U.S. Philips Corporation

Willem M Coene

Augustus J Janssen

Gerrit J Keesman

Eduard W Salomons

A method of non-recursive reconstruction of images in a High Resolution Electron Microscope (HRTEM). In an HRTEM a series of, for example, 100 images of an object is formed with each time a different setting of the astigmatism of the imaging lens or lenses. By subjecting these images to a Fourier transformation and multiplying the transformed images by a known filter function, a reconstruction of the object electron wave function is obtained by summing of the images thus filtered and transformed; said object electron wave function no longer contains the linear information which is undesirable for the reconstruction and the non-linear information which is not negligibly small for large thicknesses of the object is no longer present either.

Method of reconstructing an image in a particle-optical apparatus

The picture quality of an MPEG-coded video signal can be improved considerably by modifying selected coefficients after conventional quantization, for example by rendering them zero. The modification is such that the Lagrangian cost D+.lambda.R (D is distortion, R is bitrate) is minimal for a given value of a Lagrange multiplier .lambda.. A relatively simple process is disclosed in which the value of .lambda. is calculated by means of statistical analysis (6) of the picture to be coded. The statistical analysis comprises the estimation of the RD curve on the basis of the amplitude distribution of the coefficients. The searched .lambda. is the derivative of this curve at the desired bitrate.

Device and method for coding video pictures

In a method for the iterative formation of an image of a specimen in a particle-optical apparatus a series of experimental images (the experimental series) is recorded with each time a different setting of an imaging parameter (for example, the focal distance), and a comparable series of images is calculated on the basis of the electron wave at the specimen (the estimation). The two series are compared and on the basis thereof an electron wave is calculated (the feedback) with which a new series of images is calculated which better approximates the experimental series. This iteration step is repeated until the correspondence between the experimental series and the calculated series is sufficient, after which the associated electron wave is considered to be the desired image of the specimen. A substantial gain as regards calculation time can be achieved during the estimation step as well as during the feedback step by executing the operation of the invention by means of FFTs. This is possible by writing the correlation expressions to be calculated in both steps in accordance with the invention in such a manner that they occur as pure correlation integrals which can be calculated by means of FFTs. The calculation time required when use is made of FFTs is substantially shorter than in the case of explicit calculation of the correlation expressions in conformity with the state of the art. The calculation time can thus be reduced by a factor of the order of magnitude of 50,000.

Method for particle wave reconstruction in a particle-optical apparatus

A method for image reconstruction in a high-resolution electron microscope. The Fourier transform (29) of an electron hologram (28) is obtained which is composed of a central frequency domain CB=I.sub.hol,0 (G) and two sidebands SB+=I.sub.hol,+ (G) and SB-=I.sub.hol,- (G). The two sidebands represent the linear image information. By making use of the frequencies in the central frequency domain in the image reconstruction, a non-linear image reconstruction is performed having a resolution which is considerably higher than the achievable information limit in linear image reconstruction using only the sidebands.

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Eindhoven, Netherlands

Willem M Coene