Electrical transmission or interconnection systems – Vehicle mounted systems – Automobile
Reexamination Certificate
2000-02-25
2002-09-17
Sircus, Brian (Department: 2836)
Electrical transmission or interconnection systems
Vehicle mounted systems
Automobile
C280S785000, C701S045000
Reexamination Certificate
active
06452288
ABSTRACT:
BACKGROUND OF THE INVENTION:
Field of the Invention:
The invention lies in the automotive technology field. More specifically, the invention relates to a device for sensing an object or a person in the interior of a vehicle. The device is of the type including a laser for emitting laser pulses and an optical receiver for receiving laser pulses which are reflected or diffracted at an object or at a person.
Persons who are displaced far forward in the direction of the dashboard—such as children in so-called rearward facing baby seats on the front-seat passenger seat—are subjected to the hazard, during the operation of a motor vehicle provided with an airbag, of suffering injuries as result of the inflation impact of the airbag in the event of an accident. Modern control systems for personal protection aim at switching off the airbag in such situations or inflating it with reduced force and speed in order to avoid the risk of injury to a vehicle occupant. In order to determine the position of the vehicle occupant in the vehicle, use is preferably made of contactless, optical sensors. European published patent application No. 0 669 227 A1 discloses a device for the contactless detection of an object or of a person in the interior of a vehicle. There, the vehicle seat is irradiated by a number of LEDs. The beams which are reflected from the seat or a person or an object on the vehicle seat are registered by a photodetector field.
The light source used for the optical detection system is preferably a laser which permits positionally precise sensing owing to its monochrome radiation. Laser diodes, and in particular semiconductor laser diodes, are usually used as transmitters.
In order to avoid continuous loading of persons in the interior of the vehicle with energy from the laser, the laser is operated in a pulsed fashion. However, even in this mode of operation, the health of the vehicle occupant must not be adversely affected by the emitted laser pulses in any way.
Furthermore, the known device has the disadvantage that the optical receiver receives a reflected laser pulse with a very high energy content if an object is disposed in very close vicinity to the laser and the transmission pulse has a high energy content. Owing to the short distance between the optical detection apparatus and the object, only a small amount of the emitted energy is lost. This effect is amplified if the object has a highly reflective effect. Given such a large absorption of energy by the optical receiver, there is the hazard that the amplifier which is connected downstream may be operated in the saturation region, and precise detection of the object or of the distance between the object and the optical detection apparatus may thus no longer be possible.
SUMMARY OF THE INVENTION:
It is accordingly an object of the invention to provide a device and a method for detecting animate or inanimate objects in the vehicle interior, which overcomes the above-mentioned disadvantages of the heretofore-known devices and methods of this general type and which is improved and further developed in such a way that any hazard to persons in the interior owing to the emitted laser radiation can be prevented at any time, and at the same time correct detection data are made available.
With the foregoing and other objects in view there is provided, in accordance with the invention, a device for sensing an object (inanimate object or person) in the interior of a vehicle, comprising:
a laser for emitting laser pulses;
an optical receiver for receiving laser pulses reflected or scattered at an object in an interior of a vehicle;
a control apparatus connected to the laser and to the optical receiver for setting an energy content of a following laser pulse as a function of a characteristic variable of a registered or reflected laser pulse.
In accordance with an added feature of the invention, the control apparatus sets a transmission power of the laser.
In accordance with an additional feature of the invention, the control apparatus sets a pulse length of the laser pulse.
In accordance with yet an additional feature of the invention, the control apparatus sets a pulse length for a predefined laser power and sets a laser power differently from the predefined laser power as soon as a pulse length drops below a predefined limiting value.
In accordance with another feature of the invention, the control apparatus reduces the energy content of the following laser pulse based on a current energy content thereof if the characteristic variable of the reflected laser pulse exceeds an assigned sensitivity limiting value.
In accordance with a further feature of the invention, the control apparatus increases the energy content of the following laser pulse based on a current energy content thereof if the characteristic variable of the reflected laser pulse drops below an assigned sensitivity limiting value.
In accordance with again an added feature of the invention, the control apparatus increases the energy content of the following laser pulse only up to an assigned hazard limiting value.
In accordance with again an additional feature of the invention, the optical receiver includes a plurality of receiver elements connected to interact with the laser, and wherein the control apparatus is adapted to increase or decrease the energy content of the following laser pulse based on the current energy content thereof if the characteristic variable of at least one of the reflected laser pulses registered by the receiver elements drops below or exceeds an assigned limiting value.
In accordance with a concomitant feature of the invention, the characteristic variable is defined as a strength or a power or an energy content of the reflected laser pulse.
With the above and other objects in view there is also provided in accordance with the invention, a method for sensing an object in an interior of a vehicle, and particularly a method for operating the above-outlined device.
The method comprises:
emitting a laser pulse;
registering the reflected laser pulse after reflection at an object; and
determining an energy content of a following laser pulse to be emitted from a characteristic variable of the reflected laser pulse.
In this context, a control apparatus is provided which sets the energy content of a laser pulse as a function of a characteristic variable which is acquired by evaluating a reflected laser pulse. Here, the reflected laser pulse which is received directly before the recent emission of the laser pulse is preferably evaluated. The energy which is output by the laser is thus reduced at all times to an amount which is, on the one hand, sufficient to detect an object or a person to an adequately defined degree, but on the other hand avoids any hazard to vehicle occupants. The device is thus operated in an optimized way in terms of its detection sensitivity and its radiation loading.
The energy content of an emitted laser pulse is determined via the product of the transmission power and pulse length. The control apparatus which is preferably designed as a microprocessor or else as a circuit with discrete components preferably adjusts either the transmission power of the laser or the pulse length. The transmission power is preferably set by means of an operating current of the laser.
Characteristic variables of a registered, reflected laser pulse are, in particular, its strength/amplitude or its power or its energy content. In such a case, the optical receiver is usually a converter which converts optical signals into electrical signals. Consequently, the control apparatus preferably registers an electrical signal which is supplied by such an optical receiver, and evaluates one or more of the characteristic variables described above.
An advantageous control specification is explained below with reference to the evaluation of the energy content of a registered, reflected laser pulse. The energy content of the reflected laser pulse is determined by the product of the power and pulse length. The control specification provides that, in the event of the
Hamperl Reinhard
Mader Gerhard
Roesl Reinhard
Roth Christoph
Stierle Thomas
DeBeradinis Robert
Siemens Aktiengesellschaft
Sircus Brian
LandOfFree
Method and device for sensing and object or a person in the... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and device for sensing and object or a person in the..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and device for sensing and object or a person in the... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2883282