Abstract: The present invention relates to a transmitter for transmitting user data between a transmitter and a receiver in a multi-carrier radio communication system having a plurality of orthogonal frequency sub-carriers, said method comprising the steps of selecting a set of sub-carriers on which said user data are to be transmitted between said transmitter and said receiver. According to the present invention, the transmitter comprises: means for selecting a set of sub-carriers on which said user data are to be transmitted to said receiver, and means for sending before transmission of said user data, an indication related to a threshold to said receiver.

Abstract: The present invention relates to a method for transmitting user data between a transmitter and a receiver in a multi-carrier radio communication system having a plurality of orthogonal frequency sub-carriers, said method comprising the steps of selecting a set of sub-carriers on which said user data are to be transmitted between said transmitter and said receiver. According to the present invention, the method comprises the steps of: Sending from said transmitter, before transmission of said user data, an indication related to a threshold; Determining at the receiver a quality level for each sub carriers; Selecting at said receiver sub carriers to received said user data as a function of said indication related to a threshold and of said quality levels.

Abstract: Estimation of channel characteristics and interference level in a time-varying multi-carrier multi-user systems is carried out concurrently. To perform the estimation, a multitude of data symbols and dedicated pilot symbols are transmitted over the channel. The estimate of the interference level is used to estimate the channel parameters.

Abstract: Disclosed is a phase noise compensation apparatus to be applied to the OFDM system, comprising an ICI estimating unit for estimating inter carrier interference (ICI) using a pilot sub-carrier included in a reception signal, a estimating unit for estimating a common phase error (CPE), which is a phase noise from the reception signal as sampled, using the pilot sub-carrier, and estimating a transmission signal by removing the estimated CPE from the reception signal, a calculating unit for calculating phase change by the ICI in the reception signal by convoluting the ICI and the transmission signal, and an equalizer for compensating the calculated phase change by the ICI in the reception signal. Accordingly, phase noise can be exactly compensated by estimating as phase noise the result of convoluting a received signal where the CPE is removed in a frequency domain and the estimated ICI according to the present invention.

Abstract: On a transmitting side, input data is separated into a first data row and a second data row by the unit of predetermined symbol; one code is selected among a plurality of orthogonal codes in accordance with the separated second data row; the first data row is diffused using the selected code; and the diffused first data row is modulated to be transmitted. On a receiving side, a receiving signal is inversely diffused individually using the same plurality of orthogonal codes as the orthogonal codes on the transmitting side; a signal which is inversely diffused using a correct orthogonal code is selected among the inversely-diffused respective receiving signals; a first receiving data row is obtained from a demodulation of the selected signal; a second receiving data row corresponding to the correct orthogonal code which is selected by the selection is obtained; and receiving data is obtained by composing the first receiving data row and the second receiving data row.

Abstract: A transmitter having two or more transmit antennas includes a bit parser for providing two or more data streams to an interleaver of the transmitter. The bit parser receives bits representing data to be transmitted over the transmit antennas, and parses the bits into a number of data streams equal to a number of the transmit antennas such that the bits are divided into bit groups, each having no more than two of the bits, and each of the data streams include non-adjacent ones of the bit groups.

Abstract: A method is described comprising: transmitting a training signal from each antenna of a base station to each of a plurality of client devices utilizing tropospheric scatter, each of the client devices analyzing each training signal to generate channel characterization data, and transmitting the channel characterization data back to the base station utilizing tropospheric scatter; storing the channel characterization data for each of the plurality of client devices; receiving data to be transmitted to each of the client devices; and precoding the data using the channel characterization data associated with each respective client device to generate precoded data signals for each antenna of the base station; and transmitting the precoded data signals through each antenna of the base station to each respective client device.

Abstract: Shaped Offset Quadrature Amplitude Modulation (QAM) can be implemented within a communication system. A train or sequence of orthogonal sinc pulses can be generated for each of the in-phase and quadrature signal paths. The sinc pulses in the quadrature signal path can have a predetermined time offset relative to the pulses in the in-phase signal path. An in-phase or quadrature antipodal data signal can be used to modulate the respective sinc pulse train. Each of the in-phase and quadrature pulses can be shaped using a time domain windowing function, such as a Kaiser-Bessel window, to adjust the spectral width and spectral sidelobe level of the signal. The beta parameter of the window can be adjusted to achieve the desired signal response. The timing of the sinc pulses may need to be adjusted following the window function in order to maintain orthogonality of the pulses.

Abstract: The system for transmission and reception of QAM signals for use in telecommunication networks for any data rates at SNR (signal to noise ratio) of below 0 dB comprises two devices. The first device may be used for transmission Units (1)-(4) transform input bit information sequence (17) with the clock frequency ft (18) into two parallel m-level sequences with the clock frequency ft/2k forming the first and second channels, where k=log2(m). Unit (5) forming additional signals Cos ? ? t ? t 4 ? k , A · Sin ? ? t ? t 4 ? k , where ?t=2?ft. Units (6), (7) multiply m-level sequences of the first and second channels with signal Cos ? ? t ? t 4 ? k for removal phase ambiguity at reception end, and units (8), (9) adding with signal A · Sin ? ? t ? t 4 ? k ? t , defining level of the additional pilot-signal in output spectrum. Filters (10), (11) forming baseband QAM signal spectrum and units (12)-(16) shift of spectrum at intermediate or carrier frequency.

Abstract: A wireless communications device includes an encoder having an input for receiving an input symbol, and generates based upon the input symbol a channel symbol and an antenna control symbol. At least one transmitter is coupled to the encoder for receiving the channel symbol. An antenna switch is coupled to the encoder for receiving the antenna control symbol, and to the at least one transmitter for receiving the channel symbol to be transmitted. An antenna array is coupled to the antenna switch and includes N antenna elements, with N?2. The antenna switch selects less than N antenna elements based upon the antenna control symbol for transmitting the channel symbol.

Abstract: A GMSK/8-PSK mix-mode support for GSM/GPRS/EDGE compliant handsets is provided and may comprise transmitting bursts of different modulation types within a single GSM frame, where the different modulation types may comprise a GMSK modulated type and an 8-PSK modulated type. The method may comprise selecting the modulation type for each of the transmitted bursts in the single GSM frame. The GMSK modulated type may be used to modulate a normal data burst type and/or an access burst type. Data that may be transmitted within the single GSM frame may be stored in memory. At least a portion of the stored data may be selected for an initialization portion of the burst, and at least a portion of the stored data may be selected for a data portion of the burst.

Abstract: A method of multi-path acquisition may include estimating a contribution of acquired users of a first type to a received signal, canceling the estimated contribution from the received signal to generate a resultant signal, and performing multi-path acquisition for users of the first type and users of a second type based on the resultant signal.

Abstract: A known sequence of symbols is located within a transmitted sequence of symbols by estimating the phase differences between offset symbols within a portion or more of the transmitted sequence, estimating the phase differences between offset symbols in the known sequence, and determining that the symbols within the portion or more of the transmitted sequence are the known sequence if the phase difference estimates determined from the symbols within the portion or more of the transmitted sequence are substantially equal to the phase difference estimates determined from the known sequence.

Abstract: A communication apparatus includes a radio frequency (RF) circuit configured to operate on an RF signal. The communication apparatus also includes a digital processing circuit and a buffer circuit having a first portion and a second portion. The digital processing circuit may operate in association with the RF circuit according to a time domain isolation technique. In addition, the digital processing circuit may perform a first task on received data and may alternately store a first set of results of the first task within the first buffer portion and a second set of results of the first task within the second buffer portion. The digital processing circuit may further perform a second task on the first set of results concurrently with storing the second set of results within the second buffer portion.

Abstract: A demodulator is provided which includes a filter filtering a signal based on pass frequency bands changed at a time of a channel search and at a time of a normal reception, and a demodulation processing unit performing an orthogonal frequency division multiplex demodulation based on the filtered signal. Also, a demodulator is provided which includes a synchronization processing unit performing a synchronization processing based on an input signal and a demodulation processing unit performing an orthogonal frequency division multiplex demodulation based on the synchronization processed signal, wherein the synchronization processing unit calculates a correlation value of a signal being a delayed input signal and the input signal, and performs the synchronization processing when the correlation value satisfies a condition.

Abstract: A demodulating circuit demodulates a digital broadcasting signal and transmission control information for identifying a transmission system of the digital broadcasting signal from a transmission signal. A buffer circuit holds the transmission control information for at least one frame period. A multi circuit periodically multiplexes the transmission control information demodulated by the demodulating circuit and the transmission control information held by the buffer circuit at least in units of one frame. The multiplexed transmission control information is supplied to the buffer circuit and is also supplied to a first error correction circuit. The first error correction circuit corrects errors of the transmission control information. The transmission control information is multiplexed, and accuracy of error correction is improved by a time interleaving effect so that lead-in time is reduced.

Abstract: A calibration device for use in a radio receiver enables receiver self-calibration and self-correction of inbound RF signals. The calibration device includes an estimation module for receiving a sample digital packet and calculating imbalance parameters as a function of a portion of the sample digital packet. The calibration device further includes a correction module for applying the imbalance parameters to a received digital packet of an inbound RF signal to produce a corrected digital packet. The received digital packet may be a portion of the sample digital packet, the complete sample digital packet or a new packet.

Abstract: The present invention provides methods and apparatuses for demodulation and decoding of backscattered RFID tag signals, represented by their in-phase and quadrature components at the output of the demodulator in the receiver portion of a reader interrogator. Autocorrelation coefficients for the in-phase and quadrature components of the received signal are calculated. The in-phase and quadrature coefficients are combined. The sign of output data is determined. Embodiments of the present invention are applicable to Gen 2 RFID systems as well as any wireless telecommunications system with the corresponding data modulation and/or encoding technique.

Abstract: Methods and apparatus for determining carrier frequency error of a serial offset quadrature pulse shaped signal, such as a minimum shift keyed (MSK) signal, are disclosed. Carrier frequency error is determined by receiving a quadrature pulse shaped signal having a synchronization sequence, detecting synchronization of the quadrature pulse shaped signal, and storing a baseband inphase (I) signal and a baseband quadrature (Q) signal of the synchronization sequence while detecting synchronization. After detecting synchronization, segments of the stored baseband I and Q signals are read and correlated with a spreading sequence. Carrier frequency error is then estimated based on phase differences between each of the correlated segments.

Abstract: Methods and apparatus for synchronization (SYNC) detection of a received serial offset quadrature pulse shaped waveform modulated by a symbol SYNC sequence are provided. The waveform is serially demodulated into a serial baseband signal and serially correlated with segments of the symbol SYNC sequence. Correlation strength estimates of each of the serially correlated output signal are computed and combined to detect a coarse SYNC. The serially correlated output signals are phase corrected based upon phase change conditions and the phase corrected signals are used to detect a fine SYNC.

Abstract: A receiver including a plurality of receiver branches operable to receive signals, a plurality of sample-and-hold circuits (4), each of which is connected to corresponding one of the receiver branches at the output thereof, a switch (5) connected to the sample-and-hold circuits at outputs thereof, and a demodulating unit (7) connected to the switch (5) at the output thereof. Each of the sample-and-hold circuits (4) is operable to extract a discrete value from the output from corresponding one of the receiver branches.

Abstract: A radio frequency integrated circuit for a global positioning system (GPS) application mixes radio frequency GPS signals from an external source with a predetermined intermediate frequency that is less than 4 fo. In one embodiment, the intermediate frequency is selected to be 1.5 fo. An intermediate frequency filter then band-limits the intermediate frequency GPS signals, rolling off at a frequency in the vicinity of 2.5 MHz to achieve substantial attenuation at 3.5-4.0 MHz. An automatic gain control circuit amplifies the filtered intermediate frequency GPS signals to proper voltage levels. The amplified intermediate frequency GPS signals is then digitized by an analog-to-digital converter at a predetermined sampling rate more than twice the intermediate frequency to provide samples of a predetermined number of bits, which are then provided for base band processing by a general purpose microprocessor over an industry-standard serial bus.

Abstract: A signal processing system which discriminates between voice signals and data signals modulated by a voiceband carrier. The signal processing system includes a voice exchange, a data exchange and a call discriminator. The voice exchange is capable of exchanging voice signals between a switched circuit network and a packet based network. The signal processing system also includes a data exchange capable of exchanging data signals modulated by a voiceband carrier on the switched circuit network with umnodulated data signal packets on the packet based network. The data exchange is performed by demodulating data signals from the switched circuit network for transmission on the packet based network, and modulating data signal packets from the packet based network for transmission on the switched circuit network. The call discriminator is used to selectively enable the voice exchange and data exchange.

Abstract: Provided are a time synchronizing method and apparatus based on a time stamp. The time synchronizing method includes: transmitting a local time stamp based on a free-running local clock to a master node; receiving a response time stamp from the master node; calculating a delta time value based on the response time stamp; filtering the delta-time using a digital low pass filter running at the free-running local clock rate; and adjusting a local clock time based on the filtered delta time value.

Abstract: A method for implementing a flexible sampling-rate encoder, comprising the steps of (A) sampling an input signal at a regular time-interval to produce sampled data, (B) generating a pseudo-random bit sequence having a plurality of bits, wherein each bit corresponds to a different sampling time, (C) encoding a first set of the sampled data to generate an encoded stream when any bit in the pseudo-random bit sequence is equal to a first value, wherein each bit in the encoded stream corresponds to one of the sampling times defined in step (B), and (D) determining the different sampling time for each sample in the encoded stream.

Abstract: Clock synchronization and data recovery techniques are disclosed. For example, a technique for synchronizing a clock for use in recovering received data comprises the following steps/operations. A first clock (e.g., a data clock) is set for a first sampling cycle to a first phase position within a given unit interval in the received data. A second clock (e.g., a sweep clock) is swept through other phase positions with respect to the first phase position such that a transition from the given unit interval to another unit interval in the received data is determined. A sampling point is determined based on measurements at the phase positions associated with the second clock. The second clock is set to the phase position corresponding to the sampling point such that data may be recovered at that sampling point.

Abstract: The invention relates to an apparatus and a method for data acquisition, the apparatus being characterized in that it comprises an analog/digital converter (510) sampling at an imperfect frequency FE provided by a local clock (100) data acquired by a sensor (500) thus providing a series of sampled and dated data E[k], a time-stamping module (300) for measuring the frequency error of the local clock (100) by determining the sampling dates according to a universal time UTC(t), and a resampling module (400) for correcting the sampled and dated data E[k].

Abstract: An arbitrary metric stream is processed initially at an interim sampling rate to derive a plurality of samples. The samples are analyzed preferably to determine an estimate of the effective bandwidth of the metric stream. As a result of the analysis, an improved sampling rate is determined and adopted for further sampling. In a preferred embodiment, the improved sampling rate is a function of the effective bandwidth.

Abstract: A repeater is configured to selectively generate and transmit control message packets between wireless stations on both a transmit side and a receive side of the repeater. The repeater manages and manipulates an end to end protocol of the control message packets in a manner that does not change media access control (MAC) addresses of the end to end protocol so as to achieve a network objective, such as preventing other transmitters from transmitting while the repeater repeats a signal from its receive side to its transmit side. The control message management is applicable to analog signal repeaters as well as digital repeaters, such as symbol to symbol or packet to packet repeaters, in which physical layer control message management is performed.

Abstract: There is provided a clock transferring apparatus for synchronizing a pattern signal synchronized with a reference clock with a variable clock based on an oscillation source different from that of the reference clock, having a rate clock generating section for generating a rate clock whose number of pulses within a predetermined period is almost equal with a number of pulses of the variable clock within the predetermined period by thinning out the pulses within the reference clock, a pattern generating section for generating the pattern signal corresponding to the pulses of the rate clock and a FIFO memory that stores data of the pattern signal corresponding to the pulses of the rate clock and outputs the stored data corresponding to the pulses of the variable clock.

Abstract: Described are transmitters with RAM-DAC based pre-emphasis filters that can be updated adaptively without interfering with data transmission. The memory within the RAM-DAC is divided into active and inactive memory locations, in which active memory locations are those to be accessed in the near future, and consequently cannot be updated (written to) at a given time due without inducing a read/write conflict. One embodiment monitors incoming memory addresses to find an adequate time window for a write to take place without a read interference. Another embodiment includes two memory blocks with similar address space, one of which may be updated as the other is used to for data transmission. Some embodiments employ a RAM-DAC with reduced memory size and complexity.

Abstract: A method and circuit for dynamically changing the frequency of clock signals. The method including: detecting an edge of a first clock signal operating at a first frequency using a second clock signal operating at a second frequency; detecting an edge of the second clock signal using the first clock signal; detecting coincident edges of the first and the second clock signals; and changing the second frequency to a third frequency different from the second frequency upon detection of the coincident edges.

Abstract: Embodiments of the invention include an integrated circuit including a phase-locked loop (PLL). The integrated circuit includes a phase detector, a frequency detector, a loop filter, a digitally-controlled oscillator and a corresponding plurality of frequency dividers. The phase detector generates a first binary output based on a phase comparison of a reference clock signal to a plurality of clock phase inputs. The frequency detector generates a second binary output based on a frequency comparison of the reference clock signal to the clock phase inputs. The loop filter generates a third binary output based on the first binary output and the second binary output. The DCO feeds back the clock phase inputs, via the frequency dividers, to the phase detector based on the third binary output, and feeds back one of the clock phases to the frequency detector based on the third binary output.

Abstract: Provided is a frequency control loop circuit changing division ratios of a frequency synthesizer to oscillate frequencies in a broadband with high precision. The circuit comprises a clock oscillator, a frequency synthesizer, and a demodulator.

Abstract: A source terminated serial link can recover from a low power mode by turning on multiple current-mode drivers in a phased sequence where the phased sequence is related to a resonant characteristic of a power supply net.

Abstract: A diagonal offset clock signal distribution system and method are presented that facilitate maximized placement of a diagonal offset clock signal distribution tree.

Abstract: A neutrino telescope is made up of four devices. A neutrino modulating device velocity modulates neutrinos passing through a thin walled steel tube. This encodes the neutrinos as being different than any neutrinos found in nature. The steel tube is electrically driven to its lengthwise resonant frequency. A directive steel tube can be added, as a second device, to restrict neutrinos passing into the telescope and the directional resolution thus improved. A third device uses a barium titanate cylinder to detect forces from modulated neutrinos. An analog circuit filters and amplifies the signal as necessary. An oscilloscope can be used to measure and study the output. A fourth device uses a Blackfin processor to provide digital processing and a service computer for further processing and studying results over periods of time.

Abstract: The invention is a support system for use with a reactor vessel that defines a reactor zone and has an inlet manway providing an opening into the reactor zone. The support system comprises a manway insert that is supported by the inlet manway and extends through the opening of the inlet manway and into the reactor zone. Attached to the manway insert is attachment means for connecting a support hanger to the manway insert and for transferring the load from the support hanger to the manway insert. The support hanger has an upper end and a lower end with the upper end being fixedly attached to the attachment means and the lower end being fixedly attached to support structure means for supporting a load.

Abstract: Artifacts in the reconstructed volume data of cone beam CT systems can be removed by the application of respiration correlation techniques to the acquired projection images. To achieve this, the phase of the patients breathing is monitored while acquiring projection images continuously. On completion of the acquisition, projection images that have comparable breathing phases can be selected from the complete set, and these are used to reconstruct the volume data using similar techniques to those of conventional CT. Any phase can be selected and therefore the effect of breathing can be studied. It is also possible to use a feature in the projection images such as the patient's diaphragm to determine the breathing phase. This feature in the projection images can be used to control delivery of therapeutic radiation dependent on the patient's breathing cycle, to ensure that the tumor is in the correct position when the radiation is delivered.

Abstract: An X-ray computer tomography apparatus includes a substantially annular rotating frame supported to be rotatable around a rotation axis, a plurality of X-ray tubes discretely provided along the circumference of the rotating frame, a plurality of X-ray detectors discretely provided along the circumference of the rotating frame, a plurality of variable-opening slits which are made to respectively correspond to the plurality of X-ray tubes, and a slit control unit which individually controls the widths and central positions of openings of the plurality of slits.

Abstract: An X-ray CT apparatus includes X-ray tubes, slit mechanisms which are respectively provided for X-ray tubes and whose slit widths can be changed, two-dimensional array type X-ray detectors which form pairs with the X-ray tubes, a support mechanism which supports the X-ray tubes and the X-ray detectors so as to allow them to rotate about a rotation axis parallel to the slice direction, a correction unit which corrects data from each detection element located in an area which X-rays passing through the slit mechanism directly strike, by using data from at least one detection element located outside the area and associated with the same channel in order to reduce a scattered radiation component originating from X-rays generated by an X-ray tube other than the X-ray tube forming the pair, and a reconstruction unit which reconstructs image data on the basis of the corrected data.

Abstract: A method is disclosed for compiling computer tomographic representations using a CT system with at least two angularly offset ray sources. A first ray cone with a relatively larger fan angle and a second ray cone with a relatively smaller fan angle scan an object circularly or spirally. The first ray cone generates a first dataset A and the second ray cone generates a dataset B. The dataset B of the smaller ray cone is supplemented with other data at the edge to give an expanded dataset B+ for reconstruction of the CT representation. The expanded dataset B+ of the second, smaller ray cone and the dataset A of the first, larger ray cone is subjected to a convolution operation to give datasets B+? and A?. Finally, a back projection to reconstruct sectional images or volume data is respectively carried out from the convoluted datasets B+? and A?. The dataset B is supplemented with data of the dataset A and supplementary data are removed from the dataset B+? after the convolution but before the back projection.

Abstract: The quality of an image can be improved and radiation can effectively be utilized. In an imaging area of a subject where a main scan is performed, a specific scan area setting unit sets a specific scan area where a scan is performed under a specific scan condition allowing radiation exposure dose on the subject to be low. Then, the scan condition setting unit sets a main scan condition so that the specific scan area is scanned under the specific scan condition allowing the radiation exposure dose on the subject to be low.

Abstract: Cast collimators for use in CT imaging systems are described, as are methods of making them. Such collimators may comprise pre-patient collimators, pre-patient filter/collimator assemblies, and/or post-patient collimators. The filters and/or collimators may be made of any suitable high-density, high atomic number material such as lead, a lead alloy, tantalum, tungsten, tungsten suspended in an epoxy matrix, tungsten suspended in a slurry, or the like. Embodiments of these collimators comprise specially-designed channels and vanes that allow them to be precision cast to the necessary degree of accuracy. These channels and vanes are preferably tapered. These collimators and filter/collimator assemblies help minimize the x-ray dose to the patient by minimizing the scattered radiation creation mechanism and by collimating out much of the scattered radiation that would otherwise be subjected to the patient.

Abstract: A CT system including a multi-array detector that includes a plurality of detector cell, a data acquisition system that acquires data items representing doses pf radiation incident on the detector according to output signals of the detector cells, and a data processing unit that identifies a distribution of doses of radiation incident on the detector, which is used to construct tomographic images acquired by the data acquisition system. The data acquisition system includes a smaller number of amplifiers, which amplify signals produced by the detector cells and transmit the resultant signals, than the number of detector elements, and a switching unit that changes the continuities between the detector cells and amplifiers so that detector cells whose signals are amplified by each of the amplifiers will be changed into others juxtaposed in the direction of slices during the scanning of a subject.

Abstract: Methods and arrangement for providing digital x-ray mammography image acquisition by means of an X-ray system that includes acquiring image data by irradiating an object, such as a human breast, automatically by the system analyzing the acquired image data with respect to presence of motion blur, indicating whether motion blur is present.

Abstract: Charged and neutral particles, photons (13), photonic optics, detectors (15) and sensor arrays are used for application to molecular imaging, communication with biological organisms and monitoring and learning biological activity inside living organisms. The living organisms include among others living tissue, biological organs, cells (10), eukaryotes, prokaryotes, viruses and phages. Molecular imaging can be an effective new tool to understand the mechanisms of life and communicate, modify and control it. Techniques, methods and devices are described to achieve these aims. The probes used in molecular imaging described above will include the full spectrum of photons; charged and uncharged particles (13); chemicals; and biological probes.

Abstract: In one embodiment, a method of examining contents of an object is disclosed comprising scanning an object at first and second radiation energies, detecting radiation at the first and second energies, and calculating a function of the radiation detected at the first and second energies, for corresponding pixels. A pixel is a projection of radiation through the object onto the detector. The first functions of a plurality of pixels are grouped and a second function of the group is analyzed to determine whether the object at least potentially contains material having an atomic number greater than the predetermined atomic number. The second function may be compared to a third function, which may be a threshold having a value based, at least in part, on material having a predetermined atomic number. Systems are also disclosed.

Abstract: An X-ray inspection apparatus is disclosed. An inside area defining unit defines an area inside the rim of the can in an X-ray image created by an image formation unit. An extension area defining unit rotates a circle such that the circle externally touches the above-mentioned area, and defines an extension area whose boundary is the locus of the center of the externally touching circle. A reduction area defining unit rotates a circle having the same radius such that it internally touches the extension area, and defines a reduction area whose boundary is the locus of the center of the internally touching circle. A mask area defining unit defines a region outside the boundary of the reduction area as a mask area, and the first contaminant detection unit performs an inspection for contamination in an inspection area inside the mask area defined by an inspection area defining unit.

Abstract: The invention relates to an imaging process with a beam source attached at a first end of an holder device, and with a detector unit attached to a second end of the holder device. The holder device is moved so that the beam source is guided about an examination area along a non-circular trajectory, where the beams emitted by the beam source pass through the examination area. The detector unit acquires measurement values which depend on the intensity of the beams on the far side of the examination area. From these measurement values using a filtered back projection an image of the examination area can be reconstructed, where each measurement value is filtered along a filter line which runs parallel to the tangent of the trajectory at the respective position of the beam source.