WO2008048145A1 - Wide-screen laser beam sweeping method and device - Google Patents

Abstract

The invention relates to the wide-screen and high-speed laser beam sweeping method and device used for transmitting and receiving video and other images, which are produced by using, in a resonance activation mode, transverse oscillations, substantially two subsequently coupled oscillating linearly extended media having different linear density of a substance, for deflecting a laser beam. Said invention can be used for wide-screen and high-speed laser beam sweeping in laser TV and video projectors and video cameras, in laser copying and scanning devices, in security, measuring, monitoring and other laser systems. The simplicity of the invention makes it possible to substantially reduce the production cost of laser projection, copying and scanning systems, thereby making it possible to organise the mass production thereof.

Description

 METHOD AND DEVICE OF A WIDE-FORMAT SCAN OF A LASER BEAM

FIELD OF THE INVENTION

The invention relates to laser technology and is intended for large-format and high-speed scanning of the laser beam in laser television and video projectors and video cameras for transmitting and receiving flat and three-dimensional video images, and can also be used in laser copying and scanning equipment for transmitting and receiving images, for scanning space in security, measuring laser systems, laser surveillance systems, including in the infrared spectrum, as well as in other laser systems. The simplicity of the invention allows to significantly reduce the cost of manufacturing laser scanning systems, which makes them available for mass production.

State of the art

There is a method of large-format and high-speed scanning of an electron beam in color television picture tubes with a horizontal scanning frequency of 15625 Hz and a scanning angle of 110 ° (V.V. Pyasetskiy. Color television in questions and answers. Minsk, Polymya, 1994, Fig. V.l). However, the electron beam deflection system is not suitable for scanning a laser beam.

A known method and device for deflecting a light beam using an oscillating mirror with a magnetoelectric drive (A.S. N ° 1756853, G 02 F 1/29. Magnetoelectric deflector. Bull. N ° 31, 08.23.92.) The disadvantage of this method of deflecting light beam is a sharp decrease in the scan angle with increasing frequency, which makes it impossible to use this method in devices for large-format and high-speed scanning of the laser beam in television projectors.

Surface acoustic waves (SAWs) in solids are known (IA Viktorov. Sound surface waves in solids. M., 1981).

Surface acoustic waves in the mode of wave excitation of the surface of an oscillating medium are capable, when exposed to a laser beam, of deflecting it at high frequencies (ultrasonic and

SUBSTITUTE SHEET (RULE 26) hypersonic). The disadvantage of using surface acoustic waves in deflecting systems of the laser beam is the small deflection angle, insufficient to obtain a widescreen television image.

SUMMARY OF THE INVENTION The technical solution to which the invention is directed is to create effective conditions for wave excitation of an oscillating medium sufficient for large-format and high-speed scanning of a laser beam in television and video projectors and video cameras, as well as in all kinds of copying and scanning systems. The implementation of the invention allows simple and cheap technical solutions to provide large-format and high-speed scanning of the laser beam in television and video projectors and video cameras, as well as in all kinds of copying and scanning systems.

The term “laser beam” used earlier and further in the text is used as a broader concept and includes laser radiation, as well as LED and other types of light radiation, since the proposed method and device provide wide-format and high-speed scanning of any light beam generated as a result of focusing and / or iris any divergent light radiation. Disclosure of invention

The specified technical result is achieved by the fact that in the method of large-format high-speed scanning of the laser beam by exposing the laser beam to a deflecting system in the mode of wave excitation of an oscillating medium with a gradient linear density of matter, two sequentially coupled oscillating linearly extended media with different linear density of matter are mainly used in the mode resonant excitation of transverse vibrations of two media simultaneously, and the mode of resonant matching echnyh oscillations between two media is set from the condition relations between the oscillation wavelength of the linear media and their linear density substances:

τl where λι is the wavelength of the excitation of the medium with a higher linear density of matter τi in kg / m; λ ₂ - the wavelength of the excitation of the medium with a smaller linear SUBSTITUTE SHEET (RULE 26) the density of the substance τ ₂ in kg / m; k is a coefficient taking into account the difference in bulk density of the substance of media with different elasticities.

The specified technical result is achieved by the fact that in the device for implementing this method the deflecting system of the laser beam contains two linear mechanically conjugated strip resonators, the first resonator being equipped with an exciter and made in the form of a plate, at the end of which a second resonator is mounted, made in the form of a thin elastic strip length commensurate with the multiplicity of the resonant excitation wave λ ₂ or with ^ι Aλ2,% λg, and the whole device is additionally equipped with a device for adjusting the coordinate p the position of the second resonator in the zone of passage and deviation of the laser beam.

Brief Description of Drawings

In FIG. 1 shows a conjugation scheme of two linearly extended media 1 and 2 with different linear density of a substance with a pathogen 3 of transverse vibrations.

In FIG. 2 is a diagram of amplification of the amplitude A _{2 of} transverse vibrations in the mode of resonant excitation of a linearly extended medium with a lower linear density of the substance.

In FIG. Figure 3 presents a picture of the excitation of vibrations of a linearly extended medium with a gradient density of matter along the length and amplification of the oscillation amplitude at the end (tail) of the resonator.

In FIG. 4 is a diagram of amplification of the amplitude A _{2 of} transverse vibrations of a linearly extended medium in a volume.

In FIG. 5 shows the combination of transverse vibrations of linearly extended media in antiphase in volume.

In fig. 6 is a diagram of the device with the second strip resonator 2 fastened at the end of the first strip resonator 1 in the form of a thin elastic strip with a length commensurate with the multiplicity of the resonance excitation wave λ ₂ (full wave resonator). In fig. 7 is a diagram of a device with fastening at the end of the first strip resonator 1 of the second strip resonator 2 in the form of a thin elastic strip commensurate with 3/4 λ ₂ (three-quarter-wave resonator).

SUBSTITUTE SHEET (RULE 26) In fig. 8 is a diagram of a device with a second elastic strip resonator 2 mounted at the end of the first strip resonator 1 in the form of a thin elastic strip commensurate with 1/4 λ ₂ (quarter-wave resonator).

In fig. 9 is a schematic cross-sectional view of an apparatus for wide-format high-speed scanning of a laser beam.

In fig. 10 shows the various stages of deflection of a laser beam at a sweep angle of 180 °.

In FIG. 11 shows a second resonator in the form of an optical waveguide. In FIG. 12 shows a lightweight embodiment of the second resonator in the form of an optical waveguide.

In FIG. 13 shows a scanner with a combination of horizontal and vertical scanning of a laser beam.

The implementation of the invention In order to justify the proposed method, the following are the necessary explanations and description of the method and device widescreen high-speed scanning of the laser beam.

The proposed scanning method is based on the effect of amplifying the amplitude of oscillations in linearly extended media with a gradient density of a substance along the length in the mode of resonant excitation of transverse vibrations. Most simply, this method can be commented on as an example when the gradient density of a substance changes abruptly at the interface between two media with different linear densities of the substance. This physical effect was discovered by V.S. Leonov in 1986 in the study of oscillations of conjugate linearly extended media. The simplest example of a linearly extended medium is a narrow and thin strip of matter. Upon excitation of vibrations of such a strip at a resonant frequency, we obtain a strip resonator, characterized by the frequency, amplitude and wavelength of the oscillations, as well as the number of waves that fit on the length of the strip resonator in the standing wave mode.

The advantage of strip resonators compared to the effects of surface acoustic waves (SAWs) in solids is to obtain a significantly larger amplitude of oscillations. Can be considered

SUBSTITUTE SHEET (RULE 26) strip resonators as an element of a surface wave, when the surface is separated from a large volume of a solid, amplifying the amplitude of oscillations.

But this method uses the effect of an even more significant amplification of the amplitude of the vibrations due to the conjugation of two linearly extended media with different linear density of the substance in the mode of resonant excitation of transverse vibrations. In FIG. 1 shows a conjugation scheme of two linearly extended media 1 and 2 with different linear density of a substance with a pathogen 3 of transverse vibrations. By the linear density τ of the substance is meant the distribution of the mass of the substance along the length of the strip resonator, which is measured in kg / m, in contrast to the bulk density of the substance, measured in kg / m ³ .

To understand the physical nature of amplification of the amplitude of vibrations in conjugate linearly extended media, we consider the simplest case of resonant excitation of transverse vibrations in two conjugate strip resonators made in the form of plates and strips of material. Even with the same bulk density of the substance, the plates and strips of the same width, but of different thicknesses, have different linear densities of the substance (Fig. 1). A thicker plate 1 has a higher linear density T ₁ , compared with a linear density τ _{2 of} a thinner strip 2. Plate 1 and strip 2 are linear media with different substance densities τ _! > τ ₂ , which changes abruptly at the interface between the media, providing a linear density gradient.

The causative agent of transverse vibrations 3 (Fig. 1) in the mode of resonant excitation of the plate 1 brings it into an vibrational state represented by a standing wave with a length λi and an amplitude of oscillations Ai. In order to excite transverse vibrations in a thin strip 2, it is necessary to select the mode of its resonant excitation. In the absence of such a regime, transverse vibrations of the strip 2 are not observed. The selection of the resonant excitation mode is carried out by establishing the strict length of the strip 2, which is established from the condition of the relations between the wavelength λi and λ _{2 of the} oscillations of linear media and their linear density τi and% g of substance:

τl

SUBSTITUTE SHEET (RULE 26) In this case, an integer number of waves fit along the length of the strip resonator, and the media consistently enter the resonant excitation of the standing wave, forming nodes 3 and antinodes 4 (Fig. 2). The presence of antinodes 4 determines the amplitude of the oscillations A ₂ . If the media have different bulk density of the substance with different elasticities, then in the mathematical formula this is taken into account by the coefficient k.

In the mode of resonant excitation of two conjugate linearly extended media, the amplitude A _{2 of the} oscillations of the medium with a lower linear density of the substance increases sharply compared to the amplitude A ₁ (Fig. 2). This is explained by the fact that a large linear density of a substance with a larger mass represented by a plate 1 transmits a strong pulse to a thin strip 2 with a lower mass, sharply increasing the amplitude of its vibrations (whip effect).

A similar resonator can be called up in a continuous medium, but with a linear density gradient of the substance along the length of the type of fish tail (fins), when the wave vibrations of the whole body lead to an increase in the amplitude of the tail vibrations (Fig. 3). However, the advantage is given to the effect of amplification of the amplitude of the oscillations with an abrupt change in the linear density of the medium at the interface between two media.

For clarity, the amplification effect of the amplitude A _{2 of} transverse vibrations of a linearly extended medium in the volume is shown in FIG. 4, and in FIG. 5 shows the combination of transverse vibrations of linearly extended media in antiphase, determining the angle of rotation of the plane of the strip 2 in node 3 and the strong deformation of the medium in antinodes 4.

Having large amplitudes of oscillations of a linearly extended medium in the region of sound frequencies up to 20 kHz, various devices for wide-format high-speed scanning of a laser beam can be realized. The proposed scanning method can be used both when a laser beam passes in a zone of strong deformation of the substance at antinodes 4 and when a laser beam is reflected in a node 3. In the first case, a linearly extended medium 2 must be optically transparent and the angle of refraction of the beam will be determined by the conditions of medium deformation when its refractive index changes. In the second case, the linear medium 2 should have the properties of reflection of the laser beam.

It is this case for the regime of total reflection of the laser beam that was considered in

SUBSTITUTE SHEET (RULE 26) as an example of the implementation of this method of widescreen high-speed scan.

But before describing a specific device for implementing this scan method, it is necessary to dwell on its distinguishing features. Naturally, the device of FIG. 1, was necessary to explain the physical processes underlying this method. It is important that the device that implements this method contains two linear mechanically conjugated strip resonators. In a real device, everything is going to simplify it. To do this, it is enough to cause resonant longitudinal vibrations of the first strip resonator.

In FIG. 6 is a diagram of a device with fastening in zone 5 at the end of the first strip resonator 1 of the second strip resonator 2 in the form of a thin elastic strip with a length commensurate with the multiplicity of the resonant excitation wave λ ₂ (full-wave resonator). As the first strip resonator 1, a piezoceramic plate or tube can be used. Since the oscillation amplitude of the piezoceramic plate is negligible, this is not shown in FIG. 6. In addition to the full-wave strip resonator, a three-quarter-wave or quarter-wave resonator can be used.

In FIG. 7 is a diagram of a device with fastening at the end of the first strip resonator 1 of the second strip resonator 2 in the form of a thin elastic strip commensurate with 3/4 λ ₂ (three-quarter-wave resonator).

In FIG. 8 is a diagram of a device with a second elastic strip resonator 2 mounted at the end of the first strip resonator 1 in the form of a thin elastic strip commensurate with 1/4 λ ₂ (quarter-wave resonator). As the first strip resonator 1 can be used a steel plate with an external electromagnetic (electrodynamic) exciter 6 oscillations installed in the housing 7 of the device.

The use of full-wave, three-quarter-wave and quarter-wave strip resonators was reflected in the claims on the device. You can use, but not so efficiently, half-wave resonators. It is the presence of a full-wave, three-quarter-wave, and quarter-wave strip resonators that provides effective matching of the first and second resonators in the mode of full resonance of oscillations. Since the resonance curve is

SUBSTITUTE SHEET (RULE 26) bell shape, then resonance, but with a smaller amplitude, occurs already when approaching the regime of full-wave, three-quarter-wave and quarter-wave resonance. In the claims, this is reflected by the word “suitably”, that is, the second resonator, made in the form of a thin elastic strip with a length of “suitably” commensurate with the multiplicity of the resonant excitation wave λ ₂ or with 1/4 λ ₂ , 3/4 λ ₂ . But the maximum effect is manifested in the mode of precise resonance.

The following is a description of a device that implements a method for widescreen high-speed scanning of a laser beam (Fig. 9). The device for large-format high-speed scanning of the laser beam includes two strip resonators 1 and 2, an external vibration exciter 6, a housing 7, a device 8 for adjusting the coordinate of the second resonator in the zone of passage and deflection of the laser beam, a semiconductor laser 9. The strip resonator 1 is made in the form of a plate, at the end of which a second resonator 2 is fixed, made in the form of a thin elastic strip with a length commensurate with the multiplicity of the resonant excitation wave λ ₂ or with 1/4 λ ₂ , 3/4 λ ₂ . In this case, the drawing shows a three-quarter-wave (3/4 λ ₂ ) resonator 2. The second resonator 2 may be made of a completely light-reflecting material or may be provided with a reflective coating. The mount 5 should provide a tight contact connection of the resonators 1 and 2. The installation of the laser beam 9 in the region of the node 3 of the second resonator 2 is carried out by the device 8 (micrometer screw). In order for the laser 9 not to interfere with the scanning of the beam, the optical axis of the laser is installed at an angle to the plane of the second resonator 2 (section BB, Fig. 9).

The device operates a large-format high-speed scan of the laser beam as follows. The causative agent of oscillations 6 (in this case, external, but may also be internal) causes resonant transverse vibrations of the first strip resonator 1. The oscillations of the first resonator 1 are transmitted to the second strip resonator 2 in the resonance mode and increase the amplitude of the oscillations of the second resonator. The laser beam is fed into the region of the node 3 of the second resonator 2 and is reflected from its surface. Oscillations of the surface of the second strip resonator 2 relative to the region of the node 3 provide a wide-format and high-speed scan SUBSTITUTE SHEET (RULE 26) a laser beam at frequencies up to 20 kHz or more with a deflection angle of 30..180 °. With an increase in the sweep frequency, the beam deflection angle decreases (this dependence is not shown).

In fig. 10 shows the various steps (“a” to “f”) of deflecting a laser beam at a sweep angle of 180 °. In step a, the laser beam is deflected to the right. Depending on the phase of oscillation of the strip resonator 3, the laser beam is continuously deflected, providing a sweep angle of 180 ° (position "f"). Compared with the known laser beam scanning systems, the proposed device has parameters an order of magnitude higher and allows providing a wide-format and high-speed scanning of the laser beam, sufficient for the formation of television and video images and video signals. But most importantly, the proposed device is very cheap, which will ensure the mass and competitiveness of laser projectors in the television market and all kinds of copying and scanning laser devices.

In FIG. 11 shows the implementation of the second resonator 2 in the form of an optical fiber of elastic material. The second resonator 2, made in the form of an optical fiber of elastic material, extends along or inside the first resonator 1, and the fixed end 10 of the optical waveguide is connected to the radiation source 9 (laser or LED) through the docking unit 11 (Fig. Ha). In the manufacture of an optical fiber, fiber-optic technologies with a flat or round cross-section of the fiber are mainly used. The light beam from the radiation source 9 enters the fixed end 10 of the optical fiber of the second resonator 2 and leaves its movable end 12 (Fig. Hb). When the oscillations of the first resonator 1 are excited, the resonant oscillations of the second resonator 2, made in the form of an optical fiber from an elastic material, lead to vibrations of its movable end 12, turning the light beam at a certain angle (as an example in Fig. 1 Ib, the beam scan angle is shown in 90 °). The proposed method is aimed at creating a horizontal scan of the laser beam and provides for the subsequent frame scan of the visible image, which is solved, for example, by additional installation of a rotating or oscillating mirror system at low frequencies of 25 ... 100 Hz, without presenting a technical difficulty. As a frame sweep, a SUBSTITUTE SHEET may (RULE 26) the laser beam scanner shown in FIG. 7, 8, 9. For this, the horizontal scanning device interfaces with the vertical scanning device. In this case, the prescribed lines of the video image should be projected into the region of the node of the second resonator with the reflecting surface of the frame scanning device.

However, the proposed method allows using an additional strip resonator to provide a simple frame scan. For this, the first horizontal resonator is mounted on an additional strip resonator frame scan. In FIG. 12 shows a lightweight implementation of the second resonator in the form of an optical waveguide (A is a side view, B is a top view) and is a horizontal scanning device 15, including a sealed enclosure 13 with a transparent window 14, the first 1 and second 2 resonators. The first resonator 1 is made, for example, of a piezoceramic tube, inside which passes an optical fiber having certain elastic properties necessary to ensure oscillations. The movable end 12 of the fiber acts as a second resonator 2. The laser beam is introduced through the optical fiber, and when the oscillations of the first resonator 1 are excited, the vibrations of the second resonator 2 in the form of the movable end of the optical fiber 12 produce a horizontal scan of the laser beam (shown by arrows in B - top view ) The sealed housing 13 provides the necessary vacuum, eliminating the air resistance during vibrations of the end 12 of the fiber.

In FIG. 13 shows a scanner with a combination of horizontal and vertical scanning of a laser beam (side view), including a horizontal scanning device 15, an additional strip resonator 16, a housing 17, a magnetic system 18, windings 19 with a core 20, magnet 21, a docking optical assembly 22, and a waveguide loop 23. An additional strip resonator 16 is provided with a magnet 21 and the end is fixed in the housing 17 of the scanner. The magnetic system 18 includes a winding 19 and a core 20. The waveguide loop 23 of the optical fiber 12 is connected to the docking optical node 22. The waveguide loop 23 is necessary for bending the optical fiber during the operation of the scanner. The horizontal scanning device 15 is mounted on an additional strip resonator 16. Since the horizontal scanning device 15 is mounted through the first resonator 1 (Fig. 12), then in the formula REPLACEMENT SHEET (RULE 26) inventions noted that the "first resonator is mounted on an additional strip resonator", without violating the unity of all claims. In FIG. 13 shows that the end of the first resonator is mounted at the end of an additional strip resonator. The scanner works as follows. The magnetic system 18 acting on the magnet 21, excites low-frequency vibrations of the additional strip resonator 16, on which the horizontal scanning device 15 is mounted. The oscillations of the strip resonator 16 determine the vertical scanning angle (shown by arrows in Fig. LЗb). At the same time, the horizontal scanning device 15 provides horizontal scanning of the laser beam. As a result of the scanner, line and frame scanning of the laser beam is provided. The advantage of the proposed scanner is the complete absence of mirror systems that are used in systems of vertical and horizontal scanning of the laser beam. It should be noted that the features of this scanner require special electronic processing of a standard video signal to adapt it to the proposed horizontal and frame scanning system.

The proposed method and device can be used not only for projecting a television image using a laser beam, but also for recording a video signal when scanning a space with a laser beam equipped with a horizontal and vertical scanning system. To do this, it is enough to equip the scanning system with the simplest photodetector, for example, a photodiode. In this case, the system can be used as a video camera to record a video signal. Such a system does not require additional illumination of the object and, when using semiconductor infrared lasers, will find wide application in security and other surveillance systems.

Industrial applicability

Using the proposed technical solution provides the creation of cheap color television laser projectors, both for flat and surround (stereoscopic, and in the future - holographic) television. The laser projector is characterized by the highest image quality, brightness and color gamut of the picture, representing a home theater. In addition, this technical solution will find application for projecting images on advertising SUBSTITUTE SHEET (RULE 26) billboards, during presentations, in show business, in security and other systems.

Literature: 1. Pyasetskiy VV Color TV in questions and answers. Minsk, Polymya, 1994, Fig. V.1.

2. A.S. N ° 1756853, G 02 F 1/29. Magnetoelectric deflector. Bull. JCH ° 31, 08/23/92.

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

SUBSTITUTE SHEET (RULE 26)

Claims

Claim 1. A method for wide-format high-speed scanning of a laser beam for transmitting and receiving video and other images, including exposure to a laser beam of a deflecting system in the mode of wave excitation of an oscillating medium, characterized in that linearly extended media with a gradient density of matter in the mode of resonant excitation are used, mainly two sequentially coupled oscillating linearly extended media with different linear density of matter in the mode of resonant excitation of transverse natural oscillations simultaneously two media, the matching of resonant mode transverse vibrations of the two media is set from the condition relations between the oscillation wavelength of the linear media and their linear density substances: λ ₂ = λ _! ^ -k, τi where λ ₁ is the wavelength of the excitation of the medium with a higher linear density of the substance T ₁ in kg / m; λ ₂ is the wavelength of the excitation of the medium with a lower linear density of the substance τ ₂ in kg / m; k is a coefficient taking into account the difference in bulk density of the substance of media with different elasticities. 2. The device for implementing the method according to claim 1, comprising a deflecting system of the laser beam, characterized in that the deflecting system of the laser beam contains two linear mechanically conjugated strip resonators, the first resonator being equipped with a vibration exciter and made in the form of a plate, at the end of which a second a resonator made in the form of a thin elastic strip with a length predominantly commensurate with the multiplicity of the resonant excitation wave λ ₂ or with 1/4 λ ₂ , 3/4 λ ₂ , and the entire device is additionally equipped with a device by adjusting the coordinates of the location of the second resonator in the zone of passage and deflection of the laser beam. 3. The device according to claim 2, characterized in that the second resonator is made in the form of an optical fiber of elastic material extending along or inside the first resonator, the fixed end of the optical waveguide being connected to a radiation source (laser or LED), and the first resonator mounted on additional strip resonator. SUBSTITUTE SHEET (RULE 26)