GB2172168A - Camera tilt/pan mechanisms - Google Patents

Abstract

In order to avoid the need to tilt or pan the entire camera, for CCD-using television cameras, the internally-mounted CCD 11 comprising the camera's sensor is suitably moved to simulate tilting or panning. The movement lies within the focal plane 15 of the lens 10 and is produced by a remote controlled electric motor 14 via rack and pinion gears 12 and 13. Alternatively worm gears may be used (Fig. 4A). The CCD may be sensitive to radiation other than visible light, e.g. Infra-Red, and may be associated with an image intensifier. <IMAGE>

Description

SPECIFICATION Camera tilt/pan mechanisms This invention concerns camera tilt/pan mechanisms, and relates in particular to the mechanism used to tilt and/or pan a television camera especially one of the charge coupled device variety.

It is now common practice for some varieties of television camera to employ as their light-sensitive component a Charge Coupled Device (CCD) in place of the previously used vidicon tube. The advantages are manifold, and include all that might be expected from the replacement of a sensor device that is fragile, bulky, hard-to-fabricate, high voltage and high vacuum with one that is relatively robust, small, lightweight, easy-to-make, low voltage and solid state. The present invention is concerned with a novel design consequent upon this reduction in size and mass of the sensor.

One requirement of cameras is that they be mounted so as to be able to be tilted (to point either down or up, or somewhere else inbetween) and to be panned (to point to left or right or-again-somewhere inbetween).

Indeed in certain application, such as remotecontrolled surveillance cameras, it is necessary for the tilt/pan mechanism to be driven by a remote-controlled motor that is part of the camera arrangement. Naturally in order to tilt or pan a heavy camera in a controlled fashion the motor itself must be correspondingly substantial and powerful as must the bearings-especially those involved in tilting motion.

This creates problems especialiy if the camera and its ancilliary equipment is to be small and silent. The present invention proposes an ingenious way round these difficulties for CCDusing television cameras, and suggests that, rather than move the entire camera for tilt (and, to a limited extent for pan) the camera be kept fixed and there be suitably moved instead the internally-mounted CCD comprising the camera s sensor.

In one aspect, therefore the invention provides a CCD-sensor-using television camera wherein the CCD sensor itself is mounted within the camera body for movement in the camera lens s focal plane, and there is controllable drive means for achieving the desired degree of this movement.

Before discussing in more detail the various features of the inventive camera, it is worthwhile briefly explaining the way the invention works. The camera naturally has a lens (this will in practice be a group of lens) that gathers light from the scene being viewed and focusses it within the camera. The lens will be focussed on objects at some specific distance from the camera-all in a plane normal to the optical axis -and light from those objects in that plane is thus in focus within the camera in a corresponding plane the focal plane. It will often be the case that the field of view of the camera's lens result in an image at the focal plane which is dimensionally larger than the CCD sensor being employed to detect the light from the scene.In other words, the camera lens s field of view is somewhat wider in both orthogonal directions (i.e, both laterally and vertically for a conventional view)-than is the CCD sensor. Typically it will be the case that the scene image in the focal plane isin each direction twice as large-or, at least that over twice the CCD sensor's the focal plane image is clean and sharp enough to be useful. Accordingly if then, the CCD sensor is moved about in the focal plane it will receive light originating from different parts of the field of view.If moved up and down it will receive light from above and below the central part of the view - just as though the camera had been tilted up or down -while if moved from side to side it will receive light from to the left and right of the central part of the view-just as though the camera had been panned left or right.

The invention relates to CCD-sensor-using television cameras. The type of camera, and the nature of the CCD sensor apart from the modification involved in applying the invention-may be of any sort. Thus: Although the camera may be designed for use with any sort of (electromagnetic) radiation, most embodiments will be for use with visible (or Infra-Red) light. For the most part, therefore, the description refers simply to light, for convenience.

The invention may be employed in connection with any solid-state sensor camera. Such a camera (examples are the EEV P4310 Series) has an object lens (or lens system) that focuses light onto the sensor, and an electronics package that drives the sensor and reads its output, converting the latter into a form suitable for the rest of the television system of which the camera is but a part.

Similarly, the sensor itself may be of any type (and may, indeed, be responsive to radiation-such as Infra-Red-other than visible light). One such type is the EEV P8602 solidstate image sensor, which is a visible-light frame transfer, charge coupled device.

The camera may incorporate a CCD sensor that is associated with an image intensifier.

Though in principle the intensifier could be of any variety, and could be associated with the sensor (so as to pass its intensified image light output thereto) in any way, in practice the intensifier is very preferably (because of its small size) of the type known as a microchannel plate intensifier, linked with the sensor by a fibre optic bundle. An example of such an intensifier is the EEV P8306, which incorporates a fibre optic bundle (on its output side) onto the output face of which the sensor can be directly mounted (conveniently secured by means of an optically transparent glue).

In the camera of the invention the CCD sensor is mounted for movement in the focal plane. Assuming a conventional view with the camera aligned so that panning means left right movement while tilting means up-down movement, the CCD sensor is then mounted so that it can move at least up-down to simu late tilting, and preferably also so that it can move left-right, to simulate panning.

Of course, whether up CCD movement cor responds to an up tilt (and down movement to a down tilt, left movement to a left pan and right movement to a right pan) depends upon the lens. It will commonly be the case that the lens provides an inverted, left-right reversed, image-so that up movement corresponds to a down tilt, left movement corresponds to a right pan, and so on.

The movement may be either stepped-that is, the CCD sensor can be in one or other of a small number of positions, and is moved from one to the next without pausing intermediate the two-or it may be smoothly variable-that is, the sensor can be moved to a chosen position anywhere within its range of movement.

The way in which the CCD sensor is mounted so as to achieve the required movement capability may be any convenient. For example, for movement along one line the sensor could be mounted upon a rack that is driven back and forth by a motor-driven pinion, or upon a worm similarly driven by a screw, or upon a slide that is pushed back and forth by a pneumatic hydraulic or solenoid-controlled piston. The presently preferred method of achieving movement involves a rack-and-pinion arrangement in which the pinion itself is worm driven.

The drive means for achieving the desired movement may be of any suitable variety. As intimated above, it may-for example-be an electric motor, or a solenoid device.

Naturally, there must be incorporated drive control means whereby the degree of movement provided by the drive means may be adjusted to achieve the desired effect. These control means may be of any sort (including manual), and may control the actuation of the drive means in any appropriate way (usually electrically or electronically). Moreover the control means need not be within or on the camera itself, but can be remote therefrom, the controlling signals being passed to the drive means via-say some radio or wired communications channel.

The invention provides the ability to tilt and/or pan a television camera of the CCD-sensor-using type without physically moving the body of the camera itself. However, the degree of tilt/pan available is very much dependent upon the optics of the camera s lens, and is in any circumstances unlikely to reach the value obtainable by more conventional tilt/pan arrangements. Even so, the limited control available may be very useful.

The degree of tilt/pan achievable depends upon the size of the lens and its focal length (which both govern the size of the image in the focal plane) and upon the size of the CCD sensor itself. Obviously, the larger the image-or rather the larger is the part of the image that is still clear and viewable and the smaller the sensor the greater the simulated tilt/pan achievable by moving the sensor about in the focal plane.

Thus, using a 1 in optical system (or possibly even larger, as is the case with most 35mm SLR lens), which provides a 1 inch (2.54cm) image and a 2/3 in sensor (which is in fact 8.6 X 6.4mm) a lens of 1 10mum focal length provides a normal 4" field of view that can be varied in direction by +5 , while a 25mm lens provides a normal 16 view variable by j750 Using 1 in optics with a 1/2 in sensor (which is 6.45 X 4.8mm) the 110mum lens gives a normal view of roughly 2.5 variable by +2.5 , while a 25mm lens gives a normal view of about 11" variable by + 10.5 . As might be expected, the smaller the sensor the larger the available variation in the field of view-that is, the larger the achievable simulated tilt and/or pan.

An embodiment of the invention is now described, though by way of illustration only, with reference to the accompanying Drawings in which: Figure 1 is a schematic perspective view of the main components of a television camera according to the invention; Figure 2 is a vertical section on the optical axis of the components of Figure 1; Figure 3 is a diagram showing the relative sizes of images and CCD sensors; and Figures 4A & B are respectiveiy perspective and sectional views of a more realistic embodiment of rack-and-pinion driven slidemounted CCD sensor as used in Figure 1.

Figure 1 shows schematically the relevant components of a television camera of the invention (without its body). It includes, spaced along the optic axis, a lens group (10) and a CCD sensor (11). The sensor 11 is mounted (by means not shown) for up/down (as viewed) movement, and has fixed thereto a rack (12) engaging with a pinion (13) drivable by an electric motor (14). The rack pinion and motor are not visible in Figure 2.

The lens group 10 has a field of view of the actual scene (not shown, but to the left as viewed), and forms an image in the group's focal plane (20 in Figure 2) that extends over an area (15) significantly bigger than that of the sensor 11. Driven by the motor-activated rack-and-pinion 13 14 the sensor 11 can be moved up and down (as viewed) in the focal plane, so that light from different parts of the viewed scene (via the lens group) falls on the sensor. In this embodiment then the move ment of the sensor simulates tilting the camera.

The manner in which the CCD sensor 11 may be positioned within the image formed by the lens group 10 is shown more clearly in Figure 3. The inner circle (30) marks out the limits of the image area of a standard 1 inlens group-the outer circle (31) marks the limits of a standard 35mm lens-while the dotted and solid rectangles (32t,b and 33t,b) within that circle show the top/bottom extreme positions thereon of respectively a 1/2 in and a 2/3 in CCD sensor. Clearly, moving the chosen sensor from one extreme to the other is tantamount to tilting the camera.

In Figures 4A and B there are shown views of a more realistic rack-and-pinion driven CCD sensor. The sensor 11 is mounted on a slider support (40) having a rear wedge-shaped elongate projection (41) bearing on its rear face a rack (42: not visible in Figure 4A). The support 40 is itself mounted via the projection 41 in a correspondingly wedge-shaped slot (43) in a hollow slider mounting (44), and is driven up and down (as viewed) by a pinion (45: not visible in Figure 4D) within the mounting 44.

The pinion 45 is itself mounted on one end of a driven shaft (46) that projects laterally and out of the mounting 44; the outer shaft end carries a gear (47) that is the wheel of a worm-and-wheel arrangement. The worm (48) is mounted for rotation on the driving shaft (49) of an electric motor (50).

As can be appreciated as the motor 50 turns the worm 49 to and fro so this motion is communicated via wheel 47, shaft 46, pinion 45 and rack 42 so as to drive the slider support 40 up and down in its slot 43-and so the CCD sensor 11 is correspondingly driven up and down.

Claims (1)

1. A CCD-sensor-using television camera wherein the CCD sensor itself is mounted within the camera body for movement in the camera lens s focal plane, and there is controllable drive means for achieving the desired degree of this movement.

2. A camera as claimed in Claim 1, wherein the sensor is a visible-light, frame transfer, charge coupled device.

3. A camera as claimed in either of the preceding Claims, wherein the CCD sensor is mounted so that it can move both up-down, to simulate tilting, and left-right, to simulate panning.

4. A camera as claimed in any of the preceding Claims, wherein the movement of the CCD sensor is smoothly variabie--that is, the sensor can be moved to a chosen position anywhere within its range of movement.

5. A camera as claimed in any of the preceding Claims, wherein the way in which the CCD sensor is mounted so as to achieve the required movement capability involves a rack and pinion arrangement in which the pinion itself is worm driven.

6. A camera as claimed in any of the preceding Claims, wherein the drive means for achieving the desired movement is an electric motor.

7. A CCD-sensor-using television camera as claimed in any of the preceding Claims and substantially as described hereinbefore.

CLAIMS Amendments to the claims have been filed, and have the following effect: Claims 1 and 3 above have been deleted or textually amended.

New or textually amended claims have been filed as follows:

1. A CCD-sensor-using television camera wherein the CCD sensor itself is mounted within the camera body for movement in the camera lens's focal plane, and there is controllable drive means for achieving the desired degree of this movement.