RU2273872C1 - Telescope active adaptive electro-optic control system device - Google Patents

Abstract

FIELD: optic engineering.

SUBSTANCE: telescope active adaptive electro-optic control system device has main and secondary mirrors; wavefront general decline two-coordinate mirror connected with the first two mirrors; deformed mirror corrector; beam splitter, wavefront detector which has input connected with beam splitter; wavefront decline estimation unit, device for estimating (filtering) inclinations of wavefront, phase restorer, optimal control signal former. Reference point source forming unit is introduced into the device additionally which source has output being optically connected with wavefront common inclination two-coordinate mirror and with secondary and main mirrors of telescope.

EFFECT: increased isoplanatic angle of telescope's field of view; improved precision of correction of wavefront distortions.

3 dwg

Description

The invention relates to devices for controlling the phase of a light wave and serves to obtain the best image quality of the object under the given observation conditions by influencing the characteristics (phase correction) of the wavefront (WF) of the radiation.

An adaptive receiving device [1] is known for conducting studies to compensate for optical inhomogeneity of the atmosphere by eliminating errors in pointing the telescope at the observed object and the average tilt of the WF using the compensators and controlling the tilts of individual zones of the adaptive mirror by applying antiphase voltages to diagonally opposite drives in Group.

A device is known for an adaptive optoelectronic system (AOES) for controlling a telescope [2], designed to compensate for distortion of the WF (total tilt of the WF and the residual local tilt of the WF) due to the atmosphere and the optical path of the telescope. This device contains: a main mirror; secondary mirror; two-coordinate mirror of the general slopes of the wave front; deformable mirror corrector; control device; phase reducing agent; wavefront sensor (DVF); beam splitter; the focal plane of the image in the telescope. The device operates as follows: the measurement of the WF slopes (i.e., phase gradients) is carried out in the FEF in two orthogonal directions. In the sensor, the wavefront is divided into a matrix of subapertures (in the form of a lenslet), each of which forms in the focal plane its own image of the reference source, the position of which is tracked by the receiver. Next, the phase recovery operation is performed by spatial integration of the local slope measurement data in the phase reducer based on a special electronic computing device with an accuracy determined by the local slope measurement noise and control by the control device of the WF common slope mirror and the deformable mirror corrector to ensure the correction of WF distortions.

The prototype of the invention in technical essence is the telescope control AOES device, designed to compensate for the distortion of the WF (total tilt, defocus and residual local distortion), shown in figure 1 [3]. The device contains a main mirror (1); secondary mirror (2); two-coordinate mirror of the general slopes of the wave front (3); deformable mirror corrector (4); control device (5); phase reducing agent (6); wavefront sensor (7); beam splitter (8); the focal plane of the image in the telescope (9); device for generating optimal control signals (10); device for estimating (filtering) the slopes of the wave front (11); secondary mirror control device (12). The device operates as follows: the light signal from the telescope (1, 2) enters through the collimator to the two-coordinate mirror of the general inclination of the WF (3), then to the deformable mirror corrector (4), whence after the beam splitter (8) on the Hartmann type fiberboard (7), where is the measurement of the values of the phase gradients (slopes) of the WF. The measured values of the WF slopes arrive at the device for evaluating (filtering) the WF slopes (11), based on the systolic structure of processor elements that parallelly process the measured values of the WF slopes. Based on the signals from this device, the WF is restored in the phase reducer (6), and the electric signals generated in it corresponding to the phase of the reconstructed WF are used to generate optimal control voltages in the optimal control signal generation device (10) based on the systolic structure of the processor elements. Optimal control voltages are supplied to the control device of the telescope secondary mirror (12) as part of a voltage amplifier and an electromechanical drive that generates electrical signals by means of which a secondary actuator rotates from the electric motor to move the secondary mirror along the optical axis and to the control device (5) controlling a two-coordinate mirror of the general inclination of the WF (by tilting it in two orthogonal planes) and a deformable grain with a corrector (4) with many degrees of freedom installed in a plane conjugated with the plane of the main mirror by shifting the elementary zones (sections) of its mirror surface.

The considered devices are passive, working under natural (solar) illumination of objects. A common drawback of these devices is the small isoplanatic angle of the field of view of telescopes when observing objects in which the atmospheric perturbations of the WF are approximately the same, and the need for the presence of a natural bright reference point source (star) in this angle to enable the correction of WF distortions and obtaining a high-quality image of the object (which not always implemented in practice), as well as the impossibility of correcting the distortion of the WF and obtaining high-quality images of moving objects, because for these objects, the pointing angle, which determines the offset between the position of the moving object and the point at which it should be intercepted by the beam (telescope), is much larger than the isoplanatic angle.

The aim of the present invention is to increase the isoplanatic angle of the field of view of the telescope when observing an object by creating an artificial reference point source in it and to increase the accuracy of correcting distortions of the WF from moving objects due to optical inhomogeneities of the atmosphere and errors in pointing the telescope, in the interest of improving the quality of images of objects formed by the telescope.

The basis of the invention is the creation of a device that provides: correction of distortion of the WF due to optical inhomogeneities of the atmosphere, distortion of the optical path and errors of pointing the telescope due to the automatic effect on the characteristics (phase) of the WF radiation coming from the observed object; an increase in the isoplanatic angle of the telescope's field of view due to the creation of an artificial reference point source (star) in it; improving the accuracy of correcting WF distortions from moving objects and obtaining high-quality images of these objects due to the possibility of a more accurate measurement of WF distortions, reconstructing the WF phase and controlling the combined WF corrector, consisting of: a two-coordinate mirror of general WF slopes (3), a deformable mirror corrector (4) and a secondary mirror (2).

To achieve this goal, the proposed device of active AOES additionally introduces a device for forming a reference point source (13) based on a coherent radiation source, which allows creating an artificial reference star (in the same isoplanatic angle with the located object) in the atmosphere based on the lidar method, or by the inverse Rayleigh scattering in the atmosphere in the visible wavelength range at an altitude of 10 ... 20 km, or by excitation of resonance fluorescence of sodium atoms in the mesosphere at an altitude of about 90 km [4, 5].

Figure 2 presents a diagram of the proposed device active AOES control telescope. The device contains: a main mirror (1); secondary mirror (2); two-coordinate mirror of the general slopes of the wave front (3); deformable mirror corrector (4); control device (5); phase reducing agent (6); wavefront sensor (7); beam splitter (8); the focal plane of the image in the telescope (9); device for generating optimal control signals (10); device for estimating (filtering) the slopes of the wave front (11); secondary mirror control device (12); a device for forming a reference point source (13).

The proposed device active AOES control telescope operates as follows. The light signal from the device for forming the reference point source (13) similar to the device described in [4, 5], built on the basis of a coherent radiation source, passing a two-coordinate mirror of general tilts (3), secondary (2) and main (1) telescope mirrors, it is reflected from the located object, or, due to the Rayleigh backscattering in the atmosphere, creates a reference point source (star) located in the same planar region as the located object and returns back to the telescope. Next, the light signal from the telescope (1, 2) enters through the collimator to the two-coordinate mirror of the general inclination of the WF (3), then to the deformable mirror corrector (4), where after the beam splitter (8) on the Hartmann type fiberboard (7), where the values are measured phase gradients (slopes) of the WF. The measured values of the WF slopes arrive at the device for evaluating (filtering) the WF slopes (11), similar to the device described in [3], based on a systolic structure of processor elements that parallelly process the measured values of the WF slopes. Based on the signals from this device, the WF is restored in the phase reducer (6), according to the electric signals generated in it, corresponding to the phase of the reconstructed WF, optimal control voltages are generated in the device for generating optimal control signals (10), similar to the device given in [3], built on the basis of a systolic structure of processor elements. Optimal control voltages are supplied to the control device of the telescope secondary mirror (12) as part of a voltage amplifier and an electromechanical drive that generates electrical signals by which the secondary actuator moves along the optical axis with a screw actuator rotating from an electric motor, and to the control device (5) controlling a two-coordinate mirror of the general inclination of the WF (by tilting it in two orthogonal planes) and a deformable grain with a corrector (4) with many degrees of freedom installed in a plane conjugated with the plane of the main mirror by shifting the elementary zones (sections) of its mirror surface. In this case, an undistorted image of the located object is formed (recorded) in the focal plane of the telescope (9).

A comparative assessment of the effectiveness of the proposed device active AOES and prototype device was carried out according to the method described in [6].

Figure 3 shows the dependence of the variance of the residual error of the correction of distortion of the WF σ ² depending on the brightness of the object m for the proposed device active AOES (dashed line) and the prototype device (solid line).

Analysis of the results shown in figure 3, allows us to conclude that the proposed device of the active AOES in comparison with the prototype device allows you to: expand the scope of this active AOES by 3-4 magnitudes and get an image of the object with the required quality from less bright objects , including from moving.

The proposed device does not require significant structural refinement of the known device and can be implemented in existing telescopes.

Information sources

1. Baranov Yu.V., Belkin ND, Blokhina V.N. Analog adaptive receiving device. - Optical Journal, 1992, No. 6. S. 56-57.

2. Ryabova N.V., Zakharenkov V.F. Active and adaptive optics in large telescopes. - Optical Journal, 1992, No. 6. S.22-23.

3. The device adaptive optoelectronic control system of the telescope. - Patent No. 2224272 of February 20, 2004 (Prototype).

4. Foy R., Labeyrie A. .. - Astron. & Astrophys., 1985, No. 152, L.29.

5. Tebo A .. - OE Reports, 1991, No. 96, p.1-14.

6. Butsev S.V. The results of evaluating the quality of correction of wavefront distortions by an adaptive optical phase conjugation system. - Optical Journal, 1998, No. 6. S. 67-72.

Claims (1)

A device for an active adaptive optoelectronic control system for a telescope, containing the main and secondary mirrors, a two-coordinate mirror of the general tilt of the wavefront optically coupled to them, a deformable mirror corrector, a beam splitter, the focal plane of the image in the telescope and a wavefront sensor connected to the beam splitter by its input, which the output is connected to the input of the device for evaluating (filtering) the slopes of the wavefront, which is connected by its output to the phase reducer which is the input of the device for generating optimal control signals, the first output of which is the input of the control device connected to the first output with a two-axis mirror of the general slopes of the wavefront, and the second output is connected to a deformable mirror corrector, and the second output of the device for generating optimal control signals is connected to the secondary control device a mirror, which is connected by its output to a secondary mirror, characterized in that the device is additionally introduced during formation of the reference point source whose output is optically coupled to an xy mirror wavefront common tilts, secondary and main telescope mirrors.

Images