Projection device and method for operating a projection device

Patent metadata

Field	Value
Publication number	US-9304323-B2
Application number	US-201314371740-A
Country	US
Kind code	B2
Filing date	Jan 8, 2013
Priority date	Jan 12, 2012
Publication date	Apr 5, 2016
Grant date	Apr 5, 2016

Abstract

A projection device may include at least one first laser device and one second laser device, which is arranged opposite the first laser device. A prism is arranged between the two laser devices, wherein a polarization-dependent mirror device is arranged in the prism in such a manner that the beam of the first laser device is reflected in a direction that extends opposite the direction in which the beam of the second laser device is reflected. The polarization of the beam of the second laser device is then rotated, and the beam is deflected back to the polarization-dependent mirror device. The beam of the second laser device now passes through the mirror device without reflection due to the change in the polarization of the beam of the second laser device, such that two superposed laser beams of different polarization are available at the output of the projection device.

First claim

The invention claimed is:

1. A projection device comprising:
at least one first laser device for emitting a first radiation having a first direction of polarization; and
at least one second laser device for emitting a second radiation having the first direction of polarization;
wherein the first laser device and the second laser device are arranged opposite one another,
wherein the projection device further comprises:
a prism arranged between the first laser device and the second laser device and having a first boundary surface facing the first laser device and a second boundary surface facing the second laser device,
wherein at least one polarization-dependent mirror device is arranged in the prism and is designed in such a way that radiation having the first direction of polarization (s; p) is reflected after impinging on the polarization-dependent mirror device, wherein the polarization-dependent mirror device is arranged between the first laser device and the second laser device in such a way that the first radiation and the second radiation run oppositely to one another after reflection at the polarization-dependent mirror device;
at least one polarization modification device wherein the polarization modification device is designed to modify the direction of polarization of radiation in such a way that it passes through the polarization-dependent mirror device without reflection; and
at least one further mirror device;
wherein the polarization modification device and the further mirror device are arranged in the beam path of the second radiation after a first and before a second impingement on the polarization-dependent mirror device,
wherein the first boundary surface of the prism forms a predefinable angle not equal to 90° with the optical axis of the first laser device and the second boundary surface of the prism runs parallel to the first boundary surface.

2. The projection device as claimed in claim 1 ,
wherein the prism has a third boundary surface, which faces the polarization modification device and the further mirror device, and also a fourth boundary surface which constitutes the output of the projection device.

3. The projection device as claimed in claim 2 ,
wherein a first predefinable plane is defined by the extension direction of the polarization modification device and of the further mirror device,
wherein the third boundary surface runs perpendicularly to the first boundary surface and to the second boundary surface,
wherein the first predefinable plane is chosen in such a way that the second radiation reflected back by the further mirror device enters into the prism at the location at which it emerged from the prism.

4. The projection device as claimed in claim 2 ,
wherein a first predefinable plane is defined by the extension direction of the polarization modification device and of the further mirror device,
wherein a second predefinable plane is defined by the third boundary surface,
wherein the first predefinable plane and the second predefinable plane are chosen in such a way that the second radiation emerging from the prism in the direction of the further mirror device and the second radiation reflected back by the further mirror device run perpendicularly to the optical axis of the first laser device and of the second laser device before entering into the prism.

5. The projection device as claimed in claim 4 ,
the fourth boundary surface runs parallel to the third boundary surface.

6. The projection device as claimed in claim 4 ,
wherein the exit surface angle of the prism on the side of the third boundary surface and/or on the side of the fourth boundary surface is between 2° and 3°.

7. The projection device as claimed in claim 1 ,
wherein the absolute value of the difference between the predefinable angle and 90° is between 0.1° and 1.5°.

8. The projection device as claimed in claim 1 ,
wherein the polarization modification device is designed in such a way that the second radiation, after passing through the polarization modification device at least twice is polarized in such a way that it passes through the polarization-dependent mirror device without reflection.

9. The projection device as claimed in claim 1 ,
wherein the polarization-dependent mirror device is arranged in such a way that the second radiation, after first passage through the polarization modification device is specularly reflected at the further mirror device, subsequently passes through the polarization modification device a second time and, after the second passage, impinges on the polarization-dependent mirror device a second time.

10. The projection device as claimed in claim 1 ,
wherein the polarization modification device is an n*lambda/4 plate, wherein n is odd.

11. The projection device as claimed in claim 1 ,
wherein the second radiation, before it impinges on the polarization-dependent mirror device the second time, has a direction of polarization which is perpendicular to the first direction of polarization.

12. The projection device as claimed in claim 11 ,
wherein the first direction of polarization is an s-polarization.

13. The projection device as claimed in claim 11 ,
wherein the second radiation is p-polarized before it impinges on the polarization-dependent mirror device the second time.

14. The projection device as claimed in claim 11 ,
wherein the first direction of polarization is a p-polarization.

15. The projection device as claimed in claim 11 ,
wherein the second radiation is s-polarized before it impinges on the polarization-dependent mirror device the second time.

16. The projection device as claimed in claim 1 ,
wherein the projection device comprises:
n first laser devices, where nεN;
n second laser devices where nεN;
wherein the respective i-th first laser device is arranged opposite the respective i-th second laser device, where i=1 to n.

17. The projection device as claimed in claim 16 ,
an i-th polarization-dependent mirror device is arranged between the i-th first laser device and the i-th second laser device, where i=1 to n.

18. The projection device as claimed in claim 16 ,
wherein the i-th first laser device and the i-th second laser device are designed to emit radiation in an i-th wavelength range, where i=1 to n.

19. The projection device as claimed in claim 18 ,
wherein n=3, wherein the first wavelength range lies in the red spectrum, the second wavelength range lies in the green spectrum and the third wavelength range lies in the blue spectrum.

20. The projection device as claimed in claim 1 ,
wherein an optical device is arranged between the respective laser device and the assigned polarization-dependent mirror device.

21. A method for operating a projection device comprising at least one first laser device for emitting a first radiation having a first direction of polarization and at least one second laser device for emitting a second radiation having the first direction of polarization,
the method comprising:
providing a prism having at least one polarization-dependent mirror device which is designed to reflect radiation having the first direction of polarization;
arranging the polarization-dependent mirror device between the first laser device and the second laser device in such a way that the first radiation and the second radiation run oppositely to one another after reflection at the polarization-dependent mirror device;
modifying the direction of polarization of the second radiat

Assignees

• Osram Gmbh

Inventors

• Khrushchev Sergey

Classifications

• G02B27/283 Primary

  used for beam splitting or combining · CPC title

• G02B30/25 Primary

  using polarisation techniques · CPC title

• G02B5/3083

  Birefringent or phase retarding elements (G02B5/3008, G02B5/3016 take precedence; systems for polarisation control G02B27/286; manufacturing phase modulating patterns by lithographic processes G03F7/001) · CPC title

• G03B21/2033

  LED or laser light sources · CPC title

• H04N9/3167

  for polarizing the light beam (polarizing optical systems per se G02B27/28) · CPC title