摘要:
A television pick-up device suitable for a discontinuous recording of information during continuous operation, such as, for example, in X-ray television. When information recording is interrupted at a continuing field scanning of a target plate in the pick-up tube, the cathode thereof is supplied from a supply circuit with a higher voltage than during the field scanning during information recording. As a result thereof a negative charging of the free surface of the target plate by the more rapid electrons in the electron beam is prevented, so that at the next recording of information the picture quality on display is not poorer due to signal clipping.
摘要:
The circuit has an input terminal (1) for supplying a picture signal (CS) formed line and field-sequentially with line and field or frame periods (TV) and an output terminal (2) for supplying a processed picture signal (CS') to be applied to a picture display device (5) comprising a picture display tube operating by way of electron beam scanning (e) of a display screen (8). In the circuit the input terminal (1) is coupled to a filter circuit (10) which has a first output (11) and a second output (12) for supplying a low-frequency (CS.sub.L) or high-frequency (CS.sub.H) picture signal component, respectively. The first output (11) is coupled via an amplifier circuit (16) to a first input (21) of a time-division multiplex circuit (20) having a second input (22) to which the first output (11) and the second output (12) of the filter circuit (10) are coupled each via an amplifier circuit (17, 18) and an adder circuit (19). The time-division multiplex circuit (20) has a switching input (23) which is coupled to an output (29) of a switching signal generator (28) for supplying a periodical switching signal (VS) of the double field or frame period (2TV). An output (24) of the time-division multiplex circuit (20) is coupled to the output terminal (2) of the picture signal processing circuit. The resultant spatial time-division multiplex display yields the improved high-frequency picture resolution.
摘要:
In an apparatus for performing magnetic resonance measurements by means of an orthogonal system of excitation detection coils there is provided a switching circuit for powering and reading the coil system which includes a 1/4 .lambda. coaxial conductor as a connection between the two coil assemblies and a 1/4 .lambda. coaxial conductor with a 90.degree. phase delay as a connection between the first 1/4 .lambda. conductor and the second coil assembly and a detection device. By suitable tuning of the relevant circuit components and the coils, preferably based on 50 Ohms, a simple switching circuit with appropriate matching and phase correction is thus achieved. Specifically, the r.f. power source can be connected to the circuit via an n .lambda. conductor. In the open condition during detection, the n .lambda. conductor represents an infinite impedance for the switching circuit.
摘要:
It is known that perturbations caused by scattered-radiation in an x-ray image can be partially avoided by employing a scattered-radiation grid. A device for further improvement of an x-ray image, in that real-time correction of scattered-radiation effects is achieved, is provided according to the invention. Behind x-ray absorbing parts of the scattered-radiation grid only scattered-radiation appears, whereas both scattered-radiation and primary radiation appear behind transparent channels of the scattered-radiation grid. The scattered-radiation grid gives rise to a high-frequency intensity modulation in the x-ray image. From the high-frequency component of the corresponding video signal produced by the x-ray detector, selection signals are generated by a double pulse generator for distinguishing signal amplitudes of the video signal, corresponding to intensities behind absorbing parts and transparent parts, respectively, of the scattered-radiation grid. The selection signals are supplied to a synchronous detector to split the video signal from the x-ray detector into separated video signals corresponding to scattered-radiation and primary radiation and to scattered-radiation only, respectively. A video signal corresponding to a corrected image is obtained by subtraction of the separated video signals.
摘要:
A quadrature mode rf coil system in a magnetic resonance apparatus includes a pair of orthogonal rf coils which, for excitation and/or detection are coupled to an rf source or receiver by an electronic switching circuit built up from inductances and capacities. The switching circuit includes preferably frequency adjustable 90.degree. first delay lines feeding each coil which transforms the 50.OMEGA. coil impedance of each coil to 100.OMEGA. so that the parallel combination of transformed impedances is 50.OMEGA.. A second 90.degree. delay line is cascaded with the first delay line feeding one of the coils to establish a 90.degree. phase difference between the coils.
摘要:
An X-ray television pick-up and display system which is suitable for continuous and short-duration pick-up operation and continuous display. In continuous pick-up operation, in display on a display device an interlaced television picture is composed of two line scanning rasters in a standard manner. In short-duration pick-up operation a synchronizing pulse generator is changed over so that a single line-scanning raster comprising an integral number of lines is obtained for information pick-up, which information is stored in a signal store which for repeated signal supply is connected to the display device. As a result, the picture displayed does not show motional unsharpness and is free from flicker effects.
摘要:
An x-ray examination apparatus comprises an x-ray detector with a sensor matrix for deriving an image signal from an x-ray image. The x-ray detector is provided with a scatter grid having a regular pattern of x-ray attenuating partitions. The spatial resolution of the sensor matrix is such that the size of the smallest detectable detail in the x-ray image is larger than the distance between adjacent partitions. In particular the x-ray detector comprises an x-ray sensitive photoconductor layer for converting x-rays into electric charges, separate sensor elements include respective collecting electrodes and a semiconductor cladding layer being disposed between the photoconductor layer and the collecting electrodes. The semiconductor cladding layer has a substantial lateral electric conductivity. For example, the semiconductor cladding layer is a chlorine doped selenium layer, or a selenium, sulphur or telluride doped lead-oxide layer.
摘要:
Accumulation of charge between neighboring image lines can be prevented in a television pick-up tube in which an image pick-up face is scanned along image lines by an electron beam when a comparatively small periodic deflection is imposed on the electron beam in a direction perpendicular to the image lines. To achieve this, a magnetic deflection element in the form of a saddle-shaped coil is disposed between the vertical deflection element of the television pick-up tube and the envelope of the electron gun.
摘要:
For measurements with increased accuracy in a nuclear magnetic resonance apparatus, the detection device is equipped with one or more surface coils which act as measuring coils. To avoid mutual interference between a radio-frequency transmitting coil and the measuring coil, the measuring coil is provided with a decoupling circuit. The surface coil and the decoupling circuit form a part of a tuned circuit which is tuned to a significantly higher natural frequency during activation of the transmitting coil. On the other hand, the transmitting coil is shorted during detection with the surface coil by a low resistance shorting circuit, thereby avoiding interference with the radio-frequency transmission signals.
摘要:
As a result of the use of a slow phosphor in the exit screen of an X-ray image intensifier tube, a number of image fields can be picked up by means of the comparatively fast television camera during the afterglow of the phosphor. This enables quantum noise integration and, when use is made of a CCD camera upon display, a resolution can be achieved upon display which corresponds to the resolution of a conventional pick-up tube. Moreover, in accordance with the invention it is no longer necessary to use a controllable diaphragm and a complex interface for the asynchronous pick-up and reading of the image information.