Projection type image display device

Abstract

To provide a projection type video display device that reduces stray light incident on an image pickup device.SOLUTION: A projection type video display device comprises: a video light emitting section having a light modulation element that emits video light; a projection lens unit that enlarges and projects the video light on a projection target; a light path separation element; an image pickup device that picks up an image of external light incident through the projection lens unit and the light separation element; and a condensation optical system. The light path separation element transmits part of the video light emitted from the video light emitting section to the projection lens unit and reflects part of the external light emitted from the projection lens unit to the condensation optical system. The condensation optical system condenses the external light reflected by the light path separation element to the image pickup device. The capture angle of the external light in the condensation optical system is equal to or less than the capture angle of a lens F value of the projection lens unit.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a projection type image display device equipped with an image sensor. [Background technology]

[0002] Conventionally, a projection type image display device projects an image onto a projection target such as a screen or a building. In order to check the positional relationship (distortion) between the projection target and the projected image, the image projected onto the projection target may be photographed. The projection position is fine-tuned based on the photographed image.

[0003] When the projection type image display device and the imaging element that captures the projected image are separate, adjusting the angle of view is troublesome, so there are projection type image display devices that have an imaging element built in. By sharing the same optical axis for the optical path of the image light emitted from the projection type image display device and the optical path that captures the light reflected from the projection surface, it is possible to omit the adjustment of the angle of view.

[0004] For example, in Patent Document 1, a light path branching element is used to share the optical axis of the optical path of the image light emitted from a projection type image display device and the optical path for capturing an image of the light reflected from the projection surface. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2020-91342 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the technology described in Patent Document 1, the optical path branching element uses a polarization separation film to branch the image light incident on the imaging element, but there is a problem in that stray light generated within the optical path branching element is incident on the imaging element.

[0007] An object of the present disclosure is to provide a projection-type image display device that reduces stray light that enters an imaging element. [Means for solving the problem]

[0008] The projection type image display device according to the present disclosure includes an image light output section having a light modulation element that outputs image light obtained by modulating light from a light source device in response to an image signal, a projection lens unit that enlarges and projects the image light onto a projection target and receives external light including the image light reflected by the projection target, an optical path separation element disposed between the image light output section and the projection lens unit, an imaging element that captures the external light incident via the projection lens unit and the optical path separation element, and a focusing optical system disposed between the optical path separation element and the imaging element. The optical path separation element transmits a portion of the image light output from the image light output section to the projection lens unit and reflects a portion of the external light output from the projection lens unit to the focusing optical system. The focusing optical system focuses the external light reflected by the optical path separation element onto the imaging element. The angle of capture of the external light in the focusing optical system is equal to or smaller than the focusing angle of the lens F value of the projection lens unit. Effect of the Invention

[0009] The present disclosure can provide a projection-type image display device that reduces stray light that enters an imaging element. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 shows a configuration of a projection-type image display device according to a first embodiment. [Diagram 2] FIG. 1 shows a configuration of a projection imaging optical system according to a first embodiment. [Diagram 3] Graph showing the characteristics of the partially reflective film of the optical path splitter [Figure 4] FIG. 1 is an explanatory diagram showing an optical path of a projection imaging optical system according to a comparative example; [Diagram 5] FIG. 13 is a diagram showing a configuration of a projection imaging optical system according to a second embodiment. [Figure 6] FIG. 13 shows a configuration of a projection imaging optical system according to a third embodiment. [Figure 7]FIG. 13 shows a configuration of a projection imaging optical system according to a fourth embodiment. [Figure 8] FIG. 13 shows a configuration of a projection imaging optical system according to a fifth embodiment. [Figure 9] Graph showing the characteristics of the partially reflective film of the optical path splitter [Figure 10] FIG. 13 shows a configuration of a projection imaging optical system according to a sixth embodiment. [Figure 11] FIG. 13 shows a configuration of a projection imaging optical system according to a seventh embodiment. [Figure 12] FIG. 1 is an explanatory diagram showing the optical paths in an optical path separation element. [Figure 13] FIG. 1 is an explanatory diagram showing an image captured by an imaging element; [Figure 14] FIG. 13 shows a configuration of a projection imaging optical system according to a modification of the first embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, the embodiments will be described in detail with reference to the drawings as appropriate. However, more detailed explanation than necessary may be omitted. For example, detailed explanation of already well-known matters or duplicate explanation of substantially the same configuration may be omitted. This is to avoid the following explanation becoming unnecessarily redundant and to facilitate understanding by those skilled in the art.

[0012] It should be noted that 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.

[0013] (Embodiment 1) [1-1. Configuration of projection type image display device] A projection-type image display device 1 according to the first embodiment will be described with reference to Fig. 1. Fig. 1 is a diagram showing the configuration of the projection-type image display device 1 according to the first embodiment.

[0014] The projection type image display device 1 uses a light modulation element that emits image light obtained by modulating light from a light source device in response to an image signal. As the light modulation element that forms an image, for example, a TN (Twisted Nematic) mode or VA (Vertical Alignment) mode active matrix transmissive panel type liquid crystal display element having thin film transistors formed in the pixel area is used.

[0015] Light source device 101 is composed of, for example, a blue semiconductor laser 116, a blue solid-state light source unit 119, lenses 126, 127, a first diffusion plate 128, a first retardation plate 129, a dichroic mirror 130, condenser lenses 131, 132, 138, a quarter-wave plate 139, a diffusion reflector 140, and a phosphor wheel 111.

[0016] The light emitted from light source device 101 is incident on projection lens unit 61 via an optical system including first lens array plate 20, second lens array plate 21, polarization conversion element 22, superimposing lens 23, red-reflecting dichroic mirror 24, green-reflecting dichroic mirror 25, reflecting mirrors 26, 27, 28, relay lenses 29, 30, field lenses 31, 32, 33, liquid crystal display elements 37, 38, 39, and color synthesis prism 43 consisting of a red-reflecting dichroic mirror and a blue-reflecting dichroic mirror. Color synthesis prism 43 is, for example, a cross cube prism.

[0017] White light from light source device 101 is incident on first lens array plate 20 consisting of multiple lens elements. The light beam incident on first lens array plate 20 is divided into multiple light beams. The multiple divided light beams are converged on second lens array plate 21 consisting of multiple lenses. The lens elements of first lens array plate 20 have an opening shape similar to that of liquid crystal display elements 37, 38, 39. The focal length of the lens elements of second lens array plate 21 is determined so that first lens array plate 20 and liquid crystal display elements 37, 38, 39 are in a substantially conjugate relationship. The light emitted from second lens array plate 21 is incident on polarization conversion element 22.

[0018] Polarization conversion element 22 is composed of a polarization separation prism and a half-wave plate, and converts the natural light from light source device 101 into light with one polarization direction. Since fluorescent light is natural light, it is polarized and converted into one polarization direction, but for example, blue light enters as S-polarized light and is converted into P-polarized light. The light from polarization conversion element 22 is incident on superimposing lens 23. Superimposing lens 23 is a lens for superimposing and illuminating the light emitted from each lens element of second lens array plate 21 onto liquid crystal display elements 37, 38, and 39.

[0019] The light from superimposing lens 23 is separated into blue, green, and red color lights by red-reflecting dichroic mirror 24 and green-reflecting dichroic mirror 25, which are color separation means. The green light passes through field lens 31 and enters liquid crystal display element 37. The red light is reflected by reflecting mirror 26, then passes through field lens 32 and enters liquid crystal display element 38. The blue light is refracted and reflected by relay lenses 29, 30 and reflecting mirrors 27, 28, passes through field lens 33, and enters liquid crystal display element 39.

[0020] The three liquid crystal display elements 37, 38, 39 change the polarization state of the light incident thereon by controlling the voltage applied to the pixels in response to the video signal, and modulate the light by combining an entrance side polarizing plate and an exit side polarizing plate arranged on both sides of each liquid crystal display element 37, 38, 39 so that the transmission axis is perpendicular to each other, thereby forming green, red, and blue images. The red and blue light emitted from the liquid crystal display elements 37, 38, 39 is reflected by a red-reflecting dichroic mirror and a blue-reflecting dichroic mirror, respectively, by a color synthesis prism 43, and is synthesized with the green light and enters a projection imaging optical system 51.

[0021] [1-2. Configuration of image light emitting section and imaging element] Next, the projection imaging optical system 51 will be described with reference to Fig. 2. Fig. 2 is a diagram showing the configuration of the projection imaging optical system 51 according to the first embodiment. The projection imaging optical system 51 includes an optical path separation element 53, a projection lens unit 61, a focusing optical system 71, and an imaging element 75. The image light output section 45 includes the liquid crystal display elements 37, 38, 39, and a color synthesis prism 43.

[0022] The color synthesis prism 43, the optical path separation element 53, and the projection lens unit 61 are arranged in this order along the optical axis of the light emitted from the color synthesis prism 43. The light collecting optical system 71 and the imaging element 75 are arranged in a direction perpendicular to the optical axis of the light emitted from the color synthesis prism 43. In the first embodiment, they are arranged to the side of the optical path separation element 53.

[0023] The projection lens unit 61 enlarges and projects the image light L1 onto the screen 200, which is the projection target, and external light L2 containing the image light L1 reflected by the screen 200 is incident on the projection lens unit 61. The projection lens unit 61 includes a plurality of lenses, and one of these, lens 61a, arranged on the side of the optical path separation element, is shown in FIG.

[0024] The optical path separation element 53 transmits a part of the image light L1 emitted from the image light emission section 45 to the projection lens unit 61, and reflects a part of the external light L2 emitted from the projection lens unit 61 to the light collecting optical system 71. The optical path separation element 53 is disposed between the image light emission section 45 and the projection lens unit 61. The optical path separation element 53 is, for example, an optical path separation prism, and has a first prism 53a and a second prism 53b. The first prism 53a and the second prism 53b are bonded to each other, and a partial reflection film 53c is disposed on the bonding surface between the first prism 53a and the second prism 53b.

[0025] The partially reflective film 53c reflects a portion of each of the incident image light L1 and external light L2 and transmits the remainder. The amount of light reflected by the optical path separation element 53 is, for example, 10% or less of the amount of light incident on the optical path separation element 53. The partially reflective film 53c reflects, for example, 10% of the amount of incident light and transmits 90%.

[0026] 3, the partial reflection film 53c has a property such that the transmittance of S-polarized light Lsa incident at 45 degrees to the partial reflection film 53c is approximately 89%, and the transmittance of P-polarized light Lpa is 99%. In the case of such a partial reflection film 53c, an average of 94% of the amount of image light L1 emitted from the image light emitting section 45 is transmitted toward the projection lens unit 61, and the remaining approximately 6% is reflected to the opposite side to the imaging element 75. Conversely, approximately 6% of the external light L2 incident from the projection lens unit 61 is reflected toward the imaging element 75.

[0027] The image light L1 that is emitted from the image light emitting portion 45 and transmitted through the optical path separation element 53 is magnified by the projection lens unit 61 and projected onto the screen 200, and an image Im1 is displayed on the screen 200. The image light L1 that constitutes the image Im1 on the screen 200 is reflected by the screen 200, is included in the external light L2, enters the projection lens unit 61, and travels toward the optical path separation element 53.

[0028] The external light L2 incident on the optical path splitting element 53 is reflected by the partial reflection film 53c, and its traveling direction is changed by 90 degrees.

[0029] The light collecting optical system 71 collects the external light L2 reflected by the optical path splitting element 53 onto the imaging element 75. The light collecting optical system 71 is disposed between the optical path splitting element 53 and the imaging element 75. The light collecting optical system 71 includes, for example, a concave lens 71a that diverges the incident external light L2, a convex lens 71b that collects the external light L2 diverged by the concave lens 71a onto the imaging element 75, and a first light absorbing portion 71c that is disposed between the concave lens 71a and the convex lens 71b and absorbs the external light L2 diverged by the concave lens 71a by a predetermined angle or more. In the light collecting optical system 71, the concave lens 71a is disposed on the optical path splitting element 53 side, and the convex lens 71b is disposed on the imaging element 75 side. The light collecting optical system 71 may include a lens that reduces aberration in addition to the concave lens 71a and the convex lens 71b. The first light absorbing portion 71c is composed of an optical diaphragm provided in the light collecting optical system 71, an aperture diaphragm of the convex lens 71b, etc. The first light absorbing portion 71c is, for example, a metal plate cut out into a circular shape or a glass plate painted black.

[0030] The capture angle θ1 of the external light L2 in the light collecting optical system 71 is equal to or smaller than the collection angle θ2 of the lens F-number of the projection lens unit 61. For example, when the F-number of the projection lens unit 61 is F2.4, the capture angle θ1 of the light emitted from the lens 61a is about ±12 degrees around the optical axis. Note that FIG. 2 shows a case where the capture angle θ1 and the collection angle θ2 are equal.

[0031] The imaging element 75 captures an image of external light L2 including an image Im1 that is incident via the projection lens unit 61, the optical path separation element 53, and the focusing optical system 71. The imaging element 75 is, for example, a CMOS sensor or a CCD sensor.

[0032] [1-3. Effects, etc.] As described above, in the first embodiment, the projection type image display device 1 includes an image light output section 45 having liquid crystal display elements 37, 38, 39 that outputs image light L1 obtained by modulating light from a light source device 101 in response to an image signal, and a projection lens unit 61 that enlarges and projects the image light L1 onto a screen 200 and into which external light L2 including the image light L1 reflected by the screen 200 is incident. The projection type image display device 1 includes an optical path separation element 53 arranged between the image light output section 45 and the projection lens unit 61, an imaging element 75 that images the external light L2 incident via the projection lens unit 61 and the optical path separation element 53, and a focusing optical system 71 arranged between the optical path separation element 53 and the imaging element 75. The optical path separation element 53 transmits a portion of the image light L1 emitted from the image light emission section 45 to the projection lens unit 61, and reflects a portion of the external light L2 emitted from the projection lens unit 61 to the converging optical system 71. The converging optical system 71 collects the external light L2 reflected by the optical path separation element 53 onto the imaging element 75, and an acceptance angle θ1 of the external light L2 in the converging optical system 71 is equal to or smaller than a collection angle θ2 of the lens F-number of the projection lens unit 61.

[0033] Even if the image light L1 and the external light L2 are reflected in the optical path separation element 53 and the projection lens unit 61 to generate stray light Lt, the capture angle θ1 of the external light L2 in the converging optical system 71 is equal to or smaller than the collection angle θ2 of the lens F value of the projection lens unit 61, so that the stray light Lt incident on the converging optical system 71 at an angle larger than the capture angle θ1 can be attenuated. Therefore, it is possible to reduce the stray light incident on the imaging element 75. In particular, since the stray light Lt is repeatedly reflected in the optical path separation element 53 and therefore tends to have a wide angular distribution, it is possible to block and attenuate the stray light Lt incident on the converging optical system 71 at an angle larger than the capture angle θ1.

[0034] Here, the reduction of the stray light Lt will be further described with reference to Fig. 4. Fig. 4 is an explanatory diagram showing the optical path of a projection imaging optical system 51H of a comparative example.

[0035] As shown in FIG. 4, the projection imaging optical system 51H includes a prism spacer 72 for back focus alignment of an imaging element 75, instead of the light collecting optical system 71 of the projection imaging optical system 51 of this embodiment.

[0036] In a configuration in which the optical path length from the screen 200 to the liquid crystal display elements 37, 38, 39 is made equal to the optical path length from the screen 200 to the image sensor 75 by the optical path separation element 53 and the prism spacer 72, stray light Lt originating from the image light L1, which is generated by the optical path separation element 53 and the projection lens unit 61, enters the image sensor 75 at any angle. In particular, when the external light L2 is dark, such as at night, the S / N ratio decreases and the external light L2 cannot be properly captured.

[0037] 2, the projection imaging optical system 51 of the present embodiment has the light collecting optical system 71 disposed between the optical path splitting element 53 and the imaging element 75, and therefore can reduce the incidence of the stray light Lt emitted from the optical path splitting element 53 toward the imaging element 75 onto the imaging element 75. Therefore, the noise of the stray light Lt can be reduced, and an image Im1 with an improved S / N ratio can be captured.

[0038] In the projection imaging optical system 51 of this embodiment, a first optical path length between the screen 200 and the liquid crystal display elements 37, 38, 39 via the projection lens unit 61 and the optical path separation element 53 is different from a second optical path length between the screen 200 and the imaging element 75 further via the light collecting optical system 71. This makes it possible to reduce the incidence of stray light Lt emitted from the optical path separation element 53 toward the imaging element 75 into the imaging element 75.

[0039] (Embodiment 2) Next, a projection-imaging optical system 51A and a projection-type image display device 1A according to a second embodiment will be described with reference to Fig. 5. Fig. 5 is a diagram showing the configuration of the projection-imaging optical system 51A according to the second embodiment.

[0040] 5, the projection imaging optical system 51A of the second embodiment is provided with a reflected light attenuation section 81 in the projection imaging optical system 51 of the first embodiment. Other than this point and the points described below, the configuration of the projection type image display device 1 of the first embodiment and the projection type image display device 1A of the second embodiment are the same, so the description will be omitted.

[0041] The reflected light attenuating section 81 is disposed on the opposite side of the image pickup element 75 with respect to the optical path splitting element 53, and is disposed to the side of the optical path splitting element 53 in Fig. 5. Therefore, the optical path splitting element 53 is disposed between the reflected light attenuating section 81 and the light collecting optical system 71.

[0042] The reflected light attenuating section 81 attenuates the stray light Lt emitted from the optical path separation element 53 toward the reflected light attenuating section 81. The reflected light attenuating section 81 has a reflected light attenuating plate 81a and a second light absorbing section 81b.

[0043] The reflected light attenuation plate 81a suppresses the stray light Lt incident from the optical path separation element 53 from being reflected toward the optical path separation element 53. The reflected light attenuation plate 81a is disposed at an angle with respect to the optical path separation element 53. A plurality of reflected light attenuation plates 81a may be used and disposed in a triangular shape.

[0044] The second light absorbing portion 81b absorbs the stray light Lt reflected by the reflected light attenuation plate 81a. The second light absorbing portion 81b is, for example, a container that houses the reflected light attenuation plate 81a, and has an opening 81c on the light path separation element side.

[0045] The projection imaging optical system 51A and the projection type image display device 1A in the second embodiment include a reflected light attenuating section 81 that attenuates at least a part of the image light L1 reflected by the optical path separation element 53. It is possible to prevent stray light Lt, which was originally image light L1, from exiting the optical path separation element 53, reflecting off a structure external to the optical path separation element 53, and then entering the optical path separation element 53 again and heading toward the imaging element 75, and it is possible to improve the S / N ratio of the imaging element 75.

[0046] Moreover, the reflected light attenuating section 81 is disposed on the opposite side of the image pickup element 75 with respect to the optical path separation element 53, and includes a reflected light attenuating plate 81a disposed at an angle with respect to the optical path separation element 53, and a second light absorbing section 81b that absorbs the image light reflected by the reflected light attenuating plate 81a. Since the reflected light attenuating plate 81a is disposed at an angle with respect to the optical path separation element 53, when the stray light Lt that was originally the image light L1 is reflected by the reflected light attenuating plate 81a, the amount of light traveling in a direction different from the optical path separation element 53 increases. Furthermore, since the second light absorbing section 81b absorbs the stray light Lt reflected by the reflected light attenuating plate 81a, it is possible to prevent the stray light Lt from traveling again toward the image pickup element 75.

[0047] (Embodiment 3) Next, a projection imaging optical system 51B and a projection type image display device 1B according to a third embodiment will be described with reference to Fig. 6. Fig. 6 is a diagram showing the configuration of the projection imaging optical system 51B according to the third embodiment.

[0048] 6, in the projection imaging optical system 51B of the third embodiment, the light-collecting optical system 71 of the projection imaging optical system 51 of the first embodiment is a reduction optical system. Other than this and the points described below, the configurations of the projection type image display device 1 of the first embodiment and the projection type image display device 1B of the third embodiment are the same, so description thereof will be omitted.

[0049] The condensing optical system 71B of the projection imaging optical system 51B in the third embodiment is a reduction optical system. Therefore, the lateral magnification when an image is formed on the imaging element 75B via the projection imaging optical system 51B and the condensing optical system 71B is smaller than the lateral magnification when the projection imaging optical system 51B forms an image on the liquid crystal display elements 37, 38, and 39. Therefore, when capturing the same image, the size of the imaging element 75B can be made smaller than the size of the liquid crystal display elements 37, 38, and 39. This allows the entire projection type image display device 1 to be made smaller and less expensive. In particular, in the case of a high-brightness projection type image display device 1, the liquid crystal display elements 37, 38, and 39 tend to be large, so if the condensing optical system 71B in such a projection type image display device 1 is made a reduction optical system, the advantages of further miniaturization and cost reduction can be obtained.

[0050] According to the projection imaging optical system 51B and the projection type image display device 1B of the third embodiment, the light collecting optical system 71B is configured by a reduction optical system, the liquid crystal display elements 37, 38, 39 and the image sensor 75B are in a non-conjugate relationship with respect to the projection lens unit 61, and the sizes of the liquid crystal display elements 37, 38, 39 and the image sensor 75B are different. This allows the image sensor 75B to be smaller than the liquid crystal display elements 37, 38, 39, and allows the projection type image display device 1B to be made smaller and less expensive.

[0051] (Embodiment 4) Next, a projection imaging optical system 51C and a projection type image display device 1C according to a fourth embodiment will be described with reference to Fig. 7. Fig. 7 is a diagram showing the configuration of the projection imaging optical system 51C according to the fourth embodiment.

[0052] 7, the projection imaging optical system 51C of the fourth embodiment has a configuration in which a DMD (digital micromirror device) is provided instead of a liquid crystal display element in the image light emitting section 45 of the projection imaging optical system 51 of the first embodiment. Other than this point and the points described below, the configuration of the projection type image display device 1 of the first embodiment and the projection type image display device 1C of the fourth embodiment are the same, so the description thereof will be omitted.

[0053] Image light output section 45C in embodiment 4 includes DMDs 37C, 38C, and 39C as light modulation elements, and projection type image display device 1C and image light output section 45C include a color separation / combination prism 44 instead of red-reflecting dichroic mirror 24, green-reflecting dichroic mirror 25, and color combination prism 43 of embodiment 1. Projection type image display device 1C and image light output section 45C also include a total reflection prism 46.

[0054] The projection type image display device 1C has a rod integrator and a relay optical system (not shown) instead of the first lens array plate 20, the second lens array plate 21, the polarization conversion element 22, and the superimposing lens 23 in the projection type image display device 1 of embodiment 1, and the light emitted from the light source device 101 is emitted as uniform white light by the rod integrator.

[0055] The light emitted from the rod integrator enters a total reflection prism 46 with a minute gap via a relay lens system (not shown). The light that enters the total reflection prism 46 at an angle equal to or greater than the total reflection angle is reflected by the minute gap, changes its direction, and enters a color separation / combination prism 44 made up of three blocks with minute gaps.

[0056] Of the light incident on the first block 44a of the color separation / combining prism 44 from the total reflection prism 46, the blue light is first reflected by a spectrally-characteristic reflective film that has the property of reflecting blue light, then changes its direction and travels toward the total reflection prism 46, where it enters a tiny gap between the total reflection prism 46 and the color separation / combining prism 44 at an angle greater than the total reflection angle, and enters the DMD 38C, which displays a blue image.

[0057] Next, the red light among the light incident on the color separation / synthesis prism 44 is reflected by a spectrally-characteristic reflective film provided between the second block 44b and the third block 44c of the color separation / synthesis prism 44, which has spectral characteristics that reflect light in the red wavelength region and transmit green light, and changes its direction of travel toward the first block 44a.

[0058] The red light, whose direction of travel has been changed, is reflected again by a minute gap provided between the first block 44a and the second block 44b of the color separation / combining prism 44, and its direction of travel is changed again to enter the red DMD 39C.

[0059] In addition, green light among the light incident on color separation / combining prism 44 reflects light in the red wavelength region provided between second block 44b and third block 44c of color separation / combining prism 44, passes through a spectrally-differentiated reflective film having a spectral characteristic that transmits green light, proceeds directly to third block 44c, and is incident on DMD 37C for green.

[0060] DMDs 37C, 38C, and 39C change the direction of light travel by changing the direction of the mirror for each pixel in response to a video signal for each color from a control unit (not shown).

[0061] The green light, whose direction of travel has been changed by the green DMD 37C in accordance with the video signal, enters the third block 44c of the color separation / combination prism 44 and passes through a reflective film with spectral characteristics provided between the third block 44c and the second block 44b of the color separation / combination prism 44.

[0062] The red light, whose traveling direction has been changed by the red DMD 39C in response to the video signal, enters the second block 44b of the color separation / combining prism 44 and is reflected by being incident at an angle equal to or greater than the total reflection angle into a minute gap provided between the second block 44b and the first block 44a of the color separation / combining prism 44. The red light then changes its traveling direction to the third block 44c of the color separation / combining prism 44, where it is reflected by a reflective film with spectral characteristics provided between the second block 44b and the third block 44c of the color separation / combining prism 44, changing its traveling direction and being combined with the green light.

[0063] The light combined by the spectrally-differential reflective film travels toward the first block 44a of the color separation / combination prism 44, and is transmitted by entering a minute gap provided between the second block 44b and the first block 44a of the color separation / combination prism 44 at an angle less than the total reflection angle.

[0064] Furthermore, the blue light, whose traveling direction has been changed by blue DMD 38C in response to the video signal, enters first block 44a of color separation / combination prism 44, travels toward total reflection prism 46, and travels toward second block 44b of color separation / combination prism 44 by being incident at an angle equal to or greater than the total reflection angle into a gap provided between total reflection prism 46 and color separation / combination prism 44. Thereafter, the blue light is reflected by a reflective film with spectral characteristics provided on the first block 44a side in front of the minute gap provided between first block 44a and second block 44b of color separation / combination prism 44, changes its traveling direction toward total reflection prism 46, is combined with light from green DMD 37C and red DMD 39C, and enters total reflection prism 46.

[0065] The image light L1 from the DMDs 37C, 38C, and 39C incident on the total reflection prism 46 passes through the total reflection prism 46 and is incident on the optical path separation element 53. The light collecting optical system 71 is designed so that the external light L2 can be imaged on the imaging element 75 in accordance with the optical path lengths of the total reflection prism 46 and the color separation / combination prism 44.

[0066] According to projection imaging optical system 51C and projection type image display device 1C in embodiment 4, even if the light modulation element is a DMD, it is possible to reduce stray light incident on imaging element 75, similar to a liquid crystal image display element. Note that although image light output section 45C has three DMDs 37C, 38C, and 39C, it may have a configuration having only one DMD.

[0067] (Embodiment 5) Next, a projection imaging optical system 51D and a projection type image display device 1D according to a fifth embodiment will be described with reference to Fig. 8. Fig. 8 is a diagram showing the configuration of the projection imaging optical system 51D according to the fifth embodiment.

[0068] 8, the projection imaging optical system 51D of the fifth embodiment has a configuration in which the image light output section 45 of the first embodiment has a narrowband retardation plate 52. The projection type image display device 1 of the first embodiment and the projection type image display device 1D of the fifth embodiment have the same configuration except for this point and the points described below, so the description will be omitted. In this embodiment, S-polarized light is polarized light having a vibration plane perpendicular to the paper surface of the drawing, and P-polarized light is polarized light having a vibration plane parallel to the paper surface of the drawing.

[0069] Narrowband retarder 52 aligns the polarization states of the image light emitted from liquid crystal display elements 37, 38, and 39 and emits the aligned image light to optical path separation element 53D. In the fifth embodiment, as an example, P-polarized image light Lp is emitted from liquid crystal display element 37, and S-polarized image light Ls is emitted from liquid crystal display elements 38 and 39. Narrowband retarder 52 converts the incident S-polarized image light Ls into P-polarized image light Lp1 and emits it, and emits the incident P-polarized image light Lp as it is as P-polarized image light Lp1. Narrowband retarder 52 is disposed between color synthesis prism 43 and optical path separation element 53D.

[0070] In the fifth embodiment, narrowband retarder 52 converts the incident S-polarized and P-polarized image light into P-polarized light and outputs the converted light, but it may convert the incident S-polarized light into S-polarized light. Thus, image light output section 45D outputs image light in a first polarization state, which is either P-polarized light or S-polarized light.

[0071] Furthermore, the partial reflection film 53Dc of the optical path separation element 53D is a polarization separation film that transmits the incident P-polarized image light Lp1 and reflects the S-polarized component Lns of the incident external light to bend its traveling direction by 90 degrees. Therefore, the image light Lp1 incident from the narrowband retardation plate 52 transmits through the optical path separation element 53D and is emitted toward the projection lens unit 61. The polarization separation film is, for example, a polarizing beam splitter.

[0072] The characteristics of the partial reflection film 53Dc of the optical path separation element 53D according to the fifth embodiment will be described with reference to Fig. 9. Fig. 9 is a graph showing the transmittance of the partial reflection film 53Dc of the optical path separation element 53D according to the fifth embodiment for P-polarized light and S-polarized light.

[0073] The partially reflective film 53Dc has a characteristic that the transmittance of the S-polarized light Lsa incident at an angle of 45 degrees to the partially reflective film 53Dc is approximately 0%, and the transmittance of the P-polarized light Lpa is approximately 97%. By using the narrowband retardation plate 52 to align the image light from the color synthesis prism 43 to P-polarized light, approximately 97% of the image light proceeds to the screen 200 side, and approximately 3% of the image light is reflected to the side of the optical path separation element 53 opposite the focusing optical system 71.

[0074] Conversely, of the external light L2 incident from the projection lens unit 61, all of the S-polarized component is reflected towards and taken in by the imaging element 75. If the external light L2 is unpolarized, 50% of the external light L2 is reflected towards and taken in by the imaging element 75. When polarization characteristics are utilized as the projection light and a liquid crystal display element is used as the light modulation element, the utilization efficiency of the projection light is higher when the partial reflection film 53Dc is a polarization separation film.

[0075] Image light Lp1 constituting image Im1 on screen 200 is reflected by screen 200 and enters optical path separation element 53 via projection lens unit 61 as part of external light L2. Since image light Lp1 is P-polarized light, it passes through partial reflection film 53Dc without being reflected. The S-polarized component of external light L2 is reflected by partial reflection film 53Dc, has its traveling direction changed by 90 degrees, and enters imaging element 75 via focusing optical system 71. Therefore, imaging element 75 can capture an image of screen 200 on which image Im1 is not displayed.

[0076] According to the projection imaging optical system 51D and the projection type image display device 1D of embodiment 5, even if the optical path separation element 53D is configured to transmit and reflect light utilizing the polarization characteristics of light, it is possible to reduce the incidence of stray light Lt generated within the projection lens unit 61 and the optical path separation element 53D on the imaging element 75 by the focusing optical system 71.

[0077] (Embodiment 6) A projection imaging optical system 51E and a projection type image display device 1E according to a sixth embodiment will now be described with reference to Fig. 10. Fig. 10 is a diagram showing the configuration of the projection imaging optical system 51E according to the sixth embodiment.

[0078] 8, the projection imaging optical system 51E of the sixth embodiment has a configuration in which the image light emitting section 45 of the fifth embodiment further includes a quarter-wave plate 55 and a polarizing plate 73. Other than this point and the points described below, the projection type image display device 1D of the fifth embodiment and the projection type image display device 1E of the sixth embodiment have the same configuration, so the description thereof will be omitted.

[0079] The quarter-wave plate 55 is disposed on the optical axis between the optical path separation element 53D and the projection lens unit 61, and converts the incident linearly polarized light into circularly polarized light and outputs it, and converts the incident circularly polarized light into linearly polarized light and outputs it. Therefore, the quarter-wave plate 55 converts the P-polarized image light Lp1 incident from the narrowband retardation plate 52 into circularly polarized image light Lc. The image light Lc output from the quarter-wave plate 55 is magnified by the projection lens unit 61 and projected onto the screen 200, and the image Im1 is displayed on the screen 200.

[0080] Circularly polarized image light Lc constituting image Im1 on screen 200 is reflected by screen 200, enters projection lens unit 61, travels toward optical path separation element 53, and enters quarter-wave plate 55. The circularly polarized image light Lc that has entered quarter-wave plate 55 is converted into S-polarized image light Ls and enters optical path separation element 53.

[0081] The S-polarized image light Ls incident on the optical path separation element 53 is reflected by the partial reflection film 53Dc, has its traveling direction changed by 90 degrees, and is incident on the light collecting optical system 71. The S-polarized image light Ls incident on the light collecting optical system 71 passes through the light collecting optical system 71 and is incident on the polarizing plate 73.

[0082] Polarizing plate 73 is disposed between collecting optical system 71 and imaging element 75, and transmits linearly polarized light. In the sixth embodiment, polarizing plate 73 transmits S-polarized image light Ls and blocks other light in a polarization state other than S-polarized light. Therefore, S-polarized image light Ls that has passed through collecting optical system 71 is transmitted through polarizing plate 73 and enters imaging element 75, but stray light other than S-polarized light is blocked by polarizing plate 73. The surface of polarizing plate 73 facing imaging element 75 is larger than the imaging surface of imaging element 75.

[0083] Since the polarizing plate 73 is disposed between the optical path separating element 53 and the imaging element 75, the P-polarized stray light Lt emitted from the optical path separating element 53 toward the imaging element 75 can be blocked by the polarizing plate 73. This prevents the P-polarized stray light Lt from entering the imaging element 75 and reduces the noise of the stray light Lt, making it possible to capture an image Im1 with a significantly improved S / N ratio.

[0084] In this way, the image Im1 projected onto the screen 200 is converted to S-polarized light when it enters the optical path separation element 53 again via the projection lens unit 61, thereby increasing the amount of light from the external image traveling toward the imaging element 75 and amplifying the signal.

[0085] According to the projection imaging optical system 51E and the projection type image display device 1E of embodiment 6, the partially reflective film 53Dc is provided with a quarter-wave plate that transmits the image light Lp1 in a first polarization state incident from the image light output section 45 and reflects the light Ls in a second polarization state, which is the other of the P polarized and S polarized light, and is disposed between the optical path separation element 53 and the projection lens unit 61 and converts the image light Lp1 in the first polarization state into circularly polarized image light Lc and converts the circularly polarized image light Lc reflected by the screen 200 into image light Ls in a second polarization state, and a polarizing plate 73 that is disposed between the optical path separation element 53 and the imaging element 75 and transmits external light in the second polarization state.

[0086] The image light Lp1 emitted from the image light output unit 45 has either P-polarized light or S-polarized light, and is converted by a quarter-wave plate into circularly polarized image light Lc emitted from the image light output unit 45 and projected onto the screen 200. The image Im1 projected onto the screen 200 is reflected by the screen 200 and enters the quarter-wave plate again as part of the external light, and is converted from the circularly polarized image light Lc into the other polarized light different from the polarized light when it was emitted from the image light output unit 45. This other polarized light is reflected by the optical path separation element 53 to change its traveling direction, and passes through the polarizing plate 73 to enter the imaging element 75.

[0087] In this way, the polarization state of the image light Lp1 emitted from the light path separation element 53 toward the screen 200 and the polarization state of the image light Ls included in the external light L2 reflected by the screen 200 and incident on the light path separation element 53 are different polarization states, either P polarization or S polarization, respectively, so that the polarizing plate 73 can allow only the light in the polarization state of the image light reflected by the screen 200 to be incident on the imaging element 75. Therefore, even if the image light Lp1 incident from the image light output unit 45 becomes stray light due to reflection in the light path separation element 53 and travels toward the imaging element 75 and passes through the light collecting optical system 71, it can be blocked by the polarizing plate 73. In addition, since the external light L2 other than the image light is generally natural light, only the light component having the same polarization state as the image light reflected by the screen 200 can be incident on the imaging element 75. Therefore, the image light reflected by the screen 200 and the image Im1 on the screen 200 illuminated by external light can be captured simultaneously.

[0088] Polarizing plate 73 may be configured to be rotatable manually or by a motor. By adjusting the rotation angle of polarizing plate 73, the amount of S-polarized image light Ls incident on image sensor 75 can be adjusted, and the balance with the amount of external light taken in can be adjusted.

[0089] (Embodiment 7) Next, a projection imaging optical system 51F and a projection type image display device 1F according to the seventh embodiment will be described with reference to Fig. 11. Fig. 11 is a diagram showing the configuration of the projection imaging optical system 51F according to the seventh embodiment.

[0090] 11, the projection imaging optical system 51F of the seventh embodiment is configured such that the quarter wavelength plate 55 of the projection imaging optical system 51E of the sixth embodiment is removable from the optical path of the image light Lp entering the projection lens unit 61 from the optical path separation element 53. Other than this point and the points described below, the projection type image display device 1E of the sixth embodiment and the projection type image display device 1F of the seventh embodiment have the same configuration, so description thereof will be omitted.

[0091] The projection imaging optical system 51F includes a drive unit 91 that inserts and removes the quarter-wave plate 55 on the optical path of the image light entering the projection lens unit 61 from the optical path separation element 53. The drive unit 91 inserts and removes the quarter-wave plate 55 on the optical path in response to an instruction from a user. The drive unit 91 is composed of, for example, an actuator and a rod. The drive unit 91 may rotate the quarter-wave plate 55 to insert and remove the quarter-wave plate 55 on the optical path. Note that the drive unit 91 may be omitted and the user may manually insert and remove the quarter-wave plate 55 from the optical path.

[0092] In the seventh embodiment, a movable object hm may be present in front of the screen 200. The object hm is, for example, a human or a robot. In the seventh embodiment, a part of the projected image light is projected onto the screen 200 as an image Im2, and a part of the image light is projected onto the object hm as an image Im3. In FIG. 11, characters are projected as an example of the images Im2 and Im3.

[0093] The object hm may be irradiated with illumination light Ln1 from an external illumination light source 210, or may be irradiated with environmental light around the screen. The illumination light Ln1 or environmental light is unpolarized light, and the illumination light Ln1 or environmental light irradiates the object hm and is reflected by the object hm. The reflected light Ln2 passes through the projection lens unit 61 and enters the ¼ wavelength plate 55.

[0094] The projection imaging optical system 51F may further include an image processing unit 93 and a control unit 95. The image processing unit 93 recognizes an object hm that can move in front of the screen 200 in the image captured by the imaging element 75. The image processing unit 93 is, for example, a processor or an arithmetic circuit such as an FPGA.

[0095] The control unit 95 controls the liquid crystal display elements 37, 38, and 39 so that the image Im3 follows the movement of the object hm recognized by the image processing unit 93. The control unit 95 is, for example, a processor or an arithmetic circuit such as an FPGA.

[0096] Next, the change in the properties of light caused by inserting and removing the quarter-wave plate 55 on the optical path will be further described with reference to Figs. 12 and 13. Fig. 12 is an explanatory diagram showing the optical path in the optical path separation element, Fig. 12(a) is an explanatory diagram showing the optical path of the projection imaging optical system 51F in a state where the quarter-wave plate 55 is arranged on the optical path, and Fig. 12(b) is an explanatory diagram showing the optical path of the projection imaging optical system 51F in a state where the quarter-wave plate 55 is removed from the optical path. Fig. 13 is an explanatory diagram showing an image captured by the imaging element 75, Fig. 13(a) is an image captured with the quarter-wave plate 55 arranged on the optical path, and Fig. 13(b) is an image captured with the quarter-wave plate 55 removed from the optical path.

[0097] 12(a), when the quarter-wave plate 55 is present on the optical path, the unpolarized reflected light Ln2 is transmitted through the quarter-wave plate 55 and the phase of the unpolarized reflected light Ln2 is rotated, but the unpolarized reflected light Ln2 still exits from the quarter-wave plate 55. The reflected light Ln2 exiting from the quarter-wave plate 55 enters the optical path splitting element 53, where only the S-polarized component Lns is reflected by the partial reflection film 53c, and the traveling direction is changed by 90 degrees to proceed toward the imaging element 75. The remaining component Lnv of the reflected light Ln2 passes through the partial reflection film 53c and proceeds straight toward the narrowband retardation plate 52. The S-polarized component Lns of the reflected light Ln2 exits from the optical path splitting element 53, passes through the focusing optical system 71 and the polarizing plate 73, and enters the imaging element 75. As a result, the S-polarized component Lns of the reflected light Ln2 is imaged by the imaging element 75 together with the S-polarized image light Ls that is projected onto the screen 200 and reflected.

[0098] Therefore, when a quarter-wave plate 55 is present on the optical path, as shown in FIG. 13(a), it is possible to capture an image Im2 projected onto the screen 200, an object hm illuminated by the illumination light Ln1 from the external illumination light source 210, and an image Im3 projected onto the object hm.

[0099] 12(b), when the quarter-wave plate 55 is removed from the optical path and is not present on the optical path, the P-polarized image light Lp1 emitted from the image light emitting portion 45 is projected directly onto the screen 200. The image Im2 projected onto the screen 200 and the image Im3 projected onto the object hm are the P-polarized image light Lp1. The image light Lp1 reflected by the screen 200 and the object hm passes through the projection lens unit 61 and also passes through the optical path separation element 53, and does not proceed to the imaging element 75.

[0100] Therefore, only the S-polarized component Lns of the reflected light Ln2 is reflected by the partial reflection film 53c of the optical path separation element 53 and travels toward the imaging element 75. As a result, the P-polarized image light Lp1 projected onto the screen 200 and reflected is not captured, and only the S-polarized component Lns of the reflected light Ln2 is captured by the imaging element 75.

[0101] Therefore, when the quarter-wave plate 55 is not present on the optical path, an image composed only of the illumination light and the ambient light reflected by the screen 200 and the object hm is captured, as shown in Fig. 12(b). In this way, since an image not affected by the projection light can be captured, the object hm is detected using the image not including the projection light, and the detection and the projection image are combined to enable mapping that follows the object hm.

[0102] According to the projection imaging optical system 51F and the projection type image display device 1F in the seventh embodiment, the ¼ wavelength plate 55 is removable and insertable on the optical path of the image light incident from the optical path separation element 53 to the projection lens unit 61. This makes it possible to capture images of the image Im2 projected on the screen 200, the object hm illuminated with the illumination light Ln1 from the external illumination light source 210, and the image Im3 projected on the object hm, as well as to capture an image made up of only the illumination light and environmental light reflected by the screen 200 and the object hm.

[0103] Furthermore, since the amount of illumination light and ambient light is often small, as shown in Fig. 13(b), when capturing an image excluding a projection image, it is desirable to reliably remove stray light generated from the optical path separation element 53 and the lens 61a of the projection lens unit 61 so as not to enter the imaging element 75. Therefore, a configuration for removing stray light using the light collecting optical system 71 is highly effective. Furthermore, since the configuration for removing stray light according to the second embodiment is also highly effective, it is also very useful to combine the seventh embodiment with the second embodiment.

[0104] In addition, at least a portion of the projection target includes a movable object hm, and the projection type image display device 1F is equipped with an image processing unit 93 that recognizes the object hm in the image captured by the image sensor 75 through image processing, and a control unit 95 that displays and controls the image light emitted from the image light emitting unit 45 in accordance with the movement of the object hm so as to project the image light onto the object hm in the image.

[0105] (Other embodiments) As described above, the above embodiment has been described as an example of the technology disclosed in this application. However, the technology in this disclosure is not limited to this, and can be applied to embodiments in which modifications, substitutions, additions, omissions, etc. are made. In addition, it is also possible to combine the components described in the above embodiment to create a new embodiment.

[0106] In each embodiment, when S-polarized and P-polarized image light are used, the polarization states of these may be interchanged. For example, the image light output from narrowband retarder 52 may be S-polarized, and the image light incident on image sensor 75 may be P-polarized.

[0107] In each embodiment, an optical path splitting prism is used as the optical path splitting element 53, but this is not limiting. The optical path splitting element 53 may be a mirror on which a partial reflection film 53c is formed.

[0108] In FIG. 2 for explaining the first embodiment, the capture angle θ1 of the external light L2 in the light collecting optical system 71 and the collection angle θ2 of the lens F value of the projection lens unit 61 are shown as the same angle, but this is not limited thereto. For example, as shown in FIG. 14, the capture angle θ1 of the external light L2 in the light collecting optical system 71 may be smaller than the collection angle θ2 of the lens F value of the projection lens unit 61. In the projection imaging optical system 51G of the projection type image display device 1G according to the modified example, the light collecting optical system 71G of the projection imaging optical system 51G includes a second light absorbing portion 71d between the concave lens 71a and the second prism 53b, and the second light absorbing portion 71d makes the capture angle θ1 smaller than the collection angle θ2. Even with such a configuration, the stray light Lt incident on the light collecting optical system 71G at an angle larger than the capture angle θ1 can be further attenuated.

[0109] As described above, the embodiment has been described as an example of the technology in the present disclosure. For this purpose, the attached drawings and detailed description have been provided. Therefore, among the components described in the attached drawings and detailed description, not only components essential for solving the problem but also components that are not essential for solving the problem in order to exemplify the above technology may be included. Therefore, the fact that these non-essential components are described in the attached drawings or detailed description should not be used to immediately determine that these non-essential components are essential.

[0110] Furthermore, since the above-described embodiments are intended to illustrate the technology in the present disclosure, various modifications, substitutions, additions, omissions, and the like can be made within the scope of the claims or their equivalents.

[0111] (Outline of the embodiment) (1) The projection type image display device of the present disclosure includes an image light output section having a light modulation element that outputs image light obtained by modulating light from a light source device in response to an image signal, and a projection lens unit that enlarges and projects the image light onto a projection target and receives external light including the image light reflected by the projection target. The projection type image display device includes an optical path separation element disposed between the image light output section and the projection lens unit, an imaging element that images the external light incident via the projection lens unit and the optical path separation element, and a focusing optical system disposed between the optical path separation element and the imaging element. The optical path separation element transmits a portion of the image light output from the image light output section to the projection lens unit and reflects a portion of the external light output from the projection lens unit to the focusing optical system. The focusing optical system focuses the external light reflected by the optical path separation element onto the imaging element, and the angle at which the external light is taken in by the focusing optical system is equal to or smaller than the focusing angle of the lens F value of the projection lens unit.

[0112] As a result, even if stray light occurs due to reflection of the image light inside the optical path separation element and the projection lens unit, the angle at which external light is captured in the light collecting optical system is equal to or smaller than the angle at which the image light is emitted to the screen, so that the stray light that is incident on the light collecting optical system at an angle larger than the angle can be attenuated, thereby reducing the stray light that is incident on the imaging element.

[0113] (2) In the projection type image display device of (1), a first optical path length from the projection target to the light modulation element via the projection lens unit and the light path separation element is different from a second optical path length from the projection target to the imaging element.

[0114] (3) In the projection type image display device of (1) or (2), the focusing optical system has a concave lens that diverges incident external light, a convex lens that focuses the external light diverged by the concave lens onto the imaging element, and a first light absorbing section that is disposed between the concave lens and the convex lens and absorbs the external light diverged by the concave lens at a predetermined angle or more.

[0115] (4) In the projection type image display device according to any one of (1) to (3), a reflected light attenuating section is provided that attenuates at least a part of the image light reflected by the optical path separating element.

[0116] (5) In the projection type image display device of (4), the reflected light attenuating unit is arranged on the opposite side of the optical path separating element from the imaging element, and includes a reflected light attenuating plate arranged at an angle with respect to the optical path separating element, and a second light absorbing unit that absorbs the image light reflected by the reflected light attenuating plate.

[0117] (6) In the projection type image display device according to any one of (1) to (5), the amount of light reflected by the optical path splitting element is 10% or less of the amount of light incident on the optical path splitting element.

[0118] (7) In any one of the projection-type image display devices (1) to (6), the focusing optical system is composed of a reduction optical system, the light modulation element and the imaging element are in a non-conjugate relationship with respect to the projection lens unit, and the size of the light modulation element and the size of the imaging element are different.

[0119] (8) In any one of the projection-type image display devices (1) to (7), the optical path separation element has a plurality of prisms and a partially reflective film that is disposed on the bonding surface where the plurality of prisms are bonded together and that reflects a portion of each of the incident image light and external light and transmits the remainder.

[0120] (9) In the projection type image display device of (8), the partial reflection film is a polarized light separation film.

[0121] (10) In the projection type image display device of (9), the image light output section has a plurality of light modulation elements and a narrowband retardation plate that aligns the polarization state of each image light output from the plurality of light modulation elements.

[0122] (11) In the projection type image display device of (9) or (10), the image light output section outputs image light in a first polarization state, which is either P polarization or S polarization, and the polarization separation film transmits the image light in the first polarization state incident from the image light output section and reflects light in a second polarization state, which is the other of P polarization and S polarization. The projection type image display device includes a quarter-wave plate disposed between the light path separation element and the projection lens unit, which converts the image light in the first polarization state into circularly polarized image light and converts the circularly polarized image light reflected by the projection target into image light in the second polarization state, and a polarizing plate disposed between the light path separation element and the imaging element, which transmits external light in the second polarization state.

[0123] (12) In the projection type image display device of (11), the polarizing plate is rotatable.

[0124] (13) In the projection type image display device of (11) or (12), the quarter-wave plate is removable and insertable onto the optical path of the image light that enters the projection optical system from the optical path separation element.

[0125] (14) The projection type image display device of (13) further comprises a drive unit that inserts and removes the quarter wavelength plate onto the optical path of the image light that enters the projection lens unit from the optical path separation element.

[0126] (15) In the projection type image display device of (13) or (14), at least a portion of the projection target includes a movable object, and the projection display device is equipped with an image processing unit that recognizes the object in the image captured by the image sensor through image processing, and a control unit that displays and controls the image light emitted from the image light emitting unit to follow the movement of the moving object so as to project the image light onto the moving object in the image. [Industrial Applicability]

[0127] The present disclosure can be used in a projection-type image display device that projects an image. [Explanation of symbols]

[0128] 1, 1A, 1B, 1C, 1D, 1E, 1F, 1G, 1H Projection type image display device 37, 38, 39 Liquid crystal display element 37C, 38C, 39C DMD 43 Color synthesis prism 44 Color Separation / Combining Prism 44a First Block 44b Second Block 44c Third Block 45, 45C, 45D Image light output section 46 Total Reflection Prism 51, 51A, 51B, 51C, 51D, 51E, 51F, 51G, 51H Projection imaging optical system 52 Narrowband retarder 53, 53D Optical path separation element 53a First Prism 53b Second Prism 53c, 53Dc Partially reflective coating 55 1 / 4 wave plate 61 Projection lens unit 61a Lens 71, 71B Condensing optical system 71a Concave lens 71b Convex lens 71c First light absorbing portion 72 Prism Spacer 73 Polarizing Plate 75, 75B image sensor 81 Reflected light attenuation section 81a Reflection attenuation plate 81b second light absorbing portion 81c aperture 91 Drive unit 93 Image Processing Section 95 Control Unit 101 Light source device 200 screens 210 External lighting source hm object Im1, Im2, Im3 video L1, Lc, Lp, Lp1, Ls Image light L2 External light Ln1 Illumination light Ln2 Reflected light Lns S-polarized component Lnv remaining components Lpa P polarization Lsa S-polarized Lt stray light

Claims

1. an image light emitting section having a light modulation element that emits image light obtained by modulating light from a light source device in accordance with an image signal; a projection lens unit that projects the image light onto a projection target and receives external light including the image light reflected by the projection target; an optical path separation element disposed between the image light output portion and the projection lens unit; an imaging element that captures an image of the external light incident via the projection lens unit and the optical path separation element; a focusing optical system disposed between the optical path separation element and the imaging element, the optical path separation element transmits a portion of the image light emitted from the image light emission section to the projection lens unit, and reflects a portion of the external light emitted from the projection lens unit to the light collecting optical system; the light collecting optical system collects the external light reflected by the optical path separation element onto the image sensor; The focusing optical system includes: a first lens, which is a concave lens that diverges incident external light; a second lens which is a convex lens that condenses the external light diverged by the first lens onto the image sensor; A first light absorbing portion is disposed between the first lens and the second lens and absorbs external light diverged by the first lens at a predetermined angle or more. Projection type image display device.

2. a first optical path length from the projection target to the light modulation element via the projection lens unit and the light path separation element is different from a second optical path length from the projection target to the image sensor; 2. The projection type image display device according to claim 1.

3. a reflected light attenuating unit that attenuates at least a part of the image light reflected by the optical path separation element; 3. The projection type image display device according to claim 1.

4. the reflected light attenuating unit is disposed on the opposite side of the optical path splitting element from the image pickup element, and includes a reflected light attenuating plate disposed at an angle with respect to the optical path splitting element, and a second light absorbing unit that absorbs image light reflected by the reflected light attenuating plate.

4. The projection type image display device according to claim 3.

5. the amount of light reflected by the optical path splitting element is 10% or less of the amount of light incident on the optical path splitting element; 5. The projection type image display device according to claim 1.

6. the light collecting optical system is constituted by a reduction optical system, the light modulation element and the image pickup element are in a non-conjugate relationship with respect to the projection lens unit, The size of the light modulation element is different from the size of the image pickup element.

6. The projection type image display device according to claim 1.

7. The optical path splitting element is A plurality of prisms; a partial reflection film disposed on a bonding surface where the plurality of prisms are bonded, the partial reflection film reflecting a part of each of the incident image light and the incident external light and transmitting the rest; 7. The projection type image display device according to claim 1.

8. The partially reflective film is a polarization separation film.

8. The projection type image display device according to claim 7.

9. the image light output unit includes a plurality of the light modulation elements, a narrowband retardation plate for aligning the polarization states of the image light beams emitted from the plurality of light modulation elements; 9. The projection type image display device according to claim 8.

10. the image light output unit outputs image light in a first polarization state, which is either P polarization or S polarization; the polarization separation film transmits the image light in the first polarization state incident from the image light output portion and reflects the other of the P-polarized light and the S-polarized light in a second polarization state; a quarter-wave plate disposed between the optical path separation element and the projection lens unit, which converts the image light in the first polarization state into circularly polarized image light and converts the circularly polarized image light reflected by the projection target into image light in a second polarization state; a polarizing plate disposed between the optical path separation element and the image sensor, the polarizing plate transmitting external light in the second polarization state; 10. The projection type image display device according to claim 8.

11. The polarizing plate is rotatable.

11. The projection type image display device according to claim 10.

12. the quarter-wave plate is insertable and removable on the optical path of the image light incident on the projection lens unit from the optical path separation element; 12. The projection type image display device according to claim 10 or 11.

13. a drive unit that inserts and removes the quarter-wave plate on an optical path of image light that is incident on the projection lens unit from the optical path separation element, 13. The projection type image display device according to claim 12.

14. At least a portion of the projection target includes a movable object; an image processing unit that recognizes the object in the image captured by the imaging element through image processing; a control unit that controls an image signal to be transmitted to the light modulation element in accordance with a movement of the object so as to project the image light onto the object in the image, 14. The projection type image display device according to claim 12 or 13.

15. an angle at which the external light is captured in the light collecting optical system is equal to or smaller than a light collecting angle of a lens F-number of the projection lens unit; 2. The projection type image display device according to claim 1.

Images