WO2013007248A1

WO2013007248A1 - Method for mixing light beams of different colors, light beam combining device, and use thereof

Info

Publication number: WO2013007248A1
Application number: PCT/DE2012/100188
Authority: WO
Inventors: Bastian Blase
Original assignee: Technische Universität Berlin
Priority date: 2011-07-13
Filing date: 2012-06-26
Publication date: 2013-01-17
Also published as: DE102011051818A1

Abstract

The invention relates to a method for mixing light beams of different colors using a beam combining device. According to the method, light beams of different colors to be mixed are generated using corresponding light sources and are irradiated as circularly polarized light beams via corresponding light inlet surfaces into a polarizing beam splitter of the beam combining device. Each of the light beams of different colors is split in the polarizing beam splitter into a sub-beam with a first linear polarization and a sub-beam with a second linear polarization that is formed perpendicular to the first linear polarization. The light beams are mixed in the beam splitter in order to form mixed color light such that the mixed color light exiting the beam splitter through a mixed light outlet surface comprises the sub-beam with the first linear polarization and the sub-beam with the second linear polarization for each of the mixed light beams of different colors. Light beams which are generated by the light sources and which are initially not circularly polarized are circularly polarized while passing through an optical functional element in a passage direction towards the beam splitter prior to being irradiated into the beam splitter.

Description

Method for mixing light beams of different colors,

Lichtstrahlkombinier- device and their use

The invention relates to a method for mixing light beams of different colors, a Lichtstrahlokombinier- device and their use.

Background of the invention

By means of color addition, it is possible to produce light of almost any color. Whether LC displays with RGB color pixels or luminescence conversion, in all cases a superimposed impression is created by mixing individual primary colors. Here, there is both the desire to achieve the most authentic color reproduction, as well as to set a desired color temperature. For this purpose, it is necessary to be able to regulate the three basic colors, namely red, green and blue, independently of each other. While temperature radiators such as incandescent lamps can change their color temperature (at the cost of varying the intensity), luminescence radiators are usually fixed in frequency due to fixed energy band gaps. Thermal radiators emit only a few percent of usable light in the visible range. The predominant part is infrared radiation, which is not only unsuitable for the application, but is often also harmful and has to be dissipated with expenditure and further energy requirement or reduced by absorption by cooling.

Light sources with discrete spectra, ie LEDs or lasers, emit only in the desired wavelength range, so that they can be used much more efficiently for color addition. Semiconductor light sources now have the highest efficiency and are also characterized by a comparatively compact design. In addition, unlike gas or solid-state lasers, semiconductor lasers directly convert the input energy into electromagnetic radiation.

White light sources, which consist of thermal radiators, also require significantly greater design effort and installation space in order to accommodate adequate cooling and filter elements. When used in medical technology, this leads to the fact that such light sources are in stationary operating rooms with additional supply lines next to the operating table and that the light pipe must be guided, for example an endoscope. In addition to delivering important space in the surgeon's workspace, however, the fiber optic cable presents an increased holding load on the endoscope for the assistant and restricts its mobility and that of the instrument. There is therefore a need for a space-saving and efficient light source, in particular for a direct arrangement in the endoscope. The proximal placement of a light source in the handle allows use for both rigid and flexible endoscopes since in both cases the light is transported to the tip by optical fibers. Since the cooling options are limited in the instrument, such a solution can only be achieved with efficient light sources. The proximal placement leaves more room for optimal adjustment of the spectrum and allows higher limits for the maximum permissible temperature. However, since suitable materials and elements of luminescent emitters emit only certain discrete wavelengths, the possibility of combining available light sources is limited. In particular, in the illumination of organic surfaces in the abdomen when using known cold and LED light sources to a distorted color rendering of the considered areas, which is considered by the user to be unacceptable.

A constructive obstacle is often the spatially separated placement and orientation of the light sources, since their emitted light power is usually to bundle and rectify. Beam combiners or mixers are available, but usually have the disadvantage that they have a polarizing effect and transmit only one of the two polarization directions of the light as desired. As a result, their efficiency drops to 50%. In addition, the unused beam component must either be dissipated as heat or even unwanted spurious radiation is detrimental to the mixing device. Therefore, most beam combiners can only be used with polarized light, as shown for example in documents WO 85/01590 or US Pat. No. 5,067,799.

Documents WO 85/01590, US Pat. No. 5,067,799, WO 01/02884, US 2006/033837 and WO 2008/095609 describe the use of retardation plates in light beam propagation. One way to change the polarization direction of light is to use so-called retardation plates, λ / 2 half-wave retarders rotate the linear Polarization direction of light at an adjustable angle. λ / 4 quarter wave retardation plates convert linearly polarized into circularly polarized light and vice versa. The essential advantage of the present invention is to be able to use both linearly polarized portions. In order to convert the polarization direction of reflected radiation, the properties of optical isolators are used. For example, linearly polarized light is circularly polarized clockwise as it passes through a λ / 4 plate. When reflected on a mirror behind, it becomes left-handed polarization. After another pass of the λ / 4 plate is again formed linearly polarized light whose field vector is now perpendicular to the original incident light. This arrangement therefore has the same effect as a λ / 2 plate. However, the phase rotation Δφ is reciprocal

2 ^■ %

rok dependent on the wavelength λ of the transmitted light: Αφ = d · Δη.

λ

Therefore, normal retardation plates are only suitable for a certain wavelength. Representations as in US 5,067,799, where two different wavelengths are to undergo the same phase rotation, are misleading.

The document US 2011/0007392 discloses a light combiner for mixing light of different wavelengths by means of a polarizing beam splitter. The beam splitter has a reflector device and a quarter-wave retardation plate. Unpolarized light from LED light sources (LED light emitting diode) enters the beam splitter, is mixed and emerges as mixed light. Similar devices are described in documents WO 2010/059453 A2 and US 2011/0149547 Al.

An illumination system with several LEDs is disclosed in the document US 2009/0040754 AI.

Summary of the invention

The object of the invention is to provide improved technologies for mixing or blending light beams combining different colors of light. This object is achieved by a method for mixing light beams of different colors according to independent claim 1 and a Lichtstrahlkombinier- device according to independent claim 10. Furthermore, a medical instrument according to claim 12 is provided. Finally, according to the independent claim 13, the use of the Lichtstrahlkombinier- device is provided for the spectral light decomposition. Advantageous embodiments are the subject of dependent subclaims.

A method is provided for mixing light beams of different colors by means of a light beam combining device. In the method, light beams of different colors to be mixed with associated light sources are generated and irradiated as circularly polarized light beams via associated light-emitting surfaces in a polarizing beam splitter of the beam combiner. The light beams of different colors are in the polarizing beam splitter each divided into a sub-beam with a first linear polarization and a sub-beam with a second linear polarization, which is formed perpendicular to the first linear polarization. The light beams for forming mixed color light are mixed in the beam splitter, such that the mixed color light leaving the beam splitter through a mixed light exit surface for the mixed light beams of different color comprises the partial beam with the first linear polarization and the partial beam with the second linear polarization. Light beams generated by the light sources and initially not circularly polarized are circularly polarized before being irradiated into the beam splitter when passing through an optical functional element in a direction of passage to the beam splitter. Furthermore, a Lichtstrahlkombinier- device is provided with an optical functional element, a polarizing beam splitter and a plurality of polarizing reflection elements. The optical functional element is disposed in front of the beam splitter and configured to circularly polarize light beams generated by light sources and not circularly polarized in a passage direction to the beam splitter. The polarizing beam splitter is configured via associated light entry surfaces of the beam splitter in these incident and to be mixed light beams of different colors each in a sub-beam with a first linear polarization and a sub-beam with a second linear polarization perpendicular is formed for the first linear polarization, to divide and form of the divided partial beams mixed color light. The plurality of polarizing reflection elements are arranged opposite the beam splitter such that partial beams emerging from the beam splitter during light mixing are reflected back into the beam splitter and in this case the linear polarization is converted from the first into the second linear polarization or vice versa. The beam splitter has a mixed light exit surface, through which emerges the mixed color light formed which, for the mixed light beams of different color, respectively comprises the partial beam with the first linear polarization and the partial beam with the second linear polarization.

By means of the disclosed technologies, it is possible to almost completely incorporate the light provided for light mixing or light mixing combining into the additive color mixing in the mixing or combining process, so that the incident light rays of different color almost completely enter the mixed color light. For the light beams which are circularly polarized before collapsing in the polarizing beam splitter, the mixed light generated comprises in each case the component with the two linearly polarized components, which in turn are generated in the polarizing beam splitter. By controlling the light intensity for the light beams of different colors, the proportions of the color components in the mixed light can be set individually, so that a desired mixed light color can be produced depending on the application.

With the functional element, at least one circularly polarizing functional element is functionally formed, which can also be referred to as a circular polarizer. Circular polarizers can be assigned individually or together to the incident light beams of different colors. In one embodiment, the optical functional elements are arranged opposite different surface regions of the polarizing beam splitter.

In one embodiment, the beam guided in the polarizing beam splitter are all substantially spatially overlapping. It can be provided that the light beams of different color, which are generated with one or more light sources, are guided through an associated collimation optics. Other beam shaping measures may be provided alternatively or additionally.

It may be provided the use of low divergent light sources. For example, laser light sources can be used, which usually emit (partially) polarized light. The proposed technologies allow, in contrast to known structures even with not completely polarized light, to couple the emitted radiation almost completely and to use both polarization states.

In order to simultaneously achieve a high coupling efficiency in an optional downstream optical fiber, the divergence angle of the emitted radiation should not exceed the numerical aperture of the fiber. Unpolarized light sources such as LEDs have emittance angles of partially more than 120 to 150 ° and can therefore only be coupled in to a small extent. The generated radiation can be collimated only conditionally, since the phase space as a product of local and momentum space of the considered light source is substantially larger than that of the fiber. Since, according to the Liouville theorem, the focusability of a light beam is limited, the cross section of the light bundle increases with increasing collimation, thus again exceeding the entrance surface of the fiber.

A preferred embodiment provides that light beams having at least three different colors are irradiated in the beam splitter and mixed / combined. In one embodiment, the light beams of different color are mixed to white light. For example, it can be provided to mix light of red, green and blue color. By means of variation of the color components of the mixture, different white light forms can be produced.

In an expedient embodiment it can be provided that the light beams of different colors are irradiated via spatially separated surface sections of the beam splitter in the polarizing beam splitter. For example, the light beams can be irradiated via different side surfaces. Preferably, a further development provides that, when mixing the light beams of different colors on the optical functional element, partial beams incident on the optical functional element in a direction opposite to the passage direction from the beam splitter are reflected back into the beam splitter at the optical functional element, in which case the first linear polarization of the incident on the optical functional element sub-beam in the second linear polarization or vice versa is converted. In this embodiment, the optical functional elements serve not only the formation of circularly polarized light beams, which are then incident on the polarizing beam splitter, but also the reflection of partial beams that emerge from the beam splitter in the process of light mixing or combination. These beams are reflected back by the functional element in the beam splitter, in which case the linear polarization of the reflected beams is converted. It may be provided in one embodiment to carry out the circular polarization of the incident rays on the one hand and the reflection of emerging from the beam splitter in the light mixture partial beams on the other hand with separate optical functional elements. In this alternative embodiment, circularly polarizing optical functional elements and light-reflecting optical functional elements are then provided.

In an advantageous embodiment it can be provided that the light beams generated by the light sources in the optical functional element in the passage direction an outer λ / 4 plate, a reflection layer for reflecting the incident from the beam splitter on the optical functional element partial beams and an inner λ / 4 Go through plate. The λ / 4 plate is an optical retardation plate which rotates the polarization direction of the transmitted light. The inner λ / 4 plate is preferably an achromatic λ / 4 plate, so that the effect rotating the polarization direction occurs at light of different wavelengths. The reflection layer can be configured as one or more layers. Preferably, it is dichroic, which corresponds to spectral selectivity, in that one part of the light spectrum is reflected and another part of the light spectrum is transmitted. The reflection depends on the wavelength of the incident light. The optical functional element in the embodiment as a layer arrangement or in other embodiments can be arranged directly on associated surfaces of the polarizing beam splitter. Alternatively, between the optimal a functional space and an associated surface of the beam splitter to be formed a gap, for example, an air gap. The outer λ / 4 plate is either narrow-band in terms of the optical effects caused by it to incident light beams, ie the optical effect occurs only in a narrow wavelength range, or broadband.

Achromatic retardation plates, which can preferably be used, form a possibility of overcoming the dependence of the optical effects they imply on the wavelength, since they permit a constant phase shift over a very broad frequency range. Combinations of different birefringent materials such as quartz with magnesium fluoride offer solutions to this problem. The proposed device uses achromatic retardation plates - in contrast to the prior art - to rotate the polarization, which is not possible with normal retarder plates. Combined with a polarizing beam splitter, this makes it possible to use both linearly polarized portions of the light to achieve twice the efficiency of other devices, as well as to use light sources that are not or only partially polarized by nature , This opens up a new spectrum of applications for additive color mixing. By using achromatic retardation plates, for example, the efficiency compared to normal retardation plates can be increased. Achromatic retardation plates allow a constant and identical phase shift of light from multiple light sources in a wide frequency range. This allows the maximum use of both polarization states of several light sources.

A further development can provide that the light beams of different colors in the beam splitter at a polarizing boundary layer are respectively divided into the sub-beam with the first linear polarization and the sub-beam with the second linear polarization. In one embodiment, the polarizing boundary layer is formed in the region of superposed surfaces of two prisms. While a partial beam with the first linear polarization is totally reflected at the interface, the partial beam passes with the second linear polarization. A preferred embodiment provides that

a first-color light beam, which is circularly polarized, is irradiated through a first light-entry surface in the beam splitter,

- The light beam of the first color is divided at a polarizing partial reflection surface of the beam splitter, such that a reflected partial beam of first color with the first linear polarization on a back of the partial reflection surface is reflected to a second polarizing reflection element and a transmitted partial beam of first color with the second linear polarization through the Partial reflection surface passes through to the mixed light exit surface,

- The reflected partial beam of the first color of the second reflection element is reflected back into the beam splitter, in which case the linear polarization is converted from the second to the first linear polarization, and passes from the back of the partial reflection surface therethrough to a third polarizing reflection element and

- The transmitted partial beam of the first color is then reflected by the third reflection element back into the beam splitter, in which case the linear polarization is converted from the first to the second linear polarization, and the transmitted partial beam of first color on the front of the reflection surface is reflected to the mixed light exit surface. In an expedient embodiment can be provided that

a second color light beam, which is circularly polarized, is irradiated through a second light entry surface in the beam splitter,

- The light beam of the second color is divided at the partial reflection surface of the beam splitter, such that a reflected partial beam of the second color is reflected with the first linear polarization on the back of the partial reflection surface to a first polarizing reflection element and a transmitted partial beam of the second color with the second linear polarization through the partial reflection surface passes through to the third reflection element,

- The reflected partial beam of the second color of the first reflection element is reflected back into the beam splitter, in which case the linear polarization of the first to the second linear polarization is converted, and from the back of the partial reflection surface passes through them to the mixed light exit surface and - The transmitted partial beam of the second color of the third reflection element is reflected back into the beam splitter, in which case the linear polarization is converted from the second to the first linear polarization, and the transmitted partial beam of second color is then reflected on the front of the reflection surface to the mixed light exit surface.

An advantageous embodiment provides that

a third color light beam, which is circularly polarized, is irradiated through a third light entrance surface in the beam splitter,

- The light beam of the third color is divided at the partial reflection surface of the beam splitter, such that a reflected partial beam of the third color is reflected with the first linear polarization on the front of the partial reflection surface to the mixed light exit surface and a transmitted partial beam of third color with the second linear polarization through the partial reflection surface gets to the second reflection element,

- The reflected partial beam of the third color of the second reflection element is reflected back into the beam splitter, in which case the linear polarization is converted from the second to the first linear polarization, and is reflected from the back of the partial reflection surface to the first reflection element and

- The reflected partial beam of the third color of the first reflection element is reflected back into the beam splitter, in which case the linear polarization is converted from the first to the second linear polarization, and then passes from the back through the reflection surface to the mixed light exit surface.

In conjunction with the light mixing device, advantageous embodiments can be provided correspondingly to the explanations given.

In one embodiment, the light beams of different colors are irradiated via spatially separated surface sections of the beam splitter in the polarizing beam splitter.

In the medical instrument can be provided to arrange the Lichtstrahlkombinier- device in a handle portion, for example in the grip of an endoscope. The foregoing description explains the process of spectral light mixing. By reversing the physical processes in the Lichtstrahlkombinier- device, this can be used for spectral light decomposition. In this case, mixed color light is irradiated into the polarizing beam splitter, which is there then decomposed, including the external polarization / reflection elements into separate monochromatic light beams of different colors, which in turn can be supplied for use. As a result, a method for the spectral decomposition of mixed color light is then created in separate monochromatic light beams, the beam path of the individual beams / partial beams is just inverse to the process of light mixing. By way of example, white light radiated in through the mixed color light exit surface is decomposed into the components red, green and blue light beam which emerge at the different entrance surfaces of the polarizing beam splitter.

Description of exemplary embodiments

In the following, further embodiments will be explained with reference to figures of a drawing. Hereby show:

1 is a schematic representation of a light mixing or light combining device,

FIG. 2 is a graph showing the spectral delay accuracy of achromatic quarter wave retardation plates (aQWP). FIG.

3 shows a graphic representation of the reflectivity of a dichroic coating with transmission in the long-wave, red region,

4 shows a graph for the reflectivity of a dichroic coating with transmission in the short-wave, blue range,

5 shows a graph for the reflectivity of a dichroic coating with bandpass properties in the green range,

6 is a schematic representation of an endoscope with a distal camera unit (chip-on-the-tip) with a device for mixing light,

7 shows a schematic arrangement of an endoscope with grip-side camera and rod lens system for the optical representation with a device for mixing light,

8 shows a schematic arrangement of an endoscope with grip-side camera and fibers for image guidance for optical imaging with a device for light mixing. Polarizing beam splitters divide electromagnetic radiation into two partial beams whose electric field vector oscillates vertically (s-polarized) and parallel (p-polarized) linearly polarized to the refraction plane. While the parallel polarized partial beam without refraction penetrates and transmits the boundary surface of the beam splitter, the perpendicularly polarized partial beam experiences a total reflection at the interface of the beam splitter, comparable to the beam paths in a Glan-Taylor prism.

In this way, two spatially separated sub-beams with p- and s-polarized E-field vectors can be generated from unpolarized light, which can be used for further applications. For use as a light source, however, this division usually represents a significant disadvantage, since usually only one of the two partial beams is used. By employing polarization, spectrally selective reflection and the property of optical isolators, the present invention enables the use of both partial beams for several spatially separated light sources so as to achieve approximately 100% of the light used for additive color mixing of the individual beams of all light sources.

1 shows a schematic representation of a device with a divider or combiner of light, which is made up of two partial prisms 1 and 2, which are provided with a polarizing boundary layer or surface 3 at their contact surface. The two prisms 1, 2 form a polarizing beam splitter (PBS). At three of the four entrance / exit faces of the PBS is an achromatic quarter wave retardation plate (aQWP) 4a, 4b, 4c which transforms linearly polarized light into circularly polarized light and vice versa. The main advantage over normal quarter wave retarder plates (QWP) is that the retardation of aQWP is wavelength independent for a wide range of wavelengths.

Each of the three aQWPs 4a, 4b, 4c is provided with one or more dichroic layers 5a, 5b, 5c or alternatively dichroic mirrors, which, however, all have different reflection / transmission limit frequencies. What is essential is their ability to reflect and transmit polarization-independent and spectrally selective. Behind each of the three dichroic layers 5a, 5b, 5c, which act as dichroic mirrors are feasible, there is another QWP 6a, 6b, 6c. Behind these outer QWPs 6a, 6b, 6c, a respective light source 7, 8, 9 is arranged, which can be preceded by a respectively suitable parallelizing collimating optics (not shown) for better transmission. The outer QWPs 6a, 6b, 6c are either likewise broadband aQWPs or normal QWPs adapted to their wavelengths when using narrowband light sources such as lasers.

The described function has only such a high transmission of approximately 100%, if the used, but not necessarily identical aQWP 4a, 4b, 4c have a very good delay accuracy. Fig. 2 shows a preferred spectral course of a suitable aQWP, as it is also commercially available. In the case of very narrow-band light sources such as lasers, the outer QWPs 6a, 6b, 6c are preferably adapted directly to them, or suitable aQWPs can be used both for lasers and for broadband light sources. Important are the spectral reflection and transmission properties of the dichroic coatings / dichroic mirrors 5a, 5b, 5c. Depending on the narrow band of the light sources 7, 8, 9 used on the sides 10, 11, 12 of the beam splitter, they are adapted to this. For a red light source 7, a suitable spectral reflection curve is shown in FIG. Its reflection behavior is similar to a spectral lowpass. Fig. 4 shows a suitable course for a blue light source 9. This is similar to a spectral high pass. Finally, FIG. 5 shows an optimum spectral profile of the coating for a green light source 8. The typical course of a bandpass can be achieved either with a single dichroic material or by combining a low and high pass of different cutoff frequency as in FIG. 3 and FIG. In FIGS. 3 to 5, in each case the wavelength λ is plotted along the x-axis.

An essential advantage of the present invention is that it can vary the color temperature and the subjective color impression. Since the three light sources 7, 8, 9 can be controlled individually and their intensities can be variably adjusted, it is possible for the user to adapt a white balance to his own feelings. This property solves a problem Lem, the well-known light sources, especially when used in the endoscopic area, had: the emitted spectrum was often described by users as "cold", the imaged structures were "unnatural". Thanks to the individual adjustment, it is possible with the proposed device to avoid the previously mandatory automatic white balance and to control the color reproduction by directly influencing the light sources. For example, if the intensity of the red light source is increased while reducing the intensity of the blue light source, then a "warmer" hue can be set at a constant radiation power.

The green light beam 8a, shown here generally with two arbitrary proportions of linear p- and s-polarized light, passes through the quarter-wave outer retarder plate (QWP) 6b, which converts the two linearly polarized portions to left and right circularly polarized light. Both portions then pass through a dichroic coating or a dichroic mirror 5 b, which is transparent or transparent to light of the light source used, for longer or shorter wavelengths, however. This is followed by an achromatic quarter-wave retardation plate (aQWP) 4b, which causes both components to undergo another quarter-wave phase rotation, so that the s-polarized component of the beam 8a is now linearly p-polarized and vice versa. The light beam 8b after the components 6b, 5b, 4b thus has the same properties as 8a. The beam 8b enters through the interface 1 1 in the first prism 1 of the polarizing beam splitter and strikes the polarizing boundary layer 3. At this the p-polarized portion in prism 2 is transmitted (beam 8c) and passes through the interface 13 of the Prisma 2 off. The s-polarized portion 8d is reflected at the interface 3 and enters the aQWP 4a after leaving the prism 1, passes through it, is reflected at the dichroic coating or the dichroic mirror 5a, and again passes aQWP 4a in the opposite direction. After leaving aQWP 4a and reentering prism 1, beam 8d has undergone a phase shift of one-quarter wavelength twice, ie a phase shift of π / 2, ie it has only circularly polarized from s-polarized to left or right a phase jump of π and then became circular from right or left to p-polarized. The now p-polarized beam 8e passes through the beam splitter, passes through aQWP 4c, is reflected at the dichroic coating or dichroic mirror 5c and sent back through aQWP 4c. After a double pass of aQWP 4c and a phase rotation of twice a quarter wavelength, the p-polarized beam 8e has been converted to the s-polarized beam 8f. Upon re-entry into prism 2, beam 8f is reflected at the boundary layer 3 and exits as beam 8g through 13 like beam 8c. Both the p- and the s-polarized beam portion of beam 8a have thus been completely transmitted.

The red light beam 7a, also shown with two arbitrary proportions of linear p- and s-polarized light, passes through the quarter-wave outer retarder plate (QWP) 6a, which converts the two linearly polarized portions to right and left circularly polarized light. Both parts then pass through a dichroic coating or a dichroic mirror 5a, which is transparent to light of the light source used, but reflective for shorter wavelengths. This is followed by an achromatic quarter-wave retardation plate (aQWP) 4a, which causes both components to undergo another quarter-wave phase rotation, so that beam 7b has the same properties as beam 7a. Beam 7b enters the first prism 1 of the polarizing beam splitter through the interface 10 and strikes the polarizing boundary layer 3. At this point, the p-polarized component 7d is transmitted into prism 2 and exits from prism 2 through the interface 12. Beam 7d then passes through aQWP 4c, is reflected at 5c and again passes through 4c. In this case, the p-polarized beam 7d undergoes two quarter-wave phase rotations and reenters as s-polarized beam 7f through 12 in FIG. At the interface 3, it is reflected and passes through the prism 2 before leaving through 13. The s-polarized portion 7c is reflected to 3 and enters after exiting prism 1 through the interface 11 in the aQWP 4b, passes through this, is at the reflected dichroic coating 5b and passes aQWP 4b again in the opposite direction. After leaving aQWP 4b and reentering prism 1, beam 7c has undergone a quarter-wavelength phase shift twice, ie a phase shift of π / 2, so that it first polarized circularly from s-polarized to left or right, and a phase shift of π and was then circularly p-polarized from right or left. The now p-polarized beam 7e passes through the beam splitter and exits through 13. Both the p- and the s-polarized beam portion of beam 7a have thus been completely transmitted.

The blue light beam 9a, again represented with two arbitrary proportions of linear p- and s-polarized light, passes through the outer quarter-wave retardation plate (QWP) 6c, which converts the two linearly polarized portions to left and right circularly polarized light. Both parts then pass through 5c, which is transparent to light of the light source used, but reflective for longer wavelengths. This is followed by an achromatic quarter-wave retardation plate (aQWP) 4c, which causes both components to undergo a further quarter-wave phase rotation, so that the s-polarized component of the beam 9a is now linearly p-polarized and vice versa. The light beam 9b is again identical to the beam 9a and enters through the interface 12 in the second prism 2 of the polarizing beam splitter and strikes the polarizing boundary layer 3. At this the s-polarized portion 9c is reflected and passes through the prism interface 13 2 off.

The p-polarized portion 9d is transmitted at the interface 3, passes through prism 1 and enters the aQWP 4a through the surface 10, passes through it, is reflected at the dichroic coating or the dichroic mirror 5a, and traverses aQWP 4a again in the opposite direction. After leaving aQWP 4a and reentering prism 1, beam 9d has undergone a phase shift of one-quarter wavelength twice, ie a phase shift of half a wavelength. Thus, it was first circularly polarized from p-polarized to left or right, and a phase jump of π occurred upon reflection and then became circularly s-polarized from right or left. The now s-polarized beam 9e passes through 1, is reflected at the interface 3, now leaves the prism 1 as a beam 9f through surface 1 1, passes through aQWP 4b, is reflected at the dichroic coating 5b and sent back through aQWP 4b. After a double pass of aQWP 4c and a phase shift of twice a quarter wavelength, the s-polarized beam 9f has been converted to the p-polarized beam 9g. Upon reentry into prism 1 through area 11, beam 9g is transmitted at interface 3 and exits through surface 13 like beam 9c. Both the p- and the s-polarized beam portion of beam 9a have thus been completely transmitted. Not shown but just as suitable are KoUimieroptiken between the light sources 7, 8, 9 and the outer QWP 6a, 6b, 6c to lelisieren the light before entering the device. Also not shown, but just as possible is a focusing optics after the mixed light exit surface 13 to bundle the transmitted light of all light sources, for example, in a narrow optical fiber.

6 shows a schematic representation of an endoscope 60 with a distal camera unit (chip-on-the-tip). In the handle portion 61, a device for light mixing 62 is arranged, as described above with reference to embodiments.

FIG. 7 shows a schematic arrangement of another endoscope 70 with a grip-side camera 71 and a rod lens system 72 for optical imaging. In the grip portion 73 is comparable to the endoscope 60 in Fig. 6, a device for light mixture 62 is formed. Finally, FIG. 8 shows a schematic representation of another endoscope 80 with grip-side camera 81 and fibers 82 for image guidance for optical imaging. The light mixing device 62 is again located in the handle portion 83, that is distal to the light exit of the endoscope 80. The features of the invention disclosed in the foregoing description, claims and drawings may be used alone or in any combination for the purpose of practicing the invention be different in importance.

Claims

claims

A method for mixing light rays of different colors by means of a beam combining device, wherein in the method

Light beams of different colors to be mixed are generated with associated light sources and are irradiated as circularly polarized light beams via assigned light entry surfaces into a polarizing beam splitter of the beam combining device,

the light beams of different colors in the polarizing beam splitter are in each case divided into a partial beam with a first linear polarization and a partial beam with a second linear polarization, which is formed perpendicular to the first linear polarization,

the mixed-light light beams are mixed in the beam splitter such that the mixed color light leaving the beam splitter through the mixed light exit surface for the mixed light beams of different color comprises the first linear polarization sub-beam and the second linear polarization sub-beam,

wherein light rays generated by the light sources and initially not circularly polarized before being irradiated into the beam splitter when passing through an optical function element in a direction of passage to the beam splitter are circularly polarized out.

2. Method according to claim 1, characterized in that light beams having at least three different colors are irradiated and mixed in the beam splitter.

3. The method according to claim 1 or 2, characterized in that the light beams of different colors are irradiated via spatially separated surface sections of the beam splitter in the polarizing beam splitter.

4. The method according to at least one of the preceding claims, characterized in that when mixing the light beams of different colors on the optical functional element partial beams which are incident against the passage direction of the beam splitter away on the optical functional element, at the optical func- Onselement be reflected back into the beam splitter, in which case the first linear polarization of the incident on the optical functional element sub-beam is converted into the second linear polarization or vice versa.

5. The method according to at least one of the preceding claims, characterized in that the light beams generated by the light sources in the optical functional element in the passage direction an outer λ / 4 plate, a reflection layer for reflecting the incident from the beam splitter on the optical functional element partial beams and a go through inner λ / 4 plate.

6. The method according to claim 1, characterized in that the light beams of different colors in the beam splitter at a polarizing boundary layer are respectively divided into the sub-beam with the first linear polarization and the sub-beam with the second linear polarization.

7. The method according to at least one of the preceding claims, characterized in that e e n e c e s e that t

a light beam of first color, which is circularly polarized, is irradiated through a first light entry surface in the beam splitter,

- The transmitted partial beam of the first color is then reflected by the third reflection element back into the beam splitter, in which case the linear polarization of the is converted into the second linear polarization, and the transmitted partial beam of first color on the front side of the reflection surface is reflected to the mixed light exit surface.

Method according to at least one of the preceding claims, characterized in that

- The reflected partial beam of the second color of the first reflection element is reflected back into the beam splitter, in which case the linear polarization is converted from the first to the second linear polarization, and passes from the back of the partial reflection surface through the latter to the mixed light exit surface and

- The transmitted partial beam of the second color of the third reflection element is reflected back into the beam splitter, in which case the linear polarization is converted from the second to the first linear polarization, and the transmitted partial beam of second color is then reflected on the front of the reflection surface to the mixed light exit surface.

Method according to at least one of the preceding claims, characterized in that

a third color light beam, which is circularly polarized, is radiated through a third light entry surface in the beam splitter,

the light beam of the third color is divided at the partial reflection surface of the beam splitter, such that a reflected partial beam of third color is reflected with the first linear polarization on the front side of the partial reflection surface towards the mixed light exit surface and a transmitted third beam partial beam is reflected with the second linear Polarization passes through the partial reflection surface to the second reflection element,

Lichtstrahlkombinier- device, comprising an optical functional element, a polarizing beam splitter and a plurality of polarizing reflection elements, wherein

the optical functional element is arranged upstream of the beam splitter and is configured to circularly polarize light beams, which are generated by light sources and are not circularly polarized, in a direction of passage to the beam splitter,

- The polarizing beam splitter is configured to divide via associated light entry surfaces of the beam splitter in these incident and to be mixed light beams of different colors each in a sub-beam with a first linear polarization and a sub-beam with a second linear polarization, which is formed perpendicular to the first linear polarization, and from the split Partial rays to form mixed color light,

- The plurality of polarizing reflection elements are arranged opposite the beam splitter, such that in the light mixing emerging from the beam splitter partial beams are reflected back into the beam splitter and in this case the linear polarization of the first to the second linear polarization or vice versa is converted, and

- The beam splitter has a mixed light exit surface through which emerges the mixed color light formed, which comprises for each of the mixed light beams of different colors the partial beam with the first linear polarization and the partial beam with the second linear polarization.

11. Lichtstrahlkombinier- device according to claim 10, characterized in that the plurality of reflection elements in the beam path of the incident on the beam splitter light beams of different colors are arranged. 12. Medical instrument, in particular endoscope, with a Lichtstrahlkombinier- device according to claim 10 or 11.

13. Use of the Lichtstrahlkombinier- device according to claim 10 or 11 for the spectral light decomposition.