INVENTION DESCRIPTION WITH CLAIMS AND DRAWINGS

METHOD OF LARGE-ANGLE HIGH DEFLECTING FREQUENCY SCANNING

OF LASER BEAM FOR TRANSMISSION AND RECEIVING

VIDEO AND OTHER IMAGES AND DEVICE FOR ITS REALIZATION

Field of the invention

The invention is related to laser technology and intended for large-angle high deflecting frequency scanning of laser beam in laser television and video projectors and video cameras for transmission and receiving flat and volume video images and could be applied also to laser copying and scanning equipment for transmission and receiving images, to scanning space in security and measuring systems, laser monitoring systems, including infrared range, as well as to other laser systems. Simplicity of the invention allows significantly decrease production cost of laser scanning systems and makes them available for mass manufacturing.

Background of the invention

There is well known method of large-angle high deflecting frequency electron beam scanning in color TV kinescopes with frequency of line scanning of 15625 Hz and deflecting angle of 110° (V. V. Pyasetsky. Color TV in questions and answers. Minsk, Polymya, 1194, fig. V.1). However, the electron beam scanning system is not applicable to scanning laser beam.

There is known method of deflection of light beam by oscillating mirror with magneto-electrical drive (Authorship certificate No 1756853, G 02 F 1/29/ Magneto-electrical deflector. Bull. No 31, 23.08.92).

Demerit of the known method of light beam deflection is the significant decrease of scanning angle with increase of frequency, which makes impossible the use of this method in devices for large-angle high deflecting frequency laser beam scanning in TV projectors.

There are known surface acoustic waves (SAW) in solid bodies (I. A. Victorov. Sound surface waves in solid bodies. M., 1981). Surface acoustic waves in condition of wave exciting of the surface of oscillating medium are able to deflect laser beam on high frequencies (ultrasound and hypersound). Demerit of surface acoustic waves in laser beam scanning systems is the small deflecting angle, insufficient for large-angle TV image.

Summary of the invention

Technical solution, for achievement of which this invention is intended, is the creation of effective conditions for waves exciting of oscillating medium sufficient for large-angle high deflecting frequency laser beam scanning for TV and video projectors and cameras, as well as for different copying and scanning systems.

Realization of offered invention allows providing large-angle high deflecting frequency laser beam scanning for TV and video projectors and cameras, as well as for different copying and scanning systems by use of simple and cheap technical solutions.

The term "laser beam" used above and hereinafter shall be understood in more wide sense, which includes laser radiation, light emitting diode radiation and other kinds of light radiation, because the offered method provides the large format and high speed scanning of any light beam, formed in result of focusing and/or blinding any divergent light beam.

Disclosure of the invention

The mentioned technical result is achieved by the fact that in the method of large-angle high deflecting frequency laser beam scanning the system, which deflects the laser beam, is in the mode of wave exciting of oscillating medium with gradient linear density of substance. There are principally used two series-connected oscillating linearly extended media with different linear density of substance in the mode of simultaneous resonant excitation of transverse oscillations of two media, when the mode of resonant matching of transverse oscillations of two media is established from the following relation between wave-length of oscillations of linearly extended media and their linear densities of substances:

where l₁ - wave-length of excitation of medium with greater linear density t₁ (kg/m); l₂ - wave-length of excitation of medium with smaller linear density t₂ (kg/m); k - coefficient considering the difference of volume density of media with different elasticity.

This result is achieved by the following way: in device for realization of this method the system of laser beam deflection contains two linearly extended, mechanically coupled strip resonators, the first of which is equipped by exciter of oscillations and made in form of plate, on the edge of which there is fixed the second resonator made in form of thin elastic strip with the length proportional to resonant exciting wavelength l₂ or 1/4 l₂, 3/4 l₂, and the device is equipped with appliance for adjustment of coordinate of location of the second resonator in the zone of propagation and deflection of laser beam.

Short description of figures

Figure 1 shows the scheme of connection of two linearly extended media 1 and 2 with different linear density with exciter of transverse oscillations 3.

Figure 2 shows the scheme of amplifier of amplitude A₂ of transverse oscillations in the mode of resonant exciting of linearly extended medium with lower linear density of substance.

Figure 3 shows the picture of exciting of oscillations of linearly extended medium with gradient density of substance along the length and amplification of oscillations on the edge (tail) of resonator.

Figure 4 shows the scheme of amplification of amplitude A₂ of transverse oscillations in linearly extended medium in volume.

Figure 5 shows alignment of transverse oscillations of linearly extended media in antiphase in volume.

Figure 6 shows the scheme of the device with fixing on the edge of the first strip resonator 1 of the second strip resonator 2 in form of thin elastic strip with the length proportional to resonant exciting wavelength l₂ (full-wave resonator).

Figure 7 shows the scheme of the device with fixing on the edge of the first strip resonator 1 of the second strip resonator 2 in form of thin elastic strip with the length proportional to 3/4 l₂ (three-quarter-wave resonator).

Figure 9 schematically shows the device for large-angle high deflecting frequency laser beam scanning in section.

Figure 10 shows different stages of deflection of laser beam with 180° angle of deflection.

Figure 11 shows variant of the second resonator in form of optical light guide.

Figure 12 shows simplified variant of the second resonator in form of optical light guide.

Figure 13 shows the scanner with coupled line and frame scanning of laser beam.

Realization of the invention

In order to found the offered method there are given necessary explanations and description of the method and device for large-angle high deflecting frequency laser beam scanning.

The offered method of scanning is based on the effect of amplification of amplitude of oscillations in linearly extended media with gradient of density of substance along the length in the mode of resonant exciting of transverse oscillations. In the simplest way this method could be commented on example, when the gradient density of substance is changed by step on boundary surface of two media with different linear densities of substance. This physical effect was discovered by V. S. Leonov in 1986 during investigation of oscillation of coupled linearly extended media. The simplest example of linearly extended medium is the narrow and thin strip of substance. In case of exciting of oscillations of such strip on resonant frequency we shall obtain the strip resonator, which is characterized by frequency, amplitude and wave-length of oscillations, as well as by the number of waves housed on the length of the strip resonator in standing wave mode.

Advantage of the strip resonators in comparison with effects of surface acoustic waves (SAW) in solid media is in significantly bigger amplitudes of oscillations. It is possible to consider the strip resonators as an element of surface wave, when the surface is separated from a big volume of solid body, amplifying amplitude of oscillations.

But in this method is used the effect of much more significant amplification of amplitude of oscillations due to connection of two linearly extended media with different linear density of substance on the mode of resonant exciting of transverse oscillations. Figure 1 shows the scheme of connection of two linearly extended media 1 and 2 with different linear density of substance with the exciter of transverse oscillations 3. Linear density t of substance means distributions of mass of substance along the length of the strip resonator (in kg/m) in opposite to volume density (kg/m³).

In order to understand the physical nature of amplification of amplitude of oscillations in coupled linearly extended media let us consider the simplest case of resonant exciting of transverse oscillations in two coupled strip resonators made in form of plates and strips of substance. Even in case of similar volume density plates and strips with similar width, but with different thickness have different linear density of substance (fig.1). More thick plate 1 has bigger linear density t₁ in comparison with the linear density t₂ of more thin strip 2. The plate 1 and the strip 2 are the linearly extended media with different density of substance t₁ > t₂, which is changed by step in place of contact of media, providing gradient of linear density.

The exciter of transverse oscillations 3 (fig. 1) in the mode of resonant exciting of the plate1 brings it into oscillation condition, which is represented by the standing wave with wavelength l₁ and amplitude A₁. In order to excite transverse oscillations in the thin strip 2 it is necessary to choose the mode of its resonant exciting. In absence of such mode the transverse oscillations of the strip 2 are not observed. The choice of the mode of resonant exciting is made by determination of precise length of the strip 2, which is made on the basis of relations between wavelengths l₁ and l₂ of oscillations of linear media and their linear density of substance t₁ and t₂:

In this case the resonator accommodates the integer number of waves, and media coherently come into the mode of resonant exciting of standing wave, forming nodes 3 and antinodes 4 (fig. 2). The presence of antinodes 4 determines amplitude of oscillations A₂. If media have different volume density of substance with different elasticity, than in mathematical formula this fact is regulated by the coefficient k.

In the mode of resonant exciting of two coupled linearly extended media the amplitude A₂ of oscillations of the medium with lower density is sharply increased in comparison with the amplitude A₁ (Fig. 2). It could be explained by the fact that the plate 1 with higher linear density of substance with bigger mass transfers the strong impulse to the thin strip 2 with smaller mass, sharply increasing the amplitude of its oscillations (effect of whip).

The similar resonance could be excited in continuous media with the gradient of linear density of substance along the length, as fishtail (flapper), when the wave oscillations of the body result in amplification of the amplitude of oscillations of the tail (Fig. 3). However, the effect of amplification of oscillation in case of the step change of linear density on the boundary surface of two media is preferred.

The example of the effect of amplification of the amplitude A₂ of transverse oscillations of the linearly extended medium in volume is shown in Figure 4, and Figure 5 shows alignment of transverse oscillations of linearly extended media in antiphase, which determines the deflection angle of the strip 2 in the node 3 and strong deformation of medium in the antinode 4.

Having big amplitudes of oscillations of linearly extended medium in the range of sound frequencies up to 20 kHz it is possible to realize different devices for large-angle high deflecting frequency scanning of laser beam. The offered method of scanning could be used both in case of propagation of laser beam in zone of strong deformation of substance in the antinodes 4, and in case of reflection of laser beam in the node 3. In the first case the linearly extended media 2 must be optically transparent, and the angle of refraction will be determined by conditions of deformation of the medium, when the coefficient of refraction is changed. In the second case the linear media 2 must reflect the laser beam. The case of total reflection of laser beam is provided as example of realization of this method of large-angle high deflecting frequency scanning.

But before description of a specific device for realization of this method of scanning, it is necessary to describe its features. Naturally that the device, shown in fig. 1, was necessary for explanation of physical processes, which this method is based on. It is important that the device for realization of this method includes two linear, mechanically coupled strip resonators. In the real device everything is made for its simplification. It is enough to excite resonant longitudinal oscillations of the first strip resonator.

Figure 6 shows the scheme of the device with fixing in the zone 5 on the edge of the first strip resonator 1 of the second strip resonator 2 in form of thin elastic strip with the length proportional to resonant exciting wavelength l₂ (full-wave resonator). A piezoceramic plate or tube could be used as the first strip resonator. Amplitude of oscillations of piezoceramic plate is very small and it is not shown in fig. 6. Apart from the full-wave resonator there could be used three-quarter-wave and quarter-wave resonator.

Figure 8 shows the scheme of the device with fixing on the edge of the first strip resonator 1 of the second strip resonator 2 in form of thin elastic strip with the length proportional to 1/4 l₂ (quarter-wave resonator). A steel plate with external electromagnetic (electrodynamic) exciter 6, fixed inside the housing 7 of device, could be used as the first strip resonator.

The use of full-wave, three-quarter-wave and quarter-wave string resonators is reflected in the patent claim of the invention. Half-wave resonators could also be used, but not so effectively. Exactly the presence of full-wave, three-quarter-wave and quarter-wave string resonators ensures the effective matching of the first and the second resonators in the mode of full resonant oscillations. Forasmuch as the resonant curve has the bell-shaped form, the resonance, but with smaller amplitude, is achieved with approach of the mode of full-wave, three-quarter-wave and quarter-wave resonance. In the patent claim it is reflected by the word "principally", i. e. the second resonator made in form of thin elastic strip with the length "principally" proportional to resonant exciting wavelength l₂ or 1/4 l₂, 3/4 l₂. But the maximal effect is achieved in the mode of exact resonance.

Description of the device, realizing the method of large-angle high deflecting frequency scanning is presented below (fig. 9).

The device for large-angle high deflecting frequency scanning of laser beam includes two strip resonators 1 and 2, external exciter of oscillations 7, housing 7, appliance 8 for adjustment of coordinate of location of the second resonator in the zone of propagation and deflection of laser beam, semiconductor laser 9.

The strip resonator 1 is made in form of plate, on the edge of which there is fixed the second resonator 2 made in form of thin elastic strip with the length proportional to the resonant exciting wavelength l₂ or 1/4 l₂ or 3/4 l₂. In this case there is shown the three-quarter-wave (3/4 l₂) resonator 2. The second resonator 2 could be made of completely light-reflecting material or may be equipped with the reflecting covering. The fastening 5 must provide the solid contact connection of the resonators 1 and 2. Adjustment of laser beam 9 in area of the node 3 of the second resonator 2 is provided by the device 8 (micrometer screw). In order to prevent interruption of laser beam scanning by laser 9, the optical axis of laser is installed under an angle to the surface of the second resonator 2 (section B-B, fig. 9).

The device of large-angle high deflecting frequency scanning of laser beam operates as follows. The exciter of oscillations 6 (in this case - external, but it could be the internal one) excites resonant transverse oscillations of the first strip resonator 1. Oscillations of the first resonator 1 are transferred to the second strip resonator 2 in the mode of resonance with amplification of amplitude of oscillations of the second resonator. The laser beam is directed to the area of the node 3 of the second resonator 2 and reflected by its surface. Oscillations of the surface of the second strip resonator 2 in area of the node 3 provide large-angle high deflecting frequency scanning of laser beam on frequencies up to 20 kHz and more with angle of deflection from 30° to 180°. With increasing the frequency of scanning the angle of deflection is decreased (this relation is not presented).

Figure 10 shows different stages ("а" - "f") of deflection of laser beam with deflection angle of 180°. On the stage "a" the laser beam is deflected to the right. Subject to the phase of oscillations of the strip resonator 2, the laser beam is continuously deflected, providing the angle of deflection of 180° (position "f"). In comparison with known systems of scanning of laser beam the offered device has ten times higher parameters and allows to have large-angle high deflecting frequency scanning of laser beam, which is enough to create TV and video image and video signal. But the main point is that the offered device is very cheap, and this allows ensuring the mass production and competitive ability of laser projectors on the market of TV equipment and different copying and scanning equipment.

Figure 11 shows variant of the second resonator 2 in form of optical light guide made of elastic material. The second resonator 2 in form of optical light guide made of elastic material located inside or along the first resonator 1, and the fixed end 10 of the optical light guide is connected with the source of radiation 9 (laser or light emitting diode) through the fitting device 11 (fig. 11a). The optical fiber technologies with flat or round section of fiber are used for production of the optical light guide. The light beam from the source of radiation 9 goes to the fixed end 10 of the optical light guide of the second resonator 2 and radiates from its movable end 12 (fig. 11b). Exciting of oscillations of the first resonator 1 resonant oscillations of the second resonator 2 made in form of elastic optical light guide results in oscillations of its movable end 12, deflecting the light beam on fixed angle (as an example figure 11b shows deflection angle of 90°).

This method is directed on creation of the system of line scanning of laser beam and does not consider the frame scanning system, which could be solved by the system of rotating or oscillation mirror on low frequencies from 25 to 100 Hz and not connected with technical difficulties.

It is possible to use the device of deflecting of laser beam, shown in figures 7, 8 and 9 as the system of frame scanning. For this purpose the device of line scanning is coupled with the device of frame scanning. In this case lines of video image should be projected in area of the node of the second resonator with reflecting surface of the device of frame scanning.

However, the offered method allows providing the simple system of frame scanning, using an additional strip resonator. For this purpose the first resonator of line scanning should be fixed on the additional strip resonator of frame scanning.

Figure 12 shows the simplified version of the second resonator in form of optical light guide (A - side view, B - upper view). It is the device of line scanning 15, which includes the hermetic housing 13 with the transparent window 14, the first 1 and the second 2 resonators. The first resonator 1 is made, for example, of piezoceramic tube, inside of which the optical light guide with elastic properties, necessary for oscillations, is installed. The movable end 12 of the light guide works as the second resonator 2. Laser beam passes through the light guide. After exciting of oscillations of the first resonator 1, oscillations of the second resonator 2 in form of movable end of the optical light guide 12 provide the line scanning of laser beam (shown by arrows on B - upper view). The hermetic housing 13provides the necessary vacuum, which excludes air friction for oscillations of the end of light guide 12.

Figure 13 shows the scanner with coupled system of line and frame scanning of laser beam (side view), including the device of line scanning 15, additional strip resonator 16, housing 17, magnetic system 18, coils 18 with core 20, magnet 21, coupling optical unit 22, light guide loop 23. The additional strip resonator 16 is equipped with magnet 21 and fixed on the housing of the scanner 17. Magnetic system 18 includes the coil 19 and core 20. The light guide loop 23 of the optical light guide 12 is connected with the coupling optical unit 22. The light guide loop 23 is necessary for curving of the optical light guide in process of scanner operation. The device of line scanning 15 is installed on the additional strip resonator 16. Since the fixing of device of line scanning 15 is made through the first resonator 1 (fig. 12), the formula of invention states that "the first resonator is installed on the additional strip resonator" without violation of integrity of all items of the formula. Figure 13 shows that the end of the first resonator is installed on the end of the additional strip resonator.

The scanner operates in the following way. The magnetic system 18 influencing magnet 21 excites low frequency oscillations of the additional strip resonator 16 with the device of line scanning 15. Oscillations of the strip resonator 16 determine the angle of frame scanning in vertical direction (shown by arrows in fig. 13b). Simultaneously the device of line scanning 15 provides line scanning of laser beam in horizontal direction. In result the scanner provides both line and frame scanning of laser beam. The advantage of the offered scanner is the complete absence of mirror systems, which are used in systems of frame and line scanning of laser beam. It is necessary to note that the features of operation of this scanner require the special electronic processing of standard video signal for its adaptation to the offered system of frame and line scanning.

The offered method and device applied not only for projection of TV image by laser beam, but for recording of video signal in process of scanning of area by laser beam with the system of line and frame scanning. For this purpose it is enough to equip the system of scanning by the simplest photo-receiver, for example, by photo-diode. In this case the system could be used as video camera for recording of video signal. Such system does not require additional illumination of an object, and in case of the use of semiconductor infrared laser it will find wide application in security and other systems of control.

That is why the offered method and device could be used not only in projection of TV image by laser beam, but for recording of video signal during scanning of space by laser beam with systems of line and frame scanning. It is enough to equip the system of scanning by the simple photo receiver, in particular, by photodiode. In this case the system could be used as video camera for recording of video signal. Such system does not require the additional illumination of an object, and with use of semiconductor infrared lasers could be widely applied in security systems and other systems of observation.

Industrial applicability

The use of the offered technical solution will allow producing cheap color TV laser projectors both for flat and for volume (stereoscopic), and in future holographic television. The laser projector is characterized by highest quality of image, brightness and color saturation of an image, being the home cinema. Furthermore, this technical solution could be used for projection of images on advertising panels, for presentations, in show business, in security and other systems.

Literature:

1. Pyasetsky V. V. Color television in questions and answers. Minsk, Polymya, 1884, fig. V.1.

2. Certificate of authorship No 1756853, G 02 F 1/29. Magneto-electrical deflector. Bull. No 31, 23.08.92.

3. Viktorov I. A. Sound surface waves in solid media. M., 1981.

Claims

1. The method of large-angle high deflecting frequency scanning of laser beam for transmission and receiving video and other images, which includes the influence of deflecting system on laser beam in the mode of wave exciting of oscillating medium, discrepant by the fact that there are used linearly extended media with gradient density of substance in the mode of resonant exciting, principally two coupled oscillating linearly extended media with different linear density of substance in the mode of resonant exciting of transverse oscillations of simultaneously two media, and the mode of resonant matching of transverse oscillations of two media is established from relation between wave-length of oscillations of linearly extended media and their linear densities of substances:

2. The device for realization of the method, described in paragraph 1, which includes the system of deflection of laser beam, discrepant by the fact that the laser beam deflecting system contains two linear, mechanically coupled strip resonators, the first of which is equipped by the exciter of oscillations and made in form of plate, on the edge of which there is fixed the second resonator made in form of thin elastic strip with the length proportional to resonant exciting wavelength l₂ or 1/4 l₂, 3/4 l₂, and the device is equipped with appliance for adjustment of coordinate of location of the second resonator in the zone of propagation and deflection of laser beam.

3.The device according to item 2, which is distinguished by the fact that the second resonator is made of elastic material in form of optical light guide, which passes along or inside of the first resonator, the fixed end of the optical light guide is connected with the source of radiation (laser or light emitting diode) and the first resonator is installed on the additional strip resonator.

Abstract

There are offered the method and the device for large-angle high deflecting frequency scanning of laser beam for transmission and receiving video and other images, which are realized in result of the use principally two series-connected oscillating linearly extended media with different linear density of substance, deflecting the laser beam, in the mode of resonant exciting of transverse oscillations.

The invention could be used for large-angle high deflecting frequency scanning of laser beam in laser TV and video projectors and video cameras, in laser copying and scanning equipment, in security and measurement laser systems, laser systems of observation, as well as in other laser systems. Simplicity of the invention allows significantly decrease cost of production of laser projection and scanning systems, and it makes them available for mass production.

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