Security system comprising a self-mixing laser sensor and method of driving such a security system
First Claim
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1. A security system comprising:
- a sensor module (15) comprising at least one laser sensor (10) working with self-mixing interference, the laser sensor having a Rayleigh range;
at least one optical element for focusing light;
a control circuit (30) and security means;
wherein the sensor module (15) comprises means to generate first measurement data which are directly or indirectly related to at least one first velocity component of an object (400, 351, 700) relative to the sensor module (15), and wherein the control circuit (30) comprises means to receive the first measurement data generated by the sensor module (15) and to activate the security means in dependence upon the first measurement data received from the sensor module as soon as the first measurement data exceeds a defined first threshold value;
wherein the laser sensor (10) in combination with the at least one optical element has a focal region (12) between the optical element and the object, and the distance between the focal region (12) and the object is greater than one Rayleigh range.
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Abstract
A security system is described, comprising a sensor module (15) which accommodates a laser sensor (10) working with self-mixing interference. The laser sensor (10) generates measurement data which are related to the velocity of an object such as the body of a human being and, optionally, the distance between the laser sensor (10) and the object. Dependent on the measurement data assembled by the laser sensor (10) and supplied to a control circuit (30) such as an airbag computer, the airbag computer activate security means such as an airbag (35)in order to prevent injuries of the human body. Furthermore, a method of driving such a security system is described.
30 Citations
14 Claims
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1. A security system comprising:
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a sensor module (15) comprising at least one laser sensor (10) working with self-mixing interference, the laser sensor having a Rayleigh range; at least one optical element for focusing light; a control circuit (30) and security means; wherein the sensor module (15) comprises means to generate first measurement data which are directly or indirectly related to at least one first velocity component of an object (400, 351, 700) relative to the sensor module (15), and wherein the control circuit (30) comprises means to receive the first measurement data generated by the sensor module (15) and to activate the security means in dependence upon the first measurement data received from the sensor module as soon as the first measurement data exceeds a defined first threshold value; wherein the laser sensor (10) in combination with the at least one optical element has a focal region (12) between the optical element and the object, and the distance between the focal region (12) and the object is greater than one Rayleigh range. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A method of driving a security system comprising a sensor module (15), wherein the sensor module (15) comprises at least one laser sensor (10) working with self-mixing interference, the security system further comprising at least one optical element for focusing light, a control circuit (30) and security means (35), the laser sensor (10) comprising at least one laser (100) having a laser cavity and at least one detector (200), and wherein the method comprises the steps of:
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generating laser light (7) in the laser cavity, employing the optical element to focus the laser light (7) to a focal region between the optical element and an object, and the distance between the focal region and the object is greater than one Rayleigh range, illuminating the object (400, 361, 700) with the laser light (7), reflecting a part of the laser light (7) by the object (400, 361, 700), interfering of the reflected laser light (8) and the optical wave in the laser cavity, sensing the interference of the reflected laser light (8) and the optical wave in the laser cavity by means of the detector (200), generating first measurement data which are directly or indirectly related to at least a first velocity component of the object (400, 361, 700) by means of the detector (200), receiving the first measurement data by means of the control circuit (30), evaluating the received first measurement data with a defined threshold value by means of the control circuit (30), and activating the security means (35) as soon as the first measurement data exceeds a defined first threshold value.
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Specification