JP2004271891A - Projector device - Google Patents

Abstract

An object of the present invention is to reduce the loss of projection light in an optical component that extracts reflected light from a screen from a projection optical path and maintain the brightness of the screen.
A projector device that drives an image display element based on a video signal, irradiates light from a light source to the image display element, and projects an image on the image display element onto a screen surface via a projection lens system. In the above, a 1/4 wavelength plate is placed on the optical axis in or in front of the projection lens system, and a prism type PBS is placed on the optical axis in the projection lens system behind the 1/4 wavelength plate. A CCD is placed at an image forming position of the screen reflection light on the side exit optical path of the PBS, and the projection lens system is driven based on a video signal output from the CCD to perform focus adjustment.
[Selection diagram] Fig. 1

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a projector device having an autofocus function.
[0002]
[Prior art]
As a small and lightweight projector device, a method using a liquid crystal panel or a micro mirror is generally used.
For example, a liquid crystal projector device forms an image on a liquid crystal panel and projects the image modulated light on a screen or a wall surface by a projection lens.
The user needs to adjust the focus, angle of view, and the like of the projected image to make the projected image clear in order to view the projected image comfortably. However, the conventional projector apparatus attempts to focus the projected image. In this case, a projected image is projected on a screen by inputting an external video signal such as a television signal or a video signal, and the user adjusts the focus by manually operating, for example, a focus lens while watching the projected image. This is commonly done.
In such a situation, various proposals have also been made regarding automation of focus adjustment, and for a projector device having an autofocus function using reflected light from a screen, for example, a “liquid crystal projection device” ( Patent Literature 1) and “Autofocus System in Projection Optical Equipment” (see Patent Literature 2) are disclosed.
In the former, a half mirror is provided between a projection lens and a liquid crystal panel to adjust the focus by extracting reflected light from reflection from a screen.
In the latter, a reflection mirror is provided between the projection lens and the liquid crystal panel, and the focus is adjusted by extracting the reflected light from the reflection from the screen.
[0003]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 06-186474 [Patent Document 2]
Japanese Patent Application Laid-Open No. 05-72469
[Problems to be solved by the invention]
However, in the focus automatic adjustment in these conventional technologies, a half mirror or a reflection mirror is provided between the projection lens system and the liquid crystal panel. There was a problem that the brightness of the screen was lowered and a problem that the back focus was long.
[0005]
[Means for Solving the Problems]
Therefore, in order to solve the above problem, a projector device according to the present invention employs a 波長 wavelength plate placed in a projection optical path, a PBS placed behind the plate, and reflected light from a screen emitted to the side of the PBS. Adjust the focus. As a result, since the loss of the light amount in the quarter-wave plate and the PBS is very small, the brightness of the screen remains almost unchanged.
In addition, the projector device according to the present invention drives an image display element based on a video signal, irradiates light from a light source to the image display element, and causes an image on the image display element to be displayed on a screen via a projection lens system. In a projection device, a quarter-wave plate is placed on the optical axis in or in front of the projection lens system, and a prism type PBS is placed on the optical axis in the projection lens system behind the quarter-wave plate. Then, a CCD is placed at an image forming position of the screen reflected light on the side exit optical path of the PBS, and the projection lens system is driven based on a video signal output from the CCD to perform focus adjustment.
In the projector device according to the present invention, the image display element is a liquid crystal panel of each of three colors, the light from the light source is split into three colors by a dichroic mirror, and the three color liquid crystal panels are irradiated, and the transmitted light is dichroic. It is also possible to dispose a 1/4 wavelength plate and a prism type PBS in the projection lens system portion on the optical path after combining by a prism or a dichroic mirror.
Further, the prism type PBS is preferably arranged at the position of the stop of the projection lens system.
[0006]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic structural diagram of an optical block when the present invention is applied to a liquid crystal projector device, and FIG. 2 is a diagram showing a main part of FIG. In FIG. 1, reference numeral 1 denotes a lamp. Light emitted from the lamp 1 is blocked from ultraviolet rays and heat rays by a filter 2, passes through a fly-eye lens 3 and a condenser lens 4, and reaches dichroic mirrors 5 and 6. The dichroic mirrors 5 and 6 separate the incident white light into three colors, and pass through the mirror 7, the condenser lens 12, the condenser lens 13, the relay lens 8, the mirror 9, the relay lens 10, the mirror 11, and the condenser lens 14, respectively. The liquid crystal panels 15 to 17 serving as image display elements are irradiated. The three colors of light transmitted through the liquid crystal panels 15 to 17 respectively enter the dichroic prism 18, are combined, and emitted to the right in the drawing. Here, the dichroic prism 18 can be replaced with a dichroic mirror. A projection lens system 19 is arranged on the optical path of the light emitted from the dichroic prism 18. The prism type PBS 20 is placed near the position of the stop in the projection lens system 19. A CCD 21 is arranged at an image forming position on the optical path of the emitted light on the side surface of the prism type PBS 20. Further, a quarter-wave plate 22 is arranged in front of the projection lens system 19 in close proximity. The quarter-wave plate 22 may be arranged in the projection lens system 19 if it is in front of the PBS 20.
[0007]
As shown in FIG. 2, by disposing the prism type PBS 20 and the 波長 wavelength plate 22 in the portion of the projection lens system 19, the projection light emitted from the dichroic prism 18 and incident on the projection lens system 19 is Since the P-wave component contained in the projection light passes and the S-wave component is reflected, only the P-wave component passes through the projection lens system 19. Next, the projection light is projected on the screen 23 with the phase shifted by ４ wavelength by the 波長 wavelength plate 22. A part of the projection light projected on the screen 23 is reflected, the reflected light travels backward in the projection optical path, and is incident on the quarter-wave plate 22 again. Here, the phase of the reflected light is again shifted by ４ wavelength, and the phase is shifted by 波長 wavelength in the round trip for convenience. When the projected light of the P wave component returns as reflected light, it returns to the S wave component. Become. The reflected light of the S-wave component is reflected by the prism type PBS 20 and emitted from the side, and forms an image on the CCD 21. A video signal is output from the CCD 21 and input to a focus control unit including a microcomputer (not shown), and the focus of the projected image on the screen 23 is adjusted by repeating pattern recognition of the central portion of the image and focus adjustment of the projection lens system 19. You. As described above, in the present invention, by using the prism type PBS 20 and the quarter wavelength plate 22 to separate the reflected light from the screen 23 from the optical path of the projection light, the prism type PBS 20 and the quarter wavelength plate are used. Since the loss of the projection light on the plate 22 is very small, a bright projection image is obtained on the screen 23.
[0008]
【The invention's effect】
As described above, according to the present invention, a 波長 wavelength plate is placed in the projection optical path and a PBS is placed behind the λ wavelength plate, and the reflected light of the screen is taken out of the PBS and adjusted in focus. Since the loss of the projection light in the PBS is very small, a bright projection image can be obtained on the screen.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an optical block when the present invention is applied to a liquid crystal projector.
FIG. 2 is a diagram showing a main part of FIG. 1;
[Explanation of symbols]
REFERENCE SIGNS LIST 1 lamp 2 filter 3 fly-eye lens 4 condenser lens 5, 6 dichroic mirror 7 mirror 8 relay lens 9 mirror 10 relay lens 11 mirror 12 to 14 condenser lens 15 to 17 liquid crystal panel 18 dichroic prism 19 projection lens system 20 prism type PBS
21 CCD
22 quarter wave plate 23 screen

Claims (4)

A 波長 wavelength plate is placed in the projection optical path and a PBS is placed behind the 波長 wavelength plate, and the reflected light from the screen passes through the ４ wavelength plate and is emitted to the side of the PBS, and focuses using the emitted light. A projector device for performing adjustment. A projector device that drives an image display element based on a video signal, irradiates light from a light source to the image display element, and projects an image on the image display element onto a screen via a projection lens system. A quarter-wave plate placed on the optical axis in or in front of the system, a prismatic PBS placed on the optical axis in the projection lens system behind this quarter-wave plate, and the side of this PBS And a means for adjusting the focus by driving the projection lens system based on a video signal output from the CCD, the CCD being located at the image forming position of the screen reflected light on the one exit optical path. Characteristic projector device. The projector device according to claim 2,
The image display device is a liquid crystal panel for each of three colors, the light from the light source is split into three colors by a dichroic mirror, and the three color liquid crystal panels are irradiated, and the transmitted light is synthesized by a dichroic prism or a dichroic mirror. A projector device comprising a quarter-wave plate and a prism type PBS arranged in a projection lens system on an optical path. The projector device according to claim 2, wherein
A projector device, wherein the prism type PBS is arranged at a position of a stop of a projection lens system.

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