The adjustment for each photodetector corrects not only for the range, but also for the offset, providing two correction values.
解答例
In a preferred embodiment, the low and high voltage reference levels for an analog to digital converter are adjusted from values stored for each photodetector for each color to produce corrected digital outputs.
In a preferred embodiment, the adjustment is done by scanning a pair of test strips using the varying LED powers and exposure times which provide the coarse adjustment.
One test strip is a light gray, and the other is a dark gray.
The values for these samples are then determined, and offset and range corrections are calculated.
The calculated corrections are extrapolations corresponding to white and black values at the end of the range, but are not measured in this way to avoid clipping effects at range extremes, and are applied as appropriate references to obtain corrected digital outputs.
In another aspect of the invention, the LEDs are arranged in an interleaved fashion, with multiple colors being in the same row.
The timing is varied by varying the on-time of the LEDs, with blue LEDs being on longer than the green and red colors, which are on the same, shorter period of time.
The periods of time are chosen by determining the minimum amount of time the green and red LEDs can be on and still match the photosensor output for blue, with the blue LEDs being turned on to the maximum power for the maximum amount of time available to achieve the desired scanning rate.
For a fuller understanding of the nature and advantages of the invention, reference should be made to the ensuing detailed description taken in conjunction with the company drawings.
The invention proposes an emergency call system for a motor vehicle for automatically transmitting an emergency call to an external receiving station.
The motor vehicle has measuring means, for example in the form of a radar system (6), for determining the relative speed and the distance of the vehicle in relation to another vehicle or an obstacle.
If the current relative speed exceeds a predetermined limit value for a given distance, it is assumed that a collision is unavoidable, and an emergency call by a transmitter (3) provided in the motor vehicle is activated.
Advantageously, the vehicle position, ascertained by means of a navigation system (4), is transmitted to the receiving station with the emergency call.
The invention also provides for the emergency call system to be connected to further sensors (6), suitable for detecting a collision, so that the emergency call can be revoked if an actual collision is not reported by such a sensor within a predetermined time period.
The invention relates to an emergency call system for a motor vehicle, having a transmitter, provided in the motor vehicle, for automatically transmitting an emergency call to an external receiving station, and having a signal generator, the transmitter and the signal generator being connected to an arithmetic and logic unit which activates the emergency call if there is an appropriate signal from the signal generator, and to a method for automatically transmitting an emergency call from a motor vehicle to a receiving station using a transmitter.
Such an emergency call system is disclosed in WO 90/03899.
A signal from a signal generator triggers an automatic emergency call.
The signal generator can be an air bag, an alarm system or a temperature or gas sensor.
The system can therefore activate an alarm using a mobile radio device in the event of the vehicle having a collision or being stolen, depending on the signal generator used.
In addition, the emergency call system contains a navigation unit for determining and transmitting the position of the vehicle together with the emergency call.
Further information, such as vehicle-related data, vehicle type, dangerous goods class, the telephone number, an accident report, a fire warning and the number of vehicle occupants can be transmitted with the emergency call.
A disadvantage of this system, however, is that, in the event of a collision, the emergency call device can become damaged and is therefore sometimes inoperable.
This means that the emergency call can no longer be transmitted.
The object of the invention is therefore to specify an emergency call system which avoids this disadvantage and ensures that the emergency call is transmitted reliably.
A further object of the invention is to specify a method for automatically transmitting an emergency call from a motor vehicle to a receiving station.
The former object is achieved in an emergency call system of generic type in that the emergency call system contains means for determining a probability level for an imminent accident using the signals from the signal generator, and the emergency call can be activated if a limit value for the probability level is exceeded.
In particular, the emergency call system contains, as the signal generator, measuring means connected to the arithmetic and logic unit for determining the relative speed and the distance of the motor vehicle in relation to another vehicle or an obstacle, in which case the arithmetic and logic unit can perform a comparison between the relative speed determined using the measuring means and a maximum permissible value for the relative speed at the measured distance, and the emergency call can be activated if the maximum permissible relative speed for a given distance is exceeded.
The emergency call can thus be activated even before an accident or a collision between the motor vehicle and another vehicle or an obstacle.
The method according to the invention is distinguished in that the distance and the relative speed of the motor vehicle in relation to another vehicle or an obstacle are ascertained, the relative speed ascertained is compared with a defined, maximum permissible relative speed for the distance ascertained, and an emergency call is triggered if the particular relative speed of the motor vehicle exceeds the defined, maximum permissible relative speed.
