Patent Description:
The use of radar based devices to detect speeding vehicles is now well known. Fixed site devices, either providing a measure of instantaneous speed or working with other fixed devices to provide a measure of an average speed over a set distance, may be fixed at positons by the roadside. Where more flexibility is desired it is known to provide handheld portable devices which are sometimes referred to as speed guns. These may also use radar to detect the speed of the vehicles and are primarily used by the police to enforce speed limits on the public highway.

To date, portable speed measurement devices have been relatively expensive because of the need to calibrate the devices and also the need for a relatively high degree of operator training. This has prevented the widespread adoption of radar based devices by the public. There have been attempts to provide more consumer oriented speed detection devices although these have been limited in functionality. For instance a continuous wave (CW) radar to detect a speeding object within its field of view, such as a baseball. The device cannot however discriminate between multiple devices within the field of view as it cannot determine any information about the range of the object. The device is therefore unsuitable for use in detecting vehicle speeds where there may be multiple vehicles in view, as is common on the increasingly crowded public highways in many countries.

It is an object of the present invention to provide a low cost radar based apparatus for detecting speeding vehicles that is both relatively low cost and is simple and intuitive to use.

We are aware of the teachings of <CIT> which discloses a wearable pedestrian safety radar system including a harness, a portable radar device and a display. The device detects the speed of oncoming vehicles and a camera captures images of the vehicle.

According to a first aspect the invention provides a portable speed detection and recording system as claimed in claim <NUM>.

By providing a radar device that can be used with a portable electronic device to form a system in accordance with the invention, a low cost system is achieved primarily because most users will already have a suitable portable electronic device such as a smartphone or tablet. This is taken a step further by using the portable device as the user interface for setting the range at which the speed is captured by the radar device, eliminating in some cases the need to provide that user interface on the radar device itself. Further ease of use is achieved by the portable device automatically capturing the image when the trigger is received, so that the user merely has to point the device towards the approaching vehicles to capture speed and images. The radar device, by filtering out vehicles that are not in the set range or speed reduces the power consumed as there is no need to perform the calculations needed to determine speed or transmit information to the portable device.

The radar device measures distance to objects, e.g. vehicles, in a pulsed mode and whenever in range then determines the speed of the object. However it is preferable that the radar device in the first instance measures the speed of the vehicle and only if it is above a threshold speed will the radar device measure the distance to the object, a trigger being sent if the vehicle is in the defined range. This reduces power as it means range is only calculated for vehicles travelling at speeds above the threshold, since range detection inherently is more computationally intensive and hence more power hungry.

The radar device, in use, may apply a digital filter, such as a FIR filter, prior to the full Doppler range process to detect that a target vehicle speed is above the set threshold. When a speed is detected above the set threshold the radar device may then be configured to apply full range Doppler processing to the data to obtain range and Doppler data, i.e. range plus speed.

The digital filter allows a 'quick process' to give speed information only using the same source data that can be used for full range plus speed processing (i.e. no time/power overhead of capturing new data if a speeding target is initially found). The filter design may approximate a bandpass filter which reduces the signal bandwidth and hence noise, still allowing target speed data to pass with reasonable amplitude for all ranges. This quick look method saves considerable processing overhead (power consumption) should no targets be present.

The radar device may include a memory in which the range information received in the control signal, or indicated by the value of the control signal is stored. This may be updated whenever a new control signal is received which has updated values. The control signal may therefore only be sent at times when the user wants to change the range. At all other times, the range information used to determine if a vehicle is in range will be extracted from the memory by the processing unit.

The trigger signal sent to the portable device may comprise a measurement of speed and the device may take a picture whenever the speed indicated by the trigger signal exceeds a preset or user defined value. The trigger signal may therefore comprise a numerical value which is indicative of the speed.

The trigger signal may be sent at defined intervals of time for as long as a vehicle is detected, for instance every <NUM>/<NUM>th of a second. Each value sent may be indicative of the instantaneous speed of the vehicle when the vehicle is detected. In this case, the camera may capture an image each time a trigger signal is received.

Sending the speed of all vehicles in range as the trigger signal, or all vehicles in range and above the speed threshold, enables a live view of the speed to be presented on a screen of the portable device.

The trigger signal is only sent to the portable device when the speed of the vehicle exceeds a preset or user defined value. This reduces the power consumption of the device. The speed may be displayed on a screen of the device when it is received.

The speed threshold may be stored in a memory of the radar device where it is accessed by the processing means when in use.

The radar device may be arranged to receive a further control signal that encodes the speed threshold and in response to receiving this signal may set the minimum threshold speed used by the radar device. This control signal may be combined with the control signal that sets the range.

The trigger signal may be sent to the portable device only once, corresponding to the first instance at which a vehicle is detected in the defined range and exceeds the predefined minimum speed. This further reduces the power consumed, with the minor disadvantage that the speed transmitted may not correspond to the highest speed for the detected vehicle in the defined range. In most instances where the range of distances is narrow, say <NUM> or less, this is not a significant drawback as the vehicle is unlikely to be increase significantly over such as small distance.

The radar device may be configured to transmit to the portable device a synchronization signal indicative of the settings of the radar device, i.e. the range and speed thresholds. This signal may be transmitted when the radar device is first connected to the a portable device, for instance during a set up or pairing process determined by the communication protocol used to transmit signals from the radar device to the portable device. This synchronization signal may include, for instance, the MAC address of the portable device for connection across a Wi-Fi network, or a BD_ADDR for connection using Bluetooth.

The portable device may include a screen on which images captured by the camera are displayed. This may be a continuous stream of captured images depending on the camera image capture rate, and may lag a little behind real time due to that capture time. Portable devices, such as smart phones, today nearly all have suitable cameras and screens that can be used to display the captured scene.

The radar device may include in a memory a default range of distances and optionally a default predefined minimum speed which determines when a trigger signal is to be produced. This allows the apparatus to function even when a user has not sent any control signal to the device, for instance on initial purchase.

The control signals that may be sent from the portable device to the radar device may be indicative of at least one of an identity of the portable electronic device or an identity of the camera for determining camera settings, or the camera settings themselves.

The portable electronic device may be configured to communicate with a database, the database including information about the portable electronic device and/or optimized camera settings.

The control signals sent to the radar device to set the range may be selected so as to configure the radar device to send the trigger signal when the target vehicle is at an optimum range for image size and quality of the camera, as determined by the camera settings.

In an alternative the portable electronic device may instead set the focal length and zoom of the camera automatically from the range information it sends to the radar device.

The camera settings may be manually controllable by a user, the control signals provided to the radar device being at least partially derived from these camera settings.

The camera settings may be manually controllable via a user operable interface of the portable electronic device.

The camera settings may include one or more of the focal length, field of view, zoom, or f-number.

The portable electronic device may include location determining means for detecting the location at which the image is captured.

The portable electronic device may be configured to time stamp each image.

The data may be stored as image metadata. Optionally, this data may be used to produce a composite image of the image and the data.

The portable electronic device includes firmware that captures the images from the camera and processes the trigger signal and data transmitted from the radar device, and software in the form of an app that controls both the settings of the camera and radar device.

The software may automatically optimize the image of a target vehicle detected by the radar device. The portable electronic device app may be operable in use to enable the user to setup the radar detector trigger settings such as the speed, range threshold and target direction of travel using the portable device app.

The radar device preferably communicates with the portable electronic device over a wireless communication means. For example, the wireless communication means may be one of Bluetooth®, Bluetooth® LE, Wi-Fi, NFC or ANT+. However, it is within the scope of the invention in at least one arrangement that the radar device communicates with the portable electronic device using a hard wired connection.

The radar device may comprise a housing with a single power button, the housing otherwise being devoid of any user operable interface, the control and user interaction being performed using the portable electronic device. It may be a small, pocket sized housing that can fit within the hand of a user.

The system includes a mount for physically securing the radar device to the portable electronic device.

The FMCW radar is pulsed to reduce power.

The radar device may in use, be configured to apply an FIR filter followed by Doppler process to detect that a target vehicle is present within the range of target speeds but not detect the range, and when a target vehicle is present in the speed range, the radar device is configured to apply full range Doppler processing to the data to obtain range and Doppler speed data.

The device may include wireless communication means for receiving the control signal from the portable electronic device and transmitting the trigger signal to the portable device.

The radar device may comprise a housing with a single power button, the housing otherwise being devoid of any user operable interface.

The radar device may comprise a mount for mounting the radar device to a portable electronic device.

The radar device may be small enough to fit in the hand, and may for instance by comparable in size to a mobile phone.

The radar may be powered from a battery such as a single <NUM>. 6V AA battery. To reduce power consumption, the radar and processing circuit of the radar device is configured to be powered up to take measurements for only a fraction of each frame period. For instance, the radar may be configured to be powered up for <NUM> in every <NUM> frame period.

The device may include a memory which stores the minimum and maximum ranges for a trigger signal, and also stores a threshold speed below which a vehicle does not generate a trigger signal when detected.

The control signals may be indicative of at least one of an identity of the portable electronic device or an identity of the camera for determining camera settings, or the camera settings themselves.

The method may further comprise the step of the portable electronic device communicating with a database to obtain information about the portable electronic device and/or optimized camera settings.

The method may further comprise the step of determining the location of the portable electronic device and storing this information with the image.

The method may further comprise the step of automatically optimizing the image of a target vehicle.

The method may further comprise the step of applying an FIR filter followed by Doppler process to detect that a target vehicle is present.

When a target vehicle is present, the method may include the step of applying full range Doppler processing to the data to obtain range and Doppler (speed) data.

There will now be described, by way of example only, one embodiment of the present invention with reference to the accompanying drawings of which:.

As shown in <FIG>, a portable speed detection and recording system <NUM> for detecting speeding vehicles comprises in combination a portable electronic device <NUM> having a camera and a separate portable radar device <NUM> having a radar antenna <NUM>. The two devices <NUM>, <NUM> may be secured together using a clip <NUM> fixed to the housing of the radar device that fits around the side edges of the portable electronic device.

In this example the portable electronic device <NUM> comprises a smartphone having a screen <NUM> on a front face, and a camera <NUM> on the rear face. The camera <NUM> could be on the same face as the screen. When it is on the rear face, as shown, it is important that the radar device <NUM> when secured to the smartphone does not obscure the scene viewed by the camera <NUM>. Also, the antenna <NUM> of the radar detector <NUM> when fixed should have a field of view for detecting vehicles that corresponds, or at least overlaps, with the field of view of the camera. <FIG> shows the field of view of the camera <NUM>, the edges of which are denoted by dashed lines and the field of view of the antenna <NUM>, the edges of which are denoted by a line of crosses, when in a typical usage mode to observe vehicles on a highway.

The key parts of a smartphone are well known and so will not be described here in any detail. The invention requires a smartphone to have a camera and a wireless or wired connection to the radar device. <FIG> is a block diagram showing the key parts of the radar device. It comprises a small housing which contains a battery <NUM> and a battery powered, pulsed, frequency modulated continuous wave (FMCW) radar, in this example consuming a very low power from a single built in <NUM> volt AA cell battery. The radar comprises an antenna <NUM> and a processing unit <NUM> that provides drive signals to the antenna and analyses the signals detected by the antenna. The processing unit <NUM> runs a set of program instructions <NUM> stored in a memory <NUM> of the device.

The radar device includes a radio frequency receiver/transmitter <NUM> for receiving control signals from the portable electronic device and for transmitting trigger signals to the portable electronic device <NUM>. The control signals in this example encode a range of distances within which a vehicle is to be detected, and a minimum speed above which a vehicle must be travelling for the radar device to trigger a chain of events leading to smartphone capturing an image of a speeding vehicle. The control signal may also encode a direction of travel for targets that the device is to detect, allowing the device to selectively detect targets moving towards, or from, or both towards and from the device. The control signals may take many forms, and may include actual range values (for instance <NUM> or 30KPH) although the range could be encoded in numerous different ways so long as the radar device can interpret the encoding.

<FIG> shows exemplary upper and lower range boundaries as dotted lines, defining a zone within which a trigger may be generated and outside of which the trigger signal is not generated or is suppressed.

The processing means of the radar device <NUM> in use determines the speed of a vehicle that is detected by the radar antenna <NUM> and that is within the range of distances, and if this is above a threshold set in the device this speed measurement is sent to the portable electronic device as a trigger signal.

The memory <NUM> of the radar device stores the range information and speed threshold information. The device <NUM> may initially ship with a preset range, and can be modified on receipt of control signals from the smartphone. The memory <NUM> also includes a speed threshold, below which detected vehicles are ignored.

The smartphone <NUM> also includes a receiver and transmitter, for transmitting the control signals to the radar device and receiving the trigger signal. The transmitted signals are generated by a computer program- a software "app" that is run on the smartphone. The app, when running, guides the user through a process to pair the smartphone to the radar device, in this example using a Bluetooth protocol.

All the user needs to do, when in use, is hold the camera so that a portion of highway where vehicles are to be detected is in the field of view of the camera, activate the app, and turn on the radar device. The app optimizes the camera settings to ensure that a vehicle in the target range of the radar device will be in focus and at a suitable zoom level, for instance to enable the number plate of the vehicle to be clearly identified in a captured image. The app communicates with the radar device to set up the device to capture vehicle data in a range of interest as set by the user.

It has a simple user interface for the user to configure the detector trigger settings. An example interface, presented on the screen of the smartphone is shown in <FIG> of the drawings.

The user interface of the app in this example provides the following features:.

An exemplary operation of the smartphone app may be as follows.

Claim 1:
A portable speed detection and recording system (<NUM>) for detecting speeding vehicles, comprising in combination a portable electronic device (<NUM>) having a camera (<NUM>) and a separate portable radar device (<NUM>), in which the radar device comprises:
a battery powered, frequency modulated continuous wave FMCW radar, that is repeatedly powered up and powered down in a series of pulses, whereby when powered up the radar operates as an FMCW radar to take measurements, a receiver for receiving a control signal from the portable electronic device that is indicative of a range of distances within which the radar device, in use, is to output a trigger signal indicating the detection of a moving target vehicle and outside of which the radar device does not output a trigger signal, a processing means for determining from the radar the speed of a vehicle that is detected by the radar only when that vehicle is within the said range of distances as determined by the radar, the radar not determining the speed of targets outside of that range, the radar device further including a transmitter for sending to the portable electronic device a trigger signal that encodes at least the speed of the target vehicle,
and in which the portable electronic device is configured to capture an image of the target with the camera in response to receiving the trigger signal from the radar device and to store the image together with the data representing the speed of the target vehicle, and in which the trigger signal is sent to the portable device only when the speed of the vehicle determined by the radar exceeds a preset or user defined value.