WO2023149536A1

WO2023149536A1 - Prism group and projection-type video display device

Info

Publication number: WO2023149536A1
Application number: PCT/JP2023/003533
Authority: WO
Inventors: 紀和山本
Original assignee: パナソニックＩｐマネジメント株式会社
Priority date: 2022-02-07
Filing date: 2023-02-03
Publication date: 2023-08-10

Abstract

This prism group comprises a TIR prism and an imaging light reflecting prism. The TIR prism: reflects illumination light supplied by an illumination optical system and guides the illumination light to an optical modulation element; transmits projection light generated by the reflection at the optical modulation element, and outputs the projection light to a projection optical system on the front side of a projection optical axis along the projection optical axis; and reflects imaging light, which is at least portion of external light entering from the projection optical system and propagating in a direction opposing the front side of the projection optical axis, and guides the imaging light to the imaging light reflecting prism. The imaging light reflecting prism internally reflects the imaging light that has entered from the TIR prism, and guides the imaging light to an imaging element along an imaging optical axis on a plane substantially orthogonal to the projection optical axis.

Description

Prism group and projection type image display device

The present disclosure relates to a prism group and a projection image display device including the same.

Conventionally, both a projection optical system that has an imaging element inside the main body and projects projection light onto a projection target, and an imaging optical system that forms an image on the imaging element using light from the projection target as external light. A projection type image display device having a Such a projection-type image display device has a function of projecting an image onto a projection target and capturing an image of the projected image. 2. Description of the Related Art As this type of projection-type image display apparatus, for example, the apparatus described in Patent Document 1 is known.

A projector (projection-type image display apparatus) described in Patent Document 1 is provided 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. there is The light emitted from the light emitting element enters the TIR prism through the projection lens, is reflected by the reflecting surface of the TIR prism, is emitted, and forms an image on the 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. In the configuration of the projector, the imaging optical system is arranged in a direction inclined with respect to the projection optical axis, and the imaging light is taken out. In such an arrangement, it may be difficult to incorporate the imaging optical system inside the projector device, which causes a problem of increasing the size of the device. In addition, in the configuration of the projector disclosed in Patent Document 1, if an optical component such as a mirror is provided outside the TIR prism to bend the optical path of the imaging light, it is difficult to reduce the size of the apparatus due to the spread of the light beam. Therefore, there has been a demand for a projection-type image display apparatus that can be made more compact than before.

SUMMARY OF THE INVENTION Accordingly, an object of the present disclosure is to solve the above-described problems. An object of the present invention is to provide a group and a projection type image display device having the same.

In order to achieve the above object, the prism group according to the present disclosure includes a TIR prism and an imaging light reflecting prism. , transmits the projection light generated by being reflected by the light modulation element, outputs it along the projection optical axis to the projection optical system on the front side of the projection optical axis, further enters from the projection optical system, and passes through the projection optical axis The imaging light, which is at least part of the external light propagating in the direction facing the front side of the TIR prism, is reflected and guided to the imaging light reflecting prism, and the imaging light reflecting prism internally reflects the imaging light incident from the TIR prism. , along the imaging optical axis in a plane substantially perpendicular to the projection optical axis to the imaging device.

According to the prism group according to one aspect of the present disclosure, the imaging optical system can be easily incorporated inside the equipment of the projection image display device, and the size reduction of the projection image display device can be facilitated.

1 is a schematic diagram showing the overall configuration of a projection display apparatus of Example 1 according to an embodiment of the present disclosure; FIG. FIG. 2 is a layout diagram of the inside of the equipment viewed from the projection optical system side of the projection-type image display apparatus of FIG. 1 ; 1 is a perspective view showing a configuration of a prism group according to an embodiment of the present disclosure; FIG. 4 is a cross-sectional view of a prism group according to an embodiment of the present disclosure; FIG. FIG. 5 is a diagram showing an example of reflection characteristics of a visible region partial reflection coat in the prism group according to the embodiment of the present disclosure; FIG. 5 is a diagram showing an example of reflection characteristics of an infrared region partial reflection coat in the prism group according to the embodiment of the present disclosure; 2 is a diagram showing an example of the spectrum of projection light incident on the projection optical system of FIG. 1; FIG. FIG. 5 is a cross-sectional view of a prism group according to Modification 1 of the embodiment of the present disclosure; FIG. 7 is a cross-sectional view of a prism group according to Modification 2 of the embodiment of the present disclosure; Cross section showing reflection of DMD-OFF light in the prism group according to Modification 1 (FIG. 9A) and the prism group according to Modification 2 (FIG. 9B) of the embodiment of the present disclosure It is a diagram. FIG. 5 is a diagram showing how imaging light propagates through a prism group according to an embodiment of the present disclosure; FIG. 5 is a diagram showing how imaging light propagates through a prism group according to an embodiment of the present disclosure; FIG. 5 is a schematic diagram showing the configuration of a projection imaging optical system of a projection image display apparatus of Example 2 according to an embodiment of the present disclosure;

According to the first aspect of the present disclosure, the TIR prism and the imaging light reflecting prism are provided, and the TIR prism reflects the illumination light supplied by the illumination optical system, guides it to the light modulation element, and reflects the light from the light modulation element. transmits the projection light generated by the projection optical axis, outputs it to the projection optical system on the front side of the projection optical axis along the projection optical axis, further enters from the projection optical system, and faces the front side of the projection optical axis The imaging light, which is at least part of the external light propagating in the direction, is reflected and guided to the imaging light reflecting prism, which internally reflects the imaging light incident from the TIR prism, substantially along the projection optical axis. To provide a prism group that leads to an imaging device along an imaging optical axis in a plane orthogonal to each other.

According to this aspect, the imaging optical system can be easily incorporated inside the equipment of the projection image display device, and the size reduction of the projection image display device can be facilitated.

According to the second aspect of the present disclosure, the TIR prism includes a first prism and a second prism arranged in order along the projection optical axis from the front side of the projection optical axis, and illumination of the second prism The illumination light reflecting surface that reflects light and the projection light incident surface of the first prism on which the projection light is incident are arranged to face each other with a parallel gap therebetween. It has an imaging light incident surface through which light passes, and is arranged adjacent to the first prism via the imaging light incident surface, and the imaging light is internally reflected multiple times in the TIR prism and the imaging light reflecting prism, and the imaging light is captured. The prism group of the first aspect is provided, wherein the optical axis lies in a direction orthogonal to or near a longitudinal axis along which imaging light passes through the TIR prism and the imaging light reflecting prism.

A third aspect of the present disclosure provides the prism group according to the second aspect, wherein the imaging light reflecting prism is integrally configured with the first prism on the imaging light incident surface.

According to a fourth aspect of the present disclosure, the prism according to the second aspect, wherein the imaging light reflecting prism and the first prism are arranged separately with a parallel gap on the imaging light incident surface. Serve the flock.

According to a fifth aspect of the present disclosure, the TIR prism further includes a third prism positioned between the first prism and the second prism, the third prism facing the first prism surface and , a second prism surface forming an angle with the first prism surface, the first prism surface and the projection light incident surface of the first prism being joined, the second prism surface and the second prism surface The prism group according to any one of the second to fourth aspects is provided, wherein the illumination light reflecting surfaces of and are arranged opposite to each other with a parallel gap therebetween.

According to the sixth aspect of the present disclosure, the projection light incident surface is provided with a visible region partial reflection coat, and the visible region partial reflection coat has a reflectance of 2% or more and 15% or less with respect to light in the visible region. and reflecting the imaging light.

According to the seventh aspect of the present disclosure, the projection light incident surface is provided with an infrared partial reflection coat, and the infrared partial reflection coat has a reflectance of 50% or more with respect to infrared light. Provide a group of prisms according to any one of the second to fifth aspects for reflecting light.

According to an eighth aspect of the present disclosure, the imaging light reflecting prism has an internal reflection surface, the imaging light is internally reflected by the internal reflection surface, and the internal reflection surface is directed in a direction in which the imaging light is internally reflected. Provide a prism group according to any one of the first to seventh aspects, having a concave shape.

According to the ninth aspect of the present disclosure, the imaging light forms an intermediate image within the imaging light reflecting prism, the intermediate image is formed at the position of the imaging element, and the intermediate image is spaced apart from the internal reflecting surface. A prism group according to the eighth aspect, located.

According to the tenth aspect of the present disclosure, the imaging light reflecting prism has an imaging light exit surface, the imaging light is transmitted through the imaging light exit surface and is emitted to the imaging element, and the imaging light exit surface includes the imaging light The prism group according to any one of the first to ninth aspects is provided, which has a convex shape facing the direction in which the light exits to the imaging device.

According to an eleventh aspect of the present disclosure, an illumination optical system that supplies illumination light in the visible range, a prism member including the prism group according to any one of the first to tenth aspects, and the illumination optical system one or more light modulation elements that spatially modulate incident light guided by a prism member to generate projection light corresponding to image information; Provided is a projection type image display device comprising a projection optical system for displaying an image and an imaging device for receiving imaging light output from an imaging light reflection prism and converting it into an electrical image signal.

By appropriately combining any of the various embodiments described above, the respective effects can be achieved.

Hereinafter, embodiments will be described in detail with reference to the drawings as appropriate. However, more detailed description than necessary may be omitted. For example, detailed descriptions of well-known matters and redundant descriptions of substantially the same configurations may be omitted. This is to avoid unnecessary verbosity in the following description and to facilitate understanding by those skilled in the art.

The accompanying drawings and the following description are provided to allow 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, each element is exaggerated for ease of explanation.

<<Embodiment>>
Hereinafter, a prism group according to an embodiment of the present disclosure and a projection type image display device including the prism group will be described with reference to FIGS. 1 to 12. FIG. As a specific example of the projection display apparatus to which the prism group according to the present disclosure is applied, a single-panel projection display apparatus (Example 1) having one light modulation element and three light modulation elements are provided. A three-panel projection type image display apparatus (Embodiment 2) will be described.

(Configuration of projection-type image display device 600 of embodiment 1)
The configuration of the projection display apparatus 600 of Example 1 according to the embodiment of the present disclosure will be described below with reference to FIGS. 1 and 2. FIG. FIG. 1 is a schematic diagram showing the overall configuration of a projection display apparatus 600 of Example 1 according to the embodiment of the present disclosure. 1A and 1B are schematic diagrams showing the overall configuration of the projection image display device 600 in the XZ plane of the drawing. (c) of FIG. 1 is a schematic diagram showing the prism group 300, the imaging optical system 440, etc. viewed in the −Z direction from the left side of (a) of FIG. 1, that is, from the +Z side of (a) of FIG. is. Note that the projection-type image display device according to the embodiment of the present disclosure is, for example, a high-brightness projector and may be used for projection mapping or the like, and may be a low-brightness projector for home use. may

A projection-type image display apparatus 600 in FIG. 1 includes an illumination optical system 200 that supplies illumination light, and a projection imaging optical system 500 . The illumination optical system 200 includes a light source unit 20, afocal lenses 31 and 32, a diffusion plate 41, a λ/4 plate 42, condenser lenses 33, 34 and 35, a dichroic mirror 45, a rod integrator 46, It includes a phosphor wheel 50, a color wheel 60, and lenses 73, 74, 75 forming an illumination light relay optical system.

<Illumination optical system>
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 around 455 nm and is used as image light and also as excitation light for exciting the phosphors of 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 collimator lens 22, converged by the afocal lenses 31 and 32, transmitted through the diffusion plate 41, and directed to the dichroic mirror 45. Incident.

In the present 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 and the P-polarized blue light and other colored lights can pass through. The blue light reflected by the dichroic mirror 45 travels approximately in the −Z direction, passes through the λ/4 plate 42, is condensed by the condenser lenses 33 and 34, and enters the phosphor wheel 50. excites the phosphor to emit light.

As the phosphor wheel 50 rotates, different segments of the phosphor layer are excited by the incident blue light to generate fluorescence including, for example, yellow emission component light, green emission component light, and the like. can. Also, 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, becoming P-polarized blue component light, which passes through the dichroic mirror 45 . do. The blue component light and the emission component light of each color gamut transmitted through the dichroic mirror 45 travel substantially in the Z direction and enter the color wheel 60 via the condenser lens 35 .

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

The light emitted from the rod integrator 46 passes through the lenses 73, 74, and 75 constituting the illumination light relay optical system, is emitted from the illumination optical system 200, and becomes the illumination light Ls of white light as a time average. The light enters the projection imaging optical system 500 .

<Projection imaging optical system>
Next, the projection imaging optical system 500 includes a prism group 300 , an optical modulation element 400 , a projection optical system 420 , an imaging optical system 440 and an imaging element 450 . Further, in the present embodiment, the imaging optical system 440 and the imaging device 450 are arranged on the YZ plane substantially perpendicular to the projection optical axis Oa1 in the X direction in the drawing, and the imaging light Li is projected onto the imaging optical axis Ob1 in the +Y direction. incident on the imaging element 450 along (shown in (c) of FIG. 1).

In the projection imaging optical system 500 , the prism group 300 is composed of a TIR (Total Internal Reflection) prism 310 (total internal reflection prism) and an imaging light reflection prism 350 . In this embodiment, the TIR prism 310 is configured by joining a substantially triangular prism-shaped first prism 320 and a second prism 330 with a small gap therebetween. Using total reflection, the TIR prism 310 deflects the traveling direction of the incident illumination light Ls and guides it to the light modulation element 400 . The imaging light reflecting prism 350 is positioned adjacent to the TIR prism 310 . The imaging light reflecting prism 350 and the TIR prism 310 may be configured separately (FIG. 7) or integrated (FIGS. 4 and 8). In FIG. 1, the configuration in which the imaging light reflection prism 350 and the TIR prism 310 are separated is shown. The imaging light reflecting prism 350 further reflects and deflects the incident imaging light Li reflected by the TIR prism 310 and guides it to the imaging element 450 . The configuration of the prism group 300 will be detailed later.

The light modulation element 400 uses a DMD (Digital Mirror Device), which modulates the component light of each color gamut included in the illumination light Ls based on the video signal, and becomes the projection light Lp for each pixel. DMD-ON light ( ON light) or DMD-OFF light Lf (OFF light). 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.

The projection light Lp passes through the TIR prism 310, is output from the projection light exit surface 321, and propagates to the projection optical system 420 along the projection optical axis Oa1. A lens group LGp included in the projection optical system 420 enlarges and projects the projection light Lp onto a projection object such as the screen 430 to display an image.

On the other hand, the imaging light Li, which is at least part of the external light Le reflected from the screen 430 in the −X direction in the figure, is used to capture the projected image by the imaging device 450 built in the projection imaging optical system 500. can do.

As shown, the external light Le enters from the projection optical system 420, propagates in the -X direction along the projection optical axis Oa1, and exits the projection optical system side of the first prism 320 of the TIR prism 310. Incident on surface 321 . In the TIR prism 310 , the imaging light Li, which is at least part of the external light Le, is internally reflected and deflected to enter the imaging light reflection prism 350 . The imaging light Li incident on the imaging light reflecting prism 350 is further internally reflected and deflected within the imaging light reflecting prism 350, and emitted from the imaging light exit surface 353 of the imaging light reflecting prism 350 along the imaging optical axis Ob1. It is introduced into the imaging optical system 440 in the +Y direction.

The imaging optical system 440 can be composed of a plurality of optical components, and can be composed of a relay optical system composed of a plurality of lenses in this embodiment. The imaging light Li emitted from the imaging light exit surface 353 and propagating along the imaging optical axis Ob1 in the +Y direction can be imaged on the imaging device 450 by the imaging optical system 440 . Note that the present disclosure does not limit the magnification of image formation by the imaging optical system, and the imaging optical system 440 may be a reduction imaging optical system, or may be an equal magnification or magnification imaging optical system. . The imaging element 450 can be composed of 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.

<Arrangement inside the projection display device>
Next, the arrangement inside the projection display apparatus 600 according to the embodiment of the present disclosure will be described with reference to FIG. FIG. 2 is a layout diagram of the interior of the projection display apparatus 600 of FIG. 1 as viewed from the projection optical system side. However, FIG. 1 is a configuration example in which the imaging optical system 440 and the imaging device 450 are arranged on the −Y side of the prism group 300, and FIG. A configuration example arranged on the Y side is shown.

When viewed from the side of the projection optical system 420 in FIG. 1, that is, in the −X direction from the top of FIG. Located below the lens group LGp, the light modulation element 400 is located approximately in the center of the lens group LGp. The illumination light Ls emitted from the illumination optical system 200 is deflected by the folding mirror 47, passes through the relay lens group 48, the TIR prism 310 and the imaging light reflecting prism 350, along the longitudinal axis Ob2 of the prism group 300. The light enters the prism group 300 approximately in the +Z direction in the drawing.

The DMD-ON light (projection light Lp, not shown in FIG. 2) from the light modulation element 400 is emitted in the +X direction shown, and the DMD-OFF light Lf is deflected in a direction near the longitudinal axis Ob2 of the prism group 300. be done.

If the lens group LGp is designed to have a short back focus, the apparatus can be made smaller and less expensive. It is configured as close as possible in the range. Therefore, the space inside the housing 600A is small in the illustrated X direction, which is the direction in which the projection light Lp is emitted, and the layout of optical components and the like is limited in terms of design.

In the projection-type image display device 600 according to the present disclosure, as described above, the imaging light Li, which is at least part of the external light Le incident in the −X direction in the drawing from the projection optical system, passes through the prism group 300 multiple times. By being reflected and deflected, it can be introduced into the imaging element 450 along the imaging optical axis Ob1 in the YZ plane substantially perpendicular to the projection optical axis Oa1. As a result, the imaging optical system 440 can be easily installed inside the apparatus without interfering with the projection optical system 420, and the projection type image can be displayed without changing the projection optical system provided in the conventional projection type image display apparatus. It can be used for display devices. This makes it possible to improve or expand the functions of the device at low cost.

Further, by internally reflecting and deflecting the imaging light Li a plurality of times inside the prism group 300, the air-equivalent length of propagation of the imaging light can be shortened. A reduction in lens diameter and thickness is possible. This makes it possible to reduce the size of the projection display apparatus more easily than before.

In addition, as shown in FIG. 2, in an actual projection-type image display apparatus, when viewed from the projection optical system, the illumination light Ls incident on the prism group 300 is directed from the lower right of the drawing to the long side of the housing 600A. It is designed to be incident from an oblique direction of 45 degrees. This is because the rotation axis of the micromirror of the DMD as the light modulation element 400 is inclined by 45 degrees. Therefore, the prism group 300 that guides the illumination light Ls to the light modulation element 400 is also arranged such that the longitudinal axis Ob2 is inclined about 45 degrees with respect to the long side of the housing 600A. With such an arrangement, the space on the side of the longitudinal axis Ob2 of the prism group 300 inside the device is small, as illustrated. Furthermore, if the image pickup optical system is placed near the direction in which the DMD-OFF light Lf is guided, the influence of stray light due to the DMD-OFF light Lf increases.

In the present embodiment, as shown in FIG. 2 , the imaging light Li is internally reflected multiple times in the prism group 300, so that the imaging light Li is located in a direction orthogonal to the longitudinal axis Ob2 of the prism group 300 or in the vicinity thereof. It can be guided along the optical axis Ob1. As a result, the influence of stray light caused by the DMD-OFF light Lf can be suppressed, and the space inside the device can be effectively used, leading to further downsizing of the device.

Although FIG. 2 shows the imaging optical axis Ob1 to be substantially orthogonal to the longitudinal axis Ob2 of the prism group 300, the present disclosure is not limited to this. The imaging optical axis Ob1 may be arranged near the direction orthogonal to the longitudinal axis Ob2 of the prism group 300 . 1 and 2, the imaging optical system 440 and the imaging device 450 may be arranged on either side of the prism group 300 along the imaging optical axis Ob1.

<Structure of Prism Group 300>
The configuration of the prism group 300 of the projection imaging optical system 500 according to the embodiment will be described with reference to FIGS. For clarity, each light beam is shown with only the chief ray.

FIG. 3 is a perspective view showing the configuration of the prism group 300 according to the embodiment of the present disclosure. FIG. 4 is a cross-sectional view of prism group 300 according to an embodiment of the present disclosure. Also, the prism group 300 in FIG. 3 is shown in a configuration in which the imaging light reflecting prism 350 and the TIR prism 310 are integrally formed.

The TIR prism 310 includes a first prism 320 and a second prism 330 having a substantially triangular prism shape. , are arranged in order 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 400 . The first prism 320 has a projection light entrance surface 322 and a projection light exit surface 321 for the projection light Lp that is reflected by the light modulation element 400 and travels in the +X direction. The first prism 320 and the second prism 330 are joined with a parallel gap 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 400 passes through the second prism 330, enters the first prism 320, further passes through the first prism 320, and exits from the projection light exit surface 321. It is output to the projection optical system along the axis Oa1 and imaged. The DMD-OFF light Lf is removed by passing through the TIR prism 310 in a direction deflected from the projection optical axis Oa1.

The imaging light reflection prism 350 arranged adjacent to the first prism 320 has an imaging light entrance surface 351 , an internal reflection surface 352 and an imaging light exit surface 353 . In this embodiment, the first prism 320 of the TIR prism 310 and the imaging light reflection prism 350 are integrally formed on the imaging light incident surface 351 .

As shown, the external light Le incident on the first prism 320 in the -X direction from the projection optical system (not shown in FIG. 3) forms a beam spot S1 on the projection light incident surface 322. As shown in FIG. The projection light incident surface 322 is partially reflective coated, and at least part of the incident external light Le is internally reflected by the partially reflective coating as imaging light Li, reaches the projection light exit surface 321, and forms a beam spot S2. do. Subsequently, the imaging light Li is internally reflected by the projection light exit surface 321 , reaches the imaging light incident surface 351 of the imaging light reflecting prism 350 , passes through the imaging light incident surface 351 , and enters the imaging light reflecting prism 350 .

In the imaging light reflecting prism 350, the imaging light Li forms a beam spot S3 on the internal reflection surface 352 and is internally reflected, and then emitted from the imaging light exit surface 353 along the imaging optical axis Ob1 in the +Y direction in the drawing, thereby performing imaging. An image can be formed on the imaging element by the optical system 440 .

As described above, in the present embodiment, the imaging light Li is internally reflected three times in the prism group 300, and then lies on the YZ plane substantially orthogonal to the projection optical axis Oa1, and It can be introduced into the imaging device 450 along the imaging optical axis Ob1 located in the direction orthogonal to the directional axis Ob2 or in the vicinity thereof. Note that the present disclosure does not limit the number of internal reflections of the imaging light Li within the prism group 300 . Although not limited to this, preferably, the imaging light Li may be totally reflected by the projection light exit surface 321 and enter the imaging light reflection prism 350 . This makes it possible to efficiently use the imaging light.

5A and 5B are diagrams showing examples of reflection characteristics of the partially reflective coating in the prism group 300 according to the embodiment of the present disclosure. The partial reflection coat applied to the projection light incident surface 322 may be a visible partial reflection coat (FIG. 5A) or an infrared partial reflection coat (FIG. 5B).

When the visible region partial reflection coating is applied, the visible region projection light Lp incident on the projection light incident surface 322 from the light modulation element 400 is also partly reflected by the reflection characteristics of the visible region partial reflection coating. A loss occurs in the light Lp. In the case of the present embodiment, the visible region partial reflection coating shown in FIG. 5A has a reflectance of 2% or more and 15% or less with respect to light in the visible region with a wavelength of 400 nm to 700 nm. As a result, a part of external light in the visible range can be taken in as imaging light to capture an image without causing a large loss in the projection light Lp. Note that the reflection characteristics of the visible region partial reflection coat are not limited to this.

On the other hand, when the infrared region partial reflection coating is applied, as shown in FIG. 5B, in the present embodiment, the infrared region partial reflection coating reflects 50% or more of infrared light having a wavelength of 750 nm or more. reflect the imaging light with an index. Note that the reflection characteristics of the infrared region partial reflection coat are not limited to this.

FIG. 6 is a diagram showing an example of the spectrum of projection light incident on the projection optical system 420 of FIG. As shown in FIG. 6, the projection light incident on the projection optical system includes a blue light component LB of approximately 440 nm to 470 nm, a green light component LG of 520 nm to 570 nm, and a red region (yellow light component of 590 nm to 650 nm). ), and does not contain a light component in the infrared region. Therefore, by taking in external light in the infrared region as imaging light and transmitting approximately 100% of the projection light Lp in the visible region, it is possible to perform imaging without loss of projection light. Imaging using infrared rays can be used to detect or track motion in a completely dark place, and is used in night photography, night vision surveillance cameras, and the like.

(Prism group 300a according to modification 1)
Next, a modified example of the prism group 300 will be described with reference to FIGS. 7 and 8. FIG. FIG. 7 is a cross-sectional view of a prism group 300a according to Modification 1 of the embodiment of the present disclosure, and FIG. 8 is a cross-sectional view of a prism group 300b according to Modification 2 of the embodiment of the present disclosure.

Similar to the prism group 300 shown in FIGS. 3-4, the prism group 300a shown in FIG. 7 is composed of a TIR prism 310a and an imaging light reflection prism 350a. As shown, the prism group 300a differs from the prism group 300 in that the imaging light reflection prism 350a is formed separately from the TIR prism 310a at the imaging light incident surface 351a.

As shown in FIG. 7, in the prism group 300a, 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 separated from each other with a parallel gap between the prism surface 323a and the imaging light incident surface 351a.

In the prism group 300a, the 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. At least part of the incident external light Le is internally reflected as imaging light Lia by the partial reflection coat of the projection light entrance surface 322a, reaches the projection light exit surface 321a, and forms a beam spot S2a. Subsequently, the imaging light Lia is internally reflected by the projection light exit surface 321a, passes through the prism surface 323a, reaches the imaging light incident surface 351a of the imaging light reflecting prism 350a, is transmitted therethrough, and enters the imaging light reflecting prism 350a. Incident. In the imaging light reflecting prism 350a, the imaging light Lia forms a beam spot S3a on the internal reflection surface 352a, is internally reflected by the internal reflection surface 352a, and is emitted from the imaging light exit surface 353a.

As described above, the projection light Lp is transmitted through the TIR prism and emitted to the projection optical system. Since the high-energy projection light Lp generates heat when passing through the TIR prism, the TIR prism must be made of a heat-resistant glass material. In the prism group 300, if the imaging light reflecting prism is integrally formed with the TIR prism, the imaging light reflecting prism made of glass is required because it is affected by heat conduction. Also, in order to suppress the occurrence of aberration due to changes in the refractive index, it is desirable that the imaging light reflection prism 350 be made of the same glass material as the TIR prism 310 . On the other hand, in the prism group 300a shown in FIG. 7, the imaging light reflecting prism 350a is formed separately from the TIR prism 310a to suppress heat conduction. can be produced by adopting Therefore, by forming the imaging prism separately from the TIR prism, it is possible to select materials with a high degree of freedom. Since optical parts made of resin have excellent workability, there is also the advantage that prism members having optical surfaces with complicated geometric shapes can be manufactured at low cost.

(Prism group 300b according to modification 2)
A prism group 300b shown in FIG. 8 is composed of a TIR prism 310b, an imaging light reflecting prism 350b, and a third prism 340, and differs from the prism group 300 in that the third prism 340 is provided. As shown, in this embodiment, the first prism 320b of the TIR prism 310b and the imaging light reflection prism 350b are integrally formed. However, the present disclosure is not so limited. In the prism group 300b, the first prism 320b of the TIR prism 310b and the imaging light reflecting prism 350b may be formed separately, similar to the prism group 300a shown in FIG.

As shown in FIG. 8, the third prism 340 of the prism group 300b 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 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 facing each other with a parallel gap therebetween. Although not limited to this, in the present 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 to 10 degrees, and in this embodiment form an apex angle A of about 3 degrees. .

In the prism group 300b, 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. At least part of the incident external light Le is internally reflected as imaging light Lib by the partial reflection coat of the projection light entrance surface 322b, reaches the projection light exit surface 321b, and forms a beam spot S2b. Subsequently, the imaging light Lib is internally reflected by the projection light exit surface 321b and enters the imaging light reflection prism 350b. In the imaging light reflection prism 350b, the imaging light Lib forms a beam spot S3b on the internal reflection surface 352b, is internally reflected by the internal reflection surface 352b, and is emitted from the imaging light exit surface 353b.

For comparison, FIG. 8 also shows a beam spot S3a formed by the imaging light Lia on the internal reflecting surface 352a (not shown) of the imaging light reflecting prism 350a in the prism group 300a shown in FIG. As shown, the beam spot S3b formed by the imaging light Lib in the prism group 300b is smaller than the beam spot S3a, and the center position of the beam spot S3b is closer to the projection optical axis Oa1 than the center position of the beam spot S3a. is close by a distance D to the side. It can be seen that the propagation optical path of the imaging light Lib within the prism group 300b is shorter than the propagation optical path of the imaging light Lia within the prism group 300a.

In the prism group 300b, the reason why the beam spot S3b formed by the imaging light Lib on the internal reflecting surface of the imaging light reflecting prism has changed in this way is that the third prism 340 is provided. As shown in FIG. 8, the second prism 330b is configured such that an illumination light reflecting surface 331b and a bottom surface 332b perpendicular to the projection optical axis Oa1 form an angle α1. The angle α1 is restricted by the characteristics of the DMD as the light modulation element 400 and cannot be designed freely. Since the illumination light reflecting surface 331b and the projection light incident surface 322b are arranged facing each other across a parallel gap, the angle of reflection 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 formed 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. , the reflection angle of the imaging light Lib on the projection light incident surface 322b can be adjusted. Thereby, the propagation optical path of the imaging light Lib can be shortened, and the prism group 300b can be made more compact.

Furthermore, by providing the wedge-shaped third prism 340, the influence of stray light within the prism group 300b can be suppressed. This will be described with reference to FIG. FIG. 9 shows DMD-OFF in a prism group 300a ((a) in FIG. 9) according to Modification 1 of the embodiment of the present disclosure and a prism group 300b ((b) in FIG. 9) according to Modification 2. FIG. 4 is a cross-sectional view showing reflection of light;

As shown in FIG. 9, the DMD-OFF light Lf passes through the TIR prism and is removed. At that time, the DMD-OFF light Lf is partially reflected by the visible region partial reflection coat on the projection light incident surface. In the prism group 300a shown in FIG. 9A, part of the DMD-OFF light Lf reflected by the projection light incident surface 322a (OFF light Lf1a) is light-modulated by the inclination angle α1 of the projection light incident surface 322a. After entering the element 400 and being reflected by the light modulation element 400, it enters the prism group 300a and becomes stray light. On the other hand, in the prism group 300b shown in FIG. 9B, the inclination angle α2 of the projection light incident surface 322b is greater than the inclination angle α1 of the projection light incident surface 322a by the apex angle A of the third prism 340. growing. As a result, part of the DMD-OFF light Lf (OFF light Lf1b) reflected by the projection light incident surface 322b does not enter the light modulation element 400 and is removed. By providing the third prism 340 in this way, the tilt angle of the projection light incident surface 322b can be appropriately adjusted, and the influence of stray light within the prism group 300b due to the DMD-OFF light can be suppressed. .

(Curvature Design of Prism Surface of Imaging Light Reflecting Prism)
A case where the internal reflection surface and the imaging light exit surface of the prism group imaging light reflection prism according to the embodiment of the present disclosure are given curvature will be described with reference to FIGS. 10-11. FIG. 10 is a diagram showing how imaging light propagates through a prism group 300 ((a) in FIG. 10) and a prism group 300c ((b) in FIG. 10) according to the embodiment of the present disclosure. FIG. 11 is a diagram showing how imaging light propagates through a prism group 300 (FIG. 11(a)) and a prism group 300d (FIG. 11(b)) according to the embodiment of the present disclosure.

As described above, the external light Le forms the beam spot S1 on the projection light incident surface 322 (see FIGS. 3 and 4), and at least a part of the external light Le is internally reflected as the imaging light Li, and the projection light It reaches the exit surface 321 (see FIGS. 3 and 4) to form a beam spot S2 and is internally reflected to enter the imaging light reflection prism 350 . Further, the beam spot S3 is formed on the internal reflecting surface 352 of the imaging light reflecting prism 350 and is internally reflected, and then emitted from the imaging light exit surface 353 . As shown in FIGS. 10(a) and 11(a), in the practice of the present disclosure, external light Le reflected from screen 430 (shown in FIG. 1) and propagating in the −X direction is projected onto the projection optical system. 420 and enters the prism group 300 . At this time, after the external light Le is converged by the projection optical system 420 to form the beam spot S1, the imaging light Li, which is at least part of the external light Le, is converged to form the beam spot S2. After being incident on the imaging light reflection prism 350 , the imaging light Li further converges to form an intermediate image Ms at a position conjugate with the screen 430 with respect to the lens group LGp of the projection optical system 420 . In this embodiment, the intermediate image Ms is formed at a position spaced apart from the internal reflection surface 352 . After forming the intermediate image Ms, the imaging light Li gradually expands as it travels toward the internal reflection surface 352 and forms a beam spot S3 on the internal reflection surface 352 . The imaging light Li is reflected by the internal reflection surface 352 toward the imaging light exit surface 353 , passes through the imaging light exit surface 353 , is emitted, and forms an image on the imaging device 450 by the imaging optical system 440 .

In the prism group 300c shown in (b) of FIG. 10, the same reference numerals are given to the same elements as those of the prism group 300 of (a) of FIG. 10, and the description thereof is omitted. In the present embodiment, in the prism group 300c, the internal reflection surface 352c of the imaging light reflecting prism 350c is configured to have a concave shape C1 in the direction in which the imaging light Lic is internally reflected on the internal reflection surface 352c. can do. The concave shape C1 can focus the reflected imaging light as a concave mirror with positive power. In this way, by giving curvature to the internal reflection surface 352c of the imaging light reflecting prism, the spread of the imaging light Lic within the prism group 300c is suppressed, and thus the spread of the emitted imaging light Lic is defined. can be done. Therefore, the imaging optical system 440c in the latter stage can be constructed using thin optical parts having a smaller diameter than the imaging optical system 440 shown in FIG. 10(a). As a result, the propagation optical path length of the imaging light Lic to the imaging element 450 can be shortened by the distance d1 from the propagation optical path length of the imaging light Li emitted from the prism group 300, as shown in the drawing. Therefore, it is possible to make the imaging optical system even more compact.

Next, in a prism group 300d shown in (b) of FIG. 11, the same reference numerals are given to the same elements as those of the prism group 300 of (a) of FIG. 11, and description thereof will be omitted. In the present embodiment, in the prism group 300d, the imaging light exit surface 353d of the imaging light reflecting prism 350d can be configured to have a convex shape C2 in the direction in which the imaging light Lid is emitted to the imaging element 450. can. The shape C2 of the convex surface can converge the emitted imaging light as a convex lens with positive power. In this way, by imparting a curvature to the imaging light exit surface 353d of the imaging light reflecting prism, it is possible to define the spread of the emitted imaging light Lid. Therefore, the imaging optical system 440d in the latter stage can reduce the number of parts of the optical system compared to the imaging optical system 440 shown in FIG. 10(a). As a result, the propagation optical path length of the imaging light Lid to the imaging device 450 can be shortened by a distance d2 from the propagation optical path length of the imaging light Li emitted from the prism group 300, as shown in the drawing. Therefore, it is possible to make the imaging optical system even more compact.

Although not shown here, the imaging light incident surface 351 of the imaging light reflecting prism can also have a curvature. By imparting curvature to one or more prism surfaces of the imaging light reflecting prism, the imaging optical system can be made compact, and the entire apparatus can be further miniaturized.

(Configuration of projection imaging optical system 500A of Example 2)
FIG. 12 is a schematic diagram showing a configuration of a projection imaging optical system 500A of a projection image display apparatus of Example 2 according to the embodiment of the present disclosure. The projection-type image display apparatus according to the present embodiment is a three-panel type projection-type image display apparatus, and includes an illumination optical system and a projection imaging optical system. Since the illumination optical system has a well-known configuration, FIG. 12 does not show the illumination optical system, but shows only the projection imaging optical system 500A. FIG. 12(b) is a schematic diagram showing the configuration of the projection imaging optical system 500A in the illustrated XZ plane, and FIG. 12(a) is the left side of FIG. is a schematic view showing the projection imaging optical system 500A viewed in the -Z direction from the +Z side of (b) of FIG.

As shown in FIG. 12, the projection imaging optical system 500A includes a prism member 360. As shown in FIG. Prism member 360 is configured by prism group 300A and color separation/synthesis prism 380A according to the embodiment of the present disclosure. The prism group 300A is located on the front side (on the side of the projection optical system 420A) of the color separation/synthesis prism 380A. Illumination light LsA of each color gamut from the illumination optical system passes through TIR prism 310A of prism group 300A and enters color separation/combination prism 380A.

The color separation/synthesis prism 380A includes prisms 381A, 382A, and 383A arranged in order from the projection optical system 420A side along the projection optical axis Oa1. The light of each color gamut included in the incident illumination light is color-separated by the color separation/synthesis prism 380A and separately guided to the three corresponding light modulation elements 401, 402, and 403. FIG. Each of the light modulation elements 401, 402, and 403 modulates incident light of each color gamut based on a video signal, and transmits the modulated light components of each color gamut again to each of the three prisms of the color separation/synthesis prism 380A. reflect.

The color separation/synthesis prism 380A guides the light for projection (DMD-ON light) reflected by the DMD within each prism to the projection optical axis Oa1, performs color synthesis again, and outputs the synthesized projection light LpA along the projection optical axis Oa1. along the +X direction. Light not to be projected (DMD-OFF light, not shown) is deflected away from the projection optical axis Oa1 and removed. Projection light LpA is output from color separation/combination prism 380A, passes through TIR prism 310A on the front side of projection optical axis Oa1, and propagates to projection optical system 420A. The projection optical system 420A enlarges and projects the projection light LpA onto the screen 430A to display an image.

On the other hand, the external light LeA reflected from the screen in the −X direction in the figure enters from the projection optical system 420A, propagates in the −X direction along the projection optical axis Oa1, and enters the first prism 320A of the TIR prism 310A. do. At least part of the external light LeA is reflected as imaging light LiA within the first prism 320A, deflected, and enters the imaging light reflecting prism 350A. Subsequently, the imaging light LiA incident on the imaging light reflecting prism 350A is further reflected and deflected within the imaging light reflecting prism 350A, and is emitted from the imaging light exit surface 353A of the imaging light reflecting prism 350A along the imaging optical axis Ob1. be. The emitted imaging light LiA travels in the +Y direction in the drawing, is introduced into the imaging optical system 440A, and forms an image on the imaging element 450A by the imaging optical system 440A.

In this way, the imaging light LiA, which is at least a part of the external light LeA incident in the −X direction in the drawing from the projection optical system, is reflected multiple times in the prism group 300A, thereby substantially perpendicular to the projection optical axis Oa1. It can be introduced into the imaging device 450A along the imaging optical axis Ob1 on the YZ plane. As a result, as described above, the imaging optical system 440A can be easily incorporated into the apparatus without interfering with the projection optical system 420A. In addition, by reflecting and deflecting the imaging light LiA inside the prism group 300A, the air-equivalent length of propagation of the imaging light can be shortened, facilitating miniaturization of the projection display apparatus.

As described above, the above embodiment has been described as an example of the technology disclosed in the present application. However, the technology in the present disclosure is not limited to this, and can also be applied to embodiments with modifications, replacements, additions, omissions, and the like. Moreover, it is also possible to combine the constituent elements described in each of the above embodiments to form a new embodiment.

Note that the present disclosure does not limit the shape of each prism. For example, each prism constituting the prism group may have a substantially triangular prism shape, a substantially quadrangular prism shape, or may have another shape.

Also, the present disclosure does not limit the prism surfaces included in each prism. For example, the TIR prism and the imaging light reflection prism may further include another prism surface, and the imaging light may be reflected by the other prism surface.

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

As described above, the embodiment has been described as an example of the technology of the present disclosure. To that end, the accompanying drawings and detailed description have been provided. Therefore, among the components described in the attached drawings and detailed description, there are not only components essential for solving the problem, but also components not essential for solving the problem in order to exemplify the above technology. can also be included. Therefore, it should not be determined that those non-essential components are essential just because they are described in the attached drawings and detailed description.

Although the present disclosure has been fully described in relation to preferred embodiments with reference to the accompanying drawings, various modifications are possible within the scope indicated in the claims. Such modifications and embodiments obtained by appropriately combining technical means disclosed in different embodiments are also included in the technical scope of the present disclosure.

The present disclosure is applicable to prisms and to 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 diffusion plate 42 λ/4 plate 45 dichroic mirror 46 rod integrator 50 phosphor wheel 60 color wheel 73, 74, 75 Lens constituting illumination light relay optical system 47 Mirror 48 Relay lens group 300, 300a, 300b, 300c, 300d, 300A Prism group 310, 310a, 310b, 310A TIR prism 320, 320a, 320b, 320A, 330, 330b, 340, 381A, 382A, 383A Prism 350, 350a, 350b, 350c, 350d, 350A Imaging light reflection prism 321, 321a, 321b Projection light exit surface 322, 322a, 322b Projection light entrance surface 323a, 341, 342 Prism surface 331, 331b Illumination light reflecting surface 351, 351a Imaging light incident surface 352, 352a, 352b, 352c Internal reflection surface 353, 353a, 353b, 353d, 353A Imaging light exit surface 360 Prism member 380A Color separation/synthesis prism 400, 401, 402 , 403 light modulation element (DMD)
420, 420A Projection optical system 430, 430A Screen 440, 440c, 440d, 440A Imaging optical system 450, 450A Imaging device 500, 500A Projection imaging optical system C1 Concave shape C2 Convex shape Ls, LsA Illumination light Lp, LpA Projection light Le, LeA External light Li, Lia, Lib, Lic, Lid, LiA Imaging light S1, S2, S3, S1a, S2a, S3a, S1b, S2b, S3b Beam spot Lf DMD-OFF light Oa1 Projection optical axis Ob1 Imaging optical axis Ob2 Longitudinal axis of prism group Ms Intermediate image 600 Projection type image display device 600A Housing of projection type image display device

Claims

comprising a TIR prism and an imaging light reflection prism,
The TIR prism is
The illumination light supplied by the illumination optical system is reflected and guided to the light modulation element, and the projection light generated by being reflected by the light modulation element is transmitted, along the projection optical axis in front of the projection optical axis. The imaging light, which is at least a part of the external light that is incident from the projection optical system and propagated in the direction opposite to the front side of the projection optical axis, is reflected to perform the imaging. leading to a light reflecting prism,
The imaging light reflecting prism is
internally reflecting the imaging light incident from the TIR prism and guiding it to an imaging device along an imaging optical axis in a plane substantially orthogonal to the projection optical axis;
Prism group.
The TIR prism includes a first prism and a second prism arranged in order from the front side of the projection optical axis along the projection optical axis,
an illumination light reflecting surface of the second prism on which the illumination light is reflected and a projection light incident surface of the first prism on which the projection light is incident are arranged to face each other with a parallel gap therebetween,
The imaging light reflecting prism has an imaging light incident surface through which the imaging light from the TIR prism passes, and is arranged adjacent to the first prism via the imaging light incident surface,
the imaging light is internally reflected multiple times within the TIR prism and the imaging light reflection prism;
the imaging optical axis is located in a direction perpendicular to or near a longitudinal axis along which the imaging light passes through the TIR prism and the imaging light reflecting prism;
The prism group according to claim 1.
The imaging light reflecting prism is configured integrally with the first prism on the imaging light incident surface,
The prism group according to claim 2.
The imaging light reflecting prism and the first prism are arranged separately with a parallel gap on the imaging light incident surface,
The prism group according to claim 2.
the TIR prism further includes a third prism positioned between the first prism and the second prism;
The third prism has a first prism surface and a second prism surface forming an angle with the first prism surface, and the projected light from the first prism surface and the first prism is the second prism surface and the illumination light reflecting surface of the second prism are arranged to face each other with a parallel gap therebetween;
The prism group according to claim 2.
The projection light incident surface is coated with a visible region partial reflection coating,
The visible region partial reflection coat reflects the imaging light with a reflectance of 2% or more and 15% or less for light in the visible region.
The prism group according to claim 2.
The projection light incident surface is coated with an infrared region partial reflection coat,
The infrared region partial reflection coat reflects the imaging light with a reflectance of 50% or more for light in the infrared region,
The prism group according to claim 2.
The imaging light reflecting prism has an internal reflective surface,
at least a portion of the imaging light is internally reflected at the internally reflective surface;
wherein the internal reflection surface has a concave shape in a direction in which the imaging light is internally reflected;
The prism group according to claim 1.
The imaging light forms an intermediate image within the imaging light reflecting prism, and forms the intermediate image at the position of the imaging device,
the intermediate image is spaced from the internally reflective surface;
A prism group according to claim 8 .
The imaging light reflecting prism has an imaging light exit surface,
the imaging light is transmitted through the imaging light exit surface and emitted to the imaging element;
The imaging light exit surface has a convex shape in a direction in which the imaging light is emitted to the imaging device,
The prism group according to claim 1.
an illumination optical system that supplies illumination light in the visible range;
a prism member including the prism group according to any one of claims 1 to 10;
one or more light modulation elements that spatially modulate the incident light supplied by the illumination optical system and guided by the prism member to generate the projection light according to image information;
a projection optical system that enlarges and projects the projection light transmitted through the TIR prism to display an image;
an imaging device that receives the imaging light output from the imaging light reflecting prism and converts it into an electrical image signal;
comprising
Projection type image display device.