The invention relates to developing a signal to represent each block of an image contained in a frame being interpolated in a motion interpolated system such that the error between the frame being interpolated and the reference frames is minimized without placing any predetermined limitation on the values of either the weights or the displacements employed as motion vectors. The weights and displacements required to achieve the minimization of the interpolation error are jointly determined on a block by block basis. A set of groups having a candidate displacement from each reference frame and, in accordance with an aspect of the invention, their corresponding best weights are determined. An error signal which would result if each member of the set of groups of candidate displacements from each reference frame and their corresponding best weights were employed to represent the block is evaluated. The group having the lowest error signal is either selected to represent the block or as a starting point for the selection of a new set of groups. By employing other aspects of the invention, the number of groups which need be evaluated to represent the block can be reduced from a predetermined maximum number.

The invention relates to developing a signal to represent each block of an image contained in a frame being interpolated in a motion interpolated system such that the error between the frame being interpolated and the reference frames is minimized without placing any predetermined limitation on the values of either the weights or the displacements employed as motion vectors. The weights and displacements required to achieve the minimization of the interpolation error are jointly determined on a block by block basis. A set of groups having a candidate displacement from each reference frame and, in accordance with an aspect of the invention, their corresponding best weights are determined. An error signal which would result if each member of the set of groups of candidate displacements from each reference frame and their corresponding best weights were employed to represent the block is evaluated. The group having the lowest error signal is either selected to represent the block or as a starting point for the selection of a new set of groups. By employing other aspects of the invention, the number of groups which need be evaluated to represent the block can be reduced from a predetermined maximum number.

A method for compensating pattern placement errors during writing a pattern on a target in a charged-particle multi-beam exposure apparatus is presented. A layout is generated by exposing a plurality of beam field frames using a beam of electrically charged particles, wherein each beam field frame has a respective local pattern density, corresponding to exposure doses imparted to the target when exposing the respective beam field frames. During writing the beam field frames, the actual positions thereof deviate from their respective nominal positions by a placement error as a result of build-up effects within said exposure apparatus, depending on the local pattern density evolution during writing the beam field frames. To compensate this displacement, a displacement behavior model established beforehand is employed to predict the displacements; a local pattern density evolution is determined, displacements of the beam field frames are predicted based on the local pattern density evolution and the displacement behavior model, and the beam field frames are repositioned accordingly based on the predicted values.

A blocking matching motion estimation apparatus estimates a displacement of a search block in a current frame with respect to each of candidate blocks in a previous frame to produce motion vectors and error functions representing the similarity between the search block and a candidate block. The motion estimating apparatus employs a weight function to weight a number of error functions based on a MSE measurement and selects a weighted error function entailing a minimum error to produce a motion vector corresponding thereto. The weight function includes a local variance for a localized subblock defined in the search block. Another embodiment of the weight function includes a gradient of pixels in the search block filtered by a 2-dimensional gradient filter.

An apparatus for determining a motion vector representing a displacement between a current frame and a previous frame of video signals comprises an error detector for comparing the error functions calculated from block matching sections each other and selecting M number error functions in the order of their magnitude beginning from a smallest, a displacement vector selector for selecting M number of displacement vectors from displacement vectors generated from candidate block formation sections, a candidate block selector for selecting M number of candidate blocks, M number of boundary matching sections for generating M sets of boundary differences, M number of comparison and counting sections for comparing boundary differences in one of the M sets of boundary differences with a predetermined value, to count the number of the boundary differences having a value larger than the predetermined value; and an optimum motion vector selector for selecting a counted number having a minimum value to determine one of said M number of displacement vectors which corresponds to the selected counted number, as the motion vector for the search block.

A digital Wiener filtering method is proposed which applies motion compensation by successive approximations of increasing resolution to determine displacement vectors for two successive image frames, a vector defining a real displacement only being applied to a block of one of the frames when the mean absolute error associated with that vector is not greater than a given fraction of the mean absolute error between that block and the corresponding block of the other frame. The current frame is then filtered block-by-block, with the blocks overlapping. In this filtering, each block is a 3D volume of pixels from the current frame and blocks selected from the preceding and succeeding frames so as to correspond according to the displacement vectors. In one embodiment, the filtering comprises applying a 3D FFT to convert to a power spectrum in the frequency domain, followed by attenuation according to a Wiener filter and conversion from the frequency domain by the inverse FFT.