Laser sensor module
The invention describes a laser sensor module comprising at least one Vertical Cavity Surface Emitting Laser ( 100 ) and at least one driving circuit ( 120 ). The driving circuit ( 120 ) is adapted to provide electrical energy to the Vertical Cavity Surface Emitting Laser ( 100 ) such that the Vertical Cavity Surface Emitting Laser ( 100 ) emits laser pulses ( 345 ) with a pulse length ( 356 ) of less than 100 ns and a duty cycle of less than 5% in comparison to a continuous laser emission. The driving circuit ( 120 ) is further adapted to provide additional energy to the Vertical Cavity Surface Emitting Laser ( 100 ) at least 100 ns prior to at least a part of the laser pulses ( 345 ) such that the part of the laser pulses ( 345 ) are emitted under defined optical conditions. The invention further describes a distance detection device comprising the laser sensor module and a method of driving the laser sensor module. The additional energy is preferably provided by means of a current pre-pulse ( 335 ) which is applied to the V(E)CSEL prior to preferably each laser pulse ( 345 ). The current pre-pulse is preferably arranged such that no laser light is emitted by means of the V(E)CSEL. The V(E)CSEL are enabled to emit the laser pulses ( 345 ) under defined optical conditions such that the time of emission and the pulse shape of the laser pulses ( 345 ) is well defined. Well defined time of emission and the pulse shape of the laser pulses ( 345 ) enable a reliable detection of reflected laser light ( 117 ) which corresponds to the emission of the respective laser pulse ( 345 ).
1. A laser sensor module comprising:
at least one Vertical Cavity Surface Emitting Laser, the at least one Vertical Cavity Surface Emitting Laser having a laser aperture; and
at least one driving circuit,
wherein the driving circuit is arranged to provide electrical energy to the Vertical Cavity Surface Emitting Laser such that the Vertical Cavity Surface Emitting Laser emits laser pulses,
wherein the laser pulses have a pulse length of less than 100 ns and a duty cycle of less than 5% in comparison to a continuous laser emission,
wherein the driving circuit is arranged to provide additional energy to the Vertical Cavity Surface Emitting Laser at least 100 ns prior to at least a part of the laser pulses such that the part of the laser pulses are emitted under defined optical conditions,
wherein the driving circuit is arranged to provide a pre-current to the Vertical Cavity Surface Emitting Laser in which no laser light is emitted prior to the part of the laser pulses,
wherein the pre-current is arranged such that a smooth temperature profile is established across the laser aperture such that a thermal lens is formed at the laser aperture,
wherein the Vertical Cavity Surface Emitting Laser is arranged to operate in a stable mode.
2. The laser sensor module according to claim 1 , wherein the pre-current comprises at least one current pre-pulse between two subsequent laser pulses.
3. The laser sensor module according to claim 2 , wherein the driving circuit is arranged to provide a time gap ( 354 ) of at least 10 ns between the current pre-pulse and the laser pulse emitted after the current pre-pulse in which the peak current is less than 50% of a laser threshold current of the Vertical Cavity Surface Emitting Laser is provided to the Vertical Cavity Surface Emitting Laser.
4. The laser sensor module according to claim 1 ,
wherein the Vertical Cavity Surface Emitting Laser comprises at least one heat management structure,
wherein the heat management structure is arranged to establish the smooth temperature profile across the laser aperture of the Vertical Cavity Surface Emitting Laser between two subsequent laser pulses,
wherein the heat management structure is arranged to increase heat removal at the rim of the laser aperture in comparison to the center of the laser aperture.
5. The laser sensor module according to claim 1 , wherein the Vertical Cavity Surface Emitting Laser comprises an optical feedback element.
6. The laser sensor module according to claim 1 further comprising an array of Vertical Cavity Surface Emitting Lasers,
wherein the driving circuit is arranged to provide a pre-current to at least a portion of the Vertical Cavity Surface Emitting Lasers of the array,
wherein the pre-current is arranged such that different pre-currents are provided to at least a first and a second Vertical Cavity Surface Emitting Laser of the array.
7. The laser sensor module according to claim 6 further comprising, wherein the pre-current is arranged relative to the position of the Vertical Cavity Surface Emitting Laser within the array.
8. The laser sensor module according to claim 1 further comprising an array of Vertical Cavity Surface Emitting Lasers,
wherein the driving circuit is arranged to provide a current pre-pulse to at least a part of the Vertical Cavity Surface Emitting Lasers of the array,
wherein the current pre-pulse is arranged such that Vertical Cavity Surface Emitting Lasers which are controlled by the driving circuit to emit the laser pulse start lasing within a predefined time period,
wherein the predefined time period is related to a thermal cross talk between neighboring Vertical Cavity Surface Emitting Lasers.
9. A laser sensor module comprising:
at least one Vertical Cavity Surface Emitting Laser, the at least one Vertical Cavity Surface Emitting Laser having a laser aperture; and
at least one driving circuit,
wherein the driving circuit is arranged to provide electrical energy to the Vertical Cavity Surface Emitting Laser such that the Vertical Cavity Surface Emitting Laser emits laser pulses,
wherein the laser pulses have a pulse length of less than 100 ns and a duty cycle of less than 5% in comparison to a continuous laser emission,
wherein the driving circuit is arranged to provide additional energy to the Vertical Cavity Surface Emitting Laser at least 100 ns prior to at least a part of the laser pulses such that the part of the laser pulses are emitted under defined optical conditions,
wherein the driving circuit is arranged to provide a pre-current to the Vertical Cavity Surface Emitting Laser in which no laser light is emitted prior to the part of the laser pulses,
wherein the pre-current is arranged such that a smooth temperature profile is established across the laser aperture such that a thermal lens is formed at the laser aperture,
wherein a temperature difference between a center of the laser aperture and a rim of the laser aperture at the beginning of emission of the part of the laser pulses is at least 2 K.
10. A laser sensor module comprising:
at least one Vertical Cavity Surface Emitting Laser, the at least one Vertical Cavity Surface Emitting Laser having a laser aperture; and
at least one driving circuit,
wherein the driving circuit is arranged to provide electrical energy to the Vertical Cavity Surface Emitting Laser such that the Vertical Cavity Surface Emitting Laser emits laser pulses,
wherein the laser pulses have a pulse length of less than 100 ns and a duty cycle of less than 5% in comparison to a continuous laser emission,
wherein the driving circuit is arranged to provide additional energy to the Vertical Cavity Surface Emitting Laser at least 100 ns prior to at least a part of the laser pulses such that the part of the laser pulses are emitted under defined optical conditions,
wherein the driving circuit is arranged to provide a pre-current to the Vertical Cavity Surface Emitting Laser in which no laser light is emitted prior to the part of the laser pulses,
wherein the pre-current is arranged such that a smooth temperature profile is established across the laser aperture such that a thermal lens is formed at the laser aperture,
wherein the pre-current comprises a constant offset current provided between two laser pulses.
11. A laser sensor module comprising:
at least one Vertical Cavity Surface Emitting Laser, the at least one Vertical Cavity Surface Emitting Laser having a laser aperture; and
at least one driving circuit,
wherein the driving circuit is arranged to provide electrical energy to the Vertical Cavity Surface Emitting Laser such that the Vertical Cavity Surface Emitting Laser emits laser pulses,
wherein the laser pulses have a pulse length of less than 100 ns and a duty cycle of less than 5% in comparison to a continuous laser emission,
wherein the driving circuit is arranged to provide additional energy to the Vertical Cavity Surface Emitting Laser at least 100 ns prior to at least a part of the laser pulses such that the part of the laser pulses are emitted under defined optical conditions,
wherein the driving circuit is arranged to provide a pre-current to the Vertical Cavity Surface Emitting Laser in which no laser light is emitted prior to the part of the laser pulses,
wherein the pre-current is arranged such that a smooth temperature profile is established across the laser aperture such that a thermal lens is formed at the laser aperture,
wherein the pre-current comprises at least one current pre-pulse between two subsequent laser pulses,
wherein the current pre-pulse comprises a maximum current amplitude which is higher than a laser threshold current of the Vertical Cavity Surface Emitting Laser.
12. A distance detection device comprising:
at least one laser sensor module, the at least one laser sensor module comprising:
at least one Vertical Cavity Surface Emitting Laser, the at least one Vertical Cavity Surface Emitting Laser having a laser aperture; and
at least one driving circuit,
wherein the driving circuit is arranged to provide electrical energy to the Vertical Cavity Surface Emitting Laser such that the Vertical Cavity Surface Emitting Laser emits laser pulses,
wherein the laser pulses have a pulse length of less than 100 ns and a duty cycle of less than 5% in comparison to a continuous laser emission,
wherein the driving circuit is arranged to provide additional energy to the Vertical Cavity Surface Emitting Laser at least 100 ns prior to at least a part of the laser pulses such that the part of the laser pulses are emitted under defined optical conditions,
wherein the driving circuit is arranged to provide a pre-current to the Vertical Cavity Surface Emitting Laser in which no laser light is emitted prior to the part of the laser pulses,
wherein the pre-current is arranged such that a smooth temperature profile is established across the laser aperture such that a thermal lens is formed at the laser aperture,
at least one photo-detector, wherein the at least one photo-detector is arranged to receive reflected laser light of at least one laser pulse,
an evaluator,
wherein the evaluator is arranged to identify reflected laser light of a corresponding laser pulse,
wherein the evaluator is arranged to determine a time of flight,
wherein the time of flight is the time between a time of reception of the reflected laser light and a time of emission of the corresponding laser pulse.
13. A method of driving a laser sensor module for time of flight measurements comprising at least one Vertical Cavity Surface Emitting Laser, the method comprising:
providing electrical energy to the Vertical Cavity Surface Emitting Laser such that the Vertical Cavity Surface Emitting Laser emits laser pulses, wherein each pulse has a pulse length of less than 100 ns and a repetition rate of less than 5% in comparison to a continuous laser emission;
providing additional energy by means of a pre-current to the Vertical Cavity Surface Emitting Laser at least 100 ns prior to at least a part of the laser pulses in which no laser light is emitted prior to the part of the laser such that the part of the laser pulses are emitted under defined optical conditions,
arranging the pre-current such that a smooth temperature profile is established across a laser aperture of the Vertical Cavity Surface Emitting Laser such that a thermal lens is formed at the laser aperture,
operating the Vertical Cavity Surface Emitting Laser in a stable mode.
14. The method according to claim 13 , wherein the method further comprises:
determining a first thermal energy generated in the Vertical Cavity Surface Emitting Laser during emission of the laser pulse;
determining the additional energy to be provided;
determining a pulse shape of a pre-current based on the determined additional energy.