A variety of systems is known, for example from US-A-5740049, in which so-called reckoning systems are used for determining both the location of, for example, a vehicle and characteristics of the movement thereof.

While such known systems can employ a variety of techniques and accuracy verification measures, these generally exhibit an additional hardware/software requirement which can introduce unnecessary complexity, cost, and in some cases size restraints for the proposed system.

The present invention seeks to provide for an apparatus and method for use in movement determination and which exhibit advantages over known such apparatus and methods.

According to a first aspect of the present invention there is provided movement detection apparatus having an optical disk drive for the retrieval of data from an optical disk, the apparatus including means for monitoring signals derived from the optical disk drive during the said data retrieval, and arranged to identify an anomaly in the retrieved signals indicative of motion of the disk drive.

By monitoring such anomalies, and therefore identifying likely movement of the disk drive, it is possible therefore to identify likely movement of the device or apparatus/equipment within which the disk drive is mounted, for example in a vehicle or handheld mobile communications device.

In particular, since the optical disk drive is in any case already provided within the device, apparatus or equipment, there is no additional hardware overhead in incorporating the present invention since the invention makes advantageous use of signals and data readily available during operation of the optical disk drive.

The subject matters of Claims 2,3 and 4 relate to different anomalies that can be identified in accordance with particular aspects of the present invention.

In accordance with the features of Claims 5-8, the invention can be advantageously provided for use as part of a vehicular navigation system, or a location/movement system associated with a handheld portable radio communications device.

As confirmed in Claims 9 and 10, while the apparatus of the present invention can provide for movement indication per se, the signals derived in accordance with the present invention can be advantageously employed in verifying signals derived from standard navigation/movement systems.

In accordance with another aspect of the present invention, there is provided a method of detecting movement of a device, including the steps of monitoring data signals obtained from an optical disk drive mounted within the device and during the retrieval of data therefrom and so as to identify an anomaly in the signal arising in response to motion of the device.

As should therefore be appreciated, the invention advantageously relates to the provision of dead-reckoning information for use in navigation applications from outputs of a disk drive pickup. In particular, the radial and/or focus error signals arising in an optical disk drive are employed to provide an indication of motion of the optical disk drive and apparatus associated therewith. Also, or in addition, variations in data rate may be employed to provide an indication of angular motion of the optical disk drive and the device/apparatus associated therewith. It is therefore possible in accordance with the present invention to obtain dead-reckoning information without requiring dedicated sensors.

The invention is described further hereinafter, by way of example only, with reference to the accompanying drawing which is a schematic block diagram of apparatus embodying the present invention.

It is known that automotive navigation devices often contain optical disk drives (currently for example CD or DVD) and which are used to store map database information. With the advent of Small Form Factor Optical drives, such convenient database storage could also find use within handheld GPS receivers.

Further, optical disk drives incorporate a number of feedback systems to track the spiral on the disk and to recover the data accurately from the disk.

One actuator is needed to move a lens in a direction normal to the disk surface to track the variations in distance between the surface and photo-detectors such that pits and lands can be read. Similarly a radial actuator is used to track eccentricities in the spiral in the plane of the disc. As well as coping with variations due to disc imperfections, these servo systems also seek to compensate for mechanical shock to the system so that such shocks do not disrupt the output of data. The present invention seeks to determine any difference or anomaly in the signals so as to retrieve information concerning the movement of the drive unit and thus the device/apparatus within which it is mounted.

Also, Phase Locked Loops (PLLs) are employed for recovering data from the disk at different rates. Current disk drives typically seek to maintain constant angular velocity (CAV) or so-called zoned-CAV, which dictates that there is a difference in data rate between the inside and outside of the disk.

Due to the inertia of the disk, any angular acceleration of the drive, and thus the device/apparatus within which it is mounted, will be reflected in the momentary data rate from the disk and, as such, can be determined by the PLL.

Navigational systems, for example satellite-based systems, such as the Global Positioning System (GPS), provide an accurate and reliable means of determining a position, although there are however some limitations.

Even when a GPS receiver is stationary, it may nevertheless still register a small movement. Through the monitoring of, for example, focus, radial or PLL signals derived from a disk drive within the receiver, it proves possible to accurately verify whether the receiver is actually at rest or moving even slowly. This means that the given output position can be locked if truly at rest and so as to give the user an improvement in the accuracy and reliability of the locational data.

Due to the low available signal power, GPS does not work in indoor environments, nor under heavy foliage or in tunnels. For this reason, automotive navigation systems often incorporate dead-reckoning functionality based on wheel sensors, magnetic compasses or gyroscopes to provide back- up position signaling during the, possibly short, periods when the GPS receiver is unable to function. The piezoelectric gyroscopes that are typically used for such dead reckoning can prove unreliable unless continually calibrated to determine their zero-point. In accordance with an embodiment of the present invention, the angular motion information derived from the PLL in the disk drive is employed either to replace the gyroscope entirely, or at least to provide a turn/no-turn indication that can assist when calibrating the gyroscope. Depending on its orientation relative to the vehicle, the radial error signal could also be used for such a purpose.

A particular advantage of the invention is that appropriate means are already present in known devices and navigation systems such that there is limited hardware overhead in adopting the invention. That is, the radial and focus servo error signals can be employed to provide linear motion information.

The channel PLL can be employed to provide angular motion information.

Turning now to the drawing, there is illustrated an optical disk drive 10 for retrieving data from an optical disk 12 by means of an optical pickup 14.

The signals then output from the optical pickup 14 are delivered to a signal processor 16 which in turn provides an output signal 18 for subsequent display/manipulation of the data retrieved from the optical disk 12.

Also output from the signal processor 16 are a series of error signals 20,22, 24 which, in this embodiment, comprise a radial error signal 20, a focus error signal 22 and a data rate signal 24.

Each of these signals 20-24 is then delivered to an anomaly processor 26 having sections 28,30, 32 for processing the error signals 20,22, 24 respectively and so as to output anomaly signals 34,36, 38.

The anomaly signals 34,36 are derived from the radial error signals and focus error signals and are employed as an indicator of linear movement of the optical disk drive, and thus the device/apparatus within which the optical disk drive 10 is mounted.

The anomaly signal 38 relates to the data rate signal 24 derived from the signal processor 16 and serves as an indicator of angular acceleration of the optical disk drive 10, and thus the apparatus within which the optical disk drive 10 is mounted, which can serve as an indicator of change of direction of movement of the aforesaid device/apparatus.

Thus, through the identification of changes in the error signals 20-24, the output signals 34-38 can be developed and used both as a prime indicator of motion/direction changes, and/or so as to verify movement and directional changes identified in accordance with a separate monitoring and/or positional system.

Thus, to conclude, the present invention proposes the use of the radial and/or focus error signals in the optical drive to give a simple indication, or ready confirmation, of linear motion of the unit. Furthermore, measured variations in data rate (for a given set motor speed) as the unit is turned in the plane of the disk rotation may yield information about angular motion. This information, at the very least, could be used to determine whether motion is present or not. GPS alone may register small movements when the receiver is stationary due to inherent inaccuracies in the system, so such information for dead-reckoned position updates would require further investigation.

Also, it should be appreciated that the invention is not restricted to the details of the foregoing embodiment. For example, the invention can be arranged such that only one or two of the error signals or data rate signals are

monitored for producing a respective one or two output anomaly signals. Also, anomalies in the signals mentioned can be employed to confirm movement when calibrating vehicular devices such as an odometer, or accelerometer, often included within a dead-reckoning subsystem.