Patent Description:
<CIT> discloses a dual phosphor-wheel projection system using lasers, dichroic mirrors, two phosphor wheels, and an integrator to sequentially generate red, green, and blue light.

For a better understanding of the various examples described herein and to show more clearly how they may be carried into effect, reference will now be made, by way of example only, to the accompanying drawings in which:.

Video projection systems generally use a source of light and there are many different types of sources of light. Human perception of color depends on receptors in the retina, referred to as cones. These cones come in three varieties, referred to as L, M, and S (Long, Medium, and Short). The terminology is a reference to the wavelength of light each cone type is most sensitive to. The color model can be simplified to state the individual cones are sensitive to red, green, or blue light. This then implies a source of light for a video projection systems should include sources of red, green, and blue (RGB) light.

Historically, white lamps have been used as the light source. These lamps are then filtered to generate the individual red, green, and blue components. Some video projection systems use three independent Spatial Light Modulators (SLMs) to form images. In these systems, the three color components are separated spatially, and directed to the individual SLM devices, and then recombined. In other systems (e.g. <NUM>-Chip systems using one SLM), the separation occurs temporarily. A common approach in these systems is to place a set of dichroic filters around the circumference of a wheel, place the wheel between the white light source and the SLM and then spin the wheel at a high speed. In a single SLM system (e.g. a <NUM>-Chip system), the SLM is then synchronized to the colors emitted via the spinning wheel to generate alternating sequences of red, green, and blue sub images which combine to make a perceived single image by the viewer.

The primary drawback of this approach is the limited life span of lamps that provide white light, which lead to frequent replacement of such lamps. An alternative approach is to use solid state illumination (SSI), which comes in several varieties. These include Light Emitting Diodes (LEDs), and direct laser illumination. While LED may be effective in low brightness applications, the large etendue of LED lights sources inherently limits how much light can be coupled onto an SLM. Direct laser (e.g. using RGB lasers and/or red lasers, green lasers and blue lasers) takes advantage of the very small etendue individual laser beams have. Multiple lasers can easily be combined onto a single SLM allowing very high brightness to be achieved. The main drawback is cost: green and red lasers, especially, that produce enough light for use in a video projection system tend to be very expensive. A second drawback is speckle, which is an image artifact caused by the use of coherent light and is generally considered to be visually distracting.

The present specification utilizes a Laser-Phosphor (LaPh) hybrid approach that includes relatively low cost blue lasers. For example, as described herein, a blue laser is used as a source of blue light, for example to illuminate an SLM. Such a blue laser is also used to illuminate a phosphorous material (e.g. a phosphor), which will then emit broader band light at wavelengths longer than the blue light of the laser, and which is filtered (e.g. using dichroic mirrors) to generate red light and/or green light.

In some LaPh systems, a single phosphor wheel is used in conjunction with a color wheel. For example, a blue laser may be combined with two spinning wheels, a segmented phosphor wheel and a segmented color wheel. The segmented phosphor wheel may have two segments: a transparent segment, and a phosphor segment coated with a phosphor that emits yellow light (e.g. a combination of red light and green light) when illuminated by blue light. The segmented color wheel second consists of a transparent segment, a red dichroic filter segment, and a green dichroic filter segment. The wheels are spun in a synchronous manner and the blue laser is operated continuously. During "red" time, the blue laser shines directly on the phosphor which emits yellow light, which is directed to the red filter on the color wheel resulting in red light which is directed towards an SLM. During "green" time, the blue laser continues to shine on the phosphor which emits yellow light, which is directed to the green filter on the color wheel resulting in green light which is directed towards the SLM. During "blue" time the blue laser shines through the transparent segments of the segmented phosphor wheel and the segmented color wheel, which is directed towards the SLM, for example using a fold mirror which directs the blue light to a dichroic combiner where it is relayed to the SLM.

A first problem of LaPh systems is referred to as "quenching", which is a well-known limitation of phosphor materials. The process of converting blue light into yellow light is not <NUM>% efficient. In a phosphor wheel design, the conversion process will have under ideal conditions an efficiency of about <NUM>%. The bulk of the losses will be absorbed by the phosphor material causing it to heat. As the heat rises the efficiency drops causing even more heating. This potentially leads to a thermal runaway situation and puts a limitation on the total amount of light that can be generated. Hence, phosphor materials may have a "quenching limit", which may be a maximum amount of excitation power input to the phosphor material before the efficiency begins to degrade (e.g. decrease) due to heating. The quenching problem may be especially problematic when generating red light as many phosphors used in LaPh systems do not tend to efficiently generate red light.

A second problem of LaPh systems is achieving "deeper" reds. For example, phosphor materials that emit "red" light tend to emit light of wavelengths that range from yellow to orange, with a tail of the orange light including some red light. Such phosphor materials be referred as being "red deficient". While increasing the percent of relative display time allocated to red may partially alleviate this problem, in general such an approach may affect the color cycle time. While adding more blue lasers may also mitigate the problem, for example to illuminate the yellow-orange phosphor with two or more lasers, such an approach may cause the phosphor approach or exceed the quenching limit.

A third problem of LaPh systems is referred to as "spoke time". The light impinging on the phosphor wheel, and again on the color wheel, will have a physical spot size. As the total amount of power goes up the spot size will tend to increase. As the color wheel spins it will not transition between colors instantaneously. Rather, there will be an intermediate period where the color is some combination of starting and ending colors. This transition period or "spoke" light cannot be used as a primary color. Although techniques exist to recapture the spoke light and use it as white light, in general the system efficiency is negatively impacted by this spoke.

A fourth problem of LaPh systems is a limited number of color cycles per video frame. The human eye is generally able to detect changes in an image. This is especially true if the eye is moving. When generating full color images from a sequential series of pure RGB sub-images the frequency of the sub-images should be very high in order to escape detection. For <NUM> video, to escape detection 12x (<NUM>) or higher may be required. However, each color cycle introduces spoke time (e.g. time to transition between colors). The more color cycles the more spokes. This reduces the time available for pure colors and puts a practical limit on the order of 6x (<NUM>) on a color wheel system.

As such, provided herein is a dual color wheel system for a projector that generally mitigates the various problems described above using three blue lasers, one red laser, and independent, non-segmented, phosphor wheels. The first phosphor wheel includes a phosphor that emits in a range of yellow to orange wavelengths (e.g. see <FIG>), including a relatively small amount of red wavelengths. The second phosphor wheel includes a phosphor that emits in a range of green to yellow wavelengths (e.g. see <FIG>).

A first blue laser is a source of blue light which does not make use of the phosphor wheels. Speckling effects from the first blue laser may be mitigated using integrators and/or diffusers in projection optics, and the like. Furthermore, a wavelength of the first blue laser may be selected to achieve a given blue color point for the system.

Blue light from a second blue laser impinges on the first phosphor of the first phosphor wheel which emits light in a range of yellow to red wavelengths, which is filtered using dichroic mirrors to output red light, which is combined with red light from the red laser (e.g., which does not make use of the phosphor wheels). Put another way, the red laser supplements the red light output by the first phosphor of the first phosphor wheel, and/or vice versa, allowing the first laser to be operated at below the quenching limit, while taking advantage of a lower power red laser than would be necessary if a higher power red laser were the only source of red light in the system; such a lower power red laser further tends to have a lower cost relative to such a higher power laser. Hence, the low output of red light by the blue laser/phosphor combination is supplemented by the red laser, or vice versa, and a wavelength of the red laser may be selected to achieve a given red color point for the system, and similarly the color point of the red light emitted by the phosphor may be "tuned" using dichroic mirrors, as described herein, to assist in achieving the given red color point for the system.

Blue light from a third blue laser impinges on the second phosphor of the second phosphor wheel which emits light in a range of green to yellow wavelengths, which is filtered using dichroic mirrors to output green light. The color point of the green light may be "tuned" using dichroic mirrors, as described herein.

The dual color wheel system may include other components, such as any suitable arrangement of dichroic mirrors to transmit, and/or reflect (as described herein) the red light, the green light and the blue light to one or more light integrators, which may provide the light to a spatial light modulator. The dichroic mirrors may further be configured to tune or filter the green light and the red light emitted by the phosphors.

In some examples, four dichroic mirrors may be used, while in other examples three dichroic mirrors may be used. Such dichroic mirrors are generally understood to reflect or direct some wavelengths of light, and transmit other wavelengths of light, and the wavelengths of light that are reflected or transmitted by a given dichroic mirror may be selected based on the wavelengths of light emitted by the first phosphor and the second phosphor, for example to "tune" the red light and the green light (and optionally the blue light) generated by the system provided herein.

The lasers may be operated in a sequence, for example by a controller (e.g. such as a processor and the like) for example to produce the red light, the blue light and the green light in a sequence (of any suitable order), which may be directed to one SLM which may be operated in a sequence, for example also by the controller, to generate corresponding red images, green images and blue images, which may be sequentially projected to form RGB images.

In general, the provided system may at least partially mitigate the aforementioned problems with of LaPh systems. For example, the quenching limit/deeper red problems are generally mitigated by supplementing the red light emitted by the first phosphor with red light emitted by the red laser. Spoke time is generally reduced e.g. compared to when a color wheel and a segmented phosphor wheel are used) as the phosphor wheels used herein are unsegmented and hence transitions between colors occur primarily by turning lasers on and off. Furthermore, reduction of spoke time generally increases a number of color cycles that may occur per video frame (e.g. compared to when a color wheel and a segmented phosphor wheel are used). Furthermore, as there are two sources of red light in the system, the red light emitted by the first phosphor and the red light emitted by the red laser, a lower power/lower cost red laser may be used. Furthermore, as there are two sources of red light in the provided system, one coherent (e.g., the red light emitted by the red laser) and one not coherent (e.g., the red light emitted by the first phosphor), speckle will be reduced relative to when only one coherent source of red light (e.g., the red laser) was used to provide red light.

An aspect of the present specification provides a dual phosphor wheel projection system comprising: a first laser to generate first blue light; a second laser to generate second blue light; a third laser to generate third blue light; a fourth laser to generate first red light; a first phosphor arranged on a first phosphor wheel; a second phosphor arranged on a second phosphor wheel; a first dichroic mirror; a second dichroic mirror; and a third dichroic mirror; at least one light integrator, wherein the first dichroic mirror is configured to direct the first blue light from the first laser to the second dichroic mirror, and the second dichroic mirror is configured to direct the first blue light from the first dichroic mirror to the at least one light integrator, wherein the first dichroic mirror is further configured to direct the second blue light from the second laser to the first phosphor, arranged on the first phosphor wheel, the first phosphor configured to convert the second blue light to longer wavelengths that includes second red light, wherein the second dichroic mirror is further configured to direct the second red light to the at least one light integrator and transmit others of the longer wavelengths, wherein the at least one light integrator combines the first red light and the second red light, wherein the third dichroic mirror is configured to: direct the first red light from the fourth laser to the at least one light integrator; and direct the third blue light from the third laser to the second phosphor, arranged on the second phosphor wheel, wherein the second phosphor configured to convert the third blue light to respective longer wavelengths that includes green light, wherein the third dichroic mirror is further configured to transmit the green light to the at least one light integrator.

Attention is next directed to <FIG>, which depicts a dual phosphor wheel system <NUM>, interchangeably referred to hereafter as the system <NUM>. The system <NUM> comprises a plurality of lasers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> interchangeably referred to hereafter, collectively, as the lasers <NUM> and, generically, as a laser <NUM>. This convention will be used elsewhere in the present specification.

The lasers <NUM> include: a first laser <NUM>-<NUM> to generate first blue light; a second laser <NUM>-<NUM> to generate second blue light; a third laser <NUM>-<NUM> to generate third blue light; and fourth laser <NUM>-<NUM> to generate first red light. Hence, the first laser <NUM>-<NUM>, the second laser <NUM>-<NUM>, and the third laser <NUM>-<NUM> may be respectively referred to herein as the first blue laser <NUM>-<NUM>, the second blue laser <NUM>-<NUM>, and the third blue laser <NUM>-<NUM>; similarly, the fourth laser <NUM>-<NUM> may be referred to herein as the red laser <NUM>-<NUM> The operation of the lasers <NUM> will be described in more detail with respect to <FIG>, <FIG>, and <FIG>.

The system <NUM> further comprises a first phosphor wheel <NUM>-<NUM> and a second phosphor wheel <NUM>-<NUM> (e.g. the phosphor wheels <NUM> and/or a phosphor wheel <NUM>). In particular, the system <NUM> comprises a first phosphor <NUM> arranged on the first phosphor wheel <NUM>-<NUM> and a second phosphor <NUM> arranged on the second phosphor wheel <NUM>-<NUM>. It is understood that the phosphor wheels <NUM> spin and/or rotate continuously while the system <NUM> is in operation, for example at respective speeds that are selected to prevent a given phosphor <NUM>, <NUM> from being damaged by light from the lasers <NUM>-<NUM>, <NUM>-<NUM> and/or selected to ensure that heat is distributed in a phosphor wheel <NUM> in a manner that reduce chances of a quenching limit from being reached (e.g. see <FIG>, described in more detail below). In some examples, the phosphor wheels <NUM> may have some (e.g., slight) non-uniformities about a respective circumference; in these examples, spinning and/or rotation of the phosphor wheels <NUM> may be synchronized a color cycling rate (e.g., a rate at which the system <NUM> cycles through red, green and blue) to ensure those non-uniformities occur at same and/or similar times in the color cycle so that any variance in color due to the non-uniformities may be calibrated and/or corrected (e.g., by varying respective brightness and/or RGB ratios of images generated in the system <NUM>).

Attention is briefly directed to <FIG>, which generically depicts a phosphor wheel <NUM>, and is understood to comprise a plate <NUM>, and the like, which as depicted may be circular, but may be any suitable shape. The plate <NUM> rotates around a hub <NUM>, as represented by an arrow <NUM>, for example via a motor (not depicted), with an unsegmented phosphor <NUM>, <NUM> annularly arranged around the plate <NUM> (e.g. the phosphors <NUM>, <NUM> form a respective annulus on a respective plate <NUM> and are continuous/unsegmented on a respective plate <NUM>). The arrangement of components of the system <NUM>, and dimensions of the plate <NUM> and an annulus formed by the first phosphor <NUM> or the second phosphor <NUM> are selected such that light from a laser <NUM>, and in particular a blue laser <NUM>-<NUM>, <NUM>-<NUM>, impinges on a phosphor <NUM>, <NUM> as the plate <NUM> rotates, exciting the phosphor <NUM>, <NUM>, and the phosphor <NUM>, <NUM> emits light of longer wavelengths. The blue lasers <NUM>-<NUM>, <NUM>-<NUM> are hence understood to be "pump" lasers as the blue lasers <NUM>-<NUM>, <NUM>-<NUM> are used to "pump" and/or excite the phosphors <NUM>, <NUM>. Wavelength of the light emitted by a phosphor <NUM>, <NUM> is understood to depend on a type and/or material of the phosphor <NUM>, <NUM>. Furthermore, rotation of the plate <NUM> is understood to distribute power and heat from a blue laser <NUM>-<NUM>, <NUM>-<NUM> over an area to reduce the possibility of reaching a quenching limit of a phosphor <NUM>, <NUM> (e.g. see <FIG>, described in more detail below).

Furthermore, as will be described in more detail with respect to <FIG> and <FIG>, the blue lasers <NUM>-<NUM>, <NUM>-<NUM> that are used to excite a phosphor <NUM>, <NUM> may be about <NUM>, but may also depend on a type and/or material of the phosphor <NUM>, <NUM>.

Attention is next briefly directed to <FIG> which depicts example phosphor spectra <NUM> of four examples of a phosphor <NUM>, and two examples of a phosphor <NUM>. In particular, each of the phosphor spectra <NUM> depict relative intensity of wavelengths of light output by a phosphor <NUM>, <NUM> when excited by a blue laser <NUM>-<NUM>, <NUM>-<NUM> of wavelength <NUM>.

The phosphors <NUM> are understood to emit wavelengths that range from about <NUM> to about <NUM>, or in a green to orange/red range, however, dominant (e.g. most intense) wavelengths are in a yellow to orange/red range (e.g. <NUM> to <NUM>) with a tail of red wavelength light (e.g. <NUM> and above). Put another way, the first phosphor <NUM> may be configured to emit light in a range of yellow to red (or green to red) wavelengths. In general, a phosphor <NUM> is used as one source of red light in the system <NUM> (e.g. in addition to the red laser <NUM>-<NUM>).

The phosphors <NUM> are understood to emit wavelengths that range from about <NUM> to about <NUM>, or in a green to yellow/orange range, however, dominant (e.g. most intense) wavelengths are in a green to yellow range (e.g. <NUM> to <NUM>) with a long tail that includes a relatively small amount of red wavelength light (e.g. <NUM> and above). Put another way, the second phosphor <NUM> may be configured to emit light in a range of in a range of green to yellow wavelengths. In general, a phosphor <NUM> is used as a source of green light in the system <NUM>.

Furthermore, as understood from the phosphor spectra <NUM>, some phosphors (e.g. a phosphor <NUM>) are "richer" in relatively "shorter" wavelengths (e.g. as depicted, greens) and other phosphors (e.g. a phosphor <NUM>) are "richer" in relatively "longer" wavelengths (e.g. as depicted, reds). In particular, the "green" phosphors <NUM> are richer in green light, and deficient in red light. In a single phosphor wheel type system, a green phosphor <NUM> would be an undesirable choice as not enough red light could be produced using a green phosphor <NUM> to meet RGB requirements (e.g. a given color point) of a projection system. In the present specification, however, a "green" phosphor <NUM> is only used to produce green light, and the red deficiency of such "green" phosphors <NUM> becomes an advantage since dichroic mirrors (described below) used to filter out wavelengths other than those corresponding to green, can be designed to reject and/or filter less light to achieve a given color point. Similarly, the "red-yellow" phosphors <NUM> are richer in red light, and deficient in green light; hence, use of a "red-yellow" phosphor <NUM>, over a pure yellow phosphor, to generate red light may provide an improvement in efficiency to produce deeper red colors. Hence, the dual phosphor wheel system <NUM> described may enable the system <NUM> to output a very pure green light without compromising red performance, and to have a deeper red color without compromising green performance.

The phosphors <NUM>, <NUM> may hence be of any suitable respective phosphor material which have the phosphor spectra <NUM> depicted in <FIG>, or similar, and/or the phosphors <NUM>, <NUM> may be of any suitable respective phosphor material. Put another way, the phosphor <NUM> may be of any suitable material, having any suitable phosphor spectrum that includes red light (e.g., in a range of about <NUM> to about <NUM>), and the phosphor <NUM> may be of any suitable material, having any suitable phosphor spectrum that includes green light (e.g., in a range of about <NUM> to about <NUM>).

Returning to <FIG>, the system <NUM> further comprises: a first dichroic mirror <NUM>-<NUM>, a second dichroic mirror <NUM>-<NUM>, a third dichroic mirror <NUM>-<NUM>, and a fourth dichroic mirror <NUM>-<NUM> (e.g. dichroic mirrors <NUM> and/or a dichroic mirror <NUM>). As will be explained with reference to <FIG> and <FIG>, however, the fourth dichroic mirror <NUM>-<NUM> may be optional.

Furthermore, as depicted, the system <NUM> optionally comprises heat sinks <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> (e.g. heat sinks <NUM> or a heat sink <NUM>) integrated with and/or behind respective dichroic mirrors <NUM>, for example to absorb heat from a respective laser <NUM> and/or lasers <NUM>, and/or light, that interact with a dichroic mirror <NUM> and/or to absorb light that is discarded by a dichroic mirror <NUM>. However, not all the dichroic mirrors <NUM> may be associated with a heat sink <NUM>; rather, only those dichroic mirrors <NUM> that receive light directly from a laser <NUM> may be associated with a heat sink <NUM>. For example, as will become apparent, the dichroic mirrors <NUM>-<NUM>, <NUM>-<NUM> interact directly with the lasers <NUM>, hence, the system <NUM> may include heat sinks <NUM>-<NUM>, <NUM>-<NUM> only at dichroic mirrors <NUM>-<NUM>, <NUM>-<NUM> which absorb light discarded by a dichroic mirror <NUM>-<NUM>, <NUM>-<NUM> (e.g. not directed to a phosphor <NUM>, <NUM> and/or not directed to another dichroic mirror <NUM>). The heat sinks <NUM> are depicted in dashed lines to indicate their optionality.

Furthermore, as depicted, the system <NUM> further comprises at least one light integrator <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> (e.g. light integrators <NUM> or a light integrator <NUM>, though the light integrators <NUM> or a light integrator <NUM> will be interchangeably referred to herein as integrators <NUM> or an integrator <NUM>).

In particular, the dichroic mirrors <NUM> are understood to transmit or reflect certain respective ranges of wavelengths of light, for example towards a phosphor wheel <NUM>, towards another dichroic mirror <NUM> and/or towards a light integrator <NUM> as will be explained in more detail below.

As will become apparent, in the system <NUM>, the integrator <NUM>-<NUM> may receive light from the dichroic mirror <NUM>-<NUM> and the integrator <NUM>-<NUM> may receive light from the dichroic mirror <NUM>-<NUM>. Furthermore, the integrators <NUM>-<NUM>, <NUM>-<NUM> may direct light into the integrator <NUM>-<NUM>, which may have an output end having an aspect ratio similar to, and/or the same as, a spatial light modulator (SLM) <NUM> of a projector of which the system <NUM> is a component.

In particular, the integrators <NUM> may comprise integrating rods that mix light received therein into a uniform distribution. As depicted, the integrators <NUM>-<NUM>, <NUM>-<NUM> may both include a <NUM>-degree section that acts as an internal fold mirror, for example upon which light from a respective dichroic mirror <NUM>-<NUM>, <NUM>-<NUM> may impinge (e.g. see <FIG>, <FIG> and <FIG>) and be reflected towards the integrator <NUM>-<NUM>, an input end of which is located at output ends of the integrators <NUM>-<NUM>, <NUM>-<NUM>. Hence, light from the dichroic mirror <NUM>-<NUM> will receive a first pass light integration through the integrator <NUM>-<NUM> and light from the dichroic mirror <NUM>-<NUM> will receive a first pass light integration through the integrator <NUM>-<NUM>, and light from either or both of the integrators <NUM>-<NUM>, <NUM>-<NUM> will receive a second pass light integration by the integrator <NUM>-<NUM> before being directed, for example, to an SLM <NUM>, which may be component of the system <NUM>, or a projection device external to the system <NUM> that receives light from the system <NUM>. The integrators <NUM> may further be configured (e.g. be of respective lengths) to reduce and/or eliminate speckle due to the lasers <NUM>-<NUM>, <NUM>-<NUM> and/or the system <NUM> may comprise one or more diffusers (not depicted) to reduce and/or eliminate such speckle.

The SLM <NUM> may include any suitable spatial light modulator such as a digital micromirror device (DMD), a liquid crystal on silicon (LCOS) device, and the like.

As depicted, the system <NUM> further comprises a controller <NUM>, such as a processor and/or a plurality of processors, including but not limited to one or more central processors (CPUs) and/or one or more graphics processing units (GPUs) and/or one or more processing units; either way, the controller <NUM> comprises a hardware element and/or a hardware processor. In some implementations, the controller <NUM> can comprise an ASIC (application-specific integrated circuit) and/or an FPGA (field-programmable gate array) specifically configured to control the lasers <NUM>, and to communicate with components controlling the SLM <NUM>, for example to coordinate colors of light generated by the system <NUM> with images formed by the SLM <NUM>. While not depicted, the system <NUM> may further comprise, and/or a projection device external to the system <NUM> that receives light from the system <NUM> may further comprise, a source of the images that the SLM <NUM> is to form, such as a video file, and the like, which may be stored at a memory (not depicted) and/or received via a communication interface (not depicted), and the like.

Furthermore, the system <NUM> may further comprise, or a projection device external to the system <NUM> that receives light from the system <NUM> may further comprise, projection optics between the output end of the integrator <NUM>-<NUM> and the SLM <NUM>, and the like, a content player and/or generator and/or a rendering device (e.g. to "play" a video file, and the like), and/or any other suitable component used to play and/or project images.

As previously mentioned, the dichroic mirror <NUM>-<NUM> may be optional, however in this instance, a portion of the other components of the system are rearranged relative to the integrators <NUM>-<NUM>, <NUM>-<NUM>. For example, attention is directed to <FIG>, which depicts a system <NUM> that is substantially similar to the system <NUM>, with like components having like numbers. However, comparing the system <NUM>, <NUM>, it is apparent that the dichroic mirror <NUM>-<NUM> is omitted from the system <NUM>, and furthermore the lasers <NUM>-<NUM>, <NUM>-<NUM>, the second phosphor wheel <NUM>-<NUM>, and the dichroic mirror <NUM>-<NUM> are rotated <NUM>° relative to the integrator <NUM>-<NUM>. In particular, as will next be explained, the dichroic mirror <NUM>-<NUM> in the system <NUM> causes a <NUM>° redirection/reflection of light from the dichroic mirror <NUM>-<NUM> into the integrator <NUM>-<NUM>. Furthermore, as will also next be explained, while the dichroic mirror <NUM>-<NUM> may provide some further filtering of light from the dichroic mirror <NUM>-<NUM>, such filtering may be optional.

Attention is next directed to <FIG>, <FIG>, and <FIG>, which are substantially similar to <FIG>, with like components having like numbers. While the heat sinks <NUM> are not depicted for simplicity, one or more of the heat sinks <NUM> may nonetheless be present.

In particular, <FIG>, <FIG> and <FIG> depict the system <NUM> being respectively operated in a blue mode and/or blue time period, a red mode and/or red time period, and a green mode and/or green time period. It is understood that the controller <NUM> may control the lasers <NUM> to be on or off depending on the mode and/or time period, and furthermore the controller <NUM> may control the SLM <NUM> to form a respective blue, red or green image in the blue mode and/or blue time period, the red mode and/or red time period, and the green mode and/or green time period. Hence, while not depicted, it is understood that that the controller <NUM> is in communication with components for turning the lasers <NUM> on and off, and furthermore the controller <NUM> is in communication with components for controlling the SLM <NUM>. Alternatively, a component that controls an image of the SLM <NUM> may communicate with the controller <NUM> to indicate a mode and/or time period in which the system <NUM> should operate, with the controller <NUM> controlling the lasers <NUM> accordingly. Furthermore, while the various modes are described in an order of blue, red, green, the modes may occur in any suitable order.

Furthermore, in the following description, relative angles of components of the system <NUM> are described. However, such relative angles are understood to be merely examples and any other suitable relative angles are within the scope of the present specification.

With attention directed to <FIG>, in the blue mode, the first laser <NUM>-<NUM> is on, and the other lasers <NUM> are off, and the first laser <NUM>-<NUM> generates first blue light <NUM> (also labelled "B"), and a wavelength of the first blue light <NUM> of the first blue laser <NUM>-<NUM> may be selected to meet a given color point of the system <NUM>; in particular, as the first laser <NUM>-<NUM> is the primary source of blue light in the system <NUM>, the wavelength of the first blue laser <NUM>-<NUM> may be selected to meet given color specifications that the system <NUM> is to meet. In a particular example, wavelength of the first blue light <NUM> of the first blue laser <NUM>-<NUM> may be about <NUM>, which may be different from a wavelength of the blue lasers <NUM>-<NUM>, <NUM>-<NUM> of <NUM>, which are selected to excite the phosphors <NUM>, <NUM>. However, the first blue light <NUM> of the first blue laser <NUM>-<NUM> may be about of any suitable wavelength that corresponds to blue light (e.g., about <NUM> to about <NUM>).

As depicted, the first blue light <NUM> is emitted towards a side of the first dichroic mirror <NUM>-<NUM>, which is understood to be at <NUM>° to the first laser <NUM>-<NUM>, angled towards the second dichroic mirror <NUM>-<NUM>.

With brief reference to <FIG>, which depicts a transmission curve <NUM> of the first dichroic mirror <NUM>-<NUM>, it is understood that the first dichroic mirror <NUM>-<NUM> transmits light above about <NUM> and reflects light below about <NUM>; between about <NUM> and about <NUM>, the first dichroic mirror <NUM>-<NUM> partially transmits and partially reflects light in region that may be referred to as a "transition region". Furthermore, a transmission wavelength cutoff is indicated (e.g. a wavelength of about <NUM> in the transition region where the transmission and reflection are each about <NUM>%). The first dichroic mirror <NUM>-<NUM> is understood to comprise a band-pass filter that generally transmits light above the wavelength cutoff, and reflects light below the wavelength cutoff.

Similarly, with brief reference to <FIG>, which depicts a transmission curve <NUM> of the second dichroic mirror <NUM>-<NUM>, it is understood that the second dichroic mirror <NUM>-<NUM> transmits light between about <NUM> and about <NUM>, and reflects light below about <NUM> and also reflects light above about <NUM>; in the regions between about <NUM> and about <NUM>, and between about <NUM> and about <NUM>, the second dichroic mirror <NUM>-<NUM> partially transmits and partially reflects light, which may also be referred to as transition regions. Furthermore, a transmission short wavelength cutoff and transmission long wavelength cutoff are indicated (e.g. a wavelength of about <NUM> in the lower wavelength transition region where the transmission and reflection are each about <NUM>%, and a wavelength of about <NUM> in the higher wavelength transition region where the transmission and reflection are each about <NUM>% ). The second dichroic mirror <NUM>-<NUM> is understood to comprise a band-pass filter that generally transmits light between the short and long wavelength cutoffs, and reflects light above and below, respectively, the short and long wavelength cutoffs.

Returning to <FIG>, as the wavelength of the first blue light <NUM> is <NUM> (e.g. in the reflection range of both dichroic mirrors <NUM>-<NUM>, <NUM>-<NUM>, with <NUM> also indicated in <FIG>), the first dichroic mirror <NUM>-<NUM> reflects the first blue light <NUM> towards the second dichroic mirror <NUM>-<NUM>, which is at <NUM>° to the first dichroic mirror <NUM>-<NUM> and about parallel to the fold mirror of the first integrator <NUM>-<NUM>. As such, the first blue light <NUM> is directed and/or reflected from the second dichroic mirror <NUM>-<NUM> to the fold mirror of the first integrator <NUM>-<NUM>, which reflects the first blue light <NUM> into the body of the first integrator <NUM>-<NUM>. <FIG> further illustrates that the fold mirror of the first integrator <NUM>-<NUM> is arranged to reflect the first blue light <NUM> into the body of the first integrator <NUM>-<NUM> (e.g. the fold mirror the first integrator <NUM>-<NUM> is at about <NUM>° to an output face of the first integrator <NUM>-<NUM>). The first blue light <NUM> is hence integrated by the first integrator <NUM>-<NUM>, and further integrated by the third integrator <NUM>-<NUM>, and provided to the SLM <NUM> to form a blue image and/or blue sub-image (e.g. of an RGB image).

Put another way, the first dichroic mirror <NUM>-<NUM> is configured to direct the first blue light <NUM> from the first laser <NUM>-<NUM> to the second dichroic mirror <NUM>-<NUM>, and the second dichroic mirror <NUM>-<NUM> is configured to direct the first blue light <NUM> from the first dichroic mirror <NUM>-<NUM> to the at least one light integrator <NUM>.

With attention directed to <FIG>, in the red mode, the second laser <NUM>-<NUM> and the fourth laser <NUM>-<NUM> are both on. With fourth laser <NUM>-<NUM> generates first red light <NUM>-<NUM> (also labelled R-<NUM>), and a wavelength of the first red light <NUM>-<NUM> of the red laser <NUM>-<NUM> may be selected to meet a given color point of the system <NUM>; in particular, as the fourth laser <NUM>-<NUM> is one of two sources of red light in the system <NUM>, that operate concurrently, the wavelength of the first red light <NUM>-<NUM> of the red laser <NUM>-<NUM> may be selected to meet given color specifications that the system <NUM> is to meet in combination with the second red light <NUM>-<NUM>. In a particular example, wavelength of the first red light <NUM>-<NUM> of the red laser <NUM>-<NUM> may be about <NUM>. However, the first red light <NUM>-<NUM> of the red laser <NUM>-<NUM> may be of any suitable wavelength that corresponds to red light (e.g., about <NUM> to about <NUM>).

As depicted, the first red light <NUM>-<NUM> is emitted towards a side of the third dichroic mirror <NUM>-<NUM>, which is understood to be at <NUM>° to the fourth laser <NUM>-<NUM>, angled towards the fourth dichroic mirror <NUM>-<NUM>.

With brief reference to <FIG>, which depicts a transmission curve <NUM> of the third dichroic mirror <NUM>-<NUM>, it is understood that the third dichroic mirror <NUM>-<NUM> transmits light between about <NUM> and about <NUM>, and reflects light below about <NUM> and also reflects light above about <NUM>; in the regions between about <NUM> and about <NUM>, and between about <NUM> and about <NUM>, the third dichroic mirror <NUM>-<NUM> partially transmits and partially reflects light (e.g. transition regions). Furthermore, a transmission short wavelength cutoff and transmission long wavelength cutoff are indicated (e.g. a wavelength of about <NUM> in the lower wavelength transition region where the transmission and reflection are each about <NUM>%, and a wavelength of about <NUM> in the higher wavelength transition region where the transmission and reflection are each about <NUM>% ). The third dichroic mirror <NUM>-<NUM> is understood to comprise a band-pass filter that generally transmits light between the short and long wavelength cutoffs, and reflects light above and below, respectively, the short and long wavelength cutoffs.

Similarly, with brief reference to <FIG>, which depicts a transmission curve <NUM> of the fourth dichroic mirror <NUM>-<NUM>, it is understood that the fourth dichroic mirror <NUM>-<NUM> transmits light between about <NUM> and about <NUM>, and reflects light below about <NUM> and also reflects light above about <NUM>; in the regions between about <NUM> and about <NUM>, and between about <NUM> and about <NUM>, the fourth dichroic mirror <NUM>-<NUM> partially transmits and partially reflects light (e.g. transition regions). Furthermore, a transmission short wavelength cutoff and transmission long wavelength cutoff are indicated (e.g. a wavelength of about <NUM> in the lower wavelength transition region where the transmission and reflection are each about <NUM>%, and a wavelength of about <NUM> in the higher wavelength transition region where the transmission and reflection are each about <NUM>% ). The fourth dichroic mirror <NUM>-<NUM> is understood to comprise a yellow notch filter (e.g. a type of band pass filter) that generally transmits yellow light between the short and long wavelength cutoffs, and reflects light above and below, respectively, the short and long wavelength cutoffs.

While specific transmission curves of the dichroic mirrors <NUM> are described herein, it is understood that the transmission curves of the dichroic mirrors <NUM> may be adapted according to wavelengths of light emitted by the first blue laser <NUM>-<NUM>, the red laser <NUM>-<NUM>, or by the phosphors <NUM>, <NUM>.

Returning to <FIG>, as the wavelength of the first red light <NUM>-<NUM> is <NUM> (e.g. in the reflection range of both dichroic mirrors <NUM>-<NUM>, <NUM>-<NUM> as also indicated in <FIG>), the third dichroic mirror <NUM>-<NUM> reflects the first red light <NUM>-<NUM> towards a side of the fourth dichroic mirror <NUM>-<NUM>, which is at <NUM>° to the third dichroic mirror <NUM>-<NUM> and about parallel to the fold mirror of the second integrator <NUM>-<NUM> (e.g. the fold mirror the second integrator <NUM>-<NUM> is at about <NUM>° to an output face of the second integrator <NUM>-<NUM>).

As such, the first red light <NUM>-<NUM> is directed and/or reflected from the fourth dichroic mirror <NUM>-<NUM> to the fold mirror of the second integrator <NUM>-<NUM>, which reflects the first red light <NUM>-<NUM> into the body of the second integrator <NUM>-<NUM>. <FIG> further illustrates that the fold mirror of the second integrator <NUM>-<NUM> is arranged to reflect the first red light <NUM>-<NUM> into the body of the second integrator <NUM>-<NUM>. The first red light <NUM>-<NUM> is hence integrated by the second integrator <NUM>-<NUM> and further integrated by the third integrator <NUM>-<NUM>, and provided to the SLM <NUM> to form a red image and/or red sub-image (e.g. of the RGB image).

However, with attention further directed to <FIG>, in the red mode, the second laser <NUM>-<NUM> is also on and generates second blue light <NUM> (e.g. also labelled "R-<NUM>"), and a wavelength of the second blue light <NUM> of the second blue laser <NUM>-<NUM> may be selected to selected to excite the phosphor <NUM>, as previously described. For example, a wavelength of the second blue light <NUM> of the second blue laser <NUM>-<NUM> may be <NUM>.

As depicted, the second blue light <NUM> is emitted towards a side of the first dichroic mirror <NUM>-<NUM>, which is understood to be at <NUM>° to the second laser <NUM>-<NUM>, angled towards the first phosphor wheel <NUM>-<NUM>. Hence it is understood that the lasers <NUM>-<NUM>, <NUM>-<NUM> are on opposite sides of the first dichroic mirror <NUM>-<NUM> and hence respective blue light <NUM>, <NUM> from the lasers <NUM>-<NUM>, <NUM>-<NUM> are directed/reflected in opposite directions.

As the wavelength of the second blue light <NUM> is <NUM> (e.g. in the reflection range of the first dichroic mirror <NUM>-<NUM>, as also indicated in <FIG>), the first dichroic mirror <NUM>-<NUM> reflects the second blue light <NUM> towards the first phosphor wheel <NUM>-<NUM>, and specifically towards the phosphor <NUM>, which is excited and emits second red light <NUM>-<NUM> (e.g. as depicted in <FIG>) as well as other colors in a respective phosphor spectrum <NUM>.

The second red light <NUM>-<NUM>, and other colors, are emitted towards the first dichroic mirror <NUM>-<NUM>. Comparing a phosphor spectra <NUM> of the phosphor <NUM> of <FIG> with the transmission curve <NUM> of the first dichroic mirror <NUM>-<NUM> of <FIG>, it is understood that the wavelengths of the light emitted by the phosphor <NUM> that are above about <NUM> (e.g. green to red) are transmitted through the first dichroic mirror <NUM>-<NUM> towards the second dichroic mirror <NUM>-<NUM>, while other wavelengths (e.g. blue) are reflected or partially reflected.

Comparing the phosphor spectra <NUM> of the phosphor <NUM> of <FIG> with the transmission curve <NUM> of the second dichroic mirror <NUM>-<NUM> of <FIG>, it is understood that the wavelengths of the light that are transmitted through the first dichroic mirror <NUM>-<NUM> towards the second dichroic mirror <NUM>-<NUM>, that are above about <NUM> (e.g. the second red light <NUM>-<NUM>) are reflected towards the fold mirror of the first integrator <NUM>-<NUM>, and that light below about <NUM> is transmitted (or partially transmitted) through the second dichroic mirror <NUM>-<NUM> (e.g. green to orange).

Indeed, it is understood that a multiplication of a phosphor spectra <NUM> of the phosphor <NUM>, by transmission curve of the first dichroic mirror <NUM>-<NUM>, and by the reflectance curve of the second dichroic mirror <NUM>-<NUM> (e.g. <NUM> minus the transmission curve <NUM> of <FIG>), generally yield the spectra of the second red light <NUM>-<NUM> that enters the first integrator <NUM>-<NUM>. As such, the dichroic mirrors <NUM>-<NUM>, <NUM>-<NUM>, and more specifically the second dichroic mirror <NUM>-<NUM>, generally acts as a filter to select and/or filter the second red light <NUM>-<NUM> from the other colors of light emitted by the first phosphor <NUM>. Put another way, one or more of the first dichroic mirror <NUM>-<NUM> and the second dichroic mirror <NUM>-<NUM> may be further configured to refine the second red light <NUM>-<NUM> to shift a peak wavelength thereof (e.g. a dominant wavelength that results from the filtering).

Similar to the first blue light <NUM>, the second red light <NUM>-<NUM> is directed and/or reflected from the second dichroic mirror <NUM>-<NUM> to the fold mirror of the first integrator <NUM>-<NUM>, which reflects the second red light <NUM>-<NUM> into the body of the first integrator <NUM>-<NUM>. Hence, the second dichroic mirror <NUM>-<NUM> both directs the second red light <NUM>-<NUM> to the first integrator <NUM>-<NUM> and filters the second red light <NUM>-<NUM>. Furthermore, the second red light <NUM>-<NUM> is integrated by the first integrator <NUM>-<NUM> and the third integrator <NUM>-<NUM>, and the third integrator <NUM>-<NUM> further combines and integrates the first red light <NUM>-<NUM> and the second red light <NUM>-<NUM> and provides the combined red light <NUM> to the SLM <NUM> to form the red image and/or the red sub-image (e.g. of the RGB image).

Indeed, again with reference to <FIG>, a sharpness and/or position of the transition region of the second dichroic mirror <NUM>-<NUM> between <NUM> and <NUM> may be selected to more precisely select and/or filter the second red light <NUM>-<NUM>, for example to be around the <NUM> of the first red light <NUM>-<NUM>. For example, by making the transition region of the second dichroic mirror <NUM>-<NUM> "sharper", such as by narrowing the transition region to about <NUM> to about <NUM>, more green, yellow, and orange light may be filtered from the second red light <NUM>-<NUM> to shift a color point of the second red light <NUM>-<NUM> towards <NUM>, though this may also have an effect of decreasing brightness of the second red light <NUM>-<NUM>. Alternatively, and/or in addition, by shifting the transition region from <NUM> and <NUM> to <NUM> to <NUM> (e.g. same width, but higher in wavelength), more green, yellow, and orange light may be filtered from the second red light <NUM>-<NUM> to shift a color point of the second red light <NUM>-<NUM> towards <NUM>, though this may also have an effect of decreasing brightness of the second red light <NUM>-<NUM>. It is understood that such sharpening and/or shifting of the transition region of the second dichroic mirror <NUM>-<NUM> (or any of the dichroic mirrors <NUM>), occurs during manufacture of the second dichroic mirror <NUM>-<NUM>, (or during manufacture of any of the dichroic mirrors <NUM>).

Regardless, it is understood that, as the first red light <NUM>-<NUM> and the second red light <NUM>-<NUM> are combined, both the lasers <NUM>-<NUM>, <NUM>-<NUM> may have lower power requirements than when only one of the <NUM>-<NUM>, <NUM>-<NUM> were used to generate red light in the system <NUM>. Furthermore, use of both the lasers <NUM>-<NUM>, <NUM>-<NUM> enables the second laser <NUM>-<NUM> to be operated at a power that is below a quenching limit of the first phosphor <NUM>.

A color of the red light that exits the third integrator <NUM>-<NUM> is understood to be a combination of the color of the first red light <NUM>-<NUM> and the second red light <NUM>-<NUM>, and which may be tuned by selecting a sharpness and/or position of the transition region of the second dichroic mirror <NUM>-<NUM> between <NUM> and <NUM>, though such selecting may affect the brightness of the second red light <NUM>-<NUM> when the transition region is shifted towards higher wavelengths. However, it is understood that transition region may be from wavelengths shorter than <NUM> and/or to wavelengths longer than <NUM>, and may depend on a given brightness and/or a given red color (e.g. red color point) and/or a given white point (e.g. color of white light that results from the combination of the red, green and blue light generated by the system <NUM>).

From at least the description of <FIG>, it is understood that the first dichroic mirror <NUM>-<NUM> is further configured to direct the second blue light <NUM> from the second laser <NUM>-<NUM> to the first phosphor <NUM>, arranged on the first phosphor wheel <NUM>-<NUM>, the first phosphor <NUM> configured to convert the second blue light <NUM> to longer wavelengths that includes the second red light <NUM>-<NUM>, and the second dichroic mirror <NUM>-<NUM> is further configured to direct the second red light <NUM>-<NUM> to the at least one light integrator <NUM> and transmit (or partially transmit) others of the longer wavelengths, and the at least one light integrator <NUM> combines the first red light <NUM>-<NUM> and the second red light <NUM>-<NUM>. It is further understood that the third dichroic mirror <NUM>-<NUM> is configured to: direct the first red light <NUM>-<NUM> from the fourth laser <NUM>-<NUM> to the at least one light integrator <NUM>.

With attention directed to <FIG>, in the green mode, the third laser <NUM>-<NUM> is on, and the other lasers <NUM> are off. The third laser <NUM>-<NUM> generates third blue light <NUM>, and a wavelength of the third blue light <NUM> of the third blue laser <NUM>-<NUM> may be selected to selected to excite the phosphor <NUM>, as previously described. For example, the wavelength of the third blue light <NUM> may be about <NUM>.

As depicted, the third blue light <NUM> is emitted towards a side of the third dichroic mirror <NUM>-<NUM>, which is understood to be at <NUM>° to the third laser <NUM>-<NUM>, angled towards the second phosphor wheel <NUM>-<NUM>. Hence it is understood that the lasers <NUM>-<NUM>, <NUM>-<NUM> are on opposite sides of the third dichroic mirror <NUM>-<NUM> and hence blue light <NUM> from the laser <NUM>-<NUM>, and red light <NUM>-<NUM> from the laser <NUM>-<NUM> are directed/reflected in opposite directions.

As the wavelength of the third blue light <NUM> is <NUM> (e.g. in the reflection range of the third dichroic mirror <NUM>-<NUM> as also indicated in <FIG>), the third dichroic mirror <NUM>-<NUM> reflects the third blue light <NUM> towards the second phosphor wheel <NUM>-<NUM>, and specifically towards the phosphor <NUM>, which is excited and emits green light <NUM> (e.g. as depicted in <FIG>) as well as other colors in a respective phosphor spectrum <NUM>.

The green light <NUM>, and other colors, are emitted towards the third dichroic mirror <NUM>-<NUM>. Comparing a phosphor spectra <NUM> of the phosphor <NUM> of <FIG> with the transmission curve <NUM> of the third dichroic mirror <NUM>-<NUM> of <FIG>, it is understood that the wavelengths of the light emitted by the phosphor <NUM> that are between about <NUM> and about <NUM> (e.g. green to orange) are transmitted through the third dichroic mirror <NUM>-<NUM> towards the fourth dichroic mirror <NUM>-<NUM>, while other wavelengths (e.g. blue and red) are reflected or partially reflected.

Comparing the phosphor spectra <NUM> of the phosphor <NUM> of <FIG> with the transmission curve <NUM> of the fourth dichroic mirror <NUM>-<NUM> of <FIG>, it is understood that the wavelengths of the light that are transmitted through the third dichroic mirror <NUM>-<NUM> towards the fourth dichroic mirror <NUM>-<NUM>, that are below about <NUM> (e.g. the green light <NUM>) or above <NUM> (e.g. the first red light <NUM>-<NUM>) are reflected towards the fold mirror of the second integrator <NUM>-<NUM>, while other wavelengths (e.g. yellow to orange) are transmitted and/or partially transmitted,. While red light emitted by the phosphor <NUM> (e.g. above about <NUM>) in the green mode may also be reflected, <FIG> shows that the phosphor <NUM> is generally red deficient and hence red light won't significantly contribute to the color point of the green light <NUM>. Hence, it is understood that the transmission curve <NUM> of the fourth dichroic mirror <NUM>-<NUM> is selected to reflect the red light <NUM>, as well as filter the green light <NUM> from other colors emitted by the phosphor <NUM>.

Indeed, it is understood that a multiplication of a phosphor spectra <NUM> of the phosphor <NUM>, by the transmission curve of the third dichroic mirror <NUM>-<NUM>, and by the reflectance curve of the fourth dichroic mirror <NUM>-<NUM> (e.g. <NUM> minus the transmission curve <NUM> of <FIG>), generally yield the spectra of the green light <NUM> that enters the second integrator <NUM>-<NUM>. As such, the dichroic mirrors <NUM>-<NUM>, <NUM>-<NUM>, and more specifically the fourth dichroic mirror <NUM>-<NUM>, generally acts as a filter to select and/or filter the green light <NUM> from the other colors of light emitted by the second phosphor <NUM>. Put another way, one or more of the third dichroic mirror <NUM>-<NUM> and the fourth dichroic mirror <NUM>-<NUM> may be further configured to refine the green light <NUM> to shift a peak wavelength thereof (e.g. a dominant wavelength that results from the filtering).

Similar to the red light <NUM>, the green light <NUM> is directed and/or reflected from the fourth dichroic mirror <NUM>-<NUM> to the fold mirror of the second integrator <NUM>-<NUM>, which reflects the green light <NUM> into the body of the second integrator <NUM>-<NUM>. Hence, the fourth dichroic mirror <NUM>-<NUM> both directs the green light <NUM> to the second integrator <NUM>-<NUM> and filters the green light <NUM>. Furthermore, the green light <NUM> is hence integrated by the second integrator <NUM>-<NUM> and further integrated by the third integrator <NUM>-<NUM>, which provides the green light <NUM> provided to the SLM <NUM> to form the green image and/or the green sub-image (e.g. of the RGB image).

Indeed, again with reference to <FIG>, a sharpness and/or position of the transition region of the fourth dichroic mirror <NUM>-<NUM> between about <NUM> and about <NUM> may be selected to more precisely select and/or filter the green light <NUM>, for example to a given color point.

For example, again with reference to <FIG>, a sharpness and/or position of the transition region of the fourth dichroic mirror <NUM>-<NUM> between about <NUM> and about <NUM> may be selected to more precisely select and/or filter the green light <NUM>. For example, by making the transition region of the fourth dichroic mirror <NUM>-<NUM> "sharper", such as by narrowing the transition region to about <NUM> to about <NUM>, more yellow and orange light may be filtered from the green light <NUM> to shift a color point of the green light <NUM> to a deeper green, though this may also have an effect of decreasing brightness of the green light <NUM>. Alternatively, and/or in addition, by shifting the transition region from <NUM> and <NUM>, to <NUM> to <NUM> (e.g. same width, but higher in wavelength), more yellow, and orange light may be filtered from the green light <NUM> to shift a color point of the green light <NUM> to a deeper green, though this may also have an effect of decreasing brightness of the green light <NUM>. It is understood that such sharpening and/or shifting of the transition region of the fourth dichroic mirror <NUM>-<NUM> (or any of the dichroic mirrors <NUM>), occurs during manufacture of the fourth dichroic mirror <NUM>-<NUM>, (or during manufacture of any of the dichroic mirrors <NUM>).

It is further understood that the third dichroic mirror <NUM>-<NUM> may also be adapted for such filtering, for example by narrowing the transmission region of the third dichroic mirror <NUM>-<NUM> to reflect yellow light and orange light, however the transmission curve of the dichroic mirror <NUM>-<NUM> may be constrained at least by having to maintain reflection of the third blue light <NUM> and reflection of the first red light <NUM>-<NUM>. Hence, for example, the dichroic mirror <NUM>-<NUM> should reflect the third red light <NUM> and the first red light <NUM>-<NUM>, as described herein, though the transmission short cutoff wavelength may be increased and/or the transmission long cutoff wavelength may be decreased to achieve "purer" greens.

It is further understood that the third dichroic mirror <NUM>-<NUM> is configured to: direct the first red light <NUM>-<NUM> from the fourth laser <NUM>-<NUM> to the at least one light integrator <NUM> (e.g. via the fourth dichroic mirror <NUM>-<NUM>); and direct the third blue light <NUM> from the third laser <NUM>-<NUM> to the second phosphor <NUM>, arranged on the second phosphor wheel <NUM>-<NUM>.

It is further understood that the second phosphor <NUM> is configured to convert the third blue light <NUM> to respective longer wavelengths that includes the green light <NUM>, and the third dichroic mirror <NUM>-<NUM> is further configured to transmit the green light <NUM> to the at least one light integrator <NUM> (e.g. via the fourth dichroic mirror <NUM>-<NUM>).

While it is understood that the fourth dichroic mirror <NUM>-<NUM> is optional, it is understood that when the fourth dichroic mirror <NUM>-<NUM> is present, the third dichroic mirror <NUM>-<NUM> is configured to direct the first red light <NUM>-<NUM> from the fourth laser <NUM>-<NUM> to the at least one light integrator <NUM> via the fourth dichroic mirror <NUM>-<NUM>, and the fourth dichroic mirror <NUM>-<NUM> is configured to direct the first red light <NUM>-<NUM> from the third dichroic mirror <NUM>-<NUM> to the at least one light integrator <NUM>. It is furthermore understood that that when the fourth dichroic mirror <NUM>-<NUM> is present the third dichroic mirror <NUM>-<NUM> is further configured to transmit the green light <NUM> to the at least one light integrator <NUM> via the fourth dichroic mirror <NUM>-<NUM>, the fourth dichroic mirror <NUM>-<NUM> is further configured to direct the green light <NUM> to the at least one light integrator <NUM> and transmit and/or partially transmit, others of the respective longer wavelengths that are emitted by the phosphor <NUM>.

Attention is next directed to <FIG> which depicts the system <NUM> with all four lasers <NUM> in operation. <FIG> is provided to for simplicity to show similarities and differences between the systems <NUM>, <NUM> in operation. Hence, while all four lasers <NUM> are in operation in <FIG>, it is understood that the system <NUM> may be operated in a blue mode, a red mode and a green mode, similar to as respectively depicted in <FIG>, <FIG>, and <FIG>, with the first laser <NUM>-<NUM> being on the blue mode and the other lasers <NUM> being off, the second laser <NUM>-<NUM> and the third lasers <NUM>-<NUM> being on in the red mode and the other lasers <NUM> being off, and the fourth laser <NUM>-<NUM> being on in the green mode with the other lasers <NUM> being off.

As depicted, in the system <NUM>, the paths of the first blue light <NUM>, the second blue light <NUM> and the second red light <NUM>-<NUM> are similar to, and/or the same as, the paths of the first blue light <NUM>, the second blue light <NUM> and the second red light <NUM>-<NUM> in the system <NUM>.

However, as the lasers <NUM>-<NUM>, <NUM>-<NUM>, the second phosphor wheel <NUM>-<NUM>, and the third dichroic mirror <NUM>-<NUM> are rotated <NUM>° relative to the integrator <NUM>-<NUM>, as compared to the system <NUM>, the first red light <NUM>-<NUM> is directed and/or reflected from the third dichroic mirror <NUM>-<NUM> into the second integrator <NUM>-<NUM>, and similarly the green light <NUM> is transmitted through the third dichroic mirror <NUM>-<NUM> into the second integrator <NUM>-<NUM>. Hence, if the third dichroic mirror <NUM>-<NUM> of the system <NUM> has the same transmission curve <NUM> as in the system <NUM> (e.g. as depicted in <FIG>), less filtering of the green light <NUM> may occur, though the transmission curve <NUM> of the third dichroic mirror <NUM>-<NUM> of the system <NUM> may tuned to better filter the green light <NUM>, as described above.

Summarizing the at least one light integrator <NUM>, it is understood that in the depicted examples, the at least one light integrator <NUM> comprises: a first light integrator <NUM>-<NUM> configured to receive the first blue light <NUM> and the second red light <NUM>-<NUM> from the second dichroic mirror <NUM>-<NUM>; a second light integrator <NUM>-<NUM> configured to receive the green light <NUM>-<NUM> and the first red light <NUM>-<NUM> from the third dichroic mirror <NUM>-<NUM> (e.g. directly as in the system <NUM>, or via the fourth dichroic mirror <NUM>-<NUM> in the system <NUM>); and a third light integrator <NUM>-<NUM> to combine respective light from the first light integrator <NUM>-<NUM> and the second light integrator <NUM>-<NUM>. Furthermore, the at least one light integrator <NUM> is arranged to provide light received at the at least one light integrator <NUM> to a spatial light modulator <NUM>. Furthermore, while the integrators <NUM> are depicted as three separate components, the integrators <NUM> may be provided as one integrator <NUM> (or two or more integrators <NUM>), and the like, having the same shape and/or configuration and/or functionality as the three depicted integrators <NUM>.

Attention is next <FIG> which depicts quenching curves <NUM>, <NUM> for two different candidate phosphors that may be used in the system <NUM> (and/or the system <NUM>). In particular, the quenching curves <NUM>, <NUM> show output power (in Watts) of two different phosphors as a function of excitation power (in Watts). At excitation powers below about 80W (e.g. 80W of power ae being input to the two phosphorus by a laser), phosphor conversion efficiency will be typically between <NUM> and <NUM>% (e.g. between 10W and 80W excitation power, the output powers are about <NUM> to <NUM>% of the excitation power). The remaining excitation power is converted to waste heat, causing a temperature of a phosphor to rise. As a temperature of a phosphor increases its conversion efficiency decreases; put another way, as excitation power is increased, the efficiency of a phosphor is reduced and eventually a quench point may be reached in which output power decreases with excitation power. While the phosphor having the quenching curve <NUM> does not have a quench point, the phosphor having the quenching curve <NUM> has a quench point at about 140W excitation power. Presuming that the phosphors <NUM><NUM> have respective quench curves similar to the quenching curve <NUM>, it is preferable to operate the lasers <NUM>-<NUM>, <NUM>-<NUM> at an excitation power that is below a quench point of the phosphor <NUM> to maximize efficiency. This problem may be exacerbated when one phosphor wheel is used (e.g. in the prior art) that includes different phosphors (e.g. emitting different colors) having different quench points, as a laser would have to be operated at an excitation power that is below the smallest of the quench points. Hence, splitting thermal load of the system across the two phosphor wheels <NUM> provides flexibility as the lasers <NUM>-<NUM>, <NUM>-<NUM> according to respective quench points of the phosphors <NUM>, <NUM>. Furthermore, use of the first red light <NUM>-<NUM> of the red laser <NUM>-<NUM> to supplement the second red light <NUM>-<NUM> produced by the phosphor <NUM> may enable the second laser <NUM>-<NUM> to be operated at a lower relative power that is below a quench point, for example as compared to when the red laser <NUM>-<NUM> is not used. Put another way, wherein the first red light <NUM>-<NUM> and the second red light <NUM>-<NUM> supplement each other and/or form a combined red color from the combination of the first red light <NUM>-<NUM> and the second red light <NUM>-<NUM> and/or supplement each other's respective brightness.

Hence, it is generally understood that the second laser <NUM>-<NUM> is operated at a power that is below a quenching limit of the first phosphor <NUM>, and the third laser <NUM>-<NUM> is operated at a respective power that is below a respective quenching limit of the second phosphor <NUM>.

Attention is next directed to <FIG>, which depicts a method <NUM> of controlling the system <NUM> (or the system <NUM>). The operations of the method <NUM> may correspond to machine readable instructions that are executed by the controller <NUM>. The method <NUM> of need not be performed in the exact sequence as shown and likewise various blocks may be performed in parallel rather than in sequence. Accordingly, the elements of method <NUM> are referred to herein as "blocks" rather than "steps. " The method <NUM> may be implemented on variations of the system <NUM>, as well (including, but not limited to, the system <NUM>).

The method <NUM> starts (e.g. at "START") and the controller <NUM> implements the blue mode by turning on the first blue laser <NUM>-<NUM> at a block <NUM>, while the other lasers <NUM> are controlled to be off; the SLM <NUM> is, in parallel, controlled to provide a blue sub-image at the block <NUM>. The SLM <NUM> may be controlled by the controller <NUM> at the block <NUM> and/or the controller <NUM> may implement the block <NUM> by receiving a command from another controller that is controlling the SLM <NUM>, at the block <NUM>, to provide the blue sub-image. In general, the block <NUM> is illustrated by <FIG> in which the first blue light <NUM> illuminates the SLM <NUM>.

In the red mode, which as depicted follows the blue mode, the controller <NUM> turns on the second blue laser <NUM>-<NUM> and the third blue laser <NUM>-<NUM> at a block <NUM>, while the other lasers <NUM> are controlled to be off; the SLM <NUM> is, in parallel, controlled to provide a red sub-image at the block <NUM>. The SLM <NUM> may be controlled by the controller <NUM> at the block <NUM> and/or the controller <NUM> may implement the block <NUM> by receiving a command from another controller that is controlling the SLM <NUM>, at the block <NUM>, to provide the red sub-image. In general, the block <NUM> is illustrated by <FIG> in which the red light <NUM> illuminates the SLM <NUM>.

In the green mode, which as depicted follows the red mode, the controller <NUM> turns on the fourth blue laser <NUM>-<NUM> at a block <NUM>, while the other lasers <NUM> are controlled to be off; the SLM <NUM> is, in parallel, controlled to provide a green sub-image at the block <NUM>. The SLM <NUM> may be controlled by the controller <NUM> at the block <NUM> and/or the controller <NUM> may implement the block <NUM> by receiving a command from another controller that is controlling the SLM <NUM>, at the block <NUM>, to provide the green sub-image. In general, the block <NUM> is illustrated by <FIG> in which the green light <NUM> illuminates the SLM <NUM>.

Hence, in general, the controller <NUM> is configured to: during a blue time period, control the first laser <NUM>-<NUM> to emit the first blue light <NUM>; during a red time period, control the second laser <NUM>-<NUM> to emit the second blue light <NUM> and control the fourth laser <NUM>-<NUM> to emit the first red light <NUM>-<NUM>; and during a green time period, control the third laser <NUM>-<NUM> to emit the third blue light <NUM>.

While the method <NUM> is described with respect to the blue mode, the red mode and the green mode being implemented in a specific sequence, the modes may be implemented in any suitable sequence.

Furthermore the modes may be implemented for any suitable respective time periods, for example to achieve a given white point in the system <NUM> or the system <NUM> (e.g. a color of light achieved by combing the blue light <NUM>, the red light <NUM> and the green light <NUM>).

Furthermore the turning on given lasers <NUM> in a given mode and controlling the SLM <NUM> to provide a respective sub-image need happen in exact coordination. For example, respective lasers <NUM> may be turned on, and other lasers <NUM> may be turned off, in a given mode before the SLM <NUM> is controlled to provide a given sub-image, or respective lasers <NUM> may be turned on, and other lasers <NUM> may be turned off, in a given mode after the SLM <NUM> is controlled to provide a given sub-image. However, the SLM <NUM> is generally controlled to provide a given sub-image for a given mode only when lasers <NUM> of another mode are off (e.g. for the red mode, the SLM <NUM> is controlled to provide the red sub-image after the first blue laser <NUM>-<NUM> is off, but the SLM <NUM> may be controlled to provide the red sub-image before or after the lasers <NUM>-<NUM>, <NUM>-<NUM> are on; similarly, the SLM <NUM> is controlled to stop providing the red sub-image before the fourth blue laser <NUM>-<NUM> is on).

Hence, red, green, and blue periods of light may be allocated according to a light budget, for example by turning the lasers <NUM> on and off. An efficiency of each color channel (e.g. a red color channel provided the red mode, a green color channel provided the green mode, and a blue color channel provided the blue mode) may vary, as will the amount of source laser light, which may result in a different brightness for a given color relative to the other colors. Video systems in general operate according to a balance of red, green, and blue light that when summed results in a specific white point. The relative duty cycles of red, green, and blue light may hence be chosen based on the amount of each color available in the specific implementation.

According to the present specification, during the time periods allocated to red, two sets of lasers <NUM>-<NUM>, <NUM>-<NUM> are active and/or on in the system <NUM> (or the system <NUM>) as depicted in <FIG>. Blue light from the second laser <NUM>-<NUM>, of wavelength <NUM>, is generally directed to the first dichroic mirror <NUM>-<NUM>, with the wavelength <NUM> being in a reflection portion of the transmission curve <NUM> of the first dichroic mirror <NUM>-<NUM> (e.g. below the transmission wavelength cutoff). Hence, light from the from the second laser <NUM>-<NUM> is directed to the "red" phosphor <NUM> at the first phosphor wheel <NUM>-<NUM>. The phosphor <NUM> generally fluoresces emitting yellow to red light (e.g. see <FIG>) which is directed back towards the first dichroic mirror <NUM>-<NUM>. The yellow to red light is in a transmission portion of the transmission curve <NUM> of the first dichroic mirror <NUM>-<NUM> and is hence transmitted to the second dichroic mirror <NUM>-<NUM>. The transmission curve <NUM> of the second dichroic mirror <NUM>-<NUM> is selected to transmit green to yellow light and reflect red (or blue light). This will have the effect of filtering the yellow to red light, converting it into a red color upon reflection to the integrator <NUM>-<NUM>.

The choice of where to place a long wavelength cutoff of the transmission curve <NUM> of the second dichroic mirror <NUM>-<NUM> may depend on the phosphor material chosen for the phosphor <NUM> of the first phosphor wheel <NUM>-<NUM> and on a desired color of red to be emitted by the third integrator <NUM>-<NUM>. For example, when the system <NUM> is to be provided at or in a projector that is to be operated according to the REC. <NUM> display standard, the long wavelength cutoff may be selected to be a shorter wavelength as the REC. <NUM> display standard does not require deeply saturated colors. A projector that is to be operated according to the DCI P3 color standard may require a long wavelength cutoff at a longer wavelength, and a projector that is to be operated according to the REC. <NUM> may require a long wavelength cutoff at a wavelength that is longer still.

Attempting to achieve "deeper" reds (e.g. reds that are well above <NUM>) reveals a further challenge of LaPh display systems as phosphor materials tend to be red deficient. Increasing the percent of display time allocated to red may alleviate some of this problem, but in general this solution may be not sufficient. Adding more pump lasers (e.g. more than one second laser <NUM>-<NUM> may be used) may also mitigate the problem, up until a quenching limit is reached. However, as provided herein, using the red laser <NUM>-<NUM> as a direct red laser source may help achieve a given white balance and/or white color point.

During the red display time, the red laser <NUM>-<NUM> (e.g. of wavelength <NUM>) will simultaneously be on with the laser <NUM>-<NUM>, and light from the red laser <NUM>-<NUM> is directed to the third dichroic mirror <NUM>-<NUM>. The third dichroic mirror <NUM>-<NUM> may have a transmission long wavelength cutoff chosen to be below the wavelength of the red laser <NUM>-<NUM>. The red light from the of the red laser <NUM>-<NUM> will hence reflected and/or directed to the fourth dichroic mirror <NUM>-<NUM>, which also has a transmission long wavelength cutoff chosen to be below the wavelength of the red laser <NUM>-<NUM>. The red light from the red laser <NUM>-<NUM> will again be reflected, towards integrator <NUM>-<NUM>.

During the green display time, the third blue laser <NUM>-<NUM> (e.g. of wavelength <NUM>) is on and light therefrom is directed towards the third dichroic mirror <NUM>-<NUM>, which comprises a band-pass filter having a transmission low wavelength cutoff chosen to be above the wavelength of the third blue laser <NUM>-<NUM>, and a transmission high wavelength cutoff chosen to reflect the light emitted by the red laser <NUM>-<NUM>. Light from the third blue laser <NUM>-<NUM> will reflect off the third dichroic mirror <NUM>-<NUM> and be directed to the green phosphor <NUM> of the second phosphor wheel <NUM>-<NUM>, and the green phosphor <NUM> will fluoresce, emitting green to yellow light. This green to yellow light is directed towards, and is transmitted through, the third dichroic mirror <NUM>-<NUM> and impinges on the fourth dichroic mirror <NUM>-<NUM>, acts as a yellow notch filter and hence reflects the green light towards integrator <NUM>-<NUM> (as the yellow light is transmitted).

During the blue display time, the first blue laser <NUM>-<NUM> (e.g. of wavelength <NUM>) is on and light therefrom is directed towards the first dichroic mirror <NUM>-<NUM>, which comprises a band-pass filter having a transmission wavelength cutoff chosen to be above the wavelength of the first blue laser <NUM>-<NUM>. Light from the first blue laser <NUM>-<NUM> will reflect off the first dichroic mirror <NUM>-<NUM> and be directed to the second dichroic mirror <NUM>-<NUM>. The transmission low wavelength cutoff of the second dichroic mirror <NUM>-<NUM> is selected chosen to be above the wavelength of the first blue laser <NUM>-<NUM> and hence the light from the first blue laser <NUM>-<NUM> is reflected by the second dichroic mirror <NUM>-<NUM> towards the integrator <NUM>-<NUM>.

Hence, by having two independent phosphor wheels <NUM>, the choice of phosphors <NUM>, <NUM> may be optimized for the individual red and green colors as compared to using phosphor to provide both red and green (e.g. and blue).

A final colorimetry of a projector that uses the system <NUM> (or the system <NUM>) may will depend on the wavelengths of the lasers <NUM> that are selected, types of phosphor materials that are selected, and the cutoff wavelengths of the various dichroic mirrors <NUM>. It is hence understood the present specification provides systems <NUM>, <NUM> that allow for flexibility in optimizing for different operating color points, brightness, colorimetry, etc..

As already discussed, phosphor materials are temperature sensitive. It is furthermore understood that the lasers <NUM> may be temperature sensitive. In choosing the wavelengths cutoffs for the various dichroic mirrors <NUM>, it may be important to provide heat sinks <NUM> to absorb rejected light. For example, light that does not get directed towards the integrators <NUM> will be absorbed somewhere inside the system <NUM> (or the system <NUM>) and converted to heat. Hence, the wavelengths cutoffs may be chosen such that waste light is filtered by transmission through either the third dichroic mirror <NUM>-<NUM> or the fourth dichroic mirror <NUM>-<NUM>. A light absorbing heat sink <NUM> added to the dichroic mirrors <NUM>-<NUM>, <NUM>-<NUM> may allow for optimal thermal management. Put another way, in some examples, the system <NUM>, or the system <NUM>, may further comprise one or more heat sinks <NUM> arranged to absorb one or more of heat and waste light from one or more of the first dichroic mirror <NUM>-<NUM>, the second dichroic mirror <NUM>-<NUM>, the third dichroic mirror <NUM>-<NUM>, and the fourth dichroic mirror <NUM>-<NUM>.

Hence, use of two independent phosphor wheels <NUM> may reduce the thermal load on each individual phosphor wheel <NUM> (e.g. with unsegmented phosphors <NUM>, <NUM>), which may enhance efficiency and brightness as compared to when only one phosphor wheel <NUM> is used (e.g. with segmented phosphors). A speed at switching between colors is limited in the systems <NUM>, <NUM> by the ability to turn the lasers <NUM> on and off, however by selecting lasers <NUM> that have short on and of times, turning a laser <NUM> on and off may occur in about a <NUM> time period, which may reduce and/or eliminate the spoke time issues experienced in prior art LaPh systems. Reducing and/or eliminating spoke time may increases the amount of time allocated to pure colors, further increasing system efficiency and brightness. Such fast switching may also enable fast(er) color cycling rates. In a practical system, a color cycling rate may be limited by a switching rate of an SLM (e.g. time to switch between sub-images), hence with switching times of the lasers <NUM> being about <NUM>, the switching time of a projector that uses the system <NUM> (or the system <NUM>) may be independent of the switching times of the lasers <NUM>.

As should by now be apparent, the operations and functions of the devices described herein are sufficiently complex as to require their implementation on a computer system, and cannot be performed, as a practical matter, in the human mind. In particular, computing devices such as set forth herein are understood as requiring and providing speed and accuracy and complexity management that are not obtainable by human mental steps, in addition to the inherently digital nature of such operations (e.g., a human mind cannot interface directly with digital projectors, or lasers, among other features and functions set forth herein).

In this specification, elements may be described as "configured to" perform one or more functions or "configured for" such functions. In general, an element that is configured to perform or configured for performing a function is enabled to perform the function, or is suitable for performing the function, or is adapted to perform the function, or is operable to perform the function, or is otherwise capable of performing the function.

It is understood that for the purpose of this specification, language of "at least one of X, Y, and Z" and "one or more of X, Y and Z" can be construed as X only, Y only, Z only, or any combination of two or more items X, Y, and Z (e.g., XYZ, XY, YZ, XZ, and the like). Similar logic can be applied for two or more items in any occurrence of "at least one. " and "one or more. " language.

The terms "about", "substantially", "essentially", "approximately", and the like, are defined as being "close to", for example as understood by persons of skill in the art. In some examples, the terms are understood to be "within <NUM>%," in other examples, "within <NUM>%", in yet further examples, "within <NUM>%", and in yet further examples "within <NUM>%".

Persons skilled in the art will appreciate that in some examples, the functionality of devices and/or methods and/or processes described herein can be implemented using pre-programmed hardware or firmware elements (e.g., application specific integrated circuits (ASICs), electrically erasable programmable read-only memories (EEPROMs), etc.), or other related components. In other examples, the functionality of the devices and/or methods and/or processes described herein can be achieved using a computing apparatus that has access to a code memory (not shown) which stores computer-readable program code for operation of the computing apparatus. The computer-readable program code could be stored on a computer readable storage medium which is fixed, tangible and readable directly by these components, (e.g., removable diskette, CD-ROM, ROM, fixed disk, USB drive). Furthermore, it is appreciated that the computer-readable program can be stored as a computer program product comprising a computer usable medium. Further, a persistent storage device can comprise the computer readable program code. It is yet further appreciated that the computer-readable program code and/or computer usable medium can comprise a non-transitory computer-readable program code and/or non-transitory computer usable medium. Alternatively, the computer-readable program code could be stored remotely but transmittable to these components via a modem or other interface device connected to a network (including, without limitation, the Internet) over a transmission medium. The transmission medium can be either a non-mobile medium (e.g., optical and/or digital and/or analog communications lines) or a mobile medium (e.g., microwave, infrared, free-space optical or other transmission schemes) or a combination thereof.

Claim 1:
A dual phosphor wheel projection system comprising:
a first laser to generate first blue light;
a second laser to generate second blue light;
a third laser to generate third blue light;
a fourth laser to generate first red light;
a first phosphor arranged on a first phosphor wheel;
a second phosphor arranged on a second phosphor wheel;
a first dichroic mirror;
a second dichroic mirror; and
a third dichroic mirror;
at least one light integrator,
wherein the first dichroic mirror is configured to direct the first blue light from the first laser to the second dichroic mirror, and the second dichroic mirror is configured to direct the first blue light from the first dichroic mirror to the at least one light integrator,
wherein the first dichroic mirror is further configured to direct the second blue light from the second laser to the first phosphor, arranged on the first phosphor wheel, the first phosphor configured to convert the second blue light to longer wavelengths that includes second red light, wherein the second dichroic mirror is further configured to direct the second red light to the at least one light integrator and transmit others of the longer wavelengths, wherein the at least one light integrator combines the first red light and the second red light,
wherein the third dichroic mirror is configured to: direct the first red light from the fourth laser to the at least one light integrator; and direct the third blue light from the third laser to the second phosphor, arranged on the second phosphor wheel,
wherein the second phosphor configured to convert the third blue light to respective longer wavelengths that includes green light, wherein the third dichroic mirror is further configured to transmit the green light to the at least one light integrator.