (2) or wherein the light coming from the lighting unit (1) can be guided to the DMD chip (2) by means of a TIR prism (5). Device according to one of the preceding claims, characterized in that a beam splitter (4) is arranged between the lighting unit (1) and the DMD chip (2) and / or a TIR prism (5), from which beam splitter a reflected light beam can be deflected onto the detector (3).
9. Device according to claim 7 or 8, characterized in that a light beam emanating from the illumination unit (1) can be guided through a first lens (6) and a second lens (7) before the light beam strikes the TIR prism (5) and / or the DMD chip (2).
10. Device according to claim 8 or 9, characterized in that a beam splitter (4) is arranged between a first lens (6) and a second lens (7). 11 . Device according to one of the preceding claims, characterized in that light beams emanating from the DMD chip (2) to the sample (13) can be guided through a third lens (8) alone or through a third lens (8), a fourth lens (9) and a fifth lens (10) before they impinge on the sample (13).
12. Device according to one of claims 8 to 11, characterized in that a detector lens (11) or sixth lens (11) is arranged between a beam splitter (4) and the detector (3).
13. Device according to one of the preceding claims, characterized in that a single mirror of the DMD chip (2) functions as a pinhole.
14. Arrangement comprising a device according to one of the preceding claims, characterized in that the illumination device has an illumination unit (1') or swept source OCT illumination unit (1'), the emitted light of which can be split into a sample arm (16) and a reference arm (17), wherein the light signals from the sample arm (16) and the reference arm (17) can be superimposed on the detector (3) in such a way that they interfere, and wherein OCT images can be generated from the interference signals by means of an evaluation device. The arrangement according to claim 14, characterized in that the light from the sample arm (16) can be guided to the DMD chip (2) via a feed lens (18), wherein the light from the reference arm (17) can be guided to the DMD chip (2) via a deflection mirror or reference light beam splitter (19).