CA2429420A1 - Laser transmitter - Google Patents
Laser transmitter Download PDFInfo
- Publication number
- CA2429420A1 CA2429420A1 CA002429420A CA2429420A CA2429420A1 CA 2429420 A1 CA2429420 A1 CA 2429420A1 CA 002429420 A CA002429420 A CA 002429420A CA 2429420 A CA2429420 A CA 2429420A CA 2429420 A1 CA2429420 A1 CA 2429420A1
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- Prior art keywords
- laser
- intensity
- transmitter
- profile
- laser beam
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/02—Structural details or components not essential to laser action
- H01S5/022—Mountings; Housings
- H01S5/0225—Out-coupling of light
- H01S5/02253—Out-coupling of light using lenses
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/005—Optical components external to the laser cavity, specially adapted therefor, e.g. for homogenisation or merging of the beams or for manipulating laser pulses, e.g. pulse shaping
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- Physics & Mathematics (AREA)
- Condensed Matter Physics & Semiconductors (AREA)
- General Physics & Mathematics (AREA)
- Electromagnetism (AREA)
- Optics & Photonics (AREA)
- Optical Communication System (AREA)
Abstract
The invention relates to a laser emitter, in particular, for free space data transmission and/or weapon simulators, comprising a laser diode (11), generating a laser beam (10) from laser impulses and an emitter lens (13), arranged after the laser diode (11) in the beam path, for influencing the beam profile (15) and the intensity distribution in the beam profile (15). In order to achieve a high range with an effective area (16) of the laser beam (10) almost constant over distance, the emitter lens (13) is so arranged that the intensity in the beam profile (15) falls away, as a square of the separation (r), from a spatially limited intensity maximum in the centre of the profile out towards the profile edge.
Description
S T N A T L A S E 1 a k t r o n i k G m b H
Bremen LASER TRANSMITTER
T~chniaal Field The invention relates to a laser transmitter, in particular for free-space data transmission and/or shooting simulation of the type defined in the preamble of claim 1.
When used in shooting simulators, a laser transmitter of this type, installed on the weapon, interacts with a laser receiver installed on the target which, after receipt of a laser beam consisting of a plurality of laser impulses, evaluates the shooting data transmitted with a coding of the laser impulses by means of detectors situated on the target to determine and assess a hit.
The laser beam is thereby collimated circularly by the transmitter optics and controlled in its spatial expansion of the beam profile, the intensity distribution as well as the divergence. Known transmitter optics have classic spherical or aspherical lines which produce a good collimation of the laser beam with a Gaussian intensity distribution in the remote field within the beam profile of the laser beam, whereby the intensity diminishes with increasing range and the diameter of the laser beam increases at first relative to a minimum intensity. As a result of the diameter changing with the range of the laser beam, the effective cross section of the laser beam changes and, from a specif is range, the effective cross section decreases again and, finally, the intensity maximum also falls below the detection threshold of the laser receiver and the maximum range of the laser transmitter is set with that. The effective cross section of the laser beam should be understood to be the intensity limit and is defined by the predetermined sensitivity of the laser receiver receiving the laser beam. It is that area of the beam profile in which the intensity exceeds this intensity limit. Below this limit, the laser impulses of the laser beam reaching the laser receiver are ignored.
The limited maximum range of the laser transmitter can also not be increased by a higher output of the laser diode since the laser transmitter must meet the requirements of laser class 1 to ensure that the eyes are protected, for applications such as free-space data transmission or shooting simulation, and the permissible threshold value of the output is preset by the size of the light source.
Prior Art A known device for emitting a light beam to illuminate a remote target area (DE 693 11 344 72) is used in an optical free-space communication system in which an optical signal is emitted by the device over distances of up to several kilometers. The device has a coherent light source which throws light on a hologram. A lens is placed between the light source and hologram, said lens expanding the light beam or at least partially aligns it parallel before it falls. onto the hologram. The hologram contains a transparent plastic plate on which a replica of the surface relief neutral pattern is made from an original pattern. The pattern itself is protected by a transparent disk. The pattern is a neutral pattern produced by means of a computer which is derived from a mathematical model and composed of repeated lines. Every line pattern is created in such a way that it produces a matrix of beams which together form a combined beam with a preset shape and/or distribution in the remote field. In one embodiment, the neutral pattern is a binary phase pattern in all lines which alternatively delays the phase of the incident light. By changing the phase of the incident light, the direction of expansion is changed, so that multiple beams of light which emerge from the hologram spread within the angle of the combined beam in variably scattered directions, so that a refocussing of the light beam is prevented.
In a known semiconductor light source unit (DE 43 07 570 A1) in which the semiconductor laser generates a laser beam with an elliptical cross-sectional profile, an optical device is provided for obtaining an essentially circular remote field profile, said optical device enlarging the angle of divergence of the laser beam in a direction parallel to the short axis of the elliptical cross-sectional profile. An optical device of this type is, for example, a bar lens or a cylinder lens. The cylinder lens can be simultaneously used to correct the light intensities or intensity distribution of the laser beam. By a suitable design of the cylinder lens, e.g. by forming an additional convex surface, the light intensity extending according to a Gaussian distribution curve with an elliptical profile is changed into an almost bell-shaped intensity distribution in the circular remote field profile, the angular area of divergence being reduced thereby. As a result, the peripheral part of the laser beam can be used effectively to increase the light intensity and thus reduce the light output.
Description of the Invention The object of the invention is to produce a circularly collimated laser beam in a laser transmitter of the aforementioned type which, while adhering to the regulations governing eye protection, has a substantially greater range and an effective cross section which can be adapted to the special application, is approximately constant over the range and can be varied as the customer desires.
According to the invention, the object is solved by the features in claim 1.
The laser transmitter according to the invention has the advantage that the novel intensity distribution in the beam profile of the laser beam produces an effective cross section within spatially definable limits which can be made almost constant and then only varies slightly with the distance from the laser transmitter. The intensity is extremely great in the centre of the beam profile and diminishes greatly toward the edge of the effective cross section, so that the effective cross section within a very large range is independent from the distance. By bundling the laser output on the spatially limited intensity peak in the centre of the beam profile, the range of the laser transmitter can be increased considerably with the increased intensity in the effective cross section of the laser beam. In addition, the alignment of the laser transmitter to the axis of the bore of the weapon or to the aiming telescope securely connected with the weapon can be easily tested, without the expensive adjustment devices used thusfar, with the laser transmitter of the invention, connected with a weapon, e.g. with the weapon of a shooting simulator, and the laser transmitter adjusted in this way after each longer training session, as prescribed. To this end, only the reticle of the aiming telescope must be directed to a laser detector situated at a distance of some hundred meters and the laser transmitter adjusted until the laser detector detects laser light. The laser detector has a very slight sensitivity, i.e. a very high intensity threshold, above which it is only capable of detecting laser impulses. As a result of the sensitivity-dependent intensity distribution in the beam profile of the laser beam, the effective cross section of the laser beam is relatively small with the high intensity threshold of the laser detector, so that only a slight, neglible deviation occurs during adjustment between the reticle and the centre of the effective cross section. The effective cross section of the laser beam should be understood as the intensity limit which is defined by the sensitivity of the laser detector. It is that area of the beam profile in which the intensity exceeds the intensity limit.
Advantageous embodiments of the laser transmitter according to the invention with advantageous improvements and developments of the invention can be found in the further claims.
According to a preferred embodiment of the invention, the variation in intensity in the beam profile approximates the function I(r) - ID (ro / r)2 with r ~ 0, wherein ID is a preset minimum intensity, r the distance from the centre of the beam profile and ro the radius of the effective cross section defined by the minimum intensity ID in the remote field. The minimum intensity is given by the sensitivity of the laser receiver detecting the laser beam and is the intensity limit below which the laser receiver no longer reacts to the laser impulses. When the intensity losses in the laser beam due to absorption in the air are ignored, which is permissible e.g. for a distance of up to 100 - 200 m from the laser transmitter, the noted function can be accurately realized. When taking the absorption losses into account, which is absolutely necessary for larger ranges, the variation in intensity deviates more or less from the noted function. The variation in intensity realized produces a constant effective cross section over a very large range.
According to an advantageous embodiment of the invention, the ' CA 02429420 2003-05-20 transmitter optics have diffractive optical elements with micro-relief surfaces. A miniaturization of the optics is made possible by these optical elements in comparison to a conventional lens system. In particular, the transition to a microstructural technology can be accomplished by means of the laser transmitter of the invention with the optical and electronic components.
According to an advantageous embodiment of the invention, the transmitter optics are designed in such a way that the effective cross section of the laser beam is almost unchanged in the extreme short range in spite of the cross sectionally smaller beam profile, in particular, it does not become smaller than in the remote range.
For this purpose, the transmitter optics are designed in such a way it gives a higher divergence to the low-intensity peripheral area of the laser beam than to the remaining area. As a result, the laser beam is expanded in the short range without the expansion in the remote field being noticeable. Divergence or expansion of the laser beam refers to the change of the beam diameter relative to the intensity maximum.
According to an advantageous embodiment of the invention, a holographic diffuser is situated between the laser diode and the transmitter optics. The known holographic diffuser, which largely scatters the laser light produced by the laser diode in direction of the beam and, as a result, has a considerably improved degree of effectiveness compared to conventional diffusers which scatter light in all directions, causes an enlargement of the apparent size of the light source, as a result of which the threshold value of the permissible laser output is fallen below since the unchanged laser output is now distributed on a larger surface. This, in turn, enables the increase in the output of the laser diode until the permissible threshold value is again attained, so that the intensity and thus the range of the laser beam also increases with the increased laser output. Since laser diodes having the appropriate output can be obtained on the market, the range of the laser transmitter can be increased above 4000 m. In addition, the effective cross section can also be controlled with the holographic diffuser since the divergence of the laser beam areas that interact with the diffuser, e.g. of the peripheral area of the beam, can be changed.
Brief Description of the Drawings The invention is described in greater detail in the following with reference to an embodiment illustrated in the drawings, showing:
Fig. 1 a schematic side view of a laser transmitter for a shooting simulator, Fig. 2 a diagram of the intensity distribution in the beam profile of the laser beam emitted by the laser transmitter according to Fig. 1.
Methods for Carrying Out the Invention The laser transmitter shown only schematically in Fig. 1 is used, for example, in a shooting simulator and arranged on~the weapon in such a way that a transmission direction runs parallel to the barrel of the weapon. The laser transmitter interacts with a laser receiver installed on the target which has a plurality of light detectors distributed over the target and an electronic evaluation mechanism. When the laser beam consisting of laser impulses transmitted by the laser transmitter is received by the light detectors, the shooting data transmitted by the weapon to the target by means of the coding of the laser impulses are evaluated by the evaluation mechanism to determine and assess the hit.
The laser transmitter has a laser diode 11 with transmitter electronics 12, transmitter optics 13 and a holographic diffuser 14 situated between laser diode 11 and transmitter optics 13. The aforementioned components are combined in a housing 17. The laser diode 11 with the transmitter electronics 12 generates a laser beam composed of laser impulses which is circularly collimated by means of the transmitter optics 13 and controlled in the spatial expansion of the beam profile, the intensity distribution over the beam profile and the divergence. The transmitter optics 13 consist of diffractive elements with a micro-relief surface, by means of which a 3D beam is formed, i.e. also a distance-dependent control of the laser beam 10 in addition to the control of the beam cross section. The holographic diffuser 14 serves to improve the optical properties with respect to homogeneity and cross section of the laser beam 10 and to realize higher ranges.
Preferably, the transmitter optics 13 and holographic diffuser 14 are combined and realized by means of one to three individual optical elements. This enables a reduction in price, a reduction in the structural space, it minimizes the adjustment expenditure and increases the robustness of the laser transmitter, which is desirable, in particular, for military applications.
The known holographic diffuser 14 contains a special microstructure and differs from conventional diffusers by its considerably higher degree of effectiveness which is determined thereby that the laser light is only scattered in the direction of the beam. The diffuser 14 causes an enlargement of the apparent size of the light source formed by the laser diode 11, so that the output of the laser diode 11 is thereby enlarged while maintaining the threshold values for laser class 1 and, as a result, the range of the laser transmitter can be increased. The diffractive elements of the transmitter optics 13 and the diffuser 14 are made of plastic or glass.
However, other substances can also be used for wavelengths beyond the transparency of glass and plastic.
The diffractive elements of the transmitter optics 13 are designed in such a way that there is a spatially limited, extremely large intensity maximum in the centre M of the beam profile 15, which is indicated in Fig. 1, having a steep slope. The intensity distribution over the beam cross section is shown in Fig. 2, wherein the variation in intensity is a function of the intensity dependent on the distance r from the centre M of the beam profile 15. In the embodiment of Fig. 2, the intensity curve of the function I~r) - In fro / r)2. r ~ 0, suffices, wherein ro is the radius of the effective cross section of the laser beam 10 and ID is the intensity limit of the laser receiver. Taking the absorption losses in air into account, the actual variation in intensity of such a curve is merely approximated. Of course, the function does not apply for r=0, since the intensity also assumes a finite value in the centre.
To better illustrate it, the effective cross section 16 of the laser beam 10 is shown turned by 90° in the plane of the drawing in Fig. 2. This effective cross section 16 is understood to be the intensity limit which is defined by the previously set sensitivity of the laser receiver on the target interacting with the laser transmitter for shooting simulation. It is that area of the beam profile in which the intensity exceeds the intensity limit. The laser receiver is thereby designed in such a way that the laser impulses of the laser beam 10 reaching the laser receiver below this intensity limit, indicated by ID in Fig. 2, are ignored by the laser receiver.
The variation in intensity I over the radius r of the beam cross section is shown in Fig. 2. As can be readily seen, the effective cross section 16 of the laser beam 10 is almost independent of the intensity I due to the steep slope, so that the effective cross section 16 does not change, or changes only insignificantly, even with larger ranges. The effective cross section 16 is thus independent of the target distance and more or less constant.
In addition to the increase of the range by the holographic diffuser 14, the described variation in intensity in the beam profile 15 obtained by appropriate design of the transmitter optics 13 also contributes to the range increase since, due to the spatially limited intensity peak in the centre of the beam profile 13 , the laser receiver on the target is acted upon, at the same range and the same transmitter output, with a substantially higher intensity than is the case with a e.g. Gaussian or homogeneous intensity distribution over the beam profile 15.
Furthermore, the diffractive elements of the transmitter optics 13 are designed in such a way that the effective cross section 16 of the laser beam 10 which is almost constant in the remote range also does not appreciably diminish at very small distances from the laser transmitter. To this end, the divergence of the peripheral area of the laser beam 10 vis-a-vis the remainng beam area is enlarged by an appropriate design of the transmitter optics 13, so that an enlarged beam cross section is produced in the short range with the low-intensity peripheral beams which no longer exists in the remote range due to the low intensity of the peripheral beams.
The beam cross section enlarged in the short range also results in an enlarged effective cross section of the laser beam in the short range.
The invention is not restricted to the described embodiment. Thus, by a specific design of the transmitter optics, the almost constant effective cross section of the laser beam, described above, can be changed, i.e. enlarged or reduced, over the entire range of the laser transmitter also within limits and in range sections.
However, the described intensity assessment is thereby maintained in the beam profile.
The use of the described laser transmitter is not only restricted to the described application for shooting simulation in which, in addition to a hit simulation, data regarding the assessment of the hit on the target are also transmitted by means of the laser beam.
The laser transmitter can also be used for pure communication purposes, e.g. for a transmission of any data and information desired over a free space.
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Bremen LASER TRANSMITTER
T~chniaal Field The invention relates to a laser transmitter, in particular for free-space data transmission and/or shooting simulation of the type defined in the preamble of claim 1.
When used in shooting simulators, a laser transmitter of this type, installed on the weapon, interacts with a laser receiver installed on the target which, after receipt of a laser beam consisting of a plurality of laser impulses, evaluates the shooting data transmitted with a coding of the laser impulses by means of detectors situated on the target to determine and assess a hit.
The laser beam is thereby collimated circularly by the transmitter optics and controlled in its spatial expansion of the beam profile, the intensity distribution as well as the divergence. Known transmitter optics have classic spherical or aspherical lines which produce a good collimation of the laser beam with a Gaussian intensity distribution in the remote field within the beam profile of the laser beam, whereby the intensity diminishes with increasing range and the diameter of the laser beam increases at first relative to a minimum intensity. As a result of the diameter changing with the range of the laser beam, the effective cross section of the laser beam changes and, from a specif is range, the effective cross section decreases again and, finally, the intensity maximum also falls below the detection threshold of the laser receiver and the maximum range of the laser transmitter is set with that. The effective cross section of the laser beam should be understood to be the intensity limit and is defined by the predetermined sensitivity of the laser receiver receiving the laser beam. It is that area of the beam profile in which the intensity exceeds this intensity limit. Below this limit, the laser impulses of the laser beam reaching the laser receiver are ignored.
The limited maximum range of the laser transmitter can also not be increased by a higher output of the laser diode since the laser transmitter must meet the requirements of laser class 1 to ensure that the eyes are protected, for applications such as free-space data transmission or shooting simulation, and the permissible threshold value of the output is preset by the size of the light source.
Prior Art A known device for emitting a light beam to illuminate a remote target area (DE 693 11 344 72) is used in an optical free-space communication system in which an optical signal is emitted by the device over distances of up to several kilometers. The device has a coherent light source which throws light on a hologram. A lens is placed between the light source and hologram, said lens expanding the light beam or at least partially aligns it parallel before it falls. onto the hologram. The hologram contains a transparent plastic plate on which a replica of the surface relief neutral pattern is made from an original pattern. The pattern itself is protected by a transparent disk. The pattern is a neutral pattern produced by means of a computer which is derived from a mathematical model and composed of repeated lines. Every line pattern is created in such a way that it produces a matrix of beams which together form a combined beam with a preset shape and/or distribution in the remote field. In one embodiment, the neutral pattern is a binary phase pattern in all lines which alternatively delays the phase of the incident light. By changing the phase of the incident light, the direction of expansion is changed, so that multiple beams of light which emerge from the hologram spread within the angle of the combined beam in variably scattered directions, so that a refocussing of the light beam is prevented.
In a known semiconductor light source unit (DE 43 07 570 A1) in which the semiconductor laser generates a laser beam with an elliptical cross-sectional profile, an optical device is provided for obtaining an essentially circular remote field profile, said optical device enlarging the angle of divergence of the laser beam in a direction parallel to the short axis of the elliptical cross-sectional profile. An optical device of this type is, for example, a bar lens or a cylinder lens. The cylinder lens can be simultaneously used to correct the light intensities or intensity distribution of the laser beam. By a suitable design of the cylinder lens, e.g. by forming an additional convex surface, the light intensity extending according to a Gaussian distribution curve with an elliptical profile is changed into an almost bell-shaped intensity distribution in the circular remote field profile, the angular area of divergence being reduced thereby. As a result, the peripheral part of the laser beam can be used effectively to increase the light intensity and thus reduce the light output.
Description of the Invention The object of the invention is to produce a circularly collimated laser beam in a laser transmitter of the aforementioned type which, while adhering to the regulations governing eye protection, has a substantially greater range and an effective cross section which can be adapted to the special application, is approximately constant over the range and can be varied as the customer desires.
According to the invention, the object is solved by the features in claim 1.
The laser transmitter according to the invention has the advantage that the novel intensity distribution in the beam profile of the laser beam produces an effective cross section within spatially definable limits which can be made almost constant and then only varies slightly with the distance from the laser transmitter. The intensity is extremely great in the centre of the beam profile and diminishes greatly toward the edge of the effective cross section, so that the effective cross section within a very large range is independent from the distance. By bundling the laser output on the spatially limited intensity peak in the centre of the beam profile, the range of the laser transmitter can be increased considerably with the increased intensity in the effective cross section of the laser beam. In addition, the alignment of the laser transmitter to the axis of the bore of the weapon or to the aiming telescope securely connected with the weapon can be easily tested, without the expensive adjustment devices used thusfar, with the laser transmitter of the invention, connected with a weapon, e.g. with the weapon of a shooting simulator, and the laser transmitter adjusted in this way after each longer training session, as prescribed. To this end, only the reticle of the aiming telescope must be directed to a laser detector situated at a distance of some hundred meters and the laser transmitter adjusted until the laser detector detects laser light. The laser detector has a very slight sensitivity, i.e. a very high intensity threshold, above which it is only capable of detecting laser impulses. As a result of the sensitivity-dependent intensity distribution in the beam profile of the laser beam, the effective cross section of the laser beam is relatively small with the high intensity threshold of the laser detector, so that only a slight, neglible deviation occurs during adjustment between the reticle and the centre of the effective cross section. The effective cross section of the laser beam should be understood as the intensity limit which is defined by the sensitivity of the laser detector. It is that area of the beam profile in which the intensity exceeds the intensity limit.
Advantageous embodiments of the laser transmitter according to the invention with advantageous improvements and developments of the invention can be found in the further claims.
According to a preferred embodiment of the invention, the variation in intensity in the beam profile approximates the function I(r) - ID (ro / r)2 with r ~ 0, wherein ID is a preset minimum intensity, r the distance from the centre of the beam profile and ro the radius of the effective cross section defined by the minimum intensity ID in the remote field. The minimum intensity is given by the sensitivity of the laser receiver detecting the laser beam and is the intensity limit below which the laser receiver no longer reacts to the laser impulses. When the intensity losses in the laser beam due to absorption in the air are ignored, which is permissible e.g. for a distance of up to 100 - 200 m from the laser transmitter, the noted function can be accurately realized. When taking the absorption losses into account, which is absolutely necessary for larger ranges, the variation in intensity deviates more or less from the noted function. The variation in intensity realized produces a constant effective cross section over a very large range.
According to an advantageous embodiment of the invention, the ' CA 02429420 2003-05-20 transmitter optics have diffractive optical elements with micro-relief surfaces. A miniaturization of the optics is made possible by these optical elements in comparison to a conventional lens system. In particular, the transition to a microstructural technology can be accomplished by means of the laser transmitter of the invention with the optical and electronic components.
According to an advantageous embodiment of the invention, the transmitter optics are designed in such a way that the effective cross section of the laser beam is almost unchanged in the extreme short range in spite of the cross sectionally smaller beam profile, in particular, it does not become smaller than in the remote range.
For this purpose, the transmitter optics are designed in such a way it gives a higher divergence to the low-intensity peripheral area of the laser beam than to the remaining area. As a result, the laser beam is expanded in the short range without the expansion in the remote field being noticeable. Divergence or expansion of the laser beam refers to the change of the beam diameter relative to the intensity maximum.
According to an advantageous embodiment of the invention, a holographic diffuser is situated between the laser diode and the transmitter optics. The known holographic diffuser, which largely scatters the laser light produced by the laser diode in direction of the beam and, as a result, has a considerably improved degree of effectiveness compared to conventional diffusers which scatter light in all directions, causes an enlargement of the apparent size of the light source, as a result of which the threshold value of the permissible laser output is fallen below since the unchanged laser output is now distributed on a larger surface. This, in turn, enables the increase in the output of the laser diode until the permissible threshold value is again attained, so that the intensity and thus the range of the laser beam also increases with the increased laser output. Since laser diodes having the appropriate output can be obtained on the market, the range of the laser transmitter can be increased above 4000 m. In addition, the effective cross section can also be controlled with the holographic diffuser since the divergence of the laser beam areas that interact with the diffuser, e.g. of the peripheral area of the beam, can be changed.
Brief Description of the Drawings The invention is described in greater detail in the following with reference to an embodiment illustrated in the drawings, showing:
Fig. 1 a schematic side view of a laser transmitter for a shooting simulator, Fig. 2 a diagram of the intensity distribution in the beam profile of the laser beam emitted by the laser transmitter according to Fig. 1.
Methods for Carrying Out the Invention The laser transmitter shown only schematically in Fig. 1 is used, for example, in a shooting simulator and arranged on~the weapon in such a way that a transmission direction runs parallel to the barrel of the weapon. The laser transmitter interacts with a laser receiver installed on the target which has a plurality of light detectors distributed over the target and an electronic evaluation mechanism. When the laser beam consisting of laser impulses transmitted by the laser transmitter is received by the light detectors, the shooting data transmitted by the weapon to the target by means of the coding of the laser impulses are evaluated by the evaluation mechanism to determine and assess the hit.
The laser transmitter has a laser diode 11 with transmitter electronics 12, transmitter optics 13 and a holographic diffuser 14 situated between laser diode 11 and transmitter optics 13. The aforementioned components are combined in a housing 17. The laser diode 11 with the transmitter electronics 12 generates a laser beam composed of laser impulses which is circularly collimated by means of the transmitter optics 13 and controlled in the spatial expansion of the beam profile, the intensity distribution over the beam profile and the divergence. The transmitter optics 13 consist of diffractive elements with a micro-relief surface, by means of which a 3D beam is formed, i.e. also a distance-dependent control of the laser beam 10 in addition to the control of the beam cross section. The holographic diffuser 14 serves to improve the optical properties with respect to homogeneity and cross section of the laser beam 10 and to realize higher ranges.
Preferably, the transmitter optics 13 and holographic diffuser 14 are combined and realized by means of one to three individual optical elements. This enables a reduction in price, a reduction in the structural space, it minimizes the adjustment expenditure and increases the robustness of the laser transmitter, which is desirable, in particular, for military applications.
The known holographic diffuser 14 contains a special microstructure and differs from conventional diffusers by its considerably higher degree of effectiveness which is determined thereby that the laser light is only scattered in the direction of the beam. The diffuser 14 causes an enlargement of the apparent size of the light source formed by the laser diode 11, so that the output of the laser diode 11 is thereby enlarged while maintaining the threshold values for laser class 1 and, as a result, the range of the laser transmitter can be increased. The diffractive elements of the transmitter optics 13 and the diffuser 14 are made of plastic or glass.
However, other substances can also be used for wavelengths beyond the transparency of glass and plastic.
The diffractive elements of the transmitter optics 13 are designed in such a way that there is a spatially limited, extremely large intensity maximum in the centre M of the beam profile 15, which is indicated in Fig. 1, having a steep slope. The intensity distribution over the beam cross section is shown in Fig. 2, wherein the variation in intensity is a function of the intensity dependent on the distance r from the centre M of the beam profile 15. In the embodiment of Fig. 2, the intensity curve of the function I~r) - In fro / r)2. r ~ 0, suffices, wherein ro is the radius of the effective cross section of the laser beam 10 and ID is the intensity limit of the laser receiver. Taking the absorption losses in air into account, the actual variation in intensity of such a curve is merely approximated. Of course, the function does not apply for r=0, since the intensity also assumes a finite value in the centre.
To better illustrate it, the effective cross section 16 of the laser beam 10 is shown turned by 90° in the plane of the drawing in Fig. 2. This effective cross section 16 is understood to be the intensity limit which is defined by the previously set sensitivity of the laser receiver on the target interacting with the laser transmitter for shooting simulation. It is that area of the beam profile in which the intensity exceeds the intensity limit. The laser receiver is thereby designed in such a way that the laser impulses of the laser beam 10 reaching the laser receiver below this intensity limit, indicated by ID in Fig. 2, are ignored by the laser receiver.
The variation in intensity I over the radius r of the beam cross section is shown in Fig. 2. As can be readily seen, the effective cross section 16 of the laser beam 10 is almost independent of the intensity I due to the steep slope, so that the effective cross section 16 does not change, or changes only insignificantly, even with larger ranges. The effective cross section 16 is thus independent of the target distance and more or less constant.
In addition to the increase of the range by the holographic diffuser 14, the described variation in intensity in the beam profile 15 obtained by appropriate design of the transmitter optics 13 also contributes to the range increase since, due to the spatially limited intensity peak in the centre of the beam profile 13 , the laser receiver on the target is acted upon, at the same range and the same transmitter output, with a substantially higher intensity than is the case with a e.g. Gaussian or homogeneous intensity distribution over the beam profile 15.
Furthermore, the diffractive elements of the transmitter optics 13 are designed in such a way that the effective cross section 16 of the laser beam 10 which is almost constant in the remote range also does not appreciably diminish at very small distances from the laser transmitter. To this end, the divergence of the peripheral area of the laser beam 10 vis-a-vis the remainng beam area is enlarged by an appropriate design of the transmitter optics 13, so that an enlarged beam cross section is produced in the short range with the low-intensity peripheral beams which no longer exists in the remote range due to the low intensity of the peripheral beams.
The beam cross section enlarged in the short range also results in an enlarged effective cross section of the laser beam in the short range.
The invention is not restricted to the described embodiment. Thus, by a specific design of the transmitter optics, the almost constant effective cross section of the laser beam, described above, can be changed, i.e. enlarged or reduced, over the entire range of the laser transmitter also within limits and in range sections.
However, the described intensity assessment is thereby maintained in the beam profile.
The use of the described laser transmitter is not only restricted to the described application for shooting simulation in which, in addition to a hit simulation, data regarding the assessment of the hit on the target are also transmitted by means of the laser beam.
The laser transmitter can also be used for pure communication purposes, e.g. for a transmission of any data and information desired over a free space.
_.._.. .-.__._._ _..._._..__._.._ __._._.~_~ _~_...__..
Claims (5)
1. A laser transmitter, in particular for free-space data transmission and/or shooting simulation, having a laser diode (11) generating a laser beam (10) from laser impulses and transmitter optics (13) inserted behind the laser diode (11) in the beam path to control the beam profile (15) and the intensity distribution in the beam profile of the laser beam (10), characterized in that the transmitter optics (13) are designed such that the intensity in the beam profile (15) drops from a spatially limited intensity maximum in the centre of the profile to the periphery of the profile approximately with the reciprocal value of the square of the distance (r) from the centre of the beam profile (M) and in that the spatial limit of the intensity maximum is determined by an effective cross section (16) of the laser beam (10) in which the intensity exceeds a minimum intensity (I D) which is preset by the sensitivity of a laser receiver detecting the laser beam (10) in the remote range.
2. The laser transmitter according to claim 1, characterized in that the variation in intensity in the beam profile approximates the function 1(r) = I D (r o / r)2 with r ~ 0, wherein ID is the preset minimum intensity, r the distance from the centre of the beam profile (M) and r o the radius of the effective cross section defined the remote range.
3. The laser transmitter according to claim 1 or 2, characterized in that the transmitter optics (13) have diffractive elements with micro-relief surfaces.
4. The laser transmitter according to claim 4 [sic], characterized in that the transmitter optics (13) are designed in such a way that the low-intensity peripheral area of the laser beam (10) has a divergence that is enlarged in such a way compared to the remaining area that the effective cross section (16) of the laser beam (10) is more or less unchanged in the extreme short range.
5. The laser transmitter according to any one of claims 1 to 4, characterized in that a holographic diffuser (14) is situated between the laser diode (11) and the transmitter optics (13).
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE10057666.4 | 2000-11-21 | ||
| DE10057666A DE10057666A1 (en) | 2000-11-21 | 2000-11-21 | laser transmitter |
| PCT/EP2001/011109 WO2002043196A2 (en) | 2000-11-21 | 2001-09-26 | Laser emitter |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2429420A1 true CA2429420A1 (en) | 2002-05-30 |
Family
ID=7664061
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002429420A Abandoned CA2429420A1 (en) | 2000-11-21 | 2001-09-26 | Laser transmitter |
Country Status (5)
| Country | Link |
|---|---|
| EP (1) | EP1350288A2 (en) |
| AU (1) | AU2002213962A1 (en) |
| CA (1) | CA2429420A1 (en) |
| DE (1) | DE10057666A1 (en) |
| WO (1) | WO2002043196A2 (en) |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0429243A3 (en) * | 1989-11-17 | 1991-12-27 | Minnesota Mining And Manufacturing Company | Beam shaping system using diffraction |
| US5245619A (en) * | 1992-01-03 | 1993-09-14 | Kronberg James W | Generation of low-divergence laser beams |
| US5499262A (en) * | 1992-03-18 | 1996-03-12 | Rohm Co., Ltd. | Semiconductor laser light source unit |
| EP0580905A1 (en) * | 1992-07-28 | 1994-02-02 | BRITISH TELECOMMUNICATIONS public limited company | Optical radiation devices |
| DE19536451A1 (en) * | 1995-09-29 | 1997-04-10 | Siemens Ag | Infrared transmitter |
-
2000
- 2000-11-21 DE DE10057666A patent/DE10057666A1/en not_active Withdrawn
-
2001
- 2001-09-26 CA CA002429420A patent/CA2429420A1/en not_active Abandoned
- 2001-09-26 EP EP01982355A patent/EP1350288A2/en not_active Withdrawn
- 2001-09-26 WO PCT/EP2001/011109 patent/WO2002043196A2/en not_active Application Discontinuation
- 2001-09-26 AU AU2002213962A patent/AU2002213962A1/en not_active Abandoned
Also Published As
| Publication number | Publication date |
|---|---|
| WO2002043196A3 (en) | 2003-07-31 |
| WO2002043196A2 (en) | 2002-05-30 |
| DE10057666A1 (en) | 2002-06-06 |
| EP1350288A2 (en) | 2003-10-08 |
| AU2002213962A1 (en) | 2002-06-03 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Dead |