Projection imaging optical system and projection type image display device

Abstract

The projection imaging optical system according to the present disclosure is used for a projection-type image display device. The present invention comprises: a projection lens that forms a first image on a first plane using a light beam of projection light emitted in the front direction along a first optical axis from a light modulation element; a prism optical system that deflects and emits, along a second optical axis, a light beam of imaging light which is at least part of light beams of external light entering through the projection lens and which propagates, from the first plane, in the direction opposed to the front direction, wherein an intermediate image is formed inside the prism optical system by the light beam of the imaging light; and an imaging optical system that forms a second image on a second plane using a light beam of imaging light emitted from the prism optical system. The first plane and the position of the intermediate image have conjugate relation with respect to the projection lens. The projection lens is configured to have aberration correcting performance for the first image. The prism optical system and the imaging optical system are configured to have, in cooperation with the projection lens, aberration correcting performance for the second image.

Description

[Technical field]

[0001] The present disclosure relates to a projection imaging optical system and a projection-type image display device including the same. [Background technology]

[0002] Conventionally, there has been known a projection type image display device that has an image sensor inside the main body, and includes both a projection optical system that projects projection light onto a projection target, and an image capturing optical system that forms an image on the image sensor using light from the projection target as external light. Such a projection type image display device has a function of projecting an image onto the projection target and capturing an image of the projected image. Examples of this type of projection type image display device include those described in Patent Document 1 or Patent Document 2.

[0003] The projector (projection type image display device) described in Patent Document 1 uses a TIR prism as an optical path branching element, while the projection type image display device described in Patent Document 2 uses a total internal reflection prism arranged on the optical path between the projection optical system and the color synthesis optical system as a light separation optical system that guides external light to an imaging element. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2013-218262 A [Patent Document 2] JP 2020-64206 A Summary of the Invention

[0005] However, as the imaging optical system is made smaller, the pixels of the imaging element become smaller and more precise, and the imaging optical system needs to have the ability to correct various aberrations accordingly. In the imaging optical system using a prism as the light path branching element described in Patent Document 1 or Patent Document 2, since both the entrance surface and the exit surface of the prism are refractive surfaces, there is a problem that the image quality of the acquired image is reduced due to chromatic aberration caused by the chromatic dispersion of the refractive index and the occurrence of new spherical aberration caused by the insertion of an optical surface. In order to correct these aberrations, the imaging optical system must be arranged to increase the number of optical components, for example, by providing multiple lenses to correct the aberrations. However, in the configuration of a conventional projector optical system, when considering the incorporation of an imaging optical system having an aberration correction performance without interfering with the arrangement and optical design of the projection optical system, there is a drawback that the entire optical system becomes large.

[0006] The present invention has been made in consideration of the above circumstances, and has an object to provide a projection imaging optical system that can be incorporated into a projection-type image display device without interfering with the arrangement and optical design of the projection optical system, and that can achieve aberration correction for the entire system.

[0007] In order to achieve the above-mentioned object, the projection imaging optical system of the present disclosure is a projection imaging optical system used in a projection-type video display device, and includes: a projection lens that forms a first image on a first surface using rays of projection light emitted in a forward direction along a first optical axis from a light modulation element; a prism optical system that deflects rays of imaging light, which are at least a part of the rays of external light that are propagated from the first surface in a direction opposite to the forward direction and incident via the projection lens, and emits them along a second optical axis, thereby forming an intermediate image by the rays of imaging light; and an imaging optical system that forms a second image on the second surface using the rays of imaging light emitted from the prism optical system, wherein the positions of the first surface and the intermediate image are in a conjugate relationship with respect to the projection lens, and the projection lens is configured to have aberration correction performance in the first image, and the prism optical system and the imaging optical system, in combination with the projection lens, are configured to have aberration correction performance in the second image.

[0008] According to an aspect of the present disclosure, the projection imaging optical system can be incorporated into a projection-type image display device without interfering with the layout and optical design of the projection optical system, and can correct aberrations in the entire system, thereby enabling the projection-type image display device to have excellent imaging performance and be compact. [Brief description of the drawings]

[0009] [Figure 1] 1 is a schematic diagram illustrating a configuration of a projection imaging optical system according to a first embodiment of the present disclosure and an optical path through which a chief ray passes. [Diagram 2] 1 is a schematic diagram showing an overall configuration of a projection type image display device using a projection imaging optical system according to a first embodiment. [Diagram 3] 3 is a schematic diagram showing the arrangement of the projection and imaging optical system of the projection-type image display device of FIG. 2 having the configuration of the projection and imaging optical system according to the first embodiment, and light propagation. FIG. [Figure 4A] 4 is a diagram showing axial chromatic aberration and spherical aberration at the position of a light modulation element in the projection imaging optical system in FIG. [Figure 4B] 4 is a diagram showing axial chromatic aberration and spherical aberration at the position of an intermediate image of the projection imaging optical system of FIG. 3. [Diagram 5] FIG. 4 is a perspective view showing a configuration of a prism optical system of the projection imaging optical system in FIG. [Figure 6] FIG. 4 is a cross-sectional view of a prism optical system of the projection imaging optical system of FIG. [Figure 7] 11 is a cross-sectional view of a prism optical system according to a first modified example of the embodiment of the present disclosure. [Figure 8] 11 is a cross-sectional view of a prism optical system according to a second modified example of the embodiment of the present disclosure. [Figure 9] 11 is a schematic diagram illustrating a configuration of a projection imaging optical system according to a second embodiment of the present disclosure and an optical path through which a chief ray passes. FIG. [Figure 10] 5 is a schematic diagram showing the arrangement of the projection and imaging optical system of the projection-type image display device of FIG. 2 having the configuration of the projection and imaging optical system according to the second embodiment, and light propagation. FIG. [Figure 11]FIG. 11 is a schematic diagram illustrating a configuration of a projection imaging optical system according to a third embodiment of the present disclosure and an optical path through which a chief ray passes. [Figure 12] 10 is a schematic diagram showing the arrangement of the projection and imaging optical system of the projection-type image display device of FIG. 2 having the configuration of the projection and imaging optical system according to Example 3, and light propagation. [Figure 13] 1 is a lens arrangement diagram showing a configuration of an imaging optical system of a projection imaging optical system according to Example 1. FIG. [Figure 14] 4 is a diagram showing longitudinal aberration associated with the imaging optical system of the projection imaging optical system according to Example 1. FIG. [Figure 15] 4 is a diagram showing surface data of the imaging optical system of the projection imaging optical system according to Example 1. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] According to a first aspect of the present disclosure, there is provided a projection imaging optical system for use in a projection-type video display device, the projection imaging optical system comprising: a projection lens that forms a first image on a first surface using rays of projection light emitted in a forward direction along a first optical axis from a light modulation element; a prism optical system that deflects rays of imaging light, which are at least a part of the rays of external light that are propagated from the first surface in a direction opposite to the forward direction and incident via the projection lens, and emits them along a second optical axis, thereby forming an intermediate image by the rays of imaging light; and an imaging optical system that forms a second image on the second surface using the rays of imaging light emitted from the prism optical system, wherein the positions of the first surface and the intermediate image are in a conjugate relationship with respect to the projection lens, the projection lens is configured to have an aberration correction performance in the first image, and the prism optical system and the imaging optical system are configured to have an aberration correction performance in the second image, in combination with the projection lens.

[0011] According to this aspect, it is possible to provide a projection imaging optical system that can be incorporated inside a projection type image display device without interfering with the arrangement and optical design of the projection optical system and that can achieve aberration correction for the entire system.

[0012] According to a second aspect of the present disclosure, there is provided a projection imaging optical system as described in the first aspect, in which the projection lens constitutes at least a part of a projection optical system that displays an image by enlarging and projecting a light beam of projection light from a light modulation element onto a first surface.

[0013] According to a third aspect of the present disclosure, there is provided a projection imaging optical system as defined in the first or second aspect, wherein the prism optical system internally reflects incident imaging light rays multiple times, and the second optical axis lies in a plane substantially perpendicular to the first optical axis.

[0014] According to a fourth aspect of the present disclosure, there is provided a projection imaging optical system as set forth in any one of the first to third aspects, in which the prism optical system and the imaging optical system are configured to cancel out axial chromatic aberration and spherical aberration occurring in the imaging light ray at the position of the intermediate image.

[0015] According to a fifth aspect of the present disclosure, there is provided a projection imaging optical system according to any one of the first to fourth aspects, wherein the prism optical system has two or more internal reflective surfaces, and at least one of the two or more internal reflective surfaces is formed into a curved surface having a concave shape so as to impart positive power to a reflected ray of imaging light.

[0016] According to a sixth aspect of the present disclosure, there is provided a projection imaging optical system as defined in any one of the first to fifth aspects, wherein the prism optical system has an exit surface that transmits and emits the imaging light rays toward the imaging optical system, and the exit surface is formed into a curved shape so as to impart positive power to the transmitted imaging light rays.

[0017] According to a seventh aspect of the present disclosure, there is provided the projection imaging optical system as defined in the fifth or sixth aspect, in which a part of the prism optical system and the imaging optical system constitute an imaging light relay optical system that forms an intermediate image on a second surface.

[0018] According to an eighth aspect of the present disclosure, there is provided the projection imaging optical system according to any one of the first to seventh aspects, wherein the imaging optical system is configured as an optical system that reduces and forms the second image on an imaging element.

[0019] According to a ninth aspect of the present disclosure, there is provided a projection imaging optical system according to any one of the first to seventh aspects, wherein the imaging optical system is configured as an optical system that forms an equal-magnification or enlarged image of the second image on an imaging element.

[0020] According to a tenth aspect of the present disclosure, there is provided a projection type image display device comprising: an illumination optical system that supplies illumination light; one or more light modulation elements that spatially modulate the light supplied by the illumination optical system and guided by a prism optical system to enter the projection type image display device and generate projection light corresponding to image information; the projection imaging optical system according to any one of the first to ninth aspects; and an imaging element that converts a second image formed by the projection imaging optical system into an electrical image signal.

[0021] Any of the above-described various embodiments may be appropriately combined to achieve the effects of each of the embodiments.

[0022] Hereinafter, the embodiments will be described in detail with reference to the drawings as appropriate. However, more detailed explanation than necessary may be omitted. For example, detailed explanation of already well-known matters or duplicate explanation of substantially the same configuration may be omitted. This is to avoid the following explanation becoming unnecessarily redundant and to facilitate understanding by those skilled in the art.

[0023] In addition, the accompanying drawings and the following description are provided for those skilled in the art to fully understand the present disclosure, and are not intended to limit the subject matter described in the claims. In addition, in each drawing, each element is exaggerated for ease of explanation.

[0024] <Embodiment> Hereinafter, a projection imaging optical system according to an embodiment of the present disclosure and a projection-type image display device including the same will be described with reference to Fig. 1 to Fig. 12. Note that, as a specific example of a projection-type image display device to which the projection imaging optical system according to the present disclosure is applied, a single-panel projection-type image display device including a single light modulation element will be described.

[0025] Example 1 Fig. 1 is a schematic diagram showing a configuration of a projection imaging optical system LS10 according to a first embodiment of the present disclosure and an optical path through which a chief ray passes. Note that an inset (a) in Fig. 1 is a diagram simply showing a propagation path of a projection light Lp, and an inset (b) is a diagram simply showing a propagation path of an imaging light Li.

[0026] A projection imaging optical system LS10 according to an embodiment of the present disclosure is configured with a projection lens LG10, a prism optical system PG10, and an imaging optical system LG20, and can be provided in a projection-type image display device.

[0027] As shown in the inset (a) of Fig. 1, a projection light Lp propagating in the +X direction along a first optical axis Oa is emitted from a light modulation element D10 of the projection type image display device, and a projection optical system PS10 is disposed that uses the light rays of the projection light Lp to enlarge and project from the light modulation element D10 onto a first surface W10 to display an image. The projection optical system PS10 is composed of a projection lens LG10 and an optical member PP10, and has a first optical axis Oa in the X direction as a reference axis. The optical member PP10 may include optical members such as a prism, an optical filter, a cover glass, etc., and may include a part of the prism optical system PG10 of the projection imaging optical system LS10.

[0028] Specifically, for example, the light modulation element D10 can be located at a conjugate point on the reduction side of the projection optical system PS10. A ray of the projection light Lp emitted from the light modulation element D10 passes through the projection lens LG10 in the +X direction shown in the figure along the first optical axis Oa, and forms a first image M10 by the projection optical system PS10, for example, on a first surface W10 located at a conjugate point on the enlargement side.

[0029] As shown in the inset (b) of FIG. 1, the projection imaging optical system LS10 can form an image on the second surface W20 using the light rays of the external light Le propagating from the first surface W10 in the -X direction shown in the figure. The prism optical system PG10 of the projection imaging optical system LS10 deflects the light rays of the imaging light Li, which is at least a part of the light rays of the external light Le incident via the projection lens LG10, and outputs them to the imaging optical system LG20 in the +Y direction shown in the figure. The imaging optical system LG20 uses the second optical axis Ob in the Y direction shown in the figure as a reference axis, and forms an image of the light rays of the imaging light Li output from the prism optical system PG10 on the second surface W20. In addition, an intermediate image Ms10 is formed inside the prism optical system PG10, and the intermediate image Ms10 is relayed by the imaging light relay optical system RS10 and is imaged on the second surface W20.

[0030] Specifically, the light beam of the external light Le passes through the projection lens LG10 from the first surface W10 along the first optical axis Oa in the illustrated −X direction and enters the prism optical system PG10. For example, the prism optical system PG10 may have prism surfaces P1, P2, and P3 that are multiple internal reflection surfaces and a prism surface P4 that is a transmission surface for the light beam of the imaging light Li, which is at least a part of the external light Le. In this embodiment, the imaging light Li is deflected by internal reflections R1, R2, and R3 in order at the prism surfaces P1, P2, and P3, and is emitted from the prism surface P4 along the second optical axis Ob. At this time, inside the prism optical system PG10, the light beam of the imaging light Li is internally reflected R1 and R2 at the prism surfaces P1 and P2, and then forms an intermediate image Ms10 at a position Im in the prism optical system PG10 that is in a conjugate relationship with the first surface W10. Thereafter, the light ray of the imaging light Li advances further in the prism optical system PG10, undergoes internal reflection R3 at the prism surface P3, and then passes through the prism surface P4 to be emitted along the second optical axis Ob, passes through the imaging optical system LG20 in the illustrated Y direction, and forms a second image M20 on the second surface W20. Here, the imaging light relay optical system RS10 refers to a lens system that is disposed between the intermediate image Ms10 and the second surface W20 and images the intermediate image Ms10 on the second surface W20. In the present disclosure, the imaging light relay optical system RS10 may be constituted by the imaging optical system LG20, or may be constituted by a part of the prism optical system PG10 and the imaging optical system LG20. This will be described in detail later.

[0031] In this manner, in the projection type image display device, the projection imaging optical system LS10 and the projection optical system PS10 are configured to share the projection lens LG10. In addition, although not limited thereto, the projection imaging optical system LS10 and the projection optical system PS10 may be configured to share a part of the prism optical system PG10.

[0032] It should be understood that Fig. 1 conceptually illustrates the configuration of the main parts of the projection imaging optical system LS10 and the optical path through which the chief ray passes, and is not limited to the specific aspects of each component. For example, the prism optical system may be configured in a manner different from that shown in Fig. 1 in terms of the number, shape, and arrangement of the prism elements included therein, or the internal reflective surfaces and transmissive surfaces for the imaging light.

[0033] In this embodiment, in the projection optical system PS10, the projection lens LG10 can include a plurality of lens elements. The projection lens LG10 can be configured to have an aberration correction performance in the first image M10, for example, by combining with the reduction-side optical member PP10. The aberration correction configuration of the projection optical system can adopt a conventionally known optical design, and a detailed description will be omitted in this specification.

[0034] The projection imaging optical system LS10 guides and emits the imaging light Li, which is at least a part of the rays of the external light Le, in the direction of the second optical axis Ob via the projection lens LG10, the prism optical system PG10, and the imaging optical system LG20 in this order, and forms an intermediate image in the prism optical system PG10 on the second surface W20. At this time, the prism optical system PG10 and the imaging optical system LG20 are configured in combination with the projection lens LG10 to have an aberration correction performance in the second image M20.

[0035] In this manner, in this embodiment, the rays of the imaging light Li, which is at least a part of the rays of the external light Le coaxially incident with the projection light Lp along the first optical axis Oa, are deflected by multiple internal reflections within the prism optical system PG10 and guided toward the second surface W20 along the second optical axis Ob, improving the degree of freedom in the arrangement of the optical system. As a result, the projection imaging optical system LS10 can be configured to achieve aberration correction performance in the second image M20 using multiple optical components, and can be incorporated inside the projection-type image display device without interfering with the arrangement of the projection optical system PS10.

[0036] Moreover, the projection imaging optical system LS10 of the present embodiment is configured to form an intermediate image inside the prism optical system PG10 by utilizing the propagation optical path length of the imaging light Li inside the prism optical system PG10, and image the intermediate image outside the prism optical system PG10. With such a configuration, in the second imaging M20, by positioning the object side inside the medium of the prism optical system PG10, a sufficient distance can be secured to insert the imaging optical system LG20 having an aberration correction configuration on the image plane side, and the specifications of the entire optical system can be controlled more freely. In this way, aberration correction of the entire system can be realized without interfering with the optical design of the projection optical system PS10. The detailed configuration of the projection imaging optical system LS10 will be described in a projection type image display device to which the projection imaging optical system according to the present disclosure is applied as a specific example.

[0037] (Configuration of a projection-type image display device 600 using a projection imaging optical system according to the first embodiment) Hereinafter, the configuration of a projection-type image display device 600 using a projection imaging optical system according to an embodiment of the present disclosure will be described with reference to FIGS. 2 to 8. FIG. 2 is a schematic diagram showing the overall configuration of a projection-type image display device 600 using a projection imaging optical system according to Example 1. Also, (a) and (b) of FIG. 2 are schematic diagrams showing the overall configuration of the projection-type image display device 600 in the illustrated XZ plane. (c) of FIG. 2 is a schematic diagram showing the prism optical system PG100 and the imaging optical system LG200 of the projection-type image display device 600 as viewed from the left side of (a) of FIG. 2, that is, from the +Z side of (a) of FIG. 2 toward the -Z direction. Note that the projection-type image display device according to the embodiment of the present disclosure may be, for example, a high-brightness type projector used for projection mapping, or may be a low-brightness type projector for home use.

[0038] The projection-type image display device 600 in FIG. 2 includes an illumination optical system 200 that supplies illumination light, and a projection imaging system 500.

[0039] <Illumination optical system> The illumination optical system 200 includes a light source unit 20, afocal lenses 31 and 32, a diffuser plate 41, a λ / 4 plate 42, condenser lenses 33, 34, and 35, a dichroic mirror 45, a rod integrator 46, a phosphor wheel 50, a color wheel 60, and lenses 73, 74, and 75 that constitute an illumination light relay optical system.

[0040] In the illumination optical system 200, the light source unit 20 is composed of, for example, a plurality of semiconductor lasers (LD) or light emitting diodes (LED). In this embodiment, a semiconductor laser element 21 that emits blue light can be used. The blue light emitted from the semiconductor laser element 21 has a wavelength of about 455 nm and is used as image light and also as excitation light for exciting the phosphor of the phosphor wheel 50. The blue light emitted from the semiconductor laser element 21 is emitted in the illustrated −X direction, collimated by the collimating lens 22, and then focused by the afocal lenses 31 and 32, transmitted through the diffusion plate 41, and incident on the dichroic mirror 45.

[0041] In this embodiment, the light emitted from light source unit 20 is, for example, S-polarized blue light, and dichroic mirror 45 reflects the S-polarized blue light and can transmit P-polarized blue light and other colored light. The blue light reflected by dichroic mirror 45 travels approximately in the -Z direction, passes through λ / 4 plate 42, and is collected by condenser lenses 33 and 34 to enter phosphor wheel 50, where it excites the phosphors in phosphor wheel 50 to emit light.

[0042] As the phosphor wheel 50 rotates, different segments of the phosphor layer are excited by the incident blue light, and can generate fluorescence including, for example, luminescent component light in a yellow range and luminescent component light in a green range. In addition, a part of the blue light that has passed through the λ / 4 plate 42 is reflected by the phosphor wheel 50 and passes through the λ / 4 plate 42 again to become P-polarized blue component light, which is transmitted through the dichroic mirror 45. The blue component light and luminescent component light of each color range that have passed through the dichroic mirror 45 proceed in the approximate Z direction, pass through the condenser lens 35, and enter the color wheel 60.

[0043] Color wheel 60 is controlled to rotate synchronously with phosphor wheel 50, and splits the incident light according to the transmission characteristics of the different segments. The light generated by phosphor wheel 50 and color wheel 60, which rotate synchronously, enters rod integrator 46 and is homogenized there so that component light of each color gamut, including red, green, blue, yellow, etc., is emitted in a time-division manner.

[0044] The light emitted from the rod integrator 46 passes through lenses 73, 74, and 75 that constitute the illumination light relay optical system, and then is emitted from the illumination optical system 200 and becomes illumination light Ls that is white light on a time average, and enters the projection imaging system 500.

[0045] <Projection Imaging System> Next, the projection imaging system 500 includes a prism optical system PG100, a light modulation element D100, a projection optical system 420, an imaging optical system LG200, and an imaging element 450. In this embodiment, the imaging optical system LG200 and the imaging element 450 are disposed on a YZ plane that is approximately perpendicular to the projection optical axis Oa1 in the X direction shown in the figure, and the imaging light Li is incident on the imaging element 450 along the imaging optical axis Ob1 in the +Y direction (shown in FIG. 2(c)).

[0046] In this embodiment, in the projection imaging system 500, the prism optical system PG100 is composed of a TIR (Total Internal Reflection) prism 310 (internal total reflection prism) and an imaging light reflecting prism 350. In this embodiment, the TIR prism 310 is composed of a first prism 320 and a second prism 330, each of which has a substantially triangular prism shape, joined together with a small gap therebetween. The TIR prism 310 deflects the incident illumination light Ls by utilizing total reflection, and guides it to the light modulation element D100. The imaging light reflecting prism 350 is disposed adjacent to the TIR prism 310. The imaging light reflecting prism 350 and the TIR prism 310 may be configured separately (FIG. 7) or integrally (FIGS. 6 and 8). In FIG. 2, the imaging light reflecting prism 350 and the TIR prism 310 are shown as being configured separately. The imaging light reflecting prism 350 further reflects and deflects the imaging light Li that has been reflected by the TIR prism 310 and is incident thereon, and guides it to the imaging element 450. The configuration of the prism optical system PG100 will be described in detail later.

[0047] The light modulation element D100 uses a DMD (Digital Mirror Device), which modulates component light of each color gamut contained in the illumination light Ls based on a video signal and distributes it to DMD-ON light (ON light) that becomes the projection light Lp for each pixel, or DMD-OFF light Lf (OFF light) that is not used for the projection light Lp. The projection light Lp for projection is emitted in the +X direction along the projection optical axis Oa1, and the DMD-OFF light Lf is deflected from the projection optical axis Oa1 and removed.

[0048] The projection light Lp passes through the TIR prism 310, is output from the projection light exit surface 321, and is propagated along the projection optical axis Oa1 to the projection optical system 420. In this embodiment, the projection optical system 420 is configured with a projection lens LG100, and enlarges and projects the projection light Lp onto a projection target such as a screen 430 to display an image.

[0049] On the other hand, the projected image can be captured by the imaging element 450 built into the projection imaging system 500 using imaging light Li, which is at least a part of the external light Le reflected from the screen 430 in the illustrated −X direction.

[0050] As shown in the figure, external light Le enters from the projection optical system 420, propagates in the -X direction along the projection optical axis Oa1, and enters the projection light exit surface 321 on the projection optical system side of the first prism 320 of the TIR prism 310. Within the TIR prism 310, imaging light Li, which is at least a part of the external light Le, is internally reflected and deflected and enters the imaging light reflecting prism 350. The imaging light Li that enters the imaging light reflecting prism 350 is further internally reflected and deflected within the imaging light reflecting prism 350, and is emitted from the imaging light exit surface 353 of the imaging light reflecting prism 350 along the imaging optical axis Ob1, and is introduced into the imaging optical system LG200 in the +Y direction shown in the figure.

[0051] The imaging optical system LG200 may include a plurality of optical components, and in this embodiment, is configured by a lens group 440. The imaging light Li emitted from the imaging light emission surface 353 and propagating along the imaging optical axis Ob1 in the +Y direction can be imaged on the imaging element 450 by the imaging optical system LG200. Note that the present disclosure does not limit the magnification of the imaging optical system, and the imaging optical system LG200 may be configured as an optical system that forms a reduced image on the imaging element 450, or may be configured as an optical system that forms an image at the same magnification or an enlarged image on the imaging element 450. The imaging element 450 may be configured by a solid-state imaging element such as a CCD image sensor or a CMOS image sensor, and converts the received imaging light Li into an electrical image signal.

[0052] In order to make the device smaller and less expensive inside the projection type image display device, in the projection optical system, the projection lens LG100 and the projection light exit surface 321 of the prism optical system PG100 on the projection optical system side are configured as close as possible without interfering with each other. Therefore, there is little space inside the device in the direction of emission of the projection light Lp, and the arrangement of optical components is limited in terms of design.

[0053] In the projection type image display device 600 according to the present disclosure, as described above, the imaging light Li is internally reflected and deflected multiple times within the prism optical system PG100. This allows the imaging light Li, which is at least a part of the external light Le incident along the projection optical axis Oa1 in the illustrated −X direction, to be guided toward the imaging element 450 along the imaging optical axis Ob1 in the YZ plane substantially perpendicular to the projection optical axis Oa1. This allows the projection imaging optical system LS100 included in the projection type image display device 600 to be easily incorporated inside the device without interfering with the projection optical system arranged along the projection optical axis Oa1. The arrangement of the projection imaging optical system LS100 of the projection type image display device 600 will be described below with reference to FIG. 3.

[0054] <Layout of the projection imaging optical system LS100> FIG. 3 is a conceptual diagram showing the arrangement and light propagation of the projection imaging optical system LS100 of the projection type image display device 600 of FIG. 2 having the configuration of the projection imaging optical system according to the first embodiment. The projection imaging optical system LS100 of the projection type image display device 600 shown in FIG. 3 applies the configuration of the projection imaging optical system LS10 according to the first embodiment shown in FIG. 1. Note that, in FIG. 3, for ease of understanding, the curved optical path of the imaging light Li is expanded into a straight line to show the manner of light propagation. That is, in FIG. 3, the imaging optical axis Ob1 on the YZ plane is expanded equivalently coaxially with the projection optical axis Oa1 on the XZ plane, and the optical path of the projection light Lp on the XZ plane and the optical path of the imaging light Li deflected to the YZ plane in the prism optical system PG100 are illustrated on the same plane.

[0055] 3, the projection imaging optical system LS100 according to the embodiment of the present disclosure is composed of a projection lens LG100, a prism optical system PG100, and an imaging optical system LG200. Note that in this embodiment, the projection lens LG100 constituting the projection optical system 420 can include multiple lens elements, and is shown here in a simplified form.

[0056] The projection optical system PS100 is composed of a projection lens LG100 and an optical member PP100, and has a projection optical axis Oa1 in the X direction as a reference axis. The optical member PP100 can include optical members such as a prism, an optical filter, and a cover glass, and in this embodiment, can include, for example, a cover glass such as the light modulation element D100, and a part of the prism optical system PG100.

[0057] In this embodiment, the light modulation element D100 is located at a conjugate point on the reduction side of the projection optical system PS100. The light beam of the projection light Lp emitted from the light modulation element D100 passes through the projection lens LG100 in the +X direction of the XZ plane along the projection optical axis Oa1, and forms a first image M100 on a first surface W100 at a conjugate point on the enlargement side by the projection optical system PS100. In this embodiment, the first surface W100 is the screen 430.

[0058] A ray of external light Le passes from the first surface W100 along the projection optical axis Oa1 in the -X direction of the XZ plane, passes through the projection lens LG100, and enters the prism optical system PG100. In this embodiment, prism surfaces P1, P2, and P3 of the prism optical system PG100 are the projection light entrance surface 322 and the projection light exit surface 321 of the TIR prism 310, and the internal reflection surface 352 of the imaging light reflecting prism 350, respectively.

[0059] At least a part of the external light Le, the imaging light Li, is internally reflected and deflected by the prism surfaces P1, P2, and P3 in order, and is emitted from the prism surface P4 along the imaging optical axis Ob1 in the YZ plane. In this embodiment, the prism surface P4 that transmits the imaging light Li is the imaging light emission surface 353 of the imaging light reflecting prism 350. Inside the prism optical system PG100, the light rays of the imaging light Li are reflected by the prism surfaces P1 and P2, and then form an intermediate image Ms100 in the prism optical system PG100 that is conjugate with the first surface W100. Thereafter, the light rays of the imaging light Li further travel within the prism optical system PG100, are reflected by the prism surface P3, and are transmitted through the prism surface P4 to be emitted along the imaging optical axis Ob1, and pass through the imaging optical system LG200 in the Y direction of the YZ plane. In this way, the imaging light relay optical system RS100 relays the intermediate image Ms100 to form the second image M20 on the second surface W200. In this embodiment, the imaging optical system LG200 is composed of a lens group 440, and the second surface W200 is an imaging element 450. The imaging light relay optical system RS100 is composed of the lens group 440 included in the imaging optical system LG200.

[0060] In this embodiment, the projection lens LG100 is configured to have an aberration correction performance in the first image M100 on the first surface W100 (screen 430) by combining with the reduction-side optical member PP100.

[0061] The projection imaging optical system LS100 guides and emits the imaging light Li, which is at least a part of the light rays of the external light Le, in the direction of the imaging optical axis Ob1 via the projection lens LG100, the prism optical system PG100, and the imaging optical system LG200 in this order, and forms an intermediate image in the prism optical system PG100 on a second surface W200 (image sensor 450). At this time, the prism optical system PG100 and the imaging optical system LG200 are configured in combination with the projection lens LG100 to have an aberration correction performance in the second image M200.

[0062] In this manner, in this embodiment, the rays of the imaging light Li, which are at least a part of the rays of the external light Le incident along the projection optical axis Oa1 on the XZ plane, are deflected and guided toward the second surface W200 along the imaging optical axis Ob1 on the YZ plane. Also, an intermediate image Ms100 is formed inside the prism optical system PG100, and the prism optical system PG100 and the imaging optical system LG200 are configured to cancel aberrations occurring in the rays of the imaging light Li, which are at least a part of the rays of the external light Le that have passed through the projection lens LG100, thereby realizing aberration correction of the entire system of the projection imaging optical system LS100.

[0063] In this embodiment, the prism optical system PG100 and the imaging optical system LG200 are combined with the projection lens LG100 to correct the aberration of the entire system, so that the intermediate image Ms100 formed in the prism optical system PG100 has aberration. Figures 4A and 4B are diagrams showing the longitudinal chromatic aberration and spherical aberration of the projection imaging optical system LS100 of Figure 3. Figure 4A shows the chromatic aberration and spherical aberration at the position of the light modulation element D100, and Figure 4B shows the chromatic aberration and spherical aberration at the position of the intermediate image Ms100. Note that the aberration curves in Figures 4A and 4B show the aberration values ​​of the longitudinal chromatic aberration and spherical aberration for each of the e-line (light with a wavelength of 546.1 nm), g-line (light with a wavelength of 435.8 nm), c-line (light with a wavelength of 656.3 nm), f-line (light with a wavelength of 486.1 nm), and d-line (light with a wavelength of 587.6 nm).

[0064] In this embodiment, in the projection optical system PS100, the light modulation element D100 is located at a conjugate point on the reduction side of the projection optical system PS100, and the first surface W100 is located at a conjugate point on the enlargement side. In addition, the combination of the projection lens LG100 and the optical member PP100 is configured to have an aberration correction performance in the first image formation M100 on the first surface W100. Therefore, as shown in FIG. 4A, aberration correction is performed on the chromatic aberration and spherical aberration for the light beam from the first surface W100 at the position of the light modulation element D100.

[0065] In this case, as shown in Fig. 4B, the light rays of the imaging light Li incident on the prism optical system PG100 via the projection lens LG100 from the first surface W100 tend to have an increase in axial chromatic aberration indicated by an arrow B1 and an over-spherical aberration indicated by an arrow B2 at the position of the intermediate image Ms100. In this embodiment, the prism optical system PG100 and the imaging optical system LG200 are configured to cancel out aberrations occurring in the light rays of the imaging light Li, which are at least a part of the light rays of the external light Le transmitted through the projection lens LG100, in the second image formation M200, in particular, the axial chromatic aberration (arrow B1) and spherical aberration (arrow B2) occurring in the light rays of the imaging light Li at the position of the intermediate image Ms100. In this way, the prism optical system PG100 and the imaging optical system LG200, which are configured to have aberration correction performance in the second image M200, can achieve aberration correction of the entire system without interfering with the projection lens LG100, which is configured to have aberration correction performance in the first image M100.

[0066] Moreover, the projection imaging optical system LS100 of this embodiment employs a configuration in which the optical path is bent within the prism optical system PG100. This makes it possible to suppress the spread of the light flux of the imaging light Li, and to guide the light ray of the imaging light Li toward the imaging element 450 along the imaging optical axis Ob1 in the YZ plane substantially perpendicular to the projection optical axis Oa1. This makes it possible to arrange a plurality of optical components necessary for the aberration correction configuration in the imaging optical system LG200 constituting the imaging optical system without interfering with the arrangement of the projection optical system PS100. The configuration of the prism optical system PG100 will be described below with reference to FIGS. 5 and 6.

[0067] <Configuration of the prism optical system PG100> Fig. 5 is a perspective view showing the configuration of the prism optical system PG100 of the projection imaging optical system LS100 of Fig. 3. Fig. 6 is a cross-sectional view of the prism optical system PG100 of the projection imaging optical system LS100 of Fig. 3. The prism optical system PG100 of Fig. 5 is shown as having an integral configuration of an imaging light reflecting prism 350 and a TIR prism 310. For clarity, each light beam is shown as only the chief ray.

[0068] The TIR prism 310 includes a first prism 320 and a second prism 330, each of which has a substantially triangular prism shape. The first prism 320 and the second prism 330 are arranged in order from the front side (the +X side in the figure) of the projection optical axis Oa1 along the projection optical axis Oa1. The second prism 330 has an illumination light reflecting surface 331, and the incident illumination light Ls is totally reflected by the illumination light reflecting surface 331 and introduced into the light modulation element D100. The first prism 320 has a projection light incident surface 322 and a projection light exit surface 321 for the projection light Lp that is reflected by the light modulation element D100 and travels in the +X direction. The first prism 320 and the second prism 330 are joined together with a parallel gap provided between the projection light incident surface 322 and the illumination light reflecting surface 331. As a result, the projection light Lp from the light modulation element D100 passes through the second prism 330 and enters the first prism 320, and then passes through the first prism 320 again to be output from the projection light exit surface 321 along the projection optical axis Oa1 to the projection optical system and form an image. The DMD-OFF light Lf passes through the TIR prism 310 in a direction deflected from the projection optical axis Oa1 and is removed.

[0069] The imaging light reflecting prism 350 arranged adjacent to the first prism 320 has an imaging light incident surface 351, an internal reflection surface 352, and an imaging light exit surface 353. In this embodiment, the first prism 320 and the imaging light reflecting prism 350 of the TIR prism 310 are integrally configured at the imaging light incident surface 351.

[0070] As shown in the figure, external light Li incident on the first prism 320 in the -X direction from the projection optical system (not shown in FIG. 5) forms a beam spot S1 on the projection light incident surface 322 (prism surface P1). The projection light incident surface 322 is coated with a partial reflection coating, and the imaging light Li, which is at least a part of the incident external light Li, is internally reflected by the partial reflection coating and reaches the projection light exit surface 321 (prism surface P2) to form a beam spot S2. Next, the imaging light Li is internally reflected at the projection light exit surface 321, reaches the imaging light entrance surface 351 of the imaging light reflecting prism 350, and passes through the imaging light entrance surface 351 to enter the imaging light reflecting prism 350.

[0071] In the imaging light reflecting prism 350, the imaging light Li forms a beam spot S3 on the internal reflecting surface 352 (prism surface P3) and is internally reflected, and then is emitted from the imaging light emitting surface 353 (prism surface P4) along the imaging optical axis Ob1 in the +Y direction shown in the figure, and can be imaged on the imaging element 450 by the imaging optical system LG200.

[0072] Thus, in this embodiment, the imaging light Li can be internally reflected three times within the prism optical system PG100, and then introduced into the imaging element 450 along the imaging optical axis Ob1 in the YZ plane substantially perpendicular to the projection optical axis Oa1. Note that the present disclosure does not limit the number of times the imaging light Li is internally reflected within the prism optical system PG100. Also, although not limited thereto, preferably, at least a portion of the imaging light Li may be totally reflected at the projection light exit surface 321 (prism surface P2) and enter the imaging light reflecting prism 350. This allows the imaging light to be used efficiently.

[0073] The partial reflection coating applied to the projection light incident surface 322 (prism surface P1) may be a visible partial reflection coating or an infrared partial reflection coating. When a visible partial reflection coating is applied, the projection light Lp in the visible range incident on the projection light incident surface 322 from the light modulation element D100 is also partially reflected due to the reflection characteristics of the visible partial reflection coating, so that loss occurs in the projection light Lp. In the case of this embodiment, the visible partial reflection coating has a reflectance of 2% or more and 15% or less for light in the visible range with a wavelength of 400 nm to 700 nm. This allows imaging by taking in part of external light in the visible range without causing a large loss in the projection light Lp. It should be noted that the reflection characteristics of the visible partial reflection coating are not limited to this.

[0074] On the other hand, when an infrared partial reflection coating is applied, in this embodiment, the infrared partial reflection coating reflects imaging light with a reflectance of 50% or more for infrared light with a wavelength of 750 nm or more. The reflection characteristics of the infrared partial reflection coating are not limited to this. In general, the projection light incident on the projection optical system is light in the visible range with a wavelength of 400 nm to 700 nm and does not contain light components in the infrared range. Therefore, by taking in external light in the infrared range as imaging light and transmitting approximately 100% of the projection light Lp in the visible range, imaging can be performed without any loss in the projection light.

[0075] <Configuration of the Prism Optical System According to the Modified Example> Next, a prism optical system PG100a according to Modification 1 and a prism optical system PG100b according to Modification 2 of the prism optical system PG100 will be described with reference to Figures 7 and 8. Figure 7 is a cross-sectional view of the prism optical system PG100a according to Modification 1 of the embodiment of the present disclosure, and Figure 8 is a cross-sectional view of the prism optical system PG100b according to Modification 2 of the embodiment of the present disclosure.

[0076] The prism optical system PG100a shown in Fig. 7 is composed of a TIR prism 310a and an imaging light reflecting prism 350a, similar to the prism optical system PG100 shown in Fig. 5-6. As shown in the figure, the prism optical system PG100a differs from the prism optical system PG100 in that the imaging light reflecting prism 350a is formed separately from the TIR prism 310a at the imaging light incident surface 351a.

[0077] 7, in the prism optical system PG100a, the first prism 320a has a prism surface 323a adjacent to the imaging light reflecting prism 350a. The first prism 320a and the imaging light reflecting prism 350a are formed between the prism surface 323a and the imaging light incident surface 351a and separated by a parallel gap.

[0078] In the prism optical system PG100a, external light Le incident on the first prism 320a in the -X direction forms a beam spot S1a on the projection light incident surface 322a (prism surface P1). Due to the partial reflection coating of the projection light incident surface 322a, at least a part of the incident external light Le is internally reflected as imaging light Lia, reaches the projection light exit surface 321a (prism surface P2) and forms a beam spot S2a. Subsequently, the imaging light Lia is internally reflected at the projection light exit surface 321a, transmits through the prism surface 323a, reaches and transmits through the imaging light incident surface 351a of the imaging light reflecting prism 350a, and enters the imaging light reflecting prism 350a. In the imaging light reflecting prism 350a, the imaging light Lia forms a beam spot S3a on the internal reflecting surface 352a (prism surface P3), and after being internally reflected by the internal reflecting surface 352a, is emitted from the imaging light emitting surface 353a (prism surface P4).

[0079] As described above, the projection light Lp passes through the TIR prism and is emitted to the projection optical system. When passing through the TIR prism, heat is generated by the high-energy projection light Lp, so the TIR prism needs to be made of a heat-resistant glass material. In the prism optical system PG100, if the imaging light reflecting prism is formed integrally with the TIR prism, it is affected by heat conduction, so a glass imaging light reflecting prism is necessary. In addition, in order to suppress the occurrence of aberration due to a change in refractive index, it is desirable to make the imaging light reflecting prism 350 from the same glass material as the TIR prism 310. On the other hand, in the prism optical system PG100a shown in FIG. 7, the imaging light reflecting prism 350a is formed separately from the TIR prism 310a, so that heat conduction is suppressed, and therefore it can be made by adopting a glass material or a resin material different from that of the TIR prism 310a. Therefore, by forming the imaging prism separately from the TIR prism, a high degree of freedom in material selection is possible. Another advantage of resin optical components is that they have excellent processability, making it possible to manufacture prism members having optical surfaces with complex geometric shapes at low cost.

[0080] The prism optical system PG100b shown in FIG. 8 is composed of a TIR prism 310b, an imaging light reflecting prism 350b, and a third prism 340, and is different from the prism optical system PG100 in that it includes the third prism 340. As shown in the figure, in this embodiment, the first prism 320b and the imaging light reflecting prism 350b of the TIR prism 310b are integrally configured. However, the present disclosure is not limited to this. In the prism optical system PG100b, the first prism 320b and the imaging light reflecting prism 350b of the TIR prism 310b may be formed separately, similar to the prism optical system PG100a shown in FIG. 7.

[0081] As shown in FIG. 8, the third prism 340 of the prism optical system PG100b has a first prism surface 341 and a second prism surface 342. The first prism surface 341 is joined to the projection light incident surface 322b of the first prism 320b of the TIR prism 310b. The second prism surface 342 intersects with the first prism surface 341 at an angle. The second prism surface 342 and the illumination light reflecting surface 331b of the second prism 330b of the TIR prism 310b are arranged opposite to each other with a parallel gap therebetween. Although not limited thereto, in this embodiment, the third prism 340 has a wedge shape. The first prism surface 341 and the second prism surface 342 preferably form an apex angle A of 2 degrees to 10 degrees, and in this embodiment, form an apex angle A of about 3 degrees.

[0082] In the prism optical system PG100b, the external light Le incident on the first prism 320b in the -X direction forms a beam spot S1b on the projection light incident surface 322b (prism surface P1). Due to the partial reflection coating of the projection light incident surface 322b, at least a part of the incident external light Le is internally reflected as imaging light Lib, reaches the projection light exit surface 321b (prism surface P2), and forms a beam spot S2b. Next, the imaging light Lib is internally reflected on the projection light exit surface 321b, and enters the imaging light reflecting prism 350b. In the imaging light reflecting prism 350b, the imaging light Lib forms a beam spot S3b on the internal reflection surface 352b (prism surface P3), and after being internally reflected on the internal reflection surface 352b, is emitted from the imaging light exit surface 353b (prism surface P4).

[0083] For comparison, Fig. 8 also shows a beam spot S3a formed by the imaging light Lia on the internal reflection surface 352a (not shown) of the imaging light reflecting prism 350a in the prism optical system PG100a shown in Fig. 7. As shown in the figure, the beam spot S3b formed by the imaging light Lib in the prism optical system PG100b is smaller than the beam spot S3a, and the center position of the beam spot S3b is closer to the projection optical axis Oa1 side by a distance D than the center position of the beam spot S3a.

[0084] In the prism optical system PG100b, the beam spot S3b formed on the internal reflection surface of the imaging light reflecting prism by the imaging light Lib changes in this way because the third prism 340 is provided. As shown in FIG. 8, the second prism 330b is configured such that an angle α1 is formed between an illumination light reflecting surface 331b and a bottom surface 332b perpendicular to the projection optical axis Oa1. The angle α1 is limited by the characteristics of the DMD as the light modulation element D100 and cannot be freely designed. In addition, since the illumination light reflecting surface 331b and the projection light incident surface 322b are arranged opposite to each other with a parallel gap therebetween, the reflection angle of the imaging light on the projection light incident surface is also limited. Therefore, by providing the wedge-shaped third prism 340, the angle β between the projection light incident surface 322b and the projection optical axis Oa1 can be increased by the apex angle A of the wedge-shaped third prism 340, thereby adjusting the reflection angle of the imaging light Lib at the projection light incident surface 322b. This makes it possible to make the prism optical system PG100b more compact.

[0085] In this way, the optical path of the imaging light Li can be folded in the prism optical system of this embodiment, and the imaging light Li can be emitted to the imaging optical system LG200 along the imaging optical axis Ob1 in the YZ plane substantially perpendicular to the projection optical axis Oa1 at the time of incidence. The imaging optical system LG200 has a plurality of optical elements arranged to achieve aberration correction performance, and can be easily incorporated into the projection type image display device without interfering with the arrangement of the projection optical system PS100. In addition, the imaging optical system LG200 may be configured as an imaging optical system that changes the imaging magnification by relatively moving each optical element of the imaging optical system LG200 as necessary, and forms a reduced image on the imaging element 450, or as an imaging optical system that forms an image at the same magnification or an enlarged image.

[0086] In this embodiment, the imaging optical system LG200 can include a plurality of lens elements including, for example, a positive lens, a negative lens, a cemented lens, and the like. The imaging optical system LG200 and the prism optical system of this embodiment are configured to cancel aberration occurring in the light beam of the imaging light Li, which is at least a part of the light beam of the external light Le transmitted through the projection lens LG100, and have an aberration correction performance in the second image formation M200. The imaging optical system LG200 and the prism optical system are combined with the projection lens LG100, which has an aberration correction performance for the projection light Lp, to realize aberration correction of the entire system. The aberration correction configuration of the imaging optical system LG200 can adopt a conventionally known optical design.

[0087] As a configuration of the imaging optical system, an optical system with a magnification of 1:1 may be mainly composed of four lens groups each having positive, negative, negative, and positive powers, such as a double Gauss, and further, in order to correspond to the image side telecentricity of the projection lens, an image plane correction lens having a positive power may be added to the prism optical system side, so that a five-group lens group configuration having positive, positive, negative, negative, and positive powers may be obtained from the prism optical system side to the imaging element side. Here, the two lens groups having negative powers are configured as a cemented convex and concave lens to correct various aberrations including chromatic aberration.

[0088] When the effective sizes of the light modulation element and the imaging element are different, the imaging optical system is configured so as to form an image on the imaging element with a lateral magnification that matches the size ratio. Figures 13-15 are design examples of the imaging optical system with a lateral magnification of 0.4. Figure 13 is a lens arrangement diagram showing the configuration of the imaging optical system according to Example 1. Figure 14 is a diagram showing the longitudinal aberration of the imaging optical system according to Example 1. Figure 15 is a diagram showing surface data of the imaging optical system according to Example 1. Various data are as follows. ·Focal length: f=50.6mm F value: F1.6 (aperture diameter φ5.6mm) ·Optical total length: 55mm ·Horizontal magnification: 0.4x Since the lateral magnification is 0.4, as shown in Figs. 13 and 15, the imaging optical system LG200 is composed of five lens groups having positive, positive, negative, positive, and positive powers in this order from the prism optical system PG100 side to the imaging element 450 side. The first lens group is composed of lens element L1. The second lens group is composed of lens element L2. The third lens group is composed of a cemented lens of lens element L3 and lens element L4. The fourth lens group is composed of a cemented lens of lens element L5 and lens element L6. The fifth lens group is composed of lens element L7. In addition, an aperture Ap is disposed between lens element L4 and lens element L5, and an IR cut filter IR and a window glass WG are disposed between lens element L7 and the imaging element 450.

[0089] In this case, as mentioned above, the total optical length is 55 mm, and the F-number is F1.6. For example, if the F-number of the light on the prism optical system side is F2.0, the F-number on the imaging element side will be F0.85 due to the lateral magnification, but since crosstalk occurs due to the on-chip microlens of the small imaging element, a correction is made to cut the light at the aperture Ap in the imaging optical system and make it F1.6.

[0090] As shown in FIG. 3, in this embodiment, an intermediate image Ms100 is formed by the light beam of the imaging light Li inside the prism optical system. In the configuration of a conventional optical system, when the light beam of the imaging light that has passed through the prism is imaged without forming an intermediate image, the specifications of the optical system are limited by the constraint relationship between the focal length of the entire optical system, the size and shape of the prism, and the angle of view of the optical system. Therefore, the projection imaging optical system LS100 of this embodiment is configured to form an intermediate image Ms100 inside the prism optical system by utilizing the propagation optical path length of the imaging light Li inside the prism optical system, and the imaging light relay optical system RS100 is configured to image the intermediate image outside the prism optical system. With this configuration, in the image formation M200, by positioning the object side inside the medium of the prism optical system, a sufficient distance can be secured to insert the imaging optical system LG200 having an aberration correction configuration on the image plane side, and the specifications of the entire optical system can be controlled more freely. This makes it possible to realize aberration correction of the entire system without interfering with the optical design of the projection optical system PS100.

[0091] In this embodiment, the intermediate image Ms100 is formed in front of the internal reflection surface of the prism optical system. Preferably, the intermediate image Ms100 is formed in front of the final internal reflection surface (prism surface P3) of the prism optical system. This makes it possible to suppress the spread of the emitted imaging light beam. In this embodiment, as shown in FIG. 3, the intermediate image Ms100 is formed in front of the internal reflection surface 352 (prism surface P3) of the imaging light reflecting prism 350. Furthermore, by providing a curvature to one or more prism surfaces of the prism optical system, the spread of the emitted imaging light Li beam can be controlled, and the projection imaging optical system can be made more compact. In this case, the imaging light relay optical system is composed of a part of the prism optical system and the imaging optical system.

[0092] Specifically, in this embodiment, for example, the internal reflection surface 352 (prism surface P3) and / or the imaging light exit surface 353 (prism surface P4) of the prism optical system PG100 are provided with a curvature so as to impart positive power to the imaging light ray, thereby making it possible to reduce the number and aperture of the lens elements constituting the imaging optical system LG200. This makes it possible to realize aberration correction performance of the entire system and to realize a compact imaging optical system. Hereinafter, with reference to Figs. 9 to 12, the configurations of the projection imaging optical system having a curvature on the prism surface according to the second and third embodiments of the present disclosure will be described.

[0093] Example 2 FIG. 9 is a schematic diagram showing the configuration of a projection imaging optical system LS10A according to a second embodiment of the present disclosure and the optical path through which the principal ray passes. Note that the inset (a) of FIG. 9 is a diagram simply showing the propagation path of the projection light Lp, and the inset (b) is a diagram simply showing the propagation path of the imaging light Li. FIG. 10 is an image diagram showing the arrangement of the projection imaging optical system LS100A of the projection type image display device of FIG. 2 having the configuration of the projection imaging optical system according to the second embodiment and the propagation of light. Note that, in FIG. 10, in order to facilitate understanding, the curved optical path of the imaging light Li is expanded into a straight line to show the manner of light propagation, as in FIG. 3. That is, in FIG. 10, the imaging optical axis Ob1 on the YZ plane is expanded equivalently coaxially with the projection optical axis Oa1 on the XZ plane, and the optical path of the projection light Lp on the XZ plane and the optical path of the imaging light Li deflected to the YZ plane in the prism optical system PG100A are illustrated on the same plane.

[0094] In the projection imaging optical system LS10A shown in Fig. 9, the same elements as those in the projection imaging optical system LS10 in Fig. 1 are denoted by the same reference numerals, and the description thereof will be omitted. As shown in the figure, the projection imaging optical system LS10A according to the second embodiment differs from the projection imaging optical system LS10 according to the first embodiment in the prism surface P3A of the prism optical system PG10A. The prism surface P3A is formed into a curved surface having a concave shape that imparts positive power to the reflected imaging light rays.

[0095] In this embodiment, inside the prism optical system PG10A, the light rays of the imaging light Li are internally reflected R1, R2 by the prism surfaces P1, P2, and then form an intermediate image Ms10 at a position Im in the prism optical system PG10A that is conjugate with the first surface W10. After that, the light rays of the imaging light Li proceed further inside the prism optical system PG10A and are internally reflected R3 by the prism surface P3A. At this time, the light rays of the imaging light Li are focused by the positive power of the concave prism surface P3A, and are transmitted through the prism surface P4 and emitted along the second optical axis Ob, pass through the imaging optical system LG20A in the Y direction shown in the figure, and form a second image M20A on the second surface W20. In this case, the concave shape of the prism surface P3A of the prism optical system PG10A focuses the light rays of the imaging light Li as a concave mirror. The imaging light relay optical system RS10A is composed of the concave surface of the prism surface P3A of the prism optical system and the imaging optical system LG20B. The imaging optical system LG20A can be composed with a small number of lens elements and a small aperture due to the convergence of the incident imaging light Li. This allows the projection imaging optical system LS10A to be made even more compact.

[0096] In the projection imaging optical system LS100A shown in Fig. 10, the same elements as those in the projection imaging optical system LS100 in Fig. 3 are denoted by the same reference numerals, and the description thereof will be omitted. As shown in the figure, in the present embodiment, in the prism optical system PG100A, the internal reflection surface 352A (prism surface P3A) of the imaging light reflecting prism 350A can be configured to have a shape of a concave surface C1 facing the direction in which the imaging light Li is internally reflected by the internal reflection surface 352A. The shape of the concave surface C1 can focus the imaging light reflected as a concave mirror having a positive power. The imaging light relay optical system RS100A is configured by the concave surface C1 of the internal reflection surface 352A of the prism optical system PG100A and the lens group 440A provided in the imaging optical system LG200A. In this way, by providing a curvature to the internal reflection surface 352A of the imaging light reflecting prism 350A, the spread of the imaging light Li within the prism optical system PG100A is suppressed, and the spread of the light flux of the outgoing imaging light LiA can be regulated to form the second image M200A. Therefore, the subsequent imaging optical system LG200A can be configured using thinner optical components with smaller optical component diameters than the imaging optical system LG200 shown in Fig. 3. This allows the configuration of a compact imaging optical system.

[0097] Example 3 Next, FIG. 11 is a schematic diagram showing the configuration of a projection imaging optical system LS10B according to a third embodiment of the present disclosure and the optical path through which the principal ray passes. Note that the inset (a) of FIG. 11 is a diagram simply showing the propagation path of the projection light Lp, and the inset (b) is a diagram simply showing the propagation path of the imaging light Li. FIG. 12 is an image diagram showing the arrangement of the projection imaging optical system LS100B of the projection type image display device of FIG. 2 having the configuration of the projection imaging optical system according to the third embodiment and the propagation of light. Note that, in FIG. 12, similar to FIG. 3, in order to facilitate understanding, the curved optical path of the imaging light Li is expanded into a straight line to show the mode of light propagation. That is, in FIG. 12, the imaging optical axis Ob1 on the YZ plane is expanded equivalently coaxially with the projection optical axis Oa1 on the XZ plane, and the optical path of the projection light Lp on the XZ plane and the optical path of the imaging light Li deflected to the YZ plane in the prism optical system PG100B are illustrated on the same plane.

[0098] In the projection imaging optical system LS10B shown in Fig. 11, the same elements as those in the projection imaging optical system LS10 in Fig. 1 are denoted by the same reference numerals, and description thereof will be omitted. As shown in the figure, the projection imaging optical system LS10B according to Example 3 differs from the projection imaging optical system LS10 according to Example 1 in the prism surface P4B of the prism optical system PG10B. The prism surface P4B is formed into a curved surface having a convex shape that imparts positive power to the ray of imaging light that transmits therethrough.

[0099] In this embodiment, inside the prism optical system PG10B, the light rays of the imaging light Li are internally reflected R1, R2 by the prism surfaces P1, P2, and then form an intermediate image Ms10 at a position Im in the prism optical system PG10B that is in a conjugate relationship with the first surface W10. After that, the light rays of the imaging light Li further advance in the prism optical system PG10B, and after being internally reflected R3 by the prism surface P3, they reach the prism surface P4B, which is a transmitting surface. At this time, the light rays of the imaging light Li are focused by the positive power of the convex prism surface P4B, and are transmitted through the prism surface P4B and emitted along the second optical axis Ob, and pass through the imaging optical system LG20B in the illustrated Y direction to form a second image M20B on the second surface W20. In this case, the convex shape of the prism surface P4B of the prism optical system PG10B functions as a convex lens to focus the light rays of the imaging light Li. The imaging light relay optical system RS10B is composed of the convex surface of the prism surface P4B of the prism optical system and the imaging optical system LG20B. The imaging optical system LG20B can be configured with a small number of lens elements and a small aperture due to the convergence of the incident imaging light Li. This allows the projection imaging optical system LS10B to be made even more compact.

[0100] In the projection imaging optical system LS100B shown in FIG. 12, the same elements as those in the projection imaging optical system LS100 in FIG. 3 are denoted by the same reference numerals, and the description thereof will be omitted. As shown in the figure, in the present embodiment, in the prism optical system PG100B, the imaging light exit surface 353B (prism surface P4) of the imaging light reflecting prism 350B can be configured to have a shape of a convex surface C2 facing the direction in which the imaging light Li is emitted to the second surface W200 (imaging element 450). The shape of the convex surface C2 can focus the imaging light emitted as a convex lens having a positive power. The imaging light relay optical system RS100B is configured by the convex surface C2 of the imaging light exit surface 353B of the prism optical system PG100B and the lens group 440B provided in the imaging optical system LG200B. In this way, by providing a curvature to the imaging light exit surface 353B of the imaging light reflecting prism 350B, the spread of the light flux of the exiting imaging light LiB can be regulated to form the second image M200B. Therefore, the number of optical components of the subsequent imaging optical system LG200B can be reduced compared to the imaging optical system LG200 shown in Fig. 3. This makes it possible to configure a compact imaging optical system.

[0101] As described above, the above-mentioned embodiments have been described as examples of the technology disclosed in this application. However, the technology in this disclosure is not limited to these, and can be applied to embodiments in which modifications, substitutions, additions, omissions, etc. are made. In addition, it is also possible to combine the components described in each of the above-mentioned embodiments to create a new embodiment.

[0102] The present disclosure does not limit the shape of each prism. For example, each prism constituting the prism optical system may be substantially triangular prism-shaped or substantially quadrangular prism-shaped, or may have another shape.

[0103] In the above embodiment, the prism surface of the prism optical system is described as being concave or convex, but the present disclosure is not limited thereto. For example, one or more prism surfaces of the prism optical system may be configured to have a free-form curved surface shape.

[0104] In addition, in the above embodiment, a single-panel projection type image display device having a single light modulation element has been described, but the present disclosure is not limited thereto. The projection imaging optical system according to the present disclosure can also be applied to, for example, a three-panel projection type image display device having three light modulation elements, and the prism optical system according to the present disclosure can include a color separation / combination prism of the three-panel projection type image display device.

[0105] As described above, the embodiment has been described as an example of the technology in the present disclosure. For this purpose, the attached drawings and detailed description have been provided. Therefore, among the components described in the attached drawings and detailed description, not only components essential for solving the problem but also components that are not essential for solving the problem in order to exemplify the above technology may be included. Therefore, the fact that these non-essential components are described in the attached drawings or detailed description should not be used to immediately determine that these non-essential components are essential.

[0106] Although the present invention has been fully described in relation to the preferred embodiment with reference to the accompanying drawings, various modifications are possible within the scope of the claims, and such modifications and embodiments obtained by appropriately combining the technical means disclosed in the different embodiments are also included within the technical scope of the present invention. [Industrial Applicability]

[0107] The present disclosure is applicable to imaging optical systems and various projection-type image display devices. [Explanation of symbols]

[0108] LS10, LS100, LS10A, LS100A, LS10B, LS100B Projection imaging optical system 200 Illumination optical system 20 Light source unit 21 Semiconductor laser element 22 Collimating lens 31,32 Afocal lenses 33,34,35 Condenser lens 41 Diffuser 42 λ / 4 plate 45 Dichroic Mirror 46 Rod Integrator 50 Phosphor Wheel 60 Color Wheel 73, 74, 75 Lenses constituting the illumination light relay optical system 310,310a,310b TIR Prism 320, 320a, 320b, 330, 330b, 340 Prism 350, 350a, 350b, 350A, 350B Imaging light reflecting prism 321, 321a, 321b Projection light exit surface 322, 322a, 322b Projection light entrance surface 331,331b Illumination light reflecting surface 351, 351a Imaging light incidence surface 352,352a,352b,352A Internal reflective surface 353, 353a, 353b, 353B Imaging light exit surface 420 Projection Optical System 430 Screens 440, 440A, 440B Lens Group 450 image sensor 500 Projection Imaging System 600 Projection type image display device C1 concave C2 convex Ls illumination light Lp Projection Light Le External Light Li, Lia, Lib, LiA, LiB Imaging light S1, S2, S3, S1a, S2a, S3a, S1b, S2b, S3b Beam spot Lf DMD-OFF light Oa, Oa1, Ob, Ob1 Optical axis Ms10,Ms100 intermediate image D10, D100 Light Modulation Device (DMD) M10, M100, M20, M20A, M20B, M200, M200A, M200B Imaging W10,W100,W20,W200 Imaging plane P1, P2, P3, P3A, P4, P4B, 323a, 341, 342 prism surfaces LG10,LG100 Projection Lens LG20, LG200, LG20A, LG200A, LG20B, LG200B Imaging optical system PG10,PG100,PG100b,PG10A,PG100a,PG10B,PG100A,PG100B Prism optical system RS10, RS100, RS10A, RS100A, RS10B, RS100B Imaging optical relay optical system PS10,PS100 Projection optical system PP10, PP100 Optical components

Claims

1. A projection imaging optical system for use in a projection-type image display device, comprising: a projection lens that forms a first image on a first surface using a beam of projection light emitted in a forward direction along a first optical axis from the light modulation element; a prism optical system that deflects an imaging light beam, which is at least a part of an external light beam that is propagated from the first surface in a direction opposite to the forward direction and is incident via the projection lens, and outputs the imaging light beam along a second optical axis, and an intermediate image is formed therein by the imaging light beam; an imaging optical system that forms a second image on a second surface by using the light beam of imaging light emitted from the prism optical system; Equipped with a position of the intermediate image is in a conjugate relationship with respect to the projection lens, and the projection lens is configured to have an aberration correction performance in the first image formation, The prism optical system and the imaging optical system are configured to have an aberration correction performance in the second image formation in combination with the projection lens. Projection imaging optical system.

2. the projection lens constitutes at least a part of a projection optical system that projects a light beam of the projection light from the light modulation element onto the first surface to display an image. The projection imaging optical system according to claim 1 .

3. The prism optical system internally reflects the incident imaging light beam multiple times; the second optical axis lies in a plane substantially perpendicular to the first optical axis. The projection imaging optical system according to claim 1 .

4. the prism optical system and the imaging optical system are configured to cancel axial chromatic aberration and spherical aberration occurring in the light beam of the imaging light at the position of the intermediate image. The projection imaging optical system according to claim 1 .

5. The prism optical system has two or more internal reflective surfaces; At least one of the two or more internal reflective surfaces is formed into a curved surface having a concave shape so as to impart positive power to the reflected light beam of the imaging light. The projection imaging optical system according to claim 1 .

6. the prism optical system has an exit surface that transmits and emits at least a portion of the imaging light toward the imaging optical system, the exit surface is formed in a curved shape so as to give positive power to the light ray of the imaging light passing therethrough; The projection imaging optical system according to claim 1 .

7. a part of the prism optical system and the imaging optical system constitute an imaging light relay optical system that forms the intermediate image on the second surface. The projection imaging optical system according to claim 5 .

8. The imaging optical system is configured as an optical system that reduces and forms the second image on an imaging element. The projection imaging optical system according to claim 1 .

9. The imaging optical system is configured as an optical system that forms an image of the second image on an imaging element at a magnification of 1:1 or a magnified image. The projection imaging optical system according to claim 1 .

10. an illumination optical system for supplying illumination light; The projection imaging optical system according to claim 1 , one or more light modulation elements that spatially modulate the light supplied by the illumination optical system and guided by the prism optical system to be incident thereon, and generate the projection light according to image information; an image pickup element that converts the second image formed by the projection imaging optical system into an electrical image signal; Equipped with Projection type image display device.

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