RU2082994C1 - Device for recording large-size holograms - Google Patents

Abstract

FIELD: holography. SUBSTANCE: device recording large-size holograms includes source of coherent radiation, holographic interferometer which reference and object arms are optically coupled to registering medium deposited on photoplate. Photoregistration unit and former of controlling signals of device are manufactured in the form of two channels. Each channel has lens mounted between photoregistration unit and registering medium. Lens in first channel is put behind first region of registering medium and lens in second channel is placed behind second region of registering medium which does not cross with first one. Comparator, electron key and phase shifter are installed additionally. Formers of controlling signals of first and second channels are additionally provided with one synchronous amplifier each. EFFECT: simplified design, enhanced operational reliability. 2 cl, 3 dwg

Description

 The invention relates to holography, in particular to devices for producing holograms and can be used to create large format holographic optical elements (GOEs) (holographic diffraction gratings, zone plates, beam splitters, aberration correctors, and others) used in precision optical devices [1, 2] and also for recording large-sized graphic holograms. When creating such holograms, there are two problems limiting the obtaining of large dimensions and high accuracy of parameters: 1, the need to form sufficiently powerful noiseless coherent beams that provide high (10-100 J) photolayer illumination energy with high reproducibility of their spatial and energy parameters; 2 the need to obtain a given interference field (IP) on large diameter photographic plates (> 0.2 m) with high stability of its position in space (of the order of 0.01-0.1 μm) during the exposure time (tens of minutes). The use of pulsed lasers allows us to solve the latter problem, however, significant technical difficulties arise in the implementation of the former. Therefore, methods for recording large-sized holograms using continuous-wave lasers using methods of active stabilization of the phase difference of the recording waves (or the relative phase of the PI) on a photographic plate are most widely used. Active stabilization of an IP is based on automatic compensation of random phase disturbances using a negative feedback circuit consisting of an electronic amplifier and a phase-shifting element mounted in the support arm of a holographic interferometer [3] The working signal is usually the values indirectly associated with the IP bias, generated by using an additional interferometer [3] projection microscope [3] auxiliary GOE [4] However, in the case of recording large-sized holograms, the use of such methods is ok little use is called as auxiliary elements have large dimensions and make a significant own phase noise, which leads to the formation of false correction signals.

 A device for recording large-sized holograms is known, in which a self-diffraction method is used for recording and reading by exposure beams by the exposure beams [5]. The device consists of a coherent radiation source, a holographic interferometer, in which an objective beam is formed in one shoulder, and reference beams installed in the other the supporting arm of the phase-shifting device connected to the sinusoidal signal generator, a photographic plate with a recording medium having the property of self-diffraction by exposure to radiation, placed behind the photographic medium unit connected to the control signal generator, whose output is connected to the other phase shifter, established in the object arm of the interferometer.

 In this device, the role of the auxiliary hologram is played by the primary holographic structure (or so-called latent image) that occurs at the time of recording in the phase recording medium, on which the beams are defracted due to the phenomenon of self-diffraction. As a result of the interaction of the reference and object beams with each other and with the latent image recorded by them, the light intensity behind the recording medium received by the photographic registration unit depends on the phase relations between the reference and object beams. A random change in the phase difference between the reference and object beams (phase noise) leads to a change in the intensity of light received by the photodetectors of the photographic registration unit, and therefore to a change in the electrical signal at its output. To increase the sensitivity of determining phase noise, a compulsory, small in magnitude modulation of the phase difference Φ of the reference and object beams and registration of the signal at the modulation frequency are used. Forced modulation of the value of F is carried out using a phase-shifting device controlled by a sinusoidal signal generator. Registration and amplification of the electrical signal at the modulation frequency and generation of the development signal is performed in the driver of the control signal. The shaper includes a resonant amplifier and a synchronous detector, the signal from which is supplied to the phase-shifting element to compensate for the initial phase noise. The disadvantage of this device is a narrow scope limited by phase recording media and low stability of the interference field due to the low level of the self-diffraction signal compared to the noise level.

 The closest technical solution that we have chosen as a prototype is a device for recording large-sized holograms [6] consisting of a coherent radiation source, a holographic interferometer, the reference and object arms of which are optically coupled to a recording medium deposited on a photographic plate, which has the property of self-diffraction under the influence of radiation, installed behind the medium of the photoregistration unit connected to the driver of the control signal, two phase shifting devices, one of which is is dined with the output of the sinusoidal signal generator, and the other with the control signal generator, made in the form of a series-connected algebraic adder and a synchronous amplifier.

 In this device, stabilization of the position of the interference field relative to the recorded primary holographic structure (ASO) becomes possible not only for the phase, but for the amplitude and amplitude-phase recording medium. The use of two photodetectors in the photographic recording unit and an algebraic adder in the control unit made it possible to increase the sensitivity of the system and record holograms in any recording media.

 The disadvantages of this device are its complexity, the lack of direct quality control of the recorded hologram and the poor quality of phase correction. The low quality of the correction is due to the small ratio of the magnitude of the control signal to the noise, which leads to a low quality of the hologram. The increased complexity of the device in question is associated with the fact that in the case of recording large-sized holograms, the phase noise dF is different at different points of the photographic plate, therefore, in the absence of recording quality control, it becomes necessary to use multi-element large-sized photodetector arrays coupled to complex multi-element phase correctors. A decrease in the magnitude of the control signal (self-diffraction signal) is associated with a decrease in the power density of the detected beams as the dimensions of the photographic plate grow at a fixed laser power. The increase in noise in such a device is due to the appearance of additional phase noise associated with the interaction of the elements of a multi-element phase corrector.

 The technical effect of the device we have proposed is to improve the quality of large-sized holograms. The device is quite simple to manufacture, does not require the use of multi-element phase correctors and photodiode arrays, allows you to record high-quality holograms with an effective diameter of up to 1.5 m using serial continuous-wave lasers in a standard holographic laboratory.

 The technical effect is achieved by the fact that the device is made in the form of an interferometer for recording holograms combined with a tracking system for recording quality and a phase correction system in which phase noise is compensated by two simple single-element phase-shifting devices, one of which eliminates the phase noise component that is inhomogeneous over the hologram field .

 In the study, we showed that the self-diffraction signal at the output of the algebraic adder, measured at the modulation frequency W (or at a frequency of 2Ω), can be used to control the quality of the amplitude-phase holographic structure during exposure when the phase (or amplitude) components dominate in it. The measurements of the quality of the holographic structure in real time at different points (regions) of a horizontally and vertically mounted large-sized photographic plate showed that to obtain high-quality holograms, it is sufficient to use only two regions of the recording medium necessary for reading self-diffraction signals. Studies of the dependence of the magnitude of these signals on the parameters of the medium and the electronic circuit allowed us to create a simple device with technical characteristics that ensure the achievement of the specified technical effect.

 In FIG. 1 shows a block diagram of the proposed device. A device for recording large-sized holograms contains a coherent radiation source 1, a translucent mirror 2, “blind” mirrors 3, 4 and 5, one of which 3 is mounted on a magnetostrictive element and forms the first phase-shifting device, the other 4 and 5 are mounted on piezoelectric elements and form the second and a third phase-shifting device, respectively lenses 6, forming the reference and object beams of the desired configuration, a sinusoidal signal generator 7, a recording medium 8, lenses 9, focusing the radiation on the photographic registration unit 10, driver 11 control signals, comparator 12, electronic key 13.

 In FIG. Figure 2 shows the dependence of the control signal on the exposure time at the output of an additional synchronous amplifier installed in the first (solid curves) and second (dashed curves) channel with the device turned off (curves 1 and 1 '), with a single-channel (curves 2 and 2') and two-channel (curves 3 and 3 ') operating mode of the device.

 In FIG. 3 shows an example of a specific embodiment of a device for recording large-sized holograms on a vertically mounted photographic plate. The size of the areas of the recording mediums 1 and 11 is regulated using apertures 14, photodetectors 15 make up a photographic recording unit, adders 16 and synchronous amplifiers 17, 18, 19 and 20 make up a control signal generator, two outputs of which are connected to a comparator 12, the output of which is connected to an electronic key 13.

 The device operates as follows.

The light beam from the coherent radiation source 1 is divided by a translucent mirror 2 into two beams, one of which (reference) is sent to the photographic plate 8 using the lens 6 and the phase shifting device 5. The other beam (object) passes through the phase shifting device 3, the lens 6, the phase shifting device 4 and also sent to a photographic plate on which there is a layer of a holographic recording medium. The interference field (IP) arising from the interference of the reference and object beams is recorded on the photographic plate as a primary holographic structure. As a result of self-diffraction, the reference and object beams that have passed through the recording medium contain information both about the nature of the ASG and its random displacements relative to the IS. To read this information, two lenses 9 are installed behind the photographic plate, focusing the light on the photodetectors of the two-channel photographic recording unit 10, the output of which is connected to a two-channel control signal generator 11, which consists of algebraic adders connected to synchronous amplifiers. At the output of the photoregistration unit of each channel, the photocurrent has harmonic components at frequencies of 0, W, 2Ω, etc. at the output of the algebraic adder in each channel, depending on the type of recording medium, a total U ⁺ or difference U ^- signal ^is generated at the indicated harmonics. It is known that when the amplitude (phase) component of the amplitude-phase ASG dominates, the signal U _Ω + (U _2Ω -) is used to form the control signal for the phase corrector. Therefore, if a recording medium with a predominantly amplitude ASG is used, then in each channel one of the synchronous amplifiers is tuned to the frequency W and a control signal U _Ω + proportional to the phase noise dF is removed at its output. In the case of a predominantly phase ASG, these amplifiers are tuned to a frequency of 2Ω and the signal U _2Ω -, also proportional to dF, is removed at their output.

Our studies have shown that in the case of a predominantly amplitude ASG, the value of (U _2Ω +) ^{2 is} proportional to the diffraction efficiency h, which is a measure of the quality of the hologram. In the case of a predominantly phase hologram, such a quantity proportional to h is (U _Ω -) ² .

, то в качестве опорного используется сигнал контроля основного канала, сопряженного с областью регистрирующей среды, в которой качество ПГС не хуже допустимого η≥η_o, где η_o требуемое значение дифракционной эффективности ПГС). Если сигнал контроля второго канала меньше, чем величина сигнала контроля первого канала, то на выходе компаратора вырабатывается сигнал, который, поступая на управляющий вход электронного ключа 13, открывает его. Сигнал управления со второго фазового усилителя основного канала поступает на фазосдвигающее устройство 4, которое компенсирует однородно распределенную по полю фотопластинки фазовую помеху. Сигнал управления со второго фазового усилителя второго канала поступает на второй вход электронного ключа. В случае, когда ключ открыт, сигнал с его выхода поступает на фазосдвигающее устройство 5, которое компенсирует неоднородно распределенную помеху по полю фотопластины. Таким образом, с помощью двухканального фазового корректора, сопряженного с двумя областями регистрирующей среды, можно скомпенсировать помеху и записать качественную голограмму. Выбор числа требуемых областей, их размер и местоположение на пластине определялся исходя из теоретического анализа и измерения сигналов контроля.Measurement of the indicated values made it possible, firstly, to carry out operational control of the recording quality at each point of the photographic plate, thereby determining the distribution of dF over the hologram field and identifying the minimum number of channels sufficient to effectively compensate for dF, and secondly, to actively influence the phase correction process precisely in those areas of the photographic plate where the value of h is less than permissible. To do this, in each channel, an additional synchronous amplifier is installed, tuned to a frequency of 2Ω, if the ASG is mainly amplitude, or to the frequency W, if the ASG is mainly phase. The control signals from these amplifiers are fed to a comparator 12, in which the control signal is compared with the reference (permissible) value. Since the values of the control signals monotonically increase during exposure time as a function of

, then the control signal of the main channel, coupled with the region of the recording medium, in which the quality of the CBC is not worse than the permissible η≥η _o , where η _{o the} required value of the diffraction efficiency of the CBC), is used as a reference. If the control signal of the second channel is less than the value of the control signal of the first channel, then a signal is generated at the output of the comparator, which, entering the control input of the electronic key 13, opens it. The control signal from the second phase amplifier of the main channel is fed to the phase-shifting device 4, which compensates for phase noise uniformly distributed over the field of the photographic plate. The control signal from the second phase amplifier of the second channel is fed to the second input of the electronic key. In the case when the key is open, the signal from its output is fed to the phase-shifting device 5, which compensates for the nonuniformly distributed noise along the field of the photographic plate. Thus, using a two-channel phase corrector coupled to two regions of the recording medium, it is possible to compensate for the noise and record a high-quality hologram. The choice of the number of required areas, their size and location on the plate was determined on the basis of theoretical analysis and measurement of control signals.

,
где R₀ и S₀ амплитуда опорной R и объектной S волн;
Φ(X₂, Y₂, t) заданная фаза ИП в точке X₂, Y₂ относительно фазы в некоторой точке, принятой за начало отсчета;
dF(X₂, Y₂, t) отклонение фазы ИП в точке X₂, Y₂ от F.In the case of recording a hologram, the IP intensity recorded on a photographic plate located in the X ₂ Y ₂ plane is determined by the expression:

,
where R ₀ and S _{0 the} amplitude of the reference R and object S waves;
Φ (X ₂ , Y ₂ , t) the given phase of the PI at the point X ₂ , Y ₂ relative to the phase at some point taken as the reference point;
dF (X ₂ , Y ₂ , t) deviation of the IP phase at the point X ₂ , Y ₂ from F.

,
где Φ_N фазовая помеха ИП, вызванная главным образом трудноконтролируемыми механическими и тепловыми воздействиями на оптическую систему;
Φ_с фазовый сдвиг ИП, обусловленный движением фазового корректора;
Φ_d амплитуда вспомогательной фазовой модуляции ИП.If the method for measuring phase noise in the active IP stabilization system is used using auxiliary harmonic modulation of the phase of the reference wave at frequency W and the extraction signal is extracted by synchronous detection at this frequency, the value of dF can be represented as

,
where Φ _{N is the} IP phase noise caused mainly by hardly controlled mechanical and thermal influences on the optical system;
Φ _{with the} phase shift of the IP, due to the movement of the phase corrector;
Φ _{d the} amplitude of the auxiliary phase modulation of the PI.

The amplitude Φ _d should be much smaller than Φ _N. The tolerance on δΦ in the exposure process is determined by the allowable decrease in diffraction efficiency h and / or the signal-to-noise ratio of the SOE compared with values achievable (all other things being equal) in an ideal recording scheme. If the criterion for the quality of the hologram is to take a decrease in h by 10%, then the permissible value of dF for disturbances such as harmonic oscillations will be p / 5 ..

When recording small holograms, the dependence of Φ _{N /} on X ₂ , Y _{2 is} very weak, therefore, to stabilize the IP, the simplest active system with a piston-type corrector refuses suitable, for which Φ _{c is} also independent of X ₂ , Y ₂ . In the case of large-diameter holograms, a typical situation is when Φ _N , and therefore, δΦ, is different at different points of the photographic plate.

,
где k=2π/λ (l длина волны, используемая при записи). Из выражения (3) видно, что изменение величины F может быть вызвано смещением источников света и фотопластины вдоль любого направления, однако для типичных условий голографической записи указанные смещения вдоль некоторых направлений настолько малы, что зависимостью dF от них можно пренебречь. В частности нами показано, что при установке на голографической плите фотопластины и формирующей оптики в вертикальном положении можно не учитывать смещение источников света вдоль вертикальной оси ∂y_R≈∂y₁≈0, а также поперечные смещения фотопластины ∂y₂≈∂x₂≈0.The main reasons that lead to the appearance of phase noise, depending on the coordinates X ₂ , Y ₂ , are fluctuations in the refractive index of air n _a , the displacement of the sources of the object and reference waves, as well as cantilever and membrane oscillations of the photographic plate. The fluctuations n _{a are} caused by the presence of a temperature gradient grad T in the room and at grad T <0.01 deg / m they can be neglected, which is achieved by installing insulating fencing and moving the heat sources outside the holographic plate. Consider the indicated dependence for a fairly common case of recording a hologram by two diverging spherical reference R and object S waves formed by light sources having coordinates X _R , Y _R , Z _R } and X ₁ , Y ₁ , Z ₁ }, respectively. The photographic plate is located in the plane (X ₂ , Y ₂ ), which is located at a distance d ₁ = z ₂ from the origin. The expression for the quantity dF at an arbitrary point with coordinates X ₂ , Y ₂ , Z ₂ } taking into account n _a = 1 in the paraxial approximation takes the form

,
where k = 2π / λ (l is the wavelength used for recording). It can be seen from expression (3) that the change in the value of F can be caused by the displacement of light sources and the photographic plate along any direction, however, for typical conditions of holographic recording, these displacements along some directions are so small that the dependence of dF on them can be neglected. In particular, we have shown that when installing a photographic plate and forming optics on a holographic plate in a vertical position, we can ignore the displacement of light sources along the vertical axis ∂y _R ≈∂y ₁ ≈0, as well as the transverse displacements of the photographic plate ∂y ₂ ≈∂x ₂ ≈ 0.

,
где k₁ и k₂ коэффициенты преобразования электрического сигнала в величину фазового смещения фазосдвигающего устройства в I и II канале соответственно;
U₁ и U₂ амплитуды сигналов управления, полученные при единичной площади регистрирующей среды в I и II канале, соответственно.Real-time measurements of the quality of the recorded ASG recorded showed that under the conditions of a holographic laboratory, the greatest contribution to the formation of an inhomogeneous (two-dimensional) component of phase noise over the hologram field is made by cantilever (with vertical installation of the photographic plate) and membrane (with horizontal installation of the photographic plate) vibrations. This allowed us to use only two regions (I and II) of the recording medium, coupled to two channels of the photographic recording unit, for reading the self-diffraction signal and generating the correction signal. For horizontal installation, the second region (II) is the area in the center of the photographic plate; for vertical installation, the area adjacent to the upper face of the photographic plate. For a given radiation power density on the photographic plate, the amplitude of the control signal in channels I and II is proportional to the areas of the recording medium conjugated with this channel, S ₁ and S _2, respectively. The minimum area values are determined from the conditions

,
where k ₁ and k _{2 are the} coefficients of the conversion of the electrical signal into the phase displacement of the phase-shifting device in channel I and II, respectively;
U ₁ and U _{2 are the} amplitudes of the control signals obtained for a unit area of the recording medium in channel I and II, respectively.

,
где i=1,2;
δΦ_доп допустимое среднеквадратичное значение фазовой помехи, усредненное за время экспонирования;
grad₁ градиент изменения величины фазовой помехи δΦ_i в области фотопластины с площадью S_i вдоль направления

с наибольшим изменением величины δΦ.Conditions (4) and (5) are necessary but not sufficient for recording high-quality holograms in the case of a quantity δΦ nonuniform in the field of the photographic plate, since the fulfillment of these conditions at the time t = t ₀ due to an increase in S ₁ and S ₂ can lead to a deterioration of phase compensation at subsequent times. This is due to the inadequacy of the local response of the phase corrector to the amount of phase noise at an arbitrary point on the photographic plate for large values of S ₁ and S ₂ . Therefore, in addition to the natural upper restriction on the quantities S ₁ ≅ S / 2 and S ₂ ≅ S / 2 (where S is the area of the hologram), the condition

,
where i = 1,2;
δΦ _additional allowable rms phase noise averaged over the exposure time;
grad ₁ gradient of the phase noise δΦ _i in the area of the photographic plate with an area S _i along the direction

with the largest change in δΦ.

Since the value of dF _{dop in a} complex way associated with a given value of η _dop , the maximum value of S _i is determined empirically, based on the measured permissible value of the control signal.

In the particular case of a vertically mounted photographic plate, region I adjacent to the lower part of the photographic plate is interfaced with the first (main) channel, one output of which is connected to a piston-type phase corrector. This phase corrector compensates for the phase noise component that is uniform across the field of the photographic plate. Since the nonuniform component of the quantity δΦ is small in the lower part of the photographic plate, dF is compensated in region I, and the area S ₁ is determined by conditions (4) and (6). At the same time, in region II, conjugated with the second (additional) channel, there is a purely nonuniform field component dF, which is compensated by a phase-shifting device that rotates the wavefront relative to the horizontal axis, which is located so that when the phase-shifting device 5 is in region 1 a homogeneous phase noise component did not occur. It should be noted that in the case when the phase noise manifests itself in the form of membrane oscillations of the photographic plate, a flexible mirror with a single-element axisymmetric piezoelectric drive can be used as a simple phase-shifting device in the second channel.

 To study the conditions for the formation of control and control signals on a photographic plate with an effective diameter of 0.7 m, two regions with a diameter of 100 mm were identified by installing shielding diaphragms behind it. The first of the regions (I) is located in the lower part, and the other (II) in the upper part of the plate (Fig. 2). Films of a chalcogenide glassy semiconductor (CGS) and layers of bichromated gelatin (BCG) were used as the recording medium. The same figure shows the time dependences of the control signal recorded on a storage oscilloscope, obtained when the device for recording large-sized holograms (curves 1 and 1 ') is turned off, when the first (curves 2 and 2') and the second (curves 3 and 3 ') are turned on . It is seen that in the two-channel mode, phase correction takes place in both regions, while in the single-channel mode of operation, only partial correction of the phase noise of the IP occurs in the upper part of the photographic plate. With the phase correction system turned off, we were not able to get high-quality holograms.

 In the present invention, it is new that in a device containing a coherent radiation source, a holographic interferometer, the reference and object arms of which are optically coupled to a recording medium deposited on a photographic plate, which has the property of self-diffraction under the influence of radiation, a photographic recording unit installed behind the medium connected to the signal former control, phase-shifting devices, the first of which is connected to the output of the sinusoidal signal generator, and the second with the output For, the photoregistration unit and the control signal generator are made in the form of two channels, a lens is installed between the photoregistration unit and the recording medium in each channel, and the lens of the first channel is installed behind the first region of the recording medium, the lens of the second channel is behind the second region that does not intersect with the first, a comparator, an electronic switch, a phase shifting device are installed, one synchronous amplifier is additionally installed in the driver of the control signal of the first and second channel, output the first of them is connected to the reference input of the comparator, the output of the second to another input of the comparator, the output of which is connected to the first input of the electronic key, the second output of the second channel is connected to the second input of the key, the output of which is connected to the third phase-shifting device.

 In FIG. 3 shows an example of a specific implementation of the devices. The device is assembled on a standard holographic plate type SIN-1. The beam of an argon laser 1 (LGN-512) operating at a wavelength of 488 nm and having an average power of 1 W is split into two by a beam splitter 2. Next, the reference beam passes through a micro-lens 6, which forms a diverging wavefront of the desired configuration and is reflected from the phase-shifting device 5 of a rotary type, hits a vertically mounted photographic plate 8. The object beam, reflected from the phase-shifting device 3, connected to the sinusoidal signal generator 7, passes through the micro-lens 6, phase-shifting device 4 orshnevogo type and interfere on a photographic plate with a reference beam. Phase shifting devices 4 and 5 are made in the form of mirrors mounted on a KP-1 piezoelectric substrate. As a phase-shifting device 3, a mirror on a substrate of magnetostrictive material was used. The BCG layers and CGS films were used as recording media. Behind the recording medium, diaphragms 14 are installed, forming the size of regions I and II of the recording medium, interfaced with the first and second channels of the photodetector, respectively. Behind the diaphragms, lenses 9 are installed, focusing the rays of the reference and object beams (dotted in FIG. 3) to the photodetectors 15, which make up the photographic recording unit. FDK-142 type photodetectors were used. From the output of the photodetectors, the signals arrive at the algebraic adders 16, where the addition or subtraction of the incoming signals occurs, depending on the type of recording medium used. In each channel, from the output of the adder, the signal is fed to synchronous amplifiers, one of which is tuned to the frequency W = 55 kHz, and the other 2Ω. The adder and amplifiers 19 and 20, as well as the adder and amplifiers 17 and 18 make up the first and second channels of the control signal generator, respectively. From the output of the amplifier 19, a control signal is supplied to the reference input of the comparator 12. This signal is compared with the signal from the amplifier 18 of the second channel. In the case when the signal in the second channel is less than in the reference (first), the signal from the output of the comparator opens the key 13. In this case, the control signal from the output of the amplifier 17 passes the electronic key and from its output is fed to the phase shifting device 5. Control the signal from the synchronous amplifier 20 is fed directly to the phase shifter 4. When the hologram recorder is turned on, the position of the interference field is corrected using the first channel, coupled to region 1 of the recording medium adjacent to the lower edge of the photographic plate, where there is only phase noise uniform in the hologram field. Using the second channel, coupled with the II region of the recording medium adjacent to the upper edge of the photographic plate, the phase noise inhomogeneous in the field of the hologram is compensated mainly due to cantilevered oscillations of the photographic plate. In this case, the reflective plane of the phase-shifting device is rotated relative to the horizontal axis passing through the point of intersection of the lower aperture beam with this plane.

 To obtain preliminary information on the micro displacements of the photographic plate, interferometric studies of its vibrations were carried out. An auxiliary SP with a low spatial frequency was formed upon interference of the reference beam reflected from the photographic plate and reflected from the additional mirror of the object beams. The experiments showed that the displacements of the auxiliary PI at different points of the plate with a diameter of 230 mm within the measurement error l / 8 have the same amplitude. At the same time, similar studies of oscillations and drifts of the plate 0.5 • 0.5 m (effective diameter 0.7 m) showed that noticeable periodic micro displacements of the upper part of the plate relative to its lower part are taking place. Therefore, when recording volumetric transmission GOEs with a diameter of 230 mm on BCG layers, the phase correction system was used in a single-channel mode. When registering the GOE on a plate of 0.5 • 0.5 m, phase correction was carried out in a two-channel mode. The application of the proposed device made it possible to obtain: volumetric GOE on a BCG with a diameter of 230 mm with diffraction efficiency η = 85% (with an exposure time of 15 min) and relief-phase GOE on a CGW on photographic plates with an effective diameter of 0.7 m with a diffraction efficiency of 60% (at exposure time 50 min). For the volumetric GOEs shown, η was measured in the recording scheme, and for RF the GOEs in the self-collimation scheme using TE-polarized radiation with a wavelength of 633 nm.

 Thus, thanks to a new design solution based on reading the quality of the recorded hologram in real time and on studying the dependences of the phase noise distribution on the hologram recording facilities, the proposed simple device can significantly increase the yield of large-sized hologram samples and improve their quality.

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Claims (2)

 1. A device for recording large-sized holograms, including a coherent radiation source, a holographic interferometer, the reference and object arms of which are optically coupled to a recording medium deposited on a photographic plate, which has the property of self-diffraction under the influence of radiation, a photographic recording unit installed behind the medium, connected to the control signal generator, phase shifting devices, the first of which is connected to the output of the sinusoidal signal generator, and the second to the output of the driver, This is because the photoregistration unit and the control signal generator are made in the form of two channels, a lens is installed in each channel between the photoregistration unit and the recording medium, the lens of the first channel being installed behind the first region of the recording medium, the lens of the second channel behind the second region not intersecting with the first additionally installed a comparator, an electronic key, a phase shifter, in the driver of the control signal of the first and second channels is additionally installed on one synchronous rer, the output of the first of them connected to the reference input of the comparator, the second output to another input of the comparator, whose output is connected to a first input of an electronic key, the second output of the second channel is connected to the second input key, whose output is connected to a third phase shifter.  2. The device according to claim 1, characterized in that the first region of the recording medium is adjacent to the lower boundary of the vertically mounted photographic plate, the second region to the upper boundary of the photographic plate, the first phase-shifting device is made in the form of a mirror that performs reciprocating motion along the normal to its reflective surface , the third phase-shifting device is a flat mirror that rotates its reflective surface relative to the horizontal axis lying on this surface or its extension.

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