GB2077448A - Remote control camera - Google Patents

Abstract

A device for measuring the distance between a remote control camera and a photographic subject is mounted on the camera and supplies electrical signals to a read-out device, enabling the camera operator to focus the camera lens. The distance-measuring device may be an ultrasonic or infra-red, radar device.

Description

SPECIFICATION System for assessing focus distances when using a remotely controlled camera This invention relates to the assessment of focus distances and the focussing of remotely controlled cameras.

The basic requirement of all photography is that the lens of the camera should be focussed at a certain distance to ensure that the image of the scene being photographed is correctly in focus at the film plane. For various reasons it is not always practicable to follow the normal routines of either setting the lens focussing by means of a scale, focussing the image on a ground glass or other type of focussing screen temporarily placed in the film plane or in an equivalent plane, or using a tapemeasure to determine the distance at which the focus should be set.

This is especially the case if the camera is situated remotely from the operator and must be focussed on a subject which is also out of reach of the operator.

Systems of automatic focus have been proposed which by means of ultrasonic or infra-red or other monitoring systems produce an assement of the focussing distance to the subject being photographed and automatically adjusts the lens without aid from the operator.

In the realms of professional photography, particularly cinematography, such systems are not always viable for the following reasons.

1. The scene may involve two objects, say two people, who have to be in focus, but between them is a space, so that when the camera is directed to photograph the two people, the focussing device is directed to the space. In such instances the background might be considerably further away than the people to be photographed and the tendency is for the focussing device to sense perhaps the background if indeed it senses anything at all resulting in incorrect focussing of the lens.

2. It may be necessary to focus on two or more objects one close to the camera and one more distant, and to calculate an optimum focus distance between the two objects, bearing in mind the depth of field of the lens, to achieve a satisfactory focus of the two objects. Again the above described automatic focus systems cannot cope with this situation.

3. In cinematography it may be necessary to move the camera in the course of a shot between several objects with spaces between them, in which case an automatic focussing system would tend to hunt and set itself to all sorts of unrequired distances during such movement.

It is an object of the present invention to overcome these disadvantages.

Accordingly in one aspect the present invention provides a focus detecting device operative to measure a focussing distance from the device to an item to be photographed by means of ultrasonic waves or infra-red or other monitoring systems and to give a read-out or display of the distance measured which may be read by a camera operator either on the device, or at a point remote from the device.

The focus detecting device may be provided with remote control means by which it may be aimed at selected objects to be photographed and thus to measure the focussing distance to them.

In association with such focus device, the camera to be used to photograph the subject may be provided with remote control lens focussing in the form of a servo-drive to operate the lens focus in response to a calibrated input control, or in the form of close-circuit television camera or other electronic means to enable the camera operator to remotely control the lens and observe its focussed setting.

Thus with the focussing device the focussing distance can be measured and the camera set.

In one arrangement the focussing device may be attached to the camera so that as it is panned and tilted either directly or remotely by the camera operator, it is possible for the operator to read-out the various focussing distances either directly on the instrument, or remotely, and to set the focus on the camera lens as required.

In order to promote a fuller understanding of the above and other aspects of the present invention, some embodiments will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1A shows schematically the arrangement of three distance measuring devices, while Figure 1 B shows the zones seen by those devices, Figure 2A and Figure 28 show similarly an arrangement with four measuring devices.

Figure 3 shows in schematic plan another arrangement utilising two devices, and Figure 4 shows a schematic arrangement of electronic circuitry associated with the measuring devices of Figures 1 and 2.

Figure 1A shows schematically three distance measuring devices which are of known type perse and may operate by the use of ultrasonic rays, infra-red light or other suitable means to give an electrical output signal of the distance of an object or subject to be photographed from the device.

Three such devices are arranged in association with a camera such as a cinematographic camera which is remotely operated by conventional means in a manner known per se. The devices indicated as A, B and C in Figure 1 are arranged so that the areas of an object that they sense overlap as depicted schematically by the zones A, B and C in Figure 1 B.

Thus when the camera with which the measuring devices are associated, is directed towards a subject to be photographed, the three devices A, B and C give an electrical signal based on a distance measured from the camera to that part of the subject which falls in the respective zone A, B or C.

As shown schematicaliy in Figure 4, the electrical device from the measuring devices A, B and C are spaced to an electronic circuit indicated at 10 which is arranged in known mannerperseto select the two signals which represent the most similar distance measured, thus rejecting the third signal. The two selected signals are based on lines 11 and 12 to a further electronic circuit 13 which in known manner perse averages the signals on lines 11 and 12 to give a signal on the line 14 respective of the average distance measured by the two selected devices. The signal on the line 14 is supplied to a digital display device 15 which operates in known mannerperseto give a read-out of the distance measured from the camera to the subject to be photographed.The read-out 15 may be provided at any suitable position so that a remote operator of a camera is given a reliable read-out of the distance of the subject to be photographed. The averaging and rejection of the most different signal helps to ensure that the read-out is not influenced by the background objects and other factors as with prior art devices.

The arrangement shown in Figure 2A and 2B operates in an exactly similar manner to that described above, only with four measuring devices A, B, C and D providing signals to the device 10 which again selects the two most similar distance signals for averaging.

Figure 3 shows another arrangement in which two measuring devices A and B, again of known type per se, are associated with a camera and spaced apart in such fashion that their operative measuring axes are adjustable so that they can be set to converge on or near the measured distance from the camera to subject. With this arrangement the outputs from the two measuring devices may be averaged in a circuit similar to that indicated at 13 in Figure 4 with the result being displayed in similar fashion. With this arrangement, the operator can ensure that both measuring devices are directed to the subject and thus not influenced by other objects.In a modification of the arrangement in Figure 3, several measuring devices can be similarly angularly directed with one or more of the measurements in the fashion discussed with regards to Figures 1 and 2 above, with the remaining two or more signals being averaged.

It will be appreciated that any of the above measuring systems may be mounted on a remote control camera so that they move with that camera.

In the alternative, the measuring device may be mounted so that it itself may be removed under remote control in known mannerperse and thus directed to any particular subject in any part of the field of view of the camera, or indeed outside the field of view of the camera. Again a number of such devices may be provided, each giving a remote reading to a camera operator or a director, and the devices may not necessarily be associated with the camera but can be used to give distance measurements from a particular point to subjects being photographed.

Thus it can be seen that the arrangement enables a camera operator to have a remote reading of the distance measured, particularly from a camera to a subject, so that the operator may by remote control, focuss the camera in accordance with the reading. It will be appreciated that the read-out device 15 may be based on the camera itself if desired, and may indeed be duplicated at several points.

Claims (10)

1. Afocus distance measuring device for use with a camera arranged to be directed by remote control at a chosen subject to be photographed, and to give an electrical signal indicative of the distance to the object to a read-out device at a point remote from the device of the distance measured.

2. A device as claimed in Claim 1, in which the measuring device is mounted on or associated with the camera which is remote controlled to move with it to be directed at the subject.

3. A device as claimed in Claim 2, in which the measuring device is movable under remote control relative to the camera to be directed at a subject in a chosen part of the field of view of the camera.

4. A device as claimed in Claim 1,2 or 3, in which the measuring device comprises an ultrasonic or infra-red radar device arranged to produce an electrical output signal indicative of the measured distance.

5. A device as claimed in any one of Claims 1 to 4, in which the measuring device comprises a plurality of transducers each arranged to give an electrical output signal indicative of the distance to the subject, and means is provided to average the electrical distance signals by two or more of such transducers.

6. A device as claimed in Claim 5, in which means is provided to select the electrical signals from the two transducers which give the closest distance measurement for such averaging.

7. A device as claimed in Claim 5 or 6, in which three such transducers are provided.

8. A device as claimed in Claim 5 or 6, in which four such transducers are provided.

9. A device as claimed in Claim 5,6,7 or 8, in which said transducers are directed to sense overlapping areas at the subject.

10. Afocus distance measuring device substantially as herein described with reference to the accompanying drawings.