JPH0451031A - Projecting device - Google Patents

Abstract

PURPOSE:To miniaturize a device and to obtain a bright projection screen by dividing a luminous flux from a light source into two parts by a polarized beam splitter or a half prism, etc., and irradiating a screen to be projected with respective luminous fluxes in a state where the irradiated plane is divided into two by the respective luminous fluxes. CONSTITUTION:After dividing the luminous flux from the light source 3 into two parts; S polarized component and P polarized component by the polarized beam splitter 4 or the half prism, etc., the S polarized component is converted by 90 deg. in a polarization direction by a liquid crystal panel 6 so that the polarization direction may become the same as that of the other polarized component. and it is radiated on the screen to be projected, for example, a liquid crystal panel 8 through Fresnel's lenses 9, 13 and 10, and then, the luminous flux which is radiated on the liquid crystal panel 8 is projected on a screen through a projection lens 14. Thus, the focal distance of the Fresnel's lens can be shortened, the device can be miniaturized, and furthermore, the bright projection screen can be obtained by reducing the loss of a light beam.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a projection device for enlarging and projecting materials onto a projection surface in a conference or a training session.

(Prior technology) Conventionally, materials written on paper to be enlarged and projected on a screen at meetings and seminars have been used (manager/positive film, as well as liquid crystal display that connects to a personal computer and allows the screen to be changed freely). In the case of this LCD panel, there is no need to convert the data in the personal computer to transparency or slides, which saves money and time. By being able to simulate the case, even more effective projection can be achieved.

(Problem to be solved by the invention) However, most liquid crystal panels use birefringence to display images, so in order to project images, the light rays incident on the liquid crystal must be converted into linearly polarized light with a certain directionality. In order to do this, it is necessary to install a polarizing plate on the incident surface side of the liquid crystal, and in that case, about 60% of the light rays will be absorbed here, which may have the disadvantage of making the projection screen dark. Ta.

In addition, as shown in FIGS. 4 and 5, in order to converge the luminous flux divergingly irradiated from the light source 104 composed of the lamp 101, the reflector 102, and the condenser lens 103 onto the projection lens 105, the projection screen is A Fresnel lens 1 is generally placed over the liquid crystal plate 106 and the polarizing plates 107 and 108 before and after it.
09.110, but in that case, in order to miniaturize the device, the focal length of this Fresnel lens 109 must be shortened. If the incident occurs at a critical angle of 109 or more, it will be reflected without being refracted, or it will become dark due to the cosine fourth power law, and the focal length will be the projected screen, in this case,
There was a drawback in that it could only be shortened to about 70% of the diagonal length of the liquid crystal plate 106.

Therefore, an object of the present invention is to divide the light beam from a light source into two using a polarizing beam splitter or a half prism, etc., and to irradiate the projected screen with each light beam in a form where the irradiation surface is divided into two for each light beam, thereby creating a Fresnel lens. In addition, the beam split by the polarizing beam splitter is made to match the polarization direction of the other split beams with a liquid crystal plate or a retardation plate, thereby reducing the loss of light beams. The object of the present invention is to provide a bright projection device with reduced brightness.

(Means for Solving the Problems) The present invention includes a spectroscopic element such as a polarizing beam splitter or a half prism that divides a luminous flux from a light source into two, and an irradiation surface that is also divided into two in order to irradiate each of the two divided spectral components. A projection device equipped with a divided projection screen and a projection lens for projecting light beams from the projection screen onto the screen, and when a polarizing beam splitter is used as a splitting element, a polarizing element and a projection lens are used. A polarization converting means such as a liquid crystal or a retardation plate can be interposed between the projection screen and the polarization direction of the light beam divided into two from the polarizing element, and the projection screen can be a liquid crystal panel. can be,
Furthermore, a Fresnel lens can be provided at the position of the projection screen to converge the light flux that irradiates the projection screen onto the projection lens.

(Operation of the Invention) In the case of a projection device configured in this manner, the light beam from the light source is split into two into an S-polarized component and a P-polarized component by a polarizing element such as a polarizing beam splitter or a half prism, and then the S-polarized component is divided into two. The polarization direction of the liquid crystal plate is converted by 90 degrees so that it becomes the same polarization direction as the other polarization components, and is irradiated to a projection screen, for example, a liquid crystal panel, via a Fresnel lens, and the light beam irradiated to the liquid crystal panel is transmitted to the projection lens. is projected onto the screen through the

(Effects of the Invention) In this way, the present invention divides a light beam from a light source into two using a polarizing beam splitter or a splitting element such as a half prism, and uses each light beam to illuminate a projected screen whose irradiation surface is divided into two for each light beam. By using irradiation, the focal length of the Fresnel lens can be shortened, the device can be made more compact, and the polarization direction of the light beam split by the polarizing beam splitter can be changed to another split light beam using a polarization conversion means such as a liquid crystal or a retardation plate. By making the polarization direction coincide with the polarization direction of , it is possible to reduce the loss of light rays and obtain a bright projection screen.

(Example) Next, the configuration of an example of the present invention will be described with reference to the drawings.

A light beam from a light source 3 composed of a lamp 1 and a reflector 2 enters a polarizing beam splitter 4, and the S-polarized component of the incident light beam is reflected by a 45° reflecting surface 5 of the polarizing beam splitter 4, and then passes through a liquid crystal plate. Alternatively, a polarization conversion means such as a retardation plate, in this case, is arranged so that the polarization axis on the incident surface side is perpendicular to the C direction, and the liquid crystal is tilted by 90 degrees inside.
A projection screen whose irradiation surface is divided into two through the liquid crystal plate 6 and the concave lens 7, in which the polarization axis of the emitted light beam is in the C direction, in this case, the size corresponding to one surface 8A of the divided liquid crystal screen 8. The light beam passes through the Fresnel lens 9 and the Fresnel lens 1O of a size corresponding to the entire liquid crystal screen 8, and becomes a light beam that irradiates one surface 8A of the liquid crystal screen 8, and the P-polarized light component of the light beam incident on the polarizing beam splitter 4 is directly transmitted to the polarizing beam splitter. 4 and reflected by a mirror 11, the irradiated surface is divided into two by passing through a concave lens 12. A Fresnel lens 13 has a size corresponding to the other surface 8B of the liquid crystal screen 8, and a Fresnel lens 13 has a size corresponding to the entire liquid crystal screen 8. The light beams pass through the Fresnel lens 10 and illuminate the other surface 8B of the liquid crystal screen 8, and the polarization axes of both light beams coincide in the C direction, so that all the light beams incident on the liquid crystal screen 8 can be used.

Therefore, the light beams from the polarizing beam splitter 4 and the mirror 11 are converged through the Fresnel lenses 9, 10, and 13, and then irradiated onto the projection lens 14, and then projected onto a projection surface (not shown).

Next, the functions and effects of this embodiment will be explained in comparison with the conventional example shown in FIGS. 4 and 5.

That is, FIGS. 4 and 5 show a conventional projection device having a liquid crystal plate 106 with a screen diagonally long and an aspect ratio of 4.3, and the focal length of the Fresnel lens 109 on the incident surface side is about 0.7L. It has become.

On the other hand, in the case of the projection device 15 of this embodiment shown in FIGS. 1 to 3, the light beam split into two by the polarizing beam splitter 4 is sent to the liquid crystal screen 8, which has a 2-part irradiation surface on each light beam side. By irradiating the light, the focal length of the Fresnel lens 9 on the incident surface side is shortened to about 0.5L.

That is, as shown in FIG. 1, if the irradiation surface of the liquid crystal screen 8 with a long screen diagonal and an aspect ratio of 4:3 is divided into two by its long side, the diagonal of each of the two halves of the screen 8A and 8B is Long 0.
72L and an aspect ratio of 3:2, the focal length F of the Fresnel lens 9.13 centered on the center of each screen can be shortened to F = 0.72L x 0.7 = 0°5L.

Here, Fig. 3 shows that the polarization direction of one of the light beams, which is divided by the polarizing beam splitter 4 into two mutually orthogonal linearly polarized lights, is rotated by 90 degrees using the liquid crystal plate 6 or the retardation plate to match the polarization direction of the other light beam. A method is shown in which the polarization axis of the liquid crystal screen 8 is C.
When the liquid crystal plate 6 is in the direction, the light beam that illuminates the 8B portion of the liquid crystal screen is transmitted, but the light beam that illuminates the 8A portion of the liquid crystal screen will be blocked if the liquid crystal plate 6 is not present.

The liquid crystal plate 6 is arranged so that the polarization axis on the incident surface side is perpendicular to the C direction, and the liquid crystal is internally tilted by 90 degrees, so that the emitted light beam is in the C direction, and the polarization directions of both light beams are the same. All available.

Furthermore, when the polarization axis of the liquid crystal screen 8 is perpendicular to the C direction, a liquid crystal plate 6' may be arranged after the mirror 11 instead of the liquid crystal plate 6, with the polarization axis of the incident side surface perpendicular to the C direction. Accordingly, the polarization directions of both light beams can be made to coincide with each other.

In addition, when the polarization axis of the liquid crystal screen 8 has an angle of 45 degrees with the C direction, the light beam irradiating the liquid crystal screen 8A portion of one of the irradiation surfaces divided into two has a 45-tailed liquid crystal plate 6.
By arranging the liquid crystal plate 6' tilted by 145 degrees for the light beam that illuminates the liquid crystal screen 8B portion of the other irradiation surface divided into two, the polarization directions of both light beams can be made to match each other. .

As a result, the conventional utilization efficiency P of the luminous flux on the liquid crystal screen 8 is:
Letting the diagonal of the projected screen be L, and considering the ratio of the rectangular transmission area to the circular irradiation area, P = (315)LX
(415) L/ [(L/2)2x 3.14] /
2 (which is harmful because only one direction of polarized light is used) = 30.5%, whereas the utilization efficiency P° of the present invention is P' =
(315)Lx(215)L/ [(0,72L/2)
2x3.14]59.0% =1. 9P, which is 1.9 times more efficient than the conventional method.

In this way, an efficient and bright projection device 15 can be obtained by using the polarization component in the direction that was conventionally discarded, and in a projection device that does not use polarization, the polarization beam splitter can be replaced with a non-polarized half beam. By replacing it with a prism and removing the liquid crystal plate 6, a compact projection device can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of the main part of an embodiment of the present invention, FIG. 2 is a side view thereof, FIG. 3 is an enlarged side view of the main part, and FIG. 4 is a perspective view of the main part of a conventional embodiment. Figure 5 is a side view thereof. 3: Light source 4: Polarizing beam splitter 6: Liquid crystal plate 7: Concave lens 8: Liquid crystal screen 8A: One surface 8B of the irradiation surface that divided the liquid crystal screen 8 into two = The other surface 9 of the irradiation surface that divided the liquid crystal screen 8 into two .10.13:
Fresnel lens 11: Mirror 12: Concave lens 15: Projection device

Claims (4)

[Claims] (1) A spectroscopic element such as a polarizing beam splitter or a half prism that divides the luminous flux from a light source into two, a projection screen whose irradiation surface is also divided into two in order to irradiate each of the divided spectral components, and the target screen. 1. A projection device comprising: a projection lens for projecting light rays from a projection screen onto a screen. (2) A patent claim characterized in that a polarization conversion means such as a liquid crystal or a retardation plate is interposed between the polarizing element and the projection screen in order to match the polarization direction of the two-split light beam from the polarizing element. The projection device according to item 1. (3) The projection device according to claim 1 or 2, wherein the projection screen is a liquid crystal panel. (4) Claims 1, 2, or 3, characterized in that a Fresnel lens is provided at the position of the projection screen for converging the light flux that illuminates the projection screen onto the projection lens.
Projection device as described in Section.