WO1998000746A1 - Process and arrangement for image representation on a large-screen projection surface by a digital mirror device (dmd) projector having a dmd chip - Google Patents

Abstract

A digital micromirror device chip (DMD) projector having a DMD chip is complemented by a light polarisation rotary disc which produces a simultaneous representation of images per picture element to be represented and consequently finally per image. If images for the one eye are shown using the one polarisation direction, and images for the other eye using the other polarisation direction, an observer wearing glasses which have two appropriately light-polarised lenses sees three dimensional images on a large-screen projection surface.

Description

description

Method and arrangement for displaying images on a large-screen projection surface by means of a DMD projector having a DMD chip

The invention relates to methods for displaying images on a large-screen projection surface by means of a DMD projector having a DMD chip (digital micromirror device chip) according to the preambles of claims 1 and 4, and an arrangement according to the preamble of claim 8.

There are various versions of television or computer projectors that can project an image onto a large-screen projection surface. One of them is concerned with DMD projectors. A DMD projector is used for two-dimensional display of graphics, etc. usable. The image is not generated directly on a screen, but is projected over a distance in the air onto a flat, white surface.

A DMD projector has a special processor, on the surface of which several thousand small individually controllable mirrors (micromirrors) are attached. By changing the orientation of the individual mirrors, an image is generated which is brought onto a projection surface via optics.

In the German magazine Funkschau, 1995, pages 34 and 35, the principle of a DMD projector is described under the column Technology and the title "Micromirror in the large-screen projection". According to this, the DMD projector, among other important elements, such as the DMD chip, a color turntable that rotates at a multiple speed compared to a line deflection frequency used for image display. The color turntable is transparent. As a circular sector-shaped color filter, it has single circular sectors of the colors red, green and blue. In a basic embodiment, it has the color turntable only one Color filter, which is then distributed over the entire color turntable.

The principle of operation of the DMD projector is based on the fact that the light rays of a light source shine through the color turntable and are directed onto the micromirrors of the DMD chip. Each micromirror throws the incoming light onto a pixel on the large-screen projection surface. Appropriate control of the respective micromirror ensures that a color mixture is produced which is required for the representation of the individual image point. This color mixing is accomplished in that the respective micromirror always throws a light beam onto the large-screen projection surface for a correspondingly long period of time when a corresponding color beam is offered to it by the color filter. From the colors red, green and blue, all the colors in between can also be generated on the large-screen projection surface from white to black. In order to make this possible, the color turntable, if there is, for example, only one color filter with the three individual color sectors for the colors red, green and blue, has to rotate at least three times as fast as a line deflection frequency is set to at least once from all three colors per pixel to be able to choose. If several color filters are provided on the color turntable or if the color turntable rotates even faster by a corresponding factor, a micromirror can select accordingly more often within one image buildup pass.

Lenses in front of and behind the color turntable and projection optics at the exit of the DMD projector, for example, are not so crucial for describing the functional principle, but they should nevertheless be mentioned. The lens in front of the color turntable focuses the light source light rays. The lens after the color turntable distributes the colored light evenly over the surface of the DMD chip. The projection optics direct the light for each pixel to the corresponding point on the large-screen projection surface.

Other references that deal with large-screen projection using a DMD projector, but do not go beyond the prior art described above, are: G.A. Feather: Micromirrors and Digital Processing. In: Photonics Spectra, May 1995, pp. 118 to 124, and J.M. Younse: Mirrors on a chip. In: IEEE SPECTRUM, Nov. 1993, H. 11, pp. 27 to 31.

As mentioned at the beginning, a DMD projector is suitable for two-dimensional displays. Three-dimensional representations are not possible.

The object of the present invention is therefore to specify at least one method and an arrangement for three-dimensional image display on a large image projection surface by means of a DMD projector having a DMD chip.

This object is achieved by methods which have the characterizing features of claims 1 and 4 and by an arrangement according to the features of claim 8.

The methods are based on the fact that the light rays from the light source of the DMD projector are not only passed through the color turntable but also through a light polarization turntable.

In a first case, the light polarization turntable has two partial surfaces polarizing in different polarization directions and rotates at least twice as fast as the color turntable. With appropriate control of the micromirrors of the DMD chip, image points can be generated in this way that were generated with light in one polarization direction and with light in the other polarization direction. All in all images in one direction and images in the other polarization direction.

If the images of one and the other polarization direction are superimposed in a suitable form, for example, a viewer with polarization glasses, the glasses of which are designed such that one glass corresponds to the polarization direction of the one image and the other glass corresponds to the polarization direction of the other image is polarized, see an image with a three-dimensional effect.

The same is achieved in a second case if the light polarization turntable is unidirectionally polarized and the individual micromirrors are controlled in such a way that a first rotational position of the light polarization turntable in which the current polarization direction is the determining factor for the generation of a pixel in a first polarization direction unidirectional light polarization turntable is decisive, and for the generation of a pixel in a second polarization direction the rotational position of the light polarization turntable is decisive, which is rotated by 90 degrees with respect to the aforementioned first rotational position. In the one case, for example, the image point is generated with a horizontal and in the second case with a vertical polarization direction.

To carry out the method, the color turntable is assigned, for example, a light polarization turntable rotating at least twice as fast, with partial surfaces polarizing in two different polarization directions.

With a corresponding control of the micromirrors, however, the assignment of a light polarization turntable is sufficient, which has a total area polarizing in a unidirectional direction. Here, however, the effective surfaces can be only those areas are used which are assigned to sectors of the circle which are arranged in pairs opposite one another and under two pairs the pairs are arranged at right angles to one another and thus crossed overall.

It is also possible to combine the color turntable and the light polarization turntable into one component. In this case, at least two pairs, each with color filters lying opposite one another, are provided uniformly distributed over the color turntable area and are in turn light-polarizing with polarization directions that alternate between two polarization directions.

Further advantageous embodiments of the invention are the subject of subclaims.

The two different polarization directions required are then selected such that their courses are aligned perpendicular to one another. In this case there is a maximum difference in the directions of polarization. Crosstalk between the two images having different polarization directions is avoided as best as possible.

The two differently polarized images can be superimposed either by line-by-line or by a full-area change in the polarization directions.

A particularly advantageous effect results if the different polarization directions within the respective sectors are selected in such a way that in one case the polarization direction has a circular structure and in the other case a radiation-like structure. In this case, a slight change in polarization direction is caused by the rotary movement of the light polarization rotary Disc prevented during the scanning of light rays through the micromirrors. Such a change can be disregarded in the case of horizontally and vertically arranged polarization directions if the scanning of the light beams takes place in a very narrow range, for example +/- 5% of a respective central position of the respective circular sectors.

Several exemplary embodiments of the invention are explained in more detail below with reference to the drawing. Show in it

1 shows a schematic representation of a DMD projector according to the invention, and

FIGS. 2a to 2f each show an exemplary embodiment for a light polarization turntable of the DMD projector according to FIG. 1.

The essential components of a DMD projector are shown in FIG. These are a light source LQ, a first lens L1, a color turntable FDS, a second lens L2, a DMD chip CH, a projection optics PO and a large image projection surface GBPF. The surface of the DMD chip CH has a large number of small, individually controllable micromirrors MS.

The light source LQ emits light source light rays. These go through the first lens L1 and are bundled. The bundled light penetrates the FDS color hub. After the color turntable FDS, the light source light beams are directed through the second lens L2. After the second lens L2, the light source light beams hit the micromirrors MS of the DMD chip CH. The light source beams are reflected as light beams by the micromirrors MS and are projected onto all large-screen projection surfaces GBPF by the projection optics PO. The color turntable FDS has a circular sector-shaped color filter that has individual circular sectors for the colors red, green and blue. The color of the respective single circle sector is identified by one of the letters R, G and B. R stands for the color red, G stands for the color green and B stands for the color blue.

In the exemplary embodiment described, the color turntable FDS has only one color filter. In other exemplary embodiments, however, several color filters could also be provided. According to FIG. 1, the only color filter is arranged evenly distributed over the entire available area.

A motor M is responsible for the rotary movement of the color filter. The FDS color hub directs the colors red, green and blue sequentially onto the large-screen projection pool GBPF. By selecting the color for a correspondingly long period of time, a correspondingly colored image point is generated on a single image point on the large image projection surface GBPF, for which a micromirror MS of the DMD chip CH is responsible. To make this possible, the color turntable FDS rotates at a multiple speed of a line deflection frequency selected for the image construction. Examples include his 3 * 50kHz = 150kHz or 3 * 100kHz = 300kHz.

For a more detailed description of the DMD projector, please refer to the sources mentioned above. Likewise, the procedure for image generation has already been described above, so that repetition can be omitted here.

In order to be able to generate a three-dimensional image on the large image projection area GBPF, the DMD projector has a light polarization turntable LPDS between the first lens L1 and the color turntable FDS. The light polarization turntable LPDS is only shown schematically in FIG. 1. Special configurations of the light polarization turntable LPDS are shown in FIGS. 2a to 2f.

According to FIG. 2a, the light polarization turntable LPDS has two partial areas which polarize the light passing through in two different polarization directions. The directions of polarization are perpendicular to each other. The partial areas each take up half of the total area.

According to FIG. 2b, the light polarization turntable LPDS has a unidirectional direction of polarization. This can be recognized by the lines over the entire surface of the light polarization turntable LPDS. Several circle sectors are drawn within the total area, two of which are designated by the reference symbol WB. The reference symbol WB stands for the fact that these circular sectors represent an effective area of the total area. The circle segments representing an effective area are each arranged in two opposite directions. The circle segments, each arranged in two, are arranged in a crossed manner. Because of this arrangement, the one two opposite circular sectors essentially have a transverse polarization direction, while the other two opposite circular sectors have a longitudinal polarization direction. In conjunction with the rotation of the light polarization turntable LPDS, the micromirrors MS of the DMD chip CH in turn thereby have the possibility of generating pixels with two different polarization directions. The advantage here is that the -

Time intervals within which the corresponding light-polarized light beams are selected are relatively short because, due to the rotation of the light polarization turntable LPDS and the unidirectionally directed light polarization of the light polarization turntable LPDS, the polarization direction rotates with time. A stretching However, the error of +/- 5% based on an average that is optimal keeps the error within acceptable limits.

In order to avoid errors as described above, the polarization directions can be selected in such a way that one polarization direction has a circular structure and the other polarization direction has a radiation-like structure. Starting from a light polarization turntable LPDS, this is illustrated in FIG. 2a in FIG. 2c. Due to such structured polarization directions, an error as described above can no longer occur because it remains constant over a predetermined period of time.

This principle is applied to a light polarization turntable LPDS according to FIG. 2b in FIG. 2d. The lines are only drawn in the effective areas for clarity. To what extent other areas should be co-structured is a technical question.

The light polarization turntables LPDS according to Figures 2a to 2d are independent disks. The light polarization turntables LPDS according to FIGS. 2e and 2f are combined with the color turntable FDS to form a single component. The light polarization turntable according to FIG. 2e is based on a unidirectional polarization direction and the light polarization turntable according to FIG. 2f is based on a circular or radiation-shaped polarization direction. Also in FIGS. 2e and 2f, only the effective areas WB are drawn in a structured manner. Further structuring is conceivable, as in the other cases.

The color filters with the individual circle sectors for the colors red R, green G and blue B are implemented within the effective areas WB. In particular in the embodiments according to FIGS. 2e and 2f, further color filters can also be provided.

Due to the different types of possible light polarization turntables LPDS, the methods for generating the images superimposed on the large-screen projection surface GBPF are also different. Thus, when using light polarization turntables LPDS according to FIGS. 2a to 2d, it is necessary for the light polarization turntable LPDS to rotate at a correspondingly higher speed than the color turntable FDS in order to enable a selection of light beams with two different light polarizations for each color sector of the color filter. When using light polarization turntables according to FIGS. 2e and 2f, this is not necessary because here the color filter is often provided with each of the respective light polarization structures.

In summary, it is stated that a DMD chip (DMD chip (Digital Micromirror Device Chip)) is supplemented by a light polarization turntable, which enables a quasi-simultaneous display of pictures with two different light polarization directions per picture element to be displayed and thus ultimately per picture. If images are shown for one eye with one and images for the other eye with the other polarization direction, an observer with glasses that has two correspondingly light-polarized glasses can see images displayed three-dimensionally on a large-screen projection flat GBPF. The quasi-simultaneous display of two images with different polarization directions can take place row by row and / or column by column or in each case over the whole area alternating in the polarization directions.

In projectors with DMD chips, color can also be generated by DMD chips for one of the colors red, green and blue. In this case, a color rotation Disc. However, the principle according to the invention also works because the idea of the invention lies in the use of the light polarization turntable, which can still be used in the same way as described above.

The invention is not limited to large-screen projection surfaces. Small areas can also be used for image display.

Claims

claims 1. A method for displaying images on a large-screen projection area (GBPF) by means of a DMD projector having a DMD chip (CH), the light source light rays of which are produced by a color rotary disk (FDS) rotating at a multiple speed of a line deflection frequency used for displaying the image At least one circular sector-shaped color filter (FF) consisting of individual color sectors of the colors red (R), green (G) and blue (B) can be directed onto the micromirror (MS) of the DMD chip (CH), from which light rays can be directed to assigned pixels Large-screen projection area (GBPF) in a required color mixture, produced from overlays caused by corresponding individual controls of the respective micromirrors (MS) of the at least one color filter (FF) at respective times in one of the colors red (R), green (G) and blue (B) provided light beams are steerable, characterized in that for a three-dimensional sional image representation, the light source light beams are successively passed through the color turntable (FDS) and through a light polarization turntable (LPDS) rotating at least twice as fast as the color turntable (FDS) with partial surfaces polarizing in two different polarization directions, and through corresponding individual controls of the micromirrors (MS) of the DMD chip (CH), by means of which a color selection for a correspondingly long period of time and a selection of a light polarization direction is carried out for each pixel, light beams for two superimposed images polarized in one of the two polarization directions of the light polarization turntable (LPDS) the large screen projection area (GBPF) are thrown. 2. The method according to claim 1, characterized in that the light source light beams are thrown through a light polarization turntable (LPDS) with mutually perpendicular polarization directions. 3. The method according to claim l, characterized in that the light source light rays are thrown through a light polarization turntable (LPDS) with mutually circular and radiating polarization directions. 4. A method for displaying images on a large-screen projection surface (GBPF) by means of a DMD projector having a DMD chip (CH), the light source light rays of which by means of a color turntable (FDS) rotating at a multiple speed of a line deflection frequency used for the image display, with at least one Circular sector-shaped color filters (FF) consisting of individual color sectors of the colors red (R), green (G) and blue (B) are directed onto the micromirrors (MS) of the DMD chip (CH), from which light rays point to the respective pixels Large-screen projection area (GBPF) in a required color mixture, produced from overlays caused by corresponding individual controls of the respective micromirrors (MS) of the at least one color filter (FF) at respective times in one of the colors red (R), green (G) and blue (B) provided light rays are directed, characterized in that for a three-dimensional image representation, the light source light beams are successively passed through the color turntable (FDS) and through a light polarization turntable (LPDS) with a total area polarizing in a unidirectional direction, and that through corresponding individual controls of the micromirror (MS) of the DMD chip (CH ) depending on the rotational positions of the light polarization turntable (LPDS), in which polarization directions of the light polarization turntable (LPDS) are rotated by 90 degrees, light beams for two superimposed images, each polarized in one of the two rotational position-dependent polarization directions, in the direction of the large-screen projection surface (GBPF) to be thrown. 5. The method according to any one of claims 1 to 4, characterized in that the color is generated by means of a color turntable by several DMD chips for each of the colors red (R), green (G) and blue (B). 6. The method according to any one of claims 1 to 5, characterized in that the superimposition of the images is generated by a line-by-line image change. 7. The method according to any one of claims 1 to 5, characterized in that the superimposition of the images is generated by a full-area image change. 8.. Arrangement for image display on a large image projection surface (GBPF) by means of a DMD chip having a DMD chip (CH), which has a color turntable (FDS) rotating at multiple speeds of a line deflection frequency used for image display with at least one circular sector-shaped color filter (FF ) consisting of individual color sectors of the colors red (R), green (G) and blue (B), characterized in that the color turntable (FDS) has an at least twice as fast rotating light polarization turntable (LPDS) with two different directions of polarization is assigned to polarizing partial surfaces in the beam path.