Projection type image display device

Abstract

To provide a projection type video display device that increases the quantity of light incident on an image pickup device.SOLUTION: A projection type video display device comprises: a video light emitting section that emits video light in a first polarization state being any one of a P-polarization and an S-polarization; a light path separation section having a polarization separation film that transmits the video light in the first polarization state incident from the video light emitting section and reflects light in a second polarization state being the other of the P-polarization and the S-polarization; a projection lens unit that enlarges and projects the video light transmitting through the light path separation section on a projection target and on which external light including the video light reflected on the projection target is incident; a 1 / 4 wavelength plate that is arranged between the light path separation section and the projection lens unit, converts the video light in the first polarization state into circularly polarized video light, and converts the circularly polarized video light reflected on the projection target into video light in the second polarization state; an image pickup device that picks up an image of the external light through the projection lens unit and the light path separation section; and a polarizing plate that is arranged between the light path separation section and the image pickup device, and transmits the external light in the second polarization state.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 image sensor, but since only half the amount of light reflected from the projection object can be used, there is a problem that the amount of light captured by the image sensor is small.

[0007] An object of the present disclosure is to provide a projection-type image display device that increases the amount of light incident on 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 that outputs image light in a first polarization state, which is either P polarized light or S polarized light; an optical path separation section that has a polarization separation film that 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 polarized light and S polarized light; a projection lens unit that enlarges and projects the image light that has transmitted through the optical path separation section onto a projection target and into which external light including the image light reflected by the projection target is incident; a quarter-wave plate that is disposed between the optical path separation section and the projection lens unit and 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; an imaging element that images the external light via the projection lens unit and the optical path separation section; and a polarizing plate that is disposed between the optical path separation section and the imaging element and transmits the external light in the second polarization state. Effect of the Invention

[0009] The present disclosure can provide a projection-type image display device that increases the amount of light incident on 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] An explanatory diagram showing the optical path of stray light in an optical path separation prism. [Figure 4] FIG. 13 shows a configuration of a projection imaging optical system according to a modification of the first embodiment. [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] An explanatory diagram showing the light path in the light path separation prism [Figure 9] FIG. 1 is an explanatory diagram showing an image captured by an imaging element; 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, as an image forming means, for example, a TN (Twisted Nematic) mode or VA (Vertical Alignment) mode active matrix transmissive panel type liquid crystal display element in which thin film transistors are formed in the pixel area.

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

[0021] [1-2. Configuration of the emission section and image sensor] 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 of the first embodiment. The projection imaging optical system 51 includes an image light output section 45, an optical path separation prism 53, a quarter-wave plate 55, a projection lens unit 61, a prism spacer 71, a polarizing plate 73, and an imaging element 75. The image light output section 45 includes liquid crystal display elements 37, 38, and 39, a color synthesis prism 43, and a narrowband retardation plate 52. In this embodiment, the S-polarized light is polarized light having a vibration plane perpendicular to the paper surface of the drawing, and the P-polarized light is polarized light having a vibration plane parallel to the paper surface of the drawing.

[0022] The color synthesis prism 43, the narrowband retardation plate 52, the optical path separation prism 53, the ¼ wavelength plate 55, 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 prism spacer 71, the polarizing plate 73, and the image pickup 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 above the optical path separation prism 53.

[0023] Narrowband retardation plate 52 aligns the polarized light emitted from liquid crystal display elements 37, 38, and 39, and emits it to optical path separation prism 53. In the first embodiment, as an example, S-polarized image light Ls is emitted from liquid crystal display element 37, and P-polarized image light Lp is emitted from liquid crystal display elements 38 and 39, but narrowband retardation plate 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.

[0024] The optical path separation prism 53 has a polarization separation film 53a, which transmits the incident P-polarized image light Lp1 and reflects the incident S-polarized image light Ls 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 prism 53 and exits toward the quarter-wave plate 55.

[0025] The quarter-wave plate 55 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.

[0026] Circularly polarized image light Lc that constitutes image Im1 on screen 200 enters projection lens unit 61, travels toward optical path separation prism 53, and enters quarter-wave plate 55. The circularly polarized image light Lc that enters quarter-wave plate 55 is converted into S-polarized image light Ls and enters optical path separation prism 53.

[0027] The S-polarized image light Ls incident on the optical path separating prism 53 is reflected by the optical path separating prism 53 , has its traveling direction changed by 90 degrees, and is incident on the prism spacer 71 .

[0028] The prism spacer 71 is an element for back focus alignment of the imaging element 75. The S-polarized image light Ls incident on the prism spacer 71 passes through the prism spacer 71 and enters the polarizing plate 73.

[0029] Polarizing plate 73 transmits linearly polarized light. In the first 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 transmitted through prism spacer 71 transmits 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.

[0030] The imaging element 75 captures an image Im1 by the incident S-polarized light. The imaging element 75 is, for example, a CMOS sensor or a CCD sensor.

[0031] In this way, the image Im1 projected onto the screen 200 is converted to S-polarized light when it enters the optical path separation prism 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.

[0032] [1-3. Effects, etc.] As described above, in the first embodiment, the projection type image display device 1 includes the image light output section 45 that outputs the image light Lp1 in a first polarization state, which is either P-polarized light or S-polarized light, and the light path separation prism 53 having the polarization separation film 53a that transmits the image light in the first polarization state incident from the image light output section 45 and reflects the light in the second polarization state, which is the other of P-polarized light and S-polarized light. The projection type image display device 1 further includes a projection lens unit 61 that enlarges and projects the image light Lp1 transmitted through the light path separation prism 53 onto the screen 200 and receives external light including the image light reflected by the screen 200, and a quarter-wave plate that is disposed between the light path separation prism 53 and the projection lens unit 61, 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. The projection type image display device 1 further includes an imaging element 75 that images external light via the projection lens unit 61 and the optical path separating prism 53, and a polarizing plate 73 that is disposed between the optical path separating prism 53 and the imaging element 75 and transmits external light in a second polarization state.

[0033] 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 light Lc, which is 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 external light, and is converted from the circularly polarized 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 prism 53 to change its traveling direction, and passes through the polarizing plate 73 to enter the imaging element 75.

[0034] In this way, the polarization of the image light Lp1 emitted from the light path separation prism 53 toward the screen 200 and the polarization of the image light Ls as external light reflected by the screen 200 and incident on the light path separation prism 53 are different polarization states, either P polarization or S polarization, respectively, so that the polarizing plate 73 can make only the light in the polarization state of the image light reflected by the screen 200 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 prism 53 and travels toward the imaging element 75, it can be blocked by the polarizing plate 73. In addition, since external light other than the image light is generally natural light, it is possible to make only the light component having the same polarization state as the image light reflected by the screen 200 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 simultaneously captured.

[0035] Here, the reduction of noise due to stray light will be further described with reference to Fig. 3. Fig. 3 is an explanatory diagram showing the optical path of stray light in the optical path separation prism 53, Fig. 3(a) is an explanatory diagram showing the optical path of a projection imaging optical system without a polarizing plate, and Fig. 3(b) is an explanatory diagram showing the optical path of a projection imaging optical system with a polarizing plate.

[0036] 3(a), P-polarized image light Lp1 incident on optical path separation prism 53 from narrowband retarder 52 is not completely transmitted through polarization separation film 53a of optical path separation prism 53, and a part of it is reflected to become stray light Lpt that repeatedly reflects within optical path separation prism 53. A part of this P-polarized stray light Lpt is emitted from optical path separation prism 53 towards imaging element 75. Therefore, since the P-polarized stray light Lpt is incident on imaging element 75 separately from the S-polarized image light Ls reflected from screen 200, an image in which noise of stray light Lpt is superimposed on image Im1 projected on screen 200 is captured.

[0037] 3(b), the projection imaging optical system 51 of the first embodiment has a polarizing plate 73 disposed between the optical path separating prism 53 and the imaging element 75, so that the P-polarized stray light Lpt emitted from the optical path separating prism 53 toward the imaging element 75 can be blocked by the polarizing plate 73. This prevents the P-polarized stray light Lpt from entering the imaging element 75 and reduces the noise of the stray light Lpt, so that an image Im1 with a significantly improved S / N ratio can be captured.

[0038] 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.

[0039] Next, a modified example of the first embodiment will be described with reference to Fig. 4. Fig. 4 is a diagram showing the configuration of a projection imaging optical system 51 of a modified example of the first embodiment. In the first embodiment, the prism spacer 71, the polarizing plate 73, and the image sensor 75 are arranged above the optical path separating prism 53, but this is not limiting. The prism spacer 71, the polarizing plate 73, and the image sensor 75 may be arranged on the side of the optical path separating prism 53. The phase of the narrowband retarder 52 of the modified example is inverted by 90 degrees from the phase of the narrowband retarder 52 of the first embodiment.

[0040] (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.

[0041] 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.

[0042] The reflected light attenuating section 81 is disposed on the opposite side of the polarizing plate 73 and the image pickup element 75 with respect to the optical path separating prism 53, and is disposed below the optical path separating prism 53 in Fig. 5. Therefore, the optical path separating prism 53 is disposed between the reflected light attenuating section 81 and the prism spacer 71.

[0043] The reflected light attenuating section 81 attenuates stray light emitted from the optical path separation prism 53 toward the reflected light attenuating section 81. The reflected light attenuating section 81 has a reflected light attenuating plate 81a and a reflected light absorbing section 81b.

[0044] The reflected light attenuation plate 81a suppresses the stray light Lpt incident from the optical path separation prism 53 from being reflected toward the optical path separation prism 53. The reflected light attenuation plate 81a is disposed at an angle with respect to the optical path separation prism 53. A plurality of reflected light attenuation plates 81a may be used and disposed in a triangular shape.

[0045] The reflected light absorbing section 81b absorbs the stray light Lpt reflected by the reflected light attenuation plate 81a. The reflected light absorbing section 81b is, for example, a container that houses the reflected light attenuation plate 81a, and has an opening 81c on the side of the optical path separation prism.

[0046] The projection imaging optical system 51A and the projection type image display device 1A in the second embodiment include a reflected light attenuating unit 81 that is disposed on the opposite side of the optical path separating prism 53 from the imaging element 75 and attenuates the image light reflected within the optical path separating prism 53. It is possible to suppress stray light Lpt, which was originally image light Lp, from being emitted from the optical path separating prism 53 in the direction opposite to the imaging element 75, being reflected by a structure external to the optical path separating prism 53, and being incident on the optical path separating prism 53 again and heading toward the imaging element 75. This makes it possible to prevent temperature rise and deterioration due to high temperature of the polarizing plate 73 when the luminance of the light from the light source device 101 is increased, and improves the reliability of the projection imaging optical system 51A.

[0047] Moreover, the reflected light attenuating section 81 has a reflected light attenuating plate 81a disposed at an angle with respect to the optical path separating prism 53, and a reflected 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 separating prism 53, when the stray light Lpt that was originally the image light Lp is reflected by the reflected light attenuating plate 81a, the amount of light traveling in a direction different from the optical path separating prism 53 increases. Furthermore, since the reflected light absorbing section 81b absorbs the stray light Lpt reflected by the reflected light attenuating plate 81a, it is possible to prevent the stray light Lpt from traveling again toward the imaging element 75.

[0048] (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.

[0049] 6, the projection-imaging optical system 51B of the third embodiment is the projection-imaging optical system 51 of the first embodiment provided with a diaphragm 83. 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.

[0050] The diaphragm 83 reduces stray light incident from the optical path separating prism 53 to the imaging element 75. The diaphragm 83 is disposed between the polarizing plate 73 and the optical path separating prism 53, for example, between the polarizing plate 73 and the prism spacer 71. The diaphragm 83 has an opening 83a in the center. The size of the opening 83a is large enough to allow the luminous flux of the image light reflected by the screen 200 to pass through. By disposing the diaphragm 83 between the polarizing plate 73 and the optical path separating prism 53, it is possible to reduce the incidence of stray light Lpt due to the lenses 61a and 61b in the projection lens unit 61 into the imaging element 75.

[0051] The projection imaging optical system 51B and the projection type image display device 1B in the third embodiment include a diaphragm 83 disposed between the optical path separation prism 53 and the polarizing plate 73. This makes it possible to reduce the incidence of stray light Lpt in the projection lens unit 61 on the image sensor 75. Since it is possible to reduce noise due to stray light, the image sensor 75 can capture an image Im1 with a further improved S / N ratio.

[0052] (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.

[0053] 7, the projection imaging optical system 51C of the fourth embodiment is configured such that the quarter wavelength plate 55 of the projection imaging optical system 51 of the first embodiment is removable from the optical path of the image light Lp incident on the projection lens unit 61 from the optical path separation prism 53. Other than this point and the points described below, the projection type image display device 1 of the first embodiment and the projection type image display device 1B of the third embodiment have the same configuration, so description thereof will be omitted.

[0054] The projection imaging optical system 51C includes a drive unit 91 that inserts and removes the quarter-wave plate 55 on the optical path of the image light incident on the projection lens unit 61 from the optical path separation prism 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.

[0055] In the fourth 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 fourth 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. 7, characters are projected as an example of the images Im2 and Im3.

[0056] 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.

[0057] The projection imaging optical system 51C 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.

[0058] The control unit 95 controls the liquid crystal display elements 37, 38, and 39, which are light modulation elements, so as to cause the image Im3 to follow 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.

[0059] 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. 8 and 9. Fig. 8 is an explanatory diagram showing the optical path in the optical path separation prism, Fig. 8(a) is an explanatory diagram showing the optical path of the projection imaging optical system 51C in a state where the quarter-wave plate 55 is arranged on the optical path, and Fig. 8(b) is an explanatory diagram showing the optical path of the projection imaging optical system 51C in a state where the quarter-wave plate 55 is removed from the optical path. Fig. 9 is an explanatory diagram showing an image captured by the imaging element 75, Fig. 9(a) is an image captured with the quarter-wave plate 55 arranged on the optical path, and Fig. 9(b) is an image captured with the quarter-wave plate 55 removed from the optical path.

[0060] As shown in FIG. 8A, 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 separation prism 53, where only the S-polarized component Lns is reflected by the polarization separation film 53a, and the traveling direction is changed by 90 degrees to proceed toward the imaging element 75. The remaining light component Lnv of the reflected light Ln2 passes through the polarization separation film 53a and proceeds straight toward the narrowband retardation plate 52. The S-polarized component Lns of the reflected light Ln2 exits from the optical path separation prism 53, passes through the prism spacer 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.

[0061] Therefore, when a quarter-wave plate 55 is present on the optical path, as shown in FIG. 9(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.

[0062] 8(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 Lp2 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 Lp2. The image light Lp2 reflected by the screen 200 and the object hm passes through the projection lens unit 61 and also passes through the optical path separation prism 53, and does not proceed to the imaging element 75.

[0063] Therefore, only the S-polarized component Lns of the reflected light Ln2 is reflected by the polarization separation film 53a of the optical path separation prism 53 and travels toward the imaging element 75. As a result, the P-polarized image light Lp2 projected onto and reflected by the screen 200 is not captured, and only the S-polarized component Lns of the reflected light Ln2 is captured by the imaging element 75.

[0064] 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. 9(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.

[0065] According to the projection imaging optical system 51C and the projection type image display device 1C in the fourth embodiment, the ¼ wavelength plate 55 is removable and insertable on the optical path of the image light incident from the optical path separation prism 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 composed only of the illumination light and environmental light reflected by the screen 200 and the object hm.

[0066] Furthermore, since illumination light and ambient light often have a low amount of light, as shown in Fig. 9(b), in order to capture an image excluding the projection image, it is desirable to reliably remove stray light generated from the optical path separation prism 53 and the lenses 61a and 61b of the projection lens unit 61 so as not to enter the imaging element 75. Therefore, since the configurations for removing stray light according to the second and third embodiments are very effective, it is also very useful to combine the fourth embodiment with the second and third embodiments.

[0067] In addition, at least a portion of the projection target includes a movable object hm, and the projection type image display device 1C 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.

[0068] (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.

[0069] In each embodiment, S-polarized and P-polarized image light are used, but the polarization states 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.

[0070] In each embodiment, the optical path separating portion is the optical path separating prism 53, but is not limited to this. The optical path separating portion may be a mirror on which a polarized light separating film 53a is formed.

[0071] In each embodiment, the image light output unit 45 includes three liquid crystal display elements as a light modulation unit, but is not limited to this. The image light output unit 45 may include a DMD (digital micromirror device) instead of the liquid crystal display elements. The image light output from the DMD is also polarized by the narrowband retarder 52, so that the same effect as in the embodiment can be obtained.

[0072] 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.

[0073] 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.

[0074] (Outline of the embodiment) (1) A projection type image display device according to the present disclosure includes an image light output section that outputs image light in a first polarization state, which is either P-polarized light or S-polarized light, and an optical path separation section that has a polarization separation film that 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-polarized light and S-polarized light. The projection type image display device includes a projection lens unit that enlarges and projects the image light that has transmitted through the optical path separation section onto a projection target, and into which external light including the image light reflected by the projection target is incident, and a quarter-wave plate that is disposed between the optical path separation section and the projection lens unit and 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. The projection type image display device includes an image sensor that captures external light via the projection lens unit and the optical path separation section, and a polarizing plate that is disposed between the optical path separation section and the image sensor and transmits external light in the second polarization state.

[0075] As a result, the polarization of the image light emitted from the optical path separation unit toward the projection target and the polarization of the image light as external light reflected by the projection target and entering the optical path separation unit are different polarization states, either P polarization or S polarization, so the polarizing plate allows only the light in the polarization state of the image light reflected by the projection target to enter the imaging element. Therefore, even if the image light entering from the image light exit unit becomes stray light due to reflection within the optical path separation unit and travels toward the imaging element, it can be blocked by the polarizing plate. Also, as for external light, only light components in the same polarization state as the image light reflected by the projection target enter the imaging element, so it is possible to reduce the imaging of external light other than the image light reflected by the projection target.

[0076] (2) In the projection type image display device of (1), the polarizing plate is rotatable.

[0077] (3) In the projection type image display device of (1) or (2), a reflected light attenuating section is provided, which is disposed on the opposite side of the optical path separating prism from the imaging element, and which attenuates the image light reflected within the optical path separating prism.

[0078] (4) In any one of the projection-type image display devices (1) to (3), the reflected light attenuating unit includes a reflected light attenuating plate arranged at an angle with respect to the optical path separation prism, and a reflected light absorbing unit that absorbs the image light reflected by the reflected light attenuating plate.

[0079] (5) In the projection type image display device according to any one of (1) to (4), a diaphragm is disposed between the optical path separation prism and the polarizing plate.

[0080] (6) In the projection type image display device according to any one of (1) to (5), the quarter-wave plate is insertable and removable on the optical path of the image light that enters the projection lens unit from the optical path separation prism.

[0081] (7) In the projection type image display device of (6), a drive unit is provided that inserts and removes the quarter wavelength plate on the optical path of the image light that enters the projection lens unit from the optical path separation prism.

[0082] (8) In the projection type image display device of (6) or (7), 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 imaging unit 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]

[0083] The present disclosure can be used in a projection-type image display device that projects an image. [Explanation of symbols]

[0084] 1, 1A, 1B Projection type image display device 37, 38, 39 Liquid crystal display element 37 Green 38 Red 39 Blue 43-color synthesis prism (cross cube prism) 45 Image light output section 51, 51A, 51B Projection imaging optical system 52 Narrowband retarder 53 Optical path separation prism 53a Polarization separation film 55 1 / 4 wave plate 61 Projection lens unit 61a, 61b Lenses 71 Prism Spacer 73 Polarizing Plate 75 Image sensor 81 Reflected light attenuation section 83 Aperture 83a opening 91 Drive mechanism 93 Image Processing Section 95 Control Unit 101 Light source device 111 Phosphor Wheel 200 screens 210 External lighting source hm object Im1, Im2, Im3 video Ln2 Reflected light lpt stray light Ls video light

Claims

1. an image light output unit that outputs image light in a first polarization state, which is either P polarization or S polarization; an optical path separation unit having a polarization separation unit that transmits the image light in the first polarization state incident from the image light output unit and reflects light in the other second polarization state of either P polarization or S polarization; a projection lens unit that enlarges and projects the image light that has passed through the optical path separation unit onto a projection target, and into which external light including the image light that has been reflected by the projection target is incident; a retardation plate disposed between the optical path separation unit 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; an image pickup element that captures an image of the external light via the projection lens unit and the optical path separation unit; a polarizing plate disposed between the optical path separation unit and the image sensor, the polarizing plate transmitting external light in the second polarization state; a reflected light attenuating unit that attenuates the image light reflected in the optical path separating unit; A projection type image display device comprising:

2. The polarizing plate is rotatable.

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

3. The reflected light attenuation unit is disposed on the opposite side of the image sensor with respect to the optical path separation unit.

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

4. The reflected light attenuating unit is a reflected light attenuation plate disposed at an angle with respect to the optical path separation unit; The projection type image display device according to claim 1 , further comprising: a reflected light absorbing section that absorbs the image light reflected by the reflected light attenuation plate.

5. a diaphragm disposed between the optical path separation unit and the polarizing plate; 5. The projection type image display device according to claim 1.

6. the retardation plate is insertable and removable on the optical path of the image light incident on the projection lens unit from the optical path separation unit; 6. The projection type image display device according to claim 1.

7. a drive unit that inserts and removes the retardation plate on an optical path of image light that is incident on the projection lens unit from the optical path separation unit, 7. The projection type image display device according to claim 6.

8. 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 display of the image light emitted from the image light emission unit in accordance with a movement of the object so as to project the image light onto the object in the image, 8. The projection type image display device according to claim 6 or 7.

Images