WO2016080114A1

WO2016080114A1 - Projection device

Info

Publication number: WO2016080114A1
Application number: PCT/JP2015/079126
Authority: WO
Inventors: 佐野永悟
Original assignee: コニカミノルタ株式会社
Priority date: 2014-11-17
Filing date: 2015-10-15
Publication date: 2016-05-26
Also published as: JPWO2016080114A1

Abstract

This projection device is provided with an illumination optical system 20, a polarized beam splitter 30, an image display element 40, a projection optical system 10, and an imaging element 60, wherein the imaging element 60 is arranged on the side in which P-polarized light having lesser reflection light components on a projection surface 1a transmits, and influence of unnecessary reflection light on the projection surface 1a, including S-polarized light at a high rate, is reduced. Further, for illumination light, the imaging element 60 is arranged on the side in which the S-polarized light is emitted from the polarized beam splitter 30, and a reflection-type liquid crystal element 40 is arranged on the side in which the P-polarized light is emitted from the polarized beam splitter 30. A polarized beam restriction section 80 for cutting the S-polarized light is provided between the polarized beam splitter 30 and the imaging element 60, and accordingly the S-polarized light can be prevented from entering the imaging element 60 directly and influence of stray light in the optical system can be inhibited.

Description

Projection device

The present invention relates to a projection apparatus that projects an image, and more particularly to a projection apparatus that can capture a projected image.

In recent years, a projection apparatus that enlarges and projects an image displayed on an image display element onto a screen by a projection optical system, not only simply projecting a PC screen onto a screen, but also projecting the PC screen onto a whiteboard or the like, Some of them have interactive functions, such as writing handwritten characters and recording the information as images, or detecting the movement of the presenter and advancing the projection screen page. In addition, a projection apparatus that realizes this requires various correction processes according to usage conditions such as trapezoidal distortion correction of projection images and brightness correction according to the surrounding environment.

If simple trapezoidal distortion correction or brightness correction is performed, or if only simple movements of a person are detected, the number of pixels of the imaging device is sufficient, but handwritten characters are superimposed on the projected image. In order to capture as image data, a mega-class resolution is required, and it is desired that an imaging lens used for the resolution has high performance.

Also, when projecting onto a relatively glossy surface such as a whiteboard to add handwriting, fluorescent light on the ceiling or sunlight from the window is reflected on the projection surface, making it difficult to read handwritten characters Such a problem occurs.

As an imaging device for such an interactive function, a projection optical system is not provided as a separate unit from the projection optical system, but a part of the optical path of the projection optical system is branched so that the projection optical system can be used as a common imaging optical system. An idea to be used (referred to as an integrated type in this specification) has been proposed (for example, Patent Documents 1 and 2).

By integrating the projection optical system as an imaging optical system as it is, various aberrations that occur in the lens system, including distortion aberrations that occur in the projection optical system, can be canceled at the time of shooting. A distorted photographed image can be obtained. In addition, since the optical axis of the projection optical system and the optical axis of the photographing optical system match, there is no parallax between the projected image and the photographed image, and a special image is used when superimposing handwritten characters on the projected image. No processing is required.

However, Patent Documents 1 and 2 do not mention countermeasures such as reflection of unnecessary light on the projection surface described above. Further, in the integrated optical system, since the image sensor is disposed at a position close to the illumination optical system, stray light in the optical system may enter the image sensor and cause deterioration of the captured image. Is not mentioned.

JP 2001-343703 A JP 2012-68364 A

The present invention has been made in view of the above-mentioned background art, and is not affected by unnecessary reflected light on the projection surface or stray light in the optical system, and has a low-resolution and high-resolution captured image. An object is to provide a projection apparatus that can be secured.

In order to achieve the above object, a projection apparatus reflecting one aspect of the present invention is an illumination optical system that emits illumination light, and transmits or reflects incident light according to the polarization direction of linearly polarized light of incident light. A polarizing beam splitter (hereinafter also referred to as PBS), an image display element on which light from the illumination optical system enters through the polarizing beam splitter, and an image by the image display element to be projected through the polarizing beam splitter A projection optical system that magnifies and projects onto a surface, and an image sensor for capturing an image on the projection surface. The projection optical system is used in common when imaging, and the optical path and image on the projection side are captured by a polarizing beam splitter. And is separated from the light path from the illumination optical system by the polarization separation surface of the polarization beam splitter and deviates from the light path toward the image display element. An imaging device is arranged on the side where the P-polarized light from the projection surface advances with reference to the projection surface, and polarization restriction that cuts S-polarization with reference to the projection surface between the polarization beam splitter and the imaging device. Is provided.
As a result, an optical system in which the projection optical system and the photographing optical system are integrated is used, and is not affected by unnecessary reflected light on the projection surface or stray light in the optical system, and has low distortion and no parallax. In addition, it is possible to provide a projection device that can ensure a high-resolution captured image.

It is a figure explaining the structure of the projection apparatus of 1st Embodiment which concerns on this invention. 2A and 2B are a rear view and a side view for explaining an example of the installation state of the projection apparatus shown in FIG. It is a graph explaining the relationship between the incident angle of the unnecessary light to a screen, and a reflectance. It is a graph explaining the relationship between a slow ratio and a reflectance. It is a figure explaining the structure of the projection apparatus of 2nd Embodiment. It is a figure explaining the structure of the projection apparatus of 3rd Embodiment.

[First Embodiment]
The structure and the like of the projection apparatus according to the first embodiment of the present invention will be described below with reference to the drawings.

As shown in FIG. 1, a projection apparatus 100 according to the first embodiment enables imaging when projecting an image, and includes a projection optical system 10, an illumination optical system 20, a polarization beam splitter 30, and a reflective liquid crystal element. 40, an image driving circuit 50, an imaging device 60, an imaging driving circuit 70, a polarization limiting unit 80, and a control circuit 90.

Although the detailed description is omitted, the projection optical system 10 enlarges an image obtained from the reflective liquid crystal element 40 as an image display element and projects it on a screen or other projection target (not shown). The projection optical system 10 is composed of a plurality of lens groups, and focusing and zooming can be performed by moving some lens groups in the direction of the optical axis OA ′. The optical axis OA ′ of the projection optical system 10 is shifted in parallel from the center of the reflective liquid crystal element 40 (the optical axis OA of the illumination optical system 20) in order to project the projected image obliquely with respect to the projection target. Yes.

The illumination optical system 20 includes a light source 21, a uniformizing optical system 22, and the like. The uniformizing optical system 22 two-dimensionally uniformizes the illuminance of the light irradiated on the reflective liquid crystal element 40 with respect to the cross section perpendicular to the optical axis OA by dividing and superimposing the light emitted from the light source 21.

The polarization beam splitter (PBS) 30 is a pair of right-angle prisms bonded together, and on the bonded surface, linearly polarized light in a predetermined direction incident from the illumination optical system 20 is selectively applied to the inclined surface of one right-angle prism. A polarization separation surface 31 made of a polarization separation film that is transmitted through is formed. Thereby, the illumination light emitted from the illumination optical system 20 can be transmitted and incident on a reflective liquid crystal element 40 described later. Further, the polarization beam splitter 30 can reflect the modulated light emitted from the reflective liquid crystal element 40 and make it incident on the projection optical system 10. Further, the photographing light returned from the projection optical system 10 can be transmitted and incident on the image sensor 60. In other words, the polarization beam splitter 30 has four

surfaces

30a, 30b, 30c, and 30d that are opposed to the polarization separation surface 31 in an inclined state, and the first surface 30a is light of the illumination optical system 20. The second surface 30 b faces the reflective liquid crystal element 40, the third surface 30 c faces the projection optical system 10, and the fourth surface 30 d faces the image sensor 60. Although the details will be described later, the polarization separation surface 31 reflects S-polarized light with reference to this and transmits P-polarized light. With respect to S-polarized light with reference to the polarization separation surface 31, illumination optics is used. The group consisting of the system 20 and the image sensor 60 and the group consisting of the projection optical system 10 and the reflective liquid crystal element 40 are separated from each other in the optical path and become independent from each other. On the other hand, with respect to P-polarized light with the polarization separation surface 31 as a reference, the group consisting of the illumination optical system 20 and the reflective liquid crystal element 40 and the group consisting of the projection optical system 10 and the imaging element 60 are separated in the optical path and independent of each other. It will be in the state.

The reflective liquid crystal element 40 is a display element (image display element) that forms image light, and can be said to be a light modulation element in that image light is formed from illumination light by changing a spatial reflectance. The reflective liquid crystal element (image display element) 30 is an image display panel that is a plate-like electronic component. The reflection type liquid crystal element 40 is a micro display also called LCOS (Liquid crystal on silicon), in which a circuit is directly formed on the surface of a silicon chip and a liquid crystal layer is sandwiched between a counter substrate. The reflective liquid crystal element 40 modulates illumination light by changing the arrangement of liquid crystal molecules when a voltage corresponding to a driving signal is applied to a liquid crystal layer for each pixel, and displays a desired image by reflection. It is. At this time, when P-polarized light based on the polarization separation surface 31 is incident on the reflective liquid crystal element 40 as illumination light, S-polarized light based on the polarization separation surface 31 is reflected as video light.

The image driving circuit 50 is a circuit portion that operates the reflective liquid crystal element 40 based on an image signal. The image drive circuit 50 operates based on a control signal from a control circuit 90 described later, and outputs a drive signal corresponding to the image signal to the reflective liquid crystal element 40 to perform an image display operation.

The image sensor 60 is a solid-state image sensor and is a CMOS image sensor that detects a subject image. An image formed by the projection optical system 10 is projected onto the photoelectric conversion unit or the imaging surface (not shown) of the imaging element 60. That is, on the photoelectric conversion unit of the image sensor 60, an image of a whiteboard or other projection object is reduced and projected by the projection optical system 10 also used as an imaging optical system. Note that the image pickup device 60 is not limited to the above-described CMOS type image sensor, and may be one to which another device such as a CCD is applied. Note that the angle of view or area covered by the image sensor 60 is larger than the angle of view or area of the range where display is performed on the projection object by the reflective liquid crystal element 40.

The imaging driving circuit 70 outputs YUV and other digital pixel signals to an external circuit, and receives a voltage and a clock signal for driving the imaging element 60 from the control circuit 90, thereby causing an image on the imaging element 60. The detection operation is performed.

The polarization limiting unit 80 is an optical element that is interposed between the polarization beam splitter 30 and the image sensor 60, and is S-polarized light with reference to the polarization separation surface 31 (resulting in S with reference to the projection surface 1a described later). (Polarized light). As the polarization limiting unit 80, for example, an absorption type glass polarizer, a reflection type polarizer using a wire grid, a reflection type polarizer in which multiple layers of birefringent dielectrics are stacked, and other polarization filters may be used. it can. By providing the polarization limiting unit 80, it is possible to prevent the S-polarized component of the illumination light from the illumination optical system 20 from entering the image sensor 60 through the polarization separation surface 31 of the polarization beam splitter 30 and preventing shooting.

The control circuit 90 can appropriately operate the image driving circuit 50, the imaging driving circuit 70, and the like based on a program incorporated therein or an instruction from an operation unit (not shown). The control circuit 90 outputs a drive signal or an image signal to the image drive circuit 50 based on, for example, a video signal or other signal input from the outside, and causes the reflective liquid crystal element 40 to perform a display operation. In addition, the control circuit 90 can perform various image processing on the imaging data obtained from the imaging device 60 via the imaging drive circuit 70, for example, and can store the acquired imaging data or processed data. it can.

Referring to FIGS. 2A and 2B, the usage state or installation state of the projection apparatus 100 shown in FIG. 1 will be described. The projection apparatus 100 is disposed so as to face the lower side of the front face with respect to the projection surface 1a such as a whiteboard, a screen, or the like. Here, the reflected light from the projection surface 1a that is incident on the projection optical system 10 of the projection apparatus 100 includes an S-polarized component and a P-polarized component with respect to the projection surface 1a. Here, the S-polarized light component with respect to the projection surface 1a is perpendicular to the plane formed by the central axis of the projection light and the normal line at the center of the projection image where the central axis of the projection light intersects the projection surface 1a. The P-polarized component is a polarized component that oscillates in a direction parallel to the plane. 2A and 2B, the S-polarized light and the P-polarized light with the projection surface 1a as a reference coincide with the S-polarized light and the P-polarized light with the polarization separation surface 31 of the polarizing beam splitter 30 as a reference. That is, the S-polarized light has an electric field vector common to the projection apparatus 100 and the projection surface 1a and vibrates perpendicularly to the yz plane extending vertically.

Returning to FIG. 1 and the like, the operation of the projection apparatus 100 will be described. First, the light path during projection will be described. The light beam emitted from the light source 21 passes through the uniformizing optical system 22 for making the illuminance on the reflective liquid crystal element (image display element) 40 uniform, and is polarized light for separating the polarization state of the light beam into two. The light enters the beam splitter 30. The illustrated polarization beam splitter 30 has a polarization separation surface 31 that reflects the S polarization component and transmits the P polarization component. The P-polarized light beam transmitted through the polarization separation surface 31 enters the reflective liquid crystal element 40, and only the S-polarized light beam (modulation component) reflected and emitted from the reflective liquid crystal element 40 is reflected by the polarization separation surface 31. Then, the light enters the projection optical system 10 and is projected onto the projection surface 1a.

Next, the ray path at the time of imaging will be described. When photographing a handwritten character or a projected image written on a whiteboard or the like having the projection surface 1a, light rays from the projection surface 1a have passed through the projection optical system 10 so as to travel in the same optical path as during projection. Later, the light enters the polarization beam splitter 30 and is separated into an S-polarized component and a P-polarized component by the polarization separation surface 31. Here, the image sensor 60 is arranged in a direction in which the P-polarized component passing through the polarization separation surface 31 is emitted with respect to the polarization beam splitter 30, and only the P-polarized component transmitted through the polarization separation surface 31 is applied to the image sensor 60. Incident light is recorded as an image.

As described above, by using the polarizing beam splitter 30, the imaging optical device 10 is disposed so as to face the fourth surface 30 d adjacent to the second surface 30 b that faces the reflective liquid crystal element 40. Can be used as it is as a photographing optical system. By doing so, when taking a projection image, the light beam passes through the projection optical system 10 in the opposite direction to that during projection. Therefore, distortion aberration generated in the projection optical system 10 and other reductions in resolving power are reduced. The resulting lateral chromatic aberration will be cancelled. Therefore, it is possible to obtain a low distortion image with high resolution up to the peripheral part. Further, since the projection optical system 10 and the photographing optical system can be configured with substantially the same optical path, no parallax occurs between the projected image and the photographed image.

In the projection apparatus 100, a polarization limiting unit 80 is provided between the polarization beam splitter 30 and the imaging device 60 as means for cutting the S-polarized light component separated from the illumination light by the polarization separation surface 31 of the polarization beam splitter 30. Yes. Thereby, it is possible to prevent the light from the illumination optical system 20 from directly entering the image sensor 60, and to suppress the influence of stray light in the optical system.

As shown in FIG. 3, there is a difference depending on the incident angle in the reflectance on the material surface of S-polarized light and P-polarized light (for example, Eugene Hecht, Yoshiharu Ozaki and Toshimitsu Asakura, “Hech Optics II (See page 103 of Maruzen Publishing). That is, unnecessary reflected light on the projection surface 1a contains a large amount of S-polarized light components. Therefore, the imaging element 60 is arranged on the side through which the P-polarized light component that is not easily affected by unnecessary light at the time of photographing, in other words, on the side from which the S-polarized light component of the illumination optical system 20 exits from the polarization beam splitter 30. It is desirable that By doing so, the influence of unnecessary reflected light on the projection surface 1a can be reduced, and handwritten characters can be read accurately.

In the above chart of FIG. 3, it is assumed that the refractive index of the medium that reflects unnecessary light is 1.5. For example, a surface of a whiteboard is assumed as the projection surface 1a. The whiteboard is coated with enamel or iron. Enamel includes phthalate resin enamel, and the refractive index of phthalate resin enamel is about 1.5.

Hereinafter, quantitative numerical results regarding the influence of unnecessary light on the projection surface 1a will be shown. As shown in FIG. 2B and the like, for example, it is assumed that the projection apparatus 100 is disposed below the projection surface 1a and is projected upward with respect to the projection surface 1a. At this time, it is assumed that unnecessary light FH such as sunlight or a ceiling lamp enters the projection surface at an angle of 45 ° and enters the projection optical system 10 of the projection apparatus 100. In this case, the two polarization components when the intensity of the unnecessary light FH is 1 are 0.008 for the P polarization component and 0.092 for the S polarization component due to the characteristics shown in FIG. On the other hand, the light from the regular projection image and the characters written on the projection surface 1a (referred to as regular light) passes through the projection optical system 10, and then the polarization component is separated by the polarization beam splitter 30, and the S polarization component. Therefore, the amount of light incident on the image sensor 60 is 0.5 with respect to the normal light intensity of 1. Usually, the intensity of the unnecessary light FH is higher than the intensity of the normal light, and assuming that the unnecessary light intensity is 10 times the normal light intensity, the normal light intensity incident on the image sensor 60 and the unnecessary light intensity are The unnecessary light FH is 0.08 with respect to 0.5 light (ratio of normal light to unnecessary light FH is 1: 0.16), and it can be seen that the unnecessary light FH can be sufficiently reduced with respect to normal light. .

On the other hand, when the positional relationship between the image sensor 60 and the reflective liquid crystal element 40 is reversed, the S-polarized component easily reaches the image sensor 60. When calculated under the same conditions as described above, the normal light is 0.5. In contrast, the unnecessary light FH becomes 0.92 (the ratio of the normal light and the unnecessary light FH is 1: 1.84), and the unnecessary light FH is incident on the image sensor 60 with an intensity higher than that of the normal light. It becomes. The results are summarized in Table 1 below. From this result, it can be seen that it is desirable that the image sensor 60 be disposed on the side where the S-polarized component is emitted from the polarization beam splitter 30 in the light beam of the illumination optical system 20.
[Table 1]

Hereinafter, the slow ratio of the projection optical system 10 will be described. 2A and 2B, the slow ratio Tr is a value obtained by dividing the projection distance D (the distance from the projection apparatus 100 to the projection surface 1a) by the horizontal size W of the projection image PG. For ease of explanation, it is assumed that the projection image PG has an aspect ratio of 16: 9, and the projection apparatus 100 projects from the same height as the lower end of the projection image PG. In this case, the unnecessary light FH that is reflected at the largest angle on the projection surface 1a and enters the projection apparatus 100 is reflected at the upper end of the projection surface 1a. Therefore, when the slow ratio Tr is determined, the vertical size H obtained from the horizontal size W is obtained, and the maximum incident angle θ of the unnecessary light FH incident on the projection device 100 can be determined.

FIG. 4 is a graph of the reflectance for each polarization of the unnecessary light FH from the maximum angle of the unnecessary light FH when the slow ratio Tr is changed. When the slow ratio Tr decreases, the reflection angle of the unnecessary light FH incident on the projection apparatus 100 correspondingly on the projection surface 1a tends to increase. Therefore, it is preferable to perform projection so that the slow ratio Tr is in the following range so that the difference between the reflectances of the S-polarized component and the P-polarized component is increased and the significance of arranging the polarization limiting unit 80 is increased.
0.1 <Tr <1.0 (1)
By falling below the upper limit value of the conditional expression (1), unnecessary light FH reflected at a relatively large angle on the projection surface 1a is incident on the projection apparatus 100. Therefore, as shown in FIG. Thus, the difference in reflectance between the S-polarized component and the P-polarized component becomes larger, and the polarization limiting unit 80 is arranged between the polarizing beam splitter 30 and the image sensor 60 to capture unnecessary light FH such as reflection of an illumination lamp. It can be said that the suppression effect increases. On the contrary, if the slow ratio is too small, the reflection angle of the unnecessary light FH on the projection surface 1a becomes too large, and the difference between the reflectances of the S-polarized light and the P-polarized light becomes small. That is, even when exceeding the lower limit value of the conditional expression (1), it is possible to avoid the incident angle of the unnecessary light FH from being excessively increased and the difference in reflectance between the S-polarized light and the P-polarized light from being reduced. 80 can be disposed between the polarizing beam splitter 30 and the image sensor 60 to maintain the effect of suppressing unnecessary light FH shooting such as the reflection of an illumination lamp.

In the projection apparatus 100 shown in FIG. 1, the separation characteristics of the polarization separation surface 31 of the polarization beam splitter 30 can be reversed. That is, the S-polarized light with the polarization separation surface 31 as a reference is transmitted, and the P-polarized light with the polarization separation surface 31 as a reference is reflected. In this case, although illustration is omitted, the arrangement relationship between the reflective liquid crystal element 40 and the image sensor 60 is changed, the image sensor 60 is disposed opposite to the second surface 30b, and the reflective liquid crystal element 40 is opposed to the fourth surface 30d. Deploy. Then, the polarization limiting unit 80 interposed between the polarization beam splitter 30 and the image sensor 60 cuts S-polarized light having the polarization separation surface 31 as a reference (resulting in S-polarized light having the projection surface 1a as a reference). Shall.

In the projection apparatus 100 according to the embodiment described above, the image sensor 60 is disposed on the side that transmits the P-polarized light with a small amount of reflected light on the projection surface 1a during photographing. Thereby, the influence of unnecessary reflected light on the projection surface 1a having a large proportion of S-polarized light is reduced. In addition, by providing a polarization limiting unit 80 that cuts S-polarized light between the polarization beam splitter 30 and the image sensor 60, the S-polarized light is cut, the influence of unnecessary reflected light is reduced, and handwritten characters are accurate. Can be read.

In the projection apparatus 100, for the illumination light from the illumination optical system 20, the image sensor 60 is arranged on the side where the S-polarized light is emitted from the polarizing beam splitter 30, and the P-polarized light is emitted on the side where the polarized light is emitted from the polarizing beam splitter 30. A reflective liquid crystal element 40 is disposed. By providing the polarization limiting unit 80 that cuts S-polarized light between the polarization beam splitter 30 and the image sensor 60, the S-polarized light with respect to the polarization separation surface 31 is prevented from directly entering the image sensor 60 from the illumination optical system 20. It is possible to suppress the influence of stray light in the optical system.

[Second Embodiment]
Hereinafter, the projection apparatus according to the second embodiment will be described. Note that the projection apparatus of the second embodiment is a modification of the projection apparatus of the first embodiment, and items that are not particularly described are the same as those of the first embodiment.

As shown in FIG. 5, in the case of the projection apparatus 100 according to the second embodiment, a polarization conversion element 82 that aligns the polarization direction is disposed on the illumination optical system 20 side of the polarization beam splitter 30. The polarization conversion element 82 is a combination of, for example, a polarization beam splitter and a wavelength plate, and converts S polarization into P polarization among S polarization and P polarization included in illumination light emitted from the illumination optical system 20. Thereby, only substantially P-polarized illumination light can be made incident on the polarization beam splitter 30, and not only the loss of the light source light is reduced, but also the light leaking to the image sensor 60 side can be surely reduced. In this case, the P-polarized light is incident on the polarization beam splitter 30 from the polarization conversion element 82 with reference to the polarization separation surface 31, but as a result, the P-polarized light is incident on the projection surface 1a. It also becomes.

[Third Embodiment]
The projector according to the third embodiment will be described below. The projection apparatus according to the third embodiment is a modification of the projection apparatus according to the first embodiment, and matters not specifically described are the same as those in the first embodiment.

As shown in FIG. 6, in the case of the projection apparatus 100 of the third embodiment, the paper surface is a horizontal xz plane. That is, in this arrangement, the S-polarized light with respect to the projection surface 1 a becomes the P-polarized light with the polarization separation surface 31 as a reference. In order to cope with this, in the projection apparatus 100, the arrangement relationship between the reflective liquid crystal element 40 and the imaging element 60 is changed, the imaging element 60 is arranged opposite to the second surface 30b, and the reflective liquid crystal element is arranged on the fourth surface 30d. 40 are arranged opposite to each other. However, the separation characteristic of the polarization separation surface 31 of the polarization beam splitter 30 remains as in the first embodiment. As a result, the illumination light emitted from the illumination optical system 20 is reflected by the polarization separation surface 31 to enter the reflection type liquid crystal element 40, and the modulated light emitted from the reflection type liquid crystal element 40 is reflected by the polarization separation surface 31. The light is incident on the projection optical system 10 by being transmitted. Further, the imaging light returned from the projection optical system 10 is reflected by the polarization separation surface 31 to be incident on the image sensor 60. In the above, the illumination light incident on the reflective liquid crystal element 40 is P-polarized light with respect to the projection surface 1a (that is, S-polarized light with reference to the polarization separation surface 31) and is incident on the projection optical system 10. The projection light is S-polarized light with respect to the projection surface 1a (that is, P-polarization with reference to the polarization separation surface 31), and the image light incident on the image sensor 60 is based on the projection surface 1a. P-polarized light (that is, S-polarized light with the polarization separation surface 31 as a reference). In this case, the polarization limiting unit 80 interposed between the polarization beam splitter 30 and the image sensor 60 cuts S-polarized light with the projection surface 1a as a reference (resulting in P-polarized light with the polarization separation surface 31 as a reference). It shall be.

The projector 100 according to the embodiment has been described above, but the projector according to the present invention is not limited to the above. For example, the specific configurations of the projection optical system 10 and the illumination optical system 20 are not limited to those shown in the drawings, and can be changed as appropriate according to the application. The projection device may project downward or may project in the left-right direction. In any case, it is possible to cut S-polarized light which is large in the reflected light component on the projection surface 1a and reaches the image sensor 60.

Claims

An illumination optical system that emits light for illumination;
A polarization beam splitter that separates light by transmitting or reflecting incident light according to the polarization direction of linearly polarized light of the incident light; and
An image display element on which light from the illumination optical system enters through the polarization beam splitter;
A projection optical system that magnifies and projects an image by the image display element onto a projection surface via the polarization beam splitter;
An image sensor for capturing an image on the projection surface,
When imaging, the projection optical system is used in common, and the polarizing beam splitter separates the projection-side optical path and the imaging-side optical path,
Of the light from the illumination optical system, the light is separated from the polarization separation surface of the polarization beam splitter and deviated from the light path toward the image display element, and the projection surface from the projection surface is used as a reference. The image sensor is arranged on the side where the P-polarized light travels,
A projection apparatus in which a polarization limiting unit that cuts S-polarized light with respect to the projection surface is provided between the polarization beam splitter and the imaging element.
The imaging device is disposed on a side of the light from the illumination optical system on the side where S-polarized light with respect to the polarization separation surface of the polarization beam splitter is reflected by the polarization separation surface and emitted from the polarization beam splitter. Item 4. The projection device according to Item 1.
The projection optical system projects an image by the image display element upward or downward toward the projection surface,
3. The imaging device is disposed on a side where P-polarized light with respect to the projection surface from the projection surface as a reference passes through a polarization separation surface of the polarization beam splitter and exits from the polarization beam splitter. The projection apparatus described in 1.
The projection apparatus according to any one of claims 1 to 3, wherein the following conditional expression is satisfied.
0.1 <Tr <1.0 (1)
here,
Tr: Slow ratio of the projection optical system
The projection apparatus according to any one of claims 1 to 4, wherein the polarization limiting unit is an absorptive polarizing filter disposed between the polarization beam splitter and the imaging device.
The projection apparatus according to any one of claims 1 to 4, wherein the polarization limiting unit is a reflective polarizing filter disposed between the polarization beam splitter and the imaging device.
The projection apparatus according to any one of claims 1 to 6, wherein a polarization conversion element that aligns a polarization direction is disposed on the illumination optical system side of the polarization beam splitter.