DE29720997U1 - Flat screen - Google Patents

Description

Flat screen

Dr.-Ing. Gerd-P. Fehlert

Description

High-resolution and large format screen with reduced depth.

The image is constructed using vertical projection. The image content of a line is directed vertically onto the corresponding reflective and mechanically controlled line within the image plane. The light then hits a screen coated with RGB phosphors. The necessary flicker frequency is achieved using a binary line sequence.

Preview

In principle, the following imaging procedures exist:

• the projection method

the image area is illuminated by a source
(Braun tube, laser projector, ...)

• the matrix method

the image surface is a matrix of self-luminous pixels (LCD matrix, plasma screen, ...)

The first method is always associated with a projection distance between the screen plane and the radiation source. With picture tubes and rear light projections, the depth increases with the size of the image. The picture tube has reached its maximum performance. The high vacuum, the high electrical voltages with their well-known side effects and the magnetic sensitivity are particularly disadvantageous. With front-light projectors, viewers walking past can cast shadows on the screen. The best viewing conditions are only in slightly darkened rooms.

The second method enables the construction of a flat screen. Flat screens are usually plasma screens or they have an LCD active matrix. However, the technical complexity increases two-dimensionally with the number of pixels per line and the number of lines per image. As the size of the screen increases, a number of manufacturing problems arise. A 100Hz screen with 3x8 bit resolution is not within sight with LCD technology.

Vertical projection

A third possibility is to combine certain properties of the two processes. This requires the image to be constructed in two functional units. One unit is formed by mechanically controllable reflectors that take over the cell-shaped image construction. The visible screen thus consists of the physical lines that are fixed in their xy position and move in the z axis.

The second unit is a line-shaped source at the bottom (and/or top) edge of the screen, whose rays generate the image line content. The rays of this image line are directed vertically to the opposite edge of the screen and interrupted by the physical line corresponding to the line content. The rays are reflected forward onto a screen by the reflective surface of the moving line.

In contrast to matrix screens, the number of signal sources only grows one-dimensionally with the number of pixels per line. Since all pixels in a line are activated in parallel, the line frequency is also the highest processing frequency (only with pulse width modulation to generate the different gray values does this frequency increase by a factor of 256).

Structure of the mechanical lines

Next to the right and left edges of the image there is a shaft with eccentrically mounted control discs. A continuous string with a reflective surface inclined at 45 degrees is stretched around each pair of discs. The number of continuous strings corresponds to the number of image lines.

Each shaft is driven by its own synchronous motor, both motors are synchronized with each other and with the image signal. The synchronization of both motors ensures that no forces are transmitted via the endless strings. The use of brushless motors also increases their service life and reduces noise.

If the full circle of 360 degrees is divided by the number of lines, you get an angle that determines the offset of the control disks from one another. If the control disks are arranged in sequence offset by this angle, the result is an image structure without interlacing. There is freedom of choice when it comes to the structure of the control disks. If an interlacing process is to be implemented, the order of the control disks is determined according to an appropriate scheme.

Control of mechanical lines

Each strip is activated twice per rotation of the control disc, once during forward motion and once again after 180 degrees during rewind. Half a rotation of the control disc is enough to activate all lines. With a control shaft speed of 750 revolutions per minute, 25 full images are generated per second.

To generate the necessary flicker frequency, an interlaced method is used, which is based on a binary line structure. To do this, all even-numbered lines are activated in the first field. Then half of the remaining gaps are closed in the second field, and so on. With 1025 lines, 10 fields are created, with three lines in the last field. Since the time per line is constant, the subsequent field is built in half the time of the previous field.

The limit of the corresponding mathematical sequence yields the value three. The flicker frequency is therefore 75 Hertz at 25 full frames per second. This binary distribution of the line structure is part of the mechanical control.

Since the eye cannot find three lines anywhere in the image that have been constructed according to the same pattern, the eye is overwhelmed and the impression of a calm overall image is created. The following numerical scheme shows the structure for a 17-line image.

1 .Partial image

2. Partial image

3. Partial image

4. Part 1

11

15

17

Generation of parallel light rays

For the arrangement described above, a narrow, straight light source with a parallel beam path is required. This is achieved by a mirrored strip that is curved in the form of a concave mirror. The filament is located at the focal point of the curved mirror strip. The width of the mirror strip corresponds to the length of the cylindrical filament. This filament is located in the focal axis of the concave mirror.

The light-emitting surface of the concave mirror corresponds to the screen width times the length of the filament cylinder (e.g. 160cm x 0.5cm). A cell-shaped aperture limits the
Exit opening.

Summary and Outlook

The frequency of each individual line is 25 Hz. The fast switching time from line to line is caused by the phase speed of the mechanical 25 Hz wave that moves vertically through the image. Despite the mechanics, the performance is no less than that of picture tubes. The aim is to have a screen with the data 90 cm x 160 cm, flicker-free display of approx. 1000 picture lines.

Advantages of this device over conventional picture tubes:

• it is free from high voltages and electric fields

• it is insensitive to magnetic influences

• there is no risk of implosion due to a high vacuum

• the low specific gravity

• the unproblematic and inexpensive production.

Competing products to this device are screens with plasma technology or LCD matrix screens.

Claims (4)

Dr.-lng. Gerd-P. Fehlert Kriegerheimstraße 60 D-42115 Wuppertal Date:26.11.1997 Tel 0202-271233-0 Fax 0202-271233-1 German Patent Office D-80 297 Munich Subject: Claim for protection of a utility model flat screen 1. Cell-shaped structure of an electronic image, characterized in that that each individual image line is controlled mechanically, the image content of a line is generated at the bottom of the screen and is projected vertically upwards (vertical projection), this beam path is interrupted by the corresponding physical (mechanically movable) line and its light is reflected forward onto a screen. 2. Mechanically operating flat screen characterised by that reflective endless strings take over the cell-shaped image structure and each string is controlled by two eccentrics rotating in the same direction. 3. Generation of a high flicker frequency characterized by that the line structure follows a binary pattern. 4. Generation of the linear light source characterized in that a narrow reflecting strip in the form of a concave mirror converts the light from a filament into parallel light rays and this light is limited by a linear gap. Dr.-lng. Gerd-P. Fehlert