Camera-mountable fiber optic transceiver system

A system includes a multiplexing transceiver which is adapted to mount directly between a video camera and a camera battery pack, eliminating the need for triaxial adapters or other electrical cables at the camera and video production facility. A fiber optic cable carries upstream and downstream television signals between the camera-mountable transceiver and a remote base station transceiver. The camera-mountable transceiver includes a transmitter adapted for converting an electrical information input signal received from the camera to an optical output signal. The transceiver further includes a receiver adapted for converting an optical input signal received from the fiber optic cable to an electrical information output signal. A transceiver housing includes a first plate on a first side for mounting the housing to the camera and a second plate on a second side for mounting the housing to a power source.

BACKGROUND

In the television broadcast industry, there are several types of television production methodologies, including electronic news gathering/satellite news gathering (ENG/SNG), electronic field production (EFP) and outside broadcast (OB). ENG/SNG applications typically feature a single camera with a built-in video tape recorder (VTR) which is most often used as a stand-alone camcorder for recording live events locally to tape.FIG. 1shows a prior art camera system12. This camera can also serve as a “live” camera from the scene of the news event. At that point, it is commonly connected to a video production vehicle control center11via either copper cables or coaxial cables17.

In the copper cable approach, the camera is connected to the truck with multiple copper cables which typically include one-to-three coax cables with BNC connectors for video signals and one-to-four shielded twisted audio pairs with XLR connectors for audio and intercom signals as well as power if the camera is not powered by a local battery. Alternatively, a minority of crews make use of products which multiplex all of the required signals, as well as power, over a single coax cable. U.S. Pat. No. 5,345,592 discloses such a system.

In Electronic Field Production (EFP), multiple cameras connect to a “production center” (usually a small truck) via copper cables or coax, or via another cable, known as “multicore.” Multicore is a 26-conductor cable that carries power and all of the required signals over discreet copper wires. Multicore is limited in distance, and is heavy, inflexible, expensive, and hard to repair in the field.

Outside Broadcast (OB) features multiple cameras (three or more) serviced by cameras with triaxial capability. This application includes sports, live music concerts, scripted programs shot outside of studios, and other shows where large crews shoot action that is confined within a prescribed area and is fairly predictable. The OB camera can be remotely controlled and powered from a local or distant camera control unit (CCU), sometimes called a base station, through a transmission medium known as triaxial cable.

The triaxial cable is a shielded coaxial cable designed to simultaneously transmit various bi-directional information and/or control signals and provide power from the CCU to the camera. Signals typically may include program video (component, composite, serial digital interface, high definition or other), program audio, return video, viewfinder video, genlock, return audio, IFB (interrupt foldback), Teleprompter, tally, call, intercom, and bi-directional camera control data. These signals may be analog, such as AM or FM, and/or digital in nature. Power may be in the form of AC or DC. Since there is typically only one physical cable, it is the function of the camera system's triaxial adapter to encode and/or modulate the required video, audio, intercommunications and data signals onto the proper frequencies. These frequencies are typically frequency division multiplexed for transmission, with assigned frequencies traveling in their specified directions on the triaxial cable. Other techniques, such as digital hybrid transmission, may also be used in addition to frequency division multiplexing techniques. The triaxial adapter demodulates the composite signal at either of the receiving ends of the triaxial cable into the respective baseband signals. The triaxial adapter may be contained within the camera and/or CCU ends, or may be separate units that attach to the camera and/or CCU ends.

Since the information signals are typically high frequency broadband RF signals, the effective distance over which the camera and CCU can communicate and operate is limited to one to three kilometers. In addition, a trend in the industry has been towards cameras having higher performance and wider information bandwidths, thus further limiting the distance of a wideband, component triaxial camera system to approximately one kilometer. In order to compensate, users may utilize a larger, heavier cable, which may increase distance, but also increases time and labor to deploy and take up the cable. This distance limitation often interferes with the user's ability to produce the desired programming.

Some camera manufacturers provide a fiber optic interface directly on the camera and on the CCU. However, these solutions can require significant investments in new cameras, CCUs and supporting infrastructure.

Video cameras for ENG or EFP applications typically are equipped with a specialized battery mount that provides a rugged, secure and reliable attachment of the battery to the camera. Known systems for battery mounting include Anton/Bauer, PAG, and Sony V-mount.

SUMMARY

There is a need in the broadcast industry to enhance the operating distance of cameras, especially in electronic news gathering (ENG), satellite news gathering (SNG) and electronic field production (EFP) applications, without having to modify the camera and control hardware and without the need for costly investments in supporting infrastructure. There is also a need for such enhancements to provide a compact, convenient and secure mounting arrangement.

The above and other problems are solved by the camera-mountable fiber optic transceiver system of the present approach. The system includes a multiplexing transceiver which is adapted to mount directly between a video camera and a camera battery pack, eliminating the need for triaxial adapters or other electrical cables at the camera and remote equipment. A fiber optic cable carries upstream and downstream television signals between the camera-mountable transceiver and a remote base station transceiver. Fiber optic cable combines the advantages of increasing distance with smaller, lightweight cabling. Fiber optic cable eliminates all types of electromagnetic and radio frequency interference as well as ground faults and hum. With transparency, bandwidth and small cable size, the present system can deliver television signals at thirty times the distance of ordinary coaxial or triaxial cable type systems.

Accordingly, a transceiver of the present system provides an interface between a camera and a fiber optic cable. The transceiver includes a transmitter adapted for converting an electrical information input signal received from the camera to an optical output signal. The transceiver further includes a receiver adapted for converting an optical input signal received from the fiber optic cable to an electrical information output signal. The electrical information signals can include video, audio and data signals.

A housing that holds the transmitter and receiver is adapted for mounting to the camera. In an embodiment, the housing includes a first plate on a first side for mounting the housing to the camera, and a second plate on a second side for mounting the housing to a battery or other power source. Power is passed from the battery to the camera through the housing, and tapped off to power the transceiver. In some embodiments, the plates for mounting the housing are compatible with standard battery mounts which avoids the need to modify the cameras to support the transceiver.

According to an aspect of the system, the transmitter includes a multiplexer for multiplexing plural camera information signals to a multiplexed electrical input signal and an electrical-to-optical converter for converting the multiplexed electrical input signal to the optical output signal.

According to another aspect of the system, the receiver includes an optical-to-electrical converter that converts the optical input signal to a multiplexed electrical signal and a demultiplexer for demultiplexing the multiplexed electrical signal to plural remote information signals.

According to another aspect of the present approach, a system includes a camera-mountable optical transceiver for transmitting a downstream optical signal and for receiving an upstream optical signal; a remote optical transceiver for transmitting the upstream optical signal and for receiving the downstream optical signal; and a fiber optic cable coupled between the camera-mountable optical transceiver and the remote optical transceiver for carrying the downstream and upstream optical signals. The camera-mountable optical transceiver includes a housing for mounting to the camera.

The present system has particular applicability for ENG, SNG and other events where the events themselves may be some distance from the production base station. The present system further saves time and labor in arranging outside broadcast events. Use of fiber optic cables can eliminate more than 90% of the typical cable weight of copper cables. The system can also be used in metropolitan applications, directly linking remote venues to production studio via leased “dark fiber” (replacing microwave links), and in pre-fibered venues and campuses, avoiding the need to pull copper cables.

DETAILED DESCRIPTION

A prior art camera control system is shown inFIG. 2A. The system includes a camera control unit (CCU)10linked to a camera12using a cable14. The CCU10and the camera12each include a connector16,18respectively for coupling television program signals to the cable14. Specifically, the CCU10transmits program signal CU and the camera12originates program signal CA. The signals CU and CA may include, for example, program video, return video, viewfinder video, gen-lock, intercom and other audio program signals. The cable14can be copper, coaxial, triaxial or multicore type. The CCU10connects the multiple signals CU, CA over multiple cables17to a video production facility11.

Note that a camera control panel (not shown) may also be included, either integral with the CCU10, or more commonly, mounted separately and connected to the CCU.

In a triaxial type system, the electrical signals CA and CU are conventional television signals typically arranged in a frequency division multiplex (FDM) format of the individual video, audio, and control signals which in aggregate have a typical bandpass of about 100 MHz.

FIG. 2Bshows a fiber optic triaxial camera control system20such as that disclosed in U.S. Pat. No. 6,115,159, the contents of which are incorporated herein by reference. The system20generally comprises a camera control interface unit22, a camera interface unit24, and a fiber optic cable30. The control interface unit22is linked to CCU10using a section of standard triaxial cable14A. Similarly, the camera interface unit24is linked to camera12using a triaxial cable section14B. Similar toFIG. 1, multiple signals CU, CA are connected between the CCU10and the video production facility over multiple cables17.

The control interface unit22and the camera interface unit24each provide an electro/optical and opto/electrical conversion function. The control interface unit22converts FDM signal CU received on triaxial cable14A to provide optical signal OCU on fiber optic cable30. The optical signal OCU is transmitted on fiber optic cable30to the camera interface unit24where it is converted back to electrical FDM signal CU and coupled to the triaxial cable14B and passed to camera12. In a similar manner, the camera interface unit24converts FDM signal CA received from the camera12on triaxial cable14B to provide optical signal OCA which is transmitted on fiber optic cable30to the control interface unit22. The control interface unit22converts the optical signal OCA back to electrical FDM signal CA for transmission to the CCU10on triaxial cable14A.

FIG. 3Ashows a diagram of a system of the present approach that includes a camera transceiver unit46and a base station transceiver unit38. The camera transceiver unit is mounted between a camera48and a battery or other power supply44. The base station transceiver unit is coupled to a remote video production facility11. The camera transceiver unit is connected to the base station transceiver unit by a fiber optic cable30. The fiber optic cable is multimode or single mode optical fiber.

Rather than dealing with FDM formatted signals, the present system operates directly with baseband television signals (e.g., composite, HDTV, SDI or other), thereby avoiding altogether the need for expensive and complex triaxial adapters at either end of the connection. Accordingly, baseband television signals designated BCA originate from the camera48and are coupled to the camera transceiver unit46via cables50. The electrical signals BCA are converted to optical signal OBCA for transmission downstream on fiber optic cable30to the base station transceiver unit38. In a similar manner, the base station transceiver unit38converts baseband television signals designated BCU originated from the video production facility11. The BCU and BCA signals are carried between the video production facility11and the base unit38over multiple cables designated34. The BCU signals are converted to optical signal OBCU which is carried upstream on fiber optic cable30. The signals are shown inFIG. 3B. It should be understood that the principles of the present approach also apply to embodiments that do not include camera control equipment.

As described further herein, the camera transceiver unit is housed in a housing that has plates on opposite sides that allow the housing to be mounted between a battery and camera.

Referring toFIGS. 4A and 4B, a block diagram of an embodiment of the camera transceiver unit46is shown and is now described in more detail. The camera transceiver unit connects camera signals on a 12 pin connector170. The camera signals include camera video in172; return video out176; audio1(camera) in180; tally relay contacts182and headset trigger signal183. The return video out signal176is coupled to a return video out BNC connector164. Additional signals from the camera include a black burst out signal178coupled to BNC connector168, an auxiliary video in BNC connector signal162, headset signals118A,118B on XLR connector118, return audio out XLR signal116and an audio2input XLR signal114.

A 10 pin connector184provides additional signals to and from the camera. These remote signals include camera remote control input186, camera remote control output190, RS232 input192, RS232 output194, and a nominal 12 volt DC power signal196. In addition, a camera remote control format control signal188is provided, the function of which is described in further detail below.

The camera unit receives a nominal 12 volt battery input signal195from a 12 volt battery pack that is connected to the housing of the camera unit as described further below. An auto-select circuit198selects between 12 VDC power signal196from the camera and the 12 VDC battery signal195to supply a power supply156that distributes power via distribution lines156A. Power loop through191connects the 12 VDC battery signal195through to the camera from the battery.

The camera video in signal172is coupled to an anti-alias filter174which removes extraneous signals from the camera video input. Likewise, the auxiliary video in signal162is filtered via anti-alias filter166. The filtered video signals are input to a video auto-select circuit134. The video auto-select circuit selects between the auxiliary video and the program video signals to provide one of the signals for transmission to the base station unit. The selected video signal is coupled to an off-set cancellation circuit136which removes DC off-set in the video signal. The output of the off-set cancellation circuit136is input to a 12 bit video analog-to-digital (A/D) converter138. The video A/D converter circuit138samples the composite video signal at 31.1040 mega samples per second with 12 bits per sample.

The audio input signals114,118A and180are amplified in amplifier circuit120. For audio2input signal114, input level select circuit110provides user-selectable gains of 40 dB and 60 dB for a microphone input or unity gain for line level input. The amplified audio signals are connected to a pair of stereo audio A/D converter circuits122. The audio A/D converter circuit122provides 24 bit samples that are sampled at the rate of 48.6 kilo samples per second. The outputs of the audio A/D converter circuit122include a serialized data signal that includes left and right stereo samples, and a left/right indicator signal. Audio1signal180uses the left channel of one of the stereo A/D converter circuits122. The headset signal118uses the right channel of the first audio A/D circuit. The audio2signal is coupled to the second stereo audio A/D converter.

The digital output161of the 12 bit video A/D converter circuit138and the digital output159of the 24 bit audio A/D converter circuits122are coupled to a multiplexer124. The multiplexer multiplexes the signals at a rate of 31.1040 mega words per second resulting in an aggregate bit rate of 622.080 megabits per second. In an embodiment, the multiplexer124is a HDMP-1032 multiplexer provided by Hewlett Packard. Additional data inputs to the multiplexer124include data signals157from remote signal connector184. The output of the multiplexer124is a serial bit stream that is connected to a laser diode driver circuit132. The laser driver circuit drives a laser diode.

In order to minimize optical fiber usage, the laser diode132may be coupled to a wavelength division multiplexer (WDM)140. The optical signal OBCA produced by the laser diode is at a first wavelength λ1, such as 1310 nm. In the opposite direction, the optical signal OBCU from the base station transceiver unit38(FIG. 3A) is received at port42and may be coupled via the WDM140. The optical signal OBCU is at a second wavelength λ2, such as 1550 nm. In general, the optical wavelengths are preferably selected from wavelengths in the range of 1300 nm to 1550 nm. The WDM140splits the optical signals λ1and λ2.

In another embodiment, the WDM140can instead be a two-way coupler, in which case λ1=λ2with bi-directional transmission on a single optical fiber.

It should be noted that while the preferred embodiment of the present system employs wavelength division multiplexing to provide transmission of optical signals OBCU and OBCA on a single optical fiber, other embodiments of the invention can have a separate optical fiber for each direction of transmission. In such embodiments, the wavelength division multiplexing is not employed, and λ1can be the same as λ2.

On the receive side of the wave division multiplexer140an optical signal at 1550 nanometers is received on the fiber port42. This receive optical signal is coupled to an optical pre-amp stage150which provides optical amplification to bring the signal to a useful level. The optical pre-amp circuit150also includes an optical/electrical converter the output of which is provided to a demultiplexer154. The digital output of the demultiplexer154includes digital video signals151,149, data signals153and audio signal155. In an embodiment, the demultiplexer154is a HDMP-1034 multiplexer provided by Hewlett Packard.

Video signal149is coupled to a 1:2 video data demultiplexer148. The 1:2 demultiplexer decodes data for the return video that is sampled at half the data rate to use only 4 bits on a corresponding multiplexer at the base station unit38(FIG. 3A) as described further herein. The decoded video output from the 1:2 demultiplexer148and the digital video signal151are 8 bit sample signals that are converted to baseband analog video signals by video D/A converters146A,146B. The video D/A converter146A operates at 15.5520 mega samples per second; the video D/A converter146B operates at 31.1040 mega samples per second. The baseband analog video signals are filtered by filters145,147and amplified by amplifier block144to provide return video out signal176and black burst out signal178.

The audio signal155is provided to an AES/EBU demultiplexer circuit130which takes serial data from the demultiplexer154and converts that serial data into 24 bit sample signals coupled to audio digital-to-analog (D/A) converter circuit128. The AES/EBU demultiplexer is used to simplify the decoding of the signals by the D/A converter128. The audio D/A converter128operates at 48.6 kilo samples per second. The baseband analog audio signals output from the audio D/A converter128are amplified by amplifier block126to provide output audio signals116,118B.

As noted, the remote signals include a camera remote control input and a camera remote control output signal186,190. The camera remote control signals can take on formats that include a bi-directional 2-wire format, RS422, and RS232 format. A format control signal187is included in the cable received from the camera in the 10 pin connector184. Depending on the type of signals used by the camera, a particular cable is pre-made to select a particular format. The selected format is indicated by having one of the pins in the 10 pin connector coupled to ground, 12 volts or left open. The pin state is interpreted by camera remote control format control circuit188.

An auxiliary data I/O functions block152provides input amplifiers for the different data types for camera remote control input186and232input192. The data I/O block also provides output levels for the proper data types for232output194and camera remote control output190.

The main system clock is derived from the camera system clock158(FIG. 4B) which supplies all the clocks for the system. From the data that is received at the base station unit, the base station unit recovers that same clock and uses it as its transmission medium for the data that returns back to the camera unit. Recovered receiver section system clock160(FIG. 4B) uses a clock recovered from the base station unit to provide clock to the received side functions in the camera unit.

Referring toFIGS. 5A and 5B, a block diagram of the base station transceiver unit38is shown and is now described in more detail. The base station transceiver unit38provides similar electro-optical functionality to the camera transceiver unit46(FIG. 3A). In general, signals between the video production facility11and the base station transceiver unit38correspond to signals carried to and from the camera transceiver unit46on the fiber optic cable30.

Baseband analog signals received from the video production facility11(FIG. 3A) include return video in212, black burst in214, return audio in206and headset signal208B on XLR connector208. The video production facility11(FIG. 3A) receives baseband analog signals from the base station transceiver unit that include program/auxiliary video out210, audio1out202, audio2out204and headset signal208A on XLR connector208.

Additional signals between the video production facility11and the base station transceiver unit include tally signal226and RS232 data input/output signals228,230through 9 pin D type connector216, and camera remote control input/output data signals232,236with program signal233on data port 9 pin D type connector218.

The base station transceiver unit receives a DC input power signal220that connects to a power supply254. The power supply also receives an input from an internal battery line238and distributes power to lines254A.

The return video in212and black burst in214signals are coupled to respective anti-alias filters222,224to remove extraneous signals from the video signals. The filtered video signals are amplified in amplifier block250which can also include a dither insertion function. In particular, a dither signal that generally comprises a filtered noise source can be applied to the analog video signal as a means to integrate the steps resulting from the digitizing process. The noise is “shaped” (filtered) so as not to interfere with the analog signal being digitized.

The amplified black burst signal is input to an 8 bit video A/D converter264which samples at 31.1040 mega samples per second to provide digital data output signal269. The amplified return video signal is input to an 8 bit video A/D converter262which samples the signal at 15.5520 mega samples per second, half the rate of A/D converter264. The output of A/D converter262is multiplexed in 2:1 video data multiplexer268to provide a digital data output signal267.

The audio input signals206,208plus a sidetone mix signal242, are amplified in amplifier circuit246. The amplified audio signals are connected to 24 bit audio A/D converter circuit258operating at 48.6 kilo samples per second. An AES/EBU multiplexer266receives signals output from the audio A/D converter258and multiplexes them together into one serial stream265to simplify the transmission of the data. In an embodiment, the AES/EBU multiplexer266includes user bits in addition to audio data inputs. The tally signal226can be carried as one of the user bits.

An auxiliary data I/O functions block252provides input amplifiers for the different data types for camera remote control input232and RS232 input228. The data I/O block also provides output levels for the proper data types for RS232 output230and camera remote control output236.

The encoded digital audio signal265is multiplexed together with digital video data outputs267,269and data signals271in a multiplexer276. The multiplexer276operates at a rate of 31.1040 mega words per second resulting in an aggregate bit rate of 622.080 mega bits per second. The output of the multiplexer276is a serial bit stream that is connected to a laser diode driver circuit278that drives a laser diode coupled to a WDM280. In one embodiment, the optical signal OBCU produced by the laser diode is at wavelength λ2, such as 1550 nm. In the opposite direction, the optical signal OBCA from the camera transceiver unit46(FIG. 3A) is received at port40and may be coupled via the WDM280. The optical signal OBCA is at wavelength λ1, such as 1310 nm. The WDM280splits the optical signals λ1and λ2.

On the receive side of the wave division multiplexer280an optical signal at 1310 nanometers is received on the fiber port40. This receive optical signal is coupled to an optical pre-amp stage284which provides optical amplification to bring the signal to a useful level. The optical pre-amp circuit284also includes an optical/electrical converter the output of which is provided to a demultiplexer286. The digital output of the demultiplexer286includes digital audio signal257, digital video signal259and data signal261.

The digital audio signal257is provided to two 24 bit audio D/A converters256which converts the signal257to provide analog audio1signal202, audio2signal204and headset signal208A. An amplifier circuit244provides gain for these audio output signals and provides the sidetone mix signal242.

The digital video signal259is coupled to a 12 bit video D/A converter260that operates at 31.1040 mega samples per second. The baseband analog video output from the D/A converter260is filtered by filter249and amplified by amplifier block248to provide program/auxiliary video output signal210.

The data signal261is coupled to the auxiliary data I/O block252to provide the proper levels to the video production facility11(FIG. 3A).

At initial power up of the base station transceiver unit, system clock for the base unit is provided by local clock270. After a period of operation, the base unit recovers clock from the data received from the camera transceiver unit and subsequently the base unit switches from the local clock270to recovered clock272using an auto select circuit274.

Having described the electrical and optical functions of the present system, the mechanical aspects are now described in further detail.

FIG. 6Ashows a perspective view of an embodiment of a housing302for the camera transceiver unit46.FIG. 6Bshows a right side view of the housing. A front panel350of the housing includes BNC connectors312,314,316; XLR connectors318,320,322; Hirose connectors324,326. Other connector arrangements are possible and the particular configuration is shown for illustration purposes only. An ST type or other type fiber cable receptacle328is positioned at a 45 degrees angle below the front panel. Rails330protect the fiber cable receptacle.

A left side304of the housing includes a mounting plate306(FIG. 6A). A second mounting plate308is attached on the opposite side310. The plates306,308shown are of the PAG battery mount type. However, it should be understood that other types of battery mounting systems can be used with the principles of the present system, including those mounting systems provided by Anton/Bauer, Sony and others.

FIG. 7illustrates a configuration of the camera transceiver unit46aligned for mounting between camera48and power source or battery44. In this configuration, plates306A,306B and308A,308B are shown as Anton/Bauer “Gold Mount” type, though as noted, other types of battery mounting systems can be used. In a typical arrangement without the present transceiver system, plate308B of the power source44mounts to plate306B attached to the camera48. With the present system, the housing302is aligned between the camera48and the power source44such that plates308B,306A are connected. Likewise, plates308A,306B are connected. As configured and as described above, the camera transceiver unit46is capable of tapping 12 VDC from the power source44and passing power through to the camera48.

Use of standard or other types of battery mounting systems to mount the housing between the camera and the battery provides several advantages. One advantage includes enabling a user to quickly, effectively and easily remove and replace the fiber optic transceiver. Another advantage is that the fiber optic transceiver housing maintains the same operational advantages for battery pack connections without replacing or upgrading ENG/EFP camera equipment.