System for performing confocal ophthalmoscopy

Abstract

The present invention relates to a system for performing confocal ophthalmoscopy, comprising an illumination device for illuminating a sample (13) and a lens arrangement having a plurality of lenses (6-11) for directing a light beam from the illumination device to the sample (13) and directing the light beam returning from the sample (13) to a detector (3). The present invention aims to provide a system capable of imaging with the best possible image quality, and therefore the present invention is characterized in that the illumination device has a DMD chip (2) that can direct the light beam to the sample (13) and can direct the light beam reflected and returning from the sample (13) to the detector (3).

Description

[Technical Field]

[0001] The present invention relates to a system according to the preamble of claim 1. [Background technology]

[0002] Scanning laser ophthalmoscopy (SLO) uses a laser. To examine the fundus, the laser is guided onto the fundus and shines light onto the fundus. When the light is reflected by the fundus, this reflected light is analyzed and used to obtain an image. The laser usually scans the fundus, generating a grid pattern. The grid pattern usually progresses from left to right and then vertically. In this way, a clear image of the area of ​​the fundus being examined can be obtained.

[0003] Scanning laser ophthalmoscopy is based on a similar principle to scanning laser microscopy, which uses the lens of the human eye as the objective, in contrast to scanning laser microscopy, in which an artificial objective is provided in the microscope.

[0004] Optical imaging in ophthalmology often uses conventional scanning techniques, including line scan systems and confocal scanning laser systems with two separate scanners for the X and Y directions.

[0005] Equipment for performing scanning laser ophthalmoscopy using conventional scanners typically includes relatively expensive components, such as a line camera and a vibrating scanner. Conventional line cameras have low optical sensitivity compared to individual detectors, and when used, imaging is confocal in only one axis. Vibrating resonant scanners can be prone to misalignment, exhibit sinusoidal motion, and sometimes generate significant noise. Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention is therefore based on the objective of defining a system capable of imaging with the best possible image quality. [Means for solving the problem]

[0007] The present invention achieves the above-mentioned object by means of the features of claim 1.

[0008] The illumination device therefore comprises a DMD chip that can direct a light beam onto the sample and direct the light beam reflected back from the sample onto a detector.

[0009] In accordance with the present invention, it was first recognized that imaging systems using so-called digital mirror devices (DMDs) as scanners are already known, and that in this known concept the DMD or DMD chip is used only as an illumination unit.

[0010] Furthermore, the prior art recognized that light returning from the eye, i.e., reflected or scattered light, does not return through the DMD chip, but is previously deflected by a beam splitter onto a high-resolution 2D camera chip, where it generates an image.

[0011] Furthermore, it was recognized that this structure is not confocal, resulting in poor image quality: high-resolution conventional CMOS or CCD camera chips have significantly lower light sensitivity compared to individual detectors.

[0012] It was also recognized that scanning the entire DMD chip pixel by pixel would result in relatively slow frame rates for high resolution images.

[0013] Finally, the present invention recognizes that a confocal architecture using a DMD chip can achieve high frame rates with high resolution. Such a system has the advantageous characteristics of good image quality due to the confocal architecture. The system has the advantage of having essentially no large moving parts, being absolutely optically stable, and being quiet.

[0014] The use of DMD chips ensures a long-life and robust technology, and the system has the advantage of providing robust digital imaging that is free from scanner drift, sine waves, jitter, etc.

[0015] A DMD chip consists of individual optical elements, i.e. tiny mirrors or micromirrors, which can be moved, and in particular tilted, independently of the other mirrors in order to redirect or reflect light incident on them from one direction in another.

[0016] In this context, a light beam or light beam bundle can be directed along the same optical path from the DMD chip to the sample and back from the sample to the DMD chip as a reflected light beam or light beam bundle, so that the same individual mirrors of the DMD chip can be used to illuminate the sample with the light beam or light beam bundle incident thereon and to receive the light beam or light beam bundle reflected from the sample. Thus, in this system, the pinhole size and pinhole shape can be tuned by interconnecting the individual mirrors of the DMD chip. Depending on the resolution, this system can be cost-effective, compact, and significantly less expensive than other scanning systems.

[0017] Here, the detector can be designed as an area detector and / or an MPPC array detector. In this way, a confocal structure and digital scanning with a DMD chip are possible. When using a human eye as a sample, on the object side, the DMD chip is imaged onto the retina, and on the detector side, the DMD chip is imaged onto the detector array.

[0018] The DMD chip has a surface divided into a predetermined number of segments, the detector also has a surface divided into a predetermined number of segments, and each segment of the DMD chip optically corresponds to a segment of the detector to generate an image, so that the DMD chip is optically imaged onto the detector array.

[0019] The segments of the DMD chip can all be equal in size, and the segments of the detector can all be equal in size. While the DMD chip can be configured with multiple mirrors to simulate individual segments, particularly their size, the detector actually has spatially / physically limited segments. Therefore, the DMD chip can be adjusted relative to the detector. Alternatively or additionally, the segments of the DMD chip can be the same size as the segments of the detector. Dividing the DMD chip and the detector into individual, identical segments allows them to be scanned in parallel.

[0020] Each segment of the DMD chip can be assigned exactly one segment of the detector, so that the DMD chip can be imaged or projected onto the surface of the sample to be examined on the sample side and onto the surface of the detector on the detector side. In this way, light returning from the sample or the eye can pass through the DMD chip and be directed onto a segmented detector or a segmented detector array. In this case, the DMD chip is not only used for illumination. The individual mirrors of the DMD chip act as pinholes, so that it actually exhibits a confocal effect. The size and shape of the pinholes are therefore variable.

[0021] The illumination device can have an illumination unit, from which light can be directed onto the DMD chip. In this way, the DMD chip can be used for illumination and become part of the illumination device. Alternatively, light from the illumination unit can be directed onto the DMD chip by a TIR prism. A TIR prism is generally two prisms stacked on top of each other, which provides a particularly compact way to direct incident light onto the DMD chip.

[0022] A beam splitter can be placed between the illumination unit and the DMD chip and / or TIR prism, which can deflect the light beam reflected from the sample onto the detector, so that the reflected light hits the detector and the confocal principle is maintained.

[0023] The light beam emitted from the illumination unit may be directed through a first lens and a second lens before hitting the TIR prism and / or the DMD chip, and thus a beam splitter may be disposed between the two lenses axially spaced apart from each other.

[0024] Against this background, a beam splitter can be placed between the first and second lenses, which allows the reflected light to be directed to a detector.

[0025] The light beam emitted from the DMD chip to the sample can be directed through only the excitation lens or the third lens, or optionally through fourth and fifth lenses, before hitting the sample. Either lens configuration can achieve a confocal design in which the lens of the human eye functions as part of the optical configuration. In some cases, only a single lens is used, resulting in a low parts count design, while in other cases, three lenses are used to easily accommodate, for example, additional optical components.

[0026] A detector lens or a sixth lens can be placed between the beam splitter and the detector. In this way, the light can be focused onto the detector. The sample or human eye is imaged onto the DMD chip and the detector.

[0027] Each individual mirror of the DMD chip can function as a pinhole aperture, so that each individual mirror of the DMD chip functions as a so-called pinhole, thus realizing the confocal principle.

[0028] In a configuration involving a system of the type described herein, the illumination device may have an illumination unit or a swept-source OCT illumination unit, the light emitted by which may be split into a sample arm and a reference arm, the optical signals from the sample arm and the reference arm may be superimposed at a detector so as to interfere with each other, and an evaluation device may generate an OCT image from the interference signal. In this way, the DMD chip is used for OCT imaging. The system used is characterized by fixed imaging.

[0029] The sample arm light can be directed to the DMD chip through a feed lens, and the reference arm light can be directed to the DMD chip through a deflection mirror or a reference beam splitter. If a swept-source OCT illumination unit is used, the unit illuminates the DMD chip.

[0030] The system described here can be used for both confocal scanning laser 2D imaging and OCT imaging, and in particular can be combined with swept-source OCT (SS-OCT).

[0031] The term Optical Coherence Tomography (commonly abbreviated as OCT) is understood as an imaging method that allows obtaining two- and three-dimensional images from light-scattering structures.

[0032] Although imaging of the retina of the human eye is described herein, the described system can be used for other applications. [Brief explanation of the drawings]

[0033] [Figure 1] 1 depicts a system for performing confocal ophthalmoscopy having multiple lenses between a DMD chip or TIR prism and a human eye. [Figure 2]Schematic representation of a detector (left) with a surface divided into segments, a DMD chip (center) with a surface divided into simulated segments, the size and number of segments corresponding to those of the detector, and an image (right) taken using the DMD chip and detector made up of segments. [Figure 3] 1 depicts a system for performing confocal ophthalmoscopy with only one lens between the DMD tip or TIR prism and the human eye. [Figure 4] 1 represents the configuration for OCT imaging. DETAILED DESCRIPTION OF THE INVENTION

[0034] 1 shows a system for performing confocal ophthalmoscopy, comprising an illumination device for illuminating a sample 13, and a lens arrangement having a plurality of lenses 6-11 for directing a light beam from the illumination device to the sample 13 and directing the light beam returning from the sample to a detector 3. The illumination device has a DMD chip 2 that can direct the light beam to the sample 13 and direct the light beam reflected back from the sample 13 to the detector 3.

[0035] In this regard, Figure 1 shows a schematic representation of the function of a confocal optical setup for imaging the fundus, in particular the retina 12. A human eye is used as sample 13. The setup comprises a system with an illumination device having an illumination unit 1 and a DMD chip 2.

[0036] The system further comprises a detector 3 designed as an MPPC array detector (MPPC stands for "Multi-pixel photon counter") and various other optical components for directing the beam, namely a beam splitter 4, a TIR prism 5 and various optical lenses 6-11.

[0037] The light beam or light beam bundle is guided along the same optical path when traveling from the DMD chip 2 to the sample 13 and when returning from the sample to the DMD chip 2 as a reflected light beam or light beam bundle, so that the same individual mirrors of the DMD chip 2 can be used to illuminate the sample 13 with the light beam or light beam bundle incident thereon and to receive the light beam or light beam bundle reflected from the sample 13.

[0038] The detector 3 is designed as an area detector, ie an MPPC array detector.

[0039] The center diagram of Figure 2 shows that the DMD chip 2 has a surface divided into a predetermined number of simulated segments 2a. The left diagram of Figure 2 shows that the detector 3 also has a surface divided into a predetermined number of segments 3a. Each of the segments 2a of the DMD chip 2 optically corresponds to a segment 3a of the detector 3, thereby generating the image 15 shown on the right side of Figure 2.

[0040] The segments 2a of the DMD chip 2 are all equal in size, and the segments 3a of the detector 3 are all equal in size. The segments 2a of the DMD chip 2 optically correspond to the segments 3a of the detector 3.

[0041] 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 of the retina 12 of the sample 13 to be examined, and on the detector side onto the surface of the detector 3. As a result, the retina 12 is imaged onto the DMD chip 2 and onto the detector 3.

[0042] The illumination device has an illumination unit 1, and light from the illumination unit 1 can be directed onto a DMD chip 2. In this manner, the DMD chip 2 is used to illuminate a sample 13. Figure 1 illustrates that light from the illumination unit 1 is directed by a TIR prism 5 onto the DMD chip 2, and from there towards the sample 13.

[0043] A beam splitter 4 is disposed between the illumination unit 1 and the TIR prism 5, which can deflect the light beam reflected from the sample 13 onto the detector 3. The light beam emitted from the illumination unit 1 can be directed through a first lens 6 and a second lens 7 before entering the TIR prism 5 and from there onto the DMD chip 2. The beam splitter 4 is disposed between the first lens 6 and the second lens 7.

[0044] The light beam emitted from the DMD chip 2 to the sample 13 is directed through a third lens 8, a fourth lens 9, and a fifth lens 10 before hitting the sample 13. The sample 13, in this case the human eye, uses its lenses 20 to deflect or focus the light beam or light beam bundle onto the retina 12.

[0045] A detector lens 11 or sixth lens 11 is placed between the beam splitter 4 and the detector 3. The individual mirrors of the DMD chip 2 act as pinhole apertures to limit the amount of light.

[0046] FIG. 3 shows another system constructed similarly to the system according to FIG. 1, but omitting two lenses from the lens arrangement.

[0047] In both the apparatus of Figures 1 and 3, the detector 3, the DMD chip 2, and the retina 12 of the eye 13 are optically imaged onto each other.

[0048] The DMD chip 2 consists of a large number of individually actuable mirrors, which are imaged onto the retina 12 via the above-mentioned optics. Each individual mirror can correspond to one pixel of the generated image 15. The surface area of ​​each individual mirror is very small; the diagonal of such a surface is approximately 10 μm.

[0049] The mirrors can be controlled and moved very quickly, with typical operating frequencies of 30 kHz or higher.

[0050] Detection is achieved by coupling a photosensitive detector 3 into the illumination path 14 via a beam splitter 4 to detect light returning from the sample 13, i.e. the eye. The DMD chip 2 is imaged via optics on the surface of the detector 3.

[0051] To generate image 15, the individual mirrors are switched individually at high speed to scan the fundus point by point, similar to conventional laser scanning systems.

[0052] In this way, light is directed from the mirrors through the optical path to the fundus. Light reflected or scattered at the fundus returns along the same optical path and is directed onto the detector 3 via each currently active mirror and beam splitter 4.

[0053] The intensity at the detector 3 is greatest when the light beam is reflected point-wise from the focal plane. Light from outside the focal plane is hardly reflected by the active mirror. In this way, the confocal principle is realized. The measured values ​​at the detector 3 are assigned to individual points, from which a two-dimensional image 15 can be constructed.

[0054] 2 illustrates the use of an area detector having multiple individually readable segments or channels 3a as detector 3, instead of individual photosensitive detectors. Accordingly, the DMD chip 2 is similarly divided into segments 2a.

[0055] The so-called pixel clock or image generation rate can be significantly increased by using segments operating in parallel.

[0056] The spatial separation (or division and parallel scanning of each segment) of the active mirrors or pixels of the DMD chip 2 maintains the confocal principle, in contrast to CCD or CMOS cameras.

[0057] The illumination unit 1 is used for uniform planar illumination of the optically active DMD chip 2. An aperture stop is imaged onto the DMD chip 2. Although in FIGS. 1 and 3 the beam is directed via a TIR prism 5, this can also be achieved without it. Since the light amount is distributed over the entire surface of the DMD chip 2 or the corresponding surface of the retina 12, a high light output is required. This can be achieved, for example, using IR LEDs.

[0058] Figure 4 shows an arrangement essentially including a system according to Figure 1. The illumination device comprises an illumination unit 1' or a swept-source OCT illumination unit 1', the light emitted by which can be split into a sample arm 16 and a reference arm 17, the optical signals from the sample arm 16 and the reference arm 17 can be superimposed in an interferometric manner by a detector 3, and an OCT image can be generated from the interference signal by an evaluation device.

[0059] Light from the sample arm 16 can be directed to the DMD chip 2 via the feed lens 18, the first lens 6, and the illumination path 14, and light from the reference arm 17 can be directed to the DMD chip 2 via a deflection mirror or reference light beam splitter 19 and the excitation lens 8.

[0060] Light in sample arm 16 travels from DMD chip 2 to sample 13. Light reflected from sample 13 returns to DMD chip 2 and from there passes through TIR prism 5 and beam splitter 4 onto detector 3.

[0061] The light in the reference arm 17 is directed by a separation lens 21 and a coupling lens 22 onto the reference light beam splitter 19, from where it is directed through an excitation lens 8 towards the DMD chip 2, and from there via a TIR prism 5 and a beam splitter 4 to the detector 3.

[0062] At the detector 3, the light beams of the sample arm 13 and the reference arm 17 interfere. By evaluating this interference, an OCT image can be generated.

[0063] In this regard, FIG. 4 depicts an extension of the system described herein for use in optical coherence tomography (OCT).

[0064] Figure 4 shows the optical setup for OCT imaging. The illumination unit 1' is designed here as a swept source and is divided into two arms: a sample arm 16 and a reference arm 17. At the detector 3, the optical signals from the sample arm 16 and the reference arm 17 are superimposed again and interfere. The lengths of the two arms 16, 17 must be adapted to each other.

[0065] For example, a frequency of 32 kHz can be operated using a swept source. Using 64 channels, an effective A-scan rate of 2 MHz can thus be achieved, which is eight times faster than a frequency of 250 kHz. 2D laser scanning, OCT, and patient display can be performed via the same DMD chip. Due to its compact dimensions, binocular solutions are also conceivable. [Explanation of symbols]

[0066] 1, 1' irradiation unit 2 DMD chips 3. Detector 4 Beam splitter 5 TIR Prism 6 First Lens 7 Second Lens 8 The Third Lens 9 The Fourth Lens 10 The Fifth Lens 11 Detector lens 12 Retina 13 Samples 14 Irradiation Path 15 images 16 Sample Arm 17 reference arm 18 Feed Lens 19 Reference beam splitter 20 Human eye lens 21 Separable lens 22 Coupling Lens

Claims

1. A system for performing confocal ophthalmoscopy, comprising an illumination device for illuminating a sample (13), and a lens arrangement having a plurality of lenses (6-11) for directing a light beam from the illumination device to the sample (13) and directing the light beam returning from the sample to a detector (3), The illumination device has a DMD chip (2) that can direct a light beam to the sample (13) and direct the light beam reflected back from the sample (13) to the detector (3). system.

2. 2. The system of claim 1, wherein a light beam or light beam bundle can be directed along the same optical path when traveling from the DMD chip (2) to the sample (13) and when returning from the sample to the DMD chip (2) as a reflected light beam or light beam bundle, so that the same individual mirrors of the DMD chip (2) can be used to illuminate the sample (13) with a light beam or light beam bundle incident thereon and to receive a light beam or light beam bundle reflected from the sample (13).

3. 3. System according to claim 1 or 2, characterized in that the detector (3) is designed as an area detector and / or an MPPC array detector.

4. The system according to any one of claims 1 to 3, characterized in that the DMD chip (2) has a surface divided into a predetermined number of segments (2a), the detector (3) has a surface similarly divided into a predetermined number of segments (3a), and each of the segments (2a) of the DMD chip (2) optically corresponds to a segment (3a) of the detector (3) to generate an image (15).

5. 5. The system of claim 4, wherein the segments (2 a) of the DMD chip (2) are all equal in size, the segments (3 a) of the detector (3) are all equal in size, and / or the segments (2 a) of the DMD chip (2) are equal in size to the segments (3 a) of the detector (3).

6. 6. The system according to claim 4 or 5, characterized in that each segment (2 a) of the DMD chip (2) is assigned exactly one segment (3 a) 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).

7. The system according to any one of claims 1 to 6, characterized in that the illumination device has an illumination unit (7) and can direct light from the illumination unit (1) onto the DMD chip (2), or can direct light from the illumination unit (1) onto the DMD chip (2) by a TIR prism (5).

8. 8. The system according to claim 1, wherein a beam splitter (4) capable of deflecting the reflected light beam onto the detector (3) is arranged between the illumination unit (1) and the DMD chip (2) and / or the TIR prism (5).

9. 9. The system according to claim 7 or 8, characterized in that the light beam emitted from the illumination unit (1) can be directed through a first lens (6) and a second lens (7) before hitting the TIR prism (5) and / or the DMD chip (2).

10. 10. A system according to claim 8 or 9, characterized in that the beam splitter (4) is arranged between the first lens (6) and the second lens (7).

11. The system according to any one of claims 1 to 10, characterized in that the light beam emitted from the DMD chip (2) to the sample (13) can be guided through the third lens (8) only or through the third lens (8), the fourth lens (9) and the fifth lens (10) before hitting the sample (13).

12. 12. The system according to any one of claims 8 to 11, characterized in that a detector lens (11) or a sixth lens (11) is arranged between the beam splitter (4) and the detector (3).

13. System according to any one of the preceding claims, characterized in that the individual mirrors of the DMD chip (2) function as pinhole apertures.

14. 14. An arrangement comprising a system according to any one of claims 1 to 13, characterized in that the illumination device comprises an illumination unit (1') or a swept-source OCT illumination unit (1'), the light emitted by which can be split into a sample arm (16) and a reference arm (17), the optical signals from the sample arm (16) and the reference arm (17) can be superimposed in an interferometric manner by the detector (3), and an evaluation device can generate an OCT image from the interference signal.

15. 15. The arrangement according to claim 14, wherein the light of the sample arm (16) can be directed to the DMD chip (2) via a feed lens (18) and the light of the reference arm (17) can be directed to the DMD chip (2) via a deflection mirror or a reference light beam splitter (19).

Images