Spatial light modulator and low-pass filtering for slit-lamp microscopes

Abstract

The slit lamp microscope includes a microscope assembly (8) that projects an object plane (11) onto an eyepiece (18) or camera (16), and an illumination assembly (9) having a spatial light modulator (24). The illumination assembly includes a beam splitter (70) that acts as a low-pass filter to suppress the spatial frequencies of the pixels of the light modulator (24) and produce more uniform illumination. In other embodiments, actuators (90-98) may be used to deflect at least a portion of the illumination imaging optics (26) to produce a low-pass filtered image of the spatial light modulator (24).

Description

[Technical Field]

[0001] The present invention relates to a slit-lamp microscope, i.e., an ophthalmic microscope adapted to illuminate a patient's eye with a slit-shaped or otherwise structured illumination field and to examine the eye through a microscope device. The structured illumination is generated using an electronically controlled spatial light modulator. [Background technology]

[0002] Conventionally, the illumination system for a slit lamp microscope includes a slit aperture and an illumination imaging optical system adapted to project the slit aperture into the object plane.

[0003] International Publication No. 2021144000 describes a slit-lamp microscope in which the slit aperture is replaced by a high-resolution spatial light modulator. This type of slit-lamp microscope illuminates the eye with a slit-shaped illumination field or another type of structured light field, and allows for the rapid and easy adaptation of the illumination structure to current requirements. [Overview of the project] [Problems that the invention aims to solve]

[0004] The problem that this invention aims to solve is to further improve the illumination quality of this type of slit-lamp microscope. [Means for solving the problem]

[0005] This problem is solved by the slit-lamp microscope of claim 1. Therefore, the slit-lamp microscope includes at least the following elements: i) Microscope apparatus: This apparatus projects the object surface into the eyepiece and / or camera of a slit-lamp microscope. During operation, the patient's eye is positioned within the object surface so that it can be examined through the microscope apparatus. ii) Illumination device: This device is applied to generate a structured, adaptable illumination field within the object surface. This device includes the following elements: a) At least one light source: The light source generates radiation to be projected into the object's surface. b) Electronically controlled spatial light modulator: This modulator is applied to spatially modulate light from a light source. This modulator has a pixel modulator array, for example, an array of mirrors or liquid crystal light bulbs. This array has a spatial frequency fx along a first dimension and a spatial frequency fy along a second dimension, and the two dimensions extend transversely to each other, and in particular orthogonally to each other. c) Illumination imaging optical system: These optical systems project a pixel modulator array toward the object plane, thereby generating a structured light field within the object plane. The structure of this light field (e.g., boundaries) can be defined by setting spatial light modulators to a desired pattern.

[0006] According to the present invention, the imaging optical system includes a low-pass filter that attenuates at least one of the spatial frequencies fx and fy in the object plane.

[0007] In the absence of such a low-pass filter, the structure of the pixel modulator array is projected into the image plane to at least a certain extent. As described below, this makes it possible to generate perceptible periodic modulation of light within the bright area of ​​the object plane at spatial frequencies corresponding to fx and fy, respectively. By incorporating a low-pass filter, that is, by reducing the transmission of the spatial frequencies of fx and / or fy into the object plane, this modulation is reduced, thereby making it possible to obtain more homogeneous illumination within the bright area of ​​the light.

[0008] In particular, a low-pass filter attenuates the modulation transfer function T between the spatial light modulator and the object surface at spatial frequencies fx much larger than the spatial frequency fx / 10. That is, if T1 is the modulation transfer function of an illumination imaging optical system without a low-pass filter, and T2 is the modulation transfer function of an illumination imaging optical system with a low-pass filter, then, T1(fx) / T2(fx) is at least 5 times, and especially at least 10 times, larger than T1(fx / 10) / T2(fx / 10).

[0009] Conveniently, the same applies to dimension y, namely T1(fy) / T2(fy) is at least 5 times, and especially at least 10 times, larger than T1(fy / 10) / TZ(fy / 10).

[0010] Advantageously, the low-pass filter is applied to attenuate the transmission of spatial frequencies fx and / or fy into the object plane to at least one-tenth, and especially at least one-twentieth, of the spatial frequencies fx / 10 and fy / 10, respectively. In other words, for example, for the first dimension x: - If T2(fx) is the modulation transfer function of the illumination imaging optical system at spatial frequency fx, and - T2(fx / 10) is the modulation transfer function of the illumination imaging optical system at spatial frequency fx / 10, In that case, the ratio of T2(fx / 10) / T2(fx) will exceed 10, and especially exceed 20.

[0011] Advantageously, this type of attenuation, at least one-tenth, is achieved for both spatial frequencies fx and fy.

[0012] Low-pass filters may be based on various principles, such as imperfect imaging, temporal variations in imaging, and / or beam splitting. These techniques can be used individually or in combination.

[0013] In one embodiment, the low-pass filter is structured and adapted to generate at least two spatially offset images of a spatial light modulator on the object plane. Using two or more such offset images, it becomes possible to provide low-pass filtering along at least one dimension of the pixel modulator array. To provide low-pass filtering along both dimensions x, y of the array, the filter must generate at least three images that are offset from each other along at least two different, i.e., non-collinear directions.

[0014] Advantageously, the low-pass filter generates at least four images of the spatial light modulator having mutual offsets along at least two different (i.e., non-collinear) directions within the object plane.

[0015] In a very simple embodiment, the low-pass filter includes at least one beam splitter in the illumination path after the spatial light modulator (i.e., between the spatial light modulator and the object plane). This beam splitter may be applied to generate at least two, and in particular at least four, mutually offset light fields, which can then be used to generate mutually offset images within the object plane.

[0016] Additionally or alternatively, the low-pass filter may include an actuator applied to move at least one optical element of the illumination imaging optics between at least a first and a second position to produce at least two spatially offset images in the object plane. Alternatively or additionally, the actuator may be applied to move a spatial light modulator between at least a first and a second position to produce at least two spatially offset images in the object plane. In both cases, the microscope includes a control unit applied to operate the actuator periodically.

[0017] Advantageously, the frequency of the periodic drive is at least 40 Hz, and especially at least 100 Hz, in order to produce the impression of a flicker-free, continuous overlap of at least two images for the human observer.

[0018] In yet another embodiment, the illumination optical system has a Fourier plane corresponding to the Fourier transform of a spatial light modulator, and the low-pass filter includes a spatial filter within the Fourier plane. This spatial filter blocks at least the spatial frequencies fx and / or fy, and preferably the harmonics thereof.

[0019] In a further embodiment, the low-pass filter may be implemented by an illumination imaging optical system that projects an image of the spatial light modulator into an image plane offset from the object plane by at least 500 μm.

[0020] In another embodiment, the low-pass filter may include a diffuser plate, particularly a diffractive diffuser plate.

[0021] The present invention will be better understood when considering the following detailed description of the invention, and objects other than those described above will become apparent. Such description refers to the reference of the accompanying drawings.

Brief Description of the Drawings

[0022]

Figure 1

Figure 2

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Figure 5

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Figure 8

Figure 9

Modes for Carrying Out the Invention

[0023] Overview Figure 1 shows one embodiment of a slit-lamp microscope.

[0024] The microscope has, for example, a base 1 placed on a desk, a translationally displaceable stage 2 attached to the base 1, a first arm 3, and a second arm 4.

[0025] Stage 2 is linearly displaceable along two horizontal directions in relation to Base 1.

[0026] Arms 3 and 4 are mounted on stage 2 and rotate around a common vertical pivot axis 5.

[0027] The device may further include a headrest 7 mounted on the base 1 to accommodate the patient's head.

[0028] Arm 3 supports the microscope device 8, and arm 4 supports the illumination device 9, also known as a "slit lamp."

[0029] The microscope apparatus 8 has an optical axis 12. The apparatus includes microscope optical systems 14, 15, such as an objective lens 14 and a zoom optical system 15, which project an image of the eye 10 onto a camera 16 and / or into the eyepiece 18. A beam splitter 20 or a flip mirror may be provided to split the light between these components.

[0030] The illumination device 9 rotates around a pivot axis 5. This illumination device is applied to project a structured light beam onto the eye 10 being examined. This illumination device includes a light source 22, a spatial light modulator 24, and an illumination imaging optical system 26 including at least one lens 27.

[0031] The light source 22 may include several units that emit different wavelengths, for example, red, green, blue, and in the infrared region of the optical spectrum. These units may be controlled separately to change the color of the light source 22.

[0032] Advantageously, the light source 22 includes at least one LED and / or semiconductor laser. This type of light source is advantageous because the LED and semiconductor laser can be pulsed quickly and precisely.

[0033] The illumination imaging optical system 26 projects light from the modulator 24 onto, for example, the front surface of the eye 10, via a deflection mirror 28, for example, mounted on the arm 4. The front surface of the eye 10 is assumed to be positioned on the object plane 11, which is the optically conjugate plane of the spatial light modulator 24 in relation to the illumination imaging optical system 26. Note that, as explained in the "defocusing" section below, in one embodiment, the object plane 11 is not precisely within the optical conjugate plane of the spatial light modulator 24.

[0034] The pivot axis 5 is located within the object plane 11 to keep the center of the image in focus while rotating one or both of the arms 3 and 4.

[0035] The lighting device 9 can be positioned above or below the deflection mirror 28.

[0036] The control unit 32 controls the components of the microscope. In particular, the control unit may include, for example, a microprocessor 34 and a memory 36. The microprocessor 34 is programmed to perform steps for controlling the microscope, and the memory 36 stores the data and / or instructions for doing so.

[0037] Lighting device Figure 2 shows a more detailed embodiment of the lighting device 9. This lighting device is designed to project a defined contoured illumination field onto the eye 10. The illumination field may be, for example, circular, rectangular, or slit-shaped. Even though the lighting device is referred to as a “slit lamp” in this specification, the illumination field does not need to be slit-shaped at all. It can take any shape.

[0038] In this embodiment, the lighting device 9 includes four separate light sources 22a to 22d with different spectral emission characteristics, which together form the "light source" 22 of the lighting device. For example, these light sources 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.

[0039] Light from each light source is effectively sighted using the sighting optical systems 40a to 40d.

[0040] Three dichroic mirrors 42a, 42b, and 42c are used to coaxially combine the light from light sources 22a to 22d.

[0041] The combined illumination light is passed through a homogenization optical system 44, such as a fly-eye lens array as described in U.S. Patent No. 6,507,434.

[0042] The two cylindrical lenses 46a, 46b, the additional lens 46c, and the homogenization optical system 44 also work together to spread the light beam along one direction, giving this light beam an elongated cross-section, for example, a cross-section with a width-to-height ratio of 16:9, in order to better match it with the shape factors typically available for a spatial light modulator, for example.

[0043] The mirror 48 deflects light into an assembly of two prisms 50a and 50b with a gap 52 between them.

[0044] The light beam passes through prism 50a, gap 52, and prism 50b and reaches the spatial light modulator 24.

[0045] In the illustrated embodiment, the spatial light modulator 24 is a DMD ("Digital Micromirror Device") having a two-dimensional array of individually rotating micromirrors 60 that act as pixel modulators. A control unit 32 is applied to control the alignment of each micromirror 60 between at least a first and a second position.

[0046] When the given mirror 60 is in the first position, light from the light source 22 is reflected by the given mirror as shown by line 54, passes through the first surface 62a of the prism 50b, is completely reflected by the second surface 62b of the prism 50b (in the gap 52), and exits through the third surface 62c of the prism 50b in the direction shown by line 56.

[0047] However, when the given mirror 60 is in the second position, light from the light source is reflected by the given mirror and passes through the first surface 62a, but not completely reflected at the second surface 62b. Some of the light exits through surface 62b. The reflected portion leaves the prism 50b through another surface, though not in the direction 56, and does not pass through, for example, the aperture of the illumination imaging optical system 26.

[0048] Therefore, the control unit 32 can individually set each pixel (each micromirror 60) of the spatial light modulator 24 to an on state and an off state, thereby defining the contour and shape of the light field at the target 10 (shown in Figure 2 as to be positioned within the object surface 11 of the illumination device).

[0049] Light from the pixels of the spatial light modulator 24 enters an illumination imaging optical system 26, which may include one or more lenses. From there, this light can pass through the deflection mirror 28 and reach the object plane 11.

[0050] The illumination imaging optical system projects the spatial light modulator 24 onto the target 10; that is, in the illumination imaging optical system 26, the target 10 lies on an object plane 11 which is a conjugate plane to the plane 64 of the spatial light modulator 24.

[0051] Figure 3 shows a subdivision of the 64 mirrors 60 of the spatial light modulator 24 in the first position (i.e., their on position). As can be seen, the mirrors 60 form a two-dimensional array extending along the first and second dimensions x and y. The spacing of the pixels along x is dx, and the spacing along y is dy. The mirrors 60 have extensions ex and ey, respectively, which are typically smaller than dx and dy, i.e., gaps 61 that do not reflect light exist between the mirrors 60.

[0052] Assuming that all the mirrors 60 in the modulator section of Figure 3 are in their first position, the illumination pattern within the object surface 11 generated by these mirrors would appear as shown in Figure 4, assuming that the imaging of the illumination imaging optical system is substantially perfect (Note: The dark areas in Figure 4 represent the illuminated portions within the object surface 11).

[0053] As can be seen here, an array of irradiation regions 66 extending along directions x' and y' is created, and this array has spacing dx' along direction x' and spacing dy' along direction y'.

[0054] Between the illuminated areas 66, there are unilluminated areas 68 corresponding to the gaps 61 between the mirrors 60. Therefore, the illumination is heterogeneous.

[0055] When the eye 10 is examined at high magnification using the microscope device 8, this heterogeneous pattern within the bright areas of the object surface 11 may become apparent. This is especially true for examinations that rely on specular reflection of light on the eye, such as when examining the anterior or posterior surface of the cornea to examine the endothelium, or when examining the anterior or posterior lateral surface of the lens. Heterogeneous illumination is also particularly evident when recording a cross-sectional view of the eye with narrow-slit illumination.

[0056] Although artifacts caused by heterogeneous lighting can be removed from camera images using image processing, such processing can be difficult, especially when the lighting structure interferes with the camera's pixel structure, and is impossible when directly examining the microscope image through the eyepiece. Similarly, any such processing would potentially reduce the resolution of the microscope apparatus 8.

[0057] Low-pass filter To reduce artifacts caused by uneven lighting, the lighting system is equipped with low-pass filters, such as beam splitters or other means, as described in the following sections.

[0058] In other words, the purpose of this low-pass filter is to suppress (i.e., attenuate) the spatial frequencies fx=1 / dx and / or fy=1 / dy along x and y when the spatial light modulator 24 is imaged within the object surface 11.

[0059] In the coordinate system of the object plane 11, the spatial frequencies fx and fy of the optical modulator correspond to spatial frequencies fx'=1 / dx' and fy'=1 / dy'.

[0060] In the following, T is defined as the modulation transfer function of the illumination imaging optical system 26, which is a function of the spatial frequency f in the spatial light modulator 24 (see https: / / en.wikipedia.org / wiki / Optical_transfer_function). f is the spatial frequency of dimensions x and y (Note: For simplicity, we assume that both dimensions x and y have the same modulation transfer function T. Otherwise, Tx(f) and Ty(f) may be used).

[0061] Figure 5 shows the modulation transfer function T1(f) of the illumination imaging optical system 26 when there is no low-pass filter. As can be seen here, T1 is attenuated at higher frequencies, but at least one residual modulation transfer occurs at frequency fx.

[0062] Figure 5 further shows the modulation transfer function T2(f) of the illumination imaging optical system 26 when a low-pass filter is present. As can be seen here, the low-pass filter produces a strong attenuation at fx, but at lower spatial frequencies such as fx / 10, it produces only a much smaller attenuation. Therefore, with respect to a given brightness of the illuminated area of ​​the target on the object surface, illumination heterogeneity at fx is suppressed.

[0063] As mentioned above, advantageously, the attenuation of the modulation transfer function at fx / 10 is at least one-fifth, and especially at least one-tenth, of that at fx. That is, T1(fx) / T2(fx) is at least five times, and especially at least ten times, greater than T1(fx / 10) / T2(fx / 10).

[0064] The same applies to fy as well.

[0065] As can be seen in Figure 5, the modulation transfer function T2(f) with a low-pass filter should be significantly smaller at fx compared to lower frequencies such as fx / 10, to the point where illumination heterogeneity at fx is almost invisible. Therefore, as mentioned above, the ratio T2(fx / 10) / T2(fx) is favorably greater than 10, and especially greater than 20. The same is favorably true for fy.

[0066] Figure 5 shows a further variation of the modulation transfer function under T2'(f) in the presence of a low-pass filter. In this variation, the modulation transfer function T2'(f) has a minimum at fx, and then rises again to higher frequencies, e.g., 1.5·fx, thereby improving the imaging quality for high-frequency components of the illumination pattern that are not caused by the iterative structure of the spatial light modulator. However, T2'(f) should favorably decrease again toward the second harmonic frequency 2·fx.

[0067] Thus, more generally, the modulation transfer function T2(fx) at frequency fx is advantageously at least one half compared to the modulation transfer function at T2(1.5·fx) at frequency 1.5fx, i.e., T2(fx) < T2(1.5·fx) / 2. In particular, T2(1.5·fx) at frequency 1.5·fx is advantageously at least twice that at T2(2·fx) at frequency 2·fx, i.e., T2(2·fx) < T2(1.5·fx) / 2.

[0068] Such frequency synchronization of the modulation transfer function is most favorably achieved using Fourier filtering techniques, as will be explained below.

[0069] There are various ways to implement such low-pass filtering, some of which are explained in the following section.

[0070] Beam splitter A first embodiment of the low-pass filter is shown in FIG. 6. In this embodiment, the low-pass filter includes a beam splitter 70. This low-pass filter is disposed in the path of the illumination light after the spatial light modulator 24 and before the object plane 11, and is arranged to generate at least two, particularly at least four, mutually offset light fields.

[0071] In the illustrated embodiment, the beam splitter 70 includes a first birefringent plate 72, a quarter-wave retardation plate 74, and a second birefringent plate 76, and the quarter-wave retardation plate 74 is disposed between the birefringent plates 72, 76.

[0072] The first birefringent plate 72 has an optical axis disposed advantageously at 45° with respect to its input surface for splitting the incident light 78a into two light fields 78b, 78c of equal intensity (here, it is assumed that the incident light 78a is unpolarized. If it is partially or fully polarized, one or more polarizers and / or wavelength retardation plates may be used to adapt the polarization so that the light fields 78b, 7

[0073] Since the light fields 78b and 78c after the first birefringent plate 72 are linearly polarized, a quarter-wavelength phase difference plate 74 is used to convert these polarizations into circularly polarized light.

[0074] Subsequently, the optical fields 78b and 78c enter the second birefringent plate 76. Here again, the second birefringent plate 76 has an optical axis positioned at a 45° angle to its input surface in order to split the incident optical fields 78b and 78c once more. The second birefringent plate 76 is oriented differently from the first birefringent plate 72 in order to produce splitting in different directions. Thus, at the output side of the beam splitter 70, the incident light 78a is split into four mutually offset optical fields 80a, 80b, 80c, and 80d.

[0075] Advantageously, the four optical fields 80a to 80d are offset from each other along the rectangular directions rx and ry corresponding to dimension x.

[0076] The offset between the light fields along rx and ry is approximately half the spacing dx and dy of mirror 80, respectively, for the reasons explained below.

[0077] The beam splitter 70 may be positioned adjacent to the prism 50b, particularly adjacent to the first surface 62a or the third surface 62c. Advantageously, the beam splitter may be assembled to one of these surfaces, and in particular, bonded to it. Placing a transparent filler (e.g., adhesive) between the prism 50b and the beam splitter 70 to prevent a gap between the two components is highly advantageous because it reduces the number of surfaces that light must traverse.

[0078] In the embodiment shown in Figure 2, the beam splitter 70 is shown as being disposed on a third surface 62c, with a transparent filler material 71 between the two components.

[0079] As mentioned, the beam splitter 70 functions as a low-pass filter. In particular, when not positioned too close to the lens 27, the beam splitter effectively divides the image of the spatial light modulator 24 in the object plane 11 (as shown in Figure 4 without the beam splitter) into spatially offset images as illustrated in Figure 7.

[0080] To illustrate these four images, Figure 7 shows a single mirror 60 in each of these four images, outlined with different dashed lines, as reference numbers 82a to 82d.

[0081] As can be seen by comparing Figures 4 and 7, the lighting pattern in Figure 7 is more uniform than that in Figure 4. In other words, the mirror structure is not as obvious, and therefore a better quality image is produced.

[0082] The image offset along direction x' is mx', and the offset along direction y' is my'. The offsets must be within the range that "blurs" the unilluminated area 68 in Figure 4. Thus, favorably, mx' = dx' / 2 and my' = dy' / 2. However, the offsets may deviate from these figures if the gap between the mirrors 60 is not too large. Along x', the offset mx' is favorably between 0.2·dx' = 0.2 / fx' and 0.8·dx' = 0.8 / fx'. Similarly, along y', the offset my' is favorably between 0.2·dy' = 0.2 / fy' and 0.8·dy' = 0.8 / fy'. Favouritely, mx' is between 0.4 / fx' and 0.6 / fx', and my' is between 0.4 / fy' and 0.6 / fy'.

[0083] Beam splitters based on birefringent plates are, for example, described in "Dimensioning of Optical Birefringent Anti-Alias ​​Filters for Digital Cameras, Proc. of 2010 IEEE 17" thAs described by Schoberl et al. in the International Conference on Image Processing, Sept. 26-29, Hong Kong, it has been known for a completely different application, namely as an anti-aliasing filter deployed on a camera chip. This document refers to stacks of M=2, M=3, M=4 and even more mutually rotated birefringent plates, which are equally applicable in this context.

[0084] Therefore, more generally speaking, the beam splitter 70 advantageously includes at least two birefringent plates 72, 76 of different orientations, and a quarter-wavelength phase difference plate 74 disposed between each pair of birefringent plates 72, 76.

[0085] Instead of using a birefringent beam splitter, the technique may use other types of beam splitters that generate two or more mutually offset light fields. For example, translucent mirrors can be used to split the light, and the resulting light fields can be redirected and guided by the mirrors to be parallel and with a desired offset.

[0086] Actuator In another type of embodiment, the low-pass filter may include one or more actuators.

[0087] Such actuators 90 are shown by dashed lines in Figure 2, as they are positioned on the deflection mirror 28 of the illumination imaging optical system 26. The actuators 90, which may include, for example, one or more piezoelectric elements, are applied to change the tilt angle of the deflection mirror 28 to offset the image of the spatial light modulator 24 in the object plane 11.

[0088] Advantageously, the actuator 90 is applied to tilt the deflection mirror 28 around two transverse axes to produce an image offset along both directions x' and y' within the object plane 11.

[0089] The actuator 90 is periodically operated by the control unit 32 to rapidly move the image. If such movement is fast enough, for example, with a period of at least 40 Hz, and preferably at least 100 Hz, several spatially offset images are generated on the object surface 11 for the human observer, which again blurs the unilluminated area 68 in Figure 4, thereby producing more uniform illumination.

[0090] Instead of moving the deflection mirror 28 (or in addition to it), another part of the illumination imaging optical system 26 may be moved by an actuator. For example, Figure 2 shows another actuator 92 applied to periodically move the lens 27, and another actuator reference no. 94 applied to move the prism assemblies 50a, 50b or a part thereof.

[0091] In a further modification, the system may include an actuator 96 for moving the spatial light modulator 24 along directions x and / or y.

[0092] In yet another embodiment, as illustrated in Figure 1, an actuator 98 may be provided to move the entire lighting device 9.

[0093] To determine whether a given actuator-based device is a low-pass filter in the sense of the present invention, the image of the spatial light modulator 24 on the object surface 11 is, advantageously, averaged over a period of time to obtain a “subjective image,” i.e., an image as perceived by a human observer. Such averaging occurs while the actuator is being operated periodically. The averaging is, advantageously, for a period of at least 2.5 ms (corresponding to 40 Hz), and more particularly for a period of at least 5 ms (corresponding to 20 Hz). At this time, low-pass filtering is detected by testing whether specific frequencies fx' and / or fy' in the subjective image are suppressed by at least half, and more particularly by at least one-fifth, as described above.

[0094] Fourier filtering In yet another embodiment, the filter 100 is positioned within the back focal plane (Fourier plane) 102 of the lens 27 (see Figure 2). This plane holds the Fourier transform of the image from the spatial light modulator 24. The filter 100 is applied to suppress the Fourier components corresponding to the spatial frequencies fx and fy, and preferably their higher harmonics.

[0095] For narrowband illumination, the filter 100 may consist of a simple aperture that, for example, blocks spatial frequencies above a given threshold, such as 0.8fx and 0.8fy.

[0096] If it is desired to block only fx and fy and their harmonics, as illustrated by the modulation transfer function T2' in Figure 5, the filter 100 may be calculated, for example, from the Fourier transform of the pattern generated by the spatial light modulator (i.e., the pattern shown in Figure 4). Such a filter 100 is shown in Figure 8, where the dark areas indicate the parts that block light.

[0097] As is known to those skilled in the art, the Fourier transform in the back focal plane 102 scales with the wavelength of light. Therefore, if the light source 22 is a broadband light source, the filter 100 may include, for example, several superimposed color filters that are thought to be attributable to various wavelengths, each color filter blocking spatial frequency components fx, fy (and their harmonics) in a wavelength range centered on the wavelength from which it originates.

[0098] As shown in the embodiment of Figure 2, various wavelengths λ i When several individual light sources 22a to 22d are present, the filter 100 is advantageous in terms of wavelength λ iThis includes several wavelength-selective filters that block the spatial frequency fk and its harmonics. For example, Figure 9 shows a filter that is the same as the one in Figure 8 but scaled to approximately twice the wavelength. For example, the filter in Figure 9 would absorb at the first (longer) wavelength λ1 (in the dark region) (but not at λ2, or absorbs very little), while the filter in Figure 8 would absorb at the second (shorter) wavelength λ2 (in the dark region) (but absorbs very little at λ1, or absorbs very little).

[0099] Therefore, more generally speaking, filter 100 is advantageous for several different wavelengths λ i The spatial frequency fk and, advantageously, the filter includes several wavelength-selective filters that suppress its harmonics, and the filters are different wavelengths λ i It includes a light-blocking structure whose size has been scaled. Advantageously, in this case, the illuminating device 9 has a wavelength λ i This includes several light sources with different emission spectra, where the emission is maximized.

[0100] Defocusing In another embodiment, the low-pass filter may be implemented by intentionally defocusing the illumination imaging optical system 26. For example, the lens 27 may be sized to project the image of the spatial light modulator not toward the object plane 11, but toward an imaging plane 104 (as illustrated in Figure 2) that is offset from the object plane 11 by an offset r of at least 500 μm.

[0101] As described above, the lighting device 9 rotates around a vertical pivot axis 5, which lies within the object plane 11. Therefore, such defocusing implies that the image from the spatial light modulator 24 will be either in front of or behind the pivot axis 5.

[0102] As shown in Figure 2, the object plane 11 is best positioned between the microscope device 8 and the imaging plane 104, that is, the imaging plane 104 is positioned behind the object plane 11 as it is visible from the microscope device 8. This is advantageous because, if the microscope device 8 is adjusted (which is common) so that the user's eye is focused to infinity to clearly see the object in the object plane 11, it becomes even more difficult for the user to focus on the imaging plane 104, i.e., the likelihood of the user "accidentally" focusing on the imaging plane 104 becomes lower.

[0103] In another embodiment, such defocusing may be implemented by introducing spherical aberration within the lens 27 or within other components of the imaging optical system 26.

[0104] Spherical aberration, and higher-order spherical aberrations as well, are aberrations independent of the position and rotation of the illumination field (e.g., defocus) and can be used to intentionally and uniformly blur the image of a spatial light modulator across the entire surface of the object to form a low-pass filter. Similarly, other aberrations, such as astigmatism, act as low-pass filters. Advantageously, a combination of classical higher-order aberrations can be used to generate the desired low-pass filter.

[0105] Diffuser In yet another embodiment, a diffuser plate 106 disposed between the spatial light modulator 24 and the object surface 11 may be used as a low-pass filter. Such a diffuser plate may be disposed on the first surface 62a or the third surface 62c of the prism 50b, for example, similar to the beam splitter 70. Alternatively, it may be disposed in the Fourier plane, for example.

[0106] Advantageously, the diffuser plate 106 is a diffracting diffuser plate, that is, a diffuser plate that uses diffraction to diffuse light.

[0107] Note In the embodiments described above, the low-pass filter is applied to suppress spatial frequencies fx and fy along x and y. Alternatively, the low-pass filter may similarly be designed to suppress only one of these spatial frequencies, particularly when the illumination device is designed such that one of the corresponding frequencies fx' and fy' is much larger than the other, especially on the object surface 11. In that case, since the larger frequency may exceed the resolution of the microscope device 8, it may be necessary to suppress only the smaller frequency.

[0108] The various embodiments of the low-pass filter described above may be combined with a beam splitter for one direction x and with an actuator for the other direction y.

[0109] In the embodiments described above, the light source and the spatial light modulator are separate elements. Alternatively, they may also be formed by a single device having a light source array, in which case each light source defines illumination within one pixel.

[0110] While currently preferred embodiments of the present invention have been illustrated and described, it should be clearly understood that the present invention is not limited thereto and can be implemented and practiced in various other forms within the scope of the following claims. [Configuration 1] i) A microscope device (8) that projects an object surface (11) into at least one of an eyepiece lens (18) and a camera (16); ii) a) At least one light source (22); b) An electronically controlled spatial light modulator (24) including an array of pixel modulators extending along the first and second dimensions (x, y), where the pixel modulators have spatial frequencies fx and fy along the first and second dimensions (x, y); c) An illumination imaging optical system (26) that projects the array toward the object surface (11). The illumination device (9) includes a low-pass filter (70, 90 - 100, 106) that attenuates at least one of the spatial frequencies fx and fy within the object surface (11), the slit lamp microscope. [Configuration 2] T1 is the modulation transfer function of the illumination imaging optical system (26) that does not have a low-pass filter (70, 90 - 100, 1) between the spatial light modulator (24) and the object surface (11), T2 is the modulation transfer function of the illumination imaging optical system (26) that has a low-pass filter (70, 90 - 100, 1) between the spatial light modulator (24) and the object surface (11), and T1(fx) / T2(fx) is at least 5 times, particularly at least 10 times larger than T1(fx / 10) / T2(fx / 10). Particularly, T1(fy) / T2(fy) is similarly at least 5 times, particularly at least 10 times larger than T1(fy / 10) / T2(fy / 10), the microscope according to Configuration 1. [Configuration 3] When T2 is the modulation transfer function of the illumination imaging optical system (26) that has a low-pass filter (70, 90 - 100, 1) between the spatial light modulator (24) and the object surface (11), T2(fx / 10) / T2(fx) exceeds 10, particularly exceeds 20, the microscope according to Configuration 1 or 2. [Configuration 4] T2(fx) < T2(1.5·fx) / 2, particularly T2(2·fx) < T2(1.5·fx) / 2, the microscope according to Configuration 3. [Configuration 5] The low-pass filter (70, 90 - 96, 100, 1) is adapted to generate at least two spatially offset images (82a - 82d) of the spatial light modulator (24) on the object surface (11), the microscope according to any one of Configurations 1 to 4. [Configuration 6] In the object plane (11), the images (82a-82d) of the spatial light modulator (24) have an offset mx' between 0.2 / fx' and 0.8 / fx', particularly between 0.4 / fx' and 0.6 / fx', along the first imaged dimension, where fx' and fy' are the spatial frequencies of the array in the image at the imaging plane, according to the microscope in configuration 5. [Composition 7] The microscope according to configuration 5 or 6, wherein low-pass filters (70, 90-100, 106) are adapted to produce at least four spatially offset images (82a-82d) of a spatial light modulator (24) on the object plane (11). [Structure 8] The microscope according to any one of configurations 1 to 7, wherein the low-pass filters (70, 90-100, 106) include at least one beam splitter (70) after the spatial light modulator (24), and the beam splitter (70) is adapted to generate at least two mutually offset light fields (80a-80d). [Composition 9] The microscope according to configuration 8, wherein the beam splitter (70) is adapted to generate at least four mutually offset light fields (80a to 80d). [Configuration 10] The microscope according to configuration 9, wherein the beam splitter (70) includes at least two birefringent plates (72, 76) of different orientations and a quarter-wavelength phase difference plate (74) disposed between each pair of birefringent plates (72, 76). [Composition 11] The lighting device (9) is An array of individually rotating mirrors (60), wherein each mirror (60) has a first and a second position, A prism (50b) having first, second and third surfaces (62a, 62b, 62c), wherein, for a predetermined mirror (60) in a first position, light from a light source (22) is reflected by the predetermined mirror (60), passes through the first surface (62a), is completely reflected by the second surface (62b), and exits through the third surface (62c), while for a predetermined mirror (60) in a second position, light from a light source (22) is reflected by the predetermined mirror (60), passes through the second surface (62e), and is not completely reflected by the second surface (62b), the prism (50b) includes The microscope according to configuration 9 or 10, wherein the beam splitter (70) is positioned adjacent to the prism (50b). [Composition 12] The microscope according to configuration 11, wherein the beam splitter (70) is disposed on a first or third surface (62a, 62c), particularly on the third surface (62c). [Composition 13] The microscope according to configuration 12, wherein a beam splitter (70) is connected to a first or third surface (62a, 62c) via a transparent filler (71). [Composition 14] The low-pass filters (70, 90-100, 106) include actuators (90-100) adapted to move at least one optical element of the illumination imaging optical system (26) and / or the spatial light modulator (24) between at least first and second positions to generate at least two spatially offset images (82a-82d) on the object plane (11). The microscope is as described in any one of configurations 1 to 13, comprising a control unit (32) adapted to periodically operate actuators (90-100). [Composition 15] The microscope according to configuration 14, wherein the illumination imaging optical system (26) includes at least one deflection mirror (28) that deflects light from a spatial light modulator (24) toward an object plane (11), and an actuator (90) is adapted to change the tilt angle of at least one of the deflection mirrors (28). [Composition 16] The microscope according to any one of configurations 1 to 15, wherein the illumination optical system has a Fourier plane (102) that holds the Fourier transform of a spatial light modulator (24), and a low-pass filter (100) suppresses the Fourier component of the image of the spatial light modulator (24) within the Fourier plane (102). [Composition 17] The low-pass filter (100) uses several different wavelengths λ i Regarding the spatial frequency fk, it includes several wavelength-selective filters that favorably suppress its harmonics, and the wavelength-selective filters are different wavelengths λ i A microscope according to configuration 16, comprising a scaled blocking structure. [Composition 18] The lighting device (9) emits wavelength λ i The microscope according to configuration 17, comprising several light sources (22a-22d) having different emission spectra that produce maximum emission at a given point. [Composition 19] The lighting device (9) rotates around a pivot axis (5) located within the object surface (11), A microscope according to any one of configurations 1 to 18, wherein low-pass filters (70, 90-100, 106) are implemented by an illumination imaging optical system (26) that projects an image of a spatial light modulator (24) into an imaging plane (104) offset by at least 500 μm from the object plane. [Configuration 20] The microscope according to configuration 19, wherein the object plane (11) is positioned between the microscope device (8) and the imaging plane (104). [Composition 21] A microscope according to any one of configurations 1 to 20, comprising a low-pass filter (70, 90-100, 106), a diffuser plate (106), particularly a diffraction diffuser plate.

Claims

1. i) A microscope device (8) that projects the object surface (11) into at least one of the eyepiece (18) and the camera (16), ii) an illumination device (9) comprising: a) at least one light source (22); b) an electronically controlled spatial light modulator (24) including an array of pixel modulators extending along first and second dimensions (x, y), wherein the pixel modulators have spatial frequencies fx and fy along the first and second dimensions (x, y); and c) an illumination imaging optical system (26) that projects the array toward the object plane (11), The lighting device (9) includes a low-pass filter (70, 90-100, 106) that attenuates at least one of the spatial frequencies fx and fy within the object surface (11), A microscope in which, when T1 is the modulation transfer function of the illumination imaging optical system (26) without low-pass filters (70, 90-100, 106) between the spatial light modulator (24) and the object surface (11), and T2 is the modulation transfer function of the illumination imaging optical system (26) having the low-pass filters (70, 90-100, 106) between the spatial light modulator (24) and the object surface (11), T1(fx) / T2(fx) is at least 5 times greater than T1(fx / 10) / T2(fx / 10).

2. i) A microscope device (8) that projects the object surface (11) into at least one of the eyepiece (18) and the camera (16), ii) an illumination device (9) comprising: a) at least one light source (22); b) an electronically controlled spatial light modulator (24) including an array of pixel modulators extending along first and second dimensions (x, y), wherein the pixel modulators have spatial frequencies fx and fy along the first and second dimensions (x, y); and c) an illumination imaging optical system (26) that projects the array toward the object plane (11), The lighting device (9) includes a low-pass filter (70, 90-100, 106) that attenuates at least one of the spatial frequencies fx and fy within the object surface (11), When T2 is the modulation transfer function of the illumination imaging optical system (26) having the low-pass filters (70, 90-100, 106) between the spatial light modulator (24) and the object surface (11), T2(fx / 10) / T2(fx) is greater than 10, the microscope.

3. The microscope according to claim 2, wherein T2(fx) < T2(1.5・fx) / 2.

4. i) A microscope device (8) that projects the object surface (11) into at least one of the eyepiece (18) and the camera (16), ii) an illumination device (9) comprising: a) at least one light source (22); b) an electronically controlled spatial light modulator (24) including an array of pixel modulators extending along first and second dimensions (x, y), wherein the pixel modulators have spatial frequencies fx and fy along the first and second dimensions (x, y); and c) an illumination imaging optical system (26) that projects the array toward the object plane (11), The lighting device (9) includes a low-pass filter (70, 90-100, 106) that attenuates at least one of the spatial frequencies fx and fy within the object surface (11), A microscope in which the low-pass filters (70, 90-96, 100, 106) are adapted to generate at least two spatially offset images (82a-82d) of the spatial light modulator (24) on the object plane (11).

5. The microscope according to claim 4, wherein, on the object plane (11), the images (82a to 82d) of the spatial light modulator (24) have an offset mx' between 0.2 / fx' and 0.8 / fx' along the first imaged dimension, where fx' and fy' are the spatial frequencies of the array in the image on the imaging plane.

6. The microscope according to claim 4, wherein the low-pass filters (70, 90-100, 106) are adapted to generate at least four spatially offset images (82a-82d) of the spatial light modulator (24) on the object plane (11).

7. i) A microscope device (8) that projects the object surface (11) into at least one of the eyepiece (18) and the camera (16), ii) an illumination device (9) comprising: a) at least one light source (22); b) an electronically controlled spatial light modulator (24) including an array of pixel modulators extending along first and second dimensions (x, y), wherein the pixel modulators have spatial frequencies fx and fy along the first and second dimensions (x, y); and c) an illumination imaging optical system (26) that projects the array toward the object plane (11), The lighting device (9) includes a low-pass filter (70, 90-100, 106) that attenuates at least one of the spatial frequencies fx and fy within the object surface (11), The low-pass filters (70, 90-100, 106) include at least one beam splitter (70) after the spatial light modulator (24), the beam splitter (70) being adapted to generate at least two mutually offset light fields (80a-80d), in a microscope.

8. The microscope according to claim 7, wherein the beam splitter (70) is adapted to generate at least four mutually offset light fields (80a to 80d).

9. The microscope according to claim 8, wherein the beam splitter (70) includes at least two birefringent plates (72, 76) of different orientations and a quarter-wavelength phase difference plate (74) disposed between each of the two birefringent plates (72, 76).

10. The lighting device (9) is An array of individually rotating mirrors (60), wherein each mirror (60) has a first and a second position, A prism (50b) having first, second and third surfaces (62a, 62b, 62c), wherein, for a predetermined mirror (60) in the first position, light from the light source (22) is reflected by the predetermined mirror (60), passes through the first surface (62a), is completely reflected by the second surface (62b), and exits through the third surface (62c), while for the predetermined mirror (60) in the second position, light from the light source (22) is reflected by the predetermined mirror (60), passes through the second surface (62e), and is not completely reflected by the second surface (62b), the prism (50b) includes The microscope according to claim 8, wherein the beam splitter (70) is disposed adjacent to the prism (50b).

11. The microscope according to claim 10, wherein the beam splitter (70) is disposed on the first or third surface (62a, 62c).

12. The microscope according to claim 11, wherein the beam splitter (70) is connected to the first or third surface (62a, 62c) via a transparent filler (71).

13. i) A microscope device (8) that projects the object surface (11) into at least one of the eyepiece (18) and the camera (16), ii) an illumination device (9) comprising: a) at least one light source (22); b) an electronically controlled spatial light modulator (24) including an array of pixel modulators extending along first and second dimensions (x, y), wherein the pixel modulators have spatial frequencies fx and fy along the first and second dimensions (x, y); and c) an illumination imaging optical system (26) that projects the array toward the object plane (11), The lighting device (9) includes a low-pass filter (70, 90-100, 106) that attenuates at least one of the spatial frequencies fx and fy within the object surface (11), The low-pass filters (70, 90-100, 106) include actuators (90-100) adapted to move at least one optical element of the illumination imaging optical system (26) and / or the spatial light modulator (24) between at least first and second positions to generate at least two spatially offset images (82a-82d) on the object plane (11). The microscope comprises a control unit (32) adapted to periodically operate the actuators (90-100).

14. The microscope according to claim 13, wherein the illumination imaging optical system (26) includes at least one deflection mirror (28) that deflects light from the spatial light modulator (24) toward the object plane (11), and the actuator (90) is adapted to change the tilt angle of at least one of the deflection mirrors (28).

15. The microscope according to claim 1 or 2, wherein the illumination imaging optical system (26) has a Fourier plane (102) that holds the Fourier transform of the spatial light modulator (24), and the low-pass filter (100) suppresses the Fourier component of the image of the spatial light modulator (24) within the Fourier plane (102).

16. The microscope according to claim 15, wherein the low-pass filter (100) includes several wavelength-selective filters that suppress the spatial frequency fk and, advantageously, its harmonics for several different wavelengths λi, and the wavelength-selective filters include a cutoff structure scaled for the different wavelengths λi.

17. The microscope according to claim 16, wherein the illumination device (9) includes several light sources (22a to 22d) having different emission spectra that produce maximum emission at wavelength λi.

18. i) A microscope device (8) that projects the object surface (11) into at least one of the eyepiece (18) and the camera (16), ii) an illumination device (9) comprising: a) at least one light source (22); b) an electronically controlled spatial light modulator (24) including an array of pixel modulators extending along first and second dimensions (x, y), wherein the pixel modulators have spatial frequencies fx and fy along the first and second dimensions (x, y); and c) an illumination imaging optical system (26) that projects the array toward the object plane (11), The lighting device (9) includes a low-pass filter (70, 90-100, 106) that attenuates at least one of the spatial frequencies fx and fy within the object surface (11), The lighting device (9) rotates around a pivot axis (5) located within the object surface (11), A microscope in which the low-pass filters (70, 90-100, 106) are implemented by an illumination imaging optical system (26) that projects an image of the spatial light modulator (24) into an imaging plane (104) offset by at least 500 μm from the object plane.

19. The microscope according to claim 18, wherein the object surface (11) is positioned between the microscope device (8) and the imaging surface (104).

20. The microscope according to claim 1 or 2, wherein the low-pass filter (70, 90-100, 106) includes a diffuser plate (106).

Images