Abstract: The static magnetic fields of an NMR imaging apparatus should be maintained constant in intensity in order to obtain satisfactory NMR images. Coils used to generate the static magnetic fields, and the supporting frames therefor, are subject to heat expansion due to changes in the temperature, which causes fluctuations in the intensity of the generated static magnetic fields. In the invention, the temperatures of the coils, frames, atmosphere and cooling water, and the amount of cooling water, are detected, and the energizing current for the static magnetic field coils is selectively controlled, based on the detected quantities, to thereby maintain constant the intensity of the generated static magnetic fields.

Abstract: In an examination method and apparatus utilizing nuclear magnetic resonance, high frequency pulses for producing nuclear magnetic resonance are applied by successively imposing a first 90.degree. pulse, a first 180.degree. pulse, a second 90.degree. pulse, and a second 180.degree. pulse substantially immediately after the second 90.degree. pulse, and a next pulse sequence is initiated upon elapse of a wait time after the second 180.degree. pulse has been applied. The wait time is rendered much shorter than the conventional prior art wait times for high speed scanning operation, by forcibly aligning magnetization M first with the direction of a -Z direction axis and then with the direction of a +Z direction axis, using the second 90.degree. pulse and the second 180.degree. pulse. By applying a number of first 180.degree. pulses, a number of nuclear magentic resonance signals are produced for additionally shortening the overall measurement time.

Abstract: An optical scale reader comprises a light source for radiating a beam of coherent light on a reflective scale, a half mirror for mixing light beams from the light source which are reflected and diffracted by the scale for interference with each other, an optical system for causing the interfering light beams leaving the half mirror on its opposite sides to be 90.degree. out of phase with each other so that the light beams will fall on the half mirror at a particular angle of incidence, photodetectors for detecting the interfering light beams, respectively, which have left the half mirror, and a signal processor for processing first and second electric signals which are supplied from the photodetectors and 90.degree. out of phase with each other to generate a signal indicative of the distance which the scale has moved. There is also disclosed a position control device incorporating the optical scale reader.

Abstract: A 4 coil type air core coil magnet used for NMR imaging apparatus, wherein each coil assembly comprises a plurality of pancake coil elements in layers, and in each of the coil elements the configuration of a predetermined portion and the winding length of the end portion is selectively controlled and connecting wiring between each coil element is parallel to the axis of the four coil assemblies, whereby highly uniform magnetic fields are obtained.

Abstract: A coil assembly comprises four coils for generating a static magnetic field in an NMR imaging apparatus, wherein the dimensions of the coils are selected so that the flatness of the cross section of the coils, the current turns ratio, and the radius ratio, are within certain limits. The assembly so constructed produces highly uniform magnetic field, is small in size, and light-weight, and consumes a lower amount of power, and can be manufactured inexpensively.

Abstract: An examination method and apparatus utilizes a nuclear magnetic resonance technique in which the body of a subject to be examined is placed in a uniform static magnetic field and subjected to an electromagnetic wave having a frequency which induces nuclear magnetic resonance, a magnetic field is also applied to the subject body to specify an area of the body from which nuclear magnetic resonance (NMR) signals are radiated, and such nuclear magnetic resonance signals from the specified body area are received. A first 90.degree. pulse as the electromagnetic wave is applied to the body to excite the same, and then a 180.degree. pulse is applied to the body to produce an echo signal. A second 90.degree. pulse is to the body when the echo signal is maximum to thereby allow a magnetization to return to a state of thermal equilibrium. The foregoing sequence of the steps is repeated at prescribed intervals.

Abstract: A resonance thermometer utilizing nuclear quadrupole resonance, nuclear magnetic resonance or like resonance-absorption phenomenon. The thermometer includes an oscillator for oscillatively detecting a resonance in a resonant material, a means for modulating the oscillation frequency of the oscillator at a low frequency, a first detecting means with a short time constant for detecting a component from the modulated output of the oscillator, and a second detecting means with a long time constant for detecting a component from the modulated output of the oscillator. The oscillator frequency is swept in linear ramp fashion at high speed until an output from the first detecting means occurs, at which point the frequency sweep is stopped. The precise resonance-absorption frequency of the resonant material then is found by using the output of the second detecting means, and the temperature is derived from the precise resonance-absorption frequency.