CN103048701B - Atmospheric optical parameter measurer for astronomical site survey - Google Patents

Abstract

The instrument for measuring atmospheric optical parameters for astronomical site selection is composed of a small telescope, a CCD image sensor and a computer. Split mirror; on the optical axis at the rear of the entrance pupil of the small telescope, there are installed in sequence: a splitting mirror, a four-channel photon counting component, an optical imaging relay mirror and a CCD image sensor; among them, the four-channel photon counting component is located at On the focal plane of the small telescope; the grid reticle and the wide-field eyepiece are located above the beam splitter; the output of the four-channel photon counting component and the CCD image sensor is connected to the computer. The atmospheric optical parameter measuring instrument for astronomical site selection of the present invention can simultaneously measure atmospheric seeing, free atmospheric layer seeing, equihalation angle and approximate turbulence intensity profile, and the atmospheric optical parameter measuring instrument for astronomical site selection is convenient for installation and adjustment Good reliability.

Description

Measuring Instrument for Atmospheric Optical Parameters for Astronomical Siting

technical field

The invention relates to the field of atmospheric optics, in particular to an atmospheric optical parameter measuring instrument for astronomical site selection, which is a measuring device for measuring atmospheric optical parameters.

Background technique

In the case of using the adaptive optics system, it is necessary to know the local and current atmospheric seeing parameters, which are also indispensable and important parameters for the site selection of the observatory and astronomical observation. The parameter that quantitatively describes the atmospheric seeing is the atmospheric coherence length, which characterizes the atmospheric coherence at a certain lateral distance in a certain optical path, and is widely used in characterizing the full-range atmospheric turbulence intensity and adaptive optical phase correction technology.

The equihalation angle is a main parameter that determines the corrected field of view of the adaptive optics system, which characterizes the angular dependence of the wavefront of the light wave that reaches the observation point through atmospheric turbulence. If the angle between two beams of light arriving at the system from different directions exceeds the equihalation angle, the correlation between them will degrade rapidly.

When the light wave is transmitted in the turbulent atmosphere, the light wave parameters (intensity, phase, and propagation direction, etc.) fluctuate due to the turbulent disturbance. This fluctuation is caused by the random change of the refractive index. Drift and expansion, image transmission, etc. provide basis. At the same time, through the distribution of turbulent intensity along with the path, other parameters that characterize turbulent conditions can be calculated, such as coherence length, equihalation angle, etc.

At present, the existing atmospheric seeing monitors, such as the differential image motion monitor, monitor the atmospheric seeing in real time by counting the relative motion of a single star image through two small apertures on the pupil plane. This kind of instrument has a simple structure and is widely used to measure the seeing of stations. In my country, this kind of seeing monitor has been operated in the Yunnan Astronomical Observatory, the Xinglong Observatory of the National Astronomical Observatory, and the western astronomical site.

Its specific structure and working principle are: usually place an entrance pupil splitting mirror with two sub-holes (50-100mm) on the entrance pupil of a small-caliber (about 350mm) telescope, and place a small wedge-angle wedge mirror on the sub-holes, The wavefront reaching the sub-hole is tilted, so that the same target star produces non-overlapping double images after passing through the two sub-holes, and finally records a series of double images with the CCD image sensor, and calculates the variance of the relative positions of the double images, namely Seeing can be calculated.

The measurement of the equihalation angle needs to be converted by measuring the intensity of atmospheric turbulence. The most convenient method is to use the starlight scintillation method, that is, to measure the equihalation angle according to the fluctuation variance of the star’s light intensity.

Based on the measurement methods of atmospheric seeing and iso-halation angle, there are existing instruments that can measure these two parameters simultaneously or by changing the pupil template. The multi-aperture blaze sensor measures the star image blaze on apertures of different sizes, and uses the relationship between blaze and turbulence to obtain free atmospheric seeing and equihalation angles.

At present, the measurement methods of turbulence intensity profile mainly include sounding balloon, wind profile wave radar inversion, and sodar measurement, but they all have their own shortcomings, such as direct measurement of data in non-light wave bands, and the measurement accuracy is not good. High, limited measurement distance, and other parameters are required for supporting measurement, which limits the target range and accuracy of measurement. However, the multi-aperture blaze sensor that uses light wave band measurement directly measures the measurand, which has the advantage of real-time, and can simultaneously measure multiple atmospheric optical parameters such as free atmosphere seeing, iso-halo angle, and approximate turbulence intensity profile, and has been successfully configured. Go to Cerro Tololo, Mauna Kea, Cerro Paranal, 30-meter telescope site selection, Antarctic Dome C, etc. to conduct site surveys. In addition, the combination of multi-aperture blaze sensor and differential image motion monitor makes full use of the advantages of both, and is successfully applied to the site selection of a 30-meter telescope. There is no successful application of multi-aperture blaze sensors for measurement in our country, and there is also a lack of research on its key technologies. However, the structure of the multi-aperture blaze sensor is complicated, the processing is difficult, and the on-site installation and adjustment are difficult.

Therefore, there is a need for a new instrument for measuring atmospheric optical parameters for astronomical siting, which needs to make full use of the advantages of multi-aperture blaze sensors and differential image motion monitors, and at the same time satisfy the convenience of on-site installation and long-term reliability. And this measuring instrument has not yet occurred in the prior art.

Invention content

The object of the present invention is to provide a kind of astronomical site selection atmospheric optical parameter measuring instrument that can measure atmospheric seeing degree, free atmospheric layer seeing degree, equihalation angle and approximate turbulence intensity profile simultaneously, this kind of astronomical site selection atmospheric optical parameter measurement instrument The instrument is easy to install and adjust, and has good reliability.

The technical scheme of the patent of the present invention is as follows: an astronomical siting atmospheric optical parameter measuring instrument is composed of a small telescope, a CCD image sensor and a computer, and is characterized in that:

In front of the entrance pupil of the small telescope, there are installed in sequence: a collimator U1 with a grid reticle, and an entrance pupil splitter U2 (that is, the entrance pupil divider U2 is located at the entrance pupil of the small telescope, and the parallel light The tube U1 is installed in front of the entrance pupil splitter U2, and its light source is a grid reticle);

On the optical axis behind the entrance pupil of the small telescope, there are sequentially installed: an openable beam splitter (abbreviated as a beam splitter), a four-channel photon counting unit U3, an optical imaging relay mirror and a CCD image sensor; wherein, The four-channel photon counting unit U3 is located on the focal plane of the small telescope;

The grid reticle and the wide-field eyepiece are located above the openable and closable beamsplitter;

The outputs of the four-channel photon counting components and the CCD image sensor are connected to the computer.

In other words, the astronomical siting atmospheric optical parameter measuring instrument of the present invention is mainly composed of a collimator, an entrance pupil splitter, a small telescope, an openable beam splitter, a grid reticle, an eyepiece, a four-channel photon counting component, an optical imaging It consists of relay mirror, CCD image sensor and computer. A parallel light pipe is installed in front of the entrance pupil splitter, and its light source is a grid reticle; the entrance pupil divider is located at the entrance pupil of the small telescope, and it consists of a through hole, two wedge mirrors with the same wedge angle and a set of wedges Mirror group; the wedge mirror group is composed of 3 ring-shaped wedge mirrors and 1 wedge mirror with the same center and wedge angle; a beam splitter that can be opened and closed is installed in front of the focal plane of the small telescope, and a grid reticle is installed above the beam splitter and the eyepiece; four-channel photon counting components are installed on the focal plane of the small telescope, and the central axis of the four-channel photon counting component is a through hole, and four photomultiplier tubes are installed around the end of the through hole; the optical imaging relay mirror divides the central area of the focal plane Imaging onto the CCD image sensor.

In the above solution, the structure of the four-channel photon counting component is: a support with a central axis as a through hole; four photomultiplier tubes evenly distributed on the same circle are provided on the support.

The structure of the entrance pupil splitting mirror is: a support with a through hole is provided; the support is provided with two wedge mirrors of the same wedge angle, a through hole and a wedge mirror evenly distributed on the same circle group; the wedge angle of two wedge mirrors is 25″.

The contents and functions of the above-mentioned components are explained as follows:

When the beam splitter snaps together, the parallel light waves from the collimator pass through the through hole of the entrance pupil splitting mirror and the small telescope, and are split by the beam splitter. One light wave is imaged on the grid reticle, and the other light wave is relayed by optical imaging. The mirror is imaged on the CCD image sensor for system installation and adjustment. When the beam splitter bounces off, the parallel light waves from the collimator pass through the through hole of the entrance pupil splitter mirror and the small telescope system, and are directly imaged by the optical imaging relay mirror on the CCD image sensor, and the auxiliary system automatically adjusts the focus.

When the beam splitter is opened, the light wave from the single star is deflected by two wedge mirrors with the same wedge angle on the entrance pupil splitter mirror, and then divided into two beams of light waves, which are incident on the small telescope and simultaneously imaged on the CCD image by the optical imaging relay mirror. Image sensor, used for atmospheric seeing measurement; the light wave from a single star is deflected by the wedge mirror group on the entrance pupil splitter mirror and then divided into four light waves, which are incident on the small telescope and converged on four of the four-channel photon counting components On a photomultiplier tube for blaze measurements. The computer uses the relationship between flare and turbulence to directly measure the seeing degree and equihalation angle of the free atmosphere, and at the same time uses the inverse problem calculation algorithm to restore the approximate turbulence intensity profile.

The object of the present invention is to provide a kind of astronomical site selection atmospheric optical parameter measuring instrument that can measure atmospheric seeing degree, free atmospheric layer seeing degree, equihalation angle and approximate turbulence intensity profile simultaneously, this kind of astronomical site selection atmospheric optical parameter measurement instrument The instrument is easy to install and adjust, and has good reliability. Compared with the prior art, the beneficial effects of the present invention are: (1) Structurally, collimator, grid reticle and wide-field eyepiece are used to facilitate on-site installation and adjustment of the system. (2) The structure adopts collimator and CCD image sensor, and the auxiliary system automatically adjusts the focus. (3) There is no public report on the entrance pupil splitting mirror spectroscopic method. This technology glues the entrance pupil splitter into independent components, and the external vibration does not affect the performance of the entrance pupil splitter. This technology facilitates the on-site installation and adjustment of the atmospheric optical parameter measuring instrument for astronomical siting, and greatly improves the reliability.

Description of drawings

Fig. 1 is a structural diagram of the optical path of the present invention.

Fig. 2 is a structural schematic diagram of the entrance pupil splitting mirror and four-channel photon counting components of the present invention.

Detailed ways

Embodiment 1, an instrument for measuring atmospheric optical parameters for astronomical siting. See Figures 1 and 2: the small telescope 1 has an aperture of Φ355.6 mm, a focal length of 3910 mm, and apochromatic broadband imaging at 400-700 nanometers, with a center wavelength of 550 nanometers. The collimator U1 is installed in front of the entrance pupil splitter U2, and it has a grid reticle. The entrance pupil splitting mirror U2 is located at the entrance pupil of the small telescope, and it is composed of a support 7 with a Φ100mm through hole, a Φ100mm wedge mirror 8, a Φ100mm wedge mirror 10, and a wedge mirror group 9; the wedge angle of the wedge mirrors 8 and 10 is 25° "; Wedge mirror group 9 consists of an annular wedge mirror with an outer diameter of Φ85.25mm and an inner diameter of Φ58.5mm, an annular wedge mirror with an outer diameter of Φ58.5mm and an inner diameter of Φ33mm, an annular wedge mirror with an outer diameter of Φ33mm and an inner diameter of Φ19.5mm, and a wedge mirror with a diameter of Φ19.5mm The mirrors are rotated 90° and glued together. The wedge angles of the wedge mirrors in the wedge mirror group 9 are all 24', and they share the center of the circle. The openable beam splitter 2 is located in front of the focal plane of the small telescope. The outer diameter is Φ42.5mm. Scribing plate 3 and 70° wide field of view Ultima LX 32mm eyepiece 4 are located above the beam splitter 2. The four-channel photon counting unit U3 is located on the focal plane of the small telescope, which includes a support 11 whose central axis is a through hole, the model is R1635P Hamamatsu Photomultiplier tubes 12, 13, 14 and 15. The optical imaging relay mirror 5 is located behind the four-channel photon counting part U3, and it images the central area of the focal plane onto the CCD image sensor 6. The model of the CCD image sensor 6 is JAI-BM141GE .

The combination of the collimator U1 and the CCD image sensor 6 assists the automatic focusing of the system. The openable beam splitter 2, grid reticle 3 and wide-field eyepiece 4 are convenient for on-site installation and adjustment of the system. The combination of wedge mirror 8, wedge mirror 10, small telescope 1, optical imaging relay mirror 5 and CCD image sensor 6 realizes atmospheric seeing monitoring. The combination of the wedge mirror group 9, the small telescope 1 and the four-channel photon counting unit U3 realizes the single star flare monitoring. Various atmospheric optical parameters such as atmospheric seeing degree, free atmospheric seeing degree, equihalation angle and approximate turbulence intensity profile can be obtained after calculation by atmospheric comprehensive parameter measurement and analysis software.

Claims (2)

1. an atmospheric optical parameter measurer for astronomical site survey, is made up of race glass, CCD image sensor and computing machine, it is characterized in that:

In the front at described race glass entrance pupil place, be provided with successively: with parallel light tube (U1), entrance pupil segmentation mirror (U2) of grid graticule;

On the optical axis at the rear at described race glass entrance pupil place, be provided with successively: can the spectroscope of folding, four-way photon counting parts (U3), optical imagery relay lens and ccd image sensor; Wherein, four-way photon counting parts (U3) are positioned on race glass focal plane;

Another grid graticule (3) and wide visual field eyepiece be positioned at described can spectroscopical top of folding;

The output of described four-way photon counting parts, ccd image sensor, connects described computing machine;

The structure of described four-way photon counting parts is: be provided with the bearing that axis is through hole; This bearing is provided with four photomultipliers be evenly distributed on same circle;

The structure of described entrance pupil segmentation mirror is: be provided with the bearing with through hole; This bearing is provided with the wedge mirror of two the identical angles of wedge be evenly distributed on same circle, a through hole and a wedge mirror group;

The wedge mirror of two identical angles of wedge in described entrance pupil segmentation mirror, its angle of wedge is 25 ".

2. atmospheric optical parameter measurer for astronomical site survey according to claim 1, is characterized in that: the bore of described race glass is Φ 355.6mm, and focal length is 3910mm, and 400 ~ 700 nanometer apochromatism broadband imagings, centre wavelength is 550 nanometers.