WO1993021736A1

WO1993021736A1 - Image splitter for security cameras and the like

Info

Publication number: WO1993021736A1
Application number: PCT/US1993/003661
Authority: WO
Inventors: Donald E. Degnan; Howard A. Schaad; Michael L. Hightower
Original assignee: Cromwell Marketing Co., Inc.
Priority date: 1992-04-21
Filing date: 1993-04-19
Publication date: 1993-10-28
Also published as: AU4106993A

Abstract

An apparatus for providing a pair of discrete images to a left mirror (24) and a right mirror (23) joined at an edge (30) therebetween and adjustably disposed at an angle between approximately 60° and 120°, preferably 90°, to each other. The mirrors are mounted such that images transmitted through each of a pair of windows of a housing are reflected by the mirrors towards a camera assembly, and the mirrors are bevelled at the joining edge such that the image generated from the area within and between the respective surfaces thereof is minimized. The mirror assembly is capable of being tilted upward toward the lens of the camera and further comprises an auxiliary lens pair for correcting image distortion which may subsequently occur. In the event the angle between the mirrors are adjusted such that the interface between the reflected images is blurred, a vertical black bar is generated to blank the blurred portion prior to transmission to the video monitor.

Description

IMAGE SPLITTER FOR SECURITY CAMERAS AND THE LIKE FIELD OF THE INVENTION The present invention relates generally to video surveillance systems, and in particular to the use of a pair of mirrors adjustably fixed at a predetermined angle in relation to the lens of a television security camera to provide simultaneously a fixed split image of an area under surveillance thereto.

BACKGROUND OF THE INVENTION In the field of video surveillance, it is desired to provide the maximum amount of surveillance of the secured area with the minimum amount and complexity of security camera equipment. Television security cameras are often mounted in fixed positions at locations which provide the greatest possible viewing area per camera. When corridors intersect, it is common practice to install two or more cameras in fixed positions at the intersection, with each camera pointed towards a different corridor. In addition, when a long corridor must be monitored, it is common to utilize multiple cameras in fixed positions at various points thereof.

In order to monitor each of the images from the various cameras,' it is necessary to provide means for switching from the image provided by one camera to the next. Alternatively, multiple video monitors can be used, corresponding to the number of cameras in the system. Both these methods of monitoring the large number of images provided by the various fixed point cameras are, however, costly. An alternative way to provide greater coverage is to provide a security camera with means for panning the area under surveillance, rather than fixing the camera in one position. To accomplish this, servo motor drive assemblies are implemented with automatic pan or remote control mechanisms. Typically, a security guard located at a strategically located guard station will operate such remote control devices.

In addition, numerous devices exist in the prior art which operate to move assemblies of mirrors and prisms in order to provide a fixed position security camera with greater surveillance capability. Such mechanisms are also costly and must be aligned and serviced in order to maintain the needed reliability.

Although the use of automatic or semi-automatic drive assemblies enables the reduction of the number of security cameras and corresponding monitors, such assemblies are costly to install^land maintain. Moreover, the chance of failure of mechanical panning devices is considerably detrimental in high security applications. Further, the use of such prior art techniques provide only one view for transmission to a monitor at any given time.

In addition, it is the practice of security camera installers and technicians to place security cameras at a height which is well above the heads of people populating the area under view. In so doing it is necessary to install the camera on an angle so that it points downward. ^l" The image thus captured and displayed is projected on the monitor in an angular position, i.e., those standing erect will appear slanted or standing in a bent position. Such display may cause difficulty in proper viewer identification.

Accordingly, the present invention is an apparatus for providing a pair of discrete images to a fixed security camera of the charge coupled device (CCD) type, which comprises a pair of mirrors disposed at a predetermined angle with respect to the camera such that each mirror reflects a discrete image towards the camera and the resulting image captured by the camera is a composite of the two discrete reflected images. As will become evident from the detailed description of the present invention provided below, the mirrors in the apparatus are joined at an angle in the area proximate the middle of the composite image. There, the edges of the mirrors abut and may form a blurred vertical line on the composite image, which is undesirable since it may hinder the focus mechanisms of the surveillance system.

A black bar generator is therefore desired in order to furnish a video blanking signal, or black bar, to cover the blurred line formed by the mirror edges such that the left image and the right image are clearly separated by a sharply defined black bar and focusing by the surveillance system is not inhibited.

The prior art discloses various methods of providing simultaneous images to a video monitor. Reference is made to United States Patents Nos. 3,006,993; 3,578,906; 4,070,695; 4,177,512 and 4,331,962. It will be readily noted that each of these prior art references describe the use of a vidicon camera with modifications to the monitor or terminal. The prior art does not teach means for selectively providing a video blanking signal at a desired location on the screen which can be implemented with CCD camera technology, and which is an "add-on" ^"*" circuit that does not require the modification of the monitor or camera circuitry. Accordingly, in view of the drawbacks of the prior art, it is an object of the present invention to provide video surveillance of a large area with minimal cost and chance of failure.

It is a further object of the present invention to enable a security camera to monitor discrete optical images from two directions simultaneously, thus eliminating the need for mechanical devices which scan areas of a geometrical size too large or of too complex a structure for one security camera to capture. It is a further object of the present invention to provide an attachment for a standard commercially available security camera to generate discrete images of different areas for simultaneous display on a standard commercially available monitor without additional electronic modifications thereto. It is a further object of the present invention to enable a security camera to correct the transmitted images detected by the security camera after said images have been altered in vertical perspective as a result of the physical placement of the camera to capture the scene below.

It is a further object of the present invention to provide security cameras with a set of wide angle auxiliary lenses one on either side of the security camera housing with means for adjusting the geometrical positioning of each lens in such a manner that each lens will replace a portion of the field of view which, by virtue of the lens splitting characteristics of the invention, has been reduced to one half its normal size.

It is a further object of the present invention to provide straight ahead viewing of a secured area while offering an additional choice of right hand or left hand viewing simultaneously.

It is In object of the present invention to provide a black bar generator in order to furnish a video blanking signal to cover the blurred line sometimes formed by the mirror edges of the dual image video surveillance system such that the left image and the right image are clearly separated by a sharply defined black bar and focusing by the surveillance system is not inhibited.

It is a further object of the present invention to provide a black bar generator which can be used with a CCD type video camera without modifications thereto.

It is a further object of the present invention to provide a black bar generator which can be implemented without modifications to the existing monitor. SUMMARY OF THE INVENTION In accordance with these and other objects, the present invention is an apparatus for providing a pair of discrete images to a fixed security camera. The apparatus has a housing, a platform slidably engaged within the housing, a camera assembly mounted on the platform, and an angled mirror assembly comprising a pair of mirrors and a means for adjusting the angles of the mirrors thereby changing their angular position with respect to their alignment with the area being surveyed. The angles of the mirrors can be adjusted independently of each other. In addition, on'e mirror or both mirrors can be removed for partial or full straight ahead viewing, and a wide angle lens and lens adapter assembly is secured to the platform in place of the removed mirror. The hinged platform section that supports the mirror assembly is hinged, thereby allowing the assembly to be tipped toward the camera lens, thus compensating for the angle of the camera with respect to the objects being viewed that are aligned below the camera. The housing has a pair of windows through which a pair of wide angle lenses situated on opposite sides thereof will be able to captu e the broadest possible field of view.

The mirror assembly has a left mirror and a right mirror joined at an edge therebetween and adjustably disposed at an angle between approximately 60° and 120°, preferably 90°, to each other. The mirrors are mounted on the angled mirror assembly such that images transmitted through each of the auxiliary lenses are reflected by the mirrors towards the camera, and the mirrors are bevelled at the joining edge such that the image generated from the area within and between the respective surfaces thereof is minimal. As a result, a left image incident upon the left mirror is reflected thereby towards the camera, and a right image incident upon the right mirror is reflected thereby towards the camera, and the resultant image captured by said camera is composed of a split image of the left image and the right image.

The camera assembly mounted on the platform comprises a camera mounting platform, a camera and a lens. The camera mounting platform comprises a bearing surface through which the lens protrudes thus aligning the camera exactly at the center of the leading edge of the mirrors at the point where the mirrors are joined. Also provided herein is a black bar generator circuit for providing a composite video signal comprised of a vertical black bar superimposed over an input video signal from a CCD type television camera. The black bar generator is used to block out an unwanted portion of the composite television signal, prohibiting the signal from appearing on the screen. As such, the blurred line which may appear at the intersection of the discrete left and right images due to the imperfect joint formed by the bevelled mirror edges is blanked, thus eliminating any deleterious effects which may result from the capture of said blurred line. This blanking is accomplished in the circuit between the CCD camera and the monitor, thus eliminating the' need for more complex television monitoring systems. The width of the bar is adjustable and the location of the bar is free for placement by the operator. The operator needs only to adjust the bar to an area to be blocked out leaving the unblocked portion to be viewed on the screen.

There is disclosed herein a stand alone circuit that when added to the output of a CCD camera will cause a vertical black line to appear on the video monitor connected to the camera. Adjustable in location (with reference to the surface area of the screen) and width of line, the user is free to select and identify a specific area of the screen for complete definition. The black bar generator circuit comprises means for generating a sync pulse synchronous with the input video signal, means for generating a black bar timing pulse synchronous with said sync pulse, means for clamping the input video signal with said black bar timing pulse to provide the composite video signal, and means for isolating the input video signal from said clamping means. The black bar timing pulse generation means can comprise means for delaying said black bar timing pulse from said sync pulse, means for adjusting said delay, and means for adjusting the pulse width of said black bar timing pulse.

BRIEF DESCRIPTION OF THE DRAWING FIGURE 1 is a block diagram of a television security system employing the image splitter and black bar generator of the preferred embodiment of the present invention;

FIGURE 2 is a perspective view of the image splitter assembly of Figure 1;

FIGURE 3 is a perspective view of the camera mounting platform;

FIGURE ^■*"4(a) is a top plan view of the image splitter assembly of Figure 1; FIGURE 4(b) is a side view of the image splitter assembly of Figure 1;

FIGURE 4(c) is a perspective view of the image splitter assembly of Figure 1 with the right mirror removed and a right straight ahead viewing lens adapter inserted in its place for straight ahead viewing thereby;

FIGURE 4(d) is a perspective view of the right straight ahead viewing lens adapter employed in Figure 4(c);

FIGURE 4(e) is a perspective view of the left straight ahead viewing lens adapter; FIGURE 5 is an additional top plan view of the image splitter assembly of Figure 1;

FIGURE 6(a) is a side view of the image splitter assembly of Figure 1 which depicts camera mounted in standard mode;

FIGURE 6(b) is a side view of the image splitter assembly of Figure 1 which depicts the repositioning of the camera;

FIGURE 6(c) is a side view of the image splitter assembly of Figure 1 which depicts the angular correction of the mirror block assembly;

FIGURE 7 is an illustration of the auxiliary lens of the image splitter assembly of Figure 1;

FIGURE 8 is a side plan view of the auxiliary lens mounting block of the image splitter assembly of Figure 1;

FIGURE 9 shows the image splitter assembly of Figure 1 capturing a first image in straight ahead viewing mode and a second image in right side viewing mode;

FIGURE 10 shows the image splitter assembly of

Figure 1 capturing a first image in left side viewing mode with an auxiliary lens in place and a second image in right side viewing mode without an auxiliary lens in place;

FIGURE 11 is a block diagram of the black bar generator of Figure 1;

FIGURE 12a is a detailed schematic of the black bar generator of Figure 11; FIGURE 12b is a detailed schematic of the black bar generator of Figure 11.

FIGURE 13 is a partially exploded perspective view of the image splitter of the present invention;

FIGURE 14 is a top plan view of the assembled platform of the image splitter of Figure 13; FIGURE 15 is a side view of the image splitter of Figure 13;

FIGURE 16 is a top plan view of the housing of the image splitter of Figure 13; FIGURE 17 is a side view of the housing of the image splitter of Figure 13;

FIGURE 18 is a pictorial of the image capture of the image splitter of Figure 13;

FIGURE 19 shows the image captured by the image splitter of Figure 13, as seen on a television monitor connected thereto;

FIGURE 20 is a perspective view of the camera mounting assembly of the image splitter of Figure 13;

FIGURE 21 shows the bevels of the front edges of the mirror pair of the image splitter of Figure 13;

FIGURE 22 shows the means of assembling the platform and the camera mounting block of the image splitter of Figure 13; and

FIGURE 23 is a front view showing the platform and housing of the image splitter of Figure 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The block diagram of Figure 1 depicts a television security system 100 comprising an image splitter assembly 101, a black bar generator circuit 102, a black bar generator power supply 103, a conventional monitor 104 and a conventional videocassette recorder

(VCR) 105. As shown, the black bar generator 102 is connected in series between the output of the image splitter assembly 101 and the input of the monitor 104.

Referring to Figures 2, 3, 4 and 5, the image splitter assembly 101 comprises a housing 2, a platform

3, an angled mirror assembly 22 mounted on section 3A of the platform 3, and a camera mounting assembly 13 mounted on the platform 3 by first threaded bolt 18. The camera mounting assembly 13 comprises a CCD television camera 4, a lens 5, a face plate 15 and a supporting plate 12. Camera 4 rests on a mounting board 14 and. is held in place by a second threaded bolt 34. Camera mounting assembly 13 is slidably mounted to platform 3 by the first threaded bolt 18, which protrudes through platform 3 and is threadedly connected to supporting plate 12.

A hole 20 is cut out of face plate 15 giving a bearing surface to lens 5. Aligning lens 5 and inserting it through hole 20 positions the primary lens directly in front of corner 30 of mirror pdir 6. In the preferred embodiment, a BURLE TC652EA CCD type security camera 4 and six millimeter lens 5 are used, although the image splitter assembly 101 can be designed to accommodate a broad range of security cameras and lenses within the spirit and scope of the invention.

The angled mirror assembly 22 is shown mounted on section 3A of platform 3. Platform 3 is connected to section 3A by hinge 38. Mirror pair 6 of the mirror assembly 22 is mounted to section 3A and faces camera 4. Section 3A is free to move swingingly about the hinge 38 in an arc upwardly^ and back toward the camera lens 5; the leading edge travels toward the lens 5 in an arc or semi- circle. The hinge 38 is of the living hinge or other conventional type suitable and/or common to the materials and design characteristics usually associated with production of plastic assemblies such as the preferred embodiment. Further illustrated is mirror pair 6 as having a left mirror 24 for left viewing and a right mirror 23 for right viewing and are fastened to the vertical angular support members 8. The leading edges of the vertical angular support members 8 and the leading edge of the left mirror 24 and the right mirror 23 are bevelled to form a near perfect abutment, thus allowing mirror pair 6 to reflect the image from left mirror 24 and the image from the right mirror 23 to the camera 4.

By bevelling and joining tightly the front edges of the left mirror 24 and the right mirror 23 of the mirror pair 6 to the desired angle, the distinct image generated by the corner 30 will be kept at a minimum width. This will allow the camera 4 to capture and focus on only the left image generated by left mirror 24 and the right image generated by right mirror 23, and not be affected by any image generated by the corner 30. Thus, the effect of the corner 30 on the focus function of camera 4 will be minimized, which maximizes the focusing features of the lens 5 of camera 4.

Further to the description offered herein the preferred function of the mirror pair 6 positioning body is illustrated in Figure 6. As can be seen from Figures 1 and 2, the juxtaposition of the camera 4 and the mirror assembly 22 enables an image captured by the left mirror 24 and an image captured by the right mirror 23 to be reflected simultaneously to the camera 4 as a split screen image. The platform 3 along with its containments is mounted inside housing 2, which provides a window pair 16 so as to allow" for a window on the left and a window on the right that are aligned with a pair of auxiliary lens 40. The auxiliary lens pair 40 are of the wide angle type in order to capture a larger field of view, and are brought into focus with the lens 5 so that the image viewed therein will be transmitted to camera 4; as reflected by mirrors 23 and 24 respectively. Figure 10 illustrates the advantage of using the wide angle auxiliary lens 40. In figure 10, an auxiliary lens 40 is used with the left mirror 24 but not with the right mirror 23. As can be seen, the field of view reflected by the left mirror 24 is considerably greater than that reflected by the right mirror 23. The corner 30 formed at the abutment of the left mirror 24 and the right mirror 23 is at an angle a which is between approximately 60 degrees and 120 degrees, preferably 90 degrees. The mirror pair 6 is attached to a pair of angular support members 8. The angular support members 8 are joined by a spring 27 and connecting bar 32 combination as shown in Figure 5.

In the preferred embodiment, angled mirror assembly 22 is removable from section 3A allowing for a straight ahead viewing mode. To implement straight ahead viewing, front cover 39, shown in Figure 2(a), is removed, thereby exposing front window 17. Angular support members 8 may be removed as a pair or singularly thus allowing for a choice between viewing left and straight ahead, viewing right and straight ahead, completely straight ahead, or the previously described left and right viewing. As an example. Figure 9 shows the left mirror 24 removed so that the camera 4 captures an image composed of a straight ahead view on the left side and a right angled view on the right side. Moreover, the angular position of each mirror may be changed independently of the other, as is described below.

Figures 4 and 5 illustrate details of the mirror block assembly 22 wherein a pair of platforms 28 are centered at their joined leading edge 29, and positioned by shaped pivot block 35, connecting bar 32 and first screw pair 25a. First screw pair 25a pass through a radially shaped groove 33 and are threadedly connected to connecting bar 32. Platform pair 28 are thus held together by spring 27. Spring 27 is anchored in place by second screw pair 26. A positive torque delivering force is transferred against platform cam lobes 28a and 28b as torque is applied to mirror positioning knobs 31, which are shown in Figure 1. As mirror positioning knobs 31 are rotated, torque is transferred to rotary cam pair 25. As rotary cam pair 25 rotates, torque is transferred to cam lobes 28a and 28b. Spring 27 forces cam lobes 28a and 28b against cam pair 25 for positive alignment. Figures 7 and 8 illustrate the auxiliary lens assembly 48. Lens frame support 41 holds wide angle lens 40 in place and provides a slidably adjustable member for alignment of lens 40 with window 16 and mirror pair 6. Groove 43 is held into position by lock screw 42. Lens pair 40 are of the negative meniscus type; in the preferred embodiment are approximately 52 mm in diameter with an edge thickness of approximately 7 to 8 mm having an optical power of 4 diopters. Support platform 47 is free to move adjustably inward or outward in relation to the camera 4; whichever is required for best focus by virtue of mounting screws (not illustrated for clarity) which anchor the entire assembly from grooved positions on the bottom side of platform 3. Stanchion 44 is held in place on platform 47 by a pair of hold down screws 46. Lock screw 42 is threaded to hold frame 41 in place and anchor at hole pair 45.

When partial straight ahead viewing is desired, the appropriate mirror 23 (right) or 24 (left) is removed and a straight ahead viewing lens adapter 49 (right) or 36 (left) is used in its place. Figure 4(c) illustrates an embodiment wherein the left mirror 24 has been removed and the left straight ahead viewing lens adapter 36 and left straight ahead viewing lens 37 have been inserted in its place, whereby the resulting image captured by the camera 4 will be a composite of the side image captured by the right mirror 23 and the straight ahead image captured by the lens 37.

The left straight ahead viewing lens 37 and the right straight ahead viewing lens 50 are wide angle lenses and are the same in optical type and geometry as the auxiliary lenses 40 described above. Figure 4(d) illustrates the left straight ahead viewing adapter 36. As can be seen, the left straight ahead viewing lens 37 is aligned so as to be off center, so that when the adapter 36 is mounted to the stanchion 44, the lens 37 will be situated in the proximity of the center of the lens 5 of the camera 4. Similarly, in Figure 4(e), the right straight ahead viewing lens 50 is aligned so as to be off center, so that when the right straight ahead viewing adapter 49 is mounted to the stanchion 44, the lens will likewise be situated in the proximity of the center of the lens 5 of the camera 4.

The adapter 36 is fastened by a threaded bolt to stanchion 44, thereby providing a slidable base for positioning the lens 37 to center for focus alignment with the lens 5 of the camera 4.

Figure 6 illustrates the positioning of camera 4, mirror pair 6 and auxiliary lens assembly 48. In the practice of securing camera platform 3 and the containments thereon at an angle above the area being viewed, camera 4 may capture and project an image that because of the angle used to capture the scene below often distorts the posture of persons captured in the field of view. ϊn this event camera platform 3 may be repositioned away from mirror pair 6 allowing section 3A with mirror assembly 22 thereby attached to be raised at the forward end; thus section 3A is tipped upward, tipping mirror pair 6 toward the camera 4 on an angle with respect to the horizontal plane of camera 4. Thus repositioned, the image captured by auxiliary lens 40, reflected off mirror pair 6 and transmitted to the camera 4 will be corrected and brought into a more upright and easily viewed position.

Figure 6 illustrates how first threaded bolt 18 when loosened will allow camera mounting platform 13 to be slideably moved away from mirror pair 6 and corner 30. This will expand the space therebetween, allowing room for mirror pair 6 to be tipped towards lens 5. Figure 4 illustrates section 3A adjustment support block 10 with positioning screw 9. Adjustment support block 10 is rigidly fastened to platform 3, adjustment screw 9 is threadedly passed through adjustment support block 10. As adjustment screw 9 is tightened, the hinged section of section 3A tilts upward pivoting at hinge 38 causing mirror pair 6 to tilt toward lens 5. After being so positioned, auxiliary lens pair 40 must now be adjusted via set screws 42 to the desired position for focus alignment.

Practice has taught' that the degree of corrective angle made to the tilt of mirror assembly 6 will be approximately one half that of the installed angle of platform 3.

The corner 30 formed by the abutment of the leading edges of the mirror pair 6 provides a discrete image to the camera 4. Since this corner image is undesired, the bevel angles of the left mirror 24 and the right mirror 23 are such that the corner is minimized when the mirrors are furthest apart from each other, i.e. when a = 120°. As the mirrors are adjusted inwardly by the operation of'the positioning knobs 31, the cam pair 25 and the cam lobes 28a and 28b, a gap will result at the corner 30 due to the separation of the leading edges of the mirrors. It is therefore necessary to provide for the blanking of that video portion which transmits the discrete image generated by the corner 30.

This video blanking of the image generated by the corner 30 is provided by the black bar generator 102 of the present invention. The black bar generator 102 places a vertical black bar over the video signal (VIDEO IN) output by the camera 4. The location of the black bar on the monitor 104 and its width are independently adjustable. The black bar is used to visually separate the left and right halves of the image captured by the camera 4 by making a dividing object between the two sides. The black bar is generated by blanking the video, thus forcing the video luminance signal to video black levels at the appropriate time. Referring to the block diagram of Figure 11, the black bar generator 102 of the preferred embodiment comprises an isolation buffer 72, a sync generator 74, a black bar timing circuit 76, a video clamping circuit 78, and an output buffer 80. The sync generator 74 generates a digital sync pulse upon detection of a video signal at VIDEO IN. The digital sync pulse triggers the black bar timing circuit 76, which in turn generates a black bar pulse used to blank the video at the desired time. The delay of the black bar pulse is adjustable so that the resulting black bar can be located at the desired location on the monitor 104. The width of the black bar pulse is likewise adjustable so that the width of the black bar on the monitor 104 can controlled.

The VIDEO IN signal is coupled to the video clamping circuit 78 via the isolation buffer 72. The video clamping circuit 78 clamps the VIDEO IN to ground potential for the duration of the black bar pulse, as provided by the black bar timing circuit 76, and outputs the resulting COMPOSITE VIDEO signal. COMPOSITE VIDEO is then input to the output buffer 80, which provides the VIDEO OUT signal directly to the monitor 104.

The black bar generator 102 of the preferred embodiment will now be described in further detail with reference to Figure 12a. VIDEO IN is an RS-170 compatible video signal and is injected into a BNC connector Jl. Ul, which in the preferred embodiment is a LM1881 integrated circuit, receives VIDEO IN and outputs a composite sync at logic levels.

The composite sync signal triggers U2B, which a one-shot monostable multivibrator. This one-shot generates the delay from the leading edge of the horizontal sync signal to the location of the beginning of the black bar. This delay determines the left to right location of the vertical black bar. The position of the bar is adjusted by changing the one-shot firing time which is controlled by variable resistor VRl. Upon completion of the one-shot period, U2B's Q output pin drops to 0 volts which triggers U2A, the other half of the dual monostable multivibrator circuit. U2A outputs a pulse that clamps the video to ground which produces the black bar on the output video. The width of the bar is controlled by U2A and is adjustable by the variable resistor VR2.

VIDEO IN is processed by a buffer amplifier comprised of Ql and Q2. The two transistors form a darlington amplifier connected in an emitter follower configuration. This buffer amplifier isolates VIDEO IN from the video clamping circuit 78 that follows the buffer amplifier. Ul generates a signal that occurs during the color burst period of the video. This pulse turns on Q5 which pulls the video at its collector to ground potential during the color burst. This clamping action sets the video black level to 0 volts at the base o Q3. Q3 and^1' Q4 form another darlington amplifier configured as an emitter follower. The only difference between this amplifier and the Ql - Q2 amplifier is the use of a NPN and PNP transistor pair for Q3 and Q4, respectively. The signal at Q3's emitter is shifted by approximately .7 volts lower than its base.

The signal at Q4's emitter is shifted by a similar voltage higher than its base. This causes a net voltage shift of 0 volts. So, the signal at the base of Q3 is the same as the output of the amplifier at the emitter of Q4.

Since the black level of the video at the emitter of Q4 is near 0 volts, the video is forced to black by clamping the video to ground at the time of the desired black bar. The black bar timing pulse that is generated by the output of U2A turns on Q7, the clamping transistor.

The video then is input into U3 of the output buffer 20. U3 is a video buffer amplifier configured to drive a 75 ohm load. The output level is adjusted to 1 volt peak to peak by variable resistor VR3.

Referring to Figure 12b, components BR1, U4, U5 and associated capacitors make up a full wave bridge rectifier, a +5 volt regulator circuit, and a -5 volt regulator circuit used to power the other circuits.

Referring generally to Figures 13, 14 and 15, the image splitter 1 comprises a housing 2, a platform 3, and an angled mirror assembly 22 and a camera mounting block 13 mounted on the platform 3. The camera mounting block 13 comprises a television camera 4 and a lens 5. In the preferred embodiment, a CHINON CX-500 CCD type security camera and lens are used, although the image splitter 1 can be designed to accommodate a broad range of security cameras and lenses within the spirit and scope of the invention.

The angled mirror assembly 22 is mounted on a front end of the'platform 3 such that a mirror pair 6 of the mirror assembly 22 faces the camera 4. As can be seen from Figure 17, the juxtaposition of the camera 4 and the mirror assembly 22 enables a left image 26 and a right image 27 to be captured simultaneously by the camera 4 as a split screen image, which is shown in Figure 18. The platform 3 is mounted in the housing 2, which provides a window pair 16 so as to allow the left image 26 and the right image 27 to be viewed by the camera 4 via the angled mirror assembly 22.

The pair of shaped metallic mirrors 6 comprises a left mirror 23 and a right mirror 24 which are mounted on the mirror assembly 22. The left mirror 23 and the right mirror 24 are bevelled at their front edges 28 and 29, respectively, as shown in Figure 20, in order to form a corner 30 at an angle between approximately 60° and 120°, preferably 90°, to each other. The mirror pair 6 is attached to a pair of mirror mounting leading edge walls 8, which in turn are held in place by a pair of triangular block assemblies 9. The triangular block assemblies 9 are each joined to opposite sides of a hinge 12. The sleeve of the hinge 12 is inserted over a pin 7, the position of which can be selected by insertion into any of a plurality of holes 18 in the platform 3. Thus, the pin 7 provides location and support for the hinge 12 such that the mirror pair 6 will deliver the left image 26 and the right image 27 to the camera 4.

By bevelling and joining tightly the front edges of the left mirror 23 and the right mirror 24 of the mirror pair 6 to the appropriate angle, as shown in detail in Figure 20, corner 30 will be formed. This will allow the camera 4 to capture and focus on only the left image 26 and the right image 27 as shown in Figure 7 and will not be affected by an image of the corner 30 of the mirror pair 6. This functions to maximize the focusing features of the camera 4.

The cartiera 4 is mounted to the platform 3 in the following manner. Figures 15 and 20 depict a camera mounting block 13, which is comprised of a flat bottom portion 31 of generally rectangular shape for supporting the camera 4, and a flat front face 32 joined to the bottom portion 31 at a 90° angle. The front face 32 comprises a mounting hole 20, through which a threaded collar 21 is held in place by three tabs 14. The collar 21 comprises two sets of threads; an external set 33 matched to a standard C-mount in size, shape and dimension; and an internal set 34 matched to a lens 5 to be used in the particular installation. The collar 21 is threaded onto the C-mount lens cavity of the camera 4 and is then inserted into the mounting hole 20. The tabs 14 are then installed with associated hold down screws 15 so as to firmly hold the collar 21 within the mounting hole 20. The lens 5 is then threaded onto the opposite side of the collar 21. In this fashion, the camera 4 and lens 5 are securely fastened to the mounting block 13.

The dimensions utilized in the preferred embodiment for the above described manner of mounting the camera 4 are as follows. The front face 32 is approximately 2.16 inches in height, 2.24 inches in width and .375 inches thick. The inside diameter of the collar 21 is approximately 1.477 inches, and the outside diameter is approximately 1.737^' inches. By securing the camera 4 and the lens 5 to the' mounting block 13 in the above described manner, convenient interchangeability of lenses and cameras is obtained.

The platform 3 comprises a groove 11 positioned as shown in Figure 10. The mounting block 13 is secured to the platform 3 with hold down screws inserted from the underside of the platform 3, through the groove 11, and into threaded holes 19 on the underside of the bottom portion 31. The use of the groove 11 allows the mounting block 13, and therefore the camera 4, to be aligned slidably along the platform 3 as desired. While this manner of mounting the camera 4 is implemented in the preferred embodiment, it is understood that any means known in the art for attaching the camera 4 to the platform 3 or the housing 2 can be used.

Referring to Figures 13, 16, 17, and 23, the assembled platform 3 can then be inserted into the housing 2 as follows. The housing 2 is generally rectangular in shape and comprises a window pair 16 located at the front portion thereof. The assembled platform 3 is slidably mounted inside the housing 2 by means of tracks 35 and 36 thereon, which engage flanged edges 37 and 38 of the platform 3, respectively. The platform 3 is then secured to the housing 2 by means by conventional hold down screws. Once secured, the left image 26 and the right image 27 are transmitted through the window pair 16 and reflected by the mirror pair 6 to the lens 5 and the camera 4. In the preferred embodiment, the length of the housing 2 is approximately 8.625 inches long, the outside width is approximately 5 inches, and the depth at the open end is approximately 2.75 inches. The platform 3 is approximately 3 inches wide and 7.625 inches long. The invention disclosed herein is not limited to the generation of a single bar. Those schooled in such art will readily understand that plurality of bars could be generated through simple additions to the basic circuitry. Further, although preferred embodiments of the invention have been described in the foregoing detailed description and illustrated in the accompanying drawings, it will be understood that the invention is not limited to the embodiments disclosed, but is capable of numerous rearrangements, modifications and substitutions of parts and elements without departing from the spirit of the invention. Accordingly, the present invention is intended to encompass such rearrangements, modifications and substitutions of parts and elements as fall within the spirit and scope of the appended claims.

Claims

CLAIMS:

1. An image splitting optical system comprising:

(a) a platform;

(b) optical means fixedly secured to said platform and disposed thereon to provide simultaneously to a camera a pair of images, said optical means comprising a pair of mirrors joined at an edge and disposed at a predetermined angle between approximately 60° and 120° to each other, said mirrors mounted on said platform such that a pair of images are reflected by said mirrors towards said camera; and

(c) means for securing a camera to said platform.

2. The image splitting optical system of Claim 1 further comprising a housing for enclosing said platform, said housing comprising a pair of windows disposed to enable transmission of images therethrough.

3. The image splitting optical system of Claim 2 wherein said mirrors are bevelled at said joining edge such that no image is generated from the area within and between the respective surfaces thereof.

4. The image splitting optical system of Claim 3 further comprising a camera and a lens attached to said means for securing a camera.

5. An apparatus for providing a pair of images to a fixed security camera, said apparatus comprising:

(a) a housing comprising a pair of windows situated on opposite sides thereof; (b) a platform slidably engaged within said housing;

(c) a camera assembly comprising a camera mounting block, a camera and a lens mounted to said camera mounting block, wherein said camera assembly is slidably mounted along a groove of said platform; and (d) an angled mirror assembly comprising a pair of mirrors comprising a left mirror and a right mirror joined at an edge therebetween and disposed at approximately 90° to each other, said mirrors mounted on said angled mirror assembly such that images transmitted through each of said windows of said housing are reflected by said mirrors towards said camera, said mirrors bevelled at a joining edge such that no image is generated from the area within and between the respective surfaces thereof; whereby a left image incident upon the left mirror is reflected thereby at approximately a 90° angle towards said camera, and a right image incident upon the right mirror is reflected thereby at approximately a 90° angle towards said camera, and the resultant image captured by said camera is composed of a split image of the left image and the right image.

6. The image splitting optical system of Claim 1 further comprising means for adjusting said predetermined angle between said mirrors.

7. The image splitting optical system of Claim 6 in which said mirror angle adjustment means comprises: ^v a) a pair of mirror mounting platforms upon which each mirror is fixedly mounted, each of said mirror mounting platforms comprising cam lobes; b) a spring member fixed at each end thereof to each of said mounting platforms so as to urge said platforms toward each other; c) a pair of cams, each of said cams disposed in intimate relation to each of said mounting platform cam lobes; d) a pair of adjustment knobs, each of said adjustment knobs eccentrically connected to each of said cams such that torque applied to each of said adjustment knobs is transferred via its eccentrically connected cam its associated cam lobe, thus urging the associated mounting platform away from the opposite platform or allowing said spring to draw the associated mounting platform towards the opposite platform, as desired; and e) means for securing each of said mounting platforms in fixed relation to each other after a desired adjustment has been made.

8. The image splitting optical system of Claim 1 in which said platform comprises a hinged section upon which said optical means is fixedly mounted, said hinged section capable of swinging in an upwards arc, and means for adjusting the angle o'f said hinged section.

9. The image splitting optical system of Claim 8 further comprising a pair of auxiliary lenses, each of said auxiliary lenses being adjustedly mounted on said platform and between each of said mirrors and each desired image to be captured thereby, such that said auxiliary lenses compensate for any distortion in said captured images.

10. The image splitting optical system of

Claim 9 in which said auxiliary lenses are of the wide angle type.

11. A¹" black bar generator circuit for providing a composite video signal comprised of a vertical black bar superimposed over a video signal input from a charge coupled device type television camera, said circuit comprising: a) means for generating a sync pulse synchronous with the input video signal; b) means for generating a black bar timing pulse synchronous with said sync pulse; c) means for clamping the input video signal with said black bar timing pulse to provide the composite video signal; and d) means for isolating the input video signal from said clamping means.

12. The circuit of Claim 11 wherein said black bar timing pulse generation means comprises means for delaying said black bar timing pulse from said sync pulse, means for adjusting said delay, and means for adjusting the pulse width of said black bar timing pulse.

13. The circuit of Claim 12 further comprising output buffer means coupled to said video clamping means.

14. A television security system comprising a charge coupled device type camera which provides a video signal comprising a pair of images from two different locations, a video monitor, and means coupled between said camera and said monitor to generate a vertical black bar superimposed on the video signal output from said camera.

15. The system of Claim 14 wherein said black bar generation means comprises means for situating said black bar at a desired located on the monitor and means for adjusting the width of said black bar.

16. A black bar generator circuit for providing a video signal comprised of a vertical black bar superimposed over a video signal input from a charge coupled device type television camera to a video monitor, said circuit comprising: a) means to provide a digital sync pulse synchronous with said input video signal; b) a first monostable multivibrator triggered by said sync pulse, the output of said first monostable multivibrator comprising a pulse with a leading edge and a trailing edge, the pulse width of said first monostable multivibrator being adjustable; c) a second monostable multivibrator triggered by the trailing edge of the pulse output by said first monostable multivibrator, the pulse width of said second monostable multivibrator being adjustable; d) a buffer amplifier comprising a pair darlington amplifiers connected in an emitter-follower configuration coupled to said input video signal to isolate said signal from the camera and to provide a buffered video signal; e) video clamping means comprising a transistor comprising a base and collector, the base being coupled to the pulse generated by said second monostable multivibrator and the collector being coupled to the buffered video signal, the collector output of which thus comprises a composite video signal; and f) output buffer means to drive said composite video signal to the monitor; whereby said pulse generated by said second monostable multivibrator turns on said video clamping transistor and clamps said buffered video signal to ■ ground potential during the duration of said pulse such that the composite video signal is driven to ground for a preselected time after the beginning of said video input signal and for a preselected duration, whereby a vertical black bar is generated over a preselected portion of the video signal provided to the monitor.

17. An image splitting optical system comprising:

(a) ^l'a platform;

(b) means for mounting a camera on said platform;

(c) optical means fixedly secured to said platform and disposed thereon to provide simultaneously to said camera mounting means a pair of images, said optical means comprising a pair of mirrors joined at an edge and disposed at a predetermined angle between approximately 60° and 120° to each other, said mirrors mounted on said platform such that a pair of images are reflected by said mirrors towards said camera mounting means; and (d) a black bar generating circuit means, coupled to said camera mounting means, for providing a composite video signal comprised of a vertical black bar superimposed over a video signal output from a camera, said circuit comprising:

(i) means for generating a sync pulse synchronous with the video signal;

(ii) means for generating a black bar timing pulse synchronous with said sync pulse;

(iii) means for clamping the input video signal with said black bar timing pulse to provide the composite video signal; and

(iv) means for isolating the input video signal from said clamping means'.

18. The image splitting optical system of Claim 17 further comprising a camera mounted on said camera mounting means and coupled to said black bar generating circuit means.

19. The image splitting optical system of Claim 1 in which at least one of said mirrors is removed from said platform and replaced by a wide angle lens to provide for partial straight ahead viewing.