DE102015122440A1 - Laser projection device - Google Patents

Abstract

The invention, which relates to a laser projection device (1), has for its object to provide a laser projection device (1), which allows improved image display while reducing the interference in image reproduction (Speckle). This object is achieved in that at least two first laser diodes (10a), which generate laser light from a first spectral range and at least two second laser diodes (10b), which generate laser light from a second spectral range, are arranged in the light source (2) first combination optics (11) for combining the laser light of the first laser diodes (10a) to form a first laser beam and a second combination optics (13) for combining the laser light of the second laser diodes (10b) to form a second laser beam that a first superimposition means (17) is arranged, which combines the laser light of the first laser beam and the laser light of the second laser beam to form a combined laser beam.

Description

The invention relates to a laser projection device, comprising an image generation unit, an optical module and a projection surface, wherein the image generation unit includes a light source and a means for generating an image to be displayed.

By means of a so-called head-up display, it is known to project information into its field of vision to a user, such as a driver or a pilot. Thus, it is possible for a driver's attention to be directed to what is happening in front of the vehicle when driving a motor vehicle, while he / she can capture the information projected into the field of view.

The displayable information includes the display of operating conditions, such as speed, engine speed, payload, equipment and information of a navigation, radar or target acquisition system. In addition, information about currently applicable route restrictions, such as overtaking bans and speed limits or the current setting of the ACC (Adaptive Cruise Control) and others, can also be displayed in vehicles, for example.

Such head-up displays usually have an image-forming unit which provides the information to be displayed in the form of an image, an optical module which allows the beam path within the head-up display to an exit opening and is also referred to as mirror optics, as well as a projection surface , to display the picture.

It is also known from the prior art to use a laser as light source in the image generation unit, this embodiment of a head-up display being referred to below as a laser projection arrangement.

When using a laser as the light source and a sufficiently coherent illumination of an optically rough object surface to be considered, which has unevenness of the order of magnitude of the wavelength, disturbances in the image reproduction, so-called speckle patterns or light granulations, can be observed. Another term also used for this purpose when using a laser is laser granulation.

These disturbances in the image reproduction are understood to be both individual light spots, also referred to as image noise, as well as occurring interference patterns in the generated image.

To reduce the disturbances in the image reproduction is known from the prior art from US 7796330 B2 a solution with two relatively movable diffusers known.

In the US 7762673 describes a solution which uses an additional optics at the output of the laser to divide the laser beam using optical fibers into two sub-beams, which are temporally and spatially coherent.

From the US 11/378552 is a combination of beams with a difference frequency mixture known to reduce the interference.

The disadvantages of the known prior art are in most unwanted moving parts in the system, as in the above approach with a movable diffuser, the additional use of long optical fibers or additional optical cavities, which leads to a larger size of the units and increases the cost.

The object of the invention is to provide a laser projection device, which allows improved image display while reducing the interference in image reproduction (Speckle).

In addition, the aim is to keep the cost and cost of producing a laser projection device low.

The object is achieved by an article having the features according to claim 1 of the independent claims. Further developments are specified in the dependent claims.

The present invention utilizes multiple groups of laser diodes (LD), with a plurality of laser diodes arranged in each group, for each color spectrum to be generated in the generation of a light beam.

By using a number of n spectrally independent laser diodes in several groups, the disturbances in the image reproduction according to the rule 1 / √n are reduced to a fraction of the original value.

It is intended to combine the laser light of a plurality of laser diodes arranged in a group, which generate laser light from a first spectral range, in a combination optical system to form a first laser beam.

It is advantageous, at least two laser diodes, which laser light from a first Generate spectral range, arrange each group. However, there is no limit to this number. Increasing the number of laser diodes per color spectrum is advantageous because it can further reduce disturbances in image reproduction.

A particular advantage of using a plurality of laser diodes per color spectrum is also that the brightness is increased to a value n times the original brightness, achievable with a laser diode.

Thus, the invention provides a laser projection array with improved image quality.

It is intended to arrange at least two first laser diodes, which generate laser light from a first spectral range, and at least two second laser diodes, which generate laser light from a second spectral range.

The laser light of the first laser diodes and the laser light of the second laser diodes are combined by means of a combination optical system to form a first and a second laser beam. To generate a light beam to be emitted by the light source, the laser light of the first and the second laser beam is combined in a first superimposition means to form a combined laser beam. In one embodiment of the invention, it is provided to output this combined laser beam from the light source.

In an advantageous development, it is provided to produce a further third laser beam, which is provided by means of a plurality of third laser diodes and a further combination optics. This third laser beam is then combined in a second superimposing means with the combined laser beam to form a sum laser beam. In this variant, the sum laser beam thus generated is output from the light source.

The invention provides, for example, within the first laser diodes, which generate laser light from a first spectral range of a red color spectrum, to arrange two or more laser diodes, which generate laser light with different wavelengths within the red color spectrum. This combination of different wavelengths advantageously reduces the disturbances in the image reproduction.

Within the second and third laser diodes, which for example generate laser light from a second and a third spectral range of a green and blue color spectrum, laser diodes with different wavelengths are also arranged within the respective color spectrum. In this case, a further reduction of the disturbances in the image reproduction is achieved.

In a particular embodiment of the invention it is provided that the laser diodes within a group, such as the first laser diodes, have different polarizations. The replacement of different polarizations in one or more groups leads to a further advantageous reduction of the disturbances in the image reproduction according to the rule 1 / √2.

It is intended to arrange a combination optics for combining the laser light of a plurality of laser diodes of a group, which combines the light of the individual laser diodes into a laser beam. This combination optics can be realized for example by volume Brag gratings (VBG). For example, two or more laser beams of similar frequency and polarization can be combined. This combination is particularly advantageous when used in a head-up display.

According to the present invention, it is provided to combine the laser light of at least two groups of laser diodes into a laser beam by means of a combination lens and a superimposition means and to output them as light of the light source of the laser projection device. Alternatively, the laser light of three or more groups of laser diodes can be combined to form a laser beam to be output from the light source of a laser projection device.

In an advantageous embodiment of the invention, it is provided to arrange diodes within the group of the first laser diodes, which generate laser light from the red color spectrum. Within the group of second laser diodes diodes are arranged, which generate laser light from the green color spectrum, and within the group of third laser diodes diodes are arranged, which generate laser light from the blue color spectrum. This assignment is exemplary and can be adapted by a person skilled in the properties of the light source to be met.

Further details, features and advantages of embodiments of the invention will become apparent from the following description of exemplary embodiments with reference to the accompanying drawings. Show it:

1 : A schematic representation of a laser projection device according to the prior art and

2 : a partial representation of the light source according to the invention.

In the 1 is a schematic representation of a laser projection device 1 shown. The laser projection arrangement 1 includes a light source 2 , which may be a laser in a specific embodiment of a laser projection device, as well as a means 3 for generating an image to be displayed.

This agent 3 for generating the image to be displayed may be in the form of a display, on which the image to be displayed is generated. This display can be powered by one of the light source 2 generated light beam are irradiated or illuminated. Alternatively, the image to be displayed on the average 3 exist in digital form and by imprinting the image information on that of the light source 2 generated light beam and a corresponding deflection of the beam in an X-direction and a Y-direction, for example by means of a suitable rotating mirror generated. Here, the representation of the image to be generated is similar to the principle of the cathode ray tube, in which the beam writes the image line by line on a projection surface. The way of generating the image to be displayed with the means 3 is here only exemplified, since this has no significant influence on the present invention.

The light source 2 and the means 3 for generating the image to be displayed are commonly used as an image forming unit 4 or PGU (picture generating unit).

That of the imaging unit 4 generated image is in the laser projection arrangement 1 for example via an optical module 5 , which is also referred to as a so-called mirror system and exemplifies a first and a second mirror 6 deflected, deflected so that the deflected light rays in a fixed region of a projection plane 7 , such as a windshield impact. This defined area is preferably chosen such that it is in the field of vision of a viewer or driver 8th a motor vehicle is located.

Projected in the field of view, the driver takes 8th the virtual image 9 next to the current traffic events true. Since the virtual image 9, as in the 1 shown at a distance in front of the windshield 7 It can be shown to the driver 8th , as shown in the current traffic events, appear.

In the example of 1 is one of the mirrors 6 executed in a concave shape. Through this concave design as well as possibly also arranged in the beam path lenses, which are not shown, it is possible to make an adjustment of the virtual image to be generated in terms of its size, shape and the position of the appearance.

The 2 shows the imaging unit essential to the invention 4 the laser projection arrangement 1 , In this come for each spectral range of the light to be generated (red, green, blue) several spectrally independent laser diodes ( 10a . 10b . 10c ) for use.

These are red laser diodes 10a provided for the emission of light from the red spectral range, while green laser diodes 10b Light from the green and blue laser diodes 10c Emit light from the blue spectral range.

The generated laser light of the red laser diodes 10a , in the 2 are exemplary three red laser diodes 10a each shown with different polarizations, is in a first combination optics 11 for example, by means of a volume Bragg grating (VBG) to a first partial laser beam 12 merged.

In the 2 Also shown is that the light of three green laser diodes 10b each with different polarizations in a second combination optics 13 to a second partial laser beam 14 be merged. The same applies in the example for the light of three blue laser diodes 10c each with different polarizations whose light in a third combination optics 15 to a third partial laser beam 16 is merged.

For generating a sum laser beam 20 , which contains the color spectra red, green and blue, in a first step, the first partial laser beam 12 with the second partial laser beam 14 in a first overlay means 17 to a combined laser beam 18 merged. In a subsequent second step then the combined laser beam 18 with the third part laser beam 16 in a second overlay means 19 to the humming laser beam 20 combined.

Like in the 2 shown are the overlay means 17 and 19 executed and arranged so that the light of the three partial laser beams 12 . 14 and 16 to a common zoom laser beam 20 superimposed.

The sum laser beam generated according to the invention 20 is from the light source 2 the laser projection arrangement 1 issued or provided.

In the example of 2 is shown that the sum laser beam 20 the means 3 for generating the image to be displayed via a mirror arrangement 21 is supplied.

In this mirror arrangement 21 can be used to deflect the sum laser beam 20 For example, so-called microsystems MEMS (micro-electromechanical system) come in the form of micro-mirror actuators used.

In the case of micromirror actuators, a distinction is usually made between so-called microscanners (English: microscanner or scanning micromirror) and area light modulators (SLMs).

In microscanners, the modulation of a beam takes place on a continuously moving individual mirror, wherein the light is guided in a projection over a projection surface, which, for example, the means 3 can be. In area light modulators, the modulation of the light takes place via a matrix of mirrors, the individual mirrors being controlled and deflected accordingly.

Such micromirror actuators allow the light of the strong light source according to the invention 2 so distract that over the means 3 and an optics module 5 a virtual picture 9 on a projection plane 7 , like a windshield, is projected.

The execution of the mirror arrangement 21 as well as the agent 3 is not limited to the embodiments described and can be advantageously adapted by a person skilled in the respective task without affecting the essence of the invention. Each form of tilting mirror can, for example, as a mirror assembly 21 be used.

Thus, by the use of the light source according to the invention 2 in a laser projection arrangement 1 Improved image quality by reducing noise in image reproduction (Speckle). The value of the reduction of the disturbance is dependent on the number n of the light source 2 used laser diodes 10a . 10b . 10c ,

It is possible to achieve a reduction to 1 / √n times the original value of the disturbances in the image reproduction. At the same time, the image brightness is increased to n times the original brightness, assuming the use of only one laser diode 10a . 10b . 10c in the light source 2 ,

LIST OF REFERENCE NUMBERS

1

 Laser projection device

2

 light source

3

 Means for generating the image to be displayed

4

 Image generation unit (PGU)

5

 Optical module / mirror system

6

 mirror

7

 Projection plane / windshield

8th

 Driver / observer / viewer

9

 virtual picture

10a

 Laser diodes (first, red)

10b

 Laser diodes (second, green)

10c

 Laser diodes (third, blue)

11

 first combination optics

12

 first laser beam

13

 second combination optics

14

 second laser beam

15

 third combination optics

16

 third laser beam

17

 first overlay means

18

 combined laser beam

19

 second overlay means

20

 Hum laser beam

21

 Mirror arrangement / microsystem (MEMS)

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 7796330 B2 [0008]
• US 7762673 [0009]
• US 11/378552 [0010]

Claims (6)

Laser projection arrangement ( 1 ) comprising an image forming unit ( 4 ), an optical module ( 5 ) and a projection surface ( 7 ), wherein the image generation unit ( 4 ) a light source ( 2 ) and a means ( 3 ) for generating an image to be displayed, characterized in that in the light source ( 2 ) at least two first laser diodes ( 10a ) which generate laser light from a first spectral range and at least two second laser diodes ( 10b ), which generate laser light from a second spectral range, are arranged such that a first combination optics ( 11 ) for combining the laser light of the first laser diodes ( 10a ) to a first laser beam ( 12 ) and a second combination optics ( 13 ) for combining the laser light of the second laser diodes ( 10b ) to a second laser beam ( 14 ) are arranged such that a first superposition means ( 17 ) is arranged, which the laser light of the first laser beam ( 12 ) and the laser light of the second laser beam ( 14 ) to a combined laser beam ( 18 ) united. Laser projection arrangement ( 1 ) according to claim 1, characterized in that at least two third laser diodes ( 10c ), which generate laser light from a third spectral range, are arranged such that a third combination optic ( 15 ) is arranged, which the laser light of the third laser diode ( 10c ) to a third laser beam ( 16 ) that a second overlay means ( 19 ) is arranged, which the laser light of the combined laser beam ( 18 ) and the laser light of the third laser beam ( 16 ) to a sum laser beam ( 20 ) united. Laser projection arrangement ( 1 ) according to claim 1 or 2, characterized in that within the first laser diode ( 10a ) and / or the second laser diodes ( 10b ) and / or the third laser diode ( 10c ) two laser diodes ( 10a . 10b . 10c )) are arranged with each other within the respective spectral range wavelengths. Laser projection arrangement ( 1 ) according to one of claims 1 to 3, characterized in that within the first laser diode ( 10a ) and / or the second laser diodes ( 10b ) and / or the third laser diode ( 10c ) two laser diodes ( 10a . 10b . 10c ) are arranged with mutually different polarizations. Laser projection arrangement ( 1 ) according to one of claims 1 to 4, characterized in that at the location of the first and / or the second and / or the third combination optics ( 11 . 13 . 15 ) a volume Brag grating (VBG) is arranged. Laser projection arrangement ( 1 ) according to claim 1 or 2, characterized in that within the first laser diode ( 10a ) Laser diodes ( 10a ), which generate laser light from the red color spectrum, within the second laser diode ( 10b ) Laser diodes ( 10b ), which generate laser light from the green color spectrum and within the third laser diode ( 10c ) Laser diodes ( 10c ), which generate laser light from the blue color spectrum, are arranged.

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