JP2565918B2 - Reflective magnifying projector - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a reflection-type magnifying projection device that magnifies and displays image information on a screen by using a transmission-type liquid crystal cell.

2. Description of the Related Art Generally, in a reflective OHP (over head projector), it is known that heat spots are generated on the screen due to the configuration of the illumination optical system. This is also the case when a transmissive liquid crystal cell display device is installed on a reflective OHP and enlarged projection is performed.

FIG. 3 shows the structure of a conventional reflection type magnifying projection apparatus using a reflection type OHP. First, the transmissive liquid crystal cell 1
Is provided. The transmissive liquid crystal cell 1 has a sun-gate structure in which a liquid crystal layer 2 is sandwiched between upper and lower substrates 3 and 4. An incident side polarization plate 5 and a lower polarization plate 6 are provided on both surfaces of such a transmissive liquid crystal cell 1. Reference numeral 7 is a drive circuit board. The liquid crystal display device having such a configuration is installed on the Fresnel reflector 9 having the reflection film 8, and the surface is covered with the protective cover 10.

In such a configuration, image information is input to the liquid crystal layer 2 and an image to be magnified and projected is formed. Then, the transmissive liquid crystal cell 1 is illuminated by the reflective OHP illumination light source 11 through the incident side polarization plate 5. Here, the light transmitted through the transmissive liquid crystal cell 1 is reflected by the reflective film 8 of the Fresnel reflector 9 and is transmitted through the transmissive liquid crystal cell 1 again. The light transmitted through the liquid crystal cell 1 is again transmitted through the incident side polarization plate 5 and the protective cover 10 and is emitted as projection image light. The projection optical system 14 including the projection lens 12, the reflection mirror 13 and the like indicates an arrow A
Directionally projected on a screen (not shown).

In such a reflection-type magnifying projection device, a heat spot 15 is generated, for example, in the central portion of the incident-side polarizing plate 5 based on the reflection of part of the irradiation light on the incident-side polarizing plate 5 or the reflection on the liquid crystal cell 1. Is. Such a heat spot 15 is enlarged and projected as a projection spot image 16 together with the image, and appears as a bright spot on the screen. That is, the reflection state on the entire surface of the reflection mirror 13 is not uniform. Therefore, when considering the entire image displayed on the screen, this is one of the causes of substantially lowering the contrast of the display screen, and lowers the display quality.

The present invention has been made in view of the above circumstances, and provides a reflection-type magnifying projection device capable of preventing the contrast from being lowered by a heat spot and performing magnified projection display on the entire screen in a state where the contrast is uniform. With the goal.

Structure In order to achieve the above object, the present invention inputs image information to a transmissive liquid crystal cell, irradiates the transmissive liquid crystal cell with light, and transmits the light transmitted through the transmissive liquid crystal cell to the transmissive liquid crystal cell. In the reflection type magnifying projection device that reflects the light transmitted through the transmission type liquid crystal cell on the screen by the projection optical system including the reflection mirror, the reflection from the heat spot generation part The incident-side polarization plate and the liquid crystal cell protection plate of the transmissive liquid crystal cell are installed so as to be inclined so that the light is directed to the outside of the optical path of the projection optical system.

An embodiment of the present invention will be described below with reference to FIG. The same parts as those shown in FIG. 3 are designated by the same reference numerals. In this embodiment, the incident side polarization plate 5 and the protective cover 10 are separated from the transmission type liquid crystal cell 1 side and installed in an inclined state with a predetermined angle with respect to the horizontal state. More specifically, it is configured as a protective cover 10 with the incident side polarizing plate 5 formed by adhering the incident side polarizing plate 5 to the lower surface. At this time, the angle of inclination between the incident side polarizing plate 5 and the protective cover 10 is such that the projection spot image 16 from the heat spot 15 generating portion of the incident side polarizing plate 5 and the protective cover 10 is outside the optical path of the projection optical system 14. It is set so as to be in a state that does not face the screen side. On the other hand, the transmissive liquid crystal cell 1 is installed on the Fresnel reflection plate 9 in close contact or adhesion.

In such a configuration, the light illuminated by the illumination light source 11 and passing through the transmissive liquid crystal cell 1 is reflected by the reflective film 8 of the Fresnel reflector 9 and emitted from the incident side polarization plate 5 as in the conventional case. The image is enlarged and projected on the screen by the projection optical system 14. At this time, the projected spot image 16 reflected from the heat spots 15 formed on the protective cover 10 and the incident side polarizing plate 5 is not reflected by the reflection mirror 13 and the like because the protective cover 10 and the incident side polarizing plate 5 are inclined. Projection optics
It is not reflected in the 14 optical paths. Yotsutte, heat spot
The projected spot image 16 corresponding to 15 does not appear on the screen.

At this time, it is inevitable in terms of optical system design that the effects of heat spots due to the substrates 3 and 4, the lower polarization plate 6 and the Fresnel reflection plate 9 of the transmissive liquid crystal cell 1 remain. That is, unless the transmissive liquid crystal cell 1 is adhered or adhered onto the Fresnel reflection plate 8, an image shift occurs between the reflected image due to the reflected light and the reflected image due to the incident light, and an optical double image is formed. This is because it will occur. However, in such a state, due to the transmittance of the incident side polarizing plate 5, there is little heat spot due to the reflected light at the transmissive liquid crystal cell 1 and the lower polarizing plate 6 located under the incident side polarizing plate 5, As in the present embodiment, most of the heat spots can be removed by removing the heat spot reflected light from the protective cover 10 and the incident side polarization plate 5 out of the optical path.

The protective cover 10 and the incident side polarization plate 5 are, for example, the second
Tilt in the opposite direction as shown and heat
The reflected light from the part may be directed to the outside of the optical path of the projection optical system 14.

Effect As described above, the present invention tilts the incident side polarization plate and the liquid crystal cell protection plate of the transmissive liquid crystal cell so that the reflected light from the heat spot generating portion is directed to the outside of the optical path of the projection optical system including the reflection mirror. Since it is installed on the screen, it is possible to project and display the image with the heat spot compatible reflected light that occupies most of it not projected on the screen.
It is possible to make the reflection state on the entire surface of the reflection mirror substantially uniform, and to make the display image in which the contrast of the entire screen is uniform and easy to see.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing an embodiment of the present invention, FIG. 2 is a schematic sectional view showing a modified example, and FIG. 3 is a schematic sectional view showing a conventional example. 1 ... Transmissive liquid crystal cell, 5 ... incident side polarizing plate, 8 ... Fresnel reflector, 10 ... protective cover (liquid crystal cell protective plate),
13 …… Reflecting mirror, 14 …… Projection optical system

Claims (1)

(57) [Claims] 1. Image information is input to a transmissive liquid crystal cell, the transmissive liquid crystal cell is irradiated with light, and the light transmitted through the transmissive liquid crystal cell is placed on the lower surface of the transmissive liquid crystal cell. In a reflection-type magnifying projection device in which light reflected by a plate and transmitted through the transmission-type liquid crystal cell again is projected on a screen by a projection optical system including a reflection mirror, the reflected light from a heat spot generating portion is reflected by the projection optical system. A reflection type magnifying projection apparatus, wherein the incident side polarization plate and the liquid crystal cell protection plate of the transmission type liquid crystal cell are installed so as to be directed out of the optical path.