Abstract: The present invention relates to a method and a circuit arrangement for controlling a stepper motor, e.g. in a panoramic X-ray apparatus. In the method of the invention, the control data of a processor (5) is first converted into an analog signal with a digital-analog converter (6), and the signal thus obtained is integrated with an integrating circuit (7,10), whereafter the signal is converted into pulses controlling the stepper motor (9) with a voltage-frequency converter (8). The circuit arrangement comprises preferably one or two integrators. In consequence, the changes in the speed of rotation of the stepper motor can be made stepless, whereby the stresses directed at the mobile parts are small, and mechanical oscillation caused by high momentary forces is avoided. In addition, the loading of the processor can be made uniform. Error correction circuits employing feedback are employed to enhance operation of the invention.

Abstract: The invention relates to a method used in the panoramic X-ray photography of a patient's set of teeth and a device for carrying out constant enlargement also in those spots (21) of the dental arch where the X-ray beam (12) is not perpendicular to the tangent (23) of the dental arch (20). Constant enlargement is achieved by selecting, on the film (13), a speed profile which follows the formula: v.sub.f =((A+B/A).times.v1.times.1/ cos (b), where v.sub.f is the speed of the film, v.sub.1 is a component of the propagation speed of the intersection of the X-ray beam and the spot to be photographed which is perpendicular to the X-ray beam, A is the distance between the focus of the X-ray source and the spot to be photographed, B is the distance between the spot to be photographed and the film, and b is the angle between the tangent (23) of the spot in question of the dental arch and the normal (22) of the X-ray beam.

Abstract: The invention relates to a panoramic X-ray photography apparatus having a rotatably mounted supporting arm (1) which has at one end an X-ray source (2) and at the opposite end an image receptor (3), in which case the object is placed between the X-ray source (2) and the image receptor (3) and the imaging is carried out by rotating the supporting arm. The idea of the invention is that a simple panoramic X-ray photography apparatus can also be used for tomography, since the object to be imaged, i.e. the denture, contains mainly vertical surfaces and a horizontal oscillating movement suffices for blurring them. An additional idea is that by moving the bearing shaft (4) of the supporting arm along a circle arc portion during blurring, the fulcrum can be shifted to outside the bearing shaft, thus eliminating certain limitations imposed by the mechanics of a conventional X-ray photography apparatus with respect to the area to be imaged and the location of the supporting arm.