JPH0196632A - Projecting device - Google Patents

Abstract

PURPOSE:To improve light transmissivity at the time of projecting operation and to obtain a bright projection image by allowing the polarizing plate of a liquid crystal display device to be attached on and detached from an optical path from a light source, and detaching the polarizing plate from the optical path when an image of a display film is projected. CONSTITUTION:The polarizing plate 15 on the top surface side of the liquid crystal display device 12 is provided rotatably to one lower side of the frame body of a projection lens 10 through a hinge 19 and freely attachable to and detachable from the liquid crystal display device 12. The polarizing plate 16 on the reverse surface side is fitted to a slider 20 provided slidably between a Fresnel lens 3 on the top surface of a case 1 and the liquid crystal display device 12, and freely attachable to and detachable from the liquid crystal display device 12. Then when the display of a display film consisting of a transparent film is projected, the polarizing plate 15 is rotated to one side of the projection lens 10 through the hinge 19, the polarizing plate 16 is extracted outward with the slider 20 and detached from the optical path extending from the light source 2 to the projection lens 10, and the display film 21 is arranged on the top surface of the liquid crystal display panel 13. Consequently, a bright projection image is obtained with the sufficient quantity of light.

Description

DETAILED DESCRIPTION OF THE INVENTION OBJECTS OF THE INVENTION (Field of Industrial Application) The present invention relates to a projection device such as an overhead projector equipped with a liquid crystal display.

(Prior Art) In overhead projectors and the like, devices are used in which a liquid crystal display is combined to project a display based on data from a computer.

FIG. 3 shows an over-the-radar projector as described above. This overhead O-director is
A light m2 is housed in the case 1, and a Fresnel lens 3 is provided at the top opening of the case 1.

Further, a support 4 is erected on one side of the case 1, and the focal path lI! Focus adjustment knob 6 of adjuster 115
The cylindrical body 7 with
An arm 8 is protruded from the side of this cylinder 7, and this arm 8
A support frame 9 is attached to the tip of the support frame 9, and a projection lens 10 facing above the Fresnel lens 3 and a reflecting mirror 11 whose inclination angle can be adjusted are attached above the support frame 9.
A Fresnel lens 3, a projection lens 10, and a reflection 111 are arranged on the optical axis of the light 112.

In the upper part of the case 1, a liquid crystal display 12 for forming a projection display is disposed between the Fresnel lens 3 and the projection lens 10.

This liquid crystal display 12 has a liquid crystal display panel 13, a driving circuit 14 thereof, and two polarizing plates 15 and 16 provided on both sides of the liquid crystal display panel 13, and provides display data to the driving circuit 14. A computer 17 is connected.

Then, the computer 17 lights up and displays a display pattern on the liquid crystal display panel 13 according to data given to the drive circuit 14 of the liquid crystal display 12, and the light from the light source 2 is passed through the Fresnel lens 3, the polarizing plate 16, the liquid crystal display panel 13, and the polarized light. It passes through a plate 15 and a projection lens 10, and is projected by a reflecting mirror 11.

(Problems to be solved by the invention) In the above-mentioned over-rad projector,
In addition to obtaining a display pattern for projection using a liquid crystal display, a display film in which a display is coated on a normal transparent film may be used. In this case, in order to maximize the light transmittance of the liquid crystal display, it is necessary to operate the liquid crystal display and input all lighting data. However, even in the fully lit state when the liquid crystal display is operated, the light transmittance of the liquid crystal display is
Since there are two polarizing plates, the amount of light is as low as about 30%, and a sufficient amount of light cannot be obtained, resulting in a dark projection screen.

An object of the present invention is to provide a bright projection screen with sufficient light even when projecting using a display film made of a transparent film, in addition to display using a liquid crystal display.

(Structure of the Invention) (Means for Solving the RFA Problem) The present invention includes a light source, a Fresnel lens and a projection lens provided on the optical axis of the light source, and the Fresnel lens and the projection lens are connected together. In the projection device, the polarizing plate of the liquid crystal display is detachably provided in the optical path between the Fresnel lens and the projection lens. be.

(Function) In the present invention, when displaying and projecting with a liquid crystal display, a polarizing plate is placed against the liquid crystal display, and when projecting using a display film, the polarizing plate is placed on the liquid crystal display. ie from the light path by the light source to increase the light transmission from the light source when projected through the display film.

(Example) An example of the present invention will be described below with reference to FIGS. 1 and 2.

Note that parts corresponding to those in FIG. 3 are designated by the same reference numerals.
Detailed explanation will be omitted.

Overherad projector as this projection device,
Basically, like the device shown in Fig. 3 above, case 1, light +
1!2, Fresnel lens 3, support 4, cylinder body 7 with focus adjustment knob 6 of focal length adjustment mechanism 5, arm 8, support frame 9, projection lens 10, reflector 11, liquid crystal display panel 1
3, a liquid crystal display 12 having a drive circuit 14, and a computer 17.

Then, the polarizing plate 1 on the upper surface side of the liquid crystal display 12
5 is a hinge 1 on the lower end side of the frame of the projection lens 10.
9, it is rotatably provided between the lower surface side and one side of the projection lens 10, and is detachably attached to the liquid crystal display 12. Further, the polarizing plate 16 on the lower surface side of the liquid crystal display 12 is attached to a slider 20 slidably provided between the Fresnel lens 3 on the upper surface of the case 1 and the liquid crystal display 12. It can be attached and detached freely.

Then, when projecting the display on the liquid crystal display 12, as shown in FIG.
At the same time, the lower polarizing plate 16 is arranged on the lower surface side of the liquid crystal display panel 13. In other words, the two polarizing plates 15 and 16 are used for projection from the light source 2 through the Fresnel lens 3 and the liquid crystal display panel 13. It is placed in the optical path leading to the lens 10 and projected in the same manner as described above.

In addition, when projecting a display on a display film made of a normal transparent film, the power to the liquid crystal display 12 is turned off, and the upper polarizing plate 15 is attached to the hinge 1 as shown in FIG.
9 rotates the projection lens 10 to one side, and the lower polarizing plate 16 is extracted outwardly by the slider 20, that is, the two polarizing plates 15 and 16 are transferred from the light source 2 to the projection lens 10. The display film 21 is removed from the optical path leading to the liquid crystal display panel 13, and the display film 21 is placed on the upper surface of the liquid crystal display panel 13.

By doing so, the light transmittance from the light source 2 is improved from about 30% when the polarizing plates 15 and 16 are used to a high efficiency of more than 95%, and the light from the light source 2 can be used more effectively. This makes it possible to obtain a projection screen that is about three times brighter than the conventional one shown in FIG.

In the above embodiment, the polarizing plate is detachably attached using a hinge and a slider, but the attaching and detaching mechanism is not limited to this, and other mechanisms may be used.

〔Effect of the invention〕

According to the present invention, the polarizing plate of the liquid crystal display is made detachable from the optical path from the light source, and the polarizing plate is removed from the optical path when projecting using a display film, thereby greatly improving the light transmittance during projection. You can get a bright projection screen.

[Brief explanation of the drawing]

1 and 2 are block diagrams showing one embodiment of the apparatus of the present invention, and FIG. 3 is a block diagram showing a conventional apparatus. 2...Light source, 3...Fresnel lens, 10...Projection lens, 12...Liquid crystal display, 15.16...Polarizing plate. October 8, 1986 Inventor: Arai
Sakae Patent Applicant: Toshiba Corporation

Claims (1)

[Claims] (1) A projection device comprising a light source, a Fresnel lens and a projection lens provided on the optical axis of the light source, and a liquid crystal display having a polarizing plate disposed between the Fresnel lens and the projection lens. In the above, the polarizing plate of the liquid crystal display is
A projection device characterized in that the Fresnel lens and the projection lens are detachably installed in an optical path between the Fresnel lens and the projection lens.