Cyclography

ЦИКЛОГРАФИЯ (from Greek kyclos- circle and gra-pho- write), the most accurate of the methods developed up to the present time for the photographic registration of movements. C. arose in the 1890s as a modification of chronophotography (see). The first cyclographic shots were obtained in Marey's laboratory; at the same time, cyclographic shooting using spark discharges as a light source, and later Geissler tubes, was applied by Braune and Fischer to the study of the kinematics of joints and human movements during walking. After a long interruption in very primitive forms, it was again applied by Gilbreth, Thun, and Townsend. In 1921, this method was applied in our country by N. Tikhonov and K. Kekcheev, who introduced a number of improvements. By the present time, the technique of C. has reached a high level of development as a result of the work of several Moscow laboratories. C. in its basic form is the photographing of the trace of movement of some point light source onto a stationary photosensitive surface. By placing one or several point lamps on the moving points of the human body and photographing them, the researcher obtains a cyclogram of the movement of these points in the form of curves representing the planar projection of the trajectories of movement. If the lamps are fed with intermittent current or the objective is periodically opened and closed, then instead of solid lines on the shot, dashes are obtained, and the distances between successive points of the dash in time will depend on the frequency of interruption of the current in the lamps or on the speed of operation of the objective shutter. Such a cyclogram with time marks on its trajectories is called a chronocyclogram.

In modern C., the light sources are special miniature incandescent lamps with a point spiral filament (lamp diameter up to 2.5%). The speed of rotation of the shutter is the most responsible moment of work, requiring high accuracy. The best methods of measurement are stroboscopic, consisting in illuminating with intermittent light of strictly stable frequency (through a neon lamp) a certain socket with a special pattern, which seems to be stopped if the frequency of intermittent light is equal to the number of revolutions of the motor multiplied by the number of petals of the socket.

Bernstein's sockets (Fig. 3 and 4) allow measuring any rotation speeds with an accuracy of up to 1%: they consist of a series of concentric circles with alternating figures on them. When such a socket, connected to the shutter motor shaft and illuminated with intermittent light of stable frequency, rotates, all its circles seem to be solid gray, and one appears to be stopped (Fig. 5) and indicates the desired rotation speed on the scale adjacent to the socket. Significantly more accurate is not to measure the shutter speed, but to automatically stabilize it at the expense of the same strictly stable frequency source (e.g., an electromagnetic tuning fork of elinvar) through a low-frequency electronic amplifier and the Lacroix or Tonrard wheel (Fig. 2). Any high frequencies can be used in cyclography; practically the most common frequencies are from 60 to 250 per second. If the points being shot, in their movement, do not return periodically to the same place, but are transferred in one direction further (e.g., during walking or running), then the cyclogram is clear and distinct (Fig. 6). In the case of cyclic movement, however, indistinct clusters of trajectories are inevitably obtained on the shot. For shooting such cyclic movements, a variety of C. - kinocyclography, consisting in cyclographic shooting onto a uniformly moving film, is used (Fig. 7). With this method, any movements, even the most tangled and small, become clear. The camera used for kinocyclographic shooting, of the design of P. Pavlenko (VIEM), is shown in Fig. 8.

To study non-planar movements occurring in three dimensions, a single point of view is insufficient. Three methods can be applied here: 1) stereoscopic shooting with two objectives with parallel optical axes, covered by one large shutter. The accuracy of this method is generally small. 2) Convergent shooting with two or several cameras, the optical axes of whose objectives meet at some point. With this method, separate shutters are used near each camera, connected by some precise synchronization device. This method is very accurate, but requires well-aligned objectives and impeccable synchronization. 3) Mirror shooting with one camera, in which the object is seen simultaneously from two points of view: in the direct image and in the reflection from a large mirror. The method is very accurate and at the same time simple, as it needs neither alignment of objectives nor synchronization of shutters. Control of cyclo-shooting is carried out centrally from a distribution panel, in which all elements of shooting control are concentrated. A finished cyclographic shot is the most accurate document of movement; if it is made according to all the rules of modern technique, it ensures spatial accuracy up to 0.5% of natural size and temporal accuracy up to ±0.005%. Analysis of cyclographic and kinocyclographic planar and mirror shots of movement has already grown by itself into a whole science - cyclogrammetry. A correctly performed analysis allows determining from a cyclographic shot a) the positions successively occupied by the object in space (coordinates), b) the angles between identifying lines on the object at all successive moments of movement, c) the speeds of the object's points, d) the accelerations of these points, e) angular speeds and angular accelerations. In the presence of data on the masses of moving parts, cyclogrammetric analysis allows further establishing a quantitative picture of the course of efforts in the centers of gravity of the elements of the moving system and in the general center of gravity of the whole system, and measuring the force moments of muscle groups. The data obtained in this way possess a high degree of accuracy, unattainable by any other modern registration method. C. and its varieties are applied in the study of labor movements with the aim of their rationalization; in labor pedagogy - with the aim of analyzing correct and incorrect methods of training (training in production skills, playing musical instruments, etc.). Next, C. finds application in the field of study and rationalization of labor and labor adaptations of the disabled (blind, amputated, etc.). Finally, an extremely wide field for the application of C. is clinical practice, where this method allows studying very accurately the most diverse pathologies in the motor sphere. Here one should mention organic lesions of the central and peripheral nervous system, functional disorders in the area of tendon reflexes, tonic and labyrinthine reflexes, etc., further motor and psychomotor phenomena in mental illnesses, etc.