RU2082281C1 - Color video projector - Google Patents

Abstract

FIELD: TV devices. SUBSTANCE: device has three lasers 1, 2, 3 which output three basic colors: red, green and blue. Lasers are connected in series to color adder 4, collimator 5, light gate unit 6, and projection lens unit 7 which outputs light to projection screen. This results in possibility to exclude electromechanical sweeping devices. EFFECT: precise matching of color constituents of picture, increased quality of picture. 2 dwg

Description

 The invention relates to systems for reproducing a television image, and more particularly, to a color video projection technique.

 Video projection is the main means of reproducing television and other images with a screen diagonal of more than 1 m.

 Light valve type video projects are widely used, which use a sufficiently powerful external light source and a light valve device that controls the transmission or reflection of the radiation generated by this source on the projection screen in accordance with the intensity of the corresponding video signal (see, for example, H. Johannes "Jhe History of the EIDOPHOR Large Screen Television Projector, Publisher Gretag Aktiengesellschaft, Zurich, 1989.) The main disadvantage of this type of color video projection is the difficulty in ensuring accurate and stable Information on the screen of three color components of the image.

 For many years, the possibility of obtaining color images on a large screen using lasers has been attracting attention. In 1965, a projector was proposed containing three lasers emitting light in three primary colors (see, for example, the Federal Republic of Germany patent N 1268187 N 04 N 9/31, 1968).

 In 1986, a laser projector model was created that actually repeats the original idea, which is based on the use of an electromechanical system for scanning light beams (RSand. Laser-TV, (k) eine Erfindung des "tapfeven Schneiderleins". Fernseh-und Kino-Technik, 1993 J. 47, N 9, S 561-562). This is precisely the main and insurmountable drawback of existing laser video projectors, which has become an obstacle to their any noticeable distribution.

 This video projector is closest to the invention. It contains three lasers with light radiation of three primary colors, optically coupled to the adder of these radiation. Between lasers and projection optics, which provides images on a projection screen, there is a block for modulating lasers with video signals and vertical and horizontal scanning. In fact, it is made in the form of individual (for each laser) intensity modulators (for example, in the form of Kerr cells), controlled by video signals of three primary colors, and common to three electromechanical vertical and horizontal electromechanical units. The electromechanical sweep system is based on the use of an oscillating mirror for vertical deflection and a rapidly rotating multi-faceted mirror drum for horizontal deflection. Such a sweep system requires extremely high manufacturing accuracy and complex precision systems to maintain a stable (accurate to phase) rotation speed at a drum speed of tens of thousands of revolutions per minute. It is noted, "that even small violations led to the appearance of interfering horizontal stripes in the image, as was observed during the demonstration." To reduce the rotation speed when creating the device (see the above article), they even went to the reduction of the field frequency from 50 Hz (or 60 Hz for the US TV standard M) to 48.8 Hz, which required the use of a special scan standard converter for pairing with standard television sources.

 An object of the invention is the creation of such a color video projector, which does not require the use of an electromechanical scanning system.

 The technical result is achieved by the fact that the projector contains three lasers with light emissions of three primary colors, optically coupled to a sequentially arranged adder of these emissions, a modulation and sweep unit and a projection optics unit. The modulation and sweep unit is made in the form of a light valve device, to the inputs of which a video signal with alternating primary color signals along the fields, vertical and horizontal synchronization signals and a color synchronization signal are input, an optical collimator is introduced between the radiation adder and the light valve device, and laser excitation control inputs are connected the outputs of the entered electronic switch, the inputs of which are fed a vertical synchronization signal and a color synchronization signal.

 Due to the complete exclusion of electromechanical devices, a significant simplification of the projector’s implementation and at the same time an improvement in image quality (due to the exact combination of the three color components of the image on the screen) are achieved.

 Figure 1 presents the structural diagram of the proposed video projector, and figure 2 shows a timing diagram of the alternate activation of the lasers.

 The color video projector (Fig. 1) contains three lasers 1, 2, 3 with light radiation in the three primary colors red R, green G and blue B. The lasers are optically connected in series with the adder 4 of these light emissions, a collimator 5, a light valve device 6 and a unit projection optics 7, from where light enters the projection screen (not shown in the figure).

 The control inputs of the excitation of the lasers 1,2, 3 are connected to the corresponding outputs of the electronic switch 8, the inputs of which are supplied with signals of vertical and color synchronization CS. A color video signal with alternating color fields R, G, B is fed to the video input of the light valve device, and vertical V and horizontal synchronization signals H are input to the synchronization inputs.

 Video projector works as follows.

 The electronic switch 8 includes the lasers alternately in the fields in a certain sequence, for example, cyclically in the order of the laser numbers in the figure. As a result, the adder 4 during each sequential field receives radiation of only one of the primary colors. From the output of the adder 4, the radiation passes through a collimator forming a beam, the cross section of which is in accordance with the size of the working area of the light valve device 6 (which is substantially substantially larger than the laser beam cross section). In the light valve device 6, under the action of a video signal and vertical and horizontal synchronization signals, a light modulating zone is formed, the transmission or reflection of which at each point is proportional to the values of the video signal in this image. A single color video signal with alternating color fields from the corresponding video signal (for example, from a color television camera with alternating color fields) is supplied to the video input of the light valve device. Moreover, in order to ensure that the “color” of the video field matches the color of the currently emitting laser, a color burst signal from the video source is supplied to the input of the switch 8. The projection optics unit (which may contain a lens and, if necessary, mirrors) forms a color image on the projection screen.

 The electronic switch 8 can be performed by conventional radio electronics, for example, using a three-ring counter, which receives vertical synchronization pulses at the clock input, and color synchronization pulses “tied” to fields of a certain color are fed to the reset input. Figure 2 shows the pulses of vertical V and color synchronization CS received at the input of the switch, and three sequences of pulses for switching on color lasers generated at its outputs IR, IG, IB.

 In the proposed projector can be used gas lasers or other laser light sources.

 As a light-valve device, for example, an Eidofor-type device can be used, in which slit ("schlieren") optics and a liquid light-modulating medium are used to modulate the light received from a separate source, on which a relief is created in vacuum using an electron beam modulated by a video signal and deployed vertically and horizontally using conventional television type deviation systems.

 The main advantages of a color video projector are as follows.

 It excludes the electromechanical sweep commonly used in laser projectors.

 An exact geometric combination of three color images is not required, since a field-consistent projection through a single optical system and a single light-valve device is used. At the same time, it is not necessary to use a rotating disk with light filters, as in sequential-type light valve projectors with a light source based on a xenon lamp (as in Eidofor type projectors). Thus, in this projector, movable electromechanical elements are completely excluded, and all work operations are carried out only by electronic and optical methods.

 If necessary, use the proposed projector with sources of signals of the same type to pair with such sources, you can use the electronic converter of the television standard according to ed. testimonial. N 1262745, CL H 04 N 9/12.

Claims (1)

 A color video projector containing three lasers with light emissions of three primary colors, optically coupled to an adder of these emissions, as well as a sequentially located modulation and sweep unit and projection optics unit, characterized in that the modulation and sweep unit is made in the form of a light valve device with the possibility of applying to its video signal inputs with alternating primary color signals across the fields, vertical and horizontal synchronization and color synchronization, as well as between the radiation adder and the light a valve device inserted optical collimator, a drive control inputs to the laser respective outputs connected inputted electronic switch configured to input vertical sync and color burst.

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