Optical system

Abstract

Provided is an optical system having: a first optical system having a polarization conversion element for aligning a polarization direction of light including light of a plurality of colors with a predetermined polarization direction and generating illumination light including light of a plurality of colors; a first polarization rotation element disposed at a first pupil position within the first optical system and including a first divided region and a second divided region having polarization characteristics different from each other with respect to first color light among the light of a plurality of colors emitted from the polarization conversion element; a polarizer disposed between the polarization conversion element and the first polarization rotation element within the first optical system and reducing light in a polarization direction other than the predetermined polarization direction included in the light emitted from the polarization conversion element; and a plurality of light valves each illuminated by at least the first color light among the light of a plurality of colors included in the illumination light generated by the first optical system.

Description

Technical Field

[0001] This disclosure relates to an optical system suitable for projectors and the like. Background Technology

[0002] Examples of projector types that perform full-color displays include single-board types using a common light valve for various colors of light (R, G, and B, blue), and three-board types using different light valves for the three colors of light, etc. (see PTL 1 to 4). When blue light with a short wavelength is continuously incident on a single light valve, the valve degrades. PTL 1 proposes using two light valves for blue light, thereby extending the lifespan of the light valves.

[0003] Citation List

[0004] Patent documents

[0005] [PTL 1] Japanese Unexamined Patent Application Publication No. 2018-13655

[0006] [PTL 2] Japanese Unexamined Patent Application Publication No. 2001-324762

[0007] [PTL 3] Japanese Unexamined Patent Application Publication No. 2008-165058

[0008] [PTL 4] Japanese Unexamined Patent Application Publication No. 2006-343721

[0009] Public content

[0010] For example, in situations where two blue light valves are used to extend the valve life, it is difficult to improve contrast in a configuration that simply splits the blue light into two.

[0011] The goal is to provide an optical system that can improve contrast.

[0012] An optical system according to an embodiment of the present disclosure includes: a first optical system comprising a polarization conversion element that aligns the polarization direction of light comprising multiple colors with a predetermined polarization direction, the polarization conversion element generating illumination light comprising multiple colors; a first polarization rotation element disposed at a first pupil position within the first optical system and comprising a first segmentation region and a second segmentation region, wherein the first segmentation region and the second segmentation region have polarization characteristics different from each other relative to a first color light among the multiple colors emitted from the polarization conversion element; a polarizer disposed within the first optical system between the polarization conversion element and the first polarization rotation element, the polarizer reducing light in polarization directions other than the predetermined polarization direction included in the light emitted from the polarization conversion element; and a plurality of light valves, each light valve being illuminated by at least a first color light among the multiple colors of light included in the illumination light generated by the first optical system.

[0013] In an optical system according to an embodiment of the present disclosure, a first polarization rotation element, including a first segmented region and a second segmented region having different polarization characteristics, is arranged at a first pupil position within the first optical system, and a polarizer is provided within the first optical system to reduce light in the light emitted from the polarization conversion element that has polarization directions other than a predetermined polarization direction. Attached Figure Description

[0014] [ Figure 1 [Illustrated diagram] is a configuration diagram that schematically shows an example of the overall configuration of an optical system according to a first embodiment of the present disclosure.

[0015] [ Figure 2 [Illustrated diagram] is a schematic diagram showing an example configuration of a phosphor wheel in an optical system according to the first embodiment.

[0016] [ Figure 3 [ ] is an explanatory diagram illustrating an example of the configuration and function of a first region-segmented wavelength-selective waveplate in an optical system according to a first embodiment.

[0017] [ Figure 4 [ ] is an explanatory diagram illustrating an example of the configuration and function of a second region-segmented wavelength-selective waveplate in an optical system according to the first embodiment.

[0018] [ Figure 5 [ ] is a configuration diagram schematically showing an example of the general configuration of an optical system according to the first embodiment.

[0019] [ Figure 6 ] is shown in Figure 5 The diagram illustrates the first example of the optical path of the return light generated in the configuration example shown.

[0020] [ Figure 7 ] is shown in Figure 5 The diagram illustrates a second example of the optical path of the returned light generated in the configuration example shown.

[0021] [ Figure 8 ] is shown in Figure 5 The diagram illustrates a third example of the optical path of the returned light generated in the configuration example shown.

[0022] [ Figure 9 ] is shown in Figure 5 The diagram illustrates the fourth example of the optical path of the returned light generated in the configuration example shown.

[0023] [ Figure 10 [ ] is a configuration diagram schematically showing an example of the configuration of the main parts of an optical system according to a second embodiment.

[0024] [ Figure 11 [ ] is a characteristic diagram illustrating an example of the transmission characteristics of a region-segmented wavelength-selective mirror in an optical system according to the second embodiment.

[0025] [ Figure 12 [ ] is an explanatory diagram showing an example of the optical path of the returned light generated in the optical system according to the second embodiment.

[0026] [ Figure 13 [ ] is a configuration diagram schematically showing an example of the configuration of the main parts of an optical system according to a third embodiment.

[0027] [ Figure 14 [ ] is a characteristic diagram illustrating an example of the reflection characteristics of a region-segmented wavelength-selective mirror in an optical system according to a third embodiment.

[0028] [ Figure 15 [ ] is an explanatory diagram showing an example of the optical path of the returned light generated in the optical system according to the third embodiment.

[0029] [ Figure 16 [ ] is a configuration diagram schematically showing an example of the configuration of the main parts of an optical system according to a fourth embodiment.

[0030] [ Figure 17 [Illustration diagram] is an illustration of a first modified example of the region segmentation pattern of a first region segmentation wavelength selective waveplate.

[0031] [ Figure 18 [This is an illustrative diagram showing a second modified example of the region segmentation pattern of the first region segmentation wavelength selective waveplate.]

[0032] [ Figure 19[Illustration diagram] is an illustration of a third modified example of the region segmentation pattern of a first region segmentation wavelength selective waveplate.

[0033] [ Figure 20 [This is an illustrative diagram schematically showing a fourth modified example of the region segmentation pattern of the first region segmentation wavelength selective waveplate.]

[0034] [ Figure 21 [Illustration diagram] is an illustration of a fifth modified example of the region segmentation pattern of the first region segmentation wavelength selective waveplate.

[0035] [ Figure 22 [This is an explanatory diagram illustrating a sixth modified example of the region segmentation pattern of the first region segmentation wavelength selective waveplate.] Detailed Implementation

[0036] The embodiments of this disclosure will now be described in detail with reference to the accompanying drawings. It should be noted that the description is given in the following order.

[0037] 0. Comparison Examples

[0038] 1. First embodiment (optical system including region-segmented polarization rotation element)

[0039] 1.1 Configuration and function of the optical system according to the first embodiment ( Figures 1 to 4 )

[0040] 1.2 Example of desired configuration of the optical system according to the first embodiment ( Figure 5 )

[0041] 1.3 Effects

[0042] 2. Second embodiment (optical system including wavelength-selective reflection elements to reduce unwanted light) Figures 6 to 12 )

[0043] 3. Third embodiment (optical system including wavelength-selective reflection elements to reduce unwanted light) Figures 13 to 15 )

[0044] 4. Fourth embodiment (including an optical system with an absorptive polarizer to reduce unwanted light) Figure 16 )

[0045] 5. Fifth Embodiment (Changes in the Segmentation Structure of the Polarization Rotation Element) Figures 17 to 22 )

[0046] 6. Other embodiments

[0047] <0. Comparison Example>

[0048] (Based on the overview and issues of the optical system in the comparative example)

[0049] In optical systems used in projectors and the like, configurations comprising multiple light valves are known. In such optical systems, wavelength or polarization is typically used to split the illumination light for the multiple light valves. For example, PTL 1 (Japanese Unexamined Patent Application Publication No. 2018-13655) discloses a configuration example in which a wavelength-selective waveplate is used to split the light in the blue band for two light valves. This reduces the blue band light, which can easily lead to light valve degradation, by half, thereby extending the lifespan of the entire optical system.

[0050] However, in the configuration example disclosed in PTL 1, the light in the blue band can be split for two light valves, but the polarized light emitted from each light valve is orthogonal to each other. This means that contrast cannot be increased by using a post-polarizer in the subsequent projection optics system, which leads to problems in achieving high contrast. A similar configuration can be provided by using a dichroic mirror or dichroic prism instead of a wavelength-selective waveplate. However, wavelength separation (color separation) using a dichroic mirror requires a steep separation characteristic near the separated wavelength region, and is extremely difficult to manufacture.

[0051] Furthermore, as described in PTL 2 (Japanese Unexamined Patent Application Publication No. 2001-324762), a method for achieving high wavelength separation efficiency by utilizing pupil distribution is known. However, in this method, a single plate (single optical valve) is driven in a field sequence by color filters of various colors, which leads to a reduction in overall light utilization efficiency, even if the wavelength separation efficiency is favorable.

[0052] In view of the above, this disclosure proposes a novel light splitting and light synthesis technique using pupil conjugation as a light splitting method. Various methods using this technique have been considered, and this technique has the following advantages.

[0053] 1. It can eliminate the orthogonality of light emitted from each optical valve and align the polarization direction. Therefore, providing a rear polarizer or rear quarter-wave plate can improve contrast.

[0054] 2. It can significantly improve efficiency. In particular, the wavelength separation efficiency remains higher than that of wavelength-selective waveplates, which makes it possible to improve the overall light utilization efficiency. In addition, it can selectively provide a post-polarizer effect for the light emitted from each optical valve in this state, and can increase contrast.

[0055] In the following embodiments, examples of configurations in which an optical system according to the technology of this disclosure is applied to a projector are described. However, the technology of this disclosure is not only applicable to projectors, but also to exposure apparatuses, etc.

[0056] <1. First Embodiment>

[0057] [1.1 Configuration and function of the optical system according to the first embodiment]

[0058] (Optical System Overview)

[0059] Figure 1 An example of the general configuration of an optical system according to a first embodiment of the present disclosure is shown schematically.

[0060] The first embodiment provides a configuration example using two light valves. In this first embodiment, to suppress degradation in the light valves caused by blue light, the blue light is split between the two light valves, reducing the amount of blue light by half, thereby increasing lifespan. Additionally, this also aims to increase contrast.

[0061] Furthermore, in the first embodiment, a case is described where multiple colors of light include first to third colors of light. Each of the first to third colors of light is, for example, any one of R (red), G (green), and B (blue) colors of light. In the first embodiment, for example, blue light corresponds to a specific example of "first color light" in the art of this disclosure; for example, green light corresponds to a specific example of "second color light" in the art of this disclosure; and, for example, red light corresponds to a specific example of "third color light" in the art of this disclosure.

[0062] like Figure 1 As shown, the optical system according to the first embodiment includes an illumination optical system 1 and a projection optical system 2. Furthermore, the optical system according to the first embodiment includes a first optical valve 31 and a second optical valve 32 located in the optical path between the illumination optical system 1 and the projection optical system 2, and a PBS (polarizing beam splitter) 41.

[0063] The illumination optical system 1 includes a blue light source 10, a phosphor wheel 11, a condenser lens 12, a QWP (1 / 4 wave plate) 13, a wavelength selective PBS 14, a notch filter 15, a lens array 16, a PS converter 17, a first region segmented wavelength selective wave plate 51, and a relay lens 18.

[0064] The projection optical system 2 includes multiple lenses 21, a second region-segmented wavelength-selective waveplate 52, and a back polarizer 22.

[0065] It is important to note that, in Figure 1 In this diagram, the direction orthogonal to the plane of the paper is defined as the S-polarized light for PBS 41, while the direction orthogonal to the optical axis and parallel to the plane of the paper is defined as the P-polarized light for PBS 41. Furthermore, depending on the situation, the direction corresponding to the S-polarized light for PBS 41 is referred to as the Z-direction, and the direction corresponding to the P-polarized light for PBS 41 is referred to as the Y-direction. This also applies to the other figures below. Furthermore, this also applies to the other embodiments below.

[0066] The illumination optical system 1 corresponds to a specific example of the "first optical system" in this disclosure. The projection optical system 2 corresponds to a specific example of the "second optical system" in this disclosure. The first region-segmented wavelength-selective waveplate 51 corresponds to a specific example of the "first polarization rotation element" in this disclosure. The second region-segmented wavelength-selective waveplate 52 corresponds to a specific example of the "second polarization rotation element" in this disclosure. The PS converter 17 corresponds to a specific example of the "polarization conversion element" in this disclosure.

[0067] The illumination optical system 1 generates illumination light comprising multiple colors of light in mutually different wavelength bands. The illumination optical system 1 has a wavelength separation function to separate light in at least one wavelength band into multiple colors of light. The illumination optical system 1 generates R, G, and B colored light as said multiple colors of light and emits said colored light toward PBS 41.

[0068] A first region-segmented wavelength-selective waveplate 51 is arranged at the pupil position P1 of the illumination optical system 1. The first region-segmented wavelength-selective waveplate 51 includes multiple segmented regions with mutually different polarization effects. The multiple segmented regions in the first region-segmented wavelength-selective waveplate 51 are, for example, those described later. Figure 3 Regions A and B are shown in the diagram.

[0069] The first light valve 31 and the second light valve 32 are each illuminated, for example, by at least blue light from a plurality of colors of light. The photoluminescence filter (PBS) 41 directs each color of light from the illumination optical system 1 onto at least one of the first light valve 31 or the second light valve 32 according to the polarization direction. The PBS 41 directs blue light onto the first light valve 31 and the second light valve 32 by splitting the blue light according to different polarizations. Furthermore, the PBS 41, for example, directs green light onto one of the first light valve 31 and the second light valve 32 (the first light valve 31). Furthermore, the PBS 41, for example, directs red light onto the other of the first light valve 31 and the second light valve 32 (the second light valve 32). Additionally, the PBS 41, according to the polarization direction, directs each color of light modulated by the first light valve 31 and the second light valve 32 toward the projection optical system 2.

[0070] For example, the first light valve 31 and the second light valve 32 each modulate at least one color of light from a variety of colors according to the image signal.

[0071] Each color of light, modulated by the first light valve 31 and the second light valve 32, is incident on the projection optical system 2 via the PBS 41. The projection optical system 2 projects the image generated by the first light valve 31 and the second light valve 32 onto a projection plane, such as a screen not shown.

[0072] The second region-segmented wavelength-selective waveplate 52 is arranged at the pupil position P2 of the projection optical system 2. The second region-segmented wavelength-selective waveplate 52 includes multiple segmented regions with mutually different polarization effects. The multiple segmented regions in the second region-segmented wavelength-selective waveplate 52 are, for example, those described later. Figure 4 Regions A′ and B′ are shown in the diagram.

[0073] The pupil position P1 of the illumination optical system 1 and the pupil position P2 of the projection optical system 2 are conjugate to each other. Each segmented region in the plurality of segmented regions of the first region segmented wavelength selective waveplate 51 and each segmented region in the plurality of segmented regions of the second region segmented wavelength selective waveplate 52 are conjugate to each other.

[0074] The pupil position P1 of the illumination optical system 1 corresponds to a specific example of the "first pupil position" in the present disclosure. The pupil position P2 of the projection optical system 2 corresponds to a specific example of the "second pupil position" in the present disclosure.

[0075] It should be noted that the "first pupil position" in this disclosure can be a position near the first pupil position. Therefore, the "first polarization rotation element" (first region-segmented wavelength-selective waveplate 51) in this disclosure can be arranged near the first pupil position (pupil position P1). However, in this disclosure, the first polarization rotation element is preferably arranged in the "first optical system" (illumination optical system 1) on the optical path between the "polarization conversion element" (PS converter 17) and the relay lens 18.

[0076] It should be noted that the "second pupil position" in this disclosure can be a position near the second pupil position. Therefore, the "second polarization rotation element" (second region-segmented wavelength-selective waveplate 52) in this disclosure can be arranged near the second pupil position (pupil position P2). However, in this disclosure, the second polarization rotation element is preferably arranged in the "second optical system" (projection optical system 2) in the optical path between the two lenses before and after the aperture position.

[0077] The post-polarizer 22 is arranged in the output optical path of the second region segmented wavelength selective waveplate 52.

[0078] (Detailed configuration and function of each component)

[0079] Figure 2 An example configuration of the phosphor wheel 11 is shown schematically. Figure 3 An example of the configuration and function of the first region segmentation wavelength selective waveplate 51 is shown. Figure 4 An example of the configuration and function of the second region segmentation wavelength selective waveplate 52 is shown.

[0080] For example, the blue light source 10 is a blue laser. The phosphor wheel 11 has a phosphor region 111 and a polarization-maintaining diffuser region 112, such as... Figure 2 As shown, yellow (Ye) light is obtained by irradiating phosphor region 111 with blue light as excitation light. Polarization-maintaining diffuser region 112 does not have a polarization effect, but rather reflects blue light. Therefore, a time-averaged white beam obtained by repeating yellow, blue, yellow, blue... over time is emitted from phosphor wheel 11.

[0081] Blue light emitted from blue light source 10 is reflected by wavelength-selective PBS 14, then passes through quarter-wave plate 13 to be converted into circularly polarized light, which is then incident on phosphor wheel 11 via condenser lens 12. Light emitted from phosphor wheel 11 passes again through quarter-wave plate 13 to be converted into p-polarized light for wavelength-selective PBS 14. The p-polarized light is then emitted by wavelength-selective PBS 14 to the transmission side. Similarly, yellow light extracted from phosphor wheel 11 is reflected and then emitted by wavelength-selective PBS 14 to the transmission side. The yellow light generated by phosphor wheel 11 is in an unpolarized state, and wavelength-selective PBS 14 transmits all of the yellow light.

[0082] Blue and yellow light emitted from the wavelength-selective PBS 14 pass through the notch filter 15 and lens array 16, and then through the PS converter 17, thereby aligning their polarization state with a predetermined direction (here, for example, polarized light in the Y direction (P-polarized light)). Figure 3 The first region segmentation wavelength selective waveplate 51, which exhibits the characteristics shown, is arranged in the portion of the illumination optical system 1 that immediately follows the pupil (first pupil).

[0083] Figure 3 An example of the configuration and function of a first-region segmented wavelength-selective waveplate 51 is shown. The first-region segmented wavelength-selective waveplate 51 includes a first segmented region and a second segmented region, and the first and second segmented regions have mutually different polarization characteristics, for example, relative to blue light. For example, Figure 3 Region A in the present disclosure corresponds to a specific example of the "first segmentation region" in the present disclosure, and Region B corresponds to a specific example of the "second segmentation region" in the present disclosure.

[0084] For example, in the first region-divided wavelength-selective waveplate 51, the upper half (region A) is a 45-degree tilted half-waveplate that acts only on green, and the lower half (region B) is a 45-degree tilted half-waveplate that acts on both green and blue. It should be noted that in Figure 3In the diagram, the small white circles represent the illumination distribution within this pupil. This also applies to illustrations related to other pupil portions. In the first region-segmented wavelength-selective waveplate 51, when the waveplate is applied to the illumination light, the polarized light of red light does not rotate in any region to become Y-polarized light (P-polarized light). Furthermore, the polarized light of green light rotates 90 degrees in any region to become Z-polarized light (S-polarized light). Additionally, the polarized light of blue light is in a mixed state of non-rotated polarized light (Y-polarized light (P-polarized light)) and 90-degree rotated polarized light (Z-polarized light (S-polarized light)).

[0085] It should be noted that the polarization characteristics of the first region-segmented wavelength-selective waveplate 51 are not limited to those described above, and other configurations are also possible. For example, in the first region-segmented wavelength-selective waveplate 51, the upper half (region A) can be a half-waveplate tilted at 45 degrees and acting on both red and blue light, while the lower half (region B) can be a half-waveplate tilted at 45 degrees and acting only on red light. In this case, the polarized light of green light in the first region-segmented wavelength-selective waveplate 51 does not rotate in any region. Furthermore, the polarized light of red light rotates 90 degrees in any region. Additionally, the polarized light of blue light is in a mixed state of non-rotated polarized light and 90-degree rotated polarized light.

[0086] When the luminous flux of each color reaches the PBS 41 via the relay lens 18 after passing through the first region-segmented wavelength-selective waveplate 51, each color of light is selectively guided to the first light valve 31 and the second light valve 32 according to its respective polarization state. Red light is P-polarized and reaches the second light valve 32. Green light is S-polarized and reaches the first light valve 31. Blue light is in a mixed state of P-polarized and S-polarized light, and half of the blue light reaches each of the first light valve 31 and the second light valve 32. In the case where reflective liquid crystal is used for the first light valve 31 and the second light valve 32, performing a white display on each light valve causes a rotation of each polarized light, which changes each incident polarized light into an orthogonal emitted polarized light. Therefore, in the first light valve 31, red and blue light are emitted as S-polarized light, and in the second light valve 32, blue and red light are emitted as P-polarized light. Therefore, performing a white display causes all light passing through the PBS 41 to be emitted to the projection optics system 2.

[0087] Typically, due to the characteristics of the polarizing film, the PBS 41 tends to have a slightly larger Rp (reflected P-polarized component) than Ts (transmitted S-polarized component). Therefore, the possibility of contrast formation on the second light valve 32 side is smaller compared to the first light valve 31 side. One reason is that during black display, more P-polarized light generated by the second light valve 32 leaks to the projection optics system 2 side than S-polarized light generated by the first light valve 31. In the case of a single-plate configuration using only one light valve, the configuration is performed by using the first light valve 31 side, which only improves contrast; however, the case of a two-plate configuration using two light valves is a factor that significantly weakens contrast. Therefore, in order to achieve a contrast ratio of approximately 1000:1 in the case where the F-number of the illumination optics system 1 is approximately F / 2.5 to 3 (and in the case including the notch filter 15), it is necessary to align the polarization direction and improve the contrast by means of the post-polarizer 22 (the analyzer after the PBS 41).

[0088] In the optical system according to the first embodiment, when the back polarizer 22 is arranged immediately after the PBS 41, the amount of light is reduced by half because the polarization state of the blue light is orthogonal. This is improved by using the conjugation effect of the pupil, which is the most significant feature of the optical system according to the first embodiment.

[0089] That is, in the optical system according to the first embodiment, the second region-segmented wavelength-selective waveplate 52 is arranged at the position P2 of the pupil (second pupil) of the projection optical system 2 after exiting the PBS 41.

[0090] Figure 4 An example of the configuration and function of the second region-segmented wavelength-selective waveplate 52 is shown. The second region-segmented wavelength-selective waveplate 52 includes a third segmented region and a fourth segmented region, and the third and fourth segmented regions have, for example, different polarization characteristics relative to blue light. Figure 4 Region A' in the present disclosure corresponds to a specific example of the "third segmentation region" in the present disclosure, and region B' corresponds to a specific example of the "fourth segmentation region" in the present disclosure.

[0091] The pupil of the projection optics system 2 is conjugate to the pupil of the illumination optics system 1, and because it has already undergone light valve reflection, it provides regional vertical inversion for each conjugate portion. Therefore, as... Figure 4As shown, the region conjugate to region A of the first region-segmented wavelength-selective waveplate 51 is the lower region A' of the second region-segmented wavelength-selective waveplate 52, and the region conjugate to region B of the first region-segmented wavelength-selective waveplate 51 is the upper region B' of the second region-segmented wavelength-selective waveplate 52. Conjugation means that light that has passed through region A of the first region-segmented wavelength-selective waveplate 51 will necessarily pass through region A' of the second region-segmented wavelength-selective waveplate 52, and light that has passed through region B of the first region-segmented wavelength-selective waveplate 51 will necessarily pass through region B' of the second region-segmented wavelength-selective waveplate 52. Therefore, the P-polarized and S-polarized blue light in the mixed state are selectively incident on regions B' and A', respectively. Subsequently, the polarization of the blue light does not change in region A', and the polarization of the blue light rotates 90 degrees in region B'. Furthermore, in any region, the polarization of the red light does not rotate, and the polarization of the green light rotates 90 degrees, thereby aligning the polarization of various colors of light after passing through the second region-segmented wavelength-selective waveplate 52 with the S-polarized light.

[0092] It should be noted that the polarization characteristics of the second region-segmented wavelength-selective waveplate 52 are not limited to those described above, and other configurations are also possible. For example, in the second region-segmented wavelength-selective waveplate 52, region A' can be a half-waveplate tilted at 45 degrees that acts on both red and blue light, and region B' can be a half-waveplate tilted at 45 degrees that acts only on red light. In this case, the polarized light of green light does not rotate in any region of the second region-segmented wavelength-selective waveplate 52. Furthermore, the polarized light of red light rotates 90 degrees in any region. Additionally, the polarized light of blue light rotates 90 degrees in region A', but does not rotate in region B'.

[0093] The post-polarizer 22 is arranged to cut off the P-polarized light that has passed through the second region-splitting wavelength-selective waveplate 52, which improves contrast. In an experimental system simulating the optical system according to the first embodiment, as an experimental result, a white contrast ratio of approximately 1000:1 was obtained at F / 2.5, and the amount of blue light could be split into approximately half for the first optical valve 31 and the second optical valve 32, respectively. Therefore, the hypothesized effect has been demonstrated.

[0094] In the optical system according to the first embodiment, when yellow light is emitted from the phosphor wheel 11, green light is selectively guided to the first light valve 31 side, and red light is selectively guided to the second light valve 32 side. Furthermore, when blue light is emitted from the phosphor wheel 11, half of the blue light is guided to each of the first light valve 31 and the second light valve 32. In each light valve, a harmonic output of each color light is performed during the time period corresponding to each color light. That is, pupil conjugation is used to enhance contrast while splitting the blue light into two. As described above, the main objective is to significantly extend the lifetime of the entire optical system by splitting the blue light, which causes a shortened light valve lifetime, into two to reduce the incident light amount by half. In this sense, the ideal wavelength for splitting the light into two is 500 nm or less.

[0095] It should be noted that a comparative example of the configuration of the optical system according to the first embodiment is the projector described in PTL 3 (Japanese Unexamined Patent Application Publication No. 2008-165058). In the projector described in PTL 3, a region-segmented delay plate is arranged near the pupil within the projection optical system, and the light is split into two by polarization within the projection optical system. However, there is a qualitative difference between simply splitting the light by polarization within the projection optical system and applying region-segmented polarization on a portion conjugate to the region segmented in the pupil of the illumination optical system 1, as in the optical system according to the first embodiment. That is, in the former, an equal polarization effect is applied to the light generated by any light valve. In contrast, the latter is characterized by using a conjugate relationship so that a specific polarization effect can be applied only to the light reaching a specific light valve.

[0096] [1.2 Example of desired configuration of the optical system according to the first embodiment]

[0097] Figure 5 The overall configuration of an example of a desired configuration of an optical system according to the first embodiment is schematically shown.

[0098] Figure 5 The optical system shown includes an illumination optical system 1A, which replaces... Figure 1 The illumination optical system 1 is shown in the optical system. In addition to the configuration of the illumination optical system 1, the illumination optical system 1A further includes a pre-polarizer 50.

[0099] In the illumination optical system 1A, a pre-polarizer 50 is arranged between the PS converter 17 and the first region-segmented wavelength-selective waveplate 51. The pre-polarizer 50 reduces the amount of light emitted from the PS converter 17 that is not polarized in a predetermined direction. Figure 5The example is a polarizer for light in polarization directions other than P-polarized light. For example, to provide favorable rectification and increase the extinction ratio, a wire grid with a reflective metallic structure is preferably used as the pre-polarizer 50. Arranging the pre-polarizer 50 between the PS converter 17 and the first region-segmented wavelength-selective waveplate 51 makes it possible to reduce light in polarization directions other than the predetermined polarization direction that is not aligned with the PS converter 17. This makes further improvement in contrast possible.

[0100] [1.3 Effect]

[0101] As described above, in the optical system according to the first embodiment, a first region-segmented wavelength-selective waveplate 51, comprising multiple segmented regions having mutually different polarization effects, is arranged at the pupil position P1 of the illumination optical system 1, and a second region-segmented wavelength-selective waveplate 52, comprising multiple segmented regions having mutually different polarization effects, is arranged at the pupil position P2 of the projection optical system 2, which is conjugate to the first pupil position, thereby enabling the improvement of contrast.

[0102] According to the optical system of the first embodiment, in addition to the anticipated improvement in contrast, color uniformity on the projection plane can be prevented by aligning the polarized light of the final emitted light in the projection optical system 2 in one direction. Furthermore, with the use of two light valves relative to one PBS 41, the contrast is enhanced, which makes it possible to reduce the size of the entire optical system.

[0103] Furthermore, according to the optical system of the first embodiment, in the illumination optical system 1A ( Figure 5 In the process of arranging a pre-polarizer 50 to reduce light in the polarization direction other than the predetermined polarization direction in the light emitted from the PS converter 17, it is possible to further improve the contrast.

[0104] It should be noted that the effects described herein are merely exemplary and not limiting, and other effects may also exist. The same applies to the effects of the other embodiments described below.

[0105] <2. Second Embodiment>

[0106] Next, an optical system according to a second embodiment of this disclosure will be described. It should be noted that in the following description, components substantially the same as those in the optical system according to the first embodiment described above are indicated by the same reference numerals, and their descriptions are appropriately omitted.

[0107] As described above, in the optical system according to the first embodiment, such as Figure 5In the configuration example shown, arranging a pre-polarizer 50 between the PS converter 17 and the first region-segmented wavelength-selective waveplate 51 enables improved contrast. However, in the case where the pre-polarizer 50 is arranged, the returned light from the first optical valve 31 or the second optical valve 32 may become unwanted light reflected by the pre-polarizer 50 and return to the first optical valve 31 or the second optical valve 32 as illumination light. In the optical system according to the second embodiment, a configuration for reducing the generation of unwanted light is described. Before describing the configuration of the optical system according to the second embodiment, the principle of generating unwanted light is first described.

[0108] (The principle behind generating unnecessary light)

[0109] Figures 6 to 8 Shown in Figure 5 The first to third examples of the optical paths of the returned light generated in the configuration examples shown.

[0110] It is important to note that Figures 6 to 8 Only the configurations needed to illustrate the main parts are shown. Furthermore, Figures 6 to 8 Examples are given relative to Figure 5 The illustrated configuration example shows the case where the PS converter 17 aligns the incident light with the S-polarized light as a predetermined polarization direction. Various colors of light, including red, green, and blue, are incident as S-polarized light onto the first region-segmented wavelength-selective waveplate 51. Figures 6 to 8 In this configuration, the pre-polarizer 50 is configured to transmit only S-polarized light and reflect light in polarization directions other than S-polarized light. Figures 6 to 8 In this configuration, the first region-segmented wavelength-selective waveplate 51 is configured to rotate the polarized light of red light by 90 degrees in all regions, and not rotate the polarized light of green light in any region. Furthermore, in... Figures 6 to 8 In the middle, the first region segmentation wavelength selective waveplate 51 is configured to be in the upper region ( Figure 3 In region A), the polarized blue light is rotated 90 degrees, and in the lower region ( Figure 3 No rotation is performed in region B).

[0111] First, refer to Figure 6The return light for each of the red and green light is described. A first region-segmented wavelength-selective waveplate 51 rotates the polarization of red light in all regions, thus emitting P-polarized red light across all regions from the first region-segmented wavelength-selective waveplate 51. The P-polarized red light passes through the relay lens 18 while remaining P-polarized, reaching the second light valve 32 via the PBS 41. The second light valve 32 does not rotate the polarization during blackout; therefore, the red light is reflected by the second light valve 32 while remaining P-polarized, becoming P-polarized return light that returns to the first region-segmented wavelength-selective waveplate 51 again. The first region-segmented wavelength-selective waveplate 51 rotates the polarization of red light in all regions, and thus the P-polarized return light becomes S-polarized return light to reach the pre-polarizer 50. The pre-polarizer 50 is configured to transmit S-polarized light, and thus the S-polarized return light passes through the pre-polarizer 50 as is. Therefore, for red light, no unwanted light is generated.

[0112] For green light, the first region-segmented wavelength-selective waveplate 51 does not rotate the polarized light in all regions, and thus emits S-polarized green light across all regions from the first region-segmented wavelength-selective waveplate 51. The S-polarized green beam propagates through the relay lens 18 while remaining S-polarized to reach the first light valve 31. The first light valve 31 does not rotate the polarized light during black display; therefore, the green light is reflected by the first light valve 31 while remaining S-polarized and becomes S-polarized return light, returning again to the first region-segmented wavelength-selective waveplate 51. The first region-segmented wavelength-selective waveplate 51 does not rotate the polarized light in all regions, and thus the S-polarized return light reaches the pre-polarizer 50 as is. The pre-polarizer 50 is configured to transmit S-polarized light, and thus the S-polarized return light passes through the pre-polarizer 50 as is. Therefore, for green light, no unwanted light is generated. That is, in Figure 6 In this configuration, no unnecessary light is generated for the return light of red and green light.

[0113] Next, refer to Figure 7 and 8 Provide a description of the return light of blue light.

[0114] First, refer to Figure 7This describes the return light of blue light that returns to the lower region after passing through the upper region of the first region-segmented wavelength-selective waveplate 51. The first region-segmented wavelength-selective waveplate 51 rotates the polarization of the blue light in the upper region, and thus emits P-polarized blue light from the upper region of the first region-segmented wavelength-selective waveplate 51. The P-polarized blue light passes through the relay lens 18 while remaining P-polarized, and reaches the second light valve 32 via the PBS 41. The second light valve 32 does not rotate the polarization of the light during blackout; therefore, the blue light is reflected by the second light valve 32 while remaining P-polarized, and becomes the P-polarized return light returning to the lower region of the first region-segmented wavelength-selective waveplate 51. The first region-segmented wavelength-selective waveplate 51 does not rotate the polarization of the blue light in the lower region, and thus the P-polarized return light reaches the pre-polarizer 50 while remaining P-polarized. The pre-polarizer 50 is configured to transmit S-polarized light and reflect P-polarized light, and thus the P-polarized return light becomes unnecessary light with sufficient light reflected by the pre-polarizer 50 and returns to the second light valve 32 again.

[0115] Next, refer to Figure 8 This describes the return light of blue light that returns to the upper region after passing through the lower region of the first region-segmented wavelength-selective waveplate 51. The first region-segmented wavelength-selective waveplate 51 does not rotate the polarization of the blue light in the lower region, and therefore emits S-polarized blue light from the lower region of the first region-segmented wavelength-selective waveplate 51. The S-polarized blue light propagates through the relay lens 18 while remaining S-polarized to reach the first light valve 31. The first light valve 31 does not rotate the polarization of the light during blackout; therefore, the blue light is reflected by the first light valve 31 while remaining S-polarized, and becomes S-polarized return light returning to the upper region of the first region-segmented wavelength-selective waveplate 51. The first region-segmented wavelength-selective waveplate 51 rotates the polarization of the blue light in the upper region, and therefore makes it P-polarized return light and reaches the pre-polarizer 50. The pre-polarizer 50 is configured to transmit S-polarized light and reflect P-polarized light, and thus the P-polarized return light becomes unnecessary light with sufficient light reflected by the pre-polarizer 50 and returns to the first optical valve 31 again.

[0116] Figure 9 Shown in Figure 5 The fourth example of the optical path of the returning light generated in the configuration example shown.

[0117] It is important to note that Figure 9 Only the configuration of the main parts required for explanation is shown. Furthermore, Figure 9 This illustrates the case where the PS converter 17 aligns the incident light with the P-polarized light as a predetermined polarization direction, similar to... Figure 5The configuration example shown. Various colors of light, including red, green, and blue, are incident as P-polarized light onto the first region-segmented wavelength-selective waveplate 51. Figure 9 In this configuration, the pre-polarizer 50 is configured to transmit only P-polarized light and reflect light in polarization directions other than P-polarized light. Figure 9 In the middle, the first region segmentation wavelength selective waveplate 51 is configured to be in the upper region ( Figure 3 In region A), the polarized blue light is rotated 90 degrees, and in the lower region ( Figure 3 No rotation is performed in region B).

[0118] Figure 9 The optical path of the blue light returning to the lower region after passing through the upper region of the first region-segmented wavelength-selective waveplate 51 is shown. The first region-segmented wavelength-selective waveplate 51 rotates the polarization of the blue light in the upper region, and thus emits S-polarized blue light from the upper region of the first region-segmented wavelength-selective waveplate 51. The S-polarized blue light passes through the relay lens 18 while remaining S-polarized, and reaches the first light valve 31 via the SBS 41. The first light valve 31 does not rotate the polarization of the light during blackout; therefore, the blue light is reflected by the first light valve 31 while remaining S-polarized, and becomes S-polarized return light returning to the lower region of the first region-segmented wavelength-selective waveplate 51 again. The first region-segmented wavelength-selective waveplate 51 does not rotate the polarization of the blue light in the lower region, and thus the S-polarized return light reaches the pre-polarizer 50 while remaining S-polarized. The pre-polarizer 50 is configured to transmit P-polarized light and reflect S-polarized light, and thus the S-polarized return light becomes unnecessary light with sufficient light reflected by the pre-polarizer 50 and returns to the first optical valve 31 again.

[0119] As described above, in the optical system according to the first embodiment, when the pre-polarizer 50 is configured between the PS converter 17 and the first region-segmented wavelength-selective waveplate 51, unwanted blue light is generated regardless of whether the polarized light emitted from the PS converter 17 is S-polarized or P-polarized. This particularly leads to a deterioration of the black level of the contrast, thereby affecting the projected image.

[0120] (Configuration and function of the optical system according to the second embodiment)

[0121] Figure 10 An example configuration of the main parts of the optical system according to the second embodiment is shown schematically.

[0122] It is important to note that Figure 10 Only the configuration of the main parts required for explanation is shown. Furthermore, Figure 10 Examples are given relative to Figure 5The illustrated configuration example shows the PS converter 17 aligning the incident light with the S-polarized light, for example, as a predetermined polarization direction. Various colors of light, such as red, green, and blue, are incident as S-polarized light onto the first region-segmented wavelength-selective waveplate 51. Figure 10 In this configuration, the pre-polarizer 50 is configured, for example, to transmit only S-polarized light and, for example, to reflect light in polarization directions other than S-polarized light. Figure 10 In, for example, the first region-segmented wavelength-selective waveplate 51 is configured to rotate the polarized light of red light by 90 degrees in all regions, and not rotate the polarized light of green light in any region. Furthermore, in Figure 10 In, for example, the first region segmentation wavelength selective waveplate 51 is configured to be in the upper region ( Figure 3 In region A), the polarized blue light is rotated 90 degrees, and in the lower region ( Figure 3 No rotation is performed in region B).

[0123] The optical system according to the second embodiment includes an illumination optical system 1B, which replaces... Figure 5 The illumination optical system 1A is shown. In addition to the configuration of the illumination optical system 1A, the illumination optical system 1B further includes a region-segmented wavelength-selective mirror 180. The region-segmented wavelength-selective mirror 180 corresponds to a specific example of a "wavelength-selective reflective element" in the art of this disclosure.

[0124] A region-segmented wavelength-selective mirror 180 is arranged in the optical path between the first region-segmented wavelength-selective waveplate 51 and each of the first and second optical valves 31 and 32. Figure 11 In the configuration example, the relay lens 18 includes a first lens 181 and a second lens 182. A region-segmented wavelength-selective mirror 180 is arranged in the optical path between the first lens 181 and the second lens 182 in the relay lens 18.

[0125] The region-segmented wavelength-selective mirror 180 is a wavelength-selective reflective element that reduces the return light of blue light from at least one of the first optical valve 31 or the second optical valve 32 back to the pre-polarizer 50. The region-segmented wavelength-selective mirror 180 is arranged to be tilted relative to the optical axis of the optical path between the first region-segmented wavelength-selective waveplate 51 and each of the first optical valve 31 and the second optical valve 32.

[0126] Figure 11 An example of the transmission characteristics of a region-segmented wavelength-selective mirror in an optical system according to a second embodiment is shown. The region-segmented wavelength-selective mirror 180 is located in the upper region of the first region-segmented wavelength-selective waveplate 51. Figure 3 Region A in the middle or the lower region ( Figure 3A wavelength-dependent polarizing dichroic plate is present in a region corresponding to at least one segmented region in region B). Therefore, the region-segmented wavelength-selective mirror 180 can be arranged in a region corresponding to at least one segmented region in the upper or lower region of the first region-segmented wavelength-selective waveplate 51.

[0127] exist Figure 10 In the configuration example, the region-segmented wavelength-selective mirror 180 has a configuration that exists only for the region corresponding to the upper region in the first region-segmented wavelength-selective waveplate 51. Figure 11 The wavelength-dependent characteristics are shown. That is, in the region corresponding to the upper region of the first region-segmented wavelength-selective waveplate 51, for example, the region-segmented wavelength-selective mirror 180 has the characteristic of transmitting red and green light and reflecting blue light for S-polarized light. Furthermore, in the region corresponding to the upper region of the first region-segmented wavelength-selective waveplate 51, for example, the region-segmented wavelength-selective mirror 180 has the characteristic of transmitting red, green, and blue light for P-polarized light. Furthermore, in the region corresponding to the lower region of the first region-segmented wavelength-selective waveplate 51, for example, the region-segmented wavelength-selective mirror 180 has the characteristic of transmitting red, green, and blue light regardless of the polarization direction. In this way, in the region corresponding to the lower region of the first region-segmented wavelength-selective waveplate 51, it is sufficient to transmit each color of light regardless of the polarization direction, and therefore, the region-segmented wavelength-selective mirror 180, which has wavelength dependence across all regions, can be configured to be arranged only in the region corresponding to the upper region of the first region-segmented wavelength-selective waveplate 51.

[0128] Figure 12 An example of the optical path of the returning light generated in the optical system according to the second embodiment is shown.

[0129] In a region corresponding to one of the upper and lower regions of the first region-segmented wavelength-selective waveplate 51, the region-segmented wavelength-selective mirror 180 transmits all the multi-colored light from that segmented region. Furthermore, in a region corresponding to one of the upper and lower regions of the first region-segmented wavelength-selective waveplate 51, the region-segmented wavelength-selective mirror 180 reflects the blue light returning to the first region-segmented wavelength-selective waveplate 51 from at least one of the first optical valve 31 or the second optical valve 32. Furthermore, in a region corresponding to the other segmented region of the first region-segmented wavelength-selective waveplate 51, the region-segmented wavelength-selective mirror 180 transmits all the multi-colored light from said other segmented region.

[0130] Figure 12 Showing the removal of the reference above Figure 8 The aforementioned state of unwanted light caused by the return light of blue light that passes through the lower region of the first region segmented wavelength-selective waveplate 51 and returns to the upper region. In the optical system according to the second embodiment, for example, as... Figure 12 As shown, S-polarized blue light is emitted from the lower region of the first region-division wavelength-selective waveplate 51. In the region corresponding to the lower region of the first region-division wavelength-selective waveplate 51, the region-division wavelength-selective mirror 180 transmits the S-polarized blue light as is, and thus the S-polarized blue light propagates through the relay lens 18 while remaining S-polarized to reach the first light valve 31. The first light valve 31 does not rotate the polarized light during black display; therefore, the blue light is reflected by the first light valve 31 while remaining S-polarized, and becomes S-polarized return light returning to the upper region of the first region-division wavelength-selective waveplate 51. Here, the region-division wavelength-selective mirror 180, which has the characteristic of reflecting S-polarized blue light, is arranged in the region corresponding to the upper region of the first region-division wavelength-selective waveplate 51, and thus the return light of blue light does not reach the upper region of the first region-division wavelength-selective waveplate 51, but is reflected to the outside of the optical path. This eliminates unnecessary light caused by the return light of S-polarized blue light returning to the upper region. It should be noted that in the region of the region-segmented wavelength-selective mirror 180 corresponding to the upper region of the first region-segmented wavelength-selective waveplate 51, blue light is transmitted for P-polarized light to reach the second optical valve 32. Furthermore, the region-segmented wavelength-selective mirror 180 has the characteristic of transmitting red and green light regardless of polarization, and therefore red and green light reach the first optical valve 31 or the second optical valve 32 without any problems. This makes it possible to selectively remove only S-polarized blue light, which is unwanted light.

[0131] Other configurations, functions, and effects may be substantially similar to those in the optical system according to the first embodiment described above.

[0132] <3. Third Embodiment>

[0133] Next, an optical system according to a third embodiment of this disclosure will be described. It should be noted that, hereinafter, components substantially the same as those in the optical system according to the first or second embodiment described above are indicated by the same reference numerals, and their descriptions are appropriately omitted.

[0134] In the optical system according to the third embodiment, a configuration is described that reduces the generation of unnecessary light due to the arrangement of the pre-polarizer 50, similar to the optical system according to the second embodiment.

[0135] Figure 13 An example configuration of the main parts of an optical system according to a third embodiment is shown schematically.

[0136] It is important to note that Figure 13 Only the configuration of the main parts required for explanation is shown. Furthermore, Figure 13 Examples are given relative to Figure 5 The illustrated configuration example shows the case where the PS converter 17 aligns the incident light with the S-polarized light, for example, as a predetermined polarization direction. Various colors of light, such as red, green, and blue, are incident as S-polarized light onto the first region-segmented wavelength-selective waveplate 51. Figure 13 In this configuration, the pre-polarizer 50 is configured, for example, to transmit only S-polarized light and, for example, to reflect light in polarization directions other than S-polarized light. Figure 13 In this configuration, for example, the first region-segmented wavelength-selective waveplate 51 is configured to rotate the polarized light of red light by 90 degrees in all regions, and not rotate the polarized light of green light in any region. Furthermore, in... Figure 13 In, for example, the first region segmentation wavelength selective waveplate 51 is configured to be in the upper region ( Figure 3 In region A), the polarized blue light is rotated 90 degrees, and in the lower region ( Figure 3 No rotation is performed in region B).

[0137] The optical system according to the second embodiment includes an illumination optical system 1C, which replaces... Figure 5 The illumination optical system 1A is shown. In addition to the configuration of the illumination optical system 1A, the illumination optical system 1C further includes a region-segmented wavelength-selective mirror 190. The region-segmented wavelength-selective mirror 190 corresponds to a specific example of a "wavelength-selective reflective element" in the art of this disclosure.

[0138] A region-segmented wavelength-selective mirror 190 is arranged in the optical path between the first region-segmented wavelength-selective waveplate 51 and each of the first and second optical valves 31 and 32. Figure 13 In the configuration example, the relay lens 18 includes a first lens 181 and a second lens 182. A region-segmented wavelength-selective mirror 190 is arranged in the optical path between the first lens 181 and the second lens 182 in the relay lens 18, and is configured to bend the optical path by 90 degrees between the first lens 181 and the second lens 182.

[0139] The region-segmented wavelength-selective mirror 190 is a wavelength-selective reflective element that reduces the return light of blue light from at least one of the first optical valve 31 or the second optical valve 32 back to the pre-polarizer 50. The region-segmented wavelength-selective mirror 190 is arranged to be tilted relative to the optical axis of the optical path between the first region-segmented wavelength-selective waveplate 51 and each of the first optical valve 31 and the second optical valve 32.

[0140] Figure 14An example of the reflection characteristics of a region-segmented wavelength-selective mirror in an optical system according to a third embodiment is shown. The region-segmented wavelength-selective mirror 190 is located in the upper region of the first region-segmented wavelength-selective waveplate 51. Figure 3 Region A in the middle or the lower region ( Figure 3 A wavelength-dependent polarizing dichroic plate is present in a region corresponding to at least one segmented region in region B) of the first region-segmented wavelength-selective waveplate 51. Therefore, the region-segmented wavelength-selective mirror 190 can be arranged in a region corresponding to at least one segmented region in the upper or lower region of the first region-segmented wavelength-selective waveplate 51. It should be noted that in the case where the region-segmented wavelength-selective mirror 190 is arranged only in a region corresponding to one of the upper and lower regions, a total reflection mirror is arranged in the other region.

[0141] exist Figure 13 In the configuration example, the region-segmented wavelength-selective mirror 190 has a configuration that exists only for the region corresponding to the lower region in the first region-segmented wavelength-selective waveplate 51. Figure 14 The wavelength-dependent characteristics are shown. That is, in the region corresponding to the lower region of the first region-segmented wavelength-selective waveplate 51, for example, the region-segmented wavelength-selective mirror 190 has the characteristic of reflecting red and green light and transmitting blue light for P-polarized light. Furthermore, in the region corresponding to the lower region of the first region-segmented wavelength-selective waveplate 51, for example, the region-segmented wavelength-selective mirror 190 has the characteristic of reflecting all red, green, and blue light for S-polarized light. Furthermore, in the region corresponding to the upper region of the first region-segmented wavelength-selective waveplate 51, for example, the region-segmented wavelength-selective mirror 190 has the characteristic of reflecting all red, green, and blue light regardless of the polarization direction. In this way, in the region corresponding to the upper region of the first region-segmented wavelength-selective waveplate 51, it is sufficient to reflect each color of light regardless of the polarization direction, and therefore, the region-segmented wavelength-selective mirror 180, which has wavelength dependence across all regions, can be configured to be arranged only in the region corresponding to the lower region of the first region-segmented wavelength-selective waveplate 51.

[0142] Figure 15 An example of the optical path of the returning light generated in the optical system according to the third embodiment is shown.

[0143] In a region corresponding to one of the upper and lower regions of the first region-segmented wavelength-selective waveplate 51, the region-segmented wavelength-selective mirror 190 reflects all the multi-colored light from that segmented region. Furthermore, in a region corresponding to one of the upper and lower regions of the first region-segmented wavelength-selective waveplate 51, the region-segmented wavelength-selective mirror 190 transmits the return light of blue light returning to the first region-segmented wavelength-selective waveplate 51 from at least one of the first optical valve 31 or the second optical valve 32. Additionally, in a region corresponding to the other segmented region of the first region-segmented wavelength-selective waveplate 51, the region-segmented wavelength-selective mirror 190 reflects all the multi-colored light from the other segmented region.

[0144] Figure 15 Showing the removal of the reference above Figure 7 The described state is caused by the return light of blue light that passes through the upper region of the first region-divided wavelength-selective waveplate 51 and returns to the lower region, resulting in unwanted light. In the optical system according to the third embodiment, for example, as... Figure 15 As shown, P-polarized blue light is emitted from the upper region of the first region-division wavelength-selective waveplate 51. In the region corresponding to the upper region of the first region-division wavelength-selective waveplate 51, the region-division wavelength-selective mirror 190 reflects the P-polarized blue light as is, and thus the P-polarized blue light propagates through the relay lens 18 while remaining P-polarized to reach the second light valve 32. The second light valve 32 does not rotate the polarized light during blackout; therefore, the blue light is reflected by the second light valve 32 while remaining P-polarized, and becomes P-polarized return light returning to the lower region of the first region-division wavelength-selective waveplate 51. Here, the region-division wavelength-selective mirror 190, which has the characteristic of reflecting P-polarized light, is arranged in the region corresponding to the lower region of the first region-division wavelength-selective waveplate 51, and thus the return light of the blue light does not reach the lower region of the first region-division wavelength-selective waveplate 51, but is transmitted to the outside of the optical path. This eliminates unnecessary light caused by the return light of P-polarized blue light returning to the lower region. It should be noted that in the region corresponding to the lower region of the first region-segmented wavelength-selective waveplate 51 in the region-segmented wavelength-selective mirror 190, blue light is reflected for S-polarized light to reach the first optical valve 31. Furthermore, the region-segmented wavelength-selective mirror 190 functions as a total internal reflection mirror for both red and green light, regardless of polarization, and thus both red and green light reach the first optical valve 31 or the second optical valve 32 without any problems. This makes it possible to selectively remove only P-polarized blue light that is unwanted.

[0145] Other configurations, functions, and effects may be substantially similar to those in the optical system according to the first embodiment described above.

[0146] <4. Fourth Embodiment>

[0147] Next, an optical system according to a fourth embodiment of this disclosure will be described. It should be noted that, hereinafter, components substantially the same as those in the optical systems according to any of the first to third embodiments described above are indicated by the same reference numerals, and their descriptions are appropriately omitted.

[0148] In the optical system according to the fourth embodiment, a configuration for reducing the generation of unnecessary light caused by the arrangement of the pre-polarizer 50 is described, similar to the optical system according to the second embodiment.

[0149] Figure 16 An example configuration of the main parts of an optical system according to the fourth embodiment is shown schematically.

[0150] The optical system according to the fourth embodiment includes an illumination optical system 1D, in place of... Figure 5 The illumination optical system 1A is shown. In contrast to the configuration of the illumination optical system 1A, the illumination optical system 1D includes a pre-polarizer 50A instead of the pre-polarizer 50. The pre-polarizer 50A corresponds to a specific example of an "absorption-type polarizer" in the art of this disclosure.

[0151] The pre-polarizer 50A is a broadband absorptive polarizer that absorbs the return light of blue light returning from at least one of the first optical valves 31 or the second optical valve 32 via the first region-segmented wavelength-selective waveplate 51. Since the pre-polarizer 50A is an absorptive polarizer, it is preferably provided with a cooling component 500, such as a heat sink, to cool the pre-polarizer 50A.

[0152] It is important to note that Figure 16 Only the configuration of the main parts required for explanation is shown. Furthermore, similar to... Figure 5 The configuration example shown is as follows. Figure 16 This example illustrates a scenario where the PS converter 17 aligns the incident light with P-polarized light as a predetermined polarization direction. Various colors of light, including red, green, and blue, are incident as P-polarized light onto the first region-segmented wavelength-selective waveplate 51. Figure 16 In this configuration, the pre-polarizer 50A is configured to transmit only P-polarized light and absorb light in polarization directions other than P-polarized light. Figure 16 In the middle, the first region segmentation wavelength selective waveplate 51 is configured to be in the upper region ( Figure 3 In region A), the polarized blue light is rotated 90 degrees, and in the lower region ( Figure 3 No rotation is performed in region B).

[0153] Figure 16 The optical path of the blue light returning to the lower region after passing through the upper region of the first region-segmented wavelength-selective waveplate 51 is shown. The first region-segmented wavelength-selective waveplate 51 rotates the polarization of the blue light in the upper region, and thus emits S-polarized blue light from the upper region of the first region-segmented wavelength-selective waveplate 51. The S-polarized blue light passes through the relay lens 18 while remaining S-polarized, and reaches the first light valve 31 via SBS 41. The first light valve 31 does not rotate the polarization of the light during blackout; therefore, the blue light is reflected by the first light valve 31 while remaining S-polarized, and becomes the S-polarized return light returning to the lower region of the first region-segmented wavelength-selective waveplate 51. The first region-segmented wavelength-selective waveplate 51 does not rotate the polarization of the blue light in the lower region, and thus the S-polarized return light reaches the pre-polarizer 50A while remaining S-polarized. The pre-polarizer 50A is configured to transmit P-polarized light and absorb S-polarized light, and thus the S-polarized return light is absorbed by the pre-polarizer 50 in the lower region, thereby preventing the generation of unwanted light.

[0154] Furthermore, the first region-segmented wavelength-selective waveplate 51 does not rotate the polarized light for blue light in the lower region, and therefore P-polarized blue light is emitted from the lower region of the first region-segmented wavelength-selective waveplate 51. The P-polarized blue light passes through the relay lens 18 while remaining P-polarized light, and reaches the second light valve 32 via PBP 41. The second light valve 32 does not rotate the polarized light during black display; therefore, the blue light is reflected by the second light valve 32 while remaining P-polarized light, and becomes P-polarized return light returning to the upper region of the first region-segmented wavelength-selective waveplate 51. The first region-segmented wavelength-selective waveplate 51 rotates the polarized light for blue light in the upper region, and therefore the P-polarized return light becomes S-polarized light to reach the pre-polarizer 50A. The pre-polarizer 50A is configured to transmit P-polarized light and absorb S-polarized light, and therefore the S-polarized return light in the upper region is absorbed by the pre-polarizer 50A, thereby preventing the generation of unwanted light.

[0155] In this way, in the optical system according to the fourth embodiment, the generation of unwanted light can be reduced for both S-polarized light and P-polarized light.

[0156] Other configurations, functions, and effects may be substantially similar to those in the optical system according to the first embodiment described above.

[0157] <5. Fifth Embodiment>

[0158] Next, an optical system according to a fifth embodiment of this disclosure will be described. It should be noted that, hereinafter, components substantially the same as those in the optical systems according to any of the first to fourth embodiments described above are indicated by the same reference numerals, and their descriptions are appropriately omitted.

[0159] In the first embodiment described above, the region segmentation pattern of the first region-segmented wavelength-selective waveplate 51 has been described as having a segmentation structure divided into an upper half and a lower half; however, the region segmentation pattern of the first region-segmented wavelength-selective waveplate 51 is not limited to a segmentation structure divided into an upper half and a lower half, but can have various segmentation structures. Similarly, the region segmentation pattern of the second region-segmented wavelength-selective waveplate 52 is not limited to a segmentation structure also divided into an upper half and a lower half, but can have various segmentation structures. For both the first region-segmented wavelength-selective waveplate 51 and the second region-segmented wavelength-selective waveplate 52, it is sufficient to have region segmentation patterns that are conjugate to each other. Hereinafter, a modification example of the region segmentation pattern used for the first region-segmented wavelength-selective waveplate 51 will be described.

[0160] Figure 17 A first modified example of the region segmentation pattern of the first region segmentation wavelength-selective waveplate 51 is schematically shown. For example... Figure 17 As shown, for example, the first region-segmented wavelength-selective waveplate 51 can have the following configuration: wherein, having the same as Figure 3 Region A in the diagram corresponds to multiple strip-shaped first segmented regions with polarization characteristics and has the same polarization characteristics as... Figure 3 In region B, the polarization characteristics of multiple strip-shaped second segmented regions are arranged alternately.

[0161] Figure 18 A second modified example of the region segmentation pattern of the first region segmentation wavelength-selective waveplate 51 is schematically shown. For example... Figure 18 As shown, for example, the first region-segmented wavelength-selective waveplate 51 can have the following configuration: wherein, having the same as Figure 3 The polarization characteristics of region A in the diagram are represented by multiple first segmented regions and regions with polarization characteristics corresponding to region A. Figure 3 The polarization characteristics of region B are divided into multiple second-divided regions arranged in a grid pattern.

[0162] Here, as described in the second embodiment, in the optical system according to the first embodiment, in such a way... Figure 5In the case where the pre-polarizer 50 is arranged as shown in the configuration example, there is a possibility that the returned light from the first optical valve 31 or the second optical valve 32 may become unnecessary light reflected by the pre-polarizer 50 and return to the first optical valve 31 or the second optical valve 32 as illumination light. In this case, in the first region-segmented wavelength-selective waveplate 51, the positions of the light rays in the forward path, which are the origin of the returned light, and the positions of the light rays in the return path, are point-symmetrical to each other according to the principle of reflection. Furthermore, in the first region-segmented wavelength-selective waveplate 51, unnecessary light is generated due to the difference in polarization characteristics between the positions of the light rays in the forward path and the positions of the light rays in the return path. Therefore, it is preferable that the first region-segmented wavelength-selective waveplate 51 has a segmentation structure in which the first segmentation region and the second segmentation region are point-symmetrically distributed in at least a portion of the region. To reduce unnecessary light, it is preferable that the first region-segmented wavelength-selective waveplate 51 has a segmentation structure in which the first segmentation region and the second segmentation region are point-symmetrically distributed in at least half or more of the region. Hereinafter, Figures 19 to 22 Examples are shown of segmentation structures in which the first segmentation region and the second segmentation region are point-symmetrically distributed in at least half or more of the region of the wavelength-selective waveplate 51 in the first region segmentation.

[0163] Figure 19 A third modified example of the region segmentation pattern of the first region segmentation wavelength selective waveplate 51 is schematically shown. Figure 19 It shows a kind of one in which relative to Figure 17 The segmentation structure in the image shows that the first and second segmentation regions are point-symmetrically distributed across all regions.

[0164] Figure 20 A fourth modified example of the region segmentation pattern of the first region segmentation wavelength selective waveplate 51 is schematically shown. Figure 20 It shows a kind of one in which relative to Figure 18 The segmentation structure in the image shows that the first and second segmentation regions are point-symmetrically distributed across all regions.

[0165] Figure 21 A fifth modified example of the region segmentation pattern of the first region segmentation wavelength selective waveplate 51 is schematically shown. Figure 21 This paper illustrates a segmentation structure in which the polarization characteristics of the central region and the polarization characteristics of the outer region are different from each other, and the first segmentation region and the second segmentation region are point-symmetrically distributed across all regions.

[0166] Figure 22 A sixth modified example of the region segmentation pattern of the first region segmentation wavelength-selective waveplate 51 is schematically shown. An example in which, relative to... Figure 20The segmentation structure in the image shows that the first and second segmentation regions are point-symmetrically distributed for approximately half or more of the region.

[0167] It should be noted that, from a manufacturing perspective, it is preferable that there are fewer boundaries between the first and second segmented regions. Furthermore, also from an optical performance perspective, it is preferable that there are fewer boundaries between the first and second segmented regions. Therefore, for example, Figure 20 The segmentation structure in the text is more preferred.

[0168] The segmentation structure of the wavelength-selective waveplate 51 that allows the first region to be segmented is a point-symmetric segmentation structure for at least half or more of the region, for example, as shown in the figure. Figures 19 to 22 As shown, this enables the reduction of unnecessary light generation without employing the optical system configuration according to the second to fourth embodiments described above.

[0169] Other configurations, functions, and effects may be substantially similar to those in the optical system according to the first embodiment described above.

[0170] <6. Other Embodiments>

[0171] The technology based on this disclosure is not limited to the descriptions of the various embodiments above, and can be modified in a wide variety of ways.

[0172] For example, this technology may also have the following configurations.

[0173] According to the present technology with the following configuration, a first polarization rotation element comprising a first segmented region and a second segmented region having different polarization characteristics is arranged at a first pupil position in a first optical system, and a polarizer is further arranged in the first optical system to reduce the amount of light in the light emitted from the polarization conversion element that is polarized in a direction other than a predetermined polarization direction, thereby enabling the improvement of contrast. (1)

[0175] An optical system, comprising:

[0176] A first optical system includes a polarization conversion element that aligns the polarization direction of light comprising multiple colors of light with a predetermined polarization direction, and the first optical system generates illumination light comprising the multiple colors of light.

[0177] A first polarization rotation element is arranged at a first pupil position within the first optical system and includes a first segmented region and a second segmented region, wherein the first segmented region and the second segmented region have different polarization characteristics relative to the first color light among the multiple colors of light emitted from the polarization conversion element.

[0178] A polarizer, disposed within the first optical system between the polarization conversion element and the first polarization rotation element, the polarizer reducing light in the light emitted from the polarization conversion element that includes light in polarization directions other than the predetermined polarization direction; and

[0179] Multiple light valves, each of which is illuminated by at least the first color light among the multiple colors of light included in the illumination light generated by the first optical system. (2)

[0181] The optical system according to (1) further includes a wavelength selective reflective element arranged in the optical path between the first polarization rotating element and the plurality of optical valves, the wavelength selective reflective element reducing the return light of the first color light from at least one of the plurality of optical valves back to the polarizer. (3)

[0183] According to the optical system of (2), the wavelength selective reflective element is arranged to be tilted relative to the optical axis of the optical path between the first polarization rotating element and the plurality of optical valves. (4)

[0185] According to any one of (2) or (3), the optical system wherein the wavelength selective reflection element is arranged in a region corresponding to at least one of the first segmented region or the second segmented region in the first polarization rotation element. (5)

[0187] According to the optical system described in (4), in a region corresponding to one of the first segmented region and the second segmented region, the wavelength-selective reflective element transmits all of the multiple colors of light from the one segmented region and reflects the return light of the first color light returning to the polarizer from at least one of the plurality of optical valves. (6)

[0189] According to the optical system described in (5), in a region corresponding to another segmented region in the first segmented region and the second segmented region, the wavelength-selective reflective element transmits all of the multiple colors of light from the other segmented region. (7)

[0191] According to the optical system described in (4), in the region corresponding to one of the segmented regions of the first segmented region and the second segmented region, the wavelength selective reflective element reflects all of the multiple colors of light from the one segmented region and transmits the return light of the first color light returning to the polarizer from at least one of the plurality of optical valves. (8)

[0193] According to the optical system described in (7), in a region corresponding to another segmented region in the first segmented region and the second segmented region, the wavelength-selective reflective element reflects all of the multiple colors of light from the other segmented region. (9)

[0195] According to the optical system of (1), the polarizer includes an absorptive polarizer that absorbs the return light of the first color light returning from at least one of the plurality of optical valves via the first polarization rotation element. (10)

[0197] The optical system according to (9) further includes a cooling component for cooling the absorption polarizer. (11)

[0199] According to the optical system described in (1), the first polarization rotation element has a segmentation structure in at least a portion of the region in which the first segmentation region and the second segmentation region are point-symmetrically distributed. (12)

[0201] According to the optical system of (11), the first polarization rotation element has a segmentation structure in at least half or more of the region in which the first segmentation region and the second segmentation region are point-symmetrically distributed. (13)

[0203] The optical system according to any one of (1) to (12) further includes:

[0204] A second optical system, wherein the multi-color light modulated by the plurality of light valves is incident on the second optical system; and

[0205] The second polarization rotation element is arranged in the second optical system at a second pupil position conjugate to the first pupil position, and includes a third segmented region and a fourth segmented region, wherein the third segmented region and the fourth segmented region have polarization characteristics different from each other relative to the first color light among the multiple colors of light emitted from the plurality of light valves. (14)

[0207] According to the optical system described in (13), the first segmented region and the second segmented region in the first polarization rotation element are respectively conjugate to the third segmented region and the fourth segmented region in the second polarization rotation element. (15)

[0209] According to the optical system of (13) or (14), wherein the second optical system includes a projection optical system that projects the image generated by the plurality of light valves onto a projection plane. (16)

[0211] The optical system according to any one of (1) to (15), wherein

[0212] The plurality of optical valves includes a first optical valve and a second optical valve.

[0213] The multiple colors of light include a first color light, a second color light, and a third color light.

[0214] The first color light is incident on the first light valve and the second light valve.

[0215] The second color light is incident on one of the first and second light valves, and

[0216] The third color light is incident on another light valve in the first and second light valves.

[0217] This application claims the benefit of Japanese priority patent application JP2020-8634, filed with the Japan Patent Office on January 22, 2020, the entire contents of which are incorporated herein by reference.

[0218] Those skilled in the art will understand that various modifications, combinations, sub-combinations and alterations may occur depending on design requirements and other factors, as long as they are within the scope of the appended claims or their equivalents.

Claims

1. An optical system comprising: a first optical system including a polarization conversion element that aligns a polarization direction of light including a plurality of color lights with a predetermined polarization direction, the first optical system generating illumination light including the plurality of color lights; a first polarization rotation element arranged at a first pupil position within the first optical system and including a first divided region and a second divided region, wherein the first divided region and the second divided region have polarization characteristics different from each other with respect to a first color light among the plurality of color lights emitted from the polarization conversion element; a polarizer arranged between the polarization conversion element and the first polarization rotation element within the first optical system, the polarizer reducing light in a polarization direction other than the predetermined polarization direction included in light emitted from the polarization conversion element; and a plurality of light valves each illuminated by at least the first color light among the plurality of color lights included in the illumination light generated by the first optical system.

2. The optical system according to claim 1, further comprising a wavelength-selective reflection element arranged on an optical path between the first polarization rotation element and the plurality of light valves, the wavelength-selective reflection element reducing return light of the first color light returned to the polarizer from at least one light valve among the plurality of light valves.

3. The optical system according to claim 2, wherein the wavelength-selective reflection element is arranged to be inclined with respect to an optical axis of an optical path between the first polarization rotation element and the plurality of light valves.

4. The optical system according to claim 2, wherein the wavelength-selective reflection element is arranged in a region corresponding to at least one divided region among the first divided region or the second divided region in the first polarization rotation element. in a region corresponding to one divided region among the first divided region and the second divided region, the wavelength-selective reflection element transmits all of the plurality of color lights from the one divided region and reflects return light of the first color light returned to the polarizer from at least one light valve among the plurality of light valves.

5. The optical system of claim 4, wherein, in a region corresponding to another divided region among the first divided region and the second divided region, the wavelength-selective reflection element transmits all of the plurality of color lights from the another divided region.

6. The optical system of claim 5, wherein, in the region corresponding to the one divided region among the first divided region and the second divided region, the wavelength-selective reflection element reflects all of the plurality of color lights from the one divided region and transmits return light of the first color light returned to the polarizer from at least one light valve among the plurality of light valves.

7. The optical system of claim 4, wherein, in the region corresponding to the another divided region among the first divided region and the second divided region, the wavelength-selective reflection element reflects all of the plurality of color lights from the another divided region.

8. The optical system of claim 7, wherein, ​ 9.The optical system according to claim 1, wherein the polarizer includes an absorption-type polarizer that absorbs return light of the first color light returned from at least one of the plurality of light valves via the first polarization rotation element. 10.The optical system according to claim 9, further comprising a cooling member that cools the absorption-type polarizer. 11.The optical system according to claim 1, wherein the first polarization rotation element has a division structure in which the first division region and the second division region are point-symmetrically distributed in at least a part of the area. 12.The optical system according to claim 11, wherein the first polarization rotation element has a division structure in which the first division region and the second division region are point-symmetrically distributed in at least half or more of the area. 13.The optical system according to claim 1, further comprising: a second optical system on which the plurality of color lights modulated by the plurality of light valves are incident; and a second polarization rotation element disposed at a second pupil position inside the second optical system that is conjugate to the first pupil position, and including a third division region and a fourth division region, wherein the third division region and the fourth division region have different polarization characteristics from each other with respect to the first color light among the plurality of color lights emitted from the plurality of light valves. 14.The optical system according to claim 13, wherein the first division region and the second division region in the first polarization rotation element are mutually conjugate to the third division region and the fourth division region in the second polarization rotation element, respectively. 15.The optical system according to claim 13, wherein the second optical system includes a projection optical system that projects an image generated by the plurality of light valves onto a projection plane. 16.The optical system according to claim 1, wherein the plurality of light valves include a first light valve and a second light valve, the plurality of color lights include a first color light, a second color light, and a third color light, the first color light is incident on the first light valve and the second light valve, the second color light is incident on one of the first light valve and the second light valve, and the third color light is incident on the other of the first light valve and the second light valve. ​ ​ ​ ​ ​ ​ ​ ​

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