Ophthalmic microscope with micromirror balance

Abstract

An ophthalmic microscope has an illumination device (9) for projecting light onto an eye (10) to be observed and a microscope device (8) with a camera (16) for viewing the eye. The illumination device (9) generates pulsed light. The light is pulsed at at least twice the camera frame rate to reduce flicker. The illumination device (9) uses columns of a micromirror array as spatial light modulators (24) and controls the mirrors to achieve balanced deflection within a frame period, which increases the service life of the microscope.

Description

Technical Field

[0001] The present invention relates to an ophthalmic microscope, in particular a slit lamp microscope, having an illumination device adapted to generate illumination pulses on the eye and a microscope apparatus having a camera for recording images of the eye. In particular, it relates to a microscope in which the illumination device comprises an electronically controlled spatial light modulator comprising a two-dimensional array of micromirrors.

[0002] The invention also relates to a method for operating such a device. Background Art

[0003] US 5943118 describes an ophthalmic microscope having an illumination device for generating illumination pulses and a microscope having a camera. The device includes an electronically controlled spatial light modulator comprising an array of micromirrors, each of which can be electronically controlled and brought into an on or off position, which allows the generation of an arbitrary illumination pattern on the eye to be observed. Summary of the Invention

[0004] The problem to be solved by the present invention is to increase the service life of such equipment.

[0005] This problem is solved by the device and the method according to the independent claims.

[0006] Thus, the present invention relates to an ophthalmic microscope comprising at least the following elements:

[0007] i) Illumination device for generating illumination pulses: The illumination device is adapted and configured to generate individual light pulses for illuminating the eye to be examined. It comprises at least the following elements:

[0008] a) At least one light source: This is the part of the lighting device that generates light.

[0009] b) Electronically controlled spatial light modulator: This part is constructed to spatially modulate light. The spatial light modulator comprises a two-dimensional array of micro-mirrors, each micro-mirror being individually deflectable to a first and a second position. In this context, the micro-mirrors are advantageously of a size less than 1 mm. 2 , especially less than 100mm 2 area of ​​the reflector.

[0010] c) Illumination imaging optics: This part is configured to project light onto the eye. Advantageously, it projects the image of the spatial light modulator onto the eye, thereby generating a defined illumination pattern on the eye.

[0011] ii) Microscope apparatus: The microscope apparatus is suitable for recording images of the eye. It comprises at least the following elements:

[0012] a) Microscopic optical device: The microscopic optical device generates an image of the eye.

[0013] b) At least one electronic camera: The camera is adapted to record an image of the projection from the microscopic optical device. The image is recorded in repetitive frame cycles. In each frame cycle, the camera records one frame of the image.

[0014] iii) Control unit: The control unit controls the operation of the elements of the device.

[0015] According to a first aspect of the invention, the camera has a frame signal output which carries a signal indicating the time at which the camera records a frame. In particular, it can generate a single pulse synchronized with each frame it employs, i.e., synchronized with the integration phase of that frame.

[0016] The control unit is configured to bring each micro - mirror of the spatial light modulator into a first position during a time t1 and into a second position during a time t2 for a set of N ≤ 100 consecutive frame cycles of the camera. In other words, t1 corresponds to the time during which a given micro - mirror is in its first position during the set of N consecutive frame cycles, and t2 corresponds to the time during which the given micro - mirror is in its second position during the same set of N consecutive frame cycles. According to the invention, t1 and t2 are balanced in the sense that 0.1 < t1 / t2 < 10.

[0017] It is noted that for at least some of the micro - mirrors, t1 and t2 are generally different, i.e., in the most general case, t1 and t2 depend on the position i, j of the mirror in the modulator.

[0018] The invention contemplates the following aspect: increasing the service life of such a spatial light modulator by balancing the positions of the micro - mirrors. For light modulators used in image or movie projection, this balancing is naturally achieved by the continuous change of the image or movie frames and their RGB channels. However, in an ophthalmic microscope, for a large number of examinations, the illumination pattern is the same or similar, which leads to an imbalance in the positions of the mirrors. This imbalance can be compensated by simply moving the mirrors to their less - used positions when the microscope is not being used for examination. However, the invention is based on the understanding that balancing can also occur when the device is in use (i.e., when recording consecutive frames). This eliminates the need to perform balancing when the device is not in use.

[0019] Advantageously, balancing is performed on each individual frame cycle, i.e., N = 1. This simplifies the operation of the device as it eliminates the need to "schedule" the mirror positions over two or more frame cycles.

[0020] The closer the ratio of t1 to t2 is to 1, the better the balancing becomes. Thus, advantageously, 0.2 < t1 / t2 < 5, particularly 0.33 < t1 / t2 < 3.

[0021] The light source is advantageously pulsed, ie the control unit is configured to pulse the light source. Advantageously, this is done in a manner synchronized with the frame period of the camera.

[0022] If the microscope uses pulsed illumination, the control unit can be adapted to:

[0023] - bringing the pixel into a given configuration during the dark phase preceding a given light pulse, and

[0024] - Light pulses are only activated when the pixel is in the desired configuration.

[0025] In this case, the dark phase is before the light modulator is set up with the light pulse. This setting can take some time, for example because the pixels are slow or because it takes time to feed the pattern information sequentially into the light modulator, so it is best done before the light pulse.

[0026] The device may further comprise several light sources and at least one light detector adapted to measure the light intensity at a position between the light source and the spatial light modulator, i.e. the brightness of the light source independent of the state of the light modulator. In that case, the method or the control unit may be adapted to perform at least the following two steps:

[0027] - Put the light modulator into non-transmissive mode: In this mode, no light is projected onto the eye even if the light source is turned on.

[0028] - When the light modulator is in the non-transmissive mode, a light source is pulsed to measure the brightness of the light source.

[0029] This allows the current brightness of the light source to be controlled intermittently, in particular while recording a series of image frames. This information can then be used, for example, to adjust the current through the light source during a light pulse, while simultaneously recording the on-time of the pixels of the light modulator as the frame is recorded, in order to achieve a defined illumination. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The present invention will be better understood and other objects besides those set forth above will become apparent when the following detailed description is considered. This description refers to the accompanying drawings, in which:

[0031] Figure 1 An embodiment of an ophthalmic microscope is shown,

[0032] Figure 2 shows an embodiment of components of a lighting device,

[0033] Figure 3 is a schematic representation of a micromirror-based spatial light modulator, and

[0034] Figure 4 An embodiment of a timing diagram for various components of a device is shown. DETAILED DESCRIPTION

[0035] Overview

[0036] Figure 1 An embodiment of an ophthalmic microscope, in particular a slit lamp microscope, is shown.

[0037] The microscope has a base 1 placed on a table, for example, a translationally displaceable stage 2 mounted to the base 1 , a first arm 3 , and a second arm 4 .

[0038] The stage 2 can be linearly displaced relative to the base 1 along the horizontal directions x and z.

[0039] The arms 3 and 4 are mounted to the stage 2 and pivot about a common vertical pivot axis 5 (ie an axis parallel to the vertical direction y).

[0040] The apparatus may further comprise a headrest 7 mounted to the base 1 for receiving the patient's head.

[0041] Arm 3 carries microscopy equipment 8 and arm 4 carries lighting equipment 9 (such as a slit lamp).

[0042] The microscope apparatus 8 has an optical axis 12. It comprises microscope optics 14, 15 (such as an objective 14 and zoom optics 15) which project an image of the eye 10 onto a camera 16 and optionally an eyepiece 18. A beam splitter 20 may be provided to split the light between these components.

[0043] The illumination device 9 is adapted to project a structured light beam onto the eye to be examined 10. It comprises a light source 22, a spatial light modulator 24 and illumination imaging optics 26.

[0044] The light source 22 may for example comprise several units emitting different wavelengths, for example in the red, green, blue and infrared ranges of the spectrum. These units may be controlled separately in order to change the color of the light source 22.

[0045] Advantageously, the light source 22 comprises at least one LED and / or semiconductor laser. This type of light source is advantageous because LEDs and semiconductor lasers can be pulsed quickly and precisely.

[0046] Illumination imaging optics 26 projects light from modulator 24 onto the front surface of, for example, eye 10, e.g., via a mirror 28 mounted to arm 4. Assume that the front surface of eye 10 is located at target plane 11, which is an optically conjugate plane of spatial light modulator 24 with respect to illumination imaging optics 26.

[0047] The lighting device 9 may be arranged above or below the reflector 28 .

[0048] The control unit 32 controls the components of the microscope. In particular, it may comprise, for example, a microprocessor 34 and a memory 36. The microprocessor 34 is programmed to perform the steps of the method described below, and the memory 36 contains data and / or instructions for doing so.

[0049] The camera 16 is adapted to record a series of individual frames of the image projected thereon.

[0050] It has a frame signal output 38a which carries a signal indicating the time at which a frame is recorded. It also has a data output 38b for transmitting the recorded image. Both outputs 38a, 38b can be connected to the control unit 32.

[0051] The camera 16 may be, for example, a CCD camera or any other semiconductor-based camera (such as Sony's IMX series cameras).

[0052] In semiconductor cameras, the process of recording a frame involves integrating the light signal over a certain period of time. At the end of the integration period, the image can be read out.

[0053] The signal at the frame signal output 38a is synchronized with this integration phase and, depending on the camera type, it may be emitted, for example, at the beginning or at the end of the integration phase.

[0054] lighting equipment

[0055] Figure 2 A more detailed embodiment of an illumination device 9 is shown. It is designed to project an illumination field with a well-defined, sharp outline onto a target, such as an eye 10. For example, the illumination field can be circular, rectangular, or slit-shaped. Even though the illumination device is referred to herein as a "slit lamp," the illumination field need not be slit-shaped at all. It can take any shape.

[0056] In this embodiment, the lighting device 9 includes four light sources 22a-22d having different spectral emission characteristics. For example, they may include an infrared light source, a red light source, a green light source, and a blue light source. Advantageously, the light sources are LEDs. In particular, each light source may be a single LED.

[0057] The light from each light source is substantially collimated by means of collimating optics 40a-40d.

[0058] Three dichroic mirrors 42a, 42b, 42c are used to combine the light from the light sources 22a-22d into a coaxial beam.

[0059] The combined light passes through homogenising optics 44, such as a fly's eye lens array, for example as described in US 6,507,434.

[0060] The two cylindrical lenses 46a, 46b, another lens 46c and the homogenizing optics 44 together also widen the beam in one direction, e.g. giving it an elongated cross-section, e.g. with an aspect ratio of 16:9, to better match the typical available form factor of a spatial light modulator.

[0061] The reflector 48 deflects the light into an assembly of two prisms 50a, 50b with a gap 52 therebetween.

[0062] The light beam passes through prism 50 a , gap 52 , and prism 50 b and reaches spatial light modulator 24 .

[0063] In the embodiment shown, the spatial light modulator 24 is a DMD ("digital micromirror device") having a two-dimensional array of individually deflectable micromirrors. The control unit 32 is adapted to control the alignment of each micromirror, for example between a first and a second position.

[0064] Figure 3 A cross-sectional view of two micro-mirrors 60 of such a DMD is shown schematically. Each mirror 60 is held by a resilient support 62 and can be deflected by means of an electrode 64. Devices of this type are known to those skilled in the art.

[0065] For the micro-mirror 60 in the first position, light travels along Figure 2 The light traveling in this direction 54 is reflected back into the prism 50b. The light traveling in this direction 54 is subjected to total internal reflection at the interface between the second prism 50b and the gap 52 and is reflected into the Figure 2 In the direction indicated by 56.

[0066] With the micro-mirror 60 in the second position, light is still reflected back to the prism 50b, but in a different direction ( Figure 2 ), along which direction it does not satisfy the conditions for total internal reflection at the interface with gap 52. The small portion that remains reflected at this interface will travel in a direction different from direction 56 and will not be further processed by the illumination imaging optics 26 described below.

[0067] Thus, the control unit 32 is able to individually set each pixel of the spatial light modulator 24 (each micromirror 60) to an on and off state, thereby defining the profile and shape of the light field at the target 10 (which is assumed to be located in the target plane 11 of the lighting device).

[0068] Light from a pixel of spatial light modulator 24 enters illumination imaging optics 26 , which may include one or more lenses. From there, it passes through mirror 28 to target 10 .

[0069] The illumination imaging optics images the spatial light modulator 24 onto the target 10 , ie, the target 10 is at a target plane 11 , which is a conjugate plane of the plane 62 of the spatial light modulator 24 with respect to the illumination imaging optics 26 .

[0070] operate

[0071] The process of recording a series of frames with the aid of the camera 16 is Figure 4 Shown in.

[0072] As from Figure 4 As can be seen in the first row, the camera goes through integration and processing stages, which can also be at least partially overlapped.

[0073] During each integration phase, the pixels of the camera integrate the light that hits them. The corresponding signals are then locked, converted into digital values, and read out by the control unit 32 during the processing phase. This process repeats itself in repeated frame periods.

[0074] Advantageously, the camera 16 operates in a free-running mode, ie, it repeatedly records frames without waiting for an external trigger signal. This allows the camera 16 to be operated at a high frame rate.

[0075] Each integration phase is marked by a camera synchronization signal, e.g. Figure 4 If the camera 16 is operating in free-running mode, this is the signal on the frame signal output 38a.

[0076] Depending on the specific hardware used, the signal “camera sync” can, for example, coincide with the start or end of the integration phase.

[0077] The control unit 32 operates the spatial light modulator 24 and the light source 22 in synchronization with the "camera sync" signal, such as Figure 4 As shown in the third to fifth rows of

[0078] In the embodiment shown, the control unit 32 operates the lighting device 9 in four operating phases I1, I2, I3, and I4 during one frame period. These phases are repeated in each frame period. The camera's integration phase falls within the operating phase I1, while the operating phases I2-I4 are outside the integration phase.

[0079] In the operating phase I1, the spatial light modulator 24 is configured for a suitable configuration (pattern) PI of pixels. Advantageously, this configuration is fully set before the integration phase begins (see Figure 4 ).

[0080] Only then is the light source 22 turned on (see Figure 4 ) to start the first light pulse L1.

[0081] In the example shown, configuration P1 is maintained throughout the entire integration phase. Furthermore, the light source 22 remains switched on throughout the entire integration phase (light pulse L1 ).

[0082] When the integration phase is over, the light source 22 is switched off.

[0083] The integration phase may be shorter than the first operating phase I1 .

[0084] In the operating phase I2, the spatial light modulator 24 enters the second configuration (mode) P2, while the light source 22 remains off.

[0085] In the operating phase I3 , the spatial light modulator 24 enters the third configuration (mode) P3 and the light source 22 is switched on again in order to generate light pulses L2 , which are switched off again before or at the end of the operating phase I3 .

[0086] In the operational phase I4, the spatial light modulator 24 is set to the fourth configuration (mode) P4 and the light source 22 remains off.

[0087] The process is then repeated with phases I1 - I4 and possibly different configurations P1 ', P2', P3', P4'.

[0088] In one embodiment, the configuration is as follows:

[0089] The configuration P1 corresponds to the desired illumination pattern during the recording of the corresponding frame. It can remain constant throughout the integration phase. Alternatively, however, it can be changed during the integration phase, for example by switching individual pixels from their on state to their off state in order to individually reduce the illumination brightness of said pixels.

[0090] Configuration P3 advantageously corresponds to configuration P1, i.e. it has the same pixel switching on and off as configuration P1. This generates two identical illumination patterns at twice the frame rate at the eye, thus reducing flicker as described above.

[0091] Configurations P2 and P4 are advantageously the "inverse" of configurations P1 and P3, i.e., when a pixel is on in configurations P1 or P3, the same pixel is off in configurations P2 and P4, and vice versa. This is based on the understanding that by periodically placing each mirror in its two positions for similar periods of time, the time until the DMD spatial light modulator fails can be increased. This embodiment uses the dark phase between light pulses L1, L2 to achieve this.

[0092] Advantageously, the operating stages I1-I4 have equal or similar lengths to compensate for strains in the support 62 of the mirror 60 of the spatial light modulator 24. Advantageously, the length of the longest of the operating stages II-I4 is no more than 10 times, in particular no more than 5 times, and in particular no more than 3 times, the length of the shortest of the operating stages I1-I4.

[0093] Figure 4 The solution achieves two goals:

[0094] 1. It balances the mirror deflections in the spatial light modulator 24, thereby reducing modulator aging.

[0095] 2. It allows light pulses to be generated at double the frame rate of the camera 16, thereby reducing flicker.

[0096] To achieve objective 1, more generally, the control unit 32 can be configured to, over one frame period of the camera 16 (i.e., over one period of the integration and processing phase), i.e., for each frame, cause each micromirror 60 of the spatial light modulator 24 to enter its first position during time t1 and to enter its opposite second position during time t2, wherein t1 and t2 are comparable, i.e., wherein

[0097] 0.1 <t1 / t2<10, (1)

[0098] Especially among them

[0099] 0.2 <t1 / t2<5, (2)

[0100] Especially among them

[0101] 0.33 <t1 / t2<3。 (3)

[0102] To achieve objective 2, more generally, the control unit 32 can be configured to generate at least two separate light pulses over one frame period of the camera 16, i.e., for each frame, where one of the light pulses falls into the integration phase of the camera 16 and the other (one or more) light pulses fall outside the integration phase.

[0103] Advantageously, the light pulses L1, L2 have equal duration (particularly within 10%), and the spatial light modulator 24 has the same configuration (pattern) for all light pulses, and the light pulses are separated by dark phases of equal length (i.e., the dark phases have equal lengths, particularly within 10%). This further reduces flicker.

[0104] Advantageously, the repetition rate of the light pulses is at least 70 Hz.

[0105] If Goal 1 is not required (eg, because a spatial light modulator that is insensitive to unbalanced pixel settings, such as an LCD modulator, is used), then the configuration of spatial light modulator 24 can be any mode during operating phases 12 and 14.

[0106] If target 2 is not required (eg because the frame rate of camera 16 is inherently high enough to avoid flickering effects), then operation phases I3 and I4 may be omitted.

[0107] If both objectives 1 and 2 are to be achieved, the control unit 32 is advantageously adapted to cause the spatial light modulator 24 to enter configurations P2 and P4 between the light pulses L1, L2 that are opposite to the configurations P1 and P3 during the light pulses. In this context, "opposite" first and second configurations means that if in the first configuration a given pixel is in its first state during time ta and in its second state during time tb, then in the second configuration it will be (with an accuracy of 10% or better) in the first state during time tb and in the second state during time ta.

[0108] if Figure 4 If the process shown in is to be synchronized with the frame signal output terminal 38a, then the operating phases I1-I4 should be synchronized with the integration phase of the camera 16 so that each integration phase falls within a defined position of the first operating phase I1.

[0109] To this end, the control unit 32 is advantageously adapted to predict the time when the camera 16 will record the next frame, since, for example, it may be necessary to configure the spatial light modulator 24 before the integration phase of the camera 16 begins, i.e. - before Figure 4 In the embodiment - before the camera synchronization pulse arrives.

[0110] For this purpose, the control unit 32 may, for example, use an estimate of the time tf between two consecutive frames.

[0111] This estimate of the time tf may for example be a value stored by the manufacturer in the control unit 32. Alternatively, the control unit 32 may measure it during operation, ie it may determine it from the time at which the camera 16 recorded the previous frame.

[0112] Then, depending on the time at which the camera 16 recorded the last frame, ie depending on the time of the last camera synchronization pulse, the time of the next camera synchronization pulse, ie the time of the next integration phase, can be predicted.

[0113] This allows the control unit 32 to prepare at least a part of the lighting device 9, such as the spatial light modulator 34 and / or the light source 22, before the predicted time of the next integration phase.

[0114] Position balance of micromirrors

[0115] As mentioned above with reference to relationships (1), (2), or (3), the position of the micromirror 60 is advantageously balanced, at least to some extent, to reduce mechanical strain.

[0116] This balance occurs over no more than N consecutive frame periods of the camera, i.e., it is not satisfied within each single frame period, but rather over the total times t1 and t2 of a larger number N of frame periods, where N ≤ 100, which can satisfy relations (1), (2) or (3).

[0117] However, advantageously, relations (1), (2) or (3) are satisfied for a smaller number of periods, such as N≤10, to further reduce asymmetric strain.

[0118] In the most advantageous embodiment, N=1, i.e., balancing in the sense of relations (1), (2), or (3) occurs over each single frame period. This greatly simplifies the control of the device, since it eliminates the need to "plan" the mirror positions over two or more frame periods.

[0119] During the period when the light source is operating and the camera is integrating, the position of each micro-mirror 60 is given by the amount of light to be generated for the corresponding pixel. Therefore, the balancing to satisfy the relationship (1), (2) or (3) advantageously occurs during the time when at least one of the following conditions is satisfied:

[0120] -The camera is not integrating, and / or

[0121] -The light source is not on.

[0122] Advantageously, however, the balancing occurs when the light source is not illuminated, thereby reducing the risk of unwanted glint in the patient's eye.

[0123] Note that for at least some micro-mirrors, t1 and t2 are typically different, i.e., in the most general case, t1 and t2 depend on the positions i, j of the mirrors in the modulator, i.e., if i≠i' and / or j≠j', then t1(i,j) can be different from t1(i',j').

[0124] For example, one pixel can remain dark while integrating the image, while another pixel can remain bright while integrating the image. Even a third pixel can remain bright during the first part of the integration and switch to dark during the second part of the integration to achieve pixel-by-pixel brightness modulation. In these cases, the times t1 and t2 can be different for two or all three types of pixels.

[0125] This technique is particularly important if there is only a single light source or if there are several light sources that are turned on in an overlapping manner, i.e. if there is at least one time in the frame period when all the light sources are on (especially during the camera integrating the image (i.e. recording the frame)). This is in contrast to RGB projector systems, where the color channels are projected sequentially, i.e. only one color channel is active at a time - in such systems, balancing is much easier to achieve.

[0126] Brightness and / or color monitoring

[0127] The lighting device 9 may further comprise at least one light sensor for monitoring the brightness of the light source(s).

[0128] Such sensors allow monitoring and control of the brightness of the light sources 22a-22d, as their efficiency varies with temperature and depending on the age of the light sources.

[0129] In particular, the control unit 32 may be adapted to monitor the brightness of the light source to generate calibration parameters and to use these calibration parameters to control the light source, eg by adjusting the current to the light source.

[0130] For example, and as Figure 2 As shown in FIG, there may be one such light sensor 58a, 58b, 58c, 58d associated with each light source 22a, 22b, 22c, 22d positioned to receive a portion of the light from its light source and generate a signal indicative of its brightness.

[0131] However, a single light sensor 58 can advantageously be positioned to measure the light from all of the several light sources 22a-22d. This can be achieved, for example, by positioning sensor 58 at a location where the light from all of the light sources 22a-22d is combined, for example by utilizing parasitic reflections from dichroic beam splitter 42c, which is the last dichroic beam splitter. This is optimized to project all light onto spatial light modulator 24. However, since it is not a perfect dichroic beam splitter in reality, a small portion of the light from each light source is reflected off the optical axis of the lighting device and can be used to monitor brightness 58 using light sensor 58.

[0132] In this embodiment, in order to measure the brightness of each light source individually, the control unit 32 can be equipped to perform a calibration measurement outside the integration phase of the camera 16. Such a calibration measurement may comprise the following steps:

[0133] - Placing the spatial light modulator 24 in a non-transmissive configuration.

[0134] Exactly one of the light sources 22a-22d is switched on and the brightness signal of the light source is measured by means of the light sensor 58.

[0135] As mentioned, this approach is best performed when the device includes a light sensor 58 positioned to measure the light from all several light sources. In particular, this light sensor is arranged to receive off-axis light from the last dichroic beam splitter used to combine the light from the light sources.

[0136] This calibration phase is performed for all light sources sequentially, either in the same frame period of the camera 16 or in separate frame periods.

[0137] The calibration phase can be inserted, for example, during, before or immediately after the operating phases I2 or I4.

[0138] Optionally, the modes in configurations I2 and I4 may be adapted to compensate for the time that the mirror spends in its closed position during the calibration phase, so as to maintain the condition of equation (1).

[0139] This monitoring is particularly useful when the lighting device includes several light sources 22a-22d of different colors, such as red, green and blue LEDs. In this case, the brightness of each of them can be monitored, which allows the relative brightness values ​​of the light sources to be adjusted in order to maintain the desired spectral composition (i.e., hue, such as the desired color temperature of white light), advantageously in a control loop.

[0140] Thus, advantageously, the light sources 22a-22d have different colors (i.e., their central wavelengths differ by at least 20 nm). In that case, the method performed by the control unit of the device may comprise the step of using calibration measurements for the light sources 22a-22d in order to maintain a desired relative brightness between at least two of the light sources 22a-22d when they are switched on simultaneously while recording frames with the aid of a camera.

[0141] notes

[0142] In the above embodiments, the lighting device 9 comprises several individual light sources 22a-22d, for example two, three, four or even more light sources. However, it may also comprise only a single light source, such as a white light LED.

[0143] In a first aspect of the invention, the camera 16 generates a main signal for triggering the lighting device 9, ie, Figure 3 The signal "camera sync" in is generated by the camera 16. However, in other embodiments of the invention, the camera 16 can also be operated in a trigger mode, i.e. it integrates frames upon receipt of an external trigger. In that case, the control unit 32 can, for example, generate a trigger signal that triggers the recording of frames by means of the camera 16, i.e. Figure 4 The signal “camera sync” in may be generated not by the camera 16 but by the control unit 32 .

[0144] While there are shown and described presently preferred embodiments of the invention, it is to be distinctly understood that the invention is not limited thereto but may be otherwise variously embodied and practiced within the scope of the appended claims.

Claims

1. An ophthalmic microscope, comprising i) an illumination device (9), which generates illumination pulses (L1, L2) and has a) at least one light source (22, 22a - 22d), b) an electronically controlled spatial light modulator (24), comprising a two-dimensional array of micromirrors (60) that can be individually deflected to a first position and a second position, and c) illumination imaging optics (26), ii) a microscope device (8), having a) microscope optics (14, 15) and b) at least one electronic camera (16), and iii) a control unit (32), wherein the control unit (32) is configured to bring each micromirror (60) of the spatial light modulator (24) into the first position during a time t1 and into the second position during a time t2 for a set of N ≤ 100 consecutive frame periods of the camera (16), where 0.1 < t1 / t2 < 10.

2. The microscope according to claim 1 where 0.2 < t1 / t2 < 5, and / or where t1 / t2 > 0.6 or t1 / t2 < 0.

4.

3. The microscope according to claim 1 where 0.33 < t1 / t2 < 3, and / or where t1 / t2 > 0.6 or t1 / t2 < 0.

4.

4. The microscope according to any one of the preceding claims 1 - 3, wherein N ≤ 10.

5. The microscope according to any one of the preceding claims 1 - 3, wherein N = 1.

6. The microscope according to claim 1, wherein the control unit (32) is configured to pulsate the light source (22, 22a - 22d).

7. The microscope according to claim 1, wherein the control unit (32) is configured to pulsate the light source (22, 22a - 22d) in a manner synchronized with the frame period.

8. The microscope according to claim 6, wherein the control unit (32) is configured to - bring pixels into a given configuration during a dark phase before a given light pulse, and - initiate the light pulse only when the pixels are in the given configuration.

9. The microscope according to any one of claims 6 - 8, wherein the control unit (32) is configured to generate at least two separate light pulses (L1, L2) for each frame recorded by the camera (16), wherein one of the light pulses (L1) falls within the integration phase of the camera (16), and the other one or more light pulses (L2) fall outside the integration phase, wherein during the integration phase, the pixels of the camera integrate the light impinging on them.

10. The microscope according to claim 9, wherein the light pulses (L1, L2) have equal durations, for all light pulses (L1, L2), the spatial light modulator (24) has the same configuration (P1, P3), and the light pulses are separated by dark phases of equal length.

11. The microscope as claimed in claim 10, wherein the control unit (32) is adapted to bring the spatial light modulator (24) between light pulses (L1, L2) into a configuration (P2, P4) opposite to the configuration (P1, P3) during the light pulses (L1, L2).

12. The microscope according to any one of the preceding claims 1 to 3, further comprising at least one light sensor (58a-58d, 58) adapted to measure the light intensity between the light source (22, 22a-22d) and the spatial light modulator (24), wherein the control unit (32) is configured to - putting the spatial light modulator (24) into a non-transmissive mode, and - pulsing the at least one light source (22, 22a-22d) to measure the brightness of the light source (22, 22a-22d) when the spatial light modulator (24) is in the non-transmissive mode.

13. The microscope according to any one of the preceding claims 1 to 3, further comprising at least one light sensor (58a-58d, 58) for monitoring the brightness of the light source (22, 22a-22d), wherein the control unit (32) is adapted to monitor the brightness of the light source (22, 22a-22d) by means of the light sensor (58a-58d, 58) to generate calibration parameters and to control at least one light source (22, 22a-22d) using the calibration parameters.

14. The microscope according to claim 13, comprising several light sources (22a-22d), wherein the control unit (32) is adapted to perform calibration measurements outside the integration phase of the camera (16), wherein in the integration phase the pixels of the camera integrate the light impinging on them, wherein the calibration measurements comprise the following steps - placing the spatial light modulator (24) in a non-transmissive configuration, and - activating exactly one of the light sources (22a-22d) and measuring the brightness signal with the aid of the light sensor (58).

15. A method for operating an ophthalmic microscope, wherein the microscope comprises i) lighting equipment (9), having a) at least one light source (22, 22a-22d), b) an electronically controlled spatial light modulator (24) comprising a two-dimensional array of micromirrors (60) individually deflectable to a first position and a second position, and c) illumination imaging optics (26), ii) Microscope equipment (8), having a) microscope optics (14, 15) and b) at least one electronic camera (16), and iii) a control unit (32), The method comprises the following steps: For a set of N≤100 consecutive frame periods of the camera (16), each micromirror (60) of the spatial light modulator (24) is brought into a first position during time t1 and into a second position during time t2, wherein 0.1 <t1 / t2<10。 16. The method of claim 15, comprising the step of pulsing the light source (22, 22a-22d).

17. The method of claim 15, comprising the step of pulsing the light source (22, 22a-22d) in synchronization with the frame period.

18. The method of claim 16, comprising the steps of: - bring the pixel to a given configuration during the dark phase preceding a given light pulse, and - Light pulses are initiated only when the pixels are in a given configuration.

19. The method according to any one of claims 16 to 18, comprising the steps of: For each frame recorded by the camera (16), at least two separate light pulses (L1, L2) are generated, wherein one of the light pulses (L1) falls into an integration phase of the camera (16) and the other one or more light pulses (L2) fall outside the integration phase, wherein during the integration phase the pixels of the camera integrate the light impinging on them.

20. The method of claim 19, wherein The light pulses (L1, L2) have equal duration, For all light pulses (L1, L2), the spatial light modulator (24) has the same configuration (P1, P3), and The light pulses are separated by dark phases of equal length.

21. The method of claim 20, comprising the step of bringing the spatial light modulator (24) between the light pulses (L1, L2) into a configuration (P2, P4) opposite to the configuration (P1, P3) during the light pulses (L1, L2).

22. The method of any one of claims 15-18, wherein the microscope further comprises at least one light sensor (58a-58d, 58) adapted to measure light intensity between the light source (22, 22a-22d) and the spatial light modulator (24), The method comprises the following steps - placing the spatial light modulator into a non-transmissive mode, and - pulsing the at least one light source (22, 22a-22d) to measure the brightness of the light source (22) when the spatial light modulator is in the non-transmissive mode.

23. The method according to any one of claims 15 to 18, wherein the microscope comprises at least one light sensor (58a-58d, 58) and comprises the steps of monitoring the brightness of the light source (22, 22a-22d) by means of the light sensor (58a-58d, 58) and generating calibration parameters, and The calibration parameters are used to control the light source (22, 22a-22d).

24. The method according to claim 23, wherein the microscope comprises several light sources (22a-22d), wherein the method comprises a step of calibrating the measurement outside the integration phase of the camera (16), wherein During the integration phase, the pixels of the camera integrate the light that strikes them, wherein the calibration measurement comprises the following steps - placing the spatial light modulator (24) in a non-transmissive configuration, and - activating exactly one of the light sources (22a-22d) and measuring the brightness signal with the aid of the light sensor (58).

25. The method of claim 24, wherein the light sources (22a-22d) have different colors, and wherein the method further comprises the step of using calibration measurements for the light sources (22a-22d) so as to maintain a desired relative brightness between at least two of the light sources (22a-22d) when the at least two light sources are turned on simultaneously when recording a frame.

26. The method of any one of claims 15 to 18, wherein The microscope comprises a single light source, or The microscope comprises several light sources, and there is at least one time in a frame period when all light sources are switched on.

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