High framerate and high dynamic range electron microscopy
Methods and systems for acquiring transmission electron microscope video data on a rolling-shutter detector at an enhanced frame rate and without temporal distortions are described. Also described are methods to enhance the dynamic range of image and diffraction data acquired using a transmission electron microscope. The disclosed methods and systems may also be applicable to photon detection and imaging systems.
1. A method for acquiring transmission electron microscope data, the method comprising:
a) providing a transmission electron microscope comprising a two-dimensional deflector configured to deflect electrons transmitted or scattered by a sample positioned at a sample plane, wherein the two-dimensional deflector is positioned between the sample plane and a two-dimensional detector array;
b) modulating a deflector control signal such that the electrons are sequentially deflected to a series of two or more sub-regions of the two-dimensional detector array, thereby capturing a detector array read-out cycle data set within a series of detector array readout cycles corresponding to a pattern of the electrons deflected to each of the series of two or more sub-regions; and
c) synchronizing a modulation of the deflector control signal with a read-out signal of the two-dimensional detector array such that each of the series of two or more sub-regions captures a data set within the series of detector array read-out cycles, wherein the modulation of the deflector control signal is synchronized with a rolling shutter synchronization signal for the two-dimensional detector array such that the electrons are directed to a sub-region within the series of two or more sub-regions that is not actively being read out.
2. The method of claim 1 , wherein the two-dimensional deflector is a two-dimensional electrostatic deflector or a two-dimensional electromagnetic deflector.
3. The method of claim 1 , wherein the series of two or more sub-regions comprises sub-regions of a single two-dimensional detector.
4. The method of claim 1 , wherein the series of two or more sub-regions comprises different detectors within the two-dimensional detector array.
5. The method of claim 1 , wherein the two-dimensional detector array comprises a charge-coupled device (CCD) image sensor, a complementary metal oxide semiconductor (CMOS) image sensor, an electron direct detection (EDD) camera, or a time-of-flight (ToF) image sensor.
6. The method of claim 5 , wherein a duty cycle for acquiring the transmission electron microscrope data is at least 90% without incurring temporal distortion of the transmission electron microscope data.
7. The method of claim 5 , wherein the data set captured by each of the series of two or more sub-regions comprises a frame of image or diffraction data.
8. The method of claim 7 , further comprising: collecting a plurality of frames of image or diffraction data; and processing the plurality of frames of image or diffraction data for the series of two or more sub-regions to create video data comprising a framerate that is at least 4×faster than a read-out rate of the CCD image sensor, the CMOS, or ToF image sensor.
9. The method of claim 1 , wherein a switching time for the two-dimensional deflector is less than 10 microseconds.
10. The method of claim 1 , wherein the deflector control signal is modulated such that a dwell time for deflecting the electrons to each of the series of two or more sub-regions is different for at least one of the series of two or more sub-regions.
11. The method of claim 1 , wherein a dwell time for deflecting the electrons to the series of two or more sub-regions ranges from about 1 microsecond to about 100 milliseconds.
12. The method of claim 1 , wherein each of the series of two or more sub-regions of the two-dimensional detector array comprises an individual detector.
13. The method of claim 1 , wherein the data set captured by the series of two or more sub-regions is processed to correct for distortions introduced by a deflection within the deflector control signal.