RU2297657C1 - Projection display - Google Patents

Abstract

FIELD: optics.

SUBSTANCE: projection display includes body, positioned inside which are projection screen, spatial light modulator, optical system and Fresnel reflector. Body has flat face side, on which projection screen is situated. Light source is made with possible generation of light beam and sending of same to spatial light modulator, while spatial light modulator is built with possible insertion of image information into light beam, and optical system is mounted along the route of light beam behind spatial modulator and made with possible redirection of light beams into Fresnel mirror, working surface of which consists of a set of concentric zones and which is positioned inside the body in front of projection screen.

EFFECT: creation of projection display, resistant to deformations, in which in case of screen deformation good image quality is ensured.

6 cl, 3 dwg

Description

The invention relates to optical devices of a projection type and may find application in the design of projection displays.

Currently, there are projection displays with panels of pixels (LCD, DMD, etc.), which use wide-angle optical systems with significant angles of incidence of rays on the projection screen, which provide an increase in the image and reduce the size of the display. At the same time, the user observes on the screen an enlarged image of the projected panel.

However, in the event of a deformation of the display screen in such displays, the rays will be strongly displaced on the surface of the display and not reach the specified point, which will lead to a deterioration of the image on the screen.

US Pat. No. 4,936,657 [1] describes a liquid crystal projection display having an optical system providing large angles of incidence of light rays onto a screen including a Fresnel lens that directs light to a projection scattering lens, after passing through which light rays enter the screen.

Closest to the claimed invention is a projection display, described in US patent No. 6824274 [2], on the front panel of which there is a projection screen, a projector, an optical system and an aspherical reflector that projects the image onto the screen. This display is selected as a prototype of the claimed invention.

The disadvantages of the above analogue and prototype are as follows. In both displays, light rays are projected onto the screen at large angles, and in case of deformation of the surface of the screen, the rays will move strongly on the surface of the screen and will not reach the specified point, and the extreme rays of the light beam will pass along the surface of the screen (Figure 1.2), which will result to sharp deterioration of the image on the screen. That is, the above projection displays of the analogue and prototype are unstable to screen deformations.

The objective of the claimed invention is the creation of a projection display that is resistant to deformation, in which when the screen is deformed, good image quality is ensured.

The problem is solved by creating a projection display, which includes a housing inside which there is a projection screen, a light source, a spatial light modulator, an optical system and a Fresnel reflector, the housing having a flat front side, the projection screen is located in the front side of the housing, the light source made with the possibility of forming a beam of light and directing it to the spatial light modulator, while the spatial light modulator is configured to make info a view of the image into the light beam, and the optical system is located along the light beam behind the spatial modulator and is configured to direct light beams to a Fresnel mirror, the working surface of which consists of many concentric zones and which is located inside the housing opposite the projection screen and is configured to reflect the light beam in such a way that each beam of the light beam falls on the surface of the projection screen at an angle close to the normal.

For the display to function, it is essential that the optical system includes at least one refractive optical element.

For the display to function, it is essential that the optical system includes at least one reflective optical element.

For the display to function, it is important that the Fresnel mirror is designed so that the smaller the distance, i.e. the step, between concentric zones, the better the image quality on the screen.

For the display to function, it is essential that the Fresnel mirror has an off-axis displacement, the coordinates of which are determined depending on the characteristics of the light beam.

For the display to function, it is important that the spatial modulator be in the form of a DMD matrix.

The technical result of the claimed invention is to provide resistance to deformation of the screen due to the use of a Fresnel mirror directing light rays onto the screen of the projection display at an angle close to a right angle.

For a better understanding of the present invention, the following is a detailed description thereof with corresponding drawings.

Figure 1 - diagram of the incidence of rays on the projection screen of the display at a large angle:

1.1. - under normal conditions.

1.2. - with a deformed screen.

Figure 2 - diagram of a projection display made according to the invention.

Figure 3 is a diagram of a Fresnel mirror made according to the invention.

The projection display includes a housing 1, inside which there is a projection screen 2, a light source 3, a spatial modulator in the form of a DMD matrix 4, an optical system 5 and a Fresnel mirror 6. The housing 1 has a flat front side. The projection screen 2 is located in the front side of the housing 1. The light source 3 is located near the front side of the housing 1 under the projection screen 2 and is configured to generate a beam of light and direct it to the DMD matrix 4. DMD matrix 4 is configured to enter image information into a beam of light. The optical system 5 is located along the light beam behind the DMD matrix 4 and is configured to direct the light beam to the Fresnel mirror 6. The Fresnel mirror 6 consists of many concentric zones, is located on the rear side of the housing 1 parallel to the projection screen 2 and is configured to reflect the beam light in such a way that each beam of the light beam falls on the surface of the projection screen 2 at an angle close to the normal.

The display operates as follows. The light beam from the light source 3 is reflected from the DMD matrix 4, passes through the optical system 5, after which the output beam incident at a large angle on the Fresnel mirror 6. The Fresnel mirror 6 has a complex reflective surface, consisting of many flat concentric zones that reflect the rays as if the mirror were tilted nonlinearly for each beam of light. The best image quality on the screen is achieved when light is reflected on the mirror with the smallest step (the distance between the zones). The reflection angle varies from zone to zone, but light beams redirected by the Fresnel mirror 6 from all zones follow directly to the projection screen 2, while the angles of incidence on the screen 2 become close to normal. In this case, in the case of deformation of the projection screen 2, the light beams will not shift slightly on its surface, and therefore, there will be no image degradation.

The working part of the Fresnel reflector 6 is shown in Fig.3. In general, it has an off-axis arrangement, concentric structure of zones. The off-axis displacement coordinates are calculated depending on the characteristics of the incident radiation.

Although the above embodiment of the invention has been set forth to illustrate the present invention, it is clear to those skilled in the art that various modifications, additions and substitutions are possible without departing from the scope and meaning of the present invention disclosed in the attached claims.

Claims (6)

1. A projection display including a housing with a projection screen, a light source, a spatial light modulator, an optical system and a Fresnel reflector, the housing having a flat front side, the projection screen located in the front side of the housing, the light source is configured to form the light beam and directing it to the spatial light modulator, while the spatial light modulator is configured to introduce image information into the light beam, and the optical the system is located along the light beam behind the spatial modulator and is configured to direct light beams to a Fresnel mirror, the working surface of which consists of many concentric zones and which is located inside the housing opposite the projection screen and is configured to reflect the light beam so that each beam light falls on the surface of the projection screen at an angle close to normal. 2. The projection display according to claim 1, characterized in that the optical system includes at least one refractive optical element. 3. The projection display according to claim 1, characterized in that the optical system includes at least one reflective optical element. 4. The projection display according to claim 1, characterized in that the Fresnel mirror is designed so that the smaller the distance between the concentric zones, the better the image quality on the screen. 5. The projection display according to claim 1, characterized in that the Fresnel mirror has an off-axis displacement, the coordinates of which are determined depending on the characteristics of the light beam. 6. The projection display according to claim 1, characterized in that the spatial modulator is made in the form of a DMD matrix.

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