JP7796896B2 - Projection-type image display device - Google Patents

Description

This disclosure relates to a prism group and a projection-type image display device equipped with the same.

Projection-type image display devices have been known in the past that have both a projection optical system with an image sensor built into the main body that projects projection light onto a projection target, and an imaging optical system that uses external light from the projection target to form an image on the imaging sensor. Such projection-type image display devices have the function of projecting an image onto the projection target and capturing the projected image. One example of this type of projection-type image display device is described in Patent Document 1.

The projector (projection-type image display device) described in Patent Document 1 is equipped with a TIR prism that guides illumination light from a light source to a light modulation element and outputs light reflected by the light modulation element to a projection optical system. Light emitted from a light-emitting element enters the TIR prism via a projection lens, is reflected by the reflective surface of the TIR prism, and is then imaged on an imaging element.

JP 2013-218262 A

In the projector described in Patent Document 1, a TIR prism is used as an optical path branching element for illumination light, projection light, and imaging light. The interface between the two prisms that make up the TIR prism transmits the projection light to form an image on the screen, while simultaneously reflecting light from the screen and emitting it as imaging light toward the imaging element. With this type of prism configuration, the prism interface reflects not only the imaging light but also a portion of the projection light. This results in a loss of projection light, resulting in a decrease in brightness. Furthermore, in order to maintain the amount of projection light, the amount of imaging light taken in is limited. This limits imaging sensitivity, making it difficult to achieve sufficient imaging sensitivity, especially in dark environments.

In this way, there is a demand to capture light propagating in the opposite direction to the light exiting the prism without affecting the light exiting the prism.

The purpose of this disclosure has been made in consideration of these circumstances, and is to provide a group of prisms that can capture light propagating in the opposite direction to the light emitted from the prism without affecting the light emitted from the prism, and a projection-type image display device equipped with the same.

In order to achieve the above-mentioned objective, the prism group according to the present disclosure is a prism group that reflects illumination light and guides it to a light modulation element on the rear side, and transmits light reflected by the light modulation element and guides it forward, and includes a first prism having a first prism surface and receiving the illumination light; a second prism having a second prism surface arranged on the front side of the first prism and facing the first prism surface via an air gap; a third prism having a third prism surface; a support member that supports the first prism, second prism, and third prism so that they can move between a first position and a second position relative to a first optical axis; and at a first position, the first prism reflects the received illumination light at the first prism surface to the light modulation element, and transmits the first light generated by reflection at the light modulation element through the first prism surface to emit it forward, the second prism transmits the first light incident from the first prism through the second prism surface to emit it forward along a first optical axis, and at the second position, the third prism receives the second light propagating rearward along the first optical axis, and reflects at least a part of the received second light at the third prism surface to deflect it to emit it from the third prism along a second optical axis different from the first optical axis.

A prism group according to one aspect of the present disclosure can capture light propagating in the opposite direction to the light exiting the prism without affecting the light exiting the prism.

FIG. 1 is a schematic diagram showing an overall configuration of a projection-type video display device according to a first embodiment of the present disclosure. FIG. 2 is a perspective view showing an exemplary configuration of a prism group of the projection-type image display device of FIG. 1. 2 is a diagram showing the layout of the inside of the projection type image display device of FIG. 1 as seen from outside the projection lens, illustrating the layout of the prism group at the projection position. 2 is a diagram showing the layout of the inside of the projection type image display device of FIG. 1 as seen from outside the projection lens, illustrating the layout of the prism group at the imaging position. FIG. 1 is a perspective view illustrating propagation of projection light through a group of prisms at a projection position according to an embodiment of the present disclosure. 5 is a side view showing the propagation of projection light through the prism group at the projection position of FIG. FIG. 1 is a perspective view illustrating propagation of external light through a group of prisms at an imaging position according to an embodiment of the present disclosure. FIG. 7 is a side view showing the propagation of external light through the prism group at the imaging position of FIG. FIG. 10 is a side view illustrating propagation of external light through a prism group at an imaging position according to a first modification of the embodiment of the present disclosure; FIG. 10 is a side view illustrating a prism group according to a second modification of the embodiment of the present disclosure, showing propagation of external light through the prism group at an imaging position; 1 is a diagram illustrating propagation and imaging of external light by a group of prisms according to an embodiment of the present disclosure. 1 is a diagram illustrating propagation and imaging of external light by a group of prisms according to an embodiment of the present disclosure. FIG. 10 is a schematic diagram illustrating the configuration of a projection imaging optical system of a projection-type image display device according to a second embodiment of the present disclosure, showing the configuration of the projection imaging optical system in the XY plane. FIG. 10 is a schematic diagram illustrating the configuration of a projection imaging optical system of a projection-type image display device according to a second embodiment of the present disclosure, showing the configuration of the projection imaging optical system in the XZ plane.

According to a first aspect of the present disclosure, a prism group that reflects illumination light and guides it to a rearward light modulation element and transmits light reflected by the light modulation element and guides it forward includes a first prism having a first prism surface and receiving the illumination light, a second prism having a second prism surface disposed forward of the first prism and facing the first prism surface via an air gap, a third prism having a third prism surface, and a support member that supports the first prism, the second prism, and the third prism so that they can move between a first position and a second position in a direction intersecting a first optical axis, and the first position In the arrangement, a first prism reflects received illumination light at the first prism surface to a light modulation element, and transmits first light generated by reflection at the light modulation element through the first prism surface to emit it forward; a second prism transmits the first light incident from the first prism through the second prism surface to emit it forward along a first optical axis; and a third prism, at a second position, receives second light propagating rearward along the first optical axis, reflects at least a part of the received second light at the third prism surface, and deflects it to emit it from the third prism along a second optical axis different from the first optical axis.

According to this aspect, it is possible to capture light propagating in the opposite direction to the light exiting the prism without affecting the light exiting the prism.

According to a second aspect of the present disclosure, there is provided a prism group as described in the first aspect, further comprising a drive unit for driving the movement between the first position and the second position.

According to a third aspect of the present disclosure, there is provided a prism group as described in the first or second aspect, in which at least a portion of the second light emitted from the third prism along the second optical axis is incident on an imaging optical system, the imaging optical system includes an imaging element and is configured to image at least a portion of the second light on the imaging element, and a support member supports the imaging optical system so as to move together with the first prism, the second prism, and the third prism.

According to a fourth aspect of the present disclosure, there is provided a prism group described in any one of the first to third aspects, wherein the third prism surface has a reflectivity different from that of the first prism surface in the wavelength region of the first light.

According to a fifth aspect of the present disclosure, there is provided a prism group described in any one of the first to fourth aspects, wherein the support member is configured to support the first prism, the second prism, and the third prism so that they can be moved between a first position and a second position in a plane perpendicular to the first optical axis.

According to a sixth aspect of the present disclosure, there is provided a prism group as described in the fifth aspect, in which the support member is configured to support the first prism, the second prism, and the third prism movably between a first position and a second position so as to intersect with the propagation direction of the illumination light in a plane perpendicular to the first optical axis.

According to a seventh aspect of the present disclosure, there is provided a prism group described in any one of the first to sixth aspects, wherein the second optical axis is in a plane perpendicular to the first optical axis.

According to an eighth aspect of the present disclosure, there is provided a prism group as described in the seventh aspect, wherein the third prism internally reflects the second light multiple times within the third prism, and the second optical axis is arranged to intersect the propagation direction of the illumination light in a plane perpendicular to the first optical axis.

According to a ninth aspect of the present disclosure, there is provided a prism group described in any one of the first to eighth aspects, in which the third prism is arranged forward of the first prism, and the first prism surface and the third prism surface are joined together.

According to a tenth aspect of the present disclosure, there is provided a prism group described in any one of the first to ninth aspects, wherein the third prism is disposed forward of the first prism and further includes a fourth prism disposed between the third prism and the first prism, the fourth prism having a fourth prism surface and a fifth prism surface that forms an angle with the fourth prism surface, and wherein the fourth prism surface and the first prism surface are bonded together, and the fifth prism surface and the third prism surface are bonded together.

According to an eleventh aspect of the present disclosure, there is provided a group of prisms described in any one of the first to tenth aspects, wherein the third prism includes a fifth prism and a sixth prism, the fifth prism and the sixth prism have adjacent prism faces, and the adjacent prism faces are arranged opposite each other with a parallel gap between them.

According to a twelfth aspect of the present disclosure, there is provided a group of prisms described in any one of the first to eleventh aspects, wherein the second prism surface is coated with an anti-reflection coating, and the anti-reflection coating has a transmittance of 96% or more for the first light.

According to a thirteenth aspect of the present disclosure, there is provided a prism group described in any one of the first to twelfth aspects, wherein the third prism surface is coated with a visible partial reflective coating, and the visible partial reflective coating has a reflectivity of 50% or more for light in the visible range.

According to a fourteenth aspect of the present disclosure, there is provided a prism group described in any one of the first to twelfth aspects, wherein the third prism surface is coated with an infrared partial reflection coating, and the infrared partial reflection coating has a reflectivity of 50% or more for light in the infrared range.

According to a fifteenth aspect of the present disclosure, there is provided a group of prisms described in any one of the first to fourteenth aspects, wherein the third prism has a prism surface having two or more reflective surfaces that internally reflect at least a portion of the second light, and at least one of the reflective surfaces is configured to totally reflect at least a portion of the second light.

According to a sixteenth aspect of the present disclosure, there is provided a group of prisms described in any one of the first to fifteenth aspects, wherein the third prism has a prism surface having two or more reflective surfaces that internally reflect at least a portion of the second light, and at least one of the reflective surfaces has a concave shape facing the direction of internal reflection of at least a portion of the second light.

According to a 17th aspect of the present disclosure, there is provided a prism group described in any one of the first to sixteenth aspects, wherein the third prism has a sixth prism surface that transmits at least a portion of the second light and emits it from the third prism, and the sixth prism surface has a convex shape facing the direction in which at least a portion of the second light emits from the third prism.

According to an 18th aspect of the present disclosure, there is provided a prism group described in any one of the 1st to 17th aspects, configured so that at least a portion of the second light forms an intermediate image within the third prism.

According to a 19th aspect of the present disclosure, there is provided a projection-type image display device comprising: an illumination optical system that supplies illumination light in the visible range; a prism member including a prism group described in any one of the first to eighteenth aspects; one or more light modulation elements that spatially modulate the light supplied by the illumination optical system and guided by the prism member to enter the projection light in accordance with image information; a projection optical system that displays an image by magnifying and projecting the first light emitted from the prism group along the first optical axis; and an image sensor that receives at least a portion of the second light emitted from the prism group along the second optical axis and converts it into an electrical image signal.

According to a 20th aspect of the present disclosure, there is provided a projection-type image display device as described in the 19th aspect, in which one or more light modulation elements are arranged in a fixed position relative to the first optical axis.

In addition, by appropriately combining any of the various embodiments described above, the effects of each can be achieved.

The following describes the embodiments in detail, with reference to the drawings as appropriate. However, more detailed explanations than necessary may be omitted. For example, detailed explanations of matters that are already well known or duplicate explanations of substantially identical configurations may be omitted. This is to avoid unnecessary redundancy in the following explanation and to make it easier for those skilled in the art to understand.

The accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the present disclosure, and are not intended to limit the subject matter described in the claims. Also, in each drawing, the dimensions of each element are exaggerated for ease of explanation.

<Embodiment>
Prism groups according to embodiments of the present disclosure and projection-type image display devices including the same will be described below with reference to Figures 1 to 10B. As projection-type image display devices to which the prism groups according to the present disclosure are applied, a single-panel projection-type image display device including one light modulation element (Embodiment 1) and a three-panel projection-type image display device including three light modulation elements (Embodiment 2) will be described.

(Embodiment 1)
<Projection-type image display device>
The configuration of a projection-type image display device 600 according to Example 1 of the present disclosure will be described below with reference to FIGS. 1 and 2. FIG. 1 is a schematic diagram illustrating the overall configuration of the projection-type image display device 600 according to Example 1 of the present disclosure. Also, FIGS. 1A and 1B are schematic diagrams illustrating the overall configuration of the projection-type image display device 600 on the illustrated X-Z plane. FIG. 1C is a schematic diagram illustrating the prism group 300 and the imaging optical system 360 as viewed from the left side of FIG. 1A, i.e., from the +Z side of FIG. 1A toward the -Z direction. FIG. 2 is a perspective view illustrating an exemplary configuration of the prism group 300 of the projection-type image display device 600 of FIG. 1.

The projection-type image display device 600 in Figure 1 comprises an illumination optical system 200 that supplies illumination light, and a projection imaging optical system 500. As shown in Figure 1(b), 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.

<Configuration of illumination optical system>
In the illumination optical system 200, the light source unit 20 is configured, for example, with a plurality of semiconductor lasers (LDs) or light-emitting diodes (LEDs). 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 approximately 455 nm and is used as image light as well as excitation light for exciting the phosphors in the phosphor wheel 50. The blue light emitted from the semiconductor laser element 21 is emitted in the −X direction in the figure, collimated by the collimating lens 22, and then focused by the afocal lenses 31 and 32. The blue light passes through the diffuser plate 41 and enters the dichroic mirror 45.

In this embodiment, the light emitted from the light source unit 20 is, for example, S-polarized blue light, and the dichroic mirror 45 reflects the S-polarized blue light while transmitting P-polarized blue light and other colored light. The blue light reflected by the dichroic mirror 45 travels approximately in the -Z direction, passes through the λ/4 plate 42, and is focused by lenses 33 and 44 before entering the phosphor wheel 50, where it excites the phosphors in the phosphor wheel 50 to emit light.

When the phosphor wheel 50 rotates, different segments of the phosphor layer are excited by the incident blue light, generating fluorescence containing, for example, yellow and green emission component light. Furthermore, a portion of the blue light that passes through the λ/4 plate 42 is reflected by the phosphor wheel 50 and passes through the λ/4 plate 42 again, becoming P-polarized blue component light, which then passes through the dichroic mirror 45. The blue component light and emission component light of each color range that passes through the dichroic mirror 45 travels in approximately the Z direction, passes through the condenser lens 35, and enters the color wheel 60.

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

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, becoming white light illumination light Ls on a time average, which enters the projection imaging optical system 500.

<Configuration of Projection Imaging Optical System>
As shown in FIGS. 1A and 1C , the projection imaging optical system 500 includes a prism group 300, an imaging optical system 360, a light modulation element 400, and a projection optical system 420. The light modulation element 400 can be configured using a digital micromirror device (DMD). The projection optical system 420 includes a projection lens and can enlarge and project projection light Lp onto a projection target 450 such as a screen or a three-dimensional object to display an image. In this embodiment, the imaging optical system 360 can be configured with an imaging relay optical system 361 including multiple lenses and an imaging element 365, as shown in FIG. 1C . Meanwhile, imaging light Lim, which is a portion of external light Li propagating in the opposite direction to the projection light Lp, enters the imaging optical system 360 and can be imaged on the imaging element 365 by the imaging relay optical system 361. The image sensor 365 converts the received image light into an electrical image signal. In this specification, the projection light Lp may be referred to as the “first light” and the external light Li may be referred to as the “second light.”

The configuration of prism group 300 will be described with reference to FIG. 2. In this embodiment, as shown in FIG. 2, prism group 300 is composed of prism unit 350 and support member 370. Prism unit 350 is composed of prism 310, prism 320, and prism 330. Prism unit 350 may be an integrated configuration of three prisms 310, 320, and 330, or may be configured with each prism separated by a gap between adjacent prisms. The configuration of prism unit 350 will be described in detail later. Furthermore, in this specification, prism 310, prism 320, and prism 330 may be referred to as the "first prism," the "second prism," and the "third prism," respectively.

As shown in FIG. 2, the projection lens 421 constituting the projection optical system 420 is disposed in front of the prism group 300 (the +X side in the figure) and may include multiple lenses centered about the projection optical axis Oa1 (also referred to as the "first optical axis" in this specification). The light modulation element 400 is disposed behind the prism group 300 (the -X side in the figure) and faces the projection lens 421 across the prism group 300. In this embodiment, the projection optical system 420 and the light modulation element 400 are disposed in fixed positions with respect to the projection optical axis Oa1, and the prism unit 350 is supported by a support member 370 so that it can move between the projection position P1 and the imaging position P2 in a direction intersecting the projection optical axis Oa1. FIG. 2 shows the prism unit 350 at the projection position P1. The arrangement of the prism group 300 at the projection position P1 and the imaging position P2 will be described in detail later. In this specification, the projection position P1 may be referred to as a "first position," and the imaging position P2 may be referred to as a "second position."

2, the support member 370 includes two guide rails 371 arranged parallel to each other in the Y direction, and a mounting surface 372 that can slide on the guide rails 371. The prism unit 350 is attached to the upper surface of the mounting surface 372, and in this embodiment, is configured to move between the projection position P1 and the imaging position P2 by translational motion along the guide rails 371. In this embodiment, the imaging optical system 360 is further arranged on the upper surface of the mounting surface 372, and the support member 370 supports the imaging optical system 360 so that it moves together with the prism unit 350.

The imaging optical system 360 is configured as an imaging optical system that takes in at least a portion of external light as imaging light and forms an image on the imaging element. In this embodiment, the imaging optical system 360 is shown as a reduced imaging optical system that reduces the imaging light received and forms a reduced image on the imaging element 365, but the present disclosure is not limited to this. The imaging optical system 360 may be configured, for example, to reduce the imaging light on the imaging element, or to form an image at the same magnification.

In this embodiment, the movement of the prism unit 350 and the imaging optical system 360 supported by the support member 370 is driven by a drive unit 375. As shown, the drive unit 375 can be configured with a motor 376, a shaft 377 connected to the motor 376, and a pair of bearing members 378 that can slide on the respective guide rails 372. The drive unit 375 is attached to a support base 379 that is arranged in a fixed position relative to the projection optical axis Oa1, and is connected to the mounting surface 372 via the bearing members 378, and drives the movement of the prism unit 350 and the imaging optical system 360 between the projection position P1 and the imaging position P2.

Specifically, when the drive unit 375 operates, the shaft 377 is rotated by the drive of the motor 376. The bearing member 378 is configured to be able to slide along the guide rail 371 as the shaft 372 rotates. As the bearing member 378 moves, the prism unit 350 and imaging optical system 360 supported on the mounting surface 372 of the support member 370 can move along the guide rail 373. The support base 379 supports the connection between the motor 376 and shaft 377 of the drive unit 375, the tip of the shaft 377, and the guide rail 371 of the support member 370. 2, the support base 379 is provided with an opening 373 through which light passes, at a position corresponding to the light modulation element 400, so that at projection position P1, illumination light Ls (not shown in FIG. 2) enters the light modulation element 400 via the prism group 300, and projection light Lp from the light modulation element 400 is emitted to the projection lens 421 via the prism group 300. Note that a similar opening (not shown) through which light passes can also be provided on the mounting surface 372 of the support member 370.

Furthermore, the drive unit 375 according to the present disclosure is not limited to the above configuration. The drive unit 375 may adopt the configuration of other conventionally known drive mechanisms, and further detailed description will be omitted in this specification. Furthermore, the movement of the prism unit 350 is not limited to being driven by the drive unit 375. For example, the prism unit 350 can be moved manually by providing an operating lever on the support member 370.

2, the prism unit 350 is supported by the support member 370 so that it can move between the projection position P1 and the imaging position P2 by translational motion, but the present disclosure is not limited to this. For example, the support member 370 may include a rotation axis (not shown), and the prism unit 350 may be supported so that it can move between the projection position P1 and the imaging position P2 by curvilinear motion such as rotational motion or swing.

The position of the prism group 300 within the projection-type image display device 600 and the arrangement of the prism group 300 at the projection position P1 and the imaging position P2 are explained with reference to Figures 3A and 3B.

<Arrangement of Prism Groups at Projection Position and Imaging Position>
Fig. 3A is a diagram showing the internal layout of the projection-type image display device 600 of Fig. 1 as viewed from outside the projection lens 421, illustrating the layout of the prism group 300 at projection position P1. Fig. 3B is a diagram showing the internal layout of the projection-type image display device 600 of Fig. 1 as viewed from outside the projection lens 421, illustrating the layout of the prism group 300 at imaging position P2.

When viewed from the projection optical system 420 side of Figure 1, i.e., from above in Figure 1, in the -X direction, inside the housing 600A of the projection type image display device 600, the prism group 300 is located below the projection lens 421 of the projection optical system 420, and the light modulation element 400 is positioned at a position roughly corresponding to the center of the projection lens 421, i.e., at a position where the projection optical axis Oa1 passes.

When the prism group 300 is at the projection position P1 shown in FIG. 3A, the illumination light Ls emitted from the illumination optical system 200 is deflected by the folding mirror 47, propagates through the relay lens group 48 along the Ds direction in the Y-Z plane shown in the figure, and enters the prism group 300 from the prism surface 312 of the prism 310. The incident illumination light Ls is reflected by the prism 310 and then enters the light modulation element 400. As shown in FIG. 3A, when the prism group 300 is at the projection position P1, the prism 320 is positioned in front of the light modulation element 400. At this time, the prism 320 is positioned so that the projection optical axis Oa1 passes through it (see FIG. 2). The DMD-ON light (projection light Lp shown in FIG. 2) from the light modulation element 400 passes through the prism 320, exits along the projection optical axis Oa1 in the +X direction shown in the figure, and enters the projection lens 421. The projection optical system 420 displays an image by enlarging and projecting the projection light Lp introduced through the projection lens 421 onto the projection object 450. On the other hand, the DMD-OFF light Lf (shown in FIG. 3A) is deflected and excluded from the projection light.

Next, when the prism group 300 moves to the imaging position P2, as shown in FIG. 3B, the prism 330 is positioned in front of the light modulation element 400. At this time, the prism 330 is located at a position where the projection optical axis Oa1 passes through (see FIG. 6). External light Li propagating from the projection object 450 through the projection lens 421 in the -X direction as shown is incident on the prism 330 along the projection optical axis Oa1 in the -X direction as shown, and is reflected and deflected within the prism 330, and imaging light Lim, which is a portion of the external light Li, is emitted from the prism 330 along the imaging optical axis Ob1. The emitted imaging light Lim enters the imaging optical system 360 and forms an image on the imaging element 365.

In this way, at projection position P1, the prism group 300 guides projection light Lp from the light modulation element 400 along the projection optical axis Oa1 to the projection optical system 420. At imaging position P2, it introduces at least a portion of external light Li incident from the projection optical system 420 along the projection optical axis Oa1 into the imaging optical system 360. By moving the prism group 300 between projection position P1 and imaging position P2, coaxial projection and imaging can be achieved separately. This allows external light propagating in the opposite direction to the projection light to be captured without affecting the projection light emitted from the prism. The coaxial configuration of projection and imaging allows convenient optical adjustment of the projection optical system and projection position adjustment, etc., using the imaging by the imaging optical system, ensuring excellent projection. Furthermore, sufficient external light can be captured as needed without reducing the amount of projection light, thereby improving imaging sensitivity.

Inside the projection-type image display device 600, the projection lens 421 is designed to have a short back focus, which allows for a more compact and cost-effective device. Therefore, the projection optical system 420 and the prism surface 322 of the projection prism 320 of the prism group 300 (see Figure 1) are configured as close as possible to each other without interfering with each other. As a result, there is little space inside the housing 600A in the X direction shown in Figure 3A or 3B, which is the emission direction of the projection light Lp, and the placement of optical components, etc. is also limited by design.

In the projection-type image display device 600 according to the present disclosure, the support member 370 (shown in FIG. 2) can support the prism unit 350 so that it can move between the projection position P1 and the imaging position P2 in a plane perpendicular to the projection optical axis Oa1 (the Y-Z plane in the figure). Furthermore, external light Li incident from the projection optical system in the -X direction in the figure can be reflected and deflected within the prism group 300, thereby being introduced into the imaging optical system 360 along the imaging optical axis Ob1 (also referred to herein as the "second optical axis") in the plane perpendicular to the projection optical axis Oa1 (the Y-Z plane in the figure). This allows the prism group 300 to be easily incorporated into equipment without interfering with the projection optical system, and to be moved between the projection position P1 and the imaging position P2. Here, "plane perpendicular to Oa1" means "plane substantially perpendicular to Oa1."

In addition, as shown in Figures 3A and 3B, an actual projection-type image display device is designed so that, when viewed from the projection lens 421, illumination light Ls incident on the prism group 300 in the Y-Z plane propagates from the bottom right in the direction Ds, which is approximately 45 degrees diagonal to the long side of the housing 600A, and enters the prism group 300. This is because the rotation axis of the micromirrors of the DMD serving as the light modulation element 400 is tilted at 45 degrees. Therefore, the prism surface 312 of the prism 310 of the prism group 300 is arranged so that it is approximately perpendicular to the propagation direction Ds of the illumination light Ls. With this arrangement, as shown in the figure, there is little space within the projection-type image display device 600 in the propagation direction Ds of the illumination light Ls in the Y-Z plane.

In this embodiment, the support member 370 can be configured to support the prism unit 350 movably between the projection position P1 and the imaging position P2 in the movement direction Dm that intersects the propagation direction Ds of the illumination light Ls in the Y-Z plane. Furthermore, by internally reflecting the external light Li multiple times within the prism group 300, it can be guided along the imaging optical axis Ob1 that intersects the propagation direction Ds of the illumination light Ls. This allows for efficient use of the internal space of the projection-type image display device 600, resulting in a compact device configuration. Furthermore, in this embodiment, as shown in the figure, the support member 370 is configured to support the prism unit 350 movably between the projection position P1 and the imaging position P2 in the movement direction Dm that is generally perpendicular to the propagation direction Ds of the illumination light Ls in the Y-Z plane. Furthermore, the imaging optical axis Ob1 is also positioned in a direction that is generally perpendicular to the propagation direction Ds of the illumination light Ls in the Y-Z plane. This allows for the overall device to be compact.

In this embodiment, prisms 310 and 320 are configured to move simultaneously. As will be explained in detail later, prisms 310 and 320 are arranged opposite each other at prism surfaces 311 and 321 with a parallel air gap between them, forming a so-called TIR (Total Internal Reflection) prism. By moving prisms 310 and 320 simultaneously, a stable air gap can be easily maintained between them, ensuring stable projection.

In addition, in this embodiment, the prism unit 350 can have an integrated configuration of three prisms 310, 320, and 330. This allows for a stable prism configuration and shortens the amount of movement between the projection position P1 and the imaging position P2. As mentioned above, the imaging optical system 360 can be configured as a reduced imaging optical system. This allows for easy movement together with the prism group 300.

Furthermore, when illumination light Ls passes through the relay lens group 48 and enters the prism group 300 in the direction Ds in the illustrated Y-Z plane, it forms an illumination light incident beam spot SO on the prism surface 312 of the prism 310. The diameter of the illumination light incident beam spot SO may be larger than the width w of the prism 320, as shown in FIG. 3A. Here, the width w of the prism 320 is the length of the prism 320 on a plane parallel to the prism surface 312 of the prism 310, and indicates the length of the prism 320 in the illustrated Y direction. After entering the prism surface 312, the illumination light Ls can be further converged within the prism group 300 by the relay lens group 48 and then enter the light modulation element 400. In this way, the prism 320 can be configured with a width w smaller than the illumination light Ls incident beam spot SO. This allows for a compact design of the prism group 300 and shortens the amount of movement between the projection position P1 and the imaging position P2.

<Propagation of projected light and external light through a group of prisms>
The propagation of projection light when the prism group 300 is at the projection position P1 will be described with reference to Figures 4 and 5. Figure 4 is a perspective view showing the propagation of projection light by the prism group 300 at the projection position P1 according to an embodiment of the present disclosure. Figure 5 is a side view showing the propagation of projection light by the prism group 300 at the projection position P1 in Figure 4.

As shown in Figure 4, when the prism group 300 is at the projection position P1, the second prism 320 is located in front of the light modulation element 400, at a position where the projection optical axis Oa1 passes. The illumination light Ls is incident on the first prism 310.

As shown in FIG. 5, prism 310 and prism 320 can be configured as approximately triangular prisms. Prism 310 has prism surface 312 and prism surface 311, and prism 320 has prism surface 321 and prism surface 322. In this embodiment, prism 320 is disposed on the front side (the +X side in the figure) of prism 310. Prism surface 311 of prism 310 and prism surface 321 of prism 320 are disposed parallel to and opposite each other with an air gap between them, forming a TIR prism, which allows illumination light Ls to be totally reflected at prism surface 311. Illumination light Ls passes through prism surface 312 and enters prism surface 311 at an incident angle greater than or equal to the critical angle, where it is totally reflected and enters light modulation element 400. In this specification, prism surface 311 may be referred to as the "first prism surface," and prism surface 321 may be referred to as the "second prism surface."

The DMD used as the light modulation element 400 modulates the component light of each color gamut contained in the illumination light Ls based on a video signal, and distributes it for each pixel into DMD-ON light or DMD-OFF light Lf, which becomes projection light Lp. Projection light Lp is emitted in the +X direction along the projection optical axis Oa1, while DMD-OFF light Lf is deflected away from the projection optical axis Oa1 and removed. Projection light Lp passes through prism surface 311 and reaches prism surface 321 of prism 320. Prism surface 321 is coated with an anti-reflection coating, allowing projection light Lp to transmit with a transmittance of 96% or more. Projection light Lp that passes through prism surface 321 exits from prism surface 322 and enters the front projection lens 421 along the projection optical axis Oa1.

Next, the propagation of external light when the prism group 300 is at the imaging position P2 will be described with reference to Figures 6 and 7. Figure 6 is a perspective view showing the propagation of external light through the prism group 300 at the imaging position P2 according to an embodiment of the present disclosure. Figure 7 is a side view showing the propagation of external light through the prism group 300 at the imaging position P2 in Figure 6.

As shown in Figure 6, when the prism group 300 is at the projection position P2, the third prism 330 is located in front of the light modulation element 400, at a position where the projection optical axis Oa1 passes through. At this time, external light Li propagating through the projection lens 421 in the -X direction as shown enters the prism 330 in the -X direction as shown along the projection optical axis Oa1, and is reflected and deflected within the prism 330.

As shown in Figure 7, prism 330 has prism surfaces 331, 332, 333, and 334. Hereinafter, to make it easier to explain the propagation of light within prism 330, prism surfaces 331, 332, 333, and 334 will be referred to as the "first reflecting surface 331," "second reflecting surface 332," "third reflecting surface 333," and "exit surface 334," respectively. Furthermore, in this specification, prism surface 331 may be referred to as the "third prism surface," and prism surface 334 may be referred to as the "sixth prism surface."

In this embodiment, prism 330 is disposed on the forward side (+X side in the figure) of prism 310, and by bonding first reflecting surface 331 to prism surface 311, prism 330 and prism 310 can be formed as a single unit. Bonding first reflecting surface 331 to prism surface 311 suppresses the generation of stray light within prism group 300 and prevents double images caused by gaps between prism surfaces, ensuring imaging accuracy. Furthermore, by forming prism 330 integrally with prism 310, a compact and stable prism group 300 can be formed. However, the present disclosure is not limited to this. Depending on the application, for example, prism 330 can be configured separately from prism 310.

In this embodiment, prism 330 and prism 320 are arranged adjacent to each other. This allows for the construction of a compact prism group 300 and the reduction in the amount of movement between projection position P1 and imaging position P2. Furthermore, prism 330 and prism 320 may be integrally formed by joining adjacent prism surfaces, or may be arranged separated by a gap. Furthermore, third prism 330 can be manufactured using a different glass material or resin material from that used for first prism 310 and second prism 320. Resin optical components have excellent processability, which offers the advantage of enabling prism components with optical surfaces of complex geometric shapes to be manufactured at low cost.

4 and 7 show the second reflecting surface 332 of prism 330 and the prism surface 322 of prism 320 as being configured to be at the same height and on the same plane, but the present disclosure is not limited to this. Prism 330 and prism 320 can be configured with any dimensions that are different from each other in thickness in the illustrated X direction, width in the illustrated Y direction, or length in the illustrated Z direction.

External light Li that passes through the projection lens 421 from the projection object (not shown) and enters the prism 330 in the -X direction along the projection optical axis Oa1 forms a beam spot S1 on the first reflecting surface 331.

In this embodiment, the first reflecting surface 331 is coated with a partial reflection coating, and at least a portion of the incident external light Li is internally reflected by the partial reflection coating and reaches the second reflecting surface 332. Meanwhile, the light Lif transmitted through the first reflecting surface 331 passes through the prism 310 and passes through the group of prisms.

In this embodiment, the second reflecting surface 332 can be configured to totally reflect at least a portion of the incident external light Li. This allows for efficient use of external light. At least a portion of the external light Li reflected by the first reflecting surface 331 is incident on the second reflecting surface 332 at an angle of incidence greater than or equal to the critical angle, forms a beam spot S2 on the second reflecting surface 332, and is totally reflected and incident on the third reflecting surface 333.

At least a portion of the external light Li that is totally reflected by the second reflecting surface 332 and incident on the third reflecting surface 333 forms a beam spot S3 on the third reflecting surface 333 and is further reflected internally, and the imaging light Lim is emitted from the exit surface 334 along the imaging optical axis Ob1, introduced into the imaging optical system 360, and imaged on the imaging element 365.

In this way, in this embodiment, the external light Li is deflected by three internal reflections within the prism 330 and can be introduced into the imaging optical system 360 along the imaging optical axis Ob1, which is in the Y-Z plane substantially perpendicular to the projection optical axis Oa1 and intersects the propagation direction Ds of the illumination light in the Y-Z plane (shown in Figures 3A and 3B).

Note that the present disclosure does not limit the number of prism surfaces (reflective surfaces) included in prism 330 or the number of times external light Li is reflected within prism 330. Prism 330 may have more prism surfaces, and external light Li may be further reflected by other prism surfaces within prism 330. Furthermore, in this embodiment, prism 330 is configured so that at least a portion of external light Li is totally reflected by second reflective surface 332 and incident on third reflective surface 333, but the present disclosure is not limited to this. At least a portion of external light Li may be partially internally reflected by second reflective surface 332 and incident on third reflective surface 333.

The partial reflective coating applied to the first reflective surface 331 may be a visible range partial reflective coating or an infrared range partial reflective coating. A visible range partial reflective coating can reflect at least a portion of external light, for example, with a reflectance of 50% or more for light in the visible range with a wavelength of 400 nm to 700 nm. When an infrared range partial reflective coating is applied, it can reflect external light with a reflectance of 50% or more for light in the infrared range with a wavelength of 750 nm or more. Infrared imaging can be used to detect or track motion in places with no light at all, and is used in night photography and night-vision surveillance cameras.

As described with reference to Figures 4 and 5, at projection position P1, projection light Lp passes through prism surface 311 of first prism 310 and prism surface 321 of second prism 320 in that order along projection optical axis Oa1, and is emitted from prism surface 322 to projection lens 421. On the other hand, at imaging position P2 shown in Figures 6 and 7, external light Li travels in the -X direction along projection optical axis Oa1 and is incident on prism surface 331 of third prism 330. Projection light Lp does not enter prism surface 331. Therefore, for example, prism surface 331 can be configured to have a reflectivity different from that of prism surface 311 of first prism 310 and/or prism surface 321 of second prism 320 in the wavelength range of projection light Lp.

For example, if a visible partial reflective coating is applied to the prism surface 331 that receives external light Li, and if visible projection light Lp enters the prism surface 331, some of the light will be reflected due to the reflective characteristics of the visible partial reflective coating, resulting in a loss of the emitted projection light Lp. In this embodiment, by moving the prism unit 350 between the projection position P1 and the imaging position P2, it is possible to prevent the projection light Lp from passing through the prism surface 331 and emitting it, and external light Li can be efficiently taken in without affecting the projection light Lp.

The third prism 330 and the second prism 320 can also be configured as a single prism with adjacent prism surfaces joined together. This single prism can be configured so that, on the prism surface adjacent to the first prism 310, one region transmits the projection light Lp and the other region receives the external light Li, with the two regions having different reflectivities in the wavelength range of the projection light Lp. This prevents the projection light Lp from passing through the region that receives the external light Li and emitting it, allowing the external light Li to be efficiently introduced without affecting the projection light Lp, by moving the prism unit 350 between the projection position P1 and the imaging position P2.

While the prism group 300 composed of three prisms has been described above, the present disclosure is not limited thereto. Below, modified examples of the prism group 300 will be described with reference to FIGS. 8A and 8B. FIG. 8A is a side view of the prism group 300a according to Modification 1 of the embodiment of the present disclosure, showing the propagation of external light through the prism group 300a at the imaging position P2. FIG. 8B is a side view of the prism group 300b according to Modification 2 of the embodiment of the present disclosure, showing the propagation of external light through the prism group 300b at the imaging position P2. Note that the configurations of the first and second prisms of the prism group 300a and the prism group 300b, as well as the propagation of projected light at the projection position P1, are similar to those of the prism group 300, and therefore will not be illustrated or described here.

(Variation 1 of the present embodiment)
8A differs from prism group 300 in that third prism 330a is composed of prisms 340a and 340b. In this specification, prism 340a may be referred to as the "fifth prism" and prism 340b may be referred to as the "sixth prism."

As shown in Figure 8A, in prism group 300a, prisms 340a and 340b that make up prism 330a have adjacent prism surfaces 343a and 343b. Prism surface 343a of prism 340a and prism surface 343b of prism 340b are arranged opposite each other with a parallel gap between them.

In the prism group 300a, external light Li incident on prism 330a in the -X direction forms a beam spot S1a on the first reflecting surface 341a. Due to the partially reflective coating applied to the first reflecting surface 341a, at least a portion of the incident external light Li is internally reflected, reaches the second reflecting surface 342a, and forms a beam spot S2a. Subsequently, at least a portion of the external light Li is internally reflected by the second reflecting surface 342a, passes through prism surfaces 343a and 343b, and then reaches the third reflecting surface 344b. At the third reflecting surface 344b, it forms a beam spot S3a and is further internally reflected, and imaging light Lima is emitted from the exit surface 345b along the imaging optical axis Ob1.

In prism group 300a, prism 340b, which constitutes prism 330a, is constructed separately from prism 340a, and can therefore be made using a different glass or resin material than prism 340a. Therefore, by forming third prism 330 separately, a high degree of freedom in material selection is possible, and for example, it can be constructed from a resin prism, which is highly processable. Note that third prism 330 can also be constructed from three or more prisms depending on the application.

(Variation 2 of the present embodiment)
Prism group 300b shown in Fig. 8B differs from prism group 300 in that it includes a fourth prism 340c between prism 310 and prism 330b. Note that Fig. 8B shows prism 330b as being composed of a single prism, but the present disclosure is not limited thereto. Prism 330b can be composed of multiple prisms, similar to prism 330a shown in Fig. 8A.

As shown in FIG. 8B, fourth prism 340c of prism group 300b has prism surface 341c and prism surface 342c. Prism surface 341c and prism surface 342c intersect at apex angle A. In this embodiment, prism surface 341c can be bonded to prism surface 311 of prism 310, and prism surface 342c can be bonded to prism surface 331b of prism 330b. Although not limited thereto, in this embodiment, fourth prism 340c has a wedge shape as shown. Prism surface 341c and prism surface 342c preferably form an apex angle A of 2 to 10 degrees, and in this embodiment, the apex angle A is approximately 3 degrees. In this specification, prism surface 341c may be referred to as the "fourth prism surface," and prism surface 342c may be referred to as the "fifth prism surface."

In prism group 300b, external light Li incident on prism 330b in the -X direction forms a beam spot S1b on first reflecting surface 331b. Due to the partially reflective coating on first reflecting surface 331b, at least a portion of the incident external light Li is internally reflected, reaching second reflecting surface 332b and forming beam spot S2b. Next, external light Li is internally reflected by second reflecting surface 332b and reaching third reflecting surface 333b. It forms beam spot S3b on third reflecting surface 333b and is further internally reflected, and imaging light Limb is emitted from exit surface 334b along imaging optical axis Ob1.

For comparison, Figure 8B also shows beam spot S3 formed by external light Li on the third reflecting surface 333 (not shown in Figure 8B) of prism 330 in the prism group 300 shown in Figure 7. As shown, in prism group 300b, beam spot S3b formed by external light Li on the third reflecting surface 333b of prism 330b is smaller than beam spot S3. Furthermore, the center position of beam spot S3b is closer to the projection optical axis Oa1 by a distance D than the center position of beam spot S3. As such, it can be seen that the propagation optical path of external light within prism group 300b is shorter than the propagation optical path of external light within prism group 300.

In the prism group 300b, the beam spot S3b formed by the external light Li on the third reflecting surface 333b of the prism 330b changes in this manner because of the presence of the fourth prism 340c. As shown in FIG. 8B, the prism 310 is configured such that the prism surface 311 and the base surface 313, which is perpendicular to the projection optical axis Oa1, form an angle α1. This angle α1 is limited by the characteristics of the DMD as the light modulation element 400. In the prism group 300 shown in FIG. 7, the prism surface 311 of the prism 310 is joined to the first reflecting surface 331 of the prism 330. This limits the angle between the first reflecting surface 331 of the prism 330 and the projection optical axis Oa1, thereby limiting the reflection angle of the external light Li at the first reflecting surface 331. Therefore, by providing a wedge-shaped fourth prism 340c in the prism group 300b shown in Fig. 8B, the angle β formed between the first reflecting surface 331b and the projection optical axis Oa1 can be increased by the apex angle A of the wedge-shaped fourth prism 340c, compared to the prism group 300 in Fig. 7, and the reflection angle of the external light Li at the first reflecting surface 331b can be adjusted. This makes it possible to make the prism group more compact, and by adjusting the propagation path length of the external light within the prism group, it is possible to realize an optical system design with a high degree of freedom.

(Curvature Design of the Prism Surface of the Third Prism)
9A and 9B , a case where the reflecting surface and the exit surface of the third prism 330 according to the embodiment of the present disclosure are provided with curvature will be described. FIG. 9A is a diagram illustrating the propagation and imaging of external light by the prism group 300 ( FIG. 9A (a)) and the prism group 300c ( FIG. 9A (b)) according to the embodiment of the present disclosure. FIG. 9B is a diagram illustrating the propagation and imaging of external light by the prism group 300 ( FIG. 9B (a)) and the prism group 300d ( FIG. 9B (b)) according to the embodiment of the present disclosure. For ease of understanding, FIGS. 9A and 9B illustrate the propagation of light by expanding the curved optical path of external light Li within the third prism into a straight line in the XY plane. The prism group 300c and the prism group 300d have the same configurations of the first and second prisms and the same propagation of the projection light at the projection position P1 as the prism group 300, and therefore will not be illustrated or described.

As described above, external light Li forms a beam spot S1 on the first reflecting surface 331 of the third prism 330, is at least partially internally reflected, reaches the second reflecting surface 332 and forms beam spot S2, is further internally reflected, reaches the third reflecting surface 333, forms beam spot S3, and is then internally reflected before being emitted from the exit surface 334 (see Figures 6 and 7). As shown in Figures 9A(a) and 9B(a), in an implementation of the present disclosure, external light Li reflected from the projection target 450 (shown in Figure 1) and propagating in the -X direction passes through the projection optical system 420 and enters the prism group 300. At this time, a portion of the external light Li converges through the projection optical system 420 to form beam spot S1, and then converges again to form beam spot S2. After being reflected by the second reflecting surface 332, a portion of the external light Li further converges, and an intermediate image Ms is formed within the prism group 300 at a position conjugate to the projection surface with respect to the lens system that constitutes the projection optical system 420. In this embodiment, the intermediate image Ms is formed on the optical path between the second reflecting surface 332 and the third reflecting surface 333. After forming the intermediate image M, a portion of the external light Li gradually expands as the light beam travels toward the third reflecting surface 333, forming a beam spot S3 on the third reflecting surface 333. Then, a portion of the external light Li is reflected by the third reflecting surface 333 toward the exit surface 334, and imaging light Lim passes through the exit surface 334 along the imaging optical axis Ob1, is emitted from the prism 330, enters the imaging optical system 360, and is imaged on the image sensor 360.

In the prism group 300c shown in FIG. 9A(b), elements similar to those in the prism group 300 in FIG. 9A(a) are designated by the same reference numerals, and their description will be omitted. In this embodiment, in the prism group 300c, the third reflecting surface 333c of the third prism 330c can be configured to have a concave shape C1 facing the direction in which the external light Li is internally reflected by the third reflecting surface 333c. The concave shape C1 can converge the reflected and emitted imaging light as a concave mirror with positive power. In this way, by imparting a curvature to the third reflecting surface 333c of the prism 330c, the spread of the external light Li within the prism group 300c is suppressed, thereby defining the spread of the luminous flux of the emitted imaging light Limc. 9A(a) 的光学部件的径小，可以使用厚度小的厚度。 As a result, as shown in the figure, the optical path length of the imaging light Limc from the prism 330c to the imaging element 365 can be shortened by a distance d1 compared to the optical path length of the imaging light Lim emitted by the prism group 300. Therefore, the imaging optical system can be made compact.

Next, in the prism group 300d shown in FIG. 9B(b), elements similar to those in the prism group 300 in FIG. 9B(a) are designated by the same reference numerals, and their description will be omitted. In this embodiment, in the prism group 300d, the exit surface 334d of the third prism 330d can be configured to have a convex shape C2 facing the direction in which the external light Li is emitted to the imaging element 365. This convex shape C2 can converge the emitted imaging light as a convex lens with positive power. In this way, by imparting a curvature to the exit surface 334d of the prism 330d, the spread of the luminous flux of the emitted imaging light Limd can be defined. Therefore, the imaging optical system 360d can reduce the number of optical components compared to the imaging optical system 360 shown in FIG. 9B(a). As a result, as shown in the figure, the propagation optical path length of the imaging light Limd from being emitted from the prism 330d to the imaging element 365 can be shortened by a distance d2 compared to the propagation optical path length of the imaging light Lim emitted by the prism group 300. Therefore, it is possible to further compactify the imaging optical system.

Furthermore, the present disclosure is not limited to providing curvature to one prism surface of the third prism. It is also possible to provide curvature to multiple prism surfaces of the third prism. In this way, the imaging optical system can be configured compactly, making it easier to further miniaturize the entire device.

(Embodiment 2)
<Projection imaging optical system>
A projection imaging optical system 500A of a projection display device according to a second embodiment of the present disclosure will be described with reference to FIGS. 10A and 10B. FIG.

The projection-type image display device according to the second embodiment is a three-panel projection-type image display device, and includes an illumination optical system and a projection-image capturing optical system. Because the illumination optical system is a well-known configuration, FIGS. 10A and 10B do not show the illumination optical system, and only show the projection-image capturing optical system 500A. FIG. 10A is a schematic diagram showing the configuration of the projection-image capturing optical system 500A of the projection-type image display device according to the second embodiment of the present disclosure, illustrating the configuration of the projection-image capturing optical system 500A in the X-Y plane. FIG. 10B is a schematic diagram showing the configuration of the projection-image capturing optical system 500A of the projection-type image display device according to the second embodiment of the present disclosure, illustrating the configuration of the projection-image capturing optical system 500A in the X-Z plane.

As shown in Figures 10A and 10B, the projection imaging optical system 500A includes a prism member 380. The prism member 380 is composed of a prism group 300A according to an embodiment of the present disclosure and a color separation/combining prism 300B. The prism group 300A is located in front of the color separation/combining prism 300B (the +X side in the figure). The illumination light LsA of each color gamut from the illumination optical system is totally reflected by the first prism 310A of the prism group 300A and enters the color separation/combining prism 300B.

The color separation/combining prism 300B includes prisms 300B1, 300B2, and 300B3 arranged in sequence along the projection optical axis Oa1 from the projection optical system 420A side. The color separation/combining prism 300B separates the light of each color gamut contained in the incident illumination light and directs it separately to three corresponding light modulation elements 401, 402, and 403. Each light modulation element 401, 402, and 403 is positioned in a fixed position relative to the projection optical axis Oa1, modulates the incident light of each color gamut based on a video signal, and reflects the modulated light components of each color gamut back to each of the three prisms of the color separation/combining prism 300B.

The color separation/combining prism 300B guides the projection light (DMD-ON light) reflected by the DMD within each prism to the optical axis O, where it combines the colors again and emits the combined projection light LpA in the +X direction along the projection optical axis Oa1. Light that is not projected (DMD-OFF light, not shown) is deflected away from the projection optical axis Oa1 and removed. The projection light LpA is output from the color separation/combining prism 300B and enters the front group of prisms 300A.

Prism group 300A has a configuration similar to that of prism group 300 according to Example 1 described above. Detailed explanation will be omitted here.

At projection position P1, projection light LpA passes through first prism 310A and second prism 320A of prism group 300A in order, exits along projection optical axis Oa1, and propagates to projection optical system 420A. Projection optical system 420A enlarges and projects projection light LpA, which has exited from prism group 300A along projection optical axis Oa1, onto projection target 450A to display an image.

Meanwhile, at imaging position P2, external light LiA reflected from projection object 450A in the -X direction enters projection optical system 420A, propagates in the -X direction along projection optical axis Oa1, and enters third prism 330A of prism group 300A. In third prism 330A, at least a portion of external light LiA is internally reflected multiple times and then emitted from third prism 330A along imaging optical axis Ob1. Imaging light LimA emitted from prism group 300A along imaging optical axis Ob1 travels in the +Y direction, is introduced into imaging optical system 360, and is imaged on image sensor 365.

In this way, at projection position P1, prism group 300A guides projection light LpA from light modulation elements 401, 402, and 403 along projection optical axis Oa1 to projection optical system 420A, and at imaging position P2, guides imaging light LimA, which is a portion of external light LiA incident from projection optical system 420A along projection optical axis Oa1, to imaging optical system 360. Prism group 300A is supported by a support member (not shown) so that it can move between projection position P1 and imaging position P2, and can capture external light propagating in the opposite direction to the projection light without affecting the projection light emitted from prism group 300A.

Furthermore, the prism group 300A can be configured to move in the Y-Z plane substantially perpendicular to the projection optical axis Oa1. External light LiA incident from the projection optical system in the illustrated -X direction can be introduced into the imaging optical system 360 along the imaging optical axis Ob1 in the Y-Z plane substantially perpendicular to the projection optical axis Oa1 by being internally reflected multiple times within the prism 330A. Furthermore, the imaging optical system 360 is configured as a reduced imaging optical system and can move between the projection position P1 and the imaging position P2 together with the prism group 300A. As a result, as described above, the prism group 300A can be easily incorporated into equipment, facilitating the miniaturization of projection-type image display devices.

As mentioned above, the above 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 also be applied to embodiments in which modifications, substitutions, additions, omissions, etc. are made. It is also possible to combine the components described in each of the above embodiments to create new embodiments.

Note that this disclosure does not limit the shape or configuration of each prism. For example, each prism constituting a prism group can be configured in any shape depending on the application, may include any number of prism surfaces, or may be composed of multiple prisms.

In addition, in the above embodiment, the prism surface of the third prism is described as being concave or convex, but the present disclosure is not limited to this. For example, one or more prism surfaces of the third prism may be configured to have a free-form surface shape.

As stated above, the embodiments have been described as examples of the technology disclosed herein. For this purpose, the accompanying drawings and detailed description have been provided. Therefore, the components described in the accompanying drawings and detailed description may include 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. Therefore, the fact that these non-essential components are described in the accompanying drawings or detailed description should not be interpreted as immediately indicating that these non-essential components are essential.

While this disclosure has been fully described in connection with preferred embodiments with reference to the accompanying drawings, various modifications are possible within the scope of the claims. Such modifications, as well as embodiments obtained by appropriately combining the technical means disclosed in different embodiments, are also within the technical scope of this disclosure.

This disclosure is applicable to prisms and various projection-type image display devices.

200 Illumination optical system 20 Light source unit 21 Semiconductor laser element 22 Collimating lens 31, 32 Afocal lens 33, 34, 35 Condenser lens 41 Diffuser plate 42 λ/4 plate 45 Dichroic mirror 46 Rod integrator 50 Phosphor wheel 60 Color wheel 73, 74, 75 Lenses constituting illumination light relay optical system 47 Mirror 48 Relay lens group 300, 300a, 300b, 300c, 300d, 300A Prism group 300B Color separation/combining prism 310 First prism 320 Second prism 330, 330a, 330b, 330c, 330d Third prism 340a, 340b, 340c Prism 350 Prism unit 360 Imaging optical system 361 Imaging relay optical system 365 Imaging element 370 Support member 371 Guide rail 372 Mounting surface 373 Opening 375 Driving unit 376 Motor 377 Shaft 378 Bearing member 379 Support base 380A Prism member 400, 401, 402, 403 Light modulation element (DMD)
420, 420A Projection optical system 450, 450A Projection target object 500, 500A Projection imaging optical system Ls, LsA Illumination light Lp, LpA Projection light Li, LiA External light Lim, LimA Imaging light S0, S1, S2, S3 Beam spot Lf DMD-OFF light Oa1 Projection optical axis Ob1 Imaging optical axis Ds Illumination light propagation direction Dm Prism group movement direction Ms Intermediate image 600 Projection type image display device 600A Housing of projection type image display device

Claims (20)

an illumination optical system that supplies illumination light in the visible range;
one or more light modulation elements arranged on the rear side of the first optical axis, which spatially modulate incident light and generate projection light according to image information;
a projection optical system disposed in front of the first optical axis and configured to enlarge and project incident light to display an image;
a prism member including a group of prisms that reflect the illumination light and guide it to the light modulation element, and transmit the light reflected by the light modulation element and guide it to the projection optical system ;
Equipped with
The prism group is
a first prism having a first prism surface and configured to receive the illumination light;
a second prism disposed on the front side of the first prism and having a second prism surface disposed opposite to the first prism surface via an air gap;
a third prism having a third prism surface;
a support member that supports the first prism, the second prism, and the third prism so as to be movable between a first position and a second position in a direction intersecting the first optical axis;
Equipped with
the second prism and the third prism are arranged side by side in a direction of movement between the first position and the second position,
In the first position,
the first prism reflects the received illumination light to the light modulation element at the first prism surface, and transmits first light generated by reflection at the light modulation element through the first prism surface and emits it toward the front side; the second prism transmits the first light incident from the first prism through the second prism surface and emits it toward the front side along the first optical axis;
In the second position,
the third prism receives second light propagating toward the rear side along the first optical axis, reflects at least a portion of the received second light by the third prism surface, and deflects the second light so as to be emitted from the third prism along a second optical axis different from the first optical axis;
Projection-type image display device . further comprising a drive unit for driving the movement between the first position and the second position;
2. The projection type image display device according to claim 1. an imaging optical system configured to receive at least a portion of the second light emitted from the third prism and form an image;
The support member is
the imaging optical system is supported so as to move together with the first prism, the second prism, and the third prism;
3. The projection type image display device according to claim 1 or 2. the third prism surface has a reflectance different from that of the first prism surface in the wavelength region of the first light;
3. The projection type image display device according to claim 1 or 2. The support member is
a support structure configured to support the first prism, the second prism, and the third prism so as to be movable between the first position and the second position in a plane perpendicular to the first optical axis;
3. The projection type image display device according to claim 1 or 2. The support member is
the first prism, the second prism, and the third prism are supported movably between the first position and the second position so as to intersect with a propagation direction of the illumination light in a plane orthogonal to the first optical axis;
6. The projection type image display device according to claim 5. the second optical axis is in a plane perpendicular to the first optical axis;
3. The projection type image display device according to claim 1 or 2. the third prism internally reflects the second light multiple times within the third prism;
the second optical axis is disposed so as to intersect with the propagation direction of the illumination light in a plane perpendicular to the first optical axis;
8. The projection type image display device according to claim 7. the third prism is disposed on the front side of the first prism, and the first prism surface and the third prism surface are cemented together;
3. The projection type image display device according to claim 1 or 2. the third prism is disposed on the front side of the first prism;
further comprising a fourth prism disposed between the third prism and the first prism;
The fourth prism has a fourth prism surface and a fifth prism surface that forms an angle with the fourth prism surface, and is configured so that the fourth prism surface and the first prism surface are joined together, and the fifth prism surface and the third prism surface are joined together.
3. The projection type image display device according to claim 1 or 2. the third prism includes a fifth prism and a sixth prism,
the fifth prism and the sixth prism have prism surfaces adjacent to each other,
The adjacent prism surfaces are arranged opposite each other with a parallel gap therebetween.
3. The projection type image display device according to claim 1 or 2. the second prism surface is coated with an anti-reflection film;
the anti-reflection film has a transmittance of 96% or more with respect to the first light;
3. The projection type image display device according to claim 1 or 2. the third prism surface is coated with a visible partial reflection coating;
The visible light partial reflective coating has a reflectance of 50% or more for light in the visible light range.
3. The projection type image display device according to claim 1 or 2. the third prism surface is coated with an infrared partial reflection coating;
The infrared partial reflective coating has a reflectance of 50% or more for light in the infrared range.
3. The projection type image display device according to claim 1 or 2. the third prism has a prism surface having two or more reflective surfaces that internally reflect at least a portion of the second light;
At least one of the reflective surfaces is configured to totally reflect at least a portion of the second light.
3. The projection type image display device according to claim 1 or 2. the third prism has a prism surface having two or more reflective surfaces that internally reflect at least a portion of the second light;
At least one of the reflecting surfaces has a concave shape toward the direction of the internal reflection of at least a portion of the second light.
3. The projection type image display device according to claim 1 or 2. the third prism has a sixth prism surface that transmits at least a portion of the second light and causes the second light to exit the third prism;
the sixth prism surface has a convex shape in a direction in which at least a part of the second light is emitted from the third prism.
3. The projection type image display device according to claim 1 or 2. At least a portion of the second light is configured to form an intermediate image within the third prism.
3. The projection type image display device according to claim 1 or 2. moreover ,
an image pickup element that receives at least a portion of the second light emitted from the prism group along the second optical axis and converts the received light into an electrical image signal;
Equipped with
3. The projection type image display device according to claim 1 or 2 . the one or more light modulation elements are disposed at fixed positions relative to the first optical axis;
20. The projection type image display device according to claim 19.