WO1992010063A1

WO1992010063A1 - Surveillance systems

Info

Publication number: WO1992010063A1
Application number: PCT/AU1991/000539
Authority: WO
Inventors: Albert Henry William Kluver; Ramon Desmond Pearce
Original assignee: Trafalgar Security Pty. Ltd.
Priority date: 1990-11-21
Filing date: 1991-11-21
Publication date: 1992-06-11

Abstract

A surveillance system uses movable video camera optics (30, 60, 114, 123, 148) with a semi-conductor video chip (117, 124, 162) the image orientation at a monitor being adjusted as the camera is panned about the area being surveyed. Video signals are relayed via bus bars (211, 212) to a receiver with the lines balanced for more effective transmission.

Description

Title; "SURVEILLANCE SYSTEMS" FIELD OF THE INVENTION

THIS INVENTION relates to various improvements in surveillance systems of the type which employ a camera mounted to permit panning over a field of view. BACKGROUND OF THE INVENTION

Prior Patent Specification No. AU-47808/90 sets out a description of a surveillance system in which a video camera is mounted for movement along a track. The lens of the camera may be panned typically through

180° from an elevated position. In a tracked system, the image at a monitor might be oriented with the top of the image being the forward direction along the track.

When the tracked camera is then panned to the left or the right, the image at the monitor rolls through an angle with angular movement to one side or the other depending on whether panning is to one side or the other. With a dome mounted camera, a correctly oriented image at one extreme will be inverted at the other. OBJECT OF THE INVENTION

It is one object of the present invention to provide camera structures whereby more correctly oriented images are presented on the monitor throughout the extremes of panning permitted to the camera. NATURE OF THE INVENTION

The invention achieves its objects in provision of a surveillance system in a surveillance system of the type in which a video camera is used to monitor an area under surveillance comprising:- a video camera; a movable mounting for the video camera; the camera being mounted on the movable mounting to typically look forwardly and downwardly; the movable mounting being controllable to pan the video camera through an angular displacement;

SUBSTITUTESHEET characterised in that provision is made to rotate the image as the camera pans to maintain a desired orientation to the image on a monitor therefor.

In prior Patent Specification No. AU-47808/90 transmission of video signals is effected along parallel conductors. This system was limited in what distance the camera might be advanced along its track before reception problems were experienced as a result of the standing waves that existed in the improperly terminated parallel conductor transmission line. In practice, at a certain distance colour could be lost, regained for a time but with an increasing degradation of the received image as distance increased.

It is a second object of the invention to provide circuitry which creates a balanced line to improve reception.

The invention achieves this object in provision of a surveillance system in a surveillance system of the type in which a movable video camera is used to monitor an area under surveillance, said surveillance system comprising:- a video camera; a movable mounting means for the video camera by which the video camera may be moved along a path through the area under surveillance; and a camera track defining the path for the video camera on which the movable mounting means is entrained to carry the video camera along the path; the camera track including a bus bar system by which communication with the movable mounting means and the video camera is effected; characterised in that: the video camera output is applied to the bus bar system for transmission to a receiver in a balanced format. DESCRIPTION OF THE DRAWINGS

In order that preferred embodiment of the invention may be readily understood and carried into practical effect, reference is now made to the accompanying drawings, wherein:-

FIG. 1 is a partly broken-away side elevational view of part of an extended track type surveillance system;

FIG. 2 is a sectional view taken along line 2-2 in FIG. 1;

FIG. 3 is a partly broken-away elevational view of the system from the side opposite to that shown in FIG. 1;

FIG. 4 is a cross-sectional view, to larger scale, taken along line 4-4 in FIG. 1;

FIG. 5 is a partly broken-away side elevational view of a dome type surveillance system;

FIG. 6 is a sectional view taken along line 6-6 in FIG. 5; FIG. 7 is a partly broken-away front elevational view of the device shown in FIG.s 5 and 6;

FIG. 8 is a sectional view of the device along line 8-8 in FIG. 7;

FIG. 9 is a side elevation of a first embodiment by which an image reversal may be generated;

FIGS. 10 and 11 are side elevations and plan views of a second embodiment whereby an image reversal may be generated;

FIGS. 12, 13 and 14 are side elevation, front elevation and plan views of a third embodiment wherein an image reversal is effected;

FIG. 15 is a circuit diagram indicating the circuitry which is employed at the camera to place the video output onto bus bars; FIG. 16 is a---circuit diagram indicating the circuitry which is employed at the receiver to take video signals off the bus bars; and

FIGS. 17 and 18 are views showing a form of electrical contact which might be used in tracked camera systems.

DETAILED EMBODIMENTS

Referring initially to FIGS. 1 to 4 inclusive a surveillance system includes a mounting channel 10 which may be an aluminum extrusion and is fixed, inverted, in any suitable manner under a ceiling 11. The side flanges 12 of the channel terminate, at the bottom, in inturned flanges or rails 13. The top member or web 14 of the mounting channel is rebated, at its side edges, to receive the top edges of a shroud 15 which may be of sheet plastics material shaped so that its upper parts are parallel and vertical, its lower part being semi-circular in cross-section. The shroud is tinted so as to be translucent but of limited transparency. The shroud is secured by screws 16 through its upper sides and engaged in longitudinal ribs 17 on the side flanges 12. Dust seal strips 18 are interposed between the side flanges, below the ribs 17 and the shroud sides.

The mounting channel web 14 is formed with a shallow longitudinal recess in which is seated and adhesively secured a band 19 of flexible insulating material with equally spaced parallel longitudinal grooves in which are secured conductor strips 20 which may suitably be of copper. A camera carrier, indicated generally at 21, is located and freely movable longitudinally within the shroud 15. The carrier includes a box-like body 22 having parallel side bars 23 at its top. Transverse axles through these bars carry a pair of drive wheels 24 and a pair of free wheels 25, all travelling on the rails 13 of the mounting channel 10. A reversible electric motor 26 within the carrier body is operatively connected by gear and differential or by a belt drive to the axles of the drive wheels 24 so that 5 the carrier can be advanced or retracted along the rails.

A tubular shaft 27 rotatable in a bearing 28 at the front of the carrier body 22 carries at its front a clevis 29. A video camera lens assembly 30 is

10 held by a clamp ring 31 having diametrically opposed trunnions 32 rotatable in bearings in the arms of the clevis 29. Fixed on one of the trunnions 32 is a toothed sector 33. A shaft 34 passing rotatably through the tubular shaft 27 is the input shaft to a gear box

15 contained within the head of the clevis 29 of which the perpendicular output shaft 35 carries a pinion wheel 36 which meshes with the toothed sector.

Within the carrier body 22 a reversible and variable speed electric motor (not shown) is

20 operatively connected through reduction gearing to the tubular shaft 27 so that this shaft, and with it the clevis 29 and the camera lens assembly 30, can be oscillated from side to side to pan the camera lens. A further electric motor (not shown) within the carrier

25 body is operatively connected to the shaft 34 and may be operated to drive the pinion 36 in either direction to cause the camera lens assembly 30 to be titled or angled, forwardly or rearwardly, about the trunnions 32.

The output electronics package for the CCD-

30 type video camera is separated from the lens assembly 30, being enclosed in a housing 37 which is partly within, and partly extended to the rear of the carrier body 22, a flexible assembly 38 of electrical leads being carried from the lens assembly to the carrier body

35 and thence to the appropriate terminals of the camera output. On top of the carrier body 22 is a transverse series of spring-loaded contact points 39, one contact point making electrical connection with each of the conductor strips 20. The output of the camera is displayed, in usual manner, on remote display means of any well known type.

As the carrier is advanced or retracted, a transverse cleaning pad 40, extending from the top of the carrier body 22 and spring-loaded upwardly, bears against and cleans all of the conductor strips 20.

The tilting of the camera lens in each direction is limited, an arm 41 centrally fixed on the trunnion 32 remote from that carrying the toothed sector 33 having threadedly engaged therein a pair of tilt limit adjustment screws 42 which, when brought to actuator arms 43 of micro-switches carried in a housing 44 on the clevis 29, break the circuit of the tilt motor driving the shaft 34.

The embodiment of the invention shown in FIGS. 5 to 8 inclusive is a surveillance system of fixed, rather than travelling type. It includes a top or fixed mounting disc 50 which may be secured under a ceiling, for example, and which is rebated to receive closely the top of an inverted-dome shaped outer shroud 51 of semi- opaque plastics material, of which the upper part is cylindrical, the bottom being hemispherical. A pivot shaft 52 extends coaxially downwards from the mounting disc 50 and rotatable on this shaft is a bearing 53 passing coaxially through a rotatable carrier disc 54. The carrier disc 54 is peripherally rebated to accept the top of an inner shroud 55 which, like the outer shroud, is semi-opaque and is equidistantly spaced within the outer shroud, being, like the outer shroud, of cylindrical form at ^"its upper part with a hemispherical bottom which, however, is divided by a parallel-sided viewing aperture 56.

A pair of carrier arms 57 and 58 extend downwardly from the rotatable carrier disc 54 and are rigidly connected by a cross-member 59. A video camera lens assembly 60 has opposed lateral trunnions 61 rotatable in bearings in the lower parts of the carrier arms 57 and 58 and fixed on one of these trunnions is a lower pinion wheel 62 meshing with one toothed end of a double-sector member 63 oscillatable on a stub axle 64 on carrier arm 57. The toothed other end of the double-sector member meshes with a drive pinion wheel 65. this pinion wheel is driven by a power unit 66 which incorporates two independent reversibly electric motors (not shown) of which one drives, through reduction gearing, the drive pinion wheel 65 to act through the double-sector member and the lower pinion wheel 62 to tilt the camera lens assembly through about 180 degrees about the horizontal axis of its trunnions 61. Micro-switches 67 restrict the angle through which the camera lens is tilted when acted on by the sides of the upper part of the toothed double-sector member 63.

The second motor of the power unit 66 acts through reduction gearing to rotate or pan in either direction the rotatable carrier disc 54, and therefore the camera lens assembly relative to the fixed carrier pivot shaft 52.

The under side of the fixed mounting disc 50 is formed with a circular recess to receive an adhesively secured annulus 68 of a resiliently deformable insulating material which is formed with a series of concentric grooves to accept a series of annular copper conductor strips 69. Mounted on the lower or rotatable disc 54 is a radially arranged block 70 of insulating material in which are set a series of copper/silver contact points 71 spring-loaded upwardly and arranged in two staggered rows so that each point makes electrical contact with one of the conductor strips 69.

As in the embodiment of the invention described with reference to FIGS. 1 to 4, the CCD - type camera output electronics package is separate from the camera lens assembly, being enclosed in a housing 72 attached to the support arm 58 which is stepped for this purpose, the rotatable disc 54 being formed with a radial recess to receive the upper part of the housing

72. A flexible assembly 73 of electrical leads (not shown) is connected between the contact points 71 for the performance of the various functions of the device, as before described. A dark-colour arcuate baffle strip 74 is fixed on the lens assembly 60 to approach closely and more or less close that part of the arcuate aperture 56 which at any time is not aligned with the camera lens.

In connection with the three embodiments of FIGS. 9 to 14 each system may comprise a lens, lens mount, clutch or the like and charge coupled device

(CCD) by which to generate an electric signal representative of what the lens sees.

In each case, the CCD chip is mounted rotatively relative to the lens. . To stabilise chip and lens, a clutch or like mechanism may be introduced between the two. Either of mechanical or electrical means may be employed to effect a rotation of the CCD chip at the appropriate time as will be described below. By these means, rotation of the chip reorients its image on the monitor so that the image inversion problem is overcome.

In FIG. 9 is seen a camera 110 adapted for movement along a track on wheels 111 and 112 with brushes 113 making contact with an overhead system of bus bars. The camera has a lens 114 which in the drawing is pointed downwardly. The lens 114 is mounted in a lens holder 115 on a shaft 116 which may be turned by a motor (not shown) inside camera body 121. By this means the lens 114 may be rotated to pan left or right. The optical image produced by lens 114 is directed onto a detector such as a charge coupled device (CCD) mounted in housing 117 behind the lens 114. In order that the image orientation on the monitor may be controlled, the CCD housing 117 is mounted rotatively relative to the lens. In essence the CCD sensor chip is rotated in a plane perpendicular to the optic axis of the lens. In order to stabilise the image, the CCD sensor chip needs to be locked relative to the lens and a slipping clutch mechanism 118 may be inserted therebetween.

To rotate the CCD chip, the CCD housing 117 may have mounted thereto a gear 119 which meshes with a fixed gear 120 attached to camera body 121. The planes of these two gears is at right angles. When lens 114 is panned left or right, the effect of the meshed gears is to cause CCD housing 117 to rotate and the sensor chip rotates relative to the optic axis to cause a reorientation of the image it provides to a remote monitor. By this means, inverted images are avoided. It will be clear that the rate of turning of the chip will depend upon the gear ratio. The arc over which turning is effected may be made small and the angular extent of the fixed segmental gear 120 which is engaged with gear 119 will be determined accordingly. Gear 120 need only exist as a short segment to effect rotation of lens 114 over a part of the lens' angular travel when the gear ratio is appropriately chosen. The mechanism of FIG. 9 has the result that totally inverted images may be avoided but at various directions of the lens 114, the image of the camera may be at an angle on the monitor.

In FIGS. 10 and 11 is seen a travelling camera similar to that of FIG. 9, but this time the camera lens is able to be oriented with an additional degree of freedom and the rotation of the CCD chip is established electro-mechanically. A lens system 123 provides an image to a chip in CCD housing 124 and this assembly is turned on shaft 125 being mounted rotatively between the arms of yoke 126 on a shaft 127. Shaft 127 is turned by lever arm 128 with a geared end meshed with gear 129 on shaft 142 to motor 141. By this means the lens may be moved to selected angles fore and aft of the camera body.

The CCD housing 124 may be rotated by a motor 130 driving gear 131 and intermediate gear 132 which is meshed with gear 133 attached to housing 124. The CCD housing may again be clutched to lens 123 by a slipping clutch 145 fitted to support plate 146 which is attached to the lens housing and provides a surface for mounting of motor 130, gear 132 and relays 136, 143 and 144 described below. In addition to gear 133 which is attached to the CCD housing 124 there is also attached thereto a cam 134 with a node 135 on its periphery, which node engages with relays such as 136 to action them. The main support shaft 125 is turned by motor 137 and it too is provided with a cam 138 which has a node thereon which actions relays 139 and 140.

In operation of the above camera, rotation of the lens assembly either left or right would create improperly oriented images as before except that motor 130 may be activated to turn the CCD sensor chip to correct the orientation. Correct rotation of the chip is effected by logic control utilising the output of the various relays. As the lens assembly is panned left or right, the orientation is determined by what relays are tripped by cam 138. Knowing the orientation of the camera, motor 130 can be actioned and the chip may be turned until cam 134 actions relays whose condition signals that rotation is complete. By this means, as the lens moves through a vertically downward direction of view, chip housing 124 may be turned to a degree producing a perfectly vertical monitor image. The time in which this is achieved is dependent upon choice of motor speed and gear ratios. The controller required to sequence the action will be readily assembled using standard electronic techniques.

In FIGS. 13 to 14 is seen a dome camera. Shown here is a mechanical means of affecting image orientation. It should be clear that the electro- mechanical means of FIGS. 10 and 11 could be utilised in the dome camera.

In the drawings a lens 148 is shown oriented downwards mounted in a yoke 149 attached to a support on shaft 152 underneath plate 151. Plate 151 carries bus bars 153 which are swept by contacts 154. The orientation of the lens 148 relative to yoke 149 is established by motor 155 driving gear 157 on output shaft 156. Gear 157 meshes with gear 158 to turn gear 159 on shaft 160 which carries the lens. With the system in this form inverted images would occur except that provision is made to rotate CCD sensor housing 162. CCD housing 162 may be clutched to lens 148 by slipping clutch 161. Housing 162 is provided with a gear 163 meshed with a segmented gear 164 at right angles thereto on yoke 149. Panning the lens causes the meshed gears to rotate the housing in the same manner as in the embodiment of FIG. 8. Housing 162 when in rectangular form, presents flat sides and these, when correctly oriented, lie in the plane of the yoke arms. Arms 166 and 167 provide faces 168 and 169 against which housing 162 may bear as the lens 148 is tilted. At the centre of arms 166 and 167, where they attach to yoke 149, the arms are recessed to permit housing 162 to turn. With properly selected gear ratios, housing 162 may be turned sufficiently to mesh with the bearing surfaces 168 and 169. The gears 165 and 164 should disengage prior to housing 162 meeting the bearing surfaces and any incorrect angle of housing 162 will be corrected on contact with lips 165 at the inner ends of bearing surfaces 168 and 169.

In the foregoing examples, orientation is achieved by rotation of the CCD chip relative to the camera optics. This is a relatively simple procedure by which to effect a change of orientation. Clearly the same result may be achieving electronically with manipulation of the video signal using video processing techniques. Such techniques exist and will be known to a man skilled in the art. In implementing such control, sensors indicating the camera position might be used to signal to video processing equipment the degree of re¬ orientation that should be implemented to achieve a desired image orientation at the video monitor. The camera sensor output might be fed to control circuitry using digital logic under program control to effect generation of a desired video image orientation. Standard electronic engineering techniques are all that are required to achieve this.

In FIG. 15 operational amplifier IC1 is a buffer between the camera output 210 and bus bars 211 and 212 presenting a high resistance to the camera which then sees its preferred 75 load 215. The video signal is presented to the non-inverting input of the op amp IC1 to place its output on bus bar 211. IC2 is operated as an invertor to put a signal on bus bar 212 with a phase 180 out of step .with the signal on bus bar 211. Resistance Rl and R2 are preferably each 1/2 Zo (the line impedance of bus bars 211 and 212).

In FIG. 16, at the receiver end, bus bars 211 and 212 are terminated by resistance R3 and R4 which are each preferably 1/2 of Zo to produce a balanced termination. The video signal on the bus bars 211 and 212 is tapped by an amplifier 216 comprising IC3, IC4 and IC5 connected in a manner providing good common mode rejection with a high input resistance so as not to affect the bus bar termination. The output of amplifier 216 is provided to an output socket 217 via a 75 resistance 218. The forward resistance of amplifier 216 is low so that a monitor connected at 217 sees its preferred 75 line. In the amplifier circuit 216, at 219, there is a connected a circuit 220 by which compensation may be made for loss of high frequencies as the camera distances increases.

In the above circuit the operational amplifiers may be high-speed, lower power devices such as Analog Devices Op Amp AD847. Such a device operates with low power requirements.

In the circuit of FIG. 16, the value of the resistance at 221 can be adjusted to vary the gain. A doubling of this resistance halves the gain.

In FIGS. 17 and 18 is seen a design for a brush which the tracked cameras may use to contact the bus bar system. Each bus bar is swept by a brush 370 which may be pinned to the camera by any suitable means 371. Brush 370 has fore and aft arms 372 and 373. The material of brush 370 may be a resilient electrical material and arms 372 and 373 may be upwardly sprung against a bus bar, in use, to maintain electrical contact. The ends of arms 372 and 373 are cut to provide a series of digits across the ends such as 374, 375 and 376. This design is found advantageous in cameras tracked around curves. The two digitated arms providing a more reliable electrical contact then the more usual wiper type contact.

Claims

1. A surveillance system of the type in which a video camera is used to monitor an area under surveillance comprising:-

5 a video camera; a movable mounting for the video camera; the camera being mounted on the movable mounting to typically look forwardly and downwardly; the movable mounting being controllable to 10 pan the video camera through an angular diplacement; characterised in that provision is made to rotate the image as the camera pans to maintain a desired orientation to the image on a monitor therefor.

2. A surveillance system as claimed in Claim 1 15 wherein: the video camera comprises optics which are panned in through a plane, its image being applied to a movably mounted semi-conductor imaging chip which converts the light image of the camera optics into an

20 electrical video output for transmission to the monitor, the semi-conductor imaging chip being rotatable in the focal plane of the video camera optics to effect a change of orientation of the image at the monitor, the rotation of the semi-conductor imaging chip being

25 coupled to the angular disposition of the video camera in the said plane in which it pans.

3. A surveillance system as claimed in Claim 2 wherein: I the rotation of the semi-conductor imaging 30 chip is effected continuously as the camera pans, the semi-conductor imaging chip being mounted to a rotatable gear which is co-planar with the image plane of the camera optics, the rotatable gear being meshed with a fixed gear which is mounted with its axis orthogonal to 35 that of the rotatable gear.

4. A surveillance system as claimed in Claim 3 wherein: the rotation of the semi-conductor imaging chip is effected over a portion of the angular displacement of the video camera as the camera pans with the fixed gear being a segmental gear meshing with the rotatable gear over only the portion of the angular displacement meshing occurring about the vertically downwards position.

5. A surveillance system as claimed in Claim 2 wherein: rotation of the semi-conductor imaging chip is effected electro-mechanically or electronically with rotation effected to maintain an image at the monitor which is oriented vertically.

6. A surveillance system as claimed in Claim 5 wherein: rotation of the semi-conductor imaging chip is effected by control logic which responds to the position signals relayed thereto from position sensors which sense the orientation of the video camera.

7. A surveillance system as claimed in any one of Claims 1 to 6 wherein: the movable mounting means is rotatably movable about a vertical axis, the video camera optics and semi-conductor chip are mounted to the movable mounting means on a panning means by which they may swing angularly in a plane through the vertical axis and the semi-conductor imaging means is rotated about the axis of the camera optics by a gear assembly.

8. A surveillance system of the type in which a movable video camera is used to monitor an area under surveillance, said surveillance system comprising:- a video camera; a movable mounting means for the video 17 camera by which the video camera may be moved along a path through the area under surveillance; and a camera track defining the path for the video camera on which the movable mounting means is 5 entrained to carry the video camera along the path; the camera track including a bus bar system by which communication with the movable mounting means and the video camera is effected; characterised in that: 10 the video camera output is applied to the bus bar system for transmission to a receiver in a balanced format.

9. A surveillance system as claimed in Claim 8 wherein:

15 the output of the video camera is applied to a buffer by which the camera sees its preferred load and the buffer applies the video signal to the bus bar system.

10. A surveillance system as claimed in Claim 9 20 wherein: the buffer circuit applies the video signal to two lines, 180° out of phase, through resistances equal to one-half the line impedance.

11. A surveillance system as claimed in Claim 10 25 wherein: two operational amplifiers are used to buffer the video camera output to the bus bar lines, one applying a non-inverted signal to the line, the other an inverted signal.

30 12. A surveillance system as claimed in any one of Claims 8 to 11 wherein: at the receiver end of the bus bar, the lines carrying the video signal are terminated by resistances equal to one-half the line impedance and the

35 signal is tapped by an amplifier providing its output to a video monitor.

13. A surveillance system as claimed in Claim 12 wherein: the amplifier provides common mode rejection with a high input resistance and a low forward resistance.

14. A surveillance system as claimed in Claim 13 wherein: the amplifier includes compensation for loss of high frequencies.