IES84050Y1 - A video signal transmission system, and a method for transmitting a video signal from a remotely mounted video camera to a vehicle mounted video signal processing unit - Google Patents

Abstract

ABSTRACT A video signal transmission system for transmitting video signals from a remotely mounted video camera (2) to a vehicle mounted video signal processing unit (4) for subsequent display on a visual display screen (5). An on—board master control unit (3), which controls the operation of the video camera (2), receives video signals from the video camera (2), and relays the video signals to the video signal processing unit (4). Initially, a master microprocessor (15) of the master control unit (3) determines the least noisy channel, and appropriately sets the transmission channel of a slave transmitter (41) of the video camera (2) and the receive channel of a master receiver (19) of the master control unit (3) to the channel of least noise. A master transmitter (18) of the master control unit (3) under the control of the master microprocessor (15) transmits control signals for reception by a slave receiver (40) of the video camera (2) for controlling the operation of the video camera (2) and for selecting the transmission channel of the slave transmitter (41). In order to minimise power consumption, the master transmitter (18) under the control of the master microprocessor (15) outputs a predetermined signal at predetermined intervals while the slave transmitter (41) is transmitting for reception by the slave receiver (40). Absence of reception of the predetermined signal by the slave receiver (40) indicates that the video camera (2) is out of range of the master control unit (3), and the video camera (2) is put into a sleep mode.

Description

A video signal transmission system, and a method for transmitting a video signal from a remotely mounted video camera to a vehicle mounted video signal processing unit The present invention relates to a video signal transmission system for transmitting video signals from a remotely mounted video camera to a vehicle mounted video signal processing unit, for example, to an on-board video signal processing unit in a motor vehicle, for subsequent display on a vehicle mounted visual display screen.

The invention also relates to a method for transmitting a video signal from a remotely mounted video camera to a vehicle mounted video signal processing unit for subsequent display on a vehicle mounted visual display screen.

According to the invention there is provided a video signal transmission system for transmitting a video signal from a remotely mounted video camera to a vehicle mounted video signal processing unit for subsequent display on a vehicle mounted visual display screen, the transmission system comprising: a video camera suitable for mounting remotely of the vehicle, a vehicle mounted master control means for controlling transmission of video signals from the video camera to the vehicle mounted signal processing unit, a vehicle mounted master transmitter operable under the control of the master control means for transmitting control signals from the master control means to the video camera for controlling operation of the video camera, a vehicle mounted master receiver for receiving video signals from the video camera, the master receiver having at least two selectable channels for receiving video signals from the video camera, the channels being selectable by the master control means, the master receiver comprising an amplifier, and a gain control means for controlling the gain of the amplifier for amplifying the received signals to a predetermined power level, a slave control means associated with the video camera for operating the video camera in response to the control signals received from the master control means, a slave receiver associated with the video camera for receiving the control signals from the master control means transmitted by the master transmitter for relaying to the slave control means, and a slave transmitter associated with the video camera for transmitting video signals therefrom to the master control means, the slave transmitter having at least two selectable channels on which video signals from the video camera are transmittable, the frequencies of the respective channels of the slave transmitter corresponding to the frequencies of the respective channels of the master receiver, the master control means comprising: a first selecting means for sequentially selecting at least some of the channels of the master receiver, a reading means for reading a gain signal from the gain control means of the master receiver indicative of the amplification factor by which the received signals from the respective selected channels are amplified to bring the received signals to the predetermined power level, and a second selecting means responsive to the gain signal for selecting the channel of the slave transmitter and the master receiver on which the video signals are to be communicated from the video camera to the master control means, the master control means being responsive to the second selecting means selecting the channel, for setting the channel of the master receiver to the selected channel, and for outputting a channel select signal through the master transmitter to the slave control means, the channel select signal indicating the identity of the channel of the slave transmitter which is to be selected by the slave control means for transmitting the video signals from the video camera to the master control means, and the slave control means is responsive to the channel select signal for selecting the channel of the slave transmitter.

In one embodiment of the invention the second selecting means is responsive to the gain signal for selecting the channel of the master transmitter in which the received signal is amplified by one of the higher amplification factors.

In another embodiment of the invention the first selecting means is operable under the control of the master control means when the slave transmitter is not transmitting, and preferably, the reading means reads the signals received by the master receiver for determining if any of the channels selected by the first selecting means contains a video signal, and advantageously, the second selecting means is responsive to the reading means and the gain signal for selecting the channel as the channel of the master receiver, the received signal on which is amplified by the highest amplification factor not containing a video signal. in another embodiment of the invention the first selecting means is operated under the control of the master control means in response to a camera activation signal inputted to the master control means for activating the video camera.

In another embodiment of the invention the slave control means is responsive to the channel select signal for activating the video camera to commence operation.

In a further embodiment of the invention the first select means is operable under the control of the master control means for sequentially selecting the respective channels of the master receiver.

In a still further embodiment of the invention the signals received on the selected channels of the master receiver when the channels are sequentially selected by the first selecting means should ideally be noise.

In one embodiment of the invention the master control means comprises a means for transmitting a predetermined signal at predetermined intervals through the master transmitter to the slave control means after the channel select signal has been transmitted to the slave control means, and the slave control means is responsive to the absence of one of the predetermined signals at one of the predetermined intervals for deactivating the video camera.

Preferably, the slave control means does not deactivate the video camera until at least two consecutive predetermined signals at consecutive predetermined intervals are absent.

Advantageously, the slave control means does not deactivate the video camera until at least three consecutive predetermined signals at consecutive predetermined intervals are absent.

Preferably, the slave control means operates the slave receiver for receiving the predetermined signals when the slave transmitter is transmitting video signals from the video camera.

Advantageously, the master control means operates the master transmitter for outputting the predetermined signal at the predetermined intervals on a predetermined channel. Advantageously, the slave control means operates the slave receiver for receiving the predetermined signal at the predetermined intervals on a channel corresponding to the predetermined channel on which the predetermined signal is being transmitted by the master transmitter. in another embodiment of the invention the master transmitter is a narrow band transmitter, and the slave receiver is a narrow band receiver, and the slave control means sweeps the slave receiver through frequency channels corresponding to frequency channels of the narrow band receiver for determining the channel on which the predetermined signal is being transmitted at the predetermined intervals by the master transmitter.

In a still further embodiment of the invention the video camera comprises a light source for providing light for facilitating operation of the video camera in the dark.

Preferably, the light source is provided by at least one light emitting diode, and preferably, the light source is provided by a plurality of light emitting diodes, and advantageously, each light emitting diode outputs light with a relatively high infrared content. Advantageously, the slave control means is responsive to the channel select signal for activating the light source when the video camera is being activated. in one embodiment of the invention the video signals received by the master receiver are relayed by the master control means to the vehicle mounted video signal processing unit. in another embodiment of the invention the master control means controls the operation of the transmission system so that the video signals relayed to the vehicle mounted video signal processing unit are such that the image displayed on the visual display is oriented in an orientation similar to that in which the image would appear in a rear view mirror of the vehicle.

Additionally, the invention provides a method for transmitting a video signal from a remotely mounted video camera to a vehicle mounted video signal processing unit for subsequent display on a vehicle mounted video display screen, the method comprising the steps of: mounting a video camera remotely of the vehicle, providing a vehicle mounted master control means for controlling transmission of video signals from the video camera to the vehicle mounted signal processing unit, providing a vehicle mounted master transmitter operable under the control of the master control means for transmitting control signals from the master control means to the video camera for controlling operation of the video camera, providing a vehicle mounted master receiver for receiving video signals from the video camera, the master receiver having at least two selectable channels for receiving video signals from the video camera, the channels being selectable by the master control means, the master receiver being provided with an amplifier and a gain control means for controlling the gain of the amplifier for amplifying the received signals to a predetermined power level, providing a slave control means associated with the video camera for operating the video camera in response to the control signals received from the master control means, providing a slave receiver associated with the video camera for receiving the control signals from the master control means transmitted by the master transmitter for relaying to the slave control means, providing a slave transmitter associated with the video camera for transmitting video signals therefrom to the master control means, the slave transmitter having at least two selectable channels on which video signals from the video camera are transmittable, the frequencies of the respective channels of the slave transmitter corresponding to the frequencies of the respective channels of the master receiver, the method further comprising the steps of providing the master control means with: a first selecting means for sequentially selecting at least some of the channels of the master receiver, a reading means for reading a gain signal from the gain control means of the master receiver indicative of the amplification factor by which the received signals from the respective selected channels are amplified to bring the received signals to the predetermined power level, a second selecting means responsive to the gain signal for selecting the channel of the slave transmitter and the master receiver on which the video signals are to be communicated from the video camera to the master control means, the master control means being responsive to the second selecting means selecting the channel, for setting the channel of the master receiver to the selected channel, and for outputting a channel select signal through the master transmitter to the slave control means, the channel select signal indicating the identity of the channel of the slave transmitter which is to be selected by the slave control means for transmitting the video signals from the video camera to the master control means, and the slave control means is responsive to the channel select signal for selecting the channel of the slave transmitter.

In one embodiment of the invention the second selecting means selects the channel as the channel of the master transmitter on which the received signal is amplified by one of the higher amplification factors. in another embodiment of the invention the first selecting means is operated under the control of the master control means when the slave transmitter is not transmitting, and preferably, the reading means reads the signals received by the master receiver for determining if any of the channels selected by the first selecting means contains a video signal, and advantageously, the second selecting means selects the channel as the channel of the master receiver, the received signal on which is amplified by the highest amplification factor not containing a video signal.

In another embodiment of the invention the at least some of the channels of the master receiver are sequentially selected by the first selecting means for determining the amplification factors required for amplifying the signals received on the sequentially selected channels in response to a camera activation signal inputted to the master control means for activating the video camera. in another embodiment of the invention the video camera is activated in response to the channel select signal.

In a further embodiment of the invention each of the channels of the master receiver are sequentially selected by the first selecting means for determining the amplification factors required for amplifying the respective received signals. in a still further embodiment of the invention the signals received on the selected channels of the master receiver when the channels are sequentially selected by the first selecting means should ideally be noise.

In one embodiment of the invention the master control means is operated for transmitting a predetermined signal at predetermined intervals through the master transmitter to the slave control means after the channel select signal has been transmitted to the slave control means, and the slave control means is responsive to the absence of one of the predetermined signals at one of the predetermined interval for deactivating the video camera.

Preferably, the video camera is not deactivated until at least two consecutive predetermined signals at consecutive predetermined intervals are absent.

Advantageously, the video camera is not deactivated until at least three consecutive predetermined signals at consecutive predetermined intervals are absent.

Preferably, the slave control means is operated for operating the slave receiver for receiving the predetermined signal when the slave transmitter is transmitting video 7 signals from the video camera.

In a still further embodiment of the invention the video camera comprises a light source for providing light for facilitating operation of the video camera in the dark, and preferably, the light source is provided by a plurality of light emitting diodes, and advantageously, each light emitting diode outputs light of a relatively high infrared content. Advantageously, the slave control means is operated in response to the channel select signal for activating the light source when the video camera is being activated.

The invention also provides a video camera for use with the video signal transmission system, and the invention further provides a master control unit for use with the video signal transmission system.

The invention will be more clearly understood from the following description of an embodiment thereof, which is given by way of example only, with reference to the accompanying drawings, in which: Fig. 1 is a block representation of a video signal transmission system according to the invention for transmitting a video signal from a remotely mounted video camera to a vehicle mounted video signal processing unit, Fig. 2 is a front elevational view of the remotely mounted video camera of the system of Fig. 1, Fig. 3 is a top plan view ofthe video camera of Fig. 2, Fig. 4 is a perspective view of a portion of the video camera of Fig. 2, Fig. 5 is a perspective view of the portion of Fig. 4 of the video camera of Fig. with part of the video camera removed, Fig. 6 is a partly cross-sectional front elevational view of a detail of the portion of the video camera which has been removed from the portion illustrated in the perspective view of Fig. 5, Fig. 7 is a top plan view of a portion of the detail of Fig. 6 of the video camera of Fig. 2, and Fig. 8 is a top plan view of another portion of the detail of Fig. 6 of the video camera of Fig. 2.

Referring to the drawings and initially to Fig. 1, there is illustrated a video signal transmission system according to the invention, indicated generally by the reference numeral 1, for use with a motor vehicle (not shown) for transmitting video signals from a remotely mounted video camera also according to the invention, the circuit of which is illustrated in block representation in Fig. 1, and is indicated generally by the reference numeral 2, to a vehicle mounted on-board video signal processing unit 4 for subsequent display on a visual display screen 5 also mounted in the motor vehicle. Such on-board video signal processing units are commonly provided in motor vehicles for processing video signals read from a compact disc or a DVD with route map data for displaying the map of a route to be followed or being followed on an on-board visual display screen. Such on-board video signal processing units may also be provided for processing video signals transmitted by television stations for displaying a television programme on the visual display screen 5. Such on-board video signal processing units and visual display screens located in motor vehicles will be well known to those skilled in the art, and it is not intended to describe the video signal processing unit or the visual display screen in further detail. An on- board master control unit, also according to the invention, which is illustrated in block representation in Fig. 1, and which is indicated generally by the reference numeral 3, is located on-board the motor vehicle for controlling the operation of the video camera 2, and for receiving video signals from the video camera 2 and for relaying the video signals to the video signal processing unit 4. ln this embodiment of the invention the video camera is suitable for mounting on the vehicle or remotely of the vehicle. When mounted on the vehicle, typically, the video camera 2 is mounted to the rear of the vehicle for presenting a view to the rear of the vehicle on the visual display screen 5 to a driver for assisting in reversing of the vehicle. When mounted remotely of the vehicle, the video camera 2 would typically be located for capturing images of an area within which the vehicle is to be or is being manoeuvred.

A camera receiving unit (not shown) is provided for mounting on the rear of the vehicle or any other desired location in or on the vehicle for receiving the video camera 2 when the camera is to be mounted on the rear of the vehicle, and also for orienting the video camera 2 so that the video camera 2 videos the area into which the vehicle is being reversed or othen/vise manoeuvred. When located in the camera receiving unit (not shown), the video camera 2 communicates with the master control unit 3 through an infrared communication link. A first infrared transmitter/receiver unit 11 of the infrared communication link is provided in the master control unit 3, and is located in the camera receiving unit (not shown). A second infrared transmitter/receiver unit 12 of the infrared communication link is located in the video camera 2 for communicating with the first infrared transmitter/receiver unit 11. A port 7 in a housing 8 of the video camera 2, see Fig. 2, is provided for facilitating infrared transmissions between the second infrared transmitter/receiver 12 in the video camera 2 and the first infrared transmitter/receiver 11 in the camera receiving unit (not shown).

The video camera 2 is powered by a rechargeable battery (not shown) which is charged from the electrical system of the motor vehicle when the video camera 2 is located in the camera receiving unit (not shown). A pair of electrical contacts 10 located on the housing 8 of the video camera 2, see Fig. 2, engage a corresponding pair of electrical contacts (not shown) located in the camera receiving unit for powering the video camera 2 when the video camera 2 is located in the camera receiving unit, and for charging the battery of the video camera 2.

Returning now to the on-board master control unit 3, the master control unit 3 comprises a master control means, namely, a master microprocessor 15, which controls the operation of the video transmission system 1, and also controls the operation of the video camera 2 through the video signal transmission system 1. A master radio transmitter 18, which in this embodiment of the invention is a narrow band transmitter is operated under the control of the master microprocessor 15 for transmitting control signals to the video camera 2, as will be described below. A master video receiver 19, which is also operated under the control of the master microprocessor 15, receives video signals from the video camera 2 for relaying to the video signal processing unit 4. The master receiver 19 is a multi-channel ISM band receiver comprising four selectable channels for receiving video signals from the video camera 2, as will also be described below. An antenna and a front end filter 17 of the master receiver 19 receives signals, which are relayed to a tuning circuit 20, which selects the appropriate one of the four receiving channels of the master receiver 19, as will be described below. A demodulation and correction circuit 21 demodulates the received video signals, and under the control of the master microprocessor 15, the demodulated video signals are relayed to the video signal processing unit 4 for display on the visual display screen 5.

The tuning circuit 20 comprises a signal mixer 22 for mixing received signals from the antenna and front end filter 17 of the master receiver 19 with a frequency signal outputted by a programmable local oscillator 25 which is operated under the control of the master microprocessor 15 for setting the channel frequency of the master receiver 19 to a selected channel frequency. An intermediate frequency variable gain amplifier 26 amplifies the intermediate frequency signal outputted by the mixer 22. A gain control circuit 28 controls the gain of the amplifier 26 so that the intermediate frequency signal is amplified to a constant predetermined power level.

The microprocessor 15 reads the gain control signal from the gain control circuit 28, which is supplied to the intermediate frequency amplifier 26, for determining the gain factor by which the intermediate frequency signal is amplified by the intermediate frequency amplifier 26 for a purpose to be described below.

Turning now to the video camera 2, the video camera 2 comprises a CMOS video camera unit 35 which is operated under the control of a slave control means, namely, a slave microprocessor 36. A slave radio receiver 40 operated under the control of the slave microprocessor 36 communicates the slave microprocessor 36 with the master microprocessor 15 for receiving control signals from the master microprocessor 15 for controlling the operation of the video camera 2 and the video camera unit 35. The slave radio receiver 40 is a narrow band receiver having a corresponding receiving frequency range as the master transmitter 18, and is of the type capable of sweeping through the frequency range for detecting a valid control signal from the master transmitter 18. Such sweeping techniques in radio receivers for detecting a valid signal will be well known to those skilled in the art. A slave video signal transmitter 41, which is also operated under the control of the slave microprocessor 36 transmits video signals from the video camera unit 35 for reception by the master receiver 19. The slave transmitter 41 is a multl—channe| transmitter, and is operable under the control of the slave microprocessor 36 for transmitting the video signals from the video camera unit 35 on four selectable channels, the respective frequencies of which correspond to the frequencies of the selectable channels of the master receiver 19.

A light source, in this embodiment of the invention six light emitting diodes 39 which have a high infrared light content are provided in the video camera 2 for illuminating an area being videoed by the video camera unit 35. The arrangement and location of the light emitting diodes 39 is described in more detail with reference to Figs. 3 to 8. The light emitting diodes 39 are operated under the control of the slave microprocessor 36 in response to control signals received from the master microprocessor 15.

The operation of the video signal transmission system will now be described. When the video camera 2 is mounted remotely of the vehicle (not shown) the video camera 2 awaits a channel select signal from the master control unit 3, which indicates to the slave microprocessor 36, firstly that the video camera 2 is to be activated to transmit video signals to the master control unit 3, and secondly the identity of the channel of the slave transmitter 41 on which the video signals from the video camera unit 35 are to be transmitted. The master control unit 3 is initially activated in response to a video activation signal for outputting the channel select signal to the video camera 2.

The video activation signal which is applied to the master control unit 3 is inputted by a user through a suitable input means located in the vehicle. The input means may be a push button switch (not shown) which would be operated by the driver or an individual in the vehicle, or any other suitable arrangement for inputting the video activation signal.

On receipt of the video activation signal. and before outputting the channel select signal to the video camera 2, the master control unit 3 initially determines which of the four channels of the master receiver 19 and the slave transmitter 41 is the optimum channel for transmission of the video signals, in other words, which is the least noisy of the four channels.

The least noisy channel is determined as follows. The microprocessor 15 on receipt of the video activation signal operates the tuning circuit 20 of the master receiver 19 for sequentially selecting the four receiving channels. The signals received by the master receiver 19 on each of the selected channels are gained up to a predetermined power level by the amplifier 26 under the control of the gain control circuit 28. Since the video camera 2 at this stage is not transmitting, the only signals which should be received on the four channels as the channels are being sequentially selected is noise. The master microprocessor 15 reads the gain control signal from the gain control circuit 28 for determining the amplification factor by which the received signals, in other words, the noise is amplified to bring the signal to the predetermined power level on each channel. The master microprocessor 15 also reads the signals received on each of the channels to determine if any of the signals are video signals, which would indicate that a video camera other than the video camera 2 or other video transmitter is transmitting video signals, which would interfere with the video signals to be transmitted by the video camera 2. On the amplification factor having been determined for all four channels, and on the presence or othenrvise of video signals on any of the channels being detected, the master microprocessor 15 selects the channel on which the amplification factor is highest, and which does not contain a video signal. The channel with the highest amplification factor is the channel which will have the lowest noise level. The master microprocessor 15 sets the master receiver 19 to receive on the selected channel, and then transmits the channel select signal through the master transmitter ‘I8 for reception by the slave receiver 40 of the video camera 2. The slave microprocessor 36 on receiving the channel select signal operates the slave transmitter 41 to transmit on the channel identified in the channel select signal, and simultaneously activates the video camera unit 35 and the light emitting diodes 39.

Video signals received by the master receiver 19 are passed through the tuning circuit 20 and the demodulation and correction circuit 21, from which the video signals are relayed to the video signal processing unit 4 for display on the visual display screen 5.

Additionally, in order to minimise the power consumption of the video camera 2, the master microprocessor 15 at suitable predetermined intervals outputs a predetermined signal for reception by the slave receiver 40 of the video camera 2.

The slave microprocessor 36 continuously watches for the predetermined signal at the predetermined intervals. in the absence of two predetermined signal being received during two consecutive predetermined intervals, which would indicate that the video camera 2 is outside the receiving range of the master receiver 19, the slave microprocessor 36 deactivates the video camera unit 35 and the light emitting diodes 39 and goes into a sleep mode, awaiting the next channel select signal.

Referring now to Figs. 2 to 8, the video camera unit 35 is mounted on a main printed circuit board 50 which carries control circuitry for the video camera unit 35, which is located on the printed circuit board by surface mounted technology (SMT). The main printed circuit board 50 is located in the housing 8 of the video camera 2 in a pair of main guide tracks 53, which align the video camera unit 35 with a lens 54 in the housing 8. A secondary printed circuit board 55 carries the six light emitting diodes 39 of relatively high infrared content, and is located in the housing 8 in a pair of secondary guide tracks 56. An opening 57 in the secondary printed circuit board accommodates the video camera unit 35 therethrough. Connectors 59 and are provided on the main and secondary printed circuit boards 50 and 55, respectively, for electrically connecting the printed circuit boards 50 and 55 to control circuitry which comprises the slave microprocessor 36, the slave transmitter 41, the slave receiver 40 and the infrared transmitter/receiver 12, and other relevant circuitry (not shown) which is also located in the housing 8, but not illustrated in Figs. 2 to 8.

In order that the connectors 59 and 60 are accessible for connecting to the control circuitry of the video camera 2, it is important that the main and secondary printed circuit boards 50 and 55 should be located in the housing with their respective side edges 62 and 63 arranged so that the connectors 59 and 60 are located one above the other as illustrated in Fig. 4. A locating means for so locating the secondary printed circuit board 55 relative to the main printed circuit board 50 is provided by a key 65 located on the video camera unit 35 for engaging a corresponding key-way 66 formed in the opening 57 of the secondary printed circuit board 55. A recess 68 formed in the secondary printed circuit board 55, co-operates with an alignment projection 69 in the housing 8 for correctly locating the main and secondary printed circuit boards 50 and 55 in the housing 8, and for preventing misassembly of the main and secondary printed circuit boards 50 and 55 in the housing 8.

The main and secondary printed circuit boards 50 and 55 are assembled and located in the housing 8 as follows. Initially, the stuffed secondary printed circuit board 55 is mounted to the stuffed main printed circuit board 50 by engaging the video camera unit 35 on the main printed circuit board 50 in the opening 57 of the secondary printed circuit board 55, with the key 65 of the video camera unit engaging the key-way 66. The assembled main and secondary printed circuit boards 50 and 55 are then engaged in the housing 8 by sliding the main and secondary printed circuit boards 50 and 55 into the main and secondary guide tracks 53 and 56, respectively. In this way, the connectors 59 and 60 together with the side edges 62 and 63 are located on corresponding sides of the video camera unit 35, with the connectors 59 and 60 one above the other, and thus can readily be connected to the remaining control circuitry in the housing 8 by suitable connectors.

In order that the connectors 59 and 60 are located for facilitating connection of leads thereto from the other circuitry in the housing 8, the alignment projection 69 prevents the main and secondary printed circuit boards 50 and 55 being incorrectly located in the housing 8.

While the main receiver and the slave transmitter have been described as comprising four selectable channels, it will be readily apparent to those skilled in the art that the master receiver and the slave transmitter may be provided with any desired number of selectable channels. It will also be appreciated that while the master control unit has been described as outputting a predetermined signal at predetermined intervals for reception by the video camera, while this is desirable, it is not essential, and furthermore, where the master control unit does output such predetermined signals at predetermined intervals, the signals may be outputted at predetermined intervals of any desired time period, and furthermore, the video camera may be responsive to the absence of more than two consecutive predetermined signals before becoming deactivated.

The invention is not limited to the embodiment hereinbefore described, which may be varied in construction and detail.

Claims (5)

Claims

1. A video signal transmission system for transmitting a video signal from a remotely mounted video camera to a vehicle mounted video signal processing unit for subsequent display on a vehicle mounted visual display screen, the transmission system comprising: a video camera suitable for mounting remotely of the vehicle, a vehicle mounted master control means for controlling transmission of video signals from the video camera to the vehicle mounted signal processing unit, a vehicle mounted master transmitter operable under the control of the master control means for transmitting control signals from the master control means to the video camera for controlling operation of the video camera, a vehicle mounted master receiver for receiving video signals from the video camera, the master receiver having at least two selectable channels for receiving video signals from the video camera, the channels being selectable by the master control means, the master receiver comprising an amplifier, and a gain control means for controlling the gain of the amplifier for amplifying the received signals to a predetermined power level, a slave control means associated with the video camera for operating the video camera in response to the control signals received from the master control means, a slave receiver associated with the video camera for receiving the control signals from the master control means transmitted by the master transmitter for relaying to the slave control means, and a slave transmitter associated with the video camera for transmitting video Us signals therefrom to the master control means, the slave transmitter having at least two selectable channels on which video signals from the video camera are transmittable, the frequencies of the respective channels of the slave transmitter corresponding to the frequencies of the respective channels of the master receiver, the master control means comprising: a first selecting means for sequentially selecting at least some of the channels of the master receiver, a reading means for reading a gain signal from the gain control means of the master receiver indicative of the amplification factor by which the received signals from the respective selected channels are amplified to bring the received signals to the predetermined power level, and a second selecting means responsive to the gain signal for selecting the channel of the slave transmitter and the master receiver on which the video signals are to be communicated from the video camera to the master control means, the master control means being responsive to the second selecting means selecting the channel, for setting the channel of the master receiver to the selected channel, and for outputting a channel select signal through the master transmitter to the slave control means, the channel select signal indicating the identity of the channel of the slave transmitter which is to be selected by the slave control means for transmitting the video signals from the video camera to the master control means, and the slave control means is responsive to the channel select signal for selecting the channel of the slave transmitter.

2. A video signal transmission system as claimed in Claim 1 in which the second selecting means is responsive to the gain signal for selecting the channel of the master transmitter in which the received signal is amplified by one of the higher amplification factors.

3. A video signal transmission system as claimed in Claim 1 or 2 in which the master control means comprises a means for transmitting a predetermined signal at predetermined intervals through the master transmitter to the slave control means after the channel select signal has been transmitted to the slave control means, and the slave control means is responsive to the absence of one of the predetermined signals at one of the predetermined intervals for deactivating the video camera.

4. A video signal transmission system for transmitting a video signal from a remotely mounted video camera to a vehicle mounted video signal processing unit for subsequent display on a vehicle mounted video display screen, the video signal transmission system being substantially as described herein with reference to and as illustrated in the accompanying drawings.

5. A method for transmitting a video signal from a remotely mounted video camera to a vehicle mounted video signal processing unit for subsequent display on a vehicle mounted video display screen, the method comprising the steps of: mounting a video camera remotely of the vehicle, providing a vehicle mounted master control means for controlling transmission of video signals from the video camera to the vehicle mounted signal processing unit, 26 providing a vehicle mounted master transmitter operable under the control of the master control means for transmitting control signals from the master control means to the video camera for controlling operation of the video camera, providing a vehicle mounted master receiver for receiving video signals from the video camera, the master receiver having at least two selectable channels for receiving video signals from the video camera, the channels being selectable by the master control means, the master receiver being provided with an amplifier and a gain control means for controlling the gain of the amplifier for amplifying the received signals to a predetermined power level, providing a slave control means associated with the video camera for operating the video camera in response to the control signals received from the master control means, providing a slave receiver associated with the video camera for receiving the control signals from the master control means transmitted by the master transmitter for relaying to the slave control means, providing a slave transmitter associated with the video camera for transmitting video signals therefrom to the master control means, the slave transmitter having at least two selectable channels on which video signals from the video camera are transmittable, the frequencies of the respective channels of the slave transmitter corresponding to the frequencies of the respective channels of the master receiver, the method further comprising the steps of providing the master control means with: a first selecting means for sequentially selecting at least some of the channels of the master receiver, a reading means for reading a gain signal from the gain control means of the master receiver indicative of the amplification factor by which the received signals from the respective selected channels are amplified to bring the received signals to the predetermined power level, a second selecting means responsive to the gain signal for selecting the channel of the slave transmitter and the master receiver on which the video signals are to be communicated from the video camera to the master control means, the master control means being responsive to the second selecting means selecting the channel, for setting the channel of the master receiver to the selected channel, and for outputting a channel select signal through the master transmitter to the slave control means, the channel select signal indicating the identity of the channel ofthe slave transmitter which is to be selected by the slave control means for transmitting the video signals from the video camera to the master control means, and the slave control means is responsive to the channel select signal for selecting the channel of the slave transmitter. F.F. GORMAN & CO.