Gatan, Inc.

Ondrej L Krivanek

Paul E Mooney

Daniel N Bui

Niklas Dellby

A method and apparatus are provided for CTD imaging device multiple read-out speeds with optimized operation at all of the available speeds. Image signals from a CTD imaging device are digitally sampled at a defined frequency with the read-out electronics being matched to the defined frequency for optimum operation at that frequency. Digital samples taken during both a first (reset reference) portion of each image signal and a second (image voltage) portion of each image signal are then discarded if taken during a noisy/unstable part of the image signal or accumulated and averaged if taken during a stable part of the image signal. The accumulated and averaged digital samples are then algebraically combined to produce signals representative of an image generated by the CTD imaging device. The read-out speed of the CTD imaging device is a fraction of the sampling speed and can be selected by setting an integer divisor for the defined sampling frequency. Selected ones of the samples are retained based on the selected read-out speed. For the fastest read-out speed, the number of samples taken per imaging signal is one and the divisor is equal to one. Selected slower speeds determine which samples are discarded and which samples are accumulated, averaged and combined to produce signals representative of an image generated by the CTD imaging device.

Method and apparatus for multiple read-out speeds for a CTD

A precision-controlled slit mechanism having an adjustable width which is both accurate and reproducible is provided for apparatuses which are designed to exclude portions of an energy spectrum prior to analysis such as energy-selected imaging filters in electron microscopes. The slit mechanism includes a pair of slit halves, a light source for directing light between the slit halves, a detector for measuring the intensity of light passing from the light source through the slit halves, and an actuator for adjusting the width of the opening between the slit halves in response to the intensity of light measured by the detector.

Precision-controlled slit mechanism for electron microscope

An apparatus designed to be positioned in the projection chamber of an electron microscope to detect electron images and/or diffraction patterns from a sample and convert those electron images into light images is provided. The apparatus transfers light images to an imaging sensor for recording while enhancing resolution of the light images by absorbing substantially all laterally scattered light before it reaches the imaging sensor.

Resolution-enhancement device for an optically-coupled image sensor for

An apparatus for improving the resolution of images produced by an electron microscope is provided and includes an electron beam forming an electron image, a support structure mounted in the path of the electron beam, with the support structure transmitting the electron image. Scintillating material is coated onto the side of the support structure opposite that on which the electron image is incident, the scintillating material converting the electron image into a light image. A mirror is provided for deflecting the optical path of the light image into a CCD camera positioned to receive and record the light image.

Apparatus for improved image resolution in electron microscopy

A method and an apparatus comprising a transmission electron microscope, an electron camera, a computer, and microscope control electronics. The electron camera captures an image produced by the electron microscope, the computer transforms the image into a digital diffractogram, and determines the microscope defocus and astigmatism by analyzing the diffractogram. The computer uses the determined astigmatism and defocus values to stigmate the microscope, and to set the defocus to a user-selected value. The computer also changes the direction of electron illumination to different values, and works out the true location of the optic axis of the microscope from the changes in the diffractograms recorded for the different illumination directions.

Autoadjusting electron microscope

A method and an apparatus comprising an electron gun, two energy analyzers, an energy-selecting slit with intensity sensors, a feedback circuit, a sample, and an electron detector. The beam produced by the electron gun is dispersed according to the energies of the electrons by the first energy analyzer. The dispersed beam impinges on a slit which monochromates the beam by selecting a narrow pass-band of energies. The two halves of the slit are equipped with electron intensity sensors whose output is used by a feedback circuit to stabilize the position of the dispersed beam on the slit so as to counteract instabilities in the power supplies of the electron gun and of the analyzer. The monochromated electron beam then passes through a sample, and the transmitted beam is dispersed according to the energies of the electrons by the second energy analyzer. The power supplies of the two analyzers are linked so that the energy selected by the second analyzer tracks the energy selected by the first analyzer. The second analyzer therefore automatically tracks instabilities in the gun high voltage, and the whole apparatus is able to achieve much higher energy resolution than if all the power supplies were operated independently.

High resolution electron energy loss spectrometer

An apparatus comprising a cooled slow-scan charge-coupled device camera mounted in a chamber attached to a projection or specimen chamber of an electron microscope, and a vacuum valve separating the camera chamber from the microscope chamber. The operation of the vacuum valve is linked to the microscope vacuum system such that the valve remains open while the microscope chamber is under vacuum, but closes if the microscope chamber is about to be let up to atmospheric pressure, and stays closed until the microscope chamber is evacuated again. In an alternate embodiment of the invention, the camera is inserted by a pneumatically operated piston to the microscope chamber, and is withdrawn and sealed off in a separate vacuum chamber in the microscope chamber is about to be let up to air.

Cooled CCD camera for an electron microscope

Quadruple lenses 30, 31 and 32 and sextupole lenses 40, 41, 42, and 43 are interposed between a energy-dispersing device 17 and an electron imaging device 50 in an energy-selected electron imaging filter. The energy-dispersing device produces a focussed spectrum 21 of electron energies in the plane of an energy-selecting slit 20, and the quadrupole and sextupole lenses transform the spectrum into an energy-selecting slit may also be either removed or opened wide, and the quadrupole lenses may be refocussed, so that the electron imaging device directly observes a magnified spectrum of the electron energies.

Energy-selected electron imaging filter

An electron beam attenuator decreases the intensity of an electron beam incident on a parallel electron detector by alternately deflecting the electron beam onto and away from the detector. A power supply controlling the attenuator is synchronized with the operation of the detector such that the electron beam only strikes the detector when the detector is not being read-out. The ratio of the time that the electron beam is incident on the detector to the time that the beam is off the detector is varied to give an adjustable attenuation of the detected electron signal. The intensity of the electron beam incident on the detector is monitored by a sensor separate from the parallel detector. When the beam intensity exceeds a pre-determined threshold, the attenuator is automatically activated, in order to prevent damage to the detector.

Variable-attenuation parallel detector

Quadrupole electron lenses 21, 22, 23 and 24 are disposed between an energy-dispersing device 15 and a parallel detector 50 in an electron energy-loss spectrometer. The power and polarity of the quadrupole lenses may be adjusted to simultaneously provide the desired energy dispersion of the spectrum, and a precise match between the width of the spectrum and the width of the parallel detector. Additional quadrupole lenses may be interposed between quadrupole lens 24 and the detector 50 to further increase the energy dispersion.

Growing community of inventors

Lafayette, CA, United States of America

Ondrej L Krivanek