CAMERA MOUNT

Abstract: A camera mount having drag mechanisms which are controlled electronically, as by applying a control signal to a transducer or cell able to convert the applied signal into a force. In an embodiment, the mount (10) has a manual or servo actuator (12) which incorporates an electrorheological cell. The electric field across the cell is controlled by application of a voltage signal (15) derived from a control signal (18) which is adjustable to enable the torque-versus-speed characteristic of the mount to be selected for both pan and tilt.

Description: Title Camera Mount Field of the invention This invention relates generally to camera mounts, and in particular to mounts for cinematograph and television cameras equipped with pan and tilt controls. For convenience such a camera is referred to hereinafter simply as a TV camera. Background to the invention TV cameras are mounted in such a way that the camera can be freely rotated about a vertical axis to enable pan motion and freely rotated about a horizontal axis to enable tilt motion. The resistance to pan and tilt motions is known as the drag. In some TV camera mounts, the drag is variable by means of an external adjuster over a limited range sufficient to accommodate different types and weights of camera which may be fitted to the mount, production requirements and individual requirements of the camera operative. Drag adjustment, when provided, is achieved by wholly mechanical mechanisms which either introduce or withdraw a fixed supplementary damping or vary frictional damping. The range of drag adjustment is determined by design, and is relatively small. Thus currently available TV camera mounts are relatively inflexible in that torque-versus-speed performance SUBSTITUTE SHEET (determined by the drag) cannot be varied outside the predetermined limited range. Moreover, the drag cannot be readily adjusted to compensate for alterations in camera field of view, even though the torque-versus-speed performance required clearly varies with different fields of view. It is an object of the present invention to provide an improved TV camera mount. The invention According to the invention, there is provided a TV camera mount having a drag mechanism on at least one and preferably both of the pan and tilt axes, wherein the or each drag mechanism is controlled electronically. The invention may be achieved by a drag mechanism which comprises a transducer or cell which converts an electrical signal into a force. This force may be applied to the pan and/or tilt axis to create drag. The electronic drag mechanism may replace a mechanical drag control mechanism. Separate cells may enable pan and tilt drag to be independently controlled. Conveniently, the cell is provided in the head of the mount to which the camera attaches, in such a manner that the pan and tilt drag can be influenced, and an adjustable control signal is applied to the cell to adjust the properties of the cell in such a manner that a desired torque-versus-speed characteristic is obtained. SUBSTITUTE SHEET Examples of suitable cells are cells of electrorheological (ER) fluid and piezo-electric cells. The nature of the control signal may itself be adjusted by setting switches or by a potentiometer or by input of a personal code via a membrane keypad or the like. Adjustment of the applied control signal, for example, an applied electric field, in this way makes available a large family of linear torque-versus-speed relationships. In a more complex arrangement, the magnitude of the control signal is determined by one or more torque and/or velocity sensors in the head of the mount. Thus, a torque sensor at the head of the mount, for example in the manually operable pan bar, may determine the force being applied to the mount to cause panning or tilting motion of the camera. Additionally, velocity sensors attached to the head of the mount may determine the speed of rotation about the vertical and the horizontal axis. The sensor outputs can then be fed to control electronics where said output signals are processed to develop the control signal for the cell. In this way the torque-versus-speed characteristic is automatically controlled by the sensors. Conveniently, in the control electronics, the sensor output signals are read and the required value of the control signal applied to the cell obtained either from a "look-up table" or by use of a suitable algorithm. In the more complex arrangement above described, it is possible to introduce non-linear torque-versus-speed characteristics, thus enabling hitherto difficult SUBSTITUTE SHEET - A - requirements for camera mounts, such as whip-pan, to be incorporated. Alternatively or additionally, the control signal may be at least in part developed from a signal dependent on the field of view of the camera, thus making it possible to adjust the drag in a manner which at least partially compensates for changing field of view. In practice, the control signal can be developed in a microprocessor which enables complex torque-versus-speed relationships to be obtained. A number of these relationships can be stored in a memory to allow exact matching of performance with operational requirements, rapid change of performance between "takes" or "shots" and tailoring of performance to individual predilection. Description of embodiments Embodiments of the invention are exemplified with reference to the accompanying drawings, in which:- Figure 1 shows a simple embodiment in diagrammatic manner; Figure 2 is a graph showing torque-versus-speed characteristics; and Figure 3 shows a more complex arrangement in diagrammatic manner. Referring to Figure 1, a camera mount 10 having a manual or servo actuator 12 incorporates a cell 14 of electro¬ rheological (ER) fluid. SUBSTITUTE SHEET The electric field across the ER fluid cell 14 is controlled by application of a high voltage signal 15 obtained from a voltage generator 16. The magnitude of the applied high voltage is controllable by a control signal 18 applied to the generator 16. This control signal may be obtained from such means as a potentiometer, a key pad or a preprogrammed device such as a swipe card. The amplitude of the control signal 18 is in turn adjustable by the camera operative to enable the torque- versus-speed characteristic of the camera mount, in both pan and tilt, to be changed according to requirements. Figure 2 shows that, with the arrangement of Figure 1, a family of linear torque (T)-versus-speed (W) characteristics is obtainable for different applied high voltages HV 1 , HV 2 , HV 3 etc. In the more complex arrangement of Figure 3, the camera mount head 10 incorporates torque and speed sensors 19 which feed back output signals 20 to control electronics 22 governed by a microprocessor 24. The sensor output signals are processed or conditioned in control electronics 22, compared in the microprocessor 24 with preset values and a required value for the control signal 26 applied to the voltage generator 16 obtained from a "look-up" table stored in memory. One or more additional control signals 28 may also be fed into the microprocessor. The additional control signal may be a signal equivalent to the control signal 18 of Figure 1 and/or a signal derived from the field of view of the camera. SUBSTITUTE SHEET Relatively complex non-linear torque-versus-speed characteristics can be obtained from the arrangement of Figure 3 and, dependently on the programming of the microprocessor 24, various required characteristics of camera mounts, such as whip-pan, can be incorporated. Various modifications of the above-described and illustrated arrangements are possible within the scope of the invention as hereinafter claimed. For example, by use of two ER fluid cells, pan and tilt drag can be individually and independently controlled. Moreover, the use of one or more cells of ER fluid is not essential in that other transducers or cells which can provide an adjustable force responsively to a control signal may be employed. Thus, in an alternative embodiment, the ER actuators in the above-described embodiment are replaced by piezo¬ electric actuators. In other respects, operation of the alternative embodiment is substantially in accordance with previous description. SUBSTITUTE SHEET

Claims: Claims 1. .A camera mount having a drag mechanism for at least one of the pan and tilt axes, wherein the or each drag mechanism is controlled electronically. 2. A camera mount as claimed in claim 1, wherein drag mechanisms on both the pan and tilt axes are electronically controlled. 3. A camera mount according to claim 1 or claim 2, having, for control of the or each drag mechanism, an electronic control means comprising a transducer or cell which is able to convert an applied control signal into a force. 4. A camera mount according to claim 3, wherein the cell is a cell of electrorheological fluid. 5. A camera mount according to claim 3, wherein the transducer is a piezo-electric transducer. 6. A camera mount according to claim 3 or claim 4 or claim 5, wherein the control signal is or produces an electric field applied to the cell. 7. A camera mount according to claim 3 or claim 4 or claim 5, wherein the control signal is or produces a voltage signal applied to the transducer. 8. A camera mount according to any of claims 3 to 7, SUBSTITUTE SHEET wherein the control signal is derived from an external source . 9. A camera mount according to claim 8, wherein the external source is a potentiometer. 10. A camera mount according to claim 8, wherein the external source is a keypad. 11. A camera mount according to claim 8, wherein the external source is a preprogrammed device such as a swipe card. 12. A camera mount according to any of claims 3 to 7, wherein the control signal is derived from a microprocessor receiving inputs from sensors on the camera mount. 13. A camera mount according to claim 12, wherein the sensors are responsive to torque and/or velocity. 14. A camera mount according to claim 12 or claim 13, wherein the control is effected in accordance with linear torque-speed performance curves. 15. A camera mount according to claim 12 or claim 13, wherein the control is effected in accordance with non¬ linear torque-speed performance curves. 16. A camera mount according to claim 15, wherein the performance curves available include whip-pan. 17- A camera mount substantially as hereinbefore described with reference to the accompanying drawings SUBSTITUTE SHEET

Inventors: CURRY RICHARD GRAHAM, CURRY, RICHARD, GRAHAM
Applicants: CURRY RICHARD GRAHAM, VINTEN GROUP PLC
Application year: 1993
Main classification: F16M11
IPC codes: F16M11