DE102011051818A1 - A method of mixing light rays of different colors, light beam combining device and their use - Google Patents

Abstract

The invention relates to a method for mixing light beams of different colors by means of a beam combining device, wherein in the method light beams of different colors to be mixed with associated light sources generated and irradiated as circularly polarized light beams via associated light entry surfaces in a polarizing beam splitter of the beam combining, the light beams different Colors in the polarizing beam splitter are each split into a sub-beam having a first linear polarization and a sub-beam having a second linear polarization formed perpendicular to the first linear polarization, and the light beams are mixed to form mixed color light in the beam splitter such that the Beam splitter through a mixed light exit surface leaving mixed color light for the mixed light beams of different colors each sub-beam with the first linear pole Arisierung and the sub-beam with the second linear polarization comprises. The invention further relates to a light beam combining device, a medical instrument and the use of the light beam combining device. (1)

Description

The invention relates to a method for mixing light beams of different colors, a Lichtstrahlkombinier 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 vast majority is infrared radiation, which is not only unsuitable for the application, but is often harmful and must be dissipated with effort and further energy requirements 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 a significantly greater design effort and space to accommodate adequate cooling and filtering 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 to 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 portion must either be dissipated as heat or even unwanted secondary radiation is harmful to the mixing device. Therefore, most beam combiners are usable only with polarized light, which is for example in the documents WO 85/01590 or US 5,067,799 is shown.

In the documents WO 85/01590 . US 5,067,799 . WO 01/02884 . US 2006/033837 and WO 2008/095609 describes 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 retardation plates rotate the linear polarization direction of light by 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 again linearly polarized light, the field vector is now perpendicular to originally incident light stands. This arrangement therefore has the same effect as a λ / 2 plate. However, the phase rotation Δφ is reciprocally dependent on the wavelength λ of the transmitted light: Δφ = 2 · π / λ · D · .DELTA.n.

Therefore, normal retardation plates are only suitable for a certain wavelength. Depictions like in US 5,067,799 where two different wavelengths should experience the same phase rotation are therefore misleading.

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 11. Furthermore, a medical instrument according to claim 13 is provided. Finally, according to independent claim 14, the use of the Lichtstrahlkombinier device for spectral light decomposition is provided. Advantageous embodiments are the subject of dependent subclaims.

• – Lichtstrahlen unterschiedlicher zu mischender Farben mit zugeordneten Lichtquellen erzeugt und als zirkular polarisierte Lichtstrahlen über zugeordnete Lichteintrittsflächen in einem polarisierenden Strahlteiler der Strahlkombiniervorrichtung eingestrahlt werden,
• – die Lichtstrahlen unterschiedlicher Farben in dem polarisierenden Strahlteiler jeweils in einen Teilstrahl mit einer ersten Linearpolarisation und einen Teilstrahl mit einer zweiten Linearpolarisation, die senkrecht zur ersten Linearpolarisation gebildet ist, aufgeteilt werden, und
• – die Lichtstrahlen zum Ausbilden von Mischfarblicht in dem Strahlteiler gemischt werden, derart, dass das den Strahlteiler durch eine Mischlichtaustrittsfläche verlassende Mischfarblicht für die gemischten Lichtstrahlen unterschiedlicher Farbe jeweils den Teilstrahl mit der ersten Linearpolarisation und den Teilstrahl mit der zweiten Linearpolarisation umfasst.

The invention includes the idea of a method for mixing light beams of different colors by means of a Lichtstrahlkombinier device, wherein 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 in a polarizing beam splitter of the beam combiner,
• - The light beams of different colors in the polarizing beam splitter are 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, and
• - The light beams are mixed to form Mischfarblicht in the beam splitter, such that the beam splitter through a mixed light exit surface leaving mixed color light for the mixed light beams of different colors each comprise the partial beam with the first linear polarization and the partial beam with the second linear polarization.

• – einem polarisierenden Strahlteiler, der konfiguriert ist, über zugeordnete Lichteintrittsflächen des Strahlteilers in diesen einfallende und zu mischende Lichtstrahlen unterschiedlicher Farben, die zirkular polarisiert sind, jeweils in einen Teilstrahl mit einer ersten Linearpolarisation und einen Teilstrahl mit einer zweiten Linearpolarisation, die senkrecht zur ersten Linearpolarisation gebildet ist, aufzuteilen und aus den aufgeteilten Teilstrahlen Mischfarblicht zu bilden, und
• – mehreren polarisierenden Reflexionselementen, die dem Strahlteiler gegenüberliegend angeordnet sind, derart, dass beim Lichtmischen aus dem Strahlteiler austretende Teilstrahlen in den Strahlteiler zurück reflektiert werden und hierbei die Linearpolarisation von der ersten in die zweite Linearpolarisation oder umgekehrt gewandelt wird,

wobei der Strahlteiler eine Mischlichtaustrittsfläche aufweist, durch die das gebildete Mischfarblicht austritt, welches für die gemischten Lichtstrahlen unterschiedlicher Farbe jeweils den Teilstrahl mit der ersten Linearpolarisation und den Teilstrahl mit der zweiten Linearpolarisation umfasst.Furthermore, a Lichtstrahlkombinier device is provided with

• - A polarizing beam splitter, which is configured, via associated light entry surfaces of the beam splitter in these incident and to be mixed light beams of different colors, which are circularly polarized, each into a sub-beam with a first linear polarization and a sub-beam with a second linear polarization perpendicular to the first linear polarization is made to divide and form mixed color light from the split part rays, and
• A plurality of polarizing reflection elements, which 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 to the second linear polarization or vice versa,

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

With the aid of the invention, it is possible to include the light provided for combining by light mixing or light almost completely in the additive color mixing in the mixing or combining process, so that the irradiated 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 portion 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 depending on the application, a desired mixed light color can be generated.

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.

A preferred embodiment of the invention 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, can be provided to mix light red, green and blue color. By varying the color components of the mixture, different white light characteristics can be generated.

In an expedient embodiment of the invention 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.

An advantageous embodiment of the invention provides that generated by the light sources and initially not circularly polarized light beams are polarized circularly before being irradiated in the beam splitter when passing through an optical functional element in a direction of passage to the beam splitter. With the functional element is functionally formed at least one circularly polarizing functional element, which can also be referred to as a circular polarizer. The incident light beams of different colors can be assigned individually or jointly to circular polarizers. In one embodiment, the optical functional elements are arranged opposite different surface regions of the polarizing beam splitter.

Preferably, a further development of the invention provides that when mixing the light beams of different colors on the optical functional element partial beams which are incident in a direction opposite to the passage direction of the beam splitter on the optical functional element, are reflected back to the optical functional element in the beam splitter, Here, the first linear polarization of the incident on the optical functional element sub-beam is converted into the second linear polarization or vice versa. In this embodiment, the optical functional elements serve not only the formation of circularly polarized light beams, which then come to 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 still 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 of the invention 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 / Go through 4-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, a gap may be formed between the optical functional element and an associated surface of the beam splitter, for example an air gap. The outer λ / 4 plate is either narrowband with respect to the optical effects caused by it on incident light beams, i. H. 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.

A development of the invention can provide that the light beams of different colors in the beam splitter at a polarizing boundary layer in each case in the sub-beam with the first Linear polarization and split the partial 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.

• – ein Lichtstrahl erster Farbe, der zirkular polarisiert ist, durch eine erste Lichteintrittsfläche in dem Strahlteiler eingestrahlt wird,
• – der Lichtstrahl erster Farbe an einer polarisierenden Teilreflexionsfläche des Strahlteilers geteilt wird, derart, das ein reflektierter Teilstrahl erster Farbe mit der ersten Linearpolarisation auf einer Rückseite der Teilreflexionsfläche zu einem zweiten polarisierenden Reflexionselement reflektiert wird und ein durchgelassener Teilstrahl erster Farbe mit der zweiten Linearpolarisation durch die Teilreflexionsfläche hindurch zu der Mischlichtaustrittsfläche gelangt,
• – der reflektierte Teilstrahl erster Farbe von dem zweiten Reflexionselement in den Strahlteiler zurück reflektiert wird, wobei hierbei die Linearpolarisation von der zweiten in die erste Linearpolarisation gewandelt wird, und von der Rückseite der Teilreflexionsfläche durch diese hindurch zu einem dritten polarisierenden Reflexionselement gelangt und
• – der durchgelassene Teilstrahl erster Farbe dann von dem dritten Reflexionselement zurück in den Strahlteiler reflektiert wird, wobei hierbei die Linearpolarisation von der ersten in die zweite Linearpolarisation gewandelt wird, und der durchgelassene Teilstrahl erster Farbe auf der Vorderseite der Reflexionsfläche zu der Mischlichtaustrittsfläche reflektiert wird.

A preferred development of the invention provides that

• A light beam of first color, 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.

• – ein Lichtstrahl zweiter Farbe, der zirkular polarisiert ist, durch eine zweite Lichteintrittsfläche in dem Strahlteiler eingestrahlt wird,
• – der Lichtstrahl zweiter Farbe an der Teilreflexionsfläche des Strahlteilers geteilt wird, derart, das ein reflektierter Teilstrahl zweiter Farbe mit der ersten Linearpolarisation auf der Rückseite der Teilreflexionsfläche zu einem ersten polarisierenden Reflexionselement reflektiert wird und ein durchgelassener Teilstrahl zweiter Farbe mit der zweiten Linearpolarisation durch die Teilreflexionsfläche hindurch zu dem dritten Reflexionselement gelangt,
• – der reflektierte Teilstrahl zweiter Farbe von dem ersten Reflexionselement in den Strahlteiler zurück reflektiert wird, wobei hierbei die Linearpolarisation von der ersten in die zweite Linearpolarisation gewandelt wird, und von der Rückseite der Teilreflexionsfläche durch diese hindurch zu der Mischlichtaustrittsfläche gelangt und
• – der durchgelassene Teilstrahl zweiter Farbe von dem dritten Reflexionselement zurück in den Strahlteiler reflektiert wird, wobei hierbei die Linearpolarisation von der zweiten in die erste Linearpolarisation gewandelt wird, und der durchgelassene Teilstrahl zweiter Farbe dann auf der Vorderseite der Reflexionsfläche zu der Mischlichtaustrittsfläche reflektiert wird.

In an expedient embodiment of the invention 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 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.

• – ein Lichtstrahl dritter Farbe, der zirkular polarisiert ist, durch eine dritte Lichteintrittsfläche in dem Strahlteiler eingestrahlt wird,
• – der Lichtstrahl dritter Farbe an der Teilreflexionsfläche des Strahlteilers geteilt wird, derart, dass ein reflektierter Teilstrahl dritter Farbe mit der ersten Linearpolarisation auf der Vorderseite der Teilreflexionsfläche zu der Mischlichtaustrittsfläche hin reflektiert wird und ein durchgelassener Teilstrahl dritter Farbe mit der zweiten Linearpolarisation durch die Teilreflexionsfläche hindurch zu dem zweiten Reflexionselement gelangt,
• – der reflektierte Teilstrahl dritter Farbe von dem zweiten Reflexionselement in den Strahlteiler zurück reflektiert wird, wobei hierbei die Linearpolarisation von der zweiten in die erste Linearpolarisation gewandelt wird, und von der Rückseite der Teilreflexionsfläche zu dem ersten Reflexionselement reflektiert wird und
• – der reflektierte Teilstrahl dritter Farbe von dem ersten Reflexionselement zurück in den Strahlteiler reflektiert wird, wobei hierbei die Linearpolarisation von der ersten in die zweite Linearpolarisation gewandelt wird, und dann von der Rückseite durch die Reflexionsfläche hindurch zu der Mischlichtaustrittsfläche gelangt.

An advantageous embodiment of the invention provides 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 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 may be provided according to the foregoing explanations.

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 for spectral light decomposition can be used. 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. For example, white light irradiated via the mixed color light exit surface is split into the components red, green and blue light beam that emerge at the different entrance surfaces of the polarizing beam splitter.

Description of preferred embodiments of the invention

The invention will be explained in more detail below with reference to preferred embodiments with reference to figures of a drawing. Hereby show:

1 a schematic representation of a light mixing or Lichtkombinier device,

2 a graph for the spectral delay accuracy of achromatic quarter-wave retardation plates (aQWP),

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

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

5 a graphic representation of the reflectivity of a dichroic coating with bandpass properties in the green range,

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

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

8th a schematic arrangement of an endoscope with griffseitiger 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. The present invention, through the use of polarization, spectrally selective reflection and the property of optical isolators, allows the use of both partial beams for a plurality of 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 combinator of light, consisting of two partial prisms 1 and 2 constructed with a polarizing boundary layer or surface 3 are provided at their contact surface. The two prisms 1 . 2 form a polarizing beam splitter (PBS). At three of the four entrance / exit surfaces 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 retardation plates (QWP) is that the delay of aQWP is wavelength independent for a wide range of wavelengths.

Each of the three aQWP 4a . 4b . 4c is with one or more dichroic layers 5a . 5b . 5c or alternatively dichroic mirrors, which, however, all have different reflection / transmission marginal 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 are executable as dichroic mirrors, is another QWP 6a . 6b . 6c , Behind this outer QWP 6a . 6b . 6c is each a light source 7 . 8th . 9 arranged, which for better transmission, a respective suitable parallelizing collimating optics (not shown) can be connected upstream. The outer QWP 6a . 6b . 6c are either also broadband aQWP or, when using narrowband light sources such as lasers, matched to their wavelength normal QWP.

The described function has such a high transmission of approximately 100% only if the used, but not necessarily identical aQWP 4a . 4b . 4c have a very good deceleration accuracy. 2 shows a preferred spectral course of a suitable aQWP, as it is also commercially available. For very narrowband light sources such as lasers, the outer QWPs are 6a . 6b . 6c preferably adapted directly to this, or it can, both for laser and for broadband light sources, suitable aQWP can be used.

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 used 7 . 8th . 9 on the pages 10 . 11 . 12 of the beam splitter, they are adapted to this. For a red light source 7 is in

3 a suitable spectral reflection curve is shown. Its reflection behavior is similar to a spectral lowpass. 4 shows a suitable gradient for a blue light source 9 , This is similar to a spectral high pass. In 5 Finally, an optimal spectral profile of the coating for a green light source 8th to recognize. The typical course of a bandpass can either with a single dichroic material or by combining a low and high pass of different cutoff frequency as in 3 and 4 be achieved. In the 3 to 5 along the x-axis in each case the wavelength λ is plotted.

An essential advantage of the present invention is that it can vary the color temperature and the subjective color impression. Because the three light sources 7 . 8th . 9 individually controlled and their intensities can be variably adjusted, it is possible for the user to adjust a white balance to his own senses. This property solves a problem that 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. If, for example, the intensity of the red light source is increased while reducing the intensity of the blue light source, a "warmer" hue can be set with constant radiation power.

Hereinafter, the process of light beam mixing or combination will be described with reference to FIG 1 explained in detail.

The green ray of light 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 components to left and right circularly polarized light. Both parts then pass through a dichroic coating or a dichroic mirror 5b which is transparent to light of the light source used, but reflective for longer or shorter wavelengths. This is followed by an achromatic quarter-wave retardation plate (aQWP) 4b , which causes both components to undergo another quarter-wave phase rotation, such that the s-polarized portion of the beam 8a now linear p-polarized and vice versa. The light beam 8b according to the components 6b . 5b . 4b has the same characteristics as 8a on. The beam 8b passes through the interface 11 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 transmitted (beam 8c ) and passes through the interface 13 from the prism 2 out. The s-polarized portion 8d will be at the interface 3 reflects and enters after leaving prism 1 into the aQWP 4a a, goes through this, becomes at the dichroic coating or the dichroic mirror 5a reflects and goes through aQWP 4a again in the opposite direction.

After leaving aQWP 4a and re-entry into Prisma 1 has beam 8d twice a phase rotation of a quarter wavelength, so experience a phase rotation of π / 2, was thus only polarized s-polarized to the left or right circularly, experienced in the reflection of a phase jump of π and was then from right or left circular to p-polarized , The now p-polarized beam 8e goes through the beam splitter, goes through aQWP 4c , is at the dichroic coating or the dichroic mirror 5c reflected and back through aQWP 4c cleverly. After a double pass of aQWP 4c and a phase rotation of twice a quarter wavelength is the p-polarized beam 8e to the s-polarized beam 8f been converted. Upon re-entry into Prisma 2 will beam 8f at the boundary layer 3 reflects and acts as a beam 8g by 13 like ray 8c out. Both the p- and the s-polarized beam component of beam 8a So they have been completely passed through.

The red ray of light 7a , also shown with two arbitrary proportions of linear p- and s-polarized light, passes through the outer quarter-wave retardation plate (QWP) 6a , which converts the two linearly polarized components to right and left circularly polarized light. Both parts then pass through a dichroic coating or a dichroic mirror 5a which is transparent to the light source used, but reflective to shorter wavelengths. This is followed by an achromatic quarter-wave retardation plate (aQWP) 4a , which lets both shares undergo another quarter wave phase rotation, so that beam 7b the same properties as ray 7a has. beam 7b passes through the interface 10 in the first prism 1 of the polarizing beam splitter and strikes the polarizing boundary layer 3 , At this the p-polarized portion 7d in prism 2 transmits and passes through the interface 12 from prism 2 out. beam 7d then runs through the aQWP 4c , we then 5c reflects and goes through again 4c , The p-polarized beam experiences this 7d two quarter-wave phase rotations and occurs as s-polarized beam 7f by 12 in again 2 one. At the interface 3 it is reflected and goes through before leaving 13 the prism 2 , The s-polarized portion 7c we then 3 reflects and enters after leaving prism 1 through the interface 11 into the aQWP 4b a, goes through this, gets at the dichroic coating 5b reflects and goes through aQWP 4b again in the opposite direction. After leaving aQWP 4b and re-entry into Prisma 1 has beam 7c twice a phase rotation of a quarter wavelength, so experience a phase rotation of π / 2, was thus only polarized s-polarized to the left or right circularly, experienced in the reflection of a phase jump of π and was then from right or left circular to p-polarized , The now p-polarized beam 7e goes through the beam splitter and passes through 13 out. Both the p- and the s-polarized beam component of beam 7a So they have been completely passed through.

The blue ray of light 9a represented again with two arbitrary proportions of linear p and s polarized light, the outer quarter wave retardation plate (QWP) passes through 6c , which converts the two linearly polarized components to left and right circularly polarized light. Both shares then go through 5c which is transparent to 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 another quarter-wave phase rotation so that the s-polarized portion of beam 9a now linear p-polarized and vice versa. The light beam 9b is again identical to ray 9a and passes 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 reflects and passes through the interface 13 from prism 2 out.

The p-polarized portion 9d will be at the interface 3 transmits, goes through prism 1 and enters the area 10 into the aQWP 4a a, goes through this, becomes at the dichroic coating or the dichroic mirror 5a reflects and goes through aQWP 4a again in the opposite direction. After leaving aQWP 4a and re-entry into Prisma 1 has beam 9d twice a phase rotation of a quarter wavelength, so experience a phase rotation of half a wavelength, so was only polarized from p-polarized to left or right circular polarized, experienced a phase shift of π in reflection and was then circularly s-polarized from right or left. The now s-polarized beam 9e goes through 1 , will be at the interface 3 reflected, now leaves as a beam 9f the prism 1 by area 11 , goes through aQWP 4b , is at the dichroic coating 5b reflected and back through aQWP 4b cleverly. After a double pass of aQWP 4c and a phase rotation of twice a quarter wavelength is the s-polarized beam 9f to the p-polarized beam 9g been converted. Upon re-entry into Prisma 1 by area 11 will beam 9g at the interface 3 transmits and passes through area 13 like ray 9c out. Both the p- and the s-polarized beam component of beam 9a So they have been completely passed through.

Not shown but equally usable are collimating optics between the light sources 7 . 8th . 9 and the outer QWP 6a . 6b . 6c to parallelize the light before entering the device. Also not shown, but just as possible is a focusing optics after the mixed light exit surface 13 in order to bundle the passing light of all the light sources, for example, into a narrow optical fiber.

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

7 shows a schematic arrangement of another endoscope 70 with grip-sided camera 71 and a rod lens system 72 for optical imaging. In the grip section 73 is similar to the endoscope 60 in 6 a device for light mixing 62 educated.

Finally shows 8th a schematic representation of another endoscope 80 with grip-sided camera 81 and fibers 82 to the image line for the optical image. The device for light mixing 62 is back in the grip section 83 arranged, ie distal to the light exit of the endoscope 80 ,

The features of the invention disclosed in the above description, the claims and the drawings may be of importance both individually and in any combination for the realization of the invention in its various embodiments.

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

• WO 85/01590 [0006, 0007]
• US 5067799 [0006, 0007, 0008]
• WO 01/02884 [0007]
• US 2006/033837 [0007]
• WO 2008/095609 [0007]

Claims (14)

A method for mixing light beams 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 in a polarizing beam splitter of the beam combiner, - The light beams of different colors in the polarizing beam splitter are 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, and - The light beams are mixed to form Mischfarblicht in the beam splitter, such that the beam splitter through a mixed light exit surface leaving mixed color light for the mixed light beams of different colors each comprise the partial beam with the first linear polarization and the partial beam with the second linear polarization. A method according to claim 1, characterized in that light beams are irradiated with at least three different colors in the beam splitter and mixed. A method according to claim 1 or 2, characterized in that the light beams of different colors are irradiated via spatially separated surface portions of the beam splitter in the polarizing beam splitter. Method according to at least one of the preceding claims, characterized in that light beams generated by the light sources and initially not circularly polarized are polarized circularly before being irradiated in the beam splitter when passing through an optical functional element in a direction of passage to the beam splitter. A method according to claim 4, 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, are reflected back to the optical functional element in 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. A method according to claim 4 or 5, 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 an inner λ / Go through 4-plate. Method according to at least one of the preceding claims, characterized in that the light beams of different colors are divided in the beam splitter at a polarizing boundary layer respectively into the sub-beam with the first linear polarization and the sub-beam with the second linear polarization. Method according to at least one of the preceding claims, characterized in that - a light beam of first color, which is circularly polarized, is irradiated through a first light entrance surface in the beam splitter, - the light beam of first color is shared at a polarizing partial reflection surface of the beam splitter, such a reflected partial beam of first color is reflected with the first linear polarization on a rear side of the partial reflection surface to a second polarizing reflection element and a transmitted partial beam of the first color with the second linear polarization passes through the partial reflection surface to the mixed light exit surface, - the reflected partial beam of first color from 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 from the back of the partial reflection surface by this e passes through 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 the first color is reflected on the front side of the reflection surface to the mixed light exit surface. Method according to at least one of the preceding claims, characterized in 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 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 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. Beam combining device, with - A polarizing beam splitter, which is configured, via associated light entry surfaces of the beam splitter in these incident and to be mixed light beams of different colors, which are circularly polarized, each into a sub-beam with a first linear polarization and a sub-beam with a second linear polarization perpendicular to the first linear polarization is made to divide and form mixed color light from the split part rays, and - A plurality of polarizing reflection elements, which are arranged opposite the beam splitter, such that light rays 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, wherein the beam splitter has a mixed light exit surface through which the mixed color light formed emerges, which in each case comprises the partial beam with the first linear polarization and the partial beam with the second linear polarization for the mixed light beams of different color. Lichtstrahlkombinier device according to claim 11, 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 and configured to provide the mixed to be mixed, circularly polarized light beams of different colors of light sources previously generated light beams circularly. Medical instrument, in particular endoscope, with a light beam combining device according to claim 11 or 12. Use of the light beam combining device according to claim 11 or 12 for the spectral decomposition of light.

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