EP4710161A1

EP4710161A1 - Light generating device using a single quarter wave plate for producing white light

Info

Publication number: EP4710161A1
Application number: EP24722228.4A
Authority: EP
Inventors: Rifat Ata Mustafa Hikmet; Ties Van Bommel
Original assignee: Signify Holding BV
Current assignee: Signify Holding BV
Priority date: 2023-05-09
Filing date: 2024-04-25
Publication date: 2026-03-18
Also published as: CN121100305A; WO2024231131A1

Abstract

The invention provides a light generating system comprising a first light generating device, a second light generating device, a diffuser element, a polarization changing element, and a first polarizing beam splitter, wherein: (A) the first light generating device is configured to generate first device light having a first peak wavelength (λp1); wherein the second light generating device is configured to generate second device light having a second peak wavelength (λp2); wherein |λc1-λc1|≥10 nm; wherein each of the first light generating device and the second light generating device comprises a diode laser or a superluminescent diode; (B) the light generating system is configured such that: (a) the first device light and the second device light reaching the first polarizing beam splitter both comprise a first type of linearly polarized light; (b) the first device light and the second device light propagate: (i) via the first polarizing beam splitter, where at least part of the first device light and the second device light, dependent upon the type of linear polarization, are reflected or transmitted; (ii) through the polarization changing element, which is configured to convert linearly polarized light into elliptically polarized light, (iii) to the diffuser element, where at least part of the first device light and at least part of the second device light are diffused into diffused first device light and diffused second device light, respectively, while a sense of the elliptically polarized light is altered to an opposite sense; (c) at least part of the diffused first device light and at least part of the diffused second device light, propagate: (i) through the polarization changing element, where at least part of the elliptically polarized light is converted into a second type of linearly polarized light, different from the first type of linearly polarized light, to (ii) the first polarizing beam splitter, where at least part of the diffused first device light and at least part of the diffused second device light, dependent upon the type of linear polarization, are transmitted or reflected; and (C) the polarization changing element comprises an λ/4 wave plate configured to be an (n/k1)*λ/4 wave plate for the first peak wavelength (λp1) and an (m/k2)*λ/4 wave plate for the second peak wavelength (λp2), wherein n and m are odd positive integers, |n-m| is an even positive integer, and wherein k1 and k2 are each individually selected from the range of 0.8-1.2.

Description

Light generating device using a single quarter wave plate for producing white light

FIELD OF THE INVENTION

The invention relates to a light generating system. The invention further relates to a lighting device comprising such light generating system.

BACKGROUND OF THE INVENTION

Stage lighting engines are known in the art. For instance, US20200333699A1 describes a light source apparatus including a first light source configured to emit light in a first wavelength band, a second light source configured to emit light in a second wavelength band different from the first wavelength band, a light amount ratio changer configured to change a light amount ratio between a first polarized light component and a second polarized light component in light of the first wavelength band, a polarization beam splitter configured to split the first polarized light component and the second polarized light component, a wavelength converter configured to convert the light of the first wavelength band obtained from the first polarized light component, into light in a third wavelength band including the second wavelength band, and a light combiner configured to combine light in the first wavelength band and light in the second wavelength band with each other.

JP7081328B discloses a light source device having a blue laser light-emitting element, a red laser light-emitting element, a light composition element, a diffuse reflection element, a phosphor, a polarization separation and composition element that has a polarization separation function for a first red fluorescent component, light from the red laser light-emitting element, and light from the blue light-emitting element, and a first phase difference plate. The polarization separation and composition element guides, to the diffusion reflection element, a first blue polarization component obtained by polarizing and separating the light from the blue laser light-emitting element and the light from the red laser lightemitting element, and guides, to the phosphor, a second blue polarization component obtained by polarizing and separating the light from the blue laser light-emitting element. The polarization separation and composition element emits red diffusion light, blue diffusion light, a red polarization separation component obtained by polarizing and separating the first red fluorescent component, and a main fluorescent component excluding the first red fluorescent component from fluorescence, in one direction to generate illumination light.

US2018/066828A1 discloses an illuminator that includes a first light source unit that outputs first light beams and a second light source unit that outputs second light beams. A polarization combining element combines the first and second light beams with each other. A polarization state conversion element which receives the combined light includes retardation elements that are separate from one another and arranged in a first direction. The light source units are so configured that first regions through which the first light beams pass and second regions through which the second light beams pass are alternately arranged in the first direction in the polarization state conversion element. A polarization separation element separates the combined light having passed through the polarization state conversion element into first light and second light. A wavelength conversion element converts the first light into third light. The illuminator outputs the second light and the third light.

SUMMARY OF THE INVENTION

High brightness light sources can be used in various applications including spots, stage-lighting, headlamps, home and office lighting, and automotive lighting. For this purpose, laser-phosphor technology can be used, wherein a laser provides laser light and a remote phosphor converts laser light into converted light. A relatively straightforward way to produce white light using lasers is to use blue laser light in combination with phosphor converted light to produce white light. There appears to be a desire to provide high intensity (white) light with a good color rendering index (CRI) and optical components. It may further be desired to have a high brightness light source for general lighting applications tunable in the broad range of color space/CCTs with good color rendering. Usually, to achieve color tuneability, a combination of several sources with different starting color points may be required (being e.g. various sources with different phosphors, different primary colors from direct emitters (e.g. RGB) or a combination of those). In order to create a high brightness color-tunable light source, these multiple sources may need to be optically combined with good color mixing, and without additional increase of etendue. However, for systems with direct RGB lasers, barring impractical primary laser wavelengths requirements, e.g. due to intrinsic narrow spectral width of laser lines and/or practical limitations, e.g. to certain limited spectral ranges, the optical combination of multiple sources often results in a relatively low CRI. Further, for systems with more than one phosphor converter, the etendue tends to increase substantially (such as at least x2 times), which may be undesired for high brightness applications. Further, prior art systems may require a multi-channel driver and/or additional color mixing. Such additional necessary features as described here make the lighting arrangement bulkier, less efficient, and more expensive. Hence, problems associated with current laser lighting fixtures may come with the desire to create compact high-power devices.

Hence, it is an aspect of the invention to provide an alternative light generating system, which preferably further at least partly obviates one or more of above-described drawbacks. The present invention may have as object to overcome or ameliorate at least one of the disadvantages of the prior art, or to provide a useful alternative.

According to a first aspect, the invention provides a light generating system comprising a first light generating device, a second light generating device, a diffuser element, a polarization changing element, and a first polarizing beam splitter. In embodiments, the first light generating device may be configured to generate first device light having a first peak wavelength (kpl). Therefore, in embodiments, the first light generating device may comprise a diode laser or a superluminescent diode. In embodiments, the second light generating device may be configured to generate second device light having a second peak wavelength (Zp2). Especially, in embodiments, the first peak wavelength (Xp 1) and the second peak wavelength (Xp2) may differ. More especially, in embodiments, | pl- kpl|>10 nm. Therefore, in embodiments, the second light generating device may comprise a diode laser or a superluminescent diode. In embodiments, the light generating system may be configured such that first device light and second device light reaching the first polarizing beam splitter may both comprise (the same type of) polarized light. Further, in embodiments, the light generating system may be configured such that, dependent upon a polarization of the first device light, the first device light may propagate via (i) the first polarizing beam splitter, where at least part of the first device light may be reflected or transmitted, and (ii) the polarization changing element, to the diffuser element, where at least part of the first device light may be diffused into diffused first device light. Especially, at least part of the first device light may be diffused into diffused first device light while maintaining at least part of its polarization. Yet further, in embodiments, the light generating system may be configured such that, dependent upon a polarization of the second device light, the second device light may propagates via (i) the first polarizing beam splitter, where at least part of the second device light may be reflected or transmitted, and (ii) the polarization changing element, to the diffuser element, where at least part of the second device light may be diffused into diffused second device light. Especially, at least part of the second device light may be diffused into diffused second device light while maintaining at least part of its polarization. Yet further, in embodiments, the light generating system may be configured such that at least part of the diffused first device light, generated at the diffuser element, and at least part of the diffused second device light, generated at the diffuser element, may propagate (from the diffuser element) through the polarization changing element, to the first polarizing beam splitter. In embodiments, at the first polarizing beam splitter at least part of the diffused first device light and at least part of the diffused second device light may be transmitted or reflected.

Especially, in embodiments, at least part of the diffused device light incident on the first polarizing beam splitter may be transmitted or reflected to provide a beam of light comprising one or more of the diffused first device light and the diffused second device light. In embodiments, the polarization changing element may comprise a X/4 wavelength plate configured to be an n^th order X/4 wavelength plate for the first peak wavelength (Xpl) and to be an m^th order X/4 wavelength plate for the second peak wavelength (Xp2). Especially, in embodiments, n and m may be odd positive integers. Further, especially, in embodiments, Inml may be an even positive integer. Hence, in specific embodiments, the invention provides a light generating system comprising a first light generating device, a second light generating device, a diffuser element, a polarization changing element, and a first polarizing beam splitter, wherein: (A) the first light generating device may be configured to generate first device light having a first peak wavelength (Xpl); wherein the first light generating device may comprise a diode laser or a superluminescent diode; (B) the second light generating device may be configured to generate second device light having a second peak wavelength (Xp2); wherein the first peak wavelength (Xpl) and the second peak wavelength (Xp2) may differ, wherein |Xpl-Xpl |>10 nm; wherein the second light generating device may comprise a diode laser or a superluminescent diode; (C) the light generating system may be configured such that: (a) first device light and second device light reaching the first polarizing beam splitter may both comprise polarized light; (b) dependent upon a polarization of the first device light, the first device light may propagate via (i) the first polarizing beam splitter, where at least part of the first device light may be reflected or transmitted, and (ii) the polarization changing element, to the diffuser element, where at least part of the first device light may be diffused into diffused first device light, while maintaining at least part of its polarization; (c) dependent upon a polarization of the second device light, the second device light may propagate via (i) the first polarizing beam splitter, where at least part of the second device light may be reflected or transmitted, and (ii) the polarization changing element, to the diffuser element, where at least part of the second device light may be diffused into diffused second device light, while maintaining at least part of its polarization; (d) at least part of the diffused first device light, generated at the diffuser element, and at least part of the diffused second device light, generated at the diffuser element, may propagate through the polarization changing element, to the first polarizing beam splitter, where at least part of the diffused first device light and at least part of the diffused second device light may be transmitted or reflected; and (D) the polarization changing element may comprise a X/4 wavelength plate configured to be an n^th order X/4 wavelength plate for the first peak wavelength (Xpl) and to be an m^th order X/4 wavelength plate for the second peak wavelength (Xp2), wherein in specific embodiments n and m are odd positive integers, and wherein in specific embodiments |n-m| is an even positive integer.

With such a system, a high power light generating system may be provided. Further, such system may allow control of spectral power distribution of an output system light (of a high power system). Yet, such system may in a safe way provide high power light. In addition to high optical power, the system may also provide high radiance (or luminance), i.e., a high optical power density of the source. Further, the compactness of the system may be maintained, less optical components given less reflection losses may be obtained, and a lower bill-of-material and assembly cost may be achieved.

As indicated above, the light generating system may, in embodiments, comprise a first light generating device, a second light generating device, a diffuser element, a polarization changing element, and a first polarizing beam splitter.

In embodiments, the first light generating device may be configured to generate first device light. Especially, in embodiments, the first device light may have a first peak wavelength (Xpl). In embodiments, the first peak wavelength (Xpl) may be selected from one of the blue wavelength range, the green wavelength range, or the red wavelength range. Hence, in embodiments, the first device light may be one of blue first device light, green first device light, or red first device light. Further, in embodiments, the first light generating device may comprise a solid state light source. Especially, the first light generating device may, in embodiments, comprise a diode laser or a superluminescent diode, see also further below. Similarly, in embodiments, the second light generating device may be configured to generate second device light. Especially, in embodiments, the second device light may have a second peak wavelength (Xp2). In embodiments, the second peak wavelength (Xp2) may be selected from one of the blue wavelength range, the green wavelength range, or the red wavelength range. Hence, in embodiments, the second device light may be one of blue second device light, green second device light, or red second device light. Further, in embodiments, the second light generating device may comprise a solid state light source. Especially, the second light generating device may, in embodiments, comprise a diode laser or a superluminescent diode, see also further below.

In embodiments, the first light generating device and the second light generating device may have a different peak wavelength (kp). In specific embodiments, the first peak wavelength (kpl) and the second peak wavelength (Zp2) may differ at least 20 nm, such as at least 50 nm, like at least 100 nm. For example, in some embodiments, the first peak wavelength (kpl) and the second peak wavelength (Zp2) may (even) differ at least 200 nm. Hence, in embodiments, | p 1 -Z.p2|>20 nm. Further, in embodiments |A,pl-kp2|< 400 nm, such as |A,pl-kp2|< 350 nm.

Herein, the phrases “first light generating device”, “second light generating device”, and similar phrases may also, in embodiments, refer to a plurality of respectively (first or second) light generating devices selected from the same bin, i.e., a plurality of light generating devices which may provide device light having essentially the same spectral power distributions.

In embodiments, the first device light and the second device light may comprise (linearly) polarized light, such as one of p polarized light, or s polarized light. Especially, in embodiments, the first device light and the second device light may essentially be (linearly) polarized device light. In other embodiments, the first device light and the second device light may be made polarized or the polarization of the device light may be tuned, e.g. through the use of a polarizing beam splitter, a polarizer, or a (metallic) reflector (to provide the (desired) (linearly) polarized device light). In embodiments, in an operational mode, the light generating system may be configured such that the first light generating device and the second light generating device may generate first device light and second device light, respectively. Especially, in such embodiments, (at least part of) the first device light and (at least part of) the second device light may be directed towards the first polarizing beam splitter. In other words, in such embodiments, (at least part of) the first device light and (at least part of) the second device light may reach the first polarizing beam splitter, i.e., the device light may be incident on the polarizing beam splitter. Whether the device light reaches the polarizing beam splitter, and thus whether device light is received by the polarizing beam splitter, may depend on whether also the respective device is operated.

Further, in embodiments, in an operational mode, the light generating system may be configured such that first device light and second device light reaching the first polarizing beam splitter may both comprise polarized light. Especially, in embodiments, the light generating system may, in an operational mode, be configured such that first device light and second device light reaching the first polarizing beam splitter may both comprise the same type of polarized light. More especially, in embodiments, the light generating system may, in an operational mode, be configured such that first device light and second device light reaching the first polarizing beam splitter may both comprise a (same) first type of (linearly) polarized light. Hence, in such embodiments, the first device light and the second device light reaching the first polarizing beam splitter may both comprise first linearly polarized light having the same polarization direction. For example, in embodiments, the first device light and the second device light may both comprise s polarized light. In particular, in embodiments, the first device light and the second device light may both comprise p polarized light. Hence, in embodiments, the first device light and the second device light may both comprise linearly polarized light.

The phrase “device light reaching a polarizing beam splitter comprises polarized light”, and similar phrases, may indicate that when device light reaches the PBS, then the device light comprises polarized light, which can either be due to starting with polarized (device) light having the desired polarization, or by starting with unpolarized (device) light, and converting this light, e.g. with the use of a polarizer, into polarized (device) light having the desired polarization, or by starting with polarized (device) light having a less or no desired polarization and converting this light, e.g. with the use of a polarizer, into (device) light having the desired polarization.

Further, as mentioned above, the light generating system may comprise a polarization changing element. Especially, in embodiments, the polarization changing element may be configured downstream of the first light generating device and the second light generating device and upstream of the diffuser element. Hence, in embodiments, the polarization changing element may be configured in an optical path between the (first and second) light generating devices and the diffuser element. As such, in embodiments, the polarization changing element may be configured in a light-receiving relationship with the (first and second) light generating devices, especially via one or more optics (such as the first polarizing beam splitter), see also above and below.

Especially, a polarization changing element may be configured to convert linearly polarized light (such as s polarized or p polarized light) into elliptically (or even circularly) polarized light. In embodiments, a polarization changing element may be an element that induces a phase shift between the two orthogonal linear polarization components (s and p) of the light. The most common way is to use birefringent material (birefringent rotators), such as a quarter-wave plate. When the polarization changing element is not exactly a quarter-wave plate and/or when a X/4 wave plate fast axis is placed at an angle of not exactly 45° then (a first type of) linearly polarized light may become elliptically polarized. When such elliptically polarized light is reflected from a metallic surface (such as from the diffuser element, see also further below) the handedness of the elliptical polarization is altered to the opposite sense. When elliptically polarized light with an opposite sense goes through the same X 4 wave plate again it may be converted into altered polarized light with a linear polarization component with a polarization direction which is rotated by 90° relative to the (first type of) linearly polarized light.

A polarized light beam may have a propagation axis, an electric field vector and a magnetic field vector. The polarization of light may especially refer to the direction of the electric field vector and the magnetic field vector of the light. Unlike linearly polarized and non-polarized light, elliptically polarized light may have a rotational “sense” of the polarization, which may refer to a direction of rotation of the electric field vector around the propagation axis. When approaching waves of light are viewed end-on, the direction of polarization can be either left-handed or right-handed, i.e., the rotational “sense” may be lefthanded or right-handed. Clockwise rotation of the vector may especially be referred to as right-handed polarization, whereas counterclockwise rotation may be referred to as lefthanded polarization. In cases where the electric field vector and the magnetic field vector of the polarization ellipse are equal but shifted in phase 90°, the polarization of the light may be categorized as circularly polarized light. Hence, circularly polarized light may be an extreme embodiment of elliptical polarization. Circularly polarized light may thus also be either right- handed or left-handed in sense. In cases where the electrical component vector in elliptically polarized light goes to zero, the light may become linearly polarized.

In specific embodiments, the polarization changing element may comprise a X/4 wave plate. Especially, in embodiments, the polarization changing element may comprise a X/4 wave plate configured to be an n^th order X/4 wave plate for the first peak wavelength (Xpl) of the first device light. However, a slight freedom in the n'^h order of the X/4 wave plate may exist. Therefore, in specific embodiments, the polarization changing element may comprise a X/4 wave plate configured to be an (n/kl)*X/4 wave plate for the first peak wavelength (Xpl). Likewise, in embodiments, the polarization changing element may comprise a X/4 wave plate configured to be an m^th other X/4 wave plate for the second peak wavelength (Xp2) of the second device light. However, a slight freedom in the m^th order of the X/4 wave plate may exist. Therefore, in specific embodiments, the polarization changing element may comprise a X/4 wave plate configured to be an (m/k2)*X/4 wave plate for the second peak wavelength (Xp2). Hence, in embodiments, the polarization changing element may comprise a X/4 wave plate configured to be a X/4 wave plate for both the first peak wavelength (Xpl) and the second peak wavelength (Xp2), but at different orders respectively. In embodiments, n may be at least one, such as at least three, like at least five, i.e., n>l. Similarly, in embodiments, m may be at least one, such as at least three, like at least five, i.e., m>l. Especially, in embodiments, n and m may both be positive integers, more especially odd positive integers. However, as mentioned above, the orders for the first peak wavelength (Xpl) and the second peak wavelength (Xp2) may especially differ. Hence, in embodiments, n may be unequal to m, i.e. |n-m|>l, more especially |n-m|>2. Especially, in embodiments, Inml may be a positive integer, more especially an even positive integer. Furthermore, in embodiments, as mentioned above, there may be a slight freedom in the orders n and m, i.e., the odd integers selected for n and m may be varied slightly (or corrected) by the factors kl and k2, respectively. Hence, in embodiments, kl and k2 may be correction factors and may each be individually selected from the range of 0.8-1.2, such as from the range of 0.9-1.1, like from the range of 0.95-1.05. The efficiency of the polarization changing element may improve the closer the correction factor is to 1.

In embodiments, an alternative for the polarization changing element may be to use the Faraday effect, in which case the phase shift is caused by an applied magnetic field (Faraday rotators). The light generating system may thus comprise a polarization changing element. Further, in embodiments, the light generating system may comprise a first polarizing beam splitter. In embodiments, the first polarizing beam splitter may be configured downstream of the first light generating device and the second light generating device and upstream of the polarization changing element. Especially, in embodiments, the first polarizing beam splitter may be configured in a light receiving relationship with the first light generating device and the second light generating device. Especially, in embodiments, the first polarizing beam splitter may be used to combine beams of the two types of light generating devices.

In embodiments, a polarizing beam splitter may be configured to transmit at least part of one of the first device light and the second device light (and optionally third device light, see also further below) and to reflect at least part of the other one of the first device light and the second device light (and optionally third device light). Especially, in embodiments, the polarizing beam splitter may be configured to transmit at least (80%, especially at least) 90%, such as at least 95%, like at least 98% of one of the first device light and the second device light (and optionally third device light). In such embodiments, the polarizing beam splitter may be configured to reflect at least (80%, especially at least) 90%, such as at least 95%, like at least 98% of the other one of the first device light and the second device light (and optionally third device light). For example, in embodiments, the polarizing beam splitter may be configured to transmit at least 90% of p polarized device light (e.g. p polarized first and second device light) and to reflect at least 90% of s polarized device light (e.g. s polarized first and second device light). Hence, the polarizing beam splitter may be at least 80% transmissive for one type (especially polarization) of device light and at least 80% reflective for another type (especially polarization) of device light.

Hence, in embodiments, the first polarizing beam splitter may be configured to transmit and/or reflect at least part of the device light in dependence of its (linear) polarization direction. Especially, in embodiments, the first polarizing beam splitter may be configured to transmit s-polarized light or p-polarized light, and to reflect p-polarized light or s-polarized light. Hence, in embodiments, the first polarizing beam splitter may be configured to transmit s-polarized light, and to reflect p-polarized light. In other embodiments, the first polarizing beam splitter may be configured to transmit p-polarized light, and to reflect s-polarized light. Hence, in some embodiments, the first polarizing beam splitter may especially be transmissive for at least part of the device light incident on the first polarizing beam splitter.

The terms “upstream” and “downstream” relate to an arrangement of items or features relative to the propagation of the light from a light generating means (here the especially the light source), wherein relative to a first position within a beam of light from the light generating means, a second position in the beam of light closer to the light generating means is “upstream”, and a third position within the beam of light further away from the light generating means is “downstream”.

In embodiments, the first device light and second device light may propagate (from the first light generating device and the second light generating device, respectively) to the first polarizing beam splitter. At the first polarizing beam splitter at least part of the first device light and at least part of the second device light may, dependent upon the type of linear polarization, be reflected or transmitted. In some embodiments, at least 80%, especially at least 90%, including at least 95% of the first device light may be reflected at the first polarizing beam splitter. Similarly, in some embodiments, at least 80%, especially at least 90%, including at least 95% of the second device light may be reflected at the first polarizing beam splitter. In other embodiments, at least 80%, especially at least 90%, including at least 95% of the first device light may be transmitted at the first polarizing beam splitter.

Similarly, in embodiments, at least 80%, especially at least 90%, including at least 95% of the second device light may be transmitted at the first polarizing beam splitter. Reflection or transmission of the first device light and the second device light may especially depend upon the type of linear polarization of the device light (e.g. p polarized light may be transmitted and s polarized light may be reflected, or vice versa).

Herein, in embodiments a polarizing beam splitter may be configured to reflect at least 80%, especially at least 90%, including at least 95% of light comprising a first linear polarization, and to transmit at least 80%, especially at least 90%, including at least 95% of light comprising a second linear polarization, wherein the first and second linear polarizations differ, and are selected from s polarization and p polarization.

In embodiments, the first device light and the second device light may especially be reflected or transmitted by the first polarizing beam splitter such that the first device light and the second device light may propagate via the first polarizing beam splitter to the polarization changing element. As described above, at the polarization changing element a phase shift of the polarization of the first device light and the second device light occurs. Thus, in embodiments, first device light and second device light having the (same) first type of linear polarization are changed into first device light and second device light having the (same) first type of elliptical polarization (or even circular polarization) having a first sense (of elliptical polarization). The now elliptically (or circularly) polarized first device light and second device light may, in embodiments, propagate from the polarization changing element to the (reflective) diffuser element. In embodiments, at the (reflective) diffuser element at least part of the first (elliptically polarized) device light and at least part of the second (elliptically polarized) device light may be diffused into diffused first device light and diffused second device light having a (same) second type of elliptical polarization having a second sense (of elliptical polarization) opposite from the first sense. Hence, especially, the diffuser element may be configured to diffuse at least part of the (elliptically polarized) first device light into (elliptically polarized) diffused first device light and at least part of the (elliptically polarized) second device light into (elliptically polarized) diffused second device light, while a sense of the elliptically polarized light may be altered to an opposite sense. In embodiments, assuming the polarization changing element (especially the quarter-wave plate) works ideally and produces circularly polarized light, the (reflective) diffuser element may essentially only change the sense of circularly polarized light. Thus, in such embodiments, when the device light goes through the X/4 wave plate circularly polarized light becomes linearly polarized light which is rotated by an angle of 90° relative to the first type of linearly polarized light. However, in embodiments, when the (reflective) diffuser element does not work efficiently the device light after going through the X/4 wave plate has a component which is not rotated by 90° relative to the first type of linearly polarized light. Herein, in embodiments a 90° rotated component of the diffused first device light may be at least 80%, especially at least 90%, including at least 95%. In specific embodiments, a 90° rotated component of the diffused first device light may be 100%. Similarly, in embodiments, a 90° rotated component of the diffused second device light may be at least 80%, especially at least 90%, including at least 95%. In specific embodiments, a 90° rotated component of the diffused second device light may be 100%.

Therefore, in embodiments, the first device light and the second device light may propagate: (i) via the first polarizing beam splitter, where at least part of the first device light and the second device light, dependent upon the type (or direction) of linear polarization, may be reflected or transmitted; (ii) through the polarization changing element, which may be configured to convert linearly polarized light into elliptically (or circularly) polarized light, (iii) to the diffuser element, where at least part of the first device light and at least part of the second device light may be diffused into diffused first device light and diffused second device light, respectively, while a sense of the elliptically (or circularly) polarized light may be altered to an opposite sense.

As described above, at least part of the first device light and at least part of the second device light may be diffused, i.e., reflected and redirected to larger distribution of angles, by the diffuser element. Hence, herein, the term “diffuser element” may refer to an element that changes the direction of light falling onto it. Further, in embodiments, the diffuser element may (also) change the sense of polarization of light incident on and redirected by the diffuser element. For example, in such embodiments, the diffuser element may be configured to convert elliptically polarized light having a first sense (e.g. right- handed elliptically polarized light) into elliptically polarized light having a second (opposite) sense (e.g. left-handed elliptically polarized light). In embodiments, instead of “diffuser element” also the term “polarization maintaining diffuser element” or “(facetted and/or wavy) reflective optical element” may be applied. In embodiments, such a diffuser element may comprise a diffusing material, such as one or more selected from the group comprising a glass, a polymeric material, and a metal. An example of a reflective diffuser element may be a metallic coated glass diffuser showing 90-98% reflectance. In embodiments, the diffuser may thus comprise a metallic diffuser element(, such as e.g. a metallic reflector). Especially, in such embodiments, the diffuser element may comprise a metallic diffuser element comprising a non-flat surface. For example, in embodiments, the diffuser element may comprise a metallic diffuser element comprising one or more of a parabolic, a (semi- )spherical, facetted and a wavy surface. The diffuser may, in embodiments, essentially consist of a metallic material. In other embodiments, the diffuser may comprise a layer comprising a metallic material (e.g. evaporated onto a substrate by physical vapor deposition (PVD)). The metallic layer may further be protected, e.g., covered by a transparent layer, such as a metal oxide layer (e.g. Aluminum Oxide). Hence, especially, in embodiments, the diffuser may comprise one or more materials selected from the group comprising aluminum, gold, copper, and silver.

Hence, in embodiments, the diffuser element may be configured to generate diffused first device light and diffused second device light, while the sense of the elliptically polarized light may be altered to the opposite sense. Thus, the diffuser element may change the direction (or sense) of the polarized light, but the elliptically polarized light may essentially stay elliptically polarized light. Therefore, in specific embodiments, the polarization changing element may comprise a X/4 waveplate. The X/4 waveplate may, in embodiments, be configured to (i) convert linearly polarized light into elliptically (such as circularly) polarized light and (ii) elliptically (such as circularly) polarized light into linearly polarized light. In this way, p-polarized light can be converted in diffused s-polarized light, and s-polarized light can be converted in diffused p-polarized light. Especially, in embodiments, at least part of the diffused light, comprising elliptically polarized light, may propagate from the diffuser element to the polarization changing element, and then be converted into a second type of polarized light, different from the first type of polarized light, which may further propagate to the first polarizing beam splitter. In embodiments, the second type of polarized light may have a component which is (essentially) 90° rotated with respect to the first type of linearly polarized light (e.g. a 90° rotation of p polarized light to s polarized light or vice versa). At the first polarizing beam splitter, at least part of the 90° rotated (linearly polarized) diffused device light may be transmitted or reflected. Hence, in specific embodiments, at least part of the diffused first device light and the diffused second device light, generated at the diffuser element, may propagate (from the diffuser element) through the polarization changing element, to the first polarizing beam splitter. Especially, at the polarization changing element, in embodiments, at least part of the elliptically polarized (diffused device) light may be converted into the second type of (linearly) polarized light having a linearly polarized component with a linear polarization direction which is rotated by 90° with respect to the polarization direction of first (linearly) polarized light.

Further, in some embodiments, at least part of the (linearly polarized) diffused first device light and at least part of the (linearly polarized) diffused second device light may be transmitted at the first polarizing beam splitter. In other embodiments, at least part of the (linearly polarized) diffused first device light and at least part of the (linearly polarized) diffused second device light may be reflected at the first polarizing beam splitter. Especially, in embodiments, whether the diffused first device light and the diffused second device light may be transmitted or reflected by the first polarizing beam splitter may be dependent upon the type of (linear) polarization (e.g. p polarized light may be transmitted and s polarized light may be reflected, or vice versa).

In embodiments, at least part of the diffused device light incident on the first polarizing beam splitter may be transmitted or reflected to provide a beam of light comprising one or more of the diffused first device light and the diffused second device light. The beam of light may, in embodiments, escape from the light generating system as system light. Especially, in embodiments, the system light may be white light. In other embodiments, the beam of light may be at least partly converted into luminescent material light (see also further below), which may escape the light generating system.

Hence, in embodiments where the (first and second) device light (having one of p or s polarization) may be reflected by the first polarizing beam splitter, the diffused (first and second) device light having the second type of (linearly) polarized light may be transmitted by the first polarizing beam splitter. Whereas conversely, in embodiments where the (first and second) device light having the second type of linearly polarized light may be transmitted by the first polarizing beam splitter, the diffused (first and second) device light (having the other one of p or s polarization) may be reflected by the first polarizing beam splitter. The transmittance or reflectance at the first polarizing beam splitter may thus especially be dependent upon the polarization of the device light incident on the first polarizing beam splitter.

Further, the system may in embodiments comprise further optics than described above. The term “optics” may especially refer to (one or more) optical elements. Hence, the terms “optics” and “optical elements” and “optical component” may refer to the same items. The optics may include one or more or mirrors, reflectors, collimators, lenses, prisms, diffusers, phase plates, polarizers, diffractive elements, gratings, dichroics, arrays of one or more of the afore-mentioned, etc. Alternatively or additionally, the term “optics” may refer to a holographic element or a mixing rod. In embodiments, the optics may include one or more of beam expander optics and zoom lens optics. See further above for examples of optics. In embodiments, the optics may comprise an integrator, like a “Koehler integrator” (or “Kohler integrator”). In specific embodiments, the system may further comprise one or more of integrating optics, collimation optics, and homogenization optics. One or more of them are also depicted in the accompanying drawings. For example, in embodiments, the light generating system may comprise one or more of integrating optics, collimation optics, and homogenization optics configured downstream of the first polarizing beam splitter. Especially, in such embodiments, the one or more of integrating optics, collimation optics, and homogenization optics may be configured to combine and/or homogenize the diffused first device light and the diffused second device light transmitted or reflected by the first polarizing beam splitter into a beam of system light. Hence, in embodiments, the light generating system may be configured to generate (a beam of) system light comprising one or more of diffused first device light and diffused second device light.

As described above, the light generating system may comprise light generating devices. A light generating device may especially be configured to generate device light. Therefore, the light generating device may comprise a light source. The light source may especially be configured to generate light source light. In embodiments, the device light may essentially consist of the light source light. In other embodiments, the device light may essentially consist of converted light source light. In yet other embodiments, the device light may comprise (unconverted) light source light and converted light source light. Light source light may be converted with a luminescent material into luminescent material light and/or with an upconverter into upconverted light (see also below). The term “light generating device” may also refer to a plurality of light generating devices which may provide device light having essentially the same spectral power distributions. In (other) specific embodiments, the term “light generating device” may also refer to a plurality of light generating devices which may provide device light having different spectral power distributions.

The term “light source” may in principle relate to any light source known in the art. It may be a conventional (tungsten) light bulb, a low pressure mercury lamp, a high pressure mercury lamp, a fluorescent lamp, an LED (light emissive diode). In a specific embodiment, the light source comprises a solid state LED light source (such as an LED or laser diode (or “diode laser”)). The term “light source” may also relate to a plurality of light sources, such as 2-2000 (solid state) LED light sources. Hence, the term LED may also refer to a plurality of LEDs. Further, the term “light source” may in embodiments also refer to a so-called chip-on-board (COB) light source. The term “COB” especially refers to LED chips in the form of a semiconductor chip that is neither encased nor connected but directly mounted onto a substrate, such as a PCB. Hence, a plurality of light emitting semiconductor light source may be configured on the same substrate. In embodiments, a COB is a multi LED chip configured together as a single lighting module.

A position where system light escapes from the light generating system may also be indicated as light exit. This may be a light transmissive window or an opening (in the system). The light transmissive window may in embodiments be provided by an optical component.

The term “light source” may refer to a semiconductor light-emitting device, such as a light emitting diode (LEDs), a laser diode, a resonant cavity light emitting diode (RCLED), a vertical cavity laser diode (VCSELs), an edge emitting laser (EEL), a photonic crystal surface emitting laser (PCSEL), a vertical external cavity surface emitting laser (VECSEL), etc... The term “light source” may also refer to an organic light-emitting diode (OLED), such as a passive-matrix (PMOLED) or an active-matrix (AMOLED). In a specific embodiment, the light source comprises a solid-state light source (such as an LED or laser diode). In an embodiment, the light source comprises an LED (light emitting diode). The terms “light source” or “solid state light source” may also refer to a superluminescent diode (SLED). The term LED may also refer to a plurality of LEDs. The term “light source” may (thus) refer to a light generating element as such, like e.g. a solid state light source, or e.g. to a package of the light generating element, such as a solid state light source, and one or more of a luminescent material comprising element and (other) optics, like a lens, a collimator. A light converter element (“converter element” or “converter”) may comprise a luminescent material comprising element. For instance, a solid state light source as such, like a blue LED, is a light source. A combination of a solid state light source (as light generating element) and a light converter element, such as a blue LED and a light converter element, optically coupled to the solid state light source, may also be a light source (but may also be indicated as light generating device). Hence, a white LED is a light source (but may e.g. also be indicated as (white) light generating device). In embodiments, the term “light source” may also refer to a combination of a light source, like an LED, and an optical filter, which may change the spectral power distribution of the light generated by the light source. Especially, the term “light generating device” may be used to address a light source and further (optical components), like an optical filter and/or a beam shaping element, etc. The phrases “different light sources” or “a plurality of different light sources”, and similar phrases, may in embodiments refer to a plurality of solid-state light sources selected from at least two different bins. Likewise, the phrases “identical light sources” or “a plurality of same light sources”, and similar phrases, may in embodiments refer to a plurality of solid-state light sources selected from the same bin.

The term “solid state light source”, or “solid state material light source”, and similar terms, may especially refer to semiconductor light sources, such as a light emitting diode (LED), a laser diode, or a superluminescent diode.

The term “laser light source” especially refers to a laser. Such laser may especially be configured to generate laser light source light having one or more wavelengths in the UV, visible, or infrared, especially having a wavelength selected from the spectral wavelength range of 200-2000 nm, such as 300-1500 nm. The term “laser” especially refers to a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. Especially, in embodiments the term “laser” may refer to a solid-state laser. In specific embodiments, the terms “laser” or “laser light source”, or similar terms, refer to a laser diode (or diode laser). The term “solid state material laser”, and similar terms, may refer to a solid state laser like based on a crystalline or glass body dopes with ions, like transition metal ions and/or lanthanide ions, to a fiber laser, to a photonic crystal laser, to a semiconductor laser, such as e.g. a vertical cavity surface-emitting laser (VCSEL), etc. Instead of the term “solid state light source” also the term “semiconductorbased light source” may be applied. Hence, the term “semiconductor-based light source” may e.g. refer to one or more of a light emitting diode (LED), a laser diode, and a superluminescent diode. Hence, the light generating device may comprise one or more of a light emitting diode (LED), a laser diode, and a superluminescent diode.

A light-emitting diode (LED) is especially a semiconductor light source that emits light when current flows through it. Electrons in the semiconductor may recombine with electron holes, releasing energy in the form of photons. The color of the light (corresponding to the energy of the photons) may be determined by the energy required for electrons to cross the band gap of the semiconductor.

A laser diode (or diode laser) may be a semiconductor device substantially similar to a light-emitting diode in which a diode pumped directly with electrical current can create lasing conditions at the diode's junction. This is known to a person skilled in the art.

Superluminescent diodes are known in the art. A superluminescent diode may be indicated as a semiconductor device which may be able to emit low-coherence light of a broad spectrum like an LED, while having a brightness in the order of a laser diode. Superluminescent diodes are e.g. described in US2020192017, or in “Edge Emitting Laser Diodes and Superluminescent Diodes”, Szymon Stanczyk, Anna Kafar, Dario Schiavon, Stephen Najda, Thomas Slight, Piotr Perlin, Book Editor(s): Fabrizio Roccaforte, Mike Leszczynski, First published: 03 August 2020 https://doi.org/10.1002/9783527825264.ch9 in chapter 9,3 superluminescent diodes, or in Abdullah A. Alatawi, et al., Optics Express Vol. 26, Issue 20, pp. 26355-26364, https://doi.org/10.1364/QE.26.026355.

Hence, in embodiments, the first light generating device may comprise a (first) diode laser. In such embodiments, the first device light may comprise polarized light. Especially, the first device light may comprise p polarized or s polarized light. Similarly, in embodiments, the second light generating device may comprise a (second) diode laser. In such embodiments, the second device light may comprise polarized light. Especially, the second device light may comprise p polarized or s polarized light. For example, in embodiments, the first device light and the second device light may both comprise p polarized light. In other embodiments, the first device light and the second device light may both comprise s polarized light. However, in yet other embodiments, the first device light and the second device light may (also) comprise different polarized light. Hence, in specific embodiments, the first light generating device may comprise a diode laser, wherein the first device light may comprise p polarized or s polarized laser light; and wherein the second light generating device may comprise a diode laser, wherein the second device light may comprise p polarized or s polarized laser light. In specific embodiments, the first type of linearly polarized light is p polarized light, and wherein the second type of linearly polarized light is s polarized light.

In an aspect of the invention, the invention may especially provide a light generating system comprising a first light generating device, a second light generating device, a diffuser element, a polarization changing element, and a first polarizing beam splitter. In embodiments, the first light generating device may be configured to generate first device light having a first peak wavelength (kpl). Similarly, in embodiments, the second light generating device may be configured to generate second device light having a second peak wavelength (Xp2). The first peak wavelength (kp l ) and the second peak wavelength (Zp2) may, in embodiments, differ. Especially, in embodiments, |Z,pl-Z,p2|>10 nm. Further, in embodiments, each of the first light generating device and the second light generating device may comprises a diode laser or a superluminescent diode. In embodiments, in an operational mode, the light generating system may be configured such that the first device light and the second device light reaching the first polarizing beam splitter may both comprise a first type of (linearly) polarized light. Further, in embodiments, in an operational mode, the light generating system may be configured such that the first device light and the second device light may propagate: (i) via the first polarizing beam splitter, through the polarization changing element, to the diffuser element. At the first polarizing beam splitter, in embodiments, at least part of the first device light and the second device light, dependent upon the type of (linear) polarization, may thus be reflected or transmitted. Further, in embodiments, the polarization changing element may be configured to convert linearly polarized light (incident on the polarization changing element) into elliptically polarized light. Yet further, in embodiments, at the diffuser element at least part of the first device light and at least part of the second device light may be diffused into diffused first device light and diffused second device light, respectively. Such diffusion may especially, in embodiments, occur while a sense of the elliptically polarized light may be altered to an opposite sense. Yet further, in embodiments, in an operational mode, the light generating system may be configured such that at least part of the diffused first device light and at least part of the diffused second device light, may propagate: (i) through the polarization changing element, to (ii) the first polarizing beam splitter. At the polarization changing element, in embodiments, at least part of the elliptically polarized light may especially be converted into a second type of (linearly) polarized light, different from the first type of (linearly) polarized light. Further, in embodiments, at the first polarizing beam splitter at least part of the diffused first device light and at least part of the diffused second device light, dependent upon the type of linear polarization, may be transmitted or reflected. Furthermore, in embodiments, the polarization changing element may comprise a X/4 wave plate. The polarization changing element may especially, in embodiments, be configured to be an (n/kl)*X/4 wave plate for the first peak wavelength ( pl) and an (m/k2)*X/4 wave plate for the second peak wavelength ( p2). In embodiments, n and m may be odd positive integers. Especially, in embodiments, |n-m| may be an even positive integer. Further, in embodiments, kl and k2 may each be individually selected from the range of 0.8-1.2. Hence, in specific embodiments, the invention provides a light generating system comprising a first light generating device, a second light generating device, a diffuser element, a polarization changing element, and a first polarizing beam splitter, wherein: (A) the first light generating device is configured to generate first device light having a first peak wavelength ( pl); the second light generating device is configured to generate second device light having a second peak wavelength ( p2); wherein |Xp 1 -Xp2|> 10 nm; wherein each of the first light generating device and the second light generating device comprises a diode laser or a superluminescent diode; (B) the light generating system is configured such that: (a) the first device light and the second device light reaching the first polarizing beam splitter both comprise a first type of linearly polarized light; (b) the first device light and the second device light propagate: (i) via the first polarizing beam splitter, where at least part of the first device light and the second device light, dependent upon the type of linear polarization, are reflected or transmitted; (ii) through the polarization changing element, which is configured to convert linearly polarized light into elliptically polarized light, (iii) to the diffuser element, where at least part of the first device light and at least part of the second device light are diffused into diffused first device light and diffused second device light, respectively, while a sense of the elliptically polarized light is altered to an opposite sense; (c) at least part of the diffused first device light and at least part of the diffused second device light, propagate: (i) through the polarization changing element, where at least part of the elliptically polarized light is converted into a second type of linearly polarized light, different from the first type of linearly polarized light, to (ii) the first polarizing beam splitter, where at least part of the diffused first device light and at least part of the diffused second device light, dependent upon the type of linear polarization, are transmitted or reflected; and the polarization changing element comprises a X/4 wave plate configured to be an (n/kl)*X/4 wave plate for the first peak wavelength (kpl ) and an (m/k2)*X/4 wave plate for the second peak wavelength (Xp2), wherein in specific embodiments n and m are (especially odd) positive integers, wherein in specific embodiments |n-m| is a positive integer, especially an even positive integer, and wherein kl and k2 are each individually selected from the range of 0.8-1.2.

Herein, kl and k2 are correction factors for choosing a combination of peak wavelengths and quarter waveplate which may not completely fit to each other. For instance, a quarter waveplate for a wavelength x, selected from 380-780 nm, may still have quarter waveplate function at x+2 nm, or even x+ 5 nm. Hence, kl and/or k2 are not necessarily 1, but may be chosen from the range of 0.8-1.2.

In some embodiments, the correction factors kl and k2 may be equal, i.e. kl=k2. Especially, in specific embodiments, kl=k2=l. Further, in such embodiments, the polarization changing element may be configured to convert the first device light and the second device light, comprising the first type of linearly polarized light, into circularly polarized first device light and circularly polarized second device light. The diffuser element may, in such embodiments, be configured to diffuse at least part of the (circularly polarized) first device light and at least part of the (circularly polarized) second device light into (circularly polarized) diffused first device light and (circularly polarized) diffused second device light, respectively. Especially, in embodiments, the diffuser element may do so while a sense of the circularly polarized light may be altered to an opposite sense. For example, in embodiments, right-handed circular polarization may be altered to left-handed circular polarization, or vice versa. The polarization changing element may further, in embodiments, (also) be configured to convert at least part of the (circularly polarized) diffused first device light and at least part of the (circularly polarized) diffused second device light into diffused first device light and diffused second device light comprising the second type of (linearly) polarized light, with a linear polarization component with a polarization direction which is rotated by 90° relative to the first type of linearly polarized light. Hence, in embodiments, the invention may provide the light generating system as described above, wherein kl=k2=l; wherein the polarization changing element is configured to convert the first device light and the second device light, comprising the first type of linearly polarized light, into circularly polarized first device light and circularly polarized second device light; wherein the diffuser element is configured to diffused at least part of the first device light and at least part of the second device light into diffused first device light and diffused second device light, respectively, while a sense of the circularly polarized light is altered to an opposite sense; wherein the polarization changing element is configured to convert at least part of the diffused first device light and at least part of the diffused second device light into diffused first device light and diffused second device light comprising the second type of linearly polarized light.

As described above, circularly polarized light may, in embodiments, be a limiting case of elliptically polarized light. Especially, in embodiments, circularly polarized light may occur when the electric field vector and the magnetic field vector may be equal but shifted in phase exactly 90°, i.e., a quarter wavelength. Therefore, in such embodiments, the polarization changing element may especially be a quarter-wave plate. When a quarter-wave plate fast axis is placed at an angle of 45° with respect to the polarization direction of linearly polarized light circularly polarized light is obtained. When such circularly polarized light is reflected from a metallic surface the handedness of circular polarization is altered to the opposite sense (right handed circularly polarized light becomes left handed and vice versa). When circularly polarized light with an opposite sense goes through the same quarter-wave plate it becomes linearly polarized light with the direction of linear polarization 90° rotated with respect to the initial polarization direction of the linearly polarized light, (for example s polarized light becomes p polarized and vice versa). As mentioned above, in embodiments, the first device light and the second device light may have a different peak wavelength (kp) Especially, in embodiments, one of the first peak wavelength (kpl) and the second peak wavelength (Zp2) may be selected from the wavelength range of 430-490 nm, such as from the range of 440-470 nm, i.e., the blue wavelength range. More especially, in such embodiments, the other one of the first peak wavelength (kpl) and the second peak wavelength (Zp2) may be selected from the wavelength range of 600-680 nm, such as from the range of 620-670 nm, i.e., the red wavelength range. Further, in embodiments, the first peak wavelength (kpl) and the second peak wavelength (Zp2) may differ at least 50 nm, such as at least 100 nm, like at least 200 nm, i.e., |Xp2-Xp 1 |>50 nm. Yet further, in embodiments, the first peak wavelength (kpl) and the second peak wavelength (Zp2) may differ at most 500 nm, such as at most 400 nm, like at most 300 nm, i.e., |Xp2-Xp 11<500 nm. Hence, in embodiments, one of the first peak wavelength (kpl) and the second peak wavelength (Zp2) is selected from the wavelength range of 430-490 nm, and the other one of the first peak wavelength (kpl) and the second peak wavelength (Zp2) is selected from the wavelength range of 600-680 nm; wherein |Xp2- kpl|>50 nm.

Such embodiments may be beneficial as using a first light generating device and a second light generating device with a relatively large difference in peak wavelength may provide the components necessary for providing high brightness white output light.

Further, in specific embodiments, one of the first peak wavelength (kpl) and the second peak wavelength (Zp2) may be selected from the wavelength range of 440-460 nm, and the other one of the first peak wavelength (kpl) and the second peak wavelength (Zp2) may be selected from the wavelength range of 630-660 nm.

Hence, in embodiments, especially, one of the first device light and the second device light may be blue device light, whereas the other one of the first device light and the second device light may be red device light.

The terms “violet light” or “violet emission”, and similar terms, may especially relate to light having a wavelength in the range of about 380-440 nm. In specific embodiments, the violet light may have a centroid wavelength in the 380-440 nm range. The terms “blue light” or “blue emission”, and similar terms, may especially relate to light having a wavelength in the range of about 440-490 nm (including some violet and cyan hues). In specific embodiments, the blue light may have a centroid wavelength in the 440-490 nm range. The terms “green light” or “green emission”, and similar terms, may especially relate to light having a wavelength in the range of about 490-560 nm. In specific embodiments, the green light may have a centroid wavelength in the 490-560 nm range. The terms “yellow light” or “yellow emission”, and similar terms, may especially relate to light having a wavelength in the range of about 560-590 nm. In specific embodiments, the yellow light may have a centroid wavelength in the 560-590 nm range. The terms “orange light” or “orange emission”, and similar terms, may especially relate to light having a wavelength in the range of about 590-620 nm. In specific embodiments, the orange light may have a centroid wavelength in the 590-620 nm range. The terms “red light” or “red emission”, and similar terms, may especially relate to light having a wavelength in the range of about 620-750 nm. In specific embodiments, the red light may have a centroid wavelength in the 620-750 nm range. The terms “cyan light” or “cyan emission”, and similar terms, especially relate to light having a wavelength in the range of about 490-520 nm. In specific embodiments, the cyan light may have a centroid wavelength in the 490-520 nm range. The terms “amber light” or “amber emission”, and similar terms, may especially relate to light having a wavelength in the range of about 585-605 nm, such as about 590-600 nm. In specific embodiments, the amber light may have a centroid wavelength in the 585-605 nm range. The phrase “light having one or more wavelengths in a wavelength range” and similar phrases may especially indicate that the indicated light (or radiation) has a spectral power distribution with at least intensity or intensities at these one or more wavelengths in the indicate wavelength range. For instance, a blue emitting solid state light source will have a spectral power distribution with intensities at one or more wavelengths in the 440-495 nm wavelength range.

As described above, the polarization changing element may comprise a X/4 wave plate configured to be an n^th order X/4 wave plate for the first centroid wavelength (Xcl) and to be an m^th order X/4 wave plate for the second centroid wavelength (Xc2). Especially, in embodiments, n=l, such as n=3, or such as n=5, or such as n=7, especially n=9, like n=l 1. Likewise, in embodiments, m=l, such as m=3, or such as m=5, or such as m=7, especially m=9, like m=l 1. Especially, in embodiments, |n-m|=2. For example, in embodiments, n may be 5 and m may be 3, i.e., the polarization changing element may be configured to be a 5^th order X/4 wave plate for the first peak wavelength (Xpl) and to be a 3^rd order X/4 wave plate for the second peak wavelength (Xp2). In other embodiments, n may be 9 and m may be 7, i.e., the polarization changing element may be configured to be a 9^th order X/4 wave plate for the first peak wavelength (Xpl) and to be a 7^th order X/4 wave plate for the second peak wavelength (Xp2). Hence, in specific embodiments, n and m are individually selected from 1, 3, 5, and 7, and |n-m|=2. However, in other embodiments |n-m|=4 may apply. Such embodiments may be advantageous as a single element may provide function for multiple sources of light, thus providing a compact system for providing light from a combination of different light sources, such as different colors of light sources.

To combine the first device light (having the first peak wavelength (kpl)) and the second device light (having the second peak wavelength (Zp2)) further optics may be applied. Therefore, in embodiments, the light generating system may further comprise one or more first dichroic beam splitters. The one or more first dichroic beam splitters may, in embodiments, be configured downstream of the first light generating device and the second light generating device, and configured upstream of the first polarizing beam splitter. Hence, the one or more dichroic beam splitters may be configured in a light receiving relationship with the first light generating device and the second light generating device. As such, in embodiments, the one or more first dichroic beam splitters may be configured to combine at least part of the first device light and at least part of the second device light. Hence, in specific embodiments, the light generating system may further comprise one or more first dichroic beam splitters configured downstream of the first light generating device and the second light generating device, and configured upstream of the first polarizing beam splitter, wherein the one or more first dichroic beam splitters may be configured to combine at least part of the first device light and at least part of the second device light.

Such embodiments may be beneficial as the addition of dichroic beam splitters in the light generating system may help guide light with different spectral power distributions through the system such that the light may follow a desired light path (and may thus pass through desired optical elements, such as the polarization changing element).

As indicated above, the first device light and the second device light may have a different peak wavelength (kp), hence, the first device light and the second device light may differ in the spectral power distribution they provide. One of the devices may have a different wavelength than the other one, such as a peak wavelength (kp), and a dichroic beam splitter may be used to combine the beams of the two different light generating devices.

Hence, the device light of the first type and device light of the second type may have different spectral power distributions and/or different color points. In specific embodiments, colors or color points of a first type of light and a second type of light may be different when the respective color points of the first type of light and the second type of light differ with at least 0.01 for u’ and/or with at least 0.01 for v’, even more especially at least 0.02 for u’ and/or with at least 0.02 for v’. In yet more specific embodiments, the respective color points of first type of light and the second type of light may differ with at least 0.03 for u’ and/or with at least 0.03 for v’. Here, u’ and v’ are color coordinates of the light in the CIE 1976 UCS (uniform chromaticity scale) diagram. Spectral power distributions of different sources of light having peak wavelengths differing at least 10 nm, such as at least 20 nm, or even at least 30 nm may be considered different spectral power distributions, e.g. different colors. In general, the differences in peak wavelengths will not be larger than about 400 nm, such as not more than 350 nm.

In embodiments, one of the first device light and the second device light may have a wavelength selected from the blue wavelength range (see also above), more especially have a peak wavelength (kp) selected from the blue wavelength range. In such embodiments, the other one of the first device light and the second device light may have a wavelength selected from the red wavelength range (see also above), more especially have a peak wavelength (kp) selected from the red wavelength range.

In embodiments, the first dichroic beam splitter may be used to combine the beams of the two types of light generating devices. Especially, the first dichroic beam splitter may be configured downstream of the two different types of light generating devices and upstream of the first polarizing beam splitter.

In embodiments, the first dichroic beam splitter may be configured to transmit at least part of one of the first device light and the second device light and to reflect at least part of the other one of the first device light and the second device light. Especially, in embodiments, the first dichroic beam splitter may be configured to transmit at least (80%, especially at least) 90%, such as at least 95%, like at least 98% of one of the first device light and the second device light. In such embodiments, the first dichroic beam splitter may be configured to reflect at least (80%, especially at least) 90%, such as at least 95%, like at least 98% of the other one of the first device light and the second device light. For example, in embodiments, the first dichroic beam splitter may be configured to transmit at least 90% of the first device light (e.g. blue device light) and to reflect at least 90% of the second device light (e.g. red device light). Hence, the one or more first dichroic beam splitters may be at least 80% transmissive for one type (especially color) of device light and at least 80% reflective for another type (especially color) of device light.

Examples of such dichroic beam splitters are e.g. a short-pass cut-off dichroic plate, or a long-pass cut-off dichroic plate. In specific embodiments, the first dichroic beam splitter may be designed for a 45° angle of incidence (of the device light). Especially, a centroid wavelength of the first device light and the second device light may be selected such that the centroid wavelength of the first device light and the centroid wavelength of the second device light are spectrally positioned at two opposite sides of a cut-on / cut-off wavelength of a dichroic filter comprised by the first dichroic beam splitter. Hence, the centroid wavelength of the first device light and the centroid wavelength of the second device light, may be selected such, that the first dichroic beam splitter may spectrally substantially separate them, and essentially transmit one and essentially reflect the other.

In embodiments, the light generating system may comprise one first dichroic beam splitter as described above. For example, in such embodiments, the first dichroic beam splitter may be selected having a dichroic wavelength with a cut-on / cut-off wavelength for separating light having a blue wavelength and light having a red wavelength. In other embodiments, the light generating system may comprise two (different) first dichroic beam splitters as described above. For example, in such embodiments, one of the first dichroic beam splitters may be selected having a dichroic wavelength with a cut-on / cut-off wavelength for separating light having a blue wavelength and light having a red wavelength, whereas the other one of the first dichroic beam splitters may be selected having a dichroic wavelength with a cut-on / cut-off wavelength for separating light having a blue wavelength and light having a green wavelength.

In some embodiments, the light generating system may (also) comprise one or more reflectors. The one or more reflectors may be configured in a light receiving relationship with one of the first device light and the second device light. Especially, in embodiments, the one or more reflectors may be configured to reflect one of the first device light and the second device light to the one or more first dichroic beam splitters. For example, in embodiments, the first light generating device may provide first device light (directly) to the one or more first dichroic beam splitters, whereas the second light generating device may provide second device light to the one or more first dichroic beam splitters via one or more reflectors. Hence, in such embodiments, the first device light and the second device light may follow essentially the same path through the light generating system after reaching the one or more first dichroic beam splitters.

Further, in embodiments, the light generating system may (further) comprise a third light generating device. In such embodiments, the light generating system may also further comprise a second polarizing beam splitter, a second polarization changing element, and a second diffuser element. In embodiments, the third light generating device may be configured to generate third device light having a third peak wavelength (Xp3). Especially, in embodiments, the first peak wavelength (kpl), the second peak wavelength (Zp2), and the third peak wavelength (Ap3) may mutually differ. Further, in embodiments, the third light generating device may comprise a diode laser or a superluminescent diode. In embodiments, the light generating system may (further) be configured such that third device light reaching the second polarizing beam splitter may comprise polarized light (of a different type as of the first device light and the second device light). Further, in embodiments, the light generating system may be configured such that the third device light may propagate through (i) the second polarizing beam splitter, through (ii) the second polarization changing element, (iii) to the second diffuser element. At the second polarizing beam splitter, in embodiments, dependent upon a polarization of the third device light, at least part of the third device light may be reflected or transmitted. Further, in embodiments, the second polarization changing element may be configured to convert linearly polarized light into elliptically polarized light. Yet further, in embodiments, at the second diffuser element, at least part of the third device light may be diffused into diffused third device light, while a sense of the elliptically polarized light may be altered to an opposite sense and while maintaining at least part of its polarization. Yet further, in embodiments, the light generating system may be configured such that at least part of the diffused third device light may propagate (from the second diffuser element) via the second polarization changing element, to the second polarizing beam splitter, where at least part of the diffused third device light may be transmitted or reflected to the first polarizing beam splitter. In embodiments, at the second polarization changing element at least part of the elliptically polarized (diffused third) light may be converted into a type of (linearly) polarized light. Especially, in such embodiments, at least part of the elliptically polarized (diffused third) light may be converted into a type of (linearly) polarized light different from which (type of linearly polarized light of) the third device light reached the second polarization changing element. Further, in embodiments, at the second polarizing beam splitter, at least part of the diffused third device light may be transmitted or reflected to the first polarizing beam splitter. Especially, in embodiments, the diffused third device light may be transmitted or reflected dependent upon the type of linear polarization. Yet further, in embodiments, at the first polarizing beam splitter the diffused third device light may be transmitted or reflected. Hence, in specific embodiments, the light generating system further comprises a third light generating device, a second polarizing beam splitter, a second polarization changing element, and a second diffuser element, wherein: (A) the third light generating device is configured to generate third device light having a third peak wavelength (Zp3); wherein the first peak wavelength (kpl ), the second peak wavelength (Xp2), and the third peak wavelength (Ap3) mutually differ; wherein the third light generating device comprises a diode laser or a superluminescent diode; (B) the light generating system is configured such that: (a) third device light reaching the second polarizing beam splitter comprises polarized light; (b) the third device light propagates: (i) through the second polarizing beam splitter, where dependent upon a polarization of the third device light, at least part of the third device light is reflected or transmitted, (ii) through the second polarization changing element, which is configured to convert linearly polarized light into elliptically polarized light, (iii) to the second diffuser element, where at least part of the third device light is diffused into diffused third device light, while a sense of the elliptically polarized light is altered to an opposite sense; and (c) at least part of the diffused third device light propagates (i) via the second polarization changing element, where at least part of the elliptically polarized light is converted into a type of linearly polarized light, different from which the third device light reached the second polarization changing element, (ii) to the second polarizing beam splitter, where at least part of the diffused third device light, dependent upon the type of linear polarization, is transmitted or reflected to the first polarizing beam splitter.

Such embodiments may be beneficial as the addition of a third light source may provide better tuning of the correlated color temperature (CCT) and spectral power distribution of the output light of the system (or “system light”). Especially, with the above described system, different colors of light may be combined to provide high brightness white light with improved color rendering index (CRI). Hence, the invention provides a stage light engine using a single quarter wave plate for combining more laser colors for producing high CRI white light.

As indicated above, the light generating system may, in embodiments, comprise a third light generating device, a second polarizing beam splitter, a second polarization changing element, and a second diffuser element. In embodiments, the third light generating device may be configured to generate third device light. Especially, in embodiments, the third device light may have a third peak wavelength (Xp3). In embodiments, the third peak wavelength (Zp3) may be selected from one of the blue wavelength range, the green wavelength range, or the red wavelength range. Hence, in embodiments, the third device light may be one of blue third device light, green third device light, or red third device light. Further, in embodiments, the third light generating device may comprise a solid state light source. Especially, the third light generating device may, in embodiments, comprise a diode laser or a superluminescent diode, see also further below.

In embodiments, the third peak wavelength (Zp3) may especially be selected such that the first peak wavelength (kpl), the second peak wavelength (Zp2), and the third peak wavelength(kp3) may mutually differ. Especially, in embodiments, the first peak wavelength (kpl) the second peak wavelength (Zp2), and the third peak wavelength (Zp3) may mutually differ at least 10 nm, such as at least 20 nm, like at least 50 nm. Hence, in embodiments, |Z,pl-kp2|>20 nm, | pl- p31>20 nm, and | p2- p31>20 nm. Further, in embodiments, , the first peak wavelength (kpl) the second peak wavelength (Zp2), and the third peak wavelength (Zp3) may mutually differ at most 300 nm, such as at most 200 nm, like at most 100 nm, i.e., |Xp 1 -Zp2|<300 nm, |Xp 1 -Ap3 |<300 nm, and | p2- p3 |<300 nm Especially, in embodiments, of the first device light (having the first peak wavelength (kpl)), the second device light (having the second peak wavelength (Zp2)), and the third device light (having the third peak wavelength ( p3 )) one may be blue device light, another may be green device light and yet another may be red device light. Hence, in such embodiments, the first, second and third light generating devices may together provide RGB (red, green, blue) device light.

The third device light may, in embodiments, comprise polarized light, such as especially linearly polarized light. Especially, in embodiments, the third device light may essentially be (linearly) polarized device light. In other embodiments, the third device light may be made polarized or the polarization of the device light may be tuned, e.g. through the use of a polarizing beam splitter or a reflector.

In embodiments, in an operational mode, the light generating system may be configured such that third device reaching the second polarizing beam splitter may comprise polarized light. Especially, in embodiments, the light generating system may, in an operational mode, be configured such that third device light reaching the second polarizing beam splitter may comprise a different type of polarized light as of the first device light and the second device light. For example, in embodiments, the first device light and the second device light may both comprise s polarized light, whereas the third device light may comprise p polarized light, or vice versa. However, in embodiments, the first device light, the second device light, and the third device light may all comprise linearly polarized light.

Further, as mentioned above, the light generating system may comprise a second polarization changing element. Especially, in embodiments, the second polarization changing element may be configured downstream of the third light generating device and upstream of the second diffuser element. Hence, in embodiments, the second polarization changing element may be configured in an optical path between the third light generating device and the second diffuser element. As such, in embodiments, the second polarization changing element may be configured in a light-receiving relationship with the third light generating device, especially via one or more optics (such as the second polarizing beam splitter), see also above and below. Especially, the second polarization changing element may be configured to convert linearly polarized light (such as s polarized or p polarized light) into elliptically polarized light.

The light generating system may thus comprise a second polarization changing element. Further, in embodiments, the light generating system comprises a second polarizing beam splitter. In embodiments, the second polarizing beam splitter may be configured downstream of the third light generating device and upstream of the second polarization changing element. Especially, in embodiments, the second polarizing beam splitter may be configured in a light receiving relationship with the third light generating device. In embodiments, the second polarizing beam splitter may be configured to transmit and/or reflect at least part of the third device light in dependence of its (linear) polarization. Especially, in embodiments, the second polarizing beam splitter may be configured to transmit s-polarized light or p-polarized light, and to reflect p-polarized light or s-polarized light. Hence, in embodiments, the second polarizing beam splitter may be configured to transmit s-polarized light, and to reflect p-polarized light. In other embodiments, the second polarizing beam splitter may be configured to transmit p-polarized light, and to reflect s- polarized light. Hence, in some embodiments, the second polarizing beam splitter may especially be transmissive for at least part of the device light incident on the second polarizing beam splitter.

In embodiments, the third device light may propagate (from the third light generating device) to the second polarizing beam splitter. At the second polarizing beam splitter at least part of the third device light may, dependent upon the type of linear polarization, be reflected or transmitted. In some embodiments, at least 80%, especially at least 90%, including at least 95% of the third device light may be reflected at the second polarizing beam splitter. In other embodiments, at least 80%, especially at least 90%, including at least 95% of the third device light may be transmitted at the second polarizing beam splitter. Reflection or transmission of the third device light may especially depend upon the type of linear polarization of the device light (e.g. p polarized light may be transmitted and s polarized light may be reflected, or vice versa).

In embodiments, the third device light may especially be reflected or transmitted by the second polarizing beam splitter such that the third device light may propagate through the second polarizing beam splitter to the second polarization changing element. As described above, at the second polarization changing element a phase shift of the polarization of the third device light may occur, i.e., the linearly polarized third device light may be changed into elliptically polarized light (or even circularly polarized light). The now elliptically polarized third device light may, in embodiments, propagate from the second polarization changing element to the second diffuser element. In embodiments, at the (reflective) diffuser element at least part of the third device light may be diffused into diffused third device light. Especially, the second diffuser element may be configured to diffuse at least part of the third device light into diffused third device light, while a sense of the elliptically polarized light may be altered to an opposite sense. In embodiments, at the second diffuser element at least 80%, especially at least 90%, including at least 95% of the third device light may be diffused into diffused third device light, while a sense of the elliptically polarized light may be altered to an opposite sense. Further, in such embodiments, with the diffusion of the third device light at least part of the polarization of the light may be maintained. Hence, in embodiments, the second diffuser element may be configured to generate diffused third device light, while the sense of the elliptically polarized light may be altered to the opposite sense. For example, right-handed elliptically polarized light may be altered to left-handed elliptically polarized light, or vice versa.

Further, in embodiments, at least part of the diffused third device light, comprising elliptically polarized light, will propagate from the second diffuser element to the second polarization changing element, and then be converted into a (third) type of (linearly, especially altered) polarized light, which has a major linear polarization component which is 90° rotated relative to the polarization direction of the third device light which reached the second polarization changing element, which may further propagate to the second polarizing beam splitter. At the second polarizing beam splitter, at least part of the altered (linearly) polarized diffused third device light may be transmitted or reflected. In some embodiments, at least part of the altered (linearly) polarized diffused third device light may be transmitted at the second polarizing beam splitter. In other embodiments, at least part of the altered (linearly) polarized diffused third device light may be reflected at the second polarizing beam splitter. Especially, in embodiments, whether the diffused third device light may be transmitted or reflected by the second polarizing beam splitter may be dependent upon the type of (linear) polarization (e.g. p polarized light may be transmitted and s polarized light may be reflected, or vice versa).

In embodiments, at least part of the diffused third device light incident on the second polarizing beam splitter may be transmitted or reflected (as a second beam of light comprising the diffused third device light) to the first polarizing beam splitter. At the first polarizing beam splitter, the second beam of light may, in embodiments, be transmitted or reflected. Especially, in embodiments, at the first polarizing beam splitter, the second beam of light may be combined with the first beam of light to provide the system light.

In other embodiments, the light generating system as described above may further comprise a third light generating device (without a second polarizing beam splitter, a second polarization changing element, and a second diffuser element). In embodiments, the third light generating device may be configured to generate third device light having a third peak wavelength (Zp3). Especially, in embodiments, the first peak wavelength (kpl), the second peak wavelength (Zp2), and the third peak wavelength (Zp3) may mutually differ. For example, in embodiments, the first, second and third light generating devices may together provide RGB (red, green, blue) device light. Further, in embodiments, the third light generating device may comprise a diode laser or a superluminescent diode. In embodiments, the light generating system may (further) be configured such that third device light reaching the first polarizing beam splitter may comprise polarized light (of the same type as of the first device light and the second device light, i.e., the first type of polarization). Further, in embodiments, the light generating system may be configured such that the third device light may propagate via the first polarizing beam splitter, through the polarization changing element, to the diffuser element. In such embodiments, at the first polarizing beam splitter at least part of the third device light may be reflected or transmitted, dependent upon a polarization of the third device light. Further, in embodiments, the polarization changing element may be configured to convert linearly polarized light not elliptically polarized light, i.e., linearly polarized third device light incident on the polarization changing element may be converted into elliptically polarized third device light. At the diffuser element, in embodiments, at least part of the (elliptically polarized) third device light may be diffused into diffused (elliptically polarized) third device light, while a sense of the elliptically polarized light may be altered to an opposite sense. Further, in embodiments, the light generating system may be configured such that at least part of the diffused third device light may propagate (from the diffuser element) through the polarization changing element to the first polarizing beam splitter. In embodiments, at the polarization changing element at least part of the elliptically polarized (third device) light may be converted into a type of (linearly) polarized light, different from which the third device light reached the polarization changing element. Especially, in such embodiments, the diffused third device light may be converted into the second type of (linearly) polarized light, different from the first type of linearly polarized light. Further, in embodiments, at the first polarizing beam splitter at least part of the diffused third device light may, dependent upon the type of linear polarization, be transmitted or reflected. Especially, in embodiments, at least part of the diffuse third device light may be transmitted or reflected to provide a beam of light comprising one or more of the diffused first device light, the diffused second device light, and the diffused third device light. Furthermore, in embodiments, the polarization changing element may comprise a X/4 wavelength plate configured to be a p^th order X/4 wavelength plate for the third peak wavelength (Xp3). Especially, in such embodiments, the X/4 wave plate may be configured to be a (p/k3)*X/4 wave plate for the third peak wavelength (Xp3). More specially, in embodiments, p may be an odd positive integer, especially p>E Additionally, in embodiments, |n-p|>l and |m-p|>l, especially, |n-p| and |m-p| may be positive integers, especially even positive integers. Furthermore, in such embodiments, k3 may be selected from the range of 0.8-E2. Hence, in specific embodiments, the light generating system further comprises a third light generating device, wherein: (A) the third light generating device is configured to generate third device light having a third peak wavelength (Xp3); wherein the first peak wavelength (Xpl), the second peak wavelength (Xp2), and the third peak wavelength (Xp3) mutually differ; wherein the third light generating device comprises a diode laser or a superluminescent diode; (B) the light generating system is configured such that: (a) third device light reaching the first polarizing beam splitter comprises polarized light; (b) the third device light propagates: (i) via the first polarizing beam splitter, where at least part of the third device light, dependent upon a polarization of the third device light, is reflected or transmitted, (ii) through the polarization changing element, (iii) to the diffuser element, where at least part of the third device light is diffused into diffused third device light, while a sense of the elliptically polarized light is altered to an opposite sense; (c) at least part of the diffused third device light propagates: (i) through the polarization changing element, where at least part of the elliptically polarized light is converted into a type of linearly polarized light, different from which the third device light reached the polarization changing element, (ii) to the first polarizing beam splitter, where at least part of the diffused third device light, dependent upon the type of linear polarization, is transmitted or reflected; and (C) the X/4 wave plate is configured to be a (p/k3)*X/4 wave plate for the third peak wavelength (Xp3), wherein in specific embodiments p is an odd positive integer, wherein in specific embodiments |n-p| and |m-p| are positive integers, especially even positive integers, and wherein k3 is selected from the range of 0.8-E2.

Such embodiments may be beneficial as, compared to the previously described light generating system comprising the third light generating device, the system may comprise less elements, i.e., the system may be less bulky. Hence, the embodiments as described here may be beneficial as the addition of a third light source may provide better tuning of the correlated color temperature (CCT) and spectral power distribution of the output light of the system (or “system light”). Especially, with the above described system, different colors of light may be combined to provide high brightness white light with improved color rendering index (CRI), without increasing the bulkiness of the system.

Hence, in embodiments, the system may essentially be the same system comprising a first light generating device, a second light generating device, a diffuser element, a polarization changing element, and a first polarizing beam splitter as described above, but with the additional third light generating device, which has been described in more detail above.

Here, in embodiments, in an operational mode, the light generating system may be configured such that first device light, second device light and third device light reaching the first polarizing beam splitter may all comprise polarized light. Especially, in embodiments, the light generating system may, in an operational mode, be configured such that first device light, second device light, and third device light reaching the first polarizing beam splitter may all comprise the same type of polarized light, especially linearly polarized light. For example, in embodiments, the first device light, the second device light and the third device light may all comprise s polarized light. In particular, in embodiments, the first device light, the second device light, and the third device light may all comprise p polarized light.

As the path of the device light through the light generating system is, in embodiments, (largely) dependent upon the type of polarization of the device light, the first device light, the second device light, and the third device light (having the same type of polarization) may follow essentially the same path through the light generating system. Hence, in embodiments, the third device light may follow the same path through the light generating system as described above for the first device light and the second device light.

Further, as described above, the polarization changing element may comprise a X/4 wave plate configured to be (i) an (n/kl)*X/4 wave plate for the first peak wavelength (Xpl) (ii) an (m/k2)*X/4 wave plate for the second peak wavelength (Xp2). Additionally, in embodiments as described here, the /4 wave plate may further be configured to be a (p/k3)*X/4 wave plate for the third peak wavelength (Xp3). Hence, in embodiments, the polarization changing element may comprise a X/4 wave plate configured to be a X/4 wave plate for both the first peak wavelength (Xpl), the second peak wavelength (Xp2), and the third peak wavelength (Zp3), but at different orders respectively. In embodiments, p may be at least one, such as at least three, like at least five, i.e., p>l. Especially, in embodiments, p may be a positive integer, more especially an odd positive integer. As mentioned above, the orders for the first peak wavelength (kpl), the second peak wavelength (Zp2), and the third peak wavelength (Zp3) may especially differ. Hence, in embodiments, p may be unequal to n, i.e., |n-p|>l, more especially |n-p|>2Especially, in embodiments, |n-p| may be a positive integer, more especially an even positive integer. Additionally or alternatively, in embodiments, p may be unequal to m, i.e., |m-p|>l, more especially |m-p|>2. Especially, in embodiments, |m-p| may be a positive integer, more especially, an even positive integer. Furthermore, in embodiments, as mentioned above, there may be a slight freedom in the order p, i.e., the odd integer selected for p may be varied slightly (or corrected) by the factor k3. Hence, in embodiments, k3 may be a correction factor and may each be selected from the range of 0.8-1.2, such as from the range of 0.9-1.1, like from the range of 0.95-1.05.

In embodiments, the light generating devices may thus be different. Especially, in embodiments, the first, second and third light generating devices may be different with respect to both their peak wavelengths. More especially, in embodiments, the first peak wavelength (kpl), the second peak wavelength (Zp2), and the third peak wavelength (Zp3), may be selected in mutually different wavelength ranges. The mutually different wavelength ranges may especially, in embodiments, be selected from the blue wavelength range, the green wavelength range, and the red wavelength range. In embodiments, for the blue wavelength range the peak wavelength may be selected from the range of 400-495 nm, such as from the range of 420-490 nm, like from the range of 440-490 nm especially from the range of 450-470 nm. Further, in embodiments, for the green wavelength range the peak wavelength may be selected from the range of 495-575 nm, such as from the range of 495-570, like from the range of 500-560 nm, especially from the range of 520-540 nm. Yet further, in embodiments, for the red wavelength range the peak wavelength may be selected from the range of 595-780 nm, such as from the range of 600- 760 nm, like from the range of 620-750 nm, especially from the range of 630-720 nm. Hence, in specific embodiments, the first peak wavelength (kpl), the second peak wavelength (Zp2), and the third peak wavelength (Zp3), are selected in mutually different wavelength ranges selected from 440-490 nm, 500-560 nm, and 620-750 nm.

As the first, second and third light generating devices may be different with respect to their peak wavelengths, in embodiments, the light generating system may further comprise one or more first dichroic beam splitters, see also further above. In embodiments, the first dichroic beam splitter may be used to combine the beams of the three types of light generating devices. Especially, the first dichroic beam splitter may be configured downstream of the three different types of light generating devices and upstream of the first polarizing beam splitter.

In embodiments, the first dichroic beam splitter may be configured to transmit at least part of one (or two) of the first device light, the second device light and the third device light, and to reflect at least part of the other (one or) two of the first device light, the second device light, and the third device light. For example, in embodiments, the first dichroic beam splitter may be configured to transmit at least 90% of the first device light and the second device light (e.g. blue device light and green device light) and to reflect at least 90% of the third device light (e.g. red device light).

Further, in embodiments, the light generating system may comprise two (different) first dichroic beam splitters as described above. For example, in such embodiments, one of the first dichroic beam splitters may be selected having a dichroic wavelength with a cut-on / cut-off wavelength for separating light having a blue wavelength and light having a red wavelength, whereas the other one of the first dichroic beam splitters may be selected having a dichroic wavelength with a cut-on / cut-off wavelength for separating light having a blue wavelength and light having a green wavelength.

The light generating system may, in embodiments, further comprise a fourth light generating device, a first luminescent material, and one or more second dichroic beam splitters. In embodiments, the fourth light generating device may be configured to generate fourth device light having a fourth peak wavelength (Zp4). Especially, in embodiments, the fourth light generating device may comprise a diode laser or a superluminescent diode. Further, in embodiments, the first luminescent material may be configured to convert at least part of the fourth device light into first luminescent material light. Yet further, in embodiments, the one or more second dichroic beam splitters may be configured to reflect or transmit at least part of the fourth device light. Further, the one or more second dichroic beam splitters may be configured to transmit or reflect at least part of the first luminescent material light. In such embodiments, the light generating system may be configured such that at least part of the first luminescent material light may propagate via the one or more second dichroic beam splitters to the first polarizing beam splitter. At the one or more second dichroic beam splitters, in embodiments, the first luminescent material light may be reflected or transmitted. Especially, in embodiments, the first luminescent material light may be reflected or transmitted at the one or more second dichroic beam splitters to the first polarizing beam splitter. In embodiments, at the first polarizing beam splitter at least part of the first luminescent material light may be reflected or transmitted in the same direction as the direction where diffused first device light and the diffused second device light are transmitted or reflected to by the first polarizing beam splitter. Hence, in embodiments, at least part of the first luminescent material light may be reflected or transmitted in the same direction as the diffused first device light and the diffused second device light, propagating from the polarization changing element to the first polarizing beam splitter, may be transmitted or reflected to by the first polarizing beam splitter. Hence, in embodiments, the light generating system further comprises a fourth light generating device, a first luminescent material, and one or more second dichroic beam splitters, wherein: (A) the fourth light generating device is configured to generate fourth device light having a fourth peak wavelength (Zp4 ); wherein the fourth light generating device comprises a diode laser or a superluminescent diode; (B) the first luminescent material is configured to convert at least part of the fourth device light into first luminescent material light; (C) the one or more second dichroic beam splitters are configured to reflect or transmit at least part of the fourth device light, and to transmit or reflect at least part of the first luminescent material light; and (D) the light generating system is configured such that at least part of the first luminescent material light propagates: (i) via the one or more second dichroic beam splitters, (ii) to the first polarizing beam splitter, where at least part of the first luminescent material light is reflected or transmitted in the same direction as the diffused first device light and the diffused second device light, propagating from the polarization changing element to the first polarizing beam splitter, is transmitted or reflected to by the first polarizing beam splitter.

With such embodiments high brightness white light with an improved color rendering index (CRI) may be achieved using a luminescent converter.

In embodiments, the fourth light generating device may be configured to generate fourth device light. Especially, in embodiments, the fourth device light may have a fourth peak wavelength (Zp4). In embodiments, the fourth peak wavelength (Zp4) may be essentially the same wavelength as one of the first peak wavelength (kpl), the second peak wavelength (Zp2) and the third peak wavelength (Zp3). Herein, the phrase “essentially the same wavelength as X” and similar phrases may refer to a wavelength being either exactly the same wavelength as the wavelength X, which it refers to, or to a wavelength substantially similar to the wavelength X, such as X±20 nm, especially X±10 nm, like X±5 nm. For example, in embodiments, the fourth peak wavelength may be essentially the same wavelength (Zp4) as the first peak wavelength (Zp4), i.e., Xp4=Z,pl or kp4=Z,pl±20 nm (, especially Xp4=Xpl±10 nm), such as Xp4=Xpl±5 nm. However, in other embodiments, the fourth peak wavelength may be different from all three of the first peak wavelength (kpl), the second peak wavelength (Zp2) and the third peak wavelength (Zp3). For example, in embodiments, the fourth peak wavelength (Zp4) may be selected from the blue wavelength range. In other embodiments, e.g., the fourth peak wavelength (Zp4) may be selected from the green wavelength range. Further, in embodiments, the fourth light generating device may comprise a solid state light source. Especially, the fourth light generating device may, in embodiments, comprise a diode laser or a superluminescent diode, see also further above.

In embodiments, the fourth light generating device and the first luminescent material may be selected such, and the first luminescent material may be configured such that the first luminescent material may convert at least part of the fourth device light into first luminescent material light. Hence, in embodiments, the first luminescent material may be configured to convert at least part of the fourth device light into first luminescent material light, such as at least 60% of the fourth device light, like at least 70% of the fourth device light, especially at least 80% of the fourth device light, such as at least 90% of the fourth device light, including at least 95% of the fourth device light.

Especially, the luminescent body may be configured in the reflective mode. In the reflective mode, thermal management may be easier, as a substantial part of the luminescent material may be in thermal contact with a thermally conductive element, like a heatsink or heat spreader. In embodiments, the luminescent body may be configured on a rotatable phosphor device, such as a phosphor wheel.

The luminescent material may in other embodiments be operated in the transmissive mode. Herein, when an element is indicated to be operated in a transmissive mode this may, in embodiments, imply that at one or more wavelengths the part of the radiation that is transmitted may be larger than the part of the radiation that is reflected or absorbed. Herein, when an element is indicated to be operated in a reflective mode this may in embodiments imply that at one or more wavelengths the part of the radiation that is reflected may be larger than the part of the radiation that is transmitted or absorbed. Hence, the luminescent material may be translucent and be light scattering for part of the received device light.

The luminescent material may be provided as luminescent body. Hence, the system may comprise a luminescent body comprising the luminescent material.

The term “luminescent material” especially refers to a material that can convert first radiation, especially one or more of UV radiation and blue radiation, into second radiation. In general, the first radiation and second radiation have different spectral power distributions. Hence, instead of the term “luminescent material”, also the terms “luminescent converter” or “converter” may be applied. In general, the second radiation has a spectral power distribution at larger wavelengths than the first radiation, which is the case in the so- called down-conversion. In specific embodiments, however the second radiation has a spectral power distribution with intensity at smaller wavelengths than the first radiation, which is the case in the so-called up-conversion.

In embodiments, the “luminescent material” may especially refer to a material that can convert radiation into e.g. visible and/or infrared light. For instance, in embodiments the luminescent material may be able to convert one or more of UV radiation and blue radiation, into visible light. The luminescent material may in specific embodiments also convert radiation into infrared radiation (IR). Hence, upon excitation with radiation, the luminescent material emits radiation. In general, the luminescent material will be a down converter, i.e. radiation of a smaller wavelength is converted into radiation with a larger wavelength (Xe_X<Xem), though in specific embodiments the luminescent material may comprise up-converter luminescent material, i.e. radiation of a larger wavelength is converted into radiation with a smaller wavelength (k >km).

In embodiments, the term “luminescence” may refer to phosphorescence. In embodiments, the term “luminescence” may also refer to fluorescence. Instead of the term “luminescence”, also the term “emission” may be applied. Hence, the terms “first radiation” and “second radiation” may refer to excitation radiation and emission (radiation), respectively. Likewise, the term “luminescent material” may in embodiments refer to phosphorescence and/or fluorescence.

The term “luminescent material” may also refer to a plurality of different luminescent materials. Examples of possible luminescent materials are indicated below. Hence, the term “luminescent material” may in specific embodiments also refer to a luminescent material composition. Instead of the term “luminescent material” also the term “phosphor” may be applied. These terms are known to the person skilled in the art.

In embodiments, luminescent materials are selected from garnets and nitrides, especially doped with trivalent cerium or divalent europium, respectively. The term “nitride” may also refer to oxynitride or nitridosilicate, etc. Alternatively or additionally, the luminescent material(s) may be selected from silicates, especially doped with divalent europium. In specific embodiments the luminescent material comprises a luminescent material of the type AsBsO^Ce, wherein A in embodiments comprises one or more of Y, La, Gd, Tb and Lu, especially (at least) one or more of Y, Gd, Tb and Lu, and wherein B in embodiments comprises one or more of Al, Ga, In and Sc. Especially, A may comprise one or more of Y, Gd and Lu, such as especially one or more of Y and Lu. Especially, B may comprise one or more of Al and Ga, more especially at least Al, such as essentially entirely Al. Hence, especially suitable luminescent materials are cerium comprising garnet materials. Embodiments of garnets especially include A3B5O12 garnets, wherein A comprises at least yttrium or lutetium and wherein B comprises at least aluminum. Such garnets may be doped with cerium (Ce), with praseodymium (Pr) or a combination of cerium and praseodymium; especially however with Ce. Especially, B may comprise aluminum (Al); however, in addition to aluminum, B may also partly comprise gallium (Ga) and/or scandium (Sc) and/or indium (In), especially up to about 20% of B, more especially up to about 10 % of B (i.e. the B ions essentially consist of 90 or more mole % of Al and 10 or less mole % of one or more of Ga, Sc and In); B may especially comprise up to about 10% gallium. In another variant, B and O may at least partly be replaced by Si and N. The element A may especially be selected from the group consisting of yttrium (Y), gadolinium (Gd), terbium (Tb) and lutetium (Lu). Further, Gd and/or Tb are especially only present up to an amount of about 20% of A. In a specific embodiment, the garnet luminescent material comprises (Yi.xLuxfB O^ Ce, wherein x is equal to or larger than 0 and equal to or smaller than 1. The term “:Ce”, indicates that part of the metal ions (i.e. in the garnets: part of the “A” ions) in the luminescent material is replaced by Ce. For instance, in the case of (Yi._xLu_x)3A150i2:Ce, part of Y and/or Lu is replaced by Ce. This is known to the person skilled in the art. Ce will replace A in general for not more than 10%; in general, the Ce concentration will be in the range of 0.1 to 4%, especially 0.1 to 2% (relative to A). Assuming 1% Ce and 10% Y, the full correct formula could be (Yo.iLuo.89Ceo.oi)3Al₅Oi2. Ce in garnets is substantially or only in the trivalent state, as is known to the person skilled in the art.

In embodiments, the luminescent material (thus) comprises A3B5O12 wherein in specific embodiments at maximum 10% of B-0 may be replaced by Si-N.

Alternatively or additionally, wherein the luminescent material may comprises a luminescent material of the type A3SieNn:Ce³⁺, wherein A comprises one or more of Y, La, Gd, Tb and Lu, such as in embodiments one or more of La and Y.

In embodiments, the luminescent material may alternatively or additionally comprise one or more of MS:Eu²⁺ and/or LSi Nx Eu^2- and/or MalSiN3:Eu²⁺ and/or Ca2AlSi3O2Ns:Eu²⁺, etc., wherein M comprises one or more of Ba, Sr and Ca, especially in embodiments at least Sr. Hence, in embodiments, the luminescent may comprise one or more materials selected from the group consisting of (Ba,Sr,Ca)S:Eu, (Ba,Sr,Ca)AlSiN3:Eu and (Ba,Sr,Ca)2SisN8:Eu. In these compounds, europium (Eu) is substantially or only divalent, and replaces one or more of the indicated divalent cations. In general, Eu will not be present in amounts larger than 10% of the cation; its presence will especially be in the range of about 0.5 to 10%, more especially in the range of about 0.5 to 5% relative to the cation(s) it replaces. The term “:Eu”, indicates that part of the metal ions is replaced by Eu (in these examples by Eu²⁺). For instance, assuming 2% Eu in CaAlSiNvEu, the correct formula could be (Cao.9sEuo.o2)AlSiN3. Divalent europium will in general replace divalent cations, such as the above divalent alkaline earth cations, especially Ca, Sr or Ba. The material (Ba,Sr,Ca)S:Eu can also be indicated as MS:Eu, wherein M is one or more elements selected from the group consisting of barium (Ba), strontium (Sr) and calcium (Ca); especially, M comprises in this compound calcium or strontium, or calcium and strontium, more especially calcium. Here, Eu is introduced and replaces at least part of M (i.e. one or more of Ba, Sr, and Ca). Further, the material (Ba,Sr,Ca)2SisN8:Eu can also be indicated as NESis Eu, wherein M is one or more elements selected from the group consisting of barium (Ba), strontium (Sr) and calcium (Ca); especially, M comprises in this compound Sr and/or Ba. In a further specific embodiment, M consists of Sr and/or Ba (not taking into account the presence of Eu), especially 50 to 100%, more especially 50 to 90% Ba and 50 to 0%, especially 50 to 10% Sr, such as Bai. Sro. Si Ns Eu (i.e. 75 % Ba; 25% Sr). Here, Eu is introduced and replaces at least part of M, i.e. one or more of Ba, Sr, and Ca). Likewise, the material (Ba,Sr,Ca)AlSiN3:Eu can also be indicated as MalSiNvEu, wherein M is one or more elements selected from the group consisting of barium (Ba), strontium (Sr) and calcium (Ca); especially, M comprises in this compound calcium or strontium, or calcium and strontium, more especially calcium. Here, Eu is introduced and replaces at least part of M (i.e. one or more of Ba, Sr, and Ca). Eu in the above indicated luminescent materials is substantially or only in the divalent state, as is known to the person skilled in the art.

The term “luminescent material” herein especially relates to inorganic luminescent materials.

Alternatively or additionally, also other luminescent materials may be applied. For instance quantum dots and/or organic dyes may be applied and may optionally be embedded in transmissive matrices like e.g. polymers, like PMMA, or polysiloxanes, etc. etc.. Different luminescent materials may have different spectral power distributions of the respective luminescent material light. Alternatively or additionally, such different luminescent materials may especially have different color points (or dominant wavelengths).

As indicated above, other luminescent materials may also be possible. Hence, in specific embodiments the luminescent material is selected from the group of divalent europium containing nitrides, divalent europium containing oxynitrides, divalent europium containing silicates, cerium comprising garnets, and quantum structures. Quantum structures may e.g. comprise quantum dots or quantum rods (or other quantum type particles) (see above). Quantum structures may also comprise quantum wells. Quantum structures may also comprise photonic crystals.

Hence, in embodiments, the first luminescent material may be configured to generate first luminescent material light. To help guide the fourth device light and the luminescent material light on their respective optical paths, the light generating system may, in embodiments, comprise the one or more second dichroic beam splitters. Therefore, in embodiments, the one or more second dichroic beam splitters may be configured downstream of the fourth light generating device and upstream of the luminescent material.

Dichroic beam splitters have been described above. Especially, in embodiments, a second dichroic beam splitter may be configured to reflect light with one peak wavelength, while transmitting light with another peak wavelength. Here, in an operational mode, in embodiments, the one or more second dichroic beam splitters may be configured to reflect at least part of the fourth device light and to transmit at least part of the first luminescent material light. Alternatively, in another operational mode, in embodiments, the one or more second dichroic beam splitters may be configured to transmit at least part of the fourth device light and to reflect at least part of the first luminescent material light.

Furthermore, in an operational mode, in embodiments, the light generating system may be configured such that at least part of the first luminescent material light may propagate (from the luminescent material) via the one or more second dichroic beam splitters to the first polarizing beam splitter. Especially, in such embodiments, the first luminescent material light may propagate to the first polarizing beam splitter in essentially the same direction as the direction where the diffused first device light and the diffused second device light may be transmitted or reflected to by the first polarizing beam splitter. Hence, in such embodiments, the first luminescent material light, the diffused first device light, and the diffused second device light may be combined into a beam of system light propagating out of the system from the first polarizing beam splitter. Especially, in embodiments, the beam of system light may be white system light.

Therefore, in embodiments, the first polarizing beam splitter may be transmissive for at least part of the first luminescent material light. Especially, in embodiments, the first polarizing beam splitter may be transmissive for at least 60%, such as at least 70%, like at least 80%, especially at least 90%, more especially at least 95% of the first luminescent material light (received by the first polarizing beam splitter).

As illustrated with the embodiments described above, the light generating system may thus be configured to combine different types of device light, especially having different peak wavelengths. Especially, in embodiments, the light generating may be configured to generate system light comprising one or more of diffused first device light (transmitted or reflected at the first polarizing beam splitter), diffused second device light (transmitted or reflected at the first polarizing beam splitter), and diffused third device light (transmitted or reflected at the first polarizing beam splitter). Additionally or alternatively, in embodiments, the light generating system may be configured to generate system light comprising one or more of the diffused first device light, the diffused second device light, the diffused third device light, and the first luminescent material light (transmitted at the first polarizing beam splitter. Hence, in specific embodiments, the light generating system is configured to generate system light comprising one or more of diffused first device light, diffused second device light, diffused third device light, and optionally first luminescent material light.

The light generating system may be part of or may be applied in e.g. office lighting systems, household application systems, shop lighting systems, home lighting systems, accent lighting systems, spot lighting systems, theater lighting systems, fiber-optics application systems, projection systems, self-lit display systems, pixelated display systems, segmented display systems, warning sign systems, medical lighting application systems, indicator sign systems, decorative lighting systems, portable systems, automotive applications, (outdoor) road lighting systems, urban lighting systems, green house lighting systems, horticulture lighting, digital projection, or LCD backlighting. The light generating system (or luminaire) may be part of or may be applied in e.g. optical communication systems or disinfection systems.

Therefore, in embodiments, the light generating system may be configured to generate white light. Especially, in embodiments, the light generating system may be configured to provide in an operational mode (of the light generating system) system light. The system light may thus, in embodiments, be white light. Especially, in embodiments, the system light may have a correlated color temperature selected from the range of 1800-12000 K, such as from the range of 2000-10000 K, like from the range of 2000-7000 K. Furthermore, in embodiments, the light generating system may comprise a control system. The control system may especially be configured to control a spectral power distribution and radiant flux of the system. Hence, in specific embodiments, the light generating system may be configured to provide, in an operational mode, system light having a correlated color temperature selected from the range of 1800-12000 K; wherein the light generating system may further comprise a control system, wherein the control system may be configured to control a spectral power distribution and radiant flux of the system light.

The term “white light”, and similar terms, herein, is known to the person skilled in the art. It may especially relate to light having a correlated color temperature (CCT) between about 1800 K and 20000 K, such as between 2000 and 20000 K, especially 2700- 20000 K, for general lighting especially in the range of about 2000-7000 K, such as in the range of 2700 K and 6500 K. In embodiments, e.g. for backlighting purposes, or for other purposes, the correlated color temperature (CCT) may especially be in the range of about 7000 K and 20000 K. Yet further, in embodiments the correlated color temperature (CCT) is especially within about 15 SDCM (standard deviation of color matching) from the BBL (black body locus), especially within about 10 SDCM from the BBL, even more especially within about 5 SDCM from the BBL. In specific embodiments, the correlated color temperature (CCT) may be selected from the range of 6000-12000 K, like selected from the range of 7000-12000 K, like at least 8000 K. Yet further, in embodiments the correlated color temperature (CCT) may be selected from the range of 6000-12000 K, like selected from the range of 7000-12000 K, in combination with a CRI of at least 70.

The term “controlling” and similar terms especially refer at least to determining the behavior or supervising the running of an element. Hence, herein “controlling” and similar terms may e.g. refer to imposing behavior to the element (determining the behavior or supervising the running of an element), etc., such as e.g. measuring, displaying, actuating, opening, shifting, changing temperature, etc.. Beyond that, the term “controlling” and similar terms may additionally include monitoring. Hence, the term “controlling” and similar terms may include imposing behavior on an element and also imposing behavior on an element and monitoring the element. The controlling of the element can be done with a control system, which may also be indicated as “controller”. The control system and the element may thus at least temporarily, or permanently, functionally be coupled. The element may comprise the control system. In embodiments, the control system and element may not be physically coupled. Control can be done via wired and/or wireless control. The term “control system” may also refer to a plurality of different control systems, which especially are functionally coupled, and of which e.g. one control system may be a master control system and one or more others may be slave control systems. A control system may comprise or may be functionally coupled to a user interface.

The system, or apparatus, or device may execute an action in a “mode” or “operation mode” or “mode of operation” or “operational mode”. The term “operational mode may also be indicated as “controlling mode”. Likewise, in a method an action or stage, or step may be executed in a “mode” or “operation mode” or “mode of operation” or “operational mode”. This does not exclude that the system, or apparatus, or device may also be adapted for providing another controlling mode, or a plurality of other controlling modes. Likewise, this may not exclude that before executing the mode and/or after executing the mode one or more other modes may be executed.

However, in embodiments a control system may be available, that is adapted to provide at least the controlling mode. Would other modes be available, the choice of such modes may especially be executed via a user interface, though other options, like executing a mode in dependence of a sensor signal or a (time) scheme, may also be possible. The operation mode may in embodiments also refer to a system, or apparatus, or device, that can only operate in a single operation mode (i.e. “on”, without further tunability).

Hence, in embodiments, the control system may control in dependence of one or more of an input signal of a user interface, a sensor signal (of a sensor), and a timer. The term “timer” may refer to a clock and/or a predetermined time scheme.

In yet a further aspect, the invention also provides a lamp or a luminaire comprising the light generating system as defined herein. The luminaire may further comprise a housing, optical elements, louvres, etc. etc... The lamp or luminaire may further comprise a housing enclosing the light generating system. The lamp or luminaire may comprise a light window in the housing or a housing opening, through which the system light may escape from the housing. In yet a further aspect, the invention also provides a projection device comprising the light generating system as defined herein. Especially, a projection device or “projector” or “image projector” may be an optical device that projects an image (or moving images) onto a surface, such as e.g. a projection screen. The projection device may include one or more light generating systems such as described herein. Hence, in an aspect the invention also provides a lighting device selected from the group of a lamp, a luminaire, a projector device, a disinfection device, a photochemical reactor, an automotive lighting device, and an optical wireless communication device, comprising the light generating system as defined herein. Yet, in an aspect the invention also provides a stage lighting device comprising the lighting device as described herein. The lighting device may comprise a housing or a carrier, configured to house or support, one or more elements of the light generating system. For instance, in embodiments the lighting device may comprise a housing or a carrier, configured to house or support one or more of the first light generating device, the second light generating device, and one or more of the aforementioned optics. The lighting device may also be an automotive lighting device, such as a headlamp (or headlight) of a motorized vehicle (like a car, a truck, a bus, a coach, a tractor, a boat, an airplane, etc.).

The term “centroid wavelength”, also indicated as c, is known in the art, and refers to the wavelength value where half of the light energy is at shorter and half the energy is at longer wavelengths; the value is stated in nanometers (nm). It is the wavelength that divides the integral of a spectral power distribution into two equal parts as expressed by the formula kc = X I(k) / (S I( A)), where the summation is over the wavelength range of interest, and I (A) is the spectral energy density (i.e. the integration of the product of the wavelength and the intensity over the emission band normalized to the integrated intensity). The centroid wavelength may e.g. be determined at operation conditions.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings in which corresponding reference symbols indicate corresponding parts, and in which:

Fig. la-d schematically depict some embodiments of the light generating system.; and

Fig. 2 schematically depicts some application embodiments. The schematic drawings are not necessarily to scale.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Fig. 1 schematically depicts some embodiments of the invention. The invention especially provides a light generating system 1000 comprising (at least) a first light generating device 110, a second light generating device 120, a diffuser element 710, a polarization changing element 810, and a first polarizing beam splitter 1525. The first light generating device 110 may especially, in embodiments, be configured to generate first device light 111 having a first peak wavelength (kpl ). Similarly, the second light generating device 120 may, in embodiments, be configured to generate second device light 121 having a second peak wavelength (Zp2). In embodiments, the first peak wavelength (kpl) and the second peak wavelength (Zp2) may be different, i.e., A,pl^Z,p2. Especially, in embodiments, |kcl-kcl|>10 nm. Further, in embodiments, each of the first light generating device 110 and the second light generating device 110 comprises a diode laser or a superluminescent diode.

Fig. la schematically depicts a specific embodiment of the invention. Here especially, the light generating system 1000 is configured (in an operational mode) such that: the first device light 111 and the second device light 121 reaching the first polarizing beam splitter 1525 both comprise a first type of linearly polarized light pl (e.g. p-polarized light).

Further, the light generating system 1000 is configured such that the first device light 111 and the second device light 121 propagate: (from the respective light generating devices 110,120) (i) through the first polarizing beam splitter 1525, (ii) through the polarization changing element 810, (iii) to the diffuser element 710. Especially, as depicted here, the second device light 121 may propagate from the second light generating device 120 via a reflector 570 to the first polarizing beam splitter 1525. At the first polarizing beam splitter at least part of the first device light 111 and the second device light 121, dependent upon the type of linear polarization, are reflected or transmitted. Especially, as depicted here, the first device light 111 and the second device light 121 having the first type of linearly polarized light pl are transmitted by the first polarizing beam splitter 1525. In embodiments, the polarization changing element 810 is configured to convert linearly polarized light into elliptically polarized light. Hence, the first type of linearly polarized device light pl transmitted or reflected by the first polarizing beam splitter 1525 reaching the polarization changing element 810 is converted into a first type of elliptically polarized light el. For example, p polarized first device light 111 and p polarized second device light 121 reaching the polarization changing element 810 are thus converted into the first type of elliptically polarized el first device light 111 and the first type of elliptically polarized el second device light 121, respectively. At the diffuser element 710 at least part of the first device light 111 and at least part of the second device light 121 are diffused into diffused first device light 711 and diffused second device light 721, respectively, while a sense of the elliptically polarized light is altered to an opposite sense. Hence, if the sense of the first type of elliptically polarized device light el was right-handed, after diffusion of the light the sense of a second type of elliptically polarized light e2 is altered to left-handed, and vice versa.

Subsequently, the light generating system 1000 is configured (in an operational mode) such that: at least part of the diffused first device light 711 and at least part of the diffused second device light 721, propagate: (from the diffuser element 710) (i) through the polarization changing element 810, (ii) to the first polarizing beam splitter 1525. At the polarization changing element 810 at least part of the second type of elliptically polarized light e2 is converted into a second type of (linearly) polarized light p2, different from the first type of linearly polarized light el. For example at least part of the (second type of) elliptically polarized e2 diffused first device light 711 and at least part of the (second type of) elliptically polarized e2 diffused second device light 721 is converted into s polarized diffused first device light 711 and s polarized diffused second device light 721, respectively. At the first polarizing beam splitter 1525 at least part of the diffused first device light 711 and at least part of the diffused second device light 721, dependent upon the type of linear polarization, are reflected or transmitted. Especially, as depicted here, the diffused first device light 711 and the diffused second device light 721 are reflected by the first polarizing beam splitter 1525. Especially, the diffused first device light 711 and the diffused second device light 721 are reflected by the first polarizing beam splitter 1525 are reflected to provide a beam 1010 of light comprising one or more of the diffused first device light 711 and diffused second device light 721.

For the light generating system 1000 to function as described, in embodiments, the polarization changing element 810 especially comprises an X/4 wave plate configured to (i) convert (the first type of) linearly polarized light pl into (a first type of) circular polarized light (el) and (ii) (a second type of) circularly polarized light (e2) into (the second type of) linearly polarized light p2. Especially, the X/4 wave plate is configured to be an (n/kl)*X/4 wave plate for the first peak wavelength (Xpl) and an (m/k2)*X/4 wave plate for the second peak wavelength (Xp2). In embodiments, n and m may be odd positive integers. Further, in embodiments, |n-m| may be an even positive integer. Furthermore, in embodiments, kl and k2 are each individually selected from the range of 0.8-1.2.

In specific embodiments (not depicted) kl=k2=l. Especially, in such embodiments, the polarization changing element 810 may be configured to convert the first device light 111 and the second device light 121, comprising the first type of linearly polarized light pl, into (the first type of) circularly polarized (el) first device light 111 and (the first type of) circularly polarized (el) second device light 121, respectively. Further, in such embodiments, the diffuser element 710 may be configured to diffuse at least part of the first device light 111 and at least part of the second device light 121 into diffused first device light 711 and diffused second device light 721, respectively. The diffuser element 710 may especially do so while a sense of the (first type of) circularly polarized light (el) is altered to an opposite sense, i.e., right-handed circular polarization may be altered to left-handed circular polarization, and vice versa. Yet further, in such embodiments, the polarization changing element 810 may (also) be configured to convert at least part of the (second type of circularly polarized e2) diffused first device light 711 and at least part of the (second type of circularly polarized e2) diffused second device light 721 into diffused first device light 711 and diffused second device light 721 comprising the second type of (linearly) polarized light p2.

In embodiments, one of the first peak wavelength (kpl) and the second peak wavelength (Zp2) may be selected in the wavelength range of 430-490 nm. Especially, in such embodiments, the other one of the first peak wavelength (kpl) and the second peak wavelength (Ap2) may be selected from the wavelength range of 600-680 nm. Furthermore, in embodiments, |Xp2-Xpl |>50 nm.

In specific embodiments, one of the first peak wavelength (kpl) and the second peak wavelength (Zp2) may be selected in the wavelength range of 440-460 nm. In such embodiments, the other one of the first peak wavelength (kpl) and the second peak wavelength (Ap2) may be selected from the wavelength range of 630-660 nm.

Further, in embodiments, n and m may be individually selected from 1, 3, 5, and 7, and |n-m|=2.

Yet further, in embodiments, the diffuser element 710 may comprise a metallic diffuser comprising a non-flat surface (not shown here).

In specific embodiments, the first light generating device 110 comprises a diode laser. Especially, the first device light 111 comprises p polarized or s polarized laser light. Further, in such embodiments, the second light generating device 120 comprises a diode laser. Especially, the second device light 121 comprises p polarized or s polarized laser light. For example, in embodiments, the first type of linearly polarized light is p-polarized light, and the second type of linearly polarized light is s-polarized light.

The light generating system 1000 may further, in embodiments, comprise one or more first dichroic beam splitters 1515. As depicted in Fig. 1, a first dichroic beam splitter 1525 may especially be configured downstream of the first light generating device 110 and the second light generating device 120 (and the third light generating device 130, see Fig. lb- c and below), and configured upstream of the first polarizing beam splitter 1525. In embodiments, the one or more first dichroic beam splitters 1515 are configured to combine at least part of the first device light 111 and at least part of the second device light 121 (and the third device light 131, see Fig. Ib-c and below).

Reference 570 may, in embodiments, refer to a reflector 570. Especially, as depicted in Fig. la, the reflector 570 may be configured to reflect second device light 121 to the first polarizing beam splitter 1525.

Further, in embodiments, the light generating system 1000 may additionally comprise one or more of integrating optics, collimation optics, and homogenization optics. For instance, reference 550 refers to integrators, which may especially be used to beam shape and homogenize light.

Yet further, in embodiments, the light generating system may comprise a control system 300. In embodiments, the light generating system 1000 is configured to provide in an operational mode (of the light generating system 1000) system light 1001. Especially, the system light 1001 may have a correlated color temperature selected from the range of 1800-12000 K. In embodiments, the control system 300 may be configured to control a spectral power distribution and radiant flux of the system light 1001.

Fig. lb schematically depicts another specific embodiment of the invention. Here especially, the light generating system 1000 further comprises a third light generating device 130, a second polarizing beam splitter 2525, a second polarization changing element 281, and a second diffuser element 2710.

In embodiments, the third light generating device 130 may be configured to generate third device light 131 having a third peak wavelength (Xp3 ). The first peak wavelength (kpl), the second peak wavelength (Zp2), and the third peak wavelength (Ap3) may especially, in embodiments, mutually differ. For example, in embodiments, the first light generating device 110, the second light generating device 120 and the third light generating device 130 may have peak wavelengths selected from the red, green and blue wavelength ranges, i.e., they may together provide red, green, and blue (RGB) device light 101. Further, in embodiments, the third light generating device 130 may comprise a diode laser or a superluminescent diode.

Here especially, the light generating system 1000 is configured (in an operational mode) such that third device light 131 reaching the second polarizing beam splitter 2525 comprises polarized light. Especially, the third device light 131 reaching the second polarizing beam splitter 2525 may comprise polarized light of a different type as of the first device light 111 and the second device light 121. Hence, as depicted in Fig. lb, the third device light 131 may be the second type of (e.g. s) polarized light p2, whereas the first device light 111 and the second device light 121 may be the first type of (e.g. p) polarized light pl.

Further, the light generating system 1000 is configured such that the third device light 131 propagates: (from the third light generating devices 130) (i) through the second polarizing beam splitter 2525, (ii) through the second polarization changing element 2810, (iii) to the second diffuser element 2710. At the second polarizing beam splitter at least part of the third device light 131, dependent upon the type of linear polarization, is reflected or transmitted. Especially, as depicted here, the (second type of) linearly polarized p2 third device light 131 is transmitted by the second polarizing beam splitter 2525. In embodiments, the second polarization changing element 2810 is configured to convert (the second type of) linearly polarized light p2 into (the second type of) elliptically polarized light e2. Hence, linearly polarized device light transmitted or reflected by the second polarizing beam splitter 2525 reaching the second polarization changing element 2810 is converted into elliptically polarized light. Here, the second type of (e.g. s) polarized p2 third device light 131 reaching the second polarization changing element 2810 is thus converted into the second type of elliptically polarized e2 third device light 131. At the second diffuser element 2710 at least part of the third device light 131 is diffused into diffused third device light 731, while a sense of the elliptically polarized light is altered to an opposite sense. Hence, here especially, the second type of elliptically polarized e2 third device light 131 is diffused into a first type of elliptically polarized el diffused third device light 731, wherein the first type and the second type of elliptically polarized light have an opposite sense.

Subsequently, the light generating system 1000 is configured (in an operational mode) such that: at least part of the diffused third device light 731 propagates: (from the second diffuser element 2710) (i) through the second polarization changing element 2810, (ii) to the second polarizing beam splitter 2525. At the second polarization changing element 2810 at least part of the second type of elliptically polarized e2 light is converted into the first type of linearly polarized light pl, different from the second type of linearly polarized light p2. Here especially, at least part of the first type of elliptically polarized el diffused third device light 731 is converted into first type of (e.g. p) polarized pl diffused third device light 731. At the second polarizing beam splitter 2525 at least part of the diffused third device light 731, dependent upon the type of linear polarization, is reflected or transmitted. Especially, as depicted here, the first type of (e.g. p) polarized pl diffused third device light is reflected by the second polarizing beam splitter 2525. Especially, the first type of (e.g. p) polarized pl diffused third device light 731 is reflected by the second polarizing beam splitter 2525 to the first polarizing beam splitter 1525 (where the diffused third device light 731 is transmitted, as depicted here, or reflected, not depicted).

Fig. 1c schematically depicts another specific embodiment of the invention. Here especially, the light generating system 1000 comprises the third light generating device 130, without the second polarizing beam splitter 2525, the second polarization changing element 281, and the second diffuser element 2710.

In embodiments, the third light generating device 130 may be configured to generate third device light 131 having a third peak wavelength (Xp3 ). The first peak wavelength (kpl), the second peak wavelength (Zp2), and the third peak wavelength (Zp3) may especially, in embodiments, mutually differ. Further, in embodiments, the third light generating device 130 may comprise a diode laser or a superluminescent diode.

Here especially, the light generating system 1000 is configured (in an operational mode) such that third device light 131 reaching the first polarizing beam splitter 1525 comprises polarized light. Especially, the third device light 131 reaching the first polarizing beam splitter 1525 may comprise polarized light of the same type as of the first device light 111 and the second device light 121. Hence, as depicted in Fig. 1c, the third device light 131 may be first type of (e.g. p) linearly polarized light pl .

Further, the light generating system 1000 is configured such that the third device light 131 propagates: (from the third light generating devices 130) (i) through the first polarizing beam splitter 1525, (ii) through the polarization changing element 810, (iii) to the diffuser element 710. At the first polarizing beam splitter 1525 at least part of the third device light 131, dependent upon the type of linear polarization, is reflected or transmitted. Especially, as depicted here, the first type of linearly polarized pl third device light 131 is transmitted by the first polarizing beam splitter 1525. In embodiments, the polarization changing element 810 is configured to convert the first type of linearly polarized light pl into a first type of elliptically polarized light el. Hence, the first type of linearly polarized device light pl transmitted or reflected by the first polarizing beam splitter 1525 reaching the polarization changing element 810 is converted into the first type of elliptically polarized light el. Here, (the first type of) linearly polarized pl third device light 131 reaching the polarization changing element 810 is thus converted into (the first type of) elliptically polarized el third device light 131. At the diffuser element 710 at least part of the third device light 131 is diffused into diffused third device light 731, while a sense of the elliptically polarized light is altered to an opposite sense. Hence, here especially, the first type of elliptically polarized el third device light 131 is diffused into a second type of elliptically polarized e2 diffused third device light 731, wherein the first type and the second type of elliptically polarized light have an opposite sense.

Subsequently, the light generating system 1000 is configured (in an operational mode) such that: at least part of the diffused third device light 731 propagates: (from the diffuser element 710) (i) through the polarization changing element 810, (ii) to the first polarizing beam splitter 1525. At the polarization changing element 810 at least part of the second type of elliptically polarized e2 light is converted into a second type of (linearly) polarized light p2, different from the first type of linearly polarized light pl. Here especially, at least part of the second type of elliptically polarized e2 diffused third device light 731 is converted into the second type of (e.g. s) linearly polarized p2 diffused third device light 731. At the first polarizing beam splitter 1525 at least part of the diffused third device light 731, dependent upon the type of linear polarization, is reflected or transmitted. Especially, as depicted here, the second type of (e.g. s) linearly polarized p2 diffused third device light is reflected by the first polarizing beam splitter 1525. Especially, the second type of linearly polarized p2 diffused third device light 731 is together with the second type of linearly polarized p2 diffused first device light 711 and the second type of linearly polarized p2diffused second device light 721 reflected by the first polarizing beam splitter 1525 to provide a beam 1010 of light comprising one or more of the diffused first device light 711, the diffused second device light 721, and the diffused third device light 731.

For the light generating system 1000 to function as described, in embodiments, the polarization changing element 810 especially comprises an X/4 wave plate configured to (i) convert linearly polarized light into circular polarized light and (ii) circularly polarized light into linearly polarized light. Especially, the X/4 wave plate is configured to (additionally) be an (p/k3)*X/4 wave plate for the third peak wavelength (Xp3. In embodiments, p may be an odd positive integer. More especially, in embodiments, |n-p| and |m-p| may be even positive integers. Yet further, in embodiments, k3 is selected from the range of 0.8-1.2.

In embodiments, the first peak wavelength (Xpl), the second peak wavelength (Xp2), and the third peak wavelength (Xp3), are selected in mutually different wavelength ranges. Especially, in embodiments, the first peak wavelength (Xpl), the second peak wavelength (Xp2), and the third peak wavelength (Xp3), are selected in mutually different wavelength ranges selected from 440-490 nm, 500-560 nm, and 620-750 nm. Fig. Id schematically depicts another specific embodiment of the invention. Here especially, the light generating system 1000 comprises a fourth light generating device 140, a first luminescent material 210, and one or more second dichroic beam splitters 2515.

In embodiments, the fourth light generating device 140 may be configured to generate fourth device light 141 having a fourth peak wavelength (Zp4). The fourth peak wavelength (Zp4) may, in embodiments, be essentially the same as one of the first peak wavelength (kpl), the second peak wavelength (Zp2), and the third peak wavelength (Zp3). However, in other embodiments, the fourth peak wavelength (Zp4) may be a different wavelength. Further, in embodiments, the fourth light generating device 140 may comprise a diode laser or a superluminescent diode.

Further, the first luminescent material 210 may, in embodiments, be configured to convert at least part of the fourth device light 141 into luminescent material light 211.

Here especially, the light generating system 1000 is configured (in an operational mode) such that the one or more second dichroic beam splitters 2515 are configured to reflect or transmit at least part of the fourth device light 141, and to transmit or reflect at least part of the first luminescent material light 211. Especially, as depicted here, the one or more second dichroic beam splitters 2515 are configured to transmit at least part of the fourth device light 141, and to reflect at least part of the first luminescent material light 211.

Further, the light generating system 1000 is configured such that at least part of the first luminescent material light 211 propagates: (i) through the one or more second dichroic beam splitters 2515, (ii) to the first polarizing beam splitter 1525. At the one or more second dichroic beam splitters 2515 the luminescent material light 211 is reflected (as depicted here) or transmitted (not depicted). At the first polarizing beam splitter 1525 at least part of the first luminescent material light is reflected (not depicted) or transmitted (as depicted here). Especially, it is reflected (or transmitted) in the same direction as the direction where the diffused first device light 711 and the diffused second device light 721 (propagating from the polarization changing element 810 to the first polarizing beam splitter 1525), is transmitted (not depicted) or reflected (as depicted here) to by the first polarizing beam splitter 1525.

Therefore, in embodiments, the first polarizing beam splitter 1525 may be transmissive for at least part of the first luminescent material light 211. In embodiments, in an operational mode (of the light generating system 1000), the light generating system 1000 may be configured to generate system light 1001. Especially, in embodiments, the system light 1001 may comprise one or more of the diffused first device light 711 (transmitted or reflected at the first polarizing beam splitter 1525), the diffused second device light 721 (transmitted or reflected at the first polarizing beam splitter 1525), the diffused third device light 731 (transmitted or reflected at the first polarizing beam splitter 1525), and optionally the first luminescent material light 211.

Fig. 2 schematically depicts an embodiment of a luminaire 2 comprising the light generating system 1000 as described above. Reference 301 indicates a user interface which may be functionally coupled with the control system 300 comprised by or functionally coupled to the light generating system 1000. Fig. 2 also schematically depicts an embodiment of lamp 1 comprising the light generating system 1000. Reference 3 indicates a projector device or projector system, which may be used to project images, such as at a wall, which may also comprise the light generating system 1000. Hence, Fig. 2 schematically depicts embodiments of a lighting device 1200 selected from the group of a lamp 1, a luminaire 2, a projector device 3, a disinfection device, a photochemical reactor, an automotive lighting device and an optical wireless communication device, comprising the light generating system 1000 as described herein. In embodiments, such lighting device may be a lamp 1, a luminaire 2, a projector device 3, a disinfection device, or an optical wireless communication device. Lighting device light escaping from the lighting device 1200 is indicated with reference 1201. Lighting device light 1201 may essentially consist of system light 1001, and may in specific embodiments thus be system light 1001. Reference 1300 refers to a space, such as a room. Reference 1305 refers to a floor and reference 1310 to a ceiling; reference 1307 refers to a wall.

The term “plurality” refers to two or more. The terms “substantially” or “essentially” herein, and similar terms, will be understood by the person skilled in the art. The terms “substantially” or “essentially” may also include embodiments with “entirely”, “completely”, “all”, etc. Hence, in embodiments the adjective substantially or essentially may also be removed. Where applicable, the term “substantially” or the term “essentially” may also relate to 90% or higher, such as 95% or higher, especially 99% or higher, even more especially 99.5% or higher, including 100%. The term “comprise” also includes embodiments wherein the term “comprises” means “consists of’. The term “and/or” especially relates to one or more of the items mentioned before and after “and/or”. For instance, a phrase “item 1 and/or item 2” and similar phrases may relate to one or more of item 1 and item 2. The term "comprising" may in an embodiment refer to "consisting of but may in another embodiment also refer to "containing at least the defined species and optionally one or more other species". Use of the verb "to comprise" and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. Unless the context clearly requires otherwise, throughout the description and the claims, the words “comprise”, “comprising”, and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the sense of “including, but not limited to”. The article "a" or "an" preceding an element does not exclude the presence of a plurality of such elements.

Furthermore, the terms first, second, third and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein.

The devices, apparatus, or systems may herein amongst others be described during operation. As will be clear to the person skilled in the art, the invention is not limited to methods of operation, or devices, apparatus, or systems in operation.

It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims.

In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim.

The invention may be implemented by means of hardware comprising several distinct elements. In a device claim, or an apparatus claim, or a system claim, enumerating several means, several of these means may be embodied by one and the same item of hardware. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

The invention also provides a control system that may control the device, apparatus, or system, or that may execute the herein described method or process.

The invention further applies to a device, apparatus, or system comprising one or more of the characterizing features described in the description and/or shown in the attached drawings. The invention further pertains to a method or process comprising one or more of the characterizing features described in the description and/or shown in the attached drawings.

The various aspects discussed in this patent can be combined in order to provide additional advantages.

Claims

CLAIMS:

1. A light generating system (1000) comprising a first light generating device

(110), a second light generating device (120), a diffuser element (710), a polarization changing element (810), and a first polarizing beam splitter (1525), wherein: the first light generating device (110) is configured to generate first device light (111) having a first peak wavelength (Xpl); the second light generating device (120) is configured to generate second device light (121) having a second peak wavelength (Xp2); wherein |Xcl-Xcl|>10 nm; wherein each of the first light generating device (110) and the second light generating device (110) comprises a diode laser or a superluminescent diode; the light generating system (1000) is configured such that:

(a) the first device light (111) and the second device light (121) reaching the first polarizing beam splitter (1525) both comprise a first type of linearly polarized light (pl);

(b) the first device light (111) and the second device light (121) propagate: (i) via the first polarizing beam splitter (1525), where at least part of the first device light (111) and the second device light (121), dependent upon the type of linear polarization, are reflected or transmitted; (ii) through the polarization changing element (810), which is configured to convert linearly polarized light into elliptically polarized light, (iii) to the diffuser element (710), where at least part of the first device light (111) and at least part of the second device light (121) are diffused into diffused first device light (711) and diffused second device light (721), respectively, while a sense of the elliptically polarized light is altered to an opposite sense;

(c) at least part of the diffused first device light (711) and at least part of the diffused second device light (721), propagate: (i) through the polarization changing element (810), where at least part of the elliptically polarized light is converted into a second type of linearly polarized light (p2), different from the first type of linearly polarized light (pl), to (ii) the first polarizing beam splitter (1525), where at least part of the diffused first device light (711) and at least part of the diffused second device light (721), dependent upon the type of linear polarization, are transmitted or reflected; and the polarization changing element (810) comprises an /4 wave plate configured to be an (n/kl)*X/4 wave plate for the first peak wavelength (Xpl) and an (m/k2)*X/4 wave plate for the second peak wavelength (Zp2), wherein n and m are odd positive integers, |n-m| is an even positive integer, and wherein kl and k2 are each individually selected from the range of 0.8-1.2.

2. The light generating system (1000) according to claim 1, wherein: kl=k2=l; the polarization changing element (810) is configured to convert at least part of the first device light (111) and at least part of the second device light (121), comprising the first type of linearly polarized light (pl), into circularly polarized first device light (111) and circularly polarized second device light (121); the diffuser element (710) is configured to diffuse at least part of the first device light (111) and at least part of the second device light (121) into diffused first device light (711) and diffused second device light (721), respectively, while a sense of the circularly polarized light is altered to an opposite sense; the polarization changing element (810) is configured to convert at least part of the diffused first device light (711) and at least part of the diffused second device light (721) into diffused first device light (711) and diffused second device light (721) comprising the second type of linearly polarized light (p2).

3. The light generating system (1000) according to any one of the preceding claims, wherein one of the first peak wavelength (kpl) and the second peak wavelength (Ap2) is selected in the wavelength range of 430-490 nm, and the other one of the first peak wavelength (kpl) and the second peak wavelength (Ap2) is selected from the wavelength range of 600-680 nm; wherein |Xp2-Xp 11>50 nm; and wherein the diffuser element (710) comprises a metallic diffuser element comprising a non-flat surface.

4. The light generating system (1000) according to claim 3, wherein one of the first peak wavelength (kpl) and the second peak wavelength (Zp2) is selected in the wavelength range of 440-460 nm, and the other one of the first peak wavelength (kpl) and the second peak wavelength (Zp2) is selected from the wavelength range of 630-660 nm; and wherein n and m are individually selected from 1, 3, 5, and 7, and |n-m|=2.

5. The light generating system (1000) according to any one of the preceding claims, wherein the first light generating device (110) comprises a diode laser, wherein the first device light (111) comprises p polarized or s polarized laser light; wherein the second light generating device (120) comprises a diode laser, wherein the second device light (121) comprises p polarized or s polarized laser light; wherein the first type of linearly polarized light is p-polarized light, and wherein the second type of linearly polarized light is s- polarized light.

6. The light generating system (1000) according to any one of the preceding claims, further comprising one or more first dichroic beam splitters (1515) configured downstream of the first light generating device (110) and the second light generating device (120), and configured upstream of the first polarizing beam splitter (1525), wherein the one or more first dichroic beam splitters (1515) are configured to combine at least part of the first device light (111) and at least part of the second device light (121).

7. The light generating system (1000) according to any one of the preceding claims 1-6, further comprising a third light generating device (130), a second polarizing beam splitter (2525), a second polarization changing element (2810), and a second diffuser element (2710), wherein: the third light generating device (130) is configured to generate third device light (131) having a third peak wavelength (Xp3 ); wherein the first peak wavelength (kpl ), the second peak wavelength (Zp2), and the third peak wavelength (Zp3) mutually differ; wherein the third light generating device (130) comprises a diode laser or a superluminescent diode; the light generating system (1000) is configured such that:

(a) third device light (131) reaching the second polarizing beam splitter (2525) comprises polarized light (p2);

(b) the third device light (131) propagates: (i) via the second polarizing beam splitter (2525), where dependent upon a polarization of the third device light (131), at least part of the third device light (131) is reflected or transmitted, (ii) through the second polarization changing element (2810), which is configured to convert linearly polarized light (p2) into elliptically polarized light, (iii) to the second diffuser element (2710), where at least part of the third device light (131) is diffused into diffused first device light (731), while a sense of the elliptically polarized light is altered to an opposite sense; and

(c) at least part of the diffused third device light (731) propagates: (i) through the second polarization changing element (2810), where at least part of the elliptically polarized light is converted into a type of linearly polarized light (pl), different from which the third device light (131) reached the second polarization changing element (2810), (ii) to the second polarizing beam splitter (2525), where at least part of the diffused third device light (731), dependent upon the type of linear polarization, is transmitted or reflected to the first polarizing beam splitter (525).

8. The light generating system (1000) according to any one of the preceding claims 1-6, further comprising a third light generating device (130), wherein: the third light generating device (130) is configured to generate third device light (131) having a third peak wavelength (Xp3 ); wherein the first peak wavelength (Xpl ), the second peak wavelength (Xp2), and the third peak wavelength (Xp3) mutually differ; wherein the third light generating device (130) comprises a diode laser or a superluminescent diode; the light generating system (1000) is configured such that:

(a) third device light (131) reaching the first polarizing beam splitter (1525) comprises polarized light (pl);

(b) the third device light (131) propagates: (i) via the first polarizing beam splitter (1525), where at least part of the third device light (131), dependent upon a polarization of the third device light (131), is reflected or transmitted, (ii) through the polarization changing element (810), (iii) to the diffuser element (710), where at least part of the third device light (131) is diffused into diffused third device light (731), while a sense of the elliptically polarized light is altered to an opposite sense;

(c) at least part of the diffused third device light (731) propagates: (i) through the polarization changing element (810), where at least part of the elliptically polarized light is converted into a type of linearly polarized light (p2), different from which the third device light (131) reached the polarization changing element (810), (ii) to the first polarizing beam splitter (1525), where at least part of the diffused third device light (731), dependent upon the type of linear polarization, is transmitted or reflected; and the /4 wave plate is configured to be a p/k3 *X/4 wave plate for the third peak wavelength (Xp3), wherein p is an odd positive integer, |n-p| and |m-p| are even positive integers, and wherein k3 is selected from the range of 0.8-1.2.

9. The light generating system (1000) according to any one of the preceding claims 7-8, wherein the first peak wavelength (Xpl), the second peak wavelength (Xp2), and the third peak wavelength (Zp3), are selected in mutually different wavelength ranges selected from 440-490 nm, 500-560 nm, and 620-750 nm.

10. The light generating system (1000) according to any one of the preceding claims 8-9, further comprising one or more first dichroic beam splitters (1515), as defined in in claim 6, configured downstream of the first light generating device (110), the second light generating device (120), and the third light generating device (130), and configured upstream of the first polarizing beam splitter (1525), wherein the one or more first dichroic beam splitters (1515) are configured to combine at least part of the first device light (111), at least part of the second device light (121), and at least part of the third device light (131).

11. The light generating system (1000) according to any one of the preceding claims, further comprising a fourth light generating device (140), a first luminescent material (210), and one or more second dichroic beam splitters (2515), wherein: the fourth light generating device (130) is configured to generate fourth device light (141) having a fourth peak wavelength (Zp4); wherein the fourth light generating device (140) comprises a diode laser or a superluminescent diode; the first luminescent material (210) is configured to convert at least part of the fourth device light (141) into first luminescent material light (211); the one or more second dichroic beam splitters (2515) are configured to reflect or transmit at least part of the fourth device light (141), and to transmit or reflect at least part of the first luminescent material light (211); and the light generating system (1000) is configured such that at least part of the first luminescent material light (211) propagates: (i) via the one or more second dichroic beam splitters (2515), (ii) to the first polarizing beam splitter (1525), where at least part of the first luminescent material light is reflected or transmitted in the same direction as where the diffused first device light (711) and the diffused second device light (721), propagating from the polarization changing element (810) to the first polarizing beam splitter (1525), is transmitted or reflected to by the first polarizing beam splitter (1525).

12. The light generating system (1000) according to claim 11, wherein the first polarizing beam splitter (1525) is transmissive for at least part of the first luminescent material light (211).

13. The light generating system (1000) according to any one of the preceding claims, wherein the light generating system (1000) is configured to generate system light (1001) comprising one or more of (a) diffused first device light (711), diffused second device light (721), diffused third device light (731) according to any one of claims 7-10, and optionally first luminescent material light (211) according to any one of claims 11-12.

14. The light generating system (1000) according to claim 13, wherein the light generating system (1000) is configured to provide in an operational mode system light (1001) having a correlated color temperature selected from the range of 1800-12000 K; wherein the light generating system (1000) further comprises a control system (300), wherein the control system (300) is configured to control a spectral power distribution and radiant flux of the system light (1001).

15. A lighting device (1200) selected from the group of a lamp (1), a luminaire (2), a projector device (3), a disinfection device, a photochemical reactor, an automotive lighting device, and an optical wireless communication device, comprising the light generating system (1000) according to any one of the preceding claims.