JP7151398B2 - Optical device and image projection device - Google Patents

Description

The present invention relates to optical devices and image projection devices.

A DLP (Digital Light Processor) projector projects light output from a light source such as a lamp onto a light modulation element through a light tunnel, and projects an image generated by the light modulation element onto a screen or the like using a projection optical system. Are known.

For example, a DMD (Digital Micromirror Device) is used as the light modulation element. A DMD generates an image by modulating light emitted from a light tunnel based on image data input from an external device such as a personal computer. The light tunnel is a substantially rectangular parallelepiped optical member that uniformizes the luminance distribution of the light incident from the light source and outputs it, and irradiates the light modulation element with rectangular illumination light.

In such an image projection apparatus, it has been proposed to provide a plurality of light tunnels with different cross-sectional aspect ratios and switch the light tunnel to be used based on the aspect ratio of image data (Patent Document 1).

Image data incident on the image projection apparatus from an external device is generally oblong in the horizontal direction longer than the vertical direction, such as an aspect ratio of 10:16. Therefore, each of the plurality of light tunnels described in Patent Document 1 has a laterally long cross-sectional shape.

However, in recent years, image projection apparatuses often process vertically long image data such as portrait images because they also accept image data output from portable display devices such as smartphones.

For this reason, in the conventional image projection device, the light tunnel irradiates the horizontally long illumination area set on the horizontally long light modulation element. Light on both sides of the field must be discarded so as not to lead to the projection optics.

Therefore, in the conventional image projection apparatus, when projecting a vertically long image, part of the illumination light is discarded, so the light utilization efficiency is low.

The technology disclosed has been devised to solve this problem in view of the above circumstances, and aims to suppress a decrease in light utilization efficiency when projecting a vertically long image.

The disclosed technology includes a light source that outputs light, a horizontally long rectangular image generation surface, an optical modulation element that modulates light irradiated to the image generation surface to generate an image, and a trapezoidal cross section. and a light tunnel for irradiating the image generation surface with the light output from the light source with a uniform luminance distribution , wherein an illumination area on the image generation surface by the light tunnel is trapezoidal. wherein the height of the trapezoidal shape is equal to the length of the short side of the image generation surface, and the lengths of the base and top sides are each smaller than the length of the long side of the image generation surface .

It is possible to suppress a decrease in light utilization efficiency when projecting a vertically long image.

1 is a perspective view illustrating an image projection device according to a first embodiment; FIG. 2 is a block diagram illustrating the functional configuration of the image projection device according to the first embodiment; FIG. 3 is a perspective view illustrating an illumination optical system unit; FIG. 1 is a perspective view showing a schematic configuration of a light tunnel; FIG. FIG. 4 is a diagram showing the relationship between the image generation surface of the DMD and the illumination area by the light tunnel; FIG. 10 is a diagram showing the relationship between an image generation surface and an illumination area in a conventional projector; FIG. 4 is a diagram showing a state in which the projector is installed in a posture directed obliquely upward; It is a figure explaining keystone distortion correction. 1 is a perspective view showing a schematic configuration of a light tunnel used in an image projection device according to a first embodiment; FIG. FIG. 10 is a diagram showing the relationship between the image generation surface of the DMD and the illumination area by the light tunnel in the second embodiment;

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments for carrying out the invention will be described with reference to the drawings. In each drawing, the same components are denoted by the same reference numerals, and redundant description may be omitted.

<First Embodiment>
An image projection apparatus according to a first embodiment of the present invention will be described below.

[Configuration of image projection device]
FIG. 1 is a perspective view illustrating the projector 1 according to the first embodiment. The projector 1 is an example of an image projection device, has an exit window 3 and an external I/F 9, and is internally provided with an optical engine 15 (see FIG. 2) that generates a projected image. In the projector 1, for example, when a video signal (image data) is input from an external device connected to the external I/F 9, the optical engine 15 generates an image P based on the input image data. It is projected onto the screen S from the exit window 3 as shown.

1, the X direction is the width direction of the projector 1, the Y direction is the depth direction of the projector 1, and the Z direction is the height direction of the projector 1. As shown in FIG. In the following description, the side facing the exit window 3 of the projector 1 may be referred to as the upper side, and the side opposite to the exit window 3 may be referred to as the lower side. Also, the Y direction is called the horizontal direction, and the Z direction is called the vertical direction.

In this embodiment, an external device that inputs a video signal to the projector 1 is, for example, a smart phone. Also, in this embodiment, the smartphone inputs to the projector 1 vertically long image data whose length in the vertical direction is greater than the length in the horizontal direction. The video signal is not limited to still image data, and may be moving image data.

FIG. 2 is a block diagram illustrating the functional configuration of the projector 1 according to the embodiment.

As shown in FIG. 2, the projector 1 has a power supply 4, a main switch SW5, an operation section 7, an external I/F 9, a system control section 10, a fan 20, and an optical engine 15.

A power supply 4 is connected to a commercial power supply and supplies power to the system control unit 10, the fan 20, the optical engine 15, and the like.

The main switch SW5 is used for ON/OFF operation of the projector 1 by the user. When the main switch SW5 is turned on, the power supply 4 starts supplying power to each part of the projector 1, and when the main switch SW5 is turned off, the power supply 4 stops supplying power to each part of the projector 1.

The operation unit 7 is buttons or the like for receiving various operations by the user, and is provided on the top surface of the projector 1, for example. The operation unit 7 receives user operations such as adjusting the size, color tone, and focus of the projection image P, for example. A user operation received by the operation unit 7 is sent to the system control unit 10 .

The external I/F 9 is an interface for inputting video signals, and includes a VGA (Video Graphics Array) input terminal such as a D-Sub connector, an HDMI (registered trademark) (High-Definition Multimedia Interface) terminal, and an S-VIDEO terminal. , and RCA terminals. In addition, the external I/F 9 includes communication units such as a wired LAN (Local-Area Network) and a wireless LAN. The external I/F 9 receives a video signal from a connected external device.

The system control section 10 has an image control section 11 . The system control unit 10 includes, for example, a CPU, a ROM, a RAM, etc. The functions of each unit are realized by the CPU working together with the RAM to execute programs stored in the ROM.

The image control unit 11 controls the DMD 51 as an optical modulation element provided in the image display unit 50 of the optical engine 15 based on the video signal (image data) input from the external I/F 9 .

The fan 20 rotates under the control of the system controller 10 to cool the light source 30 of the optical engine 15 .

The optical engine 15 is an optical device having a light source 30 , an illumination optical system unit 40 , an image display unit 50 and a projection optical system unit 60 . The optical engine 15 projects the image P onto the screen S under the control of the system control unit 10 .

The light source 30 is, for example, a high-pressure mercury lamp, a xenon lamp, an LED, or the like, and is controlled by the system control section 10 to irradiate the illumination optical system unit 40 with light.

The illumination optical system unit 40 has a color wheel 401 , a light tunnel 402 and the like (see FIG. 3), and guides light emitted from the light source 30 to the DMD 51 within the image display unit 50 .

The DMD 51 has an image generation surface on which a plurality of movable micromirrors are arranged in a lattice. Each micromirror corresponds to one pixel. Each micromirror of the DMD 51 has a mirror surface tiltable about a torsion axis, and is ON/OFF driven based on a control signal transmitted from the image control unit 11 .

The tilt angle of the micromirror is controlled so that the light from the light source 30 is reflected to the projection optical system unit 60, for example, when it is in the “ON state”. Further, when the micromirror is in the "OFF state", for example, the tilt angle is controlled in the direction in which the light from the light source 30 is reflected toward the OFF light plate.

In this manner, the DMD 51 controls the tilt angle of each micromirror according to the control signal sent from the image control section 11 and modulates the light guided by the illumination optical system unit 40 to generate the image P. FIG.

The projection optical system unit 60 is a projection unit that has a plurality of projection lenses, mirrors, etc., and projects the image P generated by the DMD 51 onto the screen S by enlarging it.

[Illumination optical system unit]
FIG. 3 is a perspective view illustrating the illumination optical system unit 40. FIG. As shown in FIG. 3 , illumination optical system unit 40 has color wheel 401 , light tunnel 402 , relay lenses 403 and 404 , cylinder mirror 405 and concave mirror 406 .

The color wheel 401 is, for example, a disk provided with filters of R (red), G (green), and B (blue) at different portions in the circumferential direction. The color wheel 401 rotates at high speed to time-divide the light emitted from the light source 30 into RGB colors.

The light tunnel 402 is an illumination uniformizing element that uniformizes the luminance distribution of incident light and outputs it, and is fixed in the illumination optical system unit 40 . The light tunnel 402 is, for example, a substantially rectangular parallelepiped optical transmission medium having a rectangular hollow formed by laminating plate glass or the like. The light tunnel 402 makes the luminance distribution uniform by multiple reflection of the light of each color of RGB transmitted through the color wheel 401 on the inner surface, and guides the light to the relay lenses 403 and 404 .

The light tunnel 402 may be anything that can function as an illumination homogenizing element, such as a light integrator, a glass rod, or the like.

Relay lenses 403 and 404 are arranged on the optical path between light tunnel 402 and DMD 51 . The relay lenses 403 and 404 collect the light emitted from the light tunnel 402 while correcting axial chromatic aberration.

Cylinder mirror 405 and concave mirror 406 reflect the light emitted from relay lenses 403 and 404 toward DMD 51 . DMD 51 modulates the reflected light from concave mirror 406 to generate image P. FIG.

[Light Tunnel]
FIG. 4 is a perspective view showing a schematic configuration of the light tunnel 402. As shown in FIG. As described above, the light tunnel 402 has a substantially rectangular parallelepiped shape, and thus has a rectangular cross section 402c. Here, the cross section 402c is a plane obtained by cutting the light tunnel 402 in a direction orthogonal to its longitudinal direction.

The length of the short side of the cross section 402c is a, and the length of the long side is b. The aspect ratio (horizontal-to-horizontal ratio) of the cross section 402c is set to match the aspect ratio of the portrait image, for example, "a:b=3:4". The shape of the light entrance surface 402a and the light exit surface 402b is the same as the shape of the cross section 402c.

Light output from the light source 30 and transmitted through the color wheel 401 is incident on the light incident surface 402a. The light emitted from the light exit surface 402 b is rectangular light having the same aspect ratio a:b as the portrait image, and illuminates the image generation surface of the DMD 51 via the relay lenses 403 and 404 .

FIG. 5 is a diagram showing the relationship between the image generation surface 51a of the DMD 51 and the illumination area 410 by the light tunnel 402. As shown in FIG. In FIG. 5, the H direction is the direction corresponding to the horizontal direction (Y direction). The V direction is a direction corresponding to the vertical direction (Z direction).

The illumination area 410 is an area illuminated by light emitted from the light tunnel 402 and has the same aspect ratio as the cross-sectional shape of the light tunnel 402 . That is, the length LH in the H direction of the illumination area 410 and the length LV in the V direction have a relationship of "LH:LV=a:b". On the other hand, the image generation surface 51a has a rectangular shape, and the length DH in the H direction is longer than the length DV in the V direction.

The illumination region 410 is included in the image generation plane 51a, and the length LV of the long side is set to match the length DV of the short side of the image generation plane 51a. That is, the illumination area 410 is set so that the short sides match the long sides of the image generation surface 51a and satisfy the relationships of "LV=DV" and "LH<DH". Also, the illumination region 410 is positioned at the center of the image generation surface 51a with respect to the H direction, which is the long side direction of the image generation surface 51a.

The DMD 51 generates an image P by driving micromirrors within the illumination area 410 on the image generation surface 51a. A region 51b other than the illumination region 410 of the image generation surface 51a is not illuminated with light. Although the micromirror does not have to be driven in this non-illumination area 51 b , it is preferable to keep it in an OFF state so as not to guide incident light to the projection optical system unit 60 . The non-illumination area 51b is an unused area that is not used for image generation.

That is, in the case of projecting a portrait image, all the illumination light applied to the illumination area 410 is used for image generation, so that the DMD 51 does not discard part of the illumination light, and light loss is minimized. Since it does not occur, a decrease in luminance is suppressed.

[effect]
FIG. 6 is a diagram showing the relationship between an image generation surface and an illumination area in a conventional projector. A conventional projector has a light tunnel whose cross-sectional shape is oblong. The DMD has an image generation surface 500 shaped similarly to the above embodiment, and an illumination area 510 by a light tunnel is set to cover the image generation surface 500 .

In a conventional projector, when projecting a vertically long image, the image is generated by driving a micromirror in a vertically long area 501 located in the center of the image generating surface 500 . Since the area 502 other than the area 501 of the image generation surface 500 is an unused area that is not used for image generation, it is necessary to discard the illumination light by turning off the micromirrors.

On the other hand, in the projector 1 of the present embodiment, the cross section 402c of the light tunnel 402 has a vertically elongated shape with an aspect ratio corresponding to a vertically elongated image. Since it is not necessary to discard the illumination light that is used for generation, it is possible to suppress a decrease in light utilization efficiency.

In the conventional projector, since the projection area is horizontally long, when projecting a vertically long image, it is necessary to change the direction of the projector to make the projection area vertically long, which limits the installation location. In addition, in a conventional projector, if the direction of the projector is not changed, a vertically long image is projected in a part of the horizontally long projection area. position adjustment may be required.

On the other hand, since the projector 1 of this embodiment projects a vertically long image onto a vertically long projection area, adjustment such as changing the orientation of the projector 1 is unnecessary.

<Second embodiment>
An image projection apparatus according to a second embodiment of the present invention will be described below.

Depending on the situation where the installation location of the projector 1 is limited to, for example, the vicinity of the screen S, the projector 1 may have to be installed in a posture facing obliquely upward as shown in FIG. In such a case, as shown in FIG. 8, the shape of the image projected onto the screen S becomes trapezoidal as indicated by P1.

The projector 1 can perform trapezoidal distortion correction (keystone correction) for correcting image data so that an image whose shape is distorted into a trapezoidal shape is approximated to a rectangle indicated by symbol P2. However, trapezoidal distortion correction is performed by processing such as thinning out pixels with reference to the short side of the trapezoid, so that the image quality and brightness of the projected image are degraded.

Such trapezoidal distortion occurs not only when the projector 1 is installed, but also when the screen S is tilted.

FIG. 9 is a perspective view showing a schematic configuration of the light tunnel 402 included in the projector 1 of the second embodiment. In the second embodiment, the cross section 402c of the light tunnel 402 is shaped (trapezoidal) in accordance with the inclination of the projector 1 or the screen S. FIG. Specifically, of the two sides (bottom side and top side) facing each other in the vertical direction in the cross section 402c of the light tunnel 402, the side corresponding to the short side of the trapezoidally distorted projected image is lengthened. For example, as shown in FIG. 7, when the projector 1 is installed in a posture that faces obliquely upward, and the lower side of the projected image P becomes narrow (see FIG. 8), the cross-sectional shape of the light tunnel 402 is: The side corresponding to the lower side of the projection image P is lengthened.

FIG. 10 is a diagram showing the relationship between the image generation surface 51a of the DMD 51 and the illumination area 410 by the light tunnel 402 in the second embodiment. In this embodiment, the illumination area 410 has a trapezoidal shape corresponding to the cross-sectional shape of the light tunnel 402 . The height LV of this trapezoid is equal to the length DV of the short side of the image generation surface 51a. The lengths of the base and top sides of the trapezoid are smaller than the length DH of the long side of the image generation surface 51a.

As in the first embodiment, the DMD 51 generates the image P by driving micromirrors within the illumination area 410 of the image generation surface 51a. A region 51b other than the illumination region 410 of the image generation surface 51a is not illuminated with light. Although the micromirror does not have to be driven in this non-illumination area 51 b , it is preferable to keep it in an OFF state so as not to guide incident light to the projection optical system unit 60 . The non-illumination area 51b is an unused area that is not used for image generation.

That is, in the case of projecting a portrait image, all the illumination light applied to the illumination area 410 is used for image generation, so that the DMD 51 does not discard part of the illumination light, and light loss is minimized. Since it does not occur, a decrease in luminance is suppressed.

Further, by forming the cross section 402c of the light tunnel 402 into a shape that matches the inclination of the projector 1 or the screen S, the projected image P becomes rectangular.

Therefore, in the second embodiment, in an installation situation in which trapezoidal distortion occurs in the projected image P, the projected image P can be corrected into a rectangular shape without performing trapezoidal distortion correction (image processing) involving image quality and luminance.

The image projection apparatuses according to the first and second embodiments described above are particularly useful in situations where installation locations are limited, such as when projecting paintings in art museums.

In addition, it is also preferable that the light tunnel 402 having a different cross-sectional shape can be exchanged from the illumination optical system unit 40 . A light tunnel 402 having a cross-sectional shape suitable for the installation situation may be attached to the illumination optical system unit 40 .

Although the present invention has been described above based on each embodiment, the present invention is not limited to the requirements shown in the above embodiments. These points can be changed within the scope of the present invention, and can be determined appropriately according to the application form.

1 Projector (image projection device)
11 image control unit 15 optical engine (optical device)
30 light source 40 illumination optical system unit 50 image display unit 51 DMD (light modulation device)
51a image generation surface 51b non-illumination area 60 projection optical system unit (projection section)
401 color wheel 402 light tunnel 402a light entrance surface 402b light exit surface 402c cross section 403, 404 relay lens 405 cylinder mirror 406 concave mirror 410 illumination area 500 image generation surface 510 illumination area

Japanese Patent Application Laid-Open No. 2003-348496

Claims (5)

a light source that outputs light;
a light modulation element having a horizontally long rectangular image generation surface and modulating light irradiated onto the image generation surface to generate an image;
a light tunnel that has a trapezoidal cross section and irradiates the image generation surface with the light output from the light source with a uniform luminance distribution;
has
The illumination area on the image generation surface by the light tunnel has a trapezoidal shape, the height of the trapezoid being equal to the length of the short side of the image generation surface, and the length of the base and the top side of the image generation surface. optical device smaller than the length of the long side of 2. The optical device according to claim 1 , wherein the illumination area is positioned at the center of the image generation surface with respect to the long side direction of the image generation surface. 3. An optical device according to any one of claims 1 or 2 , comprising a relay lens arranged between the light tunnel and the light modulating element. 4. The optical device according to any one of claims 1 to 3 , further comprising a projection section for projecting an image generated by said light modulation element. an optical device according to any one of claims 1 to 4 ;
an image control unit that controls the light modulation element based on image data;
An image projection device having

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