RU2746169C1 - Method for measuring the wave front modes of light wave by holographic wave front mode sensor and device for implementing the method - Google Patents

Abstract

FIELD: optical instrumentation.SUBSTANCE: invention relates to the field of optical instrumentation and concerns a method for measuring the Zernike wave front modes by a holographic wave front mode sensor. The mode measurement method contains an iterative process that involves increasing the diameter of the measured wave front, from a diameter value significantly smaller than the maximum diameter of the measured wave front to a value equal to the maximum diameter of the measured wave front. The method includes measuring the amplitude of the wave front modes at different values of the wave front diameter and reducing the wave front aberrations in each iterative cycle with a wave front corrector.EFFECT: increased measurement speed and the number of measured Zernike wave front modes.3 cl, 6 dwg, 2 tbl

Description

The invention relates to optical instrumentation, and in particular to methods for measuring the shape of the wavefront of a light wave and to sensors of the wavefront of a light wave. A number of methods for measuring wavefront and wavefront sensors are known. The Shack-Hartmann sensor measures the inclination of individual sections of the wavefront to the optical axis of the sensor [1]. The measured slopes are used to calculate the shape of the wavefront. In a curvature sensor, the wavefront shape is calculated based on the intensity distributions of the light wave incident on the lens, measured on both sides of the lens focal plane [2] or on one side of the focal plane [3]. In astronomy, a pyramidal wavefront sensor is used, in which the image of a star falls on the top of a tetrahedral pyramid, and 4 images of the exit pupil of the telescope appear. The wavefront shape is found from the intensity distributions of these images [4, 5]. In these sensors, the distribution of light intensity is measured by CCD or CMOS matrices, the signals from millions of light-sensitive pixels of which must undergo a complex processing process in order to obtain a picture of the wavefront. The need for complex processing of a large number of signals reduces the speed of wavefront measurement and necessitates the use of expensive computers and expensive software when wavefront measurements need to be performed at high speed. For example, in astronomical telescope wavefront sensors that measure wavefront distortions caused by atmospheric turbulence, mainframe servers are used to process sensor signals.

This disadvantage is absent in holographic mode wavefront sensors that measure the amplitudes of the wavefront modes of a light wave [6,7,8,9]. The wavefront is found as a superposition of the measured modes. The number of signals from the holographic mode sensor is twice the number of measured modes and amounts to tens. A small number of signals, a simple process for their processing and the ability to measure signals with photodiodes provide a high speed of wavefront measurement.

One of the disadvantages of holographic mode sensors is the low intensity of signal waves reconstructed by the sensor holograms, due to the fact that the sensors use superimposed holograms, that is, holograms recorded in one area of the recording medium, whose diffraction efficiency is low [10]. Another disadvantage is the measurement error of the signal intensity due to the spatial displacement of the measured intensity distribution, depending on the nature of the distortion of the measured wavefront [11].

The indicated disadvantages are absent in a holographic mode sensor based on the Fourier holograms of scattered Zernike modes of the wavefront, in which holograms recorded in different parts of the recording medium are used instead of superimposed holograms [12,13]. In technical essence, this sensor is the closest to the proposed sensor and serves as its prototype. The scheme for recording holograms of this sensor is shown in Fig. 1, where 1 lens, in the front focal plane of which there is a diffuser 3, scattering wave 5 incident on a diffuser 3. A polarizer 4 is installed behind the diffuser, polarizing radiation in the direction perpendicular to the plane containing the reference and object waves of holograms. A diffuse beam of light appears in the rear focal plane of the objective 1, which serves as a reference wave when recording holograms on a recording medium 2. To measure one Zernike mode, two holograms are recorded. One hologram is recorded with a reference wave arising when wave 5 with a positive amplitude of the Zernike mode is incident on the scatterer, another hologram with a negative amplitude of the Zernike mode. To measure more modes, as many pairs of holograms are recorded as the number of Zernike modes the sensor has to measure.

The object waves of the holograms are two plane waves 6 and 7, incident on the recording medium at different angles. One plane wave is used to record holograms recorded with a positive amplitude of the reference wave mode, the other wave is used to record holograms recorded with a negative amplitude of the mode. When recording holograms, a movable diaphragm 8 is used, highlighting the areas of the recording medium 2 on which the holograms are recorded. The relative position of the 61st hologram in the form of a hexagonal lattice is shown in Fig. 2 (a). The holograms recorded with the object wave 6 are shown in Fig. 2 (b), the holograms recorded with the object wave 7 in Fig. 2 (c). The use of two object waves when recording holograms ensures the formation of gaps between the reconstructed waves sufficient to accommodate photodiodes that measure the intensity of the reconstructed waves.

When measuring the wavefront by the sensor, the measured wave 9 (Fig. 3) falls on the scatterer 3. The scattered wave emerging from the objective 1 illuminates the holograms 10, limited by the diaphragm 11. If the wavefront of wave 9 is described by the Zernike mode used in recording a pair of holograms 10 , then the holograms of this pair reconstruct two object waves, the intensities of which depend on the degree of closeness of the amplitude of the mode of the measured wave to the amplitudes of the mode used for recording the holograms. The maximum wave intensity of any reconstructed hologram of a given pair of holograms is achieved when the amplitude of the measured wave mode is equal to the amplitude of the wave mode used when recording this hologram. In this case, the intensity of the wave reconstructed by another hologram of this pair of holograms is minimal. The amplitude of the measured mode is determined from the difference between the intensities of the two reconstructed waves. The intensities of the reconstructed waves are measured by arrays of photodiodes 12 and 13 installed behind the gratings of microdiaphragms 14 and 15 located in the focal planes of the arrays of microlens 16 and 17. Each microlens receives a wave reconstructed by one of the holograms. Fig. 3 shows a case where intensities of eight waves reconstructed by eight holograms are measured.

The disadvantage of this wavefront sensor, like all other holographic mode wavefront sensors, is intermode interference that occurs when the measured wave contains more than one wavefront mode [11]. Each mode of the measured wavefront interferes with the waves reconstructed by the other wavefront modes. Due to intermode interference, known holographic mode sensors are capable of measuring wavefronts containing only a few low-amplitude modes. To reduce intermode interference, hybrid wavefront sensors have been proposed that combine a mode sensor with a Shack-Hartmann sensor [14] or a mode sensor with a curvature sensor [15]. These sensors have a disadvantage in the form of the need for complex processing of a large number of signals from the photosensitive matrix.

The purpose of the present invention is to provide a method for measuring wavefront modes and a device implementing this method, providing a high speed measurement of tens of Zernike modes of the wavefront of a coherent light wave.

This goal is achieved by the fact that the method for measuring wavefront modes contains an iterative process, during which wavefront aberrations are measured and eliminated as the diameter of the measured wavefront increases, which distinguishes the proposed method from the known iterative methods for measuring wavefront modes [16]. To implement this measurement method, a device containing a wavefront corrector and a holographic mode wavefront sensor is used. The holographic mode sensor is based on the Fourier holograms of the scattered Zernike modes of the wavefront and differs from the prototype [12,13] in that it measures the wavefront simultaneously at different diameters.

During the first cycle of the iterative process, the holographic mode wavefront sensor will measure the amplitudes of the modes, at the first, smallest diameter of the wavefront, which is small enough for it to be known a priori that with such a diameter of the wavefront, the intermode interference is so small that one or several of the first modes can be measured Zernike wavefront. The wavefront corrector reduces the mode amplitudes at the first wavefront diameter by the mode amplitudes measured by the holographic mode wavefront sensor. After decreasing the mode amplitudes by the wavefront corrector, the holographic mode wavefront sensor re-measures the amplitudes of the previously measured modes. The amplitude of each mode at the first diameter of the wavefront is found as the sum of the mode amplitude measured before the mode amplitudes decrease by the wavefront corrector and the mode amplitude measured after the wavefront correction.

In the second cycle of the iterative process, using the found amplitudes of the modes at the first diameter of the wavefront, the approximate values of the amplitudes of the Zernike modes at the second diameter of the wavefront are calculated. For each mode, its approximate value at the second diameter is found as the value of the mode amplitude, measured at the first diameter of the wavefront, multiplied by the ratio of the second diameter to the first diameter, raised to a power equal to the power of the polynomial describing the given mode. This method of calculating the approximate values of the amplitudes of the modes is based on the relations connecting the amplitudes of the modes at different diameters of the wavefront [17]. The second diameter of the wavefront is determined from the condition of its sufficiently small increase in comparison with the first diameter, at which the calculated approximate values of the modes are close to their actual values. The wavefront corrector reduces the amplitudes of the modes of the wavefront at its second diameter by values equal to the calculated approximate values of the modes, which reduces intermode interference and allows the holographic mode sensor to measure modes at the second diameter of the wavefront. The amplitude of each mode at the second diameter of the wavefront is found as the sum of the calculated approximate value of the amplitude and the amplitude of the mode measured by the holographic mode sensor after aberration correction. Additional modes can be measured at the second diameter of the wavefront that were not measured at the first diameter.

In the third cycle of the iterative process, using the found amplitudes of the modes at the second diameter of the wavefront, the approximate values of the modes at the third diameter of the wavefront are calculated. For each mode, its approximate value at the third diameter is found as the value of the mode amplitude, measured at the second diameter of the wavefront, multiplied by the ratio of the third diameter to the second diameter, raised to a power equal to the power of the polynomial describing the given mode. The third diameter of the wavefront is determined from the condition of its sufficiently small increase in comparison with the first diameter, at which the calculated approximate values of the modes are close to their actual values. The wavefront corrector reduces the amplitudes of the wavefront aberrations at its third diameter by values equal to the calculated approximate values of the modes, which ensures the smallness of intermode interference and allows the holographic mode sensor to measure modes at the third diameter of the wavefront. The amplitude of each mode at the third diameter of the wavefront is found as the sum of the calculated approximate value of the amplitude and the amplitude of the mode measured by the holographic mode sensor after correcting the wavefront. Additional modes not measured at the second diameter can be measured at the third diameter of the wavefront.

The iterative process continues in a similar manner for large wavefront diameters. The last N-th cycle of the iterative process begins by calculating the approximate values of the amplitudes of the modes at the N-th, the maximum diameter of the measured wavefront, equal to the diameter of the scatterer 3 of the sensor (Fig. 3). For each mode, its approximate value at the N-th diameter is found as the value of the mode amplitude, measured at the (N-1) -th diameter of the wavefront, multiplied by the ratio of the N-th diameter to the N-1 diameter, raised to the power equal to the power of the polynomial, describing this fashion. The value of the (N-1) -th diameter of the wavefront is determined from the condition of its sufficiently small decrease in comparison with the Nth diameter, at which the calculated approximate values of the amplitudes of the modes are close to their actual values. The wavefront corrector reduces the amplitudes of the wavefront modes at its Nth diameter by values equal to the calculated approximate values of the modes, which ensures small intermode interference and allows the holographic mode sensor to measure modes at the Nth wavefront diameter. This completes the iterative process.

The holographic mode wavefront sensor measures modes at the N-th diameter of the wavefront, at which additional modes not measured at the (N-1) -th diameter can be measured. The wavefront corrector compensates for wavefront aberrations at its Nth diameter, reducing the mode amplitudes by their measured values.

When measuring a wavefront at one of its diameters, wavefronts are simultaneously measured at all smaller diameters of the wavefront. If the holographic mode sensor, for some reason, for example, too large mode amplitudes, is unable to measure the amplitudes at one of the wavefront diameters, then the iterative process is resumed at one of the smaller wavefront diameters at which the wavefront is measured.

In the course of the iterative process, it is advisable to use the diameter of the measured wavefront, which is 0.816 part of its maximum diameter. At a given diameter, as follows from an example of implementation of the invention, the difference between the approximate calculated and actual values of the amplitudes of the Zernike modes is less.

To implement the proposed method for measuring wavefront modes, a device is used, the diagram of which is shown in Fig. 4, containing a holographic mode wavefront sensor 19 and a wavefront corrector 20, which eliminates the aberrations of the measured wave 21. The holographic mode sensor differs from its prototype in that holograms The sensors are recorded at different diameters of the wave 5 incident on the diffuser 3 (Fig. 5). To obtain a given diameter of wave 5, a diaphragm of variable diameter 18 is used, installed in front of the diffuser 3. The values of the diameters of the wave 5 and the amplitudes of the Zernike modes, when recording holograms, are determined according to the proposed method for measuring the wavefront. Recording of holograms at different diameters of wave 5 incident on the scatterer 3 allows the proposed sensor to measure wavefront modes simultaneously at different wavefront diameters. The proposed holographic mode wavefront sensor has the same arrangement of sensor elements as the known sensor shown in FIG. 3. The holograms of the proposed sensor are located within an equilateral hexagon, similar to their arrangement in Fig. 2.

List of figures

Fig. 1 is a diagram of hologram recording of a known holographic mode wavefront sensor.

Fig. 2 relative position of holograms of the holographic mode wavefront sensor

2 (a) holograms recorded using two object waves.

2 (b) holograms recorded using one object wave.

2 (c) holograms recorded using a different object wave.

Fig. 3 is a diagram of a holographic mode wavefront sensor,

4 is a schematic diagram of a device for measuring wavefront modes.

Fig. 5 is a diagram for recording holograms of the proposed holographic mode wavefront sensor.

6 is a diagram of using a device for measuring wavefront modes in conjunction with a telescopic optical system and a wavefront tilt corrector.

диаметром 300 мм распространяется на расстояние 410 метров на высоте 12 метров над поверхностью земли и отражается в обратном направлении [18].For a better understanding of the essence of the claimed invention, we give an example of implementation of the invention, when the wavefront aberrations of the light wave are caused by atmospheric turbulence. The example considers the case when a light wave with a wavelength

with a diameter of 300 mm spreads over a distance of 410 meters at a height of 12 meters above the earth's surface and is reflected in the opposite direction [18].

, величина аберраций дисперсиями мод, представленными на графике работы [18]. Дисперсии мод разных угловых частот m, отвечающие одному значению n и принятые равными их среднему значению, представлены в Таблице 1.Wave aberrations are described by Zernike modes

, the magnitude of aberrations by mode dispersions presented in the graph of [18]. Dispersions of modes of different angular frequencies m, corresponding to the same value of n and taken equal to their mean value, are presented in Table 1.

Table 1

Indices n, m Zernike modes

рад² Mode dispersions

happy ² Mode amplitudes

glad n = 2, m = -2.0.2

n = 3, m = -3, -1,1,3

n = 4, m = -4, -2,0,2,4

n = 5, m = -5, -3, -1,1,3,5

n = 6, m = -6, -4, -2,0,2,4,6

, которые мы будем считать независимыми случайными величинами равными среднеквадратическим отклонениям

мод.Table 1 also presents the amplitudes of the modes

, which we will consider as independent random variables equal to the standard deviations

Maud.

The amplitudes of the modes are random quantities and can greatly exceed the values indicated in Table 1. However, with a fairly high probability they become equal to or less than these values. At this point in time, the iterative process of measuring and compensating for aberrations begins.

In this example, a device for measuring wavefront modes, as part of a holographic mode wavefront sensor 19 and a wavefront corrector 20, must be used in conjunction with a telescopic optical system 22 and a wavefront tilt corrector 23 [19] (Fig. 6). The telescopic optical system 22 reduces the diameter of the measured wave 24 from 300 mm to 10 mm, the wavefront tilt corrector 23 eliminates the deviation of the wave propagation direction from the optical axis of the sensor.

Table 2 shows the parameters of the method for measuring wavefront modes. The first column of the table indicates the diameters of the measured wavefront in the plane of the scatterer.

table 2

Wavefront diameter
mm Dispersions of wavefront modes before and after wavefront correction rad ² The sum of the variances
mod after correction glad ² fashion
n = 2
m = 0, ± 2 fashion
n = 3,
m = ± 1, ± 3 fashion
n = 4,
m =
0, ± 2, ± 4 fashion
n = 5
m = ± 1, ± 3,
± 5 fashion
n = 6
m = 0, ± 2,
± 4, ± 6 4,00 dimension
correction
dimension - - - - 0.196 0.016 0.002 0.000 0.000 <0.196 0.016 0.002 0.000 0.000 <0.214 5.80 correction
dimension -
dimension -
- -
- -
- 0.561 0.108 0.025 0.001 0.000 0.069 0.108 0.025 0.001 0.000 0.203 7.30 correction
dimension correction
dimension -
- -
- -
- 0.960 0.304 0.094 0.012 0.003 0.120 0.016 0.094 0.012 0.003 0.245 8.16 correction
dimension correction
dimension -
dimension -
- -
- 1.296 0.462 0.174 0.031 0.012 0.057 0.021 0.174 0.031 0.012 0.295 9.10 correction
dimension correction
dimension correction
dimension -
dimension -
- 1.76 0.724 0.286 0.093 0.042 0.088 0.056 0.042 0.093 0.042 0.321 10.00 correction
dimension correction
dimension correction
dimension correction
dimension -
dimension 2,430 1,200 0.500 0.240 0.140 0.144 0.113 0.100 0.000 0.140 0.497

The first line, corresponding to the specified diameter, indicates the operations performed on this diameter, namely, measuring the wavefront or correcting the wavefront and then measuring it. The second and third lines, corresponding to the indicated diameter, indicate the dispersions of the wavefront modes before and after the wavefront correction. The dispersions of the modes of the wavefront before its correction are found using expressions [17], which make it possible to find the amplitude of the mode at a smaller diameter of the wavefront at known amplitudes of modes at a larger diameter of the wavefront, in this case, at a diameter of 10 mm.

после коррекции имеет значение менее

рад². При такой дисперсии число Штреля,At a wavefront diameter of 4 mm, the sum of the wavefront mode dispersions

after correction it matters less

happy ² . With such a variance, the Strehl number

, (1)

, (one)

large enough to measure the amplitudes of the first three modes listed in the table.

In the first cycle of the iterative process, the holographic mode sensor measures the amplitudes of these modes, then the wavefront corrector decreases their amplitudes by the amplitudes measured by the sensor, and the holographic mode sensor re-measures the amplitudes of the previously measured modes at the first wavefront diameter. The amplitude of each mode at the first diameter of the wavefront is found as the sum of the amplitude of the mode measured before the aberration decreases and the amplitude of the mode measured after the decrease in the wavefront aberrations. Then the second cycle of the iterative process begins.

,

, при коррекции и измерении волнового фронта на диаметре 8,16 мм. На предыдущем цикле аберрации

,

измеряются на диаметре волнового фронта 7,3 мм, где аберрации имеют амплитудыConsider one cycle of the iterative process for aberrations

,

, when correcting and measuring the wavefront at a diameter of 8.16 mm. On the previous cycle of aberration

,

measured at a wavefront diameter of 7.3 mm, where aberrations have amplitudes

. (2)

... (2)

равныOn the next cycle, with a diameter of 8.16 mm, the amplitude of aberrations

are equal

. (3)

... (3)

измеренных на диаметре 7,3 мм, согласно представленному способу, в соответствии с выражениемThe approximate calculated value of these amplitudes is found based on the value of the amplitudes

measured at a diameter of 7.3 mm, according to the presented method, in accordance with the expression

. (4)

... (four)

до значений равныхThe wavefront corrector reduces the aberration amplitudes by values

to values equal

,

.

,

...

,

равна 0,0189 рад² для одного значения m и как сумма дисперсий трех аберраций дисперсия равна 0,057 рад² (Таблица 2).At these amplitudes, the dispersion of aberrations is

,

is equal to 0.0189 rad ² for one value of m and as the sum of the variances of three aberrations, the variance is 0.057 rad ² (Table 2).

, поскольку для диаметра 8,16 числовой коэффициент, на который умножается амплитуда

, равен нулю. Это свойство выделяет диаметр, составляющий 0,816 от максимального диаметра измеряемого волнового фронта, из всех возможных диаметров и повышает точность, с которой находятся приближенные расчетные значения амплитуд аберраций

,

.In expression (2) there is no amplitude

, since for a diameter of 8.16 the numerical coefficient by which the amplitude is multiplied

, is equal to zero. This property distinguishes a diameter equal to 0.816 of the maximum diameter of the measured wavefront from all possible diameters and increases the accuracy with which the approximate calculated values of the aberration amplitudes are found.

,

...

, что обеспечивает возможность измерения интенсивности сигнальных волн. В рассмотренном примере способа измерения мод измеряется 72 моды Цернике, в том числе на максимальном диаметре волнового фронта измеряется 25 мод.From Table 2 it follows that the maximum dispersion of the wavefront amplitude of 0.497 rad ² occurs at the maximum wavefront diameter. For a given variance, the Strehl number

, which provides the ability to measure the intensity of signal waves. In the considered example of the method for measuring modes, 72 Zernike modes are measured, including 25 modes are measured at the maximum diameter of the wavefront.

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Claims (29)

1. A method for measuring Zernike wavefront modes with a holographic mode wavefront sensor, comprising an iterative process for measuring wavefront modes, characterized in that: - the iterative process includes an increase in the diameter of the measured wavefront, from the value of the diameter significantly smaller than the maximum diameter of the measured wavefront to the value equal to the maximum diameter of the measured wavefront; - during the first cycle of the iterative process, the holographic mode sensor measures the amplitudes of the wavefront modes at the first, smallest, diameter of the measured wavefront, which is small enough so that for a given diameter it is a priori known that with such a diameter of the wavefront, the aberrations are small enough to be able to measure the amplitudes one or more of the first Zernike modes; - on the first diameter of the wavefront, the wavefront aberrations are reduced by the wavefront corrector by values equal to the measured amplitudes of the modes; - the holographic mode sensor, after reducing the wavefront aberrations, measures the amplitudes of the previously measured modes at the first diameter of the wavefront; - the amplitude of each mode at the first diameter of the wavefront is found as the sum of the amplitude of the mode measured before the decrease in aberrations and the amplitude of the mode measured after the decrease in the aberrations of the wavefront; - in the second cycle of the iterative process, according to the found amplitudes of the modes at the first diameter of the wavefront, the approximate values of the amplitudes of the modes at the second diameter of the wavefront are calculated; for each mode, the calculated approximate value of its amplitude at the second diameter of the wavefront is found as the value of the mode amplitude found at the first diameter of the wavefront front multiplied by the ratio of the second diameter to the first diameter, raised to a power equal to the power of the polynomial describing the given mode; - the second diameter of the measured wavefront is determined from the condition of its sufficiently small increase in comparison with the first diameter of the measured wavefront, at which the calculated approximate values of the amplitudes of the modes are close to their actual values; - at the second diameter of the wavefront, the amplitudes of the wavefront aberrations are reduced by the wavefront corrector by values equal to the calculated approximate values of the amplitudes; - the holographic mode sensor, after reducing the wavefront aberrations, measures at the second diameter of the wavefront the amplitudes of the modes previously measured at the first diameter of the wavefront; - the amplitude of each mode at the second diameter of the wavefront is found as the sum of the calculated approximate value of the mode amplitude and the mode amplitude measured by the holographic mode sensor; - at the second diameter of the wavefront, the amplitudes of several subsequent Zernike modes that were not measured at the first diameter of the wavefront can be measured, while the measurement of the amplitudes of the modes at the first diameter of the wavefront continues; - in the third cycle of the iterative process, according to the found amplitudes of the modes at the second diameter of the wavefront, the approximate values of the amplitudes of the modes at the third diameter of the wavefront are calculated; for each mode, the calculated approximate value of its amplitude at the third diameter of the wavefront is found as the value of the mode amplitude found at the second diameter of the wavefront front multiplied by the ratio of the third diameter of the wavefront to the second diameter, raised to a power equal to the power of the polynomial describing the given mode; - the third diameter of the measured wavefront is determined from the condition of its sufficiently small increase in comparison with the second diameter of the measured wavefront, at which the calculated approximate values of the amplitudes of the modes are close to their actual values; - at the third diameter of the wavefront, the amplitudes of the wavefront aberrations are reduced by the wavefront corrector by values equal to the calculated approximate values of the amplitudes; - the holographic mode sensor, after reducing the wavefront aberrations, measures at the third diameter of the wavefront the amplitudes of the modes previously measured at the second diameter of the wavefront; - the amplitude of each mode at the third diameter of the wavefront is found as the sum of the calculated approximate value of the mode amplitude and the mode amplitude measured by the holographic mode sensor; - at the third diameter of the wavefront, the amplitudes of several subsequent Zernike modes that were not measured at the second diameter of the wavefront can be measured, while measuring the amplitudes of the modes at the first and second diameters of the wavefront; - the iterative process continues in a similar way with increasing diameter of the measured wavefront; - at the last Nth cycle of the iterative process, by the mode amplitudes found at the N-1 diameter of the wavefront, the approximate values of the mode amplitudes at the maximum, Nth diameter of the measured wavefront are calculated, for each mode the approximate value of its amplitude at the Nth diameter is found, as the value of the mode amplitude measured at the (N – 1) -th diameter multiplied by the ratio of the N-th diameter to the N-1 diameter, raised to a power equal to the power of the polynomial describing the given mode; - the value of the (N-1) -th diameter of the wavefront is determined from the condition of its sufficiently small decrease in comparison with the N -th diameter, at which the calculated approximate values of the amplitudes of the modes are close to their actual values; - at the N-th diameter of the wavefront, the wavefront corrector reduces the amplitudes of the wavefront modes by values equal to the calculated approximate values of the modes, which completes the iterative process; - the holographic mode wavefront sensor measures the mode amplitudes at the N-th diameter of the wavefront, at which several subsequent Zernike modes, not measured at the (N-1) -th diameter, can be measured, while the measurement of the mode amplitudes continues at all smaller diameters of the wavefront ; - the wavefront corrector reduces the wavefront aberrations at the Nth wavefront diameter by values equal to the measured mode amplitudes at the Nth wavefront diameter; - if the holographic mode sensor is unable to measure the mode amplitudes at one of the wavefront diameters, the iterative process is resumed starting from the largest wavefront diameter at which the mode amplitudes are measured. 2. A method for measuring Zernike wavefront modes according to claim 1, characterized in that in the iterative process of measuring wavefront modes, one of the measured wavefront diameters is 0.816th part of the maximum Nth wavefront diameter. 3. A device for measuring wavefront modes, containing a wavefront corrector and a holographic mode wavefront sensor located behind it, containing a lens, a diffuser, the diameter of which is equal to the diameter of the measured wavefront, located in the front focal plane of the lens; holograms located in the rear focal plane of the lens, pre-recorded on different parts of the recording medium using a diffuse reference wave emerging from the lens and plane object waves incident on the recording medium at two different angles, for each mode measured by the wavefront sensor, two holograms, one of which is recorded with a reference wave arising when a wave with a positive mode amplitude is incident on the scatterer, another hologram is recorded with a reference wave arising when a wave with a negative mode amplitude is incident on the scatterer; a polarizer installed behind the diffuser, polarizing radiation in the direction perpendicular to the plane containing the reference and object waves of the holograms; lenses located in the path of propagation of the reconstructed object waves of holograms, micro-diaphragms installed in the rear focal planes of the objectives, photodiodes installed behind micro-diaphragms, characterized in that: - holograms of the sensor are recorded at different diameters of the wave incident on the scatterer, the wave diameter takes on a number of values from the diameter of a much smaller diameter of the scatterer to a diameter equal to the diameter of the scatterer; - to change the diameter of the wave incident on the diffuser, a diaphragm of variable diameter is used, installed in front of the diffuser when recording holograms.

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