A CAMERA AND ACCESSORY

Abstract: In order to provide a hand-held camera of the camcorder type with a three-dimensional binaural sound recording facility, ear structures (10) containing microphones are mounted on opposite sides of the camera body (8), which functions in use as a dummy head. The camera may also include binaural signal processing circuits for processing the signal from the microphones prior to recording in a tape recording mechanism integral with the camera. The invention also takes the form of a camera accessory comprising a pair of ears on a cowl or frame structure.

Description: A CAMERA AND ACCESSORY This invention relates to a camera and an accessory for a camera. The invention relates particularly, through not exclusively, to hand-held moving picture or video cameras. Moving picture cameras which can record a contemporaneous soundtrack, such as for example hand-held video camcorders, are now very popular amateur purchases in developed countries. Professional versions are also available, and are used for example by journalists in television news reportage. One video recording camera of this type, disclosed in JP 03-94599, has two closely spaced microphones whose opening angle can be varied in response to the distance from camera to subject to record sound information from the area of the subject for subsequent playback together with the recorded visual information. This prior art arrangement does not, however, preserve the three-dimensional binaural positioning cues which would be apparent to a person standing at the position of the camera - for example associated with sound sources directly above or behind the head. It is a known recording studio technique to record a sound-field having these three-dimensional aural positioning cues by using an artificial head with microphones in the ears, and performing on the microphone signals binaural signal processing involving cross-talk cancellation. The present invention is based on the recognition that it is possible to incorporate into a camera, for example a hand-held video camera or camcorder, which has dimensions.which resemble in acoustic terms that of a human head, and which may be used in a wide variety of environments, both indoors and out-of-doors, a binaural signal processing arrangement, which previously has been used only in carefully controlled studio conditions. According to a first aspect of the invention there is provided a camera comprising a camera body , left and right microphones mounted on opposite sides of the camera body whereby the body forms an acoustic baffle therebetween resembling in use the acoustic properties of a human head, the microphones providing left and right channel binaural signals representative of sound received by respective microphones, and signal processing means for receiving and processing such signals. This arrangement in accordance with the invention can enable simultaneous recording of visual information and three dimensional sound-field information without a mismatch between the visual and aural positional cues, since the camera and microphones function as a dummy head sufficient to produce binaural signals containing such three dimensional sound field information. It is well known, see for example Manikin Measurements Conference Zurich/Washington - March/April 1976 - Anthropometric Manikin For Acoustic Research - M.D. Burkhard & R.M. Sachs, Chapter 2 p.4, Table 1, that the average human head is 15.1 cm in width. Although a typical width figure for a hand-held video camera may be smaller, about 9 cm, nevertheless in use the body provides sufficient bulk to provide binaural sound signals in the microphones. Further, in use, an operator will have one or more hands gripping the camera body, which will increase the effective width of the camera to that of a human head As preferred the left and right microphones are mounted in human earlike protrusions, in ducts which extend from the exterior of the protrusions inwards toward the camera body, in order more accurately to create the sound fields which exist in a human ear. By "earlike protrusions" is meant protrusions which simulate to a significant extent at least some of the acoustic characteristics of human ears, and which include internal ducts extending from the exterior of the channels to an internal position for receiving microphones. Although the protrusions may be a substantial replica of human ears, they may as preferred be adapted or "scream-lined" to take account of the operating environments in which the camera may be used, and may include covers for protecting the protrusions from accidental knocks. Preferably, the protrusions are removably attachable to the camera body. This provides the ability to replace the ear like protrusions if they become chipped or otherwise damaged. The protrusions may have covers of for example foam rubber which are such as to prevent wind noise being detected in external environments but which are not such as to interfere with the sound field being recorded. The microphones may preferably be mounted in the earlike protrusions or in or to the camera body by means of resilient, for example foam rubber, inserts This has the advantage that noise from the camera mechanisms is not transferred via the microphone mountings to the channel signals. The signal processing means normally includes tape recording means, which is present in all video cameras of the "camcorder" type. Alternatively there may be recording means of a digital type. The signal processing means may include binaural processing means, in particular cross-talk cancellation means, and filtering means for avoiding the known "twice- through- the-ears" effect. Alternatively, particularly for professional purposes, the binaural processing may be carried out at a later date on the recorded signals in a studio, for example. The camera, as stated above, will usually be of the hand-held video or camcorder type. However the invention may be applied to fixedly mounted cameras, for example on a tripod, or in an intruder security installation. The camera may alternatively be a still camera, as long as the width dimension is of the order of that of a human head. As preferred, a further microphone or pair of microphones is provided for providing a localised sound pick-up region in addition to the binaural microphones. The signals from said further microphone or pair of microphones is not subject to binaural signal processing. Such an arrangement is described and claimed in our pending International Application WO 94/22278 (our Ref. PQ 12529). In a modification of the invention, the left and right microphones are mounted on a frame structure into which a camera is removably secured, for example by means of a snap fitting. The frame may also include a handle for gripping the assembly. Alternatively, the left and right microphones may be mounted in a cowl or cover structure which wholly or at least partially envelops the camera. Such cowl or cover serves as a protective structure for the camera, and may be of a resilient material so that the resilience of the material holds the cowl on the camera body. The controls of the camera may then be operated by inserting a hand under the cowl. In a second aspect, the invention provides an accessory for a handheld camera , comprising a frame structure or cowl structure for receiving a camera body, releasable securing means for securing the camera body to the structure, the structure including left and right microphones for providing left and right channel signals representative of sound received by respective microphones positioned such that when the structure is secured to the camera body, the ears are disposed on opposite sides of the camera body,;, and including signal processing means for processing the channel signals. In one embodiment, where the structure is a cowl , it may be formed as an approximately human-head shaped housing having a cavity for a camera, the housing being either at least partly transparent or having an opening for viewing a subject therethrough and having an opening for manipulating the camera therethrough, made for example from weatherproof and/or wateφroof material. The cover advantageously comprises resilient material, which provides an element of shock-protection for the camera in use. Brief Description of the Drawings Embodiments of the invention will now be described, by way of example only, with reference to the accompanying diagrammatic drawings in which:- Figure 1 is a schematic perspective view of a first embodiment of the invention comprising a video camera with integral audio tape recording mechanism; Figure 2 is a side view of a second embodiment of the invention comprising a cowl structure enclosing a video camera; Figures 3a, 3b and 3c are sectional front elevation, end elevation, and plan views of a first form of human ear like protrusion structure for mounting to the cowl structure of Figure 2; Figures 4a, 4b, 4c are respectively sectional front, top end, and plan views of a second form of ear like protrusion for mounting in the structure of Figure 2, with Figure 4d being a rear perspective view of a modification; Figures 5a, 5b and 5c are respectively front elevation, end elevation and plan views of a frame structure for receiving and releasably securing a hand held video camera of the type shown in Figure 1 Figure 6 is a block diagram of a binaural signal processing arrangement for receiving the channel signals from the ear structures of Figures 3 or 4, and including a further central microphone with associated processing circuits; Figure 7 is a block diagram similar to that of Figure 6 but including a central microphone pair with associated processing circuits; and Figure 8 is a further embodiment of a cover structure for enclosing a hand held video camera together with a handle for holding the camera. Description of the Preferred Embodiments Referring now to Figure 1 there is shown a first embodiment of the invention comprising a video camera 2 having a lens 4 and a view finder 6. The camera body 8 has bulk which approximates in acoustic terms to that of a human head. The camera has a width indicated as w which is 9 cm .. The camera body has human ear like protrusion structures 10 as described below with reference to Figure 4. Alternatively, structures 10 may comprise simple left and right microphones held in respective mounting blocks. The camera includes an integral tape recording mechanism (not shown). Referring now to Figure 2 there is shown a second embodiment of the invention comprising a cowl structure 20 which encloses the major part of a camera body of the type shown in Figure 1 but has an open rear end 22 for permitting insertion of the camera body 8 into the cowl. The cowl has a front lens opening 24 and a rear view finder opening 26 for permitting operation of the camera. The cowl structure 20 is of a foam plastic material which has a certain amount of resilience to permit the camera body 22 to be inserted therein and to retain the camera as a reasonably close fiL The resilient material the cowl itself therefore serves as a releasable securing means for the camera. The cowl has recesses 28 on opposite sides for receiving the ear like protrusions shown in Figure 3 or 4. The cowl structure is sufficiently flexible that an operator may insert his hand in open end 22 for peration of camera controls. Although as shown in Figure 2, the cover structure is secured to the camera body by its own resilience, a separate securing means may be provided, for example a belt. The belt may be made of webbing which can be tightened in place around the camera. . Referring now to Figure 3, this shows a human ear-like protrusion structure comprising a rectangular planar mounting block 30 having centrally positioned therein a microphone 32 of the omnidirectional electret type held within a resilient foam rubber structure 34 which acts as an acoustic baffle for sounds generated internally v-zithin a camera. Extending outwardly from mounting block 30 is a human ear shaped structure comprising a fossa 35, a lower lobe 36, a central concha area 37, and a central duct 38 which extends to the microphone from the concha region 37. The mounting block 30 is adapted to be mounted in the receiving apertures 28 of Figure 2. Referring now to Figure 4, there is shown a further form of human ear like protrusion structure for mounting in the cameras of Figures 1 or 2. The structure of Figure 4 has some similarities to that of Figure 3 and similar parts are denoted by the same reference numerals. The major differences are firstly that the rectangular mounting block 40 is of smaller dimensions than that of Figure 3 The ear like structures 46 extending from block 40 are modified essentially in that the structure of Figure 3 is cut down or stream lined so that the ears occupy the same cross sectional area as the mounting blocks 40. Thus the upper fossa, the lower ear lobe, and the rear part of the ear are cut away leaving just the central concha region 37. In addition, a plastic foam cover 48 is provided surrounding the ear structure 46 for protection of the ear structure but which is of such a material that it serves as a baffle for wind noise to prevent such noise reaching the microphone 32, but permits the external sound field surrounding the camera to penetrate to microphone 32. As shown in Figure 4d, block 40 has at top and bottom two slide rails 42 which enable the structures to be slide onto receiving ribs on the camera body, in the manner of a typical camera flash attachment structure. Two electrical contact studs 49 are provided for providing electrical connection to the microphone. As shown, a protective insert 47 is provided in the microphone aperture. In use of the cameras of Figures 1 or 2, with the ear like protrusions fitted, when a scene is being recorded by the camera, an integral tape recording mechanism (not shown) within the camera is actuated. The microphones in the ear like protrusions detects the sound field surrounding the camera, and by virtue of the camera representing in terms of sound diffraction, a human head, and the ear like protrusions resembling the sound filtering characteristics of a human ear lobe, the signals generated by the microphones include all the information necessary to reproduce a three dimensional version of the sound field surrounding the camera. Since an operator will be gripping the camera body with his hands, the effective physical width of the camera body is increased to approximate to that of a hman head. The signals may be recorded directly on to the tape recording mechanism, or alternatively, as described below, may be first processed through binaural signal processing circuits. Referring now to Figure 5, this shows a further embodiment of the invention comprising a frame structure 50 for receiving and releasably securing a camera body 8, indicated by dotted lines. The frame structure includes a handle portion 52 for an operator and a tray 53 having a base surface which as shown in Figure 5c has resilient mounting pads 55 -and a central aperture 56 for permitting a screw thread connection to the base of the camera. The side walls of the tray 53 are constituted by ear like protrusions 57 generally of the form shown in Figure 4, that is cut down versions of a human ear together with protective coverings. The ear like structures 57, as shown in Figure 5c have bevelled front and rear portions 59. The sides of the tray also include rails 60 for gripping the lower edges of camera body 8, as shown in Figure 5a. The camera body is releasably secured by means of a screw-threaded connection via aperture 56. The front of the tray includes a microphone pod 62 for receiving one or a pair of further microphones as will be described below with reference to Figure 6. A further pod 64 disposed at the rear of tray 53 carries switches, LEDs and jack sockets (not shown) for operation of the camera. The tray 53 also includes (not shown) batteries for power and binaural processing circuits as will now be described with reference to Figure 6. Referring now to Figure 6, which is a block diagram of a binaural processing circuit, the circuit is generally of the form described and claimed in our copending application WO 94/22278 (our Ref: PQ 12,529). The circuit includes a left ear microphone 70 and a right ear microphone 72 which are mounted on opposite sides of a camera body and a central microphone 74 which may for example be mounted in the front pod 62 of the frame structure shown in Figure 5. The left and right microphone 70, 72 are coupled through equalising circuits 76 for cancelling the known "twice-through-the-ears" effect created in dummy head recordings. A transaural crosstalk cancellation circuit 78 provides cancellation of the wellknown crosstalk effect which arises when binaural stereo sound signal are replayed through conventional stereo loudspeakers. The signal from the central microphone 74 is coupled through a time delay circuit 80 which has a value, for example 7 milliseconds, which is large enough to avoid correlation of the central microphone signal with those of the binaural signals from microphones 70, 72. An adjustable attenuation circuit 82 is provided under user control for the central microphone signal and additional circuits 84 are provided for adding the central microphone signal to the binaural signals. Thus a satisfactory balance between the frontal microphone and the left and right microphones can be achieved.This is useful for adding emphasis to frontal objects. The right and left channel outputs are coupled to a tape recording mechanism 86, which is disposed within the camera or frame structure, and which records the signals for subsequent reproduction. Referring now to Figure 7, this shows a modified version of the circuit of Figure 6 in which a central stereo pair of microphones 90, 92 are provided, which may for example be mounted on opposite sides of pod 62 of the frame structure of Figure 5. In Figure 7, similar parts to those of Figure 6 are denoted by the same reference numeral. Each microphone 90, 92 is connected through a respective time delay circuit 94 and attenuation circuit 96 to a respective summing circuit 84. Thus the signal for microphone 90 is added to the right channel output and the signal from the left microphone 92 is added to the left channel output. However, these microphones do not contribute to the binaural three dimensional sound effect; they are provided for enabling an enhanced reception of signals directly in front of the camera, i.e., the foreground region, whereas the microphones 70, 72 capture sounds from the total sound environment of the camera, both foreground and background regions. Referring now to Figure 8, this shows an integrated camcorder structure comprising a body assembly 100 with an upper part 102 . The top surface of the upper cover part 102 has a flip-up LCD display 106.. The rear of the top surface has a row of operating buttons 108 for controlling operation of the recorder and of the camera. On opposite sides of the camera body are disposed ear like protrusions 110, generally of the type indicated in Figure 4 with external foam rubber coverings. The ear structures 110 as shown are of an arcuate type with front radial walls 112 and a rear curved surface 114 tapering down to the rear edge 116. The front of the camera has an opening 120 for the camera lens 122, and an operating handle 124 for gripping the camera has a rocker-type operating switch 126 Although omnidirectional electret microphones are used in the examples above, other microphones such as, for example, surface-mounted Pressure Zone Microphones may be used as an alternative. This would be of use for example where ear-like protrusions are not used and the microphones are directly mounted to the camera or frame structure.

Claims: CLAIMS 1. A camera comprising a camera body , left and right microphones mounted on opposite sides of the camera body whereby the body forms an acoustic baffle therebetween resembling in use the acoustic properties of a human head, the microphones providing left and right channel binaural signals representative of sound received by respective microphones, and signal processing means for receiving and processing such signals. 2. A camera according to claim 1, including securing means for securing the camera body to the structure, the structure including said left and right microphones for providing left and right channel binaural signals. 3. A camera according to claim 2, including a frame structure having a tray means for receiving and releasably securing a lower surface of the camera body, and having upstanding at the sides of the tray means mounting the left and right microphones. 4. A camera according to claim 3, wherein the tray means houses signal processing means and/or one or more further microphones. 5. A camera according to claim 2, including a cowl structure for wholly or at least partially enveloping the camera body. 6. A camera according to claim 5, wherein the releasable securing means is constituted by the resilient material of the cowl structure forming a reasonably close fit around the camera body. 7. A camera according to any of claims 2 to 6, including a handle for gripping by an operator. 8. A camera according to any preceding claim wherein each microphone is mounted in an insert of a material which is such as to act as a baffle to sound generated within the camera. 9. A camera according to any preceding claim, wherein the left and right microphones are mounted in respective human ear-like protrusion structures which include a duct extending from the exterior of the structure to the microphone. 10. A camera according to claim 9, wherein each structure includes portions resembling the fossa, concha and earlobe of a human ear. 11. A camera according to claim 9, wherein each structure is rectangular in outline and includes a portion resembling the concha of a human ear. 12. A camera according to any of claims 9 to 11, wherein each structure includes a rectangular base structure for securing to the camera body or frame or cowl structure, as appropriate. 13. A camera according to any of claims 9 to 12, wherein each structure includes a protective cover which is such as to act as a baffle for wind noise. 14. A camera according to any preceding claim, wherein the signal processing means includes a tape recording mechanism. 15. A camera according to any preceding claim, wherein the signal processing means includes binaural processing means, including cross-talk cancellation means. 16. A camera according to any preceding claim , including a third or a third and fourth microphones for detecting sound from a foreground region. 17 A camera according to claim 16, wherein the signal processing means includes a time delay means for removing any correlation between the third microphone and the left and right microphones, and addition means for adding the signal from the third microphone to that of the first and/or second microphones. 21. An accessory for a handheld camera, comprising a frame structure or cowl structure for receiving a camera body, releasable securing means for securing the camera body to the structure, the structure including left and right microphones for providing left and right channel binaural signals positioned such that when the structure is secured to the camera body, the ears are disposed on opposite sides of the camera body, and including signal processing means for processing the channel signals.

Inventors: SIBBALD ALASTAIR, SIBBALD, ALASTAIR
Applicants: CENTRAL RESEARCH LAB LTD, SIBBALD ALASTAIR, CENTRAL RESEARCH LABORATORIES LIMITED, SIBBALD, ALASTAIR
Application year: 1995
Main classification: H04N5
IPC codes: G03B17, G03B31, H04N5, H04R5, H04S1