Methods and apparatus for laterally shifting widefield images

Abstract

Optical devices for laterally shifting widefield images are described herein. An input widefield image is provided to an electrowetting cell controlled by control voltages which projects an output widefield image. The output image is tilted by a small enough amount that the output widefield image is effectively shifted laterally. The control voltages may vary in an oscillating manner in order to produce wobulation.

Description

[0001] METHODS AND APPARATUS FOR LATERALLY SHIFTING WIDEFIELD IMAGES

[0002] BACKGROUND OF THE INVENTION

[0003] This invention was made with government support under grant number R01 NS123665 awarded by the National Institutes of Health. The government has certain rights in the invention.

[0004] The following U.S. patents are incorporated herein by reference: 10,598,919 issued 24 March 2020, 11 ,221 ,435 issued 11 January 2022, 11 ,493,749 issued 8 November 2022. The following U.S. patent applications are incorporated herein by reference: 18 / 780,109 filed 22 July 2024, 63 / 555,267 filed 19 February 2024.

[0005] FIELD OF THE INVENTION

[0006] The present invention relates to apparatus and methods for laterally shifting widefield images. For example, the present invention relates to wobulation using tunable electrowetting cells.

[0007] DISCUSSION OF RELATED ART

[0008] Imaging systems, from microscopes, to cameras, to projectors are always pushing the limit on resolution. Resolution affects how much detail can be captured and displayed in an image, with impacts on many applications including consumer cameras and displays, widefield microscopy, and biomedical imaging.

[0009] Pixel shifting technologies have expanded in the last few decades as a solution to enhance the resolution of cameras and projectors, benefiting a variety of applications from consumer products to biomedical imaging. One such technique is wobulation, in which a projector frame is computationally split into multiple subframes offset by subpixel distances, so that a spatial light modulator can rapidly alternate between the subframes, resulting in increased resolution.

[0010] In existing implementations of wobulation, a digital micromirror device (DMD) is used to drive the wobulation.

[0011] SUMMARY OF THE INVENTION

[0012] Apparatus laterally shifts a widefield image using a tunable electrowetting cell. A system for shifting a widefield image includes a source for providing a widefield input image, a tunable electrowetting cell having a liquid-liquid interface shape and electrodes controlled by an applied voltage, and circuitry configured to provide varying voltages to the electrowetting cell according to a control signal. The electrowetting cell receives the widefield image and forms a widefield output image. The output image shifts essentially laterally according to the applied voltage.

[0013] The widefield image is essentially laterally shifted because the electrowetting cell tilts the widefield output image a small enough amount that the tilt doesn’t affect the image quality to any real extent. For example, output image is tilted less than 1°, and in some cases less than 0.22°.

[0014] The electrowetting cell electrodes are narrowly spaced at one end, e.g. the distance between them is under 50pm.

[0015] The source for providing a widefield input image may be an LED display. The LED display may be patterned, which is useful for projecting the patterned output widefield display onto a sample, e.g. for structured illumination in microscopy. In some cases, the pattern is wobulated, improving image resolution. Wobulation is accomplished by varying the voltage provided to the tunable electrowetting cell in an oscillating manner.

[0016] The widefield image oscillates at a rate over 10 Hz. In some cases, the oscillation exceeds 60 Hz, or 500 Hz. Microscopy using wobulation achieves higher resolution images with the same number of pixels because a higher resolution image is constructed from multiple sub-frames differing by sub-pixel shifts rather than changing the number of pixels on a sensor or SLM. The projector rapidly flickers or “wobulates” between the sub-images, resulting in a projected image with an increased resolution.

[0017] In some embodiments, a microscope includes a tunable electrowetting prism to achieve lateral shifts of a projected image. The electrowetting wobulation is applied to an optical sectioning structured illumination microscope, an imaging technique that requires multiple spatial phases, or lateral offsets, of a widefield structured illumination pattern. Wobulation, as applied to structured illumination microscopy, enables shifts of the displayed structured illumination pattern so that higher spatial frequencies can be imaged on to a sample, leading to improved optical sectioning strength in systems with minimal magnification.

[0018] Embodiments eliminate the need for mechanical moving elements because the tunable cell moves the image based on an electrical signal rather than moving a mirror (e.g., a digital micromirror device) or mechanically shifting a sensor (e.g., pixel shift cameras).

[0019] The electrowetting prism can be used to laterally shift a structured pattern while maintaining sufficient imaging quality to optically section images in a structured illumination microscope.

[0020] A tunable electrowetting prism creates small shifts of a widefield image. This approach is transmissive and can achieve up to kHz framerates. Electrowetting systems can be implemented to rapidly shift sub-images in a traditional wobulation setup or could be used to achieve a pixel shift style imaging scheme.

[0021] Electrowetting devices fabricated with multiple electrodes enable both focus tuning and scanning. They require no moving parts, are transmissive, and can be miniaturized. For example, applying electrowetting wobulation to drive lateral phase shifts for structured illumination microscopy (SIM) has benefits for miniaturized SIM imaging systems. Miniature microscopes are an innovation in which benchtop-scale microscopy techniques are implemented in a small form factor so that they are lightweight and mounted on the heads of animals like mice. These miniaturized imaging systems have become increasingly popular in neuroscience as they enable real-time imaging of neural activity in freely moving and behaving animals.

[0022] Real-time imaging can be used to correlate the role of neurons in different regions of the brain with motion and learning. Widefield imaging is commonly implemented in miniature microscopes, as light emitting diode (LED) excitation sources are low cost and light weight. Miniature microscopes have low magnification (~2X). The ability to shift the image allows good results with fewer stripes per pattern for structured illumination microscopy. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a schematic block diagram of a microscope using wobulation techniques.

[0024] Figure 2 is a schematic block diagram of a microscope using wobulation techniques with a tunable electrowetting prism.

[0025] Figure 3A is a side schematic diagram of a tunable electrowetting prism having multiple electrodes. Figure 3A is a top schematic view of the prism of Figure 3B. Figure 3C is a diagram of steering angles versus voltages for this prism.

[0026] Figure 4 is a side schematic diagram of a tunable electrowetting prism steered at two angles.

[0027] Figure 5 is a plot comparing contrast of an image from a wobulated microscope versus contrast of a pseudo-widefield microscope image.

[0028] Figure 6 is a diagram showing pattern contrast as a function of the pattern period for patterns imaged with a structured illumination microscopy with wobulation versus patterns imaged with pseudo-widefield microscopy.

[0029] Figure 7 is a plot showing the optical sectioning performance of a structured illumination microscopy with wobulation versus pseudo-widefield at a first depth.

[0030] Figure 8 is a plot showing the performance of a wobulated microscope versus a pseudo-widefield microscope at a second depth.

[0031] Figure 9 is a diagram showing the performance of a wobulated microscope versus a pseudo-widefield microscope.

[0032] Figure 10 is a plot of predicted performance of a wobulated microscope versus measured performance.

[0033] DETAILED DESCRIPTION OF THE INVENTION

[0034] A system for shifting a widefield image includes a source for providing a widefield input image, a tunable electrowetting cell having a liquid-liquid interface shape and electrodes controlled by an applied voltage, and circuitry configured to provide varying voltages to the electrowetting cell according to a control signal. The electrowetting cell receives the widefield image and forms a widefield output image. The output image shifts essentially laterally according to the applied voltage.

[0035] The widefield image is essentially laterally shifted because the electrowetting cell tilts the widefield output image a small enough amount that the tilt doesn’t affect the image quality to any real extent. For example, output image is tilted less than 1°, and in some cases less than 0.22°.

[0036] The electrowetting cell electrodes are narrowly spaced at one end, e.g. the distance between them is under 50pm.

[0037] The source for providing a widefield input image may be an LED display. The LED display may be patterned, which is useful for projecting the patterned output widefield display onto a sample, e.g. for structured illumination in microscopy. In some cases, the pattern is wobulated, improving image resolution. Wobulation is accomplished by varying the voltage provided to the tunable electrowetting cell in an oscillating manner.

[0038] The widefield image oscillates at a rate over 10 Hz. In some cases, the oscillation exceeds 60 Hz, or 500 Hz.

[0039] An experimental setup was used to demonstrate electrowetting wobulation in OS- SIM (optical sectioning structured illumination microscopy).

[0040] Figure 1 is a schematic block diagram of a microscope 100 using wobulation techniques. In this example, the microscope 100 is an epifluorescence setup with a tube lens 108 and 20x, 0.42 NA objective 110. An individually addressable microLED array 102 is patterned to create a structured excitation source 118. The LED display is followed by wobulation device 104, which is used to add small offsets to the patterned light 120. The wobulated pattern 120 is imaged onto a sample 112. Fluorescence 122 is collected by objective 110 and tube lens 108, and is separated from reflected excitation with a dichroic 106 and imaged onto a CMOS sensor 114.

[0041] One example of a wobulation device 104 is a tunable electrowetting prism (see Figure 2). Other examples include a digital micromirror device or a motorized stage to move the LED, camera sensor or the sample. Figure 2 is a schematic block diagram of a microscope 200 using a tunable electrowetting prism to achieve wobulation. An individually addressable microLED array 102 is patterned to create a structured excitation source 118. The LED display 102 is followed by a tunable electrowetting prism 204, which is used to add small offsets to the patterned light 220. The pattern is imaged onto a sample 112 in a standard epifluorescence setup with a tube lens 108 and 20x, 0.42 NA objective 110. Fluorescence 222 is collected by the objective 110 and tube lens 108 and separated from reflected excitation 222 with a dichroic 106 and imaged onto a CMOS sensor 114.

[0042] This system essentially laterally shifts the output image, because the amount of tilt applied by prism 204 is so small. The tilt may be under 1°, or in the example below under 0.22 °.

[0043] An experimental setup was used to demonstrate OS-SI M (optical sectioning structured illumination microscopy). It included a standard benchtop epifluorescence microscope. A patternable, striped microLED display 102 is used as an excitation source. The display is immediately followed by the tunable electrowetting prism 204 with the prism electrodes actuated to achieve a flat liquid-liquid interface (90° contact angle). The microLED pattern is imaged on the sample plane 112 with a tube lens 108 (Olympus SWTLU-C) and objective 110 (20x, 0.42 NA, Mitutoyo Plan Apo). The intensity at the sample plane was ~10 pW / mm2. The objective 110 was mounted on a piezo actuated stage to enable axial scanning through a sample. Fluorescence 222 from the sample is collected back through the objective 110 and tube lens 108 and is reflected by a short pass dichroic 106 (Thorlabs DMSP505R), through an emission filter (Chroma 525 / 20m) (not shown), onto a CMOS sensor 114 (FLIR BFLY-U3-23SC-C).

[0044] The striped microLED display 102 used was fabricated for the express purpose of OS-SIM, specifically in a miniature microscope. Previously, this microLED array has been demonstrated as a suitable light source for OS-SIM in a benchtop microscope. The display is composed of one hundred 20 x 2000 micron, individually addressable rows, with a light emission spectrum centered around 455 nm. The blue spectrum can be used to excite green fluorescent protein (GFP) and similar green fluorescent dyes. Patterns with equal number of stripes on and off were repeated across the display (i.e., six on, six off, repeated) to achieve a sinusoidal pattern in the sample plane 112. The microLEDs 102 were designed such that current is injected from the side of the stripe. Across a single stripe, this leads to a decrease in intensity. The injection alternates sides, stripe-to-stripe. Operating the microLED stripes in pairs reduces this inhomogeneity, for instance, operating with 2-stripes on, 2-stripes off. As the patterns get coarser, this effect is even further averaged out. As a consequence, the OS-SI M demonstration focused on coarser patterns: 12-, 20-, 24- and 40- stripes.

[0045] The images were obtained with static actuation and used calibration of applied differential voltage to offset in the sample plane. For a given pattern frequency on the LED display, the differential voltages were optimized to achieve a ±2TT / 3 phase shift for the OS-SI M reconstruction (to achieve three evenly spaced phases). OS- SIM image reconstruction used conventional methods established by Neil et al. See for example M. A. A. Neil, R. Juskaitis, and T. Wilson, "Method of obtaining optical sectioning by using structured light in a conventional microscope," Opt. Lett. 22, 1905-1907 (1997).

[0046] To calibrate the prism offset or Vdiff for each pattern frequency, a reference image of the sinusoidal pattern when the prism is actuated to flat was acquired by imaging a thin fluorescent target. Subsequently, Vdiff was increased (or decreased) from 0 until the sinusoidal pattern moved by ±1 / 3 of the period of the pattern. Figure 5 shows an example of the pattern with each of the three equally spaced phases for a 12-stripe microLED pattern. Intensity lineouts from images of the thin fluorescent flat are plotted with the device at flat or Vdiff = 0 (phase of 2TT / 3) and with the optimized Vdiff for a lateral offset (phases of 0 and 4TT / 3). The electrowetting prism beam steering angle scales linearly with the applied Vdiff. Therefore, once the differential voltage is calibrated for one pattern frequency, it can easily be scaled for any other pattern frequency. For the spatial frequencies used here, the magnitude of differential voltages ranged from 0.25 V to 0.8 V, corresponding to a steering angle of 0.07 to 0.23 degrees, depending on the period of the structured illumination. Previous characterization of electrowetting prisms with the DI / PCH liquid combination has found a 1 % drift in steering angle over 40 minutes. No drift was observed when acquiring the three subimages.

[0047] The microscope of Figure 2 is only one example of an imaging system benefiting from pixel shifting techniques such as wobulation. The two scanning modalities with the prism offer different maximum frame rates. With static scanning a camera can be triggered to acquire an image after the electrowetting prism is set to each angle. The response time should be about 60 ms for the small steering angles demonstrated, corresponding to a 16.67 Hz frame rate. Dynamic scanning with smaller scan angles could reach the kHz regime. Previous work has demonstrated a 0.5 degree steering angle at 500 Hz with dynamic scanning. The steering angles used here were less than 0.22 degrees, which would allow for faster acquisition. Electrowetting wobulation can thus be extended to a more traditional wobulation implementation for projectors as the electrowetting prism can easily exceed the 30-60 Hz range that is required. Functional imaging, which may be monitored with a miniature microscope, requires high frame rates from 10’s of Hz to the kHz regime, with the exact frame rate depending on the indicator reporting on neural activity. Pixel shift cameras often require a second per sub-image to allow for stabilization of the sensor after it moves, which would be unnecessary with our prism. The variety in sizes in which electrowetting devices can be fabricated further extends the diversity of imaging systems in which they can be implemented. Miniature microscopes commonly use lenses on the order of 3-6 mm diameters. Thus, millimeter scale electrowetting prisms, such as the one described above, could be incorporated directly in widefield miniature microscopes with a modified packaging. Another consideration is the range of tunability for scan angle. Exact requirements will depend largely on the magnification of the imaging system. The device used here has been characterized up to a scan angle of 4 degrees. However, electrowetting scanners with the same liquid combination, DI water and PCH, have reached scan angles up to 13.7 degrees. Conversely, for increased sensitivity or a smaller angle for a given differential voltage, a different liquid combination could be chosen to decrease the index of refraction contrast. The accuracy and precision of the steering angle will be limited by contact angle hysteresis and fabrication imperfections, but previous studies have demonstrated calibration procedures to overcome these issues. Although a monochromatic source was discussed here, this work could be extended to multicolor imaging systems. Chromatic aberration is likely to be small compared to the shifts applied to the optical path and could be corrected for in the system optical design. Other devices include.

[0048] Figure 3A is a schematic diagram of an example tunable electrowetting prism 204 having four electrodes. Figure 3A shows a side cross section of functionalized electrowetting prism 204. This view shows two electrodes, one controlled by V1 302 and the other controlled by V2 304. The other two electrodes controlled by V3 and V4 are shown in Figure 3B. The voltages are control signals used to control the electrowetting cells and hence shift the output image. Oscillating the voltage differentials shifts the output image back and forth, used for wobulation.

[0049] The electrodes 322, 328 controlled by V2 304 are shown in detail. The other electrodes are similarly configured. This example electrowetting prism 204 is made in 4 mm inner diameter functionalized glass cylinders 330 with an indium tin oxide (ITO) electrode layer 328, parylene HT dielectric layer 326, and hydrophobic coating 324. The example device shown in Figures 3A and 3B is filled with equal volumes deionized (DI) water 310 and 1-phenyl-1 -cyclohexene (PCH) 312.

[0050] At 455 nm wavelength, these liquids have a transmission of 84.8% and 91.1 %, respectively. Both liquids have high transmission across the visible spectrum and thus our technique can be applied to any visible wavelengths. To achieve a tunable prism, the sidewall electrode has four equally spaced gaps along the cylinder wall, creating four individually addressable electrodes, to which voltages V1 , V2, V3 and V4 are respectively applied. The electrode gaps are pictured in a top-down schematic view of the device in Fig. 3B. The gaps in the electrode are achieved with direct write photolithography, resulting in a 30 micron gap size. To add a tilt to the liquid-liquid interface, after biasing the electrodes to a voltage Vflat to achieve a flat interface, a differential voltage Vdiff about the flat voltage is applied across the scanning axis. Specifically, the electrodes are actuated in pairs so that V1 =V3=Vflat-Vdiff and V2=V4=Vflat+Vdiff, following the electrode labeling convention in Fig. 3B. Applying the differential voltage in pairs enables 1 D scanning. The electrowetting prism can be operated in two modalities to achieve shifts in an image: static actuation to each offset or continuous scanning of the electrowetting prism.

[0051] Prism 204 does not require four electrodes, as two electrodes may apply the shift. The additional electrodes may be useful to account to aberrations or to move the output image in the y plane as well as the x plane.

[0052] Figure 3B is a top schematic view of prism 204. This view shows the upper portion of each of the four electrodes. The lower portion of the electrode is not shown but is similar to 322 in Figure 3A. Voltage V1 controls the electrode having top portion 332. Voltage V2 controls the electrode having top portion 328. Voltage V3 controls the electrode having top portion 334. Voltage V4 controls the electrode having top portion 336.

[0053] Figure 3C is a diagram of steering angles versus voltages for this prism. This device can steer up to five degrees with voltages of ± 20V.

[0054] Figure 4 is a side schematic diagram of a tunable electrowetting prism steered at two angles. Since this is a side view, the beam steering is shown as up 420A and flat 420B. This might be accomplished by applying a voltage differential between V1 302 and V3 304 (see Figure 3A-C). Here, object 402 is shown as scanned between two directions 420A and 420B to form two images 412A and 412B.

[0055] Scanning side to side (here into and out of the page) would then be accomplished by applying a voltage differential between V2 306 and V4 308. This is especially useful if the pattern is other than simply parallel stripes.

[0056] Figure 9 is a plot comparing contrast of an image from a wobulated microscope versus contrast of a pseudo-widefield microscope. Figure 5 shows intensity lineouts of a 12-stripe microLED pattern 120 corresponding to three evenly spaced phases, from images with a thin fluorescent target. A phase of 2TT / 3 corresponds to the electrowetting prism 204 at flat, without an angle applied to the interface. Phases of 0 and 4TT / 3 corresponds to applying ± Vdiff , respectively. The pattern contrast is unaffected by applying the tilt to the interface.

[0057] Figure 6 is a diagram showing pattern contrast as a function of the pattern period for patterns imaged with (light) and without (black) electrowetting prism 204. The slight decrease in contrast with the addition of the prism results from the unactuated regions of the liquid-liquid interface at the electrode gaps that are necessary for scanning with an electrowetting device. The pattern contrast is only minimally affected by adding the prism 204 to the imaging system. The electrode gaps may be small, such as 50pm or less.

[0058] Figures 7, 8 and 9 illustrate the performance of pseudo-widefield and an OS-SIM (optical sectioning structured illumination microscopy) wobulated microscope imaging with a pollen autofluorescence signal. The thin fluorescent target used to characterize the pattern contrast and sectioning strength was prepared by applying a fluorescent dye (Sharpie Fluorescent Yellow Highlighter #27025) to a coverslip which is then sealed against a microscope slide. To test the imaging modality on a biological sample, the experiment used a prepared slide of mixed pollen grains (Carolina Biological Supply Inc.), which autofluoresces when exposed to visible light.

[0059] A 24-micron period pattern was used, which offered sufficient sectioning strength to resolve axial slices of the ~80 micron diameter pollen grain. Sample images at 14 and 40 microns from the top of the pollen grain, as well as the maximum intensity projection of an axial scan through the pollen grain for both pseudo-widefield and OS-SIM were analyzed.

[0060] Close to theoretical optical sectioning strengths between 13 and 34 microns FWHM are achieved with electrowetting wobulation SIM. Experimental results agree with theoretically predicted sectioning FWHMs within 2-7 microns. In addition to characterizing the sectioning strength with a thin fluorescent target, the sectioning strength is visually evident in 3D samples. The out-of-focus fluorescence is reduced in the pollen grain and features that would otherwise be lost to background are recovered in the pollen grain SIM maximum intensity projection. Figure 7 compares two images at 14 microns below the start of pollen autofluorescence signal. Intensity lineouts for the widefield (light) and SIM (black) are plotted. These lineouts show one of the pollen grain spikes and two of the nulls on surface. The contrast of these features is enhanced in the OS-SIM trace.

[0061] Figure 8 compares two images (pseudo-widefield and OS-SIM) at 40 microns below the start of a pollen autofluorescence signal. Intensity lineouts across the edge of the pollen grain are shown from both images. A reduction in signal from the center of the pollen, corresponding to out of focus fluorescence, can be seen.

[0062] Figure 9 compares the contrast of pollen features in the pseudo-widefield and OS- SIM images. It considers the contrast of the edge at the 40 micron slice, and determines contrast from Imax at the edge of the grain and Imin in the center. The contrast improved from 32% to 55%. It also considers the nulls of the pollen grain at 14 microns, where Imax is defined at the surface between nulls and Imin is determined at the null. The OS-SIM improves the contrast from 22% in the pseudo- widefield to 37%.

[0063] A slight decrease in contrast and increase in sectioning strength from adding the electrowetting prism are likely the result of the imaged light overfilling the prism, extending beyond the usable aperture of the device. The liquid-liquid interface remains unactuated near the gaps in the ITO conductive layer that enable multielectrode devices. Consequently, when actuating to flat, the interface near the unactuated regions will lead to aberrations. To overcome aberrations from the unactuated region of the prism in future applications, the usable aperture of the device can be better matched in size to the beam path of the imaging system. Another alternative could be to bias the device away from a flat liquid-liquid interface, which would lead to less disparity between the unactuated regions and the curvature of the actuated interface. Operating the prism with a curved interface would involve an additional lens to compensate.

[0064] Figure 10 is a plot of predicted performance of a wobulated microscope versus measured performance. Theoretical (x’s) and measured optical sectioning (OS) thickness (dots with error bars) are shown as a function of normalized spatial frequency. The predicted sectioning strength is determined using the Stokseth approximation assuming the NA of the imaging system without the prism, for each frequency used for characterization and provides a reference to characterize the impact of the electrowetting prism. The experimental sectioning strength is measured with a thin fluorescent target. Error bars on the measured sectioning strengths are derived from the Gaussian fits.

[0065] The theoretical sectioning strength for each of the patterns was calculated using the spatial frequencies measured in the sample plane for four patterns, and assuming a diffraction limited system. Theoretical sectioning strengths were 9.7, 15, 18, and 32 microns. The sectioning thickness was between 2 and 7 microns larger for electrowetting wobulation than for an ideal imaging system. The experimental and theoretical sectioning strengths as a function of the normalized spatial frequency are plotted in Figure 10, where the normalized spatial frequency is derived by normalizing to the theoretical maximum cutoff frequency.

[0066] One application for electrowetting wobulation in OS-SI M is to enhance display resolution so that one could employ a 2-stripe pattern instead of a 6-stripe pattern. Table 1 compares measured sectioning strength and corresponding calculated sectioning strength of a 3x coarser pattern. Each characterized pattern period includes measured wobulation optical section (OS) and theoretical sectioning strength for a pattern of 3x the period. Although the prism 204 slightly reduces the optical sectioning strength thickness for a given pattern frequency, the measured sectioning strength outperforms a 3x coarser pattern of the diffraction limited system. We can infer that reducing the pattern from 6-stripes and a traditional implementation for three phases to 2-stripes with electrowetting wobulation in a low magnification microscope will lead to enhanced sectioning.

[0067] Period [pm] Measured OS [ m] Theoretical OS for 3 Period [pm]

[0068] 12 13 27

[0069] 20 19 44

[0070] 24 25 53

[0071] 40 32 88 Table 1

[0072] Lateral resolution of a widefield microscope is unaffected by OS-SIM. Furthermore, the prism 204 is before the dichroic 106 in the beam path. Thus, electrowetting wobulation has no impact on the NA of the emission arm and by extension does not affect the lateral resolution. For widefield imaging, the lateral resolution is governed by the standard elements of the microscope. The FWHM of bead profiles of 1 .1 micron fluorescent beads is 1 ,2± 0.3 microns.

[0073] While the exemplary preferred embodiments of the present invention are described herein with particularity, those skilled in the art will appreciate various changes, additions, and applications other than those specifically mentioned, which are within the spirit of this invention.

[0074] What is claimed is:

Claims

CLAIMS1. A system for shifting a widefield image comprising: a source for providing a widefield input image; a tunable electrowetting cell having a liquid-liquid interface shape and electrodes controlled by an applied voltage; and circuitry configured to provide varying voltages to tunable electrowetting cell according to a control signal; wherein the tunable electrowetting cell is configured to receive the widefield image and form a widefield output image based on the widefield input image; and wherein the tunable electrowetting cell is configured to shift the widefield output image substantially laterally according to the applied voltage.

2. The system for shifting a widefield image of claim 1 wherein the tunable electrowetting cell tilts the widefield output image less than 1° in order to shift the widefield output image substantially laterally.

3. The system for shifting a widefield image of claim 1 wherein the tunable electrowetting cell tilts the widefield output image less than 0.22°.

4. The system for shifting a widefield image of claim 1 wherein each electrode has two sides and wherein the distance between one of the sides of a first electrode and one of the sides of a second electrode is under 50pm.

5. The system for shifting a widefield image of claim 1 wherein the source for providing a widefield input image is an LED display.

6. The system for shifting a widefield image of claim 5 wherein the LED display provides a patterned input widefield display and the tunable electrowetting cell is configured to form a patterned output widefield display based on the patterned input widefield display.

7. The system for shifting a widefield image of claim 6 further comprising optics for projecting the patterned output widefield display onto a sample.

8. The system for shifting a widefield image of claim 7 wherein the control signal is configured to wobulate the patterned output widefield display by varying the voltage provided to the tunable electrowetting cell in an oscillating manner.

9. The system for shifting a widefield image of claim 8 configured to oscillate at a rate over 10 Hz.

10. The system for shifting a widefield image of claim 1 wherein the control signal is configured to wobulate the patterned output widefield display by varying the voltage provided to the tunable electrowetting cell in an oscillating manner.11 . The system for shifting a widefield image of claim 10 configured to oscillate at a rate over 10 Hz.

12. The system for shifting a widefield image of claim 10 configured to oscillate at a rate over 60 Hz.

13. The system for shifting a widefield image of claim 10 configured to oscillate at a rate over 500 Hz.

14. The method of laterally shifting a widefield image comprising the steps of: providing a widefield input image to a tunable electrowetting cell having a liquidliquid interface shape and electrodes controlled by an applied voltage; providing a control signal based on a desired amount of image shifting; providing varying voltages to the tunable electrowetting cell according to the control signal; receiving the widefield image with the tunable electrowetting cell and forming a widefield output image based on the widefield input image; and shifting the widefield output image substantially laterally according to the applied voltage.

15. The method of laterally shifting a widefield image of claim 14 wherein the step of shifting the widefield image shifts the widefield image less than 1° in order to shift the widefield output image substantially laterally.

16. The method of laterally shifting a widefield image of claim 15 wherein the step of shifting the widefield image shifts the widefield image less than 0.22°.

17. The method of laterally shifting a widefield image of claim 14 wherein the step of providing the widefield image provides a patterned input widefield display.

18. The method of laterally shifting a widefield image of claim 14 wherein the control signal includes the step of wobulating the output widefield display by varying the voltage provided to the tunable electrowetting cell in an oscillating manner.

19. The method of laterally shifting a widefield image of claim 18 wherein the step of wobulating wobulates the output widefield display at a rate over 10 Hz.

20. The method of laterally shifting a widefield image of claim 18 wherein the step of wobulating wobulates the output widefield display at a rate over 500 Hz.

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