Light source device and projection display device

Abstract

The present application relates to a light source device and a projection display device. In a light source device using a dichroic mirror, a light source device is sought in which light use efficiency is high even without using a condensing lens made of quartz glass or the like which is expensive. A light source device includes: a laser light source which outputs light of a predetermined wavelength region in a predetermined polarization state; a dichroic mirror; a phase difference plate; a condensing optical system; a rotatable color wheel which includes a fluorescent region and a reflection region; and a reflection device. The output light of the laser light source is transmitted in this order from the dichroic mirror, the phase difference plate, and the condensing optical system, and is irradiated to the color wheel. The light of the predetermined wavelength region which is reflected by the reflection region is transmitted in this order from the condensing optical system and the phase difference plate, and is incident to the dichroic mirror, a component in the predetermined polarization state is reflected by the reflection device after being transmitted from the dichroic mirror, and is again transmitted from the dichroic mirror and emitted, and a component which is different from the predetermined polarization state is reflected by the dichroic mirror and emitted.

Description

Technical Field

[0001] This invention relates to a light source device and a projection display device equipped with a light source device. Background Technology

[0002] As a light source for projection display devices, a known light source device uses blue light (B light) emitted by a semiconductor laser (laser diode or LD) as excitation light to irradiate a phosphor, and outputs yellow light (Y light), red light (R light), green light (G light), etc., together with a portion of the blue light (B light) emitted by the semiconductor laser.

[0003] Patent Document 1 discloses a light source device in which a green-light-emitting phosphor, a red-light-emitting phosphor, and a transmission window are pre-positioned along the circumference of a color wheel. While rotating the color wheel, blue light is irradiated onto the circumference. This light source device employs an optical system that directs the green and red fluorescence emitted by the phosphors on the color wheel and the blue light transmitted through the transmission window of the color wheel in the same direction. Specifically, two mirrors guide the blue light transmitted through the transmission window to a dichroic mirror, and the dichroic mirror merges the light paths of the blue light and the fluorescence. In this light source device, because the blue light and fluorescence are guided to the dichroic mirror via different light paths, a large optical path space is required, making it difficult to miniaturize the device. Furthermore, this leads to an increase in the number of optical components such as mirrors.

[0004] Patent Document 2 discloses a light source device in which a green-light-emitting phosphor, a red-light-emitting phosphor, and a mirror surface are pre-positioned along the circumference of a color wheel. While rotating the color wheel, blue light is irradiated onto the circumference of the color wheel from a blue laser light source (LD array). In this light source device, a dichroic mirror with polarizing characteristics in the blue wavelength band and a quarter-wavelength plate are disposed between the blue laser light source (LD array) and the color wheel. In this device, the polarizing characteristics of the laser light source ensure that the optical path of the blue light reflected by the mirror surface is the same as the optical path of the fluorescence. Therefore, compared to the light source device disclosed in Patent Document 1, miniaturization can be achieved.

[0005] Patent Document 3 discloses a light source device in which the optical axis of the blue light, which also serves as the excitation light, is non-coaxial with the optical axis of the focusing device as it travels from a laser source to a focusing device. In this light source device, a color separation device with two regions having different reflective properties is positioned between the laser source and the fluorescent color wheel. Although it is an optical system that outputs blue light and fluorescence in a time-division manner, because the optical paths of the blue light, which also serves as the excitation light, and the fluorescence light are approximately the same, it can be miniaturized compared to the light source device disclosed in Patent Document 1.

[0006] Patent Document 1: Japanese Patent Publication No. 2010-256457

[0007] Patent Document 2: Japanese Patent Publication No. 2012-108486

[0008] Patent Document 3: Japanese Patent Publication No. 2019-61237

[0009] As mentioned above, the light source device described in Patent Document 2 is miniaturized compared to the light source device described in Patent Document 1. However, when used as an illumination source for a projector, it may cause degradation of the white balance of the projected image. The blue light emitted from the laser light source undergoes a polarization conversion from P-polarized to S-polarized light as it passes through the dichroic mirror and is reflected back to the dichroic mirror by the phosphor wheel. If this polarization conversion is not performed with high precision, there will be polarized light components that cannot be emitted as reflected light from the dichroic mirror, resulting in light loss of blue light and thus degrading the white balance of the projected image.

[0010] Furthermore, if polarization disorder occurs at the condenser lens positioned before the fluorescent color wheel, resulting in a component that transforms from circularly polarized light to elliptically polarized light, the amount of light reflected as S-polarized light at the dichroic mirror decreases, leading to a drop in white balance. To suppress elliptically polarized light, one method involves using materials with a low coefficient of thermal expansion, such as quartz glass, in the condenser lens; however, such materials are expensive, making them costly. Moreover, the limited variety of optical materials with low coefficients of thermal expansion further restricts the selection of optical materials and reduces the freedom of optical design.

[0011] Regarding this point, in the light source device of Patent Document 3, since the polarization characteristics of the light source are not utilized, the problems that may occur in the light source device described in Patent Document 2 do not occur when blue light is emitted. However, other problems exist. In the light source device described in Patent Document 3, the blue light reflected by the fluorescent color wheel is split into two beams by a dichroic device and then incident on a focusing device. However, such a dichroic device is difficult to manufacture simply in terms of productivity and cost. For example, when the dichroic part and the beam splitting (light segmentation) part are bonded adjacently to manufacture the dichroic device, light loss will occur if the bonding is not done with extremely high precision, and it is difficult to achieve this precision in reality using conventional bonding techniques. Furthermore, when the device is integrated rather than bonded, it is difficult to manufacture the dichroic part and the beam splitting part, which have different transmission and reflection characteristics, at low cost.

[0012] As is well known, in fluorescence-based light source devices, such as those described in Patent Documents 2 and 3, the greater the output of the excitation light illuminating the phosphor, the greater the fluorescence output. Therefore, in order to achieve a bright projector, a light source device equipped with many light LDs to output high-intensity light is considered.

[0013] However, when using an LD package containing many blue LDs to output high-intensity excitation light for phosphors and blue light for displays, it's important to note that the spectral width widens when the entire LD package is considered a single light source. For a single LD, the emission spectrum falls within a relatively narrow wavelength range. For example, according to the specifications for multimode blue LDs published on the website of Nichia Chemical Co., Ltd., the tolerance is 448nm to 462nm relative to the center wavelength of 455nm. The deviation range is approximately 14nm. In the case of an LD package containing many LDs, since the package is manufactured as a whole to ensure the dominant wavelength, the emission spectrum of each LD is not identical and deviates within the tolerance range. Furthermore, in projectors using LD light sources, to reduce speckle noise on the projected image, it is also considered to actively use multiple blue LDs with slightly different dominant wavelengths to form a light source system.

[0014] It is known that the spectrum of the output light of an LD generally changes with the increase or decrease of the LD's driving current and the change of its operating temperature. Typically, when the LD's driving current increases or the operating temperature rises, the emission spectrum tends to shift towards the longer wavelength side.

[0015] As mentioned earlier, LD packages have a wider spectral width compared to a single LD, resulting in greater spectral variation when the drive current or operating temperature changes. However, in the structure using a dichroic mirror in Patent Document 2 to emit blue light through polarization conversion, such spectral variation may lead to changes in the emission efficiency of blue light, thereby causing a deviation (deterioration) in the white balance of the projected image. Furthermore, when using the color separation device in Patent Document 3, it becomes very difficult to mass-produce the color separation device with corresponding pre-optimized characteristics when the emission spectrum variation of the LD package increases.

[0016] Therefore, in light source devices that use a portion of the blue light emitted by a semiconductor laser and fluorescence as illumination output, there is a need for a light source device that can provide stable illumination output even when the spectrum of the semiconductor laser's output light changes, and that does not require excessively large-scale installation. In this case, fluorescence is obtained by irradiating a phosphor with the blue light emitted by the semiconductor laser as excitation light. Furthermore, in light source devices using dichroic mirrors, there is a need for a light source device that achieves high light utilization efficiency even without using expensive focusing lenses such as those made of quartz glass. Additionally, there is a need for a projector device that incorporates such a light source device and can obtain a high-brightness projected image with good white balance. Summary of the Invention

[0017] A first aspect of the present invention is a light source device, characterized by comprising: a laser light source that outputs light in a predetermined wavelength region with a predetermined polarization state; a dichroic mirror disposed on the optical axis of the laser light source; a retardation plate; a focusing optical system; a rotatable color wheel having a fluorescent region and a reflective region, wherein the fluorescent region emits fluorescence when irradiated by light in the predetermined wavelength region, and the reflective region reflects light when irradiated by light in the predetermined wavelength region; and a reflecting device, wherein the output light of the laser light source is transmitted sequentially through the dichroic mirror, the retardation plate, and a portion of the focusing optical system, and irradiates the fluorescent region or the reflective region of the color wheel. Light of the predetermined wavelength region, after being reflected by the reflection region, is transmitted through the portion of the condensing optical system that is different from the aforementioned portion, and through the phase retardation plate, in that order, and then enters the dichroic mirror. The component of the light of the predetermined wavelength region that has the predetermined polarization state is reflected by the reflection device after being transmitted through the dichroic mirror, and then transmitted through the dichroic mirror again and exits. The component of the light of the predetermined wavelength region that has the predetermined polarization state is reflected by the dichroic mirror and exits. The fluorescence emitted by the fluorescent region is transmitted through the condensing optical system and the phase retardation plate in that order and enters the dichroic mirror, and is reflected by the dichroic mirror and exits.

[0018] A second aspect of the present invention is a light source device, characterized by comprising: a laser light source that outputs light in a predetermined wavelength region with a predetermined polarization state; a first dichroic mirror disposed on the optical axis of the laser light source; a second dichroic mirror disposed parallel to the first dichroic mirror on an extension line of the optical axis of the laser light source; a retardation plate; a focusing optical system; and a rotatable color wheel having a fluorescent region and a reflective region, wherein the fluorescent region emits fluorescence when irradiated by light in the predetermined wavelength region, and the reflective region reflects light when irradiated by light in the predetermined wavelength region; the output light of the laser light source, after being reflected by the first dichroic mirror, is transmitted sequentially through the retardation plate and a portion of the focusing optical system, and irradiates the color wheel. The fluorescent region or the reflective region, after being reflected by the reflective region, the light of the predetermined wavelength region is transmitted through the portion of the condensing optical system that is different from the predetermined portion and the phase retardation plate in this order and then enters the second dichroic mirror. The component of the light of the predetermined wavelength region that has the predetermined polarization state is reflected by the second dichroic mirror and then reflected by the first dichroic mirror and emitted. The component of the light of the predetermined wavelength region that has the predetermined polarization state is transmitted through the second dichroic mirror and emitted. The fluorescence emitted by the fluorescent region, after being transmitted through the condensing optical system and the phase retardation plate in this order, is partially transmitted through the first dichroic mirror and emitted, and the other part is transmitted through the second dichroic mirror and emitted.

[0019] According to the present invention, a light source device can be provided that can obtain stable illumination light output even when the spectrum of the output light of a semiconductor laser changes, and the device itself can be made not excessively large. Furthermore, a light source device using a dichroic mirror can be provided that achieves high light utilization efficiency even without using expensive condenser lenses such as those made of quartz glass. Additionally, a projector device using such a light source device can be provided that can obtain a high-brightness projected image with good white balance. Attached Figure Description

[0020] Figure 1 This is a diagram showing the outline structure of the optical system of the light source device according to Embodiment 1.

[0021] Figure 2 This is a diagram used to illustrate the travel path of the excitation light in Embodiment 1.

[0022] Figure 3 This is a diagram used to illustrate the path of fluorescence emitted by the excitation light in Embodiment 1.

[0023] Figure 4 This is a diagram used to illustrate the travel path of a portion of the blue light in Embodiment 1.

[0024] Figure 5 This is a diagram used to illustrate the travel path of another part of the blue light in Embodiment 1.

[0025] Figure 6 This is a diagram showing the outline structure of the optical system of the light source device according to Embodiment 2.

[0026] Figure 7 This is a diagram used to illustrate the travel path of a portion of the blue light in Embodiment 2.

[0027] Figure 8 This is a diagram used to illustrate the travel path of another part of the blue light in Embodiment 2.

[0028] Figure 9 This is a diagram used to illustrate the path of the fluorescence emitted by the excitation light in Embodiment 2.

[0029] Figure 10 This is a diagram used to illustrate the structure of the fluorescent color wheel.

[0030] Figure 11 This is a diagram illustrating the characteristics of the dichroic mirror used in Embodiment 1.

[0031] Figure 12 (A) is a diagram used to illustrate an example of the emission spectrum of an LD light source; Figure 12 (B) is a diagram used to illustrate another example of the emission spectrum of an LD light source; Figure 12 (C) is a graph used to illustrate the wavelength shift of the emission spectrum of an LD light source.

[0032] Figure 13 This is a diagram illustrating the characteristics of the dichroic mirror used in a variation of Embodiment 1.

[0033] Figure 14 This is a diagram showing the structure of the projector according to Embodiment 3.

[0034] Figure 15 This is a diagram used to illustrate the structure of an LD light source.

[0035] Figure 16 This is a diagram illustrating the characteristics of the dichroic mirror used in Embodiment 2.

[0036] Figure 17 (A) is a diagram used to illustrate the path of excitation light incident on the fluorescent color wheel; Figure 17 (B) is a diagram used to illustrate the path of blue light after reflection from the fluorescent color wheel.

[0037] Explanation of reference numerals in the attached figures

[0038] 1...Light source device

[0039] 2...Light source device

[0040] 11, 11'... Optical axes of the collimating lens system

[0041] 12, 12'... Optical axis of the condenser lens system

[0042] 101...LD light source

[0043] 102……convex lens

[0044] 103……Concave lens

[0045] 104... Dichroic mirror

[0046] 105……Reflective devices

[0047] 106……Phase Difference Plate

[0048] 107……convex lens

[0049] 108...convex lens

[0050] 109... Fluorescent Color Wheel

[0051] 110... motor

[0052] 601... First dichroic mirror

[0053] 602...Second dichroic mirror

[0054] 1000……Projection display device

[0055] 1001...reflection area

[0056] 1002……fluorescent region

[0057] 1401... Illumination Lens

[0058] 1402……Illumination Lens

[0059] 1403... Spatial light modulator

[0060] 1404...TIR prism

[0061] 1405... Projection Lens

[0062] 1406... Color wheel of light

[0063] 1407...lens

[0064] 1408... Focusing stick

[0065] 1501……LD

[0066] 1502... Collimating Lens Detailed Implementation

[0067] The light source device and projection display device according to embodiments of the present invention will now be described with reference to the accompanying drawings. The embodiments shown below are illustrative examples; for instance, those skilled in the art can make appropriate modifications to the technical solutions for details without departing from the spirit of the present invention.

[0068] Furthermore, in the accompanying drawings referred to in the following description of the embodiments, unless otherwise specified, the units indicated by the same reference numerals have the same function.

[0069] [Implementation Method 1]

[0070] Figure 1 This is a diagram showing the outline structure of the optical system of the light source device according to Embodiment 1. For ease of explanation, the mechanical structure, housing, electrical wiring, etc., used to mount the optical elements are omitted in this diagram.

[0071] (Structure of the light source device)

[0072] The light source device 1 includes: an LD light source 101 having multiple semiconductor lasers (LDs); a convex lens 102 and a concave lens 103 constituting a collimating lens system (collimating optical system); a dichroic mirror 104; a phase retardation plate 106; a convex lens 107 and a convex lens 108 constituting a condenser lens system (condenser optical system); a fluorescent color wheel 109; a motor 110; and a reflective device 105.

[0073] Details are as follows Figure 15 As shown, the LD light source 101 has five LDs 1501, each LD 1501 using a blue semiconductor laser with a center wavelength oscillating around 455 nm. Alternatively, a blue semiconductor laser with a center wavelength outside 455 nm can also be used. As the driving method for the lasers, continuous oscillation driven by a constant current is used. Furthermore, in Figure 1 and Figure 15 The example shown illustrates the setup with 5 LD 1501s, but the number of semiconductor lasers (LDs) is not limited to 5 and can be adjusted according to the desired light output.

[0074] Here, in Figure 12 (A) and Figure 12Example (B) illustrates the emission spectrum of light emitted from the LD light source 101. Generally, for a single LD 1501 device, the emission wavelength is a narrow spectrum. However, in the case of an LD light source 101 having multiple LD 1501s as in the light source device 1 of this embodiment, since the emission spectra of each LD 1501 are not exactly the same, the emission spectrum of the LD light source 101 as a whole is... Figure 12 (A) or Figure 12 As exemplified in (B), it exhibits a emission spectrum with a width of approximately several nm to 10 nm. This is because currently commercially available semiconductor lasers (LDs) are mass-produced with specified tolerances for the center emission wavelength. However, due to manufacturing variations, even products of the same specification exhibit deviations in their emission spectrum within the tolerance of the center emission wavelength. Thus, since multiple LD 1501s with deviations are used, the overall LD light source 101, as a whole, exhibits... Figure 12 (A) and Figure 12 As exemplified in (B), it becomes a wavelength spectral characteristic with a certain degree of extension over the wavelength range. Furthermore, Figure 12 (A) and Figure 12 The emission spectrum characteristics shown in (B) are merely an example, and the LD light source 101 used in this embodiment does not necessarily have the emission spectrum characteristics shown in the figure. It should be emphasized that when using multiple LDs, even if LDs of the same specification are used, the output light of the LD light source will have a spectral width of about several nm to about 10 nm.

[0075] Back Figure 15 Each LD 1501 is equipped with a collimating lens 1502. Generally, the beam emitted by a semiconductor laser has a predetermined angle of expansion. By setting the collimating lens 1502, the beam expansion can be suppressed, allowing a roughly parallel beam to exit from the LD 1501. The collimating lens 1502 and the package housing the LD 1501 can be integrated or separate. When separate, if multiple LD 1501s are followed by independently configured lens arrays or the like to form a light source module, the same collimation function can be achieved.

[0076] Back Figure 1 The beam emitted by the LD light source 101 is collimated by a collimating lens system consisting of a convex lens 102 and a concave lens 103, thereby adjusting the beam diameter. As described later, the output light of the LD light source 101 is used as excitation light for exciting phosphors and as blue light (B) for display. Figure 1The diagram shows a system using one convex lens 102 and one concave lens 103 as a collimating lens system, but this is just an example, and the structure of the collimating lens system is not limited to this. The beam diameter of the excitation light is appropriately set according to the number of LDs 1501 used, and correspondingly, the number, material, shape, and other optical specifications of the lenses constituting the collimating lens system, as well as their spacing, can be appropriately designed.

[0077] exist Figure 1 In this context, the optical axis of the collimating lens system is referred to as optical axis 11. Optical axis 11 is set to be perpendicular to the cross-section of the entire beam emitted by the LD light source 101 and to pass through the center.

[0078] A dichroic mirror 104 is disposed at an angle of 45 degrees relative to the optical axis 11 of the collimating lens system. Figure 11 The optical characteristics of the dichroic mirror 104 are shown. For blue light (B light) with a wavelength around 445 nm, the dichroic mirror 104 exhibits the polarization characteristic of transmitting the P-polarized component of light while reflecting the S-polarized component. Furthermore, the dichroic mirror 104 has the characteristic of reflecting green light (G light), red light (R light), or yellow light (Y light) containing both of these. The dichroic mirror 104 with such characteristics can be formed, for example, by depositing a dielectric multilayer film on a transparent glass substrate.

[0079] In this embodiment, the characteristics of the dichroic mirror 104 are set considering that the output light of the LD light source 101 has a deviation of up to about 10 nm relative to the center wavelength of 455 nm, as described above. That is, in order to suppress Figure 12 (A) and Figure 12 The loss of the output light in the emission spectrum exemplified in (B) sets the cutoff wavelength of the dichroic mirror 104 (wavelength with 50% transmittance or reflectance: half-value specification). Specifically, as Figure 11 As shown, the cutoff wavelength is set to 445 nm for S-polarized light and 465 nm for P-polarized light. By adopting this structure, the dichroic mirror 104 can transmit the blue light of the P-polarized light output from the LD light source 101 without loss.

[0080] Back Figure 1 On the optical axis 11 of the collimating lens system, a phase retardation plate 106 is provided in front of the dichroic mirror 104. As a phase retardation plate, a half-wavelength plate or a quarter-wavelength plate, etc., can be used.

[0081] For example, when using a quarter-wave plate, by appropriately adjusting the orientation of the optical axis of the quarter-wave plate, it is possible to control the intensity of the P-polarized component from 100% to 50% and the intensity of the S-polarized component from 0% to a maximum of 50% when P-polarized light is incident as linearly polarized light, thus making it circularly polarized. Furthermore, when using a half-wave plate, by appropriately adjusting the orientation of the optical axis of the half-wave plate, it is possible to change the polarization direction of the linearly polarized light when P-polarized light is incident as linearly polarized light.

[0082] In the optical path of the output light from the LD light source 101, a focusing lens system composed of convex lenses 107 and 108 is disposed in front of the phase retardation plate 106. The focusing lens system enables the output light from the LD light source 101, after being approximately parallelized by the collimating lens system, to be focused onto the phosphor color wheel 109. Figure 1 In the example shown, it consists of two convex lenses 107 and 108, but the structure of the condenser lens system is not limited to this example; it can also consist of one or more lenses. Furthermore, the shape and material of the lenses can be appropriately selected. That is, in addition to spherical lenses, aspherical or freeform lenses can also be used. If inexpensive optical materials such as BK7 are used, a light source device can be provided at a low cost.

[0083] A fluorescent color wheel 109 is positioned at the focusing point of the condenser lens system. Figure 10 The diagram shows a front view and a side view of a fluorescent color wheel 109. The fluorescent color wheel 109 uses a circular glass or metal plate as its substrate, and fluorescent regions 1002 and reflective regions 1001 are provided on its surface. The fluorescent regions 1002 are coated with phosphors, which emit red (R), green (G), or yellow (Y) fluorescence depending on the type of phosphor when irradiated by excitation light (output light from the LD light source 101). The reflective regions 1001 are areas used to reflect the output light from the LD light source 101 and are not coated with phosphors. The reflective regions 1001 are preferably pre-mirror-finished to efficiently reflect blue laser light. The substrate of the fluorescent color wheel 109 is suitable to be a metal with high thermal conductivity; to improve air cooling efficiency, unevenness or holes may also be provided on the substrate. The fluorescent color wheel 109 is connected to the motor 110, which rotates around the rotating shaft, so that the excitation light focused on the fluorescent color wheel 109 sequentially irradiates the reflective region 1001 and the fluorescent region 1002.

[0084] In this embodiment, the optical axis 11 of the collimating lens system and the optical axis 12 of the condenser lens system are parallel to each other but offset (displaced), and are in a non-coaxial relationship. In this embodiment, the output beam of the LD light source 101 is arranged such that when it is directed toward the fluorescent color wheel 109, it passes through the lower half region of the convex lenses 107 and 108 constituting the condenser lens system.

[0085] Viewed in a direction orthogonal to the optical axis 11 of the collimating lens system, a reflecting device 105 is arranged parallel to the dichroic mirror 104 at a position away from the dichroic mirror 104. The reflecting device 105 is configured such that the optical axis 12 of the condenser lens system is sandwiched between the reflecting device 105 and the optical axis 11 of the collimating lens system. If viewed along a direction parallel to the optical axis 11 of the collimating lens system, the reflecting device 105 is positioned between the LD light source 101 and the phase retardation plate 106. The size of the reflecting surface of the reflecting device 105 is approximately half the size of the optical surface of the dichroic mirror 104, and it does not obstruct the output light of the LD light source 101 incident on the dichroic mirror 104.

[0086] The reflective device 105 uses a mirror that reflects blue (B) light. The reflective device 105 preferably has a reflectivity of 95% or higher for blue (B) light, and can be fabricated, for example, by forming a dielectric multilayer film on a glass substrate. Alternatively, a reflective film can be formed on the substrate using methods such as Al vapor deposition.

[0087] (Operation of the light source device)

[0088] The operation of the light source device 1 with the above structure will now be explained.

[0089] Figure 2 This diagram illustrates the path of blue light (B-color light) emitted from the LD light source 101. During the period when the reflective region 1001 of the phosphor color wheel 109 is illuminated, the blue light (B-color light) emitted from the LD light source 101 functions as the blue light (B-color light) component used for image display. Additionally, during the period when the fluorescent region 1002 of the phosphor color wheel 109 is illuminated, the blue light (B-color light) emitted from the LD light source 101 functions as the excitation light for exciting phosphors.

[0090] First, in the LD light source 101, the output from each LD 1501 passes through the collimating lens 1502 ( Figure 15The collimated, roughly parallel blue laser beams are shown. The polarization direction of each laser beam output from the LD 1501 is pre-adjusted to P-polarization. Since the laser beams travel parallel to each other with gaps between them, they are strictly speaking spatially discrete laser beam groups. However, because the LD 1501s are arranged very close together, the laser beam group can also be treated as a single beam. That is, the LD source 101 can be considered as a source emitting a single beam.

[0091] The beam is adjusted to a predetermined beam diameter by a collimating lens system. Furthermore, in this embodiment, a convex lens 102 and a concave lens 103 are used to reduce the beam diameter emitted by the five LDs. The path of the blue beam, after its diameter is adjusted by the collimating lens system, is defined as LB1 (the direction of LB1 is aligned with the optical axis of the collimating lens system).

[0092] Blue light traveling along LB1, after passing through the collimating lens system, is incident on dichroic mirror 104 and transmitted. This is because, as... Figure 11 As shown, the characteristic of the dichroic mirror 104 is that it transmits blue light (B-color light) of P-polarized light.

[0093] The blue light (B color light) of the P-polarized light transmitted from the dichroic mirror 104 then passes through the phase retardation plate 106. The phase retardation plate 106 is a quarter-wavelength plate. Therefore, after the blue light (B color light) of the P-polarized light is transmitted through the phase retardation plate 106, the P-polarized light is transformed into circularly polarized light. If the path of the circularly polarized light beam until it reaches the fluorescent color wheel 109 is defined as LB2, the circularly polarized light traveling along LB2 is focused onto the fluorescent color wheel 109 by the focusing effect of the condenser lens system (convex lens 107, convex lens 108).

[0094] In this embodiment, the optical axis 12 of the condenser lens system and the optical axis 11 of the collimating lens system are set to be non-coaxial, i.e., optical axis offset (displacement). This is to ensure that the light illuminating the reflective area 1001 of the fluorescent color wheel 109 from the blue light (B color light) output from the LD light source 101 is emitted as blue light (B color light) for image display without loss.

[0095] The following is for reference. Figure 17 (A) Figure 17 (B) will be explained in detail. For example... Figure 17As shown in (A), blue light (B color light) traveling from LD light source 101 toward phosphor color wheel 109 passes along path LB2 in the lower half of the condenser lens system, specifically in regions 107(D) (solid line) and 108(D) (solid line) below the optical axis 12 of the condenser lens system. During the period when the blue light (B color light) illuminating the reflection region 1001 of phosphor color wheel 109 is reflected by the reflection region 1001, but instead of returning along path LB2 to the phase retardation plate 106, it is reflected as follows... Figure 17 As shown in (B), the path LB3 passes through the upper half of the condenser lens system. That is, it passes through regions 108(U) (solid line) and 107(U) (solid line) above the optical axis 12 of the condenser lens system and returns to the phase retardation plate 106. This is because the normal to the reflecting surface relative to the reflecting region 1001 is equal to the optical axis 12 of the condenser lens system, and the reflection occurs in such a way that the angle of incidence (the angle formed by the optical axis 12 and the path LB2) is equal in magnitude to the angle of reflection (the angle formed by the optical axis 12 and the path LB3).

[0096] In this series of processes, if the blue light (B-color light) converted from P-polarized light to circularly polarized light by the phase retardation plate 106 returns to the phase retardation plate 106 in its circularly polarized state, it is then converted to S-polarized light by the phase retardation plate 106 and directed along path LB4 towards the dichroic mirror 104. Figure 2 As shown, the blue light (B-color light) of the S-polarized light incident on the dichroic mirror 104 along the path LB4 is reflected by the dichroic mirror 104 and emitted along the path LBs.

[0097] exist Figure 4 The path of the light is further shown in detail. Blue light (B color light) from LD light source 101 forms the entire beam, the diameter of which is adjusted by a collimating lens system (convex lens 102 and concave lens 103). Then, it passes through dichroic mirror 104 and phase retardation plate 106, and through the lens region of the lower half of the condenser lens system, whose optical axis is displaced relative to the collimating lens system, and is focused onto the phosphor color wheel.

[0098] when Figure 10 When the reflective region 1001 of the fluorescent color wheel 109 coincides with the focal point of the blue light LB, the blue light LB is reflected and parallelized by transmission through the upper half of the optical axis 12 of the condenser lens system in the order of convex lens 108 and convex lens 107. If the path of the S-polarized light passing through the phase difference plate 106 is defined as LBs, the light traveling along the path LBs is reflected by the dichroic mirror 104. The light reflected by the dichroic mirror 104 becomes the emitted light of the light source device 1.

[0099] However, in reality, unless expensive quartz glass is used to construct the condenser lens system, circularly polarized light will be affected by birefringence when passing through convex lenses 107 and 108, causing the polarization to become disordered and transforming from high-quality circularly polarized light into elliptical polarized light. It can be assumed that the high-power laser incident on the condenser lens system causes the temperature of each lens to rise, resulting in a photoelastic effect caused by expansion, leading to birefringence and thus disordered polarization.

[0100] The result of this transformation into elliptically polarized light is that the blue light (B-color light) transmitted from the phase retardation plate 106 and incident along path LB4 onto the dichroic mirror 104 will contain a P-polarized component. Figure 11 As can be seen from the optical characteristics of the dichroic mirror 104, the blue light (B-color light) of P-polarized light will be transmitted through the dichroic mirror 104, and therefore cannot be emitted as reflected light through the path LBs.

[0101] Regarding this point, in the light source device 1 of this embodiment, as... Figure 2 As shown, a reflective device 105, parallel to the dichroic mirror 104, is arranged along the path of the blue light (B-color light) of the P-polarized light transmitted from the dichroic mirror 104. The blue light (B-color light) of the P-polarized light, after being reflected by the reflective device 105, passes through the dichroic mirror 104 again and can therefore be emitted as transmitted light through path LBp. That is, the blue light (B-color light) of the S-polarized light can be emitted through path LBs, and the blue light (B-color light) of the P-polarized light can be emitted through path LBp, which is parallel to path LBs.

[0102] exist Figure 5 The diagram shows a detailed light path for P-polarized light. Blue light (B-color light) is reflected by the reflective area of ​​the fluorescent color wheel 109, then transmitted through convex lenses 108 and 107 and parallelized. After passing through the phase retardation plate 106, the P-polarized light within the blue light (B-color light) travels along path LBp. The P-polarized light, transmitted as parallel light from the dichroic mirror 104, reaches the reflector 105. The reflector 105 is positioned parallel to and at a predetermined distance from the dichroic mirror 104. The P-polarized light, reflected by the reflector 105, is again transmitted through the dichroic mirror 104, becoming the emitted light of the light source device 1.

[0103] As explained above, according to this embodiment, even without using expensive quartz glass to construct the focusing lens system, the blue light (B color light) reflected by the reflection area 1001 of the fluorescent color wheel 109 can be emitted almost without loss.

[0104] Next, the fluorescent region 1002 ( ) of the fluorescent color wheel 109 was illuminated. Figure 10 The operation during the period when blue light (B color light) is output from the LD light source 101 will be explained. Figure 3 As shown, the blue light LB from the LD light source 101 serves as the entire beam, and its beam diameter is adjusted by the collimating lens system (convex lens 102 and concave lens 103). Then, it passes through the dichroic mirror 104 and the phase retardation plate 106, and passes through the lens region of the lower half of the condenser lens system, in which the optical axis is displaced relative to the collimating lens system, and is focused onto the fluorescent color wheel 109.

[0105] When the focusing position of blue light LB is relative to the fluorescent region 1002 ( Figure 10 When the wavelengths match, the blue light LB acts as the excitation light for the phosphor, and wavelength conversion is performed by the phosphor. In this embodiment, since a YAG-based phosphor emitting yellow light is disposed in the fluorescent region 1002, the fluorescence LY emitted by the phosphor is yellow light (Y light) containing both green (G) and red (R) bands.

[0106] The fluorescent LY is parallelized by the condenser lens system (convex lens 108, convex lens 107) and, after being transmitted through the phase retardation plate 106, enters the dichroic mirror 104. Because the dichroic mirror 104 possesses... Figure 11 As shown, the yellow (Y) band light is reflected by the dichroic mirror 104 and becomes the emitted light of the light source device 1. Furthermore, the fluorescent LY light can be considered as unpolarized light, and it remains unpolarized after passing through the phase retardation plate 106.

[0107] In this way, the fluorescence LY, which undergoes wavelength conversion due to irradiation with excitation light, can be emitted from the light source device 1 with high efficiency.

[0108] [Modification of Implementation Method 1]

[0109] Next, a variation of Embodiment 1 will be described. This variation can stably output illumination light even when, for example, the temperature of the LD rises and the spectrum of the blue light (B color light) output from the LD light source 101 shifts towards the longer wavelength side.

[0110] Due to factors such as increased driving current of the LD light source 101 or rising ambient temperature, the spectrum of blue light (B color light) output from the LD light source 101 sometimes shifts towards longer wavelengths. For example, as... Figure 12 As shown in (C), when the maximum deviation of the emission spectrum towards the longer wavelength side is set to +λ, +λ when using a projection display device can be verified in advance through experiments, etc. +λ is typically around 15nm.

[0111] In this variation, a method with... Figure 13The dichroic mirror 104 exhibits the following optical characteristics. Specifically, considering that the spectrum of blue light (B-color light) output from the LD light source 101 may change to the longer wavelength side over time, the cutoff wavelength for S-polarized light is set to 453 nm, and the cutoff wavelength for P-polarized light is set to 473 nm.

[0112] In use Figure 11 When using a dichroic mirror with the characteristics of [missing information], if the spectrum of blue light (B color light) output from the LD light source 101 is [missing information]... Figure 12 There is no problem with state (A), in such cases Figure 12 As shown by the dashed line in (C), when the light deviates towards the longer wavelength side, a portion of the blue light (B color light) will not be able to pass through the dichroic mirror 104, and the amount of light that can be used as excitation light or for display will be reduced.

[0113] Regarding this point, according to this modified example, the spectrum of blue light (B color light) output from the LD light source 101, regardless of whether it is in the range of... Figure 12 The state of (A) is still as follows: Figure 12 The dashed line in (C) indicates a deviation towards the longer wavelength side, referencing... Figures 2-5 The light path described remains unchanged. That is, the blue light (B-color light) of the P-polarized light output from the LD light source 101 is transmitted through the dichroic mirror 104 with almost no loss, regardless of whether there is a wavelength deviation, and illuminates the fluorescent color wheel 109.

[0114] Reflection area 1001 of fluorescent color wheel 109 Figure 10 Even if the reflected blue light (B color light) is distorted by the polarization caused by the condenser lens system, it is still... Figure 2 As shown, the S-polarized light component is emitted through route LBs, and the P-polarized light component is emitted through route LBp, which is parallel to route LBs.

[0115] In addition, such as Figure 3 As shown, the fluorescent region 1002 of the fluorescent color wheel 109 ( Figure 10 The resulting yellow light (gamma light) after wavelength conversion can be emitted efficiently as fluorescent LY.

[0116] As explained above, according to this modified example, even if the emission spectrum of the blue light (B-color light) output from the LD light source 101 shifts towards longer wavelengths, high light utilization efficiency is maintained, remaining unchanged from before the shift. Regarding fluorescence, it can be emitted as emitted light from the light source device 1 with good efficiency, similar to before the emission spectrum shift. This means that the light intensity and color temperature of the beam obtained through the light source device 1 are maintained extremely well. Thus, according to this modified example, a high-performance, versatile light source device can be provided that suppresses the degradation of characteristics such as output and color temperature even if the emission spectrum of the LD light source changes.

[0117] [Implementation Method 2]

[0118] Figure 6 This is a diagram showing the outline structure of the optical system of the light source device according to Embodiment 2. For ease of explanation, the mechanical structures, housing, electrical wiring, etc., used to mount the optical elements are omitted in this diagram. In Embodiment 1, a dichroic mirror and a reflecting device are used, and their sizes are different. Furthermore, Embodiment 1 shows a structure in which the fluorescence emitted by the fluorescent color wheel is reflected by the dichroic mirror.

[0119] In contrast, in Embodiment 2, a structure is provided with two dichroic mirrors of approximately the same size and wavelength characteristics. Furthermore, in Embodiment 1, the light beam from the LD light source reaches the fluorescent color wheel after being transmitted through the dichroic mirrors; in contrast, in Embodiment 2, the blue light from the LD light source is reflected by the dichroic mirrors before reaching the fluorescent color wheel, resulting in a more compact space for the light source device. The structure will be described below, but parts or functions identical to those in Embodiment 1 will be simplified or omitted.

[0120] (Structure of the light source device)

[0121] like Figure 6 As shown, the light source device 2 of this embodiment includes: an LD light source 101 equipped with multiple semiconductor lasers (LDs); a convex lens 102 and a concave lens 103 constituting a collimating lens system (collimating optical system); a first dichroic mirror 601; a second dichroic mirror 602; a phase retardation plate 106; convex lenses 107 and 108 constituting a condenser lens system; a phosphor color wheel 109; and a motor 110. Since the shape, characteristics, and functions of the LD light source 101, the collimating lens system, the phase retardation plate 106, the condenser lens system (condenser optical system), and the phosphor color wheel 109 are the same as in Embodiment 1, detailed descriptions are omitted here.

[0122] The first dichroic mirror 601 is configured such that the direction of its principal surface forms a 45-degree angle with respect to the optical axis 11' of the collimating lens system (convex lens 102 and concave lens 103). Furthermore, a second dichroic mirror 602 is disposed along the extension of the optical axis 11'. The first dichroic mirror 601 and the second dichroic mirror 602 are approximately the same size and are arranged parallel to each other at predetermined intervals.

[0123] Apart from manufacturing errors, the characteristics of the first dichroic mirror 601 and the second dichroic mirror 602 are the same, such as... Figure 16As shown, the light exhibits polarization characteristics of transmitting yellow (Y) band light containing both green (G) and red (R) wavelengths, while transmitting P-polarized light and reflecting S-polarized light for blue (B) light. The cutoff wavelength for P-polarized light is set to 445 nm, and the cutoff wavelength for S-polarized light is set to 465 nm.

[0124] (Operation of the light source device)

[0125] The following is for reference. Figure 6 The operation of the light source device 2 with the above structure will be explained. Figure 6 This diagram illustrates the path of blue light (B-color light) emitted from the LD light source 101. During the period when the fluorescent region 1002 of the phosphor color wheel 109 is illuminated, the blue light (B-color light) emitted from the LD light source 101 functions as excitation light for the phosphor. Additionally, during the period when the reflective region 1001 of the phosphor color wheel 109 is illuminated, the blue light (B-color light) emitted from the LD light source 101 functions as the blue light (B-color light) component used for image display.

[0126] First, in the LD light source 101, approximately parallel blue laser beams, collimated by the collimating lens 1502, are output from each LD 1501. In this embodiment, the polarization direction of the laser beams output from each LD 1501 is pre-adjusted to S-polarization. Since the laser beams travel parallel to each other with gaps between them, they are strictly speaking a spatially discrete group of laser beams. However, because the LD 1501s are arranged very close together, the group of laser beams can also be treated as a single beam. That is, the LD light source 101 can be considered as a light source emitting a single beam.

[0127] The beam is adjusted to a predetermined beam diameter by a collimating lens system. Furthermore, in this embodiment, a convex lens 102 and a concave lens 103 are used to reduce the beam diameter emitted by the five LDs. The path of the blue beam, after its diameter is adjusted by the collimating lens system, is set as LB1' (LB1' is aligned with the optical axis of the collimating lens system).

[0128] The blue light traveling along LB1', after passing through the collimating lens system, is incident on the first dichroic mirror 601 and reflected. This is because the first dichroic mirror 601 has the following characteristics: Figure 16 The characteristics of blue light (B-color light) reflected by S-polarized light are shown.

[0129] The blue light (B color light) of the S-polarized light, after being reflected by the first dichroic mirror 601, passes through the phase retardation plate 106. The phase retardation plate 106 is a quarter-wavelength plate. Therefore, after the blue light (B color light) of the S-polarized light is transmitted through the phase retardation plate 106, the light changes from S-polarized light to circularly polarized light. If the path of the circularly polarized light beam until it reaches the fluorescent color wheel 109 is defined as LB2', the circularly polarized light traveling along LB2' is focused onto the fluorescent color wheel 109 by the focusing effect of the focusing lens system (convex lens 107, convex lens 108).

[0130] In this embodiment, in order to ensure that the blue light (B color light) output from the LD light source 101 during the period of irradiating the reflection area 1001 of the fluorescent color wheel 109 is emitted without loss as the blue light (B color light) component for image display, the optical axis of the beam incident on the condenser lens system (the optical axis of the beam reflected from the collimating lens system through the first dichroic mirror 601 to reach the phase difference plate 106) is set to be non-coaxial with the optical axis 12' of the condenser lens system, that is, the optical axis is offset (displaced).

[0131] Blue light (B color light) traveling toward the phosphor color wheel 109 passes along path LB2' in the upper half of the condenser lens system, that is, the area above the optical axis 12' of the condenser lens system. During the period when the phosphor color wheel 109 is illuminating the reflection area 1001, the blue light (B color light) output from the LD light source 101 is reflected by the reflection area 1001, but instead of returning along path LB2' to the phase retardation plate 106, it... Figure 6 As shown, the light passes through the lower half of the condenser lens system along route LB3', that is, in the region below the optical axis 12' of the condenser lens system, and returns to the phase retardation plate 106. This is because the normal to the reflecting surface relative to the reflecting region 1001 is equal to the optical axis 12' of the condenser lens system, and the light is reflected in such a way that the angle of incidence (the angle formed by the optical axis 12' and route LB2') and the angle of reflection (the angle formed by the optical axis 12' and route LB3') are equal in magnitude.

[0132] In this series of processes, if the blue light (B-color light) converted from S-polarized light to circularly polarized light by the phase retardation plate 106 returns to the phase retardation plate 106 in its circularly polarized state, then the circularly polarized light is losslessly converted to P-polarized light by the phase retardation plate 106 and is directed along path LB4' to the second dichroic mirror 602. Then, as... Figure 6 As shown, the blue light (B-color light) of the P-polarized light incident on the second dichroic mirror 602 along the path LB4' is transmitted through the second dichroic mirror 602 and emitted along the path LBp'.

[0133] exist Figure 7The diagram shows a more detailed light path, with blue light (B color light) from LD light source 101 as the entire beam, the beam diameter of which is adjusted by a collimating lens system (convex lens 102 and concave lens 103). The light then passes through the first dichroic mirror 601 and the phase retardation plate 106, and through the lens region of the upper half of the condenser lens system, where it is focused onto the phosphor color wheel.

[0134] when Figure 10 When the reflective region 1001 of the fluorescent color wheel 109 coincides with the focal point of the blue light LB, the B-color light is reflected and parallelized by transmission through the lens region of the lower half of the optical axis 12' of the condenser lens system in the order of convex lens 108 and convex lens 107. If the path of the P-polarized light passing through the phase difference plate 106 is defined as path LBp', the light traveling along path LBp' is transmitted through the second dichroic mirror 602 and becomes the emitted light of the light source device 2.

[0135] However, in reality, unless expensive quartz glass is used to construct the condenser lens system, circularly polarized light will be affected by birefringence when passing through convex lenses 107 and 108, causing the polarization to become disordered and transforming from high-quality circularly polarized light into elliptical polarized light. It can be assumed that the high-power laser incident on the condenser lens system causes the temperature of each lens to rise, resulting in a photoelastic effect caused by expansion, leading to birefringence and thus disordered polarization.

[0136] The result of the transformation to ellipticized light is that, in the blue light (B color light) incident from the phase difference plate 106 onto the second dichroic mirror 602, as... Figure 8 As shown, it will contain S-polarized components (route LBs'). From Figure 16 As shown by the optical characteristics of the second dichroic mirror 602, the blue light (B-color light) of the S-polarized light will be reflected by the second dichroic mirror 602, and therefore cannot pass through path LBp'. Figure 6 It is emitted as transmitted light.

[0137] Regarding this point, in the light source device 2 of this embodiment, as... Figure 8 As shown, a first dichroic mirror 601 is arranged parallel to the second dichroic mirror 602 along the path LBs' of the blue light (B color light) of the S-polarized light after reflection by the second dichroic mirror 602. The blue light (B color light) of the S-polarized light after reflection by the second dichroic mirror 602 is reflected again by the first dichroic mirror 601, and therefore can be emitted as light for illumination.

[0138] Thus, according to this embodiment, as Figure 6As shown, blue light (B-color light) polarized by P can be emitted through path LBp', and blue light (B-color light) polarized by S can be emitted through path LBs' parallel to path LBp'. In other words, in the elliptically polarized blue light, the S-polarized component (path LBs') is reflected by the second dichroic mirror 602 and then further reflected by the first dichroic mirror 601 to become the emitted light of the light source device. Additionally, in the elliptically polarized blue light, the P-polarized component (path LBp') is transmitted through the second dichroic mirror 602 to become the emitted light of the light source device.

[0139] Next, refer to Figure 9 For the fluorescent region 1002 ( ) irradiated by the fluorescent color wheel 109 Figure 10 The operation during the period when blue light (B color light) is output from the LD light source 101 will be explained. Figure 9 As shown, the blue light LB' from the LD light source 101 serves as the entire beam, the diameter of which is adjusted by the collimating lens system (convex lens 102 and concave lens 103). Then, it passes through the first dichroic mirror 601 and the phase retardation plate 106, and passes through the lens region of the upper half of the condenser lens system, whose optical axis is displaced relative to the collimating lens system, and is focused onto the fluorescent color wheel 109.

[0140] When the focusing position of blue light LB' is aligned with the fluorescent region 1002 ( Figure 10 When the wavelengths match, the blue light LB' acts as the excitation light for the phosphor, and wavelength conversion is performed by the phosphor. In this embodiment, since a YAG-based phosphor emitting yellow light is disposed in the fluorescent region 1002, the fluorescence LY' emitted by the phosphor is yellow light (Y light) containing both green (G) and red (R) wavelengths. The fluorescence LY' is emitted from the phosphor over a wide angular range and is focused by the condenser lens system.

[0141] That is, the fluorescence LY' is parallelized by the condenser lens system (convex lens 108, convex lens 107), and after being transmitted from the phase retardation plate 106, it is incident on the first dichroic mirror 601 and the second dichroic mirror 602. Because the first dichroic mirror 601 and the second dichroic mirror 602 possess… Figure 16 As shown, yellow (Y) band light is transmitted through these dichroic mirrors and becomes the emitted light of the light source device 2. Furthermore, the fluorescent LY' can be considered as unpolarized light, and it remains unpolarized after passing through the phase retardation plate 106.

[0142] In this way, the fluorescence LY' that undergoes wavelength conversion due to irradiation with excitation light can be emitted from the light source device 2 with high efficiency.

[0143] Thus, the light source device 2 according to this embodiment has the following structure: light from the LD light source, which acts as both the blue light for display and the excitation light, is focused onto the fluorescent color wheel 109, and the fluorescence after wavelength conversion due to irradiation and the reflected blue light are efficiently emitted from the light source device 2 using a first dichroic mirror 601 and a second dichroic mirror 602. Specifically, the first dichroic mirror is positioned at a 45-degree angle to the optical axis of the collimating lens system, and the optical axis 11' of the collimating lens system acting as the excitation light for display is non-coaxial with the optical axis 12' of the focusing lens for the fluorescent color wheel, i.e., there is a shift (displacement). Furthermore, the second dichroic mirror is positioned parallel to the first dichroic mirror, and both the first and second dichroic mirrors can be dichroic mirrors with the same shape and characteristics. Therefore, not only are the number of components small, but low-cost optical components can also be used, enabling a small and low-cost optical system.

[0144] The use of a low-cost condenser lens system ensures that even if the reflected blue light contains elliptic polarized components, both the P-polarized and S-polarized components are emitted efficiently without light loss, thus guaranteeing sufficient blue light quantity and stable white balance. Therefore, by obtaining highly efficient fluorescence and blue light, extremely good color temperature for image light can be achieved.

[0145] [Modification of Implementation Method 2]

[0146] The following describes a variation of Embodiment 2. This variation, like the variation of Embodiment 1, allows for stable light output even when, for example, the temperature of the LD rises, causing the spectrum of blue light (B-color light) output from the LD light source 101 to shift towards longer wavelengths. Descriptions of aspects common to the variation of Embodiment 1 will be simplified or omitted.

[0147] In this variation, considering that... Figure 12 The emission spectrum of the LD light source 101 shown in (C) may deviate towards the longer wavelength side by +λ. Therefore, the cutoff wavelength of the dichroic mirror is set to be... Figure 16 The example shown deviates towards the longer wavelength side. That is, the cutoff wavelength for P-polarized light is set to 460 nm, and the cutoff wavelength for S-polarized light is set to 480 nm.

[0148] According to this modified example, the spectrum of blue light (B color light) output from the LD light source 101, regardless of whether it is in the range of... Figure 12 The state of (A) is still as follows: Figure 12 The dashed line in (C) indicates a deviation towards the longer wavelength side, referencing... Figures 6-9The light path remains unchanged. That is, the blue light (B color light) of the S-polarized light output from the LD light source 101 is reflected almost undamaged by the dichroic mirror 601 and illuminates the fluorescent color wheel 109, regardless of whether there is a wavelength deviation.

[0149] Reflection area 1001 of fluorescent color wheel 109 Figure 10 Even if the reflected blue light (B color light) is distorted by the polarization caused by the condenser lens system, it is still... Figure 8 As shown, the S-polarized component is emitted through route LBs', and as... Figure 7 The P-polarized component is emitted through route LBp', which is parallel to route LBs'.

[0150] In addition, such as Figure 9 As shown, the fluorescent region 1002 of the fluorescent color wheel 109 ( Figure 10 The resulting yellow light (gamma light) after wavelength conversion can be emitted efficiently as fluorescence LY'.

[0151] According to this modified example, even if the emission spectrum of the blue light (B-color light) output from the LD light source 101 shifts towards the longer wavelength side, the high light utilization efficiency remains unchanged. Regarding fluorescence, similarly to the shift in the emission spectrum of the excitation light, it can be efficiently emitted as the emitted light of the light source device 2. This means that the light intensity and color temperature of the beam obtained through the light source device 2 can be maintained extremely well. Thus, according to this modified example, a high-performance, versatile light source device can be provided that does not deteriorate in output, color temperature, or other characteristics even if the emission spectrum of the LD light source changes.

[0152] [Implementation Method 3]

[0153] Next, as Embodiment 3, a projection display device having the light source device involved in Embodiment 1 or its variations will be described. Regarding the light source device 1, since it is the same as in Embodiment 1 or its variations, the description will be simplified or omitted.

[0154] Figure 14 This is a typical diagram showing the optical structure of the projection display device 1000 according to this embodiment. The projection display device 1000 includes: a light source device 1, a lens 1407 (relay lens), a condenser rod 1408, a color wheel 1406, an illumination lens 1401, an illumination lens 1402, a total internal reflection (TIR) ​​prism 1404, a spatial light modulator 1403 (light modulation device), and a projection lens 1405.

[0155] As the fluorescent color wheel 109 rotates, the light source device 1 emits blue light (B color light) and yellow light (Y color light) in a time-separated manner.

[0156] Illumination light IL output from the light source device 1 is incident on lens 1407 (relay lens). Lens 1407 is set to a predetermined NA to match the F-value of the projection lens 1405, and is used to focus the light emitted from the light source device 1 onto the entrance port of the condenser rod 1408. The relay lens does not necessarily have to be a single lens. In addition, it may not be necessary if the NA is sufficient.

[0157] The condenser bar 1408, also known as a light channel or integrating bar, is an optical component commonly used in the illumination system of a projector. Alternatively, a compound eye integrator can be used instead of a condenser bar in the illumination system of a liquid crystal projector. A color wheel 1406 is disposed close to the emission side of the condenser bar 1408.

[0158] The light color wheel 1406, also known as the light color selection wheel, is a plate-shaped rotating body capable of rotating around a rotation axis. It is equipped with filters for various colors (R, Y, G) and a fan-shaped light transmission section for transmitting blue light. The color filters are provided to remove light in unwanted wavelength regions to improve the color purity of the displayed light. However, for blue light, since it is a high-purity laser, filters are not required, and therefore a light transmission section is used instead. In some cases, this light transmission section may also include a diffuser plate to ensure that the output light of other colors matches the NA (Nearest Neighbor).

[0159] The fluorescent color wheel 109 with phosphors rotates synchronously with the light color wheel 1406. The rotation timing is adjusted so that when the yellow phosphor of the former emits light, the R filter, Y filter, or G filter of the latter is located in the optical path of the illumination light IL. When the blue excitation light is reflected by the former, the light transmission part of the latter is located in the optical path of the illumination light IL.

[0160] The light transmitted from the color wheel 1406 is used as a highly pure illumination light with red (R), green (G), yellow (Y), and blue (B) colors that are repeated in a time-division manner.

[0161] Illumination lens 1401 and illumination lens 1402 are lenses that shape the illumination light propagated through the condenser bar 1408 and the light color wheel 1406 into a beam suitable for illuminating the spatial light modulator 1403, and are composed of one or more lenses.

[0162] TIR prism 1404 is an internal total internal reflection prism composed of two prisms. TIR prism 1404 causes the illumination light to undergo internal total internal reflection and be incident on the spatial light modulator 1403 at a predetermined angle, and causes the reflected light modulated by the spatial light modulator 1403 to be transmitted toward the projection lens 1405.

[0163] As the spatial light modulator 1403 (light modulation device), a digital micromirror device (DMD) with micromirrors arranged in an array is used, for example. The micromirrors corresponding to each display pixel are driven to change the reflection direction by pulse width modulation according to the brightness level of the image signal. By synchronizing the modulation operation of the spatial light modulator 1403 with the time-division multiple colors of illumination light provided from the light source device 1 via the light color wheel 1406, a color image light (IMG) can be obtained.

[0164] The projection lens 1405 is used to magnify and project the color image light IMG modulated by the spatial light modulator 1403 onto a screen (not shown), and is composed of one or more lenses. Furthermore, a screen may not be necessary when the user projects onto any wall or other surface.

[0165] By using the high-efficiency and color-balanced light source device shown in Embodiment 1 or its variations to construct a projector, it is possible to provide a small projector with high light utilization, good color temperature, and high performance even if the emission spectrum of the laser light source changes.

[0166] [Other Implementation Methods]

[0167] The implementation of this invention is not limited to the above-described embodiments, and various modifications can be made within the technical concept of this invention.

[0168] For example, in Embodiment 3, the light source device 1 of Embodiment 1 or its variant is used to construct the projection display device, but it goes without saying that if the light source device 2 of Embodiment 2 or its variant is used, a high-definition projection display device can also be constructed.

[0169] Furthermore, when a half-wavelength plate is used instead of a quarter-wavelength plate as the phase difference plate 106 in Embodiment 1, the blue light of the P-polarized light output from the LD light source 101 is converted into S-polarized light through transmission from the half-wavelength plate. After being reflected by the phosphor color wheel, it is converted back into P-polarized light through transmission from the half-wavelength plate. Thus, the blue P-polarized light is transmitted from the dichroic mirror 104, reflected by the reflector 105, and then transmitted again from the dichroic mirror 104. Figure 2 The light is emitted from the LBp path. Furthermore, even if S-polarized light becomes disordered and produces P-polarized light components during transmission from the condenser lens system, it can be converted back to S-polarized light through transmission from the 1 / 2 wavelength plate, and then transmitted through... Figure 2The light is emitted from the LBs via a specific path. Thus, by using a low-cost condenser lens system, even if the polarization of the reflected blue light becomes disordered, both the P-polarized and S-polarized components can be emitted efficiently without light loss, ensuring sufficient blue light quantity and stable white balance. Therefore, with highly efficient fluorescence and blue light, extremely good color temperature of the image light can be achieved.

[0170] Furthermore, when a half-wavelength plate is used instead of a quarter-wavelength plate as the phase difference plate 106 in Embodiment 2, the blue light of the S-polarized light output from the LD light source 101 is converted into P-polarized light through transmission from the half-wavelength plate. After being reflected by the fluorescent color wheel, it is converted back into S-polarized light through transmission from the half-wavelength plate. Thus, the blue S-polarized light is reflected by the second dichroic mirror 602 and the first dichroic mirror 601 and passes through... Figure 6 The path LBs' is emitted. Furthermore, even if P-polarized light becomes disordered and produces S-polarized light components during transmission from the condenser lens system, it can be converted back to P-polarized light through transmission from the 1 / 2 wavelength plate, and then transmitted through... Figure 6 The light is emitted along the path LBp'. Thus, by using a low-cost condenser lens system, even if the polarization of the reflected blue light becomes disordered, both the P-polarized and S-polarized components can be emitted efficiently without light loss, thereby ensuring sufficient blue light quantity and stable white balance. Therefore, with highly efficient fluorescence and blue light, extremely good color temperature of the image light can be achieved.

[0171] Furthermore, although not explicitly stated in Embodiments 1 and 2, a diffuser plate can be used, for example, to reduce speckle noise caused by blue (B) laser light on the projected image. Adding a diffuser plate to a part of the optical system within the light source device can reduce speckle noise.

[0172] Another method to reduce speckle noise is to select LDs with slightly different wavelengths and combine them appropriately to create a blue LD light source. In such an LD light source, although the emission spectrum range of the LD light source will be expanded, by appropriately setting the characteristics of the dichroic mirror in conjunction with this, even without using expensive quartz glass to construct the condenser lens system, the blue light (B color light) reflected by the reflective area of ​​the fluorescent color wheel can be emitted almost without loss.

[0173] Furthermore, the emission wavelength (center wavelength) of the LD light source does not necessarily have to be 445nm. For example, an appropriate wavelength can be selected from the range of 440nm to 470nm to set as the center wavelength. The cutoff wavelength of the dichroic mirror can be appropriately set according to the selected center wavelength.

[0174] Furthermore, a collimating lens system is not strictly necessary. The purpose of the collimating lens system is to adjust the beam diameter from the LD light source; therefore, it can be omitted if the number of LDs used is small and beam diameter adjustment is not required. Additionally, in Embodiment 1 or Embodiment 2, if a mechanism is provided that holds the retardation plate in a rotatable manner and allows for angle adjustment, the optical axis of the retardation plate can be changed by rotation. This allows for alteration of the ratio of the P-polarized and S-polarized components of the elliptically polarized light passing through the retardation plate, and adjustment of the light intensity distribution of the P-polarized and S-polarized light incident on the condenser rod. The more uniform the light intensity distribution, the better the uniformity of the illuminance distribution on the projected image.

Claims

1. A light source device, characterized in that, have: A laser light source outputs light within a predetermined wavelength range with a predetermined polarization state; A dichroic mirror is disposed on the optical axis of the laser source; Phase difference plate; Concentrating optical system; A rotatable color wheel has a fluorescent region and a reflective region, wherein the fluorescent region fluoresces when illuminated by light of a predetermined wavelength region, and the reflective region reflects light when illuminated by light of the predetermined wavelength region; and Reflective devices The output light from the laser source is transmitted sequentially through the dichroic mirror, the retardation plate, and a portion of the focusing optical system, illuminating the fluorescent or reflective region of the color wheel. Light of the predetermined wavelength region, after being reflected by the reflection region, is transmitted through the portion of the focusing optical system that differs from the aforementioned portion, and through the phase retardation plate, in that order, and then enters the dichroic mirror. The component of light in the predetermined wavelength region with the predetermined polarization state is reflected by the reflecting device after being transmitted through the dichroic mirror, and then transmitted through the dichroic mirror again before being emitted. The components of light in the predetermined wavelength region that differ from the predetermined polarization state are reflected by the dichroic mirror and emitted. The fluorescence emitted from the fluorescent region is transmitted through the focusing optical system and the phase retardation plate in this order and then incident on the dichroic mirror, and is reflected by the dichroic mirror and emitted.

2. The light source device according to claim 1, characterized in that, A collimating optical system is provided between the laser source and the dichroic mirror to collimate the output light of the laser source. The optical axis of the collimating optical system is parallel to and offset from the optical axis of the focusing optical system.

3. The light source device according to claim 1 or 2, characterized in that, The defined polarization state is P-polarized light. The cutoff wavelength of the dichroic mirror for P-polarized light is greater than that for S-polarized light.

4. A light source device, characterized in that, have: A laser light source outputs light within a predetermined wavelength range with a predetermined polarization state; A first dichroic mirror is disposed on the optical axis of the laser source; The second dichroic mirror is arranged parallel to the first dichroic mirror on the extension line of the optical axis of the laser source; Phase difference plate; Concentrating optical system; as well as A rotatable color wheel has a fluorescent region and a reflective region. The fluorescent region emits fluorescence when illuminated by light of a predetermined wavelength region, and the reflective region reflects light when illuminated by light of the predetermined wavelength region. The output light from the laser source, after being reflected by the first dichroic mirror, is transmitted sequentially through the phase retardation plate and a portion of the focusing optical system, illuminating the fluorescent region or the reflective region of the color wheel. Light of the predetermined wavelength region, after being reflected by the reflection region, is transmitted sequentially through the portion of the focusing optical system different from the first part, and through the phase retardation plate, and then enters the second dichroic mirror. The component of light in the predetermined wavelength region, representing the predetermined polarization state, is reflected by the second dichroic mirror and then by the first dichroic mirror before being emitted. The component of light in the predetermined wavelength region that differs from the predetermined polarization state is transmitted through the second dichroic mirror and emitted. The fluorescence emitted from the fluorescent region is transmitted through the focusing optical system and the phase retardation plate in this order. Part of it is transmitted through the first dichroic mirror and emitted, while the other part is transmitted through the second dichroic mirror and emitted.

5. The light source device according to claim 4, characterized in that, A collimating optical system is provided between the laser source and the first dichroic mirror to collimate the output light of the laser source, and the optical axis of the collimating optical system is orthogonal to the optical axis of the focusing optical system.

6. The light source device according to claim 4 or 5, characterized in that, The predetermined polarization state is S-polarized light. The cutoff wavelength of the dichroic mirror for S-polarized light is greater than that for P-polarized light.

7. The light source device according to any one of claims 1, 2, 4, and 5, characterized in that, The phase difference plate is a 1 / 2 wavelength plate or a 1 / 4 wavelength plate.

8. The light source device according to claim 3, characterized in that, The phase difference plate is a 1 / 2 wavelength plate or a 1 / 4 wavelength plate.

9. The light source device according to claim 6, characterized in that, The phase difference plate is a 1 / 2 wavelength plate or a 1 / 4 wavelength plate.

10. A projection display device, characterized in that, have: The light source device according to any one of claims 1 to 9; Optical modulation devices; and Projection lens.

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